@article{petrecca_christopher_velev_fedkiw_2022, title={Applications of Soft Dendritic Colloids in Li-Ion Batteries with Advanced Structure-Derived Performance}, url={https://doi.org/10.1149/MA2022-02642335mtgabs}, DOI={10.1149/MA2022-02642335mtgabs}, abstractNote={Adoption of electric vehicles and increasing demands of consumer electronics require electrochemical energy storage devices with high capacity and rate capabilities. Supply-chain and material-cost concerns as well as charge-rate limitations associated with irreversible lattice changes motivates the replacement of mixed-metal oxide cathodes in lithium-ion batteries (LIBs). Electrochemically active polymeric materials have emerged as promising candidates to replace metal oxides due to their high tunability and increased capacity. However, many of these materials suffer from poor intrinsic electronic conductivity and may be soluble into the electrolyte, causing irreversible capacity fade. Nanostructuring and composite formation are two polymer processing methods that can be leveraged to combat these drawbacks. The introduction of new nanostructured and nanocomposite cell components can decrease diffusion length scales, increase mechanical stability, and allow for higher electronic conductivity in polymer electrodes. Herein, we utilize a new class of polymeric materials called soft dendritic colloids (SDCs) as a platform for creating such nanocomposites. These fibrillar polymeric particles, formed via turbulent solvent-nonsovent induced phase separation, have hierarchical morphology, large aspect ratios and demonstrate pronounced adhesion and network-forming behavior. SDC-based materials have shown impressive results as nonwoven polyvinylidene difluoride separators in Li-ion batteries. Herein, we propose and present their use as Li-ion battery electrodes with advanced structural properties, derived from electroactive polymeric materials.}, journal={ECS Meeting Abstracts}, author={Petrecca, Michael J. and Christopher, Jerush and Velev, Orlin D. and Fedkiw, Peter S.}, year={2022}, month={Oct} }
 @article{luiso_petrecca_williams_christopher_velev_pourdeyhimi_fedkiw_2022, title={Structure-Performance Relationships of Li-Ion Battery Fiber-Based Separators}, volume={4}, ISSN={["2637-6105"]}, url={https://doi.org/10.1021/acsapm.2c00216}, DOI={10.1021/acsapm.2c00216}, abstractNote={Lithium-ion battery separators are receiving increased consideration from the scientific community. Many research efforts trend toward creating high-performance fiber-based battery separators with a small and uniform pore size to maximize ionic conductivity and cell discharge capacity. Here, we show that not only the pore size but also the pore size distribution has an important effect on these electrochemical properties. In this work, we studied nonwoven membranes fabricated from a single polymer, poly(vinylidene fluoride) (PVDF), with different pore sizes and pore size distributions using three different techniques (meltblowing, electrospinning, and shear spinning). We evaluate their performance as separators in Li-ion cells. Although meltblowing is commonly employed to produce commercial microfibers/nanofibers, electrospinning has been studied mostly in the academic literature. Shear spinning is an emerging method to fabricate nanofibrous material where, for this study, the morphology of the resulting PVDF membranes may be controlled from fibrous-like to nano-sheet-like with subsequent effects on the electrochemical properties. We show that the smaller the pore size and the wider the pore size distribution, the higher are the electrolyte uptake and ionic conductivity of the mats, resulting in improved in-use discharge capacity and rate capability of Li/LiCoO2 cells.}, number={5}, journal={ACS APPLIED POLYMER MATERIALS}, publisher={American Chemical Society (ACS)}, author={Luiso, Salvatore and Petrecca, Michael J. and Williams, Austin H. and Christopher, Jerush and Velev, Orlin D. and Pourdeyhimi, Behnam and Fedkiw, Peter S.}, year={2022}, month={May}, pages={3676–3686} }
 @article{dufficy_corder_dennis_fedkiw_khan_2021, title={Guar Gel Binders for Silicon Nanoparticle Anodes: Relating Binder Rheology to Electrode Performance}, volume={13}, ISSN={["1944-8252"]}, url={https://doi.org/10.1021/acsami.1c10776}, DOI={10.1021/acsami.1c10776}, abstractNote={Binding agents are a critical component of Si-based anodes for lithium-ion batteries. Herein, we introduce a composite hydrogel binder consisting of carbon black (CB) and guar, which is chemically cross-linked with glutaraldehyde as a means to reinforce the electrode structure during lithiation and improve electronic conductivity. Dynamic rheological measurements are used to monitor the cross-linking reaction and show that rheology plays a significant role in binder performance. The cross-linking reaction occurs at a faster rate and produces stronger networks in the presence of CB, as evidenced from higher gel elastic modulus in guar + CB gels than guar gels alone. Silicon nanoparticle (SiNP) electrodes that use binders with low cross-link densities (trxn < 2 days) demonstrate discharge capacities ∼1200 mAh g-1 and Coulombic efficiencies >99.8% after 300 cycles at 1-C rate. Low cross-link densities likely increase the capacity of SiNP anodes because of binder-Si hydrogen-bonding interactions that accommodate volume expansions. In addition, the cross-linked binder demonstrates the potential for self-healing, as evidenced by an increased elastic modulus after the gel was mechanically fragmented, which may preserve the electrode microstructure during lithiation and increase capacity retention. The composite hydrogel with integrated conductive additives gives promise to a new type of binder for next-generation lithium-ion batteries.}, number={43}, journal={ACS APPLIED MATERIALS & INTERFACES}, publisher={American Chemical Society (ACS)}, author={Dufficy, Martin K. and Corder, Ria D. and Dennis, Kimberly A. and Fedkiw, Peter S. and Khan, Saad A.}, year={2021}, month={Nov}, pages={51403–51413} }
 @article{luiso_henry_pourdeyhimi_fedkiw_2021, title={Meltblown Polyvinylidene Difluoride as a Li-Ion Battery Separator}, volume={3}, ISSN={["2637-6105"]}, url={https://doi.org/10.1021/acsapm.1c00221}, DOI={10.1021/acsapm.1c00221}, abstractNote={Among the types of Li-ion battery separators, the benefits of nonwoven mats are high porosity with low mass and low average production cost. Nonwoven polyvinylidene difluoride (PVDF) shows promise as a separator because of its chemical and mechanical stability and good absorption of organic electrolytes used in Li-ion cells. We investigated the use of a melt-blowable PVDF (Kynar resin RC 10,287, Arkema, Inc.) to produce meltblown PVDF mats, with the objective of elucidating its properties as a separator in Li-ion batteries. Meltblown PVDF mats were fabricated with high quality on a 1.2 m wide Reicofil R4 meltblown pilot line and subsequently consolidated through thermal compaction in a hydraulic press. The resulting mats showed high homogeneity (low roping and fiber entanglements), an average pore size as small as 0.9 μm, and average fiber diameter as small as 1.4 μm, yielding a high surface area and electrolyte uptake. After thermally compacting the nonwoven mat, the thickness and pore size decrease along with electrolyte absorbance and ionic conductivity. The highest conductivity of the electrolyte-infused mat was ∼9.6 mS/cm (room temperature with 1 M LiPF6 in ethylene carbonate/dimethyl carbonate 1:1 w/w), and the first-cycle capacity of a Li/LiCoO2 cell containing the meltblown PVDF separators was 140 mA h/g. Here, we assessed meltblown PVDF as a Li-ion battery separator by studying its physical, chemical, and electrochemical properties.}, number={6}, journal={ACS APPLIED POLYMER MATERIALS}, publisher={American Chemical Society (ACS)}, author={Luiso, Salvatore and Henry, James J. and Pourdeyhimi, Behnam and Fedkiw, Peter S.}, year={2021}, month={Jun}, pages={3038–3048} }
 @article{luiso_williams_petrecca_roh_velev_fedkiw_2021, title={Poly(Vinylidene Difluoride) Soft Dendritic Colloids as Li-Ion Battery Separators}, volume={168}, ISSN={["1945-7111"]}, url={https://doi.org/10.1149/1945-7111/abdfa7}, DOI={10.1149/1945-7111/abdfa7}, abstractNote={As an alternative to Li-ion battery (LIB) microporous membrane separators that are typically comprised of polyolefins, other materials and separator morphologies may yield increased cell performance. Here, we present a new class of LIB separators comprising poly(vinylidene difluoride) (PVDF)-based and highly branched, colloidal polymer particulates, called soft dendritic colloids, that are produced by shear-driven polymer precipitation within a turbulent nonsolvent flow followed by filtration. We show the morphology of the resulting PVDF particulates may be varied from fibrous dendritic colloids to thin and highly porous sheet-like particles. The use of PVDF leads to low thermal shrinkage (5% at 90 °C) and high tensile strength (<0.7% offset at 1000 psi), while the high porosity (up to 80%) and high particle surface area are responsible for high conductivity (1.2 mS cm −1 ) and electrolyte uptake (325%), and good cell capacity (112 mAh g −1 in Li/LiCoO 2 cell) with <10% loss after 50 cycles. Because shear-driven precipitation with filtration is a facile and versatile process to make a new class of polymeric LIB separators, soft dendritic colloids are promising candidates as separators for next-generation batteries.}, number={2}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, publisher={The Electrochemical Society}, author={Luiso, Salvatore and Williams, Austin H. and Petrecca, Michael J. and Roh, Sangchul and Velev, Orlin D. and Fedkiw, Peter S.}, year={2021}, month={Feb} }
 @article{luiso_williams_velev_pourdeyhimi_fedkiw_2020, title={An Ideal Structure for Li-Ion Battery Separators}, volume={MA2020-02}, url={https://doi.org/10.1149/MA2020-02453792mtgabs}, DOI={10.1149/MA2020-02453792mtgabs}, number={45}, journal={ECS Meeting Abstracts}, publisher={The Electrochemical Society}, author={Luiso, Salvatore and Williams, Austin H and Velev, Orlin D. and Pourdeyhimi, Behnam and Fedkiw, Peter S.}, year={2020}, month={Nov}, pages={3792–3792} }
 @article{ho_yildiz_bradford_zhu_fedkiw_2018, title={A silicon-impregnated carbon nanotube mat as a lithium-ion cell anode}, volume={48}, ISSN={["1572-8838"]}, DOI={10.1007/s10800-017-1140-8}, abstractNote={Silicon is a widely researched material for the anodes of lithium-ion batteries due to its high practical charge capacity of 3600 mAh g−1, which is ~ 10 times the specific capacity of conventional graphitic materials. However, silicon degrades rapidly in use due to its volumetric changes during charge/discharge of the battery, which makes it necessary to use complicated or costly methods to ameliorate capacity loss. Here, we report a novel silicon anode fabrication technique, which involves winding an aligned carbon nanotube (CNT) sheet and commensurately infiltrating it in situ with an aqueous solution containing silicon nanoparticles and hydroxypropyl guar binder. The resulting infiltrated felts were processed, evaluated, and compared to conventional silicon–carbon black anodes with the same carbon, silicon, and binder content as a proof of concept study. The felts had a large initial reversible capacity and promising rate capability. It is likely that the conductive CNT structure improved the charge transfer properties while lessening the effects of silicon volumetric expansion during lithiation. The results demonstrate that this novel anode fabrication method is viable and may be explored for further optimization. A novel fabrication method is described for the negative electrode for a lithium-ion battery: a CNT mat is formed by a drawing operation from a CNT vertical array while simultaneously being impregnated with a solution containing silicon nanoparticles and hydroxypropyl guar gum binder. The resulting CNT–Si anode structure shows improved lifetime cycling performance compared to traditional slurry-based silicon anodes.}, number={1}, journal={JOURNAL OF APPLIED ELECTROCHEMISTRY}, author={Ho, David N. and Yildiz, Ozkan and Bradford, Philip and Zhu, Yuntian and Fedkiw, Peter S.}, year={2018}, month={Jan}, pages={127–133} }
 @article{huang_li_zhu_fedkiw_2017, title={Carbon Buckypaper as an Electrocatalyst Support for Oxygen Reduction}, volume={47}, journal={Journal of Applied Electrochemistry}, author={Huang, Sheng-Yang and Li, Qingwen and Zhu, Yuntian and Fedkiw, Peter S.}, year={2017}, pages={105–115} }
 @article{huang_sodano_leonard_luiso_fedkiw_2017, title={Cobalt-Doped Iron Sulfide as an Electrocatalyst for Hydrogen Evolution}, volume={164}, ISSN={["1945-7111"]}, DOI={10.1149/2.0761704jes}, abstractNote={Iron disulfide (FeS2) promises an earth-abundant, low-cost alternative to platinum group metals for the hydrogen evolution reaction (HER), but its performance is currently limited by reactivity of active sites and poor electrical conductivity. Here we employ Ketjenblack (KB) as a support to create an Fe-based electrocatalyst with high-electrical conductivity and maximal active sites. Moreover, a systematic study on the role of cobalt (Co) dopant was carried out. Electrochemical results show enhancements in HER activity of Co-doped FeS2 [FexCo1−xS2, atomic content of Fe (x) = 0.98 – 0.32] in comparison to un-doped FeS2 in acidic electrolyte (pH = 0). The overpotential necessary to drive a current density of 10 mA/cm2 is −0.150 V and only decreases by 1 mV after 500 cycles of a durability test (cycling the potential between 0.0 and −0.15 V), indicating a long-term durability in acidic environment. This work suggests that FexCo1−xS2 offers a viable approach to improve the activity and durability of transition metal-sulfide electrocatalysts.}, number={4}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={Huang, Sheng-Yang and Sodano, Daniel and Leonard, Thomas and Luiso, Salvatore and Fedkiw, Peter S.}, year={2017}, pages={F276–F282} }
 @article{dufficy_huang_khan_fedkiw_2017, title={Effects of composition and structure on the performance of tin/graphene-containing carbon nanofibers for Li-ion anodes}, volume={7}, ISSN={2046-2069}, url={http://dx.doi.org/10.1039/C6RA26371B}, DOI={10.1039/C6RA26371B}, abstractNote={We use structure–composition relationships to engineer tin-containing nanofibers for Li-ion anodes that retain their capacities over 900 cycles.}, number={25}, journal={RSC Advances}, publisher={Royal Society of Chemistry (RSC)}, author={Dufficy, Martin K. and Huang, Sheng-Yang and Khan, Saad A. and Fedkiw, Peter S.}, year={2017}, pages={15428–15438} }
 @article{huang_li_zhu_fedkiw_2017, title={Investigation and modification of carbon buckypaper as an electrocatalyst support for oxygen reduction}, volume={47}, ISSN={["1572-8838"]}, DOI={10.1007/s10800-016-1023-4}, number={1}, journal={JOURNAL OF APPLIED ELECTROCHEMISTRY}, author={Huang, Sheng-Yang and Li, Qingwen and Zhu, Yuntian and Fedkiw, Peter S.}, year={2017}, month={Jan}, pages={105–115} }
 @article{dufficy_khan_fedkiw_2016, title={Hierarchical Graphene-Containing Carbon Nanofibers for Lithium-Ion Battery Anodes}, volume={8}, ISSN={1944-8244 1944-8252}, url={http://dx.doi.org/10.1021/ACSAMI.5B10069}, DOI={10.1021/ACSAMI.5B10069}, abstractNote={We present a method to produce composite anodes consisting of thermally reduced graphene oxide-containing carbon nanofibers (TRGO/CNFs) via electrospinning a dispersion of polyacrylonitrile (PAN) and graphene oxide (GO) sheets in dimethylformamide followed by heat treatment at 650 °C. A range of GO (1-20 wt % GO relative to polymer concentration) was added to the polymer solution, with each sample comprising similar polymer chain packing and subsequent CNF microstructure, as assessed by X-ray diffraction. An increase from 0 to 20 wt % GO in the fibers led to carbonized nonwovens with enhanced electronic conductivity, as TRGO sheets conductively connected the CNFs. Galvanostatic half-cell cycling revealed that TRGO addition enhanced the specific discharge capacity of the fibers. The optimal GO concentration of 5 wt % GO enhanced first-cycle discharge capacities at C/24 rates (15.6 mA g(-1)) 150% compared to CNFs, with a 400% capacity increase at 2-C rates (750 mA g(-1)). We attribute the capacity enhancement to a high degree of GO exfoliation. The TRGO/CNFs also experienced no capacity fade after 200 cycles at 2-C rates. Impedance spectroscopy of the composite anodes demonstrated that charge-transfer resistances decreased as GO content increased, implying that high GO loadings result in more electrochemically active material.}, number={2}, journal={ACS Applied Materials & Interfaces}, publisher={American Chemical Society (ACS)}, author={Dufficy, Martin K. and Khan, Saad A. and Fedkiw, Peter S.}, year={2016}, month={Jan}, pages={1327–1336} }
 @article{huang_fedkiw_2016, title={Pervaporation removal of water from ionic liquid solutions using Nafion membranes}, volume={51}, ISSN={["1520-5754"]}, DOI={10.1080/01496395.2016.1236816}, abstractNote={We report a pervaporation process to remove water from a solution containing ionic liquid (IL) + solvent + water. Specifically, Nafion-based membranes were employed for the separation, and tributylmethylammonium dimethylphosphate and N-methyl-2-pyrrolidone (NMP) were the IL and solvent, respectively. Membrane swelling in contact with the IL–NMP–H2O solution was accommodated by judicious use of gaskets and membrane supports. The pervaporation fluxes of water and NMP increased with temperature and flow rate of the permeate sweep gas. Among the membranes examined, a commercially available Nafion membrane (XL, Ion Power) provided the highest water (10 mg h−1 cm−2) and NMP (182 mg h−1 cm−2) fluxes. The results show that pervaporation separation is a technologically feasible method to decrease the water content of an IL–NMP–H2O solution from 1 to 0.5 wt%.}, number={18}, journal={SEPARATION SCIENCE AND TECHNOLOGY}, author={Huang, Sheng-Yang and Fedkiw, Peter S.}, year={2016}, pages={2932–2939} }
 @article{mcclure_borodin_olguin_chu_fedkiw_2016, title={Sensitivity of Density Functional Theory Methodology for Oxygen Reduction Reaction Predictions on Fe-N-4-Containing Graphitic Clusters}, volume={120}, ISSN={["1932-7455"]}, DOI={10.1021/acs.jpcc.6b08498}, abstractNote={Density functional theory (DFT) was used to examine the O2 reduction reaction on Fe–N4-containing graphitic carbon clusters (Fe–N4–G) modeled after recent experimentally identified active sites, Mössbauer spin-state predictions and electrochemical reaction behavior in alkaline media. A detailed analysis of the O2, O, H2O, OOH, and OH adsorbate interactions on the Fe–N4–G cluster with solvation and/or dispersion corrections are considered. The total and partial density of states for the α- and β-spin orbitals are compared for the adsorbate of interest, Fe atom and surrounding graphitic cluster. Relative free-energy diagrams are constructed, which allow us to compare DFT predictions to experimental results for O2 reduction on systems containing embedded Fe–N4 clusters. For all reaction steps, different DFT functionals are explored and the respective geometries, energetics, and spin-states for each adsorbate interaction are reported for six commonly used functionals including B3LYP, M06-2X, M06-L, PBE, TPSSh, and ωB97X-D. Functionals with high fractions of exact exchange were found to favor higher spin-states, as well as stronger binding of the adsorbates, making these methodologies less feasible for Fe–N4-containing electrocatalysts when compared to experimental data. Pure functionals with and without empirical correlation exhibit different ground spin-states and geometries, however the free energy diagrams yield similar conclusions at relevant overpotentials. The activation energy for the O–OH bond scission step, as well as OH desorption from the Fe–N4–G cluster are discussed since the barrier could prohibit a pure 4e– ORR. Finally, we discuss the energetically unfavorable steps for select overpotentials, which provides the experimentalist with a tuning knob for electrocatalytic design.}, number={50}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={McClure, Joshua P. and Borodin, Oleg and Olguin, Marco and Chu, Deryn and Fedkiw, Peter S.}, year={2016}, month={Dec}, pages={28545–28562} }
 @article{dufficy_luo_fedkiw_maggard_2016, title={Vacancy-induced manganese vanadates and their potential application to Li-ion batteries}, volume={52}, ISSN={["1364-548X"]}, DOI={10.1039/c6cc02249a}, abstractNote={We report on the synthesis and characterization of a novel manganese vanadate, Mn<sub>1.5</sub>(H<sub>2</sub>O)(NH<sub>4</sub>)V<sub>4</sub>O<sub>12</sub>, with rare <italic>in situ</italic> disorder of Mn(H<sub>2</sub>O)<sub>2</sub><sup>2+</sup>/2NH<sub>4</sub><sup>+</sup>.}, number={47}, journal={CHEMICAL COMMUNICATIONS}, author={Dufficy, Martin K. and Luo, Lan and Fedkiw, Peter S. and Maggard, Paul A.}, year={2016}, pages={7509–7512} }
 @article{dufficy_khan_fedkiw_2015, title={Galactomannan binding agents for silicon anodes in Li-ion batteries}, volume={3}, ISSN={2050-7488 2050-7496}, url={http://dx.doi.org/10.1039/C5TA03126E}, DOI={10.1039/C5TA03126E}, abstractNote={The high Li-extraction capacity can be owed to the favorable interactions between silicon nanoparticles and the galactomannan binders.}, number={22}, journal={Journal of Materials Chemistry A}, publisher={Royal Society of Chemistry (RSC)}, author={Dufficy, Martin K. and Khan, Saad A. and Fedkiw, Peter S.}, year={2015}, pages={12023–12030} }
 @article{mcclure_jiang_chu_fedkiw_2014, title={Oxygen electroreduction on Fe- or Co-containing carbon fibers}, volume={79}, ISSN={["1873-3891"]}, DOI={10.1016/j.carbon.2014.08.005}, abstractNote={Non-noble metal-containing electrocatalysts were prepared by an electrospinning method and evaluated as oxygen reduction electrocatalysts. Fe- or Co-containing carbon fibers were prepared by pyrolyzing electrospun polyacrylonitrile (PAN) fibers containing the respective metal precursor and are denoted Fe-PAN and Co-PAN, respectively. The Fe- or Co-PAN carbon fibers were acid-leached and subjected to a second pyrolysis, whereby the final fibers were found to be uniform in diameter with roughened surfaces. Scanning transmission electron microscopy equipped with energy dispersive spectroscopy area-mapping identified Fe or Co nanoparticulates throughout the fiber with a distribution of particulate sizes. X-ray diffractograms (XRD) revealed amorphous Fe-PAN and Co-PAN carbon fibers with no discernible Fe or Co phases, whereas high-resolution XPS scans show a range of potential Fe or Co species. Moreover, the high-resolution X-ray photoelectron spectroscopy (XPS) and peak-fitting analysis provided chemical species information for the C1s, N1s, Fe2p and Co2p regions. The physical characterizations highlighted potential beneficial components for the electrocatalysts that made their use as oxygen reduction reaction (ORR) effective. Rotating disk and ring-disk electrode experiments determined that the best Fe-PAN sample out-performed the best Co-PAN sample and even performed well in comparison to a commercial Pt/C electrocatalyst for the ORR in a high pH media.}, journal={CARBON}, author={McClure, Joshua P. and Jiang, Rongzhong and Chu, Deryn and Fedkiw, Peter S.}, year={2014}, month={Nov}, pages={457–469} }
 @article{mcclure_devine_jiang_chu_cuomo_parsons_fedkiw_2013, title={Oxygen Electroreduction on Ti- and Fe-Containing Carbon Fibers}, volume={160}, ISSN={["1945-7111"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000324810000079&KeyUID=WOS:000324810000079}, DOI={10.1149/2.029308jes}, abstractNote={A mixture of iron (II) phthalocyanine and polyacrylonitrile (PAN) was electrospun into fibers and pyrolyzed to form Fe-containing carbon fibers (Fe-PAN). Subsequent atomic layer deposition (ALD) coated the fibers with TiOy deposits (TiOy-Fe-PAN). Scanning transmission electron microscopy equipped with energy dispersive spectroscopy (STEM-EDS) detected C, Fe, and Ti across the diameter of the fiber, and X-ray photoelectron spectroscopy (XPS) revealed Fe(III) and CNx species present. After the ALD process, XPS revealed TiOy species on the Fe-PAN fibers, and heat-treating the TiOy-Fe-PAN samples created TiNxOy and TiNx species. Heat-treating Fe-PAN and TiOy-Fe-PAN samples resulted in a slight decrease in the Fe wt.% but affected an increase in the oxygen reduction reaction (ORR) activity in 0.5M H2SO4 at room temperature compared to the samples not heat treated. Moreover, the presence of Ti species decreased the production of H2O2 and increased the mass activity of the ORR on fibers subjected to cyclic potential excursions relative to samples without Ti species.}, number={8}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={McClure, Joshua P. and Devine, Christina K. and Jiang, Rongzhong and Chu, Deryn and Cuomo, Jerome J. and Parsons, Gregory N. and Fedkiw, Peter S.}, year={2013}, pages={F769–F778} }
 @article{loebl_oldham_devine_gong_atanasov_parsons_fedkiw_2013, title={Solid Electrolyte Interphase on Lithium-Ion Carbon Nanofiber Electrodes by Atomic and Molecular Layer Deposition}, volume={160}, ISSN={["1945-7111"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000326905000006&KeyUID=WOS:000326905000006}, DOI={10.1149/2.020311jes}, number={11}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={Loebl, Andrew J. and Oldham, Christopher J. and Devine, Christina K. and Gong, Bo and Atanasov, Sarah E. and Parsons, Gregory N. and Fedkiw, Peter S.}, year={2013}, pages={A1971–A1978} }
 @article{yadav_fedkiw_2012, title={Analysis of EIS Technique and Nafion 117 Conductivity as a Function of Temperature and Relative Humidity}, volume={159}, ISSN={["1945-7111"]}, DOI={10.1149/2.104203jes}, number={3}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={Yadav, Rameshwar and Fedkiw, Peter S.}, year={2012}, pages={B340–B346} }
 @article{yin_gao_pan_shen_ye_liu_fedkiw_zhang_2012, title={High-rate capability of LiFePO4 cathode materials containing Fe2P and trace carbon}, volume={199}, ISSN={["0378-7753"]}, url={https://publons.com/publon/4984276/}, DOI={10.1016/j.jpowsour.2011.10.042}, abstractNote={► High-electronic conductivity iron phosphides (Fe 2 P/FeP) are in situ introduced into the LiFePO 4 materials with particle size of sub-micron and trace carbon. ► The sub-micron size of the particles and trace carbon result in a high-tap density (1.37 g cm −3 ) for the LiFePO 4 material. ► Fe 2 P/FeP plays an important role in improving the high-rate capability of the LiFePO 4 material. ► The LiFePO 4 material provides promising high-rate capability without unduly compromising its volumetric energy density. Carbon coating and nano-scale particle size are two impactful factors in improving the rate capability of LiFePO 4 cathode materials for lithium-ion batteries. However, both factors decrease the tap density of the materials and are possibly causing unfavorable effect on the volumetric capacity of the cathode materials and thus the batteries, which is undesirable in commercial application. In the present study, LiFePO 4 materials with moderate particle size of sub-micron and trace carbon content (0.5–0.9 wt.%) are synthesized by a mechanical activation method. High-electronic conductivity iron phosphides (Fe 2 P/FeP) are in situ introduced into the LiFePO 4 materials and the amount is modified by the calcination temperature. Electrochemical testing shows that Fe 2 P/FeP plays an important role in improving the high-rate capability of LiFePO 4 with moderate particle size. The product calcined at 700 °C, which has a high-tap density of 1.37 g cm −3 correlating to a specific surface area approximately of 4 m 2 g −1 , possesses discharge capacities of 110 and 100 mAh g −1 at discharge rates of 5 C and 10 C, respectively. The introduction of Fe 2 P/FeP in an amount of ca. 5 wt.% rather than carbon coating and the moderate particle size of LiFePO 4 are promising approaches to obtain LiFePO 4 cathode material of high-rate capability without unduly compromising its volumetric capacity.}, journal={JOURNAL OF POWER SOURCES}, publisher={Elsevier BV}, author={Yin, Yuehui and Gao, Mingxia and Pan, Hongge and Shen, Lukai and Ye, Xin and Liu, Yongfeng and Fedkiw, Peter S. and Zhang, Xiangwu}, year={2012}, month={Feb}, pages={256–262} }
 @article{mcclure_thornton_jiang_chu_cuomo_fedkiw_2012, title={Oxygen Reduction on Metal-Free Nitrogen-Doped Carbon Nanowall Electrodes}, volume={159}, ISSN={["1945-7111"]}, DOI={10.1149/2.056211jes}, abstractNote={A plasma-enhanced chemical vapor deposition (PECVD) process using a CH4:H2 gas mixture creates vertically aligned carbon nanowalls (CNWs) on glassy carbon (GC) and Si substrates. Metal catalysts are not required for the nucleation and growth of CNWs on the substrates. The PECVD deposition temperatures and reaction times alter the morphology and thickness of the resulting CNW layer. A low-pressure, post-processing N2:Ar plasma treatment dopes the CNWs with nitrogen, and X-ray photoelectron spectroscopy measurements demonstrate that nitrogen is present at 4–20 atomic% with varying CNx bonding configurations dependent upon processing conditions. Raman spectroscopy shows relatively high intensity disorder bands (ID) compared to lower intensity graphitic bands (IG) indicating small crystalline domains. Rotating disk electrode voltammetry results show that the number of electrons (n) and kinetic current density (jk) of the oxygen reduction reaction both increase with nitrogen content. In addition, n and jk increase with thickness of the nitrogen-containing CNW deposit. The results indicate that nitrogen-doped CNWs have higher electrochemical reactivity than their non-doped counterparts.}, number={11}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={McClure, Joshua P. and Thornton, Jackson D. and Jiang, Rongzhong and Chu, Deryn and Cuomo, Jerome J. and Fedkiw, Peter S.}, year={2012}, pages={F733–F742} }
 @article{wang_mcclure_fedkiw_2012, title={Transport properties of proton- and hydroxide-exchange membranes for fuel cells}, volume={79}, ISSN={["0013-4686"]}, DOI={10.1016/j.electacta.2012.06.098}, abstractNote={Abstract The electro-osmotic drag coefficients (ξ) of water-vapor equilibrated Nafion® 117, a proton conductor, and Tokuyama® A201, a hydroxide conductor were determined from the steady-state voltage of a water concentration cell. The ξ values are reported, along with water uptake, ion-exchange capacity, ionic conductivity, and methanol permeability of these membranes. The room-temperature ξ of Nafion® 117 and Tokuyama® A201 is 0.99 (±0.07) and 0.61 (±0.12), respectively, and is relatively independent of water content over the relative humidity range of 14–96%. The time to steady potential in the water concentration cell was longer for the Tokuyama® A201 membrane than the Nafion® 117 membrane, which is tentatively attributed to the lower mobility of hydrated hydroxide (or carbonate from absorption of adventitious carbon dioxide) in comparison to hydronium ion.}, journal={ELECTROCHIMICA ACTA}, author={Wang, Xuhai and McClure, Joshua P. and Fedkiw, Peter S.}, year={2012}, month={Sep}, pages={126–132} }
 @article{zhang_wei_kopanski_shiue_fedkiw_2011, title={Single-Ion Conductors for Lithium Batteries via Surface-Initiated Atom Transfer Radical Polymerization}, volume={4}, ISSN={["1936-6612"]}, DOI={10.1166/asl.2011.1254}, number={2}, journal={ADVANCED SCIENCE LETTERS}, author={Zhang, Hanjun and Wei, Xuedong and Kopanski, Khalid and Shiue, Eric and Fedkiw, Peter S.}, year={2011}, month={Feb}, pages={488–491} }
 @article{azeez_fedkiw_2010, title={Conductivity of libob-based electrolyte for lithium-ion batteries}, volume={195}, ISSN={["1873-2755"]}, DOI={10.1016/j.jpowsour.2010.06.021}, abstractNote={This work reports the use of mixtures of γ-butyrolactone (GBL) and ethyl acetate (EA), with and without ethylene carbonate (EC), as solvents for lithium bis(oxalato)borate (LiBOB) salt as potential electrolytes for Li-ion cells. The effects of salt concentration, ethylene carbonate (EC) content, and temperature on the conductivity and viscosity of the mixture are reported. Results indicate that the best electrolyte for high-temperature application is that which contains 1 kmol m−3 LiBOB in GBL + EA + EC of composition 1:1:0.1 (wt). For low-temperature applications, the best electrolyte is that which contains 0.7 kmol m−3 LiBOB in GBL + EA + EC of composition 1:1:0 (wt). The product of conductivity with viscosity was essentially independent of temperature but was dependent on solvent composition showing that at fixed salt concentration, the viscosity is the major criteria affecting electrolyte conductivity rather than dielectric constant.}, number={22}, journal={JOURNAL OF POWER SOURCES}, author={Azeez, Fadhel and Fedkiw, Peter S.}, year={2010}, month={Nov}, pages={7627–7633} }
 @article{youssef_koch_fedkiw_2008, title={Influence of pulse plating parameters on the synthesis and preferred orientation of nanocrystalline zinc from zinc sulfate electrolytes}, volume={54}, ISSN={["1873-3859"]}, DOI={10.1016/j.electacta.2008.07.048}, abstractNote={Abstract The influence of pulse electrodeposition parameters (current on-time Ton, current off-time Toff, and pulse current density Jp) was investigated on the surface morphology and grain size of zinc electrodeposited from a sulfate bath containing polyacrylamide and thiourea additives. The grain size and surface morphology of zinc deposits were studied by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM), and the preferred orientation of the deposits was studied by X-ray diffraction. At constant current off-time and pulse current density, the grain size decreased asymptotically with increasing current on-time. In contrast, increase in the current off-time at constant current on-time and pulse current density resulted in grain growth. A progressive decrease of the grain size was observed with increasing pulse current density at constant current on-time and off-time. Nanocrystalline zinc with an average grain size of 38 nm was obtained at a pulse current density of 1200 mA/cm2. The crystallographic orientations developed were correlated with the change in the cathodic overpotential, the angle between the preferred oriented plane and the lowest energy of formation plane (0 0 0 2), and the pulse electrodeposition parameters.}, number={2}, journal={ELECTROCHIMICA ACTA}, author={Youssef, K. M. and Koch, C. C. and Fedkiw, P. S.}, year={2008}, month={Dec}, pages={677–683} }
 @article{zhang_zhang_shiue_fedkiw_2008, title={Single-ion conductors for lithium batteries via silica surface modification}, volume={177}, ISSN={["0378-7753"]}, url={https://publons.com/publon/7178337/}, DOI={10.1016/j.jpowsour.2007.11.064}, abstractNote={Single-ion conductors (SICs) have been prepared by free-radical polymerization of sulfonic acid-containing monomer on high-purity silica surface that was first tailored with unsaturated functionality using a silanation reaction. It was found that steric effects limited polyelectrolyte surface loading even when large amount of silane molecules were grafted by forming a cross-linked structure. The results indicate that large surface area is an important factor to achieve high-surface loading of ionic moieties. Composite electrolytes were prepared by dispersing these SICs in aprotic solvents. The effects of filler content and solvent on ionic conductivity were investigated.}, number={2}, journal={JOURNAL OF POWER SOURCES}, author={Zhang, Hanjun and Zhang, Xiangwu and Shiue, Eric and Fedkiw, Peter S.}, year={2008}, month={Mar}, pages={561–565} }
 @article{li_fedkiw_2007, title={Effect of gel electrolytes containing silica nanoparticles on aluminum corrosion}, volume={52}, ISSN={["1873-3859"]}, DOI={10.1016/j.electacta.2006.08.066}, abstractNote={We have investigated corrosion of aluminum current collectors in electrolytes containing LiTFSI salt by chronopotentiometry, cyclic voltammetery, chronoamperometry, electrochemical impedance spectroscopy, and optical microscopy. Open-circuit potentials for cells with gel electrolytes containing silica nanoparticles are relatively stable in comparison to the corresponding baseline liquid, which suggests that the Al/electrolyte interface is more stable in presence of silica nanoparticles. Cyclic voltammetery and chronoamperometry data show that the current density for Li/electrolyte/Al cells with gel electrolytes containing fumed silica was less than that for baseline liquid electrolyte. The Nyquist plot for liquid electrolyte after chronoamperometry is semicircular-like, that is a corrosion reaction occurred. After cell disassembly, black particulates are evident and pits are observed on the aluminum foil. In comparison, no corrosion products are observed for cells containing gel electrolytes, and the Nyquist plots indicate that corrosion does not occur appreciably. Gel electrolytes produce impedance spectra with a large phase lag over a wide frequency range, which is not observed for the baseline liquid electrolyte. These phenomena may be interpreted as a good film-coating behavior associated with gel electrolytes, which results in a lower aluminum corrosion rate.}, number={7}, journal={ELECTROCHIMICA ACTA}, author={Li, Yangxing and Fedkiw, Peter S.}, year={2007}, month={Feb}, pages={2471–2477} }
 @article{li_fedkiw_2007, title={Nanocomposite gel electrolytes based on fumed silica for lithium-ion batteries}, volume={154}, ISSN={["1945-7111"]}, DOI={10.1149/1.2794292}, abstractNote={Nanocomposite gel electrolytes based on silica particles dispersed in lithium bis(perfluoroethylsulfonyl)imide (LiBETI) -carbonate solvent are examined as an electrolyte system for a lithium-ion battery. Gel behavior is observed with both hydrophilic (A200) and hydrophobic (R805) fumed silicas. The silica nanoparticles affect a small decrease in conductivity but increase mechanical strength significantly (elastic modulus ). Chronoamperometry and linear sweep voltammetry results show that an Al current collector is stable in LiBETI carbonates up to . Cycling Li(Ni)/electrolyte/Li cells shows that silica nanoparticles improve the coulombic efficiency and interfacial stability in the order: 10% R805 LiBETI liquid. Cycling cells shows that both liquid and 10% R805 gel electrolytes provide good capacity and cycle performance, but the average charge/discharge voltages for the latter are more stable. Both and Li/graphite cells have less capacity fade using LiBETI than electrolyte. The gel electrolyte provides better cycle performance than its liquid counterpart because of its increased interfacial stability due to improved rheology and ability to scavenge residual moisture. Silica-based LiBETI carbonate nanocomposite gel electrolytes appear to be a promising candidate for lithium-ion batteries.}, number={12}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={Li, Yangxing and Fedkiw, Peter S.}, year={2007}, pages={A1140–A1145} }
 @article{li_yerian_khan_fedkiw_2006, title={Crosslinkable fumed silica-based nanocomposite electrolytes for rechargeable lithium batteries}, volume={161}, ISSN={["1873-2755"]}, DOI={10.1016/j.jpowsour.2006.06.015}, abstractNote={Electrochemical and rheological properties are reported of composite polymer electrolytes (CPEs) consisting of dual-functionalized fumed silica with methacrylate and octyl groups + low-molecular weight poly(ethylene glycol) dimethyl ether (PEGdm) + lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, lithium imide) + butyl methacrylate (BMA). The role of butyl methacrylate, which aids in formation of a crosslinked network by tethering adjacent fumed silica particles, on rheology and electrochemistry is examined together with the effects of fumed silica surface group, fumed silica weight percent, salt concentration, and solvent molecular weight. Chemical crosslinking of the fumed silica with 20% BMA shows a substantial increase in the elastic modulus of the system and a transition from a liquid-like/flocculated state to an elastic network. In contrast, no change in lithium transference number and only a modest decrease (factor of 2) on conductivity of the CPE are observed, indicating that a crosslinked silica network has minimal effect on the mechanism of ionic transport. These trends suggest that the chemical crosslinks occur on a microscopic scale, as opposed to a molecular scale, between adjacent silica particles and therefore do not impede the segmental mobility of the PEGdm. The relative proportion of the methacrylate and octyl groups on the silica surface displays a nominal effect on both rheology and conductivity following crosslinking although the pre-cure rheology is a function of the surface groups. Chemical crosslinked nanocomposite polymer electrolytes offer significant higher elastic modulus and yield stress than the physical nanocomposite counterpart with a small/negligible penalty of transport properties. The crosslinked CPEs exhibit good interfacial stability with lithium metal at open circuit, however, they perform poorly in cycling of lithium–lithium cells.}, number={2}, journal={JOURNAL OF POWER SOURCES}, author={Li, Yangxing and Yerian, Jeffrey A. and Khan, Saad A. and Fedkiw, Peter S.}, year={2006}, month={Oct}, pages={1288–1296} }
 @article{li_fedkiw_2006, title={Rate capabilities of composite gel electrolytes containing fumed silica nanoparticles}, volume={153}, ISSN={["1945-7111"]}, DOI={10.1149/1.2347108}, abstractNote={Rate capabilities are reported of Li/V 6 O 13 cells at room temperature (22°C) using composite gel electrolytes. The performance of cells containing base liquid electrolyte are compared with composite gel electrolytes that are formed by adding fumed silica nanoparticles to a solution of poly(ethylene glycol)dimethylether + lithium bis(trifluoromethylsulfonylimide). The discharge-charge rate capabilities are improved with addition of fumed silica. The average Coulombic efficiencies using gel electrolytes containing 10% A200, which have a native silanol surface, and 10% R805, which have an octyl-modified surface, remain at approximately 99% up to a C/2 rate, while the average Coulombic efficiency for the base liquid electrolyte decreases with increasing C rate. The improved rate capabilities for composite gel electrolytes are suggested to be related to their ability to inhibit lithium dendrite formation and form stable interfaces between electrolyte and electrodes.}, number={11}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={Li, Yangxing and Fedkiw, Peter S.}, year={2006}, pages={A2126–A2132} }
 @article{geiculescu_rajagopal_creager_desmarteau_zhang_fedkiw_2006, title={Transport properties of solid polymer electrolytes prepared from oligomeric fluorosulfonimide lithium salts dissolved in high molecular weight poly(ethylene oxide)}, volume={110}, ISSN={["1520-5207"]}, url={https://publons.com/publon/7178325/}, DOI={10.1021/jp062648p}, abstractNote={Transport properties such as ionic conductivity, lithium transference number, and apparent salt diffusion coefficient are reported for solid polymer electrolytes (SPEs) prepared using several oligomeric bis[(perfluoroalkyl)sulfonyl]imide (fluorosulfonimide) lithium salts dissolved in high molecular weight poly(ethylene oxide) (PEO). The salt series consists of polyanions in which two discrete fluorosulfonimide anions are linked together by [(perfluorobutylene)disulfonyl]imide linker chains. The restricted diffusion technique was used to measure the apparent salt diffusion coefficients in SPEs, and cationic transference numbers were determined using both potentiostatic polarization and electrochemical impedance spectroscopy methods. A general trend of diminished salt diffusion coefficient with increasing anion size was observed and is opposite to the trend observed in ionic conductivity. This unexpected finding is rationalized in terms of the cumulative effects of charge carrier concentration, anion mobility, ion pairing, host plasticization by the anions, and salt phase segregation on the conductivity.}, number={46}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Geiculescu, Olt E. and Rajagopal, Rama and Creager, Stephen E. and DesMarteau, Darryl D. and Zhang, Xiangwu and Fedkiw, Peter}, year={2006}, month={Nov}, pages={23130–23135} }
 @article{zhang_fedkiw_2005, title={Ionic transport and interfacial stability of sulfonate-modified fumed silicas as nanocomposite electrolytes}, volume={152}, ISSN={["1945-7111"]}, url={https://publons.com/publon/7178384/}, DOI={10.1149/1.2109661}, abstractNote={Degussa A200 and R711 fumed silica surfaces were modified by attaching lithium sulfonate groups through alkyl or oligomer chains, respectively, in an attempt to form single-ion conducting fumed silicas: A200-lithium propanesulfonate (A200-LiPS), R711-poly(lithium vinylsulfonate) (R711-pLiVS), and R711-poly(lithium 2-acrylamido-2-methyl-1-propanesulfonate) (R711-pLiAMPS). Conductivity, lithium transference number, and Li/electrolyte interfacial stability measurements were conducted on nanocomposite electrolytes prepared by dispersing the conducting fumed silicas into solvents consisting of oligomeric polyethylene glycol dimethyl ether (PEGdm), polyethylene oxide (PEO), or PEGdm/PEO blends. Among the three sulfonate-modified fumed silicas, the highest conductivity was always obtained using R711-pLiAMPS. A maximum room-temperature conductivity of was obtained at a surface concentration of and a Li:O mole ratio of 1:100 ( filler). The maximum lithium transference number achieved for the same R711-pLiAMPS-based system is 0.78 at a surface concentration of and a Li:O mole ration of 1:20 ( filler). Adding lithium salts to the solvent, such as lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium bis(perfluoroethylenesulfonyl)imide (LiBETI), lithium bis(oxalato)borate (LiBOB), and lithium phosphate , increases room-temperature conductivity and interfacial stability while maintaining relatively high lithium transference numbers.}, number={12}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, publisher={The Electrochemical Society}, author={Zhang, XW and Fedkiw, PS}, year={2005}, pages={A2413–A2420} }
 @article{li_zhang_khan_fedkiw_2004, title={Attenuation of aluminum current collector corrosion in LiTFSI electrolytes using fumed silica nanoparticles}, volume={7}, ISSN={["1944-8775"]}, url={https://publons.com/publon/7178368/}, DOI={10.1149/1.1756857}, abstractNote={Linear sweep voltammetry and electrochemical impedance spectroscopy were used to investigate the corrosion behavior of an aluminum current collector in contact with polymer solvent containing lithium bis(trifluoromethanesulfonyl)imide [LiN(CF 3 SO 2 ) 2 , LiTFSI] at room temperature. The electrolytes were liquid poly(ethylene glycol) dimethyl ether (Mw 250) + LiTFSI (Li:O ratio of 1:20), and composite gel electrolytes consisting of the baseline liquid electrolyte + 10 wt% fumed silica nanoparticles. Such electrolytes have potential utility in lithium-based rechargeable cells, although LiTFSI is known to affect corrosion of the commonly employed aluminum current collector. The electrochemical data indicate that aluminum corrosion is attenuated in the Presence of fumed silica nanoparticles. Possible mechanisms are discussed.}, number={8}, journal={ELECTROCHEMICAL AND SOLID STATE LETTERS}, publisher={The Electrochemical Society}, author={Li, YX and Zhang, XW and Khan, SA and Fedkiw, PS}, year={2004}, pages={A228–A230} }
 @article{yerian_khan_fedkiw_2004, title={Crosslinkable fumed silica-based nanocomposite electrolytes: role of methacrylate monomer in formation of crosslinked silica network}, volume={135}, ISSN={["0378-7753"]}, DOI={10.1016/j.jpowsour.2004.03.064}, abstractNote={The electrochemical and rheological properties of composite polymer electrolytes (CPEs) based on fumed silica with tethered crosslinkable groups are reported. These silica nanoparticles are dispersed in electrolytes consisting of poly(ethylene glycol) dimethyl ether (PEGdm)+lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to which various methacrylate monomers, such as methyl (MMA), ethyl (EMA), butyl (BMA), n-hexyl (HMA), and n-dodecyl (DMA) methacrylate, are added. The methacrylate monomer facilitates creation of chemical crosslinks between fumed silica particles and formation of a crosslinked network. In this study, the effects of concentration and alkyl chain length of the monomers on conductivity, dynamic rheology, open-circuit interfacial stability, and cell voltage in lithium–lithium cell cycling are examined. Increasing the length of the monomer alkyl chain enhances both conductivity and elastic modulus of the crosslinked CPE. In contrast, increasing monomer concentration results in higher elastic modulus, but reduced conductivity. Lithium–lithium cell cycling and open-circuit interfacial stability results did not correlate with alkyl chain length. That is, for the lithium–lithium cycling studies, all crosslinked samples exhibit higher half-cycle voltage compared to non-crosslinked samples; however, the open-circuit interfacial stability of CPEs containing BMA and HMA exhibit improved stability compared to the other monomers and the CPE without monomer.}, number={1-2}, journal={JOURNAL OF POWER SOURCES}, author={Yerian, JA and Khan, SA and Fedkiw, PS}, year={2004}, month={Sep}, pages={232–239} }
 @article{youssef_koch_fedkiw_2004, title={Improved corrosion behavior of nanocrystalline zinc produced by pulse-current electrodeposition}, volume={46}, ISSN={["1879-0496"]}, DOI={10.1016/S0010-938X(03)00142-2}, abstractNote={Pulse electrodeposition was used to produce nanocrystalline (nc) zinc from zinc chloride electrolyte with polyacrylamide and thiourea as additives. Field emission scanning electron microscopy (FESEM) was used to study the grain size and surface morphology of the deposits and X-ray diffraction was used to examine their preferred orientation. Corrosion behavior of the electrodeposited nc zinc in comparison with electrogalvanized (EG) steel in de-aerated 0.5 N NaOH solution was studied using potentiodynamic polarization and impedance measurements. A scanning electron microscope (SEM) was used to characterize the surface morphology of the EG steel before corrosion testing. Surface morphologies of nc zinc deposits and EG steel were also studied after potentiondynamic polarization by SEM. Nanocrystalline zinc (56 nm) with random orientation was produced. The estimated corrosion rate of nc zinc was found to be about 60% lower than that of EG steel, 90 and 229 μA/cm2, respectively. The surface morphology of corroded nc zinc was characterized by discrete etch pits, however, uniform corrosion was obtained after potentiodynamic polarization of EG steel. The passive film formed on the nc zinc surface seems to be a dominating factor for the corrosion behavior observed.}, number={1}, journal={CORROSION SCIENCE}, author={Youssef, KMS and Koch, CC and Fedkiw, PS}, year={2004}, month={Jan}, pages={51–64} }
 @article{youssef_koch_fedkiw_2004, title={Influence of additives and pulse electrodeposition parameters on production of nanocrystalline zinc from zinc chloride electrolytes}, volume={151}, ISSN={["1945-7111"]}, DOI={10.1149/1.1636739}, abstractNote={Pulse electrodeposition was used to produce nanocrystalline zinc from an aqueous zinc chloride electrolyte with polyacrylamide and thiourea as additives. The influence of additive concentration and pulse electrodeposition parameters, namely, current-on time, current-off time, and peak current density on the grain size, surface morphology, and preferred orientation was investigated. The grain size and surface morphology of zinc deposits were studied by scanning electron microscopy and field emission scanning electron microscopy. The preferred orientation of zinc deposits was studied by X-ray diffraction. The optimum concentrations of polyacrylamide and thiourea in the bath that give the finest grains were 0.7 and 0.05 g/L, respectively. At constant current-off time and peak current density, the grain size decreased asymptotically with increasing current-on time. An increase in the current-off time at constant current-on time and peak current density resulted in grain growth. A progressive decrease of the grain size was observed with increasing peak current density at constant current-on and -off time. Nanocrystalline zinc with an average grain size of 50 nm was obtained at a peak current density of The crystal orientations developed were correlated to the variation in the cathode overpotential accompanied with changing the electrodeposition parameters. A preferred orientation was developed at low overpotential while higher overpotential developed a dual orientation. © 2004 The Electrochemical Society. All rights reserved.}, number={2}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={Youssef, KMS and Koch, CC and Fedkiw, PS}, year={2004}, month={Feb}, pages={C103–C111} }
 @article{zhang_li_khan_fedkiw_2004, title={Inhibition of lithium dendrites by fumed silica-based composite electrolytes}, volume={151}, ISSN={["1945-7111"]}, url={https://publons.com/publon/7178366/}, DOI={10.1149/1.1767158}, abstractNote={Lithium dendrite formation is investigated via in situ microscopy in a liquid electrolyte containing polyethylene glycol dimethyl bis(trifluoromethylsulfonyl)imide and composite gel-like electrolytes formed by dispersing nanometer-size fumed silica into the liquid. Fumed silicas with either hydrophilic silanol surface groups or hydrophobic octyl surface groups were employed. Dendrites with current density-dependent morphology are formed in liquid electrolyte but addition of fumed silica inhibits their formation, with hydrophilic fumed silica having a more pronounced effect than hydrophobic silica. The dendrite inhibition effect of fumed silica is attributed to its abilities to form a continuous network with elastic-like properties and scavenge impurities from the electrolyte. © 2004 The Electrochemical Society. All rights reserved.}, number={8}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, publisher={The Electrochemical Society}, author={Zhang, XW and Li, YX and Khan, SA and Fedkiw, PS}, year={2004}, pages={A1257–A1263} }
 @article{zhou_fedkiw_2004, title={Ionic conductivity of composite electrolytes based on oligo(ethylene oxide) and fumed oxides}, volume={166}, ISSN={["1872-7689"]}, DOI={10.1016/j.ssi.2003.11.017}, abstractNote={The effects of fumed oxide fillers (SiO2, Al2O3, TiO2) and binary mixtures of oxide fillers (SiO2/Al2O3) on ionic conductivity of composite electrolytes based on poly(ethylene oxide) (PEO) oligomers (Mw=250, 500, 1000, and 2000)+lithium bis(trifluromethylsulfonyl)imide [LiN(CF3SO2)2] (LiTFSI) (Li/O=1:20) are studied using electrochemical impedance spectroscopy (EIS), differential scanning calorimeter (DSC), and Fourier transform infrared spectroscopy in the attenuated total reflectance mode (FTIR-ATR). Fillers show similar effect on conductivity in all systems: no distinguishable effect is found with filler type, and addition of filler decreases conductivity at temperatures above the melting point but increases conductivity at temperatures below. The addition of fillers stiffens polymer segments, as evidenced by enhancement in Li+–polymer interactions above the melting point seen in the IR spectra and an increase in Tg found from the DSC analysis. No reduction in ion-pairing upon addition of filler is observed from the IR spectra. The increase in conductivity at temperatures below the melting point is believed to be due to faster ion transport along the filler surface rather than through enhanced mobility of polymer segments. The insulating nature of fillers and stiffening of the polymer solvent in the presence of fillers cause a decrease in conductivity at temperatures above the melting point and is correlated solely with volume fraction of the filler.}, number={3-4}, journal={SOLID STATE IONICS}, author={Zhou, H and Fedkiw, PS}, year={2004}, month={Jan}, pages={275–293} }
 @article{zhang_khan_fedkiw_2004, title={Nanocomposite electrolytes using single-ion conducting fumed silica}, volume={7}, ISSN={["1944-8775"]}, url={https://publons.com/publon/7178367/}, DOI={10.1149/1.1792267}, abstractNote={Fumed silica surfaces were chemically modified to form single-ion conductors by attaching lithium-exchanged anionic groups (lithium 2-acrylamido-2-methyl-1-propanesulfonate, LiAMPS) to surface methacrylates on Degussa R711 fumed silica (abbreviated as R711-pLiAMPS). Surface lithium-ion contents varying from 0.7 to 9.1 nm−2 were synthesized. Conductivity and transference number measurements were conducted on nanocomposite electrolytes containing polyethylene glycol dimethyl ether A maximum room-temperature conductivity of S cm−1 was obtained at a surface content of 4.2 nm−2 and a Li:O mole ratio of 1:100 (15.8 wt % filler) with a transference number of 0.59. A maximum transference number of 0.78 was achieved at a surface surface content of 4.2 nm−2 and a Li:O mole ratio of 1:20 (48.5 wt % filler) with a conductivity of S cm−1. Adding lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) to the samples enhances room-temperature conductivity by more than two orders of magnitude while still maintaining a relatively high transference number. © 2004 The Electrochemical Society. All rights reserved.}, number={10}, journal={ELECTROCHEMICAL AND SOLID STATE LETTERS}, author={Zhang, XW and Khan, SA and Fedkiw, PS}, year={2004}, pages={A361–A364} }
 @article{singhal_capracotta_martin_khan_fedkiw_2004, title={Transport properties of hectorite based nanocomposite single ion conductors}, volume={128}, ISSN={["0378-7753"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-1542333424&partnerID=MN8TOARS}, DOI={10.1016/j.jpowsour.2003.09.064}, abstractNote={Abstract The ionic conductivity and rheological properties of clay filled nanocomposite electrolytes are reported. These electrolytes, which have potential use in lithium-ion batteries, consist of lithium-exchanged hectorite, a 2:1 layered smectite clay, dispersed in ethylene carbonate (EC) or a mixture of EC+polyethylene glycol di-methyl ether (PEG-dm, 250 MW). All samples exhibit elastic, gel-like characteristics and room temperature conductivities of order 0.1 mS/cm. A maximum in conductivity is observed at about 25 wt.% clay concentration. A maximum in hectorite basal layer spacing is also observed in the same concentration range, suggesting a direct correlation between conductivity and layer spacing. The elastic modulus and yield stress increase by two orders of magnitude and the conductivity increases by one order of magnitude with increase in hectorite concentration from 5 to 25%, which indicates the significant influence of hectorite content in determining the characteristics of these single-ion conductors. The solvent composition plays a secondary role in this regard, with addition of PEG-dm to the base EC+hectorite electrolyte producing moderate improvement in conductivity. Similarly, the addition of PEG-dm to EC+hectorite affects an increase by only a factor of three in the elastic modulus and yield stress of the electrolyte.}, number={2}, journal={JOURNAL OF POWER SOURCES}, author={Singhal, RG and Capracotta, MD and Martin, JD and Khan, SA and Fedkiw, PS}, year={2004}, month={Apr}, pages={247–255} }
 @misc{riley_fedkiw_khan_davies_2003, title={Composite electrolytes based on smectite clays and high dielectric organic liquids and electrodes}, volume={6,544,689}, number={2003 Apr. 8}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Riley, M. W. and Fedkiw, P. S. and Khan, S. A. and Davies, B.}, year={2003}, month={Apr} }
 @article{walls_riley_fedkiw_spontak_baker_khan_2003, title={Composite electrolytes from self-assembled colloidal networks}, volume={48}, ISSN={["0013-4686"]}, DOI={10.1016/S0013-4686(03)00187-7}, abstractNote={Abstract In this study, we present two approaches to developing composite electrolytes exploiting the self-assembling nature of colloidal fillers. The first system comprises of oligomers of poly(ethylene glycol) dimethyl ether, branched fumed silica particulates and lithium salt. The fumed silica forms a three-dimensional, self-supporting network that provides mechanical stability. The large pores of the network has little effect on diffusivity of ions and oligomers, lithium transference number and ionic conductivity, with the latter showing values >10 −3 S/cm at ambient conditions. The second system consists of Li exchanged hectorite clay in a mixture of low molar mass carbonates. Similar to the fumed silica, the clay provides mechanical stability through formation of a three-dimensional network. In addition, the immobile clay platelets also serve as the anion rendering the system to be a single ion conductor. Near-unity transference number is observed in this case. However, the room temperature conductivity of the clay composite is lower than the fumed silica, revealing a value of about 10 −4 S/cm. The lower conductivity can be attributed to the clay not being in a fully exfoliated form as evident from morphological analysis.}, number={14-16}, journal={ELECTROCHIMICA ACTA}, author={Walls, HJ and Riley, MW and Fedkiw, PS and Spontak, RJ and Baker, GL and Khan, SA}, year={2003}, month={Jun}, pages={2071–2077} }
 @article{zhou_fedkiw_2003, title={Cycling of lithium/metal oxide cells using composite electrolytes containing fumed silicas}, volume={48}, ISSN={["0013-4686"]}, DOI={10.1016/S0013-4686(03)00299-8}, abstractNote={Abstract The effect on cycle capacity is reported of cathode material (metal oxide, carbon, and current collector) in lithium/metal oxide cells cycled with fumed silica-based composite electrolytes. Three types of electrolytes are compared: filler-free electrolyte consisting of methyl-terminated poly(ethylene glycol) oligomer (PEGdm, Mw=250)+lithium bis(trifluromethylsufonyl)imide (LiTFSI) (Li:O=1:20), and two composite systems of the above baseline liquid electrolyte containing 10-wt% A200 (hydrophilic fumed silica) or R805 (hydrophobic fumed silica with octyl surface group). The composite electrolytes are solid-like gels. Three cathode active materials (LiCoO2, V6O13, and LixMnO2), four conducting carbons (graphite Timrex® SFG 15, SFG 44, carbon black Vulcan XC72R, and Ketjenblack EC-600JD), and three current collector materials (Al, Ni, and carbon fiber) were studied. Cells with composite electrolytes show higher capacity, reduced capacity fade, and less cell polarization than those with filler-free electrolyte. Among the three active materials studied, V6O13 cathodes deliver the highest capacity and LixMnO2 cathodes render the best capacity retention. Discharge capacity of Li/LiCoO2 cells is affected greatly by cathode carbon type, and the capacity decreases in the order of Ketjenblack>SFG 15>SFG 44>Vulcan. Current collector material also plays a significant role in cell cycling performance. Lithium/vanadium oxide (V6O13) cells deliver increased capacity using Ni foil and carbon fiber current collectors in comparison to an Al foil current collector.}, number={18}, journal={ELECTROCHIMICA ACTA}, author={Zhou, H and Fedkiw, PS}, year={2003}, month={Aug}, pages={2571–2582} }
 @article{walls_fedkiw_zawodzinski_khan_2003, title={Ion transport in silica nanocomposite electrolytes}, volume={150}, ISSN={["1945-7111"]}, DOI={10.1149/1.1544635}, abstractNote={The ion-transport properties of composite electrolytes composed of oligomers of poly(ethylene glycol) dimethyl ether, hydrophobic fumed silica, and Li(CF 3 SO 2 ) 2 N (LiTFSI) are investigated using nuclear magnetic resonance (NMR), electrophoretic NMR (ENMR), ac impedance spectroscopy, and rheology. The effects of fumed silica and salt concentration on ionic conductivity, diffusivity of ions and oligomers, and lithium transference number (T) are examined at 30°C. The fumed silica forms a self-supporting network with large pores such that the network, regardless of silica concentration, has little effect on ion-transport characteristics. Examination of the effect of salt on ion transport reveals a maximum ionic conductivity at around 1.06 M, which is attributed to a tradeoff of adding more charge carriers balanced against increased ion-ion interactions and reduced mobilities. T 1,i with respect to salt concentration surprisingly passes through a minimum around 0.35 M. The increase in T at higher concentrations is attributed to the mobilities of cations, anions, and solvating oligomer becoming constrained to the same value due to loss of free volume. The values of T Li at low salt concentrations (<0.35 M) are attributed to the ions existing in either a fully dissociated state or primarily as charged complexes. Results of T Li from ENMR and from estimation via pulse field gradient NMR (pfg-NMR) are compared showing that pfg-NMR consistently overestimates T Li . Finally, a comparison is presented of measured conductivity with that calculated from the Nernst-Einstein equation and diffusivities found from pfg-NMR measurement: we discuss possible reasons why it is inappropriate to estimate ion-pair formation by this comparison.}, number={3}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={Walls, HJ and Fedkiw, PS and Zawodzinski, TA and Khan, SA}, year={2003}, month={Mar}, pages={E165–E174} }
 @article{riley_fedkiw_khan_2003, title={Lithium hectorite clay as the ionic conductor in LiCoO2 cathodes}, volume={150}, ISSN={["1945-7111"]}, DOI={10.1149/1.1579034}, abstractNote={Cathodes based on LiCoO 2 that contain various lithium-conducting species (lithium hectorite, lithium Laponite, and lithium-exchanged Nafion) are studied in conjunction with lithium metal anodes and composite electrolytesbased upon lithium hectorite clays as the charge carrier. Performance is compared to that of cells with a standard liquid electrolyte (i.e., LiPF 6 +1:1 w/w ethylene carbonate:ethyl methyl carbonate). Effects on cathode capacity are examined for these variables: hot-press force used in construction of the porous cathode. carbon type (graphite vs. carbon black), and clay particle size. AC impedance spectroscopy is used to probe the cells and equivalent circuits are used to model the physical processes that occur. Cathodes containing 4 wt % lithium hectorite +3 wt % lithium-exchanged Nation +3 wt % carbon black exhibit discharge capacities approximately 90 mAh/g LiCoO 2 compared to that observed in a standard cell of 110 mAh/g LiCoO 2 . These clay-containing cathodes are potentially attractive for use in single-ion conducting lithium-ion batteries designed for high discharge applications.}, number={7}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={Riley, MW and Fedkiw, PS and Khan, SA}, year={2003}, month={Jul}, pages={A933–A941} }
 @article{walls_riley_singhal_spontak_fedkiw_khan_2003, title={Nanocomposite electrolytes with fumed silica and hectorite clay networks: Passive versus active fillers}, volume={13}, ISSN={["1616-301X"]}, DOI={10.1002/adfm.200304333}, abstractNote={The use of nanocomposites constitutes a versatile and robust approach in the development of novel electrolytes with tailored electrochemical and mechanical characteristics. In this study, we examine the morphology, rheology, and ion-transport properties of two types of nanocomposite electrolyte gels, one consisting of branched silica nanoparticles and the other composed of hectorite clay. In the first system with hydrophobic (fumed) silica, oligomers of poly(ethylene oxide) (PEO), and lithium salt, the silica acts as a passive filler and does not participate in ion transport. The electrochemical properties are controlled by the salt–PEO electrolyte, allowing for ionic conductivities greater than 10–3 S cm–1 at ambient temperature. At sufficiently high concentrations, the silica forms an elastic gel possessing a large open network structure that provides for unimpeded ion mobility. In the second system composed of lithium-exchanged hectorite filler, the nanoscale platelets serve as the anion. This active filler yields ionic conductivities in excess of 10–4 S cm–1 and lithium transference numbers approaching unity. Similar to fumed silica, the hectorite clay also forms an elastic gel network. However, the morphologies of the two systems are distinctively different both in terms of network structure and characteristic length scale. These morphological differences manifest themselves in different rheological responses with regard to gel modulus and yield stress.}, number={9}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Walls, HJ and Riley, MW and Singhal, RR and Spontak, RJ and Fedkiw, PS and Khan, SA}, year={2003}, month={Sep}, pages={710–717} }
 @article{saber_koch_fedkiw_2003, title={Pulse current electrodeposition of nanocrystalline zinc}, volume={341}, DOI={10.1016/s0921-5093(02)00198-3}, abstractNote={Abstract Pulse electrodeposition exhibits marked advantages over direct current electrodeposition in the control of deposit grain size, surface morphology, and preferred orientation. The effect of pulse peak current density (Jp) on the grain size and surface morphology of zinc deposits with additives (polyacrylamide and thiourea) was studied by scanning electron microscopy and field emission scanning electron microscopy. The preferred orientation of zinc deposits was studied by X-ray diffraction, and microhardness of the deposits was measured by a Knoop microhardness tester. Increasing JP dramatically changed the surface morphology and decreased the grain size. Nanocrystalline zinc (56 nm) was produced at JP=2 A cm−2. At JP equal to 0.4 A cm−2, the preferred orientation of zinc deposits was (1 1 2 2) and changed to the prismatic (1 1 2 0) orientation at Jp equal to 0.8, 1.2, and 1.6 A cm−2. However, increasing the peak current density to 2 A cm−2 altered the prismatic (1 1 2 0) to the random (1 0 1 1). The microhardness increased to approximately 8 times higher than that of pure polycrystalline zinc (0.29 GPa). Microhardness reached a maximum (2.3 GPa) at 1.6 A cm−2, then decreased to 1.5 GPa at 2 A cm−2. The hardness drop was correlated with the presence of additives and the change in texture from (1 1 2 0) to the random (1 0 1 1) with increasing Jp.}, number={1-2}, journal={Materials Science & Engineering. A, Structural Materials: Properties, Microstructure and Processing}, author={Saber, K. and Koch, C. C. and Fedkiw, Peter}, year={2003}, pages={174–181} }
 @article{rinne_hren_fedkiw_2002, title={Electrodeposition of tin needle-like structures}, volume={149}, ISSN={["0013-4651"]}, DOI={10.1149/1.1445172}, abstractNote={Electrodeposition is reported of arrays of needle-like Sn structures with tip radii ∼7 nm that can be used as electron emitters for field electron emission applications. It is well documented in the literature that in the absence of additive agents, a variety of morphological structures such as fractal, dendritic, and densely branched deposits may result from electrodeposition. It is also known that in the absence of additives, Sn dendrites can be formed. In the present research, it is shown that by controlling the electrode potential and concentration of two additive agents, a nonionic ethoxylated surfactant (Triton X-100) and a Pb(II) salt, an array of needle-like Sn structures is deposited from a Sn(II) salt in methane sulfonic acid. Although these structures may be used as electron emitters for field emission, the low melting point of Sn precludes its use in practical devices. Nevertheless, the unique preparation method that we describe may be used to investigate electrodeposited field emitter tips from higher melting metals (e.g., Ni, Pd, Ag, Au, and Cu). © 2002 The Electrochemical Society. All rights reserved.}, number={3}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={Rinne, CL and Hren, JJ and Fedkiw, PS}, year={2002}, month={Mar}, pages={C150–C158} }
 @article{zhou_fedkiw_khan_2002, title={Interfacial stability between lithium and fumed silica-based composite electrolytes}, volume={149}, ISSN={["0013-4651"]}, DOI={10.1149/1.1496483}, abstractNote={Composite electrolytes consisting of methyl-capped poly(ethylene glycol) oligomer lithium bis(trifluoromethylsulfonyl)imide and fumed silica were investigated. In particular, the effects of fumed silica-surface chemistry and weight percentage in the composite on cycling behavior of Li/electrolyte/Li, Li(Ni)/electrolyte/Li, and Li/electrolyte/metal oxide cells were studied. Four types of fumed silicas with various surface groups were employed, A200 (native hydroxyl groups), R805 (octyl-modified), R974 (methyl-modified), and FS-EG3 (ethylene oxide-modified). The presence of fumed silica enhances lithium cyclability by reducing the interfacial resistance and cell-capacity fading, regardless of surface chemistry. However, the extent of the enhancing effect of fumed silica strongly depends on its surface chemistry, with the largest effect seen with A200 and the least effect seen with FS-EG3. Increasing fumed silica weight fraction intensifies the stabilizing effect. © 2002 The Electrochemical Society. All rights reserved.}, number={9}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={Zhou, J and Fedkiw, PS and Khan, SA}, year={2002}, month={Sep}, pages={A1121–A1126} }
 @article{li_fedkiw_khan_2002, title={Lithium/V6O13 cells using silica nanoparticle-based composite electrolyte}, volume={47}, ISSN={["1873-3859"]}, DOI={10.1016/S0013-4686(02)00326-2}, abstractNote={The electrochemical behavior of Li/V6O13 cells is investigated at room temperature (22 °C) both in liquid electrolyte consisting of oligomeric poly(ethyleneglycol)dimethylether+lithium bis(trifluoromethylsulfonylimide) and composite electrolytes formed by blending the liquid electrolyte with silica nanoparticles (fumed silica). The addition of fumed silica yields a gel-like electrolyte that demonstrates the desirable property of suppressing lithium dendrite growth due to the rigidity and immobility of the electrolyte structure. The lithium/electrolyte interfacial resistance for composite gel electrolytes is less than that for the corresponding base-liquid electrolyte, and the charge–discharge cycle performance and electrochemical efficiency for the Li/V6O13 cell is significantly improved. The effect of fumed silica surface group on the electrochemical performance is discussed; the native hydrophilic silanol surface group appears better than fumed silica that is modified with a hydrophobic octyl surface moiety.}, number={24}, journal={ELECTROCHIMICA ACTA}, author={Li, YX and Fedkiw, PS and Khan, SA}, year={2002}, month={Sep}, pages={3853–3861} }
 @article{riley_fedkiw_khan_2002, title={Transport properties of lithium hectorite-based composite electrolytes}, volume={149}, ISSN={["1945-7111"]}, DOI={10.1149/1.1470652}, abstractNote={Conductivity and lithium-ion transference numbers are reported for physically gelled composite electrolytes using lithium hectorite clay as the charge carrier and carbonate solvents (ethylene carbonate, propylene carbonate, and dimethyl carbonate). Results are compared with those of typical lithium-ion battery electrolytes based on lithium hexafluorophosphate and carbonate solvents. Room-temperature conductivities of the composite electrolytes as high as S/cm were measured. Because of the nature of the anionic clay particulates creating the gel structure, near-unity lithium-ion transference numbers are expected and were observed as high as 0.98, as measured by the dc polarization method using lithium-metal electrodes. Since the carbonates react with lithium and create mobile ionic species that significantly reduce the observed lithium-ion transference number, care must be taken to minimize or eliminate the presence of the reaction-formed ionic species. These hectorite-based composite systems are possible electrolytes for rechargeable lithium-ion batteries requiring high discharge rates. © 2002 The Electrochemical Society. All rights reserved.}, number={6}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={Riley, M and Fedkiw, PS and Khan, SA}, year={2002}, month={Jun}, pages={A667–A674} }
 @article{jun_fedkiw_2001, title={Ionic conductivity of alkali-metal salts in sub- and supercritical carbon dioxide plus methanol mixtures}, volume={515}, ISSN={["1873-2569"]}, DOI={10.1016/S0022-0728(01)00636-2}, abstractNote={Abstract Ionic conductivity of lithium, sodium, and potassium perfluoroacetate salts and lithium acetate in sub- and supercritical carbon dioxide+methanol mixtures is reported as a function of CO 2 pressure and temperature. Although the mole fraction of salts was low (10 −4 –10 −2 ), the ionic conductivity was large (∼10 −5 –10 −4 S cm −1 ) compared with pure CO 2 (below measurement capabilities) and CO 2 +methanol (∼10 −7 –10 −8 S cm −1 ). In the sub-critical two-phase region, the ionic conductivity in the CO 2 -rich phase increased with pressure, but the conductivity decreased in the supercritical region with CO 2 pressure. Solvent viscosity and ion diffusivity in the single-phase region predominantly influence conductivity, whereas it is affected by salt solubility in the two-phase region.}, number={1-2}, journal={JOURNAL OF ELECTROANALYTICAL CHEMISTRY}, author={Jun, J and Fedkiw, PS}, year={2001}, month={Nov}, pages={113–122} }
 @misc{law_fedkiw_hicks_2001, title={Kolbe electrolysis in a polymer electrolyte membrane reactor}, volume={6,238,543}, number={2001 May 29}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Law, C. G. and Fedkiw, P. S. and Hicks, M. T.}, year={2001} }
 @article{zhang_fedkiw_2001, title={Study on interaction of lithium and dry Nafion membrane with ac impedance, SEM and EDAX}, volume={14}, journal={Qingdao Daxue Xuebao, Ziran Kexueban}, author={Zhang, Yali and Fedkiw, P.S.}, year={2001}, pages={51–61} }
 @article{walls_zhou_yerian_fedkiw_khan_stowe_baker_2000, title={Fumed silica-based composite polymer electrolytes: synthesis, rheology, and electrochemistry}, volume={89}, ISSN={["0378-7753"]}, DOI={10.1016/S0378-7753(00)00424-9}, abstractNote={An overview of our research is presented on developing composite polymer electrolytes (CPEs) based on low-molecular weight polyethylene oxide (PEO) (namely, poly(ethylene glycol) dimethyl ether), lithium salts (e.g. lithium triflate, lithium imide, etc.), and fumed silica. These CPEs demonstrate high room-temperature conductivites (>10−3 S/cm), mechanical strength, and form stable interfaces with lithium metal as a result of the fumed silica. The surface groups on the fumed silica determine the mechanical properties of the CPE while the low-molecular weight PEO and lithium salt determine the ionic transport properties. These CPEs show promise as electrolytes for the next generation of rechargeable lithium batteries.}, number={2}, journal={JOURNAL OF POWER SOURCES}, author={Walls, HJ and Zhou, J and Yerian, JA and Fedkiw, PS and Khan, SA and Stowe, MK and Baker, GL}, year={2000}, month={Aug}, pages={156–162} }
 @article{dudek_fedkiw_1999, title={A quartz crystal microgravimetric study of copper corrosion in alkaline carbonate solutions}, volume={86}, number={3}, journal={Plating and Surface Finishing}, author={Dudek, D. A. and Fedkiw, P. S.}, year={1999}, pages={90–94} }
 @misc{khan_fedkiw_baker_fan_raghavan_hou_1999, title={Composite electrolyte containing surface modified fumed silica}, volume={5,965,299}, number={1999 Oct. 12}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Khan, S. A. and Fedkiw, P. S. and Baker, G. L. and Fan, J. and Raghavan, S. R. and Hou, J.}, year={1999}, month={Oct} }
 @article{tsouris_amarnath_fedkiw_1999, title={Electrochemical and reactive separations - Guest editors' note}, volume={15}, number={3}, journal={Separation and Purification Technology}, author={Tsouris, C. and Amarnath, K. R. and Fedkiw, P.}, year={1999}, pages={193–196} }
 @article{dudek_fedkiw_1999, title={Electrodeposition of copper from cuprous cyanide electrolyte I. Current distribution on a stationary disk}, volume={474}, ISSN={["0022-0728"]}, DOI={10.1016/s0022-0728(99)00299-5}, abstractNote={A model is developed for electrodeposition of copper from cuprous cyanide electrolyte onto a stationary disk electrode. The solutions examined are similar to those of copper strike-plating baths, in which cuprous may exist as Cu+ and Cu(CN)n(n−1)−, n=1–4. The effects of mass transport by diffusion and migration, multiple electrode reactions, and homogeneous complexation equilibria are considered. The model elucidates the influence of solution composition, transport properties, and kinetic constants on current distribution and polarization characteristics. Because cyanide is released upon discharge of the copper–cyanide complex, the distribution of copper-containing species shifts towards higher-order complexes near the electrode surface. Changes in solution composition which effect a greater percentage of copper complex in the more saturated cyanide state decrease the uniformity of the current distribution at a given fraction of the limiting current, which occurs because higher-order complexes have a lower diffusivity; and, if higher-order species are less electroactive, these changes decrease the current density at a given applied potential. Because copper–cyanide complexes have smaller diffusion coefficients than free cyanide, the concentration gradient of CN− causes the solution potential to increase near the electrode surface, and migration enhances the transport of anionic complexes. In most cases, the current distribution becomes increasingly non-uniform with applied potential; but under some circumstances that are elucidated here, the least non-uniform current distribution may occur at an intermediate fraction of the limiting current. In all studies, the current distribution approaches the highly non-uniform primary-like distribution as the limiting current is approached.}, number={1}, journal={JOURNAL OF ELECTROANALYTICAL CHEMISTRY}, author={Dudek, DA and Fedkiw, PS}, year={1999}, month={Sep}, pages={16–30} }
 @article{dudek_fedkiw_1999, title={Electrodeposition of copper from cuprous cyanide electrolyte II. Current distribution on a rotating disk}, volume={474}, ISSN={["0022-0728"]}, DOI={10.1016/s0022-0728(99)00300-9}, number={1}, journal={JOURNAL OF ELECTROANALYTICAL CHEMISTRY}, author={Dudek, DA and Fedkiw, PS}, year={1999}, month={Sep}, pages={31–42} }
 @article{dudek_fedkiw_1999, title={Infinite dilution diffusion coefficients of complex ions from solution conductivity data}, volume={71}, ISSN={["0003-2700"]}, DOI={10.1021/ac981054i}, abstractNote={A technique is presented for determining infinite-dilution diffusion coefficients of complex ions from solution conductivity data. The method involves measuring the conductivities of dilute solutions in which the distribution of complex ions is systematically varied and statistically regressing the data to an equation that effectively relates individual ion diffusion coefficients to solution conductivity. The procedure is simple and requires no specialized equipment to perform. Unlike methods that require a concentration gradient, the solution composition is homogeneous and at equilibrium during measurements, which is a significant advantage when labile complexes are being studied. In this paper, diffusion coefficients of cuprous cyanide complexes are determined. Statistical analysis yields the infinite-dilution diffusion coefficients of Cu(CN)2-, Cu(CN)32-, and Cu(CN)43- at 25 °C as 1.43 × 10-5 ± 9%, 1.08 × 10-5 ± 9%, and 6.21 × 10-6 ± 22% cm2/s, respectively.}, number={7}, journal={ANALYTICAL CHEMISTRY}, author={Dudek, DA and Fedkiw, PS}, year={1999}, month={Apr}, pages={1469–1473} }
 @article{hicks_fedkiw_1998, title={A model for Kolbe electrolysis in a parallel plate reactor}, volume={28}, ISSN={["1572-8838"]}, DOI={10.1023/A:1003495828226}, number={11}, journal={JOURNAL OF APPLIED ELECTROCHEMISTRY}, author={Hicks, MT and Fedkiw, PS}, year={1998}, month={Nov}, pages={1157–1166} }
 @article{raghavan_riley_fedkiw_khan_1998, title={Composite polymer electrolytes based on poly(ethylene glycol) and hydrophobic fumed silica: Dynamic rheology and microstructure}, volume={10}, ISSN={["0897-4756"]}, DOI={10.1021/cm970406j}, abstractNote={Dynamic rheological techniques are used to probe the microstructures present in fumed silica-based composite polymer electrolytes. These electrolytes are obtained by dispersing hydrophobic fumed silica in a poly(ethylene glycol)−lithium salt solution and display high conductivities (σ298K > 10-3 S/cm), mechanical stability, and easy processability. The materials behave as soft solids (gels) under ambient conditions due to the presence of a three-dimensional network of silica entities. Network formation occurs as a result of van der Waals (dispersion) forces between the nonpolar surface layers on silica units. Factors which affect the van der Waals interaction, and hence the gel network density, include the nature of the PEG end group, the presence of ionic species, and the size of the hydrophobic surface group on the silica. The composites also exhibit shear-thinning behavior due to the shear-induced disruption of network bonds, and this behavior can be advantageously utilized in electrolyte processing.}, number={1}, journal={CHEMISTRY OF MATERIALS}, author={Raghavan, SR and Riley, MW and Fedkiw, PS and Khan, SA}, year={1998}, month={Jan}, pages={244–251} }
 @article{fan_raghavan_yu_khan_fedkiw_hou_baker_1998, title={Composite polymer electrolytes using surface-modified fumed silicas: conductivity and rheology}, volume={111}, ISSN={["0167-2738"]}, DOI={10.1016/S0167-2738(98)00151-9}, abstractNote={We report results from our studies on composite polymer electrolytes based on novel surface-modified fumed silicas. The electrolytes were prepared by dispersing fumed silica in a matrix formed by methyl-capped polyethylene glycol and lithium salt. Silicas with widely different surface chemistries were synthesized in order to study the effects of surface modification, with the attached surface groups ranging from non-polar alkyl moieties (C1 or C8) to polar polyethylene oxide (PEO) oligomers (MW∼200). We find, rather surprisingly, that the conductivity is independent of the type of surface group present on the silica. Moreover, the conductivity decreases only slightly on addition of fumed silica, even at high weight fraction of solids. In contrast, the rheological properties of the composites are strongly affected by both the silica surface chemistry and weight fraction. Dynamic rheology measurements reveal that fumed silicas with silanol and octyl coverage both flocculate into gels (networks). The resulting materials are mechanically stable, with the elastic modulus of the gel being strongly dependent upon weight fraction of solids. The PEO-modified silica, in contrast, gives rise to a low-viscosity suspension where the silica units exist as distinct, non-interacting species. The findings of this study have significant implications for future work on composite electrolytes, in that we can tailor the mechanical properties of the system without affecting the electrochemical behavior.}, number={1-2}, journal={SOLID STATE IONICS}, author={Fan, J and Raghavan, SR and Yu, XY and Khan, SA and Fedkiw, PS and Hou, J and Baker, GL}, year={1998}, month={Aug}, pages={117–123} }
 @article{fan_fedkiw_1998, title={Electrochemical impedance spectra of full cells: Relation to capacity and capacity-rate of rechargeable Li cells using LiCoO2, LiMn2O4, and LiNiO2 cathodes}, volume={72}, ISSN={["0378-7753"]}, DOI={10.1016/S0378-7753(97)02708-0}, abstractNote={Electrochemical impedance spectra (EIS) are reported for rechargeable lithium cells using cathodes LiMyOx (M=Co, Ni, and Mn) prepared from casting and high-pressure compacting. The composite cathodes were cast from a slurry mixture consisting of 30% NMP solvent and 70% solid (91% LiMyOx, 3% PVDF and 6% KS44 graphite) onto a 25-μm thick Al current collector. The compacted cathodes were made from the cast cathode using a laboratory press. The most compacted cathodes have the smallest impedance and the highest specific capacity and capacity-rate. Three equivalent circuits are proposed according to the effect of compaction pressure on our EIS results and work reported in the literature. The EIS results and relationship to the capacity and capacity-rate are discussed using these circuits. It appears that the ohmic resistance of the composite cathode is an important factor in the overall resistance of the cell and unfavorably affects the performance (capacity and capacity-rate) of the cathode.}, number={2}, journal={JOURNAL OF POWER SOURCES}, author={Fan, J and Fedkiw, PS}, year={1998}, month={Apr}, pages={165–173} }
 @article{hicks_fedkiw_1998, title={Kolbe electrolysis of acetic acid in a polymer electrolyte membrane reactor}, volume={145}, ISSN={["0013-4651"]}, DOI={10.1149/1.1838866}, abstractNote={A polymer electrolyte membrane (PEM) reactor is described for use in Kolbe electrolysis: the anodic oxidation of an alkyl carboxylic acid with subsequent decarboxylation and coupling to yield a dimer, . Platinized Nafion® 117 is the PEM and functions simultaneously as the electrolyte and separator. Results demonstrating the feasibility of Kolbe electrolysis in a PEM reactor are presented for the oxidation of gaseous acetic acid (in a nitrogen diluent) to ethane and carbon dioxide, with hydrogen evolution at the counter electrode. The investigation includes the following effects on current density, current efficiency, and product selectivity: acetic acid partial pressure (Ptotal ≈ 1 atm), cell voltage and temperature, phase of the catholyte (liquid water or humidified nitrogen) and the procedure used to prepare the membrane‐electrode assembly. Current densities from 0.06 to 0.4 A/cm2 with Kolbe current efficiencies of 10 to 90% were obtained for cell voltages ranging from 4 to 10 V. The best results were obtained using PEMs platinized by a nonequilibrium impregnation‐reduction method; a 75% current efficiency at 0.3 A/cm2 with a cell voltage of 6 V were measured at the following reaction conditions: 42°C reactor, 58 mm Hg acetic acid (50°C acetic acid dew point), and 42°C liquid water to the cathode. These initial results are encouraging for Kolbe electrolysis in a PEM cell; additional work, however, is needed to determine if the PEM strategy may be employed using a liquid‐phase reactant. In addition, optimal reaction conditions and downstream mass‐transfer separation requirements remain to be determined both of which are reactant specific.}, number={11}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={Hicks, MT and Fedkiw, PS}, year={1998}, month={Nov}, pages={3728–3734} }
 @article{nouel_fedkiw_1998, title={Nafion (R)-based composite polymer electrolyte membranes}, volume={43}, ISSN={["0013-4686"]}, DOI={10.1016/S0013-4686(97)10151-7}, abstractNote={Microporous poly(tetrafluoroethylene) (PTFE) and Celgard® films were used as support material for Nafion®-based composite membranes. The microporous supports were impregnated by soaking in a 18 wt% Nafion®/ethanol solution. Although there was considerable Nafion® uptake by Celgard® (43–45 wt%), the conductivity at 65°C of 0.021 S/cm (Celgard® 2400) or 0.027 S/cm (Celgard® 2500) is relatively low in comparison to that of 0.114 S/cm for Nafion® 112. In contrast, a larger uptake (∼70 wt%) and conductivity (0.101 S/cm) were measured for the microporous PTFE support. Because the Nafion®/PTFE composites are only 31 μm thick, their areal resistance is lower than that of Nafion® 112 membranes: 0.031 vs 0.036 Ω cm2. Nafion® is uniformly distributed across the PTFE support, as evidenced by EDAX visualization of Ag+-exchanged membranes, but does not completely plug the micropores, as suggested by the relatively low bubble-point and the relatively high N2 and O2 permeabilities of the composites.}, number={16-17}, journal={ELECTROCHIMICA ACTA}, author={Nouel, KM and Fedkiw, PS}, year={1998}, pages={2381–2387} }
 @article{fan_fedkiw_1997, title={Composite Electrolytes Prepared from Fumed Silica, Polyethylene Oxide Oligomers, and Lithium Salts}, volume={144}, ISSN={0013-4651}, url={http://dx.doi.org/10.1149/1.1837423}, DOI={10.1149/1.1837423}, abstractNote={The conductivity of solution electrolytes containing lithium salts (imide and triflate anions), poly(ethylene glycol), and mono‐ and dimethyl‐terminated poly(ethylene glycol) (Mw 200 to 400), and their corresponding composite electrolytes containing fumed‐silica particulates (0 to 20 weight percent) are reported. At room temperature the ionic conductivity is as high as for the composites studied, and they exhibit a gel‐like consistency but flow under shear. The electrochemical stability of the composites and compatibility with lithium metal were also examined. A large potential window (∼5.5 V) was found for Li imide‐based electrolytes. The passive film formed on lithium in contact with the composite electrolyte is relatively more stable and less resistive than that formed in contact with the parent solution electrolyte. Considering the additional advantages of processability and low volatility, these composites should be good candidate electrolytes for lithium and lithium ion batteries.}, number={2}, journal={Journal of The Electrochemical Society}, publisher={The Electrochemical Society}, author={Fan, Jiang and Fedkiw, Peter S.}, year={1997}, pages={399} }
 @article{hicks_fedkiw_1997, title={Effects of supporting electrolyte on the mass-transfer limited current for coupled chemical-electrochemical reactions}, volume={424}, ISSN={["0022-0728"]}, DOI={10.1016/S0022-0728(96)04932-7}, abstractNote={A Nernst diffusion-layer model is developed for the study of reactant diffusion-migration in electrolyte solutions with coupled chemical-electrochemical reactions. Specifically, proton reduction to hydrogen gas and the Kolbe oxidative dimerization of acetate to ethane and carbon dioxide are studied in an acetic acid solution with supporting electrolyte: an inert (LiClO4) and a reactive electrolyte (NaOH) are each considered. The model predicts concentration and potential profiles within the diffusion layer and the mass-transfer limited current density as a function of the ratio of the supporting-electrolyte concentration to that of acetic acid. For proton reduction, the ratio of the limiting to diffusion current increases with decreasing acid strength in the limit of zero supporting-electrolyte, while the opposite is true for the Kolbe oxidative dimerization of acetate. For the Kolbe oxidative dimerization of acetate in sodium hydroxide, a maximum exists in the ratio of the limiting to diffusion current when the concentration of sodium hydroxide is approximately equal to that of acetic acid. The maximum is a result of the weak-acid strong-base chemistry. Numerical calculations for proton reduction from acetic acid as a function of the supporting-electrolyte concentration are compared with published experimental data. The numerical results and experimental data are in agreement when there is an excess of supporting-electrolyte present, but diverge as the supporting-electrolyte concentration approaches zero.}, number={1-2}, journal={JOURNAL OF ELECTROANALYTICAL CHEMISTRY}, author={Hicks, MT and Fedkiw, PS}, year={1997}, month={Mar}, pages={75–92} }
 @article{walsh_fedkiw_1997, title={Nitric oxide reduction using iridium electrodes on yttria-stabilized zirconia}, volume={104}, ISSN={["0167-2738"]}, DOI={10.1016/S0167-2738(97)00402-5}, number={1-2}, journal={SOLID STATE IONICS}, author={Walsh, KJ and Fedkiw, PS}, year={1997}, month={Dec}, pages={97–108} }
 @article{yan_fedkiw_law_1996, title={A model for the Kolbe reaction of acetate in a parallel-plate reactor}, volume={26}, ISSN={0021-891X 1572-8838}, url={http://dx.doi.org/10.1007/bf00364068}, DOI={10.1007/bf00364068}, number={2}, journal={Journal of Applied Electrochemistry}, publisher={Springer Nature}, author={Yan, J. -F. and Fedkiw, P. S. and Law, C. G., Jr.}, year={1996}, month={Feb}, pages={175–185} }
 @article{ye_fedkiw_1996, title={Electrodeposition of high-surface area platinum in a well adherent nafion film on glassy carbon}, volume={41}, ISSN={0013-4686}, url={http://dx.doi.org/10.1016/0013-4686(95)00314-5}, DOI={10.1016/0013-4686(95)00314-5}, abstractNote={Abstract Platinum was electrochemically deposited within a Nafion film coated on glassy carbon (GC) to form a well adherent and high-platinum utilization electrode. Two potential-control procedures were evaluated to form a deposit: a cyclic potential scan and a constant potential, with Pt loadings ranging for each from 60–750 μg Pt cm −2 GC obtained by varying the coulombs discharged. The Pt/Nafion/GC electrodes were annealed at 170 °C before use. Transmission electron microscopy studies revealed that Pt grows as a dispersed, three-dimensional deposit within the film for both techniques. The average particle size for a loading of 60 μg cm −2 is 7.3 nm, which is in good agreement with that (7.1 nm) estimated from electrochemical formation of adsorbed hydrogen. With a Pt loading an order-of-magnitude greater, the particle number density increased, and the observed average particle is larger at 9.8 nm which is smaller than that (19.0 nm) evaluated from electrochemical hydrogen adsorption. The deposit thickness increased with loading and, for a given Pt loading, was less thick when using the steady-potential method; the latter technique, however, yielded a deposit which covered more of the GC-Nafion interface. The mass specific surface area of Pt decreased with loading and ranged from 32-8 m 2 g −1 as the loading varied from 60–640 μg cm −2 . The Pt/Nafion/GC structure is robust in that the electrode can be used to evolve hydrogen or oxygen without damaging the film. In contrast, a Nafion film on smooth Pt is lifted off the surface under similar gas-evolution conditions.}, number={2}, journal={Electrochimica Acta}, publisher={Elsevier BV}, author={Ye, Jian-Hui and Fedkiw, Peter S.}, year={1996}, month={Feb}, pages={221–231} }
 @article{cohen hubal_kimbell_fedkiw_1996, title={Incorporation of Nasal-Lining Mass-Transfer Resistance into a CFD Model for Prediction of Ozone Dosimetry in the Upper Respiratory Tract}, volume={8}, ISSN={0895-8378 1091-7691}, url={http://dx.doi.org/10.3109/08958379609034267}, DOI={10.3109/08958379609034267}, abstractNote={Inhalation of ambient concentrations of ozone (a strong oxidant) has been reported to injure regions of the monkey and rat upper respiratory tract (URT) that contain little intraepithelial mucosubstances (regions lined by transitional epithelium) and to spare adjacent regions that contain abundant stored secretory products (regions lined by respiratory epithelium). It is therefore hypothesized that mucus provides a major resistance to ozone mass transport in the URT. As part of a larger project to predict health risks of inhaled gases, a previously developed, computational fluid dynamics (CFD) model of the Fischer 344 (F344) rat nasal passage was modified to describe transport of ozone. In this study, mass-transfer resistance in the nasal lining was incorporated into the CFD model for prediction of ozone dosimetry. Static mucus and tissue layers were considered. A boundary condition was developed that incorporates mass-transfer resistance in the nasal lining due to one-dimensional diffusion and first-order reaction in the mucus and tissue phases. Physicochemical parameters for ozone were obtained from the literature. Resistance to mass transfer in the submucosal region (blood phase) was neglected due to high tissue-phase reactivity (i.e., the concentration of inhaled chemical in blood was set to zero). To study the possibility that differences in the thickness and/or quality (variation in physico-chemical properties) of mucus coating the transitional and respiratory epithelium account for reported patterns of injury, a simulation was performed into which regional differences in mucus thickness were incorporated. Results suggest that mass-transfer resistance in the mucus phase is important for describing ozone dosimetry in the URT. In addition, mucus thickness may play a role in determining the pattern of ozone-induced nasal lesions.}, number={9}, journal={Inhalation Toxicology}, publisher={Informa UK Limited}, author={Cohen Hubal, Elaine A. and Kimbell, Julia S. and Fedkiw, Peter S.}, year={1996}, month={Jan}, pages={831–857} }
 @article{hubal_fedkiw_kimbell_1996, title={Mass-transport models to predict toxicity of inhaled gases in the upper respiratory tract}, volume={80}, ISSN={8750-7587 1522-1601}, url={http://dx.doi.org/10.1152/jappl.1996.80.4.1415}, DOI={10.1152/jappl.1996.80.4.1415}, abstractNote={Mass transport (the movement of a chemical species) plays an important role in determining toxic responses of the upper respiratory tract (URT) to inhaled chemicals. Mathematical dosimetry models incorporate physical characteristics of mass transport and are used to predict quantitative uptake (absorption rate) and distribution of inhaled gases and vapors in the respiratory tract. Because knowledge of dose is an essential component of quantitative risk assessment, dosimetry modeling plays an important role in extrapolation of animal study results to humans. A survey of existing mathematical dosimetry models for the URT is presented, limitations of current models are discussed, and adaptations of existing models to produce a generally applicable model are suggested. Reviewed URT dosimetry models are categorized as early, lumped-parameter, and distributed- parameter models. Specific examples of other relevant modeling work are also presented.}, number={4}, journal={Journal of Applied Physiology}, publisher={American Physiological Society}, author={Hubal, E. A. and Fedkiw, P. S. and Kimbell, J. S.}, year={1996}, month={Apr}, pages={1415–1427} }
 @article{walsh_fedkiw_1996, title={Nitric oxide reduction using platinum electrodes on yttria-stabilized zirconia}, volume={93}, ISSN={0167-2738}, url={http://dx.doi.org/10.1016/s0167-2738(96)00517-6}, DOI={10.1016/s0167-2738(96)00517-6}, abstractNote={Abstract A high-temperature, stabilized-zirconia cell with an iridium cathode was used to electrochemically reduce low concentrations of nitric oxide (230–610 ppm) in streams containing oxygen (129–9800 ppm). A combination of thermodynamic considerations, responses to changes in the gas stream, and steady-state galvanostatic experiments suggest that the iridium electrode is converted to iridium dioxide by nitric oxide at open circuit and potentials more positive than −300 mV versus an air electrode. If the electrode is reduced to iridium metal at more negative potentials, nitric oxide can be electrochemically reduced more rapidly than oxygen.}, number={1-2}, journal={Solid State Ionics}, publisher={Elsevier BV}, author={Walsh, Kenneth J. and Fedkiw, Peter S.}, year={1996}, pages={17–31} }
 @article{ye_fedkiw_1995, title={A comparison of two post-casting treatment methods for perfluorosulfonated ionomer films}, volume={40}, ISSN={0013-4686}, url={http://dx.doi.org/10.1016/0013-4686(94)00275-6}, DOI={10.1016/0013-4686(94)00275-6}, abstractNote={Abstract The resultant effect of two post-casting treatments on the anion-rejection characteristics and adherence to a smooth Pt electrode of a perfluorosulfonate ionomer (Nafion) cast as a thin film (4 μm) from the commercially available alcohol solution is reported. The cyclic voltammetry of ferricyanide from both an acidic and neutral pH solution (2 mM sodium ferricyanide +0.2 M sulfuric acid and 50 mM sodium ferricyanide +0.2 M sodium sulfate, respectively) is used as the measure of anion rejection. Unannealed films which are cured at room temperature serve as the reference and are most permeable to ferricyanide in comparison to high-temperature (170 °C), vacuum-annealed films (20mm Hg) or films which are cured in a low-humidity environment at room temperature under 20mm Hg vacuum (drycured film). For example, after seventy hours of soaking in the neutral pH solution, the amount of ferricyanide absorbed in the unannealed film increased 390% above that after one hour. The dry-cured film, in comparison, absorbed less ferricyanide after one hour; but after seventy hours, even though the amount absorbed was still less than that in the unannealed film, the increase was 1300% above the amount after one hour. In contrast, the thermal-annealed film showed no measurable absorption of ferricyanide even after seventy hours of exposure. All films absorbed ferricyanide from the acidic solution but the thermal-annealed film exhibited the lowest amount. Thermal annealing results in the most stable film of the three: After 16 hours of exposure to 6 M sulfuric acid, the thermal-annealed film adhered to the platinum disk upon rotation, but the other two were sheared off the surface.}, number={3}, journal={Electrochimica Acta}, publisher={Elsevier BV}, author={Ye, Jian-Hui and Fedkiw, Peter S.}, year={1995}, month={Feb}, pages={291–296} }
 @article{fedkiw_song_sharma_ye_1995, title={Coulometry of a Mass-Transfer Limited Reaction with a Membrane-Covered Rotating Disk Electrode}, volume={142}, ISSN={0013-4651}, url={http://dx.doi.org/10.1149/1.2044213}, DOI={10.1149/1.2044213}, abstractNote={The transient, convective-diffusion equation for a single reactant consumed at a mass-transfer-limited rate on a rotating disk electrode (RDE) and a membrane-covered RDE is solved via a perturbation method in the Laplace domain for predicting the coulombs discharged following a potential step from open-circuit conditions. A formula is derived in each case for relating the rotation rate ω to the excess transient coulombs Q t passed during the time required to establish a steady-state current where Q t =∫ 0 ∞[I(t)-I ss ]dt. For an uncoated RDE, a plot of Q t vs. ω -1/2 is predicted to be linear through the origin with a slope proportional to the reactant diffusivity to the one-third power. For the membrane-covered RDE, a similar plot is predicted in the high-rotation rate limit to be a straight line with a nonzero intercept. The slope and intercept can be used with the formula provided for determining the diffusivity and partition coefficient of the reactant in the membrane. Experimental results are presented which validate the theoretical development}, number={6}, journal={Journal of The Electrochemical Society}, publisher={The Electrochemical Society}, author={Fedkiw, Peter S. and Song, Shihua and Sharma, Sanjay and Ye, Jian-Hui}, year={1995}, pages={1909} }
 @misc{fedkiw_1995, title={Methods of indirect electrochemistry using ionomer coated electrodes}, volume={5,399,245}, number={1995 Mar. 21}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Fedkiw, P. S.}, year={1995} }
 @article{ye_fedkiw_1994, title={Effects of Toluene and Benzoic Acid on the Kinetics of Ferrous Oxidation on Pt and Nafion-Coated Pt Electrodes}, volume={141}, ISSN={0013-4651}, url={http://dx.doi.org/10.1149/1.2054950}, DOI={10.1149/1.2054950}, abstractNote={The electrochemical kinetics of Fe2+ oxidation to Fe3+ have been investigated by cyclic and ring disk electrode voltammetry in the absence and presence of the contaminants toluene (7 mM, saturated solution) or benzoic acid (16 mM) in 1M electrolyte on (i) smooth Pt electrodes, (ii) Nafion‐coated smooth Pt electrodes, and (iii) Pt electrodes electrodeposited within a Nafion film coated onto a glassy carbon (GC) substrate. On uncoated Pt, the kinetics are adversely affected by these two organics: both the anodic transfer coefficient and the apparent standard rate constant are decreased. A 3.7 μm Nafion coating, however, effectively buffers the smooth Pt electrode from toluene, but, nevertheless, benzoic acid still affects the reaction rate. In contrast, the transfer coefficient and rate constant for Fe2+ oxidation on the Pt/Nafion/GC electrode are esseentially unaffected by either toluene or benzoic acid. Qualitative features of the voltammograms also indicate that the Nafion film protects the Pt from contamination by these aromatics: two current plateaus are observed using an uncoated Pt electrode in the presence of toluene or benzoic acid with a ratio which increases with rotation rate; with the Nafion coating on a smooth Pt electrode and in the presence of toluene, however, there is only one current plateau; in the presence of benzoic acid, two current plateaus remain, but the ratio is nearer unity and less sensitive to rotation rate. In contrast, only a single plateau current is observed using the Pt/Nafion/GC electrode. The Nafion coating is apparently an effective buffer layer against these two aromatics, but concurrently affects a decrease in the mass‐transfer limited current due to the diffusional resistance of the film.}, number={6}, journal={Journal of The Electrochemical Society}, publisher={The Electrochemical Society}, author={Ye, Jian-Hui and Fedkiw, Peter S.}, year={1994}, pages={1483} }
 @article{bakshi_fedkiw_1994, title={Optimal time-varying cell-voltage control of a parallel-plate reactor}, volume={24}, ISSN={0021-891X 1572-8838}, url={http://dx.doi.org/10.1007/bf00241309}, DOI={10.1007/bf00241309}, number={11}, journal={Journal of Applied Electrochemistry}, publisher={Springer Nature}, author={Bakshi, R. and Fedkiw, P.S.}, year={1994}, month={Nov} }
 @article{bakshi_fedkiw_1993, title={Optimal time-varying potential control}, volume={23}, ISSN={0021-891X 1572-8838}, url={http://dx.doi.org/10.1007/bf00243341}, DOI={10.1007/bf00243341}, number={7}, journal={Journal of Applied Electrochemistry}, publisher={Springer Nature}, author={Bakshi, R. and Fedkiw, P.S.}, year={1993}, month={Jul} }
 @misc{fedkiw_liu_trainham_1993, title={Process for the electrooxidation of methanol to formaldehyde and methylal}, volume={5,223,102}, number={1993 Jun. 29}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Fedkiw, P. S. and Liu, R. and Trainham, J. A.}, year={1993} }
 @article{chu_fedkiw_1993, title={The electrochemistry of a cuprous cyanide strike-plating bath}, volume={345}, ISSN={1572-6657}, url={http://dx.doi.org/10.1016/0022-0728(93)80472-t}, DOI={10.1016/0022-0728(93)80472-t}, abstractNote={The voltammetric and steady-state polarization response of a copper-disk electrode was used to study the kinetics of copper electrodeposition from a cyanide bath using a solution commonly applied for copper strike-plating (0.1 M Na2CO3 + 0.2 M CuCN + 0.6 M NaCN, pH 11.2). Systematic variation of the sodium cyanide concentration from 0.3 to 0.7 M was used to identify cuprous cyanide redox complexes Cu(CN)n(n − 1)−. The voltammetric response with and without CN− was dramatically different owing to cuprous complexation with CN−, and the voltammetric charge associated with copper oxidation is much higher than that of cuprous cyanide reduction. The major species discharged is proposed to be Cu(CN)32−, although thermodynamic calculations indicate that Cu(CN)43− is the predominant complex. Deposition of the n = 3 complex is suggested to give rise to the relatively uniform macroscopic current distribution inherent with cyanide baths and the fine-grained deposit structure. It is proposed that the cyanide released during deposition shifts the distribution of the complexes at the surface to the completely saturated state and results in a decreased local copper deposition rate since the discharge of Cu(CN)43− is considerably slower. Hence a necessary condition may be posed that any replacement (less toxic) ligand for cyanide should be chosen such that the electroactive copper complex is not saturated with the ligand, and furthermore that the most saturated state be the least electroactive. Cuprous cyanide complexes shift the copper deposition potential to more negative values which avoids displacement deposition on less noble substrates. The predominant copper cyanide species discharged in the copper strike-plating bath is proposed to be Cu(CN)32−; although Cu(CN)43− is at a higher concentration, it is not as electroactive. These kinetics give rise to the inherent good “macroscopic throwing power” observed in the cyanide bath.}, number={1-2}, journal={Journal of Electroanalytical Chemistry}, publisher={Elsevier BV}, author={Chu, Deryn and Fedkiw, Peter S.}, year={1993}, month={Feb}, pages={107–120} }
 @article{liu_her_fedkiw_1992, title={In Situ Electrode Formation on a Nafion Membrane by Chemical Platinization}, volume={139}, ISSN={0013-4651}, url={http://dx.doi.org/10.1149/1.2069162}, DOI={10.1149/1.2069162}, abstractNote={Three chemical techniques to platinize the surface of a Nafion polymer electrolyte membrane (PEM) to form a Pt/PEM electrode have been studied. The resulting Pt/PEM composites were characterized visually by transmission electron microscopy and scanning electron microscopy and electrochemically by (i) hydrogen adsorption to determine surface area, and (ii) the polarization characteristics for the oxidation of hydrogen. The Takenaka‐Torikai method was used in which a reductant diffuses through the membrane to contact and reduce platinic acid at the opposite face, and two variations of an impregnation‐reduction procedure were employed in which a cationic salt is first impregnated into the Nafion and subsequently the membrane is exposed to a reductant. A previously reported equilibrium impregnation method was modified such that the impregnation step was not carried to equilibrium and the concentration of the anionic reductant was significantly lowered. Upon judicious choice of the fabrication conditions, platinum deposited by the nonequilibrium impregnation ‐reduction procedure is concentrated in a thin (submicron), porous layer located predominantly within the membrane but near the surface where it is accessible to both gaseous reactants and a current collector. The metal distribution forms an electrode with a larger active surface area per unit weight of platinum and a better platinum utilization (mA/mg Pt for the hydrogen oxidation reaction) compared to Pt/PEM electrode prepared by the equilibrium impregnation‐reduction process or the Takenaka‐Torikai method. The chemical and physical processes which occur to affect the metal film formed in all three techniques are discussed.}, number={1}, journal={Journal of The Electrochemical Society}, publisher={The Electrochemical Society}, author={Liu, Raymond and Her, Wei-Hwa and Fedkiw, Peter S.}, year={1992}, pages={15} }
 @article{weidner_fedkiw_1992, title={Linear-sweep voltammetry in a cylindrical-pore electrode}, volume={64}, ISSN={0003-2700 1520-6882}, url={http://dx.doi.org/10.1021/ac00028a021}, DOI={10.1021/ac00028a021}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTLinear-sweep voltammetry in a cylindrical-pore electrodeJohn W. Weidner and Peter S. FedkiwCite this: Anal. Chem. 1992, 64, 4, 449–453Publication Date (Print):February 15, 1992Publication History Published online1 May 2002Published inissue 15 February 1992https://doi.org/10.1021/ac00028a021Request reuse permissionsArticle Views157Altmetric-Citations2LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alertsclose Get e-Alerts}, number={4}, journal={Analytical Chemistry}, publisher={American Chemical Society (ACS)}, author={Weidner, John W. and Fedkiw, Peter S.}, year={1992}, month={Feb}, pages={449–453} }
 @article{liu_fedkiw_1992, title={Partial Oxidation of Methanol on a Metallized Nafion Polymer Electrolyte Membrane}, volume={139}, ISSN={0013-4651}, url={http://dx.doi.org/10.1149/1.2069108}, DOI={10.1149/1.2069108}, abstractNote={The results of a study on the electro‐oxidation of methanol vapor at a platinized polymer electrolyte membrane (PEM) are reported. The PEM was Nafion 117 and serves both as a medium for proton transport and a barrier separating anodic from cathodic products. The counterelectrode was immersed in an aqueous acid solution with which the unmetallized face of the PEM was in contact. The following effects on the product distribution were studied: temperature (25 to 100°C), methanol pressure (0.5 to 54.7 kPa, at a constant total pressure of 101.3 kPa using He as a diluent), electrolyte in the counterelectrode compartment ( and 85% ), and two different electrode‐fabrication procedures. Reaction conditions were determined which produce formaldehyde, methylal, or methylformate at high selectivity. Using a PEM electrode prepared by the impregnation‐reduction (I‐R) method with a low‐water‐content electrolyte (85% ) at high temperature (100°C) and low methanol pressure (0.5 to 1 kPa) resulted in the largest selectivity for formaldehyde (∼75%). The reaction conditions for selective methylal production (∼80%) were similar except that a high methanol partial pressure was required (54.7 kPa). Selective formation of methylformate (∼75%) was found using an electrode prepared by the Takenaka‐Torikai (T‐T) method with a high‐water‐content electrolyte at low temperature (25°C) and high methanol pressure (12.9 kPa). Based upon the results, it is argued that the reaction zone in the I‐R prepared electrode is at the platinum‐membrane interface, which is of a lower water content than the reaction zone in the T‐T prepared electrode, the flooded platinum‐electrolyte interface; consequently, the former favors the two‐electron oxidation, and the latter the four‐electron oxidation which requires water to proceed.}, number={12}, journal={Journal of The Electrochemical Society}, publisher={The Electrochemical Society}, author={Liu, Raymond and Fedkiw, Peter S.}, year={1992}, pages={3514} }
 @article{wang_fedkiw_1992, title={Pulsed-Potential Oxidation of Methanol: I. Smooth Platinum Electrode With and Without Tin Surface Modification}, volume={139}, ISSN={0013-4651}, url={http://dx.doi.org/10.1149/1.2221256}, DOI={10.1149/1.2221256}, abstractNote={During the electrooxidation of methanol on platinum, an adsorbate poison forms which results in the rapid decay of the initially high current. The poison may be oxidatively removed to regenerate an active Pt surface, but only at a high anodic polarization at which a methanol fuel cell may not produce power. In this paper, an alternative strategy to steady-state (DC) operation is studied as a means of improving the average methanol oxidation rate on a smooth Pt electrode}, number={9}, journal={Journal of The Electrochemical Society}, publisher={The Electrochemical Society}, author={Wang, Shing-Ru and Fedkiw, Peter S.}, year={1992}, pages={2519} }
 @article{wang_fedkiw_1992, title={Pulsed-Potential Oxidation of Methanol: II. Graphite-Supported Platinum Electrode With and Without Tin Surface Modification}, volume={139}, ISSN={0013-4651}, url={http://dx.doi.org/10.1149/1.2069048}, DOI={10.1149/1.2069048}, abstractNote={Pulsed‐potential control is examined as an alternative to steady‐state (dc) operation as a means of increasing the oxidation rate of methanol on a graphite‐supported Pt electrode, with and without surface modification by Sn. The potential was pulsed from a low polarization (of duration ), at which methanol oxidation and poison formation occur, to a high polarization (of duration ), at which the poison is oxidatively removed; the effects of varying , , and were studied. The electrodes were prepared by ion‐exchange of onto an electro‐oxidized graphite followed sequentially by air activation and electrochemical reduction. The surface area was measured during extensive pulse‐ and triangle‐waveform polarization and decreased but remained stable at 70% of the initial value. From SEM photographs, platinum redistribution into the porous graphite and particle agglomeration were found. The time‐averaged methanol current density using the pulsed‐control strategy was significantly higher in comparison to dc control. The current density without Sn modification at (vs. RHE) increased one order‐of‐magnitude above the dc value of 0.1 mA/cm2, with current density based upon the measured Pt area; at , a four orders‐of‐magnitude increase was found above the dc value of 0.1 μA/cm2. The methanol oxidation current at 0.6 and 0.4 V using the optimum concentration of was only 10–50% higher than that obtained without it under the same pulsed control. X‐ray photoelectron spectroscopy (XPS) was used to characterize the effect of pulsed‐potential control on the oxidation states of the platinum. The pulsed electrolysis enhanced the chemical interaction between the platinum crystallites and the graphite substrate and increased the platinum oxide coverage.}, number={11}, journal={Journal of The Electrochemical Society}, publisher={The Electrochemical Society}, author={Wang, Shing-Ru and Fedkiw, Peter S.}, year={1992}, pages={3151} }
 @article{smeltzer_fedkiw_1992, title={Reduction of Nitrobenzene in a Parallel-Plate Reactor: I. Differential Conversion Using Periodic Cell-Voltage Control}, volume={139}, ISSN={0013-4651}, url={http://dx.doi.org/10.1149/1.2069412}, DOI={10.1149/1.2069412}, abstractNote={The effect of steady and periodic, step cell‐voltage control on the selectivity of the reduction of nitrobenzene in a parallel‐plate reactor was theoretically investigated. Under step cell‐voltage control, the potential is continuously oscillated from a constant high to a constant low value. Nitrobenzene (NB) is electroreduced to the intermediate phenylhydroxylamine (PHA) which may undergo further electrochemical reduction to aniline (AN) or may rearrange chemically to form the desired product, p‐aminophenol (PAP). A reactor model was developed which assumes a well‐mixed core, mass‐transfer boundary layers for NB and PHA at the cathode, concurrent hydrogen evolution, oxygen evolution at the anode, and negligible migration transport. An analytic, stationary‐state solution to the transient‐diffusion equation within the boundary layers was coupled through the reaction kinetics to an analytic solution of the one‐dimensional Laplace equation for electrolyte potential. Differential‐conversion simulations were performed in which the homogeneous reaction need not be considered because its characteristic reaction time is large compared to both those of the other reactions and to the cycle time of the control. The best periodic cell‐voltage control strategy employed in the simulations was found to produce a PHA selectivity 250% of that under steady control at the same cycle‐averaged PHA production rate. Under periodic control, PHA selectivity was shown to increase asymptotically with decreasing cycle time; high‐frequency operation lowered the depletion of NB and overabundance of PHA in the boundary layer which otherwise would occur during the high‐polarization portion of the cycle. Decreasing the duty cycle (fraction of cycle time spent at high polarization) increased the PHA selectivity since smaller duty cycles resulted in a higher NB concentration and a lower PHA concentration at the cathode surface, but simultaneously the PHA production rate decreased. Increasing the voltage of the high‐polarization portion of the cycle kinetically favors the production of PHA over AN. An increase in the mass‐transfer rate causes a like effect on the PHA selectivity and to a much smaller extent on the PHA production rate for any set of steady or periodic‐control parameters. The differential‐conversion results provide a basis for the control strategies used in integral‐conversion simulations and experiments presented in Part II of this work.}, number={5}, journal={Journal of The Electrochemical Society}, publisher={The Electrochemical Society}, author={Smeltzer, John C. and Fedkiw, Peter S.}, year={1992}, pages={1358} }
 @article{smeltzer_fedkiw_1992, title={Reduction of Nitrobenzene in a Parallel-Plate Reactor: II. Integral Conversion Using Periodic Cell-Voltage Control}, volume={139}, ISSN={0013-4651}, url={http://dx.doi.org/10.1149/1.2069413}, DOI={10.1149/1.2069413}, number={5}, journal={Journal of The Electrochemical Society}, publisher={The Electrochemical Society}, author={Smeltzer, John C. and Fedkiw, Peter S.}, year={1992}, pages={1366} }
 @article{smeltzer_fedkiw_1991, title={Current Distribution in a Parallel-Plate Reactor: A Comparison of Steady and Sinusoidal Cell-Voltage Control}, volume={138}, ISSN={0013-4651}, url={http://dx.doi.org/10.1149/1.2085477}, DOI={10.1149/1.2085477}, number={12}, journal={Journal of The Electrochemical Society}, publisher={The Electrochemical Society}, author={Smeltzer, John C. and Fedkiw, Peter S.}, year={1991}, pages={3665} }
 @article{chao_walsh_fedkiw_1991, title={Cyclic voltammetric study of the electrochemical formation of platinum oxide in a Pt/yttria-stabilized zirconia cell}, volume={47}, ISSN={0167-2738}, url={http://dx.doi.org/10.1016/0167-2738(91)90250-f}, DOI={10.1016/0167-2738(91)90250-f}, abstractNote={The electrochemical formation of platinum oxides in the O2(g), Pt/yttria-stabilized zirconia (YSZ) cell using high temperature cyclic voltammetry with a platinum paste electrode is reported. In air platinum oxides were formed on the electrode between 400 and 750°C with the maximum amount of oxide occuring near 600°C. The amount of oxide depends on the electrode potential and exposure time at the anodic-exposure potential, but tends to a saturated state determined by the temperature and potential. In the cyclic voltammograms of oxygen in air below 750°C, a distinct cathodic current peak is observed, and a smaller, poorly defined peak at more cathodic potentials is sometimes found. These current peaks are attributed to the reduction of two species of PtOx. Two poorly defined anodic waves are caused by the oxidation of platinum forming the two kinds of PtOx. The electrochemical platinum oxide formation and reduction reactions are irreversible. A mechanism for the electrochemical formation and reduction of platinum oxides is discussed.}, number={3-4}, journal={Solid State Ionics}, publisher={Elsevier BV}, author={Chao, Tsaofang and Walsh, Kenneth J. and Fedkiw, Peter S.}, year={1991}, month={Sep}, pages={277–285} }
 @article{weidner_fedkiw_1991, title={Effect of Ohmic, Mass-Transfer, and Kinetic Resistances on Linear-Sweep Voltammetry in a Cylindrical-Pore Electrode}, volume={138}, ISSN={0013-4651}, url={http://dx.doi.org/10.1149/1.2086011}, DOI={10.1149/1.2086011}, abstractNote={Extracting quantitative kinetic information from linear‐sweep voltammograms (LSV) on porous electrodes is more difficult than on planar electrodes since the electrode surface is not uniformly accessible to the bulk supply of reactant or the counterelectrode. We present here a means to account for the effect of ohmic, mass‐transfer, and kinetic resistances on LSV by modeling a pore in a porous matrix as a cylindrical‐pore electrode, and solving the mass and charge conservation equations in the context of this geometry for the simply redox reaction where both and are soluble species. Both analytical and numerical techniques are used to solve the governing equations. The calculated peak currents and potentials are correlated by simple‐to‐apply empirical formulas to the measurable parameters: sweep rate, concentration of the redox species, diffusion coefficient, conductivity of the electrolyte, and pore dimensions. Using the correlations, a methodology is established for determining if the redox reaction kinetics are irreversible or reversible (Nernstian). If the reaction is irreversible, it is shown how the standard rate constant and the transfer coefficient may be extracted from linear‐sweep voltammetry data, or if the reaction is reversible, how the number of electrons transferred may be deduced.}, number={9}, journal={Journal of The Electrochemical Society}, publisher={The Electrochemical Society}, author={Weidner, John W. and Fedkiw, Peter S.}, year={1991}, pages={2514} }
 @article{fedkiw_her_1991, title={The Faradaic—reactive impedance for a sinusoidal electrode}, volume={36}, ISSN={0013-4686}, url={http://dx.doi.org/10.1016/0013-4686(91)85318-2}, DOI={10.1016/0013-4686(91)85318-2}, abstractNote={Abstract The faradaic—reactive impedance for a sinusoidal-shaped electrode is determined from a perturbation solution to the Laplace equation in which the ratio of the amplitude to period length (A) is the perturbation parameter. Terms in the expansion up to and including fourth order in A are included, but A must be less than 1/2π for convergence. A formula for the impedance minus its infinite frequency limit is presented for the reference electrode far removed from the electrode surface. The Nyquist diagram of the imaginary versus the real component of the impedance for the sinusoidally rough surface is shown to be always perpendicular to real axis at both low and high frequency and is nearly semicircular with a diameter which, at a given amplitude, decreases asymptotically for low exchange current density but increases asymptotically for high exchange current density. At a given exchange current density, the diameter may decrease or increase with amplitude depending upon whether the exchange current density is low or high, respectively. If the Nyquist diagram for the faradaic—reactive impedance of the sinusoidal-shaped electrode is (incorrectly) interpreted as that from a planar electrode, the resulting apparent exchange current density and double-layer capacitance both differ from the actual values, and a means to correct the measurements to obtained the intrinsic values is given. The results show that for an irreversible reaction the apparent transfer coefficient determined from the slope of a plot of the inverse of the low frequency limit of the impedance versus the dc bias voltage may be nonconstant and vary with A. The impedance for an ideally blocking sinusoidal-shaped electrode is also presented. At low and high frequencies the phase lag is −π/2 and the modulus is inversely proportional to frequency, with a proportionality constant which is smaller at low frequency and is A dependent for all frequency; however, over a frequency range which is also A dependent, a deviation from the pseudo-planar behavior is found with the phase lag less than −π/2.}, number={5-6}, journal={Electrochimica Acta}, publisher={Elsevier BV}, author={Fedkiw, Peter S. and Her, Wei-Hwa}, year={1991}, month={Jan}, pages={1083–1091} }
 @article{fedkiw_potente_her_1990, title={Electroreduction of Gaseous Ethylene on a Platinized Nafion Membrane}, volume={137}, ISSN={0013-4651}, url={http://dx.doi.org/10.1149/1.2086689}, DOI={10.1149/1.2086689}, abstractNote={The electroreduction kinetics of gaseous ethylene (1 atm, 20 or 100 mole percent, ) on a platinized Nafion 117 membrane has been examined using polarization and product composition measurements. The platinum electrodes were prepared on roughened Nafion 117 by a chemical‐reduction method and characterized electrochemically by cyclic voltammetry of hydrogen adsorption and visually by SEM and TEM. Two distinctly different electrode morphologies resulted when using low (0.02N) or high (0.05N) concentration of platinic acid (all other plating variables remained constant) and, based upon visual micrographic examination, are descriptively called a mossy or film morphology electrode, respectively. The platinum deposit of the film morphology electrode was thinner and less porous and, at a given loading, resulted in higher electroactive surface area per unit weight of platinum. The ethylene reaction kinetics were found to be similar to those reported in the literature for reduction of ethylene dissolved in aqueous solutions; ethane and hydrogen were the only products detected. The film and mossy electrode morphology in the Tafel region gave similar results upon comparing the current density normalized by the platinum loading. This indicates that the platinum embedded within the Nafion, formed early in the deposition reaction and the assumed site for the electrochemistry, is similar for the two morphologies. The implications of this work for electrodes for use in solid polymer electrolyte cells for gaseous reactants are discussed.}, number={5}, journal={Journal of The Electrochemical Society}, publisher={The Electrochemical Society}, author={Fedkiw, Peter S. and Potente, James M. and Her, Wei-Hwa}, year={1990}, pages={1451} }
 @article{nolen_fedkiw_1990, title={Kinetic study of the electroreduction of nitrobenzene}, volume={20}, ISSN={0021-891X 1572-8838}, url={http://dx.doi.org/10.1007/bf01076043}, DOI={10.1007/bf01076043}, number={3}, journal={Journal of Applied Electrochemistry}, publisher={Springer Nature}, author={Nolen, T. R. and Fedkiw, P. S.}, year={1990}, month={May}, pages={370–376} }
 @misc{fedkiw_1990, title={Preparing in situ electrocatalytic films in solid polymer electrolyte membranes, composite microelectrode structures produced thereby and chloralkali process utilizing the same}, volume={4,959,132}, number={1990 Sep. 25}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Fedkiw, P. S.}, year={1990} }
 @article{nolen_fedkiw_1990, title={Reaction Selectivity Enhancement under Periodic-Current Control: The Reduction of Nitrobenzene on the Rotating Disk Electrode}, volume={137}, ISSN={0013-4651}, url={http://dx.doi.org/10.1149/1.2087049}, DOI={10.1149/1.2087049}, abstractNote={Kinetic rate equations for the reduction of nitrobenzene have been used with a mathematical model for mass transfer to a rotating disk electrode to show how periodic current control can improve the selectivity for p-aminophenol compared to dc control at the same average production rate}, number={9}, journal={Journal of The Electrochemical Society}, publisher={The Electrochemical Society}, author={Nolen, Timothy R. and Fedkiw, Peter S.}, year={1990}, pages={2726} }
 @article{weidner_fedkiw_1990, title={Reversible, linear-sweep voltammetry of a soluble redox couple:  effect of initial concentrations}, volume={62}, ISSN={0003-2700 1520-6882}, url={http://dx.doi.org/10.1021/ac00207a022}, DOI={10.1021/ac00207a022}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTReversible, linear-sweep voltammetry of a soluble redox couple: effect of initial concentrationsJohn W. Weidner and Peter S. FedkiwCite this: Anal. Chem. 1990, 62, 8, 875–877Publication Date (Print):April 1, 1990Publication History Published online1 May 2002Published inissue 1 April 1990https://doi.org/10.1021/ac00207a022RIGHTS & PERMISSIONSArticle Views145Altmetric-Citations11LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (354 KB) Get e-Alerts Get e-Alerts}, number={8}, journal={Analytical Chemistry}, publisher={American Chemical Society (ACS)}, author={Weidner, John W. and Fedkiw, Peter S.}, year={1990}, month={Apr}, pages={875–877} }
 @article{smeltzer_fedkiw_1990, title={Surface-concentration behavior in the presence of an oscillating reactant flux to the wall}, volume={45}, ISSN={0009-2509}, url={http://dx.doi.org/10.1016/0009-2509(90)85038-f}, DOI={10.1016/0009-2509(90)85038-f}, abstractNote={The purpose of this short communication is to present a useful variation on the work of Fedkiw et al. (1986) by solving the convective-diffusion equation for the case of laminar boundary-layer flow past a planar wall with a spatially uniform, but sinusoidally oscillating reactant flux to the wall}, number={4}, journal={Chemical Engineering Science}, publisher={Elsevier BV}, author={Smeltzer, John C. and Fedkiw, Peter S.}, year={1990}, pages={1144–1146} }
 @article{fedkiw_nolen_1990, title={The Diffusional (Warburg) Impedance at a Sinusoidal Shape Electrode}, volume={137}, ISSN={0013-4651}, url={http://dx.doi.org/10.1149/1.2086351}, DOI={10.1149/1.2086351}, abstractNote={La surface moyenne et l'impedance diffusionnelle sur une electrode de forme sinusoidale sont calculees en utilisant la solution de perturbation de l'equation de diffusion pour un champ de concentration}, number={1}, journal={Journal of The Electrochemical Society}, publisher={The Electrochemical Society}, author={Fedkiw, Peter S. and Nolen, Timothy R.}, year={1990}, pages={158} }
 @article{viner_fedkiw_1990, title={The Impedance of a Tubular Electrode}, volume={137}, ISSN={0013-4651}, url={http://dx.doi.org/10.1149/1.2086687}, DOI={10.1149/1.2086687}, abstractNote={A cylindrical tube is used as the basis for a two-dimensional mathematical model to calculate the impedance of a flooded porous electrode. The model incorporates charge-transfer, mass-transfer, and ohmic resistances to obtain the axial and radial dependencies of the concentration and potential profiles. A linearized Butler-Volmer kinetic expression for a simple redox reaction O + e yielding R is used, in conjuction with analytical expressions for the surface concentration and overpotential, to compute the open-circuit impedance. The results of the two-dimensional model, which omits double-layer charging, are compared with the results of a more standardly applied one-dimensional model in which radial variations are neglected, with and without double-layer charging. The simpler-to-apply one-dimensional model is found to be satisfactory when mass-transfer and ohmic resistances are small with respect to charge-transfer resistance. The omission of double-layer charging does not introduce error into the two-dimensional model in the frequency range in which capacitive-like effects are caused by mass-transfer limitations.}, number={5}, journal={Journal of The Electrochemical Society}, publisher={The Electrochemical Society}, author={Viner, Andrew S. and Fedkiw, Peter S.}, year={1990}, pages={1435} }
 @article{fedkiw_her_1989, title={An Impregnation-Reduction Method to Prepare Electrodes on Nafion SPE}, volume={136}, ISSN={0013-4651}, url={http://dx.doi.org/10.1149/1.2096772}, DOI={10.1149/1.2096772}, number={3}, journal={Journal of The Electrochemical Society}, publisher={The Electrochemical Society}, author={Fedkiw, Peter S. and Her, Wei-Hwa}, year={1989}, pages={899} }
 @article{nolen_fedkiw_1989, title={The transient diffusion-limited current to a sinusoidal wall}, volume={258}, ISSN={0022-0728}, url={http://dx.doi.org/10.1016/0022-0728(89)85113-7}, DOI={10.1016/0022-0728(89)85113-7}, abstractNote={The time-dependent limiting current to an electrode with a sinusoidal profile in a stagnant solution has been calculated by solving the transient diffusion equation. The reactant concentration was expressed as a perturbation solution using the amplitude-to-wavelength ratio as the perturbation parameter and was developed to fourth-order accuracy. Both the average current and local limiting current density are calculated as functions of time. An asymptotic analysis shows the average current at long and short times both decay as t−12, but with different proportionality coefficients. At long times the Cottrell equation is recovered, but at short times the current is always larger than the Cottrell current to a flat surface and is amplitude dependent. The results are analyzed in terms of three characteristic regions in time that reflect the relative size of the diffusion layer compared to the amplitude of the sinusoid. The time domain for which the predicted behavior could be observed experimentally is discussed.}, number={2}, journal={Journal of Electroanalytical Chemistry and Interfacial Electrochemistry}, publisher={Elsevier BV}, author={Nolen, Timothy R. and Fedkiw, Peter S.}, year={1989}, month={Jan}, pages={265–280} }
 @article{fedkiw_bogard_1988, title={A Numerical Procedure Useful for Current-Distribution Calculations on Bipolar Electrodes}, volume={135}, ISSN={0013-4651}, url={http://dx.doi.org/10.1149/1.2096106}, DOI={10.1149/1.2096106}, number={7}, journal={Journal of The Electrochemical Society}, publisher={The Electrochemical Society}, author={Fedkiw, Peter S. and Bogard, Mark A.}, year={1988}, pages={1726} }
 @article{fedkiw_weidner_kang_1988, title={Ohmic distortion of reversible voltammograms in thin-layer cells}, volume={33}, ISSN={0013-4686}, url={http://dx.doi.org/10.1016/0013-4686(88)85038-2}, DOI={10.1016/0013-4686(88)85038-2}, abstractNote={Abstract A continuum-model approach, analogous to porous electrode theory, has been applied to a thin-layer cell of rectangular and cylindrical geometry. A reversible redox couple is assumed, and the local reaction current density is related to the potential through the formula of Hubbard and Anson for a uniformily accessible thin-layer cell. The placement of the reference electrode is also accounted for in the analysis. Primary emphasis is placed on the effect of the solution-phase ohmic potential drop on the voltammogram characteristics. Correlation equations for the peak-potential displacement from E 0 ′ and the peak current are presented in terms of two dimensionless parameters.}, number={3}, journal={Electrochimica Acta}, publisher={Elsevier BV}, author={Fedkiw, Peter S. and Weidner, John W. and Kang, M.Paul}, year={1988}, month={Mar}, pages={421–424} }
 @article{fedkiw_brouns_1988, title={Periodic Electrodeposition on a Planar Electrode}, volume={135}, ISSN={0013-4651}, url={http://dx.doi.org/10.1149/1.2095613}, DOI={10.1149/1.2095613}, abstractNote={A theoretical analysis is presented of metal deposition on a planar electrode under periodic‐voltage control with simultaneous hydrogen evolution and capacitive charging. The laminar flow convective‐diffusion equation and Laplace equation are (independently) analytically solved at the stationary state with assumed known boundary conditions. An iterative procedure is applied to couple the two solutions through the nonlinear kinetics. In the calculations, primary emphasis is placed on the effect of periodic control on the uniformity of the cycle‐averaged deposit. A comparison is made between a steady‐state and stationary‐state current distribution at the same coulomb passage to the metal deposition. With this basis of comparison, it is shown that sinusoidal‐voltage control may result in either a more or less uniform deposit, depending upon the characteristic kinetic and transport parameters and the applied voltage. With all other variables remaining constant, an increase in the oscillation frequency results in a more uniform deposit; but dc control at the same fraction of the limiting current may result in a more uniform deposit.}, number={2}, journal={Journal of The Electrochemical Society}, publisher={The Electrochemical Society}, author={Fedkiw, Peter S. and Brouns, Daniel R.}, year={1988}, pages={346} }
 @article{fedkiw_traynelis_wang_1988, title={Pulsed-Potential Oxidation of Methanol}, volume={135}, ISSN={0013-4651}, url={http://dx.doi.org/10.1149/1.2095358}, DOI={10.1149/1.2095358}, abstractNote={Methanol oxidation on a platinum electrode at an overvoltage appropriate for fuel‐cell application is incomplete; a poisonous partial‐oxidation product, thought to be , is formed. The poison may be oxidatively removed to regenerate the surface, but the cell may not produce power at the requisite polarization. A periodic, pulsed‐potential control strategy was examined as a means to regenerate in situ a platinum electrode which was otherwise poisoned by methanol oxidation from a and solution at 50°C. The potential was held at a high anodic polarization (1.18V vs. NHE) for time , and for the remainder of the cycle the potential was held at a less anodic value (0.4 or 0.6V). The total cycle time was varied from 0.2 to 10s with varied from 0.05 to 0.4. The average current during each segment of the polarization cycle was calculated from the coulombs measured in that segment, and . The average current at increased with the frequency or ; the coulombic efficiency, , decreased with increasing; and, the faradaic efficiency calculated from the blank‐corrected coulomb ratio has a maximum in . The effects are more pronounced for than at 0.6V, with the average current under pulsed‐potential control increased nearly two orders of magnitude above the steady‐state current at 0.4V. The power output from a fuel cell will be increased under pulsed‐potential operation with an optimum combination of waveform parameters existing which maximize power production.}, number={10}, journal={Journal of The Electrochemical Society}, publisher={The Electrochemical Society}, author={Fedkiw, Peter S. and Traynelis, Christian L. and Wang, Shing-Ru}, year={1988}, pages={2459} }
 @article{fedkiw_newman_1987, title={Friction factors for creeping flow in sinusoidal periodically constricted tubes}, volume={42}, ISSN={0009-2509}, url={http://dx.doi.org/10.1016/0009-2509(87)87062-8}, DOI={10.1016/0009-2509(87)87062-8}, abstractNote={We present a comparative experimental study of unsteady laminar flows of a yield stress shear thinning fluid (Carbopol® 980) in two distinct configurations: a parallel plate rheometric flow and a pressure driven pipe flow. Consistently with the observations in the case of the rheometric flow, the in situ characterisation of the unsteady pipe flow reveals three distinct flow regimes: solid (plug-like), solid–fluid and fluid. In both configurations and as the flow forcing is gradually increased, the yielding emerges via an irreversible transition. The irreversibility of the deformation states is coupled to the wall slip phenomenon. Particularly, the presence of wall slip nearly suppresses the scaling of the deformation power deficit associated to the rheological hysteresis with the rate at which the material is forced. An universal scaling of the slip velocity with the wall velocity gradients and a slip length which is independent on the degree of the flow steadiness is observed in the pipe flow.}, number={12}, journal={Chemical Engineering Science}, publisher={Elsevier BV}, author={Fedkiw, Peter S. and Newman, John}, year={1987}, pages={2962–2963} }
 @article{fedkiw_potente_brouns_1986, title={Mass-transfer rates in the presence of an oscillating boundary layer}, volume={41}, ISSN={0009-2509}, url={http://dx.doi.org/10.1016/0009-2509(86)87051-8}, DOI={10.1016/0009-2509(86)87051-8}, abstractNote={Abstract The boundary-layer form of the convective-diffusion equation has been solved under a spatially uniform but sinusoidally oscillating wall-concentration boundary condition. An analytical solution for the stationary-state local wall flux is found for two cases: (i) the wall moves at a constant velocity, and (ii) the fluid flows past a static wall. The flux in the leading-edge region is in phase with the wall concentration oscillation and decays in the same manner as the steady-state flux for each case. In both cases at large dimensionless distance from the leading edge (corresponding to a high oscillation frequency), the time-dependent contribution to the flux becomes independent of streamwise position; but the time-averaged wall flux follows the normal decay of the Leveque solution when the time-averaged wall concentration is used as the boundary condition. A spatially uniform, but time-dependent, boundary layer thickness is established in marked contrast to the increasing growth under steady-state conditions. The results presented here may be used as a basis for calculating the mass-transfer rate in the presence of an arbitrary wall-concentration oscillation which may also be spatially nonuniform.}, number={7}, journal={Chemical Engineering Science}, publisher={Elsevier BV}, author={Fedkiw, Peter S. and Potente, James M. and Brouns, Daniel R.}, year={1986}, pages={1735–1741} }
 @article{fedkiw_safemazandarani_1985, title={Porous-Electrode Theory Analysis of a Variable Depth, Flow-by Electrode}, volume={38}, ISSN={0098-6445 1563-5201}, url={http://dx.doi.org/10.1080/00986448508911301}, DOI={10.1080/00986448508911301}, abstractNote={A comparison has been made between a variable-depth and constant-depth, flow-by porous electrode in which a single metal ion deposition occurs in parallel with proton reduction. Porous-electrode theory was applied to calculate the reactor's performance under limiting-current and below limiting-current conditions. The thickness profile of the variable-depth electrode was calculated—as first suggested by Kreysa—by constraining the solution phase potential drop across the electrode to remain constant and independent of streamwise position. For each reactor configuration, identical electrolyte and electrode properties, processing rate, reactant conversion, and inlet thickness were assumed. Under this basis of comparison, the results show: the space-time yield of the constant-depth electrode is larger, but the variable-depth electrode better utilizes the separator's and counterelectrode's surface area; the power requirement of the variable-depth electrode is greater; and, the current efficiency is parameter de...}, number={3-6}, journal={Chemical Engineering Communications}, publisher={Informa UK Limited}, author={Fedkiw, Peter S. and Safemazandarani, Paykan}, year={1985}, month={Nov}, pages={107–123} }
 @article{fedkiw_chao_1985, title={Selectivity modification in electroorganic reactions by periodic current control: Electroreduction of nitrobenzene}, volume={31}, ISSN={0001-1541 1547-5905}, url={http://dx.doi.org/10.1002/aic.690310925}, DOI={10.1002/aic.690310925}, abstractNote={The electroreduction of nitrobenzene in deoxygenated acid solution generates predominantly either p-aminophenol or aniline via the common electrochemically generated intermediate, phenylhydroxylamine. Square wave current control increases the reaction selectivity for p-aminophenol, which is produced in a chemical pathway from the intermediate over that obtained at the average current of the oscillation. Data collected under electrokinetic-controlled reaction conditions on a planar copper electrode in a water-propanol-sulfuric acid medium show an order of magnitude increase in selectivity at 100 Hz over that measured at the average direct current. The electrode is depolarized under periodic current control which results in lower rates of undesired electrochemical reactions with a consequential increase in chemical product selectivity. Implications and limitations of periodic electrochemical reaction rate control are discussed.}, number={9}, journal={AIChE Journal}, publisher={Wiley}, author={Fedkiw, P. S. and Chao, J. C.}, year={1985}, month={Sep}, pages={1578–1580} }
 @article{chern_koros_fedkiw_1985, title={Simulation of a hollow-fiber gas separator: the effects of process and design variables}, volume={24}, ISSN={0196-4305 1541-5716}, url={http://dx.doi.org/10.1021/i200031a020}, DOI={10.1021/i200031a020}, abstractNote={ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSimulation of a hollow-fiber gas separator: the effects of process and design variablesRey T. Chern, William J. Koros, and Peter S. FedkiwCite this: Ind. Eng. Chem. Process Des. Dev. 1985, 24, 4, 1015–1022Publication Date (Print):October 1, 1985Publication History Published online1 May 2002Published inissue 1 October 1985https://doi.org/10.1021/i200031a020RIGHTS & PERMISSIONSArticle Views484Altmetric-Citations40LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (905 KB) Get e-Alerts}, number={4}, journal={Industrial & Engineering Chemistry Process Design and Development}, publisher={American Chemical Society (ACS)}, author={Chern, Rey T. and Koros, William J. and Fedkiw, Peter S.}, year={1985}, month={Oct}, pages={1015–1022} }
 @article{mcguire_dwiggins_fedkiw_1985, title={The electrosorption of phenol onto activated carbon}, volume={15}, ISSN={0021-891X 1572-8838}, url={http://dx.doi.org/10.1007/bf00617740}, DOI={10.1007/bf00617740}, number={1}, journal={Journal of Applied Electrochemistry}, publisher={Springer Nature}, author={McGuire, Joseph and Dwiggins, Carlton F. and Fedkiw, Peter S.}, year={1985}, month={Jan}, pages={53–62} }
 @article{fedkiw_watts_1984, title={A Mathematical Model for the Iron/Chromium Redox Battery}, volume={131}, ISSN={0013-4651}, url={http://dx.doi.org/10.1149/1.2115676}, DOI={10.1149/1.2115676}, abstractNote={A mathematical model has been developed to describe the isothermal operation of a single anode-separator-cathode unit cell in a redox-flow battery and has been applied to the NASA iron/chromium system. The model, based on porous electrode theory, incorporates redox kinetics, mass transfer, and ohmic effects as well as the parasitic hydrogen reaction which occurs in the chromium electrode. A numerical parameter study was carried out to predict cell performance to aid in the rational design, scale-up, and operation of the flow battery. The calculations demonstrate: (1) an optimum electrode thickness and electrolyte flow rate exist; (2) the amount of hydrogen evolved and, hence, cycle faradaic efficiency, can be affected by cell geometry, flow rate, and charging procedure; (3) countercurrent flow results in enhanced cell performance over cocurrent flow; and (4) elevated temperature operation enhances cell performance.}, number={4}, journal={Journal of The Electrochemical Society}, publisher={The Electrochemical Society}, author={Fedkiw, Peter S. and Watts, Ricky}, year={1984}, pages={701} }
 @article{fedkiw_scott_1984, title={Selectivity Changes in Electrochemical Reaction Sequences by Modulated Potential Control}, volume={131}, ISSN={0013-4651}, url={http://dx.doi.org/10.1149/1.2115811}, DOI={10.1149/1.2115811}, abstractNote={Electro‐organic reactions typically involve the electrochemical generation of a reactive intermediate which may participate in further chemical or electrochemical reactions. It is possible to effect the product distribution in such branched reaction networks by modulating the electrode potential. Reaction rate calculations under electrokinetic‐controlled conditions for four reaction mechanisms, each involving an electrogenerated intermediate, are presented for step‐ and sinusoidal‐potential modulation. The results show that reactor operating conditions unobtainable under steady potential control are possible. The cycle‐averaged selectivity and yield of selected products may be significantly increased at the stationary state in comparison to those at an identical production rate but under dc conditions. The effect of modulation is frequency dependent; for some reaction sequences, the reaction trend at low frequency may be opposite than that at high frequency. The relative rates of a chemical reaction in parallel with an electrochemical reaction, both involving the intermediate, are more sensitive to potential modulation than either two parallel chemical or electrochemical reactions. Mass transfer limitations dampen the results of modulation. Reactor performance increases under modulated potential (or current) control possibly may be significant enough to make an electrochemical processing route economically viable.}, number={6}, journal={Journal of The Electrochemical Society}, publisher={The Electrochemical Society}, author={Fedkiw, Peter S. and Scott, William D.}, year={1984}, pages={1304} }
 @article{fedkiw_1982, title={A collocation-finite difference procedure for an elliptic partial differential equation}, volume={6}, ISSN={0098-1354}, url={http://dx.doi.org/10.1016/0098-1354(82)85008-4}, DOI={10.1016/0098-1354(82)85008-4}, abstractNote={Abstract A numerical technique to solve a second order, linear, elliptic partial differential equation (PDE) is presented. Collocation is used in one coordinate direction to reduce the PDE to a set of coupled ODE. A second order finite-difference procedure is used to solve this system of ODE. Collocation is useful in emphasizing selected areas of the field and in obtaining accurate integrations over the field. Extensions of the procedure to non-linear problems, coupled PDE, and solutions with analytically identifiable singularities are discussed.}, number={4}, journal={Computers & Chemical Engineering}, publisher={Elsevier BV}, author={Fedkiw, Peter S.}, year={1982}, month={Jan}, pages={327–330} }
 @article{fedkiw_newman_1982, title={Mass-transfer coefficients in packed beds at very low reynolds numbers}, volume={25}, ISSN={0017-9310}, url={http://dx.doi.org/10.1016/0017-9310(82)90069-2}, DOI={10.1016/0017-9310(82)90069-2}, abstractNote={Accurate, transport-controlled, mass transfer coefficients for packed beds have been measured by an electrochemical technique at low Reynolds numbers (0.00271 < v/av < 0.198). At low Péclet numbers, the data show a strong dependence upon the bed length, but this dependence diminishes at the higher flow rates. The results are correlated by a dual-sized, straight-pore model for the bed's pore volume. The bed behaves as though 1.46% of the pore volume were in pores whose diameter is 56% greater than the diameter of the remaining pores. The larger pores result in a flow maldistribution and significantly reduce mass transfer at the lower Péclet numbers. Des coefficients de transfert massique ont été mesurés avec précision dans des lits fixes par la technique électrochimique aux faibles nombres de Reynolds (0,00271 < v/av < 0,198). Aux petits nombres de Péclet, les mesures montrent une forte dépendance vis-à-vis de la longueur du lit, mais cette dépendance diminue aux débits les plus élevés. Les résultats sont représentés par un modèle simple du volume des pores du lit. Le lit se comporte comme si 1,46% du volume de pore était dans les pores dont le diamètre est 56% plus grand que le diamètres des pores restant. Les plus grands pores causent une mauvaise distribution de l'écoulement et ils réduisent nettement le transfert massique aux plus faibles nombres de Péclet. Genaue, transportbestimmte Stoffübergangskoeffizienten für Festbetten wurden mit einem elektrochemischen Verfahren für kleine Reynolds-Zahlen gemessen (0,00271 < v/av < 0,198). Bei kleinen Péclet-Zahlen zeigen die Werte einen starken Einfluβ der Länge des Bettes, aber dieser Einfluβ verringert sich bei höheren Durchsätzen. Die Ergebnisse wurden mit Hilfe eines geraden Zwei-Gröβen-Porenmodells für das Porenvolumen des Bettes korreliert. Das Bett verhielt sich so, als ob 1,46% des Porenvolumens aus Poren bestände, deren Durchmesser 56% gröβer als der Durchmesser der verbleibenden Poren war. Die gröβeren Poren haben eine Verschlechterung der Strömungsverteilung zur Folge und verringern deutlich den Stoffübergang bei kleinen Péclet-Zahlen. Элeктpoчимичecким мeтoдoм пoлyчeнь тoчныe знaчeния кoeффициeнтoB мaccoп epeнoca плoтныч cлoeB пpи мaлыч знaчeнияч чиcлa Peйнoльдca (0,00271 < v/av < 0,198). B cлyчae мaлыч знaчeний чиcлa Пeклe нaблюдaeтcя cильнaя зaBиcимocть знaчeний кoэффициeнтoB oт длины cлoя, oднaкo этa зaBиcимocть yмeньшaeтcя c yBeличeниeм cкopocти тeчeния. peзyльтaты для пopиcтoгo oбъeмa cлoя oбoбщaютcя c иoмoщью дByчмepнoй мoдeли нpямыч пop. Cлoй Beдeт ceбя, кaк ecли бы 1,46% пopиcтoгo oбъeмa нaчoдилocь B пopaч, диaмeтp кoтopыч нa 56% пpeBыщaeт диaмeтp ocтaльныч пop. Пopы бoльшeгo paзмepa BызыBaют нapyшeния B pacпpeдeлeнии пoтoкa и знaчитeльнo cнижaют пepeнoc мaccы пpи бoлee мaлыч знaчeнняч чиcлa Пeклe.}, number={7}, journal={International Journal of Heat and Mass Transfer}, publisher={Elsevier BV}, author={Fedkiw, Peter S. and Newman, John}, year={1982}, month={Jul}, pages={935–943} }
 @article{fedkiw_1981, title={Ohmic Potential Drop in Flow-Through and Flow-By Porous Electrodes}, volume={128}, ISSN={0013-4651}, url={http://dx.doi.org/10.1149/1.2127513}, DOI={10.1149/1.2127513}, abstractNote={The limiting current analysis has been applied to the flow‐through and planar flow‐by porous electrodes using a recently developed low flow rate mass transfer coefficient correlation. At the limiting current, the maximum ohmic drop in the solution is developed. The flow‐through electrode analysis is identical to that first given by Bennion and Newman. In the flow‐by electrode, the two‐dimensional structure of the potential field is taken into account. It is shown that given a maximum solution ohmic potential drop and reactant conversion, a flow‐by electrode with an aspect ratio is superior to a flow‐through electrode in that the maximum processing rate will always be higher for the range of parameters presented in this work. If the aspect ratio (length‐to‐width) of the flow‐by electrode is large, it is reasonable to assume that the potential field is governed by a one‐dimensional Laplace equation. This simplifying assumption has been examined and shown to overestimate the maximum ohmic potential drop. Given the two constraints mentioned above, a flow‐by electrode will have an optimum aspect ratio which is determined by an economic balance between greater current‐volume of the bed as increases vs. greater pumping and separator (if required) costs which also increase with .}, number={4}, journal={Journal of The Electrochemical Society}, publisher={The Electrochemical Society}, author={Fedkiw, Peter S.}, year={1981}, pages={831} }
 @article{fedkiw_1981, title={Transient analysis of a flow-through porous electrode at the limiting current}, volume={11}, ISSN={0021-891X 1572-8838}, url={http://dx.doi.org/10.1007/bf00610974}, DOI={10.1007/bf00610974}, number={2}, journal={Journal of Applied Electrochemistry}, publisher={Springer Nature}, author={Fedkiw, P. S.}, year={1981}, month={Mar}, pages={145–152} }
 @article{fedkiw_1980, title={Primary Current Distribution on a Sinusoidal Profile}, volume={127}, ISSN={0013-4651}, url={http://dx.doi.org/10.1149/1.2129876}, DOI={10.1149/1.2129876}, abstractNote={The primary current distribution at a sinusoidal profile has been solved as a perturbation problem in the amplitude‐to‐wavelength parameter. The results are also applicable to diffusion‐limited reactions on sinusoidal surfaces. The solution for the potential has been developed to the fourth order term. Wagner's solution to this problem can be recovered by including only the first two terms in the perturbation expansion. The expansion technique enables an estimate of the error caused by the neglected terms. The leveling efficiency of a mass‐transfer controlled dissolution reaction is predicted to be always less than that given by Wagner's equation. Applications of the perturbation technique to other relevant problems are discussed.}, number={6}, journal={Journal of The Electrochemical Society}, publisher={The Electrochemical Society}, author={Fedkiw, Peter}, year={1980}, pages={1304} }
 @article{fedkiw_newman_1979, title={Entrance region(Lévêquelike) mass transfer coefficients in packed bed reactors}, volume={25}, ISSN={0001-1541 1547-5905}, url={http://dx.doi.org/10.1002/aic.690250620}, DOI={10.1002/aic.690250620}, abstractNote={Calculations for the high Peclet number, entrance region (Levequelike) packed bed, mass transfer coefficient using a sinusoidal periodically constricted tube model for the void structure of the bed are presented. An inverse cube root dependence of the mass transfer coefficient on the bed depth is predicted. This length dependence is anticipated only at very low Reynolds numbers. Calculations which assume a mixing region between successive periods are also presented. No bed length dependence is anticipated in these coefficients.}, number={6}, journal={AIChE Journal}, publisher={Wiley}, author={Fedkiw, Peter and Newman, John}, year={1979}, month={Nov}, pages={1077–1080} }
 @article{fedkiw_newman_1978, title={Low Péclet number behavior of the transfer rate in packed beds}, volume={33}, ISSN={0009-2509}, url={http://dx.doi.org/10.1016/0009-2509(78)85008-8}, DOI={10.1016/0009-2509(78)85008-8}, abstractNote={Abstract The asymptotic behavior of the mass-transfer coefficient in a packed bed reactor at low Peclet numbers is dependent upon how the coefficient is defined. A singular perturbation approach coupled with heuristic arguments is used to demonstrate that the film mass-transfer coefficient in deep beds approaches a constant value as the Peclet number decreases. The film coefficient is utilized in the one-dimensional model of a bed as a sink term in the governing equation. The volumetric, or effective, mass-transfer coefficient which relates the overall reactant conversion to a logarithmic mean concentration driving force, decreases linearly with the Peclet number as the Peclet number approaches zero. The distinction between the two coefficients is important in the low Peclet number region. Analogous results apply to beat transfer. Reported experimental data support these predicted trends. It has been, demonstrated that the low Peclet number behavior of the Sherwood number in a packed bed reactor is dependent upon its defining equation. A rigorous singular perturbation approach coupled with heuristic arguments indicates that for a deep bed the effective mass-transfer coefficient (defined by eqn 1) is directly proportional to the Peclet number. The film coefficient (defined by eqn 3) approaches a constant in the same limit. These conclusions are independent of the detailed geometric void structure in the bed.}, number={8}, journal={Chemical Engineering Science}, publisher={Elsevier BV}, author={Fedkiw, Peter and Newman, John}, year={1978}, pages={1043–1048} }
 @article{fedkiw_newman_1978, title={Numerical calculations for the asymptotic, diffusion dominated mass-transfer coefficient in packed bed reactors}, volume={33}, ISSN={0009-2509}, url={http://dx.doi.org/10.1016/0009-2509(78)85212-9}, DOI={10.1016/0009-2509(78)85212-9}, abstractNote={For deep beds, the effective Sherwood number approaches a proportional relationship to the Peclet number as the Peclet number tends to zero. A sinusoidal periodically constricted tube model for the voids in the bed has been used to predict the constant of proportionality. This constant depends upon the dimensionless ratios of three lengths: the average tube radius, the oscillation amplitude, and wavelength.}, number={11}, journal={Chemical Engineering Science}, publisher={Elsevier BV}, author={Fedkiw, Peter and Newman, John}, year={1978}, pages={1563–1566} }
 @article{fedkiw_newman_1977, title={Mass transfer at high Péclet numbers for creeping flow in a packed-bed reactor}, volume={23}, ISSN={0001-1541 1547-5905}, url={http://dx.doi.org/10.1002/aic.690230307}, DOI={10.1002/aic.690230307}, abstractNote={An isotropic, homogeneous packed-bed reactor is modeled as an array of sinusoidal periodically constricted tubes (PCT). The effective asymptotic bed-Sherwood number has been calculated for mass transfer at large Péclet number with a constant wall concentration and creeping flow hydrodynamics. The bed friction factor has also been calculated. The results for these macroscopic bed quantities depend upon two ratios of the microscopic PCT period length, average radius, and sinusoidal amptitude.}, number={3}, journal={AIChE Journal}, publisher={Wiley}, author={Fedkiw, Peter and Newman, John}, year={1977}, month={May}, pages={255–263} }
 @article{dufficy_huang_khan_fedkiw, title={Effects of composition and structure on the performance of tin/graphene-containing carbon nanofibers for Li-ion anodes}, volume={7}, number={25}, journal={RSC Advances}, author={Dufficy, M. K. and Huang, S. Y. and Khan, S. A. and Fedkiw, P. S.}, pages={15428–15438} }
 @article{dufficy_khan_fedkiw, title={Galactomannan binding agents for silicon anodes in Li-ion batteries}, volume={3}, number={22}, journal={Journal of Materials Chemistry A}, author={Dufficy, M. K. and Khan, S. A. and Fedkiw, P. S.}, pages={12023–12030} }
 @article{dufficy_khan_fedkiw, title={Hierarchical graphene-containing carbon nanofibers for lithium-ion battery anodes}, volume={8}, number={2}, journal={ACS Applied Materials & Interfaces}, author={Dufficy, M. K. and Khan, S. A. and Fedkiw, P. S.}, pages={1327–1336} }
 @article{zhou_fedkiw_khan, title={Interfacial stability between lithium and fumed silica-based composite electrolytes}, volume={149}, journal={Journal of the Electrochemical Society}, author={Zhou, J. and Fedkiw, P. and Khan, S.A.}, pages={A1121–A1126} }