@article{chagnot_abello_wang_dawlaty_rodriguez-lopez_zhang_augustyn_2024, title={Influence of Finite Diffusion on Cation Insertion-Coupled Electron Transfer Kinetics in Thin Film Electrodes}, volume={171}, ISSN={["1945-7111"]}, DOI={10.1149/1945-7111/ad1d98}, abstractNote={Materials that undergo ion-insertion coupled electron transfer are important for energy storage, energy conversion, and optoelectronics applications. Cyclic voltammetry is a powerful technique to understand electrochemical kinetics. However, the interpretation of the kinetic behavior of ion insertion electrodes with analytical solutions developed for ion blocking electrodes has led to confusion about their rate-limiting behavior. The purpose of this manuscript is to demonstrate that the cyclic voltammetry response of thin film electrode materials undergoing solid-solution ion insertion without significant Ohmic polarization can be explained by well-established models for finite diffusion. To do this, we utilize an experimental and simulation approach to understand the kinetics of Li+ insertion-coupled electron transfer into a thin film material (Nb2O5). We demonstrate general trends for the peak current vs scan rate behavior, with the latter parameter elevated to an exponent between limiting values of 1 and 0.5, depending on the solid-state diffusion characteristics of the film (diffusion coefficient, film thickness) and the experiment timescale (scan rate). We also show that values < 0.5 are possible depending on the cathodic potential limit. Our results will be useful to fundamentally understand and guide the selection and design of intercalation materials for multiple applications.}, number={1}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={Chagnot, Matthew and Abello, Sofia and Wang, Ruocun and Dawlaty, Jahan and Rodriguez-Lopez, Joaquin and Zhang, Chao and Augustyn, Veronica}, year={2024}, month={Jan} }
 @article{siddiqui_n'diaye_martin_baby_dawlaty_augustyn_rodriguez-lopez_2024, title={Monitoring SEIRAS on a Graphitic Electrode for Surface-Sensitive Electrochemistry: Real-Time Electrografting}, ISSN={["1520-6882"]}, DOI={10.1021/acs.analchem.3c04407}, abstractNote={The ubiquity of graphitic materials in electrochemistry makes it highly desirable to probe their interfacial behavior under electrochemical control. Probing the dynamics of molecules at the electrode/electrolyte interface is possible through spectroelectrochemical approaches involving surface-enhanced infrared absorption spectroscopy (SEIRAS). Usually, this technique can only be done on plasmonic metals such as gold or carbon nanoribbons, but a more convenient substrate for carbon electrochemical studies is needed. Here, we expanded the scope of SEIRAS by introducing a robust hybrid graphene-on-gold substrate, where we monitored electrografting processes occurring at the graphene/electrolyte interface. These electrodes consist of graphene deposited onto a roughened gold-sputtered internal reflection element (IRE) for attenuated total reflectance (ATR) SEIRAS. The capabilities of the graphene-gold IRE were demonstrated by successfully monitoring the electrografting of 4-amino-2,2,6,6-tetramethyl-1-piperidine N-oxyl (4-amino-TEMPO) and 4-nitrobenzene diazonium (4-NBD) in real time. These grafts were characterized using cyclic voltammetry and ATR-SEIRAS, clearly showing the 1520 and 1350 cm-1 NO2 stretches for 4-NBD and the 1240 cm-1 C-C, C-C-H, and N-Ȯ stretch for 4-amino-TEMPO. Successful grafts on graphene did not show the SEIRAS effect, while grafting on gold was not stable for TEMPO and had poorer resolution than on graphene-gold for 4-NBD, highlighting the uniqueness of our approach. The graphene-gold IRE is proficient at resolving the spectral responses of redox transformations, unambiguously demonstrating the real-time detection of surface processes on a graphitic electrode. This work provides ample future directions for real-time spectroelectrochemical investigations of carbon electrodes used for sensing, energy storage, electrocatalysis, and environmental applications.}, journal={ANALYTICAL CHEMISTRY}, author={Siddiqui, Abdur-Rahman and N'Diaye, Jeanne and Martin, Kristin and Baby, Aravind and Dawlaty, Jahan and Augustyn, Veronica and Rodriguez-Lopez, Joaquin}, year={2024}, month={Jan} }
 @article{spencer_holzapfel_you_mpourmpakis_augustyn_2024, title={Participation of electrochemically inserted protons in the hydrogen evolution reaction on tungsten oxides}, ISSN={["2041-6539"]}, DOI={10.1039/d4sc00102h}, abstractNote={Understanding the mechanisms by which electrodes undergo the hydrogen evolution reaction (HER) is necessary to design better materials for aqueous energy storage and conversion. Here, we investigate the HER mechanism on tungsten oxide electrodes, which are stable in acidic electrolytes and can undergo proton-insertion coupled electron transfer concomitant with the HER. Electrochemical characterization showed that anhydrous and hydrated tungsten oxides undergo changes in HER activity coincident with changes in proton composition, with activity in the order HxWO3·H2O > HxWO3 > HxWO3·2H2O. We used operando X-ray diffraction and density functional theory to understand the structural and electronic changes in the materials at high states of proton insertion, when the oxides are most active towards the HER. H0.69WO3·H2O and H0.65WO3 have similar proton composition, structural symmetry, and electronic properties at the onset of the HER, yet exhibit different activity. We hypothesize that the electrochemically inserted protons can diffuse in hydrogen bronzes and participate in the HER. This would render the oxide volume, and not just the surface, as a proton and electron reservoir at high overpotentials. HER activity is highest in HxWO3·H2O, which optimizes both the degree of proton insertion and solid-state proton transport kinetics. Our results highlight the interplay between the HER and proton insertion-coupled electron transfer on transition metal oxides, many of which are non-blocking electrodes towards protons.}, journal={CHEMICAL SCIENCE}, author={Spencer, Michael A. and Holzapfel, Noah P. and You, Kyung-Eun and Mpourmpakis, Giannis and Augustyn, Veronica}, year={2024}, month={Mar} }
 @article{ko_hamann_fortunato_augustyn_2024, title={Recent Advances in Electrolytes for Enabling Lithium-Ion Batteries across a Wide Temperature Range}, ISSN={["1932-7455"]}, DOI={10.1021/acs.jpcc.3c06913}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Ko, Jesse S. and Hamann, Tanner and Fortunato, Jenelle and Augustyn, Veronica}, year={2024}, month={Feb} }
 @article{fortunato_shin_spencer_duin_augustyn_2023, title={Choice of Electrolyte Impacts the Selectivity of Proton-Coupled Electrochemical Reactions on Hydrogen Titanate}, ISSN={["1932-7455"]}, DOI={10.1021/acs.jpcc.3c01057}, abstractNote={Proton-coupled electron transfer (PCET) reactions involving transition metal oxides are prevalent in aqueous electrochemical systems used for energy storage and conversion. Here, we elucidate the role of electrolyte on PCET mechanisms in transition metal oxides in aqueous acidic electrolytes using layered hydrogen titanate (H2Ti3O7) as an example. We identify three processes by which electrolyte protons interact with hydrogen titanate at the electrochemical interface: (1) adsorption at the surface and/or insertion into the bulk, (2) adsorption as part of the hydrogen evolution reaction (HER) at the surface, and (3) dissolution of the hydrogen titanate. We utilize a combined experimental and computational (ReaxFF) approach to probe how the competition for protons and electrons among these processes influences electrochemical properties, including the energy storage, Coulombic efficiency (CE), rate capability, and lifetime. In an acidic buffered electrolyte (1 M H3PO4), the CE increases from an average of 48% to 71% and the specific capacity increases from 83 to 90 mAh g–1 as compared to a strong acid electrolyte (1 M H2SO4). We propose that H3PO4 mitigates the HER and hydrogen titanate dissolution, thereby increasing the operating potential window for proton adsorption/insertion for charge storage in hydrogen titanate. Material characterization and computational results indicate that adsorption of phosphate species onto the surface of hydrogen titanate may decrease its dissolution upon reduction, thereby improving electrode performance. We offer a preliminary solution to improve energy storage performance via electrolyte tuning by decreasing the prevalence of the HER and electrode dissolution.}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Fortunato, Jenelle and Shin, Yun Kyung and Spencer, Michael A. A. and Duin, Adri C. T. and Augustyn, Veronica}, year={2023}, month={Jun} }
 @article{fortunato_zydlewski_lei_holzapfel_chagnot_mitchell_lu_jiang_milliron_augustyn_2023, title={Dual-Band Electrochromism in Hydrous Tungsten Oxide}, ISSN={["2330-4022"]}, DOI={10.1021/acsphotonics.3c00921}, abstractNote={The independent modulation of visible and near-infrared light by a single material, termed dual-band electrochromism, is highly desirable for smart windows to enhance the energy efficiency of buildings. Tungsten oxides are commercially important electrochromic materials, exhibiting reversible visible and near-infrared absorption when electrochemically reduced in an electrolyte containing small cations or protons. The presence of structural water in tungsten oxides has been associated with faster electrochromic switching speeds. Here, we find that WO3·H2O, a crystalline hydrate, exhibits dual-band electrochromism unlike the anhydrous WO3. This provides a heretofore unexplored route to tune the electrochromic response of tungsten oxides. Absorption of near-infrared light is achieved at low Li+/e– injection, followed by the absorption of visible light at higher Li+/e– injection as a result of an electrochemically induced phase transition. We propose that the dual-band modulation is possible due to the more open structure of WO3·H2O as compared to WO3. This facilitates a more extended solid-solution Li+ insertion regime that benefits the modulation of near-infrared radiation via plasmon absorption. Higher degrees of Li+/e– insertion lead to polaronic absorption associated with localized charge storage. These results inform how structural factors influence the electrochemically induced spectral response of transition-metal oxides and the important role of structural water beyond optical switching speed.}, journal={ACS PHOTONICS}, author={Fortunato, Jenelle and Zydlewski, Benjamin Z. and Lei, Ming and Holzapfel, Noah P. and Chagnot, Matthew and Mitchell, James B. and Lu, Hsin-Che and Jiang, De-en and Milliron, Delia J. and Augustyn, Veronica}, year={2023}, month={Sep} }
 @article{tsai_pillai_ganeshan_saeed_gao_duin_augustyn_balke_2023, title={Effect of Electrode/Electrolyte Coupling on Birnessite (delta-MnO2) Mechanical Response and Degradation}, volume={15}, ISSN={["1944-8252"]}, url={https://doi.org/10.1021/acsami.3c02055}, DOI={10.1021/acsami.3c02055}, abstractNote={Understanding the deformation of energy storage electrodes at a local scale and its correlation to electrochemical performance is crucial for designing effective electrode architectures. In this work, the effect of electrolyte cation and electrode morphology on birnessite (δ-MnO2) deformation during charge storage in aqueous electrolytes was investigated using a mechanical cyclic voltammetry approach via operando atomic force microscopy (AFM) and molecular dynamics (MD) simulation. In both K2SO4 and Li2SO4 electrolytes, the δ-MnO2 host electrode underwent expansion during cation intercalation, but with different potential dependencies. When intercalating Li+, the δ-MnO2 electrode presents a nonlinear correlation between electrode deformation and electrode height, which is morphologically dependent. These results suggest that the stronger cation-birnessite interaction is the reason for higher local stress heterogeneity when cycling in Li2SO4 electrolyte, which might be the origin of the pronounced electrode degradation in this electrolyte.}, number={21}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Tsai, Wan-Yu and Pillai, Shelby B. B. and Ganeshan, Karthik and Saeed, Saeed and Gao, Yawei and Duin, Adri C. T. and Augustyn, Veronica and Balke, Nina}, year={2023}, month={May}, pages={26120–26127} }
 @article{hossain_romo_putnam_dawlaty_augustyn_rodriguez-lopez_2023, title={Electrode-Potential-Driven Dissociation of N-Heterocycle/BF3 Adducts: A Possible Manifestation of the Electro-Inductive Effect}, ISSN={["1521-3773"]}, DOI={10.1002/anie.202304218}, abstractNote={Recently, non-Faradaic effects were used to modify the electronic structure and reactivity of electrode-bound species. We hypothesize that these electrostatic perturbations could influence the chemical reactivity of electrolyte species near an electrode in the absence of Faradaic electron transfer. A prime example of non-Faradaic effects is acid-base dissociation near an interface. Here, we probed the near-electrode dissociation of N-heterocycle-BF3 Lewis adducts upon electrode polarization, well outside of the redox potential window of the adducts. Using scanning electrochemical microscopy and confocal fluorescence spectroscopy, we detected a potential-dependent depletion of the adduct near the electrode. We propose an electro-inductive effect where a more positive potential leads to electron withdrawal on the N-heterocycle. This study takes a step forward in the use of electrostatics at electrochemical interfaces for field-driven electrocatalytic and electrosynthetic processes.}, journal={ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, author={Hossain, Md. Sazzad and Romo, Adolfo I. B. and Putnam, Seth T. and Dawlaty, Jahan and Augustyn, Veronica and Rodriguez-Lopez, Joaquin}, year={2023}, month={May} }
 @misc{mitchell_chagnot_augustyn_2023, title={Hydrous Transition Metal Oxides for Electrochemical Energy and Environmental Applications}, volume={53}, ISSN={["1545-4118"]}, DOI={10.1146/annurev-matsci-080819-1249550}, journal={ANNUAL REVIEW OF MATERIALS RESEARCH}, author={Mitchell, James B. and Chagnot, Matthew and Augustyn, Veronica}, year={2023}, pages={1–23} }
 @article{gittins_chen_arnold_augustyn_balducci_brousse_frackowiak_gomez-romero_kanwade_koeps_et al._2023, title={Interlaboratory study assessing the analysis of supercapacitor electrochemistry data}, volume={585}, ISSN={["1873-2755"]}, DOI={10.1016/j.jpowsour.2023.233637}, abstractNote={Supercapacitors are fast-charging energy storage devices of great importance for developing robust and climate-friendly energy infrastructures for the future. Research in this field has seen rapid growth in recent years, therefore consistent reporting practices must be implemented to enable reliable comparison of device performance. Although several studies have highlighted the best practices for analysing and reporting data from such energy storage devices, there is yet to be an empirical study investigating whether researchers in the field are correctly implementing these recommendations, and which assesses the variation in reporting between different laboratories. Here we address this deficit by carrying out the first interlaboratory study of the analysis of supercapacitor electrochemistry data. We find that the use of incorrect formulae and researchers having different interpretations of key terminologies are major causes of variability in data reporting. Furthermore we highlight the more significant variation in reported results for electrochemical profiles showing non-ideal capacitive behaviour. From the insights gained through this study, we make additional recommendations to the community to help ensure consistent reporting of performance metrics moving forward.}, journal={JOURNAL OF POWER SOURCES}, author={Gittins, Jamie W. and Chen, Yuan and Arnold, Stefanie and Augustyn, Veronica and Balducci, Andrea and Brousse, Thierry and Frackowiak, Elzbieta and Gomez-Romero, Pedro and Kanwade, Archana and Koeps, Lukas and et al.}, year={2023}, month={Nov} }
 @article{elmanzalawy_innocenti_zarrabeitia_peter_passerini_augustyn_fleischmann_2023, title={Mechanistic understanding of microstructure formation during synthesis of metal oxide/carbon nanocomposites}, ISSN={["2050-7496"]}, DOI={10.1039/d3ta01230a}, abstractNote={
 In situ analysis of physicochemical processes occurring during pyrolysis synthesis of a TMO/C nanocomposite, including microstructure analysis via (S)TEM. Characterization of materials as electrodes for lithium intercalation and conversion reactions.}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Elmanzalawy, Mennatalla and Innocenti, Alessandro and Zarrabeitia, Maider and Peter, Nicolas J. and Passerini, Stefano and Augustyn, Veronica and Fleischmann, Simon}, year={2023}, month={Jun} }
 @article{fleischmann_zhang_wang_cummings_wu_simon_gogotsi_presser_augustyn_2022, title={Continuous transition from double-layer to Faradaic charge storage in confined electrolytes}, ISSN={["2058-7546"]}, DOI={10.1038/s41560-022-00993-z}, journal={NATURE ENERGY}, author={Fleischmann, Simon and Zhang, Yuan and Wang, Xuepeng and Cummings, Peter T. and Wu, Jianzhong and Simon, Patrice and Gogotsi, Yury and Presser, Volker and Augustyn, Veronica}, year={2022}, month={Mar} }
 @article{mitchell_wang_ko_long_augustyn_2022, title={Critical Role of Structural Water for Enhanced Li+ Insertion Kinetics in Crystalline Tungsten Oxides}, volume={169}, ISSN={["1945-7111"]}, DOI={10.1149/1945-7111/ac58c8}, abstractNote={
 Electrochemical ion insertion into transition metal oxides forms the foundation of several energy technologies. Transition metal oxides can exhibit sluggish ion transport and/or phase-transformation kinetics during ion insertion that can limit their performance at high rates (< 10 min). In this study, we investigate the role of structural water in transition metal oxides during Li+ insertion using staircase potentiostatic electrochemical impedance spectroscopy (SPEIS) and electrochemical quartz crystal microbalance (EQCM) analysis of WO3·H2O and WO3 thin-film electrodes. Overall, the presence of structural water in WO3·H2O improves Li+ insertion kinetics compared to WO3 and leads to a less potential-dependent insertion process. Operando electrogravimetry and 3D Bode impedance analyses of nanostructured films reveal that the presence of structural water promotes charge accommodation without significant co-insertion of solvent, leading to our hypothesis that the electrochemically induced structural transitions of WO3 hinder the electrode response at faster timescales (< 10 min). Designing layered materials with confined fluids that exhibit less structural transitions may lead to more versatile ion-insertion hosts for next-generation electrochemical technologies.}, number={3}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={Mitchell, James B. and Wang, Ruocun and Ko, Jesse S. and Long, Jeffrey W. and Augustyn, Veronica}, year={2022}, month={Mar} }
 @article{spencer_fortunato_augustyn_2022, title={Electrochemical proton insertion modulates the hydrogen evolution reaction on tungsten oxides}, volume={156}, ISSN={["1089-7690"]}, DOI={10.1063/5.0082459}, abstractNote={The development of new electrocatalysts for the hydrogen evolution reaction (HER) could reduce the dependence on Pt and other rare metals and enable large-scale production of hydrogen with near-zero carbon emissions. Mechanistic insight into the electrocatalytic activity of a material helps to accelerate the development of new electrocatalysts. Alternative electrocatalyst materials such as transition metal oxides and sulfides can undergo insertion reactions that change their properties. Recent reports indicate that the presence of inserted ions can influence the electrocatalytic activity. Here, we utilized a materials chemistry approach to understand the role of proton insertion in the HER activity of the layered tungsten oxide hydrates (WO3·xH2O, x = 1, 2). We synthesized a series of tungsten oxide hydrates along with an octylamine-pillared tungsten oxide (OA-WO3). We used cyclic voltammetry to study the electrochemical reactivity of each material and performed ex situ x-ray diffraction and Raman spectroscopy to understand bulk and surface structural changes during electrochemical cycling. We show an inverse relationship between the degree of proton insertion and HER overpotential in tungsten oxides: the lack of proton insertion leads to a high overpotential for the HER. We discuss three hypotheses for how proton insertion leads to the HER activity in WO3·xH2O: (1) proton insertion changes the electronic band structure of WO3·xH2O, (2) the presence of bulk protons can influence ΔGH,ads at the surface sites, and (3) the inserted protons may participate in the HER mechanism on WO3·xH2O. Overall, this work shows the critical role of proton insertion in enabling the high HER activity in tungsten oxides.}, number={6}, journal={JOURNAL OF CHEMICAL PHYSICS}, author={Spencer, Michael A. and Fortunato, Jenelle and Augustyn, Veronica}, year={2022}, month={Feb} }
 @misc{fortunato_jordan_newton_walsh_augustyn_2022, title={Electrochemical reactivity of atomic and molecular species under solid-state confinement}, volume={34}, ISSN={["2451-9103"]}, DOI={10.1016/j.coelec.2022.101014}, abstractNote={The nanoconfinement of electrochemically-active guest species in host solid state electrode materials provides opportunities to tune mass transport between the bulk electrolyte and inner surface of the electrode, enhance electron-transfer rates, and/or improve the stability and dispersion of active material. This review summarizes recent experimental and theoretical electrochemical studies of three types of nanoconfined guest species: (1) ion adsorption of electrolyte ions, (2) confined redox-active molecules, and (3) electrocatalytic reactions of confined ions/solvents and catalytic particles. The examples discussed in this review illustrate how the confinement of guest species within enclosed spaces with nanoscale dimensions – such as pores, pockets, channels, and interlayers – can lead to improved electrochemical performance.}, journal={CURRENT OPINION IN ELECTROCHEMISTRY}, author={Fortunato, Jenelle and Jordan, Jack W. and Newton, Graham N. and Walsh, Darren A. and Augustyn, Veronica}, year={2022}, month={Aug} }
 @article{augustyn_hatzell_malika jeffries-el_lutkenhaus_stingelin_2022, title={Introduction to the special collection in memoriam of Susan A. Odom (16 November 1980-18 April 2021)}, ISSN={["2633-5409"]}, DOI={10.1039/d2ma90085h}, abstractNote={The materials chemistry and electrochemistry communities celebrate Susan’s scientific impact and collaborative spirit with this themed issue.}, journal={MATERIALS ADVANCES}, author={Augustyn, Veronica and Hatzell, Kelsey B. and Malika Jeffries-EL and Lutkenhaus, Jodie L. and Stingelin, Natalie}, year={2022}, month={Sep} }
 @article{kabra_birn_kamboj_augustyn_mukherjee_2022, title={Mesoscale Machine Learning Analytics for Electrode Property Estimation}, volume={126}, ISSN={["1932-7455"]}, DOI={10.1021/acs.jpcc.2c04432}, abstractNote={The development of next-generation batteries with high areal and volumetric energy density requires the use of high active material mass loading electrodes. This typically reduces the power density, but the push for rapid charging has propelled innovation in microstructure design for improved transport and electrochemical conversion efficiency. This requires accurate effective electrode property estimation, such as tortuosity, electronic conductivity, and interfacial area. Obtaining this information solely from experiments and 3D mesoscale simulations is time-consuming while empirical relations are limited to simplified microstructure geometry. In this work, we propose an alternate route for rapid characterization of electrode microstructural effective properties using machine learning (ML). Using the Li-ion battery graphite anode electrode as an exemplar system, we generate a comprehensive data set of ∼17 000 electrode microstructures. These consist of various shapes, sizes, orientations, and chemical compositions, and characterize their effective properties using 3D mesoscale simulations. A low dimensional representation of each microstructure is achieved by calculating a set of comprehensive physical descriptors and eliminating redundant features. The mesoscale ML analytics based on porous electrode microstructural characteristics achieves prediction accuracy of more than 90% for effective property estimation.}, number={34}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Kabra, Venkatesh and Birn, Brennan and Kamboj, Ishita and Augustyn, Veronica and Mukherjee, Partha P.}, year={2022}, month={Sep}, pages={14413–14429} }
 @book{nanda_augustyn_2022, title={Transition Metal Oxides for Electrochemical Energy Storage}, ISBN={9783527344932 9783527817252}, url={http://dx.doi.org/10.1002/9783527817252}, DOI={10.1002/9783527817252}, publisher={Wiley}, year={2022}, month={Apr} }
 @article{saeed_fortunato_ganeshan_duin_augustyn_2021, title={Decoupling Proton and Cation Contributions to Capacitive Charge Storage in Birnessite in Aqueous Electrolytes}, volume={8}, ISSN={["2196-0216"]}, DOI={10.1002/celc.202100992}, abstractNote={Abstract Nanostructured birnessite is of interest as an electrode material for aqueous high power electrochemical energy storage as well as desalination devices. In neutral pH aqueous electrolytes, birnessite exhibits a capacitive response attributed to the adsorption of cations and protons at the outer surface and within the hydrated interlayer. Here, we utilize the understanding of proton‐coupled electron transfer (PCET) in buffered electrolytes to decouple the role of protons and cations in the capacitive charge storage mechanism of birnessite at neutral pH. We find that without buffer, birnessite exhibits primarily potential‐independent (capacitive) behavior with excellent cycling stability. Upon the addition of buffer, the capacity initially increases and the cyclic voltammograms become more potential‐dependent, features attributed to the presence of PCET with the birnessite. However, long‐term cycling in the buffered electrolyte leads to significant capacity fade and dissolution, which is corroborated through ex situ characterization. ReaxFF atomistic scale simulations support the observations that proton adsorption leads to birnessite degradation and that capacitive charge storage in birnessite is primarily attributed to cation adsorption at the outer surface and within the interlayer.}, number={22}, journal={CHEMELECTROCHEM}, author={Saeed, Saeed and Fortunato, Jenelle and Ganeshan, Karthik and Duin, Adri C. T. and Augustyn, Veronica}, year={2021}, month={Nov}, pages={4371–4379} }
 @article{boyd_ganeshan_tsai_wu_saeed_jiang_balke_duin_augustyn_2021, title={Effects of interlayer confinement and hydration on capacitive charge storage in birnessite}, ISSN={["1476-4660"]}, url={https://doi.org/10.1038/s41563-021-01066-4}, DOI={10.1038/s41563-021-01066-4}, abstractNote={Nanostructured birnessite exhibits high specific capacitance and nearly ideal capacitive behaviour in aqueous electrolytes, rendering it an important electrode material for low-cost, high-power energy storage devices. The mechanism of electrochemical capacitance in birnessite has been described as both Faradaic (involving redox) and non-Faradaic (involving only electrostatic interactions). To clarify the capacitive mechanism, we characterized birnessite's response to applied potential using ex situ X-ray diffraction, electrochemical quartz crystal microbalance, in situ Raman spectroscopy and operando atomic force microscope dilatometry to provide a holistic understanding of its structural, gravimetric and mechanical responses. These observations are supported by atomic-scale simulations using density functional theory for the cation-intercalated structure of birnessite, ReaxFF reactive force field-based molecular dynamics and ReaxFF-based grand canonical Monte Carlo simulations on the dynamics at the birnessite-water-electrolyte interface. We show that capacitive charge storage in birnessite is governed by interlayer cation intercalation. We conclude that the intercalation appears capacitive due to the presence of nanoconfined interlayer structural water, which mediates the interaction between the intercalated cation and the birnessite host and leads to minimal structural changes.}, journal={NATURE MATERIALS}, author={Boyd, Shelby and Ganeshan, Karthik and Tsai, Wan-Yu and Wu, Tao and Saeed, Saeed and Jiang, De-en and Balke, Nina and Duin, Adri C. T. and Augustyn, Veronica}, year={2021}, month={Aug} }
 @article{wang_sun_brady_fleischmann_eldred_gao_wang_jiang_augustyn_2021, title={Fast Proton Insertion in Layered H2W2O7 via Selective Etching of an Aurivillius Phase}, volume={11}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.202003335}, abstractNote={H2W2O7, a metastable material synthesized via selective etching of the Aurivillius‐related Bi2W2O9, is demonstrated as an electrode for high power proton‐based energy storage. Comprehensive structural characterization is performed to obtain a high‐fidelity crystal structure of H2W2O7 using an iterative approach that combines X‐ray diffraction, neutron pair distribution function, scanning transmission electron microscopy, Raman spectroscopy, and density functional theory modeling. Electrochemical characterization shows a capacity retention of ≈80% at 1000 mV s–1 (1.5‐s charge/discharge time) as compared to 1 mV s–1 (≈16‐min charge/discharge time) with cyclability for over 100 000 cycles. Energetics from density functional theory calculations indicate that proton storage occurs at the terminal oxygen sites within the hydrated interlayer. Last, optical micrographs collected during in situ Raman spectroscopy show reversible, multicolor electrochromism, with color changes from pale yellow to blue, purple, and last, orange as a function of proton content. These results highlight the use of selective etching of layered perovskites for the synthesis of metastable transition metal oxide materials and the use of H2W2O7 as an anode material for proton‐based energy storage or electrochromic applications.}, number={1}, journal={ADVANCED ENERGY MATERIALS}, author={Wang, Ruocun and Sun, Yangyunli and Brady, Alexander and Fleischmann, Simon and Eldred, Tim B. and Gao, Wenpei and Wang, Hsiu-Wen and Jiang, De-en and Augustyn, Veronica}, year={2021}, month={Jan} }
 @article{tsai_wang_boyd_augustyn_balke_2021, title={Probing local electrochemistry via mechanical cyclic voltammetry curves}, volume={81}, ISSN={["2211-3282"]}, DOI={10.1016/j.nanoen.2020.105592}, abstractNote={Understanding the mechanical response of an electrode during electrochemical cycling and its correlation to the device electrochemical performance is crucial to improving the performance of insertion-type energy storage devices, electrochemical actuators, water purification, ion separation and neuromorphic computing applications. In this work, we visualized the electro-chemo-mechanical coupling behaviors during charge storage of anhydrous and hydrated WO3 electrodes via in situ atomic force microscopy (AFM) and developed the concept of mechanical cyclic voltammetry (mCV) curves. The relationship between electrochemical current and strain was investigated with simplified models and the results revealed that the proton insertion/deinsertion process could be described through potential-dependent electro-chemo-mechanical coupling coefficients which might indicate changes in insertion processes during electrode cycling. The mCV mapping results highlight the local heterogeneity and show that the charging processes varied across the electrode. These local variations could be further correlated to local morphology, crystal orientations or chemical compositions with proper electrode designs.}, journal={NANO ENERGY}, author={Tsai, Wan-Yu and Wang, Ruocun and Boyd, Shelby and Augustyn, Veronica and Balke, Nina}, year={2021}, month={Mar} }
 @article{lynch_kelliher_anderson_japit_spencer_rizvi_sarac_augustyn_tracy_2021, title={Sulfidation and selenidation of nickel nanoparticles}, volume={3}, ISSN={["2637-9368"]}, url={https://doi.org/10.1002/cey2.83}, DOI={10.1002/cey2.83}, abstractNote={Abstract Transition metal chalcogenide nanoparticles (NPs) are of interest for energy applications, including batteries, supercapacitors, and electrocatalysis. Many methods have been established for synthesizing Ni NPs, and conversion chemistry to form Ni oxide and phosphides from template Ni NPs is well‐understood. Sulfidation and selenidation of Ni NPs have been much less explored, however. We report a method for the conversion of Ni template NPs into sulfide and selenide product NPs using elemental sulfur, 1‐hexadecanthiol, thiourea, trioctylphosphine sulfide, elemental selenium, and selenourea. While maintaining mole ratios of 2 mmol sulfur/selenium precursor: mmol Ni, products with phases of Ni 3 S 2 , Ni 9 S 8 , NiS, NiSO 4 ·6H 2 O, Ni 3 S 4 , Ni 3 Se 2 , and NiSe have been obtained. The products have voids that form through the Kirkendall effect during interdiffusion. Trends relating the chemical properties of the precursors to the phases of the products have been identified. While some precursors contained phosphorus, there was no significant incorporation of phosphorus in any of the products. An increase of the NP size during sulfidation and selenidation is consistent with ripening. The application of Ni sulfide and selenide NPs as electrocatalysts for the hydrogen evolution reaction is also demonstrated.}, number={4}, journal={CARBON ENERGY}, publisher={Wiley}, author={Lynch, Brian B. and Kelliher, Andrew P. and Anderson, Bryan D. and Japit, Alexander and Spencer, Michael A. and Rizvi, Mehedi H. and Sarac, Mehmet F. and Augustyn, Veronica and Tracy, Joseph B.}, year={2021}, month={Aug}, pages={582–589} }
 @article{spencer_yildiz_kamboj_bradford_augustyn_2021, title={Toward Deterministic 3D Energy Storage Electrode Architectures via Electrodeposition of Molybdenum Oxide onto CNT Foams}, volume={35}, ISSN={["1520-5029"]}, DOI={10.1021/acs.energyfuels.1c02352}, abstractNote={Three-dimensional (3D) deterministic design of electrodes could enable simultaneous high energy and power density for electrochemical energy storage devices. The goal of such electrode architectures is to provide adequate charge (electron and ion) transport pathways for high power, while maintaining high active material loading (>10 mg cm–2) for high areal and volumetric capacities. However, it remains a challenge to fabricate such electrodes with processes that are both scalable and reproducible. Toward this end, here, we demonstrate how the fabrication of such an electrode is made possible by combining tunable, free-standing, and aligned carbon nanotube (CNT) foams with aqueous electrodeposition of a model intercalation-type transition metal oxide, MoO3. Morphological characterization including X-ray microcomputed tomography indicates that the obtained composite is homogeneous. Electrodes with an active mass loading of up to 18 mg cm–2 reached near-theoretical Li-ion intercalation capacities within 1.7 h. The highest-mass loading electrodes also led to areal and volumetric capacities of 4.5 mA h cm–2 and 290 mA h cm–3, respectively, with 55% capacity retention for charge/discharge times of 10 min. Overall, this work demonstrates a scalable, deterministic 3D electrode design strategy using electrodeposition and free-standing, aligned CNT foams that lead to high areal and volumetric capacities and good rate performance due to well-distributed charge transport pathways.}, number={19}, journal={ENERGY & FUELS}, author={Spencer, Michael A. and Yildiz, Ozkan and Kamboj, Ishita and Bradford, Philip D. and Augustyn, Veronica}, year={2021}, month={Oct}, pages={16183–16193} }
 @article{saeed_boyd_tsai_wang_balke_augustyn_2021, title={Understanding electrochemical cation insertion into prussian blue from electrode deformation and mass changes}, volume={57}, ISSN={["1364-548X"]}, url={https://doi.org/10.1039/D1CC01681D}, DOI={10.1039/d1cc01681d}, abstractNote={Alkali ion insertion into Prussian blue from aqueous electrolytes is characterized with operando AFM and EQCM, showing coupling of current with deformation and mass change rates. Stable cycling occurs only with K+, attributed to its lower hydration energy. The (de)insertion of K+ results in reversible deformation even in the open framework structure.}, number={55}, journal={CHEMICAL COMMUNICATIONS}, publisher={Royal Society of Chemistry (RSC)}, author={Saeed, Saeed and Boyd, Shelby and Tsai, Wan-Yu and Wang, Ruocun and Balke, Nina and Augustyn, Veronica}, year={2021}, month={Jul}, pages={6744–6747} }
 @article{wang_boyd_bonnesen_augustyn_2020, title={Effect of water in a non-aqueous electrolyte on electrochemical Mg2+ insertion into WO3}, volume={477}, ISSN={["1873-2755"]}, DOI={10.1016/j.jpowsour.2020.229015}, abstractNote={Magnesium batteries are promising candidates for beyond lithium-ion batteries, but face several challenges including the need for solid state materials capable of reversible Mg2+ insertion. Of fundamental interest is the need to understand and improve the Mg2+ insertion kinetics of oxide-based cathode materials in non-aqueous electrolytes. The addition of water in non-aqueous electrolytes has been shown to improve the kinetics of Mg2+ insertion, but the mechanism and the effect of water concentration are still under debate. We investigate the systematic addition of water into a non-aqueous Mg electrolyte and its effect on Mg2+ insertion into WO3. We find that the addition of water leads to improvement in the Mg2+ insertion kinetics up to 6[H2O] : [Mg]2+. We utilize electrochemistry coupled to ex situ characterization to systematically explore four potential mechanisms for the electrochemical behavior: water co-insertion, proton (co)insertion, beneficial interphase formation, and water-enhanced surface diffusion. Based on these studies, we find that while proton co-insertion likely occurs, the dominant inserting species is Mg2+, and propose that the kinetic improvement upon water addition is due to enhanced surface diffusion of ions.}, journal={JOURNAL OF POWER SOURCES}, author={Wang, Ruocun and Boyd, Shelby and Bonnesen, Peter V and Augustyn, Veronica}, year={2020}, month={Nov} }
 @article{fleischmann_spencer_augustyn_2020, title={Electrochemical Reactivity under Confinement Enabled by Molecularly Pillared 2D and Layered Materials}, volume={32}, ISSN={["1520-5002"]}, DOI={10.1021/acs.chemmater.0c00648}, abstractNote={This perspective presents an overview of how confinement can be used to tune electrochemical reactivity and the concept of using molecularly pillared 2D and layered materials to experimentally stud...}, number={8}, journal={CHEMISTRY OF MATERIALS}, author={Fleischmann, Simon and Spencer, Michael A. and Augustyn, Veronica}, year={2020}, month={Apr}, pages={3325–3334} }
 @article{boyd_geise_toney_augustyn_2020, title={High Power Energy Storage via Electrochemically Expanded and Hydrated Manganese-Rich Oxides}, volume={8}, ISSN={["2296-2646"]}, DOI={10.3389/fchem.2020.00715}, abstractNote={Understanding the materials design features that lead to high power electrochemical energy storage is important for applications from electric vehicles to smart grids. Electrochemical capacitors offer a highly attractive solution for these applications, with energy and power densities between those of batteries and dielectric capacitors. To date, the most common approach to increase the capacitance of electrochemical capacitor materials is to increase their surface area by nanostructuring. However, nanostructured materials have several drawbacks including lower volumetric capacitance. In this work, we present a scalable “top-down” strategy for the synthesis of EC electrode materials by electrochemically expanding micron-scale high temperature-derived layered sodium manganese-rich oxides. We hypothesize that the electrochemical expansion induces two changes to the oxide that result in a promising electrochemical capacitor material: (1) interlayer hydration, which improves the interlayer diffusion kinetics and buffers intercalation-induced structural changes, and (2) particle expansion, which significantly improves electrode integrity and volumetric capacitance. When compared with a commercially available activated carbon for electrochemical capacitors, the expanded materials have higher volumetric capacitance at charge/discharge timescales of up to 40 s. This shows that expanded and hydrated manganese-rich oxide powders are viable candidates for electrochemical capacitor electrodes.}, journal={FRONTIERS IN CHEMISTRY}, author={Boyd, Shelby and Geise, Natalie R. and Toney, Michael F. and Augustyn, Veronica}, year={2020}, month={Aug} }
 @article{fleischmann_sun_osti_wang_mamontov_jiang_augustyn_2020, title={Interlayer Separation in Hydrogen Titanates Enables Electrochemical Proton Intercalation}, volume={8}, ISSN={["2050-7496"]}, DOI={10.1039/c9ta11098d}, abstractNote={Electrochemical proton intercalation into titanium oxides is typically limited to the near-surface region, necessitating the use of nanostructured high surface area materials to obtain high capacities. Here, we investigate the role of materials structure to extend intercalation beyond the near-surface region. Employing a series of hydrogen titanates (HTOs), we find that electrochemical protonation capacity significantly increases with interlayer structural protonation. The maximum capacity of ∼80 mA h g−1 is achieved with H2Ti3O7, which also undergoes reversible structural and optical changes during the de/intercalation process. Using quasi-elastic neutron scattering, we show that structural protons are highly confined in the HTO interlayer with only localized, but not translational, dynamics. Electrochemical protonation leads to a contraction of the H2Ti3O7 interlayer without causing significant strain in the two-dimensional titanate layers. Density functional theory calculations indicate more favorable adsorption energy for intercalated protons in H2Ti3O7 as compared to HTOs with fewer structural protons. We hypothesize that interlayer structural protons are the structural feature responsible for the high electrochemical protonation capacity in H2Ti3O7 because they effectively decrease the interconnections between the titanate layers. This enables facile compensation of the electrochemically introduced strain via one-dimensional interlayer contraction. These results demonstrate the special structural requirements for bulk proton intercalation in titanium oxides, and offer a new materials design strategy for high energy density aqueous energy storage.}, number={1}, journal={Journal of Materials Chemistry A}, author={Fleischmann, S. and Sun, Y. and Osti, N.C. and Wang, R. and Mamontov, E. and Jiang, D.E. and Augustyn, V.}, year={2020}, pages={412–421} }
 @misc{fleischmann_mitchell_wang_zhan_jiang_presser_augustyn_2020, title={Pseudocapacitance: From Fundamental Understanding to High Power Energy Storage Materials}, volume={120}, ISSN={["1520-6890"]}, DOI={10.1021/acs.chemrev.0c00170}, abstractNote={There is an urgent global need for electrochemical energy storage that includes materials that can provide simultaneous high power and high energy density. One strategy to achieve this goal is with pseudocapacitive materials that take advantage of reversible surface or near-surface Faradaic reactions to store charge. This allows them to surpass the capacity limitations of electrical double-layer capacitors and the mass transfer limitations of batteries. The past decade has seen tremendous growth in the understanding of pseudocapacitance as well as materials that exhibit this phenomenon. The purpose of this Review is to examine the fundamental development of the concept of pseudocapacitance and how it came to prominence in electrochemical energy storage as well as to describe new classes of materials whose electrochemical energy storage behavior can be described as pseudocapacitive.}, number={14}, journal={CHEMICAL REVIEWS}, author={Fleischmann, Simon and Mitchell, James B. and Wang, Ruocun and Zhan, Cheng and Jiang, De-en and Presser, Volker and Augustyn, Veronica}, year={2020}, month={Jul}, pages={6738–6782} }
 @article{mitchell_geise_paterson_osti_sun_fleischmann_zhang_madsen_toney_jiang_et al._2019, title={Confined Interlayer Water Promotes Structural Stability for High-Rate Electrochemical Proton Intercalation in Tungsten Oxide Hydrates}, ISSN={2380-8195 2380-8195}, url={http://dx.doi.org/10.1021/acsenergylett.9b02040}, DOI={10.1021/acsenergylett.9b02040}, abstractNote={There is widespread interest in determining the structural features of redox-active electrochemical energy storage materials that enable simultaneous high power and high energy density. Here, we pr...}, journal={ACS Energy Letters}, publisher={American Chemical Society (ACS)}, author={Mitchell, James B. and Geise, Natalie R. and Paterson, Alisa R. and Osti, Naresh C. and Sun, Yangyunli and Fleischmann, Simon and Zhang, Rui and Madsen, Louis A. and Toney, Michael F. and Jiang, De-en and et al.}, year={2019}, month={Nov}, pages={2805–2812} }
 @misc{spencer_augustyn_2019, title={Free-standing transition metal oxide electrode architectures for electrochemical energy storage}, volume={54}, ISSN={["1573-4803"]}, DOI={10.1007/s10853-019-03823-y}, number={20}, journal={JOURNAL OF MATERIALS SCIENCE}, author={Spencer, Michael A. and Augustyn, Veronica}, year={2019}, month={Oct}, pages={13045–13069} }
 @article{lebeau_dickey_augustyn_hesterberg_brown_2018, title={Acquisition of a microscope for in situ studies of hard and soft matter}, volume={24}, ISSN={1431-9276 1435-8115}, url={http://dx.doi.org/10.1017/S143192761801214X}, DOI={10.1017/S143192761801214X}, abstractNote={,}, number={S1}, journal={Microscopy and Microanalysis}, publisher={Cambridge University Press (CUP)}, author={LeBeau, James M. and Dickey, Elizabeth C. and Augustyn, Veronica and Hesterberg, Dean L. and Brown, Ashley C.}, year={2018}, month={Aug}, pages={2332–2333} }
 @article{boyd_dhall_lebeau_augustyn_2018, title={Charge storage mechanism and degradation of P2-type sodium transition metal oxides in aqueous electrolytes}, volume={6}, ISSN={["2050-7496"]}, DOI={10.1039/c8ta08367c}, abstractNote={Few transition metal oxides exhibit sufficient stability for aqueous ion intercalation from neutral pH electrolytes for low-cost aqueous Na+ batteries and battery-type desalinators. P2 layered Na+ manganese-rich oxides have high theoretical capacities and voltages for Na+ storage and are extensively investigated for non-aqueous Na+ batteries. However, the charge storage mechanism and factors controlling interlayer chemistry and redox behavior of these materials in aqueous electrolytes have not been determined. Here, we take a significant step in establishing their aqueous electrochemical behavior by investigating a series of P2 oxides that exhibit a range of stability in water and ambient air: Na0.62Ni0.22Mn0.66Fe0.10O2 (NaNMFe), Na0.61Ni0.22Mn0.66Co0.10O2 (NaNMCo), Na0.64Ni0.22Mn0.66Cu0.11O2 (NaNMCu), and Na0.64Mn0.62Cu0.31O2 (NaMCu). Depending on the transition metal composition and potential, all materials exhibit significant irreversible Na+ loss during the first anodic cycle followed by water intercalation into the interlayer. The presence of water causes conversion into birnessite-like phases and microscopic exfoliation of the particles. The interlayer affinity for water is primarily driven by the Na+ content, which can be tuned by the transition metal composition and the maximum anodic potential during electrochemical cycling. The interlayer water affects the reversible capacity and cycling stability of the oxides, with the highest reversible capacity (∼40 mA h g−1 delivered in ∼30 minutes) obtained with NaNMCo. These results present the first studies on the structural effects of aqueous electrochemistry in P2 oxides, highlight the significant differences in the electrochemical behavior of P2 oxides in aqueous vs. non-aqueous electrolytes, and provide guidance on how to use the transition metal chemistry to tune their aqueous charge storage behavior.}, number={44}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Boyd, Shelby and Dhall, Rohan and LeBeau, James M. and Augustyn, Veronica}, year={2018}, month={Nov}, pages={22266–22276} }
 @article{wang_mitchell_gao_tsai_boyd_pharr_balke_augustyn_2018, title={Operando Atomic Force Microscopy Reveals Mechanics of Structural Water Driven Battery-to-Pseudocapacitor Transition}, volume={12}, ISSN={["1936-086X"]}, url={http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=ORCID&SrcApp=OrcidOrg&DestLinkType=FullRecord&DestApp=WOS_CPL&KeyUT=WOS:000436910200101&KeyUID=WOS:000436910200101}, DOI={10.1021/acsnano.8b02273}, abstractNote={The presence of structural water in tungsten oxides leads to a transition in the energy storage mechanism from battery-type intercalation (limited by solid state diffusion) to pseudocapacitance (limited by surface kinetics). Here, we demonstrate that these electrochemical mechanisms are linked to the mechanical response of the materials during intercalation of protons and present a pathway to utilize the mechanical coupling for local studies of electrochemistry. Operando atomic force microscopy dilatometry is used to measure the deformation of redox-active energy storage materials and to link the local nanoscale deformation to the electrochemical redox process. This technique reveals that the local mechanical deformation of the hydrated tungsten oxide is smaller and more gradual than the anhydrous oxide and occurs without hysteresis during the intercalation and deintercalation processes. The ability of layered materials with confined structural water to minimize mechanical deformation likely contributes to their fast energy storage kinetics.}, number={6}, journal={ACS NANO}, publisher={American Chemical Society (ACS)}, author={Wang, Ruocun and Mitchell, James B. and Gao, Qiang and Tsai, Wan-Yu and Boyd, Shelby and Pharr, Matt and Balke, Nina and Augustyn, Veronica}, year={2018}, month={Jun}, pages={6032–6039} }
 @article{augustyn_mcdowell_vojvodic_2018, title={Toward an Atomistic Understanding of Solid-State Electrochemical Interfaces for Energy Storage}, volume={2}, ISSN={["2542-4351"]}, DOI={10.1016/j.joule.2018.10.014}, abstractNote={Veronica Augustyn is an Assistant Professor of Materials Science & Engineering at North Carolina State University. She received her PhD from the University of California, Los Angeles (2013) and was a Postdoctoral Fellow at the University of Texas at Austin (2013–2015). Her research is focused on the synthesis and characterization of materials operating at electrochemical interfaces, and in particular the relationships between material composition, structure, and morphology and the resulting electrochemical mechanisms. Recently, she was the recipient of a 2017 NSF CAREER Award and is a Scialog Fellow in Advanced Energy Storage at the Research Corporation for Science Advancement. Matthew McDowell is an assistant professor in the G.W. Woodruff School of Mechanical Engineering and the School of Materials Science and Engineering at the Georgia Institute of Technology. He received his PhD from Stanford University (2013) and was a postdoctoral scholar at Caltech from 2013 until 2015. His research is focused on understanding structural and chemical transformations in materials and at interfaces within electrochemical and electrical devices through the use of <i>in situ</i> and <i>operando</i> techniques. He has received the NSF CAREER Award, the AFOSR YIP Award, and the NASA Early Career Faculty Award and is a Scialog Fellow in Advanced Energy Storage. Aleksandra Vojvodic is Skirkanich Assistant Professor of Innovation in Chemical & Biomolecular Engineering at University of Pennsylvania. She received her PhD from Chalmers University of Technology, was Postdoc at Technical University of Denmark and Stanford University, and was Staff Scientist at SLAC National Accelerator Laboratory. Her research focuses on computational-driven materials design including studies of surfaces and interfaces of materials for chemical transformations, energy conversion, and storage. She received the 2017 European Federation of Catalysis Societies Young Researcher Award and the MIT Technology Review 35 Award 2016. She is a CIFAR Bio-Inspired Solar Energy fellow and a Scialog Fellow in Advanced Energy Storage.}, number={11}, journal={JOULE}, author={Augustyn, Veronica and McDowell, Matthew T. and Vojvodic, Aleksandra}, year={2018}, month={Nov}, pages={2189–2193} }
 @misc{boyd_augustyn_2018, title={Transition metal oxides for aqueous sodium-ion electrochemical energy storage}, volume={5}, ISSN={["2052-1553"]}, DOI={10.1039/c8qi00148k}, abstractNote={The electrochemical storage of sodium ions from aqueous electrolytes in transition metal oxides is of interest for energy and sustainability applications. These include low-cost and safe energy storage and energy-efficient water desalination. The strong interactions between water and transition metal oxide surfaces, as well as those between water and sodium ions, dictate the stability and electrochemical energy storage mechanisms in these materials. This review summarizes the implications of water as an electrolyte solvent for transition metal oxide electrodes, and sodium ion intercalation from neutral pH electrolytes into a diverse set of transition metal oxides. Increased control of the aqueous electrolyte/transition metal oxide interface is likely to lead to improvements in stability and capacity, which are critical breakthroughs for the implementation of transition metal oxides in aqueous sodium ion energy storage technologies.}, number={5}, journal={INORGANIC CHEMISTRY FRONTIERS}, author={Boyd, Shelby and Augustyn, Veronica}, year={2018}, month={May}, pages={999–1015} }
 @article{augustyn_gogotsi_2017, title={2D Materials with Nanoconfined Fluids for Electrochemical Energy Storage}, volume={1}, ISSN={["2542-4351"]}, DOI={10.1016/j.joule.2017.09.008}, abstractNote={<h2>Summary</h2> In the quest to develop energy storage with both high power and high energy densities, while maintaining high volumetric capacity, recent results show that a variety of 2D and layered materials exhibit rapid kinetics of ion transport by the incorporation of nanoconfined fluids.}, number={3}, journal={JOULE}, author={Augustyn, Veronica and Gogotsi, Yury}, year={2017}, month={Nov}, pages={443–452} }
 @article{wang_chung_liu_jones_augustyn_2017, title={Electrochemical Intercalation of Mg2+ into Anhydrous and Hydrated Crystalline Tungsten Oxides}, volume={33}, ISSN={0743-7463 1520-5827}, url={http://dx.doi.org/10.1021/acs.langmuir.7b00705}, DOI={10.1021/acs.langmuir.7b00705}, abstractNote={The reversible intercalation of multivalent cations, especially Mg2+, into a solid-state electrode is an attractive mechanism for next-generation energy storage devices. These reactions typically exhibit poor kinetics due to a high activation energy for interfacial charge-transfer and slow solid-state diffusion. Interlayer water in V2O5 and MnO2 has been shown to improve Mg2+ intercalation kinetics in nonaqueous electrolytes. Here, the effect of structural water on Mg2+ intercalation in nonaqueous electrolytes is examined in crystalline WO3 and the related hydrated and layered WO3·nH2O (n = 1, 2). Using thin film electrodes, cyclic voltammetry, Raman spectroscopy, X-ray diffraction, and electron microscopy, the energy storage in these materials is determined to involve reversible Mg2+ intercalation. It is found that the anhydrous WO3 can intercalate up to ∼0.3 Mg2+ (75 mAh g-1) and can maintain the monoclinic structure for at least 50 cycles at a cyclic voltammetry sweep rate of 0.1 mV s-1. The kinetics of Mg2+ storage in WO3 are limited by solid-state diffusion, which is similar to its behavior in a Li+ electrolyte. On the other hand, the maximum capacity for Mg2+ storage in WO3·nH2O is approximately half that of WO3 (35 mAh g-1). However, the kinetics of both Mg2+ and Li+ storage in WO3·nH2O are primarily limited by the interface and are thus pseudocapacitive. The stability of the structural water in WO3·nH2O varies: the interlayer water of WO3·2H2O is removed upon exposure to a nonaqueous electrolyte, while the water directly coordinated to W is stable during electrochemical cycling. These results demonstrate that tungsten oxides are potential candidates for Mg2+ cathodes, that in these materials structural water can lead to improved Mg2+ kinetics at the expense of capacity, and that the type of structural water affects stability.}, number={37}, journal={Langmuir}, publisher={American Chemical Society (ACS)}, author={Wang, Ruocun and Chung, Ching-Chang and Liu, Yang and Jones, Jacob L. and Augustyn, Veronica}, year={2017}, month={Jul}, pages={9314–9323} }
 @article{niu_mcferon_godinez-salomon_chapman_damin_tracy_augustyn_rhodes_2017, title={Enhanced Electrochemical Lithium-Ion Charge Storage of Iron Oxide Nanosheets}, volume={29}, ISSN={["1520-5002"]}, url={https://doi.org/10.1021/acs.chemmater.7b02315}, DOI={10.1021/acs.chemmater.7b02315}, abstractNote={Iron oxides are appealing cathode materials for low-cost electrochemical energy storage, but iron oxide nanoparticles (NPs) exhibit very low capacities, particularly at fast charging and discharging times, which are increasingly important for numerous applications. We report that synthesis and stabilization of iron oxide in nanosheets results in significantly improved lithium-ion charge storage capacities compared to those of iron oxide NPs at both slow and fast charging/discharging times. The iron oxide nanosheets have lateral dimensions of ∼50 nm and thicknesses of ∼1 nm and are composed of smaller crystallites. The structure of the nanosheets is consistent with maghemite, γ-Fe2O3, which contains cation defects. The γ-Fe2O3 phase is not typically observed within a nanosheet form, and γ-Fe2O3 nanosheets transform to NPs at a relatively low temperature of 200 °C. The transformation of γ-Fe2O3 from a nanosheet to an NP occurs in conjunction with removal of structural H2O. The γ-Fe2O3 nanosheets exhibited l...}, number={18}, journal={CHEMISTRY OF MATERIALS}, publisher={American Chemical Society (ACS)}, author={Niu, Sibo and McFeron, Ryan and Godinez-Salomon, Fernando and Chapman, Brian S. and Damin, Craig A. and Tracy, Joseph B. and Augustyn, Veronica and Rhodes, Christopher P.}, year={2017}, month={Sep}, pages={7794–7807} }
 @article{daubert_wang_ovental_barton_rajagopalan_augustyn_parsons_2017, title={Intrinsic limitations of atomic layer deposition for pseudocapacitive metal oxides in porous electrochemical capacitor electrodes}, volume={5}, ISSN={["2050-7496"]}, url={https://doi.org/10.1039/C7TA02719B}, DOI={10.1039/c7ta02719b}, abstractNote={By comparing the pseudocapacitive performance of ALD V2O5 in micro-, meso-, and macro-porous carbon electrodes, we describe the fundamental limits to ALD in very fine pores for pseudocapacitive charge storage. Comparing experimental trends with an ALD coating model, we find that the thermal V2O5 ALD process using vanadium triisopropoxide (VTIP) and water is unable to deposit in pores where the pore diameter is below a critical diameter of 13 A. By adding the ALD V2O5 layer onto activated carbon electrodes, we find that the energy storage capacity could be increased by 144% for carbon with micropores and macropores, whereas for carbon black powder containing only macropores (i.e. a low surface area resulting in a relatively small starting capacity) the ALD coating increased the capacity more than 40-fold. To understand the ALD coating limits, the pores of the carbon electrodes were modeled as a series of connected tubes, and the volume of V2O5 deposited determined experimentally was compared to the calculated deposition limit. Pores below this critical diameter were sealed and decreased the accessible volume for V2O5 deposition by more than half, decreasing the maximum capacity. The effect of the pore sealing by the ALD process on the capacitive response of the activated carbon based electrodes was also studied. This work highlights the intrinsic capabilities and limitations of coating microporous materials using ALD.}, number={25}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, publisher={Royal Society of Chemistry (RSC)}, author={Daubert, James S. and Wang, Ruocun and Ovental, Jennifer S. and Barton, Heather F. and Rajagopalan, Ramakrishnan and Augustyn, Veronica and Parsons, Gregory N.}, year={2017}, month={Jul}, pages={13086–13097} }
 @article{mitchell_lo_genc_lebeau_augustyn_2017, title={Transition from Battery to Pseudocapacitor Behavior via Structural Water in Tungsten Oxide}, volume={29}, ISSN={["1520-5002"]}, DOI={10.1021/acs.chemmater.6b05485}, abstractNote={The kinetics of energy storage in transition metal oxides are usually limited by solid-state diffusion, and the strategy most often utilized to improve their rate capability is to reduce ion diffusion distances by utilizing nanostructured materials. Here, another strategy for improving the kinetics of layered transition metal oxides by the presence of structural water is proposed. To investigate this strategy, the electrochemical energy storage behavior of a model hydrated layered oxide, WO3·2H2O, is compared with that of anhydrous WO3 in an acidic electrolyte. It is found that the presence of structural water leads to a transition from battery-like behavior in the anhydrous WO3 to ideally pseudocapacitive behavior in WO3·2H2O. As a result, WO3·2H2O exhibits significantly improved capacity retention and energy efficiency for proton storage over WO3 at sweep rates as fast as 200 mV s–1, corresponding to charge/discharge times of just a few seconds. Importantly, the energy storage of WO3·2H2O at such rates ...}, number={9}, journal={CHEMISTRY OF MATERIALS}, author={Mitchell, James B. and Lo, William C. and Genc, Arda and LeBeau, James and Augustyn, Veronica}, year={2017}, month={May}, pages={3928–3937} }
 @misc{augustyn_2017, title={Tuning the interlayer of transition metal oxides for electrochemical energy storage}, volume={32}, ISSN={["2044-5326"]}, DOI={10.1557/jmr.2016.337}, abstractNote={Layered transition metal oxides are some of the most important materials for high energy and power density electrochemical energy storage, such as batteries and electrochemical capacitors. These oxides can efficiently store charge via intercalation of ions into the interlayer vacant sites of the bulk material. The interlayer can be tuned to modify the electrochemical environment of the intercalating species to allow improved interfacial charge transfer and/or solid-state diffusion. The ability to fine-tune the solid-state environment for energy storage is highly beneficial for the design of layered oxides for specific mechanisms, including multivalent ion intercalation. This review focuses on the benefits as well as the methods for interlayer modification of layered oxides, which include the presence of structural water, solvent cointercalation and exchange, cation exchange, polymers, and small molecules, exfoliation, and exfoliated heterostructures. These methods are an important design tool for further development of layered oxides for electrochemical energy storage applications.}, number={1}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Augustyn, Veronica}, year={2017}, month={Jan}, pages={2–15} }
 @article{augustyn_manthiram_2015, title={Characterization of Layered LiMO2Oxides for the Oxygen Evolution Reaction of Metal-Air Batteries (M=Mn, Co, Ni)}, volume={80}, ISSN={2192-6506}, url={http://dx.doi.org/10.1002/cplu.201402107}, DOI={10.1002/cplu.201402107}, abstractNote={The behavior of layered LiMO2 (M=transition metal) oxides has been investigated systematically as a function of composition for the oxygen evolution reaction (OER) in alkaline electrolytes. The rich variety of LiMO2 compositions with the O3-type layered structure makes this class of materials an excellent testbed for understanding the effects of the nature and oxidation states of the transition-metal ions on the OER. Accordingly, the OER behaviors of a range of LiMO2 oxide solid solutions are presented here: LiCo1−xMnxO2, LiNi1−xMnxO2, and LiCo1−xNixO2 with 0.25≤x≤ 0.7. It is found that the OER activity increases with decreasing Mn content, and the Ni-rich compositions exhibit high OER activities. Furthermore, the pre-OER potential region displays contributions from surface faradaic reactions that involve Ni and Co. The overall higher activity of the Ni- and Co-rich compositions might be due to the in situ transformation of the LiMO2 surface into a highly active electrocatalyst.}, number={2}, journal={ChemPlusChem}, publisher={Wiley}, author={Augustyn, Veronica and Manthiram, Arumugam}, year={2015}, month={Feb}, pages={422–427} }
 @article{augustyn_manthiram_2015, title={Effects of Chemical versus Electrochemical Delithiation on the Oxygen Evolution Reaction Activity of Nickel-Rich Layered LiMO2}, volume={6}, ISSN={1948-7185}, url={http://dx.doi.org/10.1021/acs.jpclett.5b01538}, DOI={10.1021/acs.jpclett.5b01538}, abstractNote={Nickel-rich layered LiMO2 (M = transition metal) oxides doped with iron exhibit high oxygen evolution reaction (OER) activity in alkaline electrolytes. The LiMO2 oxides offer the possibility of investigating the influence of the number of d electrons on OER by tuning the oxidation state of M via chemical or electrochemical delithiation. Accordingly, we investigate here the electrocatalytic behavior of LiNi0.7Co0.3O2 and LiNi0.7Co0.2Fe0.1O2 before and after chemical delithiation. In addition to varying the oxidation state of the transition-metal ions, we find that chemical delithiation also affects the local chemical environment and morphology. The electrochemical response differs depending on whether the delithiation occurred ex situ chemically or in situ during the electrocatalysis. The results point to the important role of in situ transformation in LiMO2 in alkaline electrolytes during electrocatalytic cycling.}, number={19}, journal={The Journal of Physical Chemistry Letters}, publisher={American Chemical Society (ACS)}, author={Augustyn, Veronica and Manthiram, Arumugam}, year={2015}, month={Sep}, pages={3787–3791} }
 @article{colligan_augustyn_manthiram_2015, title={Evidence of Localized Lithium Removal in Layered and Lithiated Spinel Li1–xCoO2(0 ≤x≤ 0.9) under Oxygen Evolution Reaction Conditions}, volume={119}, ISSN={1932-7447 1932-7455}, url={http://dx.doi.org/10.1021/jp511176j}, DOI={10.1021/jp511176j}, abstractNote={The electrocatalytic oxygen evolution reaction performance of various forms of lithium cobalt oxide has been studied to systematically establish the surface-level catalytic mechanism. The low-temperature lithiated spinel form of LiCoO2 (designated as LT-LiCoO2) exhibits lower overpotentials than the high-temperature layered form of LiCoO2 (designated as HT-LiCoO2), but this is shown to be a result of the increased surface area afforded by lower-temperature synthesis conditions. Raman spectroscopy, along with the presence of an irreversible peak during the first cycle of the oxygen evolution reaction (OER), demonstrates that the mechanism for OER is the same for both the forms of LiCoO2. At the surface level, lithium is removed during the first cycle of the OER, forming Co3O4 on the surface, which is likely the active site during the OER. This work highlights the importance of determining the nature of the catalyst surface when investigating the electrocatalytic properties of bulk materials.}, number={5}, journal={The Journal of Physical Chemistry C}, publisher={American Chemical Society (ACS)}, author={Colligan, Nora and Augustyn, Veronica and Manthiram, Arumugam}, year={2015}, month={Jan}, pages={2335–2340} }
 @article{augustyn_therese_turner_manthiram_2015, title={Nickel-rich layered LiNi1−xMxO2(M = Mn, Fe, and Co) electrocatalysts with high oxygen evolution reaction activity}, volume={3}, ISSN={2050-7488 2050-7496}, url={http://dx.doi.org/10.1039/c5ta04637h}, DOI={10.1039/c5ta04637h}, abstractNote={An understanding of the materials characteristics that lead to high electrocatalytic activity for the oxygen evolution reaction (OER) is needed to make electrolytic hydrogen fuel production and rechargeable metal-air batteries a reality. Here, the first systematic investigation of a family of Ni-rich layered LiNi1−xMxO2 (M = Mn, Fe, and Co) oxides reveals that the catalytic activity can be tuned by varying the Ni content, nature of the transition-metal dopant, lithium content, and degree of cation ordering between Li and Ni/M. In particular, Fe-doping in LiNi1−xMxO2 imparts the most dramatic improvements in OER activity, possibly due to the flexibility of Fe to adopt different coordination geometries on the surface. X-ray photoelectron spectroscopic (XPS) data reveal that the surface of the Fe-doped sample is enriched with Fe while ex situ Raman spectroscopy indicates that the layered morphology is preserved during electrochemical cycling, but the cation disorder increases. Among the various LiNi1−xMxO2 compositions investigated, LiNi0.7Co0.3Fe0.2O2 exhibits the highest OER activity, which increases further when excess lithium and oxygen vacancies are present, and good stability. The Ni-rich LiNi1−xMxO2 samples join a growing number of highly active iron-doped systems for OER electrocatalysis in alkaline conditions.}, number={32}, journal={Journal of Materials Chemistry A}, publisher={Royal Society of Chemistry (RSC)}, author={Augustyn, Veronica and Therese, Soosairaj and Turner, Travis C. and Manthiram, Arumugam}, year={2015}, pages={16604–16612} }
 @article{come_augustyn_kim_rozier_taberna_gogotsi_long_dunn_simon_2014, title={Electrochemical Kinetics of Nanostructured Nb2O5Electrodes}, volume={161}, ISSN={0013-4651 1945-7111}, url={http://dx.doi.org/10.1149/2.040405jes}, DOI={10.1149/2.040405jes}, abstractNote={Pseudocapacitive charge storage is based on faradaic charge-transfer reactions occurring at the surface or near-surface of redox-active materials. This property is of great interest for electrochemical capacitors because of the substantially higher capacitance obtainable as compared to traditional double-layer electrode processes. While high levels of pseudocapacitance have been obtained with nanoscale materials, the development of practical electrode structures that exhibit pseudocapacitive properties has been challenging. The present paper shows that electrodes of Nb2O5 successfully retain the pseudocapacitive properties of the corresponding nanoscale materials. For charging times as fast as one minute, there is no indication of semi-infinite diffusion limitations and specific capacitances of 380 F g−1 and 0.46 F cm−2 are obtained in 40-μm thick electrodes at a mean discharge potential of 1.5 V vs Li+/Li. In-situ X-ray diffraction shows that the high specific capacitance and power capabilities of Nb2O5 electrodes can be attributed to fast Li+ intercalation within specific planes in the orthorhombic structure. This intercalation pseudocapacitance charge-storage mechanism is characterized as being an intrinsic property of Nb2O5 that facilitates the design of electrodes for capacitive storage devices. We demonstrate the efficacy of these electrodes in a hybrid electrochemical cell whose energy density and power density surpass that of commercial carbon-based devices.}, number={5}, journal={Journal of The Electrochemical Society}, publisher={The Electrochemical Society}, author={Come, Jérémy and Augustyn, Veronica and Kim, Jong Woung and Rozier, Patrick and Taberna, Pierre-Louis and Gogotsi, Pavel and Long, Jeffrey W. and Dunn, Bruce and Simon, Patrice}, year={2014}, pages={A718–A725} }
 @article{augustyn_white_ko_grüner_regan_dunn_2014, title={Lithium-ion storage properties of titanium oxide nanosheets}, volume={1}, ISSN={2051-6347 2051-6355}, url={http://dx.doi.org/10.1039/c3mh00070b}, DOI={10.1039/c3mh00070b}, abstractNote={A detailed kinetic analysis is used to determine the fundamental energy storage properties and rate capabilities of TiO2 nanosheets. These materials exhibit different properties compared to anatase nanocrystals including a shift to lower redox potentials for Li+ storage and the reversible charge storage of Na+. Nanosheets are intriguing for energy storage applications due to the fact that nearly the entire surface of the material, including specific crystal facets, can be exposed to the electrolyte.}, number={2}, journal={Mater. Horiz.}, publisher={Royal Society of Chemistry (RSC)}, author={Augustyn, Veronica and White, Edward R. and Ko, Jesse and Grüner, George and Regan, Brian C. and Dunn, Bruce}, year={2014}, pages={219–223} }
 @article{rauda_augustyn_saldarriaga-lopez_chen_schelhas_rubloff_dunn_tolbert_2014, title={Nanostructured Pseudocapacitors Based on Atomic Layer Deposition of V2O5onto Conductive Nanocrystal-based Mesoporous ITO Scaffolds}, volume={24}, ISSN={1616-301X}, url={http://dx.doi.org/10.1002/adfm.201401284}, DOI={10.1002/adfm.201401284}, abstractNote={Solution processing of colloidal nanocrystals into porous architectures using block co‐polymer templating offers a simple yet robust route to construct materials with open porosity and high surface area. These features, when realized in materials that show efficient redox activity and good conductivity, should be ideal for electrochemical energy storage because they allow for efficient electrolyte diffusion and ample surface and near‐surface redox reactions. Here, a route to synthesize nanoporous pseudocapacitors is presented using preformed ITO nanocrystals to make a conductive scaffold, coated with a conformal layer of vanadia deposited using atomic layer deposition (ALD). Two vanadia thicknesses are deposited, 2 and 7 nm, to examine the kinetics of Li+ diffusion into vanadia in a system where all other chemical and structural parameters are fixed. Porosity measurements show that the internal surface area of 2 nm vanadia samples is fully accessible; whereas for the 7 nm vanadia, there is some pore blockage that limits electrolyte diffusion. Despite this fact, composites with both thick and thin vanadia layers show high levels of pseudocapacitance, indicating fast diffusion of Li+ through even the 7 nm thick vanadia. This work thus sets a minimum accessible length‐scale of 7 nm for intercalation pseudocapacitance in orthorhombic V2O5.}, number={42}, journal={Advanced Functional Materials}, publisher={Wiley}, author={Rauda, Iris E. and Augustyn, Veronica and Saldarriaga-Lopez, Laura C. and Chen, Xinyi and Schelhas, Laura T. and Rubloff, Gary W. and Dunn, Bruce and Tolbert, Sarah H.}, year={2014}, month={Sep}, pages={6717–6728} }
 @article{augustyn_simon_dunn_2014, title={Pseudocapacitive oxide materials for high-rate electrochemical energy storage}, volume={7}, ISSN={1754-5692 1754-5706}, url={http://dx.doi.org/10.1039/c3ee44164d}, DOI={10.1039/c3ee44164d}, abstractNote={Electrochemical energy storage technology is based on devices capable of exhibiting high energy density (batteries) or high power density (electrochemical capacitors). There is a growing need, for current and near-future applications, where both high energy and high power densities are required in the same material. Pseudocapacitance, a faradaic process involving surface or near surface redox reactions, offers a means of achieving high energy density at high charge–discharge rates. Here, we focus on the pseudocapacitive properties of transition metal oxides. First, we introduce pseudocapacitance and describe its electrochemical features. Then, we review the most relevant pseudocapacitive materials in aqueous and non-aqueous electrolytes. The major challenges for pseudocapacitive materials along with a future outlook are detailed at the end.}, number={5}, journal={Energy & Environmental Science}, publisher={Royal Society of Chemistry (RSC)}, author={Augustyn, Veronica and Simon, Patrice and Dunn, Bruce}, year={2014}, pages={1597} }
 @article{rauda_augustyn_dunn_tolbert_2013, title={Enhancing Pseudocapacitive Charge Storage in Polymer Templated Mesoporous Materials}, volume={46}, ISSN={0001-4842 1520-4898}, url={http://dx.doi.org/10.1021/ar300167h}, DOI={10.1021/ar300167h}, abstractNote={Growing global energy demands coupled with environmental concerns have increased the need for renewable energy sources. For intermittent renewable sources like solar and wind to become available on demand will require the use of energy storage devices. Batteries and supercapacitors, also known as electrochemical capacitors (ECs), represent the most widely used energy storage devices. Supercapacitors are frequently overlooked as an energy storage technology, however, despite the fact that these devices provide greater power, much faster response times, and longer cycle life than batteries. Their limitation is that the energy density of ECs is significantly lower than that of batteries, and this has limited their potential applications. This Account reviews our recent work on improving pseudocapacitive energy storage performance by tailoring the electrode architecture. We report our studies of mesoporous transition metal oxide architectures that store charge through surface or near-surface redox reactions, a phenomenon termed pseudocapacitance. The faradaic nature of pseudocapacitance leads to significant increases in energy density and thus represents an exciting future direction for ECs. We show that both the choice of material and electrode architecture is important for producing the ideal pseudocapacitor device. Here we first briefly review the current state of electrode architectures for pseudocapacitors, from slurry electrodes to carbon/metal oxide composites. We then describe the synthesis of mesoporous films made with amphiphilic diblock copolymer templating agents, specifically those optimized for pseudocapacitive charge storage. These include films synthesized from nanoparticle building blocks and films made from traditional battery materials. In the case of more traditional battery materials, we focus on using flexible architectures to minimize the strain associated with lithium intercalation, that is, the accumulation of lithium ions or atoms between the layers of cathode or anode materials that occurs as batteries charge and discharge. Electrochemical analysis of these mesoporous films allows for a detailed understanding of the origin of charge storage by separating capacitive contributions from traditional diffusion-controlled intercalation processes. We also discuss methods to separate the two contributions to capacitance: double-layer capacitance and pseudocapacitance. Understanding these contributions should allow the selection of materials with an optimized architecture that maximize the contribution from pseudocapacitance. From our studies, we show that nanocrystal-based nanoporous materials offer an architecture optimized for high levels of redox or surface pseudocapacitance. Interestingly, in some cases, materials engineered to minimize the strain associated with lithium insertion can also show intercalation pseudocapacitance, which is a process where insertion processes become so kinetically facile that they appear capacitive. Finally, we conclude with a summary of simple design rules that should result in high-power, high-energy-density electrode architectures. These design rules include assembling small, nanosized building blocks to maximize electrode surface area; maintaining an interconnected, open mesoporosity to facilitate solvent diffusion; seeking flexibility in electrode structure to facilitate volume expansion during lithium insertion; optimizing crystalline domain size and orientation; and creating effective electron transport pathways.}, number={5}, journal={Accounts of Chemical Research}, publisher={American Chemical Society (ACS)}, author={Rauda, Iris E. and Augustyn, Veronica and Dunn, Bruce and Tolbert, Sarah H.}, year={2013}, month={Mar}, pages={1113–1124} }
 @article{augustyn_come_lowe_kim_taberna_tolbert_abruña_simon_dunn_2013, title={High-rate electrochemical energy storage through Li+ intercalation pseudocapacitance}, volume={12}, ISSN={1476-1122 1476-4660}, url={http://dx.doi.org/10.1038/nmat3601}, DOI={10.1038/nmat3601}, abstractNote={Pseudocapacitance is commonly associated with surface or near-surface reversible redox reactions. The kinetics of charge storage in T-Nb2O5 electrodes is now quantified and the mechanism of lithium intercalation pseudocapacitance should prove to be important in obtaining high-rate charge-storage devices. Pseudocapacitance is commonly associated with surface or near-surface reversible redox reactions, as observed with RuO2· xH2O in an acidic electrolyte. However, we recently demonstrated that a pseudocapacitive mechanism occurs when lithium ions are inserted into mesoporous and nanocrystal films of orthorhombic Nb2O5 (T-Nb2O5; refs 1, 2). Here, we quantify the kinetics of charge storage in T-Nb2O5: currents that vary inversely with time, charge-storage capacity that is mostly independent of rate, and redox peaks that exhibit small voltage offsets even at high rates. We also define the structural characteristics necessary for this process, termed intercalation pseudocapacitance, which are a crystalline network that offers two-dimensional transport pathways and little structural change on intercalation. The principal benefit realized from intercalation pseudocapacitance is that high levels of charge storage are achieved within short periods of time because there are no limitations from solid-state diffusion. Thick electrodes (up to 40 μm thick) prepared with T-Nb2O5 offer the promise of exploiting intercalation pseudocapacitance to obtain high-rate charge-storage devices.}, number={6}, journal={Nature Materials}, publisher={Springer Science and Business Media LLC}, author={Augustyn, Veronica and Come, Jérémy and Lowe, Michael A. and Kim, Jong Woung and Taberna, Pierre-Louis and Tolbert, Sarah H. and Abruña, Héctor D. and Simon, Patrice and Dunn, Bruce}, year={2013}, month={Apr}, pages={518–522} }
 @article{augustyn_dunn_2013, title={Low-potential lithium-ion reactivity of vanadium oxide aerogels}, volume={88}, ISSN={0013-4686}, url={http://dx.doi.org/10.1016/j.electacta.2012.10.145}, DOI={10.1016/j.electacta.2012.10.145}, abstractNote={Vanadium oxide aerogels are electrochemically lithiated to 0.1 V vs. Li/Li+, yielding reversible capacities of ∼1000 mAh g−1 at charge/discharge rates of C/10. This reversible behavior is significantly different from crystalline orthorhombic V2O5, which exhibits a constantly decreasing capacity with cycling. The ability of the aerogel material to be deeply cycled lies in its unique morphology: high surface area, interconnected porosity, and a fibrous network structure enable lithium storage to occur. Ex situ TEM and XPS measurements indicate, respectively, that the fibrous morphology is retained at low potentials and that the oxidation state of vanadium changes from +5 to +2 during the electrochemical cycling.}, journal={Electrochimica Acta}, publisher={Elsevier BV}, author={Augustyn, Veronica and Dunn, Bruce}, year={2013}, month={Jan}, pages={530–535} }
 @article{rauda_buonsanti_saldarriaga-lopez_benjauthrit_schelhas_stefik_augustyn_ko_dunn_wiesner_et al._2012, title={General Method for the Synthesis of  Hierarchical Nanocrystal-Based Mesoporous Materials}, volume={6}, ISSN={1936-0851 1936-086X}, url={http://dx.doi.org/10.1021/nn302789r}, DOI={10.1021/nn302789r}, abstractNote={Block copolymer templating of inorganic materials is a robust method for the production of nanoporous materials. The method is limited, however, by the fact that the molecular inorganic precursors commonly used generally form amorphous porous materials that often cannot be crystallized with retention of porosity. To overcome this issue, here we present a general method for the production of templated mesoporous materials from preformed nanocrystal building blocks. The work takes advantage of recent synthetic advances that allow organic ligands to be stripped off of the surface of nanocrystals to produce soluble, charge-stabilized colloids. Nanocrystals then undergo evaporation-induced co-assembly with amphiphilic diblock copolymers to form a nanostructured inorganic/organic composite. Thermal degradation of the polymer template results in nanocrystal-based mesoporous materials. Here, we show that this method can be applied to nanocrystals with a broad range of compositions and sizes, and that assembly of nanocrystals can be carried out using a broad family of polymer templates. The resultant materials show disordered but homogeneous mesoporosity that can be tuned through the choice of template. The materials also show significant microporosity, formed by the agglomerated nanocrystals, and this porosity can be tuned by the nanocrystal size. We demonstrate through careful selection of the synthetic components that specifically designed nanostructured materials can be constructed. Because of the combination of open and interconnected porosity, high surface area, and compositional tunability, these materials are likely to find uses in a broad range of applications. For example, enhanced charge storage kinetics in nanoporous Mn(3)O(4) is demonstrated here.}, number={7}, journal={ACS Nano}, publisher={American Chemical Society (ACS)}, author={Rauda, Iris E. and Buonsanti, Raffaella and Saldarriaga-Lopez, Laura C. and Benjauthrit, Kanokraj and Schelhas, Laura T. and Stefik, Morgan and Augustyn, Veronica and Ko, Jesse and Dunn, Bruce and Wiesner, Ulrich and et al.}, year={2012}, month={Jul}, pages={6386–6399} }
 @article{chen_augustyn_jia_xiao_dunn_lu_2012, title={High-Performance Sodium-Ion Pseudocapacitors Based on Hierarchically Porous Nanowire Composites}, volume={6}, ISSN={1936-0851 1936-086X}, url={http://dx.doi.org/10.1021/nn300920e}, DOI={10.1021/nn300920e}, abstractNote={Electrical energy storage plays an increasingly important role in modern society. Current energy storage methods are highly dependent on lithium-ion energy storage devices, and the expanded use of these technologies is likely to affect existing lithium reserves. The abundance of sodium makes Na-ion-based devices very attractive as an alternative, sustainable energy storage system. However, electrodes based on transition-metal oxides often show slow kinetics and poor cycling stability, limiting their use as Na-ion-based energy storage devices. The present paper details a new direction for electrode architectures for Na-ion storage. Using a simple hydrothermal process, we synthesized interpenetrating porous networks consisting of layer-structured V(2)O(5) nanowires and carbon nanotubes (CNTs). This type of architecture provides facile sodium insertion/extraction and fast electron transfer, enabling the fabrication of high-performance Na-ion pseudocapacitors with an organic electrolyte. Hybrid asymmetric capacitors incorporating the V(2)O(5)/CNT nanowire composites as the anode operated at a maximum voltage of 2.8 V and delivered a maximum energy of ∼40 Wh kg(-1), which is comparable to Li-ion-based asymmetric capacitors. The availability of capacitive storage based on Na-ion systems is an attractive, cost-effective alternative to Li-ion systems.}, number={5}, journal={ACS Nano}, publisher={American Chemical Society (ACS)}, author={Chen, Zheng and Augustyn, Veronica and Jia, Xilai and Xiao, Qiangfeng and Dunn, Bruce and Lu, Yunfeng}, year={2012}, month={Apr}, pages={4319–4327} }
 @article{white_singer_augustyn_hubbard_mecklenburg_dunn_regan_2012, title={In Situ Transmission Electron Microscopy of Lead Dendrites and Lead Ions in Aqueous Solution}, volume={6}, ISSN={1936-0851 1936-086X}, url={http://dx.doi.org/10.1021/nn3017469}, DOI={10.1021/nn3017469}, abstractNote={An ideal technique for observing nanoscale assembly would provide atomic-resolution images of both the products and the reactants in real time. Using a transmission electron microscope we image in situ the electrochemical deposition of lead from an aqueous solution of lead(II) nitrate. Both the lead deposits and the local Pb(2+) concentration can be visualized. Depending on the rate of potential change and the potential history, lead deposits on the cathode in a structurally compact layer or in dendrites. In both cases the deposits can be removed and the process repeated. Asperities that persist through many plating and stripping cycles consistently nucleate larger dendrites. Quantitative digital image analysis reveals excellent correlation between changes in the Pb(2+) concentration, the rate of lead deposition, and the current passed by the electrochemical cell. Real-time electron microscopy of dendritic growth dynamics and the associated local ionic concentrations can provide new insight into the functional electrochemistry of batteries and related energy storage technologies.}, number={7}, journal={ACS Nano}, publisher={American Chemical Society (ACS)}, author={White, Edward R. and Singer, Scott B. and Augustyn, Veronica and Hubbard, William A. and Mecklenburg, Matthew and Dunn, Bruce and Regan, Brian C.}, year={2012}, month={Jun}, pages={6308–6317} }
 @article{hmadeh_lu_liu_gándara_furukawa_wan_augustyn_chang_liao_zhou_et al._2012, title={New Porous Crystals of Extended Metal-Catecholates}, volume={24}, ISSN={0897-4756 1520-5002}, url={http://dx.doi.org/10.1021/cm301194a}, DOI={10.1021/cm301194a}, abstractNote={Mohamad Hmadeh,†,‡ Zheng Lu,†,‡ Zheng Liu, Felipe Gandara,†,‡ Hiroyasu Furukawa,†,‡ Shun Wan,†,‡ Veronica Augustyn, Rui Chang, Lei Liao,‡ Fei Zhou, Emilie Perre, Vidvuds Ozolins, Kazu Suenaga, Xiangfeng Duan,‡ Bruce Dunn, Yasuaki Yamamto, Osamu Terasaki, and Omar M. Yaghi*,†,‡,#,¶ †Center for Reticular Chemistry, Center for Global Mentoring, ‡Department of Chemistry and Biochemistry, and Department of Materials Science and Engineering, University of California, Los Angeles, California 90095, United States Nanotube Research Center, AIST, Tsukuba 305-8565, Japan SMBU, JEOL Ltd., Akishima, Tokyo 196-8558, Japan Department of Materials and Environmental Chemistry and EXSELENT, Stockholm University, Stockholm, Sweden Graduate School of EEWS (WCU), Korea}, number={18}, journal={Chemistry of Materials}, publisher={American Chemical Society (ACS)}, author={Hmadeh, Mohamad and Lu, Zheng and Liu, Zheng and Gándara, Felipe and Furukawa, Hiroyasu and Wan, Shun and Augustyn, Veronica and Chang, Rui and Liao, Lei and Zhou, Fei and et al.}, year={2012}, month={Aug}, pages={3511–3513} }
 @article{chen_augustyn_wen_zhang_shen_dunn_lu_2011, title={High-Performance Supercapacitors Based on Intertwined CNT/V2O5 Nanowire Nanocomposites}, volume={23}, ISSN={0935-9648}, url={http://dx.doi.org/10.1002/adma.201003658}, DOI={10.1002/adma.201003658}, abstractNote={An ideal electrical energy storage device provides both high energy and power density. [ 1 , 2 ] Supercapacitors exhibit signifi cantly higher power densities compared to batteries and would be excellent candidates for numerous electronic devices and industrial applications if their energy density could be improved. [ 3 , 4 ] Since the energy density ( E ) of a capacitor is governed by E = 1/2 CV 2 , where C is the capacitance and V is the cell potential, increasing the potential or capacitance leads to higher energy density. [ 5 ] In this context, the most commonly used electrode material (porous carbon) generally possesses double layer capacitances of around 100 F g − 1 , which can provide a specifi c energy density up to 25 Wh kg − 1 in an organic-electrolyte-based symmetric device. Somewhat greater energy densities can be reached as specifi c capacitances of up to 150 F g − 1 with carbide-derived carbon have been reported. [ 6 ]}, number={6}, journal={Advanced Materials}, publisher={Wiley}, author={Chen, Zheng and Augustyn, Veronica and Wen, Jing and Zhang, Yuewei and Shen, Meiqing and Dunn, Bruce and Lu, Yunfeng}, year={2011}, month={Feb}, pages={791–795} }
 @article{wang_li_chen_augustyn_ma_wang_dunn_lu_2011, title={High-Performance Supercapacitors Based on Nanocomposites of Nb2O5 Nanocrystals and Carbon Nanotubes}, volume={1}, ISSN={1614-6832}, url={http://dx.doi.org/10.1002/aenm.201100332}, DOI={10.1002/aenm.201100332}, abstractNote={Compared with batteries, supercapacitors often deliver signifi cantly higher power densities with longer cycling life but lower energy densities. Developing supercapacitors with improved energy density therefore becomes a highly attractive topic. Generally, energy densities of supercapacitors ( E ) are determined by E = 1⁄2 CV 2 , where C is the cell capacitance and V is the cell potential; higher cell voltage and capacitance lead to higher energy density. [ 3 ] Porous carbon, the most commonly used electrode material, possesses a double layer capacitance of 100 ∼ 150 F g − 1 in organic electrolyte, while transition metal oxides may exhibit signifi cantly higher pseudo-capacitances. Designing asymmetric supercapacitors consisting of a carbon cathode and a transition-metal-oxide anode is therefore considered as the most effective solution. [ 4 ] For instance, asymmetric cells based on Li 4 Ti 5 O 12 anode and activated carbon cathode can achieve an energy density of 40 Wh kg − 1 in organic electrolyte system, [ 5 , 6 ] which is much higher than those of carbon-based symmetric devices. Seeking better anode materials with high specifi c capacitance, low working potential, and long cycling stability therefore becomes a main theme of the fi eld. Compared with Li 4 Ti 5 O 12 with a working potential of 1.5 V and a specifi c capacity of 140 mA h g − 1 , [ 7 ] niobium pentoxide (Nb 2 O 5 ) exhibits a higher capacity ( ∼ 200 mA h g − 1 ) and a}, number={6}, journal={Advanced Energy Materials}, publisher={Wiley}, author={Wang, Xiaolei and Li, Ge and Chen, Zheng and Augustyn, Veronica and Ma, Xueming and Wang, Ge and Dunn, Bruce and Lu, Yunfeng}, year={2011}, month={Oct}, pages={1089–1093} }
 @article{kim_augustyn_dunn_2011, title={The Effect of Crystallinity on the Rapid Pseudocapacitive Response of Nb2O5}, volume={2}, ISSN={1614-6832}, url={http://dx.doi.org/10.1002/aenm.201100494}, DOI={10.1002/aenm.201100494}, abstractNote={Capacitive energy storage offers several attractive properties compared to batteries, including higher power, faster charging, and a longer cycle life. A key limitation to this electrochemical energy‐storage approach is its low energy density and, for this reason, there is considerable interest in identifying pseudocapacitor materials where faradaic reactions are used to achieve greater charge storage. This paper reports on the electrochemical properties of Nb2O5 and establishes that crystalline phases of the material undergo fast faradaic reactions that lead to high specific capacitance in short charging times. In particular, the specific capacitance for the orthorhombic phase at infinite sweep rate reaches ≈400 F g−1, which exceeds that of birnessite MnO2 in nonaqueous electrolyte and is comparable to RuO2 at the same extrapolated rate. The specific capacitances of the orthorhombic and pseudohexagonal phases are much greater than that of the amorphous phase, suggesting that the faradaic reactions which lead to additional capacitive energy storage are associated with Li+ insertion along preferred crystallographic pathways. The ability for Nb2O5 to store charge at high rates despite its wide bandgap and low electronic conductivity is very different from what is observed with other transition metal oxides.}, number={1}, journal={Advanced Energy Materials}, publisher={Wiley}, author={Kim, Jong Woung and Augustyn, Veronica and Dunn, Bruce}, year={2011}, month={Dec}, pages={141–148} }
 @article{augustyn_dunn_2010, title={Vanadium oxide aerogels: Nanostructured materials for enhanced energy storage}, volume={13}, ISSN={1631-0748}, url={http://dx.doi.org/10.1016/j.crci.2009.05.002}, DOI={10.1016/j.crci.2009.05.002}, abstractNote={The synthesis, chemistry, local structure and electrochemical properties of vanadium oxide xerogels and aerogels have much in common. The one difference in their respective synthesis routes, the means by which solvent is removed, has a significant influence on the resulting morphology. The high surface area, nanodimensional solid phase, short diffusion paths and interconnected mesoporosity of the aerogels exert a profound effect on their electrochemical properties. Our studies with V2O5 aerogels show that these materials offer the promise of achieving both high energy density and high power density because of a pseudocapacitive charge storage mechanism which develops.}, number={1-2}, journal={Comptes Rendus Chimie}, publisher={Elsevier BV}, author={Augustyn, Veronica and Dunn, Bruce}, year={2010}, month={Jan}, pages={130–141} }