@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} }
 @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{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} }
 @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{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{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} }