@article{li_abdelgaid_paudel_holzapfel_augustyn_mckone_mpourmpakis_crumlin_2025, title={<i>Operando</i> Unveiling of Hydrogen Spillover Mechanisms on Tungsten Oxide Surfaces}, ISSN={["1520-5126"]}, DOI={10.1021/jacs.4c13711}, abstractNote={Hydrogen spillover is an important process in catalytic hydrogenation reactions, facilitating H2 activation and modulating surface chemistry of reducible oxide catalysts. This study focuses on the operando unveiling of platinum-induced hydrogen spillover on monoclinic tungsten trioxide (γ-WO3), employing ambient pressure X-ray photoelectron spectroscopy, density functional theory calculations and microkinetic modeling to investigate the dynamic evolution of surface states at varied temperatures. At room temperature, hydrogen spillover results in the formation of W5+ and hydrogen intermediates (hydroxyl species and adsorbed water), facilitated by Pt metal clusters. With increasing temperature, water desorption, reverse hydrogen spillover and surface-to-bulk diffusion of hydrogen atoms compete with each other, leading initially to reoxidation and then further reduction of W atoms in the near-surface. The combined experimental results and simulations provide a comprehensive understanding of the mechanisms underlying hydrogen interaction with reducible metal oxides, lending insights of relevance to the design of enhanced hydrogenation catalysts.}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Li, Haoyi and Abdelgaid, Mona and Paudel, Jay R. and Holzapfel, Noah P. and Augustyn, Veronica and Mckone, James R. and Mpourmpakis, Giannis and Crumlin, Ethan J.}, year={2025}, month={Jan} }
 @article{holzapfel_augustyn_balland_2025, title={Fundamentals of Proton-Insertion Coupled Electron Transfer (PICET) in Metal Oxides for Aqueous Batteries}, ISSN={["2380-8195"]}, DOI={10.1021/acsenergylett.4c03076}, journal={ACS ENERGY LETTERS}, author={Holzapfel, Noah P. and Augustyn, Veronica and Balland, Veronique}, year={2025}, month={Feb} }
 @article{ding_spencer_holzapfel_chagnot_augustyn_2025, title={Interlayer pillaring influences the octahedral tilting and electrochemical capacity of tungsten oxides}, ISSN={["2050-7496"]}, DOI={10.1039/d4ta08647c}, abstractNote={Pillaring tungsten oxides with alkylammonium cations increases the interlayer spacing but decreases the band gap, leading to low electrochemical capacity.}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Ding, Ran and Spencer, Michael A. and Holzapfel, Noah P. and Chagnot, Matthew and Augustyn, Veronica}, year={2025}, month={Feb} }
 @article{holzapfel_augustyn_2025, title={Protons undermine lithium-ion batteries with positively disastrous results}, volume={17}, ISSN={["1755-4349"]}, DOI={10.1038/s41557-025-01733-y}, number={2}, journal={NATURE CHEMISTRY}, author={Holzapfel, Noah P. and Augustyn, Veronica}, year={2025}, month={Feb}, pages={163–164} }
 @article{saeed_fleischmann_kobayashi_jusys_mamontov_osti_holzapfel_song_wang_dai_et al._2024, title={Oxide Acidity Modulates Structural Transformations in Hydrogen Titanates during Electrochemical Li-Ion Insertion}, ISSN={["1520-5126"]}, DOI={10.1021/jacs.4c08063}, abstractNote={Hydrogen titanates (HTOs) form a diverse group of metastable, layered titanium oxides with an interlayer containing both water molecules and structural protons. We investigated how the chemistry of this interlayer environment influenced electrochemical Li}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Saeed, Saeed and Fleischmann, Simon and Kobayashi, Takeshi and Jusys, Zenonas and Mamontov, Eugene and Osti, Naresh C. and Holzapfel, Noah P. and Song, Haohong and Wang, Tao and Dai, Sheng and et al.}, year={2024}, month={Oct} }
 @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={Tungsten oxides undergo a significant increase in their hydrogen evolution reaction activity upon proton-insertion coupled electron transfer.}, 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{holzapfel_chagnot_abdar_paudel_crumlin_mckone_augustyn_2024, title={Solution-Phase Synthesis of Platinum-Decorated Hydrogen Tungsten Bronzes for Hydrogen Atom Transfer from Oxides to Molecules}, ISSN={["1520-5002"]}, DOI={10.1021/acs.chemmater.4c02814}, abstractNote={Hydrogen bronzes can be used as hydrogen donors for the broad class of reactions involving proton-coupled electron transfer (PCET). Here, we describe a method to prepare platinum-decorated hydrogen tungsten bronzes, Pt@HxWO3·nH2O with n = 0, 1, and 2, by reacting the pristine oxides at modest temperatures with a mild reducing agent, H3PO2, and H2PtCl6 in an aqueous solution. We explored the tunability and kinetics of this reaction and compared it with that of archetypal gas–solid hydrogen spillover. We demonstrate that the identity of the noble metal affects the extent of bronze reduction. This suggests that the mechanism proceeds via the adsorption of a hydrogen-atom species on the noble metal. Finally, we explored the ability of the Pt-decorated hydrogen tungsten bronzes to hydrogenate a model H+/e– acceptor, 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO). The bronze phases return to their fully oxidized states along with the subsequent reduction of TEMPO to TEMPOH. Overall, this work demonstrates a solution-phase method to obtain hydrogen bronzes, which can then be used to perform hydrogen transfer reactions, providing a pathway for the use of extended transition metal oxides as stoichiometric reagents for broad classes of hydrogenation reactions.}, journal={CHEMISTRY OF MATERIALS}, author={Holzapfel, Noah P. and Chagnot, Matthew and Abdar, Payman Sharifi and Paudel, Jay R. and Crumlin, Ethan J. and Mckone, James R. and Augustyn, Veronica}, year={2024}, month={Nov} }
 @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} }