@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{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={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} }