Elucidating the Origin of the Electrochemical Capacity in a Proton-Based Battery HxIrO4 via Advanced Electrogravimetry

Recently, because of sustainability issues dictated by societal demands, more importance has been given to aqueous systems and especially to proton-based battery. However, the mechanisms behind the processes leading to energy storage in such systems are still not elucidated. Under this scope, our study is structured on the selection of a model electrode material, the protonic phase HxIrO4 and the scrutiny of the interfacial processes through suitable analytical tools. Herein, we employed operando Electrochemical Quartz Crystal Microbalance (EQCM) combined with Electrochemical Impedance Spectroscopy (EIS) to provide new insights into the mechanism intervening at the Electrode-Electrolyte Interface. Firstly, we demonstrated that not only the surface or near surface but the whole particle participates in the cationic redox process. Secondly, we proved the contribution of the proton on the overall potential window together with the incorporation of water at low potentials solely. This is explained by the fact...