Proton-Coupled Electrochemistry of Metal Oxides—From Insertion to Interfacial Phenomena

Aqueous energy storage devices utilizing transition metal oxide electrodes are attractive for large scale energy storage applications. The electrochemistry of transition metal oxides in aqueous electrolytes across the entire pH scale inevitably involves protons. These can interact with oxide electrodes via numerous reactions, including surface adsorption and bulk insertion, electrodissolution/electrodeposition, and water electrolysis. The diversity of electrochemical reactivity involving protons and metal oxide electrodes provides a rich research landscape, while also complicating mechanistic understanding and performance of transition metal oxides in aqueous energy storage devices. I will discuss proton-coupled electrochemical reactions in tungsten and titanium oxides, which are among the few non-noble metal oxides that exhibit good stability in strong acids. Our studies include understanding the effects of proton insertion on metal oxide structural dynamics, optical properties, and surface reactivity, as well as the reactivity of protons at oxide surfaces towards the hydrogen evolution reaction.