(Invited) Epitaxial Oxide Surfaces: New Insights in Oxygen Electrocatalysis

Fundamental understanding of transition metal oxides for oxygen electrocatalysis is often hampered by heterogeneity of oxide powder surfaces and the composite nature of electrodes used for electrochemical measurements. Surfaces of epitaxial thin films, with well-defined crystallographic orientations and strains offer an excellent opportunity to develop insights into what parameters can govern catalytic activity and deduce active sites for oxygen electrocatalysis. In addition, these surfaces allow spectroscopic study of the chemical speciation and electronic structure in an aqueous reaction environment, using ambient pressure X-ray photoelectron and absorption spectroscopy coupled with mass spectrometry to analyze the reaction productions. Here, control of the surface homogeneity is critical for quantifying the adsorption of intermediates and comparing the reactivity between surfaces. The insights obtained from study of these epitaxial surfaces build fundamental understanding of the mechanisms of oxygen electrocatalysis, as well as guide the rational design of high surface area oxide catalysts for technical application.