(Invited) Probing the Electronic Structure of Oxide Electrocatalysts and the Formation of Reaction Intermediates

Abstract

Perovskite oxides (ABO3) are highly active for the oxygen evolution reaction (OER). Activity is observed to correlate with changes in bulk electronic structure parameters, such as metal-oxygen covalency and transition metal oxidation state. We employ spectroscopic approaches to consider such descriptors at the surface of perovskite oxides in situ, as well as their implications on the formation of surface adsorbates proposed to act as reaction intermediates during the OER.Many surface science techniques, such as X-ray photoelectron spectroscopy (XPS), collect information from inherently surface-sensitive low-energy processes, requiring operation in ultrahigh vacuum. This constraint is lifted for ambient pressure XPS, which can probe the surface in equilibrium with the gas phase at pressures up to ~a few Torr, or with thin liquid layers using a higher incident photon energy. This presentation will discuss the insights obtained with this technique regarding the electronic structure of oxide electrocatalysts in an oxidizing or humid environment, as well as the reaction intermediates of relevance to electrocatalysis.1 We will then extend the technique to probe electrocatalysts in operando,2 driving current through a thin layer of liquid electrolyte and employing a tender X-ray source.