Probing Lattice Oxygen Oxidation in Perovskite Electrocatalysts By Resonant Inelastic X-Ray Scattering

During water electrolysis, the hydrogen evolution reaction that generates hydrogen gas is unavoidably accompanied by the anodic reaction that generates oxygen via the oxygen evolution reaction (OER). However, under OER conditions, many electrocatalysts undergo structural degradation and can become amorphous. Lattice oxygen oxidation was proposed as one of the possible causes for amorphization of perovskite oxides. However, because lattice oxygen oxidation is notoriously challenging to probe in experiments, its unambiguous detection in oxide electrocatalysts has been elusive so far. Here, I will show how oxygen oxidation can be detected in single-crystalline (model) oxide electrocatalysts using high-resolution resonant inelastic X-ray scattering (RIXS). Specifically, I will present our case study of perovskite materials where the emergence of oxidized oxygen depends on the transition metal and the applied potential. An insight into the chemical environment of the oxidized oxygen and how it can be accommodated in the perovskite lattice will be provided based on the results of DFT and molecular dynamics. Finally, I will discuss how lattice oxygen oxidation is related to the degradation of oxide electrocatalysts during OER.