The role of nonmetallic ion substitution in perovskite LaCoO3 for improved oxygen evolution reaction activity

Abstract

Transition metal perovskite (ABO3) is an emerging type of oxygen evolution reaction (OER) electrocatalyst that shows reasonably good activity and moderate stability. Although efforts have been made to improve perovskite’ OER performance by various element substitution at A/B-site, the influence of ion, particularly non-metallic ion, substitutions on the OER mechanism are rarely studied. More and more evidence has shown that the metal-center theory has failed to explain lots of OER-related phenomena. Therefore, it is urgent to understand how the cation and anion sites in perovskite determine OER performance. Here, we used a Fe and P co-doped LaCoO3 as a model system to explore the influence of substitution in perovskite by combinng operando/ex-situ X-ray characterization and density functional theroy (DFT). We observed enhanced OER catalytic activities in co-doped materials, which are attributed to the stronger transition-metal-oxygen-bonding-covalency (TMOBC). The detailed analyses by O K-edge XAS, electrochemical performance, and DFT suggest that the hybridization between O 2p and transition metal 3d eg orbitals could be a more credible descriptor of perovskite for OER, which is the combination of eg orbital theory and TMOBC theory. The finding in our work provides insights into the OER catalysis mechanism on metal oxides, which could guide new design of cost-effective oxide electrocatalysts.