Atomistic investigation of doping effects on electrocatalytic properties of cobalt oxides for water oxidation

Abstract

The development of high-performance oxygen evolution reaction (OER) catalysts is crucial to achieve the clean production of hydrogen via water splitting. Recently, Co-based oxides have been intensively investigated as some of the most efficient and cost-effective OER catalysts. In particular, compositional tuning of Co-based oxides via doping or substitution is shown to significantly affect their catalytic activity. Nevertheless, the origin of this enhanced catalytic activity and the reaction mechanism occurring at catalytic active sites remain controversial. Theoretical investigations are performed on the electrocatalytic properties of pristine and transition metal (Fe, Ni, and Mn)-substituted Co oxides using first-principle calculations. A comprehensive evaluation of the doping effects is conducted by considering various oxygen local environments in the crystal structure, which helps elucidate the mechanism behind the doping-induced enhancement of Co-based catalysts. It is demonstrated that the local distortion induced by dopant cations remarkably facilitates the catalysis at a specific site by modulating the hydrogen bonding. In particular, the presence of Jahn-Teller-active Fe(IV) is shown to result in a substantial reduction in the overpotential at the initially inactive catalysis site without compromising the activity of the pristine active sites, supporting previous experimental observations of exceptional OER performance for Fe-containing Co oxides.