Revealing the direct role of cobalt in oxygen evolution reaction initiation over high-performance iridium-cobalt oxide catalysts

Abstract

The kinetic contribution of cobalt in bimetallic oxide oxygen evolution reaction (OER) catalysts, despite its extensive use, remains inadequately understood. In this study, an iridium-cobalt bimetallic oxide (Ir_0.3Co_0.7O_x) catalyst is synthesized via a melt-alkali method, which exhibits an overpotential of 235 mV at 10 mA cm_geo⁻² and >1700 h stability in acidic media. Transient potential scanning reveals that Co undergoes early-stage oxidation, promoting kinetic charge accumulation on the catalyst surface. Density functional theory calculations further demonstrate that Co promotes *OH formation by enhancing charge transfer in the initial step of the OER. Moreover, oxygen vacancies in Ir_0.3Co_0.7O_x modulate charge redistribution, stabilizing O–O coupling via the oxidation pathway mechanism. This work bridges a critical gap in the rational substitution of noble metals by elucidating the catalytic role of earth-abundant elements such as Co in accelerating key OER steps and offers significant insights for the development of cost-effective, high-efficiency acidic OER catalysts.