Efficient Oxygen Evolution Electrocatalysis on CaFe₂O₄ and Its Reaction Mechanism

Abstract

Electrochemical water splitting demands highly active, easily produced, and cost-effective electrocatalysts for the oxygen evolution reaction (OER). Herein, we present an iron (Fe)/calcium (Ca)-based bimetallic oxide, CaFe2O4, which exhibits outstanding OER activity in alkaline media. The OER specific activity of CaFe2O4 is superior to those of previously reported Fe-based bimetallic oxides composed of alkaline-earth or rare-earth metals. Remarkably, it even surpasses that of the benchmark IrO2. Furthermore, the OER performance of CaFe2O4 is stable during repeated potential cycles without any significant current loss. Density functional theory calculations imply that the outstanding OER activity of CaFe2O4 is facilitated by an unconventional mechanism via direct formation of O–O bonds between two oxygen intermediates, which are adsorbed on a multi-iron site on the catalyst surface.