Dechlorination-facilitated Deprotonation of CoFe (Oxy)hydroxide Catalysts under Electrochemical Oxygen Evolution

Abstract Dynamical structural evolution of electrocatalysts under electrochemical oxygen evolution reaction (OER) can convert inactive materials into active catalysts through ion insertion redox reactions frequently. Understanding the structural evolution based on entire lifecycle is central to in-situ electrochemically construct high-performance OER electrocatalysts, but remaining highly challenging. In this work, aiming at representative CoFe (oxy)hydroxide electrocatalysts, we present a dechlorination-facilitated deprotonation process of CoFe hydroxide precatalyst containing lattice chlorine during OER, which enables the formation of a highly active CoFe oxyhydroxide. The resultant oxyhydroxide catalyst exhibits a remarkable OER activity with an overpotential of 271 mV at a current density of 10 mA cm-2. Operando Raman spectroscopy together with density functional theory calculations further demonstrate that the dechlorination process promotes the exposure of lattice oxygen sites that are directly involved in accelerating the OER.