In Situ Coordination Environment Tuning of Cobalt Sites for Efficient Water Oxidation

Abstract

Most transition-metal-based oxygen-evolving catalyst surfaces typically experience irreversible compositional and structural variations during oxygen evolution reaction (OER) in hydrolytic and corrosive alkaline media, degrading the coordination environment of active metal sites into unified (oxy)hydroxides. Here, we present an in situ electrochemical coordination tuning of cobalt sites for OER in a strong base, where an electrolyzing soluble cobalt-2,2′-bipyridine (Co-bpy) complex partially splits the bpy ligand, leading to the deposition of active Co sites with fine coordination at room temperature. We deposited the Co sites while catalyzing water oxidation at the same condition so that this catalyst can adapt the hostile alkaline condition. This robust coordination environment involving the remaining bpy and generated (oxy)hydroxide ligands (Co–BH catalyst) sustains the highly improved OER activity over 500 h at 200 mA cm–2, outperforming other fragile Co sites with only (oxy)hydroxides. In addition, this work presents an efficient tuning of metal coordination environments to in situ generate highly active and stable metal sites in alkaline electrolytes for water splitting.