In Situ Coordination\nEnvironment Tuning of Cobalt\nSites for Efficient Water Oxidation

Abstract

Most transition-metal-based oxygen-evolving catalyst\nsurfaces typically\nexperience irreversible compositional and structural variations during\noxygen evolution reaction (OER) in hydrolytic and corrosive alkaline\nmedia, degrading the coordination environment of active metal sites\ninto unified (oxy)­hydroxides. Here, we present an in situ electrochemical\ncoordination tuning of cobalt sites for OER in a strong base, where\nan electrolyzing soluble cobalt-2,2′-bipyridine (Co-bpy) complex\npartially splits the bpy ligand, leading to the deposition of active\nCo sites with fine coordination at room temperature. We deposited\nthe Co sites while catalyzing water oxidation at the same condition\nso that this catalyst can adapt the hostile alkaline condition. This\nrobust coordination environment involving the remaining bpy and generated\n(oxy)­hydroxide ligands (Co–BH catalyst) sustains the highly\nimproved OER activity over 500 h at 200 mA cm^–2,\noutperforming other fragile Co sites with only (oxy)­hydroxides. In\naddition, this work presents an efficient tuning of metal coordination\nenvironments to in situ generate highly active and stable metal sites\nin alkaline electrolytes for water splitting.