Charge redistribution of Co on cobalt (II) oxide surface for enhanced oxygen evolution electrocatalysis

Identification of the active center is pivotal to manipulate the catalyst design for the oxygen evolution reaction. Herein, sulfur was introduced to partly occupy oxygen location in the surface structure of cobalt (II) oxide. The heterogenous ‘O-Co-S’ sites brought an enhanced oxygen evolution activity, including a five-fold intrinsic activity improvement and a reduced overpotential of 66 mV at 10 mA cm−2. Experimental and theoretical investigations reveal that the electronegativity difference between sulfur and oxygen induce the Co 3d electron accumulation along the Co-O bond. This orientated distortion optimizes the adsorption behaviors to oxygen-containing species and also favors energy band more continuous to promote electron transfer, thereby leading to improved electrochemical performance. This work provides the atomic-level understanding of the nature of active sites, which would shed light on the rational design and regulation of other material systems for advanced energy storage and conversion devices.