Increase of Co 3d projected electronic density of states in AgCoO2 enabled an efficient electrocatalyst toward oxygen evolution reaction

The rational design and precise optimization of electronic structure of catalyst are highly desirable in developing efficient oxygen evolution reaction (OER) electrocatalysts. Here we successfully tailored the surface charge of silver delafossite AgCoO2 (ACO) and turn it into an efficient OER catalysts via tuning surface charge transfer state. XAFS and NEXAFS results evidenced an increased occupied Co 3d projected state in hybrid and a synergistic electronic interaction between Ag and ACO. The ACO/Ag catalyst requires an overpotential of 271 mV to reach the current density of 10 mA cm−2, which is much smaller than that of pure ACO, most Co-oxide-based OER electrocatalysts and RuO2 (369 mV) or IrO2 (338 mV) catalysts. Moreover, density functional theory calculations show that the reduction of unoccupied Co 3d projected state in the hybrid brings optimized delocalized charge density of ACO and decreased reaction free energy barriers involved on the Co site in OER, which are essential for the unusual performance.