Nitrogen-Doped Cobalt Phosphide for Enhanced Hydrogen Evolution Activity

Development of highly efficient and durable hydrogen evolution reaction (HER) electrocatalysts has a direct impact on water splitting efficiency and cost-effectiveness. In this work, N-doped CoP2 is successfully synthesized for efficient HER in an alkaline electrolyte, which needs an overpotential of only 64 mV to drive a current density of 10 mA cm(-2), with a small Tafel slope of 47.4 mV dec(-1) and excellent stability for 15 h without any performance loss in 1 M KOH. This represents one of the best HER catalysts in the alkaline electrolyte so far. The successful doping of N into CoP2 is confirmed using X-ray photoelectron spectroscopy, X-ray absorption near-edge structure, and scanning transmission electron microscopy characterizations. It is revealed by first-principle calculations that the partial replacement of P with N not only facilitates electron transfer but also optimizes the Gibbs free energies of H*, H2O, and OH* adsorption on the P active sites, thus facilitating the HER process. This work highlights that anion modification of transition metal phosphides would be an effective and feasible method to enhance their HER activities and provide new insights for the design of novel HER electrocatalysts.