Nitrogen-Doped\nCobalt Phosphide for Enhanced Hydrogen\nEvolution Activity

Abstract

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