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 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 by XPS (X-ray photoelectron spectroscopy), XANES (X-ray absorption near-edge structure) and STEM (scanning transmission electron microscopy) characterizations. It is revealed by first-principle calculation 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, and thus facilitating the HER proces...