Boosted water electrolysis capability of NixCoyP via charge redistribution and surface activation

Water electrolysis for efficiently generating hydrogen is a key chemistry to realize the hydrogen economy. Transition metal phosphides (TMPs) have become promising catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) under alkaline conditions. But their widespread application is still limited due to the intermediates’ adsorption/desorption energy to be improved and the rare analysis of activation. Herein, we demonstrate a bifunctional catalyst, bimetallic phosphide (NixCoyP) supported by Ni foam (NF), towards HER and OER. X-ray photoelectron spectra demonstrate that the synergy between nickel and cobalt regulates the electron redistribution around active sites, which optimizes reaction intermediates’ adsorption/desorption kinetics on active sites. Post-stability analysis further reveals the surface activation phenomenon, that NixCoyP can transform into hydroxides for HER and oxyhydroxides for OER. Such behaviors allow the surface of catalysts to form new heterostructures with reorganized electronic structures to sustain the low voltage of water electrolysis and excellent stability. Density functional theory analysis proves that the NiCoP/M-OH heterostructure significantly enhances the HER properties through the optimized adsorption/desorption capacities for H* intermediates. Remarkably, this catalyst exhibits an outstanding overall water electrolysis performance.