Facile preparation of self-assembled Ni/Co phosphates composite spheres with highly efficient HER electrocatalytic performances

Because of their high catalytic activity and abundant resources, nonprecious transition metal phosphides are favorable substitutes for noble metals as hydrogen evolution reaction (HER) electrocatalysts. In this work, self-assembled Ni/Co phosphide composite N-doped carbon spheres were successfully prepared via a hydrothermal process, which had abundant exposed active sites for the HER. The as-obtained samples exhibited excellent electrocatalytic activity for the HER with an overpotential of only 160 mV (vs. RHE) at a current density of 10 mA cm(-2) in a 0.5 M H2SO4 solution and a comparatively low Tafel slope (57 mV dec(-1)). Additionally, the Ni2P/CoP spheres also show good stability after 120 h and 5000 cycles of a cyclic voltammetry test. Their highly efficient catalytic activity for the HER is attributed to the specific spherical structure, which provides exposed Ni2P and CoP for favorable adsorption and desorption of hydrogen. Therefore, nonprecious transition metal phosphide spheres may provide a promising strategy to improve the catalytic activity of HER electrocatalysts.