Controlling Surface Chemical Inhomogeneity of Ni2P/MoNiP2/MoP Heterostructure Electrocatalysts for Efficient Hydrogen Evolution Reaction

Crystalline/amorphous phase engineering is demonstrated as a powerful strategy for electrochemical performance optimization. However, it is still a considerable challenge to prepare transition metal-based crystalline/amorphous heterostructures because of the low redox potential of transition metal ions. Herein, a facile H2 -assisted method is developed to prepare ternary Ni2 P/MoNiP2 /MoP crystalline/amorphous heterostructure nanowires on the conductive substrate. The characterization results show that the content of the MoNiP2 phase and the crystallinity of the MoP phase can be tuned by simply controlling the H2 concentration. The obtained electrocatalyst exhibits a superior alkaline hydrogen evolution reaction performance, delivering overpotentials of 20 and 76 mV to reach current densities of 10 and 100 mA cm-2 with a Tafel slope of 30.6 mV dec-1 , respectively. The catalysts also reveal excellent stability under a constant 100 h operation, higher than most previously reported electrocatalysts. These striking performances are ascribed to the optimized hydrogen binding energy and favorable hydrogen adsorption/desorption kinetics. This work not only exhibits the potential application of ternary Ni2 P/MoNiP2 /MoP crystalline/amorphous heterostructure nanowires catalysts for practical electrochemical water splitting, but also paves the way to prepare non-noble transition metal-based electrocatalysts with optimized crystalline/amorphous heterostructures.