Controlling Surface Chemical Inhomogeneity of Ni 2 P/MoNiP 2 /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 H 2 -assisted method is developed to prepare ternary Ni 2 P/MoNiP 2 /MoP crystalline/amorphous heterostructure nanowires on the conductive substrate. The characterization results show that the content of the MoNiP 2 phase and the crystallinity of the MoP phase can be tuned by simply controlling the H 2 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 Ni 2 P/MoNiP 2 /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.