A Ni-Doped Molybdenum Carbide Heterojunction Catalyst for Enhanced Hydrogen Evolution Reaction

The hydrogen evolution reaction (HER) kinetics of molybdenum carbides (MoxC) are limited by excessively strong Mo–H bonds and insufficient active sites. Herein, Ni-doped MoC-Mo2C heterostructure (denoted as Ni-MoxC) catalysts are synthesized via molten salt electrolysis. The morphology, electronic structure, and electrochemical performance of Ni-MoxC can be controlled by the Ni-to-Mo molar ratio and the pre-addition of Li2CO3 in the precursor. The results show that Ni-MoxC-0.2 (Ni doping content of 0.25 wt %) exhibits optimal HER performance. It achieves overpotentials of 126 and 218 mV in 0.5 M H2SO4 and 1 M KOH at 10 mA cm–2, respectively. Meanwhile, it exhibits excellent stability in both electrolytes and a stable voltage of 1.83 V at 10 mA cm–2 when coupled with an Ir anode. The excellent performance of Ni-MoxC-0.2 is mainly dominated by the MoC/Mo2C heterojunction ratio and a larger electrochemically active surface area, and Ni doping further triggers the electron redistribution to enhance catalytic kinetics. Furthermore, the pre-addition of 5 wt % Li2CO3 in the precursor can inhibit carbon deposition and enhance the activity of Ni-MoxC-1. This work provides a feasible strategy for designing low-cost and high-performance MoxC-based HER catalysts.