Integration of Ni Doping and a Mo₂C/MoC Heterojunction for Hydrogen Evolution in Acidic and Alkaline Conditions

Although nonprecious metal catalysts based on earth-abundant 3d transition metals (TMs) are regarded as promising substitutes for a noble metal electrocatalytic hydrogen evolution reaction (HER), their large-scale application is still inhibited by their inadequate activity and durability. Here, a facile method for nonprecious metal catalysts has been developed to prepare molybdenum carbide on nitrogen-doped carbon. By optimizing the Ni doping ratio, the Ni_0.5@MoC_x/NC exhibits the lowest overpotential for 10 mA cm^-2 and superior stability in both acidic and alkaline media for HER application, outperforming most of the reported HER electrocatalysts. In addition, a theoretical simulation has also confirmed the possible mechanism for the synergistic effect with the regulative adsorption energy of hydrogen species with Ni doping and formation of a Mo₂C/MoC heterojunction in the Ni_0.5@MoC_x/NC electrocatalyst. Therefore, this work provides a new avenue for designing two-dimensional nanostructures with an optimized electronic structure for promising TM HER electrocatalysts in a wide pH range.