Gallium-modulated Ni/Mo3N2@C heterojunctions electrocatalyst for highly active and durable hydrogen evolution reaction

Water electrolysis powered by renewable energy is widely regarded as one of the most important methods for large-scale green hydrogen production. In this work, we have prepared a high-valence gallium-doped nickel-molybdenum nitride nanocomposite (Ga-Ni/Mo 3 N 2 @C) with abundant heterojunctions by a co-precipitation step and a subsequent high-temperature treatment step. The produced Ga-Ni/Mo 3 N 2 @C material benefits from a dual modification strategy (DMS) including the Ga doping-induced internal electronic construction and the carbon shell encapsulation-derived external corrosion inhibition. This DMS not only facilitates the modulation of the intrinsic activity of Ni and Mo constituents, but also strengthens the durability of the Ni/Mo 3 N 2 active components. In hydrogen evolution reaction (HER) test, Ga-Ni/Mo 3 N 2 @C exhibits ultra-low overpotentials of 9 mV at 10 mA cm −2 and 116 mV at 100 mA cm −2 , small Tafel slope of 41.2 mV dec −1 , high conductivity of 114.8 μS cm −1 and low charge transfer resistance of 0.729 Ω cm 2 . Moreover, the Ga-Ni/Mo 3 N 2 @C electrocatalyst exhibits an ultralow Arrhenius activation energy of 14.69 kJ mol −1 , lower than those of Ni/Mo 3 N 2 (20.78 kJ mol −1 ), commercial Raney Ni (41.40 kJ mol −1 ) and Pt/C catalyst (15.24 kJ mol −1 ). The Ga-Ni/Mo 3 N 2 @C-assembled electrolyzer exhibits a lower cell voltage of 1.80 V than the counterpart cells with commercial Raney Ni (2.05 V) cathode or Ni/Mo 3 N 2 (1.85 V) cathode at 3000 A m −2 and room temperature, showing negligible deterioration in performance. The utilization of high-valence Ga atoms doping and carbon shell protection effect not only modulates material electronic structure to accelerate reaction kinetics, but also inhibits the dissolution of active sites. It is believed that this study offers a novel strategy for the development of high-performance electrocatalysts in water electrolysis.