Synthesis and performance enhancement of Ni–Mo/g-C₃N₄ bimetallic composites electrocatalysts

Graphitic carbon nitride (g-C₃N₄) and Ni-Mo-based electrocatalysts have garnered significant attention for their promising performance as photocatalysts and their excellent activity in alkaline hydrogen evolution reactions (HER). In this study, Ni_xMo_y/g-C₃N₄ composites were successfully synthesized by combining a simple thermal polymerization method with a subsequent wet-chemical process and solid-state sintering. Various samples were prepared by adjusting both the loading of active sites and the Ni/Mo molar ratio, and their structures and compositions were analyzed using Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and cyclic voltammetry (CV). XRD patterns revealed a reduction in the intensity of the g-C₃N₄ (002) diffraction peak, indicating altered crystallinity. Electrochemical surface area (ECSA) analysis confirmed that increasing the active site content, peaking at a 20 wt% addition. Further investigation showed that at a Ni/Mo molar ratio of 4:1, the 20 wt% Ni_2.0Mo_0.5/g-C₃N₄ composite achieved the lowest overpotential and Tafel slope in 1 M KOH—462 mV and 98 mV/dec, respectively—owing to the synergistic effect of Ni–Mo and the prominent Ni(111) facet. Moreover, g-C₃N₄ effectively prevented the spontaneous combustion of Ni_xMo_y in air, ensuring the stability of the composite.