NixW1–x Nanoparticles as Electrocatalysts for Hydrogen Evolution in Acidic Medium

This study investigates the electrocatalytic performance of nanostructured Ni–W electrocatalysts for the hydrogen evolution reaction (HER) in an acidic medium (0.5 M H2SO4). Electrocatalysts were synthesized using a solution combustion synthesis method, followed by metal reduction under a 10 vol % H2/Ar atmosphere. By systematically varying the Ni-to-W atomic ratio in NixW1–x electrocatalysts (x = 0.1, 0.3, 0.5, 0.7, and 0.9), we identified the optimal composition for maximum HER activity. Comprehensive structural and electrochemical analyses, including X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, linear sweep voltammetry, and electrochemical impedance spectroscopy, were conducted to investigate phase composition, surface chemistry, work function (Φ), morphology, and HER catalytic activity. Among the compositions evaluated, Ni0.7W0.3 demonstrated superior HER performance, characterized by a Tafel slope of 100 ± 2 mV dec–1, an exchange current density (j0) of 677 ± 106 μA cm–2, and an overpotential (η10) of −143 ± 4 mV at a cathodic current density of −10 mA cm–2. When compared to the previously reported Ni–W electrocatalysts for acidic HER, Ni0.7W0.3 stands out as one of the most effective electrocatalysts. This remarkable performance results from an optimized phase composition, enabling synergistic interactions among the Ni–W alloy phase, metallic tungsten, and oxygen-deficient tungsten oxide species. These structural features create an enhanced electronic environment, facilitating charge transport and promoting efficient water dissociation kinetics. Moreover, the high work function of Ni0.7W0.3 contributes to improved electron transfer kinetics, effectively lowering the energy barriers of the HER process. Its well-defined nanostructure, featuring multiple active edges and facets, further increases the density of accessible active sites, enhancing catalytic activity. Collectively, these findings highlight the potential of Ni–W electrocatalysts as cost-effective and highly efficient alternatives to noble metal-based electrocatalysts for acidic water electrolysis.