Trace Ru-doped NiCo₂S₄ nanorods as highly efficient alkaline hydrogen evolution electrocatalyst

Developing alkaline hydrogen evolution reaction (HER) electrocatalysts that demonstrate high activity, outstanding stability, and remarkable cost-effectiveness continues to be a major challenge. This work proposes a "trace doping triggers synergy" strategy to successfully fabricate a ruthenium-doped NiCo₂S₄ catalyst with a well-defined nanorod array architecture on nickel foam (NF) via a combined hydrothermal-electrodeposition method. The catalyst utilizes atomically dispersed ruthenium at an ultra-low loading (∼1.2 wt%) to synergistically induce a high concentration of sulfur vacancies, collectively modulating the electronic microenvironment of the active sites and thereby overcoming the activity limitations of single modification strategies. Evaluations of the electrochemical performance reveal that the catalyst delivers remarkable activity in 1.0 M KOH: only 24 mV and 94 mV overpotentials are required to deliver current densities of 10 and 100 mA cm^-2, respectively, and remarkable stability over 120 h of operation is getting well-maintained. Calculations based on density functional theory (DFT) clarify the atomic-scale reasons behind the improved performance: Ru sites serve as efficient centers for water molecule adsorption and dissociation, which notably reduces the energy barrier for water dissociation. Concurrently, the optimized hydrogen adsorption free energy (ΔG_H⁎) on Ni sites is ascribed to the downshift of their d-band center induced by neighboring Ru dopants, synergistically constructing a multifunctional reaction interface with "well-defined roles and complementary functions" in conjunction with sulfur vacancies and electron-enriched Co sites. This work not only presents a practical catalyst with high performance and low precious metal usage but also provides new insights and a theoretical foundation for designing next-generation water electrolysis catalysts through precise electronic structure modulation.