Sulfur-Mediated Dual Modulation of V₂C Substrate and Pt Integration for Accelerated Hydrogen Spillover in Alkaline Hydrogen Evolution Catalysis

Alkaline hydrogen evolution reaction (HER) is pivotal to the hydrogen economy, yet the design o Pt-based catalysts that simultaneously deliver high activity and hold maximized atomic utilization remains an enduring bottleneck. Although MXenes have been widely explored as Pt supports, their practical scope is still limited by harsh fabrication requirements. V₂C stands out for its abundance and high conductivity; however, developing mild V₂C synthesis and mitigating structural decay remain great challenges for HER. Herein, we report a sulfur doping-assisted dual modulation strategy that enables atomic-level dispersion of Pt nanoparticles (NPs) on V₅S₈-V₂C heterostructures (Pt@V₅S₈-V₂C). This approach tailors both the architecture of the V₂C substrate and the nucleation dimension of Pt NPs, thereby generating abundant interfacial active sites for efficient alkaline HER. As a result, the optimized 1.5Pt@V₅S₈-V₂C delivers an ultralow overpotential of 28.8 mV at 10 mA cm⁻², together with good catalytic performance in an anion-exchange membrane water electrolyzer. A comprehensive combination of experimental and theoretical analyses reveals that the formation of a Pt─S─V bridge within the metal-support framework effectively regulates interfacial charge transfer and accelerates intermediate kinetics via the hydrogen spillover effect. This study advances a blueprint for atom-efficient HER electrocatalysts with industrial-level performance.