Ultrahigh-mass-activity Ru30W70/WOx catalyst for acidic hydrogen evolution: Kinetic insight into alloying–hydrogen spillover synergy

High-activity and durable precious-metal electrocatalysts dominate acidic hydrogen evolution reaction (HER), though their scarcity and exorbitant costs impede industrial implementation. Wet chemical approaches such as single-atom construction, core-shell architectures and heterostructure engineering are extensively exploited to elevate noble metal atomic utilization and mass activity. Distinct from these chemical synthetic routes, magnetron sputtering—a physical vapor deposition technique—enables accurate tuning of alloy compositions and delivers outstanding synthetic reproducibility. Herein, a series of Ru y W 100-y /WO x composites are fabricated via magnetron sputtering under ultralow Ru loading (0.01 mg cm −2 ). The optimized Ru 30 W 70 /WO x composite catalyst delivers an overpotential of merely 26 mV at a current density of 10 mA cm −2 with a Tafel slope of 55.5 mV dec −1 . It achieves a mass activity of 58.52 A mg-1 Ru at an overpotential of 200 mV, outperforming most reported Ru-based HER electrocatalysts to date. Mechanistic studies show that the performance leap stems from the stepwise synergy of alloying and hydrogen spillover. During alloy formation, directional electron transfer occurs from Ru to W, optimizing the adsorption energy of hydrogen intermediate H* and accelerating the Volmer adsorption step. The WO x support triggers efficient hydrogen spillover via strong metal–support interactions, which transports H* to the oxide surface for desorption and breaks the single-surface adsorption–desorption equilibrium limit. This synergy simultaneously boosts active-site density and intrinsic activity, achieving a dual enhancement unattainable by either effect alone. This work provides a feasible kinetic regulation strategy for designing high-performance Ru-based acidic HER catalysts with ultralow noble metal loading.