Highly Dispersed Cu Promoters Enable Efficient Ru Catalysts for Alkaline Hydrogen Evolution

Hydrogen production via alkaline water electrolysis offers a sustainable route for renewable energy conversion, yet developing Pt‑free electrocatalysts with high activity and durability remains challenging due to sluggish water dissociation kinetics. Herein, we show that regulating the dispersion state of Cu provides an effective strategy to engineer the interfacial electronic structure of Ru for efficient alkaline hydrogen evolution reaction (HER). A carbon‑supported Ru–Cu catalyst containing only ≈4 wt% Ru, in which highly dispersed hydroxyl‑coordinated Cu species are selectively anchored on Ru nanoparticles (Ru–Cu HD /C), is developed together with a Cu 2 O‑like nanocluster counterpart (Ru–Cu NC /C). In 1.0 m KOH, Ru–Cu HD /C delivers an ultralow overpotential of 14 mV at 10 mA cm −2 with a Tafel slope of 25 mV dec −1 , outperforming Ru–Cu NC /C while maintaining nearly 100% of its initial activity after 10,000 accelerated degradation cycles. Combined experiments and density functional theory calculations reveal that highly dispersed Cu–O/OH species electronically modulate neighboring Ru sites and promote water activation with balanced OH* adsorption/desorption, whereas Ru remains the primary center for hydrogen adsorption and H 2 evolution, yielding superior intrinsic HER activity and highlighting interfacial electronic engineering with highly dispersed Cu as a general strategy for designing high‑performance Pt‑free alkaline HER electrocatalysts.