Interfacial work function matching enables efficient hydrogen spillover for superior alkaline hydrogen evolution

• A design paradigm for hydrogen spillover is established by minimizing the metal-support work function difference to near-zero, achieving an ultralow energy barrier. • The optimal Ni 1 Ru 2 @Cu catalyst, with an ultralow ΔΦ of 0.03 eV, achieves exceptional alkaline HER activity (57 mV @ 20 mA cm −2 ) and outstanding stability. • A novel two-step H* spillover pathway from alloy to Cu support is identified, with the rate-determining step barrier reduced to a mere 0.12 eV. • Operando diagnostics and DFT calculations collectively validate ΔΦ and d-band center as key descriptors for the rational design of high-performance spillover catalysts. The sluggish kinetics of alkaline hydrogen evolution reaction (HER) governed by the consecutive steps of water adsorption/dissociation and hydrogen desorption remains a major obstacle to efficient green hydrogen production. Though hydrogen spillover offers a promising strategy to bridge these steps, it requires overcoming high energy barriers at the metal-support interface as a prerequisite. This study aims to design a hydrogen spillover-based binary metal-based electrocatalyst by precisely tailoring work function difference (ΔΦ) and d-band center offset (Δε d ) at the metal–metal interface, thereby minimizing the interfacial energy barrier and enhancing HER performance. We report the rational design of Ni x Ru y nanocrystals anchored on Cu nanorods (Ni x Ru y @Cu), wherein the ΔΦ and Δε d are precisely tailored to minimize the interfacial energy barrier for hydrogen spillover. The combination of operando electrochemical measurements, electrochemical analysis and density functional theory (DFT) calculations demonstrate that the optimal Ni 1 Ru 2 @Cu achieves an ultralow ΔΦ of 0.03 eV, between Ni 1 Ru 2 alloy and Cu, enabling efficient hydrogen spillover from NiRu alloys to the Cu support. This results in exceptional HER performance, requiring only 57 mV overpotential to reach 20 mA cm −2 and a small Tafel slope of 81.7 mV dec −1 , alongside remarkable long-term stability. This work not only establishes a general paradigm for the design of advanced hydrogen spillover-based catalysts but also provides fundamental insights into multi-step reactions involving hydrogen intermediates, paving the way for high-performance alkaline water electrolysis.