Coupling H* Formation with Interfacial Hydrogen Spillover through Oxygen-Vacancy Regulation for Alkaline Hydrogen Evolution

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Abstract
Efficient alkaline hydrogen evolution requires rapid water dissociation and onward migration of adsorbed hydrogen (H*), yet coordinating these sequential processes across metal–support interfaces remains challenging. Here, Ru clusters are anchored on oxygen-vacancy-rich WO3-x nanoneedle arrays (Ru/RWO), with lower-vacancy Ru/PWO as a control. Experiments and density functional theory calculations reveal that vacancy enrichment coordinates support-side water activation and subsequent H* migration. Vacancy-adjacent undercoordinated W centers act as Lewis acid sites, promoting H2O adsorption and O–H bond cleavage. Meanwhile, the reduced work-function mismatch weakens net electron withdrawal from Ru and alleviates interfacial charge accumulation, thereby mitigating excessive H* stabilization at interfacial Ru and lowering the barrier for onward migration to an adjacent Ru site within the cluster from 0.32 to 0.23 eV. Ru/RWO requires only 22 and 61 mV to deliver 10 and 100 mA cm-2, respectively, with a Tafel slope of 34.2 mV dec-1 in 1.0 M KOH, and sustains 0.5 A cm-2 for 600 h. An anion-exchange-membrane water electrolyzer reaches 1.0 A cm-2 at 1.91 V and operates for 150 h. These findings provide a coupled structural and electronic regulation strategy for synchronizing intermediate generation and transfer in multistep electrocatalysis.

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