Breaking the water dissociation–hydrogen adsorption trade-off through W single-atom engineering for alkaline hydrogen evolution

초록

The sluggish kinetics of alkaline hydrogen evolution reaction (HER) arise from conflicting electronic demands of successive elementary steps, as Volmer water dissociation favors electron-deficient centers while optimal H* adsorption requires near-thermoneutral binding. Here, we address this trade-off by incorporating isolated tungsten single atoms into layered Ni(OH)2 nanosheets on titanium foam (W-Ni(OH)2). Structural and spectroscopic analyses reveal that W incorporation imposes compressive lattice strain, augmenting octahedral crystal-field splitting and elevating Ni eg-derived states. The cathode delivers superior HER performance in 1 M KOH (η10 = 44 mV, Tafel slope = 28 mV dec−1) and performs comparably to Pt/C at higher current densities (η50 = 82 mV). Operando spectroscopy and density functional theory substantiate a cooperative site-separated mechanism wherein electron-deficient W6+ centers facilitate near-barrierless water dissociation, while nascent H* migrates to neighboring Ni sites with near-thermoneutral adsorption energetics. An anion-exchange membrane water electrolyzer achieves 1.65 V at 1.0 A cm−2 and sustains 500 mA cm−2 over 500 h with minimal voltage drift and near-unity Faradaic efficiency. This work demonstrates that dual-role single-atom engineering offers a transferable strategy for overcoming intrinsic kinetic constraints in alkaline electrocatalysis. © 2026 Elsevier B.V.

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