Concentration gradient drives rapid reverse hydrogen spillover for alkaline water electrolysis at high current...

The reverse hydrogen spillover is indispensable for boosting the alkaline hydrogen evolution reaction (HER) performance of metal-support electrocatalysts but is hindered by thermodynamic and kinetic constraints. Here, we propose to accelerate this process by engineering a pronounced concentration gradient at the support/metal interface to provide an essential kinetic driving force. Accordingly, a series of electrocatalysts were synthesized by anchoring nano-Ru onto Fe-doped Ni(OH)₂ with varying doping concentrations (Ru/Fe-Ni(OH)₂). Experiments and theoretical calculations confirm that by precise regulation of Fe doping, the local electronic structure of NiO bond is tuned to enhance water dissociation ability. The moderately Fe-doped Ni(OH)₂ (Fe_(M)-Ni(OH)₂) exhibits the strongest water dissociation ability, which creates the greatest H* concentration gradient and thus promotes reverse spillover. Consequently, the synthesized Ru/Fe_(M)-Ni(OH)₂ exhibits outstanding bifunctional electrocatalytic performance, requiring just 340 for the HER and 371 mV for the oxygen evolution reaction (OER) to achieve 1000 mA cm^-2, along with robust continuous stability exceeding 100 h. when assembled into an alkaline exchange membrane water electrolyzer (AEMWE), the device achieves 1000 mA cm^-2 at a low voltage of 1.89 V, significantly surpassing the Pt/C||RuO₂ benchmark (2.42 V), and demonstrates excellent durability for more than 100 h.