Built‐In Hydrogen Spillover Effect in Supported Catalysts for Efficient Alkaline Water Electrolysis

ABSTRACT The hydrogen (H) spillover effect on metal‐support electrocatalysts plays a significant role in improving the catalytic efficiency of the hydrogen evolution reaction (HER). However, the long reaction path and undesirable interfacial resistance cause considerable barriers in the H migration process. Herein, a small platinum atom‐island (Pt _ai ) featuring multifunctional active centers embedded in Mo ₂ C is designed, which exhibits an interface‐free atomic‐scale H spillover effect typically observed in single‐component catalysts. Experiments and calculations co‐reveal that a built‐in ultra‐short H spillover channel is established within the Pt _ai , which strikingly mitigates H migration barriers. When applied in alkaline HER, exceptionally low overpotentials ( η ₁₀ = 11.8 mV, η ₁₀₀ = 52.9 mV) are obtained for the catalyst. More importantly, corresponding alkaline anion‐exchange membrane water electrolyzers exhibit an ultralow cell voltage (1.77 V _cell ) and high stability (200 h) at an industrial current density of 1.0 A·cm ⁻² . This study proposes a novel strategy to accelerate hydrogen spillover in multicomponent catalysts through the design of interface‐free multifunctional active centers.