Reversed Hydrogen Spillover via Oxygen Vacancy Concentration Modulation for Enhanced Interfacial Hydrogen Transfer Kinetics

Utilizing the hydrogen spillover effect as a metal–support interfacial engineering strategy can enhance the hydrogen evolution efficiency. However, conventional hydrogen spillover suffers from interfacial H* transfer energy barriers. To address this, we designed an Ov-concentration-gradient WOx support using Dawson-type polyoxometalates (POMs) to spatially separate H* adsorption sites. Herein, we show that a reversed hydrogen spillover effect, where the WOx support stores and transports H* to surface Pt active sites, drastically enhances the hydrogen spillover kinetics and improves the hydrogen evolution stability. Combined experimental investigations and theoretical calculations demonstrate that increasing the Ov concentration enhances the electronic metal–support interaction (EMSI) and reduces the energy barrier for H* migration from WOx to Pt, thereby optimizing the reverse hydrogen spillover efficiency. The Ov-rich 12-Pt/WOx catalyst exhibits exceptional HER performance (η10 = 3 mV) and 1800 h stability at 200 mA cm–2. Furthermore, the entire reversed hydrogen spillover process (adsorption–migration–desorption) was dynamically tracked via complementary in situ techniques. This study elucidates the quantitative correlation between Ov concentration and reversed hydrogen spillover kinetics, providing a universal defect-engineering strategy for high-performance low-platinum HER catalysts for industrial applications in acidic media.