Engineering non-interfacial hydrogen spillover in a Ni17W3-WO2 heterostructure.

The hydrogen spillover effect offers a promising strategy to overcome the kinetic bottleneck of proton desorption in hydrogen evolution reaction catalysts. However, conventional hydrogen spillover mechanisms rely on interfacial proton transfer between distinct phases and suffer from inherent energy barriers. Here, we show a non-interfacial hydrogen spillover mechanism in a Ni17W3-WO2 heterostructure, engineered through the synergistic creation of a built-in strain gradient and directional electron transfer. This design spatially confines the complete hydrogen evolution process within the Ni17W3 phase, thereby circumventing cross-phase migration and reshaping the hydrogen adsorption energy landscape. Experimental and theoretical analyses confirm the elimination of interfacial barriers and establishment of an optimized proton-migration route. The resulting catalyst achieves a low overpotential of 21 mV at 10 mA cm-2 in 0.5 M H2SO4, along with sustained stability (>1500 hours at 500 mA cm-2) and a Faradaic efficiency of 98.65%. This work demonstrates how tailored heterostructures can bypass interfacial bottlenecks, providing guidance for developing efficient non-precious hydrogen spillover catalysts and advancing sustainable hydrogen production.