Dual roles of surface-supported Rh nanoparticles and isolated Pt species within high-entropy oxides in enhancing hydrogen evolution reaction driven by hydrogen spillover

Abstract

Hydrogen spillover has emerged as an effective approach to improving the hydrogen evolution reaction (HER) by enabling interfacial hydrogen transfer from metals to supports. As such, rational design strategies intended to reduce charge accumulation between these two components are crucial. High-entropy oxides (HEOs), which have adjustable chemical compositions, tunable oxygen vacancies and flexible electronic structures, are promising supports for spillover-based electrocatalysts. The present work investigated Rh/Pt@CrMnFeCoNiO, an amorphous HEO, as a high-performance hydrogen evolution electrocatalyst in acidic media. Various experiments and electrochemical characterizations confirmed that hydrogen spillover occurred on this material. Notably, both Rh on the HEO surface and atomically-dispersed Pt were found to promote charge transfer, accelerate hydrogen migration and facilitate hydrogen desorption. The overall hydrogen evolution pathway was found to comprise hydrogen adsorption on Rh sites with subsequent transfer to Pt sites followed by desorption from O sites. On the basis of this dual-site synergy, the Rh/Pt@CrMnFeCoNiO catalyst exhibited an ultralow overpotential of 4 mV at 10 mA cm⁻² and superior intrinsic activity compared with commercially available Pt/C. This work provides new insights into the rational design of spillover-based HER catalysts.