Mn₃O₄/Pt Oxide-on-Metal Inverse Catalyst Facilitates Hydrogen Spillover for CO₂ Hydrogenation Reaction

Hydrogen spillover, the migration of metal-activated hydrogen species across support surfaces, is key for many H-related reactions. However, questions remain about how the metal/oxide interfaces affect hydrogen spillover and hydrogenation reaction. Here, we construct Mn₃O₄-on-Pt(111) (Mn₃O₄/Pt(111)) inverse catalyst and Pt clusters-on-Mn₃O₄ (Pt/Mn₃O₄) catalyst, and image hydrogen spillover behavior using high-pressure scanning tunneling microscopy. We find that the onset H₂ partial pressure for hydrogen spillover is two orders of magnitude lower at Mn₃O₄/Pt(111) than at Pt/Mn₃O₄. This structural promotion effect was leveraged to synthesize MnO_x/Pt/C inverse catalyst by depositing MnO_x on Pt nanoparticles, which exhibits a 1.8-fold higher CO₂ conversion compared to conventional Pt/MnO_x/C catalyst during CO₂ hydrogenation. Theoretical calculations reveal that the inverse catalysts promote hydrogen spillover via weaker H adsorption and a more favorable transition-state geometry at interfacial Pt sites, particularly along the Pt─Mn─O pathway. The Pt/Mn₃O₄ interfaces feature strong H binding on Pt^δ⁺ and high H diffusion barriers, which can be partially mitigated by CO co-adsorption. These findings demonstrate that inverse structure offers both electronic and geometric advantages at the interfaces, enabling efficient hydrogen spillover for hydrogenation reactions.