Contiguous Mo Species and SMSI Effect in MoOx Reinforce Catalytic Performance in Reverse Water–Gas Shift Reaction

Abstract

Reverse water–gas shift (RWGS) reaction is a promising strategy for the effective valorization of CO₂. Because of its endothermic nature, a high-performance catalyst with high durability at high temperatures has been required. Herein, we reveal the dynamic structural changes of platinum-loaded molybdenum suboxide catalysts (Pt/MoO_x) in RWGS reaction by multiple operando and in situ measurements, and the catalyst exhibits high activity and CO selectivity, as well as high stability at 500 °C due to the emergence of contiguous Mo species (Mo--Mo) and the strong metal–support interaction (SMSI) effect in MoO_x. In situ X-ray absorption fine structure (XAFS) measurements demonstrated that the RWGS reaction is driven by reversible redox of in situ-formed MoO_x suboxide, where the contiguous Mo--Mo species in MoO_x act as activation sites for CO₂. Comprehensive analysis revealed that the MoO_x shell surrounding the Pt nanoparticles (NPs) suppresses CO adsorption, thereby resulting in high CO selectivity. Furthermore, the catalyst exhibited a continuous activity increase in the earlier stage of operation at 500 °C, which was attributed to the partial carburization of MoO_x during the reaction and the associated increase in the electron density of the Mo species. These findings advance the understanding of RWGS reaction mechanism and suggest innovative strategies for the development of high-performance oxide catalysts with enhanced stability.