Light-Assisted Catalysis and the Dynamic Nature of Surface Species in the Reverse Water Gas Shift Reaction over Cu/γ-Al₂O₃

The reverse water gas shift (RWGS) reaction converts CO₂ and H₂ into CO and water. We investigated Cu/γ-Al₂O₃ catalysts in both thermally driven and light-assisted RWGS reactions using visible light. When driven by combined visible light and thermal energy, the CO₂ conversion rates were lower than in the dark. Light-assisted reactions showed an increase in the apparent activation energy from 68 to 87 kJ/mol, indicating that light disrupts the energetically favorable pathway active in the dark. A linear correlation between irradiance and decreasing reaction rate suggests a photon-driven phenomenon. In situ diffuse reflectance infrared Fourier transform spectroscopy and TD-DFT analyses revealed that catalyst illumination causes significant, partly irreversible surface dehydroxylation, highlighting the importance of OH groups in the most favorable RWGS pathway. This study offers a novel approach to manipulate surface species and control activity in the RWGS reaction.