Suppressing Metal-Support Interaction Enhances Photothermal CO₂ Methanation on the Ru/CeO₂ Catalysts

Metal-support interactions can significantly affect the catalytic performance of heterogeneous catalysts and have been studied extensively in thermal catalysis and electrocatalysis. However, the role of strong metal-support interactions (SMSIs) in regulating photoinduced electron transfer has been rarely investigated in photocatalysis. In this study, we have prepared two model catalysts using the impregnation method─one with SMSI effect (Ru/CeO2) and the other with suppressed SMSI effect (Ru/CeO2–H2)─and tested them for photothermal CO2 methanation. The methane production rate of Ru/CeO2–H2 (275.1 mmol/gRu/h) was more than twice that of Ru/CeO2 (111.2 mmol/gRu/h) at 200 °C under light irradiation. Various characterizations and theoretical calculations suggest that hot electrons, generated by local surface plasma, transferred to the Ru/CeO2–H2 from the dispersed Ru sites, filling the oxygen vacancies in Ru/CeO2–H2, where the adsorption and activation of CO2 was enhanced under light irradiation. Also, it is evident that the electron-deficient Ru sites speed up the decomposition of H2. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies showed that CO2 methanation on Ru/CeO2–H2 and Ru/CeO2 chiefly followed the formate-intermediated pathway, although the CO-intermediated pathway was also present. This study offers a technique to enhance photothermal CO2 methanation by controlling the interaction between the metal and the support.