Synergism of Au and Ru Nanoparticles in Low-Temperature Photoassisted CO2 Methanation.

Au and Ru nanoparticles (NPs) have been deposited on Siralox® substrate by impregnation and chemical reduction, respectively (Au-Ru-S). The as-prepared material is very active in the selective CO2 methanation to CH4 at temperatures below 250 °C. In addition, Au-Ru-S shows enhanced CH4 production upon irradiation with UV/Vis light starting at temperatures higher than 200 °C, although the contribution of the photoassisted pathway of CH4 production decreases as the temperature increases. Thus, a maximum CH4 production of 204 mmol gRu -1 at 250 °C upon 100 mW cm-2 irradiation was achieved. Control experiments, in which Ru-S and Au-S materials were used, revealed that Ru NPs are the CO2 methanation active sites, while Au NPs contribute by harvesting light, mainly visible as a consequence of the strong Au plasmon band centered at 529 nm. The visible light absorbed by the plasmonic band of Au NPs could make them act ass local heaters of the neighboring Ru NPs, increasing their temperature and enhancing CH4 production.