Insight into synergetic mechanism of Au@Pd and oxygen vacancy sites for coupling light-driven H2O oxidation and CO2 reduction

Photocatalytic reduction of CO 2 with H 2 O into CH 4 is a promising way to realize solar energy utilization and CO 2 conversion, in which the key issue is how to enhance and couple CO 2 reduction as well as H 2 O oxidation. In this work, we precisely fabricated a binary functional photocatalyst by loading Au@Pd nanoparticles onto V O -rich TiO 2 through a surfactant-free deposition-reduction method, whose fine structure was confirmed by aberration-corrected HAADF-STEM, EELS, EPR and XPS. Combining photocatalytic performance with a series of in situ FTIR measurements, we clarified the role of metallic sites and semiconductor support in coupling CO 2 reduction and H 2 O oxidation. Specifically, H 2 O oxidation process was facilitated by the V O -rich TiO 2 to contribute more protons, followed by the activation of CO 2 and protons primarily by the metallic Au@Pd sites to form the surface bounded Au@Pd-CO 2 − and Au@Pd-H species. By adjusting the ratio of Au@Pd nanoparticles and V O concentration to manipulate the Au@Pd-CO 2 − /Au@Pd-H ratio, CH 4 yield of 26.32 μmol/(g·h) and selectivity of electron toward CH 4 of 96% can be observed with minimal concomitant H 2 generation. These findings could open a feasible and universal route to enhance the photocatalytic efficiency of CO 2 conversion.