Boosted charge transfer and selective photocatalytic CO2 reduction to CH4 over sulfur-doped K0.475WO3 nanorods under visible light: Performance and mechanism insight

Low visible light absorption, high carrier recombination and poor selectivity of high value-added products greatly hindered the development of photocatalytic CO2 reduction technology. Herein, a novel sulfur-doped K0.475WO3 photocatalyst was successfully prepared by the one-step calcination, which exhibited excellent performance for visible light driven photocatalytic CO2 conversion to CH4. The introduction of sulfur atoms broadens the light absorption range of the K0.475WO3 to full visible wavelengths, and the impurity level formed by sulfur doping further promotes the generation and separation of photocarriers. Combined with the analysis of the CO2-TPD and density functional theory (DFT) calculation, we found that the sulfur doping formed active adsorption sites on the surface of K0.475WO3, which provided a favorable prerequisite for the activation and hydrogenation of CO2. More importantly, in-situ DRIFTS further indicated the doping of sulfur promoted the formation of formats in the activation process of CO2, which is the key intermediate of CO2 hydrogenation. As a result, sulfur doping endows K0.475WO3 with excellent CO2 reduction ability under visible light and 87.6% selectivity to methane and still maintains good photocatalytic activity after five cycles. This work provides a new study for the visible light-driven photocatalytic conversion of CO2 to high value-added products.