Highly-active direct Z-scheme Si/TiO2 photocatalyst for boosted CO2 reduction into value-added methanol

In the present study, direct Z-scheme Si/TiO2 photocatalyst was synthesized via a facile hydrothermal reaction using tetrabutyl titanate and Si powder prepared from magnesiothermic reduction of SiO2 nanospheres. The Si/TiO2 nanospheres were composed of porous Si nanospheres with a diameter of similar to 300 nm and TiO2 nanosheets with a diameter of 50 nm and thickness of 10 nm, and demonstrated superior visible light harvesting ability to either Si nanospheres or TiO2 nanosheets. CO2 photocatalytic reduction proved that Si/TiO2 nanocomposites exhibit high activity in conversion of CO2 to methanol with the maximum photonic efficiency of 18.1%, while pure Si and TiO2 catalyst are almost inactive, which can be ascribed to the integrated suitable band composition in the Si/TiO2 Z-scheme system for CO2 reduction. The enhanced photocatalytic property of Z-scheme Si/TiO2 nanospheres was ascribed to the formation of Si/TiO2 Z-scheme system, which improved the separation efficiency of the photogenerated carriers, prolonged their longevity, and therefore boosted their photocatalytic activity.