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 ∼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.