Enhanced photocatalytic CO2 reduction over Z-scheme β-Ga2O3/TiO2 heterojunction composite catalyst: Synthesis, performance, and mechanism

TiO2, a highly promising photocatalyst, suffers from rapid recombination of photogenerated electron-hole pairs, which impedes its practical application in industrial aspect. Herein, we report the in-situ solvothermal growth of TiO2 on Ga2O3 to form a composite photocatalyst. Compared to pristine TiO2, the TiO2/Ga2O3 composite exhibited a 2.5-fold enhancement in the photocatalytic reduction of CO2 to CO and a remarkable 9.6-fold increase in CH4 production. Through experimental characterizations and density functional theory (DFT) calculations, the underlying mechanisms for the improved catalytic performance were investigated. The synergistic effects between TiO2 and Ga2O3, including efficient charge separation and transfer, as well as the creation of active sites, are believed to contribute to the enhanced photocatalytic activity of the TiO2/Ga2O3 composite for CO2 reduction. The introduction of the wide bandgap Ga2O3 allowed the formation of a Z-scheme heterojunction with TiO2 at the interface, which greatly improved the efficiency of electron-hole pair separation and migration, as well as the redox capability, thereby unleashing the performance of the TiO2 catalyst. This approach provides insights into the development of efficient, simple, and low-cost composite catalysts for the photocatalytic reduction of CO2 to valuable fuels.