Intentionally Introducing Oxygen Vacancies and Ti3+ Defects on the Surface of Bi4Ti3O12 Nanosheets for Promoting the Photoreduction of CO2 to CH3OH

Using perovskite photocatalytic reduction of CO2 and H2O to produce hydrocarbon fuels offers an attractive method to solve the energy crisis and the greenhouse effect. Bi4Ti3O12 (BTO) has received much attention in the field of photocatalysis due to its unique layered structure, but it still faces many challenges such as weak photoresponse and severe photogenerated carrier recombination. In this paper, Bi4Ti3O12 nanosheets with different concentrations of surface oxygen vacancies (VO) and Ti3+ defect were prepared by the molten salt method and NaBH4 high-temperature reduction method (HBTO). Surface defects formed obvious carrier traps on the HBTO surface, reduced the recombination rate of photogenerated electrons and holes, and adjusted the band gap structure (from 3.09 to 2.62 eV), which improved the visible light utilization of HBTO. The decrease of photoinduced carrier recombination rate and the improvement of visible light response significantly enhanced the photocatalytic CO2 reduction activity of HBTO under visible light. The CH3OH yield with the optimized HBTO-4 (NaBH4:Bi4Ti3O12 = 1:5) was 4.90 μmol·g–1·h–1, which was about 3.5 times that of the original BTO. Meanwhile, the band gap structure, electronic density of states (DOS), and work function were calculated by the density functional theory (DFT). This study provided an effective strategy for designing and preparing perovskite photocatalysts rich in surface defects for the efficient conversion of solar energy.