Defect-Engineered Bi₂₄O₃₁Cl₁₀ Nanosheets for Photocatalytic CO₂ Reduction to CO

The photocatalytic CO2 conversion efficiency of semiconductor materials still suffers from the faint CO2 surface adsorption capacity and sluggish reaction kinetics. Among the modification strategies, defect engineering is considered as a promising approach for ameliorating the catalytic performance of the bulk materials. Herein, an ionic liquid 1-dodecyl-3-methylimidazolium chloride-assisted alkali solvothermal method was employed for the synthesis of ultrathin Bi24O31Cl10 nanosheets with abundant surface oxygen vacancies (Bi24O31Cl10-OV). The existence of the surface oxygen vacancy provided sufficient catalytic sites and greatly strengthened the CO2 adsorption and activation capacity. Furthermore, a newly created energy level in the forbidden band of the Bi24O31Cl10-OV sample facilitated the photogenerated charge separation and transfer, boosting the reaction rate. Under the conditions of pure water and high-purity CO2, the total CO yield of the Bi24O31Cl10-OV sample was achieved up to 330 μmol/g after irradiation with a 300 W Xe lamp for 10 h, which was 3 and 7 times higher than the bulk counterpart and partial oxygen-repaired Bi24O31Cl10-OV sample, respectively. Furthermore, isotope labeling experiments also verified that the actual carbon source in the product CO was from CO2 molecules. These results reveal that surface oxygen vacancy engineering is an effective approach for developing high-performance bismuth-based solar fuel generation systems.