Oxygen vacancy mediation of BiOX (X=Cl, Br) towards enhanced photocatalytic CO2 reduction activity

Surface defects in semiconductors play a significant role in modulating the performance of photocatalytic reactions. However, there is still insufficient exploration regarding the influence of defects on the photocatalytic CO 2 reduction performance. In this study, we achieved controllable construction of oxygen vacancies (OVs) in BiOX (X=Cl, Br) samples through one-step solvothermal treatment in polyols by adjusting the reaction time. The introduction of OVs significantly enhanced the photocatalytic activity of BiOX (X=Cl, Br) for converting CO 2 to CO. Among all the tested BiOX (X=Cl, Br) samples with OVs, BiOCl-OV-2 and BiOBr-OV-2 samples with a moderate amount of OVs exhibited the highest CO yield of 28.51 and 15.22 μmol g cat −1 after 4 hours of irradiation, respectively. Photo-/electrochemical measurements results revealed that engineering OVs into BiOX (X=Cl, Br) effectively adjusted their electronic structure, charge density and separation; however, excessive OVs may slightly degrade their photoelectrochemical properties and thus lead to reduced photocatalytic activity. Furthermore, an appropriate amount of OV was found to enhance both CO 2 adsorption capacity and photo-generated electron reduction ability, thereby further promoting the overall efficiency of photocatalytic CO 2 conversion. Through in situ FTIR spectra analysis, we uncovered the process of photocatalytic conversion from CO 2 to CO.