Oxygen vacancies-tuned BiOBr nanosheets for accelerating CO2 and Cr(VI) photoreduction

Unsatisfactory charge separation ability and insufficient active sites are the main factors leading to low photocatalytic CO2 conversion and Cr(VI) reduction. Constructing surface defects to accelerate charge separation is an effective strategy for promoting CO2 reduction kinetics. Herein, the oxygen vacancies modulated BiOBr nanosheets were constructed by NaBH4 solution treatment. Density functional theory calculation results found that the formed oxygen vacancies would increase electron density around Bi atoms near the oxygen vacancies, and inhibiting recombination of the photoinduced carriers. Besides, abundant oxygen vacancies boosted the CO2 adsorption. Therefore, the constructed BiOBr with rich oxygen vacancies (BiOBr-ROV) shows higher evolution rates for CO (15.66 μmol g−1) and CH4 (0.22 μmol g−1) under irradiation of 300 W Xe lamp for 4 h compared with pristine BiOBr nanosheets (BiOBr) and BiOBr with deficient oxygen vacancies (BiOBr-DOV). The intermediate products in the CO2 reduction process have been detected by in-situ Fourier-transform infrared spectroscopy. Besides, the photodegradation activity of Cr(VI) over BiOBr-ROV is 98.65 % under 100 min of irradiation, which is higher than that of BiOBr (78.01 %) and BiOBr-DOV (53.67 %). The work provides a new possibility to construct photocatalysts with high-performance for solar energy conversion.