Enhanced visible light utilization of BiOI/BiOBr/Bi composite catalytic materials for photocatalytic degradation of TC and reduction of Cr(Ⅵ)

The rational design and construction of semiconductor photocatalytic materials are important significance for efficient utilization of solar energy and enhancement of photocatalytic activity. In this study, composite photocatalytic materials modified with Bi0 on the surface of BiOI/BiOBr heterojunction were successfully constructed based on the current mature electrostatic spinning technology by using solvothermal and in-situ reduction methods. The successful preparation of BiOI/BiOBr/Bi composites was confirmed by a series of characterization methods. The composite photocatalyst was applied to the degradation of pollutants, and by adjusting the addition ratio of different substances, it was found that the photocatalytic composites prepared with the addition of 0.125 mmol NaBH4 and the ratio of I/Br of 3:1 showed the best performance. The degradation efficiency of the catalyst for tetracycline hydrochloride (TC) at 10 mg/L reached 98.4 % after 180 min of visible light irradiation, and the high degradation performance of the material was maintained after five cycles. Meanwhile, the reduction efficiency of the material for Cr(VI) was 98.2 % after 100 min of visible light irradiation. Free radical trapping experiments demonstrated that photogenerated holes (h+) and superoxide radicals (•O2-) are the main active substances for photocatalytic degradation of TC. Due to the partial reduction of Bi0, the absorption of the catalyst in the near-infrared region was enlarged, which enhanced the photothermal effect of the whole material and further improved the catalyst activity.