Photocatalytic properties of Z-scheme heterojunction BiO2-x/ZnWO4 on antibiotics in water

Abstract

Heterojunction combining with two kinds of different band structures semiconductors was constructed, and its photocatalytic performance could be greatly improved with the wider optical response range. The BiO2-x/ZnWO4 composite was prepared by a simple two-step hydrothermal method. The structure, morphology and optical properties of BiO2-x/ZnWO4 were characterized by XRD, SEM and UV-vis diffuse reflectometry. The photocatalytic performance and cyclic stability of BiO2-x/ZnWO4 were studied by degrading tetracycline under visible light. The results showed that with the synergistic action between BiO2-x and ZnWO4, the photo-generated carriers of BiO2-x/ZnWO4 could be effectively separated and the light absorption capacity of BiO2-x/ZnWO4 could be significantly enhanced. After 90 min of visible light illumination, the photodegradation efficiency of the composite towards tetracycline reached 86.04%, and the light response range and photocatalytic activity of the composite were better than the monomer BiO2-x and ZnWO4. In addition, the composite displayed good light stability. The capture experiments and ESR showed that h+, O2·- and ·OH were produced by the composites under light, in which h+ and O2·- were the main active substances in the process of photocatalysis, and ·OH was the minor active species, following the order of h+>O2·->·OH. It was inferred that the electron transfer mechanism of BiO2-x/ZnWO4 was Z-scheme heterojunction.

Keywords

• photocatalysis
• zinc tungstate
• antibiotic
• z-scheme heterojunction