BiOBr/ Bi4O5Br2/PDI constructed for visible-light degradation of endocrine disrupting chemicals: Synergistic effects of bi-heterojunction and oxygen evolution

To remove endocrine disrupting chemicals (EDCs), visible-light response photocatalyst BiOBr/Bi4O5Br2/perylene diimide (PDI) with bi-heterojunction was constructed. Under visible-light irradiation, BiOBr/Bi4O5Br2/PDI could degrade 90% Bisphenol A (BPA) within 75 min, while degrade 100% 17α-ethynyl estradiol (EE2) and 17β-estradiol (E2) within 15 min. Radicals quenching experiment and EPR indicated both •O2– and holes were the main substances for EDCs degradation, and the possible degradation pathway of EDCs are proposed based on the LC-MS analysis results. In the composite of BiOBr/Bi4O5Br2/PDI, the matching energy band structure between Bi4O5Br2 and BiOBr facilitated the formation of heterojunction for strengthening the space charge separation. Meanwhile, PDI with strong photosensitivity combined with BiOBr/Bi4O5Br2 not only enhanced visible-light photocatalytic activity but also broadened the light-harvesting range. Owning to the unique one-dimensional conjugated structure and internal electric field effect, PDI could also promote the photo-carriers transfer and separation. With the bi-heterojunction effect, photo-generated electrons were transferred to BiOBr conduction band while holes were accumulated on PDI valence band. Simultaneously, holes could oxidize water with the production of oxygen following being reduced to •O2– by photo-generated electrons. Even under oxygen-poor conditions, the production of •O2– can reach 32.7 × 10-5mol•g−1•h−1, resulting in more than 85% BPA degradation within 75 min.