In situ preparation of 3D flower sphere Bi4O5Br2/Bi24O31Br10 heterojunctions by calcination for enhanced antibiotic degradation

The 3D flower sphere Bi4O5Br2/Bi24O31Br10 was successfully prepared by solvothermal method and subsequent calcination. During the calcination process, Bi4O5Br2 nanosheets polymerized gradually into Bi24O31Br10 nanosheets with the construction of heterojunctions and the morphology changed obviously with the original dense flower sphere structure assembled by nanosheets gradually changing to loose structure accompanied by a slight volume reduction. The Bi4O5Br2/Bi24O31Br10 heterojunction framed was successfully proved by XRD, HRTEM and XPS. In addition, the light absorption edge and photocurrent responses of synthesized heterojunction materials were significantly stronger than that of pure Bi4O5Br2 and Bi24O31Br10. BOB-300 showed the highest photocatalytic performance compared with single Bi4O5Br2 and Bi24O31Br10 for the degradations of CIP and TC. Moreover, the contributions of ·O2− and h+ were further studied, especially ·O2− played a primary role in the photocatalytic process. The photocatalytic mechanism and calcination reaction process for the Bi4O5Br2/Bi24O31Br10 heterojunction were proposed.