In₂O₃ Nanoparticle/Bi₄O₅Br₂ Nanosheet S-Scheme Heterojunctions with Interfacial Oxygen Vacancies for Photocatalytic Degradation of Tetracycline

The development of highly efficient photocatalysts for antibiotics contamination in water remains a severe challenge. In this study, In2O3 nanoparticle/Bi4O5Br2 nanosheet S-scheme heterojunction with interface oxygen vacancies (OVs) was constructed by a hydrothermal-calcination approach and a simple chemical precipitation process. Under simulated sunlight, this composite showed enhanced degradation efficiency for tetracycline hydrochloride (TCH) with 92.4%, which was much higher than those of pure Bi4O5Br2 (50.2%) and In2O3 (28.6%). The excellent removal efficiency was mainly attributed to the synergistic effect of S-scheme heterojunctions and interface OVs accelerating the complexation of unwanted electrons (e-) and holes (h+), thus retaining e- with the strong oxidizing ability and h+ with the strong reducing ability to participate in the reaction. In addition, the abundant OVs in In2O3 nanoparticles/ Bi4O5Br2 nanosheets could enhance the adsorption of O-2 and promote the generation of superoxide radicals (center dot O-2(-)). The toxicity of the tetracycline degradation products and the catalyst was evaluated by E. coli growth inhibition experiments. Based on the TCH intermediates detected by HPLC-MS, three possible TCH degradation pathways were proposed. This study shows that the construction of S-scheme heterojunctions with interfacial defects is an effective strategy for the preparation of efficient photocatalysts.