Preparation Of Modified Bi₄O₅Br₂ Catalyst And Study On Its Photocatalytic Degradation Of Tetracyclin

In recent years,the global consumption and use of antibiotics is still on the rise,which will increase the risk of antibiotic run-off into the water environment,thus polluting the ecological environment and threatening the survival of human beings and other life forms.In order to eliminate harmful antibiotics in water resources,photocatalysis is a green and sustainable technology in line with human long-term development goals.A bismuth-rich Bi₄O₅Br₂ has attracted many scholars’attention and research due to its inherent electric field and visible light response.However,the internal photocatalytic carrier migration resistance and slow surface reaction kinetics severely limit the photocatalytic activity.Therefore,from the perspective of regulating the built electric field of Bi₄O₅Br₂,this paper enhanced the built electric field through element doping and the construction of heterojunction,alleviated the problem of poor photo-generated carrier dynamics,and thus improved its performance in the photocatalytic degradation of antibiotics.The detail research contents and results are summarized as follows:The enhancement of the built-in electric field of Bi₄O₅Br₂ was achieved by the doping of metal ions in the lattice for the purpose of modulating the kinetics of photogenerated carrier separation.In this study,Fe-Bi₄O₅Br₂ nanosheet photocatalyst doped with Fe ions were prepared using a one-step solvothermal method.The doped Fe²⁺and Fe³⁺were substituted for Bi³⁺,thus inducing spontaneous polarization and enhancing the built-in electric field.More photogenerated charges were separated and migrated to the surface in the presence of the built-in electric field,thus increasing the photocatalytic activity of 5%Fe-Bi₄O₅Br₂ for the degradation of tetracycline to 60%.Furthermore for5%Fe-Bi₄O₅Br₂,the increased specific surface area(S_BET=64.66 m²/g)exposed abundant Fe ions and the photogenerated charges accelerated the surface Fe（II/III）conversion,thus activating H₂O₂ to produce abundant·OH and·O₂^-active species.Thus,complete degradation of tetracycline was achieved in the 5%Fe-Bi₄O₅Br₂-H₂O₂system after coupling the Fenton oxidation technique.The reaction rate constant is also4.2 times that of Bi₄O₅Br₂.By constructing Z-scheme heterojunctions,it not only formed an interface-built electric field to regulate the separation of photogenerated carriers,but also fully utilized the excellent photoreduction properties of Bi₄O₅Br₂ to realize the single-electron reduction of O₂ process.In this study,W₁₈O₄₉/Bi₄O₅Br₂ Z-scheme heterojunctions were prepared by in situ growth of W₁₈O₄₉ nanowires on Bi₄O₅Br₂ nanosheets,and electrons were transferred through the"Bi-O-W"channel after close contact between W₁₈O₄₉ and Bi₄O₅Br₂ to bend energy band and establish the Z-scheme mechanism.The charge separation efficiency was improved by the built-in electric field at the interface,and the photogenerated charges with excellent redox ability were separated,so that the strong oxidation of·O₂^-and·OH were produced by the reduction of O₂ and the oxidation of water,respectively.The photocatalytic degradation rate for tetracycline of30%W₁₈O₄₉/Bi₄O₅Br₂ was 87%,and the highest degradation rate was achieved 0.013min^-1,which is 3.3 times that of Bi₄O₅Br₂.The·O₂^-and·OH produced during the photocatalytic process played a key oxidative role in the degradation of tetracycline.