A Novel Plasmonic Photocatalyst Ag-AgBr/Bi₃O₄Cl With Enhanced Photocatalytic Activity For Tetracycline Degradation

With the widespread use of antibiotics in industry,agriculture and treatment of human diseases,a series of environmental pollution problems are threatening ecosystems and human health all over the world.Tetracycline（TC）,as a typical antibiotic,is widely added in drugs and feed additive.Due to its great chemical stability and antibacterial ability,the TC can hardly be decomposed naturally in water,and therefore has caused a lot of environment pollution.In this situation,semiconductor photocatalysis has attracted attention of researchers because of its splendid efficiency,low cost and environment friendly property.However,some traditional photocatalysts such as Ti O₂,Sr Ti O₃ and Cd S were limited by their own structural flaws,and caused them difficult to meet the needs of solving real environmental problems.Therefore,exploring high-efficiency and stable visible-light-driven photocatalysts becomes particularly important.In this paper,based on the existing research,a novel plasmonic composite photocatalyst Ag-AgBr/Bi₃O₄Cl was prepared,the possible mechanism for TC degradation and the possibility of its practical application were proposed.Specific research contents are as follows:（1）In this paper,AgBr/Bi₃O₄Cl was synthesized by hydrothermal-precipitation method for the first time,and then a novel plasmonic composite photocatalyst Ag-AgBr/Bi₃O₄Cl was successfully prepared by photo-deposition method for tetracycline degradation under visible light.Through a series of characterization methods,such as X-ray diffraction（XRD）,photoelectron spectroscopy（XPS）and transmission electron microscopy（TEM）,the diffraction peaks,structural morphology,elemental composition and chemical state of the target material were analyzed in detail.（2）The photocatalytic activities of the Bi₃O₄Cl,AgBr and Ag-AgBr/Bi₃O₄Cl were evaluated by investigating the removal rate of TC under visible light irradiation.Compared with the monomer materials,the photocatalytic activity of the composite materials in each ratio was improved obviously.30%Ag-AgBr/Bi₃O₄Cl composite photocatalyst achieved the highest photocatalytic tetracycline（TC）removal efficie ncy of70%under visible light（λ>420nm）within 30min,increasing 41%and 46%than pure Bi₃O₄Cl and Ag-AgBr,respectively.In addition,the composites also showed good stability and recyclability.After 5 rounds of cycle experiments,the degradation amount of TC was reduced by only 5%（3）It is fascinating to note that the surface plasmon resonance（SPR）effect of Ag nanoparticles played a crucial role in the degradation process of TC,which improved the photocatalytic activity in following three ways:1,Enhance the absorption intensity of visible light and expand the absorption edges from 474 nm（Bi₃O₄Cl）to 520 nm（30%Ag-AgBr/Bi₃O₄Cl）（as confirmed by SPV and DRS results）.2,Speeds up the transfer of electrons and inhibit the recombination of electro n-hole pairs in the photocatalyst（as proved by the ESI and photocurrent results）.3,Generate more reactive species like·O₂^-,h⁺and Br⁰（as confirmed by ESR and scavenge tests）.This study highlighted the role of SPR effect of Ag NPs on alleviating environmental pollution and provides a novel insight to explore the highly efficient photocatalysts.