Preparation Of Bi₄O₅Br₂-based Composite Photocatalytic Material For Degradation Performance Of Organic Pollutants In Water

Among many semiconductor photocatalysts,Bi₄O₅Br₂has attracted attention due to its excellent visible light absorption capacity and unique electronic structure,but pure Bi₄O₅Br₂has a relatively narrow band gap,which leads to a higher photogenerated carrier recombination rate and a lower photocatalytic activity.In order to promote the separation efficiency of photogenerated carriers of Bi₄O₅Br₂,the coupling with broad band gap semiconductor materials（AgI and BiOCl）were used to modify Bi₄O₅Br₂via the room temperature deposition and hydrothermal method,respectively.The main research contents are as follows:P-Bi₄O₅Br₂ photocatalyst was synthesized by polyvinylpyrrolidone（PVP）assisted hydrothermal method,and on this basis,P-Bi₄O₅Br₂/AgI 2D/0D heterojunction was synthesized by in-situ deposition method.The as-prepared composites were characterized by XRD,SEM,BET,UV-vis DRS and electrochemical analysis.The photocatalytic efficiency was evaluated by degrading rhodamine B（Rh B）under simulated sunlight.P-Bi₄O₅Br₂/AgI-50（Shorthand for PBA-50,the mass fraction of AgI in the composite material is 50%）can degrade 98%Rh B when irradiated by a 500 W xenon lamp for 90 min,and its pseudo first-order reaction rate constant was 0.04265 min^-1,which are 17.1,2.16 and2.94 times of Bi₄O₅Br₂,P-Bi₄O₅Br₂and AgI,respectively.The enhanced photocatalytic activity of P-Bi₄O₅Br₂/AgI was attributed to its better visible light capture ability,larger specific surface area and stronger separation efficiency of photogenerated carriers.In addition,the effects of PBA-50 on the photocatalytic degradation of Rh B at different doses of photocatalyst and in the presence of different anions were analyzed.Free radical capture experiments confirmed that·O₂^-and h⁺are the main active species when degrade Rh B.Based on the capture experiment and Mott-Schottky experiment,a possible photocatalytic mechanism of P-Bi₄O₅Br₂/AgIⅡ-type heterojunction was proposed.In addition,the cycle experiment showed that the P-Bi₄O₅Br₂/AgI composite photocatalyst has good photocatalytic stability and structural stability.A series of 2D/2D Bi₄O₅Br₂/BiOCl（Shorthand for BC）composite photocatalysts with different mass ratios of BiOCl were synthesized by solvothermal method.The physical and chemical properties of the catalyst were characterized by XRD,SEM,UV-vis DRS,BET,PL,photocurrent and electrical impedance analysis.Rhodamine B（Rh B）was selected as the target pollutants,and the photocatalytic degradation performance of the prepared photocatalyst was evaluated under the irradiation of a 500 W xenon lamp.The results showed that BC-3（the mass ratio of Bi₄O₅Br₂to BiOCl is 1:1）had the best photocatalytic performance among all the samples.It can degrade 99%of Rh B within 60 min.Its pseudo-first order reaction rate constant for degradation of Rh B could be 0.06813 min^-1,which is 37 and 3 times of pure Bi₄O₅Br₂and BiOCl,respectively.The enhanced photocatalytic activity of BC was attributed to its larger specific surface area and higher carrier separation efficiency.The effects of BC-3 on the photocatalytic degradation of Rh B at different doses of photocatalyst and in the presence of different anions were analyzed.Free radical capture experiment results showed that·O₂^-and h⁺are the main active species when degrade Rh B.Based on the capture experiment and Mott-Schottky experiment,a possible Bi₄O₅Br₂/BiOCl type-Ⅱheterojunction mechanism was proposed.As-prepared Bi₄O₅Br₂/BiOCl composite photocatalyst had strong photocatalytic activity and photocatalytic stability.