Study On The Preparation And Photocatalytic Performance Of BiOBr-Based Heterojunctions Composites

As a visible light responsive photocatalyst,BiOBr has a suitable band gap and a special layered structure,showing a broad development prospect in the direction of photocatalytic treatment of organic wastewater.However,pure BiOBr only absorbs a small amount of visible light,and the photocatalytic and stabilization performance is still low compared to the actual demand.In order to meet the needs of practical applications,it is necessary to modify BiOBr.In this paper,flower globular BiVO₄/BiOBr,coral-like ZnO/BiOBr and hollow core-shell ZnO/BiOBr heterojunction composites were prepared by various methods.XRD,FE-SEM,TEM,XPS,FT-IR,DRS,BET,PL and other analytical methods were applied to analyze the chemical composition,morphology,optical absorption,photocatalytic performance and photocatalytic mechanism of BiOBr-based composites.The main contents of this dissertation are given as follows:Flower globular BiVO₄/BiOBr heterojunctions were prepared by ionic liquid-hydrothermal method.Firstly,BiOBr microspheres with good dispersion were prepared by ionic liquid method.Then,BiVO₄ nanosheets were synthesized in situ on the surface of BiOBr microspheres by ion-exchange effect and then BiVO₄/BiOBr heterojunctions were formed.The method not only effectively prevented the agglomeration of BiVO₄ nanosheets,but also made BiVO₄/BiOBr heterojunction showed better photocatalytic activity than pure BiVO₄.when the theoretical molar ratio of BiVO₄ to BiOBr was 1:3,after 180 min and 140 min of visible light irradiation,respectively,the degradation rates of Rhodamine B（Rh B）and tetracycline hydrochloride（TC）by BiVO₄/BiOBr heterojunctions were 97.49%and 73.99%,respectively.They were 15.26 times and 1.19 times of pure BiVO₄,respectively.In addition,compared with pure BiOBr,its visible light absorption and stability were improved.Coral-like ZnO/BiOBr heterojunctions were prepared by chemical precipitation-ionic liquid method.First,floral ZnO composed of nanorods was synthesized by chemical precipitation method.Then BiOBr nanosheets were grown on 3D ZnO surface by hydrothermal method to form coral-like ZnO/BiOBr heterojunction with high specific surface area.The results showed that ZnO/BiOBr heterojunctions had the best photocatalytic degradation when the theoretical molar ratio of ZnO to BiOBr was 1:1.The degradation of Rh B,TC and K₂Cr₂O₇ by ZnO/BiOBr heterojunctions reached 96.7%,87.3%and 49.8%,respectively,after 40 min,45 min and 100 min of visible light irradiation,which were 9.3 times,1.7 times and 41.5 times of pure ZnO.The light absorption and carrier transfer rates of ZnO/BiOBr heterojunctions were significantly enhanced.Hollow"core-shell"ZnO/BiOBr heterojunctions were synthesized by hydrothermal-ionic liquid method for.Firstly,ZnO hollow spheres were synthesized by hydrothermal method using D-glucose and Zn（CH₃COO）₂·2H₂O as basic materials,and then BiOBr nanosheets were compounded on the surface of ZnO hollow spheres by ionic liquid method to form Z-scheme ZnO/BiOBr heterojunctions.When the theoretical molar ratio of ZnO to BiOBr was 1:1,the degradation rates of TC,Rh B and K₂Cr₂O₇ by ZnO/BiOBr heterojunctions reached 86.76%,95.33%and 58.23%,respectively,after 90 min,25 min and 180 min of visible light irradiation,which were1.35 times,1.41 times and 2.41 times of flower globular BiOBr,respectively.The rised photocatalytic properties was due to the enhencement of visible light absorption and the formation of Z-scheme heterojunctions.