Preparation And Photocatalytic Properties Of Bismuth Halide Oxide And Its Complexes

In order to solve the shortcomings of traditional semiconductor photocatalysts in the field of environmental pollution control and renewable energy development,it is an inevitable trend to explore new semiconductor photocatalysts.Due to its special crystal structure and moderate energy level distribution,bismuth halide has shown a good photocatalytic effect in the field of photocatalytic degradation of organic pollutants.Using bismuth and halogen-containing chemicals as raw materials,electron-hole recombination efficiency is low,chemical stability is strong,environmental protection is green,and many chemical synthesis methods are used to synthesize the electron-hole pair,which has the advantages of low recombination efficiency,strong chemical stability and environmental protection.Low-cost bismuth halide oxide and bismuth halide composite semiconductor photocatalysts,thenmorphology and composition of the synthesized samples were analyzed by XRD,FESEM,DRS,TEM,BET,XPS,PL and their photocatalytic mechanism was investigated.The main contents of this thesis are as follows:（1）BiOCl nanosheet with particle size between 200-600nm and thickness between 20-40nm were prepared by microwave heating method.The heterojunction of composite CdS nanoparticles semiconductor photocatalyst loaded with CdS-BiOCl was prepared and the synthesized samples were characterized.The results show that the composite CdS-BiOCl photocatalyst prepared by the above method is pure,which indicates that the two photocatalysts combine well to form a heterojunction structure.According to the degradation of Congo red（CR）organic dyes by visible light irradiation,the photocatalytic properties between them were compared.The results showed that the composite CdS-BiOCl semiconductor photocatalyst prepared by adding cadmium acetate into 0.6mmol had the best effect on the degradation of Congo red（CR）under visible light irradiation,and the photocatalytic effect was better than that of CdS.The degradation rate of BiOCl and other composite samples with acetic acid partition was up to95%after illumination by 75min.Through free radical capture measure display that superoxide radical（·O₂^-）and hole（h⁺）are the main activated matter in photocatalytic dislodge of organic dyestuff.（2）NiO nanoparticles with the size of 100nm were prepared by water bath-calcination method,and the BiOBr nanosheet with smooth surface and obvious edges were prepared by water bath method.Composite photocatalyst heterojunction（BiOBr-NiO）loaded with NiO particles on BiOBr nanosheet was prepared by ultrasonic assisted water bath method.Then the synthesized samples were characterized.The results show that the composite photocatalyst BiOBr-NiO prepared by the above method is pure,indicating that the heterojunction structure has been successfully prepared by the above chemical synthesis method.The photocatalytic properties of Congo red（CR）and rhodamine B（RhB）were compared according to the degradation of Congo red dye and rhodamine B（RhB）in different volume ratios by visible light irradiation.The results showed that under visible light irradiation,the degradation of CR and RhB with volume ratio of 1:1 was the best when the dosage of NiO was 0.1g,and the photocatalytic effect was better than that of BiOBr,NiO and other composite samples with NiO dosage.After illumination with 45min,the degradation rate was over 92%.Through the free radical capture experiment,it plays a major role in the photodegradation of dyes.The results show that superoxide radical（·O₂^-）and hole（h⁺）are the main active matter in photocatalytic degradation of organic dyes.（3）Highly ordered three-dimensional（3D）multilayer Bi₄O₅Br₂ nanoshells were prepared by green ultrasound assisted anion exchange reaction and combustion treatment.The results show that the ternary Bi₄O₅Br₂ nanoshells has a pure monoclinic phase with an average thickness of about 12 nm.The nanoshells wall is made up of 10/12 layers of nano-grains of the size of 10nm.The specific surface area is 36.18m²/g and the band gap is about 2.52eV.The possible formation process of Bi₄O₅Br₂ nanoshells was simply proposed.The photocatalytic degradation efficiency of bismuth bromide precursor and ternary Bi₄O₅Br₂ nanoshells were compared according to the degradation of resorcinol（RC）organic dyes by visible light irradiation.The results showed that the prepared Bi₄O₅Br₂nanoshells showed excellent photocatalytic activity,which was far higher than the degradation rate of BiOBr precursor nanosheet.It is also superior to other reported structures of Bi₄O₅Br₂,indicating that it can be used to degrade organic pollutants.