Preparation And Modification Of Bismuth Oxybromide Photocatalyst

Photocatalytic technology has become the research focus of recent society to solve environmental pollution problems due to its low loss and low cost.Bi OBr semiconductor photocatalyst material has attracted extensive attention due to its unique layered structure,but Bi OBr has a wide band gap（～2.9 e V）,It can only respond to some wavelengths of visible light.In order to improve the photocatalytic efficiency of Bi OBr,the following methods were used to modify it:a method of capturing photo-generated electrons and separating photo-generated charges by using the plasmon resonance effect of noble metal alloy nanoparticles;a method combining type-II recombination and noble metal modification to further Separation of photogenerated electrons and holes;separation of photogenerated charges by constructing a Z-scheme composite photocatalyst while retaining the redox ability.In this paper,several modification methods of Bi OBr photocatalyst materials were proposed,which provided some help for the development of photocatalytic technology.The main research contents of this thesis include:（1）Au Ag/Bi OBr composite photocatalyst was prepared by uniformly modifying Au Ag alloy nanoparticles on the surface of Bi OBr nanosheets by photoreduction method.The photocatalytic degradation experiments of AO7 and Rh B dyes and the reduction of Cr（VI）were carried out under simulated sunlight irradiation.The experimental results showed that the modification of noble metal nanoparticles significantly improved the photocatalytic efficiency of Bi OBr.And according to the photocatalytic cycling experiments,it was found that the Au Ag/Bi OBr composite has good photocatalytic stability.The photocatalytic mechanism of the Au Ag/Bi OBr composite was analyzed,and it was concluded that after the Au Ag alloy nanoparticles were modified on the surface of Bi OBr,they were excited by light to produce a plasmon resonance effect,which not only promoted the separation of photogenerated charges but also increased their number.（2）The Ba Ti O₃nanoparticles were modified on the surface of Bi OBr firstly by hydrothermal method,and then the Au Ag alloy nanoparticles were decorated on the surface of the bare Bi OBr nanosheets by the photoreduction method,and finally the Au Ag/Bi OBr/Ba Ti O₃composite was obtained.The photocatalytic degradation and reduction experiments were carried out under the excitation of visible light,and the experimental results showed that the modification of Au Ag alloy and Ba Ti O₃nanoparticles improved the photocatalytic efficiency of Bi OBr composite photocatalyst.The mechanism analysis of the Au Ag/Bi OBr/Ba Ti O₃composite photocatalyst shows that the photogenerated electrons in Bi OBr are captured by the Au Ag alloy,and the photogenerated holes flow to the Ba Ti O₃nanoparticles,realizing the migration of photogenerated charges in different directions,thus greatly improving the Bi OBr photocatalyst photocatalytic efficiency.（3）The Cu S/Bi OBr composite photocatalyst material was prepared through hydrothermal method.Using XRD and SEM of the product,it was concluded that Cu S nanoparticles with a particle size of about 50-100 nm were successfully decorated on the surface of Bi OBr nanosheets in this experiment.Electrochemical and fluorescence test results show that the photo-generated charge separation and transfer efficiency of the composite are higher than that of Bi OBr monomer.The results of photocatalytic degradation and reduction experiments under simulated sunlight irradiation showed that the modification of Cu S significantly improved the photocatalytic performance of Bi OBr photocatalytic materials.Analysis of the photocatalytic mechanism implyed that the potential matching of Cu S and Bi OBr constitutes a Z-scheme composite,which improves the separation efficiency of photogenerated charges while retaining the redox ability of photogenerated charges,thereby improving the photocatalytic reaction efficiency.