Synthesis And Modification Of Bismuth And Sulfide-based Semiconductors For The Photocatalytic Oxidative Coupling Of Benzyl Amine

Solar energy is one of the cleanest and most sustainable energy sources.Photocatalyst has attracted extensive attentions because of its ability to convert solar energy into chemical energy.More and more semiconductor photocatalysts have been designed and applied in photocatalytic decomposition of water,degradation of organic pollutants and organic reactions.There are a lot of semiconductor materials used as photocatalysts.However,most of them are faced with the problems of low migration efficiency and high recombination rate of photogenerated carriers.The response to visible light of semiconductor materials is also one of the issues considered by researchers.Bismuth semiconductor and transition metal sulfides are both semiconductor materials with a good light response.In this paper,multilayer bismuth salt semiconductors were synthesized and then combined with other semiconductor materials such as transition metal sulfide and metal oxide to form a photocatalytic system with the high photocatalytic performance.In the end,zinc sulfide was obtained through hydrothermal method with different surfactants.The obtained photocatalysts were all applied to the organic reaction of oxidation coupling of benzyl amine.The relevant researches are as follows:1.The rod-like CdS nanomaterials and layered Bi₂WO₆ nanomaterials were prepared by solvothermal method,respectively,and then a series of composites were obtained by compounding the two materials.The obtained materials were characterized by UV-Vis DRS,XRD,SEM,XPS and nitrogen adsorption-desorption test.The prepared catalysts were applied to the photocatalytic oxidation of benzyl amine.The mass ratio of CdS to Bi₂WO₆ in the composite with the best photocatalytic performance was 15:100.The conversion rate of benzyl amine could reach 97%and the selectivity of the corresponding imine could reach 99%.Finally,it was found that the main reactive species in the reaction was photogenic holes through the mechanism exploration experiments,and the possible reaction mechanism was also discussed.2.On the basis of the first part,another bismuth metal salt semiconductor of Bi₂MoO₆ was selected and its photocatalytic activity was enhanced by combining with the micron Cu₂O.Bi₂MoO₆ nanomaterials and Cu₂O micron materials were synthesized by solvothermal method and the two were then combined.A series of photocatalysts obtained were also applied to the photocatalytic oxidation of benzyl amine.Because Cu₂O can be used as an excellent platform for conducting electrons,the separation efficiency of photogenerated carriers in the material with illumination was improved,so that the catalytic performance of the catalyst was improved.The photoelectric properties of the samples were studied by PL and EIS.In a series of composite materials,the composite with the mass ratio of Cu₂O to Bi₂MoO₆ of 10:100 had the best photocatalytic performance.The experimental results showed that the conversion of benzyl amine was up to 98%with the selectivity up to 99%,and the lighting time was shortened one hour than the CdS/Bi₂WO₆ nanocomposites..3.The methods to improve the photocatalytic activity of materials include not only forming a reasonable and efficient photocatalytic system by combining with other materials,but also changing the synthesis process of materials and controlling the morphology of materials.Different surfactants were used to prepare ZnS nanomaterials with various structures by hydrothermal method.The results of photocatalytic activity test showed that the ZnS obtained by hydrothermal reaction with polyvinylpyrrolidone as the surfactant had the highest photocatalytic coupling efficiency of benzyl amine.The experimental results showed that the conversion of benzyl amine was 95%with the selectivity of 99%.The photocatalytic performance of ZnS was almost unchanged after four cycles of photocatalytic experiments,indicating that the prepared catalyst had a good stability.