Study On Preparation Of BiOI Heterojunctions And Its Photocatalytic Properties

BiOI has a unique interlayer structure and a good visible light response and has great potential for photocatalytic applications.However,there are problems in the application of this material such as low visible light utilization,poor stability,and poor photocatalytic activity due to the fast rate of photoelectron-hole complexation in the photocatalytic process,which affect the practical application of the material in water pollution treatment.To address the above problems,this paper uses BiOI as the main research object and adopts a surface modification method to compound BiOI with AgBiS₂ and W₁₈O₄₉ respectively to prepare heterojunctions to promote the separation of electron-hole pairs on the semiconductor material and improve photocatalytic performance.The main research work of the thesis is as follows.AgBiS₂/BiOI composites with different ratios were prepared by the precipitation method,and the preparation and photocatalytic properties of the materials were investigated.The results showed that the introduction of AgBiS₂ did not change the crystalline structure of BiOI.The photocatalytic performance study revealed that the AgBiS₂/BiOI composites had the best photocatalytic activity（degradation rate of about 94%）when the doping amount of AgBiS₂ was 0.04.Compared with pure BiOI,the degradation rate of Rh B by the composite increased 24%.After five cycles of experiments,the degradation rate of the material could still reach 94%,indicating that the AgBiS₂/BiOI composite has good stability and the type II heterojunction formed enhances the efficiency of photogenerated electron-hole separation,which in turn enhances the photocatalytic activity of the material.Different ratios of W₁₈O₄₉/BiOI composites were prepared by a chemical precipitation method to study the preparation and photocatalytic properties of the materials.The results showed that the introduction of W₁₈O₄₉ did not change the crystalline structure of BiOI.The photocatalytic performance studied showed that the composite had the best degradation effect on Rh B（98%）when the doping amount of W₁₈O₄₉ was 0.02 g.After five cycles of testing,the degradation efficiency of the material could still reach about 98%,which proved that the material has good stability.The Z-type heterojunction formed by the photocatalytic material was inferred to be able to inhibit the compounding of photogenerated carriers well and enhance the photocatalytic activity of the material through the active material trapping experiment.WN/BiOI composites with different ratios were prepared by modifying the W₁₈O₄₉ nanomaterials using a solvothermal method.PL demonstrated that the composite photocatalytic materials could well inhibit the complexation of photogenerated electron-hole pairs.The photocatalytic performance study showed that 0.02 WN/BiOI gave the best degradation effect（99%）for Rh B.The photocatalytic effect could still reach about 99%after 5 cycles of the test,and the XRD spectra after 5 cycles did not have the diffraction peak of WO₃,indicating that WN did not oxidize to WO₃ during the photocatalytic process,indicating that the prepared composite has good stability.