Preparation And Photocatalytic Properties Of Bismuth Iodide-base Photocatalytic Materials

Photocatalytic technology is a technology developed in recent years and has a very broad application prospects in environmental governance.Photocatalysts with high photocatalytic activity are the focus of people’s research.Bismuth-based photocatalysts are one of the photocatalytic materials that people often study,because of their suitable band gap and special layered structure,bismuth halide oxide photocatalysts have special layered structure and high chemical stability,but they also have many defects,such as wide band gap,low utilization of visible light,high electron hole recombination rate,small specific surface area,poor adsorption of pollutants and a series of shortcomings.Therefore,further modification on the basis of Bismuth-based photocatalysts is needed to meet the application of actual life.In this paper,BiOI-based photocatalysts are mainly studied and modified.The main research work includes the following three aspects: first,BiOI/BiOIO₃ heterojunction photocatalysts are synthesized to improve the separation efficiency of electron-hole pairs and the adsorption efficiency of pollutants,thus improving the photocatalytic performance of BiOIO₃.Second,BiOX（X=I,Cl,Br）with different morphologies can be prepared by grinding at room temperature.The photocatalyst and its photocatalytic performance were studied.Thirdly,the photocatalytic performance of BiOI was improved by loading Ag with different content.（1）BiOI/BiOIO₃ photocatalyst was synthesized by chemical deposition at room temperature.Different molar ratios of mixture photocatalyst were prepared by changing the content of BiOI.With the increase of BiOI content in the mixed photocatalyst,it was found that the diffraction peak and morphology of the crystal did not change,but the color of the sample gradually deepened and the band gap gradually decreased.By forming a mixed photocatalyst,the band gap structure of BiOIO₃ was effectively changed,the band gap was narrowed,and the optical absorption range of BiOIO₃ was extended.Compared with pure BiOIO₃,the photocatalyst with a molar ratio of 1:1 had a 4.5 times increase in the efficiency of degradation of Rhodamine B under visible light;furthermore,the photocatalyst with a molar ratio of 1:1 synthesized at room temperature was hydrothermal reacted.After the reaction,BiOIO₃ and BiOI were successfully combined.Compared with the mixed photocatalyst synthesized at room temperature,the composite photocatalyst synthesized under hydrothermal conditions has a wider light absorption range,and the photocatalytic degradation efficiency has been further improved.BiOI/BiOIO₃ heterojunction photocatalyst can absorb more visible light and effectively promote the separation of photogenerated carriers.The adsorption efficiency of pollutants has also been significantly improved,which is the main reason for the improvement of its photocatalytic performance.（2）BiOX with different morphologies was synthesized by grinding at room temperature.The spherical BiOX could be synthesized by adding PEG400 into the reactant.BiOX with film morphology was synthesized without PEG400.The specific surface area of the spherical photocatalyst was obviously larger than that flake photocatalyst,which eventually led to the adsorptive and photocatalytic properties of spherical photocatalysis are higher than those of the flake photocatalysts.The larger specific surface area is the main reason for the high photocatalytic and adsorptive activity of the spherical bismuth halide photocatalysts.（3）BiOI photocatalyst was prepared by hydrothermal method,and a series of BiOI photocatalyst samples were prepared by adjusting the p H value of the reaction solvent.When the p H value of the reaction solvent was 3,7,9 and 11,the samples were pure BiOI photocatalyst.When the p H value was 9,the photocatalytic activity of BiOI was the highest,and the degradation efficiency of Rhodamine B reached 85.4% after 160 minutes under visible light irradiation.In order to further improve the photocatalytic performance of BiOI,BiOI photocatalyst with p H 9 was used as the precursor of the reaction.Ag/BiOI photocatalyst loaded with 0.6% and 2.8% Ag were prepared by photoreduction method.Ag/BiOI photocatalyst was synthesized when the mass content of Ag was 0.6%.Ag/Ag I/BiOI photocatalyst was synthesized when the mass content of Ag was increased to 2.8%.Under visible light,the degradation data of Rhodamine B showed that BiOI had the highest adsorption efficiency in the first 30 minutes of dark reaction.With the increase of Ag content,the adsorption efficiency of Rhodamine B became worse.After 120 minutes under visible light irradiation,the degradation rates of Rhodamine B by BiOI,0.6% Ag-BiOI and 2.8% Ag-BiOI were 81%,94% and 86%,respectively.The photocatalytic activity of Ag modified BiOI was higher than that of pure BiOI.The photocatalytic activity was highest when Ag content was 0.6%.When the Ag content is too high,it reachs 2.8%,too much Ag accumulates on the surface of BiOI and I ions are unstable.Some Ag I produced by Ag and I reactions adhere to the surface of BiOI,which affects the surface reaction of BiOI and ultimately reduces its photocatalytic efficiency compared with low-content modified Ag.