Hydrothermal Controlled Preparation Of BiOX(X=Br,I) Photocatalyst And Visible Light Degradation Of Dyes

Energy shortage and environmental pollution were the two major challenges facing human society.As a fast-moving developing country,my country’s energy and environmental issues are also particularly prominent.Photocatalytic materials have great potential in solving energy and environmental problems.Bismuth-based semiconductor materials have good photoresponse in the visible light range,and the band gap between 1.7 eV～2.9 eV is better redox capability than Ti O₂（～3.20 eV）.Moreover,its unique structure can be used as an active site for degradation of organics compounds,thus enhancing its photocatalytic performance.At present,the most researched is the bismuth oxyhalide BiOX（X=Br,I）photocatalyst,compared with the traditional catalyst.Bismuth oxyhalide complements the restricted factors of titanium dioxide and has a wider range of applications.Therefore,the bismuth-based visible light photocatalyst has become a research hotspot.However,A semiconductor is produced by an excitation such as a light excitation,the high recombination efficiency of electrons（e^-）and holes（h⁺）in bismuth oxyhalide BiOX（X=Br,I）affects its photocatalytic efficiency.Currently valid to improve photocatalysts include heterojunction recombination,ion doping,and precious metal deposition.The thesis focuses on affecting the photocatalyst.By improving the preparation process,appearance control,and conducting a series of studies,the degradation efficiency of the catalyst under visible light can be improved.The specific research content is as follows:（1）Bismuth bromate powders with different concentration ratios were prepared by hydrothermal method.By changing the molar ratio of Br to I,a kind of flake and irregular bismuth bromate was obtained.When the concentration ratio of Br:I was 2:1,the photocatalytic activity of bismuth bromate was the best under visible light,and the degradation rate was 86%after 200 min.X-ray diffraction and scanning electron microscopy were used to analyze the phase composition and surface morphology.When the concentration ratio of Br:I is 2:1,the photodegradation rate first decreases and then increases with the increase of concentration,and the change of grain size is the same as that of Br:I.（2）Bismuth iodide has become a new type of high-efficiency photocatalyst due to its unique layered structure and narrow band gap structure.By simply changing the ratio of Bi and I raw materials,the paper successfully synthesized a series of bismuth oxides with different concentration ratios of Bi:I by hydrothermal method,and studied its composition,optical properties and photocatalytic properties.X-ray diffraction patterns,scanning electron microscope images,energy dispersive X-ray energy spectroscopy,X-ray photoelectron spectroscopy and ultraviolet-visible spectroscopy analysis confirmed that the prepared bismuth oxide is Bi₇O₉I₃,Bi₃O₅I₂ and BiOI microspheres,and their size and band gap vary with As the Bi content increases,it decreases.Because Bi₇O₉I₃ has a larger specific surface area and smaller band gap than Bi₃O₅I₂ and BiOI microspheres,Bi₇O₉I₃ produces more superoxide than Bi₃O₅I₂ and BiOI microspheres under simulated sunlight.Photocatalytic dye degradation experiments show that the photocatalytic performance of Bi₇O₉I₃ is the best for 100%degradation of rhodamine B within 40 minutes,followed by Bi₃O₅I₂ and BiOI degradation rates of 78.3%and 30%,respectively.