Study On Preparation And Photocatalytic Properties Of BiOBr_xI_1-x And Its Modified Materials

In recent years,semiconductor photocatalytic technology has received extensive attention in the energy and environmental fields due to its advantages in processing refractory pollutants in depth and utilizing sunlight.The bismuth oxyhalide photocatalyst is favored by researchers because of its suitable forbidden band width and layered structure.It is found that a single BiOX?X=Cl,Br,I?has its own limitations,quantum efficiency.Higher BiOCl can only absorb ultraviolet light in sunlight.BiOBr can only use a small amount of visible light,and BiOI which responds greatly to visible light is an unstable catalyst.Therefore,it is of great practical significance to develop an efficient and stable visible light catalyst.The formation of solid solution based on two kinds of semiconductor materials is an effective way to obtain an ideal photocatalyst.The solid solution catalyst can control the energy band structure of the catalyst and its photocatalytic degradation performance by changing the ratio of halogen elements.Under the premise of maintaining the layer structure of BiOBr and the unique indirect transition mode,a highly efficient and stable visible light type is formed.This paper is devoted to the preparation of high-efficiency visible light catalyst BiOBr_xI_1-x by simple hydrolysis.Then,the catalyst was modified by sodium borohydride as the reducing agent without adding external elements,and Bi/BiOBr_0.8I_0.2 composite photocatalyst was prepared.The specific research contents are as follows:?1?A series of visible light catalysts of BiOBr_xI_1-x were prepared by adjusting the element ratio of Br and I at room temperature by simple acetic acid-assisted hydrolysis.The crystal phase structure,composition,morphology,specific surface area,pore structure,interface charge transfer and UV-visible absorption of the catalyst were characterized by XRD,SEM,HRTEM,BET,XPS,PL,PC,EIS and UV-vis DRS.The performance was analyzed to determine the optimum ratio of halogens.Under the irradiation of visible light,the photocatalytic degradation performance of the catalyst was studied in depth and the reaction mechanism was proposed.Experimental data and various test results.It indicates that the photocatalytic degradation activity of the catalyst is greatly improved after the formation of solid solution.When the ratio of Br and I added forms 3D rosette BiOBr_0.8I_0.2,the degradation activity of the catalyst reaches the maximum,and the visible light absorption of the spectrum The scope has increased greatly.Further research on the catalytic mechanism of the catalyst reveals that with the increase of Br element,the valence band of the semiconductor material shows a continuous decreasing trend.Combined with the specific surface area of the catalyst,the forbidden band width and specific surface area of the semiconductor are combined to control the photogenerated electrons and holes.The generation and recombination explain the difference in the degradation activity of halogens in different proportions.Combined with the capture agent experiment and ESR characterization,the active species in the degradation process were analyzed and the degradation mechanism was proposed.?2?Based on the above research results,in order to further improve the photocatalytic performance of the catalyst.The modification of BiOBr_0.8I_0.2catalyst was carried out by using semi-metallic elemental elemental Bi.A series of Bi/BiOBr_0.8I_0.2 composite catalysts were prepared by reducing Bi³⁺of the solid solution catalyst BiOBr_0.8I_0.2 to elemental Bi by different concentrations of sodium borohydride.The obtained catalysts were characterized by XRD,SEM,HRTEM,XPS,PL,PC,UV-vis DRS,and their crystal phase structure,composition,morphology,photoelectrochemical properties and UV-visible absorption properties were analyzed.The bisphenol A was used as the target degradation product to detect the effect of the reduction of Bi element on the photocatalytic degradation activity of the catalyst.The experimental results show that when the concentration of NaBH₄ is 35 mmol/L,the catalyst reaches the maximum degradation activity,and the stability of the catalyst is confirmed by the cycle experiment.Further research on its photocatalytic mechanism found that the excellent performance of the composite photocatalyst reduced by NaBH₄ is mainly attributed to the surface plasmon resonance effect of Bi elemental.