| With the continuous progress of society,the problems of environmental pollution and energy crisis are becoming more and more serious.It is difficult to eradicate organic pollutants in water thoroughly by general physical and chemical methods.While photocatalytic technology can achieve that because of its converting solar energy into chemical energy ability.Photocatalytic material is the key factor of photocatalysis technology while traditional photocatalytic materials have drawbacks of poor photoresponse,easy recombination of photogenerated electrons and holes,and few surface active sites,thus limit their industrial application.In recent years,bismuth oxyhalide（BiOX X=Cl,Br,I）is expected to be used in the treatment of pollutants in water due to its good visible light response and photocatalytic activity.However,the pure phase bismuth oxyhalide has problems such as higher carrier recombination rate and lower carrier migration efficiency,which seriously restrict its practical application.Based on this,bismuth oxyhalide（BiOX,X=Cl,Br,I）was selected as the matrix,and bismuth oxyhalide-based photocatalytic composites with excellent photoresponse were successfully prepared through morphology control and heterostructure construction.Through the analysis of microscopic morphology,phase structure and photocatalytic performance,the structure-activity relationship between the structure and performance of bismuth oxyhalide-based photocatalytic composites was established,and the photocatalytic mechanism was combed in detail.（1）Using Bi（NO3）3·5H2O and Na Cl as the main raw materials and PVP as the surfactant,ultra-thin（2D）BiOCl nanosheets were prepared by simple solvothermal method.The CeO2/BiOCl composite materials with different molar ratios are prepared by the precipitation method,and the two-phase composite materials with best performance are selected.A series of g-C3N4/BiOCl/CeO2 composite photocatalyst materials with different mass ratios were synthesized by directly calcining porous layered g-C3N4,compounding g-C3N4 with CeO2/BiOCl photocatalytic material with the best degradation performance.And then characterized by XRD,SEM,TEM,DRS and photocatalytic degradation for the material composition,structure,optical properties and photocatalytic performance.The results show that the prepared g-C3N4/BiOCl/CeO2 three-phase composite material can effectively suppresses the recombination of photogenerated electron holes,and when the Ce:Bi molar ratio is 2:1and the mass ratio of g-C3N4 is 5%,the composite photocatalytic material shows the highest photocatalytic activity.The RhB solution can be completely degraded in 50minutes,and the results of repeated photocatalytic experiments show that the photocatalytic materials show good stability.Finally,through the capture experiment,it was clarified that the real active substances in the photocatalysis experiment were holes and superoxide radicals,and the photocatalytic mechanism of the photocatalytic composite material was discussed in detail.（2）In order to investigate the influence of the thickness of bismuth oxyhalide nanosheets and different forbidden band widths on the performance of three-phase composite materials,BiOBr photocatalytic materials were prepared directly by solvothermal using Bi（NO3）3·5H2O and Na Br as the main raw materials.And CeO2/BiOBr composite materials with different molar ratios and g-C3N4/CeO2/BiOBr three-phase composite materials with different molar ratios were prepared by the precipitation method.And then characterized through XRD,SEM,TEM,XPS,DRS and other characteristics for the material morphology and structure analysis.Rhodamine B（RhB）solution was used as simulated dye wastewater for photocatalytic degradation experiments to study and analyze the photocatalytic degradation performance of materials.The results show that the prepared 15wt%g-C3N4/CeO2/BiOBr three-phase composite material has a sandwich layered stacking structure,which can effectively suppress the recombination of photogenerated electron hole pairs.When the Ce:Bi molar ratio is 1:1 and the g-C3N4 mass ratio is 15%,the three-phase composite photocatalytic material exhibits the highest photocatalytic activity,and the degradation rate is as high as 99%in 40 min.In addition,the results of repeated photocatalytic experiments showed that after 4 cycles,the RhB degradation efficiency of photocatalytic materials remained above 89%,showing good stability.Finally,the photocatalytic mechanism of the photocatalytic composites was explored in detail through capture experiments.（3）Using Bi（NO3）3·5H2O and KI as the main raw materials,ethanol and aqueous solution as the solvent,PVP as the surfactant to prepare BiOI photocatalytic material with flower-like structure through solvothermal method to investigate the interaction of different BiOX morphology and the structure,morphology and photocatalytic activity of the prepared composite materials.CeO2/BiOI composite materials with different molar ratios and CeO2/BiOI/g-C3N4 three-phase composite materials with different mass ratios were prepared.And through XRD,SEM,TEM,XPS,DRS and other characteristics of the material to analyze the morphology,structure,photocatalytic degradation experiments.The results show that the prepared CeO2/BiOI/g-C3N4three-phase composite material has excellent photocatalytic properties and can effectively inhibit the photo-generated electron-hole-recombination.When the Ce:Bi molar ratio is 2:1 and the mass ratio of g-C3N4 is 20%,the composite photocatalytic material shows the highest photocatalytic activity.The degradation rate of RhB solution reaches 71%in 1 h,but it is less than the three-phase composite materials that is prepared by（2D）BiOCl ultra-thin nanosheets and（2D）BiOBr nanosheetst.Repeated photocatalytic experiments on 20wt%CeO2/BiOI/g-C3N4 showed that after 4 repeated experiments,the degradation efficiency of RhB was still up to 65%,indicating that the photocatalytic materials had good stability.Finally,through the capture experiment,it was clarified that the real active substances in the photocatalysis experiment were holes and superoxide radicals.Also,the photocatalytic mechanism of the 20wt%CeO2/BiOI/g-C3N4 photocatalytic composite material was deeply analyzed. |
