Preparation And Properties Of Bisumuth-based Photocatalysts With Different Microstructures

With the rapid development of science and technology in today's world,the global energy crisis and environmental pollution have aroused people's extensive concern.Using semiconductor photocatalysts to decompose organic pollutants in visible light or sunlight has become one of the effective methods to solve these problems.TiO₂ is widely used in photocatalytic degradation of organic pollutants due to its low price and high stability.However,due to its wide bandgap,it can only be excited by ultraviolet light,which limits its application under visible light irradiation.Therefore,the development of new visible photocatalyst has become one of the main research topics of photocatalysis technology.The preparation,photocatalytic performance and improvement of photocatalytic activity of solid solution photocatalysts with dominant crystal surface and heterostructure structure were studied in this paper.The morphology,specific surface area and optical properties of the photocatalyst were characterized by a variety of test techniques,such as XRD,SEM,TEM,DRS and so on.The photocatalytic properties of the prepared photocatalyst were investigated by degradation of organic pollutants such as phenol,Rhodamine B and methyl orange.The specific work is as follows:The BiOBr_xI_1-x solid solutions were successfully synthesized both in water and ethylene glycol?EG?,using a facile solvothermal method.The as-prepared BiOBr_xI_1-x solid solutions were charaterized by scanning electron microscope?SEM?,X-ray diffraction?XRD?,UV–vis spectrophotometer and so on.Meanwhile,the photocatalytic activities of BiOBr_xI_1-x solid solutions were estimated by degrading phenol under visible light irradiation??>420nm?.The SEM revealed that 2D plate-like BiOBr_xI_1-x solid solutions can be obtained in water and the microspheres were synthesized in EG solvents,while the BiOI?EG?samples were nanoparticles.Furthermore,the BiOBr_0.5I_0.5microspheres with high exposed{110}facets showed the highest photocatalytic activity with the phenol completely degraded within 80 min under visible light irradiation.A series of novel BiPO₄-BiOBr_xI_1-x p-n heterojunctions were successfully preparedby a facile solvothermal method.The photocatalysts were characterized by scanning electron microscope?SEM?,X-ray diffraction?XRD?and ultraviolet visible diffuse reflectance spectroscopy.The photocatalytic activities of BiPO₄-BiOBr_x I_1-x heterojunctions were investigated by decomposition of phenol.And the5%BiPO₄-BiOBr_0.75I_0.25.25 heterojunction shows the highest photocatalytic activity with phenol completely decomposed in 60 min.The results of photocurrent experiments indicated that the improvement of photocatalytic activity may due to the BiPO₄-BiOBr_xI_1-x p-n heterojunctions can effectively restrict the recombination rate of the photoexcited charge carriers.In addition,hole?h⁺?was the major oxidative specie during the photocatalytic process.The energy band structure in BiPO₄-BiOBr_xI_1-x heterojunctions could be adjusted by changing the mole ratio of I and Br.In this study,a series of g-C₃N₄-BiOBr_xI_1-x composites with tunable energy band structure were successfully fabricated by using a solvothermal method.Characteristics of the as-prepared photocatalysts were investigated by XRD,SEM,TEM,EDS and DRS.The photocatalytic activity of g-C₃N₄-BiOBr_xI_1-x composites were evaluated by decomposition of Rhodamine B?RhB?and phenol under visible light irradiation.And the obtained g-C₃N₄-BiOBr_xI_1-x composites exhibited excellent photocatalytic property,especially the 5%g-C₃N₄-BiOBr_0.25I_0.75.75 composite possessed of the best photocatalytic activity among all the as-prepared samples.The remarkable photocatalytic activity was mainly attributed to the appropriate band structure,the more effective separation of photogenerated electron-hole pairs and better charge transfer.In this photocatalytic system,superoxide radicals?·O₂^-?and holes?h⁺?were the main active substances for photodegradation.A novel BiIO₄/Ag₃PO₄ nanocomposite photocatalyst was successfully synthesized througth hydrothermal and chemical precipitation methods.The as-prepared samples were charaterized by scanning electron microscope?SEM?,X-ray diffraction?XRD?and ultraviolet visible diffuse reflectance spectroscopy.Moreover the photocatalytic activity was evaluated by the degradation of phenol solution under visible light irradiation.The results showed that BiIO₄/Ag₃PO₄ nanocomposite exhibited higher photocatalytic activity than pure BiIO₄ and Ag₃PO₄,and 5%BiIO₄/Ag₃PO₄ nanocomposite was recorded to have the optimum rate constant.The enhanced photocatalytic performance may due to the formation of BiIO₄/Ag₃PO₄ heterojunction interface,whose presence regarded as a favorable factor for the separation and migration of the photo-generated electrons and holes.In addition,the active species trapping experiment demonstrated that·O₂^-and·OH were the major active species during the photocatalytic process.