Study On Preparation And Photocatalytic Degradation Performance Of Surface Modified BiOBr Photocatalytic Materials

To treat the polluted water sources,photocatalysis has been recognized as a new,non-toxic and efficient technology.Recent studies have shown that photocatalytic technology has a significant effect on mineralization of organic pollutants which are structurally stable and difficult to degrade naturally,which has attracted much attention in academic circles.Among a wide variety of photocatalysts,bismuth bromide oxide(BiOBr)has triggered considerable attention owing to its unique optical properties.However,the practical application of BiOBr is limited because high electron-hole recombination rate and low utilization efficiecncy of visible light.To improve the photocatalysis and practicability of BiOBr,many methods were employed to modify BiOBr,such as building heterojunctions,metal and non-metal doping,surface modification and so on.Among them,surface modification of BiOBr has become one of the hotspots in modification research.In this paper,BiOBr based photocatalysts were prepared by a hydrothermal method with different modified materials,and the effects of conductive carbon(CC),carbon black(CB)andβ-cyclodextrin(CD)on the photocatalytic performance of BiOBr prepared were investigated.The morphology and crystal structures of the samples were analyzed by scanning electron microscope(SEM),high resolution transmission electron microscope(HRTEM)and X-ray diffraction(XRD).The optical properties and separation efficiency of photoinduced carriers of the catalysts were measured by UV-Vis diffuse reflectance(UV-Vis DRS),surface photovoltage(SPS)and electrochemical spectroscopy.The active free radicals in the reaction system were studied by nitrotetrazolium chloride(NBT)-superoxide reaction,electron paramagnetic resonance(EPR)and trapping experiments.The photocatalytic performance of the sample was evaluated by degradation of rhodamine B(RhB)used as model pollutant,and the stability of the catalyst was investigated,the experimental results are as follows:1.Oxygen-rich conductive carbon(CC)/BiOBr composites were in-situ prepared by a hydrothermal method with functional CC.Functional conductive carbon induces BiOBr to form smaller crystal particles.The visible light absorption capacity of the samples enhances.CC/BiOBr photocatalysts have rich oxygen vacancies.Oxygen vacancies improve the separation of the photogenerated charge pairs and increase the concentration of superoxide radicals in the reaction system.When the mass ratio of CC/BiOBr is 1%,the composite sample shows excellent photocatalytic performance and mineralization ability to RhB.After irradiation for 40 min under simulated sunlight,RhB can be degraded by 80%,and the photocatalytic activity is 4 times of that of the pure BiOBr.2.BiOBr photocatalysts were prepared by a hydrothermal method with the aid of functional carbon black.Moidfied BiOBr photocatalysts with oxygen vacancy(OVs)were obtained by calcination in air atmosphere.The crystal structure and crystal size of the calcined samples are different from the reference BiOBr.BiOBr photocatalysts prepared with the assistance of carbon black have flower-like 3D appearance.The characterization results show that the oxygen vacancies level in BiOBr prepared by CB is higher than that in the reference BiOBr.When the mass ratio of CB/BiOBr is 0.3%,the photocatalyst displays better photocatalytic performance than the reference of BiOBr toward degradation of RhB.rradiation for 40 min under simulated sunlight,degradation efficiency of RhB is 90%.3.BiOBr was prepared by β-cyclodextrin(CD)modification.Oxygen defects were constructed on the surface of CD/BiOBr prepared by a hydrothermal method,and the crystal structure and specific surface area of the prepared materials significantly change.Trapping experiments and NBT tests show that the content of superoxide radicals produced by BiOBr modified by β-cyclodextrin is higher than that generated by the reference BiOBr.When the mass ration of β-cyclodextrin/BiOBr is 0.1%,the sample shows better photocatalytic performance than the neat BiOBr.The degradation rate constant of RhB over CD/BiOBr(0.1%)is two times of that over the reference BiOBr.