Preparation Of Bismuth Oxyhalide-based Nanocomposites And The Mechanism Of Enhanced Photocatalytic Activity

As one of the most promising photocatalysts,BiOX?X=Cl,Br,I?was received wide attention owing to its special structure that[Bi₂O₂]²⁺slabs embedded in double slabs of X^-,which was beneficial for their potential photocatalytic applications.However,the photocatalytic activity of BiOX was still limited by its low quantum efficiency.In this thesis,BiOBr was selected as research object,and S-modified,Fe-modified,and Cu,Fe-cluster modified BiOBr composites were synthesized to improve its photocatalytic activity in photocatalysis.The main work is as followed:1.Taking thioacetamide as sulphur source,S modified BiOBr samples were successfully synthesized by simple hydrothermal method.The as-prepared samples were characterized by X-ray powder diffraction?XRD?,Fourier transform infrared?FT-IR?,X-ray photoelectron spectroscopy?XPS?,scanning electron microscopy?SEM?and so on.The results showed that RhB could be easily sensitized under visible light over S modified Bi OBr compared to pure BiOBr,which attributed to that O atom on the surface of BiOBr was replaced by S atom,thus making“electron deficiency”of BiOBr.In addition,the S modified BiOBr also possessed a higher photocatalytic activity for RhB/MO mixed solution degradation and benzyl alcohol oxidation than that of pure BiOBr via the sensitization of RhB.2.Cu,Fe cluster modified BiOBr were prepared by impregnation method at room temperature,and high resolution transmission electron microscopy?HRTEM?proved that the surface of BiOBr was sucessfully modified by Cu,Fe cluster.The diffuse reflectance ultraviolet spectra?DRS?showed that the absorption of Cu,Fe cluster modified BiOBr was obvious enhanced in 400-600 nm light,which was the characteristic absorption of the interfacial electron transfer between BiOBr and metal clusters.X-ray photoelectron spectroscopy?XPS?and cyclic voltammetry verified that the redox potential of Cu,Fe cluster was lower than the conduction band of BiOBr,which is in favour of the separation of photoelectrons and holes.The photocatalytic abilities of the nanocomposites was evaluated by degradation of RhB,the results showing that Cu,Fe cluster modified BiOBr had an better photocatalytic abilities for degradation of RhB than that of pure BiOBr.3.3D hierarchical nanostructure Fe modified BiOBr photocatalysts were successfully prepared via a facile one-step route at room temperature.The as-prepared samples was characterized by XRD,BET,SEM,HRTEM,XPS and other characterization methods to confirm its morphology and material composition.Compared with pure BiOBr,Fe???-modified Bi OBr samples possess better oxidizability than pure BiOBr for benzyl alcohol oxidation under UV light irradiation and organic dye degradation under visible ligth irradiation in the presence of H₂O₂.The improved photocatalytic oxidation and degradation ability of Fe?III?-modified BiOBr is ascribed to the enhanced photo-generated carriers separation efficiency and promoted production of·OH due to the generation of Fe²⁺ions via interfacial charge transfer from Fe³⁺ions.This work provides a facial approach to improve photocatalytic efficiency for organic synthesis and environmental remediation.