Novel Bismuth Oxyhalides-based Composite Photocatalysts: Synthesis And Their Visible-light Photocatalytic Activity

In recent years, semiconductor photocatalysts have attracted considerableattention due to their potential applications for solving energy and pollutionproblems. BiOX （X=Cl, Br, I） photocatalyst working at visible light because oftheir unique structures and electronic band structures shows the better photocatalyticperformance. BiOX （X=Cl, Br, I） as a novel family of visible-light-inducedphotocatalysts, possess remarkable photocatalytic activity in degradation of organiccompounds. However, the pure BiOX（X=Cl, Br, I） have narrow absorption in thevisible-light region, and its photocatalytic efficiencies must be further improved inorder to be suitable for practical applications.In this thesis, our research includesfollowing：（1） A series of the solid solution BiOBr_xI_1-x（x=0，0.2，0.4，0.6，0.8，1.0） havebeen synthesized by a hydrothermal method. The obtained optimal ratio ofBiOBr_xI_1-xis x=0.2. A series of Au/BiOBr_0.2I_0.8photocatalysts with different Aucontents have been synthesized by a hydrothermal combinated with photodepositionmethod. The as-prepared products were characterized by XRD, SEM, TEM,HRTEM，XPS, UV-Vis spectra, PL spectroscopy. The photocatalytic activities ofAu/BiOBr_0.2I_0.8samples under visible-light irradiation （λ>420nm） for degradation ofthe target pollution （MO, RhB, phenol） were investigated. The results show that allthe Au/BiOI samples have a fower-like architecture with the diameter of6–10μm,which is composed of numerous irregular nanoplates. Due to the surface plasmonresonance of Au metals, Au/BiOBr_0.2I_0.8show a stronger absorption in the visiblerange,compared with single BiOBr_0.2I_0.8. Au dopant can effectively restrainrecombination rate of the photoinduced electrons and holes. All the Au/BiOBr_0.2I_0.8samples exhibited much higher photocatalytic activities than the single BiOBr_0.2I_0.8in the degradation of the target pollutions, and0.6%Au/BiOBr_0.2I_0.8showed the bestactivity, whose degradation rate of MO, RhB, phenol were up to89.8%、72.7%and 32.7%, respectively.（2） Three-dimensional （3D） BiOBr_xI_1-x（x=0，0.2，0.4，0.6，0.8，1.0） microsphereshave been synthesized by a solvothermal method. According to the photocatalyticperformance test, the optimal ratio of BiOBr_xI_1-xwas obtained, namely x=0.2. Onthis basis, a series of BiOBr_0.2I_0.8/graphene composites different graphene contentwere synthesized by one-step solvothermal method. The structure and photocatalyticproperties of BiOBr_0.2I_0.8/graphene composites were studied systematically. Theresults show that the pristine BiOBr_0.2I_0.8exhibits a lot of separate microspheres withdiameters of0.5-1.5μm. All the microspheres are composed of numerousnanoplates with a thickness of about10nm and the as-obtained BiOBr_0.2I_0.8microspheres are well dispersed on graphene sheets. Compared with pureBiOBr_0.2I_0.8, BiOBr_0.2I_0.8/graphene shows s absorption in the visible range.Introduction of graphene can effectively restrain recombination rate of thephotoinduced electrons and holes. All the BiOBr_0.2I_0.8/graphene compositesexhibited much higher photocatalytic activities than the single BiOBr_0.2I_0.8in thedegradation of the target pollutions, and BiOBr_0.2I_0.8/graphene（10%） showed the bestactivity, whose degradation rate of MO, RhB, phenol were up to100.0%、100.0%and81.3%, respectively.（3） Bi₇O₉I₃was synthesized firstly by a one-step, template and surfactant-freesolution method. On this basis, the Bi₇O₉I₃/graphene composite was synthesized by asolvothermal method. Compared with pure Bi₇O₉I₃,Bi₇O₉I₃/graphene compositeshows a stronger absorption in the visible range. And the introduction of graphene caneffectively suppress the recombination of electrons and hole. The Bi₇O₉I₃/graphenesample exhibited much higher photocatalytic activity than the single Bi₇O₉I₃in thedegradation of RhB and phenol under visible light.