Preparation And Properties Of ZnO-Based Nanocomposite Photocatalytic Materials

Zinc oxide(ZnO),as an important wide bandgap oxide semiconductor material,has good photoelectric properties,chemical stability,thermal stability,low cost,non-toxic and so on.It has become one of the most widely studied semiconductor materials in the field of photocatalysis.However,ZnO has the relatively wide bandgap,low utilization rate of sunlight,and the high recombination rate of photogenerated carriers,which limit its practical application.In order to solve the above problems,a series of composite,and/or doped ZnO-based nanomaterials were prepared.The effects of different composition,different rare earth element doping and different doping amount on the structure,morphology and photocatalytic activity of ZnO photocatalyst were studied,respectively.The catalysts were characterized by X-ray powder diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),ultraviolet-visible absorption(UV-vis),Fourier transform infrared(FT-IR),Raman spectra(Raman),and photoluminescence spectroscopy(PL).The main contents of the study are as follows:Graphene oxide dispersion,graphene oxide(GO)and graphene(RGO)powders were prepared by Hummers' method.Pure ZnO and ZnO/RGO nanocomposites were prepared by solvothermal method.The crystal structure,micro-morphology and optical properties of the samples were investigated by means of XRD,SEM,TEM,FT-IR,Raman,PL and UV-vis.The photocatalytic activity of these two materials on Rhodamine B under xenon lamp irradiation was studied.The results showed that the addition of graphene can effectively improve the photocatalytic activity of ZnO nanomaterials.When the amount of graphene was10%,the degradation rate reaches 89.72%,which the photocatalytic performance was the best.Compared with pure ZnO nanomaterials,the degradation rate was increased by 60%.The noble metal Ag and different rare earth(Ce,Gd,La,Yb)doped ZnO nanomaterials were prepared by solvothermal method.Its crystal structure,morphology and optical properties were characterized by XRD,SEM,FT-IR,PL and UV-vis,respectively.The formation mechanism and optical properties of the materials under different doping conditions were discussed.Degradation of Rhodamine B revealed that the photocatalytic performance of ZnO nanomaterials had improved significantly both with Ag doping and with rare earthdoping.The photocatalytic effect was the best when Ag doping was 3%,and the degradation efficiency was 26% higher than that of pure ZnO.The photocatalytic effect of Gd doping in rare earth was the best,and the degradation efficiency was higher than that of pure ZnO by23%.And we have analyzed its photocatalytic mechanism.The sol-thermal method was used to prepare Ag and Gd doped ZnO/RGO nanocomposites.The crystal structure,micro-morphology and optical properties of the samples were characterized and observed by XRD,SEM,TEM,FT-IR,PL and UV-vis.The structural and micromorphology comparisons were made with the samples from the previous two chapters.The photocatalytic degradation activity of rhodamine B dyes under different doping or compounding conditions was discussed.For the Ag-doped ZnO/RGO nanocomposites,The experimental results showed that the photocatalytic performance of the Ag-doped ZnO/RGO nanocomposites is improved due to the more pronounced red shift of the UV absorption edge.Among them,the photocatalytic effect of the 3Ag-ZnO/10 RGO nanocomposites was the highest.Rhodamine B was essentially degraded completely at 120 min.For Gd-doped ZnO/RGO nanocomposites,there were a serious agglomeration,and the UV absorption edge had a slight red shift.The photocatalytic performance of the composite was lower than that of ZnO/10 RGO samples.Finally,the photocatalytic mechanism of the two materials was analyzed and discussed.