Synthesis And Study Of Rare Earth Ions Co-doped Zinc Oxide Photocatalyst

Zinc oxide（ZnO）has drawn much attention over the years due to its great potential for a variety of applications in many fields.The structural characteristics of crystalline materials affect their properties,and their microstructure and macrostructure can be influenced by doping and morphology control,respectively.Lanthanides are ideal metal dopants because of their unique optical properties and the 4f electronic structure that are not fully occupied,which can effectively increase the photocatalytic activity of the catalyst.Recent studies have shown that photocatalysts can be more effectively modified by co-doping two rare earth elements,which not only enhance the synergistic effect of light absorption of the photocatalyst,but also inhibit the recombination rate of photogenerated carriers.According to the above background,the effect of co-doping of rare earth metal Er and Nd on the doping activity of photocatalysts under different synthetic routes.The photocatalytic degradation performance and kinetics of photocatalysts on dye wastewater was studied.The main contents in my thesis are as follows:1.The effects of calcination temperature and precursor pH on the photocatalytic activity of ZnO were investigated.The ZnO with uniform morphology were prepared by chemical precipitation method and solvent method,respectively.On this basis,Er/Nd-ZnO photocatalysts with different doping ratios were prepared,and the optimal doping ratio of Er and Nd was obtained according to the comparison of the degradation effects of methylene blue,it was found that the atomic ratio Er to Zn in the sample prepared by precipitation method is 3%,and the atomic ratio of Nd to Zn is 2%,which has the best degradation effect;Er and Zn atoms in the sample prepared by solvothermal method.When the ratio is 1%,the atomic ratio of Nd to Zn is 1%,which has the best degradation effect.2.The photocatalytic activity of rare earth elements Er and Nd co-doped ZnO photocatalysts was investigated by photodegradation of RhB and MO.The degradation results show that the photocatalytic performance of rare earth ion co-doping is better than that of pure zinc oxide and one kind of rare earth ion doping alone.Among them,the photocatalytic effect of the samples prepared by solvothermal method is better than that of the materials prepared by precipitation method.The degradation rate of methyl orange can reach 99%in 30 minutes,while that of pure zinc oxide can only reach 46%.The reaction kinetic constants k of the 3Er/2Nd-ZnO sample prepared by precipitation method for degrading rhodamine B and methyl orange were 0.10891 min^-1 and 0.02778 min^-1,respectively.And the reaction kinetic constants k of the 1Er/1Nd-ZnO samples prepared by solvothermal degradation of rhodamine B and methyl orange were 0.09588 min^-1 and0.01558 min^-1,respectively.The degradation rate of methyl orange in 1Er/1Nd-ZnO samples can reach 98%in 30 min,while pure ZnO can only reach 46%.The kinetic rate constant of1Er/1Nd-ZnO sample in the degradation reaction of methyl orange is about three times that of pure zinc oxide.3.The structure,morphology and photocatalytic properties of the samples were characterized and analyzed by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,ultraviolet-visible absorption spectroscopy（UV-vis）and Photoluminescence spectroscopy（PL）.The variation of particle size of ZnO material after doping,lattice distortion,band gap and other changes were discussed and analyzed.It can be concluded that the co-doping of rare earth metal improves the photocatalytic performance of ZnO semiconductors and broadens the photoresponse range.4.The order of action of the main active substances of 1Er/1Nd-ZnO photocatalytic degradation of methyl orange and rhodamine B was O₂^-,·OH,h⁺和e^-and their effects on photocatalytic degradation were analyzed by capture experiments.The reasons of Er and Nd co-doping can improve the photocatalytic properties of ZnO are analyzed,including the distortion of ZnO lattice,the generation of impurity levels,the influence of preparation methods on particle size morphology,the effect of up-conversion effect on carrier efficiency and formation of Er³⁺and Nd³⁺redox pairs,etc.