Studies On The Preparation Of Oxygen Vacancy Defects-Rich ZnO Nanocomposites And Their Optical Properties

In recent years,defect engineering has been considered as an effective strategy for improving catalytic performance of ZnO,and has been widely studied.In this thesis,oxygen vacancies on ZnO nanorods surface were introduced by atmospheric heat treatment.The defect types of ZnO nanocomposites and the effect of oxygen vacancy defects on optical properties were mainly studied.The thesis is mainly divided into the following parts:1.Effect of oxygen vacancy defect regeneration on photocatalytic properties of ZnO nanorods.The ZnO with different Oxygen vacancy defect concentrations were realized by the annealing in the different atmospheres of vacuum,oxygen,air and Ar,respectively.And the Oxygen vacancy defect concentrations in the annealed ZnO nanorods follows an order of C_Vacuum>C_Ar>C_Air>C_Oxygen.Through the photocatalytic degradation test of methyl orange solution(MO),it is found that the photocatalytic performance of samples increases with the increase of Oxygen vacancy defect concentration,and the sample annealed in the vacuum atmosphere had the best performance.The regeneration ability of Oxygen vacancy defects in ZnO nanorods were studied through the oxygen-deficit atmosphere annealing after each cyclic photocatalytic test.Although the photocatalytic performance of ZnO nanorods degrades slightly with the increase of the number of cyclic test,after three cyclic tests,the Oxygen vacancy defects regenerated sample still shows excellent photocatalytic performance.The results show that the Oxygen vacancy defects in ZnO nanorods play a key role in improving the photocatalytic degradation performance,and the Oxygen vacancy defects regenerated samples still show good photocatalytic degradation performance.2.Exploration of Oxygen vacancy-rich defects ZnO/CuO composites and its optical properties.ZnO nanorods were prepared by hydrothermal method.ZnO nanorods with different oxygen vacancy defect concentrations were annealed at different temperatures in a vacuum atmosphere.It was found that the concentration of oxygen vacancy defect gradually increases as the temperature increases.The ZnO/CuO composite material with oxygen vacancy-rich defects was prepared by photo-deposition method.Through the degradation test of methylene blue solution(MB),the effect of oxygen vacancy defects on the photocatalytic performance of ZnO/CuO composite material was studied.The results show that the existence of oxygen vacancy can improve the adhesion rate of Cu²⁺,enhance the light absorption and utilization rate of the composite material,and promote the separation of photo-generated electron-hole pairs,then the photocatalytic activity is improved.Simultaneously,it also proves that excess oxygen vacancy defects are still beneficial to the photocatalytic reaction process.3.Exploration of La-doped ZnO/Ag₂CrO₄ composite material with oxygen vacancy-rich defects and its optical properties.The La-doped ZnO/Ag₂CrO₄composite material with oxygen vacancy-rich defects was synthesized by hydrothermal,atmosphere deoxidation and photodeposition methods.The effect of oxygen vacancy defects on the photocatalytic performance of the composite material on the basis of doping modification was studied.According to the characterization of PL spectra,the oxygen vacancy defect concentration of La-doped ZnO nanorods increases with the increase of annealing temperature.The photocatalytic performance of the composite material was characterized by the degradation of the MO solution,and the best photocatalytic performance was achieved in the sample annealed in the vacuum atmosphere at 700?.The results show that oxygen vacancy defects provide electrons as a donor energy level,which is beneficial to the adhesion of Ag⁺in the soluton,increase the absorption strength and improve the light utilization efficiency of La-doped ZnO/Ag₂CrO₄ composite in the photocatalytic performance test.