Preparation Of Modified Zinc Oxide Nano Photocatalytic Materials And Their Photocatalytic Properties

Semiconductor photocatalysts can decompose organic pollutants by redox reaction, and has good effects on the degradation of organic matter in the treatment of wastewater, which has gradually become the focus of attention. ZnO as a kind of excellent semiconductor material, has excellent photoelectric properties, is considered to be promising photocatalytic materials. However, ZnO has the following problems in the photocatalytic application:（1） The light response range is narrow;（2） the separation efficiency of electron and hole is low;（3） it is difficult to recover, so that the photocatalytic performance is limited. Therefore, in order to improve the photocatalytic activity of Zn O, broaden the scope of ZnO absorbed photon and make it easy for recycling, the work on the modification of ZnO by co-doping transition metal ions, building magnetic composite semiconductor and compositing with advanced carbon materials graphene are carried out. The morphology, structure and properties of the samples were characterized by means of X-ray diffraction（XRD）, Fourier transform infrared spectra（FT-IR）, transmission electron microscope（TEM） and laser Raman spectroscopy, respectively. The main contents are as follows:（1） Zn1-x FexO（0≤x≤0.05） and Zn0.98-xFe0.02CuxO（0≤x≤0.05） nanoparticles were synthesized by sol-gel method. The influence of doping contents on the crystal structure and photocatalytic activities was analyzed. The results show that, Zn1-xFexO and Zn0.98-xFe0.02 CuxO are single Hexagonal wurtzite structure with a diameter of 20 nm, indicating that the Fe and Cu ions enter the ZnO crystal lattice. Doping can significantly improve the photocatalytic activity of ZnO, and the highest degradation rate of Methylene Blue（MB） solution reached 99.5% over Zn0.97Fe0.02Cu0.01 O in 60 min under the irradiation of ultraviolet light.（2） ZnO/ZnFe₂O₄ magnetic composite semiconductor with visible light photocatalytic properties was prepared by a two-step approach. Firstly, the precursor of ZnFe₂O₄ was synthesized by hydrothermal method. Secondly, ZnO nanoparticles were coated on the surface of ZnFe₂O₄ to obtain the ZnO/ZnFe₂O₄ core-shell structure by solvothermal method. The photocatalytic activity of the composite catalyst under visible light irradiation was investigated. When the molar ratio of ZnFe₂O₄ and Zn O was 0.5, the photocatalytic activity was the highest, the degradation rate of MB solution reached 77.8% in 180 min under visible light irradiation. Because of the existence of the ZnFe₂O₄ magnetic material, the composite photocatalyst can be easily recovered by the external magnetic field.（3） In order to improve the photocatalytic activity under visible light, ZnO/ZnFe₂O₄/graphene was prepared by reduction of graphene oxide with hydrazine hydrate and ZnO/ZnFe₂O₄ magnetic composite semiconductor. The results show that when the content of graphene is 3%, the photocatalytic activity of the samples is highest and the degradation rate of MB solution reached 98% in 60 min under the irradiation of visible light. The composite photocatalyst has good stability, after 5 cycles still has 82% photocatalytic efficiency.