Research On The Preparation And Photocatalytic Properties Of Nano-Zinc Oxide Composites

In recent years,with the leap-forward development of industry and urbanization,environmental problems and energy shortage have been brought.The photocatalytic technology that has the most developing potential is using the solar energy(one of clean energy),to realize the degradation of organic pollutants in wastewater through the redox process,so that the purpose of improving the environment has been achieved.Semiconductor photocatalysts have been regarded as a hotspot in the field of materials due to their advantages of low cost and easy of preparation.The representive material systems include ZnO,TiO2,CuO,CdS,Fe2O3 and so on.Among them,ZnO,as a direct and wide-bandgap semiconductor,has been extensively studied due to its adjustable structural variety and the high electron mobility.However,several problems exsited in the ZnO photocatalysis.For example,it can only respond to ultraviolet light due to its large bandgap,which tremendously limits its absorption and utilization in visible light region.Therefore,scientists have tried to broaden their absorption to visible light by the approaches of compositing and chemical dopping.In this thesis,ZnO nanoparticles were prepared firstly and the synthesis factors that affect photocatalytic activity were exploded by the method of orthogonal experiments.Then the ZnO nanoparticles were modified by compositing with g-C3N4 and Ag3PO4,respectively.Combining with the characteristics of X-ray diffraction(XRD),scanning electron microscopy(SEM),ultraviolet-visible diffuse reflection spectrum(DRS)and X-ray photoelectron spectroscopy(XPS),the morphologies,structures and photoelectrical properties of composite photocatalysts have been analyzed.In addition,the photocatalytic activity of composite photocatalysts has been investigated by the degradation of Rhodamine B(Rh B).In the experiment,a mixed solution of polyvinylpyrrolidone(PVP)and Zn(CH3COO)2·2H2O was used as a precursor.The Zn(CH3COO)2/PVP fibers,3D network-structural ZnO aggregates and ZnO nanoparticles were sequentially obtained by the order of electrospinning,calcination and ultrasonic dispersion.By designing the orthogonal experiments,the effects of synthesis factors of ZnO nanoparticles on the photocatalytic activity were summarized.The concentration of PVP solution is major,the electrospinning voltage and calcining temperature are secondary,and the receiving distance is the weakest.The g-C3N4 was prepared by calcining method,which was composited with ZnOnanoparticles to produce the g-C3N4/ZnO composite photocatalysts.Subsequently,the photocatalytic performance of the obtained g-C3N4/ZnO composite photocatalysts was evaluated by the degradation of Rh B under simulated solar light.The results showed that all the g-C3N4/ZnO composite photocatalysts with different mass ratios have the excellent photocatalytic activity.Among them,the optimal condition of mass ratio of g-C3N4 to ZnO is 1: 4.The Ag3PO4 was synthesized by using AgNO3 and Na2HPO4 as raw materials,which was composited with ZnO nanoparticles to produce the Ag3PO4/ZnO composite photocatalysts.Also toward the degradation of Rh B,the results showed that all the Ag3PO4/ZnO composite photocatalysts with different mass ratios have the excellent photocatalytic activity.Among them,the optimal condition of mass ratio of Ag3PO4 to ZnO is 5: 8.