Studies On Preparation Of ZnO-based Nanocomposites And The Photocatalytic Performance

With the development of human industrialization and the rapid increase of population,the utilization of resources and energy has become one of the most concerned issues at present.Solar energy is a clean energy that is primitive and can be continuously utilized by humans.Photocatalysts can use solar energy to convert organic pollutants into environmentally friendly substances such as carbon dioxide and water.In recent years,the photodegradation of organic pollutants by ZnO has attracted the attention of everyone.Because ZnO has significant advantages as a photocatalyst,such as low toxicity,cost effectiveness,photochemical stability,and recyclability.However,ZnO can only absorb the ultraviolet-visible range of sunlight.Its forbidden band width is above 3 eV,and its absorption rate to sunlight is small,which seriously affects its use of sunlight.The main research focus at this stage is how to design an efficient and economical photocatalyst.In order to overcome the shortcomings of ZnO's narrow absorption range,researchers have made various efforts.Based on a large number of literatures,this study explored ZnO under two morphologies,namely ZnO nanorods and ZnO nanoparticles,and analyzed the properties of ZnO catalysts with different morphologies.Then they were loaded with GO to form a composite catalyst..The lattice structure,microscopic morphology,band gap and chemical state of the material were characterized by some modern characterization methods such as X-ray diffraction,scanning electron microscopy and UV-visible diffuse reflection absorption spectroscopy,respectively.Photocatalytic degradation tests the materials.The main research contents are as follows:(1)ZnO nanorods and ZnO nanoparticles were prepared by hydrothermal method,and then GO was prepared by hummers method.After some characterization and photocatalytic experiments,the ZnO nanorods completely degraded rhodamine B at 60 min,and the degradation rate reached 100%.The degradation rate of methyl orange solution reached 100% at 150 min.Under the same conditions,the degradation rate of organic dyes of ZnO nanoparticles is only 40% and 80%,respectively.The experimental results show that the specific surface area of ZnO nanorods is larger than that of ZnO nanoparticles,and the adsorption capacity of ZnO nanorods is stronger.Therefore,the surface reactive sites of ZnO nanorods are more in the catalytic reaction,and the photocatalytic properties of ZnO rods are higher.More superior than granular.(2)Prepared by simple hydrothermal method,the obtained product is characterized by some column characterization and photocatalytic experiments,it can be known that ZnO nanorods are wrapped on GO,and the crystal structure of ZnO nanorods is not destroyed;the band gap of composite materials It can be reduced,thereby increasing its response range to visible light and prolonging the residence time of photogenerated carriers on the conduction band.When the ratio of the mass of raw material ZnO added to the mass of GO added is 2:1,the photocatalytic degradation of rhodamine B by sample ZGO-2 is the fastest and the best,and the degradation rate reaches 100% in 30 minutes.the photocatalytic efficiency is better than pure of ZnO nanorods;the mixture of sample ZGO-2 and methyl orange is changed from orange to colorless after 75 minutes of simulated sunlight(the degradation rate is almost 100%),exhibits better photocatalytic degradation than pure ZnO nanorods.(3)ZnO nanoparticles/r-GO composite photocatalytic materials were prepared by simple hydrothermal method.The characterization of the products and the photocatalytic experiments showed that the ZnO nanoparticles were encapsulated on graphene oxide sheets.It is not destroyed;ZnO nanoparticles are supported on GO,and the specific surface area is larger and the band gap energy is lower than that of pure ZnO nanoparticles,and the graphene oxide itself has a large specific surface area and good conductivity,making more The photogenerated electrons are rapidly transferred to the GO surface to participate in the reaction,thereby improving the photocatalytic performance.When the ratio of the mass of the raw material ZnONPs to the mass of the GO added is 3:1,the degradation rate of the rhodamine B is 100% after the sample ZGO-3 is irradiated for 150 min,and the pure ZnONPs In the same environment,the degradation rate of Rhodamine B is about 83%,and the photocatalytic degradation effect of sample ZGO-3 on methyl orange is also the best.The degradation rate in 100 minutes is 100%,while pure The degradation rate of ZnONPs to methyl orange under sunlight was only 87.64%.