Preparation Of Graphite Phase Carbon Nitride Nanosheets And Composite Materials And Their Photocatalytic Properties

Graphite carbon nitride（g-C₃N₄）has the characteristics of special lamellar structure,good physical and chemical stability,suitable forbidden band width and has received extensive attention in the field of photocatalysis.However,the prepared g-C₃N₄tends to form lumps so that the specific surface area is small,and the photocatalytic performance cannot reach the expected effect.In order to maximize its potential photocatalytic performance,researchers have developed a variety of methods to prepare g-C₃N₄nanosheets or improve its photocatalytic performance by compounding with other materials.Based on this,this thesis first uses the hydrothermal reaction method to prepare two-dimensional g-C₃N₄nanosheets（WCN）.On this basis,the two-dimensional g-C₃N₄nanosheets and titanium dioxide（TiO₂）are compounded to obtain a binary composite catalyst,and then combined with graphene oxide（GO）to prepare a ternary composite catalyst.The structure of the product was characterized by scanning electron microscope（SEM）,transmission electron microscope（TEM）,atomic force microscope（AFM）,infrared spectroscopy（FTIR）,X-ray diffraction（XRD）,X-ray photoelectron spectroscopy（XPS）,ultraviolet-visible absorption spectroscopy（UV-Vis）,Raman spectroscopy（Raman）and fluorescence spectroscopy（PL）.Methylene blue（MB）solution was used to simulate pollutants in water to test the photocatalytic performance and photoelectrochemical performance of g-C₃N₄nanosheets and the photocatalytic degradation mechanism of MB was discussed.The main contents are as follows:（1）Using the hydrothermal reaction method,the melamine suspension was reacted at 200℃to form an intermediate product,and then the intermediate product was calcined to directly produce two-dimensional g-C₃N₄nanosheets,and the body g-C₃N₄（CN）and g-C₃N₄nanosheets（OCN）obtained by traditional thermal oxygen stripping method were compared.The results show that both WCN and OCN realized the stripping of CN.WCN and OCN have the same crystal structure and composition as CN.The specific surface area of WCN and OCN is 4 and 3 times that of CN,respectively.Photoelectrochemical analysis shows that WCN has better carrier migration and separation efficiency,and has better photocatalytic activity.Under visible light conditions,the photocatalytic degradation rate of WCN to methylene blue（MB）reached 82%,2.4 times and 6.7 times that of OCN and CN,respectively.WCN has excellent stability and reusability.（2）Using chemical deposition method,WCN and TiO₂are used as raw materials to prepare binary composite T-WCN,and then combine the best ratio of T-WCN with GO to obtain a ternary composite G-T-WCN.The characterization results showed that on the basis of the successful composite of WCN and TiO₂,GO was also successfully composited with T-WCN,and the ternary composite catalyst G-T-WCN was obtained,and the specific surface area of G-T-WCN is 1.1 times and 1.5 times of WCN and T-WCN respectively,the specific surface area has been increased,providing more reactive sites.Under visible light conditions,the degradation rate of G-T-WCN to MB reached 94.6%within 420 minutes,which was about 1.15 and 1.05 times that of WCN and T-WCN,respectively.The photocatalytic degradation process conforms to the first-order kinetic equation,and the rate constants of G-T-WCN photodegradation of MB are 1.7 and 1.2 times that of WCN and T-WCN,respectively.Compared with WCN and T-WCN,G-T-WCN has a faster mass transfer and diffusion rate and a smaller carrier impedance,and has better carrier migration and separation efficiency.G-T-WCN has good stability and reusable performance.Figure[36]table[7]reference[116]...