Preparation And Performance Of G-C₃N₄ Based Composite Photocatalyst

With the rapid development of modern industrialization and population,the problems of energy and environment are increasingly prominent.Semiconductor photocatalysis technology is considered as an economic,renewable,green and safe technology,which is widely used to degrade water pollutants.graphite carbon nitride（g-C₃N₄）has developed rapidly in the field of photocatalysis due to its wide range of raw materials,simple synthesis,non-toxicity,and excellent thermal and chemical stability.However,the rapid recombination of photo-generated carriers,absorption of blue-violet light in the solar spectrum,and low specific surface area have prevented the application of g-C₃N₄ in the field of photocatalytic degradation.In order to improve the photocatalytic activity of g-C₃N₄ based photocatalyst,the methods of carbon doping and sensitization were used to enhance the visible light response range,increase the specific surface area of the material and reduce the recombination rate of photocarriers.The main research contents are as follows:（1）Carbon doped g-C₃N₄（C/g-C₃N₄）composite photocatalysts were prepared by high temperature thermal condensation with urea as the precursor and 4-aminobenzoic acid as the carbon source.FT-IR,XRD,XPS,SEM,BET,UV-Vis DRS,and EIS were used to characterize the structure,morphology,specific surface area,and photoelectrochemical properties of the composite photocatalyst.The photocatalytic performance of the composite photocatalyst under simulated visible light was studied with methylene blue as the target pollutant.The results show that the doping modification of C can regulate the band structure of C/g-C₃N₄,increase the photoresponse range of the composite photocatalyst,effectively inhibit the recombination of photogenerated carriers,and significantly improve the visible light photocatalytic activity.Under the optimal ratio,the specific surface area of C_0.1%/g-C₃N₄ was 1.9 times that of g-C₃N₄.After 60min of illumination,the degradation rate of C_0.1%/g-C₃N₄ on MB in aqueous solution reached 99.8%,far higher than that of g-C₃N₄ on 78.8%.（2）g-C₃N₄ was prepared by high temperature thermal polymerization using urea as the raw material.Itmodified by Perylene diimide derivatives（PASP）was prepared by simple hydrothermal method after g-C₃N₄ was mixed with PASP.The obtained photocatalyst was systematically characterized,and the photocatalytic performance of GCNx was investigated with MB as the target pollutant.The results show that with the introduction of PASP,GCN_x has a new absorption band at 500～600 nm,which can significantly improve the response range of visible light,and reduce the recombination ratio of photogenerated electron hole pairs,providing more surface active sites with the increase of specific surface area and pore volume.In the study of the performance of MB degradation under visible light,the optimal ratio of GCN_0.02%to MB degradation rate reached 95%within 40min,and the photocatalytic reaction rate constant of GCN_0.02%was about 1.56 times of g-C₃N₄.（3）g-C₃N₄ was prepared by high temperature thermal polymerization with urea as a raw material.The g-C₃N₄composite photocatalyst（Zn Tc Pc/g-C₃N₄）sensitized by Tetracarboxyl substituted zinc phthalocyanine（Zn Tc Pc）dye was prepared by a simple hydrothermal method.The composition,morphology,and photoelectrochemical properties of the composite photocatalyst were characterized by XRD,SEM,UV-Vis DR,PL,and I-t.The photocatalytic performance of the composite photocatalyst under simulated visible light was studied using methyl orange（MO）as the target pollutant.The results show that Zn Tc Pc/g-C₃N₄ has a new absorption peak at 600～800nm,which significantly improves the absorption of visible light,and the photogenerated electron-hole pairs are rapidly separated and transferred.Compared with g-C₃N₄,the degradation rate of Zn Tc Pc_1%/g-C₃N₄increased by 52.1%after 60 min of visible light irradiation,and the photocatalytic degradation rate constant of Zn Tc Pc_1%/g-C₃N₄ reached5.3 times.