| As a non-metal semiconductor photocatalyst,graphite carbon nitride(g-C3N4)has the advantages of high stability,easy preparation,low cost and non-toxicity,and has been widely used in the field of visible light catalysis.At present,researchers tend to think that g-C3N4 is a defective tri-s-triazine structure linked by carbon and nitrogen atoms,and this structure tends to form a pi-electron conjugate structure,which is conducive to the separation of photogenerated carriers.However,the photocatalytic activity of g-C3N4 is limited by the recombination of photogenerated electron-hole pairs between layers.Researchers have successfully improved the photocatalytic activity of g-C3N4 by compounding with semiconductors,increasing specific surface area,dye sensitization and doping modification.Among them,the recombination and doping modification have become the research hotspots.This paper aims to design,synthesize and study the performance of high-efficiency visible light catalysts.The paper systematically summarizes the principle and performance of photocatalyst,the structure and basic properties of g-C3N4s and summarizes the preparation,modification methods and applications of g-O3N4.The development of nitrogen phase self-doped graphite phase nitrogen with laige specific surface area Carbonization;Ag/g-O3N4 composite photocatalyst was designed and synthesized.The relationship between the structure and properties of the prepared photocatalyst was analyzed and characterized using modem instrument technology.The main contents of this paper are as follows:(1)Graphite carbon nitride with large specific surface area and nitrogen self-doping was prepared by secondary calcination.The effect of secondaiy calcination temperature on the stiuctxire and properties of g-C3N4 was studied by controlling the secondary calcination temperature.The experimental results show that the nitrogen atom successfully replaces the sp2 hybrid carbon atom in the secondary calcined samples.The doping of nitrogen atom optimizes the electronic structure of g-C3N4 and improves the response ability of the sample to visible light.At the same time,the release of ammonia during the calcination process produces a well-developed pore structure and enlarges the specific surface area of the sample.Among them,when the secondary calcination temperature is 590?,the nitrogen doping ratio is the highest,and the photogenerated carrier separation efficiency is the most efficient The specific surface area reaches 128.06 m2/g(about 27 times of g-CsN4).Therefore,the photocatalytic degradation of methylene blue is the best,and the photodegradation rate can reach 90%in 90 minutes.(2)According to the results of(1),a series of nitrogen-doped catalysts were prepared by calcination of g-C3N4 at 59?.The effects of calcination holding time on the structure and properties of the catalysts were studied by adjusting the holding time of the secondary calcination.The experimental results show that the band gap of the secondary calcined sample is reduced and the response to visible light is enhanced due to the doping of nitrogen atoms,and the specifie surface area of the sample is increased due to the escape of ammonia gas,which improves its adsorption performance.Among them,the photocatalytic activity of g-C3N4-1 and g-C3N4-4 is affected by the serious recombination of photogenerated carriers,and the photocatalytic degradation efficiency of methylene blue is slightly higher than that of g-C3N4 due to dye sensitization.g-C3N4-2 has the best photocatalytic activity because of its highest specific surface area and photogenerated carrier separation efficiency,The photocatalytic degradation efficiency of methylene blue can reach 90%within 90 minutes.(3)Water dispersed g-C3NM was prepared by chemical oxidation metiiocl The effect of oxidation time on the structure of water dispersed g-C3N4 was studied by controlling die oxidation time.The results showed that oxidation time had no effect on the preparation of water dispersed g-C3N4.Ag/g,C3N4 composites were prepared by hydrothermal method using water dispersed g-O3N4 and silver nitrate as raw materials.The effects of silver content on the structure and properties of Ag/g-C3N4 composites were studied by controlling the silver content.The experimental results show that the lamellar structure of g-C3N4 transforms into spherical structure after the introduction of silver,and the size decreases with the increase of silver content The photocatalytic properties of the composites were improved with the increase of silver content Ag(60)/g-C3N4 exhibited the best photocatalytic properties.The photocatalytic degradation efficiency of methylene blue could reach 58%within 100 minutes with 5 mg photocatalystFigure[30]table[5]references[96]... |
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