Copolymerization Preparation Of G-C₃N₄ With Enhanced Visible Light Photocatalytic NO Removal Performance

Nitrogen oxides?NOx?is one of the major air pollutants and is an important precursor for the formation of acid rain and PM2.5.The traditional technology is mainly for industrial emissions of high concentration of NO treatment,and does not apply to the low concentration of atmospheric NO purification.Photocatalytic technology can produce oxidative active species by using sunlight or indoor light source under mild conditions,and it has a good prospect in purifying low concentration air pollution.Graphite phase carbon nitride?g-C₃N₄?is the first non-metallic visible light driven photocatalyst.However,the g-C₃N₄ obtained by the existing method has a small specific surface area,a low yield,a low photogenerated charge separation rate and a low photocatalytic activity.In order to overcome the key problems in the preparation and application of g-C₃N₄,the microstructure and electronic structure of g-C₃N₄ was optimized by means of microstructure regulation and element doping.The following conclusions were obtained:?1?cheap and efficient mesoporous g-C₃N₄ can be synthesized simply by using ammonium sulfate and dicyandiamide as the precursor one-step co-thermal polymerization.?2?The synthesis of cheap and efficient g-C₃N₄ with ammonium sulfate and urea as the precursor co-thermal polymerization can not only improve the visible photocatalytic activity of g-C₃N₄,but also improve the yield of g-C₃N₄.?3?The use of sucrose and urea as the co-thermal polymerization of the precursor can easily synthesize the cheap and efficient C-doped g-C₃N₄,which greatly improves the photocatalytic activity of g-C₃N₄.The specific research contents are as follows:?1?Soft template method for the synthesis of mesoporous g-C₃N₄ photocatalyst: a new method for the preparation of porous g-C₃N₄ by copolymerization with ammonium sulfate as a gas template was developed.Using 2.0g of ammonium sulfate and 2.0g of dicyandiamide as precursors,the mesoporous g-C₃N₄ visible light catalyst can be prepared by pyrolysis polymerization in air.The removal rate of NO in visible photocatalytic purification is increased from 24.9% to 47.1%.This is due to the larger specific surface area,mesoporous structure,higher photogenerated carrier separation efficiency and the appropriate band structure.The preparation method has the advantages of simple process and low cost of precursor,which provides a new idea for the large-scale synthesis and application of mesoporous g-C₃N₄ photocatalyst.?2?A method for simultaneous production of g-C₃N₄ in terms of yield and activity: The high performance and high yield g-C₃N₄ visible light catalyst was synthesized by copolymerization with ammonium sulfate and urea as precursors.G-C₃N₄ was synthesized by adding 1.50 g of ammonium sulfate in 10.0g of urea as a precursor and by one-step thermal polymerization.This method not only increased the removal rate of NO from g-C₃N₄ visible light from 33.2% to 46.9%,while increasing the yield of g-C₃N₄ by 10 times.The improvement of photocatalytic activity of g-C₃N₄ is achieved by the following factors: the visible light absorption capacity is improved and the hole and electron recombination rate are lower.The increase in yield of g-C₃N₄ is due to the fact that the presence of ammonium sulfate significantly reduces the activation energy required for the production of the melem to produce more melem,resulting in an increase in the utilization of the precursor.This study provides a new approach for large-scale preparation of high performance g-C₃N₄.?3?Copolymerization preparation of high activity C-doped g-C₃N₄: C-doped g-C₃N₄ was prepared by in-situ copolymerization by adding trace sucrose to 10.0g of urea as a carbon source.When the amount of sucrose was 2.0mg,the visible light purification performance of the product was greatly improved,and the NO removal rate increased from 33.2% to 56.8%.Based on the delocalized large ? bond theory,C-doping greatly inhibits the recombination of g-C₃N₄ photogenerated charge.While the specific surface area of the photocatalyst and visible light absorption are improved.The method has the advantages of simple preparation process and low cost,and provides a new method for the preparation of carbon doped photocatalyst.