Study On The Modification,Characterization And Photocatalytic Performance Of Graphite Phase Carbon Nitride

Due to the increasing environmental pollution caused by the development of industry,it is urgent to find new environmentally friendly materials.As one of the most attractive technologies in recent years,photocatalytic technology has been used to directly collect,convert and store renewable solar energy,and is widely used in the production of sustainable green solar fuels and environmental governance.Carbon nitride?g-C₃N₄?,as a metal-free semiconductor polymer,has the characteristics of high chemical stability,good thermal stability,simple raw materials,narrow band gap,and certain influence on visible light.It is widely used in photocatalysis field.Due to its unique physicochemical,optical and electrical properties,a variety of g-C₃N₄ based photocatalysts have been designed to drive various reduction and oxidation reactions under appropriate wavelengths of light irradiation.For example,hydrogen generated by water decomposition,reduction of carbon dioxide,degradation of organic pollutants,oxidation of alcohols,optical sensors,etc.However,the graphite-like carbon nitride photocatalyst synthesized by the traditional method has a small specific surface area,a wide band gap,easy photo-electron-hole recombination,and slow photo-generated carrier transport,which inhibits its photocatalytic activity.In order to make the photocatalytic activity meet the requirements,it is necessary to modify it.This article modifies it through the following three aspects,and uses rhodamine B as a simulated pollutant to investigate its degradation.The specific scheme is as follows:?1?Preparation of sulfur-doped high specific surface area g-C₃N₄ and study of its photocatalytic performance.Graphite phase carbon nitride?g-C₃N₄?has a low specific surface area and a high probability of photo-generated electron-hole recombination,which severely limits its application.Using melamine?C₃N₃?NH₂?₃?as a raw material,a graphite phase carbon nitride?p-C₃N₄?with a high specific surface area was prepared by a template method,and sulfur was doped in p-C₃N₄ by thermal polymerization to prepare sulfur.Doped with high specific surface area graphite phase carbon nitride?S-p-C₃N₄?.The photocatalytic degradation of rhodamine B,photocatalytic reduction of CO₂,and photocatalytic hydrolysis to produce hydrogen were investigated under 500W xenon lamp?with 420 nm filter?.The results show that sulfur doping can effectively reduce the photo-electron-hole recombination probability,reduce the band gap,and improve the photocatalytic activity.Among them,1.5%S-p-C₃N₄ showed the best activity.The rate of degradation of rhodamine B was 15 times that of p-C₃N₄,The rates of CO and CH₄ formation were 3.6 and 3.1 times that of p-C₃N₄,respectively,and the hydrogen production rate was 22.7?mol/g/h and 4.83 times that of p-C₃N₄.And 1.5%S-p-C₃N₄ catalyst still has very high catalytic activity after 5 times of recycling.?2?Preparation of oxygen-doped high specific surface area g-C₃N₄ and study of its photocatalytic performance.Graphite phase carbon nitride?p-C₃N₄?with a high specific surface area was prepared by using a dicyandiamine?C₂H₄N₄?as a raw material and a template method,and oxygen was doped in p-C₃N₄ by thermal polymerization to prepare an oxygen doping.Graphite phase carbon nitride with hetero-specific surface area?O-p-C₃N₄?.Photocatalytic degradation of rhodamine B and photocatalytic hydrolysis to produce hydrogen under 500W xenon lamp were used to investigate the catalytic activity.The results show that oxygen doping can effectively reduce the photo-electron-hole recombination probability and improve the photocatalytic activity.?3?High specific surface area g-C₃N₄ loaded Keggin Type Cu Mono-substituted heteropoly acid toward specific photocatalytic reduction of CO₂ to CH₄?Using melamine,sodium tungstate dihydrate,disodium hydrogen phosphate dihydrate,Cu Cl₂as raw materials,Keggin-type Cu single crystal substituted heteropolyacid(PW₁₁Cu)and high specific surface area were prepared using ether extraction method and template method,respectively.g-C₃N₄?PCN?,and PW₁₁Cu is supported in PCN by dipping method?x%PCN?.The results show that the increase of the specific surface area and the loading of PW₁₁Cu can effectively reduce the probability of photogenerated electron-hole recombination,which can significantly shift the absorption boundary,widening from 460 nm to 495 nm,and widening the light response range.The photocatalytic reduction of CO₂ was used to investigate the activity and stability of the catalyst,and the catalytic mechanism was explored.The Cu single crystal substituted for the heteropoly acid support can specifically reduce CO₂ to CH₄.And when the PW₁₁Cu load is 15%Shows the best catalytic activity.