Targeted Regulation Of Nitrogen Vacancy Content Strengthens The Mechanism Of PCN/X（X=S、B） Two Electron Production Of H₂O₂

Hydrogen peroxide（H₂O₂）is an environment-friendly oxidant,and is widely used in many fields,such as chemical industry,textile printing and dyeing industry,paper industry and wastewater treatment.However,at present,the main method to produce H₂O₂ is the anthraquinone process with high energy consumption,high pollution and high cost in the preparation process.And because the anthraquinone process can only be produced in a centralized way in the factory,there are great safety risks in the transportation and storage process.Photocatalytic H₂O₂ production is a green,efficient and low-cost process for on-site preparation of H₂O₂ using oxygen and water as raw materials and solar energy offer energy.g-C₃N₄ is a non-metallic polymer n-type semiconductor,which has the advantages of simple synthesis method,good chemical stability and cheap raw material.However,there are the following problems in the photocatalytic H₂O₂ production based on g-C₃N₄ photocatalysis:（1）g-C₃N₄ is a layered nanostructure with low specific surface area,which can’t provide more active sites for photocatalytic reaction;（2）The layer spacing of g-C₃N₄ is large,and the photogenerated electrons generated inside can’t to transported to the surface of the catalyst to participate in the photocatalytic reaction;（3）The photogenerated electron hole pair recombination rate of g-C₃N₄ is high,and the effective electron concentration participating in the photocatalytic reaction is low.In view of the above problems,through studying the modification method of g-C₃N₄ and the specific path of H₂O₂ production,a highly active two-electron ORR photocatalytic H₂O₂ production system was specific research contents are as follows:（1）The phosphorus-sulfur co-doped graphite carbon（PCN/S）was synthesized from dicyandiamide,red phosphorus,thiourea and potassium chloride by molten salt calcination.g-C₃N₄ hardly produces H₂O₂ under visible light.Phosphorus-sulfur modified g-C₃N₄ can increase the yield of H₂O₂ to 6159.5μΜwithin 3 hours,which is7.8,2.1 and 9.5 times of that for carbon nitrogen（CN）,Phosphorus modified carbon nitrogen（PCN）and sulfur modified carbon nitrogen（SCN）,respectively.The mechanism study shows that the nitrogen vacancy content in the catalyst is controlled by changing the amount of thiourea.The nitrogen vacancy acts as an electron capture trap to locally generate a largr numbr of photogenerated electrons,and the transfers the electrons to the surface of the catalyst through the internal electronic transmission channel of the catalyst to participate in the oxidation-reduction reaction and promote the production of H₂O₂.In addition,the effects of various environmental factors on H₂O₂production were systematically studied.（2）The phosphorus-boron co-doped graphite carbon（PBCN）was by molten salt method from dicyandiamide,red phosphorus,sodium boronhydride and potassium chloride.The experimental results show that the H₂O₂ yield of PBCN under visible light is 4160.5μΜin 1 hour,which is 4.5,1.6 and 3.8 times of that for carbon nitrogen（CN）,Phosphorus modified carbon nitrogen（PCN）and boron modified carbon nitrogen（BCN）,respectively.The mechanism study shows that due to the different electronnegativity,the addition of boron causes the formation of a polarization electric field inside the catalyst.The polarization electric field drives the photogenerated electrons,promotes the separation of photogenerated carries,incrases the effective electron concentration in the system,and promotes the production of H₂O₂.In addition,the application of PBCN in different systems was systematically studied.