Preparation And Catalytic Degradation Performance Of G-C₃N₄ Matrix Composites

The rapid development and progress of technology,accompanied by the rapid consumption of fossil fuels and the massive emissions of industrial pollution,have caused serious damage to the green waters and mountains on which we rely for survival.In the 21st century,the environmental protection concept of green and sustainable development is deeply rooted in people’s hearts.In order to achieve the strategic goal of carbon peaking and carbon neutrality by 2030,the development of clean energy and renewable energy is extremely urgent.The photocatalytic technology that uses sunlight as an energy driven has received extensive research and attention in recent years due to its convenience,low cost,safety,and no secondary pollution.However,photocatalytic technology still faces the problem of fast recombination speed of photo-generated charge carriers and low catalytic efficiency in practical applications.In order to improve the catalytic efficiency of the photocatalysis system,Advanced oxidation processes（AOPs）were combined with the photocatalysis system to enhance the use of light by the catalyst.Achieving efficient removal and even mineralization of organic pollutants and reducing secondary pollution is of great significance for environmental protection.1.WO₃/g-C₃N₄（W-CN）Z-scheme heterojunction was successfully prepared by simple calcination and in-situ growth using melamine and ammonium tungstate as precursors and was used for the degradation of rhodamine B（Rh B）and tetracycline（TC）.Compared with pure phase g-C₃N₄（CN）,the W-CN Z-scheme heterojunction forms a pore structure,increases the specific surface area,reduces the band gap,and increases the migration rate of photo-generated charge carriers.In the Photo-Fenton-like system,the W-CN Z-scheme heterojunction catalyst achieved degradation efficiencies of 96%and 76%for Rh B and TC within 30 min,respectively,much higher than the individual photocatalytic system.The capture experiment proved that the charge transfer in W-CN conforms to the Z-scheme mechanism,and·O₂^-and photo-generated holes play a decisive role in the photocatalytic process.After three cycles of recycling,it still maintains excellent catalytic degradation performance and has good cycling stability.There is enormous potential in the field of pollutant control.2.Cu Fe S₂/g-C₃N₄（CFS/CN）S-scheme heterojunction was successfully synthesized through simple hydrothermal and calcination methods for the catalytic degradation of Rh B in the Photo-Fenton-like system.Compared with CN nanorods,CFS/CN S-scheme hetero-catalytic junctions have a larger specific surface area,stronger light absorption ability,and faster migration rate of photo-generated charge carriers.At the same time,the CFS/CN uses metal ions as the medium for the Photo-Fenton-like system,accelerating the consumption of photogenerated electrons generated by the S heterojunction,and slowing down the recombination rate of photogenerated electron-hole pairs.At the same time,photogenerated electrons undergo a reduction reaction with metal ions,achieving the cycling process of metal ions in the Fenton-like system,and providing energy support for the Fenton-like system,thereby improving the catalytic degradation performance of Rh B.Within 15 and 20 min,The degradation efficiency of Rh B by this catalyst is 90%and 96%,respectively.At the same time,CFS/CN has good environmental adaptability and cycling stability and has good catalytic degradation performance for Rh B within the p H range of 1-11.After three cycles,the catalytic degradation performance of the catalyst for Rh B remains basically unchanged.3.Mn Co₂S₄/g-C₃N₄/DT（MCS/CN/DT）Z-scheme heterojunction was prepared by thermal polymerization combined with coprecipitation,and used to study the catalytic degradation of Rh B in SR-Photo-Fenton-like system.As the carrier of MCS/CN,DT with a porous structure makes MCS/CN reduce agglomeration and better disperse in DT pores and surfaces,thus increasing the specific surface area of MCS/CN and providing a more active site.Therefore,the catalytic degradation performance of the catalyst for Rh B is improved.The charge transfer pathway in MCS/CN/DT follows a Z-scheme mechanism,and the SR photo-Fenton system was successfully constructed using Mn and Co metal ions as mediators.Mn and Co ions accelerate the consumption of photo-generated electrons and slow down the recombination rate of photo-generated electron-hole pairs.At the same time,metal ions capture photo-generated electrons and undergo reduction reactions,achieving the cycling process of metal ions in the Fenton-like system,providing energy support for the Fenton-like system,and improving catalytic performance,The catalytic degradation of Rh B by this catalyst was 92.1%within 40 seconds.After three cycles of stability experiments,the degradation efficiency of the catalyst for Rh B was 90.6%,indicating good cycle stability.4.Graphite carbon nitride（g-C₃N₄）composite manganese cobalt-based Prussian blue（Mn Co PBA/g-C₃N₄）catalyst was successfully prepared by self-assembly method,a coprecipitation method and high-temperature annealing method,which was used to study the catalytic degradation of Rh B in SR-Photo-Fenton-like system.In Mn Co PBA/g-C₃N₄,Mn Co PBA exists as a variable valence compound with variable valence metal ions,and the SR Photo-Fenton-like system is constructed using variable valence metal ions as a medium for photocatalysis and Fenton-like reactions.This can create a synergistic effect between photocatalysis and Fenton-like reactions,accelerate the consumption of photo-generated electrons,slow down the recombination rate of photogenerated electron-hole pairs,and capture photo-generated electrons by metal ions for reduction reactions,The closed-loop cycling process of metal ions in the Fenton like the system has been achieved,providing energy support for the Fenton--like system and improving catalytic performance.The catalyst has a degradation efficiency of 96%for Rh B within 10 min.In addition,the catalyst has little effect on the catalytic degradation performance of Rh B after four cycles of experiments and has good catalytic degradation performance on Rh B in the range of p H=1-9.It is indicated that the catalyst has good environmental applicability and cyclic stability.