Modification And Regulation Of Graphitic Carbon Nitride Molecules And Morphology And Research Of Photocatalytic Performance

The energy shortage and environmental pollution caused by the excessive use of fossil energy have become an important obstacle to the sustainable development of human society.Photocatalysis technology is considered as one of the ideal ways to solve the current energy crisis and environmental pollution because it can convert solar energy into clean chemical energy and degrade organic pollutants under mild conditions only by using inexhaustible solar energy as driving energy.Among many photocatalytic materials,graphitic phase carbon nitride（g-C₃N₄）has the advantages of strong visible light response,controllable structure and morphology,stable properties and a wide range of sources.As a photocatalytic material,it has received extensive attention and research in wastewater purification and energy conversion applications.However,bulk g-C₃N₄has some shortcomings,such as low specific surface area,narrow visible light response region,severe photo-generated carrier recombination,and slow electron transfer rate between layers.As a result,its efficiency of degrading organic matter and energy conversion of wastewater is still difficult to meet the requirements of practical applications.Based on this,in this paper,the electron and morphology of g-C₃N₄are regulated by means of atomic doping and copolymerization,so as to optimize its optical absorption performance and surface interface electron transfer path,and solve the problems of bulk g-C₃N₄photogenerated carrier transmission resistance,high recombination rate and limited optical absorption,etc.The catalyst is applied to the fields of photocatalytic productivity and wastewater purification.The performance improvement mechanism is studied systematically.It mainly includes the following research contents:（1）A g-C₃N₄ nanotube co-doped with anion and cation was prepared by self-assembly and impregnation-assisted thermal polymerization.Under the coinduction of P/Ni ions,g-C₃N₄could not only maintain the hollow tubular structure,but also optimize the electronic structure and surface electron transport path.An intermediate state is established in g-C₃N₄band gap to promote the separation of photogenic carriers with light absorption capacity.Finally,the photocatalytic H₂production rate of PNCNT reachedμmol g^-1h^-1,which was 29.1 times that of pure g-C₃N₄nanotubes.（2）Using dead leaves of Bauhinia flower as natural carbon source,porous g-C₃N₄nanosheets（PCCN）with in-situ carbon doping were prepared economically and efficiently by one-step thermal polymerization.In the process of high temperature calcination,the dead leaves of Bauhinia flower release carbon dioxide and water,and the surface of g-C₃N₄is etched to form natural holes.At the same time,the high temperature calcination of dead leaves of Bauhinia will become a natural carbon source and enter the g-C₃N₄skeleton to form in situ carbon doping and introduce intermediate energy levels near the top of the conduction band,which can not only accelerate charge separation and enhance light absorption,but also inhibit the ineffective decomposition of hydrogen peroxide.The optimized PCCN10 showed good hydrogen peroxide production synergism with bisphenol A degradation activity.Under 1h visible light irradiation,the hydrogen peroxide yield reached 37.44μmol L^-1and the degradation rate of bisphenol A（BPA）reached 96%,which were 4.44 times and 3.84 times of the original g-C₃N₄,respectively.（3）A porous g-C₃N₄nanosheet with excellent antibiotic degradation performance was prepared by bridging the structure-matched aromatic copolymer（3,6-dibromocarbazole）into the tris-triazine network skeleton of g-C₃N₄with molecular copolymerization strategy.The electron and morphology of g-C₃N₄were adjusted at the molecular level.The introduction of carbazole can effectively expand theπelectron structure of g-C₃N₄and solve the problem of insufficient ability of atomic doping to expandπstructure.CBCN15 can degrade the refractory antibiotic ciprofloxacin（CIP）up to 99.9%under 40 min of visible light irradiation.In addition,hydrogen peroxide was produced in situ(91.24μmol L^-1),which was 3.11 times and 4.5 times of the original g-C₃N₄,respectively.