Preparation Of High Performance Graphitic C₃N₄ Materials And Its Degradation Mechanism For Removal Of Organic Pollutants And Hydrogen Production

Graphitic carbon nitride（g-C₃N₄）has attracted worldwide attention in the area of photoelectric catalysis due to its visible-light activity,facile synthesis from low-cost materials,chemical stability,and unique layered structure.However,its intrinsic problems of high reaction energy barrier,small specific surface area and low single-atom loading hindered its applications.Under this circumstance,the decoration of g-C₃N₄by introducing noble metals can largely promote its overall photocatalysis performance.However,the weak interaction is the key flaw to benefit the charge transport between g-C₃N₄and noble metal.As a atomic catalyst support,although g-C₃N₄has extremely high nitrogen content,the current preparation method is difficult to achieve the controllable preparation of g-C₃N₄based atomic catalyst with high loading ratio.In this thesis,the strong interaction between g-C₃N₄and precious metals with ultra-high single-atom loading ratio has been achieved by following the protocol of solvothermal reduction and supramolecular self-assembly:1)CNNT and Pt-CNNT photocatalytic materials with different contents of Pt were prepared by solvothermal method.The Pt-CNNT prepared by solvothermal reduction method realized the semi-chemical interaction between Pt and CNNT,and formed the in-plane homogenous junction of CNNT.Semi-chemical interactions and in-plane homojunctions in Pt-CNNT can reduce the charge transfer barrier,inhibit photogenerated charge recombination,improve charge separation/transfer,and accelerate H⁺reduction.In visible light（λ>Under 420 nm）irradiation,Optimized Pt-CNNT on the TOF of hydrogen production can reach 918h^-1,200 times that of Pt/CNNT.This work provides an innovative method for efficient photocatalytic hydrogen evolution.2)The g-C₃N₄-supported Fe atomic catalyst（Fe/CN）was successfully prepared followed by supramolecular assembly and high temperature calcination.The Fe/CN can effectively activate PI to selectively generate ¹O₂,which is reactive oxygen species that responsible for 4-CP degradation.The degradation rate of 4-CP was up to0.23 min^-1.The degradation reaction of 4-CP by Fe/CN activated PI has a wide p H application range,and the system also has strong anti-interference ability to common anions in real water.This provides experimental basis and theoretical support for the application of atomic catalyst materials in the efficient degradation of organic pollutants in real water.3)Mn atomic catalyst（MN₁-CN）supported by g-C₃N₄was prepared by ball milling and calcination method.The successful preparation of Mn atomic catalyst was confirmed by spherical electron microscopy.This method can regulate the Mn content,and achieve the loading capacity of up to 14.2wt%.The experimental results showed that MN₁-CN can rapidly activate PMS and efficiently degrade 4-CP.The active species quenching experiment and EPR test confirmed that ¹O₂was the most reactive species that responsible for 4-CP degradation.Moreover,the ¹O₂has high selectivity toward the 4-CP and the system has demonstrated excellent anti-ions capability in wide p H range.This work provides experimental and theoretical guidance for the selective generation of active species and a new idea for the selective degradation of organic pollutants.