Modified Graphite Phase Carbonitride-Based Photocatalytic Materials And Their Production Of H₂O₂

Graphite phase carbonitride（g-C₃N₄）is a non-metallic semiconductor connected by a plurality of tris-triazine-structured melem units.The material is safe,non-toxic and stable,and is widely used in the field of photocatalysis.However,there are still problems such as limited oxidizing power,high photoelectron and hole recombination rate.This topic is to study the preparation method and photocatalytic mechanism of modified g-C₃N₄ based materials,in order to improve its photocatalytic performance to achieve photocatalytic H₂O₂and photocatalytic Fenton degradation of pollutants.The reduced g-C₃N₄ material was prepared by heat-treating g-C₃N₄ with NaBH₄ under a N₂ atmosphere.The results of elemental analysis,FTIR and XPS characterization indicated that the reduction treatment produced nitrogen vacancies and C≡N functional groups,which were caused by the destruction of the pyridyl nitride in the g-C₃N₄ triazine ring during the reduction process.The formation of nitrogen vacancies creates intermediate levels in the band gap of the reduced g-C₃N₄ and extends the absorption wavelength of the material.The UV-vis DRS,Mott-Schottky and DFT calculations show that the reduction leads to a positive shift of the conduction band and the valence band of g-C₃N₄,and the functional group C≡N narrows the band of the reduced g-C₃N₄.The positive shift of the valence band confers the ability to reduce the oxidized water driven by visible light of the g-C₃N₄ material,which is also confirmed by electron,hole sacrificial and EPR techniques.PL characterization indicates that the reduction treatment promotes the separation of photogenerated electrons and holes and enhances the rate of charge transfer.The RDE test showed that the photocatalytic reduction of O₂ by reduced g-C₃N₄ was mainly due to the selective electron-generated H₂O₂ reaction.The reduced g-C₃N₄ prepared at 370°C exhibited pure H₂O₂(170μmol/L·h^-1)performance under pure H₂O and atmospheric atmosphere.Fe was supported on an RCN（reduced g-C₃N₄）photocatalyst to form an RCN-Fe material to construct an in situ photocatalytic Fenton system.No significant material changes were observed in the XRD and FTIR characterization,indicating that this Fe loading has less effect on the structure of the RCN material.The XPS characterization indicates that Fe is bound to the RCN material in the form of Fe₂O₃.The·O^2-and·OH quenching experiments show that the degradation of contaminants by the composite RCN-Fe is completely converted to·OH dominated,while the activity of RCN photocatalytic degradation of pollutants The substance is almost independent of·OH.The degradation effect of PNP and IPA by the former was 3 times and 15 times higher than that of the latter.The UV-vis DRS characterization and the·OH quenching experiment together demonstrate that the performance improvement in the RCN-Fe photocatalytic system is based on the effective capture of the conduction band electrons and·O^2-by the supported Fe.In addition,the photocatalytic stability of the material was demonstrated by repeated experiments in cycles.