Preparation Of Acid-modified G-C₃N₄ And Study On Photocatalytic Performance

Photocatalytic technology is a series of degradation reactions after being absorbed by photocatalysts under the action of light,which has the advantages of green,economical,sustainable,simple operation and high efficiency.As a catalytic degradation material,g-C₃N₄has attracted a lot of attention because of its good stability,strong acid and alkali resistance,at the same time,it also has unique shortcomings such as the utilization rate of visible light is not high and rapid photogenic carrier recombination.In view of these shortcomings,modified g-C₃N₄was prepared by acid modification to improve the photocatalytic degradation efficiency.（1）Compared with pure g-C₃N₄prepared by direct calcination melamine and melamine cyanic acid,the band gap of NDA1-CN is 0.4 eV narrower than that of pure g-C₃N₄,and the narrower the band gap,the narrower the band gap,the more convenient for electron transition.According to the photocatalytic degradation of pollutants to analyze the situation,the reaction rate constant K of NDA1-CN is 1.9 times that of pure g-C₃N₄when degrading rhodamine B and 1.4 times that of pure g-C3N4 when degrading methyl blue solution..（2）Using melamine and cyanic acid as raw materials,sulfuric acid and hydrochloric acid were used to assist supramolecular assembly to prepare modified graphitic phase carbon nitride NDB-CN,and according to the characterization test,it was found that the infrared absorption peak of NDB1-CN was sharper,indicating that NDB1-CN had a higher degree of polycondensation and a more uniform structure.According to the photocatalytic degradation of pollutants to analyze the situation,the reaction rate constant K of NDB1-CN is 1.32 times that of NDB3-CN when degrading rhodamine B and 1.7times that of NDB3-CN when degrading methyl blue solution.（3）Different acids were used to modify melamine,and the precursor NDC was prepared by heating in a water bath,and then modified graphitic carbon nitride NDC-CN was prepared by supramolecular assembly with the same amount of trimeric thiocyanic acid.According to the characterization results,the band gap of NDC4-CN modified with cyanuric acid was 2.63eV,which was 0.17eV wider than that of NDC1-CN,indicating that the adsorption performance of NDC4-CN was better.According to the analysis of photocatalytic degradation performance,the reaction rate constant K of NDC4-CN was3.28 times that of NDC1-CN when degrading Rhodamine B,and 1.8 times that of NDC1-CN when degrading methyl blue solution.（4）Using melamine as raw material,modified graphitic carbon nitride NDD-CN was prepared by sulfuric acid modification,and the SEM image showed that NDD3-CN had an irregular surface depression with layered sheet,block and tubular structure.According to the photocatalytic degradation of pollutants to analyze the situation,the reaction rate constant K of NDD3-CN at the degradation of rhodamine B was 15.6 times that of the blank control group and 1.44 times that of NDD1-CN,and 4.6 times that of the blank control group and 1.92 times that of NDD1-CN when degrading methyl blue solution.