Synthesis And Photocatalytic Properties Of Graphite-phase Carbon Nitride Based On Precursor Self-assembly

Graphite phase carbon nitride（g-C₃N₄）has attracted the attention of researchers due to its high stability and small band gap,but its serious photocarrier recombination and low quantum efficiency limit its practical application.To solve the above problems,in this paper,different reactants were used to prepare precursors by self-assembly method,and g-C₃N₄material was synthesized by one-step calcination method.The research contents are as follows:（1）Using melamine and cyanic acid as raw materials,the precursor was prepared by self-assembly method by adjusting the molar ratio of reactants,and the g-C₃N₄ material was obtained by calcination.With the increase of the molar ratio of cyanic acid to melamine,the photocatalytic performance of the materials improved first and then decreased.When the molar ratio was 8/10,the degradation rate of methyl blue was increased to 2.875 times of that of 1/10 under UV light.When the molar ratio was 10/10,the degradation rate of rhodamine B was 6.33 times higher than that of 1/10.（2）Different reactants were used to conduct control experiments,respectively,using melamine,sodium phosphate,melamine,phosphoric acid as raw materials,through the combination of self-assembly method and calcination method to obtain the lamellar mesoporous g-C₃N₄ material.When the molar ratio of melamine to sodium phosphate was1/1,the degradation rate of methyl blue and rhodamine B increased to 1.896 times and 3.875times than that of the material with the molar ratio of melamine to phosphoric acid was 1/1.（3）Using melamine and sulfuric acid as raw materials,the precursor was prepared by self-assembly method,and the g-C₃N₄ material was obtained after calcination.Conclusion:in a certain range,the lower the concentration of sulfuric acid,the more improved the photocatalytic performance.When the molar ratio of melamine to sulfuric acid is 1/1,the degradation rate of methyl blue increases to 1.29 times of that of 1/2.When the molar ratio was 2/1,the degradation reaction rate of rhodamine B increased to 1.136 times that of the material with the molar ratio of 1/2.（4）Using melamine and silver nitrate as raw materials,using sodium hydroxide to adjust the p H value of the solution,through self-assembly method and calcination method to prepare composite materials.It is concluded that the p H value and preparation method have influence on the microstructure.When the molar ratio of melamine,silver nitrate and sodium hydroxide is 1/1/0,the morphology is nanowires.When the mole ratio was 1/1/2,1/1/4,1/1/6,the morphology was nanotube.When the molar ratio is 1/1/8,the morphology is nanorods.The morphology after calcination is micron sphere.The precursors have adsorption properties for eosin Y and can absorb up to 44mg eosin Y per gram of precursors.After calcination,when the molar ratio of the reactant is 1/1/6,the degradation reaction rate of rhodamine B is 2.13 times that of the material with a molar ratio of 1/1/2.