The Preparation And Application Of G-C₃N₄

Graphitic carbon nitride（g-C₃N₄） has attracted many attention because of its various advantages such as hydrothermal and chemical stability, visible light response, non-poisonous, low cost production and so on. In this paper, g-C₃N₄ was synthesized by the self-condensation polymerization of melamine at 550℃ with a duration of 2h. g-C₃N₄ quantum dots and g-C₃N₄ nanosheets was obatined respectively using hydrothermal treating and high-speed shear method. The materials were characterized using BET, Diffuse Reflectance Spectra（DRS）, Raman Spectroscopy（Raman）, Scanning Electron Microscopy（SEM）, X-ray Diffraction（XRD）, Transmission Electron Microscopy（TEM） and X-ray Photoelectron Spectroscopy（XPS）.The major contents and results of the paper are sumrized as follows:1. Large scale g-C₃N₄ nanosheets were successfuly prepared using the high-speed shear exfoliation method, whose diameter is in the range of 50^-130 nm, with a thickness of about 0.7 nm. The photocatalytic decomposition rate constant toward rhodamine B（RhB） of g-C₃N₄ nanosheet is 4.2 times that of the bulk g-C₃N₄. The preparation of g-C₃N₄ nanosheets has advantages of high production yield and good dispersion in water, which enables it a good chance in industrial organic dye wastewater treatment.2. g-C₃N₄ were also synthesized in different metal chloride. The crystalline degree, band gap, solubility, and light catalytic properties have a certain degree of difference after the mofidication. The g-C₃N₄ obtained in potassium chloride at 600℃ has the highest crystalline degree, the minimum band gap in lithium chloride, and the best dispersiton in water in calcium chloride. The g-C₃N₄ obtained at 500℃has the best photocatalytic performance in calcium chloride, and the best performance at 600℃ in potassium chloride. The photocatalytic decomposition rate constants toward RhB of the above two samples, G-500 Ca and G-600 K were 0.01789 and 0.0274 respectively, while the rate constants of the g-C₃N₄ heated directly at 500℃ and 600℃ were 0.01039 and 0.01768, respectively.3. Carbon microspheres modified with g-C₃N₄ quantum dots was prepared for the first time, in which the g-C₃N₄ quantum dots were prepared using a hydrothermal method. The modified carbon microspheres have a certain degree of increase in the graphitization degree, the production yield, the nitrogen content and the specific surface area. Mesoporous pores were introduced into the carbon microspheres after air activation. The improved mesoporous microstructure is benifical to the ion transport and thus greatly improve the supercapacitor performance. The impedance performance of AC^-1 is very excellent. The mass specific capacitance is 281Fg^-1 when the current density is 2Ag^-1, and remaines 91.6% at 10Ag^-1.