Facile fabrication of graphitic carbon nitride by solvothermal method with hierarchical structure and high visible light photocatalytic activity

Background: At present, graphitic carbon nitride(g-C3N4) has been tremendously investigated as a visible light photocatalyst due to its excellent physical and chemical stability, easy fabrication, diverse morphology and tunable band structure. However, small surface area and high recombination of photogenerated electron-hole pairs hinder the photocatalytic activity of the pristine g-C3N4. Up to now, most of the g-C3N4 is prepared by the time-consuming, cumbersome and energy-consuming methods such as template and high temperature calcination.Methods: A novel graphitic carbon nitride with hierarchical structure and high photocatalytic activity was first time synthesized by the solvothermal method without high-temperature calcination using two monomers (cyanuric chloride and melamine) as the reactants. Morphologies and structure of graphitic carbon nitride were characterized by FTIR, XRD, XPS, FESEM, BET, etc. Effects of monomer molar ratio on the microstructure, band structure and electron transfer process of the samples were systematically investigated. The radical trapping experiments and Mott-Schottky analysis were carried out to reveal the photocatalytic degradation mechanism. Significant findings: Due to the high activity of Cl group of cyanuric chloride, HCl generated by condensation dramatically influences the formation of the porous structure. With the increase of cyanuric chloride molar ratio, polymerization reaction between cyanuric chloride and melamine became more complete, structure of graphite carbon nitride gradually changed from 1D nanorods to 2D layered structures, and the band structure and electron transfer properties were effectively improved. Due to the synergistic effect of specific surface area and electron transfer performance, 2-CN-1 with microporous 1D and 2D structures showed excellent photocatalytic perfor-mance (96.5% after 30 min illumination) and stability (photocatalytic performance only decreased by 4.5% after five cycles) in the condition of methyl orange (MO) concentration as high as 20 mg/L and photocatalyst amount as low as 20 mg. In this study, the effective control of graphitic carbon nitride morphology by way of new condensation mode via solvothermal method without both template and high temperature calcination provides a new strategy for the graphitic carbon nitride with high visible light photocatalytic activity.