Research Progress in Preparing Methods of g-C₃N₄ Nanosheets by Exfoliation

Graphitic carbon nitride (g-C₃N₄) is a typical sp² π conjugated polymer semiconductor material with a variety of unique physical and chemical properties. However, g-C₃N₄ obtained by a conventional calcination method has some shortcomings such as small specific surface area, a few exposed active sites, and a poor dispersibility in aqueous solution, restricting its practical application. Compared with bulk g-C₃N₄, g-C₃N₄ nanosheets obtained by different exfoliation processes have attracted much attention in the fields of energy, catalysis and sensing due to their high specific surface area, short carrier path, abundant active sites and large band gap. g-C₃N₄ has some disadvantages of nanosheet agglomeration, high energy consumption, long time consumption and low yield in the exfoliation preparation process. It is thus necessary to develop a green and cost-effective method for the preparation of g-C₃N₄ nanosheets. This paper reviewed the exfoliation mechanisms of top-down liquid exfoliation, chemical exfoliation and thermal exfoliation. The structure, composition, lamellar thickness and specific surface area of g-C₃N₄ nanosheets obtained by three methods were compared. In addition, some applications in photocatalysis were introduced, and the future development of g-C₃N₄ nanosheets was also prospected.