Gas exfoliation mechanisms of graphitic carbon nitride into few-layered nanosheets

Two-dimensional (2D) graphitic carbon nitride (g-C₃N₄) nanosheets are widely used in photocatalysis, energy storage and membrane separation owing to their high specific surface area, rapid photogenic carrier migration rate and numerous active sites. In this study, high performance g-C₃N₄ nanosheets with a particle size of about 290 nm were prepared by gas exfoliation. It was observed that the structure and properties of g-C₃N₄ nanosheets prepared at 500 °C were superior as compared to 300 °C and 400 °C. The state of g-C₃N₄ layers at different temperatures was also studied by molecular dynamics simulation. It was revealed that the liquid nitrogen (L-N₂) molecules could only penetrate the edge space between g-C₃N₄ layers at 500 °C, however, no penetration took place in the layers. The traditional gas exfoliation mechanisms were observed to be incapable in explaining this phenomenon. Combining the experimental studies and molecular dynamics simulations, a novel gas exfoliation mechanism was proposed in this study so as to prepare few-layered g-C₃N₄ nanosheets. Based on this, the L-N₂ molecules entered the edge space in g-C₃N₄ layers and subsequently pushed deeper to exfoliate the nanosheets.