The oxidative thermal exfoliation-dependent microstructure and photocatalytic performance of g-C3N4 nanosheets

The preparation of ultrathin nanosheets is conducive to increasing the material's specific surface area and introducing suitable defect sites. This facilitates the enhancement of the separation efficiency of photogenerated charge carriers and improves the adsorption and degradation efficiency toward pollutants. Various nitrogen-rich precursors were employed for the synthesis of bulk g-C3N4 (BCN) and its ultrathin nanosheets, with a focus on investigating their photocatalytic performance. The degree of polymerization of g-C3N4 influenced its hydrogen bonding and C/N ratio, affecting the ultrathin nanosheet microstructure. Oxidation disrupted the tri-s-triazine rings in the ultrathin nanosheets of g-C3N4 prepared via dicyandiamide. However, g-C3N4 prepared from urea and melamine as precursors retained its primary characteristics after thermal oxidative exfoliation, attributed to interlayer hydrogen bonds, small lateral size at low polymerization degrees, and increased vacancy defects. In the photocatalytic degradation system, two-dimensional nanosheets of g-C3N4 synthesized from urea exhibited the highest catalytic efficiency.