Engineering ultrathin oxygen-doped g-C3N4 nanosheet for boosted photoredox catalytic activity based on a facile thermal gas-shocking exfoliation effect

• O-doped g-C 3 N 4 was synthesized based on a thermal gas-shocking exfoliation effect. • The doping sites of O atoms were determined by XPS results and DFT calculations. • O-doped g-C 3 N 4 exhibited excellent photocatalytic TC degradation and H 2 evolution. Graphitic carbon nitride (g-C 3 N 4 ) is a promising star photocatalytic material due to features of non-toxic, inexpensive, and easy to prepare, but only exhibited poor performance by the high carrier recombination rate. In this work, engineering of 2D ultrathin and O doping into g-C 3 N 4 was achieved by using thermal gas-shocking effect induced via endogenous gases from the urea solution and C/N-steam reforming reaction. The experimental results revealed that the optimal sample exhibited the photo-degradation rates of tetracycline (TC) within 2 h were 87.2%, and the photocatalytic H 2 evolution rate reached 6.21 mmol h −1 g −1 . This overwhelming photocatalytic performance is attributed to following factors, including ultrathin thickness results in reduced charge transfer distance, larger specific surface area exposed more active reaction sites, and O doping forms electron-rich centers to promote carrier separation and negative shift of the conduction band for enhanced the reduction potential of photogenerated electrons. This study presents an effective strategy for preparing high-active g-C 3 N 4 photocatalysts with optimized modification.