Modified graphitic carbon nitride prepared via a copolymerization route for superior photocatalytic activity

Abstract

Molecular doping strategy has been applied for regulating the electronic band structure of graphitic carbon nitride (g-C3N4). By incorporating the electron-withdrawing impurity group of N,N′,N″-s-triazine-2,4,6-triyl-tri-p-aminobenzoic acid (H3TATAB) into the network of g-C3N4, a series of H3TATAB-doped g-C3N4 (TABCN) photocatalysts were synthesized via thermal copolymerization at 550 °C for 4 h. H3TATAB doping shifts the VB of TABCN from 1.78 eV (pristine g-C3N4) to a low position (2.07 eV for TCBCN0.8), which enhances the oxidation ability of the VB hole for producing hydroxyl radicals in aqueous solution, and, therefore, the UV photocatalytic activity of TABCN0.8 is estimated to be about twice as high as that of g-C3N4 for the degradation of AO7. Further, doping the H3TATAB impurity group into the g-C3N4 network induces plenty of defect levels below the CB of g-C3N4, which gives a significant absorbance enhancement in the visible region. As a result, the visible light photocatalytic activity of TABCN0.8 is 7.5 times higher than that of g-C3N4 for the degradation of AO7. This work may provide guidance on designing an efficient g-C3N4 polymer photocatalyst with desirable electronic structure.