Controllable synthesis for carbon self-doping and structural defect co-modified g-C3N4: Enhanced photocatalytic oxidation performance and the mechanism insight

Abstract

For the purpose of improving the photocatalytic performance of graphitic carbon nitride (g-C3N4) in the field of contaminant elimination, an in-situ malonamide-assisted strategy is provided to prepare carbon self-doping and structural defect co-modified g-C3N4 (CDCN) via preprocessing of the mixture of urea and malonamide followed by thermal copolymerization. Changing the initial malonamide dosage can precisely adjust the carbon doping level and structural defect concentration of CDCN. The characteristic results confirm that the doped C derived from malonamide was successfully implanted into the g-C3N4 framework by replacing sp2 hybrid N atoms (C−N=C) in the heptazine units, simultaneously forming some structural defects. Additionally, the preprocessing endows CDCN with good textural properties. So, the optimal CDCN20 shows remarkably enhanced visible-light photocatalytic activity in eliminating acetaminophen (APAP) and methylparaben (MPB) in water than pristine g-C3N4. By combining experimental and theoretical calculating results, the synergistic effect of C self-doping and structural defect promoting the photocatalytic performance of g-C3N4 is revealed thoroughly. This work provides a controllable strategy for synthesizing effective C self-doped g-C3N4 and a new insight into electronic structure and band structure-regulated photocatalytic oxidation mechanisms.