Synergistic effects of phosphorous/sulfur co-doping and morphological regulation for enhanced photocatalytic performance of graphitic carbon nitride nanosheets

Graphitic carbon nitride (g-C3N4) as a metal-free polymer semiconductor has received extensive attentions, but its application was drastically suppressed due to low photocatalytic activity. Herein, non-metal heteroatom co-doping is employed to extend the visible light absorption, and regulating morphology into nanosheets promotes the charge separation and transfer. Elements of P/S were successfully introduced into the carbon nitride framework by thermal condensation of their corresponding precursors with melamine. And, the presence of NH4Cl would produce abundant gas to blow CN layers separately to form thin nanosheets. The obtained P/S co-doped carbon nitride nanosheet (g-PSCNNS) sample presents enhanced absorption in visible light region and efficiencies for separation and transport of photo-generated charges. The synergistic effect of elemental co-doping and nanosheet-like morphology endues g-PSCNNS with superior photocatalytic performance for removal of organic pollutants in comparison with the pristine, P or S individual doped and P/S co-doped g-C3N4 samples. Moreover, this g-PSCNNS sample has excellent photocatalytic stability and reusability. Experiments of radical quenching demonstrate superoxide radical is the main active species in the photocatalytic process.