Insight into the influence of donor-acceptor system on graphitic carbon nitride nanosheets for transport of photoinduced charge carriers and photocatalytic H2 generation

[Display omitted] •Phenyl and O co-doped g-C3N4 nanosheets were prepared by one-step calcination.•The separated HOMO and LUMO promoted the dissociation of photoexicited charges.•The robust molecular dipole boosted the transfer of photoexicited charges.•Phenyl and O co-doped g-C3N4 nanosheets showed highly improved photocatalytic HER. The rapid recombination of photogenerated charges is one of the main restriction for promoting the photocatalytic H2 generation of graphitic carbon nitride (CN) material. Herein, donor-acceptor (D-A) system was introduced into CN nanosheets by oxygen and/or phenyl doping (DA-CN) strategy to facilitate the transport of photoinduced charge carriers and H2 generation. Experimental and theoretical results revealed that the nanosheet structure of DA-CN shortened the photoexcited charges transport length to the surface, and the D-A system embedded in DA-CN provided the dipole-induced internal electric field for charges transport. As a consequence, compared with pristine CN, DA-CN samples performed the improved transport of photogenerated charges and photocatalytic H2 evolution. Notably, DA-CN-OP (oxygen and phenyl co-doping) with the strongest dipole-induced internal electric field originated from D-A system displayed the highest photocatalytic H2 evolution rate at 7.394 mmol g−1h−1, which was 7.67 times as that of pristine CN (0.964 mmol g−1h−1). This work not only provides a simple strategy to construct highly efficient CN nanosheet photocatalyst with D-A system, but also promote the deep insight into the effect of molecular dipole originated from D-A system on the transport of photoinduced charge carriers and photocatalytic activity for CN material.