Modification of g-C3N4 nanosheets by carbon quantum dots for highly efficient photocatalytic generation of hydrogen

Carbon quantum dots-modified graphitic carbon nitride nanosheets (CNNS/CQDs) catalysts with high and stable activity for photocatalytic generation of hydrogen through water splitting were successfully constructed. [Display omitted] •Composite photocatalysts based on g-C3N4 nanosheets and CQDs were prepared.•High visible light photocatalytic activity for H2 evolution.•Effective separation and transfer of charge carriers. Carbon quantum dots (CQDs) were deposited onto graphite-like carbon nitride nanosheets (CNNS) to form CNNS/CQDs composites. The prepared CNNS/CQDs composites exhibit much higher photocatalytic activity under visible light irradiation than pure CNNS do. The CNNS/CQDs-7 sample displays the highest photocatalytic performance, with H2 production rate of 116.1μmolh−1, which is three times of that over pure CNNS (37.8μmolh−1). Photoluminescence spectroscopy and photoelectrochemical (PEC) analysis reveal that the CQDs are favorable for trapping electrons and promoting the separation of photogenerated electron-hole pairs in CNNS. A possible photocatalytic mechanism of the enhanced photocatalytic performance for H2 generation over CNNS/CQDs will be proposed in this paper.