Ultrathin g-C3N4 nanosheets coupled with carbon nanodots as 2D/OD composites for efficient photocatalytic H2 evolution

Carbon nanodots synthesized from rapeseed flower bee pollens were used to couple with ultrathin g-C3N4 nanosheets for preparing the 2D/0D type photocatalysts by a hydrothermal method. The g-C3N4 nanosheets (UCN) obtained from ammonium chloride blowing dicyandiamide methods exhibit ultrathin two-dimension structure with a series of hollow spherical structures, and CQDs are well dispersed and uniformly anchored into the UCN network via pi-pi stacking interactions. The incorporation of CQDs can effectively expand visible light absorption regions via photosensitization and suppress the recombination of photo-induced carriers. Time-resolved fluorescence spectroscopy, electron paramagnetic resonance technology and photoelectrochemical measurements together reveal that CQDs serve as electron transfer mediation to facilitate charge separation and extend the lifetime of photo-induced carriers. The UCN/CQDs-0.2% composite has the optimal H-2 evolution of 88.1 mu mol/h, 9.79, 3.02 and 1.91 folds of bulk g-C3N4 (BCN), pristine UCN and BCN/CQDs-0.2%, respectively. Consequently, the UCN/CQDs composites exhibit high photocatalytic activity of hydrogen release under the visible light irradiation. (C) 2016 Elsevier B.V. All rights reserved.