Enhanced photocatalytic H2-production activity of C-dots modified g-C3N4/TiO2 nanosheets composites.

As a new carbon-based material, carbon dots (C-dots) have got widely preference because of its excellent electronic transfer capability. In this work, a novel ternary layered C-dots/g-C3N4/TiO2 nanosheets (CGT) composite photocatalysts were prepared by impregnation precipitation methods. The optimal ternary CGT composite samples revealed high photocatalytic hydrogen evolution rate in triethanolamine aqueous solutions, which exceeded the rate of the optimal g-C3N4/TiO2 composite sample by a factor of 5 times. The improved photocatalytic activity is owed to the positive effects of C-dots and layered heterojunction structure of TiO2 nanosheets and g-C3N4 sheets. C-dots in the CGT composites can serve as electron reservoirs to capture the photo-induced electrons. The well-defined layered heterojunction structure of CGT provides the intimate contact and the strong interaction of anatase TiO2 nanosheets and g-C3N4 sheets via face-to-face orientation, which restrains the recombination of photogenerated charge carriers, and thus enhances the photocatalytic H2-production activity. Electron paramagnetic resonance and transient photocurrent response proved the strong interaction and improved interfacial charge transfer of TiO2 nanosheets and g-C3N4 sheets, respectively. The mechanism of improving the photocatalytic H2-evolution activity was further confirmed by time-resolved fluorescence, electron paramagnetic resonance, transient photocurrent response and electrochemical impedance spectroscopy.