Constructing nitrogen doped graphene quantum dots-ZnNb2O6/g-C3N4 catalysts for hydrogen production under visible light

•The NGQDs-ZnNb2O6/g-C3N4 catalysts were prepared by hydrothermal reaction.•The photocatalytic performance was measured by H2 production from water splitting.•The optimum H2 evolution rate of 5%NGQDs-ZnNb2O6/g-C3N4 is 340.9 μmol h−1 g−1.•The enhanced catalytic activity can be attributed to the heterojunction and NGQDs.

The development of efficient visible-light-driven photocatalysts for water splitting has drawn much attention. Herein, we demonstrated a novel H2-producing photocatalytic system that employed nitrogen doped graphene quantum dots (NGQDs)-ZnNb2O6/g-C3N4 heterostructures as the hydrogen evolving catalysts. The as-prepared NGQDs-ZnNb2O6/g-C3N4 heterostructures were favorable for light harvesting and charge separation, and showed highly efficient photocatalytic performance for water splitting into hydrogen. Results showed that both the ZnNb2O6/g-C3N4 (Zn/CN) mole ratio and the amount of NGQDs displayed important influence for H2 production. Moreover, the optimum synthesis conditions of the Zn/CN mole ratio (1/7) and the amount of NGQDs (5%) were both obtained, and the corresponding 5%NGQDs-Zn/7CN sample performed a much higher hydrogen-evolution rate of 340.9 μmol h−1 g−1. By the further studies, the enhanced photocatalytic activity could be ascribed to the crucial roles of NGQDs and heterojunction photocatalytic system, which resulted in an efficient charge separation and the largely enhanced photocatalytic activity. Meanwhile, the possible photocatalytic mechanism of NGQDs-ZnNb2O6/g-C3N4 was also proposed. We envision that this work creates new opportunities for constructing and designing efficient visible-light-driven photocatalysts for hydrogen evolution reaction.

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