Graphene Quantum-Dot-Modified Hexagonal Tubular Carbon Nitride for Visible-Light Photocatalytic Hydrogen Evolution

Graphene quantum dots were modified on hexagonal tubular carbon nitride to form a composite photocatalyst by freeze-drying technology. With an optimum loading amount of 0.15 wt% GQDs, the composite photocatalyst exhibits an improved visible-light photocatalytic performance for hydrogen evolution (112.1 mu mol h(-1)) that is about 9 times higher than that of bulk carbon nitride. During the photocatalytic reaction, graphene quantum dots play a photosensitizer role and an electron reservoir, which can extend the visible-light response of the photocatalyst, decrease its band gap, and improve the separation efficiency of photoinduced electron-hole pairs. The graphene quantum dots can also absorb the long-wavelength light and then emit the shorter wavelength light based on its upper transfer luminescence properties, which also contribute to the utilization of visible light. This finding demonstrates that the graphene quantum-dot modification is a promising method to improve visible-light photocatalytic activities for traditional photocatalysts.