Implanting nitrogen-doped graphene quantum dots on porous ultrathin carbon nitride for efficient metal-free photocatalytic hydrogen evolution

Mimicking natural photosynthesis to make solar power into hydrogen energy is widely perceived as a promising and sustainable way to alleviate the energy crisis and environmental pollution. However, adding metallic cocatalysts and even noble metal cocatalysts into carbon nitride-based photocatalysts still seriously restrict the practical development of photocatalytic water splitting. To address these issues, we carefully design and construct a metal-free photocatalytic system through grafting 0D nitrogen-doped graphene quantum dots (N-GQDs) on 2D porous ultrathin carbon nitride (PUCN). The incorporated N-GQDs can act as electron collectors to promote the charge separation/transfer on PUCN, and also can extend the photoabsorption region of PUCN. Thus, the metal-free N-GQDs/PUCN photocatalyst exhibits a drastically enhanced hydrogen production rate of 1248 μmol g−1 h−1, which fetches up to about 208 times as high as that of PUCN (6 μmol g−1 h−1). Notably, the photocatalytic performance of N-GQDs/PUCN is close to that of Pt/PUCN with the same cocatalyst amount (1706 μmol g−1 h−1), and metal-free N-GQDs/PUCN photocatalyst outperforms most of the reported carbon nitride-based photocatalysts with metallic cocatalysts for photocatalytic water splitting. This work offers new insight to construct metal-free carbon nitride-based photocatalysts, which will be beneficial for the practical development of photocatalytic water splitting.