A graphitic carbon nitride metal-free visible light photocatalyst with controllable carbon self-doping towards efficient hydrogen evolution

Controlling molecular defects via element doping is an effective strategy for tailoring electronic structures and charge separation in photocatalysts. However, the rational design of self-doped catalysts is generally confronted with the need for expensive reagents, high dopant ratios and environmentally unfriendly materials. Herein, carbon self-doped graphitic carbon nitride (DCN-x) is obtained via one-pot thermal polymerization of urea and D-mannitol. The sp2-hybridized nitrogen atoms are partially substituted by carbon atoms from dopants. The corresponding defects provide the photocatalyst with extended light harvesting up to 600 nm, a tunable optical bandgap, and the formation of more delocalized electrons with a uniform distribution at the defect scope of a C–C bond. In addition, increased band-tail states are found in DCN-3, which greatly enhance charge separation. A high photocatalytic hydrogen evolution rate of 3180 μmol g−1 h−1 is achieved under visible light irradiation (λ > 420 nm), which is about 5.3 fold higher than that of pristine g-C3N4. This work provides a green and economical method to synthesize g-C3N4 with controllable carbon self-doping sites for efficient energy conversion related applications.