Integration of nickel complex as a cocatalyst onto in-plane benzene ring-incorporated graphitic carbon nitride nanosheets for efficient photocatalytic hydrogen evolution

In this study, efficient visible-light-driven hydrogen evolution was achieved on novel and highly efficient photocatalysts based on nickel complex (NiL) and in-plane benzene ring-modified graphitic carbon nitride nanosheets (CN-DAPS) by copolymerization of urea and pi-electron-rich 4,4'-diaminodiphenyl sulfone (DAPS). The incorporation of in-plane benzene-ring into CN not only extends the pi-conjugated system, but also promotes the migration of photogenerated electrons and enhances absorption of visible light. In addition, NiL is covalently integrated onto CN-DAPS framework, enabling the intramolecular electron transfer from CN-DAPS to the coordinately-bonded nickel complex. Moreover, covalent combination of NiL with CN-DAPS framework further enables its dispersion in molecules. The novel photocatalysts NiL/CN-DAPS exhibit superior H-2 evolution activity, while the optimum hydrogen generation rate reaches 30.67 mu mol.h(-1). The NiL/CN-DAPS is even active for hydrogen generation even under irradiation of light with wavelength of 550 and 600 nm. The apparent quantum efficiency reaches 2.15 % at 450 nm. So to speak, the integration between the in-plane benzene-ring doped graphitic carbon nitride nanosheets aiming at high separation of charge carriers and the covalently-bonded nickel complex aiming to reduce the overpotential of photocatalytic hydrogen releasing results in a new class of photocatalysts based on non-noble-metal-based systems for efficient visible-light-driven hydrogen evolution.