L-cysteine-assisted synthesis of hierarchical NiS hollow spheres supported carbon nitride as photocatalysts with enhanced lifetime.

Novel hierarchical NiS hollow spheres modified by graphite-like carbon nitride were prepared using a facile L-cysteine-assisted solvothermal route. The NiS/g-CN composites exhibited excellent photocatalytic efficiency in rhodamine B, methyl orange and ciprofloxacin degradation as compared to single g-CN and NiS, which could be due to the synergistic effects of the unique hollow sphere-like structure, strong visible-light absorption and increased separation rate of the photoinduced electron-hole pairs at the intimate interface of heterojunctions. A suitable combination of g-CN with NiS showed the best photocatalytic performance. In addition, an electron spin resonance and trapping experiment demonstrated that the photogenerated hydroxyl radicals and superoxide radicals were the two main photoactive species in photocatalysis. A possible photocatalytic mechanism of NiS/g-CN composites under visible light irradiation is also proposed. The strategy presented here can be extended to a general strategy for constructing 3D/2D heterostructured photocatalysts for broad applications in photocatalysis.