Rational design of ternary NiS/CQDs/ZnIn2S4 nanocomposites as efficient noble-metal-free photocatalyst for hydrogen evolution under visible light

The NiS/CQDs nanocomposite (CQDs represents carbon quantum dots), with a mass ratio of NiS/CQDs to be 1.19:1 based on the ICP result, was obtained via a facile hydrothermal method from a mixture of CQDs, Ni(OAc) 2 and Na 2 S. The self-assembly of ZnIn 2 S 4 microspheres on the surface of NiS/CQDs was realized under microwave conditions to obtain a ternary NiS/CQDs/ZnIn 2 S 4 nanocomposite. The as-obtained NiS/CQDs/ZnIn 2 S 4 nanocomposite was fully characterized, and its photocatalytic hydrogen evolution under visible light irradiation was investigated. The ternary NiS/CQDs/ZnIn 2 S 4 nanocomposite showed superior photocatalytic activity for hydrogen evolution than ternary CQDs/NiS/ZnIn 2 S 4 , which was obtained by deposition of NiS in the preformed CQDs/ZnIn 2 S 4 . The superior photocatalytic performance of ternary NiS/CQDs/ZnIn 2 S 4 is ascribed to the introduction of CQDs, which act as a bridge to promote the vectorial transfer of photo-generated electrons from ZnIn 2 S 4 to NiS. This result suggests that the rational design and fabrication of ternary CQDs-based systems are important for the efficient photocatalytic hydrogen evolution. This study provides a strategy for developing highly efficient noble-metal-free photocatalysts for hydrogen evolution using CQDs as a bridge to promote the charge transfer in the nanocomposite. CQDs act as a bridge to promote the charge transfer from ZnIn 2 S 4 to NiS in the ternary NiS/CQDs/ZnIn 2 S 4 nanocomposite.