Dye-Sensitized NiS_x Catalyst Decorated on Graphene for Highly Efficient Reduction of Water to Hydrogen under Visible Light Irradiation

In this work, a highly active H₂ evolution NiS_x catalyst decorated on graphene (NiS_x/G) nanohybrid was prepared by an in situ chemical deposition method, in which nickel ion was first adsorbed onto graphene and subsequently reacted with sulfide ion to yield the NiS_x/G nanohybrid. The NiS_x/G catalyst exhibited activity for hydrogen generation 2-fold higher than that of pristine NiS_x under visible light irradiation. The highest quantum efficiency of 32.5% was reached at 430 nm when Eosin Y was used as a photosensitizer. In this system, graphene not only provided a large area and two-dimensional substrate for the confined growth of NiS_x but also greatly enhanced the transfer of photoelectrons from excited Eosin Y to the NiS_x cocatalyst because of its promotion of charge separation, leading to the great enhancement of photocatalytic hydrogen evolution.