Enhanced photocatalytic H-2 evolution over noble-metal-free NiS cocatalyst modified CdS nanorods/g-C3N4 heterojunctions

In this report, CdS nanorods/g-C3N4 heterojunctions loaded with a noble-metal-free NiS cocatalyst were for the first time fabricated by an in situ hydrothermal method. The as-synthesized heterostructured photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy, UV-visible spectroscopy, nitrogen absorption, photoluminescence (PL) spectra, transient photocurrent responses and electrochemical impedance spectroscopy (EIS) measurements. Their photocatalytic activity for hydrogen production was evaluated using an aqueous solution containing triethanolamine under visible light (lambda >= 420 nm). The results clearly demonstrated that the ternary hybridization of the NiS cocatalyst, 1D CdS nanorods and 2D g-C3N4 nanosheets is a promising strategy to achieve highly efficient visible-light-driven photocatalytic H-2 evolution. Among all the photocatalysts employed, the ternary hybrid g-C3N4-CdS-9% NiS composite materials show the best photocatalytic performance with a H-2-production rate of 2563 mu mol h(-1) g(-1), which is 1582 times higher than that of the pristine g-C3N4. The enhanced photocatalytic activity was ascribed to the combined effects of NiS cocatalyst loading and the formation of the intimate nanoheterojunctions between 1D CdS nanorods and 2D g-C3N4 nanosheets, which were favorable for promoting charge transfer, improving the separation efficiency of photoinduced electron-hole pairs from the bulk to the interfaces and accelerating the surface H-2-evolution kinetics. This work would not only provide a promising photocatalyst candidate for applications in visible-light H-2 generation, but also offer a new insight into the construction of highly efficient and stable g-C3N4-based hybrid semiconductor nanocomposites for diverse photocatalytic applications.