Enhanced photocatalytic H2 evolution over noble-metal-free NiS cocatalyst modified CdS nanorods/g-C3N4 heterojunctions

Abstract

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 (λ ≥ 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 H₂ evolution. Among all the photocatalysts employed, the ternary hybrid g-C₃N₄–CdS–9% NiS composite materials show the best photocatalytic performance with a H₂-production rate of 2563 μmol 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 H₂-evolution kinetics. This work would not only provide a promising photocatalyst candidate for applications in visible-light H₂ 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.