In this report, the CdS nanorods/g-C 3 N 4 heterojunctions loaded by noble-metal-free NiS cocatalyst were firstly fabricated by in situ hydrothermal method. The as-synthesized heterostructured photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution 10 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 NiS cocatalyst, 1D CdS nanorods and 2D g-C 3 N 4 nanosheets is a 15 promising strategy to achieve highly efficient visible-light-driven photocatalytic H 2 evolution. Among all the photocatalysts employed, the ternary hybrid g-C 3 N 4 -CdS-9%NiS composite materials show the best photocatalytic performance with a H 2 -production rate of 2563 umol h -1 g -1 , which is 1582 times higherthan that of the pristine g-C 3 N 4 . 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 20 and 2D g-C 3 N 4 nanosheets, which was favorable for promoting charge transfer, improving separation efficiency of photoinduced electron-hole pairs from bulk to interfaces and accelerating the surface H 2evolutioth 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-C 3 N 4 -based hybrid semiconductor nanocomposites for diverse photocatalytic 25 applications.

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In the present work, the earth-abundant NiS co-catalyst modified mesoporous graphite-like C3N4 (mpg-C3N4)/CNT nanocomposites were prepared via a two-step strategy: the sol-gel method and the direct precipitation process. The mpg-C3N4/CNT/NiS composite photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis absorption spectroscopy, photoluminescence spectroscopy (PL), photoelectrochemical (PEC) and electrochemical impedance spectra (EIS) experiments. The photocatalytic H2-production activity over the composite catalysts was also evaluated by using an aqueous solution containing triethanolamine under visible light (λ≥ 420 nm). The results showed that the loading of earth-abundant NiS co-catalysts onto metal-free mpg-C3N4/CNT nanocomposites can remarkably enhance their photocatalytic H2-production activity. The optimal loading amount of NiS on metal-free mpg-C3N4/CNT nanocomposites was about 1 wt%. The as-obtained mpg-C3N4/CNT/1% NiS ternary composite photocatalyst exhibits the best H2-evolution activity with the highest rate of about 521 μmol g(-1) h(-1) under visible light (λ≥ 420 nm), which is almost 148 times that of a pure mpg-C3N4/CNT sample. The enhanced photocatalytic activity can be mainly attributed to the synergistic effect of effectively promoted separation of photo-generated electron-hole pairs and enhanced H2-evolution kinetics. The co-loading of nanocarbon materials and earth-abundant co-catalysts onto metal-free mpg-C3N4 photocatalysts offers great potential for practical applications in photocatalytic H2 evolution under visible light illumination.

For converting the renewable solar energy to hydrogen (H 2 ) energy by photocatalytic (PC) overall water splitting (OWS), visible-lightdriven photocatalysts are especially desired. Herein, a model CdS/g-C 3 N 4 photocatalyst with a type II heterojunction is first demonstrated via a facile coupling of g-C 3 N 4 nanosheets and CdS nanorods. After being combined with in situ photodeposited 3 wt % Pt and 4 wt % MnO x dual cocatalysts simultaneously, the optimal visible-light-driven (λ > 400 nm) composite photocatalyst of Pt−CdS/g-C 3 N 4 −MnO x gives a H 2 generation rate of 9.244 μmol h −1 (924.4 μmol h −1 g −1 ) and a O 2 evolution rate of 4.6 μmol h −1 (460 μmol h −1 g −1 ) in pure water, which is over 420 times higher than that of pure CdS nanorods loaded with 0.5 wt % Pt. The apparent quantum efficiency (AQE) reaches about 3.389% (at 400 nm) and 1.745% (at 420 nm), respectively. The combination of a type II heterojunction and simultaneous in situ photodeposition of the dual cocatalysts results in a dramatically improved PC efficiency and a long-term stability of the CdS/g-C 3 N 4 visible-light-driven photocatalyst for OWS.