Enhanced visible-light H2 evolution of g-C3N4 photocatalysts via the synergetic effect of amorphous NiS and cheap metal-free carbon black nanoparticles as co-catalysts

In this report, g-C3N4-based photocatalysts with dual co-catalysts of amorphous NiS and carbon black were firstly synthesized through a facile two-step process. The g-C3N4/carbon black/NiS composite photocatalyst were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-vis), N-2 adsorption, photoluminescence (PL) spectra and transient photocurrent responses. The photocatalytic activities for photocatalytic hydrogen evolution under visible light irradiation (lambda >= 420 nm) were measured using an aqueous solution containing triethanolamine as an electron donor. Moreover, the results showed that the ternary g-C3N4 photocatalyst loaded by 0.5 wt% carbon black and 1.5 wt% NiS could achieve the highest H-2-production rate of 992 mu mol g(-1) h(-1) under visible-light irradiation (>420 nm), which is about 2.51 times higher than that of the corresponding binary g-C(3)N(4)11.5% NiS photocatalyst. It is believed that the enhanced photocatalytic H-2-evolution activities could be attributed to the excellent synergetic effect between the carbon black and NiS as co-catalysts on the surface of g-C3N4, leading to the improved visible light absorption, promoted charge separation and enhanced the following H-2-evolution kinetics. This work would not only demonstrate the promising potentials of carbon black as co-catalyst 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 with dual co-catalysts for diverse photocatalytic applications. (C) 2015 Elsevier B.V. All rights reserved.