Synthesis of MWNTs/g-C3N4 composite photocatalysts with efficient visible light photocatalytic hydrogen evolution activity

Novel multi-walled carbon nanotubes (MWNTs) and graphitic carbon nitride (g-C3N4) composite photocatalysts were synthesized via a facile heating method. The resulting MWNTs/g-C3N4 composite photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible diffuse reflection spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) spectroscopy. The photoelectrochemical l-t curves were tested using several on-off cycles of visible light irradiation. The visible light photocatalytic hydrogen evolution was investigated for MWNTs/g-C3N4 in methanol aqueous solutions. The optimal MWNTs content is determined to be 2.0 wt%; and corresponding H-2 evolution rate is 7.58 mu mol h(-1), about 3.7 folds that of pure g-C3N4. A possible mechanism of MWNTs on the enhancement of visible light performance is proposed. It suggests that MWNTs play key roles, which may lead to efficiently separation of the photo-generated charge carriers and, consequently, enhance the visible light photocatalytic H-2 production activity. (c) 2012 Elsevier B.V. All rights reserved.