Synthesis and Efficient Visible Light Photocatalytic Hydrogen Evolution of Polymeric g-C3N4 Coupled with CdS Quantum Dots

Novel CdS quantum dot (QD)-coupled graphitic carbon nitride (g-C 3 N 4 ) photocatalysts were synthesized via a chemical impregnation method and characterized by X-ray diffraction, transmission electron microscopy, ultraviolet–visible diffuse reflection spectroscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and photoluminescence spectroscopy. The effect of CdS content on the rate of visible light photocatalytic hydrogen evolution was investigated for different CdS loadings using platinum as a cocatalyst in methanol aqueous solutions. The synergistic effect of g-C 3 N 4 and CdS QDs leads to efficient separation of the photogenerated charge carriers and, consequently, enhances the visible light photocatalytic H 2 production activity of the materials. The optimal CdS QD content is determined to be 30 wt %, and the corresponding H 2 evolution rate was 17.27 μmol·h –1 under visible light irradiation, ∼9 times that of pure g-C 3 N 4 . A possible photocatalytic mechanism of the CdS/g-C 3 N 4 composite is proposed and corroborated by photoluminescence spectroscopy and photoelectrochemical curves.