Synthesis of g-C3N4/Au nanocomposite as a photocatalyst for hydrogen generation

In this study, g-C3N4 was prepared and the effects of two-step heat treatment on its structure and photocatalytic properties were investigated. This material was then coated with gold nanoparticles by light deposition method and the composite was examined. The photocatalytic activity of the synthesized materials was also studied for hydrogen generation using sunlight and water. Characterization of the synthesized powders was carried out using various techniques such as X-ray diffraction, transmitted electron microscopy TEM, surface area analysis (BET) and ultraviolet-visible spectrometry (UV-Vis). X-ray diffraction showed that graphitic carbon nitride has a crystalline structure and its crystallinity is reduced after two stages of thermal treatment which is due to oxidation of graphitic carbon nitride. In addition, X-ray diffraction confirms the successful sedimentation of gold on graphitic carbon nitride. Transmission electron microscopy images show gold nanoparticles having particle size of about 8 nm. The study of UV-Visible absorption spectra of the synthesized powders showed that after two stages of heat treatment, the band gap of the samples increased and the presence of gold nanoparticles increased the light absorption in the visible light region via the surface plasmon resonance phenomenon. The specific surface area of the samples after two steps heat treatment and after applying of the gold nanoparticles increased from 4.2 to 15.7 and 29.3 m2/g, respectively. Graphitic carbon nitride with two steps heat treatment and coated with gold nanoparticles produced about 1128 μmol g-1 h-1 under sunlight. The photocatalytic mechanism of the system for the production of hydrogen gas was discussed.