Abstract:

Nanosheet materials obtained from laminar compounds are new two-dimensional anisotropic nanomaterials that can even reach the sub-nanometer scale. These materials possess unique physical and chemical properties. An example of such a nanosheet materials is graphitic carbon nitride (g-C₃N₄) nanosheets transformed from bulk g-C₃N₄. Here, g-C₃N₄ nanosheets were prepared from bulk g-C₃N₄ by high-temperature thermal oxidation. The photocatalytic activity of eosin (EY)-sensitized g-C₃N₄ nanosheets for hydrogen evolution was about 2.6 times higher than that of bulk g-C₃N₄. The structure of the g-C₃N₄ nanosheets and process of electron transfer between EY and the g-C₃N₄ nanosheets were investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) analysis, fluorescence spectroscopy, and photoelectrochemical measurements. The g-C₃N₄ nanosheets possessed high specific surface area. The g-C₃N₄ nanosheets not only effectively absorbed dye molecules, but also enhanced the separation and electron transport efficiencies of photogenerated charges because of their quantum confinement effect. The quantum confinement effect of g-C₃N₄ nanosheets widened their bandgap, improved electron transfer ability along the in-plane direction, and lengthened the lifetime of photoexcited charge carriers. As a result, the photocatalytic activity of the g-C₃N₄ nanosheets was improved compared with that of bulk g-C₃N₄.

Key words: g-C₃N₄ nanosheet, Dye-sensitization, Quantum confinement effect, Photocatalysis, Hydrogen evolution