Graphene/TiO2 Nanocomposite for Efficient Visible-Light Photocatalysis: Synthesis, Characterization and Photocatalytic Applications.

The production of graphene in large quantities is an ongoing challenge for large-scale applications. A number of processes are used to produce graphene from graphene oxide but they need strong oxidizing and reducing agents [1]. However, graphene fabricated under these chemical conditions tends to have a certain number of structural defects, when compared to that produced from other techniques. For that purpose, top-down method such as the exfoliation of graphite powder in liquid phase by sonication is a very promising route due to its simplicity, its versatility and its low-cost [2]; besides, ultrasound treatment offers a suitable option to create high-quality graphene in great quantity. Graphene with the thickness of a single carbon atom owns unique physical and chemical properties including highly flexible structure, large surface area, high electrical and thermal conductivity and high chemical stability; also, in graphene, electrons have a linear relation between energy and momentum, so its band structure has no energy gap [3]. With these properties, graphene is an attractive material in applications that require a fast electron transfer, such as photocatalysis; it has been reported that graphene based semiconductor nanocomposites are considered as good photocatalyst for pollutant degradation [4]. Graphene is an ideal nanomaterial for doping TiO2 because the formation of Ti-O-C bonds extend the visible light absorption of TiO2. Moreover, electrons are easily transported from TiO2 to the graphene nano-sheets and the electron-hole recombination is significantly reduced; this is enhances the oxidative reactivity [5]. In this work, it was used an aqueous solution of a non-ionic surfactant, that acted like dispersing agent and as stabilizer to prevent layer stacking, for the direct exfoliation of graphite by sonication. The obtained graphene dispersion is characterized by X-Ray Diffraction (XRD), Dynamic Light Scattering (DLS) and UV-Visible spectroscopy, and it is used for the preparation of heterogeneous GR@TiO2 photocatalyst supported on polypropylene (PP). GR@TiO2 nanocomposites are used to treat water with environmental pollutants by photocatalytic.