Effect of graphene thickness on photocatalytic activity of TiO2-graphene nanocomposites

Reduced graphene oxide sheets (RGO) with different number of graphene layers were used as platforms for TiO2 nanoparticles deposited using hydrothermal process. The nanomaterials were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, Fourier trans form infrared spectroscopy (FTIR), photoluminescence spectroscopy (PL) and diffuse reflectance UV-vis spectroscopy (DR-UV-vis). The photocatalytic activity of the nanocomposites was investigated in a model reaction of phenol decomposition under visible light irradiation. Here, the influence of graphene thickness on its photoactivity was explored. It was found that the highest photocatalytic activity was observed for the catalyst composed of single layer graphene and decreased when a number of graphene layers was higher. This might be related to the surface and electronic properties of reduced graphene oxide arising from different number of graphene layers and its interaction with titanium dioxide: (i) higher interfacial area of TiO2-RGO with lower thickness of RGO, which could influence in enhanced transferring of photoinduced electron-hole pairs between TiO2 and RGO, hence improving their separation; (ii) variations in excitations lifetime relating to the diverse surface quality and density of trap sites of reduced graphene oxide; (iii) higher charge carriers mobility in 1-layer RGO compared to 2- and few-layers. (C) 2015 Elsevier B.V. All rights reserved.