Graphene-spindle shaped TiO₂ mesocrystal composites: facile synthesis and enhanced visible light photocatalytic performance.

Graphene (GR)-TiO2 mesocrystal composites were prepared by a facile template-free process based on the combination of sol-gel and solvothermal methods, and were characterized using field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Raman spectroscopy, UV-vis diffuse reflectance spectroscopy (UV-vis DRS), nitrogen absorption and electron spin resonance (ESR). Visible light photocatalytic performance of GR-TiO2 composites was evaluated for photocatalytic degradation of organic dye Rhodamine B. It was found that the amount of graphene oxide (GO) added obviously affects morphologies of TiO2 mesocrystals and photocatalytic activities of as-prepared nanocomposites. Composites prepared in the presence of different amounts of GO all exhibit higher photocatalytic activity than pure TiO2 mesocrystals and P25, the composite obtained by using 20mg GO presents the most uniform TiO2 mesocrystals in the composite and shows the highest photocatalytic efficiency. The mechanism for the generation of TiO2 mesocrystals in the GR-TiO2 composite is proposed and possible reasons for the enhancement in visible light photocatalytic efficiency are also discussed.