Graphene facilitated visible light photodegradation of methylene blue over titanium dioxide photocatalysts

Several graphene–titania composites (G–TiO2) were synthesized by a sol–gel method using titanium isopropoxide (or P25) as Ti-precursors and reduced graphene oxide (RGO). The structural, morphological, and physicochemical properties of the samples were thoroughly investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), UV–vis diffuse reflectance (UV–vis DRS), and thermogravimetric-differential thermal analysis (TG-DTA). A significant increase in light absorption to visible light was observed by G–TiO2 compared with that of naked TiO2. The photocatalytic activity of G–TiO2 in methylene blue bleaching under visible light (>430 nm) is much enhanced. G–TiO2 synthesized from titanium isopropoxide hydrolysis presented higher activity than that of G–TiO2(P25). Contribution of graphene on the enhancement of visible-light photocatalytic activity of the composite was discussed.

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► Graphene–titania composites (G–TiO2) were synthesized by a sol–gel method.
► G–TiO2 catalysts showed high efficiency in degradation of methylene blue under visible light.
► In situ prepared G–TiO2 presented higher activity than that of G–TiO2(P25).
► The mechanism of graphene in the enhanced visible light photocatalytic activity was proposed.