Photocatalytic activities of heterostructured TiO2-graphene porous microspheres prepared by ultrasonic spray pyrolysis

• USP method is used to prepare TiO2-graphene porous microspheres.
• XPS shows GO sheets in the composites has been reduced to graphene.
• TiO2-graphene microspheres display a red-shifted absorption edge.
• PL spectra indicate graphene can accept the photoexcited electrons from TiO2.
• TiO2-graphene shows higher photocatalytic activity than TiO2 under solar light.

TiO2-graphene porous microspheres were prepared by ultrasonic spray pyrolysis (USP) of aqueous suspension of graphene oxide containing TiO2 nanoparticles (Degussa P25). The composite microspheres were characterized with SEM, XPS, photoluminescence, Raman and UV–Vis absorption spectra. TiO2-graphene porous microspheres displayed higher photocatalytic activity for the degradation of methylene blue solution than pristine TiO2 microspheres under the irradiation of Xe lamp, and the highest activity was obtained at a weight percentage of graphene around 1%. The effect of graphene on photocatalytic activity of porous microsphere was discussed in terms of the enhanced charge separation by TiO2-graphene heterojunction, increased absorption of the visible light, as well as the possible hindrance of mass transportation in microspheres.