Two-phase hydrothermal synthesis of TiO2–graphene hybridswith improved photocatalytic activity

TiO2–graphene hybrids (TGHs) were one-pot synthesized by a simple two-phase hydrothermal method,without the synthesis of TiO2 in advance. The structures, morphologies, and photocatalytic properties ofsamples for methyl orange were characterized by X-ray diffraction, Fourier transform infrared spectroscopy,thermogravimetry and differential scanning calorimetry, transmission electron microscopy, Ramanspectrum, X-ray photoelectron spectroscopy, diffuse reflectance absorption spectrum, specific surfacearea, and photoluminescence. Experimental results show that the synthesis of TiO2, reduction of grapheneoxide, and combination of them were realized simultaneously. The as-synthesized TGHs showedimproved photodegradation performances compared to neat TiO2, commercial P25, and TGH synthesizedby a single-phase (water) method. The improved photodegradation performances of TGHs are attributedto the suppressed recombination of electrons and holes caused by the effective transfer of photo-generatedelectrons from TiO2 to graphene. Moreover, the phase transfer of sample between the water and thechloroform in the two-phase system plays a crucial role in the enhancement of photocatalytic performancesof TGHs, because through the phase transfer the aggregation of TGHs can be effectively hindered,leading to higher specific surface area, excellent adsorption capacity, and improved photocatalyticproperties.