Continuous supercritical solvothermal synthesis of TiO2–pristine-graphene hybrid as the enhanced photocatalyst

A continuous supercritical solvothermal technique was developed for synthesizing TiO 2 –graphene hybrids, with the pristine graphene sheets used as the crystallization sites and the TiO 2 nanoparticles crystallized on the graphene, forming the hybrids simultaneously. The structure and morphology of the fabricated hybrids were characterized via X-ray diffraction, transmission electron microscopy and high resolution transmission electron microscopy. The uniform hybrids were obtained at different concentrations of graphene while the temperature, pressure and resident time were fixed at 350   °C, 23   MPa, and 30   s, respectively. The TiO 2 particles formed on the hybrids were approximately 5–10   nm in size and dispersed uniformly. Compared with the pure TiO 2 and the commercial P25, the photocatalytic efficiency of the hybrids was greatly enhanced. The hybrid enabled methyl orange dye to degrade almost completely in 180   min, while only 78% and 82% of the methyl orange dye was degraded separately by the pure TiO 2 and P25. This enhanced photocatalytic performance of the hybrids is attributed to the well distributed-TiO 2 and the rapid transfer of the photo-generated electrons from the surface of the catalyst to the graphene, thereby preventing a photo-generated electron–hole recombination.