Effects of various TiO₂ nanostructures and graphene oxide on photocatalytic activity of TiO₂

The nanostructures of TiO₂ significantly affect its photocatalytic activity. In this work, various TiO₂ nanostructures have been successfully synthesized, including one-dimensional (1D) TiO₂ nanotube, 1D TiO₂ nanowire, three-dimensional (3D) TiO₂ sphere assembled by nanoparticles (TiO₂ sphere-P) and 3D TiO₂ sphere assembled by nanosheets (TiO₂ sphere-S). The results of photodegradation activity towards acid orange 7 (AO7) indicate that the photodegradation efficiency of TiO₂ sphere-S is the highest among the investigated TiO₂ nanostructures, even though the specific surface area of TiO₂ sphere-S is lower than that of TiO₂ nanotube. The best photodegradation activity of TiO₂ sphere-S can be attributed to the highest light harvesting capacity resulted from multiple reflections of light, and hierarchical mesoporous structure. In addition, the combination of TiO₂ sphere-S with graphene oxide (GO) sheets can further enhance the photodegradation efficiency of AO7 and disinfection activity of Escherichia coli (E. coli) under solar light, which is more energy efficient. The promising photocatalytic activity of GO-TiO₂ composites is originated from the enhanced light absorption and efficient charge separation. Hence, this study paves a way for improving the performance of other photocatalysts.