Controllable hydrothermal synthesis, optical and photocatalytic properties of TiO2 nanostructures

•Different surface morphologies of TiO2 films were prepared by hydrothermal synthesis method.•The surface morphologies are controlled through changing reaction time.•The influences of a shorter hydrothermal reaction time (shorter than 6h) on TiO2 films are investigated.•The surface morphology shows obvious change with increasing reaction time.•The optical properties and photocatalytic properties are influenced by reaction time.•The ratio of Ti:O is 1:2.28 and close to the atom ratio of TiO2. Different surface morphologies of TiO2 thin films were prepared by hydrothermal synthesis method on Ti substrates through changing reaction time. The microstructure, composition, optical properties and photocatalytic properties of TiO2 thin films were systematically investigated by x-ray diffraction, scanning electron microscopy, x-ray photoelectron spectrometer and ultraviolet-visible spectroscopy. As the reaction time increases, anatase structure and brookite structure of TiO2 films respectively increases and decreases, corresponding to surface morphology changes from irregular structure to regular geometrical shape structure. These structural changes are accompanied by significant variations of optical properties and photocatalytic properties including a widening of the band gap from 2.86 to 3.19eV, photocatalytic degradation efficiency from 92.5 to 98.1% and photocatalytic degradation rate from 0.032 to 0.048min−1. Among all samples, TiO2-1 shows the best photocatalytic properties. Compositional analysis indicates that TiO2 surface layer contains Ti and O elements, the ratio of Ti:O is 1:2.28 which is close to the atom ratio of TiO2.