Effects of Hydrothermal Crystallization on the Morphologies and Photocatalytic Activity of TiO<sub>2</sub> Nanotubes

Abstract

Anatase titania (TiO2) films with highly photocatalytic activity were prepared by hydrothermal treatment of amorphous TiO2 nanotubes (NTs) via electrochemical anodization of titanium (Ti) in fluorine-containing electrolyte. The as-prepared TiO2 films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). The photocatalytic activity of the as-prepared TiO2 films was evaluated by the photocatalytic degradation of methyl orange (MO) aqueous under UV-light irradiation. The effects of hydrothermal temperature and time on the morphologies, microstructure and photocatalytic activity of TiO2 films were investigated and discussed. It was found that TiO2 NTs were converted to nanoparticles after hydrothermal treatment. The mechanism of deformation of TiO2 NTs was discussed. Hydrothermal treatment enhances the phase transformation of TiO2 films from amorphous to anatase and crystallization of anatase. An optimal hydrothermal condition (150 oC for 8 h) was determined. The anatase TiO2 films prepared under optimal hydrothermal conditions posses larger surface area and higher relative anatase crystallinity and its photocatalytic activity is higher than that of anatase TiO2 films prepared under other hydrothermal conditions.