Bismuth titanate microspheres: Directed synthesis and their visible light photocatalytic activity

Bismuth titanate, Bi4Ti3O12 (BIT), with a well-defined spherical structure, was synthesized by a facile hydrothermal process without using any surfactant or template. X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) showed that BIT spheres could be fabricated in high yields by simply manipulating the concentrations of hydroxide ions. In this case, hydroxide ions seem to play a key role in controlling the formation of seeds and growth rates of BIT particles. Ultraviolet–visible (UV–vis) absorption spectra demonstrated that the band gap of BIT samples was about 2.79 eV. In addition, based on the structural analysis of samples obtained at different conditions, a possible mechanism for the formation of these distinctive morphologies was proposed. The as-prepared BIT microspheres exhibited higher photocatalytic activities in the degradation of methyl orange (MO) under visible light irradiation than that of N–TiO2. Furthermore, BIT microspheres which prepared at OH− concentration of 3 mol L−1 showed the highest photocatalytic activity.