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

Bismuth titanates, Bi₂Ti₂O₇ (BIT), with well-defined spherical structures were synthesized by a facile hydrothermal process without the use of any surfactant or template. XRD and SEM studies have shown that spheres could be fabricated in high yields by simply manipulating the concentrations of hydroxide ions. In this case, hydroxide ions seem to play a pivotal role in controlling the formation of seeds and growth rates of the BIT particles. On the basis of structural analysis of samples obtained at different concentrations of OH⁻, we also proposed a plausible mechanism to account for the formation of these distinctive morphologies under different conditions. The as-prepared BIT microspheres with good stability exhibited higher photocatalytic activities in the degradation of Rhodamine B (RhB) under visible light irradiation than that in commercial P25 TiO₂. Furthermore, the enhanced photocatalytic performance for RhB degradation was also investigated with assistance of a small amount of H₂O₂.