Preparation and characterization of polycrystalline bismuth titanate Bi12TiO20 and its photocatalytic properties under visible light irradiation

A visible-light-responsive polycrystalline Bi12TiO20 photocatalyst was prepared using a simple solid-state reaction between Bi2O3 and TiO2 powders, and its photocatalytic activity under visible light irradiation for the decomposition of methanol was investigated. The wavelength dependence of methanol decomposition proved that it is a photocatalytic reaction and that the photocatalytic activity of the photocatalyst is dominated by its light absorption. A Bi12TiO20 sample prepared with a molar ratio of Bi2O3/TiO2 = 2 exhibited the highest photoactivity among all prepared photocatalysts. After calcination at 600 degrees C, the band gap of the sample estimated from the onset of the absorption edge was about 2.78 eV. The hybridization of Bi 6s with O 2p in Bi12TiO20, which increases the mobility of the photogenerated carriers, may eliminate the recombination center, resulting in the increase of the photocatalytic activity. In addition, the existence of two mixed cubic crystalline Bi12TiO20 phases in this sample also possibly contributes to its high photocatalytic activity.