Enhanced photocatalytic performance of Bi4Ti3O12 nanosheets synthesized by a self-catalyzed fast reaction process

Single-crystalline Bi4Ti3O12 nanosheets with the exposed {001} facets have been successfully prepared using a novel self-catalyzed reaction route, which involves a fast reaction of Bi2O3 and TiO2 at 280 degrees C with the critical assistance of tartaric acid. It is believed that the formation of Bi4Ti3O12 nanosheets is driven by the massive heat released during the oxidation of tartaric acid when Bi2O3 and TiO2 are mixed. With this simplified novel process, the synthesis of high quality Bi4Ti3O12 photocatalyst can be accomplished at low temperatures of 280 degrees C in less than 10 min. The as-obtained optimum nanosheet photocatalyst exhibits high visible light photodegradation of methyl orange, indicated by the 3.92 times higher efficiency than that of the Bi4Ti3O12 nanosheets prepared by a widely acknowledged molten salt method. In addition, this Bi4Ti3O12 nanosheet photocatalyst presents high recycling ability and storage stability. The X-ray photoelectron spectrometer and electron paramagnetic resonance analyses reveal that oxygen vacancies are produced on the surface of as-prepared Bi4Ti3O12 nanosheets after the self-catalyzed reaction, which then extend the valence band width and reduce the band gap of the Bi4Ti3O12 photocatalyst. It is therefore concluded that the much enhanced photocatalytic activity of the as prepared catalyst is the synergistic effects of the valence band widening that increases the separation efficiency of the photo-generated carriers and the band gap narrowing that broadens the absorption edge of light.