Ionic liquid-assisted synthesis of Bi₁₂TiO₂₀ nanostructures and their visible-light photocatalytic performance

Bi₁₂TiO₂₀ nanostructures were prepared in an ionic liquid (1-methyl-3-butyl imidazole bromide, [BMIM]Br)–water solvent mixture through a hydrothermal process. The effect of ionic liquid on the morphology, optical and photocatalytic properties of the products was investigated. By slightly adjusting the amount of [BMIM]Br, Bi₁₂TiO₂₀ nanoparticles, nanorods and raft-like ones with different crystallinities, surface areas and bandgap energies could be obtained. In these three kinds of morphologies, Bi₁₂TiO₂₀ nanorods with average diameter of 20–30 nm and length of 100–270 nm demonstrate the highest photocatalytic performance for its degradation of methylene orange under visible-light irradiation. The results suggest that the presence of ionic liquid in the synthetic system plays a key role in tuning the phase composition, the shape, size and purity of Bi₁₂TiO₂₀ powders, and hence affects their morphology-associated optical adsorption ability and photocatalytic activity.