Reactable ionic liquid-assisted rapid synthesis of BiOI hollow microspheres at room temperature with enhanced photocatalytic activity

Abstract

BiOI hollow microspheres have been rapidly synthesized through a facile reactable ionic liquid 1-butyl-3-methylimidazolium iodine ([Bmim]I)-assisted microemulsion method at room temperature. The formation mechanism of the BiOI hollow microspheres has been investigated. The BiOI hollow microspheres were formed through self-assembly and inside-out Ostwald ripening growth mechanism. During the reactive process, the ionic liquid, which acts as the solvent, reactant and template at the same time, plays a crucial role on the formation of hollow microspheres. In addition, the influencing factors (such as the reactant, the concentration of ionic liquids and the amount of acetic acid) of the formation of BiOI hollow microsphere have also been explored. The photocatalytic ability of the as-prepared photocatalysts was evaluated using rhodamine B (RhB) as a target pollutant. After systematic characterizations, the relationship between the structure of the photocatalyst and the photocatalytic activities were also discussed in detail. It can be assumed that the enhancing photocatalytic activity of BiOI hollow microspheres could be attributed to the improved light harvesting, shortened diffusion pathways, high BET surface area and faster interfacial charge separation. O₂˙⁻ and h⁺ were the main active species for the photocatalytic degradation of RhB. It is hoped that this rapidly synthetic route at room temperature can be extended to the purposive preparation of other hollow microsphere materials.