Hydrothermal synthesis of bismuth ferrite with controllable phase structure, morphology and visible light photocatalytic activities

Bismuth ferrites powders have been successfully synthesized via a facile hydrothermal method. Phase structure, morphology and surface area of as-prepared powders are investigated by using X-ray diffraction, field emission scanning electron microscope and Brunauer-Emmett-Teller (BET) method. The effects of the Bi3+/Fe3+ precursor molar ratio and the reaction time on the phase structure evolution of bismuth ferrite are systematically studied. Three types of bismuth ferrite powders, that is, sheet-like Bi2Fe4O9, sheet-like Bi2Fe4O9 hybrid with Bi25FeO40 and BiFeO3, and cuboid-like Bi2Fe4O9 with large exposed (001) surface, are obtained by tailoring the Bi3+/Fe3+ precursor molar ratio from 1.5:1 to 1:2 and the reaction time from 4 to 12 h during hydrothermal process. A reasonable mechanism for phase structure evolution is proposed and discussed on the basis of our results. Furthermore, the optical properties and photocatalytic activities of those samples are also investigated. All these powders have small bandgap energy and the bandgap reduces with the increasing size. The differences in photocatalytic activities by the degradation of Rhodamine B are well explained from phase structure and morphology. Our studies indicate that a facile hydrothermal method can be well made use of to design and synthesize bismuth ferrite powders with controllable phase structure, morphology and photocatalytic behaviors.