Controlled Synthesis of Hollow α-FeO Microspheres Assembled With Ionic Liquid for Enhanced Visible-Light Photocatalytic Activity.

Porous self-assembled α-FeO hollow microspheres were fabricated via an ionic liquid-assisted solvothermal reaction and sequential calcinations. The concentration of the ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate [CMim]BF) was found to play a crucial role in the control of these α-FeO hollow structures. Trace amounts ionic liquid was used as the soft template to synthesize α-FeO hollow spheres with a large specific surface (up to 220 m/g). Based on time-dependent experiments, the proposed formation mechanisms were presented. Under UV light irradiation, the as-synthesized α-FeO hollow spheres exhibited excellent photocatalysis in Rhodamine B (RhB) photodegradation and the rate constant was 2-3 times higher than α-FeO particles. The magnetic properties of α-FeO hollow structures were found to be closely associated with the shape anisotropy.