Hydrothermal Synthesis and Visible-light Photocatalytic Activity of Novel Cage-like Ferric Oxide Hollow Spheres

Fe2O3 hollow spheres with novel cage-like architectures and porous crystalline shells were successfully fabricated by a controlled hydrothermal precipitation reaction using urea as a precipitating agent and carbonaceous polysaccharide spheres as templates in a mixed solvent of water and ethanol, and then calcined at 500 °C for 4 h. The as-prepared samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption−desorption isotherms, and UV−visible diffuse reflectance spectroscopy. The visible-light photocatalytic activity of the as-prepared samples was evaluated by photocatalytic decolorization of rhodamine B aqueous solution at ambient temperature under visible-light illumination in the presence of H2O2. The results indicated that the diameter, shell thickness, average crystallite size, specific surface areas, pore structures, and photocatalytic activity of Fe2O3 hollow spheres could be easily controlled by changing the concentration of FeCl3 and size of carbon spheres, respectively. With increasing FeCl3 concentration, the average crystallite size, shell thickness, and pore size increase. In contrast, specific surface areas and photocatalytic activity decrease. Further results show that other experimental conditions such as hydrothermal time and solvent composition also obviously influence the formation and morphology of hollow spheres. The samples can be more readily separated from the slurry system by filtration or sedimentation after photocatalytic reaction and reused compared to conventional nanosized powder photocatalysts. The prepared Fe2O3 hollow spheres are also of great interest in sensor, lithium secondary batteries, solar cell, catalysis, separation technology, biomedical engineering, and nanotechnology.