Micro/nanostructured α-Fe ₂O ₃ spheres: Synthesis, characterization, and structurally enhanced visible-light photocatalytic activity

Micro/nanostructured α-Fe ₂O ₃ spheres (MNFSs) were fabricated via a surfactant- and template-free method, involving the hydrothermal synthesis of FeCO ₃ precursor firstly and a subsequent thermal decomposition treatment. The product was characterized by X-ray diffraction, field emission scanning electron microscopy and transmission electron microscopy. The MNFSs had an average diameter of about 5 μm, and each contained subunits of interlinked and elongated particles with size less than 30 nm. The UV-Vis spectrum of MNFSs exhibited visible-light absorption. The visible-light photocatalytic activity of MNFSs was evaluated by using them to degrade the rhodamine 6G pollutant in water at ambient temperature under different parameters such as pH value, the amount of MNFSs and H ₂O ₂. We also found that the visible-light photocatalytic activity of MNFSs was higher than that of the micron- and nano-sized α-Fe ₂O ₃ particles. The reaction rate of MNFSs was more than twice that of nano-sized α-Fe ₂O ₃ and nearly 12 times faster than that of the micron-sized α-Fe ₂O ₃. This high photocatalytic feature of MNFSs was attributed to the high specific surface area together with their special porous structure. Importantly, these characteristics could control the rate of releasing ·OH and thus improve the utilization efficiency of ·OH. MNFSs can be easily recycled from the treated water using a magnet due to its magnetic behavior. There was no obvious decrease of the photocatalytic activity of MNFSs after being used.