Synthesis and electrochemical properties of biporous alpha-Fe2O3 superstructures

Biporous microsphere, flower and concaved cuboctahedrans like alpha-Fe2O3 superstructures have been synthesized by using a new synthetic method. Hydrothermal reaction of ferric chloride with potassium thiocyanate at 200 degrees C yields self-assembled microsphere, flower, and concaved cuboctahedrans like intermediates in ethanol, water:ethanol (1:1) mixed solvent and in water, respectively. These intermediates were further converted into corresponding alpha-Fe2O3 in a thermal decomposition process at 600 degrees C under oxygen atmospheric conditions. The influence of solvent, hydrothermal temperature, and concentration of iron precursors on the intermediate morphology was studied, and the growth mechanism has also been proposed. The synthesized intermediates and alpha-Fe2O3 were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM) and nitrogen adsorption analysis. The FE-SEM results indicated formation of biporous flowerlike morphology. The electrochemical properties of the flowerlike alpha-Fe2O3 electrodes in a Li-ion battery have been investigated. Plausible formation mechanisms of these intermediates were proposed.