Microwave synthesis, characterization, and electrochemical properties of α-Fe2O3 nanoparticles

Ultrafine α-Fe2O3 nanoparticles with an extremely narrow distribution were synthesized by microwave heating. Transmission electron microscopy (TEM) images showed that most primary particles have ellipsoid shapes, and the average diameter of the primary particles was less than 10 nm. The electron diffraction pattern and fringes in some particles in TEM images showed that these nanoparticles were single crystals. The BET surface area of the freeze-dried product was 217 m2/g. The initial discharge capacity of the α-Fe2O3 nanoparticles exceeded 1007 mA/g (cut-off voltage: 0.5 V). This large capacity corresponds to that calculated by assuming the reduction of Fe3+ to Fe0. The α-Fe2O3 nanoparticles also work as a rechargeable electrode material. The charge–discharge test between 4 V and 1.5 V gave a good rechargeable capacity of about 150 mAh/g.