Convenient Approach to °-Fe2O3 Nanoparticles: Magnetic and Electrochemical Properties

A convenient approach is reported for the synthesis of spherical maghemite (°-Fe2O3) nanoparticles. The process was realized by the controlled oxidation of Fe3O4 precursor, which originated from a facile partialreduction co-precipitation process. The starting material of hydrosulfurous sodium (Na2S2O4), which can allow reaction to proceed without any deoxygenated protection, was proven to be important in the formation of the precursor. A series of techniques, including X-ray diffraction, transmission electron microscopy and a vibrating sample magnetometer were used to characterize the product. The resultant °-Fe2O3 nanoparticles exhibited ferromagnetism at 300 K and the values of saturation magnetization and coercivity were 70 emu/g and 164 Oe, respectively. The electrochemical properties of lithium ions intercalation into °-Fe2O3 nanoparticles were tested in Te°on cells. A specific capacity of 933 mAh/g was delivered at a current density of 0.2 mA/cm2 (voltage range 3.0-0.3 V vs. Li), corresponding to the reaction of 5.7 Li+ per Fe2O3. A possible mechanism of the reaction of lithium with maghemite spinel was discussed.