Ultrafine β-FeOOH and Fe3O4obtained by precipitation method: Comparative study of electrical and electrochemical properties

Abstract

In this work, ultrafine powders of β-FeOOH and Fe3O4(specific surface area values are 101 and 135 m2/g, respectively) have been obtained by precipitation method. Frequency dependences of electrical conductivity was analyzed in the temperature range of 20 - 150 °C. It has been found that the both materials show a superlinear behavior of the frequency dependent electrical conductivity. The values of activation energies for direct current conductivity, cross-over frequency for the electrical conductivity described by Jonscher power law and the superlinear law are 0.55, 0.51 and 0.16 eV for β-FeOOH and 0.22, 0.21 and 0.1 eV for Fe3O4, respectively. According to cyclic voltammetry (scan rate in the range of 1-50 mV/s) β-FeOOH material shows a specific capacitance up to 80 F/g, while the one for the Fe3O4material is about 32 F/g. Galvanostatic cycling measurements have been done for discharge currents of 0.05 - 0.25 A/g. The specific energy and power of about 8 W h/kg and 20 W/kg were achieved for the β-FeOOH material when Fe3O4material demonstrate the specific power only up to 3.5 W/kg.