Synthesis of ZnFe2O4 nanoparticles and their asymmetric configuration with Ni(OH)2 for a pseudocapacitor

Nanosized zinc ferrite (ZnFe2O4) particles are prepared by a simple aspartic acid assisted combustion method at three different pH conditions. X-ray diffraction analysis (XRD) is used to identify the single phase formation of ZnFe2O4 and its crystal system. The particle size and shape are revealed through transmission electron microscopy (TEM) images and the particles are in the size range between 20–30 nm. The valence states of zinc, iron and oxygen are determined through X-ray photoelectron spectroscopy (XPS). The electrochemical performances of the individual electrodes and fabricated cells are studied using cyclic voltammetry (CV), galvanostatic charge–discharge analysis (GCD) and impedance spectroscopy (EIS) analysis. A maximum specific capacitance of 1235 F g−1 at 1 mA cm−2 is obtained for ZnFe2O4 prepared at pH 10. Furthermore an asymmetric supercapacitor (ASC) is fabricated using ZnFe2O4 as the negative electrode and Ni(OH)2 as the positive electrode. Interestingly, this assembled ASC delivers good energy and power densities of 33 W h kg−1 and 68 W kg−1, respectively.