Influence of Co doping on phase, structure and electrochemical properties of hydrothermally obtained CoxZn1-xFe2O4 (x=0.0-0.4) nanoparticles

In this work, CoxZn1-xFe2O4 (x = 0.0-0.4) nanoparticles (NPs) were successfully synthesized by a hydrothermal method at 200 degrees C for 12 h. X-ray diffraction revealed a pure cubic spinel phase of all samples with space group Fd-3m. Fourier transform infrared spectrometry disclosed the vibrational modes of metal oxides in the spinel structure. Scanning electron microscopy and transmission electron microscopy disclosed a uniform distribution of cuboidal shape NPs with a decreased average NPs size from 22.72 +/- 0.62 to 20.85 +/- 0.47 nm as the Co content increased. X-ray absorption near edge spectroscopy results confirmed the presence of Zn2+, Co2+ and Fe2+/Fe3+ in Co-doped samples. The pore volume, pore size and specific surface area were determined using N-2 gas adsorption/desorption isotherms by the Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) techniques. Electrochemical properties of supercapacitors, having active CoxZn1-xFe2O4 (x = 0.0-0.4) NPs as working electrodes, indicated pseudo-capacitor performance related to the Faradaic redox reaction. Interestingly, the highest specific capacitance (Csc), 855.33 F/g at 1 A/g, with a capacity retention of 90.41% after 1000 GCD cycle testing was achieved in the Co0.3Zn0.7Fe2O4 electrode.