Influence of Co doping on phase, structure and electrochemical properties of hydrothermally obtained Co(x)Zn(1−x)Fe(2)O(4) (x = 0.0–0.4) nanoparticles

In this work, Co(x)Zn(1−x)Fe(2)O(4) (x = 0.0–0.4) nanoparticles (NPs) were successfully synthesized by a hydrothermal method at 200 °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 Zn(2+), Co(2+) and Fe(2+)/Fe(3+) 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 Co(x)Zn(1−x)Fe(2)O(4) (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 Co(0.3)Zn(0.7)Fe(2)O(4) electrode.