Study of supercapacitor applications of supported and unsupported cobalt ferrite and Zn-doped cobalt ferrite nanocomposites

In this study, novel nanocomposites of CoFe₂O₄, CoFe₂O₄/MWCNTs, Co_0.5Zn_0.5Fe₂O₄, and Co_0.5Zn_0.5Fe₂O₄/MWCNTs were synthesized using the sol–gel and one-pot wet-impregnation method and further applied in the form of electrode material for their supercapacitor applications. The structural and optical properties of the as-synthesized electrode materials were investigated via X-ray diffraction, Fourier transform infrared, and Diffuse reflectance spectroscopic techniques. These materials exhibited crystallinity evident from X-ray diffraction analysis. No additional peak was envisioned upon addition of Zn to the crystal structure of CoFe₂O₄, which confirmed doping of Zn into CoFe₂O₄. Morphological analysis inferred the incorporation of synthesized ferrites into MWCNTs. The scanning electron micrographs further demonstrated a highly porous framework that provided enhanced ion transportability as well as high surface area for substantial charge storage. The electrochemical performance was evaluated using cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy for supercapacitors applications. All of these synthesized materials demonstrated good electrochemical potential, but MWCNTs-supported ferrite nanocomposites attained higher specific capacitance (CV; 175 F g⁻¹ & 590 F g⁻¹, 418 F g⁻¹ & 1123 F g⁻¹ at 15 mV s⁻¹, GCD; 19 F g⁻¹ & 217 F g⁻¹, 95 F g⁻¹ & 832 F g⁻¹ at current density of 0.1 A g⁻¹) for CoFe₂O₄, CoFe₂O₄/MWCNTs, and Co_0.5Zn_0.5Fe₂O₄, Co_0.5Zn_0.5Fe₂O₄/MWCNTs with capacitance retention of 92% and 95% after 2000 stability cycles, respectively. This inferred that CoFe₂O₄/MWCNTs and Co_0.5Zn_0.5Fe₂O₄/MWCNTs have the potential to be used for capacitive storage as well as in optical electronics due to their structural and good electrochemical properties.