Role of various redox additive electrolytes on the electrochemical performances of mixed metal oxide loaded multiwalled carbon nanotube based supercapacitors

Abstract

Electrochemical performances of the Zinc oxide/Nickel oxide loaded multi-walled carbon nanotubes (ZnO/NiO@MWCNT - ZNC) were evaluated under different electrolytes. ZNC nanocomposites (NCs), has been successfully synthesized by a simple one-step hydrothermal method and calcinated at 500 °C. The crystalline phases of ZnO, NiO, and MWCNT, present in the prepared NCs were studied by the X-ray diffraction (XRD) analysis and their structural characteristics were revealed. The calcinated samples were further characterized by Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopic (FT-IR) techniques to evaluate the morphological and functional behaviours, respectively. ZNC NCs modified working electrodes were fabricated using the doctor blade technique and their electrochemical performances were tested using different electrolytes (pure and redox additive added electrolytes), such as 1 M KOH, 1 M KOH + 0.1 M K4[Fe(CN)6], 1 M Na2SO4 and 1 M Na2SO4 + 0.1 M K4[Fe(CN)6]. Among these electrolytes, ZNC NCs modified working electrode possessed the superior electrochemical performance with the specific capacitance value of 1988.8 Fg−1 under 0.1 M K4[Fe(CN)6] added 1 M Na2SO4 aqueous electrolyte and achieved a superior specific capacitance retention of 97.2 % after 2000 GCD cycles. The fabricated asymmetrical type supercapacitors possessed the superior energy and power densities of 43.59 W h kg−1 and 4000 W kg−1, respectively under the freshly prepared redox additives added Na2SO4 aqueous electrolyte.