Electrodeposited Mn3O4-NiO-Co3O4 as a composite electrode material for electrochemical capacitor

• Composite electrodes were synthesized by in situ electrodeposition method.
• The highest specific capacitance of composite electrode is 7404 F g−1.
• The power density of composite electrode is 99 kW kg−1 at current density of 20 A g−1.
• The addition of K3Fe(CN)6 in KOH electrolyte has improved the electrochemical performance.

A simple and easy galvanostatic electrodeposition method is used to synthesise a composite electrode consisting of manganese oxide (Mn3O4), nickel oxide (NiO) and cobalt oxide (Co3O4). The influence of Co3O4 on the morphology of fixed Mn3O4-NiO particles is investigated with a field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The nature and elemental of the composite are examined by means of X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX). The electrochemical performances of an Mn3O4-NiO-Co3O4 nanostructure/SS composite electrode are studied by cyclic voltammetry (CV) and galvanostatic charge-discharge (CD) in various electrolytes, i.e. 0.5 M Na2SO4, 0.5 M KOH, 0.5 M Na2SO4/0.04 M K3Fe(CN)6 and 0.5 M KOH/0.04 M K3Fe(CN)6 electrolytes. The composite electrode prepared from 0.15 M Co deposition solution exhibits the optimum specific capacitance of 7404 F g−1 with high energy and power density of 1028 Wh kg−1 and 99 kW kg−1 at 20 A g−1 in mix KOH/0.04 M K3Fe(CN)6 electrolyte, respectively. The results show that the incorporation of K3Fe(CN)6 in KOH electrolyte influences the capacitance of Mn3O4-NiO-Co3O4 composite electrodes.