Spinel copper manganese oxide nanoparticles combined with acid-treated multi-walled carbon nanotubes (CuMn2O4/MWCNTs) were used in the development of electrodes for pseudocapacitor applications. The CuMn2O4/MWCNTs preparation involved initial synthesis of Mn3O4 and CuMn2O4 precursors followed by an energy efficient reflux growth method for the CuMn2O4/MWCNTs. The CuMn2O4/MWCNTs in a three-electrode cell assembly and in 3 M LiOH aqueous electrolyte exhibited a specific capacitance of 1652.91 F g-1 at 0.5 A g-1 current load. Similar investigation in 3 M KOH aqueous electrolyte delivered a specific capacitance of 653.41 F g-1 at 0.5 A g-1 current load. Stability studies showed that after 6000 cycles, the CuMn2O4/MWCNTs electrode exhibited a higher capacitance retention (88%) in LiOH than in KOH (64%). The higher capacitance retention and cycling stability with a Coulombic efficiency of 99.6% observed in the LiOH is an indication of a better charge storage behaviour in this electrolyte than in the KOH electrolyte with a Coulombic efficiency of 97.3%. This superior performance in the LiOH electrolyte than in the KOH electrolyte is attributed to an intercalation/de-intercalation mechanism which occurs more easily in the LiOH electrolyte than in the KOH electrolyte.
Keywords: galvanostatic charge/discharge; nanocomposite electrode; pseudocapacitor; specific capacitance; spinel metal oxide.