Pseudocapacitive Effects of Multi-Walled Carbon Nanotubes-Functionalised Spinel Copper Manganese Oxide.

Spinel copper manganese oxide nanoparticles combined with acid-treated multi-walled carbon nanotubes (CuMn 2 O 4 /MWCNTs) were used in the development of electrodes for pseudocapacitor applications. The CuMn 2 O 4 /MWCNTs preparation involved initial synthesis of Mn 3 O 4 and CuMn 2 O 4 precursors followed by an energy efficient reflux growth method for the CuMn 2 O 4 /MWCNTs. The CuMn 2 O 4 /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 CuMn 2 O 4 /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.