Ternary active site Co3O4/NiO/MnO2 electrode with enhanced capacitive performances

• Co3O4/NiO/MnO2 composite electrode provides ternary electrochemically active sites.
• The composite electrode delivers twice capacitance of Co3O4 or NiO single one.
• The optimal (Co3O4 + NiO)/MnO2 weight ratio is 3:2.

Composite electrodes with ternary active sites Co3O4/NiO/MnO2 are employed to obtain higher capacitance than single component electrode. The dependence of capacitive performances on the composition in composite oxide electrodes is investigated. Binary Co3O4/NiO composite electrodes display better capacitive performances than pure Co3O4 and NiO single ones and the optimal Co3O4/NiO ratio is 2:3. Ternary Co3O4/NiO/MnO2 composites are superior to Co3O4/NiO binary composite electrodes due to another redox reaction different from Co3O4 and NiO by introducing a third active material MnO2 into the electrode. When the (Co3O4 + NiO)/MnO2 ratio is 3:2, the ternary composite electrode delivers the discharge specific capacitance of 549 F g−1 at 0.5 A g−1, almost twice of Co3O4 and NiO single electrodes. Electrochemical impedance spectra show it comes from the decrease of the charge-transfer resistance and the total inner resistance.