Nickel–cobalt oxide/activated carbon composite electrodes for electrochemical capacitors

Nanostructured synthesis of nickel–cobalt oxide/activated carbon composite by adapting a co-precipitation protocol was revealed by transmission electron microscopy. X-ray diffraction analysis confirmed that nickel–cobalt oxide spinel phase was maintained in the pure and composite phases. Cyclic voltammetry, galvanostatic charge–discharge tests and ac impedance spectroscopy were employed to elucidate the electrochemical properties of the composite electrodes in 1.0 M KCl. The specific capacitance which was the sum of double-layer capacitance of the activated carbon and pseudocapacitance of the metal oxide increased with the composition of nickel–cobalt oxide before showing a decrement for heavily-loaded electrodes. Utilisation of nickel–cobalt oxide component in the composite with 50 wt. % loading displayed a capacitance value of ∼59 F g−1. The prepared composite electrodes exhibited good electrochemical stability.

► Novel synthesis of NiCo2O4/activated carbon (AC) composite by co-precipitation. ► NiCo2O4/AC is reported for the first time as electrode for supercapacitors. ► Subsolidus phase formed between NiCo2O4 and activated carbon. ► NiCo2O4 composite displayed a high capacitance value of ∼59 F g−1. ► Homogeneous blending of NiCo2O4 and AC ensures stability in cycle testing.