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 similar to 59 F g(-1). The prepared composite electrodes exhibited good electrochemical stability. (C) 2012 Elsevier B.V. All rights reserved.