Potentiostatically deposited nanostructured CoxNi1−x layered double hydroxides as electrode materials for redox-supercapacitors

Cobalt–nickel layered double hydroxides (CoxNi1−x LDHs) were deposited onto stainless steel electrodes by the potentiostatic deposition method at −1.0 V vs. Ag/AgCl using various molar ratios of Co(NO3)2 and Ni(NO3)2 in distilled water. Their structure and surface morphology were studied by using X-ray diffraction analysis, energy dispersive X-ray spectroscopy and scanning electron microscopy. A network of CoxNi1−x LDH nanosheets was obtained. The nature of the cyclic voltammetry and charge–discharge curves suggested that the CoxNi1−x LDHs exist in the form of solid solutions. The capacitive characteristics of the CoxNi1−x LDHs in 1 M KOH electrolyte showed that Co0.72Ni0.28 LDHs had the highest specific capacitance value, 2104 F g−1, which is also the highest yet reported value for oxide materials in general.