Production and Characterization of Electroactive Nickel Oxides Grown on Nickel Foam by Anodic Oxidation in KOH Melts for Supercapacitor Applications

The role of experimental parameters on direct oxidation of nickel foams with anodic oxidation (anodization) in molten KOH and their contribution to capacitance properties are investigated. Temperature of the melt exhibited an important role on the nature of compounds formed by anodic oxidation. On the samples anodized at 280 and 300 °C stoichiometric NiO is formed. Samples anodized in the temperature range of 150–200 °C gave very high maximum currents in CV measurements indicating the formation of electroactive nickel compounds on them. The nature of these compounds is determined as alpha nickel oxy-hydroxide (a-Ni(OH)2) by micro Raman, XRD and FT-IR measurements. Other property that determines the capacity of these electrodes is the morphology of the electroactive layer, which is controlled mainly by the duration of the treatment. 30 minutes of anodic oxidation time is determined as the optimum value. Areal capacity of the samples anodically oxidized at 200 °C for 30 min using 0.8 V cell voltage are determined as 2.73 F.cm-2 and 1.58 F.cm-2 for 1 mA.cm-2 and 20 mA.cm-2 discharge current densities respectively.