u2212 50 v bias potential was provided to the substrate the remaining steps were like the steps of sample 1 and the obtained electrode was indicated as sample 10 sample 11 the substrate was heated to 200 u00b0 c and u2212 100 v bias potential was provided to the substrate the remaining steps were like the steps of sample 1 and the obtained electrode was indicated as sample 11 the three electrode cell consisted of the ag agcl electrode served as the reference electrode pt as the counter electrode and electrodes prepared in sample 1 to sample 8 respectively as the working electrodes the cyclic voltammetric measurement was performed by an electrochemical analyzer ch instruments chi 608b usa the electrolytes were placed in a solution and degassed with purified nitrogen gas before voltammetric measurements the solution temperature was maintained at 25 u00b0 c by means of a circulating water thermostat haake dc3 and k20 germany the cyclic voltammetry cv was taken in a 0 5 m aqueous electrolyte licl ph 6 7 at a scan rate of 100 mv s u2212 1 the potential window in the range of 0 to 1 v was used in all measurements unless otherwise specified capacitance was normalized as 1 g of manganese cobalt zinc oxide impedance measurement was operated at 5 mv ac amplitude with a frequency.