DETERMINATION OF THE ELECTROACTIVE AREA OF GRAPHITE PLUS POLYETHYLENECOMPOSITE ELECTRODES - UNCOMPENSATED RESISTANCE EFFECTS AND CONVOLUTION ANALYSIS OF CHRONOAMPEROGRAMS

In this work, it is shown how the convolution analysis of chronoampero grams permits the observation of the uncompensated resistance and the natural convection effects on the electrochemical response of potassiu m ferrocyanide. The uncompensated resistance causes the current intens ity to follow the Cottrell equation only after a certain critical time . The convolution of chronoamperograms worked out at different integra tion times shows a maximum when this time is long enough. The classica l diffusion equations cannot explain this phenomenon themselves. The d evelopment of this maximum associated with the natural convection is d iscussed. If both these factors, the ohmic drop and the natural convec tion, together with the roughness factor, are considered, the electroa ctive surface for the composite can be obtained. Theoretical expressio ns have been derived for reversible and quasi-reversible systems to su pport the discussion of the experimental results. (C) 1998 Elsevier Sc ience S.A.