Some interesting peculiarities in the high frequency part of the impedancediagram obtained in the case of iron dissolution in dilute H2SO4 solution

The iron dissolution was investigated by electrode impedance spectroscopy i n 5-100 mM deaerated sulphuric acid. It was found that in contrast to highe r concentrations, in dilute electrolytes the double layer capacity calculat ed from the high frequency part of the impedance diagrams is frequency depe ndent. We evaluated the impedance diagrams and determined the impedance res ponsible for the frequency dispersion at high frequencies. An empirical exp ression was found that describes this impedance. We attribute the frequency dependence of the double layer capacity to the presence of the diffuse lay er formed in dilute electrolytes. (C) 1999 Elsevier Science Ltd. All rights reserved.