Diffusion effects in localized electrochemical impedance measurements by probe methods

An attempt to assess the influence of diffusion on localized impedance meas urements by means of probe method is presented. The influence has been demo nstrated and discussed by experiments and computer simulations. When the pr obe is positioned within the diffusion layer, the measured localized impeda nce spectra could be different from the conventional electrochemical impeda nce measurements due to the heterogeneous concentration distribution. The d eviations can be de density-dependent when the variation of conductivity is the predominant reason of the influence. When the influence of diffusion i s predominately due to the redox potential difference at the probe, the dev iation can be less de-dependent. The influence at low frequency range is mo re serious than at high frequency range. (C) 1999 The Electrochemical Socie ty. S0013-4651(98)10-048-3. All rights reserved.