The Apparent Constant-Phase-Element Behavior of an Ideally Polarized Blocking Electrode

Abstract

Two numerical methods were used to calculate the influence of geometry-induced current and potential distributions on the impedance response of an ideally polarized disk electrode. A coherent notation is proposed for local and global impedance which accounts for global, local, local interfacial, and both global and local ohmic impedances. The local and ohmic impedances are shown to provide insight into the frequency dispersion associated with the geometry of disk electrodes. The high-frequency global impedance response has the appearance of a constant-phase element ͑CPE͒ but can be considered to be only an apparent CPE because the CPE exponent ␣ is a function of frequency.

Development of quantitative Local Electrochemical Impedance Mapping: an efficient tool for the evaluation of delamination kinetics

“…The size of admittance maps is influenced by the AC frequency because the potential distribution depends on this parameter in the case of nonuniform potential distribution induced by the cell geometry. This phenomenon was first predicted theoretically by Newman [19] for a disk electrode embedded in an isolating plane, then expanded and explained in details for other systems in more recent works [20][21][22][23][24][25].…”

“…The mathematical foundation for the simulation of the potential and current distributions was adapted from the works by Newman [19,26] originally developed for a planar disk electrode embedded in a coplanar insulator and successfully applied to other cell geometries in order to investigate the edge effect of the electrode on the impedance response [21,24,25]. This treatment accounts for both the potential drop due to the ohmic resistance of the media and the electrode polarization.…”

“…A typical illustration of the z variation as a function of f was given by Huang et al [21] for the example of a blocking electrode. The local impedance was shown to depend not only on f but also on r 0 , C and σ s allowing a dimensionless frequency K to be defined as [19,21] …”

Influence of hydrogen-oxidizing bacteria on the corrosion of low carbon steel: Local electrochemical investigations

“…Similarly to the SECM, LEIS consisted in using a micro probe for measuring the local current density [21,[37][38][39]. The two devices require some similar apparatus, in particular for positioning the probe in the vicinity of the substrate.…”

“…The local impedance (z) involves the electrode potential measured with respect to a reference electrode located far from the electrode surface and the local current according to [38][39][40]:…”