Local/global admittance of blocking disk electrode. Computation and discussion. 1-Infinite series solution

• Implementation of Newman’s model within Mathematica for solving Laplace’s equation.
• Highly accurate computation of local/global immittance for a blocking disk electrode.
• Explicit formulation of low/high-frequency behaviors of local/global immittance.
• Discussion about the additivity property of interfacial and ohmic impedances.

This article mainly focuses on the local and global admittances of a disk electrode embedded in an infinite insulating plane, in the absence of faradaic reaction, so-called blocking disk electrode. The mathematical formalism involved starts from Newman’s model for the distribution of potential in the electrolytic solution surrounding the electrode, together with non-uniform current distribution on the disk. Computation is performed in this work using symbolic and numerical procedures within a computer algebra system in order to produce highly accurate admittance/impedance data. The local and global admittances of blocking disk electrode are investigated more especially, with regards to high- and low-frequency behaviors. Computed data are compared, first, to the effective values of resistance and capacitance tabulated by Newman, next, to the apparent constant-phase-element behavior of electrode impedance predicted by Huang et al. at high frequencies, and, finally, to the impedance results recently obtained by Tjelta and Sunde. The accuracy of admittance/impedance data is improved in this work, mainly at high frequencies. Finally, interfacial and ohmic contributions to the global impedance of disk electrode are computed and discussed. Additional information about the admittance/impedance of disk electrode is reported in the supplementary material associated with this article.

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