Electrochemical impedance of electrodiffusion in charged medium under $dc$ bias

TL;DR

This paper provides a theoretical analysis of the electrochemical impedance in charged media under dc bias, revealing a transition in behavior near the diffusion-limiting bias and offering analytical approximations for certain conditions.

Contribution

It introduces a theoretical model for impedance in charged media using the Nernst-Planck equation, extending understanding above the diffusion-limiting bias.

Findings

Impedance behavior transitions around the diffusion-limiting bias.

Analytical approximation for weakly charged media under overlimiting bias.

Extended impedance response analysis beyond the diffusion-limiting bias.

Abstract

An immobile charged species provides a charged medium for transport of charge carriers that is exploited in many applications, such as permselective membranes, doped semiconductors, biological ion channels, as well as porous media and microchannels with surface charges. In this paper, we theoretically study the electrochemical impedance of electrodiffusion in a charged medium by employing the Nernst-Planck equation and the electroneutrality condition with a background charge density. The impedance response is obtained under different dc bias conditions, extending above the diffusion-limiting bias. We find a transition in the impedance behavior around the diffusion-limiting bias, and present an analytical approximation for a weakly charged medium under an overlimiting bias.