Identifying Characteristic Frequencies in the Electrochemical Impedance of Ion-Exchange Membrane Systems

Abstract

In this study, the characteristic frequencies of the electrochemical impedance of ion-exchange membrane systems constituted by the membrane and two diffusion boundary layers adjacent to the membrane were investigated. Approximations of the impedance of the Randles equivalent electric circuit in multiple frequency ranges were considered, and the characteristic frequencies of the zeros and poles of orders ½ and 1 were derived. The characteristic geometric frequencies, those associated with the interfacial charge transfer and the diffusive transport processes, as well as those associated with the transitions between processes, were identified by means of analytical expressions.

Understanding the Role of Proton and Hydroxide Transport in Forward‐Bias Bipolar Membrane for Electrochemical Applications

“…We noted that in the high-frequency region (Figure S12, Supporting Information), a small semicircle was observed for all the EIS spectra with AEM, which is attributed to the ion equilibrium between the membrane-electrolyte interface due to the Donnan potential effect. [16] The same semicircle features for CEM in similar frequency regions are less discernable likely to the faster ion equilibrium for H + . The in-plane EIS curves for CEM/AEM with catalysts all showed a smaller R ct than the blank CEM/AEM (Figure 3e,f).…”

Ionic Thermoelectric Generators in Vertical and Planar Topologies Based on Fluorinated Polymer Hybrid Materials with Ionic Liquids

“…Figure 4c shows that the Nyquist plot is composed at high frequencies by a semicircle that describes the charge transfer process and at low frequencies by a straight line representative of the diffusion process. [39] Furthermore, when the temperature increases, the semicircle decreases due to the polymer chain motion and also to the increased mobility of ionic charges. [29] Considering Equation (2), Figure 4d shows the ionic conductivity value for the different samples as a function of temperature.…”