Electrochemical Pressure Impedance Spectroscopy (EPIS) as Diagnostic Method for Electrochemical Cells with Gaseous Reactants: A Model-Based Analysis. Issue 5 (15th January 2016)

• Record Type: Journal Article
• Authors: Grübl, Daniel; Janek, Jürgen; Bessler, Wolfgang G.
• Is Part Of: Journal of the Electrochemical Society. Volume 163:Issue 5(2016)
• Page Start: A599
• Page End: A610
• Publication Date: 2016-01-15
• Subjects: Electrochemical impedance spectroscopy (EIS) -- Electrochemical pressure impedance spectroscopy (EPIS) -- Fuel cell -- Gaseous reactants -- Metal-air battery -- Metal-oxygen battery -- Modeling and simulation -- Pressure diagnostics; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/2.1041603jes
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : Electrochemical impedance spectroscopy (EIS) is a widely-used diagnostic technique to characterize electrochemical processes. It is based on the dynamic analysis of two electrical observables, that is, current and voltage. Electrochemical cells with gaseous reactants or products (e.g., fuel cells, metal/air cells, electrolyzers) offer an additional observable, that is, the gas pressure. The dynamic coupling of current and/or voltage with gas pressure gives rise to a number of additional impedance definitions, for which we use the term electrochemical pressure impedance. It also gives rise to different experimental probing approaches. In this article we present a model-based study of electrochemical pressure impedance spectroscopy (EPIS). Possible quantifications and realizations of EPIS are discussed. The study of generic cell geometries consisting of gas reservoir, diffusion layer(s) and electrochemically active layer(s) reveals distinct spiral-shaped features in the Nyquist plot. Using the example of a sodium/oxygen (Na/O2 ) cell, the dynamic spatiotemporal behavior of the state variables is quantified and interpreted. Results are compared to first experimental EPIS measurements by Hartmann et al. [J. Phys. Chem. C118, 1461, 2014]. A sensitivity analysis highlights the properties of EPIS with respect to geometric, transport, and kinetic parameters. We demonstrate that EPIS is sensitive to transport parameters that are not well-accessible with standard EIS.