Use of a distribution function of relaxation times (DFRT) in impedance analysis of SOFC electrodes

Bernard A. Boukamp (Corresponding Author), Aurélie Rolle

Research output: Contribution to journalArticleAcademicpeer-review

18 Citations (Scopus)
1 Downloads (Pure)

Abstract

Electrochemical Impedance Spectroscopy (EIS) is a frequently used method to characterize electrodes for Solid Oxide Fuel Cells (SOFC) or Electrolyzer Cells (SOEC). The porous microstructures, use of composite structures and sometimes extra functional layers in an electrode, result often in impedance spectra that are difficult to analyze. Transformation of the impedance into a distribution function of relaxation times (DFRT) is about to become a new standard in EIS analysis. This inversion to the τ-domain requires solving a Fredholm integral of the second kind, which is known as an ‘ill-posed inverse problem’. Hence the resulting DFRT's should not be trusted directly. In cases were impedance data can be modelled satisfactory with an Equivalent Circuit (EqC), built of known dispersion relations (e.g. (RQ), Gerischer, Finite Length Warburg) an analytic distribution function, G(τ), can be constructed. This can be compared with the inversion results obtained from Fourier Transform (FT), Tikhonov Regularization (TR) and multi-(RQ) CNLS fits (m(RQ)fit), thus allowing evaluation and validation of these methods This is illustrated in this contribution with four examples of SOFC cathodes with quite different properties. The results apply equally well to SOFC anodes (or SOEC cathodes).

Original languageEnglish
Pages (from-to)103-111
Number of pages9
JournalSolid state ionics
Volume314
Early online date7 Dec 2017
DOIs
Publication statusPublished - 1 Jan 2018

Fingerprint

solid oxide fuel cells
Solid oxide fuel cells (SOFC)
Relaxation time
Distribution functions
relaxation time
distribution functions
impedance
Electrodes
electrodes
cell cathodes
Electrochemical impedance spectroscopy
Cathodes
inversions
cell anodes
Composite structures
Inverse problems
analytic functions
Equivalent circuits
composite structures
Fourier transforms

Keywords

  • Electrochemical Impedance Spectroscopy (EIS)
  • Electrodes
  • Finite Length Warburg (FLW)
  • Gerischer dispersion
  • Distribution function of relaxation times (DFRT)

Cite this

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title = "Use of a distribution function of relaxation times (DFRT) in impedance analysis of SOFC electrodes",
abstract = "Electrochemical Impedance Spectroscopy (EIS) is a frequently used method to characterize electrodes for Solid Oxide Fuel Cells (SOFC) or Electrolyzer Cells (SOEC). The porous microstructures, use of composite structures and sometimes extra functional layers in an electrode, result often in impedance spectra that are difficult to analyze. Transformation of the impedance into a distribution function of relaxation times (DFRT) is about to become a new standard in EIS analysis. This inversion to the τ-domain requires solving a Fredholm integral of the second kind, which is known as an ‘ill-posed inverse problem’. Hence the resulting DFRT's should not be trusted directly. In cases were impedance data can be modelled satisfactory with an Equivalent Circuit (EqC), built of known dispersion relations (e.g. (RQ), Gerischer, Finite Length Warburg) an analytic distribution function, G(τ), can be constructed. This can be compared with the inversion results obtained from Fourier Transform (FT), Tikhonov Regularization (TR) and multi-(RQ) CNLS fits (m(RQ)fit), thus allowing evaluation and validation of these methods This is illustrated in this contribution with four examples of SOFC cathodes with quite different properties. The results apply equally well to SOFC anodes (or SOEC cathodes).",
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Use of a distribution function of relaxation times (DFRT) in impedance analysis of SOFC electrodes. / Boukamp, Bernard A. (Corresponding Author); Rolle, Aurélie.

In: Solid state ionics, Vol. 314, 01.01.2018, p. 103-111.

Research output: Contribution to journalArticleAcademicpeer-review

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