Identifiability of the mechanisms governing the reaction kinetics of MIEC electrodes in solid oxide cells
File(s)
Supporting information
Author(s)
Yasin, Liam
Atkinson, Alan
Cooper, Samuel J
Bertei, Antonio
Type
Journal Article
Abstract
The oxygen reduction reaction (ORR) is the main phenomenon occurring in mixed ionic and electronic conductors (MIECs) used as air electrodes in solid oxide cells. Their optimisation requires the identification of the ORR regime, which is typically performed via electrochemical impedance spectroscopy (EIS). In this study we present a physics-based model to simulate the impedance spectra of p-type oxygen-deficient perovskite MIEC materials. The EIS response of four extreme kinetic scenarios, characterised by the rate-determining step (electron-transfer or ion-transfer) and the high/low surface coverage of adsorbed oxygen, is mechanistically interpreted for both dense films and porous electrodes. A strategy for kinetic identification is proposed based on distinctive EIS fingerprints at different oxygen partial pressures (pO2) and cathodic bias. However, distinguishing the kinetic scenarios is not free from ambiguity even in dense films since some scenarios are discriminated only via a quantitative analysis, which may be susceptible to experimental errors in real measurements, and reverse behaviours appear when combining cathodic bias with pO2 variation. More difficulties arise in porous electrodes since bulk oxygen vacancy transport interacts with the ORR response. Application of the proposed strategy using literature data for some common MIEC materials shows the typical challenges of kinetic identification when relying solely on EIS.
Date Issued
2023-12-20
Date Acceptance
2023-10-26
Citation
Electrochimica Acta, 2023, 472
ISSN
0013-4686
Publisher
Elsevier
Journal / Book Title
Electrochimica Acta
Volume
472
Copyright Statement
© 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/bync-nd/4.0/).
Identifier
http://dx.doi.org/10.1016/j.electacta.2023.143418
Publication Status
Published
Article Number
143418
Date Publish Online
2023-10-28