Modeling Electrokinetics of Oxygen Electrodes in Solid Oxide Electrolyzer Cells

Korey Cook, Jacob Wrubel, Zhiwen Ma, Kevin Huang, Xinfang Jin

Research output: Contribution to journalArticlepeer-review

9 Scopus Citations

Abstract

A microscale model is presented in this study to simulate electrode kinetics of the oxygen electrode in a solid oxide electrolyzer cell (SOEC). Two mixed ionic/electronic conducting structures are examined for the oxygen producing electrode in this work: single layer porous lanthanum strontium cobalt ferrite (LSCF), and bilayer LSCF/SCT (strontium cobalt tantalum oxide) structures. A yttrium-stabilized zirconia (YSZ) electrolyte separates the hydrogen and oxygen electrodes, as well as a gadolinium doped-ceria (GDC) buffer layer on the oxygen electrode side. Electrochemical reactions occurring at the two-phase boundaries (2PBs) and three-phase boundaries (3PBs) of single-layer LSCF and bilayer LSCF/SCT oxygen electrodes are modeled under various SOEC voltages with lattice oxygen stoichiometry as the key output. The results reveal that there exists a competition in electrode kinetics between 2PBs and 3PBs, but 3PBs are the primary reactive sites for single-layer LSCF oxygen electrode under high voltages. These locations experience the greatest oxygen stoichiometry variations and are therefore the most likely locations for dimensional changes. By applying an active SCT layer over LSCF, the 2PBs become activated to compete with the 3PBs, thus alleviating oxygen stoichiometry variations and reducing the likelihood of dimensional change. This strategy could reduce lattice structural expansion, proving to be valuable for electrode-electrolyte delamination prevention and will be the focus of future work.

Original languageAmerican English
Article number114510
Number of pages13
JournalJournal of the Electrochemical Society
Volume168
Issue number11
DOIs
StatePublished - 2021

Bibliographical note

Publisher Copyright:
© 2021 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited.

NREL Publication Number

  • NREL/JA-5700-81828

Keywords

  • bi-layer
  • conducting structure
  • dimensional changes
  • electro-kinetics
  • electrode kinetics
  • lanthanum strontium cobalt ferrite
  • micro scale models
  • oxygen electrode
  • oxygen stoichiometry
  • single layer

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