Oxygen transfer processes in (La,Sr)MnO3/Y2O3-stabilized ZrO2 cathodes: An impedance spectroscopy study

Erica Perry Murray*, Tsepin Tsai, Scott A. Barnett

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

350 Scopus citations

Abstract

Impedance spectroscopy was used to study the oxygen reaction kinetics of La0.8Sr0.2MnO3 (LSM)-based electrodes on Y2O3-stabilized ZrO2 (YSZ) electrolytes. Three types of electrodes were studied: pure LSM, LSM-YSZ composites, and LSM/LSM-YSZ bilayers. The electrodes were formed by spin coating and sintering on single-crystal YSZ substrates. Measurements were taken at temperatures ranging from 550 to 850°C and oxygen partial pressures from 1 × 10-3 to 1 atm. An arc whose resistance Re1 had a high activation energy, Ea = 1.61±0.05 eV, and a weak oxygen partial pressure dependence, (Po2)-1/6, was observed for the LSM electrodes. A similar arc was observed for LSM-YSZ electrodes, where Re1∼(Po2)-0.29 and the activation energy was 1.49±0.02 eV. The combination of a high activation energy and a weak Po2 dependence was attributed to oxygen dissociation and adsorption rate-limiting steps for both types of electrodes. LSM-YSZ composite cathodes showed substantially lower overall interfacial resistance values than LSM, but exhibited an additional arc attributed to the resistance of YSZ grain boundaries within the LSM-YSZ. At 850°C and low Po2, an additional arc was observed with size varying as (Po2)-0.80 for LSM and (Po2)-0.57 for LSM-YSZ, suggesting that diffusion had become an additional rate limiting step. Bilayer LSM/LSM-YSZ electrodes yielded results intermediate between LSM and LSM-YSZ. The results showed that most of the improvement in electrode performance was achieved for a LSM-YSZ layer only ≈2 μm thick. However, a decrease in the grain-boundary resistance would produce much better performance in thicker LSM-YSZ electrodes.

Original languageEnglish (US)
Pages (from-to)235-243
Number of pages9
JournalSolid State Ionics
Volume110
Issue number3-4
StatePublished - Jul 2 1998

Keywords

  • Cathode
  • Fuel cell
  • Impedance spectroscopy
  • Lanthanum manganese oxide
  • Oxygen transfer process

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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