Long-term stability of oxygen surface exchange kinetics of Pr0.8Ca0.2FeO3-δ against SO2-poisoning

Christian Berger, Edith Bucher*, Christian Gspan, Alexander Menzel, Werner Sitte

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

The long-term stability of the oxygen exchange kinetics of the Sr- and Co-free solid oxide fuel cell (SOFC) and solid oxide electrolyser cell (SOEC) air electrode material Pr0.8Ca0.2FeO3-δ (PCF82) is investigated by in-situ dc-conductivity relaxation measurements. The chemical oxygen surface exchange coefficient kchem is determined as a function of time at 700 °C under ideal (O2-Ar atmosphere) and accelerated ageing conditions (O2-Ar with 2 ppm SO2). In pure O2-Ar PCF82 shows fast oxygen surface exchange kinetics with kchem = 6 × 10−4 cm s−1 and excellent stability for 1000 h. Due to the addition of 2 ppm SO2 to the test gas only a moderate degradation occurs with kchem decreasing to 8 × 10−5 cm s−1 during further 1000 h. Post-test analyses by scanning (transmission) electron microscopy and X-ray photoelectron spectroscopy show S-rich secondary phases in the near-surface region of the SO2-poisoned sample. These inactive phases occur in an island-like arrangement of relatively large crystals, whereas significant amounts of the surface remain unaffected. This effect explains the high stability of the oxygen exchange kinetics of PCF82 against SO2-poisoning in comparison to state-of-the art materials like La0.6Sr0.4CoO3-δ (LSC64).

Original languageEnglish
Pages (from-to)82-89
Number of pages8
JournalSolid State Ionics
Volume326
DOIs
Publication statusPublished - 15 Nov 2018

Keywords

  • Oxygen exchange kinetics
  • Praseodymium calcium ferrite
  • Solid oxide electrolyser cell anode
  • Solid oxide fuel cell cathode
  • Sulphur dioxide poisoning

ASJC Scopus subject areas

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

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