Effect of Microstructure on the Degradation of La0.6Sr0.4CoO3– δ Electrodes in Dry and Humid Atmospheres

A. Egger*, M. Perz, E. Bucher, C. Gspan, W. Sitte

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

La0.6Sr0.4CoO3– δ electrode layers with three different microstructures were manufactured by screen-printing, spin-coating and infiltration into a porous Ce0.9Gd0.1O1.95 backbone. Electrode performance was monitored at 700 °C in 20% O2 over periods of 1,600 to 3,860 h by means of electrochemical impedance spectroscopy under open circuit conditions. Reference measurements were performed in dry atmospheres, where significant electrode activation was observed for cells with spin-coated and infiltrated electrodes. Subsequently, the relative humidity level in the surrounding atmosphere was set to 30% and further raised to 60%, thus simulating SOFC operation with ambient air without pre-drying. While no performance loss could be observed in dry atmospheres, significant degradation occurred in humid atmospheres with pronounced differences between degradation rates of half cells with different electrode microstructures. Post-test analyses by scanning electron microscopy (SEM) and transmissionscanning electron microscopy (STEM) were employed to identify the causes for the observed differences in degradation behavior. For screen-printed cells, the surface of the degraded electrodes was covered with small crystallites, probably consisting of SrO formed by Sr-segregation and surface precipitation, where humidity was found to be a crucial factor. For spin-coated and infiltrated electrodes, poisoning by impurities (Si, Cr, S) and particle coarsening were identified as potential causes.

Original languageEnglish
Pages (from-to)458-471
Number of pages14
JournalFuel Cells
Volume19
Issue number4
DOIs
Publication statusPublished - 1 Jan 2019

Keywords

  • Cathode
  • Degradation
  • Electrochemical Impedance Spectroscopy
  • Energy Conversion
  • Fuel Cells
  • Long-term Stability
  • Perovskite Phases
  • Solid Oxide Fuel Cel

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Energy Engineering and Power Technology

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