TY - JOUR
T1 - Effect of Microstructure on the Degradation of La0.6Sr0.4CoO3– δ Electrodes in Dry and Humid Atmospheres
AU - Egger, A.
AU - Perz, M.
AU - Bucher, E.
AU - Gspan, C.
AU - Sitte, W.
PY - 2019/1/1
Y1 - 2019/1/1
N2 - 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.
AB - 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.
KW - Cathode
KW - Degradation
KW - Electrochemical Impedance Spectroscopy
KW - Energy Conversion
KW - Fuel Cells
KW - Long-term Stability
KW - Perovskite Phases
KW - Solid Oxide Fuel Cel
UR - http://www.scopus.com/inward/record.url?scp=85068521116&partnerID=8YFLogxK
U2 - 10.1002/fuce.201900006
DO - 10.1002/fuce.201900006
M3 - Article
AN - SCOPUS:85068521116
SN - 1615-6846
VL - 19
SP - 458
EP - 471
JO - Fuel Cells
JF - Fuel Cells
IS - 4
ER -