Sulfur Poisoning of SOFC Cathodes

In order to examine degradation of solid oxide fuel cell (SOFC) cathodes due to a trace of SOx in air, sulfur poisoning of SOFC cathodes was investigated in an accelerated mode using SO2-concentrated air at T = 1073 K. Two different cathode materials, Sm0.5Sr0.5CoO3 (SSC) and (La0.85Sr0.15)(0.95)MnO3 (LSM), were fired on button-type La(0.8)Sr(0.2)Ga(0.8)Mg(0.15)Co(0.0)5O(3-delta) electrolytes. SO2-concentrated air (98 ppm SO2-air mixture) was selected as the source of sulfur in order to accelerate degradations due to sulfur poisoning. By exposure to SO2, the performance of SSC cathode rapidly declined, because both ohmic and polarization resistances increased. The performance of the LSM cathode slightly decreased after exposure to SO2, and the performance recovered by interrupting the feed of SO2. Secondary phases such as strontium sulfate were formed on SSC cathode after exposing SO2 and were not clearly detected on LSM cathode. The LSM cathode was more stable in SO2 concentrated air than the SSC cathode. This can be explained by the difference in the activity of strontium oxide in LSM and SSC. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3090169] All rights reserved.