Chromium Poisoning and Degradation at (La,Sr)MnO[sub 3] and (La,Sr)FeO[sub 3] Cathodes for Solid Oxide Fuel Cells

The degradation of cathode performances by chromium poisoning was studied at two cathodes [ (LSM) and ] on the electrolyte. Cathodic currents were decreased by the supply of Cr vapors under a constant overvoltage (−0.3 V vs reference electrode) at 1073 K up to 300 h. The polarization resistances increased with time to the power of 1/2 and 1/4 in and , respectively. The distributions and the amounts of Cr in the porous cathodes were measured by secondary-ion mass spectrometry: A maximum concentration of Cr was about 1000 ppm at the contact interfaces, while the surface concentration was about 100 ppm. In , the concentration of Cr is almost constant at values of 1000–1700 ppm inside the cathode. Among the supplied Cr vapors, about 7–14% of Cr atoms were reacted and condensed in the porous , while 13–21% of Cr atoms were reacted in . Chemical reactivity and electrode reaction mechanism affect the Cr poisoning and degradation of cathode performance.