Catalytic activity and performance of LSM cathode materials in single chamber SOFC

The catalytic activity of symmetrical LSM (La0.8Sr0.2MnO3) cells operated under single chamber solid oxide fuel cell (SC-SOFC) conditions was investigated for methane-to-oxygen ratios R-in between 1 and 2. The oxidation reactions over electrodes sintered at 1100 degrees C (LSM1100) and 1200 degrees C (LSM1200) were studied, and the effect of any combustion was followed through electrochemical impedance spectroscopy (EIS). The activity of the LSM oo electrode increases with temperature. Above 700 degrees C, the conversion of the oxygen species may exceed 30%. As a consequence, oxygen depletion is occurring and a low frequency semicircle in the EIS spectra becomes predominant. An increase of the sintering temperature to 1200 degrees C leads to a decrease in the catalytic activity. A LSM1100 electrode deposited on a Julich half-cell proves to reach better performance at 600 degrees C than at 700 degrees C. On such complete cells, however, the catalytic combustion becomes much more complex than on a LSM cathode alone. We are thus proposing a comprehensive parameter, R-out, that is summarizing the processes inside the single chamber reactor. (C) 2007 Elsevier B.V. All rights reserved.