Improvement of La0.8Sr0.2MnO3-δ Cathode Material for Solid Oxide Fuel Cells by Addition of YFe0.5Co0.5O3

Abstract

The high efficiency of solid oxide fuel cells with La_0.8Sr_0.2MnO_3-δ (LSM) cathodes working in the range of 800-1000 °C, rapidly decreases below 800 °C. The goal of this study is to improve the properties of LSM cathodes working in the range of 500-800 °C by the addition of YFe_0.5Co_0.5O₃ (YFC). Monophasic YFC is synthesized and sintered at 950 °C. Composite cathodes are prepared on Ce_0.8Sm_0.2O_1.9 electrolyte disks using pastes containing YFC and LSM powders mixed in 0:1, 1:19, and 1:1 weight ratios denoted LSM, LSM1, and LSM1, respectively. X-ray diffraction patterns of tested composites reveal the presence of pure perovskite phases in samples sintered at 950 °C and the presence of Sr₄Fe₄O₁₁, YMnO₃, and La_0.775Sr_0.225MnO_3.047 phases in samples sintered at 1100 °C. Electrochemical impedance spectroscopy reveals that polarization resistance increases from LSM1, by LSM, to LSM2. Differences in polarization resistance increase with decreasing operating temperatures because activation energy rises in the same order and equals to 1.33, 1.34, and 1.58 eV for LSM1, LSM, and LSM2, respectively. The lower polarization resistance of LSM1 electrodes is caused by the lower resistance associated with the charge transfer process.

Keywords: composite cathode; electrochemical impedance spectroscopy; lanthanum strontium manganite; solid oxide fuel cell; yttrium iron cobaltite.