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"Study of the Mechanisms of O2-Reduction and Degradation Operating on La0.5-xPrxBa0.5CoO3-δ Cathodes for SOFCs"
Diana Andrea Garcés, Hongqian Wang, Scott A. Barnett, Ana Gabriela Leyva and Liliana Veronica Mogni
Proc. of the "15th International Symposium on Solid Oxide Fuel Cells" (SOFC-XV), Hollywood, Florida, USA, July 23-28, 2017. Eds. S.C. Singhal and T. Kawada
ECS Trans. 78(1) (2017) 1011-1020
The oxygen reduction mechanism and time evolution behavior were studied for porous La0.5-xPrxBa0.5CoO3-δ (LPBC) electrodes deposited onto Ce0.9Gd0.1O1.95 electrolytes. Electrochemical impedance spectroscopy (EIS) measurements, performed between 400 and 800 °C as a function of pO2, show that the electrochemical response is limited by O2-gas diffusion and surface reaction (O-surface exchange + O-ion diffusion). The time evolution of the cathode resistance at 700 °C in air shows an increase from 0.03 to 0.05 Ωcm2 after 280 h of testing. Three-dimensional (3D) tomographic using focused ion beam-scanning electron microscopy (FIB-SEM) showed little changes of microstructure after the ageing. The increase in resistance was explained by an increase in the amount of a water-soluble Ba-rich surface phase by a factor of 2, after ageing of the LPBC electrode, by an etching procedure coupled with inductively coupled plasma-optical emission spectrometry (ICP-OES).
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