| Autor: |
Miara, Lincoln J., Davis, Jacob N., Basu, Soumendra N., Pal, Uday B., Gopalan, Srikanth |
| Předmět: |
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| Zdroj: |
Journal of The Electrochemical Society; 2011, Vol. 158 Issue 12, pB1523-B1531, 9p |
| Abstrakt: |
Patterned cathodes with composition (La0.87Ca0.13)0.95MnO3 (LCM) were fabricated by rf-magnetron sputter deposition on 8 mol% yttria-doped zirconia (YSZ) substrates to have a constant LCM/YSZ contact area of 0.8 cm2, but have triple phase boundary (TPB) lengths ranging from 450-1600 cm cm-2. Electrochemical impedance spectroscopy (EIS) spectra were collected over a temperature and pO2 range of 600-800°C and 10-3-1.0 atm, respectively, with no applied bias. The resultant spectra were analyzed using a state-space modeling (SSM) approach to understand the oxygen reduction reaction (ORR) kinetics. The SSM model chosen accounts for dissociative adsorption in parallel with surface diffusion to the TPB where full reduction and incorporation into the electrolyte occur. The model explains the observed trends in the experimental data, and enabled extraction of parameters. Of particular significance, the surface diffusivity, DS, was found to be 1.4 x 10-5 cm2 s-1 at 700°C, with an Arrhenius activation energy of 248 kJ mol-1. The enthalpy of adsorption was found to be -83 kJ mol-1 and almost independent of surface coverage. From the model it was determined that, in air, charge transfer resistance accounts for 40% of the total polarization resistance at 800°C whereas at 600°C it accounts for only 3%. Over much of the measured operating conditions, surface diffusivity accounts for the majority of the total polarization resistance. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Supplemental Index |
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