Electrochemical characteristics of La0.6Sr0.4CoO3-δ, Pr0.6Sr0.4CoO3-δ and Gd0.6Sr0.4CoO3-δ on Ce0.85Sm0.15O1.925 electrolyte |
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Authors: | Enn Lust Priit Möller Indrek Kivi Gunnar Nurk Silvar Kallip |
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Institution: | (1) Institute of Physical Chemisty, Tartu University, 2 Jakobi Street, 2400 Tartu, Estonia |
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Abstract: | Cyclic voltammetry, chronoamperometry and electro-chemical impedance have been used for the analysis of the following medium
temperature half-cells: Ce0.85Sm0.15O1.925| La0.6Sr0.4CoO3-δ, Ce0.85Sm0.15O1.925| Pr0.6Sr0.4CoO3-δ and Ce0.85Sm0.15O1.925| Gd0.6Sr0.4CoO3-δ. The influence of the atomic mass of the A–site cation in the perovskite cathode on the oxygen reduction kinetics has been
discussed. The total polarisation resistance, obtained from the Z′′, Z′-plots, increases with the rise of atomic mass of the cation in the A-site position. Two different time constants have been
obtained for the oxygen electroreduction process, and the replacement of La3+ by Gd3+ in the cathode material decreases somewhat the surface catalytic activity, but the noticeably higher low-frequency series
resistance, i.e. mainly diffusion-like mass transfer resistance, values have been obtained. However, the mainly diffusion-limited
process at T≤773 K for Gd0.6Sr0.4CoO3-δ and the kinetically mixed process (diffusion + charge transfer) for Pr0.6Sr0.4CoO3-δ and La0.6Sr0.4CoO3-δ have been established. At higher temperature (T≥993 K) and more negative potentials, the O2 reduction process is limited mainly by the heterogeneous charge transfer step.
Presented at the fourth Baltic Conference on Electrochemistry, Greifswald, March 13–16, 2005. |
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Keywords: | Solid oxide fuel cell Ce0 85Sm0 15O1 95 electrolyte La0 6Sr0 4CoO3-δ Pr0 6Sr0 4CoO3-δ Gd0 6Sr0 4CoO3-δ Cathode |
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