Journal
JOURNAL OF POWER SOURCES
Volume 418, Issue -, Pages 17-23Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jpowsour.2019.02.026
Keywords
Symmetrical SOFC; Redox; Sr2Fe1.5Mo0.5O6; Distribution of relaxation times; CO oxidation; Electrode kinetics
Funding
- Russian Foundation for Basic Research [17-08-00161]
- Russian Federation Government [02.A03.21.0006, 211]
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Results: of the redox cycling of the Sr2Fe1.5Mo0.5O6-delta electrode in contact with the LaGaO3-based electrolyte at 800 degrees C in air - CO/CO2 - Ar/H-2 are presented for the first time. The electrochemical impedance method was used to demonstrate that the electrode polarization resistance at fast gas cycling remained almost unchanged. In the long-term cycling from oxidizing to reducing atmospheres (and vice versa) the polarization resistance equilibrated rapidly (slowly). The kinetics of the CO oxidation in CO/CO2 gas mixtures at 800 degrees C (pO(2) approximate to 10(-16) - 10(-19) atm) near the equilibrium electrode potential was studied. By means of a complex approach to the impedance spectra analysis using the distribution of relaxation times and non-linear least squares methods, it was determined that the CO oxidation is limited by three steps: CO adsorption (CO2 desorption) at the electrode surface, oxygen hetero-exchange and the oxygen ion transport in the electrode bulk. We assume that the charge transfer and the gas diffusion do not limit the CO oxidation reaction on the Sr2Fe1.5Mo0.5O6-delta electrode.
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