Kinetics of CO oxidation and redox cycling of Sr2Fe1.5Mo0.5O6-δ electrode for symmetrical solid state electrochemical devices

• Published in: Journal of power sources Vol. 418; pp. 17 - 23
• Main Author: Osinkin, D.A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2019
• Subjects: CO oxidation; Distribution of relaxation times; Electrode kinetics; Redox; Sr2Fe1.5Mo0.5O6; Symmetrical SOFC; Redox; Electrode kinetics; Symmetrical SOFC; Distribution of relaxation times; CO oxidation; Sr2Fe1.5Mo0.5O6
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2019.02.026

of the redox cycling of the Sr2Fe1.5Mo0.5O6-δ electrode in contact with the LaGaO3-based electrolyte at 800°С in air - CO/CO2 - Ar/H2 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°С (pO2 ≈ 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-δ electrode. •CO oxidation kinetics has been studied.•DRT and NLLS methods were used for IES spectra analysis.•The CO oxidation is limited by three steps.•Redox long-term tests of SFM electrode have been performed.•The good stability of SFM electrode at redox cycling is showed.