Rate limiting steps of the porous La0.6Sr0.4Co0.8Fe0.2O3−δ electrode material |
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| Authors: | N Grunbaum L Dessemond J Fouletier F Prado L Mogni A Caneiro |
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| Institution: | 1. Laboratoire d''Electrochimie et de Physicochimie des Matériaux et des Interfaces (L.E.P.M.I.), E.N.S.E.E.G., I.N.P. Grenoble, BP 75 38402 Saint Martin D''Heres Cedex, France;2. Centro Atómico Bariloche, CNEA, 8400 S.C. de Bariloche RN, Argentina;3. CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas) Argentina |
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| Abstract: | The electrode reaction of porous La0.6Sr0.4Co0.8Fe0.2O3?δ films deposited onto Ce0.9Gd0.1O1.95 (CGO) was investigated by impedance spectroscopy within the temperature and oxygen partial pressure (pO2) ranges of 500 ≤ T ≤ 700 °C and 10? 4 < pO2 < 1 atm, respectively, using Ar and He as gas carriers. The electrochemical impedance spectroscopy (EIS) measurements reveal a high frequency (HF) and a low frequency (LF) regions in the Nyquist plane. The high frequency (HF) region was fitted with a Warburg-type impedance element, and the low frequency (LF) region was reproduced with a resistance in parallel to a constant phase element. Both, the slight dependence of the polarization resistance (RW) and the small variation of the apex frequency (fv) of the HF Warburg-type element, on pO2, suggest that this contribution corresponds to the oxygen diffusion in the bulk of the La0.6Sr0.4Co0.8Fe0.2O3?δ electrode material. The variation of the polarization resistance of the LF region (Rrcpe) with pO2 indicates that as T increases, the limiting step evolves from dissociative oxygen adsorption to oxygen gas diffusion in the pores of the mixed ionic/electronic conductor (MIEC) electrode. |
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