Comparative study of electrochemical properties of mixed conducting Ln2NiO4+δ (Ln = La, Pr and Nd) and La0.6Sr0.4Fe0.8Co0.2O3−δ as SOFC cathodes associated to Ce0.9Gd0.1O2−δ, La0.8Sr0.2Ga0.8Mg0.2O3−δ and La9Sr1Si6O26.5 electrolytes
Résumé
The present paper focuses on the comparative study of the electrochemical properties of various mixed conducting oxides used as cathode in alternative couples (cathode/electrolyte) with the aim to improve the performance of the usual couple based on LSM (La0.8Sr0.2MnO3)/YSZ (yttria stabilized zirconia). The oxygen deficient perovskite, La0.6Sr0.4Fe0.8Co0.2O3 − δ (LSFC) and the Ruddlesden-Popper phases, the nickelates Ln2NiO4 + δ (Ln = La, Pr and Nd) have been investigated as cathode materials for potential application in IT-SOFC systems, using various electrolyte materials such as cerium gadolinium oxide Ce0.9Gd0.1O2 − δ (CGO), substituted lanthanum gallate, La0.8Sr0.2Ga0.8Mg0.2O3 − δ (LSGM) and the apatite-type lanthanum silicate La9Sr1Si6O26.5 (LSSO). The chemical reactivity of cathode/electrolyte powder mixtures was investigated by XRD: the results revealed LSFC to have a good chemical compatibility with the various electrolytes while the nickelate oxides showed some reactivity and even a partial decomposition for Pr2NiO4 + δ. The electrochemical properties of these cathode materials have been investigated by impedance spectroscopy under zero dc conditions. The analysis of the impedance diagrams revealed the presence of two processes. The cathodic polarization resistances have been measured and the lowest values at 600 °C are 0.28 and 0.30 Ω*cm2 for Pr2NiO4 + δ/Ce0.9Gd0.1O2 − δ and La0.6Sr0.4Fe0.8Co0.2O3 − δ/La0.8Sr0.2Ga0.8Mg0.2O3 − δ, respectively. These results have demonstrated that both systems are suitable for IT-SOFC applications.
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