La2−xSrxCoO4−δ (x = 0.9, 1.0, 1.1) Ruddlesden-Popper-type layered cobaltites as cathode materials for IT-SOFC application

• Published in: International journal of hydrogen energy 2013-03, Vol.38 (7), p.3064-3072
• Main Authors: Hu, Y., Bouffanais, Y., Almar, L., Morata, A., Tarancon, A., Dezanneau, G.
• Format: Article
• Language: English
• Subjects: Alternative fuels. Production and utilization; Applied sciences; Cathode; Composite electrodes; Electrochemical properties; Energy; Exact sciences and technology; Fuels; Hydrogen; La2−xSrxCoO4−δ; Layered perovskite; SOFC
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2012.12.047

La2−xSrxCoO4−δ (x = 0.9, 1.0, 1.1) compounds with Ruddlesden-Popper K2NiF4-type structure have been investigated as potential cathode materials for IT-SOFC application. Materials have been prepared by citrate-nitrate combustion method. Structural evolution analysed by XRD shows a shortened Co–O–Co bond length within the perovskite layer as Sr substitution increases, while the interlayer distance at the same time increases. An oxygen stoichiometry close to 4 has been found for all compositions at room temperature. Thermal expansion coefficients have been obtained from temperature-dependent XRD analysis and show large values (>20 × 10−6 K−1) compared to the currently utilized electrolyte materials. Electrochemical characterisation has been performed by means of impedance spectroscopy on symmetric cells with CGO electrolyte. Pure electrodes have a high Area Specific Resistance, probably due to limited oxygen ion diffusion. By using composite electrode (50 wt.% CGO), an Area Specific Resistance of 0.25 Ω cm2 is obtained at approximately 700 °C for all the three compounds suggesting promising electrochemical properties for IT-SOFCs. ► La2−xSrxCoO4−δ cathode materials for solid oxide cells are studied. ► The oxygen stoichiometry at rom temperature is close to 4. ► Thermal expansion is greater than 20 × 10−6 K−1 ► Pure electrode materials present a high Area Specific Resistance. ► Composite electrodes show a low ASR of 0.25 Ω.cm2 at 700 °C.