A comparative study of La0.8Sr0.2MnO3 and La0.8Sr0.2Sc0.1Mn0.9O3 as cathode materials of single-chamber SOFCs operating on a methane-air mixture

As candidates of cathode materials for single-chamber solid oxide fuel cells, La0.8Sr0.2MnO3 (LSM) and La0.8Sr0.2Sc0.1Mn0.9 (LSSM) were synthesized by a combined EDTA-citrate complexing sol-gel process. The Solid precursors of LSM and LSSM were calcined at 1000 and 1150 degrees C, respectively, to obtain products with similar specific surface area. LSSM was found to have higher activity for methane oxidization than LSM due to LSSM's higher catalytic activity for oxygen reduction. Single cells with these two cathodes initialized by ex situ reduction had similar peak powder densities of around 220 mW cm(-2) at 825 degrees C. The cell using the LSM cathode showed higher open-circuit-voltage (OCV) at corresponding temperatures (I Lie to its reduced activity for methane oxidation relative to LSSM. A negligible effect of methane and CO2 on the cathode performance was observed for both LSM and LSSM via electrochemical impedance spectroscopy analysis. The high phase stability of LSSM under reducing atmosphere allows a more convenient in situ reduction for fuel cell initiation. The resultant cell with LSSM cathode delivered a peak power density of similar to 200 mW cm(-2) at 825 degrees C, comparable to that horn ex Situ reduction. (C) 2009 Elsevier B.V. All rights reserved.