Influence of the strontium content on the performance of La1-xSrxMnO3/Bi1.5Er0.5O3 composite electrodes for low temperature Solid Oxide Fuel Cells

Abstract The possibility to use bilayer electrolytes based on bismuth oxide conductors should lead to a drastic decrease of solid oxide fuel cell (SOFC) operation temperature and calls for a reevaluation of some of the parameters optimized for high temperature applications. In this work we reinvestigate the promising La1-xSrxMnO3/Bi1.5Er0.5O3 (LSM/ESB) composite electrodes, varying the strontium content from x ~ 0.2, the typical high temperature LSM composition, to evaluate the optimum composition. Increasing the strontium content up to x = 0.4–0.5 leads to a 14% decrease of the activation energy, resulting in a 50% decrease in the polarization resistance of symmetric cells at 500 °C compared to the traditional La0.85Sr0.15MnO3 composition with similar microstructure. The electrode performance is deteriorated by further increase in the strontium content. Based on surface composition, investigated by low energy ion scattering, we show that the SrO surface segregation proposed as the main deterioration mechanism for LSM based HT-SOFC is not an issue below 800 °C. Furthermore, we propose that the increase in performance is related to the decrease of cationic vacancies in LSM observed for high strontium content, which may help the oxygen dissociation and surface transport.