A-site cation influences on performance, structure and conductivity of a lanthanide-based perovskite electrode for symmetrical solid oxide fuel cells

Abstract

The two Alkaline Earth Metals (Aem) of Barium and Calcium are doped in a perovskite A site (such as La0.7Aem0.3Ti0.5Mn0.4Ni0.1O3) to be applied as Solid Oxide Fuel Cell (SOFC) electrodes to study the cation size implications in the resultant phase/s, electrochemical performances (as anode, cathode and in a symmetrical cell) and conductivities. Despite having a theoretically closer dopant-host cation size match, Calcium doped perovskite (LCTMN) reveals lower phase purity, however, higher performances (of 97.4 vs 28 mW cm−2) are obtained in symmetrical cells. This fact is later majorly attributed to its superior anodic efficiency (of 115.8 vs 49 mW cm−2) obtained when both materials are assembled with the reference cathode of BSCF (Ba0.5Sr0.5Co0.8Fe0.2O3). Further support is found in the analysis of the total impedances of the cells as well as the conductivities under oxidizing and reducing atmospheres. The chemical composition proximity of the chosen perovskites with the benchmark cathode La0.7Sr0.3MnO3 (LSM) supports the limiting factor of the anodic behavior. The identification of two thermal regimes in the conductivity (in hydrogen) together with the specimen average performance and conductivity differences lead to formulate a model to directly estimate a relationship between these two variables (with errors of 5.3 and 6%).