Chemical stability and compatibility of double perovskite anode materials for SOFCs

Double perovskites with composition Sr2BM0O(6 - delta) (B = Mg, Ni and Co) and Sr2Fe1.5Mo0.5O6 - delta have been proposed as potential anode material for direct hydrocarbon oxidation in solid oxide fuel cells (SOFCs). However, the phase stability under different atmospheres (H-2 and CO2) and the chemical compatibility with different electrolytes of most of these materials have not been previously studied. The chemical compatibility studies carried out by X-ray powder diffraction (XRPD) revealed high reactivity between these electrodes and zirconia based electrolytes, Zr0.84Y0.16O2 - delta, at temperatures as low as 800 C with the formation of SrMoO4 and SrZrO3 as main reaction products; however, lower chemical reactivity was found with Ce0.8Gd0.2O2 - delta. Sr2CoMoO6 - delta and Sr2NiMoO6 (- delta) phases resulted to be unstable under reducing atmosphere above 800 C, decomposing partially into Sr3MoO6 and Co/Ni metals respectively. These two materials also exhibited low resistance to carbonation in the intermediate temperature range 600-800 degrees C. Nevertheless, Sr2Fe15Mo0.5O6 (- delta) is stable under H2 and pure CO2 atmospheres. Furthermore, area specific resistances of these anode materials in symmetrical cells were determined in order to compare their electrochemical efficiency. (C) 2013 Elsevier B.V. All rights reserved.