Rock salt ordered-type double perovskite anode materials for solid oxide fuel cells

• Structural properties of B-site rock salt-type ordering anode materials
• Transport properties of Sr2 − xBaxMMoO6 − δ double perovskites
• Chemical stability of anode materials in reducing atmosphere
• Precipitation of Co and Ni from Sr2 − xBaxMMoO6 − δ in reducing conditions
• Performance of SOFC with SrBaCoMoO6 − δ-based anode

B-site rock salt-type ordered double perovskites Sr2 − xBaxMMoO6 − δ (M = Co, Ni; x = 0, 0.5, 1, 1.5 and 2) were evaluated as novel anode materials for SOFC fuel cells. Phase composition, crystal structure, oxygen content, transport properties, chemical stability in relation to ceria electrolyte and chemical stability of Sr2 − xBaxMMoO6 − δ under reducing atmospheres were studied. It was found that Sr2CoMoO6 − δ and Sr2NiMoO6 − δ possess I4/m symmetry at room temperature, while all other anode materials are cubic with Fm-3m space group. SrBaMMoO6 − δ oxides exhibit thermal expansion coefficient in the range 11.7–14.3 · 10− 6 K− 1, which is comparable to that of Ce0.8Gd0.2O1.9 electrolyte. All Sr2 − xBaxMMoO6 − δ oxides show low electrical conductivity in air (ca. 10− 3–10− 1 S cm− 1 at 800 °C). Stability studies performed in reducing conditions indicate that these materials decompose at temperatures lower than 800 °C in 5 vol.% H2 in Ar and lower than 700 °C in pure H2, which suggests that previous literature data showing enhanced conductivity in reducing conditions may not be entirely correct. Interestingly, despite total decomposition of the anode material, relatively high performance of constructed SOFCs was recorded. Moreover, addition of Ni to the anode caused an increase of power density up to 0.16 W cm− 2 at 850 °C.