Effects of high-valence Mo content on microstructure and properties of Ba2Fe2-Mo O6- anode materials for solid oxide fuel cells

Double perovskites Ba2Fe2-xMoxO6-δ (BFMox, x = 1.0–0.3) were investigated as anodes of solid oxide fuel cells (SOFCs). In H2, all the BFMox samples exhibit sufficient electrical conductivities (σ > 2 S cm−1) at 600–800 °C. However, the BFMo0.7 and BFMo0.5 compositions exhibit relatively better redox stability than the others. Furthermore, using 250-μm-thick La0.9Sr0.1Ga0.8Mg0.2O3-δ as electrolyte and Ba0.6Sr0.4Co0.9Nb0.1O3-δ as cathode, the BFMo0.7 and BFMo0.5 anode cells also show higher electrochemical performances with peak power density attaining 905 and 908 mW cm−2, respectively, at 800 °C. Additi°nally, the BFMo0.7 and BFMo0.5 anodes show good electrochemical stability for long-term H2 oxidation. However, the BFMo0.7 anode exhibits an especially high thermal expansion coefficient (TEC) ∼61.9 × 10−6 K−1 at 25–886 °C in air, nearly three times larger than that of the BFMo0.5 anode under the same condition (TEC=∼14.8 ×10−6 K−1). In view of this, the BFMo0.5 is considered to be a preferred anode candidate for SOFC.