Electrochemical performance and stability of La0·5Sr0·5Fe0·9Nb0·1O3-δ symmetric electrode for solid oxide fuel cells

Abstract Symmetric solid oxide fuel cells (SSOFCs) based on the Co-free La 0·5 Sr 0·5 Fe 0·9 Nb 0·1 O 3-δ (LSFNb) perovskite oxide are prepared by the sol-gel method. The structural stability and catalytic activity of LSFNb as an electrode for both the hydrogen oxidation reaction and oxygen reduction reaction are studied. We show that Nb substitution in La 0·5 Sr 0·5 FeO 3-δ greatly improves its chemical and phase stability under reducing atmosphere. At 800 °C, the area specific polarization resistances (ASR p ) of La 0·5 Sr 0·5 Fe 0·9 Nb 0·1 O 3-δ symmetric cells are as low as 0.06 and 0.24 Ω cm 2 in air and wet H 2 (3% H 2 O), respectively. LSFNb based electrolyte-supported SSOFCs deliver peak power densities of 1000 mW cm -2 at 850 °C in wet H 2 /air. In addition to high performance, the symmetric cell shows stable power output under load (measured for 140 h at a current density of 520 mA cm −2 , 800 °C) under air/humidified H 2 operation, indicating that LSFNb may be a particularly promising new symmetric electrode material for solid oxide fuel cells.