Sc-substituted La0.6Sr0.4FeO3−δ mixed conducting oxides as promising electrodes for symmetrical solid oxide fuel cells

• La0.6Sr0.4Fe0.9Sc0.1O3−δ oxides show good stability in both oxidizing and reducing environments.
• La0.6Sr0.4Fe0.9Sc0.1O3−δ electrodes exhibit polarization resistances of 0.015 Ω cm2 in air and 0.29 Ω cm2 in H2 at 800 °C.
• Maximum power densities of 0.56 W cm−2 are obtained at 800 °C for symmetrical La0.6Sr0.4Fe0.9Sc0.1O3−δ electrode fuel cells.

The main barrier to symmetrical solid oxide fuel cells (SOFCs), where the same catalytic materials are used simultaneously as the anodes and the cathodes, is to identify a redox-stable catalyst that exhibits superior catalytic activities for both fuel oxidation and oxygen reduction reactions. Here we report a Sc-substituted La0.6Sr0.4FeO3−δ oxide, La0.6Sr0.4Fe0.9Sc0.1O3−δ, that shows great promise as a new symmetrical electrode material with good structural stability and reasonable conductivities in air and hydrogen. We further demonstrate that nano-scale La0.6Sr0.4Fe0.9Sc0.1O3−δ catalysts impregnated into the porous La0.9Sr0.1Ga0.8Mg0.2O3−δ backbones exhibit good catalytic activities for oxygen reduction and hydrogen oxidation reactions and thereby yield low polarization resistances, e.g., 0.015 Ω cm2 in air and 0.29 Ω cm2 in hydrogen with appropriate current collection at 800 °C. Thin La0.9Sr0.1Ga0.8Mg0.2O3−δ electrolyte fuel cells with such symmetrical La0.6Sr0.4Fe0.9Sc0.1O3−δ catalysts showed maximum power densities of 0.56 and 0.32 W cm−2 when operating on 97% H2–3% H2O at 800 and 700 °C, respectively.