High-Performance SmBaMn₂O_5+δ Electrode for Symmetrical Solid Oxide Fuel Cell

The design of a symmetrical solid oxide fuel cell comprising identical anode and cathode material brings numerous advantages over a conventional cell with different anode and cathode materials. In this report, A-site layered perovskite with an SmBaMn₂O_5+δ composition is synthesized and thoroughly investigated as the electrode material for symmetrical cells. The SmBaMn₂O_5+δ material with a P4/nmm structure remains stable in both reducing and oxidizing atmospheres at elevated temperatures, but with a difference of ca. 1 mol in the oxygen content per mole of SmBaMn₂O_5+δ between the oxidized and the reduced materials. The SmBaMn₂O_5+δ material shows high electrical conductivity in air and an acceptable value in 5% H₂/Ar at 750–900 °C, and it exhibits outstanding catalytic activity toward oxygen reduction and hydrogen oxidization reactions with polarization resistance values of 0.066 and 0.313 Ω cm² in air and humidified H₂ at 900 °C, respectively. The power density of a laboratory-scale La_0.8Sr_0.2Ga_0.8Mg_0.2O_3−δ electrolyte-supported cell with SmBaMn₂O_5+δ as symmetrical electrodes reaches 782 mW cm^–2 at 900 °C. Our results demonstrate that the A-site ordered SmBaMn₂O_5+δ can be considered as an attractive electrode material for symmetrical solid oxide fuel cells.