Sr2Fe1.5Mo0.5O6 as Cathodes for Intermediate-Temperature Solid Oxide Fuel Cells with La0.8Sr0.2Ga0.87Mg0.13O3 Electrolyte

The performance of Sr 2 Fe 1.5 Mo 0.5 O 6 (SFMO) as a cathode material has been investigated in this study. The oxygen ionic conductivity of SFMO reaches 0.13 S cm −1 at 800°C in air. The chemical diffusion coefficient ( D chem ) and surface exchange constant ( k ex ) of SFMO at 750°C are 5.0 × 10 −6 cm 2 s −1 and 2.8 × 10 −5 cm s −1 , respectively, suggesting that SFMO may have good electrochemical activity for oxygen reduction. SFMO shows a thermal expansion coefficient (TEC) of 14.5 × 10 −6 K −1 the temperature range of 200–760°C in air. The polarization resistance of the SFMO cathode is 0.076 Ω cm 2 at 800°C in air under open-circuit conditions measured on symmetrical cells with La 0.8 Sr 0.2 Ga 0.87 Mg 0.13 O 3 (LSGM) electrolytes. Dependence of SFMO cathode polarization resistance on the oxygen partial pressure and the cathode overpotentials at different temperatures are also studied. SFMO shows an exchange current density of 0.186 A cm −2 at 800°C in air. Single cells with the configuration of Ni-La 0.4 Ce 0.6 O 2 (LCO)|LCO|LSGM|SFMO show peak power densities of 349, 468, and 613 mW cm −2 at 750, 800, and 850°C, respectively using H 2 as the fuel and ambient air as the oxidant. These results indicate that SFMO is a promising cathode candidate for intermediate-temperature solid oxide fuel cells with LSGM electrolyte.