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

The performance of Sr2Fe1.5Mo0.5O6 (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 degrees C in air. The chemical diffusion coefficient (D-chem) and surface exchange constant (k(ex)) of SFMO at 750 degrees C are 5.0 x 10(-6) cm(2) s(-1) and 2.8 x 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 x 10(-6) K-1 the temperature range of 200-760 degrees C in air. The polarization resistance of the SFMO cathode is 0.076 Omega cm(2) at 800 degrees C in air under open-circuit conditions measured on symmetrical cells with La0.8Sr0.2Ga0.87Mg0.13O3 (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 degrees C in air. Single cells with the configuration of Ni-La0.4Ce0.6O2 (LCO)vertical bar LCO vertical bar LSGM vertical bar SFMO show peak power densities of 349, 468, and 613 mW cm(-2) at 750, 800, and 850 degrees 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. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3556085] All rights reserved.