Synthesis and characterization of Sr2MgMoO6-delta - An anode material for the solid oxide fuel cell

The double-perovskite Sr2MgMoO6-delta (SMMO) was investigated as an anode material of a solid oxide fuel cell. Via a synthetic method based on thermal decomposition of metal complexes with ethylenediaminetetraacetic acid as the complexant, phase-pure SMMO was readily obtained. Oxygen vacancies are introduced by reduction with 5% H-2 at 800 degrees C. With a 300 mu m thick La0.8Sr0.2Ga0.83Mg0.17O2.815 disk as the electrolyte and SrCo0.8Fe0.2O3-delta as the cathode, the SMMO anode showed power densities of 0.84 W/cm(2) in H-2 and 0.44 W/cm(2) in CH4 at 800 degrees C. Moreover, it performed stably on power cycling and tolerated sulfur and moisture well. Only 1% degradation in the output was observed in H-2 containing 5 parts per million (ppm) H2S and 16% degradation in H-2 containing 50 ppm H2S compared with the output in pure H-2. Thermogravimetric analysis showed a drop in mass at around 750 degrees C in the atmospheres of both air and 5% H-2, indicative of the formation of oxygen vacancies. The mean thermal expansion coefficient was alpha = 12.7 x 10(-6) K-1 at the operating temperatures. The conductivity strongly depended on the atmosphere, and the electronic activation energies were E-a = 0.084 eV in H-2 and 0.126 eV in CH4. Our results show that SMMO is a potential anode material for operation with natural gas. (c) 2006 The Electrochemical Society.