La3+-substituted Sr2Fe1.5Ni0.1Mo0.4O6-δ as Anodes for Solid Oxide Fuel Cells

Abstract

Lanthanum-substituted LaxSr2-3x/2Fe1.5Ni0.1Mo0.4O6-δ (LaxSFNM, x=0, 0.1, 0.2, 0.3, 0.4) oxides were synthesized by the solid-state reaction method, and investigated as potential anodes for Solid Oxide Fuel Cells(SOFC). X-ray diffraction patterns of as-synthesized powders confirm the formation of the cubic perovskite structure. Reduction in H2 promotes the segregation of nano-scale metallic Fe-Ni alloy particles on the grain surfaces. Scanning electron microscopy observations indicate that increasing La3+ dopants results in a decrease in the density of the exsolved nanoparticulates. Based upon impedance measurements on symmetrical fuel cells, the anode polarization resistance decreases with the La3+ dopant increasing, and attains a minimal value of 0.16 W∙cm2 for La0.3SFNM at 750 ℃, followed by a slight increase to 0.17 W∙cm2 for La0.4SFNM. The highest catalytic activity of La0.3SFNM toward electro- oxidation of hydrogen fuels could be ascribed to the synergy between the exsolved Fe-Ni alloy nanoparticulates and the supporting LaxSFNM oxides. Thin La0.9Sr0.1Ga0.8Mg0.2O3 (LSGM) electrolyte fuel cells with La0.3SFNM anodes and SmBa0.5Sr0.5Co2O6 cathodes exhibit the highest power densities, e.g., 1.26, 0.90 and 0.52 W∙cm-2 at 750, 650 and 550 ℃, respectively. These results demonstrate La0.3SFNM oxide as a promising high performance SOFC anode.