Co-free triple perovskite La1.5Ba1.5Cu3O7±δ as a promising air electrode material for solid oxide fuel cells

La1.5Ba1.5Cu3O7 +/-delta (LBCu) complex oxide is evaluated as a Co-free candidate air electrode material for reversible Solid Oxide Cells (rSOC). LBCu is structurally and thermomechanically compatible with La0.8Sr0.2Ga0.8Mg0.2O3-delta (LSGM) electrolyte, maintains the layered (tripled along the c-axis) perovskite-related crystal structure at high temperatures, and shows reduced chemical expansion with the faster elongation ongoing perpendicular to the a-b plane. Its total thermal expansion is found to be moderate comparing to the Co-based perovskites. The onset temperature of the oxygen release from the material is low, ca. 300 degrees C in air, however, up to 800 degrees C the average oxidation state of copper remains above +2 in the oxidative atmospheres. The total electrical conductivity of LBCu correlates with the oxygen content, with the maximum of about 55-75 S cm(-1) at ca. 350 degrees C in air. Functional LBCu air electrodes can be manufactured at temperatures as low as 750-800 degrees C, with exceptionally low (for Co-free material) polarization resistance values of 0.019 Omega cm(2) at 750 degrees C, 0.041 Omega cm(2) at 700 degrees C, and 0.090 Omega cm(2) at 650 degrees C. Relatively high power output, ca. 162 mW cm(-2) at 600 degrees C, and above 458 mW cm(-2) at 750 degrees C is obtained for the laboratory-scale LSGM-supported cell.

Automated summary

The LBCu complex oxide is evaluated as a Co-free candidate air electrode material for reversible Solid Oxide Cells (rSOC). It is structurally and thermomechanically compatible with the LSGM electrolyte and maintains a layered perovskite crystal structure at high temperatures. LBCu exhibits moderate thermal expansion and its electrical conductivity correlates with the oxygen content. Functional LBCu air electrodes can be manufactured at relatively low temperatures and exhibit low polarization resistance values.