Phase Stability, Oxygen-Storage Capability, and Electrocatalytic Activity in Solid Oxide Fuel Cells of (Y, In, Ca)BaCo4–yGayO7+δ

Abstract

With an aim of enhancing their high-temperature phase stability, oxygen-storage capability, and electrocatalytic activity in intermediate-temperature solid oxide fuel cells (IT-SOFCs), RBaCo4O7+δ-based samples have been investigated with a co-substitution at the R site with Y, In, and Ca and Ga substitution at the Co site. YBaCo4–yGayO7+δ, Y1–xInxBaCo3.3Ga0.7O7+δ, Y1–xCaxBaCo3.3Ga0.7O7+δ, In1–xCaxBaCo3.3Ga0.7O7+δ, and Y0.5In0.5BaCo4–yGayO7+δ series of materials have been synthesized by a solid-state reaction, and the phase stabilities have been assessed by long-term testing at 600–800 °C for 120 h. The substitution of In for Y mitigates the phase decomposition but decreases the oxygen-storage capacity and electrochemical performance in IT-SOFCs. With In and Y co-dopants, Y0.5In0.5BaCo3.5Ga0.5O7+δ remains stable even with a smaller amount of Ga. In contrast, Ca doping reduces the phase stability regardless of its content. Via optimization of the compositions, Y0.9In0.1BaCo3.3Ga0.7O7+δ is found to exhibit t...