Electrochemical characterization of YBaCo3ZnO7+Gd0.2Ce0.8O1.9 composite cathodes for intermediate temperature solid oxide fuel cells

Abstract

YBaCo3ZnO7 + Gd0.2Ce0.8O1.9 (GDC) composites with various GDC contents (0–70 wt.%) have been investigated as cathode materials for intermediate temperature solid oxide fuel cells (SOFC). The effect of GDC incorporation on the microstructure, electrochemical properties, and thermal expansion behavior of the YBaCo3ZnO7 + GDC composites has been studied. The composite cathodes consist of smaller particles with larger surface area compared to the pure YBaCo3ZnO7 cathode, which is beneficial for providing extended triple-phase boundary (TPB) where the oxygen reduction reaction (ORR) occurs. Among the various compositions investigated, the YBaCo3ZnO7 + GDC (50:50 wt.%) composite is found to be optimum with the lowest polarization resistance (0.28 Ω cm2 at 600 °C) compared to that of pure YBaCo3ZnO7 (0.62 Ω cm2 at 600 °C). Anode-supported single cell SOFC fabricated with the YBaCo3ZnO7 + GDC (50:50 wt.%) composite cathode also exhibits excellent performance with a maximum power density of 743 mW/cm2 at 750 °C. Additionally, the YBaCo3ZnO7 + GDC (50:50 wt.%) composite shows a low thermal expansion coefficient (TEC) of 10.7 × 10−6 °C−1, which provides good compatibility with those of standard SOFC electrolytes.