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

YBaCo₃ZnO₇ + Gd_0.2Ce_0.8O_1.9 (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.