Rational Design of Two-Layer Fe-Doped PrBa 0.8 Ca 0.2 Co 2 O 6−δ Double Perovskite Oxides for High-Performance Fuel Cell Cathodes

A solid oxide fuel cell (SOFC) offers an attractive route to convert chemical energy into electrical energy; however, its commercial application is often limited by the large mismatch in thermal expansion coefficients (TECs) between the cathode and electrolyte and the insufficient activity of cathodes. Fe-doped PrBa 0.8 Ca 0.2 Co 2 O 6−δ (PBCC) are promising cathode materials due to their high conductivity and excellent oxygen-reduction activity, in which Fe doping in PBCC can decrease the TEC to achieve better compatibility with the electrolyte, but excessive Fe will inhibit the oxygen kinetics. Here, we construct a two-layer PBCC cathode (TLC), which consists of a high Fe content layer with good thermal compatibility to electrolytes and a low Fe content layer with high ionic and electronic conductivity. Compared to homogeneous PBCC electrodes, the cell with TLC has a lower activation energy and a higher peak power density (1259.3 mW cm –2 at 700 °C). Meanwhile, it exhibits admirable stability up to 200 h in constant potential mode (0.8 V), and importantly, no discernible degradation is observed in further stability tests in the constant current mode (444 mA cm –2 ) for 200 h. The results reveal that the TLC based on double perovskite Fe-doping isostructural oxide is a promising candidate electrode for SOFC.