Electrochemical properties of reduced-temperature SOFCs with mixed ionic–electronic conductors in electrodes and/or interlayers

We have investigated the electrochemical properties of two types of reduced-temperature solid oxide fuel cells (SOFCs) in which the mixed ionic–electronic conductors are used to improve their performances. Electrolyte-supported cells, in which doped LaGaO3 strengthened by Al2O3 dispersion is used as the electrolyte, were prepared and tested. Samaria-doped ceria (SDC) interlayers of 0.3-μm thickness were fired onto both surfaces of the electrolyte of 0.2-mm thickness at 1523 K, before firing the Ni–Sm0.1Ce0.9O1.95–(CeO2)0.1[(Y2O3)0.08(ZrO2)0.92]0.9 (Ni–SDC–CeYSZ) (10 mol% ceria-doped yttria-stabilized zirconia [YSZ]) cermet anode at 1723 K and La0.7Sr0.3Co0.2Fe0.8O3–Sm0.2Ce0.8O1.9 (LSCF–SDC) composite cathode at 1373 K. The cells have a nominal size of 60×60 mm2 with an effective electrode area of 4 cm2. The single cell thus prepared showed a high power density of 0.67 W cm−2 at 1073 K and long-term stability during the operation time of 1000 h. Anode-supported cells with a thin YSZ electrolyte film approximately 30 μm thick were also prepared by co-sintering of screen-printed YSZ paste on a compacted anode substrate. The cells have a nominal size of 50×50 mm2 with an effective electrode area of 4 cm2. The single cell with the LSCF–SDC composite cathode having SDC interlayer showed the maximum power density of 0.648 W cm−2 at 1023 K. The bilayer cathode also showed high resistance against degradation by Cr-poisoning.