Evaluation of (Bi0.4Sr0.6)xCo0.3Fe0.7O3−δ (x = 0.7, 0.8, 0.9, 1.0, 1.1) perovskite-type oxide as potential cathode for intermediate-temperature solid oxide fuel cells

Abstract

Perovskite-type (Bi0.4Sr0.6)xCo0.3Fe0.7O3−δ (BiSCF) oxides with various A-site proportions (x = 0.7, 0.8, 0.9, 1.0 and 1.1, denoted as BiSCF407, BiSCF408, BiSCF409, BiSCF410 and BiSCF411, respectively) have been developed and investigated as cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The crystal structure of the BiSCF sample is refined based on the Pm-3m space group with perfectly cubic structure (a = a0). The cells with thick La0.8Sr0.2Ga0.8Mg0.2O3−σ (LSGM) electrolyte (0.5 mm thickness) and symmetrical BiSCF electrodes are fabricated for electrocatalaytic activity test and it is found that the cell with BiSCF408 shows the lowest polarization resistance of 0.10 Ω cm2 at 700 °C. The LSGM electrolyte-supported (∼300 μm thickness) cell with BiSCF408 cathode exhibits power densities of 0.34 and 0.46 W cm−2 at 650 and 700 °C, respectively, with humidified H2 (∼3% H2O) as the fuel and ambient air as the oxidant. Over 100 h stability test at 600 °C indicates that a little performance decrease occurs but no interfacial damage happens even after the long-term operation, suggesting that BiSCF408 is a potential material for IT-SOFCs.