La0.6Sr0.4Co0.2Fe0.8O3–δ–Ba(Ce,Co,Y)O3–δ composite cathodes for proton-conducting ceramic fuel cells

Abstract

In this study, the applicability of Ba(Ce,Co,Y)O3–δ (BCCY) for a cathode of proton-conducting ceramic fuel cells was investigated. The electrical conductivity and transference number of BCCY were significantly affected by a cobalt content in the oxide. It was found that this material showed a mixed conduction of proton, oxide ion, and electron. The addition of cobalt into Ba(Ce,Y)O3–δ mainly increased the electronic conductivity of materials. Composite electrodes with an optimum composition of La0.6Sr0.4Co0.2Fe0.8O3–δ (LSCF)–BaCe0.7Co0.2Y0.1O3–δ (50:50 wt.%) exhibited lower polarization for the symmetrical cell test with a BaCe0.8Y0.2O3–δ electrolyte in 6.5% humidified oxygen atmosphere, as compared with La0.6Sr0.4Co0.2Fe0.8O3–δ (LSCF) itself and LSCF–BaCe0.9Y0.1O3–δ (50:50 wt.%) composite electrodes. The power generation test was performed at 600°C–700°C using a BaCe0.8Y0.2O3–δ electrolyte-supported single cell employing a LSCF–BaCe0.7Co0.2Y0.1O3–δ (50:50 wt.%) composite cathode, upon feeding 3% humidified hydrogen and pure oxygen to the anode and cathode, respectively. The cell with a LSCF–BaCe0.7Co0.2Y0.1O3–δ (50:50 wt.%) composite cathode exhibited much higher performance than that with a LSCF electrode. Consequently, the introduction of cobalt into Ba(Ce,Y)O3–δ was an effective strategy for an improvement in an oxygen reduction reaction activity of a cathode material.