Preparation and performance of Na-doped La2Ce2O7 electrolytes for protonic ceramic fuel cells

The protonic material La2Ce2O7 exhibits good tolerance to H2O and CO2 compared to BaCeO3-based materials and has become increasingly popular for operation at low-to-intermediate temperatures in protonic ceramic fuel cells. In this work, doping La2Ce2O7 with Na in a series with varying compositions is studied. All of the precursors are prepared by a common citrate-nitrate combustion method. X-ray diffraction images reveal that all of the La2-xNaxCe2O7.delta samples have a cubic structure. The La2-xNaxCe2O7.delta pellets are characterized by scanning electron microscopy and are observed to be dense without holes. The effects of Na-doping on the La2Ce2O7 electrical conductivity are carefully investigated in air at 350-800 degrees C and 5%H-2-95% Ar environments at 350-700 degrees C. It is found that different levels of Na doping in La2Ce2O7 are conducive to improving the electrical conductivity and sinterability. Among the pellets, La1.85Na0.15Ce2O7.delta exhibited the highest electrical conductivity in air and 55/a H-2-95% Ar atmospheres. Anode-supported half cells with La1.85Na0.15Ce2O7.delta electrolyte are also fabricated via a dry-pressing process, and the corresponding single cell exhibited a desirable power performance of 501 mW cm(-2) at 700 degrees C. The results demonstrate that La1.85Na0.15Ce2O7.delta is a promising proton electrolyte with high conductivity and sufficient sinterability for use in protonic ceramic fuel cells operating at reduced temperatures.