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

Abstract The protonic material La 2 Ce 2 O 7 exhibits good tolerance to H 2 O and CO 2 compared to BaCeO 3 -based materials and has become increasingly popular for operation at low-to-intermediate temperatures in protonic ceramic fuel cells. In this work, doping La 2 Ce 2 O 7 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 La 2- x Na x Ce 2 O 7- δ samples have a cubic structure. The La 2- x Na x Ce 2 O 7- δ pellets are characterized by scanning electron microscopy and are observed to be dense without holes. The effects of Na-doping on the La 2 Ce 2 O 7 electrical conductivity are carefully investigated in air at 350–800 °C and 5%H 2 -95% Ar environments at 350–700 °C. It is found that different levels of Na doping in La 2 Ce 2 O 7 are conducive to improving the electrical conductivity and sinterability. Among the pellets, La 1.85 Na 0.15 Ce 2 O 7- δ exhibited the highest electrical conductivity in air and 5% H 2 -95% Ar atmospheres. Anode-supported half cells with La 1.85 Na 0.15 Ce 2 O 7- δ 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 °C. The results demonstrate that La 1.85 Na 0.15 Ce 2 O 7- δ is a promising proton electrolyte with high conductivity and sufficient sinterability for use in protonic ceramic fuel cells operating at reduced temperatures.