A series of alkali metal elements doped La2Ce2O7 electrolytes for solid oxide fuel cells

A series of alkali metal elements (like Li, Na, K, Rb, Cs) doped La2Ce2O7 were prepared by a citrate combustion method. We systematically investigated the effects of doping from several aspects, such as structure, conductivity, morphology and performance. All powders of La1.85M0.15Ce2O7-8 (M = Li, Na, K, Rb, Cs) have fluorite structures. The electrical conductivity first increases with the increase of ion radius of doped alkali element, and then decreases with the doping of Cesium. La1.85Rb0.15Ce2O7-8 exhibits the highest conductivity of 3 x 10-3 S cm-1 in dry air and 6.21 x 10-3 S cm-1 in wet H2 at 800 ?C. La1.85Rb0.15Ce2O7-8-based single cell exhibits the highest peak power performance with 1031 mWcm-2 at 700 ?C and the stable discharge time of it is more than 200 h. Thus, Rb-doping La2Ce2O7 material is considered as a promising electrolyte in solid oxide fuel cell.