Electrochemical study on co-doped ceria–carbonate composite electrolyte

A co-doped ceria–carbonate (Ce0.8Sm0.2−xCaxO2−δ–Na2CO3) has been synthesized by a co-precipitation method. The detailed electrochemical characterizations (e.g. impedance spectra, polarization curve and IV curves) of this composite material are reported and discussed. The two phase nanocomposite electrolytes with carbonate coated on the co-doped ceria displays dual (H+/O2−) ion conduction at low temperature (300–600 °C) in solid oxide fuel cell. The observed remarkable temperature-dependent of conductivity is attributed to the softening/melting of carbonate phase as the physical state of carbonate phase transforms from solid to molten state. Coexistence of various charge carriers, oxide phase composition, and the oxide–carbonate interfacial area are investigated by Raman spectra. The enhancement of conductivity is also discussed by the general mixing rule/percolation theory of composite interfaces. The co-doping with 2nd phase gives a good approach to realize challenges for solid oxide fuel cell.

► Ceria–carbonate composite electrolyte showed excellent performance, 800 mW cm−2.
► It exhibits high co-ionic (H+/O2−) conductivity at 550 °C even with very low activation energy of 0.238 eV.
► Nanocomposite co-doped ceria–carbonate is a promising electrolyte for LTSOFC.
► General mixing rule verified that the enhanced conductivity is due to interfaces between ceria and carbonates.