Thin film ceria–bismuth bilayer electrolytes for intermediate temperature solid oxide fuel cells with La0.85Sr0.15MnO3−δ–Y0.25Bi0.75O1.5 cathodes

Abstract Thin film electrolytes of bilayer bismuth oxide/ceria are developed for intermediate temperature solid oxide fuel cells. Y 0.25 Bi 0.75 O 1.5 is deposited via Direct Current magnetron sputtering technique on an Sm 0.2 Ce 0.8 O 1.90 electrolyte film which is prepared by a dry-pressing process on an NiO–Sm 0.2 Ce 0.8 O 1.90 substrate. La 0.85 Sr 0.15 MnO 3− δ –Y 0.25 Bi 0.75 O 1.5 composite is applied onto the Y 0.25 Bi 0.75 O 1.5 film as the cathode to form a single cell. Cells with 6-μm-thick Y 0.25 Bi 0.75 O 1.5 and 26-μm-thick Sm 0.2 Ce 0.8 O 1.90 bilayer electrolytes exhibit improved open circuit voltages and power density compared with those obtained with only Sm 0.2 Ce 0.8 O 1.90 electrolytes. The open circuit voltages are comparable and power densities are higher than those previously reported for solid oxide fuel cells with thick bilayer electrolytes using noble metals such as Pt as the electrodes. Impedance spectra show that the change of electrolyte resistance is negligible while the cathodic interfacial polarization resistance decreased significantly when the Y 0.25 Bi 0.75 O 1.5 layer is added to form the Sm 0.2 Ce 0.8 O 1.90 /Y 0.25 Bi 0.75 O 1.5 bilayer electrolytes.