A chemically stable electrolyte with a novel sandwiched structure for proton-conducting solid oxide fuel cells (SOFCs)

• A novel sandwiched electrolyte structure was proposed for proton-conducting SOFCs.
• The sandwiched electrolyte showed a good chemical stability.
• Improved fuel cell performance was obtained for stable proton-conducting SOFCs.
• High film conductivity was obtained with the sandwiched electrolyte film.

A chemically stable electrolyte structure was developed for proton-conducting SOFCs by using two layers of stable BaZr0.7Pr0.1Y0.2O3 −δ to sandwich a highly-conductive but unstable BaCe0.8Y0.2O3 −δ electrolyte layer. The sandwiched electrolyte structure showed good chemical stability in both CO2 and H2O atmosphere, indicating that the BZPY layers effectively protect the inner BCY electrolyte, while the BCY electrolyte alone decomposed completely under the same conditions. Fuel cell prototypes fabricated with the sandwiched electrolyte achieved a relatively high performance of 185 mW cm− 2 at 700 °C, with a high electrolyte film conductivity of 4 × 10− 3 S cm− 1 at 600 °C.