Performance of Solid Oxide Fuel Cell Using Proton and Oxide Ion Mixed Conductors Based on BaCe1 − x Sm x  O 3 − α

ceramics were synthesized and their ionic conduction was investigated. These ceramics showed protonic and oxide ionic mixed conduction under fuel cell condition. While protonic conduction was predominant below 1027 K, oxide ionic conduction became significant as the temperature increased. Using these oxides as solid electrolyte, hydrogen‐air fuel cell could be constructed. exhibited the best cell performance among the electrolytes examined. The maximum short‐circuit current density was about 900 mA/cm2 at 1273 K. The polarization at each electrode was low. Porous nickel could be used as anode material instead of expensive platinum and as cathode material.