Properties and Application of Ceramic BaCe0.8Ho0.2O3−α

Ceramic BaCe0.8Ho0.2O3−α with orthorhombic perovskite structure was prepared by conventional solid state reaction, and its conductivity and ionic transport number were measured by ac impedance spectroscopy and gas concentration cell methods in the temperature range of 600–1000 °C in wet hydrogen and wet air, respectively. Using the ceramics as solid electrolyte and porous platinum as electrodes, the hydrogen‐air fuel cell was constructed, and the cell performance at temperature from 600–1000 °C was examined. The results indicate that the specimen was a pure protonic conductor with the protonic transport number of 1 at temperature from 600–900 °C in wet hydrogen, a mixed conductor of proton and electron with the protonic transport number of 0.99 at 1000 °C. The electronic conduction could be neglected in this case, thus the total conductivity in wet hydrogen was approximately regarded as protonic conductivity. In wet air, the specimen was a mixed conductor of proton, oxide ion and electron hole. The protonic transport numbers were 0.01–0.09, and the oxide‐ionic transport numbers were 0.27–0.32. The oxide ionic conductivity was increased with the increase of temperature, but the protonic conductivity displayed a maximum at 900 °C, due to the combined increase in mobility and depletion of the carriers. The fuel cell could work stably. At 1000 °C, the maximum short‐circuit current density and power output density were 346 mA/cm2 and 80 mW/cm2, respectively.