Ionic Conduction and Fuel Cell Performance of Ba0.97Ce0.8Ho0.2O3 Ceramic

Abstract

The perovskite-type-oxide solid solution Ba0.97Ce0.8Ho0.2O3 was prepared by high temperature solid-state reaction and its single-phase character was confirmed by X-ray diffraction. The ionic conduction of the sample was investigated using electrical methods at elevated temperatures, and the performance of the hydrogen-air fuel cell using the sample as solid electrolyte was measured, which were compared with those of BaCe0.8Ho0.2O3. In wet hydrogen, BaCe0.8Ho0.2O3 almost exhibits pure protonic conduction at 600-1000 C, and its protonic transport number is 1 at 600-900 C and 0.99 at 1000 C. Similarly, Ba0.97Ce0.8Ho0.2O3 exhibits pure protonic conduction with the protonic transport number of 1 at 600-700 C, but its protonic conduction is slightly lower than that of BaCe0.8Ho0.2O3, and the protonic transport number are 0.99-0.96 at 800-1000 C. In wet air, the two samples both show low protonic and oxide ionic conduction. For Ba0.97Ce0.8Ho0.2O3, the protonic and oxide ionic transport numbers are 0.01-0.11 and 0.30-0.31 respectively, and for BaCe0.8Ho0.2O3, 0.01-0.09 and 0.27-0.33 respectively. Ionic conductivities of Ba0.97Ce0.8Ho0.2O3 are higher than those of BaCe0.8Ho0.2O3 under wet hydrogen and wet air. The performance of the fuel cell using Ba0.97Ce0.8Ho0.2O3 as solid electrolyte is better than that of BaCe0.8Ho0.2O3. At 1000 C, its maximum short-circuit current density and power output density are 465 mA/cm2 and 112 mW/cm2, respectively.