Ionic conduction in BaCe0.85 − xZrxEr0.15O3-α and its application to ammonia synthesis at atmospheric pressure
Abstract Dense ceramic samples BaCe 0.85 − x Zr x Er 0.15 O 3-α (0.0 ≤ x ≤ 0.4) have been synthesized by heat-treating the precursor prepared through a microemulsion route. The obtained ceramic samples showed a single phase of orthorhombic perovskite. It was found that the ceramic powders of BaCe 0.85 − x Zr x Er 0.15 O 3-α were relatively stable when x ≥ 0.2 after exposure in 94% N 2  + 3% CO 2  + 3% H 2 O atmosphere at 873.15 K for 20 h. The total conductivities of the ceramic samples decreased with increasing Zr content in the samples in wet hydrogen. Among the ceramic samples studied, BaCe 0.65 Zr 0.2 Er 0.15 O 3-α displayed both a high chemical stability in 94% N 2  + 3% CO 2  + 3% H 2 O atmosphere and an acceptable conductivity at 573.15–1073.15 K. The results indicated that BaCe 0.65 Zr 0.2 Er 0.15 O 3-α was almost pure ionic conductor at 773.15–1073.15 K in wet hydrogen atmosphere. The ionic conduction was contributed mainly by proton with transference numbers of 0.95–0.81 and partially by oxide ion with transference numbers of 0.02 to 0.08. In addition, BaCe 0.65 Zr 0.2 Er 0.15 O 3-α was successfully applied to the ammonia synthesis at atmospheric pressure. The peak ammonia formation rate achieved 3.27 × 10 − 9  mol s − 1  cm − 2 under a direct current of 1.0 mA at 723.15 K.