Cobalt-doped BaZrO 3: A single phase air electrode material for reversible solid oxide cells

Abstract

BaZr 1-xCo xO 3-δ (BZC-x, x = 0.1, 0.2, 0.3, 0.4, 0.5) are prepared and identified as single phase air electrode materials for reversible solid oxide cells. BZC-x shows a typical perovskite structure with x ≤ 0.4, and slight BaCoO 3 second phase is observed with x = 0.5. Conductivity measurements suggest that BZC-x is an oxygen ion and electron mixed conductor in dry oxygen atmosphere. The electronic conductivity of BZC-x increases when increasing Co content in BZC-x specimen, while the ionic conductivity reduces. For BaZr 0.6Co 0.4O 3-δ, the electronic and ionic conductivity are 5.24 S cm -1 and 1.20 × 10 -3 S cm -1, respectively, measured at 700°C in dry oxygen. With BZC-0.4 as a single phase air electrode, the discharging and electrolysis current densities of a single cell are 299 mA cm -2 (at 0.7 V) and -935 mA cm -2 (at 1.5 V), respectively, measured at 700°C. The polarization resistance of cells using this new air electrode is only 0.19 Ω cm 2, approximately 65% lower than that using a traditional Sm 0.5Sr 0.5CoO 3-δ/BaCe 0.5Zr 0.3Y 0.2O 3-δ composite air electrode. © 2012 Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.