Cobalt-doped BaZrO3: A single phase air electrode material for reversible solid oxide cells

BaZr1−xCoxO3−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 BaCoO3 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 BaZr0.6Co0.4O3−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 cm2, approximately 65% lower than that using a traditional Sm0.5Sr0.5CoO3−δ/BaCe0.5Zr0.3Y0.2O3−δ composite air electrode.

► Cobalt-doped BaZrO3 is an ion–electron mixed conductor. ► BaZr0.6Co0.4O3−δ air electrode has good electro-performance. ► Single phase air electrode can improve the reaction rate operating in SOEC mode.