A Ca and Fe Co-Doped Layered Perovskite as Stable Air Electrode in Solid Oxide Electrolyzer Cells under High-Current Electrolysis

Abstract In this study, the electrochemical performance and the stability of Ca and Fe co-doped SmBaCo 2 O 5+δ , SmBa 0.75 Ca 0.25 CoFeO 5+δ (SBCCF), layered perovskite is examined as the air electrode for solid oxide electrolyzer cells (SOECs). In a half-cell with three-electrode configuration, the initial polarization resistance, R P , of GDC|SBCCF is 0.16 Ω cm 2 at 800 °C. Under an anodic bias of 200 mV, R P decreases to 0.03 Ω cm 2  ; however, under cathodic bias of 200 mV, R P increases to 0.18 Ω cm 2 , indicating that SBCCF is more active towards oxygen evolution reaction than oxygen reduction reaction. During the electrolysis test under 1 A cm −2 at 800 °C for 216 h, R P of GDC|SBCCF increases to 0.52 Ω cm 2 in the first 96 h and remains at 0.52 Ω cm 2 for the remaining 120 h. In contrast, R P of GDC|LSCF increases with a rate of 0.08 Ω cm 2 /100 h at the same time. This result demonstrates that SBCCF is a promising candidate as air electrode in SOECs for stable operation under high electrolysis current, which is critical to achieve high hydrogen production rate and to lower the cost of the system. Effective methods for the improvement of the performance of SBCCF will be developed in future studies.