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 SmBaCo2O5+δ, SmBa0.75Ca0.25CoFeO5+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, RP, of GDC|SBCCF is 0.16Ωcm2 at 800°C. Under an anodic bias of 200mV, RP decreases to 0.03Ωcm2 ; however, under cathodic bias of 200mV, RP increases to 0.18Ωcm2, indicating that SBCCF is more active towards oxygen evolution reaction than oxygen reduction reaction. During the electrolysis test under 1Acm−2 at 800°C for 216h, RP of GDC|SBCCF increases to 0.52Ωcm2 in the first 96h and remains at 0.52Ωcm2 for the remaining 120h. In contrast, RP of GDC|LSCF increases with a rate of 0.08Ωcm2/100h 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.