Improving Electrocatalytic Activity and Durability of Cobalt-Free Bismuth Ferrite-Based Perovskite Oxygen Electrode for Reversible Solid Oxide Cells

High electrocatalytic activity and robust thermal/chemical stability in oxygen electrode materials are critical properties for achieving high-performance and long-lifespan reversible solid oxide cells (RSOCs). Herein, a series of rare-earth element-substituted perovskite compounds Bi_0.8−xLn_xCa_0.2FeO_3−δ (Ln = La, Pr, and Nd) are explored as potential oxygen electrode materials. Particular attention is devoted to investigating their crystalline structure, oxygen exchange capabilities, electrocatalytic activity, and chemical durability. The density functional theory results indicate that praseodymium doping induces an increase in oxygen vacancies and reduces the adsorption energy of CO₂, which helps to enhance electrochemical performance and durability. Electrochemical investigations reveal that the cell employing Bi_0.7Pr_0.1Ca_0.2FeO_3−δ (BPCF) as oxygen electrode material achieves a peak power density of 1.278 W cm⁻² and an electrolysis current density of 1.19 A cm⁻² (1.3 V) at 800°C, outperforming most previously reported oxygen electrode materials. Moreover, the praseodymium-doped BPCF oxygen electrode exhibits significantly enhanced resistance to CO₂. This work presents an efficient approach for designing highly active and stable oxygen electrodes for RSOCs.