Thermodynamic Stability Assessment of MIEC Cathode Materials for Solid Oxide Fuel Cells

Mixed ionic-electronic conductor (MIEC) cathode materials such as La_(1-x)Sr_xCo_0.2Fe_0.8O_3-δ (LSCF,where x=0.2, 0.3, 0.4), Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF 5582), Sr₂Fe_1.5Mo_0.5O_6-δ (SFMO), La₂NiO_4+δ (LNO), GdBaCo₂O_6-δ (GBCO), and PrBaCo₂O_6-δ (PBCO) exhibit excellent oxygen transport properties as well as high electronic conductivity at operational temperatures of SOFCs. Their promising electrochemical performance make these materials excellent candidates for potential application as SOFC cathodes. However, their long-term thermodynamic stability in the operating environment of SOFCs, including unexpected and uncommon situations such as CO₂-leakage from the anodic side is of concern and should be thoroughly investigated prior to deploying them in cells and stacks.

This study investigates the thermodynamic stability of promising SOFC cathodes under operating conditions, in molten salt media, and through galvanic cell measurements. The cathode materials of interest are La_(1-x)Sr_xCo_0.2Fe_0.8O_3-δ (LSCF, where x=0.2, 0.3, 0.4), Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF 5582), Sr₂Fe_1.5Mo_0.5O_6-δ (SFMO), La₂NiO_4+δ (LNO), GdBaCo₂O_6-δ (GBCO), and PrBaCo₂O_6-δ (PBCO). The stability of these materials is studied in air and at various CO₂ partial pressures.