Revealing the degradation mechanism of calcium-based air electrodes in reversible solid oxide cells under chromium contaminants

Abstract

Calcium-based perovskite La_0.6Ca_0.4Fe_0.8Co_0.2O_3-δ (LCFC) with stable structure is the promising air electrode used in reversible solid oxide cells, and its application in cell stack must consider its Cr poisoning resistance ability. Herein, the Cr poisoning effect of it is studied in this work. The results indicate the strong reaction between LCFC and the Cr contaminations, forming undesirable CaCrO₄ impurities, which significantly reduce the activity of ORR/OER. Both the decayed performance and reversible stability are also observed in SOFC and SOEC modes under the Cr contaminations, and the main reason comes from the reduced activity of the oxygen surface exchange processes and the blocked gas diffusion process by the impurities. A worse degenerated performance in SOFC mode than that in SOEC mode is also found in this work. Beyond that, the mechanism of the reaction between chromium contaminants and the Ca-segregation of the electrodes is discussed by the nucleation theory.