Chromium-Induced Interfacial Deactivation in SOFCs under Practical Conditions: Mechanistic Insights into Chromium Sources and Current Load Effects

Chromium (Cr)-induced interfacial deactivation remains a critical challenge to the long-term stability of solid oxide fuel cells (SOFCs), particularly when using La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) as the cathode. In this work, the degradation behavior of SOFCs is systematically studied by varying the Cr sources (Cr₂O₃ powder and SUS430 alloy) and current densities (0.2 and 0.5 A cm^-2). The correlation between Cr volatilization rate and performance loss confirms that using Cr₂O₃ powder as the Cr source accelerates deposition and leads to more severe cathode degradation. Thus, Cr₂O₃ powder is suitable for accelerated aging tests. The results reveal that Cr deposition primarily and significantly suppresses the oxygen surface exchange and bulk diffusion processes in the LSCF cathode. Furthermore, SEM-EDS mapping confirms enhanced Cr and Sr migration toward the electrolyte under a high current load. These findings demonstrate the critical roles of Cr source volatility and electrochemical polarization in Cr-induced degradation, providing valuable mechanistic insight for developing Cr-tolerant electrodes and optimizing SOFC operation.