Chromium-Induced Interfacial Deactivation in SOFCs under Practical Conditions: Mechanistic Insights into Chromium...

Area of Science:

• Electrochemistry
• Materials Science
• Chemical Engineering

Background:

• Interfacial deactivation caused by chromium (Cr) is a major challenge for the long-term stability of solid oxide fuel cells (SOFCs).
• La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ (LSCF) is a commonly used cathode material susceptible to Cr-induced degradation.

Purpose of the Study:

• To systematically investigate the degradation behavior of SOFCs under varying chromium sources and current densities.
• To elucidate the mechanisms of Cr-induced degradation in LSCF cathodes.

Main Methods:

• SOFCs were degraded using different Cr sources (Cr₂O₃ powder and SUS430 alloy) at various current densities (0.2 and 0.5 A cm^-2).
• Performance loss was correlated with Cr volatilization rates.
• Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS) mapping was used to analyze Cr and Sr migration.

Main Results:

• Using Cr₂O₃ powder as the Cr source accelerated Cr deposition and led to more severe cathode degradation compared to SUS430 alloy.
• Cr deposition was found to suppress oxygen surface exchange and bulk diffusion processes in the LSCF cathode.
• High current density promoted Cr and Sr migration towards the electrolyte.

Conclusions:

• The volatility of the Cr source and electrochemical polarization are critical factors in Cr-induced SOFC degradation.
• Cr₂O₃ powder is suitable for accelerated aging tests to study SOFC degradation.
• Understanding these mechanisms provides insights for developing Cr-tolerant electrodes and optimizing SOFC operation.