Chromium Deposition and Poisoning of LSCF and LSM Oxygen Electrodes of Solid Oxide Electrolysis Cells

The degradation of solid oxide electrolysis cells (SOECs) is an issue of both scientific and technical importance. In this study, chromium deposition and poisoning at La_0.8Sr_0.2MnO_3+d (LSM) and La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF) oxygen electrodes are studied under SOEC operation conditions. Significant performance degradation was observed for the reaction in the presence of Fe-Cr alloy metallic interconnect, indicating that presence of gaseous Cr species significnatly poisons and degrades the electrocatalytic activity of LSM and LSCF oxygen electrodes. In the case of LSM electrodes, XRD, XPS and SIMS analysis clearly identified the deposition of SrCrO₄, CrO_2.5 and Cr₂O₃ phases on the YSZ electrolyte surface and LSM electrode inner surface for the reaction under anodic polarization conditions. In the case of LSCF, Cr deposition occurs in the electrode bulk and on the electrode surface, forming SrCrO₄. The results clearly indicate that the Cr deposition is closely related to the increased segregation of SrO species under anodic polarization conditions. The mechanism of the Cr deposition at LSM and LSCF electrodes under SOEC operation conditions is discussed.