Understanding delamination behavior of air electrode in solid oxide electrolysis cells through in situ monitoring of internal oxygen partial pressure

Abstract

In this study, we monitored the development of internal pO₂ in solid oxide electrolysis cells (SOECs) in situ using an embedded probe and a reference electrode. Three types of air electrode cells were compared: LSM (La_0.8Sr_0.2MnO_3−δ) + YSZ (Y_0.08Zr_0.92O_2−δ), LSCF (La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ) + GDC (Gd-doped ceria) and LSM + GdCeScSZ ((Gd₂O₃)_0.005(CeO₂)_0.005(Sc₂O₃)_0.1(ZrO₂)_0.89). The rate of pO₂ increase with the increase in current density was highest in the LSM + YSZ cell, reaching ∼32201 atm at 0.6 A cm⁻², resulting in air electrode delamination and intergranular fractures. This physically developed delamination with high pO₂ is akin to catastrophic failure, accelerating degradation. The LSCF + GDC cells exhibited a maximum pO₂ of ∼12.25 atm and operated stably without increasing pO₂ or delamination. In the LSM + GdCeScSZ cells, internal pO₂ was substantially suppressed to ∼10⁻³ atm, with a degradation rate comparable to that of the LSCF + GDC cell. However, the air electrode delaminated without intergranular fractures. This chemically developed delamination without high internal pO₂ does not significantly accelerate degradation. These results indicate that the delamination mechanism may vary even with the same LSM electrode, depending on its ionic conduction characteristics.