Degradation mechanism of electrolyte and air electrode in solid oxide electrolysis cells operating at high polarization
- Degradation mechanism of electrolyte and air electrode in solid oxide electrolysis cells operating at high polarization
- 김정희; 지호일; 다사리하리; 신동욱; 송휴섭; 이종호; 김병국; 제해준; 이해원; 윤경중
- solid oxide electrolyzer; impedance spectroscopy; anodic current; degradation; densification
- Issue Date
- International journal of hydrogen energy
- VOL 38, NO 3, 1225-1235
- Degradation mechanism of the electrolyte and air electrode is reported for solid oxide
electrolysis cells (SOECs). Symmetric cells composed of yttria-stabilized zirconia (YSZ)
electrolyte, Sr-doped LaMnO3±δ (LSM)/YSZ composite working and counter electrodes, and
Pt ring-type reference electrode are used to simulate the operating conditions of the air
electrode. Degradation behavior in the impedance spectra is characterized as growth of
mid-frequency arc at the initial stage, gradual increase of ohmic resistance throughout the
operation, and sharp rise of low frequency resistance at the final stage, followed by catastrophic
cell failure. Initial stage degradation is attributed to deactivation of LSM, resulting
from reduction of oxygen vacancy concentration and/or segregation of passivation species
on LSM surface under anodic current passage. Intergranular fracture, which occurs along
the grain boundaries of the YSZ electrolyte, is responsible for gradual increase of ohmic
resistance. Increase of low frequency arc at the final stage is caused by densification of the
air electrode, leading to excessive pressure build-up and delamination of the air electrode.
Cation migration, which is facilitated by oxygen excess nonstoichiometry of LSM and
externally applied electric field, is considered to be the main cause of permanent damages.
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