Understanding degradation of solid oxide electrolysis cells through modeling of electrochemical potential profiles

[Display omitted] •The maximum aO2 is found at the YSZ/CGO10 interface of a bi-layer electrolyte SOEC.•Operating cyclically between SOFC and SOEC mode can mitigate degradation.•Increasing n- to p-type electrolyte conductivity reduces volume exposed to high aO2.•Reversal of iion and aO2 distribution...

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Bibliographic Details
Published in:Electrochimica acta 2016-01, Vol.189, p.265-282
Main Authors: Chatzichristodoulou, C., Chen, M., Hendriksen, P.V., Jacobsen, T., Mogensen, M.B.
Format: Article
Language:English
Subjects:
bi-layer electrolyte
Current density
Degradation
Electrochemical potential
electrochemical potential profiles
Electrodes
Electrolytes
Electrolytic cells
Mathematical models
modeling
SOEC
Stress concentration
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Summary:[Display omitted] •The maximum aO2 is found at the YSZ/CGO10 interface of a bi-layer electrolyte SOEC.•Operating cyclically between SOFC and SOEC mode can mitigate degradation.•Increasing n- to p-type electrolyte conductivity reduces volume exposed to high aO2.•Reversal of iion and aO2 distribution can occur in heterogeneously degraded cells. Establishing the spatial distribution of the various chemical and electrochemical potentials in an operating SOEC is critical as several degradation mechanisms are tightly connected to them, but at the same time very challenging to achieve experimentally. Such distributions are presented here on the basis of a two dimensional bi-layer electrolyte SOC model including for both electrodes a description of activation, concentration, and conversion losses. An extensive parametric study is reported to illustrate the influence of the electrode polarization resistances, the ionic and electronic conductivities in the electrolyte, the gas composition, temperature, and pressure on the current density distribution over the cell and the oxygen activity distribution within the electrolyte. The developed model is further used to simulate long-term durability experiments during different stages of operation, thereby helping to rationalize microstructural and chemical changes observed in post-mortem analysis. Finally, measures to mitigate degradation by changing conditions of operation, material or electrode properties or overall cell geometry are suggested.
ISSN:0013-4686
1873-3859
DOI:10.1016/j.electacta.2015.12.067