Understanding degradation of solid oxide electrolysis cells through modeling of electrochemical potential profiles. (20th January 2016)

• Record Type: Journal Article
• Authors: Chatzichristodoulou, C.; Chen, M.; Hendriksen, P.V.; Jacobsen, T.; Mogensen, M.B.
• Is Part Of: Electrochimica acta. Volume 189(2016)
• Page Start: 265
• Page End: 282
• Publication Date: 2016-01-20
• Subjects: SOEC -- degradation -- bi-layer electrolyte -- modeling -- electrochemical potential profiles; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2015.12.067
• Languages: English
• ISSNs: 0013-4686

Abstract

Graphical abstract: Highlights: The maximum a O 2 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 a O 2 . Reversal of i i o n and a O 2 distribution can occur in heterogeneously degraded cells. Abstract: 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.