Inversion of oxygen potential transitions at grain boundaries of SOFC/SOEC electrolytes

TL;DR

This paper investigates oxygen potential transitions at grain boundaries in SOFC/SOEC electrolytes, revealing an inversion phenomenon that suggests a different transport mechanism, which is crucial for understanding electrolyte degradation.

Contribution

It uncovers an inversion of oxygen potential transitions at grain boundaries, indicating a new transport mechanism for electronic charge carriers in SOFC/SOEC electrolytes.

Findings

Large oxygen potential gradients at grain boundaries.

Inversion of oxygen potential transitions observed.

Implications for electrolyte degradation mechanisms.

Abstract

Solid oxide fuel/electrolyzer cell (SOFC/SOEC) converts energy between chemical and electrical forms inversely. Yet electrolyte degradation takes place much more severe for SOEC than SOFC during long-term operations. By solving transport equations, we found very large oxygen potential gradients and sharp oxygen potential transitions at grain boundaries of polycrystalline SOFC/SOEC electrolyte. Surprisingly, an inversion of oxygen potential transitions was identified, suggesting a fundamentally different transport mechanism for minor electronic charge carriers. Such findings could be critical to understand and eliminate SOFC/SOEC degradations in practical applications.