Theoretical Verification Necessity of Leakage Currents Using Sm Doped Ceria Electrolytes in SOFCs

ABSTRACT

Numerous approaches have been made to solve the basic transport equation that describes a solid oxide fuel cell (SOFC) with mixed conduction. Classically, the open circuit voltage (OCV) is calculated with Wagner‘s equation, which is right within the limits of linear transport theory. In order to generalize Wagner’s equation, many models have been proposed to describe the current-voltage relation in mixed ionic electronic solid conductors (MIEC) using constant field approximation to calculate an electronic current. However, experimental verification necessity of leakage currents in SOFCs using Sm doped Ceria electrolytes has already been pointed out both qualitatively and in quantities. Using the constant field approximation, the limits of linear transport theory can not be clear. In this report, a new model is expressed without using the constant field approximation. This model follows from Wagner’s equation and continuity. The calculated electronic current for doped Ceria electrolyte matches the values calculated using conventional models. But the electrical field near the cathode is large enough to cause dielectric breakdown which has never been reported. Continuity is not deniable, so there are limitations in Wagner’s equation, coming from the limits of linear transport theory.

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