Running a Solid Oxide Electrolysis Cell (SOEC) above a critical current can degrade the cell very quickly. Oxygen bubble formation has been observed in the electrolyte near the oxygen electrode, and seems to be a source of this degradation. Applying a load on a SOEC shifts the oxygen potential away from its equilibrium value, driving oxygen ions from the hydrogen to the oxygen electrode.  This, along with the applied current in the presence of a finite but small electronic conductivity in the electrolyte, is responsible for high oxygen potential under the oxygen electrode. The resulting oxygen pressure in the electrolyte can be large, in certain cases much higher than 1 atm.   Furthermore, these high pressures inside the bubble introduce significant stresses in the oxide that can lead to fracture or delamination of the cell.  We address the problem of homogeneous nucleation of bubbles containing oxygen in the electrolyte under conditions of constant current flow and determine the radius of the critical nucleus and the reversible work for the formation of the critical nucleus. The implications of these results for homogeneous nucleation of bubbles in the oxide of a SOEC will be discussed.

Oxygen bubble nucleation in solid oxide electrolysis cells

245th National Meeting (2013)

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