Zirconia based electrolytes reactions with cathodes

It can be concluded therefore that at 1273°K, a cathodic overpotential of 1.228V (with reference to an electrode maintained at an oxygen partial pressure of 1 atm.) should be sufficient to initiate a reaction between the platinum electrode and the zirconia based electrolyte... 

The electrolyte used by the fuel cell is a solid gas—impermeable zirconia known as zirconium oxide (ZrOj). This ZrOj is doped with calcium oxide (CaO) to supply enough oxide ions to carry the cell current. The oxidant air or oxygen is bubbled through the molten silver cathode, which is held inside the zirconia cup. At the fuel electrode or the carbon-based anode electrode, the oxide ions are combined with carbon monoxide (CO) and give up their electrons to an external circuit. The cell by-products CO and hydrogen, which are formed in the initial fuel decomposition, are burned outside the cell to keep the fuel cell at operating temperature. The hydrogen is not involved in the electrochemical cell reaction. 

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