Application of the mixed potential theory to the oxygen permeation process through dense ceramic membranes

摘要

We used the mixed potential theory to study the oxygen permeationprocess through dense ceramic membranes. Using a short-circuited yttria-stabilized zirconia disk to simulate a mixed conducting membrane, the oxygen permeation flux was shown to correspond to the intersection of the anodic and cathodic polarization curves on the Evans diagram. The diagram showed that the oxygen flux did not increase much when the oxygen in the permeate side was lowered to below a certain threshold. The effect was clearly seen to be due to the decrease of the surface exchange current density with decreasing oxygen partial pressures. In the presence of combustible gases, the situation reversed. New reaction mechanisms were observed.