Contribution of the surface reactions to the overall oxygen permeation of the mixed conducting membranes

Oxygen permeation through a mixed conducting membrane is essentially controlled by both the bulk diffusion and the surface reactions on the both sides of the membrane; therefore, it is important to know the proportion of surface reactions in the overall oxygen permeation to improve the oxygen permeability of membranes effectively. In this study, the contribution of surface reactions to the overall oxygen permeation was investigated in detail through the calculation and the oxygen permeation measurement of the noncoated or coated SrCo_0.4Fe_0.5Zr_0.1O _3-δ (SCFZ) mixed conducting membranes. The contribution of the surface reactions to the overall oxygen permeation was observed to increase with decreases in the membrane thickness for both the noncoated and coated membranes, and that the contribution of the surface reactions was significantly reduced by coating a porous layer. The effect of applying a porous layer on the permeate side (low oxygen partial pressure) on the decrease of the contribution of the surface reactions was more remarkable than that on the feed side (high oxygen partial pressure).