Selection of Oxygen Permeation Models for Different Mixed Ionic-Electronic Conducting Membranes

Permeation data of several mixed ionic-electronic conducting (MIEC) membranes were analyzed by two oxygen permeation models (i.e., Zhu's model and Xu-Thomson's model), respectively, to find a concise method to guide the choice of permeation models. We found that Zhu's model can well fit the permeation data of perovskite-type membranes, like Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) and BaCe0.05Fe0.95O3-delta (BCF), and dual-phase membranes, like 75 wt % Ce0.85Sm0.15O1.925-25 wt % Sm0.6Sr0.4Al0.3Fe0.7O3-delta (SDC-SSAF), whose oxygen vacancy concentrations are almost independent of the oxygen partial pressure at elevated temperatures. However, Zhu's model was not appropriate for membranes whose oxygen vacancy concentration changed obviously with oxygen partial pressure at elevated temperatures, such as La0.6Sr0.4Co0.2Fe0.8O3-delta (LSCF) and La0.7Sr0.3CoO3-delta (LSC). On the contrary, XuThomson's model can fit the data of LSCF and LSC well, but it is inapplicable for BSCF, BCF, and SDC-SSAF. Therefore, the dependence of oxygen vacancy concentration on oxygen partial pressure was suggested as an index for the selection of the permeation models. (C) 2017 American Institute of Chemical Engineers