Our group reports an oxygen permeation model that was firstly used to investigate the effect of Ba content in Ba_xSr_1-xCo_0.8Fe_0.2O_3-δ on the oxygen transport kinetics. With the increase of Ba content, the interfacial oxygen exchange resistance constants of both sides decrease quickly and then increase slightly, while bulk diffusion resistance remains monotone decreasing. The improvement of oxygen permeation flux is mainly contributed by the enhancement of interfacial oxygen exchange kinetics. It is inferred that Ba element may play an important role in the interfacial oxygen reactions. This work has been published in AIChE Journal, 2020, 66, 16291.