Surface exchange model for ITM membrane in transient stage

International audience; Mixed Ionic and Electronic Conductors (MIECs) are promising membrane materials for oxygen separation fromair at high temperature. The transient stage is critical due to the stress induced by the chemical strain, combinedwith the oxygen activity field through the membrane. In the literature, permeation models are able to predict theoxygen flux in steady state or to identify the slowest mechanism. In this paper, the proposed model aims topredict the oxygen activity fields through the membrane both in transient stage and steady state. A macroscopicapproach is proposed, the balance of a temporary species is introduced to take into account separately thedissociative adsorption, associative desorption and interface reaction between surface and bulk. New densitiesof probability are proposed to model dissociative adsorption and associative desorption in order to take intoaccount the difference between “classical” catalysis and the MIECs case. This model is implementing in the finiteelement software COMSOL Multiphysics© thanks to the combination of the modules “coefficient form PDE”and “coefficient form boundary PDE”. The results of the model are in good agreement with steady state andtransient stage experimental data. The different kinetics of oxygen release and oxygen intake are wellreproduced.