New route for high oxygen semi-permeation through surface-modified dense La1−xSrxFe1−yGayO3−δ perovskite membranes
Résumé
La1−xSrxFe1−yGayO3−δ perovskite membranes are promising candidates for catalytic membrane reactors applications due to their potential high oxygen semi-permeation fluxes and good chemical stability in working conditions. The oxygen flux through La1−xSrxFe1−yGayO3−δ perovskite membranes is mainly governed by oxygen exchanges at the membrane surface. This work shows how to strongly increase such an oxygen flux while developing a dedicated ultra-divided surface coating. Such a coating is obtained by following a route derived from sol-gel and allowing an elementary grain diameter control in the 5-10 nm range. In this way, the oxygen fluxes through the coated membrane can be increased of more than an order of magnitude in comparison to uncoated membranes. This paper clearly shows that the oxygen flux through the uncoated membrane is governed by oxygen surface exchange, while for coated membranes it is governed by a balance between surface exchange and bulk diffusion. Our surface-modified dense La1−xSrxFe1−yGayO3−δ membranes show good performance in long term in working conditions (high temperature and large oxygen partial pressure gradients).