Oxygen transport kinetics of BSCF-based high entropy perovskite membranes

Three high entropy BSCF perovskite membranes were designed by doping various cations into A- and/or B-sites to improve the oxygen permeation stability at 700-800 degrees C. The membrane with the highest mixed entropy (Delta Smix), i.e. HEBSCF-AB, can be operated stably at 750 and 800 degrees C, but unstable at 700 degrees C. To understand the degradation mechanism, the oxygen transport kinetics of the three high entropy perovskite materials were analyzed using the permeation model established by our group. An easy and feasible strategy was proposed to improve the stability of oxygen permeation. We find that the doping site has a significant influence on the bulk diffusion resistance of the membranes but has a weak effect on the interfacial exchange resistances. The continuous attenuation of HEBSCF-AB membrane at 700 degrees C is mainly caused by the increase of interfacial exchange resistance of the sweeping side, revealing the HEBSCF-AB oxide is not a stable catalyst for the oxygen evolution reaction when it is coated on the HEBSCF-AB membrane surfaces. By coating Sm0.5Sr0.5CoO3-delta (SSC) as the porous layer on the HEBSCF-AB surfaces for oxygen activation, the oxygen permeation flux at 700 degrees C becomes stable. It confirms that the simple approach is effective to improve the permeation stability and the high entropy strategy works well to restrain the phase transition of materials.