Improvement of oxygen permeation in perovskite hollow fibre membranes by the enhanced surface exchange kinetics

La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) perovskite hollow fibre membranes with an asymmetric structure were fabricated by the phase inversion–sintering technique. The oxygen permeation flux is increased noticeably due to the porous inner surface. Additional coating of a porous perovskite layer as a promoter on the inner and/or outer surfaces of the LSCF hollow fibres further promotes the oxygen permeation due to the acceleration of the surface exchange kinetics. Several typical perovskites such as SrCo0.8Fe0.2O3−δ (SCFe), Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF), SrCo0.9Sc0.1O3−δ (SCSc), SrCo0.9Nb0.1O3−δ (SCNb) as well as LSCF itself were used as the promoters. The permeation results indicate that the oxygen permeation flux of the LSCF hollow fibre membranes has been further improved remarkably by the surface-coating modification. The enhancing effect of the SrCoO3−δ (SC)-based perovskites on oxygen permeation follows the order of SCSc>BSCF>SCNb∼SCFe>LSCF. This coating strategy can be applied to evaluate the catalytic activity of the perovskites to surface exchange reactions for the preparation of oxygen permeable membranes. Coating of the perovskites on the downstream membrane surface exhibits better enhancement than on the upstream membrane surface, but coating on both membrane surfaces may promote the oxygen permeation to the largest extent. By combing the individual advantages of different perovskite oxides, the resultant composite membranes may be of high permeability, high mechanical strength and high stability.