Oxygen permeation study and improvement of Ba0.5Sr0.5Co0.8Fe0.2Ox perovskite ceramic membranes

Ba0.5Sr0.5Co0.8Fe0.2Ox (BSCF) is a promising mixed conducting material with high oxygen permeability, and has proven to be a good candidate for membrane reactors in air separation and catalytic conversion of CH4. To determine the factors impacting the oxygen permeation through the BSCF membrane, Pt, Ag catalysts were coated on the membrane surface using photolithography and electron beam evaporation methods. The results showed that the coated catalysts did not increase the oxygen flux of BSCF within the studied thickness range. However, the oxygen flux increased as the thickness of the membrane decreased. To further enhance the oxygen flux, a BSCF membrane with asymmetric geometry was prepared using a dry-pressing method. The effects of the porous substrate and the dense thin layer on the performance of the BSCF asymmetric membrane were studied. The results showed that the oxygen flux increased as the thickness of thin dense layer decreased. Further analysis indicated that the porous substrate still appears to exert a resistance on the oxygen permeation through the membrane.

Research highlights▶ Coating catalysts did not enhance oxygen flux for BSCF membranes with thickness greater than 1.85 mm and further analysis showed BSCF membrane to be bulk diffusion limited. ▶ Asymmetric BSCF membranes, containing one thin dense layer supported on the porous substrate, were successfully prepared by citrate-EDTA and dry-pressing method. ▶ As compared to BSCF dense membranes, the oxygen fluxes of BSCF asymmetric membranes were enhanced substantially, which was attributed to decreasing the constraining effect of bulk diffusion on the permeation. ▶ Adding carbon fiber with ethyl cellulose created a partially connected network of pores which resulted in enhanced oxygen permeation.