Catalytic effects in oxygen permeation through mixed-conductive LSCF perovskite membranes

The porous catalytic layer of perovskites was coated on either surface or both surfaces of the dense membranes of LSCF perovskites with nearly 1-mm thickness, and the catalytic effects on the oxygen permeation flux under the air/He gradient were investigated. The observed catalytic effects were discussed mainly on the basis of the oxygen sorption–desorption capacity (OSDC) of membrane and catalyst materials. The coating on the anode side improved the oxygen flux in any combinations of the membrane and catalyst materials having different OSDC, and an increase in the anode surface area, where oxygen association reaction takes place, is primarily responsible for the enhancement by the anode coating. The effect of the cathode coating, on the other hand, depended significantly on the relative difference in OSDC of the membrane and catalyst materials: for example, the oxygen permeation flux was enhanced and reduced by coating with perovskites having larger and smaller OSDC, respectively. It has turned out that the cathode materials should have large OSDC. The behavior of membranes modified on both sides could be understood in terms of a simple sum of the cathodic and anodic effects.