Preparation of oxygen evolution layer/La_0.6Ca_0.4CoO₃ dense membrane/porous support asymmetric structure for high-performance oxygen permeation

An asymmetric-structured membrane, in which a dense thin La_0.6Ca_0.4CoO₃ layer of 10 μm was deposited on porous La_0.6Ca_0.4CoO₃ support by a slurry dropping method, were tested for its oxygen permeability at 630-930 °C. In order to increase the oxygen permeability, porous La_0.6Ca_0.4CoO₃ and SrCo_0.8Fe_0.2O_{3 - δ} oxygen evolution layers were attached on the dense layer. It was found that the asymmetric structured membranes with the porous oxygen evolution layers showed remarkably higher oxygen permeability as compared with a conventional sintered disk-type membrane (1200 μm). This suggests that oxygen permeation through membranes of 10 μm in thickness is rate-determined by both bulk O^2- diffusion and oxygen evolution reaction. The maximum oxygen permeability reached 4.77 cm³ (STP) min^{- 1} cm^{- 2} (3.54 × 10^{- 6} mol cm^{- 2} s^{- 1}) at 930 °C for the asymmetric membrane with porous La_0.6Ca_0.4CoO₃ oxygen evolution layer of 10 μm in thickness (STP = Standard Temperature and Pressure). Further improvements in the oxygen permeability would be achieved through control of the micro-structure of the oxygen evolution layers.