Enhanced Oxygen Separation through Robust Freeze‐Cast Bilayered Dual‐Phase Membranes

Dual‐phase oxygen‐permeable asymmetric membranes with enhanced oxygen permeation were prepared by combining freeze‐casting, screen‐printing, and constraint‐sintering techniques. The membranes were evaluated under oxyfuel operating conditions. The prepared membranes are composed of an original ice‐templated La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3− δ support with hierarchically oriented porosity and a top fully densified bilayered coating comprising a 10 μm‐thick La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3− δ layer and a top protective 8 μm‐thick layer made of an optimized NiFe 2 O 4 /Ce 0.8 Tb 0.2 O 2− δ composite synthesized by the one‐pot Pechini method. Preliminary analysis confirmed the thermochemical compatibility of the three involved phases at high temperature without any additional phase detected. This membrane exhibited a promising oxygen permeation value of 4.8 mL min −1  cm −2 at 1000 °C upon using Ar and air as the sweep and feed gases, respectively. Mimicking oxyfuel operating conditions by switching argon to pure CO 2 as a sweep gas at 1000 °C and air as feed enabled an oxygen flux value of 5.6 mL min −1  cm −2 to be reached. Finally, under the same conditions and increasing the oxygen partial pressure to 0.1 MPa in the feed, the oxygen permeation reached 12 mL min −1  cm −2 . The influence of CO 2 content in the sweep gas was studied and its reversible and positive effect over oxygen permeation at temperatures equal to or above 950 °C was revealed. Finally, the membrane stability over a period of 150 h under CO 2 ‐rich sweep gas showed a low degradation rate of 2.4×10 −2  mL min −1  cm −2 per day.