Chemically and mechanically stable dual-phase membrane with high oxygen permeation flux
This contribution details our comprehensive efforts to design a chemically and mechanically stable dual-phase membrane with a high oxygen permeation flux. To enhance the mechanical and thermo-mechanical strength of the dual-phase membrane, GDC (Gd-doped ceria, Ce0.9Gd0.1O2-δ) was added at 70 vol.% to LSCF (La0.6Sr0.4Co0.2Fe0.8O3-δ) in a dual-phase membrane within the electronic threshold for electronic conductivity. The highly active coating material (SrCo0.1Fe0.8Nb0.1O3-δ, SCFN) was adopted in consideration of the relationship between the bulk diffusion (D) and surface exchange kinetics (k) of the dual-phase membrane, resulting in not only a high oxygen flux but also chemical stability in CO2. The highest oxygen permeation flux obtained was 10.41 mL·cm-2·min-1 at 1000 °C in the SCFN-coated dual-phase membrane; this is above the techno-economic target (5-10 mL·cm-2·min-1) for the commercialization of oxygen transport membranes (OTMs) and comparable to that of BSCF (Ba0.5Sr0.5Co0.8Fe0.2O3-δ) with a similar membrane thickness. The SCFN-coated dual-phase membrane also shows high CO2-stability over 200 h and thermo-mechanical stability under rapid thermal cycling (20 °C·min-1), which cannot be accomplished in single-phase membrane.