A 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 a dual-phase membrane, GDC (Gd-doped ceria, Ce 0.9 Gd 0.1 O 2− δ ) was added at 70 vol% to LSCF (La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3− δ ) in a dual-phase membrane within the electronic threshold for electronic conductivity. A highly active coating material (SrCo 0.1 Fe 0.8 Nb 0.1 O 3− 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 a CO 2 atmosphere. 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 (Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3− δ ) with a similar membrane thickness. The SCFN-coated dual-phase membrane also shows high CO 2 -stability over 200 h and thermo-mechanical stability under rapid thermal cycling (20 °C min −1 ), which cannot be accomplished in single-phase membranes. This contribution details our comprehensive efforts to design a chemically and mechanically stable dual-phase membrane with a high oxygen permeation flux.