A chemically and mechanically stable dual-phase membrane with high oxygen permeation flux

Abstract

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_0.9Gd_0.1O_2−δ) was added at 70 vol% to LSCF (La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ) in a dual-phase membrane within the electronic threshold for electronic conductivity. A highly active coating material (SrCo_0.1Fe_0.8Nb_0.1O_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 CO₂ 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_0.5Sr_0.5Co_0.8Fe_0.2O_3−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 membranes.