Highly oxygen-permeable and CO₂-stable Ce_0.8Sm_0.2O_2 − δ-SrCo_0.9Nb_0.1O_3 − δ dual-phase membrane for oxygen separation

Dual-phase composite oxide 60 wt% Ce_0.8Sm_0.2O_2 − δ-40 wt% SrCo_0.9Nb_0.1O_3 − δ (60SDC-40SCN) which exhibits high oxygen permeability and good CO₂ tolerance was developed. X-ray diffraction (XRD) patterns and dense surface topography observed by scanning electron microscopy (SEM) revealed a good compatibility of the two oxides. A high oxygen permeation flux of 1.54 mL min^− 1 cm^− 2 through the as-prepared dual-phase membrane (0.8 mm in thickness) was obtained under the gradient of air/He at 1223 K. In situ high-temperature X-ray diffraction demonstrated that SDC and SCN in 60SDC-40SCN membrane could retain their original phase structure from room temperature to 1223 K in CO₂-containing atmosphere. The oxygen permeation fluxes of 60SDC-40SCN membrane showed a good reversibility when switching the sweep gas between CO₂ and He. Comparing with single-phase SCN membrane, oxygen permeation flux of dual-phase 60SDC-40SCN membrane was more than twice when pure CO₂ acted as the sweep gas, and the oxygen permeation flux could remain stable for 120 h. All the experimental results imply that dual-phase 60SDC-40SCN membrane has a great potential in oxy-fuel combustion process.