Fabrication of CO₂-tolerant SrFe_0.8Nb_0.2O_3-δ/SrCo_0.9Nb_0.1O_3-δ dual-layer 7-channel hollow fiber membrane by co-spinning and one-step thermal process

CO₂-tolerant membranes are crucial for oxyfuel combustion systems utilizing oxygen permeable membranes. A newly constructed dual-layer 7-channel hollow fiber membrane consisting of SrFe_0.8Nb_0.2O_3-δ (SFN) porous outer layer and SrCo_0.9Nb_0.1O_3-δ (SCN) hollow fiber inner layer has been successfully fabricated by co-spinning and one-step thermal process (OSTP) approach in this work. The outer layer can have different porous structures depending on the graphite content of the spinning solution. In the OSTP approach, the in-situ reactive sintering of the membrane materials results in the two layers being well adhered and mechanically robust. At 900 °C under 80% CO₂-containing in sweeping gas, the oxygen flux of SFN/SCN dual-layer hollow fiber membrane with the porous layer of 91.8 μm was 1.98 mL min⁻¹ cm⁻², about 7.1 times as much as the SCN hollow fiber membrane (0.28 mL min⁻¹ cm⁻²) in the same situations. The porous SFN outer layer was demonstrated to prevent membrane performance degradation effectively. Furthermore, the SFN/SCN dual-layer membrane operated in a 20% CO₂-containing atmosphere for at least 200 h, maintaining an oxygen flux of 3.20 mL min⁻¹ cm⁻² without degradation. As a result of these findings, the SFN/SCN dual-layer 7-channel hollow fiber membrane has significant application potential in CO₂ capture for oxyfuel combustion.