A novel heterogeneous La_0.8Sr_0.2CoO_3−δ/(La_0.5Sr_0.5)₂CoO_4+δ dual-phase membrane for oxygen separation

Dual-phase membrane is an attractive concept that combines the advantages of two different phases into single membrane matrix. The recently reported significant enhancement of oxygen surface kinetics on the La_0.8Sr_0.2CoO_3−δ (LSC)/(La_0.5Sr_0.5)₂CoO_4+δ (LSC₂₁₄) hetero-interface due to the formation of fast oxygen transport paths along hetero-interface is adopted into dual-phase membrane to achieve enhanced oxygen permeability. The 1300°C sintered LSC/LSC₂₁₄ (4:1 weight ratio) hollow fiber displayed a maximum oxygen flux of 3.35 ml·min⁻¹·cm⁻² at 900°C and 200 ml min⁻¹ helium sweep gas flow rate, which represents up to 80% enhancement relative to that of the 1300°C sintered LSC hollow fiber at the same experimental condition. Such enhancement is enabled by the enlargement of triple phase boundaries to larger areas across the membrane surface for dual-phase case as confirmed by the significantly lower area specific resistance for LSC/LSC₂₁₄|Ce_0.8Sm_0.2O_1.9 (SDC)|LSC/LSC₂₁₄ relative to LSC|SDC|LSC symmetrical cell between 600°C and 800°C. This nominal dual-phase LSC/LSC₂₁₄ hollow fiber also showed very stable fluxes of 3.3 and 2.3 ml·min⁻¹·cm⁻² during 300-hr permeation test at 900°C and 850°C, respectively.