High oxygen permeable and CO2-tolerant SrCoxFe0.9-xNb0.1O3-δ (x = 0.1–0.8) perovskite membranes: Behavior and mechanism

Abstract The oxygen permeability and the CO 2 tolerance of SrCo x Fe 0.9-x Nb 0.1 O 3-δ (x = 0.1–0.8) perovskite membranes were investigated by varying the composition of cobalt and iron in B-site of perovskite oxides. The experimental results show that the oxygen permeability increases while the CO 2 tolerance decreases with increasing doping ratio of cobalt. The mechanism behind this trend was investigated by in situ high temperature XRD, FE-SEM, TGA, FTIR and XPS characterization techniques. These results indicated that basicity of SrCo x Fe 0.9-x Nb 0.1 O 3-δ is enhanced with increasing cobalt doping ratio because of a decrease in overall valence of B-site cations which leads to the decrease in electronegativity. Meanwhile, the decrease of valence for B-site cations also forms more oxygen vacancies which lead to the enhancement of oxygen permeability. With this trade-off between permeability and CO 2 tolerance, it is necessary to balance oxygen permeability and stability under CO 2 atmosphere for different applications. These results provide a guideline for the design of CO 2 tolerant perovskite membrane. SCFN181 (SrCo 0.1 Fe 0.8 Nb 0.1 O 3-δ ) membrane was the most stable in the series of membranes studied. High oxygen permeation flux of 0.6 mL/min/cm 2 for 35 h at 900 °C and 0.26 mL/min/cm 2 flux at 800 °C for subsequent 100 h was achieved through SCFN 181 membrane (1.1 mm-thick) swept by CO 2 . With high permeability and high CO 2 -tolerant properties, SCFN181 membrane can meet the requirements for future industrial applications.