High performance oxygen permeable membranes with Nb-doped BaBi0.05Co0.95O3−δ perovskite oxides

BaBi0.05Co0.95−xNbxO3−δ (x=0–0.2) and BaBi0.1Co0.8Nb0.1O3–δ were synthesized via solid state reaction method and fabricated into disk-shaped membranes. The surface morphology, phase structure, oxygen nonstoichiometry and oxygen permeability of the perovskite membranes were investigated by SEM, XRD, TGA techniques and oxygen permeation studies. The experimental result indicates Nb-doping can significantly enhance the oxygen permeability compared to the un-doped disk membrane. Among all compositions, BaBi0.05Co0.8Nb0.15O3−δ showed the highest oxygen flux, reaching 2.92 ml cm−2 min−1 with 1.3 mm thickness membrane at 900 °C, coupled with the lowest activation energy, which is 44.17 kJ mol−1 at 750–900 °C and 74.59 kJ mol−1 at 600–750 °C. However, further increasing Nb-doping amount leads to a decrease in the oxygen permeability. Interestingly, the order of tendency towards increasing of oxygen nonstoichiometry with increasing temperature exactly corresponds to the order of oxygen permeation flux of various samples.

► High performance BaBi0.05Co0.95Nb0.15 O3−δ (Nb-doping of 0.15) membrane. ► Highest O2 flux of 2.92 ml cm−2 min−1 (900 °C) with membrane thickness 1.3 mm. ► Lowest Ea of 44.17 kJ mol−1 at 750–900 °C and 74.59 kJ mol−1 at 600–750 °C. ► Increase in tendency of oxygen nonstoichiometry correlates with O2 permeation flux.