Iron-doping effects on the CO2 tolerance of a perovskite oxygen permeable membrane

Bao.8La0.2Co0.88-x Fe (x) Nb0.12O3-delta membranes (BLCFN) with different Fe-doping were successfully prepared by solid-state reaction method. The microstructure, oxygen permeability, thermal analysis, and oxygen permeation stability using CO2 as sweep gas were systematically investigated. After being calcined under pure CO2, BLCFN membranes remain their major perovskite phase but diffraction peaks of BaCO3, CoO appeared on the membranes which Fe content is less than 0.2. Apparent activation energy of oxygen permeation are around 60-70 kJ/mol for all membranes. With the increase of Fe-doping content, the flux through BLCFN membranes decreases but the degradation of oxygen flux becomes less pronounced when CO2 is used as sweep gas at 850 A degrees C. Enhanced CO2 resistance of the perovskite would be resulted from an increasing average binding energy due to the Fe-doping. For the membrane where the Fe-doped content equals to 0.2, the oxygen permeation flux is 0.96 mL cm(-2) min(-1) at 900 A degrees C with He sweeping. When using pure CO2 as sweep gas, the oxygen permeation flux decreases slightly in the first 50 h and then reaches a steady state of similar to 0.31 mL cm(-2) min(-1) for more than 60 h in a prolonged continuous oxygen operation. The observations indicated that a stable oxygen permeation could be realized by suitable elemental doping in a single perovskite membrane.