Effect of A-site lanthanum doping on the CO2 tolerance of SrCo0.8Fe0.2O3−-δ oxygen-transporting membranes

• Published in: Journal of membrane science 2013-06, Vol.437, p.122-130
• Main Authors: Klande, Tobias, Ravkina, Olga, Feldhoff, Armin
• Format: Article
• Language: English
• Subjects: air; artificial membranes; Carbon dioxide; Chemistry; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; helium; In-situ X-ray diffraction; lanthanum; Long-term oxygen permeation; Membranes; microstructure; oxygen; Oxygen-transporting membrane; phase transition; powders; scanning electron microscopy; sol-gel processing; temperature; Transmission electron microscopy; X-ray diffraction
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2013.02.051

The SrCo0.8Fe0.2O3−δ (SCF) perovskite was systematically doped with increasing lanthanum content up to 60wt% on the A-site to investigate the effect on CO2 tolerance. Different powders were prepared by a sol-gel method and the materials were characterized by in-situ X-ray diffraction (XRD) and long-term oxygen permeation measurements in CO2-containing atmospheres. The microstructure was investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). All powders exhibit cubic perovskite structure except the rhombohedral La0.6Sr0.4Co0.8Fe0.2O3−δ (LSCF 6482), which however, shows a phase transition into cubic perovskite structure at higher temperature. By doping 20wt% lanthanum, the tolerance against CO2 is considerably increased and doping with 60wt% lanthanum resulted in a stable oxygen permeation performance in CO2 atmosphere for at least 200h. Oxygen permeation experiments in an air/helium gradient showed that with increasing lanthanum content the oxygen permeation flux decreases. Microstructure analysis of the membranes after CO2 operation showed that the carbonate preferentially forms a dense layer at the carbon dioxide exposed sweep side of the membranes. ► In-situ high-temperature observation of formation and phase transition of SrCO3. ► Electron energy-loss spectroscopy (EELS) fine structures of SrCO3. ► La0.6Sr0.4Co0.8Fe0.2O3−δ (LSCF 6482) can be operated at least for 200h when pure CO2 as sweep gas is used.