CO2-tolerance and oxygen permeability of novel cobalt-free mixed-conductor oxygen-permeable Pr0.6Sr0.4Fe1-xNbxO3-δ membranes

A series of novel cobalt-free dense oxygen-permeable membranes of the type with Pr0.6Sr0.4Fe1-xNbxO3-δ (PSFNx, x = 0-0.1) were synthesized. Subsequently, the effects of Nb-doping on the microstructure, oxygen permeability, and stability of PSFNx were studied under a pure He or CO2 atmosphere. The structure of the material did not change in either atmospheres and its stability of the material was enhanced as the level of Nb-doping increased. For the sample with x = 0 and 0.075, carbonates and sulfates were present on the sweep side of the PSF membrane, but no impurities were detected on the sweep side of the PSFN0.075. In addition, the oxygen-permeation performance exhibited almost no attenuation when the Nb-doping content were 0.075. As revealed by X-ray photoelectron spectroscopy, the CO2 resistance of the material was enhanced by reducing the basicity of PSFNx, which was induced by the substitution of Fe with Nb.