CO₂ and water vapor-tolerant yttria stabilized bismuth oxide (YSB) membranes with external short circuit for oxygen separation with CO₂ capture at intermediate temperatures

Yttria stabilized bismuth oxide (YSB) membranes were prepared using a self-made YSB powder with sintering temperatures down to 750°C. The membrane was characterized by SEM, porosity measurement, electrochemical impedance measurement and composition detection by plasma-optical emission spectrometry. The prepared membranes were tested for air separation under a new concept in the field-pure ion conductor with external short circuit. The influences of CO₂ and water vapor in the sweep gas on the O₂ permeation behavior of the resultant YSB membranes have been investigated. The O₂ permeation fluxes of the YSB membrane decreased with increasing the CO₂ concentration in the sweep gas. Such flux decline is a very normal phenomenon due to the strong chemical adsorption of CO₂ to the membrane surface. YSB can withstand the presence of CO₂ atmospheres at high temperatures without causing any reaction between the two phases. More interesting is that, contrary to the negative effect of the water vapor on other membranes like perovskite, the presence of H₂O is beneficial for O₂ permeation through the YSB membrane. The maximum oxygen flux achieved was 1.33mlcm^-2min^-1 at 850°C for the YSB membrane with a thickness of 1mm. Thin-film membrane technology and surface modification can help to further improve the O₂ fluxes to be of practical interest.