Surface modified silver-carbonate mixed conducting membranes for high flux CO2 separation with enhanced stability

• Al2O3 colloidal coating is used to improve the wettability between molten carbonate and silver matrix.
• Higher and more stable CO2 flux density is achieved over the uncoated sample.
• The permeation characteristics of CO2 and O2 explicitly confirm the electrochemical transport mechanism of e− and CO32−.

In this paper, we demonstrate that a silver-carbonate CO2 permeation membrane with the surface of silver matrix modified by a thin coating of Al2O3 can effectively improve the flux stability over an extended period. The CO2 and O2 flux densities reached 0.39 ml cm−2 min−1 and 0.20 ml cm−2 min−1 at 650 °C, respectively, and maintained >90% of its original values for 130 h. This is in contrast with the untreated membrane in which only one-third of the original values can be retained even after 60 h. Overall, surface modification of silver matrix by a thin layer of Al2O3 coating is demonstrated as a viable method to fabricate stable silver-carbonate membranes for electrochemical CO2 capture from flue gas.