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.