Silver-molten carbonate composite as a new high-flux membrane for electrochemical separation of CO2 from flue gas

One of the major concerns of consuming fossil fuels to produce useful form of energy is the emission of CO2, a greenhouse gas that can cause climate change and ultimately threaten the survival of humanity. Controlling CO2-emission is an urgent but only practical solution to stabilize CO2 concentration in the atmosphere. In this paper, we report our effort to capture CO2 from a simulated flue gas by utilizing a dual-phase mixed carbonate-ion and electron conducting membrane, namely molten carbonate and silver. The obtained CO2 and O2 flux densities are the highest among the published metal-molten carbonate systems and relatively stable over 80-h period. The measured CO2 and O2 flux densities not only exhibit similar activation energy but also have the ratio of 2:1, favorably confirming the surface electrochemical reaction of CO2 + 1/2O2 + 2e′ = CO32−. These results demonstrate the Ag–MC dual-phase composite as a promising high-flux membrane for high-temperature electrochemical CO2 separation from flue gas with high selectivity.

► A new silver and molten carbonate dual-phase membrane for CO2 separation is reported for the first time. ► Highest CO2 flux density is achieved compared to all metal-molten carbonate systems reported. ► Excellent chemical compatibility between silver and molten carbonate. ► The permeation characteristics of CO2 and O2 confirm the electrochemical transport mechanism of electrons and carbonate-ions. ► Long-term flux behavior is interpreted by silver sintering mechanism.