We here report a mechanistic investigation into the electrochemical transport of CO2 through a dense metal-carbonate membrane. The investigation studied a total of six possible charge-transfer mechanisms involving CO32-, O-2(2-), O2- and CO52- as the active surface species, and derived the corresponding flux equation from each mechanism. The experimental CO2 flux densities measured under a range of chemical gradients were used to verify each mechanism by plotting the flux density against the corresponding flux expression of each mechanism. The results showed that CO42- scheme is the best mechanism to describe the electrochemical CO2 transport through the metal-carbonate membranes. A new transport model was also shown to describe the CO42- migration and charge-transfer. (C) 2014 Elsevier B.V. All rights reserved.