Introductory information Filename (filenames correspond to the nomenclature used for the figures in the manuscript): Figure 3: in this file there are data of impedance spectra of the porous CGO13S1 substrates (refered as 'skeleton') and corresponding composites, in air, at 250 and 600 °C. Figure 4(a): in this file there are data of carbon dioxide flux through the CGO13S1-1 composite membranes as a function of temperature, for different carbon dioxide contents in the feed-side inlet. Figure 4(b): Carbon dioxide flux (Jv) through the CGO13S2-1 (b) composite membranes as a function of temperature, for different carbon dioxide contents in the feed-side inlet Figure 5: in this file there are data of the flux of carbon dioxide measured versus time for the CGO13S1-2 composite membrane. Figure 6(a,b): in this file there are data (a) of molten carbonates (tNLC) versus the ambipolar conductivity (samb) at 600 and 700 °C, for variable oxide content (60–95 vol% with 5% increments) and (b) samb as a function of temperature for distinct oxide contents. Figure 7(a): in this file there are data of tNLC versus samb derived from impedance spectroscopy data obtained with composite membranes, magnified range covering 600, 650 and 700 °C. Figure 7(b): in this file there are data of tNLC versus samb derived from impedance spectroscopy data obtained with composite membranes for full range plot (only for 700 °C data). Figure 8(a,b): in this file there are data of potential versun current density (Evans-type diagrams) for the performance of CGO13S1 (a) and CGO13S2 (b) membranes. Figure 8(c,d): in this file there are data of potential versun current density (Evans-type diagrams) for the performance of CGO13S1 (c) and CGO13S2 (d) membranes. Figure 9: in this file there are data of partial pressure of nitrogen in the permeate-side outlet versus temperature. Figure 11: in this file there are data of impedance spectra at 250 °C in air of similar CGO porous skeletons after impedance (CGO13S1-3), permeation (CGO13S1-1) and endurance (CGO13S1-2). Dates of data collection: January 2015 - May 2016 Key words used to describe the data topic: CO2 permeation, impedance spectroscopy, ambipolar conductivity, membrane endurance, Composite electrolytes Data handling: All raw data handled as described in the manuscript or following standard procedures for similar conditions.