Figure shows the CO2 concentration with respect to time and voltage for 4 cm 2 electrodes in supercapacitive swing adsorption (SSA) experiments over five cycles. The details of the experimental setup are provided in supporting information (section S6 and Figure ). For each cycle, a decrease in concentration is initially observed as the electrodes are charged. Similarly, an increase in CO2 concentration is observed during discharging the electrodes. At full saturation, the CO2 concentration returns to a value of approximately 15 %, indicating the completion of adsorption/desorption half cycles. An increase in concentration somewhat above 15% near the end of the holding step at -1 V is seen for GP-AC, S-AC, and BPL-AC electrodes. This may be caused by some electro-oxidation of the activated carbon surface while the electrodes are charged during the first few cycles, forming additional CO2. The phenomenon of carbon electro-oxidation is well-known from the related capacitive deionization technology, since the standard reduction potential for carbon oxidation is within the charging potential window. The electrooxidation effect fully disappears after twenty charging-discharging cycles (Figure ), arguing that the irreversible chemical changes at reactive surface functionalities are completed after 20 cycles. The cycling of BPL carbon electrodes over 60 cycles shows consistent CO2 adsorption and desorption behavior and stable SSA performance (Figure ) without any measurable losses. The GCD curves and CO2 concentration profiles in Figure were used to quantitatively evaluate the energetic and adsorptive performance of the electrodes (Figure and Table ). The specific capacitance of the electrodes followed the sequence GR-AC (257 F.g -1 ) > GP-AC (233 F.g -1 ) ≃ S-AC (230 F.g -1 ) > GS-AC (196 F.g -1 ) > Y-AC (135 F.g -1 ) > BPL-AC (85.9 F.g -1 ) (black dots in Figure ). The specific capacitance is correlated with the density of the electrodes which follows the sequence GR-AC (0.19 g.cm -1 ) < GS-AC (0.25 g.cm 3 ) < GP-AC (0.28 g.cm -3 ) < S-AC (0.31 g.cm -3 ) < Y-AC (0.48 g.cm -3 ) = BPL-AC (0.48 g.cm -3 ). Lower density tends to increase gravimetric specific capacitance due to higher porosity, and more effective utilization of the carbon atoms for EDL formation (a greater fraction of the carbon atoms is on a pore surface). GR-AC has the greatest specific capacitance and the lowest density (0.19 g.cm -3 ). BPL-AC and Y-AC have the highest densities and the lowest specific capacitances. An outlier is the GS-AC which has the second-lowest density, but only the fourth-highest specific capacitance. This may be explained by the significantly higher resistance in GS-AC. BPL-AC and Y-AC have the same density, but different specific capacitances, which may be attributed to their different raw materials (bitumen coal and carbide, respectively), and the different activation methods.