Relationships between the Elemental Composition of Electrolytes and the Supercapacitive Swing Adsorption of CO₂

The adsorptive and energetic performances for supercapacitive swing adsorption of CO2 from 15% CO2/85% N2 gas mixtures in the presence of different 1.0 M aqueous electrolytes with variable cations (LiCl, KCl, MgCl2) and anions (NaF, NaBr, NaHCO3, Na2SO4) relative to 1.0 M NaCl as benchmark were determined. The adsorption and energetics for all investigated electrolytes are surprisingly similar; however, there is a somewhat greater dependence on the anions compared to the cations. The combination of the best-performing cation (Mg2+) and anion (Br–) in an MgBr2 electrolyte led to best synergistic behavior and overall best performance. In addition, seawater was also found a suitable electrolyte performing similarly to the pure salt electrolytes. The results indicate that the liquid–solid mechanism of CO2 adsorption occurs primarily at the positive electrode.