Supercapacitor Swing Adsorption of Carbon Dioxide in Positive and Negative scan: An Investigation via Impedance Analysis

The electrochemical route for CO2 storage applies the supercapacitor swing adsorption (SSA) strategy. The CO2 storage is affected by the charging/discharging region. In this work, we applied impedance analysis to estimate the effect of charging/discharging protocols on the CO2 adsorption. Here we considered three regions, only negative (0 V to -1V), only positive (0 V to 1V), and the addition of positive and negative region (1 V to -1 V). The effectiveness of SSA is estimated via the difference in double layer capacitance from high potential to low potential. In negative region, the difference in double layer capacitance from high potential to low potential is lower than that of positive region. It suggests that the SSA in positive region is higher than that of negative region. Though the double layer capacitance is high in negative region, but the difference in double layer capacitance is high in positive region. It is due to the presence of high CO2 at zero potential in negative region, while in positive region very low CO2 is present initially. The low CO2 initially allows large CO2 movement towards the interface from 1 V to 0 V in positive region. On contrary, in negative region, the high CO2 at zero potential allows low CO2 to reach at the interface in negative region. Finally, in the additional (positive and negative) zone, the advantage of low CO2 initially, and high potential for CO2 adsorption enhances the CO2 adsorption.