Landskron et al. initially proposed three mechanisms to explain how supercapacitors may capture CO2. First, the gas-solid mechanism assumes that CO2 is captured in the empty pores of the carbon electrodes upon charging (i.e. pores not filled with electrolyte take up CO2). Second, the molecular liquid-solid mechanism proposes that neutral CO2 is captured in the electrolyte-filled pores of the carbon electrodes upon charging. Finally, the ionic liquid-solid mechanism suggests that the CO2 forms negatively charged bicarbonate ions that are stored in the electric double layer in the electrolyte at the positive electrode upon charging. This latter process can occur because CO2 is in equilibrium with carbonate and bicarbonate in the presence of water (Equation ).