ELECTROCHEMICAL CARBON DIOXIDE CAPTURE TO CLOSE THE CARBON CYCLE

This supporting information provides additional data, calculations, and correlations to the main text in three


Solubility of CO2(g) and carbonate minerals
The underlying correlations for obtaining Figure 4.a and b of the main paper are given here.
Subsequently, the values of the solubility product (i.e., Ksp) of the three main forms of calcium carbonate minerals and the effect of temperature and pH on Ksp are provided.

Electrical energy consumption for CO2(g) capture: Electrolysis vs. BPMED
In this section, the underlying assumptions and calculations for obtaining Figure 14 of the main article body are provided. The aim here is to compare the electrical energy required for the CO2(g) capture and recovery using a pH-swing generated via (membrane) electrolysis and BPMED. As an example, the magnitude of pH swing here is considered to be ∆pH = 14. The required voltage (hence the energy consumption) of both methods depends strongly on the magnitude of the applied ∆pH. Note that a milder ∆pH can enable lower energy consumptions.
Using both electrolysis and BPMED, 1 mole of OH − and 1 mole of H + per mole of electron can be produced. Assuming the following reactions, each produced OH − (or H + ) ion, contributes to 1 mole of CO2(g) being captured (or recovered):  According to the Faraday's law, the electric quantity (Q) to produce 1 mole CO2(g) is 1 Faraday constant (F = 96485 C/mol). The energy involved in the pH swing can be calculate from eq. 11 from the main paper: Assuming the Coulombic efficiency for the acid-base production is 100%, the energy consumption per mole of capture CO2 (g) can then be calculated via E = F ⋅ V The required voltage for (membrane) electrolysis can be written as [7]: is the standard anode potential for oxygen evolution reaction (OER), ℎ 0 is the standard cathode potential for hydrogen evolution reaction (HER), i is the applied current density, is the total ohmic resistivity and 2/ 2 is the over potential at the anode and Standard cell potential Over-potential Ohmic losses cathode for OER and HER (i.e., the Tafel plot). The estimated value for each term is given in Table 1.S below.
Similarly, the required voltage for BPMED can be written as [8]- [10]: Where ∆pH is the difference of the pH over the BPM and is the over potential associated with the water dissociation reaction in the junction layer of the BPM. The estimated value for each term is given in Table 2.S below.
For the calculations, electrochemical cells as shown in Figure   a) (Membrane) electrolysis: The standard cell potential, E cell 0 according for the water redox is as follow: • Cathode: .
at pH=0 3. The ohmic voltage drop is ∑ , where R tot = R e + R m + R b + R c as shown in Table   1.S: Nernstian potential based on the reversible free enthalpy Over-potential Ohmic losses a) b)
Ex-situ here means that a neutral salt stream (e.g., NaCl) is used to produce high purity NaOH and HCl in BPMED. The produced acid and base are then used for CO2(g) capture and recovery in external gas absorption and desorption steps. 3. i ∑ R: The ohmic voltage losses can be estimated as shown in Table 2.S.