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The increasing CO2 concentrations in the atmosphere has lead to the overall increase of the temperature of Earth leading to global warming. Therefore there is a dire need for the carbon dioxide conversion technologies. Recently, an electrochemical process was developed for regenerating the alkaline solution in the wet scrubbing process for DAC application, and pure CO2 gas could be recovered that is suitable for storage or utilization. The process is based on a H2 -recycling electrochemical system (HRES).
The electrochemical cell contains three compartments: an anode region (A), an acidifying region (B), and a cathode region (C). They are separated by ion-selective permeable membranes M1 and M2. During the operation, protons produced from H2 oxidation at the anode are transported to the acidifying compartment where the spent solution (Na2CO3 -NaHCO3 ) coming from the air contactor is fed. The decreasing pH of the solution leads to the conversions of carbonate to hydrocarbonate (reaction 1) and hydrocarbonate to carbonic acid (reaction 2). When the solution is saturated by dissolved CO2 (solubility: 0.033 mol L−1 ), a further pH decrease leads to the release of CO2 gas (reaction 3). H2 generated in the cathode is introduced to the anode and the solution from the cathode can be reused as a DAC absorbent.
Based on the given information answer the following questions
1) What are the electrode reactions in the anode (A) and the cathode (C) respectively. Write the balanced equations for the reactions 1–3 in the acidifying region (B).
2) If the cell works at a steady state when the current passing through the cell is 2.00 A and the flow rate of the solution (0.050 mol L−1 Na2CO3 - 0.10 mol L−1 NaHCO3 ) into the region B is 10.0 mL min−1 . The pH in the anode compartment is maintained at 1 in the steady state. Calculate the generation rate of CO2 gas (in mmol min−1 ).
3) Considering that the gaseous product formed after electroreduction of Carbon dioxide is CO, which is used as a reactant to produce acetic acid in the presence of Rh(CO)2I2 catalyst. In the third step of the mechanism, predict which group will be migrated and the number of electrons at the Rh centre.