• MnO2 electrode
• thermodynamic modeling
• proton concentration process
• electrochemical cell
• CO2 capture

A proton concentration electrochemical process was developed here as an alternative approach for carbon dioxide (CO2) capture. The pH sensitivity of the CO2 hydration was employed in which it can be absorbed as bicarbonate and carbonate ions at high pH and be desorbed as gas at low pH. The absorption was performed through an absorber operating with a potassium carbonate solution, while the desorption was carried in the anode compartment of an electrochemical cell where the decrease of solution pH is made by a pseudocapacitance electrode (MnO2). A comprehensive thermodynamic model was developed to determine all the speciation and the electrochemical behavior of the system. Chemical and electrochemical measurements were performed to validate the developed model, and the results showed a very good agreement between the simulated results and experimental values. MnO2 electrode was synthesized using a co-precipitation method followed by casting on either carbon cloth or carbon felt substrates. The fabricated electrodes were characterized using X-ray photoelectron spectroscopy (XPS) to assess their chemical state, where the formation of MnO2 was confirmed. The capacitance behavior of the electrodes, which is proportional to their electrochemical performance, was evaluated using cyclic voltammetry (CV). The fabricated electrodes were also tested in a symmetrical electrochemical cell where a constant potential was applied across the cell. An alternative electrodeposition strategy was employed for the fabrication of improved MnO2 electrodes. A comprehensive study to optimize the electrode fabrication by electrodeposition was done. Several experimental measurements were performed to investigate the electrodes. For example, the electrochemical performance was evaluated using electrochemical impedance spectroscopy, CV, chronoamperometry. The morphological and chemical state of the fabricated electrodes were also investigated using scanning electron microscopy and XPS. Overall, the demonstrated model and experimental data suggest that this proton concentration process could be an attractive electrochemical-based route for CO2 capture.