Electrochemically Modulated CO₂ Removal from Oceanwaters

As the concentration of carbon dioxide is continuously increasing, there have been a lot of efforts to remove CO2 from various sources. While most of the attention has been focused on CO2capture at point sources followed by geological storage, interest in negative emission strategies also increased recently. One of the promising approaches for negative emissions is removing CO2 from ocean water. The world ocean is the largest carbon sink, containing 120 times higher concentration compared to the atmosphere. Therefore, by removing CO2 from ocean water, we can expect a reduction in CO2 concentration in the atmosphere. Considering that the CO2-reduced oceanwater should be returned to the ocean, the addition of chemicals, and the formation of undesirable compounds should be avoided. In this respect, the electrochemical approach can be a good choice because it does not require additional chemicals, and the control of voltage can tune the reactions in the system. Until now, several approaches have been made by using the electrodialysis process. However, the use of bipolar membrane for water dissociation makes this process expensive, making the application of this process sluggish. In this talk, we will present a new membrane-free approach based on electrochemical modulation of the pH to release the CO2 from ocean water. After removing CO2, the treated water is alkalized before being returned to the ocean. Using an electrochemical pH swing approach, we could successfully remove the CO2 from ocean water without employing expensive membrane or additional chemicals.