UC Irvine

Oceans are a natural carbon dioxide capture medium, requiring a pH swing to be activated and regenerated. To generate this pH swing, we demonstrate an ion-exchange membrane-free electrochemical cell that produces acid via anodic hydrogen oxidation and base via cathodic hydrogen evolution, achieving current densities of up to 500 mA/cm2. To keep theoretical voltages low, the electrodes are connected via hydrogen gas lines so that no net hydrogen is consumed or produced. Because the system is symmetric, we show that by alternating the electrode polarities, we can prevent electrode fouling from dication precipitation and operate the cell for an hour with simulated ocean water. Overall, we show that a hydrogen-looping device can be constructed without expensive and failure-prone ion-exchange membranes, resulting in an efficient, inexpensive, and durable system for generating acid and base. Acid and base are essential in direct ocean capture of carbon dioxide and other methods of carbon capture.