Development of a Membraneless Flow-Through Electrochemical Cell for Direct Ocean Capture

Abstract Marine carbon dioxide removal via direct ocean capture (DOC) is promising, but current electrochemical DOC systems remain limited by membrane costs and fouling, as well as the difficulty of achieving low energy consumption at industrially relevant current densities. Here, a membraneless electrochemical direct ocean capture (MEC-DOC) platform was developed based on Bi-mediated chloride intercalation chemistry for low-voltage pH-swing operation. Bi-coated carbon-cloth electrodes were characterized, and cell performance was evaluated under galvanostatic operation in unbuffered and bicarbonate-buffered electrolytes using galvano-dynamic and continuous modes. The MEC-DOC operated at 90 A/m2, above several reported DOC operating points and approaching the industrially relevant current-density threshold of 100 A/m2. Proton generation followed the electrode stoichiometry at high Faradaic selectivity, whereas only 59% of the generated acid was delivered to the treated stream. On this measured basis, the continuous mode required 494 kJ/molCO2 (3116 kWh/tonneCO2). These results establish MEC-DOC as a promising membrane-free pathway for scalable DOC.