Asymmetric Electrosorption in a Bio‐Inspired Reactor Enables Energy Efficient Ocean Carbon Removal

Abstract Ocean carbon removal represents a promising pathway for mitigating residual anthropogenic carbon dioxide (CO 2 ), yet existing methods are constrained by high energy demands and potential ecological risks. Here, inspired by the natural calcification process of corals, we present a bio‐inspired capacitive decarbonization (CDC) reactor that sequesters dissolved inorganic carbon (DIC) from seawater as CaCO 3 using only seawater‐derived Ca 2+ and renewable electricity. The CDC system integrates a Ca 2+ ‐selective electrode with a weak electric field to regulate ion transport and disrupt the hydration shell of Ca 2+ , enhancing its reaction with CO 3 2− . To address the limited concentration of CO 3 2− relative to Ca 2+ in seawater, we introduce an asymmetric electrosorption strategy to preferentially enrich CO 3 2− at the electrode interface, achieving a DIC conversion rate of up to 34% with an ultralow intrinsic electrochemical energy input of 2.5 kJ mol −1 CO 2 for the CDC reactor. The reactor exhibits stable continuous operation for over 100 h without fouling, enabled by spatially decoupled CaCO 3 precipitation. To mitigate the reduction in seawater alkalinity, we introduce a mineral‐assisted re‐alkalinization step that effectively restores pH and supports continued CO 2 absorption. A global integrated analysis model shows the CDC technology could remove up to 11–438 million tonnes of CO 2 by 2050–2100. This work demonstrates a scalable and low‐energy solution for durable ocean carbon removal.