Electrochemical approaches for direct ocean capture of CO2: Status, challenges, and future perspectives

Direct ocean capture (DOC) is an emerging and comparatively underexplored approach within the broader portfolio of negative emissions technologies (NETs). Ensuring its rapid yet responsible advancement requires rigorous evaluation of its performance, feasibility, and environmental impact. This review provides a comprehensive synthesis of electrochemical DOC by integrating insights from ocean carbonate chemistry, electrochemical system design, materials science, and carbon accounting. It critically examines the strengths and limitations of documented system configurations and introduces a KPI-based framework to evaluate deployment-relevant performance, including energy consumption, carbon removal efficiency, system throughput, durability, and monitoring, reporting, and verification (MRV) uncertainty. By explicitly linking physicochemical constraints, such as carbonate buffering, ion transport, and air–sea CO2 exchange, to engineering performance and system-level feasibility, the review identifies the dominant bottlenecks limiting DOC scale-up beyond laboratory and pilot systems. In addition, it evaluates pathways for process optimization, integration with renewable energy, and co-location with coastal infrastructure to improve techno-economic performance. A structured set of research priorities is developed by mapping these bottlenecks to deployment-critical performance metrics, providing a forward-looking perspective on how DOC can transition from experimental systems to scalable implementation. Collectively, this work supports informed decision-making and contributes a mechanism-to-deployment framework to guide the development of electrochemical DOC as a potentially scalable, durable, and verifiable ocean-based carbon dioxide removal (CDR) pathway.