Effective Precipitate Cleaning with a Reversible Flow Cell Sustains Stable Energy Intensity for Oceanic CO₂ Removal

Our study focuses on an experimental demonstration of a novel method for CO₂ removal from ocean water, which has captured up to 40% of all anthropogenically released CO₂ emissions, that combines H₂ and redox salt looping to induce pH swings in electrochemical flow cells. Model-driven design optimization guides 3-D printed electrolyte flow channel designs to alleviate mass-transfer limitations. A ridged flow channel with 1 mm thick fins protruding at an angle of 30° from the base reduces ferri-/ferro-cyanide redox salt concentration boundary layer thickness by up to 35% while restricting the pressure drop to less than 415 Pa. A notable feature of this work is the experimental validation of the intrinsic operando cleaning capabilities enabled by the reversible looping process, eliminating what would otherwise be process down time. Over 4 acidification/basification cycles, 86% removal of fouling from electrode surfaces is demonstrated, while distinctly maintaining a constant electrochemical energy intensity. The lab-scale, proof-of-concept experimental demonstration shows promising results, which are interpreted to provide insights and guidelines toward further enhancing scalability and efficiency of oceanic carbon removal and utilization processes.