Green methanol production using green hydrogen and oceanic carbon dioxide: an experimental study

• Integrated H-cell & E-CEM system enables direct ocean CO2 extraction and electrochemical methanol synthesis. • Methanol reached 8.7 mg/L (H-cell) and 4.2 mg/L (integrated) at 7 V, rising with electrolyte concentration. • 900 ppm methane output with 1.5 M electrolyte shows the system's potential for circular carbon utilization. Utilizing the substantial amount of CO 2 dissolved in oceans is recognized as a critical boundary for achieving carbon neutrality. This study introduces a novel, integrated three-compartment electrolytic cation exchange membrane (E-CEM) reactor with an H-cell for the direct capture of CO 2 from ocean water and its subsequent conversion into methanol. The E-CEM component first electrochemically acidifies the water to extract CO 2 , which is then directly fed into the H-cell for synthesis. While component-level tests of the H-cell demonstrated methanol yields reaching 8.7 mg/L at 2.0 M electrolyte, the fully integrated proof-of-concept system successfully produced 4.2 mg/L of methanol at 7 V. This demonstrates a complete and viable pathway from marine carbon to liquid fuel within a single apparatus. This integrated reactor design offers a scalable, green solution for a circular carbon economy, establishing a promising technology for sustainable fuel production directly from marine carbon sources.