The Xiamen Symposium on Marine Environmental Sciences (XMAS 2025)

Capturing and converting CO₂ from seawater offers a pathway to achieve net-negative emissions while providing a gigatonne-scale carbon source for the production of synthetic fuels and chemical feedstocks. Currently, CO₂ electrolyzers rely on expensive separation processes to purify the CO₂ feed. In this study, we present a directly coupled reactive capture system that captures dissolve inorganic carbon (DIC) from seawater in the form of CO₂ and electrochemically converts it into syngas. This system eliminates the need for a preliminary CO₂ purification step and produces high-purity syngas with sufficient CO content for direct industrial applications. With the Sm/Ni-N-C electrocatalyst, we attained a 33% Faradaic efficiency for CO at a current of 100 mA and a full-cell voltage of 2.7 V, producing syngas with an H₂/CO ratio close to 2. The system also demonstrated stable operation over a 10-hour period.
 

oceanwater, electrochemical, CO2, syngas