Electrochemically Regenerated Solvent for Direct Air Capture with Cogeneration of Hydrogen at Bench-scale

Project Objectives To achieve ≥90% CO2 capture from atmosphere, UK CAER is developing an intensified, cost-effective, and easily scalable process using aqueous KOH as capture solvent for direct air capture (DAC), featuring the use of a hybrid membrane absorber (MA) coupled with an electrochemical solvent regenerator (ER) that is capable of extracting carbon dioxide (CO2) from atmosphere, pre-concentrating KOH solvent followed by regenerating the solvent to release CO2 in the ER, and simultaneously refreshing the capture solvent while producing hydrogen (H2) to offset the DAC cost. To accomplish the proposed process, 3 objectives are targeted including: (1) developing a 2-unit process operation with ≥90% CO2 capture at gaseous pressure drop ≤0.2 psi in the MA while regenerating CO2 at ≤2.7 V in the ER by using a catalytic electrode and/or a desired concentration of capture solvent with internal recirculation, (2) achieving H+/K+ crossover (through a cation-exchange membrane) ratio of ≤15% in the ER by optimizing a flow channel design, thickness of a spacer, and/or a cation-exchange membrane, and (3) demonstrating a continuous and reliable DAC pilot process at the air flowrate of 10 cfm with ≥90% CO2 capture efficiency for ≥48 hours through parametric studies, thereby earning the data for next-scale development.