Development of anion exchange membrane-based electrochemical CO2 separation cells for direct air capture

Abstract

The use of direct air capture (DAC) technology, which directly captures and removes carbon dioxide (CO₂) from the atmosphere is vital for carbon neutrality. This study investigates the applicability of an electrochemical cell for separating CO₂ using an anion-exchange membrane (AEM) in DAC applications. Anions such as OH⁻, CO₃²⁻, and HCO₃⁻ are conducted through the AEM, and the cell mechanism is determined by the main ion-type transferred. The composition of the gas generated at the anode was analyzed to understand the operating mechanism. Moreover, the operating conditions of the electrochemical cell were optimized to maximize the CO₂-capture ratio. To lower the ohmic resistance of the electrochemical cell containing a dry anode, the cathode was used under excessively humid conditions along with an adequately hydrated AEM. Furthermore, the impact of serpentine and metal-foam flow fields on the cell performance was confirmed by observing the behavior of surplus water droplets on both types of systems. The fabricated device demonstrated a CO₂ capture ratio of 95.7 % with air containing 400 ppm of CO₂, confirming its viability in DAC technology. This study offers guidance for future studies regarding the development of high-performance carbon-capture systems with a widespread applicability.