Promoting CO 2 Release from CO 3 2− -Containing Solvents during Water Electrolysis for Direct Air Capture

Abstract

The pH swings from water electrolysis are leveraged to condition OH − -based facile CO 2 capture solvents using an electrochemical flow cell for direct air capture (DAC). Besides demonstrating the DAC using a membrane contactor, promoting CO 2 release from a CO 3 2− solution at the anode is specifically studied by adjusting the volumetric flow rate, anode chamber volume, residence time, and K 2 CO 3 concentration. Through case-by-case comparisons coupled with modeled results, increasing current, reducing volumetric flow rate, and/or reducing CO 3 2− concentration are the effective methods to promote CO 2 release from a CO 3 2− -containing solvent, whereas enlarging the anode chamber volume poses a minor effect. Moreover, the discrepancies between the experimental and modeled results may be caused by H + crossover rather than K + transport through the Nafion membrane during water electrolysis based upon the total alkalinity measurements for the K 2 CO 3 solutions gleaned from the anode. It is believed that such results will provide guidance to design and operate an electrochemical flow cell for electrochemistry-assisted DAC and point source CO 2 capture.