Promoting CO2 Release from CO3 2−-Containing Solvents during Water Electrolysis for Direct Air Capture

Abstract

The pH swings from water electrolysis are leveraged to condition OH−-based facile CO2 capture solvents using an electrochemical flow cell for direct air capture (DAC). Besides demonstrating the DAC using a membrane contactor, promoting CO2 release from a CO3 2− solution at the anode is specifically studied by adjusting the volumetric flow rate, anode chamber volume, residence time, and K2CO3 concentration. Through case-by-case comparisons coupled with modeled results, increasing current, reducing volumetric flow rate, and/or reducing CO3 2− concentration are the effective methods to promote CO2 release from a CO3 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 K2CO3 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 CO2 capture.