Electrochemical pH‐Swing CO 2 Capture Facilitated by Suppressed Bubble Accumulation at Electrode/Electrolyte Interfaces

Abstract Electrochemical CO 2 capture features high modularity and low system complexity. When the pH swing produced by electrolysis reactions acts as the driving force of CO 2 capture, the entire process is further endowed with enhanced tolerance to poisoning. Nevertheless, the correlation between the type of electrolysis reaction and electrochemical CO 2 capture efficiency remains poorly understood, rendering the reactor inefficient. Here, we show that the behavior of gas bubbles exerts a strong influence on CO 2 capture rates and Faradaic efficiencies. We demonstrate that eliminating bubble accumulation by suppressing H 2 evolution at the cathode/electrolyte interface facilitates CO 2 capture, which ensures the access of CO 2 to the alkaline electrode surfaces. We devise a polymer‐electrolyte CO 2 capture reactor utilizing oxygen reduction as the driving force and the cation effect to reduce the activity of H 2 formation. The system offers a capture rate of 1.40 ± 0.03 mL CO2 min −1 cm −2 at 220 mA cm −2 with a Faradaic efficiency of 83.7 ± 1.9% and poisoning resistance to O 2 and impurities in simulated flue gases. In direct air capture (DAC) mode, the reactor achieves a capture rate of about 0.029 mL CO2 min −1 cm −2 and a stable 200‐h operation at approximately 0.019 mL CO2 min −1 cm −2 and 0.95 V, outperforming existing electrochemical DAC devices.