Electrochemical pH-Swing CO₂ Capture Facilitated by Suppressed Bubble Accumulation at Electrode/Electrolyte...

Electrochemical CO₂ capture features high modularity and low system complexity. When the pH swing produced by electrolysis reactions acts as the driving force of CO₂ capture, the entire process is further endowed with enhanced tolerance to poisoning. Nevertheless, the correlation between the type of electrolysis reaction and electrochemical CO₂ capture efficiency remains poorly understood, rendering the reactor inefficient. Here, we show that the behavior of gas bubbles exerts a strong influence on CO₂ capture rates and Faradaic efficiencies. We demonstrate that eliminating bubble accumulation by suppressing H₂ evolution at the cathode/electrolyte interface facilitates CO₂ capture, which ensures the access of CO₂ to the alkaline electrode surfaces. We devise a polymer-electrolyte CO₂ capture reactor utilizing oxygen reduction as the driving force and the cation effect to reduce the activity of H₂ 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 O₂ 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.