Enhancement of amino-functionalized carbon nanotubes on the CO2 capture in a flow-electrode capacitive deionization system by accelerating gas-liquid mass transfer and reducing charge transfer resistance

Capacitive capture is an ideal technology for CO 2 separation, offering advantages of low energy consumption and minimal reagent usage. However, its performance is often limited by slow gas-liquid mass transfer. This study innovatively utilized a flow-electrode capacitive deionization (FCDI) system for capacitive CO 2 capture and introduced amino-functionalized carbon nanotubes (ACNTs) to enhance gas-liquid mass transfer, thereby improving the capacitive CO 2 capture performance of the FCDI system. We demonstrated that the FCDI using ACNT-based nanofluids as gas absorption liquid (AC-FCDI) significantly outperformed FCDI using deionized water or pristine CNT nanofluids, achieving a 131.15 % increase in CO 2 capture rate and reducing energy consumption to as low as 3.05 kJ/mol. Systematic experiments identify the optimal ACNT mass fraction (0.02 wt%) and stirring rate (130 r/min). Material characterization, including SEM, XPS and FTIR, revealed that ACNTs could not only facilitate the CO 2 transport for efficient gas-liquid mass transfer but also provide abundant amine groups that chemically adsorb CO 2 to form reversible intermediates, thereby accelerating mass transfer. Furthermore, electrochemical impedance spectroscopy (EIS) and conductivity measurements confirmed that ACNTs reduced system resistance, promoting electron and ion migration. This work established a novel material-device synergy system and elucidated the enhancement mechanism of introducing ACNTs on mass transfer processes and charge migration behavior within the system, paving the way for efficient and environmentally friendly capacitive carbon capture.