Catalytic CO₂ Capture via Ultrasonically Activating Dually Functionalized Carbon Nanotubes

High energy consumption and high cost have been the obstacles for large-scale deployment of all state-of-the-art CO₂ capture technologies. Finding a transformational way to improve mass transfer and reaction kinetics of the CO₂ capture process is timely for reducing carbon footprints. In this work, commercial single-walled carbon nanotubes (CNTs) were activated with nitric acid and urea under ultrasonication and hydrothermal methods, respectively, to prepare N-doped CNTs with the functional group of -COOH, which possesses both basic and acid functionalities. The chemically modified CNTs with a concentration of 300 ppm universally catalyze both CO₂ sorption and desorption of the CO₂ capture process. The increases in the desorption rate achieved with the chemically modified CNTs can reach as high as 503% compared to that of the sorbent without the catalyst. A chemical mechanism underlying the catalytic CO₂ capture is proposed based on the experimental results and further confirmed by density functional theory computations.