Mechanisms of pore formation on multi-wall carbon nanotubes by KOH activation

•KOH-activated MWCNTs show a characteristic peak of micropores at 0.8 nm.•Mesopores were formed by transverse sectioning and exposure of inner space.•Micropores (<1 nm) played a significant role in the physic-sorption of CO2 molecules.

The porous structures of KOH-activated multi-wall carbon nanotubes (MWCNTs) were studied over a wide range of activation conditions, through which the pore-forming mechanisms of the activated MWCNTs were elucidated. It was found that micropores (<2 nm) were developed by KOH-C redox reaction on the walls of MWCNTs, causing the formation of a characteristic peak of micropores at 0.8 nm. More importantly, the in-depth activation was found to transversely section the nanotubes, which led to the release of the catalyst particles and the formation of mesopores. The understanding of the pore-forming mechanisms of the activated MWCNTs also provided a good platform to investigate the effect of absorbent’s pore structures on its CO2 capture behavior. It was further demonstrated in this study that the micropores having pore sizes less than 1 nm played a significant role in the physic-sorption of CO2 molecules.

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