Adsorption and capillarity of nitrogen in aggregated multi-walled carbon nanotubes

Pores in aggregated multi-walled carbon nanotubes (MWNTs) can be mainly divided into inner hollow cavities of smaller diameter (narrowly distributed, mainly 3.0–4.0 nm) and aggregated pores (widely distributed, 20–40 nm), formed by the interaction of isolated MWNTs. The two types of pores shall, respectively, determine nitrogen cryogenic capillarity process under different pressures. It is worth to note that ultra-strong nitrogen capillarity in the aggregated pores (590 mg N2/g) contributes to the 78.5% of the total adsorption amount (up to 750 mg/g near to the ambient pressure), showing that the aggregated pores of the MWNTs are much more important than their inner cavities for adsorption and capillarity in some cases.