Structural and Energetic Characterizations of Thin Multi-Walled Carbon Nanotubes Using Adsorption Isotherms

The structural and energetic heterogeneity of thin multi-walled carbon nanotubes (t-MWCNTs) was evaluated from the adsorption of nitrogen and aromatic compounds (benzene, toluene, and m-xylene). The t-MWCNTs was synthesized through the catalytic vapor deposition and characterized by using nitrogen adsorption–desorption isotherm and high-resolution transmission electron microscopy (HRTEM) analyses. The equilibrium adsorption data of aromatic compounds on t-MWCNTs were measured using gravimetric apparatus at three different temperatures (303.15, 313.15 and 323.15 K) and at pressures up to 4.0 kPa. The temperature dependent Toth isotherm model was employed to correlate the experimental adsorption isotherm data. The isosteric heat of adsorption was calculated from van't Hoff equation using the temperature dependent Toth isotherm parameters. The adsorption energy distributions (AEDs) were calculated from adsorption isotherms data of nitrogen and aromatic molecules to investigate the surface energetic heterogeneity of t-MWCNTs. The results of pore size distributions, isosteric heats of adsorption and AEDs revealed that t-MWCNTs have structurally and energetically heterogeneous surface.