Comparative Study of Methane Adsorption on Single-Walled Carbon Nanotubes

Abstract

We present the combined results of ab initio and molecular mechanical calculations, computer simulations, and adsorption isotherms investigations of CH(4) adsorbed on HiPco single-walled carbon nanotubes. Isotherms and adsorption energies obtained in our model and simulations are in good agreement with ours and others experimental results. The theoretical analysis conducted for various homogeneous bundles of close-ended and open-ended tubes confirm not only the adsorption in at least two different stages but also the role played by each of the different adsorption sites on the nanotube bundles. The study of different site and nanotube sizes allows us to establish the presence of open tubes in the as-produced HiPco bundles, without regarding the role that adsorption in large interstitial channels may play. Our results also show that predicted scenarios, for the mechanism and the preferential adsorption sites depend on the size of the nanotubes and those of the bundles.

Methane in carbon nanotube: molecular dynamics simulation

“…Whcich is in accordance with the distance 0.348 nm obtained for the 1-site model of CH 4 molecules in the rigid (10,10) CNT [24]. Adsorption of methane molecules on the CNT surfaces was also studied using density functional theory (DFT) method [33][34][35][36][37][38] and second order Möller-Plesset perturbation calculations [39].…”

Description of Adsorbed Phases on Carbon Surfaces: A Comparative Study of Several Graphene Models

“…From these results one can conclude that the potential energy obtained doesn't show an important dependence on the curvature of the nanotubes, at least in the explored range. The experimental isotherms for the adsorption of methane, measured at 77.3 K, unlike the case of the adsorption on graphite that has only one step in the monolayer regime (0.2 kPa), have one sub step below this pressure and other one above it (Albesa et al, 2010). As in the case of graphite when the temperature increases, this stepwise adsorption behavior is less pronounced, and above 103 K the substeps disappear.…”

“…In other words, the two first diameters were employed to analyze G, S and T (in case of open nanotubes) sites, and the last one to IC sites. As the molecular dynamics simulations, using MM+ force field, as the calculation employing ab initio density functional theory (DFT) (Albesa et al, 2010), tell that IC sites begin to fill before the G sites. A complementary picture at molecular level, can be performed by Monte Carlo simulations (MCS) with the grand canonical ensemble, in order to take into account the behavior of a representative number of molecules in the adsorbed phase.…”

“…Section 3.2 is devoted to study the adsorption of simple gases using graphitic curved surfaces, for this end we used abs initio density functional theory (DFT) calculations for graphene sheets whose surfaces had different curvature, and discuss the relation between these model systems and experimental data for adsorption on single wall carbon nanotubes (Albesa et al, 2009;Albesa et al 2010). In section 4, Gas Separation, we present simulated adsorption isotherms obtained for two characteristic carbonaceous structures, graphite and single wall carbon nanotubes.…”

A Study of the Adsorption Properties of Single Walled Carbon Nanotubes Treated with Nitric Acid

“…Knowledge of the adsorption properties of carbon nanotubes is important for the development of nanotube-based materials for the aforementioned applications. Hence, there is considerable interest in attaining a detailed characterization of the adsorption properties of carbon nanotubes (Eswaramoorthy et al 1999;Ohba and Kaneko 2002;Yang et al 2002;Cinke et al 2003;Migone and Talapatra 2004;Krungleviciute et al 2004;Furmaniak et al 2006;Rawat et al 2008;Albesa et al 2010;Cruz et al 2010;Esteves et al 2009). …”