Nonequilibrium transport equations and ab initio study of adsorption processes on carbon nanotubes

TL;DR

This paper develops a theoretical framework using nonequilibrium statistical methods and ab initio simulations to study gas adsorption processes on carbon nanotubes, revealing adsorption sites, electronic effects, and structural reconstructions.

Contribution

It introduces a self-consistent nonequilibrium transport equation approach combined with ab initio simulations for detailed adsorption analysis on CNTs.

Findings

Identification of preferred adsorption sites for He atoms.

Demonstration of NO's impact on CNT electronic properties.

Analysis of vacancy effects leading to chemisorption of NO.

Abstract

In a theoretical study of gas adsorption on carbon nanotubes (CNT) nonequilibrium processes of ionization, polarization, surface diffusion and desorption of atoms are considered self-consistently. The approach is based on Zubarev's method of nonequilibrium statistical operator and reaction-diffusion theory. The set of nonlinear transport equations are obtained for the chosen parameters of description: the average numbers of adsorbed atoms, ionized and polarized atoms in the electromagnetic field of CNT, and the average number of atoms desorbed from the CNT surface. Ab initio simulations are conducted for a "gas-single wall carbon nanotube" system for gases of particular practical interest: He and NO. The obtained values of adsorption energy reveal preferable localization sites of absorbed He atoms as well as their dependency on adsorption distances. A significant effect of NO adsorption on CNT electronic properties is demonstrated. The effect of presence of vacancies on adsorption nature is analyzed. It is shown that under the influence of vacancy formation the CNT structure undergoes reconstruction that enables chemisorption of NO molecules.