Adsorption Kinetics of Alcohols on Single-Wall Carbon Nanotubes: An Ultrahigh Vacuum Surface Chemistry Study

Abstract

Presented are thermal desorption spectroscopy (TDS) data of alcohol adsorption on single-wall carbon nanotubes (CNTs) supported on silica. The adsorption kinetics of methanol, ethanol, propanol, 2-propanol, butanol, pentanol, and hexanol have been studied. Multimass TDS confirms molecular adsorption/desorption with low coverage binding energies, E 0, increasing linearly with the number of carbons, n . The coverage, Θ, dependence of the heat of adsorption, E d (Θ), has been obtained by a Redhead analysis. The heat of sublimation increases linearly with n whereas the zeroth-order pre-exponential factor is approximately independent of n . In addition, TDS of alkanes (butane, pentane, hexane, trimethylpentane) as well as alcohol−alkane coadsorption data have been collected to characterize possible adsorption sites. Alkane TDS leads to fingerprint curves indicating three different adsorption sites (external, groove, internal) on CNTs, in agreement with earlier studies. For most of the alcohols only one monolayer TDS peak is seen indicating a dominance of lateral interactions. However, the coadsorption data provide evidence for alcohol adsorption on interior sites of the CNTs.