Neon and CO2 Adsorption on Open Carbon Nanohorns (original) (raw)
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Argon Adsorption on Open Carbon Nanohorns
Bulletin of the American Physical Society, 2015
We have measured adsorption isotherms for argon adsorbed on a 0.1692 g sample of chemically-opened carbon nanohorns. Two clear substeps are visible in the adsorption data, corresponding to groups of stronger binding sites (lower pressure substep) and weaker binding sites (higher pressure substep). We have measured adsorption at five different temperatures in the range between 70 and 90 K. The chemically-opened nanohorns have the space at the interior of the individual nanohorns accessible to adsorbates. Consequently, higher loadings are obtained on these samples compared to those for unopened (as-produced) nanohorns. Results for the kinetics of adsorption, the effective specific surface area, and the isosteric heat of adsorption as a function of sorbent loading will be presented and compared to results from other studies on nanohorns.
Adsorption of water vapor on mesoporosity-controlled singe wall carbon nanohorn
Colloids and Interface Science Communications, 2015
The adsorption mechanism of water vapor in hydrophobic carbon mesopores is not clearly understood. Single wall carbon nanohorns (SWCNH) having different tube diameters in the range of 2 to 6 nm were oxidized at a lower temperature than the widely used temperature of 823 K. Oxidation at 633 K can selectively open thinner tubes of SWCNH and then the oxidation at different times can control the mesoporosity. The porosity of thusoxidized SWCNH was evaluated from the nitrogen adsorption isotherms at 77 K. The pore volume ratio of micropores to mesopores was in the range of 0.50 to 0.90. The linear relationship between water adsorption amount and the pore volume of micropores and small mesopores (b5 nm) was observed, showing that water molecules are adsorbed even in small mesopores by the cluster-mediated filling mechanism as well as in micropores.
Theory of Gas Adsorption in Carbon Nanostructures
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Adsorption and catalytic properties of single-wall carbon nanohorns
Chemical Physics Letters, 2000
The recently discovered single-wall carbon nanohorns (SWNH) are found to adsorb liquid ethanol eectively. The amount of liquid ethanol adsorbed by SWNHs is about 3.5 times larger than that of a super high surface area carbon. It is also found that SWNHs act as a catalyst for the oxidation of ethanol into acetaldehyde. Their thermal stability in oxygen is also discussed. Ó (J. Adelene Nisha), yudasaka@frl.cl.nec.co.jp (M. Yudasaka).
Fluid Phase Equilibria, 2005
Three different examples of adsorption and phase transitions on nanoporous carbonaceous materials are investigated using molecular simulations. In the first example, N 2 adsorption on the surface of and within a C 60 crystal is studied using the grand canonical Monte Carlo simulation. On the crystal surface, the predicted isotherm is of type II in good agreement with experiment, and N 2 molecules are found to initially occupy the octahedral voids, then the tetrahedral voids, and finally on the top of the C 60 molecules with increasing coverage. Within the crystal, the predicted isotherm is of type I, and N 2 molecules intercalate the octahedral voids. In the second example, N 2 adsorption on two types of carbon nanotube bundles is studied using the Gibbs ensemble Monte Carlo simulation to explore the role of the external surface of the nanotube bundle in the character of adsorption isotherm. The isotherm for an infinite bundle without an external surface is found to be of type I independent of temperature, while for a finite bundle with an external surface the isotherm changes from type II to I as temperature changes from subcritical to supercritical. In the third example, the capillary phase transitions of n-alkanes (from C 1 to C 8 ) in a carbon nanotube are studied using the gauge-cell Monte Carlo simulation implemented with the configurational-bias technique. At subcritical temperatures the isotherms exhibit sigmoid van der Waals loops, including stable, metastable, and unstable regions, and the coexisting vapor−liquid phases are determined from a Maxwell construction along the isotherms. The confinement of an n-alkane in a carbon nanotube decreases its critical temperature, increases its critical density, and narrows its binodal curve.
Microporous and Mesoporous Materials, 2019
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SO2 gas adsorption on carbon nanomaterials: a comparative study
Beilstein Journal of Nanotechnology
Owing to their high stability against corrosive gases, carbon-based adsorbents are preferentially used for the adsorptive removal of SO2. In the present study, SO2 adsorption on different carbon nanomaterials namely carbon nanohorns (CNHs), multiwalled carbon nanotubes (MWNTs), single-walled carbon nanotubes (SWNTs) and vertically aligned carbon nanotubes (VACNTs) are investigated and compared against the adsorption characteristics of activated carbon and graphene oxide (GO). A comprehensive overview of the adsorption behavior of this family of carbon adsorbents is given for the first time. The relative influence of surface area and functional groups on the SO2 adsorption characteristics is discussed. The isosteric heat of adsorption values are calculated to quantify the nature of the interaction between the SO2 molecule and the adsorbent. Most importantly, while chemisorption is found to dominate the adsorption behavior in activated carbon, SO2 adsorption on carbon nanomaterials oc...
Modern approaches to studying gas adsorption in nanoporous carbons
Journal of Materials Chemistry A, 2013
Conventional approaches to understanding the gas adsorption capacity of nanoporous carbons have emphasized the relationship with the effective surface area, but more recent work has demonstrated the importance of local structures and pore-size-dependent adsorption. These developments provide new insights into local structures in nanoporous carbon and their effect on gas adsorption and uptake characteristics. Experiments and theory show that appropriately tuned pores can strongly enhance local adsorption, and that pore sizes can be used to tune adsorption characteristics. In the case of H 2 adsorbed on nanostructured carbon, quasielastic and inelastic neutron scattering probes demonstrate novel quantum effects in the motion of adsorbed molecules.
Gas Adsorption Evidence of Single-Wall and Multi-Wall Carbon Nanotube Opening
MRS Proceedings, 2003
ABSTRACTCarbon nanotubes offer a surface very similar to that of graphite, a reference substrate in physisorption experiments aimed at studying substrate-adsorbate interactions. The curvature, however, introduces new questions. What are the effects of this on condensation pressures or heats of adsorption? Can one experimentally distinguish between different adsorption sites? In this study, we compare adsorption isotherms of several simple gases (Kr, Xe, CCl4) on singlewall (SWNTs) and multi-wall carbon nanotubes (MWNTs), before and after opening. For mechanically opened SWNTs, the accessibility of the adsorption sites and the molecular arrangements of the adsorbed gases are discussed. With the much bigger, well-defined MWNTs, the “cutting method” called upon a nitric acid treatment followed by a CO2 oxidation. TEM investigations and physisorption studies clearly revealed tube opening and that the inner channels became accessible to Kr molecules.
Advanced Physical Adsorption Characterization of Nanoporous Carbons
Novel Carbon Adsorbents, 2012
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