Hydrogen Adsorption in Carbon Nanostructures: Comparison of Nanotubes, Fibers, and Coals

Abstract

Single-walled carbon nanotubes (SWNT) were reported to have record high hydrogen storage capacities at room temperature, indicating an interaction between hydrogen and carbon matrix that is stronger than known before. Here we present a study of the interaction of hydrogen with activated charcoal, carbon nanofibers, and SWNT that disproves these earlier reports. The hydrogen storage capacity of these materials correlates with the surface area of the material, the activated charcoal having the largest. The SWNT appear to have a relatively low accessible surface area due to bundling of the tubes; the hydrogen does not enter the voids between the tubes in the bundles. Pressure ± temperature curves were used to estimate the interaction potential, which was found to be 580 AE 60 K. Hydrogen gas was adsorbed in amounts up to 2 wt % only at low temperatures. Molecular rotations observed with neutron scattering indicate that molecular hydrogen is present, and no significant difference was found between the hydrogen molecules adsorbed in the different investigated materials. Results from density functional calculations show molecular hydrogen bonding to an aromatic CÀC bond that is present in the materials investigated. The claims of high storage capacities of SWNT related to their characteristic morphology are unjustified.

Hydrogen adsorption by perforated graphene

“…Nanostructured carbon materials have been considered as promising candidates for hydrogen storage applications due to high surface areas and chemical stability. [1,2] Activated carbons [3,4] , carbon nanotubes, [5,6] graphite nanofibers [7] and carbide derived carbons [8] have been actively studied for hydrogen storage applications during last decades. It is known that hydrogen uptake correlates well with the BET surface area and micropore volume for most of the high surface area adsorbents including carbon materials.…”

Retracted: Electrical conductivity of hydrogenated armchair nanoribbon as a gas sensor using non-equilibrium Green's function method

“…In recent years, much attention has been focused on nanoelectronic devices [1][2][3] and molecular gas adsorption on single-walled carbon nanotubes and graphene system surfaces [4][5][6][7][8][9][10][11][12][13]. Since gas adsorption by these systems could change their electronic properties, these properties could be used as a gas sensing property.…”

Nanomaterials for renewable energy production and storage

“…278 The amount of adsorbed hydrogen is proportional to the specific surface area of the carbon material. 279,280 Recent research of hydrogen physisorption on carbon nanostructures involves efforts on increasing the surface area of carbon to provide more binding sites and incorporating functional groups (dopants) in carbon to increase the binding energy between hydrogen and carbon surfaces.…”