Biomedical Engineering Reference
In-Depth Information
theoretical data. This chapter deals with the current analytical study,
mainly focused on the nature of an indirect experiment.
2.2
Part I—Nature and Characteristics of
Hydrogen Interactions with Carbonaceous
Nanomaterials
2.2.1 Open Questions Concerning the Nature,
Mechanisms, and Characteristics of Hydrogen
Sorption by Carbon Nanostructures
According to the road map of the U.S. DOE [1-3], the goals were to
develop, by 2010, hydrogen adsorbents with a high sorption capacity
(≥6 wt% of hydrogen, H/C ≥ 0.77, and 45 g of hydrogen per liter) and
a sufficiently fast kinetics (reversibility) of hydrogen desorption at
room temperature.
Dillon
[27], authors of the probably most cited experimental
work [26] on hydrogen sorption by surface structures consisting
of bundles of single-wall nanotubes, believe that these goals can
be achieved using new carbon nanostructures characterized by
anomalous values (20-40 kJ/mol) for the hydrogen binding energies.
The previous energy values are intermediate in relation to the well-
known typical values of bond breakage energies for chemisorption
and physical sorption of hydrogen by carbon nanomaterials, for
which it is assumed [27] that:
et al.
(i) dissociative hydrogen adsorption is characterized by the
formation of bonds weaker than the typical chemical C-H
bonds;
(ii) no dissociative absorption is characterized by an interaction
stronger than the physical sorption.
Dillon
[27] related the rapid removal of adsorbed hydrogen
in process (i) to hydrogen spillover [28], in the case of process (ii),
they consider molecular adsorption of hydrogen on carbon nano-
materials subjected to structural and/or molecular modification.
The considered values of the binding energy for hydrogen and
new carbon nanostructures ideally suitable for hydrogen sorption
are (20-40 kJ/mol [27]), roughly 10 times higher than the binding
energy (rupture of van der Waals bonds) characterizing the hydrogen
et al.
