76
7 Physisorption
Another investigation employs first-principle calculation within DFT for studying
the hydrogen storage capability in Jahn–Teller slanted fullerenes modified with Ti.
It is observed that that Ti atoms make two hexagonal pyramidal structures because
of their high cohesive energy. Each Ti atom adsorbed four hydrogen molecules via
Kubas interactions, with 0.33–0.76 eV adsorption energy per molecule of hydrogen.
The calculations made in the study and the van’t Hoff desorption temperature depicted
that molecules of hydrogen are reversibly adsorbed under feasible thermodynamic
conditions with 10.5 wt. % of hydrogen [13].
In an investigation, a novel carbon-based nanomaterial was analyzed for the
hydrogen adsorption capacities. The nanoporous material can be described as the
small fullerene units covalently enclosed by parallel layers of graphene in the form
of sandwich. The fabricated nanomaterials have high surface-to-weight ratios and
promising structural stability due to the mesoporous and microporous morphology
of the nanostructures. The 3D nanomaterial model was prepared by fusing the small
fullerene entities between the consecutive layers of graphene and then by stacking up
the fullerene infused layers of graphene upon each other. The heat welding process
run by molecular dynamic simulations was used for the preparation of the materials. Grand canonical Monte Carlo calculations were used for the determination of
hydrogen adsorption abilities of the prepared nanostructures. In simulations, distinctive fullerene entities such as C 180 , C 320 , and C 540 were regarded as the core of
sandwich. The effects of lithium incorporation to the nanomaterials on hydrogen
adsorption were also studied during simulations. The simulation analysis depicted
sandwiched like nanostructure doped with lithium in Li-to-carbon ratio of 1 to 8
can surpass the gravimetric hydrogen storage capability of 5% whereas the undoped
samples can attain 3.83% at −193 °C temperature and 1 bar pressure [14].
7.3 Hydrogen Physisorption and Carbon Nanotubes
Different material nanotubes are involved in physisorption of hydrogen; however,
carbon nanotube is one of the best materials for the purpose. This is associated
with large surface area, adjustable features, and lower mass density of the carbon
nanotubes [15]. Here involvement of carbon nanotubes as well as other nanotubes in
physisorption of hydrogen will be discussed.
Another investigation discovered the hydrogen adsorption ability of boron
nanotubes and boron sheets via DFT calculations. The study also explained the electronic structure and geometry of both the boron nanotubes and sheets. The materials
possessed discontinuous ups and downs in the layers of boron atoms forming buckled
surfaces. The buckled surfaces have the height of ~ 0.8 Å, with 0.20 eV/atom more
stabilization as compared to the corresponding flat materials. The ups and downs are
not present in all of the boron nanotubes because the nanotubes with helicity do not
allow this specific arrangement of the atoms. Despite having different geometries
and the bonding features, both flat and buckled nanostructures are of metallic nature.
The nanotubes depicted 30–60 meV/molecule H 2 physisorption energies on boron
7 Physisorption
Another investigation employs first-principle calculation within DFT for studying
the hydrogen storage capability in Jahn–Teller slanted fullerenes modified with Ti.
It is observed that that Ti atoms make two hexagonal pyramidal structures because
of their high cohesive energy. Each Ti atom adsorbed four hydrogen molecules via
Kubas interactions, with 0.33–0.76 eV adsorption energy per molecule of hydrogen.
The calculations made in the study and the van’t Hoff desorption temperature depicted
that molecules of hydrogen are reversibly adsorbed under feasible thermodynamic
conditions with 10.5 wt. % of hydrogen [13].
In an investigation, a novel carbon-based nanomaterial was analyzed for the
hydrogen adsorption capacities. The nanoporous material can be described as the
small fullerene units covalently enclosed by parallel layers of graphene in the form
of sandwich. The fabricated nanomaterials have high surface-to-weight ratios and
promising structural stability due to the mesoporous and microporous morphology
of the nanostructures. The 3D nanomaterial model was prepared by fusing the small
fullerene entities between the consecutive layers of graphene and then by stacking up
the fullerene infused layers of graphene upon each other. The heat welding process
run by molecular dynamic simulations was used for the preparation of the materials. Grand canonical Monte Carlo calculations were used for the determination of
hydrogen adsorption abilities of the prepared nanostructures. In simulations, distinctive fullerene entities such as C 180 , C 320 , and C 540 were regarded as the core of
sandwich. The effects of lithium incorporation to the nanomaterials on hydrogen
adsorption were also studied during simulations. The simulation analysis depicted
sandwiched like nanostructure doped with lithium in Li-to-carbon ratio of 1 to 8
can surpass the gravimetric hydrogen storage capability of 5% whereas the undoped
samples can attain 3.83% at −193 °C temperature and 1 bar pressure [14].
7.3 Hydrogen Physisorption and Carbon Nanotubes
Different material nanotubes are involved in physisorption of hydrogen; however,
carbon nanotube is one of the best materials for the purpose. This is associated
with large surface area, adjustable features, and lower mass density of the carbon
nanotubes [15]. Here involvement of carbon nanotubes as well as other nanotubes in
physisorption of hydrogen will be discussed.
Another investigation discovered the hydrogen adsorption ability of boron
nanotubes and boron sheets via DFT calculations. The study also explained the electronic structure and geometry of both the boron nanotubes and sheets. The materials
possessed discontinuous ups and downs in the layers of boron atoms forming buckled
surfaces. The buckled surfaces have the height of ~ 0.8 Å, with 0.20 eV/atom more
stabilization as compared to the corresponding flat materials. The ups and downs are
not present in all of the boron nanotubes because the nanotubes with helicity do not
allow this specific arrangement of the atoms. Despite having different geometries
and the bonding features, both flat and buckled nanostructures are of metallic nature.
The nanotubes depicted 30–60 meV/molecule H 2 physisorption energies on boron