7.2 Hydrogen Physisorption and Fullerenes
75
7.2 Hydrogen Physisorption and Fullerenes
Fullerenes are nanomaterials with sp
2 hybridized hollow carbon cages. Commonly
found as C 60 , but other order materials like C 70 , C 78 , C 28 , and C 36 are also known
[10]. Fullerenes are actively involved in the physisorption of hydrogen.
ZhiGang et al. have reported the barrierless physisorption to chemisorption of
hydrogen molecules on the fullerenes doped with lightweight elements. The study
employed local density approximation (LDA) within density functional theory (DFT)
as process. The DFT process is capable of large systems at low computational costs.
In practice, C 35 B fullerene brought onto the space of C 35 B–H 2 stable system. The two
C 35 B molecules now behave like forceps with each attaching itself to the opposite side
of the small H 2 molecules resulting in its dissociation to H, H (with one H with each
of C 35 B). This is barrierless physisorption to chemisorption. The study suggested
that H–H bond breaking occurs because of energy discharge as C 35 B gets near to
the C 35 BH 2 . The evolved energy increased the bond length between H–H ultimately
leading to chemisorption of H 2 molecules in the hydrogen storage method. Overall
the energy decreases monotonously during this procedure [11].
In an interesting investigation, fullerene nanocages were filled with hydrogen to
determine the hydrogen storage capacity of endohedral fullerenes. The nanocages
of general formula H n @C k were analyzed for their hydrogen-storing capacities via
DFT. When large amount of hydrogen molecules were filled inside the nanocages, a
few of them get chemisorbed with carbon atoms on the interior of the nanostructures.
At most, 58 hydrogen atoms were found in interior of C60 nanocage in metastable
structure. The breaking mechanism of the fullerene was studied employing ab initio
molecular dynamics simulations. The pressure of hydrogen in the nanocage was
assessed and it was found that this pressure is few times less than hydrogen metallization pressure. The study also developed the effect of hydrogen on C−C bond
stretching in fullerene nanocages of random radii. This can help in assessing the
amount of hydrogen that can be stored in larger radii fullerenes [4].
In an investigation, hydrogen storage capability of 3D periodic fullerene pillared
graphene nanocomposites was studied for their hydrogen storage ability. The 3D
nanomaterials consisted of fullerene entities covalently combined between the layers
of graphene. Fullerenes were used as pillars in between the consecutive layers of
the graphene. They were employed for adjusting the porosity and improving the
hydrogen storage capabilities of the projected nanostructures. The volumetric and
gravimetric hydrogen storage of the nanomaterials was studied by employing Monte
Carlo calculations at both high and low pressures varying from 0.01 to 100 bars and at
different temperatures, i.e., −196 °C and 25 °C. The results of simulations depicted
that substantial improvement in hydrogen adsorption ability of the nanomaterials can
be achieved with fitting assortment of fullerene size and the conditions of hydrogen
loading. The calculation also showed that the said nanomaterials can store up to 10.3
wt.% hydrogen at −196 °C. Additionally, the nanomaterial capacity of releasing
hydrogen surpassed 7.8 wt.% for the charge at −196 °C and 100 bar pressure. The
discharge of the gas was achieved at −113 °C, 5 bar pressure [12].
75
7.2 Hydrogen Physisorption and Fullerenes
Fullerenes are nanomaterials with sp
2 hybridized hollow carbon cages. Commonly
found as C 60 , but other order materials like C 70 , C 78 , C 28 , and C 36 are also known
[10]. Fullerenes are actively involved in the physisorption of hydrogen.
ZhiGang et al. have reported the barrierless physisorption to chemisorption of
hydrogen molecules on the fullerenes doped with lightweight elements. The study
employed local density approximation (LDA) within density functional theory (DFT)
as process. The DFT process is capable of large systems at low computational costs.
In practice, C 35 B fullerene brought onto the space of C 35 B–H 2 stable system. The two
C 35 B molecules now behave like forceps with each attaching itself to the opposite side
of the small H 2 molecules resulting in its dissociation to H, H (with one H with each
of C 35 B). This is barrierless physisorption to chemisorption. The study suggested
that H–H bond breaking occurs because of energy discharge as C 35 B gets near to
the C 35 BH 2 . The evolved energy increased the bond length between H–H ultimately
leading to chemisorption of H 2 molecules in the hydrogen storage method. Overall
the energy decreases monotonously during this procedure [11].
In an interesting investigation, fullerene nanocages were filled with hydrogen to
determine the hydrogen storage capacity of endohedral fullerenes. The nanocages
of general formula H n @C k were analyzed for their hydrogen-storing capacities via
DFT. When large amount of hydrogen molecules were filled inside the nanocages, a
few of them get chemisorbed with carbon atoms on the interior of the nanostructures.
At most, 58 hydrogen atoms were found in interior of C60 nanocage in metastable
structure. The breaking mechanism of the fullerene was studied employing ab initio
molecular dynamics simulations. The pressure of hydrogen in the nanocage was
assessed and it was found that this pressure is few times less than hydrogen metallization pressure. The study also developed the effect of hydrogen on C−C bond
stretching in fullerene nanocages of random radii. This can help in assessing the
amount of hydrogen that can be stored in larger radii fullerenes [4].
In an investigation, hydrogen storage capability of 3D periodic fullerene pillared
graphene nanocomposites was studied for their hydrogen storage ability. The 3D
nanomaterials consisted of fullerene entities covalently combined between the layers
of graphene. Fullerenes were used as pillars in between the consecutive layers of
the graphene. They were employed for adjusting the porosity and improving the
hydrogen storage capabilities of the projected nanostructures. The volumetric and
gravimetric hydrogen storage of the nanomaterials was studied by employing Monte
Carlo calculations at both high and low pressures varying from 0.01 to 100 bars and at
different temperatures, i.e., −196 °C and 25 °C. The results of simulations depicted
that substantial improvement in hydrogen adsorption ability of the nanomaterials can
be achieved with fitting assortment of fullerene size and the conditions of hydrogen
loading. The calculation also showed that the said nanomaterials can store up to 10.3
wt.% hydrogen at −196 °C. Additionally, the nanomaterial capacity of releasing
hydrogen surpassed 7.8 wt.% for the charge at −196 °C and 100 bar pressure. The
discharge of the gas was achieved at −113 °C, 5 bar pressure [12].