80
7 Physisorption
electron microscopy (TEM), and hydrogen chemisorption with higher surface area
which produced smaller metallic nanoparticles at a given Pd content [28].
In an investigation, computational studies have proposed enhanced hydrogen
adsorption abilities of carbon–metal nanocomposites. The study determined the
hydrogen adsorption capacity of arranged porous carbon material supporting Pd
nanoclusters. The said nanomaterials were attained via chemical impregnation of
carbon template with the solution of H 2 PdCl 4 followed by subsequent reduction. In
the carbon porous material, 10 wt.% of palladium nanoclusters with average size of
2 nm was homogeneously dispersed. Hydrogen isotherm adsorption calculations and
thermal desorption spectroscopy (TDS) characterization were made for the determination of thermodynamic hydrogenation properties of pristine carbon template as
well as the 10 wt.% Pd nanocluster loaded carbon templates. The carbon templates
with Pd nanoparticles do not increase the hydrogen uptake at −193 °C temperature and 1.6 MPa pressure. In these conditions, the hydrogen was being stored via
physisorption; however, at 25 °C and 0.5 MPa moderate pressure the carbon templates
of 10 wt.% nanocluster of Pd depicted eight times higher uploading of the hydrogen
as compared to the pristine carbon support. TDS analysis credited rapid increase of
hydrogen adsorption to the Pd nanoclusters [29].
The hydrogen adsorptions on metallo-carbohedrene Ti 8 C 12 and nanocrystals of
Ti 14 C1 3 were investigated using first-principles calculations. The formation of carbon
hydrides was not possible in the absence of Ti atoms which acts as the catalyst
to facilitate the dissociation of hydrogen. Titanium atoms present on nanocarbide
surface form complex coordinate with several molecular hydrogen ligands. Hydrogen
adsorption capabilities of 6.1 wt.% 7.7 wt. % for Ti 8 C1 2 and for Ti 14 C1 3 , respectively, were achieved with above than 80% of the hydrogen adsorbed in the energy
ranging 0.17–0.89 eV per molecule of hydrogen. After the formation of macroscopic substance by the nanoparticles (due to hydrogen adsorption), chemisorption
of the hydrogen starts declining; however, more hydrogen molecules are adsorbed via
physisorption. The study suggested TiC nanoparticles as potential hydrogen storage
material at approximate ambient conditions [30].
7.6 Conclusion
Physisorption is a remarkable hydrogen storage phenomenon. Physisorption allows
the adsorption of the hydrogen on various material surfaces via van der Waals linkages. Nanomaterials have revolutionized the area of hydrogen storage via physisorption because of improved storage capacity. Different nanomaterials like nanotubes
and fullerenes allow the adsorption of hydrogen not only on their surface but also
inside the nanomaterials. The advanced research is needed for the utilization of these
nanomaterials in portable applications of hydrogen storage.
7 Physisorption
electron microscopy (TEM), and hydrogen chemisorption with higher surface area
which produced smaller metallic nanoparticles at a given Pd content [28].
In an investigation, computational studies have proposed enhanced hydrogen
adsorption abilities of carbon–metal nanocomposites. The study determined the
hydrogen adsorption capacity of arranged porous carbon material supporting Pd
nanoclusters. The said nanomaterials were attained via chemical impregnation of
carbon template with the solution of H 2 PdCl 4 followed by subsequent reduction. In
the carbon porous material, 10 wt.% of palladium nanoclusters with average size of
2 nm was homogeneously dispersed. Hydrogen isotherm adsorption calculations and
thermal desorption spectroscopy (TDS) characterization were made for the determination of thermodynamic hydrogenation properties of pristine carbon template as
well as the 10 wt.% Pd nanocluster loaded carbon templates. The carbon templates
with Pd nanoparticles do not increase the hydrogen uptake at −193 °C temperature and 1.6 MPa pressure. In these conditions, the hydrogen was being stored via
physisorption; however, at 25 °C and 0.5 MPa moderate pressure the carbon templates
of 10 wt.% nanocluster of Pd depicted eight times higher uploading of the hydrogen
as compared to the pristine carbon support. TDS analysis credited rapid increase of
hydrogen adsorption to the Pd nanoclusters [29].
The hydrogen adsorptions on metallo-carbohedrene Ti 8 C 12 and nanocrystals of
Ti 14 C1 3 were investigated using first-principles calculations. The formation of carbon
hydrides was not possible in the absence of Ti atoms which acts as the catalyst
to facilitate the dissociation of hydrogen. Titanium atoms present on nanocarbide
surface form complex coordinate with several molecular hydrogen ligands. Hydrogen
adsorption capabilities of 6.1 wt.% 7.7 wt. % for Ti 8 C1 2 and for Ti 14 C1 3 , respectively, were achieved with above than 80% of the hydrogen adsorbed in the energy
ranging 0.17–0.89 eV per molecule of hydrogen. After the formation of macroscopic substance by the nanoparticles (due to hydrogen adsorption), chemisorption
of the hydrogen starts declining; however, more hydrogen molecules are adsorbed via
physisorption. The study suggested TiC nanoparticles as potential hydrogen storage
material at approximate ambient conditions [30].
7.6 Conclusion
Physisorption is a remarkable hydrogen storage phenomenon. Physisorption allows
the adsorption of the hydrogen on various material surfaces via van der Waals linkages. Nanomaterials have revolutionized the area of hydrogen storage via physisorption because of improved storage capacity. Different nanomaterials like nanotubes
and fullerenes allow the adsorption of hydrogen not only on their surface but also
inside the nanomaterials. The advanced research is needed for the utilization of these
nanomaterials in portable applications of hydrogen storage.