8
1 Introduction
1.3 Storage of Hydrogen and Nanotechnology
One of the major reasons of why hydrogen is still not used as the primary source
fuel is the limitations in storage of hydrogen. The storage of the hydrogen should be
reversible at ambient conditions or it can be released from the storage material on
demand. When the hydrogen gas comes in the vicinity of the hydrogen-adsorbing
material, some of the approaching molecules (depending upon the nature of the
adsorbent) develop physical association or weak van der Waals interaction with the
material surface and get physisorbed on it. When sufficiently high energy is provided
either by altering the temperature or pressure, the molecules of hydrogen dissociates into atoms and form chemical bonds with the adsorbent, i.e., chemisorption.
Reversing the conditions of temperature or pressure releases the adsorbed hydrogen
[29].
1.3.1 Physisorption
Physisorption is a non-dissociative surface association of the hydrogen gas with the
solid surfaces. The interactions involve weak van der Waals associations between
the gaseous hydrogen molecules and the adsorbent. Different nanomaterials like
carbons nanotubes (both single walled and multiwalled), zeolites, activated carbons,
(COFs), fullerene (nanocages), and covalent-organic frameworks are capable of
storing hydrogen by physisorption [3–5]. Different studies have made use of these
nanomaterials for physisorption of hydrogen. For instance, an investigation employed
first-principle calculation within density functional theory (DFT) for studying the
hydrogen storage capability in Jahn–Teller slanted Ti-modified fullerenes. It is
observed 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]. Several other studies that use nanotechnology
in physisorption of hydrogen are elaborated in Chap. 7.
1.3.2 Chemisorption
Chemical adsorption or chemisorption is another important mechanism of hydrogen
storage. In terms of hydrogen storage, any material when gets attached to the
hydrogen it becomes a hydride. Over the last few years, the scope of materials to get
hydrogenated or hydride formation has immensely expanded. The advancement in the
formation of hydrides is accompanied by the fast development in the nanotechnology.
1 Introduction
1.3 Storage of Hydrogen and Nanotechnology
One of the major reasons of why hydrogen is still not used as the primary source
fuel is the limitations in storage of hydrogen. The storage of the hydrogen should be
reversible at ambient conditions or it can be released from the storage material on
demand. When the hydrogen gas comes in the vicinity of the hydrogen-adsorbing
material, some of the approaching molecules (depending upon the nature of the
adsorbent) develop physical association or weak van der Waals interaction with the
material surface and get physisorbed on it. When sufficiently high energy is provided
either by altering the temperature or pressure, the molecules of hydrogen dissociates into atoms and form chemical bonds with the adsorbent, i.e., chemisorption.
Reversing the conditions of temperature or pressure releases the adsorbed hydrogen
[29].
1.3.1 Physisorption
Physisorption is a non-dissociative surface association of the hydrogen gas with the
solid surfaces. The interactions involve weak van der Waals associations between
the gaseous hydrogen molecules and the adsorbent. Different nanomaterials like
carbons nanotubes (both single walled and multiwalled), zeolites, activated carbons,
(COFs), fullerene (nanocages), and covalent-organic frameworks are capable of
storing hydrogen by physisorption [3–5]. Different studies have made use of these
nanomaterials for physisorption of hydrogen. For instance, an investigation employed
first-principle calculation within density functional theory (DFT) for studying the
hydrogen storage capability in Jahn–Teller slanted Ti-modified fullerenes. It is
observed 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]. Several other studies that use nanotechnology
in physisorption of hydrogen are elaborated in Chap. 7.
1.3.2 Chemisorption
Chemical adsorption or chemisorption is another important mechanism of hydrogen
storage. In terms of hydrogen storage, any material when gets attached to the
hydrogen it becomes a hydride. Over the last few years, the scope of materials to get
hydrogenated or hydride formation has immensely expanded. The advancement in the
formation of hydrides is accompanied by the fast development in the nanotechnology.