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6 Hydrogen from Miscellaneous Sources and Nanotechnology
Municipal solid waste is also used as the source of hydrogen. Different components of the waste like biological substances, organic materials, and other undesirable components like plastic debris are involved in the generation of hydrogen.
Different studies have reported the use of these materials collectively and individual
for the preparation of hydrogen. In a study, post-consumer waste plastic obtained
from the municipal solid waste was used for the hydrogen generation by catalytic
steam reforming coupled with the gasification [4]. Waste plastic is one of the biggest
environmental hazards of the modern age. Conversion of the plastic into hydrogen
reduces the pollution on one hand and provides the clean energy on the other hand.
Several studies have reported the use of the plastics for the generation of sustainable hydrogen. A study has reported the use of mechanochemical treatment for the
generation of sustainable hydrogen from the waste plastic [5]. A study has reported
the simultaneous conversion of plastics into hydrogen-rich syngas and the carbon
nanotubes [6]. The waste plastic is commonly recycled chemically either by pyrolysis or by gasification or by both of them for the generation of important hydrocarbons. When the plastics are subjected to gasification, syngas is produced with large
percentage of hydrogen. Additionally, the plastics comes with a higher hydrogen
content and heating value, as compared to other types of municipal solid wastes and
biomass, hence making them the most suitable candidate for hydrogen generation
from the whole solid wastes [7].
Ammonia is another source of hydrogen generation. Ammonia and many of its
derivatives are used as the potential source of sustainable hydrogen. Ammonia as
the source of hydrogen seems appealing as it does not generate oxides of nitrogen
or carbon (carbon dioxide or carbon monoxide) as the by-product, and also the
concentration of the unreactive ammonia during the chemical reaction can be lowered
to 200 ppb by employing appropriate adsorber [8]. It has been reported that the
generation of H 2 by the decomposition of ammonia is economically more feasible
as compared to the reformation of methanol [9]. The evolution of hydrogen from
ammonia requires high temperature and suitable catalyst [10]. A chemical reaction
for the generation of hydrogen from ammonia can be given as [11].
2NH 3 + 6OH
−
→ N 2 (g) + 6H 2 O + 6e
−
6H 2 O + 6e
−
→ 3H 2 (g) + 6OH
−
Oxidation from metal alloys of salt solution results in the generation of hydrogen.
Magnesium alloys are notably important in this regard. It was found that the binary
alloys of Mg are capable of reacting with solutions of sodium chloride in water
[12]. Transition metals like Fe, Cu, Co, or Ni when mixed with Mg even in the small
composition like 0.2 wt.% result in the improved oxidation ability of the magnesium.
This can be associated to the high reduction potential of the transition metals [13].
A simple reaction of magnesium reacting with salts for the generation of hydrogen
is given in the equation below [14]:
6 Hydrogen from Miscellaneous Sources and Nanotechnology
Municipal solid waste is also used as the source of hydrogen. Different components of the waste like biological substances, organic materials, and other undesirable components like plastic debris are involved in the generation of hydrogen.
Different studies have reported the use of these materials collectively and individual
for the preparation of hydrogen. In a study, post-consumer waste plastic obtained
from the municipal solid waste was used for the hydrogen generation by catalytic
steam reforming coupled with the gasification [4]. Waste plastic is one of the biggest
environmental hazards of the modern age. Conversion of the plastic into hydrogen
reduces the pollution on one hand and provides the clean energy on the other hand.
Several studies have reported the use of the plastics for the generation of sustainable hydrogen. A study has reported the use of mechanochemical treatment for the
generation of sustainable hydrogen from the waste plastic [5]. A study has reported
the simultaneous conversion of plastics into hydrogen-rich syngas and the carbon
nanotubes [6]. The waste plastic is commonly recycled chemically either by pyrolysis or by gasification or by both of them for the generation of important hydrocarbons. When the plastics are subjected to gasification, syngas is produced with large
percentage of hydrogen. Additionally, the plastics comes with a higher hydrogen
content and heating value, as compared to other types of municipal solid wastes and
biomass, hence making them the most suitable candidate for hydrogen generation
from the whole solid wastes [7].
Ammonia is another source of hydrogen generation. Ammonia and many of its
derivatives are used as the potential source of sustainable hydrogen. Ammonia as
the source of hydrogen seems appealing as it does not generate oxides of nitrogen
or carbon (carbon dioxide or carbon monoxide) as the by-product, and also the
concentration of the unreactive ammonia during the chemical reaction can be lowered
to 200 ppb by employing appropriate adsorber [8]. It has been reported that the
generation of H 2 by the decomposition of ammonia is economically more feasible
as compared to the reformation of methanol [9]. The evolution of hydrogen from
ammonia requires high temperature and suitable catalyst [10]. A chemical reaction
for the generation of hydrogen from ammonia can be given as [11].
2NH 3 + 6OH
−
→ N 2 (g) + 6H 2 O + 6e
−
6H 2 O + 6e
−
→ 3H 2 (g) + 6OH
−
Oxidation from metal alloys of salt solution results in the generation of hydrogen.
Magnesium alloys are notably important in this regard. It was found that the binary
alloys of Mg are capable of reacting with solutions of sodium chloride in water
[12]. Transition metals like Fe, Cu, Co, or Ni when mixed with Mg even in the small
composition like 0.2 wt.% result in the improved oxidation ability of the magnesium.
This can be associated to the high reduction potential of the transition metals [13].
A simple reaction of magnesium reacting with salts for the generation of hydrogen
is given in the equation below [14]: