Future towards renewable hydrogen storage and powered applications
Future towards renewable hydrogen storage
and powered applications
Electrical and Electronics Engineering
Government college of Engineering
Our ecosystem will no longer be able to nurture the human
species if the exploitation and consumption of fossil fuel sources
continues at its current rate. Hydrogen holds great promise to meet
many of our future energy needs, and it addresses national security and
our environmental concerns. Hydrogen is the simplest, most abundant
element in the universe. The environmental benefits of hydrogen are also
Metal hydride, formed when metal atoms bond with
hydrogen to form stable compounds, are ideal mediums
for portable hydrogen fuel storage.
Metal hydrides are extremely well suited for use in
consumer products requiring safety and ease of
Refueling can be simply performed by replacing a
small hydrogen metal hydride canister.
Schematic of a Metal Hydride -
hydrogen is inserted in
between the atoms in a solid
As an example, the volumetric hydrogen density
of LaNi5H6 is much higher than that of
compressed hydrogen or liquid hydrogen
• Long term stability
• Long life (over 1000 charge cycles)
• Ambient temperature operation (25C nominal)
• Fast re-filing time
• Light weight aluminum metal hydrides
• Good resistance to impurities
• Safe storage due to low pressure system
• Compact in size (compared to compressed hydrogen
• Portability & mobility
Nanocrystalline Mg and Mg2Ni obtained by ball milling exhibit much
faster hydrogen sorption rates at relatively low temperatures
eg: Nanocrystalline Mg and Mg2Ni
Recent work shows that reducing the size of Mg-based hydrides to the nanometer scale can
also alter their stability, which can be characterized by the desorption energy.
The desorption energy of MgH2, which is 74 kJ/mol-H2 for bulk, decreases to 65.3 kJ/mol-
H2 when it is in nanowire form (30–50 nm in diameter).
This experimental result shows that hydrogen desorption energy decreases significantly
when the grain size is smaller than 1.3 nm.
The nanocomposite materials for hydrogen storage encompass a
catalyst and composite chemical hydrides at the nanometer scale. The catalyst
increases reaction rate. The thermodynamic stability of the nano-composite
materials can be controlled by the composite chemical hydride shaving protide
(hydride) (Hδ-) and proton (Hδ+). In addition, the hydrogen absorption kinetics
is accelerated by the nanosize materials and they may change the
thermodynamic stability of the materials.
Catalysts help the dissociation of H2 molecules or the recombination of H atoms.
Ball milling is a simple and effective way to introduce and disperse catalysts into
hydrides, and thus to generate nano sized catalysts.
Various transition metals (Pd, V, Ni), oxides (Cr2O3, Nb2O5), non-metals
(graphite) and compounds play catalytic roles in hydriding/dehydriding reactions of
TiF3-catalyzed MgH2 nanoparticles desorb 4.5 wt.% hydrogen in 6 min at 573K,
and hydrogen uptake can take place even at room temperature.
The activation energy for MgH2 decomposition was found to decrease
significantly owing to the addition of nanosized catalyst.
Mechanisms such as the ‘hydrogen pump’ and the ‘spillover effect’ have been
proposed to explain the catalytic effect.
The underlying catalytic mechanism, however, needs to be further clarified.
The introduction of complex hydrides to
hydrogen storage research has undoubtedly
broadened the materials scope and
enhanced researchers’ capability to design
and optimize new materials.
Typical complex hydrides include
amide–hydride systems,borohydrides, and
e.g. NaAlH4, have been the subject of
• Sodium Borohydrate is the most popular of many
• Solution passed through a catalyst to release H2
• Commonly a one-way process (sodium metaborate must
be returned if recycling is desired.)
• Some alternative hydrates are too expensive or toxic
• The “Millennium Cell” company uses Sodium