1. Debesh Samanta
12I170014
Hydrolysis of Complex Hydrides
for Hydrogen Generation
Submitted by- Debesh Samanta
(Roll No. 12I170014)
Under guidance of
Professor Pratibha Sharma
Department of Energy Science & Engineering
INDIAN INSTITUTE OF TECHNOLOGY- BOMBAY
April, 2013

2. Introduction
Renewable energy carrier.
Hydrogen on combustion produces clean
exhaust.
Very high energy density (142MJ/kg , around
three times higher than that of petroleum, 47
MJ/kg).
2Slide of 25

3. Different types of possible hydrogen storage and
issues related to them.
Gaseous storage :
 Very high pressure
 Low volumetric storage density
 Very high diffusivity of H2 amd metal embrittlement.
Liquid storage :
 Very low boiling point of Hydrogen (20 k)
 The refrigerator system is energy intensive process.
 boil off losses.
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4. Advantages of solid storage
 The drastic decrease in safety risk.
 Easy to initiate the reaction.
 Long time storage.
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5. Metal organic frameworks (MOF), carbon
nano-tubes, nonporous materials, Pd etc.
The metal hydrides alloys
like, MgH2, LaNi5, TiNi, NiFe.
Light metal complex hydrides
Solid hydrides used in hydrolysis
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6. Why complex hydrides?
Advantage of light metal complex hydrides
low molecular weight.
capability of carrying up to 4H-
Solubility in water.
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7. Why hydrolysis?
Thermolysis:
Advantage-Volumetric storage density is
higher
Limitation- Demands a very high temperature.
Hydrolysis:
Reaction starts even in room temperature.
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8. DOE target
Target 2010
(new)
2010 (old) 2015
(new)
2015
(old)
Ultimate
Full Fleet
System
Gravimetric
Density
(% wt)
4.5
(1.5
kWh/kg)
6
(2.0
kWh/kg)
5.5
(1.8
kWh/kg)
9
(3
kWh/kg)
7.5
(2.5
kWh/kg)
System
Volumetric
Density
(g/L)
28
(0.9
kWh/L)
45
(1.5
kWh/L)
40
(1.3
kWh/L)
81
(2.7
kWh/L)
70
(2.3
kWh/L)
System Fill Time
for 5-kg fill,
min (Fueling
Rate, kg/min)
4.2 min
(1.2
kg/min)
3 min
(1.67
kg/min)
3.3 min
(1.5
kg/min)
2.5 min
(2.0
kg/min)
2.5 min
(2.0
kg/min)
Source: DOE targets for onboard Hydrogen storage systems for light-duty vehicles: current R&D focus is on 2015 targets with potential to meet
ultimate targets. http://www1.eere.energy.gov/hydrogenandfuelcells/storage/pdfs/targets_onboard_hydro_storage.pdf. accessed on 08-Apr-138Slide of 25

9. Hydrolysis of complex hydrides
NaBH4 hydrolysis
NaBH4 + 2H2O →NaBO2 + 4H2 ∆H = -75kJ/mol H2
 If 1 gm of NaBH4 is fully ionized it produce 2.37 l of
hydrogen at STP.
 GSD is 10.8wt% which is greater than the DOE
target.
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10. NH3BH3 hydrolysis
NH3BH3 + 2H2O → NH4
+ + BO2
- + 3H2
Gravimetric hydrogen densities -19.6 wt%
LiBH4 hydrolysis
LiBH4 + 4H2O → LiOH + H3BO3 + 4H2
LiBH4 + 2H2O → LiBO2 + 4H2
Gravimetric hydrogen densities -18.5 wt.%
Volumetric hydrogen densities -121 kg H2/m3
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11. N2H4BH3 hydrolysis
N2H4BH3 + 2H2O catalyst N2H5BO2 + 3H2
Gravimetric hydrogen densities – 15.4 wt%
MgH2 hydrolysis
MgH2 + 2 H2O → 2 H2 + Mg(OH)2
Gravimetric hydrogen densities – 7.66%
LiAlH4 hydrolysis
LiAlH4 + 4 H2O → LiOH + Al(OH)3 + 4 H2
Gravimetric hydrogen densities – 10.6 wt%11Slide of 25

12. Catalytic research
The catalysts generally used in hydrolysis can
be classified as –
 Transition metal or non-noble metal catalysts
 Noble metal catalysts
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13. Catalytic researches on NaBH4
Non-noble metal catalysts
Most effective
Cobalt (II) chloride followed by Nickel(II)
And Iron, Manganese Chloride.
Cobalt mainly alloy with boron.
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14. Effect of introduction of other materials
Introduction of other elements into Co-B
catalysts increases its activity.
Reason(s)
 An increase in electron density of the
metallic Co active site.
 Surface area increases because the additive
metals inhibit Co agglomeration.
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15. Stability of Catalyst
Example
a filamentary Ni catalyst is studied over 200
catalytic cycles, and retained 76% of its initial
activity.
Reason:
Gradual formation of a film, consist of
hydrated borax (Na2B4O7.10H2O) and boron
oxide (B2O3), on the catalyst surface.
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16. Noble metal catalyst
Higher concentration of NaOH stabilizer in
solution decreases the activity of Ru. So Ru-based
catalysts may not be the most ideal choice.
The Pt catalyst loaded on LiCoO2 - one of the
most efficient catalysts for NaBH4 hydrolysis.
The most active catalyst reported is Rh loaded on
TiO2
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17. Catalytic research on NH3BH3
Non-noble metal catalyst
1. Co, Ni and Cu supported catalyst- the most
catalytically active.
2. supported Fe is catalytically inactive.
3. the amorphous Fe nano-particles form in situ in
presence of NaBH4 show exceptionally high
catalytic activity .
Reasons(3)
much greater structural distortion
much higher concentration of active sites for the
catalytic reaction 17Slide of 25

18. • Noble metal-based catalysts
The 20 wt% Pt/C catalyst shows the super high
activity and the reaction is completed in less
than 2 min.
Reason
reduction of Ptn+ (n = 4, 6) to Pto during the
course of the reaction,
Rh[(1,5-COD)(μ-Cl)]2 and Pd black have
lower activity and some noble metal oxides
(RuO2, Ag2O, Au2O3, IrO2) are almost inactive.
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19. Issues related with hydrolysis
 Water handling
 Catalytic cycle
 Reversibility of the reaction
 Heat management
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20. NaBH4 + 2H2O → NaBO2 + 4H2 + heat
NaBH4 + (2 + x)
H2O → NaBO2·xH2O + 4H2 + heat
where x is the hydration factor.
In practice, the hydrated by-product is usually
either NaBO2·2H2O or NaBO2·4H2O, which
requires an excess of water.
Water handling
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21. The activity loss in case of noble metal catalyst is
very much lower than that of non-noble metal
catalysts.
Reason of decrease in activity:
In case of NaBH4 it is the gradual formation of a
film, consist of hydrated borax (Na2B4O7.10H2O)
and boron oxide (B2O3), on the catalyst surface.
Catalytic cycle
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22. More the reversibility of the reaction cost of the
hydrolysis will be lower.
NaBO2 + 2MgH2 NaBH4 + 2MgO
NaBO2 + 2CH4 NaBH4 + 2CO + 2H2
Reversibility of the reaction
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23. NaBH4 + (2 + x) H2O → NaBO2·xH2O + 4H2 + heat
Issues at a glance
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Issue:
Cost
Issues:
Catalytic reactivity
Catalytic durability
Catalyst cost
Issues:
Recycling
Solubility
Issues:
Excess water
Storage capacity
Issue:
Heat
management

24.  Boron based compound are dominating in the process
of hydrogen generation.
• low molecular weight.
• capability of carrying up to 4Hd-
 The non-noble metal catalysts have been developed
with activity of similar level of noble metal catalysts.
 A lower-cost alternative.
 There are other issues like water handling, recovery of
reactant etc.
 Hydrolysis of NaBH4 - exothermic process and the heat
must be controlled.
Conclusion
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