L. HIMA KUMAR

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ON SOME CHALLENGING AVENUES IN HYDROGEN STORAGE
L. HIMA KUMAR CY02D017
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CONTENT

• Chapter 1 Introduction
• Chapter 2 Experimental methods
• Chapter 3 Sorption properties of Mg2Ni prepared
  by polyol reduction method
• Chapter 4 Dehydriding behavior carbon admixed
  LiAlH4
• Chapter 5 Hydrogen storage properties of
  alanates admixed nitrogen
  containing carbon nanotubes
• Chapter 6 Hydrogen storage properties of Mg-N
  and B containing carbon
  composites
• Chapter 7
• Chapter 8 Summary and conclusions

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Chapter 1 - INTRODUCTION
4
Volumetric and gravimetric densities of different
storage media
A. Züttel, Materials Today, September (2003)
18-27
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OBJECTIVE

• Improving the hydrogen storage properties of Mg
  and complex metal hydrides

STRATEGY
NaBH4
Alanates
Mg, Mg2Ni
? Synthesis of nano Mg2Ni ? Addition of
heteroatom containing carbons
Cobalt based Catalysts
Addition of carbon materials
6
Experimental setups for kinetics measurement
Hydrogen sorption measurements
of H2 absorbed by the material
Hydrogen generation kinetics measurements
7
Chapter 3 - SORPTION PROPERTIES OF Mg2Ni PREPARED
BY POLYOL REDUCTION
Synthesis of Mg2Ni
C.-M. Chen and J.-M. Jehng, Applied Catalysis A
General 267 (2004) 103110
8
TEM image of Mg2Ni alloy
XRD pattern of Mg2Ni prepared by polyol
reduction method and annealed at 623 K for 4 h
Particle size 30 to 70 nm
9
Hydrogen sorption measurements
Absorption kinetics at 25 bar
Desorption kinetics

• Maximum hydrogen storage capacity of the Mg2Ni
  is about 3.0, 3.12 and
• 3.23 wt at 473, 523 and 573 K respectively
• ? Maximum amount of hydrogen desorbed in 30 min
  was found to be 0.75, 1.61 and 2.5 wt at
  473, 523 and 573 K respectively

10
Pressure-composition isotherms of nano-Mg2Ni at
548, 573 and 603 K.
vant Hoff plot ln Peq vs. 1/T

• Hydrogen absorption capacities are 2.8, 3.03 and
  3.20 wt at 548, 573 and
• 603 K respectively
• Enthalpies and entropies of the Mg2Ni -50.03
  kJ/mol, -103.60 J/(mol K) for
• absorption and 56.35 kJ/mol, 105.36
  J/(mol K) for desorption, respectively

L.Himakumar, B. Viswanathan and S. Srinivasa
Murthy, J. Alloys and Comp. ( in press)
11
Electrochemical measurements
Working electrode Mg2Ni alloy pellet Counter
electrode Pt Reference electrode
Hg/HgO Electrolyte 6M KOH
Charging 50 mA/g for 12 h Discharging Rest
time 10 min End potential -0.6 V vs
Hg/HgO Current density 20, 50, 100 mA/g
Discharge capacity (mAh/g) Current (mA) x Time
(h) /Active weight of material (g)
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12
Discharge curve (first cycle) of Mg2Ni alloy in 6
M KOH at room temperature
Discharge capacity vs. discharge current density
Electrochemical hydrogen pressurecomposition
isotherms for Mg2Ni,
Discharge capacity as a function of cycle number
Maximum discharge capacity 408 mAh/g
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SUMMARY

• Nanosize Mg2Ni alloy, synthesized by polyol
  reduction and subsequent annealing at 573
  K has shown promising hydrogen absorption as well
  as electrochemical hydrogen absorption
  characteristics
• The maximum hydrogen storage capacity observed
  was 3.23 wt at 573 K. It absorbs 3. 2
  wt of hydrogen with in 1 min and desorbs 2.5 wt
  of hydrogen with in 15 min at 573 K
• The maximum discharge capacity was found to be
  408 mAh/g at a discharge current
  density of 20 mA/g. The materials show good
  stability for number of cycles
  degradation was only 32 of maximum discharge
  capacity after 15 cycles

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Chapter 4 - Dehydriding behavior carbon admixed
LiAlH4
Dehydrogenation reaction 3 LiAlH4 ? Li3AlH6
2 Al 3 H2 (5.3 wt H2) (1)
Li3AlH6 ? 3 LiH Al 3/2 H2 (2.6 wt. H2)
(2)
Catalyst - Transition metals Ti
V based compounds shows higher catalytic
activity
Doping of alanates - (1) wet chemical method
(2) dry method (ball milling)
Materials LiAlH4, Carbon ( Vulcan XC72R (VC),
Mesoporous carbon (MC), Black pearls 2000 (BP),
CDX 975 (CDX ))
Admixing with carbon 2 g of LiAlH4 was weighed
in argon filled glove box and to this 5 wt. of
Carbon ( VC, BP, CDX, MC , CNF) was added and
milled for 45 min.
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Surface area and dehrogenation rate for various
carbons
Dehydrogenation profiles for pure LiAlH4 LiAlH4
VC (5 wt ) and LiAlH4 MC (5 wt ) , LiAlH4
CDX (5 wt ) , LiAlH4 BP (5 wt ) at 408 K
Desorption rate BPCDX gtMCgtVC
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Dehydrogenation kinetics of LiAlH4 admixed With
5 wt of CDX at (?) 398 K (?) 408 K (?) 418 K
Dehydrogenation kinetics of LiAlH4 admixed With
(?) 5 wt (?) 7 wt (?) 9 wt CDX at 408 K
Activation energy LiAlH4 80
kJ/mol LiAlH4 C 56 kJ/mol.
L.Himakumar, B.Viswanathan and S. Srinivasa
Murthy, Bull. Cat. Soc. India, 5 (2006) 45.
17
Synthesis of carbon nanofibers

H-ZSM-5
Ni(NO3)2 Cu(NO3)2
(NH4)2CO3 , pH 9
Stirring 24 h, dry
Calcination at 773 K for 12 h
H2, 673 K for 24 h
10 wt Ni-Cu(73)/H-ZSM-5
H2, 873 K for 30 min
C2H4/H2(41), 100 ml/min for 1.5 h, 1173 K
973 K for 4 h, Air
20 HNO3 for 24 h, 48 HF
filtered, washed with water and dried at 373 K
for 8 h
Carbon nanofibers (CNF)
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SEM image of CNF
TEM image of CNF
diameter 90 nm
XRD of CNF
19

• No appreciable change in XRD of LiAlH4 after
  admixing with CNF
• Particle size ranging from 1 to 30 ?m

20
Dehydrogenation kinetics of LiAlH4 admixed with 5
wt of CNF at 398 K, 408 K and 418 K
Dehydrogenation profiles for pure LiAlH4, LiAlH4
VC (5 wt ) and LiAlH4 CNF (5 wt ) at 408 K
L.Himakumar, B. Viswanathan and S. Srinivasa
Murthy, Int. J. Hydrogen Energy ( in press)
21
Fit of the JMA model to experimental dehydrogenati
on data
Logarithmic form of JMA equation
Activation energy 46?0.2 kJ/mol
Arrhenius plot
22
Dehydrogenation profiles for (A) LiAlH4 CNF (5
wt ) and (B) LiAlH4 CNF (5 wt ) VCl3 at 408
K
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Role of carbon nanofibers

• High density of grain boundaries , Nucleation
  centers for new phases
• Dispersion of alanate particles, Provide
  shorter diffusion paths for hydrogen and
  species involved in the reactions
• The increase in the catalytic activity of
  transition metals upon co- doping with
  carbon or carbon nanofibers is due to the
  formation of bridged species for the
  transport of active species between the alanate
  and the additive particles.
• Spill over of chemical species from one phase to
  another through the assistance of ad
  lineation layer like hydrogen spill-over assisted
  by water molecules

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SUMMARY

• Carbon nanofibers were synthesized by using Ni-Cu
  (73) alloy supported on H-ZSM-5 as catalyst
  and C2H4 as carbon source
• Addition of CNFs to Lithium aluminum hydride
  improved significantly its decomposition
  kinetics by increasing the grain boundaries and
  providing the transition site for hydrogen
  transfer
• LiAlH4 doped with 3 mol VCl3 and CNFs exhibited
  rehydrogenation capacity of 3.7 wt of hydrogen
  at 373 K and 20 bar pressure

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Chapter 5 - Hydrogen storage properties of
alanates admixed nitrogen containing carbon
nanotubes
Preparation of nitrogen containing carbon
nanotubes
SEM image of NCNT
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Synthesis of Alanate-NCNT composites
Materials NaAlH4(NAH)/LiAlH4(LAH) 5 wt
NCNT Grinding 30 min in Ar filled glove box
XRD pattern for (a) LAH and LAH-NCNT (b) NAH and
NAH-NCNT composite
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b
Comparison of DSC curves for the at the scan
rate of 20 ?C/min
Kissingsers equation ln(ß/Tm2) -E/RTm
lnAR/E ß- scan rate, Tm Peak temperature,
R- gas constant, E activation energy,
A-frequency factor
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IR spectra
In-situ IR spectra
NAH
NAH NCNT
Al-H stretching frequency of NaAlH4 altered by
admixing with NCNT and results in the lowering
of decomposition temperature by 35 C which is
evidenced from FT IR and DSC studies
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Dehydrogenation studies
XRD pattern for NAH-NCNT composite after
desorbing at 473 K
Desorption profile for the NAH-NCNT composite at
473 K
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Isothermal dehydrogenation kinetics of NAH-NCNT
at 473, 483 and 493 K
Arrhenius plot
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Rehydrogenation studies
Material NAH-NCNT Temperature 473
K Pressure 80 bar
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SUMMARY

• Nitrogen containing carbon nanotubes were
  prepared by using
• AAO template.
• Al-H stretching frequency of NaAlH4 altered by
  admixing with
• NCNT and results in the lowering of
  decomposition temperature
• by 35 C which is evidenced from FT IR and
  DSC studies.
• Dehydrogenation kinetics of sodium and lithium
  aluminum
• hydrides were improved by addition of NCNT.
• NaAlH4 was rehydrogenated to give 4 wt of
  hydrogen reversibly

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Chapter 6 - Hydrogen storage properties of Mg-N
and B containing carbon composites
Preparation of boron containing carbon
SEM image of CB
H.-Q. Xiang et al., Solid State Ionics 148 (2002)
3543
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Preparation of nitrogen containing carbon
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Synthesis of Mg-C composites
Materials Mg 10 wt C
( C CB, CN, G) Ball milling Time 3 h Speed
300 RPM Ball to powder ratio 151
XRD pattern for the Mg-C composites
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SEM images of Mg- C composites
(B)
(A)
(A) Mg CB( 50?m) (B) Mg CN ( 80?m) (C) Mg
G (30?m)
(C)
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Hydrogen sorption studies
Mg- CN
Mg-CB
Mg- G
X-ray diffraction pattern for Mg-C composites
after hydrogenated at 523 K
Hydrogen absorption by Mg-C Composites at 573 K
20 bar
After 15 min the max storage capacity found to be
6 wt, 5.2 wt and 4.8 wt for Mg-CN, Mg-CB and
Mg-G respectively
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Hydrogen desorption by Mg-C Composites at 573 K
1bar
DSC profile for hydrogenated Mg-C composites
with the scan rate of 5 C/min
Boron and nitrogen containing carbon shows a
pronounced effect on the sorption properties of
Mg Dissociation temperature lowered by 20 ?C in
the case of Mg CN Compared to pure MgH2
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Chapter 7 - Catalytic effects in generation of
hydrogen from NaBH4
?
NaBH4 NaH B
H2 Hydrolysis of alkaline sodium borohydride
solution NaBH4 2 H2O
NaBO2 4 H2 Q (317 kJ)
(7.3 wt
of H2)
C. M. Kaufman and B. Sen, J. Chem. Soc., Dalton
Trans., (1985) 307 - 313
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Preparation of Co-M catalysts (M Ni, Cr, Mo and
Sn)
CoCl2.6H2O/ M- precursor in CH3OH (11
mol ratio ) NaBH4 in 0.2 M NaOH
Stirred for 30 min, RT
Filtered dried at 373 K
Co-M
Annealing in H2 atm for 3 hrs at 573 K
Co-M/Co-MO catalyst
G. N. Glavee, K. J. Klabunde, C. M. Sorensen and
G. C. Hadjipanayis Inorg. Chem. 32 (1993)474 - 477
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13 nm
15 nm
a
b
d
c
XRD pattern for (a) Co-Ni (b) CoSn and (c)Co-Cr
(d) Co-Mo
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Calibration of catalyst activity
Reaction mixture 20 ml of 1.5 wt NaBH4 1M
NaOH
L.Himakumar, B.Viswanathan and S. Srinivasa
Murthy, Bull. Cat. Soc. India, 5 (2006 ) 94.
43
XRD pattern of Co-Mo catalyst after heat
treatment at 500 ?C in H2 atm
Comparison of catalytic properties between Co-Mo
and Co-Ni (catalyst 0.1 g, solution 20 ml of
1.5 wt NaBH4 1M NaOH)

• MoOx in Co-Mo catalyst can act as oxygen source
  it induces the surface hydroxyl groups
• The hydroxyl groups are weakly bound to the
  surface of MoOx

XRD pattern of regenrated Co-Mo catalyst after
heat treatment at 300 ?C in H2 atm
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Effect of NaOH concentration
Catalyst 0.1g Co-Ni Reaction mixture 20 ml of
1.5 wt NaBH4 X wt NaOH H2O
Maximum H2 storage capacity for NaBH4 NaOH
solution as a function of NaOH concentration
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Effect of temperature
Co-Cr2O3
Co-Sn
Co-MoO3
Reaction mixture 20 ml of 1.5 wt NaBH4 10
wt NaOH H2O
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Activation energies and rate of borohydride
hydrolysis for Cobalt based catalysts

• ? Co-Metal oxide was more active than Co-Metal
  catalyst
• ? Among the examined catalysts Co-Mo showed
  higher
• catalytic activity

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SUMMARY

• Hydrogen generation by the hydrolysis of NaBH4
  using cobalt based catalysts was studied.
• The effect of temperature and NaOH concentration
  on the hydrogen generation rate were
  studied.
• ? The prepared catalyst presents good activity
  for the hydrogen generation
• ? The reaction rate increases with an increase in
  temperature and NaOH concentration up to 12
  wt.

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CONCLUSIONS

• Among the various options for solid state
  hydrogen storage, Mg based systems and
  complex metal hydrides appear to be viable
  options.
• To facilitate the desorption kinetics, the
  adaptable strategy is to introduce foreign
  materials which posses affinity for hydrogen as
  well as promote the spill over
  (transport) of hydrogen from storage systems.
• Carbon based systems have been observed to
  increase the desorption kinetics by
  facilitating the diffusion and spill over of
  hydrogen from storage systems and also
  subsequent desorption of hydrogen.
• In the case borohydrides alternate route for
  hydrogen generation based on catalytic hydrolysis
  is possible.

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• List of Publications
• L. Hima Kumar, B.Viswanathan and S. Srinivasa
  murthy, Photo/Electro chemistry and Photobiology
  in the Environment, Energy and Fuel vol 4, 2005,
  13-42. Ed. Kaneco, Research signpost.
• L. Hima Kumar, B.Viswanathan and S. Srinivasa
  Murthy, Bull. Cat. Soc. India 5 (2006) 45-54.
• L.Hima Kumar, B.Viswanathan and S. Srinivasa
  Murthy, Bull. Cat. Soc. India 5 (2006) 45-54.
• L.Hima Kumar, B.Viswanathan and S. Srinivasa
  Murthy, J. Alloys Comp 461 (2007) 72-76.
• L.Hima Kumar, B.Viswanathan and S. Srinivasa
  Murthy, Int J Hydrogen Energy 33 (2008) 366-373.
• National/International workshop/conferences
• B. Viswanathan, L. Hima Kumar and S. Srinivasa
  Murthy, Indo-Belarus workshop on Advances in
  sorption based thermal devices held at Minsk,
  Belarus, 2-3 Nov 2004.
• L. Hima Kumar, B. Viswanathan and S. Srinivasa
  Murthy, National workshop on the catalysis for
  energy, held at Banaras Hindu University,
  Varanasi, India, Feb 23rd - 25th, 2006
• L. Hima Kumar, B. Viswanathan and S. Srinivasa
  Murthy, International Workshop on Hydrogen
  Energy (Production, Storage and Application) held
  in November 5-9, 2006, Jaipur, India.

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Acknowledgement

• Prof. B. Viswanathan
• Prof. S. Srinivasa Murthy
• The Heads of Department of Chemistry and Deans
• The Doctoral committee members and faculty of the
  Department of Chemistry
• The authorities for providing the various
  facilities
• The supporting staff, fellow research scholars
  and friends
• MNES, IIT Madras, CCC for fellowship

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Thank you