1. NANOTECHNOLOGY- CARBON NANOTUBES
Presented by- Nithya Nair

2. CONTENTS
 Nanotechnology
 Introduction to the topic
 History
 Why carbon nanotubes?
 Fundamentals for Hydrogen Storage
i. Physisorption
ii.Chemisorption
 Comparison table
 Synthesis
 Doping
 Conclusion
 References

3. NANOTECHNOLOGY
Nanotechnology is the creation of useful/functional materials, devices
and systems (of any useful size ) through control manipulation of matter
on the 1-100nm length scale and the use of novel phenomena and
properties which arise because of nanometer length scale.
Nanometer
 One billionth of a meter (10-9 m)
 Hydrogen atom 0.04nm
 Proteins 1-20nm
 Chemically reactivity differs .
 Improved mechanical properties
 Increased surface area
 New chemical formulation

4. Source: Silicon Valley Toxics Coalition

5. INTRODUCTION
Carbon nanotubes are extremely thin hollow cylinders made of carbon with pores that
can store gases by the phenomena of adsorption.
Various carbon nanotubes
Single walled nanotubes (SWNT) - diameter range of 0.4 to 3nm .
Multi walled nanotubes (MWNT) - several sheets, arranged concentrically in
increasingly larger diameters with diameters in the range of 1.4 to 100 nm.
Metal doped nanotubes - Obtained by doping of various metals to carbon nanotubes.

6. HISTORY
 After Kroto & Smalley discovered Fullerene, one of carbon allotropes (a
cluster of 60 carbon atoms: C60) for the first time in 1985, Dr.Iijima, a
researcher for this new material , in Japan discovered in 1991, a thin long
straw-shaped carbon Nanotubes during TEM analysis of carbon clusters.

7. PROPERTIES
 A carbon atom in nanotube forms a hexagonal lattice of sp² bond with three
other carbon atoms.
 As the inner diameters of the tubes are extremely thin down to about
several nanometers, the tubes are called Nanotubes.
 Thermal conductivity (>3000 W/m-K),
 The elastic ability to extend ≈5.8% of its original length
 More appealing still is the disproportionately large surface area to volume
that these materials possess , for this allows for a greater potential of
interactions, both physical or chemical in nature

8. APPLICATIONS IN HYDROGEN STORAGE
 Depleting non- renewable source of energy prompting us to move to an
energy resource which is abundantly available and which is eco- friendly as
well.
 „Hydrogen‟ ,sought as future fuel because of high energy content than any
other fuel, at least 3 times than gasoline.
 Advantage- clean fuel, byproduct only water.
 Disadvantage- low energy density by volume. So difficult to store and
transport.

9. WHY CARBON NANOTUBES FOR H2 STORAGE
Available techniques for hydrogen storage-
 As cryogenic liquid
 As pressurized gas
 As physical combination with metal hydrides/complex hydrides on board
production
 By reform of methanol
 Carbon nanotubes

10. HYDROGEN STORAGE FUNDAMENTALS
Physisorption
 Based on Vander Waal‟s interaction.
 Stem from intermolecular forces between atoms that result from instantaneous
charge distribution in atoms & molecules when they approach each other.
 The interaction energy, also called the London Dispersion forces
 Adsorption on a flat carbon surface depends on the adsorption stereometry.
 An average value would be 4-5 kj mol⁻1.This represents a very weak
interaction .Therefore, hydrogen is desorbed with increasing temperature, and a
very little hydrogen adsorption is observed on carbon at elevated temperature.

11. Source:greener-industry.org.uk website

12. CHEMISORPTION
 If the π-bonding between the carbon atom were to be fully utilized, every
carbon atom could be a site for chemisorptions of one hydrogen atom.
 Desorption results of nanotubes treated with chemisorbed
hydrogen, however, can only be released at higher temperatures.
 Hydrogen storage in CNTs by chemical reaction, on the other hand , has
largely been discounted as irreversible and thus technologically less relevant

13. TABLE 1.1 VARIOUS SAMPLES OF CARBON NANOTUBES AND
THEIR HYDROGEN STORAGE CAPACITY [11],[14]
Sample % Purity H₂ (wt%) T(K) P(MPa) Ref.
SWNTs Assumed 100 5-10 133 0.04 (A.C. Dillon et al.,
1997)
SWNTs 50 4.2 300 10.1 (C. Liu et al,1999)
SWNTs High 8.25 80 7 (Y. Ye et al, 1999)
SWNTs Purified 1.2 Ambient 4.8 (Smith Jr, Bittner,Shi,
Jhonson, & Bockrath,
2003)
SWNTs 90 vol% 0.63 298 - (Ritschel et al., 2002)
SWNTs Purified 6 77 0.2 (Pradhan et al., 2002)
SWNTs Unpurified 0.93 295 0.1 (Nishimaya et al.,
2002)
SWNTs Unpurified 0.37 77 0.1 (Nishimaya et al.,
2002)
MWNTs Purified 0.25 ~300-700 Ambient (Wu et al., 2000)
MWNTs Unpurified 0.5 298 - (Ritschel et al., 2002)
MWNTs High 5-7 300 1.0 (Y. Chen et al., 2001)
MWNTs High, acid treated 13.8 300 1.0 (Y. Chen et al., 2001)
MWNTs High 0.7-0.8 300 7.0 (Badzian, Breval &
Piotrowski, 2001)

14. SYNTHESIS
Source: B lue penguin report
Schematics of a laser ablation set-up, reproduced from B. I. Yakobson and R.E. Smalley, American Scientist 85, 324 (1997).

15. METAL DOPED CARBON NANOTUBES
 Metal doping provides additional binding energy state of hydrogen.
 Transition metals doped- V, Ti, Pt and Pd.
 Storage condition : 30 atm, 300K
 Enhanced hydrogen storage capacity on doping, the reversible hydrogen storage
capacity of doped nanotubes.
April 2011 Journal of the American Chemical Society

16. CHALLENGES TO OVERCOME
 High accessible surface, large free pore volume & strong
interactions- Three main demand for high hydrogen storage
capacity.
 A more accurate & practical approach towards studying
thermodynamics, Kinetics, Adsorption /Desorption of
nanotubes.
 Mass production of carbon nanotubes with controlled
microstructures at a reasonable cost.

17. REFERENCES
1. ZHANG, Ei- fei; LUI, Ji-ping; LU, Guang- shu. “Preparation of Isolated Single Wall
Carbon Nanotubes With High Hydrogen Capacity.”[J],(The Chinese Journal Of
Process Engineering),Vol.6, No.3, June 2006.
2. Baughman, Ray H.; Anvar A. Zakhidov, and Walt A. De Heer. "Carbon Nanotubes:
The Route toward Applications." Science 297 (2002): 787-92.
3. Iijima,S., Nature(1991) 354, 56.
4. http://www.energy.gov
5. U.S. Department of Energy‟s Efficiency and Renewable Energy Website.
https://www1.eere.energy.gov/hydrogenandfuelcells/storage/current_technology.
html(2010).
6. KUNG Chaoi, “Carbon Nanotubes for Hydrogen Storage”. Nov. 2002.
7. Yunjin, “Hydrogen Storage using carbon Nanotubes.” Hefei University of
Technology, China
8. DILLON, A.C.; GENNET, T.; GELLEMEN, J.L.; JONES, K.M.; PARILLS, P.A. and
Heben, “Optimization of Single –Wall Nanotube Synthesis For Hydrogen Storage”.
National Renewable Energy Laboratory.

18. 10. NIKITIN, Anton; LI, Xialolin; ZHANG, Zhang; OGASAWARA, Hirohita; DAI, Hongjie &
NILSSON, Anders. “Hydrogen Storage in Carbon Nanotubes through the Formation of
Stable C-H Bonds” Nano Letters, 2008 Vol.8, No.1 (162-167) .
11. Dillon, A. C.; K. M. Jones; T. A. Bekkedahl; C. H. Kiang, D. S. Bethune, and M. J. Heben.
"Storage of hydrogen in single-walled carbon nanotubes." Nature 386 (1997): 377-79.
12. Liu, C., Y. Y. Fan, M. Liu, H. T. Chong, H. M. Cheng, and M. S. Dresselhaus. "Hydrogen
Storage in Single-Walled Carbon Nanotubes at Room Temperature." Science 286 (1999):
1127-129.
13. “Chemical Activation Of Single Walled Carbon Nanotubes for Hydrogen Adsorption’’.
SMITH, Milton R.; BIITTNER, Edward W.; SHI, Wei & BOCKRATH, C. Bradely.
14. Chen, Y. L., B. Liu, J. Wu, Y. Huang, H. Jiang, and K. C. Hwang. "Mechanics of hydrogen
storage in carbon nanotubes." Journal of the Mechanics and Physics of Solids 56 (2008):
3224-241.
15. http://www.nanowerk.com
16. http://www.ewels.info/science/publications/papers/2008.DopingChapter.pdf