Metal Nanoparticle/Carbon Nanotube Catalysts. Brian Morrow School of Chemical, Biological and Materials Engineering University of Oklahoma. A. Kongkanand, K. Vinodgopal, S. Kuwabata, P. V. Kamat, J, Phys. Chem. B 110 (2006) 16185-16188. Introduction. Armchair. Zigzag. Chiral.
School of Chemical, Biological and Materials Engineering
University of Oklahoma
A. Kongkanand, K. Vinodgopal, S. Kuwabata, P. V. Kamat, J, Phys. Chem. B 110 (2006) 16185-16188Introduction
Carbon nanotubes have many properties which make them ideal supports for catalytic metal nanoparticles.
However, the surfaces of nanotubes are relatively inert, and they tend to form bundles which reduces their surface areas.
Metal nanoparticle/carbon nanotube materials are being investigated for use in catalytic and electrocatalytic applications such as fuel cells.
Baughman et al., Science 297 (2002) 787
Anode (methanol oxidation):
CH3OH + H2O → CO2 + 6H+ + 6e-
Cathode (oxygen reduction):
(3/2)O2 + 6H+ + 6e- → 3H2O
CH3OH + (3/2)O2 → CO2 + 2H2O
K. Kleiner, Nature 441 (2006) 1046-1047
Possibility for powering devices such as cell phones and computers:
- Potentially 3-10 times as much power as a battery
- Methanol cheaper and easier to store than hydrogen
- Methanol crossover
- Requires catalysts, usually platinum – expensive!
Methanol oxidation - anode of direct methanol fuel cells
Oxygen reduction - cathode of direct methanol fuel cells
Langmuir 22 (2006) 2392-2396
Metal particles can be grown directly on the carbon nanotubes
- Precursor metal salts (H2PtCl6, H2PdCl6, etc.) heated and reduced
- Particle size can be controlled by temperature and reducing conditions
- Particles can be anchored by oxidizing nanotubes (via acid treatment or microwave irradiation), but this can also damage the nanotubes
Georgakilas et al., J. Mater. Chem. 17 (2007) 2679-2694
Other techniques include chemical vapor deposition, electrodeposition, laser ablation, thermal decomposition, substrate enhanced electroless deposition
Already-grown metal particles can be connect to the carbon nanotubes
Hydrophobic interactions and hydrogen bonds
Han et al. Langmuir 20 (2004) 6019
Coleman et al., J. Am. Chem. Soc. 125 (2003) 8722
Ou and Huang, J. Phys. Chem. B 110 (2006) 2031
“X-ray photoelectron spectroscopy
was employed to investigate the binding energy of d-band
electrons of Pt. As shown in Figure 6, a shift of 0.4 eV to a
higher binding energy was found in both 4d and 4f electrons of Pt deposited on PW-SWCNT, proving the role of SWCNTs in
modifying the electronic properties of Pt.”
A. Kongkanand et al.,J. Phys. Chem. B 110 (2006) 16185-16188