II International Symposium on Carbon for Catalysis ABSTRACTS

PP-I-24
SINGLE WALL CARBON NANOTUBE MATERIAL AS A SUPPORT FOR Pt
CATALYST
Krestinin A.V., Zvereva G.I., Zhigalina O.M. 1 , Kislov M.B., Raevskii A.V., Kiselev N.A. 1
Institute of Problems of Chemical Physics, RAS, Chernogolovka, Russia
1 Institute of Crystallography RAS, Moscow, Russia
e-mail: kresti@icp.ac.ru
Application of single wall carbon nanotubes (SWNTs) as a support for catalysts has
several features in comparison to other carbon materials. Purified SWNTs easily aggregate
with each other forming microcrystals (ropes) because of strong Van der Waals forces
between nanotube walls to be present as highly entangled mats formed by such ropes. Powder
of purified SWNTs produced by standard technology from the arc process raw material [1,2]
contains mostly nanotube mats in size of several tens of microns. Nevertheless the powder has
a large specific surface area of ~ 200 – 400 m 2 /g.
Nanotubes themselves and their ropes are very stable structures, which can not be broken
into pieces even under long sonication in a liquid. Standard methods of SWNT dispersion by
means of ultrasonic treatment in solutions of surface active agents do not lead to a complete
dispersion of SWNT into individual nanotubes (nano-dispersion). After sonication the
solution contains filaments of different sizes – from separate nanotubes of ~ 1,5 nm in the
diameter and less than 1 μm long up to ropes of 0.1 – 0.2 μm in the diameter and a few tens of
μm long. Due to strong optical activity of SWNT crystals [3] the level of nanotube dispersion
can be easily estimated by polarized light in an optical microscope. One can separate a SWNT
dispersion by centrifugation into several fractions, which will contain SWNT ropes of nearly
the same sizes. Specific surface area of carbon filaments into such fractions may be varied
from ~ 600 m 2 /g up to the upper limit for carbon material of ~ 1360 m 2 /g (solution of
individual nanotubes). The solutions of individual nanotubes and their ropes can be used as a
support for catalyst precipitation in wet chemistry. Due to a large specific surface area of
carbon nanostructures in the solution the catalyst particles may have small sizes of about
2 – 5 nm even by 10 –20 wt. % loading of metals (Fig.1).
A serious obstacle in the way of SWNT application in the catalysis is the high price of
purified SWNTs, which may stay at the level of $60 - $100 per 1 gram during the nearest
years [1]. Nevertheless in some occasions the high price seems not to be a hindrance. For
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