*****For immediate use August 30, 2001
NEC uses Carbon Nanotubes to Develop a Tiny Fuel Cell for Mobile Applications
-A Big Step for Next-generation Energy with Nano-technology-
TOKYO August 30, 2001 - NEC Corporation (NEC) (NASDAQ: NIPNY) (FTSE: 6701q.l)
(TSE: 6701) and the Japan Science and Technology Corporation and the Institute
of Research and Innovation today announced they have developed a tiny fuel cell
for mobile terminals using the much anticipated carbon technology raw material
- carbon nanotubes - as electrodes, confirming the fuel cell characteristic is
much improved compared with conventional type, which uses activated carbon. This
result was attained by using the minute and unique structure of the "carbon
nanohorn", which is one type of the carbon nanotube. The fuel cell has about
10-times the energy capacity compared with a lithium battery, and if used for
personal computers, in the future, a continued usage time of several days can
be expected.
The fuel cells, which directly transform the chemical reaction energy between
hydrogen and oxygen into electric energy, are seen as the energy source of the
next- generation. With their environmentally friendly and high efficiency characteristics
the cells are being researched and developed as the future energy for the automobile
and as energy generation for the home. The energy capacity is expected to become
at least 10 times that of the present highest density lithium secondary battery,
used in a wide range of applications. This new technological development is expected
to solve the currently faced problems of dramatically reducing power consumption
rates and is one big step towards achieving a practical fuel cell for mobile terminals.
Carbon nanotubes are a completely new carbon system material, which were discovered
by one of NEC's Research Fellows, Sumio Iijima in 1991, and are expected become
the typical raw material for nano-technology, applied to such broad fields as,
hydrogen storage, composite materials and electron devices. This time, the research
group, focusing on the detailed structure of the carbon nanotube examined the
possibility of applying it to fuel cell electrodes, confirming that the nanotube
has the possibility of clearly surpassing raw materials used to date.
The carbon nanotubes used for the experimental manufacturing are named nanohorns
due to their irregular horn-like shape, and were discovered three years ago by
Dr. Sumio Iijima's research group. Nanohorns have the same graphitic carbon atom
structure as normal carbon nanotubes. The main characteristic of the carbon nanohorns
is that when many of the nanohorns group together an aggregate (a secondary particle)
of about 100 nanometers is created. The advantage being, that when used as an
electrode for a fuel cell, not only is the surface area extremely large, but also,
it is easy for the gas and liquid to permeate to the inside. In addition, compared
with normal nanotubes, because the nanohorns are easily prepared with high purity
it is expected to become a low-cost raw material.
The developed tiny fuel cell, classified as a polymer electrolyte fuel cell
(PEFC), utilizes the carbon nanohorns as electrodes for catalyst support. It is
observed that very fine platinum catalyst particles are dispersed on the surfaces
of the carbon nanohorns. The size of the platinum particle is less than half of
that supported on the ordinary activated carbon (acetylene black) by the same
method. The size of the catalyst particle is one of the most important factors
that determine the performance of the fuel cell, and it is considered that, the
finer the size the better performance.
Although the reason a catalyst particle becomes fine is still not clear in
the case of the carbon nanohorn, because of the unique shape of the aggregate
it is thought that contact and grain growth of catalyst particles will be prevented.
It is also expected that by further altering the form of the carbon nanohorn the
dispersed state and the battery characteristic of the catalyst particle will improve.
In addition, because a carbon nanohorn is produced by the laser ablation method,
if a platinum catalyst is also simultaneously evaporated it is observed that a
platinum particle will naturally adhere to the surface of a carbon nanohorn. If
this method is used, the complicated catalyst supporting process through the conventional
wet process can be omitted resulting in a large cost reduction.
Until now, since the discovery of the carbon nanotube, although it has been
acknowledged as having a high possibility of being applied to semiconductors,
flat-panel displays, lightweight and high-strength raw material and fuel cells
etc., it had stopped at the fundamental research as a material stage. This development
however, is the first step for the practical utilization of carbon nanotube and
big steps towards the development and expansion of nano-technology.
NEC, the Japan Science and Technology Corporation and the Institute of Research
and Innovation will aim to practically apply the small fuel cell from here onwards
and more proactively promote the research and development including production
conditions of carbon nanotubes and the catalyst support on them.
About NEC Corporation
NEC Corporation (NASDAQ: NIPNY) (FTSE: 6701q.l) is a leading provider of Internet
solutions, dedicated to meeting the specialized needs of its customers in the
key computer, network and electron device fields through its three market-focused
in-house companies: NEC Solutions, NEC Networks and NEC Electron Devices. NEC
Corporation, with its in-house companies, employs more than 150,000 people worldwide
and saw net sales of 5,409 billion Yen (approx. US$43 billion) in fiscal year
2000-2001. For further information, please visit the NEC home page at: http://www.nec.com
***
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*1 |
Fuel Cell
Fundamentally, fuel cells directly transform the chemical reaction energy between
hydrogen and oxygen into electric energy. Power generation efficiency and energy
density are high, and the application to small mobile terminals or in the future,
automobiles is expected. The energy is very clean and environmentally friendly. |
*2 |
Electrode (Supporting Catalyst Electrode)
The Electrode is the part of the fuel cell that supports the platinum-system catalyst
to the carbon particle, and shoulders the task of ionizing the fuel, such as hydrogen,
methanol and oxygen. In order to raise catalyst efficiency, a porous carbon material
with a large surface area is needed. |
*3 |
Polymer Electrolyte Fuel Cell (PEFC)
A fuel cell, which uses a polymer ion exchange film for an electrolyte, and compared
with other types of fuel cells, has a low operation temperature of 100 degrees
C or less. The solid type also very lightweight and has a high energy-conversion
efficiency of 50%. For this reason, it is a fuel cell suitable for small mobile
applications or automobiles. Fluoride polymer films are often used because of
the high mobility of hydrogen ions and high heat resistance. |
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