This was accomplished by using a type of carbon nanotube called the "carbon nanohorn". The fuel cell thus produced 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 carbon nanotubes used for this fuel cell 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 of about 100 nanometers is created. This creates a large surface area and also allows ready diffusion of gas and liquids through the electrode.
The fuel cell discussed has platinum deposited on the nanotubes in much the same way as in the electrodes of a conventionally-designed proton exchange membrane fuel cell. Due to the fine dispersion of this platinum on the nanotubes, however, performance is improved and lower platinum loadings may be possible. A method of manufacture has been proposed which will eliminate stages of wet manufacturing and can potentially reduce costs.
NEC, the Japan Science and Technology Corporation and the Institute of Research and Innovation will aim to apply the small fuel cell in practical applications and to promote the further research and development including production conditions of carbon nanotubes and the catalyst support on them. More information can be found at www.nec.co.jp/english/today/newsrel/0108/3001.html or in Chemistry and Industry, 17th September 2001.