Tiny fuel cells power mobiles

By using carbon nanotube technology, NEC Corporation, the Japan Science and Technology Corporation and the Institute of Research have developed a tiny fuel cell for mobile phones.

The fuel cell, classified as a polymer electrolyte fuel cell (PEFC), uses the nanotubes as electrodes for catalyst support. NEC says that the cell has about 10 times the energy capacity of a lithium battery.

The carbon nanotubes used to manufacture the electrodes are named nanohorns due to their irregular horn-like shape. A research group led by Dr. Sumio Iijima discovered them three years ago.

Nanohorns have the same atomic structure as normal carbon nanotubes. The main characteristic of the carbon nanohorns, however, is that when they group together, an aggregate (a secondary particle) of about 100 nm is created. When used as an electrode for a fuel cell, not only is the surface area extremely large, but it is also easy for gas and liquid to permeate inside.

To manufacture the cell, very fine platinum catalyst particles were deposited on the surfaces of the carbon nanohorns. The size of the platinum particles are less than half as big as those that can be supported on ordinary activated carbon (acetylene black) by the same method.

That's important because the size of the catalyst particle is one of the most important factors that determine the performance of the fuel cell.

The companies hope that further work will lead to the commercialisation of the fuel cell devices.