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[cdn-nucl-l] "Carbon tubes could store hydrogen fuel"
Monday, November 8, 1999 Published at 09:16 GMT
<<...>> Carbon tubes could store hydrogen fuel
Chinese and American scientists have developed a method of storing high
quantities of hydrogen inside tiny tubes of carbon just two nanometres
(billionths of a metre) across.
The development is another step in the search for technical solutions to the
problems that currently prevent hydrogen from being used as a practical,
The gas produces no pollution and no greenhouse emissions when burned in
pure oxygen and is considered by many to be the clean energy of the future
and a replacement for fossil fuels when current reserves run out.
But whilst its energy content on a mass-for-mass basis is better than
petrol, hydrogen has difficulty competing with the fossil fuel because it is
a gas. A hydrogen gas fuel tank that contained a store of energy equivalent
to a petrol tank would be more than 3,000 times bigger than its conventional
cousin. Compressing or liquefying the gas is expensive.
Current thinking points to the absorption of hydrogen in another medium.
Metal alloys can be persuaded to absorb up to 1,000 times their own volume
of hydrogen but they are heavy and become brittle after repeated use.
Now a team from the Chinese Academy of Sciences in Shenyang, China, and the
Massachusetts Institute of Technology, Cambridge, US, has demonstrated an
effective way to absorb hydrogen into carbon nanotubes - minute cylinders
made of carbon atoms.
Wash and dry
Their research, published in the journal Science, substantially increases
the amount of hydrogen that can be absorbed using this method.
It involves soaking the nanotubes in hydrochloric acid then heating them to
500 degC for two hours. This wash-and-dry procedure removes most of the
impurities that have inhibited previous attempts to get carbon nanofibres to
The team found that its tubes would absorb one hydrogen atom for every two
carbon atoms. What is more, almost 80% of the stored hydrogen could be
released from the tubes at room temperature and pressure, with the rest
released after the tube was heated.
But hydrogen still has a long way to go before it becomes a real alternative
to fossil fuels. For a start, manufacturing anything on the nano scale is
currently hugely expensive. To produce one kilo of carbon nanotubes costs
A cheap method of making hydrogen also needs to be found. The obvious route
involves splitting water, but this in itself requires substantial amounts of
energy. One possible alternative might involve the use of a bacterial enzyme
that uses iron to make hydrogen.
Hmmmm - wonder how you can produce "substantial amounts of energy" ?
...don't count on the BBC to figure that one out !