Hawaii
Energy Policy Forum > 2003
Articles
Bio-battery runs on shots of vodka
24 March 03
NewScientist.com news service
http://www.newscientist.com/news/news.jsp?id=ns99993539
An enzyme-catalysed battery has been created that could
one day run cell phones and laptop computers on shots of vodka.The
key to the device is a new polymer that protects the fragile
enzymes used to break down the ethanol fuel, scientists told
the American Chemical Society's annual meeting in New Orleans
on Monday.
Enzyme-based batteries have the potential to be cheaper than
fuel cells that rely on expensive platinum or ruthenium catalysts.
"It sounds great," says Bob Hockaday, founder of
the company Energy Related Devices and designer of a methanol-powered
battery. "Enzymes are inexpensive and catalytically very
active."
Fuel cells work by converting into electricity the energy
released when oxygen and hydrogen react to produce water.
Pure hydrogen is an explosive gas and difficult to store,
so fuel cells often use a chemical source. Ethanol is used
in Minteer's cell, and the enzymes strip off the hydrogen.
But the enzymes are sensitive to slight changes in pH and
temperature and can rapidly degrade and become inactive. Until
now no bio-battery had enzymes that lasted for more than a
few days. Specially tailored pores The typical approach to
solving this problem has been to immobilise the enzymes by
attaching them to the fuel cell's electrodes, but they still
tend to decay too quickly to be useful.
So Shelley Minteer and her colleagues at St Louis University
in Missouri coated the electrodes with a polymer that has
specially tailored pores. These maintain a neutral pH, while
being small enough to trap the enzymes yet big enough to let
the alcohol pass through.
"The enzymes have lasted over two months now and they
are still functioning," she says. Thanks to the polymer,
the new bio-batteries have power densities 32 times greater
than those of other groups, the team claim. Toshiba has just
unveiled its first miniature fuel cell, which uses a metal
catalyst and runs on methanol. Minteer says:
"The main advantage of ethanol over methanol is that
it is simply more readily available. We have actually run
our cells off vodka and gin." Ethanol is also less toxic
and, with the enzymes used in Minteer's bio-batteries, more
productive. However, unlike the Toshiba prototype, the cell
is still too large for portable use. The group is currently
working to shrink the technology, perhaps by tweaking the
polymer-enzyme matrix in order to increase its surface area
further.
A newsletter from WWW.Green-Trust.Org
|
