Solar alchemy turns fumes back into fuels

[Henk Elegeert]

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http://www.newscientist.com/article/mg19125696.300?DCMP=NLC-nletter&nsref=mg19125696.300

"
Solar alchemy turns fumes back into fuels

     * 16 September 2006
     * NewScientist.com news service
     * Rob Edwards

IT IS the biggest contributor to climate change. Now
chemists are hoping to convert carbon dioxide into a
useful fuel, with a little help from the sun.

If they succeed, it will be possible to recycle the
greenhouse gas produced by burning fossil fuels. The
work could also lead to a way for future Mars
missions to generate fuel for their return journey
from carbon dioxide in the planet's atmosphere.

Chemists have long hoped to find a method of
bringing the combustion of fuel full circle by
turning CO2 back into useful hydrocarbons. Now
researchers at the University of Messina in Italy
have developed an electro-catalytic technique they
say could do the job. "The conversion of CO2 to fuel
is not a dream, but an effective possibility which
requires further research," says team leader
Gabriele Centi.

The researchers chemically reduced CO2 to produce
eight and nine-carbon hydrocarbons using a catalyst
of particles of platinum and palladium confined in
carbon nanotubes. These hydrocarbons can be made
into petrol and diesel.

To begin with, the researchers used sunlight plus a
thin film of titanium dioxide to act as a
photocatalyst to split water into oxygen gas plus
protons and electrons. These are then carried off
separately, via a proton membrane and wire
respectively, before being combined with CO2 plus
the nano-catalyst to produce the hydrocarbons.

Although the nano-catalysts produced two or three
times more hydrocarbons than a commercially
available catalyst, the process converted only about
1 per cent of the CO2 at room temperature. Centi
believes it will be possible to improve on that by
using higher temperatures and a larger surface area
of catalyst. It will also be necessary to boost the
efficiency of the solar water-splitting, he says.
With the right research, Centi believes that an
efficient solar-powered reactor for converting CO2
into fuel could be available "within a decade".

He presented his latest work, which is funded by the
European Union, at a meeting of the American
Chemical Society in San Francisco on 13 September.
Other chemists reacted positively, but cautiously,
to the findings. "It sounds feasible," says John
Turner from the US National Renewable Energy
Laboratory in Golden, Colorado. "The
solar-to-hydrocarbon conversion efficiency is pretty
small, but it sounds like they are just getting
started."

Ian Plumb, who researches water-splitting reactions
at the Australian national research institute CSIRO
Industrial Physics, says that unless the efficiency
is improved it will be too expensive to implement.
"But there is no doubt that what they are trying to
achieve is very worthwhile."

 From issue 2569 of New Scientist magazine, 16
September 2006, page 30
"

Onze kennis is ontoereikend? Of is Balkeje er nog
niet aan toe?

Henk Elegeert

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