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2011-08-12 06:16:19
By Hamish Pritchard Science Reporter
An enzyme from a microbe has shown how to make hydrogen more quickly and more
cheaply.
Storing and transporting energy as hydrogen is seen as vital to future energy
systems.
Turning electrical energy into chemical energy and then releasing it again on
demand is the key to this process.
A major problem though is making this reaction fast and cheap enough to be
viable.
Hydrogen can be made from water wherever electricity is available, even at
home. And with a fuel cell it can be turned back into electricity, with water
as the benign by-product.
If the electricity comes from a local renewable source such as a wind farm or
array of solar cells, this means clean, independent and portable power that can
be stored until needed.
New research published today in Science takes us a step closer to this vision.
Fuel cells need a catalyst to speed up the chemical reactions that change
hydrogen into water and electricity. Platinum is very good at this but it is
famously expensive and rare.
Some microbes, though, have known for a billion years how to make enzymes that
can do the job using cheap and abundant nickel and iron.
These natural enzymes are unfortunately difficult to obtain and do not do so
well outside the microbe.
Now researchers have managed to make a synthetic, toughened-up version.
Real-world viability
So far, they have looked at just one step in the complex reaction, where two
hydrogen atoms taken from water are snapped together to make hydrogen gas.
But their new synthetic enzyme is performing surprisingly well, in fact it's 10
times faster than the natural one, making 100,000 molecules of hydrogen gas
every second.
"This nickel-based catalyst is really very fast," said co-author Morris Bullock
of the Pacific Northwest National Laboratory in the US state of Washington.
"In general, enzymes are already a lot faster than traditional catalysts like
platinum - normally orders of magnitude faster, so this is exciting," said
Professor Gavin Walker of the University of Nottingham, who was not involved in
the study.
Although fast, at present the process still uses up too much electrical energy
to be viable for real-world applications.
However, "these results highlight the substantial promise molecular catalysts
hold for the production of hydrogen," wrote the authors.
"One of the nice things about hydrogen is that it's a versatile energy vector.
It can be generated from a number of sources - wind, solar, biomass. But can it
be done efficiently and how much will it cost? That's why this is an important
discovery - looking at cheaper alternatives for the catalysts," said Professor
Walker.
"If we can go across to using iron and nickel, that will be a lot cheaper. This
will hopefully lead to cheaper hydrogen," he added.