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.