Debut of the first practical 'artificial leaf'

Mar 27, 2011

Scientists today claimed one of the milestones in the drive for sustainable energy — development of the first practical artificial leaf. Speaking here at the 241st National Meeting of the American Chemical Society, they described an advanced solar cell the size of a poker card that mimics the process, called photosynthesis, that green plants use to convert sunlight and water into energy.

"A practical artificial leaf has been one of the Holy Grails of science for decades," said Daniel Nocera, Ph.D., who led the research team. "We believe we have done it. The artificial leaf shows particular promise as an inexpensive source of electricity for homes of the poor in developing countries. Our goal is to make each home its own power station," he said. "One can envision villages in India and Africa not long from now purchasing an affordable basic power system based on this technology."

The device bears no resemblance to Mother Nature's counterparts on oaks, maples and other green plants, which scientists have used as the model for their efforts to develop this new genre of solar cells. About the shape of a poker card but thinner, the device is fashioned from silicon, electronics and catalysts, substances that accelerate chemical reactions that otherwise would not occur, or would run slowly. Placed in a single gallon of water in a bright sunlight, the device could produce enough electricity to supply a house in a developing country with electricity for a day, Nocera said. It does so by splitting water into its two components, hydrogen and oxygen.

The hydrogen and oxygen gases would be stored in a fuel cell, which uses those two materials to produce electricity, located either on top of the house or beside it.

Nocera, who is with the Massachusetts Institute of Technology, points out that the "artificial leaf" is not a new concept. The first artificial leaf was developed more than a decade ago by John Turner of the U.S. National Renewable Energy Laboratory in Boulder, Colorado. Although highly efficient at carrying out photosynthesis, Turner's device was impractical for wider use, as it was composed of rare, expensive metals and was highly unstable — with a lifespan of barely one day.

Nocera's new leaf overcomes these problems. It is made of inexpensive materials that are widely available, works under simple conditions and is highly stable. In laboratory studies, he showed that an artificial leaf prototype could operate continuously for at least 45 hours without a drop in activity.

The key to this breakthrough is Nocera's recent discovery of several powerful new, inexpensive catalysts, made of nickel and cobalt, that are capable of efficiently splitting water into its two components, hydrogen and oxygen, under simple conditions. Right now, Nocera's leaf is about 10 times more efficient at carrying out photosynthesis than a natural leaf. However, he is optimistic that he can boost the efficiency of the artificial leaf much higher in the future.

"Nature is powered by photosynthesis, and I think that the future world will be powered by as well in the form of this artificial leaf," said Nocera, a chemist at Massachusetts Institute of Technology in Cambridge, Mass.

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User comments : 15

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sstritt
1.8 / 5 (10) Mar 27, 2011
Nocera's leaf is about 10 times more efficient at carrying out photosynthesis than a natural leaf.

I don't believe that one. Must have meant 10 times LESS efficient.
"A practical artificial leaf has been one of the Holy Grails of science for decades,"

Can we please leave the Holy Grails to Mont Python? We need a "paradigm shift" to come up with the next hackneyed phrase.
Justsayin
2.8 / 5 (8) Mar 27, 2011
"Our goal is to make each home its own power station"


Sounds like Dan is in search of a subsidy here, otherwise why couldn't you do that right here in the USA for the average American household. I have heard enough hype from this guy and will believe this when I see it producing power at or near grid parity.

RealScience
5 / 5 (9) Mar 27, 2011
sstritt - typical plant photosynthesis is only about 2% efficient, so 10x the efficiency is a not-unreasonable 20%. Some cyanobacteria acheive 20%.

A leaf has to pipe in water, capture CO2, grow its own chloroplasts and other structure, fight off preditors, etc., which are all done for the artificial leaf; by avoiding those the artificial leaf gets more design freedom, which helps to achieve higher efficiency.

Agreed that reporters need a new phrase to hackney - any suggestions?

Justsayin - Agreed that this is over-hyped.
A poker card is about 60 cm2, so at 20% efficient a card in full sun would produce 1.2 Watts. Throw in the fuel cell inefficiency and that is 10 Hhr / day maximum, which would run a single 3W LED for about 3 hours.
A solar cell that size is already less than $2, and batteries for that energy are a lot cheaper than fuel cells.

But it is a start - if fuel cells get cheap AND this can take a few hundred suns concentration, it gets interesting.
Ronan
5 / 5 (1) Mar 27, 2011
Sstrit: Actually, it's quite possible that that's an accurate value; plants are actually not all that efficient, and "ten times more efficient" could (depending on how you define the efficiency of the solar cell and of the plant) mean anywhere between 1% and 70% efficiency of capturing energy from light. The importance of this work, I gather, is not that it's achieving some unusually high level of efficiency, but that the solar cell is both relatively inexpensive and long-lasting.
ereneon
1 / 5 (3) Mar 27, 2011
"About the shape of a poker card but thinner, the device is fashioned from silicon, electronics and catalysts, substances that accelerate chemical reactions that otherwise would not occur, or would run slowly"
Catalysts only affect reaction rates, they don't cause reactions to occur that would not occur before, as this would lead to violations of the laws of thermodynamics.
http://en.wikiped...atalysis
jkbgbr
3.5 / 5 (2) Mar 27, 2011
Catalysts only affect reaction rates, they don't cause reactions to occur that would not occur before, as this would lead to violations of the laws of thermodynamics.
http://en.wikiped...atalysis

Well, wikipedia is wrong on this one.
Parsec
4.3 / 5 (4) Mar 27, 2011
"About the shape of a poker card but thinner, the device is fashioned from silicon, electronics and catalysts, substances that accelerate chemical reactions that otherwise would not occur, or would run slowly"
Catalysts only affect reaction rates, they don't cause reactions to occur that would not occur before, as this would lead to violations of the laws of thermodynamics.
http://en.wikiped...atalysis


I can take a container that contains the gases, hydrogen, and oxygen in the perfect ratio for conversion to water, and as long as it is kept in the dark, away from sparks, I could come back in a billion years and not be able to detect a single water molecule. Expose it to a catalyst, or to a tiny spark, and after a few microseconds, the entire volume will be converted to water. The energy barrier is too high for getting started by itself. But the reaction is HIGHLY exothermic and once started will quite quickly proceed to completion.
kaasinees
1.4 / 5 (11) Mar 27, 2011
That is some super container you have there Parsec.
Hydrogen will break free of metal and idk if plastic can withstand billion of years?

Hydrogen has some problems with being contained.
kaasinees
1 / 5 (8) Mar 27, 2011
Whoever rated me a 1, explain further?
fixer
5 / 5 (2) Mar 27, 2011
Even so, colour them green and make them cheap enough to buy in bulk and build a look alike tree with the storage and converter in the trunk and you have invented the fabled "money tree".
Sounds good to me!
kaasinees
1.8 / 5 (4) Mar 27, 2011
Or make roof panels from it.
TAz00
not rated yet Mar 28, 2011
Whoever rated me a 1, explain further?


You're not funny, not on the point, its not about the container.
sstritt
2 / 5 (2) Mar 28, 2011
sstritt - typical plant photosynthesis is only about 2% efficient, so 10x the efficiency is a not-unreasonable 20%. Some cyanobacteria acheive 20%.

I understand now. I was thinking of the efficiency of the energy absorption from the photon- which is very high. The whole photosynthetic process in its entirety being much lower overall.
kaasinees
1 / 5 (2) Mar 31, 2011
Whoever rated me a 1, explain further?


You're not funny, not on the point, its not about the container.


It IS about the container. How are you going to move around large amounts of hydrogen? Normal containers will break/corrode or are to weak in structure. The special containers are very expensive, this argument alone means that hydrogen is not a viable common fuel source.
TAz00
not rated yet Mar 31, 2011
It IS about the container.


It's about the energy barrier, and catalysts.

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