A team of scientists at the Massachusetts Institute of Technology has developed what it describes as the first practical artificial leaf.
The device, made from silicon, electronics and catalysts, is the same size and shape as a playing card, but thinner.
It splits water into its two components, hydrogen and oxygen. These are then stored in a fuel cell and used later to generate electricity.
“It’s really cool stuff — they’re taking a solar cell and turning it into a battery,” Carl Howe, director of anywhere consumer research at the Yankee Group, told TechNewsWorld.
“You can think of this as the first dark solar energy because it’ll give you solar energy at night in the form of light,” Howe added.
Daniel Nocera, who led the team of scientists that developed the artificial “leaf,” was not available for comment at press time.
Soon the World Will Love You, Sweet Leaf
Placing the artificial leaf it in a single gallon of water in bright sunlight could produce enough electricity to supply a house in developing countries with its daily electricity requirement, Nocera has claimed.
Much research has been conducted on the concept of an artificial leaf. Technically, the first artificial leaf was developed more than 10 years ago by John Turner of the U.S. National Renewable Energy Lab in Boulder, Colo.
However, Turner’s device used rare, expensive materials and was highly unstable.
Nocera’s device uses inexpensive materials that are widely available. It can use water from any source and is highly stable. He has shown that a prototype of his leaf in the laboratory operated continuously for at least 45 hours without a drop in activity.
Nocera has been working on this project for some time. Back in 2008 he worked with postdoctoral fellow Matthew Kanan to develop a process that would use sunlight to split water into hydrogen and oxygen.
The process was based on the researchers’ creation of a new catalyst consisting of cobalt, phosphates and an electrode.
When placed in water and electricity from any source is run through the electrode, the catalyst produces oxygen. It is combined with another catalyst such as platinum that can produce hydrogen gas from water, to duplicate photosynthesis.
The conversion of solar energy into hydrogen under ambient conditions is considered to be one of the greatest challenges scientists face in this 21st century.
Scientists believe this process could help create cheap electricity, reduce our dependence on fossil fuels, and thus help mitigate global warming.
Nocera’s Work
The technology used in Nocera’s latest artificial leaf is based on work done at the Nocera Group.
New catalysts in the Nocera labs self-assemble from water to form a partial cubane structure. They are self-healing, and they split PH-neutral water into hydrogen and oxygen at atmospheric pressure and room temperature.
Cubane is a synthetic hydrocarbon molecule that consists of eight carbon atoms arranged at the corners of a cube with one hydrogen atom attached to each carbon atom.
The catalyst operates at 100mA per square cm at 76 percent efficiency.
“Look at the numbers,” the Yankee Group’s Howe said. “At 100 mA per square cm, you get a pretty high density, so they’re probably getting some good power from the device.”
The efficiency of the artificial leaf is also impressive, Howe suggests.
“Overall, solar panels are typically in the 10 percent efficiency range nowadays, so they’re not high-efficiency devices,” Howe remarked. “If you have something that’s able to absorb sunlight at anything close to 70 percent efficiency, it’s practically turning sunlight into gold.”
The ability to split PH-neutral water has led to the discovery of an inexpensive hydrogen-producing catalyst that operates at 1,000 mA per square cm at 35 mV overpotential.
What all this means is that it could eventually enable the large-scale deployment of solar energy by providing a mechanism for its storage as fuel, the Nocera Group states.
It’s a Long, Long Road
The development of Nocera’s artificial leaf is a step in the right direction, Jim McGregor, chief technology strategist at In-Stat, told TechNewsWorld.
“This may lead us to larger solutions that let us use thermal, solar and hydrogen solutions all at one time, and that will be huge,” McGregor stated.
Relying on solar energy alone is not good enough, McGregor said.
“One of the problems with solar rays is that they heat up the equipment you use excessively,” McGregor explained. “After a certain period, the equipment gets so hot that efficiency goes down. So you want to try to mimic nature and create an ecosystem where all these technologies — thermal, solar and hydrogen — work together,” he said.
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this other article implies that the leaf itself is highly effective and produces the current to produce O2 and H2 from the water..
http://www.wired.co.uk/news/archive/2011-03/28/artificial-leaf
a google search with "artificial leaf MIT" brought several links
Richard is correct: where is the electricity to generate electrolysis coming from? Is the leaf itself generating electricity?
I hope SO can answer this question.
Also how does the leaf produce electricity at night?
Maybe it’s something like this:
http://www.ornl.gov/info/press_releases/get_press_release.cfm?ReleaseNumber=mr20110203-00
However even though it can rearrange itself back to order, I wonder about the constituents degrading over time.
OK,
So this has been an excellent description of a novel catalyst for electrolysis. Where is the solar part of this? Sounds to me like this "leaf" already assumes you have electricity. In any case, at 100mA/sq. cm, assuming you need about 2.5V of potential in the presence of this catalyst, you need about 2.5kW of power per sq. meter. At 1000mA/sq. cm, you need 25kW. Bummer that the entire electromagnetic spectrum of the sun falling on the Earth is only about 1kW per square meter. Guess this might be a good solution for Mercury. Sorry. Forgot. There’s no water there.
The real problem is getting that tiny 1kW/sq. meter from photons streaming in from the Sun to an electrical current. The best technology available can currently transform about 25% of that power, at extreme cost. This device apparently does nothing for that process, but assumes the electrical current already, and simply performs the hydrolysis after the fact. This is a great advancement for the hydrogen fuel industry, but mentioning the word solar at all in this article is disingenuous. The electricity to power this device will almost certainly come from coal or nuclear.
So you have this leaf floating in water bubbling away hydrogen and oxygen. The hard part is going to be collecting those gases and recombining them in some kind of fuel cell. Maybe a vat of leaves in a centrifuge to separate the gases? Hydrogen is still explosive (see Fukishima Dai Ichi). Lots of problems still to be solved. Excellent first step.
Is there an actual science/MIT link available for this as opposed to a paper journalism one?