Researchers led by Massachusetts
Institute of Technology professor Daniel Nocera have produced something
they’re calling an “artificial leaf”: Like living leaves, the device can
turn the energy of sunlight directly into a chemical fuel that can be
stored and used later as an energy source.
The artificial leaf – a silicon solar cell with different catalytic materials bonded onto its two sides – needs no external wires or control circuits to operate.
Simply placed in a container of water and exposed to sunlight, it quickly begins to generate streams of bubbles: oxygen bubbles from one side and hydrogen from the other.
If placed in a container that has a barrier to separate the two sides, the two streams of bubbles can be collected and stored, and used later to deliver power: for example, by feeding them into a fuel cell that combines them into water while delivering electricity.
The creation of the device is described in a paper that appears in Science. Nocera, is the senior author; it was co-authored by his former student Steven Reece (who now works at Sun Catalytix, a company started by Nocera to commercialise his solar-energy inventions).
Cheap materials
The device is made entirely of earth-abundant, inexpensive materials – mostly silicon, cobalt and nickel – and works in ordinary water. Other attempts to produce devices that could use sunlight to split water have relied on corrosive solutions or on relatively rare and expensive materials such as platinum.
The artificial leaf is a thin sheet of semiconducting silicon – the material most solar cells are made of – which turns the energy of sunlight into a flow of wireless electricity within the sheet.
Bound onto the silicon is a layer of a cobalt-based catalyst, which releases oxygen.
The other side of the sheet is coated with a layer of a nickel-molybdenum-zinc alloy, which releases hydrogen from the water.
“You can’t get more portable – you don’t need wires, it’s lightweight,” Nocera says.
It doesn’t require much in the way of additional equipment, other than a way of catching and storing the gases that bubble off.
“You just drop it in a glass of water, and it starts splitting it,” he says.
The artificial leaf – a silicon solar cell with different catalytic materials bonded onto its two sides – needs no external wires or control circuits to operate.
Simply placed in a container of water and exposed to sunlight, it quickly begins to generate streams of bubbles: oxygen bubbles from one side and hydrogen from the other.
If placed in a container that has a barrier to separate the two sides, the two streams of bubbles can be collected and stored, and used later to deliver power: for example, by feeding them into a fuel cell that combines them into water while delivering electricity.
The creation of the device is described in a paper that appears in Science. Nocera, is the senior author; it was co-authored by his former student Steven Reece (who now works at Sun Catalytix, a company started by Nocera to commercialise his solar-energy inventions).
Cheap materials
The device is made entirely of earth-abundant, inexpensive materials – mostly silicon, cobalt and nickel – and works in ordinary water. Other attempts to produce devices that could use sunlight to split water have relied on corrosive solutions or on relatively rare and expensive materials such as platinum.
The artificial leaf is a thin sheet of semiconducting silicon – the material most solar cells are made of – which turns the energy of sunlight into a flow of wireless electricity within the sheet.
Bound onto the silicon is a layer of a cobalt-based catalyst, which releases oxygen.
The other side of the sheet is coated with a layer of a nickel-molybdenum-zinc alloy, which releases hydrogen from the water.
“You can’t get more portable – you don’t need wires, it’s lightweight,” Nocera says.
It doesn’t require much in the way of additional equipment, other than a way of catching and storing the gases that bubble off.
“You just drop it in a glass of water, and it starts splitting it,” he says.
Future plans
Now that the “leaf” has been demonstrated, Nocera suggests one possible further development: tiny particles made of these materials that can split water molecules when placed in sunlight – making them more like photosynthetic algae than leaves. The advantage of that, he says, is that the small particles would have much more surface area exposed to sunlight and the water, allowing them to harness the sun’s energy more efficiently.
The new device is not yet ready for commercial production, since systems to collect, store and use the gases remain to be developed.
Ultimately, he sees a future in which individual homes could be equipped with solar-collection systems based on this principle: Panels on the roof could use sunlight to produce hydrogen and oxygen that would be stored in tanks, and then fed to a fuel cell whenever electricity is needed.
Such systems, Nocera hopes, could be made simple and inexpensive enough so that they could be widely adopted throughout the world, including many areas that do not have access to reliable sources of electricity.
Now that the “leaf” has been demonstrated, Nocera suggests one possible further development: tiny particles made of these materials that can split water molecules when placed in sunlight – making them more like photosynthetic algae than leaves. The advantage of that, he says, is that the small particles would have much more surface area exposed to sunlight and the water, allowing them to harness the sun’s energy more efficiently.
The new device is not yet ready for commercial production, since systems to collect, store and use the gases remain to be developed.
Ultimately, he sees a future in which individual homes could be equipped with solar-collection systems based on this principle: Panels on the roof could use sunlight to produce hydrogen and oxygen that would be stored in tanks, and then fed to a fuel cell whenever electricity is needed.
Such systems, Nocera hopes, could be made simple and inexpensive enough so that they could be widely adopted throughout the world, including many areas that do not have access to reliable sources of electricity.
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