25-05-2012, 12:50 PM
Artificial leaf' makes fuel from sunlight
[attachment=22986]
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 bubbles 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 once again into water while delivering an electric current.
The creation of the device is described in a paper published Sept. 30 in the journal Science. Nocera, the
Henry Dreyfus Professor of Energy and professor of chemistry at MIT, is the senior author; the paper was
co-authored by his former student Steven Reece PhD '07 (who now works at Sun Catalytix, a company
started by Nocera to commercialize his solar-energy inventions), along with five other researchers from Sun
Catalytix and MIT.
The device, Nocera explains, 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, a material whose potential for
generating fuel from sunlight was discovered by Nocera and his co-authors in 2008. The other side of the
silicon sheet is coated with a layer of a nickel-molybdenum-zinc alloy, which releases hydrogen from the
water molecules.
"I think there's going to be real opportunities for this idea," Nocera says. "You can't get more portable - you
don't need wires, it's lightweight," and 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.
[attachment=22986]
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 bubbles 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 once again into water while delivering an electric current.
The creation of the device is described in a paper published Sept. 30 in the journal Science. Nocera, the
Henry Dreyfus Professor of Energy and professor of chemistry at MIT, is the senior author; the paper was
co-authored by his former student Steven Reece PhD '07 (who now works at Sun Catalytix, a company
started by Nocera to commercialize his solar-energy inventions), along with five other researchers from Sun
Catalytix and MIT.
The device, Nocera explains, 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, a material whose potential for
generating fuel from sunlight was discovered by Nocera and his co-authors in 2008. The other side of the
silicon sheet is coated with a layer of a nickel-molybdenum-zinc alloy, which releases hydrogen from the
water molecules.
"I think there's going to be real opportunities for this idea," Nocera says. "You can't get more portable - you
don't need wires, it's lightweight," and 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.