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'Artificial leaf' makes real fuel

Dominick Reuter

The 'artificial leaf,' a device that can harness sunlight to split water into hydrogen and oxygen without needing any external connections, is seen with some real leaves, which also convert the energy of sunlight directly into storable chemical form.

It doesn't look like the leaves changing colors and piling up on the lawn, but a nature-inspired "artificial leaf" technology has taken a notable step toward the goal of producing storable and clean energy to power everything from factories to tablet computers.

The leaf is a silicon solar cell coated with catalytic materials on its side that, when placed in a container of water and exposed to sunlight, splits the H2O into bubbles of oxygen and hydrogen. The hydrogen can be stored and used as an energy source, for example to power a fuel cell.

"The device both captures the solar energy and stores it in the chemical bonds of the hydrogen and oxygen that are produced from the water," Steven Reece, a research scientist with Sun Catalytix and lead author of a paper describing the breakthrough, told me Friday.


You can check out the device in action the video below.

An "artificial leaf" made by Daniel Nocera and his team, using a silicon solar cell with novel catalyst materials bonded to its two sides, is shown in a container of water with light (simulating sunlight) shining on it. The light generates a flow of electricity that causes the water molecules, with the help of the catalysts, to split into oxygen and hydrogen, which bubble up from the two surfaces.

Courtesy of Nocera Lab/Sun Catalytix

The artificial leaf is made entirely with earth-abundant, inexpensive materials — mostly silicon, cobalt, and nickel — and it works in ordinary water. Other attempts have required more expensive catalysts such as platinum and/or extremely caustic water, noted Reece.

"What was really novel about our work is that we were able to integrate our earth-abundant catalysts with this commercial triple junction solar photovoltaic technology that would then operate under benign conditions without wires and a reasonable efficiency," he said

The breakthrough was led by Daniel Nocera at the Massachusetts Institute of Technology and was reported Thursday in the journal Science. Reece worked in Nocera's lab before moving to Sun Catalytix, which was started by Nocera to commercialize his solar energy inventions.

This new paper is the latest step in a process that has generated buzz over the years.

In 2008, the team reported on the cobalt part of the equation, which releases oxygen from water. They've now coated the other side of the silicon sheet with the nickel-molybdenum-zinc alloy, which releases hydrogen from water molecules.

"You just drop it in a glass of water, and it starts splitting it," Nocera said in a statement

He added that the device is not ready for commercial production as the systems to collect, store, and use the gases remain to be developed. "It's a step," he said. "It's heading in the right direction."

The collection and storage of the sun's energy as hydrogen fuel is a key step in overcoming one of the limitations of solar power — it generates energy when the sun is shining, but it needs to be stored somewhere to be useful at night and in cloudy weather. 

Batteries are one place to store the energy, but battery technology, while improving, is limited. Storing solar energy as hydrogen fuel could be an answer.

"Nobody disputes the beauty of the chemistry," reads a Nature News article about the technology. "But whether the system is actually useful will come down to how expensive the hydrogen is to make, and how efficiently the system can use the available energy from sunlight."

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John Roach is a contributing writer for msnbc.com.

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