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Artificial leaf mimics nature
03:58 - Source: CNN

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Daniel Nocera has created the "artificial leaf"

The low-cost device can turn water and sunlight into stored energy

It has long been dubbed the "holy grail" of energy research

Find out why you won't be getting your hands on it anytime soon

Cambridge, MA CNN  — 

As Daniel Nocera gazed down on one of his experiments in what has come to be known as the “holy grail” of energy research, his response was to shrug:

“Oh, that can’t be right.”

It was a glass of tap water with a thumb-sized strip of silicon floating in it. When he held the glass up to the light, the strip began to gently bubble.

It seemed to be splitting water into hydrogen and oxygen.

But this would mean you could take any tub of water and – with no more than a few cheap materials and a little light from the sun – produce two incredibly powerful fuels.

It couldn’t be right.

Professor Nocera went back and, for 8 months, tried to prove himself wrong.

The artificial leaf: better than nature

Scientists had split water before. By 1870, electrolysis using platinum electrodes and vast electrical currents could achieve the feat.

In the 20th century, too, simpler methods had been developed which used sunlight to power the reaction – but these, too, relied on prohibitively costly metals.

Professor Daniel Nocera

Nocera’s “artificial leaf” is different.

On either side, the silicone strip is coated with inexpensive metallic compounds – a cobalt phosphate catalyst that spurs the creation of oxygen gas, and a nickel-zinc alloy that does the same for hydrogen.

The process only uses as much energy as it can pick up from sunlight: in the lab, Nocera flicks off the light, and the bubbles disappear.

The reaction was inefficient when first demonstrated in 2008 – with little of the sunlight being locked up in the fuels – but today it beats nature at its own game.

In natural photosynthesis, the process by which all plants take in energy – and which ultimately provides the fuel for all life on earth – only very small amounts of solar energy are converted to fuel.

“The best stuff that grows in the field, a plant, it only fixes 1% of the light,” explains Nocera.

“We’re already on 7%.”

Freedom from the grid

“My vision of the world is: if you see some sun, you will be in control of your own energy supply,” says Nocera, now professor of energy at Harvard University.

First, he’s looking to the developing world where, he says, two drinking bottles of water could provide a household with a steady 100 watt power supply

The water wouldn’t even need to be clean:

“You find some water on the ground, you put it in, the water circulates over this thing that’s collecting the light just like a solar panel and then it’s splitting into hydrogen and oxygen.”

Anyone could have an artificial leaf device – which he predicts “will look