Solar Leaf: While Tea Party Slimes Energy Progress, Innovators Build the Future

October 4, 2011


It isn’t green and it doesn’t grow, but the wafer sitting in a beaker of water in Dan Nocera’s laboratory is remarkably like a leaf.

Using a silicon solar cell coated with cheap and abundant catalysts, the device uses sunlight to rip apart molecules of water, just like a photosynthesizing leaf. This produces hydrogen and oxygen gases, which bubble up on either side of the wafer (see video). The details are published today in Science1.

As with photosynthesis, the wafer ultimately stores sunlight energy as chemical bonds in a fuel: hydrogen gas, which can be piped and stored, and its energy released when required.

The parallel with nature is not exact: a real leaf does start by ripping up water, but does not end by breathing out hydrogen. Instead, it diverts the hydrogen into reactions with carbon dioxide, eventually creating sugar molecules. Nevertheless, Nocera, who works at the Massachusetts Institute of Technology in Cambridge, says that his team’s concept will aid in efforts to produce clean, cheap hydrogen from sunlight and water — perhaps even allowing houses in poor but sunny countries to produce their own fuel on demand. He has founded a company, Sun Catalytix, also in Cambridge, to commercialize his electrolytic device; its influential backers include the multinational conglomerate Tata Group.

Splitting water with sunlight to make hydrogen is not a new trick. Chemists have long used solar cells to generate electricity and sent it through wires to catalyst-covered electrodes that split water, producing hydrogen. But such devices used either expensive catalysts (such as ruthenium or platinum) or harsh acidic or basic conditions from which the solar cell had to be separated, or protected with expensive glass2,3.

Nocera and his co-worker’s device is the first to couple a solar cell and catalysts into one device, with no wires in between, and the first to work in conditions as mild as tap water. It even works with seawater, Nocera says; he has been using samples from the nearby Charles River.

2 Responses to “Solar Leaf: While Tea Party Slimes Energy Progress, Innovators Build the Future”

  1. sinchiroca Says:

    This is REALLY important technology. If these guys really can bring this to market, this will have a big impact. Back in 1975, during the “Energy Crisis”, I gave a public lecture in which I suggested that, far in the future, our best bet would be something like a leaf: a device that chemically converts sunlight into fuel. I was thinking in terms of a chemical soup, but these guys have a better way. Everything depends on the catalysts they use; if they can get something stable, efficient, and cheap, then I expect that they’ll get so rich they can hire Bill Gates as a butler.

    Of course, it all piggybacks on conventional solar PV, but the price of that, as we all know, is within striking distance of full utilization.

  2. MIT’s arch “rival”, Caltech, and many other research groups, are working on similar solutions.

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