The headline screams Sun + Water = Fuel

Chemists, of course, can already split water. But the process has required high temperatures, harsh alkaline solutions, or rare and expensive catalysts such as platinum. What Nocera has devised is an inexpensive catalyst that produces oxygen from water at room temperature and without caustic chemicals--the same benign conditions found in plants. Several other promising catalysts, including another that Nocera developed, could be used to complete the process and produce hydrogen gas.

Nocera sees two ways to take advantage of his breakthrough. In the first, a conventional solar panel would capture sunlight to produce electricity; in turn, that electricity would power a device called an electrolyzer, which would use his catalysts to split water. The second approach would employ a system that more closely mimics the structure of a leaf. The catalysts would be deployed side by side with special dye molecules designed to absorb sunlight; the energy captured by the dyes would drive the water-splitting reaction. Either way, solar energy would be converted into hydrogen fuel that could be easily stored and used at night--or whenever it's needed.

hmmm, when you unpack that what he mainly has is a catalyst system to split water. Electricity from any source does the trick. Using electricity generated by solar cells is an application of the technology, but wind, wave, geothermal, hydrokinetics, a CHP with a Stirling engine, a nuclear power plant or whatever will serve as well as solar panels. Perhaps better.

In 1991, [Michael] Grätzel invented a promising new type of solar cell. It uses a dye containing ruthenium, which acts much like the chlorophyll in a plant, absorbing light and releasing electrons. In ­Grätzel's solar cell, however, the electrons don't set off a water-splitting reaction. Instead, they're collected by a film of titanium dioxide and directed through an external circuit, generating electricity. Grätzel now thinks that he can integrate his solar cell and ­Nocera's catalyst into a single device that captures the energy from sunlight and uses it to split water. . .

The idea is that Grätzel's dye would take the place of the electrode on which the catalyst forms in Nocera's system. The dye itself, when exposed to light, can generate the voltage needed to assemble the catalyst. "The dye acts like a molecular wire that conducts charges away," Grätzel says. The catalyst then assembles where it's needed, right on the dye. Once the catalyst is formed, the sunlight absorbed by the dye drives the reactions that split water. Grätzel says that the device could be more efficient and cheaper than using a separate solar panel and electrolyzer.

I think that it would have to be quite a lot cheaper than solar cells to be worthwhile, but it is an interesting hack.

Artificial leaves and fuel-producing desalination systems might sound like grandiose promises. But to many scientists, such possibilities seem maddeningly close; chemists seeking new energy technologies have been taunted for decades by the fact that plants easily use sunlight to turn abundant materials into energy-rich molecules. "We see it going on all around us, but it's something we can't really do," says Paul Alivisatos, a professor of chemistry and materials science at the University of California, Berkeley, who is leading an effort at Lawrence Berkeley National Laboratory to imitate photosynthesis by chemical means.

But soon, using nature's own blueprint, human beings could be using the sun "to make fuels from a glass of water," as Nocera puts it. That idea has an elegance that any chemist can appreciate--and possibilities that everyone should find hopeful.

Well, yes and no. Plants really aren't very good at capturing and using sunlight - less than 1% efficient. Existing solar cells are much more efficient and they get better all the time. This is an interesting finding but it may have a long, long way to go before it yields useful applications.

Maybe it could go the other way too and help us understand how to improve plants so that they capture more sunlight. That's tough since too much captured energy can fry plant tissues. Perhaps it can help understand ways to improve existing commercial electrolyzers, though they are already orders of magnitude more efficient than Nocera's system. Or it may have no useful applications. Not all interesting knowledge is useful.