Researchers make headway in turning photons into fuel. Inside Caltech's Jorgensen Laboratory, however, more than 80 researchers are putting a lot of effort into doing the leaf's job using silicon, nickel, iron and any number of other materials that would be more at home inside a cell phone than a plant cell. Their gleaming new labs are the headquarters of the Joint Center for Artificial Photosynthesis (JCAP), a 190-person research programme funded by the US Department of Energy (DOE) with US$116 million over five years. The centre's goal is to use sunlight to make hydrogen and other fuels much more efficiently than real leaves ever made biomass.
The researchers are pursuing this goal with a certain urgency. Roughly 13% of greenhouse-gas emissions worldwide come from transportation, so phasing out polluting fuels is a key environmental target. One approach is to replace cars and light trucks with electric vehicles charged by solar cells or wind — but that cannot tackle the whole problem. Nathan Lewis, an inorganic chemist at Caltech and JCAP's scientific director, says that some 40% of current global transportation cannot be electrified. For example, barring a major breakthrough, there will never be a plug-in hybrid plane: no craft could hold enough batteries. Liquid fuels are unbeatable when it comes to convenience combined with compact energy storage
That is why funding agencies around the world — and at least a few private companies — are putting unprecedented resources into making fuels using power from the Sun, which is not only carbon-free but effectively inexhaustible. JCAP stands out not only for its scale, but also for its ambition. It is one of five Energy Innovation Hubs created by the DOE beginning in 2010 to focus on specific problems using basic research, applied research and engineering. JCAP has promised to deliver a working prototype of an artificial leaf by the time its initial grant runs out in 2015.
Although the centre has taken some important steps in that direction — including one recently reported1 — it is still a long way from delivering on that promise, “This is a really, really difficult, challenging problem,” says electrochemist John Turner of the US National Renewable Energy Laboratory in Golden, Colorado. “The payback would be huge, but it's not as simple as everyone wanted it to be when we started playing in this area 40 years ago.”
Still, the surge of funding and attention has given many researchers reason to hope for long-term success. “If you could sustain this type of effort for the next ten years,” says Michael Wasielewski, a chemist at Northwestern University in Evanston, Illinois, “it's conceivable you could have a practical solution.”