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Ask a MacArthur genius: Can a fake leaf commercialize photosynthesis?

Peidong Yang just won a Genius Grant for his work on artificial photosynthesis. (Alison Yin/AP Images for John D. & Catherine T. MacArthur Foundation)

Peidong Yang is allergic to hype — a fact that is perhaps incompatible with the MacArthur “genius” grant he was just awarded. “The biggest misunderstandings about our work come when our results are exaggerated,” he says, revealing that he worries about his current work overshadowing the challenges ahead.

For any other chemist, that worry might be premature. But for Yang, it makes sense: After all, the discovery for which he is best known — how to use tiny wires and bacteria to perform photosynthesis in what he calls an “artificial leaf” — is astonishing indeed. The leaf takes advantage of the amazing properties of semiconductor nanowires that are typically 100 to 1,000 times thinner than a human hair. These miniature wires can act like lasers, conduct electricity and even put RNA into individual cells, and now Yang has harnessed them to mimic one of nature’s most perfect systems.

[Ask a MacArthur genius: Can feces fuel cars?]

The push to reproduce photosynthesis, which converts light energy into chemical energy, has been going on for years. In his own lab and in work with the University of California at Berkeley’s Helios Solar Energy Research Center, Yang has brought nanowires to the battlefield. Real leaves breathe in carbon dioxide, take in water and use the sun to power a reaction that converts solar energy into carbohydrates. Then they release oxygen into the environment to complete the cycle.

Yang’s team knew they could use nanowires to capture solar energy, but they needed a kind of catalyst to help convert that energy into something else. When they added bacteria to the mix, they were able to close the cycle, converting carbon dioxide and water into methane, acetate and even butanol, powering the entire reaction with just the light of the sun.

“Most past efforts have focused on producing hydrogen, but CO2 was much more challenging to tackle,” said Yang. But to him, using a hybrid approach to achieve photosynthesis isn’t good enough. “We’ve demonstrated that this is feasible,” he said, “but we haven’t solved the problem yet.” Now, he’s pushing to make artificial photosynthesis entirely artificial, eliminating the bacterial component in favor of materials with longer life cycles and better durability.

If his team succeeds, they’ll potentially create a way to deal with carbon dioxide in the environment. “If you can convert that CO2 into useful chemicals and fuels,” says Yang, “you’ll be doing something really useful. You are no longer going through this old cycle of increasing CO2 concentrations.” But to do that, Yang and his team will have to figure out a way to create a veritable forest of stable, working artificial leaves that can be commercialized and widely adopted.

[Ask a MacArthur genius: Will tiny polymers replace bomb-sniffing dogs?]

He thinks it’s possible, in part because of the boost the MacArthur grant will give him and his colleagues. Not only will their work be more visible, but more money means more research opportunities and the chance to collaborate with other scientists. “This will only happen through collaboration,” said Yang, who says that the call is being answered by scientists across all disciplines. “When you’re on the boundaries of traditional disciplines, you get more discoveries.”

Luckily, he says, it’s easier to talk about minuscule technology than ever before. “Just ten or 15 years ago, people didn’t know how to appreciate the nanoscale,” he said. “Now, people are starting to appreciate nanotechnology.” They may have even more cause for appreciation when advances on that tiny scale create a way to turn CO2 pollution into abundant clean fuel with just the light of the sun. And in the future, that idea may not be hype at all.

Erin Blakemore (@heroinebook) is a freelance journalist from Boulder, Colo. She is the author of "The Heroine’s Bookshelf" (Harper). 

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