New “Bionic” Leaf Is Roughly 10 Times More Efficient Than Natural Photosynthesis

It converts CO₂ in the air into alcohol that can be burned as fuel

Join Our Community of Science Lovers!

A tree's leaf, a blade of grass, a single algal cell: all make fuel from the simple combination of water, sunlight and carbon dioxide through photosynthesis. Now scientists say they have replicated—and improved on—that trick with their own “bionic leaf.”

Chemist Daniel Nocera of Harvard University and his team joined forces with synthetic biologist Pamela Silver of Harvard Medical School and her team to craft a kind of living battery, which they call a bionic leaf for its melding of biology and technology. The device uses solar electricity from a photovoltaic panel to power the chemistry that splits water into oxygen and hydrogen. Microbes within the system then feed on the hydrogen and convert carbon dioxide in the air into alcohol that can be burned as fuel. The team's first artificial photosynthesis device appeared in 2015—pumping out 216 milligrams of alcohol fuel per liter of water—but the nickel-molybdenum-zinc catalyst that made its water-splitting chemistry possible had the unfortunate side effect of poisoning the microbes.

So the team set out in search of a better catalyst and, as recently reported in Science, the researchers found it in an alloy of cobalt and phosphorus, an amalgam already in use as an anticorrosion coating for plastic and metal parts. With this new catalyst in the bionic leaf, the team boosted version 2.0's efficiency at producing alcohol fuels such as isopropanol and isobutanol to roughly 10 percent. In other words, for every kilowatt-hour of electricity, the microbes could scrub 130 grams of CO₂ out of the air to make 60 grams of isopropanol fuel. Such a conversion is roughly 10 times more efficient than natural photosynthesis.

On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

Nocera says that by knitting fuels out of the excess CO₂ in the air, this new bioreactor technology could help mitigate planet-warming pollution problems while bringing cleaner fuels to people who lack access to modern energy.

Subscribe to Support Independent Journalism

Great science journalism requires human expertise, time, effort and creativity. And it costs money. That’s why I and the journalists here at Scientific American hope you’ll join our community.

When you subscribe, you are supporting staff and freelance journalists who are passionate about telling science stories that are true, important and compelling. Our editors and reporters are often experts in their fields, which means they understand the nuances of big discoveries and can untangle the breakthroughs from the hype. With a subscription, you are also supporting rigorous fact-checking to ensure the words we publish are precise and accurate. And you’re supporting original illustrations, graphics and photos that bring you closer to an advanced laboratory, an ice sheet in Antarctica or a space mission in orbit. You’re helping us craft other types of high-quality journalism as well: Our newsletters are carefully written, edited and curated by staffers you have or will come to know and love. Our Science Quickly podcast is based on original reporting, collaboration with editors and scientists and exacting production.

Subscriptions keep this engine running so we can continue to deliver thoughtful, rigorous and independent science journalism to you. In an era of viral misinformation, this work is crucial. If you value what we do, I hope you’ll consider joining us as a subscriber

Thank you,

Jeanna Bryner, Editor in Chief, Scientific American