The Nocera Lab's artificial and bionic leaves could transform our energy industry

 

By Caitlin McDermott-Murphy

 

We take leaves for granted. Crowded forests, hardy houseplants, and the nurturing sprouts that pop up in our gardens, all rely on the powerful chemistry performed within each leaf. In his mimicry, so does Daniel Nocera. “You can use just sunlight, air, and water, and you can do it in your backyard.”

But the science, which the American Chemical Society called a “holy grail” of chemistry, is the result of decades of intense exploration. His artificial leaf resembles a flash drive more than its namesake, but the potent chip has proven that it doesn’t need to look like its counterpart to outperform it.

Nocera’s leaf mimics photosynthesis, the chemistry a natural leaf performs to convert water and sunlight into energy. In Nocera’s lab, the thin, black, thumb-sized wafer descends into a transparent vessel and receives a bright dose of light. Bubbles—hydrogen and oxygen—form and ascend.

The light turns off, and the bubbles fade. And that’s the magic. Those gas bubbles can be captured, stored, and burned in a fuel cell to generate electricity. What’s more, Nocera’s leaf yields ten times the energy of the one growing outside your door.

 

Daniel Nocera's artificial leaf can generate ten times more energy than the ones surrounding him

 

Artificial leaf technology could provide vital energy for those living in electric deserts. Common in developing countries and rural communities, these regions are not yet trapped in the fossil fuel industry’s complex infrastructure and could build a new industry, untethered from the grid. Nocera envisions a combination power plant and gas station in everyone’s backyard, an idea he calls “personalized energy.”

But this utopic vision doesn’t play well with the established energy infrastructure. He needs a cheaper way to subvert the system to incentivize such a dramatic overhaul.

In the meantime, Nocera added a few upgrades and accessories to his invention. First, he developed a new type of flow battery that can integrate into the power grid and provide a way to store renewable energy. This storage system builds a platform for the large-scale deployment of solar energy, a small win for Nocera’s renewable revolution.

For the second improvement, he and his lab recruited a new workhorse for the leaf. They introduced a bio-engineered bacterium, Ralstonia eutropha, to speed the photosynthetic process. In the new “bionic leaf,” this bacterium breathes in the hydrogen and combines it with carbon dioxide to produce alcohol fuels. Once again, the new leaf bests nature three to one.

In a surprising twist, Ralstonia eutropha demonstrated a trick of its own. When it performs its chemistry, it creates a valuable byproduct: nitrogen-based fertilizer. Right now, agricultural fertilizer production requires high energy input, most often in the form of fossil fuels. And fertilizer distribution relies on factories connected to rail and road networks.

As the world’s population grows, this system will become untenable. Increased food demand will require increased fertilizer production, which in turn increases our reliance on diminishing fossil fuels.

The powerful Ralstonia eutropha performs its trick for free, and with impressive results. The Nocera Lab demonstrated that radishes cultivated with these microbes weigh 150 percent more than control radishes. “Quite surprisingly, it’s a fairly potent [fertilizer],” said Kelsey Sakimoto, a postdoctoral researcher on the project. “It’s grown very simply and applied very simply.” In time, the bionic leaf could ease our dependence on industrial agriculture and deliver fertilizer to farmers who are literally off the grid. 

The potential impact of Nocera’s technologies go beyond energy and agriculture. “I have an entire renewable synthesis platform that just uses sunlight and air and water,” Nocera said. “Depending on how you do the biology, I could have it make anything—plastics, maybe inorganic materials, drugs, food—directly.”

Energy and food demand will soon eclipse the capabilities of current technologies. Eventually, Nocera and his leaves could provide a way to circumvent these crises. In the meantime, they might be used to deliver much-needed resources to developing or rural communities.

“This type of science we’re doing is really important for the poor, because they don’t live in large, centralized infrastructures and distribution systems,” he said. “I like this research because it’s giving to the poor what we have in the rich part of the world, which is fuels and food.” Though it may be hard to imagine, a leaf created in a lab could be the next great equalizer. We shouldn’t take this one for granted.

No offense, nature.