Harvard’s artificial leaf improves photosynthesis and produces liquid fuel

Original news release was issued by the Harvard Gazette, written by Peter Reuell.

The need for renewable sources of energy keeps increasing no matter how much fossil fuels refuse to go away. Some are taking their green initiatives further than others, but Harvard’s new step towards accessible and efficient green energy may actually  be a huge leap. Daniel Nocera, the Patterson Rockwood Professor of Energy at Harvard University, and Pamela Silver, the Elliott T. and Onie H. Adams Professor of Biochemistry and Systems Biology at Harvard Medical School, have co-created a system that uses solar energy to split water molecules and hydrogen-eating bacteria to produce liquid fuels. Essentially, they made photosynthesis manufacturable and better.

“This is a true artificial photosynthesis system,” Nocera said. “Before, people were using artificial photosynthesis for water-splitting, but this is a true A-to-Z system, and we’ve gone well over the efficiency of photosynthesis in nature.”

But the system’s potential goes beyond production of fuel: “The beauty of biology is it’s the world’s greatest chemist — biology can do chemistry we can’t do easily,” said Silver. “In principle, we have a platform that can make any downstream carbon-based molecule. So this has the potential to be incredibly versatile.”

This isn’t the first shot that Nocera, Silver, and their colleagues have taken at a bionic leaf. The alloy used as a catalyst in its previous version required too much voltage to be efficient enough. For the new version, however, the catalyst has been redesigned using a new cobalt-phosphorous alloy that allows for lower voltage, increasing the efficiency dramatically.

Daniel Nocera (Image source: Rose Lincoln/Harvard Staff Photographer)

The system can now convert solar energy to biomass with 10 percent efficiency, Nocera said, far above the 1 percent seen in the fastest-growing plants.

Though there may yet be room for additional increases in efficiency, Nocera said the system is already effective enough to consider possible commercial applications, but within a different model for technology translation. “It’s an important discovery — it says we can do better than photosynthesis,” Nocera said. “But I also want to bring this technology to the developing world as well.”

“If you think about it, photosynthesis is amazing,” he said. “It takes sunlight, water, and air — and then look at a tree. That’s exactly what we did, but we do it significantly better, because we turn all that energy into a fuel.”

Michal Dudic

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