Space & Innovation

Bionic Leaf Uses Sunlight to Make Liquid Fuel

The process could someday replace oil drilling.

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Photo: Jessica Polka, Wikimedia Commons Harvard University researchers have found a way to simulate the photosynthesis process that occurs in plants to create a liquid alcohol fuel that someday might replace petroleum. The process utilizes solar energy to split water molecules, and then employs a hydrogen-eating bacteria to produce fuel.

The process is described in a recently published article in the journal Science, whose lead authors include postdoctoral fellow Chong Liu and graduate student Brendan Colón. Daniel Nocera, a co-author of the study and the Patterson Rockwood professor of energy at Harvard, described it in a news release as "a true artificial photosynthesis system."

Fellow co-author, Pamela Silver, a co-founder of Harvard's Wyss Institute for Biologically Inspired Engineering, said that the technology shows the potential for copying biological processes to solve problems.

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"The beauty of biology is it's the world's greatest chemist -- biology can do chemistry we can't do easily," she said. "In principle, we have a platform that can make any downstream carbon-based molecule. So this has the potential to be incredibly versatile."

The process, which the Harvard researchers call "bionic leaf 2.0," builds upon a previous effort to develop a practical form of artificial photosynthesis.

That initial project had some bugs to work out. Because the catalyst that it used to split hydrogen and oxygen -- a nickel-molybdenum-zinc alloy -- also created a reactive form of oxygen that harmed the hydrogen-consuming bacteria. To compensate, the scientists had to run that system at an abnormally high voltage, reducing its efficiency.

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This time, Nocera explained, the researchers designed a new cobalt-phosphorous alloy catalyst, which doesn't make reactive oxygen. That allowed them to lower the voltage, and that led to a dramatic increase in efficiency."

Bionic leaf 2.0 can convert solar energy into fuel with about a 10 percent efficiency rate, far above the 1 percent efficiency achieved by fast-growing plants.

As an added bonus, in addition to fuel, the system also produces PHB, a bio-plastic precursor.

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