Over the past few years, scientists have been working to create artificial leaves with the ability to mimic natural counterparts used to produce energy from water and sunlight. In 2011, the first stable and cost-effective artificial leaves were introduced; in 2013, the devices themselves were improved to self-heal and work with impure water.
Now, scientists at Harvard unveiled the bionic leaf 2.0, which increases the efficiency ten times more than natural photosynthesis.
Led by Harvard University’s Daniel Nocera and Pamela Silver, Professor of Biochemistry and Systems Biology at Harvard Medical School, the project creates a system that uses solar energy to split water molecules and hydrogen-eating bacteria to produce liquid fuels.
Similar to previous versions, the bionic leaf 2.0 is placed in water and can split the water molecules into their component gases (hydrogen and oxygen) as it absorbs solar energy. These gases can then be harvested and used in fuel cells to generate electricity. With the assistance of engineered bacteria, the hydrogen can now be used to produce liquid fuels.
The bionic 2.0 leaf notably beats the previous tests (as well as nature itself) when it comes down to the catalyst that produces the hydrogen. In prior versions, the nickel-molybdenum-zinc alloy catalyst that was used to generate the hydrogen also created reactive oxygen species, which would attack and destroy the bacteria’s DNA. To overcome the issue, the researchers had to run the system at a higher voltage, which led to a reduced overall efficiency.
With the new catalyst, the system can convert sunlight into biomass with 10 percent efficiency, a figure that is 10 times greater than even the most efficient plants.
“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.”
The researchers at Harvard demonstrated how the system can be used to form compounds like isobutanol, isopentanol, and PHB, a bio-plastic precursor. The catalysts are biologically compatible since they self-heal and do not leach material into a solution.
In its current form, the bionic 2.0 leaf is efficient enough to consider commercial applications. Nocera stated that there are plans for the technology to be used in developing countries as an inexpensive source of renewable energy, ultimately powering individual homes.
The team’s results, published in the journal Science , can be found here.
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