Bionic leaf turns sunlight into fuel


Fuel-production techniques that avoid digging into the earth are always welcome developments in today’s energy-dependent world.

Borrowing from the natural world, a team of Harvard University researchers has developed a new solution – an artificial leaf that performs a kind of photosynthesis, using sunlight to create fuel.

“If you think about it, photosynthesis is amazing,” says Harvard’s Daniel Nocera, co-author of the study.

“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.”

The process involves a combination of elements reacting with carbon dioxide to split water molecules, and bacteria that eats up all the hydrogen, leaving behind liquid fuel.

This echoes the natural process of photosynthesis, in which plants harness solar radiation to build energy-rich molecules from water and carbon dioxide.

While copying photosynthesis isn’t a new idea, there have been complications around the process in the past.

This was a second try for this research group – the first time around, the process produced molecules called reactive oxygen species that attacked the bacteria.

“For this paper, we designed a new cobalt-phosphorous alloy catalyst, which we showed does not make reactive oxygen species,” says Nocera. “That allowed us to lower the voltage, and that led to a dramatic increase in efficiency.”

Efficiency is certainly key, here – the process described by the paper, published the journal Science, creates biomass from the Sun with around 10 times the efficiency of plants.

Cobalt and phosphorous split water into molecular hydrogen and oxygen. When grown in contact with this dynamic combo, the bacterium Ralstonia eutropha eats up the hydrogen and produces biomass.

The researchers say the finding has far-reaching applications.

“It’s an important discovery – it says we can do better than photosynthesis,” says Nocera. “But I also want to bring this technology to the developing world as well.”

Further reading:
A quantum
leap for solar power
Lab Talk: heavy metal and bionic plants
Flying on
sunshine – a solar jet fuel

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