The Artificial Leaf


Chemist Daniel Nocera has successfully developed a device that closely mimics photosynthesis—an “artificial leaf” that has the ability to power our homes and cars with clean energy, applying the simple formula of sunlight and water.

Imagine if we can power the entire universe using nothing but sunlight and water? Sounds impossible? But is not that what plants have been doing for more than two billion years? It is the basic principle of photosynthesis—nature’s seemingly simple, yet, extremely reliable fuel generating process.

It all occurs in the leaf, where nature has succeeded in doing what scientists have repeatedly failed to accomplish—using sunlight to drive the splitting of water into its component parts to produce fuel—efficiently and economically.

With energy sources depleting and pollution on the rise, scientists are returning to nature and are finally starting to learn from the leaf. They appear to be on their way to unleash the power of photosynthesis, with the new artificial solar leaf that can provide for our energy needs.

The idea of the “artificial leaf” sounds simple enough: take a small, cheap, light-collecting device the size of a typical leaf, throw it in some water, and use solar energy to generate enough hydrogen gas for powering a small fuel cell. Scaled up, these solar-derived fuel cells would provide an energy storage solution that places solar power on the same consistent, reliable footing as any fossil fuel.

Various researchers have reached most of the way there only to get hung up on that little word “cheap”, but Chemist Daniel Nocera’s artificial leaf is getting close to overcoming this economic hurdle.

Rather than relying on precious metals such as platinum, his design uses a combination of the cheaper more widely available materials; cobalt phosphorus and oxygen on one side of the wafer (for water oxidation) and nickel molybdenum and zinc on the other (for reducing protons into hydrogen gas).

To further reduce the cost, Nocrea is now looking at ways to reduce the amount of silicon used in the device.

Aside from the cost, there is another huge obstacle to mainstreaming the artificial leaf concept, especially in undeveloped communities, and that is the fresh water scarcity issue.

The artificial leaves need fresh, clean water to operate efficiently, partly because of the possibility of corrosion of the catalyst in impure water and partly because impurities may build up a biofilm on the catalyst.

Nocera’s team recently solved part of the equation by coming up with a way to tweak the surface of the catalyst, roughing it up enough to prevent biofilm buildup.

Interestingly, the tweak also resulted in a self-repairing system. The roughened surface is fragile and falls apart, but it also passes through a cycle of healing and reassembly, making it last longer, thus, more economic.

Right now with just the artificial leaf, 15 bottles of drinking water and sunlight, you could have enough electricity to power a small home.

Although the price of the artificial leaf is still high for large scale commercial use, Daniel Nocrea declares that with research, they will lower the price to commercial levels in as early as five years from now.  We will be crossing our fingers.


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SCIplanet is a bilingual edutainment science magazine published by the Bibliotheca Alexandrina Planetarium Science Center and developed by the Cultural Outreach Publications Unit ...
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