Skip to Content

A Practical Artificial Leaf Begins to Unfold

A new prototype that turns the sun’s energy into hydrogen fuel could point the way to commercially viable artificial photosynthesis.
August 27, 2015

Fuel made inexpensively through artificial photosynthesis could be the ultimate renewable energy source. Now researchers at Caltech say they have built the first prototype of an artificial leaf that is both efficient and safe. They say the device, which uses light and water to make clean hydrogen fuel, could lead to a commercially viable version in the near future.

The technology harnesses the sun’s energy to split water into hydrogen and oxygen; the hydrogen could be used as fuel for vehicles or be stored for use in generating electricity. A photovoltaic material captures photons and generates electrons, which are passed on to chemical catalysts to do the water splitting. 

To be commercially viable, the system, which is inspired by plant photosynthesis, must be efficient, stable, inexpensive, and safe, says Nate Lewis, a professor of chemistry at Caltech, who led the new research. Some previous demonstrations of artificial leaf technology have shown impressive efficiency but haven’t been stable, he says. “Nothing is close, in terms of efficiency and stability and safety all combined at once, to what we’ve done here,” says Lewis.

A number of groups are pursuing artificial leaf technologies, and are taking a range of different approaches. The prize is a technology that would be better than solar power because its product is an easily stored fuel instead of intermittent electricity. But achieving artificial photosynthesis is a steep technical challenge that requires getting multiple different materials and catalysts to work together.

Key to the enhanced stability is a chemical called titanium dioxide, which the researchers used to protect the photovoltaic materials from the corrosion that occurs due to the chemical reaction that makes oxygen. They applied it as a very thin coating, using a process already used by the semiconductor industry. Crucially, the protective material is compatible with a membrane the group developed to keep the oxygen and hydrogen gas from mixing, which is an explosion hazard. It is also compatible with cheap catalysts that are already used commercially and are made of abundant materials, says Lewis.

The newly demonstrated system represents the accomplishment of a five-year project of the Joint Center for Artificial Photosynthesis, which received $122 million from the federal government in 2010 and will soon be up for new funding. The objective was to demonstrate the direct production of fuel from the sun with efficiency 10 times greater than plants.

The technology still must get a lot cheaper to be competitive with other sources of fuel. Ultimately, Lewis envisions a system that can be “rolled out like a piece of plastic” over a large area. What’s important now, he says, is the proof that achieving high efficiency safely and in a relatively stable manner is even doable. “We will work on the cost after we are walking instead of crawling.”

Keep Reading

Most Popular

A Roomba recorded a woman on the toilet. How did screenshots end up on Facebook?

Robot vacuum companies say your images are safe, but a sprawling global supply chain for data from our devices creates risk.

A startup says it’s begun releasing particles into the atmosphere, in an effort to tweak the climate

Make Sunsets is already attempting to earn revenue for geoengineering, a move likely to provoke widespread criticism.

10 Breakthrough Technologies 2023

Every year, we pick the 10 technologies that matter the most right now. We look for advances that will have a big impact on our lives and break down why they matter.

These exclusive satellite images show that Saudi Arabia’s sci-fi megacity is well underway

Weirdly, any recent work on The Line doesn’t show up on Google Maps. But we got the images anyway.

Stay connected

Illustration by Rose Wong

Get the latest updates from
MIT Technology Review

Discover special offers, top stories, upcoming events, and more.

Thank you for submitting your email!

Explore more newsletters

It looks like something went wrong.

We’re having trouble saving your preferences. Try refreshing this page and updating them one more time. If you continue to get this message, reach out to us at customer-service@technologyreview.com with a list of newsletters you’d like to receive.