“The big challenge is, how do we go from milligrams to megatons?” said Dick T. Co, a Northwestern University professor and managing director of the Solar Fuels Institute, a group that encourages collaboration among researchers in the field. “How do we make a dent in our energy portfolio when people are working in test tubes today?”
In a research building at the Lawrence Berkeley lab, with a view of San Francisco Bay in the distance, Dr. Atwater leads a team of scientists that is trying to mimic what plants do through photosynthesis. They want to take CO2 and water and, using only sunlight, turn it into fuel.
The center, started in 2010 with a grant from the Department of Energy, devoted its first five years to one aspect of photosynthesis: splitting water into its components, hydrogen and oxygen.
Dr. Atwater, Frances A. Houle, a deputy director, and Karl Walczak, a project scientist, showed some of the fruits of that work — a chip-size sandwich of semiconductor material, catalysts and membranes encased in a clear container with a water-based solution. When the chip was exposed to light, bubbles of gas — hydrogen on one side, oxygen on the other — formed, broke off and rose to the top.
By their calculations, the chip is about 10 times more efficient than a typical plant, which uses about 1 percent of the sunlight that strikes it.
The center is now working on the carbon-dioxide part of the photosynthetic equation. The goal is to integrate the two processes in a device that might look a lot like a solar panel. But rather than generating electricity, it would produce fuel — perhaps methanol, which could be burned directly or converted to gasoline.
Carbon dioxide is much more difficult to split than water, however, involving six steps, each requiring energy and a catalyst. Nature appears to do it effortlessly, but it has had millions of years of evolution to improve the process.
Much of the work at the center involves studying catalysis, through theoretical analysis and testing possible combinations of metal oxides to see how well they might work. The testing method is similar to one used for drug discovery, with equipment that can analyze large numbers of very small samples at a time.
The goal is to make a device that can make just one product, as in natural photosynthesis, but more efficiently. At the same time, the device has to be able to last for years, as solar panels do. That adds to the engineering and design challenges.
There are other research groups, and some start-ups and established companies, that are working on CO2 conversion as well. Sunfire, a company in Dresden, Germany, built a prototype to make synthetic crude oil from carbon dioxide and water. Part of the crude is diesel fuel, and in 2015, Audi used some of the Sunfire diesel to briefly power one of its cars.
The Sunfire process uses electricity, not sunlight, so the electricity would have to come from renewable sources to result in meaningful carbon reductions. Given the amount of electricity is required, a big challenge is producing fuel that could compete in price with conventional fossil fuels, said Christian von Olshausen, Sunfire’s chief technology officer.
In Berkeley, at a lab building just down the hill from the Joint Center for Artificial Photosynthesis, three young scientists have started a small company, Opus 12, to develop their own CO2-conversion device, powered by electricity.
Their idea is to exploit the fact that CO2 can be converted into many different products, by coming up with catalysts tailored to produce specific ones.
“Our vision is to design this reactor more as a platform,” said Nicholas Flanders, who founded Opus 12 with Kendra Kuhl and Etosha Cave.
The three met at Stanford, where they were working on advanced degrees. About a year ago, they received financing and other assistance, including lab space, from the Lawrence Berkeley lab under an energy-technology incubation program called Cyclotron Road.
Dr. Kuhl and Dr. Cave studied catalysis at Stanford, and though their operation is far smaller than the center’s just up the hill, they are working on developing and fine-tuning catalysts to efficiently convert CO2. “We make the secret sauce,” Dr. Kuhl said.
In their small lab, they spray catalysts for testing onto a small membrane, using modified airbrush equipment. The coated membrane is then put into a prototype reactor, about the size of a smartphone but thicker, which is hooked up to sources of CO2, water and electricity. What comes out of the reactor — proprietary information for now, the scientists say — is analyzed for its purity.
Over the next year and a half, Mr. Flanders said, the company plans to scale up their reactor to something the size of a dishwasher. That would be big enough to start generating revenue by making small amounts of products for niche applications that command a relatively high price. Because of the electricity needed, any device they make would need to use renewable electricity to maximize the CO2-reduction benefit.
Beyond that, Mr. Flanders envisions larger devices that could convert tons of carbon dioxide a day into fuels or other products. That’s still not very much, given the billions of tons of CO2 pumped into the atmosphere every day. But Opus 12 is in it for the long haul, he said.
The Joint Center for Artificial Photosynthesis is, too, although Dr. Atwater is realistic about the challenges of directly converting sunlight and CO2 into fuel.
“You can rest assured that the energy and catalysis problems of humanity will not have been resolved five years from now,” he said.
But there is growing interest in the work of Dr. Atwater and his fellow researchers, particularly after the recently signed Paris climate treaty that calls for sharp emissions reductions to combat global warming.
“We have some wind at our back that we haven’t had until recently,” he added.