New “Artificial Photosynthesis” System Produces Methane With 10x Efficiency

Innovative New System for Artificial Photosynthesis

A study from six chemists at the University of Chicago shows an innovative new system for artificial photosynthesis that is more productive than previous artificial systems by an order of magnitude. Above, an artistic illustration of the process. Credit: Illustration by Peter Allen

University of Chicago breakthrough creates methane fuel from sun, carbon dioxide, and water.

Humans have relied on fossil fuels for concentrated energy for the past two centuries. Our society has been taking advantage of the convenient, energy-dense substances packed with the proceeds from hundreds of millions of years of photosynthesis. However, that supply is finite, and fossil fuel consumption has an enormous negative impact on Earth’s climate.

“The biggest challenge many people don’t realize is that even nature has no solution for the amount of energy we use,” said University of Chicago chemist Wenbin Lin. Not even photosynthesis is that good, he said: “We will have to do better than nature, and that’s scary.”

“Artificial photosynthesis” is one possible option scientists are exploring. This entails reworking a plant’s system to make our own kinds of fuels. However, the chemical equipment in a single leaf is incredibly complex, and not so easy to turn to our own purposes.

Now, an innovative new system for artificial photosynthesis that is more productive than previous artificial systems by an order of magnitude is presented in a study published in the journal Nature Catalysis on November 10 by six chemists at the University of Chicago. Unlike regular photosynthesis, which produces carbohydrates from carbon dioxide and water, artificial photosynthesis could produce ethanol, methane, or other fuels.

Although it still has a long way to go before it can become a way for you to fuel your car every day, the method gives scientists a new direction to explore. Plus, in the shorter term, it may be useful for the production of other chemicals.

“This is a huge improvement on existing systems, but just as importantly, we were able to lay out a very clear understanding of how this artificial system works at the molecular level, which has not been accomplished before,” said Lin, who is the James Franck Professor of Chemistry at the University of Chicago and senior author of the study.

‘We will need something else’

“Without natural photosynthesis, we would not be here. It made the oxygen we breathe on Earth and it makes the food we eat,” said Lin. “But it will never be efficient enough to supply fuel for us to drive cars; so we will need something else.”

The trouble is that photosynthesis is built to create carbohydrates, which are great for fueling us, but not our cars, which need much more concentrated energy. So researchers looking to create alternates to fossil fuels have to re-engineer the process to create more energy-dense fuels, such as ethanol or methane.

In nature, photosynthesis is performed by several very complex assemblies of proteins and pigments. They take in water and carbon dioxide, break the molecules apart, and rearrange the atoms to make carbohydrates—a long string of hydrogen-oxygen-carbon compounds. Scientists, however, need to rework the reactions to instead produce a different arrangement with just hydrogen surrounding a juicy carbon core—CH4, also known as methane.

This re-engineering is much trickier than it sounds; people have been tinkering with it for decades, trying to get closer to the efficiency of nature.

Lin and his lab team thought that they might try adding something that artificial photosynthesis systems to date haven’t included: amino acids.

The team started with a type of material called a metal-organic framework or MOF, a class of compounds made up of metal ions held together by an organic linking molecules. Then they designed the MOFs as a single layer, in order to provide the maximum surface area for chemical reactions, and submerged everything in a solution that included a cobalt compound to ferry electrons around. Finally, they added amino acids to the MOFs, and experimented to find out which worked best.

“The biggest challenge many people don’t realize is that even nature has no solution for the amount of energy we use.”

Prof. Wenbin Lin

They were able to make improvements to both halves of the reaction: the process that breaks apart water and the one that adds electrons and protons to carbon dioxide. In both cases, the amino acids helped the reaction go more efficiently.

Even with the significantly improved performance, however, artificial photosynthesis has a long way to go before it can produce enough fuel to be relevant for widespread use. “Where we are now, it would need to scale up by many orders of magnitude to make an sufficient amount of methane for our consumption,” Lin said.

The breakthrough could also be applied widely to other chemical reactions; you need to make a lot of fuel for it to have an impact, but much smaller quantities of some molecules, such as the starting materials to make pharmaceutical drugs and nylons, among others, could be very useful.

“So many of these fundamental processes are the same,” said Lin. “If you develop good chemistries, they can be plugged into many systems.”

The scientists used resources at the Advanced Photon Source, a synchrotron located at the U.S. Department of Energy’s Argonne National Laboratory, to characterize the materials.

The co-first authors of the paper were Guangxu Lan (PhD’20, now with Peking University), graduate student Yingjie Fan, and Wenjie Shi (Visiting student, now with Tianjin University of Technology. The other authors of the paper were Eric You (BS’20, now a graduate student at MIT) and Samuel Veroneau (BS’20, now a PhD student at Harvard University).

Reference: “Biomimetic active sites on monolayered metal–organic frameworks for artificial photosynthesis” by Guangxu Lan, Yingjie Fan, Wenjie Shi, Eric You, Samuel S. Veroneau and Wenbin Lin, 10 November 2022, Nature Catalysis.
DOI: 10.1038/s41929-022-00865-5

Funding: University of Chicago, National Science Foundation, China Scholarship Council

8 Comments on "New “Artificial Photosynthesis” System Produces Methane With 10x Efficiency"

  1. Even if they were to achieve or even exceed the efficiency of natural photosynthesis, they are forgetting that Nature has the advantage of hundreds of millions of years to create and concentrate the methane. That is, Nature is effectively 8 orders of magnitude more efficient at providing methane!

  2. Howard Jeffrey Bender, Ph.D. | November 13, 2022 at 2:13 pm | Reply

    Since methane is a greenhouse gas at least 25x more potent than carbon dioxide, I’m rather amazed these researchers suggest we make more of it for our cars! Instead, I suggest using very small amounts of plutonium-238 as nuclear radiation sources for electricity for batteries. NASA does this for their deep space missions, where the sun is too distant for solar power. My proposal involves a speculated process different from NASA’s which, if successful, could generate clean auto and house electricity. No more fillups at gas stations, no more electric lines from power stations, no more oil politics. If we don’t fix the power issues we don’t fix the changing climate. This is part of my book on Amazon, “Gaia’s Climate Challenge – Giving Humans Their Last Chance”.

  3. Andrea Silverthorne | November 13, 2022 at 2:26 pm | Reply

    We need to tell the public what methane becomes in bulk during its oxidation water vapor and formaldehyde. It is the choice of the fossil fuel industry.

    • Do you have a source to support your claim of atmospheric methane being converted into formaldehyde (CH2O)? Wikipedia suggests that, in the atmosphere, methane (CH4) is initially converted to H2O and the methyl radical (CH3+), also known as the organic cation, methylium, by interaction with the hydroxyl (OH-) radical. Further reactions probably produce CO2, H2O, and possible O3.

      We need to tell the public facts, not fantasies or mis-truths.

  4. La fotosíntesis no tiene ningún problema por producir carbohidratos para nuestra supervivencia, ahora resulta para estos periodistas de hechos científicos que la fotosíntesis es un problema porque no produce combustibles, pero que les pasa por esas cabezas que quieren tergiversar todo.

  5. What a stupid and incorrect statement in this article. Nature has no solution to the amount of energy we use. The earth receives 173 terrawatts of energy from the sun every day and that’s 10,000x the energy we consume. Even capturing 0.5% of that would be 50x the total energy we use in a day. Fossil fields are dead, it’s just taking a while for them to die.

    • “Fossil fields [sic] are dead, it’s just taking a while for them to die.”

      That sounds more like wishful thinking than an actual fact. Although, I would agree that fossil fuels are derived from very dead organisms.

  6. What is the current efficiency of the reaction in terms of solar energy into usable (hydrocarbon) energy out?

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