Technology

Novel "artificial leaf" design ups the carbon capture rate by 100x

Novel "artificial leaf" design...
University of Illinois Chicago scientists have developed a new "artificial leaf" system to capture CO2
University of Illinois Chicago scientists have developed a new "artificial leaf" system to capture CO2
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University of Illinois Chicago scientists have developed a new "artificial leaf" system to capture CO2
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University of Illinois Chicago scientists have developed a new "artificial leaf" system to capture CO2
Diagram depicts the design of a novel "artificial leaf" device that captures carbon dioxide with great efficiency
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Diagram depicts the design of a novel "artificial leaf" device that captures carbon dioxide with great efficiency

Recreating the process of natural photosynthesis in which plants turn sunlight, water and carbon dioxide into energy is a long-pursued goal in science. Often described as an "artificial leaf," these systems could play a key role in the fight against climate change, and a team of engineers has just picked up the pace with a solution that captures carbon dioxide at 100 times the rate of current technologies.

We have looked at quite a number of artificial leaf systems over the years that use sunlight to turn water into liquid fuels and electricity. One interesting example came from engineers at the University of Illinois Chicago (UIC) in 2019. It had a unique design the creators say made it suitable for use in the real world, unlike other laboratory solutions that could only work with carbon dioxide from pressurized tanks.

The solution consisted of a standard artificial photosynthesis unit that was encased in a transparent capsule filled with water, and featured a semi-permeable outer layer. As sunlight struck the device, the water evaporated through the pores in the outer layer and carbon dioxide was drawn in to replace it, where the unit inside turned it into carbon monoxide. This CO could in turn be captured and used to make synthetic fuels.

Through some key tweaks to the design, the scientists have now taken its performance to new heights. The team used inexpensive materials to integrate an electrically charged membrane that acts as a water gradient, with both a dry and wet side. On the dry side an organic solvent attaches to the captured carbon dioxide and turns it into concentrated bicarbonate, which builds up on the membrane.

A positively charged electrode on the wet side then draws the bicarbonate across the membrane and into the watery solution, where it is converted back into carbon dioxide to make fuels or in other applications. Altering the electrical charge can speed up or slow down the rate of carbon capture, which the scientist found at its optimum could capture 3.3 millimoles per hour for each four square centimeters (0.6 sq in) of material.

Diagram depicts the design of a novel "artificial leaf" device that captures carbon dioxide with great efficiency
Diagram depicts the design of a novel "artificial leaf" device that captures carbon dioxide with great efficiency

This "flux rate" is described as very high, and more than 100 times better than existing systems. Importantly, only a negligible amount of energy was required to power the reactions, at 0.4 kilojoules per hour, less than what it takes to run a one-watt LED lightbulb. Equally impressive, the team says the system can capture carbon dioxide at a price of US$145 a ton, which is within the Department of Energy's guidelines that these technologies should cost $200 per ton or less.

“Our artificial leaf system can be deployed outside the lab, where it has the potential to play a significant role in reducing greenhouse gases in the atmosphere thanks to its high rate of carbon capture, relatively low cost and moderate energy, even when compared to the best lab-based systems,” said Meenesh Singh, assistant professor of chemical engineering in the UIC College of Engineering and corresponding author on the paper.

The device is small enough to fit in a backpack and is modular by nature, meaning multiple units can potentially be stacked on top of one another to build out devices suited for different settings.

“It’s particularly exciting that this real-world application of an electrodialysis-driven artificial leaf had a high flux with a small, modular surface area,” Singh said. “This means that it has the potential to be stackable, the modules can be added or subtracted to more perfectly fit the need and affordably used in homes and classrooms, not just among profitable industrial organizations. A small module of the size of a home humidifier can remove greater than 1 kg of CO2 per day, and four industrial electrodialysis stacks can capture greater than 300 kg of CO2 per hour from flue gas.”

The research was published in the journal Energy & Environmental Science.

Source: University of Illinois Chicago

9 comments
9 comments
Fritz
The real challenges are landfills and waste water despite solution even is profitable.
Malcolm Jacks
Novel "artificial leaf" design ups the carbon capture rate by 100x
By Nick Lavars I think this is wonderful, and hope it goes full steam ahead. I still think the combustion engine is the most efficient motor, and apart from alternative fuel to power it, maybe this Artificial leaf design can prolong it demise by making an alternative to the expensive and inefficient designe of the Catalytic Converters used today??/
Robert Kowalski
After so many years of talking about carbon capture and never capturing any noticeable amount of CO2 carbon does seem to be further out than fusion energy. Or maybe it is by design - companies emitting CO2 but promising to clean-up afterwards surely will not disappear once their gas and oil profits disappear.
Peter Forte
Carbon capture is an essential component in countering the Climate Emergency, but, what does one then do with the captured carbon? Methods of reusing or converting it in quantity are yet to be developed, and storage comes with its own problems. Yes, every bit counts, but the situation is ever more dire.
jerryd
How do you get the air CO2 into the water cost effectively? That is the problem. While some natural sources like beer, ethanol, what is needed is a system to get it from air.
Then easier electrofuel ways with just a powered catalyst and power, making HCs directly.
guzmanchinky
This is incredible, let's hope it sees the light of day (pun intended) very soon! It feels like there are billions to be made in these fields, and I hope that is motivation for many scientists to help us clean our world...
David Chorley
To filter out 1 kg of CO2 you would have to filter about 2.5 tonnes of air, which would take a huge amount of energy to filter through a machine. So there is no free lunch
2Hedz
@David Chorley close...but slight error. And you need to follow through with your calc. It's actually very doable. CO2 is 0.04% of air by volume but 0.06% by weight. Thus instead of 2500kg as you mentioned, you actually need to filter only 1667kg of air. At 1.2kg/m3 air density, that's about 1360 m3 or 48,000 ft3. Seems a lot right? But filtered in a day that's 0.94 m3/min or 33 ft3/min. That's about a twice the flow of a standard cpu fan, which only use a few watts. So this seems very practical. Really rooting for this!
GdB
Getting closer to a CO2 catalytic converter for ICE cars. If the energy cost is small then miniaturization is the remaining obstacle.