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A new system powered by hydrogen can capture 99% of carbon dioxide (CO2) from air, according to scientists.
Researchers at University of Delaware said the breakthrough, in a device the size of a soft drink can, could be a "significant advance" for CO2 capture.
It could also lead to more efficient fuel cells for use in cars.
Carbon capture and storage (CCS) is one of the new technologies that scientists hope will play an important role in tackling the climate crisis.
It involves the capture of CO2 from the burning of fossil fuels in power generation, which is then stored underground.
The Delaware research team, led by Professor Yushan Yan, reported its method in Nature Energy.
Fuel cells work by converting fuel chemical energy directly into electricity and are used in hybrid or zero-emission vehicles.
Yan and Henry Belin du Pont, chair of chemical and biomolecular engineering at University of Delaware, have been working for some time to improve hydroxide exchange membrane (HEM) fuel cells, an economical and environmentally-friendly alternative to the traditional acid-based fuel cells used today.
But HEM fuel cells are extremely sensitive to carbon dioxide in the air, with the CO2 making it hard for a HEM fuel cell to breathe.
Yan's research group has been searching for a workaround to this CO2 conundrum for over 15 years.
A few years back, the researchers realised this disadvantage might actually be a solution – for carbon dioxide removal.
Co-author Brian Setzler, assistant professor for research in chemical and biomolecular engineering, said: "Once we dug into the mechanism, we realised the fuel cells were capturing just about every bit of carbon dioxide that came into them, and they were really good at separating it to the other side."
While this isn't good for the fuel cell, the team knew if they could leverage this built-in "self-purging" process in a separate device, they could turn it into a CO2 separator.
Yan said: "It turns out our approach is very effective. We can capture 99% of the carbon dioxide out of the air in one pass if we have the right design and right configuration."
The researchers found a way to embed the power source for the electrochemical technology inside the separation membrane.
Lead author Lin Shi, a doctoral candidate, said: "It's risky, but we managed to control this short-circuited fuel cell by hydrogen. And by using this internal electrically shorted membrane, we were able to get rid of the bulky components, such as bipolar plates, current collectors or any electrical wires typically found in a fuel cell stack."
Their results showed that an electrochemical cell measuring two inches by two inches could continuously remove about 99% of the CO2 found in air flowing at a rate of approximately two litres per minute.
An early prototype spiral device about the size of a soft drink can is capable of filtering 10 litres of air per minute and scrubbing out 98% of the carbon dioxide, the researchers said.
Scaled for an automotive application, the device would be roughly the size of a 4.5 litre bottle of milk, Setzler said, but the device could be used to remove CO2 elsewhere, too.
For example, the University of Delaware-patented technology could enable lighter, more efficient carbon dioxide removal devices in spacecraft or submarines, where ongoing filtration is critical.
"We have some ideas for a long-term roadmap that can really help us get there," said Setzler.
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