New carbon capture tech could remove 99% of CO2 from air

Researchers at the University of Delaware claim to have developed a fuel cell utilising carbon capture and storage (CCS) tech that could remove as much as 99% of nearby CO2 from the air.

The electrochemical process, which is powered by hydrogen, could stand to bring more sustainable fuel cells - for use in products such as green engine cars or low-carbon flying - to the market far faster.

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The research team initially published their findings in the Nature Energy Journal on February 3 and could represent a major breakthrough for the efficacy of CCS technology - representing over 15 years of work.

Fuel cells work by converting fuel chemical energy directly into electricity and have been proposed as an alternative fuel as the world attempts to shift away from fossil fuels. Most modern concepts revolve around hydrogen fuel cells, but other chemicals such as ammonia have been suggested.

More specifically, the type used in the research were hydroxide exchange membrane (HEM) fuel cells, a greener alternative to the traditional acid-based fuel cells used today.

While powered by hydrogen, they are different to hydrogen-based fuel cells, of which the only byproduct is water.

The authors claim that HEM cells are extremely sensitive to carbon dioxide in the air, which is one major reason why they have been kept off the road. To put it simply, the CO2 stops the fuel cell from "breathing", reducing efficacy by as much as 20%.

However, a breakthrough was made a few years ago, where the team decided this weakness - a need for carbon capture - could be turned into a strength of the fuel cell.

“Once we dug into the mechanism, we realized 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,” said Brian Setzler, assistant professor for research in chemical and biomolecular engineering and paper co-author.

As stated, capturing carbon dioxide would not be great for the fuel cell, and so the process would need to be in a separate module from the main cell. Once conceptualised, the team managed to integrate this "self-purging" feature in a separate device upstream from the chemical conversion.

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The spiral-wound module takes in hydrogen and air through two separate inlets and emits carbon dioxide and carbon dioxide-free air after passing through two large-area, catalyst-coated shorted membranes.

The head of the research team Professor Yushan Yan, claims as much as 99% of the CO2 in the air surrounding the cell could be captured in a single pass should it be configured correctly. In order to achieve this, they effectively short-circuited the electrochemical process of the CCS module.

"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", said the report's lead author and doctoral candidate, Lin Shi.

Once complete, the team had a module that looked like any other electrochemical filtration membrane made for separating out gases, but the ability to capture latent carbon dioxide in the air around the cell. More specifically, it can capture this much CO2 should it be circulating at a rate of roughly 2 litres per minute - however, larger modules with higher capacities are currently being tested.

For example, an early prototype spiral device about the size of a 12-ounce tin can is capable of filtering roughly 10 litres of air per minute and scrubbing out 98% of the carbon dioxide, according to early trials.

Scaled for an automotive application, the device would be roughly the size of a gallon of milk, Setzer said, but the device could be used to remove carbon dioxide elsewhere, too. He claims it could see use in submarines or for spacecraft should it translate well to far larger modules.

“We have some ideas for a long-term roadmap that can really help us get there", he concluded.

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Shi added that as the hydrogen economy developed, and as alternative forms such as green and blue hydrogen become more prevalent - and, more importantly, cheaper - this unique CCS tech could see use in the aviation sector or for use in clean air filtration in buildings.

As of right now, the tech remains early in development but could represent a significant milestone on the road to having more portable forms of CCS technology as the energy transition and electrification on industry march to the forefront of technological developments.

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