Carbon capture device could pave way for eco-friendly fuel cells
Image credit: Dreamstime
Engineers in the US have demonstrated a way to effectively capture 99 per cent of carbon dioxide from the air using a novel electrochemical system powered by hydrogen.
According to its developers at the University of Delaware, the “game-changing” technology is a significant advance for carbon dioxide capture and could bring more environmentally friendly fuel cells closer to market.
Professor Yushan Yan, chair of chemical and biomolecular engineering, has been working for some time to improve hydroxide exchange membrane (HEM) fuel cells, an economical and environmentally friendly alternative to traditional acid-based fuel cells used today.
But the reason HEM fuels cells aren’t on the road as of late is because they are sensitive to carbon dioxide in the air. This defect quickly reduces the fuel cell’s performance and efficiency by up to 20 per cent, rendering the fuel cell no better than a petrol engine.
A few years back, the researchers found this disadvantage might be a solution – for carbon dioxide removal.
Image credit: Graphic illustration by Jeffrey C Chase
“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 great at separating it to the other side,” said Brian Setzler, assistant professor for research in chemical and biomolecular engineering.
While this isn’t ideal for the fuel cell, the team knew if they could leverage this built-in “self-purging” process in a separate device upstream from the fuel cell stack, they could turn it into a carbon dioxide separator.
“It turns out our approach is very effective. We can capture 99 per cent of the carbon dioxide out of the air in one pass if we have the right design and right configuration,” Yan explained.
For this, they embedded the power source for the electrochemical technology inside the separation membrane. The approach involved internally short-circuiting the device.
The UD research team’s spiral wound module takes in hydrogen and air through two separate inlets (shown on the left) and emits carbon dioxide and carbon dioxide-free air (shown on the right) after passing through two large-area, catalyst-coated shorted membranes. The inset image on the right shows, in part, how the molecules move within the short-circuited membrane.
Image credit: Yan lab/University of Delaware
“We controlled this short-circuited fuel cell by hydrogen. And by using this internal electrically shorted membrane, we could get rid of the bulky components, such as bipolar plates, current collectors or any electrical wires typically found in a fuel cell stack,” said Lin Shi, a doctoral candidate in the Yan group.
The research team’s results showed that an electrochemical cell measuring 2 inches by 2 inches (5cm x 5cm) could continuously remove about 99 per cent of the carbon dioxide found in the air flowing at a rate of approximately two litres per minute.
An early prototype spiral device about the size of a small fizzy drink can is able to filter 10 litres of air per minute, scrubbing out 98 per cent of the carbon dioxide, the researchers said.
Scaled for an automotive application, the device would be roughly the size of a gallon of milk [four litres], Setzer said, but the device could remove carbon dioxide elsewhere, too. For example, the UD-patented technology could enable lighter, more efficient carbon dioxide removal devices in spacecraft or submarines, where ongoing filtration is critical.
According to Shi, since the electrochemical system is powered by hydrogen, as the hydrogen economy develops, this electrochemical device could also be used in aeroplanes and buildings where air recirculation is desired as an energy-saving measure.
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