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Designing Better Fuel Cells, One Nanocarbon at a Time

Designing Better Fuel Cells, One Nanocarbon at a Time
Keith Stevenson

This series of images shows a nickel mesh electrode covered with carpet-like carbon nanofibers. Individual nanofibers are visible in the bottom right image. Scanning electron microscopy (SEM) images by: Stephen Maldonado.
Carbon nanotubes


The above simplified diagram shows how a proton exchange membrane (PEM) fuel cell works. Click to enlarge. Illustration by: Lee Clippard.
fuel-cell-diagram

An electrochemist finds new uses for carbon in an effort to boost the performance and efficiency of fuel cells

Fuel cells are poised to revolutionize energy production around the world. The technology could be at the epicenter of a new “hydrogen economy,” an economy where hydrogen, not oil or coal, ignites our engines and powers our homes. Fuel cells could supply us with safer, cleaner energy than the power plants and internal combustion engines used today.

But there’s much work to be done before that revolution, says Dr. Keith Stevenson, assistant professor in the Department of Chemistry and Biochemistry. He says that although fuels cells are two to three times more efficient than internal combustion engines, significant improvements must be made before the technology gains widespread use.

Stevenson is part of a core group of scientists at The University of Texas looking to increase the efficiency of fuel cells by improving the way the fuel, hydrogen and oxygen, is converted to electricity (see graphic).

“If you really want to make fuel cells feasible at a commercial level, you need to reduce oxygen to water more efficiently,” says Stevenson. “This is one of the hardest challenges.”

Oxygen and hydrogen combine to become water with the help of a catalyst, such as platinum, that is affixed to carbon electrodes. Both the catalyst and its carbon supports need improvement in order to increase fuel cell efficiency, Stevenson says. His research focuses on carbon electrodes—making them better supports for catalysts and improving their ability to conduct electricity.

Stevenson and his collaborators have recently constructed nano-sized hollow tubes made of carbon. The bamboo-like nanocarbons can be custom assembled into complex 3D shapes, and they show significant promise as carbon electrodes for fuel cells. Stevenson is now working on fine-tuning the new nanocarbon’s chemical and catalyst support properties.

To this end, Stevenson has discovered that he can make the carbon electrodes better by infusing them with other elements, like nitrogen. The nitrogen-doped nanocarbon electrodes make more active catalysts like platinum catalyze more oxygen reactions. These nanocarbons can also be tuned to catalyze the oxygen reduction reactions themselves.

It’s big findings at this small scale that will impact the commercialization of fuel cells. “There won’t be a revolutionary advance in fuel cell technology,” Stevenson says, “until we understand the basic mechanisms of these chemical processes and design better materials to make fuel cell reactions more efficient.”
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Sunday, 26 September 2021

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