Intelligent Energy

Graphene supes up supercapacitors

Graphene supes up supercapacitors

Posting in Design

Graphene, that one-atom-thick wonder, adds ultracapacitors to its list of potential beneficiaries. Researchers from the University of Texas report giving the devices' energy storage a boost.

Graphene has been popping up as an electrode in supercapacitor designs to help them charge quicker and store more energy. Actually the much-celebrated carbon sheet is more curving around than "popping up" in this latest case.

This ultra-thin, highly conductive material has piqued the electronics industry's interest for many reasons, including its potential to prevent devices from overheating. Within supercapacitors (or ultracapacitors), graphene has shown promise for power storage as well. Publishing yesterday in Science, engineers from the University of Texas created a new activated carbon material that could enhance a supercapacitor's holding capacity.

The researchers applied potassium hydroxide to graphene to make the single-atom-thick sheets more porous, similar to a sponge. With pores ranging from just around 1 to 5 nanometers thick, the material has a surface area up to 3,100 square meters per gram. Just a gram of the activated graphene, say the researchers, could stretch from a football field's end zone to its 50-yard line. For a supercapacitor, this increased surface area allows the electrode material to hold more energy.

And the ability to store more energy is just what supercapacitors need.

While great for quick energy fixes and frequent re-charges, they hold just a fraction of the energy batteries can. Batteries release their charge slow and steady over the long haul. But a supercapacitor able to store as much as a battery, take in and release its charge swiftly, and endure being re-charged thousands of times over? This would be very useful. Electric vehicles could benefit, as well as grids needing to regulate varying power influxes from solar and wind farms.

Last fall, another group of researchers reported in Science a design for a different type of graphene-based supercapacitor. This one could fully charge in fewer than 200 milliseconds.

Rodney Ruoff, professor of materials science and mechanical engineering at the University of Texas says in a statement:

This new material combines the attributes of both electrical storage systems...

Being so easily manufactured from one of the most abundant elements in the universe, [it] will have a broad range of impacts on research and technology in both energy storage and energy conversion.

But before the Texan researchers could be sure of what they created, they needed a closer look. Powerful electron microscopes at the Brookhaven National Laboratory in New York helped them do so. Zooming in on the material's atomic structure (above right), the scientists could see the novel 3-dimensional material consisted of curved walls just one atom thick.

Study co-auther Eric Stach of Brookhaven says in a statement:

We’re still working with Ruoff and his team to pull together a complete description of the material structure. We’re also adding computational studies to help us understand how this three-dimensional network forms, so that we can potentially tailor the pore sizes to be optimal for specific applications, including capacitive storage, catalysis, and fuel cells.

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Images: BNL and University of Texas

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Melissa Mahony

Contributing Editor

Contributing Editor Melissa Mahony has written for Scientific American Mind, Audubon Magazine, Plenty Magazine and LiveScience. Formerly, she was an editor at Wildlife Conservation magazine. She holds degrees from Boston College and New York University's Science, Health, and Environmental Reporting Program. She is based in New York. Follow her on Twitter. Disclosure