Nanowires make fuel cells go and go

YALE (US) — Nanowires coated in an innovative alloy boost the long-term performance of fuel cells by 2.4 times and could be used in laptops, cell phones, and remote sensors.

Fuel cells have long been touted as a cleaner solution to future energy needs, but the reason they aren’t already more widespread is their lack of endurance.

Over time, the catalysts used in state-of-the-art fuels cells break down, inhibiting the chemical reaction that converts fuel into electricity. Current technology relies on small particles coated with the catalyst, but the particles’ limited surface area means only a fraction of the catalyst is available at any given time.

Engineers at Yale University developed miniscule nanowires made of bulk metallic glass (BMG) that have high surface areas, thereby exposing more of the catalyst.

The research is reported in the journal ACS Nano.

Current fuel cell technology uses carbon black, an inexpensive and electrically conductive carbon material, as a support for platinum particles that transports electricity, while the platinum is the catalyst that drives the production of electricity.

The more platinum particles the fuel is exposed to, the more electricity is produced. Yet carbon black tends to corrode over time and is porous, so the platinum inside the inner pores may not be exposed.

“In order to produce more efficient fuel cells, you want to increase the active surface area of the catalyst, and you want your catalyst to last,” says Andre Taylor, assistant professor of chemical and environmental engineering.

At 13 nanometers in scale (about 1/10,000 the width of a human hair), the BMG nanowires developed by Taylor and colleague Jan Schroers, associate professor of mechanical engineering and materials science, are about three times smaller than carbon black particles.

The nanowires’ long, thin shape gives them much more active surface area per mass compared to carbon black.

In addition, rather than sticking platinum particles onto a support material, the new technology incorporates the platinum into the nanowire alloy itself, ensuring that it continues to react with the fuel over time.

It’s the nanowires’ unique chemical composition that makes it possible to shape them into such small rods using a hot-press method, says Schroers, who has developed other BMG alloys that can also be blow molded into complicated shapes.

To date the catalyst system has been tested for alcohol-based fuel cells (including those that use ethanol and methanol as fuel sources), but has potential for use in other types of fuel cells.

“This is the introduction of a new class of materials that can be used as electrocatalysts,” Taylor says.

“It’s a real step toward making fuel cells commercially viable and, ultimately, supplementing or replacing batteries in electronic devices.”

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