Taylor and Schroers engineered nanowires out of a novel material called bulk metallic glass in order to make fuel cell catalyst systems more durable and efficient. Credit: Golden Kumar and Miriam Schroers |
Fuel cells have been touted as a cleaner solution
to tomorrow’s energy needs, with potential applications in everything from cars
to computers.
But one reason fuel cells aren’t already more
widespread is their lack of endurance. Over time, the catalysts used even in
today’s state-of-the-art fuels cells break down, inhibiting the chemical
reaction that converts fuel into electricity. In addition, current technology
relies on small particles coated with the catalyst; however, the particles’
limited surface area means only a fraction of the catalyst is available at any
given time.
Now a team of engineers at the Yale School
of Engineering & Applied Science has created a new fuel cell catalyst
system using nanowires made of a novel material that boosts long-term
performance by 2.4 times compared to today’s technology. Their findings appear in ACS Nano.
Yale engineers Jan Schroers and André Taylor have
developed miniscule nanowires made of an innovative metal alloy known as a bulk
metallic glass (BMG) that have high surface areas, thereby exposing more of the
catalyst. They also maintain their activity longer than traditional fuel cell
catalyst systems.
Current fuel cell technology uses carbon black, an
inexpensive and electrically conductive carbon material, as a support for
platinum particles. The carbon 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 is porous, so the platinum inside the inner pores may not be exposed.
Carbon black also tends to corrode over time.
“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,” Taylor
said.
At 13 nm in scale, the BMG nanowires that Schroers
and Taylor developed 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 Yale team incorporated 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, said Schroers, who has developed other BMG alloys that can also be blow
molded into complicated shapes. The BMG nanowires also conduct electricity
better than carbon black and carbon nanotubes, and are less expensive to
process.
So far Taylor has tested their catalyst system for
alcohol-based fuel cells (including those that use ethanol and methanol as fuel
sources), but they say the system could be used in other types of fuel cells
and could one day be used in portable electronic devices such as laptop
computers and cell phones as well as in remote sensors.
“This is the introduction of a new class of
materials that can be used as electrocatalysts,” Taylor said. “It’s a real step toward
making fuel cells commercially viable and, ultimately, supplementing or
replacing batteries in electronic devices.”
Other authors of the paper include Marcelo Carmo,
Ryan C. Sekol, Shiyan Ding, and Golden Kumar (all of Yale Univ.).
