Fuel cells -- a clean energy technology that generates electricity using hydrogen and air -- hold the promise of helping us dramatically reduce our dependence on oil while reducing air pollution. Yet, the high costs of fuel cell catalysts, which rely on expensive precious metals like platinum and can account for up to 50 percent of the fuel cell’s cost, have been a barrier to widespread adoption of the technology.
Now a new class of catalysts -- developed by researchers at the Energy Department’s Lawrence Berkeley and Argonne National Labs -- could make fuel cells cost-competitive with other power generators. Using nanotechnology (science at very small scales), researchers have created a nanoframe catalyst that uses roughly 85 percent less platinum and has more than 30 times the catalytic activity, making it cheaper and more efficient than conventional catalysts.
To achieve these impressive results, the research team led by Argonne’s Dr. Vojislav Stamenkovic and Berkeley Lab’s Professor Peidong Yang had to reconsider the catalyst’s entire structure. While conventional fuel cell catalysts are tiny, solid nanoparticles of pure platinum, the National Lab scientists combined platinum and nickel nanoparticles to make an alloy. When left in a solution exposed to air for two weeks, the nanoparticles reacted with oxygen, causing the nickel in the particle’s interior to dissolve. The result: Scientists created a dodecahedron nanoframe -- a three-dimensional 12-sided hollow structure a thousand times smaller in diameter than a human hair.
The research team then took the nanoframes a few steps further -- applying heat to form a thin topmost skin of platinum atoms over the remaining nickel and encapsulating an ionic liquid in the nanoframe to allow more oxygen to access the platinum atoms during the fuel cell’s electrochemical reaction. They also cut the synthesis process down to only two hours to dramatically reduce the catalyst’s manufacturing time.
In addition to lowering catalyst costs -- and thereby the overall cost of fuel cells -- the new nanoframe catalyst produces power more efficiently by extracting more electrical energy during the electrochemical reaction. This means that manufacturers could reduce the size and weight of fuel cells while achieving the same -- or better -- performance, making fuel cells even cheaper for consumers.
While still in the very early stages of research, these new catalysts hold strong promise for fuel cell vehicles -- not to mention other fuel cell applications like stationary and portable power. When tested in the lab under the harsh conditions associated with vehicle use, such as rapid acceleration, the platinum nickel nanoframes showed no decrease in activity after 10,000 cycles, demonstrating high durability and are well on the way to meeting the Department’s targets of 30,000 cycles. As the next step, Argonne scientists are scaling up the catalyst production for testing in a fuel cell to understand how the nanoframe catalyst will work in practical applications.
To learn more about the nanoframe catalyst finding, visit Argonne’s website.