April 29, 2014

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.

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