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August 20th, 2010

Less platinum, better efficiency for fuel cells

Published on August 20th, 2010 | By: pwray@ceramics.org

The multimetallic nanoparticle created by Brown University chemists
for fuel-cell reactions uses a palladium core and an iron-platinum shell.

Credit: Sun Lab/Brown University

According to a Brown University press release, researchers have created a unique core-and-shell nanoparticle that uses less platinum yet performs more efficiently and lasts longer than commercially available pure-platinum catalysts at the cathode end of some fuel-cells.

A redox reaction takes place at the fuel cell’s cathode, where up to 40 percent of a fuel cell’s efficiency is lost, so, “this is a crucial step in making fuel cells a more competitive technology with internal combustion engines and batteries,” says Shouheng Sun, professor of chemistry at Brown and coauthor of the study.

The research team, which includes ACerS member and Oak Ridge National Lab researcher Karren L. More, Brown graduate student Vismadeb Mazumder and other investigators from ORNL, created a five-nanometer-wide palladium core and encircled it with a one-nanometer shell consisting of iron platinum (FePt).

The trick, Mazumder says, was in molding a shell that would retain its shape and require the smallest amount of platinum to pull off an efficient reaction. The researchers found a way to create a shell that uses only 30 percent platinum, although they expect to make thinner shells and use even less platinum.

In laboratory tests, the palladium/iron-platinum nanoparticles generated 12-times more current than commercially available pure-platinum catalysts at the same catalyst weight. The output also remained consistent over 10,000 cycles, at least 10 times longer than commercially available platinum models that begin to deteriorate after 1,000 cycles.

“This is a very good demonstration that catalysts with a core and a shell can be made readily in half-gram quantities in the lab. They’re active, and they last,” Mazumder says. “The next step is to scale them up for commercial use, and we are confident we’ll be able to do that.”

According to Sun, it is uncertain if the concept of enhanced catalysis from core/shell nanoparticles can be applied to a wide range of reactions seen in fuel cells. “Different fuel cells work in different conditions. I know our core/shell particles are good under the PEMFC conditions, but they may not survive the high operating temperature used in SOFCs.”

The findings have been published in the Journal of the American Chemical Society.

 


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