Pure-Platinum is out, Iron-Platinum is in

The cost and rapid rate of deterioration of pure-platinum catalysts has stalled the advancement of fuel-cell technology until now. Brown University chemists and authors in the Journal of American Chemical Society have found a particle that lasts longer and outperforms any commercially available pure-platinum catalyst. 

Chemists at Brown University have replaced pure-platinum catalysts with a nanoparticle consisting of a five-nanometer palladium core and an iron-platinum shell.  This new particle uses far less platinum than the former and is much more efficient and long-lasting as far as the cathode end of fuel-cell reactions go. 

At the fuel cell's cathode of this new nanoparticle, a chemistry known as oxygen reduction reaction occurs creating water as it's waste instead of carbon dioxide produced by internal combustion systems. Since the cathode is where 40 percent of a fuel cell's efficiency is depleted, this is a critical act that could help fuel-cell's become more competitive with batteries and internal combustion engines.

Lab tests show that the palladium core/iron-platinum shell nanoparticles "generated 12 times more current than commercially available pure-platinum catalysts at the same weight." In addition, the output lasted 10,000 cycles, which is 10 times longer than commercially available pure-platinum models that begin to break down after 1,000 cycles. 

According to Vismadeb Mazumder, a Brown University graduate student and co-author, the idea was to mold a shell so that it would keep its shape while requiring the least amount of platinum to make an efficient reaction. The iron-platinum shell was made by decomposing iron pentacarbonyl and reducing platinum acetylacetonate, which resulted in a shell that is only 30 percent platinum. In the future, these chemists expect to be able to make thinner shells with even less platinum. 

Currently, Mazumder and fellow co-author Shouheng Sun, professor of chemistry at Brown, are working to find why the catalytic abilities of the iron-platinum shell are increased by the palladium core. They think the transfer of electrons between the core and shell metals might be the cause, and both chemists are trying to use a more chemically active metal than palladium as the core to "confirm the transfer of of electrons in the core-shell arrangement. and its importance to the catalysts function." In addition, they created iron-platinum shells varying from one to three nanometers in width, with one-nanometer functioning the best.

"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," said Mazumder. "The next step is to scale them up for commercial use, and we are confident we'll be able to do that."

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