New nanoparticle speeds reactions

By
Tuesday, March 31, 2009

Fuel cells, devices that convert chemical energy to electrical energy, now have their own Red Bull: palladium.

Professor of Chemistry Shouheng Sun and Vismadeb Mazumder GS have created palladium nanoparticles – a new catalyst that give fuel cells the boost needed to start chemical reactions.

Before this breakthrough, most fuel cells used platinum as the catalyst driving chemical reactions forward. The new palladium nanoparticle offers a more effective alternative to the expensive platinum surfaces.

“Palladium nanoparticle catalyst is an exciting and the most promising non-platinum catalyst for fuel cell reactions,” Sun wrote in an e-mail to The Herald, adding that “for future fuel cell applications, highly active and stable” catalysts are crucial.

Palladium-catalyst fuel cells are an alternate source of energy that could be used to power laptop computers and cell phone batteries in the future, Mazumder said, adding that his and Sun’s goal was to make chemical energy production more efficient.

The palladium nanoparticles last four times longer than other “commercially available catalysts” ­- such as platinum – and require half the amount of energy to catalyze, Mazumder said.

Palladium is “twice as active and four times as stable,” he added.

By using a binding material called ligands, Sun and Mazumder were able to keep the particles separate, increasing their surface area by 40 percent and creating more space for the reaction to occur.

In previous experiments, the removal of ligands had caused particles to lose rigidity and group together, slowing the reactions.

The ligands Sun and Mazumder used “can easily be removed” using a “mild chemical wash” that does not alter the basic chemical structure of the particles, making the chemical reactions more efficient, Mazumder said.

But while palladium is cheaper than platinum and other industrial catalysts, it is still expensive – costing about $200 an ounce, Mazumder said.

Both scientists will continue researching new ways to make fuel cell devices more efficient and allow them to be “commercialized in the future.”

“The main goal is to find a cheaper alternative” to palladium, Mazumder said. “The challenge is to make affordable energy applications so that everyone can use them.”

In his e-mail, Sun wrote that their achievement demonstrates that “palladium nanoparticle catalyst can be improved with good activity and stability for practical applications.”

“This is just the tip of the iceberg,” Mazumder said.

The scientists’ discovery was published in the online edition of the Journal of the American Chemical Society earlier this month.