Diagram of oxygen reduction reaction using an icosahedral (20-faced) nanoparticle structure catalyst of palladium and platinum. Image courtesy of Manos Mavrikakis, professor of chemical and biological engineering at the University of Wisconsin-Madison.
However, researchers have discovered that using icosahedral (20-faced) nanoparticle structures for palladium/platinum catalysts reduces the cost and increases catalytic activity.
Currently, palladium is used as a cheaper alternative to platinum for catalytic functions such as car muffler systems.
What sets this new catalyst apart, however, is this new atomic arrangement. Additionally, the amount of platinum used in the palladium/platinum catalysts surface is kept to a minimum. None the less, researchers found that smaller amounts of the new catalyst were able to improve the catalytic activity in comparison to platinum and palladium alone.
"This is speaking to the precise arrangement of atoms on the surface of a nanoparticle," says Manos Mavrikakis, professor of chemical and biological engineering at the University of Wisconsin-Madison (UW-Madison). "That can make an enormous difference in how fast the reaction takes place. Theory has been instrumental for about 10 years now to demonstrate the importance of being able to tailor-make specific facets of the same material."
He added, "The goal here is to try to minimize the amount of platinum that you use, and eventually find a complete replacement of platinum. If we can move away from platinum, many of these applications have the potential to become more robust financially."
The current catalytic set-up used to test the palladium/platinum material is an oxygen reduction reaction typically seen in fuel cells. However, the research offers chemical engineers suggestions on how to design custom catalysts, on the atomic scale, for various applications using nanoparticles and quantum mechanics.
Researchers from the Georgia Institute of Technology first discovered the potential of the catalysts when working with palladium/platinum nanoparticles that were affixed onto a surface. The researchers were able to prove that the catalyst was outperforming pure platinum by dividing the current produced by the redox reaction with the amount of platinum used in the surface.
The Georgia Tech researchers then teamed up with UW-Madison to determine the cause of the discovery. Graduate student Luke Roling of UW-Madison noted the counter-intuitiveness of a catalyst using less platinum that was performing more efficiently than pure platinum.
This UW-Madison team discovered that the improved catalytic activity is due to the icosahedral structure of the nanoparticles. Therefore, it appears as if the improved surface area of the particles improves the overall ability of the catalyst. The researchers are looking into other structures and catalysts that can be improved using this technology.
In all catalytic converters the most expensive material is the catalyst itself. Reducing the costs of the catalyst while improving the catalytic ability on a per mass basis could prove very lucrative. Additionally, many of the catalytic elements are rare and create a dependence on these metals similar to our dependence on our energy reserves. As such, improved catalysts such as this nano-based palladium/platinum catalysts could help to make industry more resource and energy efficient.