“Ship in a bottle” method improves catalysts

Wenyu Huang
Wenyu Huang

A new method of preparing catalysts may improve medical MRI imaging and fuel cells for electric cars.

Wenyu Huang, an assistant professor in the Department of Chemistry, has designed a new strategy called “ship in a bottle” to use nanometer-sized particles as catalysts that cost less, last longer, and make reactions happen even faster.

Catalysts, substances that help chemical reactions happen faster and with less energy input, are used at a certain stage in the production of nearly ninety percent of industrially produced chemicals, said Huang.

The surface atoms of catalysts act as sites where chemical reactions happen quickly and easily. Because the interaction happens only on the surface, the interior atoms of a catalyst material cannot be used. In order to maximize the surface atoms so that as much catalyst material as possible can be used, Huang works to make catalysts nanoparticle-sized — so small that dramatically high percentages of atoms are on the exterior surface, acting as catalytic active sites.

Huang creates these nanoparticle heterogeneous catalysts out of intermetallic compounds: special alloys made up of more than one metal atom. Combining metals forms an alloy, in which metal atoms are typically combined in a random order. In contrast, the combined metal atoms arrange in an ordered manner in these intermetallic alloys, making them especially useful as catalysts because of their predictable surface for molecules to interact on.

However, a heating process is generally required to form these ordered alloy catalysts, which causes the particles to aggregate together, reducing surface area. In order to form the catalyst with an intermetallic structure that remains nanoparticle-sized, Huang and his colleagues came up with a "ship in a bottle" approach.

"We designed a strategy called ‘ship in a bottle’ strategy," Huang said. "You have to protect these nanoparticles, and this protection has to be able to sustain very high temperatures, so we use quartz, or silica, glass shell on the surface."

By encapsulating the intermetallic nanoparticles in quartz, which can withstand the high temperatures, the nanoparticles remain small and separate. The quartz is also porous, allowing the reactants to still access the catalyst.

Now this approach is helping improve multiple catalysts, from platinum-tin used to enhance the sensitivity of MRI imaging to platinum-zinc used in fuel cells. These works were recently published in Journal of the American Chemical Society and Angewandte Chemie International Edition, two prestigious journals in chemistry.