Splitting Water 2.0

Hydrogen’s promise as a fuel has researchers around the world focused on cheaper, cleaner ways to produce the stuff. One time-honored approach, splitting water into its constituent elements, typically requires either electricity or heat.

Now scientists at Penn State and the Virginia Commonwealth University have found a way to generate hydrogen at room temperature, by exposing selected clusters of aluminum atoms to water. The key, they say, is in the geometries of these clusters, which play a previously unknown role in determining whether they will react with water molecules.

"Our previous research suggested that electronic properties govern everything about these aluminum clusters,” explains A. Welford Castleman Jr., Eberly Family Distinguished Chair in Science and Evan Pugh Professor of chemistry and physics at Penn State. “But this new study shows that it is the arrangement of atoms within the clusters that allows them to split water."

The research team, which also includes Penn State graduate students Patrick Roach and Hunter Woodward and Virginia Commonwealth professor of physics Shiv Khanna and postdoctoral associate Arthur Reber, created individual aluminum clusters by vaporizing aluminum with a laser, then allowing the vapor to cool. They then exposed the clusters to water in a custom-designed flow-reactor, and found that they reacted differently depending on their sizes and their unique geometric structures. Three of the clusters produced hydrogen from water at room temperature, they report.

"Traditional techniques generally require a lot of energy at the time the hydrogen is generated,” Khanna notes. “But our method allows us to produce hydrogen without supplying heat, connecting to a battery, or adding electricity." He hopes to look next at the possibilities of recycling clusters for repeated use and of controlling how they release the hydrogen they produce.

"Generally, this knowledge might allow us to design new nanoscale catalysts by changing the arrangements of atoms in a cluster,” says Castleman. “The results could open up a new area of research, not only related to splitting water, but also to breaking the bonds of other molecules as well."

A. Welford Castleman Jr., Ph.D., is Eberly Family Distinguished Chair in Science and Evan Pugh professor of chemistry and physics at Penn State; awc@psu.edu. Shiv N. Khanna, Ph.D., is professor of physics at Virginia Commonwealth University; Snkhanna@vcu.edu. The team's findings appeared in the 23 January 2009 issue of the journal Science. Their research was supported by the Air Force Office of Scientific Research.

Last Updated June 01, 2009