(Nanowerk News) The Sykes Research Group at Tufts University has posted a YouTube video that provides an introduction to the study of alternative energy sources and the role that nanotechnology techniques and applications play.
The researchers use ground-breaking atomic imaging techniques to view hydrogen atoms moving on a specialized surface. Palladium alloy catalysts play a central role in a wide variety of industrially important applications such as hydrogenation reactions, separations, storage devices, and fuel cell components. The scientists at the Sykes Lab have explored the structural and electronic properties of both palladium/copper and palladium/gold alloys.
State-of-the-art imaging capabilities have allowed the group to determine the atomic composition and hydrogen dissociation activity of these important alloys.
Alloy Catalysts for a Cleaner Future
Low-temperature STM and spectroscopy is being used to investigate the atomic-scale structure of Pd/Au and Pd/Cu near-surface alloys, created by depositing Pd on both Au(111) and Cu(111) at a variety of temperatures.[1, 2] The choice of supporting metal allowed the study of Pd particles as a function of size; from individual atoms to islands ~8 nm in diameter.
The group's work has revealed that the electronic structure of isolated Pd atoms in both Au and Cu hosts is very different from bulk Pd.
This data is the first to show how the electron density in alloys varies locally at the nanoscale, as other techniques average across the whole surface. The results allow to differentiate geometric effects (how the atoms are rearranged) from ligand effects (how the electron density is distributed) and thus further the understanding about how alloys operate as such good catalysts and separation membranes.[1, 2]
The group is currently studying the uptake of hydrogen on these alloys. By varying the surface composition of Pd they are able to isolate the best species for hydrogen dissociation. Understanding the atomic nature of these catalytically active sites will allow the design of better alloys for hydrogen related applications.
While experiments performed on their low-temperature STM provide great insight into many chemical systems, the operating conditions are not necessarily practical for “real world” applications. For this reason the scientists perform parallel experiments on an electrochemical STM (EC-STM) that operates in an ambient environment (i.e. room temp. and 1 atm.).
1. Tierney, H. L.; Baber, A. E.; Sykes, E. C. H. Atomic-Scale Electronic Structure of Catalytic Sites on Pd/Cu Near Surface Alloys. In preparation2008.
2. Baber, A. E.; Tierney, H. L.; Sykes, E. C. H. Composition and Electronic Properties of Catalytically Important Pd/Au Alloys. In preparation2008.
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