Paper SS1-TuM5
An Atomic-scale View of Metal Alloy Surface Chemistry

Tuesday, October 19, 2010, 9:20 am, Room Picuris

Palladium and its alloys play a central role in a wide variety of industrially important applications such as hydrogen reactions, separations, storage devices, and fuel cell components. The exact mechanisms by which many of these processes operate have yet to be discovered. Low-temperature scanning tunneling microscopy (STM) has been used to investigate the atomic-scale structure of Pd/Au and Pd/Cu bimetallics created by depositing Pd on both Au(111) and Cu(111) at a variety of surface temperatures. We demonstrate that individual isolated Pd atoms in an inert Cu matrix are active for the dissociation of hydrogen and subsequent spillover onto Cu sites. The same mechanism does not operate for Pd in Au(111) surfaces, however, because the spillover is thermodynamically unfavorable. These results demonstrate the powerful influence an inert substrate has on the catalytic activity of individual Pd atoms supported in its surface. In addition, differential conductance spectroscopy has enabled the electronic structure of these active sites to be measured and quantitatively compared to that of the host metal.