AVS 53rd International Symposium
    Surface Science Tuesday Sessions
       Session SS1-TuM

Paper SS1-TuM12
Novel Gold Catalysts: UHV and Ambient Studies on Nanoporous Gold Surfaces

Tuesday, November 14, 2006, 11:40 am, Room 2002

Session: Reactivity of Metal Clusters
Presenter: M. Baeumer, University Bremen, Germany
Authors: M. Baeumer, University Bremen, Germany
T. Nowitzki, University Bremen, Germany
B. Juergens, University Bremen, Germany
C. Schulz, University Bremen, Germany
V. Zielasek, University Bremen, Germany
J. Biener, Lawrence Livermore National Laboratory
M. Biener, Lawrence Livermore National Laboratory
A.V. Hamza, Lawrence Livermore National Laboratory
Correspondent: Click to Email
While a lot of questions regarding the underlying mechanisms of gold catalysis are still under debate, it is evident that low-coordinated Au atoms play a decisive role for reactions such as the low-temperature oxidation of CO, for instance. In order to elucidate how low-coordinated Au atoms can be stabilized and in which way they interact with CO, we performed UHV model studies pursuing two different approaches. On the one hand, a Au(111) single crystal surface was sputtered by argon and oxygen ions, resulting in rough pit-and-mound structures. Annealing experiments clearly revealed that the oxygen sputtered surface exhibits a higher thermal stability, indicative of the stabilization of under-coordinated Au atoms by adsorbed oxygen. In both cases, two CO TPD desorption peaks are observed between 100 K and 200 K. For the oxygen sputtered surface also CO2 formation is detected concurrently with desorption of CO. On the other hand, Au was deposited on graphite as a weakly interacting support. Interestingly, the same TPD spectrum with 2 peaks is found in this case. Deposition under various conditions (variation of the support temperature, defect-assisted growth) reveals that both states are defect-related. In line with theoretical results, one state may be attributed to step edges, the other to even less coordinated sites. As a similar desorption behaviour was observed for other particle systems and rough single crystal surfaces, this seems to be a general feature. In addition to the UHV studies, we performed catalytic studies with a gold foam prepared by dealloying of a Ag/Au alloy. It exhibits a very similar morphology as compared to the sputtered Au(111) surface. We could demonstrate that this material has an unexpectedly high catalytic activity for CO oxidation at temperatures down to -20 °C. @FootnoteText@ Part of this work was performed under the auspices of the U.S. Dep. of Energy by Univ. of California, Lawrence Livermore National Laboratory under contract No.W-7405-Eng-48.