AVS 45th International Symposium
    Surface Science Division Thursday Sessions
       Session SS2-ThA

Paper SS2-ThA2
Interaction and Growth of Rh on Hydroxylated Alumina Model Substrates

Thursday, November 5, 1998, 2:20 pm, Room 309

Session: Oxide Growth and Structure
Presenter: J. Libuda, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany
Authors: J. Libuda, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany
S. Stempel, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany
M. Heemeier, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany
M. Frank, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany
A. Sandell, Lund University, Sweden
S. Andersson, Uppsala University, Sweden
P.A. Brühwiler, Uppsala University, Sweden
N. M@ao@rtensson, Uppsala University, Sweden
M. Bäumer, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany
H.-J. Freund, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Germany
Correspondent: Click to Email
In contrast to simple model surfaces, alumina supports employed in technical catalysis exhibit a variety of complex surface structures. In particular, depending on preparation, their surface can be covered to a large extend by hydroxyl groups, affecting the chemical behaviour not only with respect to adsorption of gases but also the interaction with the catalytically active metal component. In order to study the dependence of metal growth and metal oxide interaction on the surface properties of an alumina support, we have established a hydroxylation procedure based on Al deposition and subsequent water exposure, which is applied to a well ordered Al@sub 2@O@sub 3@ film grown on NiAl(110). The hydroxylated surface is characterized with respect to morphologic (Scanning Tunneling Microscopy (STM) and Spot-Profile Analysis-LEED (SPA-LEED)) and electronic properties (High Resolution Photoelectron Spectroscopy (PES)). Upon Al deposition, uniformly distributed small metallic aggregates are formed, which can be transformed to larger two-dimensional patches and three-dimensional islands by annealing. The small aggregates can be completely oxidized by water exposure. Following this treatment, characteristic features in the Al 2p and O 1s regions are observed. The growth of Rh on the modified surface has been investigated by STM and SPA-LEED and compared to previous results for the non-modified alumina support. In contrast to the non-modified support, no decoration of characteristic one-dimensional oxide defect structures is found. Instead, the formation of a high density layer of uniformly distributed aggregates is observed. The dissappearance of the characteristic O 1s and Al 2p features upon metal exposure points to a direct chemical interaction between the surface hydroxyl groups and the Rh deposided.