STM studies on model systems relevant for catalysis
Flemming Besenbacher
Institute of Physics and Astronomy and Center for Atomic-scale Materials Physics,
University of Aarhus, DK-8000 Aarhus C, Denmark
Scanning tunnelling microscopy (STM) has proven to be a fascinating and powerful
technique in the field of surface science. The fact that sets STM apart from most other
surface sensitive techniques is its ability to resolve single atoms and molecules on
surfaces and furthermore to reveal the dynamics of surface processes by recording
many sequential STM images with a fast-scanning, variable-temperature STM [1,2].
In this talk, I will show how STM can be used to give unprecedented new insight into
model systems relevant for catalysis. I will show how STM studies have led to new
insight in the morphology and edge structures of MoS2 nano-clusters [3], and how
promotor atoms like Co perturb the morphology of the MoS2 nano-clusters [4]. These
systems are of interest as model systems for hydrodesulfurization catalysts. I will
show how STM studies have lead to the design of new alloy catalysts for the steam
reforming reaction [5]. Finally I will present recent results for the atomic-scale
structural response of a Cu (110) surface to ambient H2 gas at pressures ranging from
10–13 to 1 bar using a novel high-pressure STM [6]. From atom-resolved images we
conclude that the surface responds identically to hydrogen at UHV and at atmospheric
pressures, and thus the results provide strong support for the surface science approach
to heterogeneous catalysis.
1. F. Besenbacher, Scanning Tunneling Microscopy studies of metal surfaces,
Reports on Progress in Physics 59 (1996) 1737
2. S. Horch, H.T. Lorensen, S. Helveg, E. Lægsgaard, I. Stensgaard, K.W. Jacobsen,
J.K. Nørskov and F. Besenbacher, Enhancement of surface self-diffusion of
platinum atoms by adsorbed hydrogen, Nature 398 (1999) 134
.
3. S. Helveg, J.V. Lauritsen, E.Lægsgaard, I. Stensgaard, J.K.Nørskov, B.S. Clausen,
H. Topsøe and F. Besenbacher, The atomic-scale structure of single-layer MoS2
nano-clusters, Phys. Rev. Lett. 84 (2000) 951
4. J. V. Lauritsen, S. Helveg, E.Lægsgaard, I. Stensgaard, B.S. Clausen, H. Topsøe
and F. Besenbacher, The nanostructure of CoMoS, Journal of Catalysis, Priority
Communication 197, 1 (2001
5. F. Besenbacher, I. Chorkendorff, B.S. Clausen, B. Hammer, A. Molenbroek, J.K.
Nørskov and I. Stensgaard, Design of a surface alloy catalyst for steam reforming,
Science 279 (1998) 1913
6. L. Österlund, P.B. Rasmussen, P. Thostrup, E. Lægsgaard, I Stensgaard and F.
Besenbacher, Bridging the pressure gap in Surface Science at the Atomic level,
submitted