"Catalysis from First Principles"
The objective of the meeting (held in Lyon at CECAM, from July 5 to 8, 2000) was to review the status of total-energy calculations as a basis for modelling and understanding of chemical reactions on solid surfaces. A strong focus was placed on the prospects of calculational methods becoming a tool in the design of new catalysts. An additional objective was to bring together researchers from the electronic structure and molecular-dynamics communities as well experimental surface-science and catalysis researchers from academia and industry.
The format of the workshop was a small meeting (about 40 participants), in the approximate ratio theory/experiment/industry=2/1/1. There were review talks, short presentations and ample time for discussion including short (one overhead) contributions on specific topics. Also a poster session was organized.
The meeting's web page http://www.fhi-berlin.mpg.de/th/Meetings/Lyon2000/Lyon-1.html
provides the possibility to download the workshop program, abstracts of talks and posters, and a list of participants (with full addresses).
I like to thank again the host institute, to be specific, Michel Maxeschal and Emmanuelle Crespeau at CECAM for their competent, efficient, and friendly help. I personally enjoyed the meeting and felt that it was successful.
The following report was written by Dr. Anne Chaka (The Lubrizol Corporation) and Dr. Alexander Bogicevic (Ford) and summarizes their personal impression.
Berlin-Dahlem, September 11, 2000 Matthias Scheffler
Personal notes from participants:
The discussion meeting on "Catalysis from First Principles", held in Lyon, France, was founded on contributions from 46 participating scientists from 12 different countries worldwide. A healthy division between theorists and experimentalists from both academia and industry formed a very fertile ground for information exchange and intense, yet cordial, discussions and debates. The wide range of approaches and methodologies was impressive, including atomistic design to purely empirical combinatorial and parallel approaches. All came with a common goal in mind: to improve on existing technologies and pave the road for the development of the next generation of catalysts.
This type of broad, inclusive meeting on a focused topic combines many of the best features of both large-scale conferences and smaller, more specialized workshops. It achieves several noteworthy goals:
(i) Bringing together researchers from around the world and putting them in a close environment for dynamic scientific exchange.
(ii) Allowing for critical comparisons to be made between similar methodologies, so that one can return with a sense of the quality of one's own research.
(iii) Mixing people from quite different backgrounds, i.e. industry and academia, experiment and theory, and serving to pinpoint existing gaps between science and technology as well as ways to overcome them. There is synergy to be gained by applying different methods to the same problem, as one method may be more appropriate to answer one aspect of a problem than another, yet together they provide a more complete and clear picture of complex phenomena.
(iv) Providing a very nice and comfortable forum for graduate students looking to learn about and make contact with industrial representatives.
It is clear that all of these accomplishments stand or fall with the intricate balance of attendees and the structure of the meeting, and the organizers achieved this in a very impressive way.
A consistent theme throughout the meeting was how to address the gap between fundamental and applied heterogeneous catalysis. Specifically, discussions revolved around how to link clean UHV experimental and theoretical work to real-world catalytic conditions with much higher pressures and greater materials complexity. As a very interesting and eye-opening example, Robert Schlogl (Berlin, Germany) nicely illustrated the question of "how essential is complexity" in his presentation on how Fe203 catalyzes the dehydrogenation of ethyl benzene to form styrene in commercial processes. Theoretical and UHV experimental studies have historically focused on alpha-Fe203, establishing which surface is the most stable in equilibrium with oxygen at different partial pressures in the environment (Wang, et al.), how ethyl benzene is adsorbed (Weiss, et al.), and what the fundamental steps of dehydrogenation consist of on a clean Fe203(0001) surface. Yet the most recent results from Robert Schlogl's group indicated that the rate of dehydrogenation actually increases after the catalytic surface is covered with carbon. Further investigation revealed that it is the formation of oxygenated polynuclear aromatic species on the surface, formed from the polymerization and subsequent graphitization of styrene on the surface, which were primarily responsible for activity in the commercial catalyst. To test this hypothesis, carbon nanotubes were synthesized and oxygenated, and found to have very high catalytic activity, in the total absence of iron oxide! Hence the iron oxide is important for the initial stages of styrene formation and subsequent graphitization, but is not the primary active species for the majority of the life of the commercial catalyst. This type of insight would not be possible from clean, over-simplified model experiments or calculations, and underscores the importance of bridging the pressure and materials gap and studying a reaction system in its full complexity.
The presentations of the latest experimental results highlighted the incredible degree of resolution in time and space that is now possible with current techniques. For example, Martin Wolf (Berlin, Germany) showed how femtosecond laser spectroscopy allows the distinction between electron and phonon mediated chemical reactions on a surface. Using STM, Flemming Besenbacher (Aarhus, Denmark) very graphically illustrated how promoter atoms like Co perturb the morphology of MoS2 nanoclusters used as a model system for commercial hydride sulfurization catalysts. In addition, a novel STM system, capable of operating at 1 bar, clearly showed that a Cu(110) surface responds the same to hydrogen whether under UHV or atmospheric pressure. Another key theme at the meeting was the importance of integrating theory and experiment. For complex systems, theory can provide the details of atomic structure and reactivity to aid in the interpretation of ambiguous spectra, the results of macroscopic experiments and aid in understanding reactivity at defects or within zeolites, which is difficult to probe experimentally. In the case of nanotechnology where smaller particles behave qualitatively different than their macroscopic counterparts, theory can be extremely valuable in sorting out whether this is due to electronic effects or perhaps just bringing reactants into close proximity (Uzi Landman, Atlanta, Georgia). New combinatorial approaches to catalytic design also require greater understanding and descriptors which can be obtained via theory. As Ferdi Schiith (Muhlheim, Germany) demonstrated, "Combinatorial chemistry does not mean replacing one stupid experiment with a thousand."
It is not possible in this article to mention all of the new, excellent work which was presented and discussed at the meeting. But as two of the industrial participants, we have no hesitation in stating that we found this meeting to be extremely valuable for our work for both the content and the contacts.
Anne M. Chaka The Lubrizol Corporation Ohio, U.S.A.
Alexander Bogicevic Ford Research Laboratory Michigan, U.S.A.
More details may be found in newsletter 41 from page 55