CBE Seminar: Philippe Sautet

Professor, Chemical and Biomolecular Engineering Department, Chemistry and Biochemistry Department, University of California Los Angeles

Catalytic Active Sites are Dynamical and Metastable

Abstract

The determination of the structure of heterogeneous catalytic systems is a key aspect for a detailed understanding of the nature of active sites and for the rational design of efficient catalysts. However, the situation for the catalytic active sites is complicated and the determination of their structure is not straightforward. Indeed, catalysts are not static but dynamic, fluxional, metastable and they strongly evolve under reaction conditions, creating new active sites, not present for the as prepared catalysts. The best active sites are not found on the most stable structure of the catalysts, but require first its isomerization to a highly active metastable structure. The lecture will present several examples, based on quantum chemical calculations.

The first part will focus on the modelling of small Pt cluster (Pt7 to Pt13) under hydrogen pressure and on their reactivity for alkane dehydrogenation [1,2]. The approach combines Density Functional Theory, high-dimensional Neural Networks and evolutionary techniques. It also includes grand canonical global optimization to study variable amount of adsorbed hydrogen and novel constrained global optimization methods to determine the structure of the active site that makes the reaction easiest. The approach will be extended to Cu4Ox clusters on amorphous alumina, showing that the irregular nature of the support is another parameter to generate diverse sets of supported clusters, and hence diverse catalytic reactivity. The second part will deal with single-atom catalysts, that are widely investigated heterogeneous catalysts. We will consider Rh single atoms on TiO2 as a generic example, investigating the optimal structure of the single atoms under H2 reduction, CO adsorption and its reactivity for reverse water gas shift (RWGS) reaction. The combination of theoretical and experimental studies clearly demonstrates that Rh single atoms change their structure and adapt their catalytic site under reaction conditions [3].

References

1. G. Sun, P. Sautet, Metastable Structures in Cluster Catalysis from First-Principles: Structural Ensemble in Reaction Conditions and Metastability Triggered Reactivity, J. Am. Chem. Soc. 2018, 140, 2812−2820.

2. W. Zhao, C. Chizallet, P. Sautet, P. Raybaud, Dehydrogenation mechanisms of methyl-cyclohexane on g-Al2O3 supported Pt13: Impact of cluster ductility, Journal of Catalysis 370 (2019) 118–129

3. Y. Tang, C. Asokan, M. Xu, G. W. Graham, X. Pan, P. Christopher, J. Li, P. Sautet, Rh single atoms on TiO2 dynamically respond to reaction conditions by adapting their site, Nature Communications, 2019 in press

Bio

Philippe Sautet has studied at “Ecole Polytechnique” in Paris and defended his doctorate in Theoretical Chemistry at Orsay University (Paris XI) in 1989. He then entered CNRS at the Institute of Research on Catalysis in Lyon, where he developed and lead a group devoted to the applications of theoretical chemistry to heterogeneous catalysis. He spent a sabbatical at Berkeley University. After being the director of the laboratory of Chemistry at the ENS of Lyon for 8 years, he was director of the “Institut de Chimie de Lyon”, a cluster of chemistry laboratories in Lyon, from 2007 to 2015. Philippe Sautet is now Professor at the Chemical and Biomolecular Engineering department and at the Chemistry and Biochemistry department of UCLA. He acts as vice chair for graduate studies of the Chemical and Biomolecular Engineering department.

His research interests are in the theory of the electronic structure at the interface between a solid surface and molecules and the modeling of elementary steps of heterogeneous catalysis.  His work on the simulation of the atomic scale image of surfaces obtained with the scanning tunneling microscope brought him to international attention. He is recognized for his theoretical study at the molecular scale of catalysts and catalyzed reactions. He collaborates with several experimental groups in the field.

He has published over 300 scientific papers. The impact of his research is illustrated by more than 100 invited lectures at conferences and by a H factor of 67. He received several awards including the silver medal of CNRS in 2007, the Paul Pascal Prize of the French Academy of Science in 2008 and the Pierre Süe Grand Prize of the French Chemical Society in 2012. He was elected at the French Academy of Science in 2010. In addition France distinguished him as “Chevalier de l'Ordre National du Mérite” for his action in research and research organization and as “Chevalier de l’ordre des palmes académiques” for his teaching and action towards students. He is nominated in several councils or committees and is associate editor of ACS Catalysis, an international journal published by the American Chemical Society.