Crucial role of metastable structures and restructuring of Pt clusters in catalysis

The determination of the structure of heterogeneous catalytic systems, under reaction conditions, is a key point for a detailed understanding of the nature of active sites and for the rational design of efficient catalysts. The lecture will focus on the modelling of small Pt cluster (Pt₁₃) under hydrogen pressure and on their reactivity for methane and ethane activation. The approach combines Density Functional Theory, high-dimensional Neural Networks and evolutionary techniques. The bare Pt clusters shows a large number of low energy isomers (49 in 0.5 eV). Hydrogenated clusters adopt different geometries and appear more rigid, with a smaller number of low energy isomers. These metastable isomers nevertheless play a major role for the catalytic reactivity of the hydrogen covered cluster, which cannot be described by considering the most stable structure alone. Fluxionality and accessible metastable structure are hence key characteristics for the catalytic properties of small Pt clusters.