For the optimal design of catalysts, a fundamental atomic scale understanding of the structure and electronic structure of the catalytic particle, in interaction with the support is of utmost importance. By using density functional theory (DFT), we investigate the thermodynamic, structural and electronic properties of small nanometer size Ptncluster (n = 13) interacting with four relevant g-alumina surfaces exhibiting various hydroxylation and chlorination states.We show that the presence and the chemical nature of the support surface strongly impact the stability and the shape of the particle.1 More specifically, the presence of chlorine on the (110) surface of ?-alumina stabilizes small platinum clusters. This stabilization originates from the simultaneous migrations of chlorine atoms and protons from the support towards the Pt clusters. In particular, this trend leads to a local energy minimum, as a function of cluster size, for the Pt3cluster. A detailed energetic and electronic analysis will be provided to rationalize this effect. Hydroxyl groups at the surface of (110) ?-alumina give a similar but smaller effect.The final part of the lecture will concern the adsorption properties of small supported metal particle. We show that a Pt13 particle on alumina yield a much stronger adsorption of hydrogen compared to extended surface hence leading to high H coverage (up to 3 H/Pt) and the formation of a surface hydride.2 Hydrogen uptake is associated with a change of the shape of the cluster and a weakening of the cluster/support interaction.References:C. Mager-Maury,G. Bonnard, C. Chizallet, P. Sautet and P. Raybaud, ACS Catalysis 2, 1346 (2012)C. Mager-Maury,G. Bonnard, C. Chizallet, P. Sautet and P. Raybaud, ChemCatChem 3, 200 (2011)

Catalytic particles: Controlling size and reactivity from first principles

245th National Meeting (2013)

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