(540a) Doped Metal Clusters on Oxides: Rationalization and Design through the Prism of Chemical Bonding

Ultra-small clusters of transition metals deposited on oxides can be highly-tunable and effective catalysts, and they represent an exciting electronic structure problem: every atom counts, and so does every electron. Doping and the choice for the support are two major levers in the design and rational manipulation of such sensitive catalysts. The rationale is rooted in the chemical bonding, i.e. in details of the electronic structure and explication of its precise effect on cluster shape, stability, mobility, and catalytic activity. With this prism in hand, we will present several cases when doping and surface-deposition lead to dramatic, though explainable changes in shapes and properties of clusters. We will show why mixed PtPd clusters exhibit their famous and unusual stability on oxides, as compared to pure Pt and Pd analogues. We will demonstrate how strategic doping of deposited Pd clusters with a small amount of Au leads to greater catalytic efficiency. We will explain why some clusters change shapes from globular to flat upon deposition, and why some do the exact opposite. On the fundamental level, we will deliver the emerging chemical bonding picture for surface-deposited clusters, where effects such as multiple aromaticity, covalency, first and second order Jahn-Teller effects are all in play and define the phenomena of interest. This work is done using Density Functional Theory calculations and our in-house methodology for modeling surface-deposited clusters in realistic conditions, and facilitated by collaboration with spectroscopic and surface-science experiments.