Globally Optimized Equilibrium Shapes of Zirconia-Supported Rh and Pt Nanoclusters : Insights into Site Assembly and Reactivity

Abstract

Metal−support interfaces form an active site for many important catalytic reactions. The modeling of these interfacial sites calls for approximations to set up a structure model, which in turn may significantly have an impact on studied chemistry and obtained atomistic understanding. Herein, we have employed a density functional theory-based genetic approach to obtain globally optimized nanostructures for Rh and Pt clusters on a ZrO2 support. The analysis of the obtained structures shows that Rh clusters take more compact shapes, whereas Pt prefers elongated and low-symmetry structures. We find that metal−oxide perimeter sites are structurally different, presenting varying Pt and Rh coordinations and CO adsorption energies. Our analysis shows that the presence of a support always destabilizes CO adsorption at the cluster edge, but the magnitude of destabilization varies substantially from site to site. The complexity of catalyst−support interactions demonstrates that even an inert support can intricately influence the reactivity of interfacial sites.