Density Functional Theory Study on the Nucleation and Growth of Ptn Clusters on ?-Al2O3(001) Surface

Abstract

Little is known about the detailed structural information at the interface of Ptn cluster and ?-Al2O3(001) surface, which plays an important role in the dehydrogenation and cracking of hydrocarbons. Here, the nucleation and growth of Ptn (n = 1-8, 13) clusters on a ?-Al2O3(001) surface have been examined using density functional theory. For the most stable configuration Ptn/?-Al2O3(001) (n = 1-8, 13), Ptn clusters bond to the ?-Al2O3(001) surface through Pt-O and Pt-Al bonds at the expense of electron density of the Ptn cluster. With the increase in the Ptn cluster size, both the metal-support interaction and the nucleation energies exhibit an odd-even oscillation pattern, which are lower for an even Ptn cluster size than those for its adjacent odd ones. Both the metal-surface and metal-metal interactions are competitive, which control the nanoparticle morphology transition from two-dimension (2D) to three-dimension (3D). On the ?-Al2O3(001) surface, when the metal-support interaction governs, smaller clusters such as Pt1, Pt2, Pt3, and Pt4 prefer a planar 2D nature. Alternatively, when the metal-metal interaction dominates, larger clusters such as Pt5, Pt6, Pt7, Pt8, and Pt13 exhibit a two-layer structure with one or more Pt atoms on the top layer not interacting directly with the support. Herein, the Pt4 cluster is the most stable 2D structure; Pt5 and Pt6 clusters are the transition from the 2D to the 3D structure; and the Pt7 cluster is the smallest 3D structure.