Structures and Energetics of Pt Clusters on TiO2: Interplay between Metal–Metal Bonds and Metal–Oxygen Bonds

Depositing size-selected nanoclusters on a well-defined support surface provides a way to probe the metal–support interaction and the size dependence of the catalytic activity; however, the detailed structural information at such interface is often missing. Here we examine from density functional theory the interfacial structure of Pt 4 to Pt 8 clusters on rutile TiO 2 (110). We find that Pt 4 prefers a flat, nearly square structure on TiO 2 (110), while larger clusters such as Pt 5, Pt 6, Pt 7, and Pt 8 have a two-layer structure with the top layer not interacting with the support directly. The interaction strength generally increases with the contact area between Pt n and TiO 2 (110). The interfacial structure is a result of optimizing the Pt–Pt, Pt–O, and Pt–Ti interactions: Pt 4 prefers the square planar configuration on TiO 2 (110) with more Pt–Ti interaction over a two-layer, bi-triangle configuration of more Pt–Pt bonds; Pt 8 prefers a hut-like two-layer structure over an edge-sharing bi-pyramid structure of greater internal strain. Our findings will be useful for understanding the interface of size-selected clusters on a typical reducible support such as TiO 2 and its catalytic activity for reactions such as CO oxidation.