Density Functional Theory Study of Nucleation and Growth of Pt Nanoparticles on MoS2(001) Surface

Abstract

The dispersion of Pt metallic nanoparticles on different supports is of high relevance for designing more efficient and less expensive catalysts. In order to understand the nucleation and epitaxial growth of Pt nanoparticles and thin films on MoS2 monolayers, we have systematically analyzed, by first-principles density functional calculations, the evolution of morphology and atomic structure of supported (Pt)n nanoparticles (NPs) on MoS2(001) for n ≤ 12. We find that n = 5 is the cluster size where the growth of the NPs transforms from two- to three-dimensional (2D to 3D). Owing to the topography of MoS2(001), the 2D NPs mostly attach to the support via direct bonding with Mo atoms that sit in the troughs of the surface, while the 3D NPs are bonded to the sulfur atoms that are more extended in the vacuum region. Furthermore, we find that Pt is sufficiently mobile on the surface where the number of hopping events per second is ≈103 s–1 along [101̅] and ≈10 s–1 along [11̅0] at room temperature. The somewhat large mobility suggests that monomer diffusion is not likely to be the rate-limiting step for Oswald ripening and that Pt sputtering on MoS2(001) will result in relatively large particles rather than a fine dispersion. The existence of a fast diffusion channel along [101̅] suggests that the morphology of the NPs is anisotropic.