Interaction of CO, O, and S with metal nanoparticles on Au(111): A theoretical study

Density functional theory and slab models are used to study the unusual behavior of Mo, Ni and Ru nanoparticles on a Au(111) substrate. After considering several different structures and compositions for the metal nanoparticles on the Au(111) interface, the calculations show that the metal particles energetically prefer to be embedded into the surface or form Au/metal particles/Au(111) sandwich like structures. The calculations also indicate that the observed deactivation of the Mo/Au interface to CO, O-2, and S-2 adsorption is due to the passivation of Mo as a result of the intermixing between Mo and Au. Mo atoms in the substrate can be pulled out to the surface by interacting with oxygen or sulfur adatoms, eventually forming molybdenum oxides or sulfides. This process depends on a delicate balance between the adsorbate-Mo and Mo-Au interactions, and usually requires high coverages of the adsorbate. It can lead to big changes in the morphology of nanoarrays. Ru/Au(111) and Ni/Au(111) exhibit a similar behavior to that of Mo/Au(111). Thus, the phenomena described above must be taken into consideration when preparing nanoparticles on a Au template.