Two-dimensional to three-dimensional structural transition of gold cluster Au10 during soft landing on TiO2 surface and its effect on CO oxidation

Abstract

We investigate the possible structural transition of a planar Au(10) cluster during its soft landing on a TiO(2) (110) surface with or with no oxygen defects. The collision between the gold cluster and the oxide surface is simulated using the Car-Parrinello quantum molecular dynamics method. Both high-speed and low-speed conditions typically implemented in soft-landing experiments are simulated. It is found that under a high-speed condition, the gold cluster Au(10) can undergo a sequence of structural transitions after colliding with a defect-free TiO(2) (110) surface. When the TiO(2) (110) surface possesses oxygen vacancies, however, chemical bonds can form between gold and Ti atoms if gold atoms contact directly with the vacancies. As a consequence, one oxygen vacancy is capable of trapping one Au atom, and thus can split the Au(10) into two parts while bouncing back from the surface. In addition, we study reaction pathways for the CO oxidation based on three isomer structures of Au(10) observed in the soft-landing simulation: (1) the precollision two-dimensional structure, (2) a postcollision three-dimensional (3D) structure, and (3) an intermediate (transient) 3D structure that appeared in the midst of the collision. This study allows us to examine the structure-activity relationship using the Au(10) as a prototype model catalyst.