Dynamics of Initial Hydrogen Spillover from a Single Atom Platinum Active Site to the Cu(111) Host Surface: The Impact of Substrate Electron-Hole Pairs.

The initial impulsive diffusion of hot hydrogen atoms resulted from the dissociative chemisorption of H2 at atomically dispersed Pt atoms embedded in Cu(111) is investigated using ab initio molecular dynamics. Upon dissociation, one of the two hydrogen atoms tends to roam away from the dissociation site while the other remains trapped. It is shown that the fraction of diffusion and the average diffusion length increase with the incident energy and H2 vibrational excitation, due apparently to the increased initial kinetic energy of the hot atoms. Most importantly, the strong interaction with surface electron-hole pairs, modeled using an electronic friction model, is shown to play an important role in rapid energy dissipation and significant retardation of the impulsive diffusion.