Site-selective reactivity modulation with intact reaction dynamics in H2 dissociation on single-atom alloy...

The dissociative dynamics of molecular H2 on the Au1/Ag(111) single-atom alloy (SAA) surface was systematically investigated through full-dimensional quantum dynamical calculations. A neural network-derived potential energy surface with a 4.2 meV root-mean-square error was employed to ensure high-fidelity simulations. Density functional theory calculations identified a reduced static dissociation barrier of 1.08 eV for the SAA system, compared to the 1.22 and 1.25 eV values for pristine Ag(111) and Au(111) surfaces, respectively. Despite this energetic advantage, the six-dimensional quantum dynamical analysis revealed that the dissociation probabilities for H2 in the vibrational ground (v = 0) state exceeded those on Ag(111) only at kinetic energies below 1.33 eV. This reactivity suppression at elevated energies was attributed to the site-specific modulation induced by the Au dopant, which selectively enhanced reactivities at the top-Au, hcp, and fcc sites while inhibiting those at bridge and top-Ag sites. Furthermore, the vibrational excitation, rotational alignment, and rotational excitation effects were found to closely resemble those observed for H2 dissociation on pristine Ag(111), demonstrating that the fundamental dynamical characteristics of the reaction remain qualitatively preserved despite SAA modification. These findings provide critical insights into the interplay between local electronic structure modification and global reaction dynamics in SAA systems.