Quantum dynamics of H2 dissociation on Pd1/Ag(111) and Cu1/Ag(111): Reactivity enhancement with conserved dynamics

Abstract

The dissociative dynamics of H2 on Pd1/Ag(111) and Cu1/Ag(111) single-atom alloy (SAA) surfaces were systematically investigated via full-dimensional quantum dynamical calculations. Two high-fidelity machine learning potential energy surfaces were constructed with root-mean-square errors (RMSEs) below 5.0 meV. Density functional theory calculations revealed significantly reduced static barriers of 0.22 eV for Pd1/Ag(111) and 0.73 eV for Cu1/Ag(111), compared to 1.22 eV for pristine Ag(111). Both SAA surfaces exhibited dramatically higher dissociation probabilities than Ag(111). However, this enhancement demonstrated strong energy dependence, with enhancement factors decreasing from ∼1000 at 1.0 eV to about 1.1 at 2.0 eV, indicating diminished SAA effects at elevated energies. Site-specific analysis revealed that Pd/Cu dopants selectively enhanced reactivity at bridge and fcc sites while suppressing reactivity at the top-Ag site. Remarkably, the vibrational excitation, rotational alignment, and rotational excitation effects remained qualitatively consistent with those observed on Ag(111) and Au1/Ag(111). These results demonstrate that SAAs quantitatively tune reactivity through localized electronic modifications while preserving the fundamental dynamical characteristics of H2 dissociation.