The dissociative chemisorption of water on Ni(111): Mode- and bond-selective chemistry on metal surfaces

Abstract

A fully quantum approach based on an expansion in vibrationally adiabatic eigenstates is used to explore the dissociative chemisorption of H2O, HOD, and D2O on Ni(111). For this late barrier system, excitation of both the bending and stretching modes significantly enhances dissociative sticking. The vibrational efficacies vary somewhat from mode-to-mode but are all relatively close to one, in contrast to methane dissociation, where the behavior is less statistical. Similar to methane dissociation, the motion of lattice atoms near the dissociating molecule can significantly modify the height of the barrier to dissociation, leading to a strong variation in dissociative sticking with substrate temperature. Given a rescaling of the barrier height, our results are in reasonable agreement with measurements of the dissociative sticking of D2O on Ni(111), for both laser-excited molecules with one or two quanta of excitation in the antisymmetric stretch and in the absence of laser excitation. Even without laser excitation, the beam contains vibrationally excited molecules populated at the experimental source temperature, and these make significant contributions to the sticking probability. At high collision energies, above the adiabatic barrier heights, our results correlate with these barrier heights and mode softening effects. At lower energies, dissociative sticking occurs primarily via vibrationally nonadiabatic pathways. We find a preference for O-H over O-D bond cleavage for ground state HOD molecules at all but the highest collision energies, and excitation of the O-H stretch gives close to 100% O-H selectivity at lower energies. Excitation of the O-D stretch gives a lower O-D cleavage selectivity, as the interaction with the surface leads to energy transfer from the O-D stretch into the O-H bond, when mode softening makes these vibrations nearly degenerate.

Substrate Vibrations as Promoters of Chemical Reactivity on Metal Surfaces

“…Detailed expressions for the equations of motion and the coupling terms can be found in a recent publication (37). Given some initial vibrational state, n 0 , we use standard techniques to evolve the wave packets and energyanalyze the reactive flux (33,34,36). The result is the rigid-lattice reaction probability, P 0 (E trans , n 0 ) (33,34,36).…”

Communication: Enhanced dissociative chemisorption of CO2 via vibrational excitation

“…The source of this discrepancy is not entirely clear, but it could be the error introduced by insufficiently converged parameters and the functional used in the calculations and/or surface lattice effects, as in other DC systems. 25,42,43 Indeed, increasing the number of metal layers and the size of unit cell would further lower the barrier height. The PBE functional used here does not incorporate an accurate description of the van der Waals interaction, which presumably dominates the physisorption well.…”

Quantum State–Resolved Studies of Chemisorption Reactions

“…The RPH model reproduces both the bond selectivity (130) and the mode specificity (23,(131)(132)(133) observed in the dissociative chemisorption of methane. It has also been used to model the dissociation of water on Ni(111) (134).…”

“…Jackson and coworkers (23,(130)(131)(132)(133)(134) have developed a dynamical approach that includes surface-induced IVR to model the dissociative chemisorption of methane on transition metal surfaces. In their reaction path Hamiltonian (RPH) model, they calculate the minimum energy path from reactants to products using DFT and assume that any motion orthogonal to this path can be described harmonically.…”