Two-dimensional quantum dynamics of O₂dissociative adsorption on Ag(111)

Abstract

We have investigated the quantum dynamics of O2 dissociative adsorption on a Ag (111) surface. We performed the calculations with a Hamiltonian where the O2 translational motion is perpendicular to the surface and for O2 vibrational energy. We found that dissociative adsorption occurs with an incident translational energy below the expected activation barrier, while the translational-energy dependence for adsorption probabilities is a smooth sigmoid. Thus, there are non-negligible tunneling effects in the dissociative adsorption that are affected by the activation barrier width. Moreover, the incident translational energies at the inflection points of the adsorption probabilities shift lower with increasing in vibrational quantum numbers of the incident O2. Thus, there is significant energy transfer and coupling from vibration to translational motion. The vibrational energy assists the O2 dissociative adsorption via a vibrationally assisted sticking effect.KEYWORDS: density functional theory, oxygen adsorption, dissociative adsorption, potential energy surface, tunneling effect, vibrationally assisted sticking effect 2

Atom Tunneling in Chemistry

“…surfaces and the following successive H-addition reactions -important in the process of NH 3 formationare found to be accelerated by tunneling especially at lower temperatures. [250][251][252][253][254] Even oxygen tunneling was observed in the dissociative adsorption on an Ag(111) [255] and on Pt (111) surfaces. [256] .…”

“…Furthermore, the dissociation and recombination rates of H 2 on Ni(100) and the formation of NH on a Ru(0001) surface and the following successive H addition reactions—important in the process of NH 3 formation—are found to be accelerated by tunneling, especially at lower temperatures . Even oxygen tunneling was observed in dissociative adsorption on Ag(111) and on Pt(111) surfaces . Heterogeneous catalysis, however, is often carried out at high temperatures, where tunneling is less important.…”

Hyperthermal velocity distributions of recombinatively-desorbing oxygen from Ag(111)

“…For both studies, the energetics of desorbing molecules indicate desorption from an intermediate molecular chemisorption state. Recent theoretical papers calculate significantly higher barriers for oxygen sticking on Ag (111) than we deduce from the translational energy distribution (Kunisada and Sakaguchi, 2014). The here presented data will be a valuable experimental benchmark to refine theoretical models crucial for a better understanding of surface dynamics in metal oxidation processes.…”

“…Interestingly, these values are significantly lower than calculated sticking probabilities based on first principles theory (Goikoetxea et al, 2012;Kunisada and Sakaguchi, 2014). Kunisada and Sakaguchi calculate state-resolved sticking by performing quantum dynamics calculations of O 2 dissociative desorption on Ag (111) on a before computed PES (Kunisada et al, 2011).…”

Der Tunneleffekt von Atomen in der Chemie

“…Die Dissoziation und Rekombination von H 2 auf Ni(100) und die NH‐Bildung sowie die folgenden sukzessiven H‐Additionen – wichtige Schritte bei der Entstehung von NH 3 – werden durch den Tunneleffekt insbesondere bei niedriger Temperatur beschleunigt . Sogar Sauerstoff tunnelt während der dissoziativen Adsorption auf Ag(111)‐ und Pt(111)‐Flächen . Dennoch muss beachtet werden, dass heterogen katalysierte Reaktionen oft bei höheren Temperaturen durchgeführt werden, als in diesen Studien berichtet, wodurch der Tunneleffekt hierfür eindeutig an Bedeutung verliert.…”