Adsorption, Vibration, and Diffusion of O Atoms on Rh Low-Index and (711) Stepped Defective Surfaces

Abstract

The adsorption, vibration, and diffusion of O atoms on Rh(100), Rh(111), Rh(110), and Rh(711) surfaces were studied using the 5-parameter Morse potential (5-MP) of interaction between an adatom and a metal surface cluster. Our theoretical calculations provide information about adsorption sites, adsorption geometry, binding energy, and eigenvibration. Our results agreed very well with experimental results. Four major results follow. First, the theoretical calculation showed that on the Rh(100) surface the 4-fold hollow site is the only adsorption site. Second, on the O-Rh(111) system, the 3-fold hollow site is the stable adsorption site. Third, on the Rh(110) surface at low coverage, the O atom is adsorbed preferably on the pseudo-3-fold site, while with increasing coverage, the O atom is adsorbed not only on the pseudo-3-fold site but also on the long bridge site. Last, as for the Rh(711) stepped surface, the 3-fold site on the (111) step is metastable, whereas the 4-fold sites on the (100) terrace are stable, which enables the O atoms to diffuse easily from the 3-fold to the 4-fold site at low coverage. Therefore, the O atoms are adsorbed preferrably on the stable 4-fold sites of the (100) terrace and then later as coverage increases on the metastable 3-fold site of the (110) step.

Study of the Rate-Determining Step of Rh Catalyzed CO2 Reduction: Insight on the Hydrogen Assisted Molecular Dissociation

“…As happened in the previous cases, these adsorption energy differences seem to be uncorrelated with the adsorption sites stability trend and almost identical geometrical configurations were obtained in all the three calculations. The most stable adsorbed configuration for O* is on the Hollow site, as reported in previous theoretical studies [66][67][68]. The Bridge-to-Hollow energy difference ranges between 0.12 and 0.22 eV, depending on the calculation level.…”

Bridging the structure gap: Chemistry of nanostructured surfaces at well-defined defects

“…For stepped Ni surfaces, e.g., it was shown that: (a) an O-induced missing row reconstruction occurs on Ni(771) [205]; (b) the reconstruction dynamics of O/Ni(977) is influenced by the oxygen dissolution history of the crystal [206] and (c) the heat of adsorption for oxygen at Ni(211) is considerably higher than on any LMI Ni surface, due to the higher reactivity of under-coordinated atoms [108]. For the less investigated Rh and Ru stepped surfaces the attention concentrated mainly on the chemical activity of step atoms [207,208]; for O 2 /Rh(711) [207] it was demonstrated that (111)-like steps are active sites although they are not always the most stable ones for adsorption. A reduction of the energy barriers for molecular and dissociative O 2 chemisorption was also found for stepped and strained Au(111) surfaces, which are otherwise inert [51,209].…”

Zooming in on the initial steps of catalytic NO reduction using metal clusters

“… a From Loffreda et al 105 b Vibration perpendicular to the surface. 106 c Adsorption site not specified. 107 d Adsorption site not specified.…”