Exposure of Pt(5 5 3) and Rh(1 1 1) to atomic and molecular oxygen: do defects enhance subsurface oxygen formation?

Abstract

Subsurface oxygen is known to form in transition metals, and is thought to be an important aspect of their ability to catalyze chemical reactions. The formation of subsurface oxygen is not, however, equivalent across all catalytically relevant metals. As a result, it is difficult to predict the stability and ease of the formation of subsurface oxygen in metals, as well as how the absorbed oxygen affects the chemical and physical properties of the metal. In comparing how a stepped platinum surface, Pt(5 5 3), responds to exposure to gas-phase oxygen atoms under ultra-high vacuum conditions to planar Rh(1 1 1), we are able to determine what role, if any, steps have on the capacity of a metal for subsurface oxygen formation. Despite the presence of regular defects, we found that only surface-bound oxygen formed on Pt(5 5 3). Alternatively, on the Rh(1 1 1) surface, oxygen readily absorbed into the selvedge of the metal. These results suggest that defects alone are insufficient for the formation of subsurface oxygen, and the ability of the metal to absorb oxygen is the primary factor in the formation and stabilization of subsurface oxygen.

Heterogeneous Surfaces as Structure and Particle Size Libraries of Model Catalysts

“…The PEEM observations did not provide direct evidence for the formation of subsurface oxygen, but it has been reported that on the smooth Rh(111) surface subsurface oxygen is produced at 470 K [ 31 ]. For stepped Rh surfaces, the activation energy of subsurface oxygen formation is lower than for close-packed planes such as Rh(111) [ 32 , 33 ], thus subsurface oxygen formation with an observable rate may occur at lower temperature.…”

Insight into subsurface adsorption derived from a lattice-gas model of atomic oxygen on Ag(111)

“…Subsurface adsorption of light atoms, such as hydrogen, carbon, and oxygen, has been investigated on several transition metals, including aluminum, nickel, copper, rhodium, palladium, silver, and platinum to understand their role in catalytic reactions, surface reconstruction, and surface oxidation, yet the conditions of their formation, their chemical properties, and the microscopic mechanisms of their participation in surface processes are not yet completely understood. [11][12][13][14][15][16][17][18][19][20][21][22][23][24] Lattice-gas models that include surface and subsurface sites can help to narrow the gap in fundamental knowledge by capturing the interplay between adatoms bound above and below the surface of a crystalline solid, ultimately advancing our conceptual understanding of the nature and prevalence of subsurface adsorption in surface chemistry.…”

Insight into subsurface adsorption derived from a lattice-gas model of atomic oxygen on Ag(111)

“…Subsurface adsorption of light atoms, such as hydrogen, carbon, and oxygen, has been investigated on several transition metals, including aluminum, nickel, copper, rhodium, palladium, silver, and platinum to understand their role in catalytic reactions, surface reconstruction, and surface oxidation, yet the conditions of their formation, their chemical properties, and the microscopic mechanisms of their participation in surface processes are not yet completely understood. [11][12][13][14][15][16][17][18][19][20][21][22][23][24] Lattice-gas models that include surface and subsurface sites can help to narrow the gap in fundamental knowledge by capturing the interplay between adatoms bound above and below the surface of a crystalline solid, ultimately advancing our conceptual understanding of the nature and prevalence of subsurface adsorption in surface chemistry.…”