Surface morphology of atomic nitrogen on Pt(111)

Abstract

The surface morphology of chemisorbed N on the Pt(111) surface has been studied at the atomic level with low temperature scanning tunneling microscopy (STM). When N is coadsorbed with O on the surface, they form a mixed (2 × 2)-N+O structure. When the surface is covered with N atoms only, isolated atoms and incomplete (2 × 2) patches are observed at low coverages. In a dense N layer, two phases, (√3 × √3)R30°-N and p(2 × 2)-N, are found to coexist at temperatures between 360 and 400 K. The (√3 × √3)R30° phase converts to the (2 × 2) phase as temperature increases. For both phases, nitrogen occupies fcc-hollow sites. At temperatures above 420 K, nitrogen starts to desorb. The p(2 × 2)-N phase shows a honeycomb structure in STM images with three nitrogen and three platinum atoms forming a six-membered ring, which can be attributed to the strong nitrogen binding to the underlying Pt surface.

Characteristics of sulfur atoms adsorbed on Ag(100), Ag(110), and Ag(111) as probed with scanning tunneling microscopy: experiment and theory

“…STM studies have shown that a modified tip (tip that has an extrinsic molecule/atom at the apex) can alter the appearance of atoms or molecules on a surface. 8,21,50 Species that appear as protrusions for a bare tip may appear as depressions when a tip is modified, at a constant or similar V S . However, tips can be cleaned through multiple high voltage pulses.…”

Atomic-Scale Dynamics of Surface-Catalyzed Hydrogenation/Dehydrogenation: NH on Pt(111)

“…In contrast, we found that hydrogen atoms appear as protrusions on a N-covered Pt(111) surface, making them readily observable even at very low coverages. Figure a shows the honeycomb structure of the p(2 × 2)-N phase on Pt(111), which was discussed in detail earlier . In this structure, Pt atoms that are not adjacent to N atoms are visible in the STM images and form a (2 × 2)-Pt lattice and are referred to as Pt-visible, whereas Pt atoms that are bonded to N atoms are referred to as Pt-invisible because they are not resolved.…”

“…Hydrogen atoms are also present on the surface, one of which is indicated by the white arrow, which is consistent with other STM images. Note that the brightest protrusions are residual ammonia molecules as discussed earlier . The images in Figure b–d show the topography of the surface after exposure to H 2 (g).…”

Dynamic nitroxyl formation in the ammonia oxidation on platinum via Eley–Rideal reactions

“…16,34,35 The ER surface reaction process was further tested at elevated surface temperatures. An ordered (2 Â 2) structure of N atoms has been reported on Pt(111), formed by annealing a NH 3 -O overlayer to 400 K. 36,37 Above 400 K, the surface NH x species are expected to completely dissociate into N and H. Then, low surface coverage in NH should suppress the formation of HNO. This prediction was confirmed by performing scattering experiments at elevated temperatures.…”