It's not just the defects – a curved crystal study of H₂O desorption from Ag

Abstract

Spatially-resolved temperature-programmed desorption of H2O from curved Ag surfaces resolves the causes of structure sensitivity in binding energy.

Structural Inhibition of Silver Surface Oxidation

“…The preparation chamber was equipped with a Specs ErLEED 150 with 3000D controller (LEED), a PHI 10-155 Auger Electron Spectrometer (AES), and a Hiden HAL 3F 301 RC quadrupole mass spectrometer (QMS) for temperature-programmed desorption (TPD) analysis. The curved Ag(111) crystal ( c -Ag­(111)) was obtained from Surface Preparation Labs (Zaandam, NL) and was described in detail in a previous publication . The 8 mm long c -Ag­(111) was cut at a 31° angle from a circular cylindrical crystal and polished to expose the (111) surface at the apex, the (110) steps or B-type steps on one side (+ x direction), and the (100) or A-type steps on the other side (− x direction).…”

“…We focused on the region between 1 and 2 mm from the apex on both sides of the crystal in this report. The crystal was cleaned using established procedures, , and cleanliness was verified with LEED and STM. Atomic oxygen was generated by backfilling the preparation chamber with O 2 ( P = 5 × 10 –7 Torr) that was thermally cracked over a hot Ir filament positioned about 1–2 mm from the front face of the crystal. , The atomic oxygen exposure across the crystal face was uniform and normal to the top (111) facet; the curvature resulted in only modest attenuation of the O-atom flux toward the edges of the crystal and was the same on both sides.…”

“…The crystal shape, size, and orientation are specified in the notation of Auras and Juurlink as c-Ag(111)[11̅ 0]R31°. 41 A-type steps are characterized by a square arrangement of atoms along the step facet, while B-type steps have a triangular arrangement of atoms. 41 We show that the extent of surface reconstructions of the (111) terraces was dependent on the terrace width and step geometry.…”

“…41 A-type steps are characterized by a square arrangement of atoms along the step facet, while B-type steps have a triangular arrangement of atoms. 41 We show that the extent of surface reconstructions of the (111) terraces was dependent on the terrace width and step geometry. The formation of oxygeninduced reconstruction was strongly hindered on the side containing B-type geometry steps, yet reconstruction proceeded readily at the (111) apex and on the A-type step side.…”

“…Auras and Juurlink recently reviewed the advances in the applications of such crystals in surface science and catalysis . While many different metallic and, more recently, metal oxide materials have been used, curved Ag surfaces appeared in only three studies thus far. − Crystals with a (111) apex separating sides containing A- and B-type steps − and a symmetric crystal with a (100) apex and A′-type steps both predominantly exhibited the expected variation in step density across the crystal. Beyond the very subtle difference in reversible water adsorption to these terraces and steps, , there have been no reports of the chemical reactivity of curved Ag surfaces.…”