Direct visualization of quasi-ordered oxygen chain structures on Au(110)-(1 × 2)

Abstract

The Au(110) surface offers unique advantages for atomically-resolved model studies of catalytic oxidation processes on gold. We investigate the adsorption of oxygen on Au(110) using a combination of scanning tunneling microscopy (STM) and density functional theory (DFT) methods. We identify the typical (empty-states) STM contrast resulting from adsorbed oxygen as atomic-sized dark features of electronic origin. DFT-based image simulations confirm that chemisorbed oxygen is generally detected indirectly, from the binding-induced electronic structure modification of gold. STM images show that adsorption occurs without affecting the general structure of the pristine Au(110) missing-row reconstruction. The tendency to form onedimensional structures is observed already at low coverage (<0.05ML), with oxygen adsorbing on alternate sides of the reconstruction ridges. Consistently, calculations yield preferred adsorption on the (111) facets of the reconstruction, on a 3-fold coordination site, with increased stability when adsorbed in chains. Gold atoms with two oxygen neighbors exhibit enhanced electronic hybridization with the O states. Finally, the species observed are reactive to CO oxidation at 200K and desorption of CO 2 leaves a clean and ordered gold surface.2

Development of the ReaxFF Reactive Force-Field Description of Gold Oxides

“…Both surfaces showed that the strongest O-Au bond occurs when the oxygen atoms 'straddle' the reconstructed rows of Au atoms. This is in perfect agreement with the experimental studies of these systems 38,39 and this trend is also reflected in the ReaxFF description of the system shown in fig. 6.…”

“…The work 38 demonstrates that oxygen can bind stably on these reconstructions with binding energies -0.156 to -0.349 eV. Ordered chainlike structures have been observed experimentally 39 along the surface rows of Au atoms indicating that on these surface the oxygen atoms prefer to bind close to the surface rather than deeper inside the reconstructed trench or hollow. The binding energy of oxygen atoms in these structures was determined using DFT to be -3.67 to -3.81 eV 39 .…”

“…Ordered chainlike structures have been observed experimentally 39 along the surface rows of Au atoms indicating that on these surface the oxygen atoms prefer to bind close to the surface rather than deeper inside the reconstructed trench or hollow. The binding energy of oxygen atoms in these structures was determined using DFT to be -3.67 to -3.81 eV 39 . Some discrepancies exist in the oxygen binding energies presented in work of Landmann et al 38 and Hiebel et al 39 .…”

Observation and Identification of an Atomic Oxygen Structure on Catalytic Gold Nanoparticles

“…The second structure, which was described as a precursor of a surface oxide, was observed at higher coverage when two oxygen atoms push a neighboring Au atom from the surface and form a dimer with the elevated Au atom in between as Au 2 ‐O‐Au‐O‐Au 2 , and with the O atoms in pseudo threefold sites (each O atom is bonded to three Au atoms) (Figure b). A similar structure can form on a rough single‐crystal Au surface at low coverage . In this work, a third structure is identified on surfaces of Au nanoparticles.…”

Origins of the High Reactivity of Au Nanostructures Deduced from the Structure and Properties of Model Surfaces

“…Additionally, we modeled the stepped Au (321) surface with an infinite oxide chain. Such chains of alternating Au and O atoms were previously identified as a common feature of thermodynamically stable surface configurations of the Au (111) [90,91], the Au (110) [92,93] as well as the Au (321) [94] surfaces. The latter surface features steps and terraces with both high-and low-coordinated Au atoms and therefore provides an ideal model for the rough npAu surface morphology [31,94,95].…”