Reaction of Au(111) with Sulfur and Oxygen: Scanning Tunneling Microscopic Study

Abstract

The reaction of sulfur and oxygen with the gold surface is important in many technological applications, including heterogeneous catalysis, corrosion, and chemical sensors. We have studied reactions on Au(111) using scanning tunneling microscopy (STM) in order to better understand the surface structure and the origin of gold's catalytic activity. We find that the Au(111) surface dynamically restructures during deposition of sulfur and oxygen and that these changes in structure promote the reactivity of Au with respect to SO 2 and O 2 dissociation. Specifically, the Au(111) herringbone reconstruction lifts when either S or O is deposited on the surface. We attribute this structural change to the reduction of tensile surface stress via charge redistribution by these electronegative adsorbates. This lifting of the reconstruction was accompanied by the release of gold atoms from the herringbone structure. At high coverage, clusters of gold sulfides or gold oxides form by abstraction of gold atoms from regular terrace sites of the surface. Concomitant with the restructuring is the release of gold atoms from the herringbone structure to produce a higher density of low-coordinated Au sites by forming serrated step edges or small gold islands. These undercoordinated Au atoms may play an essential role in the enhancement of catalytic activity of gold in reactions such as oxygen dissociation or SO 2 decomposition. Our results further elucidate the interaction between sulfur and oxygen and the Au(111) surface and indicate that the reactivity of Au nanoclusters on reducible metal oxides is probably related to the facile release of Au from the edges of these small islands. Our results provide insight into the sintering mechanism which leads to deactivation of Au nanoclusters and into the fundamental limitation in the edge definition in soft lithography using thiol-based self-assembled monolayers (SAMs) on Au. Furthermore, the enhanced reactivity of Au after release of undercoordinated atoms from the surface indicate a relatively insignificant role of an oxide support for high reactivity.

Self-ordered nanoporous lattice formed by chlorine atoms on Au(111)

“…It was found out that electronegative adsorbates (S, O, ClO − 4 ) induce compressive stress compensating for the tensile stress on the clean Au(111) surface. In particular, adsorption of sulfur was found to lift reconstruction completely [25,26]. Adsorption of oxygen resulted in disappearance of elbows of the herringbone reconstruction persisting the soliton walls [25].…”

“…The effect of adsorbates on the reconstruction was studied previously in a number of STM works [24][25][26][27][28]. It was found out that electronegative adsorbates (S, O, ClO − 4 ) induce compressive stress compensating for the tensile stress on the clean Au(111) surface.…”

Metal-free phthalocyanine (H2Pc) molecule adsorbed on the Au(111) surface: formation of a wide domain along a single lattice direction

“…Wang et al performed density functional theory simulation of this reconstruction and compared the areas of the fcc, hcp and ridge domains with previous experimental results [19,20,22]. They found that fcc and hcp domains occupy 31% (34%) and 19% (22%) of the total area, respectively, in theoretical (experimental) STM images.…”

“…Some gold atoms are pushed away from the usual fcc sites towards the hcp sites, and some atoms are forced to occupy the high-energy bridging sites, thus protruding from the surface. As a result, the surface displays ridges between fcc and hcp valleys [19][20][21][22].…”

Novel Self-Organized Structure of a Ag−S Complex on the Ag(111) Surface below Room Temperature

“…21,23 Sulfur adsorption on the (111) surfaces of the other two coinage metals, Au and Cu, has also been studied with STM. [24][25][26][27][28][29][30] On Cu, a complex series of apparently static structures evolve with coverage below room temperature. As for the 7 on Ag(111), they were interpreted as surface reconstructions that mimic aspects of Cu 2 S(111).…”