Complex reactions on a convertible catalyst surface: A study of the S-O-Cu system

Abstract

The interaction of clean and partially oxidized Cu(110) with sulphur was studied by scanning tunneling microscopy and density functional theory calculations in the lowcoverage range. On the clean Cu surface individual S atoms adsorb in the troughs between the Cu atom rows. Hollow sites are preferred, but long-bridge sites are occasionally occupied as well. The majority of adsorbed S, however, seems to be involved in the formation of highly mobile CuxSy clusters of various sizes. The clusters preferentially attach to steps thus changing the step morphology completely. Some of the clusters form aggregates on the terraces. On the partially oxidized surface similar clusters form and cause long-range mass transport to steps. Additionally, nanowires form in [001] direction on and along the surface oxide stress domains. These nanowires have a complex composition, exhibit different corrugations and appear sometimes as three-dimensional needles. Occasionally they flip their direction by 90°, but doing so they partially decompose. Finally, annealing of the SO -Cu surface leads to consumption of the surface oxide stripes indicating loss of oxygen presumably via SO2 formation. Simultaneously, linear sulphur chains suspended between the [001]-O-Cu-O-chains form in 110   direction. The surprising multitude of processes and products even at low-pressure, lowtemperature conditions in the comparatively simple SO -Cu system highlights the difficulty of controlling reactivity and selectivity on such convertible catalyst surfaces.

Identification of an AgS2 Complex on Ag(110)

“…Despite these differences, the common evidence that AgO 2 and AgS 2 complexes can form on the Ag(110) surface is very interesting, and may have broader ramifications, especially for interpreting mass transport. Specifically, it has been observed that both oxygen and sulfur can strongly accelerate coarsening on many coinage metal surfaces 26–31 . While M 3 S 3 is a strong candidate on the (111) surfaces, MS 2 and MO 2 are reasonable candidates for (110) and (100) surfaces.…”

“…A related system, sulfur on Cu(110), has been studied at sub-monolayer sulfur coverages. It was found that S adatoms coexist with possible Cu x S y clusters 31 . No detailed structures of these clusters have been proposed and the clusters were imaged at 77 K, leading to the clusters appearing streaky or fuzzy in STM images due to the clusters being semi-mobile on the surface.…”

Atomic structures and electronic properties of Ni or N modified Cu/diamond interface

“…The Cu(0 0 1), Cu (0 1 1), and Cu (1 1 1) slabs include five, seven, and four layer thicknesses [31,32]. In which, we take one bottom corner atom of each slab as the aiming point to put on the adsorption site defined in figure 1 to construct the composite interface.…”