Atomic Scale Surface Structure of Pt/Cu(111) Surface Alloys

Abstract

Pt–Cu bimetallic alloys are a key component in many heterogeneous catalysts that have the potential to be used in a range of industrially important reactions. Given the catalytic differences between Pt and Cu, the surface composition and geometry of Pt–Cu alloys can have a large influence on their chemistry. Extensive characterization of bulk Pt–Cu alloys has been performed; however, only a few studies have addressed surface and subsurface alloying of Pt with Cu, and none have examined the atomic scale surface structure of Pt–Cu. In this study, scanning tunneling microscopy was used to determine the local structure of surface alloys formed by physical vapor deposition of Pt onto Cu(111) over a range of alloying temperatures (315–550 K). Our results indicated that Pt and Cu were capable of intermixing at 315 K and forming multiple metastable states. Increasing the temperature of the Cu surface during the deposition of Pt altered the surface geometry and further enhanced the dispersion of Pt. The results are compared to the well-characterized Pd/Cu(111) surface alloy. A distinguishing feature of the Pt/Cu(111) surface alloy is the ability of Pt atoms to alloy directly into the Cu surface. Pt alloys as individual isolated atoms, well separated from each other, rather than more localized in regions at step edges, as is the case with Pd. This work indicates that the highly dispersed nature of Pt–Cu surface alloys should render them useful for understanding the surface chemistry of Pt at the single atom level.

The Multifaceted Reactivity of Single‐Atom Heterogeneous Catalysts

“…[14] In comparison, SAAs are characterized by two features:the more active metal is present in low concentrations,and atoms of this metal are thermodynamically more stable when surrounded by the host. [39] Furthermore,itisknown that the active metal can go into sites beneath the top-most layer (subsurface) [40] and become inaccessible in amanner similar to bulk atoms in NPs. Forpractical application, SAAs are also supported and may thus present different inequivalent atoms depending on both the relative metal concentration and the size and morphology of the NPs.…”

Carbon Monoxide Poisoning Resistance and Structural Stability of Single Atom Alloys

“…In several cases it has been shown that by doping the coinage metals with PGMs at very low molar fractions, such that these more reactive metals disperse as isolated single atoms in the surface layer of the host material, the activity of the coinage metal surface can be dramatically enhanced whilst retaining excellent reaction selectivity [11][12][13][14][15][16][17][18][19][20][21][22][23][24]. These single atom alloys (SAAs) of Sykes and co-workers exhibit tolerance to CO [18] and have been employed to catalyse hydrogenation [16][17][18][19][20], dehydrogenation [22,23], C-H activation and hydrosilylation [25] reactions with high activity and selectivity, as extended model surfaces and/or as real catalyst nanoparticles.…”

Single Atom Alloy Preparation and Applications in Heterogeneous Catalysis

“…Sykes et al . further investigated physical vapor deposition of Pt onto Cu(111) by adjusting Cu(111) temperature from 315 K to 550 K as is shown in Figure . Compared with Pd atomic dispersion mechanism on Cu(111), there is one more competing mechanism in the situation of Pt dispersion that Pt atoms could also directly exchange into the Cu terrace.…”