Abstract
Investigations on electronic and geometric structures of platinum adsorbed on monocrystalline gold surfaces are important for understanding the remarkable catalytic properties of bimetallic Pt–Au systems. Herein, the morphology of quasi-hexagonal (hex) Au(100) surface after deposition of platinum for coverage up to 0.5 monolayer (ML) has been investigated by scanning tunneling microscopy (STM). For coverage range 0.2–0.4 ML the creation of elongated islands with mono-atomic height is observed. The islands consist of flat phase of disordered Pt-Au alloy which coexists with nanowire-like features with a hex atom arrangement and quantized width. Annealing the Pt/Au(100) system at 100–150 °C changes the surface morphology. The islands disappear and the topmost layer of the surface consists of flat phase of Pt–Au alloy which coexists with the hex-stripes. Small domains of ordered c(2 × 2) structure of Pt–Au alloy are found. The electronic properties of this structure have been investigated by ab-initio calculations. The obtained results allow to distinguish the Pt from Au atoms by their appearance in the STM images. The calculated electronic structures indicate a bonding creation between Pt and Au atoms and an electron d-states redistribution of Pt in comparison to the bare Pt(100)-(1 × 1) surface.
Highlights
Investigations on electronic and geometric structures of platinum adsorbed on monocrystalline gold surfaces are important for understanding the remarkable catalytic properties of bimetallic Pt–Au systems
Surface morphology observed by us is consistent with the previous scanning tunneling microscopy (STM) investigations on the Pt/Au(100) system reported in Ref.[24]
The rectangular islands with the hex atom arrangement were detected by STM during homoepitaxy on Au(100)[19], whereas the molecular dynamics (MD) simulations revealed that widths of (6n + 1) rows are the energetically favorable configurations for Au islands[28]
Summary
Investigations on electronic and geometric structures of platinum adsorbed on monocrystalline gold surfaces are important for understanding the remarkable catalytic properties of bimetallic Pt–Au systems. The studies of model systems, like ultra-thin films of platinum on gold monocrystalline surfaces under well-defined experimental conditions are important in order to better understand the processes responsible for catalytic activity of bimetallic NPs. Gold as well as platinum crystallize in a face-centered cubic (fcc) structure with the unit cells equal a Au = 4.08 Å and aPt = 3.92 Å, and the lattice misfit is about 4%. Gold as well as platinum crystallize in a face-centered cubic (fcc) structure with the unit cells equal a Au = 4.08 Å and aPt = 3.92 Å, and the lattice misfit is about 4% For both metals, their topmost layer of {100} surfaces displays the quasi-hexagonal (hex) reconstruction instead of squared lattice[16–21]. Formula describes the width of the energetically favorable configurations of Au islands on the hex-Au(100) surface studied by molecular dynamics (MD) simulations[28]
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