Core-level shifts at the Pt/W(110) monolayer bimetallic interface

Abstract

We have measured W and Pt 4f7/2 core-level photoemission spectra from interfaces formed by ultrathin Pt layers on W(110), completing our core-level measurements of W(110)-based bimetallic interfaces involving the group-10 metals Ni, Pd, and Pt. With increasing Pt coverage the sequence of W spectra can be described using three interfacial core-level peaks with binding-energy (BE) shifts (compared to the bulk) of −0.220 ± 0.015, −0.060 ± 0.015, and +0.110 ± 0.010 eV. We assign these features to 1D, 2D pseudomorphic (ps), and 2D closed-packed (cp) Pt phases, respectively. For ~1 ps ML the Pt 4f7/2 BE is 71.40 ± 0.02 eV, a shift of +0.46 ± 0.09 eV with respect to the BE of bulk Pt metal. The W 4f7/2 core-level shifts induced by all three adsorbates are semiquantitatively described by the Born-Haber-cycle based partial-shift model of Nilsson et al. [Phys. Rev. B 38 (1988) 10357]. As with Ni/W(110), the difference in W 4f7/2 binding energies between ps and cp Pt phases has a large structural contribution. The Pt 4f lineshape is consistent with a small density of states at the Fermi level, reflective of the Pt monolayer having noble-metal-like electronic structure.

Achieving Highly Durable Random Alloy Nanocatalysts through Intermetallic Cores

“…Such compressive strain is supported by X-ray photoelectron spectroscopy (XPS), with differences in the electronic structures revealed. Specifically, the Pt 4f peaks were analyzed as corresponding electrons and demonstrated high sensitivity to the surface Pt coverage in the submonolayer regime. , Moreover, the valence band originating from d-electrons is sensitive to surface strain and shifts away from the Fermi level if the lattice strain increases . Thus, the Pt 4f 5/2 and 4f 7/2 peaks were fit with a doublet, and the asymmetric shape of the peaks is consistent with Pt metal rather than PtO x .…”

Designing Efficient Catalysts through Bimetallic Architecture: Rh@Pt Nanocubes as a Case Study

“…The well‐isolated Pt 4f and Rh 3d regions were selected for analysis (survey scan in Figure S4 for the Rh@Pt nanocubes with 1.2 Pt ML shell thickness). We note that analyzing the f orbital to study the d‐band energy is valid as core‐level shifts of the adsorbate layers are often nearly equal to the changes in the average d‐band position . High‐resolution scans of the Pt 4f 7/2 and Rh 3d 5/2 regions are shown in Figure S5, with only one feature of the doublets collected to limit acquisition time due to the small step size of the XPS measurements (0.05 eV).…”

“…We note that analyzing the fo rbitalt o study the d-band energy is valid as core-level shifts of the adsorbate layers are often nearly equal to the changes in the average d-band position. [43][44][45] High-resolution scans of the Pt 4f 7/2 and Rh 3d 5/2 regionsa re shown in Figure S5, with only one feature of the doubletsc ollected to limit acquisition time due to the smalls tep size of the XPS measurements (0.05 eV). Spectra for the Rh and Pt nanocubesa re included for reference.…”

Electronic Structure and Bond Relaxation at Na/Ta(110) Interfaces and 1D‐Chain and 2D‐Ring Ta Metal Structures on Na(110)

“…The different electronic structures and atomic coordination environments of bulk and clean surface atoms are known to cause binding energy (BE) shifts in the core and valence bands of the electrons. Energy shifts of surface atoms have been observed in defect generations, alloy formations, and chemisorption systems. For example Alexey A. Tal et al studied energy shifts in Au nanoclusters .…”

“…Different electronic structures and atomic coordination environments of bulk and clean surface atoms are known to result in BE shifts in the core and valence bands of electrons. Core level shifts of surface atoms have been observed to change in a variety of defect generation 9-12, alloy formation [13][14][15][16] , and chemisorption [17][18][19] systems, with the changes generally being attributed to the transfer of charge. However, when the process of chemisorption is accompanied by surface reconstruction, which is often the case, the BE shifts are affected by the atomic bonding and the reconstruction-induced change in the surface atomic energy density and local strain.…”