X-ray photoemission spectroscopy of Pt-Cu: A canonical alloy

Abstract

The possibility of employing x-ray photoemission valence-band spectra in a quantitative fashion for elucidation of valence-electron structure changes induced by alloying is examined.The special, or "canonical, " property of Pti "Cu, , that one of the components, Pt, displays no measurable core-level shift, permits extraction of such changes from core-level and valenceband data alone. A relation between the d-resonant level shifts and the centroid of the valence-band spectra is derived and comparison of' the centroid and core-level shifts leads to the desired information. The analysis indicates that there is»o charge transfer in the system and that only Cu has significant valence occupation changes upon alloying, corresponding to dehybridization. Furthermore, information regarding Fermi-energy shifts is extracted and not required as inputthe results suggest that the shifts of the Fermi levels cannot be identified with those of the work functions as in other work. Model calculations indicate that dehybridization is to be expected as an "antihybridization" effect for a narrow il-band metal in a wide i/-band one.

Pt–Cu Bimetallic Alloy Nanoparticles Supported on Anatase TiO2: Highly Active Catalysts for Aerobic Oxidation Driven by Visible Light

“…X-ray photoelectron spectroscopy (XPS) of the alloy catalysts (Figure S2, Supporting Information) shows Pt 4f peaks (70 and 74 eV) and a Cu 2p peak (∼932 eV) . As observed for related Pt–Cu alloy systems, − the increase in Cu amount shifts the Cu peak to lower binding energy due to the expansion of atomic distance, although the Pt peak scarcely shifts. The surface Pt/Cu ratio of metal particles on Pt 0.8 Cu 0.2 /anatase determined by XPS analysis is 4.02 mol/mol.…”

XPS core-level shifts and XANES studies of Cu-Pt and Co-Pt alloys

“…We studied the relation between the XPS core-level shifts and the valence-state changes in Cu-Pt and Co-Pt alloys through the estimation of changes in the unoccupied density of state by XANES. The Cu-Pt and Co-Pt alloys are interesting from the point of view of their catalytic 7,8 and magnetic 9 -12 properties, respectively.…”

Highly Active Carbon Supported PtCu Electrocatalysts for PEMFCs by in situ Supercritical Deposition Coupled with Electrochemical Dealloying

“…All of the XPS spectra from the prepared electrocatalysts exhibited metallic Pt and Cu peaks (see Figures S1 and S2 in Supporting Information) indicating successful conversion of the precursors during in situ SCD. Furthermore, for all of the electrocatalysts, the Cu peaks were shifted to lower binding energies due to alloying with Pt . Furthermore, pre‐annealing C 1 s spectra of PtCu/CA sim and PtCu/Vulcan sim samples exhibited a peak at around 291–292 eV that can be attributed to CF 2 species on the surface.…”