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

Abstract

The K and L 2;3 absorption edges and core-level binding-energy shifts for pure Co, Cu and Pt and Co-Pt and Cu-Pt alloys are measured to investigate changes in electronic structures of these alloys. Enhancements and depletion of the white lines in the alloys as compared to pure elements were correlated with changes in the unoccupied density of states upon alloying. We find that the Pt atoms lost d 3=2 electrons and gained d 5=2 electrons when alloyed with Cu and Co. However, the total 5d occupancy changes of the Pt were very little in Cu-Pt alloys, and this is consistent with the small shifts of Pt 4f core-level binding energy. From the quantitative analysis of Cu and Co K-edge absorption spectra, it is found that Cu and Co have significant valence occupation changes due to dehybridization of p-d states. From these results, we suggest that the core-level shifts are affected mainly by the d-valence electron changes in these alloys.

In situ XPS investigation of Pt(Sn)/Mg(Al)O catalysts during ethane dehydrogenation experiments

“…It has been observed previously that tin induces a shift of the Pt 4f7/2 core level to higher BE compared to pure Pt [54]. A shift of the Pt 4f peak to higher BE has also been reported in Co-Pt alloys [55] and upon addition of Sn to Ni-Nb-Sn-Pt alloys [56]. The shape of Pt 4f peaks at 8 Å analysis depth is the same as for the peaks at 15 Å analysis depth.…”

Low-coordinated surface atoms of CuPt alloy cocatalysts on TiO2for enhanced photocatalytic conversion of CO2

“…29 On the other hand, the shift in the Pt 4f 7/2 peak occurs only by 0.02 eV because Cu does not affect the electron density in Pt 5d states. 30 These experimental values are in agreement with the theoretical results obtained by Olovsson et al (Table 1). 31 UPS analysis also corroborates the formation of CuPt alloy.…”

Dual Cocatalysts in TiO2 Photocatalysis

“…For instance, the Cu 2p 3/2 peak of CuPt–TiO 2 has a negative shift of 0.4 eV ( Figure a) compared with Cu–TiO 2 due to the suppressed p–d hybridization, which is due to the interaction of Cu 2p electrons with wide d‐band electrons in Pt . However, the shift of Pt 4f 7/2 peak is negligible (Figure b), indicating that the electron density in Pt 5d states is not influenced by Cu atom, because of no charge transfer into the Pt d‐band in Cu–Pt alloys . The shift of binding energy can also be observed in the Au–Pt alloyed TiO 2 photocatalysts.…”