Interplay between Layer-Resolved Chemical Composition and Electronic Structure in a Sn/Pt(110) Surface Alloy

Abstract

Pt–Sn alloys play an important role as oxygen reduction reaction (ORR) catalysts in fuel cell technology both for their role in rationalizing the mechanism responsible for the better performances of bimetallic catalysts and for their practical applications.\ud Here we present a complete experimental and theoretical study on the geometric and electronic structure of a (4×1) termination over a Pt3Sn near-surface ordered alloy obtained by depositing Sn on the Pt(110) and subsequent annealing. LEED and STM measurements combined with DFT simulations, allow us to determine the atomistic structure of this phase, and to rationalize the peculiar dependence of its STM pattern on the applied bias and the compositional order in deep layers. Both photoemission\ud experiments and density functional calculations indicate that in this phase the Sn-Pt alloying process determines important changes in the electronic properties, and in particular a relevant shift of the Pt 5d band centroid with respect to clean Pt

Multiple Reaction Paths for CO Oxidation on a 2D SnOx Nano‐Oxide on the Pt(110) Surface: Intrinsic Reactivity and Spillover

“…After the ultra high vacuum (UHV) deposition of Sn on the Pt(110) surface, three distinct ordered PtSn nano‐alloys can be formed, as reported in detail in our previous studies. [15a,d,e] These surface alloys can be then converted to different nano‐oxides by dosing molecular oxygen at moderate temperature. By optimizing the growth conditions, single phases can be formed all over the surface.…”

“…The Sn 4d spectra are constituted by a large doublet that contains the contribution from several different chemically shifted components. In the following analysis, the Sn(II), Sn(IV), Sn‐Pt, and Sn‐Sn components have been taken as reference[15c,e,21] (see Table and the discussion below).…”

“…According to the data reported in Table , the Sn 4d photoemission line of the c(2 × 4) surface can be fitted by three distinct components related with the following Sn species[15a,c,21b]:Sn a at ≈24.7 eV corresponding to Sn in Pt 3 Sn;Sn b at ≈25.6 eV assigned to Sn(II);Sn c at ≈26.0 eV assigned to Sn(IV).…”

“…To optimize the activity/durability of bimetallic real electrocatalysts , a surface science–based approach applied to appropriate model systems offers a suitable route to increase our understanding of these materials. Within this context, surfaces of single crystal alloys and their oxides or, alternatively, surface alloys and oxides[15a,d,e,16a,17] can be fabricated with atomic‐scale precision by evaporating one of the two metals on the single crystal of the other, followed by thermal annealing. The processes occurring on these model electrocatalysts (such as alloying, corrosion, or redox processes) can be precisely monitored by the tools offered by modern surface science and the results can be easily transferred to real applications.…”

“…This work completes and complements our previous reports on the PtSn x /Pt(110) surface alloys and their oxidized counterparts. [15d,e] The reactivity toward CO is of particular relevance for the use of electrocatalysts in PEMFCs that use reformate gas as the main fuel.…”