Interaction of CO with PtxAg1-x/Pt(111) surface alloys: More than dilution by Ag atoms

Reactivity of CO and C2H4 on Bimetallic PtxAg1‐x/Pt(111) Surface Alloys Investigated by High‐Resolution X‐ray Photoelectron Spectroscopy

“…Notably, we find occupied bridge sites for all alloys, even for those with the highest Ag content. This is in contrast to earlier IRAS results,, where bridge CO was only detected for alloys with an Ag content below ∼30 %. The authors proposed that at higher Ag coverages large continuous Pt surface areas are missing and that it is not possible to form long‐range ordered c(4×2)‐adsorbate layers that allow for CO adsorbed on bridge sites.…”

“…confirmed that for submonolayer coverages alloy formation above 550 K is restricted to the topmost layer . Finally, a strong tendency for phase separation in these surface alloys was demonstrated by quantitative STM analysis, that is, the formation of larger homo‐atomic ensembles is preferred compared to a random distribution of surface atoms …”

“…We first discuss the formation of the Ag x Pt 1‐x /Pt(111) surface alloys that were prepared for the CO and C 2 H 4 experiments. This bimetallic system is well‐known in literature and characterized with several techniques including XPS, TPD, STM, LEED and DFT ,,. Annealing submonolayer coverages of Ag adsorbed on Pt(111) to above ∼600 K leads to the formation of a 2D surface alloy.…”

“…By varying the evaporation time it was possible to achieve the desired Ag amounts on the sample, which were in line with the intensity of the corresponding Ag 3d XP spectra. The sample temperature was kept below 200 K during evaporation and afterwards the Ag x Pt 1‐x /Pt(111) surface alloys were prepared by annealing at 800 K for 1 minute ,…”

“…Recently, two extensive studies on CO adsorption on Pt x Ag 1‐x /Pt(111) have been performed using TPD, IRAS and DFT ,. The main results are that neighboring Ag surface atoms have a large ligand effect on CO adsorption on Pt surface atoms, which results in an increased 2π* back‐donation and thus a strengthened Pt−C bond.…”