Characterization and Chemical Properties of Pd−Au Alloy Surfaces^†

Abstract

The chemisorptive behavior of CO on Pd−Au alloy films has been studied by infrared reflection−adsorption spectroscopy (IRAS). Geometric (ensemble) and electronic (ligand) effects have been addressed by comparing the results with the corresponding single-component systems. A unique CO vibrational feature at 2088 cm-1 is associated with CO adsorption on isolated Pd sites. Considering the frequency of the CO stretching mode, these data support mainly an influence of an ensemble effect on the chemical properties and contradict any significant contribution from a ligand effect. The surface concentration of isolated Pd sites can be controlled systematically by altering the bulk Pd−Au alloy composition, thus providing a method for studying isolated Pd as an active site for various catalytic reactions.

From Adlayer Islands to Surface Alloy: Structural and Chemical Changes on Bimetallic PtRu/Ru(0001) Surfaces

“…In combination with adsorption/catalysis studies on these structurally well-defined surfaces, such model systems provide an ideal test case for different effects discussed as physical origin for the modified chemical and catalytic surface properties. [6][7][8][9][10][11][12][13] As part of an extensive study on the (electro-)chemical properties of bimetallic PtRu surfaces and their correlation with their structural characteristics, [6,[13][14][15][16][17][18] herein we focus on the structural modifications encountered at the transition from an overlayer system, such as a Pt monolayer or Pt monolayer island covered Ru(0001) surface, to a surface alloy, and their effect on the chemical surface properties. The structural properties of laterally equilibrated bimetallic PtRu/Ru(0001) surfaces were already studied in detail by STM.…”

Magnetically recyclable Fe–Ni alloy catalyzed dehydrogenation of ammonia borane in aqueous solution under ambient atmosphere

“…Bimetallic nano-alloys are currently attracting much attention as catalysts due to the distinct catalytic properties from those of the pure elemental nanomaterials [1][2][3][4][5]. As catalysts, their separation and recycling are essential steps and frequently affect the overall process economy.…”

CO Oxidation over AuPd(100) from Ultrahigh Vacuum to Near-Atmospheric Pressures: The Critical Role of Contiguous Pd Atoms

“…13 CO vibrational features can be assigned accurately based on previous studies: ν CO at >2100 cm -1 corresponds to atop CO on Au sites; ν CO at 2060-2085 cm -1 , to atop CO on isolated Pd sites; and ν CO between 1900 and 2000 cm -1 , to bridging CO on contiguous Pd sites. [14][15][16] The key information addressed by Figure 1 is that gas-phase CO pressures higher than 1 × 10 -3 Torr are required to segregate a sufficient amount of Pd to the surface to form contiguous Pd sites. To be more precise, a CO pressure of ∼0.1 Torr is required for the formation of a significant population of contiguous Pd sites at the surface (supporting data 1).…”