Pd on Cu(110): growth mode monitored by LEIS

Abstract

Metal on metal deposits can have very different, and interesting, physical and chemical properties compared with those of the pure metal. In this framework we investigated the behaviour of low amounts of palladium deposited at 300 K on the (110) face of copper, but copper is known to have a lower surface energy than palladium and therefore will tend to segregate at the surface, a process that depends on the temperature.The absolute calibration of the Pd deposit was made on a polycrystalline Cu sample with the combined use of XPS and Rutherford backscattering spectroscopy: for 6 × 10 15 Pd atoms cm −2 , the intensity ratio of Pd 3d5/2 /Cu 3s is 7.2.For Pd deposited at room temperature on Cu(110), the presence of a large amount of copper at the surface is clearly evidenced by low-energy ion scattering. The Pd atomic concentration at the surface does not exceed 15% for one monolayer (ML) of Pd deposited (1 ML = 1.1 × 10 15 Pd atoms cm −2 ). This indicates either that Pd does not spray uniformly at the surface or that Cu diffusion and alloying effects do exist.These results are discussed in relation with some catalytic properties of the Pd on Cu(110) adlayers.

Influence of Preparation Methods on the Catalytic Activity of Pd–Cu/Mn2O3 Catalyst in the Hydrogenation of 1,3-Butadiene

“…Diverse methods have been employed to synthesize either single or alloy-supported Pd catalyst for the hydrogenation of 1,3-butadiene. Until recently, the preparation methods were limited to co-deposition–precipitation (DP) of metallic salts onto supports stabilized by polymers, dendrimers, , co-impregnation/impregnation (IP) of supports with prepared metallic solutions and subsequent calcinations at desired temperatures, argon-ion etching and calcinations at desired temperatures, and chemical reduction to produce metal colloids using reductants ( l -ascorbic acid, NaBH 4 , etc.) and stabilizers such as poly­(vinylpyrrolidone) (PVP) before affixing onto supports with the stabilizers removed by calcinations of the as-produced catalyst …”

The structure formed by the deposition of a sub-monolayer quantity of platinum onto Cu(110) investigated using medium energy ion scattering

“…This system has been studied primarily using scanning tunnelling microscopy (STM) [12,13,14,15,16] in combination with Auger electron microscopy (AES) [15], LEED [15,16], X-ray photoelectron spectroscopy [16] and reflection anisotropy spectroscopy [13]. There is also a report of an investigation using LEIS [17] which found that for deposition of 1 ML equivalent at room temperature only 15% of the palladium was visible in the surface layer, with copper atoms remaining visible.…”