Structure and Morphology of Silver Nanoparticles on the (111) Surface of Cerium Oxide

Francesco Benedetti,Federico Boscherini,Gabriele Gasperi,Sergio D’Addato,Maria Chiara Spadaro,Sergio Valeri,Paola Luches

doi:10.1021/jp5120527

Abstract

The structure of Ag nanoparticles of different size, supported on the cerium oxide (111) surface, was investigated by X-ray absorption fine structure at the Ag K-edge. The results of the data analysis in the near and extended energy range are interpreted with the help of the results obtained by X-ray photoelectron spectroscopy and scanning tunneling microscopy measurements and allow to obtain a detailed atomic scale description of the model system investigated. The Ag nanoparticles have an average size of a few tens of angstroms, which increases with increasing deposited Ag amount. The nanoparticles show a slight tendency to nucleate at the step edges between different cerium oxide layers and they have a face centered cubic structure with an Ag–Ag interatomic distance contracted by 3–4% with respect to the bulk value. The interatomic distance contraction is mainly ascribed to dimensionality induced effects, while epitaxial effects have a minor role. The presence of Ag–O bonds at the interface between the ...

Highlights

The structure of Ag nanoparticles of different size, supported on the cerium oxide (111) surface, was investigated by X-ray absorption fine structure at the Ag K-edge
The information obtained by X-ray absorption fine structure (XAFS) are complemented by a characterization using surface science techniques, such as X-ray photoemission spectroscopy (XPS) and scanning tunneling microscopy (STM) and give a detailed atomic scale description of the investigated system
The NPs show some tendency to nucleate at ceria step edges, many of them are located on the cerium oxide terraces

Summary

Introduction

The structure of Ag nanoparticles of different size, supported on the cerium oxide (111) surface, was investigated by X-ray absorption fine structure at the Ag K-edge. X-ray absorption fine structure (XAFS) measurements in the near and extended energy range have proved to be very useful to have information on the structure and on the oxidation state of the cations in cerium oxide[19,20,21,22] and of metallic NPs supported on cerium oxide,[23,24,25] including the Ag/CeO2 system.[9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26] previous studies addressed the structure of complex powdered systems, containing a wide variety of different NP/oxide interfaces. The same fitting ranges were used for the Ag and Ag2O reference sample spectra, to avoid systematic errors

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