Portal de Periódicos da CAPES

Alumina-Supported Vanadium Nanoparticles: Structural Characterization and CO Adsorption Properties

2004; American Chemical Society; Volume: 126; Issue: 11 Linguagem: Inglês

10.1021/ja039278s

1943-2984

Norbert Magg, Javier B. Giorgi, Martin M. Frank, Boonchuan Immaraporn, Thomas Schroeder, Marcus Bäumer, Hans‐Joachim Freund,

Advanced Chemical Physics Studies

Alumina-supported vanadium particles were prepared under ultrahigh vacuum (UHV) conditions and characterized with respect to their structural and CO adsorption properties. As supporting oxide, we used a thin, well-ordered alumina film grown on NiAl(110). This allows the application of scanning tunneling microscopy (STM), infrared reflection-absorption spectroscopy (IRAS), and X-ray photoelectron spectroscopy (XPS) without charging effects. Vanadium evaporation under UHV conditions leads to the growth of nanometer-sized particles which strongly interact with the alumina support. At very low vanadium coverages, these particles are partially incorporated into the alumina film and get oxidized through the contact to alumina. Low-temperature CO adsorption in this coverage regime permits the preparation of isolated vanadium carbonyls, of which we have identified mono-, di-, and tricarbonyls of the V(CO)(y)() type. A charge-frequency relationship was set up which allows one to quantify the extent of charge transfer from vanadium to alumina. It turns out that this charge transfer depends on the V nucleation site.