Modeling gold nanoparticles:: Morphology, electron structure, and catalytic activity in CO oxidation

Morphology, electron structure, and catalytic activity in CO oxidation over a Au/FeOx/SiO2/Si(100) model sample prepared by pulsed laser deposition (PLD) have been investigated by X-ray photoelectron spectroscopy (XPS), UV photoelectron spectroscopy (UPS), and transmission electron microscopy (TEM). Two types of sample were prepared denoted by PLD I and PLD II, the latter being prepared by multiple laser deposition alternatively by iron and gold. PLD I was characterized in "as prepared" oxidized and reduced states, the respective gold particle sizes being 3.8, 4.1, and 5 nm; the iron oxide support was amorphous after the first two treatments while it was partially crystallized after reduction. The activity in CO oxidation increased after oxidation of the sample, whereas it was diminished after subsequent reduction. XPS studies showed that higher activity was associated with amorphous iron oxide with Fe 2p binding energy = 711.3 eV. It was established that in developing the catalytic activity the gold should be metallic and the support should be amorphous with high binding energy and the reaction occurs at the perimeter of gold particles. PLD II has a slightly lower activity which might be the result of more crystalline phase in the iron oxide.