Modeling gold/iron oxide interface system

The effect of gold particle size and Au/FeO _x interface on the electronic properties and catalytic activity using samples of Au/SiO₂/Si(100), Au/FeO _x /SiO₂/Si(100), FeO _x /Au/SiO₂/Si(100) has been modelled. Nanosize gold particles of varying size were fabricated by deposition of a 10 nm thick gold film onto SiO₂/Si(100) substrate by electron beam evaporation followed by modification using low energy Ar⁺ ion bombardment or Ar⁺ ion implantation. These modifications formed Au islands of decreasing size accompanied by the strong redistribution of the Au 5d valence band structure determined by ultraviolet and X-ray photoelectron spectroscopy (UPS, XPS) and increased activity in catalytic CO oxidation. The gold/iron oxide interface was prepared by deposition of iron oxide using pulsed laser deposition (PLD). The structural properties of gold and iron oxide were characterized by XPS, atomic force microscopy (AFM), transmission electron microscopy (TEM) and secondary ion mass spectroscopy (SIMS). Generally, the formation of gold/iron oxide interface increases the catalytic activity in CO oxidation regardless of the sequence of deposition, namely either Au/FeO _x /SiO₂/Si(100) or FeO _x /Au/SiO₂/Si(100) is formed. Furthermore, the interface formed is operative in determining the catalytic activity even if gold is not exposed to the surface, but it is located underneath the iron oxide layer. This is a promoting effect of the Au nanoparticles, which is more efficient than that of the bulk like Au films.