Activity of TiO2 overlayer deposited on Au/SiO2/Si(1 0 0) model system

TiO2 layer was deposited by pulsed laser deposition (PLD) technique onto either 8- or 60-nm thick Au films supported by SiO2/Si(1 0 0). The samples were characterized in catalytic CO oxidation. Comparison was made with reference samples both of TiO2/SiO2/Si(1 0 0) and Au/SiO2/Si(1 0 0) layers. The initial activity of TiO2/Au/SiO2/Si(1 0 0) turned out to be significantly lower than that of TiO2/SiO2/Si(1 0 0), while the Au/SiO2/Si(1 0 0) was the least active. The catalytic activity of the TiO2/Au/SiO2/Si(1 0 0) samples must be attributed to active sites located on the TiO2 overlayer modified by gold underneath, since no Au was exposed to the surface according to the X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). The inhibiting effect of gold on the catalytic activity of TiO2 overlayer was discussed in terms of electronic interactions at the Au/TiO2 interface.