Structure and Properties of Ultrathin SiO x Films on Cu(111).

The metal-oxide interface plays a crucial role in catalysis, and it has attracted increasing interest in recent years. Cu/SiO 2 , as a common copper-based catalyst, has been widely used in industrial catalysis. However, it is still a challenge to clarify the structures of the interface of Cu-SiO x and the effect on catalytic performance. Herein, we prepared ultrathin SiO x films by evaporating Si onto a Cu(111) surface followed by annealing in an O 2 atmosphere, which were characterized by various surface science techniques. The results showed that a SiO x film could grow nearly layer-by-layer on the Cu(111) surface in the present condition. Both X-ray photoelectron spectroscopy (XPS) and high-resolution electron energy loss spectroscopy (HREELS) results confirmed the presence of Cu-O-Si and Si-O-Si species. Thermal stability experiments illustrated that the well-ordered silica films were stable under annealing in vacuum. The feature of CO adsorption suggested a CO-Cu δ+ species induced from the Cu δ+ -O-Si. Low-energy ion scattering spectroscopy (LEIS) and XPS results demonstrated that some Cu 2 O appeared on the surface when the 1 ML SiO x /Cu(111) was exposed in O 2 at 353 K.