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

ABSTRACT

The metal-oxide interface plays a crucial role in catalysis, and it has attracted increasing interest in recent years. Cu/SiO2, 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-SiOx and the effect on catalytic performance. Herein, we prepared ultrathin SiOx films by evaporating Si onto a Cu(111) surface followed by annealing in an O2 atmosphere, which were characterized by various surface science techniques. The results showed that a SiOx 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-Cuδ+ species induced from the Cuδ+-O-Si. Low-energy ion scattering spectroscopy (LEIS) and XPS results demonstrated that some Cu2O appeared on the surface when the 1 ML SiOx/Cu(111) was exposed in O2 at 353 K.