Growth, Structure, and Catalytic Properties of ZnOx Grown on CuOx/Cu(111) Surfaces

A catalyst with a ZnO/Cu configuration plays an important role in the synthesis of methanol from CO2 hydrogenation. In this study, scanning tunneling microscopy and X-ray photoelectron spectroscopy (XPS) were used to investigate the growth mode of small coverages of ZnOx, θoxi < 0.3 monolayer, on a Cu(111) substrate. Our results show that the modes of growth, size, and shape of the ZnO nanoparticles are strongly dependent on the Zn deposition temperature. In a set of experiments, Zn was deposited on Cu(111) or CuOx/Cu(111) surfaces at 300 K with subsequent exposure to O2 at higher temperatures (400–550 K), which exhibited small particles of ZnO (<20 nm in size) on the surface. The deposition of Zn onto CuOx/Cu(111) at elevated temperatures (450–600 K) in an oxygen ambient produced large ZnO islands (300–650 nm in size), which were very rough and spread over several terraces of Cu(111). XPS/Auger spectra showed that all of the preparation conditions stated above led to the formation ZnO/CuOx/Cu(111) surfac...