Initial stages in the oxidation and reduction of the4×4surface oxide phase on Ag{111}: A combined density-functional theory and STM simulation study

Abstract

With density-functional theory, we have examined the initial stages in the oxidation and reduction of the high coverage ${\mathrm{Ag}}_{1.83}\mathrm{O}$ oxide phase that forms on Ag{111}. Various oxidized and reduced structures have been identified and their relative energies assessed at 0 K and at finite temperatures and pressures. We find that in the temperature and pressure regime characteristic of industrial epoxidation conditions, the ${\mathrm{Ag}}_{1.83}\mathrm{O}$ oxide is easily oxidized and reduced demonstrating a high chemical flexibility of this oxide for redox reactions. In addition scanning tunneling microscopy (STM) image simulations have been performed. These reveal that as well as the ${\mathrm{Ag}}_{1.83}\mathrm{O}$ oxide structure previously proposed a second oxide overlayer is consistent with reported STM images of this system, making this different oxide overlayer another likely candidate for the surface structure obtained in the experiment.