Initial stages in the oxidation and reduction of the 4x4 surface oxide phase on Ag{111}: A combined density-functional theory and STM simulation study

With density-functional theory, we have examined the initial stages in the oxidation and reduction of the high coverage Ag1.83O 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 Ag1.83O 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 Ag1.83O 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.