Alkali metals on metals

Mathematical Modeling of Reactive Phase Separation in the System Rh(110)/K/O2 + H2

“…Under our reaction conditions, potassium does not desorb so that we have only a redistribution of a fixed amount of potassium on the surface. Potassium has a high chemical affinity to oxygen. − The strong attractive interactions between coadsorbed oxygen and potassium cause potassium to migrate from an oxygen freed part of the surface to a still oxygen covered part, as indicated schematically in the energy diagram of Figure . The gain in adsorption energy E b for potassium in the presence of coadsorbed oxygen has been demonstrated in thermal desorption experiments of Rh(110)/K/O as well as in theoretical calculations. , Experiments, in which an inhomogeneous distribution of potassium was homogenized again by turning off one of the reactants, H 2 or O 2 , showed that potassium spreads out rather rapidly on the reduced surface but comparatively slowly on the oxygen covered surface.…”

“…Alkali metals are well-known as so-called electronic promoters in a number of important catalytic reactions such as ammonia synthesis via Haber-Bosch or synthetic fuel production via Fischer−Tropsch. − Recent experiments demonstrated that alkali metals not only modify the local electronic properties of the surface but also participate in the spatiotemporal dynamics of a surface reaction. This was shown in the O 2 + H 2 reaction on a potassium covered Rh(110) surface. − Reaction fronts transporting potassium and stationary concentration patterns were observed in this system.…”