Catalytic CO oxidation on a dysprosium-promoted Pt(1 1 1) surface

Abstract

The catalytic CO oxidation reaction has been studied on a dysprosium precovered Pt(111) single-crystal surface in UHV (partial pressures of reactants up to 10−5Torr range) using mass-spectrometry. The experiments show that the CO oxidation reaction proceeds effectively on the Pt(111) surface in the presence of a submonolayer of coadsorbed Dy (0.05–0.15ML) retaining its bistable behavior known for the promoter-free Pt(111). Coadsorption of Dy leads to a remarkable shift of the reactive phase diagram (bifurcation diagram) towards higher CO pressures. An increase in the Dy coverage leads to a progressing decrease in the reaction rate, the transitions between the reactive and inactive states then become diffuse, the hysteresis collapses and at θDy≈0.75 the reaction becomes practically damped. The results are discussed in terms of redistribution of the electron density near the surface induced by the coadsorption of Dy that influences the sticking coefficient of oxygen, binding energy of reacting particles and their interaction on the substrate surface.