Modelling the NH3 + NO reaction on Pt{100}.

I. M. IRURZUN

Tandil Argentina

Conferencia; XV Congreso de la Asociación Argentina de Investigación en Fisicoquímica.; 2007

The catalytic reduction of NO on metal surfaces has been intensely studied in recent years due to the deleterious effect of NO in the atmosphere. Aside from these practical aspects, work function and mass spectrometric measurements revealed that these reactions very often exhibit interesting dynamic behavior such as multiple steady states and regular or chaotic temporal oscillations in the rate of the reaction or in the partial pressures of the reactants. These phenomena have been observed, for example, during the reduction of NO with NH3 on polycrystalline and single-crystal metal surfaces and under ultrahigh vacuum conditions where the reaction proceeds isothermally. Under such conditions the mechanism underlying the oscillatory behavior has been well established and can be explained by the existence of a reversible adsorbate-induced phase transition in the crystalline structure that causes a periodic switching between two states with different catalytic activity. The spatiotemporal distribution of adsorbates on the surface has been experimentally investigated by photoemission electron microscopy (PEEM), revealing a rich variety of spatial patterns and waves. These spatial features are well documented today and are common to a wide class of nonequilibrium systems. From the theoretical point of view, calculations based upon the Density Functional Theory have been made reveling the atomistic distribution of the chemical species, and allowing the calculation of the activation energies of the surface processes. Based upon these information kinetic models have been developed to describe temporal behavior, in the so-called mean field approximation. In the present talk we review both the experimental and theoretical information about the NO + NH3 reaction on Pt{100}and present a brand new kinetic mechanism for this reaction.