Synchrotron radiation study of chemisorptive bonding of CO on transition metals — Polarization effect on Ir(100)☆

NO adsorption on metal surfaces has been studied extensively due to its important role in many catalytic processes In the past, it was recognized that the tendency for a metal surface to dissociate NO depends on its position in the periodic table, but little was understood about the dissociation process itself Recent experimental and theoretical studies have shown that this view is oversimplified In addition to the distinction between molecular and dissociative adsorption on surfaces, the structure of NO on metal surfaces has also been the subject of detailed study and debate It is therefore timely to update our ideas about NO adsorption and reactivity Here we examine the structure of NO on surfaces, in particular the break-down of vibrational assignments and we look at how these assignments can be improved The NO dissociation process is also discussed along with the formation, and reactions, of the NO dimer, (NO)(2), on some metal surfaces

NO Chemisorption and Reactions on Metal Surfaces: A New Perspective

The adsorption of CO, O2, and H2 on Pt: I. Thermal desorption spectroscopy studies☆

The mechanism of NOx decomposition is reviewed. This reaction is first studied on metal or oxide single crystals, in order to get solid basis from catalysis on well-defined surface structures. If we understand few things about this reaction, at least the catalytic surface is known. This statement is not 100% correct, as the surface is reconstructed during the catalytic reaction; and this point is considered in the manuscript. Then we analyse this reaction on metallic catalysts supported on metal oxides. The crystallites are more or less dispersed, and the support can play the role of a modifier or of a promoter. A general consensus emerges on (i) the chemisorption of the reactant(s) which causes adsorbate-induced restructuring of the surfaces, (ii) the substrate, which is influenced by the redox properties of the support and by the particle sizes of the metallic aggregates, (iii) the fact that low-coordinated surface atoms are the more active in NO bond breaking, and (iv) the general pathways of the reaction, where redox mechanisms involving nitrosyl species, as intermediates, moving to nitrite-nitrosyl or dinitrosyl species are proposed. All these points are discussed.

Mechanism of NOx decomposition

Interaction of NO with a Ni (111) surface

We describe adsorption studies of serveral inorganic and organic species on single crystal Ni(111) using ultraviolet photoemission spectroscopy (hv=21.2 eV). Adsorbate orbital ionization energies and line shapes have been measured and surface reactions have been studied. Ionization energies for chemisorbed unsaturated hydrocarbons (C2H2, C2H4, and C6H6) exhibit large surface-induced relaxation shifts (~1–3 eV) relative to their gas phase counterparts as well as π-orbital bonding shifts (~0.9–1.5 eV). We estimate these π-d bonding interaction strengths and chemisorption energies using Mulliken's donor-acceptor theory as described by Grimley for weak chemical bonds and show that an observed surface reaction, i.e. the dehydrogenation of chemisorbed ethylene (C2H4) to chemisorbed acetylene (C2H2) for T\gtrsim230 K, becomes exothermic only for the chemisorbed species due to the π-d electron interaction.

https://iopscience.iop.org/article/10.7567/JJAPS.2S2.827/pdf

D. E. Eastman

Papers

Photoemission Studies of Inorganic (CO, O, NO) and Organic (C2H2, C2H4, C6H6) Adsorbates on Ni(111) and Surface Reactions