Core-level binding-energy shifts at surfaces and in solids

The effect of gold particle size on AuAu bond length and reactivity toward oxygen in supported catalysts

Publisher Summary This chapter discusses the catalysis by alloys in hydrocarbon reactions. With solution alloys the effect of alloying on the electronic structure is surprisingly small, and also with intermetallic compounds these effects are not very pronounced. The effect of alloying on catalytic reactions depends very much on the mechanism of the catalytic reaction and on the type of intermediates operating upon reaction. In parallel-running, simultaneous reactions, the alloying effect is very pronounced if in order for a reaction to occur, large ensembles of certain metal atoms are required. However, the fact that certain metal atoms are required is itself evidence of the importance for catalysis of the electronic structure of metal atoms. The selectivity in consecutive reactions (hydrogenation of multiple unsaturated molecules) sometimes depends on the heat of adsorption of the starting molecules and intermediate products, and as heats of adsorption are usually only marginally affected by alloying, alloying does not change this kind of selective behavior of metals.

Catalysis by Alloys in Hydrocarbon Reactions

An overview on the electronic and vibrational properties of adsorbed CO

Nature of nitrogen adsorbed on transition metal surfaces as revealed by electron spectroscopy and cognate techniques

Ultraviolet photoemission spectra of Cu atoms and clusters isolated at 7 K in Ar, Kr, and Xe matrices have been measured using He I and He II radiation. For single matrix‐isolated Cu atoms, d‐level emission around 5.1 eV below EF (9.3 eV below Evac) has been observed in all three matrices. Comparison with respective gas phase data yields a relaxation shift (for the 3d94s1 final state) of about 1.3 eV. For matrix‐isolated Cu clusters the emission peak due to d‐band emission is independent of the matrix gas, indicating that the relaxation is solely determined by the cluster itself, rather than by the surrounding matrix. In the matrices doped with clusters the emission from the np levels of the noble gas atoms is markedly modified by the dopant. It is shown that the relaxation of the np levels is dominated by the Cu clusters, yielding emission spectra similar to those from physisorbed noble gases.

D. Schmeißer

Papers

Photoemission study of matrix isolated Cu atoms and clusters

Adsorption of molecular nitrogen on copper clusters and nickel films at 7 K