Showing papers by "Jens K. Nørskov published in 1998"

Effect of Strain on the Reactivity of Metal Surfaces

Abstract: Self-consistent density functional calculations for the adsorption of O and CO, and the dissociation of CO on strained and unstrained Ru(0001) surfaces are used to show how strained metal surfaces have chemical properties that are significantly different from those of unstrained surfaces. Surface reactivity increases with lattice expansion, following a concurrent up-shift of the metal $d$ states. Consequences for the catalytic activity of thin metal overlayers are discussed.

Design of a Surface Alloy Catalyst for Steam Reforming

Abstract: Detailed studies of elementary chemical processes on well-characterized single crystal surfaces have contributed substantially to the understanding of heterogeneous catalysis. Insight into the structure of surface alloys combined with an understanding of the relation between the surface composition and reactivity is shown to lead directly to new ideas for catalyst design. The feasibility of such an approach is illustrated by the synthesis, characterization, and tests of a high-surface area gold-nickel catalyst for steam reforming.

Alkali promotion of N-2 dissociation over Ru(0001)

Abstract: Using self-consistent density functional calculations, we show that adsorbed Na and Cs lower the barrier for dissociation of N2 on Ru(0001). Since N2 dissociation is a crucial step in the ammonia synthesis reaction, we explain in this way the experimental observation that alkali metals promote the ammonia synthesis reaction over Ru catalysts. We also show that the origin of this effect is predominantly a direct electrostatic attraction between the adsorbed alkali atoms and the dissociating molecule. [S0031-9007(98)06016-5]

Process for steam reforming of hydrocarbons

Abstract: Process for catalytical steam reforming a carbonaceous feedstock without any carbon formation, wherein the feedstock is contacted with a nickel catalyst further including gold in an amount of 0.01 to 30% by weight calculated on the amount of nickel in the catalyst.

N2 Interaction with Fe Surfaces

Abstract: Recent density functional theory calculations of the energetics of N2 dissociation on Fe(111) and atomic N adsorption on all three low-index Fe surfaces have given new detailed information about precursors for dissociation, new reaction channels, and new surface structures. We analyze the consequences of this insight for the surface structures on Fe catalysts during ammonia synthesis and for the kinetics and dynamics of the N2 dissociation process.

Sulphur Bonding in Transition Metal Sulphides and MoS2 Based Structures

Abstract: In order to aid the development of new hydrodesulphurization (HDS) catalysts, several useful structure-activity relationships have been established for both unpromoted and promoted catalysts [1]. For the unpromoted catalysts, the activity has been attributed to sites at the MoS2 edges, whereas for Co or Ni promoted catalysts, mixed Co-Mo-S and Ni-Mo-S structures at the edges have been observed to be responsible for the increased activity. It is generally believed that fully coordinated sulphided catalysts will be unable to adsorb sulphur-containing molecules, and that sulphur vacancies must be created to provide catalytically active sites. The number of sulphur vacancies is hereby a key measure of the catalytic activity.