Showing papers by "Jens K. Nørskov published in 2002"
TL;DR: In this paper, it was shown that for a class of catalytic reactions there is a universal, reactant independent relation between the reaction activation energy and the stability of reaction intermediates.
1,128 citations
TL;DR: Based on density functional theory calculations, kinetic measurements, microkinetic and Monte Carlo simulations, thermogravimetric analysis (TGA) experiments, extended X-ray absorption spectroscopy (EXAFS) measurements, and experimental results from the literature, this paper presented a detailed and comprehensive mechanistic picture of the steam reforming process on a Ni catalyst.
1,002 citations
TL;DR: First principles calculations are discussed, which can aid in the establishment of chemisorption trends across the transition metals, in the characterization of reaction pathways on individual metals, and in the design of novel catalysts.
Abstract: The powerful computational resources available to scientists today, together with recent improvements in electronic structure calculation algorithms, are providing important new tools for researchers in the fields of surface science and catalysis. In this review, we discuss first principles calculations that are now capable of providing qualitative and, in many cases, quantitative insights into surface chemistry. The calculations can aid in the establishment of chemisorption trends across the transition metals, in the characterization of reaction pathways on individual metals, and in the design of novel catalysts. First principles studies provide an excellent fundamental complement to experimental investigations of the above phenomena and can often allow the elucidation of important mechanistic details that would be difficult, if not impossible, to determine from experiments alone.
881 citations
TL;DR: In this article, the authors provide a coherent description of the catalysis of the steam reforming reactions, focusing on the role of the catalyst and problems related to carbon formation, and provide a summary of the empirical evidence of the reforming reactions.
Abstract: Steam reforming reactions will play a key role in new applications of synthesis gas and in a future hydrogen economy. The aim of this review is to provide a coherent description of the catalysis of the reforming reactions. The review is not comprehensive. The first section deals with the applications of synthesis gas and hydrogen and the various synthesis gas technologies. The optimum choice of technology depends on the requirements of the gas composition and the scale of operation. Two examples are included for illustration: synthesis gas for gas-to-liquid plants and hydrogen for fuel cells. The steam reforming process is described in the second section with emphasis on the role of the catalyst and problems related to carbon formation. The third section is a summary of the empirical evidence of the catalysis of the reforming reactions. The methods of characterization are discussed, and data representing sintering, activity trends, and promotion are summarized. The fourth section is a description of the mechanism based on a combination of empirical knowledge with recent data from studies of well-defined surfaces, in-situ high-resolution electron microscopy, and calculations based on density functional theory. The central concept is the role of surface defects as the source of reactivity and the nucleation centers for whisker carbon formation.
711 citations
TL;DR: Self-consistent density functional calculations are presented showing that even an isolated Au10 cluster should be able to catalyze the CO oxidation reaction even below room temperature, and suggest that the extraordinary reactivity can be traced back to special reaction geometries available at small particles in combination with an enhanced ability of low coordinated gold atoms to interact with molecules from the surroundings.
Abstract: Gold is usually considered very noble. It does not oxidize, and the surface of gold cannot adsorb most molecules from the gas phase. Yet it has been found that nanometer size gold particles on different oxide supports can act as catalysts even at or below room temperature. We present self-consistent density functional calculations showing that even an isolated Au10 cluster should be able to catalyze the CO oxidation reaction even below room temperature. We use the calculations to analyze the origin of this effect and suggest that the extraordinary reactivity can be traced back to special reaction geometries available at small particles in combination with an enhanced ability of low coordinated gold atoms to interact with molecules from the surroundings.
684 citations
TL;DR: It is shown that density functional theory calculations have reached an accuracy and speed making it possible to use them in conjunction with an evolutionary algorithm to search for materials with specific properties to identify "super alloys".
Abstract: We show that density functional theory calculations have reached an accuracy and speed making it possible to use them in conjunction with an evolutionary algorithm to search for materials with specific properties. The approach is illustrated by finding the most stable four component alloys out of the 192 016 possible fcc and bcc alloys that can be constructed out of 32 different metals. A number of well known and new "super alloys" are identified in this way.
262 citations
TL;DR: In this paper, a systematic study of the chemisorption of both atomic (H, O, N, S, C), molecular (N2, CO, NO), and radical (CH3, OH) species on Rh(111) has been performed, using both PW91 and RPBE functionals.
Abstract: A systematic study of the chemisorption of both atomic (H, O, N, S, C), molecular (N2, CO, NO), and radical (CH3, OH) species on Rh(111) has been performed Self-consistent, periodic, density functional theory (DFT-GGA) calculations, using both PW91 and RPBE functionals, have been employed to determine preferred binding sites, detailed chemisorption structures, binding energies, and the effects of surface relaxation for each one of the considered species at a surface coverage of 025 ML The thermochemical results indicate the following order in the binding energies from the least to the most strongly bound: N2
200 citations
TL;DR: In this article, it was shown that the barrier for CO dissociation is ≃120 kJ/mol lower on the stepped Rh(211) surface than on the close-packed Rh(111) surface.
Abstract: Using periodic self-consistent density functional calculations it is shown that the barrier for CO dissociation is ≃120 kJ/mol lower on the stepped Rh(211) surface than on the close-packed Rh(111) surface. The stepped surface binds molecular CO and the dissociation products more strongly than the flat surface, but the effect is considerably weaker than the effect of surface structure on the dissociation barrier. Our findings are compared with available experimental data, and the consequences for CO activation in methanation and Fischer–Tropsch reactions are discussed.
164 citations
TL;DR: In this paper, the authors show that the strong interaction between gold and rutile TiO2(1/1/0) surface, claimed to be responsible for the enhanced reactivity of the system, does not exist for defect free supports.
123 citations
TL;DR: In this article, the chemical properties of single-atomic chains of gold atoms were investigated using density functional calculations, and the nanochains were shown to be unusually chemically active with strong chemisorption of oxygen atoms and carbon monoxide.
Abstract: The chemical properties of single-atomic chains of gold atoms are investigated using density functional calculations. The nanochains are shown to be unusually chemically active with strong chemisorption of oxygen atoms and carbon monoxide. The chemisorption energies vary significantly with the strain/stress conditions for the chain. Oxygen atoms are found to energetically prefer to get incorporated into a chain forming a new type of gold-oxygen nanochain with a conductance of one quantum unit. We suggest that the long bond lengths observed in electron microscopy investigations of gold chains can be due to oxygen incorporation.
83 citations
TL;DR: In this article, the authors demonstrate that the position of the maximum of the volcano curve is sensitive to the reaction conditions and propose the concept of optimal catalyst curves, which illustrate the nitrogen binding energies of the optimal catalysts at different temperatures, pressures and synthesis gas compositions.
TL;DR: In this article, the effect of adsorption-induced segregation on the surface composition of bimetallic alloys was studied using Monte Carlo simulations, and it was shown that adsorization of CO and O2 on a PtRu alloy increases the concentration of Ru in the surface.
TL;DR: In this article, the authors discuss how to describe catalysis by enzymes, and in particular the analogies between enzyme catalyzed reactions and surface-catalyzed reactions, and show that although analogies exist and the two kinds of catalyst can be described by similar tools, nature and human effort have come up with different solutions, which implies that new and improved catalysts may be made by learning from nature.
TL;DR: In this article, it was shown that steps on the α-Al 2 O 3 surface are enriched in oxygen and that they bind Pd atoms and small clusters much stronger than the terraces.
01 Jan 2002
TL;DR: In this article, it was shown that for a class of catalytic reactions there is a universal, reactant independent relation between the reaction activation energy and the stability of reaction intermediates.
Abstract: Based on an extensive set of density functional theory calculations it is shown that for a class of catalytic reactions there is a universal, reactant independent relation between the reaction activation energy and the stability of reaction intermediates. This leads directly to a universal relationship between adsorption energies and catalytic activity, which is used to pinpoint what it is that determines the best catalyst for a given reaction. The universality principle rationalizes a number of known facts about catalysts and points to new ways of improving them. c � 2002 Elsevier Science (USA)
Patent•
17 Oct 2002
TL;DR: In this paper, the performance of low-temperature fuel cell anodes for PENFC fuel cells and direct methanol fuel cells has been evaluated for low temperature fuel cells.
Abstract: Catalyst materials having a surface comprising a composition Mx/Pt3/Sub; wherein M is selected from the group of elements Fe, Co, Rh and Ir; or wherein M represent two different elements selected from the group comprising Fe, CO, Rh, Ir, Ni, Pd, CU, Ag, Au and Sn; and wherein Sub represents a substrate material selected from Ru and Os; the respective components being present within specific ranges, display improved properties for use inanodes for low-temperature fuel cell anodes for PENFC fuel cells and direct methanol fuel cells.