Adsorption, diffusion and desorption of chlorine on and from rutile TiO2{110}: a theoretical investigation.

The adsorption, diffusion and desorption of chlorine on and from stoichiometric, reduced and partially reduced (defective) rutile TiO2{110} are investigated using ab initio density functional theory (DFT) calculations. Theoretical results are compared with experimental investigations, and microkinetic simulations based on DFT values are then used to verify the diffusion mechanisms assumed in the experimental investigations.     

Influence of initial oxygen coverage and magnetic moment on the NO decomposition on rhodium (111)

In this study, density functional theory calculations were performed to investigate the influence of oxygen preoccupation on the nitrogen oxide decomposition on rhodium. Besides gauging the coverage dependence of the adsorption energy of NO on the (111) rhodium facet, the influence of the initial oxygen coverage on the kinetics and thermodynamics of the nitrogen oxide decomposition reaction was also studied. The results are discussed with respect to a novel NOx decomposition catalyst. Furthermore, the influence of spin effects on the adsorption geometry as well as the adsorption energy is examined. It will be addressed why spin effects only have a minor influence on the behavior of NO on a rhodium surface.     

Competitive adsorption of NO, NO2, CO2, and H2O on BaO(100): a quantum chemical study

Density functional theory (DFT) quantum chemical calculations are used to determine adsorption energies and geometries of NO, NO(2), CO(2), and H(2)O on a barium oxide (100) surface. The study includes two adsorption geometries for NO(2). All species form thermodynamically stable adsorbates, and adsorption strength increases in the order NO(2) < H(2)O < NO 相似文献   

Dynamic interplay between diffusion and reaction: nitrogen recombination on Rh{211} in car exhaust catalysis

The adsorption and diffusion of atomic nitrogen on Rh{211} as well as formation and desorption of molecular nitrogen from this surface have been investigated by means of density functional theory (DFT) calculations. The elementary step reaction mechanism derived from this comprehensive DFT study forms the foundation of a detailed microkinetic model including diffusion, recombination, and desorption of nitrogen species. It will be shown that nitrogen formation on a stepped rhodium surface is a dynamic interplay of atomic nitrogen diffusion and reaction. Moreover, evidence will be presented that not one but several on-step recombination reactions are responsible for dinitrogen formation and desorption.     

Coverage dependence of oxygen decomposition and surface diffusion on rhodium 111: a DFT study

A systematic study of oxygen adsorption, decomposition and diffusion on Rh111 and its dependence on coadsorbed oxygen molecules has been performed using density functional theory calculations. First, the bonding strength between metal surface and adsorbed oxygen molecules has been studied as a function of initial oxygen coverage. The bonding strength decreases with increasing oxygen coverage, which points towards a self-inhibition of the adsorption process. The potential energy hypersurface (PES) for the dissociation of oxygen molecules adsorbed on a threefold fcc position perpendicular to the surface was calculated using a combined linear/quadratic synchronous transit method with conjugate gradient refinements. The results indicate that a minor amount of oxygen on the surface enhances the decomposition of further oxygen molecules, while this process is inhibited at higher coverage. Moreover, PES calculations of a single site jump of atomic oxygen on rhodium 111 indicate that the activation energy increases as well with increasing oxygen coverage. All results are discussed with respect to a rhodium based catalytic NOx reduction/decomposition system proposed by Nakatsuji, which decomposes nitrogen oxides in oxygen excess.     

In-silico investigations in heterogeneous catalysis--combustion and synthesis of small alkanes

In this critical review, we cover first-principles density functional calculations relevant to alkane oxidation and synthesis over transition metal catalysts. For oxidation, we focus upon Pt, Rh, Pd and Ni surfaces, while for synthesis we consider Co, Ru, Fe and Ni. Throughout, we emphasise the insight to be gained by thinking of each kind of reaction as the inverse of the other, with the directionality determined simply by the choice of metal catalyst and the reaction conditions. We highlight particularly the role of low-coordination sites (steps, kinks, etc.) and the emerging consensus over the importance of the formyl intermediate in facilitating the rate-determining step (249 references).     

Linear relationship between activation energies and reaction energies for coverage-dependent dissociation reactions on rhodium surfaces

Evidence of a relationship between activation energies and enthalpy changes of various dissociation reactions on transition metals has been reported recently. A reconsideration of density functional theory results for dissociation energies of oxygen and NO on different rhodium surfaces (low-index and stepped) and their dependencies on oxygen precoverage reveal that also here a linear Br?nsted-Evans-Polanyi (BEP) relationship exists. The establishment of such a general concept would be of tremendous importance for the development of detailed, elementary-step reaction mechanisms, because the activation energies of reaction steps as well as their coverage dependencies could be estimated based on the adsorption energies calculated by means of DFT.