The Interaction of Water with Solid Surfaces: Fundamental Aspects Revisited

http://w0.rz-berlin.mpg.de/hjfdb/pdf/291e.pdf

Clusters and islands on oxides: from catalysis via electronics and magnetism to optics

The reforming of methane with carbon dioxide was studied over nickel supported on SiO2, TiO2, MgO and activated carbon. Specific activities on a turnover frequency basis were in the order: Ni/TiO2 > Ni/C > Ni/SiO2 > Ni/MgO. Interestingly, a 2-fold increase in activation energy for this reaction was observed over Ni/TiO2 after several hours time on stream. The reverse water-gas shift reaction was found to be close to thermodynamic equilibrium over all catalysts. Partial pressure dependencies were obtained with the Ni/C and Ni/SiO2 catalysts at 723 K for comparative purposes only, but a more thorough kinetic analysis was made with the Ni/MgO and Ni/TiO2 catalysts, which were shown previously to strongly inhibit carbon deposition. Partial pressure dependencies were obtained at 673, 698, and 723 K for Ni/TiO2 and at 773, 798, and 823 K for Ni/MgO. In situ DRIFTS studies clearly showed the presence of both linear and bridged carbon monoxide adsorption on Ni/SiO2 under reaction conditions; however, adsorbed carbon monoxide could not be identified on Ni/TiO2. A reaction model for CH4—CO2 reforming, based on CH4 activation to form CHx and CHxO decomposition as the slow kinetic steps, successfully correlated the rate data.

Catalytic reforming of methane with carbon dioxide over nickel catalysts II. Reaction kinetics

Molecular beam experiments on model catalysts

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

P. Uvdal

Papers

On the structure of dense CO overlayers

Vibrational excitations of nitric oxide adsorbed on Pd(100)

Adsorption of Water on Cu(100) and Pd(100) at Low Temperatures: Observation of Monomeric Water

The coadsorption of hydrogen and nitric oxide on Pd(100) studied by EELS