Carbon, surface hydrogen interaction

The greatest attention in the literature has been paid to the carbon-oxygcn-hydrogen interaction because of their enormous chemical relevance and the existence of a suite of chemical and physical tools for their characterization. Classes of carbons which are suitable for such studies arc carbon blacks. These materials are of high elemental purity (no inorganic impurities) and sufficient specific surface area to allow a quantitative determination of the heteroclcment content, which is the basis for any meaningful normalization of surface... 

As mentioned above, the addition of promoters, and even the formation of bimetallic particles, can provide carbon-supported iron catalysts with better performances in CO hydrogenation. The method of preparation of these systems is going to determine the final effect, always taking advantage of the relative inertness of the carbon surface. The interaction between the different components of the active phase can be maximized by using mixed-metal carbonyl complexes. Furthermore, use of these precursors allows for the preparation of catalysts with... 

The origin of a torsional barrier can be studied best in simple cases like ethane. Here, rotation about the central carbon-carbon bond results in three staggered and three eclipsed stationary points on the potential energy surface, at least when symmetry considerations are not taken into account. Quantum mechanically, the barrier of rotation is explained by anti-bonding interactions between the hydrogens attached to different carbon atoms. These interactions are small when the conformation of ethane is staggered, and reach a maximum value when the molecule approaches an eclipsed geometry. 

Nitric acid treatment lowered the methane uptake by about ten percent. This could be due to oxygen occupying sites within pores, but may be the result of weaker interaction between methane and an oxide surface as is observed for silica. Reduction of these treated carbons with hydrogen restored their original methane uptake. Clearly for methane storage, there is no advantage in modifying the carbon surface by nitric acid treatment. 

The main difference between carbon nanotubes and high surface area graphite is the curvature of the graphene sheets and the cavity inside the tube. In microporous solids with capillaries which have a width not exceeding a few molecular diameters, the potential fields from opposite walls will overlap so that the attractive force which acts upon adsorbate molecules will be increased in comparison with that on a flat carbon surface [16]. This phenomenon is the main motivation for the investigation of the interaction of hydrogen with carbon nanotubes (Figure 5.14). 

In this chapter, recent results are discussed In which the adsorption of nitric oxide and its Interaction with co-adsorbed carbon monoxide, hydrogen, and Its own dissociation products on the hexagonally close-packed (001) surface of Ru have been characterized using EELS (13,14, 15). The data are interpreted In terms of a site-dependent model for adsorption of molecular NO at 150 K. Competition between co-adsorbed species can be observed directly, and this supports and clarifies the models of adsorption site geometries proposed for the individual adsorbates. Dissociation of one of the molecular states of NO occurs preferentially at temperatures above 150 K, with a coverage-dependent activation barrier. The data are discussed in terms of their relevance to heterogeneous catalytic reduction of NO, and in terms of their relationship to the metal-nitrosyl chemistry of metallic complexes. 

Hydrogen interaction with the carbon nanostructural materials (nanotubes, nanofibers, fullerenes C60 and C70 has been intensively studied over the last years. A developed surface of nanotubes and nanofibers induced a considerable applied interest aimed at hydrogen storage and reduced consumption of organic fuel in modem industry. For the academic studies, of interest is the nature of the hydrogen interaction with the carbon nanomaterials. 

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