Carbon monoxide adsorption specific metals

The saturation coverage during chemisorption on a clean transition-metal surface is controlled by the fonnation of a chemical bond at a specific site [5] and not necessarily by the area of the molecule. In addition, in this case, the heat of chemisorption of the first monolayer is substantially higher than for the second and subsequent layers where adsorption is via weaker van der Waals interactions. Chemisorption is often usefLil for measuring the area of a specific component of a multi-component surface, for example, the area of small metal particles adsorbed onto a high-surface-area support [6], but not for measuring the total area of the sample. Surface areas measured using this method are specific to the molecule that chemisorbs on the surface. Carbon monoxide titration is therefore often used to define the number of sites available on a supported metal catalyst. In order to measure the total surface area, adsorbates must be selected that interact relatively weakly with the substrate so that the area occupied by each adsorbent is dominated by intennolecular interactions and the area occupied by each molecule is approximately defined by van der Waals radii. This... 

The Cr A and several other zeolites containing transition metal ions, which may exist in two or more valence states, were also found to be oxidation catalysts. One such system of note is the copper containing Type Y zeolite, the redox chemistry of which was studied in several recent investigations (2, 3.4, 5). These studies established the range of conditions at which copper exists in divalent, monovalent, or zerovalent state and in particular determined the reduction conditions in hydrogen and carbon monoxide atmospheres for a complete conversion of Cu Y to Cu Y but no further to Cu°. The Cu ions in type Y zeolite were reported to be specific adsorption centers for carbon monoxide ( 6), ethylene ( 7), and to catalyze the oxidation of CO (8). In the present work the Cu ions were also found to be specific adsorption centers for oxygen. 

After the brief introduction to the modem methods of ab initio quantum chemistry, we will discuss specific applications. First of all, we will discuss some general aspects of the adsorption of atoms and molecules on electrochemical surfaces, including a discussion of the two different types of geometrical models that may be used to study surfaces, i. e. clusters and slabs, and how to model the effect of the electrode potential in an ab initio calculation. As a first application, the adsorption of halogens and halides on metal surfaces, a problem very central to interfacial electrochemistry, will be dealt with, followed by a section on the ab initio quantum chemical description of the adsorption of a paradigmatic probe molecule in both interfacial electrochemistry and surface science, namely carbon monoxide. Next we will discuss in detail an issue uniquely specific to electrochemistry, namely the effect of the electric field, i. e. the variable electrode potential, on the adsorption energy and vibrational properties of chemisorbed atoms and molecules. The potential-dependent adsorption of carbon monoxide will be discussed in a separate section, as this is a much studied system both in experimental electrochemistry and ab initio quantum electrochemistry. The interaction of water and water dissociation products with metal surfaces will be the next topic of interest. Finally, as a last... 

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