Monolayer-oxide theories

This and many other similar hypotheses can be said to form the monolayer-oxide theories. Here the onset of... 

The inverse-logarithmic theory of growth of surface oxides implies that the rate of monolayer oxide formation is controlled by the rate of escape of the metal... 

According to the HN model, an increase in chemisorption energy should correlate to an upward shift in the total band center of the metal. Contrary to this theory, the monolayer of Pt/Ox system shows stronger chemisorption hut a large decrease (0.59 eV) in the <7-band center (—2.28 eV) relative to bulk Pt (111) (—1.69 eV). Furthermore, the downward shift in the band center of the bilayer Pt/Ox system (0.03 eV) is too small to account for the reduction in chemisorption energy. To explain these deviations, it is necessary to understand how CO binds to a metal surface and how the oxide support alters the electronic properties of the metal surface to allow for changes in molecular adsorption. 

There are three current theories on sulfiding the CoMo/Al catalyst monolayer, intercalation, and contact synergism. These are schematically depicted in Fig. 4. All start with the assumption of a monolayer model for the oxidized catalyst, differences appearing in the subsequent effect that sulfiding has on the monolayer structure. Space limitations preclude a full description of these models the original references should be consulted for more detail. 

In this respect and regarding the discussion on the initial passivations, as pointed out by an increasing number of writers, the oxide-film and adsorption theories do not contradict but rather supplement one another. In looking at the primary act of passivation as the formation of a tightly held monolayer containing oxide or hydroxide anions and metal... 

The ion-pair theory was invoked by Dong and coworkers to explain the behavior of adsorption of various surfactants at coassanbled Fc-teminated alkanethiol-alkylth-iolphene thiol SAMs on gold [51]. It was proposed that the adsorption of surfactants at the mixed monolayer created an energy barrier that inhibited the diffusion of counter ions present in solution from diffusing into the adsorbed layer as compensation for the oxidation of the Fc to Fc ions [51]. The creation of a barrier at an interface can be tested with electrochanical impedance spectroscopy (EIS) where an increase... 

The field of polymer-modified electrodes was established with the publication of five papers in 1978 (1,25 8). These were by Van De Mark and Miller (J 25), Merz and Bard ( ), Doblhofer, Noelte, and Ulstrup (27), and Nowak, Schultz, Umana, Abruna, and Murray (28). These workers reported the intentional adsorption of electroactive polymers to the surfaces of solid electrodes. For example, a film of poly(vinylferrocene) on the surface of a solid electrode exhibited chemically reversible electro-oxidation that was consistent with a surface coverage of at least 20 monolayers (26). In this and contemporaneous reports, electron transfer was shown to occur among sites in a rather complex and thick film on the surface of an electrode. New theory had to be developed to explain these electron transfer events. Experiments and theoretical studies were carried out to address questions generated by... 

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