Passivity catalytic properties, relation

Because the contact properties of a substance result from the formation of its surface and, as we discussed, the values of the powder electrode potential for the same given parameters describing the powder electrode, are also a function of the surface state, then it seems to be true that there should be some relation between the value of the powder electrode potential and the catalytic properties of the powder contained in it. This relation must be based on the fact that certain catalytic properties of the dispersed substance being investigated (bad or passive contact, weak contact, active contact) as regards a given chemical reaction must... 

As in other fields of nanosdence, the application of STM techniques to the study of ultrathin oxide layers has opened up a new era of oxide materials research. New emergent phenomena of structure, stoichiometry, and associated physical and chemical properties have been observed and new oxide phases, hitherto unknown in the form of bulk material, have been deteded in nanolayer form and have been elucidated with the help of the STM. Some of these oxide nanolayers are and will be of paramount interest to the field of advanced catalysis, as active and passive layers in catalytic model studies, on the one hand, and perhaps even as components in real nanocatalytic applications, on the other hand. We have illustrated with the help of prototypical examples the growth and the structural variety of oxide nanolayers on metal surfaces as seen from the perspective of the STM. The selection of the particular oxide systems presented here refleds in part their relevance in catalysis and is also related to our own scientific experience. 

A systematic analytic screening of all the possible 40 reaction schemes in which three Fe-containing surface species are involved completed by a numerical simulation finally led to selecting the reaction pattern [20] shown below. The three coverages determining the impedance properties in the active and transition domains are related to Fe(I) j, Fe (I)gj3, and Fe (II) j. The superscript ( ) indicates species involved in catalytic issolution paths. Fe(II) j5 is a precursor of the passive film whose contribution is significant only near the second maxima and beyond. 

Another property of the trap is that the tr >-vancKlium species must be catalytically inert. This is demonstrated in Figs. 6a and 6b vdiidi sbcw a dramatic reduction in MAT ox and hydrogen yields. These yields cire related to dehydrogenation ao tlvlty and provide cdear evidaioe for the passivation of vanadium catelytic activity. 

---