Rhodium surface mobility

LEED patterns at 0 = 1 /4, but was identified at lower coverages in islands surrounded by mobile sulfur atoms at platinum, rhodium and rhenium surfaces. Sautet and co-workers42 have analysed the statistical correlations between the intensities of sulfur features in p(2 x 2) islands on rhenium surfaces and also of streaks in areas between islands, which they attribute to sulfur atoms diffusing under the tip (Figure 10.12). 

The processes classified in the third group are of primary importance in elucidating the significance of electric variables in electrosorption and in the double layer structure at solid electrodes. These processes encompass interactions of ionic components of supporting electrolytes with electrode surfaces and adsorption of some organic molecules such as saturated carboxylic acids and their derivatives (except for formic acid). The species that are concerned here are weakly adsorbed on platinum and rhodium electrodes and their heat of adsorption is well below 20 kcal/mole (25). Due to the reversibility and significant mobility of such weakly adsorbed ions or molecules, the application of the i n situ methods for the surface concentration measurements is more appropriate than that of the vacuum... 

Marsh AL, Somorjai GA (2005) Structure, reactivity, and mobility of carbonaceous overlayers during olefin hydrogenation on platinum and rhodium single crystal surfaces. Top Catal 34 121... 

Band d (vco = 1800-1806 cm" ) corresponds to three-fold bridged CO on metallic rhodium particles. The intensity of band d increases systematically, its increase suggests a slow reduction of Rh(III) and Rh(I) to Rh(0). The metallic Rh may play an important role in increasing the mobility of CO on the catalyst surface and in the activation of reagents during the carbonylation reaction as observed at the hydrocarboxylation of ethylene in the presence of hydrogen (favors the appearance of metallic Rh) on RhCls/active carbon and on H[Rh(CO)2l2]/active carbon catalyst. ... 

Supported aqueous phase catalysts are well known [29, 30]. In these systems, a thin film of water present on the surface of a polar solid support is used to immobilize metal complexes, which are nonvolatile or insoluble in a mobile gaseous or liquid organic phase, respectively [30]. The concept was used successfully, for example, for the hydroformylation of oleyl alcohol over a supported rhodium complex [29]. Here, it was suggested that the reaction occurred at the interface between the aqueous and organic phase. However, the volatility of water necessitated... 

Figure 6.2. (a) Sticking coefficient as a function of coverage in the case of direct adsorption and a mobile precursor (b) adsorption isotherm of NO on the (111) surface of rhodium showing the effect of the precursor mechanism (from Borg et ai, 1994). 

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