Oxygen adsorbed rhodium

Rand DAJ, Woods R. The nature of adsorbed oxygen on rhodium, palladium and gold electrodes. J Eleetroanal Chem 1971 31(l) 29-38. 

Rand DAJ, Woods R (1971) The nature of adsorbed oxygen on rhodium, palladium, and gold electrodes. J Electroanal Chem Interfacial Electrochem 31 29-38 Michael DJ, Wightman RM (1999) Electrochemical monitoring of biogenic tunine neurotransmission in real time. J Pharm Biomed Anal 19 33 6... 

Figure 3.2.2.18 Single-scattering cluster (SSC) calculations for O Is emission at

Figure 6.28. Schematic illustration of the change in local electronic structure of an oxygen atom adsorbing on the late transition metal rhodium, the DOS of which is shown on the right-hand side. The interaction of the oxygen 2p orbital with the sp band of the transition metal is illustrated through interaction with the idealized free-electron...

The effect of oxidizing atmospheres on the reduction of NO over rhodium surfaces has been investigated by kinetic and IR characterization studies with NO + CO + 02 mixtures on Rh(lll) [63], Similar kinetics was observed in the absence of oxygen in the gas phase, and the same adsorbed species were detected on the surface as well. This result contrasts with that from the molecular beam work [44], where 02 inhibits the reaction, perhaps because of the different relative adsorption probabilities of the three gas-phase species in the two types of experiments. On the other hand, it was also determined that the consumption of 02 is rate limited by the NO + CO adsorption-desorption... 

The activities in FT reaction (expressed as turnover rates, Vt of CO transformed to hydrocarbons and oxygenates) of bulk and supported tungsten carbides are compared to that of a rhodium catalyst (3.5 wt%) supported on alumina (Table 18.6). Its dispersion (94%) has been measured by hydrogen chemisorption by assuming unity stoichiometry of adsorbed hydrogen on Rh. 

Thus we may conclude that the pre-adsorption of hydrogen had no effect on CO chemisorption on rhodium while both oxygen and carbon blocked many sites for CO chemisorption and weakened the metal-adsorbate interaction (Vjyj-c decreased, V( q increased,... 

For illustration purposes, we briefly discuss oxygen removal on cobalt. The Fischer-Tropsch reaction on this catalyst is known to be only weakly suppressed by the product water (41). The available computational results indicate that the activation energy for the reaction of adsorbed hydrogen, Hads/ with Oads to adsorbed OH species, OHads/ on cobalt is about 166 kj/mol for the flat Co(OOOl) surface and 70 kj/mol for sfepped cobalf surfaces (42). For comparison, fhe activation energy for fhis reaction on rhodium is 90 kJ/mol (43) Subsequent water formation occurs by recombination of OHads with Hads this reaction has a barrier of befween 5 and 10 kj/mol. 

The platinum catalyzed oxidation of alcohols with molecular oxygen has been known for a long time.52,53 Palladium and iridium are also effective for this reaction but not rhodium or ruthenium.54 The reaction proceeds by the initial dehydrogenation of the alcohol to produce the aldehyde or ketone with the adsorbed hydrogen then reacting with the oxygen to give water.53>55-58 These... 

A similar explanation may well be valid for a study by Yates and Sinfelt of the specific activity of rhodium catalysts supported on silica for the hydrogenolysis of ethane to methane 49). As in the example just discussed, there appears to be a sharp contrast in order of magnitude between the specific activity of catalysts with particle size below 40 A (the sensitive range of Poltorak) and above that size (130-2500 A) where bulk behavior is expected. In this case, I speculate that, with very small particles, hydrocarbon surface residues which appear to play an important role in the hydrogenolysis of ethane may well perturb the metallic character of the small rhodium particles, just like adsorbed oxygen in the case of Poltorak and co-workers. 

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