H-spillover

Jiehan et al. interpreted the blue shift in the IR band of CO with H2 sorption as indicative of proton (not atomic H) spillover from Pt onto Ti02 (containing CO) (116). The studies were reinforced with parallel studies of the conductivities of the samples. 

Coking, widely experienced in the catalysis of hydrocarbon conversion (7), can deactivate both metallic and acid catalytic sites for hydrocarbon reactions (2). Accumulation of such carbonaceous deposits affects selectivity in hydrocarbon conversion (5). Adsorbed ethene even inhibits facile o-p-Hj conversion over Ni or Pt (4 ), the surface of which it appears is very nearly covered at lower temperatures in such deposits. H spillover may enhance hydrocarbonaceous residue formation (6). Accumulated carbonaceous residues can be removed by temperature programmed oxidation, reduction and hydrogenation TPO, TPR, TPH, etc (7) as part of catalyst regeneration. 

This coadsorption has been studied for Rh loaded onto Ce02(i 11) films. As with the systems mentioned above, the interaction between water and CO depends strongly upon the oxidation state of the ceria. The origin of most of the oxidation effects are the result of the interaction of the individual components, e.g. hydroxyls form from H O only on a reduced ceria surface. Rh catalyses the decomposition of hydroxyls, leading to a decrease in the resulting recombinative H2 peak desorption temperature from 580 K in the Rh-free surface to about 500 K when Rh is present on the surface. This effect is presumably due to H spillover onto the Rh, facilitating recombination and desorption. There are subtle interactions between the coadsorbates also. The coadsorption of CO somewhat inhibits this process of recombinative H2 desorption, but the presence of the hydroxyls slightly lowers the temperature of recombinative CO desorption. 

A fast as well as a slow component was observed in the room temperature adsorption of H2 and 02 on Rh on rutile and anatase Ti02 catalysts. Both components of the H2 adsorption decreased in magnitude with increasing catalyst reduction temperature, while the fast 02 adsorption increased in magnitude and the slow 02 adsorption stayed constant. The fast H2 adsorption proved to be due to chemisorption on the metal and the slow H2 adsorption to spillover from the metal to the support. The fast 02 adsorption was due to chemisorption on the metal as well as on the support, with the concurrent reoxidation of Ti ions formed during H-spillover. The slow 02 adsorption was caused by corrosive chemisorption of the metal particles. 

Pt atom or Pt cluster on coronene H-spillover RI-TPSS/def2-TZVP [174]... 

Proceedings of the 7th International Symposium, Cancun, Mexico, October 5-8,1997 edited by C.H. Bartholomew and G.A. Fuentes Volume 112 Spillover and Migration of Surface Species on Catalysts. 

The effect of spillover was observed for different species such as H,68 O69 n,70 NO64 or CO.69 Most of the research has been carried out with hydrogen spillover. 

Examples of reverse spillover (or backspillover) are the dehydrogenation of isopentane and cyclohexane on active carbon. Deposition of a transition metal on the active carbon accelerates the recombination of H to H2 due to a reverse spillover or backspillover effect.72... 

B. Luerssen, S. Gunther, H. Marbach, M. Kiskinova, J. Janek, and R. Imbihl, Photoelectron spectromicroscopy of electrochemically induced oxygen spillover at the Pt/YSZ interface, Chem. Phys. Lett. 316, 331-335 (2000). 

Volume 17 Spillover of AdMirbnl SpKiei. Proceedings of an International Symposium, Lyon-Villeurbanne, September 12-18, 1983 edited by G.H. Pajonk,sj.Teichna- and J.E. Germain Volume 18 Structtire and Reactivity of Hodifled lites. Proceedings of an International... 

It was found in the 1960s that disperse platinum catalyst supported by certain oxides will in a number of cases be more active than a similar catalyst supported by carbon black or other carbon carrier. At platinum deposits on a mixed carrier of WO3 and carbon black, hydrogen oxidation is markedly accelerated in acidic solutions (Hobbs and Tseung, 1966). This could be due to a partial spillover of hydrogen from platinum to the oxide and formation of a tungsten bronze, H WOj (0 < a < 1), which according to certain data has fair catalytic properties. 

Had) or more strongly (Oad/OHad) bound. In Fig. 14.7, we illustrate the resulting potential-dependent adlayer formation and replacement processes for anodic (upper part) and cathodic (lower part) scan directions. In the negative-going scan, H pd formed on the Pt islands can react with OHad on neighboring Ru sites and desorb as H2O [equivalent to Reaction (14.1a)]. Spillover of further H pd from the Pt islands to the Ru terraces or direct adsorption of H pd on the Ru areas results in further OHad removal and subsequent replacement by Had. The pronounced shift of peak A from... 

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