Acetylene Decomposition on Rh(100): Theory and Experiment

Nieskens, Davy L. S.; Ample‐Navarro, Francisco; Jansen, Maarten M. M.; Curulla‐Ferré, Daniel; Ricart, Josep M.; Niemantsverdriet, J.W.

doi:10.1002/cphc.200500566

Cited by 10 publications

(8 citation statements)

References 61 publications

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“…On RhA C H T U N G T R E N N U N G (111), a similar decomposition behavior of ethylene glycol has been reported; high-resolution electron energy lose spectroscopy (HREELS) shows simultaneous dehydrogenation and CÀC bond breaking between 240 and 260 K and hydrogen desorption occurs at 280 K. [23] On RhA C H T U N G T R E N N U N G (100), ethylene glycol decomposes at higher temperatures than ethanol (290 K compared to 250-260 K [21] ) but at lower temperatures than ethylene or acetylene (CÀC bond breaking is observed around 400 K). [35,36] However, this does not follow the order in CÀC bond strength: ethylene and acetylene have the strongest CÀC bond and ethylene glycol has the weakest. The order of decomposition also changes: CÀC bond breaking in ethylene and acetylene is observed after the hydrocarbon has dehydrogenated to a CCH fragment, in ethylene glycol dehydrogenation and CÀC bond breaking are observed simultaneously, whereas the CÀC bond in ethanol is broken before complete dehydrogenation occurs.…”

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Chemistry of Ethylene Glycol on a Rh(100) Single‐Crystal Surface

2009

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The adsorption and decomposition of ethylene glycol on Rh(100) have been studied with temperature-programmed reaction spectroscopy and reflection absorption infrared spectroscopy. Ethylene glycol adsorbs onto the surface via the hydroxyl groups. At 150 K, both hydroxyl bonds are broken, forming an ethylenedioxy intermediate. At high coverage, a portion of the ethylene glycol molecules dehydrogenate only one hydroxyl bond, forming a monodentate species. These intermediates decompose further, with complete dehydrogenation and simultaneous C--C bond breaking occurring at around 290 K. Hydrogen and carbon monoxide are formed, which desorb at 290 and 500 K, respectively.

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Chemistry of Ethylene Glycol on a Rh(100) Single‐Crystal Surface

2009

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“…Our system is clearly a model one, and we do not aim at resolving the carbon-adsorption phase diagram for each metal, but only at obtaining qualitative trends on the stability of the surface carbide. The adsorption of carbon in subsurface sites for the (111) surfaces of Pd, [6,[8][9][10] Ni, [11,12] and Rh [13] have already been individually studied from DFT calculations, but their stability in reaction conditions has not been discussed.…”

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Surface of Metallic Catalysts under a Pressure of Hydrocarbon Molecules: Metal or Carbide?

Sautet¹,

Cinquini²

2010

ChemCatChem

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A fundamental approach of catalytic elementary steps at the atomic scale requires understanding both of the nature of the catalyst's active site and of the reaction pathways for the molecular reactants. The main difficulty is that these two aspects are intimately coupled. The surface structure of the catalyst plays a major role in controlling bond-breaking and bondforming processes on the reactants and complete catalytic reaction cycles can be modeled from theoretical calculations, providing insights towards the rational design of catalysts. [1] However, the presence of the reactants at a given pressure and temperature might completely modify the nature and the structure of the near-surface regions of the catalyst. In situ characterization of catalysts in conditions close to those of the reaction has shown that the electronic structure of the surface can be deeply modified by the dissolution of atoms from the reactants in the subsurface region of the catalyst. [2,3] It is hence of key importance to understand how the decomposition of reactant molecules can modify the catalyst, since the steadystate composition of the upper surface layers during the catalytic reaction completely controls the reactivity and selectivity.Transition metal catalysts are widely used in several classes of catalytic reactions with hydrocarbon reactants, including hydrogenation, dehydrogenation, hydrogenolysis, oxidation, and reforming reactions. For oxidation reactions, it is well recognized that the transition metal surface might be partially or totally oxidized in catalytic conditions. [2][3][4] The situation is less clear in the conditions of hydrogenation or hydrogenolysis, whereupon the catalyst is generally supposed to remain in the metallic phase, with various carbonaceous adsorbates on its surface. This is especially the case if noble metals such as Pt, Pd or Rh are considered. This assumption has been challenged by recent studies on alkyne-selective hydrogenation on Pd, in which it was shown by in situ spectroscopy and simulations that, in the conditions of the reaction, the surface of the catalyst is not Pd metal, but that a few layers of a carbide-type structure are formed by sacrificial decomposition of alkyne molecules. [5][6][7] For the carbon chemical potential associated to the reactants (acetylene, hydrogen), the surfaces terminated by one or two layers of carbide (with a local C concentration of 25 atomic %) are more stable than the bare Pd surface. [6] This modification of the surface nature has a key influence on the catalytic reactivity, since the carbide-terminated surface allows a selective hydrogenation, by weakening the adsorption energy of the alkene, [8] whereas stronger adsorption on the metal-terminated surface leads to total hydrogenation towards the undesired alkane.One important question is to determine whether that behavior is unique for Pd and acetylene, or whether surface carbides could be also formed for other transition metalcatalyzed hydrocarbon reactions. Besides the reactivity of hydrocarbon molecul...

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“…Ir(210) [16], Fe(100) [111][112][113], Fe(111) [112], Rh (111) [114,115], Rh(100) [114,116], Pt(111) [117], Ni (110) [118], Ru(001) and Ru(1110) [119], Pd (110) [100], Pd(100) [120], and W(211) [121]. The adsorption and reaction of C 2 H 2 on clean planar Ir (210) and clean faceted Ir (210) with average facet size of ∼14 nm have been investigated by TPD and HREELS [16].…”

Section: Reactions Of Acetylenementioning

confidence: 99%