A comparative study of the reactivities of H2O, CH3OH, and CH3OCH3 toward Al(111)

Chen, J.G.; Basu, P.; Ng, Lily; Yates, John T.

doi:10.1016/0039-6028(88)90861-8

Cited by 81 publications

(45 citation statements)

References 28 publications

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“…However, carbon is clearly present after repeated cycles. These data are comparable to those reported for Al(111) 19 and polycrystalline Al, 20 where a methoxy species forms at low temperature and decomposes around 500 K to form methane. For Al(111), methoxy formation is associated with concurrent H 2 and methanol desorption at 145 K; methane evolution is observed at about 445 K. Our data are different than those reported for Pd(111) and Pd(110), where adsorption of CH 3 -OH yields H 2 at 300-350 K, and CO at about 475 K. [21][22][23] We were unable to find literature studies of CH 3 OH on Mn.…”

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confidence: 89%

Surface Reactivity of a Sputter-Annealed Al−Pd−Mn Quasicrystal

1998

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Quasicrystals are materials with unusual atomic structure, coupled with unusual physical properties. 1 Surface properties are particularly important, because most proposed applications quasicrystals involve low-dimensional solidsscoatings, thin films, precipitates, or compositesswhere the ratio of surface area to volume is high. 2 Perhaps the most fundamental surface property is chemical reactivity. Studies under various environmental conditions suggest that quasicrystals are relatively unreactive and/ or corrosion-resistant. 3,4 It has been proposed that the surface chemistry of quasicrystals should be dominated by the suppression of the density of states at the Fermi level 5 sthe "pseudogap"swhich is characteristic of bulk quasicrystals. This hypothesis is supported by surface energy measurements conducted under atmospheric conditions, which show that the passivated surface of a quasicrystal behaves more like a covalently bonded material (e.g., Teflon) than like a metal; the polar component of the surface energy is anomalously low. 6 A low polar component suggests low surface polarizability, i.e., low free-electron density.The present study addresses the reactivity of one particular Albased quasicrystal, icosahedral (i-) Al-Pd-Mn, toward a series of simple molecules: H 2 , CO, CH 3 OH, and two iodoalkanes. Note that these molecules, and their adsorption products, form bonds to metal surfaces that are primarily covalent in nature. Hence, one might expect these adsorbates would be less sensitive to the pseudogap than to rehybridization of valence orbitals within the intermetallic. Our approach is to compare the chemistry of a clean quasicrystalline surface with the known chemistry of the clean, pure metals that comprise the intermetallic, to determine whether the quasicrystal is unusual.The i-Al-Pd-Mn sample used in these experiments was grown at the Ames Laboratory. 7 A single grain was harvested from a boule and oriented to a 5-fold axis within 0.25°with use of Laue X-ray diffraction. Inductively coupled plasma-atomic emission spectroscopy of an adjacent sample showed a composition of Al 72.8 Pd 18.6 Mn 8.6 . Prior to experiments, scanning Auger and electron microscopy showed the sample to be single phase.The experiments were performed in a well-equipped ultrahigh vacuum (UHV) chamber, with a base pressure below 1 × 10 -10

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confidence: 89%

Surface Reactivity of a Sputter-Annealed Al−Pd−Mn Quasicrystal

1998

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“…A few minutes later, a band at 1050 cm -1 is observed to develop (second trace in Figure ) and is associated with a doublet at 2950/2830 cm -1 . This signature is highly characteristic for surface-bound methylate (CH 3 O - ). The absorptions of π-bound formaldehyde and methylate grow strongly as a function of exposure time to the N 2 /H 2 flow, whereas the bands due to carbonates are decreasing continuously, which results in a narrowing of the peaks between 1700 and 1200 cm -1 (Figure ).…”

Section: Resultsmentioning

confidence: 99%

Surface Species in CO and CO₂Hydrogenation over Copper/Zirconia: On the Methanol Synthesis Mechanism

et al. 1996

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Hydrogenation reactions occurring on the surface of a copper/zirconia (Cu:Zr ) 30:70 atom %) catalyst, which had previously been loaded by adsorption of formic acid, CO, and CO2, have been studied by means of in situ diffuse reflectance FTIR spectroscopy. Besides characterizing the reactivity of adsorbates, the dynamics of CO and CO2/hydrogen reactant mixtures has been monitored over both the prereduced and unreduced catalyst, with the aim of acquiring information on the methanol synthesis mechanism. Surface formates, which have previously been identified as intermediates in the catalytic reduction of carbon oxides yielding methane, appear to be spectator species in methanol synthesis over ZrO2 supported catalysts. The latter synthesis, when using CO2 as the reactant, starts from surface carbonate, which is first reduced to yield adsorbed carbon monoxide and water. The desired methanol product is generated via surfacebound formaldehyde and methoxy species.

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“…8 The surface chemistry seems to be different at 180 K on Cu(110) and Cu(111) where adsorbed CH 3 OH desorbs intact. 9,10 Similarly, no decomposition is observed on Pd(111) till 140 K, 11 and on Pt(111), Ni(111) and Al(111) between 90 and 100 K. [12][13][14] However, on Pt(111) surface methanol decomposes to H ads and CO ads at around 140 K. 12 On the Al(110) surface the primary product at 150 K is a methoxide species, whereas on a Pd(100) surface TPD suggests the formation of methoxide at 77 K. 15,16 On a Pt(110) (2 Â 1) surface O-H bond scission was observed at around 200 K 17 and on the Pt(110) (1 Â 1) surface C-O bond scission is reported above 200 K. 18 On the hcp Zn(0001) surface the chemisorbed methanol transforms to methoxy species at 150 K, which produces CH x at higher temperatures. 19 Earlier studies showed that methanol is only molecularly adsorbed on the Au(111) and Au(110) surfaces.…”

Section: Introductionmentioning

confidence: 98%

Decomposition of methanol on Au(310)

Vinod

Niemantsverdriet

Nieuwenhuys

2005

Phys. Chem. Chem. Phys.

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Experimental results on the interaction of methanol with a Au(310) surface studied using X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD) are reported. At 80 K methanol forms a physisorbed condensed layer above 5 L of exposure. Interestingly, O-H bond scission takes place above 150 K on the surface resulting in an adsorbed methoxy species which is stable till 500 K. This is in contrast with other gold surfaces like Au(111) and Au(110) which showed no evidence for decomposition. The difference in reactivity of Au(310) surface towards methanol is interpreted in terms of the presence of special sites formed by (110) steps and (100) terraces on this surface.

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A comparative study of the reactivities of H2O, CH3OH, and CH3OCH3 toward Al(111)

Cited by 81 publications

References 28 publications

Surface Reactivity of a Sputter-Annealed Al−Pd−Mn Quasicrystal

Surface Reactivity of a Sputter-Annealed Al−Pd−Mn Quasicrystal

Surface Species in CO and CO₂Hydrogenation over Copper/Zirconia: On the Methanol Synthesis Mechanism

Decomposition of methanol on Au(310)

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A comparative study of the reactivities of H2O, CH3OH, and CH3OCH3 toward Al(111)

Cited by 81 publications

References 28 publications

Surface Reactivity of a Sputter-Annealed Al−Pd−Mn Quasicrystal

Surface Reactivity of a Sputter-Annealed Al−Pd−Mn Quasicrystal

Surface Species in CO and CO2Hydrogenation over Copper/Zirconia: On the Methanol Synthesis Mechanism

Decomposition of methanol on Au(310)

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Surface Species in CO and CO₂Hydrogenation over Copper/Zirconia: On the Methanol Synthesis Mechanism