The adsorption and reaction of methanol on oxidized copper(111) studied by Fourier transform reflection-absorption infrared spectroscopy

Chesters, M.A.; McCash, E.M.

doi:10.1016/s0584-8539(87)80059-4

Cited by 110 publications

(104 citation statements)

References 8 publications

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“…The weak feature at 2123 cm-I, which also appears in the spectrum of methanold4 at 2128 cm-I, is attributed to the combination band v(C0) + d,(CD3), in accordance with the corresponding assignment on Cu{ 11 l}. 34 The assignment of the remaining band at 2185 cm-' determines the identity of the contentious band in the methoxy RAIR spectrum. It is fairly broad (fwhm 20 cm-I) compared to the other bands (fwhm -10 cm-I), suggesting that there is more than one component involved.…”

Section: Vibrational Structure Of Methoxy On Ag{lll)supporting

confidence: 63%

Structure and Reactivity of the Surface Methoxy Species on Ag{111}

Sim¹,

Gardner

King³

1995

J. Phys. Chem.

131

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The structure and reactivity of the surface methoxy species on Ag{ 11 l} have been studied using a combination of reflection absorption infrared spectroscopy and temperature-programmed desorption. Methoxy can be generated by exposing a preoxidized Ag{ 11 l} surface to methanol at 180 K and adsorbs in an upright geometry possessing effective 3-fold symmetry, with its C-0 bond axis oriented normal to the surface at all coverages.This conclusion is based on a detailed symmetry analysis coupled with rigorous application of the metalsurface selection rule and careful assignment of the infrared absorption bands with the aid of deuterium substitution. It is shown that strong Fermi resonance interactions are the cause behind unusual features observed in the C-H stretching region of the infrared spectra of methoxy on many metal surfaces. Significant interadsorbate dipole coupling and chemicaUelectrostatic effects are responsible for the coverage-dependent frequency shifts exhibited by the infrared active bands. Methoxy is stable on Ag{ 11 11 up to 290 K, above which it decomposes to yield formaldehyde as the major product, which desorbs in a reaction-limited step that is consistent with first-order kinetics. Formate has been identified as a minor surface species when excess surface oxygen is present and acts as the intermediate in the further oxidation of formaldehyde to COZ and Hz.

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Section: Vibrational Structure Of Methoxy On Ag{lll)supporting

confidence: 63%

Structure and Reactivity of the Surface Methoxy Species on Ag{111}

Sim¹,

Gardner

King³

1995

J. Phys. Chem.

131

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“…6 These results compare well with RAIRS spectra on Ag(111) 11 and on Cu(111). 22 Quasi-relativistic DFT calculations on Pt(111) pointed to identical results. 5 Hybrid HF/DFT methods were performed for methoxide adsorbed on a less compact surface, Al(100), indicating a preference toward adsorption on 2-fold bridge sites.…”

Section: Introductionmentioning

confidence: 75%

“…4,11,22,24,31 The methyl deformation region is of no use to this matter, since the modes are too weak to be observed. This has also been the case in other RAIRS studies.…”

Section: Ch 3 O (Ads) + H (Ads) 98mentioning

confidence: 99%

The Decomposition Pathways of Methanol on Clean Ru(0001), Studied by Reflection−Absorption Infrared Spectroscopy (RAIRS)

Barros¹,

García²,

Ilharco³

2001

J. Phys. Chem. B

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The adsorption and decomposition of methanol on clean Ru(0001) were investigated by reflection−absorption infrared spectroscopy (RAIRS). At low temperature (90 K) and coverage (0.1 L), it was confirmed that methanol adsorbs dissociatively as methoxide (CH3O−). No experimental evidence was obtained of an alternative decomposition for high coverage. Different bonding sites and geometries, depending on temperature and coverage, were proposed for methoxide and correlated with the corresponding CO stretching wavenumbers. Methoxide may either undergo complete dehydrogenation into CO(ads) and H(ads), if annealed in small temperature steps (in the range between 110 and 320 K), or partial dehydrogenation into very stable η2-formaldehyde, by a one-step thermal activation (from 130 K to at least 190 K), in the presence of previously formed products (CO and atomic species). At high temperatures (≥190 K), methanol undergoes O−H, C−H, and C−O bond scission, leaving surface fragments undetectable by RAIRS. However, in a sequential dosing, the fragments from the first methanol molecules that hit the surface seem to have a passivating effect on Ru(0001). Subsequent doses undergo only partial dehydrogenation, yielding η2-formaldehyde, which was isolated on the surface in two bonding configurations: bridging [μ2-η2(C,O)-H2CO] and chelating [μ1-η2(C,O)-H2CO], characterized by the νCO mode at 1262 and 1277 cm-1, respectively. This assignment was confirmed by adsorbing CD3OH. The bridging form is favored at lower coverage. Formaldehyde prepared by sequential dosing is stable on the surface up to at least 290 K, although some dehydrogenates to CO(ads) above 190 K.

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“…As for comparison, we can note that the C-O stretching of methoxy groups on ␥-Al 2 O 3 is found at 1095 cm −1 [28], and those on ZnO and ZnO-based systems [29] at 1060 cm −1 . Methoxy groups on CuO are reported to be very labile, whose C-O stretching is found at 1070 cm −1 , and finally, those on Cu(1 1 1) [30] absorb at 1036 cm −1 . The complex weak band centered in the region 1470-1440 cm −1 (maximum at 1458 cm −1 ), and the component at 1190 cm −1 are most likely due to the bending and rocking modes, respectively, of the CH 3 of the methoxy groups.…”

Section: Ir Study Of Methanol Adsorption and Conversionmentioning

confidence: 99%