Surface science studies of catalytic promotors on Cu(110)
Surface science studies of catalytic promotors on Cu(110)
Surface science studies of both clean and modified Cu(110) surfaces utilising R.A.I.R.S., T.P.D., L.E.E.D., E.E.L.S. and Δφ measurements have been employed to assess the effects of pre-adsorbed alkali metal adatoms and surface defects on the adsorption of CO and H_3COH. CO adsorption on the clean surface exhibits an interesting coverage dependent behaviour of the R.A.I.R.S. absorption band in which the intensity of this band is observed to decrease with increasing CO coverage after the completion of a (2x1) CO adlayer. T.P.D. measurements show that this decrease is associated with the operation of strong lateral CO-CO repulsive interactions at high Co coverage and is ascribed to a tilting of the CO species away from the surface normal to minimise such interactions. For the adsorption of CO on Potassium pre-dosed surfaces a variety of perturbed CO species are observed. The nature of the species present is found to be strongly dependent on the precise coverage of Potassium present. At low alkali metal coverages the observed behaviour is interpreted in terms of the formation of ordered K/CO islands in which the CO is bound to Cu atoms and perturbed by the presence of nearby Potassium. R.A.I.R.S. measurements of Co adsorbed on relatively K free regions of the surface between such islands provides evidence for a similar though much weaker K/CO interaction at greater K-CO separation. At higher K coverages the extremely strongly perturbed CO species previously attributed to the formation of K/CO complexes are observed. In addition a more weakly bound species is observed. No vibrational features corresponding to the presence of this species have been identified by E.E.L.S. or R.A.I.R.S. which strongly implies a CO species either `lying down' at the surface or strongly screened by the presence of other surface species. Previous investigations regarding the oxidation of methanol on oxygen pre-covered Cu(110) surfaces have provided evidence for the existence of a minor reaction pathway for the formation of surface formate species. On a Cu(110) surface exhibiting regular monatomic steps this process dominates the observed behaviour and is interpreted in terms of an enhanced reactivity of the surface towards the oxidation of methoxy species at surface defect sites.
University of Southampton
1990
Slater, David Alan
(1990)
Surface science studies of catalytic promotors on Cu(110).
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Surface science studies of both clean and modified Cu(110) surfaces utilising R.A.I.R.S., T.P.D., L.E.E.D., E.E.L.S. and Δφ measurements have been employed to assess the effects of pre-adsorbed alkali metal adatoms and surface defects on the adsorption of CO and H_3COH. CO adsorption on the clean surface exhibits an interesting coverage dependent behaviour of the R.A.I.R.S. absorption band in which the intensity of this band is observed to decrease with increasing CO coverage after the completion of a (2x1) CO adlayer. T.P.D. measurements show that this decrease is associated with the operation of strong lateral CO-CO repulsive interactions at high Co coverage and is ascribed to a tilting of the CO species away from the surface normal to minimise such interactions. For the adsorption of CO on Potassium pre-dosed surfaces a variety of perturbed CO species are observed. The nature of the species present is found to be strongly dependent on the precise coverage of Potassium present. At low alkali metal coverages the observed behaviour is interpreted in terms of the formation of ordered K/CO islands in which the CO is bound to Cu atoms and perturbed by the presence of nearby Potassium. R.A.I.R.S. measurements of Co adsorbed on relatively K free regions of the surface between such islands provides evidence for a similar though much weaker K/CO interaction at greater K-CO separation. At higher K coverages the extremely strongly perturbed CO species previously attributed to the formation of K/CO complexes are observed. In addition a more weakly bound species is observed. No vibrational features corresponding to the presence of this species have been identified by E.E.L.S. or R.A.I.R.S. which strongly implies a CO species either `lying down' at the surface or strongly screened by the presence of other surface species. Previous investigations regarding the oxidation of methanol on oxygen pre-covered Cu(110) surfaces have provided evidence for the existence of a minor reaction pathway for the formation of surface formate species. On a Cu(110) surface exhibiting regular monatomic steps this process dominates the observed behaviour and is interpreted in terms of an enhanced reactivity of the surface towards the oxidation of methoxy species at surface defect sites.
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Published date: 1990
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Local EPrints ID: 461908
URI: http://eprints.soton.ac.uk/id/eprint/461908
PURE UUID: 8bfb1804-45ff-44e3-9007-3648973d43eb
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Date deposited: 04 Jul 2022 18:58
Last modified: 04 Jul 2022 18:58
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Author:
David Alan Slater
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