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Reactions of methanol and carbon monoxide on ad-atom modified platinum(111) and molybdenum(110) surfaces: Molecular orbital study

Shiller, Paul Joseph
http://rave.ohiolink.edu/etdc/view?acc_num=case1055946339

Abstract Details

1991, Doctor of Philosophy, Case Western Reserve University, Chemistry.
The oxidation of methanol to carbon dioxide is an important industrial process. Although a great deal of information is known about the entire oxidation process the individual steps of the process are not so well known. Each step on the surface is affected by the surface composition. Methanol reacts on late transition metal surfaces to ultimately yield CO and H2. In this thesis, various aspects of methanol oxidation on metal surfaces are explained with the atom superposition and electron delocalization molecular orbital (ASED-MO) method. In addition, bonding in transition metal disilyl complexes was studied. The activation barrier to the dehydrogenation of adsorbed methoxy is calculated to be less on a clean Pt surface than on an O covered Pt surface because the reaction on the O covered surface requires the electron transfer from the relatively low lying O 2p lone pair orbitals to the metal Fermi level. In the case of the clean surface there is no net electron transfer merely the rearrangement of the electrons at the Fermi level. The O stabilizes the adsorbed methoxy towards dehydrogenation. On a Mo surface adsorbed CH3O has been observed to decompose to CH3cdot and O(ads). Compared to the strong C-O bond in methan ol formed by binding CH3cdot to OH, the binding of CH3 to O2- on the Mo surface generates an electron which is promoted to the surface conduction band, weakening the C-O bond strength. This explains the thermal desorption results of Serafin and Friend, who observed CH3cdot(g) formation on heating a Mo(110) surface with adsorbed methoxy. Ad-atoms can affect the reaction rate of methanol on electrode surfaces. Sn increases the oxidation rate of methanol significantly. In our work, Ge, Sn, and Pb adsorbed onto a Pt surface are found to reduce the chemisorption energy of CO. Oxidation of the ad-atoms by binding OH to them only slightly reduces the effect while oxidation by O cancels it. When these atoms are placed substitutionally in the Pt surface the effect is small. The effect stems from a CO 4σ-Sn 5s closed-shell repulsion through the Pt surface atoms. The through space repulsion is negligible.
Alfred Anderson (Advisor)
139 p.
Chemistry, Physical
methanol; carbon monoxide; ad-atom modified platinum(111); molybdenum(110); surfaces; Molecular orbital study

Recommended Citations

Citations

  • Shiller, P. J. (1991). Reactions of methanol and carbon monoxide on ad-atom modified platinum(111) and molybdenum(110) surfaces: Molecular orbital study [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1055946339

    APA Style (7th edition)

  • Shiller, Paul. Reactions of methanol and carbon monoxide on ad-atom modified platinum(111) and molybdenum(110) surfaces: Molecular orbital study. 1991. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1055946339.

    MLA Style (8th edition)

  • Shiller, Paul. "Reactions of methanol and carbon monoxide on ad-atom modified platinum(111) and molybdenum(110) surfaces: Molecular orbital study." Doctoral dissertation, Case Western Reserve University, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=case1055946339

    Chicago Manual of Style (17th edition)

case1055946339
564
© 1991, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.