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The interaction of methanol with modified Ru(001) surfaces: The effects of oxygen and potassium
A47 reactivity versus CO. In fact unusual positively and negatively charged species are formed at 77 K by CO interaction. Monomeric (m =1) and dimeric (m = 2) negative species (which represent some of the initial products of the CO interaction) are readily transformed into more complex species when the CO pressure is increased.
Surface Science 166 (1986) 361-376 North-Holland, Amsterdam THE INTERACTION
OF METHANOL
SURFACES: THE EFFECTS Jan HRBEK
361 WITH MODIFIED
Ru(001)
OF OXYGEN AND POTASSIUM
*, R o b e r t D E P A O L A ** a n d F r i e d r i c h M . H O F F M A N N
Exxon Research and Engineering Company, Corporate Research Science Laboratories, Clinton Township, Route 22 East, Annandale, New Jersey 08801, USA Received 12 May 1985; accepted for publication 19 September 1985
The adsorption and decomposition of methanol on a Ru(001) surface modified by preadsorbed potassium and oxygen has been investigated with electron energy loss spectroscopy (EELS) and multiple mass thermal desorption spectroscopy (TDS). On ruthenium precovered with a low coverage of atomic oxygen (0o = 0.25), methoxy formation is promoted with respect to the clean surface and is found to occur at 85 K. In contrast, on ruthenium modified by "ionic" potassium (0 K = 0.10), methoxy formation is inhibited, i.e., oxygen-hydrogen bond breaking does not occur until temperatures reach 240 K. On both surfaces, the decomposition of methanol proceeds via O - H and C - H bond breaking and ultimately leads to the formation of CO and H 2. The results differ from those obtained on the clean Ru(001) surface, where methoxy formation is observed at 85 K only when exposed to small amounts of methanol, and where a significant C - O bond-breaking decomposition channel leading to the formation of water and surface carbon is also present. The differences in methanol reactivities on these low-coverage potassium- and oxygen-modified surfaces can be attributed largely to electronic modifications of the metal substrate. At higher coverages of the surface additives, a different behavior is encountered. Oxygen at 0o = 0.60 completely inhibits the formation of methoxy due to physical site blocking, while metallic potassium (0 K = 0.33) reacts directly with methanol to form potassium methoxide.
Surface Science 166 (1986) 377- 390 North-Holland, Amsterdam ANALYSIS
OF
PHOTOELECTRON
SINGLE SCATI'ERING
377 DIFFRACTION
SPECTRA
USING
SIMULATIONS
D.P. WOODRUFF
Physics Department, University of Warwick, Coventry CV4 7AL, UK Received 2 May 1985; accepted for publication 9 September 1985 Single scattering calculations of photoelectron diffraction (PhD) spectra from S adsorbed on Ni(100} are presented which investigate the influence of non-structural parameters on the sensitivity of the spectra to take-off angle and on the agreement with the experimental results of the Berkeley group. Some important comparisons are made concerning the relative importance of
Surface Science 166 (1986) 361-376 North-Holland, Amsterdam THE INTERACTION
OF METHANOL
SURFACES: THE EFFECTS Jan HRBEK
361 WITH MODIFIED
Ru(001)
OF OXYGEN AND POTASSIUM
*, R o b e r t D E P A O L A ** a n d F r i e d r i c h M . H O F F M A N N
Exxon Research and Engineering Company, Corporate Research Science Laboratories, Clinton Township, Route 22 East, Annandale, New Jersey 08801, USA Received 12 May 1985; accepted for publication 19 September 1985
The adsorption and decomposition of methanol on a Ru(001) surface modified by preadsorbed potassium and oxygen has been investigated with electron energy loss spectroscopy (EELS) and multiple mass thermal desorption spectroscopy (TDS). On ruthenium precovered with a low coverage of atomic oxygen (0o = 0.25), methoxy formation is promoted with respect to the clean surface and is found to occur at 85 K. In contrast, on ruthenium modified by "ionic" potassium (0 K = 0.10), methoxy formation is inhibited, i.e., oxygen-hydrogen bond breaking does not occur until temperatures reach 240 K. On both surfaces, the decomposition of methanol proceeds via O - H and C - H bond breaking and ultimately leads to the formation of CO and H 2. The results differ from those obtained on the clean Ru(001) surface, where methoxy formation is observed at 85 K only when exposed to small amounts of methanol, and where a significant C - O bond-breaking decomposition channel leading to the formation of water and surface carbon is also present. The differences in methanol reactivities on these low-coverage potassium- and oxygen-modified surfaces can be attributed largely to electronic modifications of the metal substrate. At higher coverages of the surface additives, a different behavior is encountered. Oxygen at 0o = 0.60 completely inhibits the formation of methoxy due to physical site blocking, while metallic potassium (0 K = 0.33) reacts directly with methanol to form potassium methoxide.
Surface Science 166 (1986) 377- 390 North-Holland, Amsterdam ANALYSIS
OF
PHOTOELECTRON
SINGLE SCATI'ERING
377 DIFFRACTION
SPECTRA
USING
SIMULATIONS
D.P. WOODRUFF
Physics Department, University of Warwick, Coventry CV4 7AL, UK Received 2 May 1985; accepted for publication 9 September 1985 Single scattering calculations of photoelectron diffraction (PhD) spectra from S adsorbed on Ni(100} are presented which investigate the influence of non-structural parameters on the sensitivity of the spectra to take-off angle and on the agreement with the experimental results of the Berkeley group. Some important comparisons are made concerning the relative importance of