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Title: Studies of metal: semiconductor interfaces in catalysis and energy conversion. Annual report, June 15, 1980-June 14, 1981

Abstract

It was shown that CO hydrogenation reactions can be performed reproducibly on a small area well characterized Ni (111) single crystal using an isolation cell technique. The activation energy for methane production (24.7 kcal/mole) and other hydrocarbon product distribution are in excellent agreement with the literature. It was demonstrated that Ni dispersed onto TiO/sub 2/ (100) acquires a negative charge and that the Ni/TiO/sub 2/ (100) exhibits a methanation activity at least 4 times that of Ni(111) with about the same activation energy. The Ni/TiO/sub 2/ also produces more higher hydrocarbons than Ni(111). The photochemical activity of Pt/SrTiO/sub 3/ in both aqueous solutions and in gas phase water was examined. The activity in aqueous solutions under different conditions of pH and Pt coverage can be explained by band bending effects. A low hydrogen yield was observed in the presence of water vapor; this was attributed to a slow photo-regeneration of active surface Ti/sup 3 +/. Preliminary high resolution electron energy loss studies on TiO/sub 2/ (100) showed strong surface phonon bands extending to 3000 cm/sup -1/.

Authors:
Publication Date:
Research Org.:
Northwestern Univ., Evanston, IL (USA)
Sponsoring Org.:
USDOE
OSTI Identifier:
6565714
Report Number(s):
COO-4946-3
DOE Contract Number:
AS02-78ER04946
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
10 SYNTHETIC FUELS; 08 HYDROGEN; ELECTRONS; ENERGY LOSSES; METHANE; SYNTHESIS; NICKEL; CATALYTIC EFFECTS; PLATINUM; TITANIUM OXIDES; CHARGED-PARTICLE TRANSPORT; WATER VAPOR; PHOTOLYSIS; CARBON MONOXIDE; HYDROGENATION; METHANATION; MONOCRYSTALS; ALKANES; CARBON COMPOUNDS; CARBON OXIDES; CHALCOGENIDES; CHEMICAL REACTIONS; CRYSTALS; DECOMPOSITION; ELEMENTARY PARTICLES; ELEMENTS; FERMIONS; FLUIDS; GASES; HYDROCARBONS; LEPTONS; LOSSES; METALS; ORGANIC COMPOUNDS; OXIDES; OXYGEN COMPOUNDS; PHOTOCHEMICAL REACTIONS; PLATINUM METALS; RADIATION TRANSPORT; TITANIUM COMPOUNDS; TRANSITION ELEMENT COMPOUNDS; TRANSITION ELEMENTS; VAPORS; 090121* - Hydrocarbon Fuels- Chemical Synthesis- (1976-1989); 080106 - Hydrogen- Production- Biosynthesis & Photochemical Processes

Citation Formats

Chung, Y W. Studies of metal: semiconductor interfaces in catalysis and energy conversion. Annual report, June 15, 1980-June 14, 1981. United States: N. p., 1981. Web. doi:10.2172/6565714.
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Chung, Y W. Studies of metal: semiconductor interfaces in catalysis and energy conversion. Annual report, June 15, 1980-June 14, 1981. United States. doi:10.2172/6565714.
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Chung, Y W. Sun . "Studies of metal: semiconductor interfaces in catalysis and energy conversion. Annual report, June 15, 1980-June 14, 1981". United States. doi:10.2172/6565714. https://www.osti.gov/servlets/purl/6565714.
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@article{osti_6565714,
title = {Studies of metal: semiconductor interfaces in catalysis and energy conversion. Annual report, June 15, 1980-June 14, 1981},
author = {Chung, Y W},
abstractNote = {It was shown that CO hydrogenation reactions can be performed reproducibly on a small area well characterized Ni (111) single crystal using an isolation cell technique. The activation energy for methane production (24.7 kcal/mole) and other hydrocarbon product distribution are in excellent agreement with the literature. It was demonstrated that Ni dispersed onto TiO/sub 2/ (100) acquires a negative charge and that the Ni/TiO/sub 2/ (100) exhibits a methanation activity at least 4 times that of Ni(111) with about the same activation energy. The Ni/TiO/sub 2/ also produces more higher hydrocarbons than Ni(111). The photochemical activity of Pt/SrTiO/sub 3/ in both aqueous solutions and in gas phase water was examined. The activity in aqueous solutions under different conditions of pH and Pt coverage can be explained by band bending effects. A low hydrogen yield was observed in the presence of water vapor; this was attributed to a slow photo-regeneration of active surface Ti/sup 3 +/. Preliminary high resolution electron energy loss studies on TiO/sub 2/ (100) showed strong surface phonon bands extending to 3000 cm/sup -1/.},
doi = {10.2172/6565714},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Feb 01 00:00:00 EST 1981},
month = {Sun Feb 01 00:00:00 EST 1981}
}
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Technical Report:
View Technical Report (0.73 MB)
DOI:  10.2172/6565714
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  • We showed that CO is chemisorbed molecularly on both Ni(111) and Ni/TiO/sub 2/(100) surfaces near room temperature, but is suppressed by a factor of 2 to 2-1/2 on the Ni/TiO/sub 2/(100) surface. X-ray photoemission reveals that the carbon 1s level for CO adsorbed on Ni/TiO/sub 2/(100) has a smaller binding energy (by about 0.6 eV) than Ni(111), indicating chemical state differences. High pressure (up to 80 Torr total pressure) CO hydrogenation studies on Ni/TiO/sub 2/(100) showed that the methanation activity is a function of the average Ni thickness, reaching a maximum of about four times that of Ni (111) atmore » a thickness of 5A. Substitution by deuterium results in no change in the methanation activity. On Ni(111), however, an inverse isotope effect was observed for the production of ethylene while on Ni/TiO/sub 2/, a normal isotope effect was observed. The magnitude of the effect is a function of temperature. The photochemical activity of TiO/sub 2/ in the photo-dissociation of water was examined in a specially constructed isolation cell with a sensitivity of 0.5 monolayer for hydrogen. We found that hydrogen can be produced via a thermally assisted process (significant only above 200/sup 0/C, with an activation energy of 27 kcal/mole) and a photon-assisted process (with no activation energy). The H/sub 2/ photo-production rate is independent of the CO partial pressure but increases monotonically with water partial pressure. At low photon intensity, the reaction rate increases approximately linearly with photon intensity, but saturates as the photon flux increases. A kinetic model was proposed that explains all these observed features. A high resolution electron energy loss spectrometer was constructed with all the electronics, computer interface and control software. Preliminary tests showed that the combined system performs as designed. Such a spectrometer will be used for vibrational studies of molecules adsorbed on surfaces.« less

  • Experimental capabilities were enhanced by the incorporation of an Al/Mg K..cap alpha.. x-ray source for x-ray photoemission studies, a micro-computer for data acquisition and analysis, an isolation cell attachment to the UHV surface analysis chamber for performing high pressure chemical reaction studies, a high intensity UV light source for photochemical studies, and finally an ultra-sensitive quartz crystal thickness monitor for controlled metal deposition. A method was developed to measure the chemical state of ad-atoms on semiconductor surfaces using x-ray photoemission. Using such a technique, it was found that the Pt atoms in contact with the SrTiO/sub 3/ (100)-(1x1) surface acquiremore » a negative charge, viz 0.6 electron/Pt-atom. By studying the line shape changes of the Ti 2p core levels, it was found that the charge transfer is via the Ti/sup 3 +/-oxygen vacancy complexes on the SrTiO/sub 3/ surface.« less

  • The installation of a multiple-technique surface analytical system capable of Auger, photoemission (UPS and XPS), low-energy electron diffraction, thermal desorption and thin-film evaporation studies was completed. An isolation cell attachment was designed for high-pressure gas-phase (1 to 1000 torr) reaction studies. By depositing nickel onto a clean ordered TiO/sub 2/(110) surface held at room temperature, an ordered overlayer was obtained as evidenced by LEED. Both energy loss and uv photoemission studies showed that there is an electron transport from nickel to TiO/sub 2/, resulting in an increase of the surface Ti/sup 3 +/ concentration and the formation of an accumulationmore » layer on the TiO/sub 2/(110) surface. In addition, uv photoemission results suggested that the Ni atoms and the surface Ti/sup 3 +/ are well dispersed on the TiO/sub 2/ surface. Auger studies on the clean SrTiO/sub 3/(100)-lxl surface showed that the strontium Auger signal decreases abruptly as the temperature is raised beyond 240/sup 0/C. This is believed to be a result of the outward displacement of the topmost TiO/sub 2/ layer relative to the second SrO layer. Platinum deposition on the SrTiO/sub 3/(100)-lxl surface results in the removal of surface Ti/sup 3 +/ and the formation of a Schottky barrier at the interface. This result is discussed in light of the recent findings in photoelectrolysis. 9 figures.« less

  • This report summarizes major findings on the photodecomposition of water on Pt/SrTiO/sub 3/. A model is presented of the strong metal-support interaction. (DLC)

  • ;
    Progress is reported on research in molecular physics involving electron-bombardment molecular dissociation. The velocity distribution of metastable and ionic fragments are measured using a pulsed electron beam and a time-of-flight technique. Fragments from the hydrogen molecule and its deuterated forms have been investigated using electron energies from 30 to 100 electron-volts. Dissociation channels via particular molecular or molecular ion excited states have been proposed to explain observed features in the velocity spectra. A similar experiment involving hydrogen fragments from the hydrogen halides is also in progress. Preliminary data show several resolved velocity groups indicating the presence of multiple dissociating channels.more » Experiments using water and hydrogen sulfide molecules are also underway. Finally, we are continuing to develop our ion mass filter which allows us to obtain separate ion velocity distributions for each mass in a situation in which several ion masses are present.« less