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Title: Manipulation and patterning of the surface hydrogen concentrationon Pd(111) electric fields

Abstract

Modification of the structure of materials at the nanoscale level is one goal of current nanoscience research. For example, by purposefully modifying the spatial distribution of adsorbates one could control the rate of chemical reactions on a local scale. Here we show how this can be accomplished in the case of H on Pd(111) through the application of local electric fields. Hydrogen adsorption on the platinum group metals is particularly interesting because these metals are used as catalysts in a variety of industrial processes, including hydrogenation and dehydrogenation reactions. Electric fields on surfaces are also of primary interest in electrochemistry where despite the considerable amount of experimental and theoretical work done to date, there still remains more work to be done before a clear understanding of phenomena at the atomic scale can be accomplished.

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
Sponsoring Org.:
USDOE Director. Office of Science. Basic EnergySciences
OSTI Identifier:
919375
Report Number(s):
LBNL-60112
Journal ID: ISSN 0044-8249; ANCEAD; R&D Project: 517950; BnR: KC0203010; TRN: US200822%%260
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Angewandte Chemie; Journal Volume: 119; Journal Issue: 30; Related Information: Journal Publication Date: 06/22/2007
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ADSORPTION; CATALYSTS; CHEMICAL REACTIONS; DEHYDROGENATION; ELECTRIC FIELDS; ELECTROCHEMISTRY; HYDROGEN; HYDROGENATION; MODIFICATIONS; PLATINUM; SPATIAL DISTRIBUTION

Citation Formats

Mitsui, T., Fomin, E., Ogletree, D.F., Salmeron, M., Nilekar,A.U., and Mavrikakis, M. Manipulation and patterning of the surface hydrogen concentrationon Pd(111) electric fields. United States: N. p., 2007. Web. doi:10.1002/ange.200604498.
Mitsui, T., Fomin, E., Ogletree, D.F., Salmeron, M., Nilekar,A.U., & Mavrikakis, M. Manipulation and patterning of the surface hydrogen concentrationon Pd(111) electric fields. United States. doi:10.1002/ange.200604498.
Mitsui, T., Fomin, E., Ogletree, D.F., Salmeron, M., Nilekar,A.U., and Mavrikakis, M. Thu . "Manipulation and patterning of the surface hydrogen concentrationon Pd(111) electric fields". United States. doi:10.1002/ange.200604498. https://www.osti.gov/servlets/purl/919375.
@article{osti_919375,
title = {Manipulation and patterning of the surface hydrogen concentrationon Pd(111) electric fields},
author = {Mitsui, T. and Fomin, E. and Ogletree, D.F. and Salmeron, M. and Nilekar,A.U. and Mavrikakis, M.},
abstractNote = {Modification of the structure of materials at the nanoscale level is one goal of current nanoscience research. For example, by purposefully modifying the spatial distribution of adsorbates one could control the rate of chemical reactions on a local scale. Here we show how this can be accomplished in the case of H on Pd(111) through the application of local electric fields. Hydrogen adsorption on the platinum group metals is particularly interesting because these metals are used as catalysts in a variety of industrial processes, including hydrogenation and dehydrogenation reactions. Electric fields on surfaces are also of primary interest in electrochemistry where despite the considerable amount of experimental and theoretical work done to date, there still remains more work to be done before a clear understanding of phenomena at the atomic scale can be accomplished.},
doi = {10.1002/ange.200604498},
journal = {Angewandte Chemie},
number = 30,
volume = 119,
place = {United States},
year = {Thu May 10 00:00:00 EDT 2007},
month = {Thu May 10 00:00:00 EDT 2007}
}
  • The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. Modification of the structure of materials at the nanoscale level is one goal of current nanoscience research. For example, by purposefully modifying the spatial distribution of adsorbates, the rate of chemical reactions could be controlled on a local scale. Herein, we show how this goal can be accomplished in the case of hydrogen on Pd(111) through the application of localmore » electric fields. Hydrogen adsorption on the Group 10 metals is particularly interesting, because these metals are used as catalysts in a variety of industrial processes, including hydrogenation and dehydrogenation reactions.[1, 2] Electric fields on surfaces are also of primary interest in electrochemistry,[3, 4] and despite the considerable amount of experimental and theoretical work done to date,[5–12] there still remains more work to be done before a clear understanding of electric-field-induced phenomena at the atomic scale can be gained.« less
  • Past scanning tunneling microscopy (STM) experiments of H manipulation on Pd(111), at low temperature, have shown that it is possible to induce diffusion of surface species as well as of those deeply buried under the surface. Several questions remain open regarding the role of subsurface site occupancies. In the present work, the interaction potential of H atoms with Pd(111) under various H coverage conditions is determined by means of density functional theory calculations in order to provide an answer to two of these questions: (i) whether subsurface sites are the final locations for the H impurities that attempt to emergemore » from bulk regions, and (ii) whether penetration of the surface is a competing route of on-surface diffusion during depletion of surface H on densely covered Pd(111). We find that a high H coverage has the effect of blocking resurfacing of H atoms travelling from below, which would otherwise reach the surface fcc sites, but it hardly alters deeper diffusion energy barriers. Penetration is unlikely and restricted to high occupancies of hcp hollows. In agreement with experiments, the Pd lattice expands vertically as a consequence of H atoms being blocked at subsurface sites, and surface H enhances this expansion. STM tip effects are included in the calculations self-consistently as an external static electric field. The main contribution to the induced surface electric dipoles originates from the Pd substrate polarisability. We find that the electric field has a non-negligible effect on the H-Pd potential in the vicinity of the topmost Pd atomic layer, yet typical STM intensities of 1-2 VÅ{sup −1} are insufficient to invert the stabilities of the surface and subsurface equilibrium sites.« less
  • The coadsorption and interactions of oxygen and hydrogen on Pd(1 1 1) was studied by scanning tunneling microscopy and density functional theory calculations. In the absence of hydrogen oxygen forms a (2 x 2) ordered structure. Coadsorption of hydrogen leads to a structural transformation from (2 x 2) to a ({radical}3 x {radical}3)R30 degree structure. In addition to this transformation, hydrogen enhances the mobility of oxygen. To explain these observations, the interaction of oxygen and hydrogen on Pd(1 1 1) was studied within the density functional theory. In agreement with the experiment the calculations find a total energy minimum formore » the oxygen (2 x 2) structure. The interaction between H and O atoms was found to be repulsive and short ranged, leading to a compression of the O islands from (2 x 2) to ({radical}3 x {radical}3)R30 degree ordered structure at high H coverage. The computed energy barriers for the oxygen diffusion were found to be reduced due to the coadsorption of hydrogen, in agreement with the experimentally observed enhancement of oxygen mobility. The calculations also support the finding that at low temperatures the water formation reaction does not occur on Pd(1 1 1).« less
  • Photoemission indicates that the formation of the surface states (surface resonances) on the (111) face of ultrathin Pd overlayers on a recrystallized Nb foil commences with the deposition of the third atomic layer and is completely established at the full fourth layer. It also shows the formation of two resonant d states at submonolayer coverages, corresponding to the interaction of Pd d levels with the Nb bulk bands and to the Pd bulk d-band resonance, respectively.