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Title: Energy level shifts at the silica/Ru(0001) heterojunction driven by surface and interface dipoles

Abstract

Charge redistribution at heterogeneous interfaces is a fundamental aspect of surface chemistry. Manipulating the amount of charges and the magnitude of dipole moments at the interface in a controlled way has attracted tremendous attention for its potential to modify the activity of heterogeneous catalysts in catalyst design. Two-dimensional ultrathin silica films with well-defined atomic structures have been recently synthesized and proposed as model systems for heterogeneous catalysts studies. R. Wlodarczyk et al. (Phys. Rev. B, 85, 085403 (2012)) have demonstrated that the electronic structure of silica/Ru(0001) can be reversibly tuned by changing the amount of interfacial chemisorbed oxygen. Here we carried out systematic investigations to understand the underlying mechanism through which the electronic structure at the silica/Ru(0001) interface can be tuned. As corroborated by both in situ X-ray photoelectron spectroscopy and density functional theory calculations, the observed interface energy level alignments strongly depend on the surface and interfacial charge transfer induced dipoles at the silica/Ru(0001) heterojunction. These observations may help to understand variations in catalytic performance of the model system from the viewpoint of the electronic properties at the confined space between the silica bilayer and the Ru(0001) surface. As a result, the same behavior is observed for the aluminosilicatemore » bilayer, which has been previously proposed as a model system for zeolites.« less

Authors:
 [1];  [2];  [2];  [2];  [2];  [2];  [2]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States); Stony Brook Univ., Stony Brook, NY (United States)
  2. Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1328366
Report Number(s):
BNL-112657-2016-JA
Journal ID: ISSN 1022-5528; R&D Project: 16068; KC0403020
Grant/Contract Number:
SC00112704
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Topics in Catalysis
Additional Journal Information:
Journal Name: Topics in Catalysis; Journal ID: ISSN 1022-5528
Publisher:
Springer
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 2D zeolites; charge transfer; surface and interface dipoles; energy level shift; density functional theory; in situ x-ray photoelectron spectroscopy

Citation Formats

Wang, Mengen, Zhong, Jian -Qiang, Kestell, John, Waluyo, Iradwikanari, Stacchiola, Dario J., Boscoboinik, J. Anibal, and Lu, Deyu. Energy level shifts at the silica/Ru(0001) heterojunction driven by surface and interface dipoles. United States: N. p., 2016. Web. doi:10.1007/s11244-016-0704-x.
Wang, Mengen, Zhong, Jian -Qiang, Kestell, John, Waluyo, Iradwikanari, Stacchiola, Dario J., Boscoboinik, J. Anibal, & Lu, Deyu. Energy level shifts at the silica/Ru(0001) heterojunction driven by surface and interface dipoles. United States. doi:10.1007/s11244-016-0704-x.
Wang, Mengen, Zhong, Jian -Qiang, Kestell, John, Waluyo, Iradwikanari, Stacchiola, Dario J., Boscoboinik, J. Anibal, and Lu, Deyu. Mon . "Energy level shifts at the silica/Ru(0001) heterojunction driven by surface and interface dipoles". United States. doi:10.1007/s11244-016-0704-x. https://www.osti.gov/servlets/purl/1328366.
@article{osti_1328366,
title = {Energy level shifts at the silica/Ru(0001) heterojunction driven by surface and interface dipoles},
author = {Wang, Mengen and Zhong, Jian -Qiang and Kestell, John and Waluyo, Iradwikanari and Stacchiola, Dario J. and Boscoboinik, J. Anibal and Lu, Deyu},
abstractNote = {Charge redistribution at heterogeneous interfaces is a fundamental aspect of surface chemistry. Manipulating the amount of charges and the magnitude of dipole moments at the interface in a controlled way has attracted tremendous attention for its potential to modify the activity of heterogeneous catalysts in catalyst design. Two-dimensional ultrathin silica films with well-defined atomic structures have been recently synthesized and proposed as model systems for heterogeneous catalysts studies. R. Wlodarczyk et al. (Phys. Rev. B, 85, 085403 (2012)) have demonstrated that the electronic structure of silica/Ru(0001) can be reversibly tuned by changing the amount of interfacial chemisorbed oxygen. Here we carried out systematic investigations to understand the underlying mechanism through which the electronic structure at the silica/Ru(0001) interface can be tuned. As corroborated by both in situ X-ray photoelectron spectroscopy and density functional theory calculations, the observed interface energy level alignments strongly depend on the surface and interfacial charge transfer induced dipoles at the silica/Ru(0001) heterojunction. These observations may help to understand variations in catalytic performance of the model system from the viewpoint of the electronic properties at the confined space between the silica bilayer and the Ru(0001) surface. As a result, the same behavior is observed for the aluminosilicate bilayer, which has been previously proposed as a model system for zeolites.},
doi = {10.1007/s11244-016-0704-x},
journal = {Topics in Catalysis},
number = ,
volume = ,
place = {United States},
year = {Mon Sep 12 00:00:00 EDT 2016},
month = {Mon Sep 12 00:00:00 EDT 2016}
}

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  • Core-ionization potentials (CIP's) are computed for Be(0001). Three core features are observed in corresponding photoelectron spectra, with CIP's shifted relative to the bulk core level by [minus]0.825, [minus]0.570, and [minus]0.265 eV. The computed CIP shifts for the outer and subsurface layers, [minus]0.60 and [minus]0.29 eV, respectively, agree with the latter two of these. It is surmised that the [minus]0.825-eV shift is associated with a surface defect. The negative signs of the Be(0001) surface core-level shifts do not fit into the thermochemical picture widely used to explain CIP shifts. The reason is that a core-ionized Be atom is too small tomore » bond effectively to the remainder of the unrelaxed Be lattice.« less
  • The authors have applied variational transition state theory with a semiclassical tunneling method to calculate the rates of hydrogen and deuterium diffusing on a Ru(0001) surface. We present diffusion coefficients and kinetic isotope effects for the temperature range from 80 to 800 K using the fitted potential and also for two modified potentials - one in which the potential along the minimum-energy path is scaled by a constant and one in which the pairwise potential parameters are modified to change the barrier height. The results for all three potentials are compared to experimental rate coefficients determined recently by laser-induced thermalmore » desorption.« less
  • The layer-dependent Debye temperature of Ru(0001) is determined by means of high-energy resolution core-level photoelectron spectroscopy measurements. The possibility to disentangle three different components in the Ru 3d{sub 5/2} spectrum of Ru(0001), originating from bulk, first-, and second-layer atoms, allowed us to follow the temperature evolution of their photoemission line shapes and binding energies. Temperature effects were detected, namely, a lattice thermal expansion and a layer-dependent phonon broadening, which was interpreted within the framework of the Hedin-Rosengren formalism based on the Debye theory. The resulting Debye temperature of the top-layer atoms is 295{+-}10 K, lower than that of the bulkmore » (T=668{+-}5 K) and second-layer (T=445{+-}10 K) atoms. While these results are in agreement with the expected phonon softening at the surface, we show that a purely harmonic description of the motion of the surface atoms is not valid, since anharmonic effects contribute significantly to the position and line shape of the different core-level components.« less
  • We present a model for the extra-atomic contributions to core-level shifts in insulating thin films on polarizable substrates. The final-state shift is calculated from the screening-dependent local fields at a photoemitting atom and shown to be comparable to the initial-state Madelung potential shift in polar crystals. For Xe(111) films, our model completely accounts for experimental results. For NaCl(100) and CaF{sub 2}(111) surfaces, we present predictions of surface core-level shifts for simple bulk terminations. We discuss corrections which can be incorporated into our model.
  • The photochemical reaction of dihydrotetraruthenium tridecacarbonyl, H[sub 2]Ru[sub 4](CO)[sub 13], was investigated by UV-visible and FT-IR absorption spectroscopies at 77 K in both a 3-methylpentane matrix and a polystyrene film. Upon irradiation at 313 nm, H[sub 2]Ru[sub 4](CO)[sub 13] undergoes clean CO dissociation yielding selectively a single product. One CO is released from each parent carbonyl cluster that reacts. Upon warming to 298 K, the efficient recombination of CO trapped in nearby sites with the photoproduct completely regenerates the parent cluster H[sub 2]Ru[sub 4](CO)[sub 13]. From these and other results, the photoproduct is identified as the coordinatively unsaturated cluster H[submore » 2]Ru[sub 4](CO)[sub 12]. The photoinduced CO dissociation is dependent on the excitation wavelength, which can be interpreted in terms of the electronic structure of the corresponding excited states. At 298 K, UV-visible light irradiation does not produce any changes in the absorption spectra irrespective of the excitation wavelength. This can be attributed to geminate recombination in which released CO efficiently recombines with H[sub 2]Ru[sub 4](CO)[sub 12]. The UV-visible and IR spectra of matrix isolated H[sub 2]Ru[sub 4](CO)[sub 12] agree with those of the photoproduct formed when H[sub 2]Ru[sub 4](CO)[sub 13] adsorbed on the surface of silica is irradiated. This spectral agreement allows the photoproduct on silica to be assigned as H[sub 2]Ru[sub 4](CO)[sub 12], which supports the previous postulate about the photochemical process occurring when H[sub 2]Ru[sub 4](CO)[sub 13] absorbed on the surface of silica is irradiated. 14 refs., 5 figs.« less