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Title: Interaction of Oxygen with TiN(001): N O Exchange and Oxidation Process

Abstract

This work presents a detailed experimental and theoretical study of the oxidation of TiN(001) using a combination of synchrotron-based photoemission and density functional theory (DFT). Experimentally, the adsorption of O{sub 2} on TiN(001) was investigated at temperatures between 250 and 450 K. At the lowest temperature, there was chemisorption of oxygen (O2,gas{yields}2Oads) without significant surface oxidation. In contrast, at 450 K the amount of O{sub 2} adsorbed increased continuously, there was no evidence for an oxygen saturation coverage, a clear signal in the Ti 2p core level spectra denoted the presence of TiO{sub x} species, and desorption of both N{sub 2} and NO was detected. The DFT calculations show that the adsorption/dissociation of O{sub 2} is highly exothermic on a TiN(001) substrate and is carried out mainly by the Ti centers. A high oxygen coverage (larger than 0.5 ML) may induce some structural reconstructions of the surface. The exchange of a surface N atom by an O adatom is a highly endothermic process ({Delta}E=2.84 eV). However, the overall oxidation of the surface layer is thermodynamically favored due to the energy released by the dissociative adsorption of O{sub 2} and the formation of N{sub 2} or NO. Both experimental and theoreticalmore » results lead to conclude that a TiN+mO{sub 2}{yields}TiO{sub x}+NO reaction is an important exit channel for nitrogen in the oxidation process.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
930540
Report Number(s):
BNL-80614-2008-JA
Journal ID: ISSN 0021-9606; JCPSA6; TRN: US200904%%578
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 126
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; TITANIUM NITRIDES; OXIDATION; PHOTOEMISSION; CHEMISORPTION; DENSITY FUNCTIONAL METHOD; DESORPTION; NITROGEN; NITRIC OXIDE; DISSOCIATION; REACTION KINETICS; national synchrotron light source

Citation Formats

Graciani,J., Fdez Sanz, J., Asaki, T., Nakamura, K., and Rodriguez, J.. Interaction of Oxygen with TiN(001): N O Exchange and Oxidation Process. United States: N. p., 2007. Web. doi:10.1063/1.2743418.
Graciani,J., Fdez Sanz, J., Asaki, T., Nakamura, K., & Rodriguez, J.. Interaction of Oxygen with TiN(001): N O Exchange and Oxidation Process. United States. doi:10.1063/1.2743418.
Graciani,J., Fdez Sanz, J., Asaki, T., Nakamura, K., and Rodriguez, J.. Mon . "Interaction of Oxygen with TiN(001): N O Exchange and Oxidation Process". United States. doi:10.1063/1.2743418.
@article{osti_930540,
title = {Interaction of Oxygen with TiN(001): N O Exchange and Oxidation Process},
author = {Graciani,J. and Fdez Sanz, J. and Asaki, T. and Nakamura, K. and Rodriguez, J.},
abstractNote = {This work presents a detailed experimental and theoretical study of the oxidation of TiN(001) using a combination of synchrotron-based photoemission and density functional theory (DFT). Experimentally, the adsorption of O{sub 2} on TiN(001) was investigated at temperatures between 250 and 450 K. At the lowest temperature, there was chemisorption of oxygen (O2,gas{yields}2Oads) without significant surface oxidation. In contrast, at 450 K the amount of O{sub 2} adsorbed increased continuously, there was no evidence for an oxygen saturation coverage, a clear signal in the Ti 2p core level spectra denoted the presence of TiO{sub x} species, and desorption of both N{sub 2} and NO was detected. The DFT calculations show that the adsorption/dissociation of O{sub 2} is highly exothermic on a TiN(001) substrate and is carried out mainly by the Ti centers. A high oxygen coverage (larger than 0.5 ML) may induce some structural reconstructions of the surface. The exchange of a surface N atom by an O adatom is a highly endothermic process ({Delta}E=2.84 eV). However, the overall oxidation of the surface layer is thermodynamically favored due to the energy released by the dissociative adsorption of O{sub 2} and the formation of N{sub 2} or NO. Both experimental and theoretical results lead to conclude that a TiN+mO{sub 2}{yields}TiO{sub x}+NO reaction is an important exit channel for nitrogen in the oxidation process.},
doi = {10.1063/1.2743418},
journal = {Journal of Chemical Physics},
number = ,
volume = 126,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • Isotopic labeling studies in ammonia oxidation and oxygen exchange have been performed over unsupported vanadia catalysts having preferential exposure of different crystal planes. All catalysts were characterized using BET surface area measurement, X-ray diffraction, laser Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, 3-D imaging, and temperature-programmed adsorption/desorption/reduction techniques. Isotopic labeling studies have been performed under steady-state conditions by using {sup 16}O{sub 2} {r_arrow} {sup 18}O{sub 2}, NH{sub 3} + {sup 16}O{sub 2} {r_arrow} NH{sub 3} + {sup 18}O{sub 2}, and {sup 14}NH{sub 3} + O{sub 2} {r_arrow} {sup 15}NH{sub 3} + O{sub 2} switches. The experimentally obtained transients havemore » been compared to those calculated through a mathematical simulation. Results of the oxygen exchange experiments show that, although there is no formation of the cross-labeled oxygen, gaseous oxygen actively exchanges with lattice oxygen on all crystal planes of V{sub 2}O{sub 5}. The oxygen located on the (010) basal plane seems to be more reactive whereas the replenishment of oxygen from the catalyst bulk appears to be faster towards the side planes of the V{sub 2}O{sub 5} crystals. The kinetic experiments performed for ammonia oxidation reaction studies suggest that there are at least two types of sites on the (010) plane responsible for this reaction, one leading to NO formation and the other one leading to N{sub 2} and N{sub 2}O formation. The type of adsorbed ammonia species formed are thought to be controlled by the immediate environment of the V = O species on the surface. 48 refs., 12 figs., 3 tabs.« less
  • The oxidation of the S/sub 3/N/sub 3//sup -/ ion in acetonitrile solution by molecular oxygen gives rise to four major products: S/sub 4/N/sub 5//sup -/, S/sub 4/N/sub 5/O/sup -/, S/sub 3/N/sub 3/O/sup -/, and S/sub 3/N/sub 3/O/sub 2//sup -/. The relative yields of these species are a function of the flow rate of oxygen, and the progress of the reaction and the structure of the various ions in solution can be analyzed by using /sup 15/N NMR spectroscopy. The crystal and molecular structures of (Ph/sub 3/P)/sub 2/N/sup +/S/sub 3/N/sub 3/O/sup -/ and (Ph/sub 3/P)/sub 2/N/sup +/S/sub 3/N/sub 2/O/sub 2//sup -/more » have been determined by x-ray diffraction. Crystals of the former are monoclinic, space group P2/sub 1//c, with a = 17.161 (2) A, b = 9.970 (1) A, c = 20.591 (2) A, ..beta.. = 104.45 (1)/sup 0/, V = 3411.7 A/sup 3/, and Z = 4. Crystals of the latter are monoclinic, space group P2/sub 1/, with a = 12.421 (1) A, b = 13.036 (1) A, c = 10.699 (1) A, ..beta.. = 103.36 (1)/sup 0/, V = 1685.6 A/sup 3/, and Z = 2. Both structures were solved by direct methods and refined by full-matrix least-squares procedures; for (Ph/sub 3/P)/sub 2/N/sup +/S/sub 3/N/sub 3/O/sup -/ the final R = 0.053 and R/sub w/ = 0.075 for 3058 reflections with I > 3sigma(I), and for (Ph/sub 3/P)/sub 2/N/sup +/S/sub 3/N/sub 3/O/sub 2//sup -/ the final R = 0.048 and R/sub w/ = 0.057 for 2312 reflections with I > 3sigma(I). The two anions S/sub 3/N/sub 3/O/sup -/ and S/sub 3/N/sub 3/O/sub 2//sup -/ both possess six-membered S/sub 3/N/sub 3/ ring structures with exocyclic oxygen atoms bonded to sulfur (in S/sub 3/N/sub 3/O/sub 2//sup -/ the oxygens are geminally substituted). Both rings exhibit significant variations in chemically equivalent bond lengths and angles. The visible spectra of S/sub 3/N/sub 3/O/sup -/ (lambda/sub max/ = 509 and 340 nm) and S/sub 3/N/sub 3/O/sub 2//sup -/ (lambda/sub max/ = 562 and 362 nm) are interpreted in terms of the expected perturbations on the ..pi..-manifold of the S/sub 3/N/sub 3//sup -/ anion; the observed absorptions are assigned to ..pi..* ..-->.. ..pi..* type excitations. 34 references, 5 figures, 6 tables.« less
  • Cerium-zirconium mixed oxides (Ce{sub x}Zr{sub 1{minus}x}O{sub 2}), precalcined at 900 C in dry air, were supplied by Rhodia Terres Rares as monophasic solid solutions. Introduction of some zirconium atoms in the ceria lattice by isomorphous substitution clearly influences the final properties of these materials as long as the cubic structure of ceria is maintained. Modifications in oxygen storage capacity (OSC measurements), redox properties (CO TPR), and oxygen exchange processes (TPIE) were studied. Ce{sub 0.63}Zr{sub 0.37}O{sub 2} was shown to have the most promising properties with the largest OSC at 400 C and the highest reactivity in O{sub 2} exchange. Allmore » mixed oxides are able to exchange very large amounts of oxygen compared to ceria, implying the participation of bulk oxygen. Furthermore, on Ce{sub x}Zr{sub (1{minus}x)}O{sub 2} samples, oxygen is predominantly exchanged via a multiple heteroexchange mechanism involving surface dioxygen species as superoxides or peroxides.« less
  • The crystal structure of potassium aqua (o-phenylenediamine-N,N,N{prime},N{prime}-tetraacetato)ferrate(III) dihydrate, (K(Fe(OH{sub 2})-(phdta)){center dot}2H{sub 2}O), has been determined by x-ray crystallography. The central iron(III) ion is seven-coordinate, with one water molecule being hydrated. Water-exchange rates of the iron(III) complex with phdta{sup 4{minus}} in aqueous solution have been studied as a function of temperature and pressure by the oxygen-17 NMR line-broadening method. Activation parameters for water exchange have been determined as follows: k(25 C) = (1.2 {plus minus} 0.2) {times} 10{sup 7} s{sup {minus}1}, {Delta}H{sup {double dagger}} = 26 {plus minus} 3 kJ mol{sup {minus}1}, {Delta}S{sup {double dagger}} = -22 {plus minus} 9 Jmore » K{sup {minus}1} mol{sup {minus}1}, and {Delta}V{sup {double dagger}} = 4.6 {plus minus} 0.2 cm{sup 3} mol{sup {minus}1}. The positive activation volume indicates that the water exchange proceeds via a dissociative interchange mechanism. 41 refs., 4 figs., 4 tabs.« less
  • It was found that the exchange of O/sup 18/ between the gaseous phase and lattice oxygen of vanadium pentoxide is not of first order from a certain degree of exchange. (auth)