The defect structure of nickel oxide surfaces as revealed by photoelectron spectroscopy

Roberts, M.W.; Smart, Roger St. C.

doi:10.1039/f19848002957

Cited by 164 publications

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“…This high binding energy Ni 2p 3/.2 peak most likely arises from OH groups adsorbed on disordered NiO. 28 As water is removed, O 2-species are formed together with Ni vacancies. Annealing at over 100°C reduces the Ni 3+ concentration ( Figure 1a).…”

Section: Resultsmentioning

confidence: 99%

State of Transition Metal Catalysts During Carbon Nanotube Growth

et al. 2009

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We study catalyst-support and catalyst-carbon interactions during the chemical vapor deposition of singlewalled carbon nanotubes by combining environmental transmission microscopy and in situ, time-resolved X-ray photoelectron spectroscopy. We present direct evidence of what constitutes catalyst functionality by comparing the behavior of Ni, Fe, Pd, and Au model catalyst films on SiO 2 during preannealing in O 2 and NH 3 and during C 2 H 2 decomposition. The catalyst metal surface supplies sites to dissociate the hydrocarbon precursor and then guides the formation of a carbon lattice and the liftoff of a carbon cap. The catalysts are sharply distinguished by their reactivity toward activation of the hydrocarbon precursor, following trends known from heterogeneous catalysis. For Fe and Ni, the active state of the catalyst is a crystalline metallic nanoparticle. Graphitic networks do not form on oxidized Fe. Pd forms a silicide on SiO 2 under our reducing conditions. Pd (silicides) and Au nanocrystals are catalytically less efficient in terms of precursor dissociation, while the low adhesion of C on Au surfaces impedes nanotube nucleation.

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Section: Resultsmentioning

confidence: 99%

State of Transition Metal Catalysts During Carbon Nanotube Growth

et al. 2009

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“…36,37 The next higher BE photoelectron peak (531.4 eV) has the chemical shift of an O (ads) species. 38 A small peak located at 533.1 eV is attributed to the presence of a dioxygen adsorbate (O 2 (ads)) at the oxide surface. These latter species were shown to be highly concentrated at the outer surface by angular dependent XPS (not shown Figure 5.…”

Section: Reactions At 300°c and 130 Pamentioning

confidence: 99%

Structure and growth of oxides on polycrystalline nickel surfaces

Payne

Grosvenor

Biesinger

et al. 2007

Surface & Interface Analysis

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The oxidation of polycrystalline nickel (Ni) metal surfaces after exposure to oxygen gas (O 2 ) at 25 and 300°C and pressures near 130 Pa, was studied using X-ray photoelectron spectroscopy (XPS). Oxide structures involving both divalent (Ni 2+ ) and trivalent (Ni 3+ ) species could be distinguished using Ni 2p spectra, while surface adsorbed O 2 and atomic oxygen (O) species could be differentiated from bulk oxide (O 2− ) using O 1s spectra. Oxide thicknesses and distributions were determined using QUASES  , and the average oxide thickness was verified using the Strohmeier formula. The reaction kinetics for oxide films grown at 300°C followed a parabolic mechanism, with an oxide thickness of greater than 4 nm having formed after 60 min. Exposure at 25°C followed a direct logarithmic mechanism with an oxide growth rate about four to five times slower than at 300°C. Reaction of a Ni (100) single crystal under comparable conditions showed much slower reaction rates compared to polycrystalline specimens. The higher reaction rate of the polycrystalline materials is attributed to grain boundary transport of Ni cations. Oxide thickness was measured on a microscopic scale for polycrystalline Ni exposed to large doses of O 2 at 25 and 300°C. The thickness of oxide was not strongly localized on this scale. However, the QUASES  analysis suggests that there is localized growth on a nanometric scale -the result of island formation. Copyright  2007 John Wiley & Sons, Ltd.KEYWORDS: X-ray photoelectron spectroscopy; nickel; oxidation; polycrystalline surfaces INTRODUCTIONThe oxidation of nickel (Ni) metal surfaces at ambient temperatures leads to the formation of thin passive films that tend to be described best using logarithmic kinetics. 1Following passivation there is little subsequent change in oxide thickness with time. 2 The mechanism is believed to follow that which was first suggested by Mott and Cabrera. 3 Reactant oxygen molecules (O 2 ) adsorb onto the surface of the metal and decompose into atomic oxygen (O (ads)). 4 The O (ads) then bonds covalently with the Ni metal atoms at the surface, weakening their attachment to the lattice. 4 Owing to the difference in electronegativity between Ni and O, a dipole forms which allows the two atoms to exchange places.4 Such a place exchange mechanism is responsible for the formation of the first one or two monolayers of oxide only. 4 Further oxidation is driven by the formation of an electric field created by the tunneling of electrons from the Ni atoms in the metal, through the thin oxide layer, to the O (ads) sitting on the surface. 1 The presence of this electric field induces the movement of ions through the oxide leading to the formation of a thicker film.1 After the film reaches a Ł Correspondence to: Brad P. Payne, Department of Chemistry, Room G-4, Western Science Centre, The University of Western Ontario, London, ON N6A 5B7, Canada. E-mail: bpayne2@uwo.ca certain thickness, the electric field is no longer strong enough to promote ion diffusion and oxidation sto...

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“…Ni(OH) 2 and NiOOH were found to fit reasonably to the multiplet line shape initially calculated for the free ions by Gupta and Sen. [9,10] NiO, which shows a well-resolved set of peaks, could only be satisfactorily fitted with the Gupta and Sen line shape by allowing variation in the binding energy positions of the multiplet contributions. For all three compounds, a broad peak associated with other intrinsic losses at a higher binding energy than the main peak multiplets, must be added to model the valley between the main peak and the satellite structures as is consistent with the inter-band losses attributed by Hagelin-Weaver et al [8,11] Roberts and Smart [12] have investigated changes in the defect structure of NiO due to heat treatment. A peak at 856.1 eV, detectable through the application of shallow takeoff angle analysis, was attributed to the presence of Ni(III).…”

Section: Introductionmentioning

confidence: 99%

X‐ray photoelectron spectroscopic chemical state quantification of mixed nickel metal, oxide and hydroxide systems

Biesinger

Payne

Lau

et al. 2009

Surface & Interface Analysis

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Quantitative chemical state X-ray photoelectron spectroscopic analysis of mixed nickel metal, oxide, hydroxide and oxyhydroxide systems is challenging due to the complexity of the Ni 2p peak shapes resulting from multiplet splitting, shake-up and plasmon loss structures. Quantification of mixed nickel chemical states and the qualitative determination of low concentrations of Ni(III) species are demonstrated via an approach based on standard spectra from quality reference samples (Ni, NiO, Ni(OH) 2 , NiOOH), subtraction of these spectra, and data analysis that integrates information from the Ni 2p spectrum and the O 1s spectra. Quantification of a commercial nickel powder and a thin nickel oxide film grown at 1-Torr O 2 and 300 • C for 20 min is demonstrated. The effect of uncertain relative sensitivity factors (e.g. Ni 2.67 ± 0.54) is discussed, as is the depth of measurement for thin film analysis based on calculated inelastic mean free paths.

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The defect structure of nickel oxide surfaces as revealed by photoelectron spectroscopy

Cited by 164 publications

References 0 publications

State of Transition Metal Catalysts During Carbon Nanotube Growth

State of Transition Metal Catalysts During Carbon Nanotube Growth

Structure and growth of oxides on polycrystalline nickel surfaces

X‐ray photoelectron spectroscopic chemical state quantification of mixed nickel metal, oxide and hydroxide systems

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