Nickel Oxide Surface Research Articles

Interference-effects in the laser-induced desorption of small molecules from surfaces: a model study

A diabatic treatment of laser-induced desorption of small molecules from surfaces is considered to be an essential step of the theoretical quantum mechanical simulation of a DIET process on an ab initio basis. The consequences of this treatment are investigated especially with respect to the resulting velocity distributions of the desorbing species. The distributions of NO desorbing from nickel oxide surfaces are characterised by a bimodal structure. In our calculations the diabatic coupling between several investigated two-state systems is introduced via the off-diagonal elements of the Hamiltonian, which determines the time evolution of the quantum system. This procedure is the basis for a discussion of the experimentally observed features in the velocity distributions in terms of a coherent diabatic picture.

Fuchs-Kliewer HREEL Phonon Spectrum of Single Crystal NiO(100) and of Ni(100)/NiO(111) and Ni(100)/NiO(100) Thin Films

The high resolution electron energy loss spectrum (HREELS) of an ionic material is generally dominated by inelastic scattering of the electron with Fuchs-Kliewer phonon modes of the lattice surface. The phonon motion, in which the cations and anions vibrate out of phase to each other, yields a substantial dipole moment and thus an intense phonon spectrum along the specular scattering direction. In NiO, the high symmetry of its fcc rocksalt structure produces a single fundamental Fuchs-Kliewer phonon mode. However, the large cross section for phonon excitation results in multiple scattering events and thus a series of losses at integral multiples of the fundamental phonon energy. We report Fuchs-Kliewer phonon spectra for single crystal NiO(100) and for thin films of nickel oxide grown on Ni(100) single crystal substrates. The NiO(100) orientation is nonpolar, with interpenetrating square arrays of cations and anions, and is the thermodynamically most stable nickel oxide surface. The entire phonon spectrum of the thin film is considerably less than that of the NiO(100) single crystal substrate due to the damping effect of the underlying Ni(100) metal. NiO(100) is produced for Ni(100) substrate temperatures <=300 K under comparable oxygen partial pressures. The NiO(100) orientation is metastable and grows to a limiting thickness of three layers. With a single loss energy of 69.6 meV, the Ni(100)/NiO(1111) Fuchs-Kliewer phonon loss is equal to that of NiO(100) but the multiple losses are more poorly developed despite the comparable thicknesses of the two thin films. The poorer definition of the phonon spectrum is believed to result from a greater amount of disorder in the metastable NiO(111) thin film.

ニッケル酸化膜の摩擦によるエキソ電子放出とエタノールの分解反応との関連

The tribochemical reaction of ethanol on oxidized nickel surfaces was studied using gas chromatography, XPS, and exoelectron emission (EEE) and surface potential (SP) measurements. Ametal surface intentionally oxidized by heating in air at 25-800°C was rubbed with the same metal sample in ethanol vapor. EEE was measured using a Geiger counter with Ar-C2H5OH counter gas. SP was measured by a vibrating reed electrometer. Two gaseous products formed with and without friction--acetaldehyde (A) and an unidentified species (B) containing a carbonyl group. Friction increased products and EEE. Products tended to increase with EEE regardless of friction. Product formation was accompanied by carbon deposition. SP for surfaces oxidized at higher temperatures was negative, but after the reaction increased positively due to carbon deposition. The change in SP correlates with the activated tribochemical reaction, EEE appears to originate when negative charge on the oxidized surface is released due to the reduction by ethanol.

ATOMIC RESOLUTION STM OF THE NiO (001) SURFACE STRUCTURE AND DEFECT SITES: c(2×2) PATTERNING AND EFFECTS OF COVALENT BONDING

Elevated temperature STM has been used to obtain atomic resolution images of flat regions, defect sites and step edges on the (001) surface of crystalline nickel oxide. Identification of surface lattice sites seen in empty and filled states (nickel and oxygen sites, respectively) is consistent with recent theoretical results according to which NiO is a charge transfer insulator with strongly correlated electrons. It has been found that certain surface defects lead to the formation of spatially delocalized hole states resulting in c(2×2) patterning in STM images. The appearance of this patterning points to the presence of a substantial covalent contribution to chemical bonding in NiO.

Surface Electronic States of Adsorbed Nitrogen Molecules on Oxidized Nickel Surface

We present a new technique to investigate the electronic surface structures of metal electrodes and experimental data on oxidized surfaces of nickel electrodes. The experimental system consists of a simple triode structure and an electromagnet to control the momentum of incident electrons. The magnetic field dependence of the transmission electron current to the metal electrodes depends on the electron density at the electrode surface. When the electron density at the surface is high, the incident electrons are scattered by quantized surface states in the surface potential barrier. On the other hand, in the case of low electron density, the incident electrons show resonance characteristics due to the presence of discrete electronic states as a result of the generation of a periodic surface potential. Molecular nitrogen adsorption causes a change in the surface potential, and the bonding states intermediate between covalent bonds and van der Waal's-like bonds are detected.

Formation of Silicate Structures in Oxidized Nickel Surfaces Using Low-temperature Plasma Reaction

Low-temperature plasma reaction with air/water/tetraethylorthosilicate mixtures applied to oxidized nickel surfaces has been shown to produce silicate structures in the oxide layer. A chemically and structurally graded metal/oxide/silicate/silica layer is formed, reducing the dissolution rate in pH 2 nitric acid by two orders of magnitude over more than 30 days. The mechanism of reaction, via SiO plasma species, has been elucidated using XPS, modified Auger parameter studies, mass spectrometric analysis of the plasma and dissolution rates.

The adsorption of methanol on NiO x/Ni{110} : Defect-controlled dissociation

The adsorption, desorption and dissociation of methanol on thin film nickel oxide surfaces grown on a Ni{110} substrate has been investigated using RAIRS. Two thin film oxides have been prepared at two different temperatures (300 and 570–650 K), referred to as the low-temperature (low T) and high-temperature (high T) oxides, respectively. At 130 K, methanol adsorbs molecularly on the regular NiO terraces. Molecular desorption occurs at around 250 K indicating weak chemisorption. However, a small concentration of a more strongly bound methoxy species is observed on the surface of the high T oxide at temperatures in excess of 350 K. In direct contrast, no dissociation to methoxy is observed to occur for methanol adsorption on the low T oxide. In an analogous manner to the dissociation of the water molecule on nickel oxide surfaces, it appears that non-lattice oxygen facilitates abstraction of the hydroxyl hydrogen resulting in the formation of adsorbed methoxy.

Investigations into the chemistry of perfluorodiethoxymethane at nickel and nickel oxide surfaces

We describe the surface chemistry of a low-molecular-weight perfluoroether with an acetal (–O–CF2–O–) unit. The acetal unit has been proposed by others as the critical moiety responsible for the decomposition of linear perfluoropolyethers at metal surfaces. Three nickel surfaces are studied, clean Ni(100), Ni(100) c(2×2)–O, and NiO(100). The experimental techniques are temperature-programmed desorption and high-resolution electron energy loss spectroscopy. Our work shows that even when a perfluoroether containing an acetal unit is used, in this case perfluorodiethoxymethane, decomposition is not apparent on any of the surfaces studied under typical ultrahigh vacuum conditions.

Interactions of alcohols with a nickel oxide(100) surface studied by high-resolution electron energy loss spectroscopy and temperature-programmed desorption spectroscopy

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTInteractions of alcohols with a nickel oxide(100) surface studied by high-resolution electron energy loss spectroscopy and temperature-programmed desorption spectroscopyMing Cheng Wu, Charles M. Truong, and D. Wayne GoodmanCite this: J. Phys. Chem. 1993, 97, 37, 9425–9433Publication Date (Print):September 1, 1993Publication History Published online1 May 2002Published inissue 1 September 1993https://doi.org/10.1021/j100139a029RIGHTS & PERMISSIONSArticle Views244Altmetric-Citations41LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts

Effect of alumina on the reduction of surface nickel oxide; morphology of the surfaces of the surfaces of Ni/Al 2O 3 catalysts

Hydrogen reduction of surface nickel oxide, formed during the low temperature oxidation of nickel, was studied for a series of Ni/Al 2O 3 catalysts. The examinations were carried out mainly by the temperature-programmed reduction (TPR) method. The results obtained show that alumina considerably inhibits the reduction, especially when the reaction proceeds in the presence of water. Analysis of the results lead to conclusion that nonstoichiometric nickel aluminate decorates corners and edges of Ni crystallites. It is supposed that this decoration is responsible for the unique properties of Ni/Al 2O 3 catalysts, e.g. low ability of the catalysts to form Ni (CO) 4 during the interaction with CO, and high thermal stability of nickel in the specimens with low alumina content.

Interactions of ammonia with a nickel oxide (100) surface studied by high-resolution electron energy loss spectroscopy and temperature programmed desorption spectroscopy

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTInteractions of ammonia with a nickel oxide (100) surface studied by high-resolution electron energy loss spectroscopy and temperature programmed desorption spectroscopyMing Cheng Wu, Charles M. Truong, and D. Wayne GoodmanCite this: J. Phys. Chem. 1993, 97, 16, 4182–4186Publication Date (Print):April 1, 1993Publication History Published online1 May 2002Published inissue 1 April 1993https://doi.org/10.1021/j100118a039RIGHTS & PERMISSIONSArticle Views304Altmetric-Citations62LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (644 KB) Get e-Alerts

Fourier-transform infrared spectroscopic study of acetonitrile adsorbed on silica-supported nickel and nickel oxide

The adsorption behaviour of acetonitrile on a silica-supported nickel surface has been investigated by Fourier-transform infrared spectroscopy. The molecule is adsorbed on the silica surface by forming a hydrogen bond between the silanol group and the nitrogen lone-pair electrons. Much stronger chemisorption occurred on either nickel or nickel oxide surfaces. The adsorption mechanism was, however, observed to be completely different for the two surfaces. On the nickel surface, acetonitrile was adsorbed by forming a σ bond via the nitrogen lone-pair electrons. In contrast, the molecule was adsorbed on the nickel oxide surface by forming di–σ bonds with the nitrile carbon and nitrogen atoms following a partial dehydrogenation of the methyl group of acetonitrile.

Ellipsometric studies of potassium octyl xanthate adsorption on nickel surfaces

Adsorption of octyl xanthate onto nickel oxide surfaces and the effect of addition of Ni 2+ or EDTA on the adsorption have been studied by in situ ellipsometry. In contrast to the typical adsorption behaviour of surfactants showing a sharp decrease in adsorption below the cmc, octyl xanthate adsorbs strongly at a concentration 1000 times below its cmc value. An adsorbed amount corresponding to a monolayer is exceeded within a few minutes except at high EDTA concentration. No plateau value was reached in any experiment. The adsorption appears to be governed by the supply of nickel ions at the surface. Multilayers, probably consisting of nickel xanthate precipitate, are formed.

UPS and XPS study of the polymer/metal interface of poly(2‐methyl‐2‐propenenitrile) electropolymerized on an oxidized nickel surface cathode

AbstractMechanisms of formation and structure of the interface between an oxidized nickel surface and poly(2‐methyl‐2‐propenenitrile) obtained by electropolymerization under cathodic polarization are studied by UPS and XPS spectroscopies. The results suggest that a direct interaction takes place between the monomer molecules and surface metallic sites freed by reduction of the metal oxides. The interface between the metal and the resulting polymer is characterized by the existence of chemical bonds of the carbon–nickel type.

Electronic structure investigation at a zirconia-nickel interface

X-ray photoelectron spectroscopy (XPS) is used to study electronic structure effects at a zirconia-nickel interface. A method is described to fabricate ZrO 2 coatings on metallic substrates under ultrahigh vacuum conditions with a sufficiently low coverage to allow examination of the interfacial region. Charging effects which relate to the size of oxide particles deposited on the metal (and not to accumulated charge on the oxide) have been identified for small ZrO 2 particles on nickel, palladium and NiO substrates equivalent to a coating approximately 6A˚thick. The charging effects show up as a broadening of the XPS Zr 3d core-level spectrum. By examining the XPS Ni 2p 3/2 and XPS valence band spectra it is found that an oxidized nickel surface layer is reduced during ZrO 2 deposition.

Potential energy hypersurface for ammonia adsorbing onto nickel oxide

The approach of an ammonia molecule to the surface of nickel oxide was probed theoretically by performing band calculations at the extended Hueckel level on model systems. A hump in the energy vs Ni-NH{sub 3} separation curve was attributed to the initial repulsion of the NH{sub 3} lone-pair electrons by the electron-rich 3d orbitals of nickel. However, once the 3d{sub z}2 orbital was pushed above the Fermi level, the antibonding component of the Ni 3d{sub z}2-NH{sub 3} lone-pair interaction was depopulated and the Ni-NH{sub 3} interaction became strongly attractive. This was demonstrated to be completely analogous to the intended crossing of occupied and unoccupied orbitals in rearrangements of small molecules. A limited study of the potential energy surface was performed, the results of which suggested that NH{sub 3} prefers to attack directly at a surface Ni atom. From the principles derived in the NiO-NH{sub 3} study, qualitative predictions concerning the dynamics of NH{sub 3} adsorbing onto Cr{sub 2}O{sub 3} and Cu{sub 2}O were made.

Solubility and phase behavior of nickel oxide in aqueous sodium phosphate solutions at elevated temperatures

A platinum-lined, flowing autoclave facility was used to investigate the solubility/phase behavior of nickel oxide (NiO) in aqueous sodium phosphate solutions between 290 and 560 K. A layer of hydrous nickel oxide was concluded to exist on the nickel oxide surface below 468 K; only at higher temperatures did the anhydrous nickel oxide phase control the nickel ion solubility behavior. The measured solubility behavior was examined via a nickel(II) ion hydrolysis/complexing model and thermodynamic functions for the hydrolysis/complexing reaction equilibria were obtained from a least-squares analysis of the data. The existence of two new nickel ion complexes are reported for the first time: Ni(OH)2(HPO4)= and Ni(OH)3(H2PO4)=. The positive entropy change associated with the formation of Ni(OH)3(H2PO4)= leads to its dominance in alkaline phosphate solutions at elevated temperatures.

The interaction of oxygen and carbon monoxide with iron oxide, nickel oxide and zinc oxide surfaces: A molecular orbital study

An atom superposition electron delocalization (ASED) molecular orbital technique is employed in this study of catalytic properties of transition metal oxides. Cluster models of stoichiometric iron oxide, nickel oxide and zinc oxide surfaces are used in the investigation of reactions of carbon monoxide, in the absence and presence of preadsorbed oxygen atoms. We predict that oxygen preferentially adsorbs to the atop metal site, suggesting the dissociative adsorption of molecular oxygen. Carbon monoxide, oriented vertically above the surface with the carbon end down, also prefers to adsorb on the atop site. Carbon dioxide is predicted to adsorb more weakly than carbon monoxide in the presence of preadsorbed oxygen atoms, and we find evidence for reaction of carbon monoxide with lattice oxygen as well. The structures and energy levels are examined, and theoretical results compared with experiments.

The interaction of oxygen and carbon monoxide with iron oxide, nickel oxide and zinc oxide surfaces: A molecular orbital study

The interaction of oxygen and carbon monoxide with iron oxide, nickel oxide and zinc oxide surfaces: A molecular orbital study

Laser-enhanced oxidation of nickel

Photoenhanced oxidation of nickel in air at 350 °C under laser irradiation with wavelengths 308 nm≤λ≤1064 nm has been studied. Significant oxidation enhancement over infrared oven heating has been observed under irradiation with short-wavelength lasers. A 690% increase in oxidation rate has been observed under irradiation with 308-nm wavelength laser. The enhanced oxidation decreased with increasing wavelength up to a threshold wavelength of λ=720 nm. The mechanism involved is believed to be the photoexcitation of adsorbed molecular oxygen at the nickel oxide surface leading to enhanced generation of the active atomic oxygen.