The Adsorption of Liquid and Vapor Water on TiO2 (110) Surfaces: The Role of Defects

1994 ◽  
Vol 357 ◽  
Author(s):  
Li-Qiong Wang ◽  
Don R. Baer ◽  
Mark. H. Engelhard
Keyword(s):  
Electron Beam ◽  
Vapor Pressure ◽  
Liquid Water ◽  
Photoelectron Spectroscopy ◽  
Surface Defects ◽  
Water Exposure ◽  
Pressure Water ◽  
Electronic Defects ◽  
Induced Defects

AbstractThe adsorption of liquid and vapor water on defective and nearly defect-free TiO2 (110) surfaces has been examined using X-ray photoelectron spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UPS). The study has focused on examining electronic defects as created in vacuum and after exposure to both liquid and vapor water. The defective surfaces were prepared by electron-beam exposure and Ar+ bombardment. With exposure up to 104 L low vapor pressure (<10−5 Torr) water to defective surfaces, little or no changes on Ti 3d defect intensities were observed, in agreement with the previous studies. However, defect intensities were greatly reduced after exposing defective surfaces to ∼ 108 L higher vapor pressure (0.2 - 0.6 Torr) water for 5 min. More significantly, XPS and UPS spectra showed that electron-beam induced defects were completely removed upon liquid water exposure, while defects created by Ar+ bombardment were only partially removed. It was found that surface defects created by Ar+ bombardment were removed more readily than sub-surface defects. For a nearly defect-free surface, water coverages were ∼ 0.02 ML at 104 L exposure to low vapor pressure water, ∼ 0.07 ML at 108 L exposure to higher vapor pressure water, and ∼ 0.125 ML with liquid water exposure, respectively.

The Interaction of Liquid and Vapor Water with Nearly Defect-Free and Defective TiO2(100) Surfaces

1996 ◽  
Vol 432 ◽  
Author(s):  
Li-Qiong Wang ◽  
P. X. Skiba ◽  
A. N. Shultz ◽  
Don R. Baer ◽  
Mark H. Engelhard
Keyword(s):  
Electron Beam ◽  
Vapor Pressure ◽  
Liquid Water ◽  
Photoelectron Spectroscopy ◽  
Surface Defect ◽  
Photoemission Spectroscopy ◽  
Water Exposure ◽  
Pressure Water ◽  
Adsorption Rates ◽  
Induced Defects

AbstractThe interaction of both liquid and vapor water on nearly defect-free and defective TiO2(100) surfaces has been investigated using X-ray photoelectron spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UPS). The study has focused on examining electronic or chemical defects as created in vacuum and after exposure to both liquid and vapor water. Defective surfaces were prepared by electron-beam exposure and Ar+ bombardment. For a nearly defect-free (100)1×1 surface, water coverage was ∼0.02 ML (1ML = 2.9×1015/cm2) at 104 L exposure to low vapor pressure water, ∼0.08 ML at 108 L exposure to higher vapor pressure water, and ∼0.12 ML with liquid water exposure, respectively. Defect intensities were greatly reduced after exposing defective surfaces to ∼102 L low vapor pressure water. More significantly, electron-beam induced defects were completely removed upon higher-pressure vapor exposure (>104 L) or liquid water exposure, while defects created by Ar+ bombardment were only partially removed. The adsorption behavior and surface defect reactivity for TiO2(100) 1×1 surfaces were compared with those for TiO2(110) surfaces. The adsorption rates for nearly defect-free (100) 1×1 and (110) surfaces are comparable. However, the rate of defect “healing” for a defective (100) surface is much faster than that for a defective (110) surface.

Laser-induced positive ion and neutral atom/molecule emission from single-crystal CaHPO 4 ·2 H 2 O: The role of electron-beam-induced defects

1999 ◽  
Vol 69 (7) ◽  
pp. S547-S552 ◽  
Author(s):  
M.L. Dawes ◽  
W. Hess ◽  
Y. Kawaguchi ◽  
S.C. Langford ◽  
J.T. Dickinson
Keyword(s):  
Electron Beam ◽  
Single Crystal ◽  
Neutral Atom ◽  
Induced Defects ◽  
Positive Ion

Role Of Surface Defects In Metal-Ceramic Bonding

1991 ◽  
Vol 238 ◽  
Author(s):  
S. M. Mukhopadhyay ◽  
C. S. Chen
Keyword(s):  
Photoelectron Spectroscopy ◽  
Active Sites ◽  
Surface Defects ◽  
Second Phase ◽  
Interfacial Chemistry ◽  
X Ray ◽  
Thin Oxide Film ◽  
Metal Ceramic

ABSTRACTThe interfacial chemistry between Ni and Al2O3 has been studied during the initial stages of bonding. We have evaporated thin films of Ni on different alumina substrates (thin oxide film on metallic Al, polished and scratched sapphire crystals, surface with second phase precipitates) and have analyzed how the interface grows, in situ, using X-ray Photoelectron Spectroscopy. It was found that a certain fraction of the first monolayer of Ni which forms on the alumina surface undergoes charge transfer to form NiO. This is due to oxygen-active sites such as unattached oxygen bonds on the surface. A measure of the concentration of such sites can therefore be obtained from the submonolayer fraction of Ni that gets oxidized. It was found that a rough surface offered less oxidation sites for Ni than a smooth one whereas a surface with second phase MgAI2O4 (spinel) precipitates offered more oxidation sites. Also, there is much less oxidation on a thin film of amorphous alumina grown on metallic Al than on a polished bulk sapphire surface. The implications of these studies to further understanding of the metal-ceramic interface have been discussed.

scholarly journals Yttrium doped phosphate-based glasses: structural and degradation analyses

2020 ◽  
Vol 6 (1) ◽  
pp. 34-49
Author(s):  
Abul Arafat ◽  
Sabrin A. Samad ◽  
Jeremy J. Titman ◽  
Andrew L. Lewis ◽  
Emma R. Barney ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Structural Changes ◽  
Xrd Analysis ◽  
Calcium Pyrophosphate ◽  
Ion Release ◽  
Subsequent Increase ◽  
Structural Characterisation ◽  
Release Studies ◽  
Degradation Properties

AbstractThis study investigates the role of yttrium in phosphate-based glasses in the system 45(P2O5)–25(CaO)– (30-x)(Na2O)–x(Y2O3) (0≤x≤5) prepared via melt quenching and focuses on their structural characterisation and degradation properties. The structural analyses were performed using a combination of solid-state nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). 31P NMR analysis showed that depolymerisation of the phosphate network occurred which increased with Y2O3 content as metaphosphate units (Q2) decreased with subsequent increase in pyrophosphate species (Q1). The NMR results correlated well with structural changes observed via FTIR and XPS analyses. XRD analysis of crystallised glass samples revealed the presence of calcium pyrophosphate (Ca2P2O7) and sodium metaphosphate (NaPO3) phases for all the glass formulations explored. Yttrium-containing phases were found for the formulations containing 3 and 5 mol% Y2O3. Degradation analyses performed in Phosphate buffer saline (PBS) and Milli-Q water revealed significantly reduced rates with addition of Y2O3 content. This decrease was attributed to the formation of Y-O-P bonds where the octahedral structure of yttrium (YO6) cross-linked phosphate chains, subsequently leading to an increase in chemical durability of the glasses. The ion release studies also showed good correlation with the degradation profiles.

Incorporation and Role of Nitrogen During Oxynitridation of Silicon Studied by Photoelectron Spectroscopy

1999 ◽  
Vol 567 ◽  
Author(s):  
Masayuki Suzuki ◽  
Yoji Saito
Keyword(s):  
Photoelectron Spectroscopy ◽  
High Vacuum ◽  
Oxide Films ◽  
Silicon Surfaces ◽  
Gaseous Mixtures ◽  
X Ray ◽  
Initial Stage ◽  
Thermal Stability Of

ABSTRACTWe tried direct oxynitridation of silicon surfaces by remote-plasma-exited nitrogen and oxygen gaseous mixtures at 700°C in a high vacuum. The oxynitrided surfaces were investigated with in-situ X-ray photoelectron spectroscopy. With increase of the oxynitridation time, the surface density of nitrogen gradually increases, but that of oxygen shows nearly saturation behavior after the rapid increase in the initial stage. We also annealed the grown oxynitride and oxide films to investigate the role of the contained nitrogen. The desorption rate of oxygen from the oxynitride films is much less than that from oxide films. We confirmed that nitrogen stabilizes the thermal stability of these oxynitride films.

The role of electrode wettability in electrochemical reduction of carbon dioxide

2021 ◽  
Author(s):  
Mengran Li ◽  
Mohamed Nazmi Idros ◽  
Yuming Wu ◽  
Thomas Burdyny ◽  
Sahil Garg ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Electrochemical Reduction ◽  
Liquid Water ◽  
Substantial Improvement ◽  
Industrial Scale ◽  
High Current ◽  
Current Densities

The electrochemical reduction of carbon dioxide (CO2RR) requires access to ample gaseous CO2 and liquid water to fuel reactions at high current densities for industrial-scale. Substantial improvement of the CO2RR...

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