X-ray photoelectron spectroscopic study of the interaction of various anions with the oxide-covered titanium metal (original) (raw)
Related papers
Ion-exchange and adsorption properties of TiO2
A study was carried out of the uptake of Cu 2+ , Ni 2+ , Co 2+ and Ca 2+ cations by hydrous titanium oxides prepared at different pH values using titanous chloride as the starting material and hydrogen peroxide as the oxidizing agent. Characterization of the oxides was carried out by nitrogen adsorption and infrared studies. The oxides were found to be amphoteric in nature and exhibited an isoelectric point of 6.6. An attempt was made to elucidate the mechanism of cation uptake which does not entail a simple ion-exchange mechanism.
First principles study of Na adsorption on TiO2 (110) surface
International Journal of Quantum Chemistry, 1998
The activation of the 110 TiO rutile surface by deposition of alkali 2 metal atoms has been the subject of some recent experimental studies. These results indicate a reduction of the surface when sodium atoms are deposited on it. In the present work, this process has been studied by means of ab initio embedded cluster calculations combined with molecular dynamics simulations. Several surface sites have been considered and our calculations show that reduction occurs selectively on fivefold coordinated titanium atoms. Geometry optimization of a representative Na-surface clusters leads to a structure in which the Na atom is symmetrically coordinated to three Ž . oxygen atoms two protruded and one basal in excellent agreement with models proposed from experimental data. A mechanism for the adsorption process in which a long-distance electron transfer from atomic Na toward a fivefold coordinated surface titanium atom followed by physisorption of the Na q cation on the surface is proposed.
Molecular Chemisorption on TiO 2 (110): A Local Point of View
Journal of Physical Chemistry B, 1998
The molecular adsorption of some probe molecules (CO, H 2 O, and H 2 S) on a 5-fold-coordinated Ti Lewis acid site of the TiO 2 rutile (110) surface is studied within the density functional theory. The substrate is modeled with a small Ti 7 O 9 cluster terminated with pseudo-hydrogens. This is found to describe the electronic and structural properties of the clean surface in good agreement with both experimental and periodic slab calculations. Adsorption energies (6.7, 19.3, and 7.0 kcal/mol for CO, H 2 O, and H 2 S, respectively) and adsorbate stretching frequencies compare favorably with available experimental data. The agreement is particularly good for the C-O stretching frequency shift (+56 cm -1 ), as was found in previous investigations carried out with the same theoretical approach on other oxides. In contrast, the HOH scissoring mode is poorly reproduced, suggesting that molecularly adsorbed H 2 O is actually involved in weak bonds with other adsorbed species. This agrees with predictions of very recent slab calculations by Lindan et al. (Phys. ReV. Lett. 1998, 80, 762). Differences with respect to calculations carried out by embedding the cluster in point-charge arrays are discussed.
Int. J. Electrochem. Sci, 2012
Different routes of preparation of metal oxide structures on titanium substrates are explored and characterized with Scanning Electron Microscopy (SEM), Energy Dispersive Elemental Analysis (EDAX), Atomic Force Microscopy (AFM) and X-ray Diffraction Spectroscopy (XRD). The aim was to look for alternative material breakthroughs and to promote the conductivity and the compatibility of the electrode by increasing the surface area of the electrode which will then increase the catalytic efficiency. The SEM and AFM micrographs showed different micro-and nano-structured morphologies for the electrodes. The XRD distinctively identified the presence of crystalline structures of IrO 2 , SnO 2 and ZnO modified electrodes.
Thickness of Anodic Titanium Oxides as a Function of Crystallographic Orientation of the Substrate
Metallurgical and Materials Transactions A, 2008
This work deals with the anodization-driven oxidation of titanium, studied as a function of the crystallographic orientation of the crystal grains of the substrate. On a polycrystalline surface, different colors appear on the surface after anodization under galvanostatic conditions at a fixed potential. The color of the oxides on individual grains is correlated to an independent set of reflectometry data relating color to thickness, to infer the approximate thickness of the oxide layer grown on each grain in the polycrystal. These data are further related to the crystallographic orientation of each grain as assessed by electron backscatter diffraction measurements. It is shown that crystallographic orientations close to (0001) lead to relatively slower oxidation as compared with inclined orientations.
Adsorption of bi-isonicotinic acid on rutile TiOsub 2
The Journal of Chemical Physics, 1999
Bi-isonicotinic acid ͑2,2Ј-bipyridine-4,4Ј-dicarboxylic acid͒ is the ligand of several organometallic dyes, used in photoelectrochemical applications. Therefore the atomic scale understanding of the bonding of this molecule to rutile TiO 2 (110) should give insight into the crucial dye-surface interaction. High resolution x-ray photoelectron spectroscopy ͑XPS͒, near edge x-ray absorption fine structure ͑NEXAFS͒, and periodic intermediate neglect of differential overlap ͑INDO͒ calculations were carried out on submonolayer bi-isonicotinic acid rutile TiO 2 (110). Data from multilayers is also presented to support the submonolayer results. For a multilayer, XPS shows that the carboxyl groups remain in the ͑pristine͒ protonated form, and NEXAFS show that the molecular plane is tilted by 57°with respect to the surface normal. For the submonolayer, the molecule bonds to the rutile TiO 2 (110) surface via both deprotonated carboxyl groups, with a tilt angle of 25°, and additionally an azimuthal orientation of 44°with respect to the ͓001͔ crystallographic direction. The adsorbant system was also investigated by quantum mechanical calculations using a periodic INDO model. The most stable theoretical adsorption geometry involves a twist around the molecular axis, such that the pyridine rings are tilted in opposite directions. Both oxygen atoms of each carboxyl group are bonded to five-fold coordinated Ti atoms ͑2M-bidentate͒, in excellent agreement with the experimental results.
Photoelectrochemical spectroscopy studies of titanium dioxide surfaces: theory and experiment
Surface Science, 1991
We describe experimental and theoretical studies of titanium dioxide. Phot~lectr~he~~l data are presented for surfaces of known structure. The oxides were grown anodically on titanium metal. We report calculations of the electronic densities of states and optical conductivities of r-utile TiO, in finite-size samples disordered by the addition of oxygen vacancies for comparison with experiments. We conclude that in less disordered surfaces the electronic structure exhibited by the photospectra is very close to that of bulk rutile TiO,. In contrast, very thin oxides showed evidence of an electronic structure dominated by localized states near the band edge. More disordered oxides gave photospectra in which transitions associated with direct band gap transitions in bulk TiOZ seem to have been suppressed. Taking the structural information on the oxides into account, we argue that this suppression is probably a matrix element effect. 0039-6028/91/$03.50 0 1991 -Elsevier Science Publishers B.V. All rights reserved Xenon bmp Multiprogrammer
Effect of anodic oxidation parameters on the titanium oxides formation
Corrosion Science, 2007
The aim of this paper is to evaluate the eVects of titanium anodic oxidation in a sulphuric acid electrolyte on the crystallinity of the oxide layer and to adjust the process parameters, in order to maximize the TiO 2 crystalline phase, specially for what concerns the anatase form. In particular, the relationship between anatase formation and anodization parameters, such as current density and applied potential, will be evidenced. From XRD analysis two opposite trends emerged: oxide conversion to anatase is promoted either by an increase in current density or by a decrease in sulphuric acid concentration.
The Photoelectrochemical Response of Various Surface Morphologies of Titanium Anodic Oxide Films
2013
Anodic oxide films of Titanium (Ti) with different surface morphologies were investigated by controlling the content of NH4F in EG electrolyte. When Ti was anodised in the low content of NH4F (1 wt%), a thin TiO2 compact oxide layer was formed. However, TiO2 nanoporous structure appeared on the surface of Ti when 3 wt% of NH4F was added. When NH4F was further increased to 5 wt%, a self-ordered nanotubular oxide structure was observed. TiO2 nanotubular structure exhibited higher photocurrent density (~0.45 mA cm -2 ) as compared to the nanoporous and compact oxide layer.