Oxidation State Of Titanium Research Articles

Catalytic activities of titania-supported nickel for carbon-dioxide methanation

Titania-supported nickel catalysts (3, 6, 12 and 20 wt% Ni/TiO2) were prepared by a sol–gel method. The results showed that the CO2 conversion increased with increasing Ni content and 20 wt% Ni/TiO2 exhibited the highest CO2 conversion and CH4 yield. The results on XRD and EXAFS revealed unit cell expansion and lattice distortion, which indicated that Ni2+ was incorporated into the TiO2 lattice. Upon increasing the Ni content, the NiO phase was observed. The oxidation states of nickel and titanium were analyzed to be +2 and +4, respectively for fresh catalysts. After pretreatment by H2, Ni2+ was converted to Ni0 and this electronic state remained unchanged during the course of methanation while Ti4+ was kept unaltered for fresh catalysts and those during the reaction. The addition of Ni led to the formation of oxygen vacancy and NiO phase which might act as adsorption sites for CO2 and H2, respectively.

Phase chemistry of Submerged Arc Welding (SAW) fluoride based slags

Phase chemical analysis of post-weld slags from Submerged Arc Welding (SAW) is applied to explain the chemical function of flux constituent compounds in the welding process. FactSage 6.4 calculations were used to aid in the interpretation of the phase chemical analyses. Five commercial agglomerated fluxes from two suppliers were used. These fluxes cover three types of fluoride based flux classes: Fluoride Basic flux, Aluminate Basic flux and Aluminate Rulile flux. Basic fluxes are based in the SiO2–Al2O3–MgO CaF2 system. The slag liquidus lowering effect of CaF2 is 19 °C/%CaF2 in the Fluoride Basic fluxes, and 4 °C/%CaF2 in the Aluminate Basic fluxes. The Aluminate Rutile flux is based in the SiO2–Al2O3–MgO–TiO2–MnO–CaF2 system. Little CaF2 addition is used in this flux since TiO2 addition lowers its liquidus temperature sufficiently. The level of CaF2 addition sets the quantity and chemistry of fluoride gas compounds formed. The main gas fluoride gas species expected to form in welding with the five fluxes are CaF2, MgF2, NaF, KF, NaAlF4, and AlF3. In addition, TiF3 is expected to form in welding with the Aluminate Rutile flux, indicating the importance of titanium oxidation state in fluoride gas formation.

Laser induced formation of copper species over TiO2 nanotubes towards enhanced water splitting performance

We proposed fast and scalable route where the ordered TiO2 nanotubes coated with thin copper layers were annealed by the laser beam of 355 nm wavelength at different fluencies in the range of 15–120 mJ/cm2. As a result, copper species are integrated with the titania substrate and the formed material exhibits unique optical absorption bands in the visible range. Moreover, X-ray photoelectron spectroscopy analysis reveals the formation of Cu2O while the 4+ oxidation state of titanium is preserved. According to the electrochemical results, the material treated by laser exhibits outstanding photoelectrochemical activity comparing to the pristine titania or the one only covered by the thin copper film. In particular, when the fluence of 60 mJ/cm2 was used for the modification of the titania decorated with Cu film, the current density recorded in KOH electrolyte reaches nearly 4.5 mA/cm2 at +2.0 V vs. Ag/AgCl/0.1 M KCl upon visible light.

Crystallinity and wettability induced osteogenic behaviors of commercially pure Ti and Ti-6Al-4V alloy implant surfaces having multiscale surface topography

The influence of multiscale topography imparted through laser texturing of titanium based bioimplant surfaces on osteogenic behaviours is investigated. The synergistic effects of surface topography, surface physical and chemical behaviours appears to have improved the initial cell adhesion and proliferation. Micro grooves having embedded nano ripples as periodic surface structures were micro-fabricated on two different grades of specimens; commercially pure titanium and Ti-6Al-4V titanium alloy. The surface characteristics, chemical composition and phase constitution of the micro-fabricated surfaces were investigated by confocal microscopy, XPS and XRD analysis. The hydrophilicity of the samples was assessed by measuring the water contact angles and the results have been correlated with the surface chemistry. The response of osteoblasts cells seeded on the laser textured surfaces in standard controlled conditions was investigated using fluorescence microscopy and SEM. The results showed that the presence of multiscale topography enhances cell adhesion and provide a definite orientation for osteoblast cells to grow along the direction of the micro grooves. Surface oxidation states of titanium along with the presence of crystalline phase and improved hydrophilicity appeared to have a major role in the preferential integration of bone tissues on the laser textured specimen surfaces.

Hybrid TiO2-ZnO Nanomaterials Prepared Using Laser Ablation in Liquid.

Hybrids of semiconductor nanomaterials often demonstrate properties that are superior to those of their components. In this study, we prepared hybrid nanomaterials of TiO2 and ZnO, which are among the most actively studied semiconductors, by means of millisecond-pulsed laser and analyzed how their morphology, particle size, and surface composition depend on preparation conditions. A series of nanomaterials were obtained via sequentially ablating Zn and Ti metal plates (in different sequences) in water, while laser pulses of lower (2.0 J/pulse) and higher (5.0 J/pulse) energy were applied. The properties of laser-produced hybrid TiO2-ZnO nanomaterials were shown to be governed by experimental conditions such as laser pulse width, pulse peak power, and reaction media (either pure water or colloid with nanoparticles). The morphology revealed nanospheres of TiO2 that decorate nanorods of ZnO or flower-like aggregates of zinc oxide. Intriguingly, after extended ablation time, titania was found to be self-doped with Ti3+ and Ti2+ ions, and the contribution of lower oxidation states of titanium could be controlled by the applied laser pulse energy. The physicochemical characteristics of hybrid nanomaterials were compared with pure ZnO and TiO2 prepared under the same laser conditions.

Hybrid density functional theoretical study of NASICON-type NaxTi2(PO4)3 (x = 1-4).

Sodium Super Ionic Conductor (NASICON) structured phosphate framework compounds represent a very attractive class of materials for their use as Na-ion battery electrodes. A series of NASICON-structured NaxTi2(PO4)3 compounds corresponding to varying degrees of sodiation (x = 1-4) have been investigated using high-level hybrid density functional theory calculations using the Linear Combination of Atomic Orbitals and Gaussian-type basis set formalism together with hybrid B1WC and HSE06 exchange-correlation functionals. Using primitive cells of NaxTi2(PO4)3 compounds with different stoichiometry, sodium sublattice structure and titanium oxidation states are constructed and analyzed using group theoretical symmetry considerations. The existence of mixed titanium oxidation states for x = 4 (Ti2+/Ti3+) and x = 2 (Ti3+/Ti4+) and a single oxidation state for x = 1 (Ti4+) and x = 3 (Ti3+) has been demonstrated. The results show a necessary set of symmetry reductions taking place due to the highest possible sodium/vacancy and titanium charge ordering with changing x. For each composition, an electroneutrality condition for the oxidation states of all atoms was applied which led to the discovery of several energy minima corresponding to different electronic configurations as identified by different Ti magnetic moments. An interesting relation between the bulk electronic properties of NaxTi2(PO4)3 compounds and the variation of sodium content was also found. In addition to sodium and titanium oxidation state charge ordering, the existence of large differences between the origin and the size of the band gap is shown. The band gap changes from the 4.05 eV 2p-3d gap in Na1Ti2(PO4)3 to the 0.59 eV 3d-3d gap in Na4Ti(PO4)3 with extra states due to mixed titanium valence. These results serve as an important electronic structure benchmark for further studies of such polyanion materials and help to explain some important properties of these systems relevant to battery applications.

Revealing the Pseudo‐Intercalation Charge Storage Mechanism of MXenes in Acidic Electrolyte

AbstractSince the discovery of Ti3C2Tx in 2011, the family of two‐dimensional transition metal carbides, carbonitrides, and nitrides (collectively known as MXenes) has quickly attracted the attention of those developing energy storage applications such as electrodes for supercapacitors with acidic aqueous electrolytes. The excellent performance of these MXenes is attributed to a pseudocapacitive energy storage mechanism, based on the non‐rectangular shape of cyclic voltammetry curves and changes in the titanium oxidation state detected by in situ X‐ray absorption spectroscopy. However, the pseudocapacitive mechanism is not well understood and no dimensional changes due to proton insertion have been reported. In this work, in situ X‐ray diffraction and density functional theory are used to investigate the charge storage mechanism of Ti3C2Tx in 1 m H2SO4. Results reveal that a 0.5 Å expansion and shrinkage of the c‐lattice parameter of Ti3C2Tx occur during cycling in a 0.9 V voltage window, showing that the charge storage mechanism is intercalation pseudocapacitance with implication for MXene use in energy storage and electrochemical actuators.

Removal of groundwater nitrates by heterogeneous supramolecular complexes-like photocatalytic system based on in-situ generated and highly active Ti3+/Ti2+ states in the reduced TiO2

In this investigation, a novel catalytic nitrate reduction method by using the in-situ generated Ti3+/Ti2+ states in the TiO2/Al catalyst was demonstrated. The Ti3+/Ti2+ states in TiO2/Al catalyst harvest the UV to near IR regions of the solar spectrum and continuously self-generated via the absorption of visible-near infrared radiations. The formation of reduced titanium oxidation states and the visible light harvesting properties of the catalyst were determined by X-ray Photoelectron Spectroscopy (XPS) analysis and diffuse reflectance transmission respectively. With the TiO2/Al catalyst, over 95% of nitrate removal could be achieved for an initial nitrate concentration of 100 ppm. Based on XPS, FTIR analysis and the reaction products, a possible nitrate reduction mechanism is proposed in which in-situ generated Ti3+/Ti2+ states can harvest visible-near infrared photons as well as found to be the active sites for the reduction of nitrates and hence function similar to supramolecular complex photocatalytic system. The catalytic system described can be easily adapted adapted for the groundwater nitrate removal.

Enhancing the activity of oxygen-evolution and chlorine-evolution electrocatalysts by atomic layer deposition of TiO2.

We report that TiO2 coatings formed via atomic layer deposition (ALD) may tune the activity of IrO2, RuO2, and FTO for the oxygen-evolution and chlorine-evolution reactions (OER and CER). Electrocatalysts exposed to ~3–30 ALD cycles of TiO2 exhibited overpotentials at 10 mA cm–2 of geometric current density that were several hundred millivolts lower than uncoated catalysts, with correspondingly higher specific activities. For example, the deposition of TiO2 onto IrO2 yielded a 9-fold increase in the OER-specific activity in 1.0 M H2SO4 (0.1 to 0.9 mA cmECSA–2 at 350 mV overpotential). The oxidation state of titanium and the potential of zero charge were also a function of the number of ALD cycles, indicating a correlation between oxidation state, potential of zero charge, and activity of the tuned electrocatalysts.

Enhanced Solar Water Splitting Performance of 50-100 nm Pore Sized TiO2 Nanotubes

Herein, we report the fabrication of titanium dioxide nanotubes via anodization technique through with and without hydrofluoric acid . The impact of hydrofluoric acid followed by annealing effect on TiO2 nanotubes for the solar water splitting performance was examined. Prepared TiO2 samples exhibited a diameter of about 50 to 100 nm sized nanotubes and hierarchical structures and they subjected to annealing. Synthesis and annealing effects on chemical, physical and photoelectrochemical water splitting activity of TiO2 samples were scrutinized. The crystalline nature, structure and surface morphologies of prepared TiO2 photocatalysts were explored by X-ray diffraction, scanning electron microscope, and the oxidation states of both titanium and oxygen was determined by X-ray photoelectron spectroscopy. As a consequence, after annealing at 500 ºC, TiO2 thin films treated with hydrofluoric acid solution (HF-TiO2) were found to exhibit a remarkable photoelectrochemical performance than bare TiO2 nanotubes under UV light irradiation. Moreover, the mechanistic insights acquired in the current research would be beneficial to design a novel and highly efficient photocatalyst for solar water splitting systems.

Ti K-edge XANES study on the coordination number and oxidation state of Titanium in pyroxene, olivine, armalcolite, ilmenite, and silicate glass during mare basalt petrogenesis

Lunar mare basalts are a product of partial melting of the lunar mantle under more reducing conditions when compared to those expected for the Earth’s upper mantle. Alongside Fe, Ti can be a major redox sensitive element in lunar magmas, and it can be enriched by up to a factor of ten in lunar basaltic glasses when compared to their terrestrial counterparts. Therefore, to better constrain the oxidation state of Ti and its coordination chemistry during lunar magmatic processes, we report new X-ray absorption near edge structure (XANES) spectroscopy measurements for a wide range of minerals (pyroxene, olivine, Fe–Ti oxides) and basaltic melt compositions involved in partial melting of the lunar mantle. Experiments were conducted in 1 bar gas-mixing furnaces at temperatures between 1100 and 1300 °C and oxygen fugacities (fO2) that ranged from air to two orders of magnitude below the Fe–FeO redox equilibrium. Run products were analysed via electron microprobe and XANES Ti K-edge. Typical run products had large (> 100 µm) crystals in equilibrium with quenched silicate glass. Ti K-edge XANES spectra show a clear shift in energy of the absorption edge features from oxidizing to reducing conditions and yield an average valence for Fe–Ti oxides (armalcolite and ilmenite) of 3.6, i.e., a 40% of the overall Ti is Ti3+ under fO2 conditions relevant to lunar magmatism (IW − 1.5 to − 1.8). Pyroxenes and olivine have average Ti valence of 3.75 (i.e., 25% of the overall Ti is trivalent), while in silicate glasses Ti is exclusively tetravalent. Pre-edge peak intensities also indicate that the coordination number of Ti varies from an average V-fold in silicate glass to VI-fold in the Fe–Ti oxides and a mixture between IV and VI-fold coordination in the pyroxenes and olivine, with up to 82% [IV]Ti4+ in the pyroxene. In addition, our results can help to better constrain the Ti3+/∑Ti of the lunar mantle phases during magmatic processes and are applied to provide first insights into the mechanisms that may control Ti mass-dependent equilibrium isotope fractionation in lunar mare basalts.

Influence of nitrogen content levels on structural properties and photocatalytic activities of nanorice-like N-doped TiO2 with various calcination temperatures

The purposes of this research were to study the effect of nitrogen content levels on structural properties and photocatalytic activities of catalysts with various calcination temperatures and to test the photocatalytic degradation of paraquat under UV and visible light. The results showed that the effect of calcination temperature was significant on physical properties and amount of nitrogen element, but insignificant on phase structure and oxidation state of titanium (Ti) atom. The N-doped TiO2 samples demonstrated only anatase phase because nitrogen dopant in TiO2 restrained the phase transformation from anatase to rutile and displayed nanorice-like morphology. The bandgap energy was about 3.07–3.18 eV. The nitrogen content was only observed at 100, 300 and 400 °C. The nitrogen (N) atom can be incorporated in TiO2 structural lattice with interstitial site. The specific surface area and nitrogen content level showed the important roles for the photodegradation of paraquat under UV and visible light irradiation.

Sol-gel Preparation of Hollow Spherical x%B-TiO2 Photocatalyst: The Effect of Boron Content on RBR X-3B Decoloration

Background: The potential of applying TiO2-based materials has been ascertained in both wastewater and polluted air. Boron is proven to be an effective dopant to promote the activity of TiO2 in our previous work. The density of hollow material is little larger than water so that the hollow photocatalyst can suspend in wastewater under stirring or aeration. Methods: The graphical spheres were prepared from glucose using hydrothermal method. The hollow spherical x%B-TiO2 was synthesized through a sol-gel route, using tetrabutyl titanate and tributyl borate in the precursor. The materials were characterized by X-ray diffraction, scanning electron microscope, infrared spectrum, X-ray photoelectron spectroscopy, and N2 adsorption-desorption techniques. Photocatalytic degradation of RBR X-3B dye was studied to show the activity of the x%B-TiO2 materials. Results: Anatase TiO2 phase forms in all the x%B-TiO2 samples despite the difference in boron content. An absolute Ti4+ oxidation state exists in the x%B-TiO2, which is hardly affected by the doped boron. XPS analysis proves the formation of B-Ti-O structure in anatase TiO2 lattice. BET surface area increases with rising boron doping content in the hollow spherical x%B-TiO2 samples. Photocatalytic activity of TiO2 is enhanced after doping boron. The photocatalytic efficiency on RBR X- 3B degradation reaches the maximum value when n(B)/n(Ti) is 8%. After five photocatalytic cycles, decoloration efficiency on 8%B-TiO2 is as much as 80% of the initial value. Conclusion: A continuous expansion of TiO2 crystal happens with increasing boron content. The Ti4+ oxidation state of titanium in the hollow spherical material is not changed after doping boron. BET surface area of the hollow spherical x%B-TiO2 increases with rising boron doping content. The hollow spherical 8%B-TiO2 has satisfactory performs for recycling and lifetime.

Ti oxidation states in Zn(Ti) coating of hot-dip galvanized steels

Chemical composition analysis of coloured surface layers of hot-dip galvanized steel sheets was studied. Samples were produced in laboratory scale and studied by mass spectrometry and electron spectroscopy methods. Zinc bath alloyed with 0.15wt% titanium content resulted in surfaces with different colours depending on the bath temperature. We proved that surface colour was determined by the thickness of surface titanium-oxide layer created during sample cooling from the bath temperature. The bath temperature dependence of the titanium-oxide layer thickness gives information about the activation energy of its formation, which is essentially the activation energy of Ti diffusion through the oxide layer. Surfaces of hot-dip galvanized samples were studied by X-ray Photoelectron Spectroscopy. Different oxidation states of titanium were identified in the oxide layer. By our measurements we could prove that depth profiling methods using low energy ion beams for surface sputtering can be applicable to determination of chemical states without modifying them. Finally, we provided experimental evidence that the surface colour was determined by light interference.

EPR of transition metal ions in microplasma coatings on the surface of Ti − 0 , 3al and Ti − 6Al − 4V titanium alloys

The study focuses on the EPR examination of titanium oxidation states and doped transition metal ions in microplasma coatings on the surface of details made of Ti−0,3al and Ti−6Al−4V titanium alloys, depending on the duration and modes of the microplasma oxidation process. No Ti3+ states are observed in the anodic mode of microplasma oxidation. When the microplasma process is conducted in the anodic-cathodic mode, paramagnetic Fe3+ and Ti3+ states are observed in the Ti−0,3al alloy, and V4+ and Ti3+ states are found in the Ti−6Al−4V alloy. The removal of the technological layer mostly containing low-temperature titanium oxides eliminates the EPR spectra of the mentioned paramagnetic states of transition metal ions. The anodic mode of microplasma oxidation followed by the anodic-cathodic mode at the final stage does not yield paramagnetic states of transition metal ions, which is very important for many applications of microplasma oxidation of coatings because the Ti3+ state is chemically active and may affect many chemical processes occurring on the oxide layer surface. Meanwhile, the inverse sequence of the microplasma oxidation modes gives rise to paramagnetic states of transition metal ions in the technological layer.

On the Charge State of Titanium in Titanium Dioxide.

The oxidation state of titanium in titanium dioxide is commonly assumed to be +4. This assignment is based on the ionic approximation and is used ubiquitously to rationalize phenomena observed with TiO2. It implies a charge state +4 and that no further oxidation of the metal center is possible. We present a comprehensive electronic structure investigation of Ti ions, TiO2 molecules, and TiO2 bulk crystals using different density functional theory and wave function-based approaches, which shows that the charge state of Ti is +3. Specifically, there is evidence of a significant remaining contribution from valence s and d electrons of Ti, including the presence of a nuclear cusp around the Ti core. The charge corresponding to valence s and d states of Ti amounts to 1 e. This suggests the possibility of further oxidation of Ti in TiO2 compounds and challenges the commonly assumed picture of assigning the oxidation state of Ti in titania to +4.

Enhanced Depth Profiling of Perovskite Oxide: Low Defect Levels Induced in SrTiO3 by Argon Cluster Sputtering

We have studied the influence of the argon cluster ion sputtering technique in the X-ray photoelectron spectroscopy (XPS) depth-profiling analysis of a strontium titanate SrTiO3 (STO) substrate, chosen as a prototype perovskite-type oxide material. Unlike “standard” sputtering technique using monatomic ions, a gentle digging through STO (without inducing a large amount of defects) has been evidenced. Several improvements are evidenced by using this low-energy abrasion process: (i) the absence of argon implantation, (ii) the creation of very few oxygen vacancies which lead in the classical way to the lowering of oxidation states of titanium and the appearance of in-gap electronic states, and (iii) the preservation of the cationic stoichiometry. In addition, electrical measurements confirm that no metal–insulator transition is evidenced using the cluster ion source, unlike the case of the monatomic ion etching. Furthermore, for the latter case, a relaxation effect of the Ar+ ion induced electronic propertie...

Controlled oxidation state of Ti in MgO-TiO 2 composite for CO 2 capture

Abstract Mesoporous MgO-TiO 2 sorbents denoted as (xMgO-TiO 2 ) with different Mg/Ti molar ratios were synthesized by single step evaporation-induced self-assemble (EISA) method for its application to CO 2 capture. The effect of Mg/Ti molar ratio of mesoporous MgO-TiO 2 sorbents on their physicochemical properties, oxidation state of titanium, and CO 2 adsorption performance was investigated. The phase of xMgO-TiO 2 was transformed in the sequence of MgTiO 3 (Mg/Ti = 1.0 and 2.0) → MgO-MgTi 2 O 4 (Mg/Ti = 3.0 and 4.0) → MgO-Mg 2 TiO 4 (Mg/Ti = 5.0). However, with the increasing Mg/Ti molar ratio, CO 2 adsorption performance increased in the order of MgTiO 3 2 O 4 2 TiO 4 . Among the sorbents tested 3.0MgO-TiO 2 showed the best CO 2 adsorption performance corresponding to ∼1 mmol/g (4.39 wt.%). It was observed that the MgTi 2 O 4 (Ti 3+ -O-Mg 2+ ) could create highly basic sites compared to MgTiO 3 and Mg 2 TiO 4 . In the process of CO 2 adsorption, high surface area (111.4 m 2 /g), large pore volume (0.45 cm 3 /g) as well as appropriate basic sites of Mg-O-Ti make it a plausible candidate for CO 2 adsorption.

Electrochemical Characterization of the Titanium/Pbs Interface By Ambient Pressure X-Ray Photoelectron Spectroscopy

A novel operando Ambient Pressure Tender X-Ray Photoelectron Spectroscopy (T-APXPS) technique, developed by beamline 9.3.1 at the Advanced Light Source (ALS) [1], allows for the first time to study in detail the corrosion phenomena at the metallic biomaterial/body fluid electrified interface under operando electrochemical conditions. “Dip and Pull” method was used in order to create a stable nanometer-thick aqueous layer on the metallic biomaterial surface (Figure 1(a)). The ionically sustained electrical contact between the liquid layer on the sample surface and the bulk electrolyte is ensured by keeping the bottom part of each electrode immersed in the electrolyte. By using synchrotron radiation in the range of tender X-rays (at an energy of 4keV), it is possible to detect photoelectrons ejected from the solid/liquid interface, directly probing complex (electro-)chemical phenomena occurring at such important spatial region. Titanium is one of the most commonly used metal biomaterials (such as dental implants or restoration) because of its biocompatibility and chemical stability in biological environments [2]. This metal is characterized by the spontaneous formation of an oxide film (mainly composed of amorphous TiO2) on the surface, which protects the bulk material for further oxidation (passive metal). Thus, the formation of the surface oxide is responsible for both biocompatibility and corrosion resistance (related to the long-term durability of the biomaterial implanted into the body and metal ion release) [3]. Changes in the chemical composition of the Ti/TiO2/electrolyte junction during cathodic/anodic polarization in simulated body fluids were characterized using operando T-APXPS technique. Experimental. An electrochemical characterization of pure polycrystalline titanium in phosphate buffer solution (PBS) was carried out. Polarization curves were used in order to determine the different potential domains (cathodic, cathodic-anodic transition and passive domain). Potentiostatic tests were conducted between potentials comprised in the range -1VAg/AgCl and 1VAg/AgCl to determine the effect of the applied potential (belonging to the different potential domains) in the electrochemical reactions occurring at the biomaterial/electrolyte interface. During the potentiostatic tests, XPS spectra of Ti2p, O1s, C1s, P2s, and Cl2p were acquired under ultra high vacuum (UHV) and hydrated conditions (i.e., T-APXPS measurements were performed exposing the sample to a water gas pressure of about 16Torr prior any electrochemical treatment). Results Figure 1(b) shows the Ti2p spectra obtained at different conditions: (i) UHV, (ii) hydrated conditions, and (iii) during operando electrochemical conditions when potentials of -1.0VAg/AgCl (cathodic domain) and 1.0VAg/AgCl (passive domain) were applied to the working electrode (WE). In those spectra, attenuation in the Ti2p intensities upon water vapor exposure and subjected to polarization conditions were both measured. This observation reveals the formation of a thin electrolyte film (of about ~15 nm) on the titanium (WE). In this talk, our findings related to the titanium polarization at different applied potentials will be shown. New features on the higher binding energy (BE) side of the Ti2p spectra were observed after increasing the applied potential towards more anodic values. The change in the Ti2p photoelectron peak points to a change of the oxidation state of titanium, with the consequent increase of the Ti+4 concentration. In addition, a demonstration of the functionality and electrochemical activity of the formed thin electrolyte film on the titanium surface will be discussed. O1s photoelectron spectra are reported in Figure 1(c). It is possible to observe that the core level peaks from the electrolyte elements (EE) undergo a rigid shift in BE (with respect to the Fermi level of the grounded WE) that follows the variation of the applied potential (U) accordingly to the relation BEEE = BE0 EE - eU. This effect demonstrates that the electrolyte layer on the WE is conductive and connected to the bulk electrolyte, allowing potential control at the solid/liquid electrified interface. The O1s spectra shows two main components, centered at 533.6eV and 536.4eV, attributed to the liquid phase water from the thin film and the gas phase water filling the chamber, respectively. A shift of 2.0eV was observed between the liquid phase peaks obtained at 1.0VAg/AgCl and -1.0VAg/AgCl, which match perfectly with the applied potential difference. In summary, the newly developed T-APXPS technique at ALS allows the operando investigation of corrosion phenomena occurring at the metallic biomaterials/electrolyte interface. The advantage of using such technique relies on the simultaneous acquisition of electrochemical and spectroscopy data which allows a direct probing of the electrochemical process occurring at the biomaterial/liquid interface, including changes in the electrolyte species and evaluation of the metal degradation under simulated biological conditions.

Facile synthesis of Cu@TiO2 core shell nanowires for efficient photocatalysis

Metallic copper is a dependable co-catalyst for improving photoactivity of TiO2 photocatalysis. Cu@TiO2 core shell nanowires (NWs) were prepared by wet chemical synthesis and characterized. The microscopy images clearly show core shell morphology in nano regime. X-ray diffraction studies reveal the metallic copper and anatase TiO2 crystallinity. The optical absorption spectra exhibit ultraviolet and visible light harvesting properties. X-ray photoelectron spectroscopy confirms the presence of oxidation states of metallic copper and titanium. The photocatalytic efficiency was investigated by degrading the methyl orange (MO) and 3wt% Cu@TiO2 core shell NWs shows highest degradation rate (k=0.02905min−1) with superior photocatalytic activity. This material could be surely meet the necessities to harvest solar energy for many energy-related applications.