TiCl4 Solution Research Articles

Facile synthesis of nanorods of tetragonal barium titanate using ethylene glycol

Tetragonal barium titanate (BaTiO3) nanorods were synthesized from hydroxide precursor by a hydrothermal/solvothermal method with 10vol% ethylene glycol as solvent. The hydroxide precursor slurry was prepared by the addition of 10M NaOH to a mixed solution of BaCl2 and TiCl4. When the above aqueous slurry was heated with water only at 200°C, cubic BaTiO3 nanocrystals formed, whereas tetragonal BaTiO3 nanorods were obtained when heated with 10vol% ethylene glycol. The crystallization of cubic BaTiO3 via dissolution–reprecipitation of precursor could be suppressed by the addition of ethylene glycol, resulting in the formation of tetragonal BaTiO3 under hydrothermal treatment at 200°C.

Improved electrochemical stability at the surface of La(0.8)Sr(0.2)CoO3 achieved by surface chemical modification.

The degradation of the surface chemistry on perovskite (ABO3) oxides is a critical issue for their performance in energy conversion systems such as solid oxide fuel/electrolysis cells and in splitting of H2O and CO2 to produce fuels. This degradation is typically in the form of segregation and phase separation of dopant cations from the A-site, driven by elastic and electrostatic energy minimization and kinetic demixing. In this study, deposition of Ti at the surface was found to hinder the dopant segregation and the corresponding electrochemical degradation on a promising SOFC cathode material, La(0.8)Sr(0.2)CoO3 (LSC). The surface of the LSC films was modified by Ti (denoted as LSC-T) deposited from a TiCl4 solution. The LSC and LSC-T thin films were investigated by electrochemical impedance spectroscopy, nano-probe Auger electron spectroscopy, and X-ray photoelectron spectroscopy (XPS), upon annealing at 420-530 °C in air up to about 90 hours. The oxygen exchange coefficient, k(q), on LSC-T cathodes was found to be up to 8 times higher than that on LSC cathodes at 530 °C and retained its stability. Sr-rich insulating particles formed at the surface of the annealed LSC and LSC-T films, but with significantly less coverage of such particles on the LSC-T. From this result, it appears that modification of the LSC surface with Ti reduces the segregation of the blocking Sr-rich particles at the surface, and a larger area on LSC surface (with a higher Sr doping level in the lattice) is available for the oxygen reduction reaction. The stabilization of the LSC surface through Ti-deposition can open a new route for designing surface modifications on perovskite oxide electrodes for high temperature electro- and thermo-chemical applications.

Probing the coordination environment of Ti(3+) ions coordinated to nitrogen-containing Lewis bases.

Multi-frequency continuous-wave and pulsed EPR techniques are employed to investigate the coordination of nitrogen-containing ligands to Ti(3+)-chloro complexes. Frozen solutions of TiCl3 and TiCl3(Py)3 dissolved in nitrogen-containing solvents have been investigated together with the TiCl3(Py)3 solid-state complex. For these different systems, the hyperfine and nuclear quadrupole data of Ti(3+)-bound (14)N nuclei are reported and discussed in the light of DFT computations, allowing for a detailed description of the microscopic structure of these systems.

Facile Preparation of TiO2 Nanobranch/Nanoparticle Hybrid Architecture with Enhanced Light Harvesting Properties for Dye‐Sensitized Solar Cells

We report TiO2 nanobranches/nanoparticles (NBN) hybrid architectures that can be synthesized by a facile solution phase method. The hybrid architecture simultaneously improves light harvesting and charge collection performances for a dye‐sensitized solar cell. First, TiO2 nanorods with a trunk length of 2 μm were grown on a fluorine‐doped tin oxide (FTO)/glass substrate, and then nanobranches and nanoparticles were deposited on the nanorods’ trunks through a solution method using an aqueous TiCl3 solution at 80°C. The relative amount of nanobranches and nanoparticles can be controlled by multiplying the number of TiCl3 treatments to maximize the amount of surface area. We found that the resultant TiO2 NBN hybrid architecture greatly improves the amount of dye adsorption (five times compared to bare nanorods) due to the enhanced surface area, while maintaining a fast charge collection, leading to a three times higher current density and thus tripling the maximum power conversion efficiency for a dye‐sensitized solar cell.

Preparation and characterization of natural zeolite supported nano TiO2photocatalysts by a modified electrostatic self-assembly method

Natural zeolite supported nano TiO2 photocatalysts were prepared by a modified electrostatic self-assembly (ESA) method. First, γ-mercaptopropyltrimethoxysilane with sulfhydryl (―SH) functional groups was modified on the zeolite powders by using a ‘dry process’. Second, silane with ―SH functional groups was oxidized to sulfonate (―SO3H) groups by using a hydrogen peroxide/glacial acetic acid mixed solution, and the surface of ―SO3H silane–zeolite was electronegative charged due to the ionization of ―SO3H. Third, the hydrolytic titanium polycation from TiCl4 solution assembled onto the electronegative charged zeolite under electrostatic attraction in the reaction solutions. Finally, zeolite supported nano TiO2 photocatalysts can be obtained after the above compounds calcined at certain temperature. The samples were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface areas, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and X-ray fluorescence (XRF). The photocatalytic activities of the samples were evaluated by the degradation of methyl orange in aqueous solution. The results showed that ESA method effectively improved the composite efficiency of zeolite with TiO2. The photocatalysts prepared by ESA method exhibited higher photocatalytic and recycling activities than that of traditional method. Copyright © 2014 John Wiley & Sons, Ltd.

Hydrothermal synthesis of rutile–anatase TiO2 nanobranched arrays for efficient dye-sensitized solar cells

Rutile–anatase TiO2 nanobranched arrays were prepared in two sequential hydrothermal-synthesis steps. The morphologies and crystalline nanostructures of the samples were investigated by controlling growth time and the concentration of the titanium precursor. All samples were characterized by field-emission scanning electron microscopy and X-ray diffraction analysis. It was found that treating the surfaces of rutile TiO2 nanorods with aqueous TiCl4 solutions allows the anatase TiO2 nanobranches to grow perpendicular to the main rutile TiO2 nanorods attached to the FTO glass. Irregularly shaped, dense TiO2 structures formed in the absence of TiCl4 treatment. A light-to-electricity conversion efficiency of 3.45% was achieved using 2.3μm tall TiO2 nanobranched arrays in a dye-sensitized solar cell. This value is significantly higher than that observed for pure rutile TiO2 nanorods.

Preparationand Characterization of Rutile-anatase Hybrid TiO2Thin Film by Hydrothermal Synthesis

Nanoporous TiO2 films are commonly used as working electrodes in dye-sensitized solar cells (DSSCs). So far, there have been attempts to synthesize films with various TiO2 nanostructures to increase the power-conversion efficiency. In this work, vertically aligned rutile TiO2 nanorods were grown on fluorinated tin oxide (FTO) glass by hydrothermal synthesis, followed by deposition of an anatase TiO2 film. This new method of anatase TiO2 growth avoided the use of a seed layer that is usually required in hydrothermal synthesis of TiO2 electrodes. The dense anatase TiO2 layer was designed to behave as the electron-generating layer, while the less dense rutile nanorods acted as electron-transfer pathwaysto the FTO glass. In order to facilitate the electron transfer, the rutile phase nanorods were treated with a TiCl4 solution so that the nanorods were coated with the anatase TiO2 film after heat treatment. Compared to the electrode consisting of only rutile TiO2, the power-conversion efficiency of the rutile-anatase hybrid TiO2 electrode was found to be much higher. The total thickness of the rutile-anatase hybrid TiO2 structures were around 4.5-5.0 µm, and the highest power efficiency of the cell assembled with the structured TiO2 electrode was around 3.94%.

Submicron-sized anatase, TiO2 with high photocatalytic activity, and (Ti, Sn)O2 nanocrystals formed via hydrothermal technique

The compositional dependence of the crystalline phase and properties of precipitates (TixSn1−xO2) in the TiO2–SnO2 system, which were hydrothermally formed at 100–200 °C from the precursor solutions of TiCl4 and SnCl4 under weakly basic conditions in the presence of tetramethylammonium hydroxide (TMAH) was investigated. Rutile-type (Ti, Sn)O2 solid solutions with nano-sized crystallite were directly formed at 180 °C in the composition range of x = 0–0.8. Nanoparticles with anatase crystallite around 10 nm as a main crystalline phase of precipitates that were formed in the compositions x = 0.9 and 1.0 showed similar photocatalytic activity. As the hydrothermal treatment temperature rose from 100 to 200 °C, the crystallite size of rutile solid solution, Ti0.5Sn0.5O2, increased from 2.5 to 8.0 nm. The optical band gap of the samples changed in the range of 2.93–3.25 eV depending on their composition in the system. At the composition of x = 1.0, submicron-sized anatase-type pure TiO2 particles (sizes of cuboid sides are around 100–120 nm) with pretty high crystallinity and superior photocatalytic activity were formed from the aqueous solution of TiCl4 under basic hydrothermal condition at 180 °C in the presence of TMAH with concentration as 1.3 times high as the condition in the case of the nano-sized anatase.

Ultrasound-assisted synthesis of titania hydrosols

0.0021–0.44 M TiO2 hydrosols have been prepared by an ultrasound-assisted method using titania hydrogel precipitated from TiCl4 solution. The hydrosols contain amorphous primary titania particles ∼5 nm in size, combined into aggregations having average sizes of 22–51 nm.

Effect of TiCl4 concentration on the structure of its aqueous solutions and on the properties and photoactivity of derived nanocrystalline titania

The influence of the concentration of aqueous TiCl4 solution on the phase formation, morphology and particle size of the titanium dioxide hydrolysis product was investigated by XRD and TEM. Significant features, observed in the Raman spectra of the TiCl4 solutions with a concentration >3 M, demonstrated that the TiCl4 had hydrolysed. As the formal concentration of TiCl4 decreased from 4.98 to 1 M, the Raman spectra changed qualitatively. Despite the changes in the Raman spectra of these precursor solutions, the TiO2 product was mainly rutile in all cases. However, at low TiCl4 concentrations small amounts of anatase were also observed. Electron microscopy suggested that the anatase particles were significantly smaller than the rutile and also indicated increasing aggregation of the product from the more dilute TiCl4 solutions. The optical properties and photoactivities of the TiO2 powders prepared at different concentrations were also investigated. The powder synthesized from 5 M TiCl4 showed the highest UV extinction. The photoactivity of the product, determined by the photocatalytic oxidation of propan-2-ol (isopropanol) to propanone (acetone), was not significantly modified by changes in the concentration of the starting TiCl4. The possibility that the relatively low area of most rutiles contributes to the reported photocatalytic activity of rutile being lower than that of anatase is discussed.

Preparation and characterization of TiO2 barrier layers for dye-sensitized solar cells.

A TiO2 barrier layer is critical in enhancing the performance of dye-sensitized solar cells (DSSCs). Two methods to prepare the TiO2 barrier layer on fluorine-doped tin dioxide (FTO) surface were systematically studied in order to minimize electron-hole recombination and electron backflow during photovoltaic processes of DSSCs. The film structure and materials properties were correlated with the photovoltaic characteristics and electrochemical properties. In the first approach, a porous TiO2 layer was deposited by wet chemical treatment of the sample with TiCl4 solution for time periods varying from 0 to 60 min. The N719 dye molecules were found to be able to insert into the porous barrier layers. The 20 min treatment formed a nonuniform but intact TiO2 layer of ∼100-300 nm in thickness, which gave the highest open-circuit voltage VOC, short-circuit photocurrent density JSC, and energy conversion efficiency. But thicker TiO2 barrier layers by this method caused a decrease in JSC, possibly limited by lower electrical conductance. In the second approach, a compact TiO2 barrier layer was created by sputter-coating 0-15 nm Ti metal films on FTO/glass and then oxidizing them into TiO2 with thermal treatment at 500 °C in the air for 30 min. The dye molecules were found to only attach at the outer surface of the barrier layer and slightly increased with the layer thickness. These two kinds of barrier layer showed different characteristics and may be tailored for different DSSC studies.

Enhanced electrochemical performance of TiO2 by Ti3+ doping using a facile solvothermal method as anode materials for lithium-ion batteries

A facile method has been developed to synthesize Ti3+-doped TiO2 nanoparticles as high-performance anode materials for Li-ion batteries. After reducing some Ti4+ ions to Ti3+ ions with zinc powders in TiCl4 solution, Ti3+-doped TiO2 was synthesized by solvothermal methode. The obtained Ti3+-doped TiO2 nanoparticles are relatively uniform and better dispersed with an average size of 30nm. Great improvement of the electrochemical performance was obtained by Ti3+-doping comparing with the pure TiO2. The Ti3+-doped TiO2 nanoparticles prepared at the Zn:Ti molar ratio of 4% are able to deliver a reversible capacity of 202.1 mAh g−1 at a current density of 100mA g−1 and exhibit superior high-rate discharge/charge capability and cycling stability at the current density up to 3000mA g−1 in a half cell configuration. The improved reversible capacity and rate capability could be ascribed to the presence of Ti3+, which improves the electrical conductivity and reduces the charge transfer resistance of the TiO2 electrode.

ChemInform Abstract: Li Intercalation into 1D TiS2(en) Chains.

AbstractHybrid organic/inorganic van der Waals solid TiS2(en) is prepared by solvothermal reaction of a sulfur solution in en mixed with a TiCl4 solution in PhCl (Teflon cup in evacuated Parr reactor, 200—220 °C, 5 d) followed by purification via repeated recrystallization of the gel‐like product and centrifugation.

Nanocrystalline Pt-doped TiO2 thin films prepared by spray pyrolysis for hydrogen gas detection

Nanostructured pure and Pt-doped TiO2 thin films were prepared by chemical spray pyrolysis technique. Aqueous solution of TiCl3·6H2O (0·01 M) was chosen as the starting solution for the preparation of pure TiO2 thin film. Aqueous solutions of PtCl6·6H2O (0·01 M) and TiCl3·6H2O (0·01 M) were mixed in volume % of 1 : 99, 2·5 : 97·5 and 5 : 95 respectively to obtain Pt-doped TiO2 thin films. The solutions were sprayed onto quartz substrate heated at 350 °C temperature to obtain the films. These thin films were fired for one hour at 550 °C. The sensing performance of these films was tested for various gases such as LPG, H2, CO2, ethanol, NH3 and Cl2 (1000 ppm). The Pt-doped TiO2 (1 : 99) was observed to be most sensitive (572) to H2 at 400 °C with high selectivity against other gases. Its response time was short (10 s) and recovery was also fast (14 s). To understand the reasons behind the gas-sensing performance of the films, their structural and microstructral properties were studied using X-ray diffraction and electron microscopy (FE–SEM and TEM), respectively. Thicknesses of all these samples were determined using Surface Profiler. The results are interpreted.

Surface treated TiO2 nanorod arrays for the improvement of water splitting

Water splitting is widely employed for the hydrogen production for its abundant sources of water and sunlight. The TiO2 nanostructures are the most promising materials because of their properties of the non-toxicity and relatively low cost. Surface treatments with TiCl4 solution and titanium butoxide solution are applied on the TiO2 nanorod arrays respectively. On the surface of the TiO2 nanorods, TiO2 nanoparticles are prepared through hydrolysis of TiCl4 and homogeneous phase of TiO2 synthesized with assist of second hydrothermal synthesis in titanium butoxide, resulting in the increase of the surface area of the TiO2. Comparing with that of the original TiO2 nanorod arrays, the incident photon-to-electron conversion efficiency (IPCE) of the TiO2–TiCl4 and TiO2–H2O samples is greatly enhanced by 25% and 250% in the ultraviolet region, respectively. The obviously enhanced activity is due to the larger surface structure after treatments, which could contribute to the improved performance in the water splitting. These surface treatments provide an efficient way to regulate the properties of the TiO2 nanorod arrays for their extensive applications in the solar device for the hydrogen production.

Large-scale preparation of nanoporous TiO2 film on titanium substrate with improved photoelectrochemical performance.

Fabrication of three-dimensional TiO2 films on Ti substrates is one important strategy to obtain efficient electrodes for energy conversion and environmental applications. In this work, we found that hierarchical porous TiO2 film can be prepared by treating H2O2 pre-oxidized Ti substrate in TiCl3 solution followed by calcinations. The formation process is a combination of the corrosion of Ti substrate and the oxidation hydrolysis of TiCl3. According to the characterizations by scanning electron microscopy (SEM), X-ray diffraction (XRD), and diffuse reflectance spectroscopy (DRS), the anatase phase TiO2 films show porous morphology with the smallest diameter of 20 nm and possess enhanced optical absorption properties. Using the porous film as a working electrode, we found that it displays efficient activity for photoelectrocatalytic decolorization of rhodamine B (RhB) and photocurrent generation, with a photocurrent density as high as 1.2 mA/cm2. It represents a potential method to fabricate large-area nanoporous TiO2 film on Ti substrate due to the scalability of such chemical oxidation process.

Enhancing dye-sensitized solar cell efficiency by anode surface treatments

In this study, titanium substrates treated with HF solution and KOH solution sequentially forming micro- and nano-structures were used for the fabrication of flexible dye-sensitized solar cells (DSSCs). After wet etching treatments, the titanium substrates were then exposed to the O2 plasma treatment and further immersed in titanium tetrachloride (TiCl4) solution. The process conditions for producing a very thin TiO2 blocking layer were studied, in order to avoid solar cell current leakage for increasing the solar cell efficiency. Subsequently, TiO2 nanoparticles were spin-coated on Ti substrates with varied thickness. The dye-sensitized solar cells on the titanium substrates were subjected to simulate AM 1.5G irradiation of 100mW/cm2 using backside illumination mode. Surface treatments of Ti substrate and TiO2 anode were found to play a significant role in improving the efficiency of DSSC. The efficiencies of the backside illumination solar cells were raised from 4.6% to 7.8% by integrating these surface treatments.

Optimized TiO2 blocking layer for dye-sensitized solar cells

A thin compact layer of TiO2 deposited on the conductive transparent substrate of a dye-sensitized solar cell photoanode, (blocking layer, BL) can enhance the performances of the entire device. In this paper, an optimized spin coating process using an alcoholic TiCl4 solution was developed and correlated to the final properties of the layer. The physicochemical characteristics of the precursor solution and the spin coating parameters were optimised to obtain a uniform layer. XRD, FE-SEM, UV–Vis spectroscopy, AFM, cyclic voltammetry and electrochemical impedance spectroscopy were used to evaluate the influence of the number of deposition cycles on the TiO2 layer. The results were compared with those obtained using a conventional dip coating technique, showing that the newly developed spin coating process produces blocking layers with superior properties. Finally, analyses of the photovoltaic performances of the complete cell confirmed that an optimized blocking layer can lead to an improvement of the solar conversion efficiency of about 84%.

Photoelectrochemical Water Splitting with Rutile TiO2 Nanowires Array: Synergistic Effect of Hydrogen Treatment and Surface Modification with Anatase Nanoparticles

Enhancing charge separation and collection in semiconducting photoelectrodes is a key issue in the area of photoelectrochemical water splitting. Herein we report that photoelectrochemical performance of rutile TiO2 nanowires arrays could be significantly enhanced by sequential treatment with hydrogen atmosphere and TiCl4 solution at elevated temperature. Hydrogen treatment increased the concentration of donors in rutile nanowires as revealed by Mott-Schottky measurements, but meanwhile increased charge recombination as evidenced by enhanced photoluminescence. Treatment with TiCl4 solution, by which rutile nanowires were modified with anatase nanoparticles, could reduce the charge recombination in hydrogen-treated TiO2 nanowires to a level even lower than pristine rutile nanowires, due to the formation of type II anatase-rutile heterojunction. Photoelectrochemical measurements in concentrated KOH solution showed that water splitting on rutile nanowire arrays was enhanced by a factor of ∼1.63 after the sequential treatment with hydrogen and TiCl4 solution at a potential of 0.22V vs. Ag/AgCl, more significantly than the enhancing factor of ∼1.35 by hydrogen treatment only, which could be attributed to the synergistic effect of hydrogen and TiCl4 treatment that improved both electron transportation along TiO2 nanowires and charge separation in the orthogonal direction.

The effect of TiO2compact layer in ZnO nanorod based CdS/CdSe quantum-dot sensitized solar cell

CdS/CdSe quantum-dot sensitized solar cells (QDSCs) were fabricated from ZnO nanorods deposited on fluorine-doped tin oxide (FTO) substrates via the application of polysulfide redox reactions and a CuS counter electrode. In the present study, a TiO2 compact layer was used to suppress the recombination process. Typically, a TiO2 compact layer prevents direct contact between the FTO and electrolyte. The TiO2 compact layer with optimal thickness was fabricated by varying the soaking time in a TiCl4 solution. In addition, the morphology and influence of the compact layer on the interface between the FTO/electrolyte were analyzed.