Titanium Source Research Articles

Synthesis of highly water-dispersible N-doped anatase titania based on low temperature solvent-thermal method

In this paper, the high-concentration aqueous dispersion N-doped anatase TiO2 is prepared based on low temperature non-aqueous solvent-thermal method by using TCl4 and NH4Cl as titanium source and nitrogen source respectively. From TEM image, we can learn that the particle is composed of spindle-shaped particles with the size from 8 to 15 nm. According to the XRD and XPS spectra of N-doped TiO2, it can be seen that, during the synthesis process, N atoms permeate into the TiO2 lattice, and the impurity level can be formed within the band gap of TiO2. The impurity level can extend to absorb UV and the visible light. As for N-doped TiO2 nanoparticle of XPS spectrum, ethanol is used as solvent to form carbonaceous species on the surface of TiO2. The carbonaceous species in visible light can excite electrons towards the TiO2 conduction band, so as to increase the number of electrons in the conduction band under visible light to improve the catalytic activity of TiO2 which possesses the feature of high catalytic activity under UV–visible light.

Temperature-dependent growth window of CaTiO3 films grown by hybrid molecular beam epitaxy

The authors report the effects of growth temperature on the self-regulated growth window of CaTiO3 thin films grown by hybrid molecular beam epitaxy (hMBE). Films were grown on (001) (La0.3Sr0.7)(Al0.65Ta0.35)O3 at temperatures between 700 and 950 °C. Calcium was supplied by a standard thermal effusion cell, while the metalorganic precursor titanium tetra-isopropoxide (TTIP) was used as the titanium source. The stoichiometric growth conditions were mapped using a combination of x-ray diffraction, reflection high energy electron diffraction, and atomic force microscopy. It is found that the growth window widened and shifted to higher TTIP fluxes with increasing temperature. Further, the shift of the growth window edge to Ti-rich conditions is three times larger than the growth window edge to Ca-rich conditions, which is discussed in general terms of the kinetic processes involved in hMBE.

Active Site Formation for Oxygen Reduction Reaction on Carbon-Support-Free Titanium Oxynitride with Boosted Activity in Acidic Media

An active site formation process for recently reported carbon-support-free titanium oxynitride (TiOxNy) catalysts is investigated to reveal the critical factors for enhancing the oxygen reduction reaction (ORR) activity in acidic media. Neither the titanium source nor the presence of a conductive oxide support is a key to displaying activity whereas an oxidized TiN surface is revealed to be necessary. The ORR activity is successfully enhanced without using a carbon support to the level of the best carbon-supported oxide-based catalyst, zirconium oxynitride on multiwalled carbon nanotube in 0.1 mol dm–3 H2SO4 solution, mainly by optimizing hydrochloric acid concentration in the precursor dispersion to increase the surface nitrogen content. The catalyst is stable; i.e., the activity remained unchanged after 20 000 potential cycles between 0.6 and 1.0 V versus reversible hydrogen electrode.

Tubular structure TiO2/C/TiO2 hybrid derived from the waste of the fluff of chinar tree

Tubular structure TiO2/C/TiO2 hybrids were successfully fabricated via impregnation-calcination method. A castoff of tubular structure FCT (the fluff of the chinar tree) was employed as template and carbon source, and economical TiCl4 was purchased as titanium source. In particular, the outer tube wall of the TiO2/C/TiO2 hybrid was constructed with interlaced and curly nanofibers. Nevertheless, the inner tube wall was assembled with spheroid-likely TiO2 nanoparticles. In addition, the graphitic carbon layer was formed between TiO2 nanofibers and nanoparticles. The FCT played a vital role in inducing and assembling the hierarchical tube structure of the TiO2/C/TiO2 hybrid. Furthermore, the design of the hydrolysis reaction during the preparation process also made contributions on building the unique structure. The hydrolysis reaction was taken place by blowing atmosphere, which could control the hydrolysis reaction at an appropriate reaction rate. Furthermore, the graphitic C layer in the TiO2/C/TiO2 hybrid could accelerate the migration and separation of the photogenerated electron during the reaction process. At appropriate carbon content, the TiO2/C/TiO2 could degrade 99% tetracycline hydrochloride (TH) under simulated sunlight irradiation within 30 min.

Morphology, structure and photowettability of TiO2 coatings doped with copper and fluorine

The work reports synthesis, structure and properties of doubly doped titanium dioxide coatings activated by ultraviolet and visible light. Copper within a concentration range of 0.4–3.4at% and fluorine within a concentration range of 1.7–9.4at% were introduced as dopants. The coatings were prepared with the help of radiofrequency plasma enhanced chemical vapor deposition technique with a single precursor compound providing both dopants and titanium (IV) chloride being a source of titanium. Elemental composition and chemical bonding analyses of the coatings were carried out with the help of X-ray photoelectron spectroscopy. The results indicate that both admixtures are chemically bound to the TiO2 matrix – a notion confirmed by Fourier transform infrared spectroscopy. Phase composition studies, performed with a low angle X-ray diffraction method, revealed a presence of a threshold concentration of the dopants affecting the coatings crystallinity. Surface morphology and its topography were studied with the help of scanning electron microscopy and atomic force microscopy. Several coatings exhibited a superhydrophilic effect upon relatively short time of illumination.

Effect of carbon-interaction on structure-photoactivity of Cu doped amorphous TiO2 catalysts for visible-light-oriented oxidative desulphurization of dibenzothiophene

Amorphous TiO2 (AT) was successfully prepared via the sol-gel technique, using different titanium sources followed by incorporation of copper via the electrochemical method to give CuO/TiO2 (CAT) catalysts. The catalysts were characterized via XRD, N2 physisorption, FTIR, TEM, EDX, XPS, ESR and UV–Vis DRS. The results verified that the use of different titanium precursors have profound effect on the physicochemical properties of the AT catalysts. Further one-pot self-doping carbon from titanium precursor during the addition of copper could greatly enhanced the photocatalytic activity of CAT on the oxidative desulphurization of dibenzothiophene (DBT). 15 CATTBOT exhibited the best performance mainly due to the narrowest band gap and higher numbers of O–Ti–C and Ti–O–C bonds, as well as appropriate amount of Ti3+ surface defects (TSD). These abovementioned properties offered good mobility of electron-hole pairs and/or trap the electrons for enhancement of photoactivity under irradiation of visible light. Kinetic studies showed that the photocatalytic oxidative desulphurization of DBT followed the pseudo-first order Langmuir-Hinshelwood model, where the adsorption was the controlling step. It is believed that these results could contribute to the synthesis of various supported catalysts for numerous applications specifically in removal of sulphur containing compounds in fuel oils.

One-Step Hydrothermal Fabrication of TiO2/Reduced Graphene Oxide for High-Efficiency Dye-Sensitized Solar Cells

A facile one-step hydrothermal method was developed to prepare TiO2/reduced graphene oxide (TiO2/RGO) composite, which contains TiO2 microspheres and two-dimensional RGO with dispersed TiO2 nanoparticles. During the hydrothermal process, reduction of graphene oxide (GO) and hydrolysis of the titanium source were both obtained. Highly electronically conductive RGO was incorporated into TiO2 photoanodes of dye-sensitized solar cells (DSSCs), which facilitated a faster electron transfer efficiency and a lower reduction in electron recombination, together with enhanced light scattering and dye adsorption. The performance measurement of the DSSCs showed that incorporation of RGO can significantly improve the photovoltaic performance of DSSCs; the short-circuit current density showed a 45.5% increase and a total conversion efficiency of 7.57% was obtained.

Titanium butoxide molar ratio effect in the TiO2 nanoparticles size and methylene blue degradation

This work focuses on the studies of titanium butoxide (Ti(OBu)4) molar ratio effect in the TiO2 nanoparticles size via solvothermal method for methylene blue degradation. The materials used for the synthesis were: Ti(OBu)4 as titanium source, anhydrous ethanol (EtOH) as solvent, and nitric acid (HNO3) as catalyst. The TiO2 nanoparticles demonstrate growth in a pure anatase phase tetragonal crystalline structure, where other phases or amorphous material is not present. The TiO2 nanoparticles reveal a rounded shaped and when the amount of titanium precursor increases, the nanoparticle size decreases. The photocatalytic degradation of methylene blue is influenced by the nanoparticle size where the material with a 2:30:2 molar ratio, Ti(OBu)4:EtOH:HNO3, presents the minor nanoparticle size and a degradation similar to results obtained by commercial TiO2 (P25) at a time of 90 min.

Recyclable Magnetic Titania Nanocomposite from Ilmenite with Enhanced Photocatalytic Activity.

Using ilmenite as a raw material, iron was converted into Fe3O4 magnetic fluid, which further was combined with titanium filtrate by a solvothermal method. Finally Fe3O4/TiO2 nanocomposites with the uniform size of 100–200 nm were prepared. This approach uses rich, inexpensive ilmenite as a titanium and iron source, which effectively reduces the production cost. The crystal structure, chemical properties and morphologies of the products were characterized by SEM, TEM, XRD, FTIR, BET, UV-Vis, XPS and VSM. The novel photocatalyst composed of face-centered cubic Fe3O4 and body-centered tetragonal anatase–TiO2 exhibits a spherical shape with porous structures, superparamagnetic behavior and strong absorption in the visible light range. Using the degradation reaction of Rhodamine B (RhB) to evaluate the photocatalytic performance, the results suggest that Fe3O4/TiO2 nanocomposites exhibit excellent photocatalytic activities and stability under visible light and solar light. Moreover, the magnetic titania nanocomposites displayed good magnetic response and were recoverable over several cycles. Based on the trapping experiments, the main active species in the photocatalytic reaction were confirmed and the possible photocatalytic mechanism of RhB with magnetic titania was proposed. The enhanced photocatalytic activity and stability, combined with excellent magnetic recoverability, make the prepared nanocomposite a potential candidate in wastewater purification.

Revisiting the Incorporation of Ti(IV) in UiO-type Metal–Organic Frameworks: Metal Exchange versus Grafting and Their Implications on Photocatalysis

The inclusion of Ti(IV) in water-stable metal-organic frameworks has been proposed as a strategy for the generation of high surface area heterogeneous photocatalysts, with UiO-66 being a promising candidate. We find that the site of binding of Ti(IV) is at linker defect sites and not incorporated into the inorganic secondary building unit through metal exchange. We also demonstrate the choice of titanium source is critical in the generation of an active hydrogen evolution catalyst, and explain the observed activity using density functional theory calculations, which also enable rational design of future Ti(IV) coordination environments in MOF catalysts

Structural regulation of hollow spherical TiO2 by varying titanium source amount and their thermal insulation property

Hollow spherical TiO2 were successfully fabricated through a template-free solvothermal route using TBT (titanium(IV) butoxide) as the titanium source and absolute ethanol as the solvent. The structural parameters like cavity size, wall thickness and overall sphere diameter of hollow spherical TiO2 were effectively controlled through tuning TBT amount. By increasing the amount of TBT, the overall sphere diameter and wall thickness of the hollow spherical TiO2 increased, the cavity structure first expanded and then gradually collapsed with the TBT increasing. Hollow spherical TiO2 possessed high light reflection and low thermal conductivity due to its hollow structure and the inherent properties, showing distinguished thermal insulation property. The structural parameters of hollow spherical TiO2 played an important role for improving of thermal insulation property. Moreover, hollow spherical TiO2 as fillers can significantly enhance the thermal insulation, UV-shielding and mechanical preformance of polyacrylate film.

Morphology and photocatalytic performance of nano-sized TiO2 prepared by simple hydrothermal method with different pH values

pH value is a key factor in the preparation of nano-sized TiO2 with hydrothermal method. Using Ti(SO4)2 as the titanium source, H2O2 as the complexing agent, NaOH and HCl as the pH value regulator, nano-sized TiO2 powder with various morphologies and sizes was synthesized. Changes in morphology, size and phase type with pH values of samples were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. Results show that under the present preparation conditions, TiO2 powder is an anatase phase with pH value less than 11, but is more likely to be a brookite phase with pH value more than 11. With the increase in pH value from 1 to 11 in hydrothermal environment, nano-sized anatase TiO2 gradually grows up in all directions. {001}, {101} and {100} groups of crystal plane are the exposed crystal planes of nano-sized anatase TiO2 for the (004), (101) and (200) facets found in high-resolution TEM image. The photocatalytic performance of nano-sized TiO2 with different morphologies was compared by measuring their photocatalytic degradation rates for methylene blue under ultraviolet light. Results show that anatase TiO2 prepared under the alkalescent hydrothermal environment (pH = 9, 11) has a better photocatalytic degrading performance. Different sizes and phases of nanoscaled TiO2 powders with different photocatalytic performances can be prepared by the control of pH value of hydrothermal solutions.

TiO2-B/Ag Nanocomposite Wires Enhanced Electrochemical Performance for Li-ion Batteries

In this work, the pristine and Ag-composited TiO2-Bronze (TiO2-B) nanowires are successfully synthesized by hydrothermal method using anatase(P25) as titanium source. The SEM, TEM results reveal that the silver particles are well distributed on the TiO2-B nanowires. Also, the TiO2-B/Ag nanowires are dispersed very well, which demonstrate more Li-ion insertion/extraction hosts exposed to the electrolyte. Moreover, the electrochemical performance tests suggest that compared with the pristine TiO2-B, the Ag-composited TiO2-B (TiO2-B/Ag) shows remarkably higher capacities (~286mAhg-1, closing to the theoretical capacity) and superior rate capability. The reasons causing this performance difference are ascribed to the added silver particles, which could reduce the Li-ion diffusion length and improve the material electrical conductivity.

Microwave-hydrothermal synthesis and photocatalytic properties of biomass charcoal/TiO2 nanocomposites

Biomass charcoal-doped titanium dioxide (C/TiO2) composites were proposed by microwave-hydrothermal and calcination method using tetrabutyl titanate as the titanium source and lignin as the carbon source. TiO2 crystals with different morphologies could be successfully adsorbed onto the surface of biomass charcoal. These products were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TG), derivative thermogravimetric (DTG), UV–vis diffuser flection spectroscopy (UV–vis), Fourier transform infrared spectroscopy (FT-IR), and Brunauer–Emmett–Teller (BET). The photocatalytic activities of the as-obtained composites were checked under visible light irradiation. The results showed that both the microwave-hydrothermal temperature and time played an important role in the microstructure and photocatalytic activity of the samples. The rapid microwave-hydrothermal with the thermal post-treatment provides a promising route for the fabrication of biomass charcoal-doped nanocomposites materials.

Synthesis and photocatalysis of flaky flower TiO 2 with sphere structure

The synthesis of nanocrystals with hierarchical structure is a well-known challenge in many fields of science and technology. In the present work, we making use of tetrabutyl titanate as a titanium source, hydrofluoric acid as an additive, successfully prepared flaky flower titanium dioxide (TiO2) with sperical nanostructures by the solvothermal method. Then we calcined some of the samples. It was found that the calcined sample presented higher crystallinity by X-ray diffraction (XRD). A series of scanning electron microscopy (SEM) characterization results indicate that the calcination causes the sheet-like structure of the sample to become larger and thicker. And the exposed specific surface area became larger. The Brunauer–Emmett–Teller N2 gas adsorption–desorption isotherms characterization results also further demonstrate that the calcined samples have a larger specific surface area than the sample before calcined. The photocatalytic activity was evaluated by measuring the degradation rate of methylene blue under UV–vis light irradiation. The results show that anatase TiO2 after calcination exhibit higher photocatalytic activity than the sample before calcination in the degradation of methylene blue under UV–vis light irradiation. It can be attributed to the synergetic effect of the architecture, high crystallinity, large specific surface areas and ostwald ripening. Scheme 1. Schematic illustration of the morphological evolution.

Solvothermal Synthesis of Hierarchical TiO2 Microstructures with High Crystallinity and Superior Light Scattering for High-Performance Dye-Sensitized Solar Cells.

In this article, hierarchical TiO2 microstructures (HM-TiO2) were synthesized by a simple solvothermal method adopting tetra-n-butyl titanate as the titanium source in a mixed solvent composed of N,N-dimethylformamide and acetic acid. Due to the high crystallinity and superior light-scattering ability, the resultant HM-TiO2 are advantageous as photoanodes for dye-sensitized solar cells. When assembled to the entire photovoltaic device with C101 dye as a sensitizer, the pure HM-TiO2-based solar cells showed an ultrahigh photovoltage up to 0.853 V. Finally, by employing the as-obtained HM-TiO2 as the scattering layer and optimizing the architecture of dye-sensitized solar cells, both higher photovoltage and incident photon-to-electron conversion efficiency value were harvested with respect to TiO2 nanoparticles-based dye-sensitized solar cells, resulting in a high power conversion efficiency of 9.79%. This work provides a promising strategy to develop photoanode materials with outstanding photoelectric conversion performance.

Modifying Titania Using the Molten-Salt-Assisted Self-Assembly Process for Cadmium Selenide-Quantum Dot-Sensitized Photoanodes.

Sensitizing titania with semiconducting quantum dots (QDs) is an important field for the development of third-generation photovoltaics. Many methods have been developed to effectively incorporate QDs over the surface of mesoporous titania, assembled from the 20–25 nm titania nanoparticles. Here, we introduce a molten-salt-assisted self-assembly (MASA) method to fabricate CdSe-modified mesoporous titania photoanodes. A mixture of ethanol, two surfactants (cetyltrimethylammonium bromide and 10-lauryl ether), silica (tetramethyl orthosilicate) or titania source (Ti(OC4H9)4, acid (HNO3), and cadmium nitrate solution was infiltrated into the pores of mesoporous titania (assembled using Degussa 25, P25) and immediately calcined at 450 °C to obtain mesoporous cadmium oxide–silica–titania (meso-CdO–SiO2–P25) or cadmium titanate–titania (meso-CdTiO3–P25) films. The MASA process is a simple method to smoothly coat or fill the pores of titania with mesoporous CdO–SiO2 or CdTiO3 that can be reacted under an H2Se atmosphere to convert cadmium species to CdSe at 100 °C. Etching of the silica films with a very dilute hydrogen fluoride solution produces mesoporous CdSe–titania (meso-CdSe–P25) electrodes. The method is flexible to adjust the CdSe/TiO2 mole ratio over a very broad range in the films. The films were characterized at every stage of the preparation to demonstrate the effectiveness of the method. The electrodes were also tested in a simple two-electrode solar cell to demonstrate the performance of the electrodes that have a power conversion efficiency of 3.35%.

Optimization of synthesis conditions of N-doped TiO2 nanoparticles using Taguchi robust design

In the current research, nitrogen doped titanium dioxide as a visible-light active photocatalyst material has been synthesized through sol-gel method. The main factors affecting the photocatalytic efficiency of N-doped titanium dioxide nanoparticles, including nanoparticle size and percent of crystallinity, have been investigated using Taguchi robust design. Water to titanium precursor ratio (H+/Ti4+), nitrogen to titanium source ratio (TEA/Ti4+), pH, and temperature were the considered factors. To clarify the crystallinity, size distribution and morphology of the synthesized nanoparticles, XRD, PSA and SEM analyses have been conducted. The results of XRD analysis revealed that acidic pH improves the formation of crystalline phase. Also, the water to titanium content ratio is inversely correlated to the crystallinity. In the case of using triethylamine (TEA) as a doping agent, the formation of crystalline phase is promoted. Moreover, a stable solution forms around the acidic pH. Addition of water increases its stability, but addition of TEA decreases it. In nonacidic pH the size of nanoparticles becomes smaller and increasing the water to titanium content ratio causes to decrease the particle size, addition of TEA also has the same influence. The microstructure and surface morphology of the N-doped TiO2 nanoparticles shows a uniform geometry and size distribution.

SnO2/TiO2 nanocomposites embedded in porous carbon as a superior anode material for lithium-ion batteries

With the objective of improving the capacity and cycling stability of SnO2-based anode materials, a new material of SnO2/TiO2 nanocomposites dispersed at porous carbon was synthesized via a route of absorption and carbonization by using Ti-MOF (MIL-125) as both titanium and carbon sources and SnCl2 as tin source. The composite shows micro-/nano-scale combined configuration: a monodisperse sub-micro cylinder structure formed by well-dispersed SnO2 and TiO2 nanoparticles in amorphous carbon matrix. Benefiting from the synergistic effect of TiO2 nanoparticle and amorphous carbon on maintaining the robust architecture as well as the uniform and stable nano-sized particles, the composite exhibits excellent performance as anode material for lithium-ion batteries: a high specific capacity of 1177mAhg−1 and 88.7% capacity retention after 100 cycles at 100mAhg−1, and a stable capacity of 487 at high current density of 2Ag−1.

Kinetics of the acid orange 7 degradation in the photocatalytic system of UV/H2O2/TS-1

In this paper, the titanium silicate (TS-1) molecular sieve was prepared through a rapid synthesis process, in which the tetrabutyl titanate used as titanium source, the tetraethyl orthosilicate used as silicon source and the tetrapropylammonium hydroxides used as template. A UV/H2O2/TS-1 photocatalytic system, including the light source of the high pressure mercury lamp (300W, main wavelength of 365nm), the oxidant of H2O2 and the photocatalyst of the prepared TS-1, was then built to investigate the kinetics of acid orange 7 (AO7) degradation. The effect of the mass concentration of TS-1, H2O2 volume fraction, initial pH value of the solution and initial concentration of the AO7 solution on the degradation rate constant (k) of the AO7 degradation was investigated. The obtained results showed that the AO7 degradation in the UV/H2O2/TS-1 photocatalytic system obeyed the first order kinetics equation. 0.2g/L TS-1 addition, 10mL/L H2O2 addition, 6.18pH value was the optimal conditions for the AO7 degradation in the reaction system and the corresponding k value (0.11879min−1) of the AO7 degradation was the highest. The azo group, the hydrogenated azo and the naphthalene of the AO7 molecules could be damaged under the optimal reaction conditions.