Ti Precursor Research Articles

Low-temperature and stable CO oxidation of in-situ grown monolithic Mn3O4/TiO2 catalysts

Transition metal oxide catalysts have attracted considerable attention for their promising potential as an alternative to replace noble metal catalysts in the application of various catalytic reactions. Herein, we report the design of monolithic Mn3O4/TiO2 catalysts in-situ grown on Ti mesh substrate for efficient and stable CO oxidation. Porous TiO2 film which is fabricated from the oxidation of Ti mesh using conventional plasma electrolytic oxide process plays an important role in the in-situ nucleation of TiO2 nanosheets with strong adhesion to maintain the long-term stable CO oxidation, as well as providing Ti precursors for the formation of TiO2 nanosheets. The decoration of Mn3O4 co-catalysts on TiO2 nanosheet support could significantly enhance the catalytic property of monolithic Mn3O4/TiO2 catalysts due to the synergetic effect. Thus, a complete CO oxidation can be achieved as low as 160 °C without the involvement of any noble metal catalyst. The novel synthesis strategy of Mn3O4/TiO2 heterogeneous catalysts shows overwhelming advantages of outstanding catalytic performance and superior stability in comparison with other traditional methods of powder-based catalysts. More importantly, it can be extended to the rational design of a variety of TiO2-based transition metal oxide catalysts which can be used for diverse applications including CO oxidation, de-NOx, CHx decomposition etc.

Optical constants and dispersion energy parameters of Zn-doped TiO2 thin films prepared by spray pyrolysis technique

The present work describes the deposition and investigation of structural and optical characteristics of bare and doped TiO2 thin films. The TiO2 products are obtained through simple and cost effective spray pyrolysis technique (SPT) using titanium (IV) butoxide as Ti precursor. The impact of Zn doping on the crystal structure and phase formation is studied by X-ray diffraction (XRD) analysis. The formation of anatase phase relative to pure TiO2 along with preferred orientation along the [101] direction is confirmed with the help of XRD analysis. Zn doping into TiO2 lattice network leads to an identical diffraction pattern. A deterioration of crystallinity is obtained in crystallite size employing the numerous methods such as Scherrer method, Williamson–Hall, Halder–Wagner and Wagner–Agua analysis in accordance with Zn. In addition, absorbance results obtained from UV–vis spectroscopy has been exerted to examine the optical characteristics. It is noted that the dopant introduction has an impact on the optical properties and the direct band gap value obtained from Tauc relation exhibits a red shift with Zn content. The influence of the Zn doping elements on the optical constants of TiO2 product has been investigated. The dielectric constants, dispersion parameters, loss factor and distribution of volume and surface energy loss of the TiO2 products have been computed as well. The as-prepared nanostructured Zn-doped TiO2 thin films can be used as potential candidates for different optoelectronic devices

Controlling the Morphology and Titanium Coordination States of TS-1 Zeolites by Crystal Growth Modifier.

Developing an effective strategy to synthesize perfect titanosilicate TS-1 zeolite crystals with desirable morphologies, enriched isolated framework Ti species, and thus enhanced catalytic oxidation properties is a pervasive challenge in zeolite crystal engineering. We here used an amino acid l-carnitine as a crystal growth modifier and ethanol as a cosolvent to regulate the morphologies and the Ti coordination states of TS-1 zeolites. During the hydrothermal crystallization process, the introduced l-carnitine can not only tailor the anisotropic growth rates of zeolite crystals but also induce the formation of uniformly distributed framework Ti species through building a suitable chemical interaction with the Ti precursor species. Condition optimizations could afford the generation of perfect hexagonal plate TS-1 crystals and elongated platelet TS-1 crystals enriched in tetrahedral framework Ti sites (TiO4) or mononuclear octahedrally coordinated Ti species (TiO6). Both samples showed significant improvement in catalytic activity for the H2O2-mediated epoxidation of alkenes. In particular, the elongated platelet TS-1 enriched in "TiO6" species afforded the highest activity in 1-hexene epoxidation, with a turnover frequency (TOF) of up to 131 h-1, which is approximately twice as high as that of the conventional TS-1 zeolite (TOF: 65 h-1) and even higher than those of the literature-reported TiO6-containting TS-1 catalysts derived from the hydrothermal post-treatment of TS-1 zeolites. This work demonstrates that the morphologies and the titanium coordination states of TS-1 zeolites can be effectively tuned by directly introducing suitable crystal growth modifiers, thus providing new opportunities for developing highly efficient titanosilicate zeolite catalysts for important catalytic applications.

One-step in-situ synthesis of porous Fe3+-doped TiO2 octahedra toward visible-light photocatalytic conversion of CO2 into solar fuel

Here, hollow Fe3+ doped TiO2 (Fe–TiO2) octahedra were obtained via one-step hydrothermal method with MIL-101(Fe) as the template as well as the iron ion source. By introducing Ti precursor onto MIL-101(Fe) followed by HF etching and hydrothermal treatment, Fe-doped TiO2 with high porosity and hollow structure was obtained. The as-synthesized Fe–TiO2 octahedra consist of numerous small nanoparticles with particle sizes between 10 and 20 nm and possess a high specific surface area of 275 m2 g−1 together with uniform mesopores of 3.7 nm in pore diameter. After heat treatment in air at 500 °C (named Fe–TiO2-500), the BET surface area and the mesopore size of the sample were changed to 202 m2 g−1 and 3.9 nm, respectively. Compared to other Fe-doping methods, this method reported here favors better and more uniform Fe doping into the TiO2 lattice and improves the porosity and specific surface area. As a result of the Fe doping, the bandgaps of Fe–TiO2 and Fe–TiO2-500 were about 2.75 eV and 2.42 eV, respectively. Fe–TiO2-500 shows excellent photocatalytic activity due to its special structure, high BET surface area and porosity. The yield of CH4 is about 7.73 μmol g−1 after loading of Pt within 12 h of reaction time under visible light illumination (λ > 420 nm).

Optimized Microwave-Based Synthesis of Thermally Stable Inverse Catalytic Core-shell Motifs for CO2 Hydrogenation.

The rational synthesis of Cu@TiO2 core@shell nanowire (NW) structures was thoroughly explored using a microwave-assisted method through the tuning of experimental parameters such as but not limited to (i) controlled variation in molar ratios, (ii) the effect of discrete Ti precursors, (iii) the method of addition of the precursors themselves, and (iv) time of irradiation. Uniform coatings were obtained using Cu/Ti molar ratios of 1:2, 1:1, 2:1, and 4:1, respectively. It should be noted that although relative molar precursor concentrations primarily determined the magnitude of the resulting shell size, the dependence was nonlinear. Moreover, additionally important reaction parameters, such as precursor identity, the means of addition of precursors, and the reaction time, were individually explored with the objective of creating a series of optimized reaction conditions. As compared with Cu NWs alone, it is evident that both of the Cu@TiO2 core-shell NW samples, regardless of pretreatment conditions, evinced much better catalytic performance, up to as much as 20 times greater activity as compared with standard Cu NWs. These results imply the significance of the Cu/TiO2 interface in terms of promoting CO2 hydrogenation, because TiO2 alone is known to be inert for this reaction. Furthermore, it is additionally notable that the N2 annealing pretreatment is crucial in terms of preserving the overall Cu@TiO2 core@shell structure. We also systematically analyzed and tracked the structural and chemical evolution of our catalysts before and after the CO2 reduction experiments. Indeed, we discovered that the core@shell wire motif was essentially maintained and conserved after this high-temperature reaction process, thereby accentuating the thermal stability and physical robustness of our as-prepared hierarchical motifs.

Surfactant-Free Approach for Engineering an Ultrathin Ti-Doped Ni(OH)2 Nanosheet on Carbon Cloth: Experimental and Theoretical Insight into Boosted Alkaline Water Oxidation Activity

Ti-based layered double hydroxides (LDHs) have enormous potential in photocatalysis, electrocatalysis, and photoelectrocatalysis. However, Ti-based LDHs are rarely reported because of the difficulties of the preparation process, in which the Ti precursors are more prone to hydrolysis into titanium hydroxide. In this work, toward robust, efficient, and earth-abundant electrocatalysts for water oxidation in alkaline environments, we have engineered Ti-doped Ni(OH)2 nanosheet arrays on carbon cloth [Ti-Ni(OH)2/CC] with a facile solvothermal and surfactant-free method. The experimental tests show that the activity of Ti-Ni(OH)2-1/CC (∼12.5 atom % Ti substitution) is optimal among these materials. In addition, the activity is correlated with the Ti substitution ratio and reversed with higher Ti doping level (≥25 atom % Ti substitution). Therein, η10 of Ti-Ni(OH)2-1/CC is as low as 196 mV, and it is still maintained at 210 mV after a long-term chronopotentiometry (CP) test at a constant current density of 10 mA cm-2 for 32 h, demonstrating superior activity and long-term durability. Density functional theory calculations further reveal that dilute Ti substitution produces extra active sites and promotes more optimal OH* adsorption to the surface of the electrocatalyst.

Efficient synthesis of dendritic PbTiO3 nanorods by hydrothermal method

The PbTiO3 nanorods were synthesized by a hydrothermal method using 4.4 mol/L ammonia solution as the pH-adjusting agent. The influence of Pb/Ti molar ratio in the Pb–Ti precursors, precursor concentration, reaction temperature, and time on formation of PbTiO3 nanorods was investigated. The dendritic PbTiO3 nanorods were obtained by controlling the process parameters. The preparation of dendritic PbTiO3 nanorods mainly involved two steps: in the first step of formation of PbTiO3 nanorods, the classical nucleation and growth dominates the nanorod growth, and in the second step of formation of dendritic PbTiO3 nanorods, the oriented attachment dominates the dendritic grain growth. The PbTiO3 nanorods grew along the [001] c-axis, and the oriented attachment was along the [001] c-axis to form the dendritic PbTiO3 nanorods.

Investigation by Thermal Cycle Simulation of Heat Affected Zone in Welded AA2014 Aluminum Alloy

An experimental strategy was developed to obtain Si-Ti-Ni transparent sols via the sol-gel process. The sol was prepared from Si(OEt)4, Ti(OBu)4 and Nickel(II) acetylacetonate. The chelating agent (2,4 pentanedione, acacH) was employed to stabilize Ti precursor in order to control their chemical reactivity, avoiding precipitation.

Preparation of Porous SiO2-TiO2-NiO Synthesized by the Sol-Gel Process and its Characterization

An experimental strategy was developed to obtain Si-Ti-Ni transparent sols via the sol-gel process. The sol was prepared from Si(OEt)4, Ti(OBu)4 and Nickel(II) acetylacetonate. The chelating agent (2,4 pentanedione, acacH) was employed to stabilize Ti precursor in order to control their chemical reactivity, avoiding precipitation.

Aliovalent Doping Engineered Ti1-XTaxO2 Layer for Ultra-Low Power Resistive Memory Devices

Resistive switching (RS) behavior in metal oxides (MO) is governed by the electric field dependent back and forth migration of oxygen vacancies (Vo). Therefore, it is important to regulate the Vos in MO matrix in a systematic manner. Foreign element doping in MO is considered to be beneficial to generate controlled Vo at the vicinity of dopant elements. Based on this, an approach was made to study the RS behavior in Ta-doped TiO2 films on Pt substrates. Prior to thin film deposition, Ti1-xTaxO2 powder was synthesized chemically using Ta and Ti precursor solutions. The Ta-doped TiO2 targets were prepared for pulsed laser deposition of the films on Pt substrates using an laser wavelength of 248 nm. Enhanced RS was observed in 1.11 at. % Ta doped sample with Ron/Roff ratio of ~104 at a voltage as low as 0.25 V. The retention and endurance of the device recorded at 104 s and 105 pulses respectively are exceptionally well. The X-ray diffraction, Secondary Ion Mass Spectroscopy, X-ray absorption spectroscopy and X-ray photoelectron spectroscopy were employed, to investigate the physical and chemical properties of the film and correlated with the improved RS at particular dopant concentration. Further, the dopant concentration dependent stoichiometry was predicted using Energy Dispersive Spectroscopy during Transmission Electron Microscopy study. These observations will be discussed in detail in the light of defect induced RS phenomenon.

Functionalized Cellulose for the Controlled Synthesis of Novel Carbon-Ti Nanocomposites: Physicochemical and Photocatalytic Properties.

Carbon–Ti nanocomposites were prepared by a controlled two-step method using microcrystalline cellulose as a raw material. The synthesis procedure involves the solubilization of cellulose by an acid treatment (H3PO4 or HNO3) and the impregnation with the Ti precursor followed of a carbonization step at 500 or 800 °C. The type of acid treatment leads to a different functionalization of cellulose with phosphorus- or oxygen-containing surface groups, which are able to control the load, dispersion and crystalline phase of Ti during the composite preparation. Thus, phosphorus functionalities lead to amorphous carbon–Ti composites at 500 °C, while TiP2O7 crystals are formed when prepared at 800 °C. On the contrary, oxygenated groups induce the formation of TiO2 rutile at an unusually low temperature (500 °C), while an increase of carbonization temperature promotes a progressive crystal growth. The removal of Orange G (OG) azo dye in aqueous solution, as target pollutant, was used to determine the adsorptive and photocatalytic efficiencies, with all composites being more active than the benchmark TiO2 material (Degussa P25). Carbon–Ti nanocomposites with a developed micro-mesoporosity, reduced band gap and TiO2 rutile phase were the most active in the photodegradation of OG under ultraviolet irradiation.

Tailoring growth process of heteroatom-doped hematite homojunction electrodes for photoelectrochemical catalysis of water oxidation reaction

Enhancing electrical conductivity is necessary to widen application of hematite (α-Fe2O3) as efficient photocatalyst for water oxidation. Doping heteroatoms and developing p-n junction are effective ways for improving carrier density and charge transfer. Heteroatoms of Ti and Mn are doped in hematite to establish p-n homojunction using hydrothermal and annealing processes for catalyzing water oxidation in this work. Ti-doping amount in Ti-doped hematite layer (Ti:Fe2O3) and hydrothermal duration for developing Mn-doped hematite layer (Mn:Fe2O3) are studied to optimize photoelectrochemical performance of hematite homojunction electrode. Optimized Mn:Fe2O3/Ti:Fe2O3 electrode prepared using 9 μl Ti precursor in hydrothermal solution and 45 min as hydrothermal time for constructing Mn:Fe2O3 shows highest photocurrent density of 2.09 mA/cm2 at 1.60 VRHE, owing to small charge-transfer resistance and high carrier density. This study illustrates importance of designing separated layers for establishing homojunction and provides useful indications for picturing recipe for creating efficient photoanode for catalyzing water oxidation.

In Vitro Cytocompatibility Assessment of Ti-Modified, Silicon-oxycarbide-Based, Polymer-Derived, Ceramic-Implantable Electrodes under Pacing Conditions.

Polymer-derived ceramics (PDC) have recently gained increased interest in the field of bioceramics. Among PDC's, carbon-rich silicon oxycarbide ceramics (SiOC) possess good combined electrical and mechanical properties. Their durability in aggressive environments and proposed cytocompatibility makes them an attractive material for fabrication of bio-MEMS devices such as pacemaker electrodes. The aim of the present study is to demonstrate the remarkable mechanical and electrical properties, biological response of PDCs modified with titanium (Ti) and their potential for application as pacemaker electrodes. Therefore, a new type of SiOC modified with Ti fillers was synthesized via PDC route using a Pt-catalyzed hydrosilylation reaction. Preceramic green bodies were pyrolyzed at 1000 °C under an argon atmosphere to achieve amorphous ceramics. Electrical and mechanical characterization of SiCxO2(1-x)/TiOxCy ceramics revealed a maximum electrical conductivity of 10 S cm-1 and a flexural strength of maximal 1 GPa, which is acceptable for pacemaker applications. Ti incorporation is found to be beneficial for enhancing the electrical conductivity of SiOC ceramics and the conductivity values were increased with Ti doping and reached a maximum for the composition with 30 wt % Ti precursor. Cytocompatibility was demonstrated for the PDC SiOC ceramics as well as SiOC ceramics modified with Ti fillers. Cytocompatibility was also demonstrated for SiTiOC20 electrodes under pacing conditions by monitoring of cells in an in vitro 3D environment. Collectively, these data demonstrate the great potential of polymer-derived SiOC ceramics to be used as pacemaker electrodes.

Morphology evolution of BaTi5O11 nanocrystals prepared by hydrothermal method and their permittivity

BaTi5O11 nanocrystals were synthesized by a hydrothermal method. The influence of Ba/Ti molar ratio in the Ba–Ti precursors on the morphology and dielectric properties of BaTi5O11 nanocrystals was investigated. In the precursors, the Ba2+ ion concentration was decreased from 0.02 to 0.01 mol/L, and the Ti4+ ion concentration was increased from 0.08 to 0.09 mol/L. The rice-like BaTi5O11 nanocrystals were synthesized at Ba/Ti molar ratios of 20:80 and 18:82, while the flower-like BaTi5O11 nanocrystals were formed at Ba/Ti molar ratios of 15:85, 12:88 and 10:90. The pure BaTi5O11 phase was synthesized at Ba/Ti molar ratio of 18:82 in the precursor, and the material had the permittivity of 38.9 at 8 GHz, which was close to that of the bulk BaTi5O11 ceramics.

Unprecedented porosity transformation of hierarchically porous TiO2 derived from Ti-Oxo clusters

Abstract Although attaining a high porosity in TiO2 is critical to enhancing its photocatalytic and photoelectric activities, its synthesis has been challenging owing to the high reactivity of conventional Ti precursors and the laborious template removal process. Thus, we herein report a versatile method for preparing hierarchically porous organic-functionalized TiO2 (HiPOTs) using Ti-oxo clusters consisting of a rigid reactive ligand, para-aminobenzoate (p-ABA). The presence of p-ABA as a structure-directing template is crucial to obtain microporous structures with sufficiently high yields. The HiPOTs gradually transform from hierarchically micro/mesoporous structures into mesoporous structures during a sol–gel process. The Brunauer–Emmett–Teller surface areas of the HiPOTs range from 242 to 739 m2/g, which are among the highest reported for porous TiO2 materials. The presence of p-ABA on the HiPOT surface decreases the band gap of TiO2 to 2.7 eV, and prolonging the sol–gel process releases greater quantities of p-ABA, thereby increasing the band gap and the crystallinity of the anatase phase. Interestingly, unlike conventional TiO2, which experiences rapid charge recombination, the Ti3+ oxidation states of HiPOTs are successfully isolated during UV irradiation and can be applied as a proof of concept to generate reactive oxygen species such as 1O2 and •O2−.

Microwave-assisted sol-gel synthesis of TiO2 in the presence of halogenhydric acids. Characterization and photocatalytic activity

The synthesis of mesoporous TiO2 nanosheets is reported using Ti(IV) Isopropoxide as Ti(IV) precursor. A sol-gel process combined with microwave activation is used. Three different halogenhydric acids (HX), were used to peptise the sol: HF(ac), HCl (ac) and HBr (ac). The three obtained TiO2-I(HX) samples were characterized by XRD, XRF, N2-adsorption, SEM, TEM, DRS and XPS. The three synthesized samples have high values of specific surfaces (between 100 m2/g and 200 m2/g) and similar band gap values (3.2–3.3 eV). The analysis of the surface composition by XPS confirms the presence of the halogenated species (F, Cl or Br) on the surface of each ones of the samples. The nanometric size (ca 5 nm) of the particles for each of the three samples was confirmed by XRD and by TEM. On the other hand, the nature of the halogenated acid used plays a role in the composition of the phases. While the TiO2-I (HF) sample was 100 % anatase, the other samples turned out to be biphasic, showing anatase/rutile in the TiO2-I(HCl) sample and anatase/brookite in the TiO2-I(HBr) sample. The samples were tested under two illumination conditions (UV and visible light) using rhodamine B and caffeine. The indirect role of the halide agent on the photocatalytic activities thereof is discussed.

Synthesis and characterization of TiO2 via sol-gel method for efficient photocatalytic degradation of antibiotic ofloxacin

The current study includes the preparation of titanium based nanoparticles for effective photo catalytic degradation of the second generation antibiotic Ofloxacin from the simulated water. The nanoparticles were synthesized by simple sol-gel method via Ti-isopropoxide as Ti precursor and calcined at 300, 350, 400, and 450 °C. The synthesized nanoparticles were characterized through Fourier transform infrared spectroscopy, photoluminescence spectroscopy, scanning electron microscopy and powder X-ray diffraction. Results of characterization study indicated the formation of anatase phase at low temperature. Degradation rate of 91, 87, 76, and 64% was achieved after 3 h of irradiations by TiO2 calcined at 300, 350, 400, and 450 °C, respectively. Results indicated that by increasing calcination temperature, degradation rate of Ofloxacin was decreased due to increase in particle size and smaller surface area. Photo catalytic degradation of Ofloxacin proved that TiO2 was an efficient catalyst for the removal of antibiotic from water samples.

Studies on interstitial carbon doping from a Ti precursor in a hierarchical TiO2 nanostructured photoanode by a single step hydrothermal route.

Carbon doping from a Ti precursor in TiO2 synthesized by a hydrothermal method was studied. The structural, optical and morphological study of the deposited material was carried out using X-ray diffraction, UV-vis spectroscopy and scanning electron microscopy characterization techniques. The elemental composition of the TiO2 deposited with different precursor concentrations was studied using X-ray photoelectron spectroscopy and electron dispersive X-ray spectroscopy. The amount of elemental carbon in the TiO2 matrix is found to be increased as the Ti precursor concentration is increased, which strengthens the proposed idea of carbon doping via a Ti precursor.

Electrochemical Disposition of Titanium Dioxide Photocatalyst on Micropores Silicon Wafer for Water Treatment Application

Titanium dioxide (TiO2), due to wide band gap, has a limited use in water treatment process because of its low activity under visible light. Such drawback is usually associated with the inadequate solar spectrum that activates its surface, i.e., most of the photoexcited electron-hole pairs tend to recombine, leading to a reduction in the photocatalytic performance. Immobilization of TiO2 on the surface of silicon is considered as a useful approach to overcome this drawback. However, the immobilization methods require high temperature and pressure, which limit the numbers and types of materials that can be utilized as a substrate. The known electrochemical deposition procedures are usually conducted through two major steps, electrochemical oxidation and hydrolysis of Ti(III) precursor to form a thin layer on the surface of the substrate, followed by thermal annealing to form crystalline phase. The present work introduces the immobilization of titanium dioxide on a microporous silicon (MPSi) wafer through direct electrochemical deposition, where titanium dioxide P25 was used in the electrolyte solution. The photocatalyst surface morphology and composition were characterized using Scan Electron Microscope (SEM), Electron Dispersive X-ray (EDX), X-ray diffraction (XRD), and X-ray Photoemission Spectroscopy (XPS) techniques. The photocatalytic activities of the new composites were investigated, and the experimental results indicate that the fabricated TiO2–MPSi showed higher methylene blue degradation rate than that of the conventional P25 catalyst. This is due to the unique photosensitivity and porous structure of the new photocatalytic composites. with the advantages of using this method, it is believed that more efficient photocatalyst can be produced.

Polyol-mediated carbon-coated Li4Ti5O12 nanoparticle/graphene composites with long-term cycling stability for lithium and sodium ion storages

Nano-sized oxides are investigated to improve rate capability by decreasing ion and electron travel length. However, extended contact area of nano-sized oxides with electrolyte causes undesirable side reactions and poor cycling stability. Interestingly, previous studies focus either on preparation of nano-sized oxides or on carbon coating to prevent side reactions. In this study, a microspherical composite of ethylene glycol-derived in situ carbon-coated Li4Ti5O12 nanoparticles and reduced graphene oxide is prepared by polyol-mediated spray drying method using ethylene glycol as a stabilizer to control particle growth and ethylene glycol coordinated with Ti precursor as a carbon source. The composite shows excellent rate capability as anode materials for lithium-ion and sodium-ion batteries. Most importantly, the composite shows 94% capacity retention after 3000 cycles at 10 C for Li+ storage and 95% capacity retention after 1000 cycles at 5 C for Na+ storage at room temperature. At 60 °C, furthermore, composite shows 93% capacity retention after 1000 cycles for Li+ storage and 95% capacity retention after 500 cycles for Na+ storage at 10 C. The post-mortem analysis confirms that in situ carbon coating on Li4Ti5O12 effectively prevents direct contact of Li4Ti5O12 nanoparticles with electrolyte, thus, blocking side reactions and greatly improving cycling stability.