Peroxotitanate Complex Research Articles

Layered titanate hierarchical spheres as a promising pseudocapacitive electrode material for high rate lithium ion batteries

Layered titanates with large interlayer spacing (ca. 0.8–0.9 nm) facilitate Li+ movement with less resistance, and are considered suitable anode materials for high power lithium ion batteries (LIBs). Herein, lepidocrocite-type titanate hierarchical spheres (W-THSs) assembled by nanowires are synthesized by supercritical hydrothermal treatment of sodium peroxotitanate complex solution and subsequent acid washing. Nanowire components in the W-THSs interpenetrate each other to form a mesoporous network with high specific surface area (183.6 m2 g−1), which provides electrolyte penetration channels, enlarged electrode/electrolyte contact area, and short charge transport path, favoring fast Li+ insertion/extraction. Consequently, W-THSs exhibits an excellent electrochemical performance, giving a high discharge capacity of 123.6 mAh g−1 even at 5.0 A g−1, and still retaining 180.8 mAh g−1 after 500 cycles at 1.0 A g−1. The rate capability of W-THSs is much superior to the compared anatase TiO2 hierarchical spheres (AHSs) obtained by calcining W-THSs in the air. Moreover, cyclic voltammetry analyses reveal that a pseudocapacitive process occurs during the Li+ storage in W-THSs, significantly contributing to the excellent rate capability.

Dual phase Li4Ti5O12-TiO2 hierarchical hollow microspheres as anode materials for high rate lithium-ion batteries

Dual phase Li4Ti5O12-TiO2 hierarchical hollow microspheres composed of nanosheets are successfully fabricated by the calcination of hydrothermal product obtained from lithium peroxotitanate complex solution. Low-cost industrial H2TiO3 particles are chosen as titanium sources, which is significant for the inexpensive and large-scale production of Li4Ti5O12-TiO2 composite material. The Li4Ti5O12-TiO2 electrode yields excellent rate capability (151, 139 and 134 mA h g-1 at 10, 20 and 25 C, respectively) and good cycling stability (96% capacity retention after 500 cycles at 10 C). The mesoporous hierarchical morphology and high grain boundary density are likely the contributing factors to the excellent electrochemical performance of Li4Ti5O12-TiO2 composite.

Scalable synthesis of hierarchical hollow Li 4 Ti 5 O 12 microspheres assembled by zigzag-like nanosheets for high rate lithium-ion batteries

Abstract Electrochemical performance, abundance and cost are three crucial criteria to comprehensively evaluate the feasibility of Li 4 Ti 5 O 12 as an electrode material for lithium-ion batteries (LIBs). Herein, hierarchical hollow Li 4 Ti 5 O 12 microspheres (HLTOMs) assembled by zigzag-like nanosheets are synthesized by hydrothermal treatment of scalable lithium peroxotitanate complex solution using low-cost commercial H 2 TiO 3 particles as titanium sources, followed by a calcination treatment. Precursor solution concentration, Li/Ti ratio, hydrothermal temperature and duration are found correlative and should be optimized to obtain pure Li 4 Ti 5 O 12 products. A high yield of HLTOMs up to 120 g L −1 was achieved. Due to the unique morphology, the HLTOMs deliver an outstanding rate capability of 139, 125 and 108 mA h g −1 at 10, 20 and 30 C, respectively, and exhibit 94% capacity retention after 1000 cycles at 30C indicating excellent stability. These values are much superior to those of commercial Li 4 Ti 5 O 12 particles (CLTOPs), showing HLTOMs are promising anode materials for LIBs.

Nitrogen-sensitized dual phase titanate/titania for visible-light driven phenol degradation

A dual-phase material (DP-160) comprising hydrated titanate (H2Ti3O7·xH2O) and anatase (TiO2) was synthesized in a low-temperature one-pot process in the presence of triethylamine (TEA) as the N-source. The unique structure exhibits strong visible light absorption. The chromophore is linked to Ti–N bonds derived from both surface sensitization and sub-surface (bulk) doping. From transmission electron microscope (TEM) and textural studies by N2 physisorption, the composite exists as mesoporous particles with a grain size of ∼20nm and mean pore diameter of 3.5nm, responsible for the high surface area (∼180m2/g). DP-160 demonstrated photocatalytic activity in the degradation of phenol under visible light (λ>420nm). The activity of the composite was further enhanced by a small addition (0.001M) of H2O2, which also gave rise to some visible light activity in the control samples. This effect is believed to be associated with the surface peroxo-titanate complex. GC–MS analyses showed that the intermediate products of phenol degradation induced by visible light irradiation of DP-160 did not differ from those obtained by UV (band-gap) irradiation of TiO2. The overall performance of the composite is attributed to efficient excitation via inter-band states (due to N-doping), surface sensitization, improved adsorptive properties of aromatic compounds due to the N-carbonaceous overlayer, and the presence of heterojunctions that are known to promote directional charge transfer in other mixed-phase titanias like Degussa P25.

Studies on influence of reflux time on synthesis of nanocrystalline TiO2 prepared by peroxotitanate complex solutions

Aqueous peroxotitanate complex (PTC) precursor was used to obtain phase pure anatase nanocrystaline TiO2. A wet chemical synthesis route was used in which number of aqueous solutions of PTC was refluxed for different time intervals to study the effect of reflux time on final product. Several characterization techniques were used such as DSC–TGA, XRD, UV–Vis, SEM and TEM. The study revealed that there is a significant influence of reflux time on structural, morphological and optical properties of TiO2. As reflux time of PTC has been increased, crystallite size found to be increased. Also, surface morphology of TiO2 nanoparticles changed from ‘hexagonal shape’ to ‘rice like’ shape and further in ‘ellipsoid rod like’ shape. Optical band gap energy and refractive index incurred to be altered with respect to reflux time of PTC. Detailed study of refluxed PTC solutions has been reported for the first time in the literature.

Evolution of Phase and Morphology of Titanium Dioxide Induced from Peroxo Titanate Complex Aqueous Solution

We demonstrate the growth of anatase TiO2 in nanospheres and rutile TiO2 in nanorods, by the hydrolysis of titanium tetraisopropoxide (TTIP) in the presence of hydrogen peroxide at 100 degrees C using sol-gel method. X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), scanning electron microscopy (SEM), and surface area measurement techniques are used to characterize the phase and shape developments of TiO2 obtained from peroxo titanate complex in an aqueous solution at 100 degrees C. Peroxo titanate complexes were prepared by a reaction of titanium hydroxide, formed by hydrolysis of titanium tetraisopropoxide (TTIP), and different amounts of hydrogen peroxide (H2O2). TEM and XRD investigations reveal that the size of spheres (anatase) and rods (rutile) are about 8 nm (diameter) and about 13 x 29 nm approximately 20 x 75 nm (width x length) respectively. The influence of molar ratio of H2O2/TTIP on the phase and morphology of TiO2 is presented. A mixture of anatase spheres and short rutile rods are formed at low H2O2/TTIP ratio while predominantly rutile a quit long rods are formed at higher H2O2/TTIP ratio.

Solvothermal Synthesis of TiO2 Nanocrystal Colloids from Peroxotitanate Complex Solution and Their Photocatalytic Activities

TiO2 nanocrystal colloids with different shapes and sizes have been prepared from a peroxotitanate complex solution starting from titanium(IV) sulfate and hydrogen peroxide (H2O2) in water/alcohol media by a solvothermal process. The TiO2 nanocrystals were characterized by transmission electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, FT-IR spectroscopy, zeta potential, and nitrogen adsorption. The TiO2 nanocrystal colloids prepared by a solvothermal process at 120 °C show a highly crystallized anatase phase. The particle sizes decreased with the increase of the alcohol/water ratio. The shapes of the particles have been controlled from the “rodlike” in pure water solvent to a “rectangular” shape in pure ethanol solvent. The photocatalytic activities of TiO2 nanocrystals were evaluated by the degradation of phenol. The photocatalytic activity of the anatase nanocrystal was closely related to the particle diameter. In addition, the possible growth mechanism of this an...

Facile preparation of large aspect ratio ellipsoidal anatase TiO 2 nanoparticles and their application to dye-sensitized solar cell

A simple one-step heat-treatment of peroxotitanate complex aqueous solution at around 100 °C was resulted in the formation of ellipsoidal anatase TiO 2 nanoparticles having a high aspect ratio with no branches. The length of these ellipsoidal TiO 2 falls in the range of 200–350 nm, depending on mole ratio of Ti 4+/H 2O 2. Dye-sensitized solar cell based on these ellipsoidal nanocrystalline TiO 2 as photoanode was fabricated and characterized.

Morphological and phase evolution of TiO 2 nanocrystals prepared from peroxotitanate complex aqueous solution: Influence of acetic acid

Nanosized anatase and rutile TiO 2 having different shape, phase and size have been prepared from aqueous solutions of peroxo titanium complex starting from titanium(IV) isopropoxide (TTIP), acetic acid and hydrogen peroxide (H 2O 2) in water/isopropanol media by a facile sol–gel process. The TiO 2 nanocrystals are characterized by powder X-ray diffraction (XRD), Raman spectroscopy, FT-IR spectroscopy, TEM, high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) techniques. The influence of pH and the sequence of addition of reaction contents on the phase and morphology of TiO 2 are studied. The reasons for the observation of only anatase and/or mixture of anatase and rutile are given.

Thick Transparent Rutile TiO2 Films Crystallized in Solution

We report a novel process for the preparation of dense, transparent TiO2 films of 2.5 mum thickness on a F-doped SnO2-covered glass substrate. The starting solution contained peroxotitanate complex ions, which are relatively stable under the experimental conditions, permitting the deposition of highly textured rutile nanocrystalline films. The nanocrystals exhibit specific orientations along the (101) and (002) crystalline planes. Kinetic studies suggest that the precipitation started from the formation of amorphous solids, followed by crystallization through a dissolution-recrystallization process. Although a minor phase of anatase was detected only for powders collected from solutions after film preparation, not for films, the transformation from amorphous to anatase was believed to occur before further transformation of anatase to rutile. The present method enables film synthesis on a surface with a large area, and therefore could be integrated into the processing of electroluminescent devices.

Micropatterning of TiO2 Thin Film in an Aqueous Peroxotitanate Solution

We report micropatterning of TiO2 thin film by a peroxotitanate complex deposition method, which was a method we developed recently. The deposition solution was obtained by dissolving titanic acid (H2TiO3) into a mixture solvent containing ammonia and hydrogen peroxide aqueous solution. The amorphous TiO2 micropattern with a high resolution was achieved by using a template of photomodified self-assembled monolayers at room temperature. The film showed high purity, flatness, and crack-free characteristics. The fundamental dielectric characteristics suggest that the micropatterned TiO2 thin films prepared by the present method are promising for application to dielectric layers.

Chain Decomposition of Bis(oxalato)peroxotitanate(IV) Complex Initiated by Ti(III), Cr(II), and V(II)

Abstract The chain decomposition of the bis(oxalato)peroxotitanate(IV) complex [Ti(O2)(ox)2]2− (ox = C2O42−) is initiated by the addition of a very small amount of reducing agent, such as Ti(III), Cr(II) or V(II). The chain length increases with increasing the concentrations of added [TiO(ox)2]2− and oxalate ion; the maximum chain length was 600 under the experimental conditions. The decomposition reaction gave 2 mol of CO2 per 1 mol of decomposed [Ti(O2)(ox)2]2−. Ti(III), Cr(II), and V(II) reductions of [Ti(O2)(ox)2]2− produced ·OH, identified by the spin-trapping technique using a 5,5-dimethyl-1-pyrroline-N-oxide radical trap. Oxygen is an inhibitor of the chain reaction in this system. The chain-decomposition mechanism is discussed.