Processing and photocatalytic properties of Cu-grafted TiO2 powder from acid treated BaTiO3

The respective influences of calcination, drying methods, and washing conditions on the morphologies, surface properties, and photocatalytic activities of TiO₂ powders prepared from acid treatments of BaTiO₃ were investigated. Rutile powder was obtained using the treatment under strong acid conditions. It possesses a bundle-like shape and comprises rutile nanorods. After calcination, characteristic voids were observed in the particles. Anatase powder was obtained by adjusting pH values of a BaTiO₃ suspension to 2.5-3. Drying at 110 °C engendered the formation of spheroidal anatase, although freeze-dried anatase particles assembled into a flake-like shape. The freeze-dried samples show lower crystallinity. With grafting Cu ions, rutile exhibited better photocatalytic performance for the decomposition of gaseous 2-propanol (IPA) under visible light, although it did not work effectively for anatase.     

Facile synthesis of α-MnO2 nanostructures for supercapacitors

Various α-MnO₂ nanostructures have been successfully synthesized by a simple hydrothermal method based on the redox reactions between the MnO₄⁻ and H₂O in mixture containing KMnO₄ and HNO₃. The effect of varying the hydrothermal time to synthesize MnO₂ nanostructures and the forming mechanism of α-MnO₂ nanorods were investigated by using XRD, SEM and TEM. The results revealed an evolvement of morphologies ranging from brushy spherical morphology to nanorods depending upon the hydrothermal time. The surface area of the synthesized nanomaterials varied from 89 to 119 m²/g. Electrochemical properties of the products were evaluated using cyclic voltammetry and galvanostatic charge–discharge studies, and the sample obtained by hydrothermal reaction for 6 h at 120 °C showed maximum capacitance with a value of 152 F/g. In addition, long cycle life and excellent stability of the material were also demonstrated.     

Preparation N-F-codoped TiO2 nanorod array by liquid phase deposition as visible light photocatalyst

An efficient method for the preparation of N-F-codoped visible light active TiO₂ nanorod arrays is reported. In the process, simultaneous nitrogen and fluorine doped TiO₂ nanorod arrays on the glass substrates were achieved by liquid phase deposition method using ZnO nanorod arrays as templates with different calcination temperature. The as-prepared samples were characterized by Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV-vis absorption spectra measurements. It was found that calcination temperature is an important factor influencing the microstructure and the amount of N and F in TiO₂ nanorod arrays samples. The visible light photocatalytic properties were investigated using methylene blue (MB) dye as a model system. The results showed that N-F-codoped TiO₂ nanorod arrays sample calcined at 450 °C demonstrated the best visible light activity in all samples, much higher than that of TiO₂ nanoparticles and P25 particles films.     

Facile fabrication of p–n heterojunctions for Cu2O submicroparticles deposited on anatase TiO2 nanobelts

In this paper, Cu₂O particle-deposited TiO₂ nanobelts with p–n semiconductor heterojunction structure were successfully prepared via a two-step preparation process to investigate electron-transfer performance between p-type Cu₂O and n-type TiO₂. Various measurement results confirm that the amount of pure Cu₂O submicroparticles, with diameters within the range of 200–400 nm and deposited on the surface of TiO₂ nanobelts, can be controlled, and that the purity of Cu₂O is heavily affected by reaction time. Visible-light photodegradation activities of Rhodamine B show that photocatalysts have little or no photocatalytic activities mainly due to their p–n heterojunction structure, indicating that there hardly appears any electron-transfer from Cu₂O to TiO₂.     

Fabrication, structure, and enhanced photocatalytic properties of hierarchical CeO2 nanostructures/TiO2 nanofibers heterostructures

Combining the versatility of electrospinning technique and hydrothermal growth of nanostructures enabled the fabrication of hierarchical CeO₂/TiO₂ nanofibrous mat. The as-prepared hierarchical heterostructure consisted of CeO₂ nanostructures growing on the primary TiO₂ nanofibers. Interestingly, not only were secondary CeO₂ nanostructures successfully grown on TiO₂ nanofibers substrates, but also the CeO₂ nanostructures were uniformly distributed without aggregation on TiO₂ nanofibers. By selecting different alkaline source, CeO₂/TiO₂ heterostructures with CeO₂ nanowalls or nanoparticles were facilely fabricated. The photocatalytic studies suggested that the CeO₂/TiO₂ heterostructures showed enhanced photocatalytic efficiency of photodegradation of dye pollutants compared with bare TiO₂ nanofibers under UV light irradiation.     

Quasi-cube ZnFe2O4 nanocrystals: Hydrothermal synthesis and photocatalytic activity with TiO2 (Degussa P25) as nanocomposite

The fabrication and photocatalytic application of zinc ferrite nanocrystals were reported. Quasi-cube ZnFe₂O₄ nanocrystals with typical small sizes of 5-15 nm were successfully synthesized by a facile hydrothermal approach. ZnFe₂O₄/P25 nanocomposite was prepared by physically grinding the ZnFe₂O₄ nanocrystals with TiO₂ (commercial Degussa P25) at ambient temperature, and it exhibited excellent photocatalytic activity for the mineralization of Rhodamine B. UV-vis measurement and photocatalytic test results showed that ZnFe₂O₄ nanocrystals exhibited effective band-gap coupling to P25 nanopowders by simply physical grinding without any surface modification or high-energy balling, which is usually adopted in conventional mixture process. This phenomenon can be attributed to the high surface activities of the as-obtained tiny ZnFe₂O₄ nanocrystals and commercial P25 nanoparticles. It may imply that the mixing process of composite materials would be simplified by further lowering the grain sizes of their component particles.     

Characterization of LiF-doped TiO2 and its photocatalytic activity for decomposition of trichloromethane

LiF-doped TiO₂ was prepared by hydrolysis of tetrabutyl titanate in a mixed LiF-H₂O-alcohol solution. The prepared LiF-doped TiO₂ powders were characterized by X-ray diffraction (XRD), differential thermal analysis-thermogravimetry (DTA-TG), X-ray photoelectron spectroscopy (XPS), UV-vis absorption spectroscopy and photoluminescence spectra (PL). The photocatalytic activity was evaluated by the decomposition of trichloromethane (CHCl₃). The results showed that LiF-doping increased the amount of O_OH and oxygen vacancy (OV) on the surface of TiO₂, which were beneficial to photocatalytic activity. LiF-doping inducted the new isolated energy band located above the valence band of TiO₂, which extended the absorption region of TiO₂ to visible light. The results of photocatalytic reaction showed that the photocatalytic activity of LiF-doped TiO₂ was 2.5 times higher than that of pure TiO₂.     

Nonaqueous sol-gel synthesis and growth mechanism of single crystalline TiO2 nanorods with high photocatalytic activity

In this paper, we report on a nonaqueous synthesis of single crystalline anatase TiO₂ nanorods by reaction between TiCl₄ and benzyl alcohol at a low temperature of 80 °C. The resulting samples were characterized with X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy, nitrogen adsorption, X-ray photoelectron spectrometry and UV-vis diffuse reflectance spectroscopy. We proposed that the TiO₂ nanorods were formed through an oriented attachment mechanism. More importantly, these single crystalline anatase TiO₂ nanorods exhibited significantly higher photocatalytic activities than commercial photocatalyst P25. This study provides an environmentally friendly and economic approach to produce highly active TiO₂ photocatalyst.     

Photocatalytic performance of Sn-doped TiO2 nanostructured thin films for photocatalytic degradation of malachite green dye under UV and VIS-lights

Sn-doped and undoped nano-TiO₂ particles have been synthesized by hydrotermal process without acid catalyst at 225 °C in 1 h. Nanostructure-TiO₂ based thin films, contain at different solid ratio of TiO₂ in coating, have been prepared on glass surfaces by spin-coating technique. The structure, surface morphology and optical properties of the thin films and the particles have been investigated by element analysis and XRD, BET and UV/VIS/NIR techniques. The photocatalytic performance of the films was tested for degradation of malachite green dye in solution under UV and VIS-lights. The results showed that the hydrothermally synthesized nano-TiO₂ particles are fully anatase crystalline form and are easily dispersed in water, the coated surfaces have nearly super-hydrophilic properties and, the doping of transition metal ion efficiently improved the photocatalytic performance of the TiO₂ thin film. The results also proved that malachite green is decomposed catalytically due to the pseudo first-order reaction kinetics.     

Facile and large-scale synthesis of hollow TiO2 nanostructures from TiCl3 solution

Hollow TiO₂ nanostructures were successfully synthesized by a hydrothermal process using TiCl₃ solution as Ti sources. The as-obtained product consists of quasi-spherical hollow nanostructures in the diameter of about 500 nm with anatase phase. The control experiments indicated that the synergism of H₂O₂ and KBF₄ plays an important role in the formation of hollow TiO₂ nanostructures. Compared with solid TiO₂ nanostructures, the photocatalytic property of hollow TiO₂ nanostructures has been markedly improved in degradation of methyl orange under UV light. This synthesis procedure is facile and thus promotes large-scale production of hollow TiO₂ nanostructures.     

Preparation of Fe-doped TiO2 nanotube arrays and their photocatalytic activities under visible light

Fe-doped TiO₂ nanotube arrays have been prepared by the template-based liquid phase deposition method. Their morphologies, structures and optical properties were investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and UV-vis absorption spectroscopy. Their photocatalytic activities were evaluated by the degradation of methylene blue under visible light. The UV-vis absorption spectra of the Fe-doped TiO₂ nanotube arrays showed a red shift and an enhancement of the absorption in the visible region compared to the undoped sample. The Fe-doped TiO₂ nanotube arrays exhibited good photocatalytic activities under visible light irradiation, and the optimum dopant amount was found to be 5.9 at% in our experiments.     

Formation of SrTiO3 from Sr-oxalate and TiO2

SrTiO₃ powder has been prepared from Sr-oxalate and TiO₂ precursors, instead of using titanyl-oxalate. Sr-oxalate was precipitated from nitrate solution onto the surface of suspended TiO₂ powders. Crystallization of SrTiO₃ from the precursor was investigated by TGA, DTA and XRD analysis. It is evident that precursor, upon heating, dehydrates in two stages, may be due to the presence of two different types of Sr-oxalate hydrates. Dehydrated precursor then decomposes into SrCO₃ and TiO₂ mixture. Decomposition of SrCO₃ and simultaneous SrTiO₃ formation occur at much lower temperature, from 800 °C onwards, due to the fine particle size of the SrCO₃ and presence of acidic TiO₂ in the mixture. The precursor completely transforms into SrTiO₃ at 1100 °C. About 90 nm size SrTiO₃ crystallites are produced at 1100 °C/1 h, due to the lower calcination temperature and better homogeneity of the precursor.     

Microwave synthesis of nanocrystalline Sb2S3 and its electrochemical properties

Nanocrystalline antimony trisulfide (Sb₂S₃) was successfully synthesized via microwave irradiation by the reaction of antimony trichloride (SbCl₃) and thiourea (CS(NH₂)₂) with PVP as the surfactant. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and high resolution TEM (HRTEM). XRD results show that the as-prepared sample is orthorhombic-phase Sb₂S₃. TEM image of the as-prepared Sb₂S₃ shows the rod-like structure. HRTEM image indicates that rodbundles of Sb₂S₃ consists of a number nanorods with the diameter ranging from 30 nm to 50 nm. Detailed HRTEM image demonstrates the preferential direction growth of the Sb₂S₃ nanorods. The electrochemical properties of Sb₂S₃ were primarily investigated by constant current charge/discharge cycling tests in lithium hexafluorophosphate (LiPF₆) solution. The possible electrochemical reaction mechanism was explained. The results indicate that the nanocrystalline Sb₂S₃ shows potential application in the field of the electrode materials.     

Controllable synthesis of self-assembled Cu2S nanostructures through a template-free polyol process for the degradation of organic pollutant under visible light

Cu₂S nanostructures were fabricated by polyol method and then characterized by X-ray diffractometer, scanning electron microscopy, transmission electron microscopy (TEM) and high resolution TEM. The morphologically different Cu₂S nanostructures such as vertically nanorod arrays, nanoflowers assembled by nanorod arrays, nanoparticles and nanowires, can be successfully synthesized under different experimental conditions. The growth mechanism for the different nanostructures is proposed. The photocatalytic activity of the prepared samples was evaluated based on the degradation of organic pollutant, active brilliant red X-3B (X-3B), under visible light. Among the Cu₂S nanostructures, self-assembled nanoflowers have the highest photocatalytic activity. In addition, the prepared Cu₂S nanostructures are found to be able to decolorize X-3B with iron ions for the formation of Fenton reagent. This study provides a more choice to prepare self-assembled nanostructures for the application of environmental pollution control.     

Nitrogen-doped TiO2 nanotubes with enhanced photocatalytic activity synthesized by a facile wet chemistry method

Nitrogen-doped TiO₂ nanotubes with enhanced photocatalytic activity were synthesized using titanate nanotubes as raw material by a facile wet chemistry method. The resulting nanotubes were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, and UV-vis absorption spectroscopy, etc. The photocatalytic activity of nitrogen-doped TiO₂ nanotubes was evaluated by the decomposition of methylene blue under artificial solar light. And it was found that nitrogen-doped TiO₂ nanotubes exhibited much higher photocatalytic activity than undoped titanate nanotubes.     

Preparation of nitrogen doped TiO2 photocatalyst by oxidation of titanium nitride with H2O2

Nitrogen doped anatase TiO₂ (N-TiO₂) were prepared by hydrothermally treating TiN with H₂O₂. The as-synthesized samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), UV-vis diffuse reflectance spectrum (DRS), Fourier transform infrared spectra (FT-IR) and X-ray photoelectron spectroscopy (XPS) techniques. The results confirmed that the hydrothermal oxidation is an effective method to prepare N-doped TiO₂ anatase. The nitrogen concentration in TiO₂ could be controlled by the concentration of H₂O₂ solution. Photocatalytic degradation of methyl orange (MO) was carried out under visible light and UV-visible light irradiation, respectively. The as-prepared optimal N-TiO₂ showed higher photocatalytic activity than N-P25 and P25, and exhibited excellent reusability.     

Properties of TiO2 prepared by acid treatment of BaTiO3

TiO₃ powders were prepared by acid treatment of BaTiO₃ and their properties were investigated. The BaTiO₃ powder was subjected to HNO₃ in concentrations ranging from 10⁻³ to 8 M at 90 °C for 0.5-6 h. Dissolution of BaTiO₃ and precipitation of TiO₂ occurred at acid concentrations of 2-5 M. BaTiO₃ dissolves completely to form a clear solution at reaction times of 0.5-1 h, but a rutile precipitate is formed after 2 h of acid treatment. By contrast, anatase is precipitated by adjusting the pH of the clear solution to 2-3 using NaOH or NH₄OH solution. The rutile crystals were small and rod-shaped, consisting of many small coherent domains connected by grain boundaries with small inclination angles and edge dislocations, giving them a high specific surface area (S_BET). With increasing HNO₃ concentration, the S_BET value increased from 100 to 170 m²/g while the crystallite size decreased from 25 to 11 nm. The anatase crystals obtained here were very small equi-axial particles with a smaller crystallite size than the rutile and S_BET values of about 270 m²/g (higher than the rutile samples). The photocatalytic activity of these TiO₂ was determined from the decomposition rate of Methylene Blue under ultraviolet irradiation. Higher decomposition rates were obtained with larger crystallite sizes resulting from heat treatment. The maximum decomposition rates were obtained in samples heated at 500-600 °C. The photocatalytic activity of the TiO₂ was found to depend more strongly on the sample crystallite size than on S_BET.     

Fabrication and characterization of mesoporous TiO2/polypyrrole-based nanocomposite for electrorheological fluid

Mesoporous TiO₂/polypyrrole (PPy)-based nanocomposite for electrorheological fluid was synthesized through one-pot method. By exploiting the combination conductivity of PPy and high dielectric constant of TiO₂, the ER fluid exhibited an enhanced effect. The shear stress was 3.3 times as high as that of mesoporous TiO₂. Powder X-ray diffraction (XRD), TEM and Fourier transform infrared (FT-IR) spectroscopy were employed to characterize the as-made samples. Using a modified rotational viscometer, the electrorheological effect was measured. Dielectric spectra were also given to explain the mechanism.     

Hydrothermal synthesis and characterization of TiO2 nanorod arrays on glass substrates

Large-scale, well-aligned single crystalline TiO₂ nanorod arrays were prepared on the pre-treated glass substrate by a hydrothermal approach. The as-prepared TiO₂ nanorod arrays were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. X-ray diffraction results show that the main phase of TiO₂ is rutile. Scanning electron microscopy and transmission electron microscopy results demonstrate that the large-scale TiO₂ nanorod arrays grown on the pre-treated glass substrate are well-aligned single crystal and grow along [0 0 1] direction. The average diameter and length of the nanorods are approximately 21 and 400 nm, respectively. The photocatalytic activity of TiO₂ nanorod arrays was investigated by measuring the photodegradation rate of methyl blue aqueous solution under UV irradiation (254 nm). And the results indicate that TiO₂ nanorod arrays exhibit relatively higher photocatalytic activity.     

Photocatalytic activity of nitrogen doped rutile TiO2 nanoparticles under visible light irradiation

This work provides the design and synthesis of nitrogen doped rutile TiO₂ nanoparticles working as efficient photocatalysts under visible light irradiation. Nitrogen doped rutile TiO₂ nanoparticles are synthesized through the surface nitridation of rutile nanoparticles, which have been prepared in advance. The experimental results show that the nitrogen element is easily doped into the lattice of TiO₂ nanoparticles and its doping amount increases with the decrease of nanocrystallite size. The photocatalytic activity of the nanoparticles under visible light irradiation is correlated not only with the amount of doped nitrogen element but also with the morphology and crystallinity of nanoparticles.