Study on the photocatalytic activity of TiN/TiO2 nanoparticle formed by ball milling

TiN/TiO₂ nanoparticle photocatalyst was prepared by ball milling of TiO₂ in H₂O solution doped with TiN. The photocatalyst was characterized by UV–Vis diffuse reflection spectroscopy, X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Based on the results of the characterization, the mechanism of the increase in photocatalytic activity was investigated. The results show that when the amount of doped TiN is 0.15 wt%, the photocatalytic activity of the TiN/TiO₂ is at its peak. Compared with TiO₂, the photoabsorption wavelength range of the TiN/TiO₂ photocatalyst red-shifts about 30 nm, and the photoabsorption intensity increases as well. The photocatalytic activities of the photocatalyst are higher than that of TiO₂ under UV and visible light irradiation. The increase of surface Ti³⁺ reactive center and the extension of the photoabsorption wavelength are the main factors for the increase in the photocatalytic activity of the TiN/TiO₂. Doped TiN neither changes the TiO₂ crystal phase nor creates new crystal phase by ball milling.     

First-principles study on anatase TiO2 codoped with nitrogen and praseodymium

The crystal structures, electronic structures and optical properties of nitrogen or/and praseodymium doped anatase TiO₂ were calculated by first principles with the plane-wave ultrasoft pseudopotential method based on density functional theory. Highly efficient visible-light-induced nitrogen or/and praseodymium doped anatase TiO₂ nanocrystal photocatalyst were synthesized by a microwave chemical method. The calculated results show that the photocatalytic activity of TiO₂ can be enhanced by N doping or Pr doping, and can be further enhanced by N+Pr codoping. The band gap change of the codoping TiO₂ is more obvious than that of the single ion doping, which results in the red shift of the optical absorption edges. The results are of great significance for the understanding and further development of visible-light response high activity modified TiO₂ photocatalyst. The photocatalytic activity of the samples for methyl blue degradation was investigated under the irradiation of fluorescent light. The experimental results show that the codoping TiO₂ photocatalytic activity is obviously higher than that of the single ion doping. The experimental results accord with the calculated results.     

Carbon-Fiber Cloth Decorated with 3D Flower-Like GO/WO3 Quantum Dots/TiO2 Microsphere with High Photocatalytic Activity under Natural Sunlight

Nanopowder photocatalyst suffers two serious problems (low photocatalytic efficiency, easy aggregation, and difficult recycling) in water treatment. For solving these issues, a 3D flower-like graphene oxide (GO)/WO₃ quantum dots (QDs)/TiO₂ microsphere (FWGT) with excellent photocatalytic property is synthesized by a hydrothermal method which can degrade 100% Rhodamine B (RhB) within 10 min under solar light irradiation. Meanwhile, a carbon-fiber cloth/FWGT (CF/FGT) membrane is constructed by decorating the FWGT microsphere on the surface of the carbon-fiber cloth. CF/FGWT membrane displays better photocatalytic activity compared with carbon-fiber cloth/flower-like GO/TiO₂ microsphere (CF/FGT) membrane, which the reaction rate constants of CF/FGWT membrane are 3.52 times higher than that of CF/FGT membrane. Moreover, the CF/FGWT membrane shows a little quality loss (about 1.7%) after several recycles, indicating the novel flexible photocatalytic membrane has great potential for purifying water.     

Effect of In-Doping on Electronic Structure and Optical Properties of Sr2TiO4

The effect of In doping on the electronic structure and optical properties of Sr2 TiO4 is investigated by a firstprinciples calculation of plane wave ultrasoft pseudopotentials based on density functional theory. The calculated results reveal that corner-shared TiO6 octahedra dominate the main electronic properties of Sr2TiO4 and the covalency of the Ti-O（1） bond in the ab plane is stronger than that of the Ti-O（2） bond along the c-axis. After In doping, there is a little lattice expansion in Sr2In0.125 Ti0.875 O4 and the interaction between the Ti-O bond near the impurity In atom is weakened. The binding energies of Sr2TiO4 and Sr2In0.125Ti0.875O4 estimated from the electronic structure calculations indicate that the crystal structure of Sr2In0.125 Ti0.875 O4 is still stable after doping, but its stability is lower than that of undoped Sr2TiO4. Moreover, the valence bands （VBs） of the Sr2In0.125Ti0.875O4 system consist of O 2p and In 4d states, and the mixing of O 2p and In 4d states makes the top VBs shift significantly to high energies, resulting in visible light absorption. The adsorption of visible light is of practical importance for the application of St2 TiO4 as a photocatalyst.     

Highly active V-TiO2 for photocatalytic degradation of methyl orange

Two kinds of vanadium-doped TiO₂ powders photocatalysts were prepared by sol-gel method in even doping and uneven doping modes, and were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-vis diffuse reflectance spectroscopy (DRS). The photocatalytic activity of TiO₂ photocatalysts doped by vanadium evenly with lower dopant level up to 0.002 mol.% is better than that of undoped TiO₂, while with higher dopant level the activity is worse. TiO₂ photocatalysts doped by vanadium unevenly with a p-n junction semiconductor structure, was shown to have a much higher photocatalytic destruction rate than that of TiO₂ photocatalysts doped by vanadium evenly and undoped TiO₂, which is ascribed mainly to the electrostatic-field-driven electron-hole separation in TiO₂ particles doped by vanadium unevenly.     

Photocatalytic Activities of Boron Doped Titanium Dioxide Nanoparticles and its Composite with Polyaniline

Abstract

Titanium dioxide (TiO₂) was doped with a nonmetalic element, boron (B), and the boron doped TiO₂ (B-TiO₂) was combined with polyaniline (Pani) through an in-situ polymerization technique. The photocatalytic activity of the prepared samples was monitored by the degradation of methylene blue under UV light irradiation. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were used to reveal the effect of boron doping on the crystalline and chemical structure of the photocatalyst, respectively. The morphological and elemental compositional characteristics of the samples were evaluated using field emission scaning electron microscopy (FE-SEM) and energy dispersive x-ray analysis. The optical band gap energy of the prepared samples was obtained by UV-Visible (UV-Vis) spectroscopy. B-TiO₂ exhibited enhanced photocatalytic performance compared to the undoped photocatalyst. Furthermore, compared with TiO₂ and B-TiO₂, Pani/B-TiO₂ displayed superior photocatalytic activity. The composite achieved almost 26% methylene blue degradation within 150?minutes. Although the boron doping enhanced the crystallinity of TiO₂ slightly, it did not affect the morphology. FTIR confirmed the presence of tri-coordinated interstitial boron in the Ti–O–B bonds. The UV-Vis spectra displayed a red shift with the incorporation of the boron atoms. The incorporation of the boron atoms in the TiO₂ crystal structure are suggested to promote the separation of the photoinduced electron-hole pairs, a possible reason for the enhanced photocatalytic activity. B-TiO₂ and its composite with polyaniline could be considered as a promising photocatalyst to remove organic dyes from the wastewater.     

Effects of Different Dispersion Methods on the Microscopical Morphology of TiO2 Film

Nanocrystalline porous TiO2 films were prepared on conducting glass supports （ITO） by processed commercial TiO2 nanometre powder （P25）. Three methods of physical dispersing for TiO2 powder, i.e. grinding, magnetic stirring, sonicleaning, were used to disperse TiO2 nanometre powder. Surface morphologies of TiO2 films were observed by optic-microscope and SEM. It is found that the surface morphologies of TiO2 films are determined not only by the dispersing methods but also by the percentage of TiO2 powder in the dispersing system. Different film morphologies can be obtained under the same preparation condition but with different dispersing methods. A lot of cracks exist on the film surface for which the TiO2 slurry is dispersed by grinding. Magnetic stirring leads to some white points and micro-holes on the film surface. Only a few of micro-holes can be observed on the film surface, in which the TiO2 slurry is dispersed by sonicleaning. Different surface morphologies can also be found with different thicknesses of TiO2 films. Different film thicknesses are due to different percentages of TiO2 powder in the slurry. The related mechanism leading to different features of the surface morphologies for the TiO2 films is discussed.     

Characterization and photocatalytic activity of Zn–TiO2/AC composite photocatalyst

Activated carbon (AC) supported Zn²⁺–TiO₂ photocatalyst was prepared by sol–gel method. The prepared samples were characterized by X-ray diffraction, scanning electron micrograph, nitrogen absorption, diffuse reflectance UV/VIS and X-ray photoelectron spectroscopy. Using toluene as a pollution target, the photocatalytic activity of photocatalyst was evaluated. The results showed that prepared photocatalyst was obviously helpful for the removal of toluene in air. The photocatalytic degradation of toluene by Zn²⁺–TiO₂/AC reached 100% for 40 min and remained 75% after 160 min, while degradation by TiO₂ was only 30%. It indicated that the photocatalytic activity of prepared photocatalyst was enhanced. It is due to Zn²⁺-doping increased the oxidation and reduction of hole–electron pairs, which was the important factor in heterogeneous photocatalysis.     

Improving the visible light photocatalytic activity of mesoporous TiO2 via the synergetic effects of B doping and Ag loading

B-doped together with Ag-loaded mesoporous TiO₂ (Ag/B–TiO₂) was prepared by a two-step hydrothermal method in the presence of boric acid, triblock copolymer surfactant, and silver nitrate, followed by heat treatment. The obtained samples were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), UV–vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption–desorption. It was revealed that all samples consist of highly crystalline anatase with mesoporous structure. For Ag/B–TiO₂, B was doped into TiO₂ matrix in the form of both interstitial B and substitutional B while Ag was deposited on the surface of B–TiO₂ in the form of metallic silver. Compared with the single B-doped or Ag-loaded TiO₂ one, mesoporous Ag/B–TiO₂ exhibits much higher visible light photocatalytic activity for the degradation of Rhodamine 6G, which can be ascribed to the synergistic effects of B doping and Ag loading by narrowing the band gap of the photocatalyst and preventing the fast recombination of the photogenerated charge carriers, respectively.     

Characterization and activity of visible-light-driven TiO2 photocatalyst codoped with lanthanum and iodine

The novel visible-light-activated La/I/TiO₂ nanocomposition photocatalyst was successfully synthesized using precipitation-dipping method, and characterized by X-ray powder diffraction (XRD), the Brunauer-Emmett-Teller (BET) method, transmission electron microscopy (TEM), thermogravimetry-differential scanning calorimetry (TG-DSC) and UV-vis diffuse reflectance spectroscopy (UV-vis DRS). The photocatalytic activity of La/I/TiO₂ was evaluated by studying photodegradation of reactive blue 19 as a probe reaction under simulated sunlight irradiation. Photocatalytic experiment results showed that the maximum specific photocatalytic activity of the La/I/TiO₂ photocatalyst appeared when the molar ratio of La/Ti was 2.0 at%, calcined at 350 °C for 2 h, due to the sample with good crystallization, high BET surface area and small crystal size. Under simulated sunlight irradiation, the degradation of reactive blue 19 aqueous solution reached 98.6% in 80 min, which showed La/I/TiO₂ photocatalyst to be much higher photocatalytic activity compared to standard Degussa P25 photocatalyst. The higher visible light activity is due to the codoping of lanthanum and iodine.     

Preparation of N-doped TiO<Subscript>2</Subscript> photocatalyst by atmospheric pressure plasma process for VOCs decomposition under UV and visible light sources

The nitrogen doped (N-doped) titanium dioxide (TiO₂) photocatalyst was prepared by the atmospheric-pressure plasma-enhanced nanoparticles synthesis (APPENS) process operated under normal temperature, i.e. the dielectric barrier discharge plasma process. The N₂ carrier gas is dissociated in the AC powered nonthermal plasma environment and subsequently doped into the TiO₂ photocatalyst that was capable of being induced by visible light sources. The APPENS process for producing N-doped TiO₂ showed a higher film deposition rate in the range of 60–94 nm/min while consuming less power (<100 W) as compared to other plasma processes reported in literatures. And the photocatalytic activity of the N-doped TiO₂ photocatalyst was higher than the commercial ST01 and P25 photocatalysts in terms of toluene removals in a continuous flow reactor. The XPS measurement data indicated that the active N doping states exhibited N 1s binding energies were centered at 400 and 402 eV instead of the TiN binding at 396 eV commonly observed in the literature. The light absorption in the visible light range for N-doped TiO₂ was also confirmed by a clear red shift of the UV-visible spectra.     

Preparation and performance of photocatalytic TiO2 immobilized on palladium-doped carbon fibers

Pd-modified carbon fibers (CFs) are obtained by a facile oxidation-reduction method and then dip-coated in a sol-gel of titanium dioxide (TiO₂) to form supported TiO₂/Pd-CF photocatalysts. The morphology of the Pd-modified CFs and the amount Pd deposited are characterized by field emission scanning electron microscopy and atomic absorption spectrometry, respectively. X-ray diffraction is used to investigate the crystal structures of the TiO₂ photocatalyst. Acid orange II is used as a model contaminant to evaluate the photocatalytic properties of the photocatalyst under UV irradiation. TiO₂/Pd-CF exhibits higher catalytic activity than TiO₂/CF towards the degradation of acid orange II. Optimum photocatalytic performance and support properties are achieved when the Pd particle loading is about 10.8 mg/g.     

TiO2的冲击波活化及其光催化活性

 实验研究了金属氧化物催化剂TiO₂在经受不同的冲击波压力处理后,对H₂S脱氢反应的光催化活性变化。结果表明,与未冲击样品相比,冲击波处理后TiO₂的光催化活性得到了明显提高。在16~34 GPa的实验压力范围内,催化活性提高了2~3倍。初步分析认为,冲击波处理使样品晶粒中生成大量残余应变和位错缺陷,以及使TiO₂能隙宽度减小,这是光催化活性提高的主要原因。     

Preparation and photocatalytic properties of silver nanoparticles loaded on CNTs/TiO2 composite

In this study, new nanoscale photocatalyst based on silver and CNTs/TiO₂ was successfully prepared by photoreduction method. The prepared Ag-CNTs/TiO₂ was characterized by TEM, XRD and XPS. The photocatalytic activity was also evaluated by photocatalytic degradation of Reactive Brilliant Red X-3B dye. The results indicated that the photocatalytic efficiency of CNTs/TiO₂ increased in the presence of Ag nanoparticles and the photocatalysis reaction followed a first order kinetics. The kinetic constant of Ag-CNTs/TiO₂ for dye degradation was nearly 1.2 times than that of CNTs/TiO₂, which indicated decorating Ag nanoparticles on CNTs/TiO₂ could enhance the photocatalytic ability.     

Temperature Dependence of the Fluorescence Emission Intensity of Eu/TiO2 Nanocrystals

The samples of europium ions doped titanium dioxide （Eu^3＋/TiO2） nanocrystals are synthesized by a modified sol-gel method with hydrothermal treatment. The x-ray diffraction and scanning electron microscopy are used to characterize the sample. The temperature-dependent fluorescence emission effect of Eu^3＋-doped samples is investigated. It is found that under the excitation of 514.5nm light, the emission intensity of Eu^3＋ reaches a maximum value at 450K among various Eu^3＋ dopant concentrations in Eu^3＋ /TiO2 nanocrystals. The variation of the emission intensity may be attributed to the photon-assist absorption and the temperature-quenching effect.     

Electronic and optical properties of pure and Mo doped anatase TiO2 using GGA and GGA+U calculations

Comparative GGA and GGA+U calculations for pure and Mo doped anatase TiO₂ are performed based on first principle theory, whose results show that GGA+U calculation provide more reliable results as compared to the experimental findings. The direct band gap nature of the anatase TiO₂ is confirmed, both by using GGA and GGA+U calculations. Mo doping in anatase TiO₂ narrows the band gap of TiO₂ by introducing Mo 4d states below the conduction band minimum. Significant reduction of the band gap of anatase TiO₂ is found with increasing Mo doping concentration due to the introduction of widely distributed Mo 4d states below the conduction band minimum. The increase in the width of the conduction band with increasing doping concentration shows enhancement in the conductivity which may be helpful in increasing electron–hole pairs separation and consequently decreases the carrier recombination. The Mo doped anatase TiO₂ exhibits the n-type characteristic due to the shifting of Fermi level from the top of the valence band to the bottom of the conduction band. Furthermore, a shift in the absorption edge towards visible light region is apparent from the absorption spectrum which will enhance its photocatalytic activity. All the doped models have depicted visible light absorption and the absorption peaks shift towards higher energies in the visible region with increasing doping concentration. Our results describe the way to tailor the band gap of anatase TiO₂ by changing Mo doping concentration. The Mo doped anatase TiO₂ will be a very useful photocatalyst with enhanced visible light photocatalytic activity.     

Investigation on a novel ZnO/TiO2–B photocatalyst with enhanced visible photocatalytic activity

A new type of composite photocatalysts (ZnO/TiO₂–B) with Zinc oxide nanoparticles dispersed on boron doped titanium dioxide was prepared via a sol–gel method. The as-prepared powders were characterized by HRTEM, XRD, XPS, UV–vis DRS, and PL techniques. The results reveal that B³⁺ ions are doped into the TiO₂ lattice in interstitial mode, while ZnO nanoparticles are dispersed on the surface of TiO₂. The absorption of photocatalysts was extended into visible light region and the photogenerated electrons and holes were separated efficiently. Hence, ZnO/TiO₂–B composite photocatalyst exhibits much better photocatalytic activity than those of pure TiO₂ and TiO₂–B on photodegradation of 4-chlorophenol under visible light irradiation.     

Ultrasound assisted synthesis of doped TiO2 nano-particles: Characterization and comparison of effectiveness for photocatalytic oxidation of dyestuff effluent

The present work deals with the synthesis of titanium dioxide nanoparticles doped with Fe and Ce using sonochemical approach and its comparison with the conventional doping method. The prepared samples have been characterized using X-ray diffraction (XRD), FTIR, transmission electron microscopy (TEM) and UV–visible spectra (UV–vis). The effectiveness of the synthesized catalyst for the photocatalytic degradation of crystal violet dye has also been investigated considering crystal violet degradation as the model reaction. It has been observed that the catalysts prepared by sonochemical method exhibit higher photocatalytic activity as compared to the catalysts prepared by the conventional methods. Also the Ce-doped TiO₂ exhibits maximum photocatalytic activity followed by Fe-doped TiO₂ and the least activity was observed for only TiO₂. The presence of Fe and Ce in the TiO₂ structure results in a significant absorption shift towards the visible region. Detailed investigations on the degradation indicated that an optimal dosage with 0.8 mol% doping of Ce and 1.2 mol% doping of Fe in TiO₂ results in higher extents of degradation. Kinetic studies also established that the photocatalytic degradation followed the pseudo first-order reaction kinetics. Overall it has been established that ultrasound assisted synthesis of doped photocatalyst significantly enhances the photocatalytic activity.     

Photocatalytic and superhydrophilicity properties of N-doped TiO2 nanothin films

Pure TiO₂ and nitrogen doped titanium dioxide (N-TiO₂) thin films were prepared by sol-gel method through spin coating on soda lime glass substrates. TiCl₄ and urea were used as Ti and N sources in the sol. XRD results showed nitrogen doping has retarded anatase to rutile phase transformation. The doping also leads to a decrease in roughness of the samples from 4 nm (TiO₂) to 1 nm (N-TiO₂). However, surface analysis by statistical methods reveals that both surfaces have self-affine structure. Optical band gap of thin films was shifted from 3.65 eV (TiO₂) to 3.47 eV (N-TiO₂). Hydrophilic conversion and photocatalytic degradation properties of thin films were investigated and exhibited that N-TiO₂ thin film has more preferable hydrophilicity and photocatalytic properties under UV illumination.