Mixed Phases Of Anatase Research Articles

Introducing dusty plasma particle growth of nanospherical titanium dioxide

In dusty plasma environments, spontaneous growth of nanoparticles from reactive gases has been extensively studied for over three decades, primarily focusing on hydrocarbons and silicate particles. Here, we introduce the growth of titanium dioxide, a wide bandgap semiconductor, as dusty plasma nanoparticles. The resultant particles exhibited a spherical morphology and reached a maximum monodisperse radius of 235 ± 20 nm after growing for 70 s. The particle grew linearly, and the growth displayed a cyclic behavior; that is, upon reaching their maximum radius, the largest particles fell out of the plasma, and the next growth cycle immediately followed. The particles were collected after being grown for different amounts of time and imaged using scanning electron microscopy. Further characterization was carried out using energy dispersive x-ray spectroscopy, x-ray diffraction, and Raman spectroscopy to elucidate the chemical composition and crystalline properties of the maximally sized particles. Initially, the as-grown particles exhibited an amorphous structure after 70 s. However, annealing treatments at temperatures of 400 and 800 °C induced crystallization, yielding anatase and rutile phases, respectively. Annealing at 600 °C resulted in a mixed phase of anatase and rutile. These findings open avenues for a rapid and controlled growth of titanium dioxide via dusty plasma.

Local electronic structures of annealing induced phases in cobalt doped TiO2 nanoparticles: a combined study of transmission electron microscopy and x-ray absorption fine structure spectroscopy

The evolution of the nanostructures and electronic properties of 5% cobalt-doped TiO2 nanoparticles (NPs) annealed at 400 °C, 600 °C, and 800 °C have been investigated to understand the structural phase transformations through chemical co-precipitation synthesis. A detailed analysis of the X-ray Diffractogram confirms that the sample annealed at 400 °C is anatase, at 600 °C, the mixed phase of anatase and rutile evolves, and at 800 °C, the sample is of rutile structure. A detailed morphological study by scanning transmission electron microscope provides the particle size, lattice spacing, and variation in polycrystalline grain growth at different phases. Electron Energy Loss Spectroscopy analysis indicates from the O K, Co, and Ti L 2,3-edges that Ti4+ ions are primarily in an octahedral symmetry with the oxygen ligands changing their structural phases from anatase to mixed phase and then stable rutile phase with increasing temperature of annealing. X-ray Absorption Near Edge Spectroscopy (XANES) extracts information about the varying oxidation states and 3-dimensional geometry of Ti-ions. The unresolved issues of the structural details at the atomic-scale picture with the local environment of the cation with a few nearest neighbour shells are derived from Extended X-ray Absorption Fine Structure (EXAFS) and pre-edge parts of the absorption spectra. The limits of EXAFS in this situation of asymmetric bond length disorder, which is typical for mixed-valence oxides, are generated to reconcile the two data and highlight the value of pre-edge XANES analysis for identifying local heterogeneities in structural and compositional motifs. TiO2 possesses unique properties depending upon its structural phase. The Ti L 2,3-edge spectrum indicates that there is an octahedron connectivity of the Oxygen atoms at the anatase state which transforms to a higher energetic tetrahedral correspondence as it proceeds towards the rutile phase. The driving force behind such interest is to modulate the properties of TiO2 NPs to better photocatalytic material and to integrate its application as a versatile energy storage device.

Tailoring visible-light active TiO2/cellulose nanocomposites with controlled crystalline structure for enhanced photocatalytic performance.

This work involves a green and simple synthesis of TiO2 nanoparticles on cellulose under mild conditions without the need for calcination via hydrolysis of titanium oxysulfate (TiOSO4). The synthesis conditions, such as sulfuric acid concentration (0-10%wt), temperature (70-90℃), and time (4-8h), focused on precisely controlling the structure of TiO2 to enhance its photocatalytic effectiveness under visible light. At a lower 2.5wt% sulfuric acid concentration, pure anatase was formed on the cellulose, while an increase in the range of 5.0-7.5wt% sulfuric acid concentration yielded a rutile phase, resulting in a mixed phase of anatase and rutile on the cellulose. The pure rutile phase was found at a low temperature (70℃), while increased temperature led to the formation of the anatase phase. These results confirmed that the formation of crystalline TiO2 phase on the cellulose depended on sulfuric acid concentration and temperature for hydrolysis. Additionally, the photocatalytic properties of the obtained materials were evaluated by degradationvisible of Rhodamine B (RhB) under UV and visible light. The findings revealed that the mixed phase (anatase/rutile) of TiO2 on the cellulose demonstrated a superior photocatalytic efficiency (99.2%) compared to pure anatase (85.75%) and rutile (75.08%) when exposed to visible light.

The Research of Different Strategies to Enhance Coulombic Efficiency of Sn/SnOx Modified TiO2 As Anode Material in Lithium-Ion Battery By in Operando Analytical Techniques

In recent years, electrochemical energy storage technologies had become global concerns due to the emergent need for electric vehicles and portable electronics. Recently, Lithium ion batteries cannot meet the requirements of gravimetric/volumetric energy density, rate capability, cycling stability, and safety in various applications. As one of the most promising anode materials for LIBs, titanium dioxide(TiO2) has received considerable attention due to its superior cycling stability, rate performance, low cost, environmental friendliness, and safety compared to traditional graphite anode. However, the major challenges of this material are poor electronic/ionic conductivity and poor theoretical capacity. In order to overcome this issue, our research has been modifying high-capacity material (e.g., Sn/SnOx) into TiO2 with an eye to promoting its capacity. Modifying Sn/SnOx into TiO2 reduces the impedance and increases the Li-ion diffusion rate. The Sn@TiO2 is synthesized by the chemical bath with Sn(BF4)2, HBF4, Na2S2O3 and TiO2 (rutile and anatase mixed phase) followed by annealing at different temperature. From the TEM and XRD results, we had successfully synthesized Sn@TiO2 core-shell structure. The table below shows that the serious fading problem of Sn@TiO2 during the first and second cycle. Active lithium loss(ALL) in the initial charge process causes irreversible capacity of LIBs due to the formation of unstable solid electrolyte interface (SEI) layer on the electrode surface. To solve the problem, pre-lithiation has been widely accepted as one of the most promising strategies to compensate for active lithium loss. Our group is about to trying various pre-lithiation techniques, such as electrochemical and chemical pre-lithiation and using in operando XRD/Raman to point out the mechanism of SEI layers. The ultimate goal would be giving out advantages and challenges of each one then finding out the optimal approach to improve cycling performance of tin-based anodes in lithium-ion batteries. Figure 1

Mixed phase anatase nanosheets/brookite nanorods TiO2 photocatalysts for enhanced gas phase CO2 photoreduction and H2 production

CO2 photoreduction and H2 photocatalytic production reactions have been studied on different TiO2 polymorphs (anatase and brookite) engineered with specific nanocrystal shape. Anatase TiO2 materials of nanosheet morphology and brookite TiO2 of nanorod morphology were developed via a hydrothermal synthesis process. Mixed-phase anatase/brookite TiO2 materials of the above extreme cases were also developed, controlling the phase composition. The materials were fully characterized by a variety of techniques including structural, morphological, textural and electronic properties characterization. N2 physisorption analysis and CO2 adsorption isotherms have shown that minimum amount of brookite phase (i.e. ca. 7 wt%) in the final material improved the textural properties and the CO2 uptake ability. Electron paramagnetic spectroscopy (EPR) provided evidences for improvements in the formation and availability of photogenerated electrons in the mixed-phase materials. CO2 photoreduction was increased by ca. 220% in the optimized mixed-phase anatase/brookite TiO2. Photocatalytic H2 production rates were also improved by ca. 140%. The results in the present study have shown that the TiO2 phase as well as the amount of each TiO2 polymorph plays vital role in photocatalytic efficiency and that the photocatalytic improvement depends greatly on the specific reactions. The new insights provided herein would be of interest for studied focusing on materials shape engineering and phase composition and their effect on activity.

Visible Light‐Driven Degradation of Trichloroethylene in Aqueous Phase with Vanadium‐Doped TiO2 Photocatalysts

The development of photocatalyzed water remediation strategies using visible (solar) light to mineralize volatile chlorinated organic compounds (VCOCs) is a long standing, not yet fully achieved goal. Herewith, a facile route is presented to synthesize vanadium‐doped TiO2 photocatalysts using a one‐step hydrothermal method. Different characterization methods are employed to investigate the physicochemical properties of as‐prepared V‐doped TiO2 samples, indicating the mixed phases of anatase, rutile, and brookite in the crystal structure addition to the mesoporous framework. The nature of the vanadium species at the TiO2 surface is assessed by X‐ray photoelectron and emission spectroscopy. The aerobic photodegradation of a common VCOC, trichloroethylene, using V‐doped catalysts is demonstrated to be much more effectively than with undoped TiO2. Importantly, the herein described V‐doped photocatalysts show high activity both under ultraviolett and visible light irradiation. Moreover, these V‐doped TiO2 photocatalysts are robust under the reaction conditions, being recyclable for at least four consecutive runs without any activity loss.

Modified Auto-Combustion Synthesis of Mesoporous TiO<sub>2</sub>-NiO Nanosheets for Selective Adsorption and Photodegradation of Alizarin Yellow Dye under Direct Sunlight and Reaction Kinetic Study

The application of a photocatalyst with effective adsorption capacity and higher photocatalytic activity under direct sunlight for the treatment of industrial effluent contaminated with dyes has received increased attention. In this work, mesoporous TiO2-NiO nanosheets were synthesized by a modified auto-combustion technique followed by thermal post-treatment at 400°C. The XRD pattern for modified auto-combusted resulting TiO2 (sc) and TiO2-NiO (sc) [5wt%NiO] nanosheets comprised of mixed-phase anatase and rutile for TiO2 and cubic for NiO. The result of SEM demonstrated that the morphology of TiO2 is a sheet and TiO2-NiO is a rod-like structure. UV-vis spectroscopy results imply that the bandgap of TiO2 and TiO2-NiO mixed phase is 3.1eV and 2.7eV. N2 sorption (BET) showed a mesoporous structure and interpret specific surface areas of 19.528m2/g and 63.215 m²/g. Adsorption of the dye on the solid catalyst is inexpensive and efficient but disposing of the adsorbed dye is challenging. Among various dye removal techniques, photocatalytic degradation under direct sunlight is significant, cost-effective, and sustainable. Photocatalytic experiments using alizarin yellow as a model pollutant showed that the degradation percentage of AY was 93.54% in 120min for 100mg of TiO2(sc) and 97% in 90min for 60mg of TiO2-NiO(sc). Degradation of AY using TiO2(sc) and TiO2-NiO(sc) follows a pseudo-first-order reaction, whereas adsorption of AY on TiO2-NiO(sc) follows the second-order kinetics, fits well in the Freundlich Isotherm model. Therefore, nanosized mesoporous TiO2-NiO(sc) nanosheets with a p-n junction are considered efficient photocatalysts under direct sunlight due to narrowing down in bandgap, larger surface, and mixed-phase.

Effects of Annealing Ambient on the Structural, Optical and Electrical Properties of TiO2:Ge Thin Films

TiO2, a semiconducting material with a wide energy band gap, has been researched intensively due to its interesting properties and many potential applications. The films properties can as well be modified by preparing the films under diverse ambient to suit diverse applications. In this work, the effects of the annealing atmosphere on the structural, optical and electrical properties of pure TiO2 and TiO2:Ge composite thin films deposited by sputtering from commercially available pure TiO2 and TiO2:Ge (85:15) targets respectively were studied. The films were deposited on fluorine doped tin oxide glass substrates by radio frequency magnetron sputtering technique at room temperature 23–25 ℃ and then annealed at 450 ℃ for one hour in three different atmospheres: air, argon and nitrogen. The XRD results revealed that, both pure TiO2 and TiO2:Ge thin films were crystalline and had a mixed phase of anatase and rutile regardless of the annealing ambient. The calculated crystallite sizes ranged between 19–21 nm with the particle sizes for TiO2:Ge films being larger compared to pure TiO2 as calculated from ImageJ software. Electrical measurements showed that the resistivity of as deposited pure TiO2 films (about 13.03 × 10–2 Ω-cm) was greater than the TiO2: Ge composite (5.91 × 10–2 Ω-cm). Furthermore, on annealing, pure TiO2 had a resistivity of 9.47 × 10–2 Ω-cm–10.4 × 10–2 Ω-cm, while the TiO2:Ge composite had a resistivity of 2.24 × 10–2 Ω-cm–3.61 × 10–2 Ω-cm depending on the annealing atmosphere. Variation of annealing atmosphere had minimal influence on the electrical resistivity of the films. The films annealed in nitrogen recorded the least resistivity values averaging about 5.86 × 10–2 Ω-cm, while those annealed in argon and air recorded a resistivity of 6.94 × 10–2 Ω-cm and 6.65 × 10–2 Ω-cm, respectively. The transmittance spectra showed that, all the annealed films were transparent in the visible region (400–700 nm) with a mean bandgap of 3.60 eV for each annealing atmosphere. It is recommended that films annealed in nitrogen atmosphere could be considered for potential applications in photovoltaics.
 Keywords: Titanium dioxide; Germanium; Ambient; Structural; Optical, Electrical

Comparative Study of Fe,N-TiO<sub>2</sub> Photocatalysts under UV Light Irradiation

Titanium dioxide (TiO2) has been acknowledged as a promising photocatalyst in environmental remediation including wastewater treatment. In this study, TiO2 nanoparticles co-doped with iron (Fe) and nitrogen (N) was synthesized via sol-gel method and subsequently followed by calcination process at 300 °C, 500 °C and 700 °C for 3 hours. The prime objective of this study is to investigate an effect of different calcination temperatures in enhancing the photocatalytic activity of synthesized TiO2 which was evaluated through the degradation of methyl orange (MO) dye. The structure and properties of the prepared samples were studied by X-Ray Diffraction (XRD), Energy Dispersive X-Ray Spectroscopy (EDX), Field Emission-Scanning Electron Microscope (FE-SEM) and Ultraviolet-Visible Spectrophotometer (UV-Vis). The results obtained from XRD showed the presence of anatase phase in all samples at 300 °C and 500 °C. Further increase of calcination temperature up to 700 °C, mixed-phase of anatase and rutile formed. XRD results also suggest that the addition of impurities has a great effect on the crystallinity and particle size of TiO2. The obvious agglomeration phenomena existed in the annealed samples with nanometer size, as observed in FESEM images. The photocatalytic performance under UV light shows that co-doped Fe, N-TiO2 at 500 °C indicated highest MO degraded of 96.5 % within 3 hours of irradiation time. From the current finding, Fe,N-TiO2 possessed the potential to be commercialized as a photocatalyst in wastewater remediation especially in treating dye pollution.

Direct dye wastewater photocatalysis using immobilized titanium dioxide on fixed substrate

Photocatalysis is a promising technology that can be applied to the dyeing of wastewater. During the process of photocatalysis, titanium dioxide (TiO2) is often used as a catalyst due to its low cost and broad availability. However, the use of TiO2 powders can result in certain difficulties associated with separating TiO2 from the treated wastewater. Therefore, immobilization of TiO2 on two different substrates, including glass and iron beads, was studied in this body of research work. The composite materials were prepared by spraying liquid dispersion onto the substrates, and the materials were then calcined at different temperatures (600–750 °C). At 700 °C calcination temperature, SEM and EDS analyses revealed that the particles of TiO2 were evenly distributed on the substrates. Importantly, the deposited TiO2 particles are mixed-phase anatase and rutile structures, both of which are considered beneficial to the photocatalysis process. Ultimately, a degree of direct dye photodegradation efficiency of 64.0 % at 4 h was achieved from the composite materials that were calcined at 700 °C. The degradation efficiency of the reused catalyst was not significantly changed in the second cycle revealing their capability in reusable. The stability of immobilized TiO2 onto the fixed substrates was still high after the second use.

Comparative study of the effect of TiO2 support composition and Pt loading on the performance of Pt/TiO2 photocatalysts for catalytic photoreforming of cellulose

Herein, catalytic aqueous phase photoreforming of cellulose was carried out over Pt/m-TiO2 (i.e., mixed phase of anatase and rutile) and Pt/anatase catalysts to investigate the effect of the TiO2 support structure and Pt loading on the production of H2. The effect of the TiO2 support on the properties of the resulting Pt/TiO2 catalysts (such as actual Pt loading and BET surface area) was not significant. At low Pt loading of 0.16 wt.%, the TiO2 supports affected the sub-nanometre Pt structures which was confirmed by the diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) characterisation (using CO as the probe). Conversely, the effect of TiO2 supports on larger Pt particles (on 1 wt.% catalysts) was insignificant possibly due to the reduced effect of restructuration of bigger Pt particles on the TiO2 supports. With an increase in Pt loading from 0.16 wt% to 1.00 wt.%, the normalised H2 production rate (with respect to the actual supported Pt amount and specific surface area of the catalysts) showed a decreasing trend over the two types of the catalysts, i.e., from 10.6 to 1.4 μmol h−1 m−2 mgPt−1 for Pt/m-TiO2, and from 8.5 to 1.2 μmol h−1 m−2 mgPt−1 for Pt/anatase. Specifically, large Pt particle sizes reduced the CO2/H2 production from cellulose photoreforming over both Pt/m-TiO2 and Pt/anatase catalysts, indicting an important role played by Pt particle size in photoreforming. Interestingly, in this study, the m-TiO2 supported catalysts only showed the benefits of enhanced charge separation across the phase junction in producing H2 with small Pt particles (at sub-nanometre), whilst, when large Pt particles (at around 1–2 nm) were supported, such a benefit was not significant in cellulose photoreforming. The promoting effect of small, sub-nm particles is attributed to the better capture of photoelectrons from bulk TiO2 and better activity of H+ coupling on small Pt particle. Further fundamental study on such guest-host interactions is devised to optimise Pt/TiO2 catalysts for improving H2 production from photoreforming reactions.

Effect of target poisoning ratios on the fabrication of titanium oxide coatings using superimposed high power impulse and medium frequency magnetron sputtering

Five titanium oxide coatings with different O/Ti ratios were grown by a superimposed high power impulse magnetron sputtering (HiPIMS) and medium frequency (MF) coating system utilizing a plasma emission monitoring feedback control. The peak power density of HiPIMS increased from 517.6 to 658.5 W/cm2 and the O/Ti ratio increased from 1.4 to 2.3 as the target poisoning ratio increased from 10% to 90%, whereas the deposition rate decreased with increasing target poisoning ratios. A pure TiO phase gradually transferred to a mixture phase of anatase and rutile TiO2 as the target poisoning ratio increased. The amount of anatase TiO2 increased with increasing target poisoning ratios and reached almost a pure anatase phase as the target poisoning ratio was 90%. The highest hardness of 16.4 GPa and the best corrosion resistance were found for the coating with pure TiO phase grown at 10% target poisoning ratio (TB10). The hardness decreased gradually as the structure changed from a pure TiO phase to the rutile and anatase mixed phases. A low hardness of 5.8 GPa and a poor corrosion resistance were obtained for the anatase rich TB90 due to its microstructure defects. Good adhesion and wear resistance were achieved for coatings deposited at 70% and 90% target poisoning ratios (TB70, TB90). Among these five coatings, TB70 coating exhibited a hardness of 12.6 GPa, good wear resistance, adequate adhesion, and fair corrosion resistance, which can be used as a functional coating with good protection property.

Deep eutectic solvent electrolysis for preparing N and P co-doped titanium dioxide for rapid photodegradation of dyestuff and antibiotic

A deep eutectic solvent electrolysis strategy for preparing N and P co-doped titanium dioxide is proposed and implemented. The solvent is constructed by the co-heating of choline phosphate and urea. Atomic ratios of N and P against TiO2 are lower than 1.37% and 0.67%, respectively. The band-gap of co-doped samples is determined to be 2.67–2.78 eV. A mixed-phase of anatase and rutile photocatalyst shows the highest efficiency for the photodegradation of methylene blue, rhodamine B, and oxytetracycline. The corresponding rate constants are 0.194, 0.112, and 0.085 min−1, respectively. The excellent performance benefits from the expected phase structure, appropriate amount of non-metals co-doping, and the matching bandwidth. Results show that the N, P co-doped TiO2 is significantly competitive with either pure TiO2 or similar doped ones. Findings also demonstrate the feasibility of preparing non-metals co-doped narrow-band-gap TiO2 by using deep eutectic solvent based pure organic solution as the electrolyte.

Effect of TiO2 nanotube phases and Pt contact morphologies on the properties of Schottky junction

The effect of the TiO2 nanotube phase and the Pt contact morphology on their Schottky junction is studied. Different annealing temperatures were used to achieve different phases. Titanium dioxide nanotube has an anatase phase when annealed at 450 °C and a mixed-phase of anatase and rutile when annealed at 550 °C. The platinum contact was deposited using the atomic layer deposition method. Different morphologies can be achieved with a varying number of coating cycles. We found that the rectification ratio of a sample with mixed-phase TiO2 nanotubes is higher than that of a sample with anatase phase TiO2 nanotubes. The rectification ratio of a device with a continuous thin film morphology contact is higher than those with a noncontinuous morphology. The highest average rectification ratio of 831 is achieved with a continuous thin film Pt coating over mixed-phase TiO2 nanotubes device.

Physicochemical Characterization and Photocatalytic Activity of Reduced TiO₂ Prepared by Birch-Type Reduction.

A simple and fast reduction method of TiO₂ was developed by the Birch-type suspension reaction. The physicochemical properties of the reduced TiO₂ (r-R-TiO₂: reduced TiO₂ in rutile phase; r-AR-TiO₂: reduced TiO₂ in mixed phase of anatase and rutile) were analyzed by X-ray diffraction, FT-IR spectrum, Raman spectrum, high resolution TEM, dynamic light scattering (DLS) and zeta potential measurements. The reduced TiO₂ showed the characteristic features in the crystallinity, lattice pattern, surface functional group and the biophysical properties of zeta potential and size. Under the reaction condition, the rutile phase of TiO₂ (R-TiO₂) was selectively reduced into r-RTiO₂ under the reaction condition. Finally r-R-TiO₂ showed photocatalytic activity on visible-light illuminated YD-38 cancer cells with high cytotoxicity.

Influence of sulfuric-acid-bath pretreatment and soaked in sulfuric acid on surface morphology and photocatalytic activity of titania coatings

Titania (TiO2) photocatalyst coatings have been fabricated by the low-cost approach of sulfuric-acid-bath pretreatment (SAP) followed soaked in sulfuric acid (SA) at room temperature then oxidated in air. The influence of the SAP and soaked conditions on the surface morphology and photocatalytic activity of TiO2 on Ti coatings was investigated. With different SAP conditions, the surface morphologies of the TiO2 on Ti coatings clearly show the formed porous-like structure. With higher SA concentration, the porous-like structure becomes obviously. With extending soaked time, the porous-like structure tends to disappear. Raman spectroscopy reveals that the formed TiO2 coatings are with mixed-phase of anatase and rutile. Compared with those of SA concentration and SAP time, the influence of the soaked time on the phase transformation is obvious. Notably, the photocatalytic activity of TiO2 on Ti coatings had been efficiently enhanced by extending the soaked time, compared with those of higher SA concentration and longer SAP time. The enhanced photocatalytic activity of TiO2 on Ti coatings could be related with the changed surface morphology, mixed-phase of anatase and rutile, and formed hydroxyl groups.

Unusual structural transformation and photocatalytic activity of Mn doped TiO2 nanoparticles under sunlight

Here, Mn doped TiO2 nanoparticles are synthesised through sol-gel technique. After doping 1 and 2 at% Mn, the mixed phase of anatase and rutile is observed, whereas 3 at% Mn doped TiO2, shows pure anatase phase. Particle size of ∼12–15 nm is estimated from TEM showing single crystalline nature evidenced from SAED patterns. Such fine particles are primarily contributes to observed unusual transformation. As a consequence, oxygen vacancies and multiple oxidation states of Mn and Ti are detected through XPS. For the first time, Mn doped TiO2 show 80–100% photocatalytic degradation of dyes, such as MB, RhB and CR, under sunlight in 1 h, which might be regarded as a practical method for the treatment of waste water. The multiple oxidation states of Ti and Mn accompanied with oxygen vacancies reveal ferromagnetism and high degradation rate of organic dyes.

Preparation, Characterization and Visible Light Photocatalytic Activities of Samarium-Doped Mixed Crystalline Phase TiO2 Nanoparticles

Mixed crystalline phase TiO2 nanoparticles with different content of Sm ion were prepared by a facile sol-gel method. The samples were characterized by XRD, XPS, UV-Vis-DRS, and PL. The influence of Sm-doping on structure and visible light photocatalytic activity of mixed phase TiO2 was evaluated by photocatalytic degradation of MB under the irradiation of fluorescent lamp. The results indicate that samarium appears two kinds of Sm3+ and Sm2+ valence state on the surface of TiO2. Sm doping can restrain the phase transition from anatase to rutile, and prevent the grain growth. Appropriate amount of Sm doping and the proportions of rutile and anatase mixed phase can effectively inhibit the recombination of photo-generated electron and hole pairs, expand the wavelength range of absorption spectrum. Moreover, the photocatalytic activity of Sm-TiO2 in MB degradation is evidently enhanced. The MB degradation rate of Sm-TiO2 samples with n(Sm): n(Ti)=0.006 is the best under the irradiation of fluorescent light when the sintered temperature T=500°C, it is 97% within 6 h, which is significantly higher than 56.4% of pure TiO2 under the same experimental conditions.

Influence of Ytterbium Doping on the Visible Light Photocatalytic Activity of Mixed Phase TiO<sub>2</sub> Nanoparticles

The TiO2 nanoparticles with different Yb doping amount were prepared by a facile sol-gel method. The samples were characterized by XRD, TEM, XPS, UV-Vis, and PL, etc. The influence of Yb-doping on structure and visible light photocatalytic activity of mixed phase TiO2 was evaluated by photocatalytic degradation of methylene blue (MB) under the irradiation of fluorescent lamp. The results show that ytterbium appeared two kinds of Yb3+ and Yb2+ valence state on the surface of TiO2. Ytterbium doping can restrain the phase transfer from anatase to rutile, prevent the grain growth, and increase the surface hydroxyl content. Appropriate amount of Yb doping and the proportions of rutile and anatase mixed phase can effectively inhibit the recombination of photogenerated electron and hole, expand the wavelength range of absorption spectrum, and improve the photocatalytic performance of TiO2. Meanwhile, the photocatalytic activity of the Yb-TiO2 samples was the best under the irradiation of fluorescent light when the sintered temperature T=500°C and n(Yb):n(Ti)=0.009, it was 95.2% within 6 h and significantly higher than 56.4% of pure TiO2 under the same experimental conditions.

Electrospinning synthesis of SiO2-TiO2 hybrid nanofibers with large surface area and excellent photocatalytic activity

Abstract In this paper, one-dimensional SiO2-TiO2 nanofibers with large surface area and high anatase thermal stability were prepared by a facile and economical electrospinning technique. The phase transformation characters of the samples with different Si/Ti ratios and calcined at different temperatures were investigate in detail. The characterization results indicate that the modification of SiO2 could effectively prevent phase transformation of TiO2 from anatase to rutile. When the Si/Ti ratio increases from 0% to 5%, TiO2 crystals changed from mixed phases of anatase and rutile to pure anatase phase after heat treated at 600 °C. Meanwhile, the surface area of 600–5% is as high as 95.96 m2/g, which is nearly 12 times that of 600–0% (8.17 m2/g). Optimization of electrospun SiO2-TiO2 nanofibers shows that SiO2-TiO2 composite nanofibers with Si/Ti ratio = 2%, calcined at 600 °C, exhibited the highest MO degradation efficiency. The mole ratios of Si/Ti above and below 2% showed negative effect on MO degradation. This study serve as significant advancement platform to designing and fabricating high efficient and stable SiO2-TiO2 composite nanofibers via facile electrospinning in a “waterless” system and it is believed to make sense in other semiconductor systems which are sensitive to moisture.