Mixture Of Anatase Research Articles

Preparation, Physico-chemical Characterization and Photocatalytic Properties of Se Doped TiO2 Nanoparticles

Selenium-doped titania nanoparticles were prepared and characterized from physico-chemical and morphological point of view, with the aim possible applications in photocatalysis. DLS measurement indicated that TiO2 particles presents two different components: the first one, with low concentration and maximum size distribution at about 20 nm, and second one, with high concentration and size distribution ranging from 40 to 250 nm (maximum at 100 nm). After doping procedure and thermal treatment at 800 ͦ C, the size distribution reveals the formation of nanoparticles with wide range of diameters, from 20 nm to 500 nm, with good stability, as demonstrated by Zeta potential values: -19 mV for TiO2 and -25 mV for Se/TiO2 particles. Ti-O-Ti and Se-O vibrational modes were identified in ATR FTIR spectra. As a consequence of thermal treatment at 800 ͦ C, morphological changes of titania particles from nanorodes to nanowires were observed. The XRD spectrum of TiO2 starting material shows the typical crystalline pattern of anatase (tetragonal), in good agreement with the standard diffraction data, while a mixture of anatase and rutile (tetragonal) was obtained after the annealing process. The results of photocatalytic activity test demonstrated that both TiO2 and Se-doped TiO2 nanoparticles can effectively decompose methylene blue under the visible light irradiation, but with Se doping, the photocatalytic capability is significantly improved.

Effect of Calcination Temperature on Photocatalytic Activity of Synthesized TiO2 Nanoparticles via Wet Ball Milling Sol-Gel Method

In this work, TiO2 nanoparticles were successfully synthesized with narrow size distribution via a wet ball milling sol-gel method. The effect of calcination temperature on photocatalytic activity was observed from particle size, crystallite size, and phase transition of TiO2 nanoparticles. Increasing calcination temperature increased particle size, crystallite size, and the crystallinity of synthesized TiO2. Phase transition depended on variation in calcination temperatures. A two-phase mixture of anatase and brookite was obtained with lower calcination temperature whereas a three-phase mixture appeared when calcination temperature was 500–600 °C. With higher temperature, the rutile phase kept increasing until it was the only phase observed at 800 °C. Anatase strongly affected the photocatalytic activity from 300 °C to 600 °C while the particle size of TiO2 was found to have a dominant effect on the photocatalytic activity between 600 °C and 700 °C. A mixture of three phases of TiO2-600 exhibited the highest methylene blue degradation with the rate constant of 9.46 × 10−2 h−1 under ultraviolet (UV) irradiation.

Preparation and photocatalytic properties of rutile TiO2 with a unique morphology and SrTiO3–TiO2 composites obtained by acid treatment of SrTiO3

In this work, rutile, anatase, and SrTiO3–TiO2 composites were prepared by acid treatment of SrTiO3 using various concentrations of HNO3 at 90 °C. The product of the acid treatment depended on the acid concentration: fine TiO2 (anatase) particles were obtained for 0.5 M, a mixture of anatase- and rutile-phase TiO2 was obtained for 1 M, and large dumbbell-like TiO2 (rutile) particles were obtained for 2, 3, and 4 M HNO3. Furthermore, SrTiO3–TiO2 (anatase) composites in which fine TiO2 (anatase) particles formed on SrTiO3 cores were produced by a short-duration acid treatment. The composite exhibited a higher photocatalytic activity than the SrTiO3, TiO2 (anatase), TiO2 (rutile), and mixture of anatase- and rutile-phase TiO2 in methylene blue decomposition. The hybridization of SrTiO3 and anatase with a large contact area was considered to prevent rapid electron–hole charge recombination and to enhance the photocatalytic activity of the composites.

Study of TiO2, SnO2 and nanocomposites TiO2:SnO2 thin films prepared by sol-gel method: Successful elaboration of variable–refractive index systems

In this research TiO2, SnO2 and TiO2:SnO2 nanocomposite thin films were fabricated by the sol–gel dip coating technique. The mixture was prepared by varying the molar ratio of SnO2 to TiO2, i.e. TiO2:SnO2 (9:1), TiO2:SnO2 (8:2) and TiO2:SnO2 (6:4)). The obtained samples were characterized by means of the Raman microscopy, Scanning Electron Microscopy (SEM), UV–Vis spectrophotometry and m-lines spectroscopy (Prism coupler). Raman analysis shows that pure TiO2 and SnO2 thin films are characterized by the vibrational modes of anatase and rutile cassiterite, respectively. Furthermore, the Raman spectra of the TiO2:SnO2 nanocomposites show the presence of a mixture of anatase and rutile TiO2 phases. The SEM images reveal that the morphology is clearly modified with SnO2 content. The ripples in the transmittance spectra decreased with increasing SnO2 content. Also, the evolution of the optical band gap seems to be consistent with the Raman analysis. A great attention has been paid to the refractive index measurements by the prism coupler technique. In this way, variable–refractive index systems have been successfully obtained using TiO2:SnO2 nanocomposite thin films.

Fabrication and synthesis of uniform TiO2 nanoporous and nanotubular structures on dual-phase Ti–6Al–4V alloy using electron-beam irradiation

Developing homogeneous TiO2 nanoporous arrays (NPAs) and nanotubular arrays (NTAs) on biphasic Ti alloys is challenging. The present study used large-pulse electron-beam (LPEB) irradiation prior to anodizing, and ascertained its effectiveness for developing homogeneous TiO2 NPAs and NTAs on a dual (α + β)-phase Ti–6Al–4V alloy for the first time. The morphological features, structural characteristics, and corrosion resistance of the TiO2 NTAs formed on the LPEB-irradiated Ti–6Al–4V alloy were compared to those obtained on the untreated alloy. The irradiation transformed the dual (α + β)-phase structure into a single α′-martensite phase with a uniform distribution of alloying elements, and enabled the formation of a smooth surface finish with reduced surface roughness. The modified surface facilitated the formation of homogenous NPAs and NTAs. Annealing in air at 500 °C for 2 h transformed the amorphous as-prepared TiO2 NTAs into a mixture of anatase and rutile phases. Despite the appearance of cracks and an increase in intertubular spacing, the NTAs did not collapse. The NTAs formed on the untreated and LPEB-irradiated Ti–6Al–4V alloy provided better corrosion protection than their nonanodized counterparts.

Стабилизированные наночастицы диоксида титана: получение, физико-химические, фотокаталитические и антимикробные свойства

Представлены результаты стабилизации наночастиц анатаза с использованием тетраизопропоксида титана Ti[OCH(CH3)2]4и изопропилового спирта без участия поверхностно-активных веществ, пригодных для биологических исследований. Показано, что гидродинамические радиусы (в суспензиях) зависят от температуры и продолжительности гидролиза, а состав (смесь анатаза и брукита, анатаза, брукита и рутила) и размеры (в высушенном состоянии) кристаллитов (рентгенография), наночастиц и агрегатов (СЭМ) определяются главным образом рН среды. Имеющая место неоднофазность образцов объяснена, в том числе, когерентным срастанием элементарных ячеек анатаза и брукита из-за их геометрического и структурного соответствия. Выявлено, что фотокаталитическая активность (ФКА; модельный краситель Rhodamine 6G, УФ-излучение) зависит от соотношения ОН/H2O (адсорбированная), а антимикробная активность в темноте (АМА) – от содержания свободной воды на поверхности наночастиц (по данным рентгеновской фотоэлектронной спектроскопии – РФЭС). Установлена наибольшая ФКА и АМА по отношению к Staphylococcus aureus и Escherichia coli у образцов с наименьшими размерами наночастиц всех уровней.

Effect of Size and Crystalline Phase of TiO₂ Nanoparticles on Photocatalytic Inactivation of Escherichia coli.

We studied the size dependent toxicity of TiO₂ nanoparticles (TiO₂ NPs; 5-50 nm) of the anatase and rutile crystalline phases (including the mixture of anatase and rutile) against the model organism Escherichia coli. All the TiO₂ NPs were characterized and their photocatalytic inactivation of E. coli was studied under the solar simulated light irradiation and dark conditions. In addition, the mechanism of toxicity was studied by measurement of reactive oxygen species (ROS), an indicator of oxidative stress. Rutile TiO₂ NPs (TiO₂-R-30 nm) of 30 nm showed the highest photocatalytic activity against E. coli (LC50 of 14.11 mg/L), followed by rutile TiO₂ NPs (TiO₂-R-50 nm) (LC50 of 35.96 mg/L). The anatase and rutile mixture of 20 nm size produced LC50 of 17.12 and 27.26 mg/L for A80%-R20% and A20%-R80% respectively, whereas none of the anatase TiO₂ NPs with various sizes (5 nm, 15 nm and 30 nm) showed any toxicity against E. coli. The results indicate that the rutile had higher photocatalytic activity than anatase and the toxicity is size dependent, while the mixture of anatase and rutile had the median toxicity. Hydroxyl radical formation is the major ROS causing oxidative stress in E. coli, the primary mechanism of toxicity.

A Nitrogen- and Self-Doped Titania Coating Enables the On-Demand Release of Free Radical Species.

For potential applications such as suppressing the onset of peri-implant infections, a doped titania coating was developed to induce free radical release because of its ability for microbial elimination. The coatability of the sol–gel precursor is robust since the suspension’s rheology can be modified to attain uniform and complete surface coverage. The coating is composed of a mixture of anatase and rutile polymorphs doped with nitrogen (N3–), and it contains substoichiometric Ti2+ and Ti3+ species. Nitrogen doping results in a 0.4 eV band gap shift, while the defects induce photocurrent generation under visible light excitation up to 650 nm. Greater currents were observed in the nitrogen-doped titania at wavelengths above 450 nm vis-à-vis its (singularly) self-doped counterparts. The (photo)electrochemical behavior and photoactivity of the coating were evaluated by assessing redox species formation in a background aqueous solution. In the absence of any illumination, the coating behaved as an insulator and inhibited the activities of both oxidative and reductive species. On the other hand, under illumination, the coating enhances oxidation processes and inhibits reduction reactions within a near-field region wherein release of free radicals occurs and is constrained (delimited).

Structural Analysis, Tribological and Hardness of Titanium Grade 2 Anodized, Using HCI and Ethylene Glycol as Electrolytic Solution

One of the main difficulties present in the materials manufacturing is the selection of substances that generate less polluting residues as well as effective in the synthesis process. In this study, we obtained TiO2 through electrochemical anodizing, using an acid easy to neutralize (hydrochloric acid), ethylene glycol and distilled water. The results showed the presence of nanostructures over the anodized surface observed by Scanning Electron Microscopy, with anatase and rutile phases, identified with Raman Spectroscopy. The presence of a nanostructured material on the surface of titanium, improved the value of Vickers Micro-hardness from 240 HV to 400 HV. It was possible to obtain a reduction of the friction coefficient from 0.8 to 0.2 as minimum value. The presence of a nanostructured layer of TiO2, with a mixture of anatase and rutile, markedly improved the mechanical properties of the titanium sheet.

The effect of tetra isopropyl orthotitanate (TIP) concentration on structural, and luminescence properties of titanium dioxide nanoparticles prepared by sol-gel method

This article focuses on the preparation of high-quality titanium dioxide (TiO2) nanoparticles (NPs) using a simple sol-gel method. The effect of varying concentration of tetra isopropyl orthotitanate (TIP) on the structural and optical properties was examined. Solutions were formed at room temperature and allowed to age, dried at 130 °C into the powder then calcined at 500 °C for 2 h. XRD results confirmed the presence of a mixture of anatase and rutile at all the varied TIP concentration. SEM micrographs showed that the TiO2 NPs were agglomerated and the morphology was somewhat spongy. The elemental composition and nature of the material were obtained by Energy Dispersive Spectroscopy (EDS) and Fourier -transform infrared spectroscopy (FTIR). UV–Vis spectra showed a blue shift which was an indication that an increase in TIP concentration increased the bandgap and favoured the formation of anatase phase. The optical bandgap obtained using the Kubelka -Munk equation was in the range of 2.7 to 3.12 eV which implied that the photoactivity will take place near visible light. Photoluminescence spectroscopy (PL) showed that an increase in diameter of the NPs improved the PL intensity. This study reveals a simple method suitable for the synthesis of a mixture of anatase and rutile TiO2 with desirable optical properties for various applications.

A study on the mechanism of Ca2+ adsorption on TiO2 and Fe2O3 with the usage of calcium ion-selective electrode.

The paper presents the quantitative characterization of the solid/water interface applying both experimental and theoretical approaches for the system of TiO2 (mixture of anatase and rutile) and Fe2O3 (maghemite) with calcium ions in the pH function. The aim of the study was also to find a bonding mechanism between Ca2+ and metal oxides surface based on the calculations from the surface complexation modeling code (GEOSURF by Sahai and Sverjensky, 1998). In order to obtain adsorption edges, a calcium ion-selective electrode (Ca-ISE) was applied for determination of Ca2+ concentration in the suspensions. The results of both the Ca-ISE and parallel spectrophotometric determination were similar. The adsorption data showed that TiO2 exhibited stronger calcium binding than Fe2O3 at pH > 8. Using 2-pK TLM (triple-layer model) it was demonstrated that mechanism of the calcium adsorption onto the metal oxides surface involved different reactions. In the case of TiO2 it involved formation of >SO-_CaOH+ predominately on the β-plane and at pH > 9 also on the 0-plane. In the case of Fe2O3 one could observe the existence of (>SO-)2_Ca2+ on the β-plane in the whole studied pH range. At pH above 7 the tetranuclear complexes (>SOH)2(>SO-)2_Ca(OH)+ were found, and at pH > 9 also >SO-_CaOH+ could be observed. On the other hand, the analysis of the ζ-potential data suggested the absence of the tetra-species on the maghemite surface. The study indicated that the properly validated calcium ion-selective electrode can be an attractive instrument for monitoring Ca2+ adsorption on metal oxides in the environment.

Structural and morphological study of thermally oxidized titanium thin films for the detection of chlorpyrifos

In this research work, titanium oxide (TiO2) thin films were grown on p-type (100) silicon substrate by thermal oxidation of RF sputtered titanium thin films in air ambient at various temperatures ranging from 500 °C to 950 °C. The XRD pattern revealed the evolution of a mixture of anatase and rutile phases at thermal oxidation temperature of 500 °C. At higher temperature (>500 °C), well oriented crystalline rutile phase was obtained for all the thermally oxidized TiO2 films. The average crystallite size of the oxidized films at 500 °C and 950 °C is estimated as 9 nm and 43 nm, respectively. The root mean square (RMS) surface roughness is found to be increased with the rise in oxidation temperature. The microstructural studies by Raman spectroscopy have also revealed a mixture of anatase and rutile peak at 500 °C. The morphological studies have revealed the enhancement in grain size with the increase in oxidation temperature with the appearance of distinct grain boundaries. The chlorpyrifos sensing behavior of the oxidized samples were carried out at room temperature. Chlorpyrifos is a neurotoxic organophosphate compound, which is most widely used as a pesticide in agricultural farm. Current-time (I-t) measurement of thermally oxidized Ti films was performed in order to detect the chlorpyrifos. A significant enhancement in the conductivity was observed with the introduction of chlorpyrifos vapors. From the current-time curve, the response and recovery time during chlorpyrifos sensing was evaluated to be around ~43 s and ~3.9 s, respectively.

Characteristics and photocatalytic behavior of Fe and Cu doped TiO2 prepared by combined sol-gel and mechanical alloying

In this paper, TiO2 gel was synthesized by the sol-gel method and then doped with Cu and Fe by mechanical alloying. Prepared photocatalysts were characterized throughout X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) and ultraviolet–visible spectrophotometer. Photocatalytic behavior of prepared samples was studied by the degradation of methylene blue (MB) under both visible and ultra-violet (UV) region. XRD results indicated that phase structures of photocatalyst were the mixture of anatase and rutile phases. The content of the anatase phase increased to a maximum of 72 wt% in Fe doped TiO2 nanopowder. The agglomeration of Cu doped TiO2 particles was more severe than that of other samples. The average particle size of the Fe doped TiO2 samples was 120 nm smaller than that of the Cu doped sample. XRD, energy dispersive spectroscopy (EDS) and TEM results confirmed the more uniform dispersion and replacement of Ti by Fe in the TiO2 lattice structure. The results from DRS analysis obviously showed the shift of absorption band gap towards the visible region upon doping TiO2 with both Cu and Fe, with the minimum value of 2.8 eV for Fe doped TiO2. PL results showed that Fe doped sample had lower electron-hole recombination rate than other TiO2 samples. Degradation kinetics and the effect of initial MB concentration were studied by the Langmuir-Hinshelwood (L-H) model. In the case of Fe doped TiO2 photocatalyst, higher adsorption capacity and reaction rate constant were obtained. 2.5 wt% Fe doping is the optimal content for the degradation of phenol and MB dye.

Development of TiO2 nanofibers based semiconducting humidity sensor: adsorption kinetics and DFT computations

The present study focuses on development of pure and Ru-doped TiO2 nanofibers as potential candidates for humidity sensing. Electrospun technique is used for fabrication of the nanofibers to evaluate their humidity sensing properties via QCM method. The obtained nanofibers are analyzed by X-ray diffraction and scanning electron microscopy techniques. The humidity adsorption kinetics and the mechanism of sensing humidity are explored, in details. The results of X-ray analyses reveal that TiO2 nanofibers with a mixture of anatase and rutile structures are successfully synthesized. Additionally, Ru reduces the crystalline size and intensity of the TiO2 peaks. The QCM results show that Ru-doping enriched the humidity sensing performance of TiO2 nanofibers. According to the DFT calculations, the introduction of Ru atoms into TiO2 leads to a sizable increase in the adsorption energy of the water molecule. It is also found that the Ru-doping makes an increase in the charge-transfer from the water molecule into the surface, which can result in an enhanced sensing response of TiO2 by decreasing the electrical resistance.

Impact of the absolute rutile fraction on TiO2 visible-light absorption and visible-light-promoted photocatalytic activity

Titanium dioxide is by far the most used semiconductor material for photocatalytic applications. Still, it is transparent to visible-light. Recently, it has been proved that a type-II band alignment for the rutile − anatase mixture would improve visible-light absorption. In this research paper we thoroughly characterised the real crystalline and amorphous phases of synthesised titanias – thermally treated at different temperatures to get distinct ratios of anatase-rutile-amorphous fraction – as well as that of three commercially available photocatalytic nano-TiO2.Optical spectroscopy showed that even a small fraction of rutile (2 wt%) is able to shift to lower energies the apparent optical band gap of an anatase-rutile mixed phase. But is this enough to attain a real photocatalytic activity promoted by merely visible-light? We tried to give an answer to that question.Photocatalytic activity was assessed in the liquid- and gas-solid phase (employing rhodamine B and 4-chlorophenol, and isopropanol, respectively, as the organic substances to degrade) using a light source irradiating exclusively in the visible-range.Photocatalytic activity results in the liquid-solid phase showed that a high surface hydroxylation led to specimen with superior visible light-promoted catalytic activity – i.e. dye and ligand-to-metal charge transfer complexes sensitisation effects, not photocatalysis sensu-strictu.On the other hand, the gas-solid phase results showed that a higher amount of the absolute rutile fraction (around 10 wt%), together with less recombination of the charge carriers, were more effective for both visible-light absorption and a “real” visible-light promoted photocatalytic oxidation of isopropanol.

Growth stages of nano-structured mixed-phase titania thin films and effect on photocatalytic activity

The development of nano-structured mixed-phase titania thin films and the relationship to photocatalytic activity (PCA) is of interest for pollution reduction and antimicrobial applications. A set of films grown by pulsed pressure metallorganic chemical vapour deposition using titanium tetraisopropoxide precursor was studied. The growth method is single-stage, scalable and produces high-quality, adherent films. Film thicknesses were 101 nm to 4.0 μm. Three growth stages were identified. All films were a mixture of anatase and rutile. Early stage films had rounded morphologies, low surface roughness and low PCA. Transition stage films developed columnar [110] orientated anatase dendrites, contained amorphous carbon and had reduced UV transmittance. Late stage films had strong anatase (220) and rutile (200) textures, contained amorphous carbon and exhibited highly branched anatase dendrites with nanoscale secondary plates. PCA was determined from degradation of stearic acid and correlated with increasing surface roughness. The most active film had formal quantum efficiency of (6.62 ± 0.64) × 10−4 molecules/photon, 59 times higher than a commercially available control. The performance is attributed to the combination of phases yielding polymorphic phase boundaries and amorphous carbon enhancing the adsorption of organic molecules, the unusual (220) anatase texture yielding nanostructured anatase dendrites in combination with nanocrystalline rutile and hierarchical porosity.

Surface anodization of the biphasic Ti13Nb13Zr biocompatible alloy: Influence of phases on the formation of TiO2 nanostructures

Here we report for the first time that the anodization of the biphasic (α'+β) Ti13Nb13Zr alloy form arrays of TiO2 nanotubes with well-defined circular geometry in the α′ phase, while nanopores of TiO2 are formed in the β phase. Samples of the Ti13Nb13Zr alloy were severely plastic deformed using High-Pressure Torsion (HPT) to refine the microstructure and to redistribute α′ and β phases. The anodization was performed using an organic electrolyte (glycerol) containing fluoride ions and a few percentages of water. All the specimens coated with nanotubes were annealed at 550 °C to crystallize the modified surface of the as-anodized samples. XRD analyses confirmed that the as-anodized amorphous nanostructures crystallize in a mixture of anatase and rutile after heat treatment, and SEM observations showed no significant morphological changes in the surface phases. The evaluation of corrosion resistance showed that anodized samples have much better corrosion properties than polished ones without any evidence of pitting corrosion. Quantitative comparison between anodized coarse-grained (α'+β)-Ti alloy and ultra-fine grained (α'+β)-Ti one showed that the nanostructuring of the (α'+β)-Ti alloy by HPT helped to improve the bioactivity when compared with the coarse-grained sample.

Influence of the Dopant Atom and the Oxygen Vacancy Site for the Oxygen Reduction Reaction on the Titanium Oxide

Polymer electrolyte membrane fuel cells (PEMFCs) are expected as one of the next generation power sources because its exhaust gas is, theoretically, only water. On the other hand, the selling price of the PEMFC mounted devices expensive, and this price inhibits the wide-spread commercialization. It is one reason for this thing that the platinum-based catalyst, which is high cost and low durability, is used as the electrocatalyst and is required large quantity to obtain the cell performance. As one of the ultimate solutions for this problem, usage of the non-platinum oxide catalyst is proffered. Recently, the group 4 and 5 transition-metal oxides are attracted attention as the non-platinum oxide catalyst since these show the activity of oxygen reduction reaction (ORR) and the high durability. In these oxides, introducing of the oxygen vacancy site in oxide surface to get high ORR activity is the common design guide for the new catalyst development. Addition, it is well known that doping niobium to the titanium oxide with the oxygen vacancy site is also effective for obtaining the high ORR activity. In other words, introducing the oxygen vacancy site and doping the other metal atom is necessary to prepare for the high ORR catalyst based on group 4 and 5 transition-metal oxide in this time. Although the active site for ORR on the oxide surface is not clear, it is speculated that the oxygen vacancy site would play the important role for ORR. However, the relationship between the dopant atom and the oxygen vacancy site has not been discussed enough in the viewpoint from ORR. In fact, the dopant atom in the previous works of literature in acidic environmental is almost the niobium, and other atoms are very few. The other hand, it is reported the calculated formation energy of oxygen vacancy site on anatase Ti M O2 (101) depends on the dopant atom. Therefore, this study describes the influence of the dopant atom and the oxygen vacancy site on the ORR activity of titanium oxide. In this study, niobium, manganese, and ruthenium were chosen as the dopant atom because their formation energy of oxygen vacancy site decreased step by step in literature. All samples were prepared by the typical sol-gel method. The oxygen vacancy site was introduced by the chemical reduction method using the sodium borohydride. Electrochemical studies were conducted in Ar- or O2-saturated 0.1 M HClO4 (60ºC) with carbon plate counter-electrode and Ag/AgCl reference-electrode. The ORR activity was evaluated by the difference current of current in Ar-saturated condition from the current in O2-saturated condition. The on-set potential of ORR current was notated as E on-set in bellow. Crystal structures before chemical reduction treatment were a mixture of anatase and rutile in all dopant species. The crystallinity of samples was decreased by chemical reduction treatment, but the clear phase transition did not observe. In the case of niobium doping, the E on-set was increased to ~0.6 V from ~0.4 V by the chemical reduction treatment. This phenome agreed with previous works, and it is thought that the enhancement effect was provided by the formation of the oxygen vacancy site. The ruthenium doped titanium oxide was also started ORR at ~0.4V. Thus, the difference of enhancement effect between niobium and ruthenium for ORR activity of titanium oxide was little before introducing the oxygen vacancy site. After introducing the oxygen vacancy site, E on-set of ruthenium doped titanium oxide was ~0.75 V. In addition, its ORR current was the highest in this study. If the ruthenium dopant was removed from titanium oxide lattice and formed the ruthenium oxide during the chemical reduction treatment, its quantity of ruthenium oxide is very low. Because the doping ratio of ruthenium was 5 mol%. Moreover, the E on-set of ruthenium oxide was ~0.6 V which was a lower value than that of reduced ruthenium doped titanium oxide. After the introducing oxygen vacancy site, the enhancement effect for ORR ability depended on the dopant species. Herein, the formation energy of oxygen vacancy site of niobium doped titanium oxide was higher than that of ruthenium doped titanium oxide. In ruthenium doped titanium oxide with oxygen vacancy site, it is speculated that the oxygen molecule is easier adsorption/desorption in comparison with niobium doped titanium oxide. At this moment, we think that the ORR activity of titanium oxide depends by the dopant atom but needs not only dopant species but also the oxygen vacancy site.

Bimetallic Ru-Ni/TiO2 catalysts for hydrogenation of N-ethylcarbazole: Role of TiO2 crystal structure

Abstract Hydrogenation of N-ethylcarbazole (NEC), the hydrogen lean form of a liquid organic hydrogen carrier, on TiO2 supported Ru-Ni bimetallic catalysts is investigated. Crystal structure of TiO2 plays a critical role on the hydrogenation activity and selectivity towards fully hydrogenated product. Ru/anatase catalyst exhibits higher selectivity but lower reactivity compared to Ru/rutile catalyst. Ni addition significantly promotes the performance of Ru/anatase catalyst while causes severe performance deterioration of Ru/rutile catalyst. Commercial P25, a mixture of anatase and rutile phases in approximate ratio A/R∼1/4, is found to be the best TiO2 support for NEC hydrogenation. Ru/P25 catalyst outperforms both Ru/rutile and Ru/anatase and its activity can be further slightly improved by Ni addition. The unexpected synergism between the two different TiO2 phases for Ru based NEC hydrogenation catalysts is related to metal-support interaction and Ru-Ni interaction.

Controllable synthesis and tunable photocatalytic activity of TiO2 nanowires via alcohol-thermal method

Titania nanowires (TiO2-NW) with tunable aspect ratios and morphologies were directly synthesized using a simple alcohol-thermal technique. Specifically, ethanol and acetic acid were used as solvents and lithium ion was used as the capping agent to promote the conversion of titanium butoxide into TiO2-NW. The morphologies and crystal phases of TiO2-NW were determined by the molar ratio of solvents and the content (mol%) of lithium ion. The band gap of TiO2-NW with pure anatase phase is slightly bigger than that of TiO2-NW with a mixture of anatase and rutile phases. All TiO2-NW could achieve effective decolorization of methyl blue (the decolorization rate is over 95%) after 35-min ultraviolet (UV) irradiation.