Anatase TiO2 Powder Research Articles

Photovoltaic performance of TiO2 using natural sensitizer extracted from Phyllanthus Reticulatus

Phyllanthus reticulatus, a natural sensitizer has been extracted from Karunelli fruit for the fabrication of TiO2 based DSSCs. The extracted dye shows the visible light optical absorption at a wavelength of around 520 nm. The presence of anthocyanin in the dye extract has been identified by the functional molecular groups such as intermolecular –OH bond, conjugate C=O stretching vibrations using FTIR. A commercial P25 TiO2 anatase powder has been employed for the fabrication of photoanode on fluorine doped tin oxide (FTO) substrate using Doctor-blade technique. The Platinum (Pt) counter electrode has been prepared using electron beam evaporation technique with a thickness of ~200 nm. To measure the photoconversion efficiency of the stacked DSSCs, the electrodes are assembled into a cell module and illuminated by a light source simulating AM 1.5 with a light intensity of 100 mW/cm2. The freshly prepared sensitizer (P. reticulatus pH ~5.5) exhibits the photo-conversion efficiency of 0.19%, while decreasing the pH of the sensitizer (pH ~1.0) enhances the photoconversion efficiency to six times (0.69%) higher than that of fresh one.

A detailed insight into the preparation of nanocrystalline TiO2 powders in supercritical carbon dioxide

This work reports detailed investigations for the preparation of nanostructured titania powders by a solvent-free sol–gel-derived process, operated in supercritical CO2 (SC-CO2) at high pressures (10–30 MPa) and large range of temperatures (373–823 K). Depending on the processing temperature, the reaction between Ti(OiPr)4 and water performed in a single supercritical phase led to the formation of either amorphous (Ti(OH)4—titanium hydroxide) or crystalline (TiO2—titanium dioxide) nanostructured particles. Crystalline (anatase) mesoporous powders with high specific surface area were obtained directly in CO2 solvent under supercritical conditions at temperatures as low as 523 K. The effect of hydrodynamic key process parameters such as stirring and water injection rate on both powder morphology and aggregation degree was also investigated in details. The optimized TiO2 anatase powders exhibited attractive photocatalytic activity, with high potential for the degradation of water pollutants.

Zr doping effect with low-cost solid-state reaction method to synthesize submicron Li4Ti5O12 anode material

To improve the electrochemical properties, fine Zr-doping Li4Ti5O12 anode materials for rechargeable lithium batteries with a uniform particle size distribution were synthesized by a modified solid-state reaction using fine Li2CO3 and TiO2 (anatase) powders as precursors with a Li:Ti molar ratio of 4:5. The use of fine Li2CO3 and TiO2 (anatase) powders as precursors prevented the formation of ZrO2 at 0.1mol Zr-doping. XRD analysis revealed that the substitution of Zr for Ti leads to the increase of lattice parameters, allowing improved Li diffusion. The discharge capacity retention increased slightly with Zr-doping and the 0.1mol Zr-doped Li4Ti5O12 electrode achieved 99% retention of discharge capacity.

Microwave-power induced green synthesis of randomly oriented mesoporous anatase TiO2 nanoparticles for efficient dye sensitized solar cells

A facile and rapid synthesis of randomly distributed mesoporous anatase TiO2 nanoparticles for DSSC application using microwave method is reported here. Nanocrystalline anatase TiO2 is achieved by a sol microwave power strategy, where low microwave power intensity (300 and 600W) for 5min irradiation has been implemented. As synthesized anatase TiO2 nanoparticles have been characterized by a range of different techniques such as XRD, SEM, TEM and BET surface area analysis. These anatase TiO2 nanoparticles possessed high surface area up to 210m2g−1. Nanocrystalline nature and anatase phase purity were revealed from XRD. SEM studies have shown that the anatase TiO2 powder synthesized were appeared as spherical aggregates and the nano size of single particles (∼10nm) were confirmed by TEM analysis. These anatase TiO2 nanoparticles were successfully employed as the working electrode for DSSC and a systematic investigation of the performance of DSSC constructed with standard N719 dye with conventional iodide/triiodide (I−/I3−) has demonstrated an efficiency of 6.6% under 100% sunlight with 55% of IPCE.

Anatase TiO2/cellulose hybrid paper: Synthesis, characterizations, and photocatalytic activity for degradation of indigo carmine dye

We report a facile easy method to deposit anatase titania (TiO[Formula: see text] on cellulose paper. The anatase TiO2/cellulose paper (ATCP) was characterized by scanning electron microscopy, transmission electron microscope, energy dispersive X-ray spectrometer, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. This hybrid paper with the anatase TiO2 content of around 13.86[Formula: see text]wt.% can serve as an eco-friendly flexible photocatalyst, which can rapidly degrade blue indigo carmine dye into a colorless solution within 30[Formula: see text]min under UV radiation. Moreover, compared to commercially available TiO2 P25 and anatase TiO2 powder, a faster decomposition rate of indigo carmine dye was acquired when using ATCP. These results suggest that this hybrid paper might be useful in the treatment of organic dye wastewater.

Modyfication of photocatalytic properties of titanium dioxide by mechanochemical method

Abstract The paper presents a simple way to improve the photocatalytic properties of titanium dioxide using mechanochemical method. The TiO2 (Anatase) powders was subjected to high-energy ball milling in dry environment and in methanol. It has been shown that it is possible to induce the phase transformation from Anatase to Rutile and produce a material with a higher photocatalytic activity in the UV light. Physicochemical characteristics of the products were based on the following methods and techniques: X-ray powder diffraction (XRD), IR and UV-Vis (DR) spectroscopy, measurements of specific surface area (BET). The photocatalytic activity of the powders was measured in the decomposition reaction of methyl orange in water.

Visible-light active mesoporous, nanocrystalline N,S-doped and co-doped titania photocatalysts synthesized by non-hydrolytic sol-gel route

Visible-light active mesoporous N,S-doped and co-doped anatase TiO2 powders were synthesized by non-hydrolytic sol-gel route, starting from TiCl4 and Ti(OiPr)4 dissolved in cyclohexane or dimethyl sulfoxide, later used as a S-doping agent. After drying in an inert atmosphere, the gels were annealed at 500°C for 3h, in air or ammonia flow, later used for N-doping. The undoped titania powder, obtained by annealing in air of the cyclohexane-based gel, was also annealed in ammonia to deduce which method is more efficient for N-doping: gel or powder annealing. The post-annealing in air after annealing in ammonia was optimized to attain the best photocatalytic activity for dye degradation under simulated visible light. The size of anatase nanocrystals decreased by doping and the specific surface area of the powders increased. The XPS analysis confirmed a successful substitution of Ti4+ by S(4+) and/or S(6+), which caused a very small band-gap narrowing. The gel annealing in ammonia was much more efficient for interstitial nitrogen incorporation in TiO2 lattice than the powder annealing. The annealing in ammonia of the gel synthesized with dimethyl sulfoxide provided the highest visible-light activity owing to high specific surface area, appropriate mesoporosity and high photoabsorption due to efficient N,S co-doping.

Grain boundary segregation and secondary-phase transition of (La,Nb)-codoped TiO2 ceramic

The formation and transition of secondary phases in (La, Nb)-codoped TiO2 ceramics were investigated using samples prepared by traditional solid-state sintering from anatase TiO2, Nb2O5, and La2O3 oxide powders. From the microstructure, crystal structure and chemical composition of these samples, as measured by SEM, XRD and EDS, the formation mechanism of the secondary phase is determined though point defect thermodynamical analysis. The results show that LaNbO4 and LaNbTiO6 secondary phases originate from segregation of the point defects NbTi· and La′Ti at grain boundaries, with elastic strain energy providing the main driving force for this segregation. An increase in sintering temperature causes more of the LaNbO4 secondary phase to transition to LaNbTiO6. A ternary phase diagram of La2O3–Nb2O5–TiO2 was plotted based on binary phase diagrams of La2O3–Nb2O5, Nb2O5–TiO2 and La2O3–TiO2, which can be used to estimate the relative content of secondary phases in samples sintered at different temperatures.

Preparation and characterisation of TiO<SUB align="right">2 thermally modified with cyclohexane vapours

In this study a simple method of preparation of UV-vis light-active TiO2 photocatalysts is presented. The new photocatalysts were obtained by thermal modification of the anatase TiO2 powder (Police, Poland) with cyclohexane. The obtained materials were investigated by means of UV-vis/DR, FTIR/DRS, XRD. BET specific surface area and carbon content was also measured. Furthermore, photocatalytic activity of the new photocatalysts were investigated under UV-vis irradiation with high UV light intensity during of phenol degradation. TiO2/C photocatalysts show higher photocatalytic activity in comparison with TiO2-starting and commercial KRONOClean 7000, regardless of calcination temperature. It was found that the smaller amount of carbon in TiO2/C photocatalyst sample the better photocatalytic activity of tested nanomaterials.

Complex doping chemistry owing to Mn incorporation in nanocrystalline anatase TiO2 powders.

Mn-doped TiO2 powders with a wide range of nominal doping levels were fabricated using a one-step hydrothermal method followed by 400 °C annealing. Anatase powders with a uniform size distribution below 10 nm were obtained. The maximum solubility of Mn in the TiO2 lattice was around 30%, beyond which the Mn3O4 compound appeared as a secondary phase. The optical absorption edges for Mn-doped anatase TiO2 were red-shifted effectively through increasing Mn content. Alloying chemistry and associated elemental valences were elaborated through combining X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and theoretical simulation in the framework of density functional theory (DFT). The results showed that the Mn species exhibited mixed valence states of 3+ and 4+ in anatase TiO2, with the latter being the key to remarkable photocatalytic performance.

Ethanol sensing properties of Zn2TiO4 particles

Zn2TiO4 particles were prepared using the ball-milling technique in ethanol solution. Zn powder mixing with anatase-TiO2 powder at ratio of 2:1 by mole were used as raw materials. The mixed powders were grounded in agate mortar for 2h, subsequently transferred into the ball-milled container with 1mm zirconia balls and, then, milled for 24h with ball-milling speeds of 200, 300 and 400rpm. The ratio of powders and zirconia balls was 1:20 by weight. After that, the powders were washed using distilled water for 4 times, dried at 80°C for 24h and calcined at 1000°C for 6h. Morphological characteristics, chemical compositions, phase formation and defect of the synthesized powder were examined. The SEM result showed that the particle size was reduced as increase in the ball-milling speed, while the EDS showed that the Zn/Ti ratio was about 2. The XRD indicated that the synthesized powders exhibited a face center cubic Zn2TiO4 phase, confirming by the Raman spectra. The Zn2TiO4 particles were fabricated as the thick film ethanol sensor and tested under 50 and 200ppm ethanol concentration at 300–500°C. Our results suggest that the Zn2TiO4 particles can be used for detection of ethanol vapor, and the sensor current increased with increasing of ethanol concentration. The highest sensitivity observed at 500°C was 3.83 for 200rpm, 1.92 for 300rpm and 2.36 for 400rpm samples. This implied that, the Zn2TiO4 sensor can be a good candidate for high temperature application.

Photoluminescent and photocatalytic properties of bismuth doped strontium aluminates blended with titanium dioxide

Bismuth co-doped long persistent phosphor (LPP) powders were obtained by a combustion synthesis technique followed by a post-annealing under carbon atmosphere. Bismuth content was varied from 1.0 to 15.0mol%. X-ray diffraction analysis revealed that the powders show mainly a mixture of three phases: the SrAl2O4, the SrAl14O25 and the Sr2Al6O11 crystalline phases. Photocatalyst composites were obtained by wet mixing of TiO2 anatase and LPP powders followed by annealing in air at 450°C. Photoluminescence measured spectra under 380nm excitation show a tunable emission from green (510nm) to greenish-blue (463nm) in which peak wavelength localization is related to the Bi content. Photoluminescence intensity decreases as Bi content increases. Degradation of methylene blue solutions, irradiated by UV light (254nm), was monitored by the decrease of its 650nm absorption peak in regular periods. The best photocatalytic activity is observed when in the composite blend a 2.0mol% of Bi content was used, and complete methylene degradation is reached after 210min. These photocatalyst composite powders are potential candidates to clean-up wastewater applications, and might be potential candidates for photocatalytic hydrogen generation in aqueous solutions.

Graphene-supported flocculent-like TiO2 nanostructures for enhanced photoelectrochemical activity and photodegradation performance

Here, novel graphene/TiO2 nanocomposite has been successfully prepared by loading flocculent-like titanate nanostructure in graphene sheets via hydrothermal method plus a subsequent annealing process. The as-obtained hybrid was characterized by X-ray diffraction, scanning electron microscopy with an energy dispersive spectroscope (EDS), Raman, and UV–vis diffuse reflectance spectra, respectively. The photoelectrochemical activities and photocatalytic degradation performance of methyl orange under the illumination of ultraviolet light were investigated, and the flocculent-like TiO2/graphene composites was found to have a superior photocatalytic activity compared to flocculent-like titanate nanostructure and commercial anatase TiO2 powder, which can be attributed to the improved light absorption and extremely efficient charge separation of the hybrid structure. The results suggest that the as-prepared flocculent-like TiO2/graphene composite is a promising photocatalyst for photoelectrochemical hydrogen production and pollution removal.

Macroporous Titanate Nanotube/TiO2 Monolith for Fast and Large-Capacity Cation Exchange

Centimeter-scale monolithic composites constituted of titanate nanotubes (TNTs) and titania nanoparticles were hydrothermally prepared from a concentrated aqueous emulsion of anatase TiO2 powder. The monolith was composed of a nanotube-interconnected framework containing micrometer-scale pores. Enhanced growth of TNTs in cavities surrounded by TNT/TiO2 aggregated particles resulted in the formation of entangled/interconnected TNT bridges between TNT/TiO2 aggregates. The macroporosity depends on a volume fraction of anatase to the aqueous solution. The resulting monolithic TNT/TiO2 composite had sufficient mechanical strength for various applications. The monolith exhibited a faster rate and a higher capacity of Li+ exchange than simple compacted TNTs. The TNT monolith has potential in cation exchange and adsorption applications, because of its macroporous flow channels.

Optimized photocatalytic degradation of caffeic acid by sol-gel TiO₂.

TiO₂anatase powder was prepared by means of the sol-gel method with titanium(IV) butoxide as precursor. The formation of a tetragonal crystal structure of TiO₂anatase at 500 °C was confirmed by X-ray powder diffraction. The characterization of the samples synthesized was complemented by scanning electron microscopy, diffuse reflectance infrared Fourier transform spectroscopy, nitrogen adsorption-desorption isotherms (Brunauer-Emmett-Teller) and diffuse reflectance spectroscopy. The photocatalytic activity of the TiO₂anatase powder was evaluated in the degradation of caffeic acid in aqueous solution under ultraviolet radiation. A central composite circumscribed design was used to assess the weight of the experimental variables, pH and amount of catalyst in the percentage of caffeic acid degraded and the optimal conditions. The optimized conditions were found to be pH = 5.2 and a load of TiO₂of 1.1 g L⁻¹. Under these conditions more than 90% of caffeic acid degradation was achieved after 30 min of lamp irradiation. At this time the mineralization reached was almost 60%.

Morphology Control of Pseudobrookite-Type MgTi<sub>2</sub>O<sub>5</sub> Powders by LiF Doping

Well-controlled fine MgTi2O5 powders, with pseudobrookite-type structure, are desired toward various industrial applications, however, commercial powders are hardly available to date. In this study, we focused the processing and characterization of well-controlled MgTi2O5 powders with/without LiF additive. MgCO3 (basic) and TiO2 anatase powders with/without 0.5 wt. % LiF additive were calcined in air at 1100 °C for 2 h to obtain the MgTi2O5 powders. SEM observation revealed that the non-doped MgTi2O5 powder consisted of equiaxed particles with the diameter of 0.5-1.5 μm, whereas, the LiF-doped MgTi2O5 powder consisted of elongated particles with the length of ~ 5-10 μm and the diameter of ~1.0-1.5 μm. The smooth surface of elongated MgTi2O5 particles demonstrates the effect of LiF doping as a flux, i.e., liquid phase formation during the reaction.

Kinetic study of formic acid degradation by Fe3+ doped TiO2 self-cleaning nanostructure surfaces prepared by cold spray

A self-cleaning solution was introduced in this paper based on sol–gel and was applied for preparing self-cleaning TiO2. Fe3+ ions have been doped into the TiO2 crystal lattice. XRD analysis indicated that the obtained TiO2 powder contains mainly the anatase phase and TiO2 powder has a crystallite size distribution of 10–12nm. SEM micrographs have also confirmed nanometric distribution of the obtained powder. A series of uniform and transparent TiO2 and Fe/TiO2 films were prepared by cold spray technique which may result in high uniformity in the final coated surfaces. Photocatalytic activity of the thin films was investigated through degradation of aqueous formic acid under UV–visible light. The Langmuir–Hinshelwood kinetic model was used to interpret quantitatively the observed kinetic experimental result. Comparative study of the obtained coated surfaces with those of uncoated surfaces, demonstrated a remarkable performance. The Fe/TiO2 films and their calcination at 650°C demonstrated the highest photocatalytic activity.

Morphology Control of Pseudobrookite-Type MgTi<sub>2</sub>O<sub>5</sub> Powders by LiF Doping

Well-controlled fine MgTi2O5 powders, with pseudobrookite-type structure, are desired toward various industrial applications, however, commercial powders are hardly available to date. In this study, we focused the processing and characterization of well-controlled MgTi2O5 powders with/without LiF additive. MgCO3 (basic) and TiO2 anatase powders with/without 0.5 wt. % LiF additive were calcined in air at 1100 °C for 2 h to obtain the MgTi2O5 powders. SEM observation revealed that the non-doped MgTi2O5 powder consisted of equiaxed particles with the diameter of 0.5-1.5 μm, whereas, the LiF-doped MgTi2O5 powder consisted of elongated particles with the length of ~ 5-10 μm and the diameter of ~1.0-1.5 μm. The smooth surface of elongated MgTi2O5 particles demonstrates the effect of LiF doping as a flux, i.e., liquid phase formation during the reaction.

Degradation of Rhodamine B Dye by TiO2Nanotubes Photocatalyst Synthesized via Alkaline Hydrothermal Method

Titanium dioxide (TiO2) nanotubes have successfully been synthesized by using one step approach of hydrothermal method. Commercial TiO2 (anatase) powder was used as precursor to synthesize the TiO2 nanotubes. The TiO2 nanotubes were synthesized at 120 o C/20 hrs in an alkaline solution of NaOH. The photocatalytic study of the as-synthesized samples was conducted by analyzing the degradation of Rhodamine B (Rh B) dye under UV light irradiation. Rh B is a toxic dye which is commonly used in textile industry. It is the one of the most common pollutants in the effluents and highly soluble in water. A comparison study was carried out in order to investigate the photocatalytic activity between the synthesized TiO2 nanotubes and the commercial TiO2 nanoparticles. Results show that the TiO2 nanotubes exhibits better photocatalytic activity in the degradation of Rh B as compared to the TiO2 nanoparticles.

Synthesis of N-doped TiO2 with Different Nitrogen Concentrations by Mild Hydrothermal Method

Nitrogen-doped nanocrystalline anatase TiO2 powders with different nitrogen-doping concentrations were synthesized at 150°C and held for 2 h under an initial pressure of 3 MPa by the mild hydrothermal method with no postheat treatment. The X-ray photoelectron spectroscopy results confirmed that substitutional and interstitial nitrogen coexisted in the TiO2 lattice and formed Ti–N and Ti–O–N linkages, respectively. The visible light absorption of nitrogen-doped TiO2 in the wavelength 400 ∼ 550 nm was greatly enhanced compared with that of un-doped TiO2. Both optical absorption and photocatalytic efficiency were elevated with increased nitrogen-doping concentration.