Visible light-irradiated degradation of alachlor on Fe-TiO<Subscript>2</Subscript> with assistance of H<Subscript>2</Subscript>O<Subscript>2</Subscript>

0.1 Fe/Ti mole ratio of Fe-TiO₂ catalysts were synthesized via solvothermal method and calcined at various temperatures: 300, 400, and 500 °C. The calcined catalysts were characterized by XRD, N₂-adsorption-desorption, UV-DRS, XRF, and Zeta potential and tested for photocatalytic degradation of alachlor under visible light. The calcined catalysts consisted only of anatase phase. The BET specific surface area decreased with the calcination temperatures. The doping Fe ion induced a red shift of absorption capacity from UV to the visible region. The Fe-TiO₂ calcined at 400 °C showed the highest photocatalytic activity on degradation of alachlor with assistance of 30 mM H₂O₂ at pH 3 under visible light irradiation. The degradation fitted well with Langmuir-Hinshelwood model that gave adsorption coefficient and the reaction rate constant of 0.683 L mg⁻¹ and 0.136 mg/L·min, respectively.     

Photocatalytic degradation of methylene blue and acetaldehyde by TiO<Subscript>2</Subscript>/glaze coated porous red clay tile

Nanosized TiO₂ sol synthesized by sol-gel method was successfully coated on the porous red clay tile (PRC tile) with micrometer sized pores. PRC tile was first coated with a low-firing glaze (glaze-coated PRC tile) and then TiO₂ sol was coated on the glaze layer. A low-fired glaze was prepared at various blending ratios with frit and feldspar, and a blending ratio glazed at 700 °C was selected as an optimum condition. Then TiO₂ sol synthesized from TTIP was dip-coated on the glazed layer (TiO₂/glaze-coated PRC tile), and it was calcined again at 500 °C. Here, these optimum calcination temperatures were selected to derive a strong bonding by a partial sintering between TiO₂ sol particles and glaze layer. Photocatalytic activity on the TiO₂/glaze-coated PRC tile was evaluated by the extent of photocatalytic degradation of methylene blue and acetaldehyde. Methylene blue with the high concentration of 150 mg/l on the surface of TiO₂/glaze-coated PRC tile was almost photodegraded within 5 hours under the condition of average UV intensity of 0.275 mW/cm₂, while no photodegradation reaction of methylene blue occurred on the glaze-coated PRC tile without TiO₂. Another photocatalytic activity was also evaluated by measuring the extent of photocatalytic degradation of gaseous acetaldehyde. The photodegradation efficiency in TiO₂/glaze-coated PRC tile showed about 77% photocatalytic degradation of acetaldehyde from 45,480 mg/l to 10,536 mg/l after the UV irradiation of 14 hours, but only about 16% in the case of the glaze-coated PRC tile.     

Effect of Ni Doping on the Structural and Optical Properties of TiO<Subscript>2</Subscript> Nanoparticles at Various Concentration and Temperature

TiO₂ nanopowders doped by Ni were prepared by sol–gel method. The effects of Ni ion (transition metal ion) doping on the physical structural and optical properties of TiO₂ have been investigated by X-ray diffraction (XRD), scanning electron microscopy and UV–Vis absorption spectroscopy. XRD results suggest that adding impurities has a significant effect on anatase phase stability, crystallinity, and particle size of TiO₂. The phase transformation from anatase to rutile was inhibited by Ni ion doped TiO₂ at temperatures 675 °C. The lowest band gap value (2.83 eV) was obtained for TiO₂-4%Ni sample calcined at 675 °C.     

Mesoporous TiO<Subscript>2</Subscript> microspheres synthesized via a facile hydrothermal method for dye sensitized solar cell applications

Mesoporous TiO₂ microspheres were successfully synthesized by a facile hydrothermal process and the obtained product was sintered at 450 °C. The sintered TiO₂ powder was characterised by powder X-ray diffraction pattern and the result shows pure anatase phase with good crystalline nature. The morphological image of field emission scanning electron microscopy and high resolution transmission electron microscopy shows spherical shape and size of the particles is around 100 to 300 nm. The Brunauer–Emmett–Teller surface area of synthesized TiO₂ material was 56.32 m² g^?1 and average pore width of synthesized materials was 7.1 and 9.3 nm. Bimodal pore structure of TiO₂ microspheres has been very effective for electrolyte diffusion into photoanode in dye sensitized solar cells. The synthesized anatase TiO₂ microsphere based dye sensitized solar cells have high surface area with light scattering effect to enhance the photocurrent and conversion efficiency than the commercial P25 photoanode material. The power conversion efficiency of synthesized mesoporous TiO₂ microspheres and commercial P25 material is 4.2 and 2.7 % respectively. Therefore bimodal mesoporous anatase TiO₂ microsphere appears to be a promising and potential candidate for dye sensitized solar cells (DSSC) application.     

Preparation and characterization of mesoporous TiO<Subscript>2</Subscript> thin film

Ordered hexagonal mesoporous TiO₂ thin film was prepared by the evaporation-induced self-assembly (EISA) method using triblock copolymer (Pluronic P123) and tetrabutyl orthotitanate (Ti(OBu ⁿ )₄, TBOT) in 1-methoxy-2-propanol (C₄H₁₀O₂, PGME) solvent. The arrangement of mesopores was identified by small-angle X-ray diffraction and transmission electron microscopy (TEM). The well-ordered hexagonal mesoporous TiO₂ had a high specific surface area of 239 m²/g and an average pore size of 6.3 nm. The structure of mesoporous TiO₂ thin film was anatase with a 5.1 nm crystallite. The absorption band shift of the mesoporous TiO₂ toward longer wavelengths as calcined at 350 °C due to the residual carbon.     

Synthesis and Photocatalytic Performance of Bi<Subscript>12</Subscript>O<Subscript>17</Subscript>Cl<Subscript>2</Subscript> Semiconductors Calcined at Different Temperatures

In the current investigation a series of oxygen-rich bismuth oxychloride Bi₁₂O₁₇Cl₂ samples through an ethylene glycol-solvothermal route were constructed at different calcination temperatures and fully characterized by X-ray diffraction patterns, scanning electron microscopy, Fourier transformed infrared spectroscopy, X-ray photoelectron spectroscopy, UV–Vis diffuse reflectance spectra, X-ray energy dispersion spectroscopy, and photoluminescence spectra. It was demonstrated that the calcination temperatures indeed had a crucial effect on the crystallinity, grain size, morphology, optical property, and charge carrier separation of Bi₁₂O₁₇Cl₂ series. These Bi₁₂O₁₇Cl₂ samples showed significantly improved photocatalytic degradation over dye Rhodamine B and colorless antibiotic tetracycline hydrochloride. Particularly, the best candidate, the sample 350 °C—Bi₁₂O₁₇Cl₂ could show apparent reaction rate constants that were nearly 28.2, 1.2 times of N–TiO₂ over Rhodamine B and tetracycline hydrochloride, respectively. The possible reason of enhancing photocatalytic performance by various Bi₁₂O₁₇Cl₂ samples calcined at different temperatures was discussed and major oxidative radicals maybe generated during photocatalytic processes were detected.     

Electrospun Sn-doped TiO2: Synthesis,structural, optical and catalytic performance as a function of Sn loading and calcination temperatures

A series of tin (Sn)-doped titania (TiO₂) composites were prepared by electrospinning and then calcined at temperatures of 500 °C, 600 °C, and 700 °C. The morpho-structural and optical properties of the resulting composites were assesed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy. In this way, the effect of the dopant amounts and calcination temperatures on the composition, morphology, band gap energy (E_g) of the prepared composites was established, as well as their photocatalytic activity towards ciprofloxacin (CIP) photodegradation. The kinetics of ciprofloxacin photodecomposition reactions was analyzed. Herein, it is reported that the nanostructured material based on ([1.5%]Sn:TiO₂) sintered at 500 °C shows a remarkable photocatalytic activity with a removal efficiency of about 100% and a rate constant of 9.685 × 10^?2 min^?1. The photocatalytic stability of this material was evaluated by reusability tests with five cycles under identical conditions for CIP photodegradation. In-depth structural investigations were undertaken to explain this remarkable photocatalytic activity towards water decontamination.     

P123 assisted morphology-engineered and hierarchical TiO<Subscript>2</Subscript> microspheres for enhanced photocatalytic activity

In this study, hierarchical titanium dioxide (TiO₂) microspheres with controlled morphology derived from calcination treatment of hierarchical titanate microspheres were fabricated. The obtained hierarchical TiO₂ microspheres with diameters of 1 to 2 µm were composed of polycrystalline anatase nanosheets with thickness of 10 nm. The morphology was manipulated by simply adjusting the molar ratio of tetrabutyl titanate/P123. At a low molar ratio of 17.04, TiO₂ microspheres composed of a large number of nanosheets closely packed together were obtained. At a high molar ratio of 34.08, TiO₂ hybrid architectures with polycrystalline anatase hierarchical microspheres and single-crystal anatase mesoporous (approximately 5 nm) nanospheres were obtained. Investigations on evolution formation revealed that P123 played a key role in the formation of a well-defined hierarchical structure. The photocatalytic performances of the obtained samples were investigated by the degradation of methylene blue and papermaking wastewater. When compared with commercial P25, the obtained hierarchical TiO₂ microspheres exhibit superior photocatalytic activity, high degradation efficiency, and good reproducibility. The product with hybrid architectures exhibited the highest photocatalytic activity. The chemical oxygen demand and the chroma removal rate of papermaking wastewater achieved 85.5 and 100%, respectively, after 12 h of photodegradation.     

One-pot synthesis of bifunctionalized TiO<Subscript>2</Subscript> mesoporous photocatalyst with visible light response

A series of Fe-doped SH/TiO₂ mesoporous photocatalysts have been firstly prepared by one-pot method using P123 as structure-directing agent. This bifunctionalized mesoporous TiO₂ possesses perfect anatase crystal structure and high surface area. The surface area of Fe-doped SH/TiO₂ mesoporous material is 4 times higher than that of P25. Based on the EPR results, it was found that trivalent Fe ions exist at low spin state and substitutes a part of Ti⁴⁺ ions into TiO₂ lattice. Fe-dropping in TiO₂ extends the adsorption band side of the resulting material to about 600 nm. Much high photocatalytic activity in the degradation of phenanthrene was obtained on the bifunctionalized mesoporous TiO₂ under visible light irradiation (λ > 420 nm), which is 6 times higher than that of pristine mesoporous TiO₂. The enhancement in the photocatalytic activity of bifunctionalized TiO₂ is ascribed to the extended absorption to visible light and strong interaction between SH-groups and PHE molecules.     

Functionalization of cotton fabric with nanosized TiO<Subscript>2</Subscript> coating for self-cleaning and antibacterial property enhancement

In this study, titanium dioxide (TiO₂) was used as coating compound to add self-cleaning and antibacterial functionality properties to the cotton fabric. TiO₂-consisting coating compounds were prepared at four different processing temperatures (20, 40, 60, and 80°C) in order to examine the influence of process temperature on average particle size. Among the prepared solutions, the one prepared at 80°C process temperature was selected for the dip coating application of the 100% cotton fabric, which formed a transparent nanosized TiO₂ film on the fibrous structure of fabric. Dip coating trials were done at five coating temperatures of 20, 40, 60, 80, and 100°C. TiO₂-coated and uncoated fabric samples were then tested to evaluate their self-cleaning and antibacterial activities. A self-cleaning activity test was conducted using uncoated and TiO₂-coated fabric samples which were stained with hot tea solution via dipping method. Stained fabric samples were illuminated under a solar simulator for the color changes to measure photocatalytic degradation of stain colors. Antibacterial performance of TiO₂-coated and uncoated fabric samples was determined against pure cultures of Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 29213.     

Synthesis of TiO2 microspheres by ultrasonic spray pyrolysis and photocatalytic activity evaluation

This work presents and discusses TiO₂ microspheres synthesized by ultrasonic spray pyrolysis. A simple setup allowed for the continuous production of TiO₂ nanocrystals. During the process, the particles experienced a short residence time (ca. 40 s) at the set temperature (700 °C), promoting phase stability and limited particle coarsening. As a result, porous anatase TiO₂ microspheres with crystallite size ～8 nm and specific surface area ～27 m² g^-1 were produced as soft spherical agglomerates of ～0.6 μm. Samples were analyzed using X-ray diffraction, BET specific surface area, SEM, TEM, XPS, and UV/Vis diffuse reflectance spectra, as well as in their photocatalytic activities. Photoactivity was evaluated through the degradation of the model contaminant acetaminophen under UV irradiation, and the results confirmed the superior performance of the synthesized TiO₂ microspheres, exceeding the commercial standard TiO₂ P25 by ca. 60% in terms of reactivity.     

Changes in the chemical composition of V2O5-loaded CVC-TiO2 materials with calcination temperatures for NH3-SCR of NOx

In this study, the aim was to evaluate the effect of calcinations temperature on the catalytic activity and chemical composition of V₂O₅/TiO₂. We prepared V₂O₅-loaded CVC-TiO₂ catalysts by a combination of chemical vapor condensation (CVC) and impregnation method at different calcination temperatures. These catalysts were analyzed for their ability to catalyze NH₃-based selective catalytic reduction of NO_x. Compared with V₂O₅ loaded P25-TiO₂ (commercial). V₂O₅/CVC-TiO₂ catalysts calcined above 200 °C exhibited better performance towards NO_x conversion than that by a commercial catalyst prepared using P25-TiO₂ (calcined at 500 °C). In addition, the NO_x conversion rate obtained with the sample calcined at 500 °C gave the best result (90 %) at a reaction temperature of 200 °C. From the XPS results, we observed that the V^4+/5+ ratio was well balanced when the V₂O₅ loaded CVC-TiO₂ sample was calcined at 500 ºC.     

Enhanced photocatalytic activity of electrospun TiO2/ZnO nanofibers with optimal anatase/rutile ratio

The photocatalytic characteristics of the TiO₂/ZnO nanofibers synthesized by electrospinning followed by calcinating at different temperatures to alter the anatase-to-rutile ratio are investigated. The results demonstrate that the photocatalytic activity of TiO₂/ZnO nanofibers is enhanced by optimizing the anatase/rutile ratio among the trade-off effects of the band-gap energy, the electron/hole recombination rate, and the surface area. When calcined at 650 °C, the TiO₂/ZnO nanofibers with optimal anatase/rutile ratio (48:52) balancing these trade-off effects have the highest photocatalytic efficiency both in the degradation of RhB in liquid and conversion of NO gas.     

Effect of surfactant in a modified sol on the physicochemical properties and photocatalytic activity of crystalline TiO<Subscript>2</Subscript> nanoparticles

This study describes the effect of amphiphilic organic molecules (surfactants) in a sol on the physicochemical properties and photocatalytic activity of crystalline TiO₂ nanoparticles prepared via a simple sol–gel route at high temperatures from 400 to 800 °C. Addition of polyoxyethylenesorbitan surfactant and polyethylene oxide and polypropylene oxide triblock copolymer as particle size inhibitors and pore directing agents into a stable titania sol affected the physicochemical properties of TiO₂ nanoparticles such as their crystallographic structure, morphology, and defect structure. With the addition of the surfactants, the ratio of anatase and rutile crystal phases of TiO₂ was controlled and an active anatase crystal phase was maintained during heat treatment up to 800 °C. Decrease in the sintering rate and inhibition in crystal growth were also observed, which resulted in higher surface area and inhibition of crystallite aggregation. Bulk defects in TiO₂ were reduced while surface defects were increased as a result of the addition of surfactants. These physicochemical properties of TiO₂ nanoparticles were correlated with photocatalytic degradation of 4-chlorophenol in water. The results revealed that high crystallinity, anatase crystal phase, high specific surface area, surface defects, and segregated morphology of TiO₂ nanoparticles, which were induced by the addition of surfactants, were more advantageous for enhancing photocatalytic destruction of the model organic compound tested in the study.     

Synthesis of TiO<Subscript>2</Subscript> Nanoparticles by Microemulsion/Heat Treated Method and Photodegradation of Methylene Blue

In this work, TiO₂ nanoparticles were prepared by microemulsion (ME)/heat treated method and its photodecomposition property of methylene blue. Microemulsion (ME) consisted of water, cyclohexane and an anionic surfactant such as bis (2-ethylhexyl) sodium sulfosuccinate (AOT). Titanium tetraisopropoxide (TTIP) was dropped into the ME solution and then then TiO₂ nanoparticles were formed by the hydrolysis reaction between TTIP in the organic solvent and the water in the core of ME. The smallest diameter of the particles was 20 nm in the system of cyclohexane with surfactant when the molar ratio of water to surfactant was 2. The effect of the process parameters (water/surfactant ratio, different temperatures) on the final characteristics has been investigated, in terms of structural phase and particle size. The TiO₂ nanoparticles were characterized by means of X-ray diffraction, Transmission and scanning electron microscopy, Fourier-Transformed infrared and differential thermal analysis. TiO₂ nanoparticles prepared in this condition were collected as amorphous powder, and converted to anatase phase at less than 350 °C, which is lower than the ordinal phase transition temperature. The crystallite size and crystallinity increase with an increase of heat treated s temperature. The particles are shown to have a spherical shape and have a uniform size distribution. The size of nanoparticles raises with an increase of water/surfactant ratio. In the photocatalytic decomposition of methylene blue, the photocatalytic activity is mainly determined by the crystallinity of TiO₂. In addition, the TiO₂ heat treated at 350 °C shows the highest activity on the photocatalytic decomposition of methylene blue (k = 1.7 × 10⁻² min⁻¹).     

Effect of preparation temperature on the formation of Sr2CeO4 phosphor particles in the spray pyrolysis

Sr₂CeO₄ phosphor particles were prepared by spray pyrolysis at various preparation temperatures. The effect of preparation temperatures on the morphology, crystal structure and photoluminescence characteristics of the post-treated Sr₂CeO₄ phosphor particles was studied. Phase pure Sr₂CeO₄ phosphor particles were not produced by spray pyrolysis without post-treatment. The optimum post-treatment temperature to produce the Sr₂CeO₄ phosphor particles with high photoluminescence intensity was 1,000 °C in spray pyrolysis. The spherical morphology of the as-prepared particles obtained at high preparation temperatures above 1,400 °C had maintained after post-treatment at 1,000 ‡C. The relative photoluminescence intensities of the Sr₂CeO₄ phosphor particles varied with the preparation temperatures in the spray pyrolysis. The as-prepared particles obtained by spray pyrolysis at preparation temperatures below 1,400 °C converted into phase pure Sr₂CeO₄ phosphor particles after post-treatment at 1,000 ‡C. The optimum preparation temperature of the as-prepared particles was 1,400 °C to produce the Sr₂CeO₄ phosphor particles with spherical shape and high photoluminescence intensity in the spray pyrolysis.     

Immobilization of TiO2 into Self‐Supporting Photocatalytic Foam: Influence of Calcination Temperature

Immobilization of photocatalytic powder is crucial to obtain industrially relevant purification processes. To achieve this goal, self‐supporting TiO₂ foams were manufactured by a polyacrylamide gel process. These gels were calcined at different temperatures to study the effect of the calcination temperature on foam characteristics (rigidity, crystallinity, and porosity) and its influence on photocatalytic activity. The results show that an optimal degradation is achieved for those foams calcined between 700 and 800°C. Calcination at higher temperatures results in a steep decrease in activity, explained by stability issues of the material due to formation of Na₂SO₄ phases and a larger rutile fraction.     

Synthesis of CaTiO3 and CaTiO3/TiO2 nanoparticulate compounds through Ca2+/TiO2 colloidal sols: Structural and photocatalytic characterization

CaTiO₃ and CaTiO₃/TiO₂ nanocompounds have been synthesized through a colloidal sol-gel route using Ca²⁺/TiO₂ nanoparticulate sols. The peptization time was determined so that as higher is the Ca²⁺ concentration, shorter is the peptization time. The obtained cryogels from the respective sols were calcined at different temperatures (300–900 °C) and the structural and morphological changes were characterized mainly by X-ray diffraction and transmission electron microscopy. In all cases, the formation of the CaTiO₃ phase was observed after calcination at temperatures as low as 500 °C. Mesoporous cryogels with nanoparticles with sizes below 50 nm were obtained and their photocatalytic activity changes as a function of the calcination temperature and the applied wavelength were determined. Quantum yield values revealed that either CaTiO₃ or the CaTiO₃/TiO₂ (0.4 M ratio) compound can be chosen as the most efficient photocatalyst at higher calcination temperatures and longer wavelengths, while TiO₂ is more effective at low calcination temperatures and shorter wavelengths.     

Facile preparation of Na-free anatase TiO2 film with highly photocatalytic activity on soda-lime glass

Na-free anatase TiO₂ film was prepared on soda-lime glass (SL-glass) from a TiF₄ aqueous solution upon addition of boric acid at 60 °C. It was found that the as-prepared TiO₂ film before calcination showed a higher photocatalytic activity than the calcined sample (500 °C). This could be attributed to the fact that the calcined TiO₂ film contained decent Na⁺ ions, which was diffused from the SL-glass substrate into the TiO₂ film during calcination, resulting in the decrease of photocatalytic activity.     

Synthesis of nickel catalysts supported on Zr-doped ordered mesoporous Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and their catalytic performance for low-temperature CO<Subscript>2</Subscript> reforming of CH<Subscript>4</Subscript>

A series of Zr-doped ordered mesoporous Al₂O₃ with various Zr contents were synthesized by evaporation-induced self-assembly strategy and the Ni-based catalysts supported on these Al₂O₃ materials were prepared by impregnation method. These catalysts with large specific surface area, big pore volume, uniform pore size possess excellent catalytic performance for the low-temperature carbon dioxide reforming of methane. The activities of these catalysts were tested in carbon dioxide reforming of methane reaction with temperature increasing from 500 to 650?°C and the stabilities of these catalysts were evaluated for long time reaction at 650?°C. It was found that when Zr/(Zr?+?Al) molar ratio?=?0.5%, the Ni/0.5ZrO₂–Al₂O₃ catalyst showed the highest activity, and exhibited superior stabilization compared to the Ni-based catalyst supported on traditional ordered mesoporous Al₂O₃. The “confinement effect” from mesoporous channels of alumina matrix is helpful to stabilize the Ni nanoparticles. As a promoter, Zr could stabilize the ordered mesoporous framework by reacting with Al₂O₃ to form ZrO₂–Al₂O₃ solid solution. Since ZrO₂ enhances the dissociation of carbon dioxide, more oxygen intermediates are given to remove the carbon formed during the reaction.