Photocatalytic performance of pure anatase nanocrystallite TiO2 synthesized under low temperature hydrothermal conditions (original) (raw)
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Materials Letters, 2006
Transparent nanocrystalline pure anatase titania (nano-TiO 2 ) was synthesized by hydrothermal process at 200 -C. Photocatalytic activity of the nano-TiO 2 as in the form of sol was tested for degradation of Methylene Blue (MB) and Reactive Red 120 (RR-120) in aqueous solutions. Structural and physico-chemical properties of the nano-TiO 2 were characterized using powder XRD, SEM, BET, FT-IR and elemental analyses. Complete photodegradation of RR-120 was successfully achieved by aid of the nano-TiO 2 whereas MB was not degraded, maybe because of reversible color change in nano-TiO 2 sol/MB mixture after the UV irradiation was stopped. Potocatalytic activity of the synthesized the nano-TiO 2 for degradation of RR-120 was compared with Degussa P-25 at optimum conditions determined for RR-120. It was found that the nano-TiO 2 can be repeatedly used with higher photocatalytic activity than Degussa P-25. D
Science and Technology of Advanced Materials, 2007
Nanocrystalline TiO2 was synthesized by controlled hydrolysis of titanium tetraisopropoxide. The anatase phase was converted to rutile phase by thermal treatment at 1023K for 11 h. The catalysts were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), Fourier-transform infrared absorption spectrophotometry (FT-IR) and N2 adsorption (BET) at 77 K. This study compare the photocatalytic activity of the anatase and rutile phases of nanocrystalline TiO2 for the degradation of acetophenone, nitrobenzene, methylene blue and malachite green present in aqueous solutions. The initial rate of degradation was calculated to compare the photocatalytic activity of anatase and rutile nanocrystalline TiO2 for the degradation of different substances under ultraviolet light irradiation. The higher photocatalytic activity was obtained in anatase phase TiO2 for the degradation of all substances as compared with rutile phase. It is concluded that the higher photocatalytic activity in anatase TiO2 is due to parameters like band-gap, number of hydroxyl groups, surface area and porosity of the catalyst.
Turkish Journal of Chemistry
A novel approach was developed for the synthesis of high-dispersed anatase nano-TiO2 by a hydrothermal process without solvent at 200°C in 1 h. It was characterized using XRD, TEM, BET and elemental analysis. Nanoparticle-TiO2 was used as a photocatalyst by considering complete degradation of Rhodamine B (RB) dye. The photocatalytic reaction parameters such as photocatalyst amount, irradiation time and dye concentration were optimized and it was found that 0.125 wt% catalyst in 30 mg/L of RB aqueous solution is adequate for full degradation of RB in 50 min with 770 W/m 2 irradiation power. Photocatalytic activity of the nanoparticle-TiO2 was compared with Degussa P-25 at optimum catalysis conditions determined for the nanoparticle-TiO2. It was concluded that when compared to Degussa P-25, the nanoparticle-TiO2 can be repeatedly used with increasing photocatalytic activity. The results revealed that the photodegradation of RB proceeds by pseudo first-order reaction kinetics in which ...
Applied Catalysis B-environmental, 2005
Nanosized titanium dioxide photocatalysts with varying amount of anatase and rutile phases have been synthesized. Homogeneous precipitation of aqueous solutions containing TiOSO 4 with urea was used to prepare porous spherical clusters of anatase TiO 2. Photoactive titania powders with variable amount of anatase and rutile phases were prepared by heating of pure anatase in the temperatutre range 800-1150 8C. The structure evolution during heating of the starting anatase powders was studied by XRD analysis in overall temperature range of phase transformation. The morphology and microstucture characteristics were also obtained by HRTEM, BET and BJH. The spherical particle morphology of TiO 2 mixtures determined by SEM was stable in air up to 900 8C. The photocatalytic activity of the sample titania TIT85/825 heated to 825 8C in air, contained 77.4% anatase and 22.6% rutile was higher than that nanocrystalline anatase powder. Titania sample TIT85/ 825 reveals the highest catalytic activity during the photocatalyzed degradation of 4-chlorophenol in aqueous suspension. #
TiO2 ANATASE NANO-POWDER PREPARED BY A GAMMA RAY IRRADIATION AND PHOTOCATALYTIC ACTIVITY
The activities of Cu/TiO2 prepared by a gamma-ray irradiation and Cu-doped TiO2 sample prepared by a sol-gel method in photodegradation of methyl orange dye were examined. Structural and properties of the solids investigated have been studied using XRD, TEM, FTIR and BET techniques. The particles of the prepared TiO2 have high surface area and an anatase phase structure. The remaining concentrations of 10 ppm MO at PH 1 reaches 0.13 and 2.25 ppm after 120 min under UV irradiation using 0.15g/L of Cu/TiO2 and Cu-TiO2 catalysts, respectively.
SCIENCE CHINA …, 2012
This paper describes the effects of temperature on the complex intermediate processes from the precursor to the fully-crystallized anatase TiO 2 nanoparticles in hydrothermal synthesis. The anatase TiO 2 nanoparticles were synthesized in a wide temperature range below 230°C. The composition, morphology, and methylene blue (MB) decoloration characteristics of the obtained products were investigated by X-ray diffraction, Fourier transform infrared spectroscope, X-ray photoelectron spectroscope, and scanning and transmission electron microscope. The dehydrating polycondensation of Ti(IV)-hydrates and the decomposition of (NH 4 ) 2 Ti 3 O 7 intermediates with the temperature increase lead to the direct formation of anatase TiO 2 nanoparticles under the hydrothermal environments. The strong MB decoloration of the hydrothermal products obtained at the low (130°C) and high (180°C) temperatures are attributed to the adsorption of Ti(IV)-hydrates and the photocatalysis of anatase TiO 2 nanoparticles, respectively.
Solar Energy
Nanocrystalline anatase TiO 2 was prepared through modified non-hydrolitic sol-gel method by reacting TiCl 4 with benzyl alcohol at room temperature. The as synthesized anatase TiO 2 was calcined at 450°C for 5 h. The size and morphology of the as synthesized and calcined TiO 2 nanoparticles were characterized using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM) and BET surface area analysis. The band gap energy was measured using Kulbeka-Munk function and the electronic state of the prepared TiO 2 was determined by X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of the prepared samples was investigated by degrading 50 mg/L of 2,4-dichlorophenol (2,4-DCP) under natural sunlight as a source of irradiation. The obtained XRD patterns of both as synthesized and calcined TiO 2 matches completely with the tetragonal anatase phase of TiO 2 . The as synthesized sample showed higher surface area (147.34 m 2 /g) with particles size ranging between 3 and 6 nm than the calcined titania (64.92 m 2 /g) of prarticle size ranging between 11 and 15 nm. Both the TiO 2 samples showed excellent photocatalytic activity for the degradation of 2,4-DCP under natural sunlight irradiation. The complete removal of 2,4-DCP is obtained after 2.5 h for calcined TiO 2 and 3.5 h for as synthesized TiO 2 suggests that the prepared photocatalysts have the potential to degrade the organic pollutants. The degradation of 2,4-DCP followed first order kinetics.
An effective method for the preparation of high temperature stable anatase TiO2 photocatalysts
Applied Surface Science, 2016
An efficient, rapid and straightforward method for the preparation of nitrogen and fluorine (N, F) codoped high temperature stable anatase using a microwave pre-treatment is reported. Using a single source, ammonium fluoride (NH4F) for both nitrogen and fluorine, effective doping of the precursor titanium isopropoxide (TTIP) was possible. These samples were characterised for their structural and optical properties using X-ray diffraction (XRD), Fourier transform IR (FTIR), Raman spectroscopy and UV-vis spectroscopy. In terms of the anatase to rutile transition enhancement using a novel microwave assisted technique, the sample prepared in a composition Fagan et al, Applied Surface Science 371, 2016, 447-452 of 1:8 TiO2: NH4F at 1200 °C was seen to be most effective, having stable anatase present at 57.1 % compared to undoped TiO2 being 100 % rutile from 900 °C. This method involves the production of ammonium oxofluorotitanates (NH4TiOF3) at low temperatures. The inclusion of these intermediates greatly reduces the particle size growth and delays the anatase to rutile transition. The photocatalytic activity of these materials was studied by analysing the degradation of an organic dye, rhodamine 6G as a model system and the rate constant was calculated by pseudo-first-order kinetics. These results showed that the doped sample (0.0225 min-1) was three times more active than the undoped sample (0.0076 min-1) and over seven times faster than the commercial TiO2 photocatalyst standard Degussa P-25 calcined at 1200 °C (0.0030 min-1). The formation of intermediate compounds, oxofluorotitanates, was identified as the major reason for a delay in the anatase to rutile transition.
Synthesis of High-Temperature Stable Anatase TiO2 Photocatalyst
In the absence of a dopant or precursor modification, anatase to rutile transformation in synthetic TiO2 usually occurs at a temperature of 600-700 °C. Conventionally, metal oxide dopants (e.g., Al2O3 and SiO2) are used to tune the anatase to rutile transformation. A simple methodology is reported here to extend the anatase rutile transformation by employing various concentrations of urea. XRD and Raman spectroscopy were used to characterize various phases formed during thermal treatment. A significantly higher anatase phase (97%) has been obtained at 800 °C with use of a 1:1 Ti(OPr)4:urea composition and 11% anatase composition is retained even after calcining the powder at 900 °C. By comparison a sample that has been prepared without urea showed that rutile phases started to form at a temperature as low as 600 °C. The effect of smaller amounts of urea such as 1:0.25 and 1:0.5 Ti(OPr)4:urea has also been studied and compared. The investigation concluded that the stoichiometric modification by urea 1:1 Ti(OPr)4:urea composition is most effective in extending the anatase to rutile phase transformation by 200 °C compared to the unmodified sample. In addition, BET analysis carried out on samples calcined at 500 °C showed that the addition of urea up to 1:1 (Ti(OPr)4:urea) increased the total pore volume (from 0.108 to 0.224 cm3/g) and average pore diameter (11 to 30 nm) compared to the standard sample. Samples prepared with 1:1 Ti(OPr)4:urea composition calcined at 900 °C show significantly higher photocatalytic activity compared to the standard sample prepared under similar conditions. Kinetic analysis shows a marked increase in the photocatalytic degradation of rhodamine 6G on going from the standard sample (0.027 min-1, decoloration in 120 min) to the urea-modified sample (0.073 min-1, decoloration in 50 min).
Applied Catalysis B: Environmental, 2005
The UV-induced photocatalytic degradation of two azo dyes, Methyl Red and Methyl Orange, has been carried out in aqueous media in the presence of oleic acid (OLEA)-and tri-n-octylphosphine oxide (TOPO)-capped anatase TiO 2 nanocrystal powders (mean particle size: 6 nm) deposited onto a quartz substrate. The progress of photodegradation was followed by combining UV-vis absorption measurements with HPLC-MS analysis. The abatement efficiency for the two organic compounds was compared with that obtained with commercial TiO 2 P25 Degussa by evaluating a few significant variables, such as the dye chemical structure, pH of the solution, and catalyst surface status. Identification of several by-products by HPLC-MS analysis has allowed to propose a reasonable degradation pathway for both target molecules. Significantly, although all titania catalysts were effective in removing both parent dyes and their related derivatives, the degradation rate by the OLEA-capped TiO 2 nanocrystals was double as that obtained with both its TOPO-capped analogous and TiO 2 P25 Degussa. It is suggested that efficient catalysis strictly depends on microscopic mechanisms that occur at the catalyst surface, basically involving specific dye adsorption and local density of terminal -OH moieties. # Fig. 3. Percentages of decoloration for: (A) MeRed and (B) MeOr obtained with different titania photocatalysts (½dye t¼0 = 3 Â 10 À5 M; irradiation time: 120 min) at different pH values. The values were estimated from the relative decay of the visible absorbance maximum.