Influence of some sol-gel synthesis parameters of mesoporous TiO2 on photocatalytic degradation of pollutants (original) (raw)
Related papers
Boletín de la Sociedad Española de Cerámica y Vidrio, 2019
In this study, the relationship between morphology, porosity, and the photocatalytic activity of the anatase phase of TiO 2 was investigated. The synthesis of anatase samples was carried out by a modified sol-gel method, using two ionic surfactants (sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB)), and polyethylene glycol (PEG) as a nonionic surfactant, or no surfactant (NS). In addition, the photocatalytic activities of the anatase samples were investigated through adsorption experiments and photodegradation using methylene blue. The experimental results showed that the specific surface area of anatase samples increased as the pore size increased, following the order SDS > NS > CTAB > PEG, and the adsorption and photodegradation of methylene blue by the anatase samples increases in the same order. The spherical morphology and porosity of the mesoporous nanoparticles of the SDS sample improved the absorption of light in the visible region. The anatase sample SDS had a low band gap value (2.97 eV), the highest specific surface area (138.72 m 2 /g), and showed the highest photocatalytic activity.
Surface and Coatings Technology, 2008
A series of mesoporous TiO 2 films on borosilicate glass with ultrafine anatase nanocrystallites were successfully synthesized using a non-acidic sol gel preparation route, which involves the use of nonionic surfactant Tween 20 as template through a self assembly pathway. The microstructure of these TiO 2 films was characterized by XRD, SEM, HR-TEM, UV-Vis spectroscopy, and N 2 adsorption-desorption isotherm analysis. Their photocatalytic activities were investigated by using creatinine as a model organic contaminate in water. It was found that all mesoporous TiO 2 films prepared with Tween 20 exhibited a partially ordered mesoporous structure. The photocatalytic activity of the TiO 2 films could be remarkably improved by increasing Tween 20 loading in the sol at the range of 50% (v/v), which yielded large amount of catalyst (anatase) on the glass support and enhanced specific surface area. The optimum Tween 20 loading was 50% (v/v) in the sol, above which good adhesion between TiO 2 films and borosilicate glass could not be maintained. The final TiO 2 film (Tween 20: final sol = 50%,v/v) exhibits high BET surface area (∼ 120 m 2 /g) and pore volume (0.1554 cm 3 /g), ultrafine anatase nanocrystallinity (7 nm), uniform and crack free surface morphology, and improved photocatalytic activity.
mesoporous anatase TiO 2 nanoparticles and their photocatalytic activities
2017
Titanium dioxide (TiO2) materials have been the focus of many promising applications due to their low-cost, availability and biocompatible properties. In this study, mesoporous anatase TiO2 nanoparticles were synthesised using a green chemistry approach. This visible-light active photocatalyst was prepared via a simple and solvent free precipitation method at low temperatures using titanium tetraisopropoxide (TTIP) as a precursor and soluble starch as the template. The effect of initial solution pH and concentration of TTIP on surface morphology and photocatalytic activities of TiO2 nanoparticles were evaluated. Based on the results obtained, the TiO2 nanocatalyst prepared using 0.01 mol of TTIP under basic conditions revealed the best photocatalytic activity. The as-synthesised nanoparticles were further characterised using X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and nitrogen adsorption analysis (NAA). The XRD spectrum confirmed that the catalyst was comp...
Science of Sintering, 2015
The titanium dioxide (TiO2) nanopowders were produced by sol-gel technique from tetrabutyl titanate as a precursor, varying the temperature ?f calcination (from 500 to 550?C with the step of 10 ?C). XRPD results have shown that all synthesized nanopowders are dominantly in anatase phase. The analysis of the shift and linewidth of the most intensive anatase Eg Raman mode confirmed the XRPD results and added the presence of small amount of highly disordered brookite phase in all samples. The analysis of pore structure from nitrogen sorption experimental data described all samples as mesoporous, with mean pore diameters in the range of 1.5 and 4.5 nm. Nanopowder properties have been related to the photocatalytic activity, tested in degradation of the textile dye (C.I. Reactive Orange 16). The sample calcined at temperature of 510?C showed the best photocatalytic performance.
Journal of Colloid and Interface Science, 2015
TiO 2 photocatalysts with a mixture of different TiO 2 crystal polymorphs have customarily been synthesized hydrothermally at high temperatures using complicated and expensive equipment. In this study TiO 2 nanoparticles with a mixture of TiO 2 crystals were synthesized using a modified sol-gel method at low temperature. In order to form nanoparticles with different polymorphs a series of samples were obtained at pH 2, 4, 7 and 9. Raw samples were calcined at different temperatures ranging from 200 to 800°C to evaluate the effect of the calcination temperature on the physico-chemical properties of the samples. XRD results revealed that a mixture of anatase and brookite can be obtained in the as-synthesized samples and in those calcined up to 800°C depending on the pH used to obtain the final product. Indeed, a mixture of anatase brookite and rutile; or a sample with only rutile phase can be yielded through further calcination of the as-prepared samples at temperatures P600°C due to phase transformation. The photocatalytic performance of the samples with a mixture of anatase-brookite; anatasebrookite-rutile; and anatase-rutile (Degussa P25 TiO 2) was exquisitely investigated in the degradation of methylene blue solutions. The samples obtained at pH 2 and calcined at 200°C possessed the highest activity of all due to its superior properties. This study elucidates a facile method suitable for the synthesis of TiO 2 with different mixtures of TiO 2 polymorphs with desirable properties for various applications.
Applied Catalysis A: General, 2010
Porous TiO 2-anatase thin films were obtained by sol-gel method using dip-coating procedure onto glassslides and silicon wafers in order to study the effect of the porous structure on the photocatalytic properties. Titania sols were synthesized using titanium isopropoxide (TISP) with two types of complexant molecules (acetyl-acetone (AcAc) or acetic acid (AcOH)) and different types of pore-generating agents as: Pluronic F127 (F127), cetyl trimethyl ammonium bromide (CTAB), sodium dodecyl sulfate (SDS), polyethylene glycol hexadecyl ether (Brij56, Brij58). The coatings were characterised by different techniques as grazing X-ray diffraction (GXRD), spectral ellipsometry, Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). Maximum thickness around 280 nm, and refractive index as low as 1.68 were obtained, indicating that the surfactants allow obtaining porous films. GXRD and TEM analysis confirm the presence of a porous structure but not ordered. TiO 2 films obtained from AcAc or AcOH with Brij58 and F127 sols present specific surface areas between 28 and 68 m 2 /g. Photocatalytic activity was studied through the degradation of methyl orange in aqueous solution under UV light exposure. Methyl orange degradation increases with the film thickness up to a maximum value of 470 nm, beyond which the efficiency does not further increase. The photocatalytic activity depends on different parameters, such as porosity, film thickness and total surface exposed to illumination.
Journal of Solid State Chemistry, 2009
Mesoporous TiO 2 -CeO 2 nanopowders responding to visible wavelength were synthesized by using a surfactant assisted sol-gel technique. They were obtained using metal alkoxide precursors modified with acetylacetone (ACA) and laurylamine hydrochloride (LAHC) as surfactant. The samples were characterized by XRD, nitrogen adsorption isotherm, SEM, TEM, and selected area electron diffraction (SAED), respectively. The 95 mol% TiO 2 -5 mol% CeO 2 system yielded single anatase phase, however, further addition of the CeO 2 formed cubic CeO 2 structure while anatase TiO 2 decreased. Additions of 5 and 10 mol% CeO 2 increased the surface area, but those of 25, 50, and 75 mol% CeO 2 did not affect it very much. By using this mixed metal oxides system, TiO 2 can be modified to respond to the visible wavelength. The mixed metal oxides had catalytic activity (evaluating the formation rate of I 3 À ) about 2-3 times higher than pure CeO 2 , while nanosize anatase type TiO 2 materials had no catalytic activity under visible light. The catalytic activity was almost proportional to the specific surface area. The formation rate of I 3 À was much improved by changing the calcination temperature and calcination period. Highest catalytic activity in this study was obtained for the 50 mol% TiO 2 -50 mol% CeO 2 nanopowders calcined at 250 1C for 24 h. r 2004 Elsevier Inc. All rights reserved.
Journal of Solid State Chemistry, 2005
Nanocrystalline TiO 2 samples with mesoporous structure were prepared via a solvothermal treatment of surfactant-stabilized TiO 2 sols. The samples were obtained from media of different acidities including nitric acid, deionized water, and ammonia (denoted as HT-1, HT-2 and HT-3, respectively). These samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N 2-sorption (BET surface area), micro-Raman spectroscopy, infrared absorption spectroscopy (FT-IR) and Xray photoelectron spectroscopy (XPS). The photocatalytic activities of the samples were tested by the self-photosensitized degradation of an azo dye, Mordant Yellow 10 (MY), in aqueous solution under visible light irradiation. The results reveal that all three samples have high surface area and are pure anatase phase. The sample prepared in nitric acid medium possesses the most ideal mesoporous structure and also exhibits a blue shift in the Raman spectrum. All three samples show much higher photocatalytic activity than the commercial P-25. The activity order of the three samples is HT-14HT-24HT-3.
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.