Surface morphology and active sites of TiO2 for photoassisted catalysis (original) (raw)
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Revista Facultad …, 2011
In this work, TiO 2 photocatalysts were synthesized using a conventional sol-gel and hydrothermal synthesis methods with steam pressure treatment. Photocatalysts were characterized by X-ray diffraction (XRD), diffuse reflectance spectra (DRS) and N 2 adsorption-desorption. The photoactivity of the samples was analyzed towards the photooxidation of the azo dye Orange II (Or-II) and phenol using different illumination setups to compare the activity features of photocatalysts. The effect of the synthesis variables such as the synthesis route, water/alcoxide and alcohol/alcoxide ratios, as well as the alcohol type was analyzed. TiO 2 photocatalysts obtained by hydrothermal synthesis have a better photoactivity than the particles synthesized by the chosen sol-gel route, reaching the Or-II degradation photoactivity of the commercial TiO 2 P25. On the other hand, the water/alcoxide ratio and alcohol type have a marked effect on the photoactivity of the hydrothermal synthesized TiO 2 , whereas the alcohol/alcoxide ratio does not have a relevant effect on the Or-II degradation photoactivity.
Journal of Molecular Catalysis A: Chemical, 2006
Sulfated (5 wt.%) TiO 2 and non-sulfated TiO 2 (rutile) modified by NH 4 VO 3 using incipient wetness impregnation technique to achieve a loading of 2 wt.% V 2 O 5 were thoroughly characterized by means of X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), UV-vis absorption spectroscopy, N 2 sorptiometry, particle size analyzer and pyridine-FT-IR that was used to investigate the acidity of the samples. Degradation of methylene blue (MB) dye was tested for the effectiveness of the samples. The results revealed that MB degradation was highly improved with V supported on TiO 2 -SO 4 and showed a conversion comprises of 98% after UV irradiation (emitting at 400 nm) for 70 min exceeding that of SO 4 free TiO 2 sample (78%) obtained at the same period of illumination. This was due to the large surface area (345 m 2 g −1 ), small crystallites size, reduced band-gap energy and presence of basic sites namely O 2 − and OH − moieties those take part in the reaction as additional oxidizing agents. The photocatalytic degradation of MB was found to follow first order rate kinetics. More information on the activity, surface texturing, kinetics and TOC removal were well evaluated, compared and discussed for all samples.
DESALINATION AND WATER TREATMENT, 2019
Various concentrations of dopants such as Mn, La, and Mo (0.25%-0.1%) were doped into TiO 2 particles. An improved sol-gel method was used to prepare these particles using titanium isopropoxide as a precursor and their photocatalytic activity was tested by studying the degradation of three different types of organic pollutants (acid blue 129, tinidazole, and metalaxyl). The prepared samples were characterized with standard analytical techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-Vis spectroscopy. The XRD analysis suggests the anatase phase with a crystalline nature. The SEM image of undoped TiO 2 exhibits high roughness and irregular shaped particles. The doped TiO 2 particles showed smaller size than undoped TiO 2 with regular shaped and high surface area. The doped TiO 2 particles also show lower band gap energy than undoped. The photocatalytic results indicate that TiO 2 with a dopant concentration of 0.75% for all metal ions shows the highest photocatalytic activity. Moreover, the Mn-doped TiO 2 (0.75%) degraded metalaxyl more efficiently as compared with other studied pollutants.
Development of Novel Photocatalytic Materials and Surfaces for Environmental Clean-up
2011
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 77K. 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 act...
advances-in-photocatalytic-materials-for-environmental-applications-.pdf
The growth of industry worldwide has extremely increased the generation and accumulation of waste by products. This has caused severe environmental problems that have become a major concern. Because of this, photo-catalytic pollutant degradation provided great opportunities and challenges in the field of environmental science. TiO2 nanoparticles have been extensively investigated for photo-catalytic decomposition of organic compounds. TiO2 is considered close to an ideal semiconductor for photo-catalysis but possesses certain limitations such as poor absorption of visible radiation and rapid recombination of photo generated electron/hole pairs. In this review article, various methods used to enhance the photo-catalytic characteristics of TiO2 including self-doping TiO2, doping TiO2 with metal and non-metal. Improving catalytic efficiency and exploring the reaction mechanism of photo-catalytic degradation of dyes as a model organic compound.
New Surface Aspects towards Photocatalytic Activity of Doped Supported Titanium Dioxide
International Journal of Photoenergy, 2016
The present work aims to synthesize nanoscale well dispersed TiO2/SiO2and TiO2/Al2O3nanoparticle photocatalysts via an impregnation method for the removal of methyl orange, which was used as a model compound of organic pollutant in wastewater, from an aqueous medium. Also within this frame work, La and Ce metals were loaded onto the surfaces of TiO2/SiO2and TiO2/Al2O3by an impregnation method to enhance the photocatalytic activity of the nanoparticles; the activities and physicochemical properties of the photocatalysts were compared before and after loading of metallic La and Ce. The oxide system was characterized by different techniques, including XRD, UV-Vis spectroscopy, FT-IR spectroscopy, SEM, and EDX spectroscopy. Finally, the optimal conditions to complete the photocatalytic oxidation of methyl orange dye were studied. This work holds promise for the efficient photodegradation of pollutants by nanoparticle photocatalysts.
Nanostructured mesoporous TiO2 particles with high specific surface area and average crystallite domain sizes in the range of 2 nm-30 nm have been synthesized via sol-gel and hydrothermal techniques. The as-produced nanoparticles have been characterized via X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area analysis, Fourier Transform Infra-Red, and Raman Spectroscopy as a function of temperature for their microstructure, morphology, optical, porosity and absorption properties. The as-synthesized TiO2 nanostructures were attempted as catalysts in the photocatalytic degradation of Rhodamine B and Sudan III dyes in a batch reactor under UV light. The results show that for catalysts calcined at 300 °C, ~100 % degradation of Sudan III dye was observed when Hydrothermal based catalyst was used whiles ~ 94 % degradation of Rhodamine B dye was observed using the sol-gel based catalysts. These synthesized TiO2 nanoparticles have promising potential applications in the degradation of a wide range of dye pollutants.
Applied Catalysis B: Environmental, 2013
A potential single crystalline photocatalyst b-Ga 2 O 3 with unique spherical morphology has been synthesized using a surfactant assisted hydrothermal process. Organic additive triblock co-polymer pluronic F127 was used as a soft template. The morphology of the material was investigated using scanning electron microscopy and it was confirmed that the nanospheres self-assembled to form microspheres with diameters in the range $1-3 mm. The crystal phase and chemical composition of the b-Ga 2 O 3 microspheres were revealed by X-ray diffraction and X-ray photoelectron spectroscopy.
The influence of titanium dioxide phase composition on dyes photocatalysis
Journal of Sol-Gel Science and Technology, 2011
A comparative study of TiO 2 powders prepared by sol-gel methods is presented. Titanium tetraisopropoxide was used as the precursor for the sol-gel processes. The effects of the annealing treatment on phase, crystallite size, porosity and photodegradation of dyes (methyl orange and methylene blue) were studied. The phase structure, microstructure and surface properties of the films were characterized by using X-ray diffraction (XRD) and Atomic Force Microscopy (AFM). The X-ray diffraction was used for crystal phase identification, for the accurate estimation of the anatase-rutile ratio and for the crystallite size evaluation of each polymorph in the samples. It was found that the only TiO 2 anatase phase of the synthesized TiO 2 develops below 500°C, between 600 and 800°C the anatase coexist with rutile and above 800°C only the rutile phase was found in the samples. Attention has been paid not only to crystal structures, but also to the porosity, the particle size and the photocatalytic properties. However, the annealing temperature was found to have significant influence on the photocatalytic properties. Different TiO 2 doctor blade thin films were obtained mixing the sol gel powder (100% anatase) and TiO 2 Aldrich with TiO 2 Degussa P25. The surfactant (Triton X100 or sodium dodecyl sulfate) affects the packing density of the particles during deposition and the photocatalytic degradation efficiency of the dyes. The photocatalytic degradation kinetics of methyl orange and methylene blue using TiO 2 thin film were investigated.