Photocatalytic Activity Of TiO2 Powders Research Articles

Preparation and characterization of Ag-doped TiO2 and its application in catalytic degradation/densification of water pollutants

A series of Ag-doped TiO2 composite were obtained by impregnation of the commercial powder TiO2 by plasma-chemically synthesized silver nanoparticles. The phase structure and morphology of the samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effect of Ag content on the antibacterial and photocatalytic activity of nanoparticles was tested. Ag doping also improved the antibacterial and photocatalytic activity of TiO2 powder. The 2.0 mole % of Ag-doped TiO2 shows 96% degradation of methylene blue (MB) within 50 min under visible light irradiation and exhibits highest photocatalytic performance.

Study of the preparation of TiO2 powder by different synthesis methods

In this work, we present a study on the preparation of TiO2 powder employing different synthesis methods as molten salt, sol-gel, combustion and hydrothermal. The structural, morphological, optical and surface properties were studied in order to evidence the characteristic of the TiO2 powder. By the molten salt method, the TiO2 powder presented a rutile-phase crystal structure with particles of micrometric size and low superficial area. When the combustion and sol gel methods were employed, the TiO2 powder had an anatase phase with a crystallite size of ∼14 nm. Different morphologies such as nanocuboids, nanobelts, nanoparticles and interconnected nanobubbles were observed. The photocatalytic activity of TiO2 powder was assessed by the rhodamine B degradation. SG-TiO2 powder showed the highest photocatalytic efficiency in comparison with the rest of the samples. The presence of intrinsic defects and hydroxyl groups plays a fundamental role in the photocatalytic activity of the TiO2 powder.

Influence of pH on the formulation of TiO2 nano-crystalline powders with high photocatalytic activity

This paper describes the effect of synthesis conditions on the formation of anatase and rutile crystalline phases and photocatalytic activity of synthesised TiO2 phase. The synthesised powders were characterised by X-ray diffraction, Raman microscopy, Scanning Electron Microscopy and UV–Vis spectroscopy. Using these characterisation techniques, the structural, morphological and optical properties as a function of formulation pH were determined. Since photocatalysis is a surface process, the mass surface charge of the powders was also measured using a Faraday Cage connected to an electrometer. The structural, morphological, optical and surface properties were correlated with the photocatalytic activity of the formulated TiO2 powders.The influence of synthesis condition on the photocatalytic activity of TiO2 powders was determined by the degradation of Methylene Blue dye under both UV-A and visible light.

Influence of crystallinity and OH surface density on the photocatalytic activity of TiO2 powders

Abstract The aim of the work was to study the influence of crystallinity and OH surface density on the photocatalytic activity of two commercial and two home-prepared TiO 2 powders. The samples were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TG) and electron paramagnetic resonance (EPR) measurements. The photoactivity of the powders was tested employing the photodegradation of 4-nitrophenol (4-NP) and the selective oxidation of 4-methoxybenzyl alcohol (4-MBA) to 4-methoxybenzaldehyde ( p -anisaldehyde) under UV irradiation. An anti-correlation between oxidant power and selectivity of the various samples was found. A higher rate of 4-NP degradation was exhibited by the most crystalline commercial samples, whereas the highest selectivity toward the synthesis of p -anisaldehyde was obtained in the presence of the least crystalline and most hydroxylated home-prepared powders.

Sol-gel preparation of Fe-doped mixed crystal TiO2 powder and its photocatalytic activity for degradation of azo fuchsine under visible light irradiation

In this work, the Fe-doped mixed crystal TiO2 photocatalyst which can utilize visible light was prepared by sol-gel and heat-treated methods. During heat-treatment, the phase transformation of Fe-doped TiO2 powder occurs and the process is characterized by XRD and TG-DTA technologies. Otherwise, the sizes and shapes of Fe-doped and undoped TiO2 powders were also compared using TEM images. The azo fuchsine in aqueous solutions, as a model compound, was treated under visible light irradiation using Fe-doped mixed crystal TiO2 powders as photocatalyst. The results showed that, under visible light irradiation, the (0.25%) Fe-doped mixed crystal TiO2 powder heat-treated at 600°C for 3.0 h behaved very high photocatalytic activities for degradation of azo fuchsine. The remarkable improvement of the photocatalytic activity of TiO2 powder was elucidated through the cooperative effects of iron doping and phase transformation. The iron doping can restrain the recombination of photogenerated electron-hole pairs and the phase transformation can enhance the absorption of visible light. Furthermore, other influence factors such as azo fuchsine concentration, solution acidity, Fe3+ ion content and irradiation time were also studied. Thus, this method is applicable for the treatment of wastewater.

Enhanced photocatalytic activity of TiO2 powders doped by Fe unevenly

Abstract Two kinds of iron (III)-doped TiO2 powders photocatalysts were prepared by even doping and uneven doping methods, and were characterized by X-ray diffraction (XRD), TEM, UV–vis spectroscopy and X-ray photoelectron spectroscopy. The photocatalytic activities of TiO2-based nanoparticles were evaluated by the photocatalytic rate of methyl orange oxidation. TiO2 photocatalysts doped by Fe unevenly are the composite powders having the junction of n-type undoped TiO2 with p-type TiO2 doped by Fe evenly, was shown to have a much higher photocatlytic destruction rate than that of TiO2 photocatalysts doped by Fe evenly and undoped TiO2.

Influence of the Synthesis pH on the Properties and Activity of Sol-Gel TiO2Photocatalysts

The activity of titania photocatalysts is highly dependent on the synthesis procedure. This work reports a study of the correlation between the photocatalytic activity and the physicochemical and photoelectrochemical properties of sol-gelTiO2powders and electrodes synthesized using different pH values and temperatures. The activity of the materials has been evaluated using the decolorization of Reactive Orange 16 (RO16) as model reaction. In contrast with the large number of studies reporting the influence of the temperature, our results point out that preparation pH has even more influence on the crystalline phases and the photocatalytic activity ofTiO2powders and photocurrents of the electrodes. However, the effects on the activity and the photocurrents recorded after immobilization on a conducting support do not vary accordingly. Consequently, our results indicate that the measurement of the photocurrent in an electrolyte media is not a good indicator of the photocatalytic activity of the unsupported system.

Photocatalysis of methylene blue on titanium dioxide nanoparticles synthesized by modified sol-hydrothermal process of TiCl4

Titanium dioxide nanoparticles were synthesized by the hydrolysis and condensation of TiCl4, an economic titanium precursor, in a mixed solvent of iso-propyl alcohol and water. As-prepared powders were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), energy filtering transmission electron microscopy (EF-TEM). To examine the photocatalytic activity of the as-prepared TiO2, the photodegradation of MB which is a typical dye resistant to biodegradation has been investigated on TiO2 powders in aqueous heterogeneous suspensions. The photocatalytic activity of TiO2 powders prepared by the hydrolysis of TiCl4 in the mixed solutions of iso-PrOH/H2O exceeded that of commercial TiO2 powders. The apparent first order rate constants (k app) for the photodegradation of methylene blue (MB) showed a good correlation with the absorbance area obtained by UV-VIS DRS on wavelength in the limits of used lamp emission 300∼420 nm.

Effects of hydrothermal temperature and time on the photocatalytic activity and microstructures of bimodal mesoporous TiO2 powders

Bimodal nanocrystalline mesoporous TiO2 powders with high photocatalytic activity were prepared by a hydrothermal method using tetrabutylorthotitanate (TiO(C4H9)4, TBOT) as precursor. The as-prepared TiO2 powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and N2 adsorption–desorption measurements. The photocatalytic activity of the as-prepared TiO2 powders was evaluated by the photocatalytic degradation of acetone (CH3COCH3) under UV-light irradiation at room temperature in air. The effects of hydrothermal temperature and time on the microstructures and photocatalytic activity of the TiO2 powders were investigated and discussed. It was found that hydrothermal treatment enhanced the phase transformation of the TiO2 powders from amorphous to anatase and crystallization of anatase. All TiO2 powders after hydrothermal treatment showed bimodal pore-size distributions in the mesoporous region: one was intra-aggregated pores with maximum pore diameters of ca. 4–8nm and the other with inter-aggregated pores with maximum pore diameters of ca. 45–50nm. With increasing hydrothermal temperature and time, the average crystallite size and average pore size increased, in contrast, the Brunauer-Emmett-Teller (BET) specific surface areas, pore volumes and porosity steadily decreased. An optimal hydrothermal condition (180°C for 10h) was determined. The photocatalytic activity of the prepared TiO2 powders under optimal hydrothermal conditions was more than three times higher than that of Degussa P25.

Synthesis, Characterization and Photocatalytic Activity of TiO2 Powders Prepared Under Different Gelling and Pressure Conditions

Homogeneous TiO2 gel powders were prepared by hydrolysis and condensation of titanium(IV) isopropoxide with HCl or SnCl2 catalysts, by working under reduced pressure or in air. Ti(IV) alkoxide was previously modified by reaction with formic or acetic acid, used as chelating ligands, when gelation was performed in acidic catalysis. Crude TiO2 xerogels were purified by water reflux treatment in order to induce a low temperature crystallisation to the anatase phase. Both crude and purified TiO2 samples were characterised by XRD, FT-IR, SEM, and N2 adsorption analysis. Thermoanalyses (TG, DTA, DTG, TG-MS, TG-GC-MS) were carried out to quantify the residual organic components in the crude TiO2 gels and to obtain stoichiometric formulas to describe their chemical compositions. XRD data of purified TiO2 powders were processed by means of a Rietveld refinement procedure to determine TiO2 polymorphs, crystallite sizes and cell parameters, before their use in photocatalytic tests. The photoactivity of the purified TiO2 anatase powders was studied by using 4-nitrophenol degradation as “probe” reaction carried out in a batch and/or a membrane photoreactor. Samples prepared by using formic acid or SnCl2 were the most photoactive, whereas specimens gelled under vacuum treatment showed detrimental effects.

A photocatalytic performance of TiO2 photocatalyst prepared by the hydrothermal method

Anatase phase nanocrystalline TiO2 powders were prepared by hydrothermal method with the TTIP (titanium tetra isopropoxide) at 200 oC in a stirred autoclave system. The effects of synthesis conditions on the physical properties of catalyst were investigated by using XRD, SEM, DLS, DSC and BET. The TiO2 powders obtained from the optimum condition showed uniform spherical shape, crystalline structure, submicron size with a sharp size distribution and few agglomerates. The optimum synthesis conditions were obtained within the covered experimental ranges. The photocatalytic activity of TiO2 powders prepared by the hydrothermal method was tested for photooxidation of methyl orange.

Comparison of the photocatalytic activity of TiO2 powder with different particle size

Comparison of the photocatalytic activity of TiO2 powder with different particle size

Correlation of the crystal structure of titanium dioxide prepared from titanium tetra-2-propoxide with the photocatalytic activity for redox reactions in aqueous propan-2-ol and silver salt solutions

Titanium dioxide (TiO2) has been prepared by the hydrolysis of titanium tetra-2-propoxide, followed by calcination at various temperatures (Tc) up to 1000 °C. The content and crystallite size of anatase in the TiO2 powders increased upon increasing Tc up to 550 °C. In the Tc range 550–600 °C a mixture of anatase and rutile was obtained. A further increase in Tc resulted in TiO2 of rutile structure only. The photocatalytic activities of these TiO2 powders for redox reactions were evaluated in the following systems: (1) aqueous propan-2-ol solution, (2) aqueous Ag2SO4 solution and (3) aqueous Ag2SO4 solution containing propan-2-ol. The anatase TiO2 showed photocatalytic activity in all these systems, the activity increasing with crystal growth. In aqueous propan-2-ol solution the activity is dramatically enhanced by partial coverage of the TiO2 with platinum black. The photocatalytic activity of the rutile TiO2 powder was comparable to or even greater than that of anatase when the reaction system included the silver salt, but was negligibly small for aqueous propan-2-ol solution regardless of the partial Pt coverage.