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1.
TiO2, TiO2/Ag and TiO2/Au photocatalysts exhibiting a hollow spherical morphology were prepared by spray pyrolysis of aqueous solutions of titanium citrate complex and titanium oxalate precursors in one-step. Effects of precursor concentration and spray pyrolysis temperature were investigated. By subsequent heat treatment, photocatalysts with phase compositions from 10 to 100% rutile and crystallite sizes from 12 to 120 nm were obtained. A correlation between precursor concentration and size of the hollow spherical agglomerates obtained during spray pyrolysis was established. The anatase to rutile transformation was enhanced with metal incorporations and increased precursor concentration. The photocatalytic activity was evaluated by oxidation of methylene blue under UV-irradiation. As-prepared TiO2 particles with large amounts of amorphous phase and organic residuals showed similar photocatalytic activity as the commercial Degussa P25. The metal incorporated samples showed comparable photocatalytic activity to the pure TiO2 photocatalysts.  相似文献   

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Commercial tiles are being produced in vast quantities. The main properties of tiles are well established but there is an increasing interest in producing ceramics with tailored-properties and advanced functionalities. One way of adding value to commercial tiles is to deposit a photocatalytic coating to obtain ‘smart’ tiles for environmental reasons, e.g. for the (photo) degradation of organic pollutants in air or in a liquid. Here, we show the manufacture of ‘smart’ tiles by formation of TiO2 coatings onto commercial tiles by a colloidal processing route based on the immersion of the substrate into a homogeneous aqueous ceramic suspension and its consolidation by agar thermogelation. The effect of the processing parameters (withdrawal rate, solid loading and gelling agent content) and the grain size on the photocatalytic activity of the final coated tiles is reported and discussed. Final coatings properties depend on the viscosity of the suspension, particle size, withdrawal rate, solid loading and gelling agent content, and hence, this dependence affects the photocatalytic activity of the coatings.  相似文献   

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TiO2 nanoparticles with a mean size of 20–30 nm were covered by ultrathin polydimethylsiloxane (PDMS) film, which shows hydrophobic properties. Surfaces consisting of the PDMS-coated TiO2 particles showed water contact angles close to 170°. In contrast to the hydrophobic films consisting of organic molecules, which can be photocatalytically decomposed on TiO2 in the presence of UV light, PDMS-coating on TiO2 was highly stable. The PDMS-coating completely suppressed the photocatalytic activity of TiO2. The unique properties of PDMS-coating can be exploited for UV protection layer and self-cleaning surfaces.  相似文献   

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A porous TiO2 glass-ceramics with high photo-oxidative activity was successfully obtained from the SiO2–Al2O3–B2O3–CaO–TiO2 glass system. Rutile-type TiO2 was observed in the crystallization temperature range of 973–1173 K. The band gap of the glass-ceramics coincided approximately with that of rutile-type TiO2. The photocatalytic activity of this glass-ceramics was about four times larger than that of a TiO2-coated photocatalyst fabricated by the sol–gel process. Furthermore, as this porous TiO2 glass-ceramics contained TiO2 in composition form, it could prevent peeling of the TiO2 from the substrate. As well, this glass-ceramics can be easily shaped into sheets, tubes, rods, etc.  相似文献   

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In this work, we investigated titanium dioxide (TiO2) nanotubes and CNT–TiO2 hybrid materials for the photocatalytic oxidation (PCO) of propene at low concentration (100 ppmv) in gaseous phase. The materials were prepared via sol–gel method using sacrificial multi-walled carbon nanotubes (CNT) as templates and subsequent heat treatments to obtain the desired crystalline phase (anatase, rutile or a mixture of both) and eventually to remove the carbon template. We also studied rutile nanotubes for the first time and demonstrate that the activity strongly depends on the crystalline composition, following rutile < anatase < anatase/rutile mixture. The enhanced activity of the anatase–rutile mixture is attributed to the decrease in the electron–hole pair recombination due to the multiphasic nature of the particles. The key result of this work is the exceptional performance of the CNT–TiO2 hybrid, which yielded the highest observed photocatalytic activity. The improved performance is attributed to synergistic effects due to the hybrid nature of the material, resulting in small anatase crystalline sizes (CNT act as heat sinks) and a reduced electron–hole pair recombination rate (CNTs act as electron traps). These results demonstrate the great potential of hybrid materials and stimulate further research on CNT-inorganic hybrid materials in photocatalysis and related areas.  相似文献   

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Pure TiO2 anatase particles with a crystallite diameters ranging from 4.5 to 29 nm were prepared by precipitation and sol–gel method, characterized by X-ray diffraction (XRD), BET surface area measurement, UV–vis and scanning electron microscopy (SEM) and tested in CO2 photocatalytic reduction. Methane and methanol were the main reduction products. The optimum particle size corresponding to the highest yields of both products was 14 nm. The observed optimum particle size is a result of competing effects of specific surface area, charge–carrier dynamics and light absorption efficiency.  相似文献   

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In this study, needle-shape TiO2 fibers were successfully fabricated inside a micro-channeled Al2O3-ZrO2 composite porous membrane system using sol-gel method. The micro-channeled Al2O3-ZrO2 composite was fabricated using the fibrous monolithic (FM) process. Pure anatase phase TiO2 was crystallized from the as-coated amorphous phase during calcination at 510 °C. The TiO2 fibers grew on the surface frame of the micro-channeled Al2O3-ZrO2 composite membrane and fully covered the inside of the micro-channeled pores. The specific surface area of the TiO2 coated membrane system was dramatically increased by over 100 fold compared to that of the non-coated system. The photocatalytic activity of the membrane was also assessed and was shown to very effectively convert organic materials. Thus, this novel membrane holds promise for use as an advanced filtration system.  相似文献   

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Rod-like N-doped TiO2/Ag composites were successfully synthesized by a modified sol–gel method, without adding any surfactants. The entire preparation differs from the traditional sol–gel synthesis of TiO2 that the reaction can get controlled by adjusting the flow speed of water vapor and NH3. Characterization results show that as-prepared samples were uniform nanorods with an average length of ca. 3 µm and a cross section diameter of ca. 150 nm. The rod-like structure was formed during the annealing process. A possible mechanism was proposed to illustrate the formation of rod-like Ag–N–TiO2. The degradation of methylene blue performed under visible light with the prepared nanorods as the photocatalyst demonstrated the photocatalytic activities of TiO2 can be improved by the synergistic effect of N doping and Ag modification. In addition, as-prepared TiO2-based photocatalyst exhibits a significantly enhanced photo-chemical stability after 5 catalytic cycles mainly due to the rod-like morphology. This indicated that they have some potential value in practical application.  相似文献   

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TiO2 particles supported on multi-walled carbon nanotubes (MWCNTs) were prepared using a sol–gel method to investigate their photocatalytic activity under simulated solar irradiation for the degradation of methyl orange (MO) in aqueous solution. The prepared composites were analyzed using XRD, SEM, EDS and UV–vis absorption spectroscopy. The results of this study indicated that there was little difference in the shape and structure of MWCNTs/TiO2 composite and pure TiO2 particles. The composite exhibited enhanced absorption properties in the visible light range compared to pure TiO2. The degradation of MO by MWCNTs/TiO2 composite photocatalysts was investigated under irradiation with simulated solar light. The results of this study indicated that MWCNTs played a significant role in improving photocatalytic performance. Different amounts of MWCNTs had different effects on photodegradation efficiency, and the most efficient MO photodegradation was observed for a 2% MWCNT/TiO2 mass ratio. Photocatalytic reaction kinetics were described using the Langmuir–Hinshelwood (L–H) model. The photocatalyst was reused for eight cycles, and it retained over 95.2% photocatalytic degradation efficiency. Possible decomposition mechanisms were also discussed. The results of this study indicated that photocatalytic reactions with TiO2 particles supported on MWCNTs under simulated solar light irradiation are feasible and effective for degrading organic dye pollutants.  相似文献   

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Pure anatase TiO2 photocatalyst with different Ag contents was prepared via a controlled and energy efficient microwave assisted method. The prepared material was further characterized by several analytical techniques like X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), surface area measurement (BET), Fourier transform-infrared spectroscopy (FT-IR), diffused reflectance spectroscopy (DRS), and thermogravimetric–differential thermal analysis (TGA–DTA). A 10 nm average crystallite size with nano-crystals of pseudo-cube like morphology was obtained for optimal (0.25 mol%) Ag doped TiO2. The present research work is mainly focused on the enhancement of degradation efficiency of methyl orange (MO) by doping of Ag in TiO2 matrix using UV light (365 nm). A 99.5% photodegradation efficiency of methyl orange was achieved by utilizing 0.25 mol% Ag doped TiO2 (1 g/dm3) at pH=3 within 70 min. Recyclability of photocatalyst was also studied, with the material being found to be stable up to five runs.  相似文献   

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Titanium dioxide thin films were deposited on quartz substrates kept at different O2 pressures using pulsed laser deposition technique. The effects of reactive atmosphere and annealing temperature on the structural, morphological, electrical and optical properties of the films are discussed. Growth of films with morphology consisting of spontaneously ordered nanostructures is reported. The films growth under an oxygen partial pressure of 3 × 10−4 Pa consist in nanoislands with voids in between them whereas the film growth under an oxygen partial pressure of 1 × 10−4 Pa, after having being subjected to annealing at 500 °C, consists in nanosized elongated grains uniformly distributed all over the surface. The growth of nanocrystallites with the increase in annealing temperature is explained on the basis of the critical nuclei-size model.  相似文献   

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In the present study, highly viscous alcoholic media, pentanol, hexanol and heptanol were used for electrophoretic deposition of ceramic (TiO2) nanoparticles as a new approach in the EPD process. Optical and scanning electron microscopy of the obtained deposits at 50 V revealed that layers with a fairly uniform microstructure were obtained in pentanol and hexanol while the layer formed in heptanol suffered from lack of uniformity and did not cover the substrate even at higher voltages up to 200 V. It was also revealed by the atomic force microscope (AFM) studies that surface roughness of the deposited layers decreased with increasing suspension viscosity. This behavior was directly attributed to high viscosity of heptanol which strongly hinders particles movement through the media. The low dielectric constant of heptanol was also considered to decrease particle deposition.  相似文献   

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A method for the preparation of efficient TiO2/multi-wall carbon nanotubes nanocomposite photocatalysts by precipitation of anatase TiO2 nanoparticles onto differently oxidized carbon nanotubes is presented. The precursor compound titanium(IV) bromide was hydrolyzed producing pure anatase phase TiO2 nanoparticles decorated on the surface of the oxidized carbon nanotubes. The oxidative treatment of the carbon nanotubes influenced the type, quantity and distribution of oxygen-containing functional groups, which had a significant influence on the electron transfer properties, i.e., the photocatalytic activity of the synthesized nanocomposites. The results of C.I. Reactive Orange 16 photodegradation in the presence of all the synthesized nanocomposites showed their better photocatalytic activity in comparison to the commercial photocatalyst Degussa P-25.  相似文献   

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The metal doped TiO2 was prepared with Fe(III), Co(II), Ni(II), Cu(II), Ag(I), La (III), Nd(III), Ho(III), and Y(III) as doped catalysts. These catalysts were carried by ceramic foams to enhance their photocatalytic efficiency, which was later studied with methylene blue (MB) and Escherichia coli (E. coli) as targets. The results suggested that the photocatalytic activities of TiO2 were enhanced when ceramic foams were used as catalyst carriers and that the photocatalytic efficiency could also be significantly increased by the dopants, especially by Ag(I) and rare earth. In the bactericidal activity testing, the inhibitory effect of TiO2 on E. coli was enhanced significantly when ceramic foams were used as carriers. Ag(I) doped TiO2 showed the greatest inhibition on E. coli. As to the E. coli cells treated by Ag(I) doped TiO2, the observation with a Scanning Electronic Microscope (SEM) suggested that the cells could no longer maintain their morphology and the spheroplasts were formed after the treatment.  相似文献   

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Nanostructural TiO2/modified multi-wall carbon nanotubes photocatalysts were prepared by hydrolysis of Ti(iso-OC3H7)4 providing chemical bonding of anatase TiO2 nanoparticles onto oxidized- or amino-functionalized multi-wall carbon nanotubes (MWCNT). The processes of functionalization of the MWCNT and the deposition of TiO2 influence the photocatalytic activity of the synthesized nanocomposites. The phase composition, crystallite size, and the structural and surface properties of the obtained TiO2/modified-MWCNT nanocomposite were analyzed from XRD, FEG-SEM, TEM/HRTEM and FTIR data, as well low temperature N2 adsorption. In the photocatalytic study, the TiO2/oxidized-MWCNT catalyst showed the highest and the TiO2/amino functionalized-MWCNT catalysts somewhat lower degradation rates, indicating that the enhancement of photocatalysis was supported by the more effective electron transfer properties of the oxygen- than amino-containing functional groups, which support the efficient charge transportation and separation of the photogenerated electron-hole pairs.  相似文献   

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