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1.
Uniform TiO2/SiO2 composite films were prepared on ITO substrates by electrodeposition, and highly photoelectrocatalytic (PEC) activity of the composite films was observed toward the degradation of methyl orange (MO) in aqueous solutions. It was further found that their PEC activity was dependent on the electrodeposition parameters including deposition time, solution pH and SiO2 content. Under the optimized condition, the PEC degradation of MO on TiO2/SiO2 composite film electrode could be enhanced about 14 times relative to that on neat TiO2 film electrode. The high PEC activity of the TiO2/SiO2 composite film electrode was mainly attributed to the enhancement of the charge separation of photo-generated electron-hole pairs by the dispersion of SiO2 nanoparticles in the TiO2 matrix with the aid of the applied electric field.  相似文献   

2.
It has been shown that incorporation of TiO2 nanoparticles into hydrophobic coatings can show self-cleaning performance. Accelerated laboratory testing indicated that the coats retain their hydrophobic nature for an extended time period. In this paper, hydrophobic polydimethylsiloxane (PDMS)/TiO2 nanocomposite coatings with a TiO2 content of 0–40% were fabricated by simple blending of a PDMS dispersion with an aqueous TiO2 nanoparticle dispersion. Their long-term hydrophobicity and self-cleaning performance were investigated both in laboratory and real-world outdoor testing. As expected, TiO2 nanoparticle-based coatings exhibited better self-cleaning relative to the TiO2-free PDMS control coating as measured by methylene blue degradation testing. Excellent long-term hydrophobicity was observed in accelerated weathering testing when they contained the appropriate levels of TiO2 nanoparticles (i.e., 0–30%). However, the same PDMS/TiO2 coatings did not show self-cleaning performance, and instead, exhibited improved dirt pickup resistance, in outdoor exposure testing. Sustained hydrophobicity was observed in outdoor exposure testing for the clear films except when TiO2 levels were at 40%. The hysteresis of water contact angle (HWCA) significantly increased for the PDMS control coating, and water beading was lost as the film surface picked up dirt. In contrast, the TiO2-based coatings with appropriate TiO2 levels maintained a relatively low HWCA after outdoor exposure and no water sheeting on rainy days was observed. This result demonstrates that while photocatalytic TiO2 nanoparticles can maintain coating hydrophobicity upon outdoor exposure, long-term self-cleaning performance in polluted environments has not yet been achieved with this type of coating under real-world conditions.  相似文献   

3.
We report the fabrication of a metal-decorated hybrid nanocomposite with TiO2 encapsulation (Metal/SiO2@TiO2, Metal=Pt or Ru) using a simple surface-modification chemical process. Metal nanoparticles capped with polyvinylpyrrolidone were successfully assembled on functionalized SiO2 via electrostatic interactions, after which a thin layer of TiO2 was coated on the surface by the sol-gel process to avoid agglomeration of the coated silica spheres. Transmission electron microscopy studies confirmed that the metal nanoparticles were uniformly distributed throughout the surface of the SiO2 with a thin layer of TiO2. In addition, X-ray diffraction was employed to ensure the crystal structure of the uniformly coated thin TiO2 layer. Even after calcination at 500 °C, the structure remained intact, confirming high thermal stability. The photocatalytic activity of the metal-decorated SiO2/TiO2 nanocomposites was evaluated using the H2 evolution reaction. The Metal/SiO2@TiO2 catalysts show the photocatalytic water splitting efficiency for H2 generation (i.e., 0.14% for Pt/SiO2@TiO2 and 0.12% for Ru/SiO2@TiO2), while there is no generation of H2 on the Metal/SiO2 without a coating layer. These results indicate that the anatase crystalline coating layer has good thermal and chemical stability and plays a significant role in photocatalytic H2 production.  相似文献   

4.
The composite semiconductor photocatalyst TiO2/SiO2 was prepared by template-hydrothermal method using carbon spheres as the template. The structural and optical properties of TiO2/SiO2 were characterized by XRD, SEM, BET, UV–Vis DRS, TG-DTA, PL techniques. The formation of hydroxyl radical on the surface of TiO2/SiO2 was studied with terephthalic acid as the probe molecule, combined with fluorescence technique. The results showed that the specific surface area of TiO2/SiO2 composite was 327.9 m2/g, and the specific surface area of TiO2/SiO2 was larger than that of pure TiO2. Photocatalytic degradation of rhodamine B showed that TiO2/SiO2 composite oxide under visible light illumination 40 min, the degradation rate was 98.6 % and the degradation rate of pure TiO2 was only 11.9 %. The apparent first-order rate constant of TiO2/SiO2 was 33 times that of pure TiO2 and more than 6 times that of P25 when the molar ratio of Ti to Si was 1:1 under visible light irradiation. Moreover, it’s also as much as 5 times that of pure TiO2 and is more than 1 times that of P25 under UV light irradiation 25 min. Based on the experimental results, ·O2 ? and h+ were suggested to be the major active species which was responsible for the degradation reaction. The increased photocatalytic activity of TiO2/SiO2 may be mainly attributed to effectively suppressing the recombination of hole/electron pairs. After the photocatalyst TiO2/SiO2 was reused 5 times, the degradation rate of rhodamine B could reach 89.2 % under visible light irradiation. Moreover, The composite semiconductor photocatalyst TiO2/SiO2 was selective towards the degradation of rhodamine B.  相似文献   

5.
The photodegradation of BTEX (benzene, toluene, ethylbenzene and xylene) in a photocatalytic fluidized bed reactor with TiO2/SiO2 was investigated. The TiO2 film was prepared using the sol-gel method and coated onto silica-gel powder. The effects of the superficial gas velocity and SiO2 size on the photodegradation of BTEX were examined in a fluidized bed reactor. At steady-state operation, above 79, 79, 99, 98, and 98% removal efficiencies were achieved for benzene, toluene, ethylbenzene, m, p-xylene and o-xylene, respectively, under optimal conditions (2.0 U mf of superficial gas velocity and 1.43 of height/diameter ratio). The reaction product such as CO2 was detected and intermediate products such as benzaldehyde, malonic acid, acetaldehyde, and formic acid were identified from the photocatalytic reaction. Also, small amounts of benzoic acid and benzyl alcohol were found through analyzing the intermediate species adsorbed on the photocatalysts. The experimental results can lead to the development of an efficient photocatalytic treatment system that utilizes solar energy and TiO2/SiO2 photocatalysts.  相似文献   

6.
Composites with enhanced hydrophilicity were prepared by adding TiO2 or SiO2 nanoparticles during the in situ polymerization of methyl methacrylate (MMA) in poly(vinylidene fluoride) (PVDF). The hydrophilicities of the PVDF/PMMA/TiO2(SiO2) composites generated in this manner were characterized by contact angle measurements and atomic force microscopy (AFM). The hydrophilicity was dependent on nanoparticle content; it gradually increased with increasing TiO2 (or SiO2) content when the TiO2 (or SiO2) content was no more than 4 wt% of PVDF. A homogeneous dispersion of the TiO2 (or SiO2) nanoparticles in the composite matrix was observed in scanning electron microscope (SEM) images. Based on Fourier transform infrared (FTIR) spectra and wide angle X-ray diffraction (WAXD) analyses, the crystalline phase composition of PVDF was not influenced by the addition of TiO2 (or SiO2); PVDF crystallized predominantly in the α phase after in situ polymerization. Nevertheless, the nanoparticles can promote the formation of the β phase of PVDF in composites; the β-phase content increased with increasing TiO2 content, while it was almost independent of SiO2 content.  相似文献   

7.
Transparent nanocrystalline TiO2 thin films with high photocatalytic activity and photo-induced wettability were successfully deposited on a glass slide. Crystal phase transformations and particle size of TiO2 were investigated. Structural and morphological properties of the films were investigated. The photocatalytic activity of the TiO2 films was evaluated. It is found that the photocatalytic activity of TiO2 thin films is significantly decreased by increasing the annealing temperature, which results in a decrease in BET surface area and an increase in crystal size. In addition, increasing film thickness within a certain range significantly improves the photocatalytic activity without causing crack formation of the TiO2 films. Photocatalytic oxidation and photo-induced wettability conversion on the films were investigated. It is found that photo-induced hydrophilic conversion is observed even on the samples annealed at high temperature. The best photo-generated activities are obtained by optimization of dip-coating cycles and annealing temperatures.  相似文献   

8.
Structural design is of great importance to the performance of photocatalysts in environmental remediation. Therefore, micro/nanofibrous morphology and nanoporous local structures have been found to be beneficial to improve the photocatalytic activity. In this investigation, we report the design and fabrication of flexible and thermal stable nanoporous SiO2–TiO2 composite fibers as efficient photocatalysts. Combining electrospinning and modified Stöber techniques, core‐shell and mesoporous SiO2 fibers with high flexibility were fabricated and employed as the scaffold for supporting TiO2 nanoparticles. A nanoporous shell of TiO2 nanoparticles was then muffled over the SiO2 fibers to form core@dual‐shell SiO2–TiO2 composite fibers with hierarchically porous structure, which were conveniently patterned into a nonwoven, recyclable film. This nonwoven film exhibits better photocatalytic activity for Rhodamine B degradation under UV irradiation compared with some other TiO2‐based materials reported in recent years.  相似文献   

9.
A photodiode based on titanium dioxide:zinc oxide (TiO2:ZnO) was fabricated to be used in optoelectronics applications. The TiO2:ZnO composite film was prepared by the sol-gel method. The structural properties of the composite film were analyzed by scanning electron microscopy and X-ray diffraction techniques. It is seen that the film is formed from the nanoparticles. The photoresponsivity properties of the TiO2:ZnO composite film/p-type silicon diode were analyzed by phototransient current and photocapacitance techniques. The diode exhibited an optoelectronic device with obtained photovoltaic and photocapacitance behaviors. It is evaluated that the TiO2:ZnO composite film/p-type silicon diode can be used as a optoelectronic device in optic communications and photoelectric applications.  相似文献   

10.
Nano-sized bismuth sulfide (Bi2S3) and titanium dioxide (TiO2) with the orthorhombic and anatase tetragonal structures, respectively, were synthesized for application as catalysts for the reduction of carbon dioxide (CO2) to methane (CH4). Four double-layered dense films were fabricated with different coating sequences—TiO2 (bottom layer)/Bi2S3 (top layer), Bi2S3/TiO2, TiO2/Bi2S3: TiO2 (1 : 1) mix, and Bi2S3: TiO2 (1 : 1) mix/Bi2S3: TiO2 (1 : 1) mix—and applied to the photoreduction of CO2 to CH4; the catalytic activity of the fabricated films was compared to that of the pure TiO2/TiO2 and Bi2S3/Bi2S3 doubled-layered films. The TiO2/Bi2S3 double-layered film exhibited superior photocatalytic behavior, and higher CH4 production was obtained with the TiO2/Bi2S3 double-layered film than with the other films. A model of the mechanism underlying the enhanced photoactivity of the TiO2/Bi2S3 double-layered film was proposed, and it was attributed in effective charge separation.  相似文献   

11.
A poly(azulene)-TiO2 composite film (PAz-TiO2) was synthesized electrochemically by oxidation of azulene in an electrolyte medium containing TiO2 nanoparticles. Polymerization was performed under magnetic stirring in an acetonitrile solution containing tetrabutylammonium hexafluorophosphate as the electrolyte salt. Influence of the concentration of TiO2 in the reaction suspension on the electrochemical and optical properties and on the structure of the composite films was studied by cyclic voltammetry, ex situ Raman and FTIR reflection spectroscopy and in situ UV–vis and FTIR spectroelectrochemical techniques. Morphology of the composite films was studied by Scanning Electron Microscopy and the amount and distribution of the TiO2 nanoparticles within the polymeric matrix by Inductively Coupled Plasma Mass Spectrometry with laser ablation. Addition of TiO2 in the reaction suspension had a small catalytic activity for the polymerization of Az. Inclusion of TiO2 nanoparticles in PAz did not affect the voltammetric behavior or the chemical structure of the formed polymer films. However, a different chain conformation and morphology of the film was formed when synthesized in presence of TiO2 compared to the plain PAz film. It was also found that the film morphology was more homogeneous when the concentration of TiO2 was ≥10 mM in the polymerization solution than films polymerized without any TiO2.  相似文献   

12.
In this work, TiO2 nanoparticles were prepared by microemulsion (ME)/heat treated method and its photodecomposition property of methylene blue. Microemulsion (ME) consisted of water, cyclohexane and an anionic surfactant such as bis (2-ethylhexyl) sodium sulfosuccinate (AOT). Titanium tetraisopropoxide (TTIP) was dropped into the ME solution and then then TiO2 nanoparticles were formed by the hydrolysis reaction between TTIP in the organic solvent and the water in the core of ME. The smallest diameter of the particles was 20 nm in the system of cyclohexane with surfactant when the molar ratio of water to surfactant was 2. The effect of the process parameters (water/surfactant ratio, different temperatures) on the final characteristics has been investigated, in terms of structural phase and particle size. The TiO2 nanoparticles were characterized by means of X-ray diffraction, Transmission and scanning electron microscopy, Fourier-Transformed infrared and differential thermal analysis. TiO2 nanoparticles prepared in this condition were collected as amorphous powder, and converted to anatase phase at less than 350 °C, which is lower than the ordinal phase transition temperature. The crystallite size and crystallinity increase with an increase of heat treated s temperature. The particles are shown to have a spherical shape and have a uniform size distribution. The size of nanoparticles raises with an increase of water/surfactant ratio. In the photocatalytic decomposition of methylene blue, the photocatalytic activity is mainly determined by the crystallinity of TiO2. In addition, the TiO2 heat treated at 350 °C shows the highest activity on the photocatalytic decomposition of methylene blue (k = 1.7 × 10−2 min−1).  相似文献   

13.
Two methods were used to obtain a catalytically active oxide coating on the surface of titanium for the catalytic afterburning of diesel soot: plasma electrochemical formation of an oxide film on the surface of titanium and extraction pyrolytic deposition of the Li2Cu2(MoO4)3 compound. The Li2Cu2(MoO4)3/TiO2 + SiO2/Ti compositions synthesized by the single-step extraction pyrolytic treatment of the oxidized surface of titanium ensured a high burning rate of soot of ∼300°C. The subsequent deposition of Li2Cu2(MoO4)3 lowers the activity of the catalyst, due probably to the growth of molybdate phase crystallites and the filling of open oxide film pores. Double lithium-copper molybdate is able to reduce appreciably the concentration of CO in the oxidation products of soot. The advantages of these methods are the possibility of forming high-cohesion durable coatings on surfaces of any complexity, the simplicity of their implementation, and high productivity and low cost. The obtained results can be recommended for use in developing methods for creating composite coatings on catalytic soot filters.  相似文献   

14.
We demonstrate that spectral selective photocatalytic multilayer films can be tailored such that they can harness the full solar spectrum for enhanced photocatalytic gas-phase oxidation of acetaldehyde. Thin films of anatase TiO2 were deposited on a thin solar absorber TiAlN film to fabricate bilayer TiO2/TiAlN films by dc magnetron sputtering on aluminium substrates. The structural and optical properties of the films were characterized by X-ray diffraction and Raman spectroscopy. The reaction rate and quantum yield for acetaldehyde removal was measured and an almost tenfold enhancement of the quantum yield was observed for the TiO2/TiAlN films compared with the single TiO2 film, on par with enhancements achieved with new heterojunction photocatalysts. The results were interpreted by a temperature-induced change of the reaction kinetics. Absorption of simulated solar light illumination resulted in a temperature increase of the TIAlN film that was estimated to be at most 126 K. We show that a concomitant temperature increase of the top layer TiO2 by 100 K shifts the water gas-surface equilibrium from multilayer to submonolayer coverage. We propose that this is the main reason for the observed enhancement of the photocatalytic activity, whereby gas phase molecules may come in direct contact with free surface sites instead of having to diffuse through a thin water film. The implications of the results for judicious control of temperature and relative humidity for efficient gas-phase photocatalysis and exploitation of selective solar absorbing films are discussed.  相似文献   

15.
PSA [poly-(styrene-methyl acrylic acid)] latex particle has been taken into account as template material in SiO2 hollow spheres preparation. TiO2-doped SiO2 hollow spheres were obtained by using the appropriate amount of Ti(SO4)2 solution on SiO2 hollow spheres. The photodecomposition of the MB (methylene blue) was evaluated on these TiO2-doped SiO2 hollow spheres under UV light irradiation. The catalyst samples were characterized by XRD, UV-DRS, SEM and BET. A TiO2-doped SiO2 hollow sphere has shown higher surface area in comparison with pure TiO2 hollow spheres. The 40 wt% TiO2-doped SiO2 hollow sphere has been found as the most active catalyst compared with the others in the process of photodecomposition of MB (methylene blue). The BET surface area of this sample was found to be 377.6 m2g−1. The photodegradation rate of MB using the TiO2-doped SiO2 catalyst was much higher than that of pure TiO2 hollow spheres.  相似文献   

16.
Nanoparticles of SiO2 or TiO2 have been added in the preparation of heat-resisting concretes of two types. The major technical and chemical characteristics have been determined. Features have been found in some of the technological operations in making the concretes of both types, and also aspects of the physicomechanical properties. Higher chemical stability has been found for heat-resisting concrete containing TiO2 nanoparticles in an NaOH solution.  相似文献   

17.
SiO2/RuO2 modified high surface area titania dioxide nanoparticles prepared by hydrogen reduction were examined for their catalytic properties towards the photodegradation of methyl orange (MO), a common water pollutant in the textile industry. The modified materials present enhanced photocatalytic activity and can decompose the MO faster than the unmodified TiO2. Results showed that doping with RuO2 only offered a marginal benefit over TiO2 alone. On the other hand, modification of TiO2with RuO2 and SiO2 resulted in a marked increase in the rate constant and the photodegradation efficiency. These results are consistent with the unique structural, morphologoical and surface characteristics of the composite titania dioxide/ruthenium dioxide/silicon dioxide materials. The lower the average particle size and roughness of the materials, the higher the percentage of photodecomposition and the rate constant. The surface doping and modification effects thus appears synergetic to the charge separation process and the photocatalytic results are explained on the basis of the mechanism that involves efficient separation of electron–hole pairs induced by the silicon dioxide particles. This enhances the ability of the modified TiO2 particles to effectively capture protons. Results also show that the modified nanoparticles can be used repeatedly over a long time without loss of efficiency.  相似文献   

18.
In this study, polymeric hindered amine light stabilizers (HALS)-functionalized silica coated rutile titanium dioxide (TiO2-SiO2) nanoparticles were prepared by encapsulating commercially available TiO2-SiO2 nanoparticles with methyl methacrylate (MMA) and 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate (PMPM) copolymers via miniemulsion polymerization. The obtained functional (TiO2-SiO2/P(MMA-co-PMPM)) fillers have been added to polyurethane acrylate (PUA) oligomers to get UV-curable nanocomposite coatings. The functionalization of the TiO2-SiO2 nanoparticles with polymeric HALS has been confirmed by infrared spectra (IR), thermogravimetric (TG), and X-ray photoelectron spectroscopy (XPS) analyses. The scanning electron microscope (SEM) micrographs indicated that homogeneous dispersion of TiO2-SiO2/P(MMA-co-PMPM) composite nanoparticles resulted in improved transparency and mechanical properties of the UV-curable PUA coatings. Rhodamine B (Rh.B) photodegradation measurement confirmed the excellent UV-shielding performance of PUA nanocomposite coatings containing TiO2-SiO2/P(MMA-co-PMPM). The addition of TiO2-SiO2/P(MMA-co-PMPM) composite nanoparticles reduced the UV-curable PUA coatings degradation rate dramatically. The UV-aging resistance of PUA coatings was improved significantly. Over all, the combination of TiO2-SiO2 nanoparticles and polymeric HALS offers an attractive way to fabricate the multi-functional fillers, which can be used to improve the mechanical properties and UV-aging resistance of PUA coatings simultaneously.  相似文献   

19.
This study describes the effect of amphiphilic organic molecules (surfactants) in a sol on the physicochemical properties and photocatalytic activity of crystalline TiO2 nanoparticles prepared via a simple sol–gel route at high temperatures from 400 to 800 °C. Addition of polyoxyethylenesorbitan surfactant and polyethylene oxide and polypropylene oxide triblock copolymer as particle size inhibitors and pore directing agents into a stable titania sol affected the physicochemical properties of TiO2 nanoparticles such as their crystallographic structure, morphology, and defect structure. With the addition of the surfactants, the ratio of anatase and rutile crystal phases of TiO2 was controlled and an active anatase crystal phase was maintained during heat treatment up to 800 °C. Decrease in the sintering rate and inhibition in crystal growth were also observed, which resulted in higher surface area and inhibition of crystallite aggregation. Bulk defects in TiO2 were reduced while surface defects were increased as a result of the addition of surfactants. These physicochemical properties of TiO2 nanoparticles were correlated with photocatalytic degradation of 4-chlorophenol in water. The results revealed that high crystallinity, anatase crystal phase, high specific surface area, surface defects, and segregated morphology of TiO2 nanoparticles, which were induced by the addition of surfactants, were more advantageous for enhancing photocatalytic destruction of the model organic compound tested in the study.  相似文献   

20.
The capabilities of TiO2-coated materials for the inactivation and removal of algae were investigated. As supports for TiO2, non-woven fabric and Ni foam were chosen. To evaluate the ability of noble metal cocatalyst additions to facilitate the photocatalytic algal inhibition of TiO2-coated materials, Pd nanoparticles were deposited on non-woven fabric-supported TiO2 by photoelectrochemical deposition. The fabric-supported Pd/TiO2 showed higher inhibition activity for algal growth compared to the fabric-supported TiO2 without Pd. In addition, Ni foam-supported TiO2 also showed high inhibition activity, both in laboratory-scale tests and open-air tests. Therefore, TiO2-coated materials with suitable coating methods such as the use of cocatalysts or large surface area can substantially inhibit algal growth. The ability of the TiO2-coated materials to inhibit algae correlated well with their activity for the photocatalytic decolorization of methylene blue, suggesting a nonspecific mechanism in the breakdown of cellular structures.  相似文献   

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