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1.
Silica aerogels and TiO2/silica aerogel composite photocatalysts were synthesized by sol–gel technique at ambient pressure using orthosilioate and tetra-n-butyl titanate as precursors, respectively. The prepared composite photocatalysts were characterized by XRD, TEM, BET surface area, FT-IR and UV–vis absorption spectra. The results showed that the TiO2/silica aerogel composite photocatalysts possess high surface area. The addition of silica aerogels inhibited the grain growth and phase transformation of anatase to rutile during calcination. The TiO2/silica aerogel composite sample calcined at 500 °C with an optimal silica aerogel content of 7 wt.% afforded the highest photocatalytic activity. The photocatalytic degradation of 2-sec-butyl-4,6-dinitrophenol (DNBP) was investigated by using this novel TiO2/silica aerogel composite photocatalyst under solar light irradiation. The effects of irradiation time, pH, catalyst concentration, temperature and initial DNBP concentration were examined as operational parameters. The optimal operational parameters were found as follows: pH as solution pH 4.82, 8 g L−1 catalyst concentration, 20 °C, and 240 min irradiation time. The kinetics of DNBP degradation by TiO2/silica aerogel composite fit well a pseudo-first-order kinetic model. The repeatability of photocatalytic activity was also tested. This study showed the feasible and potential use of TiO2/silica aerogel composite photocatalysts in degradation of toxic organic contaminants. 相似文献
2.
K. Bubacz J. Choina E. Borowiak-Paleń A.W. Morawski 《Materials Research Bulletin》2010,45(9):1085-1091
Nitrogen modified titania photocatalysts (TiO2/N) were characterized using high resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), dynamic light scattering (DLS), Raman spectroscopy and BET surface area method. The presence of nitrogen in modified photocatalysts has been studied using FT-IR and XPS analyses. The influence of the calcination temperature in the range of 100-350 °C on nanocrystallite as well as particle size of the samples and their photocatalytic activity was investigated. The calcination of TiO2/N samples caused a growth of the particle size and an increase of their crystallinity. TEM studies present changes of the diameter and shape of TiO2 particles and nanocrystallites. The XRD and the Raman response of the samples confirmed an increase of the crystallinity of the samples when annealed at higher temperatures.The photocatalytic activity of the modified photocatalysts was determined using the reaction of phenol decomposition. It was shown that phenol decomposition rate was greatly influenced by pH of the solution. The highest phenol degradation using all the modified samples was observed for pH 7.1 which is close to the PZC point established for pristine TiO2 at pH 6.8. 相似文献
3.
Alberto Estrella González Maximiliano Asomoza Ulises Arellano Sandra Cipagauta Díaz Silvia Solís 《材料科学前沿(英文版)》2017,11(3):250-261
This study describes the development of mesostructured TiO2 photocatalysts modified with PO43- to improve its specific surface area and reduce the recombination rate of the electron—hole pairs. The mesoporous photocatalyst was successfully incorporated into a high specific surface area silica matrix by the hydrolysis reaction of tetraethyl orthosilicate (TEOS). Pluronic 123 and phosphoric acid were used as the directing agent for the structure of the mesoporous TiO2 and as a source of phosphorus, respectively. TiO2, P/TiO2, TiO2-SiO2 and P/TiO2-SiO2 materials were characterized by BET, XRD, TEM-EDS, FTIR and UV-vis DRS measurements. The photoactivity of TiO2-SiO2 nanocomposites containing 15 wt.% photocatalyst/silica was evaluated in the degradation reaction of anionic dyes with UV radiation. The proposed nanomaterials showed high potential for applications in the remediation of wastewater, being able to reuse in several cycles of reaction, maintaining its photoactivity and stability. The separation and recovery time of the material is reduced between cycles since no centrifugation or filtration processes are required after the photooxidation reaction. 相似文献
4.
Ho3+-Yb3+ co-doped and Ho3+-Yb3+-Li+ tri-doped TiO2 nanocrystals were prepared using the sol-gel method. Effects of the calcination temperature and Li+ ions doping on the structure and upconversion luminescence properties of Ho3+-Yb3+ co-doped TiO2 nanocrystals were investigated. The upconversion luminescence of nanocrystals was enhanced with the reduction of the crystal lattice symmetry and the crystallinity improvement of the matrix, which were facilitated by the calcination temperature change and Li+ ions doping. The lowest lattice symmetry and the best crystallinity of the matrix resulted in the maximum luminescence intensity. 相似文献
5.
《Advanced Powder Technology》2007,18(3):329-348
TiO2 was coated on nonporous transparent silica particles of 3.2 μm diameter by deposition of sol-gel-derived TiO2 nanoparticles. Effects of water concentration, feed rate of titanium tetraisopropoxide (TTIP) solution and amount of supplied TTIP solution on the amount of TiO2 coated on the silica particles were examined. Scanning electron microscopy observation confirmed that TiO2 was coated on the silica particles in the form of ‘nanoparticles’ by using this method. Because of that, even though the TiO2 surface area decreased due to sintering after calcination at high temperature to change the crystalline phase of TiO2 to the anatase phase, the final surface area was still much larger than that of the original silica particles. The results also showed that as the water concentration increased, the amount of coated TiO2 decreased. On the other hand, when the amount of supplied TTIP solution increased, the amount of coated TiO2 increased. It was also confirmed that the feed rate of TTIP solution had little effect on the amount of coated TiO2. The photocatalytic activities of the resulting TiO2-coated silica particles were also evaluated by the photocatalytic decomposition of 2,4-dinitrophenol as a model substance. The results showed that the photocatalytic activity of the particles is not a function of the total surface area, but of the surface area in which anatase phase TiO2 is exposed to the reaction space. The sedimentation velocity of the TiO2-coated silica particles becomes about 5 orders of magnitude faster than that of the primary particles of the TiO2. This indicates that the handling of the TiO2 was also improved considerably by coating on the silica particles. 相似文献
6.
Wei Zhou Ting Li Jianqiang Wang Yang Qu Kai Pan Ying Xie Guohui Tian Lei Wang Zhiyu Ren Baojiang Jiang Honggang Fu 《Nano Research》2014,7(5):731-742
Small Ag clusters confined in the channels of ordered mesoporous anatase TiO2 have been fabricated via a vacuum-assisted wet-impregnation method, utilizing well-ordered mesoporous anatase TiO2 with high thermal stability as the host. The composites have been characterized in detail by X-ray diffraction, X-ray photoelectron spectroscopy X-ray absorption fine structure (XAFS) spectroscopy, N2 adsorption, UV-visible diffuse reflectance spectroscopy and transmission electron microscopy. The results indicate that small Ag clusters are formed and uniformly confined in the channels of mesoporous TiO2 with an obvious confinement effect. The presence of strong AgO interactions involving the Ag clusters in intimate contact with the pore walls of mesoporous TiO2 is confirmed by XAFS analysis, and favors the separation of photogenerated electron-hole pairs, as shown by steady-state surface photovoltage spectroscopy and transient-state surface photovoltage measurements. The ordered mesoporous Ag/TiO2 composites exhibit excellent solar-light-driven photocatalytic performance for the degradation of phenol. This is attributed to the synergistic effects between the small Ag clusters acting as traps to effectively capture the photogenerated electrons, and the surface plasmon resonance of the Ag clusters promoting the absorption of visible light. This study clearly demonstrates the high-efficiency utilization of noble metals in the fabrication of high-performance solar-light-driven photocatalysts. 相似文献
7.
Lanthanide oxide-doped titanium dioxide: Effective photocatalysts for the degradation of organic pollutants 总被引:8,自引:0,他引:8
K. T. Ranjit H. Cohen I. Willner S. Bossmann A. M. Braun 《Journal of Materials Science》1999,34(21):5273-5280
A series of lanthanide oxide-doped titanium dioxide photocatalysts Ln2O3/TiO2 (Ln3+ = Eu3+, Pr3+, Yb3+) were prepared. The photocatalysts reveal a substantially enhanced activity for the degradation of organic pollutants, as compared to undoped TiO2. The photodegradation processes of p-nitrobenzoic acid, (1), p-chlorophenoxyacetic acid, (2), aniline, (3), salicylic acid, (4), and trans-cinnamic acid, (5), with the different photocatalysts was examined. The photodegradation of (1)–(5) is significantly faster with Ln2O3/TiO2 photocatalysts and leads to complete mineralization of the organic compounds. The high activity of the Ln2O3/TiO2 photocatalysts is attributed to the enhanced association of the functionalized organic pollutants to lanthanide-ion surface sites. 相似文献
8.
Hierarchical TiO2/SnO2 Hollow Spheres Coated with Graphitized Carbon for High‐Performance Electrochemical Li‐Ion Storage
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A self‐templated strategy is developed to fabricate hierarchical TiO2/SnO2 hollow spheres coated with graphitized carbon (HTSO/GC‐HSs) by combined sol–gel processes with hydrothermal treatment and calcination. The as‐prepared mesoporous HTSO/GC‐HSs present an approximate yolk‐double–shell structure, with high specific area and small nanocrystals of TiO2 and SnO2, and thus exhibit superior electrochemical reactivity and stability when used as anode materials for Li‐ion batteries. A high reversible specific capacity of about 310 mAh g?1 at a high current density of 5 A g?1 can be achieved over 500 cycles indicating very good cycle stability and rate performance. 相似文献
9.
Zuoli He Wenxiu Que Yucheng He Jing Chen Haixia Xie Gangfeng Wang 《Journal of Materials Science》2012,47(20):7210-7216
Nanosphere assembled mesoporous TiO2 products with large specific surface area and high crystallinity were prepared by a combined hydrothermal and post-heating process, where absorbent cotton was used as a template. The as-synthesized samples were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 adsorption/desorption, Fourier transform infrared spectroscopy, and UV–Vis diffuse reflectance spectroscopy. Results indicate that the obtained products exhibit a unique 3D mesoporous structure and demonstrate a significantly improved photocatalytic performance, which can be attributed to concurrent effects of high surface area, the presence of accessible mesopores channels and high crystallinity. 相似文献
10.
This work demonstrated that mesoporous TiO2 (meso-TiO2) with controllable mesoporous and crystalline structures can be facilely prepared by using poly (ethylene glycol) (PEG) as structure-directing (SD) agent and peroxotitanic acid (PTA) as precursor. Meso-TiO2 with high specific surface area (157 m2?g-1), pore volume (0.45 cm3?g-1) and large mesopore size of 13.9 nm can be obtained after calcination at 450°C. Such meso-TiO2 also shows relatively high thermal stability. BET surface area still reaches 114 m2?g-1 after calcination at 550°C. In the synthesis and calcination process, PEG that plays multiple and important roles in delivering thermally stable and tunable mesoporous and crystalline structures shows to be a suitable low-cost SD agent for the controllable preparation of nanocrystalline meso-TiO2. The photocatalytic activity tests show that both high surface area and bi-crystallinity of obtained meso-TiO2 are important in enhancing the performance in photo-decomposing Rhodamine B in water. 相似文献
11.
The synthesis of rutile (TiO2) nanostructured materials at low temperature from TiCl4 aqueous solution was described. TiO2 coatings on polystyrene (PS) particles were prepared by layer-by-layer assembly technique. The samples were characterized
by DTA-TG, SEM, XPS, TEM and XRD techniques. The experimental results showed that pure rutile-TiO2 coatings with nanocrystal structure were synthesized at 100 °C. On the surface of PS particles, sphere-type TiO2 coatings exhibited uniform shape and a narrow size distribution. The amount of TO2 (wt%) and shell thickness of particles increased with the adding of coating layers. Hollow TiO2 spheres were obtained by calcination at 450 °C. TiO2/PS with 2 coating layers showed higher degradation rate. The photocatalytic activity of hollow TiO2 spheres was higher than that of TiO2/PS. 相似文献
12.
Yuxin Zhang Ming Huang Fei Li Han Zhao Zhongquan Wen 《Journal of Materials Science》2013,48(19):6728-6736
In this work, TiO2 nanoparticles/Cu nanowires (TiO2NPs@CuNWs) binary composites with tunable coverage of TiO2 nanoparticles were prepared by a facile method of mixing oleic acid-modified TiO2 nanoparticles with as-prepared Cu nanowires. Characterization studies including X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and high-resolution transmission electron microscopy were applied to investigate the structure and morphology of the as-synthesized TiO2NPs@CuNWs binary composites. The photocatalytic activity of TiO2NPs@CuNWs binary composites was examined by photodegradation of methyl orange. The enhanced photocatalytic efficiency of TiO2NPs@CuNWs nanocomposites was ascribed to the moderate specific surface area, mesoporous structures, and the electron sink effect of the Cu nanowires. In principle, our investigation indicates that the TiO2@Cu self-assembled nanostructures can be a promising candidate of composite photocatalysts. 相似文献
13.
Qing Yuan Nan Li Wangchang Geng Yue Chi Xiaotian Li 《Materials Research Bulletin》2012,47(9):2396-2402
A simple and efficient method has been developed to fabricate core–shell structured Fe3O4@SiO2@meso-TiO2 nanocomposites with enhanced photocatalytic activity in this paper. The as-made core–shell structure is composed of a central magnetite core with a strong response to external fields, an interlayer of SiO2, and an outer layer of TiO2 nanocrystals with mesoporous structure. Fe3O4@SiO2 was obtained through a sol–gel process. To avoid magnetic loss caused by magnetite core phase transition and particle reunion, we adopt a mild synthetic method to get anatase shell instead of traditional high-temperature calcination. The structure of resulting composites was characterized and their photocatalytic activities were also tested. Fe3O4@SiO2@meso-TiO2 composite exhibits higher photocatalytic activities than Fe3O4@SiO2@solid-TiO2 for the degradation of rhodamine B in aqueous suspension. The excellent photocatalytic activities are ascribed to the high surface area and pore volume created by mesoporous anatase shell. 相似文献
14.
Hiroshi Uchida Mehul N. Patel Gaurav Gupta Keith P. Johnston 《Thin solid films》2010,518(12):3169-9566
Highly ordered mesoporous titanium dioxide (titania, TiO2) thin films on indium-tin-oxide (ITO) coated glass were prepared via a Pluronic (P123) block copolymer template and a hydrophilic TiO2 buffer layer. The contraction of the 3D hexagonal array of P123 micelles upon calcination merges the titania domains on the TiO2 buffer layer to form mesoporous films with a mesochannel diameter of approximately 10 nm and a pore-to-pore distance of 10 nm. The mesoporous titania films on TiO2-buffered ITO/glass featured an inverse mesospace with a hexagonally-ordered structure, whereas the films formed without a TiO2 buffer layer had a disordered microstructure with submicron cracks because of non-uniform water condensation on the hydrophobic ITO/glass surface. The density of the mesoporous film was 83% that of a bulk TiO2 film. The optical band gap of the mesoporous titania thin film was approximately 3.4 eV, larger than that for nonporous anatase TiO2 (~ 3.2 eV), suggesting that the nanoscopic grain size leads to an increase in the band gap due to weak quantum confinement effects. The ability to form highly-ordered mesoporous titania films on electrically conductive and transparent substrates offers the potential for facile fabrication of high surface area semiconductive films with small diffusion lengths for optoelectronics applications. 相似文献
15.
Photocatalytic degradation of phenol in water was examined using Pr-doped TiO2 nanoparticles. These photocatalysts were synthesized by an acid-peptized sol–gel method from titanium tetra-isopropoxide with different concentrations of Pr(III) dopant and calcination temperatures. Several tools such as XRD, BET surface area, SEM, and EDX, were used to evaluate particle structure, size distribution, and composition. The optical absorption properties of the prepared particles were also measured. Photocatalytic activity of the particles was studied in a batch reactor containing phenol solution with 400 W UV irradiation. Parameters affecting photocatalytic process such as the catalyst crystallinity, light absorption efficiency, the dosage of catalyst, dopant and phenol concentrations were investigated. The Pr-doped TiO2 showed high activity for photocatalytic degradation of phenol. The presence of Pr ions in the TiO2 particles would cause a significant absorption shift towards the visible region. The degradation process was optimized using 1 g/L Pr-doped TiO2 with a Pr(III) concentration of 0.072 mol% after 2 h irradiation. It was shown that photodegradation followed a pseudo-first-order kinetics and the rate constant changed with phenol concentration. 相似文献
16.
The structural, morphological, and optical properties of the sol–gel derived TiO2 nanoparticles at different pH and calcination temperature were investigated in the present study. X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM), UV–Visible(Vis) spectroscopy, energy dispersive studies (EDS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoluminescence (PL) spectroscopy, BET surface area analysis, and Barrett-Joyner-Halenda (BJH) pore size distribution and pore volume analysis were used to characterize the prepared TiO2 photocatalyst. The range of crystallite size and band gap of the synthesized TiO2 samples were in the range of 20–80?nm and 2.5–3.2?eV respectively. The photocatalytic performance of prepared TiO2 photocatalysts was evaluated by photodegradation of Methylene Blue (MB) solution under simulated solar irradiation. Results illustrate that the synthesized TiO2 exhibits visible light activity at higher calcination temperature. Crystallinity and surface area plays a vital role in the overall performance of the prepared TiO2 photocatalyst. 相似文献
17.
Ke Wang Baodan Liu Jing Li Xiaoyuan Liu Yang Zhou Xinglai Zhang Xiaoguo Bi Xin Jiang 《材料科学技术学报》2019,35(4):615-622
TiO_2 nanostructures with strong interfacial adhesion and diverse morphologies have been in-situ grown on Ti foil substrate through a multiple-step method based on conventional plasma electrolytic oxidation(PEO) technology, hydrothermal reaction and ion exchange process. The PEO process is critical to the formation of TiO_2 seeding layer for the nucleation of Na_2Ti_3O_7 and H_2Ti_3O_7 mediates that are strongly attached to the Ti foil. An ion exchange reaction can finally lead to the formation of H_2Ti_3O_7 nanostructures with diverse morphologies and the calcination process can turn the H_2Ti_3O_7 nanostructures into TiO_2 nanostructures with enhanced crystallinity. The morphology of the TiO_2 nanostructures including nanoparticles(NP), nanowhiskers(NWK), nanowires(NW) and nanosheets(NS) can be easily tailored by controlling the NaOH concentration and reaction time during hydrothermal process. The morphology, composition and optical properties of TiO_2 photocatalysts were analyzed using scanning electron microscope(SEM), X-ray diffraction(XRD), photoluminescence(PL) spectroscopy and UV–vis absorption spectrum. Photocatalytic tests indicate that the TiO_2 nanosheets calcined at 500?C show good crystallization and the best capability of decomposing organic pollutants. The decoration of Ag cocatalyst can further improve the photocatalytic performance of the TiO_2 nanosheets as a result of the enhanced charger separation efficiency. Cyclic photocatalytic test using TiO_2 nanostructures grown on Ti foil substrate demonstrates the superior stability in the photodegradation of organic pollutant, suggesting the promising potential of in-situ growth technology for industrial application. 相似文献
18.
P. S. Niphadkar S. K. Chitale S. K. Sonar S. S. Deshpande P. N. Joshi S. V. Awate 《Journal of Materials Science》2014,49(18):6383-6391
TiO2–SiO2 mesoporous composite photocatalysts with different proportions (in wt%) of TiO2 and SiO2 (TiO2–SiO2 = 20:80, 40:60, 60:40, 80:20 and 100:0) were prepared by loading TiO2 on as-synthesized Si–MCM-41 using sol–gel method. The physicochemical properties of composites were investigated by powder X-ray diffraction, N2 adsorption–desorption measurements, transmission electron microscopy and UV–Vis diffuse reflectance spectroscopy. It is revealed that the titanium species are dispersed as TiO2 having interaction with the surface of the support. Even at high TiO2 loading, the mesostructural feature of MCM-41 was found to be intact without pore blockages. The change in morphology of TiO2 particle was observed with increase in TiO2 loading which may be due to different environment for the growth of TiO2. The photocatalytic evaluation of composites was carried out in production of hydrogen by water splitting. Among the prepared samples, mesoporous composite containing 60 % TiO2 (MTi60) has shown the best results (0.08805 mmol of H2/h/g of TiO2) compared to other composite photocatalysts. The catalytic performance of this sample was further enhanced (~8 times) after loading 1 % Pt in water splitting (0.70161 mmol of H2/h/g of TiO2). 1 % Pt loaded on pure TiO2 (MTi100) showed hydrogen evolution of the magnitude 0.26 mmol of H2/h/g of TiO2. TiO2–SiO2 mesoporous composite photocatalyst showed much higher activity (~1.9 times) than amorphous silica-embedded titania catalyst having same composition. 相似文献
19.
Huihu Wang Joaquim Luís Faria Shijie Dong Ying Chang 《Materials Science and Engineering: B》2012,177(11):913-919
In this work, mesoporous Au/TiO2 composites have been synthesized and tested on photodegradation of methylene blue dye solution. Mesoporous TiO2 prepared at 450 °C using triblock polymer F127 as structure-directing agent was applied as substrate, while various HAuCl4 concentrations were used for Au loading through deposition-precipitation method using urea as precipitator and hydrogen reducing process. The influences of Au loading on the microstructures of mesoporous TiO2 including degree of dispersion, particle size, surface area, light absorption, and band gap were studied with transmission electron microscopy (TEM), X-ray diffraction (XRD), diffuse reflection infrared Fourier transformed spectroscopy (DRIFT), N2 adsorption–desorption isotherm analysis (BET), and UV–Vis diffuse reflectance spectra. With Au loading, the size of TiO2 nanoparticles in Au/TiO2 composites is similar as that of TiO2 substrate. However, the degree of dispersion was greatly improved. Furthermore, an obvious surface plasmon resonance centered at 570 nm was found in UV–Vis diffuse reflectance spectra for Au/TiO2 composites. Au loading also induced an obvious red shift of light absorption from UV region to visible region and strengthened both UV and visible light absorption in contrast to substrate. Photodegradation results verified that photocatalytic activity of mesoporous TiO2 was improved by Au loading. 0.25%Au/TiO2 composite showed the highest activity, which may be ascribed to its high surface hydroxyl content and the formed Schottky junction after Au loading. These results suggested that noble metal modification is a promising way to synthesize photocatalysts with both high activity and visible light sensitivity. 相似文献
20.
Magdalena Grześkowiak Rafał J. Wróbel Joanna Grzechulska Jacek Przepiórski 《Materials Science-Poland》2014,32(1):71-79
TiO2 powders were prepared through the hydrolysis of titanium isopropoxide followed by calcination at temperatures of 200 °C to 600 °C. The obtained powders were characterized by N2 adsorption-desorption and X-ray powder diffraction. The results confirmed strong dependence between specific surface area of the TiO2 powders and both the conditions of the hydrolysis process and the calcination temperature. While calcination temperature strongly affected crystallinity of the product, no significant influence of the hydrolysis conditions on this parameter was observed. TiO2 powders prepared at various conditions were examined as catalysts for photodegradation of Acid Red 18 in water. Photoactivities of the prepared powders were influenced by both the amount of water used to hydrolyze the TiO2 precursor and the temperature of calcination process. TiO2 samples calcined at 500 °C appeared to be the most active and the photocatalytic activities of the prepared materials increased along with the amount of water used for the hydrolysis process. 相似文献