共查询到20条相似文献,搜索用时 15 毫秒
1.
《Journal of the European Ceramic Society》2006,26(9):1535-1545
One-step route based on the thermal decomposition of the double salt (NH4)2TiO(SO4)2 (ammonium titanyl sulfate, ATS) is presented to prepare size-defined aggregates of Ti-based nanoparticles with structural hierarchy. The component of Ti-based networks is tunable from anatase/rutile TiO2, nitrogen-doped TiO2, TiNxO1−x, to TiN depending on the atmospheres and reaction temperatures. The as-prepared Ti-based powders were characterized by X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectra (DRS), and BET surface area techniques. It is found that TiO2 in the predominant rutile phase could be achieved by the thermal decomposition of ATS in flowing Ar gas. Furthermore, the nitrogen-doped TiO2, TiNxO1−x solid solution and TiN were prepared by the thermal decomposition of ATS in flowing NH3 gas by varying the temperatures. The network of anatase TiO2 with a specific surface area up to 64 m2 g−1 contains large mesopores with a mean diameter of ca. 15 nm, and the large pore size allows more accessible surface and interface available for the photocatalytic degradation of large-molecule dyes. The photocatalytic activity of the prepared TiO2 and nitrogen-doped TiO2 under UV–vis light irradiation is compared to Degussa P-25 using the photocatalytic degradation of methylene blue (MB) as a model reaction. The anatase TiO2 nanoparticles derived from one-step route show the highly efficient photocatalytic activity for the degradation of MB in comparison with Degussa P-25. The presence of large-sized rutile in the TiO2 powder decreases the specific surface area and thus the powder exhibits a lower photocatalytic activity. 相似文献
2.
The synergic effect of cation doping and phase composition for the further improvement of the photocatalytic activity of TiO2 under visible light is reported for the first time. Fe3 + and Sn4 + co-doped TiO2 with optimized phase composition were synthesized through a simple soft-chemical solution method. The visible-light-driven photocatalytic activity of Fe3 + and Sn4 + co-doped TiO2 was 5 times of that of Evonik P25 TiO2 using degradation of methylene blue as model reaction. The synthesized photocatalysts were characterized by powder X-ray diffraction, UV–Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, 119Sn Mössbauer spectroscopy, and X-ray absorption fine structure spectroscopy. It is indicated that Sn4 + doping can facilitate the phase transition from anatase to rutile. The different ratios of anatase and rutile can be achieved by tuning the amount of Sn4 + doped into the lattice. Furthermore, the doping of Sn4 + into TiO2 lattice can stabilize the phase composition when Fe3 + is co-doped. In the Fe3 + and Sn4 + co-doped TiO2, Sn4 + is mainly used to tune and stabilize the phase composition of TiO2 and Fe3 + acts as a doping cation to narrow the band gap of TiO2. Both band gap and phase composition of TiO2 can be tuned effectively by the simultaneous introduction of Fe3 + and Sn4 +. The synergic effect of optimized phase composition (anatase/rutile = 25/75) and narrowed band gap should be the two main reasons for the promoted photocatalytic activity of TiO2 under visible light. 相似文献
3.
《Ceramics International》2017,43(17):15288-15295
Nano-structured TiO2 coatings were produced by suspension high velocity oxy fuel (SHVOF) thermal spraying using water-based suspensions containing 30 wt% of submicron rutile powders (~180 nm). By changing the flame heat powers from 40 kW to 101 kW, TiO2 coatings were obtained with distinctive microstructures, phases and photocatalytic behaviour. Spraying with low power (40 kW) resulted in a more porous microstructure with the presence of un-melted nano-particles and a lower content of the anatase phase; meanwhile, high powers (72/101 kW) resulted in denser coatings and rougher surfaces with distinctive humps but not necessarily with a higher content of anatase. Linear sweep voltammetry (LSV) was used to evaluate the photocatalytic performance. Surprisingly, coatings with the lowest anatase content (~20%) using 40 kW showed the best photocatalytic behaviour with the highest photo-conversion efficiency. It was suggested that this was partially owing to the increased specific surface area of the un-melted nano-particles. More importantly, the structural arrangement of the similarly sized TiO2 nano-crystallites between rutile and antase phases also created catalytic “hot spots” at the rutile−anatase interface and greatly improved the photo-activity. 相似文献
4.
Jaturong Jitputti Thitima Rattanavoravipa Surawut Chuangchote Sorapong Pavasupree Yoshikazu Suzuki Susumu Yoshikawa 《Catalysis communications》2009,10(4):378-382
Monodispersed flower-like titanate superstructure was successfully prepared by simple hydrothermal process without any surfactant or template. N2-sorption analysis, scanning electron microscopy (SEM), and X-ray diffraction (XRD) observation of as-synthesized product revealed the formation of flower-like titanate with diameter of about 250–450 nm and BET surface area (SBET) of 350.7 m2 g?1. Upon thermal treatment at 500 °C, the titanate nanosheets were converted into anatase TiO2 with moderate deformation of their structures. The as-prepared flower-like titanate showed high photocatalytic activity for H2 evolution from water splitting reaction. Moreover, the sample heat treated at 500 °C exhibited higher photocatalytic activity than that of commercial TiO2 anatase powder (ST-01). 相似文献
5.
Rutile/anatase TiO2 heterojunction nanoflowers were prepared via a facile one-step hydrothermal approach using titanium tetrachloride and urea as the raw materials, cetyl trimethyl ammonium bromide (CTAB) as the template. The prepared TiO2 nanoflowers were characterized by XRD, SEM, TEM and BET analyses. The photocatalytic performance of the as-prepared TiO2 samples for methyl blue degradation under simulated solar light was investigated. TiO2 heterojunction nanoflowers with mixed rutile/anatase phase (prepared with 3 mmol CTAB) give the highest photocatalytic activity. In addition, TiO2 nanoflowers show excellent stability after 9 cycles under the same conditions. These results suggested that the mixed phase anatase/rutile TiO2 heterojunction nanoflowers have great potential for the future photodegradation of real dye waste water. 相似文献
6.
Effects of ferrite materials as supports (CoFe2O4, NiFe2O4, and Fe3O4) on nano-TiO2 were elucidated by their use in the oxidation of methylene blue. These photocatalysts, which were synthesized by co-precipitation, were characterized by XRD, SEM, EDS and VSM. The crystalline phase of TiO2 onto magnetic MFe2O4 was formed by anatase and rutile. TiO2/CoFe2O4 exhibited the strongest magnetic property of the prepared catalysts, and the photocatalytic efficiencies followed the order TiO2/CoFe2O4 > TiO2/NiFe2O4 > TiO2/Fe3O4. MB decolorization was enhanced with the amount of TiO2 on the photocatalyst, and was moderately affected by the extent of structural distortion of ferrite supports. 相似文献
7.
M. Shamshi Hassan Touseef Amna O-Bong Yang Hyun-Chel Kim Myung-Seob Khil 《Ceramics International》2012,38(7):5925-5930
In the present study rare earth doped (Ln3+–TiO2, Ln = La, Ce and Nd) TiO2 nanofibers were prepared by the sol–gel electrospinning method and characterized by XRD, SEM, EDX, TEM, and UV-DRS. The photocatalytic activity of the samples was evaluated by Rhodamine 6G (R6G) dye degradation under UV light irradiation. XRD analysis showed that all the synthesized pure and doped titania nanofibers contain pure anatase phase at 500 °C but at 700 °C it shows both anatase and rutile phase. XRD result also shows that Ln3+-doped titania probably inhibits the phase transformation. The diameter of nanofibers for all samples ranges from 200 to 700 nm. It was also observed that the presence of rare-earth oxides in the host TiO2 could decrease the band gap and accelerate the separation of photogenerated electron–hole pairs, which eventually led to higher photocatalytic activity. To sum up, our study demonstrates that Ln3+-doped TiO2 samples exhibit higher photocatalytic activity than pure TiO2 whereas Nd3+-doped TiO2 catalyst showed the highest photocatalytic activity among the rare earth doped samples. 相似文献
8.
《Catalysis communications》2010,11(15):1985-1989
Porous TiO2 nanocrystals (PTN) were synthesized using activated carbon templates with supercritical CO2 by using the nanoscale permeation (NP) process. The photoactivity of PTN was tested by methylene blue (MB) degradation. Compared with the commercially available P-25, all PTN exhibited significant photocatalytic degradation of MB mainly due to their porous structure with high surface area, high hydroxy concentration and small crystalline size. The optimum temperature and pressure are found to be 60 °C and 26 MPa, under which obtained PTN-1 shows the highest photoactivity and slow deactivation for MB degradation after 15 trials. 相似文献
9.
《Catalysis communications》2004,5(6):283-290
In 80% aqueous ethanol, TiO2 (anatase), ZrO2, ZnO, V2O5, Fe2O3 and Al2O3 photocatalyze the oxidation of iodide ion but CdO and CdS do not; the wavelength of illumination is 365 nm. However, Fe2O3 fails to bring in a sustainable photocatalysis in 60% aqueous ethanol. The photooxidation of iodide ion on TiO2, ZrO2, ZnO, V2O5 and Al2O3 in 60% aqueous ethanol was studied as a function of [I−], amount of catalyst suspended, airflow rate, light intensity and solvent composition. The metal oxides examined show sustainable photocatalytic activity. Iodine formation is larger with illumination at 254 nm than at 365 nm. The mechanisms of photocatalysis on semiconductor and non-semiconductor surfaces have been discussed. Photocatalytic generation of iodine has been analyzed using a kinetic model. The photocatalytic efficiencies are of the order V2O5 > TiO2 > ZrO2 > ZnO > Al2O3 and V2O5 > TiO2 > ZrO2 > ZnO=Fe2O3 > Al2O3 in 60% and 80% aqueous ethanol. 相似文献
10.
Xiuzhen Wei Huijuan Wang Guangfeng Zhu Jinyuan Chen Liping Zhu 《Ceramics International》2013,39(4):4009-4016
A series of iron-doped anatase TiO2 nanotubes (Fe/TiO2 NTs) catalysts with iron concentrations ranging from 0.88 to 7.00 wt% were prepared by an ultrasonic-assisted sol-hydrothermal process. The structures and the properties of the fabricated Fe/TiO2 NTs were characterized in detail and photocatalytic activity was examined using a reactive brilliant red X-3B aqueous solution as pollutant under visible light. The lengths of the NTs were determined to range from 20 nm to 100 nm. The incorporation of the iron ions (Fe3+) into the TiO2 nanotubes shifted the photon absorbing zone from the ultraviolet (UV) to the visible wavelengths, reducing the band gap energy from 3.2 to 2.75 eV. The photocatalytic activity of the Fe/TiO2 NTs was 2–4 times higher than the values measured for the pure TiO2 nanotubes. 相似文献
11.
《Applied catalysis. B, Environmental》2007,69(3-4):99-108
Freestanding and crack-free titania–silica aerogels with high titanium content (i.e., Ti/Si = 1) were successfully prepared by adjusting the hydrolysis of the two alkoxide precursors to a comparable rate during the sol–gel processing. Two titania–silica aerogels were prepared by ethanol and CO2 supercritical drying methods. Well-dispersed, nanometer-sized anatase crystal domains (ca. 10 nm) were crystallized by high temperature, ethanol supercritical drying. The crystalline domains were solidly anchored to the aerogel network by Ti–O–Si bonds. Titania–silica aerogels prepared by CO2 supercritical drying method were devoid of TiO2 crystals. A molecular-level mixing was achieved and anatase TiO2 was only crystallized with difficulty by high temperature calcination (1073 K). Both aerogels were mesoporous and displayed similar open pore structure that is readily accessible to reactant molecules. However, only the titania–silica aerogel with anatase TiO2 prepared by ethanol supercritical drying was active for the gas phase, photocatalytic oxidation of volatile organic compounds (i.e., isopropanol and trichloroethylene). Catalysts prepared from Degussa P25 TiO2 displayed lower activity under similar reaction conditions. 相似文献
12.
《Journal of the European Ceramic Society》2006,26(13):2735-2742
Nitrogen-doped anatase, rutile and brookite titania photocatalyst TiO2−xNy which can be excited by visible light were prepared by mixing aqueous TiCl3 solutions with urea ((NH2)2CO) and various type of alcohols followed by solvothermal treatment at 190 °C. The phase composition, crystallinity, microstructure and specific surface area of titania powders greatly changed depending on the pH and type of solvents. Violet, yellowish and grayish TiO2−xNy with excellent visible light absorption and photocatalytic activity were prepared. The TiO2−xNy powders prepared in urea–methanol solution showed excellent photocatalytic ability for the oxidative destruction of nitrogen monoxide under irradiation of visible light λ > 510 nm. 相似文献
13.
《Ceramics International》2016,42(9):10892-10901
Au–TiO2/SiO2 heterogeneous catalysts with different Au contents were successfully synthesized by a facile hydrothermal process and their photocatalytic activity towards reduction of Rose Bengal (RB), Methyl Blue (MB), Rhodamine B (RhB) and Congo Red (CR) was investigated in the presence of sodium borohydride (NaBH4) for advanced oxidation process (AOP). The results reveal that 3 wt% Au loaded in TiO2/SiO2 can significantly degrade high RB concentration dye (>95%, 0.3 g/L, 12 pH) within 20 min of irradiation time. All catalysis reaction followed the pseudo-first order rate reaction with high correlation coefficient. The effect of loading of Au nanoparticles (1–5 wt%) along with variation in dye concentration (100–500 ppm), pH of solution (2–12), catalysts dosage (0.1–0.5 g/L), and reaction temperature (30–80 °C) were also studied. The present works shows the superior performance of Au–TiO2/SiO2 heterogeneous catalysts to be related to the high dispersion of Au nanoparticles in the TiO2/SiO2 and to the catalytic effect between gold and TiO2. 相似文献
14.
《Catalysis communications》2011,14(1):14-17
Si-doped TiO2 nanoparticles with anatase crystalline phase were prepared by a hydrothermal method using acetic acid as the solvent. Photoelectrochemical studies showed that the photocurrent value for the 15% Si-doped TiO2 electrode (54.4 μA) was much higher than that of the pure TiO2 electrode (16.7 μA). In addition, the 15% Si-doped TiO2 nanoparticles displayed the highest photocatalytic activity under ultraviolet light irradiation. So doping suitable amount of Si in TiO2 nanoparticles was profitable for transferring photogenerated electrons and inhibiting the recombination of photogenerated electrons and holes. As a result, the photocatalytic activity of TiO2 nanoparticles was improved. 相似文献
15.
《Journal of the European Ceramic Society》2017,37(15):4667-4672
The TiO2 ceramics were prepared by a solid-state reaction in the temperature range of 920–1100 °C for 2 h and 5 h using TiO2 nano-particles (Degussa-P25 TiO2) as the starting materials. The sinterability and microwave properties of the TiO2 ceramics as a function of the sintering temperature were studied. It was demonstrated that the rutile phase TiO2 ceramics with good compactness could be readily synthesized from the Degussa-P25 TiO2 powder in the temperature range of 920–1100 °C without the addition of any glasses. Moreover, the TiO2 ceramics sintered at 1100 °C/2 h and 920 °C/5 h demonstrated excellent microwave dielectric properties, such as permittivity (Ɛr) value >100, Q × f > 23,000 GHz and τf ≅ 200 ppm/°C. 相似文献
16.
《Journal of the European Ceramic Society》2006,26(10-11):1933-1936
Bi2O3–TiO2 composites are known to possess attractive microwave dielectric properties. However, producing LTCC analogues with equally promising dielectric properties is problematic. Here, we show that judicious choice of both TiO2 starting powders and dopants can produce composites with excellent properties. Three TiO2 powders were evaluated: 1 μm-anatase, 1 μm-rutile and a nanosized (30 nm) mixture of 75–25 anatase-rutile. The best dielectric properties were obtained by using uncalcined nanosized anatase/rutile with Bi2O3 powder. By doping this Bi2O3–TiO2 powder mixture with 0.112 wt.% CuO dielectric properties of Q × f = 9000 GHz, ɛr = 80 and τf = 0 ppm/K (at 300 K) were obtained at a sintering temperature of 915 °C. 相似文献
17.
《Ceramics International》2016,42(4):5113-5122
TiO2 nanoparticles are currently used as coating for self-cleaning building products. In order to achieve high self-cleaning efficiency for outdoor applications, it is important that titania is present as anatase phase. Moreover, it is desirable that the particle sizes are in nano-range, so that a large enough surface area is available for enhanced catalytic performance. In this work, TiO2 nanoparticles doped with 0–5 mol% Nb2O5 were synthesized by co-precipitation. Nb2O5 postponed the anatase to rutile transformation of TiO2 by about 200 °C, such that after calcination at 700 °C, no rutile was detected for 5 mol% Nb2O5-doped TiO2, while undoped TiO2 presented 90 wt% of the rutile phase. A systematic decreasing on crystallite size and increasing on specific surface area of TiO2 were observed with higher concentration of Nb2O5 dopant. Photocatalytic activity of anatase polymorph was measured by the decomposition rate of methylene blue under ultraviolet and daylight illumination and compared to commercial standard catalyst (P25). The results showed enhanced catalysis under UV and visible light for Nb2O5-doped TiO2 as compared to pure TiO2. In addition, 5 mol% Nb2O5-doped TiO2 presented higher photocatalytic activity than P25 under visible light. The enhanced performance was attributed to surface chemistry change associated with a slight shift in the band gap. 相似文献
18.
M. Fassier C.S. Peyratout D.S. Smith C. Ducroquetz T. Voland 《Journal of the European Ceramic Society》2010,30(13):2757-2762
Heterogeneous photocatalysis can be exploited for the decomposition of micro-organisms which have developed on the surfaces of building materials. In this work, the efficiency of titanium dioxide coatings on fired clay products is examined. The sol–gel method is used to synthesize a fine TiO2 powder with a specific surface area of 180 m2 g?1. Thermal treatment of the chemical gel at 340 °C leads to crystallisation in the anatase phase and with further temperature increase, crystallite growth. For thermal treatments in the range 580–800 °C, there is a progressive transition from anatase to rutile. However, despite a decrease in specific surface area of the powder attributed to aggregation/agglomeration, the coherent domain size deduced from X-ray diffraction measurements remains almost constant at 23 nm. Once the transition is completed, increase of thermal treatment temperature above 800 °C leads to further crystallite growth in the rutile phase. The thermally treated titania powders were then sprayed onto fired clay substrates and the photocatalytic activity was assessed by the aptitude of the coating to degrade methylene blue when exposed to ultraviolet light. These tests revealed that the crystallite size is the important controlling factor for photocatalytic activity rather than the powder specific surface area or the anatase/rutile polymorph ratio. 相似文献
19.
Gyeong-Taek Lim Kyung Hwan Kim Jun Park Seung-Ho Ohk Jong-Ho Kim Dong Lyun Cho 《Journal of Industrial and Engineering Chemistry》2010,16(5):723-727
Carbon-doped titanium dioxide (TiO2) nano-powders were synthesized by the aerosol flame deposition (AFD) process using 2-butanol liquid sol containing 20 wt% of titanium isopropoxide (TTIP). They were mesoporous nano-powders with particle size ranging from 20 to 40 nm, the specific surface area of 36 m2/g, and the pore size of 19 nm. They had the anatase structure and showed high photocatalytic activity not only under UV-A light but also under fluorescent light. They reduced the concentration of methylene blue (MB) from 5.0 to 1.5 ppm within 2 h under UV-A light and from 5.0 to 2.0 ppm within 4 h under fluorescent light. And, they killed 99% of Escherichia coli (E. coli) cells within 2 h and bacterial growth of the E. coli was not observed for 12 h under both UV-A and fluorescent lights. 相似文献
20.
Nano-TiO2 was synthesized with titanium sulfate by a simple economical microwave-assisted-hydrolysis method, and it was successfully coated on semi-organic-matter sulfonated coal (SC). SC as a semi-organic matter was first chosen as the substrate of nano-TiO2. Their surface morphology and structure were investigated by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). The hybrid nano-composite photocatalyst exhibited a good photocatalytic activity in degrading methylene blue (MB). Results revealed that under the assistance of microwave-process, the anatase TiO2 can be synthesized at low temperature (around 100 °C), presents a strong crystalline and has a good photocatalytic performance. 相似文献