共查询到20条相似文献,搜索用时 0 毫秒
1.
Hiromi Yamashita Masaru Harada Junko Misaka Masato Takeuchi Bernaurdshaw Neppolian Masakazu Anpo 《Catalysis Today》2003,84(3-4):191-196
The application of metal ion-implantation method has been made to improve the electronic properties of the TiO2 photocatalyst to realize the utilization of visible light. The photocatalytic properties of these unique TiO2 photocatalysts for the purification of water have been investigated. By the metal ion-implantation method, metal ions (Fe+, Mn+, V+, etc.) are accelerated enough to have the high kinetic energy (150 keV) and can be implanted into the bulk of TiO2. TiO2 photocatalysts which can absorb visible light and work as a photocatalyst efficiently under visible light irradiation were successfully prepared using this advanced technique. The UV-Vis absorption spectra of these metal ion-implanted TiO2 photocatalysts were found to shift toward visible light regions depending on the amount and the kind of metal ions implanted. They were found to exhibit an effective photocatalytic reactivity for the liquid-phase degradation of 2-propanol diluted in water at 295 K under visible light (λ>450 nm) irradiation. The investigation using XAFS analysis suggested that the substitution of Ti ions in TiO2 lattice with implanted metal ions is important to modify TiO2 to be able to adsorb visible light. 相似文献
2.
TaON and Ta3N5 as new visible light driven photocatalysts 总被引:1,自引:0,他引:1
Michikazu Hara Go Hitoki Tsuyoshi Takata Junko N. Kondo Hisayoshi Kobayashi Kazunari Domen 《Catalysis Today》2003,78(1-4):555-560
TaON and Ta3N5, Ta5+-based (oxy)nitrides, were studied as visible light driven photocatalysts. Under visible light irradiation (λ≥420 nm), the (oxy)nitrides oxidize water to O2 and reduce H+ to H2 in the presence of sacrificial reagents (Ag+ and methanol). TaON oxidizes water into O2 efficiently, with a maximum quantum yield of 10%. The photocatalytic reactions proceed via the bandgap transitions (Eg, TaON: 2.5 eV, Ta3N5: 2.1 eV) without any noticeable degradation of the catalysts. The small energy gaps of TaON and Ta3N5 are ascribed to the valence band structures consisting of N 2p orbitals. 相似文献
3.
In this research, carbon nanotube (CNT)-modified plasmonic silver-strontium titanate (Ag@ SrTiO3) nanocomposites for the degradation of the organic dye were prepared by the sol-gel method. The characterization of all products was carried out using the X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption test (BET), field emission-scanning electron microscopy (FESEM), transmission electron microscopy (TEM), UV–visible diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, electrochemical impedance spectroscopy (EIS), and transient photocurrent (TPC) studies. It was found that the incorporation of Ag in and introducing CNT into the SrTiO3 nanoparticles reduced the crystallite size to 21 nm and the band gap energy to 2.7 eV. The Reduced PL peak intensity, increased photocurrent value, and reduced charge transfer resistance approved that the Ag@SrTiO3@CNT nanocomposite had a greater charge transfer efficiency than other samples. The optimal dosage of the photocatalyst, for the complete degradation of 5 ppm of the methylene blue (MB) solution after 30 min of the visible light irradiation, was decided as 0.5 g/L. Besides, in the experimental environment, the Ag@SrTiO3@CNT sample illustrated the most significant photocatalytic performance of the degradation of methyl orange (MO) and Rhodamine B (RhB) dyes. The detailed mechanism and kinetics of the degradation procedure were clarified. Finally, the prepared system displayed increased stability and reusability in the entire cyclic degradation experiment. 相似文献
4.
Bifen Gao Yong Joo Kim Ashok Kumar Chakraborty Wan In Lee 《Applied catalysis. B, Environmental》2008,83(3-4):202-207
FeTiO3/TiO2, a new heterojunction-type photocatalyst working at visible light, was prepared by a simple sol–gel method. Not only did FeTiO3/TiO2 exhibit greatly enhanced photocatalytic activity in decomposing 2-propanol in gas phase and 4-chlorophenol in aqueous solution, but also it induced efficient mineralization of 2-propanol under visible light irradiation (λ ≥ 420 nm). Furthermore, it showed a good photochemical stability in repeated photocatalytic applications. FeTiO3 showed a profound absorption over the entire visible range, and its valence band (VB) position is close to that of TiO2. The unusually high photocatalytic efficiency of the FeTiO3/TiO2 composite was therefore deduced to be caused by hole transfer between the VB of FeTiO3 and TiO2. 相似文献
5.
Mingming Cheng Wanhong Ma Chuncheng Chen Jiannian Yao Jincai Zhao 《Applied catalysis. B, Environmental》2006,65(3-4):217-226
An organic–inorganic layered hybrid was prepared by intercalation of Fe(bpy)32+ into laponite clay. UV–vis diffuse reflectance, X-Ray diffraction, and SEM confirmed the intercalation and the strong host–guest interaction of Fe(bpy)32+ molecules with the clay matrix. Compared with laponite, the hybrid formed a solid layered structure due to the linking of laponite platelets by Fe(bpy)32+ molecules. Upon visible light irradiation (λ > 420 nm), the hybrid was found to be highly effective for the degradation of nonbiodegradable cationic organic pollutants such as Rhodamine B (RhB) and N,N-dimethylaniline by activating H2O2 at neutral pH values, but inactive toward anionic organic compounds such as Orange II and Sulforhodamine-B. The adsorption and degradation of organics on the hybrid could be controlled by changing the pH value of the suspension. The total organic carbon (TOC) removal yield of RhB was 41%. pH effect trials and the final degraded products further indicate that unless the target is adsorbed onto the clay layers the reaction could not occur. Neither OH nor OOH/O2− EPR signals were detected during the reaction. The solid support of laponite not only alters the photochemical properties of Fe(bpy)32+ but also provides a rigid microenvironment for the enrichment of local substrate molecules and thus enhances the interaction of the active center with the substrate. 相似文献
6.
采用水热合成法制备C_3N_4-BiVO_4复合光催化剂,以甲基橙为目标污染物,研究催化剂用量、甲基橙溶液初始浓度和pH值、NaCl用量对甲基橙脱色率的影响,并通过C_3N_4-BiVO_4复合光催化剂的循环使用实验,考察其重复使用性能。结果表明,在甲基橙初始浓度20 mg·L~(-1)、复合光催化剂用量3.0 g·L~(-1)及弱酸性条件下,光照反应6 h,目标污染物甲基橙脱色率达98.81%,溶液中的NaCl对催化剂降解甲基橙有抑制作用。催化剂重复使用5次后,溶液脱色率约80%,表明催化剂性能较稳定,可重复使用。 相似文献
7.
Photocatalytic degradation is one of the most promising remediation technologies in terms of advanced oxida-tion processes (AOPs) for water treatment. In this study, novel graphitic carbon nitride/titanium dioxide (g-C3N4/TiO2) composites were synthesized by a facile sonication method. The physicochemical properties of the photocatalyst with different mass ratios of g-C3N4 to TiO2 were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), N2 sorption, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and UV–vis DRS. The photocatalytic performances were evaluated by degradation of methylene blue. It was found that g-C3N4/TiO2 with a mass ratio of 1.5:1 exhib-ited the best degradation performance. Under UV, the degradation rate of g-C3N4/TiO2 was 6.92 and 2.65 times higher than g-C3N4 and TiO2, respectively. While under visible light, the enhancement factors became 9.27 (to g-C3N4) and 7.03 (to TiO2). The improved photocatalytic activity was ascribed to the interfacial charge transfer between g-C3N4 and TiO2. This work suggests that hybridization can produce promising solar materials for envi-ronmental remediation. 相似文献
8.
Petr Praus Ladislav Svoboda Richard Dvorský Martin Reli 《Ceramics International》2018,44(4):3837-3846
Tin dioxide nanoparticles were prepared in the presence of graphitized carbon nitride (g-C3N4) forming nanocomposites with different contents of SnO2 up to 40 %. G-C3N4 was synthetized by heating of melamine at 550 °C in the open air and Sn2+ ions were precipitated by sodium hydroxide in g-C3N4 aqueous dispersions. Resulting mixtures were dried by freezing at ?20 °C and calcined at 450 °C to obtain SnO2/g-C3N4 nanocomposites.The nanocomposites were characterized by common characterization methods in solid state and in their aqueous dispersions using dynamic light scattering (DLS) analysis and photocatalysis. SnO2 nanoparticles in the nanocomposites were found to have an average size of 4 nm, however, those precipitated without g-C3N4 had an average size of 14 nm. Separation of photoinduced electron and holes via heterojunction between SnO2 and g-C3N4 was demonstrated by photocatalytic decomposition of Rhodamine B (RhB) under LED visible irradiation (416 nm) and photocurrent measurements. The most photocatalytically active nanocomposite contained 10 % of SnO2. Graphitized carbon nitride was assumed to serve as a template structure for the preparation of SnO2 nanoparticles with a narrow size distribution without using any stabilizing additives. 相似文献
9.
10.
Xiangxin Yang Chundi Cao Larry Erickson Keith Hohn Ronaldo Maghirang Kenneth Klabunde 《Applied catalysis. B, Environmental》2009,91(3-4):657-662
C-, S-, N-, and Fe-doped TiO2 photocatalysts were synthesized by a facile sol–gel method. The structure and properties of catalysts were characterized by N2 desorption–adsorption, X-ray diffraction (XRD), UV–vis spectroscopy, and X-ray photoelectron spectroscopy (XPS). Results revealed that the surface area of the multi-doped TiO2 was significantly increased and the crystallite size was smaller than the pure TiO2 obtained by a similar route. Compared with TiO2, the peak position in doped-TiO2 XRD patterns was slightly shifted, which could be attributed to the distortion by the substitution of carbon, nitrogen, and sulfur dopants for some oxygen atoms and Fe3+ for Ti4+ in the lattice of TiO2. These substitutions were confirmed by XPS. In addition, these dopants were responsible for narrowing the band gap of TiO2 and shifting its optical response from ultraviolet (UV) to the visible-light region. The photocatalytic reactivities of these multi-doped TiO2 catalysts were investigated by degrading Rhodamine B (RB) in aqueous solution under visible-light irradiation (λ > 420 nm). It was found out that the reactivity was significantly enhanced and the catalyst doped with nitrogen, carbon, sulfur, and 0.3 wt% iron had the highest photocatalytic activity. 相似文献
11.
Beata Tryba Antoni W. Morawski Michio Inagaki Masahiro Toyoda 《Applied catalysis. B, Environmental》2006,63(3-4):215-221
H2O2 used in the photo-Fenton reaction with iron catalyst can accelerate the oxidation of Fe2+ to Fe3+ under UV irradiation and in the dark (in the so called dark Fenton process). It was proved that conversion of phenol under UV irradiation in the presence of H2O2 predominantly produces highly hydrophilic products and catechol, which can accelerate the rate of phenol decomposition. However, while H2O2 under UV irradiation could decompose phenol to highly hydrophilic products and dihydroxybenzenes in a very short time, complete mineralization proceeded rather slowly. When H2O2 is used for phenol decomposition in the presence of TiO2 and Fe–TiO2, decrease of OH radicals formed on the surface of TiO2 and Fe–TiO2 has been observed and photodecomposition of phenol is slowed down. In case of phenol decomposition under UV irradiation on Fe–C–TiO2 photocatalyst in the presence of H2O2, marked acceleration of the decomposition rate is observed due to the photo-Fenton reactions: Fe2+ is likely oxidized to Fe3+, which is then efficiently recycled to Fe2+ by the intermediate products formed during phenol decomposition, such as hydroquinone (HQ) and catechol. 相似文献
12.
A novel visible light sensitive photocatalyst, AgSbO3 was prepared by a conventional solid-state reaction method. This oxide belonging to a cubic-pyrochlore structure can absorb visible light with wavelength up to about 480 nm. From the band structure calculation, we found that the top of the valence band consists of the hybridized Ag 4d and O 2p orbitals and the bottom of the conduction band mainly consists of the Ag 5s and the Sb 5s orbitals. Photocatalytic activities were evaluated using O2 evolution from an aqueous silver nitrate solution and decomposition of gaseous 2-propanol under visible light irradiation. We found that AgSbO3 shows a higher O2 evolution activity than WO3 and 2-propanol can be mineralized by the AgSbO3 photocatalysis under visible light irradiation. 相似文献
13.
Fe-200 was synthesized through the calcination of iron powder at 200 °C for 30 min in air. On the basis of characterization by X-ray diffraction and X-ray photoelectron spectroscopy, Fe-200 had a core–shell structure, in which the surface layer was mainly composed of Fe2O3 with some FeOOH and FeO, and the core retained metallic iron. The kinetics and mechanism of the interfacial electron transfer on Fe-200 were investigated in detail for the photoassisted degradation of organic pollutants with H2O2. Under deoxygenated conditions in the dark, the generation of hydroxyl radicals in aqueous Fe-200 dispersion verified that galvanic cells existed at the interface of Fe0/iron oxide, indicating the electron transfer from Fe0 to Fe3+. Furthermore, the effects of hydrogen peroxide and different organic pollutants on the interfacial electron transfer were examined by the change rate of the Fe3+ concentration in the solution. The results indicated that hydrogen peroxide provided a driving force in the electron transfer from Fe2+ to Fe3+, while the degradation of organic pollutants increased the electron transfer at the interface of Fe0/iron oxide due to their reaction with OH. 相似文献
14.
Cheng Wang Jiaxiang Zhu Xiangyang Wu Hui Xu Yanhua Song Jia Yan Yongxiu Song Haiyan Ji Kun Wang Huaming Li 《Ceramics International》2014
A facile, one-step synthesis of graphene-oxide (GO)/Ag3PO4 was prepared. The as-prepared samples were characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS) and fourier transformed infrared (FT-IR) spectroscopy. The SEM image indicated that Ag3PO4 particles were mainly distributed on the surface of GO sheets uniformly. DRS analysis revealed that the samples had good visible light response. The photocatalytic activity of the composites was evaluated by the degradation of Rhodamine B (RhB) and Bisphenol A (BPA). The results indicated that the photocatalytic performance of GO/Ag3PO4 was greatly enhanced after introduction of GO. The photocatalytic degradation efficiency of colorless chemical pollutants (BPA) over GO/Ag3PO4 was higher than that of Ag3PO4, and the possible degradation path was proposed by liquid chromatography mass spectrometry (LC-MS) analysis. Moreover, the photocatalytic stability was discussed by XRD and FT-IR spectroscopy analysis. Based on the experimental results, a possible visible-light photocatalytic degradation mechanism was also discussed. 相似文献
15.
Chen Wang Jun Li Giuseppe Mele Gao-Mai Yang Feng-Xing Zhang Leonardo Palmisano Giuseppe Vasapollo 《Applied catalysis. B, Environmental》2007,76(3-4):218-226
The effect of a series of carboxylic acids (C2–C8), as solvents for the preparation by flame spray pyrolysis of LaCoO3 catalyst for the flameless combustion of methane, has been investigated. Acetic acid showed to be unsatisfactory from several points of view: low phase purity of the catalyst, higher amount of unburnt carbonaceous residua, lower catalytic activity and low thermal stability. By increasing the carbon chain length of the solvent, the consequent increase of flame temperature led to an increase of crystal phase purity and of particle size and to a decrease of specific surface area of the catalyst. Catalytic activity showed only marginally affected by the last parameter, phase purity seeming more important. Thermal resistance showed directly related to flame temperature, i.e. to the combustion enthalpy of the solvent, but a relatively high amount of residual organic matter can negatively affect this property. 相似文献
16.
Study of adsorption and degradation of acid orange 7 on the surface of CeO2 under visible light irradiation 总被引:1,自引:0,他引:1
Pengfei Ji Jinlong Zhang Feng Chen Masakazu Anpo 《Applied catalysis. B, Environmental》2009,85(3-4):148-154
Cerium dioxide was prepared by the precipitation method and found to be an efficient photocatalyst to degrade azodyes under visible light irradiation. Nonbiodegradable azodyes acid orange 7 (AO7) was selected as modal target to examine the photocatalytic activity of CeO2. AO7 could be efficiently degraded in aqueous suspension of CeO2 under visible light illumination. The catalyst was characterized by X-ray diffraction (XRD), N2 sorption, transmission electron microscopic image (TEM) and UV/vis absorption spectrum techniques. AO7 solution was quickly decolorized and partly mineralized under visible light irradiation with existing CeO2. The photodegradation rate of this azodye catalyzed by CeO2 is much faster than those occurring on commercial titania (Degussa P25) under otherwise identical conditions of visible light irradiation. Experiments were conducted to examine the adsorption mode of acid orange 7 on CeO2 and adsorption capacity at different pH values. The possible degradation pathway has been proposed for the photocatalytic degradations by using certain radical scavengers and gas chromatography–mass spectrometry (GC–MS) to determine intermediates. The enhanced photoactivity of the lanthanide oxide CeO2 was attributed to the superior adsorption capacity and special 4f electron configuration. 相似文献
17.
Hiromi Yamashita Hiroyuki Nose Yasutaka Kuwahara Yoshikatsu Nishida Shuai Yuan Kohsuke Mori 《Applied Catalysis A: General》2008,350(2):164-168
TiO2 photocatalyst loaded on Si3N4 (TiO2/Si3N4) was prepared by a conventional impregnation method and its photocatalytic performance for the degradation of organics (2-propanol) diluted in water was compared with that of TiO2 photocatalysts (TiO2/SiO2, TiO2/Al2O3, and TiO2/SiC) loaded on various types of supports (SiO2, Al2O3, and SiC). The formation of the well-crystallized anatase phase of TiO2 was observed on the calcined TiO2/Si3N4 photocatalyst, while a small anatase phase of TiO2 was observed on the TiO2/SiC photocatalyst and amorphous TiO2 species was the main component on the TiO2/SiO2 and TiO2/Al2O3 photocatalysts. The measurements of the water adsorption ability of photocatalysts indicated that the TiO2/Si3N4 photocatalyst exhibited more hydrophobic surface properties in comparison to other support photocatalysts. Under UV-light irradiation, the TiO2/Si3N4 photocatalyst decomposed 2-propanol diluted in water into acetone, CO2, and H2O, and finally, acetone was also decomposed into CO2 and H2O. The TiO2/Si3N4 photocatalyst showed higher photocatalytic activity than TiO2 photocatalyst loaded on other supports. The well-crystallized TiO2 phase deposited on Si3N4 and the hydrophobic surface of Si3N4 support are important factors for the enhancement of photocatalytic activity for the degradation of organic compounds in liquid-phase reactions. 相似文献
18.
S.E. LinW.C.J. Wei 《Journal of the European Ceramic Society》2011,31(16):3081-3086
Bismuth oxide in δ-phase is a well-known high oxygen ion conductor and can be used as an electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs). 5-10 mol% Ta2O5 are doped into Bi2O3 to stabilize δ-phase by solid state reaction process. One Bi2O3 sample (7.5TSB) was stabilized by 7.5 mol% Ta2O5 and exhibited single phase δ-Bi2O3-like (type I) phase. Thermo-mechanical analyzer (TMA), X-ray diffractometry (XRD), AC impedance and high-resolution transmission electron microscopy (HRTEM) were used to characterize the properties. The results showed that holding at 800-850 °C for 1 h was the appropriate sintering conditions to get dense samples. Obvious conductivity degradation phenomenon was obtained by 1000 h long-term treatment at 650 °C due to the formation of α-Bi2O3 phase and Bi3TaO7, and 〈1 1 1〉 vacancy ordering in Bi3TaO7 structure. 相似文献
19.
Supported Fe/C and Fe/Nafion/C catalysts for the photo-Fenton degradation of Orange II under solar irradiation 总被引:1,自引:0,他引:1
Damien Gumy Pilar Fernndez-Ibez Sixto Malato Cesar Pulgarin Octav Enea John Kiwi 《Catalysis Today》2005,101(3-4):375-382
The physicochemical properties and photocatalytic behavior of Fe/C and Fe/Nafion/C fabrics have been investigated under laboratory conditions (small vial, artificial light) and in large-scale photo-reactors under sunlight to achieve low-cost decontamination of textile and agro-chemical industry effluent wastewater. Fe-ions deposited onto chemically treated C fabrics or encapsulated in Nafion thin films cast directly onto the carbon fabrics are efficient in decomposing H2O2 used as an oxidant in the photo-assisted abatement of non-biodegradable azo-dyes used in textiles. The Orange II taken as a model pollutant quickly fades under solar irradiation even at an initial pH 6. This range of pH is not possible with the homogeneous photo-Fenton process. In contrast, the use of supported catalysts on C fabrics allows the costly pH adjustment to be avoided. This makes catalyst recovery and economical decontamination of wastewater containing non-biodegradable pollutants possible. 相似文献
20.
TiO2 varistors doped with 0.2 mol% Ca, 0.4 mol% Si and different concentrations of Ta were obtained by ceramic sintering processing at 1350 °C. The effect of Ta on the microstructures, nonlinear electrical behavior and dielectric properties of the (Ca, Si, Ta)-doped TiO2 ceramics were investigated. The ceramics have nonlinear coefficients of α = 3.0–5.0 and ultrahigh relative dielectric constants which is up to 104. Experimental evidence shows that small quantities of Ta2O5 improve the nonlinear properties of the samples significantly. It was found that an optimal doping composition of 0.8 mol% Ta2O5 leads to a low breakdown voltage of 14.7 V/mm, a high nonlinear constant of 4.8 and an ultrahigh electrical permittivity of 5.0 × 104 and tg δ = 0.66 (measured at 1 kHz), which is consistent with the highest and narrowest grain boundary barriers of the ceramics. In view of these electrical characteristics, the TiO2–0.8 mol% Ta2O5 ceramic is a viable candidate for capacitor–varistor functional devices. The characteristics of the ceramics can be explained by the effect and the maximum of the substitution of Ta5+ for Ti4+. 相似文献