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1.
Chockalingam Karunakaran Premkumar Anilkumar Paramasivan Gomathisankar 《Monatshefte für Chemie / Chemical Monthly》2010,7(3):529-537
Abstract
Ag-doped TiO2 (anatase) samples (mass fraction w Ag = 0.01 and w Ag = 0.02) of 15.9 and 14.5 nm mean particle size and 11.46 and 10.14 m2 g−1 BET surface area were prepared by photodeposition. Doping results in surface plasmon resonance of the metallic silver nanoclusters at around 500 nm, but the absorption edge remains unaltered at 365 nm. Ag-doping remarkably enhances the photooxidation of iodide ion under UV light; iodine formation with Ag/TiO2 with w Ag = 0.01 is 16 times greater than with bare TiO2. The reaction conforms to Langmuir–Hinshelwood kinetics with regard to both I− and O2. Increase of pH slows down iodine formation and sacrificial electron donors arrest the reaction. Pre-sonication of the catalyst slurry hinders the photocatalysis. Generation of iodine is much greater in acetonitrile than in water. Under the experimental conditions, Ag/TiO2 with w Ag = 0.01 is more efficient than Ag/TiO2 with w Ag = 0.02, and the enhanced photocatalysis is likely to be because of suppression of electron–hole pair recombination. Kinetic analysis reveals that increasing the Ag mass fraction from 0.01 to 0.02 enhances the surface pseudo-first-order rate constant but inhibits the adsorption of iodide ion and the oxygen molecule on the illuminated oxide surface. 相似文献2.
采用一步溶剂热法,以Cu(NO_3)_2·3H_2O为铜源,乙二醇(EG)为还原剂,聚乙烯吡咯烷酮(PVP)为表面活性剂,高温条件下制备形貌可控的Cu_2O空心球纳米材料。研究Cu(NO_3)_2·3H_2O与PVP的质量比值(w_(Cu(NO_3)_2·3H_2O)/w_(PVP))对Cu2O结构、形貌、比表面积以及光吸收特性的影响,并结合光催化机理讨论其对Cu_2O光催化性能的影响。此外,通过改变反应时间来研究Cu_2O的生长过程。结果表明,w_(Cu(NO_3)_2·3H_2O)/w_(PVP)=45时,得到的形貌为空心球表面覆盖纳米刺的Cu_2O纳米材料光催化性能最佳,在可见光辐照10 min的条件下,对甲基橙的降解率达94.3%。 相似文献
3.
El-Sayed A. El-Sharkawy 《Monatshefte für Chemie / Chemical Monthly》2006,137(12):1487-1498
Summary. The textural characteristics, including surface area, mean pore diameters, and total pore volume of Cr2O3–CuO/Al2O3 solid catalysts were determined from the low temperature adsorption of N2 at 77 K. The structural properties were investigated using XRD. The surface acidity of calcined samples was determined using
two comparable methods, including the non-aqueous titration of acidic groups with n-butylamine and dehydration/dehydrogenation activity of cyclohexanol.
XRD patterns assigned a crystalline CuO and γ-Al2O3 for 723 K calcinations products of lower Cr2O3 content. The gradual increase of calcinations temperature promoted the crystallinity of Cr2O3 and resulted in solid–solid interaction of CuO and Cr2O3 forming CuCr2O4. The textural parameters varied with both calcinations temperature and catalyst composition. The surface acid density (DAS)
increased with the increase of chromia content up to 0.132 mole% Cr2O3, while the rise of calcinations temperature led to a decrease of surface acidity.
The dehydration/dehydrogenation of cyclohexanol as well as n-butylamine titration succeeded in characterizing of surface acidity.
Present address: Chemistry Department, College of Science, King Faisal University, Al-Hofuf 31982, Saudi Arabia 相似文献
4.
S. V. Ingale P. B. Wagh A. K. Tripathi A. S. Dudwadkar S. S. Gamre P. T. Rao I. K. Singh Satish C. Gupta 《Journal of Sol-Gel Science and Technology》2011,58(3):682-688
The degradation of nitro aromatics like trinitrotoluene (TNT) released in the waste water from explosive process plants is
the serious problem due to toxic and explosive nature of TNT. The poor response of TNT to biodegradation enhanced the gravity
of the problem. We have demonstrated that high specific surface area TiO2–SiO2 nano-composite aerogel is promising photo catalyst in successful treating of TNT contaminated aqueous solution. The TiO2–SiO2 composite aerogel with nominal content of 20 and 50% TiO2, used as catalyst, were prepared by co-precursor sol–gel method using titanium isopropaxide and tetramethylorthosilicate
as source of titania and silica, respectively. The XRD studies confirmed formation of anatase phase of crystalline TiO2 with nano sized crystallites. The TiO2–SiO2 aerogel showed specific surface area of 1,107 and 485 m2/g for the aerogels containing 20 and 50% TiO2, respectively. The 100 ppm TNT solution was treated, in 700 ml capacity reaction vessel, using H2O2 oxidizer and TiO2–SiO2 aerogel catalyst in presence of UV light (8 W UV lamp). Using TiO2–SiO2 (50/50) aerogel with surface area of 485 m2/g, we succeeded to reduce the TOC to 1 ppm within 3.5 h where as using TiO2/SiO2 (20/80) aerogel with surface area of 1,107 m2/g, the TOC was reduced to about only 7 ppm in the same time. It revealed that the combination of high TiO2 content and high specific surface area is an important factor to achieve effective and faster degradation of TNT for complete
mineralization. 相似文献
5.
The transparent TiO2 thin films coated on fused-SiO2 substrates were prepared by the sol–gel method and spin-coating technique. Effects of calcination temperature on crystal
structure, grain size, surface texture, and light transmittance of the films were investigated. After calcining at 600–1,200 °C,
the thicknesses of the TiO2 films were all around 80 nm and the molecular structures of the films were anatase, even at 1,200 °C. The calcined TiO2 films had the ultraviolet light (wavelength 200–400 nm) transmittances of ≤29% and the visible light (wavelength 400–800 nm)
transmittance of ≥72%. By photocatalytically decomposing the methylene blue (MB) in water, the photocatalytic activities of
the TiO2 thin films were measured and represented using the characteristic time constant (τ) for the MB degradation. While the films
prepared at 1,000 and 1,200 °C photodecomposed about 54 mol% of the MB in water (the corresponding τ ≈ 14.8 h) after exposing to 365-nm UV light for 12 h, the films prepared at 600 and 800 °C had smaller τ (≈9.0 h) and photodecomposed
about 74 mol% of the MB in water at the same testing conditions. 相似文献
6.
Shih-Yuan Lin Ying-Chung Chen Chih-Ming Wang Chan-Chih Liu 《Journal of Solid State Electrochemistry》2008,12(11):1481-1486
Electrochromic titanium oxide (TiO2) films were deposited on ITO/glass substrates by chemical solution deposition (CSD). The stock solutions were spin-coated
onto substrates and then heated at various temperatures (200–500 °C) in various oxygen concentrations (0–80%) for 10 min.
The effects of the processing parameters on the electrochromic properties of TiO2 films were investigated. X-ray diffraction measurements demonstrated that the amorphous TiO2 films were crystallized to form anatase films above 400 °C. The electrochromic properties and transmittance of TiO2 films were measured in 1 M LiClO4–propylene carbonate (PC) non-aqueous electrolyte. An amorphous 350 nm-thick TiO2 film that was heated at 300°C in 60% ambient oxygen exhibited the maximum transmittance variation (ΔT%), 14.2%, between the bleached state and the colored state, with a ΔOD of 0.087, Q of 10.9 mC/cm2, η of 7.98 cm2/C and x in Li
x
ClO4 of 0.076 at a wavelength (λ) of 550 nm. 相似文献
7.
The InVO4 sol was obtained by a mild hydrothermal treatment (the precursor precipitation solution at 423 K, for 4 h). Novel visible-light
activated photocatalytic InVO4–TiO2 thin films were synthesized through a sol–gel dipping method from the composite sol, which was obtained by mixing the low
temperature InVO4 sol and TiO2 sol. The photocatalytic activities of the new InVO4–TiO2 thin films under visible light irradiation were investigated by the photocatalytic discoloration of methyl orange aqueous
solution. The thin films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM)
and UV–Vis absorption spectroscopy (UV–Vis). The results revealed that the InVO4 doped thin films enhanced the methyl orange degradation rate under visible light irradiation, 3.0 wt% InVO4–TiO2 thin films reaching 80.1% after irradiated for 15 h. 相似文献
8.
Suparoek Henpraserttae Pimpa Limthongkul Pisanu Toochinda 《Monatshefte für Chemie / Chemical Monthly》2010,50(2):269-277
Abstract
Impregnated Cu–Zn over Al2O3 exhibits high activity with the use of a lower amount of active metal relative to conventional co-precipitation catalysts. The activity of the catalyst could be enhanced by addition of urea to the metal salt solution during impregnation. The H2 yield from Cu–Zn catalysts with urea is 42%, while the H2 yield from catalyst without urea is only 28% in a continuous system at 250 °C and 1.2 atm. The H2 yield of the catalyst with urea in this study could compete with that of commercial catalysts. The role of urea in the Cu–Zn catalysts was investigated. X-ray diffraction (XRD) analysis of the catalysts shows that the crystal size of CuO could be reduced by the addition of urea. The XRD diffractogram of the catalyst prior to calcination also shows the formation of NH4NO3, which could aid in dissociation of metal clusters. Scanning electron microscopy (SEM) images of catalysts show the size of Cu–Zn compound clusters and also their dispersion over the Al2O3 surface on the impregnated catalysts. The addition of urea could also yield smaller Cu–Zn compound clusters and better dispersion compared with the impregnated catalyst without urea. Such impregnated Cu–Zn catalysts with urea could be alternative novel catalysts for methanol steam reforming. 相似文献9.
Cai Jin-Hua Ye Yuan-Jian Huang Jin-Wang Yu Han-Cheng Ji Liang-Nian 《Journal of Sol-Gel Science and Technology》2012,62(3):432-440
Three types of silica gel supported titanium dioxide particles immobilizing Zn(II) carboxylphenyl porphyrins appending p-CH3, p-H and p-Cl phenyl substituents (designated as ZnMP–TiO2–SiO2, ZnPP–TiO2–SiO2 and ZnCP–TiO2–SiO2, respectively) have been synthesized and characterized using SEM, XRD, IR, AFS, DRS, UV–Vis, XPS and TG. The photodegradation
of α-terpinene in aqueous suspension was used to determine the photocatalytic activity of TiO2–SiO2 samples which had been impregnated with Zn(II) porphyrins, as sensitizers. The experimental results confirmed that the photocatalytic
activitys of these composites are much higher than those of the nonmodified TiO2–SiO2 under visible light irradiation and follow the order of ZnMP–TiO2–SiO2 > ZnPP–TiO2–SiO2 > ZnCP–TiO2–SiO2. 相似文献
10.
Shuichi Naito 《Catalysis Surveys from Asia》2005,9(4):243-258
The support effects (SiO2, TiO2, Al2O3, MgO, CeO2 and ZrO2) as well as addition effect of group 6b and 7b elements were studied over various supported group 8–10 metal catalysts. Basic
oxide support improved the selectivity to CO2 and acidic support suppressed the catalytic activity and selectivity. Among the investigated catalysts Pt–Mo/TiO2 was the most active catalysts, whereas Ir–Re/SiO2 was the most selective catalysts for H2 and CO2 formation.
The mechanism of the liquid phase methanol reforming reaction over silica supported Pt–Ru catalyst was studied by kinetic
investigations. The rate of H2 formation over Pt–Ru/SiO2 catalysts was more than 20 times faster than that over Pt/SiO2 catalysts with high selectivity for CO2 (72.3%), indicating a marked addition effect of Ru. In the case of HCHO–H2O reaction over Pt–Ru/SiO2, the H2 formation rate was five times larger than that in the CH3OH–H2O reaction but selectivity to CO2 was only 4%. On the contrary, in the HCOOCH3–H2O and HCOOH–H2O reactions, both high activity and selectivity were observed over Pt–Ru/SiO2. These results clearly indicate that the CO2 formation does not proceed via HCHO decomposition and following water gas shift reaction. 相似文献
11.
Guoyi Bai Hailong Wang Huisen Ning Fei He Guofeng Chen 《Reaction Kinetics and Catalysis Letters》2008,94(2):375-383
A continuous process for the dehydrogenation of cyclohexanol to cyclohexanone on copper-based catalysts was described. The
catalysts were characterized by XRD, XPS and TPR, and Cu0 was found to be the active site for the copper-based catalysts studied. The two carrier catalysts were proved to be more
active than the single carrier ones, and the Cr additive, which mainly existed as the CuCr2O4 phase on the catalyst’s surface, was found to have a significant effect on the activity and stability of the Cu-Cr-Mg-Al
catalyst. 相似文献
12.
Ahmed A. Abd El-Raady Nasr E. Fouad Mohamed A. Mohamed Samih A. Halawy 《Monatshefte für Chemie / Chemical Monthly》2002,133(10):1351-1361
Summary. Selective decomposition of ethanol was used as a test reaction at 350°C to evaluate the catalytic activity of two Al–Mg–O
mixed oxides prepared by two different methods (wet impregnation and coprecipitation). The catalyst precursors were examined
by TG and DTA and were calcined between 500–900°C for 5 h in air. The surface area of all catalysts was measured by N2 sorption using the BET method. The total acidity and basicity were determined by TPD using pyridine and formic acid. The
catalysts were characterized by XRD analysis. It was found that the preparation method of Al–Mg–O catalyst has a great effect
on the selective decomposition of ethanol. Al–Mg–O (I) catalysts, prepared by wet impregnation, were more selective towards
ethene formation during dehydration of ethanol. This is ascribed to their high total surface acidity. On the other hand, Al–Mg–O
(II) catalysts, prepared by coprecipitation, were highly selective in the oxidative dehydrogenation of ethanol to yield acetaldehyde.
This could be attributed to their high concentration of basic sites. In addition, the production of traces of diethyl ether
was also observed (three times more for Al–Mg–O (II) than for Al–Mg–O (I)).
Corresponding author. E-mail: shalawy99@yahoo.com
Received October 12, 2001. Accepted (revised) January 7, 2002 相似文献
13.
Jun Xing Zu Peng Chen Fang Yuan Xiao Xue Yan Ma Ci Zhang Wen Dr. Zhen Li Prof. Hua Gui Yang 《化学:亚洲杂志》2013,8(6):1265-1270
Multicomponent Cu? Cu2O? TiO2 nanojunction systems were successfully synthesized by a mild chemical process, and their structure and composition were thoroughly analyzed by X‐ray diffraction, transmission electron microscopy, field‐emission scanning electron microscopy, and X‐ray photoelectron spectroscopy. The as‐prepared Cu? Cu2O? TiO2 (3 and 9 h) nanojunctions demonstrated higher photocatalytic activities under UV/Vis light irradiation in the process of the degradation of organic compounds than those of the Cu? Cu2O, Cu? TiO2, and Cu2O? TiO2 starting materials. Moreover, time‐resolved photoluminescence spectra demonstrated that the quenching times of electrons and holes in Cu? Cu2O? TiO2 (3 h) is higher than that of Cu? Cu2O? TiO2 (9 h); this leads to a better photocatalytic performance of Cu? Cu2O? TiO2 (3 h). The improvement in photodegradation activity and electron–hole separation of Cu? Cu2O? TiO2 (3 h) can be ascribed to the rational coupling of components and dimensional control. Meanwhile, an unusual electron–hole transmission pathway for photocatalytic reactions over Cu? Cu2O? TiO2 nanojunctions was also identified. 相似文献
14.
İlknur Tatlıdil Münevver Sökmen Chris Breen Francis Clegg Celal Kurtuluş Buruk Emin Bacaksız 《Journal of Sol-Gel Science and Technology》2011,60(1):23-32
In this study, both suspensions and thin films of TiO2 and silver loaded TiO2 (Ag-TiO2) were used in the photocatalytic degradation/disinfection of C. albicans. In the case of thin films coated materials, both microscope slides and steel pieces of similar dimensions were dip coated
using sol–gel solutions prepared from titanium isopropoxide. Surface analysis of the materials confirmed that thin film formation
had been succesful. After set periods of irradiation in the presence of suspension or thin film coated material, 10 μL aliquots
of the solution were withdrawn and directly cultivated on sabouraud dextrose agar for 24 h at 37 °C. The number of living
colonies was counted. The results show that both the suspensions and the thin films displayed superior antimicrobial properties
towards C. albicans. In particular the Ag-TiO2 catalyst was extremely active even in the dark, for disinfection of C. albicans. The degradation percentage over TiO2 and Ag-TiO2 thin films coated on the steel substrate was higher than those coated on glass achieving 80 and 97.9%, respectively, using
the 365 nm, near visible region light source. 相似文献
15.
Mesoporous SiO2–TiO2 was synthesized by the sol–gel method using Si(OC2H5)4, Ti(OC2H5)4, and stearyltrimethylammonium chloride. By using acetylacetone as the capping agent of Ti(OC2H5)4, homogeneous SiO2–TiO2 composite was obtained. Spherical mesoporous SiO2–TiO2 was also synthesized by the sol–gel method using W/O emulsion under microwave irradiation. The specific surface area of these
mesoporous SiO2–TiO2 materials decreased when the Ti/Si molar ratio was higher than 0.1, which indicated that Ti was homogeneously distributed
in mesoporous SiO2 matrix at Ti/Si ≦ 0.1. The photocatalytic activity of mesoporous SiO2–TiO2 materials was investigated by the degradation of methylene-blue in water under UV light irradiation. Mesoporous SiO2–TiO2 was effective for the adsorption–decomposition of methylene-blue. 相似文献
16.
An all-electron scalar relativistic calculation on Cu
n
H (n = 1–13) clusters has been performed by using density functional theory with the generalized gradient approximation at the
PW91 level. Our results reveal that the hydrogen atom prefers to occupy the two fold coordination site for Cu
n
H (n = 2, 4–6, 8, 10–13) clusters, the single fold coordination site for Cu
n
H (n = 1, 3, 7) and the three fold coordination site for Cu9H cluster. For all Cu
n
H clusters, only the Cu11 structure in Cu11H is distorted obviously. After adsorption, the Cu–Cu bond is strengthened and the Cu–H bond of odd-numbered Cu
n
H clusters is relatively stronger than that of adjacent even-numbered Cu
n
H clusters. The Cu–Cu bond-length and Cu–H bond-length for all Cu
n
H clusters of our work are significantly shorter than those of previous work. This discrepancy can be explained in terms of
the scalar relativistic effect. The most favorable adsorption between small copper clusters and hydrogen atom takes place
in the case that hydrogen atom is adsorbed onto an odd-numbered pure Cu
n
cluster and becomes Cu
n
H cluster with even number of valence electrons. The odd–even alteration of magnetic moments is observed in Cu
n
H clusters and may provide the material with tunable code capacity of “0” and “1” by adsorbing a hydrogen atom onto odd- or
even-numbered copper clusters. 相似文献
17.
Abstract
C-2-unsubstituted imidazoline-3-oxides were reduced with NaBH4 in THF to give the corresponding trans-3,5-diarylimidazolidin-1-ols, while under the same conditions C-2-substituted derivatives gave the corresponding ring–chain–ring tautomers. Treatment of the crude reaction mixture from the reduction of C-2-unsubstituted imidazoline-3-oxides with a MeOH–H2O mixture provided reductive C–N bond cleavage to give hydroxylamines, while under the same conditions ring–chain–ring tautomers remained unchanged. 相似文献18.
Gennady I. Ostapenko Antony Cox Lidiya A. Ostapenko 《Journal of Solid State Electrochemistry》2002,6(4):245-252
Using experimental potential values for a vitreous carbon electrode in contact with the RbCu4Cl3I2 solid electrolyte, the concentration of Cu2+ ions in the electrolyte was determined. At 0.5 V, the concentration of Cu2+ was 1.25×1018 cm–3. The estimated values of the Cu2+ ion concentration in RbCu4Cl3I2 (0.8%) and the potential of the vitreous carbon electrode after electrochemical decomposition of RbCu4Cl3I2 (0.606 V) correspond to experimental values of 2% and 0.58 V, respectively. This demonstrates the adequacy of the model describing
the electrode potential of Cu2+ as a function of the concentration in RbCu4Cl3I2. When the C/RbCu4Cl3I2 interface was polarized, the diffusion coefficient of Cu2+ was 1.5×10–8 cm2 s–1. Investigations of the interface between the copper electrode and RbCu4Cl3I2 were carried out by galvanostatic and potentiostatic methods. A 1-μm layer of cuprous oxide, Cu2O, was discovered on the interface of the copper electrode with RbCu4Cl3I2. This layer blocks the course of the electrochemical reaction Cu0–e–⇌Cu+ with participation of copper metal. The copper electrode behaves as an inert redox electrode at low overvoltages. In this
case, at the Cu2O/RbCu4Cl3I2 interface an electrochemical reaction with Cu2+ ion participation, Cu+–e–⇌Cu2+, takes place. The results suggest that the reaction rate is limited by slowing the Cu2+ diffusion in RbCu4Cl3I2. The initial Cu2+ ion concentration in the electrolyte near this interface is about 1.4×1017 cm–3. The exchange current density is about (4±2)×10–6 A cm–2. At potentials ϕ>8–10 mV, an electrical breakdown of the Cu2O layer takes place, allowing copper metal to ionize to Cu+. We suggest that at 10 mV<ϕ<100 mV the rate of this reaction is limited by the formation and growth of copper nuclei and
at ϕ>120 mV the reaction rate is limited by charge transfer.
Electronic Publication 相似文献
19.
Hydrogen generation over carbon-, nitrogen- and sulfur-doped TiO2 semiconductor photocatalysts (represented as C–TiO2, N–TiO2 and S–TiO2, respectively) under visible light irradiation has been achieved using various sacrificial electron donors, namely triethanolamine,
diethanolamine, monoethanolamine, triethylamine, MeOH, EtOH, EDTA, l-ascorbic acid and phenol. The highest initial rate of H2 production was found to be in the range 1,000–2,200 μmol/g/h at ambient conditions when triethanolamine was used as sacrificial
electron donor. The efficacy of hydrogen production over these photocatalysts depends strongly on the nature of the sacrificial
electron donor and decreases in the following order: C–TiO2 > S–TiO2 > N–TiO2. The results of the present studies suggest that the rate of H2 production is not simply governed by the reduction potential of the sacrificial electron donor but also by the kinetic barrier
of the electron transfer process. 相似文献
20.
Jianxia Jiao Qun Xu Limin Li Takano Tsubasa Takaomi Kobayashi 《Colloid and polymer science》2008,286(13):1485-1491
Titania–silica composite have been prepared using polyethylene glycol (PEG) with different molecular weights (M
w), PEG20000, PEG10000, and PEG2000, as template in supercritical carbon dioxide (SC CO2). The composite precursors were dissolved in SC CO2 and impregnated into PEG templates using SC CO2 as swelling agent and carrier. After removing the template by calcination at suitable temperature, the titania–silica composite
were obtained. The composite were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and nitrogen
sorption–desorption experiment. Photocatalytic activity of the samples has been investigated by photodegradation of methyl
orange. Results indicate that there are many Si–O–Ti linkages in the TiO2/SiO2 composite; the PEG template has a significant influence on the structure of TiO2/SiO2. In addition, the TiO2/SiO2 prepared with PEG10000 exhibited high photocatalytic efficiency. So this work supplies a clue to control and obtain the TiO2/SiO2 composite with different photocatalytic reactivity with the aid of suitable PEG template in supercritical CO2. 相似文献