共查询到20条相似文献,搜索用时 46 毫秒
1.
Jing Huang Shurong Wang Yingqiang Zhao Xiaoying Wang Shuping Wang Shihua Wu Shoumin Zhang Weiping Huang 《Catalysis communications》2006,7(12):1029-1034
In this paper, the CuO/TiO2 catalysts prepared by the deposition–precipitation (DP) method were extensively investigated for CO oxidation reaction. The structural characters of the CuO/TiO2 catalysts were comparatively investigated by TG-DTA, XRD, and XPS measurements. It was shown that the catalytic behavior of CuO/TiO2 catalysts greatly depended on the TiO2-support calcination temperature, the CuO loading amount and the CuO/TiO2 catalysts calcination temperature. CuO supported on the anatase phase of TiO2-support calcined at 400 °C showed better catalytic activity than those supported on TiO2 calcined at 500 and 700 °C. Among all our investigated catalysts with CuO loading from 2% to 12%, the catalyst with 8 wt% CuO loading exhibited the highest catalytic activity. The optimum calcination temperature of the CuO/TiO2 catalysts was 300 °C. The XRD results indicated that the catalytic activity of the CuO/TiO2 catalysts was related to the crystal phase and particle size of TiO2 support and CuO active component. 相似文献
2.
Two series of titania-based photocatalysts were prepared by the sputtering method, in pure Ar atmosphere at a pressure of 0.5 Pa using a vanadium target source in a direct dc mode with a discharge of 300 V. The time of deposition was varied between 1 and 10 min in order to obtain different thickness of vanadium films. The first catalysts series (samples V/TiO2(A)-n) was prepared deposing vanadium on pure TiO2 anatase, while for the second series (samples V/TiO2(AR)-n) the deposition was made onto TiO2 Degussa P25. The samples have been investigated by means of vibrational (DRIFT and Raman) and optical (UV–vis in the DRS mode). Chemical analysis of the samples was made using the ICP-AES technique, while the crystalline structure of the deposed films onto the TiO2 supports was checked by X-ray diffraction (XRD). The samples morphology was analyzed using the AFM microscopy. The photocatalytic decomposition of acetone was considered as a reaction test. The activity of the investigated catalysts was found to be influenced by both the amount of vanadium and the support nature. Among the investigated catalysts V/TiO2(AR)-32 nm exhibited the higher activity. The activity of this catalyst was also superior to that of TiO2 Degussa P25. 相似文献
3.
Xueyan Li Desong Wang Guoxiang Cheng Qingzhi Luo Jing An Yanhong Wang 《Applied catalysis. B, Environmental》2008,81(3-4):267-273
Titanium dioxide nanoparticles were modified by polyaniline (PANI) using ‘in situ’ chemical oxidative polymerization method in hydrochloric acid solutions. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared spectra (FT-IR), X-ray photoelectron spectroscopy spectrum (XPS) and UV–vis spectra were carried out to characterize the composites with different PANI contents. The photocatalytic degradation of phenol was chosen as a model reaction to evaluate the photocatalytic activities of the modified catalysts. Results show that TiO2 nanoparticles are deposited by PANI to mitigate TiO2 particles agglomeration. The modification does not alter the crystalline structure of the TiO2 nanoparticles according to the X-ray diffraction patterns. UV–vis spectra reveal that PANI-modified TiO2 composites show stronger absorption than neat TiO2 under the whole range of visible light. The resulting PANI-modified TiO2 composites exhibit significantly higher photocatalytic activity than that of neat TiO2 on degradation of phenol aqueous solution under visible light irradiation (λ ≥ 400 nm). An optimum of the synergetic effect is found for an initial molar ratio of aniline to TiO2 equal to 1/100. 相似文献
4.
Nndor Balzs Kroly Mogyorsi Dvid F. Srank Attila Pallagi Tünde Alapi Albert Oszk Andrs Dombi Pl Sipos 《Applied catalysis. B, Environmental》2008,84(3-4):356-362
Nanosized TiO2 photocatalysts were synthesized via hydrogen–air flame hydrolysis. X-ray diffraction (XRD) measurements revealed that the TiO2 samples thus prepared consisted mainly of anatase (79–98 wt%) and the rest is rutile. Average particle diameters from TEM measurements were found to vary between 48 and 63 nm. The specific surface area of the samples was found to be practically independent of the synthesis parameters employed (20–32 m2 g−1). Photocatalytic activity of the catalysts was studied by using various model compounds. In spite of their very similar properties, the initial decomposition rate of phenol and methanol showed up to threefold variations within the series of the samples, and it was significantly higher for the best catalyst than that determined for Degussa P25. Our TEM measurements demonstrated that in the less active catalysts the dominant morphology of the particles is spherical, while polyhedral (cubic or hexagonal) shapes predominate in the samples with superior photocatalytic activity. From these observations, we concluded, that the shape of the primary particles (both in the case of our home made ones and in various batches of Degussa P25) strongly influence the photocatalytic activity of titania nanoparticles. 相似文献
5.
Astri Bjørnetun Haugen Izumi KumakiriChristian Simon Mari-Ann Einarsrud 《Journal of the European Ceramic Society》2011,31(3):291-298
TiO2, TiO2/Ag and TiO2/Au photocatalysts exhibiting a hollow spherical morphology were prepared by spray pyrolysis of aqueous solutions of titanium citrate complex and titanium oxalate precursors in one-step. Effects of precursor concentration and spray pyrolysis temperature were investigated. By subsequent heat treatment, photocatalysts with phase compositions from 10 to 100% rutile and crystallite sizes from 12 to 120 nm were obtained. A correlation between precursor concentration and size of the hollow spherical agglomerates obtained during spray pyrolysis was established. The anatase to rutile transformation was enhanced with metal incorporations and increased precursor concentration. The photocatalytic activity was evaluated by oxidation of methylene blue under UV-irradiation. As-prepared TiO2 particles with large amounts of amorphous phase and organic residuals showed similar photocatalytic activity as the commercial Degussa P25. The metal incorporated samples showed comparable photocatalytic activity to the pure TiO2 photocatalysts. 相似文献
6.
Preparation of multi-walled carbon nanotube supported TiO2 and its photocatalytic activity in the reduction of CO2 with H2O 总被引:2,自引:0,他引:2
Multi-walled carbon nanotube (MWCNT) supported TiO2 composite catalysts were prepared by sol-gel and hydrothermal methods. X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy and N2-adsorption analysis were carried out to characterize the composite catalysts. In using the sol-gel method, the MWCNTs were coated with anatase TiO2 nanoparticles, and by the hydrothermal method, rutile TiO2 nanorods were uniformly deposited on the MWCNTs. The photocatalytic activities of the composite catalysts were evaluated by the reduction of CO2 with H2O. The results indicate that the addition of an appropriate amount of MWCNTs as supports for TiO2 could remarkably improve the efficiency of the photocatalytic reaction. The composite catalysts prepared by the sol-gel method lead to the main formation of C2H5OH, while HCOOH is found to be the major product on the sample prepared by the hydrothermal method. 相似文献
7.
Daria Kibanova Martin Trejo Hugo Destaillats Javiera Cervini-Silva 《Applied Clay Science》2009,42(3-4):563-568
We studied the synthesis and photocatalytic activity of small-sized TiO2 supported on hectorite and kaolinite. Deposition of TiO2 on the clay mineral surface was conducted by using a sol–gel method with titanium isopropoxide as precursor. Anatase TiO2 particles formation was achieved by hydrothermal treatment at 180 °C. Material characterization was conducted using XRD, SEM, XPS, ICP-OES, BET and porosimetry analysis. fficiency in synthesizing clay–TiO2 composites depended strongly on the clay mineral structure. Incorporation of anatase in hectorite, an expandable clay mineral, was found to be very significant (> 36 wt.% Ti) and to be followed by important structural changes at the clay mineral surface. Instead, no major structural modifications of the clay were observed for kaolinite–TiO2, as compared with the untreated material. Photocatalytic performance of clay–TiO2 composites was evaluated with ATR-FTIR following the oxidation of adsorbed toluene and d-limonene, two model air pollutants. In either case, the photocatalytic removal efficiency of these hydrophobic substrates by the synthesized clay–TiO2 composites was comparable to that observed using pure commercial TiO2 (Degussa P25). 相似文献
8.
Chang-Soo Lee Jungwon Kim J.Y. Son Wonyong Choi Hyungjun Kim 《Applied catalysis. B, Environmental》2009,91(3-4):628-633
We prepared photocatalytic TiO2 thin films which exhibited relatively high growth rate and low impurity on polymer substrate by plasma enhanced atomic layer deposition (PE-ALD) from Ti(NMe2)4 [tetrakis (dimethylamido) Ti, TDMAT] and O2 plasma to show the self-cleaning effect. The TiO2 thin films with anatase phase and bandgap energy about 3.3 eV were deposited at growth temperature of 250 °C and the photocatalytic effects were compared with commercial Activ glass. From contact angles measurement of water droplet and photo-induced degradation test of organic liquid, TiO2 thin films with anatase phases showed superhydrophilic phenomena and decomposed organic liquid after UV irradiation. The anatase TiO2 thin film on polymer substrate showed highest photocatalytic efficiency after 5 h UV irradiation. We attribute the highest photocatalytic efficiency of TiO2 thin film with anatase structure to the formation of suitable crystalline phase and large surface area. 相似文献
9.
N. Bouazza M. Ouzzine M.A. Lillo-Rdenas D. Eder A. Linares-Solano 《Applied catalysis. B, Environmental》2009,92(3-4):377-383
In this work, we investigated titanium dioxide (TiO2) nanotubes and CNT–TiO2 hybrid materials for the photocatalytic oxidation (PCO) of propene at low concentration (100 ppmv) in gaseous phase. The materials were prepared via sol–gel method using sacrificial multi-walled carbon nanotubes (CNT) as templates and subsequent heat treatments to obtain the desired crystalline phase (anatase, rutile or a mixture of both) and eventually to remove the carbon template. We also studied rutile nanotubes for the first time and demonstrate that the activity strongly depends on the crystalline composition, following rutile < anatase < anatase/rutile mixture. The enhanced activity of the anatase–rutile mixture is attributed to the decrease in the electron–hole pair recombination due to the multiphasic nature of the particles. The key result of this work is the exceptional performance of the CNT–TiO2 hybrid, which yielded the highest observed photocatalytic activity. The improved performance is attributed to synergistic effects due to the hybrid nature of the material, resulting in small anatase crystalline sizes (CNT act as heat sinks) and a reduced electron–hole pair recombination rate (CNTs act as electron traps). These results demonstrate the great potential of hybrid materials and stimulate further research on CNT-inorganic hybrid materials in photocatalysis and related areas. 相似文献
10.
Benjaram M. Reddy Seung-Cheol Lee Dae-Soo Han Sang-Eon Park 《Applied catalysis. B, Environmental》2009,87(3-4):230-238
Vanadium oxide and cerium oxide doped titania–zirconia mixed oxides were explored for oxidative dehydrogenation of ethylbenzene to styrene utilizing carbon dioxide as a soft oxidant. The investigated TiO2–ZrO2 mixed oxide support with high specific surface area (207 m2 g−1) was synthesized by a coprecipitation method. Over the calcined support (550 °C), a monolayer equivalent (15 wt.%) of V2O5, CeO2 or a combination of both were deposited by using wet-impregnation or co-impregnation methods to make the V2O5/TiO2–ZrO2, CeO2/TiO2–ZrO2 and V2O5–CeO2/TiO2–ZrO2 combination catalysts, respectively. These catalysts were characterized using X-ray diffraction (XRD), Raman, scanning electron microscopy (SEM), transmission electron microscopy (TEM), temperature preprogrammed reduction (TPR), CO2 temperature preprogrammed desorption (TPD) and BET surface area methods. All characterization studies revealed that the deposited promoter oxides are in a highly dispersed form over the support, and the combined acid–base and redox properties of the catalysts play a major role in this reaction. The V2O5–CeO2/TiO2–ZrO2 catalyst exhibited a better conversion and product selectivity than other combinations. In particular, the addition of CeO2 to V2O5/TiO2–ZrO2 prevented catalyst deactivation and helped to maintain a high and stable catalytic activity. 相似文献
11.
Paulina Grska Adriana Zaleska Ewa Kowalska Tomasz Klimczuk Janusz W. Sobczak Ewa Skwarek Wadysaw Janusz Jan Hupka 《Applied catalysis. B, Environmental》2008,84(3-4):440-447
A series of TiO2 photocatalysts were obtained using several calcination temperatures ranging from 350 to 750 °C. The photocatalysts’ characteristics by X-ray diffraction, UV–vis and FTIR diffuse reflectance spectroscopies, X-ray photoelectron spectroscopy, BET and BJH methods showed that sample active in vis region had anatase structure, about 200 m2/g specific surface area, absorbed light for λ > 400 nm and contained 10.1 at.% of C–C species. The photocatalytic activity of the catalysts was estimated by measuring the decomposition rate of phenol in 0.21 mM aqueous solution in visible and ultraviolet light. The experimental data clearly indicate correlation between the absorption intensity of irradiation by obtained powders and their photocatalytic performance in phenol degradation. An increase in absorbance over the entire vis region and the highest photocatalytic activity for phenol degradation in visible light (λ > 400 nm) occurred for photocatalyst calcinated at 350 °C. Photocatalyst processed at 450 °C had the best activity in UV light (250 < λ < 400 nm). 相似文献
12.
Two series of Ta2O5–TiO2 photocatalysts (Ta:Ti = 4:1, 1:1 and 1:4) were prepared by sol–gel technique applying triblock copolymer of Pluronic P123 and were tested in platinized form (0.3 wt.%) in photodecomposition of water under ultraviolet and visible light (λ > 300 nm). It was found the mesoporous character of tantalum containing catalysts with relatively high surface area (100–130 m2 g−1) of these samples. However, higher concentration of TiO2 in mixed oxides leads to the destruction of mesoporous character of synthesized photocatalysts. All samples were characterized with thermogravimetry, XRD, N2 physisorption, DR-UV–vis and FTIR spectroscopy. The mixed oxides of Ta2O5–TiO2 system showed much lower band-gap than pure Ta2O5 and relatively high activity in platinized state in photocatalytic hydrogen generation under visible. Doping of pure oxides and mixed systems with sulfur resulted in lowering of the band-gap values below 3 eV and much better activity in H2 evolution reaction. Non-platinized photocatalysts showed activity in liquid phase cyclohexene photooxidation at 305 K. 相似文献
13.
The preparation of Ti1−xSnxO2 nanocrystalline photocatalysts in reverse microemulsions is reported in this work. The obtained materials have been characterised by total reflection X-ray fluorescence (TXRF), X-ray diffraction (XRD) and Raman and UV–vis spectroscopies. Very good accordance between calculated and obtained compositions is observed. Undoped TiO2 prepared in this way crystallises in the anatase phase. Tin-doped anatase is formed with x < 0.05, while both anatase and rutile phases crystallise when x ≥ 0.05. When both phases coexist, a preferential doping of rutile seems to occur. When x = 0.10, a multiphase mixture containing TiO2(anatase), TiO2(rutile) and SnO2 was formed. No significant modification of the band gap is found in any case. The photocatalytic activity of the obtained catalysts is compared employing the trichloroethylene photocatalytic degradation as a test reaction. The beneficial effect of Sn4+ in the activity of TiO2 appears to be related to the formation of anatase–rutile mixtures, leading to the highest specific photocatalytic activity in the sample of composition Ti0.93Sn0.07O2, with anatase:rutile ratio close to 3. 相似文献
14.
CeO2–TiO2 (Ce:Ti = 0.25–9, molar ratio) catalysts were synthesized by a sol–gel method and the catalytic performances were evaluated in the selective synthesis of isobutene and isobutane from CO hydrogenation under the reaction conditions of 673–748 K, 1–5 MPa and 720–3000 h−1. The physical properties, such as specific surface area, cumulative pore volume, average pore diameter, crystal phase and size, of the catalysts were characterized by N2 adsorption/desorption and XRD. All the CeO2–TiO2 composite oxides showed higher surface areas than pure TiO2 and CeO2. No TiO2 phase was detected on the samples of CeO2–TiO2 in which TiO2 contents were in the range of 10–50 mol%. Crystalline Ce2O3 was detected in CeO2–TiO2 (8:2). The reaction conditions, temperature, pressure and space velocity, had obvious influences on the CO conversion and distribution of the products over CeO2–TiO2 (8:2) catalyst. 相似文献
15.
Photocatalytic reactions of imazamox at TiO2, H2O2 and TiO2/H2O2 in water interfaces: Kinetic and photoproducts study 总被引:1,自引:0,他引:1
M. Harir A. Gaspar B. Kanawati A. Fekete M. Frommberger D. Martens A. Kettrup M. El Azzouzi Ph. Schmitt-Kopplin 《Applied catalysis. B, Environmental》2008,84(3-4):524-532
The photocatalytic transformation of imazamox, a herbicide of imidazolinone family, is investigated in aqueous solution containing titanium dioxide, hydrogen peroxide or the combination of TiO2/H2O2 under simulated sunlight irradiation. The effect of parameters such as the amount of catalysts, the concentration of herbicide, and the pH were investigated by measurement of the rate constant of degradation. Experimental data obtained under different conditions describe the dependency of degradation rate on the above mentioned parameters. Consequently, kinetic parameters were experimentally determined and a pseudo-first-order kinetic was observed. Mulliken charge distributions calculated by the DFT method B3LYP/6–31+G(d) level of theory for key cationic, anionic and neutral structures of imazamox give interpretation for the dependency of photodegradation rate constant on pH. The degradation rate constants were always higher for the heterogeneous catalysis in reactions (TiO2/UV, TiO2/UV/H2O2) compared to the homogeneous systems (UV alone, H2O2/UV). In parallel, five photoproducts could be tentatively identified using Electrospray ionization Fourier transform ion cyclotron resonance mass spectroscopy based on precise chemical formula assignments. 相似文献
16.
Highly-ordered TiO2 nanotube arrays (TiNTA) were prepared by an electrochemical anodization method and used as the carrier material to load 1 wt.% Ru. The Ru/TiNTA catalyst was then applied to the combination reactions of the partial oxidation of methane reaction (POM) with the carbon dioxide reforming with methane reaction (CRM) for syngas production. In comparison with the commercial TiO2 powder (P25) supported 1 wt.% Ru catalyst, Ru/TiNTA shows higher activity and much better stability. The superior performance of Ru/TiNTA is attributed to the specific monolithic-like structure and confinement effect of TiNTA. 相似文献
17.
Aijun Duan Ruili Li Guiyuan Jiang Jinsen Gao Zhen Zhao Guofu Wan Dengqian Zhang Weiqiang Huang Keng H. Chung 《Catalysis Today》2009,140(3-4):187
TiO2-Al2O3 binary oxide supports were obtained by sol–gel methods from Tetra-n-butyl-titanate and pseudoboehmite/aluminium chloride resources. The typical physico-chemical properties of NiW/TiO2-Al2O3 catalysts with different TiO2 loadings and their supports were characterized by means of BET, XRD and UV–vis DRS, etc. The BET results indicated that the specific surface areas of NiW/TiO2-Al2O3 catalysts were as higher as that over pure γ-Al2O3 support, and the pore diameters were also large. The XRD and UV–vis DRS analyzing results showed that the Ti-containing supported catalysts existed as anatase TiO2 species and the incorporation of TiO2 could adjust the interaction between support and active metal, and impelled the higher reducibility of tungsten. The hydrodesulphurization (HDS) performance of the series catalysts were evaluated with diesel feedstock in a micro-reactor unit, and the HDS results showed that NiW/TiO2-Al2O3 catalysts exhibited higher activities of ultra deep hydrodesulphurization of diesel oil than that of NiW/Al2O3 catalyst. The optimal TiO2 content of NiW/TiO2-Al2O3 catalysts was about 15 m%, and the corresponding HDS efficiency could reach to 100%. The sulphur contents of diesel products over NiW/TiO2-Al2O3 (from pseudoboehmite/AlCl3) catalysts with suitable TiO2 content could be less than 15 ppmw, which met the sulphur regulation of Euro IV specification of ultra clean diesel fuel. 相似文献
18.
Ag-substituted (Ag sub) and Ag-impregnated (Ag imp), anatase phase nano-TiO2 have been synthesized by solution combustion technique and reduction technique, respectively. The catalysts were characterized extensively by powder XRD, TEM, XPS, FT-Raman, UV absorption, FT-IR, TGA, photoluminescence, BET surface area and isoelectric pH measurements. These catalysts were used for the photodegradation of dyes and for the selective photooxidation of cyclohexane to cyclohexanone. The photoactivities of the combustion-synthesized catalysts were compared with those of commercial Degussa P 25 (DP 25) TiO2, and Ag-impregnated DP 25 (Ag DP). For the photocatalytic degradation of dyes, unsubstituted combustion-synthesized TiO2 (CS TiO2) exhibited the highest activity, followed by 1% Ag imp and 1% Ag sub. For the photoconversion of cyclohexane, the total conversion of cyclohexane and the selectivity of cyclohexanone followed the order: 1% Ag sub > DP 25 > CS TiO2 > 1% Ag imp > 1% Ag DP. The kinetics of the photodegradation of dyes and of the photooxidation of cyclohexane were modeled using Langmuir–Hinshelwood rate equation and a free radical mechanism, respectively, and the rate coefficients were determined. The difference in activity values of the catalysts observed for these two reactions and the detailed characterization of these catalysts are described in this study. 相似文献
19.
Roberto Scotti Massimiliano DArienzo Franca Morazzoni Ignazio Renato Bellobono 《Applied catalysis. B, Environmental》2009,88(3-4):323-330
Hydrothermally produced TiO2 powders with different phase composition (anatase, rutile and mixed phase) were immobilized on glass fibers and tested in the phenol mineralization process. Both H2O2 and O2 were used as oxygen donors, and their performances were compared with those of the same TiO2 samples as slurries.The catalytic properties of the immobilized different crystalline phases, rutile and anatase, show the same trend as the slurry samples: pure rutile displays the highest catalytic efficiency in the presence of H2O2, while samples containing anatase improve the photodegradation efficacy with O2. It was suggested that the stability of the photogenerated electron–hole couple allows high activity of rutile in the presence of H2O2, while the relevant oxygen chemisorption on anatase causes high catalytic activity in the presence of O2. A four parameters kinetics model shows that both reaction steps, the phenol degradation and the mineralization of the intermediates, are photoactivated by TiO2.Photoactivity of the coated glass fibers is generally lower than that of slurries, even if their efficiencies are almost comparable when the oxidation is performed by H2O2, while much lower when the oxygen donor is O2. As a matter of fact, the morphology of immobilized catalysts shows the presence of chestnut burr aggregates of large rutile crystalline rods on the glass fiber, which are much less compact than the aggregates of small anatase particles. This preserves rutile surface area from the coarsening effects; thus, when rutile is the more active species, as in the presence of H2O2, the photocatalytic activity is less affected by immobilization. 相似文献
20.
A two-dimensional TiO2/carbon nanowall composite material was fabricated by growing carbon nanowalls on a Ti sheet with hot filament chemical vapor deposition, followed by metal-organic chemical vapor deposition using titanium isopropoxide as TiO2 precursor and argon as carrier gas. Scanning electron microscopy showed that TiO2 was uniformly coated on the entire carbon nanowall and a TiO2/carbon nanowall composite was obtained. Raman spectroscopy and X-ray diffraction indicated that the crystal phase of the TiO2 coating was anatase. The asymmetry of the current-voltage plot for the material revealed that a heterojunction was formed between the TiO2 and the carbon nanowall. As a result of this heterojunction, enhanced separation of photogenerated electrons and holes was confirmed by surface photovoltage and photocurrent measurements. The investigation of photocatalytic ability showed that the TiO2/carbon nanowall had a higher photocatalytic activity than TiO2 nanotubes for the degradation of phenol under UV light irradiation. 相似文献