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1.
Kunyaluck Kontapakdee Joongjai Panpranot Piyasan Praserthdam 《Catalysis communications》2007,8(12):2166-2170
Anatase and rutile TiO2 were used for preparation of the TiO2 supported Pd and Pd–Ag catalysts for selective hydrogenation of acetylene. It was found that Pd/TiO2-anatase exhibited higher acetylene conversion and ethylene selectivity than rutile TiO2 supported ones. However, addition of Ag to Pd/TiO2-anatase catalyst resulted in lower ethylene selectivity while that of Pd/TiO2-rutile increased. It is suggested that Ag addition suppressed the beneficial effect of the Ti3+ sites presented on the anatase TiO2 during selective acetylene hydrogenation whereas without Ti3+, Ag promoted ethylene selectivity by blocking sites for over-hydrogenation of ethylene to ethane. 相似文献
2.
A TiO2 nanoceramic film was prepared as an alternative absorber layer for infrared thermal detectors. The TiO2 film was amorphous, and its grain size increased with the ion anode voltage and oxygen flow rate. Moiré deflectometry was applied for measuring the nonlinear refractive indices of TiO2 films on polycarbonate (PC) substrates. The nonlinear refraction index was measured to be of the order of 10−8 cm2 W−1 and the change in refractive index was of the order of 10−5. The linear refractive index was correlated with the porosity. Denser TiO2 films exhibited higher linear refractive indices, obvious red-shifts and narrower absorption bands in the near-IR region. 相似文献
3.
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
4.
Direct synthesis route was developed to support TiO2–ZrO2 binary metal oxide onto the carbon templated mesoporous silicalite-1 (CS-1). Metal hydroxide modified carbon particles could play a role as hard template and simultaneously support metal components on the mesopores during the crystallization of zeolites. Such supported TiO2–ZrO2 binary metal oxides (TZ/CS-1) showed better resistance to deactivation in the oxidative dehydrogenation of ethylbenzene (ODHEB) in the presence of CO2. These catalysts were found to be active, selective and catalytically stable (10 h of time-on-stream) at 600 °C for the dehydrogenation of ethylbenzene (EB) to styrene (Sty). 相似文献
5.
Yang Liu Xiaolei Wang Fan Yang Xiurong Yang 《Microporous and mesoporous materials》2008,114(1-3):431-439
Optically transparent, crack-free, mesoporous anatase TiO2 thin films were fabricated. The Ag/TiO2 composite films were prepared by incorporating Ag in the pores of TiO2 films with an impregnation method via photoreduction. The as-prepared composite films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectronic spectra (XPS) and N2 adsorption. The release behavior of silver ions in the mesoporous composite film was also studied. Moreover, the antimicrobial behaviors of the mesoporous film were also investigated by confocal laser scanning microscopy. The antibacterial activities of the composite films were studied by a fluorescence label method using Escherichia coli (E. coli) as a model. The as-prepared mesoporous TiO2 films showed much higher antimicrobial efficiency than that of glass and commercial P25 TiO2 spinning film. The facts would result from the high surface area, small crystal size and more active sites for the mesoporous catalysis. After the doping of Ag, a significant improvement for the antimicrobial ability was obtained. To elucidate the roles of the membrane photocatalyst and the doped silver in the antimicrobial activity, cells from a silver-resistant E. coli were used. These results indicated that Ag nanoparticles in the mesoporous were not only an antimicrobial but also an intensifier for photocatalysis. The as-prepared mesoporous composite film is promising in application of photocatalysis, antimicrobial and self-clean technologies. 相似文献
6.
7.
Komateedi N. Rao Benjaram M. Reddy B. Abhishek Yeong-Hui Seo Nanzhe Jiang Sang-Eon Park 《Applied catalysis. B, Environmental》2009,91(3-4):649-656
The present study was undertaken to investigate the influence of ceria on the physicochemical and catalytic properties of V2O5/TiO2–ZrO2 for oxidative dehydrogenation of ethylbenzene to styrene utilizing CO2 as a soft oxidant. Monolayer equivalents of ceria, vanadia and ceria–vanadia combination over TiO2–ZrO2 (TZ) support were impregnated by a coprecipitation and wet impregnation methods. Synthesized catalysts were characterized by using X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, temperature programmed reduction, transmission electron microscopy and BET surface area methods. The XRD profiles of 550 °C calcined samples revealed amorphous nature of the materials. Upon increasing calcination temperature to 750 °C, in addition to ZrTiO4 peaks, few other lines due to ZrV2O7 and CeVO4 were observed. The XPS V 2p results revealed the existence of V4+ and V5+ species at 550 and 750 °C calcinations temperatures, respectively. TEM analysis suggested the presence of nanosized (<7 nm) particles with narrow range distribution. Raman measurements confirmed the formation ZrTiO4 under high temperature treatments. TPR measurements suggested a facile reduction of CeO2–V2O5/TZ sample. Among various samples evaluated, the CeO2–V2O5/TZ sample exhibited highest conversion and nearly 100% product selectivity. In particular, the addition of ceria to V2O5/TZ suppressed the coke deposition and allowed a stable and high catalytic activity. 相似文献
8.
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
9.
Akbar Eshaghi Reza MozaffariniaMahmoud Pakshir Ameneh Eshaghi 《Ceramics International》2011,37(1):327-331
TiO2 nanocomposite films with different concentrations of TiO2 MT-150A nanoparticles were immobilized on glass substrates using a dip coating process. The crystalline structure and surface chemical state of nanocomposite film properties were examined by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The specific surface area and morphology of TiO2 MT-150A nanoparticles were evaluated by the BET method and Field Emission Scanning Electron Microscopy (FE-SEM). The photocatalytic activities of films were evaluated by the methyl orange decoloring rate. XPS measurements showed that the oxygen amount (%) was related to the film composition. The composite film with 10 g/L MT-150A loading yielded the highest amount of surface oxygen (26.82%) and TiO2 rutile showed the lowest amount of surface oxygen (13.67%) in the form of surface hydroxyl groups. The remaining oxygen was identified as lattice oxygen. In addition, the nanocomposite film with 10 g/L MT-150A loading yielded the highest photocatalytic activity. 相似文献
10.
Yoshikazu Kameshima Akihiro Yoshizawa Akira Nakajima Kiyoshi Okada 《Applied Clay Science》2009,46(2):181-184
SiO2–TiO2/montmorillonite composites were prepared under acidic, neutral and basic conditions and the solid acidity of the resulting composites were determined. All the SiO2/TiO2 ratio of the colloidal particles was set at 10 but the resulting SiO2/TiO2 ratios were significantly richer in TiO2. The XRD patterns of the acidic composite showed expanding and broadening of the (001) reflection by intercalation of colloidal SiO2–TiO2 particles, but the neutral and basic composites showed only broadening of the reflections and no intercalation. The specific surface areas of the acidic, neutral and basic composites (375, 237 and 247 m2/g, respectively) were much larger than of montmorillonite (6 m2/g). The average pore sizes were about 4, 15 and 50 nm, and the amounts of solid acidic sites measured by the NH3-TPD were 178, 95 and 86 µmol/g for the acidic, neutral and basic composites, respectively. The solid acid amount of the acidic composite was twice that of a commercial catalyst, K-10, (85 µmol/g) and much higher than the guest phase SiO2–TiO2 gel (16 µmol/g) or the host phase montmorillonite (6 µmol/g). The TPD peak temperatures reflect the acid strength, and were similar in all the samples, ranging from 175° to 200 °C. 相似文献
11.
Lijuan Chen Jintao Tian Huang Qiu Yansheng Yin Xin Wang Jinhui Dai Pingwei Wu Aiping Wang Lei Chu 《Ceramics International》2009,35(8):3275-3280
The preparation of TiO2 nanofilm was conducted on common glass via the sol–gel process. Glacial acetic acid and diethanolamine were used as inhibitors to prepare acidic and alkaline TiO2 sol, respectively. XRD, SEM, and EDS characterization showed that the film prepared from acidic TiO2 sol had a narrow particle size distribution of 15–30 nm and relatively poor particle crystallization while in the case of the film from alkaline TiO2 sol the nanoparticles were in a wide range of 10–80 nm and well crystallized. The photolysis evaluation through MO degradation revealed that the film from acidic sol possessed apparently better photocatalytic activity than that from alkaline sol. Heat treatment with longer time led to a 50% increase of the photocatalytic activity for the film. 相似文献
12.
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
13.
Yong Liu Ming Meng Xin-Gang Li Li-Hong Guo Yu-Qing Zha 《Chemical Engineering Research and Design》2008,86(8):932-940
The NOx storage and reduction (NSR) catalysts Pt/K/TiO2–ZrO2 were prepared by an impregnation method. The techniques of XRD, NH3-TPD, CO2-TPD, H2-TPR and in situDRIFTS were employed to investigate their NOx storage behavior and sulfur-resisting performance. It is revealed that the storage capacity and sulfur-resisting ability of these catalysts depend strongly on the calcination temperature of the support. The catalyst with theist support calcined at 500 °C, exhibits the largest specific surface area but the lowest storage capacity. With increasing calcination temperature, the NOx storage capacity of the catalyst improves greatly, but the sulfur-resisting ability of the catalyst decreases. In situ DRIFTS results show that free nitrate species and bulk sulfates are the main storage and sulfation species, respectively, for all the catalysts studied. The CO2-TPD results indicate that the decomposition performance of K2CO3 is largely determined by the surface property of the TiO2–ZrO2 support. The interaction between the surface hydroxyl of the support and K2CO3 promotes the decomposition of K2CO3 to form –OK groups bound to the support, leading to low NOx storage capacity but high sulfur-resisting ability, while the interaction between the highly dispersed K2CO3 species and Lewis acid sites gives rise to high NOx storage capacity but decreased sulfur-resisting ability. The optimal calcination temperature of TiO2–ZrO2 support is 650 °C. 相似文献
14.
Kuk Cho Hankwon Chang Jin Ho Park Byoung Gon Kim Hee Dong Jang 《Journal of Industrial and Engineering Chemistry》2008,14(6):860-863
Titania (TiO2)–silica (SiO2) nanoparticles were synthesized from sprayed droplets of a mixture of TEOS and TTIP by flame spray pyrolysis (FSP). The effect of molar ratio between TEOS and TTIP in the mixture on the particle properties such as particle morphology, average particle diameter, specific surface area, crystal structure, etc., were determined using TEM, XRD, BET, and FT-IR. A UV-spectrometer was also used to measure the absorption spectrum and the band gap energy of the product particles. As the molar ratio of TEOS/TTIP increased by increasing TEOS concentration at the fixed TTIP concentration, the average particle diameter of the mixed oxide nanoparticles increased with maintaining uniform dispersion between TiO2 and SiO2, and crystal structure was transformed from anatase to amorphous. The band gap energy of the TiO2–SiO2 nanoparticles increased with respect to the increase of the molar ratio due to the decrease of width of UV-absorption spectrum. Photocatalytic activity of TiO2–SiO2 composite particles decreased with the concentration of TEOS. 相似文献
15.
Improved densification during the conventional sintering of KNbO3 ceramics was achieved by using small additions of TiO2. This improved densification can be explained on the basis of high-temperature chemical reactions in the system. X-ray diffractometry and electron microscopy were used in combination with diffusion-couple experiments in order to elucidate the chemical reactions between KNbO3 and TiO2. TiO2 reacts with KNbO3 forming KNbTiO5, and a low concentration of Ti incorporates in the KNbO3 structure resulting in the formation of oxygen vacancies and, consequently, in an improvement in the densification. At ∼1037 °C eutectic melting between the KNbO3 and the KNbTiO5 further improves the densification of the KNbO3 ceramics. 相似文献
16.
A.G. Muñoz 《Electrochimica acta》2007,52(12):4167-4176
The semiconducting properties of anodic grown TiO2-nanotubes were analyzed by means of the potential dependence of the interfacial capacity under different electrolyte and illumination conditions. The experimental results offer evidence for a duplex oxide film conformed by the bottom and wall of pores with different density of donors and concentration of surface states. The surface extension offered by the walls of oxide tubes is manifested in surface related effects such as the shift of the flat band potential and trapping of photoelectrons. 相似文献
17.
Yi Zhu Gai Li Shengyi Zhang Jiming Song Changjie Mao Helin Niu Baokang Jin Yupeng Tian 《Electrochimica acta》2011,(22):7550
CeO2/TiO2 composite with kernel–shell structure was synthesized by a sol–gel process. The characterization results show that the composite is made up of anatase phase TiO2 and cubic system CeO2. The electrochemiluminescence (ECL) behavior of the CeO2/TiO2 composite was studied by a cyclic voltammetry in the presence of persulfate, and the effect factors on ECL emission were discussed. Based on a series of experiments, it is proposed that the strong dual ECL emission produced by the CeO2/TiO2 composite resulted from the benefit ECL effect of interface heterojunction in composite. 相似文献
18.
Combined TiO2/SiO2 mesoporous photocatalysts with location and phase controllable TiO2 nanoparticles 总被引:1,自引:0,他引:1
E. Beyers E. Biermans S. Ribbens K. De Witte M. Mertens V. Meynen S. Bals G. Van Tendeloo E.F. Vansant P. Cool 《Applied catalysis. B, Environmental》2009,88(3-4):515-524
Combined TiO2/SiO2 mesoporous materials were prepared by deposition of TiO2 nanoparticles synthesised via the acid-catalysed sol–gel method. In the first synthesis step a titania solution is prepared, by dissolving titaniumtetraisopropoxide in nitric acid. The influences of the initial titaniumtetraisopropoxide concentration and the temperature of dissolving on the final structural properties were investigated. In the second step of the synthesis, the titania nanoparticles were deposited on a silica support. Here, the influence of the temperature during deposition was studied. The depositions were carried out on two different mesoporous silica supports, SBA-15 and MCF, leading to substantial differences in the catalytic and structural properties. The samples were analysed with N2-sorption, X-ray diffraction (XRD), electron probe microanalysis (EPMA) and transmission electron microscopy (TEM) to obtain structural information, determining the amount of titania, the crystal phase and the location of the titania particles on the mesoporous material (inside or outside the mesoporous channels). The structural differences of the support strongly determine the location of the nanoparticles and the subsequent photocatalytic activity towards the degradation of rhodamine 6G in aqueous solution under UV irradiation. 相似文献
19.
In this paper, a cerium dioxide (CeO2) modified titanium dioxide (TiO2) nanotube array film was fabricated by electrodeposition of CeO2 nanoparticles onto an anodized TiO2 nanotube array. The structural investigation by X-ray diffraction, scanning electron microscopy and transmission electron microscopy indicated that the CeO2 nanoparticles grew uniformly on the walls of the TiO2 nanotubes. The composite was composed of cubic-phase CeO2 crystallites and anatase-phase TiO2 after annealing at 450 °C. The cyclic voltammetry and chronoamperometric charge/discharge measurement results indicated that the CeO2 modification obviously increased the charge storage capacity of the TiO2 nanotubes. The charge transfer process at the surface, that is, the pseudocapacitance, was the dominate mechanism of the charge storage in CeO2-modified TiO2 nanotubes. The greater number of surface active sites resulting from uniform application of the CeO2 nanoparticles to the well-aligned TiO2 nanotubes contributed to the enhancement of the charge storage density. 相似文献
20.
We present an energy band model and a method for filling p-type CuSCN in n-type porous TiO2 film. The energy band model is based on the interface energy levels between TiO2/CuSCN heterojunction and the aqueous electrolyte. The whole deposition process is divided into three stages: the uniform nucleation on the internal surface at positive potential, the crystal growth with the cathodic potential shifting negatively and the thermal activated growth at constant potential. This was demonstrated by the electrochemical experiment combining the hydrothermal process. It was found that the obtained TiO2/CuSCN heterojunction exhibited good rectification characteristics, indicating that an intimate electrical contact was formed between the large internal surface of TiO2 film and CuSCN. This novel hydrothermal-electrochemical method may be valuable for fabricating extremely thin absorber (eta)-solar cells and other semiconductor devices. 相似文献