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1.
In this article, Pd nanoparticles supported on carbon-modified rutile TiO2 (CMRT) as a highly efficient catalyst for formic acid electrooxidation were investigated. Pd/CMRT catalyst was synthesized by using liquid phase reduction method in which Pd nanoparticles was loaded on the surface of CMRT obtained through a chemical vapor deposition (CVD) process. Pd/CMRT shows three times the catalytic activity of Pd/C, as well as better catalytic stability towards formic acid electrooxidation. The enhanced catalytic property of Pd/CMRT mainly arises from the improved electronic conductivity of carbon-modified rutile TiO2, the dilated lattice constant of Pd nanoparticles, an increasing of surface steps and kinks in the microstructure of Pd nanoparticles and slightly better tolerance to the adsorption of poisonous intermediates. 相似文献
2.
The Pd/TiO2 nanoparticles containing 5 wt.% Pd were synthesized by one-step flame spray pyrolysis (FSP) under different flame conditions. As revealed by both X-ray diffraction (XRD) and transmission electron microscopy (TEM) results, the average particle sizes of Pd/TiO2 were increased from 9.7 to 24.6 nm with increasing the precursor concentration and the feed flow rate as well as reduction of the O2 dispersing gas during FSP synthesis. Although the BET surface area and %anatase phase content were decreased with increasing Pd/TiO2 particle size, %Pd dispersion as determined from the amounts of CO chemisorption were higher on the larger size FSP-made Pd/TiO2 nanoparticles. It is suggested that the shorter residence time in flame and/or the lower combustion energy (enthalpy density) resulted in more coverage of Pd surface by the formation of Ti-O groups, rendering lower CO chemisorption ability of the smaller size Pd/TiO2. 相似文献
3.
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
4.
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
5.
The kinetics of the electrochemical lithium insertion reaction in nano-sized rutile TiO2 has been investigated using ac impedance spectroscopy. The experimental data are obtained for a rutile compound synthesized via a solution technique and characterized by a morphology corresponding to spherical particles made of a large number of very thin nanorods 20 nm thick. The results are discussed as a function of the Li content x for 0 < x ≤ 0.8 in LixTiO2, the temperature over the range 10-50 °C and the number of discharge-charge cycles. The significant linear decrease of the chemical diffusion coefficient DLivs. the lithium content and the high values of DLi found in the composition range 0 < x ≤ 0.5 are discussed and related with the electrochemical behaviour of the nano-sized material. From comparison with the bulk material, a promoting effect of the morphology on the kinetic characteristics is evidenced. For the first time an experimental evaluation of the activation energy for Li diffusion in nano-sized rutile TiO2 is obtained; the value of 0.35 eV being much lower than that reported from computational experiments for the micro-sized oxide. This work also demonstrates a new system takes place from the second cycle, characterized by a significant improvement of Li diffusion by a factor five and allowing high rates to be used. 相似文献
6.
Stéphane Fierro Lassiné Ouattara Emmanouil Passas-Lagos Christos Comninellis 《Electrochimica acta》2009,54(7):2053-7082
A model has been proposed according to which the voltammetric charge involved in the Ti/IrO2 electrodes is due to two contributions: a faradaic contribution due to surface redox activities at the IrO2 coating and a non-faradaic contribution due to the charging of electrical double layer (). The later has been proposed as a tool for the estimation of the relative surface area of the Ti/IrO2 electrodes.Differential electrochemical mass spectrometry (DEMS) measurements using H218O has demonstrated that we are dealing with an active electrode in which the surface redox couple IrO3/IrO2 acts as mediator in the oxidation of formic acid (FA).From the voltammetric measurements using different IrO2 loading and FA concentrations, the kinetic parameters of FA oxidation via the surface redox couple IrO3/IrO2 have been determined.Finally a model has been proposed considering that FA oxidation at Ti/IrO2 anodes is controlled by mass transfer. The good agreement between the experimental results and the model indicates that the surface reaction between FA and the electrogenerated IrO3 is a fast reaction. 相似文献
7.
Alumina-coated rutile TiO2 samples were prepared starting from NaAlO2 by the chemical liquid deposition method. The alumina nanofilms existed in amorphous hydrated alumina phase and anchored at the surfaces of TiO2 particles via Ti-O-Al bonding. The formation of continuous and dense alumina nanofilms on the TiO2 surface depended on the pH value of the reaction solution and the alumina loading. After coated by alumina nanofilms, the whiteness and brightness of the alumina-coated TiO2 samples increased with the increase of the alumina loading while the relative light scattering index was found to depend upon the alumina loading. 相似文献
8.
9.
J. Godnjavec J. Zabret B. Znoj S. Skale N. Veronovski P. Venturini 《Progress in Organic Coatings》2014
Surface modification and characterization of TiO2 nanoparticles as an additive in a polyacrylic clear coating were investigated. For the improvement of nanoparticles dispersion and the decreasing of photocatalytic activity, the surface of nanoparticles was modified with binary SiO2/Al2O3. The surface treatment of TiO2 nanoparticles was characterized with FTIR. Microstructural analysis was done by AFM. The size, particle size distribution and zeta potential of TiO2 nanoparticles in water dispersion was measured by DLS method. For the evaluation of particle size and the stability of nanoparticles in water dispersions with higher solid content the electroacoustic spectroscopy was made. To determine the applicability and evaluate the transmittance of the nano-TiO2 composite coatings UV–VIS spectroscopy in the wavelength range of 200–800 nm was employed. The results showed that surface treatment of TiO2 nanoparticles with SiO2/Al2O3 improves nanoparticles dispersion and UV protection of the clear polyacrylic composite coating. 相似文献
10.
Behnaz Hojjati 《Polymer》2007,48(20):5850-5858
Due to the strong tendency of nanoparticles such as metal oxides to agglomerate, homogeneous dispersion of these materials in a polymeric matrix is extremely challenging. In order to overcome this problem and to enhance the filler-polymer interaction, this study focused on living polymerization that was initialized from the surface of titania nanofillers. A new method for synthesizing TiO2/polymer nanocomposites was found with a good dispersion of the nanofillers by using the bifunctional RAFT agent, 2-{[(butylsulfanyl)carbonothioyl]sulfanyl}propanoic acid). This RAFT agent has an available carboxyl group to anchor onto TiO2 nanoparticles, and an SC(SC4H9) moiety for subsequent RAFT polymerization of acrylic acid (AA) to form n-TiO2/PAA nanocomposites. The functionalization of n-TiO2 was determined by FTIR and partitioning studies, the livingness of the polymerization was verified using GPC and NMR, while the dispersion of the inorganic filler in the polymer was studied using electron microscopy, FTIR and thermal analysis. 相似文献
11.
Xiang Li Yanling Zhang Anjie Wang Yao Wang Yongkang Hu 《Catalysis communications》2010,11(14):1129-1132
TiO2- and CeO2-promoted bulk Ni2P catalysts were prepared by impregnation and in-situ H2 temperature-programmed reduction method. The prepared catalysts were characterized by XRD and XPS. The hydrogenation activities of the catalysts were studied using 1.5 wt.% 1-heptene in toluene and 1.0 wt.% phenylacetylene in ethanol as the model feeds. The results indicate that bulk Ni2P possesses low hydrogenation activity but is tunable by simply controlling the content of the additives (TiO2 or CeO2), suggesting that TiO2 and CeO2 are effective promoters to enhance the hydrogenation activity of Ni2P. 相似文献
12.
Synthesis, characterization and catalytic activity of an ultrafine Pd/C catalyst for formic acid electrooxidation 总被引:3,自引:0,他引:3
An ultrafine Pd/C catalyst with a uniformly sized and highly dispersed nanostructure was synthesized by an improved liquid phase reduction method; in this process, a complexone (trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid, CyDTA) was used as an alternative stabilizer for the first time. Physicochemical characterizations indicated that the resulting Pd nanoparticles possessed ideal structural characteristics, including an average diameter of 2.1 nm, narrow size distribution ranging from 0.5 to 4.0 nm, no visible agglomerations, and no residual CyDTA. Electrochemical tests showed that the catalytic activity of the obtained Pd/C catalyst for formic acid electrooxidation was 2.2 times greater than that of Pd/C catalyst prepared in the absence of CyDTA. This improvement in the electrocatalytic performance was attributed to the uniformly sized and highly dispersed nanostructure, which provided a larger overall electrochemical active surface area. 相似文献
13.
The decolouring and the degradation of xylenol orange in aqueous solution photocatalyzed by band-gap-irradiated TiO2, modified with nanosized palladium particles has been studied. The photocatalytic activity of TiO2, modified with palladium, is higher than that of the semiconductig support. The adsorption properties of the catalysts, as well as the size of the palladium clusters on the surface of the support, influence the efficiency of the photocatalytic process. The rate of disappearance of the dye molecule follows a pseudo-first kinetic order according to the Langmuir–Hinshelwood model. The increase of the quantum yield of the photodestruction reaction of the studied dye is due to the formation of Schotky barriers on the metal–semiconductor interface, which serve as efficient electron traps, preventing the electron–hole recombination. 相似文献
14.
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
15.
Selective oxidation of methanol to dimethoxymethane (DMM) was conducted in a fixed-bed reactor over an acid-modified V2O5/TiO2 catalyst. The influence of the acid modification on its structure, redox and acidic properties, and catalytic performance for methanol oxidation were investigated. The results indicated that the content of vanadia in the catalyst exhibits a vital influence on the dispersion of vanadium species, while the acid modification can enhance its surface acidity. Proper amounts of the acid (W() = 15%) and V2O5 (W(V2O5) = 15%) components loaded in the acid-modified V2O5/TiO2 catalyst are able to build a bi-functional circumstance that is favorable for the formation of DMM with high activity and selectivity. As a result, for the selective oxidation of methanol, the H2SO4-modified V2O5/TiO2 catalyst gives a much higher DMM yield at 150 °C than the unmodified one. 相似文献
16.
The effect of the support nature on the performance of Pd catalysts during partial oxidation of ethanol was studied. H2, CO2 and acetaldehyde formation was favored on Pd/CeO2, whereas CO production was facilitated over Pd/Y2O3 catalyst. According to the reaction mechanism, determined by DRIFTS analyses, some reaction pathways are favored depending on the support nature, which can explain the differences observed on products distribution. On Pd/Y2O3 catalyst, the production of acetate species was promoted, which explain the higher CO formation, since acetate species can be decomposed to CH4 and CO at high temperatures. On Pd/CeO2 catalyst, the acetaldehyde preferentially desorbs and/or decomposes to H2, CH4 and CO. The CO formed is further oxidized to CO2, which seems to be promoted on Pd/CeO2 catalyst. 相似文献
17.
K. Ko
í L. Obalov L. Matjov D. Plach Z. Lacný J. Jirkovský O. olcov 《Applied catalysis. B, Environmental》2009,89(3-4):494-502
Pure TiO2 anatase particles with a crystallite diameters ranging from 4.5 to 29 nm were prepared by precipitation and sol–gel method, characterized by X-ray diffraction (XRD), BET surface area measurement, UV–vis and scanning electron microscopy (SEM) and tested in CO2 photocatalytic reduction. Methane and methanol were the main reduction products. The optimum particle size corresponding to the highest yields of both products was 14 nm. The observed optimum particle size is a result of competing effects of specific surface area, charge–carrier dynamics and light absorption efficiency. 相似文献
18.
Oxidation of CH4 over Pd supported on TiO2-doped SiO2: Effect of Ti(IV) loading and influence of SO2
A.M. Venezia G. Di Carlo G. Pantaleo L.F. Liotta G. Melaet N. Kruse 《Applied catalysis. B, Environmental》2009,88(3-4):430-437
Titania-modified silicas with different weight% of TiO2 were prepared by sol–gel method and used as supports for Pd (1 wt%) catalysts. The obtained materials were tested in the oxidation of methane under lean conditions in absence and in presence of SO2. Test reactions were consecutively performed in order to evaluate the thermal stability and poisoning reversibility. Increasing amounts of TiO2 improved the catalytic activity, with an optimum of the performance for 10 wt% TiO2 loading. Moreover, the titania-containing catalysts exhibited a superior tolerance towards SO2 by either adding it to the reactants or feeding it as a pure pretreatment atmosphere at 350 °C. Catalysts were characterized by XPS, XRD, FT-IR and BET measurements. According to the structural and surface analyses, the mixed oxides contained Si–O–Ti linkages which were interpreted as being responsible for the enhanced intrinsic activity of supported PdO with respect to PdO on either pure SiO2 or pure TiO2. Moreover, the preferential interaction of the sulfur molecule with TiO2 and the easy SOx desorption from high surface area silica were the determining factors for the superior SO2 tolerance of the TiO2-doped catalysts. 相似文献
19.
Molybdenum oxide (MoOx) was added to a Pd/C catalyst using a novel two-step procedure. The enhancement effect of MoOx on Pd/C catalyst for the electrooxidation of formic acid was verified by electrochemical experiments. Compared to the Pd/C catalyst, the experimental results showed that the addition of MoOx could significantly enhance the electrocatalytic performances for the electrooxidation of formic acid. Significant improvements in electrocatalytic activity and stability were primarily ascribed to the effect of MoOx on the Pd catalyst. In addition to the large specific surface area, the hydrogen spillover effect is speculated to have accelerated the electrooxidation rate of formic acid in the direct pathway. 相似文献
20.
Bo-Ra Kim Hyo-Jin Oh Kang-Seop Yun Sang-Chul Jung Wooseung Kang Sun-Jae Kim 《Progress in Organic Coatings》2013
For an electrochemical water splitting system, titanate nanotubular particles with a thickness of ∼700 nm produced by a hydrothermal process were repetitively coated on fluorine-doped tin oxide (FTO) glass via layer-by-layer self-assembly method. The obtained titanate/FTO films were dipped in aqueous Fe solution, followed by heat treatment for crystallization at 500 °C for 10 min in air. The UV–vis absorbance of the Fe-oxide/titanate/FTO film showed a red-shifted spectrum compared with the TiO2/FTO coated film; this red shift was achieved by the formation of thin hematite-Fe2O3 and anatase-TiO2 phases verified using X-ray diffraction and Raman results. The cyclic voltammetry results of the Fe2O3/TiO2/FTO films showed distinct reversible cycle characteristics with large oxidation–reduction peaks with low onset voltage of I–V characteristics under UV–vis light illumination. The prepared Fe2O3/TiO2/FTO film showed much higher photocurrent densities for more efficient water splitting under UV–vis light illumination than did the Fe2O3/FTO film. Its maximum photocurrent was almost 3.5 times higher than that obtained with Fe2O3/FTO film because of the easy electron collection in the current collector. The large current collection was due to the existence of a TiO2 base layer beneath the Fe2O3 layer. 相似文献