共查询到20条相似文献,搜索用时 15 毫秒
1.
He D Zeng C Xu C Cheng N Li H Mu S Pan M 《Langmuir : the ACS journal of surfaces and colloids》2011,27(9):5582-5588
Electrocatalytically active platinum (Pt) nanoparticles on a carbon nanotube (CNT) with enhanced nucleation and stability have been demonstrated through introduction of electron-conducting polyaniline (PANI) to bridge the Pt nanoparticles and CNT walls with the presence of platinum-nitride (Pt-N) bonding and π-π bonding. The Pt colloids were prepared through ethanol reduction under the protection of aniline, the CNT was dispersed well with the existence of aniline in the solution, and aniline was polymerized in the presence of a protonic acid (HCl) and an oxidant (NH(4)S(2)O(8)). The synthesized PANI is found to wrap around the CNT as a result of π-π bonding, and highly dispersed Pt nanoparticles are loaded onto the CNT with narrowly distributed particle sizes ranging from 2.0 to 4.0 nm due to the polymer stabilization and existence of Pt-N bonding. The Pt-PANI/CNT catalysts are electroactive and exhibit excellent electrochemical stability and therefore promise potential applications in proton exchange membrane fuel cells. 相似文献
2.
Marta Legawiec-Jarzyna Anna rbowata Wojciech Juszczyk 《Reaction Kinetics and Catalysis Letters》2006,87(2):291-296
Summary Vezetéknév 相似文献
3.
Lang H May RA Iversen BL Chandler BD 《Journal of the American Chemical Society》2003,125(48):14832-14836
In this contribution, we report the successful preparation of supported metal catalysts using dendrimer-encapsulated Pt nanoparticles as metal precursors. Polyamidoamine (PAMAM) dendrimers were first used to template and stabilize Pt nanoparticles prepared in solution. These dendrimer-encapsulated nanoparticles were then deposited onto a commercial high surface area silica support and thermally activated to remove the organic dendrimer. The resulting materials are active oxidation and hydrogenation catalysts. The effects of catalyst preparation and activation on activity for toluene hydrogenation and CO oxidation catalysis are discussed. 相似文献
4.
5.
P. Staiti S. Galvagno P. Antonucci A. Rositani P. Vitarelli 《Reaction Kinetics and Catalysis Letters》1984,26(1-2):111-116
Partial hydrogenation of benzene to cyclohexene has been studied on Pt/Nylon 66, Pt/MgO and Pt/TiO2. An effect of the support on the selectivity to cyclohexene was observed, Pt/Nylon showing the highest selectivity, followed by Pt/MgO and Pt/TiO2. An interaction of platinum with the more basic supports (Nylon, MgO) and a pretreatment under oxidizing conditions, results in a higher selectivity to cyclohexene.
Pt/ 66, Pt/MgO PtTiO2. , Pt/, Pt/MgO Pt/T,O2. (, MgO) .相似文献
6.
N. A. Yashtulov S. S. Gavrin V. P. Bondarenko K. I. Kholostov A. A. Revina V. R. Flid 《Russian Chemical Bulletin》2011,60(3):434-439
Platinum nanoparticles supported on porous silicon were synthesized by radiation-chemical reduction in solutions of reverse
micelles. The Pt nanoparticles obtained are electrondeficient. The degree of porosity, conductivity type, pore geometry of
the silicon matrix, and precursor parameters affect the size, shape, and charge state of the platinum catalysts. 相似文献
7.
A. Guerrero-Ruiz 《Reaction Kinetics and Catalysis Letters》1993,49(1):53-60
Hydrogen and carbon monoxide chemisorption on supported platinum catalysts have been studied volumetrically and the adsorption heats determined by microcalorimetric measurements. From the results of this study is concluded that the use of reversible (or second) isotherms as a measure of weak chemisorption would appear inadequate. 相似文献
8.
O. B. Belskaya N. M. Ostrovskii Yu. K. Demanov 《Reaction Kinetics and Catalysis Letters》1997,60(1):119-126
Cyclohexane dehydrogenation was used as a model reaction to study the dehydrogenation function of Pt/Al2O3 catalysts. Fresh and coked catalysts were tested in two ranges of reaction conditions: model conditions (T=280–340°C, P=1
atm) and the conditions used in the naphtha reforming process (T=420–460°C, P=15 atm). Intrinsic properties of the dehydrogenation
active centers were found to be identical throughout the experimental conditions. The coke deposits only block a part of the
active centers without their qualitative modification. 相似文献
9.
G. Hanschmann 《Reaction Kinetics and Catalysis Letters》1982,21(1-2):13-16
Pt[P(C6H5)3]4 has been applied for preparation of Pt/C and Pt/Al2O3 catalysts. The highest hydrogenation activity exhibited the catalysts prepared using alumina support. Activity of these catalysts is higher compared with those obtained from Pt(NH3)4Cl2.
Pt[P(C6H5)3]4 Pt/C Pt/Al2O3. , , . , Pt(NH3)4Cl2.相似文献
10.
I. É. Beck V. V. Kriventsov D. P. Ivanov E. P. Yakimchuk B. N. Novgorodov V. I. Zaikovskii V. I. Bukhtiyarov 《Journal of Structural Chemistry》2010,51(1):11-19
The possibility of controlling the state of platinum deposited on the support surface via minor changes in the catalyst preparation procedure is demonstrated using a series of highly dispersed Pt/γ-Al2O3 catalysts with different particle size of the active component. Dispersity, local structure and electronic state of supported platinum were examined by a combination of high resolution transmission electron microscopy and X-ray absorption spectroscopy (EXAFS/XANES). It was shown that various platinum species can be obtained on the surface of the support: bulk or surface Pt(II) or Pt(IV) oxides, mixed metal-oxide structures, bulk particles of metallic platinum, and two-dimensional surface Pt0 particles strongly interacting with the support. 相似文献
11.
N. B. Shitova V. A. Drozdov P. E. Kolosov M. D. Smolikov 《Reaction Kinetics and Catalysis Letters》2000,41(5):720-728
The formation of Pt/γ-Al2O3 and Pt/C catalysts from platinum carbonyl clusters H2[Pt3(CO)6]n (n = 2, 5) is studied. The strength of interaction between clusters (strong Lewis bases) and the support and the state of platinum
in catalysts are governed by the acceptor strength of the support. The formation of a stable platinum compound with a surface
of γ-Al2O3 (strong Lewis acid) is shown for a Pt/γ-Al2O3 catalyst by the method of radial distribution functions. In a Pt/C catalyst containing the same amount of Pt supported on
a carbon material known to be a weaker acceptor, metallic platinum is formed along with surface-bonded platinum. Proceeding
from the existence of the active phase of catalysts in the form of a surface platinum complex and platinum crystallites, the
properties of catalysts are discussed in the complete oxidation of methane and the dehydrogenation of cyclohexane, as well
as the high dispersity of platinum and its thermal stability 相似文献
12.
《Radiation Physics and Chemistry》1999,53(1):31-36
When ferric oxide supported on porous glass was irradiated by 40 keV He+ ions, the reduction of Fe3+ to Fe2+ species occurred. The yield of Fe2+ species, which was monitored by the Mössbauer spectroscopic measurement, increased with increasing total dose, and went up to ca. 80%. This unexpectedly large yield meant that the effect was exerted beyond the range of the incident He+ ions. Clear dose rate dependence of the Fe2+ yield was also observed. We examined the possibility that the reduction of the Fe3+ species was caused by some type of gaseous reductant produced by radiolysis of surface chemical species such as physisorbed water molecules and surface hydroxyls. 相似文献
13.
纳米碳材料负载铂催化剂在环己烷脱氢反应中的催化性能研究 总被引:2,自引:0,他引:2
制备了纳米碳材料负载铂的催化剂,通过N2吸附、TEM、XRD技术分别对载体的BET比表面积和催化剂结构、形貌和粒径大小进行了表征。考察了不同催化剂在环己烷脱氢反应中的催化性能以及温度对纳米碳颗粒负载铂催化剂活性的影响。结果表明,锚定在不同碳载体上的铂有较好的分散性,粒径较小,粒度分布范围较窄并且具有相同的晶型结构。孔状纳米碳颗粒负载铂催化剂的活性高于碳纳米管和高比表面的活性炭负载铂催化剂,并且在低温条件下已经显示了较高的活性,尤其是中空碳颗粒负载铂催化剂在环己烷脱氢反应中显示了好的活性和稳定性。 相似文献
14.
T. Yuranova L. Garamszegi Jan-Anders Manson M. Bensimon J. Kiwi 《Journal of photochemistry and photobiology. A, Chemistry》2002,150(1-3):195-205
Structured silica woven fabrics have been derivatized with functional groups able to anchor by exchange of Fe3+-ions and TiO2 showing a stable performance during the visible light induced decoloration of the Orange II azo-dye. The kinetics and efficiency of the decoloration mediated by the catalytic loaded silica fabrics with Fe3+-ions were seen to be much higher than found with homogeneous Fenton reagents (Fe3+/H2O2) with the equivalent Fe3+ content. The same was observed for derivatized membranes where TiO2 has been anchored as the active catalyst surface species. In the case of the silica Fe3+-ions loaded fabrics, the decoloration was studied as a function of the amount of H2O2 oxidant added in solution, the intensity of the applied visible light and the concentration of the initial Orange II. In the case of the silica-TiO2 fabrics the decoloration kinetics was observed to be a function of the O2 present in solution. In the case of the derivatized Fe3+ and TiO2 loaded silica fabrics, the decoloration process presented three common features: (a) the decoloration process was observed only in the presence of light pointing to a photo-induced process in both cases, (b) the decoloration was also observed to be truly catalytical following repetitive cycles for Orange II, and finally (c) the decoloration processes were limited by the mass transfer kinetics taking place at the surface of both derivatized fabric catalyst and proceeded with about the same kinetics in both cases. The numerical values for the diffusion distance of the radicals species OH√ and HO2√ as well as the decrease in the concentration of radicals away from the silica fabric during the photodegradation of Orange II is estimated by the Smoluchowski diffusion equation. 相似文献
15.
This study presented results on reduction of alumina
supported chromium and platinum–chromium catalysts using temperature
programmed reduction method (TPR). It has been shown that catalysts after
earlier oxidation step but without calcinations one undergo reduction in lower
temperature in comparison to calcined only catalysts. Moreover, addition platinum
to Cr/Al2O3 catalysts also caused
decrease of reduction temperature. It has been observed that over the examined
catalysts oxidation CO to CO2 and reduction CO to CH4
occurs. However, on Pt–Cr catalysts both reactions proceed at lower
temperature compare to Cr catalysts. 相似文献
16.
采用氯化法制备石墨烯-无定型碳复合材料(GNS@a-C),并用作质子交换膜燃料电池(PEMFC)氧还原反应Pt催化剂的载体.结果显示,所制Pt/GNS@a-C催化剂与传统商业催化剂Pt/C相比,有较好的活性和较高的稳定性:质量活性(0.121 A/mg)几乎是Pt/C(0.064 A/mg)的两倍.更重要的是,该新型催化剂加速4000圈后其电化学活性面积保留了最初的51%,与Pt/C的33%相比,前者有更好的电化学稳定性,显示它在PEMFC中将具有较好的应用潜力. 相似文献
17.
Alloyed catalysts receive considerable attention, because of their unique catalytic properties; they often show higher selectivity, activity, and stability compared to the pure metal particles. To provide insights in the origins of these features, we report the structure and the interaction of hydrogen with each of the metals in an intimately mixed platinum-gold catalyst and compare these characteristics to those in the single metal particles. X-Ray absorption spectroscopy (XAS) and electron microscopy analysis showed that the structure of the mixed particle differed from the single metal particles. The interaction of platinum with hydrogen is stronger than the H-Au interaction and the adsorption sites were different. EXAFS analysis showed that the structure of the platinum clusters changes with increasing hydrogen coverage, observed as a relaxation of the contracted Pt-Pt distance and an increase in the Pt-Pt coordination number. No such changes were observed for gold clusters. Well-mixed PtAu-alloy clusters, with a bulk Au-to-Pt ratio of two, supported on SiO(2), adsorb hydrogen on both platinum and gold atoms, which indicates that gold cannot be regarded as an inert metal. The heat of adsorption on the platinum ensembles does not decrease upon alloying; the weakening of the overall hydrogen adsorption strength when alloying platinum with gold is an ensemble-size effect. 相似文献
18.
Hydrogenation catalysts as platinum nanoparticles supported on carbon nanomaterials (singleand multi-walled nanotubes, nanofibers,
and fullerene black) have been obtained by modifying the platinum precursor with an organic base. A support pretreatment procedure
for producing carboxyl groups on the nanotube and nanofiber surface is suggested. 相似文献
19.
Bergamaski K Pinheiro AL Teixeira-Neto E Nart FC 《The journal of physical chemistry. B》2006,110(39):19271-19279
The particle size effect observed on the performance of Pt/C electrocatalysts toward the methanol oxidation reaction (MOR) has been investigated with differential electrochemical mass spectrometry (DEMS). The investigation has been conducted under both potentiodynamic and potentiostatic conditions as research on methanol electrochemical oxidation is closely related to interest in direct methanol fuel cells. The particle size effect observed on the MOR is commonly regarded as a reflection of different Pt-CO and Pt-OH bond strengths for different particle sizes. This work focuses mainly on the mechanism of methanol dehydrogenation on platinum which is central to the problem of the optimization of the efficiency of methanol electro-oxidation by favoring the CO(2) formation pathway. It was found that the partitioning of the methanol precursor among the end products on supported platinum nanoparticles is strongly dependent on particle size distribution. Also, it is postulated that the coupling among particles of different sizes via soluble products must be considered in order to understand the particle size effects on the observed trends of product formation. An optimum particle size range for efficiently electro-oxidizing methanol to CO(2) was found between 3 and 10 nm, and loss in efficiency is mostly related to the partial oxidation of methanol to formaldehyde on either too small or too large particles. The possible reasons for these observations are also discussed. 相似文献
20.
考察了具有相同金属分散度的Pt/NaY、Pt/HNaY、 Pt/HY、Pt/NaBeta和Pt/HBeta催化剂中沸石载体的酸性对在低温下(≤250 ℃)甲烷两步等温转化反应以及由甲烷解离吸附产生的表面碳物种分布的影响。由甲烷等温两步转化生成的C2+烃类产物的总量随着载体酸性的增加而明显增加;C2~C6产物的分布也发生了变化。由表面碳物种的程序升温加氢结果表明,在各种催化剂上碳物种的形式是相似的,其总量和具有活性的Cα物种的量均因载体酸性增加而增加,反应性也增大。这种因沸石载体酸性变化而引起的载体效应是由金属和载体的相互作用造成负载在酸性载体上铂粒子的贫电子性而引起,即由金属粒子电子性质的变化而引起的催化性质的变化。 相似文献