Catalytic properties of small ruthenium particles deposited on carbon

Raróg‐Pilecka, Wioletta; Szmigiel, Dariusz; Komornicki, Andrew; Zieliński, Jerzy; Kowalczyk, Z.

doi:10.1016/s0008-6223(02)00393-7

Cited by 59 publications

(55 citation statements)

References 19 publications

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“…The Pt L 3 -edge of Pt foil and [Rb 2 Pt(CN) 4 ]‚(1.5H 2 O) were also measured and used to obtain phase shifts and backscattering amplitudes of the Pt-Pt and Pt-C absorber-backscatterer pairs, respectively.…”

Section: Synthesis Of Carbon-supported Platinum Catalystsmentioning

confidence: 99%

“…There is gaining interest in Pt/C electrochemistry [1][2][3] and catalysis. [4][5][6][7][8][9][10][11] It has been shown that precious metals supported on carbon nanofibers, which can be optimized by modification of the surface groups, provide highly active and selective catalysts in hydrogenation reactions. 12,13 It has been well established that the physicochemical properties of the carbon support can have a dramatic effect on the catalytic properties of the supported metal.…”

Section: Introductionmentioning

confidence: 99%

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Metal Particle Size and Structure of the Metal−Support Interface of Carbon-Supported Platinum Catalysts as Determined with EXAFS Spectroscopy

et al. 2004

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The metal particle size and structure of the metal-support interface of platinum supported on Vulcan XC-72 (a commercial catalyst used in platinum fuel-cell electrodes) and on carbon nanofibers (CNF) have been determined with extended X-ray absorption fine structure spectroscopy (EXAFS). The CNF-supported Pt catalysts were synthesized using a homogeneous deposition precipitation (HDP) method. The amount of acidic oxygen groups on the CNF surface was modified by treatment in an inert atmosphere at different temperatures. The average first shell Pt-Pt coordination number (∼5.5) detected in Pt/CNF is much smaller than for Pt/ Vulcan XC-72 (∼8.2). The presence of oxygen-containing groups in the CNF support most probably leads to the stabilization of small Pt particles on the CNF support. A prominent interaction between the metal particles and the support atoms was detected on both kinds of catalysts, which confirms that the metal is in direct contact with the carbon support atoms. After reduction, a long metal-carbon distance around 2.62 Å was detected in both Pt/Vulcan XC-72 and Pt/CNF. After evacuation of Pt/CNF at higher temperatures, the distance between support and interfacial metal atoms decreased to 2.02 Å. Therefore, the long metal-carbon support distance is ascribed to the presence of atomic chemisorbed hydrogen in the interface between the Pt particles and the carbon support. According to the number of interfacial Pt-C bonds (four), the platinum particles supported on CNF are proposed to be in contact with a prismatic surface of the carbon support, on which oxygen groups have more stable bonds with carbon atoms. Six Pt-C bonds could be detected in the metal-support interface of Pt/Vulcan XC-72 with an even longer carbon shell at 3.62 Å, indicating that the metal particles are located on a more carbon-rich surface. This supports a structural model in which the platinum metal particles are epitaxially grown on the (0001) basal surface plane of carbon graphite.

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Section: Synthesis Of Carbon-supported Platinum Catalystsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Metal Particle Size and Structure of the Metal−Support Interface of Carbon-Supported Platinum Catalysts as Determined with EXAFS Spectroscopy

et al. 2004

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“…Currently, intensively investigated elements as catalysts for ammonia decomposition are based on ruthenium, iron, nickel, and molybdenum. [9,10] Although ruthenium was found to be the most active catalyst for ammonia decomposition, [11] iron-based catalysts are very attractive materials since the price for the raw material is more than 50 000 times lower and more stable, and because the availability of the raw material is higher. [12] To compensate the generally lower activity of iron-based catalysts, higher reaction temperatures can be principally used.…”

Section: Introductionmentioning

confidence: 99%

High‐Temperature Stable, Iron‐Based Core–Shell Catalysts for Ammonia Decomposition

Feyen

Weidenthaler

Güttel

et al. 2010

Chemistry A European J

111

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High-temperature, stable core-shell catalysts for ammonia decomposition have been synthesized. The highly active catalysts, which were found to be also excellent model systems for fundamental studies, are based on α-Fe(2)O(3) nanoparticles coated by porous silica shells. In a bottom-up approach, hematite nanoparticles were firstly obtained from the hydrothermal reaction of ferric chlorides, L-lysine, and water with adjustable average sizes of 35, 47, and 75 nm. Secondly, particles of each size could be coated by a porous silica shell by means of the base-catalyzed hydrolysis of tetraethylorthosilicate (TEOS) with cetyltetramethylammonium bromide (CTABr) as porogen. After calcination, TEM, high-resolution scanning electron microscopy (HR-SEM), energy-dispersive X-ray (EDX), XRD, and nitrogen sorption studies confirmed the successful encapsulation of hematite nanoparticles inside porous silica shells with a thickness of 20 nm, thereby leading to composites with surface areas of approximately 380 m(2) g(-1) and iron contents between 10.5 and 12.2 wt %. The obtained catalysts were tested in ammonia decomposition. The influence of temperature, iron oxide core size, possible diffusion limitations, and dilution effects of the reagent gas stream with noble gases were studied. The catalysts are highly stable at 750 °C with a space velocity of 120,000 cm(3) g(cat)(-1) h(-1) and maintained conversions of around 80 % for the testing period time of 33 h. On the basis of the excellent stability under reaction conditions up to 800 °C, the system was investigated by in situ XRD, in which body-centered iron was determined, in addition to FeN(x), as the crystalline phase under reaction conditions above 650 °C.

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“…It has been reported that group VIII metals (Fe, Ni, Ru, Ir, Co, Pt) catalyze the NH 3 decomposition reaction and Ru is generally considered to be the most active single metal catalysts [6][7][8][9]. Ru-CeO 2 /Y Zeolite [2], Ru/Al 2 O 3 [6,8], Ru/SiO 2 [6,10], Ru/C [11][12][13][14][15], Ru/MgAl 2 O 4 [9,16], Ru/CNTs [8,10,15,17], and Ru/MgO [8,10,17,18] have been proved to catalyze decomposition of NH 3 .…”

Section: Introductionmentioning

confidence: 99%

NH3 Decomposition Kinetics on Supported Ru Clusters: Morphology and Particle Size Effect

Zheng

Zhang

et al. 2007

Catal Lett

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The supported Ru clusters with mean sizes ranging from 1.9 to 4.6 nm showed a high activity towards the NH 3 decomposition reaction. The structural properties of catalysts were characterized by N 2 adsorption/desorption, X-ray diffraction (XRD) and transmission electron micrograph (TEM). Steady-state reaction kinetics revealed that the apparent activation energy increased with a decrease in Ru particle size and ranged from 79 kJ mol À1 to 122 kJ mol À1 . The decomposition rate over Ru nanoparticles showed a strong dependency on mean crystallite size and the optimum appeared at d Ru = 2.2 nm. The dependencies of reaction rate on partial pressures of NH 3 and H 2 were also sensitive to the varying Ru particle size. Experimental data could be well fitted by the Temkin-Pyzhev equation, indicating that the recombinative desorption of surface nitrogen atom acts as the rate-determining step. A compensation effect between the pre-exponential factor (k 0 ) and activation energy (E a ) was quantified.

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Catalytic properties of small ruthenium particles deposited on carbon

Cited by 59 publications

References 19 publications

Metal Particle Size and Structure of the Metal−Support Interface of Carbon-Supported Platinum Catalysts as Determined with EXAFS Spectroscopy

Metal Particle Size and Structure of the Metal−Support Interface of Carbon-Supported Platinum Catalysts as Determined with EXAFS Spectroscopy

High‐Temperature Stable, Iron‐Based Core–Shell Catalysts for Ammonia Decomposition

NH3 Decomposition Kinetics on Supported Ru Clusters: Morphology and Particle Size Effect

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