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Sample records for pt ru pd

  1. The Mechanism of Direct Formic Acid Fuel Cell Using Pd, Pt and Pt-Ru

    Science.gov (United States)

    Kamiya, Nobuyuki; Liu, Yan; Mitsushima, Shigenori; Ota, Ken-Ichiro; Tsutsumi, Yasuyuki; Ogawa, Naoya; Kon, Norihiro; Eguchi, Mika

    The electro-oxidation of formic acid, 2-propanol and methanol on Pd black, Pd/C, Pt-Ru/C and Pt/C has been investigated to clear the reaction mechanism. It was suggested that the formic acid is dehydrogenated on Pd surface and the hydrogen is occluded in the Pd lattice. Thus obtained hydrogen acts like pure hydrogen supplied from the outside and the cell performance of the direct formic acid fuel cell showed as high as that of a hydrogen-oxygen fuel cell. 2-propanol did not show such dehydrogenation reaction on Pd catalyst. Platinum and Pt-Ru accelerated the oxidation of C-OH of 2-propanol and methanol. Slow scan voltammogram (SSV) and chronoamperometry measurements showed that the activity of formic acid oxidation increased in the following order: Pd black > Pd 30wt.%/C > Pt50wt.%/C > 27wt.%Pt-13wt.%Ru/C. A large oxidation current for formic acid was found at a low overpotential on the palladium electrocatalysts. These results indicate that formic acid is mainly oxidized through a dehydrogenation reaction. For the oxidation of 2-propanol and methanol, palladium was not effective, and 27wt.%Pt-13wt.%Ru/C showed the best oxidation activity.

  2. High-activity PtRuPd/C catalyst for direct dimethyl ether fuel cells.

    Science.gov (United States)

    Li, Qing; Wen, Xiaodong; Wu, Gang; Chung, Hoon T; Gao, Rui; Zelenay, Piotr

    2015-06-22

    Dimethyl ether (DME) has been considered as a promising alternative fuel for direct-feed fuel cells but lack of an efficient DME oxidation electrocatalyst has remained the challenge for the commercialization of the direct DME fuel cell. The commonly studied binary PtRu catalyst shows much lower activity in DME than methanol oxidation. In this work, guided by density functional theory (DFT) calculation, a ternary carbon-supported PtRuPd catalyst was designed and synthesized for DME electrooxidation. DFT calculations indicated that Pd in the ternary PtRuPd catalyst is capable of significantly decreasing the activation energy of the CO and CH bond scission during the oxidation process. As evidenced by both electrochemical measurements in an aqueous electrolyte and polymer-electrolyte fuel cell testing, the ternary catalyst shows much higher activity (two-fold enhancement at 0.5 V in fuel cells) than the state-of-the-art binary Pt50 Ru50 /C catalyst (HiSPEC 12100).

  3. In situ spectroscopic ellipsometry during atomic layer deposition of Pt, Ru and Pd

    Science.gov (United States)

    Leick, N.; Weber, J. W.; Mackus, A. J. M.; Weber, M. J.; van de Sanden, M. C. M.; Kessels, W. M. M.

    2016-03-01

    The preparation of ultra-thin platinum-group metal films, such as Pt, Ru and Pd, by atomic layer deposition (ALD) was monitored in situ using spectroscopic ellipsometry in the photon energy range of 0.75-5 eV. The metals’ dielectric function was parametrized using a ‘flexible’ Kramers-Kronig consistent dielectric function because it was able to provide accurate curve shape control over the optical response of the metals. From this dielectric function, it was possible to extract the film thickness values during the ALD process. The important ALD process parameters, such as the nucleation period and growth per cycle of Pt, Ru and Pd could be determined from the thickness evolution. In addition to process parameters, the film resistivity in particular could be extracted from the modeled dielectric function. Spectroscopic ellipsometry thereby revealed itself as a feasible and valuable technique to be used in research and development applications, as well as for process monitoring during ALD.

  4. Surface noble metal modified PdM/C (M = Ru, Pt, Au) as anode catalysts for direct ethanol fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Mao, Han; Huang, Tao, E-mail: huangt@fudan.edu.cn; Yu, Aishui, E-mail: asyu@fudan.edu.cn

    2016-08-15

    In this article, we studied the surface noble metal modification on Pd nanoparticles, other than the homogeneous or core-shell structure. The surface modification will lead to the uneven constitution within the nanoparticles and thus more obvious optimization effect toward the catalyst brought by the lattice deformation. The surface of the as-prepared Pd nanoparticles was modified with Ru, Pt or Au by a moderate and green approach, respectively. XPS results confirm the interactive electron effects between Pd and the modified noble metal. Electrochemical measurements show that the surface noble metal modified catalysts not only show higher catalytic activity, but also better stability and durability. The PdM/C catalysts all exhibit good dispersion and very little agglomeration after long-term potential cycles toward ethanol oxidation. With only 10% metallic atomic ratio of Au, PdAu/C catalyst shows extraordinary catalytic activity and stability, the peak current reaches 1700 mA mg{sup −1} Pd, about 2.5 times that of Pd/C. Moreover, the PdAu/C maintains 40% of the catalytic activity after 4500 potential cycles. - Highlights: • Pd-based catalysts with complicated exposed facets. • Much enhanced electrocatalytic activity and stability with about 10% noble metal M (M = Ru, Pt, Au) on Pd nanoparticles. • The outstanding electrocatalytic performance of PdAu/C towards ethanol oxidation after the Au modification.

  5. Epitaxial Growth of Multimetallic Pd@PtM (M = Ni, Rh, Ru) Core-Shell Nanoplates Realized by in Situ-Produced CO from Interfacial Catalytic Reactions.

    Science.gov (United States)

    Yan, Yucong; Shan, Hao; Li, Ge; Xiao, Fan; Jiang, Yingying; Yan, Youyi; Jin, Chuanhong; Zhang, Hui; Wu, Jianbo; Yang, Deren

    2016-12-14

    Pt-based multimetallic core-shell nanoplates have received great attention as advanced catalysts, but the synthesis is still challenging. Here we report the synthesis of multimetallic Pd@PtM (M = Ni, Rh, Ru) nanoplates including Pd@Pt nanoplates, in which Pt or Pt alloy shells with controlled thickness epitaxially grow on plate-like Pd seeds. The key to achieve high-quality Pt-based multimetallic nanoplates is in situ generation of CO through interfacial catalytic reactions associated with Pd nanoplates and benzyl alcohol. In addition, the accurate control in a trace amount of CO is also of great importance for conformal growth of multimetallic core-shell nanoplates. The Pd@PtNi nanoplates exhibit substantially improved activity and stability for methanol oxidation reaction (MOR) compared to the Pd@Pt nanoplates and commercial Pt catalysts due to the advantages arising from plate-like, core-shell, and alloy structures.

  6. Pt, Au, Pd and Ru Partitioning Between Mineral and Silicate Melts: The Role of Metal Nanonuggets

    Science.gov (United States)

    Malavergne, V.; Charon, E.; Jones, J.; Agranier, A.; Campbell, A.

    2012-01-01

    , Ru and Pd in minerals (olivine and diopside) and in silicate melts, but also to characterize the sizes, density and chemistry of HSE nuggets when present in the samples.

  7. Screening of electrocatalysts for direct ammonia fuel cell: Ammonia oxidation on PtMe (Me: Ir, Rh, Pd, Ru) and preferentially oriented Pt(1 0 0) nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Vidal-Iglesias, F.J.; Solla-Gullon, J.; Montiel, V.; Feliu, J.M.; Aldaz, A. [Instituto de Electroquimica, Universidad de Alicante, Apartado 99, 03080 Alicante (Spain)

    2007-09-27

    Ammonia has attracted attention as a possible fuel for direct fuel cells since it is easy to handle and to transport as liquid or as concentrated aqueous solution. However, on noble metal electrodes ammonia oxidation is a sluggish reaction and the electrocatalyst needs to be improved for developing efficient ammonia fuel cells. In this work, ammonia electrooxidation reaction on 3-4-nm bimetallic PtMe (Ir, Rh, Pd, Ru) and on preferentially oriented Pt(1 0 0) nanoparticles is reported. PtMe nanoparticles have been prepared by using water-in-oil microemulsions to obtain a narrow size distribution whereas preferentially oriented Pt nanoparticles have been prepared through colloidal routes. Among all the bimetallic samples tested, only Pt{sub 75}Ir{sub 25} and Pt{sub 75}Rh{sub 25} nanoparticles show, at the low potential range, an enhancement of the oxidation density current with respect to the behaviour found for pure platinum nanoparticles prepared by the same method. In addition, two Pt(1 0 0) preferentially oriented nanoparticles of different particle size (4 and 9 nm) have been also studied. These oriented nanoparticles show higher current densities than polycrystalline Pt nanoparticles due to the sensitivity of ammonia oxidation toward the presence of surface sites with square symmetry. The reactivity of the different 4-nm nanoparticles parallels well with that expected from bulk PtMe alloys and Pt single crystal electrodes. (author)

  8. Synthesis, crystal structure, and electronic properties of high-pressure PdF2-type oxides MO2 (M = Ru, Rh, Os, Ir, Pt).

    Science.gov (United States)

    Shirako, Yuichi; Wang, Xia; Tsujimoto, Yoshihiro; Tanaka, Kie; Guo, Yanfeng; Matsushita, Yoshitaka; Nemoto, Yoshihiro; Katsuya, Yoshio; Shi, Youguo; Mori, Daisuke; Kojitani, Hiroshi; Yamaura, Kazunari; Inaguma, Yoshiyuki; Akaogi, Masaki

    2014-11-03

    The polycrystalline MO2's (HP-PdF2-type MO2, M = Rh, Os, Pt) with high-pressure PdF2 compounds were successfully synthesized under high-pressure conditions for the first time, to the best of our knowledge. The crystal structures and electromagnetic properties were studied. Previously unreported electronic properties of the polycrystalline HP-PdF2-type RuO2 and IrO2 were also studied. The refined structures clearly indicated that all compounds crystallized into the HP-PdF2-type structure, M(4+)O(2-)2, rather than the pyrite-type structure, M(n+)(O2)(n-) (n superconductivity nor a magnetic transition was detected down to a temperature of 2 K, unlike the case of 3d transition metal chalcogenide pyrites.

  9. Room temperature biogenic synthesis of multiple nanoparticles (Ag, Pd, Fe, Rh, Ni, Ru, Pt, Co, and Li) by Pseudomonas aeruginosa SM1

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, Sarvesh Kumar; Constanti, Magda, E-mail: magdalena.constanti@urv.cat [Universitat Rovira i Virgili, Departament d' Enginyeria Quimica (Spain)

    2012-03-15

    Room temperature biosynthesis of Ag, Pd, Fe, Rh, Ni, Ru, Pt, Co, and Li nanoparticles was achieved using Pseudomonas aeruginosa SM1 without the addition of growth media, electron donors, stabilizing agents, preparation of cell/cell-free extract or temperature, and pH adjustments. The resulting nanoparticles were characterized by Transmission electron microscopy and X-ray diffraction. It was observed that P. aeruginosa SM1 is capable of producing both intracellular (Co and Li) and extracellular (Ag, Pd, Fe, Rh, Ni, Ru, and Pt) nanoparticles in both crystalline and amorphous state. The FT-IR spectra clearly showed the presence of primary and secondary amines which may be responsible for the reduction and subsequent stabilization of the resulting extracellular nanoparticles which were obtained as a one-step process. This suggests toward an unknown 'selection mechanism' that reduces certain metal ions and allows others to enter the cell membrane. Finally, in this first of its kind study, single strain of bacteria was used to produce several different mono-metallic nanoparticles.

  10. Room temperature biogenic synthesis of multiple nanoparticles (Ag, Pd, Fe, Rh, Ni, Ru, Pt, Co, and Li) by Pseudomonas aeruginosa SM1

    Science.gov (United States)

    Srivastava, Sarvesh Kumar; Constanti, Magda

    2012-03-01

    Room temperature biosynthesis of Ag, Pd, Fe, Rh, Ni, Ru, Pt, Co, and Li nanoparticles was achieved using Pseudomonas aeruginosa SM1 without the addition of growth media, electron donors, stabilizing agents, preparation of cell/cell-free extract or temperature, and pH adjustments. The resulting nanoparticles were characterized by Transmission electron microscopy and X-ray diffraction. It was observed that P. aeruginosa SM1 is capable of producing both intracellular (Co and Li) and extracellular (Ag, Pd, Fe, Rh, Ni, Ru, and Pt) nanoparticles in both crystalline and amorphous state. The FT-IR spectra clearly showed the presence of primary and secondary amines which may be responsible for the reduction and subsequent stabilization of the resulting extracellular nanoparticles which were obtained as a one-step process. This suggests toward an unknown "selection mechanism" that reduces certain metal ions and allows others to enter the cell membrane. Finally, in this first of its kind study, single strain of bacteria was used to produce several different mono-metallic nanoparticles.

  11. Coexistence of magnetic order, heavy fermion and intermediate valence behaviour in Ce{sub 7}X{sub 3} (X=Ni, Ru, Pd, Pt, Ir and Rh)

    Energy Technology Data Exchange (ETDEWEB)

    Trovarelli, O. [Comision Nacional de Energia Atomica, San Carlos de Bariloche (Argentina). Centro Atomico Bariloche; Sereni, J.G. [Comision Nacional de Energia Atomica, San Carlos de Bariloche (Argentina). Centro Atomico Bariloche; Schmerber, G. [IPCMS-GEMM, 23 rue du Loess, 67037 Strasbourg (France); Kappler, J.P. [IPCMS-GEMM, 23 rue du Loess, 67037 Strasbourg (France)

    1995-02-01

    Low temperature specific heat, AC magnetic susceptibility and magnetization measurements were performed on the Ce{sub 7}X{sub 3} compounds (X=Ni, Ru, Rh, Pd, Ir and Pt). They exhibit coexistence of magnetic order (MO), heavy fermion (HF) and intermediate valence (IV) behaviour and the results are interpreted in terms of the three Ce sublattices (1Ce{sub I}, 3Ce{sub II} and 3Ce{sub III}) present in the Th{sub 7}Fe{sub 3}-type structure. From entropic considerations it is found that sublattice Ce{sub III} presents an IV behaviour in all these compounds and Ce{sub II} show MO or have a HF behaviour depending on the Ce-ligand electronic structure. The Ce{sub I} atoms (more than 6A distant from each other) exhibit MO only when the Ce{sub II} sublattice provides a high density of electronic states. ((orig.)).

  12. Carbon supported Pd-Sn and Pd-Ru-Sn nanocatalysts for ethanol electro-oxidation in alkaline medium

    CSIR Research Space (South Africa)

    Modibedi, RM

    2011-04-01

    Full Text Available the coverage of the adsorbed ethoxy (CH3COads) species on the nanocatalyst surface, thus yielding an increase in current density. Pd-Sn/C displayed better electrocatalytic activity and stability towards poisoning than Pd-Ru-Sn/C and Pt-Ru/C (E-TEK Inc...

  13. Pd and Pt-Ru anode electrocatalysts supported on multi-walled carbon nanotubes and their use in passive and active direct alcohol fuel cells with an anion-exchange membrane (alcohol = methanol, ethanol, glycerol)

    Science.gov (United States)

    Bambagioni, Valentina; Bianchini, Claudio; Marchionni, Andrea; Filippi, Jonathan; Vizza, Francesco; Teddy, Jacques; Serp, Philippe; Zhiani, Mohammad

    Palladium and platinum-ruthenium nanoparticles supported on multi-walled carbon nanotubes (MWCNT) are prepared by the impregnation-reduction procedure. The materials obtained, Pd/ MWCNT and Pt-Ru/ MWCNT, are characterized by TEM, ICP-AES and XRPD. Electrodes coated with Pd/ MWCNT are scrutinized for the oxidation of methanol, ethanol or glycerol in 2 M KOH solution in half cells. The catalyst is very active for the oxidation of all alcohols, with glycerol providing the best performance in terms of specific current density and ethanol showing the lowest onset potential. Membrane-electrode assemblies have been fabricated using Pd/ MWCNT anodes, commercial cathodes and anion-exchange membrane and evaluated in both single passive and active direct alcohol fuel cells fed with aqueous solutions of 10 wt.% methanol, 10 wt.% ethanol or 5 wt.% glycerol. Pd/ MWCNT exhibits unrivalled activity as anode electrocatalyst for alcohol oxidation. The analysis of the anode exhausts shows that ethanol is selectively oxidized to acetic acid, detected as acetate ion in the alkaline media of the reaction, while methanol yields carbonate and formate. A much wider product distribution, including glycolate, glycerate, tartronate, oxalate, formate and carbonate, is obtained from the oxidation of glycerol. The results obtained with Pt-Ru/ MWCNT anodes in acid media are largely inferior to those provided by Pd/ MWCNT electrodes in alkaline media.

  14. Selective oxidation of methylamine over zirconia supported Pt-Ru, Pt and Ru catalysts

    Institute of Scientific and Technical Information of China (English)

    Aiying Song; Gongxuan Lu

    2015-01-01

    Pt–Ru, Pt and Ru catalysts supported on zirconia were prepared by impregnation method and were tested in se-lective oxidation of methylamine (MA) in aqueous media. Among three catalysts, Ru/ZrO2 was more active than Pt/ZrO2 while Pt–Ru/ZrO2 demonstrated the best catalytic activity due to the fact that Pt addition efficiently pro-moted the dispersion of active species in bimetallic catalyst. Therefore, the~100%TOC conversion and N2 selec-tivity were achieved over Pt–Ru/ZrO2, Pt/ZrO2 and Ru/ZrO2 catalysts at 190, 220 and 250 °C, respectively.

  15. Carbon supported nanoparticles Pt Ru (Pt Ru/C electrocatalysts) prepared using electron beam irradiation; Preparacao de nanoparticulas de PtRu suportadas em carbono (eletrocatalisadores PtRu/C) utilizando feixe de eletrons

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Dionisio F. da; Oliveira Neto, Almir; Pino, Eddy S.; Linardi, Marcelo; Spinace, Estevam V. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Programa de Celulas a Combustivel], e-mail: espinace@ipen.br, e-mail: dfsilva@ipen.br

    2006-07-01

    Carbon-supported Pt Ru (electrocatalysts PtRu/C nanoparticles) were prepared submitting a water/ethylene glycol mixture containing Pt(IV) and Ru(III) ions and the carbon support to electron beam irradiation. The PtRu/C electrocatalysts were characterized by EDX, XRD and cyclic voltammetry and tested for methanol electro-oxidation aiming fuel cell application. The obtained PtRu/C electrocatalysts were more active for methanol electro-oxidation than the commercial PtRu/C ETEK electrocatalyst at ambient temperature. (author)

  16. Carbon supported nanoparticles Pt Ru (Pt Ru/C electrocatalysts) prepared using electron beam irradiation; Preparacao de nanoparticulas de PtRu suportadas em carbono (eletrocatalisadores PtRu/C) utilizando feixe de eletrons

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Dionisio F. da; Oliveira Neto, Almir; Pino, Eddy S.; Linardi, Marcelo; Spinace, Estevam V. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Programa de Celulas a Combustivel], e-mail: espinace@ipen.br, e-mail: dfsilva@ipen.br

    2006-07-01

    Carbon-supported Pt Ru (electrocatalysts PtRu/C nanoparticles) were prepared submitting a water/ethylene glycol mixture containing Pt(IV) and Ru(III) ions and the carbon support to electron beam irradiation. The PtRu/C electrocatalysts were characterized by EDX, XRD and cyclic voltammetry and tested for methanol electro-oxidation aiming fuel cell application. The obtained PtRu/C electrocatalysts were more active for methanol electro-oxidation than the commercial PtRu/C ETEK electrocatalyst at ambient temperature. (author)

  17. EXAFS Peaks and TPR Characterizing Bimetallic Interactions: Effects of Impregnation Methods on the Structure of Pt-Ru/C Catalysts

    Directory of Open Access Journals (Sweden)

    Nan-Yu Chen

    2014-01-01

    Full Text Available To investigate bimetallic interactions, Pt-Ru/C catalysts were prepared by coimpregnation (Pt-Ruco/C and successive impregnation (Ru-Ptse/C, while Pt/C, Ru/C, and reduced Pt-Rublack were used as reference. Those samples were characterized by XAS and TPR. When Pt(absorber-Ru(backscatter phase-and-amplitude correction is applied to Fourier transformed (FT EXAFS of Pt-Rublack at Pt edge, the characteristic peak of Pt-Ru interactions appears at 2.70 Å´, whereas, when Pt-Pt correction is applied, the peak appears at about 2.5 Å´. Detailed EXAFS analysis for Pt-Ruco/C and Pt-Ruse/C confirms the nature of the characteristic peak and further indicates that the interactions can semiquantitatively be determined by the relative intensity between Pt-Ru and Pt-Pt characteristic peaks. This simple method in determining bimetallic interaction can be extended to characterize Pt-Pd/γ-Al2O3. However, for Pt-Re/γ-Al2O3, Pt-Re interactions cannot be determined by the method because of the overlap of Pt-Pt and Pt-Re characteristic peaks due to similar phase functions.

  18. Pt Ru/C electrocatalysts prepared using electron beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Dionisio Furtunato da; Oliveira Neto, Almir; Pino, Eddy Segura; Brandalise, Michele; Linardi, Marcelo; Spinace, Estevam Vitorio [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)]. E-mail: espinace@ipen.br

    2007-10-15

    Pt Ru/C electrocatalysts (carbon-supported Pt Ru nanoparticles) were prepared submitting water/ethylene glycol mixtures containing Pt(IV) and Ru(III) ions and the carbon support to electron beam irradiation. The electrocatalysts were characterized by energy dispersive X ray analysis (EDX), X ray diffraction (XRD) and cyclic voltammetry and tested for methanol electro-oxidation aiming fuel cell application. The obtained Pt Ru/C electrocatalysts showed superior performance for methanol electro-oxidation at room temperature compared to commercial Pt Ru/C electrocatalyst. (author)

  19. Adsorption of formaldehyde and formyl intermediates on Pt, PtRu-, and PtRuMo-alloy surfaces: A density functional study

    Science.gov (United States)

    Cahyanto, Wahyu Tri; Shukri, Ganes; Agusta, Mohammad Kemal; Kasai, Hideaki

    2013-02-01

    Stable binding configuration for formaldehyde (H2CO) and formyl (HCO) adsorption on Pt, PtRu, and PtRuMo are studied within the frame of density functional theory (DFT). We address this study to investigate the role of Ru and Mo on the binding characteristic of formaldehyde and formyl adsorption with respect to interaction strength and charge analysis. Several binding conformation on all possible surface adsorption sites are considered in determining the most stable adsorption geometry on three surfaces. Our results show that the presence of Ru in PtRu and Mo in PtRuMo stabilize the formaldehyde and formyl, which are indicated by stronger bond strength. Further electronic structure analysis shows that the addition of Ru in PtRu and Mo in PtRuMo modifies the electronic structure of Pt's surface significantly. The presence of both impurities shifted the derived anti-bonding state - which is originally located below the fermi level in pure Pt surface - to be above the fermi level in PtRu and PtRuMo systems. This fact explains the stronger adsorption found on PtRu & PtRuMo as compared to pure Pt surface.

  20. Pt Ru/C electrocatalysts prepared using electron beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Dionisio F.; Oliveira Neto, Almir; Pino, Eddy S.; Brandalise, Michele; Linardi, Marcelo; Spinace, Estevam V. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)]. E-mails: dfsilva@ipen.br; espinace@ipen.br

    2007-07-01

    Pt Ru/C electrocatalysts (carbon-supported Pt Ru nanoparticles) were prepared submitting water/ethylene glycol solutions containing Pt(IV) and Ru(III) ions and the carbon support to electron beam irradiation. The water/ethylene glycol ratio (v/v) was evaluated as synthesis parameters. The Pt Ru/C electrocatalysts were prepared with a nominal Pt:Ru atomic ratio of 50:50 and were characterized by energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD) and tested for methanol electro-oxidation using cyclic voltammetry and chronoamperometry. The obtained Pt Ru/C electrocatalysts showed the typical fcc structure of platinum-ruthenium alloys and the electrocatalytic activity depends on the water/ethylene glycol ratio used in the preparation.

  1. Bifunctional electrocatalysis in pt-ru nanoparticle systems.

    Science.gov (United States)

    Roth, C; Benker, N; Theissmann, R; Nichols, R J; Schiffrin, D J

    2008-03-04

    Pt-Ru alloys are prominent electrocatalysts in fuel cell anodes as they feature a very high activity for the oxidation of reformate and methanol. The improved CO tolerance of these alloys has been discussed in relation to the so-called ligand and bifunctional mechanisms. Although these effects have been known for many years, they are still not completely understood. A new approach that bridges the gap between single crystals and practical catalysts is presented in this paper. Nanoparticulate model systems attached to an oxidized glassy carbon electrode were prepared by combining both ligand-stabilized and spontaneously deposited Pt and Ru nanoparticles. These electrodes showed very different voltammetric responses for CO and methanol oxidation. The cyclic voltammograms were deconvoluted into contributions attributed to Pt, Ru, and Pt-Ru contact regions to quantify the contribution of the latter to the bifunctional mechanism. Scanning transmission electron microscopy confirmed the proximity of Pt and Ru nanoparticles in the different samples.

  2. PtRu/C electrocatalysts prepared using {gamma}-irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Dionisio F.; Neto, Almir Oliveira; Pino, Eddy S.; Linardi, Marcelo; Spinace, Estevam V. [Instituto de Pesquisas Energeticas e Nucleares, IPEN/CNEN-SP, Av. Professor Lineu Prestes, 2242, Cidade Universitaria, 05508-000 Sao Paulo, SP (Brazil)

    2007-07-10

    PtRu/C electrocatalysts (carbon-supported PtRu nanoparticles) were prepared submitting water/ethylene glycol solutions containing Pt(IV) and Ru(III) ions and the carbon support to {gamma}-irradiation. The water/ethylene glycol ratio (v/v) and the total dose (kGy) were evaluated as synthesis parameters. The electrocatalysts were characterized by energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM) and cyclic voltammetry and tested for methanol electro-oxidation aiming fuel cell application. The obtained PtRu/C electrocatalysts were more active for methanol electro-oxidation than the commercial PtRu/C electrocatalyst at ambient temperature and the electrocatalytic activity depends on the water/ethylene glycol ratio used in the preparation. (author)

  3. Study of the Pt/Ru(0001) Interface

    DEFF Research Database (Denmark)

    Godowski, Jan P; Li, Zhe Shen; Bork, Jakob

    2007-01-01

    The growth process of platinum on Ru(0001) near room temperature was characterized using photoelectron spectroscopy of high resolution. The binding energy position and intensity of the Pt 4f7/2 and Ru 3d5/2 core levels as well as the shape and structure of the valence band spectra corresponding t...

  4. Fabrication of MgAl2Si2O8 : M0.01 (M = Ni2+, Cu2+, Pd2+, Pt2+ and Ru3+): catalytic effects for the reduction of 2- or 4-nitroanilines in water

    Indian Academy of Sciences (India)

    Serkan Dayan; Sevgi Öztürk; Nilgün Kayaci; Nilgun Kalaycioglu Ozpozan; Esra Öztürk

    2015-10-01

    Five new MgAl2Si2O8 : M0.01 (M = Ni2+, Cu2+, Pd2+, Pt2+ and Ru3+) materials were developed for the reduction of nitroarenes as catalysts by conventional solid state reaction at 1300°C. The prepared materials were characterized by thermal analysis, Fourier transform infrared spectroscopy, X-ray powder diffraction analysis, scanning electron microscopy, energy-dispersive X-ray analysis and nitrogen adsorption–desorption analysis. The catalytic activities of the prepared catalysts were tested in the reduction of 2- or 4-nitroanilines in aqueous media at ambient temperature in the presence of NaBH4 by UV–vis spectrophotometer. Furthermore, the MgAl2Si2O8 : M0.01 catalysts can be recovered by filtration and reused for five cycles for the reduction of 2-nitroaniline. These results show that the MgAl2Si2O8 : M0.01 catalysts can be used in practical applications in the reduction of nitroanilines.

  5. Partial phase diagram of Pd-Ag-Ru-Gd quaternary system

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    On the basis of the Ag-Pd-Gd, Ag-Ru-Gd and Pd-Ru-Gd ternary systems, the partial phase diagram of Pd-Ag-Ru-Gd(Gd<25% atom fraction) quaternary system has been studied by means of X-ray diffraction analysis, differential thermal analysis, electron probe microanalysis and optical microscopy.The 700℃ isothermal sections of the Ag-Pd-5Ru-Gd, Ag-Pd-20Ru-Gd and Ag-Pd-50Ru-Gd (Gd≤25%atom fraction) phase diagrams were determined respectively. And the 700℃ isothermal section of the PdAg-Ru-Gd (Gd≤25% atom fraction) quaternary system phase diagram was finally irferred. The section consists of four single-phase regions: solid solution Pd(Ag), (Ru), Pd3Gd and Ag51 Gd14; five two-phase regions: Pd(Ag) + (Ru), Pd(Ag) + Ag51 Gd14 , (Ru) + Ag51 Gd14 , Pd(Ag) + Pd3Gd and (Ru) +Pd3Gd; three three-phase regions: Pd(Ag) + Pd3Gd+ (Ru), Pd(Ag) + Ag51Gd14 + (Ru) and (Ru) +Ag51Gd14 + Pd3Gd; one four-phase region Pd(Ag) + (Ru) + Ag51Gd14 + Pd3Gd. No new quaternary intermetallic phase is found.

  6. Mesoporous Pt and Pt/Ru alloy electrocatalysts for methanol oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Franceschini, Esteban A. [Grupo de Celdas de Combustible, Departamento de Fisica de la Materia Condensada, Centro Atomico Constituyentes, CNEA. Av. General Paz 1499 (1650), San Martin, Buenos Aires (Argentina); Planes, Gabriel A. [Departamento de Quimica, Facultad de Ciencias Exactas, Fisicoquimicas y Naturales, Universidad Nacional de Rio Cuarto, Agencia Postal No 3, 5800, Rio Cuarto (Argentina); Williams, Federico J. [Departamento de Quimica Inorganica, Analitica y Quimica-Fisica, INQUIMAE CONICET, Facultad Ciencias Exactas y Naturales, Pabellon 2, Ciudad Universitaria, Buenos Aires (Argentina); Soler-Illia, Galo J.A.A. [Gerencia de Quimica, Centro Atomico Constituyentes, CNEA. Av. General Paz 1499 (1650), San Martin, Buenos Aires (Argentina); Corti, Horacio R. [Grupo de Celdas de Combustible, Departamento de Fisica de la Materia Condensada, Centro Atomico Constituyentes, CNEA. Av. General Paz 1499 (1650), San Martin, Buenos Aires (Argentina); Departamento de Quimica Inorganica, Analitica y Quimica-Fisica, INQUIMAE CONICET, Facultad Ciencias Exactas y Naturales, Pabellon 2, Ciudad Universitaria, Buenos Aires (Argentina)

    2011-02-15

    Mesoporous Pt and Pt/Ru catalysts with 2D-hexagonal mesostructure were synthesized using a triblock poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) copolymer (Pluronic F127 {sup registered}) template, on a gold support. Large electrochemical surface areas were observed for the catalysts prepared at high overpotentials. Compared to the Pt catalyst, the Pt/Ru alloy containing 3 at% of Ru exhibited lower onset potential and more than three times the limit mass activity for methanol oxidation. This behavior is assigned to the larger pore size of the mesoporous Pt and Pt/Ru catalysts obtained with this template that seems to improve the methanol accessibility to the active sites compared to those obtained using lyotropic liquid crystals. (author)

  7. Ordered Porous Pd Octahedra Covered with Monolayer Ru Atoms.

    Science.gov (United States)

    Ge, Jingjie; He, Dongsheng; Bai, Lei; You, Rui; Lu, Haiyuan; Lin, Yue; Tan, Chaoliang; Kang, Yan-Biao; Xiao, Bin; Wu, Yuen; Deng, Zhaoxiang; Huang, Weixin; Zhang, Hua; Hong, Xun; Li, Yadong

    2015-11-25

    Monolayer Ru atoms covered highly ordered porous Pd octahedra have been synthesized via the underpotential deposition and thermodynamic control. Shape evolution from concave nanocube to octahedron with six hollow cavities was observed. Using aberration-corrected high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy, we provide quantitative evidence to prove that only a monolayer of Ru atoms was deposited on the surface of porous Pd octahedra. The as-prepared monolayer Ru atoms covered Pd nanostructures exhibited excellent catalytic property in terms of semihydrogenation of alkynes.

  8. Ternary rare-earth aluminium intermetallics RE10TAl3 (RE = Y, Ho, Tm, Lu; T = Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt) with an ordered anti-Co2Al5 structure.

    Science.gov (United States)

    Benndorf, Christopher; Eckert, Hellmut; Janka, Oliver

    2017-01-24

    Twenty new rare-earth metal rich intermetallic aluminium compounds, RE10TAl3 (RE = Y, Ho, Tm, Lu; T = Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt), were synthesized by arc melting the elements. The compounds crystallize, in analogy to e.g. the respective Cd representatives, with a ternary ordered structure as anti-type to the hexagonal Co2Al5 type, with the space group P63/mmc. The three crystallographically independent rare-earth metal sites occupy the aluminium positions of the aristotype, while the transition metal and aluminium atoms are ordered on the two cobalt sites. Like other rare-earth rich compounds the RE10TX3 members also exhibit transition-metal-centred T@RE6 trigonal prisms as striking structural building units. The prepared compounds have been investigated by susceptibility measurements and (27)Al solid-state MAS-NMR measurements conducted on the Pauli-paramagnetic Y and Lu compounds. Some compounds show a certain amount of disorder as seen from the single crystal structure analysis and from signal broadening in the NMR investigations. By separating Knight shifts from second-order quadrupolar shifts via field dependent measurements, monotonic trends can be discerned regarding the effect of the T atom valence electron concentration and period number, as well as the effect of the closed 4f shell contributed in the Lu compounds. The results confirm that a comparison of Knight shifts within a series of isotypic compounds can reveal important electronic structure information in intermetallic systems.

  9. Submonolayered Ru Deposited on Ultrathin Pd Nanosheets used for Enhanced Catalytic Applications.

    Science.gov (United States)

    Zhang, Zhicheng; Liu, Ye; Chen, Bo; Gong, Yue; Gu, Lin; Fan, Zhanxi; Yang, Nailiang; Lai, Zhuangchai; Chen, Ye; Wang, Jie; Huang, Ying; Sindoro, Melinda; Niu, Wenxin; Li, Bing; Zong, Yun; Yang, Yanhui; Huang, Xiao; Huo, Fengwei; Huang, Wei; Zhang, Hua

    2016-12-01

    Ultrathin Pd nanosheets (NSs) coated with submonolayered Ru, referred to as Pd@Ru NSs, are synthesized via a seed-mediated growth method. The underpotential deposition can be the driving force for the formation of Pd@Ru NSs. The Pd@Ru NSs exhibit superior catalytic properties in the reduction of 4-nitrophenol and the semihydrogenation of 1-octyne, compared to the pure Pd NSs and Ru NSs.

  10. Surface Segregation in Supported Pd-Pt Nanoclusters and Alloys

    NARCIS (Netherlands)

    van den Oetelaar, L.C.A.; Nooij, O.W.; Oerlemans, S.; Denier van der Gon, A.W.; Brongersma, H.H.; Lefferts, Leonardus; Roosenbrand, A.G.; van Veen, J.A.R.

    1998-01-01

    Surface segregation processes in Pd-Pt alloys and bimetallic Pd-Pt nanoclusters on alumina and carbon supports (technical catalysts) have been investigated by determining the metal surface composition of these systems by low-energy ion scattering (LEIS). Both Pd-rich (Pd80Pt20) and Pt-rich

  11. Significantly Enhanced Hydrogen Evolution Activity of Freestanding Pd-Ru Distorted Icosahedral Clusters with less than 600 Atoms.

    Science.gov (United States)

    Dai, Zhihui; Liu, Suli; Zhang, Qinghua; Bao, Jianchun; Li, Yafei; Gu, Lin

    2017-07-24

    Freestanding metal nanoclusters can tune, precisely and effectively, the Gibbs free energy (ΔGH) of atomic hydrogen on the surface of materials. This enables the enhancement of hydrogen evolution activity. In this paper, we report a study of freestanding Pd-Ru distorted icosahedral clusters (ico-clusters) with less than 600 atoms using a simple one-pot synthesis method. This Pd-Ru ico-cluster can be used as an efficient electrocatalyst for the hydrogen evolution reaction (HER) in acidic water, which is a promising alternative to Pt. The experimental and theoretical results suggest that the fcc freestanding Pd-Ru distorted ico-clusters with less than 600 atoms ensure increased active edges and distorted defect sites that reduce the coordination number for the atoms on the catalyst surface. Furthermore, Ru is a more effective hydrogen dissociation source, while Pd has a better hydrogen storage function. Pd-Ru can tune the ΔGH of atomic hydrogen adsorbed on a catalyst and reach an optimal equilibrium state that improves the HER performance. Our studies represent a robust approach towards the development of freestanding Pd-Ru distorted ico-clusters and advanced catalysts with non-Pt content for HER and many other heterogeneous reactions. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Effect of Pt coverage in Pt-deposited Pd nanostructure electrodes on electrochemical properties

    Energy Technology Data Exchange (ETDEWEB)

    Park, Ah-Reum; Lee, Young-Woo; Kwak, Da-Hee; Park, Kyung-Won [Soongsil University, Seoul (Korea, Republic of)

    2015-06-15

    We have fabricated Pt-deposited Pd electrodes via a two-gun sputtering deposition system by separately operating Pd and Pt target as a function of sputtering time of Pt target. For Pt-deposited Pd electrodes (Pd/Pt-X), Pd were first deposited on the substrates at 20 W for 5min, followed by depositing Pt on the Pd-only electrodes as a function of sputtering time (X=1, 3, 5, 7, and 10min) at 20W on the Pt target. As the sputtering time of Pt target increased, the portion of Pt on the Pd electrodes increased, representing an increased coverage of Pt on the Pd electrodes. The Pd/Pt-7 electrode having an optimized Pt coverage exhibits an excellent electrocatalytic activity for methanol oxidation reaction.

  13. Ternary Pt-Ru-Ni catalytic layers for methanol electrooxidation prepared by electrodeposition and galvanic replacement

    OpenAIRE

    Athanasios ePapaderakis; Nikolaos ePliatsikas; Chara eProchaska; Kalliopi M. Papazisi; Balomenou, Stella P.; Dimitrios eTsiplakides; Panagiotis ePatsalas; Sotiris eSotiropoulos

    2014-01-01

    Ternary Pt-Ru-Ni deposits on glassy carbon substrates, Pt-Ru(Ni)/GC, have been formed by initial electrodeposition of Ni layers onto glassy carbon electrodes, followed by their partial exchange for Pt and Ru, upon their immersion into equimolar solutions containing complex ions of the precious metals. The overall morphology and composition of the deposits has been studied by SEM microscopy and EDS spectroscopy. Continuous but nodular films have been confirmed, with a Pt ÷ Ru ÷ Ni % bulk atomi...

  14. High-performance PdRu bimetallic catalyst supported on mesoporous silica nanoparticles for phenol hydrogenation

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Chao [The Key Laboratory of Fuel Cell Technology of Guangdong Province and The Key Laboratory for New Energy of Guangdong Universities, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou (China); Yang, Xu [Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou (China); Yang, Hui; Huang, Peiyan; Song, Huiyu [The Key Laboratory of Fuel Cell Technology of Guangdong Province and The Key Laboratory for New Energy of Guangdong Universities, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou (China); Liao, Shijun, E-mail: chsjliao@scut.edu.cn [The Key Laboratory of Fuel Cell Technology of Guangdong Province and The Key Laboratory for New Energy of Guangdong Universities, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou (China)

    2014-10-01

    Graphical abstract: The addition of Ru could significantly improve the performance of the mesoporous silica nanoparticles supported PdRu/MSN catalyst, which showed over 5 times higher mass activity than the mono-Pd/MSN towards the liquid-phase hydrogenation of phenol. The improved dispersion and the electronic interaction contributed to the enhanced catalytic activity for the catalyst towards phenol hydrogenation. - Highlights: • PdRu bimetal catalyst supported on mesoporous silica nanoparticles was prepared. • The average sizeof PdRu alloy is smaller than that of mono-Pd. • The addition of Ru to Pd modulates the electronic properties between Pd and Ru. • PdRu/MSN catalyst shows superior activity on phenol hydrogenation than Pd/MSN. • PdRu/MSN catalyst shows good selectivity for cyclohexanol to some extent. - Abstract: A high-performance PdRu bimetallic catalyst supported on mesoporous silica nanoparticles (MSN), PdRu/MSN, was prepared by a facile impregnation–hydrogen reduction method. It was found that PdRu/MSN showed 5 times higher activity than that of Pd/MSN towards the liquid-phase hydrogenation of phenol. The catalysts were characterized comprehensively by multiple techniques, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and hydrogen temperature program reduction (TPR). It was revealed that adding Ru could effectively improve the Pd dispersion and promote the electronic interaction between the Pd and Ru, both of which contribute to enhancing the catalytic activity.

  15. Modeling the electro-oxidation of CO and H2/CO on Pt, Ru, PtRu and Pt3Sn

    DEFF Research Database (Denmark)

    Liu, Ping; Logadottir, Ashildur; Nørskov, Jens Kehlet

    2003-01-01

    is developed to describe the electro-oxidation of CO and H-2 at conditions relevant to the anode of a PEM fuel cell. The model is very simple and allows us to express the kinetics of a promoted anode surface relative to the activity of pure Pt directly from the calculated adsorption energy differences...... geometry is the same. This ligand effect is ascribed to changes in the electronic structure of the surface atoms due to interactions with the surroundings, and the physical origin of the effect is discussed. The calculated adsorption energetics is used as input into a simple kinetic model, which....... In agreement with experiments, the model shows Ru, PtRu and Pt3Sn to start oxidizing CO at lower potentials than Pt. In addition, the model shows PtRu to have a considerably lower overpotential for H-2 oxidation in the presence of CO than Pt. Pt3Sn is even better than PtRu, while Ru is found to be considerably...

  16. Pt and PtRu catalyst bilayers increase efficiencies for ethanol oxidation in proton exchange membrane electrolysis and fuel cells

    Science.gov (United States)

    Altarawneh, Rakan M.; Pickup, Peter G.

    2017-10-01

    Polarization curves, product distributions, and reaction stoichiometries have been measured for the oxidation of ethanol at anodes consisting of Pt and PtRu bilayers and a homogeneous mixture of the two catalysts. These anode structures all show synergies between the two catalysts that can be attributed to the oxidation of acetaldehyde produced at the PtRu catalyst by the Pt catalyst. The use of a PtRu layer over a Pt layer produces the strongest effect, with higher currents than a Pt on PtRu bilayer, mixed layer, or either catalyst alone, except for Pt at high potentials. Reaction stoichiometries (average number of electrons transferred per ethanol molecule) were closer to the values for Pt alone for both of the bilayer configurations but much lower for PtRu and mixed anodes. Although Pt alone would provide the highest overall fuel cell efficiency at low power densities, the PtRu on Pt bilayer would provide higher power densities without a significant loss of efficiency. The origin of the synergy between the Pt and PtRu catalysts was elucidated by separation of the total current into the individual components for generation of carbon dioxide and the acetaldehyde and acetic acid byproducts.

  17. Methanol electro-oxidation on Pt-Ru-P/C and Pt-Ru-P/MWCNT in acidic medium

    CSIR Research Space (South Africa)

    Modibedi, M

    2009-06-01

    Full Text Available Pt-Ru-P was prepared by the chemical reduction method using sodium hypophoshite as a reducing agent on Vulcan XC 72 and multi-walled carbon nano-tubes (MWCNTs). Sodium citrate was added as the stabilizer during electro-catalyst preparation...

  18. London penetration depth measurements in Ba (Fe1-xTx)2As2(T=Co,Ni,Ru,Rh,Pd,Pt,Co+Cu) superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Gordon, Ryan T. [Iowa State Univ., Ames, IA (United States)

    2011-01-01

    The London penetration depth has been measured in various doping levels of single crystals of Ba(Fe1-xTx)2As2 (T=Co,Ni,Ru,Rh,Pd,Pt,Co+Cu) superconductors by utilizing a tunnel diode resonator (TDR) apparatus. All in-plane penetration depth measurements exhibit a power law temperature dependence of the form Δλab(T) = CTn, indicating the existence of low-temperature, normal state quasiparticles all the way down to the lowest measured temperature, which was typically 500 mK. Several different doping concentrations from the Ba(Fe1-xTx)2As2 (T=Co,Ni) systems have been measured and the doping dependence of the power law exponent, n, is compared to results from measurements of thermal conductivity and specific heat. In addition, a novel method has been developed to allow for the measurement of the zero temperature value of the in-plane penetration depth, λab(0), by using TDR frequency shifts. By using this technique, the doping dependence of λab(0) has been measured in the Ba(Fe1-xCox)2As2 series, which has allowed also for the construction of the doping-dependent superfluid phase stiffness, ρs(T) = [λ(0)/λ(T)]2. By studying the effects of disorder on these superconductors using heavy ion irradiation, it has been determined that the observed power law temperature dependence likely arises from pair-breaking impurity scattering contributions, which is consistent with the proposed s±-wave symmetry of the superconducting gap in the dirty scattering limit. This hypothesis is supported by the measurement of an exponential temperature dependence of the penetration depth in the intrinsically clean LiFeAs, indicative of a nodeless superconducting gap.

  19. RuS2-OsS2-IrS2的类质同象矿物系列和PdS-PtS矿物系列

    Institute of Scientific and Technical Information of China (English)

    任英忱; 邓禹仁

    1973-01-01

    Based on the results from, studies of minerals belonging to these two systems ,and by reference to pertinent data available, the authors are of thc following opinious: The system RiS2-Os4S2-IrS2 is a complete isomorphous series. Unit cell parameters and physical properties of the mincrals vary with chemical compositions in a systematic manner. PdS-FtS is a limited isomorphous series. Two groups, cooperite [including(Pd0-0.113Pt1-0.387)1.00S1.00] platinum.bearing palladium sulfides [chemical formula(Pd0.86-0.39Pt0.14-0.61)1.00S1.00] can be distinguished within this system. Beeause of differences in crystal structures between the two groups, which is also responsible for the significant differences in physical properties of these minerals, the system PdS-PtS is discontinuous, but each group itself constitutes a complete isomorphous series.

  20. Spontaneous deposition of Ru on Pt (100: morphological and electrochemical studies. Preliminary results of ethanol oxidation at Pt(100/Ru

    Directory of Open Access Journals (Sweden)

    Colle Vinicius D.

    2003-01-01

    Full Text Available In the present work ruthenium was deposited in submonolayer amounts on Pt(100 by spontaneous deposition at several deposition times. The Pt (100/Ru surfaces were analyzed using ex-situ STM to image the deposits characteristic of ruthenium on Pt (100. It was observed the formation of ruthenium islands with diameters between 1.0 and 4.5 nm with bi-atomic thickness in the center of the islands. A homogeneous distribution of the ruthenium islands on the platinum terraces was found, with no preferential deposition on steps or surface defect sites. The ruthenium coverage degree had been calculated by the decrease of charge of the hydrogen adsorption-desorption peaks in the cyclic voltammograms of the Pt(100/Ru electrodes. The Pt(100/Ru electrodes with a ruthenium coverage degree of ca. 0.3 showed a high activity for the ethanol electrooxidation. The electrochemical experimental results support strongly the bifunctional mechanism for the enhanced ethanol oxidation.

  1. Ternary Pt-Ru-Ni catalytic layers for methanol electrooxidation prepared by electrodeposition and galvanic replacement

    Directory of Open Access Journals (Sweden)

    Athanasios ePapaderakis

    2014-06-01

    Full Text Available Ternary Pt-Ru-Ni deposits on glassy carbon substrates, Pt-Ru(Ni/GC, have been formed by initial electrodeposition of Ni layers onto glassy carbon electrodes, followed by their partial exchange for Pt and Ru, upon their immersion into equimolar solutions containing complex ions of the precious metals. The overall morphology and composition of the deposits has been studied by SEM microscopy and EDS spectroscopy. Continuous but nodular films have been confirmed, with a Pt÷Ru÷Ni % bulk atomic composition ratio of 37÷12÷51 (and for binary Pt-Ni control systems of 47÷53. Fine topographical details as well as film thickness have been directly recorded using AFM microscopy. The composition of the outer layers as well as the interactions of the three metals present have been studied by XPS spectroscopy and a Pt÷Ru÷Ni % surface atomic composition ratio of 61÷12÷27 (and for binary Pt-Ni control systems of 85÷15 has been found, indicating the enrichment of the outer layers in Pt; a shift of the Pt binding energy peaks to higher values was only observed in the presence of Ru and points to an electronic effect of Ru on Pt. The surface electrochemistry of the thus prepared Pt-Ru(Ni/GC and Pt(Ni/GC electrodes in deaerated acid solutions (studied by cyclic voltammetry proves the existence of a shell consisting exclusively of Pt-Ru or Pt. The activity of the Pt-Ru(Ni deposits towards methanol oxidation (studied by slow potential sweep voltammetry is higher from that of the Pt(Ni deposit and of pure Pt; this enhancement is attributed both to the well-known Ru synergistic effect due to the presence of its oxides but also (based on the XPS findings to a modification effect of Pt electronic properties.

  2. Metamagnetic domains in [Co/Pt]/Ru multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Kiselev, N.S. [IFW Dresden (Germany); Donetsk Inst. for Physics and Technology (Russian Federation); Bran, C.; Wolff, U.; Schultz, L.; Bogdanov, A.N.; Neu, V.; Roessler, U.K. [IFW Dresden (Germany); Hellwig, O. [Hitachi GST, San Jose (United States)

    2009-07-01

    In antiferromagnetically coupled superlattices with perpendicular anisotropy, a magnetic field induces a cascade of reorientation transitions accompanied by metamagnetic multidomain states. For a micromagnetic model, we derive equilibrium sizes of stripe and bubble metamagnetic domains as functions of the antiferromagnetic exchange, magnetic field, and geometrical parameters of the multilayers. Magnetic phase diagrams display three different types of metamagnetic domains which separate the ferrimagnetic state from the antiferromagnetic and the saturated ferromagnetic state, and from ferrostripe phases. Experimental investigations have been carried out for an antiferromagnetically coupled [(Co/Pt){sub 8}Co/Ru]{sub 18} superlattice. Magnetic force microscopy (MFM) imaging in a magnetic fields reveals peculiarities of the nucleation and evolution of metamagnetic domains. Theoretical analysis of MFM data and the magnetization curves gives a consistent description of the magnetization processes in [Co/Pt]/Ru multilayers. Demagnetization processes starting from the multidomain metamagnetic states lead to specific remanents states, namely metamagnetic band and bubble topological defects.

  3. Methanol Electro-Oxidation on Pt-Ru Alloy Nanoparticles Supported on Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Yangchuan Xing

    2009-09-01

    Full Text Available Carbon nanotubes (CNTs have been investigated in recent years as a catalyst support for proton exchange membrane fuel cells. Improved catalyst activities were observed and attributed to metal-support interactions. We report a study on the kinetics of methanol electro-oxidation on CNT supported Pt-Ru alloy nanoparticles. Alloy catalysts with different compositions, Pt53Ru47/CNT, Pt69Ru31/CNT and Pt77Ru23/CNT, were prepared and investigated in detail. Experiments were conducted at various temperatures, electrode potentials, and methanol concentrations. It was found that the reaction order of methanol electro-oxidation on the PtRu/CNT catalysts was consistent with what has been reported for PtRu alloys with a value of 0.5 in methanol concentrations. However, the electro-oxidation reaction on the PtRu/CNT catalysts displayed much lower activation energies than that on the Pt-Ru alloy catalysts unsupported or supported on carbon black (PtRu/CB. This study provides an overall kinetic evaluation of the PtRu/CNT catalysts and further demonstrates the beneficial role of CNTs.

  4. Amorphous Pt@PdCu/CNT Catalyst for Methanol Electrooxidation ...

    African Journals Online (AJOL)

    A multi-walled carbon nanotube-supported, Pt decorated nano-sized ... alloy cores (denoted as Pt@PdCu/CNT) catalyst with lower Pt loading is synthesized via a ... The electrochemical activity of the Pt@PdCu/CNT catalyst is tested by cyclic ...

  5. Ánodos de Pt-Ru y Pt-Ir para Celdas de Combustible Alimentadas con Metano y Propano Directo Pt-Ru and Pt-Ir Anodes for Direct Methane and Propane Proton Exchange Membrane Fuel Cells

    Directory of Open Access Journals (Sweden)

    Bibian A Hoyos

    2007-01-01

    Full Text Available En este trabajo se evalúa el efecto de la temperatura en el desempeño de celdas de combustible de membrana de intercambio protónico alimentadas con metano y propano, utilizando oxígeno como alimentación en el cátodo. Para la oxidación de los combustibles en los ánodos, se probaron cinco catalizadores soportados en carbón: Pt, Pt85Ru15, Pt50Ru50, Pt90Ir10 y Pt50Ir50. Como catalizador en el cátodo se usó platino puro soportado en carbón. El desempeño de las celdas de combustible fue evaluado mediante curvas de polarización obtenidas a partir de los datos corriente-potencial. Los resultados indican que la oxidación de metano se ve favorecida a altas temperaturas sobre los catalizadores Pt90/Ir10, Pt50/Ir50 y Pt50/Ru50. A bajas temperaturas los mejores catalizadores resultaron ser Pt y Pt85/Ru15. La mezcla bimetálica Pt85/Ru15 fue la que presentó mejor desempeño para llevar a cabo la oxidación de propano a 30 °C.In this paper, the effect of temperature in the performance of proton exchange membrane fuel cells feed with methane and propane, using oxygen as feed to the cathode, is presented. For the fuel oxidation in the anodes, five carbon supported catalysts were tested: Pt, Pt85/Ru15, Pt50/Ru50, Pt90/Ir10, and Pt50/Ir50. Carbon-supported pure platinum was used as catalysts in the cathode side. The performance of the fuel cells was evaluated by polarization curves obtained from the current-potential data. Results indicate that methane oxidation is favoured at high temperatures on the Pt90/Ir10, Pt50/Ir50 and Pt50/Ru50 catalysts. At low temperatures the best catalysts were Pt and Pt85/Ru15. The Pt85/Ru15 bimetallic mixture showed the best performance to carry out propane oxidation at 30 °C.

  6. Synthesis and composition evolution of bimetallic Pd Pt alloy nanoparticles

    Science.gov (United States)

    Ren, Guoqiang; Shi, Honglan; Xing, Yangchuan

    2007-09-01

    This paper reports a study on the synthesis of Pd-Pt alloy nanoparticles and composition evolution of the alloys. The synthesis involves Pd and Pt acetylacetonate as the metal precursors and trioctylphosphine (TOP) as the solvent. Thermal decomposition of the Pd-TOP complex resulted in Pd nanoparticles, while substitution of Pt in the Pt-TOP complex by Pd allowed formation of the Pd-Pt alloys. It was observed that the Pd-Pt nanoparticles formed at the very beginning in the synthesis process are Pd rich with various nanoparticle sizes ranging from 1.5 to 25 nm in diameter. These nanoparticles averaged out through a digestive ripening process and reached a final size of 3.5 nm in about 10 min. The alloy compositions evolved throughout the synthesis process and only reached the preset Pd to Pt ratio of the precursors in 120 min. It was found that Pt acetylacetonate alone in TOP cannot produce Pt nanoparticles, which was attributed to the formation of a Pt-TOP complex and a strong coordination of Pt to the phosphine. This observation led us to propose an atomic exchange process between the Pt-TOP complex and the Pd atoms at the nanoparticle surface. As a result, the alloy formation process is limited by a substitution and diffusion rate of the Pt atoms at the surface of the alloy nanoparticles.

  7. Pt-Ru Catalysts Prepared by a Modified Polyol Process for Direct Methanol Fuel Cells

    Institute of Scientific and Technical Information of China (English)

    ZHANG Junmin; ZHU Fangfang; ZHANG Kunhua; LIU Weiping; GUAN Weiming

    2012-01-01

    Supported PtRu/C catalysts used in direct methanol fuel cells (DMFCs) were prepared by a new modified polyol method.Transmission electron microscopy (TEM),X-ray diffraction (XRD) and cyclic voltammograms (CVs) were carried out to characterize the morphology,composition and the electrochemical properties of the PtRu/C catalyst.The results revealed that the PtRu nanoparticles with small average particle size (≈2.5 nm),and highly dispersed on the carbon support.The PtRu/C catalyst exhibited high catalytic activity and anti-poisoned performance than that of the JM PtRu/C.It is imply that the modified polyol method is efficient for PtRu/C catalyst preparation.

  8. Kinetic study of methanol oxidation on Pt2Ru3/C catalyst in the alkaline media

    Directory of Open Access Journals (Sweden)

    A. V. TRIPKOVIC

    2007-11-01

    Full Text Available The interaction of acridine orange (AO with double-stranded (ds The electrochemical oxidation of methanol in NaOH solution was examined on a thin film Pt2Ru3/C electrode. The XRD pattern revealed that the Pt2Ru3 alloy consisted of a solid solution of Ru in Pt and a small amount of Ru or a solid solution of Pt in Ru. It was shown that in alkaline solution, the difference in activity between Pt/C and Pt2Ru3/C is significantly smaller than in acid solution. It is proposed that the reaction follows a quasi bifunctional mechanism. The kinetic parameters indicated that the chemical reaction between adsorbed COad and OHad species could be the rate limiting step.

  9. The formation mechanism of bimetallic PtRu alloy nanoparticles in solvothermal synthesis.

    Science.gov (United States)

    Mi, Jian-Li; Nørby, Peter; Bremholm, Martin; Becker, Jacob; Iversen, Bo B

    2015-10-21

    An understanding of the nucleation and growth mechanism of bimetallic nanoparticles in solvothermal synthesis is important for further development of nanoparticles with tailored nanostructures and properties. Here the formation of PtRu alloy nanoparticles in a solvothermal synthesis using metal acetylacetonate salts as precursors and ethanol as both the solvent and reducing agent has been studied by in situ synchrotron radiation powder X-ray diffraction (SR-PXRD). Unlike the classical mechanism for the synthesis of monodisperse sols, the nucleation and growth processes of bimetallic PtRu nanoparticles occur simultaneously under solvothermal conditions. In the literature co-reduction of Pt and Ru is often assumed to be required to form PtRu bimetallic nanocrystals, but it is shown that monometallic Pt nanocrystals nucleate first and rapidly grow to an average size of 5 nm. Subsequently, the PtRu bimetallic alloy is formed in the second nucleation stage through a surface nucleation mechanism related to the reduction of Ru. The calculated average crystallite size of the resulting PtRu nanocrystals is smaller than that of the primary Pt nanocrystals due to the large disorder in the PtRu alloyed structure.

  10. RuPd, RuCo, PdCo and RuPdCo materials as candidates for cathode catalyzers in PEM fuel cells; Materiales RuPd, RuCo, PdCo y RuPdCo como candidatos a catalizadores catodicos en celdas de combustible tipo PEM

    Energy Technology Data Exchange (ETDEWEB)

    Leyva Noyola, Fatima; Solorza Feria, Omar [Centro de Investigacion y Estudios Superiores del IPN, Mexico, D.F. (Mexico)]. E-mail: fleyva@cinvestav.mx

    2009-09-15

    This work reports on the catalytic activity of RuPd, RuCo, PdCo and RuPdCo material for oxygen reduction reaction (ORR). These materials were synthesized using chemical reduction with NaBH{sub 4} as a reducing agent in THF, in ambient temperature and pressure conditions. The evaluation of the catalytic activity was done using cyclic voltamperometry (CV) and rotary disc electrode (RDE) in H{sub 2}SO{sub 4} 0.5 M. The kinetic results showed that the electrochemical reaction involves 4 electrons and the transfer of the first electron is the determinant stage. The values of {alpha}, i0 and the Tafel slope were very similar for the four materials studied, around 0.4, 5x10{sup -6} mA cm{sup -2} and 60 mV dec-1, respectively. Although these values are less than those reported for nanostructured platinum, they are better than those reported for other materials such as pure Pd, which enables them to be considered as cathode catalysts for a proton exchange membrane fuel cell. [Spanish] En este trabajo se reporta la actividad catalitica de los materiales RuPd, RuCo, PdCo y RuPdCo para la reaccion de reduccion de oxigeno (RRO). Estos materiales fueron sintetizados por el metodo de reduccion quimica, usando NaBH{sub 4} como agente reductor en THF, en condiciones de temperatura y presion ambiental. La evaluacion de la actividad catalitica fue realizada usando Voltamperometria Ciclica (VC) y Electrodo Disco Rotatorio (EDR) en H{sub 2}SO{sub 4} 0.5 M. Los resultados cineticos mostraron que la reaccion electroquimica procede por la via de 4 electrones y la etapa determinante es la transferencia del primer electron. Los valores de {alpha}, i0 y pendiente de Tafel fueron muy similares para los 4 materiales estudiados, siendo estos de alrededor de 0.4, 5x10{sup -6} mA cm{sup -2} y 60 mV dec{sup -1}, respectivamente. Sin embargo, aun cuando estos valores son menores que los reportados para platino nanoestructurado, son mejores que los reportados para otros materiales como el Pd puro

  11. Preparation of PtSn/C, PtRu/C, PtRh/C, PtRuRh/C and PtSnRh/C electrocatalysts using an alcohol-reduction process for methanol and ethanol oxidation; Preparacao e caracterizacao de eletrocatalisadores PtRu, PtSn, PtRh, PtRuRh e PtSnRh para oxidacao direta de alcoois em celulas a combustivel tipo PEM utilizando a metodologia da reducao por alcool

    Energy Technology Data Exchange (ETDEWEB)

    Dias, Ricardo Rodrigues

    2009-07-01

    In this work, Pt/C, PtRh (90:10), PtRh/C (50:50), PtSn/C (50:50), PtRu (50:50)/C, PtRuRh/C (50:40:10) and PtSnRh/C (50:40:10) were prepared by an alcohol-reduction process with metal loading of 20 wt.% using H{sub 2}PtCl{sub 6}.6H{sub 2}O (Aldrich), SnCl{sub 2}.2H{sub 2}O (Aldrich),and RhCl{sub 2}.XH{sub 2}O (Aldrich) as metals sources and Vulcan XC72 as support. The electrocatalysts were characterized by EDX, XRD and cyclic voltammetry (CV). The electro-oxidation of ethanol was studied by CV, chronoamperomety at room temperature in acid medium and tests at 100 deg C on a single cell of a direct methanol or ethanol fuel cell. The EDX analysis showed that the metal atomic ratios of the obtained electrocatalysts were similar to the nominal atomic ratios used in the preparation. The diffractograms of electrocatalysts prepared showed four peaks at approximately 2{theta} =40 deg, 47 deg, 67 deg and 82 deg, which are associated with the (111), (200), (220) and (311) planes, respectively, of a face cubic-centered (fcc) structure characteristic of platinum and platinum alloys. The average crystallite sizes using the Scherrer equation and the calculated values were in the range of 2-3 nm. For Pt Sn/C and PtSnRh/C two additional peaks were observed at 2 = 34 deg and 52 deg that were identified as a SnO{sub 2} phase. Pt Sn/C (50:50) and PtSnRh/C (50:40:10) electro catalyst showed the best performance for ethanol oxidation at room temperature. For methanol oxidation at room temperature Pt Ru/C, Pt Sn/C and PtRuRh/C electrocatalysts showed the best performance. Tests at 100 deg C on a single cell of a direct ethanol fuel cell PtSnRh/C showed the best performance, for methanol oxidation PtRuRh/C showed the best performance. (author)

  12. PtRu colloid nanoparticles for CO oxidation in microfabricated reactors

    DEFF Research Database (Denmark)

    Klerke, Asbjørn; Saadi, Souheil; Toftegaard, Maja Bøg

    2006-01-01

    The catalytic activity of PtRu colloid nanoparticles for CO oxidation is investigated in microfabricated reactors. The measured catalytic performance describes a volcano curve as a function of the Pt/Ru ratio. The apparent activation energies for the different alloy catalysts are between 21 and 117...

  13. A comparative study of Pt and Pt-Pd core-shell nanocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Long, Nguyen Viet, E-mail: nguyenviet_long@yahoo.com [Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Posts and Telecommunications Institute of Technology, km 10 Nguyen Trai, Thanh Xuan, Ha Dong, Hanoi (Viet Nam); Laboratory for Nanotechnology, Vietnam National University, Ho Chi Minh, Linh Trung, Thu Duc, Ho Chi Minh (Viet Nam); Department of Molecular and Material Sciences, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasugakouen, Kasuga, Fukuoka 816-8580 (Japan); Ohtaki, Michitaka [Department of Molecular and Material Sciences, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasugakouen, Kasuga, Fukuoka 816-8580 (Japan); Hien, Tong Duy [Laboratory for Nanotechnology, Vietnam National University, Ho Chi Minh, Linh Trung, Thu Duc, Ho Chi Minh (Viet Nam); Randy, Jalem [Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Nogami, Masayuki, E-mail: nogami@nitech.ac.jp [Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)

    2011-10-30

    Highlights: > The syntheses of Pt (4-8 nm) and Pt-Pd core-shell nanoparticles (15-25 nm) are showed. > Pt-Pd core-shell catalysts possess catalytic property much better than Pt catalysts. > Pt-Pd core-shell catalysts exhibit fast and highly stable catalytic activity. > Fascinatingly, size effect is not as really important as nanostructuring effect. > Fast, stable, sensitive hydrogen adsorption is very crucial for fuel cells. - Abstract: This comparative study characterizes two types of metallic and core-shell bimetallic nanoparticles prepared with our modified polyol method. These nanoparticles consist of Pt and Pt-Pd core-shell nanocatalysts exhibiting polyhedral morphologies. The controlled syntheses of Pt metallic nanoparticles in the 10-nm regime (4-8 nm) and Pt-Pd bimetallic core-shell nanoparticles in the 30-nm regime (15-25 nm) are presented. To realize our ultimate research goals for proton exchange membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs), we thoroughly investigate the dependence of the electrocatalytic properties of the nanoparticles on the structure, size and morphology. Significant differences in the electrocatalysis are also explained in experimental evidences of both Pt and Pt-Pd nanocatalysts. We suggested that the core-shell controlled morphologies and nanostructures of the Pd nanoshell as the Pd atomic monolayers will not only play an important role in producing inexpensive, novel Pt- and Pd-based nanocatalysts but also in designing more efficient Pt- and Pd-based nanocatalysts for practical use in DMFC technology. Our comparative results show that Pt-Pd nanocatalysts with Pd nanoshells exhibited much better electrocatalytic activity and stabilization compared to Pt nanocatalysts. Interestingly, we found that the size effect is not as strong as the nanostructuring effect on the catalytic properties of the researched nanoparticles. A nanostructure effect of the core-shell bimetallic nanoparticles was identified.

  14. The electrocatalytic properties of carbon supported PtRu/C nanoalloys in oxidation of small organic molecules: Comparison with Pt/C catalyst

    Directory of Open Access Journals (Sweden)

    Lović Jelena D.

    2012-01-01

    Full Text Available The electrocatalytic activity of carbon supported PtRu/C catalysts, with different composition, toward the electrooxidation of methanol, CO and formic acid were examined in acid and alkaline solution at ambient temperature using thin-film rotating disk electrode (RDE method and compared with activity of Pt/C. The catalysts were characterized by XRD, AFM and STM techniques. XRD pattern revealed that PtRu-1/C catalyst is consisted of two structures e.g. Pt-Ru-fcc and Ru-hcp (the solid solution of Ru in Pt and the small amount of Ru or solid solution of Pt in Ru, as opposed to PtRu-2/C catalyst which is consisted of one structure mostly, Pt-Ru-fcc. According to STM images, PtRu as well as Pt, particles size were between 2 and 6 nm, which is in a good agreement with the mean particles size determined by XRD. To establish the activity and stability of the catalysts potentiodynamic and quasi steady-state measurements were performed. It was found that the activity of Pt and PtRu for CO and methanol oxidation is a strong function of pH of solution. The kinetics are much higher in alkaline than in acid solution and the difference between Pt/C and PtRu/C is much less pronounced in alkaline media. Results presented in this work indicate that activity of PtRu catalysts depends on catalyst composition, e.g. on Pt/Ru atomic ratio, as well as on alloying degree of catalysts. Comparison of CO, methanol and formic acid oxidation on PtRu-2/C, PtRu-1/C and Pt/C catalysts revealed that PtRu-2/C is the most active one. It was shown that the PtRu-2/C catalyst, due to fact that it is consisted of only one phase, with high alloying degree, through the bifunctional mechanism improved by electronic effect, achieve the activity two times higher related to PtRu-1/C in the oxidation of all organic molecules investigated, and about three times higher compared to Pt/C in the oxidation of methanol and CO, and five times higher in formic acid oxidation.

  15. Cyclic-Oxidation Behavior of Multilayered Pt/Ru-Modified Aluminide Coating

    Institute of Scientific and Technical Information of China (English)

    Yingxue Song; Hideyuki Murakami; Chungen Zhou

    2011-01-01

    Multilayered Pt/Ru modified aluminide coating for thermal barrier coating (TBC) systems has been investigated. 2 μm Pt+2μm Ru+2 μm Pt was first deposited on nickel-base superalloy DZ125 by electrodeposition, and then the coating was treated by annealing and a conventional pack-cementation aluminizing process. The cyclic oxidation tests were carried out at 1423 K in air. It was found that the thermal cyclic oxidation resistance of Pt/Ru-modified aluminide coating was comparable to that of Pt-modified aluminide coating, which was much better than simply aluminized DZ125. The addition of Ru to Pt-modified aluminide coating increased the resistance to rumpling. The microstructures and phase constitutions of the coating before and after oxidation were investigated.

  16. PtRu/C Electrocatalysts Prepared Using Gamma and Electron Beam Irradiation for Methanol Electrooxidation

    Directory of Open Access Journals (Sweden)

    Dionisio F. Silva

    2012-01-01

    Full Text Available PtRu/C electrocatalysts (carbon-supported PtRu nanoparticles were prepared in a single step submitting water/2-propanol mixtures containing Pt(IV and Ru(III ions and the carbon support to gamma and electron beam irradiation. The electrocatalysts were characterized by energy dispersive X-ray analysis (EDX, X-ray diffraction (XRD, transmission electron microscopy (TEM, and cyclic voltammetry and tested for methanol electrooxidation. PtRu/C electrocatalyst can be prepared in few minutes using high dose rate electron beam irradiation while using low dose rate gamma irradiation some hours were necessary to prepare it. The obtained materials showed the face-centered cubic (fcc structure of Pt and Pt alloys with average nanoparticle sizes of around 3 nm. The material prepared using electron beam irradiation was more active for methanol electrooxidation than the material prepared using gamma irradiation.

  17. Potential oscillations in a proton exchange membrane fuel cell with a Pd-Pt/C anode

    Science.gov (United States)

    Lopes, Pietro P.; Ticianelli, Edson A.; Varela, Hamilton

    We report in this paper the occurrence of potential oscillations in a proton exchange membrane fuel cell (PEMFC) with a Pd-Pt/C anode, fed with H 2/100 ppm CO, and operated at 30 °C. We demonstrate that the use of Pd-Pt/C anode enables the emergence of dynamic instabilities in a PEMFC. Oscillations are characterized by the presence of very high oscillation amplitude, ca. 0.8 V, which is almost twice that observed in a PEMFC with a Pt-Ru/C anode under similar conditions. The effects of the H 2/CO flow rate and cell current density on the oscillatory dynamics were investigated and the mechanism rationalized in terms of the CO oxidation and adsorption processes. We also discuss the fundamental aspects concerning the operation of a PEMFC under oscillatory regime in terms of the benefit resulting from the higher average power output.

  18. High-performance PdRu bimetallic catalyst supported on mesoporous silica nanoparticles for phenol hydrogenation

    Science.gov (United States)

    Huang, Chao; Yang, Xu; Yang, Hui; Huang, Peiyan; Song, Huiyu; Liao, Shijun

    2014-10-01

    A high-performance PdRu bimetallic catalyst supported on mesoporous silica nanoparticles (MSN), PdRu/MSN, was prepared by a facile impregnation-hydrogen reduction method. It was found that PdRu/MSN showed 5 times higher activity than that of Pd/MSN towards the liquid-phase hydrogenation of phenol. The catalysts were characterized comprehensively by multiple techniques, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and hydrogen temperature program reduction (TPR). It was revealed that adding Ru could effectively improve the Pd dispersion and promote the electronic interaction between the Pd and Ru, both of which contribute to enhancing the catalytic activity.

  19. 微波消解-双浊点萃取 ICP -MS 测定地球化学样品中的痕量铂钯钌铑%Determination of Pt,Pd,Ru,Rh in Geochemical Samples by ICP-MS with Microwave Digestion and Dual-cloud Point Extraction

    Institute of Scientific and Technical Information of China (English)

    沈宇; 张尼; 高小红; 李展; 李日升; 郑建斌

    2016-01-01

    Traditional cloud point extraction methods commonly enrich elements in the viscous surfactant. However,the viscosity of the solution will adversely affect the detection signal of the plasma.Harmful agents such as methanol are usually adopted as a thinner to reduce the viscosity of the organic phase,but the organic component affects the stability of the plasma,and organic absorption on the injection tube will enhance elemental memory effect.These disadvantages limit the widespread application of Inductively Coupled Plasma-Mass Spectrometry (ICP-MS)in cloud point extraction.A method to determine Pt,Pd,Ru, Rh in geochemical samples by ICP-MS based dual-cloud point extraction has been established,and is reported in this paper.After the microwave digestion procedure,first cloud point extraction is performed on the sample solution using DDTP as the sequestrant and Triton X-114 as the surfactant.HNO3 is added into the organic phase,and second cloud point extraction is performed by heating so that Pt,Pd,Ru,Rh enter the water phase from the organic phase. Enrichment factors are 45,33,18,35,and detection limits are 0.05,0.02,0.10 and 0.03 μg/L for Pt,Pd,Ru and Rh,respectively.The proposed method succeeds in the simultaneous enrichment of trace platinum group elements in complex matrix geochemical samples,improving the stability of the ICP-MS measurement.%传统浊点萃取技术是将待测元素富集在黏稠的表面活性剂相中,溶液的黏度会对等离子体检测信号产生影响,通常使用甲醇作为稀释剂降低有机相黏度,有机成分也对等离子体的稳定性产生影响,同时有机物在进样管路上的吸附还会提高待测元素的记忆效应,因而限制了 ICP -MS 在浊点萃取中的应用。本文建立了双浊点萃取技术 ICP -MS 测定地球化学样品中铂钯钌铑的分析方法。样品用微波消解处理后,以DDTP 为螯合剂,Triton X -114为表面活性剂,对消解溶液第一次浊点萃取

  20. Electrochemical activation of nanostructured carbon-supported PtRuMo electrocatalyst for methanol oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Huerta, M.V., E-mail: mmartinez@icp.csic.e [Instituto de Catalisis y Petroleoquimica, CSIC, Marie Curie 2, 28049 Madrid (Spain); Tsiouvaras, N.; Pena, M.A.; Fierro, J.L.G. [Instituto de Catalisis y Petroleoquimica, CSIC, Marie Curie 2, 28049 Madrid (Spain); Rodriguez, J.L.; Pastor, E. [Departamento de Quimica Fisica, Universidad de La Laguna, Astrofisico Francisco Sanchez s/n, 38071 Tenerife (Spain)

    2010-11-01

    The factors controlling the behavior and the stability of electrocatalysts based on Pt, Ru and Mo nanoparticles during exhaustive electrochemical treatment are examined. Along this treatment, it has been observed that in the case of ternary catalysts there are pronounced changes in the structure of their surface resulting in electrode activation for methanol and CO electrooxidation, whereas the activity of binary PtRu/C and PtMo/C catalysts decreases. Therefore, the role of both Ru and Mo is crucial for the electrochemical activation of the catalyst, though metal losses do occur during electrochemical process. For the first time a detailed study of this phenomenon is presented, including characterization by HRTEM, TXRF, XRD, electrochemical measurements and in situ Fourier transform infrared spectroscopy (FTIR). In order to get a deeper insight into the surface structure, chemical state, and stability of the electrocatalyst under reaction conditions, a combination of cyclic voltammetry, chronoamperometry and X-ray photoelectron spectroscopy (XPS) has been used. By comparing bulk and surface composition, our results point out to the key role of the geometric effect enhanced by previous reduction of the nanoparticles. At the end of the electrochemical treatment, Mo-PtRu/C catalysts surface was restructured with substantial enrichment in Pt and a less pronounced Mo surface enrichment, while Ru is incorporated into the Pt-Mo overlayer. These results underline the possibility of further optimization of the surface structure and composition producing PtRuMo nanoparticles with high methanol and CO oxidation activity.

  1. The role of surface Pt on the coadsorption of hydrogen and CO on Pt monolayer film modified Ru(0001) surfaces

    Science.gov (United States)

    Diemant, T.; Hartmann, H.; Bansmann, J.; Behm, R. J.

    2016-10-01

    We have investigated the impact and role of the Pt surface modification on the coadsorption of hydrogen and CO on structurally well defined bimetallic Pt monolayer island/film modified Ru(0001) surfaces with Pt contents up to a complete Pt layer, employing temperature programmed desorption (TPD) and infrared reflection absorption spectroscopy (IRRAS). Kinetic limitations in the surface diffusion are shown to play an important role for adsorption at 90 K, and lead to profound effects of the dosing sequence on the adsorption and desorption characteristics. Furthermore, they are responsible for spill-over effects during the TPD measurements, where COad becomes mobile and can spill-over from weakly bonding Pt monolayer areas to strongly bonding Pt-free Ru(0001) areas, which displaces Dad from these surface areas. The present findings are discussed in comparison with previous results on related metallic and bimetallic adsorption and coadsorption systems.

  2. Evaluation of nanostructured Pt-Ru catalyst for application in DMFC

    Energy Technology Data Exchange (ETDEWEB)

    Ocampo, A.L.; Gamboa, S.A. [Centro de Investigacion en Energia-UNAM, Morelos (Mexico); Sebastien, P.J. [Centro de Investigacion en Energia-UNAM, Morelos (Mexico)]|[Chiapas Politecnica Univ., Chiapas (Mexico); Morgado, J.; Montoya, J.A. [IMP, Eje Central Lazaro Cardenas, (Mexico); Savadogo, O. [Ecole Polytechnique, Montreal, PQ (Canada). Laboratoire d' electrochimie et de materiaux energetiques

    2006-07-01

    Slow methanol oxidation kinetics and the poisoning of the anode catalyst are the major factors that limit the performance of the direct methanol fuel cell (DMFC). Catalysts with higher catalytic activity are needed in order to overcome these challenges. Although platinum (Pt) is a good catalyst for methanol oxidation, it can be highly affected by carbon monoxide (CO) reaction intermediates. Superior catalytic activity occurs in Pt based alloys, such as platinum ruthenium (Pt-Ru), platinum molybdenum (Pt-Mo), platinum tin (Pt-Sn), and platinum osmium (Pt-Os). This is due to the bifunctional mechanism and/or by the electronic effect, which indicates a promotional effect of the alloyed metal on Pt. The most studied binary system is the Pt-Ru (ruthenium), which has shown the best catalytic activity. There are many factors that influence the physical properties and the electrochemical performance of the Pt-Ru catalyst. These include the preparation method; the atomic ratio between platinum and ruthenium; the nature of the catalyst support; and, an optional heat treatment. Other important factors such as the particle size, the morphology, the electrochemically active area, and the crystalline phase influence the physical properties. In this study, nanostructured Pt-Ru catalysts were fabricated and evaluated physicochemically and electrochemically for its use in direct methanol fuel cell (DMFC). The catalysts were synthesized from the carbonyl compounds of Pt and Ru via a pyrolysis-condensation reaction. The high resolution results showed a homogenous distribution of the nanostructured catalysts on Vulcan support. The catalyst was evaluated by XRD, HRTEM, electrochemical impedance spectroscopy and the methanol oxidation on the catalyst was studied using volt-amperometry. The performance of the catalyst was found to be similar or better than the commercial one. It was concluded that it is possible to synthesize Pt-Ru/C with good morphological characteristics and improve it

  3. High-performance core-shell PdPt@Pt/C catalysts via decorating PdPt alloy cores with Pt

    Science.gov (United States)

    Wu, Yan-Ni; Liao, Shi-Jun; Liang, Zhen-Xing; Yang, Li-Jun; Wang, Rong-Fang

    A core-shell structured low-Pt catalyst, PdPt@Pt/C, with high performance towards both methanol anodic oxidation and oxygen cathodic reduction, as well as in a single hydrogen/air fuel cell, is prepared by a novel two-step colloidal approach. For the anodic oxidation of methanol, the catalyst shows three times higher activity than commercial Tanaka 50 wt% Pt/C catalyst; furthermore, the ratio of forward current I f to backward current I b is high up to 1.04, whereas for general platinum catalysts the ratio is only ca. 0.70, indicating that this PdPt@Pt/C catalyst has high activity towards methanol anodic oxidation and good tolerance to the intermediates of methanol oxidation. The catalyst is characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The core-shell structure of the catalyst is revealed by XRD and TEM, and is also supported by underpotential deposition of hydrogen (UPDH). The high performance of the PdPt@Pt/C catalyst may make it a promising and competitive low-Pt catalyst for hydrogen fueled polymer electrolyte membrane fuel cell (PEMFC) or direct methanol fuel cell (DMFC) applications.

  4. H2-splitting on Pt/Ru alloys supported on sputtered HOPG

    DEFF Research Database (Denmark)

    Fiordaliso, Elisabetta Maria; Dahl, Søren; Chorkendorff, Ib

    2011-01-01

    that alloying Pt with Ru improves significantly the resistance toward CO poisoning with respect to pure Pt, and the resistance increases with an increasing amount of Ru in the bulk alloys. The faster hydrogen exchange rate with respect to the pure metals and the higher CO tolerance of the alloys are attributed......, and it is attributed to geometrical ensemble effects. © 2011 American Chemical Society....

  5. Synthesis and Electrocatalytic Performance of Multi-Component Nanoporous PtRuCuW Alloy for Direct Methanol Fuel Cells

    Directory of Open Access Journals (Sweden)

    Xiaoting Chen

    2015-06-01

    Full Text Available We have prepared a multi-component nanoporous PtRuCuW (np-PtRuCuW electrocatalyst via a combined chemical dealloying and mechanical alloying process. The X-ray diffraction (XRD, transmission electron microscopy (TEM and electrochemical measurements have been applied to characterize the microstructure and electrocatalytic activities of the np-PtRuCuW. The np-PtRuCuW catalyst has a unique three-dimensional bi-continuous ligament structure and the length scale is 2.0 ± 0.3 nm. The np-PtRuCuW catalyst shows a relatively high level of activity normalized to mass (467.1 mA mgPt−1 and electrochemically active surface area (1.8 mA cm−2 compared to the state-of-the-art commercial PtC and PtRu catalyst at anode. Although the CO stripping peak of np-PtRuCuW 0.47 V (vs. saturated calomel electrode, SCE is more positive than PtRu, there is a 200 mV negative shift compared to PtC (0.67 V vs. SCE. In addition, the half-wave potential and specific activity towards oxygen reduction of np-PtRuCuW are 0.877 V (vs. reversible hydrogen electrode, RHE and 0.26 mA cm−2, indicating a great enhancement towards oxygen reduction than the commercial PtC.

  6. Co oxidation on spontaneous Pt-Ru deposits on composite polymeric electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Bavio, M.A.; Kessler, T. [Departamento de Ingenieria Quimica, Facultad de Ingenieria, Universidad Nacional del Centro de la Provincia de Buenos Aires, Av. del Valle 5737, B7400JWI, Olavarria (Argentina); Castro Luna, A.M. [Instituto de Investigaciones Fisicoquimicas Teoricas y Aplicadas, INIFTA, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Diagonal 113 y 64, 1900, La Plata (Argentina)

    2010-06-15

    Composite polyaniline electrodes containing carbon nanotubes incorporated in the film and spontaneous Pt-Ru deposits as catalytic material for CO oxidation are reported. PANI films were electrosynthesized from a monomer acid solution with the addition of carbon nanotubes. Then, Pt-Ru deposits were obtained by immersing the polymeric film in H{sub 2}PtCl{sub 6} and/or RuCl{sub 3} in HCl. Three series of deposits were prepared by either immersion in a solution containing both metallic ions during a fixed time or successive immersion in different solutions containing only one of the metallic ions during half of the established time and varying the sequence as follows: (i) first in H{sub 2}PtCl{sub 6} and then in RuCl{sub 3} or (ii) first in RuCl{sub 3} and then in H{sub 2}PtCl{sub 6}. Adsorbed CO oxidation was studied by cyclic voltammetry in H{sub 2}SO{sub 4} solution. The electrodes were characterized through SEM and EDX. The different ways to obtain spontaneous Pt-Ru deposits are analyzed and their influence on CO oxidation is discussed. (author)

  7. Structure of Pt/C and PtRu/C catalytic layers prepared by plasma sputtering and electric performance in direct methanol fuel cells (DMFC)

    Energy Technology Data Exchange (ETDEWEB)

    Caillard, A.; Brault, P.; Mathias, J. [Groupe de Recherche sur l' Energetique des Milieux Ionises, UMR6606 Universite d' Orleans, CNRS, Polytech' Orleans BP6744, F-45067 Orleans Cedex 2 (France); Coutanceau, C.; Leger, J.-M. [Laboratoire de Catalyse en Chimie Organique, UMR6503 Universite de Poitiers, CNRS, F-86022 Poitiers (France)

    2006-11-08

    Plasma sputtering process was used to deposit Pt and PtRu on conductive carbon diffusion layer. Low metal loading catalysts for methanol electrooxidation were prepared and characterized by TEM and XRD. The main result is that codeposition of Pt and Ru leads to alloy phase, whereas multi-layers deposition leads to no-alloyed structure. The electrochemical performance of sputtered Pt/C electrodes was compared with that of standard electrodes, and was found lower. However, the specific activity was much higher, indicating that the catalyst utilization efficiency was higher than that obtained with a standard electrode. Then, different bimetallic PtRu/C electrodes were prepared by plasma sputtering, leading to different catalyst structures (Pt and Ru multilayer deposition or simultaneous deposition of Pt and Ru) and composition (from 100:0 to 50:50 Pt/Ru atomic ratios). At last, the different PtRu electrodes were compared in term of DMFC electrical performance. The best efficiency of the DMFC was reached when both metals Pt and Ru are simultaneously deposited (alloyed) with a ruthenium atomic ratio of 30% or 40 % Ru depending of the working potentials of the cell. (author)

  8. Strong interlayer exchange coupling and high post-annealing stability in perpendicularly magnetized [Pt/Co]/Ru/[Co/Pt] structures

    Directory of Open Access Journals (Sweden)

    Seok Jin Yun

    2016-02-01

    Full Text Available Strong interlayer exchange coupling (IEC and high post-annealing stability are demonstrated for perpendicular synthetic ferrimagnets (p-SyFs with [Pt/Co]6/Ru/[Co/Pt]3 structures. The observed IEC strength was 2.55 ergs/cm2 for a Ru thickness of 0.35 nm, representing the highest value achieved up to date for similar structures. The IEC remained strong even after annealing at 450oC, for the practically important Ru layer thickness of 0.85 nm. The biquadratic IEC, a parameter quantifying the pinhole effects in SyFs, was confirmed by analyzing the experimental results by using the total energy functional, and its strength increased with decreasing the temperature and Ru layer thickness.

  9. Interference removals on Pd, Ru and Au with ICP-QQQ-MS in PGE RM

    Science.gov (United States)

    Nadeem Hussain Bokhari, Syed; Meisel, Thomas; Walkner, Christoph

    2015-04-01

    Gold and platinum group elements (PGE) are essential industrial precious metals with high world demand due to their unique properties. Struggle for natural exploration of PGE is on great pace and recycling from industrial wastes, electronics and catalytic convertor is on the rise for PGE supply chain. Along with these developments it is becoming more challenging for analytical chemists to determine gold and PGE out of complex matrix which causes severe interferences. The current state of art is online analysis coupled with chromatographic separation of interferences. The ICP-QQQ-MS Agilent 8800 has the capability of using multi tunes and mass shifts. We aim to remove interferences on Pd+ (for direct and isotope dilution analysis) Au+ and Ru+ in lieu of chemical separations. YO+, SrOH+, ZnAr+, NiAr+, ZrO+, CuAr+, MoO+ , Ru+and Cd+ are expected interferences on Pd+ while Au+ is interfered by TaO+, HfOH+, GdAr+ and 102Ru+ ,104Ru+ by 102Pd+ ,104Pd+ etc. Initial test were performed on pure solutions of 1mg/l (interfering elements): 1 ng/l (Pd, Ru & Au) respectively. The outcomes of initial tests were applied on PGE reference material (RM) WMG-1 and SARM-7 (digested with Na2O2 sintering). The results obtained show that YO+, SrOH+ interfere (104Pd,105Pd), 104 Ru+ on (104Pd), ZnAr+ has slight interference on (104Pd and106Pd), ZrO+, NiAr+, CuAr+ interferences are negligible, MoO+ has severe interference on (108Pd, 110Pd) and that Cd+ has severe isobaric interference on (106Pd,108Pd, 110Pd). These interference have been removed by formation of Pd(NH3)3+complex. The TaO+, HfOH+ and GdAr+ interferences on Au+ are best removed by formation of Au(NH3)+ and Au(NH3)2+ complexes. 102Pd+,104Pd+interference on 102Ru+ ,104Ru+ can be removed by formation of Ru(NH3)4+ and RuO+ compounds. The results obtained comply with certified values of RM. The developed method is being tested on low concentration PGE reference materials. References: Sugiyama, N. " Removal of complex spectral

  10. Electrooxidation of ethanol on Pt and PtRu surfaces investigated by ATR surface-enhanced infrared absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Marcio F.; Camara, Giuseppe A., E-mail: giuseppe.silva@ufms.br [Departamento de Quimica, Universidade Federal do Mato Grosso do Sul, Campo Grande-MS (Brazil); Batista, Bruno C.; Boscheto, Emerson [Instituto de Quimica de Sao Carlos, Universidade de Sao Paulo, Sao Carlos-SP, (Brazil); Varela, Hamilton, E-mail: varela@iqsc.usp.br [Ertl Center for Electrochemistry and Catalysis, Gwangju Institute of Science and Technology (GIST), Gwangju (Korea, Republic of)

    2012-05-15

    Herein, it was investigated for the first time the electro-oxidation of ethanol on Pt and PtRu electrodeposits in acidic media by using in situ surface enhanced infrared absorption spectroscopy with attenuated total reflection (ATR-SEIRAS). The experimental setup circumvents the weak absorbance signals related to adsorbed species, usually observed for rough, electrodeposited surfaces, and allows a full description of the CO coverage with the potential for both catalysts. The dynamics of adsorption-oxidation of CO was accessed by ATR-SEIRAS experiments (involving four ethanol concentrations) and correlated with expressions derived from a simple kinetic model. Kinetic analysis suggests that the growing of the CO adsorbed layer is nor influenced by the presence of Ru neither by the concentration of ethanol. The results suggest that the C-C scission is not related to the presence of Ru and probably happens at Pt sites. (author)

  11. Synthesis of PtRu nanoparticles from the hydrosilylation reaction and application as catalyst for direct methanol fuel cell.

    Science.gov (United States)

    Huang, Junchao; Liu, Zhaolin; He, Chaobin; Gan, Leong Ming

    2005-09-08

    Nanosized Pt, PtRu, and Ru particles were prepared by a novel process, the hydrosilylation reaction. The hydrosilylation reaction is an effective method of preparation not only for Pt particles but also for other metal colloids, such as Ru. Vulcan XC-72 was selected as catalyst support for Pt, PtRu, and Ru colloids, and TEM investigations showed nanoscale particles and narrow size distribution for both supported and unsupported metals. All Pt and Pt-rich catalysts showed the X-ray diffraction pattern of a face-centered cubic (fcc) crystal structure, whereas the Ru and Ru-rich alloys were more typical of a hexagonal close-packed (hcp) structure. As evidenced by XPS, most Pt and Ru atoms in the nanoparticles were zerovalent, except a trace of oxidation-state metals. The electrooxidation of liquid methanol on these catalysts was investigated at room temperature by cyclic voltammetry and chronoamperometry. The results concluded that some alloy catalysts showed higher catalytic activities and better CO tolerance than the Pt-only catalyst; Pt56Ru44/C have displayed the best electrocatalytic performance among all carbon-supported catalysts.

  12. The microstructure and magnetic properties of electrodeposited Co-Pt thin films on Ru buffer layer

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, G.H. [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)], E-mail: skk94@skku.edu; Lee, C.H.; Jang, J.H. [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Park, N.J. [Department of Materials Science and Engineering, Kumoh National University of Technology, Kumi 730-701 (Korea, Republic of); Suh, S.J. [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Advanced Materials and Process Research Center for IT, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2008-11-15

    For high-density magnetic recording media, this study examined the crystal structure and the texture of electrodeposited cobalt-platinum (Co-Pt) films on Ru buffer layer. A 15-nm-thick Co-Pt film exhibited very high out-of-plane coercivity and squareness, which were 6248 Oe and 0.89, respectively. The coercivity, H{sub c}, of Co-Pt films grown on Ru buffer layer decreased significantly with increasing thickness, possibly due to the lattice misfit of 5.4% between Co-Pt and Ru, leading to the decrease of perpendicular magnetic anisotropy (PMA) of Co-Pt films as indicated by the observed hexagonal-closed-packed (HCP) (1 1-bar 0 1) plane of Co-Pt films. According to nano beam diffraction pattern (NBDP), however, Co-Pt film grown on Ru layer of HCP exhibited mixed HCP and FCC phases. Also, cross-sectional TEM image suggests that the high PMA may result from the columnar structure of physically isolated Co-Pt grains with the c-axis perpendicular to the film plane.

  13. Supported PtRu on mesoporous carbons for direct methanol fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Arbizzani, Catia; Beninati, Sabina; Soavi, Francesca; Varzi, Alberto; Mastragostino, Marina [University of Bologna, Department of Metal Science, Electrochemistry and Chemical Techniques, via San Donato 15, 40127 Bologna (Italy)

    2008-12-01

    We prepared and characterized several cryogel mesoporous carbons of different pore size distribution and report the catalytic activity of PtRu supported on mesoporous carbons of pore size >15 nm in passive and in active direct methanol fuel cells (DMFCs). At room temperature (RT), the specific maximum power of the passive DMFCs with mesoporous carbon/PtRu systems as anode was in the range 3-5 W g{sup -1}. Passive DMFC assembly and RT tests limit the performance of the electrocatalytic systems and the anodes were thus tested in active DMFCs at 30, 60 and 80 C. Their responses were also compared to those of commercial Vulcan carbon/PtRu. At 80 C, the specific maximum power of the active DMFC with C656/PtRu was 37 W g{sup -1} and the required amount of Pt per kW estimated at 0.4 V cell voltage was 31 g kW{sup -1}, a value less than half that of Vulcan carbon/PtRu. (author)

  14. Study on hydrogen evolution performance of the carbon supported PtRu alloy film electrodes

    Institute of Scientific and Technical Information of China (English)

    YANG; Bin; LI; Yang; ZAN; Lin-han

    2005-01-01

    The carbon supported PtRu alloy film electrodes having Pt about 0.10 mg/cm2 or even less were prepared by ion beam sputtering method (IBSM). It was valued on the hydrogen analyse performance, the temperature influence factor and the stability by electroanalysis hydrogen analyse method. It was found that the carbon supported PtRu alloy film electrodes had higher hydrogen evolution performance and stability, such as the hydrogen evolution exchange current density (j0) was increase as the temperature (T) rised, and it overrun 150 mA/cm2 as the trough voltage in about 0.68V, and it only had about 2.8% decline in 500 h electrolytic process. The results demonstrated that the carbon supported PtRu alloy film electrodes kept highly catalytic activity and stability, and it were successfully used in pilot plant for producing H2 on electrolysis of H2S.

  15. Soft Landing of Bare PtRu Nanoparticles for Electrochemical Reduction of Oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Grant E.; Colby, Robert J.; Engelhard, Mark H.; Moon, DaeWon; Laskin, Julia

    2015-08-07

    Magnetron sputtering of two independent Pt and Ru targets coupled with inert gas aggregation in a modified commercial source has been combined with soft landing of mass-selected ions to prepare bare 4.5 nm diameter PtRu alloy nanoparticles on glassy carbon electrodes with controlled size and morphology for electrochemical reduction of oxygen in solution. Employing atomic force microscopy (AFM) it is shown that the nanoparticles bind randomly to the glassy carbon electrode at a relatively low coverage of 7 x 104 ions µm-2 and that their average height is centered at 4 nm. Scanning transmission electron microscopy images obtained in the high-angle annular dark field mode (STEM-HAADF) further confirm that the soft-landed PtRu alloy nanoparticles are uniform in size and have a Ru core decorated with small regions of Pt on the surface. Wide-area scans of the electrodes using X-ray photoelectron spectroscopy (XPS) reveal the presence of both Pt and Ru in relative atomic concentrations of ~9% and ~33%, respectively. Deconvolution of the high energy resolution XPS spectra in the Pt4f and Ru3d regions indicates the presence of both oxidized Pt and Ru. The substantially higher loading of Ru compared to Pt and enrichment of Pt at the surface of the alloy nanoparticles is confirmed by wide-area analysis of the electrodes using time-of-flight medium energy ion scattering (TOF-MEIS) employing both 80 keV He+ and O+ ions. The activity of electrodes containing 7 x 104 ions µm-2 of bare 4.5 nm PtRu nanoparticles toward the electrochemical reduction of oxygen was evaluated employing cyclic voltammetry (CV) in 0.1 M HClO4 and 0.5 M H2SO4 solutions. In both electrolytes a pronounced reduction peak was observed during O2 purging of the solution that was not evident during purging with Ar. Repeated electrochemical cycling of the electrodes revealed little evolution in the shape or position of the voltammograms indicating high stability of the alloy nanoparticles supported on glassy

  16. Surface composition of Pt-Pd alloys treated in hydrogen

    Science.gov (United States)

    Szabo, A.; Paál, Z.; Szász, A.; Kojnok, J.; Fabian, D. J.

    1989-11-01

    Pd enrichment is observed in Pd-Pt alloy sheets when heated in He and in H 2. The surface composition was monitored by soft X-ray emission spectroscopy (SXES) and by work function measurements. A regular solution model is used to calculate the expected composition of the surface atomic layers, with and without adsorbed hydrogen, and the calculated and measured values for Pd-enrichment are compared. The possible effect of subsurface adsorbed hydrogen is discussed.

  17. Simple preparation of Pd-Pt nanoalloy catalysts for methanol-tolerant oxygen reduction

    Science.gov (United States)

    He, Wei; Liu, Juanying; Qiao, Yongjin; Zou, Zhiqing; Zhang, Xiaogang; Akins, Daniel L.; Yang, Hui

    Carbon-supported Pd-Pt bimetallic nanoparticles of different atomic ratios (Pd-Pt/C) have been prepared by a simple procedure involving the complexing of Pd and Pt species with sodium citrate followed by ethylene glycol reduction. As-prepared Pd-Pt alloy nanoparticles evidence a single-phase fcc disordered structure, and the degree of alloying is found to increase with Pd content. Both X-ray diffraction and transmission electron microscopy characterizations indicate that all the Pd-Pt/C catalysts possess a similar mean particle size of ca. 2.8 nm. The highest mass and specific activity of the oxygen reduction reaction (ORR) using the Pd-Pt/C catalysts are found with a Pd:Pt atomic ratio of 1:2. Moreover, all Pd-Pt alloy catalysts exhibit significantly enhanced methanol tolerance during the ORR than the Pt/C catalyst, ensuring a higher ORR performance while diminishing Pt utilization.

  18. Microwave-assisted synthesis and characterization of bimetallic PtRu alloy nanoparticles supported on carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Rahsepar, Mansour, E-mail: rahsepar@shirazu.ac.ir [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Zand Boulevard, Shiraz, 7134851154 (Iran, Islamic Republic of); Kim, Hasuck, E-mail: hasuckim@snu.ac.kr [Department of Chemistry, Seoul National University, 599 Gwanak-ro, Gwanak-gu, Seoul, 151-747 (Korea, Republic of); Department of Energy Systems Engineering, Daegu Gyeongbuk Institute of Science & Technology, Daegu, 711-873 (Korea, Republic of)

    2015-11-15

    Multiwalled carbon nanotube (MWCNT) supported PtRu nanoparticles were synthesized by using a microwave-assisted improved impregnation technique. X-ray diffraction, transmission electron microscopy and X-ray photo electron spectroscopy were used to characterize the prepared PtRu/MWCNT nanoparticles. The PtRu nanoparticles with a satisfactory dispersion were formed on the external surface of MWCNTs. The CO stripping experiment was performed to evaluate the poisoning resistance of the prepared PtRu/MWCNT nanoparticles. Results of electrochemical measurements indicate that the prepared PtRu/MWCNTs shows an enhanced performance toward CO poisoning. The results of characterization revealed that microwave-assisted improved impregnation technique have a high yield of alloy phase formation and could be effectively used as a simple, quick and efficient technique for preparation of bimetallic PtRu/MWCNT nanoparticles. - Highlights: • Highly dispersed PtRu/MWCNTs were formed without use of any stabilizing agent. • Microwave irradiation enhances the uniform dispersion of the PtRu nanoparticles. • Microwave-assisted improved impregnation have a high yield of alloy phase formation. • The prepared PtRu/MWCNTs shows an enhanced performance toward CO poisoning.

  19. Pt-Pd nanoelectrocatalyst of ultralow Pt content for the oxidation of formic acid: Towards tuning the reaction pathway

    Indian Academy of Sciences (India)

    Sourov Ghosh; C Retna Raj

    2015-05-01

    Synthesis of highly efficient functional electrocatalyst that favours the electrochemical oxidation of formic acid via CO-free dehydrogenation pathway is required for direct formic acid fuel cells. Traditional catalysts favour the dehydration pathway involving the generation of poisonous CO. Herein we demonstrate the superior electrocatalytic performance of Pt-Pd bimetallic nanoelectrocatalyst of ultralow Pt content and tuning the reaction pathway by controlling the Pt content. Bimetallic nanoparticles of Pt4Pd96, Pt7Pd93 and Pt47Pd53 compositions are synthesized by electrochemical co-deposition method in aqueous solution. The nanoparticles of ultralow Pt content, Pt4Pd96, favour the CO-free dehydrogenation pathway for formic acid oxidation with an onset potential of 0 V (SHE) whereas the Pt47Pd53 nanoparticles favour the dehydration pathway involving the formation of CO at high positive potential. The Pt content of the bimetallic nanoparticles actually controls the oxidation peak potential and catalytic activity. Significant negative shift (∼350 mV) in the oxidation peak potential and remarkable enhancement in the current density (2.6 times) are observed for Pt4Pd96 nanoparticles with respect to Pt47Pd53. The absence of three adjacent Pt and Pd atoms could be the reason for the suppression of CO pathway. The electrochemical impedance measurements indirectly support the CO-free pathway for the formic acid oxidation on Pt4Pd96 nanoparticles.

  20. Contribution à la cristallochimie des isotypes de ThCr 2Si 2 et CaBe 2Ge 2. I. Les systèmes La T2- xT' xGe 2 ( T, T' = Ru, Rh, Pd, Ir, Pt) et La 1- xCa xCa xIr 2Ge 2: Distribution des éléments de transition dans le type CaBe 2Ge 2

    Science.gov (United States)

    Venturini, G.; Malaman, B.; Roques, B.

    1989-03-01

    There are several singularities in the systems investigated. Although the three germanides La T2Ge 2( T = Ru, Rh, Pd) are isostructural with ThCr 2Si 2, a complete solid solution occurs only between LaRu 2Ge 2 and LaRh 2Ge 2; in the system LaRh 2Ge 2LaPd 2Ge 2, there is a range of CaBe 2Ge 2-type solid solutions. The lattice constants of the ThCr 2Si 2-type compounds vary curiously according to the valence electron concentration (VEC). The CaBe 2Ge 2-type germanides are confined in a narrow range of VEC. The new compound CaIr 2Ge 2 is then of the ThCr 2Si 2-type while LaIr 2Ge 2 is of the CaBe 2Ge 2-type. In the latter structural type, the square pyramids of Ge atoms are favorite sites for Ir or Pt atoms. These results are discussed.

  1. Carbon supported Pd-Ni and Pd-Ru-Ni nanocatalysts for the alkaline direct ethanol fuel cell (DEFC)

    CSIR Research Space (South Africa)

    Mathe, MK

    2011-08-01

    Full Text Available Carbon supported Pd-Ni and Pd-Ru-Ni nanocatalysts were prepared by the chemical reduction method, using sodium borohydride and ethylene glycol mixture as the reducing agent. The catalytic activity towards ethanol electro-oxidation in alkaline medium...

  2. Kinetic limitations in surface alloy formation: PtCu/Ru(0001)

    Science.gov (United States)

    Engstfeld, A. K.; Jung, C. K.; Behm, R. J.

    2016-01-01

    We have systematically investigated the structure and structure formation of two-dimensional PtCu monolayer surface alloys on Ru(0001) as model systems for bimetallic PtCu catalysts and surfaces by scanning tunneling microscopy (STM). The surface alloys were prepared by deposition of Pt and Cu on Ru(0001) and thermal intermixing; different procedures were developed and tested to produce bimetallic surfaces with homogeneous structure, including also a homogeneous distribution of the different surface species, while at the same time intermixing with the Ru(0001) substrate should be inhibited. STM imaging revealed that for Pt concentrations below 65% surface alloys with homogeneous distribution could be formed, while at higher concentrations in the mixed phase, up to 82%, pure Pt or Pt-rich surface areas were formed as well. At Pt contents of 0.20 0.65 line structures were observed, but of different nature. The distribution of surface atoms in the mixed phase was evaluated from STM images with chemical contrast, the related short-range order parameters were determined. The resulting structures and their energetics, the influence of different deposition and annealing procedures and the suitability of these surfaces as model systems for studies of the surface chemistry of bimetallic PtCu surfaces are discussed.

  3. Pd-Pt random alloy nanocubes with tunable compositions and their enhanced electrocatalytic activities.

    Science.gov (United States)

    Yuan, Qiang; Zhou, Zhiyou; Zhuang, Jing; Wang, Xun

    2010-03-07

    Monodisperse, highly-selective sub-10 nm Pd-Pt random alloy nanocubes have been successfully synthesized in aqueous solution, and the electrocatalytic activity of these Pd-Pt alloys towards formic acid oxidation was investigated and compared with the activity of Pd sub-10 nm nanocubes, and the commercial Pd and Pt black.

  4. Methane Direct Conversion on Mo/ZSM-5 Catalysts Modified by Pd and Ru

    Institute of Scientific and Technical Information of China (English)

    Priscila Dias Sily; Fabio Bellot Noronha; Fabio Barboza Passos

    2006-01-01

    The effect of addition of Ru and Pd to Mo/HZSM-5 catalysts used in the dehydroaromatization of methane was investigated. Catalytic tests and temperature-programmed oxidation results showed that Pd-based catalysts were more selective to naphthalene and suffered strong deactivation. The presence of Ru improved the activity and stability, with a decrease in the carbonaceous deposit probably because of a mechanism of protection of the Mo2C surface.

  5. Mixed phase Pt-Ru catalyst for direct methanol fuel cell anode by flame aerosol synthesis

    DEFF Research Database (Denmark)

    Chakraborty, Debasish; Bischoff, H.; Chorkendorff, Ib

    2005-01-01

    A spray-flame aerosol catalyzation technique was studied for producing Pt-Ru anode electrodes for the direct methanol fuel cell. Catalysts were produced as aerosol nanoparticles in a spray-flame reactor and deposited directly as a thin layer on the gas diffusion layer. The as-prepared catalyst......Ru1/Vulcan carbon. The kinetics of methanol oxidation on the mixed phase catalyst was also explored by electrochemical impedance spectroscopy. (c) 2005 The Electrochemical Society....

  6. The Effect of PtRuIr Nanoparticle Crystallinity in Electrocatalytic Methanol Oxidation

    Directory of Open Access Journals (Sweden)

    Vladimir Linkov

    2013-04-01

    Full Text Available Two structural forms of a ternary alloy PtRuIr/C catalyst, one amorphous and one highly crystalline, were synthesized and compared to determine the effect of their respective structures on their activity and stability as anodic catalysts in methanol oxidation. Characterization techniques included TEM, XRD, and EDX. Electrochemical analysis using a glassy carbon disk electrode for cyclic voltammogram and chronoamperometry were tested in a solution of 0.5 mol L−1 CH3OH and 0.5 mol L−1 H2SO4. Amorphous PtRuIr/C catalyst was found to have a larger electrochemical surface area, while the crystalline PtRuIr/C catalyst had both a higher activity in methanol oxidation and increased CO poisoning rate. Crystallinity of the active alloy nanoparticles has a big impact on both methanol oxidation activity and in the CO poisoning rate.

  7. Concave Pd-Pt Core-Shell Nanocrystals with Ultrathin Pt Shell Feature and Enhanced Catalytic Performance.

    Science.gov (United States)

    Zhang, Ying; Bu, Lingzheng; Jiang, Kezhu; Guo, Shaojun; Huang, Xiaoqing

    2016-02-10

    One-pot creation of unique concave Pd-Pt core-shell polyhedra has been developed for the first time using an efficient approach. Due to the concave feature and ultrathin Pt shell, the created Pd-Pt core-shell polyhedra exhibit enhanced catalytic performance in both the electrooxidation of methanol and hydrogenation of nitrobenzene, as compared with commercial Pt black and Pd black catalysts. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Derivation of the liquidus surface projection for the Al-Pt-Ru system from as-cast samples

    CSIR Research Space (South Africa)

    Prins, SN

    2005-11-10

    Full Text Available .% platinum. Most of the other phases showed more limited solubilities for the ternary element: similar to RuAl2, similar to Pt2Al3 and similar to PtAl contained only about 2at.% of the third component similar to Ru 4Al13 has less than 1at.% solubility...

  9. High pressure organic colloid method for the preparation of high performance carbon nanotube-supported Pt and PtRu catalysts for fuel cell applications

    Institute of Scientific and Technical Information of China (English)

    WANG; KateNing; Viola; BIRSS

    2010-01-01

    Highly dispersed,high performance Pt and PtRu catalysts,supported on multiwalled carbon nanotubes(CNTs),were prepared by a high pressure organic colloid method.The particle sizes of the active components were as small as 1.2 nm for Pt and 1.1 nm for PtRu,and the active Pt surface areas were 295 and 395 m2/g,respectively.The catalysts showed very high activities toward the anodic oxidation of methanol,evaluated by cyclic voltammetry,being up to 4 times higher than that of commercial Johnson Matthey Hispec 2000 Pt/XC-72R and 5 times better than Hispec 5000 PtRu/XC-72R catalysts.In a full air/hydrogen fuel cell,a membrane-electrode assembly prepared using our Pt/CNT and PtRu/CNT catalysts showed 50% and 100% higher performances than those prepared with commercial Johnson Matthey Pt/XC-72R and PtRu/XC-72R catalysts for the same Pt loading and operating conditions.

  10. One-pot synthesis of Pd-Pt@Pd core-shell nanocrystals with enhanced electrocatalytic activity for formic acid oxidation

    KAUST Repository

    Yuan, Qiang

    2014-01-01

    Well-defined Pd-Pt@Pd core-shell nanocrystals with a Pd-Pt alloy core and a conformal Pd shell of ~2-3 nm were directly synthesized through a one-pot, aqueous solution approach without any preformed Pd or Pt seeds. These Pd-Pt@Pd core-shell nanocrystals show an enhanced electrocatalytic activity for formic acid oxidation compared with commercial Pd black. This journal is © 2014 The Royal Society of Chemistry.

  11. Carbon Nanotubes Supported Pt-Ru-Ni as Methanol Electro-Oxidation Catalyst for Direct Methanol Fuel Cells

    Institute of Scientific and Technical Information of China (English)

    Fei Ye; Shengzhou Chen; Xinfa Dong; Weiming Lin

    2007-01-01

    Carbon nanotubes (CNTs) supported Pt-Ru and Pt-Ru-Ni catalysts were prepared by chemical reduction of metal precursors with sodium borohydride at room temperature. The crystallographic properties and composition of the catalysts were characterized by X-ray diffraction (XRD) and energy dispersive X-ray (EDX) analysis, and the catalytic activity and stability for methanol electro-oxidation were measured by electrochemical impedance spectroscopy (EIS), linear sweep voltammetries (LSV), and chronoamperometry (CA). The results show that the catalysts exhibit face-centered cubic (fcc) structure.The particle size of Pt-Ru-Ni/CNTs catalyst is about 4.8 nm. The catalytic activity and stability of the Pt-Ru-Ni/CNTs catalyst are higher than those of Pt-Ru/CNTs catalyst.

  12. Insight into the Reaction Mechanisms of Methanol on PtRu/Pt(111): A Density Functional Study

    Science.gov (United States)

    Ding, Qiuyue; Xu, Wenbin; Sang, Pengpeng; Xu, Jing; Zhao, Lianming; He, Xiaoli; Guo, Wenyue

    2016-04-01

    Periodic DFT calculations have been performed to systematically investigate the mechanisms of methanol decomposition and oxidation on the PtRu/Pt(111) surface. Geometries and energies for the primary species involved are analyzed and the reaction network has been mapped out. The calculation shows that among three initial Csbnd H, Osbnd H, and Csbnd O bond scissions of methanol, the Osbnd H bond scission is found to be the most favorable and bears a lower energy barrier than the desorption of methanol. The decomposition of CH3O occurs via the path CH3O → CH2O → CHO → CO with the limiting step of the first dehydrogenation. Although the oxidation of CO is hindered by a high barrier, the CHO oxidation to CHOOH could occur facilely. Further decomposition of formic acid to CO2 and/or CO could occur via four possible pathways, that is, initial Csbnd H, Osbnd H, and Csbnd O bond activations as well as simultaneous activation of Csbnd H and Csbnd O bonds, where the first pathway, HCOOH → COOH → CO2, is the most favorable from a kinetic point of view. Compared to that on Pt(111), methanol on PtRu/Pt(111) prefers to decomposition rather than desorption and then oxidation via the favorable non-CO path with a lower rate-determining energy barrier of CH3O → CH2O for the whole reaction, which indicates that PtRu alloy can improved tolerance toward CO poisoning compared with pure Pt.

  13. Magnetic hyperfine interaction studies of isolated Ni impurities in Pd and Pd-Pt alloys

    Science.gov (United States)

    Müller, W.; Bertschat, H. H.; Haas, H.; Spellmeyer, B.; Zeitz, W.-D.

    1989-10-01

    The magnetic hyperfine fields at isolated Ni impurities in Pd and Pd-Pt alloys were studied with the perturbed-angular-distribution (PAD) method by measuring the temperature, magnetic field, and concentration dependence of the nuclear-spin Larmor precession of isomeric states in 63Ni. The recoil-implanted Ni nuclei, as products of heavy-ion nuclear reactions, are present in extreme dilution (Pd-Pt alloys a considerable positive shift remains even at 30 at. % Pt content. The variation of the shift with Pt concentration and temperature reflects the variation of the Pd-Pt alloy susceptibility. The different contributions to the hyperfine field could be differentiated by comparing the Knight shift for Ni in Pd with its susceptibility contribution obtained from extrapolated susceptibility measurements in dilute Pd-Ni alloys. The negative core-polarization field of the impurity spin moment is compensated for by a transferred hyperfine field correlated with the host polarization in the neighborhood of the impurity. The remaining positive hyperfine field is due to a weak orbital moment of 0.3μB at the impurity site. The values obtained for the different contributions are compared with results of the Korringa-Kohn-Rostoker-coherent-potential-approximation calculations for concentrated Pd-Ni alloys extrapolated to the dilute limit.

  14. Preparation of PtRu/C and PtSn/C electrocatalysts using electron beam irradiation for direct and ethanol fuel cell; Preparacao de eletrocatalisadores PtRu/C e PtSn/C utilizando feixe de eletrons para aplicacao como anodo na oxidacao direta de metanol e etanol em celulas a combustivel de baixa temperatura

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Dionisio Furtunato da

    2009-07-01

    PtRu/C and PtSn/C electrocatalysts were prepared using electron beam irradiation. The metal ions were dissolved in water/2-propanol and water/ethylene glycol solutions and the carbon support was added. The resulting mixtures were irradiated under stirring. The effect of water/ethylene glycol and water/2-propanol (v/v) ratio, Pt:Ru and Pt:Sn atomic ratios, the irradiation time and dose rate were studied. The obtained materials were characterized by Energy dispersive analysis of X-rays (EDX), X-ray diffraction (XRD), cyclic voltammetry (CV) and Moessbauer spectroscopy. The electro-oxidation of methanol and ethanol were studied by cyclic voltammetry and chronoamperometry using the thin porous coating technique. The electrocatalysts were also tested on the Direct Methanol and Ethanol Fuel Cells. PtRu/C electrocatalysts prepared in water/ethylene glycol showed Pt:Ru atomic ratios different from the nominal ones. The results suggested that part of the Ru(III) ions were not reduced. The obtained materials showed the face-centered cubic (fcc) structure of Pt and Pt alloys with crystallite sizes of 2-3 nm. PtRu/C electrocatalysts prepared in water/2-propanol showed Pt:Ru atomic ratios similar to the nominal ones. The obtained materials also showed the fcc structure of platinum and platinum alloys with crystallite sizes of 3-4 nm. PtSn/C electrocatalysts prepared in water/ethylene glycol and water/2-propanol showed Pt:Sn atomic ratios similar to the nominal ones. The obtained materials showed the platinum (fcc) phase with crystallite sizes in the range of 2 - 4 nm and a SnO{sub 2} (cassiterite) phase. The obtained PtRu/C and PtSn/C electrocatalysts showed similar or superior performance for methanol and ethanol electro-oxidation compared to commercial PtRu/C (E-TEK) and PtSn/C (BASF) electrocatalysts. (author)

  15. Study of coordination environments around Pd and Pt in a Pd-core Pt-shell nanoparticle during heating

    Science.gov (United States)

    Nishimura, Y. F.; Hamaguchi, T.; Yamaguchi, S.; Takagi, H.; Dohmae, K.; Nonaka, T.; Nagai, Y.

    2016-05-01

    Local coordination environments around Pd and Pt in a Pd-core Pt-shell nanoparticle (NP) at temperatures ranging from 473 to 873 K was evaluated by utilizing in situ XAFS measurement technique to investigate the temperature range in which a core-shell structure is preserved. The core-shell structure was considered to be kept up to 673 K and start to change at about 773 K. Heating to 873 K accelerated atomic mixing in the core-shell NPs. Catalytic properties of the present Pd-core Pt-shell NP are available in the stoichiometric C3H6-O2 atmosphere at temperatures less than 773 K at most.

  16. Photocatalytic Reduction of Carbon Dioxide with Modify Pd, Ru on TiO2 Surface

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Photocatalytic reduction of CO2 to organic compounds was reduction in semiconductor suspension system under simulated solar in laboratory. TiO2 load catalysts were prepared in different ways, and they were used in photocatalytic reduction of CO2 . Experimental results show that the photocatalytic activity can be improve by dressing Pd, Ru on TiO2 Surface and is obvious different when catalysts were prepared in different ways. The photocatalytic mechanism of dressing Pd on TiO2 Surface; dressing Pd and Ru on TiO2 Surface were also discussed in this paper.

  17. Influence of Pt atoms on the low temperature formation of epitaxial Pd monosilicide

    Science.gov (United States)

    Kawarada, H.; Mizugaki, K.; Ohdomari, I.

    1985-01-01

    The effect of Pt concentration in Pd thin films on the nucleation and growth of PdSi and PdxPt1-xSi (ternary monosilicide) has been investigated by transmission electron microscopy (TEM). Low concentration of Pt (10 at. %) in Pd film enhances PdSi formation at lower temperature than previously reported. It has been proposed that PdSi formation is governed by its slow nucleation. However, in our studies, the nucleation of PtSi, which is substituted for that of PdSi, triggers the subsequent PdSi growth at low temperatures. High concentration of Pt (55 at. %) in Pd-Pt alloy film lowers the temperature of the phase transformation from metal-rich silicide to monosilicide (PdxPt1-xSi). The temperature is the same as that of PtSi formation. In both cases, the monosilicide layers (about 20 nm) have an epitaxial relationship with (111) Si substrates.

  18. Pt promotion and spill-over processes during deposition and desorption of upd-H(ad) and OH(ad) on Pt(x)Ru(1-x)/Ru(0001) surface alloys.

    Science.gov (United States)

    Hoster, Harry E; Janik, Michael J; Neurock, Matthew; Behm, R Jürgen

    2010-09-21

    The electrochemical adsorption of underpotential deposited hydrogen (upd-H(ad)) and OH(ad) on structurally well-defined Pt(x)Ru(1-x)/Ru(0001) surface alloys was investigated by cyclic voltammetry and density functional theory (DFT) calculations. The adsorption energies of both upd-H(ad) and OH(ad) decrease with increasing Pt content in the adsorption ensemble, shifting the onset of upd-H(ad) and OH(ad) formation to increasingly cathodic and anodic potentials, respectively. For bare Ru(0001) and for Ru(3) sites in the surface alloy, the stability regions of these two species overlap or almost overlap, respectively. Similar to previous findings for upd-H(ad) adsorption/desorption on partly Pt monolayer island covered Ru(0001) surfaces (J. Phys. Chem. B 2004, 108, 14780), we find a sharp peak at approximately 100 mV vs. RHE in each scan direction, which is attributed to a Pt catalyzed OH(ad) upd-H(ad) replacement on Ru(3) sites, via adsorption on Pt rich sites and spill-over to Ru(3) sites. The decrease of the integrated charge in these peaks with the third power of the Ru surface concentration, which for a random distribution of surface atoms reflects the availability of Ru(3) sites, supports the above assignment.

  19. Synthesis of Pt, Pd, Pt/Ag and Pd/Ag nanoparticles by microwave-polyol method

    Indian Academy of Sciences (India)

    Kirti Patel; Sudhir Kapoor; Devilal Purshottam Dave; Tulsi Mukherjee

    2005-07-01

    Pt, Pd, Pt-Ag and Pd-Ag bimetallic nanoparticles were synthesized in ethylene glycol and glycerol using the microwave technique in the presence of a stabilizer poly(N-vinylpyrrolidone) (PVP). It has been observed that PVP is capable of complexing and stabilizing nanoparticles. Mixed clusters were formed by simultaneous reduction of the metal ions. The clusters were characterized using UV-Vis spectra, XRD and dynamic light scattering. To understand the mechanism of formation of mixed nanoparticles, several experimental parameters such as in situ irradiation of mixed metal salts and mixing of individual sols were attempted.

  20. H2 splitting on Pt, Ru and Rh nanoparticles supported on sputtered HOPG

    DEFF Research Database (Denmark)

    Fiordaliso, Elisabetta Maria; Murphy, Shane; Nielsen, R.M.;

    2012-01-01

    nm. The rate of hydrogen exchange is measured in the temperature range 40–200°C at 1bar, by utilization of the H–D exchange reaction. We find that the rate of hydrogen exchange increases with the particle diameter for all the metals, and that the rate for Ru and Rh is higher than for Pt. In the case...... adlayers on the terraces of the larger particles. Experiments are also carried out in the presence of 10ppm CO. Pt is found to be very sensitive to CO poisoning and the H–D exchange rate drops below the detection limit when CO is added to the gas mixture. In the case of Ru and Rh nanoparticles, CO...... decreases the splitting rate significantly, also at 200°C. The variation of the sensitivity to CO poisoning with particle diameter for Ru and Rh is found to be weak....

  1. Solvent effects on Pt-Ru/C catalyst for methanol electro-oxidation

    Institute of Scientific and Technical Information of China (English)

    Jinwei Chen; Chunping Jiang; Hui Lu; Lan Feng; Xin Yang; Liangqiong Li; Ruilin Wang

    2009-01-01

    Alloying degree,particle size and the level of dispersion are the key structural parameters of Pt-Ru/C catalyst in fuel cells. Solvent(s) used in the preparation process can affect the particle size and alloying degree of the object substance,which lead to a great positive impact on its properties. In this work,three types of solvents and their mixtures were used in preparation of the Pt-Ru/C catalysts by chemical reduction of metal precursors with sodium borohydride at room temperature. The structure of the catalysts was characterized by X-ray diffraction (XRD) and Transmission electron microscopy (TEM). The catalytic activity and stability for methanol electro-oxidation were studied by Cyclic Voltammetry (CV) and Chronoamperometry (CA). Pt-Ru/C catalyst prepared in H_2O or binary solvents of H_2O and isopropanol had large particle size and low alloying degree leading to low catalytic activity and less stability in methanol electro-oxidation. When tetrahydrofuran was added to the above solvent systems,Pt-Ru/C catalyst prepared had smaller particle size and higher alloying degree which resulted in better catalytic activity,lower onset and peak potentials,compared with the above catalysts. Moreover,the catalyst prepared in ternary solvents of isopropanol,water and tetrahydrofuran had the smallest particle size,and the high alloying degree and the dispersion kept unchanged. Therefore,this kind of catalyst showed the highest catalytic activity and good stability for methanol electro-oxidation.

  2. Perpendicular magnetic tunnel junctions with a synthetic storage or reference layer: A new route towards Pt- and Pd-free junctions

    Science.gov (United States)

    Cuchet, Léa; Rodmacq, Bernard; Auffret, Stéphane; Sousa, Ricardo C.; Prejbeanu, Ioan L.; Dieny, Bernard

    2016-02-01

    We report here the development of Pt and Pd-free perpendicular magnetic tunnel junctions (p-MTJ) for STT-MRAM applications. We start by studying a p-MTJ consisting of a bottom synthetic Co/Pt reference layer and a synthetic FeCoB/Ru/FeCoB storage layer covered with an MgO layer. We first investigate the evolution of RKKY coupling with Ru spacer thickness in such a storage layer. The coupling becomes antiferromagnetic above 0.5 nm and its strength decreases monotonously with increasing Ru thickness. This contrasts with the behavior of Co-based systems for which a maximum in interlayer coupling is generally observed around 0.8 nm. A thin Ta insertion below the Ru spacer considerably decreases the coupling energy, without basically changing its variation with Ru thickness. After optimization of the non-magnetic and magnetic layer thicknesses, it appears that such a FeCoB/Ru/FeCoB synthetic storage layer sandwiched between MgO barriers can be made stable enough to actually be used as hard reference layer in single or double magnetic tunnel junctions, the storage layer being now a single soft FeCoB layer. Finally, we realize Pt- or Pd-free robust perpendicular magnetic tunnel junctions, still keeping the advantage of a synthetic reference layer in terms of reduction of stray fields at small pillar sizes.

  3. Electrochemical Oxidation of the Carbon Support to Synthesize Pt(Cu and Pt-Ru(Cu Core-Shell Electrocatalysts for Low-Temperature Fuel Cells

    Directory of Open Access Journals (Sweden)

    Griselda Caballero-Manrique

    2015-04-01

    Full Text Available The synthesis of core-shell Pt(Cu and Pt-Ru(Cu electrocatalysts allows for a reduction in the amount of precious metal and, as was previously shown, a better CO oxidation performance can be achieved when compared to the nanoparticulated Pt and Pt-Ru ones. In this paper, the carbon black used as the support was previously submitted to electrochemical oxidation and characterized by XPS. The new catalysts thus prepared were characterized by HRTEM, FFT, EDX, and electrochemical techniques. Cu nanoparticles were generated by electrodeposition and were further transformed into Pt(Cu and Pt-Ru(Cu core-shell nanoparticles by successive galvanic exchange with Pt and spontaneous deposition of Ru species, the smallest ones being 3.3 nm in mean size. The onset potential for CO oxidation was as good as that obtained for the untreated carbon, with CO stripping peak potentials about 0.1 and 0.2 V more negative than those corresponding to Pt/C and Ru-decorated Pt/C, respectively. Carbon oxidation yielded an additional improvement in the catalyst performance, because the ECSA values for hydrogen adsorption/desorption were much higher than those obtained for the non-oxidized carbon. This suggested a higher accessibility of the Pt sites in spite of having the same nanoparticle structure and mean size.

  4. Conversion of isopropyl alcohol over Ru and Pd loaded N-doped carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    Anas Benyounes; Mohamed Kacimi; Mahfoud Ziyad; Philippe Serp

    2014-01-01

    Ru and Pd (2 wt%) loaded on pure and on N-doped carbon nanotubes (N-CNTs) were prepared and tested using the isopropyl alcohol decomposition reaction as probe reaction. The presence of nitro-gen functionalities (pyridinic, pyrrolic, and quaternary nitrogen) on the nitrogen doped support induced a higher metal dispersion:Pd/N-CNT (1.8 nm)<Pd/CNT (4.9 nm), and Ru/N-CNT (2.4 nm)<Ru/CNT (3.0 nm). The catalytic activity of the supports was determined first. Isopropyl alcohol conversion produces acetone on CNTs while on N-CNTs it led to both dehydration and dehydro-genation products. At 210 °C and in the presence of air, the isopropyl alcohol conversion was higher on the N-CNTs (25%) than on the CNTs (11%). The Pd loaded catalysts were more active and more selective than the Ru ones. At 115 °C, the Pd catalysts were 100%selective towards acetone for a conversion of 100%, whereas the Ru catalysts led to dehydration and dehydrogenation products. The nitrogen doping induced the appearance of redox properties when oxygen is present in the reaction mixture.

  5. Characterization and evaluation of Pt-Ru catalyst supported on multi-walled carbon nanotubes by electrochemical impedance

    Energy Technology Data Exchange (ETDEWEB)

    Ocampo, A.L.; Miranda-Hernandez, M.; Sebastian, P.J. [Centro de Investigacion en Energia-UNAM, Temixco, 62580 Morelos (Mexico); Morgado, J.; Montoya, J.A. [IMP, Eje Central Lazaro Cardenas 152, 07730 D.F. Mexico (Mexico)

    2006-10-06

    In this work the authors present the results of a systematic characterization and evaluation of the carbon nanotube supported Pt-Ru (Pt-Ru/CNT) for its use as methanol oxidation catalyst. Its activity was compared with that of Pt and Pt-Ru catalysts supported on Vulcan and synthesized from carbonyl precursors, and another commercial Pt-Ru catalyst. The cyclic voltammetry, CO stripping and electrochemical impedance techniques were employed to determine the electrocatalytic activity of the catalysts. The electrochemical studies were performed in 0.5M H{sub 2}SO{sub 4} containing different concentrations of methanol (0.05-1M). The results showed a noticeable influence of the catalyst support (CNT) on the performance of the catalyst for CO oxidation. The electrochemical impedance studies allowed us to separate the different steps in the methanol oxidation reaction and to control these steps or reactions by varying the applied potential and the methanol concentration. At low methanol concentration and potentials the de-hydrogenation of methanol predominated. But, at high potential and methanol concentrations, the CO oxidation predominated. These results allowed us to clearly describe at what potential and concentration ranges the bi-functional effect of Ru becomes evident. Our results indicated that the CO oxidation occurs both on Pt and Ru. Compared to other catalysts, Pt-Ru supported on carbon nanotubes showed superior catalytic activity for CO and methanol oxidation. (author)

  6. Ni2P Makes Application of the PtRu Catalyst Much Stronger in Direct Methanol Fuel Cells.

    Science.gov (United States)

    Chang, Jinfa; Feng, Ligang; Liu, Changpeng; Xing, Wei

    2015-10-12

    PtRu is regarded as the best catalyst for direct methanol fuel cells, but the performance decay resulting from the loss of Ru seriously hinders commercial applications. Herein, we demonstrated that the presence of Ni2 P largely reduces Ru loss, which thus makes the application of PtRu much stronger in direct methanol fuel cells. Outstanding catalytic activity and stability were observed by cyclic voltammetry. Upon integrating the catalyst material into a practical direct methanol fuel cell, the highest maximum power density was achieved on the PtRu-Ni2P/C catalyst among the reference catalysts at different temperatures. A maximum power density of 69.9 mW cm(-2) at 30 °C was obtained on PtRu-Ni2P/C, which is even higher than the power density of the state-of-the-art commercial PtRu catalyst at 70 °C (63.1 mW cm(-2)). Moreover, decay in the performance resulting from Ru loss was greatly reduced owing to the presence of Ni2 P, which is indicative of very promising applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. The effect of peripheral bipyridine ligands on the photocatalytic hydrogen production activity of Ru/Pd catalysts

    NARCIS (Netherlands)

    Bindra, Gurmeet Singh; Schulz, Martin; Paul, Avishek; Soman, Suraj; Groarke, Robert; Inglis, Jane; Pryce, Mary T.; Browne, Wesley R.; Rau, Sven; Maclean, Brian J.; Vos, Johannes G.

    2011-01-01

    A pyrazine bridged ruthenium/palladium bimetallic photocatalyst with peripheral 4,4'-dicarboxyethyl-2,2'-bipyridine ligands, EtOOC-RuPd, is reported, together with its 2,2'-bipyridine analogue. Upon irradiation with visible light, EtOOC-RuPd catalyses the production of hydrogen gas whereas the compl

  8. Preparation of Pt Ru/C + rare earths by the method of reduction by alcohol for the electro-oxidation of ethanol; Preparacao de eletrocatalisadores PtRu/C + terras raras pelo metodo da reducao por alcool para a eletro-oxidacao do etanol

    Energy Technology Data Exchange (ETDEWEB)

    Tusi, M.M.; Rodrigues, R.M.S.; Spinace, E.V.; Oliveira Neto, A., E-mail: aolivei@ipen.b, E-mail: espinace@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2010-07-01

    PtRu/C electrocatalyst was prepared in a single step, while that PtRu/85%C-15%Ce, PtRu/85%C-15%La, PtRu/85%C-15%Nd and PtRu/85%C-15%Er electrocatalyst were prepared in a two step. In the first step a Carbon Vulcan XC72 + rare earth supports were prepared. In the second step PtRu electrocatalyst were prepared by an alcohol-reduction process using ethylene glycol as solvent and reducing agent and supported on Vulcan XC72 + earth rare. The obtained electrocatalysts were characterized by EDAX, XRD and chronoamperometry. The electro-oxidation of ethanol was studied by chronoamperometry at room temperature. PtRu/85%C- 15%Ce electrocatalyst showed a significant increase of performance for ethanol oxidation compared to PtRu/C electrocatalyst. (author)

  9. Microbial synthesis of bimetallic PdPt nanoparticles for catalytic reduction of 4-nitrophenol.

    Science.gov (United States)

    Tuo, Ya; Liu, Guangfei; Dong, Bin; Yu, Huali; Zhou, Jiti; Wang, Jing; Jin, Ruofei

    2017-02-01

    Bimetallic nanoparticles are generally believed to have improved catalytic activity and stability due to geometric and electronic changes. In this work, biogenic-Pd (bio-Pd), biogenic-Pt (bio-Pt), and biogenic-PdPt (bio-PdPt) nanoparticles were synthesized by Shewanella oneidensis MR-1 in the absence or presence of quinone. Compared with direct microbial reduction process, the addition of anthraquinone-2,6-disulfonate (AQDS) could promote the reduction efficiency of Pd(II) or/and Pt(IV) and result in decrease of particles size. All kinds of nanoparticles could catalyze 4-nitrophenol reduction by NaBH4 and their catalytic activities took the following order: bio-PdPt (AQDS) ∼ bio-PdPt > bio-Pd (AQDS) > bio-Pd > bio-Pt (AQDS) ∼ bio-Pt. Moreover, the bio-PdPt (AQDS) nanoparticles could be reused for 6 cycles. We believe that this simple and efficient biosynthesis approach for synthesizing bimetallic bio-PdPt nanocatalysts is important for preparing active and stable catalysts.

  10. Miniature Fuel Cell With Monolithically Fabricated Si Electrodes - Au-Pd-Pt Multilayer Catalyst -

    Science.gov (United States)

    Shirai, Ryo; Vasiljevic, N.; Hayase, Masanori

    2016-11-01

    A novel catalyst layer structure is proposed for our miniature fuel cells. In our fuel cells, conventionally porous Pt was used as a catalyst layer. In order to reduce the Pt amount, instead of porous Pt, porous Pd was formed on a Si chip and Pt was deposited atomically on the Pd by UPD-SLRR(Under Potential Deposition - Surface Limited Redox Replacement). The Pd- Pt catalyst showed satisfying performance, besides high CO tolerance was observed. Though the Pd-Pt catalyst is quite promising, Pd is also a rare metal and reduction of Pd amount is necessary. In this study, a novel Au-Pd-Pt catalyst formation strategy is proposed by UPD-SLRR, and the layered structure is preliminary fabricated.

  11. Low Pt content direct methanol fuel cell anode catalyst: nanophase PtRuNiZr

    Science.gov (United States)

    Narayanan, Sekharipuram R. (Inventor); Whitacre, Jay F. (Inventor)

    2010-01-01

    A method for the preparation of a metallic material having catalytic activity that includes synthesizing a material composition comprising a metal content with a lower Pt content than a binary alloy containing Pt but that displays at least a comparable catalytic activity on a per mole Pt basis as the binary alloy containing Pt; and evaluating a representative sample of the material composition to ensure that the material composition displays a property of at least a comparable catalytic activity on a per mole Pt basis as a representative binary alloy containing Pt. Furthermore, metallic compositions are disclosed that possess substantial resistance to corrosive acids.

  12. On the differences in the reaction mechanism for CO and CO/H{sub 2} electrooxidation on PtRu and PtSn alloy electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Gasteiger, H.A. [Univ. Ulm (Germany). Abteilung Oberflaechenchemie und Katalyse; Markovic, N.M.; Ross, P.N. Jr. [Lawrence Berkeley National Lab., CA (United States)

    1997-04-01

    Electrooxidation kinetics of mixtures of carbon monoxide and hydrogen were studied on well-characterized surfaces of Pt and alloys of PtRu and PtSn in 0.5 M H{sub 2}SO{sub 4} at room temperature and 60 C. The alloy electrode surfaces were prepared in UHV by sputter/anneal cycles and their surface compositions were determined via low energy ion scattering. Subsequently, the electrodes were transferred contamination-free from UHV into a rotating disk electrode (RDE) configuration in a conventional electrochemical cell and their activity was measured both by CO stripping voltammetry and under the continuous flow of CO and CO/H{sub 2} gas mixtures in RDE-experiments. The overpotential for the continuous oxidation of pure CO on PtSn electrodes with a Sn surface composition of x{sub Sn,s} {approximately} 0.2 is significantly smaller than on PtRu alloys (x{sub Ru,s} {approximately} 0.5) and on pure Pt. The reaction order with respect to solution phase CO is negative on PtRu alloys due to the competition between OH{sub ads} nucleation and CO adsorption on Ru surface atoms. Owing to the lack of CO adsorption on OH{sub ads}-providing Sn surface atoms, the reaction order with respect to CO is positive on PtSn electrodes. Therefore, the activity enhancement of PtSn electrodes versus PtRu and Pt electrodes is most pronounced in pure CO and decreases with the CO concentration in CO/N{sub 2} and CO/H{sub 2} mixtures.

  13. Monometallic Pd and Pt and Bimetallic Pd-Pt/Al2O3-TiO2 for the HDS of DBT: Effect of the Pd and Pt Incorporation Method

    Directory of Open Access Journals (Sweden)

    Reynaldo Martínez Guerrero

    2014-01-01

    Full Text Available The effect of the preparation method of monometallic Pd and Pt and bimetallic Pd-Pt/Al2O3-TiO2 catalysts on the hydrodesulfurization (HDS of dibenzothiophene (DBT was investigated in this study. The synthesis was accomplished using three methods: (A impregnation, (B metal organic chemical vapor deposition (MOCVD, and (C impregnation-MOCVD. The bimetallic Pd-Pt catalyst prepared by the impregnation-MOCVD method was most active for the HDS of DBT compared to those prepared by the single impregnation or MOCVD method due to the synergetic effect between both noble metals. The greater selectivity toward biphenyl indicated that this bimetallic Pd-Pt catalyst preferentially removes sulfur via the direct desulfurization mechanism. However, the bimetallic Pd-Pt catalyst prepared using the single MOCVD method did not produce any cyclohexylbenzene, which is most likely associated with the hydrogenation/dehydrogenation sites.

  14. Pd-Pt bimetallic nanodendrites with high activity for oxygen reduction.

    Science.gov (United States)

    Lim, Byungkwon; Jiang, Majiong; Camargo, Pedro H C; Cho, Eun Chul; Tao, Jing; Lu, Xianmao; Zhu, Yimei; Xia, Younan

    2009-06-05

    Controlling the morphology of Pt nanostructures can provide a great opportunity to improve their catalytic properties and increase their activity on a mass basis. We synthesized Pd-Pt bimetallic nanodendrites consisting of a dense array of Pt branches on a Pd core by reducing K2PtCl4 with L-ascorbic acid in the presence of uniform Pd nanocrystal seeds in an aqueous solution. The Pt branches supported on faceted Pd nanocrystals exhibited relatively large surface areas and particularly active facets toward the oxygen reduction reaction (ORR), the rate-determining step in a proton-exchange membrane fuel cell. The Pd-Pt nanodendrites were two and a half times more active on the basis of equivalent Pt mass for the ORR than the state-of-the-art Pt/C catalyst and five times more active than the first-generation supportless Pt-black catalyst.

  15. Mixed-phase PdRu bimetallic structures with high activity and stability for formic acid electrooxidation.

    Science.gov (United States)

    Wu, Dongshuang; Zheng, Zhaoliang; Gao, Shuiying; Cao, Minna; Cao, Rong

    2012-06-14

    Aiming at investigating the effect of structure on electrocatalytic properties, Pd(50)Ru(50) nanoparticles (NPs) with three different structures were carefully designed in a one-pot polyol process for application in formic acid electrooxidation. The three structures are: (1) single-phase PdRu nanodendrites (denoted as PR-1), (2) a mixed-phase mixture of PdRu nanodendrites and monometallic Ru NPs (denoted as PR-2), and (3) a mixed-phase mixture of monometallic Pd and Ru NPs (denoted as PR-3). From PR-1 to PR-3, the structure was varied from single-phase to mixed-phase. The relative position of Ru was altered from completely Pd-connected (PR-1), to a mixture of Pd-connected and monometallic (PR-2), and completely monometallic (PR-3). All PdRu NPs outperform the commercial Pd/C. PR-2 exhibits the highest peak current density, but its stability is slightly lower than that of PR-3. When both the current density and the durability are taken into consideration, PR-2 is the best choice of catalyst for formic acid oxidation. It indicates that both the Pd-connected Ru NPs and monometallic Ru NPs in the mixed-phase PR-2 are essential to improve the electrocatalytic properties. Our study also illustrates that the electrochemical active surface area (ECSA) and hydrogen storage capacity of the as-prepared PdRu NPs are greatly enhanced after several hundred scans in formic acid, indicating the possibility for highly restorable catalysts in direct formic acid fuel cells.

  16. Effects of Ru and Ag cap layers on microstructure and magnetic properties of FePt ultrathin films.

    Science.gov (United States)

    Liu, Mingfeng; Jin, Tianli; Hao, Liang; Cao, Jiangwei; Wang, Ying; Wu, Dongping; Bai, Jianmin; Wei, Fulin

    2015-01-01

    The effects of Ru and Ag cap layers on the microstructure and magnetic properties of the FePt ultrathin films have been investigated. The results indicate that i) The Ag cap layer segregates from the FePt/Ag bilayer, lowers the FePt ordering temperature, promotes the FePt thin films to form island structure, and enhances the coercivity; ii) The Ru cap layer increases the FePt ordering temperature, helps to maintain smooth continuous structure film, and restrains the FePt (001) orientation and perpendicular magnetic anisotropy (PMA). The effects become more pronounced for the 3-nm-thick FePt thin films. The effects can be mainly attributed to the different melting point and thermal expansion stress between the cap layer and FePt thin films.

  17. Effects of Ru and Ag cap layers on microstructure and magnetic properties of FePt ultrathin films

    Science.gov (United States)

    Liu, Mingfeng; Jin, Tianli; Hao, Liang; Cao, Jiangwei; Wang, Ying; Wu, Dongping; Bai, Jianmin; Wei, Fulin

    2015-04-01

    The effects of Ru and Ag cap layers on the microstructure and magnetic properties of the FePt ultrathin films have been investigated. The results indicate that i) The Ag cap layer segregates from the FePt/Ag bilayer, lowers the FePt ordering temperature, promotes the FePt thin films to form island structure, and enhances the coercivity; ii) The Ru cap layer increases the FePt ordering temperature, helps to maintain smooth continuous structure film, and restrains the FePt (001) orientation and perpendicular magnetic anisotropy (PMA). The effects become more pronounced for the 3-nm-thick FePt thin films. The effects can be mainly attributed to the different melting point and thermal expansion stress between the cap layer and FePt thin films.

  18. Large faceted Pd nanocrystals supported small Pt nanoparticles as highly durable electrocatalysts for oxygen reduction

    Science.gov (United States)

    Zhang, Geng; Lu, Wangting; Cao, Longsheng; Qin, Xiaoping; Ding, Fei; Tang, Shun; Shao, Zhi-Gang; Yi, Baolian

    2016-09-01

    The reduction of Pt content together with the improvement of the durability of the catalyst for oxygen reduction reaction (ORR) is required to the large-scale commercialization of proton exchange membrane fuel cells. In this work, a novel ORR catalyst consisting of large Pd nanocrystal as the core with small Pt nanoparticles supported on the Pd core is prepared by a facile one-step synthesis method. The Pd substrate is presented in the form of well-defined cuboctahedrons and icosahedrons. The type of metal precursors and Pt/Pd molar ratio are important factors to obtain this Pd-supporting-Pt structure. The Pd2-s-Pt1 catalyst with a nominal Pt/Pd atomic ratio at 1/2 shows improved ORR activity: its mass specific activity and area specific activity is 2.5 and 3.5 times that of commercial Pt/C, respectively. More importantly, the Pd2-s-Pt1 catalyst demonstrates outstanding durability against potential cycling which can be ascribed to the slow dissolution of Pd core and the structure transformation from Pd@Pt to hollow PdPt alloyed nanocages. This exciting result provides a new pathway to the design of ORR catalyst with excellent durability.

  19. Ethylene glycol oxidation on Pt and Pt-Ru nanoparticle decorated polythiophene/multiwalled carbon nanotube composites for fuel cell applications.

    Science.gov (United States)

    Selvaraj, Vaithilingam; Alagar, Muthukaruppan

    2008-01-30

    A novel supporting material containing polythiophene (PTh) and multiwalled carbon nanotubes (MWCNTs) (PTh-CNTs) is prepared by in situ polymerization of thiophene on carbon nanotubes using FeCl(3) as oxidizing agent under sonication. The prepared polythiophene/CNT composites are further decorated with Pt and Pt-Ru nanoparticles by chemical reduction of the corresponding metal salts using HCHO as reducing agent at pH = 11 (Pt/PTh-CNT and Pt-Ru/PTh-CNT). The fabricated composite films decorated with nanoparticles were investigated towards the electrochemical oxidation of ethylene glycol (EG). The presence of carbon nanotubes in conjugation with a conducting polymer produces a good catalytic effect, which might be due to the higher electrochemically accessible surface areas, electronic conductivity and easier charge-transfer at polymer/electrolyte interfaces, which allows higher dispersion of Pt and Pt-Ru nanoparticles. Such nanoparticle modified PTh-CNT electrodes exhibit better catalytic behavior towards ethylene glycol oxidation. Results show that Pt/PTh-CNT and Pt-Ru/PTh-CNT modified electrodes show enhanced electrocatalytic activity and stability towards the electro-oxidation of ethylene glycol than the Pt/PTh electrodes, which shows that the composite film is more promising for applications in fuel cells.

  20. Ethylene glycol oxidation on Pt and Pt-Ru nanoparticle decorated polythiophene/multiwalled carbon nanotube composites for fuel cell applications

    Energy Technology Data Exchange (ETDEWEB)

    Selvaraj, Vaithilingam; Alagar, Muthukaruppan [Department of Chemical Engineering, Alagappa College of Technology, Anna University, Chennai 600025 (India)

    2008-01-30

    A novel supporting material containing polythiophene (PTh) and multiwalled carbon nanotubes (MWCNTs) (PTh-CNTs) is prepared by in situ polymerization of thiophene on carbon nanotubes using FeCl{sub 3} as oxidizing agent under sonication. The prepared polythiophene/CNT composites are further decorated with Pt and Pt-Ru nanoparticles by chemical reduction of the corresponding metal salts using HCHO as reducing agent at pH = 11 (Pt/PTh-CNT and Pt-Ru/PTh-CNT). The fabricated composite films decorated with nanoparticles were investigated towards the electrochemical oxidation of ethylene glycol (EG). The presence of carbon nanotubes in conjugation with a conducting polymer produces a good catalytic effect, which might be due to the higher electrochemically accessible surface areas, electronic conductivity and easier charge-transfer at polymer/electrolyte interfaces, which allows higher dispersion of Pt and Pt-Ru nanoparticles. Such nanoparticle modified PTh-CNT electrodes exhibit better catalytic behavior towards ethylene glycol oxidation. Results show that Pt/PTh-CNT and Pt-Ru/PTh-CNT modified electrodes show enhanced electrocatalytic activity and stability towards the electro-oxidation of ethylene glycol than the Pt/PTh electrodes, which shows that the composite film is more promising for applications in fuel cells.

  1. Development of a database for the prediction of phases in Pt-based Superalloys: Cr-Pt-Ru

    Institute of Scientific and Technical Information of China (English)

    A. Watson; L.A. Cornish; R. Süss

    2006-01-01

    Work has been ongoing in building a thermodynamic database for the prediction of phase equilibria in Pt-based superalloys. The alloys are being developed for high temperature applications in aggressive environments. The database will aid the design of alloys by enabling the calculation of the composition and proportions of phases present in alloys of differ ent compositions. In order to extend this database, a preliminary assessment of the Cr-Pt-Ru system has been undertaken,using a combination of Pandat and MTDATA software. As a first step, it was necessary to provide thermodynamic models for the three associated binary systems. Owing to a lack of thermodynamic information for these systems, the binary assessments were based on phase diagrams available in the literature. Using recent experimental phase equilibria data for the ternary system, a preliminary assessment of the Cr-Pt-Ru system has been produced. In this preliminary assessment, simplified models were employed for the L12 and sigma phases with a view to extending the descriptions as new experimental information becomes available.

  2. Hyperfine specific heats of PrX 2 ( X = Ir, Pt, Rh, Ru) laves phase compounds

    Science.gov (United States)

    Greidanus, F. J. A. M.; de Jongh, L. J.; Huiskamp, W. J.; Buschow, K. H. J.

    1980-01-01

    Specific heat data below 1 K for the C-15 compounds PrX 2 (X = Ir, Pt, Rh, Ru) reveal Schottky-type anomalies, ascribed to hyperfine interactions. Apparently the 4f-moments are magnetically ordered. The values deduced for these moments are only ≈ 70% of that for J = 4, indicating that the Pr 3+ moment is partially quenched by the crystal field.

  3. Highly (110)- and (111)-oriented BiFeO3 films on BaPbO3 electrode with Ru or Pt /Ru barrier layers

    Science.gov (United States)

    Lee, Chia-Ching; Wu, Jenn-Ming; Hsiung, Chang-Po

    2007-04-01

    Highly (110)- and (111)-oriented BiFeO3 (BFO) films were fabricated with BaPbO3 (BPO )/Ru and BPO /Pt/Ru as electrode/barrier on Si substrates by rf-magnetron sputtering. The BPO /Ru and BPO /Pt/Ru stacks both induce oriented BFO films and act as diffusion barriers. The (110)- and (111)-oriented BFO films possess excellent ferroelectric properties with only minor leakage. The values of remnant polarization are almost the same, about 42μC/cm2, for (110)- and (111)-oriented BFO films. However, polarization measured under varying pulse widths demonstrates that the switching polarization in (111)-oriented BFO films is higher than in (110)-oriented films. Additionally, (111)-oriented BFO films exhibit better retention properties than (110)-oriented films.

  4. Sol-Gel Process for Making Pt-Ru Fuel-Cell Catalysts

    Science.gov (United States)

    Narayanan, Sekharipuram; Valdez, Thomas; Kumta, Prashant; Kim, Y.

    2005-01-01

    A sol-gel process has been developed as a superior alternative to a prior process for making platinum-ruthenium alloy catalysts for electro-oxidation of methanol in fuel cells. The starting materials in the prior process are chloride salts of platinum and ruthenium. The process involves multiple steps, is time-consuming, and yields a Pt-Ru product that has relatively low specific surface area and contains some chloride residue. Low specific surface area translates to incomplete utilization of the catalytic activity that might otherwise be available, while chloride residue further reduces catalytic activity ("poisons" the catalyst). In contrast, the sol-gel process involves fewer steps and less time, does not leave chloride residue, and yields a product of greater specific area and, hence, greater catalytic activity. In this sol-gel process (see figure), the starting materials are platinum(II) acetylacetonate [Pt(C5H7O2)2, also denoted Pt-acac] and ruthenium(III) acetylacetonate [Ru(C5H7O2)3, also denoted Ru-acac]. First, Pt-acac and Ru-acac are dissolved in acetone at the desired concentrations (typically, 0.00338 moles of each salt per 100 mL of acetone) at a temperature of 50 C. A solution of 25 percent tetramethylammonium hydroxide [(CH3)4NOH, also denoted TMAH] in methanol is added to the Pt-acac/Ruacac/ acetone solution to act as a high-molecular-weight hydrolyzing agent. The addition of the TMAH counteracts the undesired tendency of Pt-acac and Ru-acac to precipitate as separate phases during the subsequent evaporation of the solvent, thereby helping to yield a desired homogeneous amorphous gel. The solution is stirred for 10 minutes, then the solvent is evaporated until the solution becomes viscous, eventually transforming into a gel. The viscous gel is dried in air at a temperature of 170 C for about 10 hours. The dried gel is crushed to make a powder that is the immediate precursor of the final catalytic product. The precursor powder is converted to the

  5. Carbon-Supported PtRuMo Electrocatalysts for Direct Alcohol Fuel Cells

    Directory of Open Access Journals (Sweden)

    José L.G. Fierro

    2013-10-01

    Full Text Available The review article discusses the current status and recent findings of our investigations on the synthesis and characterization of carbon-supported PtRuMo electrocatalysts for direct alcohol fuel cells. In particular, the effect of the carbon support and the composition on the structure, stability and the activity of the PtRuMo nanoparticles for the electrooxidation of CO, methanol and ethanol have been studied. Different physicochemical techniques have been employed for the analysis of the catalysts structures: X-ray analytical methods (XRD, XPS, TXRF, thermogravimetry (TGA and transmission electron microscopy (TEM, as well as a number of electrochemical techniques like CO adsorption studies, current-time curves and cyclic voltammetry measurements. Furthermore, spectroscopic methods adapted to the electrochemical systems for in situ studies, such as Fourier transform infrared spectroscopy (FTIRS and differential electrochemical mass spectrometry (DEMS, have been used to evaluate the oxidation process of CO, methanol and ethanol over the carbon-supported PtRuMo electrocatalysts.

  6. Extended Pi-Sigma tilde orbital model for CO adsorption on Pt and Ru

    Science.gov (United States)

    Mion, Thomas; Dimakis, Nicholas; Alamgir, Faisal; Jaye, Cherno; Fischer, Daniel; McGinn, Paul; Cooper, James; Greenbaum, Steve; Smotkin, Eugene

    2011-03-01

    Several discrepencies between the predicted Blyholder-type adsobtion models and experimental, as well as DFT calculated infared spectra have been addressed for atop CO on Pt in contrast to Ru. This model correlates increased Near Edge X-Ray Absorbtion Fine Structure intensity as the result of a sub-eV downshift from CO on Ru compared to CO on Pt thereby forming a weaker C-O bond. The model accounts for the hybrid orbitals electron transfer between the CO - metal bonds while taking in to consideration the orbital polarization within the CO itself. The charge redistribution of the s-tilde orbitals and reduced charge donation from CO to the surface results in a weaker internal CO bond upon Ru relative to Pt. The extended Pi-Sigma model explains why atop C-O stretching frequencies do not correlate with carbon p-type vacancies. Calculations done on the High Performance Computing Cluster at UT-Pan American. NEXAFS was done on U7A NIST/DOW beamline at Brookheaven National Synchrotron Light Source with funding from the Army Research Office.

  7. Electro-oxidation of carbon monoxide and methanol on bare and Pt-modified Ru(1010) electrodes.

    Science.gov (United States)

    Pinheiro, A L N; Zei, M S; Ertl, G

    2005-03-21

    The activity towards CO and methanol electrooxidation of bare and platinum-modified Ru(1010) surfaces has been investigated. The structure/morphology and composition of the modified surfaces were characterized using electron diffraction techniques (LEED, RHEED) and Auger spectroscopy. The bare Ru(1010) surface exhibits a higher catalytic activity towards CO electrooxidation than the Ru(0001) surface due to the lower oxidation potential of the former surface. The early stages of surface oxidation lead to disordering of the surface and further enhancing of the electrocatalytic activity. Electrodeposition of Pt on Ru(1010) leads to epitaxial growth via a Volmer-Weber growth mode. The Pt clusters grow preferentially with the (311) plane parallel to the substrate surface with (011) rows in the layers in contact with the substrate compressed by about 3% with respect to bulk Pt, in order to match with the (1210) rows of the Ru(1010) surface. This compression leads to enhanced catalytic activity towards CO oxidation for thin Pt deposits whereas for large deposited Pt particles the dominating factor for the catalytic enhancement is the higher concentration of surface defects. On the other hand, in the case of methanol oxidation, the dominant factor in determining the catalytic activity is the concentration of adjacent Pt-Ru sites, although surface defects play an important role in the methanol dehydrogenation steps.

  8. Electrochemical characterization of SnO{sub 2} electrodes doped with Ru and Pt

    Energy Technology Data Exchange (ETDEWEB)

    Berenguer, R. [Departamento de Quimica Fisica e Instituto Universitario de Materiales, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain); Quijada, C. [Departamento de Ingenieria Textil y Papelera, Universidad Politecnica de Valencia, 1, E-03801 Alcoy (Alicante) (Spain); Morallon, E. [Departamento de Quimica Fisica e Instituto Universitario de Materiales, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain)], E-mail: morallon@ua.es

    2009-09-01

    Antimony-platinum doped tin dioxide electrodes supported on titanium have been prepared by thermal decomposition. The effect of the progressive replacement of Sb with Ru (x = 0.00; 3.25; 6.50; 13.00 at.%) on their electrochemical response in acid medium has been analysed by cyclic voltammetry. The morphology of the coatings was observed by scanning electron microscopy. Ti/SnO{sub 2}-Sb-Pt electrodes without Ru presented a cracked-mud structure, typical of oxide electrodes prepared by thermal decomposition. The introduction of Ru in the oxide layer modified the coating morphology. The roughness increased and passed through a maximum with the increase of Ru content. A relation between the surface morphology, the roughness factor, voltammetric charge and the electrochemical activity has been established. The mechanism and electrocatalytic activity towards the oxygen evolution reaction has been studied from Tafel measurements. The progressive introduction of Ru in the electrodes increased their electrocatalytic activity for the oxygen evolution reaction with a change on the mechanism from non-active to active electrodes. The electrocatalytic activity mainly depends on electronic factors.

  9. Evaluation of Pt{sub 40}Pd{sub 60}/MWCNT electrocatalyst as ethylene glycol-tolerant oxygen reduction cathodes

    Energy Technology Data Exchange (ETDEWEB)

    Morales-Acosta, D.; Arriaga, L.G. [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, Parque Tecnologico Queretaro, Sanfandila, Pedro Escobedo, C.P. 76703 Queretaro (Mexico); Alvarez-Contreras, L. [Centro de Investigacion en Materiales Avanzados S.C., Complejo Industrial Chihuahua, C. P. 31109, Chihuahua, Chih. (Mexico); Luna, S. Fraire; Varela, F.J. Rodriguez [Cinvestav Unidad Saltillo, Carr. Saltillo-Monterrey Km. 13.5, Ramos Arizpe, Coahuila, C.P. 25900 (Mexico)

    2009-07-15

    Pt-Pd/MWCNT with Pt:Pd atomic ratio 40:60 and Pt/MWCNT electrocatalyst were synthesized and evaluated as oxygen reduction reaction (ORR) cathodes for Direct Ethylene Glycol Fuel Cells (DEGFC) applications. As reference, a commercial Pt/C material was also tested. We found that Pt-Pd/MWCNT has high tolerance capability to EG and higher selectivity for the ORR compared to the Pt-alone materials. As a result, the shift in onset potential for the ORR, E{sub onset}, at Pt-Pd/MWCNT was considerably smaller than the shift at Pt/MWCNT or Pt/C. The average particle size (from XRD) was 3.5 and 4 nm for Pt/MWCNT and Pt-Pd/MWCNT, respectively. A moderate degree of alloying was determined for the Pt-Pd material. An advantageous application of Pt-Pd electrocatalysts should be in DEGFCs. (author)

  10. Catalytic Hydrotreatment of Alcell Lignin Using Supported Ru, Pd, and Cu Catalysts

    NARCIS (Netherlands)

    Kloekhorst, Arjan; Heeres, Hero

    2015-01-01

    A catalyst screening study on the catalytic hydrotreatment of Alcell lignin in a batch setup was performed using supported Ru (C, Al2O3,TiO2), Pd (C, Al2O3), and a Cu/ZrO2 catalyst with the objective to determine the best catalyst for high yields of biobased aromatics and alkylphenolics. Experiments

  11. The role of bridging ligand in hydrogen generation by photocatalytic Ru/Pd assemblies

    NARCIS (Netherlands)

    Bindra, Gurmeet Singh; Schulz, Martin; Paul, Avishek; Groarke, Robert; Soman, Suraj; Inglis, Jane L.; Browne, Wesley R.; Pfeffer, Michael G.; Rau, Sven; MacLean, Brian J.; Pryce, Mary T.; Vos, Johannes G.

    2012-01-01

    The synthesis and characterisation of two terpyridine based ruthenium/palladium heteronuclear compounds are presented. The photocatalytic behaviour of the Ru/Pd complex containing the linear 2,2':5',2 ''-terpyridine bridge (1a) and its analogue the non-linear 2,2':6',2 ''-terpyridine bridge (2a) are

  12. The role of bridging ligand in hydrogen generation by photocatalytic Ru/Pd assemblies

    NARCIS (Netherlands)

    Bindra, Gurmeet Singh; Schulz, Martin; Paul, Avishek; Groarke, Robert; Soman, Suraj; Inglis, Jane L.; Browne, Wesley R.; Pfeffer, Michael G.; Rau, Sven; MacLean, Brian J.; Pryce, Mary T.; Vos, Johannes G.

    2012-01-01

    The synthesis and characterisation of two terpyridine based ruthenium/palladium heteronuclear compounds are presented. The photocatalytic behaviour of the Ru/Pd complex containing the linear 2,2':5',2 ''-terpyridine bridge (1a) and its analogue the non-linear 2,2':6',2 ''-terpyridine bridge (2a) are

  13. Enhanced electrocatalytic performance of Pt monolayer on nanoporous PdCu alloy for oxygen reduction

    Science.gov (United States)

    Hou, Linxi; Qiu, Huajun

    2012-10-01

    By selectively dealloying Al from PdxCu20-xAl80 ternary alloys in 1.0 M NaOH solution, nanoporous PdCu (np-PdCu) alloys with different Pd:Cu ratios are obtained. By a mild electrochemical dealloying treatment, the np-PdCu alloys are facilely converted into np-PdCu near-surface alloys with a nearly pure-Pd surface and PdCu alloy core. The np-PdCu near-surface alloys are then used as substrates to fabricate core-shell catalysts with a Pt monolayer as shell and np-PdCu as core by a Cu-underpotential deposition-Pt displacement strategy. Electrochemical measurements demonstrate that the Pt monolayer on np-Pd1Cu1 (Pt/np-Pd1Cu1) exhibits the highest Pt surface-specific activity towards oxygen reduction, which is ˜5.8-fold that of state-of-the-art Pt/C catalyst. The Pt/np-Pd1Cu1 also shows much enhanced stability with ˜78% active surface retained after 10,000 cycles (0.6-1.2 V vs. RHE). Under the same condition, the active surface of Pt/C drops to ˜28%.

  14. Localized Pd overgrowth on cubic Pt nanocrystals for enhanced electrocatalytic oxidation of formic acid.

    Science.gov (United States)

    Lee, Hyunjoo; Habas, Susan E; Somorjai, Gabor A; Yang, Peidong

    2008-04-23

    Binary Pt/Pd nanoparticles were synthesized by localized overgrowth of Pd on cubic Pt seeds for the investigation of electrocatalytic formic acid oxidation. The binary particles exhibited much less self-poisoning and a lower activation energy relative to Pt nanocubes, consistent with the single crystal study.

  15. Electrochemical promotion of catalytic reactions with Pt/C (or Pt/Ru/C)//PBI catalysts

    DEFF Research Database (Denmark)

    Petrushina, Irina; Bjerrum, Niels; Bandur, Viktor;

    2007-01-01

    The paper is an overview of the results of the investigation on electrochemical promotion of three catalytic reactions: methane oxidation with oxygen, NO reduction with hydrogen at 135 degrees C and Fischer-Tropsch synthesis (FTS) at 170 degrees C in the [CH4/O-2(or NO/H-2 or CO/H-2)/Ar//Pt(or Pt...

  16. Electrochemically deposited Pd-Pt and Pd-Au codeposits on graphite electrodes for electrocatalytic H2O2 reduction.

    Science.gov (United States)

    Nagaiah, Tharamani Chikka; Schäfer, Dominik; Schuhmann, Wolfgang; Dimcheva, Nina

    2013-08-20

    Improved electrocatalytic activity and selectivity for the reduction of H2O2 were obtained by electrodepositing Pd-Pt and Pd-Au on spectrographic graphite from solutions containing salts of the two metals at varying ratio. The electrocatalytic activity of the resulting binary codeposits for H2O2 reduction was evaluated by means of the redox-competition mode of scanning electrochemical microscopy (SECM) and voltammetric methods. In a potential range from 0 to -600 mV (vs. Ag/AgCl/3 M KCl) at pH 7.0 in 0.1 M phosphate citrate buffer, the electrocatalytic activity of both Pd-Pt and Pd-Au codeposits was substantially improved as compared with the identically deposited single metals suggesting an electrocatalytic synergy of the codeposits. Pd-Pt and Pd-Au codeposits were characterized by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM). Codepositing with Au caused a change of hedgehog-like shaped Pd nanoparticles into cauliflower-like nanoparticles with the particle size decreasing with increasing Au concentration. Codepositing Pd with Pt caused the formation of oblong structures with the size initially increasing with increasing Pt content. However, the particle size decreases with further increase in Pt concentration. The improved electrocatalytic capability for H2O2 reduction of the Pd-Pt electrodeposits on graphite was further demonstrated by immobilizing glucose oxidase as a basis for the development of an interference-free amperometric glucose biosensor.

  17. Pt-Ni and Pt-M-Ni (M = Ru, Sn Anode Catalysts for Low-Temperature Acidic Direct Alcohol Fuel Cells: A Review

    Directory of Open Access Journals (Sweden)

    Ermete Antolini

    2017-01-01

    Full Text Available In view of a possible use as anode materials in acidic direct alcohol fuel cells, the electro-catalytic activity of Pt-Ni and Pt-M-Ni (M = Ru, Sn catalysts for methanol and ethanol oxidation has been widely investigated. An overview of literature data regarding the effect of the addition of Ni to Pt and Pt-M on the methanol and ethanol oxidation activity in acid environment of the resulting binary and ternary Ni-containing Pt-based catalysts is presented, highlighting the effect of alloyed and non-alloyed nickel on the catalytic activity of these materials.

  18. Certification of Pd and Pt single spikes and application to the quantification of Pt and Pd in automotive exhaust emissions

    Science.gov (United States)

    Vogl, Jochen; Meyer, Christian; Noordmann, Janine; Rienitz, Olaf; Geilert, Sonja

    2014-05-01

    Numerous epidemiological studies show the effect of increased ambient pollution. Therefore measurement networks for air quality have been installed worldwide and legislation requires the monitoring of air pollution. Besides monitoring it is also important to be able to identify, to quantify and finally to regulate the emission of distinct sources in order to improve the quality of life. Automotive vehicles are a major source of environmental pollution especially through contaminants such as CO, NOX, SOX and hydrocarbons which derive from petrol combustion, while for example Platinum Group Elements (PGE) can be present from catalytic converters. The release of PGE into the environment, however, may be damaging in terms of public health, ecological and economic interests. In order to reliably assess the risks from PGEs, traceable and thus comparable data on the release rates of PGE from automotive catalysers are needed. As no Certified Reference Materials (CRM) are available for such samples the development of analytical procedures enabling SI-traceable results will be challenging. Therefore reference procedures for Pd and Pt in automotive exhaust emissions based on isotope dilution mass spectrometry (IDMS) have been developed and applied to specifically sampled automotive exhaust emissions. Due to the commonly known advantages, IDMS often is applied for quantification PGEs, as is the case within this work. The main reasons here are the required accuracy and the low PGE mass fractions in the sample. In order to perform IDMS analysis the analyte element must be available in an isotopically enriched form as so-called spike material or solution thereof, which is mixed with the sample. Unfortunately, no certified PGE spike solutions are available yet. To fill this gap two single PGE spikes, one 106Pd and one 194Pt spike, have been produced and characterized. The selection of the isotopes, the production of the solutions and the ampoulation will be described in this

  19. Enhanced methanol electro-oxidation activity of PtRu catalysts supported on heteroatom-doped carbon

    Energy Technology Data Exchange (ETDEWEB)

    Wu Gang [Department of Applied Chemistry, Harbin Institute of Technology, Harbin 150001 (China)], E-mail: wugang@lanl.gov; Swaidan, Raja [Department of Chemical Engineering, Cooper Union, New York, NY 10003 (United States); Li Deyu; Li Ning [Department of Applied Chemistry, Harbin Institute of Technology, Harbin 150001 (China)

    2008-11-01

    A typical heteroatom (nitrogen)-doped carbon materials were successfully synthesized through the carbonization of a hybrid containing traditional carbon black covered by in situ polymerized polyaniline. The nitrogen content onto carbon can be adjusted up to 5.1 at.% by changing the coverage of polyaniline. The effects of nitrogen doping on the surface physical and electrochemical properties of carbon were studied using XPS, XRD and HRTEM, as well as CV and EIS techniques. With increasing nitrogen doping, the carbon structure became more compact, showing curvatures and dislocations in the graphene stacking. The nitrogen-doped carbon also exhibited a higher accessible surface area in electrochemical reactions, and a lower charge transfer resistance at the carbon/electrolyte interface. Moreover, to investigate the influence of nitrogen doping on the electrocatalytic activity of the PtRu/C catalyst, comparisons in CO stripping and methanol oxidation were carried out on PtRu catalysts supported by non-doped and nitrogen-doped carbon. Since the promotional roles of nitrogen doping, including the high electrochemically accessible surface area, the richness of the disordered nanostructures and defects, and the high electron density on N-doped carbon supports, contribute to the synthesis of well-dispersed PtRu particles with high Pt utilization and stronger metal-support interactions, an enhanced catalytic activity for methanol oxidation was obtained in the case of the PtRu/N-C catalyst in comparison with the traditional PtRu/C catalyst.

  20. Enhanced methanol electro-oxidation activity of PtRu catalysts supported on heteroatom-doped carbon

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Gang; Li, Deyu; Li, Ning [Department of Applied Chemistry, Harbin Institute of Technology, Harbin 150001 (China); Swaidan, Raja [Department of Chemical Engineering, Cooper Union, New York, NY 10003 (United States)

    2008-11-01

    A typical heteroatom (nitrogen)-doped carbon materials were successfully synthesized through the carbonization of a hybrid containing traditional carbon black covered by in situ polymerized polyaniline. The nitrogen content onto carbon can be adjusted up to 5.1 at.% by changing the coverage of polyaniline. The effects of nitrogen doping on the surface physical and electrochemical properties of carbon were studied using XPS, XRD and HRTEM, as well as CV and EIS techniques. With increasing nitrogen doping, the carbon structure became more compact, showing curvatures and dislocations in the graphene stacking. The nitrogen-doped carbon also exhibited a higher accessible surface area in electrochemical reactions, and a lower charge transfer resistance at the carbon/electrolyte interface. Moreover, to investigate the influence of nitrogen doping on the electrocatalytic activity of the PtRu/C catalyst, comparisons in CO stripping and methanol oxidation were carried out on PtRu catalysts supported by non-doped and nitrogen-doped carbon. Since the promotional roles of nitrogen doping, including the high electrochemically accessible surface area, the richness of the disordered nanostructures and defects, and the high electron density on N-doped carbon supports, contribute to the synthesis of well-dispersed PtRu particles with high Pt utilization and stronger metal-support interactions, an enhanced catalytic activity for methanol oxidation was obtained in the case of the PtRu/N-C catalyst in comparison with the traditional PtRu/C catalyst. (author)

  1. Preparation of high dispersion and high performance PtRu/CNTs catalyst by an organic colloid method

    Institute of Scientific and Technical Information of China (English)

    王宁卡特; 刘军民; 廖世军; V.Birss

    2006-01-01

    A high dispersion and high performance PtRu catalyst supported on carbon nanotubes was prepared by an organic colloid method. The particle size of the active components could be as small as 1.0 nm,the active surface area was about 466 m2/g(Pt). The catalytic activity toward anodic oxidation of methanol was about 3 ~ 4 times higher than that of Johnson Matthey PtRu/XC-72R catalyst. The single testing showed that the performance of the prepared catalyst was higher than that of the commercial one.

  2. Magnetic properties and microstructure of FePt/MoC/CrRu films

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, Jai-Lin, E-mail: tsaijl@dragon.nchu.edu.tw; Luo, Qi-Shao; Chen, Po-Ran; Tseng, Yun-Ting

    2015-05-15

    The FePt films with thickness of 4−10 nm were deposited on MoC/CrRu/glass at substrate temperature ranged from 260 to 410 °C by using magnetron sputtering and strong (001) textured FePt films were obtained at 380 °C and 410 °C. The multi-functional MoC conductive intermediate layer was used to resist the Cr diffusion and promote the epitaxial growth of the (001) textured FePt film which shows perpendicular magnetization and a linear-like in-plane magnetic loop. The out-of plane coercivity and shape of demagnetization curve were dominated by the ordering degree and perpendicular magnetic anisotropy which were increased with deposited temperature. The FePt film deposited at 290 °C shows continuous morphology and change to interconnected structure at 350 °C and finally form the island like structure at 380 °C and 410 °C. Each island contains many FePt grains and the smaller grains size was 12.2 nm which obtained at 5 nm thick FePt film. Perpendicular anisotropy of 1.1×10{sup 7} erg/cm{sup 3} and coercivity of 8.2 kOe have been demonstrated in 7 nm thick FePt film. - Highlights: • The MoC conductive intermediate layer was resisted the Cr diffusion. • The MoC layer promote the epitaxial growth of (001) textured FePt film. • The FePt film shows perpendicular magnetization on MoC layer.

  3. Dissociative adsorption of methane on surface oxide structures of Pd-Pt alloys

    CERN Document Server

    Dianat, Arezoo; Ciacchi, Lucio Colombi; Pompe, Wolfgang; Cuniberti, Gianaurelio; Bobeth, Manfred; 10.1021/jp905689t

    2010-01-01

    The dissociative adsorption of methane on variously oxidized Pd, Pt and Pd-Pt surfaces is investigated using density-functional theory, as a step towards understanding the combustion of methane on these materials. For Pd-Pt alloys, models of surface oxide structures are built on the basis of known oxides on Pd and Pt. The methane adsorption energy presents large variations depending on the oxide structure and composition. Adsorption is endothermic on the bare Pd(111) metal surface as well as on stable thin layer oxide structures such as the ($\\sqrt{5}\\times\\sqrt{5}$) surface oxide on Pd(100) and the PtO$_2$-like oxide on Pt(111). Instead, large adsorption energies are obtained for the (100) surface of bulk PdO, for metastable mixed Pd$_{1-x}$Pt$_x$O$_{4/3}$ oxide layers on Pt(100), and for Pd-Pt(111) surfaces covered with one oxygen monolayer. In the latter case, we find a net thermodynamic preference for a direct conversion of methane to methanol, which remains adsorbed on the oxidized metal substrates via w...

  4. Pd-Pt Catalysts on Fluorinated Alumina Support Studied by X-Ray Absorption Fine Structure

    Science.gov (United States)

    Yan, Wensheng; Li, Zhongrui; Wei, Zheng; Wei, Shiqiang

    2007-02-01

    A series of bi-metallic Pd-Pt catalysts supported on both pristine and fluorinated alumina supports were investigated with x-ray absorption spectroscopy. It was found that Pd and Pt form small alloy particles on the pristine alumina support; the composition and the cluster size of the PdPt bimetallic alloys, and the electronic properties of the metals were significantly altered on the fluorinated support. The remarkable increase in sulfur tolerance of the PdPt metallic clusters supported on the fluorine pretreated alumina can be attributed to an electronic depletion of the metals, large particle size and direct participation of the acid sites in the reaction.

  5. Improved catalytic performance of Pd nanowires for ethanol oxidation by monolayer of Pt

    Science.gov (United States)

    Huang, Zhongyuan; Zhou, Haihui; Chang, Yiwen; Fu, Chaopeng; Zeng, Fanyan; Kuang, Yafei

    2013-10-01

    Pd nanowires with diameter of 10-20 nm and length of several micrometers were prepared and monolayer of Pt was deposited on the Pd nanowires by using copper underpotential deposition and subsequent replacement of Cu by Pt. The products were characterized by using scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and energy spectrum analysis. The electrocatalytic performance of PdPt nanowires was studied by cyclic voltammetry and chronoamperometry. Electrochemical results show that the monolayer of Pt can improve not only the activity of Pd nanowires but also the stability for ethanol oxidation in alkaline medium.

  6. Single-phase aqueous approach toward Pd sub-10 nm nanocubes and Pd-Pt heterostructured ultrathin nanowires.

    Science.gov (United States)

    Yuan, Qiang; Zhuang, Jing; Wang, Xun

    2009-11-21

    Monodisperse, highly-selective sub-10 nm Pd and Rh nanocubes have been successfully synthesized and, for the first time, bimetallic Pd-Pt heterostructured ultrathin nanowires have been achieved through using Pd nanocubes as seeds by a one-pot, single-phase aqueous method.

  7. Functional separation of oxidation–reduction reactions and electron transport in PtRu/ND and conductive additive hybrid electrocatalysts during methanol oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yan; Wang, Yanhui [State Key Laboratory of Metastable Materials Science and Technology, College of Materials Science and Engineering, Yanshan University, Qinhuangdao 066004 (China); Bian, Linyan [College of Physics and Chemistry, Henan Polytechnic University, Jiaozuo, Henan 454000 (China); Lu, Rui [State Key Laboratory of Metastable Materials Science and Technology, College of Materials Science and Engineering, Yanshan University, Qinhuangdao 066004 (China); Zang, Jianbing, E-mail: jbzang@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, College of Materials Science and Engineering, Yanshan University, Qinhuangdao 066004 (China)

    2016-02-28

    Graphical abstract: - Highlights: • Functional separation of reactions and electron transport in PtRu/ND + AB (or CNT). • A conductive network was formed after the addition of AB or CNT. • PtRu/ND + AB (or CNT) exhibited enhanced activity and stability than PtRu/ND. - Abstract: Undoped nanodiamond (ND) supported PtRu (PtRu/ND) electrocatalyst for methanol oxidation reactions (MOR) in direct methanol fuel cells was prepared by a microwave-assisted polyol reduction method. Sp{sup 3}-bonded ND possesses high electrochemical stability but low conductivity, while sp{sup 2}-bonded carbon nanomaterials with high conductivity are prone to oxidation. Therefore, the functions of the supporting material were separated in this study. ND (sp{sup 3}), as a support, and AB or CNTs (sp{sup 2}), as a conductive additive, were combined to form the hybrid electrocatalysts PtRu/ND + AB and PtRu/ND + CNT for MOR. The morphology of the electrocatalysts was characterized by scanning electron microscopy and electrochemical measurements were performed using an electrochemical workstation. The results indicated that the electrocatalytic activity of PtRu/ND for MOR was improved with the addition of AB or CNTs as a conductive additive. Moreover, adding CNTs to PtRu/ND as a conductive additive showed better electrocatalytic activities than adding AB, which can be ascribed to the better electron-transfer ability of CNTs.

  8. New Synthesis of Pt-Ru Nanoparticles on Surface Modified Carbon Vulcane XC-72 as an Effective Catalyst for Direct Methanol Fuel Cell

    Institute of Scientific and Technical Information of China (English)

    Ahmad; Nozad; Golikand; Sajjad; Sadaghat; Sharehjini; Mohammad; Yari

    2007-01-01

    1 Results Pt-Ru nanoparticles are synthesised on the surface oxidized carbon Vulcane XC-72 as catalyst support by chemically anchoring Pt and Ru onto the surface of modified carbon vulcane XC-72 (by refluxing in 70% HNO3 at 120 ℃ for 12 h to introduce surface functional groups) .The nanoparticles of Pt and Ru are synthesized by reduction of H2PtCl6 and K4Ru(CN)6 with sodium borohydride in a 5.5 buffer solution of sodium citrate,the complexation of citrate with metal ions is beneficial to the formati...

  9. Solid solution alloy nanoparticles of immiscible Pd and Ru elements neighboring on Rh: changeover of the thermodynamic behavior for hydrogen storage and enhanced CO-oxidizing ability.

    Science.gov (United States)

    Kusada, Kohei; Kobayashi, Hirokazu; Ikeda, Ryuichi; Kubota, Yoshiki; Takata, Masaki; Toh, Shoichi; Yamamoto, Tomokazu; Matsumura, Syo; Sumi, Naoya; Sato, Katsutoshi; Nagaoka, Katsutoshi; Kitagawa, Hiroshi

    2014-02-05

    Pd(x)Ru(1-x) solid solution alloy nanoparticles were successfully synthesized over the whole composition range through a chemical reduction method, although Ru and Pd are immiscible at the atomic level in the bulk state. From the XRD measurement, it was found that the dominant structure of Pd(x)Ru(1-x) changes from fcc to hcp with increasing Ru content. The structures of Pd(x)Ru(1-x) nanoparticles in the Pd composition range of 30-70% consisted of both solid solution fcc and hcp structures, and both phases coexist in a single particle. In addition, the reaction of hydrogen with the Pd(x)Ru(1-x) nanoparticles changed from exothermic to endothermic as the Ru content increased. Furthermore, the prepared Pd(x)Ru(1-x) nanoparticles demonstrated enhanced CO-oxidizing catalytic activity; Pd0.5Ru0.5 nanoparticles exhibit the highest catalytic activity. This activity is much higher than that of the practically used CO-oxidizing catalyst Ru and that of the neighboring Rh, between Ru and Pd.

  10. Molecular Dynamics Simulation Study of Atomic Segregation of (PdPt)147 during the Heating Process

    Science.gov (United States)

    Xiao, X. Y.; Cheng, Z. F.; Xia, J. H.

    Research on the influence of alloy concentration and distribution on bimetallic cluster plays a key role in exploring new structural material. This paper studies the melting process of icosahedral bimetallic cluster (PdPt)147 with different Pt concentrations and different atomic distributions by using molecular dynamics with an embedded atom method. The results indicate that the mixed Pd-Pt cluster shows an irregular phenomenon between 580 and 630 K, i.e. the atomic energy decreases with the increase of temperature. This is because the surface energy of Pd is lower than that of Pt; the decreased energy due to Pd atomic segregation is larger than the increased energy due to heating during the segregation process. In addition, the temperature of Pd atomic segregation is strongly related to Pt concentration. This leads to that Pd atoms prefer to remain on the surface even after the cluster melted.

  11. Synergistic Effects in CNTs-PdAu/Pt Trimetallic Nanoparticles with High Electrocatalytic Activity and Stability

    Science.gov (United States)

    Cai, Xin-Lei; Liu, Chang-Hai; Liu, Jie; Lu, Ying; Zhong, Ya-Nan; Nie, Kai-Qi; Xu, Jian-Long; Gao, Xu; Sun, Xu-Hui; Wang, Sui-Dong

    2017-10-01

    We present a straightforward physical approach for synthesizing multiwalled carbon nanotubes (CNTs)-PdAu/Pt trimetallic nanoparticles (NPs), which allows predesign and control of the metal compositional ratio by simply adjusting the sputtering targets and conditions. The small-sized CNTs-PdAu/Pt NPs ( 3 nm, Pd/Au/Pt ratio of 3:1:2) act as nanocatalysts for the methanol oxidation reaction (MOR), showing excellent performance with electrocatalytic peak current of 4.4 A mg Pt -1 and high stability over 7000 s. The electrocatalytic activity and stability of the PdAu/Pt trimetallic NPs are much superior to those of the corresponding Pd/Pt and Au/Pt bimetallic NPs, as well as a commercial Pt/C catalyst. Systematic investigation of the microscopic, crystalline, and electronic structure of the PdAu/Pt NPs reveals alloying and charge redistribution in the PdAu/Pt NPs, which are responsible for the promotion of the electrocatalytic performance.

  12. Incorporation of metals (Pt-Ni-Ru) in the zeolite ZSM-5 through ion exchange competitive: synthesis and characterization; Incorporacao de metais (Pt-Ni-Ru) na zeolita ZSM-5 atraves da troca ionica competitiva: sintese e caracterizacao

    Energy Technology Data Exchange (ETDEWEB)

    Barbosa, A.S.; Rodrigues, M.G.F., E-mail: antusiasb@hotmail.com [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Departamento de Engenharia Quimica; Grau, J.M. [Instituto de Investigaciones en Catalisis y Petroquimica (INCAPE/FIQ/UNL-CONICET), Santa Fe (Argentina)

    2012-07-01

    Zeolites are very important materials due to their high specific surface area. Moreover, they are suitable for use as catalyst support. Noble metals supported on zeolites have been widely used as catalysts in the petrochemical industry. This paper was prepared and characterized, a powder aiming its use in heterogeneous catalysis. Support was used as ZSM-5 and the method of incorporation of the metals (Ru-PtNi) was competitive ion exchange. The materials (ZSM-5 and Pt-Ni-Ru/ZSM-5) were characterized by spectrophotometry Energy Dispersive X-ray (EDX), X-Ray Diffraction (XRD) and nitrogen physisorption (BET method). Based on the results of X-ray diffraction, it is possible to demonstrate the preservation of the structure of zeolite ZSM-5 after the competitive ion Exchange with metals (Ru-Pt-Ni) and calcination. The dispersion of metals on ZSM-5 did not change the textural characteristics of the zeolite. (author)

  13. Highly Sensitive Hydrazine Chemical Sensor Based on CNT-PdPt Nanocomposites

    Directory of Open Access Journals (Sweden)

    Sung Phil Kim

    2015-01-01

    Full Text Available Bimetallic PdPt nanoparticles were prepared using the chemical reduction method. The PdPt nanoparticles were successfully deposited on thiolated carbon nanotubes (CNTs to form a CNT-PdPt nanocomposite as an electron mediator for the fabrication of a hydrazine sensor. The PdPt nanoparticles had an average particle size of 2.3 nm and were well dispersed on the surfaces of the CNTs in the prepared CNT-PdPt nanocomposite, as demonstrated using transmission electron microscopy (TEM, energy dispersive X-ray spectroscopy (EDX, and X-ray diffraction (XRD. Based on X-ray photoelectron spectroscopy (XPS results, the estimated proportions of Pd and Pt in the CNT-PdPt nanocomposite were approximately 3.0% and 3.2%, respectively. A fabricated chemical sensor based on CNT-PdPt was found to exhibit better amperometric activity with respect to the hydrazine oxidation reaction than CNT-Pd, CNT-Pt, and commercial Pd/C and Pt/C catalysts. This sensor exhibited a linear range of 0.55–1,200 μM and a detection limit of 0.28 μM (S/N = 3 with a fast response time (within 5 s. Furthermore, the sensor could be used repeatedly for the consecutive detection of hydrazine with good reusability and storage stability. These properties demonstrate that the CNT-PdPt nanocomposite is a promising electron mediator for the fabrication of amperometric hydrazine sensors.

  14. A comprehensive study on the effect of Ru addition to Pt electrodes for direct ethanol fuel cell

    Indian Academy of Sciences (India)

    J Datta; S Singh; S Das; N R Bandyopadhyay

    2009-12-01

    The electro-oxidation of ethanol was studied over nanosized Pt and different compositions of PtRu catalysts synthesized by the borohydride reduction method. Physicochemical characterizations of the catalyst material were made by X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with EDX analysis and transmission electron microscopy (TEM). XRD patterns showed that Ru induces a contraction of the Pt lattice. EDX provided the composition of binary catalysts while TEM images indicated uniform distribution of discrete nanoparticle of the catalysts with narrow range. The electro-catalytic activities of the materials towards ethanol oxidation were investigated through electrochemical techniques, viz. cyclic voltammetry (CV), potentiodynamic polarization, chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) at room temperature. The onset potential of ethanol electro-oxidation is lowered on bimetallic PtRu catalysts compared to that on Pt alone. Of the investigated catalyst compositions the one with the highest electrocatalytic activity was found to be Pt82Ru18. This enhancement towards ethanol oxidation is explained on the basis of a structural effect and modified bi-functional mechanism.

  15. On the role of reactant transport and (surface) alloy formation for the CO tolerance of carbon supported PtRu polymer electrolyte fuel cell catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Kaiser, J.; Colmenares, L.; Jusys, Z.; Behm, R.J. [Abt. Oberflaechenchemie und Katalyse, Universitaet Ulm (Germany); Moertel, R.; Boennemann, H. [Max-Planck-Institut fuer Kohlenforschung, Muelheim a.d. Ruhr (Germany); Koehl, G.; Modrow, H.; Hormes, J. [Physikalisches Institut, Universitaet Bonn (Germany)

    2006-07-15

    The role of atomic scale intermixing for the electrocatalytic activity of bimetallic PtRu anode catalysts in reformate operated polymer electrolyte fuel cells (PEFC) was investigated, exploiting the specific properties of colloid based catalyst synthesis for the selective preparation of alloyed and non-alloyed bimetallic catalysts. Three different carbon supported PtRu catalysts with different degrees of Pt and Ru intermixing, consisting of (i) carbon supported PtRu alloy particles (PtRu/C), (ii) Pt and Ru particles co-deposited on the same carbon support (Pt+Ru/C), and (iii) a mixture of carbon supported Pt and carbon supported Ru (Pt/C+Ru/C) as well as the respective monometallic Pt/C and Ru/C catalysts were prepared and characterized by electron microscopy (TEM), X-ray absorption spectroscopy, and CO stripping. Their performance as PEFC anode catalysts was evaluated by oxidation of a H{sub 2}/2%CO gas mixture (simulated reformate) under fuel cell relevant conditions (elevated temperature, continuous reaction and controlled reactant transport) in a rotating disk electrode (RDE) set-up. The CO tolerance and H{sub 2} oxidation activity of the three catalysts is comparable and distinctly different from that of the monometallic catalysts. The results indicate significant transport of the reactants, CO{sub ad} and/or OH{sub ad}, between Pt and Ru surface areas and particles for all three catalysts, with only subtle differences from the alloy catalyst to the physical mixture. The high activity and CO tolerance of the bimetallic catalysts, through the formation of bimetallic surfaces, is explained, e.g., by contact formation in nanoparticle agglomerates or by material transport and subsequent surface decoration/surface alloy formation during catalyst preparation, conditioning, and operation. The instability and mobility of the catalysts under these conditions closely resembles concepts in gas phase catalysis. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  16. Low-energy electron diffraction investigation of epitaxial growth: Pt and Pd on Pd(100)

    Energy Technology Data Exchange (ETDEWEB)

    Flynn-Sanders, D.

    1990-09-21

    We investigate the epitaxial growth of Pt and Pd and Pd(100) via spot profile analysis using conventional low-energy electron diffraction (LEED). We resolve a central-spike and diffuse component in the spot profiles, reflecting the layer-occupations and pair-correlations, respectively. Kinetic limitations inhibit layer-by-layer growth at low temperatures. Our data suggest diffusion switches on at ca. 150 K for Pt and ca. 170 K for Pd indicating activation barriers to surface diffusion of ca. 10 and ca. 13 kcal/mol, respectively. To clarify the role of diffusion in determining the resulting film morphology, we develop a growth model that incorporates the adsorption-site requirement and predicts intensity oscillations. We present a new procedure to experimentally determine out-of-phase scattering conditions. At these energies, ring-structure is evident in the profiles during Pd growth between ca. 200 and 400 K. We report ring intensity oscillations as a function of coverage, which demonstrate the filling of individual layers.

  17. Single-particle isomeric states in 121Pd and 117Ru

    CERN Document Server

    Lalkovski, S; Bacelar, A M Denis; Gorska, M; Pietri, S; Podolyak, Zs; Bednarczyk, P; Caceres, L; Casarejos, E; Cullen, I J; Doornenbal, P; Farrelly, G F; Garnsworthy, A B; Geissel, H; Gelletly, W; Gerl, J; Grcebosz, J; Hinke, C; Ilie, G; Jaworski, G; Kisyov, S; Kojouharov, I; Kurz, N; Myalski, S; Palacz, M; Prokopowicz, W; Regan, P H; Schaffner, H; Steer, S; Tashenov, S; Walker, P M; Wollersheim, H J; Zhekova, M

    2011-01-01

    Neutron-rich nuclei were populated in a relativistic fission of 238U. Gamma-rays with energies of 135 keV and 184 keV were associated with two isomeric states in 121Pd and 117Ru. Half-lives of 0.63(5) microseconds and 2.0(3) micrisecondss were deduced and the isomeric states were interpreted in terms of deformed single-particle states.

  18. Extended IBA consistent-Q formalism applied to Ru and Pd isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Bucurescu, D.; Cata, G.; Cutoiu, D.; Constantinescu, G.; Ivascu, M.; Zamfir, N.V.

    1986-08-01

    A consistent-Q formalism extended to an IBA-1 hamiltonian applicable also in the U(5) limit, is applied to Ru and Pd isotopes with N around 60. A good description of energy levels and E2 transition in these nuclei is obtained. The model is able to reproduce the main features of this transitional region, characterized by both rigid triaxial deformation and ..gamma..-softness.

  19. Ultrasonically treated multi-walled carbon nanotubes (MWCNTs) as PtRu catalyst supports for methanol electrooxidation

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Chunwei; Hu, Xinguo; Wang, Dianlong; Dai, Changsong [Department of Applied Chemistry, Harbin Institute of Technology, Harbin 150001 (China); Zhang, Liang; Jin, Haibo [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Agathopoulos, Simeon [Department of Materials Science and Engineering, University of Ioannina, GR-451 10 Ioannina (Greece)

    2006-09-29

    In the quest of fabricating supported catalysts, experimental results of transmission electron microscopy, Raman and infrared spectroscopy indicate that ultrasonic treatment effectively functionalizes multi-walled carbon nanotubes (MWCNTs), endowing them with groups that can act as nucleation sites which can favor well-dispersed depositions of PtRu clusters on their surface. Ultrasonic treatment seems to be superior than functionalization via regular refluxing. This is confirmed by the determination of the electrochemistry active surface area (ECA) and the CO-tolerance performance of the PtRu catalysts, measured by adsorbed CO-stripping voltammetry in 0.5M sulfuric acid solution, and the real surface area of the PtRu catalysts, evaluated by Brunauer-Emmett-Teller (BET) measurements. Finally, the effectiveness for methanol oxidation is assessed by cyclic voltammetry (CV) in a sulfuric acid and methanol electrolyte. (author)

  20. Preparation and characterization of MgB2 with Pd, Pt and Re doping

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude; Pitillas, A.; Namazkar, Shahla;

    2016-01-01

    of the MgB2 superconductor. Impurity phases are formed by reaction mostly with Mg. The microstructure of the Pt, Pd and Re-based phases depends on the elements. Re-rich particles with large sizes up to 8 μm form, whereas Pt- and Pd-containing impurities are finely dispersed with a particle size that does...

  1. Interactions between interfacial water and CO adsorbed on Pt and Pt-Ru alloy surfaces under electrochemical conditions: Density-functional theory study

    Energy Technology Data Exchange (ETDEWEB)

    Santana, Juan A. [Department of Chemistry, University of Puerto Rico, San Juan, PR 00931-3346 (Puerto Rico); Ishikawa, Yasuyuki, E-mail: yishikawa@uprrp.ed [Department of Chemistry, University of Puerto Rico, San Juan, PR 00931-3346 (Puerto Rico)

    2010-12-30

    The structural and electronic properties of interfacial water and adsorbed CO on platinum and platinum/ruthenium alloy have been studied via density-functional theory calculations to gain insight into the water-adsorbate interaction under electrochemical conditions. The computational simulations reveal a new interpretation for the interaction of adsorbed CO and water at the electrochemical interfaces. The new interaction model rationalizes the observed quantitative relationship between infrared intensities for adsorbed bridging CO and water molecules that impart a high-frequency O-H stretch, ca. 3630-3660 cm{sup -1} on pure Pt and 3600-3620 cm{sup -1} on PtRu alloy. The theoretical modeling indicates that the observed feature common to both pure Pt and PtRu alloy surfaces is due to interfacial water molecules firmly hydrogen-bonded to bridging CO.

  2. Preparation of L11-CoPt/MgO/L11-CoPt tri-layer film on Ru(0001 underlayer

    Directory of Open Access Journals (Sweden)

    Mitsuru Ohtake

    2016-05-01

    Full Text Available A CoPt/MgO/CoPt tri-layer film is prepared on an Ru(0001 single-crystal underlayer at 300 °C by ultra-high vacuum magnetron sputtering. The growth behavior and the crystallographic properties are investigated by reflection high-energy electron diffraction, x-ray diffraction, and cross-sectional transmission electron microscopy. A fully epitaxial CoPt/MgO/CoPt film is formed on the Ru underlayer. The lower CoPt, the MgO, and the upper CoPt layers consist of two (111 variants whose atomic stacking sequences of close-packed plane along the perpendicular direction are ABCABC... and ACBACB... The lower and the upper CoPt layers involve metastable L11 structure, whereas the crystal structure of MgO layer is B1. Flat and atomically sharp interfaces are formed between the layers. The tri-layer film shows a strong perpendicular magnetic anisotropy reflecting the magnetocrystalline anisotropy of L11 crystal. The present study shows that an epitaxial L11-CoPt/MgO/L11-CoPt tri-layer film with perpendicular magnetic anisotropy can be formed by using a low substrate temperature of 300 °C.

  3. Structural characterization of Pt-Pd and Pd-Pt core-shell nanoclusters at atomic resolution.

    Science.gov (United States)

    Sanchez, Sergio I; Small, Matthew W; Zuo, Jian-min; Nuzzo, Ralph G

    2009-06-24

    We describe the results of a study at atomic resolution of the structures exhibited by polymer-capped monometallic and bimetallic Pt and Pd nanoclusters--models for nanoscale material electrocatalysts--as carried out using an aberration-corrected scanning transmission electron microscope (STEM). The coupling of sub-nanometer resolution with Z-contrast measurements provides unprecedented insights into the atomic structures and relative elemental speciation of Pt and Pd within these clusters. The work further defines the nature of deeply quenched states that prevent facile conversions of core-shell motifs to equilibrium alloys and the nature of nonidealities such as twinning (icosahedral cores) and atomic segregation that these structures can embed. The nature of the facet structure present in these model systems is revealed by theory directed modeling in which experimental intensity profiles obtained in Z-contrast measurements at atomic resolution are compared to simulated intensity profiles using theoretically predicted cluster geometries. These comparisons show close correspondences between experiment and model and highlight striking structural complexities in these systems that are compositionally sensitive and subject to amplification by subsequent cluster growth processes. The work demonstrates an empowering competency in nanomaterials research for STEM measurements carried out using aberration corrected microscopes, approaches that hold considerable promise for characterizing the structure of these and other important catalytic materials systems at the atomic scale.

  4. Low Pt-content ternary PdCuPt nanodendrites: an efficient electrocatalyst for oxygen reduction reaction

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Shaofang; Zhu, Chengzhou; Song, Junhua; Zhang, Peina; Engelhard, Mark H.; Xia, Haibing; Du, Dan; Lin, Yuehe

    2017-01-01

    Dendritic nanostructures are capturing increasing attentions in electrocatalysis owing to their unique structural features and low density. Herein, we report for the first time bromide ions mediated synthesis of low-Pt-content PdCuPt ternary nanodendrites via galvanic replacement reaction between Pt precursor and PdCu template in aqueous solution. The experimental results show that the ternary PdCuPt nanodendrites present enhanced electrocatalytic performance for oxygen reduction reaction in acid solution compared with commercial Pt/C as well as some state-of-the-art catalysts. In details, the mass activity of the PdCuPt catalyst with optimized composition is 1.73 A/mgPt at 0.85 V vs RHE, which is 14 times higher than that of commercial Pt/C catalyst. Moreover, the long-term stability test demonstrates its better durability in acid solution. After 5k cycles, there is still 70% electrochemical surface area maintained. This method provides an efficient way to synthesize trimetallic alloys with controllable composition and specific structure for oxygen reduction reaction.

  5. CATALYTIC AND ELECTROCATALYTIC ACTIVITY OF Pt-Ru/C ELECTRODE FOR HYDROGEN OXIDATION IN ALKALINE

    Directory of Open Access Journals (Sweden)

    D. LABOU

    2008-07-01

    Full Text Available The kinetics of the oxidation of H2 on PtRu/C gas-diffusion electrode was studied by interfacing the electrode with aqueous electrolytes at different pH values. The conducting electrolytes were KOH and HClO4 aqueous solutions with different concentrations. It is shown that the nature of the aqueous electrolyte plays the role of an active catalyst support for the PtRu/C electrode which drastically affects its catalytic properties. During the aforementioned interaction, termed electrochemical metal support interaction (EMSI, the electrochemical potential of the electrons at the catalyst Fermi level is equalised with the electrochemical potential of the solvated electron in the aqueous electrolyte. The electrochemical experiments carried out at various pH values showed that the electrochemical promotion catalysis (EPOC is more intense when the catalyst-electrode is interfaced with electrolytes with high pH values where the OH– ionic conduction prevails. It was concluded that similar to the solid state electrochemical systems EPOC proceeds through the formation of a polar adsorbed promoting layer of , electrochemically supplied by the OH- species, at the three phase boundaries of the gas exposed gas diffusion catalyst-electrode surface.

  6. The synthesis of PdPt/carbon paper via surface limited redox replacement reactions for oxygen reduction reaction

    CSIR Research Space (South Africa)

    Motsoeneng, RG

    2015-09-01

    Full Text Available Surface-limited redox replacement reactions using the electrochemical atomic layer deposition (EC-ALD) technique were used to synthesize PdPt bimetallic electrocatalysts on carbon paper substrate. Electrocatalysts having different Pd:Pt ratio were...

  7. The Electrochemical Atomic Layer Deposition of Pt and Pd nanoparticles on Ni foam for the electrooxidation of alcohols

    CSIR Research Space (South Africa)

    Modibedi, RM

    2012-10-01

    Full Text Available Electrodeposition of Pt and Pd metal by surface limited redox replacement reactions was performed using the electrochemical atomic layer deposition. Carbon paper and Ni foam were used as substrates for metal deposition. Supported Pt and Pd...

  8. PT L 3 near edge structure of halogen-bridged mixed-valence pt complexes and pd-pt mixed-metal complexes

    Science.gov (United States)

    Tanino, H.; Oyanagi, H.; Yamashita, M.; Kobayashi, K.

    1985-03-01

    X-ray absorption near edge structure (XANES) of halogen-bridged mixed-valence Pt complexes and halogen-bridged Pd-Pt mixed-metal complexes have been measured using synchrotron radiation with a high energy resolution. In Pd-Pt mixed metal complexes, we demonstrate that the degree of the valence is estimated from the intensity of the white line at the Pt L 3 edge. In the mixed-valence complexes, the electron system is proved to be the Peierls insulator with a charge density wave of renormalized d electrons of Pt, where the total valence of Pt IV- and Pt 11 is conserved without excess electrons from ligands or anions.

  9. Impact of IrRu oxygen evolution reaction catalysts on Pt nanostructured thin films under start-up/shutdown cycling

    Science.gov (United States)

    Cullen, David A.; More, Karren L.; Atanasoska, Ljiljana L.; Atanasoski, Radoslav T.

    2014-12-01

    Electron microscopy and X-ray photoelectron spectroscopy (XPS) were utilized to study the role of oxygen evolution reaction (OER) catalysts in mitigating degradation arising from start-up/shutdown events. Pt nanostructured thin films (NSTF) were coated with a Ru0.1Ir0.9 OER catalyst at loadings ranging from 1 to 10 μg cm-2 and submitted to 5000 potential cycles within a membrane electrode assembly. Analysis of the as-deposited catalyst showed that the Ir and Ru coating is primarily metallic, and further evidence is provided to support the previously reported interaction between Ru and the perylene-red support. Aberration-corrected scanning transmission electron microscopy and energy dispersive X-ray spectroscopy were used to observe the impact of the OER catalysts on Pt dissolution and migration into the membrane. Elemental mapping showed a high percentage of the Ir catalyst was maintained on the NSTF whisker surfaces following testing. The presence of the OER catalysts greatly reduced the smoothing of the Pt NSTF whiskers, which has been correlated with Pt dissolution and losses in electrochemically active surface area. The dissolution of both Ir and Pt led to the formation of IrPt nanoparticle clusters in the membrane close to the cathode, as well as the formation of a Pt band deeper in the membrane.

  10. Ru-decorated Pt nanoparticles on N-doped multi-walled carbon nanotubes by atomic layer deposition for direct methanol fuel cells

    DEFF Research Database (Denmark)

    Johansson, Anne-Charlotte Elisabeth Birgitta; Yang, R.B.; Haugshøj, K.B.

    2013-01-01

    (methylcyclopentadienyl)platinum MeCpPtMe3, bis(ethylcyclopentadienyl)ruthenium Ru(EtCp)2 and O2 as the precursors. Catalysts with 5, 10 and 20 ALD Ru cycles grown onto the CNT-supported ALD Pt nanoparticles (150 cycles) were prepared and tested towards the electro-oxidation of CO and methanol, using cyclic voltammetry...

  11. Radiolytic Synthesis of Pt-Ru Catalysts Based on Functional Polymer-Grafted MWNT and Their Catalytic Efficiency for CO and MeOH

    Directory of Open Access Journals (Sweden)

    Dae-Soo Yang

    2011-01-01

    Full Text Available Pt-Ru catalysts based on functional polymer-grafted MWNT (Pt-Ru@FP-MWNT were prepared by radiolytic deposition of Pt-Ru nanoparticles on functional polymer-grafted multiwalled carbon nanotube (FP-MWNT. Three different types of functional polymers, poly(acrylic acid (PAAc, poly(methacrylic acid (PMAc, and poly(vinylphenyl boronic acid (PVPBAc, were grafted on the MWNT surface by radiation-induced graft polymerization (RIGP. Then, Pt-Ru nanoparticles were deposited onto the FP-MWNT supports by the reduction of metal ions using γ-irradiation to obtain Pt-Ru@FP-MWNT catalysts. The Pt-Ru@FP-MWNT catalysts were then characterized by XRD, XPS, TEM ,and elemental analysis. The catalytic efficiency of Pt-Ru@FP-MWNT catalyst was examined for CO stripping and MeOH oxidation for use in a direct methanol fuel cell (DMFC. The Pt-Ru@PVPBAc-MWNT catalyst shows enhanced activity for electro-oxidation of CO and MeOH oxidation over that of the commercial E-TEK catalyst.

  12. Molecular dynamics simulation study of the melting of Pd-Pt nanoclusters

    Science.gov (United States)

    Sankaranarayanan, Subramanian K. R. S.; Bhethanabotla, Venkat R.; Joseph, Babu

    2005-05-01

    Bimetallic nanoclusters are of interest because of their utility in catalysis and sensors. The thermal characteristics of bimetallic Pt-Pd nanoclusters of different sizes and compositions were investigated through molecular dynamics simulations using quantum Sutton-Chen (QSC) many-body potentials. Monte Carlo simulations employing the bond order simulation model were used to generate minimum energy configurations, which were utilized as the starting point for molecular dynamics simulations. The calculated initial configurations of the Pt-Pd system consisted of surface segregated Pd atoms and a Pt-rich core. Melting characteristics were studied by following the changes in potential energy and heat capacity as functions of temperature. Structural changes accompanying the thermal evolution were studied by the bond order parameter method. The Pt-Pd clusters exhibited a two-stage melting: surface melting of the external Pd atoms followed by homogeneous melting of the Pt core. These transitions were found to depend on the composition and size of the nanocluster. Melting temperatures of the nanoclusters were found to be much lower than those of bulk Pt and Pd. Bulk melting temperatures of Pd and Pt simulated using periodic boundary conditions compare well with experimental values, thus providing justification for the use of QSC potentials in these simulations. Deformation parameters were calculated to characterize the structural evolution resulting from diffusion of Pd and Pt atoms. The results indicate that in Pd-Pt clusters, Pd atoms prefer to remain at the surface even after melting. In addition, Pt also tends to diffuse to the surface after melting due to reduction of its surface energy with temperature. This mixing pattern is different from those reported in some of the earlier studies on melting of bimetallics.

  13. Structure of carbon-supported Pt-Ru nanoparticles and their electrocatalytic behavior for hydrogen oxidation reaction

    Energy Technology Data Exchange (ETDEWEB)

    Velazquez, Amado; Centellas, Francesc; Garrido, Jose Antonio; Arias, Conchita; Rodriguez, Rosa Maria; Brillas, Enric; Cabot, Pere-Lluis [Laboratori d' Electroquimica dels Materials i del Medi Ambient, Departament de Quimica Fisica, Universitat de Barcelona, Marti i Franques 1-11, 08028 Barcelona (Spain)

    2010-02-01

    The electrochemical activity towards hydrogen oxidation reaction (HOR) of a high performance carbon-supported Pt-Ru electrocatalyst (HP 20 wt.% 1:1 Pt-Ru alloy on Vulcan XC-72 carbon black) has been studied using the thin-film rotating disk electrode (RDE) technique. The physical properties of the Pt-Ru nanoparticles in the electrocatalyst were previously determined by transmission electron microscopy (TEM), high resolution TEM, fast Fourier transform (FFT), electron diffraction and X-ray diffraction (XRD). The corresponding compositional and size-shape analyses indicated that nanoparticles generally presented a 3D cubo-octahedral morphology with about 26 at.% Ru in the lattice positions of the face-centred cubic structure of Pt. The kinetics for HOR was studied in a hydrogen-saturated 0.5 M H{sub 2}SO{sub 4} solution using thin-film electrodes prepared by depositing an ink of the electrocatalyst with different Nafion contents in a one-step process on a glassy carbon electrode. A maximum electrochemically active surface area (ECSA) of 119 m{sup 2} g Pt{sup -1} was found for an optimum Nafion composition of the film of about 35 wt.%. The kinetic current density in the absence of mass transfer effects was 21 mA cm{sup -2}. A Tafel slope of 26 mV dec{sup -1}, independent of the rotation rate and Nafion content, was always obtained, evidencing that HOR behaves reversibly. The exchange current density referred to the ECSA of the Pt-Ru nanoparticles was 0.17 mA cm{sup -2}, a similar value to that previously found for analogous inks containing pure Pt nanoparticles. (author)

  14. A Synthetic Pseudo-Rh: NOx Reduction Activity and Electronic Structure of Pd-Ru Solid-solution Alloy Nanoparticles.

    Science.gov (United States)

    Sato, Katsutoshi; Tomonaga, Hiroyuki; Yamamoto, Tomokazu; Matsumura, Syo; Zulkifli, Nor Diana Binti; Ishimoto, Takayoshi; Koyama, Michihisa; Kusada, Kohei; Kobayashi, Hirokazu; Kitagawa, Hiroshi; Nagaoka, Katsutoshi

    2016-06-24

    Rh is one of the most important noble metals for industrial applications. A major fraction of Rh is used as a catalyst for emission control in automotive catalytic converters because of its unparalleled activity toward NOx reduction. However, Rh is a rare and extremely expensive element; thus, the development of Rh alternative composed of abundant elements is desirable. Pd and Ru are located at the right and left of Rh in the periodic table, respectively, nevertheless this combination of elements is immiscible in the bulk state. Here, we report a Pd-Ru solid-solution-alloy nanoparticle (PdxRu1-x NP) catalyst exhibiting better NOx reduction activity than Rh. Theoretical calculations show that the electronic structure of Pd0.5Ru0.5 is similar to that of Rh, indicating that Pd0.5Ru0.5 can be regarded as a pseudo-Rh. Pd0.5Ru0.5 exhibits better activity than natural Rh, which implies promising applications not only for exhaust-gas cleaning but also for various chemical reactions.

  15. CO tolerant PtRu-MoO{sub x} nanoparticles supported on carbon nanofibers for direct methanol fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Tsiouvaras, N.; Pena, M.A.; Fierro, J.L.G. [Instituto de Catalisis y Petroleoquimica, CSIC, Marie Curie 2, 28049 Madrid (Spain); Martinez-Huerta, M.V. [Instituto de Catalisis y Petroleoquimica, CSIC, Marie Curie 2, 28049 Madrid (Spain); Facultad de Quimicas, Universidad de La Laguna, Astrofisico Francisco Sanchez s/n, 38071, La Laguna, Tenerife (Spain); Moliner, R.; Lazaro, M.J. [Instituto de Carboquimica, CSIC, Miguel Luesma Castan 4, 50018 Zaragoza (Spain); Rodriguez, J.L.; Pastor, E. [Facultad de Quimicas, Universidad de La Laguna, Astrofisico Francisco Sanchez s/n, 38071, La Laguna, Tenerife (Spain)

    2009-01-15

    Novel nanostructured catalysts based on PtRu-MoO{sub x} nanoparticles supported on carbon nanofibers have been investigated for CO and methanol electrooxidation. Carbon nanofibers are prepared by thermocatalytic decomposition of methane (NF), and functionalized with HNO{sub 3} (NF.F). Electrocatalysts are obtained using a two-step procedure: (1) Pt and Ru are incorporated on the carbon substrates (Vulcan XC 72R, NF and NF.F), and (2) Mo is loaded on the PtRu/C samples. Differential electrochemical mass spectrometry (DEMS) analyses establish that the incorporation of Mo increases significantly the CO tolerance than respective binary counterparts. The nature of the carbon support affects considerably the stabilization of MoO{sub x} nanoparticles and also the performance in methanol electrooxidation. Accordingly, a significant increase of methanol oxidation is obtained in PtRu-MoO{sub x} nanoparticles supported on non-functionalized carbon nanofiber, in parallel with a large reduction of the Pt amount in comparison with binary counterparts and commercial catalyst. (author)

  16. Controlled synthesis of Pd-Pt alloy hollow nanostructures with enhanced catalytic activities for oxygen reduction.

    Science.gov (United States)

    Hong, Jong Wook; Kang, Shin Wook; Choi, Bu-Seo; Kim, Dongheun; Lee, Sang Bok; Han, Sang Woo

    2012-03-27

    Pd-Pt alloy nanocrystals (NCs) with hollow structures such as nanocages with porous walls and dendritic hollow structures and Pd@Pt core-shell dendritic NCs could be selectively synthesized by a galvanic replacement method with uniform Pd octahedral and cubic NCs as sacrificial templates. Fine control over the degree of galvanic replacement of Pd with Pt allowed the production of Pd-Pt NCs with distinctly different morphologies. The synthesized hollow NCs exhibited considerably enhanced oxygen reduction activities compared to those of Pd@Pt core-shell NCs and a commercial Pt/C catalyst, and their electrocatalytic activities were highly dependent on their morphologies. The Pd-Pt nanocages prepared from octahedral Pd NC templates exhibited the largest improvement in catalytic performance. We expect that the present work will provide a promising strategy for the development of efficient oxygen reduction electrocatalysts and can also be extended to the preparation of other hybrid or hetero-nanostructures with desirable morphologies and functions. © 2012 American Chemical Society

  17. Carbon-supported Pd-Pt cathode electrocatalysts for proton exchange membrane fuel cells

    Science.gov (United States)

    Tang, Yongfu; Zhang, Huamin; Zhong, Hexiang; Xu, Ting; Jin, Hong

    A series of carbon-supported Pd-Pt alloy (Pd-Pt/C) catalysts for oxygen reduction reaction (ORR) with low-platinum content are synthesized via a modified sodium borohydride reduction method. The structure of as-prepared catalysts is characterized by powder X-ray diffraction (XRD) and transmission electron microscope (TEM) measurements. The prepared Pd-Pt/C catalysts with alloy form show face-centered-cubic (FCC) structure. The metal particles of Pd-Pt/C catalysts with mean size of around 4-5 nm are uniformly dispersed on the carbon support. The electrocatalytic activities for ORR of these catalysts are investigated by rotating disk electrode (RDE), cyclic voltammetry (CV), single cell measurements and electrochemical impedance spectra (EIS) measurements. The results suggest that the electrocatalytic activities of Pd-Pt/C catalysts with low platinum are comparable to that of the commercial Pt/C with the same metal loading. The maximum power density of MEA with a Pd-Pt/C catalyst, the Pd/Pt mass ratio of which is 7:3, is about 1040 mW cm -2.

  18. Mixed-PtPd-shell PtPdCu nanoparticle nanotubes templated from copper nanowires as efficient and highly durable electrocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Li, Hui-Hui; Cui, Chun-Hua; Zhao, Shuo; Yao, Hong-Bin; Gao, Min-Rui; Fan, Feng-Jia; Yu, Shu-Hong [National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230026 (China); Div. of Nanomaterials and Chemistry, Heifei National Lab. for Physical, Sciences at Microscale (China)

    2012-10-15

    The controlled synthesis of mixed-PtPd-shell PtPdCu-alloy nanoparticle nanotubes (ANNTs) is demonstrated by galvanic displacement with partially sacrificial copper-nanowire templates, and following the electrochemical leaching of the non-noble metal Cu in the acidic electrolyte. These core-shell catalysts significantly reduce the amount of expensive Pt and highly improve the electrocatalytic activity and durability through their modified electronic structure, atomic distribution, and 1D structure property. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Formation and Characterization of Pd, Pt and Pd-Pt Alloy Films on Polyimide by Catalyst-Enhanced Chemical Vapor Deposition

    Institute of Scientific and Technical Information of China (English)

    ZHOU Jinlan; CHENG Yinhua; Yousuf Hamadan; YU Kaichao

    2007-01-01

    Platinum, palladium and their alloy films on polyimide were formed by catalyst-enhanced chemical vapor deposition (CVD) in the carrier gas (N2, O2) at 220-300 ℃ under reduced pressure and normal pressure. The deposition of palladium complexes [ Pd((η3-allyl)(hfac) and Pd(hfac)2 ] gives pure palladium film,while the deposition of platinum needs the enhancement of palladium complex by mixing precursor platinum complex Pt(COD)Me2 and palladium complex in the same chamber. The co-deposition of Pd and Pt metals was used for the deposition of alloy films. During the CVD of palladium-platinum alloy, the Pd/Pt atomic ratios vary under different co-deposition conditions. These metal films were characterized by XPS and SEM, and show a good adhesive property.

  20. Preparation of PtRu/C anode electrocatalysts using gamma radiation for methanol electro-oxidation; Preparacao de eletrocatalisadores PtRu/C utilizando radiacao gama para aplicacao como anodo na oxidacao direta de metanol

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Dionisio Fortunato da

    2006-07-01

    Pt Ru/C (carbon-supported Pt Ru nanoparticles) anode electrocatalysts were prepared using radiolytic process (gamma radiation) and tested for methanol electro-oxidation. In this process, water/2-propanol and water/ethylene glycol solutions containing the metallic ions and the carbon support were submitted to gamma radiation under stirring. The water/alcohol ratio (v/v) and the total dose (kGy) were studied. A nominal Pt Ru atomic ratio of 50:50 were used in all experiments. The electrocatalysts were characterized by energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM) and cyclic voltammetry (CV). The electro-oxidation of methanol was studied by cyclic voltammetry using the thin porous coating technique. The electrocatalysts prepared in water/2-propanol showed crystallite size in the range of 3-5 nm and Pt Ru atomic ratio of 50:50. The electrocatalysts prepared in water/ethylene glycol showed crystallite size (2-3 nm) smaller than the ones obtained in water/2-propanol, however, the Pt Ru atomic ratios obtained were approximately 80:20, showing that only part of ruthenium ions were reduced. For methanol oxidation the electrocatalytic activity depends on the water/2-propanol and water/ethylene glycol ratio used in the reaction medium. The electrocatalysts prepared in water/2-propanol showed inferior performance to the ones prepared in water/ethylene glycol, which showed similar or superior performances (amperes per gram of platinum) to the commercial electrocatalyst from E-TEK. (author)

  1. Tailoring of Pd-Pt bimetallic clusters with high stability for oxygen reduction reaction

    Science.gov (United States)

    Cheng, Daojian; Wang, Wenchuan

    2012-03-01

    The composition-dependent equilibrium structure and thermal stability of Pd-Pt clusters with the size of 55 atoms, and CO, O, OH, and O2 adsorption on these clusters have been studied using molecular simulation based on the Gupta empirical potential and density functional theory (DFT) calculations. It is found that Pd43Pt12 with a three-shell onionlike structure (TS-cluster) exhibits the highest relative stability in both DFT and Gupta levels and also the highest melting point at the Gupta level among these Pd-Pt clusters. In addition, the Pd43Pt12 TS-cluster possesses the weakest CO, O, OH, and O2 adsorption strength, compared to the Pt55, Pd55, and Pd13Pt42 clusters, indicating good catalytic activities toward the oxygen reduction reaction (ORR) among these Pd-Pt clusters considered. We expect that this kind of DFT-guided strategy by controlling the composition could provide a simple way for possibly searching new electrocatalysts.

  2. Influence of alcohol additives in the preparation of electrodeposited Pt-Ru catalysts on oxidized graphite cloths

    Energy Technology Data Exchange (ETDEWEB)

    Sieben, Juan Manuel, E-mail: jmsieben@uns.edu.ar [Instituto de Ingenieria Electroquimica y Corrosion, Universidad Nacional del Sur, B8000CPB Bahia Blanca (Argentina); Duarte, Marta M.E.; Mayer, Carlos E. [Instituto de Ingenieria Electroquimica y Corrosion, Universidad Nacional del Sur, B8000CPB Bahia Blanca (Argentina)

    2011-03-03

    Research highlights: > Pt-Ru catalysts were prepared by potential pulse electrodeposition from solutions containing EtOH or EG at pH 2 and 5. > The catalyst particle size, loading and dispersion were influenced by solution pH and alcohol addition. > The deposits prepared at pH 2 exhibited large irregular agglomerates while those prepared at pH 5 presented smaller globular particles. > Pt-Ru system prepared using EG at pH 5 exhibited the best performance for CH{sub 3}OH oxidation. - Abstract: Carbon supported Pt-Ru catalysts were prepared by multiple cycles of potentiostatic pulses from aqueous diluted chloroplatinic acid and ruthenium chloride solutions in the presence of ethanol or ethylene glycol at pH 2 and 5. SEM images showed that the metallic deposit prepared at pH 2 consisted of large irregular agglomerates, whereas smaller globular particles were obtained at pH 5. In addition, the average particle size was considerably decreased in the presence of the stabilizers. The supported Pt-Ru alloys were tested as catalysts for methanol electro-oxidation in acid media. Electrocatalytic activity measurements indicated that the most active electrode was obtained with ethylene glycol as additive at pH 5.

  3. Pulse electrodeposition of Pt and Pt–Ru methanol-oxidation nanocatalysts onto carbon nanotubes in citric acid aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Chou, Huei-Yu [Department of Engineering and System Science, National Tsing Hua University, Hsinchu 30013, Taiwan, ROC (China); Hsieh, Chien-Kuo [Department of Materials Engineering, Ming Chi University of Technology, New Taipei City 24301, Taiwan, ROC (China); Tsai, Ming-Chi; Wei, Yu-Hsuan; Yeh, Tsung-Kuang [Department of Engineering and System Science, National Tsing Hua University, Hsinchu 30013, Taiwan, ROC (China); Tsai, Chuen-Horng, E-mail: tsai@aec.gov.tw [Department of Engineering and System Science, National Tsing Hua University, Hsinchu 30013, Taiwan, ROC (China)

    2015-06-01

    In this study, platinum nanoparticle/carbon nanotube (Pt NP/CNT) and platinum–ruthenium nanoparticle (Pt–Ru NP/CNT) hybrid nanocatalysts were prepared by the pulse-electrodeposition method in different aqueous solutions containing citric acid (CA) or sulfuric acid (SA). The electrocatalytic properties of the Pt NP/CNT and Pt–Ru NP/CNT electrodes prepared using different aqueous solutions were investigated for methanol oxidation. The results show that the electrochemical mass activities of these hybrid nanocatalysts prepared in the CA aqueous solution were increased by factors of 1.46 and 2.77 for Pt NPs and Pt–Ru NPs, respectively, compared with those prepared in SA aqueous solutions using the same procedure. These increased mass activities are attributed to the CA playing dual roles as both a stabilizing agent and a particle size reducing agent in the aqueous solutions. The approach developed in this work enables further reductions in the particle sizes of noble-metal nanocatalysts. - Highlights: • Pulse-electrodeposition of Pt or Pt–Ru nanoparticles on carbon nanotubes • Carbon nanotubes used as a catalyst-supporting material • Citric acid used as reducing agent in the aqueous electrodeposition solutions • Electrochemical activity for methanol oxidation improved by a factor of 1.46 to 2.77.

  4. Effect of the structure of Pt-Ru/C particles on CO{sub ad} monolayer vibrational properties and electrooxidation kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Maillard, Frederic; Chatenet, Marian [Laboratoire d' Electrochimie et de Physico-chimie des Materiaux et des Interfaces, UMR 5631, CNRS/INPG/UJF, 1130 rue de la Piscine, BP75, 38402 Saint Martin d' Heres (France); Bonnefont, Antoine [Laboratoire d' Electrochimie et de Chimie Physique du Corps Solide, Institut de chimie, UMR 7177, CNRS/Universite Louis Pasteur, 4 rue Blaise Pascal, 67000 Strasbourg (France); Guetaz, Laure [Grenoble Electron Microscopy at Minatec, LITEN/DTH/LCPEM, CEA-Grenoble, 38054 Grenoble Cedex 9 (France); Doisneau-Cottignies, Beatrice [Science et Ingenierie Materiaux Procedes, 1130 rue de la Piscine, BP75, 38402 Saint Martin d' Heres (France); Roussel, Herve [Laboratoire des Materiaux et du Genie Physique, Institut National Polytechnique de Grenoble, Minatec, 3 parvis Louis Neel, BP 257, 38016 Grenoble Cedex 1 (France); Stimming, Ulrich [Physik Department E19, Technische Universitaet, Muenchen, D-85748 Garching bei Muenchen (Germany)

    2007-12-01

    In this paper, we combined FTIR spectroscopy and CO{sub ad} stripping voltammetry to investigate CO{sub ad} adsorption and electrooxidation on Pt-Ru/C nanoparticles. The Pt:Ru elemental composition and the metal loading were determined by ICP-AES. The X-ray diffraction patterns of the Pt-Ru/C indicated formation of a Pt-Ru (fcc) alloy. HREM images revealed an increase in the fraction of agglomerated Pt-Ru/C particles with increasing the metal loading and showed that agglomerated Pt-Ru/C nanoparticles present structural defects such as twins or grain boundaries. In addition, isolated Pt-Ru/C nanoparticles have similar mean particle size (ca. 2.5 nm) and particle size distributions whatever the metal loading. Therefore, we could determine precisely the effect of particle agglomeration on the CO{sub ad} vibrational properties and electrooxidation kinetics. FTIR measurements revealed a main CO{sub ad} stretching band at ca. {sub anti} {sub {nu}}{sub CO{sub L}}=2030 cm{sup -1}, which we ascribed to a-top CO{sub ad} on Pt domains electronically modified by the presence of Ru. As the metal loading increased, the position of this band was blue shifted by ca. 5 cm{sup -1} and a shoulder around 2005 cm{sup -1} developed, which was ascribed to a-top CO{sub ad} on Ru domains. The reason for this was suggested to be the increasing size of Ru domains on agglomerated Pt-Ru/C particles, which lifts dipole-dipole coupling and allows two vibrational features to be observed (CO{sub ad}/Ru, CO{sub ad}/Pt). This is evidence that FTIR spectroscopy can be used to probe small chemical fluctuations of the Pt-Ru/C surface. Finally, we comment on the CO{sub ad} electrooxidation kinetics. We observed that CO{sub ad} was converted more easily into CO{sub 2} as the metal loading, i.e. the fraction of agglomerated Pt-Ru/C nanoparticles, increased. (author)

  5. Electroactivity of high performance unsupported Pt-Ru nanoparticles in the presence of hydrogen and carbon monoxide

    Energy Technology Data Exchange (ETDEWEB)

    Velazquez-Palenzuela, Amado; Cabot, Pere-Lluis; Centellas, Francesc; Garrido, Jose Antonio; Arias, Conchita; Rodriguez, Rosa Maria; Brillas, Enric [Laboratori d' Electroquimica dels Materials i del Medi Ambient, Departament de Quimica Fisica, Universitat de Barcelona, Marti i Franques 1-11, 08028 Barcelona (Spain)

    2010-10-15

    The electrochemical activity of high performance unsupported (1:1) Pt-Ru electrocatalyst in the presence of hydrogen and carbon monoxide has been studied using the thin-film rotating disk electrode (RDE) technique. The kinetic parameters of these reactions were determined in H{sub 2}- and CO-saturated 0.5 M H{sub 2}SO{sub 4} solutions by means of cyclic voltammetry, including CO stripping, and RDE voltammetry. Pt-Ru/Nafion inks were prepared in one step with different Nafion mass fractions, allowing determining the ionomer influence in electrocatalytic response and obtaining the kinetic current density in absence of mass-transfer effects, being 41 and 12 mA cm{sup 2} (geometrical area), for H{sub 2} and CO oxidation, respectively. These values correspond to mass activities of 1.37 and 0.40 A mg{sub Pt}{sup 1} and to specific activities of 1.52 and 0.44 mA cm{sub Pt}{sup 2}. The Tafel analysis confirmed that hydrogen oxidation was a two-electron reversible reaction, while CO oxidation exhibited an irreversible behavior with a charge-transfer coefficient of 0.42. The kinetic results for CO oxidation are in agreement with the bifunctional theory, in which the reaction between Pt-CO and Ru-OH is the rate-determining step. The exchange current density for hydrogen reaction was 0.28 mA cm{sup 2} (active surface area), thus showing similar kinetics to those found for carbon-supported Pt and Pt-Ru electrocatalyst nanoparticles. (author)

  6. Structures of small Pd Pt bimetallic clusters by Monte Carlo simulation

    Science.gov (United States)

    Cheng, Daojian; Huang, Shiping; Wang, Wenchuan

    2006-11-01

    Segregation phenomena of Pd-Pt bimetallic clusters with icosahedral and decahedral structures are investigated by using Monte Carlo method based on the second-moment approximation of the tight-binding (TB-SMA) potentials. The simulation results indicate that the Pd atoms generally lie on the surface of the smaller clusters. The three-shell onion-like structures are observed in 55-atom Pd-Pt bimetallic clusters, in which a single Pd atom is located in the center, and the Pt atoms are in the middle shell, while the Pd atoms are enriched on the surface. With the increase of Pd mole fraction in 55-atom Pd-Pt bimetallic clusters, the Pd atoms occupy the vertices of clusters first, then edge and center sites, and finally the interior shell. It is noticed that some decahedral structures can be transformed into the icosahedron-like structure at 300 and 500 K. Comparisons are made with previous experiments and theoretical studies of Pd-Pt bimetallic clusters.

  7. Structural transition and melting of onion-ring Pd Pt bimetallic clusters

    Science.gov (United States)

    Cheng, Daojian; Cao, Dapeng

    2008-08-01

    We use canonical Monte Carlo simulations to study the melting of icosahedral and decahedral onion-ring Pd-Pt bimetallic clusters consisting of 147 atoms. Structural transition from decahedron to icosahedron-like is found for the decahedral onion-ring 147-atom Pd-Pt cluster before melting. Also, the melting point of the decahedral onion-ring 147-atom Pd-Pt cluster is lower than the corresponding icosahedral cluster. In addition, at the higher temperatures after melting, the four-shell onion-ring structure becomes unstable, and can be transformed into the three-shell onion-like structure.

  8. Surface structure and relaxation during the oxidation of carbon monoxide on Pt Pd bimetallic surfaces

    Science.gov (United States)

    Lucas, C. A.; Markovic, N. M.; Ball, M.; Stamenkovic, V.; Climent, V.; Ross, P. N.

    2001-05-01

    The atomic structure and surface relaxation of Pd monolayer on Pt(1 1 1) has been studied by surface X-ray scattering, in an aqueous environment under electrostatic potential control, during the adsorption and oxidation of carbon monoxide. The results show that the Pd-Pt layer spacing contracts at the onset of CO oxidation before the Pd adlayer forms an oxide structure that is incommensurate with the Pt lattice. Both the oxide formation and the lattice contraction are fully reversible over many cycles of the applied electrode potential.

  9. Atomistic modeling of ternary additions to NiTi and quaternary additions to Ni-Ti-Pd, Ni-Ti-Pt and Ni-Ti-Hf shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Mosca, H.O., E-mail: hmosca@cnea.gov.ar [Gcia. Investigacion y Aplicaciones, CNEA, Av. Gral Paz 1499, B1650KNA San Martin (Argentina); GCMM, UTN, FRG Pacheco, Av. H. Yrigoyen 288, Gral. Pacheco (Argentina); Bozzolo, G. [Loyola University Maryland, 4501 N. Charles St., Baltimore, MD 21210 (United States); Grosso, M.F. del [Gcia. Investigacion y Aplicaciones, CNEA, Av. Gral Paz 1499, B1650KNA San Martin (Argentina); GCMM, UTN, FRG Pacheco, Av. H. Yrigoyen 288, Gral. Pacheco (Argentina); Consejo Nacional de Investigaciones Cientificas y Tecnicas, CONICET (Argentina)

    2012-08-15

    The behavior of ternary and quaternary additions to NiTi shape memory alloys is investigated using a quantum approximate method for the energetics. Ternary additions X to NiTi and quaternary additions to Ni-Ti-Pd, Ni-Ti-Pt, and Ni-Ti-Hf alloys, for X=Au, Pt, Ir, Os, Re, W, Ta,Ag, Pd, Rh, Ru, Tc, Mo, Nb, Zr, Zn, Cu, Co, Fe, Mn, V, Sc, Si, Al and Mg are considered. Bulk properties such as lattice parameter, energy of formation, and bulk modulus of the B2 alloys are studied for variations due to the presence of one or two simultaneous additives.

  10. Effects of Metal Composition and Ratio on Peptide-Templated Multimetallic PdPt Nanomaterials.

    Science.gov (United States)

    Merrill, Nicholas A; Nitka, Tadeusz T; McKee, Erik M; Merino, Kyle C; Drummy, Lawrence F; Lee, Sungsik; Reinhart, Benjamin; Ren, Yang; Munro, Catherine J; Pylypenko, Svitlana; Frenkel, Anatoly I; Bedford, Nicholas M; Knecht, Marc R

    2017-02-27

    It can be difficult to simultaneously control the size, composition, and morphology of metal nanomaterials under benign aqueous conditions. For this, bioinspired approaches have become increasingly popular due to their ability to stabilize a wide array of metal catalysts under ambient conditions. In this regard, we used the R5 peptide as a three-dimensional template for formation of PdPt bimetallic nanomaterials. Monometallic Pd and Pt nanomaterials have been shown to be highly reactive toward a variety of catalytic processes, but by forming bimetallic species, increased catalytic activity may be realized. The optimal metal-to-metal ratio was determined by varying the Pd:Pt ratio to obtain the largest increase in catalytic activity. To better understand the morphology and the local atomic structure of the materials, the bimetallic PdPt nanomaterials were extensively studied by transmission electron microscopy, extended X-ray absorption fine structure spectroscopy, X-ray photoelectron spectroscopy, and pair distribution function analysis. The resulting PdPt materials were determined to form multicomponent nanostructures where the Pt component demonstrated varying degrees of oxidation based upon the Pd:Pt ratio. To test the catalytic reactivity of the materials, olefin hydrogenation was conducted, which indicated a slight catalytic enhancement for the multicomponent materials. These results suggest a strong correlation between the metal ratio and the stabilizing biotemplate in controlling the final materials morphology, composition, and the interactions between the two metal species.

  11. Effects of Metal Composition and Ratio on Peptide-Templated Multimetallic PdPt Nanomaterials

    Energy Technology Data Exchange (ETDEWEB)

    Merrill, Nicholas A.; Nitka, Tadeusz T.; McKee, Erik M.; Merino, Kyle C.; Drummy, Lawrence F.; Lee, Sungsik; Reinhart, Benjamin; Ren, Yang; Munro, Catherine J.; Pylypenko, Svitlana; Frenkel, Anatoly I.; Bedford, Nicholas M.; Knecht, Marc R.

    2017-02-22

    It can be difficult to simultaneously control the size, composition, and morphology of metal nanomaterials under benign aqueous conditions. For this, bio-inspired approaches have become increasing popular due to their ability to stabilize a wide array of metal catalysts under ambient conditions. In this regard, we used the R5 peptide as a 3D template for the formation of PdPt bimetallic nanomaterials. Monometallic Pd and Pt nanomaterials have been shown to be highly reactive towards a variety of catalytic processes, but by forming bimetallic species, increased catalytic activity may be realized. The optimal metal-to-metal ratio was determined by varying the Pd:Pt ratio to obtain the largest increase in catalytic activity. To better understand the morphology and the local atomic structure of the materials, the bimetallic PdPt nanomaterials were extensively studied using transmission electron microscopy, extended X-ray absorption fine structure spectroscopy, X-ray photoelectron spectroscopy, and pair distribution function analysis. The resulting PdPt materials were determined to form multicomponent nanostructures where the Pt component demonstrated varying degrees of oxidation based upon the Pd:Pt ratio. To test the catalytic reactivity of the materials, olefin hydrogenation was conducted which indicated a slight catalytic enhancement for the multicomponent materials. These results suggest a strong correlation between the metal ratio and the stabilizing biotemplate in controlling the final materials morphology, composition, and the interactions between the two metal species.

  12. Effect of pressure on the Curie temperature of Mn2RuSn and Mn2PdSn

    Science.gov (United States)

    Adachi, Y.; Watanabe, T.; Kanomata, T.; Hayasaka, M.; Endo, K.; Nishihara, H.; Xu, X.; Kainuma, R.

    2017-04-01

    Effect of pressure on the Curie temperature TC of the Mn-rich Heusler alloys Mn2RuSn and Mn2PdSn has been investigated by measuring the temperature dependence of initial permeability at various pressures up to 10 kbar. It was found that the Curie temperatures of Mn2RuSn and Mn2PdSn decrease with increasing pressure. The pressure derivatives of TC were estimated to be -0.59 K/kbar for Mn2RuSn and -0.80 K/kbar for Mn2PdSn. On the basis of the experimental results, the relationship between the magnetic transition temperature and the Mn-Mn distance is discussed.

  13. σ-Aromaticity in polyhydride complexes of Ru, Ir, Os, and Pt.

    Science.gov (United States)

    Jimenez-Izal, Elisa; Alexandrova, Anastassia N

    2016-04-28

    Transition-metal hydrides represent a unique class of compounds, which are essential for catalysis, organic synthesis, and hydrogen storage. In this work we study IrH5(PPh3)2, (RuH5(P(i)Pr3)2)(-), (OsH5(P(i)Pr3)2)(-), and OsH4(PPhMe2)3 polyhydride complexes, inspired by the recent discovery of the σ-aromatic PtZnH5(-) cluster anion. The distinctive feature of these molecules is that, like in the PtZnH5(-) cluster, the metal is five-fold coordinated in-plane, and holds additional ligands at the axial positions. This work shows that the unusual coordination in these compounds indeed can be explained by σ-aromaticity in the pentagonal arrangement, stabilized by the atomic orbitals on the metal. Based on this newly elucidated bonding principle, we additionally propose a new family of polyhydrides that display a uniquely high coordination. We also report the first indications of how aromaticity may impact the reactivity of these molecules.

  14. Effect of metal support interaction on surface segregation in Pd Pt nanoparticles

    Science.gov (United States)

    De Sarkar, A.; Menon, Mahesh; Khanra, Badal C.

    2001-10-01

    In this work, we present the results of our Monte Carlo (MC) simulation studies for the segregation behavior of supported, clean and gas-covered Pd-Pt nanoparticles as a function of the metal-support interaction. For preferential Pd-support interaction, the base of the nanoparticle is found to get enriched with Pd atoms; while for preferential interaction of Pt atoms with the support the base gets enriched in Pt. The composition of the rest of the particle changes slightly with the metal-support interaction. The presence of oxygen and hydrogen atoms does not influence the role of the metal-support interaction on the surface composition of Pd-Pt nanoparticles. The simulation results are found to be in total agreement with the known experimental results.

  15. Stability and ordering properties of fcc alloys based on Rh, Ir, Pd, and Pt

    Science.gov (United States)

    Turchi, P. E. A.; Drchal, V.; Kudrnovský, J.

    2006-08-01

    Stability properties and ordering trends for the six face-centered cubic binary combinations of the four transition metals Rh, Ir, Pd, and Pt are examined in the context of electronic structure calculations. The method is based on a Green’s function description of the electronic structure of random alloys. Configurational order is treated within the generalized perturbation method. On one hand, the three alloys Pd-Rh, Pd-Ir, and Pt-Ir that have been studied experimentally are confirmed to behave like phase-separating systems. On the other hand, the other three mixtures Pd-Pt, Rh-Ir, and Pt-Rh, for which phase-separating trends have been inferred from experiments, are found to display chemical order with ordering of the (1 0 0) and (11/20) family types and a mixture of both, respectively. The origin of these results is discussed in terms of electronic structure properties.

  16. Energetic and structural analysis of 102-atom Pd-Pt nanoparticles

    Science.gov (United States)

    Pacheco-Contreras, Rafael; Arteaga-Guerrero, Alvaro; Borbon-Gonzalez, Dora Julia; Posada-Amarillas, Alvaro; Schoen, J. Christian; Johnston, Roy L.

    2009-03-01

    We present an extensive study of the structural and energetic changes of 102-atom PdmPt102-m nanoparticles as a function of composition m, where the interatomic interactions are modeled with the many-body Gupta potential. The minimum energy structures are obtained through a genetic algorithm. The excess energy is calculated, as well as the pair distribution function g(r). The radial distribution of the atoms is computed for each composition; the result indicates a multi-layer segregation for some compositions, with a shell growth sequence as follows: a core with a small number of Pd atoms is followed by an intermediate shell of Pt atoms and the external shell consists of Pd atoms. A region where Pd and Pt atoms are mixed is observed between the outermost and intermediate shells. Furthermore, the pure Pd102 and Pt102 nanoparticles have the same structure, while a variety of different structures are observed for the bimetallic clusters.

  17. Fabrication of monometallic (Co, Pd, Pt, Au) and bimetallic (Pt/Au, Au/Pt) thin films with hierarchical architectures as electrocatalysts

    Science.gov (United States)

    Qiu, Cuicui; Zhang, Jintao; Ma, Houyi

    2010-05-01

    Co thin films with novel hierarchical structures were controllably fabricated by simple electrochemical deposition in the absence of hard and soft templates, which were used as sacrificial templates to further prepare noble metal (Pd, Pt, Au) hierarchical micro/nanostructures via metal exchange reactions. SEM characterization demonstrated that the resulting noble metal thin films displayed hierarchical architectures. The as-prepared noble metal thin films could be directly used as the anode catalysts for the electro-oxidation of formic acid. Moreover, bimetallic catalysts (Pt/Au, Au/Pt) fabricated based on the monometallic Au, Pt micro/nanostructures exhibited the higher catalytic activity compared to the previous monometallic catalysts.

  18. Factors influencing the charge distribution on Pd x Pt y bimetallic nanoparticles

    Directory of Open Access Journals (Sweden)

    Carlos M. Celis-Cornejo

    2013-12-01

    Full Text Available We performed quantum mechanics calculations to elucidate the electronic behavior of Pd-Pt bimetallic nanoparticles, using density functional theory, in response to particle size and stoichiometric composition. Using neutrally charged nanoparticles and the Bader charge analysis, we found that external Pd atoms were positively charged, which agrees with previous XPS observations of supported Pd-Pt nanoparticles. From the calculations, unsupported nanoparticles exhibit an electron transfer from Pd to Pt. This result supports the idea that Pd electron-deficient species are possibly responsible of the hydrogenating function of these catalysts, in the hydrodesulfurization of dibenzothiophene. Additionally, it was found that the particle size does not affect the electronic charge distribution and the stoichiometric composition is the factor that greatly influences this property in nanoparticles.

  19. Study of PtPd Bimetallic Nanoparticles for Fuel Cell Applications

    OpenAIRE

    Esparza, Rodrigo; Santoveña,Alan; Ruíz-Baltazar, Alvaro; Angeles-Pascual,Alvaro; Bahena,Daniel; Maya-Cornejo,Jose; Ledesma-García, Janet; Pérez,Ramiro

    2017-01-01

    Bimetallic nanoparticles are of special interest for their potential applications for fuel cells, mainly for portable power applications. Among the bimetallic systems, Pt-Pd bimetallic nanoparticles have received great interest as they can be widely used as effective catalysts for various electrochemical reactions. In this work, Pt-Pd alloy bimetallic nanoparticles were synthesized through a chemical reduction method. The nanoparticles were characterized using aberration-corrected scanning/tr...

  20. Optimization of the Gilbert damping constant by annealing CoFeB films sandwiched by Ta, Ru, and Pd layers

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Cheong-Gu; Moon, Joon; Kim, Joo-Sung; Choe, Sug-Bong [Seoul National University, Seoul (Korea, Republic of); Moon, Cheol-Hyun; Min, Byoung-Chul [Korea Institute of Science and Technology, Daejeon (Korea, Republic of); Kim, Sang-Il; Park, Seung-Young [Korea Basic Science Institute, Daejeon (Korea, Republic of)

    2014-11-15

    The effects of annealing on the Gilbert damping constant and the magnetic properties are investigated in CoFeB films sandwiched by either Ta, Ru, or Pd layers. As the annealing temperature increases, the damping constant is found to be slightly decreased first and then, rapidly increased. The minimum damping constant is, thus, obtained with a 300 .deg. C-annealed Ta/CoFeB/Ta film while the samples with Ru and Pd layers exhibit their minimum at 200 .deg. C. The coercive field also exhibits a behavior similar to the damping constant; thus, an empirical correlation between them is proposed.

  1. Solid-solid transitions in Pd-Pt nanoalloys

    Science.gov (United States)

    Panizon, Emanuele; Ferrando, Riccardo

    2015-11-01

    Solid-solid transformations in Pd-Pt nanoalloys in the size range 32-38 atoms and for different compositions are computationally studied by the superposition approximation to the partition function, and by molecular dynamics simulations. A broad spectrum of transition types is shown to take place. These transition types are: (i) one-to-one type, in which the global minimum, which is dominant at low temperatures, transforms into another single isomer with increasing temperature; (ii) one-to-many type, in which the transition is from a single isomer to a family of other isomers; (iii) many-to-many type, in which the transition is between two different families of isomers; (iv) many-to-one type, in which the effect of vibrational entropy is to greatly reduce the number of relevant structures with increasing temperatures. We provide a rationale for these behaviors, which stem from the interplay between energetics and vibrational entropy effects. The vibrational entropy is explained by analyzing the vibrational density of states and the specific features of the normal modes. Quantum effects on the structural transitions are also discussed.

  2. Pt/Pd electrocatalyst electrons for fuel cells

    Science.gov (United States)

    Stonehart, P.

    1981-11-03

    This invention relates to improved electrochemical cells and to novel electrodes for use therein. In particular, the present invention comprises a fuel cell used primarily for the consumption of impure hydrogen fuels containing carbon monoxide or carbonaceous fuels where the electrode in contact with the fuel is not substantially poisoned by carbon monoxide. The anode of the fuel cell comprises a Pd/Pt alloy supported on a graphitized or partially graphitized carbon material. Fuel cells which comprise as essential elements a fuel electrode, an oxidizing electrode, and an electrolyte between said electrodes are devices for the direct production of electricity through the electrochemical combustion of a fuel and oxidant. These devices are recognized for their high efficiency as energy conversion units, since unlike conventional combustion engines, they are not subject to the limitations of the Carnot heat cycle. It is the primary object of the present invention to provide an electrode having high electrochemical activity for an electrochemical cell. It is another object of the present invention to provide an electrode having an electro-catalyst which is highly resistant to the corrosive environment of an electrochemical cell.

  3. Molybdenum-Doped PdPt@Pt Core-Shell Octahedra Supported by Ionic Block Copolymer-Functionalized Graphene as a Highly Active and Durable Oxygen Reduction Electrocatalyst.

    Science.gov (United States)

    Cho, Kie Yong; Yeom, Yong Sik; Seo, Heun Young; Kumar, Pradip; Lee, Albert S; Baek, Kyung-Youl; Yoon, Ho Gyu

    2017-01-18

    Development of highly active and durable electrocatalysts that can effectively electrocatalyze oxygen reduction reactions (ORR) still remains one important challenge for high-performance electrochemical conversion and storage applications such as fuel cells and metal-air batteries. Herein, we propose the combination of molybdenum-doped PdPt@Pt core-shell octahedra and the pyrene-functionalized poly(dimethylaminoethyl methacrylate)-b-poly[(ethylene glycol) methyl ether methacrylate] ionic block copolymer-functionalized reduced graphene oxide (Mo-PdPt@Pt/IG) to effectively augment the interfacial cohesion of both components using a tunable ex situ mixing strategy. The rationally designed Mo-PdPt@Pt core-shell octahedra have unique compositional benefits, including segregation of Mo atoms on the vertexes and edges of the octahedron and 2-3 shell layers of Pt atoms on a PdPt alloy core, which can provide highly active sites to the catalyst for ORR along with enhanced electrochemical stability. In addition, the ionic block copolymer functionalized graphene can facilitate intermolecular charge transfer and good stability of metal NPs, which arises from the ionic block copolymer interfacial layer. When the beneficial features of the Mo-PdPt@Pt and IG are combined, the Mo-PdPt@Pt/IG exhibits substantially enhanced activity and durability for ORR relative to those of commercial Pt/C. Notably, the Mo-PdPt@Pt/IG shows mass activity 31-fold higher than that of Pt/C and substantially maintains high activities after 10 000 cycles of intensive durability testing. The current study highlights the crucial strategies in designing the highly active and durable Pt-based octahedra and effective combination with functional graphene supports toward the synergetic effects on ORR.

  4. In Situ Synthesis and Characterization of Polyethyleneimine-Modified Carbon Nanotubes Supported PtRu Electrocatalyst for Methanol Oxidation

    Directory of Open Access Journals (Sweden)

    Xi Geng

    2015-01-01

    Full Text Available PtRu bimetallic nanoparticles were successfully synthesized on polyethyleneimine- (PEI- functionalized multiwalled carbon nanotubes (MWCNTs via an effective and facile polyol reduction approach. Noncovalent surface modification of MWCNTs with PEI was confirmed by FTIR and zeta potential measurements. The morphology, crystalline structure, and composition of the hybrid material were characterized by transmission electron microscopy (TEM, scanning electron microscopy (SEM, X-ray powder diffraction (XRD, and energy dispersive X-ray spectroscopy (EDX, respectively. According to SEM and TEM observations, PtRu nanoparticles with narrow size distribution were homogeneously deposited on PEI-MWCNTs. Cyclic voltammetry tests demonstrated that the as-prepared PtRu/PEI-MWCNTs nanocomposite had a large electrochemical surface area and exhibited enhanced electrocatalytic activity towards methanol oxidation in comparison with oxidized MWCNTs as catalyst support. PEI-functionalized CNTs, as useful building blocks for the assembly of Pt-based electrocatalyst, may have great potential for applications such as direct methanol fuel cell (DMFC.

  5. Synthesis of cubic PtPd alloy nanoparticles as anode electrocatalysts for methanol and formic acid oxidation reactions.

    Science.gov (United States)

    Lee, Jin-Yeon; Kwak, Da-Hee; Lee, Young-Woo; Lee, Seul; Park, Kyung-Won

    2015-04-14

    The electrocatalytic properties for electro-oxidation reactions of shape-controlled Pt-based catalysts have been improved by alloying with 2nd elements. In this study, we demonstrate cubic PtPd alloy nanoparticles synthesized using a thermal decomposition method. The cubic PtPd nanoparticles exhibit a homogeneous distribution of alloy nanostructures in the presence of Pt and Pd metallic phases. The improved electrocatalytic activity for the electro-oxidation reactions of methanol and formic acid as chemical fuels might be attributed to the cubic alloy nanostructures. Furthermore, the cubic PtPd alloy nanoparticles as electrocatalysts exhibit excellent stability for electro-oxidation reactions.

  6. Tetrapropylammonium ion influence on the synthesis of Pt Ru/carbon hybrids by hydrothermal carbonization; Influencia do ion tetrapropilamonio na sintese de hibridos PtRu/carbono por carbonizacao hidrotermica

    Energy Technology Data Exchange (ETDEWEB)

    Tusi, M.M.; Polanco, N.S.O.; Brandalise, M.; Correa, O.V.; Silva, A.C.; Oliveira Neto, A.; Linardi, M.; Spinace, E.V., E-mail: espinace@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2010-07-01

    PtRu/Carbon hybrid materials were prepared by hydrothermal carbonization using starch as carbon source and reducing agent and H{sub 2}PtCl{sub 6}.6H{sub 2}O e RuCl{sub 3}.xH{sub 2}O as metals source and catalyst of the carbonization process. The materials were prepared in the following conditions: without pH adjustment, in the absence and in the presence of tetrapropylammonium chloride (TPACl), and adjusting the pH using potassium hydroxide (KOH) or tetrapropylammonium hydroxide (TPAOH). The obtained materials were treated under argon atmosphere at 900 deg C and characterized by SEM/EDX, BET isotherm, XRD and TEM. The electro-oxidation of methanol was studied by chronoamperometry. The material prepared using TPAOH showed the best performance for methanol electro-oxidation. (author)

  7. Solvothermal synthesis of Pt-Pd alloys with selective shapes and their enhanced electrocatalytic activities

    Science.gov (United States)

    Zhang, Zhi-Cheng; Hui, Jun-Feng; Guo, Zhen-Guo; Yu, Qi-Yu; Xu, Biao; Zhang, Xin; Liu, Zhi-Chang; Xu, Chun-Ming; Gao, Jin-Sen; Wang, Xun

    2012-03-01

    Pt-Pd bimetallic alloy nanostructures with highly selective morphologies such as cube, bar, flower, concave cube, and dendrite have been achieved through a facile one-pot solvothermal synthesis. The effects of shape-controllers (sodium dodecyl sulfate (SDS), ethylenediamine-tetraacetic acid disodium salt (EDTA-2Na), NaI) and solvents (water/DMF) on the morphologies were systematically investigated. The electrocatalytic activities of these Pt-Pd alloy nanostructures toward formic acid oxidation were tested. The results indicated that these alloy nanocrystals exhibited enhanced and shape-dependent electrocatalytic activity toward formic acid oxidation compared to commercial Pt black and Pt/C catalysts.Pt-Pd bimetallic alloy nanostructures with highly selective morphologies such as cube, bar, flower, concave cube, and dendrite have been achieved through a facile one-pot solvothermal synthesis. The effects of shape-controllers (sodium dodecyl sulfate (SDS), ethylenediamine-tetraacetic acid disodium salt (EDTA-2Na), NaI) and solvents (water/DMF) on the morphologies were systematically investigated. The electrocatalytic activities of these Pt-Pd alloy nanostructures toward formic acid oxidation were tested. The results indicated that these alloy nanocrystals exhibited enhanced and shape-dependent electrocatalytic activity toward formic acid oxidation compared to commercial Pt black and Pt/C catalysts. Electronic supplementary information (ESI) available: See DOI: 10.1039/c2nr12135b

  8. Preparation and characterization of nano-sized Pt-Ru/C catalysts and their superior catalytic activities for methanol and ethanol oxidation.

    Science.gov (United States)

    Şen, Selda; Şen, Fatih; Gökağaç, Gülsün

    2011-04-21

    Carbon-supported PtRu nanoparticles (Ru/Pt: 0.25) were prepared by three different methods; simultaneous reduction of PtCl(4) and RuCl(3) (catalyst I) and changing the reduction order of PtCl(4) and RuCl(3) (catalysts II and III) to enhance the performance of the anodic catalysts for methanol and ethanol oxidation. Structure, microstructure and surface characterizations of all the catalysts were carried out by X-ray diffraction (XRD), transmission electron microscopy (TEM) coupled with energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The results of the XRD analysis showed that all catalysts had a face-centered cubic (fcc) structure with different and smaller lattice parameters than that of pure platinum, showing that the Ru incorporates into the Pt fcc structure by different ratios in all the catalysts. The typical particle sizes of all catalysts were in the range of 2-3 nm. The most active and stable catalyst for methanol and ethanol oxidation is catalyst III, in which a large amount (more than 90%) of PtRu alloy formation was observed. It has been found that this catalyst is about 8.0 and 33.4 times more active at ∼0.60 V towards the methanol and ethanol oxidation reactions, respectively, compared to the commercial Pt catalyst.

  9. Synthesis of higher alcohols from CO2 hydrogenation over a PtRu/Fe2O3 catalyst under supercritical condition.

    Science.gov (United States)

    He, Zhenhong; Qian, Qingli; Zhang, Zhaofu; Meng, Qinglei; Zhou, Huacong; Jiang, Zhiwei; Han, Buxing

    2015-12-28

    Hydrogenation of CO(2) to alcohols is of great importance, especially when producing higher alcohols. In this work, we synthesized heterogeneous PtRu/Fe(2)O(3), in which the Pt and Ru bimetallic catalysts were supported on Fe(2)O(3). The catalyst was used to catalyse CO(2) hydrogenation to alcohols. It was demonstrated that the activity and selectivity could be tuned by the bimetallic composition, and the catalyst with a Pt to Ru molar ratio of 1:2 (Pt(1)Ru(2)/Fe(2)O(3)) had high activity and selectivity at 200°C, which is very low for heterogeneous hydrogenation of CO(2) to produce higher alcohols. The conversion and the selectivity increased with increasing pressures of CO(2) and/or H(2). The catalyst could be reused at least five times without any obvious change in activity or selectivity.

  10. Dynamics of electrocatalytic oxidation of ethylene glycol, methanol and formic acid at MWCNT platform electrochemically modified with Pt/Ru nanoparticles

    CSIR Research Space (South Africa)

    Maxakato, NW

    2010-03-01

    Full Text Available Comparative electrocatalytic behavior of functionalized multiwalled carbon nanotubes (fMWCNTs) electrodecorated with Pt/Ru nanoparticles towards the oxidation of methanol (MeOH), ethylene glycol (EG) and formic acid (FA) has been investigated...

  11. Gram-Scale-Synthesized Pd2Co-Supported Pt Monolayer Electrocatalysts for Oxygen Reduction Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, W.; Sasaki, K; Su, D; Zhu, Y; Wang, J; Adzic, R

    2010-01-01

    Gram-scale synthesis of Pt{sub ML} electrocatalysts with a well-defined core-shell structure has been carried out using method involving galvanic displacement of an underpotential deposition Cu layer. The Pt shell thickness can be controlled by stepwise deposition. The Pt{at}Pd{sub 2}Co/C nanoparticles were characterized by X-ray powder diffraction, aberration-corrected scanning transmission electron microscopy, high-resolution energy-loss spectrometry, and in situ X-ray absorption spectroscopy. A complete Pt shell of 0.6 nm on a Pd{sub 2}Co core has been confirmed. The Pt{at}Pd{sub 2}Co/C core-shell electrocatalysts showed a very high activity for the oxygen reduction reaction; the Pt mass and specific activity were 0.72 A mg{sub Pt}{sup -1} and 0.5 mA cm{sup -2}, respectively (3.5 and 2.5 times higher than the corresponding values for commercial Pt catalysts), at 0.9 V in 0.1 M HClO{sub 4} at room temperature. In an accelerated potential cycling test, a loss in active surface area and a decrease in catalytic activity for gram-scale-synthesized Pt{sub ML} catalysts were also determined.

  12. Carbon nanotubes-Nafion composites as Pt-Ru catalyst support for methanol electro-oxidation in acid media

    Institute of Scientific and Technical Information of China (English)

    Shengzhou Chen; Fei Ye; Weiming Lin

    2009-01-01

    Carbon nanotubes-Nafion (CNTs-Nafion) composites were prepared by impregnated CNTs with Nafion in ethanol solution and characterized by FT-IR. Pt-Ru catalysts supported on CNTs-Nafion composites were synthesized by microwave-assisted polyol process. The physical and electrochemical properties of the catalysts were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), CO stripping voltammetry, cyclic voltammetry (CV) and chronoamperometry (CA). The results showed that the Nafion incorporation in CNTs-Nafion composites did not significantly alter the oxygen-containing groups on the CNTs surface. The Pt-Ru catalyst supported on CNTs-Nafion composites with 2 wt% Nafion showed good dispersion and the best CO oxidation and methanol electro-oxidation activities.

  13. Enhanced Stability of PtRu Supported on N-Doped Carbon for the Anode of a DMFC

    Science.gov (United States)

    2012-09-18

    Stability of PtRu Supported on N-Dop Block 13: Supplementary Note © 2012 . Published in Journal of the Electrochemical Society , Vol. Ed. 0 159, (11...sign up http://jes.ecsdl.org/subscriptions go to: Journal of The Electrochemical SocietyTo subscribe to © 2012 The Electrochemical Society F768...Journal of The Electrochemical Society , 159 (11) F768-F778 (2012) 0013-4651/2012/159(11)/F768/11/$28.00 © The Electrochemical Society Enhanced

  14. Millimeter thick ionic polymer membrane-based IPMCs with bimetallic Pd-Pt electrodes

    Science.gov (United States)

    Palmre, Viljar; Kim, Sung Jun; Kim, Kwang

    2011-04-01

    Ionic polymer metal composites (IPMC) are a low-voltage driven Electroactive Polymers (EAP) that can be used as actuators or sensors. This paper presents a comparative study of millimeter thick ionic polymer membrane-based IPMCs with high-performance Pd-Pt electrodes and conventional Pt electrodes. IPMCs assembled with different electrodes are characterized in terms of electromechanical, -chemical and mechanolelectrical properties. The SEM and energy dispersive X-ray (EDS) analysis are used to investigate the distribution of deposited electrode metals in the cross-section of Pd-Pt IPMCs. The study shows that IPMCs assembled with millimeter thick ionic polymer membranes and bimetallic Pd-Pt electrodes are superior in mechanoelectrical sensing and, also, show considerably higher blocking forces compared to the conventional type of IPMCs. Blocking forces more than 30 grams are measured under 4V DC. However, the actuation response is slower than conventional IPMCs having approximately 0.2-0.3 mm thickness.

  15. Highly efficient anode catalyst with a Ni@PdPt core–shell nanostructure for methanol electrooxidation in alkaline media

    Institute of Scientific and Technical Information of China (English)

    Pei-shu Yu; Chun-tao Liu; Bo Feng; Jia-feng Wan; Li Li; Chun-yu Du

    2015-01-01

    To enhance the electrocatalytic activity of anode catalysts used in alkaline-media direct methanol fuel cells (DMFCs), a Ni@PdPt electrocatalyst was successfully prepared using a three-phase-transfer method. The Ni@PdPt electrocatalyst was characterized by X-ray dif-fraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM) techniques. The experimental results indicate that the average particle size of the core–shell-structured Ni@PdPt electrocatalyst is approxi-mately 5.6 nm. The Ni@PdPt electrocatalyst exhibits a catalytic activity 3.36 times greater than that of PdPt alloys for methanol oxidation in alkaline media. The developed Ni@PdPt electrocatalyst offers a promising alternative as a highly electrocatalytically active anode catalyst for alkaline DMFCs.

  16. Heterostructured Au/Pd-M (M = Au, Pd, Pt) nanoparticles with compartmentalized composition, morphology, and electrocatalytic activity

    Science.gov (United States)

    Lutz, Patrick S.; Bae, In-Tae; Maye, Mathew M.

    2015-09-01

    The synthesis, processing, and galvanic exchange of three heterostructured nanoparticle systems is described. The surface accessibility and redox potential of a Au/Pd-Ag dumbbell nanoparticle, where a Au/Pd core/shell region, and a silver region make up the domains, was used to prepare the new nanostructures with controlled composition, morphology, and microstructure. Results indicate that the silver domain was particularly susceptible to galvanic displacement, and was exchanged to Au/Pd-M (M = Au, Pd, Pt). Interestingly, the dumbbell morphology remained after exchange, and the silver region was transformed to hollow, parachute, or concentric domains respectively. The morphology and microstructure change was visualized via TEM and HRTEM, and the composition changes were probed via STEM-EDS imaging and XPS. The electrocatalytic activity of the Au/Pd-M towards methanol oxidation was studied, with results indicating that the Au/Pd-Pt nanoparticles had high activity attributed to the porous nature of the platinum domains.The synthesis, processing, and galvanic exchange of three heterostructured nanoparticle systems is described. The surface accessibility and redox potential of a Au/Pd-Ag dumbbell nanoparticle, where a Au/Pd core/shell region, and a silver region make up the domains, was used to prepare the new nanostructures with controlled composition, morphology, and microstructure. Results indicate that the silver domain was particularly susceptible to galvanic displacement, and was exchanged to Au/Pd-M (M = Au, Pd, Pt). Interestingly, the dumbbell morphology remained after exchange, and the silver region was transformed to hollow, parachute, or concentric domains respectively. The morphology and microstructure change was visualized via TEM and HRTEM, and the composition changes were probed via STEM-EDS imaging and XPS. The electrocatalytic activity of the Au/Pd-M towards methanol oxidation was studied, with results indicating that the Au/Pd-Pt nanoparticles had

  17. Fast preparation of PtRu catalysts supported on carbon nanofibers by the microwave-polyol method and their application to fuel cells.

    Science.gov (United States)

    Tsuji, Masaharu; Kubokawa, Masatoshi; Yano, Ryuto; Miyamae, Nobuhiro; Tsuji, Takeshi; Jun, Mun-Suk; Hong, Seonghwa; Lim, Seongyop; Yoon, Seong-Ho; Mochida, Isao

    2007-01-16

    PtRu alloy nanoparticles (24 +/- 1 wt %, Ru/Pt atomic ratios = 0.91-0.97) supported on carbon nanofibers (CNFs) were prepared within a few minutes by using a microwave-polyol method. Three types of CNFs with very different surface structures, such as platelet, herringbone, and tubular ones, were used as new carbon supports. The dependence of particles sizes and electrochemical properties on the structures of CNFs was examined. It was found that the methanol fuel cell activities of PtRu/CNF catalysts were in the order of platelet > tubular > herringbone. The methanol fuel cell activities of PtRu/CNFs measured at 60 degrees C were 1.7-3.0 times higher than that of a standard PtRu (29 wt %, Ru/Pt atomic ratio = 0.92) catalyst loaded on carbon black (Vulcan XC72R) support. The best electrocatalytic activity was obtained for the platelet CNF, which is characterized by its edge surface and high graphitization degree.

  18. Effects of the Electrodeposition Time in the Synthesis of Carbon-Supported Pt(Cu and Pt-Ru(Cu Core-Shell Electrocatalysts for Polymer Electrolye Fuel Cells

    Directory of Open Access Journals (Sweden)

    Griselda Caballero-Manrique

    2016-08-01

    Full Text Available Pt(Cu/C and Pt-Ru(Cu/C electrocatalysts with core-shell structure supported on Vulcan Carbon XC72R have been synthesized by potentiostatic deposition of Cu nanoparticles on the support, galvanic exchange with Pt and spontaneous deposition of Ru species. The duration of the electrodeposition time of the different species has been modified and the obtained electrocatalysts have been characterized using electrochemical and structural techniques. The High Resolution Transmission Electron Microscopy (HRTEM, Fast Fourier Transform (FFT and Energy Dispersive X-ray (EDX microanalyses allowed the determining of the effects of the electrodeposition time on the nanoparticle size and composition. The best conditions identified from Cyclic Voltammetry (CV corresponded to onset potentials for CO and methanol oxidation on Pt-Ru(Cu/C of 0.41 and 0.32 V vs. the Reversible Hydrogen Electrode (RHE, respectively, which were smaller by about 0.05 V than those determined for Ru-decorated commercial Pt/C. The CO oxidation peak potentials were about 0.1 V smaller when compared to commercial Pt/C and Pt-Ru/C. The positive effect of Cu was related to its electronic effect on the Pt shells and also to the generation of new active sites for CO oxidation. The synthesis conditions to obtain the best performance for CO and methanol oxidation on the core-shell Pt-Ru(Cu/C electrocatalysts were identified. When compared to previous results in literature for methanol, ethanol and formic acid oxidation on Pt(Cu/C catalysts, the present results suggest an additional positive effect of the deposited Ru species due to the introduction of the bifunctional mechanism for CO oxidation.

  19. Reforming of Ethanol to Produce Hydrogen over PtRuMg/ZrO2 Catalyst

    Directory of Open Access Journals (Sweden)

    Josh Y. Z. Chiou

    2012-01-01

    Full Text Available A modified PtRu/ZrO2 catalyst with Mg is evaluated for the oxidative steam reforming of ethanol (OSRE and the steam reforming of ethanol (SRE. In order to understand the variation in the reaction mechanism on OSRE and SRE, further analysis of both fresh and used catalyst is concentrated on for TEM, TG, Raman, and TPR characterization. The results show that the OSRE reaction requires a higher temperature (∼390°C to achieve 100% ethanol conversion than the SRE reaction (∼2500°C. The distribution of CO is minor for both reactions (< 5% for OSRE, < 1% for SRE. This demonstrates that the water gas shift (WGS reaction is an important side-reaction in the reforming of ethanol to produce H2 and CO2. A comparison of the temperature of WGS (WGS shows it is lower for the SRE reaction (WGS∼250°C for SRE, ~340°C for OSRE.

  20. Microwave synthesis of polymer-embedded Pt-Ru catalyst for direct methanol fuel cell.

    Science.gov (United States)

    Bensebaa, Farid; Farah, Abdiaziz A; Wang, Dashan; Bock, Christina; Du, Xiaomei; Kung, Judy; Le Page, Yvon

    2005-08-18

    Platinum-ruthenium nanoparticles stabilized within a conductive polymer matrix are prepared using microwave heating. Polypyrrole di(2-ethylhexyl) sulfosuccinate, or PPyDEHS, has been chosen for its known electrical conductivity, thermal stability, and solubility in polar organic solvents. A scalable and quick two-step process is proposed to fabricate alloyed nanoparticles dispersed in PPyDEHS. First a mixture of PPyDEHS and metallic precursors is heated in a microwave under reflux conditions. Then the nanoparticles are extracted by centrifugation. Physical characterization by TEM shows that crystalline and monodisperse alloyed nanoparticles with an average size of 2.8 nm are obtained. Diffraction data show that crystallite size is around 2.0 nm. Methanol electro-oxidation data allow us to propose these novel materials as potential candidates for direct methanol fuel cells (DMFC) application. The observed decrease in sulfur content in the polymer upon incorporation of PtRu nanoparticles may have adversely affected the measured catalytic activity by decreasing the conductivity of PPyDEHS. Higher concentration of polymer leads to lower catalyst activity. Design and synthesis of novel conductive polymers is needed at this point to enhance the catalytic properties of these hybrid materials.

  1. Electrochemical oxidation of ammonia-containing wastewater using Ti/RuO2-Pt electrode

    Directory of Open Access Journals (Sweden)

    Wei-wu HU

    2009-12-01

    Full Text Available The electrochemical oxidation degradation processes for artificial and actual wastewater containing ammonia were carried out with a Ti/RuO2-Pt anode and a Ti plate cathode. We studied the effects of different current densities, space sizes between the two electrodes, and amounts of added NaCl on ammonia-containing wastewater treatment. It was shown that, after a 30-min treatment under the optimal conditions, which were a current density of 20 mA/cm2, a space size between the two electrodes of 1 cm, and an added amount of 0.5 g/L of NaCl, the COD concentration in municipal wastewater was 40 mg/L, a removal rate of 90%; and the NH3-N concentration was 7 mg/L, a removal rate of 88.3%. The effluent of municipal wastewater qualified for Class A of the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB18918-2002.

  2. Partition coefficients for Ni, Cu, Pd, Pt, Rh, and Ir between monosulfide solid solution and sulfide liquid and the formation of compositionally zoned Ni-Cu sulfide bodies by fractional crystallization of sulfide liquid

    DEFF Research Database (Denmark)

    Barnes, S.J.; Makovicky, E.; Makovicky, M.

    1996-01-01

    Many nickel–copper sulfide orebodies contain Cu- and Fe-rich portions. The Fe-rich ore is generally richer in Os, Ir, Ru, and Rh and poorer in Pt, Pd, and Au than the Cu-rich ore. In komatiite-hosted ores Ni tends to be concentrated in the Cu-rich ore, whereas in tholeiitic ores it tends to be co...

  3. PdCuPt Nanocrystals With Multi-branches for Enzyme-free Glucose Detection

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Shaofang; Zhu, Chengzhou; Song, Junhua; Engelhard, Mark H.; Xia, Haibing; Du, Dan; Lin, Yuehe

    2016-08-05

    By carefully controlling the synthesis condition, branched PtCu bimetallic templates were synthesized in aqueous solution. After the galvanic replacement reaction between PtCu templates and the Pt precursors, PdCuPt trimetallic nanocrystals with branched structures were obtained. Owing to the open structure and the optimized composition, the electrochemical experimental results reveal that the PdCuPt trimetallic nanocrystals exhibit high electrocatalytic activity, selectivity and stability for the oxidation of glucose in alkaline solution. In details, a sensitivity of 378 μA/mM/cm2 and a detection limit of 1.29 μM can be achieved. The good electrocatalytic performance should be attributed to the unique branched nanostructure as well as the synergistic effect among metals. The superior catalytic properties suggest that these nanocrystals are promising for enzyme-free detection of glucose.

  4. Structural, electronic, elastic and superconducting properties of noble metal nitrides MN{sub 2} (M = Ru, Rh, Pd)

    Energy Technology Data Exchange (ETDEWEB)

    Puvaneswari, S. [Department of Physics, E.M.G. Yadava Women' s College, Madurai, Tamilnadu 625 014 (India); Rajeswarapalanichamy, R., E-mail: rrpcaspd2003@gmail.com [Department of Physics, N.M.S.S. Vellaichamy Nadar College, Madurai, Tamilnadu 625019 (India); Sudha Priyanga, G. [Department of Physics, N.M.S.S. Vellaichamy Nadar College, Madurai, Tamilnadu 625019 (India)

    2015-02-01

    The structural stability, electronic structure, elastic and superconducting properties of noble metal nitrides MN{sub 2} (M = Ru, Rh, Pd) are investigated in tetragonal (P4/mbm), fluorite (Fm3m), orthorhombic (Pnnm), pyrite (Pa-3) and hexagonal (P6/mmm) phases using first principles calculations. The calculated lattice parameters are in good agreement with other theoretical results. Among the considered structures, RhN{sub 2} and PdN{sub 2} are found to be most stable in tetragonal structure, whereas RuN{sub 2} is stable in fluorite structure. A sequence of structural phase transition is predicted under high pressure in these metal nitrides. The electronic structure reveals that these nitrides are metallic. These metal nitrides are found to be covalent, ionic and metallic in the stable phase. The observations show that these metal nitrides are mechanically stable at ambient condition. The superconducting transition temperatures for RuN{sub 2}, RhN{sub 2} and PdN{sub 2} are found to be 1.65 K, 5.01 K and 8.7 K respectively. - Highlights: • Electronic, structural and elastic properties of RuN{sub 2}, RhN{sub 2} and PdN{sub 2} are studied. • A pressure induced structural phase transition is predicted. • Electronic structure reveals that these materials exhibit metallic behavior. • High bulk modulus indicates that RuN{sub 2}, RhN{sub 2} and PdN{sub 2} are superhard materials. • Superconducting temperature values are reported.

  5. Electrochemical characterization of IrO{sub 2}-Pt and RuO{sub 2}-Pt mixtures as bifunctional electrodes for unitized regenerative fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Escalante-Garcia, I.L.; Duron-Torres, S.M. [Univ. Autonoma de Zacatecas, Zacatecas (Mexico). Unidad Academica de Ciencias Quimicas; Cruz, J.C.; Arriaga-Hurtado, L.G. [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, Pedro Escobedo (Mexico)

    2010-07-15

    A unitized regenerative fuel cell (URFC) is a single electrochemical cell that has the potential to meet the required features of an idealized energy cycle whereby hydrogen can be produced from renewable energy sources. A URFC is a system which can operate as a polymer electrolyte water electrolyzer (PEMWE) or as a polymer electrolyte fuel cell (PEMFC). In the PEMWE mode, water is converted into hydrogen and oxygen by using electricity from solar or wind energy. In the PEMFC mode, the stored hydrogen and oxygen are supplied to generate electricity and water. Combining PEMWEs and PEMFCs remains a great challenge because several practical and structural features must be considered. The limiting reaction steps at the oxygen electrode for PEMFC or PEMWE are the oxygen reduction reaction (ORR) and the water oxidation reaction (OER), respectively. The high-efficiency therefore depends on the type of electrocatalysts and the capability of the oxygen electrode to operate under PEMFC or PEMWE conditions. As such, much research has gone into the development of a new oxygen electrode design for URFCs. Several bifunctional electrodes for OER and ORR were designed in this study using platinum (Pt) and iridium oxide (IrO{sub 2}) electrocatalysts or Pt and ruthenium oxide (RuO{sub 2}) supported electrocatalysts on Ebonex{sup R}. According to electrochemical characterization by CV, LV and EIS in aqueous 0.5 M H{sub 2}SO{sub 4}, IrO{sub 2}-Pt and RuO{sub 2}-Pt supported on Ebonex have high electrocatalytic properties for ORR and OER, indicating potential use in URFCs. IrO{sub 2} based electrodes were more stable than RuO{sub 2} based electrodes. 31 refs., 2 tabs., 6 figs.

  6. Mixed-phase Pd-Pt bimetallic alloy on graphene oxide with high activity for electrocatalytic applications

    Science.gov (United States)

    Khan, Majid; Yousaf, Ammar Bin; Chen, Mingming; Wei, Chengsha; Wu, Xibo; Huang, Ningdong; Qi, Zeming; Li, Liangbin

    2015-05-01

    Bimetallic PdPt alloy nanoparticles on graphene oxide (GO) have been prepared by a simple and facile chemical route, in which the reduction of metal precursors is carried out using CO as a reductant. Structural and morphological characterizations of GO/PdPt composites are performed using X-ray diffraction, X-ray photoelectron spectroscopy analysis and transmission electron microscopy. It is found that PdPt bimetallic nanoparticles are successfully synthesized and uniformly attached on the graphene sheets. The electrocatalytic and electrochemical properties of GO/PdPt composites including methanol oxidation reaction (MOR), oxygen reduction reaction (ORR) and methanol tolerant oxygen reduction reaction (MTORR) are studied in HClO4 aqueous solution. A significant improvement in the electrocatalytic activities is observed by increasing the atomic ratio of Pt in PdPt bimetallic alloys compared to the freestanding Pd nanoparticles on GO. The prepared GO/PdPt composites with an (Pd:Pt) atomic ratio of 40:60 exhibits higher methanol oxidation activity, higher specific ORR activity and better tolerance to CO poisoning. The results can be attributed to the collective effects of the PdPt nanoparticles and the enhanced electron transfer of graphene.

  7. Verifying predictions of the L13 crystal structure in Cd-Pt and Pd-Pt by exhaustive enumeration

    Science.gov (United States)

    Hart, Gus L. W.

    2009-07-01

    In 2001, S. Müller and A. Zunger [Phys. Rev. Lett. 87, 165502 (2001)] predicted a never-before-observed crystal structure in Ag-Pd. Recently, Curtarolo predicted the same structure to be stable in Pt-Cd and Pt-Pd [S. Curtarolo , CALPHAD: Comput. Coupling Phase Diagrams Thermochem. 29, 163 (2005)]. The predicted structure is unique in several ways. Though never seen in any other face-centered-cubic-based intermetallic binary compound or ordered alloy, it is relatively simple—it contains only four atoms per unit cell. Furthermore, the structure is the only one of this small size, except the L12 structure, that cannot be characterized as a simple stacking of layers where each layer contains only one kind of atom. We construct a first-principles-based Hamiltonian and search it for the thermodynamically stable (lowest energy) structures. Using a (practically) exhaustive enumeration of about three million of the most likely candidate structures, we find that this new structure, designated L13 , is indeed a ground state in both Cd-Pt and Pd-Pt. Experimental efforts to validate the predictions are underway.

  8. One-step synthesis of PtPdAu ternary alloy nanoparticles on graphene with superior methanol electrooxidation activity

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Yuzhen; Gu Yonge; Lin Shaoxiong; Wei Jinping; Wang Zaihua [Department of Chemistry, Lanzhou University, Lanzhou 730000 (China); Wang Chunming, E-mail: wangcm@lzu.edu.cn [Department of Chemistry, Lanzhou University, Lanzhou 730000 (China); Du Yongling; Ye Weichun [Department of Chemistry, Lanzhou University, Lanzhou 730000 (China)

    2011-10-01

    Highlights: > PtPdAu nanoparticles were synthesized on graphene sheets via chemical reduction method. > The prepared PtPdAu nanoparticles were ternary alloy with fcc structure. > The catalyst exhibited superior catalytic activity and stability for MOR in alkaline. - Abstract: Well-dispersed PtPdAu ternary alloy nanoparticles were synthesized on graphene sheets via a simple one-step chemical reduction method in ethylene glycol (EG) and water system, in which EG served as both reductive and dispersing agent. The electrocatalytic activity of PtPdAu/G was tested by methanol oxidation reaction (MOR). The catalyst was further characterized by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), which indicated that the as-synthesized PtPdAu nanoparticles with alloy structures were successfully dispersed on the graphene sheets. Electrocatalytic properties of the catalyst for MOR in alkaline have been investigated by cyclic voltammetry (CV), chronoamperometry and Tafel curves. The electrocatalytic activity and stability of PtPdAu/G were superior to PtPd/G, PtAu/G and Pt/G. In addition, the anodic peak current on PtPdAu/G catalyst was proportional to the concentration of methanol in the range of 0.05-1.00 M. This study implies that the prepared catalyst have great potential applications in fuel cells.

  9. Surface-Limited Synthesis of Pt Nanocluster Decorated Pd Hierarchical Structures with Enhanced Electrocatalytic Activity toward Oxygen Reduction Reaction.

    Science.gov (United States)

    Yang, Tao; Cao, Guojian; Huang, Qingli; Ma, Yanxia; Wan, Sheng; Zhao, Hong; Li, Na; Sun, Xia; Yin, Fujun

    2015-08-12

    Exploring superior catalysts with high catalytic activity and durability is of significant for the development of an electrochemical device involving the oxygen reduction reaction. This work describes the synthesis of Pt-on-Pd bimetallic heterogeneous nanostructures, and their high electrocatalytic activity toward the oxygen reduction reaction (ORR). Pt nanoclusters with a size of 1-2 nm were generated on Pd nanorods (NRs) through a modified Cu underpotential deposition (UPD) process free of potential control and a subsequent surface-limited redox reaction. The Pt nanocluster decorated Pd nanostructure with a ultralow Pt content of 1.5 wt % exhibited a mass activity of 105.3 mA mg(-1) (Pt-Pd) toward ORR, comparable to that of the commercial Pt/C catalyst but 4 times higher than that of carbon supported Pd NRs. More importantly, the carbon supported Pt-on-Pd catalyst displays relatively small losses of 16% in electrochemical surface area (ECSA) and 32% in mass activity after 10 000 potential sweeps, in contrast to respective losses of 46 and 64% for the commercial Pt/C catalyst counterpart. The results demonstrated that Pt decoration might be an efficient way to improve the electrocatalytic activity of Pd and in turn allow Pd to be a promising substitution for commercial Pt catalyst.

  10. Effective-medium calculations for hydrogen in Ni, Pd, and Pt

    DEFF Research Database (Denmark)

    Christensen, Ole Bøssing; Stoltze, Per; Jacobsen, Karsten Wedel;

    1990-01-01

    The effective-medium theory is applied to a study of the energetics of the hydrides of Ni, Pd, and Pt, stressing the properties of PdHθ for 0≤θ≤1. The calculated heat of solution and the heat of hydride formation for the three systems agree very well with experiment. We determine the favored...... structure for PdHθ by calculating the total energy and lattice expansion of different configurations. Vibrational frequencies and diffusion barriers of H in Pd are also treated. A simple and transparent physical picture of the hydrogen-metal interaction is developed. From the calculated energetics we make...

  11. Structures of Pd(CN)2 and Pt(CN)2: intrinsically nanocrystalline materials?

    Science.gov (United States)

    Hibble, Simon J; Chippindale, Ann M; Bilbé, Edward J; Marelli, Elena; Harris, Peter J F; Hannon, Alex C

    2011-01-03

    Analysis and modeling of X-ray and neutron Bragg and total diffraction data show that the compounds referred to in the literature as "Pd(CN)(2)" and "Pt(CN)(2)" are nanocrystalline materials containing small sheets of vertex-sharing square-planar M(CN)(4) units, layered in a disordered manner with an intersheet separation of ~3.44 Å at 300 K. The small size of the crystallites means that the sheets' edges form a significant fraction of each material. The Pd(CN)(2) nanocrystallites studied using total neutron diffraction are terminated by water and the Pt(CN)(2) nanocrystallites by ammonia, in place of half of the terminal cyanide groups, thus maintaining charge neutrality. The neutron samples contain sheets of approximate dimensions 30 Å × 30 Å. For sheets of the size we describe, our structural models predict compositions of Pd(CN)(2)·xH(2)O and Pt(CN)(2)·yNH(3) (x ≈ y ≈ 0.29). These values are in good agreement with those obtained from total neutron diffraction and thermal analysis, and are also supported by infrared and Raman spectroscopy measurements. It is also possible to prepare related compounds Pd(CN)(2)·pNH(3) and Pt(CN)(2)·qH(2)O, in which the terminating groups are exchanged. Additional samples showing sheet sizes in the range ~10 Å × 10 Å (y ~ 0.67) to ~80 Å × 80 Å (p = q ~ 0.12), as determined by X-ray diffraction, have been prepared. The related mixed-metal phase, Pd(1/2)Pt(1/2)(CN)(2)·qH(2)O (q ~ 0.50), is also nanocrystalline (sheet size ~15 Å × 15 Å). In all cases, the interiors of the sheets are isostructural with those found in Ni(CN)(2). Removal of the final traces of water or ammonia by heating results in decomposition of the compounds to Pd and Pt metal, or in the case of the mixed-metal cyanide, the alloy, Pd(1/2)Pt(1/2), making it impossible to prepare the simple cyanides, Pd(CN)(2), Pt(CN)(2), or Pd(1/2)Pt(1/2)(CN)(2), by this method.

  12. The electrochemical atomic layer deposition of Pt and Pd nanoparticles on Ni foam for the electro oxidation of alcohols

    CSIR Research Space (South Africa)

    Modibedi, RM

    2013-01-01

    Full Text Available of the electrocatalytic activity of the prepared catalysts. TABLE I. Electrochemical Activity of Pt and Pd Towards the Oxidation of Methanol. Catalyst Onset potential (V vs Ag/AgCl) If/Ib Pt/Carbon paper 0.41 4.30 Pt/Ni foam 0.38 2.16 Pd/Carbon paper* Pd.../Ni foam* -0.456 -0.429 2.86 1.30 *: methanol oxidation performed in alkaline medium TABLE II. Electrochemical Activity of Pd Towards the Oxidation of Ethanol in alkaline electrolyte. Catalyst Onset potential (V vs Ag/AgCl) If/Ib Pd...

  13. Anamperometric superoxide anion radicalbiosensor based on SOD/PtPd-PDARGO modified electrode.

    Science.gov (United States)

    Tang, Jie; Zhu, Xiang; Niu, Xiangheng; Liu, Tingting; Zhao, Hongli; Lan, Minbo

    2015-05-01

    In the present work, a high-performance enzyme-based electrochemical sensor for the detection of superoxide anion radical (O2(●-)) is reported. Firstly, we employed a facile approach to synthesize PtPd nanoparticles (PtPd NPs) on chemically reduced graphene oxide (RGO) coated with polydopamine (PDA). The prepared PtPd-PDARGO composite was well characterized by transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectra, X-ray diffraction, X-ray photoelectron spectroscopy and electrochemical methods. Then the assembled composite was used as a desired electrochemcial interface for superoxide dismutase (SOD) immobilization. Owing to the PDA layer as well as the synergistic effect of PtPd NPs, the fabricated SOD/PtPd-PDARGO sensor exhibited an outstanding sensitivity of 909.7 μA mM(-1) cm(-2) upon O2(●-) in a linear range from 0.016 mM to 0.24 mM (R(2)=0.992), with a low detection limit of 2 μM (S/N=3) and excellent selectivity, good reproducibility as well as favorable long-term stability.

  14. Structure and superconducting transition in splat-cooled U–T alloys (T = Mo, Pd, Pt)

    Energy Technology Data Exchange (ETDEWEB)

    Kim-Ngan, N.-T.H., E-mail: tarnawsk@up.krakow.pl [Institute of Physics, Pedagogical University, Podchorazych 2, 30-084 Krakow (Poland); Paukov, M. [Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 12116 Prague (Czech Republic); Sowa, S.; Krupska, M. [Institute of Physics, Pedagogical University, Podchorazych 2, 30-084 Krakow (Poland); Tkach, I.; Havela, L. [Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 12116 Prague (Czech Republic)

    2015-10-05

    Highlights: • Splat-cooled U–6 at.% Mo, U–5 at.% Pd, U–5 at.% Pt alloys become superconducting below 1 K. • U–5 at.% Pd and U–5 at.% Pt reveal only one resistivity jump at T{sub c}. • Two distinguishable resistivity drops were observed for U–6 at.% Mo. • A broad maximum was observed at T{sub c} in the specific heat. • Those splats consist of two phases having orthorhombic α- and cubic γ-U structure. - Abstract: U–T (T = Mo, Pd, Pt) alloys were prepared by splat cooling technique and characterized by X-ray diffraction. The resistivity and specific heat measurements were performed down to 0.3 K to study their superconductivity. The superconducting transition in the alloy with 6 at.% Mo (U–6%Mo) revealed by a smooth decrease below 1.5 K and a sharp drop at 0.6 K in the resistivity, while a single sharp drop was revealed at T{sub c} ≈ 0.8 K for those with 5 at.% Pd and Pt doping (U–5%Pd and U–5%Pt). With applying magnetic fields, the resistivity drops move to lower temperatures. The superconductivity transitions were revealed by only one broad peak at T{sub c} in the C(T) curves.

  15. Preparation and characterization of MgB{sub 2} with Pd, Pt and Re doping

    Energy Technology Data Exchange (ETDEWEB)

    Grivel, J.-C., E-mail: jean@dtu.dk [Department of Energy Conversion and Storage, Technical University of Denmark, 4000-Roskilde (Denmark); Pitillas, A. [Department of Energy Conversion and Storage, Technical University of Denmark, 4000-Roskilde (Denmark); Universidad Autónoma de Barcelona, 08193 Cerdanyola (Spain); Namazkar, S. [Department of Energy Conversion and Storage, Technical University of Denmark, 4000-Roskilde (Denmark); Chemical Biological Centre, Umeå University, 90187 Umeå (Sweden); Alexiou, A.; Holte, O.J. [Department of Energy Conversion and Storage, Technical University of Denmark, 4000-Roskilde (Denmark)

    2016-01-15

    Highlights: • MgB{sub 2} samples doped with Pt, Pd or Re were prepared by solid state route. • The solubility of these elements in the MgB{sub 2} lattice is negligible. • The field dependence of the normalized J{sub c} is improved in doped samples. - Abstract: Samples with Mg{sub 1−x}D{sub x}B{sub 2.04} (D = Pt, Pd or Re) nominal compositions have been synthesised by a solid-state route. None of these doping elements can be substituted for Mg in a detectable amount and their presence in the samples has no influence on the critical temperature and on the lattice parameters of the MgB{sub 2} superconductor. Impurity phases are formed by reaction mostly with Mg. The microstructure of the Pt, Pd and Re-based phases depends on the elements. Re-rich particles with large sizes up to 8 μm form, whereas Pt- and Pd-containing impurities are finely dispersed with a particle size that does not exceed 1 μm. The field dependence of the normalised critical current density is improved when Pt, Pd or Re are present in the samples.

  16. Laser-induced in situ synthesis of Pd and Pt nanoparticles on polymer films

    Science.gov (United States)

    Mehrabanian, Mehran; Morselli, Davide; Caputo, Gianvito; Scarpellini, Alice; Palazon, Francisco; Athanassiou, Athanassia; Fragouli, Despina

    2016-12-01

    We present the localized in situ formation of Pd and Pt nanoparticles embedded in chitosan solid films. This is achieved by the photo-induced reduction of metallic precursors, previously incorporated in chitosan films, through controlled UV pulsed laser irradiation. Interestingly, at high number of laser pulses, Pd and Pt follow different formation pathways, contrary to their common photoreduction mechanism occurring at low irradiation pulses. Specifically, in the case of the Pd, a photofragmentation process takes place fracturing the previously formed nanoparticles into smaller ones; whereas in the case of Pt, the prolonged irradiation promotes the nanoparticles agglomeration. The combination of both precursors in a binary solid system results in the combined formation of both Pd and Pt nanoparticles in the polymer film upon laser irradiation. The herein reported approach is an efficient and precise tool to generate size- and density-controlled Pd and Pt nanoparticles in desired areas of polymeric films, rendering this method a potential candidate for the fabrication of flexible polymeric devices for gas-sensing or electro-catalysis applications.

  17. The role of Pt and Pd in enhancing the conversion of sorbitol to hydrogen over supported Ni-Pt and Ni-Pd catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Tanksale, A.; Lu, G.Q. [Queensland Univ., Brisbane (Australia); Beltramini, J.N. [Queensland Univ., Brisbane (Australia). ARC Centre of Excellence for Functional Nanomaterials

    2009-07-01

    This study investigated the enhanced activity of bimetallic nickel-platinum (Ni-Pt) and nickel-palladium (Ni-Pd) catalysts for the production of hydrogen from reformed biomass-based products. The catalysts were prepared on an aluminum oxide (Al203) nanofibre. Mesoporous zirconia and composite silica-zirconia-ceria were used to determine the role of noble metals and supports. Desorption, oxidation, and temperature programmed reduction studies were conducted to investigate metal-metal and metal-support interactions. The study showed that Pt and Pd additions increased the reducibility of Ni catalysts. The bimetallic catalysts exhibited rates of hydrogen production 6 times higher than rates observed in pure metal catalysts. Sorbitol conversion increased from 35 per cent for the Ni catalyst to 62 per cent for the Ni-Pt catalyst. It was concluded that the alloying effect of the Ni-Pt and Ni-Pd systems lowered the carbon monoxide (CO) adsorption heat, and facilitated removal of the adsorbed CO by the water gas shift reaction.

  18. Synthesis and characterization of Pt-Pd nanoparticles with core-shell morphology: Nucleation and overgrowth of the Pd shells on the as-prepared and defined Pt seeds

    Energy Technology Data Exchange (ETDEWEB)

    Long, Nguyen Viet, E-mail: nguyenvietlong@yahoo.com [Department of Materials Scienceand Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Posts and Telecommunications Institute of Technology, km 10 Nguyen Trai, Hanoi (Viet Nam); Laboratory for Nanotechnology, Vietnam National University at Ho Chi Minh, Linh Trung, Thu Duc, Ho Chi Minh (Viet Nam); Department of Molecular and Material Sciences, Interdisciplinary Graduate School of Engineering Sciences, 6-1 Kasugakouen, Kasuga, Fukuoka 861-8580 (Japan); Hien, Tong Duy [Laboratory for Nanotechnology, Vietnam National University at Ho Chi Minh, Linh Trung, Thu Duc, Ho Chi Minh (Viet Nam); Asaka, Toru [Department of Materials Scienceand Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Ohtaki, Michitaka [Department of Molecular and Material Sciences, Interdisciplinary Graduate School of Engineering Sciences, 6-1 Kasugakouen, Kasuga, Fukuoka 861-8580 (Japan); Nogami, Masayuki, E-mail: nogami@nitech.ac.jp [Department of Materials Scienceand Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)

    2011-07-21

    Highlights: > The Pt-Pd core-shell nanoparticles based on the as-prepared Pt cores are synthesized. > Not only the Pt-Pd core-shell nanoparticles are formed, but also the separate formation of Pd nanoparticles as well. > The Pt cores without the morphological changes are protected by the Pd-shell overgrowths. > There are the co-existence of the layer-by-layer and island-on-wetting-layer growth modes of the Pd shells and the latter becomes the favorable overgrowth in the formation of core-shell structures. - Abstract: In the present research, Pt-Pd core-shell nanoparticles based on the as-prepared and defined Pt-seed cores with well-controlled size and morphology were synthesized. Their characterizations were investigated by using UV-vis spectroscopy, transmission electron microscopy (TEM), and high resolution (HR)TEM measurements. The high resolution elemental mappings were performed in the operation of high angle annular dark field (HAADF) in conjunction with scanning (S)TEM mode and X-ray energy dispersive spectroscopy (XEDS). It is found that not only the Pt-Pd core-shell nanoparticles were formed, but also the nucleation, growth, and the separate formation of single Pd nanoparticles as well. Interestingly, the as-prepared Pt cores without the morphological changes were protected by the overgrowths of the Pd shells during the successive reduction of sodium tetrachloropalladate (II) hydrate. There were the co-existence of the Frank-van der Merwe (FM) layer-by-layer and Stranski-Krastanov (SK) island-on-wetting-layer growth modes of the Pd shells on the as-prepared Pt cores. It is predicted that the SK growth became the favorable growth mode in the formation of the Pd shells in the formation Pt-Pd core-shell nanoparticles.

  19. Poisoning and regeneration of Pt-Pd/WO{sub 3}-ZrO{sub 2} short paraffin isomerization catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Canavese, Sergio; Finelli, Zunilda; Busto, Mariana; Benitez, Viviana M.; Vera, Carlos R.; Yori, Juan C., E-mail: jyori@fiq.unl.edu.a [Universidad Nacional del Litoral (UNL), Santa Fe (Argentina). Inst. de Investigaciones en Catalisis y Petroquimica

    2010-07-01

    WO{sub 3}-ZrO{sub 2} catalysts promoted with Pt and Pd were tested as paraffin isomerization catalysts using n-hexane as model compound. Sulfur and amine poisoning and regeneration tests were used to assess the impact of the addition of Pt and Pd on the deactivation resistance and regenerability. Pt and Pt Pd catalysts were the most active for n-hexane isomerization. The low activity of the Pd catalyst was attributed to poor Pd metal properties when supported over WO{sub 3}-ZrO{sub 2} and to a decrease of the number of Broensted acid sites. Pt Pd was the only catalyst capable of full regeneration after S poisoning. Amine poisoning completely suppressed the isomerization activity and the original activity could only be restored by calcination and reduction. (author)

  20. Poisoning and regeneration of Pt-Pd/WO3-ZrO2 short paraffin isomerization catalysts

    Directory of Open Access Journals (Sweden)

    Sergio Canavese

    2010-01-01

    Full Text Available WO3-ZrO2 catalysts promoted with Pt and Pd were tested as paraffin isomerization catalysts using n-hexane as model compound. Sulfur and amine poisoning and regeneration tests were used to assess the impact of the addition of Pt and Pd on the deactivation resistance and regenerability. Pt and PtPd catalysts were the most active for n-hexane isomerization. The low activity of the Pd catalyst was attributed to poor Pd metal properties when supported over WO3-ZrO2 and to a decrease of the number of BrQnsted acid sites. PtPd was the only catalyst capable of full regeneration after S poisoning. Amine poisoning completely supressed the isomerization activity and the original activity could only be restored by calcination and reduction.

  1. Alloy ratio effect of Pd/Pt nanoparticles on carbon nanotubes for catalysing methanol-tolerant oxygen reduction

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Chien-Liang, E-mail: cl_lee@url.com.t [Department of Chemical and Materials Engineering, National Kaohsiung University of Applied Science, Kaohsiung, Taiwan (China); Chiou, Hsueh-Ping; Wu, Shi-Chi; Wu, Chen-Chung [Department of Chemical and Materials Engineering, National Kaohsiung University of Applied Science, Kaohsiung, Taiwan (China)

    2010-12-30

    Pd{sub 1}Pt{sub 3}, Pd{sub 1}Pt{sub 1}, and Pd{sub 3}Pt{sub 1} nanoparticles supported on multi-wall carbon nanotubes (CNTs) were prepared by the self-regulation reduction of sodium n-dodecyl sulphate and used as catalysts in oxygen reduction reactions (ORRs). The crystal properties of these alloy nanoparticles on the CNT were measured by X-ray diffraction spectroscopy (XRD) and high-resolution transmission electron microscopy (HRTEM). The angle shifting of the XRD peak and the lattice spacing of the nanoparticles measured by HRTEM increased with an increase in Pd amount, indicating a regulable Pd-Pt ratio for the alloy nanoparticle composition. Rotating ring-disk electrode (RRDE) measurements indicate that the number of electrons catalysed by the Pd{sub 1}Pt{sub 3}/CNT, Pd{sub 1}Pt{sub 1}/CNT, and Pd{sub 3}Pt{sub 1}/CNT nanocatalysts in the ORRs were 3.98, 3.97, and 3.93, respectively. These results show that these ORRs occur via a 4-electron pathway. Linearly scanned voltammetry in the electrolyte with methanol revealed that Pd{sub 3}Pt{sub 1}/CNT has high methanol tolerance during ORRs.

  2. Effects of Ce on catalytic combustion of methane over Pd-Pt/Al2O3 catalyst.

    Science.gov (United States)

    Fan, Xing; Wang, Fan; Zhu, Tianle; He, Hong

    2012-01-01

    Activity and stability of 1%Pd-0.2%Pt/Al2O3 and 1%Pd-0.2%Pt/0.6%Ce/Al2O3 catalysts prepared by impregnation method for catalytic combustion of methane in air were investigated. The catalysts before and after reaction were characterized by BET, CO chemisorption, XRD and XP S techniques. Results showed that the presence of Ce significantly increased the activity and thermal stability of the Pd-Pt/Al2O3 catalyst towards methane combustion, which could be attributed to more highly-dispersed active PdO particles over the Pd-Pt/Ce/Al2O3 catalyst surface as well as the retarded sintering of PdO and the maintained oxidized state of surface Pd during the combustion process in the presence of Ce.

  3. Effects of Ce on catalytic combustion of methane over Pd-Pt/Al2O3 catalyst

    Institute of Scientific and Technical Information of China (English)

    Xing Fan; Fan Wang; Tianle Zhu; Hong He

    2012-01-01

    Activity and stability of 1%Pd-0.2%Pt/Al2O3 and 1%Pd-0.2%Pt/0.6%Ce/Al2O3 catalysts prepared by impregnation method for catalytic combustion of methane in air were investigated.The catalysts before and after reaction were characterized by BET,CO chemisorption,XRD and XPS techniques.Results showed that the presence of Ce significantly increased the activity and thermal stability of the Pd-Pt/Al2O3 catalyst towards methane combustion,which could be attributed to more highly-dispersed active PdO particles over the Pd-Pt/Ce/Al2O3 catalyst surface as well as the retarded sintering of PdO and the maintained oxidized state of surface Pd during the combustion process in the presence of Ce.

  4. PdPt bimetallic nanoparticles enabled by shape control with halide ions and their enhanced catalytic activities.

    Science.gov (United States)

    Zhang, Jinfeng; Wan, Lei; Liu, Lei; Deng, Yida; Zhong, Cheng; Hu, Wenbin

    2016-02-21

    In this study, a new and convenient one step approach is described for synthesizing shape controlled PdPt bimetallic nanoparticles. It is found that the resultant morphologies of these PdPt nanoparticles can be well controlled by simply altering the participation of different halide ions that serve as shape controlling agents in the reaction solution. The dendritic core-shell PdPt bimetallic nanoparticles generated with Pt atoms adopt usual island growth pattern in the presence of Cl(-) ions, whereas the introduction of Br(-) ions with a relatively strong adsorption effect facilitate the formation of a layered core-shell structure due to the layered growth mode of Pt atoms on the exterior surface of the central Pd core. Moreover, the stronger adsorption function of I(-) ions and the resulting fast atomic diffusion promoted the generation of mesoporous core-shell PdPt bimetallic nanoparticles with many pore channels. In addition, the size of these synthesized PdPt nanoparticles exhibited a significant dependence on the concentration of the halide ions involved. Due to their specific structural features and synergistic effects, these PdPt catalysts exhibited shape-dependent catalytic performance and drastically enhanced electrocatalytic activities relative to that of commercial Pt black and Pt/C toward methanol oxidation.

  5. Shape-controlled synthesis of Pt-Pd core-shell nanoparticles exhibiting polyhedral morphologies by modified polyol method

    Energy Technology Data Exchange (ETDEWEB)

    Long, Nguyen Viet, E-mail: nguyenviet_long@yahoo.com [Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Posts and Telecommunications Institute of Technology, Nguyen Trai, Hanoi (Viet Nam); Asaka, Toru; Matsubara, Takashi [Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Nogami, Masayuki, E-mail: nogami@nitech.ac.jp [Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)

    2011-04-15

    Pt-Pd core-shell nanoparticles were synthesized by a simple synthetic method. First, Pt nanoparticles were synthesized in a controlled manner via the reduction of chloroplantinic acid hexahydrate in ethylene glycol (EG) at 160 deg. C in the presence of silver nitrate and the stabilization of polyvinylpyrrolidon. AgNO{sub 3} used acts as a structure-modifying agent to the morphology of the Pt nanoparticles. These Pt nanoparticles function as the seeds for the successive reduction of sodium tetrachloropalladate (II) hydrate in EG under stirring for 15 min at 160 deg. C in order to synthesize Pt-Pd core-shell nanoparticles. To characterize the as-prepared Pt-Pd nanoparticles, transmission electron microscopy (TEM) and high-resolution TEM are used. The high-resolution elemental mappings were carried out using the combination of scanning TEM and X-ray energy-dispersive spectroscopy. The results also demonstrate the homogeneous nucleation and growth of the Pd metal shell on the definite Pt core. The synthesized Pt-Pd core-shell nanoparticles exhibit a sharp and polyhedral morphology. The epitaxial growth of the controlled Pd shells on the Pt cores via a polyol method was observed. It is suggested that Frank-van der Merwe and Stranski-Krastanov growth modes coexisted in the nucleation and growth of Pt-Pd core-shell nanoparticles.

  6. KARAKTERISASI KATALIS Pt-Pd/ZEOLIT ALAM REGENERASI PADA REAKSI HIDRODENITROGENASI PIRIDIN

    Directory of Open Access Journals (Sweden)

    Dina Asnawati

    2014-05-01

    Full Text Available Telah dilakukan penelitian tentang Karakterisasi Katalis Pt-Pd/Zeolit Alam Regenerasi pada Reaksi Hidrodenitrogenasi Piridin. Tujuan dari penelitian ini adalah untuk mempelajari karakter katalis Pt-Pd/zeolit alam baru, bekas dan hasil regenerasi pada hidrodenitrogenisasi piridin. Katalis Pt-Pd/zeolit alam terdeaktivasi diregenerasi dengan cara dioksidasi dengan gas O2 pada temperatur 350oC selama 2 jam, dan direduksi dengan gas H2 pada temperatur 400oC selama 1 jam. Karakterisasi katalis baru (fresh, terdeaktivasi dan terregenerasi meliputi penentuan luas permukaan, volume pori dan rerata jejari pori dengan alat Gas Sorption Analyzer NOVA-1000 berdasarkan adsorpsi gas N2 serta penentuan keasaman dengan metode adsorpsi gas amoniak. Hasil penelitian menunjukkan bahwa deaktivasi katalis menyebabkan penurunan luas permukaan spesifik, volume total pori dan keasaman katalis, sedangkan proses regenerasi pada katalis bekas dengan metode oksidasi dan reduksi meningkatkan luas permukaan spesifik, volume total pori, rerata jejari pori dan keasaman katalis.

  7. Comparison of Pt and Pd Modified TiO2 Gas Sensors

    Directory of Open Access Journals (Sweden)

    Maolin ZHANG

    2014-12-01

    Full Text Available Pt and Pd have been widely used to improve response properties of TiO2 based gas sensors. In this work, differences on response properties, especially the response time of Pt/TiO2 and Pd/TiO2 sensors, were carefully compared. TiO2 sensing films were modified by dipping method using H2PtCl6 and PdCl2, respectively. XRD, XPS and SEM were used to characterize the crystal structure, elemental composition and grain size of the sensing films. The defect state was characterized by the relationship between resistance and oxygen partial pressure. And the response transients to H2 and O2 were tested by voltammetry method. The difference on response properties of modified TiO2 sensors were suggested to arise from their activation energy. DOI: http://dx.doi.org/10.5755/j01.ms.20.4.6403

  8. Specific heat, resistivity, and AC susceptibility of the cubic PrX 2 compounds (X = Pt, Ru, Ir, Rh)

    Science.gov (United States)

    Greidanus, F. J. A. M.; Nieuwenhuys, G. J.; de Jongh, L. J.; Huiskamp, W. J.; Capel, H. W.; Buschow, K. H. J.

    1983-04-01

    Specific-heat, differential-susceptibility and electrical-resistivity measurements on PrX 2 (X = Ir, Pt, Rh, Ru) compounds reveal phase transitions at Tc = 11.2±0.5 K, 7.7±0.5 K, 7.9±0.5 Kand 33.9±0.5 K for X = Ir, Pt, Rh, and Ru, respective ly. From earlier neutron inelastic scattering experiments, the crystalline electric field levels of these compounds have been determined. The specific-heat results are compared with the results of a mean-field calculation, assuming bilinear exchange interactions. The presence of broad secondary maxima in the temperature dependence of the specific heat of PrRh 2, PrRu 2 and especially PrIr 2 can qualitatively be explained by the presence of biquadratic (quadrupolar) interactions. The behaviour of the susceptibility is in agreement with ferromagnetic ordering. The electrical resistivity drops markedly below Tc, and the dϱ/d T versus T curve is similar to that of the specific heat.

  9. Pt@Pd(x)Cu(y)/C core-shell electrocatalysts for oxygen reduction reaction in fuel cells.

    Science.gov (United States)

    Cochell, T; Manthiram, A

    2012-01-17

    A series of carbon-supported core-shell nanoparticles with Pd(x)Cu(y)-rich cores and Pt-rich shells (Pt@Pd(x)Cu(y)/C) has been synthesized by a polyol reduction of the precursors followed by heat treatment to obtain the Pd(x)Cu(y)/C (1 ≤ x ≤ 3 and 0 ≤ y ≤ 5) cores and the galvanic displacement of Pd(x)Cu(y) with [PtCl(4)](2-) to form the Pt shell. The nanoparticles have also been investigated with respect to the oxygen reduction reaction (ORR) in proton-exchange-membrane fuel cells (PEMFCs). X-ray diffraction (XRD) analysis suggests that the cores are highly alloyed and that the galvanic displacement results in a certain amount of alloying between Pt and the underlying Pd(x)Cu(y) alloy core. Transmission electron microscopy (TEM) images show that the Pt@Pd(x)Cu(y)/C catalysts (where y > 0) have mean particle sizes of <8 nm. Compositional analysis by energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) clearly shows Pt enrichment in the near-surface region of the nanoparticles. Cyclic voltammograms show a positive shift of as much as 40 mV for the onset of Pt-OH formation in the Pt@Pd(x)Cu(y)/C electrocatalysts compared to that in Pt/C. Rotating disk electrode (RDE) measurements of Pt@PdCu(5)/C show an increase in the Pt mass activity by 3.5-fold and noble metal activity by 2.5-fold compared to that of Pt/C. The activity enhancements in RDE and PEMFC measurements are believed to be a result of the delay in the onset of Pt-OH formation.

  10. Novel method for the synthesis of hydrophobic Pt-Ru nanoparticles and its application to preparing a Nafion-free anode for the direct methanol fuel cell.

    Science.gov (United States)

    Tu, Hung-Chi; Wang, Wen-Lin; Wan, Chi-Chao; Wang, Yung-Yun

    2006-08-17

    Pt-Ru alloy is a bimetallic catalyst most commonly used in the direct methanol fuel cell (DMFC). In this paper, a new process to synthesize an unsupported Pt-Ru colloid has been introduced. The characteristics of synthesized nanoparticles were identified by XRD, TEM/EDX, and SEM, and it shows that Ru atoms are incorporated into the Pt fcc structure and the well-dispersed particles (diameter approximately 4 nm) possess a Pt-rich feature. This catalyst shows a hydrophobic characteristic which can adsorb very well on the hydrophobic-treated carbon paper or carbon cloth without the need of Nafion. Accordingly, this method can avoid particle agglomeration, and the synthesized catalyst demonstrates strong adsorption with carbon paper. In addition, this colloid-type Nafion-free catalyst was measured via linear sweep voltammetry (LSV) and exhibited electrochemical activity for methanol oxidation comparable to the commercial one with Nafion binding.

  11. Pt Monolayer Electrocatalyst for Oxygen Reduction Reaction on Pd-Cu Alloy: First-Principles Investigation

    Directory of Open Access Journals (Sweden)

    Amra Peles

    2015-07-01

    Full Text Available First principles approach is used to examine geometric and electronic structure of the catalyst concept aimed to improve activity and utilization of precious Pt metal for oxygen reduction reaction in fuel cells. The Pt monolayers on Pd skin and Pd1-xCux inner core for various compositions x were examined by building the appropriate models starting from Pd-Cu solid solution. We provided a detailed description of changes in the descriptors of catalytic behavior, d-band energy and binding energies of reaction intermediates, giving an insight into the underlying mechanism of catalytic activity enhancement based on the first principles density functional theory (DFT calculations. Structural properties of the Pd-Cu bimetallic were determined for bulk and surfaces, including the segregation profile of Cu under different environment on the surface.

  12. CO adsorption on ionic Pt, Pd and Cu sites in Ce1−MxO2− (M=Pt2+, Pd2+, Cu2+)

    Indian Academy of Sciences (India)

    Gargi Dutta; Asha Gupta; Umesh V Waghmare; M S Hegde

    2011-07-01

    Noble metal ion substituted CeO2 in the form of Ce0.98M0.02O2− solid solution (where M=Pt, Pd, Cu) are the new generation catalysts with applications in three-way exhaust catalysis. While adsorption of CO on noble metals ions is well-known, adsorption of CO on noble metal ions has not been studied because creating exclusive ionic sites has been difficult. Using first-principles density functional theory (DFT) we have shown that CO gets adsorbed on the noble metal Pt2+, Pd2+, Cu2+ ionic sites in the respective compounds, and the net energy of the overall system decreases. Adsorption of CO on metal ions is also confirmed by Fourier transform infrared spectroscopy (FTIR).

  13. Electronic Structure of the fcc Transition Metals Ir, Rh, Pt, and Pd

    DEFF Research Database (Denmark)

    Andersen, O. Krogh

    1970-01-01

    /atom)/Ry, respectively. Spin-orbit coupling is important for all four metals and the coupling parameter varies by 30% over the d bandwidth. Detailed comparisons with de Haas—van Alphen Fermi-surface dimensions have previously been presented and the agreement was very good. Comparison with measured electronic specific......We give a complete description of a relativistic augmented-plane-wave calculation of the band structures of the paramagnetic fcc transition metals Ir, Rh, Pt, and Pd. The width and position of the d band decrease in the sequence Ir, Pt, Rh, Pd; and N(EF)=13.8,23.2,18.7, and 32.7 (states...

  14. Pd-Pt Alloy with Coral-Like Nanostructures Showing High Performance for Oxygen Electrocatalytic Reduction.

    Science.gov (United States)

    Liu, Xing-Quan; Chen, Xue-Song; Wu, Jian; Yao, Lei

    2016-03-01

    Three-dimensional (3D) Pd-Pt alloy with coral-like nanostructures were synthesized via bubble dynamic templated electrodeposition method at room temperature. The morphology of the as-prepared nanostructures was characterized using scanning electron microscopy (SEM), EDS, high-resolution transmission electron microscopy (HRTEM), respectively. Cyclic voltammetry method was adopted to evaluate the electrocatalytic activities of the synthesized electrodes toward oxygen reduction in KCl solution. The electrochemical results indicated that the Pd-Pt alloy with coral-like nanostructures hold the high performance for oxygen reduction.

  15. The Effect of Sulfur Fugacity on Pt, Pd and Au in Magmatic-Hydrothermal Systems

    Science.gov (United States)

    Bell, A.; Simon, A.

    2009-05-01

    We have constrained experimentally the effect of sulfur fugacity (fS2) and sulfide saturation on the fractionation and partitioning behavior of Pt, Pd and Au in a felsic silicate melt + sulfide crystal/melt + oxide + supercritical aqueous fluid phase + Pt + Pd + Au system. Experiments were performed at 800°C, 150 MPa, with oxygen fugacity (fO2) fixed at approximately the nickel + nickel oxide buffer (NNO). Sulfur fugacity in the experiments was varied five orders of magnitude from approximately logfS2 = 0 to logfS2 = -5 by using two different sulfide phase assemblages. Sulfide assemblage one consisted initially of chalcopyrite plus pyrrhotite and assemblage two consisted of chalcopyrite plus bornite. At run conditions, in both assemblages, pyrrhotite transformed compositionally to monosulfide solid solution (mss), chalcopyrite to intermediate solid solution (Iss), and in assemblage two chalcopyrite and bornite formed a sulfide melt. Run- product silicate glass (i.e., quenched silicate melt) and crystalline materials were analyzed by using both electron probe microanalysis (EPMA) for major elements and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for major and trace elements. The measured concentrations of Pt, Pd, and Au in quenched silicate melt in runs with logfS2 values ranging from approximately 0 to -5, do not exhibit any apparent dependence on the dissolved sulfur content of the melt. The measured Pt, Pd and Au concentrations in mss vary as a function of fS2. The measured Pt, Pd and Au concentrations in Iss do not appear to be dependent on fS2. The system variables fS2 and fO2, working in concert with each other, control the stable magmatic sulfide phase assemblage. Additionally, the system fS2 strongly influences the solubility of Pt, Pd, and Au as lattice bound components in some common crystalline magmatic sulfide phases. Both the stable magmatic sulfide phase assemblage and the solubility of Pt, Pd, and Au as constituents in

  16. Role of Van der Waals Forces in Graphene Adsorption over Pd, Pt, and Ni

    Science.gov (United States)

    Quiroga, Matias A. O.; Cabeza, Gabriela F.

    2013-06-01

    We report ab initio computations with the Vienna Ab initio Simulation Package (VASP) aimed at elucidating the adsorption mechanism of graphene-like structures on (111) Pd, Pt, and Ni surfaces. To study the adsorption properties, we simulate an already-formed graphene layer. We present a comparative discussion of the graphene interactions with the three metals, focusing on the very particular adsorption of graphene over Pd.

  17. Role of Van der Waals forces in graphene adsorption over Pd, Pt, and Ni

    Energy Technology Data Exchange (ETDEWEB)

    Quiroga, Matias A.O.; Cabeza, Gabriela F. [Instituto de Física del Sur, CONICET, Bahia Blanca, Buenos Aires (Argentina)

    2013-07-01

    We report ab initio computations with the Vienna Ab initio Simulation Package (VASP) aimed at elucidating the adsorption mechanism of graphene-like structures on (111) Pd, Pt, and Ni surfaces. To study the adsorption properties, we simulate an already-formed graphene layer. We present a comparative discussion of the graphene interactions with the three metals, focusing on the very particular adsorption of graphene over Pd. (author)

  18. Methanol oxidation on carbon supported Pt-Ru catalysts prepared by electrodeposition - Evaluation of Nafion {sup registered} 117 film effect

    Energy Technology Data Exchange (ETDEWEB)

    Sieben, J.M. [Instituto de Ingenieria Electroquimica y Corrosion (INIEC), Universidad Nacional del Sur, Av. Alem 1253 (B8000CPB) Bahia Blanca, Buenos Aires (Argentina); Duarte, M.M.E.; Mayer, C.E. [Instituto de Ingenieria Electroquimica y Corrosion (INIEC), Universidad Nacional del Sur, Av. Alem 1253 (B8000CPB) Bahia Blanca, Buenos Aires (Argentina); Comision de Investigaciones Cientificas de la Provincia de Buenos Aires (CIC) (Argentina)

    2010-03-15

    Diverse electrochemical techniques were performed in order to obtain meaningful information about the methanol oxidation reaction on nanostructured planar carbon supported Pt-Ru electrodes prepared by electrodeposition, on which a layer of Nafion ionomer was incorporated. A metallic deposit consisting of dendritic agglomerates (between 50 and 200 nm) constituted by smaller particles (6 nm) was obtained. The average bulk Ru content obtained by EDX analysis was between 23 and 25 at. %. A decrease of the activity in the electrodes for methanol oxidation was determined when the thickness of the Nafion 117 film was increased. These results may be associated with the partial blocking of the surface active sites by hydrophobic domains of the polymer, and the presence of CO{sub 2} molecules retained within the Nafion hydrophilic microchannels. EIS results indicated that methanol electro-oxidation mechanism does not change with Nafion presence. (author)

  19. Pd@Pt Core–Shell Nanoparticles with Branched Dandelion-like Morphology as Highly Efficient Catalysts for Olefin Reduction

    Science.gov (United States)

    A facile synthesis based on the addition of ascorbic acid to a mixture of Na2PdCl4, K2PtCl6, and Pluronic P123 results in highly branched core–shell nanoparticles (NPs) with a micro–mesoporous dandelion-like morphology comprising Pd core and Pt shell. The slow reduction kinetics ...

  20. Pd@Pt Core–Shell Nanoparticles with Branched Dandelion-like Morphology as Highly Efficient Catalysts for Olefin Reduction

    Science.gov (United States)

    A facile synthesis based on the addition of ascorbic acid to a mixture of Na2PdCl4, K2PtCl6, and Pluronic P123 results in highly branched core–shell nanoparticles (NPs) with a micro–mesoporous dandelion-like morphology comprising Pd core and Pt shell. The slow reduction kinetics ...

  1. The effect of methanol on the stability of Pt/C and Pt-RuO{sub x}/C catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Rufino, Elen C.G.; Olivi, Paulo [Departamento de Quimica, Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo, CEP 14040-901, Ribeirao Preto, SP (Brazil)

    2010-12-15

    The behavior of Pt/C and Pt-RuO{sub x}/C electrodes subjected to a larger number of potential scans and constant potential for prolonged time periods was investigated in the absence and presence of methanol. The structural changes were analyzed on the basis of the modifications observed in the X-ray diffraction pattern of the catalysts. Carbon monoxide stripping experiments were performed before and after the potential scans, thus enabling analysis of the behavior of the electrochemically active surface area. The resulting solutions were examined by inductively coupled plasma mass spectrometry (ICP-MS). There was reduction in the electrochemically active surface area, as well as increase in crystallite size and dissolution of catalyst components after the potential scan tests. Catalyst degradation was more pronounced in the presence of methanol, and cyclic potential conditions accelerate the degradation mechanisms. (author)

  2. Structures and energetics of 98 atom Pd-Pt nanoalloys: potential stability of the Leary tetrahedron for bimetallic nanoparticles.

    Science.gov (United States)

    Paz-Borbón, Lauro Oliver; Mortimer-Jones, Thomas V; Johnston, Roy L; Posada-Amarillas, Alvaro; Barcaro, Giovanni; Fortunelli, Alessandro

    2007-10-14

    The energetics of 98 atom bimetallic Pd-Pt clusters are studied using a combination of: a genetic algorithm technique (to explore vast areas of the configurational space); a basin-hopping atom-exchange routine (to search for lowest-energy homotops at fixed composition); and a shell optimisation approach (to search for high symmetry isomers). The interatomic interactions between Pd and Pt are modelled by the Gupta many-body empirical potential. For most compositions, the putative global minima are found to have structures based on defective Marks decahedra, but in the composition range from Pd46Pt52 to Pd63Pt35, the Leary tetrahedron (LT)--a structure previously identified for 98 atom Lennard-Jones clusters--is consistently found as the most stable structure. Based on the excess energy stability criterion, Pd56Pt42 represents the most stable cluster across the entire composition range. This structure, a Td-symmetry LT, exhibits multi-layer segregation with an innermost core of Pd atoms, an intermediate layer of Pt atoms and an outermost Pd surface shell (Pd-Pt-Pd). The stability of the Leary tetrahedron is compared against other low-energy competing structural motifs: the Marks decahedron (Dh-M), a "quasi" tetrahedron (a closed-packed structure) and two other closed-packed structures. The stability of LT structures is rationalized in terms of their spherical shape and the large number of nearest neighbours.

  3. Microstructures and magnetic properties of meta-stable Co{sub 50−X}M{sub X}Pt{sub 50} (M = Cu or Ru) thin films

    Energy Technology Data Exchange (ETDEWEB)

    Sun, An-Cheng, E-mail: acsun@saturn.yzu.edu.tw; Huang, Chuan-Fa; Chen, Sheng-Fu; Chen, Yu-Shen

    2014-11-03

    Co{sub 50−X}M{sub X}Pt{sub 50} (M = Cu or Ru) films were magnetron sputtered on textured Pt(111) underlayer on glass substrate at 350 °C. The results show that perpendicular magnetic anisotropy of superlattice L1{sub 1} phase can be maintained well with doping Cu element into CoPt film. Out-of-plane coercivity (H{sub c⊥}) was also increased with the increase of Cu content. However, disordered A1(111) structure and lower H{sub c⊥} were obtained with the addition of Ru element in CoPt film. The magnetic force microscopy images indicated that doping Cu diminished the domain size. Oppositely, doping Ru made the domain reversed incompletely. Surface morphology of Co{sub 24}Cu{sub 26}Pt{sub 50} thin film was much smoother than that of Co{sub 23}Ru{sub 27}Pt{sub 50} thin film, indicative of maintenance of the epitaxial growth of L1{sub 1}(111) from flat Pt(111) underlayer. The transmission electron microscopy (TEM) images show that the Cu element could be incorporated in L1{sub 1} CoPt grains; however, the RuPt alloy was segregated at CoPt grain boundary. The cross section TEM pictures showed that the columnar structures starting from Pt(111) underlayer and extending into magnetic CoCuPt(111) layer confirmed that epitaxy existed at CoCuPt/Pt interface. Our research demonstrates that replacing Co with Cu = 23–26 at.% effectively increases the perpendicular magnetic properties of L1{sub 1} CoPt phase, which largely increase the potential of L1{sub 1} films for the application of perpendicular magnetic media and advance spintronic device. - Highlights: • Strengthen superstructural CoPt phase with perpendicular magnetic anisotropy • Enhanced coercivity in L1{sub 1} CoPt thin films with doping 3rd elements • Impedances of domain wall motion adjusted the coercivity.

  4. In vitro degradation and biocompatibility of Fe–Pd and Fe–Pt composites fabricated by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Huang, T. [State Key Laboratory for Turbulence and Complex System, College of Engineering, Peking University, Beijing 100871 (China); Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871 (China); Cheng, J. [Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China); Zheng, Y.F., E-mail: yfzheng@pku.edu.cn [State Key Laboratory for Turbulence and Complex System, College of Engineering, Peking University, Beijing 100871 (China); Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871 (China); Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China)

    2014-02-01

    In order to obtain biodegradable Fe-based materials with similar mechanical properties as 316L stainless steel and faster degradation rate than pure iron, Fe-5 wt.%Pd and Fe-5 wt.%Pt composites were prepared by spark plasma sintering with powders of pure Fe and Pd/Pt, respectively. The grain size of Fe-5 wt.%Pd and Fe-5 wt.%Pt composites was much smaller than that of as-cast pure iron. The metallic elements Pd and Pt were uniformly distributed in the matrix and the mechanical properties of these materials were improved. Uniform corrosion of Fe–Pd and Fe–Pt composites was observed in both electrochemical tests and immersion tests, and the degradation rates of Fe–Pd and Fe–Pt composites were much faster than that of pure iron. It was found that viabilities of mouse fibroblast L-929 cells and human umbilical vein endothelial cells (ECV304) cultured in extraction mediums of Fe–Pd and Fe–Pt composites were close to that of pure iron. After 4 days' culture, the viabilities of L-929 and ECV304 cells in extraction medium of experimental materials were about 80%. The result of direct contact cytotoxicity also indicated that experimental materials exhibited no inhibition on vascular endothelial process. Meanwhile, iron ions released from experimental materials could inhibit proliferation of vascular smooth muscle cells (VSMC), which may be beneficial for hindering vascular restenosis. Furthermore, compared with that of as-cast pure iron, the hemolysis rates of Fe–Pd and Fe–Pt composites were slightly higher, but still within the range of 5%, which is the criteria for good blood compatibility. The numbers of platelet adhered on the surface of Fe–Pd and Fe–Pt composites were lower than that of pure iron, and the morphology of platelets kept spherical. To sum up, the Fe-5wt.%Pd and Fe-5wt.%Pt composites exhibited good mechanical properties and degradation behavior, closely approaching the requirements for biodegradable metallic stents. - Highlights:

  5. Magnetic properties of BaM /Pd-Pt double-layered thin film deposited at various substrate temperatures

    Science.gov (United States)

    Nahar Shams, Nazmun; Liu, Xiaoxi; Matsumoto, Mitsunori; Morisako, Akimitsu

    2005-05-01

    Crystallographic and magnetic properties of barium ferrite (BaM) thin films deposited onto Pt, Pd, and an alloy of Pd-Pt underlayers by sputtering at different substrate temperatures (Ts) from 400to600°C have been studied. It is found that the coercivity values in the perpendicular direction (Hcperp) of the BaM /Pd-Pt films are higher than those of the BaM films deposited on Pd and Pt underlayers. C-axis orientation of BaM /Pd-Pt film can be achieved at very low Ts of 450°C with a Hcperp of 2.1kOe for 30-nm BaM.

  6. Electrocatalytic performance of Pt/Ru/Sn/W fullerene electrode for methanol oxidation in direct methanol fuel cell

    Institute of Scientific and Technical Information of China (English)

    Mohammad Karimi; Forouzan Aboufazeli; Hamid Reza Lotfi Zadeh Zhad; Omid Sadeghi; Ezzatollah Najafi

    2013-01-01

    In this work,fullerene was modified by platinum,ruthenium,tin and tungsten nanoparticles.The material was characterized by XRD,ICP-OES and TEM micrograph.The average nanoparticle size on fullerene was 5 ~ 8 nm.The application of this material was investigated as a catalyst for methanol oxidation in direct methanol fuel cell.A glassy carbon electrode was modified by Pt/Ru/Sn/W fullerene and electrocatalytic activity of the electrode toward methanol oxidation in basic medium has been demonstrated and investigated using cyclic voltammetry.The catalyst showed good reactivity for methanol oxidation.

  7. Facile synthesis of Pd-Pt alloy nanocages and their enhanced performance for preferential oxidation of CO in excess hydrogen.

    Science.gov (United States)

    Zhang, Hui; Jin, Mingshang; Liu, Hongyang; Wang, Jinguo; Kim, Moon J; Yang, Deren; Xie, Zhaoxiong; Liu, Jingyue; Xia, Younan

    2011-10-25

    This article describes a new method for the facile synthesis of Pd-Pt alloy nanocages with hollow interiors and porous walls by using Pd nanocubes as sacrificial templates. Differing from our previous work (Zhang, H.; Jin, M. S.; Wang, J. G.; Li, W. Y.; Camargo, P. H. C.; Kim, M. J.; Yang, D. R.; Xie, Z. X.; Xia, Y. Synthesis of Pd-Pt Bimetallic Nanocrystals with a Concave Structure through a Bromide-Induced Galvanic Replacement Reaction. J. Am. Chem. Soc.2011, 133, 6078-6079), we complemented the galvanic replacement (between Pd nanocubes and PtCl(4)(2-)) with a coreduction process (for PdCl(4)(2-) from the galvanic reaction and PtCl(4)(2-) from the feeding) to generate Pd-Pt alloy nanocages in one step. We found that the rate of galvanic replacement (as determined by the concentrations of Br(-) and PtCl(4)(2-) and temperature) and the rates of coreduction (as determined by the type of reductant and temperature) played important roles in controlling the morphology of resultant Pd-Pt alloy nanocages. The Pd-Pt nanocages exhibited both enhanced activity and selectivity for the preferential oxidation (PROX) of CO in excess hydrogen than those of Pd nanocubes and the commercial Pt/C thanks to the alloy composition and hollow structure. In addition, as the sizes of the Pd-Pt nanocages decreased, they exhibited higher CO conversion rates and lower maximum conversion temperatures due to the increase in specific surface area.

  8. Electronic and structural properties of Fe3Pd-Pt ferromagnetic shape memory alloys

    Science.gov (United States)

    Stern, R. A.; Willoughby, S. D.; Ramirez, A.; MacLaren, J. M.; Cui, J.; Pan, Q.; James, R. D.

    2002-05-01

    Ferromagnetic shape memory (FSM) alloys are scientifically and technologically interesting materials that combine ferromagnetism with a reversible martensitic phase transformation. Fe70Pd30 has recently been shown to display a FSM effect at usable temperatures and low fields. Reported here are results of experimental studies on Fe70Pd30 and electronic structure calculations on Fe70Pd30-xPtx. The calculations show that additions of Pt by 6 at % to Fe70Pd30 can triple the magnetocrystalline anisotropy. There is, however, a large discrepancy between the measured and calculated anisotropy values of Fe70Pd30, suggesting the presence of significant disorder in the measured samples. Other calculated structural and magnetic properties are in close agreement with experimental values.

  9. Effect of nanoparticle (Pd, Pd/Pt, Ni deposition on high temperature hydrogenation of Ti-V alloys in gaseous flow containing CO

    Directory of Open Access Journals (Sweden)

    S. Suwarno

    2017-02-01

    Full Text Available The hydrogenation properties of Ti-V hydrides coated with nanoparticles have been studied in gaseous mixtures of argon and hydrogen with and without additions of 1% CO. Nanoparticles of Pd, Ni, and co-deposited Pd/Pt with particle sizes of ~30–60 nm were formed by electroless deposition on the hydride surfaces. The alloy resistance to CO could be significantly improved by particle deposition. Large amounts of hydrogen were absorbed in a CO-containing gas when Ni and Pd/Pt deposition had been applied, while pure Pd deposition had no positive effect. Ni was found to have a stronger effect than those of Pd/Pt and Pd, possibly because of the size effect of Ni nanoparticles.

  10. Analisis Sistem Pengukuran Kinerja dengan Metode Integrated Performance Measurement Systems (IPMS) Pada PT. PD. Paya Pinang

    OpenAIRE

    Alda, Tania

    2016-01-01

    Dalam era globalisasi saat ini, industri pengolahan kelapa sawit di Indonesia mengalami perkembangan yang cukup pesat. Pengukuran kinerja sangat penting bagi perusahaan, dapat membantu perusahaan untuk mengetahui tingkat performansi kerja yang baik. Saat ini, cara terbaik dalam mengukur kinerja adalah dengan mempertimbangkan stakeholder perusahaan dan mengidentifikasi kebutuhan stakeholder tersebut. PT. PD. Paya Pinang adalah salah satu perusahaan kelapa sawit swasta nasional yang melakukan p...

  11. Green and Facile Synthesis of Pd-Pt Alloy Nanoparticles by Laser Irradiation of Aqueous Solution.

    Science.gov (United States)

    Nakamura, Takahiro; Sato, Shunichi

    2015-01-01

    Solid-solution palladium-platinum (Pd-Pt) alloy nanoparticles (NPs) with fully tunable compositions were directly fabricated through high-intensity laser irradiation of an aqueous solution of palladium and platinum ions without using any reducing agents or thermal processes. Transmission electron microscopy (TEM) observations showed that nanometer-sized particles were fabricated by laser irradiation of mixed aqueous solutions of palladium and platinum ions with different feeding ratios. The crystalline nature of the NPs was precisely characterized by X-ray diffraction (XRD). Despite the fact that, for the bulk systems, a pair of XRD peak was detected between the palladium and platinum peaks because of the large miscibility gap in the Pd-Pt binary phase diagram, only a single XRD peak was seen for the Pd-Pt NPs fabricated in the present study. Moreover, the peak position shifted from that of pure palladium towards platinum with increasing fraction of platinum ions in solution. Consequently, the interplanar spacings of the alloy NPs agreed well with the estimated values obtained from Vegard's law. These observations strongly indicate the formation of solid-solution Pd-Pt alloy NPs with fully tunable compositions. This technique is not only a "green" (environmentally-friendly) and facile process, but is also widely applicable to other binary and ternary systems.

  12. Nucleation and growth mechanisms for Pd-Pt bimetallic nanodendrites and their electrocatalytic properties

    National Research Council Canada - National Science Library

    Lim, Byungkwon; Jiang, Majiong; Yu, Taekyung; Camargo, Pedro H. C; Xia, Younan

    2010-01-01

    .... These nanostructures can be easily prepared by a one-step, seeded growth method that involves the reduction of K2PtCl4 by L-ascorbic acid in the presence of 9-nm truncated octahedral Pd seeds in an aqueous solution...

  13. Structural characterization of Pt-Pd core-shell nanoparticles by Cs-corrected STEM

    Energy Technology Data Exchange (ETDEWEB)

    Esparza, R., E-mail: resparza@fata.unam.mx [Universidad Nacional Autonoma de Mexico, Centro de Fisica Aplicada y Tecnologia Avanzada (Mexico); Garcia-Ruiz, Amado F. [UPIICSA-COFAA, Instituto Politecnico Nacional (Mexico); Velazquez Salazar, J. J. [University of Texas at San Antonio, Department of Physics and Astronomy (United States); Perez, R. [Universidad Nacional Autonoma de Mexico, Centro de Fisica Aplicada y Tecnologia Avanzada (Mexico); Jose-Yacaman, M. [The University of Texas at San Antonio, Department of Physics and Astronomy (United States)

    2013-01-15

    Pt-Pd core-shell nanoparticles were synthesized using a modified polyol method. A thermal method under refluxing, carrying on the reaction up to 285 Degree-Sign C, has been performed to reduce metallic salts using ethylene glycol as reducer and poly(N-vinyl-2-pyrrolidone) as protective reagent of the formed bimetallic nanoparticles. According to other works, this type of structure has been studied and utilized to successfully increase the catalytic properties of monometallic nanoparticles Pt or Pd. Core-shell bimetallic nanoparticles were structurally characterized using aberration-corrected scanning transmission electron microscopy (Cs-STEM) equipped with a high-angle annular dark field detector, energy-dispersive X-ray spectrometry (EDS), and electron energy-loss spectroscopy (EELS). The high-resolution elemental line scan and mappings were carried out using a combination of STEM-EDS and STEM-EELS. The obtained results show the growth of the Pd shell on the Pt core with polyhedral morphology. The average size of the bimetallic nanoparticles was 13.5 nm and the average size of the core was 8.5 nm; consequently, the thickness of the shell was around 2.5 nm. The growth of the Pd shell on the Pt core is layer by layer, suggesting a Frank-van der Merwe growth mechanism.

  14. Structure and reactivity of Pd-Pt clusters produced by laser vaporization of bulk alloys

    Science.gov (United States)

    Rousset, J. L.; Cadrot, A. M.; Lianos, L.; Renouprez, A. J.

    Pd-Pt nanoclusters are obtained by the focusing of an Nd:YAG laser onto rods of alloys. The aggregates, which are produced by plasma cooling via short helium bursts synchronized with the laser pulses, are collected on amorphous carbon or silicon substrates, in a UHV chamber. Transmission electron microscopy (TEM) experiments show that the diameters of the clusters range between 1.5 and 4.5 nm, and analytical microscopy indicates that they have the same composition as the vaporized rods. Low-energy ion scattering (LEIS) also shows that the surface of the obtained clusters is Pd enriched: the Pd concentration in the first atomic layer is found to be equal to 38% for a Pd17Pt83 rod composition and 87% for the Pd65 Pt35 alloy. The catalytic activity of these clusters in the hydrogenation of 1,3-butadiene to butenes and butane is measured in static mode, with mass spectrometry detection. The reactivity of the bimetallic clusters is explained by the atomic local order and low-coordination sites considered as ``hot sites''.

  15. Dispersal and accumulation of Pt, Pd and Rh derived from a roundabout in Sheffield (UK): From stream to tidal estuary.

    Science.gov (United States)

    Prichard, H M; Jackson, M T; Sampson, J

    2008-08-15

    The Coisley Hill roundabout, a typical urban source for PGE in stream sediments, has anomalously high values of up to 408 ppb Pt, 444 ppb Pd and 113 ppb Rh in road dust, up to 416 ppb Pt and 278 ppb Pd in gulley sediment and up to 606 ppb Pt and 1050 ppb Pd in verge soil. For samples collected at the same time, the road dust values are much higher than in sediments in the Shire Brook stream, that drains the roundabout, with values of 3-64 ppb Pt, 4-57 ppb Pd and up to 7 ppb Rh. Downstream sediments from rivers Rother and Don have lower values of 2-35 ppb Pt, 2-14 ppb Pd and up to 3 ppb Rh. The Humber estuary values are low with 6-8 ppb Pt, 5-8 ppb Pd and 1-2 ppb Rh. Pt/Pd increases down catchment with Coisley Hill 0.8, Shire Brook 1.0, Trent and Don 1.5 and the Humber estuary 2.0. Pt/Rh and Pd/Rh also increase downstream. Precious metals are generally dispersed away from their vehicle catalytic source and Pd is dispersed more than Pt and Rh but Pt and Pd are re-concentrated in acid mine drainage in the Shire Brook, with concentrations varying with stream flow. Pt and Pd values are slightly elevated at the tidal limit and in mud deposited when the river is in spate. On Coisley Hill, values of 133 ppb Pt and 230 ppb Pd occur in dust from a new road surface (two weeks old when sampled). These are similar to those on much older road surfaces suggesting that Pt and Pd collect and disperse rapidly from roads. Au is low in road dust and higher values in conurbations suggest the presence of more Au sources in urban rather than in rural areas. Au values are not diluted downstream as much as PGE suggesting different processes of dispersion and sedimentation.

  16. Preparation of Pt-Ru@ polypyrrole-MWNT catalysts by gamma-irradiation and chemical reduction and their adsorption capacity for CO.

    Science.gov (United States)

    Bae, Hyoung-Bong; Oh, Sang-Hyub; Woo, Jin-Chun; Choi, Seong-Ho

    2010-10-01

    With the objective to prepare electrocatalysts with high efficiency, the Pt-Ru@PPy-MWNT catalysts were prepared by different approaches. First, the polypyrrole (PPy) as anchoring materials was coated on the surface of multi walled carbon nanotubes (MWNT) by in situ polymerization. Subsequently, Pt-Ru nanoparticles were deposited onto PPy-MWNT composite by different methods like the reduction of metal ions by gamma-irradiation and chemical reduction using formaldehyde as reducing agent assisted with stirring of magnetic bar, and assisted with microwave irradiation, and assisted with ultrasonic irradiation, in order to prepare electrocatalyst for fuel cell. The catalytic efficiency of Pt-Ru@PPy-MWNT catalyst was examined for CO stripping.

  17. Electrooxidation of H{sub 2}/CO on carbon-supported PtRuMo nanoparticles for polymer electrolyte fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Tsiouvaras, N.; Pena, M.A.; Fierro, J.L.G.; Martinez-Huerta, M.V. [CSIC, Madrid (Spain). Inst. de Catalisis y Petroleoquimica; Alcaide, F.; Alvarez, G. [CIDETEC-IK4, Donostia, San Sebastian (Spain)

    2010-07-01

    Ternary anodic PtRuMo catalysts have been prepared following a two step procedure. All catalysts prepared present PtRu metal loading of 30%wt and a Mo load of 0, 1, 2.5 and 5%wt supported on Vulcan XC 72R. Different physicochemical techniques have been employed for the analysis of the catalysts as well as electrochemical techniques in combination with FTIR for in situ studies. The fuel cell performance was evaluated at 80 C in a PEMFC fed with H{sub 2}/CO (10 ppm). Catalysts obtained exhibit good dispersion and small particle size (2.6 nm). FTIR results obtained in CO saturated confirm that lower amounts of CO are adsorbed on ternary catalysts compared with binary catalyst, whichever Mo composition was used. However, polarization curves of the catalysts show that the activity strongly depend on the composition, where PtRu-Mo(1%wt)/C displays the highest CO tolerance. (orig.)

  18. The onion-ring structure for Pd-Pt bimetallic clusters.

    Science.gov (United States)

    Cheng, Daojian; Wang, Wenchuan; Huang, Shiping

    2006-08-24

    The onion-ring structure is validated in the Pd-Pt bimetallic clusters of total atom numbers 147 and 309 through the Monte Carlo method by using the second-moment approximation of the tight-binding (TB-SMA) potentials, which is conceived in predicting the possible structures of the bimetallic clusters by He et al. [J. Am. Chem. Soc. 2003, 125, 11034] and Hwang et al. [J. Am. Chem. Soc. 2005, 127, 11140]. In the onion-ring structure, Pd atoms and Pt atoms occupy alternate layers of the clusters. The formation of the onion-ring structure can be associated with the fact that the single Pt impurity is favorable to stay in the subsurface layer and the central part of bimetallic clusters.

  19. First-principle investigation of the interactions between Pt{sub x}Ru{sub 55−x} (x = 0, 13, 42, 55) nanoparticles and [BMIM][PF{sub 6}] ionic liquid

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Ping; Liu, Chuan; Yang, Yongpeng; Huang, Shiping, E-mail: huangsp@mail.buct.edu.cn

    2015-05-01

    Highlights: • Interaction between PtRu nanoparticle and [BMIM][PF{sub 6}] is performed by DFT calculations. • The structure of Pt{sub 13}Ru{sub 42} nanoparticle is distorted induced by [BMIM][PF{sub 6}]. • The d-band center show that catalytic activities of Pt{sub 13}Ru{sub 42} and Ru{sub 55} are enhanced. • Two C atoms of [BMIM][PF{sub 6}] form the bond with Pt{sub 13}Ru{sub 42} nanoparticles. - Abstract: Density functional theory calculations have been performed to characterize the interactions between [BMIM][PF{sub 6}] ionic liquid and icosahedral Pt{sub x}Ru{sub 55−x} (x = 0, 13, 42, 55) nanoparticles. In Ru{sub 13}Pt{sub 42}–[BMIM][PF{sub 6}], only one F atom of the anion form the bond with nanoparticle, resulting in the smallest interaction energy (−0.56 eV). While in Pt{sub 13}Ru{sub 42}–[BMIM][PF{sub 6}], two F atoms of the anion together with two C atoms of cation form the bonds with nanoparticle, resulting in the biggest interaction energy (−10.65 eV). The interaction between [BMIM][PF{sub 6}] and Pt{sub 13}Ru{sub 42} is so strong that it induces a significant distortion in the original core–shell structure of Pt{sub 13}Ru{sub 42}. Moreover, after interacting with [BMIM][PF{sub 6}], the Pt{sub 55}, Pt{sub 13}Ru{sub 42} and Ru{sub 55} nanoparticles become more stable based on the negative relaxation energy. The d-band centers of Pt{sub 13}Ru{sub 42} and Ru{sub 55} shift from −1.90, −1.78 eV up to −1.78, −1.56 eV, suggesting that the catalytic activities of Pt{sub 13}Ru{sub 42} and Ru{sub 55} are enhanced.

  20. L10 ordered phase formation in FePt, FePd, CoPt, and CoPd alloy thin films epitaxially grown on MgO(001) single-crystal substrates

    Science.gov (United States)

    Ohtake, Mitsuru; Ouchi, Shouhei; Kirino, Fumiyoshi; Futamoto, Masaaki

    2012-04-01

    The FePt, FePd, CoPt, and CoPd epitaxial thin films are prepared on MgO(001) single-crystal substrates by ultrahigh vacuum RF magnetron sputtering. The effects of the magnetic material and the substrate temperature on the film growth, the film structure, and the magnetic properties are investigated. The L10 ordered phase formation is observed for FePt, FePd, and CoPt films prepared at temperatures higher than 200, 400, and 600 °C, respectively, whereas that is not recognized for CoPd films. The L10-FePd(001) single-crystal films with the c-axis normal to the substrate surface are formed, whereas the FePt and CoPt epitaxial films include L10(100) crystals whose c-axis is parallel to the substrate surface, in addition to the L10(001) crystals. Upon increasing the substrate temperature, the ordering degree increases. A higher ordering parameter is observed in the order of FePd > FePt > CoPt. The magnetic properties are influenced by the crystal structure, the crystallographic orientation of the L10 crystal, and the ordering degree.

  1. Influence of rapid thermal annealing effect on electrical and structural properties of Pd/Ru Schottky contacts to n-type GaN

    Energy Technology Data Exchange (ETDEWEB)

    Reddy, N. Nanda Kumar [Department of Physics, Sri Venkateswara University, Tirupati 517 502 (India); Reddy, V. Rajagopal, E-mail: reddy_vrg@rediffmail.com [Department of Physics, Sri Venkateswara University, Tirupati 517 502 (India); Choi, Chel-Jong [School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center (SPRC), Chonbuk National University, Jeonju 561-756 (Korea, Republic of)

    2011-11-01

    Highlights: {yields} Annealing effects on the electrical and structural properties of Ru/Pd/n-GaN SBDs are studied. {yields} The optimum annealing temperature for Pd/Ru Schottky contact is 300 deg. C. {yields} Increase in SBH upon annealing at 300 deg. C could be attributed to the formation of gallide phases. {yields} The overall surface morphology of the Pd/Ru Schottky contacts on n-GaN is fairly smooth. - Abstract: Pd/Ru metallization scheme is fabricated on n-GaN as a Schottky contact, and the electrical and structural properties have been investigated as a function of annealing temperature by current-voltage (I-V), capacitance-voltage (C-V), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) measurements. As-deposited Ru/Pd/n-GaN contact yielded Schottky barrier height (SBH) of 0.67 eV (I-V) and 0.79 eV (C-V), respectively. Further, it is observed that the Schottky barrier height increases to 0.80 eV (I-V) and 0.96 eV (C-V) for the contact annealed at 300 deg. C. However, both I-V and C-V measurements indicate that the barrier height slightly decreased when the contacts are annealed at 400 deg. C and 500 deg. C. From the above observations, the optimum annealing temperature for Pd/Ru Schottky contact is 300 deg. C. Norde method is also employed to extract the barrier height of Pd/Ru Schottky contacts which are in good agreement with those obtained by the I-V technique. X-ray photoelectron spectroscopy results shows that the Ga 2p core-level shift towards the low-energy side for the contact annealed at 300 deg. C compared to the as-deposited contact. Based on the XPS and XRD results, the reason for the increase in SBH upon annealing at 300 deg. C could be attributed to the formation of gallide phases at the Ru/Pd/n-GaN interface vicinity. The AFM results showed that the overall surface morphology of the Pd/Ru Schottky contacts on n-GaN is fairly smooth. The above observations reveal that the Pd/Ru Schottky contact is attractive for high

  2. Effect of an Sb-Doped SnO2 Support on the CO-Tolerance of Pt2Ru3 Nanocatalysts for Residential Fuel Cells

    Directory of Open Access Journals (Sweden)

    Yoshiyuki Ogihara

    2016-09-01

    Full Text Available We prepared monodisperse Pt2Ru3 nanoparticles supported on carbon black and Sb-doped SnO2 (denoted as Pt2Ru3/CB and Pt2Ru3/Sb-SnO2 with identical alloy composition and particle size distribution by the nanocapsule method. The activities for the hydrogen oxidation reaction (HOR of these anode catalysts were examined in H2-saturated 0.1 M HClO4 solution in both the presence and absence of carbon monoxide by use of a channel flow electrode at 70 °C. It was found that the CO-tolerant HOR mass activity at 0.02 V versus a reversible hydrogen electrode (RHE on the Pt2Ru3/Sb-SnO2 electrode was higher than that at the Pt2Ru3/CB electrode in 0.1 M HClO4 solution saturated with 1000 ppm CO (H2-balance. The CO tolerance mechanism of these catalysts was investigated by in situ attenuated total reflection Fourier transform infrared reflection-adsorption spectroscopy (ATR-FTIRAS in 1% CO/H2-saturated 0.1 M HClO4 solution at 60 °C. It was found, for the Pt2Ru3/Sb-SnO2 catalyst, that the band intensity of CO linearly adsorbed (COL at step/edge sites was suppressed, together with a blueshift of the COL peak at terrace sites. On this surface, the HOR active sites were concluded to be more available than those on the CB-supported catalyst surface. The observed changes in the adsorption states of CO can be ascribed to an electronic modification effect by the Sb-SnO2 support.

  3. Bifunctional electrodes with ir and Ru oxide mixtures and pt for unified regenerative cells; Electrodos bifuncionales basados en mezclas de oxidos de Ir y Ru con Pt para celdas regenerativas unificadas

    Energy Technology Data Exchange (ETDEWEB)

    Duron-Torres, S.M.; Escalante-Garcia, I.L. [Universidad Autonoma de Zacatecas, Zacatecas (Mexico); Cruz, J. C.; Arriaga-Hurtado; L.G. [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, Pedro Escobedo, Queretaro (Mexico)]. E-mail: duronsm@prodigy.net.mx

    2009-09-15

    Unified regenerative fuel cells (URFC) represent an attractive option to obtain hydrogen and generate energy using a compact device. Nevertheless, the fusion of a fuel cell (PEMFC) and a water electrolyzer continue to be a challenge because of the wide range of conditions to which this type of device is subject. Because of its kinetic characteristics, oxygen reduction reaction (ORR) in PEMFC and oxygen evolution reaction (OER) in PEMWE are the limiting stages of the URFC depending on the mode of operation. The primary focus of research related to URFC is the obtainment of bifunctional electrocatalysts that satisfactorily perform in both oxygen reactions and support the different working conditions found in a fuel cell and an electrolyzer. The present work contributes to the research on bifunctional electrocatalysts and shows some preliminary results from the electrochemical study of different Pt gcc, IrO{sub 2} and RuO{sub 2} mixtures supported in Ebonex® as oxygen electrodes. The electrochemical characterization with cyclic voltamperometry (CV), linear voltamperometry (LV) and electrochemical impedance spectroscopy (EIS) in H{sub 2}SO{sub 4} 0.5 M, in the absence and present of oxygen shows that Ebonex®-supported bifunctional electrodes IrO{sub 2}-Pt and RuO{sub 2}-Pt present reasonable electrocatalytic properties for oxygen evolution and reduction reactions and present the possibility of their use in an URFC. The Ir- based oxide electrodes show greater stability than ruthenium-oxide electrodes. [Spanish] Las celdas de combustible regenerativas unificadas (URFC) representan una atractiva opcion para la obtencion de hidrogeno y generacion de energia en un dispositivo compacto. Sin embargo, la fusion de una celda de combustible (PEMFC) y un electrolizador de agua (PEMWE) sigue siendo un reto por la amplia gama de condiciones a que se sujeta un dispositivo de este tipo. Por sus caracteristicas cineticas, la reaccion de reduccion de oxigeno (ORR) en la PEMFC y la

  4. Evaluation of the behavior of PtPd/MWCNT electrocatalysts as ethylene glycol-tolerant electrodes for oxygen oxidation reaction (ORR); Evaluacion del comportamiento de electrocatalizadores tipo PtPd/MWCNT como electrodos para la reaccion de oxidacion del oxigeno (ORR) tolerantes al etilenglicol

    Energy Technology Data Exchange (ETDEWEB)

    Morales-Acosta, D.; Arriaga, L.G. [Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, Pedro Escobedo, Queretaro (Mexico)]. E-mail: dmorales@cideteq.mx; Alvarez-Contreras, L. [Centro de Investigacion en Materiales Avanzados S. C., Chihuahua, Chihuahua (Mexico); Fraire Luna, S.; Rodriguez Varela, F.J. [Cinvestav, Unidad Saltillo, Ramos Arizpe, Coahuila, (Mexico)

    2009-09-15

    Pt-Pd/MWCNTs (atomic ratio Pt:Pd 43:57) and Pt/MWCNTs electrocatalysts were synthesized and evaluated as cathodes for oxygen reduction reaction (ORR) with the application of direct ethylene glycol fuel cells (DEGFC). A commercial PtC material was also evaluated as a reference. It was found that Pt-Pd/MWCNT has a capability for high tolerance to ethylene glycol (EG) and higher selectivity for ORR compared to a single Pt- cathode. As a result, the change in onset potential of the ORR, Eonset, in Pt-Pd/MWCNTs was considerably less than the change in Pt/MWCNTs or Pt/C. The average particle size (XRD) was 3.5nm and 4nm for Pt/MWCNTs and Pt-Pd/MWCNTs, respectively. A moderate degree of alloying was determined for the material. The application of Pt-Pd electrocatalysts in DEGFCs should be advantageous. [Spanish] Electrocatalizadores Pt-Pd/MWCNTs (relacion atomic Pt:Pd 43:57) y Pt/MWCNTs fueron sintetizados y evaluados como catodos para la reaccion de reduccion del oxigeno (ORR) con aplicacion del celdas de consumo directo de etilenglicol (Direct Ethylene Glycol Fuel Cells, o DEGFC). Como referencia, un material comercial tipo Pt/C fue tambien evaluado. Se encontro que Pt-Pd/MWCNTs tiene una alta capacidad de tolerancia al etilenglicol (EG) y una selectividad mayor hacia la ORR comparado con el catodo basado en Pt-solo. Como resultado, el cambio en potencial de inicio de la ORR, Eonset, en Pt-Pd/MWCNTs fue considerablemente menor que el cambio en Pt/MWCNTs o Pt/C. La talla de particula promedio (de XRD) fue 3.5 nm y 4 nm para Pt/MWCNTs y Pt-Pd/MWCNTs, respectivamente. Un moderado grado de aleacion fue determinado para el material. Una aplicacion ventajosa para electrocatalizadores tipo Pt-Pd debe ser en DEGFCs.

  5. Pt单层修饰Pd/C氧还原催化剂%Pt monolayer on Pd/C as electrocatalyst for oxygen reduction reaction

    Institute of Scientific and Technical Information of China (English)

    章欢; 戴煜; 胡晓宏; 陈胜利; 陈经广

    2011-01-01

    Carbon supported Pd nanoparticle catalysts (Pd/C) for oxygen reduction reaction (ORR) were synthesized by using the liquid-phase pyrolysis method and the impregnation method respectively. Although the Pd/C catalysts produced in liquid phase method possessed larger particle sizes, they exhibited higher activity for ORR and much better durability as compared with Pd/C prepared by the impregnation-reduction method. By galvanic displacement of the monolayer Cu formed on Pd nanoparticle surface through under potential deposition, Pt monolayer decorated Pd/C catalysts (PtML/Pd/C) were fabricated. The thus prepared Pt monolayer catalysts exhibited ORR activity close and durability superior to the state-of-the-art commercial Pt/C. The Pt mass activity of the PtML/Pd/C catalyst for ORR was more than 4 times higher than that given by the Pt/C, showing a great perspective of the Pt monolayer electrocatalysts in fuel cells applications.%分别利用液相热解法和浸渍还原法制备了碳载钯纳米催化剂(Pd/C),并研究了其对氧还原反应的电催化活性.与浸渍还原法相比,液相热解法得到的Pd/C催化剂虽然粒径较大,但表现出较好的氧还原反应(ORR)活性和稳定性在所制备的Pd/C催化剂基础上,通过置换欠电势沉积的Cu原子单层,获得了Pt单层修饰的Pd/C催化剂,其ORR活性较Pd/C催化剂有显著提高,且与纯Pt/C催化剂接近,而其耐久性则较纯Pt/C催化剂有显著提升,显示出Pt单层催化剂的潜在优势.

  6. Critical Factors Controlling Pd and Pt Potential in Porphyry Cu–Au Deposits: Evidence from the Balkan Peninsula

    Directory of Open Access Journals (Sweden)

    Demetrios G. Eliopoulos

    2014-03-01

    Full Text Available Porphyry Cu–Au–Pd±Pt deposits are significant Au resources, but their Pd and Pt potential is still unknown. Elevated Pd, Pt (hundreds of ppb and Au contents are associated with typical stockwork magnetite-bornite-chalcopyrite assemblages, at the central parts of certain porphyry deposits. Unexpected high grade Cu–(Pd+Pt (up to 6 ppm mineralization with high Pd/Pt ratios at the Elatsite porphyry deposit, which is found in a spatial association with the Chelopech epithermal deposit (Bulgaria and the Skouries porphyry deposit, may have formed during late stages of an evolved hydrothermal system. Estimated Pd, Pt and Au potential for porphyry deposits is consistent with literature model calculations demonstrating the capacity of aqueous vapor and brine to scavenge sufficient quantities of Pt and Pd, and could contribute to the global platinum-group element (PGE production. Critical requirements controlling potential of porphyry deposits may be from the metals contained in magma (metasomatized asthenospheric mantle wedge as indicated by significant Cr, Co, Ni and Re contents. The Cr content may be an indicator for the mantle input.

  7. Influence of hydrogen on the thermoelectric power of palladium alloyed with neighbouring elements: I. Pd/Ru/H and Pd/Rh/H alloys

    CERN Document Server

    Szafranski, A W

    2003-01-01

    Pd/Ru and Pd/Rh alloys have been loaded with hydrogen in high-pressure conditions. The resulting hydrogen contents were close to the stoichiometric composition, H/(Pd + Me) = 1. Lower hydrogen contents have been obtained by successive partial desorptions. The thermoelectric power and electrical resistance of one- and two-phase alloys have been measured simultaneously in the temperature range between 80 and 300 K. A Nordheim-Gorter type correlation of the two quantities has been observed in many cases and the partial thermopowers corresponding to electron-phonon scattering and lattice disorder could be determined. The observed anomalous behaviour of the total and partial thermopowers is attributed to virtual bound states of ruthenium or rhodium.

  8. The pilot test of Pt-Pd and Pt-Rh feeds extracted and separated with a new sulfoxide extractant

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Platinum, palladium and rhodium of the raw feeds extracted and separated with a new sulfoxide extractant (MSO)were studied in the paper. The pilot test results showed that the percentage extractions are more than 99% for platinum and palladium in Pt-Pd feed, and the percentage strippings are 100% and 99.2% with HCl and ammonia, respectively. The ratio of palladium to platinum is 0.0016 in stripping platinum solution, and the ratio of platinum to palladium is 0.0020 in stripping palladium solution. The percentage extraction of platinum is 99% in Pt-Rh feed, and the percentage stripping is 100%.The ratio of rhodium to platinum is 0.0002 in stripping platinum solution. Therefore, platinum, palladium, and rhodium feeds are separated effectively with MSO.

  9. Predictions of the Pt(8)Ti phase in unexpected systems.

    Science.gov (United States)

    Taylor, Richard H; Curtarolo, Stefano; Hart, Gus L W

    2010-05-19

    The binary A(8)B phase (prototype Pt(8)Ti) has been experimentally observed in 11 systems. A high-throughput search over all the binary transition intermetallics, however, reveals 59 occurrences of the A(8)B phase: Au(8)Zn(dagger), Cd(8)Sc(dagger), Cu(8)Ni(dagger), Cu(8)Zn(dagger), Hg(8)La, Ir(8)Os(dagger), Ir(8)Re, Ir(8)Ru(dagger), Ir(8)Tc, Ir(8)W(dagger), Nb(8)Os(dagger), Nb(8)Rh(dagger), Nb(8)Ru(dagger), Nb(8)Ta(dagger), Ni(8)Fe, Ni(8)Mo(dagger)*, Ni(8)Nb(dagger)*, Ni(8)Ta*, Ni(8)V*, Ni(8)W, Pd(8)Al(dagger), Pd(8)Fe, Pd(8)Hf, Pd(8)Mn, Pd(8)Mo*, Pd(8)Nb, Pd(8)Sc, Pd(8)Ta, Pd(8)Ti, Pd(8)V*, Pd(8)W*, Pd(8)Zn, Pd(8)Zr, Pt(8)Al(dagger), Pt(8)Cr*, Pt(8)Hf, Pt(8)Mn, Pt(8)Mo, Pt(8)Nb, Pt(8)Rh(dagger), Pt(8)Sc, Pt(8)Ta, Pt(8)Ti*, Pt(8)V*, Pt(8)W, Pt(8)Zr*, Rh(8)Mo, Rh(8)W, Ta(8)Pd, Ta(8)Pt, Ta(8)Rh, V(8)Cr(dagger), V(8)Fe(dagger), V(8)Ir(dagger), V(8)Ni(dagger), V(8)Pd, V(8)Pt, V(8)Rh, and V(8)Ru(dagger) ((dagger) = metastable, * = experimentally observed). This is surprising for the wealth of new occurrences that are predicted, especially in well-characterized systems (e.g., Cu-Zn). By verifying all experimental results while offering additional predictions, our study serves as a striking demonstration of the power of the high-throughput approach. The practicality of the method is demonstrated in the Rh-W system. A cluster-expansion-based Monte Carlo model reveals a relatively high order-disorder transition temperature.

  10. Template-engaged synthesis of RuSe 2 and Pd 17Se 15 nanotubes by reacting precursor salts with selenium nanowires

    Science.gov (United States)

    Jiang, Xuchuan; Mayers, Brian; Wang, Yuliang; Cattle, Bryan; Xia, Younan

    2004-02-01

    In the present work, nanowires of trigonal selenium ( t-Se) were reacted with Ru(acac) 3 and Pd(acac) 2 (or PdCl 2) to generate RuSe 2 and Pd 17Se 15 on the surface of each t-Se nanowire as a uniform, conformal sheath. The unreacted cores of selenium could be evaporated by heating the as-synthesized Se@RuSe 2 and Se@Pd 17Se 15 nanocables to yield selenide nanotubes with their typical wall-thickness around 6 nm. This template-engaged approach allowed for the production of both nanocables and nanotubes in a relatively large scale, and is believed to be able to get extended to synthesize other chalcogenides as tubular nanostructures.

  11. Investigation of the behavior of Pt-Ru mixtures with nafion in the oxygen reduction reaction; Investigacion del comportamiento de mezclas de Pt-Ru con nafion en la reaccion de reduccion de oxigeno

    Energy Technology Data Exchange (ETDEWEB)

    Enriquez M, O

    2005-07-01

    In this work the electrochemical study for the reduction reaction of oxygen (RRO) of ruthenium, platinum and two mixtures of Pt-Ru (10:90) and Pt-Ru (50:50); to this last its were determined the kinetic and electrochemical parameters. The platinum used was analytical platinum and the ruthenium it was obtained of the decarboxylation of 200 mg of ruthenium dode carbonyl with 200 ml of 1-2 dichlorobenzene under a reflux system by 20 hours with agitation. Decanted and centrifuged by 30 minutes, the obtained ruthenium was washed with ether and it was evaporated for it later use. The material was characterized by means of X-ray diffraction, elementary analysis, scanning electron microscopy and infrared spectroscopy. To determine the optimum quantity of nafion to be deposited on the catalytic material, they were carried out tests with different quantities deposited on the electrodes with 1, 2, 4 and 8 {mu}L, giving better result 2 {mu}L for that it was opted for to work with this proportion in the mixtures. The electrochemical performance of 2 ruthenium relationships and platinum 0.05 mg - 0.45 mg and 0.25 mg - 0.25 mg respectively were studied with a potentiostat galvanostat EG and G Princeton Applied Research model 273a; it was found that the electrode with the mixture of 0.25 mg of platinum with 0.25 mg of ruthenium has a bigger response of current intensity after to deposit the nafion in the surface. The electro active area was determined carrying out recurrent voltametry to different scanning velocities (5, 10, 20, 30, 40, 50, 60, 70 and 80 mV/s) in the non faraday region with a value of 0.2082 cm{sup 2}. The mixture Pt-Ru (50:50) it presents a first order kinetics for the RRO and it is carried out via 4 electrons; the study of current density in function of the temperature presents values of 0.47 {+-} 0.3 for the charge transfer coefficient, of 118 mV/decade for the Tafel slope and it has an activation energy of 0.39 eV. (Author)

  12. Efficiency of bimetallic PtPd on polydopamine modified on various carbon supports for alcohol oxidations

    Science.gov (United States)

    Pinithchaisakula, A.; Ounnunkad, K.; Themsirimongkon, S.; Promsawan, N.; Waenkaew, P.; Saipanya, S.

    2017-02-01

    In this work, the preparation, characterization, and electrocatalytic analysis of the catalysts on various carbon substrates for direct alcohol fuel cells were studied. Selected carbons were modified with/without polydopamine (labelled as PDA-C and C) and further metal electrodeposited incorporated onto the glassy carbon (labelled as 5Pt1Pd/PDA-C and 5Pt1Pd/C). Four various carbon materials were used e.g. graphite (G), carbon nanotube (CNT), graphene (GP) and graphene oxide (GO) and the carbons were modified with PDA denoted as PDA-G, PDA-CNT, PDA-GP and PDA-GO, respectively. The transmission electron microscopy (TEM) and scanning electron microscopy (SEM) experimental observation showed narrow size distribution of metal anchored on the PDA-C and C materials. Chemical compositions and oxidation states of the catalysts were determined by X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX). The catalytic performances for small organic electro-oxidation (e.g. methanol and ethanol) were measured by cyclic voltammetry (CV). Among different PDA-C and C catalysts, monometallic Pt showed less activity than the bimetallic catalysts. Among catalysts with PDA, the 5Pt1Pd/PDA-GO catalyst facilitated methanol and ethanol oxidations with high oxidation currents and If/Ib value and stability with low potentials while among catalysts without PDA, the 5Pt1Pd/CNT provides highest activity and stability. It was found that the catalysts with PDA provided high activity and stability than the catalysts without PDA. The improved catalytic performance of the prepared catalysts could be related to the higher active surface area from polymer modification and bimetallic catalyst system in the catalyst composites.

  13. Production of ultrapure hydrogen in a Pd-Ag membrane reactor using Ru/La{sub 2}O{sub 3} catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Faroldi, B.; Carrara, C.; Lombardo, E.A.; Cornaglia, L.M. [Instituto de Investigaciones en Catalisis y Petroquimica (FIQ, UNL-CONICET), Santiago del Estero, 2829-3000 Santa Fe (Argentina)

    2007-03-01

    Ru catalysts supported on lanthanum oxide with different loadings were prepared by wet impregnation. These solids were characterized by laser Raman spectroscopy (LSR), XPS, XRD and TPR. The catalytic activity toward hydrogen production through the dry reforming of methane was determined in a fixed-bed reactor and a membrane reactor. The reaction rate expressed per gram of Ru decreased when the metal loading increased. In the Pd-Ag membrane reactor, when the sweep gas flow rate (SG) increased, the conversions overcame the equilibrium values and the difference between CH{sub 4} and CO{sub 2} conversions decreased. Both Ru(0.6) and Ru(1.2) catalysts were able to restore the equilibrium for the dry reforming reaction up to values of SG = 30 ml min{sup -1}; Ru(0.6) was the most effective catalyst. By employing a CO{sub 2}/CH{sub 4} 1 and a SG of 0.05 mmol s{sup -1}, both a high H{sub 2} permeation flux of 5.68 x 10{sup -7} mol s{sup -1} m{sup -2} and a hydrogen recovery of 80% were obtained. Both the TPR and the Raman spectroscopy data indicated the presence of Ru(III) strongly interacting with La. Significantly, this observation was further confirmed by the appearance of Ru(III) on the surface. When the Ru content increased, the higher Ru 3d binding energy component was proposed as arising from Ru(IV). Concerning the Ru(1.2) solid, the presence of Ru(IV) was detected by means of TPR experiments, in agreement with the high proportion of Ru(IV) on the surface. Therefore, a fraction of Ru loading was present in this solid as species with weaker metal-support interaction leading to the slight deactivation of this catalyst in the membrane reactor. (author)

  14. Activated carbon fibers impregnated with Pd and Pt catalysts for toluene removal.

    Science.gov (United States)

    Liu, Zhen-Shu; Chen, Jian-Yuan; Peng, Yu-Hui

    2013-07-15

    Few studies have investigated the use of activated carbon fibers (ACFs) impregnated with noble metals for the catalytic oxidation of volatile organic compounds (VOCs). This study determined the removal efficiency of toluene as a function of time over ACF-supported metal catalysts. Two catalysts (Pt and Pd), five reaction temperatures (120, 150, 200, 250, and 300°C), and three oxygen contents (6%, 10%, and 21%) were investigated to determine the removal of toluene. To study the effects of the characteristics of the catalysts on toluene removal, the composition and morphology of the ACFs were analyzed using the BET, XPS, ICP, and FE-SEM. The results showed that the 0.42%Pd/ACFs showed greater activity for toluene removal than did 2.68%Pt/ACFs at a reaction temperature of 200°C and an oxygen content of 10%. The main removal mechanism of toluene over the 2.68%Pt/ACFs at reaction temperatures less than 200°C was adsorption. The long-term catalytic activity of the 2.68%Pt/ACFs for toluene removal at a reaction temperature of 250°C and an oxygen content of 10% could be obtained. Furthermore, toluene removal over the 2.68%Pt/ACFs at 200°C could be enhanced with increasing oxygen content.

  15. Fast response and recovery of hydrogen sensing in Pd-Pt nanoparticle-graphene composite layers

    Science.gov (United States)

    Kumar, Rakesh; Varandani, Deepak; Mehta, B. R.; Singh, V. N.; Wen, Zhenhai; Feng, Xinliang; Müllen, Klaus

    2011-07-01

    This study reports the fast response and recovery of hydrogen sensing in nanoparticle-graphene composite layers fabricated using chemical methods and comprising of isolated Pd alloy nanoparticles dispersed onto graphene layers. For 2% hydrogen at 40 °C and 1 atm pressure, a response time of Pd-Pt nanoparticle-graphene composite material are important for understanding the effect of gas adsorption on electronic conduction in graphene layers and for developing a new type of gas sensor based on changes in the electronic properties of the interface.

  16. Structure analysis of CoPt alloy film with metastable ordered phases of L11 and Bh formed on Ru(0001 underlayer

    Directory of Open Access Journals (Sweden)

    Ohtake Mitsuru

    2014-07-01

    Full Text Available CoPt alloy films of 40 nm thickness are prepared on MgO(111 substrates with and without Ru(0001 underlayer at 300 °C by radio-frequency magnetron sputtering. CoPt films with the close-packed plane parallel to the substrate surface grow epitaxially on the Ru underlayer as well as on the MgO substrate. Flat surfaces with the arithmetical mean roughness value of 0.2 nm are realized for both films. The crystal structure is determined by considering the atomic stacking sequence of close-packed plane and the order degree. The film formed on MgO substrate consists of an fcc-based L11 ordered crystal, whereas the film grown on Ru underlayer involves an hcp-based Bh ordered crystal in addition to the L11 ordered crystal. The order degrees of films formed on MgO substrate and Ru underlayer are 0.30 and 0.34, respectively. The L11 crystal consists of two variants whose stacking sequences of close-packed plane are ABCABC… and ACBACB…, while the Bh crystal is a single-crystal with the stacking sequence of ABAB… Formation of Bh crystal is promoted on the Ru underlayer. The film formed on Ru underlayer shows a strong perpendicular magnetic anisotropy reflecting the magnetocrystalline anisotropies of L11 and Bh crystals.

  17. Synthesis of Pd-Pt bimetallic nanocrystals with a concave structure through a bromide-induced galvanic replacement reaction.

    Science.gov (United States)

    Zhang, Hui; Jin, Mingshang; Wang, Jinguo; Li, Weiyang; Camargo, Pedro H C; Kim, Moon J; Yang, Deren; Xie, Zhaoxiong; Xia, Younan

    2011-04-20

    This article describes a systematic study of the galvanic replacement reaction between PtCl(6)(2-) ions and Pd nanocrystals with different shapes, including cubes, cuboctahedrons, and octahedrons. It was found that Br(-) ions played an important role in initiating, facilitating, and directing the replacement reaction. The presence of Br(-) ions led to the selective initiation of galvanic replacement from the {100} facets of Pd nanocrystals, likely due to the preferential adsorption of Br(-) ions on this crystallographic plane. The site-selective galvanic replacement resulted in the formation of Pd-Pt bimetallic nanocrystals with a concave structure owing to simultaneous dissolution of Pd atoms from the {100} facets and deposition of the resultant Pt atoms on the {111} facets. The Pd-Pt concave nanocubes with different weight percentages of Pt at 3.4, 10.4, 19.9, and 34.4 were also evaluated as electrocatalysts for the oxygen reduction reaction (ORR). Significantly, the sample with a 3.4 wt.% of Pt exhibited the largest specific electrochemical surface area and was found to be four times as active as the commercial Pt/C catalyst for the ORR in terms of equivalent Pt mass.

  18. [Determination of ru, rh and Pd in 30% trialkyl phosphine oxide (TRPO)-kerosene by inductively coupled plasma-atomic emission spectrum (ICP-AES)].

    Science.gov (United States)

    Wang, Jian-Chen; Zhang, Lin

    2013-07-01

    The determination method of Ru, Rh and Pd in 30% TRPO-kerosene ICP-AES was studied by using aqueous calibration reference solution and choosing ethanol as diluent. The effects of the contents of 30% TRPO-kerosene and aqueous solution and the concentration of HNO3 in 30% TRPO-kerosene on the intensities of Ru, Rh and Pd were described. The optimized condition for preparing samples and calibration solutions was chosen as follows: The contents of 30% TRPO-kerosene and aqueous phase were 10% (V/V) and 5% (V/V) respectively and the concentration of HNO3 30% TRPO-kerosene was 0.20 mol x L(-1). The determination method of Au, Ru and Pd was set up according to the above condition. The detection limit, precision and recovery ratio of Ru, Rh and Pd are well. The method is not only used in determination of Au, Ru and Pd in 30% TRPO-kerosene, but also used in other organic phases.

  19. Synthesis-atomic structure-properties relationships in metallic nanoparticles by total scattering experiments and 3D computer simulations: case of Pt-Ru nanoalloy catalysts.

    Science.gov (United States)

    Prasai, Binay; Ren, Yang; Shan, Shiyao; Zhao, Yinguang; Cronk, Hannah; Luo, Jin; Zhong, Chuan-Jian; Petkov, Valeri

    2015-05-07

    An approach to determining the 3D atomic structure of metallic nanoparticles (NPs) in fine detail and using the unique knowledge obtained for rationalizing their synthesis and properties targeted for optimization is described and exemplified on Pt-Ru alloy NPs of importance to the development of devices for clean energy conversion such as fuel cells. In particular, PtxRu100-x alloy NPs, where x = 31, 49 and 75, are synthesized by wet chemistry and activated catalytically by a post-synthesis treatment involving heating under controlled N2-H2 atmosphere. So-activated NPs are evaluated as catalysts for gas-phase CO oxidation and ethanol electro-oxidation reactions taking place in fuel cells. Both as-synthesized and activated NPs are characterized structurally by total scattering experiments involving high-energy synchrotron X-ray diffraction coupled to atomic pair distribution functions (PDFs) analysis. 3D structure models both for as-synthesized and activated NPs are built by molecular dynamics simulations based on the archetypal for current theoretical modelling Sutton-Chen method. Models are refined against the experimental PDF data by reverse Monte Carlo simulations and analysed in terms of prime structural characteristics such as metal-to-metal bond lengths, bond angles and first coordination numbers for Pt and Ru atoms. Analysis indicates that, though of a similar type, the atomic structure of as-synthesized and respective activated NPs differ in several details of importance to NP catalytic properties. Structural characteristics of activated NPs and data for their catalytic activity are compared side by side and strong evidence found that electronic effects, indicated by significant changes in Pt-Pt and Ru-Ru metal bond lengths at NP surface, and practically unrecognized so far atomic ensemble effects, indicated by distinct stacking of atomic layers near NP surface and prevalence of particular configurations of Pt and Ru atoms in these layers, contribute to the

  20. Ni/Carbon Hybrid Prepared by Hydrothermal Carbonization and Thermal Treatment as Support for PtRu Nanoparticles for Direct Methanol Fuel Cell

    Institute of Scientific and Technical Information of China (English)

    Marcelo Marques Tusi; Michele Brandalise; Nataly Soares de Oliveira Polanco; Olandir Vercino Correa; Antonio Carlos da Silva; Juan Carlo Villalba; Fauze Jaco Anaissi

    2013-01-01

    Ni/Carbon was prepared in two steps:initially cellulose as carbon source and NiCl2.6H20 as catalyst of the carbonization process were submitted to hydrothermal treatment at 200 ℃ and further to thermal treatment at 900 ℃ under argon atmosphere.The obtained material contains Ni nanoparticles with face-centered cubic (fcc) structure dispersed on amorphous carbon with graphitic domains.PtRu/C electrocatalysts (carbonsupported PtRu nanoparticles) were prepared by an alcohol-reduction process using Ni/Carbon as support.The materials were characterized by thermogravimetric analysis,energy-dispersive X-ray spectroscopy,Fourier transform infrared spectroscopy,X-ray diffraction,transmission electron microscopy and tested as anodes in single direct methanol fuel cell (DMFC).The performances of PtRu/C electrocatalysts using Ni/Carbon as support were superior to those obtained for PtRu/C using commercial carbon black Vulcan XC72 as support.

  1. Characterization and reactivity of Pd Pt bimetallic supported catalysts obtained by laser vaporization of bulk alloy

    Science.gov (United States)

    Rousset, J. L.; Cadete Santos Aires, F. J.; Bornette, F.; Cattenot, M.; Pellarin, M.; Stievano, L.; Renouprez, A. J.

    2000-09-01

    Bimetallic Pd-Pt clusters produced by laser vaporization of bulk alloy have been deposited on high surface alumina. Energy dispersive X-ray (EDX) analysis and transmission electron microscopy (TEM) show that they have a perfectly well-defined stoichiometry and a narrow range of size. Therefore, they constitute ideal systems to investigate alloying effects towards reactivity. Pd-Pt alloys are already known for their applications in the hydrogenation of unsaturated hydrocarbons, especially aromatics, because this system is highly resistant to sulfur and nitrogen poisoning. In this context, the catalytic properties of this system have been investigated in the hydrogenation of tetralin in the presence of hydrogen sulfide. Preliminary results show that this model catalyst is more sulfur-resistant than each of the pure supported metals prepared by chemical methods.

  2. Sintering of oxide-supported Pt and Pd nanoparticles in air studied by in situ TEM

    DEFF Research Database (Denmark)

    Simonsen, Søren Bredmose

    at elevated temperatures. The time-resolved TEM images are presented and these offer direct insight into the fundamental dynamics of the sintering process at the nano-scale. For Pt, Pd and bimetallic Pt-Pd nanoparticles it is shown that the sintering process is governed by the Ostwald ripening mechanism...... correlations between neighbouring nanoparticles in the atom-exchange process. The sintering process was also presented statistically by particle size distributions extracted from the TEM images. The statistical data agreed only partly with the mean-field kinetic models for ripening, but the deviations could......This thesis presents a fundamental study of the sintering of supported nanoparticles in relation to diesel oxidation catalysts. The sintering of supported nanoparticles is an important challenge in relation to this catalyst, as well as many other catalyst systems, and a fundamental understanding...

  3. Anisotropic thermal expansion of Ni, Pd and Pt germanides and silicides

    Science.gov (United States)

    Geenen, F. A.; Knaepen, W.; Moens, F.; Brondeel, L.; Leenaers, A.; Van den Berghe, S.; Detavernier, C.

    2016-07-01

    Silicon or germanium-based transistors are nowadays used in direct contact with silicide or germanide crystalline alloys for semiconductor device applications. Since these compounds are formed at elevated temperatures, accurate knowledge of the thermal expansion of both substrate and the contact is important to address temperature depending effects such as thermal stress. Here we report the linear coefficients of thermal expansion of Ni-, Pd- and Pt-based mono-germanides, mono-silicides and di-metal-silicides as determined by powder-based x-ray diffraction between 300 and 1225 K. The investigated mono-metallic compounds, all sharing the MnP crystal structure, as well as Pd2Si and Pt2Si exhibit anisotropic expansion. By consequence, this anisotropic behaviour should be taken into account for evaluating the crystal unit’s cell at elevated temperatures.

  4. Analysis of the applicability of Ni, Cu, Au, Pt, and Pd nanoclusters for data recording

    Science.gov (United States)

    Redel', L. V.; Gafner, S. L.; Gafner, Yu. Ya.; Zamulin, I. S.; Goloven'ko, Zh. V.

    2017-02-01

    The applicability of individual Ni, Cu, Au, Pt, and Pd nanoclusters as data bits in next generation memory devices constructed on the phase-change carrier principle is studied. To this end, based on the modified tight-binding potential (TB-SMA), structure formation from the melt of nanoparticles of these metals to 10 nm in diameter was simulated by the molecular dynamics method. The effect of various crystallization conditions on the formation of the internal structures of Ni, Cu, Au, Pt, and Pd nanoclusters is studied. The stability boundaries of various crystalline isomers are analyzed. The obtained systematic features are compared for nanoparticles of copper, nickel, gold, platinum, and palladium of identical sizes. It is concluded that platinum nanoclusters of diameter D > 8 nm are the best materials among studied metals for producing memory elements based on phase transitions.

  5. ADSORPTION BEHAVIORS OF Pt(IV) AND Pd(II) ON POLYMERIC ESTER THIOUREA RESIN

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Polymeric ester thiourea resin (PDTU-I) is a new kind of chelating resin with functional atoms S, N and O, so it is an excellent adsorbent for noble metal ions. In batch testes, the adsorption capacities of PDTU-I for Pt(IV) and Pd(II) increase with the increase of contact time, temperature and initial concentration of metal ions. The adsorption data fit Boyd’s diffusion equation of liquid film, Langmuir adsorption isotherm and Freundlich adsorption isotherm. The maximum adsorption capacities calculated by Langmuir equation are 2.54mmol/g for Pt(IV) and 4.88mmol/g for Pd(II). According to FTIR and XPS results, functional groups of PDTU-I coordinate with noble metal ions in the adsorption process.

  6. Ternary Pd2/PtFe networks supported by 3D graphene for efficient and durable electrooxidation of formic acid.

    Science.gov (United States)

    Hu, Chuangang; Zhao, Yang; Cheng, Huhu; Hu, Yue; Shi, Gaoquan; Dai, Liming; Qu, Liangti

    2012-12-18

    A newly-designed network of ternary Pd(2)/PtFe nanowires on a three-dimensional graphene framework has been fabricated via a dual solvothermal approach, which presents superior electrocatalytic activity towards the oxidation of formic acid.

  7. Abnormal infrared effects of nanometer scale thin film material of PtPd alloy in CO adsorption

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Nanometer scale thin film material of PtPd alloy supported on glassy carbon (nm-PtPd/GC) was prepared by the electrochemical codeposition method under cyclic voltammetric conditions. STM patterns demonstrated that the prepared thin films are composed of layered crystallites in elliptic form. Electrochemical in situ FTIRS studies explored the abnormal infrared effects (AIREs) of nmPtPd/GC for CO adsorption, which are ( i ) the remarkable enhancement of IR absorption, (ii) the inversion of COad band direction, and (iii) notable increase in the full width at half maximum (FWHM) of COad bands. The results demonstrated also that the enhancement factor of IR absorption varies with the thickness of PtPd alloy film and has reached a maximum value of 38.3 under the experimental conditions.

  8. Size dependence of thermoelectric power of Au, Pd, Pt nanoclusters deposited onto HOPG surface

    OpenAIRE

    Borisyuk, P. V.; V. I. Troyan; Lebedinskii, Yu Yu; Vasilyev, O S

    2016-01-01

    The paper presents the study of tunnel current-voltage characteristics of Au, Pd and Pt nanoclusters deposited onto the highly oriented pyrolytic graphite (HOPG) surface by pulsed laser deposition. The analysis of tunnel current-voltage characteristics obtained by scanning tunneling spectroscopy (STS) allowed to recover the thermoelectric power value of nanoclusters. It was found that the value of thermoelectric power of pulsed laser deposited nanoclusters depends on nanocluster material and ...

  9. Role of different Pd/Pt ensembles in determining CO chemisorption on Au-based bimetallic alloys: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Ham, Hyung Chul, E-mail: hchahm@kist.re.kr [Department of Chemical Engineering, The University of Texas at Austin, Austin, TX 78712 (United States); Fuel Cell Research Center, Korea Institute of Science and Technology, Seoul (Korea, Republic of); Manogaran, Dhivya [Department of Chemistry and Biochemistry, The University of Texas at Austin, Austin, TX 78712 (United States); Hwang, Gyeong S., E-mail: gshwang@che.utexas.edu [Department of Chemical Engineering, The University of Texas at Austin, Austin, TX 78712 (United States); Han, Jonghee; Kim, Hyoung-Juhn; Nam, Suk Woo; Lim, Tae Hoon [Fuel Cell Research Center, Korea Institute of Science and Technology, Seoul (Korea, Republic of)

    2015-03-30

    Graphical abstract: - Highlights: • Pd ensembles greatly reduce CO adsorption energy as compared to Pt ensembles. • The steeper potential energy surface of CO adsorption in Pd(1 1 1) than in Pt(1 1 1). • Switch of binding site preference in ensembles is key to determining CO adsorption. • Opposite electronic (ligand) effect in Pd and Pt ensemble. - Abstract: Using spin-polarized density functional calculations, we investigate the role of different Pd/Pt ensembles in determining CO chemisorption on Au-based bimetallic alloys through a study of the energetics, charge transfer, geometric and electronic structures of CO on various Pd/Pt ensembles (monomer/dimer/trimer/tetramer). We find that the effect of Pd ensembles on the reduction of CO chemisorption energy is much larger than the Pt ensemble case. In particular, small-sized Pd ensembles like monomer show a substantial reduction of CO chemisorption energy compared to the pure Pd (1 1 1) surface, while there are no significant size and shape effects of Pt ensembles on CO chemisorption energy. This is related to two factors: (1) the steeper potential energy surface (PES) of CO in Pd (1 1 1) than in Pt (1 1 1), indicating that the effect of switch of binding site preference on CO chemisorption energy is much larger in Pd ensembles than in Pt ensembles, and (2) down-shift of d-band in Pd ensembles/up-shift of d-band in Pt ensembles as compared to the corresponding pure Pd (1 1 1)/Pt (1 1 1) surfaces, suggesting more reduced activity of Pd ensembles toward CO adsorption than the Pt ensemble case. We also present the different bonding mechanism of CO on Pd/Pt ensembles by the analysis of orbital resolved density of state.

  10. Pt- and Pd-decorated MWCNTs for vapour and gas detection at room temperature

    Directory of Open Access Journals (Sweden)

    Hamdi Baccar

    2015-04-01

    Full Text Available Here we report on the gas sensing properties of multiwalled carbon nanotubes decorated with sputtered Pt or Pd nanoparticles. Sputtering allows for an oxygen plasma treatment that removes amorphous carbon from the surface of the carbon nanotubes and creates oxygenated surface defects in which metal nanoparticles nucleate within a few minutes. The decoration with the 2 nm Pt or the 3 nm Pd nanoparticles is very homogeneous. This procedure is performed at the device level (i.e., for carbon nanotubes deposited onto sensor substrates for many devices in one batch, which illustrates the scalability for the mass production of affordable nanosensors. The response to selected aromatic and non-aromatic volatile organic compounds, as well as pollutant gases has been studied. Pt- and Pd-decorated multiwalled carbon nanotubes show a fully reversible response to the non-aromatic volatile organic compounds tested when operated at room temperature. In contrast, these nanomaterials were not responsive to the aromatic compounds studied (measured at concentrations up to 50 ppm. Therefore, these sensors could be useful in a small, battery-operated alarm detector, for example, which is able to discriminate aromatic from non-aromatic volatile organic compounds in ambient.

  11. Formic Acid Oxidation over Hierarchical Porous Carbon Containing PtPd Catalysts

    Directory of Open Access Journals (Sweden)

    Elena Pastor

    2013-10-01

    Full Text Available The use of high surface monolithic carbon as support for catalysts offers important advantage, such as elimination of the ohmic drop originated in the interparticle contact and improved mass transport by ad-hoc pore design. Moreover, the approach discussed here has the advantage that it allows the synthesis of materials having a multimodal porous size distribution, with each pore size contributing to the desired properties. On the other hand, the monolithic nature of the porous support also imposes new challenges for metal loading. In this work, the use of Hierarchical Porous Carbon (HPC as support for PtPd nanoparticles was explored. Three hierarchical porous carbon samples (denoted as HPC-300, HPC-400 and HPC-500 with main pore size around 300, 400 and 500 nm respectively, are used as porous support. PtPd nanoparticles were loaded by impregnation and subsequent chemical reduction with NaBH4. The resulting material was characterized by EDX, XRD and conventional electrochemical techniques. The catalytic activity toward formic acid and methanol electrooxidation was evaluated by electrochemical methods, and the results compared with commercial carbon supported PtPd. The Hierarchical Porous Carbon support discussed here seems to be promising for use in DFAFC anodes.

  12. Pt-Pd bimetallic nanoparticles on MWCNTs: catalyst for hydrogen peroxide electrosynthesis

    Energy Technology Data Exchange (ETDEWEB)

    Felix-Navarro, R. M., E-mail: moi6salazar@hotmail.com; Beltran-Gastelum, M.; Salazar-Gastelum, M. I.; Silva-Carrillo, C.; Reynoso-Soto, E. A.; Perez-Sicairos, S.; Lin, S. W. [Centro de Graduados e Investigacion, Instituto Tecnologico de Tijuana (Mexico); Paraguay-Delgado, F. [Centro de Investigacion en Materiales Avanzados (Mexico); Alonso-Nunez, G. [Centro de Nanociencias y Nanotecnologia (Mexico)

    2013-08-15

    Bimetallic nanoparticles of Pt-Pd were deposited by the microemulsion method on a multiwall carbon nanotube (MWCNTs) to obtain a Pt-Pd/MWCNTs for electrocatalytic reduction of O{sub 2} to H{sub 2}O{sub 2}. The activity and selectivity of the catalyst was determined qualitatively by the rotating disk electrode method in acidic medium. The catalyst was spray-coated onto a reticulated vitreous carbon substrate and quantitatively was tested in bulk electrolysis for 20 min under potentiostatic conditions (0.5 V vs Ag/AgCl) in a 0.5 M H{sub 2}SO{sub 4} electrolyte using dissolved O{sub 2}. The bulk electrolysis experiments show that the Pt-Pd/MWCNTs catalyst is more efficient for H{sub 2}O{sub 2} electrogeneration than a MWCNTs catalyst. Nitrobenzene degradation by electrogenerated H{sub 2}O{sub 2} alone and Electro-Fenton process were also tested. Our results show that both processes decompose nitrobenzene, but the Electro-Fenton process does it more efficiently. The prepared nanoparticulated catalyst shows a great potential in environmental applications.

  13. Characterization of Pt-Pd/C Electrocatalyst for Methanol Oxidation in Alkaline Medium

    Directory of Open Access Journals (Sweden)

    S. S. Mahapatra

    2011-01-01

    Full Text Available The Pt-Pd/C electrocatalyst was synthesized on graphite substrate by the electrochemical codeposition technique. The physicochemical characterization of the catalyst was done by SEM, XRD, and EDX. The electrochemical characterization of the Pt-Pd/C catalyst for methanol electro-oxidation was studied over a range of NaOH and methanol concentrations using cyclic voltammetry, quasisteady-state polarization, chronoamperometry, and electrochemical impedance spectroscopy. The activity of methanol oxidation increased with pH due to better OH species coverage on the electrode surface. At methanol concentration (>1.0 M, there is no change in the oxidation peak current density because of excess methanol at the electrode surface and/or depletion of OH− at the electrode surface. The Pt-Pd/C catalyst shows good stability and the low value of Tafel slope and charge transfer resistance. The enhanced electrocatalytic activity of the electrodes is ascribed to the synergistic effect of higher electrochemical surface area, preferred OH− adsorption, and ad-atom contribution on the alloyed surface.

  14. Relationship between element-selective electronic states and hydrogen absorption properties of Pd-M (M =Ru ,Rh,Ag, and Au) alloys

    Science.gov (United States)

    Fujii, Kanako; Ishimatsu, Naoki; Maruyama, Hiroshi; Shishidou, Tatsuya; Hayakawa, Shinjiro; Kawamura, Naomi

    2017-01-01

    To understand how the constituent atoms participate in the hydrogenation of Pd-based alloys at ˜0.1 MPa of hydrogen pressure (PH2),we investigated the electronic states in Pd-M (M =Ru,Rh,Ag, and Au) alloys and their hydrides element-selectively by using x-ray absorption spectroscopy at the L2 ,3 edges. Spectral changes near the absorption edge demonstrate that both Pd and M atoms form bonds with H atoms in the Pd-M (M =Ru and Rh) alloys even at PH 2˜0.1 MPa. This is a striking result because high pressures of more than 1 GPa are required for the hydrogenation of Rh and Ru pure metals. In contrast, only Pd atoms bond with H atoms and the M -H bond is absent in the case of Pd-M (M =Ag and Au) alloys. Therefore, the hydrogen-induced changes in the electronic states differ between M s with fully occupied d shells and M s with partially occupied d shells. This study reveals that the thermodynamic hydrogenation properties of Pd-M alloys can be determined by a combination of the formation of the M -H bond and lattice expansion or compression by alloying Pd metal with M .

  15. Efficient photodegradation of methyl violet dye using TiO2/Pt and TiO2/Pd photocatalysts

    Science.gov (United States)

    Saeed, Khalid; Khan, Idrees; Gul, Tamanna; Sadiq, Mohammad

    2017-02-01

    Titanium oxide supported palladium (TiO2/Pd) and titanium oxide supported platinum (TiO2/Pt) nanoparticles were prepared from their precursors through the incipient wetness method. The TiO2/Pd and TiO2/Pt nanoparticles were characterized by scanning electron microscopy (SEM), and energy dispersive X-rays (EDX), while the photodegradation study of methyl violet was performed by UV/VIS spectrophotometry. The morphological study shows that the Pd and Pt were well deposited on the surface of TiO2, which was confirmed by EDX. Both TiO2/Pd and TiO2/Pt nanoparticles were used as photocatalysts for the photodegradation of methyl violet in aqueous media under UV-light irradiation. The photodegradation study revealed that the TiO2/Pd and TiO2/Pt nanoparticles degraded about 95 and 78% of dye within 20 min, respectively. The effect of various parameters such as catalyst dosage, concentration of dye, and medium on the photocatalytic degradation was examined. The activity of recovered TiO2/Pd and TiO2/Pt nanoparticles was studied.

  16. Electronic and magnetic properties of X-doped (X=Ni, Pd, Pt) WS{sub 2} monolayer

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Xu, E-mail: zhaoxu@htu.cn [College of Physics and Electronic Engineering, Henan Normal University, Xinxiang, Henan 453007 (China); Xia, Congxin [College of Physics and Electronic Engineering, Henan Normal University, Xinxiang, Henan 453007 (China); Dai, Xianqi [College of Physics and Electronic Engineering, Henan Normal University, Xinxiang, Henan 453007 (China); Department of Physics, Zhengzhou Normal University, Zhengzhou, Henan 450044 (China); Wang, Tianxing; Chen, Peng; Tian, Liang [College of Physics and Electronic Engineering, Henan Normal University, Xinxiang, Henan 453007 (China)

    2016-09-15

    We investigate the electronic and magnetic properties of X-doped (X=Ni, Pd, Pt) WS{sub 2} monolayer using the first-principles methods based on density functional theory. The results show that WS{sub 2} monolayer doped by Ni, Pd and Pt is ferromagnetic. The impurity states near the Fermi level depend highly on the atomic size and electronegativity. For different X-doped WS{sub 2}, the formation energy is lower under S-rich conditions, which indicates that it is energy favorable and relatively easier to incorporate X atom into WS{sub 2} under S-rich experimental conditions. Moreover, Ni-doped system owns the lowest formation energy compared with other atoms under S-rich experimental condition. Our studies predict X-doped (X=Ni, Pd, Pt) WS{sub 2} monolayers to be candidates for thin dilute magnetic semiconductors. Ni-doped WS{sub 2} has relatively wide half-metallic gap. So Ni-doped WS{sub 2} is the most ideal for spin injection among Ni, Pd, and Pt, which is important for application in semiconductor spintronics. - Highlights: • WS{sub 2} monolayer doped by Ni, Pd and Pt is ferromagnetic. • The formation energy is lower under S-rich conditions. • Ni-doped system owns wide half-metallic gap and the lowest formation energy. • Ni-doped WS{sub 2} is the most ideal for spin injection among Ni, Pd, and Pt.

  17. Impedance and Stability of M/CGO (M: Ni, Pd, Ru) Co-infiltrated Nb-doped SrTiO3 SOFC Anodes

    DEFF Research Database (Denmark)

    Ramos, Tania; Veltzé, Sune; Reddy Sudireddy, Bhaskar;

    2014-01-01

    at 850°C, 50% H2O/H2 decreased in the order Ni/CGO≫Pd/CGO > Ru/CGO. After 200h of exposure Ru/CGO not only continued to exhibit low impedance, with final total Rp ≅ 0.02 Ωcm2, but also negligible degradation. For comparison, Ni/CGO degraded close to a factor of 3 to ca. 0.25 Ωcm2 in an equivalent period...

  18. Genetic Pd, Pt, Au, Ag, and Rh mineralogy in Noril'sk sulfide ores

    Science.gov (United States)

    Spiridonov, E. M.; Kulagov, E. A.; Serova, A. A.; Kulikova, I. M.; Korotaeva, N. N.; Sereda, E. V.; Tushentsova, I. N.; Belyakov, S. N.; Zhukov, N. N.

    2015-09-01

    The undeformed ore-bearing intrusions of the Noril'sk ore field (NOF) cut through volcanic rocks of the Late Permian-Early Triassic trap association folded in brachysynclines. Due to the nonuniform load on the roof of intrusive bodies, most sulfide melts were squeezed, up to the tops of ore-bearing intrusions; readily fusible Ni-Fe-Cu sulfide melts were almost completely squeezed. In our opinion, not only one but two stages of mineralization developed at the Noril'sk deposits: (i) syntrap magmatic and (ii) epigenetic post-trap metamorphic-hydrothermal. All platinum-group minerals (PGM) and minerals of gold are metasomatic in the Noril'sk ores. They replaced sulfide solid solutions and exsolution structures. All types of PGM and Au minerals occur in the ores, varying in composition from pyrrhotite to chalcopyrite, talnakhite, mooihoekite, and rich in galena; they are localized in the inner and outer contact zones and differ only in the quantitative proportions of ore minerals. The aureoles of PGM and Au-Ag minerals are wider than the contours of sulfide bodies and coincide with halos of fluid impact on orebodies and adjacent host rocks. The pneumatolytic PGM and Au-Ag minerals are correlated in abundance with the dimensions of sulfide bodies. Their amounts are maximal in veins of late fusible ore composed of eutectic PbS ss and iss intergrowths, as well as at their contacts. The Pd and Pt contents in eutectic sulfide ores of NOF are the world's highest. In the process of noble-metal mineral formation, the fluids supply Pd, Pt, Au, As, Sb, Sn, Bi, and a part of Te, whereas Fe, Ni, Cu, Pb, Ag, Rh, a part of Te and Pd are leached from the replaced sulfide minerals. The pneumatolytic PGM of the early stage comprises Pd and Pt intermetallic compounds enriched in Au along with Pd-Pt-Fe-Ni-Cu-Sn-Pb(As) and (Pd,Pt,Au)(Sn,Sb,Bi,Te,As) solid solutions. Pneumatolytic PGM and Au minerals of the middle stage are products of solid-phase transformation and recrystallization of

  19. Effect of pressure on the Curie temperature of Mn{sub 2}RuSn and Mn{sub 2}PdSn

    Energy Technology Data Exchange (ETDEWEB)

    Adachi, Y., E-mail: adachy@yz.yamagata-u.ac.jp [Graduate School of Science and Engineering, Yamagata University, Yonezawa 992-8510 (Japan); Watanabe, T. [Faculty of Engineering, Yamagata University, Yonezawa 992-8510 (Japan); Kanomata, T. [Faculty of Engineering, Tohoku Gakuin University, Tagajo 985-8537 (Japan); Research Institute for Engineering and Technology, Tohoku Gakuin University, 985-8537 (Japan); Hayasaka, M.; Endo, K. [Faculty of Engineering, Tohoku Gakuin University, Tagajo 985-8537 (Japan); Nishihara, H. [Faculty of Science and Technology, Ryukoku University, Otsu 520-2194 (Japan); Xu, X.; Kainuma, R. [Department of Materials Science, Graduate School of Engineering, Tohoku University, Sendai 980-8579 (Japan)

    2017-04-15

    Effect of pressure on the Curie temperature T{sub C} of the Mn-rich Heusler alloys Mn{sub 2}RuSn and Mn{sub 2}PdSn has been investigated by measuring the temperature dependence of initial permeability at various pressures up to 10 kbar. It was found that the Curie temperatures of Mn{sub 2}RuSn and Mn{sub 2}PdSn decrease with increasing pressure. The pressure derivatives of T{sub C} were estimated to be −0.59 K/kbar for Mn{sub 2}RuSn and −0.80 K/kbar for Mn{sub 2}PdSn. On the basis of the experimental results, the relationship between the magnetic transition temperature and the Mn-Mn distance is discussed.

  20. Deep oxidation of methane on particles derived from YSZ-supported Pd-Pt-(O) coatings synthesized by pulsed filtered cathodic arc

    Energy Technology Data Exchange (ETDEWEB)

    Horwat, D.; Endrino, J.L.; Boreave, A.; Karoum,R.; Pierson, J.F.; Weber, S.; Anders, A.; Vernoux, Ph.

    2008-12-12

    Methane conversion tests were performed on Pd, PdOy, Pd0.6Pt0.4Oy and Pd0.4Pt0.6Oy thin films deposited on yttria stabilized zirconia (YSZ) substrates. Pt containing films exhibited poor activity and high reducibility. As-deposited Pd and PdOy films showed good activity and transformed, during the cycling process, to particles dispersed on the YSZ substrates. The higher reaction rate of initially PdOy films was explained by a better dispersion of the catalyst. A drop of the reaction rate was observed when the temperature exceeded 735oC and 725oC for initially Pd and PdOy, respectively, which can be associated with the high-temperature reduction of PdO into Pd.

  1. Direct evidence for active site-dependent formic acid electro-oxidation by topmost-surface atomic redistribution in a ternary PtPdCu electrocatalyst.

    Science.gov (United States)

    Cui, Chun-Hua; Li, Hui-Hui; Cong, Huai-Ping; Yu, Shu-Hong; Tao, Franklin Feng

    2012-12-25

    The active site-dependent electrochemical formic acid oxidation was evidenced by the increased coverage of Pt in the topmost mixed PtPd alloy layer of ternary PtPdCu upon potential cycling, which demonstrated two catalytic pathways only in one catalyst owing to surface atomic redistribution in an acidic electrolyte environment.

  2. Influence of method of preparation of Pt Ru/C electrocatalysts on the catalytic activity for the ethanol oxidation reaction in acidic medium; Influencia do metodo de preparacao de eletrocatalisadores PtRu/C sobre a atividade catalitica frente a reacao de oxidacao de etanol em meio acido

    Energy Technology Data Exchange (ETDEWEB)

    Gomes, Walber dos Santos; Silva, Uriel Lean Valente; Souza, Jose Pio Iudice de, E-mail: jpio@ufpa.br [Universidade Federal do Para, (UFPA), Belem, PA (Brazil). Instituto de Ciencias Exatas e Naturais. Faculdade de Quimica

    2013-09-01

    In this work the influence of variations in the borohydrate reduction method on the properties of Pt Ru/C electrocatalysts was investigated. The electrocatalysts were prepared using 1:1 ; 2:1; 5:1; 50:1 and 250:1 molar ratios of NaBH{sub 4} to metals. The reduction was also performed by dripping or by fast addition of the solution. The results showed that Pt Ru nanoparticles obtained by fast addition had the smallest crystallite sizes. It was also noted that the catalytic activity increased as the borohydrate:metal molar ratio increased. The Pt Ru/C electrocatalysts (50:1) obtained by fast addition presented the best catalytic activity for ethanol electro-oxidation. (author)

  3. Tuning Surface Structure and Strain in Pd-Pt Core-Shell Nanocrystals for Enhanced Electrocatalytic Oxygen Reduction.

    Science.gov (United States)

    Xiong, Yalin; Shan, Hao; Zhou, Zhengnan; Yan, Yucong; Chen, Wenlong; Yang, Yaxiong; Liu, Yongfeng; Tian, He; Wu, Jianbo; Zhang, Hui; Yang, Deren

    2017-02-01

    Icosahedral, octahedral, and cubic Pd@Pt core-shell nanocrystals with two atomic Pt layers are epitaxially generated under thermodynamic control. Such icosahedra exhibit remarkably enhanced catalytic properties for oxygen reduction reaction compared to the octahedra and cubes as well as commercial Pt/C, which can be attributed to ligand and geometry effects, especially twin-induced strain effect that is revealed by geometrical phase analysis. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Photocatalytic hydrogen evolution from CdS-ZnO-CdO systems under visible light irradiation: Effect of thermal treatment and presence of Pt and Ru cocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Navarro, R.M.; del Valle, F.; Fierro, J.L.G. [Instituto de Catalisis y Petroleoquimica (CSIC), C/Marie Curie 2, Cantoblanco, 28049 Madrid (Spain)

    2008-08-15

    A CdS-CdO-ZnO mixture annealed at different temperatures and loaded with Ru or Pt cocatalysts has been investigated in the production of hydrogen from aqueous solutions containing SO{sub 3}{sup 2-}+S{sup 2-} as sacrificial reagents under visible light. The physicochemical characterization of the CdS-CdO-ZnO catalyst revealed significant changes in the crystalline structure and visible light absorption capacity as a result of thermal treatments. Catalytic activity was found to be strongly dependent on physicochemical changes associated with thermal annealing. Hydrogen evolution over the CdS-CdO-ZnO catalyst was enhanced in the sample annealed at 773 K by the better contact between the CdS and CdO-ZnO phases, which improved physical charge separation. CdS-CdO-ZnO catalyst activity was significantly improved by the addition of Pt or Ru cocatalysts. Among the noble metals studied, activity promotion was higher for the sample loaded with Ru. The enhancement of activity associated with Ru loading is linked to a good interaction between Ru oxide particles and CdS, which reduces the possibility of electron-hole recombination, thus resulting in more efficient water splitting. (author)

  5. Cytotoxic Pt(IV and Ru(II complexes containing a biologically relevant edda-type ligand: A comparative study of their thermal properties

    Directory of Open Access Journals (Sweden)

    Mihajlović-Lalić Ljiljana E.

    2016-01-01

    Full Text Available The thermal behaviour of a Pt(IV and a Ru(II complex coordinated to O,O'-di-n-butyl-(S,S-ethylenediamine-N,N'-di-2-(3-cyclohexylpropanoate has been investigated using thermogravimetry (TG and differential scanning calorimetry (DSC. The study included investigation of the thermal decomposition of these complexes in the temperature range of 30 to 590°C and evaluation of activation energy for the first decomposition steps. For both metal complexes, broad DSC peaks indicated complex thermal transformation processes. The two-step decomposition of the Pt(IV complex started at 175 and ended at about 418°C, leaving elemental platinum as a final residue. On the other hand, the Ru(II analogue decomposed in three stages. Thermal degradation was evident beginning at 144°C and suggested the decomposition of a coordinated ligand as dominant process. For this complex, the proposed final residue was RuO2. Kinetic parameters for the first decomposition step were obtained by means of multi-heating rates method, in this case the Kissinger-Akahira-Sunose (KAS method. The mean activation energy calculated for 0.2 < α < 0.8 were 122.0 kJ mol−1 for the Pt(IV and 118.9 kJ mol−1 for the Ru(II complex and decreased constantly, characteristic of a multi-step process. [Projekat Ministarstva nauke Republike Srbije, br. 172035, 172055 i br. 172018

  6. Synthesis-atomic structure-properties relationships in metallic nanoparticles by total scattering experiments and 3D computer simulations: case of Pt-Ru nanoalloy catalysts

    Science.gov (United States)

    Prasai, Binay; Ren, Yang; Shan, Shiyao; Zhao, Yinguang; Cronk, Hannah; Luo, Jin; Zhong, Chuan-Jian; Petkov, Valeri

    2015-04-01

    An approach to determining the 3D atomic structure of metallic nanoparticles (NPs) in fine detail and using the unique knowledge obtained for rationalizing their synthesis and properties targeted for optimization is described and exemplified on Pt-Ru alloy NPs of importance to the development of devices for clean energy conversion such as fuel cells. In particular, PtxRu100-x alloy NPs, where x = 31, 49 and 75, are synthesized by wet chemistry and activated catalytically by a post-synthesis treatment involving heating under controlled N2-H2 atmosphere. So-activated NPs are evaluated as catalysts for gas-phase CO oxidation and ethanol electro-oxidation reactions taking place in fuel cells. Both as-synthesized and activated NPs are characterized structurally by total scattering experiments involving high-energy synchrotron X-ray diffraction coupled to atomic pair distribution functions (PDFs) analysis. 3D structure models both for as-synthesized and activated NPs are built by molecular dynamics simulations based on the archetypal for current theoretical modelling Sutton-Chen method. Models are refined against the experimental PDF data by reverse Monte Carlo simulations and analysed in terms of prime structural characteristics such as metal-to-metal bond lengths, bond angles and first coordination numbers for Pt and Ru atoms. Analysis indicates that, though of a similar type, the atomic structure of as-synthesized and respective activated NPs differ in several details of importance to NP catalytic properties. Structural characteristics of activated NPs and data for their catalytic activity are compared side by side and strong evidence found that electronic effects, indicated by significant changes in Pt-Pt and Ru-Ru metal bond lengths at NP surface, and practically unrecognized so far atomic ensemble effects, indicated by distinct stacking of atomic layers near NP surface and prevalence of particular configurations of Pt and Ru atoms in these layers, contribute to the

  7. Exploring Pd adsorption, diffusion, permeation, and nucleation on bilayer SiO2/Ru as a function of hydroxylation and precursor environment: From UHV to catalyst preparation

    Science.gov (United States)

    Pomp, Sascha; Kaden, William E.; Sterrer, Martin; Freund, Hans-Joachim

    2016-10-01

    The hydroxylation-dependent permeability of bilayer SiO2 supported on Ru(0001) was investigated by XPS and TDS studies in a temperature range of 100 K to 600 K. For this, the thermal behavior of Pd evaporated at 100 K, which results in surface and sub-surface (Ru-supported) binding arrangements, was examined relative to the extent of pre-hydroxylation. Samples containing only defect-mediated hydroxyls showed no effect on Pd diffusion through the film at low temperature. If, instead, the concentration of strongly bound hydroxyl groups and associated weakly bound water molecules was enriched by an electron-assisted hydroxylation procedure, the probability for Pd diffusion through the film is decreased via a pore-blocking mechanism. Above room temperature, all samples showed similar behavior, reflective of particle nucleation above the film and eventual agglomeration with any metal atoms initially binding beneath the film. When depositing Pd onto the same SiO2/Ru model support via adsorption of [Pd(NH3)4]Cl2 from alkaline (pH 12) precursor solution, we observe notably different adsorption and nucleation mechanisms. The resultant Pd adsorption complexes follow established decomposition pathways to produce model catalyst systems compatible with those created exclusively within UHV despite lacking the ability to penetrate the film due to the increased size of the initial Pd precursor groups.

  8. In Situ Generation of Pd-Pt Core-Shell Nanoparticles on Reduced Graphene Oxide (Pd@Pt/rGO) Using Microwaves: Applications in Dehalogenation Reactions and Reduction of Olefins.

    Science.gov (United States)

    Goswami, Anandarup; Rathi, Anuj K; Aparicio, Claudia; Tomanec, Ondrej; Petr, Martin; Pocklanova, Radka; Gawande, Manoj B; Varma, Rajender S; Zboril, Radek

    2017-01-25

    Core-shell nanocatalysts are a distinctive class of nanomaterials with varied potential applications in view of their unique structure, composition-dependent physicochemical properties, and promising synergism among the individual components. A one-pot microwave (MW)-assisted approach is described to prepare the reduced graphene oxide (rGO)-supported Pd-Pt core-shell nanoparticles, (Pd@Pt/rGO); spherical core-shell nanomaterials (∼95 nm) with Pd core (∼80 nm) and 15 nm Pt shell were nicely distributed on the rGO matrix in view of the choice of reductant and reaction conditions. The well-characterized composite nanomaterials, endowed with synergism among its components and rGO support, served as catalysts in aromatic dehalogenation reactions and for the reduction of olefins with high yield (>98%), excellent selectivity (>98%) and recyclability (up to 5 times); both Pt/rGO and Pd/rGO and even their physical mixtures showed considerably lower conversions (20 and 57%) in dehalogenation of 3-bromoaniline. Similarly, in the reduction of styrene to ethylbenzene, Pd@Pt core-shell nanoparticles (without rGO support) possess considerably lower conversion (60%) compared to Pd@Pt/rGO. The mechanism of dehalogenation reactions with Pd@Pt/rGO catalyst is discussed with the explicit premise that rGO matrix facilitates the adsorption of the reducing agent, thus enhancing its local concentration and expediting the hydrazine decomposition rate. The versatility of the catalyst has been validated via diverse substrate scope for both reduction and dehalogenation reactions.

  9. Gram-Scale Synthesized Pd2Co-Supported PtMonolayers Electrocatalysts for Oxygen Reduction Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, W.P.; Sasaki, K.; Su, D.; Zhu, Y.; Wang, J.X.; Adzic, R.R.

    2010-04-21

    Gram-scale synthesis of Pt{sub ML} electrocatalysts with a well-defined core-shell structure has been carried out using method involving galvanic displacement of an underpotential deposition Cu layer. The Pt shell thickness can be controlled by stepwise deposition. The Pt{at}Pd{sub 2}Co/C nanoparticles were characterized by X-ray powder diffraction, aberration-corrected scanning transmission electron microscopy, high-resolution energy-loss spectrometry, and in situ X-ray absorption spectroscopy. A complete Pt shell of 0.6 nm on a Pd{sub 2}Co core has been confirmed. The Pt{at}Pd{sub 2}Co/C core-shell electrocatalysts showed a very high activity for the oxygen reduction reaction; the Pt mass and specific activity were 0.72 A mg{sup -1}{sub Pt} and 0.5 mA cm{sup -2}, respectively (3.5 and 2.5 times higher than the corresponding values for commercial Pt catalysts), at 0.9 V in 0.1 M HClO{sub 4} at room temperature. In an accelerated potential cycling test, a loss in active surface area and a decrease in catalytic activity for gram-scale-synthesized Pt{sub ML} catalysts were also determined.

  10. Preparation of Pt Ru/C electrocatalysts using gamma radiation for application as anode in direct methanol fuel cell; Preparacao de eletrocatalisadores PtRu/C utilizando radiacao {gamma} para aplicacao como anodo na oxidacao direta de metanol em celulas a combustivel

    Energy Technology Data Exchange (ETDEWEB)

    Spinace, Estevam V.; Silva, Dionisio F. da; Cruz, Victor A. da; Oliveira Neto, Almir; Machado, Luci D.B.; Pino, Eddy S.; Linardi, Marcelo [Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, SP (Brazil)]. E-mail: espinace@ipen.br

    2005-07-01

    PtRu nanoparticles supported on carbon (PtRu/C electrocatalysts) were prepared submitting a water/2-propanol mixture containing the metal ions and the carbon support to gamma radiation. The water/2-propanol (v/v) and the total dose (kGy) were studied. The electrocatalysts were characterized by EDX, XRD and cyclic voltammetry. The methanol electro-oxidation was studied by cyclic voltammetry using the thin porous coating. In the studied conditions, the electrocatalytic activity of the prepared electrocatalysts depend on the water/2-propanol ratio used in the reaction medium. (author)

  11. Structures, thermal stability, and melting behaviors of free-standing pentagonal multi-shell Pd-Pt nanowires

    Science.gov (United States)

    Cheng, D.; Hou, M.

    2010-04-01

    Classical molecular dynamics and Metropolis Monte Carlo simulations were carried out to investigate the thermal stability and melting behaviors of free-standing Pd-Pt bimetallic nanowires (NWs) with pentagonal multi-shell-type (PMS-type) structure in the whole composition range. Equilibrium configurations at 100 K are predicted in the semi-grand canonical ensemble. Pd-Pt PMS-type NWs are stable with a multishell structure of alternating Pd and Pt compositions and Pd segregating systematically to the surface. On thermal heating, an interesting composition-dependent structural transformation from the PMS-type to face-centred-cubic (FCC) by overcoming a high energy barrier is observed for Pd-Pt bimetallic NWs before the melting. Consequently, the system energy is decreased. The FCC structure is found more stable than PMS-type over the whole range of composition. The melting of Pd-Pt bimetallic NWs is also studied. It is found to start at the edges, then propagate over the whole surface, and next to the interior. It occurs in a composition-dependent range of temperature.

  12. Pulse electrodeposition to prepare core-shell structured AuPt@Pd/C catalyst for formic acid fuel cell application

    Science.gov (United States)

    Lu, Xueyi; Luo, Fan; Song, Huiyu; Liao, Shijun; Li, Hualing

    2014-01-01

    A novel core-shell structured AuPt@Pd/C catalyst for the electrooxidation of formic acid is synthesized by a pulse electrodeposition process, and the AuPt core nanoparticles are obtained by a NaBH4 reduction method. The catalyst is characterized with X-ray powder diffraction and transmission electron microscopy, thermogravimetric analysis, cyclic voltammetry, CO stripping and X-ray photoelectron spectroscopy. The core-shell structure of the catalyst is revealed by the increase in particle size resulting from a Pd layer covering the AuPt core, and by a negative shift in the CO stripping peaks. The addition of a small amount of Pt improves the dispersion of Au and results in smaller core particles. The catalyst's activity is evaluated by cyclic voltammetry in formic acid solution. The catalyst shows excellent activity towards the anodic oxidation of formic acid, the mass activity reaches 4.4 A mg-1Pd and 0.83 A mg-1metal, which are 8.5 and 1.6 times that of commercial Pd/C. This enhanced electrocatalytic activity could be ascribed to the good dispersion of Au core particles resulting from the addition of Pt, as well as to the interaction between the Pd shell layer and the Au and Pt in the core nanoparticles.

  13. First principles investigation of the activity of thin film Pt, Pd and Au surface alloys for oxygen reduction

    DEFF Research Database (Denmark)

    Tripkovic, Vladimir; Hansen, Heine Anton; Rossmeisl, Jan

    2015-01-01

    Further advances in fuel cell technologies are hampered by kinetic limitations associated with the sluggish cathodic oxygen reduction reaction. We have investigated a range of different formulations of binary and ternary Pt, Pd and Au thin films as electrocatalysts for oxygen reduction. The most...... active binary thin films are near-surface alloys of Pt with subsurface Pd and certain PdAu and PtAu thin films with surface and/or subsurface Au. The most active ternary thin films are with pure metal Pt or Pd skins with some degree of Au in the surface and/or subsurface layer and the near-surface alloys....... This is particularly challenging for alloys containing Au due to a high propensity of Au to segregate to the surface. We also show that once Au is on the surface it will diffuse to defect sites, explaining why small amounts of Au retard dissolution of Pt nanoparticles. For the PtPd thin films there is no pronounced...

  14. First principles investigation of the activity of thin film Pt, Pd and Au surface alloys for oxygen reduction

    DEFF Research Database (Denmark)

    Tripkovic, Vladimir; Hansen, Heine Anton; Rossmeisl, Jan;

    2015-01-01

    active binary thin films are near-surface alloys of Pt with subsurface Pd and certain PdAu and PtAu thin films with surface and/or subsurface Au. The most active ternary thin films are with pure metal Pt or Pd skins with some degree of Au in the surface and/or subsurface layer and the near-surface alloys...... of Au with mixed Pt/Pd skins. The activity of the binary and ternary catalysts is explained through weakening of the OH binding energy caused by solute elements. However, given the low alloy formation energies it may be difficult to tune and retain the composition under operating conditions....... This is particularly challenging for alloys containing Au due to a high propensity of Au to segregate to the surface. We also show that once Au is on the surface it will diffuse to defect sites, explaining why small amounts of Au retard dissolution of Pt nanoparticles. For the PtPd thin films there is no pronounced...

  15. Selective deposition of Pt onto supported metal clusters for fuel cell electrocatalysts

    Science.gov (United States)

    Jeon, Tae-Yeol; Pinna, Nicola; Yoo, Sung Jong; Ahn, Docheon; Choi, Sun Hee; Willinger, Marc-Georg; Cho, Yong-Hun; Lee, Kug-Seung; Park, Hee-Young; Yu, Seung-Ho; Sung, Yung-Eun

    2012-09-01

    We report a new method for deposition of Pt on a metal core to develop real electrocatalysts with significantly reduced amounts of expensive Pt as well as enhanced activity for oxygen reduction reaction. Ru and Pd have different crystal structures and modify the electronic structure of Pt to a different extent (shifts in d-band center). They were chosen as core materials to examine whether hydroquinone dissolved in ethanol can be used to deposit additional Pt atoms onto preformed core nanoparticles, and whether the modified d-character of Pt on different host metals can result in the enhanced ORR activity. The physicochemical characteristics of Pd-Pt and Ru-Pt core-shell nanoparticles are investigated. The core-shell structure was identified through a combination of experimental methods, employing electron microscopy, electrochemical measurements, and synchrotron X-ray measurements such as powder X-ray diffraction, X-ray absorption fine structure, and X-ray photoelectron spectroscopy. The hydroquinone reduction method proved to be an excellent route for the epitaxial growth of a Pt shell on the metal cores, leading to enhanced ORR activities.We report a new method for deposition of Pt on a metal core to develop real electrocatalysts with significantly reduced amounts of expensive Pt as well as enhanced activity for oxygen reduction reaction. Ru and Pd have different crystal structures and modify the electronic structure of Pt to a different extent (shifts in d-band center). They were chosen as core materials to examine whether hydroquinone dissolved in ethanol can be used to deposit additional Pt atoms onto preformed core nanoparticles, and whether the modified d-character of Pt on different host metals can result in the enhanced ORR activity. The physicochemical characteristics of Pd-Pt and Ru-Pt core-shell nanoparticles are investigated. The core-shell structure was identified through a combination of experimental methods, employing electron microscopy

  16. Electrocatalysis of fuel cells reaction on Pt and Pt-bimetallic anode catalysts: A selective review

    Directory of Open Access Journals (Sweden)

    Stamenković Vojislav

    2002-01-01

    Full Text Available In this review we selectively summarize recent progress, primarily from our laboratory, in the development of interrelationships between the kinetics of the fuel cells reactions and the structure/composition of anode catalysts. The focus is placed on two types of metallic surfaces: platinum single crystals and bimetallic surfaces based on Pt. In the first part it was illustrated that the hydcogen reaction is structure sensitive process, with Pt(110 being an order of magnitude more active than either of the atomically "flatter" (100 and (111 surfaces. The hydrogen reaction on Pt(hkl modified by pseudomorphic Pd (submonolayers shows the "volcano-like" behavior, having the maximum rate on Pt(111 modified by 1 ML of Pd. The Pt(111-Pd system is used to demonstrate how the energetics of intermediates formed in the hydrogen reaction is affected by interfacial bonding and energetic constraints produced between pseudomorphic Pd films and the Pt(111 substrate. In the second part it was shown that the oxidation of Ha in the presence of CO occurs concurrently with CO oxidation on Pt and Pt bimetallic surfaces. The Pt-Ru system is used to demonstrate that both the bifunctional effect and the ligand effect contribute to the influence of Ru on the CO oxidation rate and for Hz oxidation process in the presence of CO. The knowledge is then used to create the real-life catalyst with the catalytic activities which are, to the greatest extend possible similar to the tailor-made surface.

  17. Nanosized (mu12-Pt)Pd164-xPtx(CO)72(PPh3)20 (x approximately 7) containing Pt-centered four-shell 165-atom Pd-Pt core with unprecedented intershell bridging carbonyl ligands: comparative analysis of icosahedral shell-growth patterns with geometrically related Pd145(CO)x(PEt3)30 (x approximately 60) containing capped three-shell Pd145 core.

    Science.gov (United States)

    Mednikov, Evgueni G; Jewell, Matthew C; Dahl, Lawrence F

    2007-09-19

    Presented herein are the preparation and crystallographic/microanalytical/magnetic/spectroscopic characterization of the Pt-centered four-shell 165-atom Pd-Pt cluster, (mu(12)-Pt)Pd(164-x)Pt(x)(CO)(72)(PPh(3))(20) (x approximately 7), 1, that replaces the geometrically related capped three-shell icosahedral Pd(145) cluster, Pd(145)(CO)(x)(PEt(3))(30) (x approximately 60), 2, as the largest crystallographically determined discrete transition metal cluster with direct metal-metal bonding. A detailed comparison of their shell-growth patterns gives rise to important stereochemical implications concerning completely unexpected structural dissimilarities as well as similarities and provides new insight concerning possible synthetic approaches for generation of multi-shell metal clusters. 1 was reproducibly prepared in small yields (Pd-Pt anatomy of 1 consists of: (a) shell 1 with the centered (mu(12)-Pt) atom encapsulated by the 12-atom icosahedral Pt(x)Pd(12-x) cage, x = 1.2(3); (b) shell 2 with the 42-atom nu(2) icosahedral Pt(x)Pd(42-x) cage, x = 3.5(5); (c) shell 3 with the anti-Mackay 60-atom semi-regular rhombicosidodecahedral Pt(x)Pd(60-x) cage, x = 2.2(6); (d) shell 4 with the 50-atom nu(2) pentagonal dodecahedral Pd(50) cage. The total number of crystallographically estimated Pt atoms, 8 +/- 3, which was obtained from least-squares (Pt(x)/Pd(1-x))-occupancy analysis of the X-ray data that conclusively revealed the central atom to be pure Pt (occupancy factor, x = 1.00(3)), is fortuitously in agreement with that of 7.6(7) found from an X-ray Pt/Pd microanalysis (WDS spectrometer) on three crystals of 1. Our utilization of this site-occupancy (Pt(x)Pd(1-x))-analysis for shells 1-3 originated from the microanalytical results; otherwise, the presumed metal-core composition would have been (mu(12)-Pt)Pd(164). [Alternatively, the (mu(12)-Pt)M(164) core-geometry of 1 may be viewed as a pseudo-Ih Pt-centered six-shell successive nu(1) polyhedral system, each with

  18. Electrooxidation Mechanism of Methanol at Pt-Ru Catalyst Modified GC Electrode in Electrolytes with Different pH Using Electrochemical and SERS Techniques

    Institute of Scientific and Technical Information of China (English)

    DING Yue Min; LIU Yao-Long; RAO Gui-Shi; WANG Guo-Fu; ZHONG Qi-Ling; REN Bin; TIAN Zhong-Qun

    2007-01-01

    The electrochemical and in-situ surface-enhanced Raman spectroscopy (SERS) techniques were used to investigate the electrooxidation behavior of methanol in acidic, neutral and alkaline media at a Pt-Ru nanoparticle modified glassy carbon (Pt-Ru/GC) electrode. The results showed that methanol could be dissociated spontaneously at the Pt-Ru/GC electrode to produce a strongly adsorbed intermediate, CO. It was found that CO could be oxidized more easily in the alkaline medium than in the acidic and neutral media. The peak potential of methanol oxidation was shifted from 0.663 and 0.708 V in the acidic and neutral media to -0.030 V in the alkaline medium, which is due to that the adsorption strength of CO on the Pt surface in the alkaline medium is weaker than that in the acidic and neutral media. The final product of the methanol oxidation is CO2. However, in the alkaline medium, CO2 produced would form CO32- and HCO3- resulting in the decrease in the alkaline concentration and then in the decrease in the performance of DMFC. Therefore, the performance of the alkaline DMFC is not Stable.

  19. C-O Reductive Elimination from High Valent Pt and Pd Centers

    Science.gov (United States)

    Vedernikov, Andrei N.

    Reactions of high valent platinum and palladium complexes leading to the formation of C(sp 2)-O and C(sp 3)-O bonds are involved in various catalytic applications such as oxidative functionalization of hydrocarbons, which are especially rich in the case of palladium chemistry. This Chapter emphasizes on the mechanisms of C-O reductive elimination from octahedral d 6 Pt(IV) and, in part, from Pd(IV) complexes. The nature of the leaving groups, the metal center, the presence of soft/hard spectator ligands, the number of hydrocarbyl ligands at the metal, and some other factors affecting the reactivity of such complexes are considered. As shown here, there are still uncharted territories in the area of high valent organoplatinum and organopalladium chemistry: C(sp 2)-O reductive elimination from PtIV, reactivity and reaction mechanisms of PtIII and PdIII organometallic derivatives, synthesis and reactivity of monoalkyl and monoaryl palladium(IV) complexes stabilized by O-donor ligands, and others. The rapid progress observed in this field of chemistry suggests that some of these areas will soon be explored.

  20. Effect of Pd loading in Pd-Pt bimetallic catalysts doped into hollow core mesoporous shell carbon on performance of proton exchange membrane fuel cells

    Science.gov (United States)

    Fıçıcılar, Berker; Bayrakçeken, Ayşe; Eroğlu, İnci

    A significantly active Pd-Pt/carbon electrocatalyst for polymer electrolyte membrane fuel cells was synthesized by microwave irradiation using a hollow core mesoporous shell (HCMS) carbon as catalyst support that was prepared by template replication of core/shell spherical silica particles and two different carbon precursors. Pt/Pd percent weight ratios on carbon support were varied as 20/0, 15/5, 10/10, 5/15 to 0/20. As the average pore diameter of the carbon support was increased from 3.02 nm to 3.90 nm by changing the type of the carbon precursor, fuel cell performances of the HCMS carbon based Pd-Pt bimetallic catalysts were improved significantly.

  1. Quaternary Pt{sub 2}Ru{sub 1}Fe{sub 1}M{sub 1}/C (M=Ni, Mo, or W) catalysts for methanol electro-oxidation reaction

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Min Ku; Lee, Ki Rak; Kang, Kweon Ho; Park, Geun Il [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Jeon, Hyung Joon [Kyoto University, Kyoto (Japan); McGinn, Paul J. [University of Notre Dame, Indiana (United States)

    2015-02-15

    Quaternary Pt{sub 2}Ru{sub 1}Fe{sub 1}M{sub 1}/C (M=Ni, Mo, or W) catalysts were investigated for the methanol electro-oxidation reaction (MOR). Electrocatalytic activities of the quaternary catalysts for CO electro-oxidation were studied via CO stripping experiments, and the Pt{sub 2}Ru{sub 1}Fe{sub 1}Ni{sub 1}/C and Pt{sub 2}Ru{sub 1}Fe{sub 1}W{sub 1}/C catalysts exhibited lowered on-set potential compared to that of a commercial PtRu/C catalyst. MOR activities of the quaternary catalysts were determined by linear sweep voltammetry (LSV) experiments, and the Pt{sub 2}Ru{sub 1}Fe{sub 1}W{sub 1}/C catalyst outperformed the commercial PtRu/C catalyst by 170 and 150% for the mass and specific activities, respectively. X-ray photoelectron spectroscopy (XPS) was employed to analyze surface oxidation states of constituent atoms, and it was identified that the structure of the synthesized catalysts are close to a nano-composite of Pt and constituent metal hydroxides and oxides. In addition, the XPS results suggested that the bi-functional mechanism accounts for the improved performance of the Pt{sub 2}Ru{sub 1}Fe{sub 1}Ni{sub 1}/C and Pt{sub 2}Ru{sub 1} Fe{sub 1}W{sub 1}/C catalysts.

  2. Pt monolayer shell on hollow Pd core electrocatalysts: Scale up synthesis, structure, and activity for the oxygen reduction reaction

    Directory of Open Access Journals (Sweden)

    Vukmirovic Miomir B.

    2013-01-01

    Full Text Available We report on synthesis, characterization and the oxygen reduction reaction (ORR kinetics of Pt monolayer shell on Pd(hollow, or Pd-Au(hollow core electrocatalysts. Comparison between the ORR catalytic activity of the electrocatalysts with hollow cores and those of Pt solid and Pt hollow nanoparticles has been obtained using the rotating disk electrode technique. Hollow nanoparticles were made using Ni or Cu nanoparticles as sacrificial templates. The Pt ORR specific and mass activities of the electrocatalysts with hollow cores were found considerably higher than those of the electrocatalysts with the solid cores. We attribute this enhanced Pt activity to the smooth surface morphology and hollow-induced lattice contraction, in addition to the mass-saving geometry of hollow particles.

  3. Ru-assisted synthesis of {111}-faceted Pd truncated bipyramids: a highly reactive, stable and restorable catalyst for formic acid oxidation.

    Science.gov (United States)

    Wu, Dongshuang; Cao, Minna; Cao, Rong

    2014-11-04

    {111}-Faceted Pd truncated triangular bipyramids (TTBPs) are first presented under the assistance of Ru. Attributed to their unique shape, the TTBPs are highly active and stable for formic acid oxidation. The electrochemical active surface area (ECSA) can be restored to its initial value after a harsh degradation test.

  4. Heterogenized Bimetallic Pd-Pt-Fe3O4 Nanoflakes as Extremely Robust, Magnetically Recyclable Catalysts for Chemoselective Nitroarene Reduction.

    Science.gov (United States)

    Byun, Sangmoon; Song, Yeami; Kim, B Moon

    2016-06-15

    A very simple synthesis of bimetallic Pd-Pt-Fe3O4 nanoflake-shaped alloy nanoparticles (NPs) for cascade catalytic reactions such as dehydrogenation of ammonia-borane (AB) followed by the reduction of nitro compounds (R-NO2) to anilines or alkylamines (R-NH2) in methanol at ambient temperature is described. The Pd-Pt-Fe3O4 NPs were easily prepared via a solution phase hydrothermal method involving the simple one-pot coreduction of potassium tetrachloroplatinate (II) and palladium chloride (II) in polyvinylpyrrolidone with subsequent deposition on commercially available Fe3O4 NPs. The bimetallic Pd-Pt alloy NPs decorated on Fe3O4 NPs provide a unique synergistic effect for the catalysis of cascade dehydrogenation/reduction. Various nitroarene derivatives were reduced to anilines with very specific chemoselectivity in the presence of other reducible functional groups. The bimetallic Pd-Pt-Fe3O4 NPs provide a unique synergistic effect for the catalysis of cascade dehydrogenation/reduction. The nitro reduction proceeded in 5 min with nearly quantitative conversions and yields. Furthermore, the magnetically recyclable nanocatalysts were readily separated using an external magnet and reused up to 250 times without any loss of catalytic activity. A larger scale (10 mmol) reaction was also successfully performed with >99% yield. This efficient, recyclable Pd-Pt-Fe3O4 NPs system can therefore be repetitively utilized for the reduction of various nitro-containing compounds.

  5. Etching approach to hybrid structures of PtPd nanocages and graphene for efficient oxygen reduction reaction catalysts

    Institute of Scientific and Technical Information of China (English)

    Song Bai[1; Chengming Wang[1; Wenya Jiang[1; Nana Du[1; Jing Li[1; Junteng Du[1; Ran Long[1; Zhengquan Li[2; Yujie Xiong[1

    2015-01-01

    Cathodic oxygen reduction reaction (ORR) is a highly important electrochemical reaction in renewable-energy technologies. In general, the surface area, exposed facets and electrical conductivity of catalysts all play important roles in determining their electrocatalytic activities, while their performance durability can be improved by integration with supporting materials. In this work we have developed a method to synthesize hybrid structures between PtPd bimetallic nanocages and graphene by employing selective epitaxial growth of single-crystal Pt shells on Pd nanocubes supported on reduced graphene oxide (rGO), followed by Pd etching. The hollow nature, {100} surface facets and bimetallic composition of PtPd nanocages, together with the good conductivity and stability of graphene, enable high electrocatalytic performance in ORR. The obtained PtPd nanocage-rGO structures exhibit mass activity (0.534 A.m-1) and which are 4.4 times and 3.9 times greater than the specific activity (0.482 mA-cm-2) corresponding values for Pt/C.

  6. A theoretical study of the lowest-energy PtPd co-doped silicon clusters: Chirality and fluxional transformation

    Science.gov (United States)

    Lv, Peng; Lu, Zhansheng; Yang, Feng; Zhang, Yi; Yang, Xinwei; Xu, Guoliang; Yang, Zongxian

    2017-03-01

    The lowest-energy structures of PtPdSiqn (n = 1- 7; q = 0 , ± 1) clusters are searched based on the PSO algorithm implemented in the CALYPSO code and the first-principle DFT-D computations implemented in DMol3 code. Interestingly, the chirality has been found for the lowest-energy structures of the neutral and charged PtPdSi4, neutral and anionic PtPdSi5, and cationic PtPdSi7 clusters. The first principles molecular dynamics (MD) simulations show that the fluxional transformation between the chiral configurations for neutral PtPdSi4 cluster can take place at 400 K, which is also confirmed by the rather small transformation barrier. The equivalent atoms involved in the bond breaking and formation, as well as the other atoms (modulator), may facilitate the dynamical behavior. The current finding is thus beyond imagination. It is noticeable that the current study provides a potential way to create interesting cluster with chirality and transformation, based on silicon.

  7. Anthropogenic platinum group element (Pt, Pd, Rh) concentrations in PM10 and PM2.5 from Kolkata, India.

    Science.gov (United States)

    Diong, Huey Ting; Das, Reshmi; Khezri, Bahareh; Srivastava, Bijayen; Wang, Xianfeng; Sikdar, Pradip K; Webster, Richard D

    2016-01-01

    This study investigates platinum group elements (PGEs) in the breathable (PM10) and respirable (PM2.5) fractions of air particulates from a heavily polluted Indian metro city. The samples were collected from traffic junctions at the heart of the city and industrial sites in the suburbs during winter and monsoon seasons of 2013-2014. PGE concentrations were determined by inductively coupled plasma-mass spectrometry (ICP-MS). The PGE concentrations in the samples from traffic junctions are within the range of 2.7-111 ng/m(3) for Pd, 0.86-12.3 ng/m(3) for Pt and 0.09-3.13 ng/m(3) for Rh, and from industrial sites are within the range of 3.12-32.3 ng/m(3) for Pd, 0.73-7.39 ng/m(3) for Pt and 0.1-0.69 ng/m(3) for Rh. Pt concentrations were lower in the monsoon compared to winter while Pd concentrations increased during monsoon and Rh stayed relatively unaffected across seasons. For all seasons and locations, concentrations of Pd > Pt > Rh, indicating dominance of Pd-containing exhaust converters. Most of the PGEs were concentrated in the PM2.5 fraction. A strong correlation (R ≥ 0.62) between the PGEs from traffic junction indicates a common emission source viz. catalytic converters, whereas a moderate to weak correlation (R ≤ 0.5) from the industrial sites indicate mixing of different sources like coal, raw materials used in the factories and automobile. A wider range of Pt/Pd, Pt/Rh and Pd/Rh ratios measured in the traffic junction possibly hint towards varying proportions of PGEs used for catalyst productions in numerous rising and established car brands.

  8. Improving electromechanical output of IPMC by high surface area Pd-Pt electrodes and tailored ionomer membrane thickness

    Directory of Open Access Journals (Sweden)

    Viljar Palmre

    2014-04-01

    Full Text Available In this study, we attempt to improve the electromechanical performance of ionic polymer–metal composites (IPMCs by developing high surface area Pd-Pt electrodes and tailoring the ionomer membrane thickness. With proper electroless plating techniques, a high dispersion of palladium particles is achieved deep in the ionomer membrane, thereby increasing notably the interfacial surface area of electrodes. The membrane thickness is increased using 0.5 and 1 mm thick ionomer films. For comparison, IPMCs with the same ionomer membranes, but conventional Pt electrodes, are also prepared and studied. The electromechanical, mechanoelectrical, electrochemical and mechanical properties of different IPMCs are characterized and discussed. Scanning electron microscopy-energy dispersive X-ray (SEM-EDS is used to investigate the distribution of deposited electrode metals in the cross section of Pd-Pt IPMCs. Our experiments demonstrate that IPMCs assembled with millimeter thick ionomer membranes and newly developed Pd-Pt electrodes are superior in mechanoelectrical transduction, and show significantly higher blocking force compared to conventional type of IPMCs. The blocking forces of more than 0.3 N were measured at 4V DC input, exceeding the force output of typical Nafion® 117-based Pt IPMCs more than two orders of magnitude. The newly designed Pd-Pt IPMCs can be useful in more demanding applications, e.g., in biomimetic underwater robotics, where high stress and drag forces are encountered.

  9. Hollow Au@Pd and Au@Pt core-shell nanoparticles as electrocatalysts for ethanol oxidation reactions

    KAUST Repository

    Song, Hyon Min

    2012-09-27

    Hybrid alloys among gold, palladium and platinum become a new category of catalysts primarily due to their enhanced catalytic effects. Enhancement means not only their effectiveness, but also their uniqueness as catalysts for the reactions that individual metals may not catalyze. Here, preparation of hollow Au@Pd and Au@Pt core-shell nanoparticles (NPs) and their use as electrocatalysts are reported. Galvanic displacement with Ag NPs is used to obtain hollow NPs, and higher reduction potential of Au compared to Ag, Pd, and Pt helps to produce hollow Au cores first, followed by Pd or Pt shell growth. Continuous and highly crystalline shell growth was observed in Au@Pd core-shell NPs, but the sporadic and porous-like structure was observed in Au@Pt core-shell NPs. Along with hollow core-shell NPs, hollow porous Pt and hollow Au NPs are also prepared from Ag seed NPs. Twin boundaries which are typically observed in large size (>20 nm) Au NPs were not observed in hollow Au NPs. This absence is believed to be due to the role of the hollows, which significantly reduce the strain energy of edges where the two lattice planes meet. In ethanol oxidation reactions in alkaline medium, hollow Au@Pd core-shell NPs show highest current density in forward scan. Hollow Au@Pt core-shell NPs maintain better catalytic activities than metallic Pt, which is thought to be due to the better crystallinity of Pt shells as well as the alloy effect of Au cores. © 2012 The Royal Society of Chemistry.

  10. Fabrication of Nonenzymatic Glucose Sensors Based on Multiwalled Carbon Nanotubes with Bimetallic Pt-M (M = Ru and Sn Catalysts by Radiolytic Deposition

    Directory of Open Access Journals (Sweden)

    Sun-Young Kwon

    2012-01-01

    Full Text Available Nonenzymatic glucose sensors employing multiwalled carbon nanotubes (MWNTs with highly dispersed Pt-M (M = Ru and Sn nanoparticles (Pt-M@PVP-MWNTs were fabricated by radiolytic deposition. The Pt-M nanoparticles on the MWNTs were characterized by transmittance electron microscopy, elemental analysis, and X-ray diffraction. They were found to be well dispersed and to exhibit alloy properties on the MWNT support. Electrochemical testing showed that these nonenzymatic sensors had larger currents (mA than that of a bare glassy carbon (GC electrode and one modified with MWNTs. The sensitivity (A mM−1, linear range (mM, and detection limit (mM (S/N = 3 of the glucose sensor with the Pt-Ru catalyst in NaOH electrolyte were determined as 18.0, 1.0–2.5, 0.7, respectively. The corresponding data of the sensor with Pt-Sn catalyst were 889.0, 1.00–3.00, and 0.3, respectively. In addition, these non-enzymatic sensors can effectively avoid interference arising from the oxidation of the common interfering species ascorbic acid and uric acid in NaOH electrolyte. The experimental results show that such sensors can be applied in the detection of glucose in commercial red wine samples.

  11. Preparation and Electro-catalytic Activity of Pd@Pt/C Catalyst%低铂催化剂Pd@Pt/C的制备及其电催化活性的研究

    Institute of Scientific and Technical Information of China (English)

    陈容; 黄琦杰

    2016-01-01

    The kinetics of the oxygen reduction reaction in fuel cell cathodes is sluggish that needs using large amounts of Pt to compensate, which mainly leads to the high cost of fuel cell, as well as hider the large scale application of proton exchange membrane fuel cell. In order to overcome these problems, it needs to investigate high performance, low platinum loading, excellent durability electrocatalysts. Core-shell structure catalyst, because of its special structure which can make the Pt dispersion, utilization, and activity be greatly improved as well as reduce Pt loading, has been widely recognized as being among the most promising candidates to achieve the commercialization of proton exchange membrane fuel cell. A novel pulse deposition method was used to prepare a low platinum catalyst Pd@Pt/C. For the cathodic reduction of oxygen, Pd@ Pt/C catalyst demonstrated three times higher mass activity towards the cathodic reduction of oxygen than commercial Pt/C catalyst, exhibiting competitive performance compared with commercial Pt/C catalyst.%燃料电池阴极氧还原动力学缓慢,需要使用大量的铂催化剂,导致电池高昂的成本,制约了质子交换膜燃料电池的大规模产业化。解决这个瓶颈的关键在于研究与制备高性能、低铂载量、耐久性好的燃料电池催化剂。而核壳结构催化剂因其特殊的结构可以使得Pt的分散度、利用率、活性得到很大的提高。本文采用脉冲电流沉积的方法制备了Pd@Pt/C催化剂。电化学测试结果表明, Pd@Pt/C催化剂的氧还原活性可媲美商品的20% Pt/C催化剂, Pd@Pt/C催化剂的Pt质量活性可达JM Pt/C催化剂的3.1倍。

  12. A novel Pt/Cr/Ru/C cathode catalyst for direct methanol fuel cells (DMFC) with simultaneous methanol tolerance and oxygen promotion

    Energy Technology Data Exchange (ETDEWEB)

    Perez, G.; Zinola, C.F. [Laboratorio de Electroquimica Fundamental, Facultad de Ciencias, Universidad de la Republica, Igua 4225, C.P. 11400, Montevideo (Uruguay); Pastor, E. [Departamento de Quimica Fisica, Facultad de Quimica, Universidad de La Laguna, Astrofisico F. Sanchez s/n, 38071 La Laguna, Tenerife (Spain)

    2009-12-15

    New carbon supported electrocatalysts Pt/Cr/Ru with distinct compositions and preparation methods were studied with the help of different electrochemical and spectroscopic techniques. The purposes of obtaining these catalysts lie on their possibilities towards methanol/oxygen fuel cells. In this sense, the oxygen reduction reaction and methanol oxidation reaction were analyzed using stationary and fluid dynamic methodologies. Pt{sub 7.8}/Ru{sub 1.3}/Cr{sub 0.5} and Pt{sub 8.0}/Ru{sub 2.0}/Cr{sub 0.1} were the most interesting prepared substrates, on which the first one shows the best catalytic properties towards methanol oxidation and the second the finest performance towards oxygen reduction reaction. Reaction orders with respect to oxygen for the oxygen reduction reaction were obtained being equal to 1/2 at potentials lower than 0.80 V for both catalysts. Polarization curves run for this reaction depicted two Tafel slopes, i.e. 0.09 V dec{sup -1} above 0.8 V and 0.20 V dec{sup -1} below 0.8 V for both catalysts. An analysis of the most likely mechanism for the oxygen reduction was proposed on the base of those reaction orders and Tafel slopes. (author)

  13. Structural and chelation behaviors of new Ru(II), Pt(IV) and Ir(III) gatifloxacin drug complexes: Spectroscopic characterizations

    Science.gov (United States)

    Alghamdi, Mohammed T.; Alsibaai, A. A.; El-Shahawi, M. S.; Refat, Moamen S.

    2017-02-01

    The interaction between gatifloxacin drug (GAT) with some transition metals (Ru(III), Pt(IV) and Ir(III)) yield the complexes of formulas [Ru(GAT-NH4)(Cl)3(H2O)2], [Pt(GAT-NH4)2(Cl)4]·3H2O and [Ir(GAT-NH4)2(Cl)2(H2O)2]·Cl·2H2O at pH = 7-8. The composition of the GAT complexes was confirmed by elemental data. The IR frequencies reveal the coordination of the GAT with metal ions and the coordination mode of the sbnd N atom of 3-methylpiperazinyl moiety to metal. XRD pattern show isomorphism among the complexes with similar chelation behavior. Scanning electron microscope (SEM) and transmission electron microscopy (TEM) were used to identify the particle size of GAT complexes. The thermal data reveals that various steps of decomposition of the complexes to form their metal oxide as final product. The electronic spectra and the magnetic susceptibility values reveal that the coordination and geometry of Ru3+, Pt4+ and Ir3+ complexes possess distorted octahedral geometry with six number of coordination. Thermodynamic parameters (E*, ΔS*, ΔH* and ΔG*) were calculated from TG curves dependent on Coats-Redfern and Horowitz-Metzeger non-isothermal methods.

  14. Simultaneous leaching of Pt, Pd and Rh from automotive catalytic converters in chloride-containing solutions

    Science.gov (United States)

    Hasani, M.; Khodadadi, A.; Koleini, S. M. J.; Saeedi, A. H.; Meléndez, A. M.

    2017-01-01

    Dissolution of platinum group metals (PGM; herein Pt, Pd and Rh) in different chloride-based leaching systems from spent auto catalysts was performed. Response surface methodology and a five-level-five-factor central composite design were used to evaluate the effects of 1) temperature, 2) liquid-to-solid ratio, 3) stirring speed, 4) acid concentration and 5) particle size on extraction yield of PGM by aqua regia. Analysis of variance was used to determine the optimum conditions and most significant factors affecting the overall metal extraction. In the optimum conditions, leaching of Pt, Pd and Rh was 91.58%, 93.49% and 60.15%, respectively. The effect of different oxidizing agents on the PGM dissolution in chloride medium was studied comparatively in the following leaching systems: a) aqua regia/sulfuric acid mixture, b) hydrogen peroxide in sulfuric acid (piranha solution), c) sodium hypochlorite and d) copper(II). Dissolution of Rh is increased in both aqua regia and hydrogen peroxide/hydrochloric acid solutions by adding sulfuric acid.

  15. Hydrogen-Sensing Behaviors of Pd-and Pt-SiC Schottky Diodes

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Chang Kyo; Lee, Joo Hun; Hong, Chin Soo [Soonchunhyang University (Korea); Cho, Nam Ihn [Sunmoon University (Korea)

    2000-07-01

    Hydrogen-sensing behaviors of Pd-and Pt-SiC Schottky diodes, fabricated on the same SiC substrate, have been systematically compared and analyzed as a function of hydrogen concentration and temperature by I-V and {delta}I-t methods under steady-state and transient conditions. The effects of hydrogen adsorption on the device parameters such as the barrier height are investigated. The significant differences in their hydrogen sensing characteristics have been examined in terms of sensitivity limit, linearity of response, response rate, and response time. For the investigated temperature range, Pd-SiC Schottky diode shows better performance for H{sub 2} detection than Pt-SiC Schottky diode under the same testing conditions. The physical and chemical mechanisms responsible for hydrogen detection are discussed. Analysis of the steady-state reaction kinetics using I-V method confirmed that the atomistic hydrogen process is responsible for the barrier height change in the diodes. (author). 16 refs., 10 figs.

  16. 'Click' generated 1,2,3-triazole based organosulfur/selenium ligands and their Pd(ii) and Ru(ii) complexes: their synthesis, structure and catalytic applications.

    Science.gov (United States)

    Kumar, Satyendra; Saleem, Fariha; Singh, Ajai K

    2016-07-28

    1-(2,6-Diisopropylphenyl)-4-(phenylthio/selenomethyl)-1H-1,2,3-triazole (L1/L2) was synthesized by a 'Click' reaction and treated with [Pd(CH3CN)2Cl2] for 5 h or [(η(6)-C6H6)RuCl(μ-Cl)]2 for 8 h (followed by reaction with NH4PF6) at room temperature, resulting in complexes [Pd(L)Cl2] (1 and 2) or [(η(6)-C6H6)Ru(L)Cl]PF6 (3 and 4) (L = L1 or L2), respectively. The four complexes (1-4) and ligands (L1 and L2) were characterized with (1)H, (13)C{(1)H} and (77)Se{(1)H} NMR spectroscopy and high resolution mass spectrometry. The single crystal structures of 1-4 were solved. The geometry of Pd in 1 and 2 is distorted square planar. The Pd-S and Pd-Se bond distances in 1 and 2 are 2.277(3) and 2.384(6) Å respectively. In 3 and 4, there is a pseudo-octahedral "piano-stool" type disposition of donor atoms around Ru. The Ru-S and Ru-Se bond lengths in 3 and 4 are 2.3728(12) and 2.4741(6) Å respectively. The catalytic activity of complexes 1 and 2 was explored for Suzuki-Miyaura coupling (SMC) in water and the Sonogashira coupling reaction. For various aryl bromides, including deactivated ones, complexes 1 and 2 were found to be efficient catalysts for both couplings. The optimum loading of 1 and 2 required to catalyze both coupling reactions is of the order of 0.001-2 mol% of Pd. For SMC, no additive or phase transfer catalyst was added. For catalysis of the transfer hydrogenation (TH) of aldehydes and ketones, the half-sandwich Ru(ii) complexes 3 and 4 were explored. Their optimum catalytic loading was found to be 0.1-0.4 mol% of Ru. For TH, both the water solvent and the glycerol hydrogen source are environmentally friendly. The catalytic efficiencies of 3 and 4 are comparable with those reported for other catalysts for TH carried out with 2-propanol or glycerol as a H-source. 1, with a sulfur ligand, is more efficient than 2 (Se analog) for both SMC and the Sonogashira coupling. The activities of 3 and 4 for TH are in the order Se > S.

  17. Molecular dynamics simulation of temperature and strain rate effects on the elastic properties of bimetallic Pd-Pt nanowires

    Science.gov (United States)

    Sankaranarayanan, Subramanian K. R. S.; Bhethanabotla, Venkat R.; Joseph, Babu

    2007-10-01

    Molecular dynamics simulation is used to investigate the mechanical properties of infinitely long, cylindrical bimetallic Pd-Pt nanowires, with an approximate diameter of 1.4nm and two different compositions (25% and 50% Pt). The nanowires are subjected to uniaxial tensile strain along the [001] axis with varying strain rates of 0.05%ps-1 , and 5.0%ps-1 , at simulation temperatures of 50 and 300K , to study the effects of strain rates and thermal conditions on the deformation characteristics and mechanical properties of the nanowire. The deformation and rupture mechanism of these nanowires is explored in detail. Comparisons to the behavior exhibited by pure Pd and Pt nanowires of similar diameter are also made. The effect of lattice mismatch on the observed deformation modes in bimetallic nanowires is also discussed. Our simulations indicate that Pd-Pt alloy nanowires of various compositions, with little lattice mismatch between Pd and Pt atoms, undergo similar deformation and rupture upon uniaxial stretching. It is found that yielding and fracture mechanisms depend on the applied strain rate as well as atomic arrangement and temperature. At low temperature and strain rate, where crystal order and stability are highly preserved, the calculated stress-strain response of pure Pt and Pd as well as Pd-Pt alloy nanowires showed clear periodic, stepwise dislocation-relaxation behavior. Crystalline to amorphous transformation takes place at high strain rates (5%ps-1) , with amorphous melting detected at 300K . Deformation of nanowires at higher strain rates and low temperature, where the superplasticity characteristic is significantly enhanced, results in the development of a multishell helical structure. Mechanical properties of the alloy nanowires are significantly different from those of bulk phase and are dictated by the applied strain rate, temperature, alloy composition, as well as the structural rearrangement associated with nanowire elongation. We find that Young

  18. Edge-modulated perpendicular magnetic anisotropy in [Co/Pd]n and L10-FePt thin film wires

    Science.gov (United States)

    Zhang, Jinshuo; Ho, Pin; Currivan-Incorvia, Jean Anne; Siddiqui, Saima A.; Baldo, Marc A.; Ross, Caroline A.

    2015-11-01

    Thickness modulation at the edges of nanostructured magnetic thin films is shown to have important effects on their perpendicular magnetic anisotropy. Thin film wires with tapered edges were made from [Co/Pd]20 multilayers or L10-FePt films using liftoff with a double-layer resist. The effect of edge taper on the reversal process was studied using magnetic force microscopy and micromagnetic modeling. In [Co/Pd]20, the anisotropy was lower in the tapered edge regions which switched at a lower reverse field compared to the center of the wire. The L10-FePt wires showed opposite behavior with the tapered regions exhibiting higher anisotropy.

  19. Rare earth-modified kaolin/NaY-supported Pd-Pt bimetallic catalyst for the catalytic combustion of benzene.

    Science.gov (United States)

    Zuo, Shufeng; Sun, Xuejie; Lv, Ningning; Qi, Chenze

    2014-08-13

    A new type of porous kaolin/NaY composite (KL-NY) with a large specific surface area and large pore sizes was synthesized through a one-step crystallization process, and rare earth-modified KL-NY-supported Pd-Pt catalysts were studied for benzene combustion. The results indicated that the pore volume and specific surface area of KL-NY after calcination and crystallization were 0.298 cm(3)/g and 365 m(2)/g, respectively, exhibiting appropriate pore structure and good thermal stability. Catalysts with rare earth metals greatly enhanced the activity of Pd/KL-NY, and the addition of Pt and Ce into the Pd catalyst improved the catalytic activity as well as the stability. The catalyst with an optimal Ce content and Pt/Pd molar ratio (0.2%Pd-Pt (6:1)/6%Ce/KL-NY) demonstrated the best activity for the complete oxidation of benzene at 230 °C, and the catalyst above maintained the 100% benzene conversion for 960 h.

  20. Martensitic transformation in Heusler alloys Mn{sub 2}YIn (Y=Ni, Pd and Pt): Theoretical and experimental investigation

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Hongzhi, E-mail: luo_hongzhi@163.com [School of Material Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Liu, Bohua; Xin, Yuepeng; Jia, Pengzhong; Meng, Fanbin [School of Material Science and Engineering, Hebei University of Technology, Tianjin 300130 (China); Liu, Enke; Wang, Wenhong; Wu, Guangheng [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

    2015-12-01

    The martensitic transformation and electronic structure of Heusler alloys Mn{sub 2}YIn (Y=Ni, Pd, Pt) have been investigated by both first-principles calculation and experimental investigation. Theoretical calculation reveals that, the energy difference ΔE between the tetragonal martensitic phase and cubic austenitic phase increases with Y varying from Ni to Pt in Mn{sub 2}YIn. Thus a structural transition from cubic to tetragonal is most likely to happen in Heusler alloy Mn{sub 2}PtIn. A single Heusler phase can be obtained in both Mn{sub 2}PtIn and Mn{sub 2}PdIn. A martensitic transformation temperature of 615 K has been identified in Mn{sub 2}PtIn. And in Mn{sub 2}PdIn, the austenitic phase is stable and no martensitic transformation is observed till 5 K. This indicates there may exist a positive relation between ΔE and martensitic transformation temperature. Calculated results show that Mn{sub 2}YIn are all ferrimagnets in both austenitic and martensitic phases. The magnetic properties are mainly determined by the antiparallel aligned Mn spin moments. These findings can help to develop new FSMAs with novel properties. - Highlights: • Positive relation between ΔE and martensitic transformation temperature has been observed. • Heusler alloy Mn{sub 2}PdIn has been synthesized successfully and investigated. • Martensitic transformation in Heusler alloys can be predicted by first -principles calculations.

  1. DFT study of difference caused by catalyst supports in Pt and Pd catalysis of oxygen reduction reaction

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Based on an experimental phenomenon that catalytic activity of Pt and Pd for oxygen reduction reaction (ORR) changes with catalyst supports from C to TiO2, density function theory (DFT) was used to elucidate the cause behind the difference in catalysis caused by catalyst supports. First, factors closely associated with the first electron transfer of the ORR were assessed in the light of quantum chemistry. Then intermediate (atomic oxygen, O) adsorption strength on the catalyst surface was calculated. The results show that, in terms of minimum energy difference, the best orbital symmetry match, and the maximum orbital overlap, TiO2 does bring about a very positive effect on catalysts Pd/TiO2 for the first electron transfer of the ORR. Especially, TiO2 remarkably expands the space size of Pd/TiO2 HOMO orbital and improves orbital overlap of Pd/TiO2 HOMO and O2 LUMO. The analysis of deformation density and partial density of state shows that the strong interaction between Pt and Ti leads to a strong adsorption of intermediate O on Pt/TiO2, but the strong interaction between Pd and surface O causes positive net charge of Pd and a weak adsorption of intermediate O on Pd/TiO2. Thus, the ORR can proceed more smoothly on Pd/TiO2 than Pt/TiO2 in every respect of maximum orbital overlap and rate delay by intermediate O. The research also discloses that several factors lead to less activity of TiO2-supported Pt and Pd catalysts than the C-supported ones for the ORR. These factors include the poor dispersion of Pt and Pd particles on TiO2, poor electric conduction of TiO2 carrier itself, and bigger energy difference between HOMO of TiO2-carried metallic catalysts and LUMO of O2 molecule due to electrons deeply embedded in the semiconductor TiO2 carrier.

  2. DFT study of difference caused by catalyst supports in Pt and Pd catalysis of oxygen reduction reaction

    Institute of Scientific and Technical Information of China (English)

    LI Li; WEI ZiDong; ZHANG Yi; QI XueQiang; XIA MeiRong; ZHANG Jie; SHAO ZhiGang

    2009-01-01

    Based on an experimental phenomenon that catalytic activity of Pt and Pd for oxygen reduction reac-tion (ORR) changes with catalyst supports from C to TiO2, density function theory (DFT) was used to elucidate the cause behind the difference in catalysis caused by catalyst supports. First, factors closely associated with the first electron transfer of the ORR were assessed in the light of quantum chemistry. Then intermediate (atomic oxygen, O) adsorption strength on the catalyst surface was calculated. The results show that, in terms of minimum energy difference, the best orbital symmetry match, and the maximum orbital overlap, TiO2 does bring about a very positive effect on catalysts Pd/TiO2 for the first electron transfer of the ORR. Especially, TiO2 remarkably expands the space size of Pd/TiO2 HOMO or-bital and improves orbital overlap of Pd/TiO2 HOMO and O2 LUMO. The analysis of deformation density and partial density of state shows that the strong interaction between Pt and Ti leads to a strong ad-sorption of intermediate O on Pt/TiO2, but the strong interaction between Pd and surface O causes positive net charge of Pd and a weak adsorption of intermediate O on Pd/TiO2. Thus, the ORR can proceed more smoothly on Pd/TiO2 than Pt/TiO2 in every respect of maximum orbital overlap and rate delay by intermediate O. The research also discloses that several factors lead to less activity of TiO2-supported Pt and Pd catalysts than the C-supported ones for the ORR. These factors include the poor dispersion of Pt and Pd particles on TiO2, poor electric conduction of TiO2 carrier itself, and bigger energy difference between HOMO of TiO2-carried metallic catalysts and LUMO of O2 molecule due to electrons deeply embedded in the semiconductor TiO2 carrier.

  3. Low Pt content on the Pd{sub 45}Pt{sub 5}Sn{sub 50} cathode catalyst for PEM fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Salvador-Pascual, J.J.; Solorza-Feria, O. [Depto. Quimica, Centro de Investigacion y de Estudios Avanzados del IPN, A. Postal 14-740, 07360 Mexico D.F. (Mexico); Collins-Martinez, V.; Lopez-Ortiz, A. [Centro de Investigacion en Materiales Avanzados, Miguel de Cervantes 120, 31109 Chihuahua (Mexico)

    2010-06-01

    Pd{sub 45}Pt{sub 5}Sn{sub 50} electrocatalyst was prepared by a NaBH{sub 4} reduction of PdCl{sub 2}, H{sub 2}PtCl{sub 6} and SnCl{sub 2} in THF at 0 C. This catalyst was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS) microanalysis and hydrodynamic electrochemical technique. XRD, SEM and TEM results demonstrate that the borohydrate reduction methodology enable the synthesis of conglomerated particles nanometric in size ranging from 1 to 6 nm. Oxygen reduction reaction (ORR) activity was investigated on carbon dispersed catalyst by rotating disk electrode (RDE) technique in H{sub 2}SO{sub 4} 0.5 M. The effect of temperature on the kinetics was analyzing resulting in an apparent activation energy of 42.54 {+-} 1 kJ mol{sup -1}, value which is less than the obtained for the nanostructured bimetallic PdSn electrocatalyst under the same experimental condition. The Pd{sub 45}Pt{sub 5}Sn{sub 50} electrocatalyst dispersed on a carbon powder was tested as cathode electrocatalyst in a membrane-electrode assembly (MEA) arriving to a power density of 210 mW cm{sup -2} at 0.35 V and 80 C. (author)

  4. Synthesis and Catalytic Activity of Pt Monolayer on Pd Tetrahedral Nanocrystals with CO-adsorption-induced Removal of Surfactants

    Energy Technology Data Exchange (ETDEWEB)

    Gong K.; Vukmirovic M.B.; Ma C.; Zhu Y.; Adzic R.R.

    2011-11-01

    We synthesized the Pt monolayer shell-Pd tetrahedral core electrocatalysts that are notable for their high activity and stable performance. A small number of low-coordination sites and defects, and high content of the (1 1 1)-oriented facets on Pd tetrahedron makes them a suitable support for a Pt monolayer to obtain an active O{sub 2} reduction reaction (ORR) electrocatalyst. The surfactants, used to control size and shape of Pd tetrahedral nanoparticles, are difficult to remove and cause adverse effects on the ORR. We describe a simple and noninvasive method to synthesize high-purity tetrahedral Pd nanocrystals (TH Pd) by combining a hydrothermal route and CO adsorption-induced removal of surfactants. Poly(vinylpyrrolidone) (PVP), used as a protecting and reducing agent in hydrothermal reactions, is strongly bonded to the surface of the resulting nanocrystals. We demonstrate that PVP was displaced efficiently by adsorbed CO. A clean surface was achieved upon CO stripping at a high potential (1.0 V vs RHE). It played a decisive role in improving the activity of the Pt monolayer/TH Pd electrocatalyst for the ORR. Furthermore, the results demonstrate a versatile method for removal of surfactants from various nanoparticles that severely limited their applications.

  5. Formation of hard magnetic L1{sub 0}-FePt/FePd monolayers from elemental multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Goo, Nam Hoon

    2007-06-18

    In this thesis, ordered L1{sub 0}-FePt and FePd films of different nominal compositions are prepared from Fe/Pt and Fe/Pd multilayers by annealing. In case of the L1{sub 0}-FePt films the composition of the films is modified by changing the individual elemental layer thicknesses in the multilayer precursors. This simple variation of the composition is the great advantage of the multilayer approach compared to sputtering single alloy layer from an alloy target. The formation mechanism of the fct phase from the multilayers and the microstructural properties are investigated. The characteristics of the hysteresis loop (coercivity {mu}{sub 0}H{sub c}, remanence J{sub r}) and of the intrinsic magnetic properties (anisotropy constant K{sub l}, spontaneous polarization J{sub s}, exchange constant A) of the ordered L1{sub 0}-FePt and FePd films are studied. The effects of the composition of the L1{sub 0}-FePt films on the microstructural and magnetic properties are investigated. The microstructure of these ordered L1{sub 0}-FePt films are then correlated to the magnetic properties with microstructural parameters by investigating the temperature dependence of the coercivity. (orig.)

  6. Formic acid electro-oxidation on carbon supported Pd{sub x}Pt{sub 1-x} (0 {>=} x {>=} 1) nanoparticles synthesized via modified polyol method

    Energy Technology Data Exchange (ETDEWEB)

    Baranova, Elena A., E-mail: elena.baranova@uottawa.c [Department of Chemical and Biological Engineering, University of Ottawa, 161 Louis-Pasteur St., Ottawa, ON, K1N 6N5 (Canada); Miles, Neil [Department of Chemical and Biological Engineering, University of Ottawa, 161 Louis-Pasteur St., Ottawa, ON, K1N 6N5 (Canada); Mercier, Patrick H.J.; Le Page, Yvon; Patarachao, Bussaraporn [Institute for Chemical Process and Environmental Technology, National Research Council Canada, 1200 Montreal Rd., Ottawa, ON, K1A 0R6 (Canada)

    2010-11-30

    Carbon supported nanoparticle catalysts of Pd{sub x}Pt{sub 1-x} (0 {>=} x {>=} 1) were synthesized using a modified polyol method and poly(N-vinyl-2-pyrrolidone) (PVP) as a stabilizer. Resulting nanoparticles were characterized by X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and chronoamperommetry (CA) study for formic acid electro-oxidation. Surface composition of the synthesized nanoparticles found from XPS revealed the Pt surface segregation even for the Pd-rich compositions. It is suggested that the surface segregation behavior in PdPt nanoparticles supported on carbon may be influenced, in addition to the difference in Pd and Pt surface energies, by particle size and particle interaction with the support. According to CA, the carbon supported Pd nanoparticles show the highest initial activity towards formic acid electro-oxidation at the potential of 0.3 V (RHE), due to the promotion of the direct dehydrogenation mechanism. However its stability is quite poor resulting in the fast deactivation of the Pd surface. Addition of Pt considerably improves the steady-state activity of Pd in 12 h CA experiment. CA measurements show that the most active catalyst is Pd{sub 0.5}Pt{sub 0.5} of 4 nm size, which displays narrow size distribution and Pd to Pt surface atomic ratio of 27-73.

  7. Ultrasonic-assisted synthesis of Pd-Pt/carbon nanotubes nanocomposites for enhanced electro-oxidation of ethanol and methanol in alkaline medium.

    Science.gov (United States)

    Yang, Guohai; Zhou, Yazhou; Pan, Horng-Bin; Zhu, Chengzhou; Fu, Shaofang; Wai, Chien M; Du, Dan; Zhu, Jun-Jie; Lin, Yuehe

    2016-01-01

    Herein, a facile ultrasonic-assisted strategy was proposed to fabricate the Pd-Pt alloy/multi-walled carbon nanotubes (Pd-Pt/CNTs) nanocomposites. A good number of Pd-Pt alloy nanoparticles with an average of 3.4 ± 0.5 nm were supported on sidewalls of CNTs with uniform distribution. The composition of the Pd-Pt/CNTs nanocomposites could also be easily controlled, which provided a possible approach for the preparation of other architectures with anticipated properties. The Pd-Pt/CNTs nanocomposites were extensively studied by electron microscopy, induced coupled plasma atomic emission spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, and applied for the ethanol and methanol electro-oxidation reaction in alkaline medium. The electrochemical results indicated that the nanocomposites had better electrocatalytic activities and stabilities, showing promising applications for fuel cells. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Alloying effect via comparative studies of ethanol dehydrogenation on Cu(1 1 1), Cu3Pd(1 1 1), and Cu3Pt(1 1 1)

    Science.gov (United States)

    Wu, Ruitao; Wang, Lichang

    2017-06-01

    Ethanol dehydrogenations on Cu(1 1 1), Cu3Pd(1 1 1), and Cu3Pt(1 1 1) were studied using density functional theory with a PBE functional. The α-C-H and β-C-H scissions are endothermic on all surfaces while the O-H scission is exothermic on Cu(1 1 1) and Cu3Pt(1 1 1) but endothermic on Cu3Pd(1 1 1). The ethanol dehydrogenation occurs on Cu(1 1 1) through both α-C-H and O-H scissions but on Cu3Pd(1 1 1) and Cu3Pt(1 1 1) through only α-C-H scission. Furthermore, alloying Pt or Pd with Cu shows an increase in reaction rate at 493 K by more than 3 orders of magnitude, thus illustrating the promise of alloying Pt or Pd in Cu catalysts for ethanol dehydrogenation.

  9. Platinum-group minerals from the Jinbaoshan Pd-Pt deposit, SW China: evidence for magmatic origin and hydrothermal alteration

    Science.gov (United States)

    Wang, Christina Yan; Prichard, Hazel M.; Zhou, Mei-Fu; Fisher, Peter C.

    2008-09-01

    The Jinbaoshan Pt-Pd deposit in Yunnan, SW China, is hosted in a wehrlite body, which is a member of the Permian (˜260 Ma) Emeishan Large Igneous Province (ELIP). The deposit is reported to contain one million tonnes of Pt-Pd ore grading 0.21% Ni and 0.16% Cu with 3.0 g/t (Pd + Pt). Platinum-group minerals (PGM) mostly are ˜10 μm in diameter, and are commonly Te-, Sn- and As-bearing, including moncheite (PtTe2), atokite (Pd3Sn), kotulskite (PdTe), sperrylite (PtAs2), irarsite (IrAsS), cooperite (PtS), sudburyite (PdSb), and Pt-Fe alloy. Primary rock-forming minerals are olivine and clinopyroxene, with clinopyroxene forming anhedral poikilitic crystals surrounding olivine. Primary chromite occurs either as euhedral grains enclosed within olivine or as an interstitial phase to the olivine. However, the intrusion has undergone extensive hydrothermal alteration. Most olivine grains have been altered to serpentine, and interstitial clinopyroxene is often altered to actinolite/tremolite and locally biotite. Interstitial chromite grains are either partially or totally replaced by secondary magnetite. Base-metal sulfides (BMS), such as pentlandite and chalcopyrite, are usually interstitial to the altered olivine. PGM are located with the BMS and are therefore also interstitial to the serpentinized olivine grains, occurring within altered interstitial clinopyroxene and chromite, or along the edges of these minerals, which predominantly altered to actinolite/tremolite, serpentine and magnetite. Hydrothermal fluids were responsible for the release of the platinum-group elements (PGE) from the BMS to precipitate the PGM at low temperature during pervasive alteration. A sequence of alteration of the PGM has been recognized. Initially moncheite and atokite have been corroded and recrystallized during the formation of actinolite/tremolite, and then, cooperite and moncheite were altered to Pt-Fe alloy where they are in contact with serpentine. Sudburyite occurs in veins

  10. PdM (M = Pt, Au) bimetallic alloy nanowires with enhanced electrocatalytic activity for electro-oxidation of small molecules

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Chengzhou; Guo, Shaojun; Dong, Shaojun [State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin, 130022 (China)

    2012-05-02

    A facile and general method has been developed to synthesize well-defined PdPt and PdAu alloy nanowires, which exhibit significantly enhanced activity towards small molecules, such as ethanol, methanol, and glucose electro-oxidation in an alkaline medium. Considering the important role of one-dimensional alloy nanowires in electrocatalytic systems, the present Pd-based alloy nanostructures could offer a promising new class of advanced electrocatalysts for direct alcohol fuel cells and electrochemical sensors. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. CO Sensing Performance of a Micro Thermoelectric Gas Sensor with AuPtPd/SnO₂ Catalyst and Effects of a Double Catalyst Structure with Pt/α-Al₂O₃.

    Science.gov (United States)

    Goto, Tomoyo; Itoh, Toshio; Akamatsu, Takafumi; Shin, Woosuck

    2015-12-15

    The CO sensing properties of a micro thermoelectric gas sensor (micro-TGS) with a double AuPtPd/SnO₂ and Pt/α-Al₂O₃ catalyst were investigated. While several nanometer sized Pt and Pd particles were uniformly dispersed on SnO₂, the Au particles were aggregated as particles measuring >10 nm in diameter. In situ diffuse reflectance Fourier transform Infrared spectroscopy (DRIFT) analysis of the catalyst showed a CO adsorption peak on Pt and Pd, but no clear peak corresponding to the interaction between CO and Au was detected. Up to 200 °C, CO combustion was more temperature dependent than that of H₂, while H₂ combustion was activated by repeated exposure to H₂ gas during the periodic gas test. Selective CO sensing of the micro-TGS against H₂ was attempted using a double catalyst structure with 0.3-30 wt% Pt/α-Al₂O₃ as a counterpart combustion catalyst. The sensor output of the micro-TGS decreased with increasing Pt content in the Pt/α-Al₂O₃ catalyst, by cancelling out the combustion heat from the AuPtPd/SnO₂ catalyst. In addition, the AuPtPd/SnO₂ and 0.3 wt% Pt/α-Al₂O₃ double catalyst sensor showed good and selective CO detection. We therefore demonstrated that our micro-TGS with double catalyst structure is useful for controlling the gas selectivity of CO against H₂.

  12. Oxidizing behavior of some platinum metal fluorides. [Xe complexes with Pt, Pd fluorides; Chlorine-2 oxidation by transition metal hexafluorides

    Energy Technology Data Exchange (ETDEWEB)

    Graham, L.

    1978-10-01

    The previously known compounds Xe/sub 2/F/sub 3//sup +/PtF/sub 6//sup -/, XeF/sup +/PtF/sub 6//sup -/ and XeF/sub 2/.2PtF/sub 4/(XePt/sub 2/F/sub 10/) were prepared by the interaction of XeF/sub 2/ with PtF/sub 4/. The new compounds XeF/sub 2/.PdF/sub 4/ and XeF/sub 2/.2PdF/sub 4/(XePd/sub 2/F/sub 10/) were produced by interaction of XeF/sub 2/ with either PdF/sub 4/ or Pd/sub 2/F/sub 6/. A weight loss-versus-time curve indicated the presence of 4:1, 3:1 and 2:1 XeF/sub 2//PdF/sub 4/ complexes. The thermal decomposition of XeFPtF/sub 6/ or XePd/sub 2/F/sub 10/ yields highly pure XeF/sub 4/. Thus the interaction of XeF/sub 2/ with platinum fluorides (PtF/sub 4/ or PtF/sub 5/) or palladium fluorides (Pd/sub 2/F/sub 6/ or PdF/sub 4/) provides for the conversion of XeF/sub 2/ to XeF/sub 4/. The compound XePd/sub 2/F/sub 10/ is a close structural relative of XePt/sub 2/F/sub 10/, and spectroscopic evidence suggests that both are salts of XeF/sup +/ and a polymeric (M/sub 2/F/sub 9/)/sub x//sup x-/ ion. A Xe:PtF/sub 6/ material of approximately 1:1 stoichiometry has been prepared and compared with XePdF/sub 6/(XeF/sub 2/.PdF/sub 4/). The interaction of chlorine with the third-series transition metal hexafluorides has been investigated. Gravimetric and tensimetric evidence indicate that the initial product of the Cl/sub 2/ plus IrF/sub 6/ reaction is a solid of composition Cl/sub 2/IrF/sub 6/. Vibrational spectroscopic and other evidence indicates that this solid yields a sequence of products, of which Cl/sub 3//sup +/IrF/sub 6//sup -/, Cl/sub 3//sup +/Ir/sub 2/F/sub 11//sup -/ and Ir/sub 4/F/sub 20/ have been identified, the last being the ultimate solid product of the room temperature decomposition of the adduct. A new chlorine fluoride generated in the room temperature decomposition of Cl/sub 2/IrF/sub 6/ has been tentatively formulated as Cl/sub 3/F from infrared evidence.

  13. Molecular dynamics simulation study of the melting and structural evolution of bimetallic Pd-Pt nanowires

    Science.gov (United States)

    Sankaranarayanan, Subramanian K. R. S.; Bhethanabotla, Venkat R.; Joseph, Babu

    2006-10-01

    Thermal characteristics of Pd-Pt metal nanowires with diameters ranging from 2.3 to 3.5nm and of several compositions were studied by molecular dynamics simulations utilizing the quantum Sutton-Chen potential function. Monte Carlo simulations employing bond order simulation model were used to generate the initial wire configurations that consisted of surface segregated structures. Melting temperatures were estimated based on variations in thermodynamic properties such as potential energy and specific heat capacity. We find that the melting transition temperatures for the nanowires are much lower than those of bulk alloys of the same composition and at least 100-200K higher than those of nanoclusters of the same diameter. Density distributions along the nanowire cross section and axis as well as components of shell-based diffusion coefficients and velocity autocorrelation functions were used to investigate the melting mechanism in these nanowires. Our findings indicate a surface-initiated melting process characterized by predominantly larger cross-sectional movement. This two-dimensional surface melting mechanism in nanowires differs from that in nanoclusters in which atomic movement is more isotropic in all three dimensions. Differences in the surface melting mechanism result in structural transformations from fcc-hcp type and lead to simulated phase boundaries for nanowires that are different from bulk alloys as well as from same-diameter nanoclusters. A composition and temperature dependent fcc-hcp transformation occurs prior to the melting transition in both nanowires and nanoclusters. Hcp phase occurs over a wider temperature range at Pd-rich compositions and a narrower range at low Pd compositions with the fcc-hcp and hcp-liquid transition temperatures showing a minimum at 25% Pt composition. In contrast, the nanoclusters exhibit a near-linear dependence of melting temperature on Pd composition with the hcp phase existing over a much narrower range of

  14. First principles investigation of the activity of thin film Pt, Pd and Au surface alloys for oxygen reduction

    DEFF Research Database (Denmark)

    Tripkovic, Vladimir; Hansen, Heine Anton; Rossmeisl, Jan

    2015-01-01

    of Au with mixed Pt/Pd skins. The activity of the binary and ternary catalysts is explained through weakening of the OH binding energy caused by solute elements. However, given the low alloy formation energies it may be difficult to tune and retain the composition under operating conditions...

  15. Facile and Rapid Synthesis of Ultrafine PtPd Bimetallic Nanoparticles and Their High Performance toward Methanol Electrooxidation

    Directory of Open Access Journals (Sweden)

    Tiantian Xia

    2014-01-01

    Full Text Available Uniform and sub-10 nm size bimetallic PtPd nanoparticles (NPs have been synthesized via a simple and facile method without using any surfactants at an ambient temperature. As a green and clean reductive agent, ascorbic acid (AA was employed for the coreduction of K2PtCl4 and K2PdCl4 in aqueous solution. The morphology, composition, and structure of PtPd NPs had been characterized by transmission electron microscopy (TEM, field emission high resolution transmission electron microscopy (FE-HRTEM, energy dispersive spectroscopy (EDS, X-ray diffraction (XRD, and X-ray photoelectron spectroscope (XPS. Comparing with both the monometallic Pt and Pd, the as-prepared alloy nanoparticles show superior electrocatalytic activity and better tolerance against poisoning by intermediates generated during methanol electrooxidation, which makes them a promising electrocatalysts for direct methanol fuel cells (DMFCs. Meanwhile, the green and simple approach could be easily extended to the manufacture of bimetallic or trimetallic alloy nanomaterials.

  16. Beet juice utilization: Expeditious green synthesis of nobel metal nanoparticles (Ag, Au, Pt, and Pd) using microwaves

    Science.gov (United States)

    Metal nanoparticles of Ag, Au, Pt, and Pd were prepared in aqueous solutions via a rapid microwave-assisted green method using beet juice, an abundant sugar-rich agricultural produce, served as both a reducing and a capping reagent. The Ag nanoparticles with capping prepared by b...

  17. The Crystal Growth and Characterization of CeT2Si2 Ternary Intermetallics (T = Ni, Pd, Pt)

    NARCIS (Netherlands)

    Menovsky, A.A.; Snel, C.E.; Gortenmulder, T.J.; Palstra, T.T.M.

    1986-01-01

    Bulk single crystals of the ternary intermetallic compounds CeNi2Si2, CePd2Si2 and CePt2Si2 have been grown from the melt with a modified “tri-arc” Czochralski method. The as-grown crystals were characterized by X-ray, microprobe, and chemical analyses. The measured densities were compared with the

  18. First principles investigation of the activity of thin film Pt, Pd and Au surface alloys for oxygen reduction

    DEFF Research Database (Denmark)

    Tripkovic, Vladimir; Hansen, Heine Anton; Rossmeisl, Jan;

    2015-01-01

    Further advances in fuel cell technologies are hampered by kinetic limitations associated with the sluggish cathodic oxygen reduction reaction. We have investigated a range of different formulations of binary and ternary Pt, Pd and Au thin films as electrocatalysts for oxygen reduction. The most...

  19. The Crystal Growth and Characterization of CeT2Si2 Ternary Intermetallics (T = Ni, Pd, Pt)

    NARCIS (Netherlands)

    Menovsky, A.A.; Snel, C.E.; Gortenmulder, T.J.; Palstra, T.T.M.

    1986-01-01

    Bulk single crystals of the ternary intermetallic compounds CeNi2Si2, CePd2Si2 and CePt2Si2 have been grown from the melt with a modified “tri-arc” Czochralski method. The as-grown crystals were characterized by X-ray, microprobe, and chemical analyses. The measured densities were compared with the

  20. The Sticking Probability for Hydrogen on Ni, Pd, and Pt at a Hydrogen pressure of 1 bar

    DEFF Research Database (Denmark)

    Johansson, Martin; Lytken, Ole; Chorkendorff, Ib

    2007-01-01

    A technique for measurements of the sticking probability of hydrogen on metal surfaces at high (ambient) pressure is described. As an example, measurements for Ni, Pd and Pt at a hydrogen pressure of 1 bar and temperatures between 40 and 200 degrees C are presented. The sticking probabilities...

  1. Beet juice utilization: Expeditious green synthesis of nobel metal nanoparticles (Ag, Au, Pt, and Pd) using microwaves

    Science.gov (United States)

    Metal nanoparticles of Ag, Au, Pt, and Pd were prepared in aqueous solutions via a rapid microwave-assisted green method using beet juice, an abundant sugar-rich agricultural produce, served as both a reducing and a capping reagent. The Ag nanoparticles with capping prepared by b...

  2. NMR shielding and spin-rotation constants in XCO (X = Ni, Pd, Pt) molecules

    Science.gov (United States)

    Demissie, Taye B.; Jaszuński, Michał; Malkin, Elena; Komorovský, Stanislav; Ruud, Kenneth

    2015-07-01

    Ab initio nonrelativistic and four-component relativistic DFT (density functional theory) methods are combined to study the spin-rotation and absolute nuclear magnetic resonance (NMR) shielding constants of group 10 transition metal monocarbonyls. Good agreement is obtained between the calculated and available experimental data for the spin-rotation constants and shielding spans for PdCO and PtCO. These data allow us to determine accurate absolute chemical shielding constants for all the nuclei, as well as for the unknown spin-rotation constants. We compare the four-component shielding constants with those obtained from the spin-orbit zeroth-order regular approximation, together with an assessment of the performance of different basis sets. For the first time, relativistically optimised basis sets for the heavy atoms used in the four-component calculations are shown to give converged results for both magnetic properties studied. We dedicate this article to the memory of Professor Nicholas C. Handy.

  3. Domain configurations in Co/Pd and L10-FePt nanowire arrays with perpendicular magnetic anisotropy

    Science.gov (United States)

    Ho, Pin; Tu, Kun-Hua; Zhang, Jinshuo; Sun, Congli; Chen, Jingsheng; Liontos, George; Ntetsikas, Konstantinos; Avgeropoulos, Apostolos; Voyles, Paul M.; Ross, Caroline A.

    2016-02-01

    Perpendicular magnetic anisotropy [Co/Pd]15 and L10-FePt nanowire arrays of period 63 nm with linewidths 38 nm and 27 nm and film thickness 27 nm and 20 nm respectively were fabricated using a self-assembled PS-b-PDMS diblock copolymer film as a lithographic mask. The wires are predicted to support Néel walls in the Co/Pd and Bloch walls in the FePt. Magnetostatic interactions from nearest neighbor nanowires promote a ground state configuration consisting of alternating up and down magnetization in adjacent wires. This was observed over ~75% of the Co/Pd wires after ac-demagnetization but was less prevalent in the FePt because the ratio of interaction field to switching field was much smaller. Interactions also led to correlations in the domain wall positions in adjacent Co/Pd nanowires. The reversal process was characterized by nucleation of reverse domains, followed at higher fields by propagation of the domains along the nanowires. These narrow wires provide model system for exploring domain wall structure and dynamics in perpendicular anisotropy systems.Perpendicular magnetic anisotropy [Co/Pd]15 and L10-FePt nanowire arrays of period 63 nm with linewidths 38 nm and 27 nm and film thickness 27 nm and 20 nm respectively were fabricated using a self-assembled PS-b-PDMS diblock copolymer film as a lithographic mask. The wires are predicted to support Néel walls in the Co/Pd and Bloch walls in the FePt. Magnetostatic interactions from nearest neighbor nanowires promote a ground state configuration consisting of alternating up and down magnetization in adjacent wires. This was observed over ~75% of the Co/Pd wires after ac-demagnetization but was less prevalent in the FePt because the ratio of interaction field to switching field was much smaller. Interactions also led to correlations in the domain wall positions in adjacent Co/Pd nanowires. The reversal process was characterized by nucleation of reverse domains, followed at higher fields by propagation of the

  4. Spin-orbit interaction tuning of perpendicular magnetic anisotropy in L1{sub 0} FePdPt films

    Energy Technology Data Exchange (ETDEWEB)

    Ma, X.; Lüpke, G., E-mail: gyguo@phys.ntu.edu.tw, E-mail: hbzhao@fudan.edu.cn, E-mail: gxluep@wm.edu [Department of Applied Science, College of William and Mary, 251 Jamestown Road, Williamsburg, Virginia 23187 (United States); He, P.; Ma, L.; Zhou, S. M. [Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physics Science and Engineering, Tongji University, Shanghai 200092 (China); Guo, G. Y., E-mail: gyguo@phys.ntu.edu.tw, E-mail: hbzhao@fudan.edu.cn, E-mail: gxluep@wm.edu [Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Zhao, H. B., E-mail: gyguo@phys.ntu.edu.tw, E-mail: hbzhao@fudan.edu.cn, E-mail: gxluep@wm.edu [Department of Optical Science and Engineering, Fudan University, 220 Handan Road, Shanghai 200433 (China)

    2014-05-12

    The dependence of perpendicular magnetic anisotropy K{sub u} on spin-orbit coupling strength ξ is investigated in L1{sub 0} ordered FePd{sub 1−x}Pt{sub x} films by time-resolved magneto-optical Kerr effect measurements and ab initio density functional calculations. Continuous tuning of K{sub u} over a wide range of magnitude is realized by changing the Pt/Pd concentration ratio, which strongly modifies ξ but keeps other leading parameters affecting K{sub u} nearly unchanged. Ab initio calculations predict a nearly quadratic dependence of K{sub u} on ξ, consistent with experimental data. K{sub u} increases with increasing chemical order and decreasing thermal spin fluctuations, which becomes more significant for samples with higher Pt concentration. The results demonstrate an effective method to tune K{sub u} utilizing its sensitivity on ξ, which will help fabricate magnetic systems with desirable magnetic anisotropy.

  5. Study of bimetallic Pd-Pt clusters in both free and supported phases

    Science.gov (United States)

    Rousset, J. L.; Cadrot, A. M.; Cadete Santos Aires, F. J.; Renouprez, A.; Mélinon, P.; Perez, A.; Pellarin, M.; Vialle, J. L.; Broyer, M.

    1995-06-01

    We study PdPt bimetallic clusters in both free and supported phases. These clusters have been produced with a laser vaporization source. Free clusters directly produced by the source are studied by time of flight mass spectrometry and photofragmentation technique. We observed a sequential evaporation of Pd atoms in the mixed clusters consistent with a palladium segregation process. This tendency has been also observed on supported particles from which the structure and the composition are determined by high resolution transmission electron microscopy and energy dispersive x-ray analysis. A main result is that each particle has the composition of the massic rod vaporized in the source. The supported particles are well crystallized and exhibit truncated octahedron shapes. Experimental observations are well explained using a modified tight binding model. Indeed, within this model, we found that the equilibrium shape is strongly related to the variation of the cohesive energy with atomic coordination number. Also, some preliminary results on the specific reactivity of these bimetallic clusters are presented.

  6. Catalytic activity and mechanistic approach of NO reduction by CO over M0.05Co2.95O4 (M = Rh, Pd & Ru) spinel system

    Science.gov (United States)

    Salker, A. V.; Desai, M. S. Fal

    2016-12-01

    Pd, Rh and Ru doped cobalt oxide spinels have been prepared by citric acid assisted sol-gel method to yield nano-catalysts. Compositions have been characterized by XRD, FTIR, TG/DTA, BET, SEM, TEM, TPD and XPS techniques. Simultaneous catalytic detoxification of nitric oxide and carbon monoxide is investigated over the doped and pristine catalysts. Metal doping is found to enhance the activity of the catalysts due to their better adsorption capacity. Moisture and oxygen tolerance is investigated for Rh and Pd substituted catalysts. A probable reaction mechanism on the catalyst surface has been proposed.

  7. Barrier characteristics of Pt/Ru Schottky contacts on -type GaN based on –– and –– measurements

    Indian Academy of Sciences (India)

    N Nanda Kumar Reddy; V Rajagopal Reddy

    2012-02-01

    We have investigated the current–voltage (–) and capacitance–voltage (–) characteristics of Ru/Pt/-GaN Schottky diodes in the temperature range 100–420 K. The calculated values of barrier height and ideality factor for the Ru/Pt/-GaN Schottky diode are 0.73 eV and 1.4 at 420 K, 0.18 eV and 4.2 at 100 K, respectively. The zero-bias barrier height ($\\Phi_{\\text{b}0}$) calculated from – characteristics is found to be increased and the ideality factor () decreased with increasing temperature. Such a behaviour of $\\Phi_{\\text{b}0}$ and n is attributed to Schottky barrier (SB) inhomogeneities by assuming a Gaussian distribution (GD) of barrier heights (BHs) at themetal/semiconductor interface. The current–voltage–temperature (––) characteristics of the Ru/Pt/-GaN Schottky diode have shown a double Gaussian distribution having mean barrier heights ($\\bar{\\Phi}_{\\text{b}0}$) of 1.001 eV and 0.4701 eV and standard deviations ($\\sigma_{0}$) of 0.1491 V and 0.0708 V, respectively. The modified ln($J_{0}/T^{2}$) − ($q^{2}\\sigma^{2}_{0}/2k^{2}T^{2}$) vs 10$^{3}/T$ plot gives $\\bar{\\Phi}_{\\text{b}0}$ and Richardson constant values as 0.99 eV and 0.47 eV, and 27.83 and 10.29 A/cm2K2, respectively without using the temperature coefficient of the barrier height. The difference between the apparent barrier heights (BHs) evaluated from the – and – methods has been attributed to the existence of Schottky barrier height inhomogeneities.

  8. Colorimetric detection of the flux of hydrogen peroxide released from living cells based on the high peroxidase-like catalytic performance of porous PtPd nanorods.

    Science.gov (United States)

    Ge, Shenguang; Liu, Weiyan; Liu, Haiyun; Liu, Fang; Yu, Jinghua; Yan, Mei; Huang, Jiadong

    2015-09-15

    One-dimensional PtPd porous nanorods (PtPd PNRs) were successfully synthesized through a bromide-induced galvanic replacement reaction between Pd nanowires and K2PtCl6. The PtPd PNRs were porous and alloy-structured with Pt/Pd atomic ratio up to 1:1 which were demonstrated by spectroscopic methods. We had also proved that the nanorods could function as peroxidase mimetic for the detection of H2O2, with the detection limit of 8.6 nM and the linear range from 20 nM to 50 mM. The result demonstrated that PtPd PNRs exhibited much higher affinity to H2O2 over other peroxidase mimetics due to synergistically integrating highly catalytic activity of two metals. On the basis of the peroxidase-like activity, the PtPd PNRs were used as a signal transducer to develop a novel and simple colorimetric method for the study of the flux of H2O2 released from living cell. By using 3,3,5,5-tetramethylbenzidine as substrate, the H2O2 concentration could be distinguished by naked-eye observation without any instrumentation or complicated design. The method developed a new platform for a reliable collection of information on cellular reactive oxygen species release. And the nanomaterial could be used as a power tool for a wide range of potential applications in biotechnology and medicine.

  9. New neutron diffraction results on magnetic properties of the cubic rare earth compounds HoP and PrX/sub 2/ (X = Ru, Rh, Ir, Pt)

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, P.; Haelg, W.; Kaldis, E.; Greidanus, F.J.A.M.; Buschow, K.H.J.

    1982-01-01

    Neutron diffraction studies performed on polycrystalline, NaCl type HoP in external magnetic fields yield <100> as easy directions of magnetization in the ferromagnetic state. The magnetic ordering of the MgCu/sub 2/ type Laves phase systems PrX/sub 2/ (X = Ru, Rh, Ir, Pt) was investigated on powdered samples by means of neutron diffraction. Simple ferromagnetic structures were observed. The determined Curie temperatures confirm bulk measurements, and the values of the ordered magnetic moments indicate crystal field effects.

  10. New neutron diffraction results on magnetic properties of the cubic rare earth compounds HoP and PrX2 (X=Ru, Rh, Ir, Pt)

    Science.gov (United States)

    Fischer, P.; Hälg, W.; Kaldis, E.; Greidanus, F. J. A. M.; Buschow, K. H. J.

    1982-09-01

    Neutron diffraction studies performed on polycrystalline, NaCl type HoP in external magnetic fields yield as easy directions of magnetization in the ferromagnetic state. The magnetic ordering of the MgCu2 type Laves phase systems PrX2 (X=Ru, Rh, Ir, Pt) was investigated on powdered samples by means of neutron diffraction. Simple ferromagnetic structures were observed. The determined Curie temperatures confirm bulk measurements, and the values of the ordered magnetic moments indicate crystal field effects.

  11. Electrochemical oxidation of ammonia on carbon-supported bi-metallic PtM (M = Ir, Pd, SnO{sub x}) nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Lomocso, Thegy L. [Department of Chemical and Biological Engineering, University of Ottawa, 161 Louis-Pasteur, Ottawa, ON K1N 6N5 (Canada); Baranova, Elena A., E-mail: elena.baranova@uottawa.ca [Department of Chemical and Biological Engineering, University of Ottawa, 161 Louis-Pasteur, Ottawa, ON K1N 6N5 (Canada)

    2011-10-01

    Highlights: > Oxidation of NH{sub 3} is investigated on carbon-supported Pt and PtM (M = Pd, Ir, SnO{sub x}) nanoparticles. > Carbon supported PtPd and PtIr nanoparticles show higher catalytic activity if compared to Pt nanocatalyst. > Pt{sub 7}Ir{sub 3} nanoparticles combine good catalytic activity and enhanced stability for NH{sub 3} oxidation. > Electronic effect between two metals in PtIr is responsible for increase in the catalytic activity. - Abstract: Ammonia electro-oxidation was studied in alkaline solution on carbon-supported Pt and bimetallic Pt{sub y}M{sub 1-y} (M = Pd, Ir, SnO{sub x} and y = 70, 50 at.%) nanoparticles. Catalysts were synthesized using the modified polyol method and deposited on carbon, resulting in 20 wt.% of metal loading. Particle size, structure and surface composition of the particles were investigated using TEM, XRD and XPS. Mean size of PtM bi-metallic nanoparticles varied between 2.0 and 4.7 nm, depending on the second metal (M). XRD revealed the structure of all bi-metallic particles to be face-centered cubic and confirmed alloy formation for Pt{sub y}Pd{sub 1-y} (y = 70, 50 at.%) and Pt{sub 7}Ir{sub 3}nanoparticles, as well as partial alloying between Pt and SnO{sub x}. Electrochemical behaviour of ammonia on Pt and PtM nanoparticles is comparable to that expected for bulk Pt and PtM alloys. Addition of Pd to Pt at the nanoscale decreased the onset potential of ammonia oxidation if compared to pure platinum nanoparticles; however stability of the catalyst was poor. For Pt{sub 7}(SnO{sub x}){sub 3}, current densities were similar to Pt, whereas catalyst stability against deactivation was improved. It is found that carbon supported Pt{sub 7}Ir{sub 3} nanoparticles combine good catalytic activity with enhanced stability for ammonia electro-oxidation. Electronic effect generated between two metals in the bimetallic nanoparticles might be responsible for increase in the catalytic activity of Pd- and Ir-containing catalysts, causing

  12. Synthesis of ultrathin face-centered-cubic Au@Pt and Au@Pd core-shell nanoplates from hexagonal-close-packed Au square sheets

    KAUST Repository

    Fan, Zhanxi

    2015-03-17

    The synthesis of ultrathin face-centered-cubic (fcc) Au@Pt rhombic nanoplates is reported through the epitaxial growth of Pt on hexagonal-close-packed (hcp) Au square sheets (AuSSs). The Pt-layer growth results in a hcp-to-fcc phase transformation of the AuSSs under ambient conditions. Interestingly, the obtained fcc Au@Pt rhombic nanoplates demonstrate a unique (101)f orientation with the same atomic arrangement extending from the Au core to the Pt shell. Importantly, this method can be extended to the epitaxial growth of Pd on hcp AuSSs, resulting in the unprecedented formation of fcc Au@Pd rhombic nanoplates with (101)f orientation. Additionally, a small amount of fcc (100)f-oriented Au@Pt and Au@Pd square nanoplates are obtained with the Au@Pt and Au@Pd rhombic nanoplates, respectively. We believe that these findings will shed new light on the synthesis of novel noble bimetallic nanostructures. Phase change: Ultrathin Au@Pt and Au@Pd core-shell nanoplates were prepared from Au square sheets. A phase transformation from hexagonal close-packed (hcp) to face-centered cubic (fcc) is observed upon coating the hcp Au square sheets with Pt or Pd under ambient conditions. The prepared fcc Au@Pt and Au@Pd rhombic nanoplates demonstrate unique (101)f orientation (picture shows a typical fcc Au@Pt rhombic nanoplate). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. An investigation of the internal temperature dependence of Pd-Pt cluster beam deposition: A molecular dynamics study

    Science.gov (United States)

    Chen, Cha'o.-Kuang; Chang, Shing-Cheng

    2010-02-01

    We investigated the internal temperature dependence of the Pd 1- aPt a cluster beam deposition in the present study via the molecular dynamics simulations of soft-landing. By analysis of the velocity distribution and diffusion coefficient of the bimetallic cluster, Pd atoms with better mobility improved the diffusibility of Pt atoms. The radial composition distribution showed that a Pt-core/Pd-shell structure of the cluster formed at high internal temperatures through migrations of the Pd atoms from inner to surface shells. In the soft-landing process, the diffusing and epitaxial behaviors of the deposited clusters mainly depended on the internal temperature because the incident energy of the cluster was very small. By depositing clusters at high internal temperatures, we obtained a thin film of good epitaxial growth as the energetic cluster impact. Furthermore, nonepitaxial configurations such as scattered nonepitaxial atoms, misoriented particles, and grain boundaries of (1 1 1) planes were produced in the growth of the cluster-assembled film. As the size of the incident cluster increased, the internal temperature of the cluster needed for better interfacial diffusion and contact epitaxy on the substrate also rose.

  14. Domain configurations in Co/Pd and L10-FePt nanowire arrays with perpendicular magnetic anisotropy.

    Science.gov (United States)

    Ho, Pin; Tu, Kun-Hua; Zhang, Jinshuo; Sun, Congli; Chen, Jingsheng; Liontos, George; Ntetsikas, Konstantinos; Avgeropoulos, Apostolos; Voyles, Paul M; Ross, Caroline A

    2016-03-07

    Perpendicular magnetic anisotropy [Co/Pd]15 and L10-FePt nanowire arrays of period 63 nm with linewidths 38 nm and 27 nm and film thickness 27 nm and 20 nm respectively were fabricated using a self-assembled PS-b-PDMS diblock copolymer film as a lithographic mask. The wires are predicted to support Néel walls in the Co/Pd and Bloch walls in the FePt. Magnetostatic interactions from nearest neighbor nanowires promote a ground state configuration consisting of alternating up and down magnetization in adjacent wires. This was observed over ∼75% of the Co/Pd wires after ac-demagnetization but was less prevalent in the FePt because the ratio of interaction field to switching field was much smaller. Interactions also led to correlations in the domain wall positions in adjacent Co/Pd nanowires. The reversal process was characterized by nucleation of reverse domains, followed at higher fields by propagation of the domains along the nanowires. These narrow wires provide model system for exploring domain wall structure and dynamics in perpendicular anisotropy systems.

  15. Pt@Ag and Pd@Ag core/shell nanoparticles for catalytic degradation of Congo red in aqueous solution.

    Science.gov (United States)

    Salem, Mohamed A; Bakr, Eman A; El-Attar, Heba G

    2018-01-05

    Platinum/silver (Pt@Ag) and palladium/silver (Pd@Ag) core/shell NPs have been synthesized in two steps reaction using the citrate method. The progress of nanoparticle formation was followed by the UV/Vis spectroscopy. Transmission electron microscopy revealed spherical shaped core/shell nanoparticles with average particle diameter 32.17nm for Pt@Ag and 8.8nm for Pd@Ag. The core/shell NPs were further characterized by FT-IR and XRD. Reductive degradation of the Congo red dye was chosen to demonstrate the excellent catalytic activity of these core/shell nanostructures. The nanocatalysts act as electron mediators for the transfer of electrons from the reducing agent (NaBH4) to the dye molecules. Effect of reaction parameters such as nanocatalyst dose, dye and NaBH4 concentrations on the dye degradation was investigated. A comparison between the catalytic activities of both nanocatalysts was made to realize which of them the best in catalytic performance. Pd@Ag was the higher in catalytic activity over Pt@Ag. Such greater activity is originated from the smaller particle size and larger surface area. Pd@Ag nanocatalyst was catalytically stable through four subsequent reaction runs under the utilized reaction conditions. These findings can thus be considered as possible economical alternative for environmental safety against water pollution by dyes. Copyright © 2017. Published by Elsevier B.V.

  16. Estimate of the applicability of Pd-Pt nanoalloy for data recording by the method of phase change

    Science.gov (United States)

    Redel, L. V.; Gafner, Yu. Ya.; Gafner, S. L.; Zamulin, I. S.; Goloven'ko, Zh. V.

    2017-05-01

    Based on the computer simulation, the applicability of using individual nanoclusters of Pt, Pd, and particles of the Pd-Pt nanoalloy as unites of storage of data bits in nonvolatile memory devices, store capability of which is based on the principle of the phase change of the state of the carrier of information, has been estimated. To this end, the temperature and size limits of stability of different internal structures of nanoparticles in the course of the heating (to melting) and subsequent solidification (crystallization) with different rates of heat removal have been established. The results of the computer simulation of the nanoparticles of chemically pure platinum, palladium, and their alloy with different content of Pt atoms have been compared. It has been concluded that the best material for the memory cells the store capability of which is based on the occurrence of phase transitions is the nanoclusters of the Pd-Pt alloy with 10% platinum with a diameter D ≥ 3.5 nm.

  17. Degradation mechanism of Methyl Orange by electrochemical process on RuO(x)-PdO/Ti electrode.

    Science.gov (United States)

    Du, Lin; Wu, Jin; Qin, Song; Hu, Changwei

    2011-01-01

    The electrochemical degradation of Methyl Orange in 0.1 M NaCl solution over RuO(x)-PdO/Ti anode was investigated. Chemical oxygen demand (COD), ion chromatography (IC), Fourier Transform Infrared Spectroscopy (FTIR) and Gas chromatography-mass spectrometry (GC-MS) were employed to detect the intermediates formed during the electrochemical degradation. In the present reaction system, Methyl Orange could be effectively degraded. After 1 h treatment, the discoloration could reach 97.9% with COD removal of 57.6%. The results indicated that in the presence of chloride, the electrolysis was able to oxidise the dye with partial mineralisation of carbon, nitrogen and sulfur into CO(2), NO(-)(3) and SO(2-)(4), respectively. After 8 h electrolysis, 62% of sulfur contained in Methyl Orange was transformed to SO(4)(2-), and 17.6% of nitrogen changed to NO(3)(-). The intermediates during electroprocess were detected to be low molecular weight compounds, chlorinated compounds, derivatives of benzene and long chain alkanes. Based on these data, a possible degradation mechanism of Methyl Orange was proposed.

  18. Electrochemical Dealloying of PdCu3 Nanoparticles to Achieve Pt-like Activity for the Hydrogen Evolution Reaction.

    Science.gov (United States)

    Jana, Rajkumar; Bhim, Anupam; Bothra, Pallavi; Pati, Swapan K; Peter, Sebastian C

    2016-10-20

    Manipulating the d-band center of the metal surface and hence optimizing the free energy of hydrogen adsorption (ΔGH ) close to the optimal adsorption energy (ΔGH =0) for hydrogen evolution reaction (HER), is an efficient strategy to enhance the activity for HER. Herein, we report a oleylamine-mediated (acting as the solvent, stabilizer, and reducing agent) strategy to synthesize intermetallic PdCu3 nanoparticles (NPs) without using any external reducing agent. Upon electrochemical cycling, PdCu3 transforms into Pd-rich PdCu (ΔGH =0.05 eV), exhibiting remarkably enhanced activity (with a current density of 25 mA cm(-2) at ∼69 mV overpotential) as an alternative to Pt for HER. The first-principle calculation suggests that formation of low coordination number Pd active sites alters the d-band center and hence optimal adsorption of hydrogen, leading to enhanced activity. This finding may provide guidelines towards the design and development of Pt-free highly active and robust electrocatalysts. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Use of Dendrimers during the Synthesis of Pt-Ru Electrocatalysts for PEM Fuel Cells: Effects on the Physical and Electrochemical Properties

    Directory of Open Access Journals (Sweden)

    J. C. Calderón

    2011-01-01

    Full Text Available In this work, Pt-Ru catalysts were synthesized by a novel methodology which includes the use as encapsulating molecules of dendrimers of different generation: zero (DN-0, one (DN-1, two (DN-2, and three (DN-3. Synthesized catalysts were heat-treated at 350°C, and the effects of this treatment was established from the physical (X-ray dispersive energy (XDE and X-ray diffraction (XRD and electrochemical characterization (cyclic voltammetry and chronoamperometry. Results showed that the heat-treatment benefits the catalytic properties of synthesized materials in terms of CO and methanol electrochemical oxidation. The curves for CO stripping were more defined for heat-treated catalysts, and methanol oxidation current densities were higher for these materials. These changes are principally explained from the removal of organic residues remaining on the surface of the Pt-Ru nanoparticles after the synthesis procedure. After the activation of the catalysts by heating at 350°C, the real importance of the use of these encapsulating molecules and the effect of the generation of the dendrimer become visible. From these results, it can be concluded that synthesized catalysts are good catalytic anodes for direct methanol fuel cells (DMFCs.

  20. Specific heat, differential susceptibility and electrical resistivity of PrX2 (X = Ir, Pt, Rh and Ru) laves phase compounds at temperatures 1.4 K < T < 40 K

    Science.gov (United States)

    van Dongen, J. C. M.; van der Linden, H. W. M.; Greidanus, F. J. A. M.; Nieuwenhuys, G. J.; Mydosh, J. A.; Buschow, K. H. J.

    1980-01-01

    Specific heat and differential susceptibility data of PrX 2 (X = Ir, Pt, Rh, and Ru) compounds reveal phase transitions at Tc = (11.2 ± 0.5) K, (7.7 ± 0.5) K, (7.9 ± 0.5) K and (33.9 ± 0.5) K for X = Ir, Pt, RhandRu, resp. The electrical resistivity drops markedly below Tc, and the dϱ/d T versus T curve is similar to that of the specific heat.

  1. Anticancer Potencies of Pt(II) - and Pd(II)-linked M2L4 Coordination Capsules with Improved Selectivity.

    Science.gov (United States)

    Ahmedova, Anife; Momekova, Denitsa; Yamashina, Masahiro; Shestakova, Pavletta; Momekov, Georgi; Akita, Munetaka; Yoshizawa, Michito

    2016-02-18

    Pt(II) - and Pd(II)-linked M2 L4 coordination capsules, providing a confined cavity encircled by polyaromatic frameworks, exhibit anticancer activities superior to cisplatin against two types of leukemic cells (HL-60 and SKW-3) and pronounced toxicity against cisplatin-resistant cells (HL-60/CDDP). Notably, the cytotoxic selectivities of the Pt(II) and Pd(II) capsules toward cancerous cells are up to 5.3-fold higher than that of cisplatin, as estimated through the non-malignant/malignant-cells toxicity ratio employing normal kidney cells (HEK-293). In addition, the anticancer activity of the coordination capsules can be easily altered upon encapsulation of organic guest molecules.

  2. Mass Spectrometric Studies on Metai-hexafluorobenzene Anionic Comolexes(M=Ag,Au,Pd,Pt,Pb and Bi)

    Institute of Scientific and Technical Information of China (English)

    SUN Zhang; SUN Shu-tao; LIU Hong-tao; ZHU Qi-he; GAO Zhen; TANG Zi-chao

    2009-01-01

    The anionic products from the reactions between metal(M=Ag,Au,Pd,Pt,Pb and Bi) vapour produced by laser ablation and hexafluorobenzene seeded in carrier gas(Ar) were studied by means of a homemade reflectron time-of-flight mass spectrometry(RTOF-MS).Experimental results show that the dominant products were [MmC6F6]-complexes for the reactions of Ag,Au,Pd and Pt with C6F6,while the dominant products were [MmC6Fs]- complexes for the reactions of Pb and Bi with C6F6.The formation mechanisms of the products,including the adsorption of metal cluster anions on hexafluorobenzene and the C-F cleavage induced by metal cluster anions,were discussed.

  3. Ultra-small Tetrametallic Pt-Pd-Rh-Ag Nanoframes with Tunable Behavior for Direct Formic Acid/Methanol Oxidation.

    Science.gov (United States)

    Saleem, Faisal; Ni, Bing; Yong, Yang; Gu, Lin; Wang, Xun

    2016-10-01

    Reversible tuning of ultra-small multimetallic Pt-Pd-Rh-Ag nanoframes is achieved. These nanoframes showed tunable and reversible modes for the oxidation of small organic molecules by simply inducing segregation with adsorbates, such as SO4(2-) and OH(-) . This is the first example of reversible segregation under electrocatalytic conditions in atomic-sized electrocatalysts. These nanoframes also showed a controllable activity and good stability for the oxidation of small organic molecules.

  4. Ultrasensitive detection of superoxide anion released from living cells using a porous Pt-Pd decorated enzymatic sensor.

    Science.gov (United States)

    Zhu, Xiang; Liu, Tingting; Zhao, Hongli; Shi, Libo; Li, Xiaoqing; Lan, Minbo

    2016-05-15

    Considering the critical roles of superoxide anion (O2(∙-)) in pathological conditions, it is of great urgency to establish a reliable and durable approach for real-time determination of O2(∙-). In this study, we propose a porous Pt-Pd decorated superoxide dismutase (SOD) sensor for qualitative and quantitative detection O2(∙-). The developed biosensor exhibits a fast, selective and linear amperometric response upon O2(∙-) in the concentration scope of 16 to 1,536 μM (R(2)=0.9941), with a detection limit of 0.13 μM (S/N=3) and a low Michaelis-Menten constant of 1.37 μM which indicating a high enzymatic activity and affinity to O2(∙-). Inspiringly, the proposed sensor possesses an ultrahigh sensitivity of 1270 μA mM(-1)cm(-2). In addition, SOD/porous Pt-Pd sensor exhibits excellent anti-interference property, reproducibility and long-term storage stability. Beyond our expectation, the trace level of O2(∙-) released from living cells has also been successfully captured. These satisfactory results are mainly ascribed to (1) the porous interface with larger surface area and more active sites to provide a biocompatible environment for SOD (2) the specific biocatalysis of SOD towards O2(∙-) and (3) porous Pt-Pd nanomaterials fastening the electron transfer. The superior electrochemical performance makes SOD/porous Pt-Pd sensor a promising candidate for monitoring the dynamic changes of O2(∙-)in vivo.

  5. Highly-branched mesoporous Au-Pd-Pt trimetallic nanoflowers blooming on reduced graphene oxide as an oxygen reduction electrocatalyst.

    Science.gov (United States)

    Huang, Liang; Han, Yujie; Dong, Shaojun

    2016-07-05

    Herein, we develop a one-pot, two surfactant-assisted synthesis of highly-branched mesoporous Au-Pd-Pt trimetallic nanoflowers blooming on rGO with superior electrochemical performance for the ORR. Similarly to the interaction between Pluronic F127 and hexadecylpyridinium chloride (HDPC), this method may be extended to other nonionic/ionic surfactants to synthesize all-metal branched porous nanoparticles, and shows promising applications in electrochemistry and catalysis.

  6. HZSM-5 CATALYST FOR CRACKING PALM OIL TO BIODIESEL: A COMPARATIVE STUDY WITH AND WITHOUT PT AND PD IMPREGNATION

    OpenAIRE

    Agus Budianto; Danawati Hari Prajitno; Achmad Roesyadi; Kusno Budhikarjono

    2014-01-01

    The Needs of healthy environment and green energy poses a great demand for alternative energy. Biofuel is one of the alternative energy products that are environmentally friendly. Biofuel can be made from plant oils, especially palm oil. Cracking of palm oil into biofuel is constrained by the availability of catalysts. Moreover the available catalyst still gives a low yield. This research aims to study the effect of Pt and Pd impregnation into HZSM-5 catalyst on the catalytic properties. Anot...

  7. Tomographic heating holder for in situ TEM: study of Pt/C and PtPd/Al2O3 catalysts as a function of temperature.

    Science.gov (United States)

    Gontard, Lionel C; Dunin-Borkowski, Rafal E; Fernández, Asunción; Ozkaya, Dogan; Kasama, Takeshi

    2014-06-01

    A tomographic heating holder for transmission electron microscopy that can be used to study supported catalysts at temperatures of up to ~1,500°C is described. The specimen is placed in direct thermal contact with a tungsten filament that is oriented perpendicular to the axis of the holder without using a support film, allowing tomographic image acquisition at high specimen tilt angles with minimum optical shadowing. We use the holder to illustrate the evolution of the active phases of Pt nanoparticles on carbon black and PtPd nanoparticles on γ-alumina with temperature. Particle size distributions and changes in active surface area are quantified from tilt series of images acquired after subjecting the specimens to increasing temperatures. The porosity of the alumina support and the sintering mechanisms of the catalysts are shown to depend on distance from the heating filament.

  8. Thermomechanical behavior of NiTiPdPt high temperature shape memory alloy springs

    Science.gov (United States)

    Nicholson, D. E.; Padula, S. A., II; Noebe, R. D.; Benafan, O.; Vaidyanathan, R.

    2014-12-01

    Transformation strains in high temperature shape memory alloys (HTSMAs) are generally smaller than for conventional NiTi alloys and can be purposefully limited in cases where stability and repeatability at elevated temperatures are desired. Yet such alloys can still be used in actuator applications that require large strokes when used in the form of springs. Thus there is a need to understand the thermomechanical behavior of shape memory alloy spring actuators, particularly those consisting of alternative alloys. In this work, a modular test setup was assembled with the objective of acquiring stroke, stress, temperature, and moment data in real time during joule heating and forced convective cooling of Ni19.5Ti50.5Pd25Pt5 HTSMA springs. The spring actuators were subjected to both monotonic axial loading and thermomechanical cycling. The role of rotational constraints (i.e., by restricting rotation or allowing for free rotation at the ends of the springs) on stroke performance was also assessed. Finally, recognizing that evolution in the material microstructure can result in changes in HTSMA spring geometry, the effect of material microstructural evolution on spring performance was examined. This was done by taking into consideration the changes in geometry that occurred during thermomechanical cycling. This work thus provides insight into designing with HTSMA springs and predicting their thermomechanical performance.

  9. Physical properties of polycrystalline Sm₂PdGe₆ and Sm₂PtGe₆.

    Science.gov (United States)

    Troć, R; Wawryk, R; Gofryk, K; Gribanov, A V; Seropegin, Yu D

    2011-04-13

    The compounds Sm₂TGe₆ (T = Pd, Pt,) were synthesized and characterized by x-ray diffraction, magnetization, electrical resistivity, thermoelectric power, and specific heat measurements performed in the temperature range 2-300 K. Additional resistivity and thermoelectric power measurements performed down to 0.35 K have not indicated superconductivity. These compounds crystallize in the orthorhombic structure of Ce₂NiGe₆ type and order antiferromagnetically at 23(1) and 30(1) K, respectively, showing localized magnetism of a Sm(3+) ion with a crystal field doublet level being the ground state. Below T(N), the electrical resistivity, the thermoelectric power, and the specific heat are dominated by electron-magnon scattering with an antiferromagnetic spin-wave spectrum typical of anisotropic antiferromagnetic systems. The thermoelectric power, S, achieves medium positive values at high temperatures, indicating a hole domination in electrical transport in both samples. At low temperatures, S changes its sign and becomes negative. At about 10 K a small negative maximum in S(T) occurs for both studied compounds. All the measurements carried out point to well-localized 4f-electrons in these two compounds, being strongly influenced by the crystal-electric-field effect with a significant admixture of two J-multiplets (5/2 and 7/2), typical for Sm-containing compounds.

  10. Oxygen Storage Capacity of Pt-, Pd-, Rh/CeO2-Based Oxide Catalyst

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    CZO (CeO2-ZrO2) and CZYO (CeO2-ZrO2-Y2O3) series of mixed oxides were prepared by coprecipitaion, and a part of these oxides were loaded with precious metals (PM). XRD, BET, and oxygen storage capacity (OSC) investigations were performed on samples aged at 750, 900, and 1050 ℃. It was observed that BET surface area and OSC showed a marked decrease in CeO2 aged at high temperature, and the crystallite size showed an obvious increase. The CZO samples consist of cubic- and tetragonal crystal phases, and their crystallite size increase rapidly when aged at high temperature. The CZYO samples consist of single crystal phase when the content of Y exceeds 0.15 mol, and their crystallite size increases slowly during high-temperature aging. It is concluded that additive Y can stabilize the performance of CZYO oxides. In the aged CZO and CZYO mixed-oxide systems, addition of a small amount of precious metals (Pt, Pd, Rh) increased the rate of reduction and led to an obvious improvement in OSC. OSC of CZO and CZYO with precious metals are related to their composition and the type of precious metal.

  11. Shear bond strength of a hot pressed Au-Pd-Pt alloy-porcelain dental composite.

    Science.gov (United States)

    Henriques, B; Soares, D; Silva, F S

    2011-11-01

    The purpose of this study was to evaluate the effect of hot pressing on the shear bond strength of a Au-Pt-Pd alloy-porcelain composite. Several metal-porcelain composites specimens were produced by two different routes: conventional porcelain fused to metal (PFM) and hot pressing. In the latter case, porcelain was hot pressed onto a polished surface (PPPS) as well as a roughened one (PPRS). Bond strength of all metal-porcelain composites were assessed by the means of a shear test performed in a universal test machine (crosshead speed: 0.5 mm/min) until fracture. Interfaces of fractured specimens as well as undestroyed interface specimens were examined with optical microscope, stereomicroscope, Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS). The data were analyzed using one-way ANOVA followed by Tuckey's test (p0.05). This study shows that it is possible to significantly improve metal-porcelain bond strength by applying an overpressure during porcelain firing. Copyright © 2011 Elsevier Ltd. All rights reserved.

  12. HZSM-5 CATALYST FOR CRACKING PALM OIL TO BIODIESEL: A COMPARATIVE STUDY WITH AND WITHOUT PT AND PD IMPREGNATION

    Directory of Open Access Journals (Sweden)

    Agus Budianto

    2014-05-01

    Full Text Available The Needs of healthy environment and green energy poses a great demand for alternative energy. Biofuel is one of the alternative energy products that are environmentally friendly. Biofuel can be made from plant oils, especially palm oil. Cracking of palm oil into biofuel is constrained by the availability of catalysts. Moreover the available catalyst still gives a low yield. This research aims to study the effect of Pt and Pd impregnation into HZSM-5 catalyst on the catalytic properties. Another aim is to obtain the operating conditions of the catalytic cracking process of palm oil into biofuel which gives the highest yield and selectivity, especially for biodiesel and biogasoline fractions. Catalytic cracking process was carried out in a micro fixed bed reactor with diameter of 1 cm and length of 16 cm. The reactor was filled with a catalyst. The results of the study successfully prove that Pt and Pd impregnated into HZSM-5 catalyst can increase the yield and selectivity of biodiesel. Pd and Pt are highly recommended to increase the yield and selectivity of biodiesel.

  13. Elastic and electronic properties of antiperovskite-type Pd- and Pt-based ternary carbides from first-principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Bannikov, V.V.; Ivanovskii, A.L., E-mail: ivanovskii@ihim.uran.ru

    2013-11-15

    Highlights: • 23 Pd- and Pt-based antiperovskite-type ternary carbides are probed from first principles. • Structural, elastic, electronic properties and inter-atomic bonding are evaluated. • A rich variety of mechanical and electronic properties was predicted. -- Abstract: By means of first-principles calculations, the structural, elastic, and electronic properties of a broad series of proposed Pd- and Pt-based antiperovskite-type ternary carbides AC(Pd,Pt){sub 3}, where A are Zn, Ca, Al, Ga, In, Ge, Hg, Sn, Cd, Pb, Ag, Sc, Ti, Y, Nb, Mo, and Ta, have been studied, and their stability, elastic constants, bulk, shear, and Young’s moduli, compressibility, Pugh’s indicator, Poisson’s ratio, indexes of elastic anisotropy, as well as electronic properties have been evaluated. We found that these materials should demonstrate a rich variety of mechanical and electronic properties depending on the type of A sublattices, which can include (unlike the majority of known 3d-metal-based antiperovskites) both sp elements and d atoms. We believe that the presented results will be useful for future synthesis of these phases, as well as for expanding our knowledge of this interesting group of antiperovskite-type materials.

  14. East Scandinavian and Noril'sk plume mafic large igneous provinces of Pd-Pt ores: Geological and metallogenic comparison

    Science.gov (United States)

    Mitrofanov, F. P.; Bayanova, T. B.; Korchagin, A. U.; Groshev, N. Yu.; Malitch, K. N.; Zhirov, D. V.; Mitrofanov, A. F.

    2013-09-01

    This paper compares the geological, geophysical, and isotopic geochemical data on the Paleoproterozoic East Scandinavian Pd-Pt province in the Baltic Shield and the Late Paleozoic Noril'sk Pd-Pt province in the Siberian Craton. Both provinces contain large magmatic PGE deposits: low-sulfide in the Baltic Shield and high-sulfide in the Siberian Craton. Multidisciplinary evidence shows that the East Scandinavian mafic large igneous province, which has a plume nature, is intracratonic and was not subjected to the crucial effect of subduction-related and other contamination processes, whereas the Noril'sk province is pericratonic with substantial crustal contamination of the intrusive processes. Low-sulfide Pd-Pt deposits dominate in the East Scandinavian province, while high-sulfide Ni-Cu-PGE deposits play the leading role in the Noril'sk province. The U-Pb, Sm-Nd, and Rb-Sr isotopic data indicate multistage and long-term (tens of millions of years) geological history of mafic large igneous provinces. The plume magmatism with specific geochemistry and metallogeny is probably related to lower mantle sources.

  15. Quantitative Analysis of the Reduction Kinetics Responsible for the One-Pot Synthesis of Pd-Pt Bimetallic Nanocrystals with Different Structures.

    Science.gov (United States)

    Zhou, Ming; Wang, Helan; Vara, Madeline; Hood, Zachary D; Luo, Ming; Yang, Tung-Han; Bao, Shixiong; Chi, Miaofang; Xiao, Peng; Zhang, Yunhuai; Xia, Younan

    2016-09-21

    We report a quantitative understanding of the reduction kinetics responsible for the formation of Pd-Pt bimetallic nanocrystals with two distinctive structures. The syntheses involve the use of KBr to manipulate the reaction kinetics by influencing the redox potentials of metal precursor ions via ligand exchange. In the absence of KBr, the ratio between the initial reduction rates of PdCl4(2-) and PtCl4(2-) was about 10.0, leading to the formation of Pd@Pt octahedra with a core-shell structure. In the presence of 63 mM KBr, the products became Pd-Pt alloy nanocrystals. In this case, the ratio between the initial reduction rates of the two precursors dropped to 2.4 because of ligand exchange and, thus, the formation of PdBr4(2-) and PtBr4(2-). The alloy nanocrystals took a cubic shape owing to the selective capping effect of Br(-) ions toward the {100} facets. Relative to the alloy nanocubes, the Pd@Pt core-shell octahedra showed substantial enhancement in both catalytic activity and durability toward the oxygen reduction reaction (ORR). Specifically, the specific (1.51 mA cm(-2)) and mass (1.05 A mg(-1) Pt) activities of the core-shell octahedra were enhanced by about four- and three-fold relative to the alloy nanocubes (0.39 mA cm(-2) and 0.34 A mg(-1) Pt, respectively). Even after 20000 cycles of accelerated durability test, the core-shell octahedra still exhibited a mass activity of 0.68 A mg(-1) Pt, twice that of a pristine commercial Pt/C catalyst.

  16. Enhanced electrocatalytic performance of processed, ultrathin, supported Pd-Pt core-shell nanowire catalysts for the oxygen reduction reaction.

    Science.gov (United States)

    Koenigsmann, Christopher; Santulli, Alexander C; Gong, Kuanping; Vukmirovic, Miomir B; Zhou, Wei-ping; Sutter, Eli; Wong, Stanislaus S; Adzic, Radoslav R

    2011-06-29

    We report on the synthesis, characterization, and electrochemical performance of novel, ultrathin Pt monolayer shell-Pd nanowire core catalysts. Initially, ultrathin Pd nanowires with diameters of 2.0 ± 0.5 nm were generated, and a method has been developed to achieve highly uniform distributions of these catalysts onto the Vulcan XC-72 carbon support. As-prepared wires are activated by the use of two distinctive treatment protocols followed by selective CO adsorption in order to selectively remove undesirable organic residues. Subsequently, the desired nanowire core-Pt monolayer shell motif was reliably achieved by Cu underpotential deposition followed by galvanic displacement of the Cu adatoms. The surface area and mass activity of the acid and ozone-treated nanowires were assessed, and the ozone-treated nanowires were found to maintain outstanding area and mass specific activities of 0.77 mA/cm(2) and 1.83 A/mg(Pt), respectively, which were significantly enhanced as compared with conventional commercial Pt nanoparticles, core-shell nanoparticles, and acid-treated nanowires. The ozone-treated nanowires also maintained excellent electrochemical durability under accelerated half-cell testing, and it was found that the area-specific activity increased by ~1.5 fold after a simulated catalyst lifetime.

  17. Theoretical investigation of CO adsorption on TM-doped (MgO){sub 12} (TM = Ni, Pd, Pt) nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Yang Mingxia [Division of Molecule and Materials Simulation, State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029 (China); Zhang Yonghong [Dept. of Applied Physics, Tianjin Polytechnic University, Tianjin 300160 (China); Huang Shiping, E-mail: huangsp@mail.buct.edu.cn [Division of Molecule and Materials Simulation, State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029 (China); Liu Hui [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Wang Peng; Tian Huiping [Research Institute of Petroleum Processing, SINOPEC, Beijing 100083 (China)

    2011-12-01

    CO adsorption on TM-doped magnesia nanotubes (TM = Ni, Pd and Pt) have been studied by using density functional theory. Our calculation results show that CO favors adsorption on TM-doped magnesia nanotubes in the form of C atom bonding with TM atom. Fukui indices analysis clearly exhibits that doping of impurity TM atom allows for a noticeably enhancement of nucleophilic reactivity ability of magnesia nanotube. The adsorption energies demonstrate that CO molecule is more strongly bound on the 3-fold TM atoms than the 4-fold TM atoms. This finding is well confirmed by TM-C bond length, charge transfer and C-O vibrational frequency. The high adsorption energy of 2.55 eV is found when CO adsorbs on 3-fold Pt in Pt-doped magnesia nanotubes, implying the kind of the doping TM atom has a significant influence on the chemical reactivity.

  18. Hydrogenation of tetralin in the presence of dibenzothiophene and quinoline on Pt-Pd/SiO{sub 2}-Al{sub 2}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez, O.Y.; Yu, Y.; Jentys, A.; Lercher, J.A. [Technische Univ. Muenchen, Garching (Germany). Dept. of Chemistry and Catalysis Research Center

    2012-07-01

    Three Pt-Pd catalysts with 0.3 and 0.5 wt.% of Pt and Pd, respectively, were supported on amorphous silica alumina with Al{sub 2}O{sub 3}:SiO{sub 2} wt.% ratios of 20:80, 30:70 and 55:45. The materials were characterized by physisorption of N{sub 2}, TEM, X-ray absorption spectroscopy and adsorption of pyridine and CO followed by IR spectroscopy. The EXAFS fitting and IR characterization showed that bimodal distributions of monometallic Pd and bimetallic Pt-Pd particles. The bimetallic particles in all catalysts have a Pt-rich core and a Pd-rich shell. However, the degree of alloying and proportion of exposed Pt increases with increasing concentration of Lewis acid sites (LAS) in the support, probably because the LAS are good anchoring sites for Pt species. The activity of the catalysts for the hydrogenation of tetralin in the presence of DBT and quinoline, and the corresponding selectivity to cis-decalin increase with the proportion of exposed Pt. Therefore, in the presence of DBT and quinoline the morphology of bimetallic clusters is the parameter determining its hydrogenation performance. (orig.)

  19. Pd-Cu-Pt/γ-Al2O3催化剂还原水中的硝酸盐%Catalytic Reduction of Nitrate in Water over Pd-Cu-Pt/γ-Al2O3 Catalyst

    Institute of Scientific and Technical Information of China (English)

    高建峰; 徐春彦; 王久芬; 庄源益

    2004-01-01

    以自制的高纯γ-Al2O3为载体,用双浸渍法制备了不同Pd/Cu比的Pd-Cu/γ-Al2O3催化剂,在间歇式反应器中直接处理含硝酸盐废水. 结果表明,利用不同Pd/Cu比的Pd-Cu/γ-Al2O3催化剂及Pd-Cu-Pt/γ-Al2O3催化剂,同时用甲酸为pH调节剂,在适合的条件下,于40 min内就能达到脱除硝酸盐的目的,氮脱除率可达95%. 这有可能发展成为一项有效和实用的水处理技术,特别是在以地下水作为饮用水源的农村地区.

  20. Titania Supported Pt and Pt/Pd Nano-particle Catalysts for the Oxidation of Sulfur Dioxide

    DEFF Research Database (Denmark)

    Koutsopoulos, Sotiris; Johannessen, Tue; Eriksen, Kim Michael

    2006-01-01

    Several types of titania (anatase) were used as supports for pure platinum and Pt–Pd bimetallic alloy catalysts. The preparation methods, normal wet impregnation technique and flame aerosol synthesis, obtained metal loadings of 2% by weight. The prepared catalysts were tested for SO2 oxidation...... activity at atmospheric pressure in the temperature range 250–600 °C. The SO2 to SO3 conversion efficiency of the Pt–Pd alloy was significantly higher than that of the individual metals. The effects of the preparation method and the titania type used on the properties and activity of the resulting catalyst...

  1. Nano-assemblies consisting of Pd/Pt nanodendrites and poly (diallyldimethylammonium chloride)-coated reduced graphene oxide on glassy carbon electrode for hydrogen peroxide sensors

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yanyan; Zhang, Cong; Zhang, Di; Ma, Min; Wang, Weizhen; Chen, Qiang, E-mail: qiangchen@nankai.edu.cn

    2016-01-01

    Non-enzymatic hydrogen peroxide (H{sub 2}O{sub 2}) sensors were fabricated on the basis of glassy carbon (GC) electrode modified with palladium (Pd) core-platinum (Pt) nanodendrites (Pt-NDs) and poly (diallyldimethylammonium chloride) (PDDA)-coated reduced graphene oxide (rGO). A facile wet-chemical method was developed for preparing Pd core-Pt nanodendrites. In this approach, the growth of Pt NDs was directed by Pd nanocrystal which could be regarded as seed. The PDDA-coated rGO could form uniform film on the surface of GC electrode, which provided a support for Pd core- Pt NDs adsorption by self-assembly. The morphologies of the nanocomposites were characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction (spectrum). Electrocatalytic ability of the nanocomposites was evaluated by cyclic voltammetry and chronoamperometric methods. The sensor fabricated by Pd core-Pt NDs/PDDA-rGO/GCE exhibited high sensitivity (672.753 μA mM{sup −1} cm{sup −2}), low detection limit (0.027 μM), wider linear range (0.005–0.5 mM) and rapid response time (within 5 s). Besides, it also exhibited superior reproducibility, excellent anti-interference performance and long-term stability. The present work could afford a viable method and efficient platform for fabricating all kinds of amperometric sensors and biosensors. - Highlights: • A facial wet-chemical method was developed for preparing Pd core-Pt nanodendrites. • The morphologies of graphene and Pd core-Pt nanodendrites were characterized. • A novel H{sub 2}O{sub 2} sensor was fabricated by nano-assembly. • The performance of H{sub 2}O{sub 2} sensor was evaluated by cyclic voltammetry and chronoamperometric methods.

  2. Control of magnetic anisotropy field of (001) oriented L1{sub 0}-Fe(Pd{sub x}Pt{sub 1-x}) films for MRAM application

    Energy Technology Data Exchange (ETDEWEB)

    Yoshimura, Satoru; Omiya, Shogo; Egawa, Genta; Saito, Hitoshi [Center for Geo-environmental Science, Faculty of Engineering and Resource Science, Akita University, Tegatagakuen-machi 1-1, Akita, 010-8502 (Japan); Bai Jianmin, E-mail: syoshi@gipc.akita-u.ac.jp [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, TianShui Road, S 222, LanZhou, GanSu, 730000 (China)

    2011-01-01

    L1{sub 0}-Fe(Pd,Pt) films which are expected to have tunable perpendicular magnetic anisotropy and lower ordering temperature compared with the L1{sub 0}-FePt films were fabricated and investigated in order to realize high-performance Magnetic Random Access Memory (MRAM) with spin-transfer magnetization switching method and Magnetic Domain-Wall Racetrack Memory with current-driven domain wall motion. The main results are as follows: (1) The long-range chemical order degree S for the L1{sub 0}-Fe(Pd,Pt) films with the optimized thermal treatment temperature fabricated on MgO(001) substrate was about 0.8. (2) The perpendicular coercive force and magnetic anisotropy field for the L1{sub 0}-FePd film with the thermal treatment temperature of 600 {sup 0}C were 300 Oe and 14 kOe respectively, whereas the L1{sub 0}-FePt film with the thermal treatment temperature of 800 {sup 0}C were 2000 Oe and 102 kOe, respectively. (3) The optimized ordering temperature to obtain L1{sub 0} single phase decreased continuously from 800{sup 0}C to 600{sup 0}C with the increasing Pd content for the Fe(Pd,Pt) films. (4) The perpendicular magnetic anisotropy field for the L1{sub 0}-Fe(Pd,Pt) films decreased continuously from 102 kOe to 14 kOe with the increasing Pd content. It is found that the Fe(Pd,Pd) films which have tunable perpendicular magnetic anisotropy field is one of suitable ferromagnetic material for high-performance magnetic recording devices.

  3. The influence of methanol on the chemical state of PtRu anodes in a high-temperature direct methanol fuel cell studied in situ by synchrotron-based near-ambient pressure x-ray photoelectron spectroscopy

    Science.gov (United States)

    Saveleva, Viktoriia A.; Daletou, Maria K.; Savinova, Elena R.

    2017-01-01

    Synchrotron radiation-based near-ambient pressure x-ray photoelectron spectroscopy (NAP-XPS) has recently become a powerful tool for the investigation of interfacial phenomena in electrochemical power sources such as batteries and fuel cells. Here we present an in situ NAP-XPS study of the anode of a high-temperature direct methanol fuel cell with a phosphoric acid-doped hydrocarbon membrane, which reveals an enhanced flooding of the Pt3Ru anode with phosphoric acid in the presence of methanol. An analysis of the electrode surface composition depending on the cell voltage and on the presence of methanol reveals the strong influence of the latter on the extent of Pt oxidation and on the transformation of Ru into Ru (IV) hydroxide.

  4. Global optimization of bimetallic cluster structures. II. Size-matched Ag-Pd, Ag-Au, and Pd-Pt systems

    Science.gov (United States)

    Rossi, Giulia; Ferrando, Riccardo; Rapallo, Arnaldo; Fortunelli, Alessandro; Curley, Benjamin C.; Lloyd, Lesley D.; Johnston, Roy L.

    2005-05-01

    Genetic algorithm global optimization of Ag-Pd, Ag-Au, and Pd-Pt clusters is performed. The 34- and 38-atom clusters are optimized for all compositions. The atom-atom interactions are modeled by a semiempirical potential. All three systems are characterized by a small size mismatch and a weak tendency of the larger atoms to segregate at the surface of the smaller ones. As a result, the global minimum structures exhibit a larger mixing than in Ag-Cu and Ag-Ni clusters. Polyicosahedral structures present generally favorable energetic configurations, even though they are less favorable than in the case of the size-mismatched systems. A comparison between all the systems studied here and in the previous paper (on size-mismatched systems) is presented.

  5. Role of vacancies in the relaxation of Pd-5.3 at % In-0.5 at % Ru alloy foil after hydrogen desorption

    Science.gov (United States)

    Akimova, O. V.; Avdyukhina, V. M.; Shchetinin, I. V.

    2016-02-01

    The Pd-5.3 at % In-0.5 at % Ru foil subjected to electrolytic hydrogenation and subsequent prolonged relaxation (for 55 000 h) has been studied by X-ray diffraction analysis. Diffraction reflections belonging to phases with different indium concentrations and palladium phases enriched in vacancies were found. Phase transformations observed in the absence of hydrogen occur mainly due to the vacancy migration; the vacancies formed during hydrogenation and remained in vacancy complexes and alloy matrix up to the moment of the study.

  6. Switching-off toluene formation in the solvent-free oxidation of benzyl alcohol using supported trimetallic Au-Pd-Pt nanoparticles.

    Science.gov (United States)

    He, Qian; Miedziak, Peter J; Kesavan, Lokesh; Dimitratos, Nikolaos; Sankar, Meenakshisundaram; Lopez-Sanchez, Jose Antonio; Forde, Michael M; Edwards, Jennifer K; Knight, David W; Taylor, Stuart H; Kiely, Christopher J; Hutchings, Graham J

    2013-01-01

    Trimetallic Au-Pd-Pt nanoparticles have been supported on activated carbon by the sol-immobilisation method. They are found to be highly active and selective catalysts for the solvent-free aerobic oxidation of benzyl alcohol. The addition of Pt promotes the selectivity to the desired product benzaldehyde at the expense of toluene formation. Detailed aberration corrected STEM-XEDS analysis confirmed that the supported particles are indeed Au-Pd-Pt ternary alloys, but also identified composition fluctuations from particle-to-particle which vary systematically with nanoparticle size.

  7. The intelligent catalyst having the self-regenerative function of Pd, Rh and Pt for automotive emissions control

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Hirohisa; Uenishi, Mari; Taniguchi, Masashi; Tan, Isao [Materials Research and Development Division, Daihatsu Motor Co. Ltd., Ikeda, Osaka 563-8651 (Japan); Narita, Keiichi; Kimura, Mareo [Research and Development Division, Cataler Corporation, Kakegawa, Shizuoka 437-1492 (Japan); Kaneko, Kimiyoshi [Fine Chemical Research Laboratories, Hokko Chemical Industry Co. Ltd., Atsugi, Kanagawa 243-0023 (Japan); Nishihata, Yasuo; Mizuki, Jun' ichiro [Kansai Photon Science Institute, Japan Atomic Energy Agency, Sayo, Hyogo 679-5148 (Japan)

    2006-09-30

    The self-regenerative function of precious metals in the intelligent catalyst is an epoch-making technology in the history of automotive catalysts after the 1970's. The mechanism of the self-regenerative function is studied by X-ray absorption fine-structure (XAFS) analyses. The function was realized through a cyclic movement of Pd between the outside (as Pd nanoparticles) and the inside (as Pd cations in the lattice) of the perovskite crystal in synchronization with the inherent fluctuations between reductive and oxidative (redox) atmospheres that occur in real automotive exhaust gases. As the result, the growth of Pd particles can be suppressed during the entire lifetime of the vehicle. Moreover, the speed of this function was measured at the time resolution of a 10ms by in situ energy dispersive XAFS, and it is proved that the self-regenerative function occurs at an extremely high speed. Furthermore, the new perovskite catalysts which have the self-regenerative function of Rh and Pt, as well as Pd, are discussed here. This self-regenerative function provides a new and useful tool for designing the future catalyst technology. (author)

  8. Pt{sub X}Ru{sub Y}Ir{sub Z} as a bifunctional electrocatalyst for oxygen reduction reaction in a PEM fuel cell; Pt{sub X}Ru{sub Y}Ir{sub Z} como electrocatalizador bifuncional para la reaccion redox del oxigeno en una celda tipo PEM

    Energy Technology Data Exchange (ETDEWEB)

    Morales, L.; Fernandez, A.M. [Centro de Investigacion en Energia, Universidad Nacional Autonoma de Mexico, Temixco, Morelos (Mexico)]. E-mail: limos@cie.unam.mx; Cano, U. [Instituto de Investigaciones Electricas, Cuernavaca, Morelos (Mexico)

    2009-09-15

    This work presents the synthesis and characterization of the ternary material Pt{sub X}Ru{sub Y}Ir{sub Z}, obtained by chemical reduction with NaBH{sub 4}. Two different atomic compositions were developed (sample A and B) in order to observe the kinetic effect, as suggested by the combinatorial libraries. The main objective of this synthesis is to study the oxygen reduction reaction (ORR and OER) and its potential use in the construction of a bifunctional catalyst. In addition, each of the metals are synthesized separately using the same technique in order to make the corresponding comparison. The compounds obtained were characterized by sweep electron microscopy, x-ray diffraction and composition using fluorescence and energy-dispersive x-ray spectroscopy. The results showed a displacement of the x-ray diffraction peaks for Ir and Pt in sample A, and displacement in sample B for Ru and Ir peaks. These changes suggest the possible formation of a solid solution substitution. Separate cyclic and linear voltamperometry studies were performed for the oxygen reduction and release reactions. The electrochemical analysis showed improved kinetic behavior when combining the three metals according to the composition of sample B. [Spanish] En este trabajo se presenta la sintesis y caracterizacion del material ternario Pt{sub X}Ru{sub Y}Ir{sub Z}, elaborado por la tecnica de Reduccion Quimica utilizando al NaBH{sub 4}. Se elaboraron dos composiciones atomicas diferentes (Muestra A y B) con el fin de observar el efecto cinetico, como lo sugieren las librerias combinatorias. El objetivo principal de esta sintesis es para el estudio de la Reaccion Redox del Oxigeno (RRO y REO) y su potencial uso para la construccion de un catalizador bifuncional. Asi mismo, se realiza la sintesis de cada uno de los metales por separado empleando la misma tecnica, con el proposito de realizar la comparacion correspondiente. Los compuestos obtenidos se caracterizaron por Microscopia Electronica de

  9. Estudo do efeito de tratamentos térmicos em catalisadores de PtRu/C frente à reação de oxidação de hidrogênio na presença de CO Study of the effect of thermal treatments of PtRu/C catalysts on the hydrogen oxidation reaction in the presence of CO

    Directory of Open Access Journals (Sweden)

    Pietro Papa Lopes

    2007-10-01

    Full Text Available In this work the effects of time and temperature of thermal treatments under reducing atmosphere (H2 on PtRu/C catalysts for the hydrogen oxidation reaction (HOR in the presence of CO on a proton exchange membrane fuel cell (PEMFC single cells have been studied. It can be seen that the increase of the treatment temperature leads to an increasing sintering of the catalyst particles with reduction of the active area, although the catalyst treated at 550 ºC presents more CO tolerance for the HOR.

  10. Synthesis, characterization of α-amino acid Schiff base derived Ru/Pt complexes: Induces cytotoxicity in HepG2 cell via protein binding and ROS generation

    Science.gov (United States)

    Alsalme, Ali; Laeeq, Sameen; Dwivedi, Sourabh; Khan, Mohd. Shahnawaz; Al Farhan, Khalid; Musarrat, Javed; Khan, Rais Ahmad

    2016-06-01

    We have synthesized two new complexes of platinum (1) and ruthenium (2) with α-amino acid, L-alanine, and 2,3-dihydroxybenzaldehyde derived Schiff base (L). The ligand and both complexes were characterized by using elemental analysis and several other spectroscopic techniques viz; IR, 1H, 13C NMR, EPR, and ESI-MS. Furthermore, the protein-binding ability of synthesized complexes was monitored by UV-visible, fluorescence and circular dichroism techniques with a model protein, human serum albumin (HSA). Both the PtL2 and RuL2 complexes displayed significant binding towards HSA. Also, in vitro cytotoxicity assay for both complexes was carried out on human hepatocellular carcinoma cancer (HepG2) cell line. The results showed concentration-dependent inhibition of cell viability. Moreover, the generation of reactive oxygen species was also evaluated, and results exhibited substantial role in cytotoxicity.

  11. Magnetic properties of PrX 2 compounds (X = Pt, Rh, Ru, Ir) studied by hyperfine specific heat, magnetization and neutron-diffraction measurements

    Science.gov (United States)

    Greidanus, F. J. A. M.; de Jongh, L. J.; Huiskamp, W. J.; Fischer, P.; Furrer, A.; Buschow, K. H. J.

    1983-04-01

    Magnetic ordering phenomena in rare-earth intermetallic compounds can be unravelled most advantageously in the case of simple crystallographic structure and when a combination of microscopic techniques is applied. Here we shall present the temperature and magnetic field dependence of the magnetic moment of the cubic PrX 2 compounds (X = Pt, Rh, Ru, Ir), as inferred from hyperfine specific-heat, magnetization and neutron-diffraction measurements. The results are compared with a mean-field calculation, taking crystalline electric field and bilinear (dipolar) exchange interactions into account. Adopting experimental values of the Lea, Leask and Wolf parameters x and W from inelastic neutron scattering results, we find satisfactory agreement between our magnetic data and the mean-field theory. An observed discrepancy of about 15% between the calculated and measured saturation values of the spontaneous magnetization can be explained by the presence of quadrupolar interactions.

  12. Atomic-level Pd-Pt alloying and largely enhanced hydrogen-storage capacity in bimetallic nanoparticles reconstructed from core/shell structure by a process of hydrogen absorption/desorption.

    Science.gov (United States)

    Kobayashi, Hirokazu; Yamauchi, Miho; Kitagawa, Hiroshi; Kubota, Yoshiki; Kato, Kenichi; Takata, Masaki

    2010-04-28

    We have achieved the creation of a solid-solution alloy where Pd and Pt are homogeneously mixed at the atomic level, by a process of hydrogen absorption/desorption as a trigger for core (Pd)/shell (Pt) nanoparticles. The structural change from core/shell to solid solution has been confirmed by in situ powder X-ray diffraction, energy dispersive spectra, solid-state (2)H NMR measurement, and hydrogen pressure-composition isotherms. The successfully obtained Pd-Pt solid-solution nanoparticles with a Pt content of 8-21 atom % had a higher hydrogen-storage capacity than Pd nanoparticles. Moreover, the hydrogen-storage capacity of Pd-Pt solid-solution nanoparticles can be tuned by changing the composition of Pd and Pt.

  13. Density functional theory study on the adsorption and decomposition of the formic acid catalyzed by highly active mushroom-like Au@Pd@Pt tri-metallic nanoparticles.

    Science.gov (United States)

    Duan, Sai; Ji, Yong-Fei; Fang, Ping-Ping; Chen, Yan-Xia; Xu, Xin; Luo, Yi; Tian, Zhong-Qun

    2013-04-07

    Local structures and adsorption energies of a formic acid molecule and its decomposed intermediates (H, O, OH, CO, HCOO, and COOH) on highly electrocatalytically active mushroom-like Au-core@Pd-shell@Pt-cluster nanoparticles with two atomic layers of the Pd shell and stoichiometric Pt coverage of around half-monolayer (Au@2 ML Pd@0.5 ML Pt) have been investigated by first principles calculations. The adsorption sites at the center (far away from the Pt cluster) and the edge (close to the Pt cluster) are considered and compared. Significant repulsive interaction between the edge sites and CO is observed. The calculated potential energy surfaces demonstrate that, with respect to the center sites, the CO2 pathway is considerably promoted in the edge area. Our results reveal that the unique edge structure of the Pt cluster is responsible for the experimentally observed high electrocatalytic activity of the Au@Pd@Pt nanoparticles toward formic acid oxidation. Such microscopic understanding should be useful for the design of new electrochemical catalysts.

  14. Properties of the [M(dppm)2M']2+ building blocks (M, M' = Pd or Pt): site selectivity, emission features, and frontier orbital analysis.

    Science.gov (United States)

    Clément, Sébastien; Aly, Shawkat M; Bellows, Diana; Fortin, Daniel; Strohmann, Carsten; Guyard, Laurent; Abd-El-Aziz, Alaa S; Knorr, Michael; Harvey, Pierre D

    2009-05-04

    The homodinuclear [ClM(mu-dppm)(2)MCl] complexes 1 (M = Pd) and 2 (M = Pt) react with RNC ligands (R = Ph, xylyl, p-tolyl, p-C(6)H(4)iPr) to provide the A-frame [ClPd(mu-dppm)(2)(mu-C=N-R)PdCl] (R = Ph (5a), xylyl (5b)), [ClPt(mu-dppm)(2)(mu-C=N-R)PtCl] (R = p-tolyl (4a); p-C(6)H(4)iPr (4b)), and the d(9)-d(9) M(2)-bonded [ClPt(mu-dppm)(2)Pt(CN-R)]Cl (R = xylyl (3a); p-C(6)H(4)iPr (3b)) complexes. The heterodinuclear [XPd(mu-dppm)(2)PtX] complexes 6a (X = Cl) and 6b (X = I) react with RNC (R = o-anisyl) to form the A-frame [XPd(mu-dppm)(2)(mu-C=N-R)PtX] (X = Cl (9); I (10a)) and M(2)-bonded [ClPt(mu-dppm)(2)Pt(CN-R)]Cl (10b) complexes. The dangling ligand-containing complex [ClPd(mu-dppm)(2)Pt(eta(1)-dppm=O)](BF(4)) (7) reacts with xylyl-NC stoichiometrically to produce the dicationic salt [(xylyl-NC)Pd(mu-dppm)(2)Pt(eta(1)-dppm=O)](BF(4))(2) (8). Parameters ruling the coordination site terminal versus bridging are discussed. The precursor 10a reacts with RNC (R = o-anisyl, tBu) to form the heterobimetallic bis(isonitrile) [IPd(mu-dppm)(2)(mu-C=N-o-anisyl)Pt(CN-R)]I complexes 11b and 12, respectively, demonstrating the site selectivity of the second CNR ligand coordination, Pd versus Pt. The X-ray structures of 11b and 12 were obtained. Complex 12 is the first example of an A-frame system of the Ni-triad bearing two different isocyanide ligands. Several d(9)-d(9) terminal and d(8)-d(8) A-frame homo- and heterodinuclear complexes in 2-MeTHF at 77 K were studied by UV-vis and luminescence spectroscopy. Assignments for the lowest energy absorption and emission bands are made on the basis of density functional theory and time-dependent density functional theory computations.

  15. Synthesis and reactivity of Ph/sub 2/PCH/sub 2/PPh/sub 2/- (dppm-) stabilized Pd-Co and Pd-Pt-Co clusters. Effect of platinum versus palladium on the neighboring palladium center

    Energy Technology Data Exchange (ETDEWEB)

    Braunstein, P.; de Meric de Bellefon, C.; Ries, M.

    1988-04-20

    The quantitative and regioselective synthesis of the mixed-metal cluster (PdPtCo/sub 2/(CO)/sub 7/(dppm)/sub 2/) (1b) was achieved by the reaction of the bimetallic complex (PdPtCl/sub 2/(dppm)/sub 2/) (dppm = /mu/-Ph/sub 2/PCH/sub 2/PPh/sub 2/) with (Co(CO)/sub 4/)/sup /minus//. As a result of phosphorus migration from palladium to cobalt, formal insertion of the Co(CO)/sub 3/ fragment into a metal-phosphorus bond of the precursor exclusively occurs into the more labile P /yields/ Pd bond. The lability of the exocyclic Co(CO)/sub 4/ fragment was evidenced and compared between 1b and (Pd/sub 2/Co/sub 2/(CO)/sub 7/(dppm)/sub 2/) (1a). Although a Pd-Co bond is involved, this lability is very sensitive to the neighboring metal center (Pd or Pt). Transmission of electronic effects from one metal-center to another was evidenced, and a platinum effect was observed in dissociating solvents, where 1a is partly dissociated but 1b is completely dissociated into (PdPtCo(CO)/sub 3/(S)(dppm)/sub 2/)(CO(CO)/sub 4/) (S = solvent). This is a reversible process, as is the equilibrium between 1 and halide anions. Solvento clusters were prepared that possess a labile coordination site on Pd leading to completely regioselective reactions with donor molecules, e.g., phosphines, CO, or C/sub 2/Ph/sub 2/. These ligands are labile (PR/sub 3/ < CO < C/sub 2/Ph/sub 2/ < MeCN < THF), and reversible CO uptake and substitution experiments showed that the Pd-bound CO in 4b is less labile than in 4a, indicating again a platinum effect on the reactive Pd center. The tris(bis(diphenylphosphino)methane) cationic cluster (Pd/sub 2/Co(CO)/sub 2/(dppm)/sub 3/)/sup +/ was isolated, in which all the metal-metal bonds are bridged by dppm ligands. Spectroscopic IR and /sup 1/H, /sup 31/P(/sup 1/H), and /sup 195/Pt(/sup 1/H) NMR data are discussed and confirm that in these reactions the PdMCo(dppm)/sub 2/ (M = Pd, Pt) framework is maintained.

  16. Immobilization of superoxide dismutase on Pt-Pd/MWCNTs hybrid modified electrode surface for superoxide anion detection.

    Science.gov (United States)

    Zhu, Xiang; Niu, Xiangheng; Zhao, Hongli; Tang, Jie; Lan, Minbo

    2015-05-15

    Monitoring of reactive oxygen species like superoxide anion (O2(∙-)) turns to be of increasing significance considering their potential damages to organism. In the present work, we fabricated a novel O2(∙-) electrochemical sensor through immobilizing superoxide dismutase (SOD) onto a Pt-Pd/MWCNTs hybrid modified electrode surface. The Pt-Pd/MWCNTs hybrid was synthesized via a facile one-step alcohol-reduction process, and well characterized by transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The immobilization of SOD was accomplished using a simple drop-casting method, and the performance of the assembled enzyme-based sensor for O2(∙-) detection was systematically investigated by several electrochemcial techniques. Thanks to the specific biocatalysis of SOD towards O2(∙-) and the Pt-Pd/MWCNTs - promoted fast electron transfer at the fabricated interface, the developed biosensor exhibits a fast, selective and linear amperometric response upon O2(∙-) in the concentration scope of 40-1550 μM (R(2)=0.9941), with a sensitivity of 0.601 mA cm(-2) mM(-1) and a detection limit of 0.71 μM (S/N=3). In addition, the favorable biocompatibility of this electrode interface endows the prepared biosensor with excellent long-term stability (a sensitivity loss of only 3% over a period of 30 days). It is promising that the proposed sensor will be utilized as an effective tool to quantitatively monitor the dynamic changes of O2(∙-) in biological systems.

  17. Simultaneous electrochemical detection of ascorbic acid, dopamine and uric acid based on graphene anchored with Pd-Pt nanoparticles.

    Science.gov (United States)

    Yan, Jun; Liu, Shi; Zhang, Zhenqin; He, Guangwu; Zhou, Ping; Liang, Haiying; Tian, Lulu; Zhou, Xuemin; Jiang, Huijun

    2013-11-01

    Pd-Pt bimetallic nanoparticles anchored on functionalized reduced graphene oxide (RGO) nanomaterials were synthesized via a one-step in situ reduction process, in which Pt and Pd ions were first attached to poly(diallyldimethylammonium chloride) (PDDA) functionalized graphene oxide (GO) sheets, and then the encased metal ions and GO were subjected to simultaneous reduction by ethylene glycol. The as-prepared Pd3Pt1/PDDA-RGO nanocomposites were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and electrochemical methods. In addition, an electrochemical sensor based on the graphene nanocomposites was fabricated for the simultaneous detection of ascorbic acid (AA), dopamine (DA) and uric acid (UA) in their ternary mixture. Three well-separated voltammetric peaks along with remarkable increasing electro-oxidation currents were obtained in differential pulse voltammetry (DPV) measurements. Under the optimized conditions, there were linear relationships between the peak currents and the concentrations in the range of 40-1200 μM for AA, 4-200 μM for DA and 4-400 μM for UA, with the limit of detection (LOD) (based on S/N=3) of 0.61, 0.04 and 0.10 μM for AA, DA and UA, respectively. This improved electrochemical performance can be attributed to the synergistic effect of metallic nanoparticles and RGO and the combination of the bimetallic nanoparticles. Furthermore, the practical electroanalytical utility of the sensor was demonstrated by the determination of AA, DA and together with UA in human urine and blood serum samples with satisfactory results. Copyright © 2013 Elsevier B.V. All rights reserved.

  18. Ab Initio evaluation of electron transport properties of Pt, Rh, Ir, and Pd nanowires for advanced interconnect applications

    Science.gov (United States)

    Lanzillo, Nicholas A.

    2017-05-01

    The electronic and structural properties of nanowires composed of either Pt, Ir, Rh, or Pd are calculated using density functional theory and a non-equilibrium Green's function scattering approach. The results for these nanowires are compared with Cu nanowires of comparable dimensions and evaluated for potential use in interconnect technology applications. The cohesive energies of the Pt, Rh and Ir nanowires are found to be stronger than the corresponding value for bulk Cu, indicating superior structural integrity and resistance to electromigration relative to Cu. Several of the nanowires considered are found to exhibit larger values of ballistic conductance relative to Cu, with maximum conductance occurring along the [110] crystallographic direction. Electron scattering at some representative twin grain boundaries is evaluated and an empirical resistivity model is used to quantitatively estimate the impact of grain size on total resistivity.

  19. Co/Pt and Co/Pd multilayers as a new class of magneto-optical recording materials

    Science.gov (United States)

    Zeper, W. B.; Greidanus, Franciscus J. A. M.; van Kesteren, H. W.; Jacobs, Ben A. J.; Spruit, J. H. M.; Carcia, Peter F.

    1990-08-01

    In this paper we give an overview of the magnetic and magneto-optical properties of Co/Pt and, to a less extent, Co/Pd multilayers as optimized for magneto-optical storage applications. The Co layers should be very thin, i.e. about 4 A , and the Pt layers about 10-20 A to achieve a 100 % remanent layer with perpendicular magnetic anisotropy and high coercivity (80-100 kA/m). Furthermore, the hysteresis loop becomes rectangular for total film thicknesses below about 20 nm. We measured the optical properties as a function of the wavelength of the light and calculated the figure of merit at three wavelengths (820, 633 and 410 nm) for various disk structures. Optimal figures of merit are obtained for film thicknesses below 20 nm, i.e. thicknesses that are optimum for the magnetic properties. The figure of merit at A. = 820 am for Co/Pt is comparable to that of GdTbFe and increases towards shorter wavelengths which favor higher-density recording. We discuss the recording performance using Lorentz images of the written domain patterns. Very regularly shaped domains can be written at normal writing conditions, i.e. at a laser power of 5-10 mW and fields of 25 kA/m. The highest carrier-to-noise ratio measured for Co/Pt is 51 dB (375 kHz carrier, 1.4 m/s, 10 kHz bandwidth). Aging experiments in dry oxygen-nitrogen atmosphere showed that Co/Pt multilayers are chemically stable up to 1 50 °C . Finally, no change in carrier-to-noise ratio is observed for Co/Pt multilayers with a Curie temperature below 300 °C after 2x104 write/read/erase cycles.

  20. Pd-Pt loaded graphene aerogel on nickel foam composite as binder-free anode for a direct glucose fuel cell unit

    Science.gov (United States)

    Tsang, Chi Him A.; Leung, D. Y. C.

    2017-09-01

    Fabrication of electrocatalyst for direct glucose fuel cell (DGFC) operation involves destructive preparation methods with the use of stabilizer like binder, which may cause activity depreciation. Binder-free electrocatalytic electrode becomes a possible solution to the above problem. Binder-free bimetallic Pd-Pt loaded graphene aerogel on nickel foam plates with different Pd/Pt ratios (1:2.32, 1:1.62, and 1:0.98) are successfully fabricated through a green one-step mild reduction process producing a Pd-Pt/GO/nickel form plate (NFP) composite. Anode with the binder-free electrocatalysts exhibit a strong activity in a batch type DGFC unit under room temperature. The effects of glucose and KOH concentrations, and the Pd/Pt ratios of the electrocatalyst on the DGFC performance are also studied. Maximum power density output of 1.25 mW cm-2 is recorded with 0.5 M glucose/3 M KOH as the anodic fuel, and Pd1Pt0.98/GA/NFP as catalyst, which is the highest obtained so far among other types of electrocatalyst.

  1. One-pot, template-free synthesis of Pd-Pt single-crystalline hollow cubes with enhanced catalytic activity.

    Science.gov (United States)

    Sun, Long; Zhang, Zhicheng; Xu, Biao; Wang, Xun

    2013-07-01

    Hollow structures have attracted ever-growing interest owing to their various excellent properties. However, a facile strategy for their fabrication is still desired. Herein, Pd-Pt alloy with three different morphologies, that is, cubes, hollow cubes, and truncated octahedrons, is synthesized by using a one-pot, template-free method. The mechanism and dynamics of this system is also studied in detail. In particular, the hollow cubic structure represents enhanced catalytic activity in both coupling reactions and in the electrochemical oxidation of formic acid. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Optic fiber hydrogen sensor based on high-low reflectivity Bragg gratings and WO3-Pd-Pt multilayer films

    Science.gov (United States)

    Dai, Jixiang; Yang, Minghong; Li, Zhi; Wang, Gaopeng; Huang, Chujia; Qi, Chongjie; Dai, Yutang; Wen, Xiaoyan; Cheng, Cheng; Guo, Huiyong

    2015-09-01

    A novel optic fiber hydrogen sensor is proposed in this paper. Two Bragg gratings with different reflectivity were written in single mode fiber with phase mask method by 248 nm excimer laser. The end-face of singe mode fiber was deposited with WO3-Pd-Pt multilayer films as sensing element. The peak intensity of low reflectivity FBG is employed for hydrogen characterization, while that of high reflectivity FBG is used as reference. The experimental results show the hydrogen sensor still has good repeatability when the optic intensity in the fiber is only 1/3 of its initial value. The hydrogen sensor has great potential in measurement of hydrogen concentration.

  3. Chemical order and selection of the mechanism for strain relaxation in epitaxial FePd(Pt) thin layers

    Science.gov (United States)

    Halley, D.; Marty, A.; Bayle-Guillemaud, P.; Gilles, B.; Attane, J. P.; Samson, Y.

    2004-11-01

    We observed that the relaxation mechanism of the epitaxial strain is dramatically dependent on the chemical ordering within the L10 structure in FePd(Pt) thin films. In disordered or weakly ordered layers, the relaxation takes place though perfect (1)/(2)[101] dislocations, whereas well-ordered films relax through the partial 1/6[112] Shockley dislocations, piled-up within microtwins, with a huge impact on both the morphology and the magnetic properties of the film. We show that the antiphase boundary energy is the key factor preventing the propagation of perfect dislocations in ordered alloys.

  4. Elastic stability and electronic structure of low energy tetragonal and monoclinic PdN2 and PtN2

    Institute of Scientific and Technical Information of China (English)

    Zhao Wen-Jie; Wang Yuan-Xu

    2009-01-01

    This paper studies the elastic and electronic structure properties of two new low-energy structures of PdN2 and PtN2 by first-principles calculations. It finds that tetragonal and monoclinic structures are more stable than a pyrite one. The always positive eigenvalues of the elastic constant matrix confirm that both the tetragonal and monoclinic structures are elastically stable. The origin of the low bulk modulus of the two structures is discussed. The results of the calculated density of states show that both of the two low-energy structures are metallic.

  5. Synthesis, characterization, and electronic structures of a series of two-dimensional trimetallic cluster complexes, Ru3(CO)9(mu-SnPh2)3[Pt(PBu(t)3)]x, x = 0-3.

    Science.gov (United States)

    Adams, Richard D; Captain, Burjor; Hall, Michael B; Trufan, Eszter; Yang, Xinzheng

    2007-10-10

    The triruthenium-tritin cluster complex, Ru3(CO)9(mu-SnPh2)3, 13 was obtained from the reaction of Ru3(CO)12 with Ph3SnH. Compound 13 reacts with Pt(PBut3)2 to yield three new Pt(PBut3) adducts of 13 Ru3(CO)9(mu-SnPh2)3[Pt(PBut3)]x, 14-16 x = 1 - 3 formed by the addition of Pt(PBut3) groups to the Ru-Sn bonds. The new complexes form a novel series of trimetallic complexes having planar arrangements of the metal atoms. The UV-vis absorptions of the four complexes shift progressively to longer wavelengths as the number of platinum atoms is added to the cluster. The electronic structures of these complexes have been investigated in the ground and excited states by density functional theory and time-dependent density functional theory, and this has provided a detailed understanding of the metal-metal bonding and electronic transitions that are responsible for their UV-vis absorption properties. The predicted absorption maximum for the model structures for 13, 14, 15, and 16 at 465, 508, 556, and 585 nm differ only 4-18 nm from the experimental values of 474, 490, 552, and 576 nm. The shift of principal UV-vis absorption can be explained by a lowering of the HOMO-LUMO energy gap due to interactions of the platinum atoms with the HOMO and LUMO of the Ru3Sn3 core.

  6. Theoretical Modeling of Water Exchange on [Pd(H(2)O)(4)](2+), [Pt(H(2)O)(4)](2+), and trans-[PtCl(2)(H(2)O)(2)].

    Science.gov (United States)

    Deeth, Robert J.; Elding, Lars I.

    1996-08-14

    Density functional theory is applied to modeling the exchange in aqueous solution of H(2)O on [Pd(H(2)O)(4)](2+), [Pt(H(2)O)(4)](2+), and trans-[PtCl(2)(H(2)O)(2)]. Optimized structures for the starting molecules are reported together with trigonal bipyramidal (tbp) systems relevant to an associative mechanism. While a rigorous tbp geometry cannot by symmetry be the actual transition state, it appears that the energy differences between model tbp structures and the actual transition states are small. Ground state geometries calculated via the local density approximation (LDA) for [Pd(H(2)O)(4)](2+) and relativistically corrected LDA for the Pt complexes are in good agreement with available experimental data. Nonlocal gradient corrections to the LDA lead to relatively inferior structures. The computed structures for analogous Pd and Pt species are very similar. The equatorial M-OH(2) bonds of all the LDA-optimized tbp structures are predicted to expand by 0.25-0.30 Å, while the axial bonds change little relative to the planar precursors. This bond stretching in the transition state counteracts the decrease in partial molar volume caused by coordination of the entering water molecule and can explain qualitatively the small and closely similar volumes of activation observed. The relatively higher activation enthalpies of the Pt species can be traced to the relativistic correction of the total energies while the absolute DeltaH() values for exchange on [Pd(H(2)O)(4)](2+) and [Pt(H(2)O)(4)](2+) are reproduced using relativistically corrected LDA energies and a simple Born model for hydration. The validity of the latter is confirmed via some simple atomistic molecular mechanics estimates of the relative hydration enthalpies of [Pd(H(2)O)(4)](2+) and [Pd(H(2)O)(5)](2+). The computed DeltaH() values are 57, 92, and 103 kJ/mol compared to experimental values of 50(2), 90(2), and 100(2) kJ/mol for [Pd(H(2)O)(4)](2+), [Pt(H(2)O)(4)](2+), and trans-[PtCl(2)(H(2)O)(2

  7. 分子动力学模拟Au-Pd和Ag-Pt合金的热学和力学性质%Thermal and Mechanical Properties of Au-Pd and Ag-Pt Alloy by Molecular Dynamics Simulation

    Institute of Scientific and Technical Information of China (English)

    闫雪松; 齐新; 林平; 杨磊

    2011-01-01

    利用Finnis-Sinclair势,对金属Au、Pd、Ag、Pt和合金Au3Pd、AuPd3、Ag3Pt、AgPt3的热学和力学性质进行了分子动力学模拟.首次计算了不同温度下合金的晶格常数、结合能和弹性常数,并预测了它们的熔点.通过比较发现,Au3Pd、AuPd3和Ag3Pt这3种合金的晶格常数、结合能和弹性常数介于其组分金属之间,而AgPt3的剪切模量和熔点高于其组分hg和Pt.%With the Finnis-Sinclair potential, the thermal and mechanical properties of Au, Pd, Ag, Pt pure metals and their alloys Au3Pd, AuPd3, Ag3Pt, AgPt3 were studied by molecular dynamics simulations. Lattice constants and elastic constants of Au3Pd, AuPd3, Ag3Pt and AgPt3 at different temperatures were predicted for the first time. Melting temperatures of these alloys were calculated too. Furthermore, lattice constants, elastic constants and melting temperature of pure metals Au, Pd, Ag, and Pt were calculated for comparison. It is found that for Au3Pd,AuPd3 and Ag3Pt, lattice constants, elastic constants and melting temperatures lie between those of their two components. For AgPt3, the values of shear modulus and melting temperature are higher than those for both Ag and Pt pure metals.

  8. Change in local environment upon quasicrystallization of Zr-Cu glassy alloys by addition of Pd and Pt.

    Science.gov (United States)

    Saida, Junji; Sanada, Takashi; Sato, Shigeo; Imafuku, Muneyuki; Ohnuma, Masato; Ohkubo, Tadakatsu; Hono, Kazuhiro; Matsubara, Eiichiro

    2011-05-04

    The effects of Pd and Pt, which are known quasicrystal (QC)-forming elements, on the local atomic structure in Zr(70)Cu(30) glassy alloys are investigated. A QC phase precipitates from a glassy phase above a certain temperature by a cooperative-like motion of icosahedral clusters. Quasicrystallization is accompanied by a significant change in the local environment around the Zr atoms and a slight change around the noble metal. However, the local environment around the Cu atoms remains almost the same during QC formation. It is suggested that two types of icosahedral polyhedra exist in the glassy state: one has a relatively perfect icosahedral structure formed around the Zr atoms. The other is in a distorted state around the Cu atoms. We speculate that the medium-range order (i.e. QC nucleus) has a Zr-centered icosahedral cluster as its core, and the QC grows via aggregation of possible clusters in the initial stage. Pd or Pt atoms stabilize and/or connect individual Zr-centered icosahedral clusters, facilitating the formation of the nucleus and growth of the QC phase. © 2011 IOP Publishing Ltd

  9. Session 4: Role of the Broensted acid sites for Pd/Pt catalysts in the hydrotreating of LCO fractions

    Energy Technology Data Exchange (ETDEWEB)

    Albertazzi, S.; Faraone, C.; Vaccari, A. [Bologna Univ., Dipt. di Chimica Industriale e dei Materiali, INSTM-UdR (Italy); Lenarda, M.; Storaro, L.; Talon, A. [Venezia, Univ., Dipt. di Chimica, INSTM-UdR di Venezia, VE (Italy)

    2004-07-01

    The aim of this work was to investigate the catalytic activity and thio-tolerance of the Pd-Pt metallic pair supported on porous systems almost or totally lacking of Broensted acid sites. For this purpose an Al/Ce/Mg pillared montmorillonite clay (PILC), containing almost exclusively Lewis acid sites, and a basic Mg/Al mixed oxide, obtained by calcination of a hydrotalcite-type, were used as supports for Pt/Pd and tested in the hydrogenation of naphthalene in vapour phase, chosen as model molecule of LCO fractions. All the catalysts were activated in situ under a H{sub 2} flow, using a programmed increase of the temperature from room temperature up to 450 C. The catalytic tests were performed in a micro-reactor at 6.0 MPa, investigating a wide range of reaction conditions (temperature, contact time and H{sub 2}/naphthalene feed ratio). Finally, the catalyst thio-resistance was tested, feeding increasing amounts of dibenzothiophene (DBT). The experimental results are given. (O.M.)

  10. Ni-, Pd-, or Pt-catalyzed ethylene dimerization: a mechanistic description of the catalytic cycle and the active species.

    Science.gov (United States)

    Roy, Dipankar; Sunoj, Raghavan B

    2010-03-07

    Two key mechanistic possibilities for group 10 transition metal [M(eta(3)-allyl)(PMe(3))](+) catalyzed (where M = Ni(II), Pd(II) and Pt(II)) ethylene dimerization are investigated using density functional theory methods. The nature of the potential active catalysts in these pathways is analyzed to gain improved insights into the mechanism of ethylene dimerization to butene. The catalytic cycle is identified as involving typical elementary steps in transition metal-catalyzed C-C bond formation reactions, such as oxidative insertion as well as beta-H elimination. The computed kinetic and thermodynamic features indicate that a commonly proposed metal hydride species (L(n)M-H) is less likely to act as the active species as compared to a metal-ethyl species (L(n)M-CH(2)CH(3)). Of the two key pathways considered, the active species is predicted to be a metal hydride in pathway-1, whereas a metal alkyl complex serves as the active catalyst in pathway-2. A metal-mediated hydride shift from a growing metal alkyl chain to the ethylene molecule, bound to the metal in an eta(2) fashion, is predicted to be the preferred route for the generation of the active species. Among the intermediates involved in the catalytic cycle, metal alkyls with a bound olefin are identified as thermodynamically stable for all three metal ions. In general, the Ni-catalyzed pathways are found to be energetically more favorable than those associated with Pd and Pt catalysts.

  11. Final Technical Report: First Principles Investigations for the Ensemble Effects of PdAu and PtAu Bimetallic Nanocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Ruqian Wu

    2012-05-18

    Bimetallic surfaces with tunable chemical properties have attracted broad attention in recent years due to their ample potential for heterogeneous catalysis applications. The local chemical properties of constituents are strongly altered from their parent metals by 'ligand effect', a term encompassing the influences of charge transfer, orbital rehybridization and lattice strain. In comparison to the aforementioned, the 'ensemble effect' associated with particular arrangements of the active constituents have received much less attention, despite their notable importance towards the determination of reactivity and selectivity of bimetallic catalysts. We performed theoretical studies for understanding the ensemble effects on bimetallic catalysis: (i) simulations for the formation of different ensembles on PdAu and PtAu nanoclusters; (ii) studies of the size, shape, and substrate dependence of their electronic properties; and (iii) simulations for model reactions such as CO oxidation, methanol, ethylene and water dehydrogenation on PdAu and PtAu nanoclusters. In close collaboration with leading experimental groups, our theoretical research elucidated the fundamentals of Au based bimetallic nanocatalysts.

  12. Exploring the spin states of 90Zr populated by (p,p’, (p,d, and (p,t reactions

    Directory of Open Access Journals (Sweden)

    Ota S.

    2016-01-01

    Full Text Available The 90Zr nucleus was produced by three different reactions: 90Zr(p,p’, 91Zr(p,d, and 92Zr(p,t, and the spin-parity (Jπ population of the 90Zr states produced by these reactions was studied to investigate the surrogate reaction approach, which aims at indirectly determining cross sections for compound-nuclear reactions involving unstable targets such as 89Zr(n,γ. Discrete γ-rays, associated with the de-excitation of 90Zr and 89Zr, were measured in coincidence with light ions at 90Zr excitation energies extending above the neutron separation energy. Low-lying states populated by (p,d and (p,t reactions agreed well with the previous measurements. The measured γ transition systematics were used to gain insights into the Jπ distribution of 90Zr around the neutron separation energy and it was found that the (p,p’ reaction preferentially produces lower J states than (p,d and (p,t reactions in the studied energy region.

  13. A sandwich-type immunosensor using Pd-Pt nanocrystals as labels for sensitive detection of human tissue polypeptide antigen

    Science.gov (United States)

    Wang, Yaoguang; Wei, Qin; Zhang, Yong; Wu, Dan; Ma, Hongmin; Guo, Aiping; Du, Bin

    2014-02-01

    A sandwich-type immunosensor was developed for the detection of human tissue polypeptide antigen (hTPA). In this work, a graphene sheet (GS) was synthesized to modify the surface of a glassy carbon electrode (GCE), and Pd-Pt bimetallic nanocrystals were used as secondary-antibody (Ab2) labels for the fabrication of the immunosensor. The amperometric response of the immunosensor for catalyzing hydrogen peroxide (H2O2) was recorded. And electrochemical impedance spectroscopy was used to characterize the fabrication process of the immunosensor. The anti-human tissue polypeptide antigen primary antibody (Ab1) was immobilized onto the GS modified GCE via cross-linking with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide (EDC/NHS). With Ab1 immobilized onto the GS modified GCE and Ab2 linked on Pd-Pt bimetallic nanocrystals, the immunosensor demonstrated a wide linear range (0.0050-15 ng ml-1), a low detection limit (1.2 pg ml-1), good reproducibility, good selectivity and acceptable stability. This design strategy may provide many potential applications in the detection of other cancer biomarkers.

  14. Electrocatalytic oxidation of formic acid by poly(diallyldimethylammonium chloride) and Pt/Pd-functionalized carbon nanotubes mixtures.

    Science.gov (United States)

    Kim, Min-Su; Kim, Daekun; Lee, Hyo Kyoung; Jeon, Seungwon

    2012-12-01

    Improving the catalytic activity of the anode catalyst is an important task in the direct formic acid fuel cell (DFAFC). In this study, the catalysts were prepared by dispersing either platinum or palladium metal on the surface of thiolated multi-walled carbon nanotubes (t-MWCNTs), denoted as t-MWCNT-Pt and t-MWCNT-Pd, respectively. These modified t-MWCNT and poly(diallyldimethylammonium chloride) (PDDA) were ultrasonically mixed and loading on a glassy carbon electrode (GCE) for formic acid (FA) oxidation and the catalytic activities were then investigated by using cyclic voltammetry (CV) and chronoamperometry (CA) methods. The as-formed catalysts were characterized by several methods. To optimize the catalytic performance, we investigated the catalysts separately and together (in different ratios) for FA oxidation. The PDDA mixed catalyst demonstrated a slightly better performance. These results indicated that the PDDA/(t-MWCNT-Pt + t-MWCNT-Pd) catalyst exhibited better activity than that of the corresponding other catalysts.

  15. Ferroelastic strain control of multiple nonvolatile resistance tuning in SrRuO3/PMN-PT(111) multiferroic heterostructures

    Science.gov (United States)

    Zheng, Ming; Ni, Hao; Qi, Yaping; Huang, Weiyi; Zeng, Jiali; Gao, Ju

    2017-05-01

    The electric-field-tunable resistance switching in elastically coupled SrRuO3 thin films grown on (111)-oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 ferroelectric-crystal substrates has been investigated. During the ferroelectric poling process, the resistance evolution tracks the electric-field-induced in-plane strain of the film efficiently, revealing strain but not the electrostatic charge-mediated coupling mechanism. Using 109° and 71° ferroelastic domain switching of the substrate, multiple reversible and nonvolatile resistance states can be achieved at room temperature, which is closely related to the relative proportion of in-plane polarization vectors and induced distinct in-plane strain states after domain switching. Our findings provide an approach to elucidate electrically driven domain switching dynamics and design energy efficient, high-density spintronic memory devices.

  16. EVALUACIÓN DE CELDAS DE COMBUSTIBLE DE ELECTROLITO POLIMÉRICO CON ÁNODOS Pt-M (M= Sn, Ru e Ir PARA LA OXIDACIÓN DE H2 Y CO

    Directory of Open Access Journals (Sweden)

    BIBIAN HOYOS

    2008-01-01

    Full Text Available Se evaluó el desempeño de celdas de combustible de electrolito polimérico alimentadas con hidrógeno, CO y una mezcla H2-(2%CO, utilizando oxígeno en el cátodo. Para la oxidación de los combustibles, se probaron seis catalizadores: Pt, Pt85Ru15, Pt50Ru50, Pt90Ir10, Pt50Ir50 y Pt90Sn10. Como catalizador en el cátodo se usó platino puro. Todos los catalizadores fueron soportados en carbón Vulcan XC-72R ®. La composición de los catalizadores preparados fue verificada en un Microscopio Electrónico de Barrido (SEM y las pruebas de desempeño de las celdas construidas se realizaron mediante curvas corriente-potencial. Los resultados muestran que la técnica depreparación de los electrodos produce mezclas catalíticas con composiciones muy cercanas a las nominales. Las mezclas catalíticas Pt-Ir son las que presentan el desempeño más bajo para las condiciones evaluadas en este trabajo. La mezcla Pt90Sn10 presentó un desempeño similar al del platino a bajas corrientes cuando la celda de combustible fue alimentada con hidrógeno puro y superó el desempeño de los demás catalizadores cuando la celda se alimentó con H2/(2%CO. El electrodo Pt90Sn10 pierde actividad catalítica cuando se emplea CO puro.

  17. Synthesis,characterization,and biological activities of Pt(Ⅱ) and Pd(Ⅱ)complexes with 2',3',4',5,7-pentahydroxy flavone

    Institute of Scientific and Technical Information of China (English)

    TANG Hui'An; WANG Xiaofang; YANG Sheng; WANG Liufang

    2004-01-01

    Pt(Ⅱ) and Pd(Ⅱ) complexes with 2',3',4',5,7-pentahydroxy-flavone were synthesized and characterized by elemental analysis, molar conductance, IR, 1HNMR, TG-DTA, UV-Vis spectroscopic techniques, and fluorescence analysis.The scavenging effect on the superoxide radical ( O-2 ) and the inhibitory effect on lipid peroxides were also investigated.Both the ligand and the complexes exhibit scavenging effect on superoxide radicals, and the effect of the complexes is greater than that of the ligand. The Pt(Ⅱ) complex exhibits the strongest scavenging efficiency. Both Pt(Ⅱ) and Pd(Ⅱ) complexes have the inhibitory effect on lipid peroxides, and the effect of the complexes is greater than that of the ligand, but the Pt(Ⅱ) complex has a high effect of promoting lipid peroxides.

  18. Effects of Ru Seed Layer on Structural Properties of CoCrPt-SiO2 Perpendicular Media%Ru籽晶层对CoCrPt-SiO2垂直记录层形貌及结构的影响

    Institute of Scientific and Technical Information of China (English)

    张俊敏; 王传军; 沈月; 谭志龙; 毕珺; 闻明; 周悓田

    2015-01-01

    CoCrPt-SiO2 perpendicular recording films were prepared by the magnetron sputtering with a series of Ru films as the seed layer. The microstructure of Ru seed layers and their effects on the grain size, roughness and surface morphology of CoCrPt-SiO2 granular films were also investigated. It was found that the microstructure of seed layer obviously affected the structure and grain isolation of recording layers. The grain size and roughness of CoCrPt-SiO2 recording layer increased with the increase of the thickness of Ru seed layer. The thin and rough Ru seed layer could be used for the high-density magnetic recording media, but the Ru seed layer with a proper thickness of 70 nm facilitated a perfect isolation, and consequently excellent magnetic properties could be acquired for the final products.%采用磁控溅射方法,制备了惣不同厚度Ru薄膜为籽晶层的CoCrPt-SiO2垂直磁记录薄膜。利用原子力显微镜(AFM)、透射电镜(TEM)分析 Ru 薄膜的结构和形貌,并悁究了其结构对CoCrPt-SiO2薄膜表面形貌、粗糙度及结构的愝响。结果表明,CoCrPt-SiO2记录层的晶粒尺寸和粗糙度均随着 Ru 籽晶层厚度的增加而增加,薄而粗糙的籽晶层适合于高密度磁记录介质。对于CoCrPt-SiO2记录层晶粒的优化,厚度为70 nm的Ru籽晶层有利于记录层薄膜晶粒的完全隔离,从而提高了磁记录性能。

  19. Metal nanostructures with complex surface morphology: The case of supported lumpy Pd and Pt nanoparticles produced by laser processing of metal films

    Science.gov (United States)

    Ruffino, F.; Maugeri, P.; Cacciato, G.; Zimbone, M.; Grimaldi, M. G.

    2016-09-01

    In this work we report on the formation of lumpy Pd and Pt nanoparticles on fluorine-doped tin oxide/glass (FTO/glass) substrate by a laser-based approach. In general, complex-surface morphology metal nanoparticles can be used in several technological applications exploiting the peculiarities of their physical properties as modulated by nanoscale morphology. For example plasmonic metal nanoparticles presenting a lumpy morphology (i.e. larger particles coated on the surface by smaller particles) can be used in plasmonic solar cell devices providing broadband scattering enhancement over the smooth nanoparticles leading, so, to the increase of the device efficiency. However, the use of plasmonic lumpy nanoparticles remains largely unexplored due to the lack of simply, versatile, low-cost and high-throughput methods for the controllable production of such nanostructures. Starting from these considerations, we report on the observation that nanoscale-thick Pd and Pt films (17.6 and 27.9 nm, 12.1 and 19.5 nm, respectively) deposited on FTO/glass surface irradiated by nanosecond pulsed laser at fluences E in the 0.5-1.5 J/cm2 range, produce Pd and Pt lumpy nanoparticles on the FTO surface. In addition, using scanning electron microscopy analyses, we report on the observation that starting from each metal film of fixed thickness h, the fraction F of lumpy nanoparticles increases with the laser fluence E and saturates at the higher fluences. For each fixed fluence, F was found higher starting from the Pt films (at each starting film thickness h) with respect to the Pd films. For each fixed metal and fluence, F was found to be higher decreasing the starting thickness of the deposited film. To explain the formation of the lumpy Pd and Pt nanoparticles and the behavior of F as a function of E and h both for Pd and Pt, the thermodynamic behavior of the Pd and Pt films and nanoparticles due to the interaction with the nanosecond laser is discussed. In particular, the

  20. Enhanced CO photocatalytic oxidation in the presence of humidity by tuning composition of Pd-Pt bimetallic nanoparticles supported on TiO2.

    Science.gov (United States)

    Rosseler, Olivier; Louvet, Alain; Keller, Valérie; Keller, Nicolas

    2011-05-14

    Here we put forward for the first time that the negative effect of humidity on CO photooxidation at room temperature can be overcome by adjusting the composition of Pd-Pt bimetallic particles supported on TiO(2). Consequently, optimized Pd(x)Pt(1-x)/TiO(2) materials can be considered as common and efficient photocatalysts for simultaneous elimination of CO and VOCs in the presence of humidity, i.e. for real indoor air treatment. © The Royal Society of Chemistry 2011

  1. Intercomparison of electron probe micro-analyses and particle induced X-ray emission analyses of Pt-Pd-Ni-S matrices

    Energy Technology Data Exchange (ETDEWEB)

    Merkle, R.K.W. E-mail: rkwm@scientia.up.ac.zarmerkle@postino.up.ac.za; Franklyn, C.B.; Przybylowicz, W.; Verryn, S.M.C

    2002-05-01

    Divergencies in the compositions of phases from the Pt-Pd-Ni-S system, derived from electron probe micro-analysis and micro-PIXE analysis of thick samples have been investigated. Discrepancies stem from the different penetration and excitation processes of the two techniques. A specially prepared set of targets, of varying element ratios of Pt, Pd, Ni and S, were studied in a round robin analysis using three independent experimental facilities and analytical procedures. The results allow identification of the different phases, but the observed deviations can only partly be explained by software deficiencies.

  2. Norspermidine and novel Pd(II) and Pt(II) polynuclear complexes of norspermidine as potential antineoplastic agents against breast cancer.

    Science.gov (United States)

    Silva, Tânia Magalhães; Andersson, Sara; Sukumaran, Sunil Kumar; Marques, Maria Paula; Persson, Lo; Oredsson, Stina

    2013-01-01

    New strategies are needed for breast cancer treatment and one initial step is to test new chemotherapeutic drugs in breast cancer cell lines, to choose candidates for further studies towards clinical use. The cytotoxic effects of a biogenic polyamine analogue - norspermidine - and its trinuclear Pd(II) and Pt(II) complexes - Pd(3)NSpd(2) and Pt(3)NSpd(2), respectively - were investigated in one immortalized normal-like and three breast cancer cell lines. The normal-like MCF-10A cells were least sensitive to the compounds, while growth inhibition and cell death was observed in the cancer cell lines. Norspermidine and its Pd(II) complex were generally shown to have stronger antiproliferative effects than the corresponding Pt(II) complex. Moreover, both norspermidine and the Pd(II) complex reduced the cellular activity of the growth-related enzyme, ornithine decarboxylase (ODC) to a lower level than the Pt(II) complex in most of the cell lines examined. Treatment with norspermidine or the Pd(II) complex reduced the number of colonies formed in a soft agar assay performed with the breast cancer cell lines, indicating that these compounds reduced the malignancy of the breast cancer cells. The effect of norspermidine or the Pd(II) complex on colony formation was much stronger than that observed for the Pt(II) complex. The results from a new mammalian genotoxicity screen together with those of a single cell gel electrophoresis assay indicated that none of the drugs were genotoxic at a 25 µM concentration. Overall, norspermidine and its Pd(II) complex were shown to have strong antiproliferative effects. In comparison, the effects obtained with the Pd(II) complex were much stronger than that of the Pt(II) complex. The results obtained in the present study demonstrate that the trinuclear Pd(II) complex of norspermidine (Pd(3)NSpd(2)) may be regarded as a potential new metal-based drug against breast cancer, coupling a significant efficiency to a low toxicity.

  3. Pd/Pt(1 1 1) surface structure and metal epitaxy by time-of-flight impact-collision ion scattering spectroscopy and scanning tunneling microscopy: Does lattice mismatch really determine the growth mode?

    Science.gov (United States)

    Umezawa, K.; Narihiro, E.; Ohta, Y.; Ohira, Y.; Yoshimura, M.

    2008-04-01

    We have investigated the growth of 3 ML of Pd on Pt(1 1 1) at substrate temperature of around 300 K using TOF-ICISS. Also a series of STM topographs were taken as a function of coverage of Pd atoms. The Pd-Pt(1 1 1) combination does not have lattice mismatch (less than 1%); the nearest neighbor distance of bulk Pd(1 1 1) and Pt(1 1 1) are 2.75 Å and 2.77 Å, respectively. Experimental data and computer simulations result clearly show the growth mode of Pd(1 1 1) [ 2 bar 1 1]/Pt(1 1 1) [ 2 bar 1 1] hetero epitaxy at the coverage of the Pd deposition less than 3 ML. The growth mode of Pd(1 1 1) [ 1 bar 1 bar 2 ]/Pt(1 1 1) [ 2 bar 1 1] could not be observed at all. One would expect that the growth mode of Pd atoms on Pt(1 1 1) surfaces is like homo epitaxy (layer-by-layer growth), because of no lattice mismatch (less than 1%). However, it was not. The calculated surface and interface energies and STM results show 2D or 3D dimensional island growth. Pd atoms is mainly form dense islands at the steps on Pt(1 1 1) surfaces at the coverage of 0.13 ML.

  4. A solid-polymer-electrolyte direct methanol fuel cell (DMFC) with Pt-Ru nanoparticles supported onto poly(3,4-ethylenedioxythiophene) and polystyrene sulphonic acid polymer composite as anode

    Indian Academy of Sciences (India)

    K K Tintula; S Pitchumani; P Sridhar; A K Shukla

    2010-05-01

    Nano-sized Pt-Ru supported onto a mixed-conducting polymer composite comprising poly(3,4-ethylenedioxythiophene)-polystyrene sulphonic acid (PEDOT-PSSA) is employed as anode in a solid-polymer-electrolyte direct methanol fuel cell (SPE-DMFC) and its performance compared with the SPE-DMFC employing conventional Vulcan XC-72R carbon supported Pt-Ru anode. Physical characterization of the catalyst is conducted by Fourier-transform infra-red (FTIR) spectroscopy, X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Energy dispersive X-ray analysis (EDAX) in conjunction with cyclic voltammetry and chronoamperometry. The study suggests that PEDOT-PSSA to be a promising alternative catalyst-support-material for SPE-DMFCs.

  5. Gyroscope-like molecules consisting of PdX₂/PtX₂ rotators within three-spoke dibridgehead diphosphine stators: syntheses, substitution reactions, structures, and dynamic properties.

    Science.gov (United States)

    Nawara-Hultzsch, Agnieszka J; Stollenz, Michael; Barbasiewicz, Michał; Szafert, Sławomir; Lis, Tadeusz; Hampel, Frank; Bhuvanesh, Nattamai; Gladysz, John A

    2014-04-14

    Threefold intramolecular ring-closing metatheses of trans-[MCl2(P{(CH2)(m)CH=CH2}3)2] are effected with Grubbs' catalyst. Following hydrogenation catalyzed by [RhCl(PPh3)3], the title complexes trans-[MCl2(P((CH2)n)3P)] (n=2m+2; M/n=Pt/14, 4 c; Pt/16, 4 d; Pt/18, 4 e; Pd/14, 5 c; Pd/18, 5 e) and sometimes isomers partly derived from intraligand metathesis, trans-[MCl2{P(CH2)n(CH2)n}P(CH2)n)] (4'c-e, 5'e), are isolated. These react with LiBr, NaI, and KCN to give the corresponding MBr2, MI2, and M(CN)2 species (58-99%). (13)C NMR data show that the MX2 moieties rapidly rotate within the diphosphine cage on the NMR timescale, even at -120 °C. The reaction of 4 c and KSCN gives separable Pt(NCS)2 and Pt(NCS)(SCN) adducts (13 c, 28%; 14 c, 20%), and those of 4 c,e and Ph2Zn give PtPh2 species (15 c, 61%; 15 e, 90%). (13)C NMR spectra of 13 c-15 c show two sets of CH2 signals (ca. 2:1 intensity ratios), indicating that MX2 rotation is no longer rapid. Reactions of 4 c or 4'c and excess NaC≡CH afford the free diphosphines P{(CH2)14}3P (91%) and (CH2)14P(CH2)14P(CH2)14 (90%). The latter has been crystallographically characterized as a bis(BH3) adduct. The crystal structures of eight complexes with P(CH2)14P linkages (PtCl2, PtBr2, PtI2, Pt(NCS)2, PtPh2, PdCl2, PdBr2, PdI2) and 15 e have been determined, and intramolecular distances analyzed with respect to MX2 rotation. The conformations of the (CH2)14 moieties and features of the crystal lattices are also discussed.

  6. Preparation of Pd/Pt Bimetallic Electrodes and Its Activity Toward Oxygen Reduction Reaction%Pd/Pt二元合金电极的制备及氧还原性能

    Institute of Scientific and Technical Information of China (English)

    方兰兰; 廖玲文; 刘少雄; 蔡俊; 李明芳; 陈艳霞

    2011-01-01

    利用Pt置换取代经欠电位沉积的亚单层Cu的方法,制备了不同组成的Pd/Pt二元合金电极(用Pd/Pt表示,x表示n置换取代欠电位沉积Cu过程的次数),并对其表面元素组成和氧还原性能进行了表征.在控制欠电位沉积Cu的下限电位恒定(0.34 V)的条件下,表面Pd/Pt的元素组成比通过重复Pt置换取代欠电位沉积Cu的次数(1~5次)来调控.光电子能谱(XPS)以及红外光谱实验结果表明,Pd/Pt电极表面的Pd/Pt元素组成比随着Pt沉积次数的增加而增加,对Pd/Pt电极,在电极表层约2~3 nm厚度内的Pt/Pd原子比为1:4,最表层的Pt/Pd原子比为4:1.循环伏安结果显示,随着Pt沉积次数的增加(1~5次),Pd/Pt电极表面越来越不易氧化.氧还原测试结果显示,随着Pt沉积次数(1~4次)的增加,Pd/Pt二元金属电极的氧还原活性依次增加,经过第3次沉积后其氧还原活性已优于纯Pt,而经4次以上沉积后其氧还原活性基本不变.在其它反应条件相同时,Pd/Pt电极上氧还原的半波电位与纯Pt相比右移约25 mV.可初步认为Pd/Pt二元金属体系氧还原性能的改善主要源自表层Pd原子让邻近的Pt原子上含氧物种的吸附能降低.%Pd/Pt bimetallic electrodes were prepared using under-potential deposition(UPD) of Cu following with galvanic displacement of Cu by Pt. The atomic ratios of Pt/Pd in the surface region can be tuned by holding the Cu UPD potential and changing the cycled times of UPD Cu and Pt-Cu displacement processes.Measurements using X-ray photon-electron spectroscopy(XPS) and electrochemical infrared spectroscopy( EC-IRS) with CO as probe molecules demonstrate that the atomic ratios of Pt/Pd increase monotonically with the cycle times of Cu-upd and Pt-Cu displacement. For Pd/Pt4 electrode, the average atomic ratios of Pt/Pd within 2—3 nm from the surface and at the surface are ca. 1: 4 and 4: 1, respectively. With the increase of Pt molar ratio at the surface, Pd/Pt

  7. On new ternary equiatomic scandium transition metal aluminum compounds ScTAl with T = Cr, Ru, Ag, Re, Pt, and Au

    Energy Technology Data Exchange (ETDEWEB)

    Radzieowski, Mathis; Janka, Oliver [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie; Benndorf, Christopher [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie; Muenster Univ. (Germany). Inst. fuer Physikalische Chemie; Haverkamp, Sandra [Muenster Univ. (Germany). Inst. fuer Physikalische Chemie; Eckert, Hellmut [Muenster Univ. (Germany). Inst. fuer Physikalische Chemie; University of Sao Paulo, Sao Carlos, SP (Brazil). Inst. of Physics

    2016-08-01

    The new equiatomic scandium transition metal aluminides ScTAl for T = Cr, Ru, Ag, Re, Pt, and Au were obtained by arc-melting of the elements followed by subsequent annealing for crystal growth. The samples were studied by powder and single crystal X-ray diffraction. The structures of three compounds were refined from single crystal X-ray diffractometer data: ScCrAl, MgZn{sub 2} type, P6{sub 3}/mmc, a = 525.77(3), c = 858.68(5) pm, R{sub 1} = 0.0188, wR{sub 2} = 0.0485, 204 F{sup 2} values, 13 variables, ScPtAl, TiNiSi type, Pnma, a = 642.83(4), b = 428.96(2), c = 754.54(5) pm, R{sub 1} = 0.0326, wR{sub 2} = 0.0458, 448 F{sup 2} values, 20 variables and ScAuAl, HfRhSn type, P anti 62c, a = 722.88(4), c = 724.15(4) pm, R{sub 1} = 0.0316, wR{sub 2} = 0.0653, 512 F{sup 2} values, 18 variables. Phase pure samples of all compounds were furthermore investigated by magnetic susceptibility measurements, and Pauli-paramagnetism but no superconductivity was observed down to 2.1 K for all of them. The local structural features and disordering phenomena have been characterized by {sup 27}Al and {sup 45}Sc magic angle spinning (MAS) and static NMR spectroscopic investigations.

  8. Comparative analysis of deuterium ions implanted and deuterium atoms saturated at high pressure in pure pd and Pd diluted alloys

    Science.gov (United States)

    Didyk, A. Yu.; Kulikauskas, V. S.; Wiśniewski, R.; Wilczynska, T.; Kitowski, K.

    2012-01-01

    Pd and its diluted alloys (Pd-Ag, Pd-Pt, Pd-Ru, Pd-Rh) were implanted by 25 keV deuterium ions at a fluence interval of (1.2-2.3) × 1022 m-2. The same property alloys were saturated by deuterium atoms using high pressure chamber during long period with temperature stabilization and electrical resistance measurement of standard Pd wire. The post-treatment depth distributions of deuterium and accompanied hydrogen atoms were measured immediately after implantation (ten days) and after definite time period (three months) after saturation with the usage of elastic recoil detection analysis (ERDA). After two months, the measurements were repeated. The comparison of obtained results in both series of studies allowed one to make an important observation of a relative stability of deuterium and hydrogen atoms in pure Pd and its diluted alloys.

  9. Strain effect on the magnetic properties of SrRuO{sub 3} thin films on ferroelectric PMN-PT substrates

    Energy Technology Data Exchange (ETDEWEB)

    Herklotz, Andreas; Kataja, Mikko; Schultz, Ludwig; Doerr, Kathrin [IFW Dresden, IMW, Helmholtzstrasse 20, 01069 Dresden (Germany)

    2011-07-01

    We investigate a two-component multiferroic system consisting of a ferroelectric 0.72PbMg{sub 1/3}Nb{sub 2/3}O{sub 3}-0.28PbTiO{sub 3} (PMN-PT) substrate and ferromagnetic SrRuO{sub 3} (SRO) thin films. The inverse piezoelectric effect of the substrate is used to reversibly vary the strain state of the epitaxial SRO films in order to clarify the strain dependence of the magnetic film properties. Buffer films of Sr{sub 1-x}Ba{sub x}TiO{sub 3} are introduced to vary the as-grown state of the SRO films and to cover a wider range from compressive to tensile strain. High resolution X-ray diffraction is deployed to structurally characterize the films and to determine Poisson's ratio of SRO, which is not known so far. SQUID magnetometry reveals that the Curie temperature is increasing with tensile strain, but starts to decrease again under high strain. Angular-dependent measurements provide that the easy axis orientation shows a complex dependence on strain and temperature. SQUID measurements on conventional substrates like SrTiO{sub 3} and LaAlO{sub 3} and electric transport measurements complete the data.

  10. Growth of {110}-one-axis-oriented perovskite-type oxide films using self-aligned epitaxial (101)PdO//(111) Pd double layers

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Hiroki [Department of Innovative and Engineered Material, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan); Kariya, Tetsuro [Department of Innovative and Engineered Material, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan); Sanyo Special Steel Co., Ltd, 3007, Nakashima, Shikama-ku, Himeji, Hyogo 672-8677 (Japan); Shimizu, Takao [Department of Innovative and Engineered Material, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan); Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503 (Japan); Uchiyama, Kiyoshi, E-mail: uchiyama@tsuruoka-nct.ac.jp [Department of Creative Engineering, National Institute of Technology, Tsuruoka College, 104 Inooka Sawada, Tsuruoka, Yamagata 997-8511 (Japan); Funakubo, Hiroshi [Department of Innovative and Engineered Material, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8502 (Japan); Materials Research Center for Element Strategy, Tokyo Institute of Technology, 4259 Nagatsuta, Midori, Yokohama 226-8503 (Japan)

    2016-01-29

    Self-aligned (101)-one-axis-oriented PdO layer was obtained on (111) Pd films prepared on (111)Pt/TiO{sub x}/SiO{sub 2}/Si [abbreviated as (111)Pt/Si] substrates by the heat treatment at 750 °C under atmospheric oxygen flow. Films with (110){sub c}-oriented SrRuO{sub 3} with perovskite structure were successfully deposited at 500 °C on a (101)-oriented PdO layer by an RF magnetron sputtering method due to their relatively small lattice mismatch. A (101)-oriented Sr(Zr{sub 0.8}Y{sub 0.2})O{sub 3-δ} (SZYO) film can be successfully prepared on (110){sub c}-oriented SrRuO{sub 3} and its proton conductivity is almost the same as that of (111){sub c}-oriented SZYO but slightly smaller than that of (111){sub c}-oriented one. As the conductivity is strongly affected by the film crystallinity, we can conclude that the newly fabricated (110){sub c}-oriented SZYO has almost the same crystallinity comparing to the films with other orientation. We have successfully demonstrated that the use of (101)PdO//(111)Pd double layer is a good candidate to grow {110}-one-axis-oriented perovskite thin films on Si substrates. - Highlights: • Self-aligned (101)-one-axis-oriented PdO layer were obtained on (111) Pd films • (110){sub c}SrRuO{sub 3} perovskite can be deposited successfully on (101) PdO//Pd double layer • (101){sub c}Sr(Zr{sub 0.8}Y{sub 0.2})O{sub 3–δ} perovskite is also prepared by using (110){sub c} SrRuO{sub 3} layer • (101)PdO//(111)Pd is quite effective for growing {110}-oriented perovskite films.

  11. Reactivity of ammonia ligands of the antitumor agent cisplatin: a unique dodecanuclear Pt4,Pd4,Ag4 platform for four cytosine model nucleobases.

    Science.gov (United States)

    Kampf, Gunnar; Sanz Miguel, Pablo J; Morell Cerdà, Marta; Willermann, Michael; Schneider, Alexandra; Lippert, Bernhard

    2008-01-01

    The reaction of a potential mono(nucleobase) model adduct of cisplatin, cis-[Pt(NH(3))(2)(1-MeC-N3)(H(2)O)](2+) (6; 1-MeC: 1-methylcytosine), with the electrophile [Pd(en)(H(2)O)(2)](2+) (en: ethylenediamine) at pH approximately 6 yields a kinetic product X which is likely to be a dinuclear Pt,Pd complex containing 1-MeC(-)-N3,N4 and OH bridges, namely cis-[Pt(NH(3))(2)(1-MeC(-)-N3,N4)(OH)Pd(en)](2+). Upon addition of excess Ag(+) ions, conversion takes place to form a thermodynamic product, which, according to (1)H NMR spectroscopy and X-ray crystallography, is dominated by a mu-NH(2) bridge between the Pt(II) and Pd(II) centers. X-ray crystallography reveals that the compound crystallizes out of solution as a dodecanuclear complex containing four Pt(II), four Pd(II), and four Ag(+) entities: [{Pt(2)(1-MeC(-)-N3,N4)(2)(NH(3))(2)(NH(2))(2)(OH)Pd(2)(en)(2)Ag}(2){Ag(H(2)O)}(2)](NO(3))(10) 6 H(2)O (10) is composed of a roughly planar array of the 12 metal ions, in which the metal ions are interconnected by mu-NH(2) groups (between Pt and Pd centers), mu-OH groups (between pairs of Pt atoms), and metal-metal donor bonds (Pt-->Ag, Pd-->Ag). The four 1-methylcytosinato ligands, which are stacked pairwise, as well as the four NH(3) ligands and parts of the en rings, are approximately perpendicular to the metal plane. Two of the four Ag ions (Ag2, Ag2') of 10 are labile in solution and show the expected behavior of Ag(+) ions in water, that is, they are readily precipitated as AgCl by Cl(-) ions. The resulting pentanuclear complex [Pt(2)Pd(2)Ag(1-MeC(-))(2)(NH(2))(2)(OH)(NH(3))(2)(en)(2)](NO(3))(4)7 H(2)O (11) largely maintains the structural features of one half of 10. The other two Ag(+) ions (Ag1, Ag1') of 10 are remarkably unreactive toward excess NaCl. In fact, the pentanuclear complex [Pt(2)Pd(2)AgCl(1-MeC(-))(2)(NH(2))(2)(OH)(NH(3))(2)(en)(2)](NO(3))(3)4.5 H(2)O (12), obtained from 10 with excess NaCl, displays a Cl(-) anion bound to the Ag center (2.459(3) A) and

  12. Synthesis, structural, optical and anti-rheumatic activity of metal complexes derived from (E)-2-amino-N-(1-(2-aminophenyl)ethylidene)benzohydrazide (2-AAB) with Ru(III), Pd(II) and Zr(IV).

    Science.gov (United States)

    Hosny, Nasser Mohammed; Sherif, Yousery E

    2015-02-05

    Three new metal complexes derived from Pd(II), Ru(III) and Zr(IV) with (E)-2-amino-N-(1-(2-aminophenyl)ethylidene)benzohydrazide (2-AAB) have been synthesized. The isolated complexes were characterized by elemental analyses, FT-IR, UV-Vis, ES-MS, (1)H NMR, XRD, thermal analyses (TGA and DTA) and conductance. The morphology and the particle size were determined by transmittance electron microscope (TEM). The results showed that, the ligand coordinates to Pd(II) in the enol form, while it coordinates to Ru(III) and Zr(IV) in the keto form. A square planar geometry is suggested for Pd(II) complex and octahedral geometries are suggested for Ru(III) and Zr(IV) complexes. The optical band gaps of the isolated complexes were measured and indicated the semi-conductivity nature of the complexes. The anti-inflammatory and analgesic activities of the ligand and its complexes showed that, Ru(III) complex has higher effect than the well known drug "meloxicam".

  13. Comparative study of steam reforming of methane, ethane and ethylene on Pt, Rh and Pd supported on yttrium-stabilized zirconia.

    NARCIS (Netherlands)

    Graf, P.O.; Mojet, Barbara; van Ommen, J.G.; Lefferts, Leonardus

    2007-01-01

    In the present paper steam reforming of methane, ethane and ethylene was compared on Pt, Rh and Pd supported on yttrium-stabilized zirconia (YSZ). Both reactivity and product distribution changed with the use of different catalysts. The order of activity for the hydrocarbons on Rh was C2H6 > C2H4 >

  14. A comparative study of thin coatings of Au/Pd, Pt and Cr produced by magnetron sputtering for FE-SEM

    NARCIS (Netherlands)

    Stokroos, [No Value; Kalicharan, D; Van der Want, JJL; Jongebloed, WL

    Visualization of structural details of specimens in field emission scanning electron microscopy (FE-SEM) requires optimal conductivity. This paper reports on the differences in conductive layers of Au/Pd, Pt and Cr, with a thickness of 1.5-3.0 nm, deposited by planar magnetron sputtering devices.

  15. Disentangling the physical contributions to the anomalous Hall effect and domain wall resistance in isoelectronic L10-FePd and L10-FePt alloys

    Science.gov (United States)

    Seemann, Klaus; Garcia-Sanchez, Felipe; Kakay, Attila; Schneider, Claus; Freimuth, Frank; Mokrousov, Yuriy; Bluegel, Stefan; Hertel, Riccardo

    2012-02-01

    We analyze the origin of the electrical resistance arising in domain walls of perpendicularly magnetized materials by considering a superposition of anisotropic magnetoresistance and the resistance implied by the magnetization chirality. The domain wall profiles of L10-FePd and L10-FePt are determined by micromagnetic simulations based on which we perform first principles calculations to quantify electron transport through the core and closure region of the walls. The wall resistance, being twice as high in L10-FePd than in L10-FePt, is found to be clearly dominated in both cases by a high gradient of magnetization rotation, and not by the spin-orbit interaction driven anisotropic magnetoresistance effect. Concerning the anomalous Hall effect on the other hand, we show that difference in spin-orbit interaction strength of Pt and Pd atoms leads to a pronounced cross-over from an extrinsic side jump mechanism in L10-FePd to an intrinsic Berry-phase anomalous Hall effect in L10-FePt.

  16. Comparison of the thermal stabilities of NiSi films in Ni/Si, Ni/Pd/Si and Ni/Pt/Si systems

    CERN Document Server

    Wang, R N

    2003-01-01

    The effects of different interlayer materials (Pd and Pt) deposited between Ni films and Si substrates on the NiSi thermal stability are discussed. Ni sub 0 sub . sub 9 sub 4 sub 3 Pd sub 0 sub . sub 0 sub 5 sub 7 Si and Ni sub 0 sub . sub 9 sub 4 sub 5 Pt sub 0 sub . sub 0 sub 5 sub 5 Si solid solutions were formed when the samples were annealed at high temperatures and the lattice parameters of Ni sub 0 sub . sub 9 sub 4 sub 3 Pd sub 0 sub . sub 0 sub 5 sub 7 Si were calculated according to Vegard's law. The NiSi thermal stability was enhanced by interposing a Pd or Pt interlayer, and the sample with the Pt interlayer had the highest NiSi thermal stability among all the samples studied. This is attributed to the reduction of the interface energy between NiSi and Si substrates and the decrease of the driving force for the nucleation of NiSi sub 2 , induced by formation of the NiSi(200) preferred orientation and the solid solution respectively.

  17. Adsorption of NO on the Rh-13, Pd-13, Ir-13, and Pt-13 Clusters: A Density Functional Theory Investigation

    DEFF Research Database (Denmark)

    Piotrowski, Mauricio J.; Piquini, Paulo; Zeng, Zhenhua

    2012-01-01

    of real catalyst devices. In this study, we report a density functional theory study of the adsorption properties of NO on the TM13 (TM = Rh, Pd, Ir, Pt) clusters employing the projected augmented wave method. We found that the interaction of NO with TM13 is much more complex than that for NO/TM(111...... of the binding energy of NO to the TM13 clusters compared with the TM(111) surfaces, as the antibonding NO states are not occupied for NO/TM13, and the general relationship based on the d-band model between adsorption energy and the center of gravity of the occupied d-states does not hold for the studied TM13...

  18. Ballistic and diffusive current spin polarization in L1{sub o}-ordered FePt and FePd

    Energy Technology Data Exchange (ETDEWEB)

    Seemann, Klaus M.; Baltz, Vincent; Hickey, Mark C.; Marrows, Christopher H.; Hickey, Bryan J. [E.C. Stoner Laboratory, School of Physics and Astronomy, University of Leeds, Leeds (United Kingdom); MacKenzie, Maureen; Chapman, John N. [Department of Physics and Astronomy, University of Glasgow, Glasgow (United Kingdom); Miguel, Jorge; Kuch, Wolfgang [Institut fuer Experimentalphysik, Freie Universitaet Berlin, Berlin (Germany); Kronast, Florian [BESSY, Albert-Einstein-Strasse 15, Berlin (Germany)

    2008-07-01

    We report on the discrepancy of the current spin polarization in the ballistic and diffusive electron transport regime in L1{sub o}-ordered epitaxial FePt and FePd layers. The films studied displayed a chemical long range order parameter of 0.4

  19. Enhanced catalytic performance for methane combustion of 3DOM CoFe2O4 by co-loading MnOx and Pd-Pt alloy nanoparticles

    Science.gov (United States)

    Li, Xiangyu; Liu, Yuxi; Deng, Jiguang; Xie, Shaohua; Zhao, Xingtian; Zhang, Yang; Zhang, Kunfeng; Arandiyan, Hamidreza; Guo, Guangsheng; Dai, Hongxing

    2017-05-01

    Three-dimensionally ordered macroporous (3DOM) CoFe2O4, zMnOx/3DOM CoFe2O4 (z = 4.99-12.30 wt%), and yPd-Pt/6.70 wt% MnOx/3DOM CoFe2O4 (y = 0.44-1.81 wt%; Pd/Pt molar ratio = 2.1-2.2) have been prepared using the polymethyl methacrylate microspheres-templating, incipient wetness impregnation, and bubble-assisted polyvinyl alcohol-protected reduction strategies, respectively. All of the samples were characterized by means of various techniques. Catalytic performance of the samples was measured for methane combustion. It is shown that the as-prepared samples exhibited a high-quality 3DOM structure (103 ± 20 nm in pore size) and a surface area of 19-28 m2/g, and the noble metal or alloy nanoparticles (NPs) with a size of 2.2-3.0 nm were uniformly dispersed on the macropore wall surface of 3DOM CoFe2O4. The loading of MnOx on CoFe2O4 gave rise to a slight increase in activity, however, the dispersion of Pd-Pt NPs on 6.70MnOx/3DOM CoFe2O4 significantly enhanced the catalytic performance, with the 1.81Pd2.1Pt/6.70MnOx/3DOM CoFe2O4 sample showing the highest activity (T10% = 255 °C, T50% = 301 °C, and T90% = 372 °C at a space velocity of 20,000 mL/(g h)). We believe that the excellent catalytic activity of 1.81Pd2.1Pt/6.70MnOx/3DOM CoFe2O4 was related to its well-dispersed Pd-Pt alloy NPs, high adsorbed oxygen species concentration, good low-temperature reducibility, and strong interaction between MnOx or Pd-Pt NPs and 3DOM CoFe2O4.

  20. Sensitive determination of dopamine in the presence of uric acid and ascorbic acid using TiO2 nanotubes modified with Pd, Pt and Au nanoparticles.

    Science.gov (United States)

    Mahshid, Sara; Li, Chengcheng; Mahshid, Sahar Sadat; Askari, Masoud; Dolati, Abolghasem; Yang, Lixia; Luo, Shenglian; Cai, Qingyun

    2011-06-07

    A simple modified TiO(2) nanotubes electrode was fabricated by electrodeposition of Pd, Pt and Au nanoparticles. The TiO(2) nanotubes electrode was prepared using the anodizing method, followed by modifying Pd nanoparticles onto the tubes surface, offering a uniform conductive surface for electrodeposition of Pt and Au. The performance of the modified electrode was characterized by cyclic voltammetry and differential pulse voltammetry methods. The Au/Pt/Pd/TiO(2) NTs modified electrode represented a high sensitivity towards individual detection of dopamine as well as simultaneous detection of dopamine and uric acid using 0.1 M phosphate buffer solution (pH 7.00) as the base solution. In both case, electro-oxidation peak currents of dopamine were linearly related to accumulated concentration over a wide concentration range of 5.0 × 10(-8) to 3.0 × 10(-5) M. However in the same range of dopamine concentration, the sensitivity had a significant loss at Pt/Pd/TiO(2) NTs electrode, suggesting the necessity for Au nanoparticles in modified electrode. The limit of the detection was determined as 3 × 10(-8) M for dopamine at signal-to-noise ratio equal to 3. Furthermore, the Au/Pt/Pd/TiO(2) NTs modified electrode was able to distinguish the oxidation response of dopamine, uric acid and ascorbic acid in mixture solution of different acidity. It was shown that the modified electrode possessed a very good reproducibility and long-term stability. The method was also successfully applied for determination of DA in human urine samples with satisfactory results.

  1. CO2对Pd8Y0.23Ru合金膜氢渗透性能的影响%Effect of CO2 on Hydrogen Permeation through Pd8Y0.23Ru Alloy Membrane

    Institute of Scientific and Technical Information of China (English)

    程亮; 陆光达; 张桂凯; 王晓英

    2013-01-01

    Hydrogen permeation through a Pd8Y0.23Ru alloy membrane at 300 ℃~450 ℃ has been investigated in the presence of CO2.The results show that the hydrogen permeability is greatly decreased by CO2 addition.The higher the CO2 concentration is,the more significant the reduction of hydrogen permeation will be.The coexisting CO2 gas has a poison effect on Pd8Y0.23Ru alloy membrane.The poison effect at 450 ℃ is stronger than at 300 ℃.The reduction rate of hydrogen permeation decreases with the permeation duration.Besides poison effect,the negative effects of CO2 on H2 permeation are also caused by two other factors.Firstly,for higher concentration of CO2 (>3%),mass transfer of H2 is blocked by CO2 barrier layer near the membrane surface,which is the main reason for hydrogen permeation reduction.Secondly for lower concentrations (<1%),the main reason is the effects of CO2 adsorbing on the membrane and occupying active dissociation sites of hydrogen.%在300~450℃范围内,研究氢中加入CO2对Pd8Y0.23Ru合金膜氢渗透性能的影响.结果表明,CO2的加入会大大降低膜的氢渗透率,CO2浓度越高,氢渗透率降低越多;CO2对Pd8Y0.23Ru合金膜存在一定的毒化作用,使氢渗透率下降,450℃下的毒化作用明显强于300℃,但随着时间的延长,渗透率降低速率趋缓.CO2降低氢渗透率还有另外2个因素:当CO2浓度较高(>3%,摩尔分数)时,聚集在膜表面附近的CO2对氢气传质的阻塞作用是氢渗透率降低的主要因素;当CO2浓度较低(<1%)时,CO2在膜表面吸附,占据氢的活性点位,是氢渗透率降低的主要因素.

  2. Atomically thick Pt-Cu nanosheets: self-assembled sandwich and nanoring-like structures.

    Science.gov (United States)

    Saleem, Faisal; Xu, Biao; Ni, Bing; Liu, Huiling; Nosheen, Farhat; Li, Haoyi; Wang, Xun

    2015-03-25

    Atomically thick and flexible Pt-Cu alloy nanosheets are prepared and loaded with either Pd or Pt to produce sandwich structures or nanoring-like nanosheet structures, respectively. Core-shell alloy nanoparticles containing Rh, Ir, and Ru are also prepared. All of these structures exhibit superior specific and mass activities for the oxidation of formic acid for fuel cells for portable electronic devices as compared to commercial Pd/C catalyst. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Influence of growth and anneal conditions on the surface roughness of L1{sub 0} Fe{sub 50}Pd{sub x}Pt{sub 50-x} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Jiang Xin, E-mail: xinjiang@us.ibm.com [Almaden Research Center, IBM Research, 650 Harry Road, San Jose, CA 95120 (United States); Liu Ruisheng; Gao Li; Topuria, Teya; Parkin, Stuart [Almaden Research Center, IBM Research, 650 Harry Road, San Jose, CA 95120 (United States)

    2012-09-15

    We deposit Fe{sub 50}Pd{sub x}Pt{sub 50-x} alloy thin films by magnetron sputtering onto a TiN seed layer. Chemically ordered L1{sub 0} films are obtained which display large perpendicular magnetic anisotropy. We find that the surface roughness of the film depends strongly on the growth and anneal conditions as well as the Pd composition of the film. Smooth films are obtained by deposition above the chemical ordering temperature and by removing Pd from the alloy. - Highlights: Black-Right-Pointing-Pointer FePdPt thin films with strong perpendicular magnetic anisotropy. Black-Right-Pointing-Pointer Strong dependence of surface roughness on Pd composition. Black-Right-Pointing-Pointer FePt roughness strongly influenced by the disorder to order transition process. Black-Right-Pointing-Pointer Reduced FePt film roughness by deposition above the ordering temperature.

  4. Geometry matters: inverse cytotoxic relationship for cis/trans-Ru(ii) polypyridyl complexes from cis/trans-[PtCl2(NH3)2].

    Science.gov (United States)

    Wachter, Erin; Zamora, Ana; Heidary, David K; Ruiz, José; Glazer, Edith C

    2016-08-09

    Two thermally activated ruthenium(ii) polypyridyl complexes, cis-Ru(bpy)2Cl2 and trans-Ru(qpy)Cl2 were investigated to determine the impact of the geometric arrangement of the exchangable ligands on the potential of the compounds to act as chemotherapeutics. In contrast to the geometry requirements for cisplatin, trans-Ru(qpy)Cl2 was 7.1-9.5× more cytotoxic than cis-Ru(bpy)2Cl2. This discovery could open up a new area of metal-based chemotherapeutic research.

  5. One-pot synthesis of Pd@PtNi core-shell nanoflowers supported on the multi-walled carbon nanotubes with boosting activity toward oxygen reduction in alkaline electrolyte

    Science.gov (United States)

    Liu, Sa; Wang, Yan; Liu, Liwen; Li, Mengli; Lv, Wenjie; Zhao, Xinsheng; Qin, Zhenglong; Zhu, Ping; Wang, Guoxiang; Long, Zhouyang; Huang, Fangmin

    2017-10-01

    Pt-based nanocrystals with controlled morphologies and structures are one of most promising electrocatalysts for oxygen reduction reaction (ORR). Herein, a facile one-pot wet-chemical method is developed to synthesize Pd@PtNi core-shell nanoflowers (CSNFs) supported on the multi-walled carbon nanotubes (MWNCTs). Brij 58 is demonstrated as a structure-directing agent to generate the nanoflower and ascorbic acid acts as a reductant to form a core-shell structure. By tuning the molar ratio of Pd and Pt, Pd@PtNi/MWCNTs CSNFs show obviously improved ORR activity and durability in alkaline electrolyte compared with PtNi/MWCNTs nanoflowers and commercial Pt/C. The results illustrate that the core-shell structure and porous feature of nanoflower are both beneficial to the enhancement of the catalytic properties.

  6. Solid-solution precursor to melting in onion-ring Pd-Pt nanoclusters: a case of second-order-like phase change?

    Science.gov (United States)

    Calvo, Florent

    2008-01-01

    The thermodynamical behaviour of icosahedral, multilayer Pd-Pt clusters is addressed using a combination of simulation tools, mainly parallel tempering Monte Carlo. A preferential swapping trial move is introduced to increase the chance of successfully exchanging Pd and Pt atoms in the cluster. The 2-, 3- and 4-shell, Pd-rich clusters have been studied. We generally find that the clusters melt at a temperature significantly below the bulk melting point at the same corresponding composition. More interestingly, for the smaller clusters melting is initiated by a solid-solution intermediate phase in which the overall icosahedral frame remains, but the Pd and Pt atoms can swap sites. The transition to this solid-solution phase is seen to have a continuous, second-order like character, which is interpreted from the similarity between the present system with the ferromagnetic Ising model on the 3D cubic lattice. As the cluster grows, the onion-ring structure becomes thermodynamically unstable. The 4-layer cluster already exhibits a solid-solution in its core at temperatures as low as 100 K. The bulk behaviour is thus recovered at very small scales.

  7. Influence of Phases Content on Pt/TiO2, Pd/TiO2 Catalysts for Degradation of 4-Chlorophenol at Room Temperature

    Directory of Open Access Journals (Sweden)

    D. S. García-Zaleta

    2016-01-01

    Full Text Available Different Pt/TiO2 and Pd/TiO2 catalysts were prepared by sol-gel method. The influence of different amounts of noble metals (1–5 mol-% present on the microstructure as well as the photocatalytic property under 4-chlorophenol degradation was evaluated. The anatase phase was favored at low Pt content; however, the apparition of new phases after 3 mol-% (PtO suggests a saturation lattice considering our solubility limit at 1 mol-%. Similar trend was observed when Pd was added to the TiO2 lattice. The as-prepared catalysts were deeply characterized by X-ray diffraction (XRD with the Rietveld Method, Raman spectroscopy, high resolution scanning electron microscopy (HRSEM, scanning transmission electron microscopy (STEM, Brunauer-Emmett-Teller (BET adsorption analysis, and X-Ray photoelectron spectroscopy (XPS. Unit-cell parameter of TiO2 phases varied from 30 to 93 vol-% depending on the amount of Pt or Pd added to the composite. HRTEM and HRSEM identified the phases in the catalysts and confirmed the nanometric size and morphology of the catalysts. An improvement in removal efficiency of 4-chlorophenol was obtained in all the specimens compared with the commercial Degussa P25, which can be explained in terms of phase composition and modification of the band gap.

  8. Pd(II) and Pt(II) complexes of α-keto stabilized sulfur ylide: Synthesis, structural, theoretical and catalytic activity studies

    Science.gov (United States)

    Sabounchei, Seyyed Javad; Hashemi, Ali; Sedghi, Asieh; Bayat, Mehdi; Akhlaghi Bagherjeri, Fateme; Gable, Robert W.

    2017-05-01

    Reaction of dimethyl sulfide with 2, 3‧-dibromoacetophenone led to formation of sulfonium salt [Me2SCH2C(O)C6H4-m-Br]Br (1). The resulted sulfonium salt was treated with NaOH and gave the α-keto stabilized sulfur ylide Me