WorldWideScience

Sample records for pt pd ir

  1. 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.

  2. 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...

  3. 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)

  4. 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

  5. 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.

  6. Large exchange bias enhancement in (Pt(or Pd)/Co)/IrMn/Co trilayers with ultrathin IrMn thanks to interfacial Cu dusting

    Energy Technology Data Exchange (ETDEWEB)

    Vinai, G. [SPINTEC, UMR 8191 CEA/CNRS/UJF/Grenoble-INP, CEA/INAC, 17, rue des Martyrs, 38054 Grenoble (France); Crocus Technology, 4 Place Robert Schuman, 38054 Grenoble (France); Moritz, J. [Institut Jean Lamour, UMR 7198 CNRS - Université de Lorraine, Bd des Aiguillettes, BP 70239, F-54506 Vandoeuvre-les-Nancy Cedex (France); Bandiera, S. [Crocus Technology, 4 Place Robert Schuman, 38054 Grenoble (France); Prejbeanu, I. L.; Dieny, B. [SPINTEC, UMR 8191 CEA/CNRS/UJF/Grenoble-INP, CEA/INAC, 17, rue des Martyrs, 38054 Grenoble (France)

    2014-04-21

    The magnitude of exchange bias (H{sub ex}) at room temperature can be significantly enhanced in IrMn/Co and (Pt(or Pd)/Co)/IrMn/Co structures thanks to the insertion of an ultrathin Cu dusting layer at the IrMn/Co interface. The combination of trilayer structure and interfacial Cu dusting leads to a three-fold increase in H{sub ex} as compared to the conventional IrMn/Co bilayer structure, with an increased blocking temperature (T{sub B}) and a concave curvature of the temperature dependence H{sub ex}(T), ideal for improved Thermally Assisted-Magnetic Random Access Memory storage layer. This exchange bias enhancement is ascribed to a reduction of the spin frustration at the IrMn/Co interface thanks to interfacial Cu addition.

  7. 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...

  8. Copper-based alloys, crystallographic and crystallochemical parameters of alloys in binary systems Cu-Me (Me=Co, Rh, Ir, Cu, Ag, Au, Ni, Pd, Pt)

    Energy Technology Data Exchange (ETDEWEB)

    Porobova, Svetlana, E-mail: porobova.sveta@yandex.ru; Loskutov, Oleg, E-mail: lom58@mail.ru [Tomsk State University of Architecture and Building, Russia, Tomsk, 2 Solyanaya sq, Tomsk, 634003 (Russian Federation); Markova, Tat’jana, E-mail: patriot-rf@mail.ru [Siberian State Industrial University. 42 Kirov St., Novokuznetsk, 654007 (Russian Federation); Klopotov, Vladimir, E-mail: vdklopotov@mail.ru [Research Tomsk Polytechnic University, 30 Lenin Ave., Tomsk, 634050 (Russian Federation); Klopotov, Anatoliy, E-mail: klopotovaa@tsuab.ru [Tomsk State University of Architecture and Building, Russia, Tomsk, 2 Solyanaya sq, Tomsk, 634003 (Russian Federation); National Research Tomsk State University, 36, Lenin Ave., Tomsk, 634050 (Russian Federation); Vlasov, Viktor, E-mail: vik@tsuab.ru [Tomsk State University of Architecture and Building, Russia, Tomsk, 2 Solyanaya sq, Tomsk, 634003 (Russian Federation); Research Tomsk Polytechnic University, 30 Lenin Ave., Tomsk, 634050 (Russian Federation)

    2016-01-15

    The article presents the results of the analysis of phase equilibrium of ordered phases in binary systems based on copper Cu- Me (where Me - Co, Rh, Ir, Ag, Au, Ni, Pd, Pt) to find correlations of crystallochemical and crystallographic factors. It is established that the packing index in disordered solid solutions in binary systems based on copper is close to the value of 0.74 against the background of an insignificant deviation of atomic volumes from the Zen’s law.

  9. 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.

  10. 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.

  11. Synthesis, crystal structure and physical properties of EuTGe{sub 3} (T = Co, Ni, Rh, Pd, Ir, Pt) single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Bednarchuk, Oleksandr; Gągor, Anna; Kaczorowski, Dariusz, E-mail: D.Kaczorowski@int.pan.wroc.pl

    2015-02-15

    Highlights: • Single crystals of EuTGe{sub 3} (T = Co, Ni, Rh, Pd, Ir, Pt) compounds were prepared. • The crystal structures were refined from single-crystal X-ray diffraction data. • The physical properties of oriented single crystals were determined. • For each compound, an antiferromagnetic ordering was found at low temperatures. - Abstract: Single crystals of six EuTGe{sub 3} compounds with T = Co, Ni, Rh, Pd, Ir and Pt were prepared by high-temperature solution growth method. Their crystal structures of the BaNiSn{sub 3}-type were refined from single-crystal X-ray diffraction data. The physical properties of oriented single-crystalline specimens were studied by means of magnetic susceptibility, heat capacity and electrical resistivity measurements. For each compound, an antiferromagnetic ordering was found to set in at low temperatures due to localized magnetic moments carried on divalent Eu ions. Despite the same crystal structure, the EuTGe{sub 3} compounds exhibit diverse magnetic structures with different directions of the ordered magnetic moments and a variety of dissimilar mutual arrangements of adjacent spins.

  12. 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.)).

  13. Fermi-liquid behavior of binary intermetallic compounds Y3 M (M  =  Co, Ni, Rh, Pd, Ir, Pt)

    Science.gov (United States)

    Strychalska-Nowak, Judyta; Wiendlocha, Bartłomiej; Hołowacz, Katarzyna; Reczek, Paula; Podgórski, Mateusz; Winiarski, Michał J.; Klimczuk, Tomasz

    2017-06-01

    A series of polycrystalline samples of Y3 M (M  =  Co, Ni, Rh, Pd, Ir, Pt), intermetallic binary compounds were synthesized by the arc-melting method. Powder x-ray diffraction (pXRD) confirmed the orthorhombic cementite-type crystal structure and allowed for the estimation of the lattice parameters. Physical properties were investigated by means of electrical resistivity and heat capacity measurements between 1.9 K and 300 K. All tested compounds show metallic-like behaviour with RRR values ranging from 1.3 to 8.3, and power-law ρ \\propto {{T}n} temperature dependence of resistivity was observed, with 1.6≤slant n≤slant 2.2 . No superconductivity was detected above 1.9 K. The Debye temperature, estimated from the low temperature heat capacity fit, ranged from 180 K (Y3Pt) to 222 K (Y3Co). The highest value of the Sommerfeld coefficient γ was found for Y3Pd (19.5 mJ mol-1 K-2). The pXRD pattern of Y3Rh indicated the presence of Y5Rh2, a previously unreported Pd5B2-type phase, whose unit cell parameters were refined using the LeBail method. Density functional theory calculations were performed and theoretical results revealed strong enhancement of the measured electronic specific heat, which was 30%-100% larger than computed. Quadratic temperature dependence of resistivity and enhanced electronic specific heat indicated a Fermi-liquid behavior of electrons in these materials.

  14. First principles study on the interfacial properties of NM/graphdiyne (NM = Pd, Pt, Rh and Ir): The implications for NM growing

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Zhansheng; Li, Shuo; Lv, Peng [College of Physics and Electronic Engineering, Henan Normal University, Xinxiang 453007 (China); He, Chaozheng, E-mail: hecz2013@nynu.edu.cn [College of Physics and Electronic Engineering, Nanyang Normal University, Nanyang 473061 (China); Ma, Dongwei [School of Physics, Anyang Normal University, Anyang 455000 (China); Yang, Zongxian, E-mail: yzx@henannu.edu.cn [College of Physics and Electronic Engineering, Henan Normal University, Xinxiang 453007 (China); Collaborative Innovation Center of Nano Functional Materials and Applications, Kaifeng (China)

    2016-01-01

    Graphical abstract: - Highlights: • The NM adatoms belong to embedded adsorption in 18C-hexagon of GDY. • The Rh and Ir/GDY can be applied to single metal catalysts or sensors. • A simple linear relationship between E{sub e-ads} and E{sub b} is presented. • The linear relationship can be used in the noble metal modified GDY. - Abstract: Based on the dispersion-corrected density functional calculations (DFT-D), we systematically studied the adsorption of noble metals (NM), Pd, Pt, Rh and Ir, on graphdiyne (GDY). We present a systematic study on the geometry, embedded adsorption energy and electronic structure of four different adatoms adsorbed on the GDY. The strong interaction between the NM adatoms and the GDY substrate is found with the NM embedded in the 18C-hexagon of the GDY. We investigated the mobility of the NM adatoms on the GDY, and found that the mobility barrier energy increases along with the increasing of the embedded adsorption energy. We present the NM adatoms growth of high concentrations on the GDY. Upon the analysis of the electronic structure and the frontier molecular orbitals, Rh and Ir adatoms of low concentrations (about 1.37 at%) on the GDY have the potential to be applied as single metal catalysts or gas molecule sensors.

  15. A Theoretical Study of Addition Reactions of L4M(M = Rh, Ir) and L2M(M = Pd, Pt) to Li+@C60.

    Science.gov (United States)

    Yang, Ming-Chung; Sharma, Akhilesh Kumar; Sameera, W M Chamil; Morokuma, Keiji; Su, Ming-Der

    2017-03-16

    The addition reaction of M(Cl)(CO)(PPh3)2 (M = Rh, Ir) and M(PPh3)2 (M = Pd, Pt) fragments with X@C60 (X = 0, Li+) were characterized by density functional theory (DFT) and the artificial force-induced reaction (AFIR) method. The calculated free energy profiles suggested that the η2[6:6]-addition is the most favorable reaction, which is consistent with the experimental observations. In the presence of Li+ ion, the reaction is highly exothermic, leading to η2[6:6] product of L4IrLi+@C60. In contrast, an endothermic reaction was observed in the absence of a Li+ ion. The encapsulated Li+ ion can enhance the thermodynamic stability of the η2[6:6] product. The energy decomposition analysis showed that the interaction between metal fragment and X@C60 fragment is the key for the thermodynamic stability. Among the group IA and IIA metal cations, Be2+ encapsulation is the best candidate for the development of new fullerene-transition metal complexes, which will be useful for future potential applications such as solar cells, catalysts, and electronic devices.

  16. 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...

  17. Effect of pH on the Nitrite Hydrogenation Mechanism over Pd/Al2O3 and Pt/Al2O3: Details Obtained with ATR-IR Spectroscopy

    DEFF Research Database (Denmark)

    Ebbesen, Sune Dalgaard; Mojet, Barbara L.; Lefferts, Leon

    2011-01-01

    It is well-known that activity and selectivity to N2 during nitrite hydrogenation over noble metal catalysts in water depend on the pH of the solution, but mechanistic understanding is lacking. Attenuated total reflection infrared (ATR-IR) spectroscopy is an ideal tool to perform detailed studies...... on catalytic surfaces in water. In this paper, the influence of pH was studied on adsorption and subsequent hydrogenation of nitrite in water between pH 5 and 9 over Pd/Al2O3 and Pt/Al2O3, using ATR-IR spectroscopy. On both catalysts, pH clearly influenced the surface coverage and reaction rates...

  18. 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

  19. 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.

  20. 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 ...

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Determination of Pt,Pd,Ir and Au in Ores by Inductively Coupled Plasma Atomic Emission Spectrometry after Preconcentration by Minified Nickel Sulfide Fire Assay%硫化镍试金预富集-ICP-AES测定矿石中的Pt、Pd、Ir、Au

    Institute of Scientific and Technical Information of China (English)

    刘小荣; 董守安; 冯忠; 陈丁文

    2003-01-01

    The effect of various factors on the determination o f Pt,Pd,Ir and Au by ICP-AES was investigated in detail using minified nickel su lfide fire assay preconcentration.The results indicated that after the nickel su lfide bead was dissolved in HCl,filtering the solution by fritted glass crucible and dissolving the residue with HCl+H2O2 were a comparatively ideal analyti cal scheme.During the bead dissolving the losses of Pt and Pd were negligible,th e loss of Au was quite high,and the determination of Au was only semiqantitative .The average recoveries for Pt,Pd and Ir ranged from 96% to 99% for the determin ation of μg/g level,the relative standard derivation(RSD) was 1.7 %~6.8%(n=5).The proposed procedure has been applied to analyse o f ores and concentrates.%详细研究了硫化镍试金预富集-ICP-AES测定矿石中的P t、Pd、Ir、Au的多种影响因素.结果表明硫化镍扣用盐酸溶解,多孔玻砂坩埚过滤溶液, 盐酸和双氧水溶解残渣是比较理想的分析方案.硫化镍扣溶解过程中,Pt、Pd的损失可忽略 .Au的损失相当高,仅能半定量.对于μg/g级的样品,Pt、Pd、Ir、Au的平均回收率在96% ~99%之间,相对标准偏差为1.7%~6.8%(n=5).拟定的方法已用于矿石、精矿的分析.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  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. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Magnetic field and temperature control over Pt/Co/Ir/Co/Pt multistate magnetic logic device

    Science.gov (United States)

    Morgunov, R.; Hamadeh, A.; Fachec, T.; Lvovaa, G.; Koplak, O.; Talantsev, A.; Mangin, S.

    2017-04-01

    Magnetic configurations in Pt/Co/Ir/Co/Pt synthetic ferrimagnet bilayer of strong perpendicular anisotropy have been systematically studied. Magnetization versus field hysteresis loops have been measured for different temperatures ranging from 5 to 300 K. The applied field - temperature (H-T) magnetization switching diagram has been constructed by extracting the different switching fields as a function of temperature. This switching diagram can be well explained by considering the competition between energy barrier of layer's magnetization reversal, interlayer exchange coupling, and Zeeman energy.

  4. 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.

  5. Mechanical properties of Pt-Ir and Ni-Ir binary alloys for glass-molding dies coating.

    Science.gov (United States)

    Tseng, Shih-Feng; Lee, Chao-Te; Huang, Kuo-Cheng; Chiang, Donyau; Huang, Chien-Yao; Chou, Chang-Pin

    2011-10-01

    In this study, the different compositions of Pt-Ir and Ni-Ir alloys were deposited by utilizing ion source assisted magnetron sputtering system (ISAMSS). The surface roughness and crystallite size of the Pt-Ir and Ni-Ir coatings were analyzed by atomic force microscopy (AFM) and X-ray diffraction (XRD), respectively. In addition, coatings were soaked at 700 degrees and maintained 10 min under N2 atmosphere using a glass-molding machine. The annealed coatings for oxidation test were examined by energy dispersive X-ray spectrometry (EDS) and for microhardness and reduced modulus test were evaluated by nanoindentation instrucment. The cross-sectional structures between the Pt-Ir and Ni-Ir coating layer and substrates were also examined by field emission scanning electron microscope (FESEM). The results show that surface roughness Ra from 1.25 nm to 3.426 nm was observed with increasing the Ni elements. However, the Ra is less than 2 nm measured in Ir-based coatings doped with Pt concentrations under this study. With increasing Pt and Ni doping, the microhardness of both coatings decreased significantly and the values of reduced modulus of Pt-Ir alloys are larger than that of Ni-Ir alloys. After oxidation process, the oxygen concentration of Pt-Ir coatings is less than that of Ni-Ir coatings and the Pt-Ir coatings exhibit superior properties including oxidation resistance, low surface roughness and high reduced modulus over Ni-Ir coatings, especially for the high Pt concentration coatings such as Pt-Ir 2 (55.25 at.% Pt) and Pt-Ir 3 (79.42 at.% Pt) coatings. The surface roughnesses of all specimens annealed at 700 degrees C were slightly larger than as-deposited coatings. Moreover, due to the serious oxidation occurred in Ni-Ir 3 (73.45 at.% Ni) coatings, the value of reduced modulus of this specimen coating is the lowest and the corrsponding Ra value is the largest compared with the rest of Ir-based coatings in the oxidation testing.

  6. 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.

  7. 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.

  8. 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)

  9. 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%.

  10. 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.

  11. In situ construction of Ir@Pt/C nanoparticles in the cathode layer of membrane electrode assemblies with ultra-low Pt loading and high Pt exposure

    Science.gov (United States)

    Dang, Dai; Zhang, Lei; Zeng, Xiaoyuan; Tian, Xinlong; Qu, Chong; Nan, Haoxiong; Shu, Ting; Hou, Sanying; Yang, Lijun; Zeng, Jianhuang; Liao, Shijun

    2017-07-01

    A novel membrane electrode assemblies (MEAs) with ultra-low Pt loadings and high Pt exposure in the cathode layer is prepared by spraying Ir/C catalyst ink on the membrane surface to form a substrate layer, followed by in situ pulse electrochemical deposition of a Pt shell layer on the Ir core nanoparticles in the substrate layer. It makes the Pt loadings on cathode lower to 0.044 mg/cm2. In our system, the MEA with our novel cathode exhibits excellent performance in a H2/air single fuel cell, which is comparable to that of the MEA prepared with commercial Pt/C catalyst (Johnson Matthey 40% Pt) with Pt loadings of 0.1 mg/cm2. The electrode with core-shell structured catalysts is characterized by X-ray diffraction, X-ray photoelectron spectroscopy, EDS line-scan, and scanning transmission electron microscopy. Based on the characterization results, it is found that the Pt is highly dispersed on the Ir NPs, and the electronic feature of Pt at shell layer can be tuned by the Ir core particle. Furthermore, the DFT calculation results also reveal the interaction between Pt at shell layer and Ir core. This work may provide a novel pathway to realize low Pt and high Pt utilization in low temperature fuel cells.

  12. Carbon-supported Pd-Ir catalyst as anodic catalyst in direct formic acid fuel cell

    Science.gov (United States)

    Wang, Xin; Tang, Yawen; Gao, Ying; Lu, Tianhong

    It was reported for the first time that the electrocatalytic activity of the Carbon-supported Pd-Ir (Pd-Ir/C) catalyst with the suitable atomic ratio of Pd and Ir for the oxidation of formic acid in the direct formic acid fuel cell (DFAFC) is better than that of the Carbon-supported Pd (Pd/C) catalyst, although Ir has no electrocatalytic activity for the oxidation of formic acid. The potential of the anodic peak of formic acid at the Pd-Ir/C catalyst electrode with the atomic ratio of Pd and Ir = 5:1 is 50 mV more negative than that and the peak current density is 13% higher than that at the Pd/C catalyst electrode. This is attributed to that Ir can promote the oxidation of formic acid at Pd through the direct pathway because Ir can decrease the adsorption strength of CO on Pd. However, when the content of Ir in the Pd-Ir/C catalyst is too high the electrocatalytic activity of the Pd-Ir/C catalyst would be decreased because Ir has no electrocatalytic activity for the oxidation of formic acid.

  13. Mesoporous silica nanoparticle supported PdIr bimetal catalyst for selective hydrogenation, and the significant promotional effect of Ir

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Hui; Huang, Chao; Yang, Fan [The Key Laboratory of Fuel Cell Technology of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641 (China); Yang, Xu [Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou (China); Du, Li [The Key Laboratory of Fuel Cell Technology of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641 (China); Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou (China); Liao, Shijun, E-mail: chsjliao@scut.edu.cn [The Key Laboratory of Fuel Cell Technology of Guangdong Province, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510641 (China); Key Laboratory of Renewable Energy, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences, Guangzhou (China)

    2015-12-01

    Graphical abstract: A mesoporous silica nanoparticle (MSN) supported bimetal catalyst, PdIr/MSN, was prepared by a facile impregnation and hydrogen reduction method. The strong promotional effect of Ir was observed and thoroughly investigated. At the optimal molar ratio of Ir to Pd (N{sub Ir}/N{sub Pd} = 0.1), the activity of PdIr{sub 0.1}/MSN was up to eight times and 28 times higher than that of monometallic Pd/MSN and Ir/MSN, respectively. The catalysts were characterized comprehensively by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and hydrogen temperature programmed reduction, which revealed that the promotional effect of Ir may be due to the enhanced dispersion of active components on the MSN, and to the intensified Pd–Ir electronic interaction caused by the addition of Ir. - Highlights: • Mesoporous nanoparticles were synthesized and used as support for metal catalyst. • PdIr bimetallic catalyst exhibited significantly improved hydrogenation activity. • The strong promotion of Ir was recognized firstly and investigated intensively. • PdIr exhibits 18 times higher activity than Pd to the hydrogenation of nitrobenzene. - Abstract: A mesoporous silica nanoparticle (MSN) supported bimetal catalyst, PdIr/MSN, was prepared by a facile impregnation and hydrogen reduction method. The strong promotional effect of Ir was observed and thoroughly investigated. At the optimal molar ratio of Ir to Pd (N{sub Ir}/N{sub Pd} = 0.1), the activity of PdIr{sub 0.1}/MSN was up to eight times and 28 times higher than that of monometallic Pd/MSN and Ir/MSN, respectively. The catalysts were characterized comprehensively by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and hydrogen temperature programmed reduction, which revealed that the promotional effect of Ir may be due to the enhanced dispersion of active components on the MSN, and to the intensified Pd–Ir electronic interaction

  14. 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.

  15. 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.)

  16. 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

  17. 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...

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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...

  6. Composition dependence of phase transformation behavior and shape memory effect of Ti(Pt, Ir)

    Energy Technology Data Exchange (ETDEWEB)

    Yamabe-Mitarai, Y., E-mail: mitarai.yoko@nims.go.jp [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Hara, T.; Kitashima, T. [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Miura, S. [Materials and Process Design, Division of Materials Science and Engineering, Hokkaido University, Sapporo 060-0813 (Japan); Hosoda, H. [Precision and Intelligence Laboratory (P and I Lab), Tokyo Institute of Technology, Yokohama 226-8503 (Japan)

    2013-11-15

    Highlights: ► The partial isothemal section at 1523 K was determined in Ti–Pt–Ir. ► The high-temperature shape memory effect of Ti(Pt, Ir) was investigated. ► The shape recovery ratio was 72% in Ti–10Pt–32Ir after deformation at 1123 K. ► Ir addition to TiPt is effective to improve shape memory effect of TiPt. -- Abstract: The phase transformation and high-temperature shape memory effect of Ti(Pt, Ir) were investigated. First, the Ti-rich phase boundary of Ti(Pt, Ir) was investigated by phase composition analysis by secondary electron microscopy (SEM) using an electron probe X-ray micro analyzer (EPMA), X-ray diffraction analysis and transmission electron microscopy (TEM). Then, the three alloys Ti–35Pt–10Ir, Ti–22Pt–22Ir, and Ti–10Pt–32Ir (at%) close to the phase boundary but in the single phase of Ti(Pt, Ir) were prepared by the arc melting method. The shape memory effect and crystal structure were investigated by compression loading–unloading tests and high-temperature X-ray diffraction analysis, respectively.

  7. 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.

  8. 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.

  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. 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...

  11. 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...

  12. 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.

  13. 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.

  14. Surface enrichment of Pt in stable Pt-Ir nano-alloy particles on MgAl 2 O 4 spinel in oxidizing atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Li, Wei-Zhen; Nie, Lei; Cheng, Yingwen; Kovarik, Libor; Liu, Jun; Wang, Yong

    2017-04-01

    With the capability of MgAl2O4 spinel {111} nano-facets in stabilizing small Rh, Ir and Pt particles, bimetallic Ir-Pt catalysts on the same support were investigated, aiming at further lowering the catalyst cost by substituting expensive Pt with cheaper Ir in the bulk. Small Pt-Ir nano-alloy particles (< 2nm) were successfully stabilized on the spinel {111} nano-facets as expected. Interestingly, methanol oxidative dehydrogenation (ODH) rate on the surface Pt atoms increases with oxidizing aging but decreases upon reducing treatment, where Ir is almost inactive under the same reaction conditions. Up to three times enhancement in Pt exposure was achieved when the sample was oxidized at 800 °C in air for 1 week and subsequently reduced by H2 for 2 h, demonstrating successful surface enrichment of Pt on Pt-Ir nano-alloy particles. A dynamic stabilization mechanism involving wetting\

  15. 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

  16. 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.

  17. 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)

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Microemulsion Preparation and Electrochemical Characterization of Pt/C,PtIr/C Electrocatalysts%微乳法合成Pt/C、PtIr/C催化剂及其电化学性能表征

    Institute of Scientific and Technical Information of China (English)

    曾亚平; 隋升

    2011-01-01

    以碳纳米粉(XC-72R)作为载体,以3种不同方法合成Pt/C负载型催化剂.并由X射线衍射(XRD)、透射电镜(TEM)、循环伏安法(CV)、恒电位测试(Potentiostatic)以及线性极化分析(Potentiodynamic polarization)等方法表征该催化剂.结果表明,由微乳法制得的负载型催化剂Pt/C,活性组分的颗粒尺寸为5~10 nm,均匀地分散在载体表面,电化学性能良好.而以同一微乳法由异辛烷/Triton X100/正己醇/水体系合成的含有不同Pt、Ir比例的负载型的Pt100-xIrx/C催化剂,则其中以Pt85Ir15表现出更为良好的电化学综合性能.%The Pt/C electrocatalysts were prepared by three different systems and the PtIr/C electrocatalysts were prepared with four different Ir contents.The samples were characterized by X-ray diffraction(XRD),transmission electron microscope(TEM),cyclic voltammetry(CV),potentiostatic and potentiodynamic polarizations measurements.The experimental results confirmed that the electrocatalyst particles prepared by the microemulsion method were well distributed on XC-72R supports with the active particle sizes of 5~10 nm and good electrocatalysts activity.The Pt85Ir15/C electrocatalysts showed the highest overall electrochemical activity in unitized regenerative fuel cell.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Enhanced formic acid electro-oxidation reaction on ternary Pd-Ir-Cu/C catalyst

    Science.gov (United States)

    Chen, Jinwei; Zhang, Jie; Jiang, Yiwu; Yang, Liu; Zhong, Jing; Wang, Gang; Wang, Ruilin

    2015-12-01

    Aim to further reduce the cost of Pd-Ir for formic acid electro-oxidation (FAEO), the Cu was used to construct a ternary metallic alloy catalyst. The prepared catalysts are characterized using XRD, TGA, EDX, TEM, XPS, CO-stripping, cyclic voltammetry and chronoamperometry. It is found that the Pd18Ir1Cu6 nanoparticles with a mean size of 3.3 nm are highly dispersed on carbon support. Componential distributions on catalyst are consistent with initial contents. Electrochemical measurements show that the PdIrCu/C catalyst exhibits the highest activity for FAEO. The mass activity of Pd in Pd18Ir1Cu6/C at 0.16 V (vs. SCE) is about 1.47, 1.62 and 2.08 times as high as that of Pd18Cu6/C, Pd18Ir1/C and Pd/C, respectively. The activity enhancement of PdIrCu/C should be attributed to the weakened CO adsorption strength and the removal of adsorbed intermediates at lower potential with the addition of Cu and Ir.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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...

  14. 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.

  15. 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.

  16. 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.

  17. Communication: Enhanced oxygen reduction reaction and its underlying mechanism in Pd-Ir-Co trimetallic alloys

    Science.gov (United States)

    Ham, Hyung Chul; Manogaran, Dhivya; Lee, Kang Hee; Kwon, Kyungjung; Jin, Seon-ah; You, Dae Jong; Pak, Chanho; Hwang, Gyeong S.

    2013-11-01

    Based on a combined density functional theory and experimental study, we present that the electrochemical activity of Pd3Co alloy catalysts toward oxygen reduction reaction (ORR) can be enhanced by adding a small amount of Ir. While Ir tends to favorably exist in the subsurface layers, the underlying Ir atoms are found to cause a substantial modification in the surface electronic structure. As a consequence, we find that the activation barriers of O/OH hydrogenation reactions are noticeably lowered, which would be mainly responsible for the enhanced ORR activity. Furthermore, our study suggests that the presence of Ir in the near-surface region can suppress Co out-diffusion from the Pd3Co substrate, thereby improving the durability of Pd-Ir-Co catalysts. We also discuss the relative roles played by Ir and Co in enhancing the ORR activity relative to monometallic Pd catalysts.

  18. Structural and Electrocatalytic Properties of PtIrCo/C Catalysts for Oxygen Reduction Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Loukrakpam, Rameshwori; Wanjala, Bridgid N.; Yin, Jun; Fang, Bin; Luo, Jin; Shao, Minhua; Protsailo, Lesia; Kawamura, Tetsuo; Chen, Yongsheng; Petkov, Valeri; Zhong, Chuan-Jian (Binghamton); (Penn); (UTC Power); (Toyota); (CMU)

    2015-10-15

    This paper describes the results of an investigation of the synthesis of PtIrCo nanoparticles (2-3 nm) for electrocatalytic oxygen reduction reaction. The carbon-supported PtIrCo catalysts (PtIrCo/C) were thermally treated at temperatures ranging from 400 to 900 C. The size, composition, and atomic-scale structures of the PtIrCo/C catalysts were characterized for establishing their correlation with the electrocatalytic activity toward oxygen reduction reaction. The specific activity was found to increase by a factor of 3-5 for the PtIrCo/C catalysts in comparison with Pt/C catalysts. A correlation was identified between the specific activity and the nanoparticle's fcc-type lattice parameter. The specific activity increases whereas the fcc-type lattice parameter decreases with the thermal treatment temperature. This correlation was further substantiated by analyzing the interatomic spatial parameters in the trimetallic nanoparticles based on X-ray absorption fine structure spectroscopic and high-energy XRD experiments. Implications of these findings, along with the durability of the catalysts, to the design of active electrocatalysts were also discussed.

  19. 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.

  20. 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

  1. 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.

  2. Preparation of IrO2 nanoparticles with SBA-15 template and its supported Pt nanocomposite as bifunctional oxygen catalyst

    Science.gov (United States)

    Kong, Fan-Dong; Liu, Jing; Ling, Ai-Xia; Xu, Zhi-Qiang; Wang, Hui-Yun; Kong, Qing-Sheng

    2015-12-01

    In the present work, we report the syntheses of IrO2 nanoparticles with SBA-15 template (s-IrO2), and s-IrO2 supported Pt nanocomposite (Pt/s-IrO2) as bifunctional oxygen catalyst. Physical characterizations including X-ray diffraction and transmission electron microscopy demonstrate that s-IrO2 catalyst has excellent uniformity and regularity in particle shape and much ordered distribution in geometric space, and Pt/s-IrO2 catalyst shows a uniform Pt dispersion on the surface of the s-IrO2 particles. Electrochemical analyses prove that s-IrO2 catalyst possesses superior OER activity at operating potentials; and that Pt/s-IrO2 catalyst, in comparison to Pt/commercial IrO2, has higher ESA value and ORR catalytic performance with a mechanism of four-electron pathway and a high ORR efficiency. And as a bifunctional oxygen catalyst, Pt/s-IrO2 also exhibits more remarkable OER performance than the commercial one. The s-IrO2 nanoparticles will be a promising active component (for OER), and suitable for Pt support (for ORR).

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. In situ scanning FTIR microscopy and IR imaging of Pt electrode surface towards CO adsorption

    Institute of Scientific and Technical Information of China (English)

    孙世刚; 洪双进; 陈声培; 卢国强; 戴鸿平; 肖晓银

    1999-01-01

    In situ scanning FTIR microscopy was built up for the first time in the present work, which consists of an FTIR apparatus, an IR microscope, an X-Y mapping stage, and the specially designed electrochemical IR cell and computer software. It has been demonstrated that this new space-resolvd in situ IR technique can be used to study vibration properties of micro-area, and to perform IR imaging of electrode surface. The chemical image obtained using this technique fur CO adsorption on Pt electrode illustrated, at a space-resolution of 10-2 cm, the inhomogeneity and the distribution of reactivity of micro-area of electrode surface.

  8. 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.

  9. NMR Study of Layered Transition Metal Ditelluride (Ir,Pt)Te2

    Science.gov (United States)

    Magishi, K.; Saito, T.; Koyama, K.; Matsumoto, N.; Nagata, S.

    2012-12-01

    We report the results of 125Te and 195Pt NMR measurements on (Ir,Pt)Te2 in order to elucidate the characteristic electronic states. For PtTe2, the NMR spectrum exhibits a sharp line, which shows the uniaxially symmetric powder pattern due to the anisotropic Knight shift. The Knight shift is almost independent of temperature and is larger than that for IrTe2. Also, the nuclear spin-lattice relaxation rate 1/T1 of PtTe2 is proportional to the temperature in a wide temperature range, that is, obeys the Korringa relation as expected for simple metallic systems. From the analyses of the Knight shift and 1/T1, it is suggested that the antiferromagnetic correlations slightly exist.

  10. 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.

  11. Investigation of IrO2/Pt Electrocatalysts in Unitized Regenerative Fuel Cells

    Directory of Open Access Journals (Sweden)

    V. Baglio

    2011-01-01

    Full Text Available IrO2/Pt catalysts (at different concentrations were synthesized by incipient wetness technique and characterized by XRD, XRF, and SEM. Water electrolysis/fuel cell performances were evaluated in a 5 cm2 single cell under Unitized Regenerative Fuel Cell (URFC configuration. The IrO2/Pt composition of 14/86 showed the highest performance for water electrolysis and the lowest one as fuel cell. It is derived that for fuel cell operation an excess of Pt favours the oxygen reduction process whereas IrO2 promotes oxygen evolution. From the present results, it appears that the diffusion characteristics and the reaction rate in fuel cell mode are significantly lower than in the electrolyser mode. This requires the enhancement of the gas diffusion properties of the electrodes and the catalytic properties for cathode operation in fuel cells.

  12. 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.

  13. 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.

  14. Crumpled rGO-supported Pt-Ir bifunctional catalyst prepared by spray pyrolysis for unitized regenerative fuel cells

    Science.gov (United States)

    Kim, In Gyeom; Nah, In Wook; Oh, In-Hwan; Park, Sehkyu

    2017-10-01

    Three-dimensional (3D) crumpled reduced graphene oxide supported Pt-Ir alloys that served as bifunctional oxygen catalysts for use in untized regenerative fuel cells were synthesized by a facile spray pyrolysis method. Pt-Ir catalysts supported on rGO (Pt-Ir/rGOs) were physically characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA) to observe change in composition by heat treatment, alloying, and morphological transition of the catalysts. Their catalytic activities and stabilities for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) conditions were electrochemically investigated using cyclic voltammetry (CV), linear sweep voltammetry (LSV), potential cycling and hold tests on the rotating disk electrode (RDE). Pt-Ir/rGO with no post heat-treatment (Pt-Ir/rGO_NP) showed a lower activity for ORR and OER although metal nanoparticles decorated on the support are relatively small. However, Pt-Ir/rGO showed remarkably enhanced activity following heat treatment, depending on temperature. Pt-Ir/rGO heat-treated at 600 °C after spray pyrolysis (Pt-Ir/rGO_P600) exhibited a higher activity and stability than a commercially available Pt/C catalyst kept under the ORR condition, and it also revealed a comparable OER activity and durability versus the commercial unsupported Ir catalyst.

  15. 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.

  16. 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.

  17. Direct ethanol fuel cell, CO and ethanol oxidation on core-shell C/Ni-Au-[Pt and (Pt- Ir)] catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, C.A.D.; Tremiliosi-Filho, G. [Universidade de Sao Paulo (IQSC/USP), Sao Carlos, SP (Brazil). Inst. de Quimica], Email: cesaraug@sc.usp.br; Kokoh, K.B.; Coutanceau, C.; Baranton, S. [Universite de Poitiers (France). Lab. de Catalyse en Chimie Organique (LACCO). Equipe Electrocatalyse

    2010-07-01

    In this paper presents to study of the Pt and Pt-Ir monolayer that were deposited on core-shell Ni-Au nanoparticles supported on carbon. Catalysts with the following molar ratios were prepared: Pt and Pt{sub 65}Ir{sub 35}, Pt{sub 75}Ir{sub 2}5, Pt{sub 80}Ir{sub 20} and Pt{sub 85}Ir{sub 15}. The means particle sizes were in the range of 2 - 6 nm for all catalysts. The electrochemical properties examined in the ethanol and CO oxidation by cyclic voltammetry, and In situ IR spectroscopy measurements (SPAIRS) enabled to determine intermediates and reaction products as a function of the metallic compositions of catalysts. All of the catalysts were tested as anodes of a single direct ethanol fuel cell (DEFC) tests in 1.0 M ethanol solution. As a result, higher power densities were obtained with the core-shell particles in comparison to those issued from the commercial catalyst (Pt-ETEK). Thus, the maximum power densities at 90 deg C for the different systems are: (i) commercial C/Pt catalyst (E-TEK): ca. 0.010 W cm{sup -2}, C/Ni-Au-(Pt{sub 85}Ir{sub 15}): ca. 0.013 W cm{sup -2} and C/Ni-Au-Pt: ca. 0.018 W cm{sup -2} (all core-shell systems were normalization by Pt load). As a result, the performance of the core-shell nanoparticles is much better than that produced for the commercial catalyst and the C/Ni-Au-Pt system showed the best performance. (author)

  18. 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...

  19. 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.

  20. Electrolysis of ammonia for hydrogen production catalyzed by Pt and Pt-Ir deposited on nickel foam

    Institute of Scientific and Technical Information of China (English)

    Min; Jiang; Dandan; Zhu; Xuebo; Zhao

    2014-01-01

    Electrolysis of ammonia in alkaline electrolyte solution was applied for the production of hydrogen. Both Pt-loaded Ni foam and Pt-Ir loaded Ni foam electrodes were prepared by electrodeposition and served as anode and cathode in ammonia electrolytic cell, respectively. The electrochemical behaviors of ammonia in KOH solution were individually investigated via cyclic voltammetry on three electrodes, i.e. bare Ni foam electrode, Pt-loaded Ni foam electrode and Pt-Ir loaded Ni foam electrode. The morphology and composition of the prepared Ni foam electrode were analyzed by scanning electron microscopy(SEM) and X-ray diffraction(XRD). Effects of the concentration of electrolyte solution and temperature of electrolytic cell on the electrolysis reaction were examined in order to enhance the efficiency of ammonia electrolysis. The competition of ammonia electrolysis and water electrolysis in the same alkaline solution was firstly proposed to explain the changes of cell voltage with the electrolysis proceeding. At varying current densities, different cell voltages could be obtained from galvanostatic curves.The low cell voltage of 0.58 V, which is less than the practical electrolysis voltage of water(1.6 V), can be obtained at a current density of2.5 mA/cm2. Based on some experimental parameters, such as the applied current, the resulting cell voltage and output of hydrogen gas, the power consumption per gram of H2produced can be estimated.

  1. 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...

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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)

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. Chemonuclear studies for identification for new production routes for the therapeutically useful radionuclides {sup 140}Nd, {sup 192}Ir, {sup 191}Pt, {sup 193m}Pt, und {sup 195m}Pt; Kernchemische Studien zur Entwicklung neuerer Produktionsverfahren fuer die therapierelevanten Radionuklide {sup 140}Nd, {sup 192}Ir, {sup 191}Pt, {sup 193m}Pt, und {sup 195m}Pt

    Energy Technology Data Exchange (ETDEWEB)

    Hilgers, K.

    2005-12-15

    New production routes for the therapeutically useful radionuclides {sup 140}Nd, {sup 192}Ir, {sup 191}Pt, {sup 193m}Pt and {sup 195m}Pt were investigated. Cross section data were measured using the stacked-foil technique and compared with theoretical calculations. A production method for the platinum nuclides was developed. The {sup 141}Pr(p, 2n){sup 140}Nd and {sup nat}Ce({sup 3}He, xn){sup 140}Nd reactions were investigated for production of {sup 140}Nd. Cross section data of nuclear reactions leading to the side products {sup 141}Nd, {sup 139}Nd and {sup 139}Ce could also be achieved. The experimental data were compared with theoretical calculations using the code ALICE-IPPE. A comparison of the calculated thick target yields showed that the {sup 141}Pr(p, 2n){sup 140}Nd reaction gives a higher yield. The {sup 192}Os(p, n){sup 192}Ir reaction was examined in the context of the production of {sup 192}Ir. Cross section data were determined and compared with theoretical calculations using the codes ALICE-IPPE and EMPIRE II. The yield of this reaction was compared with the yield of the reactor production of this nuclide. The reactor production seems to be more suitable because of a higher purity and yield. Cross section data were measured for the {sup 192}Os({alpha}, n){sup 195m}Pt, {sup 192}Os({alpha}, 3n){sup 193m}Pt and {sup 192}Os({sup 3}He, 4n){sup 191}Pt reactions. The activity of {sup 193m}Pt and {sup 195m}Pt was determined by X-ray spectroscopy after a chemical separation procedure. The ALICE-IPPE code was found to be inappropriate to reproduce the experimental values. The calculated yields were compared with the yields of other reactions, especially the reactor production of {sup 195m}Pt. The yield of the {sup 192}Os({alpha}, n){sup 195m}Pt reaction is lower compared to the yield of the reactor production, but offers lower target costs and higher specific activity. A production method for {sup 193m}Pt and {sup 195m}Pt was developed. Batch yields of 0.9 MBq

  18. Chemonuclear studies for identification for new production routes for the therapeutically useful radionuclides {sup 140}Nd, {sup 192}Ir, {sup 191}Pt, {sup 193m}Pt, und {sup 195m}Pt; Kernchemische Studien zur Entwicklung neuerer Produktionsverfahren fuer die therapierelevanten Radionuklide {sup 140}Nd, {sup 192}Ir, {sup 191}Pt, {sup 193m}Pt, und {sup 195m}Pt

    Energy Technology Data Exchange (ETDEWEB)

    Hilgers, K.

    2005-12-15

    New production routes for the therapeutically useful radionuclides {sup 140}Nd, {sup 192}Ir, {sup 191}Pt, {sup 193m}Pt and {sup 195m}Pt were investigated. Cross section data were measured using the stacked-foil technique and compared with theoretical calculations. A production method for the platinum nuclides was developed. The {sup 141}Pr(p, 2n){sup 140}Nd and {sup nat}Ce({sup 3}He, xn){sup 140}Nd reactions were investigated for production of {sup 140}Nd. Cross section data of nuclear reactions leading to the side products {sup 141}Nd, {sup 139}Nd and {sup 139}Ce could also be achieved. The experimental data were compared with theoretical calculations using the code ALICE-IPPE. A comparison of the calculated thick target yields showed that the {sup 141}Pr(p, 2n){sup 140}Nd reaction gives a higher yield. The {sup 192}Os(p, n){sup 192}Ir reaction was examined in the context of the production of {sup 192}Ir. Cross section data were determined and compared with theoretical calculations using the codes ALICE-IPPE and EMPIRE II. The yield of this reaction was compared with the yield of the reactor production of this nuclide. The reactor production seems to be more suitable because of a higher purity and yield. Cross section data were measured for the {sup 192}Os({alpha}, n){sup 195m}Pt, {sup 192}Os({alpha}, 3n){sup 193m}Pt and {sup 192}Os({sup 3}He, 4n){sup 191}Pt reactions. The activity of {sup 193m}Pt and {sup 195m}Pt was determined by X-ray spectroscopy after a chemical separation procedure. The ALICE-IPPE code was found to be inappropriate to reproduce the experimental values. The calculated yields were compared with the yields of other reactions, especially the reactor production of {sup 195m}Pt. The yield of the {sup 192}Os({alpha}, n){sup 195m}Pt reaction is lower compared to the yield of the reactor production, but offers lower target costs and higher specific activity. A production method for {sup 193m}Pt and {sup 195m}Pt was developed. Batch yields of 0.9 MBq

  19. 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.

  20. 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.

  1. 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).

  2. 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.

  3. 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

  4. 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.

  5. 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)

  6. 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 ...

  7. 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 ...

  8. 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.

  9. 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:

  10. 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.

  11. 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.

  12. 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.

  13. CO adsorption over Pd nanoparticles: A general framework for IR simulations on nanoparticles

    Science.gov (United States)

    Zeinalipour-Yazdi, Constantinos D.; Willock, David J.; Thomas, Liam; Wilson, Karen; Lee, Adam F.

    2016-04-01

    CO vibrational spectra over catalytic nanoparticles under high coverages/pressures are discussed from a DFT perspective. Hybrid B3LYP and PBE DFT calculations of CO chemisorbed over Pd4 and Pd13 nanoclusters, and a 1.1 nm Pd38 nanoparticle, have been performed in order to simulate the corresponding coverage dependent infrared (IR) absorption spectra, and hence provide a quantitative foundation for the interpretation of experimental IR spectra of CO over Pd nanocatalysts. B3LYP simulated IR intensities are used to quantify site occupation numbers through comparison with experimental DRIFTS spectra, allowing an atomistic model of CO surface coverage to be created. DFT adsorption energetics for low CO coverage (θ → 0) suggest the CO binding strength follows the order hollow > bridge > linear, even for dispersion-corrected functionals for sub-nanometre Pd nanoclusters. For a Pd38 nanoparticle, hollow and bridge-bound are energetically similar (hollow ≈ bridge > atop). It is well known that this ordering has not been found at the high coverages used experimentally, wherein atop CO has a much higher population than observed over Pd(111), confirmed by our DRIFTS spectra for Pd nanoparticles supported on a KIT-6 silica, and hence site populations were calculated through a comparison of DFT and spectroscopic data. At high CO coverage (θ = 1), all three adsorbed CO species co-exist on Pd38, and their interdiffusion is thermally feasible at STP. Under such high surface coverages, DFT predicts that bridge-bound CO chains are thermodynamically stable and isoenergetic to an entirely hollow bound Pd/CO system. The Pd38 nanoparticle undergoes a linear (3.5%), isotropic expansion with increasing CO coverage, accompanied by 63 and 30 cm- 1 blue-shifts of hollow and linear bound CO respectively.

  14. 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.

  15. 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...

  16. 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.

  17. 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...

  18. 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.

  19. 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''.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. Phase relations in the metal-rich portions of the phase system Pt-Ir-Fe-S at 1000 degrees C and 1100 degrees C

    DEFF Research Database (Denmark)

    Makovicky, E.; Karup-Møller, Sven

    2000-01-01

    with gamma-(Pt,Fe), Pt3Fe and PtFe which dissolve respectively at least 5.1, 29.3 and 24.0 at.% Ir at 1100 degreesC (2.2, 23.6 and less than or equal to 17.2 at.% Ir at 1000 degreesC). Gaps between the nearly Ir-free Pt-Fe alloys gamma (Pt,Fe), Pt3Fe s.s., PtFe s.s. and gamma (Fe,Pt) were estimated as 20...

  6. 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.

  7. 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.

  8. 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.

  9. Enhanced formic acid electro-oxidation on PdIr nanoparticles prepared by ethylene glycol-assisted NaBH4 reduction process.

    Science.gov (United States)

    Chen, Jinwei; Wang, Gang; Wang, Xueqin; Tian, Jing; Zhu, Shifu; Wang, Ruilin

    2013-10-01

    The carbon supported PdIr nanoparticles were synthesized by an ethylene glycol-assisted NaBH4 reduction method, and the mass ratio of Pd to Ir was optimized. Then, their performances for formic acid electro-oxidation (FAEO) were investigated. The XRD and TEM characterizations show that the prepared PdIr/C catalysts have small mean size and good dispersion of PdIr nanoparticles. The electrochemical measurements demonstrate that the PdIr/C catalysts have greatly enhanced performance for FAEO compared with the Pd/C catalyst. The PdIr/C catalysts show higher current density and more than 50 mV negative shift of onset and peak potential than that of the Pd/C catalyst. With the optimal mass ratio of Pd to Ir, the PdIr/C-5 catalyst presents the highest catalytic activity for FAEO.

  10. 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.

  11. 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.

  12. 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.

  13. Four-point probe resistance measurements using PtIr-coated carbon nanotube tips.

    Science.gov (United States)

    Yoshimoto, Shinya; Murata, Yuya; Kubo, Keisuke; Tomita, Kazuhiro; Motoyoshi, Kenji; Kimura, Takehiko; Okino, Hiroyuki; Hobara, Rei; Matsuda, Iwao; Honda, Shin-Ichi; Katayama, Mitsuhiro; Hasegawa, Shuji

    2007-04-01

    We performed four-terminal conductivity measurements on a CoSi2 nanowire (NW) at room temperature by using PtIr-coated carbon nanotube (CNT) tips in a four-tip scanning tunneling microscope. The physical stability and high aspect ratio of the CNT tips made it possible to reduce the probe spacing down to ca. 30 nm. The probe-spacing dependence of resistance showed diffusive transport even at 30 nm and no current leakage to the Si substrate.

  14. 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.

  15. Pd-Ir Core-Shell Nanocubes: A Type of Highly Efficient and Versatile Peroxidase Mimic.

    Science.gov (United States)

    Xia, Xiaohu; Zhang, Jingtuo; Lu, Ning; Kim, Moon J; Ghale, Kushal; Xu, Ye; McKenzie, Erin; Liu, Jiabin; Ye, Haihang

    2015-10-27

    Peroxidase mimics with dimensions on the nanoscale have received great interest as emerging artificial enzymes for biomedicine and environmental protection. While a variety of peroxidase mimics have been actively developed recently, limited progress has been made toward improving their catalytic efficiency. In this study, we report a type of highly efficient peroxidase mimic that was engineered by depositing Ir atoms as ultrathin skins (a few atomic layers) on Pd nanocubes (i.e., Pd-Ir cubes). The Pd-Ir cubes exhibited significantly enhanced efficiency, with catalytic constants more than 20- and 400-fold higher than those of the initial Pd cubes and horseradish peroxidase (HRP), respectively. As a proof-of-concept demonstration, the Pd-Ir cubes were applied to the colorimetric enzyme-linked immunosorbent assay (ELISA) of human prostate surface antigen (PSA) with a detection limit of 0.67 pg/mL, which is ∼110-fold lower than that of the conventional HRP-based ELISA using the same set of antibodies and the same procedure.

  16. 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).

  17. 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.

  18. 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 Me2SC(H)C(O)C6H4-m-Br (2). This ligand was reacted with [MCl2(cod)] (M = Pd, Pt; cod = 1,5-cyclooctadiene) to form the new cis- and trans-[MCl2(ylide)2] (M = Pd (cis- and trans-3), Pt (cis- and trans-4)) complexes. Characterization of the obtained compounds was performed by elemental analysis, IR, 1H and 13C NMR. Recrystallization of dichlorobis(ylide) palladium(II) and platinum(II) complexes from DMSO solution yielded the crystalline products, which X-ray diffraction data revealed that the both compounds were crystallized as cis-[MCl2(ylide)(DMSO)] (M = Pd (5), Pt (6)) complexes. Also, a theoretical study on structure and nature of the Msbnd C bonding between the Y ligand (ylide) and [MCl2·DMSO] fragments in [YMCl2·DMSO] (M = Pd, Pt) complexes has been reported via NBO and energy-decomposition analysis (EDA). Furthermore, the palladium catalyzed Suzuki-Miyaura reaction of various aryl chlorides with arylboronic acids was performed. The results showed that the Pd(II) complexes cis- and trans-3 catalyzed efficiently coupling reactions at low catalyst loading and short reaction time.

  19. 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.

  20. Large enhancement of Blocking temperature by control of interfacial structures in Pt/NiFe/IrMn/MgO/Pt multilayers

    Directory of Open Access Journals (Sweden)

    Xi Chen

    2015-09-01

    Full Text Available The Blocking temperature (TB of Pt/NiFe/IrMn/MgO/Pt multilayers was greatly enhanced from far below room temperature (RT to above RT by inserting 1 nm thick Mg layer at IrMn/MgO interface. Furthermore, the exchange bias field (Heb was increased as well by the control of interfacial structures. The evidence for a significant fraction of Mn-O bonding at IrMn/MgO interface without Mg insertion layer was provided by X-ray photoelectron spectroscopy. The bonding between Mn and O can decrease the antiferromagnetism of IrMn film, leading to lower value of TB in Pt/NiFe/IrMn/MgO/Pt multilayers. Ultrathin Mg film inserted at IrMn/MgO interface acting as an oxygen sinking layer can suppress the oxidation reactions between Mn and O and reduce the formation of Mn-O bonding greatly. The oxidation suppression results in the recovery of the antiferromagnetism of IrMn film, which can enhance TB and Heb. Furthermore, the high resolution transmission electron microscopy demonstrates that the Mg insertion layer can efficiently promote a high-quality MgO (200 texture. This study will enhance the understanding of physics in antiferromagnet-based spintronic devices.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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...

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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 ...

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  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. Pt-Ir-SnO2/C Electrocatalysts for Ethanol Oxidation in Acidic Media%酸性介质中Pt-Ir-SnO2/C电催化氧化乙醇

    Institute of Scientific and Technical Information of China (English)

    赵莲花; 光岛重德; 石原顕光; 松泽幸一; 太田健一郎

    2011-01-01

    A series of Pt-Ir-SnCVC catalysts were synthesized by a modified Bonnemann method. An electrochemical study showed that the Pt-Iro.o7-Sn02/C catalyst had a three times higher ethanol oxidation current and a two times higher CO2 formation selectivity compared with the Pt/C catalyst under an application voltage of 0.5 V vs the RHE at 25 ℃. This demonstrates that the Pt-Ir0.07-SnO2/C catalyst is a potentially ideal ethanol oxidation catalyst for direct ethanol fuel cells.%采用改良的B(o)nnemann法合成了一系列新型炭载Pt-Ir-SnO2催化剂.电化学结果表明,在室温下新型电催化剂Pt-Iro.07-SnO2/C可有效断裂乙醇中C-C键,促进乙醇在低电位下完全氧化,其CO2生成量为Pt/C催化剂的2倍.另外,该三元催化剂显著增强乙醇的氧化反应,在室温下其电流密度为Pt/C的3倍.

  20. Complexes of Pd(II) and Pt(II) with 9-Aminoacridine: Reactions with DNA and Study of Their Antiproliferative Activity

    Science.gov (United States)

    Riera, X.; Moreno, V.; Ciudad, C. J.; Noe, V.; Font-Bardía, M.; Solans, X.

    2007-01-01

    Four new metal complexes {M = Pd(II) or Pt(II)} containing the ligand 9-aminoacridine (9AA) were prepared. The compounds were characterized by FT-IR and 1H, 13C, and 195Pt NMR spectroscopies. Crystal structure of the palladium complex of formulae [Pd(9AA)(μ-Cl)]2 · 2DMF was determined by X-ray diffraction. Two 9-acridine molecules in the imine form bind symmetrically to the metal ions in a bidentate fashion through the imine nitrogen atom and the C(1) atom of the aminoacridine closing a new five-membered ring. By reaction with phosphine or pyridine, the Cl bridges broke and compounds with general formulae [Pd(9AA)Cl(L)] (where L = PPh3 or py) were formed. A mononuclear complex of platinum of formulae [Pt(9AA)Cl(DMSO)] was also obtained by direct reaction of 9-aminoacridine and the complex [PtCl2(DMSO2]. The capacity of the compounds to modify the secondary and tertiary structures of DNA was evaluated by means of circular dichroism and electrophoretic mobility. Both palladium and platinum compounds proved active in the modification of both the secondary and tertiary DNA structures. AFM images showed noticeable modifications of the morphology of the plasmid pBR322 DNA by the compounds probably due to the intercalation of the complexes between base pairs of the DNA molecule. Finally, the palladium complex was tested for antiproliferative activity against three different human tumor cell lines. The results suggest that the palladium complex of formula [Pd(9AA)(μ-Cl)]2 has significant antiproliferative activity, although it is less active than cisplatin. PMID:18364995

  1. 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.

  2. 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.

  3. Probing the electronic communication of the isocyanide bridge through the luminescence properties of the d9-d9 [ClPt(mu-dppm)2Pt(C triple bond N-PCP)]+ and A-Frame [ClPd(mu-dppm)2(mu-C=N-PCP)PdCl] complexes.

    Science.gov (United States)

    Clément, Sébastien; Aly, Shawkat Mohammed; Fortin, Daniel; Guyard, Laurent; Knorr, Michael; Abd-El-Aziz, Alaa S; Harvey, Pierre D

    2008-12-01

    The homodinuclear d9-d9 ClM(mu-dppm)2MCl2 complexes, 1 (M ) Pt) and 2 (M ) Pd) react with the conjugated and luminescent PCP-NC ligand (3, PCP ) [2.2]paracyclophane) to provide the corresponding d9-d9 terminal[ClPt(mu-dppm)2Pt(CNsPCP)]Cl (4) and d8-d8 A-frame [ClPd(mu-dppm)2(mu-CdNsPCP)PdCl] (5) isocyanide complexes, respectively. These two bimetallic complexes were characterized by IR, 1H, and 31P{1H} NMR and bychemical analysis. IR data (nu(CN) bridging vs terminal) reveal a terminal isocyanide bonding mode for 4 (2147cm(-1)) and an A-frame structure for 5 (1616 cm(-1)). The optical and emission properties of the free isocyanide 3as well as those of the homodinuclear complexes 4 and 5 were studied by UV-visible and luminescence spectroscopy and by photophysical measurements. The unexpected presence of simultaneous intraligand pipi* fluorescence and phosphorescence attributable to the organic PCP-NC ligand, as well as luminescence from the inorganic M2-bonded Pt2(mu-dppm)2 center arising from a lower energy excited LMCT state (ligand-to-metal-charge-transfer) for4 at 77 K, indicates a weak conjugation between the two chromophores and an absence of efficient singlet andtriplet energy transfers. For 5, only the fluorescence and phosphorescence bands of the PCP-NC ligand are observed [since the A-frame XPd(mu-dppm)2(mu-L)PdX (L ) isocyanide, X ) halide) is not luminescent], stressing that the NtC bridge exhibits modest electronic communication properties.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. IrPd nanoalloys: simulations, from surface segregation to local electronic properties

    Energy Technology Data Exchange (ETDEWEB)

    Andriamiharintsoa, T. H. [Institut de Physique et Chimie des Matériaux de Strasbourg CNRS-UDS UMR 7504 (France); Rakotomahevitra, A. [Institut pour la Maîtrise de l’Énergie, Faculté des sciences d’Antananarivo (Madagascar); Piccolo, L. [Institut de Recherches sur la Catalyse et l’Environnement de Lyon IRCELYON, UMR 5256 CNRS and Université Lyon 1 (France); Goyhenex, C., E-mail: christine.goyhenex@ipcms.unistra.fr [Institut de Physique et Chimie des Matériaux de Strasbourg CNRS-UDS UMR 7504 (France)

    2015-05-15

    Using semi-empirical modeling, namely tight-binding at different levels of accuracy, the chemical, crystallographic, and electronic structures of bimetallic IrPd nanoparticles are characterized. For the purpose, model cuboctahedral particles containing 561 atoms are considered. Atomistic simulations show that core–shell nanoparticles are highly stable, with a strong surface segregation of Pd, at least for one atomic shell thickness. Within self-consistent tight-binding calculations founded on the density functional theory, an accurate insight is given into the electronic structure of these materials which have a high potential as catalysts.

  10. Supergene neoformation of Pt-Ir-Fe-Ni alloys: multistage grains explain nugget formation in Ni-laterites

    Science.gov (United States)

    Aiglsperger, Thomas; Proenza, Joaquín A.; Font-Bardia, Mercè; Baurier-Aymat, Sandra; Galí, Salvador; Lewis, John F.; Longo, Francisco

    2016-11-01

    Ni-laterites from the Dominican Republic host rare but extremely platinum-group element (PGE)-rich chromitites (up to 17.5 ppm) without economic significance. These chromitites occur either included in saprolite (beneath the Mg discontinuity) or as `floating chromitites' within limonite (above the Mg discontinuity). Both chromitite types have similar iridium-group PGE (IPGE)-enriched chondrite normalized patterns; however, chromitites included in limonite show a pronounced positive Pt anomaly. Investigation of heavy mineral concentrates, obtained via hydroseparation techniques, led to the discovery of multistage PGE grains: (i) Os-Ru-Fe-(Ir) grains of porous appearance are overgrown by (ii) Ni-Fe-Ir and Ir-Fe-Ni-(Pt) phases which are overgrown by (iii) Pt-Ir-Fe-Ni mineral phases. Whereas Ir-dominated overgrowths prevail in chromitites from the saprolite, Pt-dominated overgrowths are observed within floating chromitites. The following formation model for multistage PGE grains is discussed: (i) hypogene platinum-group minerals (PGM) (e.g. laurite) are transformed to secondary PGM by desulphurization during serpentinization; (ii) at the stages of serpentinization and/or at the early stages of lateritization, Ir is mobilized and recrystallizes on porous surfaces of secondary PGM (serving as a natural catalyst) and (iii) at the late stages of lateritization, biogenic mediated neoformation (and accumulation) of Pt-Ir-Fe-Ni nanoparticles occurs. The evidence presented in this work demonstrates that in situ growth of Pt-Ir-Fe-Ni alloy nuggets of isometric symmetry is possible within Ni-laterites from the Dominican Republic.

  11. Spectroscopic, thermal characterization and cytotoxic activity of bi-, tri- and tetra-nuclear Pd(II) and Pt(II) complexes with diSchiff base ligands

    Science.gov (United States)

    Hegazy, Wael Hussein

    2014-10-01

    In this paper; new di-, tri-, and tetra-nuclear Pd(II) and Pt(II) complexes of N,N‧-bis(3,4-dihydroxybenzylidene)ethan-1,2-diamine (EDH4), N,N‧-bis(3,4-dihydroxy-benzylidene)-benzene-1,2-diamine (PDH4) and N,N‧-bis-(3,4-dihydroxybenzylidene)-4,5-dimethyl-1,2-diamine (MPDH4) ligands were synthesized by two different methods. The first method involve the synthesis of the three ligands from condensation reaction of 3,4-dihydroxybenzaldehyde (L‧H2) with ethylenediamine (en), o-phenylenediamine (o-PD), or 4,5-dimethyl-1,2-phenylendiamine (DMPD) in a mole ratio of 2:1 followed by the reaction of the resulting Schiff bases ligands with Pd(II) or Pt(II) ions in the presence of 2,2‧-dipyridyl (L) to form the di- and tri-nuclear metal complexes. The second method involve the condensation of the Pd complex LPd(II)L‧, (L = 2,2‧-dipyridyl, L‧ = 4-formylbenzene-1,2-bis(olate)) with en, o-PD, or DMPD in a mole ratio of 2:1, respectively, followed by reaction with PdCl2 to form di-, tri-, and tetra-nuclear palladium(II) complexes, respectively. Structures of ligands and metal complexes are characterized by physical properties, FT-IR spectra and nuclear magnetic resonance. The geometries of metal complexes are suggested according to elemental analysis, electronic absorption spectra, thermal analysis, atomic absorption, magnetic susceptibility and molar conductance. Cytotoxic activity against lung large cell carcinoma (H460), prostate carcinoma (DU145), breast adenocarcinoma (MCF-7), amelanotic melanoma (M-14), colon adenocarcinoma (HT-29), and chronic myelogenous leukemia (K562) is also reported.

  12. 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.

  13. 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.

  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

    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...

  15. 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...

  16. Remarkable activity of PdIr nanoparticles supported on the surface of carbon nanotubes pretreated via a sonochemical process for formic acid electro-oxidation

    Science.gov (United States)

    Chen, Jinwei; Li, Yuanjie; Liu, Shuangren; Wang, Gang; Tian, Jing; Jiang, Chunping; Zhu, Shifu; Wang, Ruilin

    2013-12-01

    It was reported for the first time that the surface treated multi-walled carbon nanotubes supported PdIr (PdIr/CNT-SCP) catalyst presents remarkable electrocatalytic activity and stability for formic acid electro-oxidation (FAEO). The surface of CNTs was functionalized by a sonochemical process for the deposition of PdIr nanoparticles (NPs). The XRD and TEM characterizations show that the prepared PdIr/CNT-SCP catalyst has small mean size and good dispersion of PdIr NPs on CNTs. The electrochemical measurements show that the onset and anodic peak potentials of FAEO on PdIr/CNT-SCP catalyst are 60 and 50 mV more negative than that on the commercial Pd/C catalyst. The mass-normalized peak current density of PdIr/CNT-SCP is 3365 mA mg-1Pd, which is 4.5, 1.4 and 2.7 times higher than that of PdIr/CNT-Untreated, PdIr/C-SCP and commercial Pd/C, respectively. It demonstrates the promotion of Ir and functionalized CNTs to Pd for FAEO.

  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. 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.

  19. 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.

  20. 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.

  1. Modifications of Poly(o-phenylenediamine Permselective Layer on Pt-Ir for Biosensor Application in Neurochemical Monitoring

    Directory of Open Access Journals (Sweden)

    Robert D. O’Neill

    2007-04-01

    Full Text Available Reports that globular proteins could enhance the interference blocking ability ofthe PPD (poly(o-phenylenediamine layer used as a permselective barrier in biosensordesign, prompted this study where a variety of modifying agents were incorporated into PPDduring its electrosynthesis on Pt-Ir electrodes. Trapped molecules, including fibrous proteinsand β-cyclodextrin, altered the polymer/modifier composite selectivity by affecting thesensitivity to both H2O2 (signal molecule in many enzyme-based biosensors and thearchetypal interference species, ascorbic acid. A comparison of electrochemical properties ofPt and a Pt-Ir alloy suggests that the benefits of the latter, more rigid, metal can be exploitedin PPD-based biosensor design without significant loss of backward compatibility withstudies involving pure Pt.

  2. 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.

  3. 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.

  4. 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.

  5. Adsorption and decomposition of monopropellant molecule HAN on Pd(100) and Ir(100) surfaces: A DFT study

    Science.gov (United States)

    Banerjee, Sourav; Shetty, Sharath A.; Gowrav, M. N.; Oommen, Charlie; Bhattacharya, Atanu

    2016-11-01

    We have performed density functional theory calculations with the generalized gradient approximation to investigate the catalytic decomposition reactions of one of the most promising monopropellants, hydroxylammonium nitrate (HAN), on two catalytically active single crystal Pd(100) and Ir(100) surfaces, aiming at exploring different reaction pathways and reactivities of these two surfaces towards the catalytic decomposition of HAN. We find that the HAN molecule binds both the Pd(100) and Ir(100) surfaces molecularly in different orientations with respect to the surface. The HONO elimination is found to possess the lowest activation energy on the Pd(100) surface; whereas, NO2 elimination is predicted to show the lowest activation energy on the Ir(100) surface. Exothermicities associated with different reaction steps are also discussed. This is the first theoretical report on the catalytic decomposition reactions of the HAN molecule on the single crystal Pd(100) and the Ir(100) surfaces using the periodic DFT calculations.

  6. 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.

  7. 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.

  8. 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.

  9. 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。

  10. Electrochemical treatment of olive oil mill wastewater using a Ti/Ta/Pt/Ir electrode

    Energy Technology Data Exchange (ETDEWEB)

    Giannes, A.; Diamadopoulos, E. [Lab. of Environmental Engineering and Management, Technical Univ. of Crete, Chania (Greece); Ninolakis, M. [Ferecarpos SA, Agia Paraskevi, Athens (Greece)

    2003-07-01

    Olive oil mill wastewater, an ecotoxic liquid associated with the production of olive oil, was treated by an electrochemical method using Ti/Ta/Pt/Ir as anode and Stainless Steel 316L as cathode. A number of experiments were run in a batch, laboratory-scale pilot-plant. The experimental plant consisted of the electrolytic cell, the recirculation reactor with cooling system and the wastewater feed system. The efficiency of the electrolytic cell was studied in relation to sodium chloride concentration, voltage and time of electrochemical treatment. Optimal conditions were at a sodium chloride concentration 3% (w/v) and 16V. At these conditions COD removal reached 70.8% after 8 h of electrolysis. Color, odor and turbidity were completely removed after short periods of treatment. However, bio-essays with Daphnia Magna and Artemia Salina indicated that the ecotoxicity of the treated wastewater remained unchanged, possibly due to the formation of chlorinated by-products. (orig.)

  11. Electrochemical Decolorization of Reactive Violet 5 Textile Dye using Pt/Ir Electrodes

    Directory of Open Access Journals (Sweden)

    Bahadır K. Körbahti

    2016-08-01

    Full Text Available Electrochemical decolorization of textile dyeing wastewater containing Reactive Violet 5 (RV5 were investigated at Pt/Ir electrodes in the presence of 75%NaCl+25%Na2CO3 (w/w supporting electrolyte mixture in a batch electrochemical reactor. Experimental parameters were operated in the range of 300-1500 mg/L textile dye concentration, 4-20 g/L 75%NaCl+25%Na2CO3 electrolyte concentration, 5-15 mA/cm2 current density, and 20-60°C reaction temperature in 15 min electrolysis time. Reactive Violet 5 decolorization increased with increasing current density and electrolyte concentration, and decreasing the textile dye concentration. Although a slight increase obtained in color removal efficiency, the temperature was not show much significant effect on decolorization. Depending on electrochemical reaction conditions, Reactive Violet 5 textile dye decolorization were obtained between 42.8-100%.

  12. 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.

  13. 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.

  14. 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.

  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. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  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)

    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.

  2. 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)

  3. 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.

  4. 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.)

  5. 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.

  6. 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.

  7. 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.

  8. 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)

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. Synthesis and Spectroscopic Studies of Mixed Ligand Complexes of Pt(II and Pd(II with Ethyl-α-Isonitrosoacetoacetate and Dienes

    Directory of Open Access Journals (Sweden)

    Anita Krishankant Taksande

    2015-12-01

    Full Text Available The mixed ligand complexes of the kind [M(L1 (L2] where M= Pt(II, Pd(II.L1 = primary ligand ethyl-α-isonitrosoacetoacetate derived from reaction between ethyl acetoacetate, acetic acid and sodium nitrite and L2=secondary ligand para-phenyldiamine (PPD are synthesized. All the prepared complexes were identified and confirmed by elemental analysis, molar conductance measurements, and infrared electronic absorption. Their complexes has been made based on elemental analysis, molar conductivity, UV-Vis, FT-IR and 1HNMR spectroscopy and magnetic moment measurements as well as thermal analysis (TGA and DTA. The elemental analysis information recommends that the stoichiometry of the complexes to be 1:2:1. The molar conductance measurements of the complexes indicate their non-electrolytic nature. The infrared spectral information showed the coordination sites of the free ligand with the central metal particle. The electronic absorption spectral information disclosed the existence of an octahedral geometry for Pt(II and Pd(II complexes. DOI: http://dx.doi.org/10.17807/orbital.v7i4.633 

  14. Preparation and characterization of platinum (Pt) and palladium (Pd) nanoparticle decorated graphene sheets and their utilization for the elimination of basic fuchsin and indigo carmine dyes

    Science.gov (United States)

    Kurt, Belma Zengin; Durmus, Zehra; Durmus, Ali

    2016-01-01

    In this study, graphene nano sheets, prepared with chemical oxidation and reduction routes via modified-Hummer method, were successfully decorated with platinum (Pt) and palladium (Pd) nanoparticles. Structural and morphological features of resulted graphene-metal nanocomposites were characterized with FT-IR, XRD, SEM and TEM methods. Anti-oxidant activity (AOA) values of nanocomposites were determined. The IC50 values of Pt-graphene and Pd-graphene nanocomposites were found to be 46.1 and 90.2 μg/mL, respectively based on the ABTS method and 80.2 and 143.7 μg/mL according to the DPPH method. It was found that the graphene-metal nanocomposites exhibited superior free radical scavenging activity compared to several types of noble metal nano particles although the nanocomposites consist of much lower amount of active metal sites than the nano-crystalline metal powders. It was consequently reported that the graphene-metal nanocomposites could be successfully used for the photocatalytic elimination of fuchsin and indigo carmine dyes under light irradiation.

  15. 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...

  16. 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.

  17. 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...

  18. 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

  19. 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...

  20. 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

  1. 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...

  2. 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...

  3. Graphene decorated with Pd4Ir nanocrystals: Ultrasound-assisted synthesis, and application as a catalyst for oxidation of formic acid.

    Science.gov (United States)

    Zhang, Lian Ying; Liu, Ze

    2017-11-01

    An effective strategy of ultrasmall and surface-clean Pd4Ir nanocrystals uniformly decorated on graphene was developed using ultrasnoic-assisted approach. The prepared Us-Pd4Ir@Graphene reduces Pd loading while holds much higher catalytic activity and better stability toward formic acid oxidation than that of commercial Pd-C, offering great promise as a superior anode catalyst for direct formic acid fuel cells. Copyright © 2017 Elsevier Inc. All rights reserved.

  4. 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.

  5. 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

  6. Strategic modulation of the photonic properties of conjugated organometallic Pt-Ir polymers exhibiting hybrid CT-excited states.

    Science.gov (United States)

    Soliman, Ahmed M; Zysman-Colman, Eli; Harvey, Pierre D

    2015-04-01

    Polymer 6, ([trans-Pt(PBu3 )2 (C≡C)2 ]-[Ir(dFMeppy)2 (N^N)](PF6 ))n , (([Pt]-[Ir](PF6 ))n ; N^N = 5,5'-disubstituted-2,2'-bipyridyl; dFMeppy = 2-(2,4-difluoro-phenyl)-5-methylpyridine) is prepared along with model compounds. These complexes are investigated by absorption and emission spectroscopy and their photophysical and electrochemical properties are measured and compared with their corresponding non fluorinated complexes. Density functional theory (DFT) and time-dependent DFT computations corroborate the nature of the excited state as being a hybrid between the metal-to-ligand charge transfer ((1,3) MLCT) for the trans-Pt(PBu3 )2 (C≡CAr)2 unit, [Pt] and the metal-to-ligand/ligand-to-ligand' charge transfer ((1,3) ML'CT/LL'CT) for [Ir] with L = dFMeppy. Overall, the fluorination of the phenylpyridine group expectedly does not change the nature of the excited state but desirably induces a small blue shift of the absorption and emission bands along a slight decrease in emission quantum yields and lifetimes.

  7. 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.

  8. 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.

  9. 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

    The partition coefficients of Pt and other Pt Group Elements (PGE) between metal and silicate D(sub Metal-Silicate) and also between silicate minerals and silicate melts D(sub Metal-Silicate) are among the most challenging coefficients to obtain precisely. The PGE are highly siderophile elements (HSE) with D(sub Metal-Silicate) >10(exp 3) due to the fact that their concentrations in silicates are very low (ppb to ppt range). Therefore, the analytical difficulty is increased by the possible presence of HSE-rich-nuggets in reduced silicate melts during experiments). These tiny HSE nuggets complicate the interpretation of measured HSE concentrations. If the HSE micro-nuggets are just sample artifacts, then their contributions should be removed before calculations of the final concentration. On the other hand, if they are produced during the quench, then they should be included in the analysis. We still don't understand the mechanism of nugget formation well. Are they formed during the quench by precipitation from precursor species dissolved homogeneously in the melts, or are they precipitated in situ at high temperature due to oversaturation? As these elements are important tracers of early planetary processes such as core formation, it is important to take up this analytical and experimental challenge. In the case of the Earth for example, chondritic relative abundances of the HSE in some mantle xenoliths have led to the concept of the "late veneer" as a source of volatiles (such as water) and siderophiles in the silicate Earth. Silicate crystal/liquid fractionation is responsible for most, if not all, the HSE variation in the martian meteorite suites (SNC) and Pt is the element least affected by these fractionations. Therefore, in terms of reconstructing mantle HSE abundances for Mars, Pt becomes a very important player. In the present study, we have performed high temperature experiments under various redox conditions in order to determine the abundances of Pt, Au

  10. 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.

  11. 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.

  12. Photonics of a conjugated organometallic Pt-Ir polymer and its model compounds exhibiting hybrid CT excited states.

    Science.gov (United States)

    Soliman, Ahmed M; Fortin, Daniel; Zysman-Colman, Eli; Harvey, Pierre D

    2012-04-13

    Trans- dichlorobis(tri-n-butylphosphine)platinum(II) reacts with bis(2- phenylpyridinato)-(5,5'-diethynyl-2,2'-bipyridine)iridium(III) hexafluorophosphate to form the luminescent conjugated polymer poly[trans-[(5,5'-ethynyl-2,2'-bipyridine)bis(2- phenylpyridinato)-iridium(III)]bis(tri-n-butylphosphine)platinum(II)] hexafluorophosphate ([Pt]-[Ir])n. Gel permeation chromatography indicates a degree of polymerization of 9 inferring the presence of an oligomer. Comparison of the absorption and emission band positions and their temperature dependence, emission quantum yields, and lifetimes with those for models containing only the [Pt] or the [Ir] units indicates hybrid excited states including features from both chromophores.

  13. 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.

  14. 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.

  15. 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.

  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. Study of the Material Transfer Characteristics and Surface Morphology Due to Arc Erosion of PtIr Contact Materials

    Institute of Scientific and Technical Information of China (English)

    WANG Saibei; XIE Ming; YANG Youcai; ZHANG Jiming; CHEN Yongtai; LIU Manmen; YANG Yunfeng; HU Jieqiong; CUI Hao

    2012-01-01

    By means of breaking tests on PtIr contact materials via a JF04C contact material testing machine,it was attempted to elucidate the characterstics of the various surface morphology and material transfer after the arc erosion process caused by break arc.The material transfer characteristics appeared in the experiments were concluded and analyzed.Meanwhile,the morphology of the anode and cathode surface were observed and analyzed by SEM.

  18. Negative effect of Ni on PtHY in n-pentane isomerization evidenced by IR and ESR studies

    Institute of Scientific and Technical Information of China (English)

    Muhammad Afif Ab Aziz; Nur Hidayatul Nazirah Kamarudin; Herma Dina Setiabudi; Halimaton Hamdan; Aishah Abdul Jalil; Sugeng Triwahyono

    2012-01-01

    Ni/PtHY with different Ni loadings was prepared by impregnating HY with hexachloroplatinic acid solution and Ni2+/N,N-dimethylformamide solution.An increase in the Ni loading decreased the crystallinity,specific surface area and meso-micropores of the catalysts.Ni interacted with hydroxyl groups to produce IR absorption bands at 3740-3500 cm-1.Increasing Ni loadings resulted in a decrease in the intensities of the broad bands at 3730-3500 cm-1 and the sharp band at 3740 cm-1 with simultaneous development of new absorbance band at 3700 cm-1 that was attributed to (-OH)Ni.The acidity of the samples did not significantly change with Ni loadings up to 1.0 wt%,which indicated that Ni mostly interacts with non-acidic silanol groups (terminal-and structural-defect OH groups).The presence of Ni decreased the activity of PtHY toward the isomerization of n-pentane because of a decrease in the number of active protonic-acid sites that formed from molecular hydrogen.IR and ESR studies confirmed that Pt facilitated the formation of protonic-acid sites from molecular hydrogen,whereas Ni,even when combined with Pt,didn't exhibit such ability.The absence of protonic-acid sites from molecular hydrogen significantly decreased the yield of iso-pentane and markedly increased the cracking products.

  19. 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.

  20. Direct imaging of thermally-activated grain-boundary diffusion in Cu/Co/IrMn/Pt exchange-bias structures using atom-probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Letellier, F.; Lardé, R.; Le Breton, J.-M., E-mail: jean-marie.lebreton@univ-rouen.fr [Groupe de Physique des Matériaux, UMR 6634 CNRS/Université et INSA de Rouen, F-76801 Saint Etienne du Rouvray (France); Lechevallier, L. [Groupe de Physique des Matériaux, UMR 6634 CNRS/Université et INSA de Rouen, F-76801 Saint Etienne du Rouvray (France); Département de GEII, Université de Cergy-Pontoise, F-95031 Cergy-Pontoise (France); Akmaldinov, K. [SPINTEC, Univ. Grenoble-Alpes/CNRS/INAC-CEA, F-38000 Grenoble (France); CROCUS Technology, F-38025 Grenoble (France); Auffret, S.; Dieny, B.; Baltz, V., E-mail: vincent.baltz@cea.fr [SPINTEC, Univ. Grenoble-Alpes/CNRS/INAC-CEA, F-38000 Grenoble (France)

    2014-11-28

    Magnetic devices are often subject to thermal processing steps, such as field cooling to set exchange bias and annealing to crystallize amorphous magnetic electrodes. These processing steps may result in interdiffusion and the subsequent deterioration of magnetic properties. In this study, we investigated thermally-activated diffusion in Cu/Co/IrMn/Pt exchange biased polycrystalline thin-film structures using atom probe tomography. Images taken after annealing at 400 °C for 60 min revealed Mn diffusion into Co grains at the Co/IrMn interface and along Pt grain boundaries for the IrMn/Pt stack, i.e., a Harrison type C regime. Annealing at 500 °C showed further Mn diffusion into Co grains. At the IrMn/Pt interface, annealing at 500 °C led to a type B behavior since Mn diffusion was detected both along Pt grain boundaries and also into Pt grains. The deterioration of the films' exchange bias properties upon annealing was correlated to the observed diffusion. In particular, the topmost Pt capping layer thickness turned out to be crucial since a faster deterioration of the exchange bias properties for thicker caps was observed. This is consistent with the idea that Pt acts as a getter for Mn, drawing Mn out of the IrMn layer.

  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. Ni(II), Pd(II) and Pt(II) complexes of (1H-1,2,4-triazole-3-ylimino)methyl]naphthalene-2-ol. Structural, spectroscopic, biological, cytotoxicity, antioxidant and DNA binding

    Science.gov (United States)

    Gaber, M.; El-Ghamry, H. A.; Fathalla, S. K.

    2015-03-01

    Metal complexes of the general formula [ML(H2O)Cl]nH2O; n = 1 for M = Ni and Pt and n = 2 for M = Pd, L = Schiff base (HL) derived from the condensation of 3-amino-1,2,4-triazole and 2-hydroxy-1-naphthaldehyde, were prepared. The synthesized ligand and its metal complexes were characterized on the basis of elemental analyses, spectral and magnetic studies as well as thermal analysis. The IR spectra revealed that the ligand is coordinated to the metal ions in bidentate manner via the N-atom of the azomethine group and the phenolic OH group. Square planar geometry was proposed for Pd(II) and Pt(II) complexes and tetrahedral for Ni(II) complex. The ligand and its metal complexes were screened against the sensitive organisms Escherichia coli as Gram-negative bacteria, Staphylococcus aureus as Gram-positive bacteria, Aspergillus flavus and Candida albicans as fungi. Moreover, the anticancer activity of the ligand and its metal complexes was evaluated in liver carcinoma (HEPG2) cell line. The results obtained indicated that the Schiff base ligand is more effective than its metal complexes towards the tested cell line. Ni(II), Pd(II) and Pt(II) complexes as well as the free Schiff base ligand were tested for their antioxidant activities. The DNA-binding properties of the studied complexes have been investigated by electronic absorption and viscosity measurements.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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...

  3. 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.

  4. 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.

  5. Self-enhanced N-(aminobutyl)-N-(ethylisoluminol) derivative-based electrochemiluminescence immunosensor for sensitive laminin detection using PdIr cubes as a mimic peroxidase

    Science.gov (United States)

    Jiang, Xinya; Wang, Huijun; Wang, Haijun; Zhuo, Ying; Yuan, Ruo; Chai, Yaqin

    2016-04-01

    Herein, a self-enhanced N-(aminobutyl)-N-(ethylisoluminol) (ABEI) derivative-based electrochemiluminescence (ECL) immunosensor was constructed for the determination of laminin (LN) using PdIr cubes as a mimic peroxidase for signal amplification. Initially, PdIr cubes with efficient peroxidase mimicking properties, large specific surface areas, and good stability and uniformity were synthesized. Then, l-cysteine (l-Cys) and ABEI were immobilized on the PdIr cubes to form the self-enhanced ECL nanocomplex (PdIr-l-Cys-ABEI). In this nanocomplex, PdIr cubes, whose catalytic constant is higher than that of horseradish peroxidase (HRP), could effectively catalyze H2O2 decomposition and thus enhance the ECL intensity of ABEI. Moreover, PdIr cubes can be easily modified with functional groups, which make them adaptable to desired supported platforms. On the other hand, l-Cys as a coreactant of ABEI could effectively enhance the luminous efficiency due to the intramolecular ECL reaction which could reduce the energy loss between l-Cys and ABEI by giving a shorter electron transfer distance. The developed strategy combined an ABEI derivative as a self-enhanced ECL luminophore and PdIr cubes as a mimic peroxidase, resulting in a significantly enhanced ECL signal output. Also, the strategy showed high sensitivity and selectivity for LN, which suggested that our new approach could be potentially applied in monitoring different proteins.

  6. 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.

  7. 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.

  8. 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)

  9. 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.

  10. 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.

  11. Modification of the hydrogenation properties of LaNi{sub 5} upon Ni substitution by Rh, Ir, Pt or Au

    Energy Technology Data Exchange (ETDEWEB)

    Prigent, J. [Chimie Metallurgique des Terres Rares, Institut de Chimie et des Materiaux Paris-Est, CNRS, Universite Paris-Est, 2-8 rue H. Dunant, 94320 Thiais Cedex (France); Laboratoire de Thermodynamique et Physico-Chimie des Hydrures et Oxydes, Universite Paris-Sud Orsay, Bat 410, 91405 Orsay (France); Joubert, J.-M., E-mail: jean-marc.joubert@icmpe.cnrs.fr [Chimie Metallurgique des Terres Rares, Institut de Chimie et des Materiaux Paris-Est, CNRS, Universite Paris-Est, 2-8 rue H. Dunant, 94320 Thiais Cedex (France); Gupta, M. [Laboratoire de Thermodynamique et Physico-Chimie des Hydrures et Oxydes, Universite Paris-Sud Orsay, Bat 410, 91405 Orsay (France)

    2012-01-15

    Highlights: > Hydrogen absorption properties of LaNi{sub 5-x}M{sub x} intermetallic compounds (M = Rh, Ir, Au). > Stability of LaNi{sub 5-x}M{sub x} (M = Rh, Pt) intermetallics and hydrides using ab initio calculations. > Influence of the substituting elements (geometric, thermodynamic and electronic) on the hydride stability. - Abstract: The hydrogenation properties of the LaNi{sub 5-x}M{sub x} (M = Rh, Ir, Au) compounds have been studied. The Ni substitution has several consequences: pressure plateau splitting and increase of plateau pressure. This latter observation disagrees with the general rule that a cell volume increase of the alloy should result in a plateau pressure lowering. In order to elucidate the origin of this anomalous behaviour, DFT calculations have been performed on both LaNi{sub 5-x}Rh{sub x} and LaNi{sub 5-x}Pt{sub x} intermetallic compounds, which, according to the present and previous experimental work, present a similar anomaly. We discuss our results in light of the models proposed in the literature. We conclude that, in the case of a Ni substitution by 4d or 5d elements, the size effect alone fails in predicting the hydrogen absorption properties while the rule of reverse stability is obeyed.

  12. 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.

  13. Assessment on the structural, elastic and electronic properties of Nb3Ir and Nb3Pt: A first-principles study

    Directory of Open Access Journals (Sweden)

    Xianfeng Li

    2017-06-01

    Full Text Available The pressure dependent behaviors on the structural, elastic and electronic properties of the A15 structure Nb3Ir and Nb3Pt were studied using first-principles calculations based on the density functional theory within generalized gradient approximation and local density approximation methods. Initially, the optimized lattice constants of Nb3Ir and Nb3Pt are consistent with the available experimental and theoretical results. Furthermore, Nb3Ir is found to be more thermodynamically stable than Nb3Pt due to its lower formation enthalpy and higher melting temperature. In addition, the elastic constants of Nb3Ir and Nb3Pt show an increasing tendency, and keep mechanically stable structures under pressures to 40 GPa. Besides, the increasing Cauchy pressures and B/G values have indicated that higher pressures can improve their ductility in both Nb3Ir and Nb3Pt. Finally, the pressure-dependent behaviors on the density of states, Mulliken charges and bond lengths are discussed for both compounds.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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

  5. 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.)

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Structural and in vitro cytotoxicity studies on 1H-benzimidazol-2-ylmethyl-N-phenyl amine and its Pd(II) and Pt(II) complexes

    Science.gov (United States)

    Abdel Ghani, Nour T.; Mansour, Ahmed M.

    2011-10-01

    [MLCl 2]· zH 2O (L = (1H-benzimidazol-2-ylmethyl)-N-phenyl amine; M = Pd, z = 0; M = Pt, z = 1) and [PdL(OH 2) 2]·2X·zH 2O (X = Br, I, NO 3, z = 0; X = SCN, z = 1) complexes were synthesized as potential anticancer compounds and characterized by elemental analysis, spectral and thermal methods. FT-IR and 1H NMR studies revealed that the benzimidazole L is coordinated to the metal ions via the pyridine-type nitrogen (N py) of the benzimidazole ring and secondary amino group (NH sec). Quantum mechanical calculations of energies, geometries, vibrational wavenumbers, and 1H NMR of the benzimidazole L and its complexes were carried out by density functional theory using B3LYP functional combined with 6-31G(d) and LANL2DZ basis sets. Natural bond orbitals (NBOs) and frontier molecular orbitals were performed at B3LYP/LANL2DZ level of theory. The synthesized ligand, in comparison to its metal complexes was screened for its antibacterial activity. The benzimidazole L is more toxic against the bacterium Staphylococcus aureus (MIC = 58 μg/mL) than the standard tetracycline (MIC = 82 μg/mL). The complexes showed cytotoxicity against breast cancer, Colon Carcinoma, and human heptacellular Carcinoma cells. The platinum complex ( 6) displays cytotoxicity (IC 50 = 12.4 μM) against breast cancer compared with that reported for cis-platin 9.91 μM.

  12. ESTUDIO EXPERIMENTAL Y SUPRAMOLECULARES DE Ni, Pd Y Pt, AUTOENSAMBLADOS COMPUTACIONAL DE POLÍGONOS CON 4,4´-BIPIRIDINA.

    Directory of Open Access Journals (Sweden)

    Paulo C Torres

    2013-12-01

    Full Text Available Los polígonos y poliedros supramoleculares presentan diversas y  novedosas aplicaciones como nanoreactores, en química de inclusión, nanosensores moleculares, entre otras. En este trabajo se presenta la síntesis, caracterización y comparación de polígonos supramoleculares autoensamblados entre complejos de tipo [M(dppe(TOF2], con centros metálicos de un mismo grupo (M = Ni, Pd y Pt y la molécula orgánica 4,4'-bipiridina. Los análisis realizados por Uv-vis, FT-IR, Raman, 1H-, 31P-, 1H COSY- y 19F- RMN, demostraron que el complejo que contiene níquel formó únicamente un cuadrado, mientras que los complejos que contienen paladio y platino presentaron un equilibrio triángulo-cuadrado. Además se realizaron cálculos PM6 para los complejos supramoleculares, considerando sistemas catíonicos y neutros, tanto en fase gaseosa como en disolución. Los resultados muestran que para los tres metales, sin importar el medio, se ve favorecida energéticamente la formación de cuadrados en comparación con la formación de triángulos. Además, se observa que los centros de Ni favorecen más la formación de cuadrados, mientras que los centros de Pd la favorecen menos. Las tendencias teóricas se encuentran en concordancia con los resultados experimentales.

  13. 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

  14. 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

  15. 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.

  16. 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.

  17. Surface studies on graphite furnace platforms covered with Pd, Rh and Ir as modifiers in graphite furnace atomic absorption spectrometry of tellurium

    Energy Technology Data Exchange (ETDEWEB)

    Pedro, Juana [Area de Química Analítica, Departamento de Química, Facultad de Ingeniería Química, Universidad Nacional del Litoral, Santiago del Estero 2829 (S3000GL.N), Santa Fe (Argentina); Stripekis, Jorge [Laboratorio de Análisis de Trazas, Departamento de Química Inorgánica, Analítica y Química Física, INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria (1428), Buenos Aires (Argentina); Departamento de Ingeniería Química, Instituto Tecnológico de Buenos Aires, Av. Eduardo Madero 399 (1106), Buenos Aires (Argentina); Bonivardi, Adrian [Area de Química Analítica, Departamento de Química, Facultad de Ingeniería Química, Universidad Nacional del Litoral, Santiago del Estero 2829 (S3000GL.N), Santa Fe (Argentina); Tudino, Mabel, E-mail: tudino@qi.fcen.uba.ar [Laboratorio de Análisis de Trazas, Departamento de Química Inorgánica, Analítica y Química Física, INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria (1428), Buenos Aires (Argentina)

    2015-05-01

    The main objective of this work is the study of correlations between the efficiency of the distribution of the permanent platinum group modifiers Pd, Rh and Ir over the graphite surface with the aim of improving analytical signal of tellurium. Modifier solution was deposited onto the platform and pyrolysed after drying. In the case of Pd, the physical vaporization/deposition technique was also tested. In order to analyze the differences amongst coverings (morphology, topology and distribution), the graphite surfaces were studied with scanning electron microscopy and energy dispersive X-ray microscopy. Micrographs for physical vaporization and pyrolytic deposition of Pd were also analyzed in order to explain the lack of signal obtained for tellurium with the first alternative. Similar micrographs were obtained for pyrolytic deposition of Ir and Rh and then, compared to those of Pd. Ir showed the most homogeneous distribution on the graphite surface and the tallest and sharpest transient. With the aim of improving the analytical signal of tellurium, the correlation between the surface studies and the tellurium transient signal (height, area and shape) is discussed. - Highlights: • Distribution of Rh, Pd and Ir onto graphite furnaces is evaluated by SEM and EDX • Micrographs and spectra showed that surface distribution could influence Te signal. • Ir showed the best signal together with the most homogeneous surface distribution. • Pd-PVD micrographs revealed the absence of graphite and no signal for Te.

  18. 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.

  19. 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.

  20. Mirrors for High Resolution X-Ray Optics---Figure Preserving IR/PT Coating

    Science.gov (United States)

    Chan, Kai-Wing; Olsen, Lawrence; Sharpe, Marton; Numata, Ai; McClelland, Ryan; Saha, Timo; Zhang, Will

    2016-01-01

    Coating stress of 10 - 20 nm of Ir is sufficiently high to distort the figure of arc-second thin lightweight mirrors. For iridium: --Stress sigma 4 GPa for 15 nm film implies 60 Nm integrated stress-- Need less than 3 N/m (or stress less than 200 MPa) for sub-arcsecond optics. Basic Approaches for Mitigation. A. Annealing the film-- Glass can be heat up to 400 C without distortion. Silicon is even more resistant.-- It was found that recovery is limited by residual thermal stress from taking the mirror down from high T. B. Coating bi-layer films with compressive stress with tensile stress. C. Front-and-back coating with magnetron sputtering or atomic layer deposition-- Sputtering involve spanning of substrates. Geometric difference in setup (convexness/concaveness of curved mirrors) does not permit precise front-and-back matching-- Atomic layer deposition can provide a uniform deposition front and back simultaneously.

  1. 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

  2. Synthesis and Characterization of Novel Cu(II, Pd(II and Pt(II Complexes with 8-Ethyl-2-hydroxytricyclo(7.3.1.02,7tridecan-13-one-thiosemicarbazone: Antimicrobial and in Vitro Antiproliferative Activity

    Directory of Open Access Journals (Sweden)

    Elena Pahonțu

    2016-05-01

    Full Text Available New Cu(II, Pd(II and Pt(II complexes, (Cu(L(H2O2(OAc (1, (Cu(HL(H2O2(SO4 (2, (Cu(L(H2O2(NO3 (3, (Cu(L(H2O2(ClO4 (4, (Cu(L2(H2O2 (5, (Pd(L(OAcH2O (6, and (Pt(L2 (7 were synthesized from 8-ethyl-2-hydroxytricyclo(7.3.1.02,7tridecan-13-one thiosemicarbazone (HL. The ligand and its metal complexes were characterized by IR, 1H-NMR, 13C-NMR, UV-Vis, FAB, EPR, mass spectroscopy, elemental and thermal analysis, magnetic susceptibility measurements and molar electric conductivity. The free ligand and the metal complexes have been tested for their antimicrobial activity against E. coli, S. enteritidis, S. aureus, E. faecalis, C. albicans and cytotoxicity against the NCI-H1573 lung adenocarcinoma, SKBR-3 human breast, MCF-7 human breast, A375 human melanoma and HL-60 human promyelocytic leukemia cell lines. Copper complex 2 exhibited the best antiproliferative activities against MCF-7 human breast cancer cells. A significant inhibition of malignant HL-60 cell growth was observed for copper complex 2, palladium complex 6 and platinum complex 7, with IC50 values of 1.6 µM, 6.5 µM and 6.4 µM, respectively.

  3. Synthesis, spectral and theoretical studies of Ni(II), Pd(II) and Pt(II) complexes of 5-mercapto-1,2,4-triazole-3-imine-2‧-hydroxynaphyhaline

    Science.gov (United States)

    Gaber, Mohamed; El-Ghamry, Hoda; Atlam, Faten; Fathalla, Shaimaa

    2015-02-01

    Ni(II), Pd(II) and Pt(II) complexes of 5-mercapto-1,2,4-triazole-3-imine-2‧-hydroxynaphthaline have been isolated and characterized by elemental analysis, IR, 1H NMR, EI-mass, UV-vis, molar conductance, magnetic moment measurements and thermogravimetric analysis. The molar conductance values indicated that the complexes are non-electrolytes. The magnetic moment values of the complexes displayed diamagnetic behavior for Pd(II) and Pt(II) complexes and tetrahedral geometrical structure for Ni(II) complex. From the bioinorganic applications point of view, the interaction of the ligand and its metal complexes with CT-DNA was investigated using absorption and viscosity titration techniques. The Schiff-base ligand and its metal complexes have also been screened for their antimicrobial and antitumor activities. Also, theoretical investigation of molecular and electronic structures of the studied ligand and its metal complexes has been carried out. Molecular orbital calculations were performed using DFT (density functional theory) at B3LYP level with standard 6-31G(d,p) and LANL2DZ basis sets to access reliable results to the experimental values. The calculations were performed to obtain the optimized molecular geometry, charge density distribution, extent of distortion from regular geometry, the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), Mulliken atomic charges, reactivity index (ΔE), dipole moment (D), global hardness (η), softness (σ), electrophilicity index (ω), chemical potential and Mulliken electronegativity (χ).

  4. Synthesis, spectral and theoretical studies of Ni(II), Pd(II) and Pt(II) complexes of 5-mercapto-1,2,4-triazole-3-imine-2'-hydroxynaphthaline.

    Science.gov (United States)

    Gaber, Mohamed; El-Ghamry, Hoda; Atlam, Faten; Fathalla, Shaimaa

    2015-02-25

    Ni(II), Pd(II) and Pt(II) complexes of 5-mercapto-1,2,4-triazole-3-imine-2'-hydroxynaphthaline have been isolated and characterized by elemental analysis, IR, (1)H NMR, EI-mass, UV-vis, molar conductance, magnetic moment measurements and thermogravimetric analysis. The molar conductance values indicated that the complexes are non-electrolytes. The magnetic moment values of the complexes displayed diamagnetic behavior for Pd(II) and Pt(II) complexes and tetrahedral geometrical structure for Ni(II) complex. From the bioinorganic applications point of view, the interaction of the ligand and its metal complexes with CT-DNA was investigated using absorption and viscosity titration techniques. The Schiff-base ligand and its metal complexes have also been screened for their antimicrobial and antitumor activities. Also, theoretical investigation of molecular and electronic structures of the studied ligand and its metal complexes has been carried out. Molecular orbital calculations were performed using DFT (density functional theory) at B3LYP level with standard 6-31G(d,p) and LANL2DZ basis sets to access reliable results to the experimental values. The calculations were performed to obtain the optimized molecular geometry, charge density distribution, extent of distortion from regular geometry, the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), Mulliken atomic charges, reactivity index (ΔE), dipole moment (D), global hardness (η), softness (σ), electrophilicity index (ω), chemical potential and Mulliken electronegativity (χ).

  5. 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 >

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. Asymmetric Hydrogenation of Ethyl 2-Oxo-4-Phenylbutyrate on Pt-Ir/Al2O3 Catalysts%Pt-Ir/Al2O3催化剂催化2-氧-4-苯基丁酸乙酯不对称加氢

    Institute of Scientific and Technical Information of China (English)

    张学勤; 何年志; 肖美添; 刘勇军; 叶静

    2013-01-01

    A series of Pt/γ-Al2O3 、Ir/γ-Al2O3 and Pt-Ir/γ-Al2O3 catalysts with different ratios of Pt and Ir were prepared by impregnation methods.The catalytic performance for asymmetric hydrogenation of ethyl 2-oxo-4-phenylbutyrate to ethyl (R)-2-hydroxy-4-phenylbutyrate was tested.The mechanism of chiral induction on cinchona-modified platinum and iridium catalysts and their physical and chemical properties were investigated by X-ray diffraction (XRD),transmission electron microscopy(TEM),H2-temperature programmed reduction (H2-TPR),X-ray photoelectron spectroscopy(XPS) and ultraviolet-visible spectroscopy(UV-Vis).The average metal particles size for Pt/γ-Al2O3 and Pt-Ir/γ-Al2O3 catalγsts were 3-4 nm; Pt and Ir existed as Pt(0) and Ir(0) for Pt-Ir/γ-Al2O3 ; Ir acted as an inactive species,covering and diluting the Pt active site in the surface.The results showed that a small amount of Ir obviously suppressed the hydrogenation activity and selectivity of Pt/γ-Al2O3.The notable differences in reaction rate and enantioselectivity of platinum and iridium attributed to different behaviour adsorption (adsorption strength,mode and conformation) of chiral modifier on the metal surface.%用浸渍法制备了一系列γ-Al2O3负载的Pt、Ir单金属及不同Pt/Ir比例的双金属催化剂,在辛可尼定修饰下用于对2-氧-4-苯基丁酸乙酯不对称加氢合成(R)-2-羟基-4-苯基丁酸乙酯反应.运用XRD、TEM、TPR、XPS、UV-Vis等表征手段,对催化剂的物化性质进行了研究,并对Pt、Ir金属表面辛可尼定手性诱导机理进行了初步探讨.结果表明,金属组分在催化剂上分散均匀,无团聚现象,平均粒径为3 ~4 nm; Pt-Ir/γ-Al2O3上Pt、Ir组分以单质形式存在;Ir作为低活性物种,在Pt/γ-Al2O3催化剂掺杂Ir组分遮盖和稀释了催化剂表面总体Pt活性位点数目,降低了Pt-Ir/γ-Al2O3催化剂加氢性能.辛可尼定在Pt、Ir表面的不同吸附行为(吸附方式、吸附强度、吸附

  12. 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.

  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. 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.

  15. In situ ATR-IR study of nitrite hydrogenation over Pd/Al2O3.

    NARCIS (Netherlands)

    Ebbesen, S.D.; Mojet, Barbara; Lefferts, Leonardus

    2008-01-01

    The mechanism of nitrite hydrogenation over a Pd/Al2O3 catalyst layer deposited on a ZnSe internal reflection element was investigated in water using attenuated total reflection infrared spectroscopy. Nitrite hydrogenates to NO(ads), NH2(ads), and NH+4 on the palladium surface. Hydrogenation of

  16. Preparation and characterization of Pt-Sn/C and Pt-Ir/C catalysts for the electrochemical oxidation of ethanol in polymer electrolyte membrane fuel cell

    CSIR Research Space (South Africa)

    Masombuka, T

    2007-11-01

    Full Text Available to be the most active metal for ethanol oxidation, however the formation of CO-intermediates poison the Pt catalyst. Literature studies have indicated that the modification of platinum by tin gives the more pronounced enhancement. Pt-Sn/C activity for ethanol...

  17. 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.

  18. 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.

  19. 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.

  20. Influence of bismuth on the structure and activity of Pt and Pd nanocatalysts for the direct electrooxidation of NaBH{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Simoes, Mario; Baranton, Steve [Laboratoire de Catalyse en Chimie Organique, Equipe Electrocatalyse, UMR 6503 CNRS, 40 avenue du recteur Pineau, F-86022 Poitiers Cedex (France); Coutanceau, Christophe, E-mail: christophe.coutanceau@univ-poitiers.f [Laboratoire de Catalyse en Chimie Organique, Equipe Electrocatalyse, UMR 6503 CNRS, 40 avenue du recteur Pineau, F-86022 Poitiers Cedex (France)

    2010-12-15

    In the past few years, borohydrides have gathered a lot of attention as an energy carrier for fuel cell application. Numerous investigations on both hydrogen generation and direct oxidation of NaBH{sub 4} have been published. Nonetheless, in our knowledge, only a few catalysts are capable to completely perform the direct oxidation of NaBH{sub 4} at low potentials without hydrogen evolution. In this work, carbon supported Pd{sub 1-x}Bi{sub x}/C and Pt{sub 1-x}Bi{sub x}/C nanocatalysts were synthesized by a 'water in oil' microemulsion method. The influence of surface modifications of Pt and Pd by Bi on the electrooxidation of sodium borohydride in alkaline media was evaluated. Physical and electrochemical methods were applied to characterize the structure and surface of the synthesized catalysts. It was verified that bismuth is present at the surface of the bimetallic catalysts and that hydrogen adsorption/desorption reactions are strongly limited on Pt and Pd surfaces with high bismuth coverage. Although the onset potential for NaBH{sub 4} oxidation on Pd{sub x}Bi{sub 1-x}/C catalysts is ca. 0.2 V higher than that for Pd/C, the presence of bismuth on palladium surface influences the reaction mechanism, limiting hydrogen evolution and oxidation in the case of Pd{sub 0.8}Bi{sub 0.2} catalyst. On Pt{sub 0.9}Bi{sub 0.1} catalyst the onset potential remains unchanged comparing to Pt/C and negligible hydrogen evolution was observed in the whole potential range where the catalyst is active. The number of exchanged electrons was calculated using the Koutecky-Levich equation and it was found that for Pt{sub 0.9}Bi{sub 0.1} catalyst, ca. 8 electrons are exchanged per BH{sub 4}{sup -} ion at low potentials. The presented results are remarkable evidencing that NaBH{sub 4} can be directly oxidized at low potentials with high energy efficiency.

  1. Crossed-Wire Laser Microwelding of Pt-10 Pct Ir to 316 LVM Stainless Steel: Part II. Effect of Orientation on Joining Mechanism

    Science.gov (United States)

    Huang, Y. D.; Pequegnat, A.; Zou, G. S.; Feng, J. C.; Khan, M. I.; Zhou, Y.

    2012-04-01

    With the increasing complexity of medical devices and with efforts to reduce manufacturing costs, challenges arise in joining dissimilar materials. In this study, the laser weldability of dissimilar joints between Pt-10 pct Ir and 316 low-carbon vacuum melted (LVM) stainless steel (SS) crossed wires was investigated by characterizing the weld geometry, joint strength, morphology of weld cross sections, and differences in joining behavior, depending on which material is subject to the incident laser beam. With the Pt-Ir alloy on top, a significant amount of porosity was observed on the surface of the welds as well as throughout the weld cross sections. This unique form of porosity is believed to be a result of preferential vaporization of 316 LVM SS alloying elements that become mixed with the molten Pt-10 pct Ir during welding. The joining mechanism documented in micrographs of cross-sectioned welds was found to transition from laser brazing to fusion welding. It is inferred that the orientation of the two dissimilar metals ( i.e., which material is subject to the incident laser beam) plays an important role in weld quality of crossed-wire laser welds.

  2. Experimental investigations of the hydrothermal geochemistry of platinum and palladium: IV. The stoichiometry of Pt(IV) and Pd(II) chloride complexes at 100 to 300°C

    Science.gov (United States)

    Gammons, C. H.

    1995-05-01

    A technique based on the common ion effect was used to obtain information on the stoichiometry of the Pt(IV) and Pd(II) chloride complexes at elevated temperature. The solubility of AgCl(s) was measured in solutions of fixed mHCl and varying ΣPt(IV) or ΣPd(II) concentration. Parallel experiments were conducted at Me/Cl mole ratios (Me = Pt or Pd) of 0.0-0.5 for mHCl = 0.03-3.0, at T = 100, 200, and 300°C. The average Cl ligand numbers for Pt ranged from 4.2 to 5.8, with the majority of values > 5. These results are adequately explained by a mixture of the simple monomeric species PtCl 62t-, PtCl 5-, and PtCl 40. The temperature dependence of the equilibrium constant for the dissociation reaction PtCl 62- = PtCl 5- + Cl - was obtained: log K = 2.40(±0.25) - 1278/ T, K (valid to 573 K), which is in good agreement with published low temperature data. The neutral PtCl 40 species may become important at 300°C and low chloride concentrations (0.016 m HCl). Extrapolation of existing data indicates that the Pt(IV) chloride complexes are stable with respect to Pt(II) chloride complexes over a range of ƒO 2-pH conditions which narrows quickly with increase in temperature. Nonetheless, PtCl 62- may be the dominant form of dissolved Pt in highly oxidized brines to at least 100°C. The average Cl ligand numbers for palladium ranged from 2.164 to 2.83, and were insensitive to temperature. These results could be explained by a mixture of PdCl 2 and PdCl 3-. However, this is in disagreement with published experimental data which indicate that PdCl 4-2 is the predominant form of aqueous Pd at high chloride concentrations. An alternate explanation is that a significant quantity of the total aqueous Pd was present as polynuclear complexes, due to the very high Pd/Cl ratios of the experiments. Insufficient data exist to discriminate between these two hypotheses.

  3. Ir0.5Pt0.5O2阳极的电催化活性及氧化电解水制备%Electrocatalytic performance of Ir0.5Pt0.5O2 anode and preparation of electrolyzed oxidizing water

    Institute of Scientific and Technical Information of China (English)

    高洁; 朱玉婵; 任占冬; 李文阳; 全姗姗; 刘晔; 王又容; 柴波

    2015-01-01

    Electrolyzed oxidizing water (EOW), as an innovative disinfectant characterized by its high efficiency, broad antimicrobial spectrum, and non-toxic residues, has been broadly used in health care industry, medicines, agriculture, and food processing. EOW is usually generated by electrolysis of a dilute NaCl solution in a chamber with two cells separated by membrane, and is obtained from the anode side. But low current efficiency and short service life of the anode in EOW generators restrict the application of EOW. Ir0.5Pt0.5O2 anode was prepared by the improved Adams fusion method. The properties of Ir0.5Pt0.5O2 anode was investigated with X-ray diffraction (XRD), scanning electron microscope (SEM) and electrochemistry cyclic voltammetry (CV). The crystal type is rutile with (101), (002) and (301) crystal planes. A large number of cellular structures were observed on the surface of the anode, which greatly increased specific surface area of the anode. With increasing specific surface area, electric charge was enhanced to 0.4 mC, which was 2.65 times of pure IrO2. Electrochemical characteristics of the anode surface, such as oxidation peaks at 1.0 V(Pt-OH) and 0.9 V(Ir3+/Ir4+) proved the formation of platinum iridium oxide. The activities of chlorine evolution and oxygen evolution were also studied through linear sweep voltammetry (LSV). Compared with IrO2, chlorine evolution activity in unit apparent surface area increased significantly, but oxygen evolution activity decreased obviously. The slope of Tafel was 56.3 mV·dec−1 for chlorine evolution reaction (CER), and the mechanism was Volmer-Heyrovsky in which the rate controlling step was electrochemical desorption. The slope of Tafel was 126.6 mV·dec−1 for oxygen evolution reaction (OER), and the rate controlling step was formation of surface hydroxide on the catalyst surface. Electrochemical surface structure and electrochemical performance of Ir0.5Pt0.5O2 oxide coatings in 1 g · L−1 NaCl solution were

  4. Quadratic scaling of intrinsic Gilbert damping with spin-orbital coupling in L10 FePdPt films: experiments and Ab initio calculations.

    Science.gov (United States)

    He, P; Ma, X; Zhang, J W; Zhao, H B; Lüpke, G; Shi, Z; Zhou, S M

    2013-02-15

    The dependence of the intrinsic Gilbert damping parameter α(0) on the spin-orbital coupling strength ξ is investigated in L1(0) ordered FePd(1-x) Pt(x) films by time-resolved magneto-optical Kerr effect measurements and spin-dependent ab initio calculations. Continuous tuning of α(0) over more than one order of magnitude is realized by changing the Pt/Pd concentration ratio showing that α(0) is proportional to ξ(2) as changes of other leading parameters are found to be negligible. The perpendicular magnetic anisotropy is shown to have a similar variation trend with x. The present results may facilitate the design and fabrication of new magnetic alloys with large perpendicular magnetic anisotropy and tailored damping properties.

  5. Adsorption and oxidation of formaldehyde on a polycrystalline Pt film electrode: An in situ IR spectroscopy search for adsorbed reaction intermediates.

    Science.gov (United States)

    Jusys, Zenonas; Behm, R Jürgen

    2014-01-01

    As part of a mechanistic study of the electrooxidation of C1 molecules we have systematically investigated the dissociative adsorption/oxidation of formaldehyde on a polycrystalline Pt film electrode under experimental conditions optimizing the chance for detecting weakly adsorbed reaction intermediates. Employing in situ IR spectroscopy in an attenuated total reflection configuration (ATR-FTIRS) with p-polarized IR radiation to further improve the signal-to-noise ratio, and using low reaction temperatures (3 °C) and deuterium substitution to slow down the reaction kinetics and to stabilize weakly adsorbed reaction intermediates, we could detect an IR absorption band at 1660 cm(-1) characteristic for adsorbed formyl intermediates. This assignment is supported by an isotope shift in wave number. Effects of temperature, potential and deuterium substitution on the formation and disappearance of different adsorbed species (COad, adsorbed formate, adsorbed formyl), are monitored and quantified. Consequences on the mechanism for dissociative adsorption and oxidation of formaldehyde are discussed.

  6. Measurements of electric quadrupole moments of neutron-deficient Au, Pt, and Ir nuclei with NMR-ON in hcp-Co

    CERN Multimedia

    Smolic, E; Hagn, E; Zech, E; Seewald, G

    2002-01-01

    The aim of the experiments is the measurement of $\\,$i) nuclear magnetic moments and electric quadrupole moments of neutron-deficient isotopes in the region Os-Ir-Pt-Au with the methods of quadrupole-interaction-resolved NMR on oriented nuclei " QI-NMR-ON " and modulated adiabatic passage on oriented nuclei " MAPON " and $\\,$ii) the magnetic hyperfine field, electric field gradient (EFG), and spin-lattice relaxation of 5d elements in ferromagnetic Fe, Ni, fcc-Co and hcp-Co.\\\\ The measurements on Au isotopes have been finished successfully. The quadrupole moments of $^{186}$Au, $^{193m}$Au, $^{195}$Au, $^{195m}$Au, $^{197m}$Au, $^{198}$Au and $^{199}$Au were determined with high precision.\\\\ For neutron-deficient Ir isotopes QI-NMR-ON measurements were performed after implantation of Hg precursors. The EFG of Ir in hcp-Co has been calibrated. Thus precise values for the spectroscopic quadrupole mo...

  7. Intracellular surface-enhanced Raman scattering (SERS) with thermally stable gold nanoflowers grown from Pt and Pd seeds

    KAUST Repository

    Song, Hyon Min

    2013-01-01

    SERS provides great sensitivity at low concentrations of analytes. SERS combined with near infrared (NIR)-resonant gold nanomaterials are important candidates for theranostic agents due to their combined extinction properties and sensing abilities stemming from the deep penetration of laser light in the NIR region. Here, highly branched gold nanoflowers (GNFs) grown from Pd and Pt seeds are prepared and their SERS properties are studied. The growth was performed at 80°C without stirring, and this high temperature growth method is assumed to provide great shape stability of sharp tips in GNFs. We found that seed size must be large enough (>30 nm in diameter) to induce the growth of those SERS-active and thermally stable GNFs. We also found that the addition of silver nitrate (AgNO3) is important to induce sharp tip growth and shape stability. Incubation with Hela cells indicates that GNFs are taken up and reside in the cytoplasm. SERS was observed in those cells incubated with 1,10-phenanthroline (Phen)-loaded GNFs. This journal is © 2013 The Royal Society of Chemistry.

  8. Search for unconventional superconductors among the YTE2Si2 compounds (TE = Cr, Co, Ni, Rh, Pd, Pt).

    Science.gov (United States)

    Pikul, Adam P; Samsel-Czekala, Malgorzata; Chajewski, Grzegorz; Romanova, Tetiana; Hackemer, Alicja; Gorzelniak, Roman; Wiśniewski, Piotr; Kaczorowski, Dariusz

    2017-03-21

    Motivated by the recent discovery of exotic superconductivity in YFe2Ge2 we undertook reinvestigation of formation and physical properties of yttrium-based 1:2:2 silicides. Here we report on syntheses and crystal structures of the YTE2Si2 compounds with TE = Cr, Co, Ni, Rh, Pd, and Pt, and their low-temperature physical properties measurements, supplemented by results of fully relativistic FPLO band structure calculations. We confirm that most of the members of that family crystallize in a tetragonal ThCr2Si2-type structure (space group I4/mmm) and have three-dimensional Fermi surface, while only one of them (YPt2Si2) forms with a closely-related primitive CaBe2Ge2-type unit cell (space group P4/nmm) and possess quasi-two-dimensional Fermi surface sheets. Physical measurements indicated that BCS-like superconductivity is observed only in YPt2Si2 (Tc = 1.54 K) and YPd2Si2 (Tc = 0.43 K), while no superconducting phase transition was found in other systems at least down to 0.35 K. Thermal analysis showed no polymorphism in both superconducting phases. No clear relation between the superconductivity and the crystal structure (and dimensionality of the Fermi surface) was observed.

  9. Reducing the Ideal Shear Strengths of ZrB2 by High Efficient Alloying Elements (Ag, Au, Pd and Pt)

    Science.gov (United States)

    Dai, Fu-Zhi; Zhou, Yanchun

    2017-02-01

    Activating the plasticity of ZrB2 is a promising approach to improve its key properties for applications in hypersonic vehicles, including high temperature strength and thermal shock resistance. The present work demonstrates that ideal shear strength of ZrB2, which is a good indicator of the critical stress for dislocation nucleation, can be significantly reduced by dissolving of appropriate alloying elements. Analyzing on the bonding nature of ZrB2 reveals that choosing alloying elements with low energy valence electrons will prevent electron transferring from alloying element to the electron deficient B-B π orbits, which will reduce the local stability of the region surrounding the alloying element. Under the criterion, elements with d electrons tending to be full-filled (Ag, Au, Pd and Pt, the full-filled state is associated with low energy level) are selected as promising candidates with their prominent efficiency in reducing ideal shear strengths verified by first-principles calculations. The results provide useful guidelines for further designs of ZrB2 based materials, especially for improving their mechanical properties.

  10. Reducing the Ideal Shear Strengths of ZrB2 by High Efficient Alloying Elements (Ag, Au, Pd and Pt).

    Science.gov (United States)

    Dai, Fu-Zhi; Zhou, Yanchun

    2017-02-24

    Activating the plasticity of ZrB2 is a promising approach to improve its key properties for applications in hypersonic vehicles, including high temperature strength and thermal shock resistance. The present work demonstrates that ideal shear strength of ZrB2, which is a good indicator of the critical stress for dislocation nucleation, can be significantly reduced by dissolving of appropriate alloying elements. Analyzing on the bonding nature of ZrB2 reveals that choosing alloying elements with low energy valence electrons will prevent electron transferring from alloying element to the electron deficient B-B π orbits, which will reduce the local stability of the region surrounding the alloying element. Under the criterion, elements with d electrons tending to be full-filled (Ag, Au, Pd and Pt, the full-filled state is associated with low energy level) are selected as promising candidates with their prominent efficiency in reducing ideal shear strengths verified by first-principles calculations. The results provide useful guidelines for further designs of ZrB2 based materials, especially for improving their mechanical properties.

  11. Recent Advances on Electro-Oxidation of Ethanol on Pt- and Pd-Based Catalysts: From Reaction Mechanisms to Catalytic Materials

    Directory of Open Access Journals (Sweden)

    Ye Wang

    2015-09-01

    Full Text Available The ethanol oxidation reaction (EOR has drawn increasing interest in electrocatalysis and fuel cells by considering that ethanol as a biomass fuel has advantages of low toxicity, renewability, and a high theoretical energy density compared to methanol. Since EOR is a complex multiple-electron process involving various intermediates and products, the mechanistic investigation as well as the rational design of electrocatalysts are challenging yet essential for the desired complete oxidation to CO2. This mini review is aimed at presenting an overview of the advances in the study of reaction mechanisms and electrocatalytic materials for EOR over the past two decades with a focus on Pt- and Pd-based catalysts. We start with discussion on the mechanistic understanding of EOR on Pt and Pd surfaces using selected publications as examples. Consensuses from the mechanistic studies are that sufficient active surface sites to facilitate the cleavage of the C–C bond and the adsorption of water or its residue are critical for obtaining a higher electro-oxidation activity. We then show how this understanding has been applied to achieve improved performance on various Pt- and Pd-based catalysts through optimizing electronic and bifunctional effects, as well as by tuning their surface composition and structure. Finally we point out the remaining key problems in the development of anode electrocatalysts for EOR.

  12. Synthesis and structural characterisation of Pd(II) and Pt(II) complexes with a flexible, ferrocene-based P,S-donor amidophosphine ligand.

    Science.gov (United States)

    Tauchman, Jiří; Císařová, Ivana; Stěpnička, Petr

    2014-01-28

    1'-Diphenylphosphino-1-{[(2-(methylthio)ethyl)amino]carbonyl}ferrocene (1), accessible via amidation of 1'-(diphenylphosphino)ferrocene-1-carboxylic acid (Hdpf) with 2-(methylthio)ethylamine, reacts with [PdCl2(cod)] (cod = cycloocta-1,5-diene) at a 1 : 1 metal-to-ligand ratio to give trans-[PdCl2(1-κ(2)P,S)] (trans-2) as the sole product. A similar reaction with [PtCl2(cod)] affords a mixture of cis- and trans-[PtCl2(1-κ(2)P,S)] (cis- and trans-3), which can be separated by fractional crystallisation. Complexation reactions performed with 2 equiv. of the ligand are less selective, yielding mixtures of the expected bis-phosphine complexes (i.e., trans-[PdCl2(1-κP)2], or a mixture of cis- and trans-[PtCl2(-κP)2]) with the respective monophosphine complexes. The structures of 1, trans-2, cis-3 and trans-3 determined by X-ray diffraction demonstrate the ability of the title ligand to act as a flexible cis- or trans-P,S-chelate donor (the ligand bite angles are 174.03(2)/173.05(2)° for trans-2/3 and 92.86(2)° for cis-3).

  13. Synthesis, characterization and anticancer studies of Ni(II), Pd(II) and Pt(II) complexes with Schiff base derived from N-methylhydrazinecarbothioamide and 2-hydroxy-5-methoxy-3-nitrobenzaldehyde

    Science.gov (United States)

    Arafath, Md. Azharul; Adam, Farook; Razali, Mohd. R.; Ahmed Hassan, Loiy E.; Ahamed, Mohamed B. Khadeer; Majid, Amin Malik S. A.

    2017-02-01

    A carbothioamide NSO tridentate Schiff base ligand (HL) and its square planar complexes Na[NiLOAc], Na[PdLOAc] and [PtLdmso] have been synthesized and characterized on the basis of melting point, elemental analysis, FT-IR, 1H NMR, 13C NMR, UV-Vis spectra. The structure of HL was elucidated with X-ray diffraction analysis. In the present study, the synthesized compounds were evaluated for their anticancer properties against three human cancer cell lines breast cancer (MCF-7), cervical (Hela), and colon (HCT-116). In addition, the cytotoxicity of the synthesized compounds was tested on a normal human cell line (human endothelial cell line EA.hy926). Among the tested compounds, the complex [NiLOAc] excelled in halting proliferation of the cervical and colon cancer cells with median inhibitory concentration (IC50) values of 28.33 and 34.4 μM, respectively. The complex, [PdLOAc] demonstrated selective cytotoxicity against breast cancer line MCF-7 with IC50 = 47.5 μM, while HL showed inhibitory effect against colon cancer cell line (HCT-116) with IC50 = 55.66 μM. The complex, [PtLdmso] showed mild activity against breast cancer (MCF-7) and cervical cancer (Hela) cells with IC50 = 64.44 and 68.3 μM, respectively, whereas, it displayed insignificant cytotoxicity against human endothelial cells (EA.hy926) with IC50 > 200 μM. Cancer cells treated with [NiLOAc] showed apoptotic features such as membrane blebbing and DNA condensation. Thus, the findings of the present study demonstrated that the series of metal complexes of HL could form the new lead for development of cancer chemotherapies to treat human cervical, breast and colon malignancies.

  14. Ultrasonic-electrodeposition of PtPd alloy nanoparticles on ionic liquid-functionalized graphene paper: towards a flexible and versatile nanohybrid electrode

    Science.gov (United States)

    Sun, Yimin; Zheng, Huaming; Wang, Chenxu; Yang, Mengmeng; Zhou, Aijun; Duan, Hongwei

    2016-01-01

    Here we fabricate a new type of flexible and versatile nanohybrid paper electrode by ultrasonic-electrodeposition of PtPd alloy nanoparticles on freestanding ionic liquid (IL)-functionalized graphene paper, and explore its multifunctional applications in electrochemical catalysis and sensing systems. The graphene-based paper materials demonstrate intrinsic flexibility, exceptional mechanical strength and high electrical conductivity, and therefore can serve as an ideal freestanding flexible electrode for electrochemical devices. Furthermore, the functionalization of graphene with IL (i.e., 1-butyl-3-methylimidazolium tetrafluoroborate) not only increases the electroactive surface area of a graphene-based nanohybrid paper electrode, but also improves the adhesion and dispersion of metal nanoparticles on the paper surface. These unique attributes, combined with the merits of an ultrasonic-electrodeposition method, lead to the formation of PtPd alloy nanoparticles on IL-graphene paper with high loading, uniform distribution, controlled morphology and favourable size. Consequently, the resultant nanohybrid paper electrode exhibits remarkable catalytic activity as well as excellent cycle stability and improved anti-poisoning ability towards electrooxidation of fuel molecules such as methanol and ethanol. Furthermore, for nonenzymatic electrochemical sensing of some specific biomarkers such as glucose and reactive oxygen species, the nanohybrid paper electrode shows high selectivity, sensitivity and biocompatibility in these bio-catalytic processes, and can be used for real-time tracking hydrogen peroxide secretion by living human cells. All these features demonstrate its promising application as a versatile nanohybrid electrode material in flexible and lightweight electrochemical energy conversion and biosensing systems such as bendable on-chip power sources, wearable/implantable detectors and in vivo micro-biosensors.Here we fabricate a new type of flexible and

  15. Distribution of Precious Metals (Ag, Au, Pd, Pt, and Rh) Between Copper Matte and Iron Silicate Slag

    Science.gov (United States)

    Avarmaa, Katri; Johto, Hannu; Taskinen, Pekka

    2016-02-01

    The distributions of precious metals (Ag, Au, Pd, Pt, and Rh) between copper matte and silica-saturated iron silicate slag were determined at 1523 K to 1623 K (1250 °C to 1350 °C), in controlled CO-CO2-SO2-Ar gas mixtures. The experiments were done in silica crucibles and a fixed partial pressure of sulfur dioxide for matte grades of 55, 65, and 75 wt pct Cu. High-temperature equilibration/quenching/electron probe X-ray microanalysis technique was used to obtain compositions of the equilibrated matte and slag. The technique was applied for the first time to the distributions of precious metals in simulated flash smelting conditions. The resolution of electron probe microanalysis became critical as the detection limits were insufficient to measure reliably the precious metals concentrations (except silver) in the slag. The distribution coefficient of silver, L m/s[Ag] = [wt pctAg in matte]/(wt pctAg in slag), was found to be between 200 and 300, which agrees well with the latest studies in the literature. For other precious metals, the minimum values of distribution coefficients were determined according to the detection limits in the slag. The values obtained were for gold and platinum >250, for palladium >1000, and for rhodium >900. The distribution coefficients of palladium, although locating above distribution coefficient of the detection limit, formed a clear dependency with a good repeatability as a function of the matte grade. It increased along with matte grade and was approximately 1000 at 50 pct Cu and 2000 to 3000 at 70 pct Cu. The precious metals replace metal in the matte structure and they are present as sulfides in the copper matte.

  16. 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.

  17. Cyclic voitammetry, convolutive voltammetry, chrono-potentiometry and digital simulation studies of [Pt(C≡C tol)_2(dppm)_2Ir(CO)_2]~+PF_6~- complex

    Institute of Scientific and Technical Information of China (English)

    El-Hallag S Ibrahim

    2009-01-01

    The electrochemical behaviour of the heterobimetallic complex [Pt(C≡C tol)_2(dppm)_2-Ir(CO)_2]~+PF_6~-was studied via cyclic voltammetry, convolutive voltammetry and chronopotentiometry at glassy carbon electrode in dichloromethane solution. The electrochemical parameters calculated from experimental data were tested and confirmed by matching the experimental cyclic voltammograms with the simu-lated data. It was found that convolutive voltammetry provided higher sensitivity, better resolution and more accurate method for determination of the electrochemical parameters than ordinary cyclic volt-ammetry.

  18. 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.

  19. 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.

  20. Catalytic Intervention of MoO3 toward Ethanol Oxidation on PtPd Nanoparticles Decorated MoO3-Polypyrrole Composite Support.

    Science.gov (United States)

    De, Abhishek; Datta, Jayati; Haldar, Ipsita; Biswas, Mukul

    2016-10-14

    Ethanol oxidation reaction has been studied in acidic environment over PtPd nanoparticles (NPs) grown on the molybdenum oxide-polypyrrole composite (MOPC) support. The attempt was focused on using reduced Pt loading on non-carbon support for direct ethanol fuel cell (DEFC) operated with proton exchange membrane (PEM). As revealed in SEM study, a molybdenum oxide network exists in polypyrrole caging and the presence of metal NPs over the composite matrix is confirmed by TEM analysis. Further physicochemical characterizations such as XRD, EDAX, and XPS are followed in order to understand the surface morphology and composition of the hybrid structure. Electrochemical techniques such as voltammetry, choroamperometry, and impedance spectroscopy along with performance testing of an in-house-fabricated fuel cell are carried out to evaluate the catalytic activity of the materials for DEFC. The reaction products are estimated by ion chromatographic analysis. Considering the results obtained from the above characterization procedures, the best catalytic performance is exhibited by the Pt-Pd (1:1) on MOPC support. A clear intervention of the molybdenum oxide network is strongly advocated in the EOR sequence which increases the propensity of the reaction by making the metallites more energy efficient in terms of harnessing sufficient numbers of electrons than with the carbon support.

  1. FT-IR Spectroscopic characterization of the intermediates in the selective catalytic reduction of NO with methane on Pd/ZrO(formula)-WO(formula) catalyst

    OpenAIRE

    Çayırtepe, İlknur

    2004-01-01

    Cataloged from PDF version of article. This work involves in situ FT-IR spectroscopic study of the routes of formation, composition and thermal stability of strongly bound NOx complexes on the surface of Pd/tungstated zirconia, and transformation of the surface NOx complexes in the presence of methane in order to elucidate the mechanism of selective catalytic reduction of NO with methane. Sol-gel polymer-template synthesis was chosen to obtain high surface area in the prepar...

  2. Isolation and Structural Characterization of a Mackay 55-Metal-Atom Two-Shell Icosahedron of Pseudo-Ih Symmetry, Pd55L12(μ3-CO)20 (L = PR3, R = Isopropyl): Comparative Analysis with Interior Two-Shell Icosahedral Geometries in Capped Three-Shell Pd145, Pt-Centered Four-Shell Pd-Pt M165, and Four-Shell Au133 Nanoclusters.

    Science.gov (United States)

    Erickson, Jeremiah D; Mednikov, Evgueni G; Ivanov, Sergei A; Dahl, Lawrence F

    2016-02-10

    We present the first successful isolation and crystallographic characterization of a Mackay 55-metal-atom two-shell icosahedron, Pd55L12(μ3-CO)20 (L = PPr(i)3) (1). Its two-shell icosahedron of pseudo-Ih symmetry (without isopropyl substituents) enables a structural/bonding comparison with interior 55-metal-atom two-shell icosahedral geometries observed within the multi-shell capped 145-metal-atom three-shell Pd145(CO)72(PEt3)30 and 165-metal-atom four-shell Pt-centered (μ12-Pt)Pd164-xPtx(CO)72(PPh3)20 (x ≈ 7) nanoclusters, and within the recently reported four-shell Au133(SC6H4-p-Bu(t))52 nanocluster. DFT calculations carried out on a Pd55(CO)20(PH3)12 model analogue, with triisopropyl phosphine substituents replaced by H atoms, revealed a positive +0.84 e charge for the entire Pd55 core, with a highly positive second-shell Pd42 surface of +1.93 e.

  3. High performance Pd-based catalysts for oxidation of formic acid

    Science.gov (United States)

    Wang, Rongfang; Liao, Shijun; Ji, Shan

    Two novel catalysts for anode oxidation of formic acid, Pd 2Co/C and Pd 4Co 2Ir/C, were prepared by an organic colloid method with sodium citrate as a complexing agent. These two catalysts showed better performance towards the anodic oxidation of formic acid than Pd/C catalyst and commercial Pt/C catalyst. Compared with Pd/C catalyst, potentials of the anodic peak of formic acid at the Pd 2Co/C and Pd 4Co 2Ir/C catalyst electrodes shifted towards negative value by 140 and 50 mV, respectively, meanwhile showed higher current densities. At potential of 0.05 V (vs. SCE), the current density for Pd 4Co 2Ir/C catalyst is as high as up to 13.7 mA cm -2, which is twice of that for Pd/C catalyst, and six times of that for commercial Pt/C catalyst. The alloy catalysts were nanostructured with a diameter of ca. 3-5 nm and well dispersed on carbon according to X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. The composition of alloy catalysts was analyzed by energy dispersive X-ray analysis (EDX). Pd 4Co 2Ir/C catalyst showed the highest activity and best stability making it the best potential candidate for application in a direct formic acid fuel cell (DFAFC).

  4. Ore mineralogy of the Serra Pelada Au-Pd-Pt deposit, Carajás, Brazil and implications for ore-forming processes

    Science.gov (United States)

    Berni, Gabriel V.; Heinrich, Christoph A.; Lobato, Lydia M.; Wall, Vic

    2016-08-01

    Serra Pelada is a world-class hydrothermal Au-Pd-Pt deposit located at the eastern border of the Amazon craton, northern Brazil. The rocks at Serra Pelada have experienced intense tropical weathering for about 70 Ma, but drill core samples preserve the primary mineralogy and hydrothermal alteration features, with extreme grades of Au, Pd and Pt individually reaching hundreds of parts per million (ppm) by weight. Mineralization at Serra Pelada occurs in hydrothermally altered metasiltstones and dolomitic metasandstones at the hinge zone of a recumbent syncline, comprising zones of hematite, chlorite-carbon, argillic, and siliceous alteration. The main hydrothermal gangue minerals are quartz, kaolinite, sericite, amesite, hematite, monazite, florencite and variable amounts of highly reflective carbonaceous matter. Hydrothermal carbon input is evident from precipitated carbon occurring along crenulation planes and veinlets associated with the precious metals. Ore and accessory minerals include a variety of sulphide, selenide, arsenide, sulphate and oxide minerals, including gold with variable metal contents, palladian gold, fischesserite, sudovikovite, sperrylite, selenian braggite, isomertieite, mertieite-II and secondary Au-Pt-Pd alloys. The composition of fischesserite varies from the ideal formula (Ag3AuSe2) towards a more Ag-rich composition, indicating a disordered solid solution form that is stable only above 260 °C, consistent with the high thermal maturity of associated carbonaceous matter approaching graphite. Primary ore and gangue minerals at Serra Pelada comprise a suite of elements that are best transported in oxidising conditions and precipitated upon reduction. This suggests that fluid mixing between a highly oxidised (metal carrier) and a reduced fluid was a key process for high-grade noble metal precipitation at Serra Pelada.

  5. Structural, elastic and thermodynamic properties of A15-type compounds V3X (X = Ir, Pt and Au) from first-principles calculations

    Science.gov (United States)

    Wang, Mingliang; Chen, Zhe; Chen, Dong; Xia, Cunjuan; Wu, Yi

    2016-12-01

    The structural, elastic and thermodynamic properties of the A15 structure V3Ir, V3Pt and V3Au were studied using first-principles calculations based on the density functional theory (DFT) within generalized gradient approximation (GGA) and local density approximation (LDA) methods. The results have shown that both GGA and LDA methods can process the structural optimization in good agreement with the available experimental parameters in the compounds. Furthermore, the elastic properties and Debye temperatures estimated by LDA method are typically larger than the GGA methods. However, the GGA methods can make better prediction with the experimental values of Debye temperature in V3Ir, V3Pt and V3Au, signifying the precision of the calculating work. Based on the E-V data derived from the GGA method, the variations of the Debye temperature, coefficient of thermal expansion and heat capacity under pressure ranging from 0 GPa to 50 GPa and at temperature ranging from 0 K to 1500 K were obtained and analyzed for all compounds using the quasi-harmonic Debye model.

  6. High-pressure/high-temperature synthesis and characterization of the first palladium or platinum containing lithium transition-metal sulfides Li2M3S4 (M=Pd, Pt)

    Science.gov (United States)

    Heymann, Gunter; Niehaus, Oliver; Krüger, Hannes; Selter, Philipp; Brunklaus, Gunther; Pöttgen, Rainer

    2016-10-01

    The new lithium transition-metal sulfides Li2M3S4 (M=Pd, Pt) were obtained via multianvil high-pressure/high-temperature syntheses at 8 GPa and 1150 °C starting from a stoichiometric mixture of lithium nitride, sulfur, and palladium or platinum. Single crystal structure analyses indicated the space group P21/c (no. 14) with the following lattice parameters and refinement results: a=492.9(1), b=1005.9(2), c=614.9(2) pm, β=110.9 (1)°, R1=0.0165, wR2=0.0308 (all data) for Li2Pd3S4 and a=498.2(1), b=1005.5(2), c=613.0(2) pm, β=110.8(1)°, R1=0.0215, wR2=0.0450 (all data) for Li2Pt3S4. The crystal structures are built up from two distinct Pd/Pt sites, one of which is a special position (0,0,0), two sulfur sites, and one lithium site. The atoms Pd2/Pt2 form isolated square planar PdS4/PtS4 units, whereas the Pd1/Pt1 atoms form pairs of square planar PdS4/PtS4 units, which are connected via a common edge. These two structural motives built up a three-dimensional network structure by linking through common corners. The lithium atoms are positioned inside of the so formed channels. Li2M3S4 (M=Pd, Pt) are isostructural to the minerals jaguéite, Cu2Pd3Se4 and chrisstanleyite, Ag2Pd3Se4, which are up to now the only representatives of this structure type. Both compounds were studied with respect to their magnetic properties and can be classified as Pauli paramagnetic or diamagnetic. Regarding the possibility of lithium mobility inside the channels, of the structure, solid state 7Li NMR and high-temperature single crystal investigations revealed localization of the lithium atoms on their crystallographic sites.

  7. Pt修饰的Pd/石墨烯纳米复合材料的制备及对乙二醇氧化反应的电催化活性%Preparation and enhanced electrocatalytic activity of Pt-modified Pd/graphene nanocomposites for ethylene glycol oxidation

    Institute of Scientific and Technical Information of China (English)

    马翔宇; 金长春; 董如林

    2015-01-01

    Pd nanoparticles/graphene (Pd/G) composites were fabricatedvia the chemical reduction method using graphite oxide and palladium nitrate,and then deposition of Pt on Pd/G was performed potentiostatically using chloroplatinic acid as precursor of platinum. Pt-modified Pd/G (Pt-Pd/G) electrodes with different platinum loadings were prepared. The microstructure of the Pt-Pd/G electrode was characterized by FE-SEM,EDX and TEM,and the results showed that metal nanoparticles with a mean diameter of 7.2 nm were evenly distributed on the surface of graphene. Electrochemical measurements revealed the high catalytic activity of Pt-Pd/G electrodes for ethylene glycol oxidation in alkaline solution. The peak current density on the Pt-Pd/G electrodes with a Pt∶Pd atomic ratio of 1∶42 was about 3.0 and 2.7 times higher than that on Pd/G and Pt/G electrodes,respectively. The catalytic activity of the Pd/G electrode was significantly improved by the deposition of a small amount of Pt. The modification method used in this study is simple but its effect is very obvious,and the approach can be used to modify other metal substrates with a second metal.%以氧化石墨(GO)和Pd(NO3)2为原料,通过化学还原法制备Pd纳米粒子-石墨烯(Pd/G)纳米复合材料,然后以H2PtCl6作为Pt前体,在Pd纳米粒子的表面恒电位沉积Pt,制备不同Pt负载量的Pd/G(Pt-Pd/G)电极。利用场发射扫描电镜(FE-SEM)、透射电镜(TEM)和X射线能谱仪(EDX)对材料的微观结构进行了表征和分析。结果显示石墨烯上的金属粒子分散均匀,平均粒径约7.2nm。电化学测试结果显示Pt-Pd/G电极对乙二醇电化学氧化反应具有良好的催化性能。当纳米粒子的Pt∶Pd原子百分比为1∶42时,其反应峰电流密度分别为Pd/G和Pt/G电极的3.0倍和2.7倍。少量的Pt沉淀可显著改进Pd/G电极的催化活性。本研究采用的修饰方法简单,修饰效果明显,可应用于其

  8. Ion-scattering study and Monte Carlo simulations of surface segregation in Pd-Pt nanoclusters obtained by laser vaporization of bulk alloys

    Science.gov (United States)

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

    1998-07-01

    Bimetallic Pd-Pt clusters deposited on amorphous carbon have been produced by laser vaporization of various bulk alloys. Energy dispersive x-ray analysis and transmission electron microscopy show that they have a perfectly well-defined stoichiometry and a narrow range of size. They constitute ideal systems to investigate segregation processes in finite solids. It is shown that low-energy ion scattering allows the determination of surface concentration, which has been found to be different from the overall one. Monte Carlo simulations coupled with a recently developed energetical model, based on a tight-binding scheme that includes bond strength modifications at surfaces, account well for the experimental finding and give information on the surface distribution of the segregating Pd atoms.

  9. NMR and NQR Studies on Non-centrosymmetric Superconductors Re7B3, LaBiPt, and BiPd

    Science.gov (United States)

    Matano, Kazuaki; Maeda, Satoki; Sawaoka, Hiroki; Muro, Yuji; Takabatake, Toshiro; Joshi, Bhanu; Ramakrishnan, Srinivasan; Kawashima, Kenji; Akimitsu, Jun; Zheng, Guo-qing

    2013-08-01

    We report the nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements for non-centrosymmetric superconductors Re7B3, LaBiPt, and BiPd containing heavy elements. For all three compounds, the spin--lattice relaxation rate 1/T1 shows a coherence peak just below Tc and decreases exponentially at low temperatures, which indicates that an isotropic superconducting gap is dominant in these compounds. In BiPd, the height of the coherence peak just below Tc is much suppressed, which suggests that there exists a substantial component of gap with nodes in this compound. Our results indicate that heavy element is not the only factor, but the extent of inversion symmetry breaking is also important to induce a large spin--orbit coupling and an unconventional superconducting state.

  10. Diode-type Gas Sensors Fabricated with a Titania Film on a Ti Plate and Pd-Pt Electrodes -Effects of Polymer Coating on the Hydrogen-sensing Properties-

    Science.gov (United States)

    Hyodo, T.; Nakaoka, M.; Kaneyasu, K.; Kato, H.; Yanagi, H.; Shimizu, Y.

    2011-10-01

    H2 responses of a diode-type gas sensor fabricated with a TiO2 film prepared by anodization of a Ti plate and Pd-Pt electrodes (Pd-Pt/TiO2) and the effects of polymer coating on the Pd-Pt/TiO2 sensor were investigated in this study. The H2 response of the Pd-Pt/TiO2 sensor in dry N2 was larger than that in dry air at 250°C, but the addition of moisture into the atmosphere reduced O2 concentration dependence of H2 response. The responses decreased drastically at lower temperature (50°C), but the responses in N2 were larger than those in air under both dry and wet conditions. The coating of polymer on the Pd-Pt/TiO2 sensor increased the H2 responses in wet air and N2 and reduced O2 concentration dependence of H2 responses.

  11. DFT study of the formate formation on Ni(111) surface doped by transition metals [Ni(111)-M; M=Cu, Pd, Pt, Rh

    Science.gov (United States)

    Nugraha; Saputro, A. G.; Agusta, M. K.; Rusydi, F.; Maezono, R.; Dipojono, H. K.

    2016-08-01

    We report on a theoretical study of the formation of formate (HCOO) from the reaction of CO2 gas and a pre- adsorbed H atom (CO2 (g) + *H → *HCOO) on Ni(111) surface doped by transition-metals [Ni(111)-M; M= Cu, Pd, Pt, Rh] by means of density functional theory (DFT) calculations. This *HCOO formation reaction is one of the most important rate- limiting steps in the methanol synthesis process. We find that the presence of transition metal doping on the first-layer of Ni(111) surface could reduce the activation barrier of this reaction [up to ~38.4%, compared to clean Ni(111) surface].

  12. Distribution of platinum group elements (Pt, Pd, Rh) in environmental and clinical matrices: Composition, analytical techniques and scientific outlook: Status report.

    Science.gov (United States)

    Hees, T; Wenclawiak, B; Lustig, S; Schramel, P; Schwarzer, M; Schuster, M; Verstraete, D; Dams, R; Helmers, E

    1998-01-01

    Trace concentrations of the platinum group elements (PGE; here: Pt, Pd and Rh) play an important role in environmental analysis and assessment. Their importance is based on 1. their increasing use as active compartments in automobile exhaust catalysts, 2. their use as cancer anti-tumor agents in medicine. Due to their allergenic and cytotoxic potential, it is necessary to improve selectivity and sensitivity during analytical investigation of matrices like soil, grass, urine or blood. This paper summarizes the present knowledge of PGE in the fields of analytical chemistry, automobile emission rates, bioavailability, toxicology and medicine.

  13. Synthesis, structure and photocatalytic activity of nano TiO2 and nano Ti1-MO2- (M = Cu, Fe, Pt, Pd, V, W, Ce, Zr)

    Indian Academy of Sciences (India)

    M S Hegde; K Nagaveni; Sounak Roy

    2005-10-01

    We have synthesized 5-7 nm size, highly crystalline TiO2 which absorbs radiation in the visible region of solar spectrum. The material shows higher photocatalytic activity both in UV and visible region of the solar radiation compared to commercial Degussa P25 TiO2. Transition metal ion substitution for Ti4+ creates mid-gap states which act as recombination centers for electron{hole induced by photons thus reducing photocatalytic activity. However, Pt, Pd and Cu ion substituted TiO2 are excellent CO oxidation and NO reduction catalysts at temperatures less than 100°C.

  14. 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

  15. Direct functionalization of M-C (M = Pt(II), Pd(II)) bonds using environmentally benign oxidants, O2 and H2O2.

    Science.gov (United States)

    Vedernikov, Andrei N

    2012-06-19

    Atom economy and the use of "green" reagents in organic oxidation, including oxidation of hydrocarbons, remain challenges for organic synthesis. Solutions to this problem would lead to a more sustainable economy because of improved access to energy resources such as natural gas. Although natural gas is still abundant, about a third of methane extracted in distant oil fields currently cannot be used as a chemical feedstock because of a dearth of economically and ecologically viable methodologies for partial methane oxidation. Two readily available "atom-economical" "green" oxidants are dioxygen and hydrogen peroxide, but few methodologies have utilized these oxidants effectively in selective organic transformations. Hydrocarbon oxidation and C-H functionalization reactions rely on Pd(II) and Pt(II) complexes. These reagents have practical advantages because they can tolerate moisture and atmospheric oxygen. But this tolerance for atmospheric oxygen also makes it challenging to develop novel organometallic palladium and platinum-catalyzed C-H oxidation reactions utilizing O(2) or H(2)O(2). This Account focuses on these challenges: the development of M-C bond (M = Pt(II), Pd(II)) functionalization and related selective hydrocarbon C-H oxidations with O(2) or H(2)O(2). Reactions discussed in this Account do not involve mediators, since the latter can impart low reaction selectivity and catalyst instability. As an efficient solution to the problem of direct M-C oxidation and functionalization with O(2) and H(2)O(2), this Account introduces the use of facially chelating semilabile ligands such as di(2-pyridyl)methanesulfonate and the hydrated form of di(2-pyridyl)ketone that enable selective and facile M(II)-C(sp(n)) bond functionalization with O(2) (M = Pt, n = 3; M = Pd, n = 3 (benzylic)) or H(2)O(2) (M = Pd, n = 2). The reactions proceed efficiently in protic solvents such as water, methanol, or acetic acid. With the exception of benzylic Pd(II) complexes, the

  16. Enhancement of order degree and perpendicular magnetic anisotropy of L10 ordered Fe(Pt,Pd) alloy film by introducing a thin MgO cap-layer

    Science.gov (United States)

    Noguchi, Youhei; Ohtake, Mitsuru; Futamoto, Masaaki; Kirino, Fumiyoshi; Inaba, Nobuyuki

    2016-07-01

    Fe50PtxPd50-x (at%, x=0-50) alloy films of 10 nm thickness with and without 2-nm-thick MgO cap-layers are prepared on MgO(001) single-crystal substrates by employing a two-step method consisting of low-temperature deposition at 200 °C followed by high-temperature annealing at 600 °C. The influences of MgO cap-layer on the structure and the magnetic properties are investigated. Fe50PtxPd50-x films epitaxially grow on the substrates at 200 °C. The Fe50Pd50 and the Fe50Pt12.5Pd37.5 films are respectively composed of (001) single-crystals with disordered fcc-based (A1) and bcc-based (A2) structures. The films with x>25 consist of mixtures of A1 and A2 crystals. The volume ratio of A2 to A1 crystal decreases with increasing the x value from 25 to 50. The in-plane and out-of-plane lattices are respectively expanded and shrunk due to accommodation of lattice mismatch between film and substrate. When the films are annealed at 600 °C, phase transformation to L10 ordered phase takes place. L10 phase transformation of Fe50PtxPd50-x film is promoted for a sample with MgO cap-layer and the order degree is higher than that without cap-layer. Furthermore, L10 ordering with the c-axis perpendicular to the substrate surface is enhanced for the film with cap-layer. The cap-layer is considered to be giving a tension stress to the magnetic film in lateral direction which promotes L10 ordering with the c-axis perpendicular to the substrate. Deposition of cap-layer is shown effective in achieving higher order degree and in enhancing perpendicular magnetic anisotropy with Fe(Pt,Pd) films.

  17. Adsorption and oxidation of formaldehyde on a polycrystalline Pt film electrode: An in situ IR spectroscopy search for adsorbed reaction intermediates

    Directory of Open Access Journals (Sweden)

    Zenonas Jusys

    2014-05-01

    Full Text Available As part of a mechanistic study of the electrooxidation of C1 molecules we have systematically investigated the dissociative adsorption/oxidation of formaldehyde on a polycrystalline Pt film electrode under experimental conditions optimizing the chance for detecting weakly adsorbed reaction intermediates. Employing in situ IR spectroscopy in an attenuated total reflection configuration (ATR-FTIRS with p-polarized IR radiation to further improve the signal-to-noise ratio, and using low reaction temperatures (3 °C and deuterium substitution to slow down the reaction kinetics and to stabilize weakly adsorbed reaction intermediates, we could detect an IR absorption band at 1660 cm−1 characteristic for adsorbed formyl intermediates. This assignment is supported by an isotope shift in wave number. Effects of temperature, potential and deuterium substitution on the formation and disappearance of different adsorbed species (COad, adsorbed formate, adsorbed formyl, are monitored and quantified. Consequences on the mechanism for dissociative adsorption and oxidation of formaldehyde are discussed.

  18. Modification of N-doped TiO2 photocatalysts using noble metals (Pt, Pd) - a combined XPS and DFT study.

    Science.gov (United States)

    Batalović, K; Bundaleski, N; Radaković, J; Abazović, N; Mitrić, M; Silva, R A; Savić, M; Belošević-Čavor, J; Rakočević, Z; Rangel, C M

    2017-03-08

    Nitrogen-doped TiO2 (N-TiO2) is considered as one of the most promising materials for various photocatalytic applications, while noble metals Pd and Pt are known as good catalysts for hydrogen evolution. This work focuses on the determination of structural and electronic modifications of N-TiO2, achieved by noble metal deposition at the surface, as a starting indicator for potential applications. We focus on the properties of easily synthesized nanocrystalline nitrogen-doped anatase TiO2, modified by depositing small amounts of Pd (0.05 wt%) and Pt (0.10 wt%), aiming to demonstrate efficient enhancement of optical properties. The chemical states of dopants are studied in detail, using X-ray photoemission spectroscopy, to address the potential of N-TiO2 to act as a support for metallic nanoparticles. DFT calculations are used to resolve substitutional from interstitial nitrogen doping of anatase TiO2, as well as to study the combined effect of nitrogen doping and oxygen vacancy formation. Based on the binding energies calculated using Slater's transition state theory, dominant contribution to the N 1s binding energy at 399.8 eV is ascribed to interstitially doped nitrogen in anatase TiO2. Given that both structure and photocatalytic properties depend greatly on the synthesis procedure, this work contributes further to establishing correlation between the structure and optical properties of the noble metal modified N-TiO2 system.

  19. Bimetallic Pd-Pt supported graphene promoted enzymatic redox cycling for ultrasensitive electrochemical quantification of microRNA from cell lysates.

    Science.gov (United States)

    Cheng, Fang-Fang; Zhang, Jing-Jing; He, Ting-Ting; Shi, Jian-Jun; Abdel-Halim, E S; Zhu, Jun-Jie

    2014-08-21

    The expression of microRNAs (miRNAs) is related to some cancer diseases. Recently, miRNAs have emerged as new candidate diagnostic and prognostic biomarkers for detecting a wide variety of cancers. Due to low levels, short sequences and high sequence homology among family members, the quantitative miRNA analysis is still a challenge. A novel electrochemical biosensor with triple signal amplification for the ultrasensitive detection of miRNA was developed based on phosphatase, redox-cycling amplification, a bimetallic Pd-Pt supported graphene functionalized screen-printed gold electrode, and two stem-loop structured DNAs as target capturers. The proposed biosensor is highly sensitive due to the enhanced electrochemical signal of Pd-Pt supported graphene and sufficiently selective to discriminate the target miRNA from homologous miRNAs in the presence of loop-stem structure probes with T4 DNA ligase. Therefore, this strategy provided a new and ultrasensitive platform for amplified detection and subsequent analysis of miRNA in biomedical research and clinical diagnosis.

  20. Magnetoresistance of ordered (Pd/sub x/Pt/sub 1-x/)/sub 3/Fe alloys in fields up to 150 kG

    Energy Technology Data Exchange (ETDEWEB)

    Kourov, N.I.; Tsiovkin, Y.N.; Volkenshtein, N.V.; Glin' skii, M.

    1985-02-01

    The longitudinal (..delta..rho/sub parallel//rho/sub 0/) and transverse (..delta..rho/sub perpendicular//rho/sub 0/) magnetoresistances of atomically ordered (Pd/sub x/Pt/sub 1-x/)/sub 3/Fe alloys are studied in magnetic fields of up to 150 kG. The magnetoresistance of the ferromagnetic Pd/sub 3/Fe is shown to obey the well-known rules for even galvanomagnetic effects. In the antiferromagnetic Pt/sub 3/Fe the longitudinal and transverse magnetoresistances are positive and are proportional to H/sup 3/2/ for fields in the range 30

  1. A general and high-yield galvanic displacement approach to Au-M (M = Au, Pd, and Pt) core-shell nanostructures with porous shells and enhanced electrocatalytic performances.

    Science.gov (United States)

    Kuai, Long; Geng, Baoyou; Wang, Shaozhen; Sang, Yan

    2012-07-23

    In this work, we utilize the galvanic displacement synthesis and make it a general and efficient method for the preparation of Au-M (M = Au, Pd, and Pt) core-shell nanostructures with porous shells, which consist of multilayer nanoparticles. The method is generally applicable to the preparation of Au-Au, Au-Pd, and Au-Pt core-shell nanostructures with typical porous shells. Moreover, the Au-Au isomeric core-shell nanostructure is reported for the first time. The lower oxidation states of Au(I), Pd(II), and Pt(II) are supposed to contribute to the formation of porous core-shell nanostructures instead of yolk-shell nanostructures. The electrocatalytic ethanol oxidation and oxygen reduction reaction (ORR) performance of porous Au-Pd core-shell nanostructures are assessed as a typical example for the investigation of the advantages of the obtained core-shell nanostructures. As expected, the Au-Pd core-shell nanostructure indeed exhibits a significantly reduced overpotential (the peak potential is shifted in the positive direction by 44 mV and 32 mV), a much improved CO tolerance (I(f)/I(b) is 3.6 and 1.63 times higher), and an enhanced catalytic stability in comparison with Pd nanoparticles and Pt/C catalysts. Thus, porous Au-M (M = Au, Pd, and Pt) core-shell nanostructures may provide many opportunities in the fields of organic catalysis, direct alcohol fuel cells, surface-enhanced Raman scattering, and so forth.

  2. 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.

  3. Self-consistent linear-muffin-tin-orbitals coherent-potential technique for bulk and surface calculations: Cu-Ni, Ag-Pd, and Au-Pt random alloys

    DEFF Research Database (Denmark)

    Abrikosov, I. A.; Skriver, Hans Lomholt

    1993-01-01

    energies and work functions for three fcc-based alloys (Cu-Ni, Ag-Pd, and Au-Pt) over the complete concentration range. The calculated mixing enthalpies for the Ag-Pd and Au-Pt systems agrees with experimental values, and the calculated concentration dependence of the lattice parameters agrees...... with experiment for all three systems. We find that the calculated surface energies and work functions in the unsegregated case exhibit a small positive deviation from a linear concentration dependence. Finally, we performed a segregation analysis based on the calculated surface energies by means of a simple...

  4. Structural and electronic properties and the fermi surface of the new non-centrosymmetric superconductors: 3.6 K CaIrSi3 and 2.3 K CaPtSi3

    Science.gov (United States)

    Bannikov, V. V.; Shein, I. R.; Ivanovskii, A. L.

    2010-09-01

    Ab initio FLAPW-GGA calculations have been performed to investigate structural properties, electronic band structure, and Fermi surface topology of the newly discovered non-centrosymmetric superconductors: 3.6 K CaIrSi3 and 2.3 K CaPtSi3. As a result, the peculiarities of the crystal structure, electronic bands, total and site-projected l-decomposed densities of states, and the shape of the Fermi surface for CaIrSi3 and CaPtSi3 were obtained and analyzed.

  5. 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.

  6. Synthesis, characterization, computational studies, antimicrobial activities and carbonic anhydrase inhibitor effects of 2-hydroxy acetophenone-N-methyl p-toluenesulfonylhydrazone and its Co(II), Pd(II), Pt(II) complexes

    Science.gov (United States)

    Özbek, Neslihan; Alyar, Saliha; Memmi, Burcu Koçak; Gündüzalp, Ayla Balaban; Bahçeci, Zafer; Alyar, Hamit

    2017-01-01

    2-Hydroxyacetophenone-N-methyl p-toluenesulfonylhydrazone (afptsmh) derived from p-toluenesulfonicacid-1-methylhydrazide (ptsmh) and its Co(II), Pd(II), Pt(II) complexes were synthesized for the first time. Synthesized compounds were characterized by spectroscopic methods (FT-IR, 1Hsbnd 13C NMR, LC-MS, UV-vis), magnetic susceptibility and conductivity measurements. 1H and 13C shielding tensors for crystal structure of ligand were calculated with GIAO/DFT/B3LYP/6-311++G(d,p) methods in CDCl3. The vibrational band assignments were performed at B3LYP/6-311++G(d,p) theory level combined with scaled quantum mechanics force field (SQMFF) methodology. The antibacterial activities of synthesized compounds were studied against some Gram positive and Gram negative bacteria by using microdilution and disc diffusion methods. In vitro enzyme inhibitory effects of the compounds were measured by UV-vis spectrophotometer. The enzyme activities against human carbonic anhydrase II (hCA II) were evaluated as IC50 (the half maximal inhibitory concentration) values. It was found that afptsmh and its metal complexes have inhibitory effects on hCA II isoenzyme. General esterase activities were determined using alpha and beta naphtyl acetate substrates (α- and β-NAs) of Drosophila melanogaster (D. melanogaster). Activity results show that afptsmh does not strongly affect the bacteria strains and also shows poor inhibitory activity against hCAII isoenzyme whereas all complexes posses higher biological activities.

  7. 1H, 1H, 2H, 2H-Perfluoroalkyl-Functionalization of Ni(II), Pd(II) and Pt(II) Mono- and Diphosphine Complexes : minimizing the Electronic Consequences for the Metal Center

    NARCIS (Netherlands)

    Koten, G. van; Wolf, E. de; Mens, A.J.M.; Gijzeman, O.L.J.; Lenthe, J.H. van; Jenneskens, L.W.; Deelman, B.J.

    2003-01-01

    A series of fluorous derivatives of group 10 complexes MCl2(dppe) and [M(dppe)2](BF4)2 (M = Ni, Pd or Pt; dppe = 1,2-bis(diphenylphosphino)ethane) and cis-PtCl2(PPh3)2 was synthesized. The influence of para-(1H,1H,2H,2H-perfluoroalkyl)dimethylsilyl-functionalization of the phosphine phenyl groups of

  8. Crystal field splittings of PrX 2 compounds (X=Pt, Rh, Ir, Ru, Ni) studied by inelastic neutron scattering

    Science.gov (United States)

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

    1983-01-01

    Neutron inelastic scattering experiments have been performed on polycrystalline samples of the cubic Laves phase compounds PrX 2(X=Pt, Rh, Ir, Ni). Measurements in the paramagnetic state yield LLW parameters 0.6< x<1 and W<0. In this region various levels cross at an x value 0.86 and as a consequence the electronic ground state in the paramagnetic regime is either the singlet Γ 1, or the non-magnetic doublet Γ 3. Measurements in the ferromagnetic state support these conclusions. The crystal-field parameters obtained can be used in model calculations of some macroscopic quantities, in particular the specific heat and the spontaneous magnetization. The variation of the x values in the present series of Laves phase compounds evidences the presence of a contribution by conduction electrons to the crystal field.

  9. 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.

  10. L{sub i} (i=1,2,3) subshell X-ray production cross-sections and fluorescence yields for Ir, Pt, Pb and Bi

    Energy Technology Data Exchange (ETDEWEB)

    Singh, P.; Sharma, M.; Shahi, J.S.; Mehta, D.; Singh, N. E-mail: nsingh@pu.ac.in

    2003-09-01

    The L{sub i} (i=1,2,3) subshell X-ray production (XRP) cross-sections were measured for {sub 77}Ir, {sub 78}Pt, {sub 82}Pb and {sub 83}Bi following direct ionization in the L{sub i} (i=1,2,3) subshells by the 59.54 keV {gamma}-rays and the L{sub 3} subshell by the Br/Rb/Sr/Y K X-rays. The photon sources consisting of an {sup 241}Am source in (i) the direct excitation mode and (ii) the secondary excitation mode together with the KBr/RbNO{sub 3}/SrCO{sub 3} /Y secondary exciter and an Si(Li) detector were used. The L{sub i} (i=1,2,3) subshell fluorescence yields ({omega}{sub i}) for these elements were deduced using the measured XRP cross-sections and the L{sub i} subshell photoionization cross-sections based on the Hartree-Fock-Slater model. The measured {omega}{sub 1} values are found to be higher upto 50% than those based on the relativistic Dirac-Hartree-Slater (RDHS) calculations, while the {omega}{sub 2} and {omega}{sub 3} values exhibit good agreement. The predicted jump in the RDHS based {omega}{sub 1} values from {sub 77}Ir to {sub 78}Pt due to onset of intense L{sub 1}-L{sub 3}M{sub 4} CK transition is not observed.

  11. Highly charged W+13, Ir+16, and Pt+17 ions as promising optical clock candidates for probing variations of the fine-structure constant

    Science.gov (United States)

    Nandy, D. K.; Sahoo, B. K.

    2016-09-01

    Transitions among the first three low-lying states in the highly charged W+13, Ir+16, and Pt+17 ions are found to be strongly forbidden with wavelengths in the optical regime. By determining their energy levels, lifetimes, and other spectroscopic properties that are decisive quantities for estimating dominant systematics due to stray electromagnetic interactions in an experiment, we demonstrate that it can be possible to measure frequencies of the lowest forbidden transitions below a 10-19 precision level in the above ions, and hence, they seem to be suitable for frequency standards. We employ a sophisticated relativistic coupled cluster method to carry out calculations of these properties of the above states involving 4 f - and 5 s -core orbitals. We also found, by estimating their relativistic sensitivity coefficients, that these clock transitions can be highly sensitive to the tiny drift in the fine-structure constant αe. Consequently, a clock based on one of these ions, particularly Pt+17, could be used for corroborating the hypothesis of temporal and spatial variation in αe.

  12. 用于质子交换膜燃料电池的高活性、高稳定性PtIrFe/C三元合金催化剂∗%Remarkably Active and Durable PtIrFe/C Ternary Alloy Catalysts with Potential Application to Proton Exchange Membrane Fuel Cells

    Institute of Scientific and Technical Information of China (English)

    杜鑫鑫; 王晓霞; 贺阳; 王健农

    2016-01-01

    采用催化裂解法制备了多孔碳,将其作为催化剂载体,利用液相还原和真空热处理工艺制备出PtIrFe/C三元合金催化剂。采用 X射线衍射、透射电子显微镜等手段对样品的结构形貌进行表征。使用电化学测试手段研究了不同热处理温度对其催化性能的影响。实验结果表明,热处理带来的合金化作用使催化剂的催化活性和耐久性得到了极大的提高。经过700℃热处理的样品,其面积比活性和质量比活性分别是传统商业 Pt/C 催化剂的3~4倍。%Using a mesoporous carbon (prepared via catalyzed pyrolysis)as a support material,PtIrFe/C alloy catalysts were synthesized by a liquid reduction and heat treatment method,and characterized by transmission electron microscopy and powder X-ray diffraction to explore and study the morphologies and crystallization properties.The an-nealing of the as prepared catalysts was performed at different temperatures,tested by electrochemical measurements, and proved to be of great importance for the improvement of the catalyst′s activity and durability due to the alloying effect.The catalysts annealed at 700 ℃ exhibited the highest area-specific activity and mass-specific activity which were 3-4 times higher than those of a commercial Pt/C catalyst.

  13. Separation Studies of Pd(II from Acidic Chloride Solutions of Pt(IV, Ni(II and Rh(III by Using 4-Aroyl-3-Phenyl-5-Isoxazolones

    Directory of Open Access Journals (Sweden)

    Koduru Janardhan Reddy

    2012-01-01

    Full Text Available This study examined the effect influence of various factors on the extraction of Pd(II to develop a new liquid-liquid extraction mechanism for the selective separation of palladium(II from its acidic chloride solutions using 4-aroyl-3-phenyl-5-isoxazolones (HA, such as 3-phenyl-4-(4-fluorobenzoyl-5- isoxazolone (HFBPI, 3-phenyl-4-benzoyl-5-isoxazolone (HPBI and 3-phenyl-4- (4-toluoyl-5-isoxazolone (HTPI. The extraction strength of Pd(II with HA were in the following order: HFBPI > HPBI > HTPI, which is opposite to that observed with their pKa values. HPBI was used to separate Pd(II from Pt(IV, Ni(II and Rh(III metal ions and calculated their separation factors (S.F. were followed in the order: Pd/Ni (40±0.4 > Pd/Pt (25±0.2 > Pd/Rh (15±0.3 > Rh/Ni (2.7±0.3 > Pt/Ni ≈ Rh/Pt (1.7±0.2. The loading and striping of Pd(II (1.12×10-4 mol L-1 were also examined using 1.0×10-3 mol L-1 HPBI in CHCl3 and 1.0 mol L-1 HCl, respectively. The results demonstrated that the maximum (97.5% extraction and desorption (89% of metal required at least 3.0 cycles. The developed method was applied successfully to the separation of palladium from synthetic water samples.

  14. The stages and duration of the Kieveiskoe and Fedorovskoe Pt-Pd deposits formation: U-Pb zircon data (Kola Peninsula)

    Science.gov (United States)

    Nitkina, Elena

    2010-05-01

    The Kola Peninsula is one of the unique geological provinces both in Russia and in the world, where Pt-Pd Kieveiskoe and Fedorovskoe deposits have been discovered (Mitrofanov, 2005). Several deposits within the Northern and Southern belts contain first hundreds of tons of estimated platinum metal resources, allowing us to ascribe the intrusions of the belts to the class of large igneous province (Schissel et al., 2002; Mitrofanov, 2005). The Kieveiskoe and Fedorovskoe deposits belong to the Pt-bearing Fedorovo-Pansky layered intrusion which is situated in the central part of the Kola Peninsula and is one of 14 major Early Proterozoic layered massifs of the Northern belt occurring at the border between Early Proterozoic volcano-sedimentary rift sequences and Archaean basement gneisses (Zagorodny, Radchenko, 1983; Bayanova, 2004). The aim of this report is to summarize all U-Pb data for Kieveiskoe and Fedorovskoe deposits including single grain dating with Pb205 tracer. At present, the following ages have been defined for the different stages of the massif evolution: 2526 - 2516 Ma - pyroxenite and gabbro of the Fedorovskoe deposit magma chamber (Nitkina, 2006), 2515 - 2518 Ma - Pt-bearing gabbro of Federovskoe stratiforme deposit; 2505 - 2496- 2485 Ma (Bayanova, 2004; Nitkina, 2006) - gabbro-norite and gabbro of the main phase of the Kieveiskoe deposit magma chamber and disseminated platinum-metal mineralization and relatively rich Cu-Ni sulphide mineralization in the basal part of the Kieveiskoe and Fedorovskoe non-stratiforme deposits; ca. 2470 Ma (Bayanova, 2004) - pegmatoid gabbro-anothosite and, probably, fluid-associated rich platinum-metal ores of the Lower Layered Horizon (Kieveiskoe deposit); ca. 2447+/-12 Ma (U-Pb zircon and baddeleyte (Bayanova, 2004)) - anorthositic injections and, probably, local lens-like rich Pt-Pd accumulations of the Upper layered Horizon (Kieveiskoe deposit). The U-Pb zircon ages of the massif evolution stages corroborate the

  15. The Dewar-Chatt-Duncanson model reversed Bonding analysis of group-10 complexes [(PMe3)2M-EX3] (M = Ni, Pd, Pt;; E = B, Al, Ga, In, Tl;; X = H, F, Cl, Br, I)

    National Research Council Canada - National Science Library

    Haunschild, Robin; Hillebrecht, Pierre; Goedecke, Catharina; Uhlemann, Till; Frenking, Gernot

    2009-01-01

    ...-acceptor complexes [(PMe 3 ) 2 M-EX 3 ] with X = H, F, Cl, Br, I;; E = B, Al, Ga, In, Tl; and M = Ni, Pd, Pt. The nature of the metal-ligand bond was investigated with an energy decomposition analysis...

  16. 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.

  17. Developing an aqueous approach for synthesizing Au and M@Au (M = Pd, CuPt) hybrid nanostars with plasmonic properties

    CERN Document Server

    Du, Jingshan; Xiong, Yalin; Lin, Zhuoqing; Zhang, Hui; Yang, Deren

    2014-01-01

    Anisotropic Au nanoparticles show unique localized surface plasmon resonance (LSPR) properties, which make it attractive in optical, sensing, and biomedical applications. In this contribution, we report a general and facile strategy towards aqueous synthesis of Au and M@Au (M = Pd, CuPt) hybrid nanostars by reducing HAuCl4 with ethanolamine in the presence of cetyltrimethylammonium bromide (CTAB). According to electron microscopic observation and spectral monitoring, we found that the layered epitaxial growth mode (i.e., Frank-van der Merwe mechanism) contributes to the enlargement of the core, while, the random attachment of Au nanoclusters onto the cores accounts for the formation of the branches. Both of them are indispensable for the formation of the nanostars. The LSPR properties of the Au nanoparticles have been well investigated with morphology control via precursor amount and growth temperature. The Au nanostars showed improved surface-enhanced Raman spectroscopy (SERS) performance for rhodamine 6G du...

  18. Electro-catalytic activity of multiwall carbon nanotube-metal (Pt or Pd) nanohybrid materials synthesized using microwave-induced reactions and their possible use in fuel cells

    Science.gov (United States)

    V, Lakshman Kumar; Ntim, Susana Addo; Sae-Khow, Ornthida; Janardhana, Chelli; Lakshminarayanan, V.; Mitra, Somenath

    2012-01-01

    Microwave induced reactions for immobilizing platinum and palladium nanoparticles on multiwall carbon nanotubes are presented. The resulting hybrid materials were used as catalysts for direct methanol, ethanol and formic acid oxidation in acidic as well as alkaline media. The electrodes are formed by simply mixing the hybrids with graphite paste, thus using a relatively small quantity of the precious metal. We report Tafel slopes and apparent activation energies at different potentials and temperatures. Ethanol electro-oxidation with the palladium hybrid showed an activation energy of 7.64 kJmol−1 which is lower than those observed for other systems. This system is economically attractive because Pd is significantly less expensive than Pt and ethanol is fast evolving as a commercial biofuel. PMID:23118490

  19. Electro-catalytic activity of multiwall carbon nanotube-metal (Pt or Pd) nanohybrid materials synthesized using microwave-induced reactions and their possible use in fuel cells.

    Science.gov (United States)

    V, Lakshman Kumar; Ntim, Susana Addo; Sae-Khow, Ornthida; Janardhana, Chelli; Lakshminarayanan, V; Mitra, Somenath

    2012-11-30

    Microwave induced reactions for immobilizing platinum and palladium nanoparticles on multiwall carbon nanotubes are presented. The resulting hybrid materials were used as catalysts for direct methanol, ethanol and formic acid oxidation in acidic as well as alkaline media. The electrodes are formed by simply mixing the hybrids with graphite paste, thus using a relatively small quantity of the precious metal. We report Tafel slopes and apparent activation energies at different potentials and temperatures. Ethanol electro-oxidation with the palladium hybrid showed an activation energy of 7.64 kJmol(-1) which is lower than those observed for other systems. This system is economically attractive because Pd is significantly less expensive than Pt and ethanol is fast evolving as a commercial biofuel.

  20. Platinum Inhibits Low-Temperature Dry Lean Methane Combustion through Palladium Reduction in Pd-Pt/Al2 O3 : An In Situ X-ray Absorption Study.

    Science.gov (United States)

    Nassiri, Hanieh; Lee, Kee-Eun; Hu, Yongfeng; Hayes, Robert E; Scott, Robert W J; Semagina, Natalia

    2017-01-18

    Palladium-platinum bimetallic catalysts supported on alumina with palladium/platinum molar ratios ranging from 0.25 to 4 are studied in dry lean methane combustion in the temperature range of 200 to 500 °C. Platinum addition decreases the catalyst activity, which cannot be explained by the decrease in dispersion or the structure sensitivity of the reaction. In situ X-ray absorption near-edge structure and extended X-ray absorption fine structure spectroscopy measurements have been conducted for monometallic Pd, Pt, and 2:1 Pd-Pt catalysts. Monometallic palladium is fully oxidized in the full temperature range, whereas platinum addition promotes palladium reduction, even in a reactive oxidizing environment. The Pd/PdO weight ratio in bimetallic Pd-Pt 2:1 catalysts decreases from 98/2 to 10/90 in the 200-500 °C temperature range under the reaction conditions. Thus, platinum promotes the formation of the reduced palladium phase with a significantly lower activity than that of oxidized palladium. The study sheds light on the effect of platinum on the state of the active palladium surface under low-temperature dry lean methane combustion conditions, which is important for methane-emission control devices. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Characterization of Ni19.5Ti50.5Pd25Pt5 High-Temperature Shape Memory Alloy Springs and their Potential Application in Aeronautics

    Science.gov (United States)

    Stebner, Aaron; Padula, Santo A.; Noebe, Ronald D.

    2008-01-01

    Shape memory alloys (SMAs) have been used as actuators in many different industries since the discovery of the shape memory effect, but the use of SMAs as actuation devices in aeronautics has been limited due to the temperature constraints of commercially available materials. Consequently, work is being done at NASA's Glenn Research Center to develop new SMAs capable of being used in high temperature environments. One of the more promising high-temperature shape memory alloys (HTSMAs) is Ni19.5Ti50.5Pd25Pt5. Recent work has shown that this material is capable of being used in operating environments of up to 250 C. This material has been shown to have very useful actuation capabilities, demonstrating repeatable strain recoveries up to 2.5% in the presence of an externally applied load. Based on these findings, further work has been initiated to explore potential applications and alternative forms of this alloy, such as springs. Thus, characterization of Ni19.5Ti50.5Pd25Pt5 springs, including their mechanical response and how variations in this response correlate to changes in geometric parameters, are discussed. The effects of loading history, or training, on spring behavior were also investigated. A comparison of the springs with wire actuators is made and the benefits of using one actuator form as opposed to the other discussed. These findings are used to discuss design considerations for a surge-control mechanism that could be used in the centrifugal compressor of a T-700 helicopter engine.

  2. Characterization of Ni19.5Ti50.5Pd25Pt5 High-Temperature Shape Memory Alloy Springs and their Potential Application in Aeronautics

    Science.gov (United States)

    Stebner, Aaron; Padula, Santo A.; Noebe, Ronald D.

    2008-01-01

    Shape memory alloys (SMAs) have been used as actuators in many different industries since the discovery of the shape memory effect, but the use of SMAs as actuation devices in aeronautics has been limited due to the temperature constraints of commercially available materials. Consequently, work is being done at NASA's Glenn Research Center to develop new SMAs capable of being used in high temperature environments. One of the more promising high-temperature shape memory alloys (HTSMAs) is Ni19.5Ti50.5Pd25Pt5. Recent work has shown that this material is capable of being used in operating environments of up to 250 C. This material has been shown to have very useful actuation capabilities, demonstrating repeatable strain recoveries up to 2.5% in the presence of an externally applied load. Based on these findings, further work has been initiated to explore potential applications and alternative forms of this alloy, such as springs. Thus, characterization of Ni19.5Ti50.5Pd25Pt5 springs, including their mechanical response and how variations in this response correlate to changes in geometric parameters, are discussed. The effects of loading history, or training, on spring behavior were also investigated. A comparison of the springs with wire actuators is made and the benefits of using one actuator form as opposed to the other discussed. These findings are used to discuss design considerations for a surge-control mechanism that could be used in the centrifugal compressor of a T-700 helicopter engine.

  3. The adsorption of CO and NO on the MoS{sub 2} monolayer doped with Au, Pt, Pd, or Ni: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Dongwei, E-mail: dwmachina@126.com [School of Physics, Anyang Normal University, Anyang 455000 (China); Ju, Weiwei [College of Physics and Engineering, Henan University of Science and Technology, Luoyang 471023 (China); Li, Tingxian; Zhang, Xiwei [School of Physics, Anyang Normal University, Anyang 455000 (China); He, Chaozheng, E-mail: hecz2013@nynu.edu.cn [Physics and Electronic Engineering College, Nanyang Normal University, Nanyang 473061 (China); Ma, Benyuan [Physics and Electronic Engineering College, Nanyang Normal University, Nanyang 473061 (China); Lu, Zhansheng; Yang, Zongxian [College of Physics and Electronic Engineering, Henan Normal University, Xinxiang 453007 (China)

    2016-10-15

    Graphical abstract: The MoS{sub 2} monolayers doped with Au, Pt, Pd, or Ni show enhanced adsorption and sensitivity toward CO or NO molecule. - Highlights: • CO and NO adsorption on the doped MoS{sub 2} monolayers is theoretically studied. • CO and NO are chemisorbed on the doped MoS{sub 2} monolayers. • Charge transfer can be observed between the adsorbed molecule and the substrates. • Molecular adsorption can induce the change in electronic structures of the doped MoS{sub 2} monolayers. - Abstract: By performing the first-principles calculation, the adsorption of CO and NO molecules on the Au, Pt, Pd, or Ni doped MoS{sub 2} monolayer has been studied. The interaction between CO or NO with the doped MoS{sub 2} monolayer is strong and belongs to the chemisorption, as evidenced by the large adsorption energy and the short distance between the adsorbed molecules and the dopants. The charge transfer and the electronic property induced by the molecule adsorption are discussed. It is found that for both CO and NO adsorption, for all the cases charge transfer between the substrates and the adsorbed molecules has been observed. For NO, the adsorption obviously induces new impurity states in the band gap or the redistribution of the original impurity states. These can lead to the change of the transport properties of the doped MoS{sub 2} monolayer, by which the adsorbed CO or NO can be detected. The present work shows that introducing appropriate dopants may be a feasible method to improve the performance of MoS{sub 2}-based gas sensors.

  4. Cu-Pt和Pd-Pt二元合金系中fcc相扩散迁移率参数的优化与计算%Assessment on Diffusion Mobilities in the fcc Cu-Pt and Pd-Pt Alloys

    Institute of Scientific and Technical Information of China (English)

    王翠萍; 张炎财; 卢勇; 蔺金燕; 余涌; 刘兴军

    2014-01-01

    利用DICTRA(diffusion controlled transformation)软件分别优化了Cu-Pt和Pd-Pt二元合金系中fcc相扩散迁移率参数与温度的函数关系,计算结果和实验数据取得了良好的一致性.基于所优化的参数计算了扩散偶的浓度曲线,计算结果与实验结果比较可知,本研究所优化的扩散迁移率参数具有良好的准确性与有效性.该研究为Cu-Pt和Pd-Pt二元合金系的动力学研究提供了基础数据.

  5. Magnesium and cadmium in covalently bonded networks. Synthesis and structure of AETMg and AETCd (AE = Ca, Sr; T = Pd, Ag, Pt, Au) with TiNiSi type structure and the solid solution Yb{sub 2-x}PtMg{sub x}

    Energy Technology Data Exchange (ETDEWEB)

    Kersting, Marcel; Johnscher, Michael; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie

    2013-07-01

    The equiatomic intermetallic compounds AETMg and AETCd (AE = Ca, Sr; T = Pd, Ag, Pt, Au) and the whole solid solution Yb{sub 2-x}PtMg{sub x} were synthesized from the elements in sealed niobium tubes in a high-frequency or a muffle furnace. All samples were characterized on the basis of their powder X-ray diffraction patterns. The structures of SrAuCd, CaPdCd, CaPtCd, CaPdMg, SrPtMg, CaAg{sub 1.017}Mg{sub 0.983}, SrAg{sub 1.032}Mg{sub 0.968}, and Yb{sub 1.792}PtMg{sub 0.208} were refined on the basis of single-crystal X-ray diffractometer data. Some of the crystals showed small homogeneity ranges. All compounds crystallize with the orthorhombic TiNiSi type structure, space group Pnma. The crystal chemistry is briefly discussed and variations in chemical bonding as a result of the electronegativity of the transition metal are described. (orig.)

  6. Strong anisotropic anomalous Hall effect and spin Hall effect in the chiral antiferromagnetic compounds Mn3X (X =Ge , Sn, Ga, Ir, Rh, and Pt)

    Science.gov (United States)

    Zhang, Yang; Sun, Yan; Yang, Hao; Železný, Jakub; Parkin, Stuart P. P.; Felser, Claudia; Yan, Binghai

    2017-02-01

    We have carried out a comprehensive study of the intrinsic anomalous Hall effect and spin Hall effect of several chiral antiferromagnetic compounds Mn3X (X = Ge, Sn, Ga, Ir, Rh and Pt) by ab initio band structure and Berry phase calculations. These studies reveal large and anisotropic values of both the intrinsic anomalous Hall effect and spin Hall effect. The Mn3X materials exhibit a noncollinear antiferromagnetic order which, to avoid geometrical frustration, forms planes of Mn moments that are arranged in a Kagome-type lattice. With respect to these Kagome planes, we find that both the anomalous Hall conductivity (AHC) and the spin Hall conductivity (SHC) are quite anisotropic for any of these materials. Based on our calculations, we propose how to maximize AHC and SHC for different materials. The band structures and corresponding electron filling, that we show are essential to determine the AHC and SHC, are compared for these different compounds. We point out that Mn3Ga shows a large SHC of about 600 (ℏ /e ) (Ωcm) -1 . Our work provides insights into the realization of strong anomalous Hall effects and spin Hall effects in chiral antiferromagnetic materials.

  7. Comparison between the Oxygen Reduction Reaction Activity of Pd5Ce and Pt5Ce

    DEFF Research Database (Denmark)

    Tripkovic, Vladimir; Zheng, Jian; Rizzi, Gian Andrea;

    2015-01-01

    confirmed that in our sample, L-Pd5Ce is the dominant phase, both in the bulk and the outermost layers, while a H-Pd5Ce-like phase is also present as a minor component far below the surface. Electrochemical ORR assessments show that the Pd overlayer in Pd5Ce is less active than the polycrystalline Pd sample...

  8. Influence of aging time on thermodynamical, structural and microstructural properties of Pd{sub 100-(x+y)}Pt{sub x}Rh{sub y-}T{sub 2}(D{sub 2}) systems; Influence de la duree de stockage sur les proprietes thermodynamiques, structurales et microstructurales des systemes Pd{sub 100-(x+y)}Pt{sub x}Rh{sub y-}T{sub 2}(D{sub 2})

    Energy Technology Data Exchange (ETDEWEB)

    Thiebaut, S

    1998-12-31

    This study has demonstrated that substitution of palladium by a few atomic percent of platinum and/or rhodium induces great changes in tritium storage properties and aging phenomena in these systems. Before aging, equilibrium pressures only depend of the global substitution rate, and not at all of the substituents nature. During storage, the decrease of plateau pressures is stronger in Pd-Pt alloys, and even more in the ternary solid solution Pd{sub 90}Pt{sub 5}Rh{sub 5}. This substitution effect was explained by a difference in the nature of defects created by {sup 3}He bubbles formation. The presence of platinum, with or without rhodium, in the lattice stabilizes self interstitial atoms isolated or in dislocation loops. These defects induce a great lattice swelling, and the tritides stability is directly proportional to the metal lattice volume. On the contrary, in pure palladium and Pd-Rh alloys, self interstitial atoms are preferentially integrated in a dislocation network, so they are without effect on the lattice parameter and consequently on the tritides stability. In all cases, Pd-Pt-Rh systems are indeed perfectly suited for tritium storage thanks to their conservation of local order and thermodynamical properties during aging. (author) 81 refs.

  9. 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.

  10. Spin crossover behaviour in one-dimensional Fe(II) compounds based on the [M(CN)4](2-) (M = Pd, Pt) units.

    Science.gov (United States)

    Zhang, Shao-Liang; Zhao, Xin-Hua; Wang, Yuan-Min; Shao, Dong; Wang, Xin-Yi

    2015-05-28

    Four one-dimensional heterobimetallic coordination polymers {Fe(pic)2[M(CN)4]}n (M = Pd(II) () and Pt(II) (), pic = 2-picolylamine), and {Fe(pypz)2[M(CN)4]}n (M = Pd(II) () and Pt(II) (), pypz = 2-(1H-pyrazol-3-yl)pyridine) have been synthesized and characterized by infrared spectroscopy, X-ray diffraction, magnetic measurements and differential scanning calorimetry (DSC). Single-crystal X-ray analyses show that all the compounds are 1D neutral zigzag chain structures in which the planar [M(CN)4](2-) anion acts as a μ2-bridging ligand, and the two pic/pypz molecules as chelating coligands. Examination of the intermolecular contacts in compounds reveals the existence of the hydrogen bonding interactions involving the hydrogen donor groups of the pic and pypz ligands and the nitrogen atoms of the non-bridging cyanide groups of the [M(CN)4](2-) anions. Weak π-π interactions were also found to be important for the formation of the 3D structures of compounds and . The SCO properties of all compounds were confirmed by the detailed structural analyses of the coordination environments of the Fe(II) centres, DSC analyses, and magnetic susceptibility measurements. Compounds and exhibit complete SCO behaviour with very narrow thermal hysteresis loops centred near the room temperature (T1/2↓ = 270 K and T1/2↑ = 272 K for and T1/2↓ = 272 K and T1/2↑ = 274 K for ), whereas and exhibit abrupt SCO at 186 and 180 K, respectively. Compared to the mononuclear species of the pic and pypz ligands, the SCO temperatures are adjusted by the different ligand field strength of the [M(CN)4)](2-) units. The cooperativity from both the coordination bonds and supramolecular interaction leads to the observation of the hysteresis loops in the Fe-pic systems and the abrupt SCO transition in the Fe-pypz systems. Furthermore, the light-induced excited-spin-state trapping (LIESST) effect was observed for .

  11. Phase stabilities of pyrite-related MTCh compounds (M=Ni, Pd, Pt; T=Si, Ge, Sn, Pb; Ch=S, Se, Te): A systematic DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Bachhuber, Frederik [University of Regensburg, Institute of Inorganic Chemistry, Universitätsstr. 31, 93040 Regensburg (Germany); School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland (New Zealand); Krach, Alexander; Furtner, Andrea [University of Regensburg, Institute of Inorganic Chemistry, Universitätsstr. 31, 93040 Regensburg (Germany); Söhnel, Tilo [School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland (New Zealand); Centre for Theoretical Chemistry and Physics, The New Zealand Institute for Advanced Study, Massey University Auckland, Auckland (New Zealand); Peter, Philipp; Rothballer, Jan [University of Regensburg, Institute of Inorganic Chemistry, Universitätsstr. 31, 93040 Regensburg (Germany); Weihrich, Richard, E-mail: richard.weihrich@chemie.uni-r.de [University of Regensburg, Institute of Inorganic Chemistry, Universitätsstr. 31, 93040 Regensburg (Germany)

    2015-03-15

    Pyrite-type and related systems appear for a wide range of binary and ternary combinations of transition metals and main group elements that form Zintl type dumbbell anion units. Those representatives with 20 valence electrons exhibit an extraordinary structural flexibility and interesting properties as low-gap semiconductors or thermoelectric and electrode materials. This work is devoted to the systematic exploration of novel compounds within the class of MTCh compounds (M=Ni, Pd, Pt; T=Si, Ge, Sn, Pb; Ch=S, Se, Te) by means of density functional calculations. Their preferred structures are predicted from an extended scheme of colored pyrites and marcasites. To determine their stabilities, competing binary MT{sub 2} and MCh{sub 2} boundary phases are taken into account as well as ternary M{sub 3}T{sub 2}Ch{sub 2} and M{sub 2}T{sub 3}Ch{sub 3} systems. Recently established stability diagrams are presented to account for MTCh ordering phenomena with a focus on a not-yet-reported ordering variant of the NiAs{sub 2} type. Due to the good agreement with experimental data available for several PtTCh systems, the predictions for the residual systems are considered sufficiently accurate. - Graphical abstract: Compositional and structural stability of MTCh compounds is investigated from first principle calculations. A conceptional approach is presented to study and predict novel stable and metastable compounds and structures of low gap semiconductors with TCh dumbbell units that are isoelectronic and structurally related to pyrite (FeS{sub 2}). - Highlights: • Study of compositional stability of MTCh vs. M{sub 3}T{sub 2}Ch{sub 2} and M{sub 2}T{sub 3}Ch{sub 3} compounds. • Study of structural stability of known and novel MTCh compounds. • Prediction of novel stable and metastable structures and compounds isoelectronic to pyrite, FeS{sub 2}.

  12. Radiochemical neutron activation analysis for 36 elements in geological material: Au, Ag, Bi, Br, Cd, Cs, Ge, In, Ir, Ni, Os, Pd, Rb, Re, Sb, Se, Sn, Te, Tl, U, and Zn as well as Sc, Y, and REE

    Energy Technology Data Exchange (ETDEWEB)

    Anders, E; Wolf, R; Morgan, J W; Ebihara, M; Woodrow, A B; Janssens, M J; Hertogen, J

    1988-01-01

    In lunar and terrestrial rocks and in meteorites, the radiochemical neutron activation method decribed here enables determination of the 21 trace and ultratrace elements Ag, Au, Bi, Br, Cd, Cs, Ga, Ge, In, Ir, Ni, Os, Pd, Rb, Re, Sb, Se, Te, Tl, U, Zn, as well as 13 rare earth elements (REE), Sc and Y. Materials, techniques and procedures are discussed. 81 refs.

  13. The atomic structural dynamics of γ-Al2O3 supported Ir-Pt nanocluster catalysts prepared from a bimetallic molecular precursor: a study using aberration-corrected electron microscopy and X-ray absorption spectroscopy.

    Science.gov (United States)

    Small, Matthew W; Sanchez, Sergio I; Menard, Laurent D; Kang, Joo H; Frenkel, Anatoly I; Nuzzo, Ralph G

    2011-03-16

    This study describes a prototypical, bimetallic heterogeneous catalyst: compositionally well-defined Ir-Pt nanoclusters with sizes in the range of 1-2 nm supported on γ-Al(2)O(3). Deposition of the molecular bimetallic cluster [Ir(3)Pt(3)(μ-CO)(3)(CO)(3)(η-C(5)Me(5))(3)] on γ-Al(2)O(3), and its subsequent reduction with hydrogen, provides highly dispersed supported bimetallic Ir-Pt nanoparticles. Using spherical aberration-corrected scanning transmission electron microscopy (C(s)-STEM) and theoretical modeling of synchrotron-based X-ray absorption spectroscopy (XAS) measurements, our studies provide unambiguous structural assignments for this model catalytic system. The atomic resolution C(s)-STEM images reveal strong and specific lattice-directed strains in the clusters that follow local bonding configurations of the γ-Al(2)O(3) support. Combined nanobeam diffraction (NBD) and high-resolution transmission electron microscopy (HRTEM) data suggest the polycrystalline γ-Al(2)O(3) support material predominantly exposes (001) and (011) surface planes (ones commensurate with the zone axis orientations frequently exhibited by the bimetallic clusters). The data reveal that the supported bimetallic clusters exhibit complex patterns of structural dynamics, ones evidencing perturbations of an underlying oblate/hemispherical cuboctahedral cluster-core geometry with cores that are enriched in Ir (a result consistent with models based on surface energetics, which favor an ambient cluster termination by Pt) due to the dynamical responses of the M-M bonding to the specifics of the adsorbate and metal-support interactions. Taken together, the data demonstrate that strong temperature-dependent charge-transfer effects occur that are likely mediated variably by the cluster-support, cluster-adsorbate, and intermetallic bonding interactions.

  14. 溶剂萃取法分离Pt、Pd、Rh%Separating Pt, Pd and Rh by Solvent Extracition

    Institute of Scientific and Technical Information of China (English)

    荆小旦

    2001-01-01

    @@ 铂族金属的再生资源经常是含有两种或两种以上铂族金属的物料,如硝酸工业报废的铂钯铑合金催化网,失效的三元汽车尾气净化催化剂(其活性组分为Pt、Pd、Rh),测温热电偶丝(Pt,Rh-Pt热电偶),玻纤工业产生的废漏板托砖等.这些物料的浸出液通常要进行一系列复杂的分离精炼作业,才能获得符合一定质量标准的单个铂族金属产品.

  15. Session 4: Enhanced sulfur resistance and catalytic properties of Pd-Pt supported on TiO{sub 2} - modified Al{sub 2}O{sub 3} in the hydrogenation of biphenyl and HDS of dibenzothiophene

    Energy Technology Data Exchange (ETDEWEB)

    Nunez, S.; Montesinos, A.; Viveros, T.; Los Reyes, J.A. de [Universidad Autonoma Metropolitana-Iztapalapa (Mexico)

    2004-07-01

    In the hydrotreatment (HDT) of petroleum cuts to produce diesel, the selection of active and highly selective catalysts for hydrogenation (HYD) of aromatics is a fundamental issue in the second stage of multi-staged processes. It is well know that precious metals (Pd-Pt mainly) are suitable for this reaction. However, sulfur compounds at low concentration may poison these catalysts. Thus, this work focuses on the evaluation in the hydrogenation of an aromatic compound of Pd-Pt catalysts supported on TiO{sub 2}-modified Al{sub 2}O{sub 3} by using two reactions in presence of sulfur, the hydrogenation (HYD) of biphenyl (BP) and the hydrodesulfurization (HDS) of dibenzothiophene (DBT). The obtained experimental results are given and explained. (O.M.)

  16. Rich spectroscopic and molecular dynamic studies on the interaction of cytotoxic Pt(II) and Pd(II) complexes of glycine derivatives with calf thymus DNA.

    Science.gov (United States)

    Eslami Moghadam, Mahboube; Saidifar, Maryam; Divsalar, Adeleh; Mansouri-Torshizi, Hassan; Saboury, Ali Akbar; Farhangian, Hossein; Ghadamgahi, Maryam

    2016-01-01

    Some amino acid derivatives, such as R-glycine, have been synthesized together with their full spectroscopic characterization. The sodium salts of these bidentate amino acid ligands have been interacted with [M(bpy)(H2O)2](NO3)2 giving the corresponding some new complexes with formula [M(bpy)(R-gly)]NO3 (where M is Pt(II) or Pd(II), bpy is 2,2'-bipyridine and R-gly is butyl-, hexyl- and octyl-glycine). Due to less solubility of octyl derivatives, the biological activities of butyl and hexyl derivatives have been tested against chronic myelogenous leukemia cell line, K562. The interaction of these complexes with highly polymerized calf thymus DNA has been extensively studied by means of electronic absorption, fluorescence and other measurements. The experimental results suggest that these complexes positive cooperatively bind to DNA presumably via groove binding. Molecular dynamic results show that the DNA structure is largely maintained its native structure in hexylglycine derivative-water mixtures and at lower temperatures. The simulation data indicates that the more destabilizing effect of butylglycine is induced by preferential accumulation of these molecules around the DNA and due to their more negative free energy of binding via groove binding.

  17. Pd-Ag Membrane Coupled to a Two-Zone Fluidized Bed Reactor (TZFBR) for Propane Dehydrogenation on a Pt-Sn/MgAl2O4 Catalyst.

    Science.gov (United States)

    Medrano, José-Antonio; Julián, Ignacio; Herguido, Javier; Menéndez, Miguel

    2013-05-14

    Several reactor configurations have been tested for catalytic propane dehydrogenation employing Pt-Sn/MgAl2O4 as a catalyst. Pd-Ag alloy membranes coupled to the multifunctional Two-Zone Fluidized Bed Reactor (TZFBR) provide an improvement in propane conversion by hydrogen removal from the reaction bed through the inorganic membrane in addition to in situ catalyst regeneration. Twofold process intensification is thereby achieved when compared to the use of traditional fluidized bed reactors (FBR), where coke formation and thermodynamic equilibrium represent important process limitations. Experiments were carried out at 500-575 °C and with catalyst mass to molar flow of fed propane ratios between 15.1 and 35.2 g min mmol-1, employing three different reactor configurations: FBR, TZFBR and TZFBR + Membrane (TZFBR + MB). The results in the FBR showed catalyst deactivation, which was faster at high temperatures. In contrast, by employing the TZFBR with the optimum regenerative agent flow (diluted oxygen), the process activity was sustained throughout the time on stream. The TZFBR + MB showed promising results in catalytic propane dehydrogenation, displacing the reaction towards higher propylene production and giving the best results among the different reactor configurations studied. Furthermore, the results obtained in this study were better than those reported on conventional reactors.

  18. Adsorption properties of Ag(I), Au(III), Pd(II) and Pt(IV) ions on commercial 717 anion-exchange resin

    Institute of Scientific and Technical Information of China (English)

    LIU Peng; LIU Guang-feng; CHEN Da-lin; CHENG Shao-yi; TANG Ning

    2009-01-01

    The adsorption properties of the four precious metal ions (Ag(Ⅰ),Au(Ⅲ),Pd(Ⅱ) and Pt(Ⅳ)) on the commercial Cl--form 717 strongly basic anion-exchange resin were studied in detail.The effects of the contact time,solution acidity,and concentrations of Cl~- and Pb~(2+) ions on the adsorption properties were studied by the batch method.Then,the column method was conducted under the optimized adsorption conditions (pH=3.0).The effects of the sample loading flow rate and the length-to-diameter ratios of the columns were investigated.The precious metal ions adsorbed could not be eluted completely after the saturated adsorption because the precious metal ions were found to be reduced to their metallic states during the adsorption process.So,it is recommended that the commercial Cl~--form 717 strongly basic anion-exchange resin should be decomposed directly to recovery the precious metals after the saturated adsorption.

  19. The adsorption of CO and NO on the MoS2 monolayer doped with Au, Pt, Pd, or Ni: A first-principles study

    Science.gov (United States)

    Ma, Dongwei; Ju, Weiwei; Li, Tingxian; Zhang, Xiwei; He, Chaozheng; Ma, Benyuan; Lu, Zhansheng; Yang, Zongxian

    2016-10-01

    By performing the first-principles calculation, the adsorption of CO and NO molecules on the Au, Pt, Pd, or Ni doped MoS2 monolayer has been studied. The interaction between CO or NO with the doped MoS2 monolayer is strong and belongs to the chemisorption, as evidenced by the large adsorption energy and the short distance between the adsorbed molecules and the dopants. The charge transfer and the electronic property induced by the molecule adsorption are discussed. It is found that for both CO and NO adsorption, for all the cases charge transfer between the substrates and the adsorbed molecules has been observed. For NO, the adsorption obviously induces new impurity states in the band gap or the redistribution of the original impurity states. These can lead to the change of the transport properties of the doped MoS2 monolayer, by which the adsorbed CO or NO can be detected. The present work shows that introducing appropriate dopants may be a feasible method to improve the performance of MoS2-based gas sensors.

  20. Pd-Ag Membrane Coupled to a Two-Zone Fluidized Bed Reactor (TZFBR for Propane Dehydrogenation on a Pt-Sn/MgAl2O4 Catalyst

    Directory of Open Access Journals (Sweden)

    Miguel Menéndez

    2013-05-01

    Full Text Available Several reactor configurations have been tested for catalytic propane dehydrogenation employing Pt-Sn/MgAl2O4 as a catalyst. Pd-Ag alloy membranes coupled to the multifunctional Two-Zone Fluidized Bed Reactor (TZFBR provide an improvement in propane conversion by hydrogen removal from the reaction bed through the inorganic membrane in addition to in situ catalyst regeneration. Twofold process intensification is thereby achieved when compared to the use of traditional fluidized bed reactors (FBR, where coke formation and thermodynamic equilibrium represent important process limitations. Experiments were carried out at 500–575 °C and with catalyst mass to molar flow of fed propane ratios between 15.1 and 35.2 g min mmol−1, employing three different reactor configurations: FBR, TZFBR and TZFBR + Membrane (TZFBR + MB. The results in the FBR showed catalyst deactivation, which was faster at high temperatures. In contrast, by employing the TZFBR with the optimum regenerative agent flow (diluted oxygen, the process activity was sustained throughout the time on stream. The TZFBR + MB showed promising results in catalytic propane dehydrogenation, displacing the reaction towards higher propylene production and giving the best results among the different reactor configurations studied. Furthermore, the results obtained in this study were better than those reported on conventional reactors.

  1. Laser synthesis of bimetallic nanoalloys in the vapor and liquid phases and the magnetic properties of PdM and PtM nanoparticles (M = Fe, Co and Ni).

    Science.gov (United States)

    Abdelsayed, Victor; Glaspell, Garry; Nguyen, Minh; Howe, James M; El-Shall, M Samy

    2008-01-01

    In this work, we present several examples of the synthesis and characterization of bimetallic nanoparticle alloys using the Laser Vaporization Controlled Condensation (LVCC) method. In the first example, the vapor phase synthesis of Au-Ag, Au-Pd, and Au-Pt nanoparticle alloys are presented. The formation of nanoalloys is concluded from the observation of one plasmon absorption band at a wavelength that varies linearly with the gold mole fraction in the nanoalloy. Both XRD data and HRTEM-EDX data confirm the formation of nanoparticle alloys and not simply mixtures of the two metal nanoparticles. Irradiation of a mixture of Au/Ag nanoparticles dispersed in water with the 532 nm unfocused laser results in efficient alloying while the 1064 nm laser radiation results only in evaporation and size reduction of the unalloyed nanoparticles. Selective absorption of the femtosecond 780 nm radiation by large Au aggregates results in the formation of smaller aggregates with fractal structures, and no evidence for the Au-Ag alloy formation. The synthesis of palladium and platinum nanoparticles alloyed with transition metals such as iron and nickel using the LVCC method is also presented. The alloyed nanoparticles (FePd, FePt, NiPd, NiPt, and FeNi) are found to be superparamagnetic.

  2. Sum Frequency Generation Vibrational Spectroscopy of 1,3-Butadiene Hydrogenation on 4 nm Pt@SiO 2 , Pd@SiO 2 , and Rh@SiO 2 Core–Shell Catalysts

    KAUST Repository

    Krier, James M.

    2015-01-14

    © 2014 American Chemical Society. 1,3-Butadiene (1,3-BD) hydrogenation was performed on 4 nm Pt, Pd, and Rh nanoparticles (NPs) encapsulated in SiO2 shells at 20, 60, and 100 °C. The core-shells were grown around polyvinylpyrrolidone (PVP) coated NPs (Stöber encapsulation) prepared by colloidal synthesis. Sum frequency generation (SFG) vibrational spectroscopy was performed to correlate surface intermediates observed in situ with reaction selectivity. It is shown that calcination is effective in removing PVP, and the SFG signal can be generated from the metal surface. Using SFG, it is possible to compare the surface vibrational spectrum of Pt@SiO2 (1,3-BD is hydrogenated through multiple paths and produces butane, 1-butene, and cis/trans-2-butene) to Pd@SiO2 (1,3-BD favors one path and produces 1-butene and cis/trans-2-butene). In contrast to Pt@SiO2 and Pd@SiO2, SFG and kinetic experiments of Rh@SiO2 show a permanent accumulation of organic material.

  3. MCl_x(M=Pd, Fe, Cr) Assisted Synthesis of Ordered Mesoporous Carbon and Their Electrocatalytic Performance after Loading with Pt Nanoparticles%MCl_x(M=Pd,Fe,Cr)对有序介孔碳的辅助合成及其负载Pt后的电催化性能

    Institute of Scientific and Technical Information of China (English)

    孙盾; 何建平; 周建华; 王涛; 狄志勇; 王道军; 丁晓春

    2010-01-01

    以MCl_x(M=Pd,Fe,Cr;x=2,3,3)为金属源,辅助合成有序介孔碳(OMC),以改善其负载Pt后的电催化性能.X射线衍射(XRD)和透射电镜(TEM)测试结果显示,适量PdCl_2的引入并未破坏介孔碳的有序结构,由于经历有机碳的高温裂解,OMC-PdCl_2主要以金属Pd为存在形式,较为均一嵌入OMC的骨架中,并在负载Pt的过程中与Pt形成二元催化剂.电化学氢吸附-脱附测试结果表明,Pt/OMC-MCl_x表现出优异的催化性能,电化学活性面积为Pt/OMC的2-4倍;其中Pt/OMC-PdCl_2最佳,活性面积达120.2 m~2·g~(-1),Pt/OMC-CrCl_3和Pt/OMC-FeCl_3次之.此外,Pt/OMC-MCl_x还具有良好的催化稳定性,经100个循环测试后,依然保持较高的催化活性,仅衰减22%-40%,使得该材料在催化领域具有很好的应用前景.

  4. Platinum(iv) prodrug conjugated Pd@Au nanoplates for chemotherapy and photothermal therapy

    Science.gov (United States)

    Shi, Saige; Chen, Xiaolan; Wei, Jingping; Huang, Yizhuan; Weng, Jian; Zheng, Nanfeng

    2016-03-01

    prepared Pd@Au-PEG-Pt nanocomposite showed excellent stability in physiological solutions and efficient Pt(iv) prodrug loading. Once injected into biological tissue, the Pt(iv) prodrug was easily reduced by physiological reductants (e.g. ascorbic acid or glutathione) into its cytotoxic and hydrophilic Pt(ii) form and released from the original nanocomposite, and the NIR laser irradiation could accelerate the release of Pt(ii) species. More importantly, Pd@Au-PEG-Pt has high tumor accumulation (29%ID per g), which makes excellent therapeutic efficiency at relatively low power density possible. The in vivo results suggested that, compared with single therapy the combined thermo-chemotherapy treatment with Pd@Au-PEG-Pt resulted in complete destruction of the tumor tissue without recurrence, while chemotherapy using Pd@Au-PEG-Pt without irradiation or photothermal treatment using Pd@Au-PEG alone did not. Our work highlights the prospects of a feasible drug delivery strategy of the Pt prodrug by using 2D Pd@Au nanoplates as drug delivery carriers for multimode cancer treatment. Electronic supplementary information (ESI) available: Synthesis process of Pt(iv) prodrug, mass data and FT-IR spectra of the intermediate product and Pt(iv) prodrug, TEM images of Pd@Au and Au NPs, thermal gravimetric analysis of nanoparticles, dispersion stability of Pd@Au-PEG-Pt NSs in different solutions, chemical reduction of Pt(ii) in a water bath, viability of different cell lines incubated with different concentrations of materials, uptake of different drugs by HeLa cells, size distribution of nanoparticles, tissue distribution by measuring the Pt amounts and zeta potential information of prodrug function nanomaterials. See DOI: 10.1039/c5nr09120a

  5. Effect of Thick Film Firing Conditions on the Solderability and Structure of Au-Pt-Pd Conductor for Low-Temperature, Co-Fired Ceramic Substrates

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez, C.L; Vianco, P.T.

    1999-03-16

    Low-temperature, co-fired ceramics (LTCC) are the substrate material-of-choice for a growing number of multi-chip module (MCM) applications. Unlike the longer-standing hybrid microcircuit technology based upon alumina substrates, the manufacturability and reliability of thick film solder joints on LTCC substrates have not been widely studied. An investigation was undertaken to fully characterize such solder joints. A surface mount test vehicle with Daisy chain electrical connections was designed and built with Dupont{trademark} 951 tape. The Dupont{trademark} 4569 thick film ink (Au76-Pt21 -Pd3 wt.%) was used to establish the surface conductor pattern. The conductor pattern was fired onto the LTCC substrate in a matrix of process conditions that included: (1) double versus triple prints, (2) dielectric frame versus no frame, and (3) three firing temperatures (800 C, 875 C and 950 C). Pads were examined from the test vehicles. The porosity of the thick film layers was measured using quantitative image analysis in both the transverse and short transverse directions. A significant dependence on firing temperature was recorded for porosity. Solder paste comprised of Sn63-Pb37 powder with an RMA flux was screen printed onto the circuit boards. The appropriate components, which included chip capacitors of sizes 0805 up to 2225 and 50 mil pitch, leadless ceramic chip carriers having sizes of 16 I/O to 68 I/O, were then placed on the circuit boards. The test vehicles were oven reflowed under a N{sub 2} atmosphere. The solderability of the thick film pads was also observed to be sensitive to the firing conditions. Solderability appeared to degrade by the added processing steps needed for the triple print and dielectric window depositions. However, the primary factor in solderability was the firing temperature. Solderability was poorer when the firing temperature was higher.

  6. PVP/Pd/IrO2/Nafion修饰微电极用于成纤维细胞中一氧化氮释放的研究%Direct Monitoring of Nitric Oxide Release from Fibrocytes with PVP/Pd/IrO2/Nafion Chemically Modified Microelectrode

    Institute of Scientific and Technical Information of China (English)

    鲜跃仲; 徐继明; 陆嘉星; 刘梅川; 蔡琪; 金利通

    2002-01-01

    采用PVP/Pd/IrO2/Nafion修饰电极对成纤维细胞中NO的释放情况进行了研究.结果表明,在正常状态下,采用NO前体L-精氨酸和乙酰胆碱对成纤维细胞进行刺激后没有NO的释放;当用脂多糖进行诱导后,则释放出高浓度的NO,加入L-精氨酸和乙酰胆碱都促进了NO的合成,而L-NNA的加入则逆转了L-精氨酸和乙酰胆碱的作用.

  7. Quantum, characterization and spectroscopic studies on Cu(II), Pd(II) and Pt(II) complexes of 1-(benzo[d]thiazol-2-yl)-3-phenylthiourea and its biological application as antimicrobial and antioxidant

    Science.gov (United States)

    Jambi, M. S.

    2017-09-01

    Divalent platinum, palladium and copper chelates of H2PhT have been isolated and identified. Their structures have been elucidated by partial elemental analyses, magnetic susceptibilities and spectroscopic estimations and additionally mass spectra. The FTIR and 1H NMR studies illustrated that H2PhT performs as mono-negative bi-dentate in Cu(II) and Pd(II) complexes while it behaves as neutral bi-dentate in both Pt(II) complexes. Both magnetic moments and spectral studies suggests a tetrahedral coordination geometry for [Cu(HPhT)(H2O)Cl] complex, a square planar geometry for both [Pd(HPhT)2] and [Pt(H2PhT)2Cl2] complexes and octahedral geometry for [Pt(H2PhT)2Cl2] complex. The molecular modeling are drawn and demonstrated both bond lengths and angles, chemical reactivity, MEP, NLO, Mulliken atomic charges, and binding energy (kcal/mol) for the investigated compounds. Theoretical infrared intensities and 1H NMR of H2PhT was computed utilizing DFT technique. An examination of the experimental and hypothetical spectra can be extremely valuable in making right assignments and analyzing the main chemical shift. DNA bioassay, antibacterial and antifungal activities of the investigated compounds have been determined.

  8. Counterion influence on the vibrational wavenumbers in ternary and quaternary metal hydride salts, A2MH6 (A = alkali metal, alkaline earth, and lanthanides; M = Ir, Fe, Ru, Os, Pt, Mn).

    Science.gov (United States)

    Gilson, Denis F R; Moyer, Ralph O

    2012-02-06

    The wavenumbers of the ν(3) metal-hydrogen stretching mode (T(1u)) in the IR spectra of both ternary and quaternary hexahydrido salts of transition metals from groups 7 to 10 ([Mn(I)H(6)](5-), [Fe(II)H(6)](4-), [Ru(II)H(6)](4-), [Os(II)H(6)](4-), [Ir(III)H(6)](3-), and [Pt(IV)H(6)](2-)) depend linearly upon the ionization energies of the counterions (alkali metal, alkaline earth, and lanthanide) with a separate line for each metal. This relationship provides quantitative support for the charge-transfer mechanism for explaining the stabilities of these compounds.

  9. SnO₂(β-Bi₂O₃)/Bi₂Sn₂O₇ nanohybrids doped with Pt and Pd nanoparticles: applications in visible light photocatalysis, electrical conductivity and dye-sensitized solar cells.

    Science.gov (United States)

    Khairy, M; Mohamed, Mohamed Mokhtar

    2015-09-07

    Bi2O3-SnO2 nanocomposites formed at a nominal molar ratio of 3 : 1 and loaded with Pd/Pt nanoparticles synthesized by a sol gel-hydrothermal method with the aid of a template were thoroughly characterized by X-ray diffraction, TEM-EDX, N2 sorptiometry, diffuse reflectance UV-Vis, FTIR, photoluminescence and electrical conductivity. It has been shown that Pd and Pt stimulate the existence of β-Bi2O3 and SnO2, respectively together with the key component Bi2Sn2O7. The photocatalytic results indicate that Pd/β-Bi2O3-Bi2Sn2O7 revealed a remarkable performance for the degradation of methylene blue (MB) dye as compared to the Pt/SnO2-Bi2Sn2O7 and Bi2O3-SnO2 samples in both the UV and visible regions. The enhanced photocatalytic activity of the Pd/β-Bi2O3-Bi2Sn2O7 nanocomposite is primarily attributed to the broad contact between the β-Bi2O3 and Bi2Sn2O7 phases, which indicates high mesoporosity and heterojunction structures resulting in separation efficacy between photo-induced electron-hole pairs. Specifically, the photosensitive β-Bi2O3 is easily excited and released electrons to be accepted by Bi2Sn2O7 and Pd that might be deposited in the interlayer between β-Bi2O3 and Bi2Sn2O7. The degradation mechanism of MB over Pd/β-Bi2O3-Bi2Sn2O7 in the visible region showed that the dye degradation proceeds through evolution of ˙O2(-) and ˙OH radicals as evaluated using photoluminescence and free radical trapping experiments. An insight into the electrical properties including the dielectric constant and impedance of the materials indicates that Pd/β-Bi2O3-Bi2Sn2O7 has the highest conductivity based on increasing the ionic transport and defects at the β-Bi2O3/Bi2Sn2O7 heterojunction. This material displayed an improved photocurrent response of a higher power conversion efficiency, exceeding that of Pt/SnO2-Bi2Sn2O7 and SnBi3 by 50% and 250%, respectively, in dye-sensitized solar cells. Picosecond-resolved photoluminescence (PL) and polarization gated PL

  10. Investigation of the nonlinear absorption of [M(Et{sub 2}timdt){sub 2} ] (M = Pd, Pt) in the pico- and nanosecond timescales using the Z-scan technique

    Energy Technology Data Exchange (ETDEWEB)

    Cassano, T [Department of Physics and CNR-INFM, University of Bari, Via Amendola 173, 70126 Bari (Italy); Tommasi, R [Department of Medical Biochemistry, Biology, and Physics, University of Bari, Piazza G. Cesare 11, 70124 Bari (Italy); Arca, M [Dipartimento di Chimica Inorganica ed Analitica, S.S. 554 Bivio per Sestu, 09042 Monserrato-Cagliari (Italy); Devillanova, F A [Dipartimento di Chimica Inorganica ed Analitica, S.S. 554 Bivio per Sestu, 09042 Monserrato-Cagliari (Italy)

    2006-06-14

    The nonlinear optical absorption of two neutral metal dithiolenes [M(Et{sub 2}timdt){sub 2}] (M = Pd and Pt) has been investigated at {lambda} = 1064 nm by the open-aperture Z-scan technique using nanosecond and picosecond pulses. For picosecond photoexcitation, both dithiolenes mainly exhibit saturable absorption. Conversely, using nanosecond pulses, a switch from saturable absorption to reverse saturable absorption has been observed depending on the central metal. Based on experimental results, energy-level structures are suggested to explain the nonlinear absorption for both temporal regimes and, in particular, the sign-reversal of nonlinear absorption.

  11. Mutagenic activity of transition-metal complexes: relation structure-mutagenic and antibacterial activity for some Pd(II), Pt(II) and Rh(I) complexes. [Salmonella typhimurium; Escherichia coli

    Energy Technology Data Exchange (ETDEWEB)

    Aresta, M.; Treglia, S.; Collucia, M.; Correale, M.; Giordano, D.; Moscelli, S.

    1984-01-01

    The inhibitory and mutagenic action of some Pd(II), Pt(II) and Rh(I) complexes towards various bacterial strains has been evaluated, and some correlations have been found between the chemical behavior of the complexes and their selection biological activity; most of the complexes cause only a DNA damage repaired by the excision repair system. Particularly, the Rh(I) complexes used in this work show selective antibacterial effects on defective but no effect on wild-type strains. 19 references, 8 figures, 10 tables.

  12. Concentrations of Platinum Group Elements (Pt, Pd, Rh in Airborne Particulate Matter (PM2.5 and PM10-2.5 Collected at Selected Canadian Urban Sites: a Case Study

    Directory of Open Access Journals (Sweden)

    Celo V.

    2013-04-01

    Full Text Available Increasing environmental concentrations of platinum group elements (PGEs, in particular platinum (Pt, palladium (Pd and rhodium (Rh, from catalytic converters has been reported worldwide. Initially it was believed that the emitted PGEs remain in the roadside environment, but recent studies have shown that fine PGE-containing particles can be transported and distributed at regional and long-range levels. Therefore, the monitoring of PGEs in airborne particulate matter (PM is important for the estimation of potential risks to human health and to the ecosystem. The aim of this study is to present the first results from an analysis on the concentration and distribution of Pt, Pd and Rh in PM collected on Teflon filters at two selected urban sites (Toronto, Ontario; Edmonton, Alberta collected within the Canadian National Air Pollution Surveillance (NAPS network. In this work, a quadruple inductively coupled plasma mass spectrometry (ICP-MS, combined with microwave assisted acid digestion using aqua regia was used. A cation exchange separation was used to alleviate the matrix-induced spectral and nonspectral interferences prior to ICP-MS analysis. To obtain sufficient material needed for PGEs analysis, fine PM (particles with aerodynamic diameter less than 2.5 mm; PM2.5 and coarse PM (with aerodynamic diameter between 2.5 and 10 mm; PM10-2.5 samples were combined into composite samples on a seasonal basis. The obtained results will be discussed and compared with literature data.

  13. Theoretical study of the structure, bonding and electronic behaviour of sandwich complexes [M3(C7H7)2X3]- (M = Ni, Pd, Pt; X = F, Cl)

    Science.gov (United States)

    Zhou, Ke; Min, Suotian; Xue, Ganglin; Huang, Wendeng

    2014-08-01

    The correlations between the structural and electronic properties of the clusters [M3X3]3- and sandwich complexes [M3(C7H7)2X3]- (where M = Ni, Pd, Pt; X = F, Cl) were studied with density functional theory (B3PW91). All of the sandwich complexes are donating and back-donating metal-ligand bonding structures. The influence of the ligand, significant variations in the Msbnd C, Msbnd X, Msbnd M, Csbnd C bond lengths and binding energies were examined to obtain qualitative and quantitative pictures of the intramolecular C7R7+-M3X33- interactions. Our theoretical investigations show that the binding energies of the sandwich complexes gradually reduce from Ni to Pt, as well as from F to Cl. Meanwhile, the geometric and electronic structures and the relative stabilities have a strong relation to each other. S1). 7-B-(H-10) is a delocalised σ orbital, which has contributions from Pt (15% s orbital of each Pt, 8% d orbital of each Pt), and there is little contribution from Cl (Table S2). 7-C-(H-11) is a delocalised π orbital, which mainly involves contribution from Pt (25% dxz and dyz of each Pt) and Cl (8.5% pz of each Cl) (Table S3). 7-D-(H-14) is a delocalised σ orbital, which is mostly composed of d orbitals (14% for each Pt) and p orbitals (16% for each Cl) (Table S4). Pt s (10%) and d (10%) orbitals mainly participate in the formations of 7-E-(H-23), and there is a 13% p orbital contribution from each Cl (Table S5). For structure 13, the LUMO is mainly s orbitals of C, and there is some contribution from the s and d orbitals of Pt (Table S6), whereas the HOMO is mainly s orbitals of C (Table S7). 13-c-(H-14) is mainly the dxz and dyz orbitals of Pt (Table S8).NICS can be used to predict and understand some of the properties of a molecule, especially its stability due to aromatic stabilisation, which is based on the negative of the magnetic shielding computed at or above the geometrical centres of rings or clusters. Systems with negative NICS values are aromatic

  14. Phosphenium Hydride Reduction of [(cod)MX2] (M = Pd, Pt; X = Cl, Br): Snapshots on the Way to Phosphenium Metal(0) Halides and Synthesis of Metal Nanoparticles.

    Science.gov (United States)

    Nickolaus, Jan; Imbrich, Dominik A; Schlindwein, Simon H; Geyer, Adrian H; Nieger, Martin; Gudat, Dietrich

    2017-03-06

    The outcome of the reduction of [(cod)PtX2] (X = Cl, Br; cod = 1,5-cyclooctadiene) with N-heterocyclic phosphenium hydrides (R)NHP-H depends strongly on the steric demand of the N-aryl group R and the nature of X. Reaction of [(cod)PtCl2] with (Dipp)NHP-H featuring bulky N-Dipp groups produced an unprecedented monomeric phosphenium metal(0) halide [((Dipp)NHP)((Dipp)NHP-H)PtCl] stabilized by a single phosphine ligand. The phosphenium unit exhibits a pyramidal coordination geometry at the phosphorus atom and may according to DFT calculations be classified as a Z-type ligand. In contrast, reaction of [(cod)PtBr2] with the sterically less protected (Mes)NHP-H afforded a mixture of donor-ligand free oligonuclear complexes [{((Mes)NHP)PtBr}n] (n = 2, 3), which are structural analogues of known palladium complexes with μ2-bridging phosphenium units. All reductions studied proceed via spectroscopically detectable intermediates, several of which could be unambiguously identified by means of multinuclear ((1)H, (31)P, (195)Pt) NMR spectroscopy and computational studies. The experimental findings reveal that the phosphenium hydrides in these multistep processes adopt a dual function as ligands and hydride transfer reagents. The preference for the observed intricate pathways over seemingly simpler ligand exchange processes is presumably due to kinetic reasons. The attempt to exchange the bulky phosphine ligand in [((Dipp)NHP)((Dipp)NHP-H)PtCl] by Me3P resulted in an unexpected isomerization to a platinum(0) chlorophosphine complex via a formal chloride migration from platinum to phosphorus, which accentuates the electrophilic nature of the phosphenium ligand. Phosphenium metal(0) halides of platinum further show a surprising thermal stability, whereas the palladium complexes easily disintegrate upon gentle heating in dimethyl sulfoxide to yield metal nanoparticles, which were characterized by TEM and XRD studies.

  15. Interaction of CO with PtxAg1-x/Pt(111) surface alloys: More than dilution by Ag atoms

    Science.gov (United States)

    Schüttler, K. M.; Mancera, L. A.; Diemant, T.; Groß, A.; Behm, R. J.

    2016-08-01

    We have investigated CO adsorption on structurally well-defined PtxAg1-x/Pt(111) surface alloys, combining temperature-programmed desorption (TPD) and infrared reflection absorption spectroscopy (IRRAS) as well as density functional theory (DFT) based calculations. This is part of a systematic approach including previous studies of CO adsorption on closely related Pt(111)- and Pd(111)-based surface alloys. Following changes in the adsorption properties with increasing Ag content and correlating them with structural changes allow us to assign desorption features to specific adsorption sites/ensembles identified in previous scanning tunneling microscopy (STM) measurements, and thus to identify and separate contributions from different effects such as geometric ensemble effects and electronic ligand/strain effects. DFT calculations give further insight into the nature of the metal-CO bond on these bimetallic sites. Most prominently, the growth of a new CO desorption feature at higher temperature (~ 550 K) in the TPD spectra of Ag-rich surface alloys, which is unique for the group of Pt(111)- and Pd(111)-based surface alloys, is attributed to CO adsorption on Pt atoms surrounded by a Ag-rich neighborhood. Adsorption on these sites manifests in an IR band down-shifted to significantly lower wave number. Systematic comparison of the present results with previous findings for CO adsorption on the related Pt(111)- and Pd(111)-based surface alloys gains a detailed insight into general trends in the adsorption behavior of bimetallic surfaces.

  16. Croissance, mise en ordre chimique et relaxation des contraintes épitaxiales dans des alliages FePd et FePt

    OpenAIRE

    2001-01-01

    The relaxation of strain in epitaxial FePd films, grown by MBE, has been studied thanks to RHEED, TEM and STM. The preferential relaxation by microtwins in well L10- ordered films grown on Pd layers has been described trough a quantitative use of STM images. This modification of the relaxation mechanism in ordered films is explained by the energy cost of ½ perfect dislocations in the L10 structure. This study outlined the role of the surface concerning the L10 ordering during growth: the orde...

  17. Study on the preparation of Pt nanocapsules

    Science.gov (United States)

    Zhang, Yi-fan; Ji, Zhen; Chen, Ke; Liu, Bo-wen; Jia, Cheng-chang; Yang, Shan-wu

    2017-01-01

    Ag@Pt core-shell nanoparticles (Ag@Pt NPs) were prepared by a co-reduction method. Pt nanocapsules with diameters of less than 10 nm were obtained by an electrochemical method. Cyclic voltammetry (CV) scanning was used to cavitate the Ag@Pt NPs, and the morphology, structure, and cavitation conditions were studied. The results indicate that the effective cavitation conditions to obtain Pt nanoparticles from Ag@Pt NPs are a scanning voltage of 0 to 0.8 V and continuous CV scanning over 2 h. This cavitation method is also applicable for the syntheses of Ir, Ru, and Ru-Pt nanocapsules.

  18. Pt(Ⅱ), Pd(Ⅱ) and Ni(Ⅱ) Complexes Binding to the N(7) Position of Guanine: Influence on the Guanine and Watson-crick GC Base Pair

    Institute of Scientific and Technical Information of China (English)

    章志强; 周立新; 和芹; 赵亚英

    2005-01-01

    Comprehensive ab initio calculations were performed on the coordination of Pt(II), Pd(II) and Ni(II) adducts to the N(7) of guanine and guanine-cytosine (GC) base pair at the DFT level. The fully optimized geometries of the metal complexes were obtained and the stabilization energies of the interaction between metal adducts and nucleobase were calculated with B3LYP method by using 6-31* basis set for the light atom. While the effective core potential (ECP) is used for metal cation. The results show that both cispalladium and cisnickel cause similar geometric changes of the base pair as cisplatin. For the coordination of metal adducts to guanine, platinum adduct possesses the highest stabilization energy; but the interaction between metal-guanine and cytosine for nickel is larger than that for platinum and palladium. It is worthy to note that hydrolysis effect can also cause significant changes in H-bonds.

  19. SÍNTESE, PROPRIEDADES E INVESTIGAÇÃO ESTRUTURAL DE 1,3-DIARILTRIAZENOS E COMPLEXOS COM Ni(II), Pd(II), Pt(II) e Hg(II)

    OpenAIRE

    Lorenzo do Canto Visentin

    2006-01-01

    O estudo de complexos de coordenação com metais de transição, envolvendo pré-ligantes triazenos desperta interesse há muitas décadas. A síntese de moléculas derivadas do triazeno 1-3-diariltriazeno e seus complexos com Ni(II), Pd(II), (Pt)(II) e Hg(II) são tema de estudo neste trabalho. Triazenos são moléculas com pares de elétrons livres. Estes elétrons podem ser doados aos metais de transição formando complexos de coordenação. As estruturas dos compostos 3-(4-bromofenil)-1-(4-nitrofenil)tri...

  20. Elastic properties of antiperovskite-type Ni-rich nitrides MNNi 3 (M=Zn, Cd, Mg, Al, Ga, In, Sn, Sb, Pd, Cu, Ag and Pt) as predicted from first-principles calculations

    Science.gov (United States)

    Bannikov, V. V.; Shein, I. R.; Ivanovskii, A. L.

    2010-11-01

    We have performed accurate ab initio total energy calculations using the full-potential linearized augmented plane wave (FP-LAPW) method with the generalized gradient approximation (GGA) for the exchange-correlation potential to systematically investigate elastic properties of 12 synthesized and hypothetical cubic antiperovskite-type Ni-rich nitrides MNNi 3, where M are Zn, Cd, Mg, Al, Ga, In, Sn, Sb, Pd, Cu, Ag and Pt. As a result, the optimized lattice parameters, independent elastic constants ( Cij), bulk-, shear- and tetragonal shear moduli, Cauchy’s pressure and some indexes of elastic anisotropy, as well as the numerical estimations of Young’s modulus, Poisson’s ratio and Pugh's indicator of brittle/ductile behavior for the corresponding polycrystalline MNNi 3 (in the Voigt-Reuss-Hill approximation) were obtained and analyzed in comparison with the available theoretical and experimental data.

  1. Elastic properties of antiperovskite-type Ni-rich nitrides MNNi{sub 3} (M=Zn, Cd, Mg, Al, Ga, In, Sn, Sb, Pd, Cu, Ag and Pt) as predicted from first-principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Bannikov, V.V.; Shein, I.R. [Institute of Solid State Chemistry, Ural Branch of the Russian Academy of Sciences, 620990 Ekaterinburg (Russian Federation); Ivanovskii, A.L., E-mail: ivanovskii@ihim.uran.r [Institute of Solid State Chemistry, Ural Branch of the Russian Academy of Sciences, 620990 Ekaterinburg (Russian Federation)

    2010-11-15

    We have performed accurate ab initio total energy calculations using the full-potential linearized augmented plane wave (FP-LAPW) method with the generalized gradient approximation (GGA) for the exchange-correlation potential to systematically investigate elastic properties of 12 synthesized and hypothetical cubic antiperovskite-type Ni-rich nitrides MNNi{sub 3}, where M are Zn, Cd, Mg, Al, Ga, In, Sn, Sb, Pd, Cu, Ag and Pt. As a result, the optimized lattice parameters, independent elastic constants (C{sub ij}), bulk-, shear- and tetragonal shear moduli, Cauchy's pressure and some indexes of elastic anisotropy, as well as the numerical estimations of Young's modulus, Poisson's ratio and Pugh's indicator of brittle/ductile behavior for the corresponding polycrystalline MNNi{sub 3} (in the Voigt-Reuss-Hill approximation) were obtained and analyzed in comparison with the available theoretical and experimental data.

  2. Ambient pressure superconductivity emerging in the antiferromagnetic phases of the novel heavy fermion compounds Ce{sub 3}PdIn{sub 11} and Ce{sub 3}PtIn{sub 11}

    Energy Technology Data Exchange (ETDEWEB)

    Kratochvilova, Marie; Prokleska, Jan; Uhlirova, Klara; Sechovsky, Vladimir; Custers, Jeroen [Department of Condensed Matter Physics, Charles University, Prague, Ke Karlovu 5, 121 16 (Czech Republic)

    2015-07-01

    Ce{sub n}T{sub m}In{sub 3n+2m} (n=1,2; m=1; T=transition metal) heavy fermion compounds are known to be on the verge of a magnetic to non-magnetic quantum critical point (QCP). In close vicinity of the QCP they exhibit an unconventional superconducting state. However, this family of compounds is interesting for an other reason. The compounds crystallize in the tetragonal structures which provide the possibility to tune the structural dimensionality from more 2D to 3D (stoichiometries: 115-218-103). This makes them ideal candidates to investigate the influence of the parameter dimensionality with respect to quantum criticality. Ce{sub 3}TIn{sub 11} (T=Pd,Pt) single crystals were prepared for the first time. Ce{sub 3}PtIn{sub 11} (Ce{sub 3}PdIn{sub 11}) exhibits two successive transitions at T{sub 1}=2.2K (T{sub 1}=1.7K) and T{sub N}=2.0K (T{sub N} =1.5K) into incommensurate and commensurate local moment antiferromagnetic states, respectively. Applying magnetic field along the c-axis gradually suppresses both transitions; they merge at 4T and split again in higher fields. Superconductivity emerges at T{sub C}=0.32K (T{sub C}=0.39K) and it is enhanced by the application of hydrostatic pressure. The unusual magnetic phase diagram will be discussed in the context of superconductivity and magnetism in related compounds.

  3. Synthesis and Characterization of New Schiff Bases Derived from N (1-Substituted Isatin with Dithiooxamide and Their Co(II, Ni(II, Cu(II, Pd(II, and Pt(IV Complexes

    Directory of Open Access Journals (Sweden)

    Ahlam J. Abdul-Ghani

    2009-01-01

    Full Text Available Three new Schiff bases of N-substituted isatin LI, LII, and LIII = Schiff base of N-acetylisatin, N-benzylisatin, and N-benzoylisatin, respectively, and their metal complexes C1a,b=[Co2(LI2Cl3]Cl, C2=[Ni(LI2Cl2]0.4BuOH, C3=[CuLICl(H2O]Cl⋅0.5BuOH, C4=[Pd(LI2Cl]Cl, C5=[Pt(L12Cl2]Cl2⋅1.8EtOH.H2O, C6a=[CoLIICl]Cl⋅0.4H2O⋅0.3DMSO, C6b=[CoLIICl]Cl⋅0.3H2O⋅0.1BuOH,C7=[NiLIICl2], C8=[CuLII]Cl2⋅H2O00000, C9=[Pd(LII2]Cl2, C10=[Pt(LII2.5Cl]Cl3, C11a=[Co(LIII]C12⋅H2O, C11b=[Co(LIII]Cl2⋅0.2H2O, and C12=[Ni(LIII2]Cl2, C13=[Ni(LIII2]Cl2 were reported. The complexes were characterized by elemental analyses, metal and chloride content, spectroscopic methods, magnetic moments, conductivity measurements, and thermal studies. Some of these compounds were tested as antibacterial and antifungal agents against Staphylococcus aureus, Proteus vulgaris, Candida albicans, and Aspergillus niger.

  4. Catalyst and process development for hydrogen preparation from future fuel cell feedstocks. Quarterly report, April 1-June 30, 1980. [Pt/Pd

    Energy Technology Data Exchange (ETDEWEB)

    Yarrington, R M; Feins, I R; Hwang, H S

    1980-07-01

    Phase II of the contract, which involved catalyst preparation and evaluation, was nearly completed this quarter. Phase III, which calls for the design and construction of a fuel processor, was started. During the quarter, four types of tests were run on the small scale catalyst screening unit. The operating line for coke-free operations was found to be approximately between 0.41 to 0.44 O/sub 2//C level. Screening at lower O/sub 2//C levels led to problems with plugging. In other tests, increased severity for screening steam reforming catalysts was obtained by doubling the space velocity. Another series of tests were run to determine the gas composition from the catalytic partial oxidation (CPO) section and to evaluate two CPO catalysts. In the other series of tests, catalysts were aged for about 20 hours using a propane, steam, and air mixture before testing with No. 2 oil for another five hours. This latter test has been used to study Pt/Rh catalysts made with various supports. Differences were readily determined for Pt/Rh supported on alpha alumina and Pt/Rh supported on stabilized alumina. This test method will find continued use in evaluating metal-support interactions. Several samples must be evaluated by this method before aging runs are made in the larger unit. After leaching alumina from a used Pt/Rh catalyst, the x-ray diffraction pattern showed the presence of a Pt-Rh alloy in the metal residue. Experiments were run to show that the alloy was formed in the reactor during testing and not during catalyst preparation. A larger version of the ATR reactor has been designed and major components are on order. Completion of the construction phase is scheduled for the next quarter.

  5. Extraction separation of Pt and Pd by potassium iodide-n-propanol system in the presence of sodium chloride%氯化钠存在下丙醇-碘化钾体系萃取分离铂、钯的研究

    Institute of Scientific and Technical Information of China (English)

    高云涛; 吴立生

    2001-01-01

    A study of extraction behaviour of Pt and Pd by potassium iodide-n-propanol system in the presence of sodium chloride has been performed and the conditions of phase separation of n-propanol and water in HCl were investigated.The experimental results indicate that the method can extraction simultaneously Pt(Ⅱ) and Pd(Ⅱ) in HCl ,the extraction effeciency of Pt and Pd are 99.8%,99.4%,respectively,the proposed method can separation Pt and Pd from Fe,Al,Pb,Zn,Ca,Mg ,Mn et al based metals and has been used for the separation Pt and Pd in anode slime ,placer platinum and wasted catalyst,and the results agreed well with those of other method.%研究了氯化钠存在下丙醇-碘化钾体系对铂(Ⅱ)、钯(Ⅱ)萃取行为及体系在盐酸介质中的分相条件。在盐酸介质中,体系可同时萃取铂(Ⅱ)、钯(Ⅱ),萃取率分别为 99.8%、99.4%,方法可用于从贱金属中分离铂、钯。对阳极泥、砂铂矿、废催化剂样品中的铂、钯进行了分离,分析结果与其它方法相符,并对萃取机理也进行了探讨。

  6. Exohedral M–C{sub 60} and M{sub 2}–C{sub 60} (M = Pt, Pd) systems as tunable-gap building blocks for nanoarchitecture and nanocatalysis

    Energy Technology Data Exchange (ETDEWEB)

    Özdamar, Burak; Boero, Mauro, E-mail: mauro.boero@ipcms.unistra.fr; Massobrio, Carlo; Felder-Flesch, Delphine; Le Roux, Sébastien, E-mail: sebastien.leroux@ipcms.unistra.fr [Institut de Physique et Chimie des Matériaux de Strasbourg, University of Strasbourg and CNRS, UMR 7504, 23 Rue du Loess, BP43, F-67034 Strasbourg (France)

    2015-09-21

    Transition metal–fullerenes complexes with metal atoms bound on the external surface of C{sub 60} are promising building blocks for next-generation fuel cells and catalysts. Yet, at variance with endohedral M@C{sub 60}, they have received a limited attention. By resorting to first principles simulations, we elucidate structural and electronic properties for the Pd–C{sub 60}, Pt–C{sub 60}, PtPd–C{sub 60}, Pd{sub 2}–C{sub 60}, and Pt{sub 2}–C{sub 60} complexes. The most stable structures feature the metal atom located above a high electron density site, namely, the π bond between two adjacent hexagons (π-66 bond). When two metal atoms are added, the most stable configuration is those in which metal atoms still stand on π-66 bonds but tends to clusterize. The electronic structure, rationalized in terms of localized Wannier functions, provides a clear picture of the underlying interactions responsible for the stability or instability of the complexes, showing a strict relationship between structure and electronic gap.

  7. Intermetallic compounds of the heaviest elements and their homologs: The electronic structure and bonding of MM', where M =Ge, Sn, Pb, and element 114, and M'=Ni, Pd, Pt, Cu, Ag, Au, Sn, Pb, and element 114

    Science.gov (United States)

    Pershina, V.; Anton, J.; Fricke, B.

    2007-10-01

    Fully relativistic (four-component) density-functional theory calculations were performed for intermetallic dimers MM', where M =Ge, Sn, Pb, and element 114, and M'=group 10 elements (Ni, Pd, and Pt) and group 11 elements (Cu, Ag, and Au). PbM and 114M, where M are group 14 elements, were also considered. The results have shown that trends in spectroscopic properties—atomization energies De, vibrational frequencies ωe, and bond lengths Re, as a function of M', are similar for compounds of Ge, Sn, Pb, and element 114, except for De of PbNi and 114Ni. They were shown to be determined by trends in the energies and space distribution of the valence ns(M ') atomic orbitals (AOs). According to the results, element 114 should form the weakest bonding with Ni and Ag, while the strongest with Pt due to the largest involvement of the 5d(Pt) AOs. In turn, trends in the spectroscopic properties of MM' as a function of M were shown to be determined by the behavior of the np1/2(M ) AOs. Overall, De of the element 114 dimers are about 1eV smaller and Re are about 0.2a.u. larger than those of the corresponding Pb compounds. Such a decrease in bonding of the element 114 dimers is caused by the large SO splitting of the 7p orbitals and a decreasing contribution of the relativistically stabilized 7p1/2(114) AO. On the basis of the calculated De for the dimers, adsorption enthalpies of element 114 on the corresponding metal surfaces were estimated: They were shown to be about 100-150kJ/mol smaller than those of Pb.

  8. P-Fluorous Phosphines as Electron-Poor/Fluorous Hybrid Functional Ligands for Precious Metal Catalysts: Synthesis of Rh(I, Ir(I, Pt(II, and Au(I Complexes Bearing P-Fluorous Phosphine Ligands

    Directory of Open Access Journals (Sweden)

    Shin-ichi Kawaguchi

    2017-01-01

    Full Text Available P-Fluorous phosphine (R2PRf, in which the perfluoroalkyl group is directly bonded to the phosphorus atom, is a promising ligand because it has a hybrid functionality, i.e., electron-poor and fluorous ligands. However, examples of P-fluorous phosphine–metal complexes are still rare, most probably because the P-fluorous group is believed to decrease the coordination ability of the phosphines dramatically. In contrast, however, we have succeeded in synthesizing a series of P-fluorous phosphine–coordinated metal complexes such as rhodium, iridium, platinum, and gold. Furthermore, the electronic properties of R2PnC10F21 are investigated by X-ray analysis of PtCl2(Ph2PnC10F212 and the infrared CO stretching frequency of RhCl(CO(R2PnC10F212. IrCl(CO(Ph2PnC10F212- and AuCl(R2PnC10F21-catalyzed reactions are also demonstrated.

  9. Double layer effects in electrocatalysis: the oxygen reduction reaction and ethanol oxidation reaction on Au(111), Pt(111) and Ir(111) in alkaline media containing Na and Li cations.

    Energy Technology Data Exchange (ETDEWEB)

    Lopes, Pietro P.; Strmcnik, Dusan; Jirkovsky, Jakub S.; Connell, Justin G.; Stamenkovic, Vojislav; Markovic, Nenad

    2016-03-15

    Oxygen reduction and ethanol oxidation reactions were studied on Au(111), Pt(111) and Ir(111) in alkaline solutions containing sodium and/or lithium cations. By keeping the same (111) surface orientation and exploring oxophilicity trends and non-covalent interactions between OHad and alkali metal cations (AMCn+), we were able to gain deep insights into the multiple roles that OHad plays in these important electrocatalytic reactions. Cyclic voltammetry experiments revealed that OHad formation initiates at distinct electrode potentials, governed by the oxophilicity of the specific metal surface, with further OHad adlayer stabilization by non-covalent alkali-cation interactions and affecting the formation of a “true oxide” layer at higher electrode potentials. Although OHad is a simple spectator for the ORR, it promotes the ethanol oxidation reaction (EOR) at lower potentials and act as spectator at high OHad coverages. By changing the alkali metal cation at the interface (Li+) on more oxophilic surfaces, it was possible to promote the EOR even more, relative to Na+, without changing the product distribution for the reaction. This cation effect suggests that OHad---Li+(H2O)x clusters can stabilize the ethoxide adlayer, thus improving the EOR activity. Our results indicate the importance of the entire electrochemical interface in determining the electrocatalytic activity during reaction.

  10. Search for protons from the 2H(d,p)3H reaction in an electrolytic cell with Pd-Pt electrodes

    Science.gov (United States)

    Rehm, K. E.; Kutschera, W.; Perlow, G. J.

    1990-01-01

    The production of protons from the 2H(d,p)3H reaction was investigated using an electrolytic cell and a proportional counter. The cathode, consisting of a 30.5-mg/cm2-thick Pd foil, separated the gas in the counter from the electrolyte (0.1M LiOD in D2O). The efficiency for proton detection was 28%. The electrolytic cell was operated with current densities up to 650 mA/cm2. Several runs with the current switched on and off and with different Pd foils have been performed with the longest run lasting more than 10 days. No difference in the count rate was observed when the electrolytic cell was on or off. From the high-energy part of the particle spectrum we obtain an upper limit for the proton production from the fusion reaction 2H(d,p)3H of 4×10-23 fusion/(dd pair/sec).

  11. Casting of MOD inlay using rings with holes on both sides: 12∼18 wt%Au-20∼26Pd-14.48∼26.48Cu-40Ag-1.5Zn-0.02Ir alloys.

    Science.gov (United States)

    Ohkuma, Kazuo; Kazama, Miku; Ogura, Hideo

    2012-01-01

    Using a casting ring with openings on both sides and a water-absorbent polymer, heterogeneity is maintained in a single casting and a precise MOD inlay can be produced. We produced 9 different kinds of gold-silver-palladium (Au-Ag-Pd) alloys by changing the ratio of palladium, gold, and copper and investing them, and changing parameters such as the angulation of the casting ring openings and the water:powder ratios to produce MOD inlay castings. We measured the expansion and shrinkage percentage of the castings in both the buccolingual and mesiodistal directions. From this experiment, we learned that precise MOD inlay castings can be produced using rings with 240° openings when invested in a thick mix having a standard water:powder ratio or using rings with 200° openings when invested in a thick mix having a water:powder ratio for a 12 wt%Au-20∼26Pd-20.48∼26.48Cu-40Ag-1.5Zn-0.02Ir alloyes.

  12. Influence of hydrogen electrosorption on surface oxidation of Pd and Pd-noble metal alloys

    Energy Technology Data Exchange (ETDEWEB)

    Lukaszewski, M.; Kedra, T.; Czerwinski, A. [Warsaw University, Department of Chemistry, Laboratory of Electrochemical Power Sources, Pasteura 1, 02-093 Warsaw (Poland)

    2009-05-15

    Electrochemical oxidation of freshly deposited Pd and its alloys with other noble metals (Au, Pt, Rh) was compared with the behavior of samples subjected to prior hydrogen absorption/desorption procedure. It was found that surface oxidation of hydrogen-treated Pd and Pd-Pt-Au deposits starts at lower potentials than on non-hydrided electrodes and is accompanied by a negative shift of surface oxide reduction peak. Pd and its alloys with Au, Pt and Rh after hydrogen treatment are also more resistant to electrochemical dissolution than freshly deposited samples. (author)

  13. The role of charge transfer in the oxidation state change of Ce atoms in the TM13-CeO2(111) systems (TM = Pd, Ag, Pt, Au): a DFT + U investigation.

    Science.gov (United States)

    Tereshchuk, Polina; Freire, Rafael L H; Ungureanu, Crina G; Seminovski, Yohanna; Kiejna, Adam; Da Silva, Juarez L F

    2015-05-28

    Despite extensive studies of transition metal (TM) clusters supported on ceria (CeO2), fundamental issues such as the role of the TM atoms in the change in the oxidation state of Ce atoms are still not well understood. In this work, we report a theoretical investigation based on static and ab initio molecular dynamics density functional theory calculations of the interaction of 13-atom TM clusters (TM = Pd, Ag, Pt, Au) with the unreduced CeO2(111) surface represented by a large surface unit cell and employing Hubbard corrections for the strong on-site Coulomb correlation in the Ce f-electrons. We found that the TM13 clusters form pyramidal-like structures on CeO2(111) in the lowest energy configurations with the following stacking sequence, TM/TM4/TM8/CeO2(111), while TM13 adopts two-dimensional structures at high energy structures. TM13 induces a change in the oxidation state of few Ce atoms (3 of 16) located in the topmost Ce layer from Ce(IV) (itinerant Ce f-states) to Ce(III) (localized Ce f-states). There is a charge flow from the TM atoms to the CeO2(111) surface, which can be explained by the electronegativity difference between the TM (Pd, Ag, Pt, Au) and O atoms, however, the charge is not uniformly distributed on the topmost O layer due to the pressure induced by the TM13 clusters on the underlying O ions, which yields a decrease in the ionic charge of the O ions located below the cluster and an increase in the remaining O ions. Due to the charge flow mainly from the TM8-layer to the topmost O-layer, the charge cannot flow from the Ce(IV) atoms to the O atoms with the same magnitude as in the clean CeO2(111) surface. Consequently, the effective cationic charge decreases mainly for the Ce atoms that have a bond with the O atoms not located below the cluster, and hence, those Ce atoms change their oxidation state from IV to III. This increases the size of the Ce(III) compared with the Ce(IV) cations, which builds-in a strain within the topmost Ce layer, and

  14. Synergetic effect of host-guest chemistry and spin crossover in 3D Hofmann-like metal-organic frameworks [Fe(bpac)M(CN)4] (M=Pt, Pd, Ni).

    Science.gov (United States)

    Bartual-Murgui, Carlos; Salmon, Lionel; Akou, Amal; Ortega-Villar, Norma A; Shepherd, Helena J; Muñoz, M Carmen; Molnár, Gábor; Real, José Antonio; Bousseksou, Azzedine

    2012-01-09

    The synthesis and characterization of a series of three-dimensional (3D) Hofmann-like clathrate porous metal-organic framework (MOF) materials [Fe(bpac)M(CN)(4)] (M=Pt, Pd, and Ni; bpac=bis(4-pyridyl)acetylene) that exhibit spin-crossover behavior is reported. The rigid bpac ligand is longer than the previously used azopyridine and pyrazine and has been selected with the aim to improve both the spin-crossover properties and the porosity of the corresponding porous coordination polymers (PCPs). The 3D network is composed of successive {Fe[M(CN)(4)]}(n) planar layers bridged by the bis-monodentate bpac ligand linked in the apical positions of the iron center. The large void between the layers, which represents 41.7% of the unit cell, can accommodate solvent molecules or free bpac ligand. Different synthetic strategies were used to obtain a range of spin-crossover behaviors with hysteresis loops around room temperature; the samples were characterized by magnetic susceptibility, calorimetric, Mössbauer, and Raman measurements. The complete physical study reveals a clear relationship between the quantity of included bpac molecules and the completeness of the spin transition, thereby underlining the key role of the π-π stacking interactions operating between the host and guest bpac molecules within the network. Although the inclusion of the bpac molecules tends to increase the amount of active iron centers, no variation of the transition temperature was measured. We have also investigated the ability of the network to accommodate the inclusion of molecules other than water and bpac and studied the synergy between the host-guest interaction and the spin-crossover behavior. In fact, the clathration of various aromatic molecules revealed specific modifications of the transition temperature. Finally, the transition temperature and the completeness of the transition are related to the nature of the metal associated with the iron center (Ni, Pt, or Pd) and also to the

  15. Determination of Pb content in samples of plant food using Pd and Pt matrix modifier%钯、铂基体改进剂测定植物性食品中的铅

    Institute of Scientific and Technical Information of China (English)

    汪鑫; 赵微; 杨剑虹

    2011-01-01

    [目的]筛选无火焰电热石墨炉原子化器测定植物性食品样品中铅的最佳基体改进剂,提高石墨炉原子吸收光谱法快速测定铅的精密度和准确度.[方法]分别采用钯盐和铂盐作为测定铅的基体改进剂,测定吸光度值,使用标准加入法分析改进效果,并探索其最佳灰化温度、原子化温度和用量.[结果]采用钯基体改进剂,改进效果显著,较未用时提高原子化温度200~300℃,且低温下(<900℃)铅的原子化损失极低,回收率达80%~113%;而以铂盐作基体改进剂无明显改进效果.[结论]测定基体成分复杂样品中的铅时,可选用钯盐作为基体改进剂,其最佳灰化温度为500℃,最佳原子化温度为2200℃,最佳使用量为25 mg/L.%[Objective]The present experiment was conducted to screen the best matrix modifier for determining the Pb content in plant food samples using electrothermal flameless graphite furnace atomizer and to improve the accuracy of graphite furnace atomic absorption spectrum. [Method]Palladium (Pd) and platinum (Pt) salts were used as matrix modi-fier to determine the Pb content using standard method to analyze their effects and the best ashing and atomization tem-perature and dosage. [ Result ]The results showed that the Pd matrix modifier had significant effect on increasing 200-300℃ of atomization temperature and lower atomization loss of Pb under low temperature (<900℃) , and the recovery rate was 80- 113%, while the Pt matrix modifier did not show significant improvements. [Conclusion]Palladium can be used as matrix modifier to determine the Pb content in samples with complicated component and the best ashing temperature is 500℃, the optimum atomization temperature is 2200℃, with the working volume 25 mg/L.

  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. Prediction of strong O-H/M hydrogen bonding between water and square-planar Ir and Rh complexes.

    Science.gov (United States)

    Janjić, G V; Milosavljević, M D; Veljković, D Ž; Zarić, S D

    2017-03-20

    Intermolecular O-H/M interactions, between a water molecule and square-planar acac complexes ([M(acac)L2]), with different types of L ligands (en, H2O, CO, CN(-), and OH(-)) and different types of metal atoms (Ir(i), Rh(i), Pt(ii), and Pd(ii)) were studied by high level ab initio calculations. Among the studied neutral complexes, the [Pd(acac)(CN)(CO)] complex forms the weakest interaction, -0.62 kcal mol(-1), while the [Ir(acac)(en)] complex forms the strongest interaction, -9.83 kcal mol(-1), which is remarkably stronger than the conventional hydrogen bond between two water molecules (-4.84 kcal mol(-1)).

  18. 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.

  19. Reaction of bis(o-phosphinophenyl)silane with M(PPh3)4 (M = Ni, Pd, Pt): synthesis and structural analysis of η2-(Si-H) metal(0) and pentacoordinate silyl metal(II) hydride complexes of the Ni triad bearing a PSiP-pincer ligand.

    Science.gov (United States)

    Takaya, Jun; Iwasawa, Nobuharu

    2011-09-21

    Reactions of bis(o-(diphenylphosphino)phenyl)methylsilane with M(PPh(3))(4) (M = Ni, Pd, Pt) were investigated. When M = Ni or Pd, synthesis and isolation of η(2)-(Si-H) complexes of mononuclear Ni(0) and Pd(0) were achieved for the first time as frozen intermediates for oxidative addition of the Si-H bond. Structural analysis by X-ray and NMR spectroscopy disclosed that their η(2)-(Si-H) structures were maintained in both solid and solution states and coordination of the Si-H bond to the metal center was relatively weak. On the other hand, reaction with a platinum(0) complex afforded two kinds of pentacoordinate silyl platinum(II) hydride complexes having a PSiP-pincer ligand, which underwent unique thermal isomerization from a square-pyramidal cis-H-Pt-Si to a trigonal-bipyramidal trans-H-Pt-Si isomer. Mechanistic investigations revealed that this isomerization proceeded via an intramolecular rearrangement process probably through a turnstile rotation.

  20. 铂钯修饰聚N-乙酰苯胺膜电极对甲酸的电催化氧化%Electrocatalytic Oxidation of Formic acid on Porous Poly(N-acetylaniline) Electrode Modified with Pt and Pd Microparticles

    Institute of Scientific and Technical Information of China (English)

    赵彦春; 兰黄鲜; 田建袅; 罗全迁; 蔡英

    2009-01-01

    由电化学方法在石墨电极表面制备了规整多孔的纳米结构聚N-乙酰苯胺(PAANI)膜,并以其为载体制备了Pt-Pd/PAANI/C二元金属微粒修饰的聚合物复合膜电极.SEM和XRD研究结果表明,Pt、Pd微粒在PAANI膜中均匀分散,有效地改善了催化剂中贵金属的分散度和电极的结构.在0.5mol/L H2SO4+0.5mol/LHCOOH溶液中的循环伏安结果表明,Pt-Pd/PAANI/C电极在酸性溶液中电催化氧化甲酸的性能明显优于直接电沉积的Pt-Pd/C电极,且表现出较高的稳定性.

  1. 钛锆复合载体负载Pt-Pd催化剂的制备及加氢脱芳性能的研究%Preparation of Pt-Pd/TiO_2-ZrO_2 Catalyst and Study of Its Hydrodearomatics Performance

    Institute of Scientific and Technical Information of China (English)

    高琳琳; 王海彦; 马骏; 魏民; 施岩

    2009-01-01

    In this paper titanium-zirconium mixed oxides with different molar ratio of Ti to Zr was prepared by improved sol-gel method. The supporters were characterized by means of BET, XRD methods, and the results showed that the TiO_2-ZrO_2 mixed supporter had much better specific surface, pore structure and textures properties than the single support or the mixed support prepared by the conventional sol-gel method. The crystal phase of the mixed supporter changed as the molar ratio of titanium to zirconium, which affected its catalytic activity. The hydrodearomatics performance of Pd-Pt/TiO_2-ZrO_2 catalyst was investigated on the fixed-bed reactor. The results indicated that the catalyst had excellent hydrodearomatics activities, and showed a stronger sulfur tolerance performance.%采用改进的溶胶-凝胶法制备钛锆(TiO_2-ZrO_2)复合氧化物载体,并用X射线衍射和N2吸附对样品进行表征.随着钛锆摩尔比的不同,复合载体具有不同的晶型结构,且实验证明对催化剂的活性有较大的影响.在小型连续固定床反应器上对TiO_2-ZrO_2复合载体负载Pt-Pd催化剂上进行加氢脱芳活性评价,结果表明,该催化剂性能优异,有较强的抗硫性能.

  2. X = Pt, Os, Ru, Ir, Rh

    African Journals Online (AJOL)

    Timothy Ademakinwa

    Department of Physics, Federal University of Technology, Akure. Nigeria. ... All structure relaxation and bulk modulus ... using the Sutton-Chen form of Embedded Atom ... In (1) - (3), c is a dimensionless quantity, r is the ij spacing ... to the large numbers of atoms involved, cubic ... in the theoretical prediction of hard materials.

  3. Synthesis and alignment of silver nanorods and nanowires and the formation of Pt, Pd, and core/shell structures by galvanic exchange directly on surfaces.

    Science.gov (United States)

    Sławiński, Grzegorz W; Zamborini, Francis P

    2007-09-25

    Here we describe the synthesis of Ag nanorods (NRs) (aspect ratio or =20) directly on surfaces by seed-mediated growth. The procedure involves attaching gold seed nanoparticles (Au NPs) to 3-mercaptopropyltrimethoxysilane (MPTMS)-functionalized silicon or glass surfaces and growing them into NRs/NWs by placing the substrates into a solution containing cetyltrimethylammonium bromide (CTAB), silver nitrate, and ascorbic acid with the pH ranging from 7 to 12. Under our conditions, Ag NRs/NWs grow optimally at pH 10.6 with a 3% yield, where spherical, triangular, and hexagonal nanostructures represent the other byproducts. The length of Ag NRs/NWs ranges from 50 nm to more than 10 microm, the aspect ratio (AR) ranges from 1.4 to >300, and the average diameter is approximately 35 nm. Approximately 40% of the 1D structures are NRs, and 60% are NWs as defined by their ARs. We also report the alignment of Ag NRs/NWs directly on surfaces by growing the structures on amine-functionalized Si(100) surfaces after an amidation reaction with acetic acid and a method to improve the percentage of Ag NRs/NWs on the surface by removing structures of other shapes with adhesive tape. Surface-grown Ag NRs/NWs also react with salts of palladium, platinum, and gold via galvanic exchange reactions to form high-surface-area 1D structures of the corresponding metal. The combination of the seed-mediated growth of Ag on Au NRs followed by the galvanic exchange of Ag with Pd leads to interesting core/shell NRs grown directly on surfaces. We used scanning electron microscopy, UV-vis spectroscopy, and X-ray photoelectron spectroscopy to characterize the surface-grown nanostructures.

  4. Durable pd-based alloy and hydrogen generation membrane thereof

    Science.gov (United States)

    Benn, Raymond C.; Opalka, Susanne M.; Vanderspurt, Thomas Henry