Measurement of benzenethiol adsorption to nanostructured Pt, Pd, and PtPd films using Raman spectroelectrochemistry.

Science.gov (United States)

Pomfret, Michael B; Pietron, Jeremy J; Owrutsky, Jeffrey C

2010-05-04

Raman spectroscopy and electrochemical methods were used to study the behavior of the model adsorbate benzenethiol (BT) on nanostructured Pt, Pd, and PtPd electrodes as a function of applied potential. Benzenethiol adsorbs out of ethanolic solutions as the corresponding thiolate, and voltammetric stripping data reveal that BT is oxidatively removed from all of the nanostructured metals upon repeated oxidative and reductive cycling. Oxidative stripping potentials for BT increase in the order Pt oxidizing potentials via cleavage of the Pt-S bond. In contrast, on nanoscale Pd and PtPd, BT is irreversibly lost due to cleavage of BT C-S bonds at oxidizing potentials, which leaves adsorbed sulfur oxides on Pd and PtPd films and effects the desulfurization of BT. While Pd and PtPd films are less sulfur-resistant than Pt films, palladium oxides, which form at higher potentials than Pt oxides, oxidatively desulfurize BT. In situ spectroelectrochemical Raman spectroscopy provides real-time, chemically specific information that complements the cyclic voltammetric data. The combination of these techniques affords a powerful and convenient method for guiding the development of sulfur-tolerant PEMFC catalysts.

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.

Microwave sinthesys and characterization of Pt and Pt-Rh-Sn electrocatalysts for ethanol oxidation

Directory of Open Access Journals (Sweden)

Jovanović Vladislava M.

2011-01-01

Full Text Available Carbon supported Pt and Pt-Rh-Sn catalysts were synthesized by microwave-polyol method in ethylene glycol solution and investigated for the ethanol electro-oxidation reaction. The catalysts were characterized in terms of structure, morphology and composition by employing XRD, STM and EDX techniques. STM analysis indicated rather uniform particles and particle size of below 2 nm for both catalysts. XRD analysis of the Pt/C catalyst revealed two phases, one with the main characteristic peaks of face centered cubic crystal structure (fcc of platinum and another related to graphite like structure of carbon support Vulcan XC-72R. However, in XRD pattern of the Pt-Rh-Sn/C catalyst diffraction peaks for Pt, Rh or Sn cannot be resolved, indicating an extremely low crystallinity. The small particle sizes and homogeneous size distributions of both catalysts should be attributed to the advantages of microwave assisted modified polyol process in ethylene glycol solution. Pt-Rh- Sn/C catalyst is highly active for the ethanol oxidation with the onset potential shifted for more than 150 mV to negative values and with currents nearly 5 times higher in comparison to Pt/C catalyst. The stability tests of the catalysts, as studied by the chronoamperometric experiments, reveal that the Pt-Rh-Sn/C catalyst is evidently less poisoned then Pt/C catalyst. The increased activity of Pt-Rh-Sn/C in comparison to Pt/C catalyst is most probably promoted by bifunctional mechanism and the electronic effect of alloyed metals.

CO tolerance of PdPt/C and PdPtRu/C anodes for PEMFC

International Nuclear Information System (INIS)

Garcia, Amanda C.; Paganin, Valdecir A.; Ticianelli, Edson A.

2008-01-01

The performance of H 2 /O 2 proton exchange membrane fuel cells (PEMFCs) fed with CO-contaminated hydrogen was investigated for anodes with PdPt/C and PdPtRu/C electrocatalysts. The physicochemical properties of the catalysts were characterized by energy dispersive X-ray (EDX) analyses, X-ray diffraction (XRD) and 'in situ' X-ray absorption near edge structure (XANES). Experiments were conducted in electrochemical half and single cells by cyclic voltammetry (CV) and I-V polarization measurements, while DEMS was employed to verify the formation of CO 2 at the PEMFC anode outlet. A quite high performance was achieved for the PEMFC fed with H 2 + 100 ppm CO with the PdPt/C and PdPtRu/C anodes containing 0.4 mg metal cm -2 , with the cell presenting potential losses below 200 mV at 1 A cm -2 , with respect to the system fed with pure H 2 . For the PdPt/C catalysts no CO 2 formation was seen at the PEMFC anode outlet, indicating that the CO tolerance is improved due to the existence of more free surface sites for H 2 electrooxidation, probably due to a lower Pd-CO interaction compared to pure Pd or Pt. For PdPtRu/C the CO tolerance may also have a contribution from the bifunctional mechanism, as shown by the presence of CO 2 in the PEMFC anode outlet

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.

CO and ethanol electro-oxidation on Pt-Rh/C

OpenAIRE

Calderón-Cárdenas, Alfredo; Ortiz-Restrepo, John E.; Mancilla-Valencia, Nelson D.; Torres-Rodriguez, Gerardo A.; Lima, Fabio H. B.; Bolaños-Rivera, Alberto; Gonzalez, Ernesto R.; Lizcano-Valbuena, William H.

2014-01-01

In this work we studied the effect of the composition and thermal treatment in H2 of Pt-Rh/C materials with atomic ratios close to Pt:Rh 3:1, 1:1 and 1:3 and metal loading of 40 wt. %, for the COads and ethanol oxidation. Catalysts were prepared by chemical reduction with formic acid and physically characterized by energy dispersive X-rays spectroscopy (EDX), electron backscattering (EBS) and transmission electron microscopy (TEM), showing Pt:Rh ratios close to the nominals values, similar av...

A thermodynamic description of the system Pd-Rh-H-D-T

Energy Technology Data Exchange (ETDEWEB)

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, UMR 7182, 2-8 Rue Henri Dunant, F-94320 Thiais (France); Thiebaut, S. [CEA/DAM/Valduc, F-21120 Is sur Tille (France)

2011-02-15

The quinary system D-H-Pd-Rh-T has been described thermodynamically by the CALPHAD approach. Previous descriptions of the binary subsystems have been used. To model the high pressure data an equation of state for the gases D{sub 2} and T{sub 2} compatible with the CALPHAD approach has been obtained similar to that previously used for H{sub 2}. A complete literature search has been undertaken for the three ternary systems H-Pd-Rh, D-Pd-Rh and Pd-Rh-T and the most significant experimental data have been selected for a thermodynamic assessment of these systems. In order to complement the available data, pressure-composition curves have been measured at different temperatures for the two last systems in the present work. Calculations and optimization of the system under para-equilibrium conditions, i.e. in pseudo-binary systems (Pd,Rh)-H, (Pd,Rh)-D or (Pd,Rh)-T, have been achieved using a pseudo-atom describing the Pd-Rh solid solution. This special method allows the presence of a miscibility gap in the binary metallic system to be dealt with. We show that a simple combination of the binary systems alone is unable to properly describe these ternary systems and that ternary interaction parameters have to be introduced. The binary and ternary systems may then be combined to perform calculations in the quinary D-H-Pd-Rh-T system. It is believed that extrapolation in systems containing different isotopes are fairly accurate provided that the so-called Toop model is used.

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

OpenAIRE

Celo V.; Zhao J. J.; Dabek-Zlotorzynska E.

2013-01-01

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...

Ethanol electro-oxidation in alkaline medium using Pd/c and PdRh/C electrocatalysts prepared by electron beam irradiation

International Nuclear Information System (INIS)

Silva, Dionisio Furtunato da; Geraldes, Adriana Napoleao; Pino, Eddy Segura; Spinace, Estevam Vitorio; Oliveira Neto, Almir; Linardi, Marcelo

2013-01-01

In this study, carbon-supported Pd (Pd/C) and bimetallic PdRh (Pd:Rh 90:10 atomic ratio) (PdRh/C) electrocatalysts were prepared using electron beam irradiation. The morphology and composition of the obtained materials were characterized by Cyclic voltammetry (VC), Chronoamperometry (CA), Energy dispersive X-ray (EDX), X-ray Diffraction (XRD) and Thermo-gravimetric analysis (TGA). The catalytic activities of the electrocatalysts toward the ethanol electro-oxidation were evaluated in alkaline medium in a single alkaline direct ethanol fuel cell (ADEFC), in a range temperature of 50 to 85 deg C. The best performances were obtained at 85 deg C (25 mW.cm -2 ) and 75 deg C (38 mW.cm -2 ) for Pd/C and PdRh/C electrocatalysts, respectively. The XRD of the PdRh/C electrocatalyst showed the presence of Pd-rich (fcc) phase. CV and CA experiments showed that PdRh/C electrocatalyst demonstrated superior activity toward ethanol electro-oxidation at room temperature, compared to Pd/C electrocatalyst. (author)

Ethanol electro-oxidation in alkaline medium using Pd/c and PdRh/C electrocatalysts prepared by electron beam irradiation

Energy Technology Data Exchange (ETDEWEB)

Silva, Dionisio Furtunato da; Geraldes, Adriana Napoleao; Pino, Eddy Segura; Spinace, Estevam Vitorio; Oliveira Neto, Almir; Linardi, Marcelo, E-mail: dfsilva@ipen.br, E-mail: drinager@ig.com.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

2013-07-01

In this study, carbon-supported Pd (Pd/C) and bimetallic PdRh (Pd:Rh 90:10 atomic ratio) (PdRh/C) electrocatalysts were prepared using electron beam irradiation. The morphology and composition of the obtained materials were characterized by Cyclic voltammetry (VC), Chronoamperometry (CA), Energy dispersive X-ray (EDX), X-ray Diffraction (XRD) and Thermo-gravimetric analysis (TGA). The catalytic activities of the electrocatalysts toward the ethanol electro-oxidation were evaluated in alkaline medium in a single alkaline direct ethanol fuel cell (ADEFC), in a range temperature of 50 to 85 deg C. The best performances were obtained at 85 deg C (25 mW.cm{sup -2}) and 75 deg C (38 mW.cm{sup -2}) for Pd/C and PdRh/C electrocatalysts, respectively. The XRD of the PdRh/C electrocatalyst showed the presence of Pd-rich (fcc) phase. CV and CA experiments showed that PdRh/C electrocatalyst demonstrated superior activity toward ethanol electro-oxidation at room temperature, compared to Pd/C electrocatalyst. (author)

Structural and physical properties of new uranium and transition element ternary stannides (Fe, Co, Ni, Ru, Rh, Pd, Ir, Pt); Proprietes structurales et physiques de nouveaux stannures ternaires a base d'uranium et d'element de transition (Fe, Co, Ni, Rh, Pd, Ir, Pt)

Energy Technology Data Exchange (ETDEWEB)

Mirambet, F

1993-12-15

This work is dedicated to the study of ternary stannides based on uranium. The author reviews the structural, magnetic and electric properties of different families of stannides. The study of the U{sub 2}M{sub 2}Sn family where M stands for Fe, Co, Ni, Ru, Rh, Pd, Ir and Pt shows that the magnetic behaviour of uranium in these compounds is strongly influenced by the transition element M, which is explained by the hybridization force 5f(U) - nd(M) that depends on the number of electrons on the d shell of the M element. For instance, for the elements whose d shell is low filled (Fe, Ru), the U{sub 2}M{sub 2}Sn stannides show no magnetic order. On the other hand, when the number of d-electrons increases, a magnetic order appears progressively.

Photoelectron diffraction study of Rh nanoparticles growth on Fe3O4/Pd(111) ultrathin film

International Nuclear Information System (INIS)

Abreu, G. J. P.; Pancotti, A; Lima, L. H. de; Landers, R.; Siervo, A. de

2013-01-01

Metallic nanoparticles (NPs) supported on oxides thin films are commonly used as model catalysts for studies of heterogeneous catalysis. Several 4d and 5d metal NPs (for example, Pd, Pt and Au) grown on alumina, ceria and titania have shown strong metal support interaction (SMSI), for instance the encapsulation of the NPs by the oxide. The SMSI plays an important role in catalysis and is very dependent on the support oxide used. The present work investigates the growth mechanism and atomic structure of Rh NPs supported on epitaxial magnetite Fe 3 O 4 (111) ultrathin films prepared on Pd(111) using the Molecular Beam Epitaxy (MBE) technique. The iron oxide and the Rh NPs were characterized using X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction and photoelectron diffraction (PED). The combined XPS and PED results indicate that Rh NPs are metallic, cover approximately 20 % of the iron oxide surface and show height distribution ranging 3–5 ML (monolayers) with essentially a bulk fcc structure.

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.

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.

Platinum-group elements fractionation by selective complexing, the Os, Ir, Ru, Rh-arsenide-sulfide systems above 1020 °C

Science.gov (United States)

Helmy, Hassan M.; Bragagni, Alessandro

2017-11-01

The platinum-group element (PGE) contents in magmatic ores and rocks are normally in the low μg/g (even in the ng/g) level, yet they form discrete platinum-group mineral (PGM) phases. IPGE (Os, Ir, Ru) + Rh form alloys, sulfides, and sulfarsenides while Pt and Pd form arsenides, tellurides, bismuthoids and antimonides. We experimentally investigate the behavior of Os, Ru, Ir and Rh in As-bearing sulfide system between 1300 and 1020 °C and show that the prominent mineralogical difference between IPGE (+Rh) and Pt and Pd reflects different chemical preference in the sulfide melt. At temperatures above 1200 °C, Os shows a tendency to form alloys. Ruthenium forms a sulfide (laurite RuS2) while Ir and Rh form sulfarsenides (irarsite IrAsS and hollingworthite RhAsS, respectively). The chemical preference of PGE is selective: IPGE + Rh form metal-metal, metal-S and metal-AsS complexes while Pt and Pd form semimetal complexes. Selective complexing followed by mechanical separation of IPGE (and Rh)-ligand from Pt- and Pd-ligand associations lead to PGE fractionation.

A DFT study of Ru, Rh, Pd, Os, Ir, and Pt clusters as catalysts for methane dissociation in a direct methane fuel cell (DMHFC)

Energy Technology Data Exchange (ETDEWEB)

Psofogiannakisa, G. [Ottawa Univ., Ottawa, ON (Canada). Dept. of Chemical Engineering; Ottawa, Univ., Ottawa, ON (Canada). Centre for Catalysis Research and Innovation; St-Amant, A. [Ottawa Univ., Ottawa, ON (Canada). Dept. of Chemistry; Ternan, M. [Ottawa Univ., Ottawa, ON (Canada). Centre for Catalysis Research and Innovation; EnPross Inc., Ottawa, ON (Canada)

2008-07-01

The rate limiting step in a direct methane hydrocarbon fuel cell (DMHFC) is the dissociative chemisorption of methane. Quantum mechanical computations were used to examine the terrace, kink, and step sites on 6 different clusters of group 8 transition metals, notably Ru, Rh, Pd, Os, Ir, and Pt. The computations involved the anodic reaction of a DMHFC with a polymer electrolyte that operates at atmospheric pressure and temperatures higher than 120 degrees C. The interaction between molecular fragments and a surface (Pt) were described and density functional theory (DFT) calculations were performed using Guassian software. The geometries of 5 different platinum clusters were examined along with their electronic energy barriers. The biggest contribution to the stabilization energy came from the overlap between the sigma bond in methane and unoccupied sd hybrid orbitals in the Pt bonding atom. The study showed that when relaxation was allowed, the displacement of the bonding metal atom was 0.36 to 0.52 A. The electronic energy barrier often increased as d-orbital occupancy increased. For the kink surface sites, the energy barriers were considerably smaller for the 5d transition metals than for the 4d transition metals. 5 refs., 1 tab.

Magnetic properties of Co/Pt-Pd multilayer thin film media

Energy Technology Data Exchange (ETDEWEB)

Inaba, N.; Igarashi, S.; Fujita, F.; Koike, K.; Kato, H. [Faculty of Engineering, Yamagata University, Yonezawa, Yamagata 992-8510 (Japan); Kirino, F. [National University of Fine Arts and Music, Taitou-ku, Tokyo 110-8714 (Japan)

2007-12-15

We investigated the dependence of magnetic properties for Co/Pt{sub 100-x}Pd{sub x} multilayer thin films on the concentration in the Pt-Pd alloy layers. Perpendicular magneto anisotropy constant K {sub p} increases with increasing Pt concentration in the Pt-Pd layer, since the interface anisotropy between the Co and the Pt-Pd layers is enhanced by the increase of the Pt concentration. The Curie temperature and the temperature dependence of K{sub p} for the specimens increase with increasing the amount of Pt in the Pt-Pd layer. These results may indicate that the lattice distortion of the Co layer caused by the interface from the Pt-Pd layer becomes larger and the increase of the distortion enhances the interface anisotropy, since the lattice misfit between the Pt-Pd and the Co increases with increasing the Pt concentration. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

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.

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

KAUST Repository

Yuan, Qiang; Huang, Dabing; Wang, Honghui; Zhou, Zhiyou; Wang, Qingxiao

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

Rare earth-rich cadmium compounds RE{sub 10}TCd{sub 3} (RE = Y, Tb, Dy, Ho, Er, Tm, Lu; T = Rh, Pd, Ir, Pt) with an ordered Co{sub 2}Al{sub 5}-type structure

Energy Technology Data Exchange (ETDEWEB)

Block, Theresa; Klenner, Steffen; Heletta, Lukas; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie

2018-04-01

Eighteen new rare earth-rich intermetallic phases RE{sub 10}TCd{sub 3} (RE = Y, Tb, Dy, Ho, Er, Tm, Lu; T = Rh, Pd, Ir, Pt) were obtained by induction melting of the elements in sealed niobium ampoules followed by annealing in muffle furnaces. All samples were characterized by X-ray powder diffraction. The structures of four representatives were refined from single-crystal X-ray diffractometer data: ordered Co{sub 2}Al{sub 5} type, P6{sub 3}/mmc, a = 951.2(1), c = 962.9(2) pm, wR = 0.0460, 595 F{sup 2} values, 20 parameters for Er{sub 10}RhCd{sub 3}; a = 945.17(4), c = 943.33(4), wR = 0.0395, 582 F{sup 2} values, 21 parameters for Lu{sub 9.89}PdCd{sub 3.11}; a = 964.16(6), c = 974.93(6) pm, wR = 0.0463, 614 F{sup 2} values, 21 parameters for Y{sub 10}Ir{sub 1.09}Cd{sub 2.91}; a = 955.33(3), c = 974.56(3) pm, wR = 0.0508, 607 F{sup 2} values, 22 refined parameters for Dy{sub 9.92}IrCd{sub 3.08}. Refinements of the occupancy parameters revealed small homogeneity ranges resulting from RE/Cd, respectively T/Cd mixing. The basic building units of the RE{sub 10}TCd{sub 3} phases are transition metal-centered RE{sub 6} trigonal prisms (TP) that are condensed with double-pairs of empty RE{sub 6} octahedra via common triangular faces. A second type of rods is formed by slightly distorted RE3 rate at Cd{sub 6}RE{sub 6} icosahedra which are condensed via Cd{sub 3} triangular faces. The shortest interatomic distances occur for RE-T, compatible with strong covalent bonding interactions. Temperature dependent magnetic susceptibility measurements were performed for RE{sub 10}RhCd{sub 3} (RE = Dy-Tm, Lu), RE{sub 10}IrCd{sub 3} (RE = Er, Tm, Lu) and RE{sub 10}PtCd{sub 3} (RE = Y, Lu). While Y{sub 10}PtCd{sub 3} and Lu{sub 10}TCd{sub 3} (T = Rh, Ir, Pt) show Pauli paramagnetic behavior, the compounds containing paramagnetic rare earth elements show Curie-Weiss behavior (the experimental magnetic moments indicate stable trivalent RE{sup 3+}) and magnetic ordering at low temperatures

A possible in vivo generator 103Pd/103mRh-Recoil considerations

International Nuclear Information System (INIS)

Rooyen, Johann van; Szucs, Zoltan; Rijn Zeevaart, Jan

2008-01-01

The use of Auger emitters as potential radiopharmaceuticals is increasingly investigated. One such radionuclide of interest is 103m Rh. This can be produced from 103 Ru or from 103 Pd in an in vivo generator. A potential problem with this concept is the recoil of the 103m Rh out of the carrier molecule and even out of the target cell. In order to determine whether this would happen in the 103 Pd/ 103m Rh case calculations were done to prove that this does not happen. From theoretical considerations it seems that the 103 Pd/ 103m Rh in vivo generator system would be possible

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.

Adsorption and oxidation of acetaldehyde on carbon supported Pt, PtSn and PtSn-based trimetallic catalysts by in situ Fourier transform infrared spectroscopy

Science.gov (United States)

Beyhan, Seden; Léger, Jean-Michel; Kadırgan, Figen

2013-11-01

The adsorption and oxidation of acetaldehyde on carbon supported Pt, Pt90Sn10 and Pt80Sn10M10 (M = Ni, Co, Rh, Pd) catalysts have been investigated by using in situ Fourier transform infrared (FTIR) spectroscopy. The result revealed that Pt90Sn10/C catalyst is not very efficient for the conversion of acetaldehyde to CO2 due to the weak adsorption of acetaldehyde in the presence of Sn. However, the addition of a third metal to Pt--Sn facilitates the C-C bond cleavage of acetaldehyde. It seems that acetaldehyde is adsorbed dissociatively on the surface of Pt80Sn10Ni10/C, Pt80Sn10Co10/C, Pt80Sn10Rh10/C catalysts, producing CH3 and CHO adsorbate species, which can be further oxidized to CO2. However, the pathway forming CO2 for Pt80Sn10Pd10/C catalyst mainly originates from the oxidation of CH3CO species. Thus, the presence of third metal in the PtSn catalyst has a strong impact upon the acetaldehyde adsorption behaviour and its reaction products.

Mechanistic Investigation of the Reduction of NOx over Pt- and Rh-Based LNT Catalysts

Directory of Open Access Journals (Sweden)

Lukasz Kubiak

2016-03-01

Full Text Available The influence of the noble metals (Pt vs. Rh on the NOx storage reduction performances of lean NOx trap catalysts is here investigated by transient micro-reactor flow experiments. The study indicates a different behavior during the storage in that the Rh-based catalyst showed higher storage capacity at high temperature as compared to the Pt-containing sample, while the opposite is seen at low temperatures. It is suggested that the higher storage capacity of the Rh-containing sample at high temperature is related to the higher dispersion of Rh as compared to Pt, while the lower storage capacity of Rh-Ba/Al2O3 at low temperature is related to its poor oxidizing properties. The noble metals also affect the catalyst behavior upon reduction of the stored NOx, by decreasing the threshold temperature for the reduction of the stored NOx. The Pt-based catalyst promotes the reduction of the adsorbed NOx at lower temperatures if compared to the Rh-containing sample, due to its superior reducibility. However, Rh-based material shows higher reactivity in the NH3 decomposition significantly enhancing N2 selectivity. Moreover, formation of small amounts of N2O is observed on both Pt- and Rh-based catalyst samples only during the reduction of highly reactive NOx stored at 150 °C, where NOx is likely in the form of nitrites.

Synthesis of bimetallic Pt-Pd core-shell nanocrystals and their high electrocatalytic activity modulated by Pd shell thickness

Science.gov (United States)

Li, Yujing; Wang, Zhi Wei; Chiu, Chin-Yi; Ruan, Lingyan; Yang, Wenbing; Yang, Yang; Palmer, Richard E.; Huang, Yu

2012-01-01

Bimetallic Pt-Pd core-shell nanocrystals (NCs) are synthesized through a two-step process with controlled Pd thickness from sub-monolayer to multiple atomic layers. The oxygen reduction reaction (ORR) catalytic activity and methanol oxidation reactivity of the core-shell NCs for fuel cell applications in alkaline solution are systematically studied and compared based on different Pd thickness. It is found that the Pd shell helps to reduce the over-potential of ORR by up to 50mV when compared to commercial Pd black, while generating up to 3-fold higher kinetic current density. The carbon monoxide poisoning test shows that the bimetallic NCs are more resistant to the CO poisoning than Pt NCs and Pt black. It is also demonstrated that the bimetallic Pt-Pd core-shell NCs can enhance the current density of the methanol oxidation reaction, lowering the over-potential by 35 mV with respect to the Pt core NCs. Further investigation reveals that the Pd/Pt ratio of 1/3, which corresponds to nearly monolayer Pd deposition on Pt core NCs, gives the highest oxidation current density and lowest over-potential. This study shows for the first time the systematic investigation of effects of Pd atomic shells on Pt-Pd bimetallic nanocatalysts, providing valuable guidelines for designing high-performance catalysts for fuel cell applications.Bimetallic Pt-Pd core-shell nanocrystals (NCs) are synthesized through a two-step process with controlled Pd thickness from sub-monolayer to multiple atomic layers. The oxygen reduction reaction (ORR) catalytic activity and methanol oxidation reactivity of the core-shell NCs for fuel cell applications in alkaline solution are systematically studied and compared based on different Pd thickness. It is found that the Pd shell helps to reduce the over-potential of ORR by up to 50mV when compared to commercial Pd black, while generating up to 3-fold higher kinetic current density. The carbon monoxide poisoning test shows that the bimetallic NCs are more

Electrical behaviour of heterobimetallic [MM'(EtCS2)4] (MM'=NiPd, NiPt, PdPt) and MM'X-chain polymers [PtM(EtCS2)4I] (M=Ni, Pd).

Science.gov (United States)

Givaja, Gonzalo; Castillo, Oscar; Mateo, Eva; Gallego, Almudena; Gómez-García, Carlos J; Calzolari, Arrigo; di Felice, Rosa; Zamora, Félix

2012-11-26

Herein, we report the isolation of new heterobimetallic complexes [Ni(0.6)Pd(1.4)(EtCS(2))(4)] (1), [NiPt(EtCS(2))(4)] (2) and [Pd(0.4)Pt(1.6)(EtCS(2))(4)] (3), which were constructed by using transmetallation procedures. Subsequent oxidation with iodine furnished the MM'X monodimensional chains [Ni(0.6)Pt(1.4)(EtCS(2))(4)I] (4) and [Ni(0.1)Pd(0.3)Pt(1.6)(EtCS(2))(4)I] (5). The physical properties of these systems were investigated and the chain structures 4 and 5 were found to be reminiscent of the parent [Pt(2)(EtCS(2))(4)I] species. However, they were more sensitively dependent on the localised nature of the charge on the Ni ion, which caused spontaneous breaking of the conduction bands. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Magnetic and structural characterizations on nanoparticles of FePt, FeRh and their composites

International Nuclear Information System (INIS)

Ko, Hnin Yu Yu; Suzuki, Takao; Nam, Nguyen T.; Phuoc, Nguyen N.; Cao Jiangwei; Hirotsu, Yoshihiko

2008-01-01

The various compositions of FePt and FeRh nanoparticles, and their composite particles have been fabricated by the solution-phase chemical method and their magnetic properties characterized. High-resolution transmission electron microscopic observations indicate that mono-dispersed FeRh and FePt/FeRh nanoparticles are fabricated with the average size of 3-5 nm. However, larger size particles are distributed in the annealed state. From X-ray diffraction results, the as-deposited FeRh nanoparticles reveal a chemically disordered fcc structure which can be transformed into CsCl-type structure through thermal annealing. Similarly, the annealed FePt nanoparticles show the L1 0 -phase fct structure although the fcc structure is apparent in the as-deposited state. It is also found that the first time in the exchange bias effect in the composite of ferromagnetic (FePt) and anti-ferromagnetic (FeRh) nanoparticles; result in a shift of the hysteresis loop after field cooling process

Energy barriers for interlayer diffusion in Pt/Pt(111) and Rh/Rh(111) homoepitaxy: small islands

Czech Academy of Sciences Publication Activity Database

Máca, František; Kotrla, Miroslav; Trushin, O. S.

1999-01-01

Roč. 49, č. 11 (1999), s. 1591-1596 ISSN 0011-4626. [Symposium on Surface Physics /8./. Třešť, 28.06.1999-02.07.1999] R&D Projects: GA MŠk OC P3.80 Institutional research plan: CEZ:AV0Z1010914 Keywords : molecular statics * energy barriers * Pt and Rh Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.328, year: 1999

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

Science.gov (United States)

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

2016-06-01

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

Activity of PtSnRh/C nanoparticles for the electrooxidation of C1 and C2 alcohols

International Nuclear Information System (INIS)

Teran, Freddy E.; Santos, Deise M.; Ribeiro, Josimar; Kokoh, Kouakou B.

2012-01-01

A systematic investigation of alcohol adsorption and oxidation on binary and ternary electrocatalysts in acid medium was performed. Binary (PtRh) and ternary (PtRhSn) were prepared by the Pechini modified method on carbon Vulcan XC-72, and different nominal compositions were characterized by energy dispersive X-ray and X-ray diffraction (XRD) techniques. The XRD results showed that the Pt 80 Rh 20 /C and Pt 70 Sn 10 Rh 20 /C electrocatalysts consisted of the Pt displaced phase, suggesting the formation of a solid solution between the metals Pt/Rh and Pt/Sn. Electrochemical investigations on these different electrode materials were carried out as a function of the electrocatalyst composition, in acid medium (0.5 mol dm −3 H 2 SO 4 ), and in the absence and presence of different alcohols (methanol, ethanol and ethylene glycol). The electrochemical results obtained at room temperature have shown that the Pt 70 Sn 10 Rh 20 /C catalyst display better catalytic activity for alcohol oxidation compared with the binary catalyst. In situ reflectance infrared spectroscopy measurements have shown that the oxidation of alcohols mentioned produced CO 2 at low potentials indicating that the materials synthesized could be used as efficient anodes in the fuel cell applications. - Highlights: ► Pt-based catalysts were synthesized by thermal decomposition polymeric precursors. ► Pt 70 Sn 10 Rh 20 /C displays better catalytic activity for the oxidation of alcohols. ► The co-catalysts tin and rhodium promote the removal of CO to CO 2 at low potentials. ► Ethylene glycol is oxidizing strongly to CO 2 at low potentials. ► Pt 70 Sn 10 Rh 20 /C catalyst is an efficient anode material for a direct alcohol fuel cell.

Synthesis of Pd and Rh metal nanoparticles in the interlayer space of organically modified montmorillonite

International Nuclear Information System (INIS)

Patel, Hasmukh A.; Bajaj, Hari C.; Jasra, Raksh Vir

2008-01-01

This study reports the synthesis of palladium and rhodium metal nanoparticles supported on montmorillonite (MMT) and partially organically modified MMT (POMM) using tetraamine palladium and hexaamine rhodium complex as precursor for palladium and rhodium respectively. The synthesized nanoparticles were characterized by powder X-ray diffraction PXRD and TEM. The PXRD study shows characteristic crystallographic planes for Pd and Rh metal and confirm the formation of metal nanoparticles in MMT and POMM. The TEM images reveal the effect of organic modification of MMT on decreasing particle size of Pd and Rh metal. The Pd and Rh metal nanoparticles are agglomerated in pristine MMT while nanoparticles are well dispersed in POMM. ICP-AES analysis was carried out to estimate quantitative amount of Pd and Rh metal in MMT and POMM

A computer calculation of the ternary Mo-Pd-Rh phase diagram

International Nuclear Information System (INIS)

Guerler, R.; Pratt, J.N.

1993-01-01

Thermodynamic coefficients for the phases in the binary Mo-Pd, Pd-Rh and Mo-Rh systems were derived by the assessment of the available experimental data using the binary Lukas optimization program. The resulting coefficients were first successfully utilised in reestablishing the binaries. The coefficients thus obtained in the binary computation were combined with ternary descriptions to compute ternary isothermal sections. Although no ternary interaction term was involved in the construction of the isotherms, the section calculated at 1373 K is found to be consistent with the experimentally established isothermal section at the same temperature. The location of three-phase field (bcc+hcp+fcc) and phase boundaries in both isotherms are matching reasonably well. Combining only binary coefficients of these phases, it is possible to construct reasonable isothermal sections at different temperatures. Following this conclusion, isothermal sections ranging from 1373 to 2673 K of the ternary Mo-Pd-Rh system were calculated. (orig.)

Activity of PtSnRh/C nanoparticles for the electrooxidation of C1 and C2 alcohols

Energy Technology Data Exchange (ETDEWEB)

Teran, Freddy E. [Universite de Poitiers, IC2MP UMR CNRS 7285, ' Equipe E-lyse' , 4 rue Michel Brunet-B27, BP 633, 86022 Poitiers cedex (France); Santos, Deise M. [Departamento de Quimica, CCE-UFES, Av. Fernando Ferrari, 514, Goiabeiras-Vitoria, ES (Brazil); Ribeiro, Josimar, E-mail: josimar.ribeiro@ufes.br [Universite de Poitiers, IC2MP UMR CNRS 7285, ' Equipe E-lyse' , 4 rue Michel Brunet-B27, BP 633, 86022 Poitiers cedex (France); Departamento de Quimica, CCE-UFES, Av. Fernando Ferrari, 514, Goiabeiras-Vitoria, ES (Brazil); Kokoh, Kouakou B. [Universite de Poitiers, IC2MP UMR CNRS 7285, ' Equipe E-lyse' , 4 rue Michel Brunet-B27, BP 633, 86022 Poitiers cedex (France)

2012-07-01

A systematic investigation of alcohol adsorption and oxidation on binary and ternary electrocatalysts in acid medium was performed. Binary (PtRh) and ternary (PtRhSn) were prepared by the Pechini modified method on carbon Vulcan XC-72, and different nominal compositions were characterized by energy dispersive X-ray and X-ray diffraction (XRD) techniques. The XRD results showed that the Pt{sub 80}Rh{sub 20}/C and Pt{sub 70}Sn{sub 10}Rh{sub 20}/C electrocatalysts consisted of the Pt displaced phase, suggesting the formation of a solid solution between the metals Pt/Rh and Pt/Sn. Electrochemical investigations on these different electrode materials were carried out as a function of the electrocatalyst composition, in acid medium (0.5 mol dm{sup -3} H{sub 2}SO{sub 4}), and in the absence and presence of different alcohols (methanol, ethanol and ethylene glycol). The electrochemical results obtained at room temperature have shown that the Pt{sub 70}Sn{sub 10}Rh{sub 20}/C catalyst display better catalytic activity for alcohol oxidation compared with the binary catalyst. In situ reflectance infrared spectroscopy measurements have shown that the oxidation of alcohols mentioned produced CO{sub 2} at low potentials indicating that the materials synthesized could be used as efficient anodes in the fuel cell applications. - Highlights: Black-Right-Pointing-Pointer Pt-based catalysts were synthesized by thermal decomposition polymeric precursors. Black-Right-Pointing-Pointer Pt{sub 70}Sn{sub 10}Rh{sub 20}/C displays better catalytic activity for the oxidation of alcohols. Black-Right-Pointing-Pointer The co-catalysts tin and rhodium promote the removal of CO to CO{sub 2} at low potentials. Black-Right-Pointing-Pointer Ethylene glycol is oxidizing strongly to CO{sub 2} at low potentials. Black-Right-Pointing-Pointer Pt{sub 70}Sn{sub 10}Rh{sub 20}/C catalyst is an efficient anode material for a direct alcohol fuel cell.

Ethanol electrooxidation on Pt/C and Pd/C catalysts promoted with oxide

Energy Technology Data Exchange (ETDEWEB)

Xu, Changwei [Department of Chemistry and Institute of Nanochemistry, Jinan University, Guangzhou 510632 (China); State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Shen, Pei kang [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Liu, Yingliang [Department of Chemistry and Institute of Nanochemistry, Jinan University, Guangzhou 510632 (China)

2007-02-10

This research aims to investigate Pd-based catalysts as a replacement for Pt-based catalysts for ethanol electrooxidation in alkaline media. The results show that Pd/C has a higher catalytic activity and better steady-state behaviour for ethanol oxidation than that of Pt/C. The effect of the addition of CeO{sub 2} and NiO to the Pt/C and Pd/C electrocatalysts on ethanol oxidation is also studied in alkaline media. The electrocatalysts with a weight ratio of noble metal (Pt, Pd) to CeO{sub 2} of 2:1 and a noble metal to NiO ration 6:1 show the highest catalytic activity for ethanol oxidation. The oxide promoted Pt/C and Pd/C electrocatalysts show a higher activity than the commercial E-TEK PtRu/C electrocatalyst for ethanol oxidation in alkaline media. (author)

Optical characterization of broad plasmon resonances of Pd/Pt nanoparticles

Science.gov (United States)

Valizade-Shahmirzadi, N.; Pakizeh, T.

2018-04-01

In this paper, optical properties of nanoparticles (nanodisks and nanospheres) composed of photofunctional metals like palladium (Pd) and platinum (Pt) over a large dimension range are investigated using the electromagnetic simulation and quasi-static theory. These characteristics are compared with their counterparts in plasmonic gold (Au) nanoparticles. Pd/Pt-nanodisks with larger dimension have higher absorption and lower scattering efficiencies than Au-nanodisks that accompany with lower extinction efficiencies and broader resonances. Although an increment in the dimension (diameter and height) of Au/Pd/Pt-nanoparticles decreases the absorption-to-scattering ratios, these ratios are less sensitive to the height size in Au-nanodisks, which causes their LSPR spectra become much broader. It is noteworthy that the LSPR quality factor of Pd nanoparticles is improved by considering the radiative damping and depolarization in quasi-static method unlike the Au nanoparticles. The importance of the highly absorptive Pd/Pt nanoparticles can be traced in the photo-functionalized and energy applications.

Magnetic spin configuration in Fe{sub 50}Pt{sub 50-x}Rh{sub x} alloys

Energy Technology Data Exchange (ETDEWEB)

Fenske, J.; Lott, D.; Schreyer, A. [GKSS Research Centre (Germany); Mankey, G.J. [University of Alabama, MINT Center (United States); Schmidt, W.; Schmalzl, K. [Juelich Research Centre (Germany); Tartakowskaya, E. [Institute for Magnetism, National Ukrainian Accademy of Science (Ukraine)

2010-07-01

FePt-based alloys are typically the material of choice for magnetic information storage media. The high magnetic moment of Fe gives a large magnetization and the large atomic number of Pt results in a high magnetic anisotropy. This combination enables the written bits to be smaller than ever before. One way to control the magnetic properties in these materials is through the introduction of a third element into the crystal matrix e.g. Rh. When Rh is added to replace Pt in the equiatomic alloy, new magnetic phases emerge. Bulk samples of Fe{sub 50}Pt{sub 50-x}Rh{sub x} studied by magnetization measurements refer to three different phase transitions with increasing temperature: (I) An antiferromagnetic (AF)-paramagnetic (PM) transition for 30Pt{sub 50-x}Rh{sub x} films with different Rh concentrations. These films were examined by neutron diffraction in dependence of temperature and magnetic field. By the use of polarized and unpolarized neutron diffraction we could develop a detailed model of the magnetic spin structure in these thin films.

Ultra-low Pt decorated PdFe Alloy Nanoparticles for Formic Acid Electro-oxidation

International Nuclear Information System (INIS)

Zhou, Yawei; Du, Chunyu; Han, Guokang; Gao, Yunzhi; Yin, Geping

2016-01-01

Highlights: • A cost-efficient way is used to prepare transition-noble metal alloy nanoparticles. • The Pd 50 Fe 50 /C catalyst shows excellent activity for formic acid oxidation (FAO). • Much activity enhancement of FAO is acquired by ultra-low Pt decorated Pd 50 Fe 50 . • A synergistic mechanism between Pt clusters and PdFe is proposed during the FAO. - Abstract: Palladium (Pd), has demonstrated promising electro-catalytic activity for formic acid oxidation, but suffers from extremely low abundance. Recently alloying with a transition metal has been considered as an effective approach to reducing the loading of Pd and enhancing the activity of Pd-based catalysts simultaneously. Herein, carbon supported PdFe nanoparticles (NPs) are synthesized at room temperature by using sodium borohydride as reducing agent and potassium ferrocyanide as Fe precursor. The Pd 50 Fe 50 alloy sample annealed at 900 °C for 1 h shows the best catalytic activity among Pd x Fe 1-x (x = 0.2, 0.4, 0.5, 0.6, and 0.8) towards formic acid oxidation. To further improve both catalytic activity and stability, the ultra-low Pt (0.09 wt %) decorated Pd 50 Fe 50 NPs (PtPd/PdFe) are prepared via the galvanic replacement reaction. Compared with Pd 50 Fe 50 /C, the PtPd/PdFe/C Exhibits 1.52 times higher catalytic activity and lower onset potential (−0.12 V). The significant enhancements of formic acid oxidation can be attributed to the accelerated dehydrogenation reaction of formic acid by Pt atomic clusters. Moreover, the PtPd/PdFe/C also demonstrates better tolerance to poisons during formic acid oxidation.

Engineering Pt/Pd Interfacial Electronic Structures for Highly Efficient Hydrogen Evolution and Alcohol Oxidation.

Science.gov (United States)

Fan, Jinchang; Qi, Kun; Zhang, Lei; Zhang, Haiyan; Yu, Shansheng; Cui, Xiaoqiang

2017-05-31

Tailoring the interfacial structure of Pt-based catalysts has emerged as an effective strategy to improve catalytic activity. However, little attention has been focused on investigating the relationship between the interfacial facets and their catalytic activity. Here, we design and implement Pd-Pt interfaces with controlled heterostructure features by epitaxially growing Pt nanoparticles on Pd nanosheets. On the basis of both density functional theory calculation and experimental results, we demonstrate that charge transfer from Pd to Pt is highly dependent on the interfacial facets of Pd substrates. Therefore, the Pd-Pt heterostructure with Pd(100)-Pt interface exhibits excellent activity and long-term stability for hydrogen evolution and methanol/ethanol oxidation reactions in alkaline medium, much better than that with Pd (111)-Pt interface or commercial Pt/C. Interfacial crystal facet-dependent electronic structural modulation sheds a light on the design and investigation of new heterostructures for high-activity catalysts.

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.

Experimental determination of the hydrolysis constants of Pt sup 2+ and Pd sup 2+ at 25C from the solubility of Pt and PD in aqueous hydroxide solutions

Energy Technology Data Exchange (ETDEWEB)

Wood, S.A. (McGill Univ., Montreal, Quebec (Canada))

1991-07-01

The solubilities of Pt and Pd metal were measured at 25C in 10{sup {minus}4} to 10.0 molal NaOH solutions under a reduced oxygen atmosphere in order to determine the stoichiometry and stability constants for Pt and Pd hydroxide complexes. Equilibration times of over one year were employed. The Pd data are consistent with the existence of Pd(OH){sub 2}{sup 0}(aq) from pH 9 to 12 and Pd(OH){sub 3}{sup {minus}} from pH 12 to 15.5. No conclusive evidence for a Pd(OH){sub 4}{sup 2{minus}} complex was obtained, but the data do not preclude its existence at high pH. For Pt, the data are consistent with a single complex for pH = 9 to 15.5, i.e., Pt(OH){sub 2}{sup 0}(aq). A graphical treatment of the data yields the following cumulative stability constants: log {beta}{sub 2} = 18.9 {plus minus} 1.0 and log {beta}{sub 3} = 20.9 {plus minus} 1.0 for Pd and log {beta}{sub 2} = 29.9 {plus minus} 1.0 for Pt. The stepwise stability constant for Pd(OH){sub 3}{sup {minus}} log K{sub 3} = 2.0 is in relatively good agreement with that derived from data in the literature (log K{sub 3} = 1.8). However, the cumulative stability constants for Pd measured in this work are considerably smaller than those reported in the literature. The log{beta}{sub 2} = 29.9 {plus minus} 1.0 value measured for Pt compares relatively well with a theoretically estimated value of 28.3. The data suggest that the predominant inorganic form of Pt and Pd in freshwaters may be the neutral hydroxide species. In seawater, the hydroxide complex of Pt is also predicted to predominate over the chloride complex, but, in the case of Pd, the hydroxide complex appears to be less stable and it is presently not clear whether the chloride or the hydroxide complex will predominate. In fluids responsible for serpentinization, Pt and Pd may also be mobilized as hydroxide complexes.

High activity of cubic PtRh alloys supported on graphene towards ethanol electrooxidation.

Science.gov (United States)

Rao, Lu; Jiang, Yan-Xia; Zhang, Bin-Wei; Cai, Yuan-Rong; Sun, Shi-Gang

2014-07-21

Cubic PtRh alloys supported on graphene (PtxRhy/GN) with different atomic ratio of Pt and Rh were directly synthesized for the first time using the modified polyol method with Br(-) for the shape-directing agents. The process didn't use surface-capping agents such as PVP that easily occupy the active sites of electrocatalysts and are difficult to remove. Graphene is the key factor for cubic shape besides Br(-) and keeping catalysts high-dispersed. The X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to characterize the structure and morphology of these electrocatalysts. The results showed that they were composed of homogeneous cubic PtRh alloys. Traditional electrochemical methods, such as cyclic voltammetry and chronoamperometry, were used to investigate the electrocatalytic properties of PtxRhy/GN towards ethanol electrooxidation. It can be seen that PtxRhy/GN with all atomic ratios exhibited high catalytic activity, and the most active one has a composition with Pt : Rh = 9 : 1 atomic ratio. Electrochemical in situ FTIR spectroscopy was used to evaluate the cleavage of C-C bond in ethanol at room temperature in acidic solutions, the results illustrated that Rh in an alloy can promote the split of C-C bond in ethanol, and the alloy catalyst with atomic ratio Pt : Rh = 1 : 1 showed obviously better performance for the C-C bond breaking in ethanol and higher selectivity for the enhanced activity of ethanol complete oxidation to CO2 than alloys with other ratios of Pt and Rh. The investigation indicates that high activity of PtxRhy/GN electrocatalyst towards ethanol oxidation is due to the specific shape of alloys and the synergistic effect of two metal elements as well as graphene support.

Comparing Pt/SrTiO3 to Rh/SrTiO3 for hydrogen photocatalytic production from ethanol

KAUST Repository

Wahab, A. K.; Odedairo, T.; Labis, J.; Hedhili, Mohamed N.; Delavar, A.; Idriss, H.

2013-01-01

Photocatalytic hydrogen production from ethanol as an example of biofuel is studied over 0.5 wt% Rh/SrTiO3 and 0.5 wt% Pt/SrTiO3 perovskite materials. The rate of hydrogen production, rH2, over Pt/SrTiO3 is found to be far higher than that observed over Rh/SrTiO3 (4 × 10−6 mol of H2 g catal. −1 min−1 (1.1 × 10−6 mol of H2 m catal. −2 min−1) compared to 0.7 × 10−6 mol of H2 g catal. −1 min−1 (5.5 × 10−8 mol of H2 m catal. −2 min−1), respectively, under UV excitation with a flux equivalent to that from the sun light (ca. 1 mW cm−2). Analyses of the XPS Rh3d and XPS Pt4f indicate that Rh is mainly present in its ionic form (Rh3+) while Pt is mainly present in its metallic form (Pt0). A fraction of the non-metallic state of Rh in the catalyst persisted even after argon ion sputtering. The tendency of Rh to be oxidized compared to Pt might be the reason behind the lower activity of the former compared to the later. On the contrary, a larger amount of methane are formed on the Rh containing catalyst compared to that observed on the Pt containing catalyst due to the capacity of Rh to break the carbon–carbon bond of the organic compound.

Comparing Pt/SrTiO3 to Rh/SrTiO3 for hydrogen photocatalytic production from ethanol

KAUST Repository

Wahab, A. K.

2013-08-13

Photocatalytic hydrogen production from ethanol as an example of biofuel is studied over 0.5 wt% Rh/SrTiO3 and 0.5 wt% Pt/SrTiO3 perovskite materials. The rate of hydrogen production, rH2, over Pt/SrTiO3 is found to be far higher than that observed over Rh/SrTiO3 (4 × 10−6 mol of H2 g catal. −1 min−1 (1.1 × 10−6 mol of H2 m catal. −2 min−1) compared to 0.7 × 10−6 mol of H2 g catal. −1 min−1 (5.5 × 10−8 mol of H2 m catal. −2 min−1), respectively, under UV excitation with a flux equivalent to that from the sun light (ca. 1 mW cm−2). Analyses of the XPS Rh3d and XPS Pt4f indicate that Rh is mainly present in its ionic form (Rh3+) while Pt is mainly present in its metallic form (Pt0). A fraction of the non-metallic state of Rh in the catalyst persisted even after argon ion sputtering. The tendency of Rh to be oxidized compared to Pt might be the reason behind the lower activity of the former compared to the later. On the contrary, a larger amount of methane are formed on the Rh containing catalyst compared to that observed on the Pt containing catalyst due to the capacity of Rh to break the carbon–carbon bond of the organic compound.

Significance of β-dehydrogenation in ethanol electro-oxidation on platinum doped with Ru, Rh, Pd, Os and Ir.

Science.gov (United States)

Sheng, Tian; Lin, Wen-Feng; Hardacre, Christopher; Hu, P

2014-07-14

In the exploration of highly efficient direct ethanol fuel cells (DEFCs), how to promote the CO2 selectivity is a key issue which remains to be solved. Some advances have been made, for example, using bimetallic electrocatalysts, Rh has been found to be an efficient additive to platinum to obtain high CO2 selectivity experimentally. In this work, the mechanism of ethanol electrooxidation is investigated using the first principles method. It is found that CH3CHOH* is the key intermediate during ethanol electrooxidation and the activity of β-dehydrogenation is the rate determining factor that affects the completeness of ethanol oxidation. In addition, a series of transition metals (Ru, Rh, Pd, Os and Ir) are alloyed on the top layer of Pt(111) in order to analyze their effects. The elementary steps, α-, β-C-H bond and C-C bond dissociations, are calculated on these bimetallic M/Pt(111) surfaces and the formation potential of OH* from water dissociation is also calculated. We find that the active metals increase the activity of β-dehydrogenation but lower the OH* formation potential resulting in the active site being blocked. By considering both β-dehydrogenation and OH* formation, Ru, Os and Ir are identified to be unsuitable for the promotion of CO2 selectivity and only Rh is able to increase the selectivity of CO2 in DEFCs.

Phase diagrams of two dimensional Pd{sub x}Ag{sub 1-x}/Pd(111) and Pt{sub x}Ag{sub 1-x}/Pt(111) surface alloys

Energy Technology Data Exchange (ETDEWEB)

Engstfeld, Albert K.; Roetter, Ralf T.; Bergbreiter, Andreas; Hoster, Harry E.; Behm, R. Juergen [Institute of Surface Chemistry and Catalysis, Ulm University (Germany)

2011-07-01

The distribution of Ag and Pd or Pt in Ag{sub x}Pd{sub 1-x}/Pd(111) and Ag{sub x}Pt{sub 1-x}/Pt(111) surface alloys was studied by high resolution UHV-STM. The alloys were prepared by evaporating Ag on the respective substrate and subsequent annealing to 800 K. From quantitative 2D atom distributions we can show that AgPt tends towards two dimensional clustering and AgPd towards a 'quasi' random distribution, with small deviations for low and high coverages. From effective pair interactions, we are able to calculate the surface mixing energy and determine 2D phase diagrams. Furthermore we will elucidate whether the size mismatch or the differences in the intermetallic bonding are the dominant factor for the respective distribution in the surface alloy.

Synthesis and characterization of supported Pt and Pt alloys nanoparticles used for the catalytic oxidation of sulfur dioxide

DEFF Research Database (Denmark)

Koutsopoulos, Sotiris; Eriksen, Kim Michael; Fehrmann, Rasmus

2006-01-01

pressure in the temperature range of 250–700 °C. The effect of doping the active metal with rhodium and palladium was also studied. The catalytic activities of the supported catalysts were found to follow the order Pt–Pd/CPG > Pt–Rh/CPG > Pt/CPG. A significant synergistic effect of the Pt–Pd alloy...

Gallium-containing Heusler phases ScRh{sub 2}Ga, ScPd{sub 2}Ga, TmRh{sub 2}Ga and LuRh{sub 2}Ga. Magnetic and solid state NMR-spectroscopic characterization

Energy Technology Data Exchange (ETDEWEB)

Heletta, Lukas; Seidel, Stefan; Poettgen, Rainer [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie; Benndorf, Christopher [Leipzig Univ. (Germany). Inst. fuer Mineralogie, Kristallographie und Materialwissenschaften; Eckert, Hellmut [Muenster Univ. (Germany). Inst. fuer Physikalische Chemie; Sao Paulo Univ., Sao Carlos (Brazil). Inst. of Physics

2017-10-01

The gallium-containing Heusler phases ScRh{sub 2}Ga, ScPd{sub 2}Ga, TmRh{sub 2}Ga and LuRh{sub 2}Ga have been synthesized by arc-melting of the elements followed by different annealing sequences to improve phase purity. The samples have been studied by powder X-ray diffraction. The structures of Lu{sub 0.97}Rh{sub 2}Ga{sub 1.03} (Fm3m, a=632.94(5) pm, wR2=0.0590, 46 F{sup 2} values, seven variables) and Sc{sub 0.88}Rh{sub 2}Ga{sub 1.12} (a=618.91(4) pm, wR2=0.0284, 44 F{sup 2} values, six variables) have been refined from single crystal X-ray diffractometer data. Both gallides show structural disorder through Lu/Ga and Sc/Ga mixing. Temperature dependent magnetic susceptibility measurements showed Pauli paramagnetism for ScRh{sub 2}Ga, ScPd{sub 2}Ga, and LuRh{sub 2}Ga and Curie-Weiss paramagnetism for TmRh{sub 2}Ga. {sup 45}Sc and {sup 71}Ga solid state MAS NMR spectroscopic investigations of the Sc containing compounds confirmed the site mixing effects typically observed for Heusler phases. The data indicate that the effect of mixed Sc/Ga occupancy is significantly stronger in ScRh{sub 2}Ga than in ScPd{sub 2}Ga.

Production of Pd 103 seed from Rh targets for brachytherapy

International Nuclear Information System (INIS)

Afarideh, H.; Ardaneh, K.; Sadeghi, M.

2000-01-01

The suitability of a given radionuclide for brachytherapy is determined by its half-life, the type of energy, and abundance (number per decay) of its emission. The half-life of a radionuclide must be long enough to permit shipping and implant preparation with an acceptable loss of source strength due to decay, but it must also be short enough to permit source sizes sufficiently small for the intended application. Pd-103 is a low energy photon emitter available for permanent interstitial implantation. Pd-103 has energy and safety characteristics similar to I-125, but its initial peripheral dose rate is approximately three times greater. This may provide improved control of rapidly proliferating tumours. Although Pd-103 has been used for various kinds of cancers, it is almost exclusively used for prostate cancer, the most common cancer, and the death rate from this cancer is the highest. There are two cyclotron production routes for Pd-103, Ag (p,xn) 103 Pd and Rh (p,n) 103 Pd. For a cyclotron with low energy (such as 30Mev that we have in Iran, Karaj, NRCAM) only Rh target can be used. The target material should be deposited on a special designed Cu substrate and the separation process should isolate the desired radionuclide from target material as well as Cu. Our work plan for production of Pd 103 in Karaj, Iran, is as follows: In the first year of the CRP we are going to complete the literature survey of Pd production and perform the relevant experiments as described later. In the second year of the CRP we will construct suitable hot cells for Pd production and also do research for development of Pd seeds. In the last year of the CRP we are going to finalise all the work done during the last two years and propose the automation system for routine production

Preparation of ternary Pt/Rh/SnO2 anode catalysts for use in direct ethanol fuel cells and their electrocatalytic activity for ethanol oxidation reaction

Science.gov (United States)

Higuchi, Eiji; Takase, Tomonori; Chiku, Masanobu; Inoue, Hiroshi

2014-10-01

Pt, Rh and SnO2 nanoparticle-loaded carbon black (Pt/Rh/SnO2/CB) catalysts with different contents of Pt and Rh were prepared by the modified Bönnemann method. The mean size and size distribution of Pt, Rh and SnO2 for Pt-71/Rh-4/SnO2/CB (Pt : Rh : Sn = 71 at.%: 4 at.%: 25 at.%) were 3.8 ± 0.7, 3.2 ± 0.7 and 2.6 ± 0.5 nm, respectively, indicating that Pt, Rh and SnO2 were all nanoparticles. The onset potential of ethanol oxidation current for the Pt-65/Rh-10/SnO2/CB and Pt-56/Rh-19/SnO2/CB electrodes was ca. 0.2 V vs. RHE which was ca. 0.2 V less positive than that for the Pt/CB electrode. The oxidation current at 0.6 V for the Pt/Rh/SnO2/CB electrode (ca. 2% h-1) decayed more slowly than that at the Pt/SnO2/CB electrode (ca. 5% h-1), indicating that the former was superior in durability to the latter. The main product of EOR in potentiostatic electrolysis at 0.6 V for the Pt-71/Rh-4/SnO2/CB electrode was acetic acid.

Facile synthesis of octahedral Pt-Pd nanoparticles stabilized by silsesquioxane for the electrooxidation of formic acid

International Nuclear Information System (INIS)

Li, Yusong; Hao, Furui; Wang, Yihong; Zhang, Yihong; Ge, Cunwang; Lu, Tianhong

2014-01-01

Graphical abstract: The octahedral Pt-Pd alloy nanoparticles (octahedral Pt-Pd NPs) with dominant {111} facets were successfully synthesized through a facile route in the presence of octa(3-aminopropyl) silsesquioxane as the capping agent and complexing agent, methanol as the reductant and solvent. The octahedral Pt-Pd NPs display the significantly enhanced electrocatalytic activity, increased CO tolerance and favourable stability for the electrooxidation of formic acid. - Highlights: • Octa Pt-Pd nanoparticles were synthesized with silsesquioxane as capping agent. • Octa Pt-Pd nanoparticles display uniform morphology and favorable dispersibility. • Octa Pt-Pd nanoparticles have high catalytic activity for formic acid by direct process. - Abstract: The octahedral Pt-Pd alloy nanoparticles (octahedral Pt-Pd NPs) with dominant {111} facets were successfully synthesized through a facile route in the presence of octa(3-aminopropyl) silsesquioxane as the capping agent and complexing agent, methanol as the reductant and solvent. Their morphology, composition and structure were charactered by transmission electron microscopy (TEM), energy dispersive spectrum (EDS) and X-ray diffraction (XRD). The electrocatalytic activity, CO tolerance and stability of the octahedral Pt-Pd NPs for the electrooxidation of formic acid were investigated by cyclic voltammetry, CO stripping voltammetry and chronoamperometry, respectively. Compared with the Pt nanoparticles and commercial Pt black, the octahedral Pt-Pd NPs display a significantly enhanced electrocatalytic activity, increased CO tolerance and favourable stability for the electrooxidation of formic acid. Therefore, the octahedral Pt-Pd NPs might be an alternative candidate for the anode catalyst for the electrooxidation of formic acid in future

A constitutional investigation of the Mo-Pd-Rh ternary system at 1100deg C

International Nuclear Information System (INIS)

Guerler, R.; Pratt, J.N.

1991-01-01

Phase relations in the system Mo-Pd-Rh were studied at 1100deg C using conventionally melted and ultrarapidly solidified samples. Optical microscopy, X-ray diffraction, scanning electron microscopy and electron probe microanalysis were used for phase characterisation. The complete isothermal section at 1100deg C was established. The Mo bcc phase was found to have a very limited solid solution range whereas the ternary fcc solid solution originating on the Pd-Rh binary is the dominant phase in the system at this temperature. The centre of the isothermal is dominated by the ternary extension of the Mo-Rh hcp intermediate phase. The three phase (bcc+fcc+hcp) equilibrium region is located very near to the Mo-Pd binary system. No additional ternary intermediate phases were observed. The results are consistent with an isothermal section reported at higher temperatures. (orig.)

Ternary Pt9RhFex Nanoscale Alloys as Highly Efficient Catalysts with Enhanced Activity and Excellent CO-Poisoning Tolerance for Ethanol Oxidation.

Science.gov (United States)

Wang, Peng; Yin, Shibin; Wen, Ying; Tian, Zhiqun; Wang, Ningzhang; Key, Julian; Wang, Shuangbao; Shen, Pei Kang

2017-03-22

To address the problems of high cost and poor stability of anode catalysts in direct ethanol fuel cells (DEFCs), ternary nanoparticles Pt 9 RhFe x (x = 1, 3, 5, 7, and 9) supported on carbon powders (XC-72R) have been synthesized via a facile method involving reduction by sodium borohydride followed by thermal annealing in N 2 at ambient pressure. The catalysts are physically characterized by X-ray diffraction, scanning transmission electron microscopy, and X-ray photoelectron spectroscopy, and their catalytic performance for the ethanol oxidation reaction (EOR) is evaluated by cyclic and linear scan voltammetry, CO-stripping voltammograms, and chronopotentiometry. All the Pt 9 RhFe x /C catalysts of different atomic ratios produce high EOR catalytic activity. The catalyst of atomic ratio composition 9:1:3 (Pt/Rh/Fe) has the highest activity and excellent CO-poisoning tolerance. Moreover, the enhanced EOR catalytic activity on Pt 9 RhFe 3 /C when compared to Pt 9 Rh/C, Pt 3 Fe/C, and Pt/C clearly demonstrates the presence of Fe improves catalytic performance. Notably, the onset potential for CO oxidation on Pt 9 RhFe 3 /C (0.271 V) is ∼55, 75, and 191 mV more negative than on Pt 9 Rh/C (0.326 V), Pt 3 Fe/C (0.346 V), and Pt/C (0.462 V), respectively, which implies the presence of Fe atoms dramatically improves CO-poisoning tolerance. Meanwhile, compared to the commercial PtRu/C catalyst, the peak potential on Pt 9 RhFe 3 /C for CO oxidation was just slightly changed after several thousand cycles, which shows high stability against the potential cycling. The possible mechanism by which Fe and Rh atoms facilitate the observed enhanced performance is also considered herein, and we conclude Pt 9 RhFe 3 /C offers a promising anode catalyst for direct ethanol fuel cells.

Electrochemical and structural characterization of carbon-supported Pt-Pd bimetallic electrocatalysts prepared by electroless deposition

Energy Technology Data Exchange (ETDEWEB)

Ohashi, Masato; Beard, Kevin D.; Ma Shuguo; Blom, Douglas A.; St-Pierre, Jean; Van Zee, John W. [Department of Chemical Engineering, University of South Carolina, Columbia, SC 29208 (United States); Monnier, John R., E-mail: monnier@cec.sc.ed [Department of Chemical Engineering, University of South Carolina, Columbia, SC 29208 (United States)

2010-10-01

Electrochemical and structural characteristics of various Pt-Pd/C bimetallic catalysts prepared by electroless deposition (ED) methods have been investigated. Structural analysis was conducted by X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy (EDS). Monometallic Pt or Pd particles were not detected by EDS, indicating the ED methodology formed only bimetallic particles. The size of the Pt-Pd bimetallic particles was smaller than those of a commercially available Pt/C catalyst. The morphology of the Pt on Pd/C catalysts was identified and corresponded to Pd particles partially encapsulated by Pt. The electrochemical characteristics of the lowest Pd loading catalyst (7.0% Pt on 0.5% Pd/C) for the oxygen reduction reaction (ORR) have been investigated by the rotating ring disk electrode technique. The electrochemical activity was equal or lower than the commercially available Pt/C catalyst; however, the amount of hydrogen peroxide observed at the ring was reduced by the Pd, suggesting that such a catalyst has the potential to decrease ionomer degradation in applications. The Pt on Pd/C catalysts also show a higher tolerance to ripening induced by potential cycling. Therefore, catalyst suitability cannot be judged solely by its initial performance; information related to specific degradation mechanisms is also needed for a more complete assessment.

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.

Magnetic properties and configuration of Fe{sub 50}Pt{sub 50*x}Rh{sub x} films

Energy Technology Data Exchange (ETDEWEB)

Fenske, Jochen; Lott, Dieter; Schreyer, Andreas [Helmholt-Zentrum, Geesthacht (Germany); Schmidt, Wolfgang; Schmalzl, Karin [IFF Forschungszentrum, Juelich (Germany); JCNS at ILL (France); Mankey, Gary J. [MINT Center, University of Alabama (United States); Klose, Frank [Ansto, Bragg Institute (Australia); Tartakowskaya, Helena [Institute for Magnetism, National Accademy of Scinece (Ukraine)

2011-07-01

Ordered FePt alloys with L1{sub 0} structure are known as materials with FM order and a high magnetic moment of Fe providing a large magnetization. The large atomic number of Pt on the other hand results in a high magnetic anisotropy. If grown in thin films, the high anisotropy often results in perpendicular magnetization which is the preferred orientation for current magnetic recording media. One way to control the magnetic properties in these materials is through the introduction of a third element into the crystal matrix e.g. Rh. When Rh is added to replace Pt in the equiatomic alloy, new magnetic phases emerge. Here we present neutron diffraction studies on the magnetic properties of different 200nm thick Fe{sub 50}Pt{sub 50*x}Rh{sub x} films in dependence of the temperature and external magnetic fields. Additional resonant x-ray measurements on the Fe and Pt absorption edges provide additional information about the magnetic moments on these sites.

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.

Effective adsorption/electrocatalytic degradation of perchlorate using Pd/Pt supported on N-doped activated carbon fiber cathode

Energy Technology Data Exchange (ETDEWEB)

Yao, Fubing; Zhong, Yu [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Yang, Qi, E-mail: yangqi@hnu.edu.cn [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Wang, Dongbo, E-mail: dongbowang@hnu.edu.cn [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China); Chen, Fei; Zhao, Jianwei; Xie, Ting; Jiang, Chen; An, Hongxue; Zeng, Guangming; Li, Xiaoming [College of Environmental Science and Engineering, Hunan University, Changsha 410082 (China); Key Laboratory of Environmental Biology and Pollution Control, Hunan University, Ministry of Education, Changsha 410082 (China)

2017-02-05

Highlights: • Pd/Pt-NACF served as an adsorption/electrocatalysis electrode to reduce perchlorate. • The possible mechanisms involved in the reaction process were explained. • The reusability and stability of Pd/Pt-NACF bifunctional material was evaluated. - Abstract: In this work, Pd/Pt supported on N-doped activated carbon fiber (Pd/Pt-NACF) was employed as the electrode for electrocatalytic degradation of perchlorate through adsorption/electroreduction process. Perchlorate in solution was firstly adsorbed on Pd/Pt-NACF and then reduced to non-toxic chloride by the catalytic function of Pd/Pt at a constant current (20 mA). Compared with Pd/Pt-ACF, the adsorption capacity and electrocatalytic degradation efficiency of Pd/Pt-NACF for perchlorate increased 161% and 28%, respectively. Obviously, positively charged N-functional groups on NACF surface enhanced the adsorption capacity of Pd/Pt-NACF, and the dissociation of hydrogen to atomic H* by the Pd/Pt nanostructures on the cathode might drastically promote the electrocatalytic reduction of perchlorate. The role of atomic H* in the electroreduction process was identified by tertiary butanol inhibition test. Meanwhile, the perchlorate degradation performance was not substantially lower after three successive adsorption/electrocatalytic degradation experiments, demonstrating the electrochemical reusability and stability of the as-prepared electrode. These results showed that Pd/Pt-NACF was effective for electrocatalytic degradation of perchlorate and had great potential in perchlorate removal from water.

Site dependence of the Kondo scale in CePd{sub 1-x}Rh{sub x} evidenced by thermopower

Energy Technology Data Exchange (ETDEWEB)

Stockert, Ulrike; Hartmann, Stefanie; Deppe, Micha; Caroca-Canales, Nubia; Geibel, Christoph; Steglich, Frank [Max Planck Institute for Chemical Physics of Solids, Dresden (Germany); Sereni, Julian [Division Bajas Temperaturas, Centro Atomico Bariloche (Argentina)

2015-07-01

CePd{sub 1-x}Rh{sub x} undergoes a continuous evolution from ferromagnetic order in CePd to an intermediate-valence (IV) ground state for CeRh. Close to the disappearance of magnetic order at x{sub cr} ∼ 0.87 unusual behavior of the ac susceptibility and the specific heat was observed. It was explained with a broad distribution of local Kondo temperatures T{sub K} from below 2 K to above 50 K due to the disorder introduced by Pd-Rh exchange. The thermopower S is very sensitive to Kondo scattering even for diluted 4f systems. In Ce compounds a large positive maximum in S(T) is usually observed around T{sub K}. We studied S(T) in CePd{sub 1-x}Rh{sub x} in order to evaluate the presence of Kondo scattering and the involved energy scales. Pure CeRh shows typical IV behavior with a large maximum at 220 K and small values at low T. Already 5 % Pd substitution leads to a strong enhancement of the low-T thermopower. Even larger values are found around x{sub cr}, while the high-T maximum shifts only moderately. Our results are in line with the existence of low (local) Kondo scales in the presence of IV behavior at high Rh content x > x{sub cr}. For lower Rh content a decreasing (average) Kondo scale is found.

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

International Nuclear Information System (INIS)

Long, Nguyen Viet; Asaka, Toru; Matsubara, Takashi; Nogami, Masayuki

2011-01-01

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 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.

Effects of metal composition and ratio on peptide-templated multimetallic PdPt nanomaterials

International Nuclear Information System (INIS)

Merrill, Nicholas A.; Nitka, Tadeusz T.; McKee, Erik M.; Merino, Kyle C.; Drummy, Lawrence F.

2017-01-01

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. Finally, 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.

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.

Determination of the equilibrium miscibility gap in the Pd-Rh alloy system using metal nanopowders obtained by decomposition of coordination compounds

Energy Technology Data Exchange (ETDEWEB)

Shubin, Yu.V., E-mail: shubin@niic.nsc.ru; Plyusnin, P.E.; Korenev, S.V.

2015-02-15

Highlights: • The Pd-Rh phase diagram has been experimentally reinvestigated. • The true equilibrium was achieved with the two-way approach. • The critical point of the miscibility gap lie at 58 at.% Rh and 820 °C. - Abstract: The Pd-Rh phase diagram has been reinvestigated in the subsolidus region using X-ray diffraction, scanning and transmission electron microscopy. The true equilibrium at the miscibility boundary was achieved with the two-way approach. Nanosized powders of metastable solid solutions and two-phase palladium-rhodium mixtures were used to shorten the time required to equilibrate the system. The initial samples were prepared by decomposition of coordination compounds [Pd(NH{sub 3}){sub 2}Cl{sub 2}], [Rh(NH{sub 3}){sub 5}Cl]Cl{sub 2}, [Pd(NH{sub 3}){sub 4}]{sub 3}[Rh(NO{sub 2}){sub 6}]{sub 2} and [Pd(NH{sub 3}){sub 4}][Rh(NH{sub 3})(NO{sub 2}){sub 5}]. The obtained phase diagram exhibits miscibility gap wider than generally accepted with the critical point of solubility at 58 at.% Rh and 820 °C.

Catalytic hydrodechlorination of trichloroethylene in a novel NaOH/2-propanol/methanol/water system on ceria-supported Pd and Rh catalysts.

Science.gov (United States)

Cobo, Martha; Becerra, Jorge; Castelblanco, Miguel; Cifuentes, Bernay; Conesa, Juan A

2015-08-01

The catalytic hydrodechlorination (HDC) of high concentrations of trichloroethylene (TCE) (4.9 mol%, 11.6 vol%) was studied over 1%Pd, 1%Rh and 0.5%Pd-0.5%Rh catalysts supported on CeO2 under conditions of room temperature and pressure. For this, a one-phase system of NaOH/2-propanol/methanol/water was designed with molar percentages of 13.2/17.5/36.9/27.6, respectively. In this system, the alcohols delivered the hydrogen required for the reaction through in-situ dehydrogenation reactions. PdRh/CeO2 was the most active catalyst for the degradation of TCE among the evaluated materials, degrading 85% of the trichloroethylene, with alcohol dehydrogenation rates of 89% for 2-propanol and 83% for methanol after 1 h of reaction. Fresh and used catalysts were characterized by Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), and Thermogravimetric analysis (TGA). These results showed important differences of the active phase in each catalyst sample. Rh/CeO2 had particle sizes smaller than 1 nm and the active metal was partially oxidized (Rh(0)/Rh(+δ) ratio of 0.43). This configuration showed to be suitable for alcohols dehydrogenation. On the contrary, Pd/CeO2 showed a Pd completed oxidized and with a mean particle size of 1.7 nm, which seemed to be unfavorable for both, alcohols dehydrogenation and TCE HDC. On PdRh/CeO2, active metals presented a mean particle size of 2.7 nm and more reduced metallic species, with ratios of Rh(0)/Rh(+δ) = 0.67 and Pd(0)/Pd(+δ) = 0.28, which showed to be suitable features for the TCE HDC. On the other hand, TGA results suggested some deposition of NaCl residues over the catalyst surfaces. Thus, the new reaction system using PdRh/CeO2 allowed for the degradation of high concentrations of the chlorinated compound by using in situ hydrogen liquid donors in a reaction at room temperature and pressure. Copyright © 2015 Elsevier Ltd. All rights reserved.

Recoil effect on β-decaying in vivo generators, interpreted for 103Pd/103mRh

International Nuclear Information System (INIS)

Szucs, Zoltan; Rooyen, Johann van; Zeevaart, Jan Rijn

2009-01-01

The use of Auger emitters as potential radiopharmaceuticals is being increasingly investigated. One of the radionuclides of interest is 103m Rh, which can be produced from 103 Ru or 103 Pd in an in vivo generator. A potential problem, however, is the recoil of the 103m Rh out of the carrier molecule and even out of the target cell. In order to determine the likelihood of this happening in the 103 Pd/ 103m Rh, case calculations were made to prove that this does not happen. The equations were generalised for all radionuclides with an atomic mass of 10-240 as a tool for determining the recoil threshold of any β-emitting radionuclide.

Excitation function and yield for the 103Rh(d,2n)103Pd nuclear reaction: Optimization of the production of palladium-103

International Nuclear Information System (INIS)

Manenti, Simone; Alí Santoro, María del Carmen; Cotogno, Giulio; Duchemin, Charlotte; Haddad, Ferid; Holzwarth, Uwe; Groppi, Flavia

2017-01-01

Deuteron-induced nuclear reactions for the generation of 103 Pd were investigated using the stacked-foil activation technique on rhodium targets at deuteron energies up to E d = 33 MeV. The excitation functions of the reactions 103 Rh(d,xn) 101,103 Pd, 103 Rh(d,x) 100g,cum,101m,g,102m,g Rh and 103 Rh(d,2p) 103 Ru have been measured, and the Thick-Target Yield for 103 Pd has been calculated.

Localized Pd Overgrowth on Cubic Pt Nanocrystals for Enhanced Electrocatalytic Oxidation of Formic Acid

Energy Technology Data Exchange (ETDEWEB)

Lee, H.; Habas, S.E.; Somorjai, G.A.; Yang, P.

2008-03-20

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.

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.

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: �

Electrochemical characterization of Pt-Ru-Pd catalysts for methanol oxidation reaction in direct methanol fuel cells.

Science.gov (United States)

Choi, M; Han, C; Kim, I T; An, J C; Lee, J J; Lee, H K; Shim, J

2011-01-01

PtRuPd nanoparticles on carbon black were prepared and characterized as electrocatalysts for methanol oxidation reaction in direct methanol fuel cells. Nano-sized Pd (2-4 nm) particles were deposited on Pt/C and PtRu/C (commercial products) by a simple chemical reduction process. The structural and physical information of the PtRuPd/C were confirmed by TEM and XRD, and their electrocatalytic activities were measured by cyclic voltammetry and linear sweep voltammetry. The catalysts containing Pd showed higher electrocatalytic activity for methanol oxidation reaction than the other catalysts. This might be attributed to an increase in the electrochemical surface area of Pt, which is caused by the addition of Pd; this results in increased catalyst utilization.

Phase stability and magnetism in NiPt and NiPd alloys

International Nuclear Information System (INIS)

Paudyal, Durga; Mookerjee, Abhijit

2004-01-01

We show that the differences in stability of 3d-5d NiPt and 3d-4d NiPd alloys arise mainly due to relativistic corrections. The magnetic properties of disordered NiPd and NiPt alloys also differ due to these corrections, which lead to increase in the separation between the s-d bands of 5d elements in these alloys. For the magnetic case we also analyse the results in terms of splitting of majority and minority spin d band centres of the 3d elements. We further examine the effect of relativistic corrections to the pair energies and order-disorder transition temperatures in these alloys. The magnetic moments and Curie temperatures have also been studied along with the short range ordering/segregation effects in NiPt/NiPd alloys

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.

Nano-structured Pd{sub x}Pt{sub 1-x}/Ti anodes prepared by electrodeposition for alcohol electrooxidation

Energy Technology Data Exchange (ETDEWEB)

Lu Jinlin; Lu Shanfu; Wang Deli; Yang Meng [School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Liu Zili [School of Chemistry and Chemical Engineering, Guangzhou University, No. 601 Huangpudadao, Guangzhou 510006, Guangdong (China); Xu Changwei [School of Chemistry and Chemical Engineering, Guangzhou University, No. 601 Huangpudadao, Guangzhou 510006, Guangdong (China)], E-mail: cwxuneuzsu@126.com; Jiang, S.P. [School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798 (Singapore)], E-mail: mspjiang@ntu.edu.sg

2009-09-30

Nano-structured Pd{sub x}Pt{sub 1-x} (x = 0-1) composite catalysts supported on Ti substrate are successfully prepared by electrodeposition method, and the morphology and phase of the catalysts are analyzed by field emission scanning electron microscope (FE-SEM) and X-ray energy dispersion spectroscopy (EDS). The activity and stability of the Pd{sub x}Pt{sub 1-x}/Ti composite catalysts are assessed for the electrooxidation of alcohols (methanol, ethanol and 2-propanol) in alkaline medium using cyclic voltammetry and chronoamperometry techniques. The results show that the Pd and Pt form Pd{sub x}Pt{sub 1-x} nano-structured composite catalysts, uniformly distributed on the Ti substrate. The electrocatalytic activity and stability of the Pd{sub x}Pt{sub 1-x} nanocatalysts depend strongly on the atomic ratios of Pd and Pt. Among the synthesized catalysts, the Pd{sub 0.8}Pt{sub 0.2}/Ti displays the best catalytic activity and stability for the electrooxidation reaction of alcohols investigated in alkaline medium under conditions in this study, and shows the potential as electrocatalysts for direct alcohol fuel cells.

Shell model studies in the N = 54 isotones 99Rh, 100Pd

International Nuclear Information System (INIS)

Ghugre, S.S.; Sarkar, S.; Chintalapudi, S.N.

1996-01-01

The shell model in reproducing the observed level is used to investigate the observed level sequences in 99 Rh and 100 Pd within the spherical shell model framework. Shell model calculations have been performed using the code OXBASH

Spin pumping damping and magnetic proximity effect in Pd and Pt spin-sink layers

Science.gov (United States)

Caminale, M.; Ghosh, A.; Auffret, S.; Ebels, U.; Ollefs, K.; Wilhelm, F.; Rogalev, A.; Bailey, W. E.

2016-07-01

We investigated the spin pumping damping contributed by paramagnetic layers (Pd, Pt) in both direct and indirect contact with ferromagnetic Ni81Fe19 films. We find a nearly linear dependence of the interface-related Gilbert damping enhancement Δ α on the heavy-metal spin-sink layer thicknesses tN in direct-contact Ni81Fe19 /(Pd, Pt) junctions, whereas an exponential dependence is observed when Ni81Fe19 and (Pd, Pt) are separated by 3 nm Cu. We attribute the quasilinear thickness dependence to the presence of induced moments in Pt, Pd near the interface with Ni81Fe19 , quantified using x-ray magnetic circular dichroism measurements. Our results show that the scattering of pure spin current is configuration-dependent in these systems and cannot be described by a single characteristic length.

Three dimensional PtRh alloy porous nanostructures: tuning the atomic composition and controlling the morphology for the application of direct methanol fuel cells

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yuan [Department of Chemistry, Shanghai University, Shanghai 200444 (China); Department of Chemical Engineering, Case Western Reserve University, Cleveland, OH 44106 (United States); Janyasupab, Metini; Liu, Chung-Chiun [Department of Chemical Engineering, Case Western Reserve University, Cleveland, OH 44106 (United States); Liu, Chen-Wei [Institute of Material Sciences and Engineering, National Central University, Chung-Li 320 (China); Li, Xinxin [State Key Laboratory of Transducer Technology, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Xu, Jiaqiang [Department of Chemistry, Shanghai University, Shanghai 200444 (China)

2012-09-11

A strategy for the synthesis of PtRh alloy 3D porous nanostructures by controlled aggregation of nanoparticles in oleylamine is presented. The atomic ratio between the two components (Pt and Rh) is tuned by varying the concentration of precursor salts accommodating the oxidation of methanol. The morphology of PtRh alloy nanostructure is controlled by elevating the temperature of the reaction system to 240 C. The prepared 3D porous nanostructures provide a high degree of electrochemical activity and good durability toward the methanol oxidation reaction compared to those of the commercial Pt/C (E-TEK) and PtRh nanoparticles. Therefore, the 3D alloy porous nanostructures provide a good opportunity to explore their catalytic properties for methanol oxidation. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

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

driving force for surface segregation, diffusion to defects or surface self-assembling. On the basis of stability and activity analysis we conclude that the near surface alloy of Pd in Pt and some PdAu binary and PtPdAu ternary thin films with a controlled amount of Au are the best catalysts for oxygen......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...

Synthesis and hydrogenation application of Pt-Pd bimetallic nanocatalysts stabilized by macrocycle-modified dendrimer

Science.gov (United States)

Jin, Zhijun; Xiao, Haiyan; Zhou, Wei; Zhang, Dongqiao; Peng, Xiaohong

2017-12-01

Different generations of poly(propylene imine) (Gn-PPI) terminated with N-containing 15-membered triolefinic macrocycle (GnM) (n = 2, 3, 4, 5) were prepared. The bimetallic nanoparticle catalysts GnM-(Ptx/Pd10-x) (x = 0, 3, 5, 7, 10) were prepared by the synchronous ligand-exchange reaction between GnM and the complexes of Pt(PPh3)4 and Pd(PPh3)4. The structure and catalytic properties of GnM-(Ptx/Pd10-x) were characterized via Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, energy-dispersive spectroscopy and inductively coupled plasma atomic emission spectroscopy. The novel bimetallic Pd-Pt nanoparticle catalysts stabilized by dendrimers (DSNs) present higher catalytic activities for the hydrogenation of dimeric acid (DA) than that of nitrile butadiene rubber (NBR). It can be concluded that bimetallic Pd-Pt DSNs possess alloying and synergistic electronic effects on account of the hydrogenation degree (HD) of DA and NBR. Furthermore, the HD of DA and NBR shows a remarkable decrease with the incremental generations (n) of GnM-(Pt3/Pd7) (n = 2, 3, 4, 5).

Pt-Pd nanoelectrocatalyst of ultralow Pt content for the oxidation of ...

Indian Academy of Sciences (India)

formic acid oxidation on Pt4Pd96 nanoparticles. Keywords. ..... Choi J H, Jeong K J, Dong Y, Han J, Lim T H, Lee J S ... Rhee C K, Kim B J, Ham C, Kim Y J, Song K and Kwon ... Wang R, Liao S and Ji S 2008 J. Power Sources 180 205. 18.

Influence of ceria on the thermally durability of Pt/Rh automotive catalyst

International Nuclear Information System (INIS)

Muraki, H.; Zhang, G.

1998-01-01

Full text: The use of cerium oxide as an oxygen storage component in automotive three-way catalysts has been well established. More recently the requirement of the three-way catalysts against the increase of the severity in emission standards has focused attention on the development of more active, durable catalysts. The thermally durability of Pt/Rh catalyst can be achieved by the utilization of thermally stable ceria as well as optimization of washcoat composition and structure in order to control the extent of interaction between PGM and ceria. In the present paper, we describe the influence of newly developed washcoat components and PGM interaction with ceria on catalytic performance. First, to clear that the interaction between PGM and ceria contributes to catalytic performance, several kinds of catalysts which have the varied interactions between PGM and ceria were prepared using engineered washcoat techniques and evaluated in the model gas reactor. It was obvious that the difference in performance among them after aging derived from a diversity of interactions between Pt, Rh, and ceria. Second, for the purpose of determining the thermally durability of the developed Pt/Rh catalyst, the catalysts including the current catalyst were aged under three different temperatures and evaluated on engine dynamometer. Result of engine dynamometer evaluation revealed that significant improvement in the thermal durability can be achieved by optimizing the PGM-ceria interaction. In conclusion, we recognize that a thermal durability of a three-way catalyst can be improved by the stabilization of proper PGM-ceria interaction after aging as well as the utilization of thermally durable ceria material

Structural and magnetic properties of UCo1/3T2/3Al solid solutions (T = Ru, Pt, Rh)

International Nuclear Information System (INIS)

Andreev, A. V.; Bordallo, H. N.; Chang, S.; Nakotte, H.; Schultz, A. J.; Sechovsky, V.; Torikachvili, M. S.

1999-01-01

We report on neutron diffraction studies of UCo 1/3 T 2/3 Al (T = Ru, Pt, Rh). All three solid solutions form in the hexagonal ZrNiAl structure. The Ru-containing compound is found to be chemically ordered, while the Pt-containing compound is nearly disordered and the Rh-containing compound is purely disordered. All three compounds exhibit long-range magnetic order with rather small U moments

Pt-Rh alloys. Investigation of creep rate and rupture time at high temperatures

Energy Technology Data Exchange (ETDEWEB)

Trumic, Biserka; Gomidzelovic, Lidija; Marjanovic, Sasa; Ivanovic, Aleksandra; Dimitrijevic, Silvana [Belgrade Univ., Bor (Serbia). Inst. of Mining and Metallurgy; Krstic, Vesna

2013-02-01

The results of experimental investigation of creep rate and rupture time of the alloys of Pt-Rh system are presented in this paper. Selected alloys with 7-40 wt.-% Rh content were examined using a universal device for tensile testing of materials at high temperatures, and monitoring structure changes of the samples by electron microscopy. Investigations were performed in the temperature range between 1200 C and 1700 C at a stress between 2 MPa and 15 MPa. (orig.)

A determination method of Ru, Rh and Pd in high-level liquid waste (HLLW) by cation exchange separation and ICP-AES measurement

International Nuclear Information System (INIS)

Cao Desheng; Duan Shirong; Qin Fengzhou; Li Jinying; Zhang Huaili

1992-01-01

The authors describe a determination method of Ru, Rh and Pd in HLLW with cation-exchange separation and ICP-AES measurement. A sample of HLLW was treated with the hydrochloride acid containing enough sodium chloride, then passed through a strongly acidic cation-exchange resin column, the Ru, Rh and Pd as chloro-complexes go to the eluate while the interference elements are absorbed on the resins in the column. The Ru, Rh and Pd are collected and determined by ICP-AES. The obtained results show that the recovery is 90% and the relative standard deviation is 6% as the Ru content within the range (35-230) x 10 -6 ; the recovery is 106% and RSD is 10% as the Rh content within (2-20) x 10 -6 ; and the recovery of Pd is 72% as its content less than 2 x 10 -6

Facile synthesis of hierarchical dendritic PtPd nanogarlands supported on reduced graphene oxide with enhanced electrocatalytic properties

Science.gov (United States)

Li, Shan-Shan; Zheng, Jie-Ning; Ma, Xiaohong; Hu, Yuan-Yuan; Wang, Ai-Jun; Chen, Jian-Rong; Feng, Jiu-Ju

2014-05-01

A simple and facile method is developed for one-pot preparation of hierarchical dendritic PtPd nanogarlands supported on reduced graphene oxide (PtPd/RGO) at room temperature, without using any seed, organic solvent, or complex apparatus. It is found that octylphenoxypolyethoxyethanol (NP-40) as a soft template and its amount are critical to the formation of PtPd garlands. The as-prepared nanocomposites are further applied to methanol and ethanol oxidation with significantly enhanced electrocatalytic activity and better stability in alkaline media.A simple and facile method is developed for one-pot preparation of hierarchical dendritic PtPd nanogarlands supported on reduced graphene oxide (PtPd/RGO) at room temperature, without using any seed, organic solvent, or complex apparatus. It is found that octylphenoxypolyethoxyethanol (NP-40) as a soft template and its amount are critical to the formation of PtPd garlands. The as-prepared nanocomposites are further applied to methanol and ethanol oxidation with significantly enhanced electrocatalytic activity and better stability in alkaline media. Electronic supplementary information (ESI) available: Experimental section, Fig. S1-S12 and Tables S1 and S2. See DOI: 10.1039/c3nr06808k

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.

Adsorption of Rh(III) complexes from chloride solutions obtained by leaching chlorinated spent automotive catalysts on ion-exchange resin Diaion WA21J

International Nuclear Information System (INIS)

Shen Shaobo; Pan Tonglin; Liu Xinqiang; Yuan Lei; Wang Jinchao; Zhang Yongjian; Guo Zhanchen

2010-01-01

It was found that Rh, Pd and Pt contained in the spent ceramic automotive catalysts could be effectively extracted by dry chlorination with chlorine. In order to concentrate Rh(III) ions contained in the chloride solutions obtained, thermodynamic and kinetics studies for adsorption of Rh(III) complexes from the chloride solutions on an anionic exchange resin Diaion WA21J were carried out. Rh, Pd, Pt, Al, Fe, Si, Zn and Pb from the chloride solution could be adsorbed on the resin. The distribution coefficients (K d ) of Rh(III) decreased with the increase in initial Rh(III) concentration or in adsorption temperature. The isothermal adsorption of Rh(III) was found to fit Langmuir, Freundlich and Dubinin-Kaganer-Radushkevich models under the adsorption conditions. The maximum monolayer adsorption capacities Q max based on Langmuir adsorption isotherms were 6.39, 6.61 and 5.81 mg/g for temperatures 18, 28 and 40 deg. C, respectively. The apparent adsorption energy of Rh was about -7.6 kJ/mol and thus Rh(III) adsorption was a physical type. The experimental data obtained could be better simulated by pseudo-first-order kinetic model and the activation energy obtained was 6.54 J/mol. The adsorption rate of Rh(III) was controlled by intraparticle diffusion in most of time of adsorption process.

Dual-functional Pt-on-Pd supported on reduced graphene oxide hybrids: peroxidase-mimic activity and an enhanced electrocatalytic oxidation characteristic.

Science.gov (United States)

Zhang, Xiahong; Wu, Genghuang; Cai, Zhixiong; Chen, Xi

2015-03-01

In this study, a facile hydrothermal method was developed to synthesize Pt-on-Pd supported on reduced graphene oxide (Pt-on-Pd/RGO) hybrids. Because of the synergistic effect between Pt-on-Pd and RGO, the obtained Pt-on-Pd/RGO had superior peroxidase-mimic activities in H2O2 reduction and TMB oxidation. The reaction medium was optimized and a sensing approach for H2O2 was developed with a linear range from 0.98 to 130.7 μM of H2O2. In addition, the characteristic of electrocatalytic oxidation of methanol was investigated. The peak current density value, j(f), for the Pt-on-Pd/RGO hybrid (328 mA mg(Pt)(-1)) was about 1.85 fold higher than that of commercial Pt black (177 mA mg(Pt)(-1)) and, also, more durable electrocatalytic activity could be obtained. For the first time, the dual-functional Pt-on-Pd/RGO with peroxidase-mimic activity and an enhanced electrocatalytic oxidation characteristic was reported. Copyright © 2014 Elsevier B.V. All rights reserved.

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.

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...

Studies of valence of selected rare earth silicides determined using Si K and Pd/Rh L{sub 2,3} XANES and LAPW numerical studies

Energy Technology Data Exchange (ETDEWEB)

Zajdel, P., E-mail: pawel.zajdel@us.edu.pl [Institute of Physics, University of Silesia, ul. Uniwersytecka 4, 40-007 Katowice (Poland); Kisiel, A., E-mail: andrzej.kisiel@uj.edu.pl [M. Smoluchowski Institute of Physics, Jagiellonian University, ul. Lojasiewicza 11, 30-348 Kraków (Poland); Szytuła, A., E-mail: andrzej.szytula@uj.edu.pl [M. Smoluchowski Institute of Physics, Jagiellonian University, ul. Lojasiewicza 11, 30-348 Kraków (Poland); Goraus, J., E-mail: jerzy.goraus@us.edu.pl [Institute of Physics, University of Silesia, ul. Uniwersytecka 4, 40-007 Katowice (Poland); Balerna, A., E-mail: antonella.balerna@lnf.infn.it [Laboratori Nazionali di Frascati, INFN, Lab DAPHINE-Light, Via E. Fermi 40, I-00044 Frascati (Italy); Banaś, A., E-mail: slsba@nus.edu.sg [Singapore Synchrotron Light Source, National University of Singapore, 5 Research Link, Singapore 117603 (Singapore); Starowicz, P., E-mail: pawel.starowicz@uj.edu.pl [M. Smoluchowski Institute of Physics, Jagiellonian University, ul. Lojasiewicza 11, 30-348 Kraków (Poland); Konior, J., E-mail: jerzy.konior@uj.edu.pl [M. Smoluchowski Institute of Physics, Jagiellonian University, ul. Lojasiewicza 11, 30-348 Kraków (Poland); Cinque, G., E-mail: gianfelice.cinque@diamond.ac.uk [Diamond Light Source, Harwell Campus, OX11 0DE Chilton-Didcot (United Kingdom); Grilli, A., E-mail: antonio.grilli@lnf.infn.it [Laboratori Nazionali di Frascati, INFN, Lab DAPHINE-Light, Via E. Fermi 40, I-00044 Frascati (Italy)

2015-12-01

Highlights: • The Si K and Pd L{sub 3} edges of R{sub 2}PdSi{sub 3} (R = Ce, Nd, Tb, Dy, Ho, Er) and HoRh{sub 2−x}Pd{sub x}Si{sub 2} are reported. • The R–Si bonds possess polar and 4d5s bands of Pd and Rh metallic characters. • There is no indication of Ce having a different valence than the other rare earths. • The positions and features of the calculated edges exhibit a fair agreement up to ≈10 eV. • The supercell used for Ho{sub 2}PdSi{sub 3} is good enough to reproduce the Si K edge. - Abstract: We report on the investigation of Si and Pd/Rh chemical environments using X-ray Absorption Near Edge Spectroscopy in two different families of rare earth silicides R{sub 2}PdSi{sub 3} (R = Ce, Nd, Tb, Dy, Ho, Er) and HoRh{sub 2−x}Pd{sub x}Si{sub 2} (x = 0, 0.5, 0.75, 1.0, 1.5, 1.8, 2.0). The Si K, Pd L{sub 3} and Rh L{sub 3} absorption edges were recorded in order to follow their changes upon the variation of 4f and 4d5s electron numbers. In both cases it was found that the Si K edge was shifted ≈0.5 eV toward lower energies, relative to pure silicon. In the first family, the shift decreases with increasing number of f-electrons, while the Si K edge remains constant upon rhodium–palladium substitution. In all cases the Pd L{sub 3} edge was shifted to higher energies relative to metallic Pd. No visible change in the Pd L{sub 3} position was observed either with a varying 4f electron count or upon Pd/Rh substitution. Also, the Rh L{sub 3} edge did not change. For two selected members, Ho{sub 2}PdSi{sub 3} and HoPd{sub 2}Si{sub 2}, the Wien2K’09 (LDA + U) package was used to calculate the electronic structure and the absorption edges. Si K edges were reproduced well for both compounds, while Pd L{sub 3} only exhibited a fair agreement for the second compound. This discrepancy between the Pd L{sub 3} theory and experiment for the Ho{sub 2}PdSi{sub 3} sample can be attributed to the specific ordered superstructure used in the numerical calculations

Electrocatalysis of the hydrogen oxidation in the presence of CO on RhO{sub 2}/C-supported Pt nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Freitas, K.S.; Lopes, P.P. [Instituto de Quimica de Sao Carlos, USP, C.P. 780, Sao Carlos, SP 13560-970 (Brazil); Ticianelli, E.A., E-mail: edsont@iqsc.usp.b [Instituto de Quimica de Sao Carlos, USP, C.P. 780, Sao Carlos, SP 13560-970 (Brazil)

2010-12-15

This work presents a study on the kinetics of the hydrogen oxidation reaction (HOR) in the absence and in the presence of CO in ultra thin porous layer and in PEM fuel cell electrodes formed with Pt supported on RhO{sub 2}/C substrates. Together with the electrochemical measurements, the structural and electronic properties of these catalysts were characterized, enabling to correlate their structural and electronic properties with the HOR kinetics. The results show that the presence of Rh oxides leads to an emptying of the Pt 5d band and a consequent reduction of the back-donation of electrons from Pt to CO, weakening the Pt-CO bond and diminishing the CO degree of coverage on Pt, leaving more sites available to HOR. These changes in the electronic spectra do not lead to any perceptible change in the kinetics or the reaction of pure hydrogen. Also, the formation of CO{sub 2} monitored by the MS experiments in the fuel cell anode outlet indicates that the bifunctional mechanism is also operative, but the major CO tolerance is achieved by the electronic effect induced by the RhO{sub 2} support.

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.

Oxidative leaching process with cupric ion in hydrochloric acid media for recovery of Pd and Rh from spent catalytic converters

Energy Technology Data Exchange (ETDEWEB)

Nogueira, C.A., E-mail: carlos.nogueira@lneg.pt [Laboratório Nacional de Energia e Geologia, I.P., Campus do Lumiar, 1649-038 Lisboa (Portugal); Paiva, A.P., E-mail: appaiva@fc.ul.pt [Centro de Química e Bioquímica, Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade de Lisboa, 1749-016 Lisboa (Portugal); Oliveira, P.C. [Laboratório Nacional de Energia e Geologia, I.P., Campus do Lumiar, 1649-038 Lisboa (Portugal); Costa, M.C., E-mail: mcorada@ualg.pt [Centro de Ciências do Mar, Departamento de Química e Farmácia, Faculdade de Ciências e de Tecnologia, Campus de Gambelas, 8005-139 Faro (Portugal); Costa, A.M. Rosa da, E-mail: amcosta@ualg.pt [Centro de Investigação em Química do Algarve, Departamento de Química e Farmácia, Faculdade de Ciências e de Tecnologia, Campus de Gambelas, 8005-139 Faro (Portugal)

2014-08-15

Highlights: • A new leaching process based on Cu{sup 2+}/HCl media for recovering Pd and Rh from spent autocatalytic converters is presented. • Palladium and rhodium were efficiently leached, with attained maximum yields of 95% and 86%, respectively. • Temperature, time, and HCl and Cu{sup 2+} concentrations were found to be significant factors in the leaching of Pd and Rh. - Abstract: The recycling of platinum-group metals from wastes such as autocatalytic converters is getting growing attention due to the scarcity of these precious metals and the market pressure originated by increase of demand in current and emerging applications. Hydrometallurgical treatment of such wastes is an alternative way to the most usual pyrometallurgical processes based on smelter operations. This paper focuses on the development of a leaching process using cupric chloride as oxidising agent, in HCl media, for recovery of palladium and rhodium from a spent catalyst. The chloride media allows the adequate conditions for oxidising and solubilising the metals, as demonstrated by equilibrium calculations based on thermodynamic data. The experimental study of the leaching process revealed that Pd solubilisation is clearly easier than that of Rh. The factors temperature, time, and HCl and Cu{sup 2+} concentrations were significant regarding Pd and Rh leaching, the latter requiring higher factor values to achieve the same results. Leaching yields of 95% Pd and 86% Rh were achieved under optimised conditions (T = 80 °C, t = 4 h, [HCl] = 6 M, [Cu{sup 2+}] = 0.3 M)

Synthesis of Pd@Pt Core-shell Nanoparticles based on Photochemical Seed Growth Method and Co-reduction Method and the Electrocatalytic Performance

Directory of Open Access Journals (Sweden)

Li Shanshan

2016-01-01

Full Text Available A series of Pd@Pt nanoparticles were synthesized based on electrochemical seed growth method and co-reduction method in polyethylene-glycol and acetone solution system. The TEM/HR-TEM and XPS characterization proved that the prepared composite nanoparticles present core-shell structure and analyzed the chemical state of the particles. The electrocatalytic performance of Pd@Pt particles was studied by using the electrochemical workstation. The results showed that the Pd@Pt/C catalyst of different molar ratios of Pd to Pt exhibited preferable catalytic activity and stability for the methanol catalytic oxidation reaction. Among which, the Pd@Pt nanoparticles (Pd:Pt=1:1 prepared by co-reduction method, presented highest catalytic activity, which is 2 times higher than that of Pt/C catalyst. The high catalytic activity produced by the core-shell structure was briefly discussed.

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.

Potential of zero free charge of Pd overlayers on Pt(1 1 1)

International Nuclear Information System (INIS)

El-Aziz, A.M.; Hoyer, R.; Kibler, L.A.; Kolb, D.M.

2006-01-01

Differential capacitance measurements of Pd overlayers on a Pt(1 1 1) electrode in dilute aqueous NaF solutions have been performed as a function of film thickness in order to determine the potential of zero free charge (pzfc). The pzfc of the first, pseudomorphic Pd monolayer on Pt(1 1 1) is -0.21 V versus SCE. By increasing the amount of deposited Pd, a clear shift of the pzfc to more positive values is observed. After deposition of an equivalent of 10 monolayers, the value approaches that of a massive Pd(1 1 1) electrode (-0.12 V versus SCE). The pzfc's for the various Pd coverages are correlated with surface structure information, derived from STM images (R. Hoyer, L.A. Kibler, D.M. Kolb, Electrochim. Acta 49 (2003) 63). Variations in the pzfc are discussed in the context of an electronic modification by the underlying substrate and are compared with corresponding data for Pd overlayers on Au(1 1 1)

Use of Pd-Pt loaded graphene aerogel on nickel foam in direct ethanol fuel cell

Science.gov (United States)

Tsang, Chi Him A.; Leung, D. Y. C.

2018-01-01

A size customized binder-free bimetallic Pd-Pt loaded graphene aerogel deposited on nickel foam plate (Pd-Pt/GA/NFP) was prepared and used as an electrode for an alkaline direct ethanol fuel cell (DEFC) under room temperature. The effect of fuel concentration and metal composition on the output power density of the DEFC was systematically investigated. Under the optimum fuel concentration, the cell could achieve a value of 3.6 mW cm-2 at room temperature for the graphene electrode with Pd/Pt ratio approaching 1:1. Such results demonstrated the possibility of producing a size customized metal loaded GA/NFP electrode for fuel cell with high performance.

Synthesis and structure of Sr{sub 2}Pd{sub 2}In and Sr{sub 2}Pt{sub 2}In

Energy Technology Data Exchange (ETDEWEB)

Muts, I. [Inst. fuer Anorganische und Analytische Chemie, Univ. Muenster (Germany); Inorganic Chemistry Dept., Ivan Franko National Univ. of Lviv (Ukraine); Nilges, T.; Rodewald, U.C.; Poettgen, R. [Inst. fuer Anorganische und Analytische Chemie, Univ. Muenster (Germany); Zaremba, V.I. [Inorganic Chemistry Dept., Ivan Franko National Univ. of Lviv (Ukraine)

2007-12-15

The new intermetallic compounds Sr{sub 2}Pd{sub 2}In and Sr{sub 2}Pt{sub 2}In were synthesized from the elements in sealed tantalum tubes in a water-cooled sample chamber of an induction furnace. Both indides crystallize with the HT-Pr{sub 2}Co{sub 2}Al-type structure: C2/c, a = 1048.7(2), b = 603.5(2), c = 830.6(1) pm. {beta} = 103.68(2) , wR2 = 0.0492, 743 F{sup 2} values for Sr{sub 2}Pd{sub 2}In; a = 1026.8(2), b = 599.0(1), c = 830.3(2) pm, {beta} = 103.17(1) , wR2 = 0.0666, 885 F{sup 2} values for Sr{sub 2}Pt{sub 2}In with 25 variables per refinement. The shortest interatomic distances occur for the Pd-In (Pt-In) and Pd-Pd (Pt-Pt) contacts. The strontium atoms are embedded in complex three-dimensional polyanionic networks of compositions [Pd{sub 2}In] and [Pt{sub 2}In]. (orig.)

Hydrogen Production by Steam Reforming of Ethanol on Rh-Pt Catalysts: Influence of CeO2, ZrO2, and La2O3 as Supports

Directory of Open Access Journals (Sweden)

Bernay Cifuentes

2015-11-01

Full Text Available CeO2-, ZrO2-, and La2O3-supported Rh-Pt catalysts were tested to assess their ability to catalyze the steam reforming of ethanol (SRE for H2 production. SRE activity tests were performed using EtOH:H2O:N2 (molar ratio 1:3:51 at a gaseous space velocity of 70,600 h−1 between 400 and 700 °C at atmospheric pressure. The SRE stability of the catalysts was tested at 700 °C for 27 h time on stream under the same conditions. RhPt/CeO2, which showed the best performance in the stability test, also produced the highest H2 yield above 600 °C, followed by RhPt/La2O3 and RhPt/ZrO2. The fresh and aged catalysts were characterized by TEM, XPS, and TGA. The higher H2 selectivity of RhPt/CeO2 was ascribed to the formation of small (~5 nm and stable particles probably consistent of Rh-Pt alloys with a Pt surface enrichment. Both metals were oxidized and acted as an almost constant active phase during the stability test owing to strong metal-support interactions, as well as the superior oxygen mobility of the support. The TGA results confirmed the absence of carbonaceous residues in all the aged catalysts.

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

DEFF Research Database (Denmark)

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

2012-01-01

The equilibrium hydrogen exchange rate between adsorbed and gas phase hydrogen at 1bar is measured for Pt, Ru and Rh nanoparticles supported on a sputtered HOPG substrate. The particles are prepared by Electron Beam Physical Vapor Deposition and the diameter of the particles varies between 2 and ...

High-quality graphene grown on polycrystalline PtRh{sub 20} alloy foils by low pressure chemical vapor deposition and its electrical transport properties

Energy Technology Data Exchange (ETDEWEB)

Yang, He; Shen, Chengmin, E-mail: cmshen@iphy.ac.cn; Tian, Yuan; Bao, Lihong; Chen, Peng; Yang, Rong; Yang, Tianzhong; Li, Junjie; Gu, Changzhi; Gao, Hong-Jun [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

2016-02-08

High-quality continuous uniform monolayer graphene was grown on polycrystalline PtRh{sub 20} alloy foils by low pressure chemical vapor deposition. The morphology of graphene was investigated by Raman spectroscopy, scanning electron microscopy, and atomic force microscopy. Analysis results confirm that high quality single-layer graphene was fabricated on PtRh{sub 20} foil at 1050 °C using a lower flux of methane under low pressure. Graphene films were transferred onto the SiO{sub 2}/Si substrate by the bubbling transfer method. The mobility of a test field effect transistor made of the graphene grown on PtRh{sub 20} was measured and reckoned at room temperature, showing that the carrier mobility was about 4000 cm{sup 2} V{sup −1} s{sup −1}. The results indicate that desired quality of single-layer graphene grown on PtRh{sub 20} foils can be obtained by tuning reaction conditions.

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

Science.gov (United States)

Wang, Jian-Chen; Zhang, Lin

2013-07-01

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

Extraction behaviour and mechanism of Pt(iv) and Pd(ii) by liquid-liquid extraction with an ionic liquid [HBBIm]Br.

Science.gov (United States)

Liu, Wenhui; Wang, Qi; Zheng, Yan; Wang, Shubin; Yan, Yan; Yang, Yanzhao

2017-06-06

In this study, a method of one-step separation and recycling of high purity Pd(ii) and Pt(iv) using an ionic liquid, 1-butyl-3-benzimidazolium bromate ([HBBIm]Br), was investigated. The effects of [HBBIm]Br concentration, initial metal concentration, and loading capacity of [HBBIm]Br were examined in detail. It was observed that [HBBIm]Br was a very effective extractant for selectively extracting Pd(ii) and precipitating Pt(iv). Through selectively extracting Pd(ii) and precipitating Pt(iv), each metal with high purity was separately obtained from mixed Pd(ii) and Pt(iv) multi-metal solution. The method of one-step separation of Pd(ii) and Pt(iv) is simple and convenient. The anion exchange mechanism between [HBBIm]Br and Pt(iv) was proven through Job's method and FTIR and 1 H NMR spectroscopies. The coordination mechanism between [HBBIm]Br and Pd(ii) was demonstrated via single X-ray diffraction and was found to be robust and distinct, as supported by the ab initio quantum-chemical studies. The crystals of the [PdBr 2 ·2BBIm] complex were formed first. Moreover, the influence of the concentrations of hydrochloric acid, sodium chloride, and sodium nitrate on the precipitation of Pt(iv) and extraction of Pd(ii) was studied herein. It was found that only the concentration of H + could inhibit the separation of Pt(iv) because H + could attract the anion PtCl 6 2- ; thus, the exchange (anion exchange mechanism) between the anions PtCl 6 2- and Br - was prevented. However, both the concentration of H + and Cl - can obviously inhibit the extraction of Pd(ii) because H + and Cl - are the reaction products and increasing their concentration can inhibit the progress of the reaction (coordination mechanism).

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...

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.

Facile synthesis of porous Pt-Pd nanospheres supported on reduced graphene oxide nanosheets for enhanced methanol electrooxidation

Science.gov (United States)

Li, Shan-Shan; Lv, Jing-Jing; Hu, Yuan-Yuan; Zheng, Jie-Ning; Chen, Jian-Rong; Wang, Ai-Jun; Feng, Jiu-Ju

2014-02-01

In this study, a simple, facile, and effective wet-chemical strategy was developed in the synthesis of uniform porous Pt-Pd nanospheres (Pt-Pd NSs) supported on reduced graphene oxide nanosheets (RGOs) under ambient temperature, where octylphenoxypolye thoxyethanol (NP-40) is used as a soft template, without any seed, organic solvent or special instruments. The as-prepared nanocomposites display enhanced electrocatalytic activity and good stability toward methanol oxidation, compared with commercial Pd/C and Pt/C catalysts. This strategy may open a new route to design and prepare advanced electrocatalysts for fuel cells.

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...... a model calculation of the phase diagram of hydrogen in palladium in qualitative agreement with experiment. On this basis we propose a new explanation of the peculiarities of the Pd-H system....

A microwave assisted one-pot route synthesis of bimetallic PtPd alloy cubic nanocomposites and their catalytic reduction for 4-nitrophenol

Science.gov (United States)

Zhang, Jian; Gan, Wei; Fu, Xucheng; Hao, Hequn

2017-10-01

We herein report a simple, rapid, and eco-friendly chemical route to the one-pot synthesis of bimetallic PtPd alloy cubic nanocomposites under microwave irradiation. During this process, water was employed as an environmentally benign solvent, while dimethylformamide served as a mild reducing agent, and polyvinylpyrrolidone was used as both a dispersant and a stabilizer. The structure, morphology, and composition of the resulting alloy nanocomposites were examined by x-ray diffraction, transmission electron microscopy, and energy dispersive x-ray spectroscopy. A detailed study was then carried out into the catalytic activity of the PtPd nanocomposites with a Pt:Pd molar ratio of 50:50 in the reduction of 4-nitrophenol (4-NP) by sodium borohydride as a model reaction. Compared with pristine Pt and Pd monometallic nanoparticles (PtNPs and PdNPs), the bimetallic PtPd alloy nanocomposites exhibited enhanced catalytic activities and were readily recyclable in the reduction of 4-NP due to synergistic effects.

Thermodynamical study of boron doped CeX{sub 3} (X=Pd, Rh)

Energy Technology Data Exchange (ETDEWEB)

Sharma, Ramesh [Dept. of Physics, Mewar University, Chittorgarh Rajasthan-India (India); Dwivedi, Shalini; Sharma, Yamini, E-mail: sharma.yamini62@gmail.com [Theoretical Condensed Matter Physics Laboratory, Dept. of Physics, Feroze Gandhi College, Raebareli-229001 U.P (India)

2016-05-06

The structural, electronic, thermal, and optical properties of cubic non magnetic CeX{sub 3}(X=Pd, Rh) compounds which crystallize in the Au{sub 3}Cu structure have been studied using the projected augmented wave (PAW) method within the density functional theory (DFT) with generalized gradient approximation (GGA) for exchange correlation potential. In this paper we have calculated the band structure which are interpreted using the density of states. The optical properties such as extinction coefficients clearly illustrate the changes in CeX{sub 3} due to intercalation of boron. Lattice instability is observed in CePd{sub 3}B from the calculated dynamical properties.

Green synthesis of Pt-on-Pd bimetallic nanodendrites on graphene via in situ reduction, and their enhanced electrocatalytic activity for methanol oxidation

International Nuclear Information System (INIS)

Cai, Zhi-xiong; Liu, Cong-cong; Wu, Geng-huang; Chen, Xiao-mei; Chen, Xi

2014-01-01

Graphical abstract: - Highlights: • Porous 3D dendrite-like structure of Pt-on-Pd bimetallic nanostructures supported on graphene were prepared. • The surface of nanostructures was very “clean” because of the surfactant-free formation process and the use of green reagent. • The hetero-nanostructures showed excellent electrocatalytic performance in methanol oxidation. - Abstract: A green synthesis of Pt-on-Pd bimetallic nanodendrites supported on graphene (GPtPdNDs) with a Pd interior and a dendrite-like Pt exterior was achieved using a two-step preparation, mixing graphene and PdCl 4 2− first, then adding PtCl 4 2− and ethanol without any other solvent. The morphology, structure and composition of the thus-prepared GPtPdNDs were characterized by transmission electron microscopy (TEM), high resolution TEM, energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. Because no halide ions (refer in particular to Br - , I − ) or surfactant was involved in the synthesis, the prepared GPtPdNDs were directly modified onto a glassy carbon electrode and showed excellent electrocatalytic performance in methanol oxidation without any pretreatments. Moreover, with the special structure of PtPdNDs and the synergetic effects of Pt and Pd and the enhanced electron transfer by graphene, the GPtPdNDs composites exhibited higher electrocatalytic activity and better tolerance to Pt nanoparticles supported on graphene (GPtNPs) and Pt/C for methanol oxidation

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.

Monitoring Pt and Rh in urban aerosols from Buenos Aires, Argentina

Energy Technology Data Exchange (ETDEWEB)

Bocca, Beatrice; Caimi, Stefano; Caroli, Sergio [Istituto Superiore di Sanita, Viale Regina Elena 299, 00161, Rome (Italy); Smichowski, Patricia; Gomez, Dario [Comision Nacional de Energia Atomica, Unidad de Actividad Quimica, Centro Atomico Constituyentes, Av. Gral. Paz 1499, B1650KNA-San Martin, Pcia. de Buenos Aires (Argentina)

2006-04-01

Vehicular traffic is the main source of platinum group elements (PGEs) in highly populated urban areas like Buenos Aires where a traffic density of 1,500,000 vehicles day{sup -1} (corresponding to 7500 vehicles km{sup -2}) is estimated. Since there is no information on the levels of PGEs in Buenos Aires, a pilot study was undertaken to ascertain the amount of two major PGEs, namely Pt and Rh, in the atmosphere of this city. To this end, 49 samples of PM-10 particulate matter were collected during 7 days in seven representative sampling sites located downtown Buenos Aires and spread over an area of about 30 km{sup 2}. The collection of particulate matter was performed on ash-free glass-fiber filters using high volume samplers with PM-10 sampling heads. Filters loaded with the particulate matter were subjected to microwave (MW)-assisted acid digestion using a combination of HNO{sub 3}, HF and HClO{sub 4}. The resulting solutions were evaporated and then diluted with 0.1 mol l{sup -1} HCl. Analyses were performed by sector field inductively coupled plasma-mass spectrometry (SF-ICP-MS) and special attention was paid to the control of mass interferences. Statistical analysis was performed on the experimental data obtained for the element concentrations taking also into account local meteorological data for the monitored period. The highest concentrations of Pt and Rh were detected at two sites (Hospital Aleman and Casa Rapallini) located in streets with traffic consisting mostly of passenger cars. The Pt content (in pg m{sup -3}) in airborne particulate matter was found to vary from 2.3 to 47.7, with a mean value of 12.9+/-7, and that of Rh from 0.3 to 16.8, with a mean value of 3.9+/-2.8. These concentrations are by far below the levels for which adverse health effects might be expected to occur, i.e., around 100 ng m{sup -3}. On the other hand, monitoring of PGEs should be carried out in a systematic fashion to detect possible dramatic increases from today

Barrier height and interface effect of Pt-n-GaN and Pd-n-GaN Schottky diodes

International Nuclear Information System (INIS)

Khan, M.R.H.; Saha, S.L.; Sawaki, N.

1999-01-01

Schottky barriers on n-type GaN films by Pt and Pd are fabricated and characterized. A thin Pt or Pd layer is deposited on n-GaN layers to form Schottky contacts in a vacuum below 1x10/sup -6/ Torr. The area of all diodes is 3.46 x 10-4 cm/sup 2/. Several samples of Pt-n GaN and Pd-n GaN were studied. The ideality factor of Pt-n-GaN diode is 1.26 and of Pd-n-GaN is 1.17. The breakdown voltage of Pt-n-GaN and Pd-n-GaN diodes is 21 V and 26 V respectively. In both the cases the leakage current varies between 1x10-9 A and 5x 10-9 A. The Schottky barrier heights (phi/sub B/ ) of Pt-GaN diode is been determined to be 1.02 eV by current voltage (I-V) and 1.07 eV by capacitance (C-V) measurements Also, phi/sub B/ of Pd-GaN diode is determined to be 0.91 eV by I-V and 0.98 eV, by C-V measurements. The departure of the values of the ideality factor is considered to be due to spatial inhomogeneities at the meal semiconductor interface. The difference in the values of phi/sub B/ determined by I-V and C-V measurements is attributed to the deformation of the spatial barrier distribution. (author)

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 are......, Pt. The transition between beta- and alpha-phase in the H-Pd system has a significant effect on the activity for Pd....

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.

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...

Accurate Determination of Platinum, Palladium, and Rhodium in Ryegrass using Collision Cell Inductively Coupled Plasma Mass Spectrometry with Xenon as Collision Gas

International Nuclear Information System (INIS)

Amr, M.A.

2011-01-01

Inductively coupled plasma mass spectrometry with an octupole collision cell was used for determination of Pt, Pd and Rh in ryegrass (Lolium multiflorum) which was grown hydroponically. Xenon was used as a collision gas to reduce serious polyatomic interferences formed by combination of matrix elements such as CI, Cu, Hf, Sr, Zn, Zr, Y and REE with O, N, C, and Ar. The detection limits for Pt, Pd and Rh in spiked ryegrass are 1.8, 4.2, and 0.8 ppt, respectively. The results for Pt, Pd and Rh in reference materials (NIST SRM 2557, recycled monolith auto catalyst) are in agreement with the certified values. The bioaccumulation of Pt, Pd and Rh by ryegrass grown hydroponically with nutrient solutions containing Pt, Pd and Rh was studied. The obtained results showed that most of the studied metals were accumulated in roots, and only a small fraction was metabolized and transported to leaves. The highest bioaccumulation factors were obtained for Pd and Rh in roots and for Pt in leaves

Nonenzymatic sensing of glucose at neutral pH values using a glassy carbon electrode modified with graphene nanosheets and Pt-Pd bimetallic nanocubes

International Nuclear Information System (INIS)

Chen, Xiaomei; Tian, Xiaotian; Zhao, Limin; Huang, Zhiyong; Oyama, Munetaka

2014-01-01

We report on a nonenzymatic method for the determination of glucose using an electrode covered with graphene nanosheets (GNs) modified with Pt-Pd nanocubes (PtPdNCs). The latter were prepared on GNs by using N,N-dimethylformamide as a bifunctional solvent for the reduction of both metallic precursors and graphene oxide, and for confining the growth of PtPdNCs on the surface. The modified electrode displays strong and sensitive current response to the electrooxidation of glucose, notably at pH 7. The sensitivities increase in the order of Pt 1 Pd 5 NCs< Pt 1 Pd 3 NCs< Pt 5 Pd 1 NCs< Pt 3 Pd 1 NCs< Pt 1 Pd 1 NCs. At an applied potential of +0.25 V, the electrode responds linearly (R = 0.9987) to glucose in up to 24.5 mM concentration, with a sensitivity of 1.4 μA cm −2 M −1 . The sensor is not poisoned by chloride, and not interfered by ascorbic acid, uric acid and p-acetamidophenol under normal physiological conditions. The modified electrode also displays a wide linear range, good stability and fast amperometric response, thereby indicating the potential of the bimetallic materials for nonenzymatic sensing of glucose. (author)

Energy conversion using Pt-Pd/C anode catalyst in direct 2-propanol fuel cell

Directory of Open Access Journals (Sweden)

S. S. Mahapatra

2016-06-01

Full Text Available The Pt-Pd/C electrocatalyst was synthesized on graphite substrate by the electrochemical codeposition technique. The Physico-chemical characterization of the catalyst was done by SEM, XRD and EDX. The electrochemical characterization of the Pt-Pd/C catalyst for 2-propanol electro-oxidation was studied over a range of 2-propanol concentrations in alkaline medium using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. The activity of 2-propanol oxidation increased with the increase of 2-propanol concentration, at 2-propanol concentration greater than 1.0 M, no change in the oxidation peak current density is because of excess 2-propanol 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 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.

Ternary indides Eu{sub 2}Pd{sub 2}In and Eu{sub 2}Pt{sub 2}In

Energy Technology Data Exchange (ETDEWEB)

Muts, Ihor [Inorganic Chemistry Department, Ivan Franko National University of Lviv (Ukraine); Institut fuer Anorganische und Analytische Chemie, Westfaelische Wilhelms-Universitaet Muenster (Germany); Zaremba, Vasyl I. [Inorganic Chemistry Department, Ivan Franko National University of Lviv (Ukraine); Poettgen, Rainer [Institut fuer Anorganische und Analytische Chemie, Westfaelische Wilhelms-Universitaet Muenster (Germany)

2012-01-15

The indides Eu{sub 2}Pd{sub 2}In and Eu{sub 2}Pt{sub 2}In were synthesized from the elements in sealed tantalum tubes in an induction furnace. The samples were characterized by powder X-ray diffraction. The structures were refined on the basis of single-crystal X-ray diffractometer data: HT-Pr{sub 2}Co{sub 2}Al type, C2/c, a = 1035.7(2), b = 592.9(1), c = 823.6(2) pm, β = 104.26(1) , wR2 = 0.026, 1075 F{sup 2} values, 25 variables for Eu{sub 2}Pd{sub 2}In and a = 1017.2(2), b = 588.7(1), c = 826.5(1) pm, β = 103.76(1) , wR2 = 0.062, 706 F{sup 2} values, 25 variables for Eu{sub 2}Pt{sub 2}In. The indium atoms have four platinum (palladium) neighbors in strongly distorted tetrahedral coordination at Pt-In and Pd-In distances ranging from 273 to 275 pm. These InPd{sub 4/2} and InPt{sub 4/2} units are condensed via common edges to infinite InPd{sub 2} and InPt{sub 2} chains, which are surrounded by the europium atoms. The chains form the motif of hexagonal rod packing. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

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 ...

Preparation of a Pd-Pt alloy on alumina and its application for a gas chromatography

Energy Technology Data Exchange (ETDEWEB)

Lee, Minsoo [Korea Atomic Energy Research Institute, 150 Deokjin-dong, Yuseong, Daejeon 305-353 (Korea, Republic of)]. E-mail: minm@kaeri.re.kr; Paek, Seungwoo [Korea Atomic Energy Research Institute, 150 Deokjin-dong, Yuseong, Daejeon 305-353 (Korea, Republic of); Ahn, Do-Hee [Korea Atomic Energy Research Institute, 150 Deokjin-dong, Yuseong, Daejeon 305-353 (Korea, Republic of); Kim, Kwang-Rag [Korea Atomic Energy Research Institute, 150 Deokjin-dong, Yuseong, Daejeon 305-353 (Korea, Republic of); Yim, Sung-Paal [Korea Atomic Energy Research Institute, 150 Deokjin-dong, Yuseong, Daejeon 305-353 (Korea, Republic of); Chung, Hongsuk [Korea Atomic Energy Research Institute, 150 Deokjin-dong, Yuseong, Daejeon 305-353 (Korea, Republic of)

2007-08-30

In this study we attempted to obtain a Pd-Pt alloy on alumina (PPA) by using an impregnation and alcohol reduction method for the purpose of a hydrogen isotopes separation, in which {alpha}-alumina powder was impregnated into an ethanol water (1/1, w/w) solution containing PdCl{sub 2}, PtCl{sub 2}, and polyvinylpyrrolidone (PVP, MW = 10,000). The sample was dried, reduced by hydrogen, and thermally treated at 1073 K. Thus, two kinds of PPA (Pd content 17 and 29 wt%) were achieved. The produced PPA showed a good crystallinity from the XRD analysis and it exhibited an adequate hydrogen desorption isotherm as a packing material for the separation of hydrogen isotopes. GC columns packed with PPA and Cu powder were used for the separation of a 29.2% D{sub 2}-H{sub 2} gas mixture at 303 and 343 K. The experimental result showed a good separation efficiency of the hydrogen isotopes for the GC process. Consequently, the suggested technique for the production of a Pd-Pt alloy on alumina was proven to be successful.

Simple preparations of Pd6Cl12, Pt6Cl12, and Qn[Pt2Cl8+n], n=1, 2 (Q=TBA+, PPN+) and structural characterization of [TBA][Pt2Cl9] and [PPN]2[Pt2Cl10].C7H8.

Science.gov (United States)

Dell'Amico, Daniela Belli; Calderazzo, Fausto; Marchetti, Fabio; Ramello, Stefano; Samaritani, Simona

2008-02-04

The hexanuclear Pd6Cl12, i.e., the crystal phase classified as beta-PdCl2, was obtained by reacting [TBA]2[Pd2Cl6] with AlCl3 (or FeCl3) in CH2Cl2. The action of AlCl3 on PtCl42-, followed by digestion of the resulting solid in 1,2-C2H4Cl2 (DCE), CHCl3, or benzene, produced Pt6Cl12.DCE, Pt6Cl12.CHCl3, or Pt6Cl12.C6H6, respectively. Treating [TBA]2[PtCl6] with a slight excess of AlCl3 afforded [TBA][Pt2Cl9], whose anion was established crystallographically to be constituted by two "PtCl6" octahedra sharing a face. Dehydration of H2PtCl6.nH2O with SOCl2 gave an amorphous compound closely analyzing as PtCl4, reactive with [Q]Cl in SOCl2 to yield [Q][Pt2Cl9] or [Q]2[Pt2Cl10], depending on the [Q]Cl/Pt molar ratio (Q=TBA+, PPN+). A single-crystal X-ray diffraction study has shown [PPN]2[Pt2Cl10].C7H8 to contain dinuclear anions formed by two edge-sharing PtCl6 octahedra.

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

A set of electrochemical and X-ray spectroscopy measurements have been used conjointly with density functional theory (DFT) simulations to study the activity and stability of Pd5Ce for the oxygen reduction reaction. A polycrystalline Pd5Ce rod has been selected as a model catalyst to test if resu......-Pd5Ce is more facile, requires less atom rearrangement, than transformation from Pt5Ce to Pt3Ce, which might explain the kinetic stability of Pt5Ce at low temperatures....

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.

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

CERN Document Server

Szafranski, A W

2003-01-01

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

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

2015-01-01

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. PMID:26694397

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.

Synthesis and characterization of Pd-on-Pt and Au-on-Pt bimetallic nanosheaths on multiwalled carbon nanotubes

International Nuclear Information System (INIS)

Wang Shuangyin; Jiang, San Ping; Wang Xin

2011-01-01

The authors have successfully synthesized Pd-on-Pt (thickness: 12 nm) and Au-on-Pt bimetallic nanosheaths on multiwalled carbon nanotubes (MWCNTs) via a seed-mediated growth approach. Pt nanoparticles as seeds were pre-deposited on MWCNTs with uniform distribution followed by the successive seed-mediated growth of metal atoms reduced by a weak reducing agent, ascorbic acid. The essential role of pre-deposited nanoseed particles on MWCNTs was demonstrated. The as-prepared materials were characterization by transition electron microscopy, energy-dispersive X-ray spectroscopy, and element mapping tools. The current strategy extends the classical seed-mediated growth method to prepare bimetallic nanosheath on MWCNT support.

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.)

Automotive catalyst strategies for future emission systems

International Nuclear Information System (INIS)

Williamson, W.B.; Summers, J.C.; Scaparo, J.A.

1992-01-01

This paper reports that while significant advances in Pt/Rh three-way catalyst (TWC) formulations have been accomplished, the use of Pd-containing catalysts for three-way emission control are of interest for overall noble metal cost reduction, lower Rh usage, and potential durability improvements. Applications of Pd are demonstrated for replacement of Pt in conventional Pt/Rh TWC systems, for use in Pd-only three-way catalysts and for lowering methanol and formaldehyde emissions at close-coupled locations on a methanol-fueled vehicle. The individual contributions of Pt, Pd and Rh for aged three-way performance indicate significant advantages of using Pd over Pt. A comparison of vehicle system control strategies illustrates that higher system temperatures significantly lower HC emissions, while air/fuel control strategies are most critical in lowering NO x emissions

Bimetallic magnetic PtPd-nanoparticles as efficient catalyst for PAH removal from liquid media

Science.gov (United States)

Zanato, A. F. S.; Silva, V. C.; Lima, D. A.; Jacinto, M. J.

2017-11-01

Monometallic Pd- and bimetallic PtPd-nanoparticles supported on a mesoporous magnetic magnetite@silica matrix resembling a core-shell structure (Fe3O4@mSiO2) have been fabricated. The material was characterized by transmission electron microscope (TEM), high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM), X-ray photoelectron spectra (XPS), energy dispersive spectroscopy (EDS) and inductively coupled plasma mass spectrometry (ICP-MS). The catalysts were applied in the removal of anthracene from liquid phase via catalytic hydrogenation. It was found that anthracene as a model compound could be completely converted into the partially hydrogenated species by the monometallic and bimetallic solids. However, during the recycling study the bimetallic material (Fe3O4@mSiO2PtPd-) showed an enhanced activity towards anthracene removal compared with the monometallic materials. A single portion of the PtPd-based catalyst can be used up to 11 times in the hydrogenation of anthracene under mild conditions (6 atm of H2, 75 °C, 20 min). Thanks to the presence of a dense magnetic core, the catalysts were capable of responding to an applied external magnetic field and once the reaction was completed, catalyst/product separation was straightforward.

Recent advances in platinum monolayer electrocatalysts for oxygen reduction reaction: Scale-up synthesis, structure and activity of Pt shells on Pd cores

Energy Technology Data Exchange (ETDEWEB)

Sasaki, K., E-mail: ksasaki@bnl.go [Brookhaven National Laboratory, Chemistry Department, Upton, NY 11973 (United States); Wang, J.X. [Brookhaven National Laboratory, Chemistry Department, Upton, NY 11973 (United States); Naohara, H. [Toyota Motor Corporation, Susono 410-1193 (Japan); Marinkovic, N. [University of Delaware, Department of Chemical Engineering, Newark, DE 19716 (United States); More, K. [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Inada, H. [Hitachi High Technologies America, Pleasanton, CA 94588 (United States); Adzic, R.R., E-mail: adzic@bnl.go [Brookhaven National Laboratory, Chemistry Department, Upton, NY 11973 (United States)

2010-03-01

We have established a scale-up synthesis method to produce gram-quantities of Pt monolayer electrocatalysts. The core-shell structure of the Pt/Pd/C electrocatalyst has been verified using the HAADF-STEM Z-contrast images, STEM/EELS, and STEM/EDS line profile analysis. The atomic structure of this electrocatalyst and formation of a Pt monolayer on Pd nanoparticle surfaces were examined using in situ EXAFS. The Pt mass activity of the Pt/Pd/C electrocatalyst for ORR is considerably higher than that of commercial Pt/C electrocatalysts. The results with Pt monolayer electrocatalysts may significantly impact science of electrocatalysis and fuel-cell technology, as they have demonstrated an exceptionally effective way of using Pt that can resolve problems of other approaches, including electrocatalysts' inadequate activity and high Pt content.

Recent advances in platinum monolayer electrocatalysts for oxygen reduction reaction: Scale-up synthesis, structure and activity of Pt shells on Pd cores

International Nuclear Information System (INIS)

Sasaki, K.; Wang, J.X.; Naohara, H.; Marinkovic, N.; More, K.; Inada, H.; Adzic, R.R.

2010-01-01

We have established a scale-up synthesis method to produce gram-quantities of Pt monolayer electrocatalysts. The core-shell structure of the Pt/Pd/C electrocatalyst has been verified using the HAADF-STEM Z-contrast images, STEM/EELS, and STEM/EDS line profile analysis. The atomic structure of this electrocatalyst and formation of a Pt monolayer on Pd nanoparticle surfaces were examined using in situ EXAFS. The Pt mass activity of the Pt/Pd/C electrocatalyst for ORR is considerably higher than that of commercial Pt/C electrocatalysts. The results with Pt monolayer electrocatalysts may significantly impact science of electrocatalysis and fuel-cell technology, as they have demonstrated an exceptionally effective way of using Pt that can resolve problems of other approaches, including electrocatalysts' inadequate activity and high Pt content.

Electrochemical oxidation of ethanol using PtRh/C electrocatalysts in alkaline medium and synthesized by sodium borohydride and alcohol reduction

International Nuclear Information System (INIS)

Fontes, Eric Hossein

2017-01-01

PtRh/C were prepared by the following atomic proportions: (100,0), (0,100), (90,10), (70,30) and (50,50). The methods employed in the synthesis of these materials were reduction by sodium borohydride and reduction by alcohol. The metal salts used were H 2 PtCl 6 3•6H 2 0 and (RhNO 3 ) 3 , the support used was Carbon black XC72 and the bulk metal composition was 20% and 80% of support. The electrocatalysts were characterized by Energy Dispersive X-ray spectroscopy, X-ray diffraction and Transmission electron microscopy. The ethanol electrochemical oxidation mechanism was investigated by in situ Fourier Transform Infrared Spectroscopy couple to an Attenuated Total Reflection technique. The electrocatalytic activity were evaluated by Cyclic Voltammetry, Linear Sweep Voltammetry and Chronoamperometry techniques. The Fuel Cells tests were made in a single direct alcohol fuel cell with alkaline membrane. The working electrodes were prepared by a thin porous coating technique. X-ray diffraction allowed to verify metallic alloys, segregate phases and to calculate the percentage of metallic alloys. It was else possible to identify crystallographic phases. Infrared Spectroscopy allowed to verify that the electrochemical oxidation of ethanol was carried out by an incomplete mechanism. PtRh(70:30)/C prepared by sodium borohydride produced large amounts of carbon dioxide and acetaldehyde. Rh/C showed electrocatalytic activity when compared with other materials studied.

Performance PtSnRh electrocatalysts supported on carbon-Sb2O5.SbO2 for the electro-oxidation of ethanol, prepared by an alcohol-reduction process

International Nuclear Information System (INIS)

Castro, Jose Carlos

2013-01-01

PtSnRh electrocatalysts supported on carbon-Sb 2 O 5 .SnO 2 , with metal loading of 20 wt%, were prepared by an alcohol-reduction process, using H 2 PtCl 6 .6H 2 O (Aldrich), RhCl 3 .xH 2 O (Aldrich) and SnCl 2 .2H 2 O (Aldrich), as source of metals; Sb 2 O 5 .SnO 2 (ATO) and carbon Vulcan XC72, as support; and ethylene glycol as reducing agent. The electrocatalysts obtained were characterized physically by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The diffractograms showed which PtSnRh/C-ATO electrocatalysts had FCC structure of Pt and Pt alloys, besides several peaks associated with SnO 2 and ATO. The average sizes of crystallites were between 2 and 4 nm. TEM micrographs showed a good distribution of the nanoparticles on the support. The average sizes of particles were between 2 and 3 nm, with good agreement for the average size of the crystallites. The performances of the electrocatalysts were analyzed by electrochemical techniques and in real conditions of operation using single direct ethanol fuel cell. In the chronoamperometry at 50 deg C, the electrocatalysts with carbon (85 wt%) and ATO (15 wt%) support, showed the best activity, and the atomic proportions which achieved the best results were PtSnRh(70:25:05) e (90:05:05). PtSnRh(70:25:05)/85C+15ATO electrocatalysts showed the best performance in a direct ethanol fuel cell. (author)

Methanol and ethanol electrooxidation on Pt and Pd supported on carbon microspheres in alkaline media

Energy Technology Data Exchange (ETDEWEB)

Xu, Changwei; Cheng, Liqiang; Liu, Yingliang [Department of Chemistry and Institute of Nanochemistry, Jinan University, Guangzhou 510632 (China); Shen, Peikang [State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China)

2007-05-15

Noble metal (Pt, Pd) electrocatalysts supported on carbon microspheres (CMS) are used for methanol and ethanol oxidation in alkaline media. The results show that noble metal electrocatalysts supported on carbon microspheres give better performance than that supported on carbon black. It is well known that palladium is not a good electrocatalyst for methanol oxidation, but it shows excellently higher activity and better steady-state electrolysis than Pt for ethanol electrooxidation in alkaline media. The results show a synergistic effect by the interaction between Pd and carbon microspheres. The Pd supported on carbon microspheres in this paper possesses excellent electrocatalytic properties and may be of great potential in direct ethanol fuel cells. (author)

Geochemical behaviour of palladium in soils and Pd/PdO model substances in the presence of the organic complexing agents L-methionine and citric acid.

Science.gov (United States)

Zereini, Fathi; Wiseman, Clare L S; Vang, My; Albers, Peter; Schneider, Wolfgang; Schindl, Roland; Leopold, Kerstin

2016-01-01

Risk assessments of platinum group metal (PGE) emissions, notably those of platinum (Pt), palladium (Pd) and rhodium (Rh), have been mostly based on data regarding the metallic forms used in vehicular exhaust converters, known to be virtually biologically inert and immobile. To adequately assess the potential impacts of PGE, however, data on the chemical behaviour of these metals under ambient conditions post-emission is needed. Complexing agents with a high affinity for metals in the environment are hypothesized to contribute to an increased bioaccessibility of PGE. The purpose of this study is to examine the modulating effects of the organic complexing agents, L-methionine and citric acid, on the geochemical behavior of Pd in soils and model substances (Pd black and PdO). Batch experimental tests were conducted with soils and model substances to examine the impacts of the concentration of complexing agents, pH and length of extraction period on Pd solubility and its chemical transformation. Particle surface chemistry was examined using X-ray photoelectron spectroscopy (XPS) on samples treated with solutions under various conditions, including low and high O2 levels. Pd was observed to be more soluble in the presence of organic complexing agents, compared to Pt and Rh. Pd in soils was more readily solubilized with organic complexing agents compared to the model substances. After 7 days of extraction, L-methionine (0.1 M) treated soil and Pd black samples, for instance, had mean soluble Pd fractions of 12.4 ± 5.9% and 0.554 ± 0.024%, respectively. Surface chemistry analyses (XPS) confirmed the oxidation of metallic Pd surfaces when treated with organic complexing agents. The type of organic complexing agent used for experimental purposes was observed to be the most important factor influencing solubility, followed by solution pH and time of extraction. The results demonstrate that metallic Pd can be transformed into more bioaccessible species in the presence of

Exploring the metal coordination properties of the pyrimidine part of purine nucleobases: isomerization reactions in heteronuclear Pt(II)/Pd(II) of 9-methyladenine.

Science.gov (United States)

Ibáñez, Susana; Albertí, Francisca M; Sanz Miguel, Pablo J; Lippert, Bernhard

2011-10-17

The synthesis and characterization of three heteronuclear Pt(2)Pd(2) (4, 5) and PtPd(2) (6) complexes of the model nucleobase 9-methyladenine (9-MeA) is reported. The compounds were prepared by reacting [Pt(NH(3))(3)(9-MeA-N7)](ClO(4))(2) (1) with [Pd(en)(H(2)O)(2)](ClO(4))(2) at different ratios r between Pt and Pd, with the goal to probe Pd(II) binding to any of the three available nitrogen atoms, N1, N3, N6 or combinations thereof. Pd(II) coordination occurs at N1 and at the deprotonated N6 positions, yet not at N3. 4 and 5 are isomers of [{(en)Pd}(2){N1,N6-9-MeA(-)-N7)Pt(NH(3))(3)}(2)](ClO(4))(6)·nH(2)O, with a head-head orientation of the two bridging 9-MeA(-) ligands in 4 and a head-tail orientation in 5. 6 is [{(en)Pd}(2)(OH)(N1,N6-9MeA(-)-N7)Pt(NH(3))(3)](ClO(4))(4)·4H(2)O, hence a condensation product between [Pt(NH(3))(3)(9-MeA-N7)](2+) and a μ-OH bridged dinuclear (en)Pd-OH-Pd(en) unit, which connects the N1 and N6 positions of 9-MeA(-) in an intramolecular fashion. 4 and 5, which slowly interconvert in aqueous solution, display distinct structural differences such as significantly different intramolecular Pd···Pd contacts (3.124 0(16) Å in 4; 2.986 6(14) Å in 5), among others. Binding of (en)Pd(II) to the exocyclic N6 atom in 4 and 5 is accompanied by a large movement of Pd(II) out of the 9-MeA(-) plane and a trend to a further shortening of the C6-N6 bond as compared to free 9-MeA. The packing patterns of 4 and 5 reveal substantial anion-π interactions.

Rapid, general synthesis of PdPt bimetallic alloy nanosponges and their enhanced catalytic performance for ethanol/methanol electrooxidation in an alkaline medium.

Science.gov (United States)

Zhu, Chengzhou; Guo, Shaojun; Dong, Shaojun

2013-01-14

We have demonstrated a rapid and general strategy to synthesize novel three-dimensional PdPt bimetallic alloy nanosponges in the absence of a capping agent. Significantly, the as-prepared PdPt bimetallic alloy nanosponges exhibited greatly enhanced activity and stability towards ethanol/methanol electrooxidation in an alkaline medium, which demonstrates the potential of applying these PdPt bimetallic alloy nanosponges as effective electrocatalysts for direct alcohol fuel cells. In addition, this simple method has also been applied for the synthesis of AuPt, AuPd bimetallic, and AuPtPd trimetallic alloy nanosponges. The as-synthesized three-dimensional bimetallic/trimetallic alloy nanosponges, because of their convenient preparation, well-defined sponge-like network, large-scale production, and high electrocatalytic performance for ethanol/methanol electrooxidation, may find promising potential applications in various fields, such as formic acid oxidation or oxygen reduction reactions, electrochemical sensors, and hydrogen-gas sensors. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Martensitic transformation in Heusler alloys Mn2YIn (Y=Ni, Pd and Pt): Theoretical and experimental investigation

International Nuclear Information System (INIS)

Luo, Hongzhi; Liu, Bohua; Xin, Yuepeng; Jia, Pengzhong; Meng, Fanbin; Liu, Enke; Wang, Wenhong; Wu, Guangheng

2015-01-01

The martensitic transformation and electronic structure of Heusler alloys Mn 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 2 YIn. Thus a structural transition from cubic to tetragonal is most likely to happen in Heusler alloy Mn 2 PtIn. A single Heusler phase can be obtained in both Mn 2 PtIn and Mn 2 PdIn. A martensitic transformation temperature of 615 K has been identified in Mn 2 PtIn. And in Mn 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 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 2 PdIn has been synthesized successfully and investigated. • Martensitic transformation in Heusler alloys can be predicted by first -principles calculations

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.

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.

Oxidative leaching process with cupric ion in hydrochloric acid media for recovery of Pd and Rh from spent catalytic converters.

Science.gov (United States)

Nogueira, C A; Paiva, A P; Oliveira, P C; Costa, M C; da Costa, A M Rosa

2014-08-15

The recycling of platinum-group metals from wastes such as autocatalytic converters is getting growing attention due to the scarcity of these precious metals and the market pressure originated by increase of demand in current and emerging applications. Hydrometallurgical treatment of such wastes is an alternative way to the most usual pyrometallurgical processes based on smelter operations. This paper focuses on the development of a leaching process using cupric chloride as oxidising agent, in HCl media, for recovery of palladium and rhodium from a spent catalyst. The chloride media allows the adequate conditions for oxidising and solubilising the metals, as demonstrated by equilibrium calculations based on thermodynamic data. The experimental study of the leaching process revealed that Pd solubilisation is clearly easier than that of Rh. The factors temperature, time, and HCl and Cu(2+) concentrations were significant regarding Pd and Rh leaching, the latter requiring higher factor values to achieve the same results. Leaching yields of 95% Pd and 86% Rh were achieved under optimised conditions (T = 80 °C, t = 4h, [HCl] = 6M, [Cu(2+)] = 0.3M). Copyright © 2014 Elsevier B.V. All rights reserved.

Sintering of oxide-supported Pt and Pd nanoparticles in air studied by in situ TEM

DEFF Research Database (Denmark)

Simonsen, Søren Bredmose

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...... of Pt, Pd and bimetallic Pt-Pd nanoparticles supported on a flat and homogeneous Al2O3 or SiO2 surface. By using in situ TEM on the planar model catalysts it was possible to directly monitor the detailed dynamical changes of the individual nanoparticles during exposure to oxidizing conditions...

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.)

Performance PtSnRh electrocatalysts supported on carbon-Sb{sub 2}O{sub 5}.SbO{sub 2} for the electro-oxidation of ethanol, prepared by an alcohol-reduction process; Desempenho de eletrocatalisadores PtSnRh suportados em carbono-Sb{sub 2}O{sub 5}.SnO{sub 2} para a oxidacao eletroquimica do etanol, preparados pelo metodo de reducao por alcool

Energy Technology Data Exchange (ETDEWEB)

Castro, Jose Carlos

2013-07-01

PtSnRh electrocatalysts supported on carbon-Sb{sub 2}O{sub 5}.SnO{sub 2}, with metal loading of 20 wt%, were prepared by an alcohol-reduction process, using H{sub 2}PtCl{sub 6}.6H{sub 2}O (Aldrich), RhCl{sub 3}.xH{sub 2}O (Aldrich) and SnCl{sub 2}.2H{sub 2}O (Aldrich), as source of metals; Sb{sub 2}O{sub 5}.SnO{sub 2} (ATO) and carbon Vulcan XC72, as support; and ethylene glycol as reducing agent. The electrocatalysts obtained were characterized physically by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The diffractograms showed which PtSnRh/C-ATO electrocatalysts had FCC structure of Pt and Pt alloys, besides several peaks associated with SnO{sub 2} and ATO. The average sizes of crystallites were between 2 and 4 nm. TEM micrographs showed a good distribution of the nanoparticles on the support. The average sizes of particles were between 2 and 3 nm, with good agreement for the average size of the crystallites. The performances of the electrocatalysts were analyzed by electrochemical techniques and in real conditions of operation using single direct ethanol fuel cell. In the chronoamperometry at 50 deg C, the electrocatalysts with carbon (85 wt%) and ATO (15 wt%) support, showed the best activity, and the atomic proportions which achieved the best results were PtSnRh(70:25:05) e (90:05:05). PtSnRh(70:25:05)/85C+15ATO electrocatalysts showed the best performance in a direct ethanol fuel cell. (author)

Variations of color with alloying elements in Pd-free Au-Pt-based high noble dental alloys

International Nuclear Information System (INIS)

Shiraishi, Takanobu; Takuma, Yasuko; Miura, Eri; Fujita, Takeshi; Hisatsune, Kunihiro

2007-01-01

The effects of alloying addition of a small amount of base metals (In, Sn, Fe, Zn) on color variations in Pd-free Au-Pt-based high noble dental alloys were investigated in terms of rectilinear and polar color coordinates. The ternary Au-Pt-X (X = In, Sn, Fe, Zn) and quaternary Au-Pt-In-Y (Y = Sn, Fe, Zn) alloys were prepared from high purity component metals. The amount of alloying base metals, X and Y, were restricted up to 2 at.%. The alloying addition of a small amount of Fe, In, Sn, to a binary Au-10 at.% Pt alloy (referred to as AP10) effectively increased chroma, C *. On the other hand, the addition of Zn to the parent alloy AP10 did not change color coordinates greatly. The increase in chroma in the present Au-Pt-based high noble alloys was attributed to the increase in the slope of spectral reflectance curve at its absorption edge near 515 nm. It was found that the addition of a small amount of Fe to the parent alloy AP10 markedly increased lightness, L *, and the addition of Sn gave a very light tint of red to the parent alloy. Although red-green chromaticity index a * contributed to chroma to some extent, contribution of yellow-blue chromaticity index b * was much greater in determining chroma in this Pd-free Au-Pt-based multi-component alloys. The present results are expected to be valuable in case color is to be taken into account in designing Pd-free Au-Pt-based high noble dental alloys

Variations of color with alloying elements in Pd-free Au-Pt-based high noble dental alloys

Energy Technology Data Exchange (ETDEWEB)

Shiraishi, Takanobu [Department of Dental and Biomedical Materials Science, Unit of Basic Medical Sciences, Graduate School of Biomedical Sciences, Nagasaki University, 1-7-1 Sakamoto, Nagasaki 852-8588 (Japan)]. E-mail: siraisi@nagasaki-u.ac.jp; Takuma, Yasuko [Department of Dental and Biomedical Materials Science, Unit of Basic Medical Sciences, Graduate School of Biomedical Sciences, Nagasaki University, 1-7-1 Sakamoto, Nagasaki 852-8588 (Japan); Miura, Eri [Department of Dental and Biomedical Materials Science, Unit of Basic Medical Sciences, Graduate School of Biomedical Sciences, Nagasaki University, 1-7-1 Sakamoto, Nagasaki 852-8588 (Japan); Fujita, Takeshi [Department of Dental and Biomedical Materials Science, Unit of Basic Medical Sciences, Graduate School of Biomedical Sciences, Nagasaki University, 1-7-1 Sakamoto, Nagasaki 852-8588 (Japan); Hisatsune, Kunihiro [Department of Dental and Biomedical Materials Science, Unit of Basic Medical Sciences, Graduate School of Biomedical Sciences, Nagasaki University, 1-7-1 Sakamoto, Nagasaki 852-8588 (Japan)

2007-06-15

The effects of alloying addition of a small amount of base metals (In, Sn, Fe, Zn) on color variations in Pd-free Au-Pt-based high noble dental alloys were investigated in terms of rectilinear and polar color coordinates. The ternary Au-Pt-X (X = In, Sn, Fe, Zn) and quaternary Au-Pt-In-Y (Y = Sn, Fe, Zn) alloys were prepared from high purity component metals. The amount of alloying base metals, X and Y, were restricted up to 2 at.%. The alloying addition of a small amount of Fe, In, Sn, to a binary Au-10 at.% Pt alloy (referred to as AP10) effectively increased chroma, C *. On the other hand, the addition of Zn to the parent alloy AP10 did not change color coordinates greatly. The increase in chroma in the present Au-Pt-based high noble alloys was attributed to the increase in the slope of spectral reflectance curve at its absorption edge near 515 nm. It was found that the addition of a small amount of Fe to the parent alloy AP10 markedly increased lightness, L *, and the addition of Sn gave a very light tint of red to the parent alloy. Although red-green chromaticity index a * contributed to chroma to some extent, contribution of yellow-blue chromaticity index b * was much greater in determining chroma in this Pd-free Au-Pt-based multi-component alloys. The present results are expected to be valuable in case color is to be taken into account in designing Pd-free Au-Pt-based high noble dental alloys.

Carbon supported Pd-Co-Mo alloy as an alternative to Pt for oxygen reduction in direct ethanol fuel cells

Energy Technology Data Exchange (ETDEWEB)

Rao, Ch. Venkateswara [National Centre for Catalysis Research, Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036, TN (India); Viswanathan, B., E-mail: bvnathan@acer.iitm.ernet.i [National Centre for Catalysis Research, Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036, TN (India)

2010-03-01

Carbon black (CDX975) supported Pd and Pd-Co-Mo alloy nanoparticles are prepared by the reduction of metal precursors with hydrazine in reverse microemulsion of water/Triton-X-100/propanol-2/cyclohexane. The as-synthesized Pd-Co-Mo/CDX975 is heat treated at 973, 1073 and 1173 K to promote alloy formation. The prepared materials are characterized by powder XRD and EDX. Face-centred cubic structure of Pd is evident from XRD. The chemical composition of the respective elements in the catalysts is evaluated from the EDX analysis and observed that it is in good agreement with initial metal precursor concentrations. Oxygen reduction measurements performed by linear sweep voltammetry indicate the good catalytic activity of Pd-Co-Mo alloys compared to Pd. This is due to the suppression of (hydr)oxy species on Pd surface by the presence of alloying elements, Co and Mo. Among the investigated catalysts, heat-treated Pd-Co-Mo/CDX975 at 973 K exhibited good ORR activity compared to the catalysts heat treated at 1073 and 1173 K. This is due to the small crystallite size and high surface area. Rotating disk electrode (RDE) measurements indicated the comparable ORR activity of heat-treated Pd-Co-Mo/CDX975 at 973 K with that of commercial Pt/C. Kinetic analysis reveals that the ORR on Pd-Co-Mo/CDX975 follows the four-electron pathway leading to water. Moreover, Pd-Co-Mo/CDX975 exhibited substantially higher ethanol tolerance during the ORR than Pt/C. Good dispersion of metallic nanoparticles on the carbon support is observed from HRTEM images. Single-cell direct ethanol fuel cell tests indicated the comparable performance of Pd-Co-Mo/CDX975 with that of commercial Pt/C. Stability under DEFC operating conditions for 50 h indicated the good stability of Pd-Co-Mo/CDX975 compared with that of Pt/C.

Fabrication of catalytically active Au/Pt/Pd trimetallic nanoparticles by rapid injection of NaBH4

International Nuclear Information System (INIS)

Zhang, Haijun; Lu, Lilin; Cao, Yingnan; Du, Shuang; Cheng, Zhong; Zhang, Shaowei

2014-01-01

Graphical abstract: The synthesis and characterization of 2.0 nm-diameter Au/Pt/Pd nanoparticles are reported. The catalytic activity for glucose oxidation of the nanoparticles is several times higher than that of Au nanoparticles with nearly same size. - Highlights: • PVP-protected Au/Pt/Pd trimetallic nanoparticles (TNPs) of 2.0 nm in diameter were prepared. • The catalytic activity of TNPs is several times higher than that of Au nanoparticles. • Negatively charged Au atoms in the TNPs were confirmed by DFT calculation. - Abstract: Au/Pt/Pd trimetallic nanoparticles (TNPs) with an alloyed structure and an average diameter of about 2.0 nm were prepared via reducing the corresponding ions with rapidly injected NaBH 4 , and characterized by UV–vis, TEM and HR-TEM. The catalytic activity of as-prepared TNPs for the aerobic glucose oxidation is several times higher than that of Au monometallic nanoparticles with about the same average size, which could be attributed to the catalytically active sites provided by the negatively charged Au atoms as a result of the electron donation from the neighboring Pd atoms. This was well supported by the electron density calculations based on the density functional theory

Adsorption of HCN molecules on Ni, Pd and Pt-doped (7, 0) boron nitride nanotube: a DFT study

Science.gov (United States)

Habibi-Yangjeh, Aziz; Basharnavaz, Hadi

2018-05-01

We studied affinity of pure and Ni, Pd and Pt-doped (7, 0) boron nitride nanotubes (BNNTs) to toxic HCN molecules using density functional theory calculations. The results indicated that the pure (7, 0) BNNTs can weakly adsorb HCN molecules with adsorption energy of -0.2474 eV. Upon adsorption of HCN molecules on this nanotube, the band gap energy was decreased from 3.320 to 2.960 eV. The more negative adsorption energy between these transition metal-doped (7, 0) BNNTs and HCN molecules indicated that doping of (7, 0) BNNTs with Ni, Pd and Pt elements can significantly improve the affinity of BNNTs toward this gas. Additionally, it was found that the interaction energy between HCN molecules and Pt-doped BNNTs is more negative than those of the Ni and Pd-doped BNNTs. These observations suggested that the Pt-doped (7, 0) BNNTs are strongly sensitive to HCN molecules and therefore it may be used in gas sensor devices for detecting this toxic gas.

Understanding of the structure activity relationship of PtPd bimetallic catalysts prepared by surface organometallic chemistry and ion exchange during the reaction of iso-butane with hydrogen

KAUST Repository

Al-Shareef, Reem A.; Harb, Moussab; Saih, Youssef; Ould-Chikh, Samy; Roldan, Manuel A.; Anjum, Dalaver H.; Guyonnet, Elodie Bile; Candy, Jean-Pierre; Jan, Deng-Yang; Abdo, Suheil F.; Aguilar-Tapia, Antonio; Proux, Olivier; Hazemann, Jean-Louis; Basset, Jean-Marie

2018-01-01

Well-defined silica supported bimetallic catalysts Pt100-x Pdx were prepared by Surface Organometallic Chemistry (SOMC) and Ionic-Exchange (IE) methods. For all investigated catalysts, iso-butane reaction with hydrogen under differential conditions led to the formation of methane and propane, n-butane, and traces of iso-butylene. The total reaction rate decreased with increasing the Pd loading for both catalysts series as a result of decreasing turnover rate of both isomerization and hydrogenolysis. In the case of Pt100-x Pdx(SOMC) catalysts, the experimental results in combination with DFT calculations suggested a selective coverage of Pt (1 0 0) surface by agglomerated Pd atoms like “islands”, assuming that each metal roughly keeps its intrinsic catalytic properties with relatively small electron transfer from Pt to Pd in the case of Pt-rich sample and from Pd to Pt in the case of Pd-rich sample. For the PtPd catalysts prepared by IE, the catalytic behavior could be explained by the formation of a surface alloy between Pt and Pd in the case of Pd-rich sample and by the segregation of a small amount of Pd on the surface in the case of Pt-rich sample, as demonstrated by TEM, EXAFS and DFT. The catalytic results were explained by a structure activity relationship based on the proposed mechanism of CH bond and CC bond activation and cleavage for iso-butane hydrogenolysis, isomerization, cracking and dehydrogenation.

Understanding of the structure activity relationship of PtPd bimetallic catalysts prepared by surface organometallic chemistry and ion exchange during the reaction of iso-butane with hydrogen

KAUST Repository

Alshareef, Reem Abdul aziz Hamed

2018-04-25

Well-defined silica supported bimetallic catalysts Pt100-x Pdx were prepared by Surface Organometallic Chemistry (SOMC) and Ionic-Exchange (IE) methods. For all investigated catalysts, iso-butane reaction with hydrogen under differential conditions led to the formation of methane and propane, n-butane, and traces of iso-butylene. The total reaction rate decreased with increasing the Pd loading for both catalysts series as a result of decreasing turnover rate of both isomerization and hydrogenolysis. In the case of Pt100-x Pdx(SOMC) catalysts, the experimental results in combination with DFT calculations suggested a selective coverage of Pt (1 0 0) surface by agglomerated Pd atoms like “islands”, assuming that each metal roughly keeps its intrinsic catalytic properties with relatively small electron transfer from Pt to Pd in the case of Pt-rich sample and from Pd to Pt in the case of Pd-rich sample. For the PtPd catalysts prepared by IE, the catalytic behavior could be explained by the formation of a surface alloy between Pt and Pd in the case of Pd-rich sample and by the segregation of a small amount of Pd on the surface in the case of Pt-rich sample, as demonstrated by TEM, EXAFS and DFT. The catalytic results were explained by a structure activity relationship based on the proposed mechanism of CH bond and CC bond activation and cleavage for iso-butane hydrogenolysis, isomerization, cracking and dehydrogenation.

A dual-type responsive electrochemical immunosensor for quantitative detection of PCSK9 based on n-C60-PdPt/N-GNRs and Pt-poly (methylene blue) nanocomposites.

Science.gov (United States)

Li, Yan; He, Junlin; Chen, Jun; Niu, Yazhen; Zhao, Yilin; Zhang, Yuchan; Yu, Chao

2018-03-15

In this study, a dual-type responsive electrochemical immunosensor was developed for the quantitative detection of proprotein convertase subtilisin/kexin type 9 (PCSK9), a potential biomarker of cardiovascular disease in serum. N-doped graphene nanoribbons (N-GNRs) with good conductivity were used as the sensing matrix modifying the glassy carbon electrode. Palladium platinum alloy (PdPt) nanoparticles with high catalytic performance toward the reduction of hydrogen peroxide (H 2 O 2 ) were reduced onto amino-functionalized fullerene (n-C 60 -PdPt) and significantly amplified the electrochemical signal recorded by the amperometric i-t curve. Furthermore, staphylococcus protein A (SPA) with antibody orientation function was introduced to improve the immunoreaction efficiency. Accordingly, a label-free immunosensor was fabricated based on n-C 60 -PdPt/N-GNRs for the quick detection of PCSK9. Meanwhile, to realize ultrasensitive detection of PCSK9, Pt-poly (methylene blue) (Pt-PMB) nanocomposites synthesized by a one-pot method for the first time were used as a novel signal label, which exhibited uniform morphology as well as good conductivity and produced an electrochemical signal recorded by differential pulse voltammetry (DPV). Herein, a novel sandwich-type immunosensor was designed using n-C 60 -PdPt/N-GNRs as the sensing matrix and Pt-PMB as the signal label for sensitive detection of PCSK9. Under optimal conditions, the label-free immunosensor showed a linear range of 10pgmL -1 to 100ngmL -1 with a detection limit of 3.33pgmL -1 (S/N=3), and the sandwich-type immunosensor exhibited a linear range of 100 fg mL -1 to 100ngmL -1 with a detection limit of 0.033pgmL -1 (S/N=3) for PCSK9 detection, indicating its potential application in clinical bioassay analysis. Copyright © 2017 Elsevier B.V. All rights reserved.

Accumulation of platinum group elements by the marine gastropod Littorina littorea

Energy Technology Data Exchange (ETDEWEB)

Mulholland, Rachel [School of Geography, Earth and Environmental Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA (United Kingdom); Turner, Andrew, E-mail: aturner@plymouth.ac.uk [School of Geography, Earth and Environmental Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA (United Kingdom)

2011-04-15

The accumulation and trophic transfer of the platinum group elements (PGE): Rh, Pd and Pt; have been studied in short-term (5 day) exposures conducted in aquaria containing the marine macroalga, Ulva lactuca, and/or the grazing mollusc, Littorina littorea. Metals added to sea water (to concentrations of 20 {mu}g L{sup -1}) were taken up by U. lactuca in the order Rh, Pt > Pd and by L. littorea in the order Pd {>=} Pt {>=} Rh, with greatest metal accumulation in the latter generally occurring in the visceral complex and kidney. When fed contaminated alga, accumulation of Rh and Pd by L. littorea, relative to total available metal, increased by an order of magnitude, while accumulation of Pt was not readily detected. We conclude that the diet is the most important vector for accumulation of Rh and Pd, while accumulation of Pt appears to proceed mainly from the aqueous phase. - Research highlights: > Platinum group elements are accumulated by, Littorina littorea. > The aqueous phase and diet are important vehicles for Rh and Pd accumulation by the snail. > Grazing molluscs may serve as biomonitors of coastal PGE contamination. - Platinum group elements are accumulated by the marine snail, Littorina littorea, from both the aqueous phase and the diet.

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.

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.

Crystal structure and physical properties of new Ca{sub 2}TGe{sub 3} (T = Pd and Pt) germanides

Energy Technology Data Exchange (ETDEWEB)

Klimczuk, T., E-mail: tomasz.klimczuk@pg.gda.pl [Faculty of Applied Physics and Mathematics, Gdansk University of Technology, Narutowicza 11/12, 80–233 Gdansk (Poland); Xie, Weiwei [Department of Chemistry, Princeton University, Princeton, NJ 08544 (United States); Winiarski, M.J.; Kozioł, R.; Litzbarski, L.S. [Faculty of Applied Physics and Mathematics, Gdansk University of Technology, Narutowicza 11/12, 80–233 Gdansk (Poland); Luo, Huixia; Cava, R.J. [Department of Chemistry, Princeton University, Princeton, NJ 08544 (United States)

2016-11-15

The crystallographic, electronic transport and thermal properties of Ca{sub 2}PdGe{sub 3} and Ca{sub 2}PtGe{sub 3} are reported. The compounds crystalize in an ordered variant of the AlB{sub 2} crystal structure, in space group P6/mmm, with the lattice parameters a = 8.4876(4) Å/8.4503(5) Å and c = 4.1911(3) Å/4.2302(3) Å for Ca{sub 2}PdGe{sub 3} and Ca{sub 2}PtGe{sub 3}, respectively. The resistivity data exhibit metallic behavior with residual-resistivity-ratios (RRR) of 13 for Ca{sub 2}PdGe{sub 3} and 6.5 for Ca{sub 2}PtGe{sub 3}. No superconducting transition is observed down to 0.4 K. Specific heat studies reveal similar values of the Debye temperatures and Sommerfeld coefficients: Θ{sub D} = 298 K, γ = 4.1 mJ mol{sup −1} K{sup −2} and Θ{sub D} = 305 K, γ = 3.2 mJ mol{sup −1} K{sup −2} for Ca{sub 2}PdGe{sub 3} and Ca{sub 2}PtGe{sub 3}, respectively. The low value of γ is in agreement with the electronic structure calculations.

Fabrication of catalytically active Au/Pt/Pd trimetallic nanoparticles by rapid injection of NaBH{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Zhang, Haijun, E-mail: zhanghaijun@wust.edu.cn [College of Materials and Metallurgy, Wuhan University of Science and Technology, Wuhan, Hubei Province 430081 (China); State Key Laboratory Breeding Base of Refractories and Ceramics, Wuhan University of Science and Technology, Wuhan 430081 (China); Lu, Lilin [College of Chemical Engineering and Technology, Wuhan University of Science and Technology, Wuhan 430081 (China); Cao, Yingnan; Du, Shuang [College of Materials and Metallurgy, Wuhan University of Science and Technology, Wuhan, Hubei Province 430081 (China); State Key Laboratory Breeding Base of Refractories and Ceramics, Wuhan University of Science and Technology, Wuhan 430081 (China); Cheng, Zhong [College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072 (China); Zhang, Shaowei [State Key Laboratory Breeding Base of Refractories and Ceramics, Wuhan University of Science and Technology, Wuhan 430081 (China)

2014-01-01

Graphical abstract: The synthesis and characterization of 2.0 nm-diameter Au/Pt/Pd nanoparticles are reported. The catalytic activity for glucose oxidation of the nanoparticles is several times higher than that of Au nanoparticles with nearly same size. - Highlights: • PVP-protected Au/Pt/Pd trimetallic nanoparticles (TNPs) of 2.0 nm in diameter were prepared. • The catalytic activity of TNPs is several times higher than that of Au nanoparticles. • Negatively charged Au atoms in the TNPs were confirmed by DFT calculation. - Abstract: Au/Pt/Pd trimetallic nanoparticles (TNPs) with an alloyed structure and an average diameter of about 2.0 nm were prepared via reducing the corresponding ions with rapidly injected NaBH{sub 4}, and characterized by UV–vis, TEM and HR-TEM. The catalytic activity of as-prepared TNPs for the aerobic glucose oxidation is several times higher than that of Au monometallic nanoparticles with about the same average size, which could be attributed to the catalytically active sites provided by the negatively charged Au atoms as a result of the electron donation from the neighboring Pd atoms. This was well supported by the electron density calculations based on the density functional theory.

Toxicity of platinum, palladium and rhodium to Daphnia magna in single and binary metal exposure experiments.

Science.gov (United States)

Zimmermann, Sonja; Wolff, Carolina; Sures, Bernd

2017-05-01

Mainly due to automobile traffic, but also due to other sources, the platinum group elements (PGE) platinum (Pt), palladium (Pd) and rhodium (Rh) are introduced into aquatic biotopes where they accumulate in sediments of lakes and rivers. However, the toxicity of these noble metals to aquatic organisms is not well understood and especially toxicity studies under standardized condition are lacking. Thus, the toxicity of Pt, Pd and Rh to Daphnia magna was tested in single metal exposure experiments according to OECD guideline 202. Immobility and lethality was recorded after 24 h and 48 h of exposure and EC 50 and LC 50 , respectively, were determined. As the nominal exposure concentration of Pd differed significantly from the quantified concentration, the control of the real exposure concentration by chemical analysis is mandatory, especially for Pd. The toxicity decreased in the order Pd > Pt ≫ Rh with e.g. LC 50 (48 h) values of 14 μg/L for Pd, 157 μg/L for Pt and 56,800 μg/L for Rh. The exposure period had a clear effect on the toxicity of Pt, Pd and Rh. For Pt and Rh the endpoint immobility was more sensitive than the endpoint lethality whereas Pd toxicity was similar for both endpoints. The Hill slopes, which are a measure for the steepness of the concentration-response curves, showed no significant discrepancies between the different metals. The binary metal exposure to Pt and Pd revealed a more-than-additive, i.e. a synergistic toxicity using the toxic unit approach. The present study is a start to understand the toxicity of interacting PGE. The modes of action behind the synergistic effect are unclear. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of Ce on performance and physicochemical properties of Pt-containing automotive emission control catalysts

International Nuclear Information System (INIS)

Nunan, J.G.; Silver, R.G.; Bradley, S.A.

1992-01-01

Present-day automotive emission control catalysts contain noble metals such as Pt, Pd and Rh all on an alumina support with a variety of promoters. Ce is one of the most important promoters. In this paper, the interaction between Pt and Ce is studied using TPR and STEM on a variety of catalysts. The degree of Pt/Ce interaction is increased by decreasing CeO 2 crystallite size, and to a lesser extent by increasing CeO 2 loading. Direct Pt/Ce interaction leads to a synergistic reduction of both Pt and surface Ce. This reduction qualitatively correlates with catalyst performance after activation in a reducing gas. It is proposed that this synergistic reduction of Pt and Ce is associated with observed improvements in catalyst performance using a non-oscillating exhaust gas

The Effect of Surface Site Ensembles on the Activity and Selectivity of Ethanol Electrooxidation by Octahedral PtNiRh Nanoparticles.

Science.gov (United States)

Erini, Nina; Beermann, Vera; Gocyla, Martin; Gliech, Manuel; Heggen, Marc; Dunin-Borkowski, Rafal E; Strasser, Peter

2017-06-01

Direct ethanol fuel cells are attractive power sources based on a biorenewable, high energy-density fuel. Their efficiency is limited by the lack of active anode materials which catalyze the breaking of the C-C bond coupled to the 12-electron oxidation to CO 2 . We report shape-controlled PtNiRh octahedral ethanol oxidation electrocatalysts with excellent activity and previously unachieved low onset potentials as low as 0.1 V vs. RHE, while being highly selective to complete oxidation to CO 2 . Our comprehensive characterization and in situ electrochemical ATR studies suggest that the formation of a ternary surface site ensemble around the octahedral Pt 3 Ni 1 Rh x nanoparticles plays a crucial mechanistic role for this behavior. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Solvent-free Hydrodeoxygenation of Bio-oil Model Compounds Cyclopentanone and Acetophenone over Flame-made Bimetallic Pt-Pd/ZrO2 Catalysts

Science.gov (United States)

Jiang, Yijiao; Büchel, Robert; Huang, Jun; Krumeich, Frank; Pratsinis, Sotiris E.; Baiker, Alfons

2013-01-01

Bimetallic Pt-Pd/ZrO2 catalysts with different Pt/Pd atomic ratio and homogeneous dispersion of the metal nanoparticles were prepared in a single step by flame-spray pyrolysis. The catalysts show high activity and tuneable product selectivity for the solvent-free hydrodeoxygenation of the bio-oil model compounds cyclopentanone and acetophenone. PMID:22674738

O{sub 2} adsorption and dissociation on the Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and 13) tri-metallic nanoparticles: A DFT study

Energy Technology Data Exchange (ETDEWEB)

Li, Sha; Yang, Yongpeng; Huang, Shiping, E-mail: huangsp@mail.buct.edu.cn

2017-07-15

Highlights: • O{sub 2} adsorption and dissociation on Pd{sub 13-n}Ni{sub n}@Pt{sub 42} NPs are performed by DFT. • Adsorption energies of O{sub 2} and O are strongly affected by the coordination number. • Adsorption energy and d-band center displays the opposite change tendency. • Ni{sub 13}@Pt{sub 42} is the most active catalyst among Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and 13) NPs. - Abstract: Density functional theory calculations are performed to investigate O{sub 2} adsorption and dissociation on the icosahedral Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and 13) tri-metallic nanoparticles. The parallel adsorption of O{sub 2} on Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and 13) is stronger than the vertical adsorption. The adsorption of O{sub 2} on the bridge site (B1) is favorable in the Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and 13) nanoparticles, while the adsorption of O atom on the hollow site (H1) is preferred. The adsorption energies of O{sub 2} and O are strongly affected by the coordination number. Low coordination site shows strong adsorption of O{sub 2} and O on the Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and 13) nanoparticles. The adsorption energies of O{sub 2} and O atoms are found to be correlated well with the d-band center of surface Pt. For the Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and13) nanoparticles catalysts, the ORR activity follows the order of Ni{sub 13}@Pt{sub 42} > Pd{sub 13}@Pt{sub 42} > Pd{sub 12}Ni{sub 1}@Pt{sub 42} > Pd{sub 1}Ni{sub 12}@Pt{sub 42}, illustrating that the Ni{sub 13}@Pt{sub 42} is the strongest ORR activity among the Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and13) nanoparticles catalysts. Our results have important significance to understand the mechanism of O{sub 2} dissociation on the Pd{sub 13-n}Ni{sub n}@Pt{sub 42} (n = 0, 1, 12, and 13) tri-metallic nanoparticles.

Porous platinum nanoparticles and PdPt nanocages for use in an ultrasensitive immunoelectrode for the simultaneous determination of the tumor markers CEA and AFP

International Nuclear Information System (INIS)

Liu, Na; Feng, Feng; Liu, Zhimin; Ma, Zhanfang

2015-01-01

We describe the use of porous platinum nanoparticles (pPt NPs) and PdPt nanocages (PdPt NCs) in an electrochemical immunoassay for two tumor markers (CEA and AFP) directly in serum and with enhanced detection performance. The pPt NPs possess a high specific surface area and electrical conductivity, while the PdPt NCs display excellent catalytic property and high loading capacity. The PdPt NCs were labeled with anti-CEA and thionine, and the PdPt NCs were labeled with anti-AFP and ferrocene. The resulting electrode displayed a large decrease of the anodic peak current and an increase of cathodic peak current for hydrogen peroxide (H 2 O 2 ). The dual square wave voltammetric immunoassay was performed at −0.1 V (for CEA) and +0.6 V (for AFP) after exposure to a sample containing CEA and AFP and in the presence of H 2 O 2 . CEA can be detected in the 0.05 to 200 ng mL −1 concentration range and AFP between 0.03 and 100 ng mL −1 . The limits of detection are 1.4 pg mL −1 for CEA and 1 pg mL −1 for AFP (at an SNR of 3). The sensitivity of the method (expressed as slope vs. concentration) is better by a factor of 4.6 to 100 compared to conventional electrochemical immunoassays. Analytical data obtained with diluted serum samples were in good agreement with reference values obtained via a standard ELISA. Negligible cross-reactivity is found between CEA and AFP. In our opinion, this approach paves the way for developing other kinds of electrochemical immunosensors based on the use of pPt NPs and PdPt NCs as materials for designing new electrode interfaces. (author)

Ion flotation of rhodium(III) and palladium(II) with anionic surfactants.

Science.gov (United States)

He, X C

1991-03-01

The ion flotation of rhodium(III) and palladium(II) with some anionic surfactants has been investigated. Two flotation procedures are proposed for the separation of some platinum metals, based on differences in the kinetic properties of the chloro-complexes of rhodium(III), palladium(II) and platinum(IV). The first involves the selective flotation of Rh(H(2)O)(3+)(6) from PdCl(2-)(4) and PtCl(2-)(6) in dilute hydrochloric acid with sodium dodecylbenzenesulfonate (SDBS). After precipitation of the hydroxide and redissolution in dilute acid, the Rh(III) is converted into Rh(H(2)O)(3+)(6), Pd(II) and Pt(IV) remaining as PdCl(2-)(4) and PtCl(2-)(6) respectively, and separation is achieved by floating the Rh(H(2)O)(3+)(6) with SDBS. The second is for separation of Pd(II). Prior to flotation, the solution of PdCl(2-)(4) and PtCl(2-)(6) is heated with ammonium acetate to convert PdCl(2-)(4) into Pd(NH(3))(2+)(4). The chloro-complex of Pt(IV) is unaffected. The complex cation, Pd(NH(3))(2+)(4), is then selectively floated with SDBS. The procedures are fast, simple and do not require expensive reagents and apparatus.

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.

2018-01-01

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 32.17 nm for Pt@Ag and 8.8 nm 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.

Geometric structures of thin film: Pt on Pd(110) and NiO on Ni(100)

Energy Technology Data Exchange (ETDEWEB)

Warren, Oden L. [Iowa State Univ., Ames, IA (United States)

1993-07-01

This thesis is divided into 3 papers: dynamical low-energy electron- diffraction investigation of lateral displacements in topmost layer of Pd(110); determination of (1x1) and (1x2) structures of Pt thin films on Pd(110) by dynamical low-energy electron-diffraction analysis; and structural determination of a NiO(111) film on Ni(100) by dynamical low-energy electron-diffraction analysis.

The Study on the Performance of Carbon Supported PtSnM (M = W, Pd, and Ni) Ternary Electro-Catalysts for Ethanol Electro-Oxidation Reaction.

Science.gov (United States)

Noh, Chang Soo; Heo, Dong Hyun; Lee, Ki Rak; Jeon, Min Ku; Sohn, Jung Min

2016-05-01

PtSn/C and Pt5Sn4M/C (M = W, Pd, Ni) electrocatalysts were prepared by impregnation method using NaBH4 as a reducing agent. Chemical composition, crystalline size, and alloy formation were determined by EDX, XRD and TEM. The average particle sizes of the synthesized catalysts were approximately 3.64-4.95 nm. The electro-chemical properties were measured by CO stripping, cyclic voltammetry, linear sweep voltammetry, and chronoamperometry. The maximum specific activity of the electro-catalysts for ethanol electro-oxidation was 406.08 mA m(-2) in Pt5Sn4Pd/C. The poisoning rate of the Pt5Sn4Pd/C (0.0017% s(-1)) was 4.5 times lower than that of the PtSn/C (0.0076% s(-1)).

NO reduction by CO over noble-metal catalysts under cycled feedstreams

International Nuclear Information System (INIS)

Muraki, H.; Fujitani, Y.

1986-01-01

The reduction of NO with CO was studied over α-Al/sub 2/O/sub 3/-supported Pt, Pd, Rh, Ru, and Ir catalysts. The activities were measured by using cycled feeds and steady noncycled feed. The activity sequence of the catalysts tested was Rh > Ru > Ir > Pd > Pt. The activities of Pt and Pd catalysts were increased under the cycled feed. The periodic operation effect on the Pt catalyst was more predominant than that on the Pd catalyst. The order of periodic operation effect corresponded to the order of their susceptibility to CO self-poisoning

DNA-Binding Studies of Some Potential Antitumor 2,2'-bipyridine Pt(II)/Pd(II) Complexes of piperidinedithiocarbamate. Their Synthesis, Spectroscopy and Cytotoxicity.

Science.gov (United States)

Mansouri-Torshizi, Hassan; Eslami-Moghadam, Mahboube; Divsalar, Adeleh; Saboury, Ali-Akbar

2011-12-01

In this study two platinum(II) and palladium(II) complexes of the type [M(bpy)(pip-dtc)]NO3 (where M=Pt(II) or Pd(II), bpy=2,2'-bipyridine, pip-dtc=piperidinedithiocarbamate) were synthesized by reaction between diaquo-2,2'-bipyridine Pt(II)/Pd(II) nitrate and sodium salt of dithiocarbamate. These cationic water soluble complexes were characterized by elemental analysis, molar conductance, IR, electronic and 1H NMR spectroscopic studies. The cyclic dithiocarbamate was found to coordinate as bidentate fasion with Pt(II) or Pd(II) center. Their biological activities were tested against chronic myelogenous leukemia cell line, K562, at micromolar concentration. The obtained cytotoxic concentration (IC50) values were much lower than cisplatin. The interaction of these complexes with highly polymerized calf thymus DNA (ct-DNA) was extensively studied by means of electronic absorption, fluorescence, circular dichroism and other measurements. The experimental results, thermodynamic and binding parameters, suggested that these complexes cooperatively bind to DNA presumably via intercalation. Moreover, the tendency of the Pt(II) complex to interact with DNA was more than that of Pd(II) complex.

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

International Nuclear Information System (INIS)

Mao, Han; Huang, Tao; Yu, Aishui

2016-01-01

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"−"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.

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.

Electrochemical oxidation of ethanol using PtRh/C electrocatalysts in alkaline medium and synthesized by sodium borohydride and alcohol reduction; Oxidação eletroquímica do etanol utilizando eletrocatalisadores PtRh/C em meio alcalino e sintetizados via borohidreto de sódio e redução por álcool

Energy Technology Data Exchange (ETDEWEB)

Fontes, Eric Hossein

2017-07-01

PtRh/C were prepared by the following atomic proportions: (100,0), (0,100), (90,10), (70,30) and (50,50). The methods employed in the synthesis of these materials were reduction by sodium borohydride and reduction by alcohol. The metal salts used were H{sub 2}PtCl{sub 6}3•6H{sub 2}0 and (RhNO{sub 3}){sub 3}, the support used was Carbon black XC72 and the bulk metal composition was 20% and 80% of support. The electrocatalysts were characterized by Energy Dispersive X-ray spectroscopy, X-ray diffraction and Transmission electron microscopy. The ethanol electrochemical oxidation mechanism was investigated by in situ Fourier Transform Infrared Spectroscopy couple to an Attenuated Total Reflection technique. The electrocatalytic activity were evaluated by Cyclic Voltammetry, Linear Sweep Voltammetry and Chronoamperometry techniques. The Fuel Cells tests were made in a single direct alcohol fuel cell with alkaline membrane. The working electrodes were prepared by a thin porous coating technique. X-ray diffraction allowed to verify metallic alloys, segregate phases and to calculate the percentage of metallic alloys. It was else possible to identify crystallographic phases. Infrared Spectroscopy allowed to verify that the electrochemical oxidation of ethanol was carried out by an incomplete mechanism. PtRh(70:30)/C prepared by sodium borohydride produced large amounts of carbon dioxide and acetaldehyde. Rh/C showed electrocatalytic activity when compared with other materials studied.

Fluid inclusion and oxygen-isotope evidence for low-temperature Au-Pt-Pd (± U) mineralization at Corronation Hill, NT

International Nuclear Information System (INIS)

Mernagh, T.

1992-01-01

The fluid inclusion and isotope data have been used to constrain the ore genesis models for the Au-Pt-Pd-U mineralization at Coronation Hill. The fluid inclusions demonstrate that the ore fluid was strongly saline with an unusually high CaCl 2 content, and that the mineralisation was probably formed from a boiling fluid at around 140 deg C. Furthermore, the fluids were highly oxidised and the replacement of earlier chlorite by hematite is common throughout the deposit. It is concluded that both U-rich and U-poor Au-Pt-Pd mineralisation were formed by descending, low-temperature, highly oxidised, very saline, meteoric fluids. The segregation of U was controlled by fluid-rock interaction in the feldspathic or carbonate rocks. Interaction with carbonaceous or chloritic rocks resulted in a reduction in fO 2 , and consequent precipitation of U, Au, Pt and Pd. The other two types of metal associations can be explained by further reaction of the mineralizing fluids. 3 figs

Atomic layer deposition of Pd and Pt nanoparticles for catalysis: on the mechanisms of nanoparticle formation

International Nuclear Information System (INIS)

Mackus, Adriaan J M; Weber, Matthieu J; Thissen, Nick F W; Garcia-Alonso, Diana; Vervuurt, René H J; Assali, Simone; Bol, Ageeth A; Verheijen, Marcel A; Kessels, Wilhelmus M M

2016-01-01

The deposition of Pd and Pt nanoparticles by atomic layer deposition (ALD) has been studied extensively in recent years for the synthesis of nanoparticles for catalysis. For these applications, it is essential to synthesize nanoparticles with well-defined sizes and a high density on large-surface-area supports. Although the potential of ALD for synthesizing active nanocatalysts for various chemical reactions has been demonstrated, insight into how to control the nanoparticle properties (i.e. size, composition) by choosing suitable processing conditions is lacking. Furthermore, there is little understanding of the reaction mechanisms during the nucleation stage of metal ALD. In this work, nanoparticles synthesized with four different ALD processes (two for Pd and two for Pt) were extensively studied by transmission electron spectroscopy. Using these datasets as a starting point, the growth characteristics and reaction mechanisms of Pd and Pt ALD relevant for the synthesis of nanoparticles are discussed. The results reveal that ALD allows for the preparation of particles with control of the particle size, although it is also shown that the particle size distribution is strongly dependent on the processing conditions. Moreover, this paper discusses the opportunities and limitations of the use of ALD in the synthesis of nanocatalysts. (paper)

Impact of humic substances on the aqueous solubility, uptake and bioaccumulation of platinum, palladium and rhodium in exposure studies with Dreissena polymorpha

International Nuclear Information System (INIS)

Sures, Bernd; Zimmermann, Sonja

2007-01-01

Zebra mussels (Dreissena polymorpha) were exposed to different types of water containing PGE salts (PtCl 4 , PdSO 4 , RhCl 3 ) to investigate the influence of humic substances on the aqueous solubility, uptake and bioaccumulation of noble metals. The results showed a time dependent decrease of the aqueous PGE concentrations in tank water for all groups. This could mainly be related to non-biological processes. The aqueous solubility of Pd and Rh was higher in humic water compared with non-chlorinated tap water, whereas Pt showed opposing results. Highest metal uptake rates and highest bioaccumulation plateaus were found for Pd, followed by Pt and Rh. Pd uptake and bioaccumulation was significantly hampered by humic substances, whose presence appear to increase Pt uptake and bioaccumulation. No clear trend emerged for Rh. Differences in effects of humic matter among the PGE may be explained by formation of metal complexes with different fractions of humic substances. - Precious metal accumulation in Dreissena polymorpha is affected by humic substances

Atomistic simulations of the structures of Pd-Pt bimetallic nanoparticles and nanowires

OpenAIRE

Yun, Kayoung; Cha, Pil-Ryung; Lee, Jaegab; Kim, Jiyoung; Nam, Ho-Seok

2015-01-01

Bimetallic nanoalloys such as nanoparticles and nanowires are attracting significant attention due to their vast potential applications such as in catalysis and nanoelectronics. Notably, Pd-Pt nanoparticles/nanowires are being widely recognized as catalysts and hydrogen sensors. Compared to unary systems, alloys present more structural complexity with various compositional configurations. Therefore, it is important to understand energetically preferred atomic structures of bimetallic nanoallo...

Pt-Rh/g Al2O3 Influence of Catalyst Preparation Methods on Metallic Particle Dispersion and Size Distribution

Directory of Open Access Journals (Sweden)

N.M. da Fonseca

1998-06-01

Full Text Available - Pt-Rh/Al2O3 catalysts were prepared by successive incipient impregnations or coimpregnation. Characterization was achieved by H2 chemisorption and transmission electron microscopy. It was verified that method of preparation, ratio of metal weights and sequence of deposition are factors that result in very distinct catalysts.

Absolute calibration of the Rh-103(n,n')Rh-103m reaction rate

International Nuclear Information System (INIS)

Taylor, W.H.; Murphy, M.F.; March, M.R.

1979-05-01

The uncertainties in determining the absolute values of the Rh-103(n, n') Rh-103m reaction rate (which is widely used as a neutron damage flux monitor) have been reduced to approximately +-5%. This has been achieved with the use of a calibrated source of Pd-103-Rh-103m activity supplied by the IAEA. Agreement to within 3% between measured and calculated values of the reaction rate (normalised to the U-238 fission rate) has been achieved. (author)

Isolation and X-ray structures of four Rh(PCP) complexes including a Rh(I) dioxygen complex with a short O-O bond

KAUST Repository

Hayashi, Yukiko

2013-07-01

The reaction of RhCl3·H2O with tBu2P(CH2)5PtBu 2 afforded several complexes including [RhIII(H)Cl{ tBu2- P(CH2)2CH(CH2) 2PtBu2}] (1), [RhIIIHCl 2{tBu2P(CH2)5P tBu2}]2 (2), [RhICl{ tBu2P(CH2)2CH=CHCH2P tBu2}] (3) and [RhICl{tBu 2PCH2C(O)CH=CHCH2PtBu2}] (4). X-ray crystal structures of 3 and 4 showed that the C=C bond on the C 5 unit of tBu2P(CH2) 5PtBu2 is bound to Rh(I) in a η2 configuration. In 4, the Rh atom has a trigonal pyramidal coordination geometry. The X-ray crystal structure of 2 consists of two rhodium( III) centers bridged by two tBu2P(CH2)5P tBu2 ligands with two phosphorus atoms, one from each ligand, trans to one another. The crystal structure of the rhodium oxygen adduct with 1,3-bis(di-t-butylphosphinomethyl) benzene [RhO2{ tBu2PCH2(C6H3)CH 2PtBu2}] (5) was also investigated. In this species the O2 is η2 coordinated to the Rh(I) center with asymmetric Rh-O bond lengths (2.087(7) and 1.998(8) Å). The O-O bond distance is short (1.337(11) Å) with νO-O of 990.5 cm -1. DFT calculations on complex 5 yielded two η2- O2 structures that differed in energy by only 0.76 kcal/mol. The lower energy one (5a) had near C2 symmetry, and had nearly equal Rh-O bond lengths, while the higher energy structure (5b) had near Cs symmetry and generally good agreement with the experimental structure. The calculated UV-Vis and IR spectra of complex 5 are in excellent agreement with experiment. © 2012 Elsevier Ltd. All rights reserved.

Isolation and X-ray structures of four Rh(PCP) complexes including a Rh(I) dioxygen complex with a short O-O bond

KAUST Repository

Hayashi, Yukiko; Szalda, David J.; Grills, David C.; Hanson, Jonathan C.; Huang, Kuo-Wei; Muckerman, James T.; Fujita, Etsuko

2013-01-01

The reaction of RhCl3·H2O with tBu2P(CH2)5PtBu 2 afforded several complexes including [RhIII(H)Cl{ tBu2- P(CH2)2CH(CH2) 2PtBu2}] (1), [RhIIIHCl 2{tBu2P(CH2)5P tBu2}]2 (2), [RhICl{ tBu2P(CH2)2CH=CHCH2P tBu2}] (3) and [RhICl{tBu 2PCH2C(O)CH=CHCH2PtBu2}] (4). X-ray crystal structures of 3 and 4 showed that the C=C bond on the C 5 unit of tBu2P(CH2) 5PtBu2 is bound to Rh(I) in a η2 configuration. In 4, the Rh atom has a trigonal pyramidal coordination geometry. The X-ray crystal structure of 2 consists of two rhodium( III) centers bridged by two tBu2P(CH2)5P tBu2 ligands with two phosphorus atoms, one from each ligand, trans to one another. The crystal structure of the rhodium oxygen adduct with 1,3-bis(di-t-butylphosphinomethyl) benzene [RhO2{ tBu2PCH2(C6H3)CH 2PtBu2}] (5) was also investigated. In this species the O2 is η2 coordinated to the Rh(I) center with asymmetric Rh-O bond lengths (2.087(7) and 1.998(8) Å). The O-O bond distance is short (1.337(11) Å) with νO-O of 990.5 cm -1. DFT calculations on complex 5 yielded two η2- O2 structures that differed in energy by only 0.76 kcal/mol. The lower energy one (5a) had near C2 symmetry, and had nearly equal Rh-O bond lengths, while the higher energy structure (5b) had near Cs symmetry and generally good agreement with the experimental structure. The calculated UV-Vis and IR spectra of complex 5 are in excellent agreement with experiment. © 2012 Elsevier Ltd. All rights reserved.

Practical chemical analysis of Pt and Pd based heterogeneous catalysts with hard X-ray photoelectron spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Yoshikawa, H., E-mail: YOSHIKAWA.Hideki@nims.go.jp [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Matolínová, I.; Matolín, V. [Charles University in Prague, Faculty of Mathematics and Physics, V Holešovičkách 2, 18000 Prague 8 (Czech Republic)

2013-10-15

Highlights: •Hard X-ray photoelectron spectroscopy (HAXPES) enables interface analysis of catalyst. •HAXPES enables overall analysis of porous film of Pt-doped CeO{sub 2} and related catalyst. •HAXPES enables analysis of trace elements for Pd and Pt{sub 3}Ni nanoparticle catalysts. -- Abstract: Interfacial properties including configuration, porosity, chemical states, and atomic diffusion greatly affect the performance of supported heterogeneous catalysts. Hard X-ray photoelectron spectroscopy (HAXPES) can be used to analyze the interfaces of heterogeneous catalysts because of its large information depth of more than 20 nm. We use HAXPES to examine Pt-doped CeO{sub 2} and related thin film catalysts evaporated on Si, carbon, and carbon nanotube substrates, because Pt-doped CeO{sub 2} has great potential as a noble metal-based heterogeneous catalyst for fuel cells. The HAXPES measurements clarify that the dopant material, substrate material, and surface pretreatment of substrate are important parameters that affect the interfacial properties of Pt-doped CeO{sub 2} and related thin film catalysts. Another advantage of HAXPES measurement of heterogeneous catalysts is that it can be used for chemical analysis of trace elements by detecting photoelectrons from deep core levels, which have large photoionization cross-sections in the hard X-ray region. We use HAXPES for chemical analysis of trace elements in Pd nanoparticle catalysts immobilized on sulfur-terminated substrates and Pt{sub 3}Ni nanoparticle catalysts enveloped by dendrimer molecules.

Photoemission study of 5f localization in UPd/sub 3-x/(Pt,Rh)/sub x/

International Nuclear Information System (INIS)

Arko, A.J.; Koelling, D.D.; Dunlap, B.D.; Mitchell, A.W.

1987-10-01

Photoemission measurements in the two systems UPd/sub 3-x/(Pt,Rh)/sub x/ show that the 5f spectra are consistent with localized 5f electrons (peak in spectral weight is below E/sub F/ for all x within the double hexagonal DO 24 phase) while at both phase transitions the 5f peaks lock in at E/sub F/ consistent with intinerancy. A satellite 5f peak representative of d-screening is observed in both localized and itinerant systems. 17 refs., 3 figs

Thermochemical investigations on intermetallic UMe3 compounds (Me=Ru,Rh,Pd)

International Nuclear Information System (INIS)

Wijbenga, G.

1981-10-01

The subject of this thesis is the determination of the thermodynamic properties of the intermetallic compounds of uranium with the light platinum metals, ruthenium, rhodium and palladium. These intermetallics are formed as very stable compounds during fission in nuclear fuel by the reaction of the fission products Ru, Rh and Pd with the matrix. Methods for the preparation of URu 3 , URh 3 and UPd 3 , experiments showing the chemical reactivities of these compounds, and studies of the stoichiometry of hexagonal UPd 3 by X-ray diffraction of solubility experiments of UN and palladium in UPd 3 , are described. Thermodynamic properties of the UMe 3 compounds have been obtained using several experimental thermodynamic techniques: fluorine bomb calorimetry, low-temperature cryogenic calorimetry, high-temperature drop calorimetry and EMF measurements of reversible cells. (Auth.)

Spin Crossover in Fe(II)-M(II) Cyanoheterobimetallic Frameworks (M = Ni, Pd, Pt) with 2-Substituted Pyrazines.

Science.gov (United States)

Kucheriv, Olesia I; Shylin, Sergii I; Ksenofontov, Vadim; Dechert, Sebastian; Haukka, Matti; Fritsky, Igor O; Gural'skiy, Il'ya A

2016-05-16

Discovery of spin-crossover (SCO) behavior in the family of Fe(II)-based Hofmann clathrates has led to a "new rush" in the field of bistable molecular materials. To date this class of SCO complexes is represented by several dozens of individual compounds, and areas of their potential application steadily increase. Starting from Fe(2+), square planar tetracyanometalates M(II)(CN)4(2-) (M(II) = Ni, Pd, Pt) and 2-substituted pyrazines Xpz (X = Cl, Me, I) as coligands we obtained a series of nine new Hofmann clathrate-like coordination frameworks. X-ray diffraction reveals that in these complexes Fe(II) ion has a pseudo-octahedral coordination environment supported by four μ4-tetracyanometallates forming its equatorial coordination environment. Depending on the nature of X and M, axial positions are occupied by two 2X-pyrazines (X = Cl and M(II) = Ni (1), Pd (2), Pt (3); X = Me and M(II) = Ni (4), Pd (5)) or one 2X-pyrazine and one water molecule (X = I and M(II) = Ni (7), Pd (8), Pt (9)), or, alternatively, two distinct Fe(II) positions with either two pyrazines or two water molecules (X = Me and M(II) = Pt (6)) are observed. Temperature behavior of magnetic susceptibility indicates that all compounds bearing FeN6 units (1-6) display cooperative spin transition, while Fe(II) ions in N5O or N4O2 surrounding are high spin (HS). Structural changes in the nearest Fe(II) environment upon low-spin (LS) to HS transition, which include ca. 10% Fe-N distance increase, lead to the cell expansion. Mössbauer spectroscopy is used to characterize the spin state of all HS, LS, and intermediate phases of 1-9 (see abstract figure). Effects of a pyrazine substituent and M(II) nature on the hyperfine parameters in both spin states are established.

Green synthesis of noble nanometals (Au, Pt, Pd) using glycerol under microwave irradiation conditions

Science.gov (United States)

A newer application of glycerol in the field of nanomaterials synthesis has been developed from both the economic and environmental points of view. Glycerol can act as a reducing agent for the fabrication of noble nanometals, such as Au, Pt, and Pd, under microwave irradiation. T...

Investigation of the problems associated with the Pt-20 Rh clads of the viking heat sources VF-3 and VF-7

International Nuclear Information System (INIS)

Zielinski, R.E.

1975-01-01

The investigation was undertaken to determine why the emissive coatings of the Viking Heat Sources VF-3 and VF-7 had flaked off the Pt-20 Rh clad material. During the course of the investigation, two additional, unusual phenomena were observed: a surface reaction zone on the uncoated Pt-20 Rh surfaces and grain boundary reactions in the weld zone of the clad. It seems that all three phenomena were the result of a complicated reaction couple that involved the heat source materials, storage container materials, and environment. Vapor transport mechanisms were responsible for the phenomena which were observed. The vapor transport mechanisms were probably initiated because of the impurities that were in both the heat source and storage container materials. The mechanisms resulted in significant changes in these heat sources because vapor transport was allowed to continue in a static environment for an unusually long period of time. (U.S.)

Absolute calibration of the Rh-103 (n, n') Rh-103m reaction rate

International Nuclear Information System (INIS)

Taylor, W.H.; Murphy, M.F.; March, M.R.

1979-05-01

The uncertainties in determining the absolute values of the Rh-103 (n, n') Rh-103m reaction rate (which is widely used as a neutron damage flux monitor) have been reduced to ∼±5%. This has been achieved with the use of a calibrated source of Pd-103-Rh-103m activity supplied by the I.A.E.A. Agreement to within 3% between measured and calculated values of the reaction rate (normalised to the U-238 fission rate) has been achieved. (author)

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.

Spin-orbit driven phenomena in the isoelectronic L 10 -Fe(Pd,Pt) alloys from first principles

Science.gov (United States)

Kudrnovský, J.; Drchal, V.; Turek, I.

2017-12-01

The anomalous Hall effect (AHE) and the Gilbert damping (GD) are studied theoretically for the partially ordered L 10 -Fe(Pd,Pt) alloys. The varying alloy order and the spin-orbit coupling, which are due to the change in the Pd/Pt composition, allow for a chemical tuning of both phenomena which play an important role in the spintronic applications. The impact of the antisite disorder on the residual resistivity, AHE, and GD is studied from first principles using recently developed methods employing the Kubo-Bastin approach and the nonlocal torque operator method. The most interesting result is a different behavior of samples with low and high chemical orders. Good agreement between calculated and measured concentration trends is obtained for all quantities studied, while the absolute GD values are underestimated.

Hollow Au@Pd and Au@Pt core-shell nanoparticles as electrocatalysts for ethanol oxidation reactions

KAUST Repository

Song, Hyon Min; Anjum, Dalaver H.; Sougrat, Rachid; Hedhili, Mohamed N.; Khashab, Niveen M.

2012-01-01

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

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

pH-dependent release of trace elements including platinum group elements (PGEs) from gasoline and diesel catalysts

Science.gov (United States)

Sucha, Veronika; Mihaljevic, Martin; Ettler, Vojtech; Strnad, Ladislav

2014-05-01

The release of trace metals and platinum group elements (PGEs) from automobile exhaust catalysts represents a remarkable source of higly dispersed environmental contamination. Especially, PGEs have shown increasing research interest due to their possible bioaccessibility. In our research, we focused on leaching behaviour of trace metals from gasoline and diesel automobile catalysts. While catalysts for gasoline engines contain a mixture of Pt-Pd-Rh or Pd-Rh, catalysts for diesel engines are composed only of Pt. We used dust from two crushed gasoline and two crushed diesel catalysts (new and aged). The dust of gasoline catalysts contains significant concentrations of Pt (700 mg.kg-1), Pd (11 000 mg.kg-1) and Rh (700 mg.kg-1). And the dust of diesel catalysts are composed of Pt (3 900 mg.kg-1) and they contains negligible amounts of Pd dan Rh (leaching of trace metals from dust we used pH-stat leaching test according to the European standard CEN/TS 14997. The concentrations of cations: PGEs (Pt, Pd a Rh), K, Na, Ca, Mg, Al, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb, La and Ce were determined by inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectrometry (AAS), and anions: F-, Cl-, SO42- and NO3- by high-performance liquid chromatography. Although the dusts from catalysts were relatively stable to acid/base influence, the leaching of trace metals from catalysts showed a dependence on pH. Generally, the highest concentrations were released under acidic conditions. The leaching of PGEs was higher for Pt in diesel catalysts and for Pd and Rh in gasoline catalysts. The highest concentrations of Zn and Pb were observed in old catalysts. The rare earth metals were released more from gasoline catalysts. Catalysts particles represent health risk especially with respect to their PGEs contents.

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. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Impact of humic substances on the aqueous solubility, uptake and bioaccumulation of platinum, palladium and rhodium in exposure studies with Dreissena polymorpha

Energy Technology Data Exchange (ETDEWEB)

Sures, Bernd [Department of Applied Zoology/Hydrobiology, University of Duisburg-Essen, D-45177 Essen (Germany)]. E-mail: bernd.sures@uni-due.de; Zimmermann, Sonja [Department of Applied Zoology/Hydrobiology, University of Duisburg-Essen, D-45177 Essen (Germany)

2007-03-15

Zebra mussels (Dreissena polymorpha) were exposed to different types of water containing PGE salts (PtCl{sub 4}, PdSO{sub 4}, RhCl{sub 3}) to investigate the influence of humic substances on the aqueous solubility, uptake and bioaccumulation of noble metals. The results showed a time dependent decrease of the aqueous PGE concentrations in tank water for all groups. This could mainly be related to non-biological processes. The aqueous solubility of Pd and Rh was higher in humic water compared with non-chlorinated tap water, whereas Pt showed opposing results. Highest metal uptake rates and highest bioaccumulation plateaus were found for Pd, followed by Pt and Rh. Pd uptake and bioaccumulation was significantly hampered by humic substances, whose presence appear to increase Pt uptake and bioaccumulation. No clear trend emerged for Rh. Differences in effects of humic matter among the PGE may be explained by formation of metal complexes with different fractions of humic substances. - Precious metal accumulation in Dreissena polymorpha is affected by humic substances.

Absolute calibration of the Rh-103 (n, n') Rh-103m reaction rate

Energy Technology Data Exchange (ETDEWEB)

Taylor, W.H.; Murphy, M.F.; March, M.R. [Reactor Physics Division, Atomic Energy Establishment, Winfrith, Dorchester, Dorset (United Kingdom)

1979-05-15

The uncertainties in determining the absolute values of the Rh-103 (n, n') Rh-103m reaction rate (which is widely used as a neutron damage flux monitor) have been reduced to {approx}{+-}5%. This has been achieved with the use of a calibrated source of Pd-103-Rh-103m activity supplied by the I.A.E.A. Agreement to within 3% between measured and calculated values of the reaction rate (normalised to the U-238 fission rate) has been achieved. (author)

The sticking probability for H-2 on some transition metals at a hydrogen pressure of 1 bar

DEFF Research Database (Denmark)

Johansson, Martin; Lytken, Ole; Chorkendorff, Ib

2008-01-01

The sticking probability for hydrogen on films of Co, Ni, Cu, Ru, Rh, Pd, Ir, and Pt supported on graphite has been measured at a hydrogen pressure of 1 bar in the temperature range 40–200 °C. The sticking probability is found to increase in the order Ni, Co, Ir, Pd, Pt, Rh, and Ru at temperature...

Anthrobiogeochemical platinum, palladium and rhodium cycles of earth: Emerging environmental contamination

Science.gov (United States)

Mitra, Arijeet; Sen, Indra Sekhar

2017-11-01

Anthrobiogeochemical cycles have been a subject of scientific research for many decades as they are important for identifying possible sources, sinks, and pathways of an element in the environment. In this study, we quantified global cycles for the platinum group elements (PGE; platinum (Pt), palladium (Pd) and rhodium (Rh)). We quantified the stocks of Pt, Pd, and Rh in Earth's various reservoirs, such as the core, mantle, consolidated crust, biomass, seawater, unconsolidated sediments, and atmosphere, as well as coal and petroleum deposits. We further quantified their fluxes, both natural and anthropogenic, between each reservoir, by identifying the flows across the hydrosphere, geosphere, biosphere, atmosphere and anthroposphere, including from mining activities, fossil fuel and biomass burning, construction activities, soil erosion, human contributions to net primary productivity, riverine transport, aeolian dust movement, primary production, volcanic eruption, sea-salt spray, crustal subduction, crust formation at mid ocean ridges, PGE recovery from recycling processes, and cosmic dust inputs at the Earth's surface. Stocks of PGEs were quantified by multiplying the mass of the reservoir by the average Pt, Pd and Rh concentration in the reservoir, whereas Pt, Pd and Rh fluxes were calculated by multiplying the rate of mass movement across the reservoirs with the Pt, Pd and Rh concentrations of the material. Uncertainties were explicitly incorporated in stock and flow estimations through Monte Carlo simulations. Our calculations reveal that the total surficial anthropogenic Pt, Pd, and Rh mobilizations were greater than their corresponding natural surficial mobilizations. We show that crustal subduction and crustal formation is the most important natural flow and contributes 21-42% of total PGE mobilization. When Earth's surficial processes are considered, soil erosion is the dominant flow for Rh and Pt mobilization, comprising 33% and 13%, respectively, of the

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; Zhu, Yihan; Huang, Xiao; Han, Yu; Wang, Qingxiao; Liu, Qing; Huang, Ying; Gan, Chee Lip; Zhang, Hua

2015-01-01

@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

Structure determination of chitosan-stabilized Pt and Pd based bimetallic nanoparticles by X-ray photoelectron spectroscopy and transmission electron microscopy

International Nuclear Information System (INIS)

Wu, Lihua; Shafii, Salimah; Nordin, Mohd Ridzuan; Liew, Kong Yong; Li, Jinlin

2012-01-01

Chitosan (CTS)-stabilized bimetallic nanoparticles were prepared at room temperature (rt.) in aqueous solution. Palladium (Pd) and platinum (Pt) were selected as the first metals while iron (Fe) and nickel (Ni) functioned as the second metals. In order to obtain the noble metal core-transition metal shell structures, bimetallic nanoparticles were prepared in a two-step process: the preparation of mono noble metallic (Pd or Pt) nanoparticles and the deposition of transition metals (Fe or Ni) on the surface of the monometallic nanoparticles. The structures of the nanoparticles were studied using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The XPS results show that Pd and Pt exist mainly in zero valences. The presence of Fe and Ni in the bimetallic nanoparticles affects the binding energy of Pd and Pt. Moreover, the studies of O 1s spectra indicate the presence of Fe or Ni shells. The analyses of TEM micrographs give the particle size and size distributions while the high-resolution TEM (HRTEM) micrographs show the existence of noble metal core lattices. The results confirm the formation of noble metal core-transition metal shell structures. -- Highlights: ► Chitosan-stabilized bimetallic nanoparticles were prepared at room temperature in aqueous solution. ► The presence of Fe or Ni shells was proven by XPS study. ► The existence of noble metal cores covered by amorphous shells was indicated by TEM study. ► The formation of noble metal core-transition metal shell structures was confirmed.

PdM (M = Pt, Au) bimetallic alloy nanowires with enhanced electrocatalytic activity for electro-oxidation of small molecules.

Science.gov (United States)

Zhu, Chengzhou; Guo, Shaojun; Dong, Shaojun

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 © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigation of the magnetic phase transition in thin Fe{sub 50}Pt{sub 50-x}Rh{sub x} films by neutron diffraction

Energy Technology Data Exchange (ETDEWEB)

Fenske, Jochen; Lott, Dieter; Schreyer, Andreas [GKSS Research Centre, Geesthacht (Germany); Mankey, Gary J. [MINT Center, The University of Alabama, Tuscaloosa, AL (United States); Schmidt, Wolfgang; Schmalzl, Karin [JCNS, Juelich (Germany)

2008-07-01

In the last years perpendicular recording plays a major role in the development of novel magnetic data storage. Here, materials with high anisotropy are used which delivers good thermal stability. However in order to write the bits a high magnetic field is necessary. By the use of soft underlayers the write field can be significant reduced. Fe{sub 50}Pt{sub 50-x}Rh{sub x} is a promising candidate for such an underlayer. Magnetization measurements of the bulk samples for x=10 refer to a antiferromagnetic (AF)/ferromagnetic (FM) phase transition at about 150 K when heated. Additional magnetostriction measurements indicate that the phase transition could also be induced by applying a magnetic field. The FM state lowers the high anisotropy and therefore the high write field. The AF state helps to stabilize the recording media via exchange interaction. For technical applications the use of thin films are essential to save space and costs for the next generation of magnetic storage devices. Here we present results on several thin Fe{sub 50}Pt{sub 50-x}Rh{sub x} films with different concentration of Rh. The films were examined by polarized and unpolarized neutron diffraction in dependence of temperature and magnetic field.

Surface morphology of scale on FeCrAl (Pd, Pt, Y) alloys

International Nuclear Information System (INIS)

Amano, T.; Takezawa, Y.; Shiino, A.; Shishido, T.

2008-01-01

The high temperature oxidation behavior of Fe-20Cr-4Al, floating zone refined (FZ) Fe-20Cr-4Al, Fe-20Cr-4Al-0.5Pd, Fe-20Cr-4Al-0.5Pt and Fe-20Cr-4Al-(0.01, 0.02, 0.05, 0.1, 0.2, 0.5)Y alloys was studied in oxygen for 0.6-18 ks at 1273-1673 K by mass gain measurements, X-ray diffraction and scanning electron microscopy. The mass gains of FeCrAl, FZ FeCrAl, FeCrAlPd and FeCrAlPt alloys showed almost the same values. Those of FeCrAl-(0.01, 0.02, 0.05, 0.1, 0.2, 0.5)Y alloys decreased with increasing yttrium of up to 0.1% followed by an increase with the yttrium content after oxidation for 18 ks at 1473 K. Needle-like oxide particles were partially observed on FeCrAl alloy after oxidation for 7.2 ks at 1273 K. These oxide particles decreased in size with increasing oxidation time of more than 7.2 ks at 1473 K, and then disappeared after oxidation for 7.2 ks at 1573 K. It is suggested that a new oxide develops at the oxygen/scale interface. The scale surface of FeCrAl alloy showed a wavy morphology after oxidation for 7.2 ks at 1273 K which then changed to planar morphology after an oxidation time of more than 7.2 ks at 1573 K. On the other hand, the scale surfaces of other alloys were planar after all oxidation conditions in this study. The scale surfaces of FeCrAl, FZ FeCrAl, FeCrAlPd and FeCrAlPt alloys were rough, however, those of FeCrAl-(0.1, 0.2, 0.5)Y alloys were smooth. The oxide scales formed on FeCrAl-(0.1, 0.2, 0.5)Y alloys were found to be α-Al 2 O 3 with small amounts of Y 3 Al 5 O 12 , and those of the other alloys were only α-Al 2 O 3

Synthesis and spectroscopic studies of biologically active tetraazamacrocyclic complexes of Mn(II, Co(II, Ni(II, Pd(II and Pt(II

Directory of Open Access Journals (Sweden)

Monika Tyagi

2014-01-01

Full Text Available Complexes of Mn(II, Co(II, Ni(II, Pd(II and Pt(II were synthesized with the macrocyclic ligand, i.e., 2,3,9,10-tetraketo-1,4,8,11-tetraazacycoletradecane. The ligand was prepared by the [2 + 2] condensation of diethyloxalate and 1,3-diamino propane and characterized by elemental analysis, mass, IR and 1H NMR spectral studies. All the complexes were characterized by elemental analysis, molar conductance, magnetic susceptibility measurements, IR, electronic and electron paramagnetic resonance spectral studies. The molar conductance measurements of Mn(II, Co(II and Ni(II complexes in DMF correspond to non electrolyte nature, whereas Pd(II and Pt(II complexes are 1:2 electrolyte. On the basis of spectral studies an octahedral geometry has been assigned for Mn(II, Co(II and Ni(II complexes, whereas square planar geometry assigned for Pd(II and Pt(II. In vitro the ligand and its metal complexes were evaluated against plant pathogenic fungi (Fusarium odum, Aspergillus niger and Rhizoctonia bataticola and some compounds found to be more active as commercially available fungicide like Chlorothalonil.

Temperature effect on the electrode kinetics of ethanol oxidation on Pd modified Pt electrodes and the estimation of intermediates formed in alkali medium

International Nuclear Information System (INIS)

Mahapatra, S.S.; Dutta, A.; Datta, J.

2010-01-01

Ethanol has been recognized as the ideal fuel for direct alcohol fuel cell (DAFC) systems due to its high energy density, non-toxicity and its bio-generation. However the complete conversion of ethanol to CO 2 is still met with challenges, due to dearth of suitable catalysts for the electro-oxidation. In the present work the effect of temperature on the catalytic oxidation of ethanol in alkaline medium over electrodeposited Pt and Pt-Pd alloyed nano particles on carbon support and also on the product formation during the course of reaction have been studied within the temperature range of 20-80 o C. The information on surface morphology, structural characteristics and bulk composition of the catalyst was obtained using SEM, XRD and EDX. BET surface area and pore widths of the catalyst particles were calculated by applying the BET equation to the adsorption isotherms. The electrochemical techniques like cyclic voltammetry, chronoamperometry and impedance spectroscopy were employed to investigate the electrochemical parameters related to electro-oxidation of ethanol in alkaline pH on the catalyst surfaces under the influence of temperature. The results show that the oxidation kinetics of ethanol on the alloyed Pt-Pd/C catalysts is significantly improved compared to that on Pt alone. The observations were interpreted in terms of the synergistic effect of higher electrochemical surface area, preferred OH - adsorption on the surface and the ad-atom contribution of the alloyed matrix. A pronounced influence of temperature on the reaction kinetics was manifested in the diminution of charge transfer resistance and activation energy of the ethanol oxidation with Pd incorporation into the Pt matrix, ensuring greater tolerance of the alloyed catalyst towards ethanolic residues. The higher yield of the reaction products like acetate and CO 3 -2 on the alloyed catalyst compared to Pt alone in alkaline medium, as estimated by ion chromatography, further substantiates the

Temperature effect on the electrode kinetics of ethanol oxidation on Pd modified Pt electrodes and the estimation of intermediates formed in alkali medium

Energy Technology Data Exchange (ETDEWEB)

Mahapatra, S.S.; Dutta, A. [Department of Chemistry, Bengal Engineering and Science University, PO-B. Garden, Shibpur, Howrah 711 103, West Bengal (India); Datta, J., E-mail: jayati_datta@rediffmail.co [Department of Chemistry, Bengal Engineering and Science University, PO-B. Garden, Shibpur, Howrah 711 103, West Bengal (India)

2010-12-01

Ethanol has been recognized as the ideal fuel for direct alcohol fuel cell (DAFC) systems due to its high energy density, non-toxicity and its bio-generation. However the complete conversion of ethanol to CO{sub 2} is still met with challenges, due to dearth of suitable catalysts for the electro-oxidation. In the present work the effect of temperature on the catalytic oxidation of ethanol in alkaline medium over electrodeposited Pt and Pt-Pd alloyed nano particles on carbon support and also on the product formation during the course of reaction have been studied within the temperature range of 20-80 {sup o}C. The information on surface morphology, structural characteristics and bulk composition of the catalyst was obtained using SEM, XRD and EDX. BET surface area and pore widths of the catalyst particles were calculated by applying the BET equation to the adsorption isotherms. The electrochemical techniques like cyclic voltammetry, chronoamperometry and impedance spectroscopy were employed to investigate the electrochemical parameters related to electro-oxidation of ethanol in alkaline pH on the catalyst surfaces under the influence of temperature. The results show that the oxidation kinetics of ethanol on the alloyed Pt-Pd/C catalysts is significantly improved compared to that on Pt alone. The observations were interpreted in terms of the synergistic effect of higher electrochemical surface area, preferred OH{sup -} adsorption on the surface and the ad-atom contribution of the alloyed matrix. A pronounced influence of temperature on the reaction kinetics was manifested in the diminution of charge transfer resistance and activation energy of the ethanol oxidation with Pd incorporation into the Pt matrix, ensuring greater tolerance of the alloyed catalyst towards ethanolic residues. The higher yield of the reaction products like acetate and CO{sub 3}{sup -2} on the alloyed catalyst compared to Pt alone in alkaline medium, as estimated by ion chromatography, further

Selective enhancement of main olfactory input to the medial amygdala by GnRH.

Science.gov (United States)

Blake, Camille Bond; Meredith, Michael

2010-03-04

In male hamsters mating behavior is dependent on chemosensory input from the main olfactory and vomeronasal systems, whose central pathways contain cell bodies and fibers of gonadotropin-releasing hormone (GnRH) neurons. In sexually naive males, vomeronasal organ removal (VNX), but not main olfactory lesions, impairs mating behavior. Intracerebroventricular (i.c.v.)-GnRH restores mating in sexually naive VNX males and enhances medial amygdala (Me) immediate-early gene activation by chemosensory stimulation. In sexually experienced males, VNX does not impair mating and i.c.v.-GnRH suppresses Me activation. Thus, the main olfactory system is sufficient for mating in experienced-VNX males, but not in naive-VNX males. We investigated the possibility that GnRH enhances main olfactory input to the amygdala in naive-VNX males using i.c.v.-GnRH and pharmacological stimulation (bicuculline/D,L-homocysteic acid mixture) of the main olfactory bulb (MOB). In sexually naive intact males there was a robust increase of Fos protein expression in the anteroventral medial amygdala (MeAv) with MOB stimulation, but no effect of GnRH. There was no effect of stimulation or GnRH in posterodorsal medial amygdala (MePd). In naive-VNX animals, GnRH increased Fos in MeAv and MePv. Only combined MOB stimulation and i.c.v.-GnRH produced a significant increase in Fos in the dorsal (reproduction-related) portion of MeP (MePd). When the animals were sexually experienced before VNX, a condition in which GnRH does not enhance mating, i.c.v.-GnRH combined with MOB stimulation suppressed Fos expression in MePd. This suggests a more selective effect of GnRH on olfactory input in MePd than elsewhere in medial amygdala of VNX males. 2009 Elsevier B.V. All rights reserved.

Environmental routes for platinum group elements to biological materials. A review

Energy Technology Data Exchange (ETDEWEB)

Ek, Kristine H.; Morrison, Gregory M. [Water Environment Transport, Chalmers University of Technology, SE 412 96 Goteborg (Sweden); Rauch, Sebastien [R.M. Parsons Laboratory 48-108, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

2004-12-01

The increased use of platinum group elements (PGE) in automobile catalysts has led to concern over potential environmental and biological accumulation. Platinum (Pt), palladium (Pd) and rhodium (Rh) concentrations have increased in the environment since the introduction of automobile catalysts. This review summarises current knowledge concerning the environmental mobility, speciation and bioavailability of Pt, Pd and Rh. The greater proportion of PGE emissions is from automobile catalysts, in the form of nanometer-sized catalyst particles, which deposit on roadside surfaces, as evidenced in samples of road dust, grass and soil. In soil, PGE can be transformed into more mobile species through complexation with organic matter and can be solubilised in low pH rainwater. There are indications that environmentally formed Pd species are more soluble and hence more mobile in the environment than Rh and Pt. PGE can reach waterbodies through stormwater transport and deposition in sediments. Besides external contamination of grass close to roads, internal PGE uptake has been observed for plants growing on soil contaminated with automobile catalyst PGE. Fine particles of PGE were also detected on the surface of feathers sampled from passerines and raptors in their natural habitat, and internal organs of these birds also contained PGE. Uptake has been observed in sediment-dwelling invertebrates, and laboratory studies have shown an uptake of PGE in eel and fish exposed to water containing road dust.The available evidence indicates that the PGE, especially Pd, are transported to biological materials through deposition in roots by binding to sulphur-rich low molecular weight species in plants. PGE uptake to exposed animals have uptake rates in the following order: Pd>Pt>Rh. The liver and kidney accumulate the highest levels of PGE, especially Pd. Urinary Pd and Rh, but not Pt, levels are correlated with traffic intensity. Dental alloys may lead to elevated urinary Pt levels

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 procedure The chemicals used in the preparation were Platinum solution (1mM H2PtCl6 pH = 1, SA Precious Metals), Pd solution (1mM PdCl2 pH = 1, SA Precious Metals), (copper sulphate solution (1mM CuSO4.5H2O pH = 1, Merck) were prepared in perchloric...

Ternary Pt/Rh/SnO2 electrocatalysts for oxidizing ethanol to CO2.

Science.gov (United States)

Kowal, A; Li, M; Shao, M; Sasaki, K; Vukmirovic, M B; Zhang, J; Marinkovic, N S; Liu, P; Frenkel, A I; Adzic, R R

2009-04-01

Ethanol, with its high energy density, likely production from renewable sources and ease of storage and transportation, is almost the ideal combustible for fuel cells wherein its chemical energy can be converted directly into electrical energy. However, commercialization of direct ethanol fuel cells has been impeded by ethanol's slow, inefficient oxidation even at the best electrocatalysts. We synthesized a ternary PtRhSnO(2)/C electrocatalyst by depositing platinum and rhodium atoms on carbon-supported tin dioxide nanoparticles that is capable of oxidizing ethanol with high efficiency and holds great promise for resolving the impediments to developing practical direct ethanol fuel cells. This electrocatalyst effectively splits the C-C bond in ethanol at room temperature in acid solutions, facilitating its oxidation at low potentials to CO(2), which has not been achieved with existing catalysts. Our experiments and density functional theory calculations indicate that the electrocatalyst's activity is due to the specific property of each of its constituents, induced by their interactions. These findings help explain the high activity of Pt-Ru for methanol oxidation and the lack of it for ethanol oxidation, and point to the way to accomplishing the C-C bond splitting in other catalytic processes.

Phase Transformation and Shape Memory Effect of Ti-Pd-Pt-Zr High-Temperature Shape Memory Alloys

Science.gov (United States)

Yamabe-Mitarai, Yoko; Takebe, Wataru; Shimojo, Masayuki

2017-12-01

To understand the potential of high-temperature shape memory alloys, we have investigated the phase transformation and shape memory effect of Ti-(50 - x)Pt- xPd-5Zr alloys ( x = 0, 5, and 15 at.%), which present the B2 structure in the austenite phase and B19 structure in the martensite phase. Their phase transformation temperatures are very high; A f and M f of Ti-50Pt are 1066 and 1012 °C, respectively. By adding Zr and Pd, the phase transition temperatures decrease, ranging between 804 and 994 °C for A f and 590 and 865 °C for M f. Even at the high phase transformation temperature, a maximum recovery ratio of 70% was obtained for one cycle in a thermal cyclic test. A work output of 1.2 J/cm3 was also obtained. The recovery ratio obtained by the thermal cyclic test was less than 70% because the recovery strain was training effect was also investigated.

Highly Active, Carbon-supported, PdSn Nano-core, Partially ...

African Journals Online (AJOL)

Carbon-supported, Pt partially covered, PdSn alloy nanoparticles (Pt-PdSn/C) were synthesized via a metathetical reaction of PdSn alloy nanoparticles, and a platinum precursor. The electrochemical activity was evaluated by methanol oxidation. The Pt-PdSn/C catalysts were characterized by transmission electron ...

Electrocatalytic oxidation of methanol on (Pb) lead modified by Pt, Pt-Ru and Pt-Sn microparticles dispersed into poly(o-phenylenediamine) film

Energy Technology Data Exchange (ETDEWEB)

Golikand, Ahmad Nozad; Maragheh, Mohammad Ghannadi; Irannejad, Leila [Jaber Ibn Hayan Research Lab., Atomic Energy Organization of Iran (AEOI), Tehran (Iran); Golabi, Seyed Mehdi [Electroanalytical Chemistry Lab., Faculty of Chemistry, University of Tabriz, Tabriz (Iran)

2005-08-18

The electrocatalytic oxidation of methanol at a (Pb) lead electrode modified by Pt, Pt-Ru and Pt-Sn microparticles dispersed into poly(o-phenylenediamine) (PoPD) film has been investigated using cyclic voltammetry as analytical technique and 0.5M sulfuric acid as supporting electrolyte. It has been shown that the presence of PoPD film increases considerably the efficiency of deposited Pt and Pt alloys microparticles toward the electrocatalytic oxidation of methanol. The catalytic activity of Pt particles is further enhanced when Ru and especially Sn, is co-deposited in the polymer film. The effects of various parameters such as concentration of methanol, medium temperature as well as the long term stability of modified electrodes have also been investigated. (author)

A genosensor for detection of consensus DNA sequence of Dengue virus using ZnO/Pt-Pd nanocomposites.

Science.gov (United States)

Singhal, Chaitali; Pundir, C S; Narang, Jagriti

2017-11-15

An electrochemical genosensor based on Zinc oxide/platinum-palladium (ZnO/Pt-Pd) modified fluorine doped tin oxide (FTO) glass plate was fabricated for detection of consensus DNA sequence of Dengue virus (DENV) using methylene blue (MB) as an intercalating agent. To achieve it, probe DNA (PDNA) was immobilized on the surface of ZnO/Pt-Pd nanocomposites modified FTO electrode. The synthesized nano-composites were characterized by high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray analysis (EDX), atomic force microscopy (AFM), scanning electron microscopy (SEM), UV-Vis spectroscopy, X-ray diffraction (XRD) analysis and Fourier transform infra-red (FTIR) spectroscopy. This PDNA modified electrode (PDNA/ZnO/Pt-Pd/FTO) served as a signal amplification platform for the detection of the target hybridized DNA (TDNA). The hybridization between PDNA and TDNA was detected by reduction in current, generated by interaction of anionic mediator, i.e., methylene blue (MB) with free guanine (3'G) of ssDNA. The sensor showed a dynamic linear range of 1 × 10 -6 M to 100 × 10 -6 M with LOD as 4.3 × 10 -5 M and LOQ as 9.5 × 10 -5 M. Till date, majorly serotype specific biosensors for dengue detection have been developed. The genosensor reported here eliminates the possibility of false result as in case of serotype specific DNA sensor. This is the report where conserved sequences present in all the serotypes of Dengue virus has been employed for fabrication of a genosensor. Copyright © 2017 Elsevier B.V. All rights reserved.

Separation of 103Pd from metal Rhodium by dry distillation

International Nuclear Information System (INIS)

Szuecs, Z.; Takacs, S.

2009-01-01

Complete text of publication follows. Introduction. The use of Auger emitters as potential radiopharmaceuticals is increasingly investigated. One such radionuclide of interest is 103m Rh. This can be produced from 103 Ru or from 103 Pd in an in vivo generator. It has been proven on theoretical considerations that use of 103 Pd/ 103m Rh in vivo generator will be successful in delivering 103 mRh to a target site when complexed to a tumor selective carrier. 103 Pd is widely used in internal radiotherapy with one of the production routes via the irradiation of Rh by protons in a cyclotron. The charged particle production of 103 Pd is the only way for no-carrier -added production of this radionuclide, which is required for use in nuclear medicine. However, the widely used separation technique to get 103 Pd from the target material (as well as recovery of the Rh) by wet chemistry is a very complicated, labour intensive and expensive procedure, resulting in low yields of 103 Pd and high amounts of radioactive waste. An alternative more efficient separation and production technology can be developed based on differential evaporation. The principle is the following: The produced 103 Pd 'contaminating' new element within the crystal structure of the Rh target can be forced to diffuse out from the deformed crystal lattice by heating up the target. In this process the 103 Pd accumulates on the surface of the target from where it can be evaporated. A prerequisite for this process is that the target metal (Rh) has a different partial pressure than the evaporated metal (Pd). The thick target yield is 6MBq/μ Ah and the activities of potential contaminating radioisotopes produced by side reaction are negligible, if the energy of the irradiating beam will be chosen precisely. The natural abundance of 116 Cd is 7,5%, it means that the price of the enriched material is reasonable. A potential cyclotron facility with α-beam was found at JINR, Dubna, Russia where the radiochemical

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.

Investigations on the bioavailability of traffic-related platinum group elements (PGE) to the aquatic fauna with special consideration being given to palladium; Untersuchungen zur Bioverfuegbarkeit Kfz-emittierter Platingruppenelemente (PGE) fuer die aquatische Fauna unter besonderer Beruecksichtigung von Palladium

Energy Technology Data Exchange (ETDEWEB)

Sures, B.; Thielen, F.; Zimmermann, S. [Karlsruhe Univ. (T.H.) (Germany). Zoologisches Inst.

2002-07-01

The uptake and accumulation of the traffic-related platinum group elements (PGE) Pt, Pd and Rh by the aquatic fauna was investigated. Zebra mussels, eels and barbels were maintained in water containing either road dust or ground catalytic converter material. Following the exposure, samples of fish liver and kidney, as well as the soft tissues of the mussels, were analysed. Our results revealed that all three catalytic noble metals were accumulated by aquatic organisms. The highest bioavailability was found for Pd, followed by Pt and Rh. The concentration factor of Pd for Dreissena polymorpha was 5 times higher compared with Pb and only 6 times lower than the essential element Cu. With regard to the increasing emission of Pd the level of this metal has to be monitored very carefully in the environment. (orig.) [German] Die Aufnahme und Anreicherung der Kfz-buertigen Platingruppenelemente (PGE) Pt, Pd und Rh durch aquatische Tiere wurde an Dreikantmuscheln, Aalen und Barben untersucht. Hierzu wurden die Testorganismen in Wasser mit Strassenstaub einer stark befahrenen Strasse oder mit zerriebenem Autokatalysatormaterial ueber mehrere Wochen exponiert und anschliessend Leber und Niere der Fische sowie das Weichgewebe der Muscheln analysiert. Im Rahmen dieser Studien konnte nachgewiesen werden, dass alle drei Edelmetalle durch Fische wie durch Muscheln aufgenommen und angereichert werden. Fuer Pd fand sich die hoechste Bioverfuegbarkeit, gefolgt von Pt und Rh. Das Ausmass der Aufnahme von Pd durch Dreissena polymorpha war ca. 5fach hoeher als von Pb und 6fach niedriger verglichen mit dem essenziellen Element Cu. In Anbetracht der steigenden Emission von Pd sollte ein Umweltmonitoring die Verbreitung von Pd in der Umwelt klaeren. (orig.)

Graphene blended with SnO2 and Pd-Pt nanocages for sensitive non-enzymatic electrochemical detection of H2O2 released from living cells.

Science.gov (United States)

Fu, Yamin; Huang, Di; Li, Congming; Zou, Lina; Ye, Baoxian

2018-07-19

This paper described a novel, facile and nonenzymatic electrochemical biosensor to detect hydrogen peroxide (H 2 O 2 ). The sensor was fabricated based on Pd-Pt nanocages and SnO 2 /graphene nanosheets modified electrode (PdPt NCs@SGN/GCE). The electrochemical behavior of PdPt NCs@SGN/GCE exhibited excellent catalytic activity toward H 2 O 2 with fast response, high selectivity, superior sensitivity, low detection limit of 0.3 μM and large linear range from 1 μM to 300 μM. Under these obvious advantages, the constructed biosensor provided to be reliable for determination of H 2 O 2 secreted from human cervical cancer cells (Hela cells). Hence, the proposed biosensor is a promising candidate for detection of H 2 O 2 in situ released from living cells in clinical diagnostics. Copyright © 2018 Elsevier B.V. All rights reserved.

Toward hybrid Au nanorods @ M (Au, Ag, Pd and Pt) core-shell heterostructures for ultrasensitive SERS probes

Science.gov (United States)

Xie, Xiaobin; Gao, Guanhui; Kang, Shendong; Lei, Yanhua; Pan, Zhengyin; Shibayama, Tamaki; Cai, Lintao

2017-06-01

Being able to precisely control the morphologies of noble metallic nanostructures is of essential significance for promoting the surface-enhanced Raman scattering (SERS) effect. Herein, we demonstrate an overgrowth strategy for synthesizing Au @ M (M = Au, Ag, Pd, Pt) core-shell heterogeneous nanocrystals with an orientated structural evolution and highly improved properties by using Au nanorods as seeds. With the same reaction condition system applied, we obtain four well-designed heterostructures with diverse shapes, including Au concave nanocuboids (Au CNs), Au @ Ag crystalizing face central cube nanopeanuts, Au @ Pd porous nanocuboids and Au @ Pt nanotrepangs. Subsequently, the exact overgrowth mechanism of the above heterostructural building blocks is further analysed via the systematic optimiziation of a series of fabrications. Remarkably, the well-defined Au CNs and Au @ Ag nanopeanuts both exhibit highly promoted SERS activity. We expect to be able to supply a facile strategy for the fabrication of multimetallic heterogeneous nanostructures, exploring the high SERS effect and catalytic activities.

Photoinduced Glycerol Oxidation over Plasmonic Au and AuM (M = Pt, Pd and Bi) Nanoparticle-Decorated TiO2 Photocatalysts

Science.gov (United States)

Jedsukontorn, Trin; Saito, Nagahiro; Hunsom, Mali

2018-01-01

In this study, sol-immobilization was used to prepare gold nanoparticle (Au NP)-decorated titanium dioxide (TiO2) photocatalysts at different Au weight % (wt. %) loading (Aux/TiO2, where x is the Au wt. %) and Au–M NP-decorated TiO2 photocatalysts (Au3M3/TiO2), where M is bismuth (Bi), platinum (Pt) or palladium (Pd) at 3 wt. %. The Aux/TiO2 photocatalysts exhibited a stronger visible light absorption than the parent TiO2 due to the localized surface plasmon resonance effect. Increasing the Au content from 1 wt. % to 7 wt. % led to increased visible light absorption due to the increasing presence of defective structures that were capable of enhancing the photocatalytic activity of the as-prepared catalyst. The addition of Pt and Pd coupled with the Au3/TiO2 to form Au3M3/TiO2 improved the photocatalytic activity of the Au3/TiO2 photocatalyst by maximizing their light-absorption property. The Au3/TiO2, Au3Pt3/TiO2 and Au3Pd3/TiO2 photocatalysts promoted the formation of glyceraldehyde from glycerol as the principle product, while Au3Bi3/TiO2 facilitated glycolaldehyde formation as the major product. Among all the prepared photocatalysts, Au3Pd3/TiO2 exhibited the highest photocatalytic activity with a 98.75% glycerol conversion at 24 h of reaction time. PMID:29690645

H electro-insertion into Pd/Pt(1 1 1) nanofilms: an original method for isotherm measurement coupled to in situ surface X-ray diffraction structural study

International Nuclear Information System (INIS)

Soldo-Olivier, Y.; Sibert, E.; Previdello, B.; Lafouresse, M.C.; Maillard, F.; De Santis, M.

2013-01-01

In order to get a thorough comprehension of the mechanisms governing hydrogen insertion into nanometric metallic films, we have studied ultra-thin Pd/Pt(1 1 1) layers. In this paper we propose an original method allowing the measurement of hydrogen insertion electrochemical isotherms. The use of a hanging meniscus rotating disc electrode and a new calculation approach permit to remove the contributions to the insertion charge of both hydrogen evolution and hydrogen oxidation reactions. Indeed, compared to hydrogen insertion such terms become non-negligible in the case of nanometric deposits, due to their large surface/bulk atom ratio. We have measured hydrogen insertion isotherms for Pd/Pt(1 1 1) films from 14 ML down to 4 ML. Independently from the film thickness, the maximum hydrogen insertion rate (H/Pd) max is smaller than that of bulk Pd. The so-called two-phase region is still present, but contrarily to bulk Pd it is characterized by a slope. Both hydrogen solubility and the two-phase domain width diminish with the decrease of the film thickness. In the present work the behaviour of hydrogen electrochemical insertion isotherms is interpreted in the light of the Pd nanofilms structure obtained with in situ surface X-ray diffraction. The lattice constraints induced by the substrate result in a lower insertion rate in the Pd deposit close to the Pt–Pd interface. Only the outermost region of the film is relaxed and behaves like bulk Pd. This description quantitatively accounts for the experimental behaviour of (H/Pd) max as a function of the film thickness. The obtained Pd/Pt(1 1 1) films structure also corresponds to the presence of non-equivalent hydrogen insertion sites, surely contributing to the slope observed in the two-phase domain

Efficient Synthesis of MCu (M = Pd, Pt, and Au) Aerogels with Accelerated Gelation Kinetics and their High Electrocatalytic Activity.

Science.gov (United States)

Zhu, Chengzhou; Shi, Qiurong; Fu, Shaofang; Song, Junhua; Xia, Haibing; Du, Dan; Lin, Yuehe

2016-10-01

To accelerate hydrogel formation and further simplify the synthetic procedure, a series of MCu (M = Pd, Pt, and Au) bimetallic aerogels is synthesized from the in situ reduction of metal precursors through enhancement of the gelation kinetics at elevated temperature. Moreover, the resultant PdCu aerogel with ultrathin nanowire networks exhibits excellent electrocatalytic performance toward ethanol oxidation, holding promise in fuel-cell applications. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

Owing to the excellent near infrared (NIR) light absorption and efficient passive targeting toward tumor tissue, two-dimensional (2D) core-shell PEGylated Pd@Au nanoplates have great potential in both photothermal therapy and drug delivery systems. In this work, we successfully conjugate Pd@Au nanoplates with a platinum(iv) prodrug c,c,t-[Pt(NH3)2Cl2(O2CCH2CH2CO2H)2] to obtain a nanocomposite (Pd@Au-PEG-Pt) for combined photothermal-chemotherapy. The 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.Owing to the excellent near infrared (NIR) light absorption and efficient passive targeting toward tumor tissue, two-dimensional (2D) core-shell PEGylated Pd@Au nanoplates have great potential in both photothermal therapy and drug delivery systems. In this work, we successfully conjugate Pd@Au nanoplates with a platinum(iv) prodrug c,c,t-[Pt(NH3)2Cl2(O2CCH2CH2CO2H)2] to obtain a nanocomposite (Pd@Au-PEG-Pt) for combined photothermal-chemotherapy. The

Electrochemical gene sensor for Mycoplasma pneumoniae DNA using dual signal amplification via a Pt-Pd nanowire and horse radish peroxidase

International Nuclear Information System (INIS)

Liu, Linlin; Xiang, Guiming; Jiang, Dongneng; Du, Chunlan; Liu, Chang; Huang, Weiwei; Pu, Xiaoyun

2016-01-01

A dually amplified DNA biosensor was constructed for the determination of the DNA of Mycoplasma pneumoniae (M. pneu). A gold electrode was modified with 3,4,9,10-perylenetetracarboxylic acid dianhydride (PTCDA; a π-stacking perylene semiconductor dye with outstanding electronic and optical properties), a layer of gold nanoparticles (nano-Au), and capture DNA. Pt-Pd nanowires served as carriers for the co immobilization of complementary probe (CP2) and the mediator thionine (Thi). Horseradish peroxidase (HRP) acted as a blocking reagent and signal enhancer. Following base pairing, the modified Pt-Pd nanowires were captured on the surface of the gold electrode. After addition of H 2 O 2 , the Pt-Pd nanowires and HRP both catalyzed the reduction of H 2 O 2 and promoted the electron transfer via the mediator Thi, resulting in an amplified electrochemical signal. The electrical signal, best measured at a working voltage of −200 mV (vs a SCE), is logarithmically related to the concentration of the M. pneu DNA in the 0.1 pM to 20 nM concentration range, and the detection limit (at an S/N ratio of 3) is 0.03 pM. The assay is robust, sensitive and specific. Conceivably, it is a cost-effective alternative to the established PCR method for the detection of M. pneu in clinical samples. (author)

Transition metal-centered trigonal prisms as building units in RE{sub 14}T{sub 3}In{sub 3} (RE = Y, Ho, Er, Tm, Lu; T = Pd, Ir, Pt) and Y{sub 4}IrIn

Energy Technology Data Exchange (ETDEWEB)

Zaremba, R.; Rodewald, U.C.; Poettgen, R. [Inst. fuer Anorganische und Analytische Chemie, Univ. Muenster (Germany)

2007-12-15

The indides RE{sub 14}T{sub 3}In{sub 3} (RE = Y, Ho, Er, Tm, Lu; T = Pd, Ir, Pt) and Y{sub 4}IrIn were synthesized from the elements by are-melting and subsequent annealing for crystal growth. Their structures were characterized on the basis of X-ray powder and single crystal data: Lu{sub 14}Co{sub 3}In{sub 3}-type, space group P4{sub 2}/nmc, a = 970.2(1), c = 2340.7(5) pm for Y{sub 13.95}Pd{sub 3}In{sub 3.05}, a = 959.7(1), c = 2309.0(5) pm for Ho{sub 14}Pd{sub 2.95}In{sub 3}, a = 955.5(1), c = 2305.1(5) pm for Er{sub 14}Pd{sub 3}In{sub 3}, a = 950.9(1), c = 2291.6(5) pm for Tm{sub 13.90}Pd{sub 3}In{sub 3.10}, a = 944.4(1), c = 2275.5(5) pm for Lu{sub 13.93}Pd{sub 3}In{sub 3.07}, a = 962.9(1), c = 2343.0(5) pm for Y{sub 13.86}Ir{sub 2.97}In{sub 3.02}, a = 967.6(1), c = 2347.8(5) pm for Y{sub 13.92}Pt{sub 3.05}In{sub 2.91}, and Gd{sub 4}RhIn-type, space group F anti 43m, a = 1368.6(2) pm for Y{sub 4}IrIn. The main structural motifs are transition metal-centered trigonal prisms of the rare Earth elements which are condensed to two-dimensional networks in the RE{sub 14}T{sub 3}In{sub 3} indides and to a three-dimensional one in Y{sub 4}IrIn. The indium atoms in both structure types show segregation in the metal-rich matrix, i.e. In{sub 2} dumbbells in the RE{sub 14}T{sub 3}In{sub 3} indides (309 pm In2-In2 in Y{sub 13.86}Ir{sub 2.97}In{sub 3.02}) and In{sub 4} tetrahedra (322 pm In-In) in Y{sub 4}IrIn. The crystal chemical peculiarities of both structure types are discussed. (orig.)

Histopathological alterations and induction of hsp70 in ramshorn snail (Marisa cornuarietis) and zebrafish (Danio rerio) embryos after exposure to PtCl(2).

Science.gov (United States)

Osterauer, Raphaela; Köhler, Heinz-R; Triebskorn, Rita

2010-08-01

The platinum group metals (PGMs) platinum (Pt), palladium (Pd), and rhodium (Rh) are used in automobile catalytic converters, from which they have been emitted into the environment to an increasing degree during the last 20 years. Despite the bioavailability of these metals to plants and animals, studies determining the effects of PGMs on organisms are extremely rare. In the present study, effects of various concentrations of PtCl(2) (0.1, 1, 10, 50 and 100 microg/L) were investigated with respect to the induction of hsp70 and histopathological alterations in the zebrafish, Danio rerio and the ramshorn snail, Marisa cornuarietis. Histopathological investigations revealed effects of Pt on both species, which varied between slight and strong cellular reactions, depending on the PtCl(2) concentration. The hsp70 level in M. cornuarietis did not show an increase following Pt exposure whereas it was significantly elevated at 100 micorg/L PtCl(2) in D. rerio. Copyright 2010 Elsevier B.V. All rights reserved.

Platinum, palladium, and rhodium analyses of ultramafic and mafic rocks from the Stillwater Complex, Montana

Science.gov (United States)

Page, Norman J; Riley, Leonard Benjamin; Haffty, Joseph

1969-01-01

Analyses by a combination fire- assay-solution-optical-emission spectrographic method of 137 rocks from the Stillwater Complex, Mont., indicate that platinum, palladium, and rhodium are preferentially concentrated in chromitite zones. The A chromitite zone (21 samples) has an average of 988.9 ppb (pans per billion, 10-9) Pt, 2290.2 ppb Pd, and 245.9 ppb Rh and reaches a maximum (to date) of 8,000 ppb Pt, 11,000 ppb Pd, and 1,700 ppb Rh.

Voltage Oscillations in a Polymer Electrolyte Membrane Fuel Cell with Pd-Pt/C and Pd/C Anodes.

Science.gov (United States)

Nogueira, Jéssica Alves; Varela, Hamilton

2017-10-01

Polymer electrolyte membrane fuel cells (PEMFC) fed with H 2 contaminated with CO may exhibit oscillatory behavior when operated galvanostatically. The self-organization of the anodic overpotential is interesting because it can be accompanied by an increase in the average performance. Herein we report experimental studies of voltage oscillations that emerge in a PEMFC equipped with a Pd/C or PdPt/C anode and fed with H 2 contaminated with CO (100 ppm). We used on-line mass spectrometry to investigate how the mass fragments associated with CO 2 and CO ( m / z 44 and 28, respectively) varied with the voltage oscillations. Overall, we observed that oscillations in the anodic overpotential are in phase with that of the CO and CO 2 signals. This fact is consistent with an autonomous adsorption-oxidation cyclic process. For both anodes, it has been observed that, in general, an increase in current density implies an increase in oscillatory frequency. By using CO stripping, we also discuss how the onset of CO oxidation is related to the maximum overpotential reached during a cycle, whereas the minimum overpotential can be associated with the catalytic activity of the electrode for H 2 oxidation.

New determination of the half-lives of 57Co, 103Ru, sup(103m)Rh, 103Pd, and 109Cd

International Nuclear Information System (INIS)

Vaninbroukx, R.; Grosse, G.; Zehner, W.

1981-01-01

The half-lives of five radionuclides were redetermined by photon-counting techniques using NaI(Tl)- and Si(Li) detectors. The results are: 57 Co: (271.90 +- 0.09)d, 103 Ru: (39.260 +- 0.020)d, sup(103m)Rh: (56.114 +- 0.020)m, 103 Pd: (16.991 +- 0.019)d, and 109 Cd: (461.90 +- 0.30)d. The quoted uncertainties, corresponding to a lσ level, take into account random and systematic uncertainties. (author)

Constitutional studies in the palladium-rhodium-tellurium (-oxygen) system. A contribution to elucidate the behaviour of Pd, Rh and Te in the vitrification process of high-level waste concentrates (HLWC)

International Nuclear Information System (INIS)

Hartmann, T.

1996-01-01

In the vitrification process of high-level waste concentrates (HLWC) from the reprocessing of nuclear spent fuel elements, about 30 different elements have to be immobilized in a solid matrix consisting of an alkali borosilicate glass. Most of the waste oxides are dissolved in the alkali borosilicate melt and become structural elements of the glasses when cooled. This, however, applies only partly to the platinum metals Ru, which forms RuO 2 , and palladium and rhodium, which deposit as sparingly soluble and electrically conducting tellurides. This might considerably impair the technical process of HLWC vitrification. Therefore, constitutional studies on the Pd-Rh-Te system became necessary. The phase diagram of the Pd-Rh-Te ternary system at temperatures of 1150, 1100, 1050, 1000, 950, 900 and 750 C was determined under inertial conditions. Oxygen exerts a major influence on the system. Already under limited availability of oxygen, the rhodium contents of the solid solution phases α 1 and α 2 are clearly diminished. Rhodium of the phases becomes oxidized selectively. The three-phase field α 1 +α 2 +L is shifted to higher palladium and tellurium contents, even oxygen is available to a limited extend only. With the oxygen in the air, the extension of the three-phase space is reduced markedly. The complex process chemistry of Pf, Rh and Te during the vitrification can be described by the state of the Pd-Rh-Te ternary system after annealing in (air) oxygen for limited periods of time. (orig./MM) [de

The Mechanism of Rh-Catalyzed Transformation of Fatty Acids to Linear Alpha olefins

Directory of Open Access Journals (Sweden)

Sondre H. Hopen Eliasson

2017-12-01

Full Text Available Linear alpha olefins (LAOs are key commodity chemicals and petrochemical intermediates that are currently produced from fossil resources. Fatty acids are the obvious renewable starting material for LAOs, which can be obtained via transition-metal-catalyzed decarbonylative dehydration. However, even the best catalysts that have been obtained to date, which are based on palladium, are not active and stable enough for industrial use. To provide insight for design of better catalysts, we here present the first computationally derived mechanism for another attractive transition-metal for this reaction, rhodium. By comparing the calculated mechanisms and free energy profiles for the two metals, Pd and Rh, we single out important factors for a facile, low-barrier reaction and for a stable catalyst. While the olefin formation is rate limiting for both of the metals, the rate-determining intermediate for Rh is, in contrast to Pd, the starting complex, (PPh32Rh(COCl. This complex largely draws its stability from the strength of the Rh(I–CO bond. CO is a much less suitable ligand for the high-oxidation state Rh(III. However, for steric reasons, rhodium dissociates a bulkier triphenylphosphine and keeps the carbonyl during the oxidative addition, which is less favorable than for Pd. When compared to Pd, which dissociates two phosphine ligands at the start of the reaction, the catalytic activity of Rh also appears to be hampered by its preference for high coordination numbers. The remaining ancillary ligands leave less space for the metal to mediate the reaction.

Balance of Nanostructure and Bimetallic Interactions in Pt Model Fuel Cell Catalysts

DEFF Research Database (Denmark)

Friebel, Daniel; Viswanathan, Venkatasubramanian; Miller, Daniel J.

2012-01-01

We have studied the effect of nanostructuring in Pt monolayer model electrocatalysts on a Rh(111) single-crystal substrate on the adsorption strength of chemisorbed species. In situ high energy resolution fluorescence detection X-ray absorption spectroscopy at the Pt L3 edge reveals characteristic...... changes of the shape and intensity of the “white-line” due to chemisorption of atomic hydrogen (Had) at low potentials and oxygen-containing species (O/OHad) at high potentials. On a uniform, two-dimensional Pt monolayer grown by Pt evaporation in ultrahigh vacuum, we observe a significant destabilization...... of both Had and O/OHad due to strain and ligand effects induced by the underlying Rh(111) substrate. When Pt is deposited via a wet-chemical route, by contrast, three-dimensional Pt islands are formed. In this case, strain and Rh ligand effects are balanced with higher local thickness of the Pt islands...

Application of the Auger and X-ray photoelectron electronic spectroscopies to the study of superficial segregation in the system Pt-Rh

International Nuclear Information System (INIS)

Volpe, M.A.; Castellani, N.J.; Leroy, D.B.

1987-01-01

The Auger and X-ray photoelectron spectroscopies are applied to the study of the superficial segregation in the system of the binary alloy Pt-Rh. The methodology for the cleaning of the samples, which is essential for the obtainment of reproducible results, has been established. The spectra qualitative analysis allows to identify the element segregated. The application of the Gallon model permits to develop a quantitative study of the phenomenon. (S.M.) [es

Electric-field effects on magnetic anisotropy in Pd/Fe/Pd(0 0 1) surface

International Nuclear Information System (INIS)

Haraguchi, Shinya; Tsujikawa, Masahito; Gotou, Junpei; Oda, Tatsuki

2011-01-01

Electric-field (EF) effects have been studied on magnetic anisotropy in the metallic surfaces Pt/Fe/Pt(0 0 1) and Pd/Fe/Pd(0 0 1) by means of the first-principles electronic structure calculation which employs the generalized gradient approximation. The variation of anisotropy energy with respect to the EF is found to be opposite to each other. The modulus rate of the variation is larger by a few factors in the Pt substrate than in the Pd one. These results agree qualitatively well with the available experimental data. The electronic structures are presented and the origins in EF effects are discussed along a line of the second perturbative fashion.

High performance Pd–Rh/YBaCo4O7/γ-Al2O3 three-way catalysts for gasoil engine

Directory of Open Access Journals (Sweden)

Brou Albert Kouadio

2017-11-01

Full Text Available The evaluation of catalytic activity for Rh–Pd/YBa(Co1−xMx4O7/γ-Al2O3 (M = Al, Ce, Zr, and La showed that the efficiency of NOx reduction depends strongly on the nature of the OSMs. Among a series of oxygen storage materials, YBa(Co1−xMx4O7 (M = Ce, Zr, La, Ga and In studied for catalyst enhancement, only the catalyst with YBa(Co0.9Ce0.14O7 has better conversion efficiency respectively (85% of NO, 96% of CO and 92% of HC. After treatment at 1000 °C for 3 h, these fresh catalysts showed a substantial decrease of their catalytic activities, only Rh–Pd/YBa(Co0.9Ce0.14O7/γ-Al2O3 retains its high catalytic activity. Keywords: Chemical synthesis, X-ray diffraction, Oxygen storage and catalytic activity

PALLADIUM, PLATINUM, RHODIUM, RUTHENIUM AND IRIDIUM IN PERIDOTITES AND CHROMITITES FROM OPHIOLITE COMPLEXES IN NEWFOUNDLAND.

Science.gov (United States)

Page, Norman J; Talkington, Raymond W.

1984-01-01

Samples of spinel lherzolite, harzburgite, dunite, and chromitite from the Bay of Islands, Lewis Hills, Table Mountain, Advocate, North Arm Mountain, White Hills Periodite Point Rousse, Great Bend and Betts Cove ophiolite complexes in Newfoundland were analyzed for the platinum-group elements (PGE) Pd, Pt, Rh, Ru and Ir. The ranges of concentration (in ppb) observed for all rocks are: less than 0. 5 to 77 (Pd), less than 1 to 120 (Pt), less than 0. 5 to 20 (Rh), less than 100 to 250 (Ru) and less than 20 to 83 (Ir). Chondrite-normalized PGE ratios suggest differences between rock types and between complexes. Samples of chromitite and dunite show relative enrichment in Ru and Ir and relative depletion in Pt and Pd.

An investigation of the mimetic enzyme activity of two-dimensional Pd-based nanostructures

Science.gov (United States)

Wei, Jingping; Chen, Xiaolan; Shi, Saige; Mo, Shiguang; Zheng, Nanfeng

2015-11-01

In this work, we investigated the mimetic enzyme activity of two-dimensional (2D) Pd-based nanostructures (e.g. Pd nanosheets, Pd@Au and Pd@Pt nanoplates) and found that they possess intrinsic peroxidase-, oxidase- and catalase-like activities. These nanostructures were able to activate hydrogen peroxide or dissolved oxygen for catalyzing the oxidation of organic substrates, and decompose hydrogen peroxide to generate oxygen. More systematic investigations revealed that the peroxidase-like activities of these Pd-based nanomaterials were highly structure- and composition-dependent. Among them, Pd@Pt nanoplates displayed the highest peroxidase-like activity. Based on these findings, Pd-based nanostructures were applied for the colorimetric detection of H2O2 and glucose, and also the electro-catalytic reduction of H2O2. This work offers a promising prospect for the application of 2D noble metal nanostructures in biocatalysis.In this work, we investigated the mimetic enzyme activity of two-dimensional (2D) Pd-based nanostructures (e.g. Pd nanosheets, Pd@Au and Pd@Pt nanoplates) and found that they possess intrinsic peroxidase-, oxidase- and catalase-like activities. These nanostructures were able to activate hydrogen peroxide or dissolved oxygen for catalyzing the oxidation of organic substrates, and decompose hydrogen peroxide to generate oxygen. More systematic investigations revealed that the peroxidase-like activities of these Pd-based nanomaterials were highly structure- and composition-dependent. Among them, Pd@Pt nanoplates displayed the highest peroxidase-like activity. Based on these findings, Pd-based nanostructures were applied for the colorimetric detection of H2O2 and glucose, and also the electro-catalytic reduction of H2O2. This work offers a promising prospect for the application of 2D noble metal nanostructures in biocatalysis. Electronic supplementary information (ESI) available: TEM images, EDX and dispersion stability of Pd-based nanomaterials

Electronic Absorption and MCD Spectra for Pd(AuPPh(3))(8)(2+), Pt(AuPPh(3))(8)(2+), and Related Platinum-Centered Gold Cluster Complexes.

Science.gov (United States)

Adrowski, Michael J.; Mason, W. Roy

1997-03-26

Electronic absorption and 7.0 T magnetic circular dichroism (MCD) spectra in the UV-vis region, 1.6 to approximately 4.0 &mgr;m(-)(1) (1 &mgr;m(-)(1) = 10(4) cm(-)(1)) are reported for [Pd(AuPPh(3))(8)](NO(3))(2) and [Pt(AuPPh(3))(8)](NO(3))(2) in acetonitrile solutions at room temperature. The MCD spectra are better resolved than the absorption spectra and consist of both A and B terms. The spectra are interpreted in terms of D(4)(d)() skeletal geometry and MO's that are approximated by 5s and 6s orbitals for Pd and Pt/Au atoms, respectively. The lowest energy excited configurations and states are attributed to intraframework (IF) Au(8)(2+) transitions. Evidence is also presented for Pt 5d --> Au 6s transitions in the MCD spectra for Pt(AuPPh(3))(8)(2+). Acetonitrile solution absorption and MCD spectra for the related Pt-centered cluster complexes [Pt(CO)(AuPPh(3))(8)](NO(3))(2), [Pt(AuP(p-tolyl)(3))(8)](NO(3))(2), [Pt(CuCl)(AuPPh(3))(8)](NO(3))(2), [Pt(AgNO(3))(AuPPh(3))(8)](NO(3))(2), [Pt(Hg)(2)(AuPPh(3))(8)](NO(3))(2), [Pt(HgCl)(2)(AuPPh(3))(8)](BF(4))(2), and [Pt(HgNO(3))(2)(AuPPh(3))(8)](BF(4))(2) are also reported and interpreted within the context of the model developed for the M(AuPPh(3))(8)(2+) complexes.

Investigation of palladium-103 production and IR07-103Pd brachytherapy seed preparation

International Nuclear Information System (INIS)

Saidi, Pooneh; Sadeghi, Mahdi; Enferadi, Milad; Aslani, Gholamreza

2011-01-01

Highlights: → We report the cyclotron production of 103-palladium via 103 Rh(p,n) 103 Pd reaction. → 103 Pd was absorbed on resin beads for brachytherapy seed preparation. → The optimum absorption of 103 Pd in resin was achieved at 0.5 M HCl. → Version 5 of MCNP code was employed to model a new 103 Pd brachytherapy seed. - Abstract: In this study, design and fabrication of 103 Pd brachytherapy seed was investigated. The excitation functions of 103 Rh(p,n) 103 Pd and 103 Rh(d,2n) 103 Pd reactions were calculated using EMPIRE (version 3.1 Rivoli), ALICE/ASH and TALYS-1.2 codes, the TENDL-2010 database and compared with the published data. Production of 103 Pd was done via 103 Rh(p,n) 103 Pd nuclear reaction. The target was bombarded with 18 MeV protons at 200 μA beam current for 15 h. After irradiation and radiochemical separation of the electroplated rhodium target, the optimum condition for absorption of 103 Pd into Amberlite (registered) IR-93 resin was achieved at 0.5 M HCl. Version 5 of the (MCNP) Monte Carlo radiation transport code was employed to calculate the dosimetric parameters around the 103 Pd brachytherapy seed. Finally the calculated results were compared with published results for other commercial sources.

The sticking probability for H-2 in presence of CO on some transition metals at a hydrogen pressure of 1 bar

DEFF Research Database (Denmark)

Johansson, Martin; Lytken, Ole; Chorkendorff, Ib

2008-01-01

The sticking probability for H-2 on Ni, Co, Cu, Rh, Ru, Pd, it and Pt metal films supported on graphite has been investigated in a gas mixture consisting of 10 ppm carbon monoxide in hydrogen at a total pressure of 1 bar in the temperature range 40-200 degrees C. Carbon monoxide inhibits the stic......The sticking probability for H-2 on Ni, Co, Cu, Rh, Ru, Pd, it and Pt metal films supported on graphite has been investigated in a gas mixture consisting of 10 ppm carbon monoxide in hydrogen at a total pressure of 1 bar in the temperature range 40-200 degrees C. Carbon monoxide inhibits...... the sticking probability significantly for all the metals, even at 200 degrees C. In the presence of 10 ppm CO, the sticking probability increases in the order It, Pt, Ni, Co, Pd, Rh, Ru, whereas for Cu, it is below the detection limit of the measurement, even in pure H2. The sticking probability for H2...

Effect of flattened surface morphology of anodized aluminum oxide templates on the magnetic properties of nanoporous Co/Pt and Co/Pd thin multilayered films

Science.gov (United States)

Nguyen, T. N. Anh; Fedotova, J.; Kasiuk, J.; Bayev, V.; Kupreeva, O.; Lazarouk, S.; Manh, D. H.; Vu, D. L.; Chung, S.; Åkerman, J.; Altynov, V.; Maximenko, A.

2018-01-01

For the first time, nanoporous Al2O3 templates with smoothed surface relief characterized by flattened interpore areas were used in the fabrication of Co/Pd and Co/Pt multilayers (MLs) with strong perpendicular magnetic anisotropy (PMA). Alternating gradient magnetometry (AGM) revealed perfectly conserved PMA in the Co/Pd and Co/Pt porous MLs (antidot arrays) with a ratio of remanent magnetization (Mr) to saturation magnetization (MS) of about 0.99, anisotropy fields (Ha) of up to 2.6 kOe, and a small deviation angle of 8° between the easy magnetization axis and the normal to the film surface. The sufficient magnetic hardening of the porous MLs with enhanced coercive field HC of up to ∼1.9 kOe for Co/Pd and ∼1.5 kOe for Co/Pt MLs, as compared to the continuous reference samples (∼1.5-2 times), is associated with the pinning of the magnetic moments on the nanopore edges. Application of the Stoner-Wohlfarth model for fitting the experimental M/MS(H) curves yielded clear evidence of the predominantly coherent rotation mechanism of magnetization reversal in the porous films.

Adsorption of Ruthenium, Rhodium and Palladium from Simulated High-Level Liquid Waste by Highly Functional Xerogel - 13286

Energy Technology Data Exchange (ETDEWEB)

Onishi, Takashi [Fukushima Fuels and Materials Department O-arai Research and Development Center Japan Atomic Energy Agency, Narita-cho 4002, O-arai-machi, Ibaraki, 311-1393 (Japan); Koyama, Shin-ichi [Fukushima Fuels and Materials Department O-arai Research and Development Center Japan Atomic Energy Agency, Narita-cho 4002, O-arai-machi, Ibaraki, 311-1393 (Japan); Mimura, Hitoshi [Dept. of Quantum Science and Energy Engineering, Graduate School of Engineering, Tohoku University Aramaki-Aza-Aoba 6-6-01-2,Aoba-ku, Sendai-shi, Miyagi-ken, 980-8579 (Japan)

2013-07-01

Fission products are generated by fission reactions in nuclear fuel. Platinum group (Pt-G) elements, such as palladium (Pd), rhodium (Rh) and ruthenium (Ru), are also produced. Generally, Pt-G elements play important roles in chemical and electrical industries. Highly functional xerogels have been developed for recovery of these useful Pt-G elements from high - level radioactive liquid waste (HLLW). An adsorption experiment from simulated HLLW was done by the column method to study the selective adsorption of Pt-G elements, and it was found that not only Pd, Rh and Ru, but also nickel, zirconium and tellurium were adsorbed. All other elements were not adsorbed. Adsorbed Pd was recovered by washing the xerogel-packed column with thiourea solution and thiourea - nitric acid mixed solution in an elution experiment. Thiourea can be a poison for automotive exhaust emission system catalysts, so it is necessary to consider its removal. Thermal decomposition and an acid digestion treatment were conducted to remove sulfur in the recovered Pd fraction. The relative content of sulfur to Pd was decreased from 858 to 0.02 after the treatment. These results will contribute to design of the Pt-G element separation system. (authors)

Temperature dependence of the electric field gradient in AgPd and AgPt alloys

International Nuclear Information System (INIS)

Krolas, K.

1977-07-01

The measurements of temperature dependence of the electric field gradient (EFG) on 111 Cd nuclei in AgPd and AgPt alloys were performed using the time dependent perturbed angular correlation method. The EFG caused by impurities distributed in further coordination shells decrease stronaer with increasing temperature than the EFG due to single impurity being the nearest neighbour of the probe atom. These results were explained assuming different modes of thermal vibrations of single impurity atoms and impurity complexes in silver host lattice. (author)

Pd-Pt alloys nanowires as support-less electrocatalyst with high synergistic enhancement in efficiency for methanol oxidation in acidic medium.

Science.gov (United States)

Rana, Moumita; Patil, Pramod K; Chhetri, Manjeet; Dileep, K; Datta, Ranjan; Gautam, Ujjal K

2016-02-01

In a facile approach, Pd73Pt27 alloy nanowires (NWs) with large aspect ratios were synthesized in high yield by using sacrificial templates. Unlike majority of processes, our synthesis was carried out in aqueous solution with no intermittent separating stages for the products, while maintaining the NW morphology up to ∼30% of Pt. Upon evaporation of their dispersion, the NWs transform into a stable porous membrane due to self-entanglement and can be directly lifted and employed for electrocatalytic applications without external catalyst supports. We show that the NW membranes exhibit efficient electrocatalytic performance for methanol oxidation reaction (MOR) with 10 times higher mass activity and 4.4 times higher specific activity in acidic media as compared to commercial Pt catalysts. The membrane electrocatalysts is robust and exhibited very good stability with retention of ∼70% mass-activity after 4000 potential cycles. Since Pd was found to be inert towards MOR in acidic medium, our investigation provides a direct estimate of synergistic enhancement of efficiency. Over 10 times increment of mass activity appears to be significantly higher than previous investigations in various other reaction media. Copyright © 2015 Elsevier Inc. All rights reserved.

Computational modelling of Ti50Pt50-xMx shape memory alloys (M: Ni, Ir or Pd and x = 6.25-43.75 at.%)

CSIR Research Space (South Africa)

Modiba, Rosinah M

2017-09-01

Full Text Available The ab initio density functional theory approach was employed to study the effect of Ni, Ir or Pd addition to the TiPt shape memory alloy. The supercell approach in VASP was used to substitute Pt with 6.25, 18.75, 25.00, 31.25 and 43.75 at.% Ni, Ir...

Salt-induced phase separation for the determination of metals as their diethyldithiocarbamate complexes by high-performance liquid chromatography

International Nuclear Information System (INIS)

Mueller, B.J.; Lovett, R.J.

1987-01-01

Reversed-phase high-performance liquid chromatography with ultraviolet detection can be used to determine trace levels of Pt(II), Pd(II), Rh(III), Co(III), Ru(III), and Ir in aqueous solution following complexation with diethyldithiocarbamate. The metal complexes are extracted into acetonitrile from aqueous solution by the addition of a saturated salt solution. Quantitative metal recovery from aqueous solution is achievable for most metals for a wide solution pH range. Detection limits for the metals are <3 ng of metal/mL of original aqueous sample. Analyses of real samples are highly reproducible and sensitive. Ir an interfere in the determination of Pt(II) and Rh(III). A general protocol for chromatographic separation and determination of Pt(II), Pd(II), Rh(III), Ru(III), and Ir in aqueous solution is presented

A Reactive Oxide Overlayer on Rh Nanoparticles during CO Oxidation and Its Size Dependence Studied by in Situ Ambient Pressure XPS

International Nuclear Information System (INIS)

Grass, Michael E.; Zhang, Yawen; Butcher, Derek R.; Park, Jeong Y.; Li, Yimin; Bluhm, Hendrik; Bratlie, Kaitlin M.; Zhang, Tianfu; Somorjai, Gabor A.

2008-01-01

CO oxidation is one of the most studied heterogeneous reactions, being scientifically and industrially important, particularly for removal of CO from exhaust streams and preferential oxidation for hydrogen purification in fuel cell applications. The precious metals Ru, Rh, Pd, Pt, and Au are most commonly used for this reaction because of their high activity and stability. Despite the wealth of experimental and theoretical data, it remains unclear what is the active surface for CO oxidation under catalytic conditions for these metals. In this communication, we utilize in situ synchrotron ambient pressure X-ray photoelectron spectroscopy (APXPS) to monitor the oxidation state at the surface of Rh nanoparticles during CO oxidation and demonstrate that the active catalyst is a surface oxide, the formation of which is dependent on particle size. The amount of oxide formed and the reaction rate both increase with decreasing particle size.

Separation and preconcentration of platinum-group metals from spent autocatalysts solutions using a hetero-polymeric S, N-containing sorbent and determination by high-resolution continuum source graphite furnace atomic absorption spectrometry.

Science.gov (United States)

Eskina, Vasilina V; Dalnova, Olga A; Filatova, Daria G; Baranovskaya, Vasilisa B; Karpov, Yuri A

2016-10-01

This paper describes the potential of high-resolution continuum source graphite furnace atomic absorption spectrometry for determination of Pt, Pd and Rh after separation and concentration by original in-house developed heterochain polymer S, N-containing sorbent. The methods of sample preparation of spent ceramic-based autocatalysts were considered, two of which were used: autoclave decomposition in mixture of acids HCl:HNO3 (3:1) and high-temperature melting with K2S2O7. Both methods anyway limit the direct determination of analytes by HR CS GFAAS. Using the first method it is an incomplete digestion of spent autocatalysts samples, since the precipitate is Si, and the rhodium metal dissolves with difficulty and partially passes into solution. In contrast to the first method, the second method allow to completely transfer analytes into solution, however, the background signal produced by the chemical composition of the flux, overlaps the analytical zone. It was found, that Pt, Pd and Rh contained in the spent ceramic automotive catalysts could be effectively separated and concentrated by heterochain polymer S, N-containing sorbent, which has high sorption capacity, selectivity and resistant to dilute acids. The chosen HR CS GFAAS analysis conditions enable us to determine Pt, Pd and Rh with good metrological characteristics. The concentrations of Pt, Pd and Rh in two samples of automobile exhaust catalysts were found in range of 0.00015-0.00050; 0.170-0.189; 0.0180-0.0210wt%, respectively. The relative standard deviation obtained by HR CS GFAAS was not more than 5%. Limits of detection by HR CS GFAAS achieved were 6.2·10(-6)wt% for Pt, 1.8·10(-6)wt% for Pd, and 3.4·10(-6)wt% for Rh. Limits of determination achieved by HR CS GFAAS were 1.1·10(-5)wt% for Pt, 6.9·10(-5)wt% for Pd, and 8.3·10(-5)wt% for Rh. To control the accuracy of PGM in sorption concentrates by HR CS GFAAS method, it was appropriate to conduct an inter-method comparative experiment. The

London penetration depth measurements in Ba (Fe_1-xT_x)₂As₂(T=Co,Ni,Ru,Rh,Pd,Pt,Co+Cu) superconductors

Energy Technology Data Exchange (ETDEWEB)

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

2011-01-01

The London penetration depth has been measured in various doping levels of single crystals of Ba(Fe_1-xT_x)₂As₂ (T=Co,Ni,Ru,Rh,Pd,Pt,Co+Cu) superconductors by utilizing a tunnel diode resonator (TDR) apparatus. All in-plane penetration depth measurements exhibit a power law temperature dependence of the form Δλ_ab(T) = CTⁿ, indicating the existence of low-temperature, normal state quasiparticles all the way down to the lowest measured temperature, which was typically 500 mK. Several different doping concentrations from the Ba(Fe_1-xT_x)₂As₂ (T=Co,Ni) systems have been measured and the doping dependence of the power law exponent, n, is compared to results from measurements of thermal conductivity and specific heat. In addition, a novel method has been developed to allow for the measurement of the zero temperature value of the in-plane penetration depth, λ_ab(0), by using TDR frequency shifts. By using this technique, the doping dependence of λ_ab(0) has been measured in the Ba(Fe_1-xCo_x)₂As₂ series, which has allowed also for the construction of the doping-dependent superfluid phase stiffness, ρ_s(T) = [λ(0)/λ(T)]². By studying the effects of disorder on these superconductors using heavy ion irradiation, it has been determined that the observed power law temperature dependence likely arises from pair-breaking impurity scattering contributions, which is consistent with the proposed s±-wave symmetry of the superconducting gap in the dirty scattering limit. This hypothesis is supported by the measurement of an exponential temperature dependence of the penetration depth in the intrinsically clean LiFeAs, indicative of a nodeless superconducting gap.

Isobaric yields and radiochemistry of near-target residues in the interaction of 12C and 16O with 103Rh at an incident energy of 400 MeV

International Nuclear Information System (INIS)

Buthelezi, E.Z.; Steyn, G.F.; Walt, T.N. Van der; Aardaneh, K.; Gadioli, E.; Albertini, F.; Cerutti, F.; Connell, S.H.; Cowley, A.A.; Nortier, F.M.

2003-01-01

Production cross sections of residues with mass near to that of the target were measured in 12 C and 16 O induced reactions on Rh at an incident energy of 400 MeV. An ion-exchange method has been developed for the separation of Rh, Pd and Ag nuclides from all other produced activities. Rh and Ag nuclides were separated from elements such as Pd, Ru, and Tc, amongst others, on an AG1-X8 anion exchange resin in 6M HCl. The Ag nuclides were then removed from the effluent using a precipitation technique so that only Rh remained in the final solution. The Pd was afterwards separated from Ru and Tc by eluting it from the resin with 5% ammonia solution. This procedure made it possible to accurately measure production cross sections for 103m Rh and 103 Pd. Cross sections for the production of various other observed residues are also presented. The results are consistent with an enhanced isobaric yield in the near-target mass region. The radiochemical separation technique is also suitable for the routine production of Pd and Rh nuclides, e.g., 103 Pd and 101m Rh, in proton-induced reactions on Rh targets. (author)

Acetylene and carbon monoxide oxidation over a Pt/Rh/CeO2/γ-Al2O3 automotive exhaust gas catalyst: kinetic modelling of transient experiments

NARCIS (Netherlands)

Harmsen, J.M.A.; Hoebink, J.H.B.J.; Schouten, J.C.

2001-01-01

The transient kinetics of acetylene (C2H2) conversion by oxygen over a commercial Pt/Rh/CeO2/¿-Al2O3 three-way catalyst have been modelled. Experiments to validate the model were carried out in a fixed-bed reactor with two separate inlets, enabling alternate feeding of acetylene and oxygen.

Effect of PW12–GPK on the acid characteristics of Ni-, Pd- and Pt- catalysts deposited onto pillared Al montmorillonite

Directory of Open Access Journals (Sweden)

D. Zhumadullaev

2012-03-01

Full Text Available Acid characteristics of Ni-, Pd-, Pt- catalyzers , deposited to Al pillared CaH montmorillonite modified by heteropolyacid H3PW12O40·xH2O (PW12 by ammonia thermoadsorbtion method has been studied.

[Bifunctional chelates of Rh-105, Au-199, and other metallic radionuclides as potential radiotherapeutic agents

International Nuclear Information System (INIS)

1991-01-01

Progress during this period is reported under the following headings: Diethylenetriamine based and related bifunctional chelating agents and their complexation with Rh-105, Au-198, Pd-109, cu-67, In-111, and Co-57; studies of Pd-109, Rh-105 and Tc-99m with bifunctional chelates based on phenylenediamine; establishment of an appropriate protein assay method for conjugated proteins; studies of new bifunctional Bi, Tri and tetradentate amine oxime ligands with Rh-105; IgG and antibody B72.3 conjugation studies by HPLC Techniques with bifunctional metal chelates; and progress on ligand systems for Au(III)

[Bifunctional chelates of Rh-105, Au-199, and other metallic radionuclides as potential radiotherapeutic agents

Energy Technology Data Exchange (ETDEWEB)

1991-12-31

Progress during this period is reported under the following headings: Diethylenetriamine based and related bifunctional chelating agents and their complexation with Rh-105, Au-198, Pd-109, cu-67, In-111, and Co-57; studies of Pd-109, Rh-105 and Tc-99m with bifunctional chelates based on phenylenediamine; establishment of an appropriate protein assay method for conjugated proteins; studies of new bifunctional Bi, Tri and tetradentate amine oxime ligands with Rh-105; IgG and antibody B72.3 conjugation studies by HPLC Techniques with bifunctional metal chelates; and progress on ligand systems for Au(III).

(Bifunctional chelates of Rh-105, Au-199, and other metallic radionuclides as potential radiotherapeutic agents)

Energy Technology Data Exchange (ETDEWEB)

1991-01-01

Progress during this period is reported under the following headings: Diethylenetriamine based and related bifunctional chelating agents and their complexation with Rh-105, Au-198, Pd-109, cu-67, In-111, and Co-57; studies of Pd-109, Rh-105 and Tc-99m with bifunctional chelates based on phenylenediamine; establishment of an appropriate protein assay method for conjugated proteins; studies of new bifunctional Bi, Tri and tetradentate amine oxime ligands with Rh-105; IgG and antibody B72.3 conjugation studies by HPLC Techniques with bifunctional metal chelates; and progress on ligand systems for Au(III).

Ni(II, Pd(II and Pt(II complexes with ligand containing thiosemicarbazone and semicarbazone moiety: synthesis, characterization and biological investigation

Directory of Open Access Journals (Sweden)

SULEKH CHANDRA

2008-07-01

Full Text Available The synthesis of nickel(II, palladium(II and platinum(II complexes with thiosemicarbazone and semicarbazone of p-tolualdehyde are reported. All the new compounds were characterized by elemental analysis, molar conductance measurements, magnetic susceptibility measurements, mass, 1H-NMR, IR and electronic spectral studies. Based on the molar conductance measurements in DMSO, the complexes may be formulated as [Ni(L2Cl2] and [M(L2]Cl2 (where M = Pd(II and Pt(II due to their non-electrolytic and 1:2 electrolytic nature, respectively. The spectral data are consistent with an octahedral geometry around Ni(II and a square planar geometry for Pd(II and Pt(II, in which the ligands act as bidentate chelating agents, coordinated through the nitrogen and sulphur/oxygen atoms. The ligands and their metal complexes were screened in vitro against fungal species Alternaria alternata, Aspergillus niger and Fusarium odum, using the food poison technique.

An electro-hydraulic servo control system research for CFETR blanket RH

Energy Technology Data Exchange (ETDEWEB)

Chen, Changqi [Hefei University of Technology, Hefei 230009, Anhui (China); Tang, Hongjun, E-mail: taurustang@126.com [Hefei University of Technology, Hefei 230009, Anhui (China); Qi, Songsong [Hefei University of Technology, Hefei 230009, Anhui (China); Cheng, Yong; Feng, Hansheng; Peng, Xuebing; Song, Yuntao [Institute of Plasma Physics Chinese Academy of Sciences, Hefei 230031, Anhui (China)

2014-11-15

Highlights: • We discussed the conceptual design of CFETR blanket RH maintenance system. • The mathematical model of electro-hydraulic servo system was calculated. • A fuzzy adaptive PD controller was designed based on control theory and experience. • The co-simulation models of the system were established with AMESim/Simulink. • The fuzzy adaptive PD algorithm was designed as the core strategy of the system. - Abstract: Based on the technical design requirements of China Fusion Engineering Test Reactor (CFETR) blanket remote handling (RH) maintenance, this paper focus on the control method of achieving high synchronization accuracy of electro-hydraulic servo system. Based on fuzzy control theory and practical experience, a fuzzy adaptive proportional-derivative (PD) controller was designed. Then a more precise co-simulation model was established with AMESim/Simulink. Through the analysis of simulation results, a fuzzy adaptive PD control algorithm was designed as the core strategy of electro-hydraulic servo control system.

An electro-hydraulic servo control system research for CFETR blanket RH

International Nuclear Information System (INIS)

Chen, Changqi; Tang, Hongjun; Qi, Songsong; Cheng, Yong; Feng, Hansheng; Peng, Xuebing; Song, Yuntao

2014-01-01

Highlights: • We discussed the conceptual design of CFETR blanket RH maintenance system. • The mathematical model of electro-hydraulic servo system was calculated. • A fuzzy adaptive PD controller was designed based on control theory and experience. • The co-simulation models of the system were established with AMESim/Simulink. • The fuzzy adaptive PD algorithm was designed as the core strategy of the system. - Abstract: Based on the technical design requirements of China Fusion Engineering Test Reactor (CFETR) blanket remote handling (RH) maintenance, this paper focus on the control method of achieving high synchronization accuracy of electro-hydraulic servo system. Based on fuzzy control theory and practical experience, a fuzzy adaptive proportional-derivative (PD) controller was designed. Then a more precise co-simulation model was established with AMESim/Simulink. Through the analysis of simulation results, a fuzzy adaptive PD control algorithm was designed as the core strategy of electro-hydraulic servo control system

Successful treatment of Rh alloimmunization in a twin pregnancy: case report

Directory of Open Access Journals (Sweden)

Rahimi Sharbaf F

2008-09-01

Full Text Available "n Normal 0 false false false EN-US X-NONE AR-SA MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;} Background: The prevalence of Rh alloimmunization has decreased following the use of anti-D immunoglobulin. With serial amniocentesis, Doppler sonography of the middle cerebral artery and treatment of anemia with intrauterine blood transfusion, perinatal mortality has declined. However, Rh alloimmunization in twin pregnancies poses a diagnostic and therapeutic challenge."n"n Case report: We are reporting, for the first time in Iran, the successful treatment of severe Rh alloimmunization in a dichorionic- diamnionic twin pregnancy leading to the live births of both neonates. Before treatment, the fetal hemoglobin levels were 3.1g/dL and 3.9g/dL, with ascites in both fetuses. The fetuses were treated with several IUTs."n"n Results: After treatment, the neonates were delivered, weighing 2200 and 2300g, with good Apgar scores, at a gestational age of 34 weeks. "n"n Conclusion: 10% of population in Iran is Rh-negative, although Prophylaxis for Rh alloimmunization is universal, as other part of the world it cannot irrigated. For the best management of these cases, we need a well-equipped referral center."n"n Keywords: Twin, pregnancy, Rh alloimmunization, intrauterine blood transfusion, Doppler, middle cerebral

High pressure stability of the monosilicides of cobalt and the platinum group elements

International Nuclear Information System (INIS)

Hernandez, J.A.; Vočadlo, L.; Wood, I.G.

2015-01-01

Highlights: • We model the high-pressure phases of cobalt- and platinum-group-monosilicides. • CoSi, RuSi, OsSi transform with pressure from the ε-FeSi to the CsCl structure. • RhSi and IrSi transform with pressure from the MnP structure to the ε-FeSi structure. • PdSi and PtSi transform with pressure from the MnP structure to the CuTi structure. - Abstract: The high pressure stability of CoSi, RuSi, RhSi, PdSi, OsSi, IrSi and PtSi was investigated by static first-principles calculations up to 300 GPa at 0 K. As found experimentally, at atmospheric pressure, CoSi, RuSi and OsSi were found to adopt the cubic ε-FeSi structure (P2 1 3) whereas RhSi, PdSi, IrSi and PtSi were found to adopt the orthorhombic MnP (Pnma) structure. At high pressure, CoSi, RuSi and OsSi show a phase transition to the CsCl structure (Pm3 ¯ m) structure at 270 GPa, 7 GPa and 6 GPa respectively. RhSi and IrSi were found to transform to an ε-FeSi structure at 10 GPa and 25 GPa. For PdSi and PtSi, a transformation from the MnP structure to the tetragonal CuTi structure (P4/nmm) occurs at 13 GPa and 20 GPa. The pressure dependence of the electronic density of states reveals that RuSi and OsSi are semiconductors in the ε-FeSi structure and become metallic in the CsCl structure. RhSi and IrSi are metals in the MnP structure and become semimetals in their high pressure ε-FeSi form. CoSi in the ε-FeSi configuration is a semimetal. PdSi and PtSi remain metallic throughout up to 300 GPa

Problems, possibilities and limitations of inductively coupled plasma atomic emission spectrometry in the determination of platinum, palladium and rhodium in samples with different matrix composition

Energy Technology Data Exchange (ETDEWEB)

Petrova, P.; Velichkov, S. [Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bontchev Str. bl. 11, 1113 Sofia (Bulgaria); Velitchkova, N. [Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bontchev Str., bl.24, 1113 Sofia (Bulgaria); Havezov, I. [Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bontchev Str. bl. 11, 1113 Sofia (Bulgaria); Daskalova, N., E-mail: das15482@svr.igic.bas.b [Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bontchev Str. bl. 11, 1113 Sofia (Bulgaria)

2010-02-15

The economic and geological importance of platinum group of elements has led to the development of analytical methods to quantify them in different types of samples. In the present paper the quantitative information for spectral interference in radial viewing 40.68 MHz inductively coupled plasma atomic emission spectrometry in the determination of Pt, Pd and Rh in the presence of complex matrix, containing Al, Ca, Fe, Mg, Mn, P and Ti as matrix constituents was obtained. The database was used for optimum line selections. By using the selected analysis lines the following detection limits in ng g{sup -1} were obtained: Pt 1700, Pd-1440, Rh-900. The reached detection limits determine the possibilities and limitation of the direct ICP-AES method in the determination of Pt, Pd and Rh in geological and environmental materials. The database for spectral interferences in the presence of aluminum can be used for the determination of platinum group of elements in car catalysts. The accuracy of the analytical results was experimentally demonstrated by two certified reference materials that were analyzed: SARM 7, Pt ore and recycled auto-catalyst certified reference material SRM 2556.

Cross section measurement for the reaction /sup 103/Rh (n,n') /sup 103m/Rh

International Nuclear Information System (INIS)

Paulsen, A.; Liskien, H.; Vaninbroukx, R.; Widera, R.

1980-01-01

The excitation function for the reaction /sup 103/Rh (n,n') /sup 103m/Rh was measured by the activation technique from 0.2 to 6.1 MeV in 0.1-MeV steps and from 13.0 to 16.7 MeV in 1-MeV steps. This excitation function is normalized through an absolute measurement at 1.8 MeV. This measurement is based on n-p scattering for neutron flux determination and on liquid scintillation counting of /sup 103m/Rh separated from /sup 103/Pd solutions for the activity determination. The total uncertainty of the cross-section results is typically + or -5% above 0.5 MeV (about + or -10% above 13 MeV). Concurrence with existing data is good except below 0.35 MeV, where the present results are considerably higher

New organometallic salts as precursors for the functionalization of carbon nanotubes with metallic nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Alonso-Nunez, G., E-mail: galonso@cnyn.unam.mx; Garza, L. Morales de la; Rogel-Hernandez, E.; Reynoso, E. [Universidad Nacional Autonoma de Mexico, Centro de Nanociencias y Nanotecnologia (Mexico); Licea-Claverie, A.; Felix-Navarro, R. M. [Instituto Tecnologico de Tijuana, Centro de Graduados e Investigacion (Mexico); Berhault, G. [UMR 5256 CNRS-Universite de Lyon, Institut de Recherches sur la Catalyse et l' Environnement de Lyon (France); Paraguay-Delgado, F. [Centro de Investigacion en Materiales Avanzados S. C. (Mexico)

2011-09-15

New organometallic salts were synthesized in aqueous solution and were used as precursors for the functionalization of carbon nanotubes (CNT) by metallic nanoparticles. The precursors were obtained by reaction between HAuCl{sub 4}, (NH{sub 4}){sub 2}PtCl{sub 6}, (NH{sub 4}){sub 2}PdCl{sub 6}, or (NH{sub 4}){sub 3}RhCl{sub 6} with cetyltrimethylammonium bromide (CTAB). The as-obtained (CTA){sub n}Me{sub x}Cl{sub y} salts (with Me = Au, Pt, Pd, Rh) were characterized by Fourier-transform infra-red (FTIR) spectroscopy, {sup 1}H nuclear magnetic resonance (NMR) spectroscopy, and thermogravimetric analysis. These precursors were then used to synthesize metallic nanoparticles of Au, Pt, Pd, and Rh over multiwalled carbon nanotubes (MWCNT). Characterization by scanning transmission electron microscopy (STEM) and thermogravimetric analysis under air reveals that the CNT-supported catalysts exhibit high loading and good dispersion of the metallic nanoparticles with small average particle sizes. The present preparation procedure therefore allows obtaining high densities of small metallic nanoparticles at the surface of MWCNT.

X-ray fluorescence determination of Au, Pd and Pt from chloride solutions after preconcentration on cellulose filters

International Nuclear Information System (INIS)

Gordeeva, V.P.; Glazkova, S.V.; Tsysin, G.I.; Ivanov, V.M.; Zolotov, Yu. A.

2003-01-01

The aim of this work was synthesis of new sorption cellulose filters for dynamic preconcentration of Au, Pd and Pt from chloride solutions and subsequent XRF determination of these elements on the filters. New filters were prepared by impregnation of a filter paper with solution of tri-n-octylamine and paraffin in hexane (TOA-filters). The effect of paraffin and TOA concentration in hexane on a content of nitrogen in a filter was studied. It was found that Au(III), Pd(II) and Pt(IV) were quantitatively recovered on the TOA-filters (filtering surface diameter of 23 mm, thickness of 0.15 mm) from 0.5 - 1 M HCl at a flow rates of 2-5 ml min-1 from 10-100 ml of solution. The mathematical model of sorption dynamics was offered for the estimation of potential possibilities of new impregnated sorbents and for the evaluation of optimum dynamic conditions allowing to achieve of maximum concentration efficiency (CE max ). The elements were determined directly on the filters by XRF spectrometer. Palladium was also determined on the TOA-filters after formation of coloured compounds of metal with 4-(2-pyridylazo)resorcinol (PAR) by diffuse reflectance spectroscopy with the calculation of calorimetric characteristics and using test-scale. (authors)

Kinetic study of the ethene oxidation by oxygen in the presence of carbon dioxide and steam over Pt/Rh/CeO2/g-Al2O3

NARCIS (Netherlands)

Nibbelke, R.H.; Kreijveld, R.J.M.; Hoebink, J.H.B.J.; Marin, G.B.M.M.; Kruse, N.

1998-01-01

The oxidation of ethene by oxygen in the presence of steam and carbon dioxide over a commercially available Pt/Rh/CeO2/¿-Al2O3 three-way automotive catalyst was studied. Experiments were carried out in a fixed-bed micro reactor under intrinsic conditions, i.e. in the absence of external and internal

Feasibility test for production and separation of 103Pd

International Nuclear Information System (INIS)

Szuecs, Z.; Takacs, S.; Hunyadi, M.; Gacsi, Z.; Zeevaart, J.R.

2011-01-01

Complete text of publication follows. 103 Pd as a well-known Auger-emitter is commonly employed in brachytherapy, but the ultra-short range stopping of Auger-electrons can be more potentially exploited in applications of targeted radionuclide therapy in the future. The no-carrier-added production of 103 Pd is practically possible through charged particle induced reactions. However, separation techniques of 103 Pd from the target material (typically Rh), as well as its recovery by wet chemistry are expensive, and yields high amounts of radioactive waste. An alternative and more efficient procedure, called drydistillation method (DDM), is based on differences between the isothermal vapor pressures of the radionuclide element and the target element. In an appropriately selected temperature region the diffusion and out-gassing rates of radionuclides from the solid matrix of the target material are enhanced. Optimal irradiation parameters were determined in previous experiments at ATOMKI. Separation of 103 Pd was demonstrated at the Isotope Separator Laboratory with an evaporating-condensing system (Fig. 1). Figure 1. Evaporation-condensation system at the Isotope Separator Laboratory of ATOMKI. The irradiated Rh foil was kept above 1800?C in vacuum for several hours. The evaluation of γ-spectra of the Rh foil and the 103 Pd condensed on a low-temperature substrate (Fig. 2). The analysis resulted in a radiochemical yield of about 99.5% for 103 Pd and a radionuclidic purity of better than 99% with respect to the level of 101 Rh in the end product. Acknowledgement. The work was partly supported by the Hungarian TeT Bilateral Cooperation (OMFB- 00138/2009) and by the South African NRF (UID 68768).

Synthesis and characterization of Pd@M(x)Cu(1-x) (M = Au, Pd, and Pt) nanocages with porous walls and a yolk-shell structure through galvanic replacement reactions.

Science.gov (United States)

Xie, Shuifen; Jin, Mingshang; Tao, Jing; Wang, Yucai; Xie, Zhaoxiong; Zhu, Yimei; Xia, Younan

2012-11-19

This paper describes the synthesis of Pd@M(x)Cu(1-x) (M = Au, Pd, and Pt) nanocages with a yolk-shell structure through galvanic replacement reactions that involve Pd@Cu core-shell nanocubes as sacrificial templates and ethylene glycol as the solvent. Compared with the most commonly used templates based on Ag, Cu offers a much lower reduction potential (0.34 versus 0.80 V), making the galvanic reaction more easily to conduct, even at room temperature. Our structural and compositional characterizations indicated that the products were hollow inside, and each one of them contained porous M-Cu alloy walls and a Pd cube in the interior. For the Pd@Au(x)Cu(1-x) yolk-shell nanocages, they displayed broad extinction peaks extending from the visible to the near-IR region. Our mechanistic study revealed that the dissolution of the Cu shell preferred to start from the slightly truncated corners and then progressed toward the interior, because the Cu {100} side faces were protected by a surface capping layer of hexadecylamine. This galvanic approach can also be extended to generating other hollow metal nanostructures by using different combinations of Cu nanostructures and salt precursors. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Influence of adsorbed carbon dioxide on hydrogen electrosorption in palladium-platinum-rhodium alloys

International Nuclear Information System (INIS)

Lukaszewski, M.; Grden, M.; Czerwinski, A.

2004-01-01

Carbon dioxide electroreduction was applied to examine the processes of hydrogen electrosorption (adsorption, absorption and desorption) by thin electrodeposits of Pd-Pt-Rh alloys under conditions of cyclic voltammetric (CV) experiments. Due to different adsorption characteristics towards the adsorption product of the electroreduction of CO 2 (reduced CO 2 ) exhibited by the alloy components hydrogen adsorption and hydrogen absorption signals can be distinguished on CV curves. Reduced CO 2 causes partial blocking of hydrogen adsorbed on surface Pt and Rh atoms, without any significant effect on hydrogen absorption into alloy. It reflects the fact that adsorbed hydrogen bonded to Pd atoms does not participate in CO 2 reduction, while hydrogen adsorbed on Pt and Rh surface sites is inactive in the absorption reaction. In contrast, CO is adsorbed on all alloy components and causes a marked inhibition of hydrogen sorption (both adsorption and absorption)/desorption reactions

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 

Atomic resolution structural insights into PdPt nanoparticle–carbon interactions for the design of highly active and stable electrocatalysts

International Nuclear Information System (INIS)

Slanac, Daniel A.; Li Lin; Mayoral, Alvaro; Yacaman, Miguel José; Manthiram, Arumugam; Stevenson, Keith J.; Johnston, Keith P.

2012-01-01

Graphical abstract: - Abstract: Interfacial interactions between sub-4 nm metal alloy nanoparticles and carbon supports, although not well understood at the atomic level, may be expected to have a profound influence on catalytic properties. Pd 3 Pt 2 alloy particles comprised of a disordered surface layer over a corrugated crystalline core are shown to exhibit strong interfacial interactions with a ∼20–50 nm spherical carbon support, as characterized by probe aberration corrected scanning transmission electron microscopy (pcSTEM). The disordered shells were formed from defects introduced by Pd during arrested growth synthesis of the alloy nanoparticles. The chemical and morphological changes in the catalyst, before and after cyclic stability testing (1000 cycles, 0.5–1.2 V), were probed with cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and pcSTEM. The strong metal–support interaction, along with the uniform alloy structure raised the mass activity by a factor of 1.8 versus pure Pt. The metal–support interactions also mitigated nanoparticle coalescence, dissolution, and ripening, resulting in only a 20% loss in mass activity (versus 60% for pure Pt on carbon) after the cyclic stability test. The design of alloy structure, guided by insight from atomic scale pcSTEM, for enhanced catalytic activity and stability, resulting from strong wetting with a deformable disordered shell, has the potential to be a general paradigm for improving catalytic performance.

Effect of Platinum Group Metal Doping in Magnesium Diboride Wires

DEFF Research Database (Denmark)

Grivel, Jean-Claude; Alexiou, Aikaterini; Namazkar, Shahla

2016-01-01

The effect of some platinum group metals(PGM = Rh, Pd, and Pt) on the microstructure and critical current density of Cu/Nb-sheathed MgB2 wires has been studied using Mg1-x PGMxB2 powders with low doping levels. It was found that Pt and Pd do not enter the MgB2 lattice and have only limited influe...

Aromatization of n-octane over Pd/C catalysts

KAUST Repository

Yin, Mengchen; Natelson, Robert H.; Campos, Andrew A.; Kolar, Praveen; Roberts, William L.

2013-01-01

Gas-phase aromatization of n-octane was investigated using Pd/C catalyst. The objectives were to: (1) determine the effects of temperature (400-600 °C), weight hourly space velocity (WHSV) (0.8-∞), and hydrogen to hydrocarbon molar ratio (MR) (0-6) on conversion, selectivity, and yield (2) compare the activity of Pd/C with Pt/C and Pt/KL catalysts and (3) test the suitability of Pd/C for aromatization of different alkanes including n-hexane, n-heptane, and n-octane. Pd/C exhibited the best aromatization performance, including 54.4% conversion and 31.5% aromatics yield at 500 °C, WHSV = 2 h-1, and a MR of 2. The Pd/C catalyst had higher selectivity towards the preferred aromatics including ethylbenzene and xylenes, whereas Pt/KL had higher selectivity towards benzene and toluene. The results were somewhat consistent with adsorbed n-octane cyclization proceeding mainly through the six-membered ring closure mechanism. In addition, Pd/C was also capable of catalyzing aromatization of n-hexane and n-heptane. © 2012 Elsevier Ltd. All rights reserved.

Improvement of energy conversion efficiency and power generation in direct borohydride-hydrogen peroxide fuel cell: The effect of Ni-M core-shell nanoparticles (M = Pt, Pd, Ru)/Multiwalled Carbon Nanotubes on the cell performance

Science.gov (United States)

Hosseini, M. G.; Mahmoodi, R.

2017-12-01

In this study, core@shell nanoparticles with Ni as a core material and Pt, Pd and Ru as shell materials are synthesized on multiwalled carbon nanotube (MWCNT) as catalyst support using the sequence reduction method. The influence of Ni@Pt, Ni@Pd and Ni@Ru core@shell nanoparticles on MWCNT toward borohydride oxidation in alkaline solution is investigated by various three-electrode electrochemical techniques. Also, the impact of these anodic electrocatalysts on the performance of direct borohydride-hydrogen peroxide fuel cell (DBHPFC) is evaluated. The structural and morphological properties of electrocatalysts are studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS). The results of three electrode investigations show that Ni@Pd/MWCNT has excellent catalytic activity since borohydride oxidation current density on Ni@Pd/MWCNT (34773.27 A g-1) is 1.37 and 9.19 times higher than those of Ni@Pt/MWCNT (25347.27 A g-1) and Ni@Ru/MWCNT (3782.83 A g-1), respectively. Also, the energy conversion efficiency and power density of DBHPFC with Ni@Pd/MWCNT (246.82 mW cm-2) increase to 34.27% and 51.53% respect to Ni@Pt/MWCNT (162.24 mW cm-2) and Ni@Ru/MWCNT (119.62 mW cm-2), respectively. This study reveals that Ni@Pd/MWCNT has highest activity toward borohydride oxidation and stability in fuel cell.

Experimental investigation of air relative humidity (RH) cycling tests on MEA/cell aging in PEMFC. Pt. I. Study of high RH cycling test with air RH at 62%/100%

Energy Technology Data Exchange (ETDEWEB)

Huang, B.T.; Chatillon, Y.; Bonnet, C.; Lapicque, F. [Laboratoire Reactions et Genie des Procedes, CNRS-Nancy University, Nancy (France); Leclerc, S. [Laboratoire d' Energetique et de Mecanique Theorique et Appliquee, CNRS-Nancy University, Vandoeuvre-les-Nancy (France); Hinaje, M.; Rael, S. [Groupe de Recherche en Electrotechnique et Electronique de Nancy, CNRS-Nancy University, Vandoeuvre-les-Nancy (France)

2012-06-15

The effect of high air relative humidity (RH) cycling (RH{sub C} 62%/100%) on the degradation mechanisms of a single (5 x 5 cm{sup 2}) proton exchange membrane fuel cells was investigated. The cell performance was compared to a cell operated at constant humidification (RH{sub C} = 62%). Runs were conducted over approximately 1,500 h at 0.3 A cm{sup -2}. The overall loss in cell performance for the high RH cycling test was 12 {mu}V h{sup -1} whereas it was at 3 {mu}V h{sup -1} under constant humidification. Impedance spectroscopy reveals that the ohmic and charge transfer resistances were little modified in both runs. H{sub 2} crossover measurement indicated that both high RH cycling and constant RH test did not promote serious effect on gas permeability. The electroactive surface loss for anode and cathode during high air RH cycling was more significant than at constant RH operation. The water uptake determined by {sup 1}H nuclear magnetic resonance within the membrane electrode assembly (MEA) after high RH cycling was reduced by 12% in comparison with a fresh MEA. Transmission electron microscopy showed bubbles and pinholes formation in the membrane, catalyst particles agglomeration (also observed by X-ray diffraction), catalyst particles migration in the membrane and thickness reduction of the catalytic layers. Scanning electron microscopy was conducted to observe the changes in morphology of gas diffusion layers after the runs. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

LEED crystallography studies of the structure of clean and adsorbate-covered Ir, Pt and Rh crystal surfaces

International Nuclear Information System (INIS)

Koestner, R.J.

1982-08-01

There have only been a few Low Energy Electron Diffraction (LEED) intensity analyses carried out to determine the structure of molecules adsorbed on metal surfaces; most surface crystallography studies concentrated on the structure of clean unreconstructed or atomic adsorbate-covered transition metal faces. The few molecular adsorption systems already investigated by dynamical LEED are CO on Ni(100), Cu(100) and Pd(100) as well as C 2 H 2 and C 2 H 4 adsorbed on Pt(111). The emphasis of this thesis research has been to extend the applicability of LEED crystallography to the more complicated unit cells found in molecular overlayers on transition metals or in there constructed surfaces of clean transition metals

Strength of FePd/MgO and FePt/MgO interfaces from first principles

Science.gov (United States)

Černý, M.

2018-04-01

Cleavage characteristics such as the cleavage energy and the cleavage stress of FePd/MgO and FePt/MgO interfaces are computed from first principles. Considering several possible cleavage planes, the weakest link in these systems is found as the plane with the lowest cleavage stress. This weakest plane is identified in both systems with the interface plane, where the cohesion is reduced by 30% compared to the MgO bulk. Two distinct models of tensile test are employed to verify the results and convergence of computed values with respect to size of the simulation cell is discussed.

103Pd decay

International Nuclear Information System (INIS)

Belyavenko, V.S.; Borozenets, G.P.; Vishnevskij, I.N.; Zheltonozhskij, V.A.

1986-01-01

103 Pd decay in different chemical states has been investigated. The change of the partial half-life period equal to 0.67±0.15% has been detected. The γ-spectrum has been measured to a high precision. The new data have been obtained on population probabilities of 103 Rh excited states and the total energy of decay for 103 Pd has been determined to a high precision (543.0±0.8). The values of log ft have been determined

Induction of heat shock proteins (hsp70) in the zebra mussel (Dreissena polymorpha) following exposure to platinum group metals (platinum, palladium and rhodium): Comparison with lead and cadmium exposures

Energy Technology Data Exchange (ETDEWEB)

Singer, Christoph [Zoologisches Institut I-Oekologie, Universitaet Karlsruhe, Geb. 07.01, Kornblumenstrasse 13, D-76131 Karlsruhe (Germany); Zimmermann, Sonja [Zoologisches Institut I-Oekologie, Universitaet Karlsruhe, Geb. 07.01, Kornblumenstrasse 13, D-76131 Karlsruhe (Germany); Sures, Bernd [Zoologisches Institut I-Oekologie, Universitaet Karlsruhe, Geb. 07.01, Kornblumenstrasse 13, D-76131 Karlsruhe (Germany)]. E-mail: dc11@rz.uni-karlsruhe.de

2005-10-05

An increasing number of papers concentrate on the availability and uptake of platinum group elements (PGE) by different organisms. These metals are discharged into the environment from different anthropogenic sources, such as automobile catalytic converters, hospitals and other medical institutions. As the effects of these precious metals on organisms remain unclear, the induction of heat shock proteins (hsp70) in zebra mussels (Dreissena polymorpha) following exposure to soluble salts of platinum, palladium and rhodium was compared with the hsp70 induction in mussels following exposure to cadmium and lead. Mussels were sampled weekly during a period of 10 weeks and analyzed for their metal concentration and their hsp70 level. Highest metal uptake was found for Cd, followed by Pt, Pb and Pd. Rh demonstrated the lowest uptake rate. A clear time-dependent increase of hsp70 levels occurred in all exposed mussels. Concentrations of hsp70 started to rise between days 18 and 25, except for the Pt-exposed group, where the initial increase was between days 25 and 32. All groups reached maximal hsp70 concentrations at day 39. Subsequently, hsp70 levels decreased to initial levels for the remaining exposure period. Threshold metal levels for the hsp70 induction varied among the metals and increased in the order: Rh < Pd {<=} Pb < Pt < Cd. Highest hsp70 values were found for mussels exposed to Pd, with a 25-fold higher level than in the controls, followed by Pt- and Rh-exposed mussels, which showed a 19-fold increase. The hsp70 levels of the mussels exposed to Cd and Pb were much lower, showing 6- and 12-fold higher values than the control, respectively. The clear induction of hsp70 due to exposure to Pt, Pd and Rh gives evidence for strong cellular effects of these metals, especially, when compared with lead and cadmium. Among the metals tested, Pd seems to have the highest potential as inducer for hsp70 production due to its low threshold level in combination with the

Induction of heat shock proteins (hsp70) in the zebra mussel (Dreissena polymorpha) following exposure to platinum group metals (platinum, palladium and rhodium): Comparison with lead and cadmium exposures

International Nuclear Information System (INIS)

Singer, Christoph; Zimmermann, Sonja; Sures, Bernd

2005-01-01

An increasing number of papers concentrate on the availability and uptake of platinum group elements (PGE) by different organisms. These metals are discharged into the environment from different anthropogenic sources, such as automobile catalytic converters, hospitals and other medical institutions. As the effects of these precious metals on organisms remain unclear, the induction of heat shock proteins (hsp70) in zebra mussels (Dreissena polymorpha) following exposure to soluble salts of platinum, palladium and rhodium was compared with the hsp70 induction in mussels following exposure to cadmium and lead. Mussels were sampled weekly during a period of 10 weeks and analyzed for their metal concentration and their hsp70 level. Highest metal uptake was found for Cd, followed by Pt, Pb and Pd. Rh demonstrated the lowest uptake rate. A clear time-dependent increase of hsp70 levels occurred in all exposed mussels. Concentrations of hsp70 started to rise between days 18 and 25, except for the Pt-exposed group, where the initial increase was between days 25 and 32. All groups reached maximal hsp70 concentrations at day 39. Subsequently, hsp70 levels decreased to initial levels for the remaining exposure period. Threshold metal levels for the hsp70 induction varied among the metals and increased in the order: Rh < Pd ≤ Pb < Pt < Cd. Highest hsp70 values were found for mussels exposed to Pd, with a 25-fold higher level than in the controls, followed by Pt- and Rh-exposed mussels, which showed a 19-fold increase. The hsp70 levels of the mussels exposed to Cd and Pb were much lower, showing 6- and 12-fold higher values than the control, respectively. The clear induction of hsp70 due to exposure to Pt, Pd and Rh gives evidence for strong cellular effects of these metals, especially, when compared with lead and cadmium. Among the metals tested, Pd seems to have the highest potential as inducer for hsp70 production due to its low threshold level in combination with the

All-proportional solid-solution Rh–Pd–Pt alloy nanoparticles by femtosecond laser irradiation of aqueous solution with surfactant

Energy Technology Data Exchange (ETDEWEB)

Sarker, Md. Samiul Islam, E-mail: samiul-phy@ru.ac.bd; Nakamura, Takahiro; Sato, Shunichi [Tohoku University, Institute of Multidisciplinary Research for Advanced Materials (Japan)

2015-06-15

Formation of Rh–Pd–Pt solid-solution alloy nanoparticles (NPs) by femtosecond laser irradiation of aqueous solution in the presence of polyvinylpyrrolidone (PVP) or citrate as a stabilizer was studied. It was found that the addition of surfactant (PVP or citrate) significantly contributed to reduce the mean size of the particles to 3 nm for PVP and 10 nm for citrate, which was much smaller than that of the particles fabricated without any surfactants (20 nm), and improved the dispersion state as well as the colloidal stability. The solid-solution formation of the Rh–Pd–Pt alloy NPs was confirmed by the XRD results that the diffraction pattern was a single peak, which was found between the positions corresponding to each pure Rh, Pd, and Pt NPs. Moreover, all the elements were homogeneously distributed in every particle by STEM-EDS elemental mapping, strongly indicating the formation of homogeneous solid-solution alloy. Although the Rh–Pd–Pt alloy NPs fabricated with PVP was found to be Pt rich by EDS observation, the composition of NPs fabricated with citrate almost exactly preserved the feeding ratio of ions in the mixed solution. To our best knowledge, these results demonstrated for the first time, the formation of all-proportional solid-solution Rh–Pd–Pt alloy NPs with well size control.

Platinum monolayer electrocatalysts for oxygen reduction: effect of substrates, and long-term stability

Directory of Open Access Journals (Sweden)

J. ZHANG

2005-03-01

Full Text Available We describe a novel concept for a Ptmonolayer electrocatalyst and present the results of our electrochemical, X-ray absorption spectroscopy, and scanning tunneling microscopy studies. The electrocatalysts were prepared by a new method for depositing Pt monolayers involving the galvanic displacement by Pt of an underpotentially deposited Cu monolayer on substrates of Au (111, Ir(111, Pd(111, Rh(111 and Ru(0001 single crylstals, and Pd nanoparticles. The kinetics of O2 reduction showed significant enhancement with Pt monolayers on Pd(111 and Pd nanoparticle surfaces in comparisonwith the reaction on Pt(111 and Pt nanoparticles, respectively. This increase in catalytic activity is attributed partly to the decreased formation of PtOH, as shown by in situ X-ray absorption spectroscopy. The results illustrate that placing a Pt monolayer on a suitable substrate of metal nanoparticles is an attractive way of designing better O2 reduction electrocatalysts with very low Pt contents.

Platinum-Group Elements in Soils and Street Dust of the Southeastern Administrative District of Moscow

Science.gov (United States)

Ladonin, D. V.

2018-03-01

The contents of five platinum-group metals (Ru, Rh, Pd, Ir, and Pt) in soils and street dust of the Southeastern administrative district (SEAD) of Moscow have been determined. The contents of these elements in soils may considerably exceed their natural abundances in the lithosphere and are characterized by considerable variability and asymmetric frequency distribution. A close correlation between Rh, Pd, and Pt contents in soils and street dust has been shown. The data on the contents of the elements and the ratios between them suggest that motor vehicles are the major source of pollution of soils and street dust in the studied district.

Identification of a Catalytically Highly Active Surface Phase for CO Oxidation over PtRh Nanoparticles under Operando Reaction Conditions

Science.gov (United States)

Hejral, U.; Franz, D.; Volkov, S.; Francoual, S.; Strempfer, J.; Stierle, A.

2018-03-01

Pt-Rh alloy nanoparticles on oxide supports are widely employed in heterogeneous catalysis with applications ranging from automotive exhaust control to energy conversion. To improve catalyst performance, an atomic-scale correlation of the nanoparticle surface structure with its catalytic activity under industrially relevant operando conditions is essential. Here, we present x-ray diffraction data sensitive to the nanoparticle surface structure combined with in situ mass spectrometry during near ambient pressure CO oxidation. We identify the formation of ultrathin surface oxides by detecting x-ray diffraction signals from particular nanoparticle facets and correlate their evolution with the sample's enhanced catalytic activity. Our approach opens the door for an in-depth characterization of well-defined, oxide-supported nanoparticle based catalysts under operando conditions with unprecedented atomic-scale resolution.

3D-macroporous chitosan-based scaffolds with in situ formed Pd and Pt nanoparticles for nitrophenol reduction.

Science.gov (United States)

Berillo, Dmitriy; Cundy, Andrew

2018-07-15

3D-macroporous chitosan-based scaffolds (cryogels) were produced via growth of metal-polymer coordinated complexes and electrostatic interactions between oppositely charged groups of chitosan and metal ions under subzero temperatures. A mechanism of reduction of noble metal complexes inside the cryogel walls by glutaraldehyde is proposed, which produces discrete and dispersed noble metal nanoparticles. 3D-macroporous scaffolds prepared under different conditions were characterised using TGA, FTIR, nitrogen adsorption, SEM, EDX and TEM, and the distribution of platinum nanoparticles (PtNPs) and palladium nanoparticles (PdNPs) in the material assessed. The catalytic activity of the in situ synthesised PdNPs, at 2.6, 12.5 and 21.0 μg total mass, respectively, was studied utilising a model system of 4-nitrophenol reduction. The kinetics of the reaction under different conditions (temperature, concentration of catalyst) were examined, and a decrease of catalytic activity was not observed over 17 treatment cycles. Increasing the temperature of the catalytic reaction from 10 to 22 and 35 °C by PdNPs supported within the cryogel increased the kinetic rate by 44 and 126%, respectively. Turnover number and turnover frequency of the PdNPs catalysts at room temperature were in the range 0.20-0.53 h -1 . The conversion degree of 4-nitrophenol at room temperature reached 98.9% (21.0 μg PdNPs). Significantly less mass of palladium nanoparticles (by 30-40 times) was needed compared to published data to obtain comparable rates of reduction of 4-nitrophenol. Copyright © 2018 Elsevier Ltd. All rights reserved.

Gibbs Free Energy of Formation for Selected Platinum Group Minerals (PGM

Directory of Open Access Journals (Sweden)

Spiros Olivotos

2016-01-01

Full Text Available Thermodynamic data for platinum group (Os, Ir, Ru, Rh, Pd and Pt minerals are very limited. The present study is focused on the calculation of the Gibbs free energy of formation (ΔfG° for selected PGM occurring in layered intrusions and ophiolite complexes worldwide, applying available experimental data on their constituent elements at their standard state (ΔG = G(species − ΔG(elements, using the computer program HSC Chemistry software 6.0. The evaluation of the accuracy of the calculation method was made by the calculation of (ΔGf of rhodium sulfide phases. The calculated values were found to be ingood agreement with those measured in the binary system (Rh + S as a function of temperature by previous authors (Jacob and Gupta (2014. The calculated Gibbs free energy (ΔfG° followed the order RuS2 < (Ir,OsS2 < (Pt, PdS < (Pd, PtTe2, increasing from compatible to incompatible noble metals and from sulfides to tellurides.

LEED crystallography studies of the structure of clean and adsorbate-covered Ir, Pt and Rh crystal surfaces

Energy Technology Data Exchange (ETDEWEB)

Koestner, R.J.

1982-08-01

There have only been a few Low Energy Electron Diffraction (LEED) intensity analyses carried out to determine the structure of molecules adsorbed on metal surfaces; most surface crystallography studies concentrated on the structure of clean unreconstructed or atomic adsorbate-covered transition metal faces. The few molecular adsorption systems already investigated by dynamical LEED are CO on Ni(100), Cu(100) and Pd(100) as well as C/sub 2/H/sub 2/ and C/sub 2/H/sub 4/ adsorbed on Pt(111). The emphasis of this thesis research has been to extend the applicability of LEED crystallography to the more complicated unit cells found in molecular overlayers on transition metals or in there constructed surfaces of clean transition metals.

Steam reforming of methane over Pt/Rh based wire mesh catalyst in single channel reformer for small scale syngas production

DEFF Research Database (Denmark)

Sigurdsson, Haftor Örn; Kær, Søren Knudsen

2012-01-01

of a catalytic parallel plate type heat exchanger (CPHE) reformer stack, where coated Pt/Rh based wire mesh is used as a catalyst. Heat is supplied to the endothermic reaction with infrared electric heaters. All the experiments were performed under atmospheric pressure and at stable operating conditions......The purpose of this study is to investigate a small scale steam methane reformer for syngas production for a micro combined heat and power (mCPH) unit under different operational conditions. The study presents an experimental analysis of the performance of a specially built single channel...... to evaluate the effect of flow maldistribution in a CPHE reformer stack on the CH4 conversion and H2 yield....

Hydrogen poisoning of the CO oxidation reaction on Pt and Pd under ultrahigh vacuum conditions

International Nuclear Information System (INIS)

Strozier, J.A.

1977-01-01

The poisoning by hydrogen of the catalyzed oxidation of CO on Pt and Pd under ultrahigh vacuum conditions was investigated. ac pulsing techniques are used in which the pressure of the reactant CO in the reaction chamber is modulated periodically by means of a fast piezoelectric ultrahigh vacuum valve, and the ac component of the product CO 2 is recorded mass spectroscopically by phase-sensitive techniques. The ac CO 2 production rate is measured as a function of hydrogen pressure (1 - 10 x 10 -9 toor) at constant CO and O 2 pressures (approximately equal to 5 x 10 -8 torr), and constant temperature (approximately equal to 700 K). Exact theoretical calculations of CO 2 production rates were carried out employing several models, i.e., oxygen burn-off by hydrogen, incorporating both the Eley-Rideal and Langmuir-Hinshelwood mechanisms. From a comparison with the experimental results, the probable reaction is of the Langmuir-Hinshelwood type and the relevant rate constant is also determined. These results are compared with other results in the literature on hydrogen oxidation on the surface of Pt

Experimental investigation of air relative humidity (RH) cycling tests on MEA/cell aging in PEMFC. Pt. II. Study of low RH cycling test with air RH at 62%/0%

Energy Technology Data Exchange (ETDEWEB)

Huang, B.T.; Chatillon, Y.; Bonnet, C.; Lapicque, F. [Laboratoire Reactions et Genie des Procedes, CNRS-Nancy University, Nancy (France); Leclerc, S. [Laboratoire d' Energetique et de Mecanique Theorique et Appliquee, CNRS-Nancy University, Vandoeuvre-les-Nancy (France); Hinaje, M.; Rael, S. [Groupe de Recherche en Electrotechnique et Electronique de Nancy, Nancy University, Vandoeuvre-les-Nancy (France)

2012-06-15

The effect of low relative humidity (RH) cycling (RH{sub C} 62%/0%) on the degradation mechanisms of a single proton exchange membrane fuel cell (5 x 5 cm{sup 2}) was investigated and compared to a cell operated at constant humidification (RH{sub C} = 62%). The overall cell performance loss was near 33 {mu}V h{sup -1}, which is greater than the voltage decay under constant RH condition near 3 {mu}V h{sup -1}. The electroactive surface was reduced but to an acceptable level. Impedance spectroscopy revealed that the ohmic and charge transfer resistances were reduced by the likely improved hydration of the ionomeric layer at the catalyst due to hydrogen crossover. This was so important that H{sub 2} starvation was finally responsible for the collapse of the cell after 650 h. Transmission electron microscopy showed occurrence of various phenomena, e.g., bubbles and pinholes formation in the membrane due to local overheat from hydrogen combustion at the cathode, and thickness reduction of catalytic layers. The water up take obtained by {sup 1}H NMR within the membrane electrode assembly (MEA) after low RH cycling reduced by 24% compared to a fresh MEA. Observations are also compared to those obtained at high RH cycling (RH{sub C} 62%/100%) presented in Part I of this study [1]. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Growth of carbon structured over Pd, Pt and Ni: A comparative DFT study

Science.gov (United States)

Quiroga, Matías Abel

2013-03-01

To elucidate the graphene-like structures mechanisms growth over the M(1 1 1) surface (M = Pd, Pt and Ni) we performed ab initio calculus in the frame of density functional theory with the exchange-correlation functional treated according to the Generalized Gradient Approximation (GGA). In order to avoid the problem that represent the complex interaction between the well formed graphene layer and the metallic surface, we recreate the carbon rings formation initial steps, by adding one by one carbon atoms over M(1 1 1) surface. With this strategy, the chemical bonding is always present until the graphene layer is well formed, in which case the GGA neglects van der Waals dispersive forces. We investigate the electronic properties by studying the band structure and the density of states.

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

OpenAIRE

Du, Jingshan; Yu, Junjie; 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...

Spin-orbit driven phenomena in the isoelectronic L1.sub.0./sub.-Fe(Pd,Pt) alloys from first principles

Czech Academy of Sciences Publication Activity Database

Kudrnovský, Josef; Drchal, Václav; Turek, Ilja

2017-01-01

Roč. 96, č. 21 (2017), s. 1-7, č. článku 214437. ISSN 2469-9950 R&D Projects: GA ČR GA15-13436S Institutional support: RVO:68378271 ; RVO:68081723 Keywords : anomalous Hall effect * Gilbert damping * partial order * first-principles * Fe(Pd,Pt) alloys Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 3.836, year: 2016

Spatial variation of contaminant elements of roadside dust samples from Budapest (Hungary) and Seoul (Republic of Korea), including Pt, Pd and Ir.

Science.gov (United States)

Sager, Manfred; Chon, Hyo-Taek; Marton, Laszlo

2015-02-01

Roadside dusts were studied to explain the spatial variation and present levels of contaminant elements including Pt, Pd and Ir in urban environment and around Budapest (Hungary) and Seoul (Republic of Korea). The samples were collected from six sites of high traffic volumes in Seoul metropolitan city and from two control sites within the suburbs of Seoul, for comparison. Similarly, road dust samples were obtained two times from traffic focal points in Budapest, from the large bridges across the River Danube, from Margitsziget (an island in the Danube in the northern part of Budapest, used for recreation) as well as from main roads (no highways) outside Budapest. The samples were analysed for contaminant elements by ICP-AES and for Pt, Pd and Ir by ICP-MS. The highest Pt, Pd and Ir levels in road dusts were found from major roads with high traffic volume, but correlations with other contaminant elements were low, however. This reflects automobile catalytic converter to be an important source. To interpret the obtained multi-element results in short, pollution index, contamination index and geo-accumulation index were calculated. Finally, the obtained data were compared with total concentrations encountered in dust samples from Madrid, Oslo, Tokyo and Muscat (Oman). Dust samples from Seoul reached top level concentrations for Cd-Zn-As-Co-Cr-Cu-Mo-Ni-Sn. Just Pb was rather low because unleaded gasoline was introduced as compulsory in 1993. Concentrations in Budapest dust samples were lower than from Seoul, except for Pb and Mg. Compared with Madrid as another continental site, Budapest was higher in Co-V-Zn. Dust from Oslo, which is not so large, contained more Mn-Na-Sr than dust from other towns, but less other metals.

Study of the influence of platinum, palladium and rhodium on duckweed (Lemna minor).

Science.gov (United States)

Bednarova, Ivana; Mikulaskova, Hana; Havelkova, Barbora; Strakova, Lenka; Beklova, Miroslava; Sochor, Jiri; Hynek, David; Adam, Vojtech; Kizek, Rene

2014-01-01

Road traffic pollutants and the residues of cytostatics that are widely used in anti-cancer therapy are a significant sources of platinum group elements (PGE; Pt, Pd and Rh) in environment. These metals can migrate into sewage and thus pollute surface waters. The purpose of our study was to evaluate the effect of PtCl4 on the antioxidant and enzymatic activity of duckweed (Lemna minor), a bioindicator of the aquatic environment. The study was performed using a 7-day conventional test based on the OECD 221 (CSN EN ISO 20079)--Lemna sp. Growth Inhibition Test. We also conducted a microbiotest to analyse the effects of PtC4, PdCl2 and RhCl3 on the morphology and vegetative growth of colonies of this plant and compared their inhibitory effects during the microbiotest. We observed inhibition of colony growth and clear morphological changes. Antioxidant and enzymatic activities increased with platinum doses increased. The 168hEC50 of PtCl4 was 12.16 μM (95% confidence interval = 9.88-14.44) and the 168hEC50 of PdCl2 was 50.39 (95% confidence interval = 23.83-76.96). The greatest inhibition of growth by RhCl3 was observed at 25 μM. The obtained results suggest that L. minor phytotoxicity tests should be widely used in the biomonitoring.

Particle swarm optimization of the stable structure of tetrahexahedral Pt-based bimetallic nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Liu, Tun-Dong; Fan, Tian-E [Center for Cloud Computing and Big Data, Department of Automation, Xiamen University, Xiamen 361005 (China); Shao, Gui-Fang, E-mail: gfshao@xmu.edu.cn [Center for Cloud Computing and Big Data, Department of Automation, Xiamen University, Xiamen 361005 (China); Zheng, Ji-Wen [Center for Cloud Computing and Big Data, Department of Automation, Xiamen University, Xiamen 361005 (China); Wen, Yu-Hua [Institute of Theoretical Physics and Astrophysics, Department of Physics, Xiamen University, Xiamen 361005 (China)

2014-08-14

Bimetallic nanoparticles, enclosed by high-index facets, have great catalytic activity and selectivity owing to the synergy effects of high-index facets and the electronic structures of alloy. In this paper, a discrete particle swarm optimization algorithm was employed to systematically investigate the structural stability and features of tetrahexahedral Pt-based bimetallic nanoparticles with high-index facets. Different Pt/Ag, Pt/Cu, Pt/Pd atom ratios and particle sizes were considered in this work. The simulation results reveal that these alloy nanoparticles exhibit considerably different structural characteristics. Pt–Ag nanoparticles tend to form Pt–Ag core–shell structure. Pt–Cu nanoparticles are preferred to take multi-shell structure with Cu on the outer surface while Pt–Pd nanoparticles present a mixing structure in the interior and Pd-dominated surface. Atomic distribution and bonding characteristics were applied to further characterize the structural features of Pt-based nanoparticles. This study provides an important insight into the structural stability and features of Pt-based nanoparticles with different alloys. - Highlights: • We explore the structural stability of Pt-based alloy NPs by a discrete PSO. • Our study discovers the different structural characteristics for Pt-based NPs. • Alloy composition and size have important effects on the surface segregation. • Our work shows strong phase separation for Pt–Ag NPs while weak for Pt–Pd NPs.

Particle swarm optimization of the stable structure of tetrahexahedral Pt-based bimetallic nanoparticles

International Nuclear Information System (INIS)

Liu, Tun-Dong; Fan, Tian-E; Shao, Gui-Fang; Zheng, Ji-Wen; Wen, Yu-Hua

2014-01-01

Bimetallic nanoparticles, enclosed by high-index facets, have great catalytic activity and selectivity owing to the synergy effects of high-index facets and the electronic structures of alloy. In this paper, a discrete particle swarm optimization algorithm was employed to systematically investigate the structural stability and features of tetrahexahedral Pt-based bimetallic nanoparticles with high-index facets. Different Pt/Ag, Pt/Cu, Pt/Pd atom ratios and particle sizes were considered in this work. The simulation results reveal that these alloy nanoparticles exhibit considerably different structural characteristics. Pt–Ag nanoparticles tend to form Pt–Ag core–shell structure. Pt–Cu nanoparticles are preferred to take multi-shell structure with Cu on the outer surface while Pt–Pd nanoparticles present a mixing structure in the interior and Pd-dominated surface. Atomic distribution and bonding characteristics were applied to further characterize the structural features of Pt-based nanoparticles. This study provides an important insight into the structural stability and features of Pt-based nanoparticles with different alloys. - Highlights: • We explore the structural stability of Pt-based alloy NPs by a discrete PSO. • Our study discovers the different structural characteristics for Pt-based NPs. • Alloy composition and size have important effects on the surface segregation. • Our work shows strong phase separation for Pt–Ag NPs while weak for Pt–Pd NPs

Investigation of the magnetic properties in thin Fe50Pt50-xRhx films by neutron diffraction

Energy Technology Data Exchange (ETDEWEB)

Fenske, J.; Lott, D.; Schreyer, A. [GKSS Research Centre (Germany); Mankey, G.J. [University of Alabama, MINT Center (United States); Schmidt, W.; Schmalzl, K. [Juelich Research Centre (Germany); Tartakowskaya, E. [Institute for Magnetism, National Accademy of Science (United States)

2009-07-01

FePt-based alloys are typically the material of choice for magnetic information storage media. The high magnetic moment of Fe gives a large magnetization and the large atomic number of Pt results in a high magnetic anisotropy. This combination enables the written bits to be smaller than ever before, since magnetic grains with a high magnetic anisotropy are more thermally stable. One way to control the magnetic properties in these materials is through the introduction of a third element into the crystal matrix, e.g. Rh. When Rh is added to replace Pt in the equiatomic alloy, new magnetic phases emerge. Bulk samples of Fe{sub 50}Pt{sub 40}Rh{sub 10} for example, studied by magnetization measurements refer to an antiferromagnetic (AF)/ferromagnetic (FM) phase transition at about 150 K when heated. Additional magnetostriction measurements indicate that the phase transition could also be induced by applying a magnetic field. Here we present results on several Fe{sub 50}Pt{sub 50-x}Rh{sub x} films. These films were examined by neutron diffraction in dependence of temperature and magnetic field. The observed magnetic behaviours differ significant from the behaviour of the bulk system.

Enhancement of ethanol oxidation at Pt and PtRu nanoparticles dispersed over hybrid zirconia-rhodium supports

Science.gov (United States)

Rutkowska, Iwona A.; Koster, Margaretta D.; Blanchard, Gary J.; Kulesza, Pawel J.

2014-12-01

A catalytic material for electrooxidation of ethanol that utilizes PtRu nanoparticles dispersed over thin films of rhodium-free and rhodium-containing zirconia (ZrO2) supports is described here. The enhancement of electrocatalytic activity (particularly in the potential range as low as 0.25-0.5 V vs. RHE), that has been achieved by dispersing PtRu nanoparticles (loading, 100 μg cm-2) over the hybrid Rh-ZrO2 support composed of nanostructured zirconia and metallic rhodium particles, is clearly evident from comparison of the respective voltammetric and chronoamperometric current densities recorded at room temperature (22 °C) in 0.5 mol dm-3 H2SO4 containing 0.5 mol dm-3 ethanol. Porous ZrO2 nanostructures, that provide a large population of hydroxyl groups in acidic medium in the vicinity of PtRu sites, are expected to facilitate the ruthenium-induced removal of passivating CO adsorbates from platinum, as is apparent from the diagnostic experiments with a small organic molecule such as methanol. Although Rh itself does not show directly any activity toward ethanol oxidation, the metal is expected to facilitate C-C bond splitting in C2H5OH. It has also been found during parallel voltammetric and chronoamperometric measurements that the hybrid Rh-ZrO2 support increases activity of the platinum component itself toward ethanol oxidation in the low potential range.

Synthesis and electrochemical study of Pt-based nanoporous materials

International Nuclear Information System (INIS)

Wang Jingpeng; Holt-Hindle, Peter; MacDonald, Duncan; Thomas, Dan F.; Chen Aicheng

2008-01-01

In the present work, a variety of Pt-based bimetallic nanostructured materials including nanoporous Pt, Pt-Ru, Pt-Ir, Pt-Pd and Pt-Pb networks have been directly grown on titanium substrates via a facile hydrothermal method. The as-fabricated electrodes were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction and electrochemical methods. The active surface areas of these nanoporous Pt-based alloy catalysts are increased by over 68 (Pt-Pd), 69 (Pt-Ru) and 113 (Pt-Ir) fold compared to a polycrystalline Pt electrode. All these synthesized nanoporous electrodes exhibit superb electrocatalytic performance towards electrochemical oxidation of methanol and formic acid. Among the five nanoporous Pt-based electrodes, the Pt-Ir shows the highest peak current density at +0.50 V, with 68 times of enhancement compared to the polycrystalline Pt for methanol oxidation, and with 86 times of enhancement in formic acid oxidation; whereas the catalytic activity of the nanoporous Pt-Pb electrode outperforms the other materials in formic acid oxidation at the low potential regions, delivering an enhanced current density by 280-fold compared to the polycrystalline Pt at +0.15 V. The new approach described in this study is suitable for synthesizing a wide range of bi-metallic and tri-metallic nanoporous materials, desirable for electrochemical sensor design and potential application in fuel cells

Synthesis and electrochemical study of Pt-based nanoporous materials

Energy Technology Data Exchange (ETDEWEB)

Wang Jingpeng [Department of Chemistry, Lakehead University, Thunder Bay, Ontario P7B 5E1 (Canada); Department of Chemistry, University of Guelph, Guelph, Ontario N1G 2W1 (Canada); Holt-Hindle, Peter; MacDonald, Duncan [Department of Chemistry, Lakehead University, Thunder Bay, Ontario P7B 5E1 (Canada); Thomas, Dan F. [Department of Chemistry, University of Guelph, Guelph, Ontario N1G 2W1 (Canada); Chen Aicheng [Department of Chemistry, Lakehead University, Thunder Bay, Ontario P7B 5E1 (Canada)], E-mail: aicheng.chen@lakeheadu.ca

2008-10-01

In the present work, a variety of Pt-based bimetallic nanostructured materials including nanoporous Pt, Pt-Ru, Pt-Ir, Pt-Pd and Pt-Pb networks have been directly grown on titanium substrates via a facile hydrothermal method. The as-fabricated electrodes were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction and electrochemical methods. The active surface areas of these nanoporous Pt-based alloy catalysts are increased by over 68 (Pt-Pd), 69 (Pt-Ru) and 113 (Pt-Ir) fold compared to a polycrystalline Pt electrode. All these synthesized nanoporous electrodes exhibit superb electrocatalytic performance towards electrochemical oxidation of methanol and formic acid. Among the five nanoporous Pt-based electrodes, the Pt-Ir shows the highest peak current density at +0.50 V, with 68 times of enhancement compared to the polycrystalline Pt for methanol oxidation, and with 86 times of enhancement in formic acid oxidation; whereas the catalytic activity of the nanoporous Pt-Pb electrode outperforms the other materials in formic acid oxidation at the low potential regions, delivering an enhanced current density by 280-fold compared to the polycrystalline Pt at +0.15 V. The new approach described in this study is suitable for synthesizing a wide range of bi-metallic and tri-metallic nanoporous materials, desirable for electrochemical sensor design and potential application in fuel cells.0.

Synthesis and electrochemical study of Pt-based nanoporous materials

Energy Technology Data Exchange (ETDEWEB)

Wang, Jingpeng [Department of Chemistry, Lakehead University, Thunder Bay, Ontario P7B 5E1 (Canada); Department of Chemistry, University of Guelph, Guelph, Ontario N1G 2W1 (Canada); Holt-Hindle, Peter; MacDonald, Duncan; Chen, Aicheng [Department of Chemistry, Lakehead University, Thunder Bay, Ontario P7B 5E1 (Canada); Thomas, Dan F. [Department of Chemistry, University of Guelph, Guelph, Ontario N1G 2W1 (Canada)

2008-10-01

In the present work, a variety of Pt-based bimetallic nanostructured materials including nanoporous Pt, Pt-Ru, Pt-Ir, Pt-Pd and Pt-Pb networks have been directly grown on titanium substrates via a facile hydrothermal method. The as-fabricated electrodes were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction and electrochemical methods. The active surface areas of these nanoporous Pt-based alloy catalysts are increased by over 68 (Pt-Pd), 69 (Pt-Ru) and 113 (Pt-Ir) fold compared to a polycrystalline Pt electrode. All these synthesized nanoporous electrodes exhibit superb electrocatalytic performance towards electrochemical oxidation of methanol and formic acid. Among the five nanoporous Pt-based electrodes, the Pt-Ir shows the highest peak current density at +0.50 V, with 68 times of enhancement compared to the polycrystalline Pt for methanol oxidation, and with 86 times of enhancement in formic acid oxidation; whereas the catalytic activity of the nanoporous Pt-Pb electrode outperforms the other materials in formic acid oxidation at the low potential regions, delivering an enhanced current density by 280-fold compared to the polycrystalline Pt at +0.15 V. The new approach described in this study is suitable for synthesizing a wide range of bi-metallic and tri-metallic nanoporous materials, desirable for electrochemical sensor design and potential application in fuel cells. (author)

New catalysts for exhaust gas cleaning

Energy Technology Data Exchange (ETDEWEB)

Haerkoenen, M [Kemira Metalkat Oy, Oulu (Finland)

1997-12-31

Major challenge for future catalyst systems was to develop thermally more stable washcoats for close coupled operating conditions and for engines operating under high speed and load conditions. To design these future emission systems extensive research and development was undertaken to develop methods to disperse and stabilize the key catalytic materials for operation at much higher temperatures. Second priority was to design catalysts that are more effective under low temperature exhaust conditions and have improved oxygen storage properties in the washcoats. Incorporating new materials and modified preparation technology a new generation of metallic catalyst formulations emerged, those being trimetallic K6 (Pt:Pd:Rh and bimetallic K7) (Pd+Pd:Rh). The target was to combine the best property of Pt:Rh (good NO{sub x} reduction) with that of the good HC oxidation activity of Pd and to ensure that precious metal/support interactions were positively maintained. Both K6 and K7 concepts contain special catalyst structures with optimized washcoat performance which can be brick converter configuration. Improvement in light-off, thermal stability and transient performance with these new catalyst formulations have clearly been shown in both laboratory and vehicle testing. (author) (20 refs.)

New catalysts for exhaust gas cleaning

Energy Technology Data Exchange (ETDEWEB)

Haerkoenen, M. [Kemira Metalkat Oy, Oulu (Finland)

1996-12-31

Major challenge for future catalyst systems was to develop thermally more stable washcoats for close coupled operating conditions and for engines operating under high speed and load conditions. To design these future emission systems extensive research and development was undertaken to develop methods to disperse and stabilize the key catalytic materials for operation at much higher temperatures. Second priority was to design catalysts that are more effective under low temperature exhaust conditions and have improved oxygen storage properties in the washcoats. Incorporating new materials and modified preparation technology a new generation of metallic catalyst formulations emerged, those being trimetallic K6 (Pt:Pd:Rh and bimetallic K7) (Pd+Pd:Rh). The target was to combine the best property of Pt:Rh (good NO{sub x} reduction) with that of the good HC oxidation activity of Pd and to ensure that precious metal/support interactions were positively maintained. Both K6 and K7 concepts contain special catalyst structures with optimized washcoat performance which can be brick converter configuration. Improvement in light-off, thermal stability and transient performance with these new catalyst formulations have clearly been shown in both laboratory and vehicle testing. (author) (20 refs.)

The production of 103Pd and 109Cd from a proton irradiated tandem natAg/natAg targets

International Nuclear Information System (INIS)

Ineza, C.; Mphahlele, J.

2014-01-01

This paper describes a new method for the production of 103 Pd and 109 Cd using the 66 MeV proton beam of iThemba LABS on a tandem natural silver target (Ag/Ag). The radiochemical separation of the Pd radionuclides ( 103 Pd, 100 Pd) from the bulk nat Ag was done using a Chelex-100 chelating resin column. The recovery of 103 Pd from the irradiated nat Ag target was found to be >98 % without any Ag or Rh impurities detected. The radiochemical separation of 109 Cd from the bulk nat Ag target was done by the precipitation of Ag ions by Cu followed by the separation of 109 Cd, traces of Ag, Cu 2+ and Rh using a AG1-X10 anion exchange resin column. The recovery yield of 109 Cd was >99 % without any Ag or Rh impurities detected. (author)

Investigation of the (p,p'), (p,d) and (p,t) reactions on some light Sn isotopes

International Nuclear Information System (INIS)

Blankert, P.J.

1979-01-01

The results are presented of the 112 Sn(p,p') 112 Sn reaction. Apart from the usual distorted-wave analysis the excitation of some states is described in the coupled-channels formalism. The results of the 112 Sn(p,d) 111 Sn and the 112 Sn(p,t) 110 Sn reactions are also reported. From the (p,d) reaction quasi-particle energies and occupation numbers are determined. Two-step DWBA calculations are performed for some states that are assumed to result from the coupling of a quasiparticle to the 2 + 1 or 3 - 1 state of the even core. In the gross structure above 3 MeV of excitation, pickup strength from deeply-bound hole states is observed. The (p,t) reaction provided spin and parity of a number of levels in 110 Sn. A two-step DWBA analysis of the excitation of the ground state and first excited 2 + state shows the importance of second-order processes. The combined results of the (p,t) reactions on 112 Sn, 114 Sn and 116 Sn are given with some emphasis on the systematic features. The derivation is given of some expressions for spectroscopic amplitudes necessary in the two-step DWBA calculations for the (p,t) reactions. For all reactions a comparison is made with other existing data and with the results of model calculations. (Auth.)

Determination of palladium, platinum and rhodium in used automobile catalysts and active pharmaceutical ingredients using high-resolution continuum source graphite furnace atomic absorption spectrometry and direct solid sample analysis

Energy Technology Data Exchange (ETDEWEB)

Resano, Martín, E-mail: mresano@unizar.es [Department of Analytical Chemistry, Aragón Institute of Engineering Research (I3A), University of Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza (Spain); Flórez, María del Rosario [Department of Analytical Chemistry, Aragón Institute of Engineering Research (I3A), University of Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza (Spain); Queralt, Ignasi [Institute of Earth Sciences Jaume Almera ICTJA-CSIC, Sole Sabarís s/n, 08028 Barcelona (Spain); Marguí, Eva [Department of Chemistry, Faculty of Sciences, Universitat de Girona, Campus Montilivi s/n, 17071 Girona (Spain)

2015-03-01

This work investigates the potential of high-resolution continuum source graphite furnace atomic absorption spectrometry for the direct determination of Pd, Pt and Rh in two samples of very different nature. While analysis of active pharmaceutical ingredients is straightforward and it is feasible to minimize matrix effects, to the point that calibration can be carried out against aqueous standard solutions, the analysis of used automobile catalysts is more challenging requiring the addition of a chemical modifier (NH{sub 4}F·HF) to help in releasing the analytes, a more vigorous temperature program and the use of a solid standard (CRM ERM®-EB504) for calibration. However, in both cases it was possible to obtain accurate results and precision values typically better than 10% RSD in a fast and simple way, while only two determinations are needed for the three analytes, since Pt and Rh can be simultaneously monitored in both types of samples. Overall, the methods proposed seem suited for the determination of these analytes in such types of samples, offering a greener and faster alternative that circumvents the traditional problems associated with sample digestion, requiring a small amount of sample only (0.05 mg per replicate for catalysts, and a few milligrams for the pharmaceuticals) and providing sufficient sensitivity to easily comply with regulations. The LODs achieved were 6.5 μg g{sup −1} (Pd), 8.3 μg g{sup −1} (Pt) and 9.3 μg g{sup −1} (Rh) for catalysts, which decreased to 0.08 μg g{sup −1} (Pd), 0.15 μg g{sup −1} (Pt) and 0.10 μg g{sup −1} (Rh) for pharmaceuticals. - Highlights: • Solid sampling HR CS GFAAS permits the fast and direct determination of Pd, Pt and Rh. • 2 determinations suffice for the 3 elements (2 of them can be measured simultaneously). • Samples as different as car catalysts and pharmaceuticals can be accurately analyzed. • Aqueous standards (pharmaceuticals) or a solid CRM (catalysts) is used for calibration. �

Characterization of electroless Au, Pt and Pd contacts on CdTe and ZnTe by RBS and SIMS techniques

Energy Technology Data Exchange (ETDEWEB)

Roumie, M. E-mail: mroumie@cnrs.edu.lb; Hageali, M.; Zahraman, K.; Nsouli, B.; Younes, G

2004-06-01

Rutherford backscattering spectrometry (RBS) was applied to characterize Au, Pt and Pd contacts on II-VI semiconductor materials, CdTe and ZnTe, used as nuclear detectors. Electroless thin film depositions were prepared by changing the concentration of the reaction solution. Contrary to the deposition reaction time, it was observed that the amount of solution dilution degree had a considerable effect on increasing the thickness of the metal layer. Furthermore, PICTS electrical measurements confirmed the depth profile analysis performed by RBS and SIMS.

Steady-State Spectroscopic Analysis of Proton-Dependent Electron Transfer on Pyrazine-Appended Metal Dithiolenes [Ni(pdt)2], [Pd(pdt)2], and [Pt(pdt)2] (pdt = 2,3-Pyrazinedithiol).

Science.gov (United States)

Kennedy, Steven R; Kozar, Morgan N; Yennawar, Hemant P; Lear, Benjamin J

2016-09-06

We report the structural, electronic, and acid/base properties of a series of ML2 metal dithiolene complexes, where M = Ni, Pd, Pt and L = 2,3-pyrazinedithiol. These complexes are non-innocent and possess strong electronic coupling between ligands across the metal center. The electronic coupling can be readily quantified in the monoanionic mixed valence state using Marcus-Hush theory. Analysis of the intervalence charge transfer (IVCT) band reveals that that electronic coupling in the mixed valence state is 5800, 4500, and 5700 cm(-1) for the Ni, Pd, and Pt complexes, respectively. We then focus on their response to acid titration in the mixed valence state, which generates the asymmetrically protonated mixed valence mixed protonated state. For all three complexes, protonation results in severe attenuation of the electronic coupling, as measured by the IVCT band. We find nearly 5-fold decreases in electronic coupling for both Ni and Pt, while, for the Pd complex, the electronic coupling is reduced to the point that the IVCT band is no longer observable. We ascribe the reduction in electronic coupling to charge pinning induced by asymmetric protonation. The more severe reduction in coupling for the Pd complex is a result of greater energetic mismatch between ligand and metal orbitals, reflected in the smaller electronic coupling for the pure mixed valence state. This work demonstrates that the bridging metal center can be used to tune the electronic coupling in both the mixed valence and mixed valence mixed protonated states, as well as the magnitude of change of the electronic coupling that accompanies changes in protonation state.

Isotope dilution inductively coupled plasma quadrupole mass spectrometry in connection with a chromatographic separation for ultra trace determinations of platinum group elements (Pt, Pd, Ru, Ir) in environmental samples.

Science.gov (United States)

Müller, M; Heumann, K G

2000-09-01

An isotope dilution inductively coupled plasma quadrupole mass spectrometric (ID-ICP-QMS) method was developed for the simultaneous determination of the platinum group elements Pt, Pd, Ru, and Ir in environmental samples. Spike solutions, enriched with the isotopes 194Pt, 108Pd, 99Ru, and 191Ir, were used for the isotope dilution step. Interfering elements were eliminated by chromatographic separation using an anion-exchange resin. Samples were dissolved with aqua regia in a high pressure asher. Additional dissolution of possible silicate portions by hydrofluoric acid was usually not necessary. Detection limits of 0.15 ng x g(-1), 0.075 ng x g(-1), and 0.015 ng x g(-1) were achieved for Pt, Pd, Ru, and Ir, respectively, using sample weights of only 0.2 g. The reliability of the ID-ICP-QMS method was demonstrated by analyzing a Canadian geological reference material and by participating in an interlaboratory study for the determination of platinum and palladium in a homogenized road dust sample. Surface soil, sampled at different distances from a highway, showed concentrations in the range of 0.1-87 ng x g(-1). An exponential decrease of the platinum and palladium concentration with increasing distance and a small anthropogenic contribution to the natural background concentration of ruthenium and iridium was found in these samples.

Crystal Growth and Characterization of MT2Si2 Ternary Intermetallics (M = U, RE and T = 3d, 4d, 5d Transition Metals)

NARCIS (Netherlands)

Menovsky, A.A.; Moleman, A.C.; Snel, G.E.; Gortenmulder, T.J.; Palstra, T.T.M.

1986-01-01

Bulk single crystals of the ternary intermetallic compounds UT2Si2 (T = Ni, Pd, Pt and Ru), LaT2Si2 (T = Pd and Rh) and LuPd2Si2 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

Oxygen reduction reaction (orr) on bimetallic AuPt and AuPd(1 0 0)-electrodes: Effects of the heteroatomic junction on the reaction paths

Science.gov (United States)

Schulte, E.; Belletti, G.; Arce, M.; Quaino, P.

2018-05-01

The seek for materials to enhance the oxygen reduction reaction (orr) rate is a highly relevant topic due to its implication in fuel cell devices. Herein, the orr on bimetallic electrocatalysts based on Au-M (M = Pt, Pd) has been studied computationally, by performing density functional theory calculations. Bimetallic (1 0 0) electrode surfaces with two different Au:M ratios were proposed, and two possible pathways, associative and dissociative, were considered for the orr. Changes in the electronic properties of these materials with respect to the pure metals were acknowledged to gain understanding in the overall reactivity trend. The effect of the bimetallic junction on the stability of the intermediates O2 and OOH was also evaluated by means of geometrical and energetic parameters; being the intermediates preferably adsorbed on Pt/Pd atoms, but presenting in some cases higher adsorption energies compared with bare metals. Finally, the kinetics of the Osbnd O bond breaking in O2∗ and OOH∗ adsorbed intermediates in the bimetallic materials and the influence of the Au-M junction were studied by means of the nudge elastic-band method. A barrierless process for the scission of O2∗ was found in Au-M for the higher M ratios. Surprisingly, for Au-M with lower M ratios, the barriers were much lower than for pure Au surfaces, suggesting a highly reactive surface towards the orr. The Osbnd O scission of the OOH∗ was found to be a barrierless process in Ausbnd Pt systems and nearly barrierless in all Ausbnd Pd systems, implying that the reduction ofO2 in these systems proceeds via the full reduction of O2 to H2O , avoiding H2O2 formation.

Uptake of traffic-related heavy metals and platinum group elements (PGE) by plants

Energy Technology Data Exchange (ETDEWEB)

Schaefer, J.; Hannker, D.; Eckhardt, J.D.; Stueben, D. [Institute of Petrography and Geochemistry, University of Karlsruhe, Karlsruhe (Germany)

1998-04-23

The distribution of the platinum group elements (PGE) caused by traffic emissions from autoexhaust catalysts has been determined in soils and different types of plants. The plants (spinach, cress, phacelia, stinging nettle) were cultivated on different soils collected from areas adjacent to a German highway and on uncontaminated sandy and clayey soils. The main result of the experiments was a measurable transfer of PGE from contaminated soil to plants. Following the definition of Sauerbeck (Beurteilung von Schwermetallkontaminationen im Boden. Frankfurt/Main: Dechema-Fachgespraeche, 1989:281-316), Pt, Rh and Pd transfer coefficients are within the range of immobile to moderately mobile elements, such as Cu. The transfer coefficient decreases from Pd>Pt{>=}Rh. Palladium therefore is the most biologically available of this element group

Assessment of sublethal endpoints after chronic exposure of the nematode Caenorhabditis elegans to palladium, platinum and rhodium.

Science.gov (United States)

Schertzinger, Gerhard; Zimmermann, Sonja; Grabner, Daniel; Sures, Bernd

2017-11-01

The aim of this study was to investigate chronic effects of the platinum-group elements (PGE) palladium (Pd), platinum (Pt) and rhodium (Rh) on the nematode Caenorhabditis elegans. Aquatic toxicity testing was carried out according to ISO 10872 by determining 96 h EC 50 values for sublethal endpoints, including growth, fertility and reproduction. Single PGE standard solutions were used as metal source. Based on the EC 50 values for Pt, reproduction (96 h EC 50  = 497 μg/L) was the most sensitive endpoint followed by fertility (96 h EC 50  = 726 μg/L) and growth (96 h EC 50  = 808 μg/L). For Pd, no precise EC 50 values could be calculated due to bell-shaped concentration response curves, but the 96 h EC 50 for reproduction ranged between 10 and 100 μg/L. Pd and Pt had effects on all endpoints. With raising element concentrations reproduction was inhibited first. At a certain concentration, fertility was also affected, which in turn had an additional effect on reproduction. Growth inhibition can also lead to a loss of fertility if the worms do not reach an appropriate body size to become fertile. Rhodium showed no inhibition of any endpoint between concentrations of 100 to 10,000 μg Rh/L. The results of this study allow the following order of PGE with respect to decreasing toxicity to C. elegans: Pd > Pt » Rh. Copyright © 2017 Elsevier Ltd. All rights reserved.

Noble metal catalyzed aqueous phase hydrogenation and hydrodeoxygenation of lignin-derived pyrolysis oil and related model compounds.

Science.gov (United States)

Mu, Wei; Ben, Haoxi; Du, Xiaotang; Zhang, Xiaodan; Hu, Fan; Liu, Wei; Ragauskas, Arthur J; Deng, Yulin

2014-12-01

Aqueous phase hydrodeoxygenation of lignin pyrolysis oil and related model compounds were investigated using four noble metals supported on activated carbon. The hydrodeoxygenation of guaiacol has three major reaction pathways and the demethylation reaction, mainly catalyzed by Pd, Pt and Rh, produces catechol as the products. The presence of catechol and guaiacol in the reaction is responsible for the coke formation and the catalysts deactivation. As expected, there was a significant decrease in the specific surface area of Pd, Pt and Rh catalysts during the catalytic reaction because of the coke deposition. In contrast, no catechol was produced from guaiacol when Ru was used so a completely hydrogenation was accomplished. The lignin pyrolysis oil upgrading with Pt and Ru catalysts further validated the reaction mechanism deduced from model compounds. Fully hydrogenated bio-oil was produced with Ru catalyst. Copyright © 2014 Elsevier Ltd. All rights reserved.

ANODE CATALYST MATERIALS FOR USE IN FUEL CELLS

DEFF Research Database (Denmark)

2002-01-01

Catalyst materials having a surface comprising a composition M¿x?/Pt¿3?/Sub; wherein M is selected from the group of elements Fe, Co, Rh and Ir; or wherein M represent two different elements selected from the group comprising Fe, CO, Rh, Ir, Ni, Pd, CU, Ag, Au and Sn; and wherein Sub represents...

Highly active carbon supported ternary PdSnPtx (x=0.1-0.7) catalysts for ethanol electro-oxidation in alkaline and acid media.

Science.gov (United States)

Wang, Xiaoguang; Zhu, Fuchun; He, Yongwei; Wang, Mei; Zhang, Zhonghua; Ma, Zizai; Li, Ruixue

2016-04-15

A series of trimetallic PdSnPtx (x=0.1-0.7)/C catalysts with varied Pt content have been synthesized by co-reduction method using NaBH4 as a reducing agent. These catalysts were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and chronoamperometry (CA). The electrochemical results show that, after adding a minor amount of Pt dopant, the resultant PdSnPtx/C demonstrated more superior catalytic performance toward ethanol oxidation as compared with that of mono-/bi-metallic Pd/C or PdSn/C in alkaline solution and the PdSnPt0.2/C with optimal molar ratio reached the best. In acid solution, the PdSnPt0.2/C also depicted a superior catalytic activity relative to the commercial Pt/C catalyst. The possible enhanced synergistic effect between Pd, Sn/Sn(O) and Pt in an alloyed state should be responsible for the as-revealed superior ethanol electro-oxidation performance based upon the beneficial electronic effect and bi-functional mechanism. It implies the trimetallic PdSnPt0.2/C with a low Pt content has a promising prospect as anodic electrocatalyst in fields of alkali- and acid-type direct ethanol fuel cells. Copyright © 2016 Elsevier Inc. All rights reserved.

Au-Pt-Pd-U mineralization in the Coronation Hill-El Sherana region, NT

International Nuclear Information System (INIS)

Wyborn, L.

1992-01-01

In 1990 BMR's Minerals and Land Use program conducted an geochemical and geophysical survey to provide the best possible basis for estimating the resource potential of the Kakadu Conservation Zone. Combining the old and new data, an integrated model for the deposit types has been developed. Although differing in metal content, all mines and prospects of the Coronation Hill region share similar timing and structural controls, suggesting that they are related to one geochemical system. The presence or absence of U in the Au-Pt-Pd mineralisation appears related to geological differences, primarily in host-rock composition. U-bearing deposits are hosted mainly in carbonaceous shales, although some U is associated with chloritic zones. Deposits lacking U, best developed at Coronation Hill, occur in a broad range of host rocks, including quartz-feldspar porphyry, green tuffaceous shale, diorite, dolomite, and sedimentary breccias. Although seemingly diverse rock types, the common components of these U-poor host units are feldspar and/or carbonate. 1 tab., 3 figs

Hierarchical Bi{sub 2}WO{sub 6} architectures decorated with Pd nanoparticles for enhanced visible-light-driven photocatalytic activities

Energy Technology Data Exchange (ETDEWEB)

Zhang, Jinniu; Chen, Tianhua [School of Physics and Information Technology, Shaanxi Normal University, Xi’an, 710062 (China); Lu, Hongbing, E-mail: hblu@snnu.edu.cn [School of Physics and Information Technology, Shaanxi Normal University, Xi’an, 710062 (China); Yang, Zhibo; Yin, Feng; Gao, Jianzhi; Liu, Qianru [School of Physics and Information Technology, Shaanxi Normal University, Xi’an, 710062 (China); Tu, Yafang [Department of Physics, Institute for Interdisciplinary Research, Jianghan University, Wuhan, 430056 (China)

2017-05-15

Highlights: • A new kind of Pd decorated Bi{sub 2}WO{sub 6} hierarchical microarchitecture was synthesized. • Pd nanoparticles remarkably improved the photocatalytic activity of Bi{sub 2}WO{sub 6}. • The photo-generated holes and ·O{sub 2}{sup −} played a crucial role in the degradation of RhB. • The photocatalytic enhancement mechanism of the Pd-Bi{sub 2}WO{sub 6} composites was proposed. - Abstract: A new kind of hierarchical Pd-Bi{sub 2}WO{sub 6} architecture decorated with different molar ratios of Pd to Bi, has been fabricated by a hydrothermal process, followed by a chemical deposition method. The photocatalytic activities of the pure Bi{sub 2}WO{sub 6} and Pd-Bi{sub 2}WO{sub 6} nanocatalyst were examined in the degradation of Rhodamine B (RhB) dyes and phenol under visible light. The photocatalytic results showed that the Pd-Bi{sub 2}WO{sub 6} nanocomposites possessed observably enhanced photocatalytic activities. Particularly, the 2.0% Pd loaded Bi{sub 2}WO{sub 6} had the highest photocatalytic activity, exhibiting a nearly complete degradation of 30 mg/L RhB and 10 mg/L phenol within only 50 and 60 min, respectively. In addition, the trapping experiment results indicated that the photo-generated holes (h{sup +}) and ·O{sub 2}{sup −} played a crucial role in the degradation of RhB. According to the experimental results, the photocatalytic degradation mechanism of Pd-Bi{sub 2}WO{sub 6} was also proposed. The enhanced photocatalytic activities were ascribed to the combined effects of the highly efficient separation of electrons and holes, improved visible light utilization and increased BET specific surface areas of the Pd-Bi{sub 2}WO{sub 6} nanocomposites.

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, Weizhen; Nie, Lei; Chen, Ying; 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\

Facile synthesis of Pt–Pd bimetallic nanoparticles by plasma discharge in liquid and their electrocatalytic activity toward methanol oxidation in alkaline media

Energy Technology Data Exchange (ETDEWEB)

Kim, Sung-Min; Lee, Yu-Jin [Center for Surface Technology and Applications, Korea Aerospace University, Gyeonggi-do, 412-791 (Korea, Republic of); Department of Materials Engineering, Korea Aerospace University, Gyeonggi-do, 412-791 (Korea, Republic of); Kim, Jung-Wan [Center for Surface Technology and Applications, Korea Aerospace University, Gyeonggi-do, 412-791 (Korea, Republic of); Division of Bioengineering, InCheon National University, Incheon, 406-772 (Korea, Republic of); Lee, Sang-Yul, E-mail: sylee@kau.ac.kr [Center for Surface Technology and Applications, Korea Aerospace University, Gyeonggi-do, 412-791 (Korea, Republic of); Department of Materials Engineering, Korea Aerospace University, Gyeonggi-do, 412-791 (Korea, Republic of)

2014-12-01

The Pt–Pd bimetallic nanoparticles for direct methanol fuel cell applications were successfully prepared by plasma discharge in aqueous solution. The obtained nanoparticles were characterized by energy dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, and transmission electron microscopy. During plasma discharge, the nanoparticles were produced from the erosion of electrodes. It was noted that the erosion amount of anode electrodes was much greater than that of cathode electrodes so that the composition of Pt–Pd bimetallic nanoparticles could be changed with different power types and electrode configurations. Diffraction patterns fitted from Gaussian devolution indicated that the crystalline phase of Pt{sub 40}Pd{sub 60} products was composed of pure Pt, pure Pd and Pt–Pd alloy phases. The morphology of synthesized nanoparticles showed that nanowires connected with quasi-spherical nanoparticles with 2–3 nm in diameter were observed and large spherical particles with > 50 nm in diameter were also detected intermittently. The cyclic voltammetric measurement and continuous potential scan demonstrated that Pt{sub 40}Pd{sub 60} had much higher catalytic activity and better resistance to CO poisoning than Pt{sub 94}Pd{sub 6} and Pt{sub 1}Pd{sub 99} for methanol oxidation. These results indicate that the Pt{sub 40}Pd{sub 60} could be an excellent candidate for the direct methanol fuel cell applications.

Performance of new generation TWC catalytic systems working under different conditions in order to reduce the emission of a global warming gas: N{sub 2}O

Energy Technology Data Exchange (ETDEWEB)

Mac-Beath, I.; Castillo, S.; Camposeco, R.; Moran-Pineda, M. [Instituto Mexicano del Petroleo, Mexico, D.F. (Mexico). Programa de Ingenieria Molecular

2010-07-01

In this work, three-way catalytic systems (TWC-K, TWC-M and TWC-P) were prepared and tested experimentally in order to analyze N{sub 2}O emissions. Various types and quantities of precious metals (Pt-Pd-Rh), and different mixed oxides (CexBayLazMgwO{sub 2}-Al{sub 2}O{sub 3}) to prepare the supports were used. The catalytic tests were carried out by using common exhaust gases from a gasoline engine under different oxidizing conditions. The TWC catalytic compositions were based on catalytic converters used in retrofitting programs in the Metropolitan Area in Mexico City. Fresh and aged TWC catalytic samples were tested; in both conditions, the catalytic compositions were characterized by BET, TEM-EDS and XRD in order to analyze the efficiency of the catalytic behavior. Due to the fact that the 4{sup th} TWC generation (Pd-Only TWC) has Pd as main active metal, the tested TWC catalytic samples were synthesized by having Pd in a higher proportion with regard to Pt and Rh used as complements with some differences in support composition. (orig.)

Infrared and swelling study of wet-spun films of DNA\\cdot[(bipy)Pt(en)]^2+ as a function of hydration

Science.gov (United States)

Kuebler, A.; Whitson, K. B.; Marlowe, R. L.; Lee, S. A.; Rupprecht, A.

1997-11-01

A ladder-like conformation of DNA has been induced by the binding of bipyridyl-Pt(II)-ethylenediamine (denoted as [(bipy)Pt(en)]^2+) at a relative humidity (RH) of 75%.(Arnott et al.,) Nature 287, (1980) 561. We report the first study of oriented films of this complex as a function of hydration by using Fourier transform infrared (IR) spectroscopy and optical microscopy. Vibrational modes between 800 and 1000 cm-1 are localized in the phosphodiester backbone and are sensitive to changes in the geometry of the molecule. The IR spectrum of this region is substantially different at 59% RH than at higher humidities, implying that a conformational change occurs as the RH is lowered below 75%. Optical microscopy measurements of small pieces of films of the complex also show changes at low RH. These trends are consistent with an order-disorder transition occurring as the RH is lowered The measurements also show that the DNA\\cdot[(bipy)Pt(en)]^2+) are very stable at the highest humidities.

Spectroscopic, electrochemical and photovoltaic properties of Pt(ii) and Pd(ii) complexes of a chelating 1,10-phenanthroline appended perylene diimide.

Science.gov (United States)

Işık Büyükekşi, Sebile; Şengül, Abdurrahman; Erdönmez, Seda; Altındal, Ahmet; Orman, Efe Baturhan; Özkaya, Ali Rıza

2018-02-20

In this study, a bis-chelating bridging perylene diimide ditopic ligand, namely N,N'-di(1,10-phenanthroline)-1,6,7,12-tetrakis-(4-methoxyphenoxy)perylene tetracarboxylic acid diimide (1), was synthesized and characterized. Further reactions of 1 with d 8 metal ions such as Pt(ii) and Pd(ii) having preferential square-planar geometry afforded the novel triads [(Cl 2 )M(ii)-(1)-M(ii)(Cl 2 )] where M(ii) = Pt(ii) (2), and Pd(ii) (3), respectively. The isolated triads and the key precursor were fully characterized by FT-IR, 1D-NMR ( 1 H NMR and 13 C DEPT NMR), 2D-NMR ( 1 H- 1 H COSY, 1 H- 13 C HSQC, 1 H- 13 C HMBC), MALDI-TOF mass and UV/Vis spectroscopy. The electrochemical properties of 1, 2 and 3 were investigated by cyclic voltammetry as well as in situ spectroelectrochemistry and also in situ electrocolorimetric measurements. These compounds were shown to exhibit net colour changes suitable for electrochromic applications. The compounds exhibited remarkably narrow HOMO-LUMO gaps, leading to their ease of reduction at low negative potentials. More importantly, dye-sensitized solar cells (DSSCs) were also fabricated using 1-3 to clarify the potential use of these complexes as a sensitizer. Analysis of the experimental data indicated that 2 has good potential as a sensitizer material for DSSCs.

In vitro investigations of platinum, palladium, and rhodium mobility in urban airborne particulate matter (PM10, PM2.5, and PM1) using simulated lung fluids.

Science.gov (United States)

Zereini, Fathi; Wiseman, Clare L S; Püttmann, Wilhelm

2012-09-18

Environmental concentrations of platinum group elements (PGE) have been increasing since the introduction of automotive catalytic converters to control harmful emissions. Assessments of the human health risks of exposures to these elements, especially through the inhalation of PGE-associated airborne particulate matter (PM), have been hampered by a lack of data on their bioaccessibility. The purpose of this study is to apply in vitro methods using simulated human lung fluids [artificial lysosomal fluid (ALF) and Gamble's solution] to assess the mobility of the PGE, platinum (Pt), palladium (Pd), and rhodium (Rh) in airborne PM of human health concern. Airborne PM samples (PM(10), PM(2.5), and PM(1)) were collected in Frankfurt am Main, Germany. For comparison, the same extraction experiments were conducted using the standard reference material, Used Auto Catalyst (monolith) (NIST 2557). Pt and Pd concentrations were measured using isotope dilution ICP-Q-MS, while Rh was measured directly with ICP-Q-MS (in collision mode with He), following established matrix separation and enrichment procedures, for both solid (filtered residues) and extracted sample phases. The mobilized fractions measured for PGE in PM(10), PM(2.5), and PM(1) were highly variable, which can be attributed to the heterogenic nature of airborne PM and its composition. Overall, the mobility of PGE in airborne PM samples was notable, with a mean of 51% Rh, 22% Pt, and 29% Pd present in PM(1) being mobilized by ALF after 24 h. For PM(1) exposed to Gamble's solution, a mean of 44% Rh, 18% Pt, and 17% Pd was measured in solution after 24 h. The mobility of PGE associated with airborne PM was also determined to be much higher compared to that measured for the auto catalyst standard reference material. The results suggest that PGE emitted from automotive catalytic converters are likely to undergo chemical transformations during and/or after being emitted in the environment. This study highlights the need

Chemical synthesis, phase transformation and magnetic proprieties of FePt and FePd nanoparticles

International Nuclear Information System (INIS)

Delattre, Anastasia

2010-01-01

This work aims at understanding the chemical synthesis of FePt and FePd nanoparticles (NPs), and at exploring how to implement the phase transformation from the chemically disordered to the L10 phase, without coalescence. Using hexadecanenitrile instead of oleylamine, we obtain NPs with a more homogenous internal composition, instead of core-shell NPs. Through a systematic study (designed experiment relying on Taguchi tables), we developed the FePd synthesis, while evidencing the role of each ligand and of the reductor. To induce the crystalline phase transformation while avoiding coalescence, we explored two ways. In the first one, atomic vacancies are introduced in the NPs through light ion irradiation, atomic mobility being ensured by annealing at moderate temperature (300 C). As a result, the blocking temperature is multiplied by 4, due to anisotropy enhancement. However, strong chemical ordering in the L10 phase cannot be achieved. The second approach relies on the dispersion of the NPs in a salt (NaCl) matrix, prior to annealing at 700 C: high chemical ordering is achieved, and the blocking temperature is beyond 400 C. We then developed a single-step process to remove the salt by dissolution in water and to re-disperse NPs in stable aqueous or organics solutions. These high magnetic anisotropy NPs are then readily available for further chemical or manipulation steps, with applied perspectives in areas such as data storage, or biology. (author)

γ-detected NMR of sup(103m)RhFe

International Nuclear Information System (INIS)

Kempter, H.; Klein, E.

1977-01-01

Using the method of γ-detection, the NMR in the metastable 40 keV-state of 103 Rh in Fe (thin foils with diffused 103 Pd activity) was measured in external fields of 0.5 to 14 kG. We find a zero-field resonance frequency of ν 0 = (550.3 +- 0.5) MHz and a slope of dν/dH = -(0.933 +- 0.017) MHz/kG, yielding g = 1.22 +- 0.02. The resulting value for the hyperfine field, Hsub(hf) = (590 +- 10) kG, is inconsistent with that of an NMR measurement in the ground state of 103 Rh. Possible reasons for this discrepancy are discussed. (orig.) [de

High-Performance Rh ₂ P Electrocatalyst for Efficient Water Splitting

Energy Technology Data Exchange (ETDEWEB)

Duan, Haohong [Department; Chemistry; Li, Dongguo [Materials; Tang, Yan [Department; amp, Molecular; He, Yang [Department; Ji, Shufang [Department; Wang, Rongyue [Materials; Lv, Haifeng [Materials; Lopes, Pietro P. [Materials; Paulikas, Arvydas P. [Materials; Li, Haoyi [Department; amp, Molecular; Mao, Scott X. [Department; Wang, Chongmin [Environmental; Markovic, Nenad M. [Materials; Li, Jun [Department; amp, Molecular; Stamenkovic, Vojislav R. [Materials; Li, Yadong [Department

2017-04-05

The search for active, stable, and cost-efficient electrocatalysts for hydrogen production via water splitting could make a substantial impact on energy technologies that do not rely on fossil fuels. Here we report the synthesis of rhodium phosphide electrocatalyst with low metal loading in the form of nanocubes (NCs) dispersed in high-surface-area carbon (Rh2P/C) by a facile solvo-thermal approach. The Rh2P/C NCs exhibit remarkable performance for hydrogen evolution reaction and oxygen evolution reaction compared to Rh/C and Pt/C catalysts. The atomic structure of the Rh2P NCs was directly observed by annular dark-field scanning transmission electron microscopy, which revealed a phosphorus-rich outermost atomic layer. Combined experimental and computational studies suggest that surface phosphorus plays a crucial role in determining the robust catalyst properties.

The thermal stability and catalytic performance of Ce-Zr promoted Rh-Pd/γ-Al2O3 automotive catalysts

International Nuclear Information System (INIS)

Wu Xiaodong; Xu Luhua; Weng Duan

2004-01-01

The noble metals (Rh, Pd) supported on alumina promoted with Ce-Zr mixed oxides were investigated as catalysts under diverse oxidants/reductants ratios of simulated automotive exhaust feed gas. Aging test was performed in air at 1000 deg. C for 20 h. Both fresh and aged catalysts, as well as alumina-supported Ce-Zr mixed powders, were characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET) and X-ray photoelectron spectroscopy (XPS). The results confirmed the oxygen storage capacity of Ce-Zr mixed oxides favored CO, C 3 H 8 and NO conversions in stationary versus dynamic stoichiometric operation. The accelerated aging of the systems produced inconspicuous effect on the phase structure, specific surface area and chemical state of these samples. Accordingly, the aged samples still showed low light-off temperature and broad λ-window, which suggested the relative low relevance of the thermal degradation on the overall catalytic performance of the system

Co-catalytic effect of Rh and Ru for the ethanol electro-oxidation in amorphous microparticulated alloys

Energy Technology Data Exchange (ETDEWEB)

Blanco, Tamara C.; Pierna, Angel R.; Barroso, Javier [Dpto. de Ingenieria Quimica y del Medio Ambiente, Universidad del Pais Vasco, San Sebastian (Spain)

2011-11-15

The ethanol electro-oxidation on platinum catalyst in acid media leads to the formation of acetaldehyde and acetic acid as main products. Another problem is the poisoning of the electro-catalyst surface with CO formed during the fuel oxidation reaction. To increase the performance of Direct Ethanol Fuel Cells (DEFCs) it is necessary to develop new electrode materials or modification of the existing Pt catalysts. This work presents the electrochemical response to ethanol and CO oxidation of different compositional amorphous alloys obtained by ball milling technique, used as electrodes. Alloys with Ni{sub 59}Nb{sub 40}Pt{sub 0.6}Rh{sub 0.4} and Ni{sub 59}Nb{sub 40}Pt{sub 0.6}Rh{sub 0.2}Ru{sub 0.2} composi-tions were studied. The current density towards ethanol oxidation decreases with the presence of ruthenium; however, this electrode shows the best tolerance to CO, with lower surface coverage (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Co-catalytic effect of Rh and Ru for the ethanol electro-oxidation in amorphous microparticulated alloys

International Nuclear Information System (INIS)

Blanco, Tamara C.; Pierna, Angel R.; Barroso, Javier

2011-01-01

The ethanol electro-oxidation on platinum catalyst in acid media leads to the formation of acetaldehyde and acetic acid as main products. Another problem is the poisoning of the electro-catalyst surface with CO formed during the fuel oxidation reaction. To increase the performance of Direct Ethanol Fuel Cells (DEFCs) it is necessary to develop new electrode materials or modification of the existing Pt catalysts. This work presents the electrochemical response to ethanol and CO oxidation of different compositional amorphous alloys obtained by ball milling technique, used as electrodes. Alloys with Ni 59 Nb 40 Pt 0.6 Rh 0.4 and Ni 59 Nb 40 Pt 0.6 Rh 0.2 Ru 0.2 composi-tions were studied. The current density towards ethanol oxidation decreases with the presence of ruthenium; however, this electrode shows the best tolerance to CO, with lower surface coverage (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Electrochemical CO2 and CO reduction on metal-functionalized porphyrin-like graphene

DEFF Research Database (Denmark)

Tripkovic, Vladimir; Vanin, Marco; Karamad, Mohammedreza

2013-01-01

Porphyrin-like metal-functionalized graphene structures have been investigated as possible catalysts for CO2 and CO reduction to methane or methanol. The late transition metals (Cu, Ag, Au, Ni, Pd, Pt, Co, Rh, Ir, Fe, Ru, Os) and some p (B, Al, Ga) and s (Mg) metals comprised the center of the po......Porphyrin-like metal-functionalized graphene structures have been investigated as possible catalysts for CO2 and CO reduction to methane or methanol. The late transition metals (Cu, Ag, Au, Ni, Pd, Pt, Co, Rh, Ir, Fe, Ru, Os) and some p (B, Al, Ga) and s (Mg) metals comprised the center...... instead of CO2. Volcano plots were constructed on the basis of scaling relations of reaction intermediates, and from these plots the reaction steps with the highest overpotentials were deduced. The Rh-porphyrin-like functionalized graphene was identified as the most active catalyst for producing methanol...... from CO, featuring an overpotential of 0.22 V. Additionally, we have also examined the hydrogen evolution and oxidation reaction, and in their case, too, Rh-porphyrin turned out to be the best catalyst with an overpotential of 0.15 V. © 2013 American Chemical Society....

Growth and maturational changes in dense fibrous connective tissue following 14 days of rhGH supplementation in the dwarf rat

Science.gov (United States)

Kyparos, Antonios; Orth, Michael W.; Vailas, Arthur C.; Martinez, Daniel A.

2002-01-01

The purpose of this study was to investigate the impact of recombinant human growth hormone (rhGH) on patella tendon (PT), medial collateral ligament (MCL), and lateral collateral ligament (LCL) on collagen growth and maturational changes in dwarf GH-deficient rats. Twenty male Lewis mutant dwarf rats, 37 days of age, were randomly assigned to Dwarf + rhGH (n = 10) and Dwarf + vehicle (n = 10) groups. The GH group received 1.25 mg rhGH/kg body wt twice daily for 14 days. rhGH administration stimulated dense fibrous connective tissue growth, as demonstrated by significant increases in hydroxyproline specific activity and significant decreases in the non-reducible hydroxylysylpyridinoline (HP) collagen cross-link contents. The increase in the accumulation of newly accreted collagen was 114, 67, and 117% for PT, MCL, and LCL, respectively, in 72 h. These findings suggest that a short course rhGH treatment can affect the rate of new collagen production. However, the maturation of the tendon and ligament tissues decreased 18-25% during the rapid accumulation of de novo collagen. We conclude that acute rhGH administration in a dwarf rat can up-regulate new collagen accretion in dense fibrous connective tissues, while causing a reduction in collagen maturation. Copyright 2002 Elsevier Science Ltd.

Effects of Stoichiometry on Transformation Temperatures and Actuator-Type Performance of NiTiPd and NiTiPdX High-Temperature Shape Memory Alloys

Science.gov (United States)

Bigelow, Glen S.; Gaydosh, Darrell; Garg, Anita; Padula, Santo A., II; Noebe, Ronald D.

2007-01-01

High-temperature shape memory NiTiPd and NiTiPdX (X=Au, Pt, Hf) alloys were produced with titanium equivalent (Ti+Hf) compositions of 50.5, 50.0, 49.5, and 49.0 at.%. Thermo-mechanical testing in compression was used to evaluate the transformation temperatures, transformation strain, work output, and permanent deformation behavior of each alloy to study the effects of quaternary alloying and stoichiometry on high-temperature shape memory alloy behavior. Microstructural evaluation showed the presence of second phases for all alloy compositions. No load transformation temperatures in the stoichiometric alloys were relatively unchanged by Au and Pt substitutions, while the substitution of Hf for Ti causes a drop in transformation temperatures. The NiTiPd, NiTiPdAu and NiTiPdHf alloys exhibited transformation temperatures that were highest in the Ti-rich compositions, slightly lower at stoichiometry, and significantly reduced when the Ti equivalent composition was less than 50 at.%. For the NiTiPdPt alloy, transformation temperatures were highest for the Ti-rich compositions, lowest at stoichiometry, and slightly higher in the Ni-rich composition. When thermally cycled under constant stresses of up to 300 MPa, all of the alloys had transformation strains, and therefore work outputs, which increased with increasing stress. In each series of alloys, the transformation strain and thus work output was highest for stoichiometric or Ti-rich compositions while permanent strain associated with the constant-load thermal cycling was lowest for alloys with Ni-equivalent-rich compositions. Based on these results, basic rules for optimizing the composition of NiTiPd alloys for actuator performance will be discussed.

Part II: Oxidative Thermal Aging of Pd/Al2O3 and Pd/CexOy-ZrO2 in Automotive Three Way Catalysts: The Effects of Fuel Shutoff and Attempted Fuel Rich Regeneration

Directory of Open Access Journals (Sweden)

Qinghe Zheng

2015-10-01

Full Text Available The Pd component in the automotive three way catalyst (TWC experiences deactivation during fuel shutoff, a process employed by automobile companies for enhancing fuel economy when the vehicle is coasting downhill. The process exposes the TWC to a severe oxidative aging environment with the flow of hot (800 °C–1050 °C air. Simulated fuel shutoff aging at 1050 °C leads to Pd metal sintering, the main cause of irreversible deactivation of 3% Pd/Al2O3 and 3% Pd/CexOy-ZrO2 (CZO as model catalysts. The effect on the Rh component was presented in our companion paper Part I. Moderate support sintering and Pd-CexOy interactions were also experienced upon aging, but had a minimal effect on the catalyst activity losses. Cooling in air, following aging, was not able to reverse the metallic Pd sintering by re-dispersing to PdO. Unlike the aged Rh-TWCs (Part I, reduction via in situ steam reforming (SR of exhaust HCs was not effective in reversing the deactivation of aged Pd/Al2O3, but did show a slight recovery of the Pd activity when CZO was the carrier. The Pd+/Pd0 and Ce3+/Ce4+ couples in Pd/CZO are reported to promote the catalytic SR by improving the redox efficiency during the regeneration, while no such promoting effect was observed for Pd/Al2O3. A suggestion is made for improving the catalyst performance.

Effect of Ni and noble metals (Ru, Pd and Pt) on performance of bifunctional MoP/SiO2 for hydroconversion of methyl laurate

Science.gov (United States)

Nie, Ziyang; Zhang, Zhena; Chen, Jixiang

2017-10-01

SiO2 supported bifunctional MoP catalysts modified with different metal promoters (Ni, Ru, Pd, Pt), where Mo/Ni and Mo/M(M = Ru, Pd and Pt) atomic ratios was respectively 10 and 40, were prepared by TPR method from the phosphate precursors. It was found that the introduction of metal promoters facilitated the reduction of phosphate precursor and enhanced the dispersion of MoP. However, the MoP catalyst acidity was scarcely influenced by the small amount of metal promoters. In the hydroconversion of methyl laurate, the promoters enhanced the MoP catalyst activity for conversion of methyl laurate and hydrogenation of alkenes (intermediate), but reduced isomerization ability. Among the promoters, Ru was an optimum to decrease selectivity to alkenes while maintain high selectivity to iso-alkanes, and Mo40RuP showed better stability than MoP. At 380 °C and 3.0 MPa, the conversion of methyl laurate, the total selectivity to C11 and C12 hydrocarbons and the selectivity to iso-alkanes maintained at 100%, ∼94% and ∼30% on Mo40RuP during 102 h, respectively. The good stability of Mo40RuP is ascribed to that the presence of Ru prevented the sintering of MoP particles and suppressed carbon deposition.

Lattice thermal conductivity of disordered NiPd and NiPt alloys

International Nuclear Information System (INIS)

Alam, Aftab; Mookerjee, Abhijit

2006-01-01

Numerical calculations of lattice thermal conductivity are reported for the binary alloys NiPd and NiPt. The present work is a continuation of an earlier paper by us (Alam and Mookerjee 2005 Phys. Rev. B 72 214207), which developed a theoretical framework for the calculation of configuration-averaged lattice thermal conductivity and thermal diffusivity in disordered alloys. The formulation was based on the augmented space theorem (Mookerjee 1973 J. Phys. C: Solid State Phys. 6 L205) combined with a scattering diagram technique. In this paper we shall show the dependence of the lattice thermal conductivity on a series of variables like phonon frequency, temperature and alloy composition. The temperature dependence of κ(T) and its relation to the measured thermal conductivity is discussed. The concentration dependence of κ appears to justify the notion of a minimum thermal conductivity as discussed by Kittel, Slack and others (Kittel 1948 Phys. Rev. 75 972, Brich and Clark 1940 Am. J. Sci. 238 613; Slack 1979 Solid State Physics vol 34, ed H Ehrenreich, F Seitz and D Turnbull (New York: Academic) p 1). We also study the frequency and composition dependence of the thermal diffusivity averaged over modes. A numerical estimate of this quantity gives an idea about the location of the mobility edge and the fraction of states in the frequency spectrum which is delocalized

Design of Pd/PANI/Pd sandwich-structured nanotube array catalysts with special shape effects and synergistic effects for ethanol electrooxidation.

Science.gov (United States)

Wang, An-Liang; Xu, Han; Feng, Jin-Xian; Ding, Liang-Xin; Tong, Ye-Xiang; Li, Gao-Ren

2013-07-24

Low cost, high activity, and long-term durability are the main requirements for commercializing fuel cell electrocatalysts. Despite tremendous efforts, developing non-Pt anode electrocatalysts with high activity and long-term durability at low cost remains a significant technical challenge. Here we report a new type of hybrid Pd/PANI/Pd sandwich-structured nanotube array (SNTA) to exploit shape effects and synergistic effects of Pd-PANI composites for the oxidation of small organic molecules for direct alcohol fuel cells. These synthesized Pd/PANI/Pd SNTAs exhibit significantly improved electrocatalytic activity and durability compared with Pd NTAs and commercial Pd/C catalysts. The unique SNTAs provide fast transport and short diffusion paths for electroactive species and high utilization rate of catalysts. Besides the merits of nanotube arrays, the improved electrocatalytic activity and durability are especially attributed to the special Pd/PANI/Pd sandwich-like nanostructures, which results in electron delocalization between Pd d orbitals and PANI π-conjugated ligands and in electron transfer from Pd to PANI.

Pd-Pt Catalysts on Mesoporous SiO2-Al2O3 with Superior Activity for HDS of 4,6-Dimethyldibenzothiophene: Effect of Metal Loading and Support Composition

Czech Academy of Sciences Publication Activity Database

Vít, Zdeněk; Gulková, Daniela; Kaluža, Luděk; Kupčík, Jaroslav

2015-01-01

Roč. 179, DEC 2015 (2015), s. 44-53 ISSN 0926-3373 R&D Projects: GA ČR GAP106/11/0902 Institutional support: RVO:67985858 ; RVO:61388980 Keywords : Pd-Pt catalyst * mesoporous silica-alumina * 4,6-DMDBT Subject RIV: CF - Physical ; Theoretical Chemistry ; CA - Inorganic Chemistry (UACH-T) Impact factor: 8.328, year: 2015

Behaviour of palladium(II), platinum(IV), and rhodium(III) in artificial and natural waters: Influence of reactor surface and geochemistry on metal recovery

Energy Technology Data Exchange (ETDEWEB)

Cobelo-Garcia, Antonio [School of Earth, Ocean and Environmental Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA (United Kingdom)]. E-mail: antonio.cobelo-garcia@plymouth.ac.uk; Turner, Andrew [School of Earth, Ocean and Environmental Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA (United Kingdom); Millward, Geoffrey E. [School of Earth, Ocean and Environmental Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA (United Kingdom); Couceiro, Fay [School of Earth, Ocean and Environmental Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA (United Kingdom)

2007-03-07

The recovery of dissolved platinum group elements (PGE: Pd(II), Pt(IV) and Rh(III)) added to Milli-Q[reg] water, artificial freshwater and seawater and filtered natural waters has been studied, as a function of pH and PGE concentration, in containers of varying synthetic composition. The least adsorptive and/or precipitative loss was obtained for borosilicate glass under most of the conditions employed, whereas the greatest loss was obtained for low-density polyethylene. Of the polymeric materials tested, the adsorptive and/or precipitative loss of PGE was lowest for fluorinated ethylene propylene (Teflon[reg]). The loss of Pd(II) in freshwater was significant due to its affinity for surface adsorption and its relatively low solubility. The presence of natural dissolved organic matter increases the recovery of Pd(II) but enhances the loss of Pt(IV). The loss of Rh(III) in seawater was significant and was mainly due to precipitation, whereas Pd(II) recovery was enhanced, compared to freshwater, because of its complexation with chloride. The results have important implications regarding protocols employed for sample preservation and controlled laboratory experiments used in the study of the speciation and biogeochemical behaviour of PGE.

Highly ordered FEPT and FePd magnetic nano-structures: Correlated structural and magnetic studies

International Nuclear Information System (INIS)

Lukaszew, Rosa Alejandra; Cebollada, Alfonso; Clavero, Cesar; Garcia-Martin, Jose Miguel

2006-01-01

The micro-structure of epitaxial FePt and FePd films grown on MgO (0 0 1) substrates is correlated to their magnetic behavior. The FePd films exhibit high chemical ordering and perpendicular magnetic anisotropy. On the other hand FePt films exhibit low chemical ordering, with nano-grains oriented in two orthogonal directions, forcing the magnetization to remain in the plane of the films

Study of NaBH4 reaction with RhCl3·4H2O and H2PtCl6·6H2O in dimethylformamide

International Nuclear Information System (INIS)

Khain, V.S.; Val'kova, V.P.

1988-01-01

Data on study of NaBH 4 reactions with RhCl 3 x4H 2 O and H 2 PtCl 6 x6H 2 O in dimethylformamide, which is a good solvent of both complex hydride and compounds of platinum metals are presented. Rhodium (3) and platinum (4) reduction by sodium tetrahydridoborate in dimethylformamide proceeds quantitatively up to element state. Depositions of powder-like rhodium and platinum or their sols stable up to 8 months are formed depending on the ratio of concentrations of the reacting substances. Stoichiometry of redox-reactions is established based on spectrophotometric, gasovolumetric measurements,

Thermodynamic assessment of the rhodium-ruthenium-oxygen (Rh-Ru-O) system

Science.gov (United States)

Gossé, S.; Bordier, S.; Guéneau, C.; Brackx, E.; Domenger, R.; Rogez, J.

2018-03-01

Ruthenium (Ru) and rhodium (Rh) are abundant platinum-group metals formed during burn-up of nuclear fuels. Under normal operating conditions, Rh and Ru accumulate and predominantly form metallic precipitates with other fission products like Mo, Pd and Tc. In the framework of vitrification of high-level nuclear waste, these fission products are poorly soluble in molten glasses. They precipitate as metallic particles and oxide phases. Moreover, these Ru and Rh rich phases strongly depend on temperature and the oxygen fugacity of the glass melt. In case of severe accidental conditions with air ingress, oxidation of the Ru and Rh is possible. At low temperatures (T 1422 K for rhodium sesquioxide and T > 1815 K for ruthenium dioxide), they may decompose into (Rh)-FCC or (Ru)-HCP metallic phases and radiotoxic volatile gaseous species. A thermodynamic assessment of the Rh-Ru-O system will enable the prediction of: (1) the metallic and oxide phases that form during the vitrification of high-level nuclear wastes and (2) the release of volatile gaseous species during a severe accident. The Calphad method developed herein employs a thermodynamic approach in the investigation of the thermochemistry of rhodium and ruthenium at high temperatures. Current literature on the thermodynamic properties and phase diagram data enables preliminary thermodynamic assessments of the Rh-O and Ru-O systems. Additionally, select compositions in the ternary Rh-Ru-O system underwent experimental tests to complement data found in literature and to establish the phase equilibria in the ternary system.

Effect of Rh oxide as a cocatalyst over Bi{sub 0.5}Y{sub 0.5}VO{sub 4} on photocatalytic overall water splitting

Energy Technology Data Exchange (ETDEWEB)

Chen, Wei, E-mail: chanwee@henu.edu.cn [College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, Henan (China); Yang, Bingbing; Yu, Qingtao; Mao, Liqun [College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, Henan (China); Fan, Zeyun [Research Center for Combustion and Environmental Technology, Shanghai Jiao Tong University, Shanghai 200240 (China); Wang, Qizhao [College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070 (China); Shangguan, Wenfeng, E-mail: shangguan@sjtu.edu.cn [Research Center for Combustion and Environmental Technology, Shanghai Jiao Tong University, Shanghai 200240 (China)

2015-11-15

Graphical abstract: - Highlights: • The effect of cocatalysts as active sites for water splitting was investigated. • Rh{sub 2}O{sub 3} was found to give the highest photocatalytic activity. • Compared to Pt, NiO, Rh{sub 2}O{sub 3} can reduce more overpotential of O{sub 2} evolution. • Rh{sub 2}O{sub 3} also promote the separation of electrons and holes apparently. - Abstract: Pt, Rh{sub 2}O{sub 3}, NiO nanoparticles as cocatalysts were loaded on BYV solid solution photocatalysts by an impregnation method to promote photocatalytic activity for overall water splitting. The cocatalysts loading could enhance the photocatalytic activity significantly. The (photo)electrochemical measurements and HR-TEM, PL analyses revealed that the effect of cocatalysts acted as active sites depended on the efficient separation of photoinduced charge carriers as well as the reduction of the overpotential of O{sub 2} evolution. Among the cocatalysts in this study, Rh{sub 2}O{sub 3} was found to give the highest photocatalytic activity. This is because, compared to Pt and NiO, Rh{sub 2}O{sub 3} nanoparticles are able to not only reduce more overpotential of O{sub 2} evolution, but also extremely promote the separation of electrons and holes. 0.5 wt% Rh{sub 2}O{sub 3}/BYV exhibited the highest photocatalytic activity for H{sub 2} and O{sub 2} evolution, reaching 104.4 μmol/h and 50.9 μmol/h, respectively. The present work will be useful to instruct cocatalyst loading for obtaining the photocatalysts with high photocatalytic activity for overall water splitting.

Rh Incompatibility

Science.gov (United States)

... type is called Rh. Rh factor is a protein on red blood cells. Most people are Rh-positive; they have Rh factor. Rh-negative people don't have it. Rh factor is inherited though genes. When you're pregnant, blood from your baby can cross into your ...

Self-regenerative function of the intelligent automotive catalyst

International Nuclear Information System (INIS)

Tanaka, Hirohisa; Nishihata, Yasuo

2007-01-01

Intelligent catalyst, in which noble metals are used as an active part of automotive catalyst, has been considered for keeping up their sufficient activity. The noble metals have a function of cleaning up the exhaust gas as well as that of self-regeneration. In 2002, a Pd system has been put to practical use, and continuously Rh and Pt systems have been commercialized. Now the catalyst has been used in more than three million vehicles. In this report, the atomic level mechanism of the catalyst and its self-regeneration function getting from analyses using synchrotron radiation are introduced. By the analysis using the Spring-8, the mechanism of keeping the active state of the Pd Perovskite Oxide without degradation was identified. The DXAFS (Dispersive X-ray Absorption Fine Structure) analysis in the ESRF (European Synchrotron Radiation Facility) made clear the self-regeneration mechanism of the Pd Perovskite Oxide. This knowledge could lead to the practical development of the Rh and Pt systems. The catalyst technology is counted on balancing resources of the noble metal and environmental sustainability. (A.H.)

Ab initio random structure search for 13-atom clusters of fcc elements

International Nuclear Information System (INIS)

Chou, J P; Hsing, C R; Wei, C M; Cheng, C; Chang, C M

2013-01-01

The 13-atom metal clusters of fcc elements (Al, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au) were studied by density functional theory calculations. The global minima were searched for by the ab initio random structure searching method. In addition to some new lowest-energy structures for Pd 13 and Au 13 , we found that the effective coordination numbers of the lowest-energy clusters would increase with the ratio of the dimer-to-bulk bond length. This correlation, together with the electronic structures of the lowest-energy clusters, divides the 13-atom clusters of these fcc elements into two groups (except for Au 13 , which prefers a two-dimensional structure due to the relativistic effect). Compact-like clusters that are composed exclusively of triangular motifs are preferred for elements without d-electrons (Al) or with (nearly) filled d-band electrons (Ni, Pd, Cu, Ag). Non-compact clusters composed mainly of square motifs connected by some triangular motifs (Rh, Ir, Pt) are favored for elements with unfilled d-band electrons. (paper)

Palladium, platinum, rhodium, ruthenium, and iridium in chromitites from the Massif du Sud and Tiebaghi massif, New Caledonia.

Science.gov (United States)

Page, N.J.; Cassard, D.; Haffty, J.

1982-01-01

The massive and disseminated podiform chromitites from 43 mines and other occurrences in the area contain up to (in ppb) Pd 9, Pt 45, Rh 31, Ir 410 and Ru 1300. The possble origins of the chromitites are discussed. -K.A.R.

Electron paramagnetic resonance of K3Rh(CN)6 irradiated with electrons in KCl

International Nuclear Information System (INIS)

Vugman, N.V.

1970-07-01

Using a simple theory, it was estimated the electronic density of the diamagnetic complex Rh (CN) 3- 6 in a KCl lattice. The g// and g1 values were determined by EPR, and the experimental results fit the theoretical calculations. (M.W.O.) [pt

Systematic study of hyperfine fields in Rh2 Y Z type Heusler alloys with 119 Sn impurity using Moessbauer spectroscopy

International Nuclear Information System (INIS)

Ramos, S.M.M.

1985-01-01

The magnetic hyperfine fields in the Heusler alloys Rh 2 Mn .98 Ge Sn 02 , Rh 2 Mn Ge .98 Sn .02 , Rh 2 Mn Pb .98 Sn .02 and Rh 2 Mn Sn has been studied by 119 Sn Moessbauer spectroscopy at 293 K, 77 K, 4.2 K and 293 K with applied external magnetic field. The results show that when one compare the magnetic hyperfine fields systematic with the Heusler alloys X 2 Mn Z (X = Co, Ni, Cu, Pd, and Z = s p metal), this systematic is similar to the Co alloys, although can not explained by the currents models for the Heusler alloys. (author)

Ferromagnetism of Pd-Fe (abstract)

Science.gov (United States)

Griffith, G.; Carnegie, D. W., Jr.; Claus, H.

1984-03-01

We present new low field ac susceptibility measurements on Pd1-xFex alloys (0.002≤X<0.01). The Curie temperature TC, determined from these measurements, are significantly lower than those previously obtained in higher magnetic fields [G. J. Nieuwenhuys, Adv. Phys. 24, 515 (1975)]. We also found that for a given sample, TC depends very sensitively on its heat treatment. As an example, for an alloy with 0.4 at. % Fe, TC can be varied between 4 and 10 K. In other alloys, like PdNi or RhNi similar changes in TC are due to changes in the degree of atomic short-range order [S. Crane, D. W. Carnegie, Jr., and H. Claus, J. Appl. Phys. 53, 2179 (1982)]. However, for PdFe we show evidence that the changes in TC are due to absorption of small amounts of oxygen, the samples with the highest amount of oxygen having the highest TC. It thus seems that oxygen has the opposite effect from hydrogen on the exchange enhanced susceptibility of Pd [J. A. Mydosh, Phys. Rev. Lett. 33, 1562 (1974)].

Magnesium and cadmium in covalently-bonded Lonsdaleite networks: Synthesis, structure, and conding of AETMg{sub 2} and SrTCd{sub 2} (AE = Ca, Sr; T = Pd, Ag, Pt, Au)

Energy Technology Data Exchange (ETDEWEB)

Kersting, Marcel; Johnscher, Michael; Poettgen, Rainer [Institut fuer Anorganische und Analytische Chemie, Universitaet Muenster, Corrensstrasse 30, 48149 Muenster (Germany); Matar, Samir F. [Universite Bordeaux, ICMCB, UPR 9048, 33600 Pessac (France)

2013-04-15

The alkaline earth metal compounds AETMg{sub 2} and AETCd{sub 2} (AE = Ca, Sr; T = Pd, Ag, Pt, Au) were synthesized by induction-melting (or in muffle furnaces) of the elements in sealed niobium ampoules. The new phases were characterized by powder X-ray diffraction. The structures of SrPdMg{sub 2} and SrPdCd{sub 2} were investigated by X-ray diffraction on single crystals: MgCuAl{sub 2} type, Cmcm, a = 436.42(4), b = 1130.1(1), c = 820.54(7) pm, wR{sub 2} = 0.0115, 511 F{sup 2} values for SrPdMg{sub 2} and a = 443.5(2), b = 1063.0(2), c = 810.2(2) pm, wR{sub 2} = 0.0296, 386 F{sup 2} values for SrPdCd{sub 2} with 16 variables for each refinement. The magnesium and cadmium atoms build up [TMg{sub 2}] and [TCd{sub 2}] polyanionic networks, which leave cavities for the calcium and strontium atoms. The bonding variations within the polyanions, which are mainly influenced by the length of the b axis are discussed. Ab initio calculations of electronic structure, charge densities, and chemical bonding, characterize SrPdMg{sub 2} with a larger cohesive energy than SrPdCd{sub 2}. This is illustrated by larger bonding Pd-Mg interactions, opposite to compensating Pd-Cd between bonding and antibonding states. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

High-Performance Rh ₂ P Electrocatalyst for Efficient Water Splitting

Energy Technology Data Exchange (ETDEWEB)

Duan, Haohong; Li, Dongguo; Tang, Yan; He, Yang; Ji, Shufang; Wang, Rongyue; Lv, Haifeng; Lopes, Pietro P.; Paulikas, Arvydas P.; Li, Haoyi; Mao, Scott X.; Wang, Chongmin; Markovic, Nenad M.; Li, Jun; Stamenkovic, Vojislav R.; Li, Yadong

2017-04-05

Search for active, stable and cost-efficient electrocatalysts for hydrogen production via water splitting could make substantial impact to the energy technologies that do not rely on fossil fuels. Here we report the synthesis of rhodium phosphide electrocatalyst with low metal loading in the form of nanocubes (NCs) dispersed in high surface area carbon (Rh2P/C) by a facile solvo-thermal approach. The Rh2P/C NCs exhibit remarkable performance for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) compared to Rh/C and Pt/C catalysts. The atomic structure of the rhodium phosphide nanocubes was directly observed by annular dark-field scanning transmission electron microscopy (ADF-STEM), which revealed phosphorous-rich outermost atomic layer. Combined experimental and computational studies suggest that surface phosphorous plays crucial role in determining the robust catalyst properties.

Synthesis and hydrogenation application of Pt–Pd bimetallic nanocatalysts stabilized by macrocycle-modified dendrimer

Science.gov (United States)

Xiao, Haiyan; Zhou, Wei; Zhang, Dongqiao; Peng, Xiaohong

2017-01-01

Different generations of poly(propylene imine) (Gn-PPI) terminated with N-containing 15-membered triolefinic macrocycle (GnM) (n = 2, 3, 4, 5) were prepared. The bimetallic nanoparticle catalysts GnM-(Ptx/Pd10−x) (x = 0, 3, 5, 7, 10) were prepared by the synchronous ligand-exchange reaction between GnM and the complexes of Pt(PPh3)4 and Pd(PPh3)4. The structure and catalytic properties of GnM-(Ptx/Pd10−x) were characterized via Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, energy-dispersive spectroscopy and inductively coupled plasma atomic emission spectroscopy. The novel bimetallic Pd–Pt nanoparticle catalysts stabilized by dendrimers (DSNs) present higher catalytic activities for the hydrogenation of dimeric acid (DA) than that of nitrile butadiene rubber (NBR). It can be concluded that bimetallic Pd–Pt DSNs possess alloying and synergistic electronic effects on account of the hydrogenation degree (HD) of DA and NBR. Furthermore, the HD of DA and NBR shows a remarkable decrease with the incremental generations (n) of GnM-(Pt3/Pd7) (n = 2, 3, 4, 5). PMID:29308263

RH-TRU Waste Content Codes (RH-Trucon)

International Nuclear Information System (INIS)

2007-01-01

The Remote-Handled Transuranic (RH-TRU) Content Codes (RH-TRUCON) document describes the inventory of RH-TRU waste within the transportation parameters specified by the Remote-Handled Transuranic Waste Authorized Methods for Payload Control (RH-TRAMPAC).1 The RH-TRAMPAC defines the allowable payload for the RH-TRU 72-B. This document is a catalog of RH-TRU 72-B authorized contents by site. A content code is defined by the following components: A two-letter site abbreviation that designates the physical location of the generated/stored waste (e.g., ID for Idaho National Laboratory [INL]). The site-specific letter designations for each of the sites are provided in Table 1. A three-digit code that designates the physical and chemical form of the waste (e.g., content code 317 denotes TRU Metal Waste). For RH-TRU waste to be transported in the RH-TRU 72-B, the first number of this three-digit code is '3.' The second and third numbers of the three-digit code describe the physical and chemical form of the waste. Table 2 provides a brief description of each generic code. Content codes are further defined as subcodes by an alpha trailer after the three-digit code to allow segregation of wastes that differ in one or more parameter(s). For example, the alpha trailers of the subcodes ID 322A and ID 322B may be used to differentiate between waste packaging configurations. As detailed in the RH-TRAMPAC, compliance with flammable gas limits may be demonstrated through the evaluation of compliance with either a decay heat limit or flammable gas generation rate (FGGR) limit per container specified in approved content codes. As applicable, if a container meets the watt*year criteria specified by the RH-TRAMPAC, the decay heat limits based on the dose-dependent G value may be used as specified in an approved content code. If a site implements the administrative controls outlined in the RH-TRAMPAC and Appendix 2.4 of the RH-TRU Payload Appendices, the decay heat or FGGR limits based

RH-TRU Waste Content Codes (RH-TRUCON)

International Nuclear Information System (INIS)

2007-01-01

The Remote-Handled Transuranic (RH-TRU) Content Codes (RH-TRUCON) document describes the inventory of RH-TRU waste within the transportation parameters specified by the Remote-Handled Transuranic Waste Authorized Methods for Payload Control (RH-TRAMPAC).1 The RH-TRAMPAC defines the allowable payload for the RH-TRU 72-B. This document is a catalog of RH-TRU 72-B authorized contents by site. A content code is defined by the following components: A two-letter site abbreviation that designates the physical location of the generated/stored waste (e.g., ID for Idaho National Laboratory [INL]). The site-specific letter designations for each of the sites are provided in Table 1. A three-digit code that designates the physical and chemical form of the waste (e.g., content code 317 denotes TRU Metal Waste). For RH-TRU waste to be transported in the RH-TRU 72-B, the first number of this three-digit code is '3.' The second and third numbers of the three-digit code describe the physical and chemical form of the waste. Table 2 provides a brief description of each generic code. Content codes are further defined as subcodes by an alpha trailer after the three-digit code to allow segregation of wastes that differ in one or more parameter(s). For example, the alpha trailers of the subcodes ID 322A and ID 322B may be used to differentiate between waste packaging configurations. As detailed in the RH-TRAMPAC, compliance with flammable gas limits may be demonstrated through the evaluation of compliance with either a decay heat limit or flammable gas generation rate (FGGR) limit per container specified in approved content codes. As applicable, if a container meets the watt*year criteria specified by the RH-TRAMPAC, the decay heat limits based on the dose-dependent G value may be used as specified in an approved content code. If a site implements the administrative controls outlined in the RH-TRAMPAC and Appendix 2.4 of the RH-TRU Payload Appendices, the decay heat or FGGR limits based

RH-TRU Waste Content Codes (RH-TRUCON)

Energy Technology Data Exchange (ETDEWEB)

Washington TRU Solutions LLC

2007-08-01

The Remote-Handled Transuranic (RH-TRU) Content Codes (RH-TRUCON) document describes the inventory of RH-TRU waste within the transportation parameters specified by the Remote-Handled Transuranic Waste Authorized Methods for Payload Control (RH-TRAMPAC).1 The RH-TRAMPAC defines the allowable payload for the RH-TRU 72-B. This document is a catalog of RH-TRU 72-B authorized contents by site. A content code is defined by the following components: • A two-letter site abbreviation that designates the physical location of the generated/stored waste (e.g., ID for Idaho National Laboratory [INL]). The site-specific letter designations for each of the sites are provided in Table 1. • A three-digit code that designates the physical and chemical form of the waste (e.g., content code 317 denotes TRU Metal Waste). For RH-TRU waste to be transported in the RH-TRU 72-B, the first number of this three-digit code is “3.” The second and third numbers of the three-digit code describe the physical and chemical form of the waste. Table 2 provides a brief description of each generic code. Content codes are further defined as subcodes by an alpha trailer after the three-digit code to allow segregation of wastes that differ in one or more parameter(s). For example, the alpha trailers of the subcodes ID 322A and ID 322B may be used to differentiate between waste packaging configurations. As detailed in the RH-TRAMPAC, compliance with flammable gas limits may be demonstrated through the evaluation of compliance with either a decay heat limit or flammable gas generation rate (FGGR) limit per container specified in approved content codes. As applicable, if a container meets the watt*year criteria specified by the RH-TRAMPAC, the decay heat limits based on the dose-dependent G value may be used as specified in an approved content code. If a site implements the administrative controls outlined in the RH-TRAMPAC and Appendix 2.4 of the RH-TRU Payload Appendices, the decay heat or FGGR

RH-TRU Waste Content Codes (RH-TRUCON)

Energy Technology Data Exchange (ETDEWEB)

Washington TRU Solutions

2007-05-30

The Remote-Handled Transuranic (RH-TRU) Content Codes (RH-TRUCON) document describes the inventory of RH-TRU waste within the transportation parameters specified by the Remote-Handled Transuranic Waste Authorized Methods for Payload Control (RH-TRAMPAC).1 The RH-TRAMPAC defines the allowable payload for the RH-TRU 72-B. This document is a catalog of RH-TRU 72-B authorized contents by site. A content code is defined by the following components: • A two-letter site abbreviation that designates the physical location of the generated/stored waste (e.g., ID for Idaho National Laboratory [INL]). The site-specific letter designations for each of the sites are provided in Table 1. • A three-digit code that designates the physical and chemical form of the waste (e.g., content code 317 denotes TRU Metal Waste). For RH-TRU waste to be transported in the RH-TRU 72-B, the first number of this three-digit code is “3.” The second and third numbers of the three-digit code describe the physical and chemical form of the waste. Table 2 provides a brief description of each generic code. Content codes are further defined as subcodes by an alpha trailer after the three-digit code to allow segregation of wastes that differ in one or more parameter(s). For example, the alpha trailers of the subcodes ID 322A and ID 322B may be used to differentiate between waste packaging configurations. As detailed in the RH-TRAMPAC, compliance with flammable gas limits may be demonstrated through the evaluation of compliance with either a decay heat limit or flammable gas generation rate (FGGR) limit per container specified in approved content codes. As applicable, if a container meets the watt*year criteria specified by the RH-TRAMPAC, the decay heat limits based on the dose-dependent G value may be used as specified in an approved content code. If a site implements the administrative controls outlined in the RH-TRAMPAC and Appendix 2.4 of the RH-TRU Payload Appendices, the decay heat or FGGR

Creation of Novel Solid-Solution Alloy Nanoparticles on the Basis of Density-of-States Engineering by Interelement Fusion.

Science.gov (United States)

Kobayashi, Hirokazu; Kusada, Kohei; Kitagawa, Hiroshi

2015-06-16

Currently 118 known elements are represented in the periodic table. Of these 118 elements, only about 80 elements are stable, nonradioactive, and widely available for our society. From the viewpoint of the "elements strategy", we need to make full use of the 80 elements to bring out their latent ability and create innovative materials. Furthermore, there is a strong demand that the use of rare or toxic elements be reduced or replaced while their important properties are retained. Advanced science and technology could create higher-performance materials even while replacing or reducing minor or harmful elements through the combination of more abundant elements. The properties of elements are correlated directly with their electronic states. In a solid, the magnitude of the density of states (DOS) at the Fermi level affects the physical and chemical properties. In the present age, more attention has been paid to improving the properties of materials by means of alloying elements. In particular, the solid-solution-type alloy is advantageous because the properties can be continuously controlled by tuning the compositions and/or combinations of the constituent elements. However, the majority of bulk alloys are of the phase-separated type under ambient conditions, where constituent elements are immiscible with each other. To overcome the challenge of the bulk-phase metallurgical aspects, we have focused on the nanosize effect and developed methods involving "nonequilibrium synthesis" or "a process of hydrogen absorption/desorption". We propose a new concept of "density-of-states engineering" for the design of materials having the most desirable and suitable properties by means of "interelement fusion". In this Account, we describe novel solid-solution alloys of Pd-Pt, Ag-Rh, and Pd-Ru systems in which the constituent elements are immiscible in the bulk state. The homogeneous solid-solution alloys of Pd and Pt were created from Pd core/Pt shell nanoparticles using a

Magnetic properties of Co-Rh and Ni-Rh nanowires

International Nuclear Information System (INIS)

Sondon, Tristana; Saul, Andres; Guevara, Javier

2007-01-01

We have calculated the magnetic properties of pure Ni, Co and Rh, and alloyed Co-Rh and Ni-Rh free-standing nanowires by an ab initio method. We have found that the pure Co and Ni wires present an enhanced magnetic moment with respect to their bulk values, and we have obtained that a magnetic order appears for pure Rh wires. For concentrations up to 50% Rh, in the alloyed Ni-Rh linear chains there is an enhancement of the total magnetic moment with respect to the pure nanowires, and in the case of Co-Rh the alloying with Rh enhances the Co magnetic moment. In both systems we obtain very high Rh magnetic moments

Phase transformations in the Cu.6 Pd.4 alloy

International Nuclear Information System (INIS)

Imakuma, K.

1977-01-01

Order-disorder and structural transformations in the Cu-Pd 60-40% (Cu. 6 Pd. 4 ) alloy by means of a temperature and time dependent treatment are studied. The structural transformations by x-rays diffraction are also studied, where the bcc, fcc and tetragonal phases were observed. A qualitative analyze of the resistivity kinetics are made [pt

Investigations of Pd-Cu electrocatalyst for oxygen reduction reaction in acidic media with RDE method

Energy Technology Data Exchange (ETDEWEB)

Fouda-Onana, F.; Bah, S.; Savadogo, O. [Ecole Polytechnique de Montreal, Montreal, PQ (Canada). Laboratoire de nouveaux materiaux pour l' energie et l' electrochimie

2008-07-01

The kinetics of the oxygen reduction reaction (ORR) has been studied extensively with different platinum bi-metallic alloys such as Pt-Fe, Pt-Ni, Pt-Co. However, palladium-based bi-metallic alloys are being considered as a substitute for platinum in electrocatalysts. This paper reported on a study that investigated the ORR on bi-metallic Pd-Cu electrocatalyst. Different contents in Cu were analyzed and an optimal Cu composition leading to the highest ORR activity was found. A mechanism of the ORR kinetics for this catalyst was introduced based on the value of the Tafel slope. A smooth increase in surface area up to 50 per cent Cu was observed to a constant value of 23 cm{sup 2}. Such behaviour was due to the high dispersion of Pd as Cu increased and segregated. A volcano-shape was found between the kinetic current, activation energy and the Cu composition. The maximum exchange current density and the lowest activation energy were found for Pd50Cu50, which corresponded to the highest surface area. All Pd-Cu alloys presented a higher kinetic current than Pd alone. 3 refs., 1 tab., 3 figs.

RH-TRU Waste Content Codes (RH TRUCON)

International Nuclear Information System (INIS)

2007-01-01

The Remote-Handled Transuranic (RH-TRU) Content Codes (RH-TRUCON) document describes the inventory of RH-TRU waste within the transportation parameters specified by the Remote-Handled Transuranic Waste Authorized Methods for Payload Control (RH-TRAMPAC).1 The RH-TRAMPAC defines the allowable payload for the RH-TRU 72-B. This document is a catalog of RH-TRU 72-B authorized contents by site. A content code is defined by the following components: (1) A two-letter site abbreviation that designates the physical location of the generated/stored waste (e.g., ID for Idaho National Laboratory [INL]). The site-specific letter designations for each of the sites are provided in Table 1. (2) A three-digit code that designates the physical and chemical form of the waste (e.g., content code 317 denotes TRU Metal Waste). For RH-TRU waste to be transported in the RH-TRU 72-B, the first number of this three-digit code is ''3''. The second and third numbers of the three-digit code describe the physical and chemical form of the waste. Table 2 provides a brief description of each generic code. Content codes are further defined as subcodes by an alpha trailer after the three-digit code to allow segregation of wastes that differ in one or more parameter(s). For example, the alpha trailers of the subcodes ID 322A and ID 322B may be used to differentiate between waste packaging configurations. As detailed in the RH-TRAMPAC, compliance with flammable gas limits may be demonstrated through the evaluation of compliance with either a decay heat limit or flammable gas generation rate (FGGR) limit per container specified in approved content codes. As applicable, if a container meets the watt*year criteria specified by the RH-TRAMPAC, the decay heat limits based on the dose-dependent G value may be used as specified in an approved content code. If a site implements the administrative controls outlined in the RH-TRAMPAC and Appendix 2.4 of the RH-TRU Payload Appendices, the decay heat or FGGR

RH-TRU Waste Content Codes (RH TRUCON)

Energy Technology Data Exchange (ETDEWEB)

Washington TRU Solutions

2007-05-01

The Remote-Handled Transuranic (RH-TRU) Content Codes (RH-TRUCON) document describes the inventory of RH-TRU waste within the transportation parameters specified by the Remote-Handled Transuranic Waste Authorized Methods for Payload Control (RH-TRAMPAC).1 The RH-TRAMPAC defines the allowable payload for the RH-TRU 72-B. This document is a catalog of RH-TRU 72-B authorized contents by site. A content code is defined by the following components: • A two-letter site abbreviation that designates the physical location of the generated/stored waste (e.g., ID for Idaho National Laboratory [INL]). The site-specific letter designations for each of the sites are provided in Table 1. • A three-digit code that designates the physical and chemical form of the waste (e.g., content code 317 denotes TRU Metal Waste). For RH-TRU waste to be transported in the RH-TRU 72-B, the first number of this three-digit code is “3.” The second and third numbers of the three-digit code describe the physical and chemical form of the waste. Table 2 provides a brief description of each generic code. Content codes are further defined as subcodes by an alpha trailer after the three-digit code to allow segregation of wastes that differ in one or more parameter(s). For example, the alpha trailers of the subcodes ID 322A and ID 322B may be used to differentiate between waste packaging configurations. As detailed in the RH-TRAMPAC, compliance with flammable gas limits may be demonstrated through the evaluation of compliance with either a decay heat limit or flammable gas generation rate (FGGR) limit per container specified in approved content codes. As applicable, if a container meets the watt*year criteria specified by the RH-TRAMPAC, the decay heat limits based on the dose-dependent G value may be used as specified in an approved content code. If a site implements the administrative controls outlined in the RH-TRAMPAC and Appendix 2.4 of the RH-TRU Payload Appendices, the decay heat or FGGR