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Sample records for hydrophobic platinum catalyst

  1. Preparation and characterization of hydrophobic platinum-doped carbon aerogel catalyst for hydrogen isotope separation

    Indian Academy of Sciences (India)

    M K Singh; R Singh; A Singh; D K Kohli; U Deshpande; P K Gupta

    2014-10-01

    We report preparation of hydrophobic platinum-doped carbon aerogel (PtCA) catalyst and its characterization for catalytic exchange reactions between hydrogen isotopes. The PtCA powder was synthesized by sol–gel polymerization method, mixed with colloidal PTFE solution, and coated on Dixon rings to obtain hydrophobic catalyst. The Pt cluster size in PtCA powder was observed to vary from 3 to 5 nm for a change in resorcinol to alkali molar ratio in synthesis solution from 20 to 200. Transmission electron microscopy of powder showed that the Pt clusters were uniformally dispersed and Pt0 metallic content estimated by X-ray photoelectron spectroscopy (XPS) was found to be of ∼ 70%. The catalytic activity was found to depend on Pt cluster size and was higher for smaller cluster size. For the smallest achieved Pt cluster size of 3 nm, catalytic activity of ∼ 0.8 m3 (STP) s-1 m-3 was obtained for hydrogen isotope exchange in atmospheric pressure conditions.

  2. UV-induced polymerization of size-controlled platinum/poly[styrene-divinylbenzene-tri(propylene glycol diacrylate] hydrophobic catalyst beads in microfluidics

    Directory of Open Access Journals (Sweden)

    Jun Wei

    2015-10-01

    Full Text Available The catalytic exchange of hydrogen isotopes between hydrogen and water has been known to be a very useful process for the separation of tritium from tritiated water. For the process, a highly active hydrophobic catalyst is needed. This study provides an effective fabrication method of size-controlled platinum/poly[styrene-divinylbenzene-tri(propylene glycol diacrylate] [Pt/poly(SDB-TPGDA] hydrophobic catalyst beads with a narrow size distribution. Platinum nanoparticles were prepared by γ-ray-induced reduction in the aqueous phase first, and then uniformly dispersed in SDB-TPGDA comonomer after the hydrophobization of platinum nanoparticles with alkylamine stabilizers. The porous Pt/poly(SDB-TPGDA hydrophobic catalyst beads were synthesized by the UV-initiated polymerization of the mixture droplets prepared in a capillary-based microfluidic system. The size of as-prepared catalyst beads can be controlled in the range of 200–1,000 μm by adjusting the flow rate of dispersed and continuous phases, as well as the viscosity of the continuous phase. Sorbitan monooleate and cyclohexanol were used as coporogens to control the porosities of the catalyst beads.

  3. UV-induced polymerization of size-controlled platinum/poly[styrene-divinylbenzene-tri(propylene glycol) diacrylate] hydrophobic catalyst beads in microfluidics

    Energy Technology Data Exchange (ETDEWEB)

    Wi, Jun; Li, Xiang; Song, Tong; Song, Zi Fan; Chang, Zhen Qi [School of Nuclear Science and Technology, University of Science and Technology of China, Hefei (China); Meng, Da Qiao [Si Chuan Institute of Materials and Technology, Jiang You (China)

    2015-10-15

    The catalytic exchange of hydrogen isotopes between hydrogen and water has been known to be a very useful process for the separation of tritium from tritiated water. For the process, a highly active hydrophobic catalyst is needed. This study provides an effective fabrication method of size-controlled platinum/poly[styrene-divinylbenzene-tri(propylene glycol) diacrylate] [Pt/poly(SDB-TPGDA)] hydrophobic catalyst beads with a narrow size distribution. Platinum nanoparticles were prepared by γ-ray-induced reduction in the aqueous phase first, and then uniformly dispersed in SDB-TPGDA comonomer after the hydrophobization of platinum nanoparticles with alkylamine stabilizers. The porous Pt/poly(SDB-TPGDA) hydrophobic catalyst beads were synthesized by the UV-initiated polymerization of the mixture droplets prepared in a capillary-based microfluidic system. The size of as-prepared catalyst beads can be controlled in the range of 200-1,000 μm by adjusting the flow rate of dispersed and continuous phases, as well as the viscosity of the continuous phase. Sorbitan monooleate and cyclohexanol were used as coporogens to control the porosities of the catalyst beads.

  4. Novel non-platinum metal catalyst material

    DEFF Research Database (Denmark)

    2014-01-01

    The present invention relates to a novel non-platinum metal catalyst material for use in low temperature fuel cells and electrolysers and to fuel cells and electrolysers comprising the novel non-platinum metal catalyst material. The present invention also relates to a novel method for synthesizing...... the novel non-platinum metal catalyst material....

  5. Examining the surfaces in used platinum catalysts

    Directory of Open Access Journals (Sweden)

    Trumić B.

    2009-01-01

    Full Text Available For the purpose of finding more advanced platinum catalyst manufacturing technologies and achieving a higher degree of ammonia oxidation, metallographic characterization has been done on the surface of catalyst gauzes and catalyst gripper gauzes made from platinum and palladium alloys. For the examined samples of gauzes as well as the cross section of the wires, a chemical analysis was provided. The purpose of this paper is the metallographic characterization of examined alloys carried out by way of electronic microscopic scanning, X-rays as well as chemical assays which contributed greatly to a better understanding of the surface deactivation, in other words a better consideration of structural changes occurring on the wire surface.

  6. Development of radioactive platinum group metal catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H.S.; Kim, Y.S.; Kim, Y.E. [and others

    1999-03-01

    The fission product nuclides generated during the irradiation of reactor fuel include many useful elements, among them platinum group metals such as ruthenium, rhodium and palladium which are of great industrial importance, occur rarely in nature and are highly valuable. In this research, the authors reviewed various PGM recovery methods. Recovery of palladium from seven-component simulated waste solutions was conducted by selective precipitation method. The recovery yield was more than 99.5% and the purity of the product was more than 99%. Wet-proof catalyst was prepared with the recovered palladium. The specific surface area of the catalyst support was more than 400m{sup 2}/g.The content of palladium impregnated on the support was 1 to 10 wt. %. Hydrogen isotope exchange efficiency of more than 93% to equilibrium with small amount of the catalyst was obtained. It was turned out possible to consider using such palladium or other very low active PGM materials in applications where its activity is unimportant as in nuclear industries. (author). 86 refs., 44 tabs., 88 figs.

  7. Development of radioactive platinum group metal catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H.S.; Kim, Y.S.; Kim, Y.E. [and others

    1999-03-01

    The fission product nuclides generated during the irradiation of reactor fuel include many useful elements, among them platinum group metals such as ruthenium, rhodium and palladium which are of great industrial importance, occur rarely in nature and are highly valuable. In this research, the authors reviewed various PGM recovery methods. Recovery of palladium from seven-component simulated waste solutions was conducted by selective precipitation method. The recovery yield was more than 99.5% and the purity of the product was more than 99%. Wet-proof catalyst was prepared with the recovered palladium. The specific surface area of the catalyst support was more than 400m{sup 2}/g.The content of palladium impregnated on the support was 1 to 10 wt. %. Hydrogen isotope exchange efficiency of more than 93% to equilibrium with small amount of the catalyst was obtained. It was turned out possible to consider using such palladium or other very low active PGM materials in applications where its activity is unimportant as in nuclear industries. (author). 86 refs., 44 tabs., 88 figs.

  8. Study of supported platinum catalysts by anomalous scattering

    Energy Technology Data Exchange (ETDEWEB)

    Georgopoulos, P.; Cohen, J.B.

    1985-01-01

    Platinum metal catalysts supported on silica gel and alumina were examined by wide-angle anomalous x-ray scattering at the Cornell High Energy Synchrotron Source. Complete removal of the support background features is achieved by this method, eliminating errors due to inaccurate background estimation. Platinum diffraction patterns from very-high-percentage metal-exposed catalysts were obtained for the first time, as well as from platinum supported on alumina. This technique is suitable for examining catalysts under working conditions and is superior to EXAFS for determinations of particle morphology and size distribution. 10 references, 8 figures.

  9. Exhaust system having a gold-platinum group metal catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Ragle, Christie Susan [Havana, IL; Silver, Ronald G [Peoria, IL; Zemskova, Svetlana Mikhailovna [Edelstein, IL; Eckstein, Colleen J [Metamora, IL

    2011-12-06

    A method of providing an exhaust treatment device is disclosed. The method includes applying a catalyst including gold and a platinum group metal to a particulate filter. The concentration of the gold and the platinum group metal is sufficient to enable oxidation of carbon monoxide and nitric oxide.

  10. Interfacial electronic effects control the reaction selectivity of platinum catalysts

    Science.gov (United States)

    Chen, Guangxu; Xu, Chaofa; Huang, Xiaoqing; Ye, Jinyu; Gu, Lin; Li, Gang; Tang, Zichao; Wu, Binghui; Yang, Huayan; Zhao, Zipeng; Zhou, Zhiyou; Fu, Gang; Zheng, Nanfeng

    2016-05-01

    Tuning the electronic structure of heterogeneous metal catalysts has emerged as an effective strategy to optimize their catalytic activities. By preparing ethylenediamine-coated ultrathin platinum nanowires as a model catalyst, here we demonstrate an interfacial electronic effect induced by simple organic modifications to control the selectivity of metal nanocatalysts during catalytic hydrogenation. This we apply to produce thermodynamically unfavourable but industrially important compounds, with ultrathin platinum nanowires exhibiting an unexpectedly high selectivity for the production of N-hydroxylanilines, through the partial hydrogenation of nitroaromatics. Mechanistic studies reveal that the electron donation from ethylenediamine makes the surface of platinum nanowires highly electron rich. During catalysis, such an interfacial electronic effect makes the catalytic surface favour the adsorption of electron-deficient reactants over electron-rich substrates (that is, N-hydroxylanilines), thus preventing full hydrogenation. More importantly, this interfacial electronic effect, achieved through simple organic modifications, may now be used for the optimization of commercial platinum catalysts.

  11. Preparative characteristics of hydrophobic polymer catalyst for the tritium removal

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Hee Suk; Choi, H. J.; Lee, H. S.; Ahn, D. H.; Kim, K. R.; Paek, S. W.; Kim, J. G.; Chung, H. S

    2001-05-01

    The optimum method for the fabrication of hydrophobic catalyst was selected and the apparatuses for the preparation of catalyst support with high yield was developed for the large scale production. Also, we summarized the method of improving the physical property of the catalyst support, the loading characteristics of Pt metal as a catalyst, and the characteristics of the apparatus for the fabrication of the catalysts on a large scale.

  12. Deactivation of platinum catalysts by oxygen 2. Nature of the catalyst deactivation

    Energy Technology Data Exchange (ETDEWEB)

    Dijkgraaf, P.J.M.; Duisters, H.A.M.; Kuster, B.F.M.; van der Wiele, K. (Univ. of Technology, Eindhoven (Netherlands))

    1988-08-01

    The effect of different start-up procedures on the deactivation of a 5% Pt/C catalyst used for the oxidation of D-gluconate has been investigated. Results have been obtained both in a stirred tank reactor for batch experiments and in an apparatus for continuous oxidation processes. The deactivation of the catalyst is not explicable by formation of platinum oxides. A model is proposed for the deactivation of platinum catalysts by oxygen, based on penetration of oxygen atoms into the platinum lattice.

  13. PLATINUM: a web tool for analysis of hydrophobic/hydrophilic organization of biomolecular complexes.

    Science.gov (United States)

    Pyrkov, Timothy V; Chugunov, Anton O; Krylov, Nikolay A; Nolde, Dmitry E; Efremov, Roman G

    2009-05-01

    The PLATINUM (Protein-Ligand ATtractions Investigation NUMerically) web service is designed for analysis and visualization of hydrophobic/hydrophilic properties of biomolecules supplied as 3D-structures. Furthermore, PLATINUM provides a number of tools for quantitative characterization of the hydrophobic/hydrophilic match in biomolecular complexes e.g. in docking poses. These complement standard scoring functions. The calculations are based on the concept of empirical Molecular Hydrophobicity Potential (MHP). The PLATINUM web tool as well as detailed documentation and tutorial are available free of charge for academic users at http://model.nmr.ru/platinum/. PLATINUM requires Java 5 or higher and Adobe Flash Player 9. Supplementary data are available at Bioinformatics online.

  14. Platinum on Carbon Nanofibers as Catalyst for Cinnamaldehyde Hydrogenation

    NARCIS (Netherlands)

    Plomp, A.J.

    2009-01-01

    The aim of the work described in this thesis was to investigate the role and nature of nanostructured carbon materials, oxygen surface groups and promoters on platinum-based catalysts for the selective hydrogenation of cinnamaldehyde. The selective hydrogenation of cinnamaldehyde to cinnamyl alcohol

  15. Platinum on Carbon Nanofibers as Catalyst for Cinnamaldehyde Hydrogenation

    NARCIS (Netherlands)

    Plomp, A.J.

    2009-01-01

    The aim of the work described in this thesis was to investigate the role and nature of nanostructured carbon materials, oxygen surface groups and promoters on platinum-based catalysts for the selective hydrogenation of cinnamaldehyde. The selective hydrogenation of cinnamaldehyde to cinnamyl alcohol

  16. SILICA-BOUND CROWN ETHERS PLATINUM COMPLEX AS HYDROSILYLATION CATALYST

    Institute of Scientific and Technical Information of China (English)

    CHEN Yuanyin; MENG Lingzhi; LI Liping; LUO Jieqi; HU Jinchang

    1993-01-01

    Silica-bound 15-Crown-5, 18-Crown-6 with a spacer of propyloxymethyl and their platinum complexes have been synthesized. It was found that they were efficient catalysts for the hydrosilylation of olefins with triethoxysilane in the temperature range of 60 to 130 ℃ .

  17. Sulfur tolerant zeolite supported platinum catalysts for aromatics hydrogenation

    Energy Technology Data Exchange (ETDEWEB)

    Bergem, Haakon

    1997-12-31

    The increased demand for transportation fuels at the expence of heavier fuel oil has forced the refinery industry to expand their conversion capacity with hydrotreating as one of the key processes. A shift towards more diesel powered vehicles along with tightening fuel regulations demanding cleaner fuels has lead to increasing interest in catalytic processes for the manufacturing of such environmentally acceptable fuels. This provides the motivation for this thesis. Its main objective was to study possible catalysts active for desulfurization, hydrogenation, and ring-opening of aromatics all in the presence of sulfur. A close examination of the physical properties and kinetical behaviour of the chosen catalysts has been performed. A high pressure reactor setup was designed and built for activity measurements. Zeolite supported platinum catalysts were prepared and both the metal and acid functions were characterized utilizing various experimental techniques. Hydrogenation of toluene was used as a model reaction and the effect of sulfur adsorption on the activity and kinetic behaviour of the catalysts was investigated. The catalyst samples showed hydrogenation activities comparable to a commercial Pt/Al2O3 catalyst. There were no clear differences in the effect of the various sulfur compounds studied. Platinum supported on zeolite Y gave considerably more sulfur tolerant catalysts compared to Al2O3 as support. 155 refs., 58 figs., 36 tabs.

  18. Formic acid oxidation at platinum-bismuth catalysts

    Directory of Open Access Journals (Sweden)

    Popović Ksenija Đ.

    2015-01-01

    Full Text Available The field of heterogeneous catalysis, specifically catalysis on bimetallic surfaces, has seen many advances over the past few decades. Bimetallic catalysts, which often show electronic and chemical properties that are distinct from those of their parent metals, offer the opportunity to obtain new catalysts with enhanced selectivity, activity, and stability. The oxidation of formic acid is of permanent interest as a model reaction for the mechanistic understanding of the electrooxidation of small organic molecules and because of its technical relevance for fuel cell applications. Platinum is one of the most commonly used catalysts for this reaction, despite the fact that it shows a few significant disadvantages: high cost and extreme susceptibility to poisoning by CO. To solve this problem, several approaches have been used, but generally, they all consist in the modification of platinum with a second element. Especially, bismuth has received significant attention as Pt modifier. According to the results presented in this survey dealing with the effects influencing the formic acid oxidation it was found that two types of Pt-Bi bimetallic catalysts (bulk and low loading deposits on GC showed superior catalytic activity in terms of the lower onset potential and oxidation current density, as well as exceptional stability compared to Pt. The findings in this report are important for the understanding of mechanism of formic acid electrooxidation on a bulk alloy and decorated surface, for the development of advanced anode catalysts for direct formic acid fuel cells, as well as for the synthesis of novel low-loading bimetallic catalysts. The use of bimetallic compounds as the anode catalysts is an effective solution to overcoming the problems of the formic acid oxidation current stability for long term applications. In the future, the tolerance of both CO poisoning and electrochemical leaching should be considered as the key factors in the development

  19. Synthesis of nanosized platinum based catalyst using sol-gel process

    Science.gov (United States)

    Ingale, S. V.; Wagh, P. B.; Bandyopadhyay, D.; Singh, I. K.; Tewari, R.; Gupta, S. C.

    2015-02-01

    The nano-sized platinum based catalysts using high surface area silica support have been prepared by sol-gel method. Tetramethoxysilane (TMOS) diluted in methanol was hydrolyzed to form a porous silica gel. Platinum (2%) was loaded at sol state using platinum chloride solution. After gelation, the solvent from the gel pores was extracted at ambient temperature which resulted in porous silica matrix incorporated with nanosized platinum. X-ray diffraction studies indicated the presence of elemental platinum in the silica-platinum composites. Transmission electron microscopy of the platinum -silica composites revealed that nanosized platinum particles of about 5-10 nm are homogeneously dispersed in silica matrix. Chemisorptions studies showed high dispersion (more than 50%) of platinum on silica support with specific surface area of 400 m2/g which puts them as promising candidates as catalyst in heterogeneous reactions.

  20. X-ray characterization of platinum group metal catalysts

    Science.gov (United States)

    Peterson, Eric J.

    Platinum group metals (PGMs) are used extensively as catalysts, employed in several sectors of the world energy economy. Fuel cells employing PGM catalysts show promise as power sources in the proposed hydrogen economy, using alcohols as hydrogen storage media. Currently, the most economically important application for PGMs is for the mitigation of emissions from internal combustion engines via catalytic converters. In all applications, efficient use of these expensive metals to fabricate robust catalysts is of the utmost importance. Understanding the catalyst structure/property relationship is the key to the improvement of existing catalysts and the discovery of new catalysts. For example, catalyst particle size can have profound effects on catalyst activity, as in the case of gold nanoparticles. Catalyst particle size control and stability is also important for the efficient use of PGM metals and catalyst deactivation prevention. The challenge is to identify and characterize structural features and determine if and how these features may relate to catalytic properties. The ultimate goal is to simultaneously measure catalyst structural characteristics and catalytic properties under operando conditions, unambiguously establishing the structure/property link. X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) are important techniques used for the characterization of PGM catalysts. Microstructural information such as crystallite size, as small as ~ 1 nm, and microstrain can be obtained from Bragg diffraction peak shapes in X-ray diffraction patterns, and long range crystal structure information is found in the intensities and positions of these peaks. In contrast, X-ray absorption spectroscopy provides information about the chemical state and local structure of selected atoms. From the average nearest neighbor coordination numbers, crystallite sizes can also be inferred, with particularly high sensitivity in the sub-nm size range. Electron microscopy

  1. Porous platinum-based catalysts for oxygen reduction

    Science.gov (United States)

    Erlebacher, Jonah D; Snyder, Joshua D

    2014-11-25

    A porous metal that comprises platinum and has a specific surface area that is greater than 5 m.sup.2/g and less than 75 m.sup.2/g. A fuel cell includes a first electrode, a second electrode spaced apart from the first electrode, and an electrolyte arranged between the first and the second electrodes. At least one of the first and second electrodes is coated with a porous metal catalyst for oxygen reduction, and the porous metal catalyst comprises platinum and has a specific surface area that is greater than 5 m.sup.2/g and less than 75 m.sup.2/g. A method of producing a porous metal according to an embodiment of the current invention includes producing an alloy consisting essentially of platinum and nickel according to the formula Pt.sub.xNi.sub.1-x, where x is at least 0.01 and less than 0.3; and dealloying the alloy in a substantially pH neutral solution to reduce an amount of nickel in the alloy to produce the porous metal.

  2. Single-Atom Catalyst of Platinum Supported on Titanium Nitride for Selective Electrochemical Reactions.

    Science.gov (United States)

    Yang, Sungeun; Kim, Jiwhan; Tak, Young Joo; Soon, Aloysius; Lee, Hyunjoo

    2016-02-05

    As a catalyst, single-atom platinum may provide an ideal structure for platinum minimization. Herein, a single-atom catalyst of platinum supported on titanium nitride nanoparticles were successfully prepared with the aid of chlorine ligands. Unlike platinum nanoparticles, the single-atom active sites predominantly produced hydrogen peroxide in the electrochemical oxygen reduction with the highest mass activity reported so far. The electrocatalytic oxidation of small organic molecules, such as formic acid and methanol, also exhibited unique selectivity on the single-atom platinum catalyst. A lack of platinum ensemble sites changed the reaction pathway for the oxygen-reduction reaction toward a two-electron pathway and formic acid oxidation toward direct dehydrogenation, and also induced no activity for the methanol oxidation. This work demonstrates that single-atom platinum can be an efficient electrocatalyst with high mass activity and unique selectivity.

  3. Pyrometallurgical Recovery of Platinum Group Metals from Spent Catalysts

    Science.gov (United States)

    Peng, Zhiwei; Li, Zhizhong; Lin, Xiaolong; Tang, Huimin; Ye, Lei; Ma, Yutian; Rao, Mingjun; Zhang, Yuanbo; Li, Guanghui; Jiang, Tao

    2017-09-01

    As an important secondary resource with abundant platinum group metals (PGMs), spent catalysts demand recycling for both economic and environmental benefits. This article reviews the main pyrometallurgical processes for PGM recovery from spent catalysts. Existing processes, including smelting, vaporization, and sintering processes, are discussed based in part on a review of the physiochemical characteristics of PGMs in spent catalysts. The smelting technology, which produces a PGM-containing alloy, is significantly influenced by the addition of various collectors, such as lead, copper, iron, matte, or printed circuit board (PCB), considering their chemical affinities for PGMs. The vaporization process can recover PGMs in vapor form at low temperatures (250-700°C), but it suffers high corrosion and potential environmental and health risks as a result of involvement of the hazardous gases, mainly Cl2 and CO. The sintering process serves as a reforming means for recycling of the spent catalysts by in situ reduction of their oxidized PGMs components. Among these processes, the smelting process seems more promising although its overall performance can be further improved by seeking a suitable target-oriented collector and flux, together with proper pretreatment and process intensification using an external field.

  4. Monodisperse Platinum and Rhodium Nanoparticles as Model Heterogeneous Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Grass, Michael Edward [Univ. of California, Berkeley, CA (United States)

    2008-09-01

    Model heterogeneous catalysts have been synthesized and studied to better understand how the surface structure of noble metal nanoparticles affects catalytic performance. In this project, monodisperse rhodium and platinum nanoparticles of controlled size and shape have been synthesized by solution phase polyol reduction, stabilized by polyvinylpyrrolidone (PVP). Model catalysts have been developed using these nanoparticles by two methods: synthesis of mesoporous silica (SBA-15) in the presence of nanoparticles (nanoparticle encapsulation, NE) to form a composite of metal nanoparticles supported on SBA-15 and by deposition of the particles onto a silicon wafer using Langmuir-Blodgett (LB) monolayer deposition. The particle shapes were analyzed by transmission electron microscopy (TEM) and high resolution TEM (HRTEM) and the sizes were determined by TEM, X-ray diffraction (XRD), and in the case of NE samples, room temperature H2 and CO adsorption isotherms. Catalytic studies were carried out in homebuilt gas-phase reactors. For the nanoparticles supported on SBA-15, the catalysts are in powder form and were studied using the homebuilt systems as plug-flow reactors. In the case of nanoparticles deposited on silicon wafers, the same systems were operated as batch reactors. This dissertation has focused on the synthesis, characterization, and reaction studies of model noble metal heterogeneous catalysts. Careful control of particle size and shape has been accomplished though solution phase synthesis of Pt and Rh nanoparticles in order to elucidate further structure-reactivity relationships in noble metal catalysis.

  5. Durable PROX catalyst based on gold nanoparticles and hydrophobic silica

    KAUST Repository

    Laveille, Paco

    2016-01-20

    3 nm gold nanoparticles (Au NP) obtained by direct chemical reduction of AuPPh3Cl in the presence of methyl-terminated silica exhibit superior durability for low temperature CO oxidation in the presence of hydrogen (PROX). The activity of hydrophobic Au/SiO2-R972 indeed appears much more stable with time-on-stream than those of the OH-terminated, hydrophilic Au/TiO2 and Au/Al2O3 catalysts, with similar Au NP size. This enhanced stability is attributed to the peculiar catalyst surface of Au/SiO2-R972. Not only may the support hydrophobicity concentrate and facilitate reactant adsorption and product desorption over Au NP, but methyl-terminated SiO2-R972 likely also inhibits carbonatation of the Au/support interface. Hence, at a temperature at which H2/H2O “cleaning” of the carbonate-contaminated Au/Al2O3 and Au/TiO2 surface is inefficient (< 100°C), passivated Au/SiO2-R972 displays much more stable PROX activity. Besides, the virtual absence of surface hydroxyl groups, which provide sites for water formation in H2/O2 atmospheres, can also account for the improved PROX selectivity (>85%) observed over Au/SiO2-R972. This new example, of CO oxidation activity of gold nanoparticles dispersed over a hydrophobic, “inert” support, clearly emphasizes the role of hydrogen as a promoter for the gold-catalyzed oxidation of CO at low temperature. Unlike support-mediated oxygen activation, hydrogen-only mediated oxygen activation takes full advantage of the hydrophobic surface, which is much more resistant against CO2 and thus remains free of poisonous carbonate species, as compared with hydroxyl-terminated catalysts. Hence, although the absence of surface hydroxyl groups prevents the hydrophobic Au/SiO2-R972 catalyst to reach the state-of-the-art activities initially displayed by Au/TiO2 and Au/Al2O3, it brings long-term stability with time-on-stream and superior selectivity, which opens up promising perspectives in the development of viable PROX catalysts based on gold.

  6. Platinum group metal recovery and catalyst manufacturing process

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H. S.; Kim, Y. S.; Yoo, J. H.; Lee, H. S.; Ahn, D. H.; Kim, K. R.; Lee, S. H.; Paek, S. W.; Kang, H. S.

    1998-03-01

    The fission product nuclides generated during the irradiation of reactor fuel include many useful elements, among them platinum group metal such as ruthenium, rhodium and palladium which are of great industrial importance, occur rarely in nature and are highly valuable. In this research, the authors reviewed various PGM recovery methods. Recovery of palladium from seven-component simulated waste solution was conducted by selective precipitation method. The recovery yield was more than 99.5% and the purity of the product was more than 99%. Wet-proof catalyst was prepared with the recovered palladium. The specific surface area of the catalyst support was more than 400 m{sup 2}/g. The content of palladium impregnated on the support was 10 wt.%. Hydrogen isotope exchange efficiency of 93 % to equilibrium with small amount of the catalyst was obtained. It was turned out possible to consider using such palladium or other very low active PGM materials in applications where its actively is unimportant as in nuclear industries. (author). 63 refs., 38 tabs., 36 figs.

  7. Development of Ultra-Low Platinum Alloy Cathode Catalysts for PEM Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Popov, Branko N. [Univ. of South Carolina, Columbia, SC (United States). Dept. of Chemical Engineering; Weidner, John [Univ. of South Carolina, Columbia, SC (United States)

    2016-01-07

    The goal of this project is to synthesize a low cost PEM fuel cell cathode catalyst and support with optimized average mass activity, stability of mass activity, initial high current density performance under H2/air (power density), and catalyst and support stability able to meet 2017 DOE targets for electrocatalysts for transportation applications. Pt*/ACCS-2 catalyst was synthesized according to a novel methodology developed at USC through: (i) surface modification, (ii) metal catalyzed pyrolysis and (iii) chemical leaching to remove excess meal used to dope the support. Pt* stands for suppressed platinum catalyst synthesized with Co doped platinum. The procedure results in increasing carbon graphitization, inclusion of cobalt in the bulk and formation of non-metallic active sites on the carbon surface. Catalytic activity of the support shows an onset potential of 0.86 V for the oxygen reduction reaction (ORR) with well-defined kinetic and mass transfer regions and 2.5% H2O2 production. Pt*/ACCS-2 catalyst durability under 0.6-1.0 V potential cycling and support stability under 1.0-1.5 V potential cycling was evaluated. The results indicated excellent catalyst and support performance under simulated start-up/shut down operating conditions (1.0 – 1.5 V, 5000 cycles) which satisfy DOE 2017 catalyst and support durability and activity. The 30% Pt*/ACCS-2 catalyst showed high initial mass activity of 0.34 A/mgPGM at 0.9 ViR-free and loss of mass activity of 45% after 30,000 cycles (0.6-1.0 V). The catalyst performance under H2-air fuel cell operating conditions showed only 24 mV (iR-free) loss at 0.8 A/cm2 with an ECSA loss of 42% after 30,000 cycles (0.6-1.0 V). The support stability under 1.0-1.5 V potential cycling showed mass activity loss of 50% and potential loss of 8 mV (iR-free) at 1.5 A/cm2. The ECSA loss was 22% after 5,000 cycles. Furthermore, the Pt*/ACCS-2 catalyst showed an

  8. Investigation of the oxidation of NO over platinum catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Despres, J.; Koebel, M.; Elsener, M.; Wokaun, A.

    2002-03-01

    The oxidation of NO to NO{sub 2} over Pt/SiO{sub 2} was investigated in the temperature range 150-450{sup o}C. Powdered catalysts were prepared by incipient wetness impregnation, followed by calcination and reduction. The feed gas typically contained oxygen, nitrogen monoxide, water and nitrogen. The concentration of NO in the feed was varied at constant concentration of O{sub 2} in order to study its influence on the reaction. A decrease of the conversion with increasing concentration of NO was observed. A similar study was performed with various oxygen concentrations at constant concentration of NO. Oxygen involved in the surface reaction originates from the dissociative chemisorption of O{sub 2} on the platinum surface. (author)

  9. Polyaniline-functionalized carbon nanotube supported platinum catalysts.

    Science.gov (United States)

    He, Daping; Zeng, Chao; Xu, Cheng; Cheng, Niancai; Li, Huaiguang; Mu, Shichun; Pan, Mu

    2011-05-03

    Electrocatalytically active platinum (Pt) nanoparticles on a carbon nanotube (CNT) with enhanced nucleation and stability have been demonstrated through introduction of electron-conducting polyaniline (PANI) to bridge the Pt nanoparticles and CNT walls with the presence of platinum-nitride (Pt-N) bonding and π-π bonding. The Pt colloids were prepared through ethanol reduction under the protection of aniline, the CNT was dispersed well with the existence of aniline in the solution, and aniline was polymerized in the presence of a protonic acid (HCl) and an oxidant (NH(4)S(2)O(8)). The synthesized PANI is found to wrap around the CNT as a result of π-π bonding, and highly dispersed Pt nanoparticles are loaded onto the CNT with narrowly distributed particle sizes ranging from 2.0 to 4.0 nm due to the polymer stabilization and existence of Pt-N bonding. The Pt-PANI/CNT catalysts are electroactive and exhibit excellent electrochemical stability and therefore promise potential applications in proton exchange membrane fuel cells.

  10. Preparation of MgO supported platinum nanoparticle catalyst using toluene dispersed platinum sol

    Science.gov (United States)

    Seth, Jhumur; Nepak, Devadutta; Chaudhari, Vijay R.; Prasad, Bhagavatula L. V.

    2017-10-01

    An effective way of anchoring Pt nanoparticles on MgO using toluene dispersed platinum nanoparticles (Pt-NPs) as one of the ingredient is demonstrated. The usage of particles dispersed in toluene allows the retention of size and size distribution of preformed Pt-NPs even after deposition on MgO support with high active surface area, which is crucial for heterogeneous catalysis. The catalyst thus prepared, displayed selective hydrogenation of cinnamaldehyde to cinnamyl alcohol with high turn on frequency (TOF - 105 h-1) with respect to the total Pt content. We attribute this efficient catalytic performance to the uniform distribution and deposition of Pt on the active MgO support and its better accessible surface as evidenced by the cyclic-voltammetry results.

  11. Hydrogenation of ortho-nitrochlorobenzene on activated carbon supported platinum catalysts

    Institute of Scientific and Technical Information of China (English)

    JIANG Cheng-jun; YIN Hong; CHEN Zhi-rong

    2005-01-01

    Platinum/carbon catalyst is one of the most important catalysts in hydrogenation of ortho-nitrochlorobenzene to 2,2'-dichlorohydrazobenzene. The preparation process and the supports of catalysts are studied in this paper. Raw materials and preparation procedure of the activated carbon have great influences on the compositions and surface structure of platinum/carbon catalysts. Platinum catalysts supported on activated carbon with high purity, high surface area, large pore volume and appropriate pore structure usually exhibit higher activities for hydrogenation of ortho-nitrochlorobenzene to 2,2'-dichlorohydrazobenzene.The catalyst prepared from H2PtCl6 with pH=3 shows greater catalytic performance than those prepared under other conditions.

  12. Thermally stable single-atom platinum-on-ceria catalysts via atom trapping

    Energy Technology Data Exchange (ETDEWEB)

    Jones, John; Xiong, Haifeng; DelaRiva, Andrew; Peterson, Eric J.; Pham, Hien; Challa, Sivakumar R.; Qi, Gongshin; Oh, Se H.; Wiebenga, Michelle H.; Pereira Hernandez, Xavier I.; Wang, Yong; Datye, Abhaya K.

    2016-07-08

    Catalysts based on single atoms of scarce precious metals can lead to more efficient use through enhanced reactivity and selectivity. However, single atoms on catalyst supports can be mobile and aggregate into nanoparticles when heated at elevated temperatures. High temperatures are detrimental to catalyst performance unless these mobile atoms can be trapped. We used ceria powders having similar surface areas but different exposed surface facets. When mixed with a platinum/ aluminum oxide catalyst and aged in air at 800°C, the platinum transferred to the ceria and was trapped. Polyhedral ceria and nanorods were more effective than ceria cubes at anchoring the platinum. Performing synthesis at high temperatures ensures that only the most stable binding sites are occupied, yielding a sinter-resistant, atomically dispersed catalyst.

  13. The role of support and promoter on the oxidation of sulfur dioxide using platinum based catalysts

    DEFF Research Database (Denmark)

    Koutsopoulos, Sotiris; Rasmussen, Søren Birk; Eriksen, Kim Michael

    2006-01-01

    The catalytic oxidation of SO2 to SO3 was studied over platinum based catalysts in the absence and the presence of dopants. The active metal was supported on silica gel or titania (anatase) by impregnation. The activities of the silica supported catalysts were found to follow the order PtRh/SiO2...

  14. Nanostructured oxygen sensor--using micelles to incorporate a hydrophobic platinum porphyrin.

    Directory of Open Access Journals (Sweden)

    Fengyu Su

    Full Text Available Hydrophobic platinum(II-5,10,15,20-tetrakis-(2,3,4,5,6-pentafluorophenyl-porphyrin (PtTFPP was physically incorporated into micelles formed from poly(ε-caprolactone-block-poly(ethylene glycol to enable the application of PtTFPP in aqueous solution. Micelles were characterized using dynamic light scattering (DLS and atomic force microscopy (AFM to show an average diameter of about 140 nm. PtTFPP showed higher quantum efficiency in micellar solution than in tetrahydrofuran (THF and dichloromethane (CH₂Cl₂. PtTFPP in micelles also exhibited higher photostability than that of PtTFPP suspended in water. PtTFPP in micelles exhibited good oxygen sensitivity and response time. This study provided an efficient approach to enable the application of hydrophobic oxygen sensors in a biological environment.

  15. Novel Hydrophobic Pt/Inorganic Catalyst Used in Hydrogen Isotope Exchange Reaction

    Directory of Open Access Journals (Sweden)

    JIA Qing-qing1;HU Shi-lin1;FENG Xiao-yan2;LIU Ya-ming1

    2016-11-01

    Full Text Available To improve the performance of hydrophobic catalyst and extend its using range, this research adopted the porous columnar inorganic carriers (ø=5 mm to prepare the hydrophobic catalyst used in hydrogen isotopes exchange reaction, the hydrophilic carriers became hydrophobic with the nanostructured CeO2 coating and the catalyst were then fabricated by convenient impregnation method. The samples were characterized by XRD、SEM、EDX、XPS and CO adsorption. The catalytic activity were tested through catalytic exchange reaction between hydrogen and saturated water vapor to investigate the effect of micro structured CeO2 on the catalyst properties. It turned out that the nano-CeO2 coating could build favorable hydrophobic environment for the catalysts and had almost no influence on the pore structure properties of carriers. Although the hydrophobic coating would lead to the decrease of Pt particle dispersion and metallic Pt content, it could make the Pt particles mostly deposit on the surface layer of the catalysts, which would make more Pt particle participate in the reaction at the same time. The catalytic activity of the novel Pt/inorganic catalyst could reach to 80% of the mature Pt/organic catalyst. After being flushed by water for 12 weeks, the catalytic activity of Pt/inorganic catalyst decreased less than 5%. The novel hydrophobic catalyst with good activity and stability was practical and had great application prospects.

  16. Noble Metal Catalysts for Mercury Oxidation in Utility Flue Gas: Gold, Palladium and Platinum Formulations

    Energy Technology Data Exchange (ETDEWEB)

    Presto, A.A.; Granite, E.J

    2008-07-01

    The use of noble metals as catalysts for mercury oxidation in flue gas remains an area of active study. To date, field studies have focused on gold and palladium catalysts installed at pilot scale. In this article, we introduce bench-scale experimental results for gold, palladium and platinum catalysts tested in realistic simulated flue gas. Our initial results reveal some intriguing characteristics of catalytic mercury oxidation and provide insight for future research into this potentially important process.

  17. Electro-oxidation of Formic Acid on Carbon Supported Edge-Truncated Cubic Platinum Nanoparticles Catalysts

    Institute of Scientific and Technical Information of China (English)

    LI She-Qiang; FU Xing-Qiu; HU Bing; DENG Jia-Jun; CHEN Lei

    2009-01-01

    The oxidation of formic acid on edge-truncated cubic platinum nanoparticles/C catalysts is investigated. X-ray photoelectron spectroscopy analysis indicates that the surface of edge-truncated cubic platinum nanoparticles is composed of two types of coordination sites. The oxidation behavior of formic acid on edge-truncated cubic platinum nanoparticles/C is investigated using cyclic voltammetry. The apparent activation energies are found to be 54.2, 55.0, 61.8, 69.5, 71.9, 69.26, 65.28kJ/mol at 0.15, 0.3, 0.4, 0.5, 0.6, 0.65, 0.7 V, respectively. A specific surface area activity of 1.76mA·cm~(-2) at 0.4 V indicates that the edge-truncated cubic Platinum nanoparticles are a promising anode catalyst for direct formic acid fuel cells.

  18. Investigating the performance of catalyst layer micro-structures with different platinum loadings

    Energy Technology Data Exchange (ETDEWEB)

    Khakaz-Baboli, Moben; Harvey, David; Pharoah, Jon

    2012-07-01

    In this study a four-phase micro-structure of a PEFC catalyst layer was reconstructed by randomly placing overlapping spheres for each solid catalyst phase. The micro-structure was mirrored to make a micro-structure. A body-fit computational mesh was produced for the reconstructed micro-structure in OpenFOAM. Associated conservation equations were solved within all the phases with electrochemical reaction as the boundary condition at the interface between ionomer and platinum phases. The study is focused on the platinum loading of CL. The polarization curves of the micro-structure performance have been compared for different platinum loadings. This paper gives increased insight into the relatively greater losses at decreased platinum loadings.

  19. Surface features and catalytic performance of platinum/alumina catalysts in slurry-phase hydrogenation

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez-Ortiz, M.A.; Gonzalez-Marcos, M.P.; Arnaiz-Aguilar, S.; Gonzalez-Marcos, J.A.; Gonzalez-Velasco, J.R. (Univ. del Pais Vasco/Euskal Hirrika Unibertsitatea, Bilbao (Spain). Dept. de Ingenierlla Quimica)

    1993-11-01

    Several platinum catalysts supported on three commercial [gamma]-aluminas were prepared by impregnation and anionic exchange using aqueous solutions of H[sub 2]PtCl[sub 6]. A number of methods were used to characterize the precursors as well as the final catalysts, including TGA, TPR, and hydrogen chemisorption at 298 K. TPR measurements showed two reduction peaks for the catalysts: the first one corresponding to reduction of the metal precursor to platinum and the second one associated to formation of a surface complex, Pt-Al[sub 2]O[sub 3[minus]x], With partial reduction of the support. The activity of the different catalysts was tested in the slurry-phase hydrogenation of benzene. The results obtained in the activity measurements have been correlated to the characteristics of the catalysts.

  20. CROWN FUNCTIONALIZED LINEAR POLYSILOXANE PLATINUM COMPLEX AS HYDROSILYLATION CATALYST

    Institute of Scientific and Technical Information of China (English)

    CHEN Yuanyin; LU Xueran; GONG Shuling; ZHANG Baolian

    1994-01-01

    A modified method of preparing crown functionalized linear polysiloxane has been described.4'-allylbenzo-15-crown-5 was subjected to hydrosilylation with methyldichlorosilane,followed by polycondensation with silanol-terminated polydimethylsiloxane to give the title crown functionalized linear polysiloxane. It was found that the polysiloxane could be coordinated with platinum salt to form platinum complex, which could catalyze the hydrosilylation of olefins with triethoxysilane efficiently.

  1. Dearomatization of jet fuel on irradiated platinum-supported catalyst

    Science.gov (United States)

    Múčka, V.; Ostrihoňová, A.; Kopernický, I.; Mikula, O.

    The effect of ionizing radiation ( 60Co γ-rays) on Pt-supported catalyst used for the dearomatization of jet fuel with distillation in the range 395-534 K has been studied. Pre-irradiation of the catalyst with doses in the range 10 2-5 × 10 4 Gy leads to the partial catalyst activation. Irradiation of the catalyst enhances its resistance to catalyst poisons, particularly to sulphur-compounds, and this is probably the reason for its catalytic activity being ˜60-100% greater than that of un-irradiated catalyst. Optimum conditions for dearomatization on the irradiated catalyst were found and, by means of a rotary three-factorial experiment, it was shown that these lie at lower temperatures and lower pressures than those for un-irradiated catalyst.

  2. Hydrogenation of cottonseed oil with nickel, palladium and platinum catalysts

    Science.gov (United States)

    A number of commercial catalysts have been used to study hydrogenation of cottonseed oil, with the goal of minimizing trans fatty acid (TFA) content. Despite the different temperatures used, catalyst levels, and reaction times, the data from each catalyst type fall on the same curve when the TFA le...

  3. Membrane fuel cell cathode catalysts based on titanium oxide supported platinum nanoparticles.

    Science.gov (United States)

    Gebauer, Christian; Jusys, Zenonas; Wassner, Maximilian; Hüsing, Nicola; Behm, R Jürgen

    2014-07-21

    The potential of platinum catalysts supported on pure, nitrogen-, or carbon-doped titania for application in the oxygen reduction reaction (ORR), as a cathode catalyst in polymer electrolyte membrane fuel cells, is investigated. The oxide supports are synthesized by using a sol-gel route. Modification with nitrogen and carbon doping is achieved by thermal decomposition of urea and the structure-directing agent P123. Platinum nanoparticles are prepared by reduction of a Pt(IV) salt in ethylene glycol and subsequently immobilized on different support materials. Structural and electronic properties of the support materials and the resulting catalysts are characterized by various methods, including X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. These results and electrochemical characterization of the support materials and platinum nanoparticle catalysts indicate distinct support effects in the catalysts. The electrocatalytic performance of these catalysts in the ORR, as determined in rotating ring disc electrode measurements, is promising. Also here, distinct support effects can be identified. Correlations with the structural/electronic and the electrochemical properties are discussed, as well as the role of metal-support interactions.

  4. Oxygen reduction on carbon supported platinum catalysts in high temperature polymer electrolytes

    DEFF Research Database (Denmark)

    Qingfeng, Li; Bergqvist, R. S.; Hjuler, H. A.

    1999-01-01

    Oxygen reduction on carbon supported platinum catalysts has been investigated in H3PO4, H3PO4-doped Nafion and PBI polymer electrolytes in a temperature range from 80 to 190°C. Compared with pure H3PO4, using the H3PO4 doped Nafion and PBI polymer electrolytes can significantly improve the oxygen...

  5. Carbon Supported Polyaniline as Anode Catalyst: Pathway to Platinum-Free Fuel Cells

    CERN Document Server

    Zabrodskii, A G; Malyshkin, V G; Sapurina, I Y

    2006-01-01

    The effectiveness of carbon supported polyaniline as anode catalyst in a fuel cell (FC) with direct formic acid electrooxidation is experimentally demonstrated. A prototype FC with such a platinum-free composite anode exhibited a maximum room-temperature specific power of about 5 mW/cm2

  6. Hydroisomerization of Ethylbenzene on Mordenite-Based Bifunctional Catalysts with Different Platinum Contents

    Directory of Open Access Journals (Sweden)

    Fernandes L.D.

    1998-01-01

    Full Text Available A commercial Na-mordenite sample underwent ion exchange with HCl. The ion-exchanged sample was sequentially submitted to hydrothermal treatments at 823, 873 and 923 K, each followed by acid leaching of the extraframework alumina (EFAL generated. Six mordenite samples, presenting different framework and extraframework compositions, were obtained. These samples were used to prepare bifunctional catalysts by mixing them with Pt/Al2O3 in different proportions. The generated samples presented distinct platinum contents and were tested in the hydroisomerization reaction of ethylbenzene. A maximum xylene selectivity at about 0.45 wt% of platinum was observed. Normally, the total activity increased as the platinum content increased; this effect was more pronounced in the samples which presented lower mesoporosity. The most dealuminated sample, which presented a high mesoporosity, did not show any change in activity with the increase in platinum content.

  7. Nano carbon supported platinum catalyst interaction behavior with perfluorosulfonic acid ionomer and their interface structures

    DEFF Research Database (Denmark)

    Andersen, Shuang Ma

    2016-01-01

    behavior of Nafion ionomer on platinized carbon nano fibers (CNFs), carbon nano tubes (CNTs) and amorphous carbon (Vulcan). The interaction is affected by the catalyst surface oxygen groups as well as porosity. Comparisons between the carbon supports and platinized equivalents are carried out. It reveals......, the ionomer may have an adsorption preference to the platinum nano particle rather than to the overall catalyst. This was verified by a close examination on the decomposition temperature of the carbon support and the ionomer. The electrochemical stability of the catalyst ionomer composite electrode suggests...

  8. Graphene-supported platinum catalysts for fuel cells

    DEFF Research Database (Denmark)

    Seselj, Nedjeljko; Engelbrekt, Christian; Zhang, Jingdong

    2015-01-01

    the past 15 years. It is focused on polymer electrolyte membrane fuel cells as an environmentally benign and feasible energy source. Graphene is used as a promising support material for Pt catalysts. It ensures high catalyst loading, good electrocatalysis and stability. Attention has been drawn...... to structural sensitivity of the catalysts, as well as polymetallic and nanostructured catalysts in order to improve the oxygen reduction reaction. Characterization methods including electrochemical, microscopic and spectroscopic techniques are summarized with an overview of the latest technological advances...

  9. A comparative study on the influence of the platinum catalyst in poly(dimethylsiloxane) based networks synthesis

    DEFF Research Database (Denmark)

    Bejenariu, Anca Gabriela; Poulsen, Julie Øblom; Skov, Anne Ladegaard

    2009-01-01

    The aim of the project is to find the best of three Pt catalysts and their appropriate quantity in order to obtain soft networks in one hour at room temperature. How the choice of catalyst influences the final elastomeric properties is also evaluated. The differences between the catalysts are the...... are the solvent and the platinum concentration....

  10. Nanolithographic Fabrication and Heterogeneous Reaction Studies ofTwo-Dimensional Platinum Model Catalyst Systems

    Energy Technology Data Exchange (ETDEWEB)

    Contreras, Anthony Marshall [Univ. of California, Berkeley, CA (United States)

    2006-05-20

    In order to better understand the fundamental components that govern catalytic activity, two-dimensional model platinum nanocatalyst arrays have been designed and fabricated. These catalysts arrays are meant to model the interplay of the metal and support important to industrial heterogeneous catalytic reactions. Photolithography and sub-lithographic techniques such as electron beam lithography, size reduction lithography and nanoimprint lithography have been employed to create these platinum nanoarrays. Both in-situ and ex-situ surface science techniques and catalytic reaction measurements were used to correlate the structural parameters of the system to catalytic activity.

  11. Catalytic wet-air oxidation of a chemical plant wastewater over platinum-based catalysts.

    Science.gov (United States)

    Cybulski, Andrzej; Trawczyński, Janusz

    2006-01-01

    Catalytic wet-air oxidation (CWAO) of wastewater (chemical oxygen demand [COD] = 1800 mg O2/dm3) from a fine chemicals plant was investigated in a fixed-bed reactor at T = 393-473 K under total pressure of 5.0 or 8.0 MPa. Catalysts containing 0.3% wt. of platinum deposited on two supports, mixed silica-titania (SM1) and carbon black composites (CBC) were used. The CBC-supported catalyst appeared to be more active than the SM1-supported one. A slow decrease of activity of the platinum on SM1 (Pt-SM1) during the long-term operation is attributed to recrystallization of titania and leaching of a support component, while the Pt-CBC catalyst is deteriorated, owing to combustion of the support component. The power-law-kinetic equations were used to describe the rate of COD removal at CWAO over the catalysts. The kinetic parameters of COD reduction for the wastewater were determined and compared with the kinetic parameters describing phenol oxidation over the same catalysts. Rates of COD removal for the wastewater were found higher than those for phenol oxidation over the same catalysts and under identical operating conditions.

  12. Determination of platinum in waste platinum-loaded carbon catalyst samples using microwave-assisted sample digestion and ICP-OES

    Science.gov (United States)

    Ma, Yinbiao; Wei, Xiaojuan

    2017-04-01

    A novel method for the determination of platinum in waste platinum-loaded carbon catalyst samples was established by inductively coupled plasma optical emission spectrometry after samples digested by microwave oven with aqua regia. Such experiment conditions were investigated as the influence of sample digestion methods, digestion time, digestion temperature and interfering ions on the determination. Under the optimized conditions, the linear range of calibration graph for Pt was 0 ˜ 200.00 mg L-1, and the recovery was 95.67% ˜ 104.29%. The relative standard deviation (RSDs) for Pt was 1.78 %. The proposed method was applied to determine the same samples with atomic absorption spectrometry with the results consistently, which is suitable for the determination of platinum in waste platinum-loaded carbon catalyst samples.

  13. Aged nano-structured platinum based catalyst: effect of chemical treatment on adsorption and catalytic activity.

    Science.gov (United States)

    Shim, Wang Geun; Nahm, Seung Won; Park, Hyuk Ryeol; Yun, Hyung Sun; Seo, Seong Gyu; Kim, Sang Chai

    2011-02-01

    To examine the effect of chemical treatment on the adsorption and catalytic activity of nanostructured platinum based catalyst, the aged commercial Pt/AC catalyst was pretreated with sulfuric acid (H2SO4) and a cleaning agent (Hexane). Several reliable methods such as nitrogen adsorption, X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and inductively coupled plasma (ICP) were employed to characterize the aged Pt/AC catalyst and its chemically pretreated Pt/AC catalysts. The catalytic and adsorption activities of nano-structured heterogeneous Pt/AC catalyst were investigated on the basis of toluene oxidation and adsorption isotherm data. In addition, the adsorption isotherms of toluene were used to calculate the adsorption energy distribution functions for the parent catalyst and its pre-treated nano-structured Pt/AC catalysts. It was found that sulfuric acid aqueous treatment can enhance the catalytic performance of aged Pt/AC catalyst toward catalytic oxidation of toluene. It was also shown that a comparative analysis of the energy distribution functions for nano-structured Pt/AC catalysts as well as the pore size distribution provides valuable information about their structural and energetic heterogeneity.

  14. Liquid-phase benzene isopropylation using alumina solid lewis superacid-supported platinum catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, K.; Honda, K.; Kitahara, D.; Miyamoto, M.; Shiga, M.; Ayame, A. [Muroran Inst. of Tech., Hokkaido (Japan)

    2000-03-01

    Supporting platinum on alumina solid Lewis superacid (AmLSA; J. C. S., Chem. Commun., 645 (1989)) was prepared by using of the in situ CVD technique at 773 K with Ar{sup +}-sputtered platinum fine particles and dry chlorine, followed by reduction with hydrogen at 673 K. The AmLSA-supported platinum catalyst (Pt/AmLSA) was applied to isopropylation of benzene with propene in the hydrogen stream at ambient temperature, using a semibatch reactor. Products were mono-, di-, tri-, and tetra-isopropylbenzenes. Conversion of propene to propane was below 1 %, and a trace amount of cyclohexane from benzene was also observed. Deactivation of AmLSA due to strong adsorption of poly-substituted benzenes and/or propene oligomers was remarkably depressed by supporting platinum and supplying hydrogen into the propene stream. Consequently, the activity of Pt/AmLSA catalyst had increased almost 1.5 times that of AmLSA. At the same level of benzene conversion, the product distribution f isopropyl-substituted benzenes obtained on Pt/AmLSA was identical to that on AmLSA, and had shifted slightly into the mono-substituted benzene side compared with the result on AmLSA in the absence of hydrogen. In the isopropylation of benzene with 2-chloropropane, the results quite similar to those described above were obtained. From the above observations, synergetic effects of platinum supporting and hydrogen supplying were considered to be due to the presence of hydrogen atoms spilled over from the platinum surface to the strong Lewis acid sites. (author)

  15. Kinetics of benzene hydrogenation on supported platinum, palladium, rhodium and ruthenium catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Nakano, K.; Fueda, Y.; Kusunoiki, K.; Uchino, T.

    1982-10-01

    Although benzene hydrogenation has been widely utilized as a test reaction for the investigation of catalytic activity, the reaction mechanism has not been well elucidated. As to the Langmuir-Hinshelwood rate equations, there have been many reports for the reaction on nickel catalysts, but few papers have been published on platinum metal catalysts, especially on rhodium and ruthenium catalysts. In this communication, reaction rates were measured for benzene hydrogenation over commercially available Pt-, Pd-, Rh- and Ru-Al/sub 2/O/sub 3/ catalysts and the rate equation was derived. The thermodynamic consistency of the rate equation was then tested in the light of the rules established by Boudart et al. and Vannice et al.

  16. Ionic Liquids as Solvents for Rhodium and Platinum Catalysts Used in Hydrosilylation Reaction

    Directory of Open Access Journals (Sweden)

    Witold Zielinski

    2016-08-01

    Full Text Available A group of imidazolium and pyridinium based ionic liquids has been synthetized, and their ability to dissolve and activate the catalysts used in hydrosilylation reaction of 1-octane and 1,1,1,3,5,5,5-heptamethyltrisiloxane was investigated. An organometallic catalyst as well as inorganic complexes of platinum and rhodium dissolved in ionic liquids were used, forming liquid solutions not miscible with the substrates or with the products of the reaction. The results show that application of such a simple biphasic catalytic system enables reuse of ionic liquid phase with catalysts in multiple reaction cycles reducing the costs and decreasing the amount of catalyst needed per mole of product.

  17. Hydrophobic Catalysts For Removal Of NOx From Flue Gases

    Science.gov (United States)

    Sharma, Pramod K.; Hickey, Gregory S.; Voecks, Gerald E.

    1995-01-01

    Improved catalysts for removal of nitrogen oxides (NO and NO2) from combustion flue gases formulated as composites of vanadium pentoxide in carbon molecular sieves. Promotes highly efficient selective catalytic reduction of NOx at relatively low temperatures while not being adversely affected by presence of water vapor and sulfur oxide gases in flue gas. Apparatus utilizing catalyst of this type easily integrated into exhaust stream of power plant to remove nitrogen oxides, generated in combustion of fossil fuels and contribute to formation of acid rain and photochemical smog.

  18. Tin-Platinum catalysts interactions on titania and silica

    Energy Technology Data Exchange (ETDEWEB)

    Nava, N. [Instituto Mexicano del Petroleo Lazaro Cardenas 152, 07730 Mexico, D.F. (Mexico)], E-mail: tnava@imp.mx; Del Angel, P. [Instituto Mexicano del Petroleo Lazaro Cardenas 152, 07730 Mexico, D.F. (Mexico); Salmones, J. [Instituto Politecnico Nacional-ESIQIE UPALM, 07738 Mexico, D.F. (Mexico); Baggio-Saitovitch, E. [Centro Brasileiro de Pesquisas Fisicas, Rua Dr. Xavier Sigaud 150, 22290-180 Rio de Janeiro, Brasil (Brazil); Santiago, P. [Instituto de Fisica, UNAM, Mexico, D. F., 04510 Mexico (Mexico)

    2007-09-30

    Pt-Sn was supported on titania and silica, and the resulting interactions between the components in prepared samples and the resulting interactions between the components before and after treatment with hydrogen were characterized by Moessbauer spectroscopy, X-ray diffraction, Rietveld refinement, high-resolution transmission electron microscopy (HRTEM) and catalytic tests data. Results show the presence of Pt and SnO{sub 2} after calcinations, and Pt{sub 3}Sn, PtSn and PtSn{sub 3} after reduction. Rietveld analysis shows that some Ti{sup 4+} are replaced by Sn{sup 4+} atoms in the titania structure. Finally, HRTEM and the practically absence of activity observed confirms that metallic platinum is encapsulated.

  19. Preparation of low-platinum-content platinum-nickel, platinum-cobalt binary alloy and platinum-nickel-cobalt ternary alloy catalysts for oxygen reduction reaction in polymer electrolyte fuel cells

    Science.gov (United States)

    Li, Mu; Lei, Yanhua; Sheng, Nan; Ohtsuka, Toshiaki

    2015-10-01

    A series of low-platinum-content platinum-nickel (Pt-Ni), platinum-cobalt (Pt-Co) binary alloys and platinum-nickel-cobalt (Pt-Ni-Co) ternary alloys electrocatalysts were successfully prepared by a three-step process based on electrodeposition technique and studied as electrocatalysts for oxygen reduction reaction (ORR) in polymer-electrolyte fuel cells. Kinetics of ORR was studied in 0.5 M H2SO4 solution on the Pt-Ni, Pt-Co and Pt-Ni-Co alloys catalysts using rotating disk electrode technique. Both the series of Pt-Ni, Pt-Co binary alloys and the Pt-Ni-Co ternary alloys catalysts exhibited an obvious enhancement of ORR activity in comparison with pure Pt. The significant promotion of ORR activities of Pt-Ni and Pt-Co binary alloys was attributed to the enhancement of the first electron-transfer step, whereas, Pt-Ni-Co ternary alloys presented a more complicated mechanism during the electrocatalysis process but a much more efficient ORR activities than the binary alloys.

  20. Graphene-Supported Platinum Catalyst-Based Membrane Electrode Assembly for PEM Fuel Cell

    Science.gov (United States)

    Devrim, Yilser; Albostan, Ayhan

    2016-08-01

    The aim of this study is the preparation and characterization of a graphene-supported platinum (Pt) catalyst for proton exchange membrane fuel cell (PEMFC) applications. The graphene-supported Pt catalysts were prepared by chemical reduction of graphene and chloroplatinic acid (H2PtCl6) in ethylene glycol. X-ray powder diffraction, thermogravimetric analysis (TGA) and scanning electron microscopy have been used to analyze structure and surface morphology of the graphene-supported catalyst. The TGA results showed that the Pt loading of the graphene-supported catalyst was 31%. The proof of the Pt particles on the support surfaces was also verified by energy-dispersive x-ray spectroscopy analysis. The commercial carbon-supported catalyst and prepared Pt/graphene catalysts were used as both anode and cathode electrodes for PEMFC at ambient pressure and 70°C. The maximum power density was obtained for the Pt/graphene-based membrane electrode assembly (MEA) with H2/O2 reactant gases as 0.925 W cm2. The maximum current density of the Pt/graphene-based MEA can reach 1.267 and 0.43 A/cm2 at 0.6 V with H2/O2 and H2/air, respectively. The MEA prepared by the Pt/graphene catalyst shows good stability in long-term PEMFC durability tests. The PEMFC cell voltage was maintained at 0.6 V without apparent voltage drop when operated at 0.43 A/cm2 constant current density and 70°C for 400 h. As a result, PEMFC performance was found to be superlative for the graphene-supported Pt catalyst compared with the Pt/C commercial catalyst. The results indicate the graphene-supported Pt catalyst could be utilized as the electrocatalyst for PEMFC applications.

  1. Measurement, by adsorption, of the dispersion of platinum on supported catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Castells, R.C.

    1979-12-01

    A gas chromatographic pulsed adsorption technique similar to that of Freel was used in hydrogen and oxygen chemisorption measurements, and in ''titrating'' adsorbed hydrogen with oxygen pulses (H-O) and adsorbed oxygen with hydrogen pulses (O-H) on the surfaces of a Houdry 3H (0.30-0.70% platinum/alumina) catalyst and of 3.7 and 2.3% Pt/silica catalysts. In successive H-O and O-H titration cycles, hydrogen and oxygen consumption increased, leveling off after 8-10 cycles for Pt/alumina and after 3-4 cycles for the Pt/silica catalyst. The adsorption of hydrogen increased, whereas that of oxygen decreased with increasing number of cycles. The H-O titration sequence was a more accurate method of measuring metal dispersion than hydrogen adsorption or the O-H sequence.

  2. Formic acid electrooxidation on carbon supported platinum catalyst with preferential plane orientation

    Directory of Open Access Journals (Sweden)

    Krstajić Mila N.

    2015-01-01

    Full Text Available Pt-based nanocatalysts supported on Vulcan XC-72R carbon, were prepared by water-in-oil microemulsion method, with addition of various amounts of HCl in the water phase. Polyethileneglycoldodecylether (BRIJ 30 was used as a surfactant, which influenced the Pt surface structure, along with HCl. Catalysts prepared with addition of 0, 15, 25 and 35 % of HCl during the synthesis, were electrochemically characterised in 0,5 M H2SO4 using cyclic voltammetry and CO oxidation. Formic acid electrooxidation was examined on all investigated catalysts, in terms of their electrocatalytic activity and stability. Platinum loading on carbon support was examined by Thermogravimetric analysis. Catalysts showed different features in hydrogen region, and slight differences in formic acid oxidation mechanisms.

  3. Kinetics studies of d-glucose hydrogenation over activated charcoal supported platinum catalyst

    Science.gov (United States)

    Ahmed, Muthanna J.

    2012-02-01

    The kinetics of the catalytic hydrogenation of d-glucose to produce d-sorbitol was studied in a three-phase laboratory scale reactor. The hydrogenation reactions were performed on activated charcoal supported platinum catalyst in the temperature range 25-65°C and in a constant pressure of 1 atm. The kinetic data were modeled by zero, first and second-order reaction equations. In the operating regimes studied, the results show that the hydrogenation reaction was of a first order with respect to d-glucose concentration. Also the activation energy of the reaction was determined, and found to be 12.33 kJ mole-1. A set of experiment was carried out to test the deactivation of the catalyst, and the results show that the deactivation is slow with the ability of using the catalyst for several times with a small decrease in product yield.

  4. Platinum-group elements. Quantification in collected exhaust fumes and studies of catalyst surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Palacios, M.A.; Gomez, M.M.; Moldovan, M. [Departamento de Quimica Analitica, Facultad de CC Quimicas, Universidad Complutense de Madrid, 28040- Madrid (Spain); Morrison, G.; Rauch, S. [Chalmers University of Technology, Gothenburg (Sweden); McLeod, C.; Ma, R. [University of Sheffield, Sheffield (United Kingdom); Laserna, J.; Lucena, P. [University of Malaga, Malaga (Spain); Caroli, S.; Alimonti, A.; Petrucci, F.; Bocca, B. [Istituto Superiore di Sanita, Rome (Italy); Schramel, P.; Lustig, S.; Zischka, M. [GSF-Forschung, Neuherberg (Germany); Wass, U.; Stenbom, B. [Volvo, Gothenberg (Sweden); Luna, M. [Ford, Madrid (Spain); Saenz, J.C. [Instituto Nacional de Tecnica Aeroespacial, INTA, Madrid (Spain); Santamaria, J.; Torrens, J.M. [Seat, Barcelona (Spain)

    2000-07-20

    Automotive catalytic converters, in which Pt, Pd and Rh (platinum-group elements; PGEs) are the active components for eliminating several noxious components from exhaust fumes, have become the main source of environmental urban pollution by PGEs. This work reports on the catalyst morphology through changes in catalyst surface by scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) and laser-induced breakdown spectrometry (LIBS) from fresh to aged catalytic converters. The distribution of these elements in the fresh catalysts analysed (Pt-Pd-Rh gasoline catalyst) is not uniform and occurs mainly in a longitudinal direction. This heterogeneity seems to be greater for Pt and Pd. PGEs released by the catalysts, fresh and aged 30000 km, were studied in parallel. Whole raw exhaust fumes from four catalysts of three different types were also examined. Two of these were gasoline catalysts (Pt-Pd-Rh and Pd-Rh) and the other two were diesel catalysts (Pt). Samples were collected following the 91441 EUDC driving cycle for light-duty vehicle testing. The results show that at 0 km the samples collected first have the highest content of particulate PGEs and although the general tendency is for the release to decrease with increasing number of samples taken, exceptions are frequent. At 30000 km the released PGEs in gasoline and diesel catalysts decreased significantly. For fresh gasoline catalysts the mean of the total amount released was approximately 100, 250 and 50 ng km{sup -1} for Pt, Pd and Rh, respectively. In diesel catalysts the Pt release varied in the range 400-800 ng km{sup -1}. After ageing the catalysts up to 30000 km, the gasoline catalysts released amounts of Pt between 6 and 8 ng km{sup -1}, Pd between 12 and 16 ng km{sup -1} and Rh between 3 and 12 ng km{sup -1}. In diesel catalysts the Pt release varied in the range 108-150 ng km{sup -1}. The soluble portion of PGEs in the HNO{sub 3} collector solution represented less than 5% of the

  5. Platinum supported catalysts for carbon monoxide preferential oxidation: Study of support influence

    Energy Technology Data Exchange (ETDEWEB)

    Padilla, R.; Rodriguez, L.; Serrano-Lotina, A.; Daza, L. [Instituto de Catalisis y Petroleoquimica (CSIC), C/Marie Curie 2, Campus Cantoblanco, 28049 Madrid (Spain); Benito, M. [Instituto de Catalisis y Petroleoquimica (CSIC), C/Marie Curie 2, Campus Cantoblanco, 28049 Madrid (Spain); Centro de Investigaciones Energeticas Medioambientales y Tecnologicas (CIEMAT), Av. Complutense 22, 28040 Madrid (Spain)

    2009-07-01

    The aim of this work is to study the influence of the addition of different oxides to an alumina support, on surface acidity and platinum reducibility in platinum-based catalysts, as well as their effect on the activity and selectivity in CO preferential oxidation, in presence of hydrogen. A correlation between surface acidity and acid strength of surface sites and metal reducibility was obtained, being Pt-support interaction a function of the acid sites concentration under a particular temperature range. In platinum supported on alumina catalysts, CO oxidation follows a Langmuir-Hinshelwood mechanism, where O{sub 2} and CO compete in the adsorption on the same type of active sites. It is noteworthy that the addition of La{sub 2}O{sub 3} modifies the reaction mechanism. In this case, CO is not only adsorbed on the Pt active sites but also on La{sub 2}O{sub 3}, forming bridge bonded carbonates which leads to high reactivity at low temperatures. An increase on temperature produces CO desorption from Pt surface sites and favours oxygen adsorption producing CO{sub 2}. CO oxidation with surface hydroxyl groups was activated producing simultaneously CO{sub 2} and H{sub 2}. (author)

  6. Acetaldehyde behavior over platinum based catalyst in hydrogen stream generated by ethanol reforming

    Energy Technology Data Exchange (ETDEWEB)

    de Lima, Adriana F.F. [Laboratorio de Catalise, Instituto Nacional de Tecnologia, Av. Venezuela 82/507, 20081-310 Rio de Janeiro, RJ (Brazil); Instituto de Quimica e INOG (Instituto Nacional de Oleo Gas), UERJ-CNPq, FAPERJ, Universidade do Estado do Rio de Janeiro, Rua Sao Francisco Xavier, 524, 20550-900 Rio de Janeiro, RJ (Brazil); Colman, Rita C. [Departamento de Engenharia Quimica e de Petroleo, Universidade Federal Fluminense, Av. Passos da Patria, 156/bl E/240, 24210-240 Niteroi, RJ (Brazil); Zotin, Fatima M.Z. [Instituto de Quimica e INOG (Instituto Nacional de Oleo Gas), UERJ-CNPq, FAPERJ, Universidade do Estado do Rio de Janeiro, Rua Sao Francisco Xavier, 524, 20550-900 Rio de Janeiro, RJ (Brazil); CETEM-MCT, Av. Pedro Calmon, 900, Cidade Universitaria, 21941-908 Rio de Janeiro, RJ (Brazil); Appel, Lucia G. [Laboratorio de Catalise, Instituto Nacional de Tecnologia, Av. Venezuela 82/507, 20081-310 Rio de Janeiro, RJ (Brazil)

    2010-12-15

    Due to the greenhouse effect, hydrogen production from bioethanol reforming is a very important subject in heterogeneous catalysis research. Pt based catalysts are employed in H{sub 2} purification processes and also as electrocatalysts of PEM (''Proton Exchange Membrane'') fuel cells. Hydrogen obtained from ethanol reforming may contain, as contaminants, acetaldehyde and small amounts of CO. This aldehyde can be decarbonylated on Pt based catalysts generating carbon monoxide and methane, rendering the hydrogen purification more challenging. Moreover, acetaldehyde might also change the electrocatalyst behavior. Therefore, this contribution aims at studying the acetaldehyde behavior in the presence of platinum based catalysts in hydrogen atmosphere. The Pt/SiO{sub 2}, Pt/USY catalysts and an electrocatalyst were characterized by n-butylamine, H{sub 2} and CO{sub 2} adsorption, ATG/DTG measurements and cyclohexane dehydrogenation reaction. It was observed that the acid-basic properties of the supports promote condensation reactions. When in contact with Pt based catalysts, acetaldehyde undergoes C-C and C=O bond scissions. The former occurs at a wide range of temperatures, whereas the latter only at low temperatures (<200 C). The C-C bond scission (decarbonylation) produces methane and CO. The C=O bond scission generates carbon residues on the catalyst as well as oxygen species, which in turn is able to eliminate CO from the catalytic surface. The data also show that decarbonylation is not a structure-sensitive reaction. (author)

  7. Reaction selectivity studies on nanolithographically-fabricated platinum model catalyst arrays

    Energy Technology Data Exchange (ETDEWEB)

    Grunes, Jeffrey Benjamin

    2004-05-15

    In an effort to understand the molecular ingredients of catalytic activity and selectivity toward the end of tuning a catalyst for 100% selectivity, advanced nanolithography techniques were developed and utilized to fabricate well-ordered two-dimensional model catalyst arrays of metal nanostructures on an oxide support for the investigation of reaction selectivity. In-situ and ex-situ surface science techniques were coupled with catalytic reaction data to characterize the molecular structure of the catalyst systems and gain insight into hydrocarbon conversion in heterogeneous catalysis. Through systematic variation of catalyst parameters (size, spacing, structure, and oxide support) and catalytic reaction conditions (hydrocarbon chain length, temperature, pressures, and gas composition), the data presented in this dissertation demonstrate the ability to direct a reaction by rationally adjusting, through precise control, the design of the catalyst system. Electron beam lithography (EBL) was employed to create platinum nanoparticles on an alumina (Al{sub 2}O{sub 3}) support. The Pt nanoparticle spacing (100-150-nm interparticle distance) was varied in these samples, and they were characterized using x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM), both before and after reactions. The TEM studies showed the 28-nm Pt nanoparticles with 100 and 150-nm interparticle spacing on alumina to be polycrystalline in nature, with crystalline sizes of 3-5 nm. The nanoparticle crystallites increased significantly after heat treatment. The nanoparticles were still mostly polycrystalline in nature, with 2-3 domains. The 28-nm Pt nanoparticles deposited on alumina were removed by the AFM tip in contact mode with a normal force of approximately 30 nN. After heat treatment at 500 C in vacuum for 3 hours, the AFM tip, even at 4000 nN, could not remove the platinum nanoparticles. The

  8. Reaction selectivity studies on nanolithographically-fabricated platinum model catalyst arrays

    Energy Technology Data Exchange (ETDEWEB)

    Grunes, Jeffrey Benjamin [Univ. of California, Berkeley, CA (United States)

    2004-05-01

    In an effort to understand the molecular ingredients of catalytic activity and selectivity toward the end of tuning a catalyst for 100% selectivity, advanced nanolithography techniques were developed and utilized to fabricate well-ordered two-dimensional model catalyst arrays of metal nanostructures on an oxide support for the investigation of reaction selectivity. In-situ and ex-situ surface science techniques were coupled with catalytic reaction data to characterize the molecular structure of the catalyst systems and gain insight into hydrocarbon conversion in heterogeneous catalysis. Through systematic variation of catalyst parameters (size, spacing, structure, and oxide support) and catalytic reaction conditions (hydrocarbon chain length, temperature, pressures, and gas composition), the data presented in this dissertation demonstrate the ability to direct a reaction by rationally adjusting, through precise control, the design of the catalyst system. Electron beam lithography (EBL) was employed to create platinum nanoparticles on an alumina (Al2O3) support. The Pt nanoparticle spacing (100-150-nm interparticle distance) was varied in these samples, and they were characterized using x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM), both before and after reactions. The TEM studies showed the 28-nm Pt nanoparticles with 100 and 150-nm interparticle spacing on alumina to be polycrystalline in nature, with crystalline sizes of 3-5 nm. The nanoparticle crystallites increased significantly after heat treatment. The nanoparticles were still mostly polycrystalline in nature, with 2-3 domains. The 28-nm Pt nanoparticles deposited on alumina were removed by the AFM tip in contact mode with a normal force of approximately 30 nN. After heat treatment at 500 C in vacuum for 3 hours, the AFM tip, even at 4000 nN, could not remove the platinum

  9. Oxygen reduction on carbon supported platinum catalysts in high temperature polymer electrolytes

    DEFF Research Database (Denmark)

    Qingfeng, Li; Hjuler, Hans Aage; Bjerrum, Niels

    2000-01-01

    improve the oxygen reduction kinetics due to increased oxygen solubility and suppressed adsorption of phosphoric acid anions. Further enhancement of the catalytic activity can be obtained by operating the polymer electrolytes at higher temperatures. Efforts have been made to develop a polymer electrolyte......Oxygen reduction on carbon supported platinum catalysts has been investigated in H3PO4, H3PO4-doped Nafion and polybenzimidazole (PBI) polymer electrolytes in a temperature range up to 190 degrees C. Compared with pure H3PO4, the combination of H3PO4 and polymer electrolytes can significantly...

  10. High sintering resistance of size-selected platinum cluster catalysts by suppressed ostwald ripening

    DEFF Research Database (Denmark)

    Wettergren, Kristina; Schweinberger, Florian F.; Deiana, Davide;

    2014-01-01

    Employing rationally designed model systems with precise atom-by-atom particle size control, we demonstrate by means of combining noninvasive in situ indirect nanoplasmonic sensing and ex situ scanning transmission electron microscopy that monomodal size-selected platinum cluster catalysts...... on different supports exhibit remarkable intrinsic sintering resistance even under reaction conditions. The observed stability is related to suppression of Ostwald ripening by elimination of its main driving force via size-selection. This study thus constitutes a general blueprint for the rational design...

  11. Ruthenium–Platinum Catalysts and Direct Methanol Fuel Cells (DMFC: A Review of Theoretical and Experimental Breakthroughs

    Directory of Open Access Journals (Sweden)

    Ana S. Moura

    2017-02-01

    Full Text Available The increasing miniaturization of devices creates the need for adequate power sources and direct methanol fuel cells (DMFC are a strong option in the various possibilities under current development. DMFC catalysts are mostly based on platinum, for its outperformance in three key areas (activity, selectivity and stability within methanol oxidation framework. However, platinum poisoning with products of methanol oxidation led to the use of alloys. Ruthenium–platinum alloys are preferred catalysts active phases for methanol oxidation from an industrial point of view and, indeed, ruthenium itself is a viable catalyst for this reaction. In addition, the route of methanol decomposition is crucial in the goal of producing H2 from water reaction with methanol. However, the reaction pathway remains elusive and new approaches, namely in computational methods, have been ensued to determine it. This article reviews the various recent theoretical approaches for determining the pathway of methanol decomposition, and systematizes their validation with experimental data, within methodological context.

  12. Improved and selective platinum recovery from spent alpha-alumina supported catalysts using pretreated anionic ion exchange resin.

    Science.gov (United States)

    Shams, K; Goodarzi, F

    2006-04-17

    Improved and selective recovery of platinum from a spent dehydrogenation platinum alpha-alumina supported catalyst using a strong basic ion exchange resin is reported. Platinum and other precious metal group (PMG) complexes are leached using concentrated hydrochloric acid along with about 0.20 vol.% nitric acid as an oxidizing agent from de-coked and crushed spent catalyst. Effects of hydrochloric acid concentration, time, and temperature in leaching stage are investigated. The strong basic anionic resin is treated by sodium hydroxide solution to replace chloride anion by hydroxyl group ion. The supernatant of the leaching process is passed through a fixed column of hydroxylated strong base anionic resin. The treated resin on which the platinum complex is adsorbed is dried and burned in an oxidizing atmosphere at 750-800 degrees C. The recovered gray metallic powder is mainly platinum. Results compared with those obtained from untreated anionic resin show that adsorption of platinum complexes onto the treated anionic resin is more selective and the yield of separation is considerably improved. The breakthrough curves of the pretreated anion exchanger and that of untreated exchange resin reveals that the capacity of the hyroxilated resin is decreased by about 14%. These breakthrough curves can be used for calculation of height of a practical exchange plate (HPEP) for design purposes.

  13. Nano-structured Platinum-based Catalysts for the Complete Oxidation of Ethylene Glycol and Glycerol

    Science.gov (United States)

    Falase, Akinbayowa

    Direct alcohol fuel cells are a viable alternative to the traditional hydrogen PEM fuel cell. Fuel versatility, integration with existing distribution networks, and increased safety when handling these fuels increases their appeal for portable power applications. In order to maximize their utility, the liquid fuel must be fully oxidized to CO2 so as to harvest the full amount of energy. Methanol and ethanol are widely researched as potential fuels to power these devices, but methanol is a toxic substance, and ethanol has a much lower energy density than other liquids such as gasoline or glucose. Oxidation of complex fuels is difficult to realize, due to difficulty in breaking carbon-carbon bonding and poisoning of the catalysts by oxidative byproducts. In order to achieve the highest efficiency, an anode needs to be engineered in such a way as to maximize activity while minimizing poisoning effects of reaction byproducts. We have engineered an anode that uses platinum-based catalysts that is capable of completely oxidizing ethylene glycol and glycerol in neutral and alkaline media with little evidence of CO poisoning. We have constructed a hybrid anode consisting of a nano-structured PtRu electrocatayst with an NAD-dependent alcohol dehydrogenase for improved oxidation of complex molecules. A nano-structured PtRu catalyst was used to oxidize ethylene glycol and glycerol in neutral media. In situ infrared spectroscopy was used to verify complete oxidation via CO2 generation. There was no evidence of poisoning by CO species. A pH study was performed to determine the effect of pH on oxidative current. The peak currents did not trend at 60 mV/pH unit as would be expected from the Nernst equation, suggesting that adsorption of fuel to the surface of the electrode is not an electron-transfer step. We synthesized nano-structured PtRu, PtSn, and PtRuSn catalysts for oxidation of ethylene glycol and glycerol in alkaline media. The PtRu electrocatalyst the highest oxidative

  14. Selective oxidation of glycerol by using a hydrotalcite-supported platinum catalyst under atmospheric oxygen pressure in water.

    Science.gov (United States)

    Tsuji, Akihiro; Rao, Kasanneni Tirumala Venkateswara; Nishimura, Shun; Takagaki, Atsushi; Ebitani, Kohki

    2011-04-18

    A hydrotalcite-supported platinum (Pt/HT) catalyst was found to be a highly active and selective heterogeneous catalyst for glycerol oxidation in pure water under atmospheric oxygen pressure in a high glycerol/metal molar ratio up to 3125. High selectivity toward glyceric acid (78 %) was obtained even at room temperature under air atmosphere. The Pt/HT catalyst selectively oxidized the primary hydroxyl group of 1,2-propandiol to give the corresponding carboxylic acid (lactic acid) as well as glycerol. The activity of the catalyst was greatly influenced by the Mg/Al ratio of hydrotalcite. Glycerol conversion increased with increasing the Mg/Al ratio of hydrotalcite (from trace to 56 %). X-ray absorption fine structure (XAFS) measurements indicated that the catalytic oxidation activity was proportional to the metallic platinum concentration, and more than 35 % of metallic platinum was necessary for this reaction. TEM measurements and titration analysis by using benzoic acid suggested that the solid basicity of hydrotalcite plays important roles in the precise control of platinum size and metal concentration as well as the initial promotion of alcohol oxidation.

  15. Activity targets for nanostructured platinum-group-metal-free catalysts in hydroxide exchange membrane fuel cells

    Science.gov (United States)

    Setzler, Brian P.; Zhuang, Zhongbin; Wittkopf, Jarrid A.; Yan, Yushan

    2016-12-01

    Fuel cells are the zero-emission automotive power source that best preserves the advantages of gasoline automobiles: low upfront cost, long driving range and fast refuelling. To make fuel-cell cars a reality, the US Department of Energy has set a fuel cell system cost target of US$30 kW-1 in the long-term, which equates to US$2,400 per vehicle, excluding several major powertrain components (in comparison, a basic, but complete, internal combustion engine system costs approximately US$3,000). To date, most research for automotive applications has focused on proton exchange membrane fuel cells (PEMFCs), because these systems have demonstrated the highest power density. Recently, however, an alternative technology, hydroxide exchange membrane fuel cells (HEMFCs), has gained significant attention, because of the possibility to use stable platinum-group-metal-free catalysts, with inherent, long-term cost advantages. In this Perspective, we discuss the cost profile of PEMFCs and the advantages offered by HEMFCs. In particular, we discuss catalyst development needs for HEMFCs and set catalyst activity targets to achieve performance parity with state-of-the-art automotive PEMFCs. Meeting these targets requires careful optimization of nanostructures to pack high surface areas into a small volume, while maintaining high area-specific activity and favourable pore-transport properties.

  16. Activity targets for nanostructured platinum-group-metal-free catalysts in hydroxide exchange membrane fuel cells.

    Science.gov (United States)

    Setzler, Brian P; Zhuang, Zhongbin; Wittkopf, Jarrid A; Yan, Yushan

    2016-12-06

    Fuel cells are the zero-emission automotive power source that best preserves the advantages of gasoline automobiles: low upfront cost, long driving range and fast refuelling. To make fuel-cell cars a reality, the US Department of Energy has set a fuel cell system cost target of US$30 kW(-1) in the long-term, which equates to US$2,400 per vehicle, excluding several major powertrain components (in comparison, a basic, but complete, internal combustion engine system costs approximately US$3,000). To date, most research for automotive applications has focused on proton exchange membrane fuel cells (PEMFCs), because these systems have demonstrated the highest power density. Recently, however, an alternative technology, hydroxide exchange membrane fuel cells (HEMFCs), has gained significant attention, because of the possibility to use stable platinum-group-metal-free catalysts, with inherent, long-term cost advantages. In this Perspective, we discuss the cost profile of PEMFCs and the advantages offered by HEMFCs. In particular, we discuss catalyst development needs for HEMFCs and set catalyst activity targets to achieve performance parity with state-of-the-art automotive PEMFCs. Meeting these targets requires careful optimization of nanostructures to pack high surface areas into a small volume, while maintaining high area-specific activity and favourable pore-transport properties.

  17. Effect of titania on the characteristics of a Tin-Platinum catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Morales-Gil, P., E-mail: moralesp@imp.mx; Nava, N. [Instituto Mexicano del Petróleo (Mexico); Baggio-Saitovitch, E. [Centro Brasileiro de Pesquisas Físicas (Brazil)

    2015-06-15

    Pt-Sn bimetallic catalysts dispersed on alumina are commonly used for reforming and dehydrogenation reactions. In this research work, Pt and Sn were supported on titania. The resulting interactions between the components in the prepared samples, before and after treatment with hydrogen, were studied by Mössbauer spectroscopy, X-ray diffraction and Rietveld refinement. The results show the presence of Pt and SnO{sub 2} after calcinations. After the reduction process, metallic Pt, PtSn, and Pt{sub 3}Sn alloys were identified. The Rietveld refinement analysis shows that some Ti{sup 4+} atoms were replaced by Sn{sup 4+} atoms in the titania structure. Finally, the Mössbauer spectroscopy and X-ray diffraction results indicate that metallic platinum and SnO{sub 2} are encapsulated by a TiOx layer.

  18. Platinum-tin oxide core-shell catalysts for efficient electro-oxidation of ethanol.

    Science.gov (United States)

    Du, Wenxin; Yang, Guangxing; Wong, Emily; Deskins, N Aaron; Frenkel, Anatoly I; Su, Dong; Teng, Xiaowei

    2014-08-06

    Platinum-tin (Pt/Sn) binary nanoparticles are active electrocatalysts for the ethanol oxidation reaction (EOR), but inactive for splitting the C-C bond of ethanol to CO2. Here we studied detailed structure properties of Pt/Sn catalysts for the EOR, especially CO2 generation in situ using a CO2 microelectrode. We found that composition and crystalline structure of the tin element played important roles in the CO2 generation: non-alloyed Pt46-(SnO2)54 core-shell particles demonstrated a strong capability for C-C bond breaking of ethanol than pure Pt and intermetallic Pt/Sn, showing 4.1 times higher CO2 peak partial pressure generated from EOR than commercial Pt/C.

  19. Role of bonding mechanisms during transfer hydrogenation reaction on heterogeneous catalysts of platinum nanoparticles supported on zinc oxide nanorods

    Science.gov (United States)

    Al-Alawi, Reem A.; Laxman, Karthik; Dastgir, Sarim; Dutta, Joydeep

    2016-07-01

    For supported heterogeneous catalysis, the interface between a metal nanoparticle and the support plays an important role. In this work the dependency of the catalytic efficiency on the bonding chemistry of platinum nanoparticles supported on zinc oxide (ZnO) nanorods is studied. Platinum nanoparticles were deposited on ZnO nanorods (ZnO NR) using thermal and photochemical processes and the effects on the size, distribution, density and chemical state of the metal nanoparticles upon the catalytic activities are presented. The obtained results indicate that the bonding at Pt-ZnO interface depends on the deposition scheme which can be utilized to modulate the surface chemistry and thus the activity of the supported catalysts. Additionally, uniform distribution of metal on the catalyst support was observed to be more important than the loading density. It is also found that oxidized platinum Pt(IV) (platinum hydroxide) provided a more suitable surface for enhancing the transfer hydrogenation reaction of cyclohexanone with isopropanol compared to zero valent platinum. Photochemically synthesized ZnO supported nanocatalysts were efficient and potentially viable for upscaling to industrial applications.

  20. Bimetallic Catalysts and Platinum Surfaces Studied by X-ray Absorption Spectroscopy and Scanning Tunnelling Microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Roenning, Magnus

    2000-07-01

    Bimetallic catalyst systems used in Fischer-Tropsch synthesis (Co-Re/Al{sub 2}O{sub 3}) and in the naphtha reforming process (Pt-Re/Al{sub 2}O{sub 3}) have been studied in situ using X-ray absorption spectroscopy (EXAFS). Additionally, the adsorption of ethene on platinum single crystal surfaces has been investigated using scanning tunnelling microscopy. In situ EXAFS at the cobalt K absorption edge have been carried out at 450{sup o}C on the hydrogen reduction of a rhenium-promoted Co{sub 3}O{sub 4}/Al{sub 2}O{sub 3} catalyst. Reductions carried out using 100% hydrogen and 5% hydrogen in helium gave different results. Whereas the reduction using dilute hydrogen leads to bulk-like metallic cobalt particles (hcp or fcc), reaction with pure hydrogen yields a more dispersed system with smaller cobalt metal particles (< 40 A). The results are rationalised in terms of different degrees of reoxidation of cobalt by the higher and lower concentrations of water generated during the reduction of cobalt oxide by 100% and 5% hydrogen, respectively. Additionally, in both reduction protocols a small fraction (3 -4 wt%) of the cobalt content is randomly dispersed over the tetrahedral vacancies of the alumina support. This dispersion occurs during reduction and not calcination. The cobalt in these sites cannot be reduced at 450 {sup o}C. The local environments about the rhenium atoms in Co-Re/{gamma}-A1{sub 2}O{sub 3} catalyst after different reduction periods have been studied by X-ray absorption spectroscopy. A bimetallic catalyst containing 4.6 wt% cobalt and 2 wt% rhenium has been compared with a corresponding monometallic sample with 2 wt% rhenium on the same support. The rhenium L{sub III} EXAFS analysis shows that bimetallic particles are formed after reduction at 450{sup o}C with the average particle size being 10-15 A. Rhenium is shown to be reduced at a later stage than cobalt. The fraction of cobalt atoms entering the support obstructs the access to the support for the

  1. Reduction of Furfural to Furfuryl Alcohol in Liquid Phase over a Biochar-Supported Platinum Catalyst

    Directory of Open Access Journals (Sweden)

    Ariadna Fuente-Hernández

    2017-02-01

    Full Text Available In this work, the liquid phase hydrogenation of furfural has been studied using a biochar-supported platinum catalyst in a batch reactor. Reactions were performed between 170 °C and 320 °C, using 3 wt % and 5 wt % of Pt supported on a maple-based biochar under hydrogen pressure varying from 500 psi to 1500 psi for reaction times between 1 h and 6 h in various solvents. Under all reactive conditions, furfural conversion was significant, whilst under specific conditions furfuryl alcohol (FA was obtained in most cases as the main product showing a selectivity around 80%. Other products as methylfuran (MF, furan, and trace of tetrahydrofuran (THF were detected. Results showed that the most efficient reaction conditions involved a 3% Pt load on biochar and operations for 2 h at 210 °C and 1500 psi using toluene as solvent. When used repetitively, the catalyst showed deactivation although only a slight variation in selectivity toward FA at the optimal experimental conditions was observed.

  2. Revealing the semiconductor–catalyst interface in buried platinum black silicon photocathodes

    Energy Technology Data Exchange (ETDEWEB)

    Aguiar, Jeffery A.; Anderson, Nicholas C.; Neale, Nathan R.

    2016-01-01

    Nanoporous 'black' silicon semiconductors interfaced with buried platinum nanoparticle catalysts have exhibited stable activity for photoelectrochemical hydrogen evolution even after months of exposure to ambient conditions. The mechanism behind this stability has not been explained in detail, but is thought to involve a Pt/Si interface free from SiOx layer that would adversely affect interfacial charge transfer kinetics. In this paper, we resolve the chemical composition and structure of buried Pt/Si interfaces in black silicon photocathodes from a micron to sub-nanometer level using aberration corrected analytical scanning transmission electron microscopy. Through a controlled electrodeposition of copper on samples aged for one month in ambient conditions, we demonstrate that the main active catalytic sites are the buried Pt nanoparticles located below the 400-800 nm thick nanoporous SiOx layer. Though hydrogen production performance degrades over 100 h under photoelectrochemical operating conditions, this burying strategy preserves an atomically clean catalyst/Si interface free of oxide or other phases under air exposure and provides an example of a potential method for stabilizing silicon photoelectrodes from oxidative degradation in photoelectrochemical applications.

  3. Catalytic Wet Air Oxidation of Oxalic Acid using Platinum Catalysts in Bubble Column Reactor: A Review

    Directory of Open Access Journals (Sweden)

    A. K. Saroha

    2010-01-01

    Full Text Available Wastewater treatment and re-use of industrial process water are critical issue for the development of human activities andenvironment conservation. Catalytic wet air oxidation (CWAO is an attractive and useful technique for treatment of effluentswhere the concentrations of organic pollutants are too low, for the incineration and other pollution control techniquesto be economically feasible and when biological treatments are ineffective, e.g. in the case of toxic effluents. In CWAO,combustion takes place on a Pt/Al2O3 catalysts usually at temperatures several degrees below those required forthermal incineration. In CWAO process, the organic contaminants dissolved in water are either partially degraded by meansof an oxidizing agent into biodegradable intermediates or mineralized into innocuous inorganic compounds such as CO2,H2O and inorganic salts, which remain in the aqueous phase. In contrast to other thermal processes CWAO produces no NOx,SO2, HCl, dioxins, furans, fly ash, etc. This review paper presents the application of platinum catalysts in bubble columnreactor for CWAO of oxalic acid.

  4. Bimetallic Catalysts and Platinum Surfaces Studied by X-ray Absorption Spectroscopy and Scanning Tunnelling Microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Roenning, Magnus

    2000-07-01

    Bimetallic catalyst systems used in Fischer-Tropsch synthesis (Co-Re/Al{sub 2}O{sub 3}) and in the naphtha reforming process (Pt-Re/Al{sub 2}O{sub 3}) have been studied in situ using X-ray absorption spectroscopy (EXAFS). Additionally, the adsorption of ethene on platinum single crystal surfaces has been investigated using scanning tunnelling microscopy. In situ EXAFS at the cobalt K absorption edge have been carried out at 450{sup o}C on the hydrogen reduction of a rhenium-promoted Co{sub 3}O{sub 4}/Al{sub 2}O{sub 3} catalyst. Reductions carried out using 100% hydrogen and 5% hydrogen in helium gave different results. Whereas the reduction using dilute hydrogen leads to bulk-like metallic cobalt particles (hcp or fcc), reaction with pure hydrogen yields a more dispersed system with smaller cobalt metal particles (< 40 A). The results are rationalised in terms of different degrees of reoxidation of cobalt by the higher and lower concentrations of water generated during the reduction of cobalt oxide by 100% and 5% hydrogen, respectively. Additionally, in both reduction protocols a small fraction (3 -4 wt%) of the cobalt content is randomly dispersed over the tetrahedral vacancies of the alumina support. This dispersion occurs during reduction and not calcination. The cobalt in these sites cannot be reduced at 450 {sup o}C. The local environments about the rhenium atoms in Co-Re/{gamma}-A1{sub 2}O{sub 3} catalyst after different reduction periods have been studied by X-ray absorption spectroscopy. A bimetallic catalyst containing 4.6 wt% cobalt and 2 wt% rhenium has been compared with a corresponding monometallic sample with 2 wt% rhenium on the same support. The rhenium L{sub III} EXAFS analysis shows that bimetallic particles are formed after reduction at 450{sup o}C with the average particle size being 10-15 A. Rhenium is shown to be reduced at a later stage than cobalt. The fraction of cobalt atoms entering the support obstructs the access to the support for the

  5. Simple cerium-triethanolamine complex: Synthesis, characterization, thermal decomposition and its application to prepare ceria support for platinum catalysts used in methane steam reforming

    Science.gov (United States)

    Wattanathana, Worawat; Nootsuwan, Nollapan; Veranitisagul, Chatchai; Koonsaeng, Nattamon; Laosiripojana, Navadol; Laobuthee, Apirat

    2015-06-01

    Cerium-triethanolamine complex was synthesized by simple complexation method in 1-propanol solvent using cerium(III) chloride as a metal source and triethanolamine as a ligand. The structures of the prepared complex were proposed based on FT-IR, FT-Raman and ESI-MS results as equimolar of triethanolamine and cerium chelated complex having monomeric tricyclic structure with and without chloride anion as another coordinating group known as ceratrane. The complex was used as a precursor for ceria material done by thermal decomposition. XRD result revealed that when calcined at 600 °C for 2 h, the cerium complex was totally turned into pure ceria with cubic fluorite structure. The obtained ceria was then employed to synthesize platinum doped ceria catalysts for methane steam reforming. Various amounts of platinum i.e. 1, 3, 5 and 10 mol percents were introduced on the ceria support by microwave-assisted wetness impregnation using ammonium tetrachloroplatinate(II). The platinum-impregnated ceria powders were subjected to calcination in 10% hydrogen/helium atmosphere at 500 °C for 3 h to reduce platinum(II) to platinum(0). XRD patterns of the catalysts confirmed that the platinum particles doped on the ceria support were in the form of platinum(0). Catalytic activity test showed that the catalytic activities got higher as the amounts of platinum doped increased. Besides, the portions of coke formation on the surface of catalysts were reduced as the amounts of platinum doped increased.

  6. Biogenic platinum and palladium nanoparticles as new catalysts for the removal of pharmaceutical compounds.

    Science.gov (United States)

    Martins, Mónica; Mourato, Cláudia; Sanches, Sandra; Noronha, João Paulo; Crespo, M T Barreto; Pereira, Inês A C

    2017-01-01

    Pharmaceutical products (PhP) are one of the most alarming emergent pollutants in the environment. Therefore, it is of extreme importance to investigate efficient PhP removal processes. Biologic synthesis of platinum nanoparticles (Bio-Pt) has been reported, but their catalytic activity was never investigated. In this work, we explored the potential of cell-supported platinum (Bio-Pt) and palladium (Bio-Pd) nanoparticles synthesized with Desulfovibrio vulgaris as biocatalysts for removal of four PhP: ciprofloxacin, sulfamethoxazole, ibuprofen and 17β-estradiol. The catalytic activity of the biological nanoparticles was compared with the PhP removal efficiency of D. vulgaris whole-cells. In contrast with Bio-Pd, Bio-Pt has a high catalytic activity in PhP removal, with 94, 85 and 70% removal of 17β-estradiol, sulfamethoxazole and ciprofloxacin, respectively. In addition, the estrogenic activity of 17β-estradiol was strongly reduced after the reaction with Bio-Pt, showing that this biocatalyst produces less toxic effluents. Bio-Pt or Bio-Pd did not act on ibuprofen, but this could be completely removed by D. vulgaris whole-cells, demonstrating that sulfate-reducing bacteria are among the microorganisms capable of biotransformation of ibuprofen in anaerobic environments. This study demonstrates for the first time that Bio-Pt has a high catalytic activity, and is a promising catalyst to be used in water treatment processes for the removal of antibiotics and endocrine disrupting compounds, the most problematic PhP. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Catalytic wet oxidation of ammonia solution: activity of the nanoscale platinum-palladium-rhodium composite oxide catalyst.

    Science.gov (United States)

    Hung, Chang-Mao

    2009-04-15

    Aqueous solutions of 400-1000 mg/L of ammonia were oxidized in a trickle-bed reactor (TBR) in this study of nanoscale platinum-palladium-rhodium composite oxide catalysts, which were prepared by the co-precipitation of H(2)PtCl(6), Pd(NO(3))(3) and Rh(NO(3))(3). Hardly any of the dissolved ammonia was removed by wet oxidation in the absence of any catalyst, whereas about 99% of the ammonia was reduced during wet oxidation over nanoscale platinum-palladium-rhodium composite oxide catalysts at 503 K in an oxygen partial pressure of 2.0 MPa. A synergistic effect exists in the nanoscale platinum-palladium-rhodium composite structure, which is the material with the highest ammonia reduction activity. The nanometer-sized particles were characterized by TEM, XRD and FTIR. The effect of the initial concentration and reaction temperature on the removal of ammonia from the effluent streams was also studied at a liquid hourly space velocity of under 9 h(-1) in the wet catalytic processes.

  8. POLYMER-PLATINUM COMPLEX CATALYSTS FOR OXIDATION OF METHANOL TO FORMALDEHYDE

    Institute of Scientific and Technical Information of China (English)

    HUANG Meiyu; HUANG Li; ZHENG Qingyao; WANG Dianxun; JIANG Yingyan

    1984-01-01

    Two kinds of polymer-platinum complexes: silica-supported poly-γ-diphenylphosphinopropyl-siloxane-platinum complex and silica-supported polyphenylsilazane-platinum complex, have been found very active and selective in catalyzation of oxidation of methanol to formaldehyde at room temperature and under an atmospheric oxygen pressure. Their catalytic activities are greatly affected by P or N/Pt gram atomic ratio.

  9. Platinum impact assessment

    OpenAIRE

    Yip, Joyce Pui Yan

    2007-01-01

    This paper presents a comprehensive strategic analysis of Company X's strategies to mitigate its risks from volatile platinum prices, since Platinum is a critical component of fuel cells. It is recommended that Company X consider leasing platinum to lower cash flow requirements to meet its platinum demand over the next 5 years. A shorter platinum leasing period will reduce Company X's platinum market risk. OEMs can set up metal accounts with catalyst suppliers to eliminate Company X from plat...

  10. Theoretical studies on membranes and non-platinum catalysts for polymer electrolyte fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Ushiyama, Hiroshi [Department of Chemical System Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan ushiyama@chemsys.t.u-tokyo.ac.jp (Japan)

    2015-12-31

    Mechanism of proton transfer among high-density acid groups in the interface between organic and inorganic materials for polymer electrolyte fuel cells has been theoretically examined. It has been clearly shown that the interactions between the phosphate groups at the surface of the inorganic material, zirconium phosphate (ZrP), and the adsorbed water molecules are relatively large and a strong hydrogen-bond network is generated locally. Because of the strong interactions, water molecules can be attached to ZrP and the O–O distance becomes shorter than that in bulk water systems. Because of the short O–O distances and the delocalized charge of each atom, the activation energy of proton transfer at the ZrP surface decreases and causes high proton conductivity even under conditions of high temperature and low humidity. Based on the above studies, the origin of the high proton conductivity of hybrid electrolytes is also discussed. We will also discuss the mechanism of oxygen reduction reaction on non-platinum catalysts such as Ta{sub 3}N{sub 5}.

  11. Hydrogenation of o-cresol on platinum catalyst: Catalytic experiments and first-principles calculations

    Science.gov (United States)

    Li, Yaping; Liu, Zhimin; Xue, Wenhua; Crossley, Steven P.; Jentoft, Friederike C.; Wang, Sanwu

    2017-01-01

    Catalytic experiments were performed for the hydrogenation of o-cresol in n-dodecane over a platinum catalyst. Batch reactions analyzed with an in-situ ATR IR probe suggest that the hydrogenation results in the formation of the final product, 2-methyl-cyclohexanol, with 2-methyl-cyclohexanone as the intermediate product. Ab initio density-functional theory was employed to investigate the atomic-scale mechanism of o-cresol hydrogenation on the Pt(111) surface. The formation of 2-methyl-cyclohexanone was found to involve two steps. The first step is a hydrogen abstraction, that is, the H atom in the hydroxyl group migrates to the Pt surface. The second step is hydrogenation, that is, the pre-existing H atoms on Pt react with the carbon atoms in the aromatic ring. On the other hand, 2-methyl-cyclohexanonol may be produced through two paths, with activation energies slightly greater than that for the formation of 2-methyl-cyclohexanone. One path involves direct hydrogenation of the aromatic ring. Another path involves three steps, with the partial hydrogenation of the ring as the first step, hydrogen abstraction of the sbnd OH group as the second, and hydrogenation of remaining C atoms and the O atom the last.

  12. Glycerol electro-oxidation on a carbon-supported platinum catalyst at intermediate temperatures

    Science.gov (United States)

    Ishiyama, Keisuke; Kosaka, Fumihiko; Shimada, Iori; Oshima, Yoshito; Otomo, Junichiro

    2013-03-01

    The electro-oxidation of glycerol on a carbon-supported platinum catalyst (Pt/C) in combination with a reaction products analysis was investigated at intermediate temperatures (235-260 °C) using a single cell with a CsH2PO4 proton conducting solid electrolyte. A high current density was achieved. The main products were H2, CO2 and CO but the formation of C2 compounds, such as glycolic acid and ethane, was also observed. In addition, several C3 compounds were detected as minor products. A reaction products analysis revealed that the C-C bond dissociation ratio of glycerol was 70-80% at both low and high potentials (>200 mV vs. reversible hydrogen electrode) at 250 °C, suggesting that rapid dissociation occurs on Pt/C. The reaction products analysis also suggested that hydrogen production via thermal decomposition and/or steam reforming of glycerol (indirect path) and direct electro-oxidation of glycerol (direct path) proceed in parallel. More detailed reaction paths involving C1, C2 and C3 reaction products are discussed as well as the possible rate-determining step in glycerol electro-oxidation at intermediate temperatures.

  13. Catalytic activity vs. size correlation in platinum catalysts of PEM fuel cells prepared on carbon black by different methods

    Energy Technology Data Exchange (ETDEWEB)

    Nores-Pondal, F.J.; Granada, M.; Corti, H.R. [Departamento de Fisica de la Materia Condensada, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica (CNEA), General Paz 1499, 1650 San Martin, Buenos Aires (Argentina); Vilella, I.M.J.; de Miguel, S.R.; Scelza, O.A. [Instituto de Investigaciones en Catalisis y Petroquimica (INCAPE), Facultad de Ingenieria Quimica (Universidad Nacional del Litoral) - CONICET, Santiago del Estero 2654, 3000 Santa Fe (Argentina); Troiani, H. [Departamento de Fisica, Centro Atomico Bariloche, Comision Nacional de Energia Atomica (CNEA), Av. Bustillo 9500, 8400 San Carlos de Bariloche (Argentina)

    2009-10-15

    In this work nanoparticulated platinum catalysts have been prepared on carbon Vulcan XC-72 using three methods starting with chloroplatinic acid as a precursor: (i) formic acid as a reductor agent; (ii) impregnation method followed by reduction in hydrogen atmosphere at moderated temperature; and (iii) microwave-assisted reduction in ethylene glycol. The catalytic and size studies were also performed on a commercial Pt catalyst (E-Tek, De Nora). The characterization of the particle size and distribution was performed by means of transmission electron microscopy (TEM) and X-ray diffraction (XRD). The characterizations of the catalytic and electrocatalytic properties of the catalysts were determined by studying the cyclohexane dehydrogenation reaction (CHD) and the behavior under cyclic voltammetry (CV) in sulfuric acid solutions. The measured electrochemical activity, along with the hydrogen chemisorption of the catalysts allows the estimation of effective particle sizes, which are much larger than those measured by TEM and XRD. The catalysts prepared by reduction with formic acid and ethylene glycol (microwave-assisted) show electrochemical activities very close to those of the commercial catalyst, and are almost insensitive to the Pt dispersion or Pt particle size. The chemical activity in CHD correlates well with the metallic dispersion determined by hydrogen chemisorption, indicating similar accesibility of H{sub 2} and cyclohexane to the catalyst surface. (author)

  14. The influence of reduction methods and conditions on the activity of alumina-supported platinum catalysts for the liquid phase hydrogenation of benzaldehyde in ethanol

    Energy Technology Data Exchange (ETDEWEB)

    Arai, M.; Obata, A.; Nishiyama, Y. [Tohoku Univ., Sendai (Japan)

    1997-02-01

    The activities of supported metal catalysts depend on various preparation variables, including the method of reduction. A variety of reduction procedures can be applied to the preparation of supported metal catalysts. Previously, the authors used a solid-liquid reduction by sodium tetrahydroborate solution for preparing supported platinum catalysts. In this reduction, platinum precursors adsorbed on supports were brought into contact with the reducing solution. The alumina-supported platinum catalysts prepared in this way were found to display interesting activities in the liquid-phase hydrogenation of {alpha},{beta}-unsaturated aldehydes; they were highly selective to the formation of unsaturated alcohols. The selective hydrogenation of C=O bonds of {alpha},{beta}-unsaturated aldehydes is difficult to achieve with platinum catalysts without using some additives like tin and iron. The maximum temperature that the supported platinum catalysts went through was 110{degrees}C, required for the removal of water. This thermal history is a possible reason for the catalytic activity observed. Following those observations, in the present work, the authors have further examined the influence of reduction procedures by using hydrazine as well as sodium tetrahydroborate and different temperatures common during gas-phase reduction with hydrogen. The catalytic activity has been tested by the liquid-phase hydrogenation of benzaldehyde (BAL) in ethanol under mild conditions. 12 refs., 3 figs.

  15. Selective hydrogenation of halogenated arenes using porous manganese oxide (OMS-2) and platinum supported OMS-2 catalysts.

    Science.gov (United States)

    McManus, Iain J; Daly, Helen; Manyar, Haresh G; Taylor, S F Rebecca; Thompson, Jillian M; Hardacre, Christopher

    2016-07-04

    Porous manganese oxide (OMS-2) and platinum supported on OMS-2 catalysts have been shown to facilitate the hydrogenation of the nitro group in chloronitrobenzene to give chloroaniline with no dehalogenation. Complete conversion was obtained within 2 h at 25 °C and, although the rate of reaction increased with increasing temperature up to 100 °C, the selectivity to chloroaniline remained at 99.0%. Use of Pd/OMS-2 or Pt/Al2O3 resulted in significant dechlorination even at 25 °C and 2 bar hydrogen pressure giving a selectivity to chloroaniline of 34.5% and 77.8%, respectively, at complete conversion. This demonstrates the potential of using platinum group metal free catalysts for the selective hydrogenation of halogenated aromatics. Two pathways were observed for the analogous nitrobenzene hydrogenation depending on the catalyst used. The hydrogenation of nitrobenzene was found to follow a direct pathway to aniline and nitrosobenzene over Pd/OMS-2 in contrast to the OMS and Pt/OMS-2 catalysts which resulted in formation of nitrosobenzene, azoxybenzene and azobenzene/hydrazobenzene intermediates before complete conversion to aniline. These results indicate that for Pt/OMS-2 the hydrogenation proceeds predominantly over the support with the metal acting to dissociate hydrogen. In the case of Pd/OMS-2 both the hydrogenation and hydrogen adsorption occur on the metal sites.

  16. Thermal Balance of the Magneto-Hydro-Dynamic Pump for Recovery of Platinum Group Metals from Spent Auto Catalysts

    Directory of Open Access Journals (Sweden)

    Gil S.

    2016-03-01

    Full Text Available Every new car should be equipped with the catalyst, which limits the amount of harmful chemical compounds such as NOx, CH and CO emitted to the air. Auto catalyst consists of the ceramic or metallic carrier, on which is the layer with Platinum Group Metals playing catalytic role. There are many methods using for recovery those valuable metals from spent auto catalyst, however evry of those methods have some limitations. Proces described in the article is the modified method of metal collector, which used magnetohydrodynamic pump. Rotary electromagnetic field generates in the liquid metal rotary current, which as a consequence washing out the PGM metals from the ceramic carriers. Considering the possibilities of commercialization of the described method, the energy balance was made. From that balance the energetic efficiency of the unit was determined and the analysis of the temperature distribution was shown thermographycally.

  17. Accelerating Oxygen-Reduction Catalysts through Preventing Poisoning with Non-Reactive Species by Using Hydrophobic Ionic Liquids.

    Science.gov (United States)

    Zhang, Gui-Rong; Munoz, Macarena; Etzold, Bastian J M

    2016-02-05

    Developing cost-effective electrocatalysts for the oxygen reduction reaction (ORR) is a prerequisite for broad market penetration of low-temperature fuel cells. A major barrier stems from the poisoning of surface sites by nonreactive oxygenated species and the sluggish ORR kinetics on the Pt catalysts. Herein we report a facile approach to accelerating ORR kinetics by using a hydrophobic ionic liquid (IL), which protects Pt sites from surface oxidation, making the IL-modified Pt intrinsically more active than its unmodified counterpart. The mass activity of the catalyst is increased by three times to 1.01 A mg(-1) Pt @0.9 V, representing a new record for pure Pt catalysts. The enhanced performance of the IL-modified catalyst can be stabilized after 30 000 cycles. We anticipate these results will form the basis for an unprecedented perspective in the development of high-performing electrocatalysts for fuel-cell applications.

  18. Platinum catalysts recovery of the proton exchange membrane fuel cell; Recuperacao de catalisadores de platina da celula a combustibel de membrana polimerica trocadora de protons

    Energy Technology Data Exchange (ETDEWEB)

    Fukurozaki, S.H.; Seo, E.S.M. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Ciencia e Tecnologia de Materiais. Lab. de Processamento de Residuos

    2006-07-01

    Currently, platinum is the most feasible catalyst for the Proton Exchange Membrane Fuel Cells - PEMFC. Along with platinum's significant importance in this energy system are the high cost of this noble metal and its detrimental effects on the environment. Therefore, recycling this material seems as an alternative to decrease its impacts on the environment and, at the same time, to provide a reduction of the system's costs. A search was conducted for literature and studies about platinum recycling methods. However, only two techniques of platinum recovery, which are still in development, were found. In face of this situation, a recovery method of platinum from deactivated Membrane Electrode Assembly - MEA's was developed, with attention to aspects related to the environment and the necessary requirements for its primary recycling. The results found showed a high recovery ratio and a possibility to reintroduce this metal into the production cycle. (author)

  19. The Effect of Platinum on Stability of the B2O3/TiO2-ZrO2 Catalyst for Beckmann Rearrangement of Cyclohexanone Oxime

    Institute of Scientific and Technical Information of China (English)

    Dong Sen MAO; Guan Zhong LU

    2006-01-01

    The addition of platinum over the B2O3/TiO2-ZrO2 remarkably enhanced its catalytic stability in the vapor phase Beckmann rearrangement of cyclohexanone oxime under the carrier gas of H2. The content of coke deposited on catalyst surface was decreased from 1.92% over the B2O3/TiO2-ZrO2 to 1.14% over the platinum promoted B2O3/TiO2-ZrO2 after reaction of six hours. This result indicates that the platinum added on the B2O3/TiO2-ZrO2 catalyst plays an important role in reducing the coke formation on the catalyst surface.

  20. Study of pyrolyzed hemin/C as non-platinum cathodic catalyst for direct methanol fuel cells

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Biological reduction of O2 to H2O justifies a serious look at heme as a potential O2 reduction reaction(ORR) catalyst for low temperature fuel cells.In this study,a novel non-platinum electrocatalyst for ORR was prepared through hemin,which is hydrochloride of heme,supported on Black Pearls 2000 carbon black(Hm-BP) pyrolyzed at 700-900℃ in Ar atmosphere.The physical and electrocatalytic properties of as-prepared catalysts were characterized by TGA,XRD,XPS,TEM,rotating disk electrode(RDE) and rotating ring disk electrode(RRDE).It has found that the catalyst treated at 750℃(Hm-BP-750) exhibits the best property among the Hm-BP catalysts prepared.The onset potential of ORR on the Hm-BP-750 at 30℃ was measured ca.0.90 V(vs.RHE) in 0.1 M H2SO4,and mass current density was reached 15.3 mA mg-1 at 0.75 V.It has revealed that O2 could be reduced directly to water in a 4e process between 0.9 and 0.83V,and the yield of H2O2 was 0-18% in the potential range of 0.83-0.63 V.This methanol-tolerant catalyst also presents excellent stability in medium-term test of direct methanol fuel cell at 80℃.

  1. Preparation of Ceramic Hydrophobic Catalyst Capable of Withstanding Temperature up to 800 ℃%耐温800℃陶瓷疏水催化剂的研制

    Institute of Scientific and Technical Information of China (English)

    但贵萍; 王晓丽; 邱咏梅; 张东; 杜阳

    2011-01-01

    用强酸对多孔疏水材料进行表面改性,获得疏水多孔陶瓷载体.采用浸渍法制备出耐温达800℃陶瓷基疏水催化剂,分别在低浓度氢-空气环境(φ(H2)=10-3)和低活度氚水环境(氚的放射性浓度1 570 kBq/L)中对其催化氧化效率和催化交换效率进行了测试,结果表明,在该疏水催化剂存在条件下,催化氧化反应的单程转化率为95%;同位素催化交换的单程转化率为81.7%.%In order to prepare hydrophobia catalyst which can withstand higher temperature and can be used for catalisis of reaction between hydrogen and oxygen and used for decontam-ination of tritium-containing gases. The ceramic hydrophobic catalyst carrier was prepared by processing porous hydrophobic zeolite with strong acid. Then the ceramic hydrophobic carrier was cavered with platinum by chemical deposition of Pt from a H2 PtCl6 solution in acetone. Its catalytic-oxidation activation in lower hydrogen atmosphere and its isotopic ex-changing activation in lower HTO solution were studied. The results show that the catalyst can withstand temperature up to 800 ℃. When the catalyst is used at room temperature a conversion efficiency of 95% for catalyzing the oxidation of hydrogen, and a conversion effi-ciency of 81. 7% for catalizing the T-H isotopic exchange between HTOH2 are observed.

  2. An Efficient and Stable Hydrophobic Molecular Cobalt Catalyst for Water Electro-oxidation at Neutral pH

    KAUST Repository

    Chen, Ba-Tian

    2016-06-14

    The synthesis of a library of molecular water oxidation catalysts based on the Co complex of tris(2-benzimidazolylmethyl)amine is described. Hydrophobicity was identified as the key variable in mediating the catalytic competence of the complexes. The change in this parameter correlates with both the conformational mobility of the ligand core and the structural changes in the local solvent environment around the metal site. The optimal Co complex identified is hydrophobic, because of three semifluorinated side chains. It catalyzes water electro-oxidation efficiently at neutral pH, with an overpotential of 390 mV and a turnover frequency (TOF) of 1.83 s-1 in the absence of soluble Co salts. The catalyst can be immobilized through physisorption, and it remains stable in prolonged electrolysis experiments. © 2016 American Chemical Society.

  3. Structure, activity, and stability of platinum alloys as catalysts for the oxygen reduction reaction

    DEFF Research Database (Denmark)

    Vej-Hansen, Ulrik Grønbjerg

    and dealloying due to kinetic barriers, despite the thermodynamic driving force for dissolution. This is followed by our results on trying to decouple the strain and ligand effects for platinum skin structures, and determining whether there is any correlation between adsorption energy and surface stability...... in these systems. We find that there is such a correlation for some adsorbates, indicating that there exists a limit for the stability of an overlayer for a given adsorption strength. Finally, we introduce our work on platinum alloy nanoparticles, and our attempt to isolate the features which result...... in the increased activity that has been seen experimentally. We show how the platinum-platinum distance at the surface is decreased for a variety of alloy phases in the core, with greater compression of the overlayer for core phases with lattice parameters which are either much smaller or much larger than pure...

  4. Indium- and Platinum-Free Counter Electrode for Green Mesoscopic Photovoltaics through Graphene Electrode and Graphene Composite Catalysts: Interfacial Compatibility.

    Science.gov (United States)

    Yin, Jie; Zhou, Huawei; Liu, Zhicheng; Nie, Zhonghao; Li, Yinhao; Qi, Xuan; Chen, Baoli; Zhang, Yingtian; Zhang, Xianxi

    2016-03-01

    The scarcity and noble indium and platinum (Pt) are important elements in photoelectric nanomaterials. Therefore, development of low cost alternative materials to meet different practical applications is an urgent need. Two-dimensional (2D) layered graphene (GE) with unique physical, mechanical, and electrical properties has recently drawn a great deal of attention in various optoelectronic fields. Herein, the large scale (21 cm × 15 cm) high-quality single layer graphene (SLG) and multilayer graphene on a flexible plastic substrate PET were controllably prepared through layer-by-layer (LBL) transfer using the thermal release adhesive transfer method (TRA-TM). Transmission and antibending performance based on PET/GE were superior to traditional PET/ITO. The square resistance of a nine-layer graphene electrode reached approximately 58 Ω. Combined with our newly developed and highly effective Fe3O4@RGO (reduced graphene oxide) catalyst, the power conversion efficiency of the dye-sensitized solar cell (DSC) using flexible PET/GE conductive substrate was comparable to that of the DSC using the PET/ITO substrate. The desirable performance of PET/GE/Fe3O4@RGO counter electrodes (low-cost indium- and platinum-free counter electrodes) is attributed to the interfacial compatibility between 2D graphene composite catalyst (Fe3O4@RGO) and 2D PET/GE conductive substrate. In addition, DSCs that use only PET/GE (without Fe3O4@RGO catalyst) as counter electrodes can also achieve a photocurrent density of 6.30 mA cm(-2). This work is beneficial for fundamental research and practical applications of graphene and graphene composite in photovoltaics, photocatalytic water splitting, supercapacitors.

  5. Heterogeneous platinum-catalyzed hydrogenation of dialkyl(diolefin)platinum(II) complexes: A new route to platinum surface alkyls

    OpenAIRE

    McCarthy, Thomas J.; Shih, Yen-Shiang; Whitesides, George M.

    1981-01-01

    Platinum metal catalyzes the reduction of dialkyl(diolefin)platinum(II) complexes by dihydrogen to alkanes and platinum(0). The reaction involves adsorption of the platinum(II) complex on the platinum(0) catalyst surface with conversion of the alkyl moieties to platinum surface alkyls; these appear as alkane products. The platinum atom originally present in the soluble organoplatinum species becomes part of the platinum(0) surface.

  6. The Manipulation of Hydrophobicity in Catalyst Design for Applications of Aerobic Alcohols Oxidation and Electrocatalytic Water Oxidation

    KAUST Repository

    Chen, Batian

    2016-05-17

    Hydrophobicity is the generalized characteristic of non-polar substances that brings about their exclusion from aqueous phases. This property, entropic in its nature, drives key self-assembly and phase separation processes in water. Protein folding, the formation of DNA double helix, the existence of lipid bilayers and the wetting properties of leaf surfaces are all due to hydrophobic interactions. Inspired by Nature, we aimed to use hydrophobicity for creating novel and improved catalytic systems. (I) A number of fluorous amphiphilic star block-copolymers containing a tris(benzyltriazolylmethyl)amine motif have been prepared. These polymers assembled into well-defined nanostructures in water, and their mode of assembly could be controlled by changing the composition of the polymer. The polymers were used for enzyme-inspired catalysis of alcohol oxidation. (II) An enzyme-inspired catalytic system based on a rationally designed multifunctional surfactant was developed. The resulting micelles feature metal-binding sites and stable free radical moieties as well as fluorous pockets that attract and preconcentrate molecular oxygen. In the presence of copper ions, the micelles effect chemoselective aerobic alcohol oxidation under ambient conditions in water, a transformation that is challenging to achieve nonenzymatically. (III) Development of a facile means of photo/electrocatalytic water splitting is one of the main barriers to establishing of a solar hydrogen economy. Of the two half-reactions involved in splitting water into O2 and H2, water oxidation presents the most challenge due to its mechanistic complexity. A practical water oxidation catalyst must be highly active, yet inexpensive and indefinitely stable under harsh oxidative conditions. Here, I shall describe the synthesis of a library of molecular water oxidation catalysts based on the Co complex of tris(2-benzimidazolylmethyl)amine, (BimH)3. A wide range of catalysts differing in their electronic properties

  7. Research of platinum catalysts used in PEM fuel cell%质子交换膜燃料电池含Pt催化剂的研究

    Institute of Scientific and Technical Information of China (English)

    雷一杰; 李彤; 顾军; 于涛; 邹志刚

    2011-01-01

    作为质子交换膜燃料电池的主要用催化剂,Pt的研究对质子交换膜燃料电池运用和普及起着至关重要的作用.为此,近年来一系列大量的基于Pt催化剂的不同形貌、不同成分、不同载体的研究大大地推进了Pt催化剂技术的发展.%As the main catalyst used in proton exchange membrane fuel cell(PEMFC), the platinum research plays a vital role on the application and popularization of PEMFC. In this respect, a great deal of effort has been put into the morphologies, ingredients, supporters based on the platinum catalysts in recent years, which has promoted the catalyst technology.

  8. The platinum catalyst layer in polymer-electrolyte fuel cells[Dissertation 17127]; Die Platinkatalysatorschicht in Polymerelektrolyt-Brennstoffzellen. Beitraege zum Verstaendnis und zur Optimierung

    Energy Technology Data Exchange (ETDEWEB)

    Reiner, A.

    2007-07-01

    This illustrated, comprehensive dissertation by Dr. Andreas Reiner presents an in-depth analysis of polymer electrolyte fuel cells (PEFC) and in particular, their platinum catalyst layer. First of all, the thermodynamics and kinetics involved are reviewed, along with components, their efficiencies and the catalyst layer. The methods used, including scanning electron microscope, x-ray and Rutherford spectroscopy are discussed. The structure and composition of co-sputtered catalyst layers and their production are described. Electro-chemical activation and the electro-chemical properties of the layers are discussed. The second part of the dissertation deals with the principle of hydrogen under-potential deposition. This method provides information about the electrochemically active platinum surface fraction. The results of investigations made are presented and discussed.

  9. Modeling the cathode in a proton exchange membrane fuel cell using density functional theory How the carbon support can affect durability and activity of a platinum catalyst

    Science.gov (United States)

    Groves, Michael Nelson

    The current global energy and environmental challenges need to be addressed by developing a new portfolio of clean power producing devices. The proton exchange membrane fuel cell has the potential to be included and can fit into a variety of niches ranging from portable electronics to stationary residential applications. One of the many barriers to commercial viability is the cost of the cathode layer which requires too much platinum metal to achieve a comparable power output as well as would need to be replaced more frequently when compared to conventional sources for most applications. Using density functional theory, an ab initio modeling technique, these durability and activity issues are examined for platinum catalysts on graphene and carbon nanotube supports. The carbon supports were also doped by replacing individual carbon atoms with other second row elements (beryllium, boron, nitrogen, and oxygen) and the effect on the platinum-surface interaction along with the interaction between the platinum and the oxygen reduction reaction intermediates are discussed. Keywords: proton exchange membrane fuel cell, density functional theory, platinum catalyst, oxygen reduction reaction, doped carbon surfaces

  10. Performance of Platinum Nanoparticles / Multiwalled Carbon Nanotubes / Bacterial Cellulose Composite as Anode Catalyst for Proton Exchange Membrane Fuel Cells

    Directory of Open Access Journals (Sweden)

    Henry Fonda Aritonang

    2017-05-01

    Full Text Available Highly dispersed platinum (Pt nanoparticles / multiwalled carbon nanotubes (MWCNTs on bacterial cellulose (BC as anode catalysts for proton exchange membrane fuel cells (PEMFC were prepared with various precursors and their electro-catalytic activities towards hydrogen oxidation at 70 oC under non-humidified conditions. The composite was prepared by deposition of Pt nanoparticles and MWCNTs on BC gel by impregnation method using a water solution of metal precursors and MWCNTs followed by reducing reaction using a hydrogen gas. The composite was characterized by using TEM (transmission electron microscopy, EDS (energy dispersive spectroscopy, and XRD (X-ray diffractometry techniques. TEM images and XRD patterns both lead to the observation of spherical metallic Pt nanoparticles with mean diameter of 3-11 nm well impregnated into the BC fibrils. Preliminary tests on a single cell indicate that renewable BC is a good prospect to be explored as a membrane in fuel cell field. Copyright © 2017 BCREC Group. All rights reserved Received: 21st November 2016; Revised: 26th February 2017; Accepted: 27th February 2017 How to Cite: Aritonang, H.F., Kamu, V.S., Ciptati, C., Onggo, D., Radiman, C.L. (2017. Performance of Platinum Nanoparticles / Multiwalled Carbon Nanotubes / Bacterial Cellulose Composite as Anode Catalyst for Proton Exchange Membrane Fuel Cells. Bulletin of Chemical Reaction Engineering & Catalysis, 12 (2: 287-292 (doi:10.9767/bcrec.12.2.803.287-292 Permalink/DOI: http://dx.doi.org/10.9767/bcrec.12.2.803.287-292

  11. Hydrogen and/or syngas from steam reforming of glycerol. Study of platinum catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Pompeo, Francisco; Santori, Gerardo; Nichio, Nora N. [Facultad de Ingenieria, Universidad Nacional de La Plata, 1 esq 47, 1900 La Plata (Argentina); CINDECA, Facultad de Ciencias Exactas, Universidad Nacional de La Plata-CONICET, 47 N 257, 1900 La Plata (Argentina)

    2010-09-15

    In the present work, Pt catalysts prepared on different supports were evaluated in order to apply them in the steam reforming of glycerol reaction to obtain hydrogen and/or synthesis gas at temperatures lower than 450 C. A strong support effect on the behavior of catalysts was determined. The presence of intermediate products allowed to propose a scheme of reactions that would explain the results obtained at different space times and temperatures studied. Materials with acid properties demonstrated low activity to gaseous products, with formation of lateral products due to dehydration and condensation reactions, which would lead to coke formation and to a fast catalyst deactivation. On the contrary, the catalyst prepared with a support with neutral properties permitted to obtain a catalyst with excellent activity levels to gaseous products, high selectivity to H{sub 2}, and a very well stability in time. (author)

  12. Influence of Yttrium and Ytterbium on Reaction Performance of Platinum-Rhenium Reforming Catalyst

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The influence of yttrium and ytterbium on the catalytic performance of Pt-Re reforming cata-lysts was studied in a continuous flow pressurized microreactor-chromatograph system and pilot unit. Theresults of micro-reactor test showed that both yttrium and ytterbium could improve the selectivity of Pt-Recatalysts for the conversion ofn-heptane as well as MCP into aromatics, but also suppressed their activityas well. Pilot test results showed that yttrium and ytterbium enhanced both the selectivity and activity ofPt-Re catalysts for naphtha reforming. Yttrium showed more improvement than ytterbium. The perfor-mance difference between microreactor test and pilot test might be due to the difference in improvement ofcatalytic stability of yttrium or ytterbium modified Pt-Re catalysts. Yttrium and ytterbium improved thecoking resistance of yttrium or ytterbium modified Pt-Re catalysts. TEM determination results indicatedthat both yttrium and ytterbium had improved the thermal stability of Pt-Re catalysts.

  13. REDUCTION OF NITRIC OXIDE BY CARBON MONOXIDE OVER A SILICA SUPPORTED PLATINUM CATALYST: INFRARED AND KINETIC STUDIES

    Energy Technology Data Exchange (ETDEWEB)

    Lorimer, D.H.

    1978-08-01

    The reduction of nitric oxide by carbon monoxide over a 4.5 weight precent platinum catalyst supported on silica was studied at 300 C. Reaction rate data was obtained together with in situ infrared spectra of species on the catalyst surface. The kinetics of the system were found to exhibit two distinct trends, depending on the molar ratio of CO/NO in the reactor. For net reducing conditions (CO/NO> 1) the catalyst underwent a transient deactivation, the extent of which was dependent on the specific CO/NO ratio during reaction. Reactivation of the catalyst was obtained with both oxidizing and reducing pretreatments. For molar feed ratios of CO/NO less than one, carbon monoxide conversion was typically 95 to 100%, resulting in strongly oxidizing conditions over the catalyst. Under these conditions no deactivation was apparent. Infrared spectra recorded under reaction conditions revealed intense bands at 2075 and 2300 cm{sup -1} , which were identified as carbon monoxide adsorbed on Pt and Si-NCO, respectively. Isocyanate bands formed under reducing conditions were more intense and exhibited greater stability than those formed under oxidizing conditions. A reaction mechanism based on the dissociation of nitric oxide as the rate-limiting step was used to correlate nitric oxide reaction rates and nitrous oxide selectivities observed under reducing conditions. As part of this mechanism it is assumed that nitrous bxide is formed via a Langmuir-Hinshelwood process in which an adsorbed nitrogen atom reacts with an adsorbed nitric oxide molecule. The nitric oxide reaction rate was found to be first order in nitric oxide partial pressure, and inverse second order in carbon monoxide partial pressure. A mechanism is proposed to qualitatively explain the deactivation process observed under reducing conditions. The essential part of this mechanism is the formation of an isocyanate species on the Pt crystallites of the catalyst and the subsequent transient diffusion of these

  14. Load cycle durability of a graphitized carbon black-supported platinum catalyst in polymer electrolyte fuel cell cathodes

    Science.gov (United States)

    Takei, Chikara; Kakinuma, Katsuyoshi; Kawashima, Kazuhito; Tashiro, Keisuke; Watanabe, Masahiro; Uchida, Makoto

    2016-08-01

    We focus on Pt degradation occurring during fuel cell vehicle (FCV) combined drive cycles involving load and open circuit voltage (OCV) just after startup and during idling. Load cycle durability is evaluated as a function of OCV/load holding time, load rate and relative humidity (RH) with a graphitized carbon black-supported platinum catalyst (Pt/GCB) in the cathode. The degradation of Pt/GCB is suppressed for shorter OCV holding times, lower load rates and lower RH. Scanning ion microscopy (SIM) images of membrane cross-sections indicate that the amount of Pt deposited in the membrane decreases during drive cycles involving load with short OCV holding times. Investigations of the Pt distribution in the cathode catalyst layer (CL) by using scanning TEM-EDX show that the dissolution of Pt is suppressed on the membrane side in the CL. The Pt dissolution is accelerated by the high Pt oxidation due to the long OCV holding time. A load cycle with both long OCV holding time and low load inhibits the Pt2+ migration into the membrane but accelerates the Pt particle growth due to electrochemical Ostwald ripening; meanwhile, a load cycle with long OCV holding time at lower RH prevents both the Pt dissolution and particle growth.

  15. A solar-powered microbial electrolysis cell with a platinum catalyst-free cathode to produce hydrogen.

    Science.gov (United States)

    Chae, Kyu-Jung; Choi, Mi-Jin; Kim, Kyoung-Yeol; Ajayi, Folusho F; Chang, In-Seop; Kim, In S

    2009-12-15

    This paper reports successful hydrogen evolution using a dye-sensitized solar cell (DSSC)-powered microbial electrolysis cell (MEC) without a Pt catalyst on the cathode, indicating a solution for the inherent drawbacks of conventional MECs, such as the need for an external bias and catalyst. DSSCs fabricated by assembling a ruthenium dye-loaded TiO(2) film and platinized FTO glass with an I(-)/I(3)(-) redox couple were demonstrated as an alternative bias (V(oc) = 0.65 V). Pt-loaded (0.3 mg Pt/cm(2)) electrodes with a Pt/C nanopowder showed relatively faster hydrogen production than the Pt-free electrodes, particularly at lower voltages. However, once the applied photovoltage exceeded a certain level (0.7 V), platinum did not have any additional effect on hydrogen evolution in the solar-powered MECs: hydrogen conversion efficiency was almost comparable for either the plain (71.3-77.0%) or Pt-loaded carbon felt (79.3-82.0%) at >0.7 V. In particular, the carbon nanopowder-coated electrode without Pt showed significantly enhanced performance compared to the plain electrode, which indicates efficient electrohydrogenesis, even without Pt by enhancing the surface area. As the applied photovoltage was increased, anodic methanogenesis decreased gradually, resulting in increasing hydrogen yield.

  16. bis-Nitrile and bis-Dialkylcyanamide Platinum(II) Complexes as Efficient Catalysts for Hydrosilylation Cross-Linking of Siloxane Polymers.

    Science.gov (United States)

    Islamova, Regina M; Dobrynin, Mikhail V; Ivanov, Daniil M; Vlasov, Andrey V; Kaganova, Elena V; Grigoryan, Galina V; Kukushkin, Vadim Yu

    2016-03-05

    cis- and trans-Isomers of the platinum(II) nitrile complexes [PtCl2(NCR)2] (R = NMe2, N(C₅H10), Ph, CH2Ph) were examined as catalysts for hydrosilylation cross-linking of vinyl-terminated polydimethylsiloxane and trimethylsilyl-terminated poly(dimethylsiloxane-co-ethylhydrosiloxane) producing high quality silicone rubbers. Among the tested platinum species the cis-complexes are much more active catalysts than their trans-congeners and for all studied platinum complexes cis-[PtCl2(NCCH2Ph)2] exhibits the best catalytic activity (room temperature, c = 1.0 × 10(-4) mol/L, τpot-life 60 min, τcuring 6 h). Although cis-[PtCl₂(NCCH2Ph)2] is less active than the widely used Karstedt's catalyst, its application for the cross-linking can be performed not only at room temperature (c = 1.0 × 10(-4) mol/L), but also, more efficiently, at 80 °C (c = 1.0 × 10(-4)-1.0 × 10(-5) mol/L) and it prevents adherence of the formed silicone rubbers to equipment. The usage of the cis- and trans-[PtCl2(NCR)2] complexes as the hydrosilylation catalysts do not require any inhibitors and, moreover, the complexes and their mixtures with vinyl- and trimethylsilyl terminated polysiloxanes are shelf-stable in air. Tested catalysts do not form colloid platinum particles after the cross-linking.

  17. Carbon-supported platinum alloy catalysts for phenol hydrogenation for making industrial chemicals

    Energy Technology Data Exchange (ETDEWEB)

    Srinivas, S.T.; Song, C.

    1999-07-01

    Phenol is available in large quantities in liquids derived from coal and biomass. Phenol hydrogenation is an industrially important reaction to produce cyclohexanone and cyclohexanol. Cyclohexane, cyclohexene and benzene are obtained as minor products in this reaction. Cyclohexanone is an important intermediate in the production of caprolactam for nylon 6 and cyclohexanol for adipic acid production. In USA, cyclohexanol and cyclohexanone are produced by benzene hydrogenation to cyclohexane over nickel or noble metal catalysts, followed by oxidation of cyclohexane to produce a mixture of cyclohexanol and cyclohexanone. Then cyclohexanol is dehydrogenated in the presence of Cu-Zn catalyst to cyclohexanone. Usually phenol hydrogenation is also carried out by using Ni catalyst in liquid phase. However, a direct single-step vapor phase hydrogenation of phenol to give cyclohexanone selectively is more advantageous in terms of energy savings and process economics, since processing is simplified and the endothermic step of cyclohexanol dehydrogenation can be avoided, as demonstrated by Montedipe and Johnson Matthey using promoted Pd/Al{sub 2}O{sub 3} catalyst. While it is not the purpose of this paper to dwell on the relative merits of these routes, it is necessary to mention that while using monometallic catalysts, generally the problem of catalyst deactivation of sintering as well as coking is frequently encountered. Addition and alloying of noble metal (e.g. Pt) with a second metal can result in a catalyst with better selectivity and activity in the reaction which is more resistant to deactivation. This paper presents the results on the single-step vapor phase hydrogenation of phenol over carbon-supported Pt-M (M=Cr, V, Zr) alloy catalysts to yield mainly cyclohexanone or cyclohexanol.

  18. Influences of Platinum Precursors and Solution Acidities on REO-Based Catalysts Performances

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Important effects exist between precious metals and rare earths oxides in three-way catalyst, especially the coordinated effects. These effects were studied by using H2PtCl6, Pt(NH3)2(NO2)2 and Pt(OH)2(C2H5ONH2)2 as Pt precursors, and the mixed oxide of (Ce-Zr-La-Pr)O as base material to prepare a series of catalysts, and their performances of the catalysts were studied by TPR and CO pulse titration technologies. The results shown that Pt precursors and their solutions pH values influenced the oxygen storage capabilities, the active metal distribution degrees of the catalysts obviously, and every catalyst prepared by different precursors had an optimal pH values. It indicates that the active metals precursors and their solutions acidities have outstanding influences on the catalysts performances for the mutual effects existing between the active metals and the Rare Earth metal oxides, which results from the mate groups of the precursors and the solution acidity.

  19. Parametric study of the partial oxidation of propane over nickel and platinum based catalysts

    Science.gov (United States)

    Mukka, Mayuri

    Hydrogen production though the partial oxidation of propane over 1%Pt/CeO 2 and 1%Ni/CeO2 catalysts was studied in a fixed-bed reactor. The purpose of the experiments was to study the pathways, priority and the sequence of reactions which occur over each catalyst system. A temperature of 600°C and O2/C3H8 ratio of 1.78 was used for all the runs. The space velocity was varied by varying the flowrates (100, 200, 300, 400 sccm), and also the catalyst loadings. Seven species were found at the outlet of the reactor (C3H8, O2, H2, CO, CO2, H2O and C3H 6). All the species except H2O were analyzed quantitatively by the gas chromatograph. The following reactions can occur during the process at 600°C: total oxidation, partial oxidation, steam reforming, dry reforming, water gas shift, dehydrogenation and water formation. Of these, a Gaussian elimination process yields four independent reactions. This results in ten sets of possible independent reactions. For each set, a material balance on the six outlet compositions allows the calculation of rates of each of the four reactions in the set. Sets containing negative rates for irreversible reactions are discarded. To confirm the validity of sets containing dry reforming, steam reforming and water gas shift, these reactions were carried out over the catalysts at the experimentally determined outlet conditions for the propane partial oxidation process. For the 1%Ni/CeO2 catalyst, both dry and steam reforming reactions were favorable, but the water gas shift reaction was not favorable. The activities of the 1%Pt/CeO2 catalyst for dry reforming and steam reforming were insignificant. The water gas shift reaction was not conducted over the 1%Pt/CeO2 catalyst as no feasible set contained this reaction. These results, coupled with the effect of weight hourly space velocity, allows us to evaluate the relative importance of each reaction in each allowable set as a function of contact time. The results indicate that the pathways

  20. Preparation of highly active AlSBA-15-supported platinum catalyst for thiophene hydrodesulfurization

    OpenAIRE

    KANDA, Yasuharu; AIZAWA, Tomohiro; Kobayashi, Takao; UEMICHI, Yoshio; NAMBA, Seitaro; SUGIOKA, Masatoshi

    2007-01-01

    The catalytic activities of various noble metals (Pt, Pd, Rh, and Ru) supported on siliceous SBA-15 and Al-containing SBA-15 (AlSBA-15) for hydrodesulfurization (HDS) of thiophene at 350 C were investigated. AlSBA-15 was prepared by a grafting method using aluminum isopropoxide (Al(OC3H7)3) hexane solution. The HDS activity of Pt/AlSBA-15 catalyst was the highest among those of various supported noble metal catalysts, and this activity was higher than that of commercial CoMo/Al2O3 HDS catalys...

  1. Effects of tungsten oxide on the activity and thermal stability of a sulfate-derived titania supported platinum catalyst for propane oxidation

    Institute of Scientific and Technical Information of China (English)

    Xiaodong Wu; Zhou Zhou; Duan Weng; Bin Wang

    2012-01-01

    A Pt/WO3/TiO2 catalyst for propane oxidation was prepared by a stepwise wet impregnation method,and was aged at 800℃ for 5 hr.Compared to the sulfate-derived titania supported catalyst,the introduction of tungsten oxide as stable Brφnsted acid sites led to the formation of more metallic platinum active sites at the Pt/WO3 interface.The dissociation of surface intermediates for propane oxidation was promoted on the WO3-modified catalyst.This,as well as the inhibition effects of tungsten oxide on the sintering of anatase and the phase transformation to rutile,resulting in a high activity and thermal stability for the Pt/WO3/TiO2 catalyst.

  2. Treatment of ammonia by catalytic wet oxidation process over platinum-rhodium bimetallic catalyst in a trickle-bed reactor: effect of pH.

    Science.gov (United States)

    Hung, Chang-Mao; Lin, Wei-Bang; Ho, Ching-Lin; Shen, Yun-Hwei; Hsia, Shao-Yi

    2010-08-01

    This work adopted aqueous solutions of ammonia for use in catalytic liquid-phase reduction in a trickle-bed reactor with a platinum-rhodium bimetallic catalyst, prepared by the co-precipitation of chloroplatinic acid (H2PtCl6) and rhodium nitrate [Rh(NO3)3]. The experimental results demonstrated that a minimal amount of ammonia was removed from the solution by wet oxidation in the absence of any catalyst, while approximately 97.0% of the ammonia was removed by wet oxidation over the platinum-rhodium bimetallic catalyst at 230 degrees C with an oxygen partial pressure of 2.0 MPa. The oxidation of ammonia has been studied as a function of pH, and the main reaction products were determined. A synergistic effect is manifest in the platinum-rhodium bimetallic structure, in which the material has the greatest capacity to reduce ammonia. The reaction pathway linked the oxidizing ammonia to nitric oxide, nitrogen, and water.

  3. METHYLENE BLUE MINERALISATION BY ELECTROCHEMICAL PROCESS MEDIATED BY COBALT CATALYST ON PLATINUM ELECTRODES

    Directory of Open Access Journals (Sweden)

    Ouarda BRAHMIA

    2015-12-01

    Full Text Available In this study, the electrochemical decolorization of the Methylene Blue dye on Platinum electrodes was assessed. Direct oxidation results demonstrate a partial pollutant degradation reaching a maximum of 64 %. However, the addition of a small amount of a redox mediator Co2+/3+ is efficiently able to electrocatalyse the Methylene blue oxidation by shortening significantly the treatment time and enhancing clearly the dye decolorization rate. Nearly complete decolorization was achieved (92 % in 1h 45min. The most striking results achieved within the cyclic voltammetry study demonstrate undoubtedly the pollutant mineralisation. Electrochemical experiments were performed using the spectrophotometric method, which is very convenient, easy and allows monitoring the spectral changes as well as the determination of the dye concentration during the process. The kinetics data show a first-order indirect oxidation kinetics. A mechanism was proposed to explain the different phenomenon during the electrochemical process.

  4. Modeling Low-Platinum-Loading Effects in Fuel-Cell Catalyst Layers

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Wonseok; Weber, Adam Z.

    2011-01-20

    The cathode catalyst layer within a proton-exchange-membrane fuel cell is the most complex and critical, yet least understood, layer within the cell. The exact method and equations for modeling this layer are still being revised and will be discussed in this paper, including a 0.8 reaction order, existence of Pt oxides, possible non-isopotential agglomerates, and the impact of a film resistance towards oxygen transport. While the former assumptions are relatively straightforward to understand and implement, the latter film resistance is shown to be critically important in explaining increased mass-transport limitations with low Pt-loading catalyst layers. Model results demonstrate agreement with experimental data that the increased oxygen flux and/or diffusion pathway through the film can substantially decrease performance. Also, some scale-up concepts from the agglomerate scale to the more macroscopic porous-electrode scale are discussed and the resulting optimization scenarios investigated.

  5. Characterization of the surfaces of platinum/tin oxide based catalysts by Fourier transform spectroscopy (FTIR)

    Science.gov (United States)

    Keiser, Joseph T.

    1989-01-01

    The Laser Atmospheric Wind Sounder (LAWS) Program has as one of its goals the development of a satellite based carbon dioxide laser for making wind velocity measurements. The specifications for this laser include the requirement that the laser operate at a repetition rate of 10 Hertz continuously for three years. Earth-based carbon dioxide lasers can operate for only a short time on a single charge of gas because the lasing action causes the CO2 to break down into CO and O2. Therefore, earth-based CO2 lasers are generally operated in a flow through mode in which the spent gas is continually exhausted and fresh gas is continually added. For a satellite based system, however, a recirculation system is desired because it is not practical to send up extra tanks of CO2. A catalyst which could enable a recirculating CO2 laser to function continuously for three years needs to be developed. In the development of a catalyst system there are many variables. Obviously, not all possible formulations can be tested for three years, therefore, an accurate model which is based on the reaction mechanism is needed. The construction of a multistep reaction mechanism is similar to the construction of a jigsaw puzzle. Different techniques each supply a piece of the puzzle and the researcher must put the pieces together. Transmission infrared spectroscopy was shown to be very useful in supplying some of the information needed to elucidate reaction mechanisms. The purpose was to see what kind of information might be obtained about the NASA catalyst using infrared absorption spectroscopy. Approximately 200 infrared spectra of the prototype Pt/tin oxide catalyst and its precursor components are observed under a variety of different conditions. The most significant observations are summarized.

  6. Synergistic effect between Sn and K promoters on supported platinum catalyst for isobutane dehydrogenation

    Institute of Scientific and Technical Information of China (English)

    Yiwei Zhang; Yuming Zhou; Lihui Wan; Mengwei Xue; Yongzheng Duan; Xuan Liu

    2011-01-01

    Catalytic dehydrogenation of isobutane has recently received considerable attention because of the increasing demand for isobutene.In this study,the synergistic effect between Sn and K on PtSnK/γ-Al2O3 catalysts has been investigated by changing the content of Sn.It was found that with the presence of potassium,suitable addition of Sn could not only increase the metal dispersion,but also reduce the catalyst acidity.In these cases,the synergistic effect could also strengthen the interactions between the metal and support,which resulted in an increase in both catalytic activity and stability.In our experiments,Pt-0.6SnK/Al catalyst exhibited the lowest deactivation rate (12.4%) and showed a selectivity to isobutene higher than 94% at the isobutane conversion of about 45.3% after running the reaction for 6 h.However,with the excessive loading of Sn,surface property of active sites and the interactions between metal and support were changed.As a result,the initial optimal ratio between the metallic function and acid function would be destroyed,which was disadvantageous to the reaction.

  7. Beneficial effects of rhodium and tin oxide on carbon supported platinum catalysts for ethanol electrooxidation

    Science.gov (United States)

    Soares, Layciane A.; Morais, Claudia; Napporn, Teko W.; Kokoh, K. Boniface; Olivi, Paulo

    2016-05-01

    This work investigates ethanol electrooxidation on Pt/C, PtxRhy/C, Pt-SnO2/C, and PtxRhy-SnO2/C catalysts synthesized by the Pechini and microwave-assisted polyol methods. The catalysts are characterized by energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), and X-ray diffraction (XRD) techniques. The electrochemical properties of these electrode materials are examined by cyclic voltammetry and chronoamperometry experiments in acid medium. The products obtained during ethanol electrolysis are identified by high performance liquid chromatography (HPLC). The adsorbed intermediates are evaluated by an in situ reflectance Infrared Spectroscopy technique combined with cyclic voltammetry. Catalysts performance in a direct ethanol fuel cell (DEFC) is also assessed. The electrical performance of the electrocatalysts in a single DEFC at 80 °C decreases in the following order Pt70Rh30SnO2 > Pt80Rh20SnO2 > Pt60Rh40SnO2 ∼ PtSnO2 > PtxRhy ∼ Pt, showing that the presence of SnO2 enhances the ability of Pt to catalyze ethanol electrooxidation.

  8. Platinum(0-1,3-divinyl-1,1,3,3-tetramethyldisiloxane Complex as a Pt Source for Pt/SnO2 Catalyst

    Directory of Open Access Journals (Sweden)

    Agnieszka Martyla

    2014-01-01

    Full Text Available This paper presents new preparation method of Pt/SnO2, an important catalytic system. Besides of its application as a heterogenic industrial catalyst, it is also used as a catalyst in electrochemical processes, especially in fuel cells. Platinum is commonly used as an anode catalyst in low temperature fuel cells, fuelled with alcohols of low molecular weight such as methanol. Platinum(0-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex was used as a precursor of metallic phase. The aim of the research was to obtain a highly active in electrochemical system Pt/SnO2 catalyst with low metal load. Considering small size of Pt crystallites, it should result in high activity of Pt/SnO2 system. The presented method of SnO2 synthesis allows for obtaining support consisting of nanoparticles. The effect of the thermal treatment on activity of Pt/SnO2 gel was demonstrated. The system properties were investigated using TEM, FTIR (ATR, and XRD techniques to describe its thermal structural evolution. The results showed two electrocatalytical activity peaks for drying at a temperature of 430 K and above 650 K.

  9. Soluble Platinum Nanoparticles Ligated by Long-Chain N-Heterocyclic Carbenes as Catalysts.

    Science.gov (United States)

    Martínez-Prieto, Luis M; Rakers, Lena; López-Vinasco, Angela M; Cano, Israel; Coppel, Yannick; Philippot, Karine; Glorius, Frank; Chaudret, Bruno; van Leeuwen, Piet W N M

    2017-09-18

    Soluble platinum nanoparticles (Pt NPs) ligated by two different long-chain N-heterocyclic carbenes (LC-IPr and LC-IMe) were synthesized and fully characterized by TEM, high-resolution TEM, wide-angle X-ray scattering (WAXS), X-ray photoelectron spectroscopy (XPS), and solution NMR. The surface chemistry of these NPs (Pt@LC-IPr and Pt@LC-IMe) was investigated by FT-IR and solid state NMR using CO as a probe molecule. A clear influence of the bulkiness of the N-substituents on the size, surface state, and catalytic activity of these Pt NPs was observed. While Pt@LC-IMe showed no activity in the hydroboration of phenylacetylene, Pt@LC-IPr revealed good selectivity for the trans-isomer, which may be supported by a homogeneous species. This is the first example of hydroboration of acetylenes catalyzed by non-supported Pt NPs. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Platinum nanoparticles–manganese oxide nanorods as novel binary catalysts for formic acid oxidation

    Directory of Open Access Journals (Sweden)

    Mohamed S. El-Deab

    2012-01-01

    Full Text Available The current study proposes a novel binary catalyst system (composed of metal/metal oxide nanoparticles as a promising electrocatalyst in formic acid oxidation. The electro-catalytic oxidation of formic acid is carried out with binary catalysts of Pt nanoparticles (nano-Pt and manganese oxide nanorods (nano-MnOx electrodeposited onto glassy carbon (GC electrodes. Cyclic voltammetric (CV measurements showed that unmodified GC and nano-MnOx/GC electrodes have no catalytic activity. While two oxidation peaks were observed at nano-Pt/GC electrode at ca. 0.2 and 0.55 V (corresponding to the direct oxidation of formic acid and the oxidation of the poisoning CO intermediate, respectively. The combined use of nano-MnOx and nano-Pt results in superb enhancement of the direct oxidation pathway. Nano-MnOx is shown to facilitate the oxidation of CO (to CO2 by providing oxygen at low over-potential. This leads to retrieval of Pt active sites necessary for the direct oxidation of formic acid. The higher catalytic activity of nano-MnOx/nano-Pt/GC electrode (with Pt firstly deposited compared to its mirror image electrode (i.e., with MnOx firstly deposited, nano-Pt/nano-MnOx/GC reveals that the order of the electrodeposition is an essential parameter.

  11. Stabilizing a Platinum1 Single-Atom Catalyst on Supported Phosphomolybdic Acid without Compromising Hydrogenation Activity.

    Science.gov (United States)

    Zhang, Bin; Asakura, Hiroyuki; Zhang, Jia; Zhang, Jiaguang; De, Sudipta; Yan, Ning

    2016-07-11

    In coordination chemistry, catalytically active metal complexes in a zero- or low-valent state often adopt four-coordinate square-planar or tetrahedral geometry. By applying this principle, we have developed a stable Pt1 single-atom catalyst with a high Pt loading (close to 1 wt %) on phosphomolybdic acid(PMA)-modified active carbon. This was achieved by anchoring Pt on the four-fold hollow sites on PMA. Each Pt atom is stabilized by four oxygen atoms in a distorted square-planar geometry, with Pt slightly protruding from the oxygen planar surface. Pt is positively charged, absorbs hydrogen easily, and exhibits excellent performance in the hydrogenation of nitrobenzene and cyclohexanone. It is likely that the system described here can be extended to a number of stable SACs with superior catalytic activities.

  12. Selective production of methane from aqueous biocarbohydrate streams over a mixture of platinum and ruthenium catalysts.

    Science.gov (United States)

    Neira D'Angelo, Maria Fernanda; Ordomsky, Vitaly; van der Schaaf, John; Schouten, Jaap C; Nijhuis, Tjeerd Alexander

    2014-02-01

    A one-step process for the selective production of methane from low-value aqueous carbohydrate streams is proposed. Sorbitol, used herein as a model compound, is fully converted to methane, CO2 , and a minor amount of H2 by using a physical mixture of Pt and Ru (1:5 in mass basis) at 220 °C and 35 bar. This conversion is the result of hydrogenolysis of part of the sorbitol over Ru and the in situ production of H2 through the aqueous-phase reforming of the remaining carbohydrate over Pt. A synergistic effect of the combination of these two catalysts results in the rapid and highly selective conversion of the carbohydrate to methane. This process offers the possibility of upgrading a low-value carbohydrate stream into a valuable fuel with no addition of H2. Exergy analysis reveals that nearly 80 % of the exergy of the reactant is recovered as methane.

  13. Stabilization of supported platinum nanoparticles on gamma-alumina catalysts by addition of tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Contreras, Jose L., E-mail: jlcl@correo.azc.uam.m [Universidad Autonoma Metropolitana-Azcapotzalco. Energia, CBI, Av. Sn. Pablo 180, Col. Reynosa, 02200, Mexico, D.F. (Mexico); Universidad Autonoma Metropolitana-Iztapalapa Depto. Ingenieria de Procesos e Hidraulica, A.P. 55-534, 09340 Mexico, D.F. (Mexico); Fuentes, Gustavo A. [Universidad Autonoma Metropolitana-Iztapalapa Depto. Ingenieria de Procesos e Hidraulica, A.P. 55-534, 09340 Mexico, D.F. (Mexico); Zeifert, Beatriz; Salmones, Jose [Instituto Politecnico Nacional, ESIQIE, Av. IPN s/n Edif. 8, UPALM, Mexico, D.F. 07738 (Mexico)

    2009-08-26

    The thermal stabilization of Al{sub 2}O{sub 3} using W{sup 6+} ions has been found useful to the synthesis of Pt/Al{sub 2}O{sub 3} catalysts. The simultaneous and sequential methods were used to study the effect of W{sup 6+} upon Pt/gamma-Al{sub 2}O{sub 3} reducibility, Pt dispersion, and benzene hydrogenation. The W/Pt atomic ratios were from 0.49 to 12.4. In the first method we found that the W{sup 6+} ions delayed reduction of a fraction of Pt{sup 4+} atoms beyond 773 K. At the same time, W{sup 6+}inhibited sintering of the metallic crystallites once they were formed on the surface. For the sequential sample with a W/Pt atomic ratio of 3.28 W{sup 6+} did not inhibit the H{sub 2} reduction of Pt oxides even below of 773 K, the Pt oxides were reduced completely. After reduction at 1073 K, sequential samples impregnating Pt on WO{sub x}-gamma-Al{sub 2}O{sub 3} were more active and stable during benzene hydrogenation. TOF of the reaction did not change when the W/Pt atomic ratio, preparation technique and reduction temperature changed and its value was of 1.1 s{sup -1}. W{sup 6+} ions promoted high thermal stability of Pt crystallites when sequential catalysts were reduced at 1073 K and decreased their Lewis acidity.

  14. Liquid-phase processing of fast pyrolysis bio-oil using platinum/HZSM-5 catalyst

    Science.gov (United States)

    Santos, Bjorn Sanchez

    Recent developments in converting biomass to bio-chemicals and liquid fuels provide a promising sight to an emerging biofuels industry. Biomass can be converted to energy via thermochemical and biochemical pathways. Thermal degradation processes include liquefaction, gasification, and pyrolysis. Among these biomass technologies, pyrolysis (i.e. a thermochemical conversion process of any organic material in the absence of oxygen) has gained more attention because of its simplicity in design, construction and operation. This research study focuses on comparative assessment of two types of pyrolysis processes and catalytic upgrading of bio-oil for production of transportation fuel intermediates. Slow and fast pyrolysis processes were compared for their respective product yields and properties. Slow pyrolysis bio-oil displayed fossil fuel-like properties, although low yields limit the process making it uneconomically feasible. Fast pyrolysis, on the other hand, show high yields but produces relatively less quality bio-oil. Catalytic transformation of the high-boiling fraction (HBF) of the crude bio-oil from fast pyrolysis was therefore evaluated by performing liquid-phase reactions at moderate temperatures using Pt/HZSM-5 catalyst. High yields of upgraded bio-oils along with improved heating values and reduced oxygen contents were obtained at a reaction temperature of 200°C and ethanol/HBF ratio of 3:1. Better quality, however, was observed at 240 °C even though reaction temperature has no significant effect on coke deposition. The addition of ethanol in the feed has greatly attenuated coke deposition in the catalyst. Major reactions observed are esterification, catalytic cracking, and reforming. Overall mass and energy balances in the conversion of energy sorghum biomass to produce a liquid fuel intermediate obtained sixteen percent (16 wt.%) of the biomass ending up as liquid fuel intermediate, while containing 26% of its initial energy.

  15. Oxygen Reduction on Platinum

    DEFF Research Database (Denmark)

    Nesselberger, Markus

    This thesis investigates the electro reduction of oxygen on platinum nanoparticles, which serve as catalyst in low temperature fuel cells. Kinetic studies on model catalysts as well as commercially used systems are presented in order to investigate the particle size effect, the particle proximity...... carbon (HSAC) supported Pt nanoparticle (Pt/C) catalysts (of various size between 1 and 5 nm). The difference in SA between the individual Pt/C catalysts (1 to 5 nm) is very small and within the error of the measurements. The factor four of loss in SA when comparing platinum bulk and Pt/C can largely...

  16. H{sub 2}/air alkaline membrane fuel cell performance and durability, using novel ionomer and non-platinum group metal cathode catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Piana, Michele; Boccia, Massimiliano; Filpi, Antonio; Flammia, Elisa; Miller, Hamish A.; Orsini, Marco; Salusti, Francesca; Santiccioli, Serena [Acta S.p.A., Fuel cell Technology, via di Lavoria 56/G, I-56042 Crespina (PI) (Italy); Ciardelli, Francesco; Pucci, Andrea [Department of Chemistry and Industrial Chemistry, University of Pisa, Via, Risorgimento 35, I-56126 Pisa (Italy)

    2010-09-15

    The development of H{sub 2}/air alkaline membrane fuel cells (AMFCs) enables the use of non-platinum group metal (PGM) catalysts which are intrinsically stable and have an activity similar to platinum in alkaline media for the oxygen reduction reaction (ORR). As opposed to PEMFCs, the research and development of these types of catalysts for AMFC has had little attention and even less has been given to the development of alkaline membranes and ionomers. Acta S.p.A. has developed recently new non-PGM ORR catalysts with activity higher than Pt in alkaline media. More importantly, a new anionic ionomer derived from cheap starting materials with optimum performance has been produced. In this paper we demonstrate the use of this new ionomer in H{sub 2}/air AMFCs showing the first polarization and durability data, with current densities higher than those recently reported in the literature. Furthermore, we report the effect of CO{sub 2} on AMFC performance, showing the possibility of use of such alkaline devices not only in outer-space applications, but also with atmospheric air for large scale devices. (author)

  17. Sum Frequency Generation Vibrational Spectroscopy of Colloidal Platinum Nanoparticle Catalysts: Disordering versus Removal of Organic Capping

    KAUST Repository

    Krier, James M.

    2012-08-23

    Recent work with nanoparticle catalysts shows that size and shape control on the nanometer scale influences reaction rate and selectivity. Sum frequency generation (SFG) vibrational spectroscopy is a powerful tool for studying heterogeneous catalysis because it enables the observation of surface intermediates during catalytic reactions. To control the size and shape of catalytic nanoparticles, an organic ligand was used as a capping agent to stabilize nanoparticles during synthesis. However, the presence of an organic capping agent presents two major challenges in SFG and catalytic reaction studies: it blocks a significant fraction of active surface sites and produces a strong signal that prevents the detection of reaction intermediates with SFG. Two methods for cleaning Pt nanoparticles capped with poly (vinylpyrrolidone) (PVP) are examined in this study: solvent cleaning and UV cleaning. Solvent cleaning leaves more PVP intact and relies on disordering with hydrogen gas to reduce the SFG signal of PVP. In contrast, UV cleaning depends on nearly complete removal of PVP to reduce SFG signal. Both UV and solvent cleaning enable the detection of reaction intermediates by SFG. However, solvent cleaning also yields nanoparticles that are stable under reaction conditions, whereas UV cleaning results in aggregation during reaction. The results of this study indicate that solvent cleaning is more advantageous for studying the effects of nanoparticle size and shape on catalytic selectivity by SFG vibrational spectroscopy. © 2012 American Chemical Society.

  18. Mechanistic studies of NO{sub x} reduction reactions under oxidative atmosphere on alumina supported 0.2wt% platinum catalyst treated under microwave. Part 2

    Energy Technology Data Exchange (ETDEWEB)

    Ringler, Sandrine; Girard, Paule; Maire, Gilbert; Garin, Francois [Laboratoire d`Etudes de la Reactivite Catalytique, des Surfaces et Interfaces (LERCSI), UMR 7515 du CNRS - ECPM, Universite Louis Pasteur - Institut Le Bel 4, rue Blaise Pascal 67, 070 Strasbourg Cedex (France); Hilaire, Stephanie; Roussy, Georges [Laboratoire de Spectroscopie et des Techniques Micro-Ondes LSTM, Universite de Nancy I, BP 239 54506, Vandoeuvre-les-Nancy Cedex (France)

    1999-03-08

    Reduction of nitrogen oxides under oxidative atmosphere is a very extensively studied reaction, but it is still very difficult to understand and to follow the various pathways of the reaction. Two alumina supported 0.2wt% platinum catalysts, reduced by hydrogen in an oven heated either by microwave irradiations or by Joule effect, with different metal dispersion of 60% and 90%, respectively, were studied. By the use of labelled compounds we were able to show the presence of an exchange reaction between 15N16O and 15N18O which occurred on both catalysts. It means that [15N16O18O] is the intermediate species. Such product, 15N18O, is less formed on the microwave catalyst `MW` than on the classical one `CT`. Experiments were performed at 22 and 550Torr, between 150C and 250C. Near atmospheric pressure, `MW` catalyst gives higher initial rates for 15N{sub 2} formation than the `CT` catalysts. At low temperature, the nitrogen selectivity is higher on `MW` catalyst than on the other catalyst. From the apparent activation energy values, one may deduce that several mechanisms are responsible for the 15N{sub 2} formation depending on the reaction temperature and the catalyst used. On the 0.2% Pt/Al{sub 2}O{sub 3} `CT` catalyst, an additive process between propene and 15NO takes place at low temperature giving nitroso and oxime intermediate species. At high temperature, a partial oxidation of propene occurs, giving a ketone, before the 15NO reduction to 15N{sub 2}. With this catalyst only two sites with different activity are involved. On the 0.2% Pt/Al{sub 2}O{sub 3} `MW` catalyst the reactants are seated on three sites with different activity. This particularity reinforce the proposals concerning the `MW` catalyst which may exhibit particular shapes for the aggregates having different crystallographic orientations. What is surprising, for this `MW` catalyst, is the fact that we already observed a specific reactivity under reductive atmosphere in reforming reactions and now

  19. Mechanistic Insights into the Structure-Dependent Selectivity of Catalytic Furfural Conversion on Platinum Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Qiuxia; Wang, Jianguo; Wang, Yang-Gang; Mei, Donghai

    2015-11-01

    The effects of structure and size on the selectivity of catalytic furfural conversion over supported Pt catalysts in the presence of hydrogen have been studied using first principles density functional theory (DFT) calculations and microkinetic modeling. Four Pt model systems, i.e., periodic Pt(111), Pt(211) surfaces, as well as small nanoclusters (Pt13 and Pt55) are chosen to represent the terrace, step, and corner sites of Pt nanoparticles. Our DFT results show that the reaction routes for furfural hydrogenation and decarbonylation are strongly dependent on the type of reactive sites, which lead to the different selectivity. On the basis of the size-dependent site distribution rule, we correlate the site distributions as a function of the Pt particle size. Our microkinetic results indicate the critical particle size that controls the furfural selectivity is about 1.0 nm, which is in good agreement with the reported experimental value under reaction conditions. This work was supported by National Basic Research Program of China (973 Program) (2013CB733501) and the National Natural Science Foundation of China (NSFC-21306169, 21176221, 21136001, 21101137 and 91334103). This work was also partially supported by the US Department of Energy (DOE), the Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle. Computing time was granted by the grand challenge of computational catalysis of the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL). EMSL is a national scientific user facility located at Pacific Northwest National Laboratory (PNNL) and sponsored by DOE’s Office of Biological and Environmental Research.

  20. Electrochemical oxidation of carbon monoxide: from platinum single crystals to low temperature fuel cells catalysts. Part I: Carbon monoxide oxidation onto low index platinum single crystals

    Directory of Open Access Journals (Sweden)

    PHILIP N. ROSS JR

    2001-12-01

    Full Text Available The electrochemical oxidation of carbon monoxide and the interfacial structure of the CO adlayer (COads on platinum low index single crystals, Pt(111, Pt(100 and two reconstruction of Pt(110, were examined using the rotation disk electrode method in combination with the in situ surface X-ray diffraction scattering technique. The mechanism of CO oxidation is discussed on the basis of the findings that, depending on the potential, two energetic states of COads exist on the platinum surfaces. Thus, at lower potentials, weakly bonded states (COads,w and at higher potentials strongly bonded states (COads,s are formed. The mechanism of the oxidation of hydrogen-carbon monoxide mixtures is also proposed.

  1. Catalyst layers for PEMFC manufactured by flexography printing process: performances and structure

    Energy Technology Data Exchange (ETDEWEB)

    Bois, C.; Blayo, A.; Chaussy, D. [Laboratory of Pulp and Paper Science and Graphic Arts (LGP2) (UMR 5518 CNRS-CTP-INPG), Grenoble Institute of Technology (INP Grenoble - PAGORA), St Martin d' Heres (France); Vincent, R.; Mercier, A.G.; Nayoze, C. [Commissariat a l' Energie Atomique et aux Energies Alternatives (CEA)/DRT/LITEN, Laboratoire des Composants Piles a Combustible, Electrolyse et Modelisation (LCPEM), Grenoble (France)

    2012-04-15

    This article focuses on the potential of a classic printing process, flexography, for manufacturing proton exchange membrane fuel cells (PEMFCs). Gas diffusion electrodes (GDEs) are produced by deposition of a water-based catalyst ink on a gas diffusion layer (GDL). The affinity between the ink and the GDL is quantified. Thus, the strong hydrophobic character of the GDL and the poor printability of the ink are demonstrated. However, the permeability of the GDL allows developing a multilayer protocol. The deposition by superimposition of ink layers allows control of the platinum amount and to obtain catalyst layers with a similar density of platinum nanoparticles to coated samples. At similar platinum loading, flexography and coating made catalyst layers offer similar performances, which confirm the relevance of flexography in catalyst layer manufacturing. Structural characterization shows that manufacturing protocol and process has an influence on catalyst layer microstructure. However, catalyst layer cracking and aggregation are increased with the catalyst layer thickness, diminishing the charge and gas diffusion into the catalyst layer resulting in performance degradation. Consequently, a catalyst layer with 0.46 mgPt cm{sup -2} reaches similar performances to catalyst layers with 1.77 and 2.01 times less platinum loading. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Highly active carbon supported palladium catalysts decorated by a trace amount of platinum by an in-situ galvanic displacement reaction for formic acid oxidation

    Science.gov (United States)

    Li, Zuopeng; Li, Muwu; Han, Mingjia; Wu, Xin; Guo, Yong; Zeng, Jianhuang; Li, Yuexia; Liao, Shijun

    2015-03-01

    Aimed at reducing platinum usage and improved catalytic activity for formic acid oxidation, a series of Pt decorated Pd/C catalysts are prepared by an in-situ galvanic displacement reaction between freshly prepared Pd/C ink and H2PtCl6 in an aqueous solution. The catalysts with 4 nm particle sizes and 20 wt.% loadings have been characterized by transmission electron microscopy, thermogravimetric analysis and X-ray photoelectron spectroscopy (XPS). The electrochemical evaluations by cyclic voltammetry are conducted to test out the CO tolerance and catalytic activities. In addition to XPS analysis, a theoretical calculation has been attempted the first time to find out the surface Pd/Pt molar ratios. The decay rate of the catalysts has been evaluated by the percentage of the forward/backward peak current retained using the value at the 20th cycle divided by that in the first cycle. Compared with a Pd/C benchmark, all Pt decorated Pd/C register enhanced activity while the cost remains virtually unchanged. The optimized catalyst is found to have a Pd/Pt molar ratio of 75:1 but with 2.5 times activity relative to that of Pd/C.

  3. A Platinum Monolayer Core-Shell Catalyst with a Ternary Alloy Nanoparticle Core and Enhanced Stability for the Oxygen Reduction Reaction

    Directory of Open Access Journals (Sweden)

    Haoxiong Nan

    2015-01-01

    Full Text Available We synthesize a platinum monolayer core-shell catalyst with a ternary alloy nanoparticle core of Pd, Ir, and Ni. A Pt monolayer is deposited on carbon-supported PdIrNi nanoparticles using an underpotential deposition method, in which a copper monolayer is applied to the ternary nanoparticles; this is followed by the galvanic displacement of Cu with Pt to generate a Pt monolayer on the surface of the core. The core-shell Pd1Ir1Ni2@Pt/C catalyst exhibits excellent oxygen reduction reaction activity, yielding a mass activity significantly higher than that of Pt monolayer catalysts containing PdIr or PdNi nanoparticles as cores and four times higher than that of a commercial Pt/C electrocatalyst. In 0.1 M HClO4, the half-wave potential reaches 0.91 V, about 30 mV higher than that of Pt/C. We verify the structure and composition of the carbon-supported PdIrNi nanoparticles using X-ray powder diffraction, X-ray photoelectron spectroscopy, thermogravimetry, transmission electron microscopy, and energy dispersive X-ray spectrometry, and we perform a stability test that confirms the excellent stability of our core-shell catalyst. We suggest that the porous structure resulting from the dissolution of Ni in the alloy nanoparticles may be the main reason for the catalyst’s enhanced performance.

  4. The pH-dependent release of platinum group elements (PGEs) from gasoline and diesel fuel catalysts: Implication for weathering in soils.

    Science.gov (United States)

    Suchá, Veronika; Mihaljevič, Martin; Ettler, Vojtěch; Strnad, Ladislav

    2016-04-15

    Powdered samples of new and old gasoline catalysts (Pt, Pd, Rh) and new and old diesel (Pt) catalysts were subjected to a pH-static leaching procedure (pH 2-9) coupled with thermodynamic modeling using PHREEQC-3 to verify the release and mobility of PGEs (platinum group elements). PGEs were released under acidic conditions, mostly exhibiting L-shaped leaching patterns: diesel old: 5.47, 0.005, 0.02; diesel new: 68.5, 0.23, 0.11; gasoline old: 0.1, 11.8, 4.79; gasoline new 2.6, 25.2, 35.9 in mg kg(-1) for Pt, Pd and Rh, respectively. Only the new diesel catalyst had a strikingly different leaching pattern with elevated concentrations at pH 4, probably influenced by the dissolution of the catalyst carrier and washcoat. The pH-static experiment coupled with thermodynamic modeling was found to be an effective instrument for understanding the leaching behavior of PGEs under various environmental conditions, and indicated that charged Pt and Rh species may be adsorbed on the negatively charged surface of kaolinite or Mn oxides in the soil system, whereas uncharged Pd and Rh species may remain mobile in soil solutions.

  5. Process for applying a catalytically active coating, particularly one containing platinum and/or palladium on catalyst carrier. Verfahren zum Aufbringen eines katalytisch aktiven, insbesondere Platin und/oder Palladium enthaltenden Ueberzugs auf Katalysatortraeger

    Energy Technology Data Exchange (ETDEWEB)

    Bozon, A.; Lakatos, E.; Koberstein, E.; Pletka, H.D.; Voelker, H.

    1981-09-03

    The invention concerns an improved process for applying a platinum and/or palladium, coating or films, possibly one containing other platinum group metals and/or nonprecious metals, by means of solutions of the metal compounds on the outer surface of porous catalyst carriers, i.e. those having a large surface. It was found that aquaeous solutions of ammonium chloride can be used to advantage to pre-charge the catalyst carrier, instead of the previously used organic solvents, where the saturation of the catalyst carrier must not be exceeded. After impregnation with an aquaeous solution of the catalytically active elements, the liquid is finally removed by heating. In the engine exhaust gas test, the catalysts according to the invention proved superior to the conventional ones.

  6. Catalytic wet oxidation of aqueous methylamine: comparative study on the catalytic performance of platinum-ruthenium, platinum, and ruthenium catalysts supported on titania.

    Science.gov (United States)

    Song, Aiying; Lu, Gongxuan

    2015-01-01

    Promotion of the dispersion of Ru species supported on TiO2 was achieved by introduction of Pt component and the role of Pt in enhancing the catalytic performances of Pt-Ru was investigated with catalytic wet air oxidation of methylamine used as a probing reaction. It was found that Pt-Ru/TiO2 displayed a much better catalytic performance compared with Pt/TiO2 and Ru/TiO2 catalysts due to having the highest dispersion of active species. Both high total organic carbon conversion and nitrogen selectivity (∼100%) over Pt-Ru/TiO2 catalyst were achieved at low temperature (200 °C). X-ray photoelectron spectroscopy characterization indicated that there were strong interactions between metal particles and the support, which may increase the catalytic performance of catalysts.

  7. Photocatalytic oxidation of NO{sub x} over TiO{sub 2}/HZSM-5 catalysts in the presence of water vapor: Effect of hydrophobicity of zeolites

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Gaofei [The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, College of Environmental Science and Engineering, South China University of Technology, Guangzhou 510006 (China); Hu, Yun, E-mail: huyun@scut.edu.cn [The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, College of Environmental Science and Engineering, South China University of Technology, Guangzhou 510006 (China); Jiang, Shumei; Wei, Chaohai [The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, College of Environmental Science and Engineering, South China University of Technology, Guangzhou 510006 (China)

    2012-07-15

    Highlights: Black-Right-Pointing-Pointer The photooxidation of NO{sub x} over TiO{sub 2}/HZSM-5 was tested in the presence of water vapor. Black-Right-Pointing-Pointer TiO{sub 2}/HZSM-5 exhibited higher NO conversion and lower NO{sub 2} formation than pure TiO{sub 2}. Black-Right-Pointing-Pointer Water vapor related to relative humidity and water pre-adsorption was effect factor. Black-Right-Pointing-Pointer TiO{sub 2} hybridized with hydrophobic HZSM-5 zeolite retained high reactivity. Black-Right-Pointing-Pointer Photocatalytic reactivity of TiO{sub 2}/HZSM-5 depended on hydrophobicity of zeolites. - Abstract: TiO{sub 2} hybridized with HZSM-5 zeolites photocatalysts were prepared by a simple solid state dispersion method. The physicochemical properties of the catalysts were characterized by X-ray diffraction, UV-vis diffuse reflectance and FT-IR spectroscopy. The photocatalytic oxidation of NO{sub x} over TiO{sub 2}/HZSM-5 having different Si/Al ratios was carried out under various levels of humidity and different pre-adsorption times in dark. The TiO{sub 2}/HZSM-5 composite catalysts exhibited higher NO conversion and lower NO{sub 2} formation than pure TiO{sub 2}. Pre-adsorption with water vapor and the high humidity during the photoreaction were harmful to the reactivity of TiO{sub 2} hybridized with hydrophilic HZSM-5 zeolite. However, the photocatalytic reactivity of TiO{sub 2} hybridized with hydrophobic zeolite varied little with increase in humidity. The results indicated that the high photocatalytic reactivity of TiO{sub 2}/HZSM-5 catalysts is largely depended on the hydrophobicity of the zeolites.

  8. Activity of platinum/carbon and palladium/carbon catalysts promoted by Ni2 P in direct ethanol fuel cells.

    Science.gov (United States)

    Li, Guoqiang; Feng, Ligang; Chang, Jinfa; Wickman, Björn; Grönbeck, Henrik; Liu, Changpeng; Xing, Wei

    2014-12-01

    Ethanol is an alternative fuel for direct alcohol fuel cells, in which the electrode materials are commonly based on Pt or Pd. Owing to the excellent promotion effect of Ni2 P that was found in methanol oxidation, we extended the catalyst system of Pt or Pd modified by Ni2 P in direct ethanol fuel cells. The Ni2 P-promoted catalysts were compared to commercial catalysts as well as to reference catalysts promoted with only Ni or only P. Among the studied catalysts, Pt/C and Pd/C modified by Ni2 P (30 wt %) showed both the highest activity and stability. Upon integration into the anode of a homemade direct ethanol fuel cell, the Pt-Ni2 P/C-30 % catalyst showed a maximum power density of 21 mW cm(-2) , which is approximately two times higher than that of a commercial Pt/C catalyst. The Pd-Ni2 P/C-30 % catalyst exhibited a maximum power density of 90 mW cm(-2) . This is approximately 1.5 times higher than that of a commercial Pd/C catalyst. The discharge stability on both two catalysts was also greatly improved over a 12 h discharge operation.

  9. 从炭载体废催化剂回收铂钯%Recovery of Palladium and Platinum from Carbon Supported Waste Catalysts

    Institute of Scientific and Technical Information of China (English)

    刘时杰

    2014-01-01

    The carbon supported catalysts, Pd/C and Pt/C, are the very important chemical catalysts. The incineration technology is the most simple method for the recovery of platinum or palladium from the waste catalysts. The processes and technologies to prevent the loss of flying-ash during burning were introduced and some examples were listed. The principle of supercritical water oxidation (SCWO) and its technical processes were discussed, and its application prospect was reviewed.%Pd/C、Pt/C是非常重要的化工催化剂。最简单的从废催化剂中回收钯或铂的方法是焚烧法。介绍了工艺过程及防止焚烧时飞扬损失的各种技术措施,列举了应用实例。探讨了超临界水氧化法(SCWO)的原理,工艺过程及处理炭载体废催化剂的应用前景。

  10. Self-Assembled Coral-like Hierarchical Architecture Constructed by NiSe2 Nanocrystals with Comparable Hydrogen-Evolution Performance of Precious Platinum Catalyst.

    Science.gov (United States)

    Yu, Bo; Wang, Xinqiang; Qi, Fei; Zheng, Binjie; He, Jiarui; Lin, Jie; Zhang, Wanli; Li, Yanrong; Chen, Yuanfu

    2017-03-01

    For the first time, self-assembled coral-like hierarchical architecture constructed by NiSe2 nanocrystals has been synthesized via a facile one-pot DMF-solvothermal method. Compared with hydrothermally synthesized NiSe2 (H-NiSe2), the DMF-solvothermally synthesized nanocrystalline NiSe2 (DNC-NiSe2) exhibits superior performance of hydrogen evolution reaction (HER): it has a very low onset overpotential of ∼136 mV (vs RHE), a very high cathode current density of 40 mA/cm(2) at ∼200 mV (vs RHE), and an excellent long-term stability; most importantly, it delivers an ultrasmall Tafel slope of 29.4 mV dec(-1), which is the lowest ever reported for NiSe2-based catalysts, and even lower than that of precious platinum (Pt) catalyst (30.8 mV dec(-1)). The superior HER performance of DNC-NiSe2 is attributed to the unique self-assembled coral-like network, which is a benefit to form abundant active sites and facilitates the charge transportation due to the inherent high conductivity of NiSe2 nanocrystals. The DNC-NiSe2 is promising to be a viable alternative to precious metal catalysts for hydrogen evolution.

  11. The influence of the hydrophobic agent, catalyst, solvent and water content on the wetting properties of the silica films prepared by one-step sol–gel method

    Energy Technology Data Exchange (ETDEWEB)

    Ramezani, Maedeh, E-mail: m.ramezani@merc.ac.ir [Division of Nanotechnology and Advanced Materials, Materials and Energy Research Center, P.O. Box 31787-316, Karaj (Iran, Islamic Republic of); Vaezi, Mohammad Reza [Division of Nanotechnology and Advanced Materials, Materials and Energy Research Center, P.O. Box 31787-316, Karaj (Iran, Islamic Republic of); Kazemzadeh, Asghar [Division of Semiconductors, Materials and Energy Research Center, P.O. Box 31787-316, Karaj (Iran, Islamic Republic of)

    2015-01-30

    Graphical abstract: - Highlights: • Transparent, hydrophobic, uniform silica film by sol–gel co-precursor process. • Preparation of silica coatings from ETES and Iso-OTMS in different molar ratios. • Decreasing in hydrophobicity of the films with increasing in Iso-TMS molar ratio. • By changing the molar ratio of component, different size of particles was obtained. - Abstract: In this paper, we used one-step sol–gel process to prepare the hydrophobic silica films on the glass substrate from the ethyltriethoxysilane (ETES) as a precursor and iso-octyltrimethoxysilane (Iso-OTMS) as a hydrophobic agent. In order to study the effect of the hydrophobic agent on the water repellent properties of the silica films, the alcosol was prepared by keeping constant the molar ratio of ETES:EtOH:H{sub 2}O at 1:36.2:6.3, with 6 M ammonium hydroxide and Iso-OTMS/ETES molar ratio varied from 0.2 to 1.4. Also, we investigated the influence of the other sol–gel reaction parameters, such as catalyst, solvent and water content and their effect on the morphology and hydrophobic properties of the silica films. The results revealed that by altering the molar ratio of NH{sub 4}OH, EtOH and H{sub 2}O, different sizes of silica nanoparticles from 41.24 to 86.16 nm were obtained. The silica films were characterized by atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM) images, contact angle measurement (CA) and percentage of optical transmission.

  12. Quasi-homogeneous hydrogenation with platinum and palladium nanoparticles stabilized by dendritic core-multishell architectures.

    Science.gov (United States)

    Schwarze, Michael; Keilitz, Juliane; Nowag, Sabrina; Parapat, Riny Y; Haag, Rainer; Schomäcker, Reinhard

    2011-05-17

    Platinum and palladium nanoparticles, supported and stabilized by polymeric core-shell architectures, proved to be active catalysts for hydrogenation reactions. Here, two different reactions were used as probes to investigate the influence of the polymeric support: the hydrogenation of α-methyl styrene (AMS) to cumene and the partial hydrogenation of 1,5-cyclooctadiene (COD). We found that the stability of the nanoparticles and the rate of reaction are higher in the presence of a hydrophobic octadecyl shell within a three-shell polymer system. The kinetic study of AMS hydrogenation showed much higher activities for palladium nanoparticles than for platinum nanoparticles, and the obtained results (e.g., 35 kJ/mol for the activation energy) are of the same order of magnitude as reported earlier for palladium supported on alumina. A methanol/n-heptane biphasic mixture was tested for catalyst recycling and allowed for highly efficient catalyst separation with very low metal leaching.

  13. Controlling the dispersion of supported polyoxometalate heterogeneous catalysts: impact of hybridization and the role of hydrophilicity–hydrophobicity balance and supramolecularity

    Directory of Open Access Journals (Sweden)

    Gijo Raj

    2014-10-01

    Full Text Available The hybridization of polyoxometalates (POMs through an organic–inorganic association offers several processing advantages in the design of heterogeneous catalysts. A clear understanding of the organization of these hybrid materials on solid surfaces is necessary to optimise their properties. Herein, we report for the first time the organization of Keggin phosphotungstic [PW12O40]3− and Wells–Dawson (WD phosphomolybdic [P2Mo18O62]6− anions deposited on mica (hydrophilic, and highly oriented pyrolytic graphite (HOPG (hydrophobic surfaces. Next, the supramolecular organization of the organic–inorganic hybrid materials formed from the association of POM anions and dimethyldioctadecylammonium bromide (DODA is investigated as a function of the hydrophilic or hydrophobic nature of the surfaces. The height of the Keggin-POM anions, measured with tapping mode (TM-AFM is always in good agreement with the molecular dimension of symmetric Keggin-POM anions (ca. 1 nm. However, the asymmetric WD-POM anions form monolayer assemblies on the surfaces with the orientation of their long molecular axis (ca. 1.6 nm depending on the hydrophilic or hydrophobic properties of the substrate. Namely, the long axis is parallel on mica, and perpendicular on HOPG. When hybridized with DODA, the organization of the hybrid material is dictated by the interaction of the alkyl side chains of DODA with the substrate surface. On HOPG, the DODA–POM hybrid forms small domains of epitaxially arranged straight nanorod structures with their orientation parallel to each other. Conversely, randomly distributed nanospheres are formed when the hybrid material is deposited on freshly cleaved mica. Finally, a UV–ozone treatment of the hybrid material allows one to obtain highly dispersed isolated POM entities on both hydrophilic and hydrophobic surfaces. The hybridization strategy to prevent the clustering of POMs on various supports would enable to develop highly dispersed POM

  14. 烧结-溶出法从废催化剂中回收铂%Recovery of Platinum from Spent Catalysts by Sintering- leaching

    Institute of Scientific and Technical Information of China (English)

    王明; 戴曦; 邬建辉; 张保钢; 吴永谦; 陈田庄

    2011-01-01

    The sintering -leaching method was used in order to dissolve the alumina in spent catalysts. Platinum was then recovered from the residues after enriching process. The results showed: 1) the residual carbon was 0.54% with a high decoking rate of 92.66% , after roasting the spent catalysts at 600℃ for 1 h; 2) the residue rate was 5.04% , the dissolution rate of alumina and sodium oxide were 98.10% and 99. 25% , respectively, and the platinum was enriched 17. 87 times with the one - step sintering - leaching process: the cinder was added sodium hydroxide with a molecular proportion of 1. 2, then sintered at 800℃ for 2 h, the clinker was leached at 95℃ for 10 min.%采用烧结-溶出法溶解废催化剂中氧化铝基体,使铂富集,进而从不溶渣中回收铂.研究结果表明:废催化剂于600℃焙烧1h,炭残余量为0.54%,脱炭率达到92.66%;烧渣按配料分子比1.2配料,800℃烧结反应2h,熟料于95℃热水溶出10 min,一次烧结-溶出,渣率为5.04%,氧化铝溶出率为98.10%,氧化钠溶出率为99.25%,铂富集了17.87倍.

  15. Controlled Surface Segregation Leads to Efficient Coke-Resistant Nickel/Platinum Bimetallic Catalysts for the Dry Reforming of Methane

    Energy Technology Data Exchange (ETDEWEB)

    Li, Lidong [King Abdullah Univ. of Science and Technology, Thuwal (Saudi Arabia); Zhou, Lu [King Abdullah Univ. of Science and Technology, Thuwal (Saudi Arabia); Ould-Chikh, Samy [King Abdullah Univ. of Science and Technology, Thuwal (Saudi Arabia); Anjum, Dalaver H. [King Abdullah Univ. of Science and Technology, Thuwal (Saudi Arabia); Kanoun, Mohammed B. [King Abdullah Univ. of Science and Technology, Thuwal (Saudi Arabia); Scaranto, Jessica [SABIC Corporate Research and Innovation Center, Thuwal (Saudi Arabia); Hedhili, Mohamed N. [King Abdullah Univ. of Science and Technology, Thuwal (Saudi Arabia); Khalid, Syed [Brookhaven National Lab. (BNL), Upton, NY (United States); Laveille, Paco V. [King Abdullah Univ. of Science and Technology, Thuwal (Saudi Arabia); D' Souza, Lawrence [SABIC Corporate Research and Innovation Center, Thuwal (Saudi Arabia); Clo, Alain [King Abdullah Univ. of Science and Technology, Thuwal (Saudi Arabia); Basset, Jean-Marie [King Abdullah Univ. of Science and Technology, Thuwal (Saudi Arabia)

    2015-02-03

    The surface composition and structure are of vital importance for heterogeneous catalysts, especially for bimetallic catalysts, which often vary as a function of reaction conditions (known as surface segregation). The preparation of bimetallic catalysts with controlled metal surface composition and structure is very challenging. In this study, we synthesize a series of Ni/Pt bimetallic catalysts with controlled metal surface composition and structure using a method derived from surface organometallic chemistry. Moreover, the evolution of the surface composition and structure of the obtained bimetallic catalysts under simulated reaction conditions is investigated by various techniques, which include CO-probe IR spectroscopy, high-angle annular dark-field scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy, extended X-ray absorption fine structure analysis, X-ray absorption near-edge structure analysis, XRD, and X-ray photoelectron spectroscopy. It is demonstrated that the structure of the bimetallic catalyst is evolved from Pt monolayer island-modified Ni nanoparticles to core–shell bimetallic nanoparticles composed of a Ni-rich core and a Ni/Pt alloy shell upon thermal treatment. The catalysts are active for the dry reforming of methane, and their catalytic activities, stabilities, and carbon formation vary with their surface composition and structure.

  16. Continuous preparation of carbon-nanotube-supported platinum catalysts in a flow reactor directly heated by electric current

    Directory of Open Access Journals (Sweden)

    Alicja Schlange

    2011-10-01

    Full Text Available In this contribution we present for the first time a continuous process for the production of highly active Pt catalysts supported by carbon nanotubes by use of an electrically heated tubular reactor. The synthesized catalysts show a high degree of dispersion and narrow distributions of cluster sizes. In comparison to catalysts synthesized by the conventional oil-bath method a significantly higher electrocatalytic activity was reached, which can be attributed to the higher metal loading and smaller and more uniformly distributed Pt particles on the carbon support. Our approach introduces a simple, time-saving and cost-efficient method for fuel cell catalyst preparation in a flow reactor which could be used at a large scale.

  17. Process for the separation and recovery of palladium and platinum from spent automobile catalyst leach liquor using LIX 84I and Alamine 336.

    Science.gov (United States)

    Reddy, B Ramachandra; Raju, B; Lee, Jin Young; Park, Hyung Kyu

    2010-08-15

    Spent catalysts from automobile industry contain environmentally critical and economically valuable metals such as Pt, Pd, Fe, Ni, Mn, and Cr. In this paper, we present a process for the selective separation and complete recovery of palladium (Pd) and platinum (Pt) from hydrochloric acid leach liquors of spent automobile catalyst employing solvent extraction method. Typical composition of leach liquor used for the present study contains (mg/L): Pd-150, Pt-550, Mn-500, Ni-1000, Fe-1500, Cr-100 and 3 M HCl. Selective separation of Pd from the leach liquor is achieved with 0.5 vol.% LIX 84I (2-hydroxy-5-nonylacetophenone oxime in a mixture with a high flash point hydrocarbon diluent) in kerosene at an aqueous to organic (A/O) ratio of 3 in 2 stages, with an enrichment factor of three. Quantitative stripping of Pd from loaded organic is achieved with 0.5 M thiourea and 1 M HCl. Co-extraction of Fe and Pt with 5 vol.% Alamine 336 (tertiary amine of mixed tri-octyl/decyl amine) in kerosene followed by selective scrubbing of Fe with dilute HCl and complete stripping of Pt from loaded organic was proposed with 0.5 M thiourea and 0.1 M HCl. Purity of Pd and Pt strip solutions are 99.7%. Finally, the present process can solve environmental related issues and at the same time recover valuable metals in pure form.

  18. A Pd/C-CeO2 Anode Catalyst for High-Performance Platinum-Free Anion Exchange Membrane Fuel Cells.

    Science.gov (United States)

    Miller, Hamish A; Lavacchi, Alessandro; Vizza, Francesco; Marelli, Marcello; Di Benedetto, Francesco; D'Acapito, Francesco; Paska, Yair; Page, Miles; Dekel, Dario R

    2016-05-10

    One of the biggest obstacles to the dissemination of fuel cells is their cost, a large part of which is due to platinum (Pt) electrocatalysts. Complete removal of Pt is a difficult if not impossible task for proton exchange membrane fuel cells (PEM-FCs). The anion exchange membrane fuel cell (AEM-FC) has long been proposed as a solution as non-Pt metals may be employed. Despite this, few examples of Pt-free AEM-FCs have been demonstrated with modest power output. The main obstacle preventing the realization of a high power density Pt-free AEM-FC is sluggish hydrogen oxidation (HOR) kinetics of the anode catalyst. Here we describe a Pt-free AEM-FC that employs a mixed carbon-CeO2 supported palladium (Pd) anode catalyst that exhibits enhanced kinetics for the HOR. AEM-FC tests run on dry H2 and pure air show peak power densities of more than 500 mW cm(-2) .

  19. Controlled surface segregation leads to efficient coke-resistant nickel/platinum bimetallic catalysts for the dry reforming of methane

    KAUST Repository

    Li, Lidong

    2015-02-03

    Surface composition and structure are of vital importance for heterogeneous catalysts, especially for bimetallic catalysts, which often vary as a function of reaction conditions (known as surface segregation). The preparation of bimetallic catalysts with controlled metal surface composition and structure is very challenging. In this study, we synthesize a series of Ni/Pt bimetallic catalysts with controlled metal surface composition and structure using a method derived from surface organometallic chemistry. The evolution of the surface composition and structure of the obtained bimetallic catalysts under simulated reaction conditions is investigated by various techniques, which include CO-probe IR spectroscopy, high-angle annular dark-field scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy, extended X-ray absorption fine structure analysis, X-ray absorption near-edge structure analysis, XRD, and X-ray photoelectron spectroscopy. It is demonstrated that the structure of the bimetallic catalyst is evolved from Pt monolayer island-modified Ni nanoparticles to core-shell bimetallic nanoparticles composed of a Ni-rich core and a Ni/Pt alloy shell upon thermal treatment. These catalysts are active for the dry reforming of methane, and their catalytic activities, stabilities, and carbon formation vary with their surface composition and structure. The reform of reforming: A series of alumina-supported Ni/Pt bimetallic nanoparticles (NPs) with controlled surface composition and structure are prepared. Remarkable surface segregation for these bimetallic NPs is observed upon thermal treatment. These bimetallic NPs are active catalysts for CO2 reforming of CH4, and their catalytic activities, stabilities, and carbon formation vary with their surface composition and structure.

  20. Platinum and palladium nano-structured catalysts for polymer electrolyte fuel cells and direct methanol fuel cells.

    Science.gov (United States)

    Long, Nguyen Viet; Thi, Cao Minh; Yong, Yang; Nogami, Masayuki; Ohtaki, Michitaka

    2013-07-01

    In this review, we present the synthesis and characterization of Pt, Pd, Pt based bimetallic and multi-metallic nanoparticles with mixture, alloy and core-shell structure for nano-catalysis, energy conversion, and fuel cells. Here, Pt and Pd nanoparticles with modified nanostructures can be controllably synthesized via chemistry and physics for their uses as electro-catalysts. The cheap base metal catalysts can be studied in the relationship of crystal structure, size, morphology, shape, and composition for new catalysts with low cost. Thus, Pt based alloy and core-shell catalysts can be prepared with the thin Pt and Pt-Pd shell, which are proposed in low and high temperature proton exchange membrane fuel cells (PEMFCs), and direct methanol fuel cells (DMFCs). We also present the survey of the preparation of Pt and Pd based catalysts for the better catalytic activity, high durability, and stability. The structural transformations, quantum-size effects, and characterization of Pt and Pd based catalysts in the size ranges of 30 nm (1-30 nm) are presented in electro-catalysis. In the size range of 10 nm (1-10 nm), the pure Pt catalyst shows very large surface area for electro-catalysis. To achieve homogeneous size distribution, the shaped synthesis of the polyhedral Pt nanoparticles is presented. The new concept of shaping specific shapes and morphologies in the entire nano-scale from nano to micro, such as polyhedral, cube, octahedra, tetrahedra, bar, rod, and others of the nanoparticles is proposed, especially for noble and cheap metals. The uniform Pt based nanosystems of surface structure, internal structure, shape, and morphology in the nanosized ranges are very crucial to next fuel cells. Finally, the modifications of Pt and Pd based catalysts of alloy, core-shell, and mixture structures lead to find high catalytic activity, durability, and stability for nano-catalysis, energy conversion, fuel cells, especially the next large-scale commercialization of next

  1. Stability of Porous Platinum Nanoparticles: Combined In Situ TEM and Theoretical Study

    DEFF Research Database (Denmark)

    Chang, Shery L. Y.; Barnard, Amanda S.; Dwyer, Christian

    2012-01-01

    Porous platinum nanoparticles provide a route for the development of catalysts that use less platinum without sacrificing catalytic performance. Here, we examine porous platinum nanoparticles using a combination of in situ transmission electron microscopy and calculations based on a first...

  2. Platinum metals in the environment

    Energy Technology Data Exchange (ETDEWEB)

    Zereini, Fathi [Frankfurt Univ. (Germany). Dept. of Environmental Analytical Chemistry; Wiseman, Clare L.S. (ed.) [Toronto Univ. (Canada). School of the Environment

    2015-03-01

    This book contains the five chapters with the following topics: 1. SOURCES OF PGE EMISSIONS ELEMENTS: Sources of Platinum Group Elements (PGE) in the Environment; Impact of Platinum Group Element Emissions from Mining and Production Activities. 2. ANALYTICAL METHODS FOR THE DETERMINATION OF PGE IN BIOLOGICAL AND ENVIRONMENTAL MATRICES: Appraisal of Biosorption for Recovery, Separation and Determination of Platinum, Palladium and Rhodium in Environmental Samples; On the Underestimated Factors Influencing the Accuracy of Determination of Pt and Pd by Electrothermal Atomic Absorption Spectrometry in Road Dust Samples; Application of Solid Sorbents for Enrichment and Separation of Platinum Metal Ions; Voltammetric Analysis of Platinum in Environmental Matrices; Speciation Analysis of Chloroplatinates; Analysis of Platinum Group Elements in Environmental Samples: A Review. 3. OCCURRENCE, CHEMICAL BEHAVIOR AND FATE OF PGE IN THE ENVIRONMENT: Brazilian PGE Research Data Survey on Urban and Roadside Soils; Platinum, Palladium and Rhodium in a Bavarian Roadside Soil; Increase of Platinum Group Element Concentrations in Soils and Airborne Dust During the Period of Vehicular Exhaust Catalysts Introduction; Platinum-Group Elements in Urban Fluvial Bed Sediments-Hawaii; Long-Term Monitoring of Palladium and Platinum Contents in Road Dust of the City of Munich, Germany; Characterization of PGEs and Other Elements in Road Dusts and Airborne Particles in Houston, Texas; Accumulation and Distribution of Pt and Pd in Roadside Dust, Soil and Vegetation in Bulgaria; Increase of the Environmental Pt Concentration in the Metropolitan Area of Mexico City Associated to the Use of Automobile Catalytic Converters; Solubility of Emitted Platinum Group Elements (Pt, Pd and Rh) in Airborne Particulate Matter (PM10) in the Presence of Organic Complexing Agents; The Influence of Anionic Species (Cl{sup -}, NO{sub 3}{sup -}, SO{sub 4}{sup 2-}) on the Transformation and Solubility of Platinum in

  3. Pt/C催化邻硝基氯苯加氢反应的动力学研究%Kinetics of Ortho-nitrochlorobenzene Hydrogenation on Platinum/Carbon Catalyst

    Institute of Scientific and Technical Information of China (English)

    蒋成君; 尹红; 陈志荣

    2004-01-01

    The kinetics of catalytic hydrogenation of ortho-nitrochlorobenzene to 2,2′-dichloroazoxybenzene on platinum/carbon catalyst is investigated in a slurry reactor with the temperature range of 313-343 K, and orthochloroaniline is formed as a byproduct. Models based on Rideal-Eley and Langmuir-Hinshelwood mechanism have been proposed based on the rate data and the kinetic regime. The former model can be used to fit the experimental data better. Reaction controlling steps are physical adsorption of hydrogen and adsorbed ortho-nitrochlorobenzene reacted on the surface of catalyst.

  4. Characterization of the surfaces of platinum/tin oxide based catalysts by Fourier Transform Infrared Spectroscopy (FTIR)

    Science.gov (United States)

    Keiser, Joseph T.; Upchurch, Billy T.

    1990-01-01

    A Pt/SnO2 catalyst has been developed at NASA Langley that is effective for the oxidation of CO at room temperature (1). A mechanism has been proposed to explain the effectiveness of this catalyst (2), but most of the species involved in this mechanism have not been observed under actual catalytic conditions. A number of these species are potentially detectable by Fourier Transform Infrared Spectroscopy (FTIR), e.g., HOSnO sub x, HO sub y PtO sub z, Pt-CO, and SnHCO3. Therefore a preliminary investigation was conducted to determine what might be learned about this particular catalyst by transmission FTIR. The main advantage of FTIR for this work is that the catalyst can be examined under conditions similar to the actual catalytic conditions. This can be of critical importance since some surface species may exist only when the reaction gases are present. Another advantage of the infrared approach is that since vibrations are probed, subtle chemical details may be obtained. The main disadvantage of this approach is that FTIR is not nearly as sensitive as the Ultra High Vacuum (UHV) surface analytical techniques such as Auger, Electron Spectroscopy for Chemical Analysis (ESCA), Electron Energy Loss Spectroscopy (EELS), etc. Another problem is that the assignment of the observed infrared bands may be difficult.

  5. Influence of Preparation Method on the Metal Cluster Size of Platinum/ZSM-5 Catalysts as studied with EXAFS.

    NARCIS (Netherlands)

    Koningsberger, D.C.; Kampers, F.W.H.; Engelen, C.W.R.; Hooff, J.H.C. van

    1990-01-01

    The size of Pt particles introduced into the channels of ZSM-5 zeolite by two different preparation methods has been studied with EXAFS. ZSM-5 was loaded with 2 wt 5% Pt by ion exchange and by impregnation. By careful calcination of the catalysts the dispersion was maintained. The EXAFS measurements

  6. Design of Highly Selective Platinum Nanoparticle Catalysts for the Aerobic Oxidation of KA-Oil using Continuous-Flow Chemistry.

    Science.gov (United States)

    Gill, Arran M; Hinde, Christopher S; Leary, Rowan K; Potter, Matthew E; Jouve, Andrea; Wells, Peter P; Midgley, Paul A; Thomas, John M; Raja, Robert

    2016-03-01

    Highly active and selective aerobic oxidation of KA-oil to cyclohexanone (precursor for adipic acid and ɛ-caprolactam) has been achieved in high yields using continuous-flow chemistry by utilizing uncapped noble-metal (Au, Pt & Pd) nanoparticle catalysts. These are prepared using a one-step in situ methodology, within three-dimensional porous molecular architectures, to afford robust heterogeneous catalysts. Detailed spectroscopic characterization of the nature of the active sites at the molecular level, coupled with aberration-corrected scanning transmission electron microscopy, reveals that the synthetic methodology and associated activation procedures play a vital role in regulating the morphology, shape and size of the metal nanoparticles. These active centers have a profound influence on the activation of molecular oxygen for selective catalytic oxidations.

  7. Influence of complexing agents on the preparation of bimetallic platinum-ruthenium catalysts supported on O-functionalized graphite cloths

    Energy Technology Data Exchange (ETDEWEB)

    Sieben, J.M., E-mail: jmsieben@uns.edu.a [Instituto de Ingenieria Electroquimica y Corrosion (INIEC), Universidad Nacional del Sur., Av. Alem 1253, (B8000CPB) Bahia Blanca (Argentina); Duarte, M.M.E.; Mayer, C.E. [Instituto de Ingenieria Electroquimica y Corrosion (INIEC), Universidad Nacional del Sur., Av. Alem 1253, (B8000CPB) Bahia Blanca (Argentina)

    2010-02-18

    Electrodeposition of bimetallic Pt-Ru catalysts on O-functionalized graphite cloths from H{sub 2}PtCl{sub 6} and RuCl{sub 3} solutions containing trisodium citrate (Cit) and disodium dihydrogen ethylenediaminetetraacetate (Na{sub 2}H{sub 2}EDTA) was investigated. SEM analysis of the electrode prepared without complexant showed a relatively compact and rough deposit displaying a 'tree cortex' structure, whereas uniform size and globular shape particles regularly distributed over the support surface were obtained using citrate and Na{sub 2}H{sub 2}EDTA as complexants. In addition, XRD diffraction and EDX analysis revealed that the catalysts prepared using the complexants showed smaller size particles and lower Ru content. Electrocatalytic activity measurements indicated that the most active electrode for methanol oxidation was obtained with Na{sub 2}H{sub 2}EDTA as additive.

  8. Platinum Metal-Free Catalysts for Selective Soft Oxidative Methane → Ethylene Coupling. Scope and Mechanistic Observations.

    Science.gov (United States)

    Peter, Matthias; Marks, Tobin J

    2015-12-09

    Using abundant soft oxidants, a high methane-to-ethylene conversion might be achievable due to the low thermodynamic driving force for over-oxidation. Here we report on the oxidative coupling of methane by gaseous S2 (SOCM). The catalytic properties of Pd/Fe3O4 are compared with those of Fe3O4, and it is found that high ethylene selectivities can be achieved without noble metals; conversion and selectivity on Fe3O4 are stable for at least 48 h at SOCM conditions. SOCM data for 10 oxides are compared, and ethylene selectivities as high as 33% are found; the C2H4/C2H6 ratios of 9-12 observed at the highest S2 conversions are significantly higher than the C2H4/C2H6 ratios usually found in the CH4 coupling with O2. Complementary in-detail analytical studies show that, on Mg, Zr, Sm, W, and La catalysts, which strongly coke during the reaction, lower ethylene selectivities are observed than on Fe, Ti, and Cr catalysts, which only coke to a minor extent. Further catalyst-dependent changes during SOCM in surface area, surface composition, and partial conversion to oxysulfides and sulfides are discussed. Evidence concerning the reaction mechanism is obtained taking into account the selectivity for the different reaction products versus the contact time. CH4 coupling proceeds non-oxidatively with the evolution of H2 on some catalysts, and evidence is presented that C2H4 and C2H2 formation occur via C2H6 and C2H4 dehydrogenation, respectively.

  9. Preparation of hydrophobic coatings

    Science.gov (United States)

    Branson, Eric D.; Shah, Pratik B.; Singh, Seema; Brinker, C. Jeffrey

    2009-02-03

    A method for preparing a hydrophobic coating by preparing a precursor sol comprising a metal alkoxide, a solvent, a basic catalyst, a fluoroalkyl compound and water, depositing the precursor sol as a film onto a surface, such as a substrate or a pipe, heating, the film and exposing the film to a hydrophobic silane compound to form a hydrophobic coating with a contact angle greater than approximately 150.degree.. The contact angle of the film can be controlled by exposure to ultraviolet radiation to reduce the contact angle and subsequent exposure to a hydrophobic silane compound to increase the contact angle.

  10. Copolymers Based on Indole-6-Carboxylic Acid and 3,4-Ethylenedioxythiophene as Platinum Catalyst Support for Methanol Oxidation

    Directory of Open Access Journals (Sweden)

    Tzi-Yi Wu

    2015-10-01

    Full Text Available Indole-6-carboxylic acid (ICA and 3,4-ethylenedioxythiophene (EDOT are copolymerized electrochemically on a stainless steel (SS electrode to obtain poly(indole-6-carboxylic acid-co-3,4-ethylenedioxythiophenes (P(ICA-co-EDOTs. The morphology of P(ICA-co-EDOTs is checked using scanning electron microscopy (SEM, and the SEM images reveal that these films are composed of highly porous fibers when the feed molar ratio of ICA/EDOT is greater than 3/2. Platinum particles can be electrochemically deposited into the P(ICA-co-EDOTs and PICA films to obtain P(ICA-co-EDOTs-Pt and PICA-Pt composite electrodes, respectively. These composite electrodes are further characterized using X-ray photoelectron spectroscopy (XPS, SEM, X-ray diffraction analysis (XRD, and cyclic voltammetry (CV. The SEM result indicates that Pt particles disperse more uniformly into the highly porous P(ICA3-co-EDOT2 fibers (feed molar ratio of ICA/EDOT = 3/2. The P(ICA3-co-EDOT2-Pt nanocomposite electrode exhibited excellent catalytic activity for the electrooxidation of methanol in these electrodes, which reveals that P(ICA3-co-EDOT2-Pt nanocomposite electrodes are more promising for application in an electrocatalyst as a support material.

  11. Lanthanum oxide promoted rhodium/titania and rhodium-platinum/titania catalysts for alcohol formation from synthesis gas

    Energy Technology Data Exchange (ETDEWEB)

    Bond, G.C.; Richards, D.G.

    1986-12-15

    TiO/sub 2/-supported Rh and Rh-Pt catalysts have been studied for the selective formation of oxygenates from synthesis gas. The addition of La/sub 2/O/sub 3/ as a promoter significantly increased the C/sub 2/H/sub 5/OH selectivities and formation rates. Pt addition increased the overall activity and in combination with La/sub 2/O/sub 3/ led to higher alcohol selectivities of 25% compared with 6% for an unpromoted Rh catalyst. A pronounced induction period was observed for CH/sub 3/OH and C/sub 2/H/sub 5/OH formation, attributed to changes in the nature of the catalytically active sites. A simple theoretical model is used to illustrate the parallel trends in C/sub 2/H/sub 5/OH and hydrocarbon formation after the induction period. Temperature-programmed reduction showed that the La/sub 2/O/sub 3/ increased the stability of Rh oxide. The main role of La/sub 2/O/sub 3/ appears to be promotion of the formation of the C/sub 2/H/sub 5/OH precursor, while Pt increased the rate of hydrogenation. 26 refs., 8 figs., 3 tabs.

  12. Novel RuCoSe as non-platinum catalysts for oxygen reduction reaction in microbial fuel cells

    Science.gov (United States)

    Rozenfeld, Shmuel; Schechter, Michal; Teller, Hanan; Cahan, Rivka; Schechter, Alex

    2017-09-01

    Microbial electrochemical cells (MECs) are explored for the conversion of acetate directly to electrical energy. This device utilizes a Geobacter sulfurreducens anode and a novel RuCoSe air cathode. RuCoSe synthesized in selected compositions by a borohydride reduction method produces amorphous structures of powdered agglomerates. Oxygen reduction reaction (ORR) was measured in a phosphate buffer solution pH 7 using a rotating disc electrode (RDE), from which the kinetic current (ik) was measured as a function of potential and composition. The results show that ik of RuxCoySe catalysts increases in the range of XRu = 0.25 > x > 0.7 and y < 0.15 for all tested potentials. A poisoning study of RuCoSe and Pt catalysts in a high concentration acetate solution shows improved tolerance of RuCoSe to this fuel at acetate concentration ≥500 mM. MEC discharge plots under physiological conditions show that ∼ RuCo2Se (sample S3) has a peak power density of 750 mW cm-2 which is comparable with Pt 900 mW cm-2.

  13. Platinum availability for future automotive technologies.

    Science.gov (United States)

    Alonso, Elisa; Field, Frank R; Kirchain, Randolph E

    2012-12-04

    Platinum is an excellent catalyst, can be used at high temperatures, and is stable in many aggressive chemical environments. Consequently, platinum is used in many current industrial applications, notably automotive catalytic converters, and prospective vehicle fuel cells are expected to rely upon it. Between 2005 and 2010, the automotive industry used approximately 40% of mined platinum. Future automotive industry growth and automotive sales shifts toward new technologies could significantly alter platinum demand. The potential risks for decreased platinum availability are evaluated, using an analysis of platinum market characteristics that describes platinum's geophysical constraints, institutional efficiency, and dynamic responsiveness. Results show that platinum demand for an automotive fleet that meets 450 ppm greenhouse gas stabilization goals would require within 10% of historical growth rates of platinum supply before 2025. However, such a fleet, due largely to sales growth in fuel cell vehicles, will more strongly constrain platinum supply in the 2050 time period. While current platinum reserves are sufficient to satisfy this increased demand, decreasing platinum ore grade and continued concentration of platinum supply in a single geographic area are availability risk factors to platinum end-users.

  14. Photo-Promoted Platinum Nanoparticles Decorated MoS2@Graphene Woven Fabric Catalyst for Efficient Hydrogen Generation.

    Science.gov (United States)

    Li, Xiao; Zhang, Li; Zang, Xiaobei; Li, Xinming; Zhu, Hongwei

    2016-05-01

    Hydrogen production from water splitting has been considered as an effective and sustainable method to solve future energy related crisis. Molybdenum sulfides (e.g., MoS2) show promising catalytic ability in hydrogen evolution reaction (HER). Combining MoS2 with conductive carbon-based materials has aroused tremendous research interest recently. In this work, a highly efficient multiple-catalyst is developed for HER by decorating Pt nanoparticles (Pt NPs) on MoS2@graphene protected nickel woven fabrics (NiWF) substrate, which comprises the following components: (i) Graphene protected NiWF acts as the underlying substrate, supporting the whole structure; (ii) MoS2 nanoplates serve as a central and essential photosensitive component, forming a heterostructure with graphene simultaneously; and (iii) on the basis of the intrinsic photoluminescence effect of MoS2, together with the photoelectric response at the MoS2/graphene interface, Pt NPs are successfully deposited on the whole structure under illumination. Particularly and foremost, this work emphasizes on discussion and verification of the underlying mechanism for photopromoted electroless Pt NPs deposition. Due to this assembly approach, the usage amount of Pt is controlled at ∼5 wt % (∼0.59 at. %) with respect to the whole catalyst. MoS2@Substrate with Pt NPs deposited under 643 nm illumination, with the synergistic effect of MoS2 active sites and Pt NPs, demonstrates the most superior electrocatalytic performance, with negligible overpotential and low Tafel slope of 39.4 mV/dec.

  15. Preparation and Properties of Supported Platinum Catalyst for Methanol Catalytic Combustion at Room Temperature%甲醇室温催化燃烧负载型铂催化剂的制备及性能研究

    Institute of Scientific and Technical Information of China (English)

    张春; 王晓红; 曾志刚; 胡志宇

    2011-01-01

    以铂为活性组分,氧化铝颗粒、单晶硅片及单晶硅片支撑的氧化铝薄膜为载体,制备了甲醇室温催化燃烧催化剂,研究了载体种类、载体性质、制备方法及铂负载量对催化剂活性的影响.结果表明,所制备的催化剂均可使甲醇在室温下燃烧;作为甲醇燃烧催化剂的载体,氧化铝优于单晶硅,薄膜状氧化铝优于颗粒状氧化铝.当载体种类和性质均相同时,化学分散法制备的催化剂活性高于磁控溅射法.就活性组分而言,增大其负载量并不一定能提高催化活性,本实验中,当铂的负载量下降两个数量级后,单位质量铂上甲醇的转化量提高了26倍.%Different kinds of Pt catalysts were prepared to study their room-temperature combustion of methanol. The effect of support species, support properties and platinum loading on the performance of the catalysts were studied. The results showed that all these catalysts can catalyze the methanol combusting at room temperature. As the catalyst support, alumina film/Si is better than alumina paritcle. When the species and properties of the support are all same, the catalysts prepared by chemical dispersion method is better than that prepared by magnetron sputtering method. Besides, increasing the platinum loading may not reasonably increase the catalytic activity. In our experiments , the methanol conversion of unit mass of platinum increased by 26 times when platinum loading decreased two orders of magnitude.

  16. Alternative alloys for catalysts and platinum jewelry? New structures in Pt-Hf and Pt-Mo

    Science.gov (United States)

    Gilmartin, Erin; Corbitt, Jacqueline; Hart, Gus

    2009-03-01

    The only known intermetallic structure with an 8:1 stoichiometry is that of Pt8Ti. It is intriguing that an ordered phase would occur at such low concentrations of the minority atom, but this structure occurs in about a dozen binary intermetallic systems. The formation of an ordered phase in an alloy can significantly enhance the performance of the material, particularly the hardness. We have taken a broad look at possible systems where this phase forms. Using first-principles, we calculated the stability of this structure relative to experimentally known phases for more than 80 Pt/Pd binary systems. We find the Pt8Ti structure is a possible ground state in more than 20 cases. Our experimental collaborators have verified our prediction in Pt-Mo and observed order-hardening in Pt-Hf. We discuss the discovery of new ground states that are likely to be verified experimentally and their impact on materials for Pt- and Pd-based catalysts and jewelry.

  17. The Origin of Sulfur Tolerance in Supported Platinum Catalysts: The Relationship between Structural and Catalytic Properties in Acidic and Alkaline Pt/LTL.

    NARCIS (Netherlands)

    Koningsberger, D.C.; Miller, J.T.

    1996-01-01

    The reactivity, structure, and sulfur tolerance is compared for platinum supported on acidic and alkaline LTL zeolite. In the absence of sulfur, EXAFS spectroscopy indicates that small metallic platinum particles of approximately 6 to 14 atoms/cluster are present. The TOF for neopentane hydrogenolys

  18. Fate of platinum metals in the environment.

    Science.gov (United States)

    Pawlak, Justyna; Łodyga-Chruścińska, Elżbieta; Chrustowicz, Jakub

    2014-07-01

    For many years now automotive exhaust catalysts have been used to reduce the significant amounts of harmful chemical substances generated by car engines, such as carbon monoxide, nitrogen oxides, and aromatic hydrocarbons. Although they considerably decrease environmental contamination with the above-mentioned compounds, it is known that catalysts contribute to the environmental load of platinum metals (essential components of catalysts), which are released with exhaust fumes. Contamination with platinum metals stems mainly from automotive exhaust converters, but other major sources also exist. Since platinum group elements (PGEs): platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru) and iridium (Ir) seem to spread in the environment and accumulate in living organisms, they may pose a threat to animals and humans. This paper discusses the modes and forms of PGE emission as well as their impact on the environment and living organisms.

  19. Platinum Group Organometallics Based on "Pincer" Complexes: Sensors, Switches, and Catalysts In memory of Prof. Dr. Luigi M. Venanzi and his pioneering work in organometallic chemistry, particularly in PCP pincer chemistry.

    Science.gov (United States)

    Albrecht, Martin; van Koten, Gerard

    2001-10-15

    Since the first reports in the late 1970s on transition metal complexes containing pincer-type ligands-named after the particular coordination mode of these ligands-these systems have attracted increasing interest owing to the unusual properties of the metal centers imparted by the pincer ligand. Typically, such a ligand comprises an anionic aryl ring which is ortho,ortho-disubstituted with heteroatom substituents, for example, CH(2)NR(2), CH(2)PR(2) or CH(2)SR, which generally coordinate to the metal center, and therefore support the M-C sigma bond. This commonly results in a terdentate and meridional coordination mode consisting of two metallacycles which share the M-C bond. Detailed studies of the formation and the properties of a large variety of pincers containing platinum group metal complexes have provided direct access to both a fundamental understanding of a variety of reactions in organometallic chemistry and to a range of new applications of these complexes. The discovery of alkane dehydrogenation catalysts, the mechanistic elucidation of fundamental transformations (for example, C-C bond activation), the construction of the first metallodendrimers for sustainable homogeneous catalysis, and the engineering of crystalline switches for materials processing represent only a few of the many highlights which have emanated from these numerous investigations. This review discusses the synthetic methodologies that are currently available for the preparation of platinum group metal complexes containing pincer ligands and especially emphasizes different applications that have been realized in materials science such as the development and engineering of sensors, switches, and catalysts.

  20. Characterization of electrochemically modified polycrystalline platinum surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Krebs, L.C.; Ishida, Takanobu.

    1991-12-01

    The characterization of electrochemically modified polycrystalline platinum surfaces has been accomplished through the use of four major electrochemical techniques. These were chronoamperometry, chronopotentiommetry, cyclic voltammetry, and linear sweep voltammetry. A systematic study on the under-potential deposition of several transition metals has been performed. The most interesting of these were: Ag, Cu, Cd, and Pb. It was determined, by subjecting the platinum electrode surface to a single potential scan between {minus}0.24 and +1.25 V{sub SCE} while stirring the solution, that the electrocatalytic activity would be regenerated. As a consequence of this study, a much simpler method for producing ultra high purity water from acidic permanganate has been developed. This method results in water that surpasses the water produced by pyrocatalytic distillation. It has also been seen that the wettability of polycrystalline platinum surfaces is greatly dependent on the quantity of oxide present. Oxide-free platinum is hydrophobic and gives a contact angle in the range of 55 to 62 degrees. We have also modified polycrystalline platinum surface with the electrically conducting polymer poly-{rho}-phenylene. This polymer is very stable in dilute sulfuric acid solutions, even under applied oxidative potentials. It is also highly resistant to electrochemical hydrogenation. The wettability of the polymer modified platinum surface is severely dependent on the choice of supporting electrolyte chosen for the electrochemical polymerization. Tetraethylammonium tetrafluoroborate produces a film that is as hydrophobic as Teflon, whereas tetraethylammonium perchlorate produces a film that is more hydrophilic than oxide-free platinum.

  1. Phosphoric acid fuel cell platinum use study

    Science.gov (United States)

    Lundblad, H. L.

    1983-01-01

    The U.S. Department of Energy is promoting the private development of phosphoric acid fuel cell (PAFC) power plants for terrestrial applications. Current PAFC technology utilizes platinum as catalysts in the power electrodes. The possible repercussions that the platinum demand of PAFC power plant commercialization will have on the worldwide supply and price of platinum from the outset of commercialization to the year 2000 are investigated. The platinum demand of PAFC commercialization is estimated by developing forecasts of platinum use per unit of generating capacity and penetration of PAFC power plants into the electric generation market. The ability of the platinum supply market to meet future demands is gauged by assessing the size of platinum reserves and the capability of platinum producers to extract, refine and market sufficient quantities of these reserves. The size and timing of platinum price shifts induced by the added demand of PAFC commercialization are investigated by several analytical methods. Estimates of these price shifts are then used to calculate the subsequent effects on PAFC power plant capital costs.

  2. Application of Ion Beam Processing Technology in Production of Catalysts

    Directory of Open Access Journals (Sweden)

    Mykola G. Bannikov, Javed A. Chattha

    2012-08-01

    Full Text Available In this paper, the applicability of Ion Beam Processing Technology for making catalysts has been inves-tigated. Ceramic substrates of different shapes and metal fibre tablets were implanted by platinum ions and tested in nitrogen oxides (NOx and carbon monoxide (CO conversion reactions. Effectiveness of the implanted catalysts was compared to that of the commercially produced platinum catalysts made by impregnation. Platinum-implanted catalyst having fifteen times less platinum content showed the same CO conversion efficiency as the commercially pro-duced catalyst. It was revealed that the effectiveness of the platinum-implanted catalyst has complex dependence on the process parameters and the optimum can be achieved by varying the ions energy and the duration of implantation. Investigation of the pore structure showed that ion implantation did not decrease the specific surface area of the catalyst.Key Words: Catalyst, Ion Implantation, Noble metals.

  3. Stabilizing platinum in phosphoric acid fuel cells

    Science.gov (United States)

    Remick, R. J.

    1982-01-01

    Platinum sintering on phosphoric acid fuel cell cathodes is discussed. The cathode of the phosphoric acid fuel cell uses a high surface area platinum catalyst dispersed on a conductive carbon support to minimize both cathode polarization and fabrication costs. During operation, however, the active surface area of these electrodes decreases, which in turn leads to decreased cell performance. This loss of active surface area is a major factor in the degradation of fuel cell performance over time.

  4. Methanol-Tolerant Platinum-Palladium Catalyst Supported on Nitrogen-Doped Carbon Nanofiber for High Concentration Direct Methanol Fuel Cells

    Directory of Open Access Journals (Sweden)

    Jiyoung Kim

    2016-08-01

    Full Text Available Pt-Pd catalyst supported on nitrogen-doped carbon nanofiber (N-CNF was prepared and evaluated as a cathode electrode of the direct methanol fuel cell (DMFC. The N-CNF, which was directly synthesized by the catalytic chemical vapor deposition from acetonitrile at 640 °C, was verified as having a change of electrochemical surface properties such as oxygen reduction reaction (ORR activities and the electrochemical double layer compared with common carbon black (CB. To attain the competitive oxygen reduction reaction activity with methanol tolerance, the Pt and Pd metals were supported on the CB or the N-CNF. The physical and electrochemical characteristics of the N-CNF–supported Pt-Pd catalyst were examined and compared with catalyst supported on the CB. In addition, DMFC single cells using these catalysts as the cathode electrode were applied to obtain I-V polarization curves and constant current operating performances with high-concentration methanol as the fuel. Pt-Pd catalysts had obvious ORR activity even in the presence of methanol. The higher power density was obtained at all the methanol concentrations when it applied to the membrane electrode assembly (MEA of the DMFC. When the N-CNF is used as the catalyst support material, a better performance with high-concentration methanol is expected.

  5. Stabilizing platinum in phosphoric acid fuel cells

    Science.gov (United States)

    Remick, R. J.

    1981-10-01

    A carbon substrate for use in fabricating phosphoric acid fuel cell cathodes was modified by catalytic oxidation to stabilize the platinum catalyst by retarding the sintering of small platinum crystallites. Results of 100-hour operational tests confirmed that the rate of platinum surface area loss observed on catalytically oxidized supports was less than that observed with unmodified supports of the same starting material. Fuel cell electrodes fabricated from Vulcan XC-72R, which was modified by catalytic in a nitric oxide atmosphere, produced low platium sintering rates and high activity for the reduction of oxygen in the phosphoric acid environment.

  6. Catalytic oxidation of formaldehyde over activated carbon-supported platinum catalysts at room temperature%室温下活性炭载纳米铂催化剂对空气中甲醛的去除效果

    Institute of Scientific and Technical Information of China (English)

    黄海保; 张路; 梁耀彰; 叶信国

    2013-01-01

    Objective To explore catalytic oxidation of gaseous formaldehyde over activated carbon- supported platinum catalysts (Pt/AC) at room temperature. Methods Pt/AC catalysts were prepared by liquid reduction method using NaBH4 as the reducing agent. The effect of Pt loading (0.1% ,0.5% and 1% ) on formaldehyde removal was investigated. Results Reduced Pt nanoparticles of 18 ran diameter could be observed by transmission electron microscope. Formaldehyde removal efficiency was 98.2% in case of 0.5% Pt loading after reaction for 5 h. Conclusion The prepared Pt/AC catalysts in this study can be used for the efficient removal of formaldehyde in air.%目的 探讨活性炭载纳米铂催化剂对空气中甲醛的去除效果.方法 采用硼氢化钠液相还原法制备活性炭载纳米铂催化剂,观察不同载铂量(0.1%,0.5%和1%)对甲醛去除率的影响.结果 透射电镜观察显示,活性炭载铂为还原态纳米粒子(d≈18 nm),铂负载量为0.5%时,反应5h甲醛去除率为98.2%.结论 本研究制备的活性炭载纳米铂催化剂可有效去除空气中甲醛.

  7. Electro catalyst of platinum prepared by CVD for the oxygen reduction reaction; Electrocatalizador de platino preparado por CVD para la reaccion de reduccion de oxigeno

    Energy Technology Data Exchange (ETDEWEB)

    Garcia C, M.A.; Fernandez V, S.M. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico); Vargas G, J.R. [IPN, ESIQIE, 07300 Mexico D.F. (Mexico)

    2004-07-01

    In this work it is reported the preparation and characterization of platinum films obtained by the technique of chemical vapor deposition at low pressure, better well-known as LPCVD for their initials in English (Low Pressure Chemical Vapor Deposition). The technique has several industrial applications and in this work it is explored their possible use to prepare applicable electrocatalysts in fuel cells. The films were characterized by XRD, SEM, EDS and they were proven for to determine their acting in the Oxygen reduction reaction (Orr) in sulfuric acid 0.5 M, the results show that the material presents good activity for the reaction in study. (Author)

  8. Performance enhancement of air-breathing proton exchange membrane fuel cell through utilization of an effective self-humidifying platinum-carbon catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Poh, Chee Kok; Lin, Jianyi [Institute of Chemical Engineering and Sciences, 1 Pesek Road, Jurong Island, Singapore 627833 (Singapore); Department of Physics, National University of Singapore, Singapore 117542 (Singapore); Tian, Zhiqun; Lim, San Hua [Institute of Chemical Engineering and Sciences, 1 Pesek Road, Jurong Island, Singapore 627833 (Singapore); Bussayajarn, Narissara [Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, Singapore 638075 (Singapore); Tang, Zhe; Chua, Daniel [Department of Materials Science and Engineering, National University of Singapore, Singapore (Singapore); Su, Fabing [State Key Laboratory of Multi-phase Complex System, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190 (China); Feng, Yuan Ping [Department of Physics, National University of Singapore, Singapore 117542 (Singapore)

    2010-12-15

    One issue with air-breathing proton exchange membrane fuel cells (AB-PEMFCs) is that the reactants are not externally humidified, and thus the membrane or the catalyst layers might dry out due to electro-osmotic drag, diffusion and evaporation at the opening cathode. This results in a drop in internal ionic conductivity and thus in cell performance. Here, the preparation and characterization of self-humidifying carbon-supported Pt catalyst using citric acid modified carbon black (CA-CB) as the catalyst support are reported. Pt/CA-CB is highly hydrophilic due to the functional groups attached on the carbon support, which endows the ability to retain water in the membrane electrolyte assembly (MEA) and thereby help to improve the performance of AB-PEMFCs. A maximum power density of 204 mW cm{sup -2} can be achieved in an air-breathing PEMFC stack using Pt/CA-CB, a thick polymer membrane (NRE212) and a circular opening cathode. A 23.4% enhancement in the output power density is obtained by using Pt/CA-CB in place of a commercial catalyst when oblique slit cathodes are employed. This self-humidifying catalyst is particularly suitable for portable PEMFC applications. (author)

  9. Catalyst with core-shell structure and low platinum loading:A review on their design,preparation and the effects of core structure and composition on catalyst performance%核壳结构低铂催化剂:设计、制备及核的组成及结构的影响

    Institute of Scientific and Technical Information of China (English)

    陈丹; 舒婷; 廖世军

    2013-01-01

      核壳结构低铂催化剂具有可大幅提高贵金属铂的利用率、有效降低燃料电池铂使用量及成本的重要特点,被誉为质子交换膜燃料电池大规模商业化的希望之所在,相关研究已成为燃料电池领域最为热门的课题之一。本文综述了近年来提出的各种高性能核壳结构催化剂的设计思路及新型制备技术,介绍了各种不同组成和结构的核壳结构催化剂性能及特点以及在核壳结构催化剂表征技术方面的最新进展。最后对核壳结构催化剂制备技术的发展和应用前景进行了展望:通过发展或改进制备工艺,制备各种形貌组成可控以及高活性低Pt载量的核壳结构催化剂,有望实现质子交换膜燃料电池商业化。%Core-shell structured catalyst is recognized as a promising catalyst for large scale commercialization of PEM fuel cells,as it can significantly enhance the utilization of precious platinum,reduce the amount of platinum catalyst used and sharply save the cost of fuel cells. Investigation on core-shell structured catalyst is becoming one of the hottest topics in fuel cell field. This paper is aimed to introduce the latest developments and achievements on the design,preparation technology,and investigations on the effects of core composition and structure on the performance of core-shell structured catalyst,as well as the latest development of characterization techniques for core-shell structure. Furthermore,prospects for the development of new preparation technology and the application of this type catalyst are discussed. Research directions are suggested to advance the future works in this field,i.e.,it is expected to achieve the commercialization of proton exchange membrane fuel cell through the development or improvement of the preparation process of the core-shell structured catalysts with controllability on morphology,high activity and low Pt platinum loading.

  10. The effects of platinum on nickel electrodes in the nickel hydrogen cell

    Science.gov (United States)

    Zimmerman, Albert H.

    1991-01-01

    Interactions of platinum and platinum compounds with the nickel electrode that are possible in the nickel hydrogen cell, where both the nickel electrode and a platinum catalyst hydrogen electrode are in intimate contact with the alkaline electrolyte, are examined. Additionally, a mechanism of nickel cobalt oxyhydroxide formation in NiH2 cells is presented.

  11. A kinetic rate expression for the time-dependent coke formation rate during propane dehydrogenation over a platinum alumina monolithic catalyst.

    NARCIS (Netherlands)

    van Sint Annaland, M.; Kuipers, J.A.M.; van Swaaij, Willibrordus Petrus Maria

    2001-01-01

    Coke formation rates under propane dehydrogenation reaction conditions on a used monolithic Pt/y-Al2O3 catalyst have been experimentally determined in a thermogravimetric analyser (TGA) as a function of time on stream covering wide temperature and concentration ranges. For relatively short times on

  12. The Role of Non-Conventional Supports for Single-Atom Platinum-Based Catalysts in Fuel-Cell Technology: A Theoretical Surface Science Approach

    Science.gov (United States)

    2013-02-05

    on the thermodynamic stability of platinized TiN. 15. SUBJECT TERMS fuel cells , Theoretical modeling , electrodes 16. SECURITY CLASSIFICATION OF...system are reported for various surface coverages of Pt. We find that atomic Pt does not bind preferably to the clean TiN surface, but under typical PEM ...could be a promising catalyst for PEM fuel cells. Introduction: Proton exchange membrane fuel cells (PEMFCs) have found wide potential

  13. A Model gamma-Alumina-Supported Rhenium-Platinum Catalyst Prepared from [Re2Pt(CO)12]: 1. Synthesis and Spectroscopic Characterization.

    NARCIS (Netherlands)

    Koningsberger, D.C.; Fung, A.S.; McDeVitt, M.R.; Tooley, P.A.; Kelley, M.J.; Gates, B.C.

    1993-01-01

    Catalysts supported on -Al2O3 were prepared from [Re2Pt(CO)12], and from Pt (NH3)4(NO3)2 and NH4ReO4. The former samples were characterized by infrared and X-ray photoelectron spectroscopies (XPS) and by temperature-programmed reduction (TPR); the latter were characterized by TPR. [Re2Pt(CO)12] was

  14. Platinum and Other Transition Metal Nanoclusters (Pd, Rh) Stabilized by PAMAM Dendrimer as Excellent Heterogeneous Catalysts: Application to the Methylcyclopentane (MCP) Hydrogenative Isomerization.

    Science.gov (United States)

    Deraedt, Christophe; Melaet, Gérôme; Ralston, Walter T; Ye, Rong; Somorjai, Gabor A

    2017-03-08

    Pt, Rh, and Pd nanoclusters stabilized by PAMAM dendrimer are used for the first time in a gas flow reactor at high temperature (150-250 °C). Pt nanoclusters show a very high activity for the hydrogenation of the methylcyclopentane (MCP) at 200-225 °C with turnover freqency (TOF) up to 334 h(-1) and selectivity up to 99.6% for the ring opening isomerization at very high conversion (94%). Rh nanoclusters show different selectivity for the reaction, that is, ring opening isomerization at 175 °C and cracking at higher temperature whereas Pd nanoclusters perform ring enlargement plus dehydrogenation, while maintaining a high activity. The difference in these results as compared to unsupported/uncapped nanoparticles, demonstrates the crucial role of dendrimer. The tunability of the selectivity of the reaction as well as the very high activity of the metal nanoclusters stabilized by dendrimer under heterogeneous conditions open a new application for dendrimer catalysts.

  15. Bridging the pressure gap: In situ atomic-level investigations of model platinum catalyst surfaces under reaction conditions by scanning tunneling microscopy

    Energy Technology Data Exchange (ETDEWEB)

    McIntyre, B.J.

    1994-05-01

    Results of this thesis show that STM measurements can provide information about the surfaces and their adsorbates. Stability of Pt(110) under high pressures of H2, O2, and CO was studied (Chap. 4). In situ UHV and high vacuum experiments were carried out for sulfur on Pt(111) (Chap.5). STM studies of CO/S/Pt(111) in high CO pressures showed that the Pt substrate undergoes a stacking-fault-domain reconstruction involving periodic transitions from fcc to hcp stacking of top-layer atoms (Chap.6). In Chap.7, the stability of propylene on Pt(111) and the decomposition products were studied in situ with the HPSTM. Finally, in Chap.8, results are presented which show how the Pt tip of the HPSTM was used to locally rehydrogenate and oxidize carbonaceous clusters deposited on the Pt(111) surface; the Pt tip acted as a catalyst after activation by short voltage pulses.

  16. Oxygen-reducing catalyst layer

    Energy Technology Data Exchange (ETDEWEB)

    O' Brien, Dennis P. (Maplewood, MN); Schmoeckel, Alison K. (Stillwater, MN); Vernstrom, George D. (Cottage Grove, MN); Atanasoski, Radoslav (Edina, MN); Wood, Thomas E. (Stillwater, MN); Yang, Ruizhi (Halifax, CA); Easton, E. Bradley (Halifax, CA); Dahn, Jeffrey R. (Hubley, CA); O' Neill, David G. (Lake Elmo, MN)

    2011-03-22

    An oxygen-reducing catalyst layer, and a method of making the oxygen-reducing catalyst layer, where the oxygen-reducing catalyst layer includes a catalytic material film disposed on a substrate with the use of physical vapor deposition and thermal treatment. The catalytic material film includes a transition metal that is substantially free of platinum. At least one of the physical vapor deposition and the thermal treatment is performed in a processing environment comprising a nitrogen-containing gas.

  17. 改性介孔硅负载铂催化合成农用增效剂%Modified mesoporous silica supporting platinum catalyst for synthesis of agricultural synergist

    Institute of Scientific and Technical Information of China (English)

    谢慧琳; 张蔚欣; 朱贵有; 胡文斌; 廖列文; 贾振宇; 刘其海

    2016-01-01

    Pt/CS-SiO2 catalyst was prepared by impregnating platinum on chitosan modified mesoporous silica and characterized by Fourier Transform Infrared Spectroscopy (FTIR), nitrogen adsorption-desorption (BET), thermogravimetric analysis (TGA). Catalytic performance was evaluated in hydrosilylation of polyether and trisiloxane for synthesizing agricultural synergist. The experimental results showed that Pt was successfully incorporated on modified mesoporous silica at content of 0.85%. The new catalyst had excellent reusability, which still maintained high activity with greater than 90% of both conversion and selectivity after reused seven times. The optimal synthesis condition for agricultural synergist was a mixture of polyether and trisiloxane at a molar ratio of 1:1.1 and 105℃ for 3 h. The agricultural synergist exhibited excellent stability in neutral aqueous solution by hydrolysis assessment at various pH conditions.%通过壳聚糖(CS)改性介孔二氧化硅,并负载铂得到 Pt/CS-SiO2催化剂,采用红外光谱(FTIR)、氮气吸附脱附(BET)、热重分析(TG)等对催化剂进行表征,同时考察了 Pt/CS-SiO2催化聚醚和三硅氧烷反应合成农用增效剂。结果表明:Pt成功负载在改性介孔硅上,Pt含量为0.85%;催化剂具有良好的重复使用性,使用7次后仍有较高活性,转化率和选择性均在90%以上;合成农用增效剂的最优工艺为 n(MDHM):n(HDE)=1:1.1,反应温度为105℃,反应时间为3 h。测试产物在不同pH的水溶液中的水解性能,发现其在中性条件下可以比较稳定地存在。

  18. Negative resistance for methanol electro-oxidation on platinum/carbon (Pt/C) catalyst investigated by an electrochemical impedance spectroscopy

    Science.gov (United States)

    Cai, Guang-Xu; Guo, Jian-Wei; Wang, Jia; Li, Song

    2015-02-01

    The poisoning of Pt-based catalyst occurs generally during methanol electro-oxidation. Though traditional electrochemical techniques have probed these issues intensively, it is amazing to find that the negative resistance presents in the intermediate potential zone during an electrochemical impedance spectroscopy (EIS) measurement. Based on the chemical reaction analysis, we establish an EIS model and make some numerical analyses, thus determining the specific EIS shapes and equivalent circuits relating to various potential zones. These results not only compensate the drawback for traditional electrochemical approaches, but also reveal the dynamic adsorption of CO and OH species on Pt surfaces, providing a chance for understanding bifunctional mechanism towards quantitative manners. Significantly, we clarify that the negative resistance begins from the maximum catalysis of methanol electro-catalysis and ends in the initial passive state on Pt surfaces, offering a tool for further improvement. Interestingly, our discovery for negative resistance is consistent with that in general electrochemical system, facilitating its extension and direction in future.

  19. Synthesis of platinum nanoparticle electrocatalysts by atomic layer deposition

    Science.gov (United States)

    Lubers, Alia Marie

    Demand for energy continues to increase, and without alternatives to fossil fuel combustion the effects on our environment will become increasingly severe. Fuel cells offer a promising improvement on current methods of energy generation; they are able to convert hydrogen fuel into electricity with a theoretical efficiency of up to 83% and interface smoothly with renewable hydrogen production. Fuel cells can replace internal combustion engines in vehicles and are used in stationary applications to power homes and businesses. The efficiency of a fuel cell is maximized by its catalyst, which is often composed of platinum nanoparticles supported on carbon. Economical production of fuel cell catalysts will promote adoption of this technology. Atomic layer deposition (ALD) is a possible method for producing catalysts at a large scale when employed in a fluidized bed. ALD relies on sequential dosing of gas-phase precursors to grow a material layer by layer. We have synthesized platinum nanoparticles on a carbon particle support (Pt/C) by ALD for use in proton exchange membrane fuel cells (PEMFCs) and electrochemical hydrogen pumps. Platinum nanoparticles with different characteristics were deposited by changing two chemistries: the carbon substrate through functionalization; and the deposition process by use of either oxygen or hydrogen as ligand removing reactants. The metal depositing reactant was trimethyl(methylcyclopentadienyl)platinum(IV). Functionalizing the carbon substrate increased nucleation during deposition resulting in smaller and more dispersed nanoparticles. Use of hydrogen produced smaller nanoparticles than oxygen, due to a gentler hydrogenation reaction compared to using oxygen's destructive combustion reaction. Synthesized Pt/C materials were used as catalysts in an electrochemical hydrogen pump, a device used to separate hydrogen fuel from contaminants. Catalysts deposited by ALD on functionalized carbon using a hydrogen chemistry were the most

  20. 氢-水液相交换疏水催化剂制备及活性影响因素研究进展%Hydrophobic Catalysts for Liquid Phase Catalytic Exchange: A Review of Preparation Methods and Influencing Factors of Catalytic Activities

    Institute of Scientific and Technical Information of China (English)

    胡胜; 熊亮萍; 侯京伟; 罗顺忠; 罗阳明

    2012-01-01

    Liquid phase catalytic exchange (LPCE) between liquid water and gaseous hydrogen has been developed for various applications, such as tritium recovery, water upgrade and heavy-water production. Good wetproofing properties of the hydrophobic catalysts can make the reaction to proceed smoothly. In this article, the preparation methods of the hydrophobic catalysts and the factors affecting the catalytic activities are reviewed. In particular, progress on the hydrophobic Pt/C/inert carrier catalysts is introduced, including the selection of inert carrier and active metal carrier, and the preparation methods of carbon-supported Pt based catalysts. Basic research activities on controllable fabrication of hydro-phobic catalysts are discussed, including the LPCE reaction mechanism, and the relation between the microstructure of active metal and the catalytic activity, etc. Finally, questions remaining to be answered and future directions in the field of hydrophobic catalysts are dis-cussed.%氢-水液相催化交换反应(LPCE)可用于含氚废水处理、含氚重水提氚、重水升级和重水生产等工艺,疏水催化剂是实现LPCE的关键.本文对疏水催化剂的制备方法及活性影响因素进行了综述,重点介绍了Pt/C/惰性载体类疏水催化剂的研究进展,包括惰性载体、活性金属载体的选择,碳负载Pt基催化剂制备方法,详细介绍了围绕疏水催化剂制备开展的基础研究工作,如LPCE微观反应机理,活性金属微观结构与催化活性的关系等.对疏水催化剂这一领域有待解决的问题及下一步的研究方向进行了探讨.

  1. PLATINUM AND FUEL CELLS

    Science.gov (United States)

    Platinum requirements for fuel cell vehicles (FCVS) have been identified as a concern and possible problem with FCV market penetration. Platinum is a necessary component of the electrodes of fuel cell engines that power the vehicles. The platinum is deposited on porous electrodes...

  2. Mineral resource of the month: platinum group metals

    Science.gov (United States)

    Loferski, Patricia J.

    2010-01-01

    The article focuses on platinum group metals (PGMs) and their properties. According to the author, PGMs, which include iridium, osmium, palladium, platinum, rhodium, and ruthenium, are among the rarest mineral commodities in the Earth's crust. PGMs are primarily used as catalytic converters that clean harmful exhaust from vehicle engines. They are also used in the chemical industry as catalysts in the production of nitric acid and in the petroleum refining industry.

  3. Autonomous movement of platinum-loaded stomatocytes.

    Science.gov (United States)

    Wilson, Daniela A; Nolte, Roeland J M; van Hest, Jan C M

    2012-02-26

    Polymer stomatocytes are bowl-shaped structures of nanosize dimensions formed by the controlled deformation of polymer vesicles. The stable nanocavity and strict control of the opening are ideal for the physical entrapment of nanoparticles which, when catalytically active, can turn the stomatocyte morphology into a nanoreactor. Herein we report an approach to generate autonomous movement of the polymer stomatocytes by selectively entrapping catalytically active platinum nanoparticles within their nanocavities and subsequently using catalysis as a driving force for movement. Hydrogen peroxide is free to access the inner stomatocyte cavity, where it is decomposed by the active catalyst (the entrapped platinum nanoparticles) into oxygen and water. This generates a rapid discharge, which induces thrust and directional movement. The design of the platinum-loaded stomatocytes resembles a miniature monopropellant rocket engine, in which the controlled opening of the stomatocytes directs the expulsion of the decomposition products away from the reaction chamber (inner stomatocyte cavity).

  4. Metal Oxide-Supported Platinum Overlayers as Proton-Exchange Membrane Fuel Cell Cathodes

    DEFF Research Database (Denmark)

    Tripkovic, Vladimir; Abild-Pedersen, Frank; Studt, Felix

    2012-01-01

    We investigated the activity and stability of n=(1, 2, 3) platinum layers supported on a number of rutile metal oxides (MO2; M=Ti, Sn, Ta, Nb, Hf and Zr). A suitable oxide support can alleviate the problem of carbon corrosion and platinum dissolution in Pt/C catalysts. Moreover, it can increase t...

  5. The Hydrophobic Effect.

    Science.gov (United States)

    Huque, Entazul M.

    1989-01-01

    Discusses the physical basis and current understanding of hydrophobic effects. The thermodynamic background of the effects, hydrophobic hydration, and hydrophobic interactions are described. Four existing controversies are outlined. (YP)

  6. Bio-inspired routes for synthesizing efficient nanoscale platinum electrocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Jennifer N. [Univ. of California, San Diego, CA (United States); Wang, Joseph [Univ. of California, San Diego, CA (United States)

    2014-08-31

    The overall objective of the proposed research is to use fundamental advances in bionanotechnology to design powerful platinum nanocrystal electrocatalysts for fuel cell applications. The new economically-viable, environmentally-friendly, bottom-up biochemical synthetic strategy will produce platinum nanocrystals with tailored size, shape and crystal orientation, hence leading to a maximum electrochemical reactivity. There are five specific aims to the proposed bio-inspired strategy for synthesizing efficient electrocatalytic platinum nanocrystals: (1) isolate peptides that both selectively bind particular crystal faces of platinum and promote the nucleation and growth of particular nanocrystal morphologies, (2) pattern nanoscale 2-dimensional arrays of platinum nucleating peptides from DNA scaffolds, (3) investigate the combined use of substrate patterned peptides and soluble peptides on nanocrystal morphology and growth (4) synthesize platinum crystals on planar and large-area carbon electrode supports, and (5) perform detailed characterization of the electrocatalytic behavior as a function of catalyst size, shape and morphology. Project Description and Impact: This bio-inspired collaborative research effort will address key challenges in designing powerful electrocatalysts for fuel cell applications by employing nucleic acid scaffolds in combination with peptides to perform specific, environmentally-friendly, simultaneous bottom-up biochemical synthesis and patterned assembly of highly uniform and efficient platinum nanocrystal catalysts. Bulk synthesis of nanoparticles usually produces a range of sizes, accessible catalytic sites, crystal morphologies, and orientations, all of which lead to inconsistent catalytic activities. In contrast, biological systems routinely demonstrate exquisite control over inorganic syntheses at neutral pH and ambient temperature and pressures. Because the orientation and arrangement of the templating biomolecules can be precisely

  7. Behind platinum's sparkle.

    Science.gov (United States)

    Yam, Vivian W W

    2010-09-01

    As a rare and precious metal that is also resistant to wear and tarnish, platinum is known to be particularly well-suited to jewellery. Vivian Yam reflects on how, beyond its prestigious image, platinum has also found its way into a variety of fields ranging from the petrochemical to the pharmaceutical industry.

  8. Tethered catalysts for the hydration of carbon dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Valdez, Carlos A; Satcher, Jr., Joe H; Aines, Roger D; Wong, Sergio E; Baker, Sarah E; Lightstone, Felice C; Stolaroff, Joshuah K

    2014-11-04

    A system is provided that substantially increases the efficiency of CO.sub.2 capture and removal by positioning a catalyst within an optimal distance from the air-liquid interface. The catalyst is positioned within the layer determined to be the highest concentration of carbon dioxide. A hydrophobic tether is attached to the catalyst and the hydrophobic tether modulates the position of the catalyst within the liquid layer containing the highest concentration of carbon dioxide.

  9. Chemistry of Platinum and Palladium Metal Complexes in Homogeneous and Heterogeneous Catalysis: A Mini Review

    Directory of Open Access Journals (Sweden)

    Mehrban Ashiq

    2013-04-01

    Full Text Available Transition metal complexes of platinum and palladium are most widely used in catalysis. Many synthetic reactions have been carried out with such complexes (used as a catalyst which have specifically polymer ligands, through hydrosilylation, acetoxylation, hydrogenation, hydro-formylation, oligo-merisation and polymerization. Almost many platinum and palladium catalysts are heterogeneous in nature i.e. the reaction taking place on a solid surface. Now from few years homogeneous catalysts which are completely soluble in the liquid phase reactant, has acknowledged too much attention, yet having small industrial applications, mainly due to the striving of platinum and palladium complexes separation from the catalytic products. More recently a transitional type of platinum and palladium catalysts have been synthesized through attachment of the activated transition metal complexes on the surface of polymer support particularly insoluble which has been establish to offer encouraging new collection of catalysts for effective research on synthesis. Many of such complexes will be based on the palladium and platinum metals group. The major objective of this review is to inaugurate the relationship among the reactivity’s of homogeneous platinum and palladium complexes and heterogeneous complexes of these metals (those bonded to the surface of metals.

  10. Platinum recycling going green via induced surface potential alteration enabling fast and efficient dissolution

    Science.gov (United States)

    Hodnik, Nejc; Baldizzone, Claudio; Polymeros, George; Geiger, Simon; Grote, Jan-Philipp; Cherevko, Serhiy; Mingers, Andrea; Zeradjanin, Aleksandar; Mayrhofer, Karl J. J.

    2016-01-01

    The recycling of precious metals, for example, platinum, is an essential aspect of sustainability for the modern industry and energy sectors. However, due to its resistance to corrosion, platinum-leaching techniques rely on high reagent consumption and hazardous processes, for example, boiling aqua regia; a mixture of concentrated nitric and hydrochloric acid. Here we demonstrate that complete dissolution of metallic platinum can be achieved by induced surface potential alteration, an ‘electrode-less' process utilizing alternatively oxidative and reductive gases. This concept for platinum recycling exploits the so-called transient dissolution mechanism, triggered by a repetitive change in platinum surface oxidation state, without using any external electric current or electrodes. The effective performance in non-toxic low-concentrated acid and at room temperature is a strong benefit of this approach, potentially rendering recycling of industrial catalysts, including but not limited to platinum-based systems, more sustainable. PMID:27767178

  11. Platinum recycling going green via induced surface potential alteration enabling fast and efficient dissolution

    Science.gov (United States)

    Hodnik, Nejc; Baldizzone, Claudio; Polymeros, George; Geiger, Simon; Grote, Jan-Philipp; Cherevko, Serhiy; Mingers, Andrea; Zeradjanin, Aleksandar; Mayrhofer, Karl J. J.

    2016-10-01

    The recycling of precious metals, for example, platinum, is an essential aspect of sustainability for the modern industry and energy sectors. However, due to its resistance to corrosion, platinum-leaching techniques rely on high reagent consumption and hazardous processes, for example, boiling aqua regia; a mixture of concentrated nitric and hydrochloric acid. Here we demonstrate that complete dissolution of metallic platinum can be achieved by induced surface potential alteration, an `electrode-less' process utilizing alternatively oxidative and reductive gases. This concept for platinum recycling exploits the so-called transient dissolution mechanism, triggered by a repetitive change in platinum surface oxidation state, without using any external electric current or electrodes. The effective performance in non-toxic low-concentrated acid and at room temperature is a strong benefit of this approach, potentially rendering recycling of industrial catalysts, including but not limited to platinum-based systems, more sustainable.

  12. Electrochemical oxidation of carbon monoxide: from platinum single crystals to low temperature fuel catalysts. Part II: Electrooxidation of H2, CO and H2/CO mixtures on well characterized PtMo alloy

    Directory of Open Access Journals (Sweden)

    PHILIP N. ROSS JR.

    2003-03-01

    Full Text Available The oxidation of hydrogen and hydrogen–carbon monoxide mixture has been investigated on well-characterized metallurgically prepared platinum–molybdenum (PtMo alloys. It was concluded that the optimum surface concentration of molybdenum is near 23 mol.%. Based on experimentally determined parameters and simulations, the mechanism of the oxidation of CO/H2 mixtures is discussed.

  13. Decomposition of the Precursor [Pt(NH3)4](OH)2, Genesis and Structure of the Metal-Support Interface of Alumina Supported Platinum Particles: A Structural Study Using TPR, MS and XAFS Spectroscopy.

    NARCIS (Netherlands)

    Koningsberger, D.C.; Muñoz-Paez, A.

    1995-01-01

    During the preparation of alumina supported platinum catalysts, the precursor [Pt(NH3)4](OH)2 decomposes to a neutral Pt(NH3)zO species during the drying process at 120 'C. Treatment in flowing hydrogen at 180 'C leads to partial reduction of the platinum ammine complex and formation of platinum met

  14. Platinum hypersensitivity and desensitization.

    Science.gov (United States)

    Miyamoto, Shingo; Okada, Rika; Ando, Kazumichi

    2015-09-01

    Platinum agents are drugs used for various types of cancer. With increased frequency of administration of platinum agents, hypersensitivity reactions appear more frequently, occurring in over 25% of cases from the seventh cycle or second line onward. It then becomes difficult to conduct treatment using these agents. Various approaches have been investigated to address hypersensitivity reactions to platinum agents. Desensitization, which gradually increases the concentration of the anticancer drug considered to be the antigen until the target dosage, has been reported as being particularly effective, with a success rate of 80-100%. The aims of this paper are to present the current findings regarding hypersensitivity reactions to platinum agents and to discuss attempts of using desensitization against hypersensitivity reactions worldwide. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  15. Manufacture of Catalyst Systems for Ammonia Conversion

    Institute of Scientific and Technical Information of China (English)

    GAKH S.V.; SAVENKOV D.A.

    2012-01-01

    Platinum catalyst gauzes have been in use since the moment of development of the process of catalyst oxidation of ammonia for production of nitric acid or hydrocyanic acid.Catalyst gauzes are usually made of platinum or its alloys with rhodium and palladium.These precious metals have remarkable properties that make them ideal catalysts for acceleration of the ammonia/oxygen reaction.In 2008,OJSC "SIC ‘Supermetal’" and Umicore AG&Co.KG launched a production line for Pt-alloy-based catalyst systems to be used for ammonia oxidation in the production of weak nitric acid.Catalyst systems consist of a pack of catalyst gauzes and a pack of catchment gauzes,which are made using flat-bed knitting machines and wire-cloth looms.Today,up-to-date catalyst systems MKSpreciseTM are being manufactured,the basic advantages of which are an individual structure of gauzes and composition of the material,which allows to define precisely the position of each gauze in the catalyst pack,a high activity of the catalyst pack,direct catching of platinum and rhodium in the catalyst system,and a reasonable combination of single- and multilayer types of gauzes.This makes it possible to vary the configuration of the catalyst and select an optimum composition of the system to ensure the maximum efficiency of the ammonia oxidation process.We also produce the catchment systems that allow to find the best decision from the economic point view for each individual case.

  16. Catalyst and electrode research for phosphoric acid fuel cells

    Science.gov (United States)

    Antoine, A. C.; King, R. B.

    1987-01-01

    An account is given of the development status of phosphoric acid fuel cells' high performance catalyst and electrode materials. Binary alloys have been identified which outperform the baseline platinum catalyst; it has also become apparent that pressurized operation is required to reach the desired efficiencies, calling in turn for the use of graphitized carbon blacks in the role of catalyst supports. Efforts to improve cell performance and reduce catalyst costs have led to the investigation of a class of organometallic cathode catalysts represented by the tetraazaannulenes, and a mixed catalyst which is a mixture of carbons catalyzed with an organometallic and a noble metal.

  17. 火焰原子吸收光谱法测定尾气净化金属载体催化剂中铂钯铑%Determination of platinum, palladium, rhodium in metal carrier catalyst for exhaust gas purification by flame atomic absorption spectrometry

    Institute of Scientific and Technical Information of China (English)

    施意华; 王晟; 杨仲平; 靳晓珠; 胡圣虹; 邓水平

    2012-01-01

    建立了火焰原子吸收光谱法测定尾气净化金属载体催化剂中Pt、Pd、Rh含量的新方法.研究了试样分解方法、共沉淀条件、测定干扰因素及消除方法.采用盐酸-超声波处理尾气净化金属载体催化剂,过滤,不溶物用过氧化钠分解,盐酸酸化后全部转化为样品溶液.在含2~3 mol/L盐酸的样品溶液.中,加入10 mg氧化碲和10 mL 200 g/L氯化亚锡溶液共沉淀富集样品溶液中的Pt、Pd、Rh,与基体元素Fe、Ni、Al、Cr、Na等完全分离,共沉淀物用王水溶解后,采用火焰原子吸收光谱法测定Pt、Pd、Rh.方法的检出限分别为:Pt 4.72 μg/g,Pd1.13μg/g,Rh 1.06 μg/g.将本方法用于实际样品分析,结果与电感耦合等离子体原子发射光谱法测定值一致,相对标准偏差(RSD,n=11)分别为:3.0%(Pt),1.9%(Pd),4.2%(Rh).%A novel method for the determination of platinum, palladium and rhodium in metal carrier catalyst for exhaust gas purification was established by flame atomic absorption spectrometrometry (FAAS). The sample decomposition method) coprecipitation condition, interference factor and elimination method were studied. The metal carrier catalyst sample for exhaust gas purification was treated by hydrochloric acid-ultrasonic wave, and filtrated. The insoluble substance was decomposed with sodium peroxide and acidized with hydrochloric acid, and then it was mixed with sample solution. 10 mg of tellurium oxide and 10 mL of 200 g/L SnCl2 solution were added to sample solution in the medium of 2-3 mol/L hydrochloric acid for the coprecipitation, enrichment and separation of palladium, platinum and rhodium from matrix elements such as Fe, Ni, Al, Cr and Na. After the coprecipitate was dissolved with aqua regia, the content of palladium, platinum and rhodium was determined by flame a-tomic absorption spectrometry. The detection limits of method for Pt, Pd and Rh are 4. 72,1.13 and 1. 06,respectively. The proposed method was applied to

  18. Autothermal reforming catalyst having perovskite structure

    Science.gov (United States)

    Krumpel, Michael; Liu, Di-Jia

    2009-03-24

    The invention addressed two critical issues in fuel processing for fuel cell application, i.e. catalyst cost and operating stability. The existing state-of-the-art fuel reforming catalyst uses Rh and platinum supported over refractory oxide which add significant cost to the fuel cell system. Supported metals agglomerate under elevated temperature during reforming and decrease the catalyst activity. The catalyst is a perovskite oxide or a Ruddlesden-Popper type oxide containing rare-earth elements, catalytically active firs row transition metal elements, and stabilizing elements, such that the catalyst is a single phase in high temperature oxidizing conditions and maintains a primarily perovskite or Ruddlesden-Popper structure under high temperature reducing conditions. The catalyst can also contain alkaline earth dopants, which enhance the catalytic activity of the catalyst, but do not compromise the stability of the perovskite structure.

  19. Toxicity of platinum compounds.

    Science.gov (United States)

    Hartmann, Jörg Thomas; Lipp, Hans-Peter

    2003-06-01

    Since the introduction of platinum-based combination chemotherapy, particularly cisplatin, the outcome of the treatment of many solid tumours has changed. The leading platinum compounds in cancer chemotherapy are cisplatin, carboplatin and oxaliplatin. They share some structural similarities; however, there are marked differences between them in therapeutic use, pharmacokinetics and adverse effects profiles [1-4]. Compared to cisplatin, carboplatin has inferior efficacy in germ-cell tumour, head and neck cancer and bladder and oesophageal carcinoma, whereas both drugs seem to have comparable efficacy in advanced non-small cell and small cell lung cancer as well as ovarian cancer [5-7]. Oxaliplatin belongs to the group of diaminocyclohexane platinum compounds. It is the first platinum-based drug that has marked efficacy in colorectal cancer when given in combination with 5-fluorouracil and folinic acid [8,9]. Other platinum compounds such as oral JM216, ZD0473, BBR3464 and SPI-77, which is a pegylated liposomal formulation of cisplatin, are still under investigation [10-13], whereas nedaplatin has been approved in Japan for the treatment of non-small cell lung cancer and other solid tumours. This review focuses on cisplatin, carboplatin and oxaliplatin.

  20. One-step flame synthesis of an active Pt/TiO2 catalyst for SO2 oxidation

    DEFF Research Database (Denmark)

    Johannessen, Tue; Koutsopoulos, Sotiris

    2002-01-01

    size of the platinum particles supported on aggregated nano-particles of TiO2 is approximately 2 nm. The high SO2-oxidation activity of the catalyst proves that platinum is not hidden in the titania matrix. The flame-produced catalyst showed catalytic activity similar to samples prepared by wet......Flame synthesis as a route for production of composite metal oxides has been employed for the one-step synthesis of a supported noble metal catalyst, i.e. a Pt/TiO2 catalyst, by simultaneous combustion of Ti-isopropoxide and platinum acetylacetonate in a quench-cooled flame reactor. The average...

  1. One-step flame synthesis of an active Pt/TiO2 catalyst for SO2 oxidation

    DEFF Research Database (Denmark)

    Johannessen, Tue; Koutsopoulos, Sotiris

    2002-01-01

    Flame synthesis as a route for production of composite metal oxides has been employed for the one-step synthesis of a supported noble metal catalyst, i.e. a Pt/TiO2 catalyst, by simultaneous combustion of Ti-isopropoxide and platinum acetylacetonate in a quench-cooled flame reactor. The average...... size of the platinum particles supported on aggregated nano-particles of TiO2 is approximately 2 nm. The high SO2-oxidation activity of the catalyst proves that platinum is not hidden in the titania matrix. The flame-produced catalyst showed catalytic activity similar to samples prepared by wet...

  2. Ru4+ ion in CeO2 (Ce0.95Ru0.05O2−): A non-deactivating, non-platinum catalyst for water gas shift reaction

    Indian Academy of Sciences (India)

    Preetam Singh; N Mahadevaiah; Sanjit K Parida; M S Hegde

    2011-09-01

    Hydrogen is a clean energy carrier and highest energy density fuel. Water gas shift (WGS) reaction is an important reaction to generate hydrogen from steam reforming of CO. A new WGS catalyst, Ce1−RuO2− (0 ≤ ≤ 0.1) was prepared by hydrothermal method using melamine as a complexing agent. The Catalyst does not require any pre-treatment. Among the several compositions prepared and tested, Ce0.95Ru0.05O2− (5% Ru4+ ion substituted in CeO2) showed very high WGS activity in terms of high conversion rate (20.5 mol.g-1.s-1 at 275°C) and low activation energy (12.1 kcal/mol). Over 99% conversion of CO to CO2 by H2O is observed with 100% H2 selectivity at ≥ 275°C. In presence of externally fed CO2 and H2 also, complete conversion of CO to CO2 was observed with 100% H2 selectivity in the temperature range of 305-385°C. Catalyst does not deactivate in long duration on/off WGS reaction cycle due to absence of surface carbon and carbonate formation and sintering of Ru. Due to highly acidic nature of Ru4+ ion, surface carbonate formation is also inhibited. Sintering of noble metal (Ru) is avoided in this catalyst because Ru remains in Ru4+ ionic state in the Ce1−RuO2− catalyst.

  3. Hydrophobic Forces in Flotation

    OpenAIRE

    Pazhianur, Rajesh R

    1999-01-01

    An atomic force microscope (AFM) has been used to conduct force measurements to better understand the role of hydrophobic forces in flotation. The force measurements were conducted between a flat mineral substrate and a hydrophobic glass sphere in aqueous solutions. It is assumed that the hydrophobic glass sphere may simulate the behavior of air bubbles during flotation. The results may provide information relevant to the bubble-particle interactions occurring during flotation. The glass ...

  4. Oxidation catalyst

    Science.gov (United States)

    Ceyer, Sylvia T.; Lahr, David L.

    2010-11-09

    The present invention generally relates to catalyst systems and methods for oxidation of carbon monoxide. The invention involves catalyst compositions which may be advantageously altered by, for example, modification of the catalyst surface to enhance catalyst performance. Catalyst systems of the present invention may be capable of performing the oxidation of carbon monoxide at relatively lower temperatures (e.g., 200 K and below) and at relatively higher reaction rates than known catalysts. Additionally, catalyst systems disclosed herein may be substantially lower in cost than current commercial catalysts. Such catalyst systems may be useful in, for example, catalytic converters, fuel cells, sensors, and the like.

  5. 应用于氧还原反应的石墨烯-无定形碳核壳结构复合材料载铂催化剂%Core-shell graphene@amorphous carbon composites supported platinum catalysts for oxygen reduction reaction

    Institute of Scientific and Technical Information of China (English)

    吴惠; 彭焘; 寇宗魁; 张建; 程坤; 何大平; 潘牧; 木士春

    2015-01-01

    采用氯化法制备石墨烯-无定型碳复合材料(GNS@a-C),并用作质子交换膜燃料电池(PEMFC)氧还原反应Pt催化剂的载体.结果显示,所制Pt/GNS@a-C催化剂与传统商业催化剂Pt/C相比,有较好的活性和较高的稳定性:质量活性(0.121 A/mg)几乎是Pt/C (0.064 A/mg)的两倍.更重要的是,该新型催化剂加速4000圈后其电化学活性面积保留了最初的51%,与Pt/C的33%相比,前者有更好的电化学稳定性,显示它在PEMFC中将具有较好的应用潜力.%A core‐shell graphene nanosheets (GNS) and amorphous carbon composite (GNS@a‐C) was pre‐pared by a chlorination method and used as a highly efficient catalyst support for oxygen reduction reaction. Herein, GNS as a shell, with excellent conductivity, high surface area, and corrosion re‐sistance, served as a protecting coating to alleviate the degradation of amorphous carbon core. Platinum nanoparticles were homogeneously deposited on the carbon support (Pt/GNS@a‐C) and showed a good catalytic activity and a higher electrochemical stability when compared with a commercial Pt/C catalyst. The mass activity of Pt/GNS@a‐C catalyst was 0.121 A/mg, which was almost twice as high as that of Pt/C (0.064 A/mg). Moreover, Pt/GNS@a‐C retained 51%of its initial electrochemical specific area after 4000 operating cycles when compared with Pt/C (33%). Thus, the prepared catalyst featured excellent electrochemical stability, showing promise for application in polymer electrolyte membrane fuel cells.

  6. Platinum incorporation in the Na Y zeolite through impregnation method, and characterization by XRD, FTIR and nitrogen adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, A.S.; Sousa, B.V.; Andrade, A.C.C.; Rodrigues, M.G.F. [Universidade Federal de Campina Grande (UFCG), PB (Brazil). Centro de Ciencias e Tecnologia. Unidade Academica de Engenharia Quimica], e-mail: alfredinad@yahoo.com.br, e-mail: biancaviana_cg@yahoo.com.br, e-mail: meiry@deq.ufcg.edu.br; Rangel, M.C. [Universidade Federal da Bahia (UFBA), Salvador, BA (Brazil). Inst. de Quimica. Grupo de Estudos em Cinetica e Catalise

    2007-07-01

    Supported metal catalysts are widely used in petroleum refining, chemical and petroleum industries. These catalysts are important in ammonia synthesis, conversion of hydrocarbons with water vapor to synthesis gas, reforming, hydrocracking, ... Platinum has long been used in cracking, hydrogenation and dehydrogenation processes. The aim of this project is the Na Y zeolitic sample preparation through impregnation for incipient humidity, with 0,5% concentration of platinum, aiming its use as a catalyst in the steam reforming reaction. The characterization techniques used were: X Rays Diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR) and Nitrogen Adsorption (BET Method). From the obtained results through the techniques mentioned previously it is possible to evidence that the platinum impregnation process did not change the Na Y zeolite structure. Through the superficial specific area (BET) it was possible to observe that the platinum impregnation process caused a decrease in the specific area due to the reduction to the accessibility to the micropores of the zeolitic structure. (author)

  7. 金鸡纳-铂催化2-氧代-4-苯基丁酸乙酯的不对称加氢%Enantioselective Hydrogenation of Ethyl 2-Oxo-4-phenylbutyrate on Cinchona-Platinum Catalysts

    Institute of Scientific and Technical Information of China (English)

    夏涛; 任其龙; 吴平东

    2005-01-01

    Enantioselective hydrogenation of ethyl 2-oxo-4-phenylbutyrate to ethyl (R)-2-hydroxy-4-phenyl- bu-tyrate on Pt/γ-Al2O3 modified by 10,11-dihydrocinchonidine was studied by investigating the influences of the amount of modifier, initial concentration of reactant, pressure and temperature on conversion and enantiometric excess in a stirred autoclave and the effects of the liquid velocity, gas velocity, modifier concentration and various catalytic beds in a trickle-bed reactor. The maximum optical yields were about 50% and 60% in the two types of reactors, respectively. It was assumed that the total hydrogenation rate included the reaction rates over the unmodified and modified active sites on platinum surface and a kinetic model, which fitted the experimental data well in autoclave, was obtained. A simplified plug-flow model was proposed to describe the bed average efficiency of trickle-bed reactor.

  8. 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.

  9. Biomineralization of platinum by microorganisms

    Science.gov (United States)

    Pavlova, L. M.; Radomskaya, V. I.; Shumilova, L. P.; Ionov, A. M.; Sorokin, P.

    2017-04-01

    The mechanism of platinum biomineralization by microscopic fungi is displayed based on data of electron microscopy, infrared and X-ray photoelectronic spectroscopy. It was suggested the platinum sorption process by microscopic fungi has some stages. The initial interaction is carried out by the mechanisms of physical and chemical sorption. Hereafter the reduction process of adsorbed platinum ions up to zero state is performed, probably, for account of organic compounds, which are produced by fungi biomass as metabolism result, and the process terminates by nulvalent particles aggregating up to nanosize forms. Obtained data on the platinum biomineralization extends the concept concerning the character of forming platinum nanoparticles in carbonous paleobasin.

  10. Preparation of hydrophobic organic aeorgels

    Science.gov (United States)

    Baumann, Theodore F.; Satcher, Jr., Joe H.; Gash, Alexander E.

    2007-11-06

    Synthetic methods for the preparation of hydrophobic organics aerogels. One method involves the sol-gel polymerization of 1,3-dimethoxybenzene or 1,3,5-trimethoxybenzene with formaldehyde in non-aqueous solvents. Using a procedure analogous to the preparation of resorcinol-formaldehyde (RF) aerogels, this approach generates wet gels that can be dried using either supercritical solvent extraction to generate the new organic aerogels or air dried to produce an xerogel. Other methods involve the sol-gel polymerization of 1,3,5 trihydroxy benzene (phloroglucinol) or 1,3 dihydroxy benzene (resorcinol) and various aldehydes in non-aqueous solvents. These methods use a procedure analogous to the one-step base and two-step base/acid catalyzed polycondensation of phloroglucinol and formaldehyde, but the base catalyst used is triethylamine. These methods can be applied to a variety of other sol-gel precursors and solvent systems. These hydrophobic organics aerogels have numerous application potentials in the field of material absorbers and water-proof insulation.

  11. Effect of Graphitic Content on Carbon Supported Catalyst Performance

    Energy Technology Data Exchange (ETDEWEB)

    Patel, Anant; Artyushkova, Kateryna; Atanassov, Plamen; Harvey, David; Dutta, Monica; Colbow, Vesna

    2011-07-01

    The effect of graphitic content on carbon supported platinum catalysts was investigated in order to investigate its influence on catalyst performance. Four catalysts of varying surface areas and graphitic content were analyzed using XPS, HREELS, and tested using RDE experiments. The catalysts were also heat treated at 150oC and 100%RH as means to uniformly age them. The heat treated samples were analyzed using the same methods to determine what changes had occurred due to this aging process. When compared to the BOL catalysts, heat treated catalysts displayed increased graphitic carbon and platinum metalic content, however they also showed depressed catalytic activity. The primary cause is still under investigation, though it is believed to be related to loss of amorphous carbon content.

  12. Effect of Graphitic Content on Carbon Supported Catalyst Performance

    Energy Technology Data Exchange (ETDEWEB)

    A. Patel; K. Artyushkova; P. Atanassov; David Harvey; M. Dutta; V. Colbow; S. Wessel

    2011-07-01

    The effect of graphitic content on carbon supported platinum catalysts was investigated in order to investigate its influence on catalyst performance. Four catalysts of varying surface areas and graphitic content were analyzed using XPS, HREELS, and tested using RDE experiments. The catalysts were also heat treated at 150 C and 100%RH as means to uniformly age them. The heat treated samples were analyzed using the same methods to determine what changes had occurred due to this aging process. When compared to the BOL catalysts, heat treated catalysts displayed increased graphitic carbon and platinum metallic content, however they also showed depressed catalytic activity. The primary cause is still under investigation, though it is believed to be related to loss of amorphous carbon content.

  13. High catalytic activity and pollutants resistivity using Fe-AAPyr cathode catalyst for microbial fuel cell application

    OpenAIRE

    Carlo Santoro; Alexey Serov; Claudia W. Narvaez Villarrubia; Sarah Stariha; Sofia Babanova; Kateryna Artyushkova; Schuler, Andrew J.; Plamen Atanassov

    2015-01-01

    For the first time, a new generation of innovative non-platinum group metal catalysts based on iron and aminoantipyrine as precursor (Fe-AAPyr) has been utilized in a membraneless single-chamber microbial fuel cell (SCMFC) running on wastewater. Fe-AAPyr was used as an oxygen reduction catalyst in a passive gas-diffusion cathode and implemented in SCMFC design. This catalyst demonstrated better performance than platinum (Pt) during screening in “clean” conditions (PBS), and no degradation in ...

  14. Platinum- and platinum alloy-coated palladium and palladium alloy particles and uses thereof

    Science.gov (United States)

    Adzic, Radoslav; Zhang, Junliang; Mo, Yibo; Vukmirovic, Miomir Branko

    2010-04-06

    The present invention relates to particle and nanoparticle composites useful as oxygen-reduction electrocatalysts. The particle composites are composed of a palladium or palladium-alloy particle or nanoparticle substrate coated with an atomic submonolayer, monolayer, bilayer, or trilayer of zerovalent platinum atoms. The invention also relates to a catalyst and a fuel cell containing the particle or nanoparticle composites of the invention. The invention additionally includes methods for oxygen reduction and production of electrical energy by using the particle and nanoparticle composites of the invention.

  15. Prediction of coal hydrophobicity

    Energy Technology Data Exchange (ETDEWEB)

    Labuschagne, B.C.J. [Council for Scientific and Industrial Research, Pretoria (South Africa). Div. of Energy Technology; Wheelock, T.D.; Guo, R.K.; David, H.T. [Iowa State Univ. of Science and Technology, Ames, IA (United States); Markuszewski, R. [Ames Lab., IA (United States)

    1988-12-31

    Many coals exhibit a certain degree of native hydrophobicity. The more hydrophobic coals (the higher-rank coals) are easily beneficiated by froth flotation or oil agglomeration, while the more hydrophilic coals (the lower-rank coals) are floated or agglomerated with difficulty. Coals of different ranks and often even of the same rank sometimes differ greatly in hydrophobicity as measured by contact angle or natural floatability. Although the degree of hydrophobicity of a coal is related to its rank and has been correlated with other surface properties of the coal , the known information is still not sufficient to allow a good estimation to be made of the hydrophobicity of a given coal and does not explain the variation of coal hydrophobicity as a function of rank. A statistical analysis of previously published data, as well as newly acquired data, shows that coal hydrophobicity correlates better with moisture content than with carbon content, and better with the moisture/carbon molar ratio than with the hydrogen/carbon or oxygen/carbon atomic ratios. These findings indicate that there is a strong association between hydrophobicity and coal moisture content.

  16. SILICA—BOUND 1,7—DITHIA—4—AZA—10,13,16—TRIOXACYCLOOCTADECANE AND ITS PLATINUM COMPLEX

    Institute of Scientific and Technical Information of China (English)

    CHENYuanyin; MENGLingzhi; 等

    1992-01-01

    Dithia-monoaza 18-Crown-6 and its immobilization product,silica-bound 1,7-dithia-4-aza-10,13,16-trioxa-cyclooctadecane via a spacer of three carbon atoms,and its platinum complex have been synthesized.It is found that the platinum complex is an efficient hydrosilylation catalyst for olefins.The XPS data of the platinum complex are reported.

  17. Transformation de l'heptane normal en présence de catalyseurs à base de mordénite larges pores échangée à l'argent et imprégnée de platine Transformation of Normal Heptanes in the Presence of Catalysts with a Large-Pore Mordenite Base Exchanged with Silver and Lmpregnated with Platinum

    Directory of Open Access Journals (Sweden)

    Montarnal R.

    2006-11-01

    Full Text Available Les résultats obtenus dans l'étude des transformations de l'heptane normal, sous pression d'hydrogène sur mordénite échangée à l'argent et imprégnée de 0,5 % en poids de platine, sont interprétés dans le cadre d'un mécanisme bifonctionnel. Toutefois, pour rendre compte de l'influence de la pression partielle d'hydrogène sur les vitesses d'isomérisation et de craquage, il est nécessaire de faire intervenir, pour le craquage par bêta scission des carbocations, un mécanisme bisite impliquant la participation d'un proton voisin du carbocation, tous deux liés au support acide. The results obtained from research on transformations of normal heptane, under hydrogen pressure and using silver-exchanged platinum-impregnated large-pore mordenite as catalyst, are interpreted within the framework of a bifunctional mechanism. However, to take into consideration the influence of hydrogen partial pressure on the isomerization and cracking rates, a twin-sitemechanism must be used for cracking by the beta cleavage of carbonium ions, implying the participation of a proton in the vicinity of the carbonium ion, and with both sites boing linked to the acid support.

  18. NETWORK CROWN ETHER POLYMERS WITH CENTRIC FUNCTIONAL GROUP (Ⅳ) SYNTHESIS OF NETWORK CROWN ETHER POLYMER WITH PENDANT DIETHYLAMINO THIAALKYL GROUP AND ITS PLATINUM COMPLEX

    Institute of Scientific and Technical Information of China (English)

    CHEN Yuanyin; MENG Lingzhi; YIN Yihua; GENG Chengai

    1994-01-01

    The title polymer was prepared from 5-diethylamino-3-thia-pentyl glycidyl ether and diethylene glycol bisglycidyl ether via ring-opening copolymerization. It was found that this reaction could be catalyzed by sodium, but not Lewis acid. The obtained polymer can coordinate with platinum compound, and the platinum complex is a new kind of catalyst for the hydrosilylation of olefins with triethoxysilane.

  19. Characterization of three-way automotive catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Kenik, E.A.; More, K.L. [Oak Ridge National Laboratory, TN (United States); LaBarge, W. [General Motors-AC Delco Systems, Flint, MI (United States)] [and others

    1995-05-01

    This has been the second year of a CRADA between General Motors - AC Delco Systems (GM-ACDS) and Martin Marietta Energy Systems (MMES) aimed at improved performance/lifetime of platinum-rhodium based three-way-catalysts (TWC) for automotive emission control systems. While current formulations meet existing emission standards, higher than optimum Pt-Rh loadings are often required. In additionk, more stringent emission standards have been imposed for the near future, demanding improved performance and service life from these catalysts. Understanding the changes of TWC conversion efficiency with ageing is a critical need in improving these catalysts.

  20. Nickel supported on nitrogen-doped carbon nanotubes as hydrogen oxidation reaction catalyst in alkaline electrolyte

    National Research Council Canada - National Science Library

    Zhuang, Zhongbin; Giles, Stephen A; Zheng, Jie; Jenness, Glen R; Caratzoulas, Stavros; Vlachos, Dionisios G; Yan, Yushan

    2016-01-01

    .... Here we report that a composite catalyst, nickel nanoparticles supported on nitrogen-doped carbon nanotubes, has hydrogen oxidation activity similar to platinum-group metals in alkaline electrolyte...

  1. Effect of Supports on the Catalytic Performance of Platinum Catalysts in Preparing o-Phenylphenol%载体对Pt催化剂制备邻苯基苯酚催化性能的影响

    Institute of Scientific and Technical Information of China (English)

    丁洁莲; 曾崇余

    2012-01-01

    分别以活性炭(AC)、γ-Al2O3 、MgO、TiO2为载体,氯铂酸为活性金属前驱体,采用等体积浸渍法制得不同载体负载的Pt催化剂,考察了它们对环己烯基环己酮(dimer)脱氢制备邻苯基苯酚(OPP)的催化活性和选择性.并用X射线衍射(XRD)、X射线光电子能谱(XPS)、H2程序升温脱附(H2-TPD)、CO2程序升温脱附(CO2TPD)等对催化剂进行表征.结果表明,载体对所制备的催化剂表面Pt含量、酸碱性和对氢吸附能力等微观性能有影响,以γ-Al2O3为载体制备的Pt-K/γ-Al2O3催化剂,由于催化剂表面Pt质量分数高达0.41%,碱性强和碱中心多,利于氢和中间产物在催化剂表面的吸附,从而提高环己烯基环己酮的转化率和OPP选择性.Pt/γ-Al2 O3催化剂在LHSV0.12h1、H2空速33 mL/(g·h)、反应温度380℃的条件下,在200 t/a的工业化装置运转8000h后,环己酮二聚物转化率仍能达99%以上,OPP选择性达90%以上.%Pt-K/AC,Pt-K/γ-Al2O3,Pl-K/MgO and Pt-K/TiO2 catalysts with different supports were prepared by impregnation method using AC.-γAl2O3 ,MgO and TiO2 as the support, respectively, and H2PtCl6 as the precursor. The catalytic performance of the catalysts in preparing o-phenylphenol(OPP) through dehydrogenation of cyclohexanone dimers was evaluated in a fixed bed reactor. These catalysts were characterized by means of X-ray diffraction, X-ray photoelectron spectroscopy, H2 temperature programmed desorption and CO2 temperature programmed desorption. The results show that the Pt content,basicity and adsorption of hydrogen of the Pt catalysts were influenced by the different supports. Pt-K/γ-Al2O3 had the highest surface Pt content (0. 41% ) ,and more surface base sites were favorable to the adsorption of hydrogen and intermediate products and consequently increased the conversion of dimers and the selectivity for OPP. The conversion of the dimers and the selectivity of OPP were respectively over 99% and 90% with 0. 12 h

  2. Investigation of Pt-Ti doped carbon aerogel as bi-metallic catalyst for H/D exchange process

    Science.gov (United States)

    Bhartiya, Sushmita; Kohli, D. K.; Singh, Ashish; Singh, Rashmi; Singh, M. K.

    2017-05-01

    Platinum (Pt) carbon based catalyst for hydrogen-deuterium (H/D) exchange between hydrogen and water is one of the benign processes being explored for heavy water production. Platinum being precious, presents a significant contribution on overall cost of catalyst. Titanium (Ti), a potential catalyst was explored for the H/D exchange to reduce the cost of catalyst. Titanium oxide co-doped with platinum in carbon aerogel (CA) was investigated for the exchange process. The present studies involve synthesis and characterization of TiO2 nanoparticles doped in carbon aerogel. Pt and TiO2 doping (5% by weight for both) in CA was used to prepare the bimetallic PtTi-CA catalyst. The H/D exchange efficiency obtained for the PtTi-CA catalyst (with 50% Pt economy) was 57% which compares well with Pt-CA catalyst having exchange efficiency of 67%.

  3. The study on carbon nanotubes-supported Pt catalysts for PEMFC

    Institute of Scientific and Technical Information of China (English)

    朱捷; 朱红; 康晓红; 葛奉娟; 杨玉国

    2004-01-01

    Carbon nanotube-supported-platinum (Pt/CNTs) and carbon-supported-platinum (Pt/C) catalysts were prepared by in situ chemical reduction method and analyzed by TEM and XRD. Then the experiments were carried out to test the performance of PEMFCs with the Pt electrodes. The results showed that in both catalyst, Pt was of small particle size (about 4 nm) and Pt/CNTs exhibited higher catalytic activity than Pt/C.

  4. Synergistic effect of Brønsted acid and platinum on purification of automobile exhaust gases.

    Science.gov (United States)

    Fu, Wei; Li, Xin-Hao; Bao, Hong-Liang; Wang, Kai-Xue; Wei, Xiao; Cai, Yi-Yu; Chen, Jie-Sheng

    2013-01-01

    The catalytic purification of automobile exhaust gases (CO, NOx and hydrocarbons) is one of the most practiced conversion processes used to lower the emissions and to reduce the air pollution. Nevertheless, the good performance of exhaust gas purification catalysts often requires the high consumption of noble metals such as platinum. Here we report that the Brønsted acid sites on the external surface of a microporous silicoaluminophosphate (SAPO) act as a promoter for exhaust gas purification, effectively cutting the loading amount of platinum in the catalyst without sacrifice of performance. It is revealed that in the Pt-loaded SAPO-CHA catalyst, there exists a remarkable synergistic effect between the Brønsted acid sites and the Pt nanoparticles, the former helping to adsorb and activate the hydrocarbon molecules for NO reduction during the catalytic process. The thermal stability of SAPO-CHA also makes the composite catalyst stable and reusable without activity decay.

  5. Electrocatalytic activity of PtAu/C catalysts for glycerol oxidation.

    Science.gov (United States)

    Jin, Changchun; Sun, Chao; Dong, Rulin; Chen, Zhidong

    2012-01-01

    The electrocatalytic oxidation of glycerol on PtAu/C catalysts has been investigated by cyclic voltammetry. PtAu bimetallic nanoparticles are prepared by chemical reduction. Carbon-supported PtAu catalysts are found to exhibit high electrocatalytic activity for the oxidation of glycerol in alkaline solution in terms of oxidation potential and current density as well as stability, and PtAu/C catalysts with different Pt:Au composition ratios show no much difference in catalytic activity. In acidic solution, PtAu/C catalysts exhibit similar to Pt/C catalysts in activity, but the advantage of the PtAu/C catalysts in terms of per unit mass of platinum is still obvious. The PtAu/C catalysts, in a wide Pt:Au ratio range, show a remarkable enhancement in the mass specific activity of platinum with decreasing platinum content in both alkaline and acidic solutions. This is of significance for reducing the usage of platinum and indicates that though platinum acts as main active sites, gold also plays an important role in the function of PtAu/C catalysts.

  6. Studies on PEM fuel cell noble metal catalyst dissolution

    DEFF Research Database (Denmark)

    Andersen, S. M.; Grahl-Madsen, L.; Skou, E. M.

    2011-01-01

    A combination of electrochemical, spectroscopic and gravimetric methods was carried out on Proton Exchange Membrane (PEM) fuel cell electrodes with the focus on platinum and ruthenium catalysts dissolution, and the membrane degradation. In cyclic voltammetry (CV) experiments, the noble metals were...... found to dissolve in 1 M sulfuric acid solution and the dissolution increased exponentially with the upper potential limit (UPL) between 0.6 and 1.6 vs. RHE. 2-20% of the Pt (depending on the catalyst type) was found to be dissolved during the experiments. Under the same conditions, 30-100% of the Ru...... (depending on the catalyst type) was found to be dissolved. The faster dissolution of ruthenium compared to platinum in the alloy type catalysts was also confirmed by X-ray diffraction measurements. The dissolution of the carbon supported catalyst was found one order of magnitude higher than the unsupported...

  7. Adhesion enhancement for liquid silicone rubber and different surface by organosilane and Pt catalyst at room temperature

    Indian Academy of Sciences (India)

    Fang Wang; Yanni Li; Dan Wang

    2013-11-01

    Surface modification of aluminum, glass, epoxy resin, polypropylene and polyethylene via corona discharge pretreatment and platinum catalyst addition to promote their adhesion with liquid silicone rubber is reported. The corona-pretreated substrate surface was silanized with vinyltrimethoxysilane to generate vinyl groups on the surface, which could be initiated by platinum catalyst to form vinyl radicals. Then, the vinyltrimethoxysilane modified substrate was dipped into platinum catalyst solution to introduce platinum on the vinyltrimethoxysilane surface. The modified aluminum surface was characterized by X-ray photoelectron spectroscopy (XPS). The strong adhesion property between liquid silicone rubber and different surface was achieved by introducing a small amount of vinyltrimethoxysilane and platinum catalyst, followed by curing at low temperature. XPS result indicated the formation of vinyltrimethoxysilane coating on aluminum surface. Peel strength for liquid silicone rubber/vinyltrimethoxysilane–platinum surface was over 3.2 kN/m compared to only 1.1 kN/m for liquid silicone rubber/vinyltrimethoxysilane–aluminum. The cohesive failure in the bulk of liquid silicone rubber was observed for liquid silicone rubber/vinyltrimethoxysilane–platinum surface. It is assumed that the cross-linking reactions between vinyl groups in the vinyltrimethoxysilane coating and unsaturated terminal group of liquid silicone rubber occur due to the existence of platinum catalyst.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2006-07-01

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

  9. Platinum nitride with fluorite structure

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Rong; Zhang, Xiao-Feng

    2005-01-31

    The mechanical stability of platinum nitride has been studied using first-principles calculations. By calculating the single-crystal elastic constants, we show that platinum nitride can be stabilized in the fluorite structure, in which the nitrogen atoms occupy all the tetrahedral interstitial sites of the metal lattice. The stability is attributed to the pseudogap effect from analysis of the electronic structure.

  10. Formic Acid Oxidation at Platinum-Bismuth Clusters

    DEFF Research Database (Denmark)

    Lovic, J. D.; Stevanovic, S. I.; Tripkovic, D. V.

    2014-01-01

    Formic acid oxidation was studied on platinum-bismuth deposits on glassy carbon (GC) substrate. The catalysts of equimolar ratio were prepared by potentiostatic deposition using chronocoulometry. Bimetallic structures obtained by two-step process, comprising deposition of Bi followed by deposition...... of Pt, were characterized by AFM spectroscopy which indicated that Pt crystallizes preferentially onto previously formed Bi particles. The issue of Bi leaching (dissolution) from PtBi catalysts, and their catalytic effect alongside the HCOOH oxidation is rather unresolved. In order to control Bi...... dissolution, deposits were subjected to electrochemical oxidation, in the relevant potential range and supporting electrolyte, prior to use as catalysts for HCOOH oxidation. Anodic striping charges indicated that along oxidation procedure most of deposited Bi was oxidized. ICP mass spectroscopy analysis...

  11. High Selective Hydrogenation of Acetophenone Catalyzed by Alumina Supported Platinum Nanoclusters

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A new preparation and reduction method of γ-Al2O3 supported and PVP stabilized platinum nanoclusters was studied.The catalyst exhibited very high activity and selectivity for acetophenone hydrogenation in isopropanol-KOH solution at 25~60°C and P H2=1~5 MPa.

  12. Electronic metal-support interaction enhanced oxygen reduction activity and stability of boron carbide supported platinum

    Science.gov (United States)

    Jackson, Colleen; Smith, Graham T.; Inwood, David W.; Leach, Andrew S.; Whalley, Penny S.; Callisti, Mauro; Polcar, Tomas; Russell, Andrea E.; Levecque, Pieter; Kramer, Denis

    2017-06-01

    Catalysing the reduction of oxygen in acidic media is a standing challenge. Although activity of platinum, the most active metal, can be substantially improved by alloying, alloy stability remains a concern. Here we report that platinum nanoparticles supported on graphite-rich boron carbide show a 50-100% increase in activity in acidic media and improved cycle stability compared to commercial carbon supported platinum nanoparticles. Transmission electron microscopy and x-ray absorption fine structure analysis confirm similar platinum nanoparticle shapes, sizes, lattice parameters, and cluster packing on both supports, while x-ray photoelectron and absorption spectroscopy demonstrate a change in electronic structure. This shows that purely electronic metal-support interactions can significantly improve oxygen reduction activity without inducing shape, alloying or strain effects and without compromising stability. Optimizing the electronic interaction between the catalyst and support is, therefore, a promising approach for advanced electrocatalysts where optimizing the catalytic nanoparticles themselves is constrained by other concerns.

  13. Platinum monolayer electrocatalyst on gold nanostructures on silicon for photoelectrochemical hydrogen evolution.

    Science.gov (United States)

    Kye, Joohong; Shin, Muncheol; Lim, Bora; Jang, Jae-Won; Oh, Ilwhan; Hwang, Seongpil

    2013-07-23

    Pt monolayer decorated gold nanostructured film on planar p-type silicon is utilized for photoelectrochemical H2 generation in this work. First, gold nanostructured film on silicon was spontaneously produced by galvanic displacement of the reduction of gold ion and the oxidation of silicon in the presence of fluoride anion. Second, underpotential deposition (UPD) of copper under illumination produced Cu monolayer on gold nanostructured film followed by galvanic exchange of less-noble Cu monolayer with more-noble PtCl6(2-). Pt(shell)/Au(core) on p-type silicon showed the similar activity with platinum nanoparticle on silicon for photoelectrochemical hydrogen evolution reaction in spite of low platinum loading. From Tafel analysis, Pt(shell)/Au(core) electrocatalyst shows the higher area-specific activity than platinum nanoparticle on silicon demonstrating the significant role of underlying gold for charge transfer reaction from silicon to H(+) through platinum catalyst.

  14. Design criteria for stable Pt/C fuel cell catalysts.

    Science.gov (United States)

    Meier, Josef C; Galeano, Carolina; Katsounaros, Ioannis; Witte, Jonathon; Bongard, Hans J; Topalov, Angel A; Baldizzone, Claudio; Mezzavilla, Stefano; Schüth, Ferdi; Mayrhofer, Karl J J

    2014-01-01

    Platinum and Pt alloy nanoparticles supported on carbon are the state of the art electrocatalysts in proton exchange membrane fuel cells. To develop a better understanding on how material design can influence the degradation processes on the nanoscale, three specific Pt/C catalysts with different structural characteristics were investigated in depth: a conventional Pt/Vulcan catalyst with a particle size of 3-4 nm and two Pt@HGS catalysts with different particle size, 1-2 nm and 3-4 nm. Specifically, Pt@HGS corresponds to platinum nanoparticles incorporated and confined within the pore structure of the nanostructured carbon support, i.e., hollow graphitic spheres (HGS). All three materials are characterized by the same platinum loading, so that the differences in their performance can be correlated to the structural characteristics of each material. The comparison of the activity and stability behavior of the three catalysts, as obtained from thin film rotating disk electrode measurements and identical location electron microscopy, is also extended to commercial materials and used as a basis for a discussion of general fuel cell catalyst design principles. Namely, the effects of particle size, inter-particle distance, certain support characteristics and thermal treatment on the catalyst performance and in particular the catalyst stability are evaluated. Based on our results, a set of design criteria for more stable and active Pt/C and Pt-alloy/C materials is suggested.

  15. Design criteria for stable Pt/C fuel cell catalysts

    Directory of Open Access Journals (Sweden)

    Josef C. Meier

    2014-01-01

    Full Text Available Platinum and Pt alloy nanoparticles supported on carbon are the state of the art electrocatalysts in proton exchange membrane fuel cells. To develop a better understanding on how material design can influence the degradation processes on the nanoscale, three specific Pt/C catalysts with different structural characteristics were investigated in depth: a conventional Pt/Vulcan catalyst with a particle size of 3–4 nm and two Pt@HGS catalysts with different particle size, 1–2 nm and 3–4 nm. Specifically, Pt@HGS corresponds to platinum nanoparticles incorporated and confined within the pore structure of the nanostructured carbon support, i.e., hollow graphitic spheres (HGS. All three materials are characterized by the same platinum loading, so that the differences in their performance can be correlated to the structural characteristics of each material. The comparison of the activity and stability behavior of the three catalysts, as obtained from thin film rotating disk electrode measurements and identical location electron microscopy, is also extended to commercial materials and used as a basis for a discussion of general fuel cell catalyst design principles. Namely, the effects of particle size, inter-particle distance, certain support characteristics and thermal treatment on the catalyst performance and in particular the catalyst stability are evaluated. Based on our results, a set of design criteria for more stable and active Pt/C and Pt-alloy/C materials is suggested.

  16. Uso de un Líquido Iónico como Catalizador para la Oxidación de Alcoholes Hidrofóbicos de Alto Peso Molecular The Use of an Ionic Liquid Catalyst for the Oxidation of Hydrophobic High Molecular Weight Alcohols

    Directory of Open Access Journals (Sweden)

    Nadia Guajardo

    2010-01-01

    Full Text Available Se realizaron pruebas de oxidación del docosanol hacia su respectivo ácido en un reactor discontinuo, usando un líquido iónico como catalizador compuesto por el catión Aliquat®336 y el anión poliperoxometalato {PO4[WO(O22]4}3-. Los resultados obtenidos permiten inferir que solo el agua oxigenada puede ser utilizado efectivamente como agente oxidante y confirmando la efectiva transferencia del oxigeno activo entre las fases acuosa y orgánica, además se constató que el paso limitante de la reacción global corresponde a la conversión del docosanol hacia el intermedio reacción (aldehído para la cual se estimó una constante cinética de 0,26 L mole-1 h-1 mientras que la cinética de la posterior oxidación hacia el ácido fue estimada en 1,3 L mole-1 h-1 (ambas a 90 °C. Luego de 6 horas de reacción a 90°C fueron obtenidas conversiones máximas de 81% y selectividads de 55%, operando con una relación molar H2O2/alcohol igual a 3 y relación másica alcohol/catalizador igual a 100.Catalytic batch oxidation runs of an hydrophobic high molecular weight alcohol (docosanol to the acid were performed using a functionalized ionic liquid composed by an Aliquat®336 cation and a polyperoxometalate {PO4[WO(O22]4}3- anion as a catalyst. The active oxygen is efficiently transferred by the catalyst from the aqueous to the alcoholic phase in accordance with an experimentally validated reaction scheme. Only the hydrogen peroxide was used effectively as an oxidant, giving an 81 % conversion and a 55% yield after 6 hours at 90ºC, with a H2O2/alcohol molar ratio that equal 3 and an alcohol/catalyst mass ratio that equal 100. The calculated kinetic constants, at 90ºC, for the docosanol oxidation to the aldehyde intermediate and the further oxidation towards docosanoic acid were 0,26 and 1,3 L mole-1 h-1, respectively.

  17. Hydrophobic, Porous Battery Boxes

    Science.gov (United States)

    Bragg, Bobby J.; Casey, John E., Jr.

    1995-01-01

    Boxes made of porous, hydrophobic polymers developed to contain aqueous potassium hydroxide electrolyte solutions of zinc/air batteries while allowing air to diffuse in as needed for operation. Used on other types of batteries for in-cabin use in which electrolytes aqueous and from which gases generated during operation must be vented without allowing electrolytes to leak out.

  18. Hydrophobic treatment of concrete

    NARCIS (Netherlands)

    Vries, J. de; Polder, R.B.

    1996-01-01

    As part of the maintenance policy of the Dutch Ministry of Transport, Civil Engineering Division, hydrophobic treatment of concrete was considered as an additional protective measure against penetration of aggressive substances, for instance deicing salts in bridge decks. A set of tests was designed

  19. Hydrophobic treatment of concrete

    NARCIS (Netherlands)

    Vries, J.de; Polder, R.B.

    1997-01-01

    As part of the maintenance policy of the dutch Ministry of Transport, Civil Engineering Division, hydrophobic treatment of concrete was considered as an additional protective measure against penetration of aggressive substances, for instance deicing salts in bridge decks. A set of tests was designed

  20. Oxygen Reduction on Platinum

    DEFF Research Database (Denmark)

    Nesselberger, Markus

    bands are observed on the Pt/C layer: bands arising from the functional groups of the carbon support, bands related to water and hydronium, and bands related to the sulfur anion interaction with the catalyst. The correlation of the anion absorption to the ORR current leads to the proposition that anion...

  1. Design of colloidal Pt catalysts encapsulated by silica nano membranes for enhanced stability in H2S streams

    NARCIS (Netherlands)

    Calderone, V.R.; Schütz-Widoniak, J.; Bezemer, G.L.; Bakker, G.; Steurs, C.; Philipse, A.P.

    2010-01-01

    Poisoning of platinum catalysts by sulphur compounds is a significant problem that prevents their application in untreated gas streams. We introduce a novel concept to circumvent the poisoning problem by encapsulating individual platinum nano-particles with silica layers that act as selective membra

  2. Off-gas catalyst. Abgaskatalysator

    Energy Technology Data Exchange (ETDEWEB)

    Saris, L.; Kloeck, H.

    1987-02-19

    The invention deals with a waste gas catalyst with a thermo-resistant SiO{sub 2} and Al{sub 2}O{sub 3} containing carrier of snarled ceramic fibres which form between themselves the flow paths for the waste gas to be purified and which are coated with platinum, palladium and/or rhodium. The ceramic fibres forming the carrier consist of SiO{sub 2} and Al{sub 2}O{sub 3} and have a diameter of 1 to 10 {mu}m. (orig./RB).

  3. The effect of hydrophobic absorbent for reducing charge recombination to improve dye-sensitized solar cell performance

    Science.gov (United States)

    Sae-Kung, C.; Hatha, E.; Sichanugrist, P.; Pungwiwut, N.; Laosooksathit, S.

    2007-09-01

    Normally, it has been widely acceptable that dye sensitized solar cell (DSSC) plays important roles compared to the conventional solar cells such as monocrystalline, polycrystalline, and even amorphous silicon in accordance with its low manufacturing and fabrication cost. However, the DSSC consists of many interfaces between anode and cathode such as semiconductor to dye and dye to electrolyte and electrolyte to platinum catalyst at the cathode. Therefore, the effect of charge recombination at dye-electrolyte interface is a major role to cell efficiency. One of major implementations to alleviate the recombination effect could be efficiently solved by adding hydrophobic co-adsorbent to dye solution. The co-absorbent molecule will be anchored to titanium dioxide semiconductor like dye and can be the barrier to protect the interface of the triiodide, dye and mesoporous titanium dioxide (TiO II). In our works, we investigate on various hydrophobic co-adsorbent such as 1-adamantane acetic acid, cholic acid and chenodeoxy cholic acid. The amounts of the co-absorbent were varied as well as the amount of dye N719. It was found that the cholic and chenodeoxy cholic acid increase photovoltage and photocurrent, especially when the concentration was increased. This may be due to shift of conduction band (CB) to negative direction by the co-absorbent but 1-adamantane-acetic acid could not resist charge recombination. In addition multilayer of titanium dioxide was also studied on the effect of conversion efficiency. The maximum 4 layers of TiO II provided the best cell performance of 8.3 efficiency with the presence of cholic acid.

  4. Catalysis on oriented ultrathin films of platinum on Al/sub 2/O/sub 3/

    Energy Technology Data Exchange (ETDEWEB)

    Glassl, H.; Hayek, K.

    1982-03-26

    The selectivity of the hydrogenolysis of methylcyclopentane on model thin film catalysts was investigated and the morphology of the particles was checked in parallel by transmission electron microscopy and transmission electron diffraction. The catalysts were island-stage platinum films of defined orientation obtained by evaporating platinum onto (100)- and (111)-oriented NaCl substrates, backing with Al/sub 2/O/sub 3/ and dissolving the substrate. The catalysts were quite inactive as long as the single-crystal surface was unchanged, and any increase in activity was accompanied by a change in morphology. The results are compared with those obtained on non-oriented films as well as on bulk single-crystal surfaces.

  5. Performance of metal alloys as hydrogen evolution reaction catalysts in a microbial electrolysis cell

    NARCIS (Netherlands)

    Jeremiasse, A.W.; Bergsma, J.; Kleijn, J.M.; Saakes, M.; Buisman, C.J.N.; Cohen Stuart, M.A.; Hamelers, H.V.M.

    2011-01-01

    H2 can be produced from organic matter with a microbial electrolysis cell (MEC). To decrease the energy input and increase the H2 production rate of an MEC, a catalyst is used at the cathode. Platinum is an effective catalyst, but its high costs stimulate searching for alternatives, such as non-nobl

  6. Hydrophobic interactions and chemical reactivity

    NARCIS (Netherlands)

    Otto, Sijbren; Engberts, Jan B.F.N.

    2003-01-01

    This perspective describes how kinetic studies of organic reactions can be used to increase our understanding of hydrophobic interactions. In turn, our understanding of hydrophobic interactions can be used as a tool to influence chemical reactions.

  7. Hydrophobic interactions and chemical reactivity

    NARCIS (Netherlands)

    Otto, Sijbren; Engberts, Jan B.F.N.

    2003-01-01

    This perspective describes how kinetic studies of organic reactions can be used to increase our understanding of hydrophobic interactions. In turn, our understanding of hydrophobic interactions can be used as a tool to influence chemical reactions.

  8. Highly trifluoromethylated platinum compounds.

    Science.gov (United States)

    Martínez-Salvador, Sonia; Forniés, Juan; Martín, Antonio; Menjón, Babil

    2011-07-11

    The homoleptic, square-planar organoplatinum(II) compound [NBu(4)](2) [Pt(CF(3))(4)] (1) undergoes oxidative addition of CF(3) I under mild conditions to give rise to the octahedral organoplatinum(IV) complex [NBu(4)](2) [Pt(CF(3))(5)I] (2). This highly trifluoromethylated species reacts with Ag(+) salts of weakly coordinating anions in Me(2)CO under a wet-air stream to afford the aquo derivative [NBu(4)][Pt(CF(3))(5) (OH(2))] (4) in around 75% yield. When the reaction of 2 with the same Ag(+) salts is carried out in MeCN, the solvento compound [NBu(4) ][Pt(CF(3))(5)(NCMe)] (5) is obtained in around 80% yield. The aquo ligand in 4 as well as the MeCN ligand in 5 are labile and can be cleanly replaced by neutral and anionic ligands to furnish a series of pentakis(trifluoromethyl)platinate(IV) compounds with formulae [NBu(4)][Pt(CF(3))(5) (L)] (L=CO (6), pyridine (py; 7), tetrahydrothiophene (tht; 8)) and [NBu(4)](2) [Pt(CF(3))(5)X] (X=Cl (9), Br (10)). The unusual carbonyl-platinum(IV) derivative [NBu(4)][Pt(CF(3))(5) (CO)] (6) is thermally stable and has a ν(CO) of 2194 cm(-1). The crystal structures of 2⋅CH(2)Cl(2), 5, [PPh(4) ][Pt(CF(3))(5)(CO)] (6'), and 7 have been established by X-ray diffraction methods. Compound 2 has shown itself to be a convenient entry to the chemistry of highly trifluoromethylated platinum compounds. To the best of our knowledge, compounds 2 and 4-10 are the organoelement compounds with the highest CF(3) content to have been isolated and adequately characterized to date.

  9. Phase transfer of platinum nanoparticles from aqueous to organic solutions using fatty amine molecules

    Indian Academy of Sciences (India)

    Ashavani Kumar; Hrushikesh M Joshi; Anandrao B Mandale; Rajendra Srivastava; Suguna D Adyanthaya; Renu Pasricha; Murali Sastry

    2004-08-01

    In this report we demonstrate a simple process based on amine chemistry for the phase transfer of platinum nanoparticles from an aqueous to an organic solution. The phase transfer was accomplished by vigorous shaking of a biphasic mixture of platinum nanoparticles synthesised in an aqueous medium and octadecylamine (ODA) in hexane. During shaking of the biphasic mixture, the aqueous platinum nanoparticles complex via either coordination bond formation or weak covalent interaction with the ODA molecules present in the organic phase. This process renders the nanoparticles sufficiently hydrophobic and dispersible in the organic phase. The ODA-stabilised platinum nanoparticles could be separated out from hexane in the form of a powder that is readily redispersible in weakly polar and nonpolar organic solvents. The ODA-capped platinum nanoparticles show high catalytic activity in hydrogenation reactions and this is demonstrated in the efficient conversion of styrene to ethyl benzene. The nature of binding of the ODA molecules to the platinum nanoparticles surface was characterised by thermogravimetry, transmission electron microscopy (TEM), X-ray photoemission spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR).

  10. Elaboration, physical and electrochemical characterizations of CO tolerant PEMFC anode materials. Study of platinum-molybdenum and platinum-tungsten alloys and composites; Elaborations et caracterisations electrochimiques et physiques de materiaux d'anode de PEMFC peu sensibles a l'empoisonnement par CO: etude d'alliages et de composites a base de platine-molybdene et de platine-tungstene

    Energy Technology Data Exchange (ETDEWEB)

    Peyrelade, E.

    2005-06-15

    PEMFC development is hindered by the CO poisoning ability of the anode platinum catalyst. It has been previously shown that the oxidation potential of carbon monoxide adsorbed on the platinum atoms can be lowered using specific Pt based catalysts, either metallic alloys or composites. The objective is then to realize a catalyst for which the CO oxidation is compatible with the working potential of a PEMFC anode. In our approach, to enhance the CO tolerance of platinum based catalyst supported on carbon, we studied platinum-tungsten and platinum-molybdenum alloys and platinum-metal oxide materials (Pt-WO{sub x} and Pt-MoO{sub x}). The platinum based alloys demonstrate a small effect of the second metal towards the oxidation of carbon monoxide. The platinum composites show a better tolerance to carbon monoxide. Electrochemical studies on both Pt-MoO{sub x} and Pt-WO{sub x} demonstrate the ability of the metal-oxides to promote the ability of Pt to oxidize CO at low potentials. However, chrono-amperometric tests reveal a bigger influence of the tungsten oxide. Complex chemistry reactions on the molybdenum oxide surface make it more difficult to observe. (author)

  11. Surface engineering of hierarchical platinum-cobalt nanowires for efficient electrocatalysis

    Science.gov (United States)

    Bu, Lingzheng; Guo, Shaojun; Zhang, Xu; Shen, Xuan; Su, Dong; Lu, Gang; Zhu, Xing; Yao, Jianlin; Guo, Jun; Huang, Xiaoqing

    2016-06-01

    Despite intense research in past decades, the lack of high-performance catalysts for fuel cell reactions remains a challenge in realizing fuel cell technologies for transportation applications. Here we report a facile strategy for synthesizing hierarchical platinum-cobalt nanowires with high-index, platinum-rich facets and ordered intermetallic structure. These structural features enable unprecedented performance for the oxygen reduction and alcohol oxidation reactions. The specific/mass activities of the platinum-cobalt nanowires for oxygen reduction reaction are 39.6/33.7 times higher than commercial Pt/C catalyst, respectively. Density functional theory simulations reveal that the active threefold hollow sites on the platinum-rich high-index facets provide an additional factor in enhancing oxygen reduction reaction activities. The nanowires are stable in the electrochemical conditions and also thermally stable. This work may represent a key step towards scalable production of high-performance platinum-based nanowires for applications in catalysis and energy conversion.

  12. Understanding platinum-induced ototoxicity.

    Science.gov (United States)

    Langer, Thorsten; am Zehnhoff-Dinnesen, Antoinette; Radtke, Susanne; Meitert, Johannes; Zolk, Oliver

    2013-08-01

    Childhood cancer survival rates are now nearly 80% in more developed European countries because of improved therapies and better supportive care. Platinum chemotherapy drugs, such as cisplatin and carboplatin, are the cornerstone of many effective therapeutic protocols for childhood cancer. However, the antitumor efficacy of cisplatin and carboplatin comes at the cost of ototoxicity, which affects at least 60% of pediatric patients. Although ototoxicity is not life threatening, it can have debilitating effects on patients' quality of life. Recently, many initiatives have been launched with the ultimate goal of reducing cisplatin and high-dose carboplatin ototoxicity without compromising antitumor efficacy. This review addresses the incidence of platinum ototoxicity and its clinical presentation, time course, and early diagnostic evaluation. Genetic and non-genetic risk factors for platinum-associated ototoxicity, and their predictive value, are discussed. Recent developments in the prevention of platinum ototoxicity are also summarized. Copyright © 2013 Elsevier Ltd. All rights reserved.

  13. Highly sensitive silicon microreactor for catalyst testing

    DEFF Research Database (Denmark)

    Henriksen, Toke Riishøj; Olsen, Jakob Lind; Vesborg, Peter Christian Kjærgaard;

    2009-01-01

    by directing the entire gas flow through the catalyst bed to a mass spectrometer, thus ensuring that nearly all reaction products are present in the analyzed gas flow. Although the device can be employed for testing a wide range of catalysts, the primary aim of the design is to allow characterization of model...... catalysts which can only be obtained in small quantities. Such measurements are of significant fundamental interest but are challenging because of the low surface areas involved. The relationship between the reaction zone gas flow and the pressure in the reaction zone is investigated experimentally......, it is found that platinum catalysts with areas as small as 15 mu m(2) are conveniently characterized with the device. (C) 2009 American Institute of Physics. [doi:10.1063/1.3270191]...

  14. Hydrophobic sugar holograms

    Science.gov (United States)

    Mejias-Brizuela, N. Y.; Olivares-Pérez, A.; Páez-Trujillo, G.; Hernández-Garay, M. P.; Fontanilla-Urdaneta, R.; Fuentes-Tapia, I.

    2008-02-01

    The sugar matrix is used to record of phase holograms; it was modified with the purpose of obtaining a hydrophobic material to improve the stability of the registered image and to stimulate the photosensitivity of the sugar. The new material is formed by a sugar, pectin and vanillin dissolution. The diffraction efficiency parameter increases in comparison with only the sugar matrix, obtaining already of 10%.

  15. Kinetics of methanol electrooxidation on Pt/C and PtRu/C catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Diaz, V.; Ohanian, M. [Instituto de Ingenieria Quimica, Facultad de Ingenieria, J. Herrera y Reissig 565, Universidad de la Republica, 11300 Montevideo (Uruguay); Zinola, C.F. [Laboratorio de Electroquimica Fundamental, Facultad de Ciencias, Igua 4225, Universidad de la Republica, 11400 Montevideo (Uruguay)

    2010-10-15

    This paper analyzes the performance of platinum and platinum:ruthenium carbon-supported catalysts modified by the application of in-situ cathodic polarizations towards the methanol oxidation reaction. These new electrodes are characterized by electrochemical techniques together with transmission electron microscopy images to envisage the dispersion of the catalyst. We measure methanol electrooxidation current transients, fitting the results with a general kinetic equation for a mixed mass and charge transfer processes for adsorbed reactant species. The kinetic equation also helps to predict the exponent of the chronoamperometric decay as directly related to the fractal dimension of the catalyst surface and to discuss the possible processes involved in the electrocatalytic reaction. (author)

  16. Inorganic nanocarriers for platinum drug delivery

    Directory of Open Access Journals (Sweden)

    Ping’an Ma

    2015-12-01

    Full Text Available Nowadays platinum drugs take up almost 50% of all the clinically used anticancer drugs. Besides cisplatin, novel platinum agents including sterically hindered platinum (II drugs, chemically reductive platinum (IV drugs, photosensitive platinum (IV drugs, and multinuclear platinum drugs have been developed recently, with a few entering clinic trials. Rapid development of nanobiotechnology makes targeted delivery of anticancer platinum agents to the tumor site possible, while simultaneously minimizing toxicity and maximizing the drug efficacy. Being versatile drug carriers to deliver platinum drugs, inorganic nanovehicles such as gold nanoparticles, iron oxide nanomaterials, carbon nanotubes, mesoporous nanosilica, metal-organic frameworks (MOFs, have been extensively studied over the past decades. In contrast to conventional polymeric and lipid nanoparticles, inorganic nanoparticles based drug carriers are peculiar as they have shown excellent theranostic effects, revealing themselves an indispensable part of future nanomedicine. Here, we will elaborate recent research advances on fabrication of inorganic nanoparticles for platinum drug delivery.

  17. Highly active carbon supported Pd cathode catalysts for direct formic acid fuel cells

    Science.gov (United States)

    Mikolajczuk-Zychora, A.; Borodzinski, A.; Kedzierzawski, P.; Mierzwa, B.; Mazurkiewicz-Pawlicka, M.; Stobinski, L.; Ciecierska, E.; Zimoch, A.; Opałło, M.

    2016-12-01

    One of the drawbacks of low-temperature fuel cells is high price of platinum-based catalysts used for the electroreduction of oxygen at the cathode of the fuel cell. The aim of this work is to develop the palladium catalyst that will replace commonly used platinum cathode catalysts. A series of palladium catalysts for oxygen reduction reaction (ORR) were prepared and tested on the cathode of Direct Formic Acid Fuel Cell (DFAFC). Palladium nanoparticles were deposited on the carbon black (Vulcan) and on multiwall carbon nanotubes (MWCNTs) surface by reduction of palladium(II) acetate dissolved in ethanol. Hydrazine was used as a reducing agent. The effect of functionalization of the carbon supports on the catalysts physicochemical properties and the ORR catalytic activity on the cathode of DFAFC was studied. The supports were functionalized by treatment in nitric acid for 4 h at 80 °C. The structure of the prepared catalysts has been characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscope (TEM) and cyclic voltammetry (CV). Hydrophilicity of the catalytic layers was determined by measuring contact angles of water droplets. The performance of the prepared catalysts has been compared with that of the commercial 20 wt.% Pt/C (Premetek) catalyst. The maximum power density obtained for the best palladium catalyst, deposited on the surface of functionalized carbon black, is the same as that for the commercial Pt/C (Premetek). Palladium is cheaper than platinum, therefore the developed cathode catalyst is promising for future applications.

  18. ORR viability of alumina-supported platinum nanocluster: exploring oxidation behaviour by DFT.

    Science.gov (United States)

    Nigam, Sandeep; Majumder, Chiranjib

    2017-07-26

    While alumina-supported platinum particles are versatile for several oxidation reactions, their viability as ORR catalysts has not been explored to date. Therefore, to assess the prospects of alumina-supported platinum nanoclusters in ORRs, a systematic DFT study has been carried out to explore the oxidation behavior of a Ptn@Al2O3 (n = 1-7, 10) cluster. The results are compared with the oxidation behavior of the corresponding gas phase platinum cluster and that of an extended Pt(111) slab. Both supported and unsupported clusters activate adsorbed oxygen molecules and energetically favor dissociative chemisorption of oxygen, leading to stable oxide formation with Pt-O-Pt linkages. However, the influence of the alumina substrate downshifts the d-band centre of the platinum cluster, which not only reduces the reaction enthalpy of oxidation by 8-10%, but also elongates the Pt-O bond of the oxide product by 3-8%. These observations indicate that removal of oxide will be relatively easier for supported clusters than for unsupported clusters. Cluster binding is found to sustain during oxidation, as oxidation of the platinum host cluster results in reduction of the distance between the cluster and support surface. While the gas phase Pt10 cluster does not show any similarity to the oxidation behavior shown by THE Pt(111) slab, the Pt10@Al2O3 cluster reveals close resemblance. Both the Pt(111) slab and Pt10@Al2O3 cluster form similar oxide products, having tri-coordinated oxygen with comparable Pt-O bond distances. The observed resemblance has been attributed to the similarity in the electronic structure and d-band centre position of the platinum surface and alumina-supported Pt10 cluster. Whilst this similar oxidation behaviour of the Pt10@Al2O3 cluster endorses its viability as an ORR catalyst, further modulation of this catalyst is desirable to improve its potential.

  19. Homogeneous catalysts

    CERN Document Server

    Chadwick, John C; Freixa, Zoraida; van Leeuwen, Piet W N M

    2011-01-01

    This first book to illuminate this important aspect of chemical synthesis improves the lifetime of catalysts, thus reducing material and saving energy, costs and waste.The international panel of expert authors describes the studies that have been conducted concerning the way homogeneous catalysts decompose, and the differences between homogeneous and heterogeneous catalysts. The result is a ready reference for organic, catalytic, polymer and complex chemists, as well as those working in industry and with/on organometallics.

  20. SYNTHESIS AND CATALYTIC BEHAVIOR OF POLYSILOXANE-SUPPORTED FULLERENE PLATINUM OR RHODIUM COMPLEXES

    Institute of Scientific and Technical Information of China (English)

    Peng-fei Fang; Yuan-yin Chen; Shu-ling Gong; Lei Guo; Qiu-sheng Lu; Ling Zhu

    1999-01-01

    Two polysiloxanes with pendant fullerene moieties and their platinum or rhodium complexes have been prepared from C60 via amination with ω-decenylamine, followed by hydrosilylation with triethoxysilane and immobilization on fumed silica or by hydrosilylation with methyldichlorosilane and polycondensation with polydimethylsiloxanol, and then by reacting them with potassium chloroplatinite or rhodium chloride in acetone respectively under argon atmosphere. It was found that the four noble metal complexes are effective catalysts for the hydrosilylation of olefins with triethoxysilane. The regioselectivity of platinum complexes for styrene increases remarkably by introducing C60 moiety. Factors influencing catalytic activity and the mechanism have been investigated.

  1. Stimulated-healing of proton exchange membrane fuel cell catalyst

    NARCIS (Netherlands)

    Latsuzbaia, R.; Negro, E.; Koper, G.J.M.

    2013-01-01

    Platinum nanoparticles, which are used as catalysts in Proton Exchange Membrane Fuel Cells (PEMFC), tend to degrade after long-term operation. We discriminate the following mechanisms of the degradation: poisoning, migration and coalescence, dissolution, and electrochemical Ostwald ripening. There a

  2. Innovative use of platinum compounds to selectively detect live microorganisms by polymerase chain reaction.

    Science.gov (United States)

    Soejima, Takashi; Minami, Jun-Ichi; Xiao, Jin-Zhong; Abe, Fumiaki

    2016-02-01

    PCR cannot distinguish live microorganisms from dead ones. To circumvent this disadvantage, ethidium/propidium-monoazide (EMA/PMA) and psoralen to discriminate live from dead bacteria have been used for 2 decades. These methods require the use of numerous laborious procedures. We introduce an innovative method that uses platinum compounds, which are primarily used as catalysts in organic chemistry and partly used as anti-cancer drugs. Microorganisms are briefly exposed to platinum compounds in vivo, and these compounds penetrate dead (compromised) microorganisms but not live ones and are chelated by chromosomal DNA. The use of platinum compounds permits clear discrimination between live and dead microorganisms in water and milk (including Cronobacter sakazakii and Escherichia coli) via PCR compared with typically used PMA. This platinum-PCR method could enable the specific detection of viable coliforms in milk at a concentration of 5-10 CFU mL(-1) specified by EU/USA regulations after a 4-h process. For sample components, environmental water contains lower levels of PCR inhibitors than milk does, and milk is similar to infant formula, skim milk and blood; thus, the use of the platinum-PCR method could also prevent food poisoning due to the presence of C. sakazakii in dairy products. This method could provide outstanding rapidity for use in environmental/food/clinical tests. Platinum-PCR could also be a substitute for the typical culture-based methods currently used.

  3. Simultaneous Laser Thermal Lens Spectrometric Determination of Trace Platinum and Palladium in an Aqueous Solution

    Institute of Scientific and Technical Information of China (English)

    ZHANG,Xiao-Ling(张小玲); YAN,Hong-Tao(阎宏涛)

    2002-01-01

    A selective and sensitive method for determination of platinum and palladium(Ⅱ) in an aqueous solntion simultaneously by laser thermal lens spectrometry, based on the complex reaction of 2- (3,5-dichloropyridylazo)-5- dimethylaminoamiline (3,5-diCl-PADMA) with platinum and palladium, has been developed. It is shown that the palladium complex can be formed at room temperature, while the platinum complex can be only formed after being heated in a boiling water bath. By using this difference of reaction temperature and the characteristic of the complexes mentioned above, the method for simultaneous determination of platinum and palladium was established in an aqueous solution without a pre-separation. The results show that the dynamic linear ranges of determination for platinum and pallladium are 0.005-0.04 μg/mL and 0.005-0.25 μg/mL respectively, and that the detection limits are both 0.002 μg/mL. The method has been applied to the determination of platinum and palladium simultaneously in alloy and catalyst samples with satisfactory results.

  4. Simultaneous Laser Thermal Lens Spectrometric Determination of Trace Platinum and Palladium in an Aquesous Solution

    Institute of Scientific and Technical Information of China (English)

    张小玲; 阎宏涛

    2002-01-01

    A selective and sensitive method for determination of platinum and palladium(Ⅱ)in an aqueous solution simultaneously by laser thermal lens spectrometry,based on the complex reaction of 2-(3,5-dichloropyridylazo)-5-dimethylaminoamiline(3,5-diCl-PADMA) with platinum and palladium,has been developed.It is shown that the palladium complex can be fromed at room temperature, while the platinum complex can be only formed after being heated in a boiling water bath.By using this difference of reaction temperature and the characteristic of the complexes mentioned above,the method for simultaneous determination of platinum and palladium was established in an aqueous solution without a pre-separation.The results show that the dynamic linear ranges of determination for platinum and palladium are 0.005-0.04μg/mL and 0.005-0.25μg/mL respectively,and that the detection limits are both 0.002/μg/mL.The method has been applied to the determination of platinum and palladium simultaneously in alloy and catalyst samples with satisfactory results.

  5. Aligned carbon nanotube-Pt composite fuel cell catalyst by template electrodeposition

    Energy Technology Data Exchange (ETDEWEB)

    Nagle, Lorraine C.; Rohan, James F. [Tyndall National Institute, University College Cork, Lee Maltings, Prospect Row, Cork (Ireland)

    2008-10-15

    Solution phase deposition of aligned arrays of carbon nanotubes (CNTs) in a platinum (Pt) matrix composite is demonstrated. The catalyst material is electrodeposited in an oriented manner on the nanoscale using anodised aluminium oxide (AAO) templates. The catalyst performance of the composite for the oxidation of methanol is shown. The carbon monoxide (CO) tolerance is increased and the catalyst function is improved by minimising the influence of adsorbed CO on the kinetics of the methanol oxidation reaction. (author)

  6. Electrocatalytic activity of platinum nanoparticles supported on nanosilicon

    Energy Technology Data Exchange (ETDEWEB)

    Miu, M.; Kleps, I.; Danila, M.; Ignat, T.; Simion, M.; Bragaru, A.; Dinescu, A. [Laboratory of Nanotechnology, National Institute for Research and Development in Microtechnologies, Bucharest (Romania)

    2010-04-15

    Platinum (Pt) nanocatalysts were deposited on/inside of nanostructured silicon (nanoSi) matrix using physico-chemical methods, i.e. E-beam high vacuum Pt thin film and, respectively, chemically loaded Pt nanoparticles from hexachloroplatinic acid aqueous or alcoholic precursor solutions. High resolution morphological characterisations, completed by microstructural and compositional analyses have been performed to characterise the nanoSi catalyst support and to investigate the Pt thin film nanostructuration as well as the nanoparticle attachment and clustering processes, evidencing the controlling factors and conditions of the size, morphology and distribution. Furthermore, the experimental structures have been subjected to different electrochemical tests and it was revealed that significant improvement of the long term catalyst stability was achieved when the metal-porous Si nanoassemblies is formed, which represents a step closer to the realisation of the monolithic integrated Si-based microfabricated fuel cell. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  7. Green Synthesis, Characterization and Uses of Palladium/Platinum Nanoparticles

    Science.gov (United States)

    Siddiqi, Khwaja Salahuddin; Husen, Azamal

    2016-11-01

    Biogenic synthesis of palladium (Pd) and platinum (Pt) nanoparticles from plants and microbes has captured the attention of many researchers because it is economical, sustainable and eco-friendly. Plant and their parts are known to have various kinds of primary and secondary metabolites which reduce the metal salts to metal nanoparticles. Shape, size and stability of Pd and Pt nanoparticles are influenced by pH, temperature, incubation time and concentrations of plant extract and that of the metal salt. Pd and Pt nanoparticles are broadly used as catalyst, as drug, drug carrier and in cancer treatment. They have shown size- and shape-dependent specific and selective therapeutic properties. In this review, we have discussed the biogenic fabrication of Pd/Pt nanoparticles, their potential application as catalyst, medicine, biosensor, medical diagnostic and pharmaceuticals.

  8. Cross-reactivity of Halogenated Platinum Salts

    Science.gov (United States)

    Halogenated platinum (Pt) salts are well-known respiratory sensitizers associated with the development of asthma. People may be exposed to a variety of platinum compounds in different contexts (e.g. occupationally, automobile exhaust). Published reports suggest that sensitizati...

  9. Optoelectronic method for determining platinum in biological products

    Science.gov (United States)

    Radu, Simona; Ionicǎ, Mihai; Macovei, Radu Alexandru; Caragea, Genica; Forje, Mǎrgǎrita; Grecu, Iulia; Vlǎdescu, Marian; Viscol, Oana

    2016-12-01

    Of all platinum metals, platinum has the most uses and it's the most abundant and most easily to be processed. Its use in auto catalysts results in environmental contamination of crowded cities and high-traffic roads. In medicine, Pt is used as a cytostatic drug. In order to study the degree of contamination of the population with Pt or the correctness of treatment with Pt, it has been developed a method for its determination from urine or blood samples with a system Graphite Furnance - Atomic Absorption Spectrometer, (GF-AAS) Varian. There are presented the methods of sampling processing for blood or urine that followed the digest of the organic matrix. In the determination of the operating parameters for the system GF-AAS, was aimed the reducing of the nonanatomic absorbance by optimizing the drying temperatures, the calcination and atomization temperatures and the removal of the nonanatomic absorbance with D2 lamp. As a result of the use of the method are presented the concentrations of Pt in the blood or urine of a group of patients in Bucharest, a city with heavy traffic of vehicles. GF-AAS method presented is sensitive, reproducible, and relatively easy to apply with an acceptable cost. With this method, the concentration of Pt can be determined from blood and urine, both in order to establish the degree of contamination with Pt and for monitoring cancer therapy with platinum compounds.

  10. Noncovalent interactions between a trinuclear monofunctional platinum complex and human serum albumin.

    Science.gov (United States)

    Wang, Yanqing; Wang, Xiaoyong; Wang, Jing; Zhao, Yongmei; He, Weijiang; Guo, Zijian

    2011-12-19

    Interactions between platinum complexes and human serum albumin (HSA) play crucial roles in the metabolism, distribution, and efficacy of platinum-based anticancer drugs. Polynuclear monofunctional platinum(II) complexes represent a new class of anticancer agents that display distinct molecular characters of pharmacological action from those of cisplatin. In this study, the interaction between a trinuclear monofunctional platinum(II) complex, [Pt(3)LCl(3)](ClO(4))(3) (L = N,N,N',N',N",N"-hexakis(2-pyridylmethyl)-1,3,5-tris(aminomethyl)benzene) (1), and HSA was investigated using ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, circular dichroism spectroscopy, fluorescence spectroscopy, molecular docking, and inductively coupled plasma mass spectrometry. The spectroscopic and thermodynamic data show that the interaction is a spontaneous process with the estimated enthalpy and entropy changes being 14.6 kJ mol(-1) and 145.5 J mol(-1) K(-1), respectively. The reactive sites of HSA to complex 1 mainly locate within its hydrophobic cavity in domain II. Noncovalent actions such as π-π stacking and hydrophobic bonding are the primary contributors to the interaction between HSA and complex 1, which is different from the scenario for cisplatin in similar conditions. The results suggest that the connection between complex 1 and HSA is reversible, and therefore the cytotoxic activity of the complex could be preserved during blood circulation.

  11. Platinum-Catalyzed Selective Hydration of Hindered Nitriles and Nitriles with Acid- or Base-Sensitive Groups

    NARCIS (Netherlands)

    Jiang, Xiao-bin; Minnaard, Adriaan J.; Vries, Johannes G. de; Feringa, Bernard

    2004-01-01

    Hindered tertiary nitriles can be hydrolyzed under neutral and mild conditions to the corresponding amides using platinum(II) catalysts with dimethylphosphine oxide or other secondary phosphine oxides (SPOs, phosphinous acids) as ligands. We have found that this procedure also works well for

  12. Dissolution of Metal Supported Spent Auto Catalysts in Acids

    Directory of Open Access Journals (Sweden)

    Fornalczyk A.

    2016-03-01

    Full Text Available Metal supported auto catalysts, have been used in sports and racing cars initially, but nowadays their application systematically increases. In Metal Substrate (supported Converters (MSC, catalytic functions are performed by the Platinum Group Metals (PGM: Pt, Pd, Rh, similarly to the catalysts on ceramic carriers. The contents of these metals make that spent catalytic converters are valuable source of precious metals. All over the world there are many methods for the metals recovery from the ceramic carriers, however, the issue of platinum recovery from metal supported catalysts has not been studied sufficiently yet. The paper presents preliminary results of dissolution of spent automotive catalyst on a metal carrier by means of acids: H2SO4, HCl, HNO3, H3PO4. The main assumption of the research was the dissolution of base metals (Fe, Cr, Al from metallic carrier of catalyst, avoiding dissolution of PGMs. Dissolution was the most effective when concentrated hydrochloric acid, and 2M sulfuric acid (VI was used. It was observed that the dust, remaining after leaching, contained platinum in the level of 0.8% and 0.7%, respectively.

  13. Three-phase microemulsion/sol-gel system for aqueous catalysis with hydrophobic chemicals.

    Science.gov (United States)

    Abu-Reziq, Raed; Blum, Jochanan; Avnir, David

    2004-02-20

    A facile three-phase transport process is described that allows to carry out catalytic reactions in water, whereby all components are hydrophobic. According to this process a hydrophobic substrate is microemulsified in water and subjected to an organometallic catalyst, which is entrapped within a partially hydrophobized sol-gel matrix. The surfactant molecules, which carry the hydrophobic substrate, adsorb/desorb reversibly on the surface of the sol-gel matrix breaking the micellar structure, spilling their substrate load into the porous medium that contains the catalyst. A catalytic reaction then takes place within the ceramic material to form the desired products that are extracted by the desorbing surfactant, carrying the emulsified product back into the solution. The method is general and versatile and has been demonstrated with the catalytic hydrogenations of alkenes, alkynes, aromatic C=C bonds, and nitro and cyano groups.

  14. Formic Acid Electrooxidation by a Platinum Nanotubule Array Electrode

    Directory of Open Access Journals (Sweden)

    Eric Broaddus

    2013-01-01

    Full Text Available One-dimensional metallic nanostructures such as nanowires, rods, and tubes have drawn much attention for electrocatalytic applications due to potential advantages that include fewer diffusion impeding interfaces with polymeric binders, more facile pathways for electron transfer, and more effective exposure of active surface sites. 1D nanostructured electrodes have been fabricated using a variety of methods, typically showing improved current response which has been attributed to improved CO tolerance, enhanced surface activity, and/or improved transport characteristics. A template wetting approach was used to fabricate an array of platinum nanotubules which were examined electrochemically with regard to the electrooxidation of formic acid. Arrays of 100 and 200 nm nanotubules were compared to a traditional platinum black catalyst, all of which were found to have similar surface areas. Peak formic acid oxidation current was observed to be highest for the 100 nm nanotubule array, followed by the 200 nm array and the Pt black; however, CO tolerance of all electrodes was similar, as were the onset potentials of the oxidation and reduction peaks. The higher current response was attributed to enhanced mass transfer in the nanotubule electrodes, likely due to a combination of both the more open nanostructure as well as the lack of a polymeric binder in the catalyst layer.

  15. Coating Carbon Fibers With Platinum

    Science.gov (United States)

    Effinger, Michael R.; Duncan, Peter; Coupland, Duncan; Rigali, Mark J.

    2007-01-01

    A process for coating carbon fibers with platinum has been developed. The process may also be adaptable to coating carbon fibers with other noble and refractory metals, including rhenium and iridium. The coated carbon fibers would be used as ingredients of matrix/fiber composite materials that would resist oxidation at high temperatures. The metal coats would contribute to oxidation resistance by keeping atmospheric oxygen away from fibers when cracks form in the matrices. Other processes that have been used to coat carbon fibers with metals have significant disadvantages: Metal-vapor deposition processes yield coats that are nonuniform along both the lengths and the circumferences of the fibers. The electrical resistivities of carbon fibers are too high to be compatible with electrolytic processes. Metal/organic vapor deposition entails the use of expensive starting materials, it may be necessary to use a furnace, and the starting materials and/or materials generated in the process may be hazardous. The present process does not have these disadvantages. It yields uniform, nonporous coats and is relatively inexpensive. The process can be summarized as one of pretreatment followed by electroless deposition. The process consists of the following steps: The surfaces of the fiber are activated by deposition of palladium crystallites from a solution. The surface-activated fibers are immersed in a solution that contains platinum. A reducing agent is used to supply electrons to effect a chemical reduction in situ. The chemical reduction displaces the platinum from the solution. The displaced platinum becomes deposited on the fibers. Each platinum atom that has been deposited acts as a catalytic site for the deposition of another platinum atom. Hence, the deposition process can also be characterized as autocatalytic. The thickness of the deposited metal can be tailored via the duration of immersion and the chemical activity of the solution.

  16. Anodic stripping tin titration: a method for the voltammetric determination of platinum at trace levels.

    Science.gov (United States)

    Giussani, Barbara; Roncoroni, Simone; Nemenyi, Anna; Dal Santo, Vladimiro; Monticelli, Damiano; Recchia, Sandro

    2014-07-01

    We propose here a novel voltammetric method for the determination of platinum at trace levels. The method is based on the interference that platinum generates on the anodic stripping signal of tin acidic solutions: in appropriate conditions platinum uses the intermediate formation of tin(II) ions, taking place during the tin cathodic reduction, to reduce itself and to form mixed Pt(II)-Sn(II) chloro-complexes. From the analysis of the anodic stripping plots obtained after subsequent additions of tin in a Pt-containing solution, it is possible to quantify accurately and precisely the Pt concentration from 3 ppb to more than 10 ppm. This novel method is validated for the analysis of Pt in heterogeneous catalysts, but in principle could be extended to other matrixes.

  17. Formic acid oxidation at platinum-bismuth catalysts

    National Research Council Canada - National Science Library

    Popović Ksenija Đ; Lović Jelena D

    2015-01-01

    ..., activity, and stability. The oxidation of formic acid is of permanent interest as a model reaction for the mechanistic understanding of the electrooxidation of small organic molecules and because of its technical relevance...

  18. Characterizing Carbon Nanotube Supported Platinum Catalyst by Electrochemistry

    DEFF Research Database (Denmark)

    Veltzé, Sune; Andersen, Shuang Ma; Skou, Eivind Morten

    Den metode for hvorved forskellige platinbærende katalysatormaterialebærende kulstofunderlag vil blive testet elektrokemisk beskrives, hvor Elektrokemisk Masse Spektrometri nævnes som en mulighed sammen med mikroskopi....

  19. Nanostructured Platinum Alloys for Use as Catalyst Materials

    Science.gov (United States)

    Hays, Charles C. (Inventor); Narayan, Sri R. (Inventor)

    2015-01-01

    A series of binary and ternary Pt-alloys, that promote the important reactions for catalysis at an alloy surface; oxygen reduction, hydrogen oxidation, and hydrogen and oxygen evolution. The first two of these reactions are essential when applying the alloy for use in a PEMFC.

  20. Durable Catalysts for High Temperature Proton Exchange Membrane Fuel Cells

    DEFF Research Database (Denmark)

    Durability of proton exchange membrane fuel cells (PEMFCs) is recognized as one of the most important issues to be addressed before the commercialization. The failure mechanisms are not well understood, however, degradation of carbon supported noble metal catalysts is identified as a major failure...... corrosion, in turn, triggers the agglomeration of platinum particles resulting in reduction of the active surface area and catalytic activity. This is a major mechanism of the catalyst degradation and a key challenge to the PEMFC long-term durability. High temperature PEMFC, on the other hand, has attached...... the selectivity for platinum loading. Fuel cell durability tests in term of performance degradation were performed with acid doped polybenzimidazole membrane fuel cells at temperatures of up to 160°C. The tests were focused on catalyst degradation by means of a potential cycling protocol. The electrochemical...

  1. Platinum determination in nutrient plants by inductively coupled plasma mass spectrometry with special respect to the hafnium oxide interference

    Energy Technology Data Exchange (ETDEWEB)

    Lustig, S. [GSF-Research Centre for Environment and Health, Inst. for Ecological Chemistry, Neuherberg (Germany); Zang, S.; Michalke, B. [GSF-Research Centre for Environment and Health, Inst. for Ecological Chemistry, Neuherberg (Germany); Schramel, P. [GSF-Research Centre for Environment and Health, Inst. for Ecological Chemistry, Neuherberg (Germany); Beck, W. [Muenchen Univ. (Germany). Inst. for Inorganic Chemistry

    1997-04-01

    Platinum, emitted from automobile exhaust catalysts, is mainly oxidised in a humic soil, as described previously [1]. An experiment with nutrient plants was carried out to elucidate the bioavailability and accumulation of these platinum containing species. The plants [Allium cepa L. (Weiss, Fruehling), Rephanus sativus L. (Riesenbutter), Vicia faba L. (Hedin, Herzfreya), Zea mays L. (Delis) and Solanum tuberosum L. (Selma)] were grown under natural conditions. For mass balances all ways of platinum transport into and out of the system were monitored during the growing period. Plants growing in untreated soil took up less than 1% of the platinum naturally present in the soil [0.15{+-}0.11 {mu}g kg{sup -1} (78%)]. Plants growing in soil treated with a platinum containing tunnel dust took up slightly more platinum. The comparison of ICPquadrupole-MS results with those obtained by a double focusing magnetic sector ICP-MS showed a strong dependence of the platinum concentration on the Hf-content in the sample. An evaluation method for the correction of the Hf-influence for ICP-quadrupole-MS is presented. (orig.). With 1 fig., 3 tabs.

  2. Platinum Group Metals New Material

    Institute of Scientific and Technical Information of China (English)

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

    2012-01-01

    Platinum group metals (PGM) include six elements,namely Pt,Pd,Rh,Ir,Os and Ru.PGM and their alloys are the important fundamental materials for modern industry and national defense construction,they have special physical and chemical properties,widely used in metallurgy,chemical,electric,electronic,information,energy,environmental protection,aviation,aerospace,navigation and other high technology industry.Platinum group metals and their alloys,which have good plasticity and processability,can be processed to electrical contact materials,resistance materials,solder,electronic paste,temperature-measurement materials,elastic materials,magnetic materials and high temperature structural materials.

  3. Electrochemical characterization of platinum nanoparticles stabilized by amines

    Energy Technology Data Exchange (ETDEWEB)

    Ramirez-Meneses, E., E-mail: esthervincent@yahoo.co [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, CICATA-IPN Unidad Altamira, Km 14.5 Carretera Tampico-Puerto Industrial, C.P. 89600 Altamira, Tamaulipas (Mexico); Dominguez-Crespo, M.A. [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, CICATA-IPN Unidad Altamira, Km 14.5 Carretera Tampico-Puerto Industrial, C.P. 89600 Altamira, Tamaulipas (Mexico); Montiel-Palma, V. [Centro de Investigaciones Quimicas, Universidad Autonoma del Estado de Morelos, Av. Universidad 1001, Colonia Chamilpa, C.P. 62201 Cuernavaca, Morelos (Mexico); Chavez-Herrera, V.H. [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, CICATA-IPN Unidad Altamira, Km 14.5 Carretera Tampico-Puerto Industrial, C.P. 89600 Altamira, Tamaulipas (Mexico); Gomez, E. [Instituto de Quimica-Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, C.P. 04510 Mexico, D.F. (Mexico); Hernandez-Tapia, G. [Gerencia de Catalizadores y Proceso, Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas norte 152, 07730 Mexico, D.F. (Mexico)

    2009-08-26

    In this work we present the synthesis by Chaudret approach of Pt nanoparticles stabilized by primary amine (-NH{sub 2}) compounds. Their electrochemical performance as cathodes in low temperature polymer electrolite fuel cells on the oxygen reduction reaction (ORR) is also presented. Transmission electron microscopy (TEM) images of the samples show Pt nanostructures with particle size varying from 10 to 100 nm depending on the kind of the stabilizer used during the catalyst preparation. In some cases well-dispersed isolated platinum nanoparticles were observed. The activity of the dispersed catalysts (Pt/C) with respect to the ORR was investigated using steady state polarization measurements. The kinetic parameters showed that although no significant differences between the Tafel slopes of the Pt catalysts exist, transfer coefficients and exchange current densities show higher activities when the Pt nanoparticles were stabilized by tert-butylamine (TBA). The performance with respect to the ORR of the Pt/C catalyst on vulcan carbon substrate is active and comparable to that reported in the literature for state-of-art electrocatalysts.

  4. Catalysts for complete oxidation of gaseous fuels

    Energy Technology Data Exchange (ETDEWEB)

    Neyestanaki, A.K.

    1995-12-31

    This thesis presents a study on the complete oxidation of propane, natural gas and the conversion of car exhaust gases over two types of catalysts: (a) knitted silica-fibre supported catalysts and (b) metal-modified ZSM zeolite catalysts. A hybrid textile made up of an organic-inorganic hybrid fibre containing 70 % cellulose and 30 % silicic acid was used as the raw material for preparation of the fibre support for combustion catalysts. The hybrid textile was burnt to obtain a knitted silica-fibre. The changes in the surface area, pore volume and the crystallinity of the obtained support were studied as a function of burning temperature. The stability of the support in steam-rich atmospheres was tested. The knitted silica-fibre obtained by burning the hybrid textile at 1223 K was found to have sufficient strength and high BET specific surface area (140 m{sub 2}/g) to be used as a catalyst support. A series of knitted silica-fibre supported metal oxides (oxides of Co, Ni, Mn, Cr and Cu) and combinations of them, platinum-activated metal oxides (Pt-Co{sub 3}O{sub 4}, Pt-NiO, Pt-MnO{sub 2} and Pt-Cr{sub 2}O{sub 3}) as well as noble metal (Pt, Pd) catalysts were prepared. The location of the metal oxides on the catalyst was studied by SEM equipped with EDXA. The metal oxide was found to be located mostly inside the pores rather than on the exterior surface of the silica-fibre. The catalysts were characterized by XRD, N{sub 2}-physisorption, O{sub 2}-TPD and the chemisorption of propane, carbon monoxide and hydrogen. The activity of the catalysts was tested in the combustion of propane, natural gas and in the conversion of automobile exhaust gases. The effect of residence time and stoichiometry on the conversion behaviour of the catalysts was studied

  5. Olefin Epoxidation in Aqueous Phase Using Ionic-Liquid Catalysts.

    Science.gov (United States)

    Cokoja, Mirza; Reich, Robert M; Wilhelm, Michael E; Kaposi, Marlene; Schäffer, Johannes; Morris, Danny S; Münchmeyer, Christian J; Anthofer, Michael H; Markovits, Iulius I E; Kühn, Fritz E; Herrmann, Wolfgang A; Jess, Andreas; Love, Jason B

    2016-07-21

    Hydrophobic imidazolium-based ionic liquids (IL) act as catalysts for the epoxidation of unfunctionalized olefins in water using hydrogen peroxide as oxidant. Although the catalysts are insoluble in both the substrate and in water, surprisingly, they are very well soluble in aqueous H2 O2 solution, owing to perrhenate-H2 O2 interactions. Even more remarkably, the presence of the catalyst also boosts the solubility of substrate in water. This effect is crucially dependent on the cation design. Hence, the imidazolium perrhenates enable both the transfer of hydrophobic substrate into the aqueous phase, and serve as actual catalysts, which is unprecedented. At the end of the reaction and in absence of H2 O2 the IL catalyst forms a third phase next to the lipophilic product and water and can easily be recycled.

  6. Catalyst mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Masel, Richard I.; Rosen, Brian A.

    2017-02-14

    Catalysts that include at least one catalytically active element and one helper catalyst can be used to increase the rate or lower the overpotential of chemical reactions. The helper catalyst can simultaneously act as a director molecule, suppressing undesired reactions and thus increasing selectivity toward the desired reaction. These catalysts can be useful for a variety of chemical reactions including, in particular, the electrochemical conversion of CO.sub.2 or formic acid. The catalysts can also suppress H.sub.2 evolution, permitting electrochemical cell operation at potentials below RHE. Chemical processes and devices using the catalysts are also disclosed, including processes to produce CO, OH.sup.-, HCO.sup.-, H.sub.2CO, (HCO.sub.2).sup.-, H.sub.2CO.sub.2, CH.sub.3OH, CH.sub.4, C.sub.2H.sub.4, CH.sub.3CH.sub.2OH, CH.sub.3COO.sup.-, CH.sub.3COOH, C.sub.2H.sub.6, O.sub.2, H.sub.2, (COOH).sub.2, or (COO.sup.-).sub.2, and a specific device, namely, a CO.sub.2 sensor.

  7. Photo-oxidation catalysts

    Science.gov (United States)

    Pitts, J. Roland; Liu, Ping; Smith, R. Davis

    2009-07-14

    Photo-oxidation catalysts and methods for cleaning a metal-based catalyst are disclosed. An exemplary catalyst system implementing a photo-oxidation catalyst may comprise a metal-based catalyst, and a photo-oxidation catalyst for cleaning the metal-based catalyst in the presence of light. The exposure to light enables the photo-oxidation catalyst to substantially oxidize absorbed contaminants and reduce accumulation of the contaminants on the metal-based catalyst. Applications are also disclosed.

  8. Membrane-electrode structures for molecular catalysts for use in fuel cells and other electrochemical devices

    Energy Technology Data Exchange (ETDEWEB)

    Kerr, John B.; Zhu, Xiaobing; Hwang, Gi Suk; Martin, Zulima; He, Qinggang; Driscoll, Peter; Weber, Adam; Clark, Kyle

    2016-09-27

    Water soluble catalysts, (M)meso-tetra(N-Methyl-4-Pyridyl)Porphinepentachloride (M=Fe, Co, Mn & Cu), have been incorporated into the polymer binder of oxygen reduction cathodes in membrane electrode assemblies used in PEM fuel cells and found to support encouragingly high current densities. The voltages achieved are low compared to commercial platinum catalysts but entirely consistent with the behavior observed in electroanalytical measurements of the homogeneous catalysts. A model of the dynamics of the electrode action has been developed and validated and this allows the MEA electrodes to be optimized for any chemistry that has been demonstrated in solution. It has been shown that improvements to the performance will come from modifications to the structure of the catalyst combined with optimization of the electrode structure and a well-founded pathway to practical non-platinum group metal catalysts exists.

  9. Enhanced catalytic activity of solid and hollow platinum-cobalt nanoparticles towards reduction of 4-nitrophenol

    Science.gov (United States)

    Krajczewski, Jan; Kołątaj, Karol; Kudelski, Andrzej

    2016-12-01

    Previous investigations of hollow platinum nanoparticles have shown that such nanostructures are more active catalysts than their solid counterparts towards the following electrochemical reactions: reduction of oxygen, evolution of hydrogen, and oxidation of borohydride, methanol and formic acid. In this work we show that synthesised using standard galvanic replacement reaction (with Co templates) hollow platinum nanoparticles exhibit enhanced catalytic activity also towards reduction of 4-nitrophenol by sodium borohydride in water. Unlike in the case of procedures involving hollow platinum catalysts employed so far to carry out this reaction it is not necessary to couple analysed platinum nanoparticles to the surface of an electrode. Simplification of the analyzed reaction may eliminate same experimental errors. We found that the enhanced catalytic activity of hollow Pt nanoparticles is not only connected with generally observed larger surface area of hollow nanostructures, but is also due to the contamination of formed hollow nanostructures with cobalt, from which sacrificial templates used in the synthesis of hollow Pt nanostrustures have been formed. Because using sacrificial templates is a typical method of synthesis of hollow metal nanostructures, formed hollow nanoparticles are probably often contaminated, which may significantly influence their catalytic activity.

  10. Nanocarriers for delivery of platinum anticancer drugs☆

    Science.gov (United States)

    Oberoi, Hardeep S.; Nukolova, Natalia V.; Kabanov, Alexander V.; Bronich, Tatiana K.

    2014-01-01

    Platinum based anticancer drugs have revolutionized cancer chemotherapy, and continue to be in widespread clinical use especially for management of tumors of the ovary, testes, and the head and neck. However, several dose limiting toxicities associated with platinum drug use, partial anti-tumor response in most patients, development of drug resistance, tumor relapse, and many other challenges have severely limited the patient quality of life. These limitations have motivated an extensive research effort towards development of new strategies for improving platinum therapy. Nanocarrier-based delivery of platinum compounds is one such area of intense research effort beginning to provide encouraging preclinical and clinical results and may allow the development of the next generation of platinum chemotherapy. This review highlights current understanding on the pharmacology and limitations of platinum compounds in clinical use, and provides a comprehensive analysis of various platinum–polymer complexes, micelles, dendrimers, liposomes and other nanoparticles currently under investigation for delivery of platinum drugs. PMID:24113520

  11. Catalyst support effects on hydrogen spillover

    Science.gov (United States)

    Karim, Waiz; Spreafico, Clelia; Kleibert, Armin; Gobrecht, Jens; Vandevondele, Joost; Ekinci, Yasin; van Bokhoven, Jeroen A.

    2017-01-01

    Hydrogen spillover is the surface migration of activated hydrogen atoms from a metal catalyst particle, on which they are generated, onto the catalyst support. The phenomenon has been much studied and its occurrence on reducible supports such as titanium oxide is established, yet questions remain about whether hydrogen spillover can take place on nonreducible supports such as aluminium oxide. Here we use the enhanced precision of top-down nanofabrication to prepare controlled and precisely tunable model systems that allow us to quantify the efficiency and spatial extent of hydrogen spillover on both reducible and nonreducible supports. We place multiple pairs of iron oxide and platinum nanoparticles on titanium oxide and aluminium oxide supports, varying the distance between the pairs from zero to 45 nanometres with a precision of one nanometre. We then observe the extent of the reduction of the iron oxide particles by hydrogen atoms generated on the platinum using single-particle in situ X-ray absorption spectromicroscopy applied simultaneously to all particle pairs. The data, in conjunction with density functional theory calculations, reveal fast hydrogen spillover on titanium oxide that reduces remote iron oxide nanoparticles via coupled proton-electron transfer. In contrast, spillover on aluminium oxide is mediated by three-coordinated aluminium centres that also interact with water and that give rise to hydrogen mobility competing with hydrogen desorption; this results in hydrogen spillover about ten orders of magnitude slower than on titanium oxide and restricted to very short distances from the platinum particle. We anticipate that these observations will improve our understanding of hydrogen storage and catalytic reactions involving hydrogen, and that our approach to creating and probing model catalyst systems will provide opportunities for studying the origin of synergistic effects in supported catalysts that combine multiple functionalities.

  12. LDRD final report on synthesis of shape-and size-controlled platinum and platinum alloy nanostructures on carbon with improved durability.

    Energy Technology Data Exchange (ETDEWEB)

    Shelnutt, John Allen; Garcia, Robert M.; Song, Yujiang; Moreno, Andres M.; Stanis, Ronald J.

    2008-10-01

    This project is aimed to gain added durability by supporting ripening-resistant dendritic platinum and/or platinum-based alloy nanostructures on carbon. We have developed a new synthetic approach suitable for directly supporting dendritic nanostructures on VXC-72 carbon black (CB), single-walled carbon nanotubes (SWCNTs), and multi-walled carbon nanotubes (MWCNTs). The key of the synthesis is to creating a unique supporting/confining reaction environment by incorporating carbon within lipid bilayer relying on a hydrophobic-hydrophobic interaction. In order to realize size uniformity control over the supported dendritic nanostructures, a fast photocatalytic seeding method based on tin(IV) porphyrins (SnP) developed at Sandia was applied to the synthesis by using SnP-containing liposomes under tungsten light irradiation. For concept approval, one created dendritic platinum nanostructure supported on CB was fabricated into membrane electrode assemblies (MEAs) for durability examination via potential cycling. It appears that carbon supporting is essentially beneficial to an enhanced durability according to our preliminary results.

  13. Hydrogels with micellar hydrophobic (nanodomains

    Directory of Open Access Journals (Sweden)

    Miloslav ePekař

    2015-01-01

    Full Text Available Hydrogels containing hydrophobic domains or nanodomains, especially of the micellar type, are reviewed. Examples of the reasons for introducing hydrophobic domains into hydrophilic gels are given; typology of these materials is introduced. Synthesis routes are exemplified and properties of a variety of such hydrogels in relation with their intended applications are described. Future research needs are identified briefly.

  14. Hydrophobic encapsulation of hydrocarbon gases.

    Science.gov (United States)

    Leontiev, Alexander V; Saleh, Anas W; Rudkevich, Dmitry M

    2007-04-26

    [reaction: see text] Encapsulation data for hydrophobic hydrocarbon gases within a water-soluble hemicarcerand in aqueous solution are reported. It is concluded that hydrophobic interactions serve as the primary driving force for the encapsulation, which can be used for the design of gas-separating polymers with intrinsic inner cavities.

  15. [Formylation of porphyrin platinum complexes].

    Science.gov (United States)

    Rumiantseva, V D; Konovalenko, L I; Nagaeva, E A; Mironov, A F

    2005-01-01

    The formylation reaction of platinum complexes of beta-unsubstituted porphyrins was studied. The interaction of deuteroporphyrin IX derivatives with the Vilsmeyer reagent led to the selective formylation of their macrocycles in the beta position. The resulting formyl derivatives of the porphyrins are of interest for fluorescent immunoassay.

  16. Direct use of allylic alcohols for platinum-catalyzed monoallylation of amines.

    Science.gov (United States)

    Utsunomiya, Masaru; Miyamoto, Yoshiki; Ipposhi, Junji; Ohshima, Takashi; Mashima, Kazushi

    2007-08-16

    A new direct catalytic amination of allylic alcohols promoted by the combination of platinum and a large bite-angle ligand DPEphos was developed in which the allylic alcohol was effectively converted to a pi-allylplatinum intermediate without the use of an activating reagent. The use of the DPEphos ligand was essential for obtaining high catalyst activity and high monoallylation selectivity of primary amines, allowing the formation of a variety of monoallylation products in good to excellent yield.

  17. Nanocrystal and surface alloy properties of bimetallic Gold-Platinum nanoparticles

    OpenAIRE

    Mott Derrick; Luo Jin; Smith Andrew; Njoki Peter; Wang Lingyan; Zhong Chuan-Jian

    2006-01-01

    AbstractWe report on the correlation between the nanocrystal and surface alloy properties with the bimetallic composition of gold-platinum(AuPt) nanoparticles. The fundamental understanding of whether the AuPt nanocrystal core is alloyed or phase-segregated and how the surface binding properties are correlated with the nanoscale bimetallic properties is important not only for the exploitation of catalytic activity of the nanoscale bimetallic catalysts, but also to the general exploration of t...

  18. Changing water affinity from hydrophobic to hydrophilic in hydrophobic channels.

    Science.gov (United States)

    Ohba, Tomonori; Yamamoto, Shotaro; Kodaira, Tetsuya; Hata, Kenji

    2015-01-27

    The behavior of water at hydrophobic interfaces can play a significant role in determining chemical reaction outcomes and physical properties. Carbon nanotubes and aluminophosphate materials have one-dimensional hydrophobic channels, which are entirely surrounded by hydrophobic interfaces. Unique water behavior was observed in such hydrophobic channels. In this article, changes in the water affinity in one-dimensional hydrophobic channels were assessed using water vapor adsorption isotherms at 303 K and grand canonical Monte Carlo simulations. Hydrophobic behavior of water adsorbed in channels wider than 3 nm was observed for both adsorption and desorption processes, owing to the hydrophobic environment. However, water showed hydrophilic properties in both adsorption and desorption processes in channels narrower than 1 nm. In intermediate-sized channels, the hydrophobic properties of water during the adsorption process were seen to transition to hydrophilic behavior during the desorption process. Hydrophilic properties in the narrow channels for both adsorption and desorption processes are a result of the relatively strong water-channel interactions (10-15 kJ mol(-1)). In the 2-3 nm channels, the water-channel interaction energy of 4-5 kJ mol(-1) was comparable to the thermal translational energy. The cohesive water interaction was approximately 35 kJ mol(-1), which was larger than the others. Thus, the water affinity change in the 2-3 nm channels for the adsorption and desorption processes was attributed to weak water-channel interactions and strong cohesive interactions. These results are inherently important to control the properties of water in hydrophobic environments.

  19. Carbon-based metal-free catalysts

    Science.gov (United States)

    Liu, Xien; Dai, Liming

    2016-11-01

    Metals and metal oxides are widely used as catalysts for materials production, clean energy generation and storage, and many other important industrial processes. However, metal-based catalysts suffer from high cost, low selectivity, poor durability, susceptibility to gas poisoning and have a detrimental environmental impact. In 2009, a new class of catalyst based on earth-abundant carbon materials was discovered as an efficient, low-cost, metal-free alternative to platinum for oxygen reduction in fuel cells. Since then, tremendous progress has been made, and carbon-based metal-free catalysts have been demonstrated to be effective for an increasing number of catalytic processes. This Review provides a critical overview of this rapidly developing field, including the molecular design of efficient carbon-based metal-free catalysts, with special emphasis on heteroatom-doped carbon nanotubes and graphene. We also discuss recent advances in the development of carbon-based metal-free catalysts for clean energy conversion and storage, environmental protection and important industrial production, and outline the key challenges and future opportunities in this exciting field.

  20. Catalyst design for biorefining.

    Science.gov (United States)

    Wilson, Karen; Lee, Adam F

    2016-02-28

    The quest for sustainable resources to meet the demands of a rapidly rising global population while mitigating the risks of rising CO2 emissions and associated climate change, represents a grand challenge for humanity. Biomass offers the most readily implemented and low-cost solution for sustainable transportation fuels, and the only non-petroleum route to organic molecules for the manufacture of bulk, fine and speciality chemicals and polymers. To be considered truly sustainable, biomass must be derived from resources which do not compete with agricultural land use for food production, or compromise the environment (e.g. via deforestation). Potential feedstocks include waste lignocellulosic or oil-based materials derived from plant or aquatic sources, with the so-called biorefinery concept offering the co-production of biofuels, platform chemicals and energy; analogous to today's petroleum refineries which deliver both high-volume/low-value (e.g. fuels and commodity chemicals) and low-volume/high-value (e.g. fine/speciality chemicals) products, thereby maximizing biomass valorization. This article addresses the challenges to catalytic biomass processing and highlights recent successes in the rational design of heterogeneous catalysts facilitated by advances in nanotechnology and the synthesis of templated porous materials, as well as the use of tailored catalyst surfaces to generate bifunctional solid acid/base materials or tune hydrophobicity.

  1. Highly dispersed metal catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Xin; West, William L.; Rhodes, William D.

    2016-11-08

    A supported catalyst having an atomic level single atom structure is provided such that substantially all the catalyst is available for catalytic function. A process of forming a single atom catalyst unto a porous catalyst support is also provided.

  2. Platinum Activated IrO2/SnO2 Nanocatalysts and Their Electrode Structures for High Performance Proton Exchange Membrane Water Electrolysis

    DEFF Research Database (Denmark)

    Xu, Junyuan; Li, Qingfeng; Christensen, Erik

    2013-01-01

    , which was attributed to the cooperative effects of improved electric conductivity and synergistic effect of Pt and IrO2/SnO2. Furthermore, catalyst layers based on IrO2/SnO2 catalysts were optimized with respect to microstructures, pore volume and pore size distribution. The performance was obviously...... improved due to the appropriate porosity and pore size distribution. The highest electrolyser performance of 1.63 V at 2 A cm-2 was achieved at 80 °C for optimized catalyst layers containing platinum activated IrO2/SnO2 catalyst....

  3. Catalyst for Carbon Monoxide Oxidation

    Science.gov (United States)

    Davis, Patricia; Brown, Kenneth; VanNorman, John; Brown, David; Upchurch, Billy; Schryer, David; Miller, Irvin

    2010-01-01

    In many applications, it is highly desirable to operate a CO2 laser in a sealed condition, for in an open system the laser requires a continuous flow of laser gas to remove the dissociation products that occur in the discharge zone of the laser, in order to maintain a stable power output. This adds to the operating cost of the laser, and in airborne or space applications, it also adds to the weight penalty of the laser. In a sealed CO2 laser, a small amount of CO2 gas is decomposed in the electrical discharge zone into corresponding quantities of CO and O2. As the laser continues to operate, the concentration of CO2 decreases, while the concentrations of CO and O2 correspondingly increase. The increasing concentration of O2 reduces laser power, because O2 scavenges electrons in the electrical discharge, thereby causing arcing in the electric discharge and a loss of the energetic electrons required to boost CO2 molecules to lasing energy levels. As a result, laser power decreases rapidly. The primary object of this invention is to provide a catalyst that, by composition of matter alone, contains chemisorbed water within and upon its structure. Such bound moisture renders the catalyst highly active and very long-lived, such that only a small quantity of it needs to be used with a CO2 laser under ambient operating conditions. This object is achieved by a catalyst that consists essentially of about 1 to 40 percent by weight of one or more platinum group metals (Pt, Pd, Rh, Ir, Ru, Os, Pt being preferred); about 1 to 90 percent by weight of one or more oxides of reducible metals having multiple valence states (such as Sn, Ti, Mn, Cu, and Ce, with SnO2 being preferred); and about 1 to 90 percent by weight of a compound that can bind water to its structure (such as silica gel, calcium chloride, magnesium sulfate, hydrated alumina, and magnesium perchlorate, with silica gel being preferred). Especially beneficial results are obtained when platinum is present in the

  4. Catalyst Architecture

    DEFF Research Database (Denmark)

    Kiib, Hans; Marling, Gitte; Hansen, Peter Mandal

    2014-01-01

    How can architecture promote the enriching experiences of the tolerant, the democratic, and the learning city - a city worth living in, worth supporting and worth investing in? Catalyst Architecture comprises architectural projects, which, by virtue of their location, context and their combination...... of programs, have a role in mediating positive social and/or cultural development. In this sense, we talk about architecture as a catalyst for: sustainable adaptation of the city’s infrastructure appropriate renovation of dilapidated urban districts strengthening of social cohesiveness in the city development...

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

    Science.gov (United States)

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

    2017-01-18

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

  6. Development of molecular and solid catalysts for the direct low-temperature oxidation of methane to methanol.

    Science.gov (United States)

    Palkovits, Regina; von Malotki, Christian; Baumgarten, Martin; Müllen, Klaus; Baltes, Christian; Antonietti, Markus; Kuhn, Pierre; Weber, Jens; Thomas, Arne; Schüth, Ferdi

    2010-02-22

    The direct low-temperature oxidation of methane to methanol is demonstrated on a highly active homogeneous molecular catalyst system and on heterogeneous molecular catalysts based on polymeric materials possessing ligand motifs within the material structure. The N-(2-methylpropyl)-4,5-diazacarbazolyl-dichloro-platinum(II) complex reaches significantly higher activity compared to the well-known Periana system and allows first conclusions on electronic and structural requirements for high catalytic activity in this reaction. Interestingly, comparable activities could be achieved utilizing a platinum modified poly(benzimidazole) material, which demonstrates for the first time a solid catalyst with superior activity compared to the Periana system. Although the material shows platinum leaching, improved activity and altered electronic properties, compared to the conventional Periana system, support the proposed conclusions on structure-activity relationships. In comparison, platinum modified triazine-based catalysts show lower catalytic activity, but rather stable platinum coordination even after several catalytic cycles. Based on these systems, further development of improved solid catalysts for the direct low-temperature oxidation of methane to methanol is feasible.

  7. Surface characterization of platinum electrodes.

    Science.gov (United States)

    Solla-Gullón, José; Rodríguez, Paramaconi; Herrero, Enrique; Aldaz, Antonio; Feliu, Juan M

    2008-03-14

    The quantitative analysis of the different surface sites on platinum samples is attempted from pure voltammetric data. This analysis requires independent knowledge of the fraction of two-dimensional (111) and (100) domains. Specific site-probe reactions are employed to achieve this goal. Irreversibly-adsorbed bismuth and tellurium have been revealed to be sensitive to the presence of (111) terrace domains of different width whereas almost all sites involved in (100) ordered domains have been characterized through germanium adatoms. The experimental protocol follows that used with well-defined single-crystal electrodes and, therefore, requires careful control of the surface cleanliness. Platinum basal planes and their vicinal stepped surfaces have been employed to obtain calibration plots between the charge density measured under the adatom redox peak, specific for the type of surface site, and the corresponding terrace size. The evaluation of the (100) bidimensional domains can also be achieved using the voltammetric profiles, once the fraction of (111) ordered domains present in the polyoriented platinum has been determined and their featureless contribution has been subtracted from the whole voltammetric response. Using that curve, it is possible to perform a deconvolution of the adsorption states of the polycrystalline sample different from those related to (111) domains. The fraction of (100)-related states in the deconvoluted voltammogram can then be compared to that expected from the independent estimation coming from the charge involved in the redox process undergone by the irreversibly-adsorbed germanium and thus check the result of the deconvolution. The information about the surface-site distribution can also be applied to analyze the voltammetric profile of nanocrystalline platinum electrodes.

  8. Heterogeneous Catalysts

    NARCIS (Netherlands)

    Dakka, J.; Sheldon, R.A.; Sanderson, W.A.

    1997-01-01

    Abstract of GB 2309655 (A) Heterogeneous catalysts comprising one or more metal compounds selected from the group consisting of tin, molybdenum, tungsten, zirconium and selenium compounds deposited on the surface of a silicalite are provided. Preferably Sn(IV) and/or Mo(VI) are employed. The cat

  9. Method for producing hydrophobic aerogels

    Science.gov (United States)

    Hrubesh, Lawrence W.; Poco, John F.; Coronado, Paul R.

    1999-01-01

    A method for treating a dried monolithic aerogel containing non-dispersed particles, with an organometallic surface modifying agent to produce hydrophobic aerogels. The dried, porous hydrophobic aerogels contain a protective layer of alkyl groups, such as methyl groups, on the modified surfaces of the pores of the aerogel. The alkyl groups at the aerogel surface typically contain at least one carbon-metal bond per group.

  10. Request for Correction 11001 Toxicological Review of Halogenated Platinum Salts and Platinum Compounds

    Science.gov (United States)

    Request for Correction by the International Platinum Group Metals Association seeking the correction of information disseminated in the draft EPA document Toxicological Review of Halogenated Platinum Salts and Platinum Compounds: In Support of Summary Information on the Integrated Risk Information System (IRIS).

  11. PGM-free Fe-N-C catalysts for oxygen reduction reaction: Catalyst layer design

    Science.gov (United States)

    Stariha, Sarah; Artyushkova, Kateryna; Workman, Michael J.; Serov, Alexey; Mckinney, Sam; Halevi, Barr; Atanassov, Plamen

    2016-09-01

    This work studies the morphology of platinum group metal-free (PGM-free) iron-nitrogen-carbon (Fe-N-C) catalyst layers for the oxygen reduction reaction (ORR) and compares catalytic performance via polarization curves. Three different nitrogen-rich organic precursors are used to prepare the catalysts. Using scanning electron microscopy (SEM) and focused ion beam (FIB) tomography, the porosity, Euler number (pore connectivity), overall roughness, solid phase size and pore size are calculated for catalyst surfaces and volumes. Catalytic activity is determined using membrane electrode assembly (MEA) testing. It is found that the dominant factor in MEA performance is transport limitations. Through the 2D and 3D metrics it is concluded that pore connectivity has the biggest effect on transport performance.

  12. Ruthenium versus platinum on cerium materials in wet air oxidation of acetic acid

    Energy Technology Data Exchange (ETDEWEB)

    Gaalova, J. [Institute of Chemical Process Fundamentals of the CAS, Rozvojova 135, 165 02 Prague 6, CZ (Czech Republic); Barbier, J., E-mail: Jacques.barbier.jr@univ-poitiers.fr [University of Poitiers, LACCO UMR 6503, Laboratoire de Catalyse par les Metaux, 40 Avenue du Recteur Pineau, F-86022 POITIERS Cedex (France); Rossignol, S. [University of Limoges, ENSCI, 47 Avenue Albert Thomas 87000 Limoges France (France)

    2010-09-15

    This study was a comparison between Ru-catalysts and similar, previously investigated, Pt-catalysts. In this paper, ruthenium catalysts for catalytic wet air oxidation are prepared, characterized and tested. Both catalysts were supported on commercial CeO{sub 2} as well as mixed oxide Zr{sub 0.1}(Ce{sub 0.75}Pr{sub 0.25}){sub 0.9}O{sub 2}. The catalysts were characterized by measuring the oxygen storage capacities (OSC), BET, XRD, FTIR and chemisorption of hydrogen. In addition, the effect of sintering (treatments under H{sub 2}) was compared with both of the catalysts. The comparison of the results showed that initial intrinsic activity of ruthenium is not significantly influenced by the type of the support, which is contrast to platinum. Furthermore, the particle size of Ru had an important effect on CWAO activity: the higher the particle size, the better the activity. This was different with Pt-catalysts, where the optimal particle size was smaller, having about 15% of metal dispersion.

  13. Catalyst-referred etching of silicon

    Directory of Open Access Journals (Sweden)

    Hideyuki Hara et al

    2007-01-01

    Full Text Available A Si wafer and polysilicon deposited on a Si wafer were planarized using catalyst-referred etching (CARE. Two apparatuses were produced for local etching and for planarization. The local etching apparatus was used to planarize polysilicon and the planarization apparatus was used to planarize Si wafers. Platinum and hydrofluoric acid were used as the catalytic plate and the source of reactive species, respectively. The processed surfaces were observed by optical interferometry, atomic force microscopy (AFM and scanning electron microscopy (SEM. The results indicate that the CARE-processed surface is flat and undamaged.

  14. Formation of {open_quotes}metal wool{close_quotes} structures and dynamics of catalytic etching of platinum surfaces during ammonia oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Lyubovsky, M.R.; Barelko, V.V. [Institute of Chemical Physics in Chernogolovka, Moscow (Russian Federation)

    1994-09-01

    Reconstruction of a clean surface of a platinum catalyst and a platinum surface covered with gold during ammonia oxidation was studied by SEM observations. It was found that the process of catalytic etching had two sequential stages in which different crystal structures with different rates of growth formed on the surface. The first stage was the formation of parallel facets, and the second stage was the formation of individual microcrystals with perfect crystal faces. It was also found that the second state had a threshold character, beginning after some delay from the start of the reaction. A structure resembling metal wool and consisting of interlaced platinum filaments was found to form on the surface of gold-covered platinum catalysts. Characteristic features of this structure`s development are reported. The growth of filaments is attributed to the vapor-liquid-solid mechanism of whisker growth. On the basis of the observed platinum whisker formation and behavior during ammonia oxidation, a mechanism of catalyst surface reconstruction that explains observed characteristic features of the process of catalytic etching is proposed. 25 refs., 8 figs.

  15. Catalyst materials based on plasma-processed alumina nanopowder

    Directory of Open Access Journals (Sweden)

    Dubencovs Konstantins

    2012-01-01

    Full Text Available A platinum catalyst for glycerol oxidation by molecular oxygen has been developed applying the extractive-pyrolytic method and using, as a support, a fine alumina powder with an average particle size of 30-60 nm processed by plasma technology. The extractive-pyrolytic method (EPM allows affixing small amounts of catalytic metals (1-5% with the particle size ranging from several nanometers to several tens of nanometers onto the surface of the support. The prepared material - 4.8 wt. % platinum on nano-sized alumina - can be used as a catalyst for glycerol oxidation by oxygen with conversion up to 84%, in order to produce some organic acids (glyceric and lactic acid with a selectivity of about 60%.

  16. Sum Frequency Generation Studies of Hydrogenation Reactions on Platinum Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Krier, James M. [Univ. of California, Berkeley, CA (United States)

    2013-08-31

    Sum Frequency Generation (SFG) vibrational spectroscopy is used to characterize intermediate species of hydrogenation reactions on the surface of platinum nanoparticle catalysts. In contrast to other spectroscopy techniques which operate in ultra-high vacuum or probe surface species after reaction, SFG collects information under normal conditions as the reaction is taking place. Several systems have been studied previously using SFG on single crystals, notably alkene hydrogenation on Pt(111). In this thesis, many aspects of SFG experiments on colloidal nanoparticles are explored for the first time. To address spectral interference by the capping agent (PVP), three procedures are proposed: UV cleaning, H2 induced disordering and calcination (core-shell nanoparticles). UV cleaning and calcination physically destroy organic capping while disordering reduces SFG signal through a reversible structural change by PVP.

  17. Platinum Group Metal Recycling Technology Development - Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Lawrence Shore

    2009-08-19

    BASF Catalysts LLC, formerly Engelhard Corporation, has completed a project to recover Pt from PEM fuel cell membrane electrode assemblies. The project, which began in 2003, has met the project objective of an environmentally-friendly, cost-effective method for recovery of platinum without release of hydrogen fluoride. This has been achieved using a combination of milling, dispersion and acid leaching. 99% recovery of Pt was achieved, and this high yield can be scaled up using one vessel for a single leach and rinse. Leaching was been successfully achieved using a 10% solids level, double the original target. At this solids content, the reagent and utility costs represent ~0.35% of the Pt value of a lot, using very conservative assumptions. The main cost of the process is capital depreciation, followed by labor.

  18. 21 CFR 584.700 - Hydrophobic silicas.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Hydrophobic silicas. 584.700 Section 584.700 Food... DRINKING WATER OF ANIMALS Listing of Specific Substances Affirmed as GRAS § 584.700 Hydrophobic silicas. (a) Product. Amorphous fumed hydrophobic silica or precipitated hydrophobic silica (CAS Reg. No....

  19. Surface segregations in platinum-based alloy nanoparticles

    Science.gov (United States)

    Yamakawa, Shunsuke; Asahi, Ryoji; Koyama, Toshiyuki

    2014-04-01

    A phase-field model that describes the radial distributions of the ordered-disordered phase and surface segregation in a single-alloy nanoparticle is introduced to clarify the overall behavior of surface segregation of various Pt-based alloy nanoparticles. One of the obstacles to apply a platinum-transition metal alloy as a cathode electro-catalyst of a polymer electrolyte fuel cell is the need to ensure the retention of the designed surface composition in an alloy nanoparticle against the alloy combinations, a particle size, and heat treatment. From the results of calculations for CrPt, FePt, CoPt, NiPt, CuPt, PdPt, IrPt, and AuPt binary nanoparticles with diameters below 10 nm at 973.15 K, the compositional variation within a single particle was found to depend on the balance between the atomic interaction within particles and the surface free energy. In addition, the obtained specific steady-state composition of the surface varied significantly with alloy combination and particle diameter. Based on the general tendencies of a binary system to exhibit segregation, attempts to control the amount of platinum segregation on the surface using a ternary-alloy system were examined.

  20. Fabrication of superhydrophobic cotton fabrics by silica hydrosol and hydrophobization

    Energy Technology Data Exchange (ETDEWEB)

    Xu Lihui; Zhuang Wei; Xu Bi [Key Laboratory of Science and Technology of Eco-Textile, Ministry of Education, Donghua University, Shanghai 201620 (China); Cai Zaisheng, E-mail: zshcai@dhu.edu.cn [Key Laboratory of Science and Technology of Eco-Textile, Ministry of Education, Donghua University, Shanghai 201620 (China)

    2011-04-15

    Superhydrophobic cotton fabrics were prepared by the incorporation of silica nanoparticles and subsequent hydrophobization with hexadecyltrimethoxysilane (HDTMS). The silica nanoparticles were synthesized via sol-gel reaction with methyl trimethoxy silane (MTMS) as the precursor in the presence of the base catalyst and surfactant in aqueous solution. As for the resulting products, characterization by particle size analyzer, scanning electron microscopy (SEM), scanning probe microscopy (SPM), X-ray photoelectron spectroscopy (XPS), and thermal gravimetric analysis (TGA) were performed respectively. The size of SiO{sub 2} nanoparticles can be controlled by adjusting the catalyst and surfactant concentrations. The wettability of cotton textiles was evaluated by the water contact angle (WCA) and water shedding angle (WSA) measurements. The results showed that the treated cotton sample displayed remarkable water repellency with a WCA of 151.9{sup o} for a 5 {mu}L water droplet and a WSA of 13{sup o} for a 15 {mu}L water droplet.

  1. Engineering Platinum Alloy Electrocatalysts in Nanoscale for PEMFC Application

    Energy Technology Data Exchange (ETDEWEB)

    He, Ting [Idaho National Laboratory

    2016-03-01

    Fuel cells are expected to be a key next-generation energy source used for vehicles and homes, offering high energy conversion efficiency and minimal pollutant emissions. However, due to large overpotentials on anode and cathode, the efficiency is still much lower than theoretically predicted. During the past decades, considerable efforts have been made to investigate synergy effect of platinum alloyed with base metals. But, engineering the alloy particles in nanoscale has been a challenge. Most important challenges in developing nanostructured materials are the abilities to control size, monodispersity, microcomposition, and even morphology or self-assembly capability, so called Nanomaterials-by-Design, which requires interdisciplinary collaborations among computational modeling, chemical synthesis, nanoscale characterization as well as manufacturing processing. Electrocatalysts, particularly fuel cell catalysts, are dramatically different from heterogeneous catalysts because the surface area in micropores cannot be electrochemically controlled on the same time scale as more transport accessible surfaces. Therefore, electrocatalytic architectures need minimal microporous surface area while maximizing surfaces accessible through mesopores or macropores, and to "pin" the most active, highest performance physicochemical state of the materials even when exposed to thermodynamic forces, which would otherwise drive restructuring, crystallization, or densification of the nanoscale materials. In this presentation, results of engineering nanoscale platinum alloy particles down to 2 ~ 4 nm will be discussed. Based on nature of alloyed base metals, various synthesis technologies have been studied and developed to achieve capabilities of controlling particle size and particle microcomposition, namely, core-shell synthesis, microemulsion technique, thermal decomposition process, surface organometallic chemical method, etc. The results show that by careful engineering the

  2. Preparation and characterization of platinum/carbon and ruthenium/platinum/carbon nanocatalyst using the novel rotating disk-slurry electrode (RoDSE) technique

    Science.gov (United States)

    Santiago de Jesus, Diana

    An effort to develop electrochemically smaller and well-dispersed catalytic material on a high surface area carbon material is required for fuel cell applications. In terms of pure metal catalysts, platinum has shown to be the most common catalyst used in fuel cells, but suffers from poisoning when carbon monoxide is strongly adsorbed on its surface when used for direct methanol fuel cell applications. The addition of a metal with the ability to form oxides, such as ruthenium, helps to oxidize the carbon monoxide, freeing the platinum surface for new methanol oxidation. The deposition of catalysts of PtRu onto a carbon support helps to increase the active surface area of the catalyst. Vulcan X is the most commonly used of the amorphous carbon materials for fuel cell applications. Also, a high-surface-area carbon material of interest is carbon nano-onions (CNOs), also known as multilayer fullerenes. The most convenient synthetic method for CNOs is annealing nanodiamond particles, thus retaining the size of the precursors and providing the possibility to prepare very small nanocatalysts using electrochemical techniques. A rotating disk-slurry electrode (RoDSE) technique was developed as a unique method to electrochemically prepare bulk Pt/Carbon and PtRu/Carbon nanocatalysts avoiding a constant contact of the carbon support to an electrode surface during the electrodeposition process. The nanocatalysts were prepared by using a slurry that was saturated with functionalized Vulcan XC-72R and the metal precursor in sulfuric acid. The electrochemically prepared Pt/C and PtRu/C catalysts were characterized by using TEM, STEM, XRD, XRF, TGA, XPS and electrochemical techniques. A computational analysis also was done.

  3. DIRECT METHANOL FUEL CELLS AT REDUCED CATALYST LOADINGS

    Energy Technology Data Exchange (ETDEWEB)

    P. ZELENAY; F. GUYON; SM. GOTTESFELD

    2001-05-01

    We focus in this paper on the reduction of catalyst loading in direct methanol fuel cells currently under development at Los Alamos National Laboratory. Based on single-cell DMFC testing, we discuss performance vs. catalyst loading trade-offs and demonstrate optimization of the anode performance. We also show test data for a short five-cell DMFC stack with the average total platinum loading of 0.53 mg cm{sup {minus}2} and compare performance of this stack with the performance of a single direct methanol fuel cell using similar total amount of precious metal.

  4. Direct methanol fuel cells at reduced catalyst loadings

    Energy Technology Data Exchange (ETDEWEB)

    Zelenay, P. (Piotr); Guyon, F. (Francois); Gottesfeld, Shimshon

    2001-01-01

    We focus in this paper on the reduction of catalyst loading in direct methanol fuel cells currently under development at Los Alamos National Laboratory. Based on single-cell DMFC testing, we discuss performance vs. catalyst loading trade-offs and demonstrate optimization of the anode performance. We also show test data for a short five-cell DMFC stack with the average total platinum loading of 0.53 mg cm{sup -2} and compare performance of this stack with the performance of a single direct methanol fuel cell using similar total amount of precious metal.

  5. Property and performance of red mud-based catalysts for the complete oxidation of volatile organic compounds.

    Science.gov (United States)

    Kim, Sang Chai; Nahm, Seung Won; Park, Young-Kwon

    2015-12-30

    Red mud (RM) was assessed as a catalyst for the complete oxidation of volatile organic compounds (VOCs). The catalytic activity of RM was influenced by an acid treatment and the calcination temperature. Acid-treated RM (HRM) catalysts with a platinum loading (Pt/HRM) were prepared using a conventional impregnation method. Platinum catalysts supported on γ-Al2O3 (Pt/Al) were prepared for comparison. The physicochemical properties of the RM, HRM and Pt/HRM catalysts were characterized by BET analysis, ICP-AES, H2-TPD, XRD, FTIR, SEM, and FE-TEM. The acid treatment increased the BET surface area of the RM significantly, resulting in an increase in catalytic activity. Increasing the calcination temperature from 400°C to 600°C caused a decrease in its catalytic activity. Increasing the platinum loading on HRM(400) from 0.1 wt.% to 1 wt.% led to an increase in the toluene conversion, which was attributed to the better redox properties. The catalytic activities of the Pt/HRM(400) catalysts were superior to those of the Pt/Al catalysts. Benzene, toluene, o-xylene, and hexane were oxidized completely over the 1 wt.% Pt/HRM(400) catalyst at reaction temperatures less than 280°C. The presence of water vapor in the feed had a negative effect on the activity of the 1 wt.% Pt/HRM(400) catalyst.

  6. Hydrophobic aggregation of ultrafine kaolinite

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xiao-ping; HU Yue-hua; LIU Run-Qing

    2008-01-01

    The hydrophobic aggregation of ultrafine kaolinite in cationic surfactant suspension was investigated by sedimentation test, zeta potential measurement and SEM observation. SEM images reveal that kaolinite particles show the self-aggregation of edge-face in acidic media, the aggregation of edge-face and edge-edge in neutral media, and the dispersion in alkaline media due to electrostatic repulsion. In the presence of the dodecylammonium acetate cationic surfactant and in neutral and alkaline suspension, the hydrophobic aggregation of face-face is demonstrated. The zeta potential of kaolinite increases with increasing the concentration of cationic surfactant. The small and loose aggregation at a low concentration but big and tight aggregation at a high concentration is presented At pH=7 alkyl quarterly amine salt CTAB has the best hydrophobic aggregation among three cationic surfactants, namely, dodecylammonium acetate, alkyl quarterly amine salts 1227 and CTAB.

  7. Carbon Fiber Composite Monoliths as Catalyst Supports

    Energy Technology Data Exchange (ETDEWEB)

    Contescu, Cristian I [ORNL; Gallego, Nidia C [ORNL; Pickel, Joseph M [ORNL; Blom, Douglas Allen [ORNL; Burchell, Timothy D [ORNL

    2006-01-01

    Carbon fiber composite monoliths are rigid bodies that can be activated to a large surface area, have tunable porosity, and proven performance in gas separation and storage. They are ideal as catalyst supports in applications where a rigid support, with open structure and easy fluid access is desired. We developed a procedure for depositing a dispersed nanoparticulate phase of molybdenum carbide (Mo2C) on carbon composite monoliths in the concentration range of 3 to 15 wt% Mo. The composition and morphology of this phase was characterized using X-ray diffraction and electron microscopy, and a mechanism was suggested for its formation. Molybdenum carbide is known for its catalytic properties that resemble those of platinum group metals, but at a lower cost. The materials obtained are expected to demonstrate catalytic activity in a series of hydrocarbon reactions involving hydrogen transfer. This project demonstrates the potential of carbon fiber composite monoliths as catalyst supports.

  8. Carbon Fiber Composite Monoliths for Catalyst Supports

    Energy Technology Data Exchange (ETDEWEB)

    Contescu, Cristian I [ORNL; Gallego, Nidia C [ORNL; Pickel, Joseph M [ORNL; Blom, Douglas Allen [ORNL; Burchell, Timothy D [ORNL

    2006-01-01

    Carbon fiber composite monoliths are rigid bodies that can be activated to a large surface area, have tunable porosity, and proven performance in gas separation and storage. They are ideal as catalyst supports in applications where a rigid support, with open structure and easy fluid access is desired. We developed a procedure for depositing a dispersed nanoparticulate phase of molybdenum carbide (Mo2C) on carbon composite monoliths in the concentration range of 3 to 15 wt% Mo. The composition and morphology of this phase was characterized using X-ray diffraction and electron microscopy, and a mechanism was suggested for its formation. Molybdenum carbide is known for its catalytic properties that resemble those of platinum group metals, but at a lower cost. The materials obtained are expected to demonstrate catalytic activity in a series of hydrocarbon reactions involving hydrogen transfer. This project demonstrates the potential of carbon fiber composite monoliths as catalyst supports.

  9. [Platinum compounds: metabolism, toxicity and supportive strategies].

    Science.gov (United States)

    Lipp, H P; Hartmann, J T

    2005-02-09

    Although the leading platinum compounds, cisplatin, carboplatin, and oxaliplatin, share some structural similarities, there are marked differences between them in therapeutic uses, pharmacokinetics, and adverse effects profiles. Compared with cisplatin, carboplatin has inferior efficacy in germ-cell tumors, head and neck cancers, and bladder and esophageal carcinomas, whereas the two drugs appear to have comparable efficacy in ovarian cancer, extensive small-cell lung cancers (SCLC), and advanced non-small-cell lung cancers (NSCLC). Oxaliplatin belongs to the group of diaminocyclohexane (DACH) platinum compounds. It is the first platinum-based drug that has marked efficacy in colorectal cancer when given in combination with 5-fluorouracil and folinic acid. Nedaplatin has been registered in Japan, whereas other derivatives, like JM216 (which is the only orally available platinum derivative), ZD0473, BBR3464, and SPI-77 (a liposomal formulation of cisplatin), are still under investigation. The adverse effects of platinum compounds are reviewed together with possible prevention strategies.

  10. Hydrophobic effect of silica functionalized with silylated Ti-salicylaldimine complex on limonene oxidation by aqueous hydrogen peroxide

    Indian Academy of Sciences (India)

    Lai Sin Yuan; Sheela Chandren; Jon Efendi; Chin Siong Ho; Hadi Nur

    2015-11-01

    This research work describes the effect of hydrophobicity in inducing the diffusion of alkene substrates to the catalytic active sites. The aim of this research is to improve the catalytic activity by tailoring the degree of hydrophobicity of the catalyst. Silica functionalized with solid non-silylated Ti-salicylaldimine complex was prepared at room temperature by mixing imine ligand and Ti(IV) sulphate solution. The amorphous, solid complex formed was further silylated with octadecyltrimethoxysilane (OTMS) to induce hydrophobicity. The composition of the resulting silica functionalized with silylated Ti-salicylaldimine complex was varied with Ti:OTMS molar ratio in the range of 1:1/4 to 1:4 at room temperature. The successful attachment of alkylsilyl groups to silica functionalized with Ti-salicylaldimine complex was proven by the FTIR and 29Si solid state NMR spectra. The FTIR spectra showed increasing peak area for sp3 C-H stretching mode (ca. 2919 cm−1 and 2850 cm−1) and decreasing peak area for Si-OH band with increasing amount of OTMS. TGA showed less water content with higher amount of alkylsilyl groups in the catalyst. This is in agreement with the lower kinetic rate of water adsorption capacity for the hydrophobic catalysts prepared. It was observed that the hydrophobic, silica functionalized with silylated Ti-salicylaldimine complex exhibited higher substrate conversion and reusability compared to the non-silylated catalyst.

  11. Study of the re-dispersion of platinum containing bimetallic phases supported on chlorinated or neutralized alumina; Etude de la redispersion de phases bimetalliques a base de platine supportees sur alumine chloree ou neutralisee

    Energy Technology Data Exchange (ETDEWEB)

    Cholley, T.

    1997-01-31

    The re-dispersion by oxy-chlorination of platinum-tin catalysts supported on alumina constitute the matter of this work. Influence of parameters like the nature of the platinum-tin phases and particles size has been examined. The use of organometallic precursors has allowed an optimum control of the preparation and of the particles growth of the catalysts. Characterization by programmed temperature reduction (TPR), X-ray photoelectron spectroscopy (XPS), Moessbauer spectroscopy, near-edge absorption spectra (XANES) and X-ray absorption fine structure (EXAFS) has led to a better understanding of the phenomena ruling the tin reducibility. Sintering has been studied, showing that only platinum-tin alloy can sinter, while tin oxides are strongly stabilized by the support. It is shown similarly that oxy-chlorination of these catalysts causes the re-dispersion of the platinum and the platinum-tin alloy only. A re-dispersion mechanism through platinum-tin oxychloride species has been proposed. Furthermore, the main parameters influencing the re-dispersion have been highlighted. (author) 175 refs.

  12. Catalyst Architecture

    DEFF Research Database (Denmark)

    Kiib, Hans; Marling, Gitte; Hansen, Peter Mandal

    2014-01-01

    of programs, have a role in mediating positive social and/or cultural development. In this sense, we talk about architecture as a catalyst for: sustainable adaptation of the city’s infrastructure appropriate renovation of dilapidated urban districts strengthening of social cohesiveness in the city development...... meaningful for everyone. The exhibited works are designed by SANAA, Diller Scofidio + Renfro, James Corner Field Operation, JBMC Arquitetura e Urbanismo, Atelier Bow-Wow, Ateliers Jean Nouvel, COBE, Transform, BIG, Topotek1, Superflex, and by visual artist Jane Maria Petersen....

  13. Hydrophobic patches on protein surfaces

    NARCIS (Netherlands)

    Lijnzaad, P.

    2007-01-01

    Hydrophobicity is a prime determinant of the structure and function of proteins. It is the driving force behind the folding of soluble proteins, and when exposed on the surface, it is frequently involved in recognition and binding of ligands and other proteins. The energetic cost of exposing hydroph

  14. Hydrophobic Solvation: Aqueous Methane Solutions

    Science.gov (United States)

    Konrod, Oliver; Lankau, Timm

    2007-01-01

    A basic introduction to concept of a solvation shell around an apolar solute as well as its detection is presented. The hydrophobic solvation of toluene is found to be a good teaching example which connects macroscopic, phenomenological thermodynamic results with an atomistic point of view.

  15. Hydrophobic Solvation: Aqueous Methane Solutions

    Science.gov (United States)

    Konrod, Oliver; Lankau, Timm

    2007-01-01

    A basic introduction to concept of a solvation shell around an apolar solute as well as its detection is presented. The hydrophobic solvation of toluene is found to be a good teaching example which connects macroscopic, phenomenological thermodynamic results with an atomistic point of view.

  16. Influence of the Synthesis Method for Pt Catalysts Supported on Highly Mesoporous Carbon Xerogel and Vulcan Carbon Black on the Electro-Oxidation of Methanol

    OpenAIRE

    2015-01-01

    Platinum catalysts supported on carbon xerogel and carbon black (Vulcan) were synthesized with the aim of investigating the influence of the characteristics of the support on the electrochemical performance of the catalysts. Three synthesis methods were compared: an impregnation method with two different reducing agents, sodium borohydride and formic acid, and a microemulsion method, in order to study the effect of the synthesis method on the physico-chemical properties of the catalysts. X-ra...

  17. Evaluating the role of Lead In A Novel Ternary Catalysts For DMFCs

    CERN Document Server

    Halder, Aditi; Trahan, Matthew; Mukerjee, Sanjeev

    2012-01-01

    The current density at lower potential is highly desirable in fuel cell technology and crucial center point for designing a new catalyst. By alloying platinum with various other metals, the improvisation of the fuel cell catalyst has achieved a lot of attention and interests. In this article, a novel porous ternary alloy PtPb@Ru as anode catalysts for direct methanol fuel cell had been synthesized by micro-emulsion technique. The catalysts had been characterized by various spectroscopic and microscopic techniques. The activity and durability of the catalysts had been tested by running cyclic voltammetry in 0.1 M HClO4 and 1M Methanol. To explain the many fold increase in current density of the PtPb@Ru catalysts in comparison to the commercial available PtRu catalysts, in situ X-ray absorption spectroscopy (XAS) measurements, at the PtL3 edge (XANES and EXAFS) were carried out on the PtPb@Ru catalysts in an electrochemical cell. The down-shift in the d-band center of platinum observed in the XAS study, might b...

  18. Low-Temperature CO Oxidation over a Ternary Oxide Catalyst with High Resistance to Hydrocarbon Inhibition.

    Science.gov (United States)

    Binder, Andrew J; Toops, Todd J; Unocic, Raymond R; Parks, James E; Dai, Sheng

    2015-11-02

    Platinum group metal (PGM) catalysts are the current standard for control of pollutants in automotive exhaust streams. Aside from their high cost, PGM catalysts struggle with CO oxidation at low temperatures (oxide catalyst composed of copper oxide, cobalt oxide, and ceria (dubbed CCC) that outperforms synthesized and commercial PGM catalysts for CO oxidation in simulated exhaust streams while showing no signs of inhibition by propene. Diffuse reflectance IR (DRIFTS) and light-off data both indicate low interaction between propene and the CO oxidation active site on this catalyst, and a separation of adsorption sites is proposed as the cause of this inhibition resistance. This catalyst shows great potential as a low-cost component for low temperature exhaust streams that are expected to be a characteristic of future automotive systems. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Low metal loading catalysts used for the selective hydrogenation of styrene

    Energy Technology Data Exchange (ETDEWEB)

    Badano, Juan; Lederhos, Cecilia; Quiroga, Monica; L' Argentiere, Pablo [Consejo Nacional de Investigaciones Cientificas y Tecnicas, Santa Fe (Argentina). Universidad Nacional del Litoral. Inst. de Investigaciones en Catalisis y Petroquimica; Coloma-Pascual, Fernando [Universidad de Alicante (Spain). Facultad de Ciencias. Servicios Tecnicos de Investigacion

    2010-07-01

    A series of Group VIII metal catalysts was obtained for the semi-hydrogenation of styrene. Catalysts were characterized by Hydrogen Chemisorption, TPR and XPS. Palladium, rhodium and platinum low metal loading prepared catalysts presented high activity and selectivity (ca. 98%) during the semi-hydrogenation of styrene, being palladium the most active catalyst. The ruthenium catalyst also presented high selectivity (ca. 98%), but the lowest activity. For the palladium catalyst, the influence of the precursor salt and of the reduction temperature on the activity and selectivity were studied. The following activity series was obtained: PdN-423 > PdCl-673 > PdCl-373> PtCl-673 > RhCl-673 >> RuCl-673. As determined by XPS, differences in activity could be attributed, at least in part, to electronic effects (author)

  20. Immobilization of Platinum Nanoparticles on 3,4-diaminobenzoyl-Functionalized Multi-Walled Carbon Nanotube and its Electrocatalytic Activity

    Science.gov (United States)

    2012-01-01

    650 C was 48 wt%, which is attributed to thermo-oxidative stripping of the DAB moiety (Fig. 2b). The value agreed well with the feed ratio of DAB...1979b) The use of linear potential sweep voltammetry and of ac voltammetry for the study of the surface electro- chemical reaction of strongly adsorbed...Xin Q (2003) Preparation and characterization of multiwalled carbon nanotube-supported platinum for cathode catalysts of direct methanol fuel cells

  1. Investigation of nanostructured platinum-nickel supported on the titanium surface as electrocatalysts for alkaline fuel cells

    Science.gov (United States)

    Tamašauskaitė-Tamašiūnaitė, L.; Balčiūnaitė, A.; Vaiciukevičienė, A.; Selskis, A.; Pakštas, V.

    2012-06-01

    This study involves the formation of nanostructured platinum-nickel supported on the titanium surface catalysts using the galvanic displacement technique and investigation of their electrocatalytic activity toward the oxidation of borohydride, methanol and ethanol in an alkaline media by cyclic voltammetry and chronoamperometry. Scanning electron microscopy, Energy Dispersive X-ray Spectroscopy and X-ray diffraction were used to characterize the surface structure, composition and morphology. The nanoPt(Ni)/Ti and nanoPt/Ti catalysts exhibited a higher catalytic efficiency to the oxidation of borohydride, ethanol and methanol as compared with that of pure Pt.

  2. Single crystal studies of platinum alloys for oxygen reduction electrodes

    DEFF Research Database (Denmark)

    Ulrikkeholm, Elisabeth Therese

    In this thesis the discovery, characterization and testing of new catalysts for the oxygen reduction reaction (ORR) is investigated. Experiments on sputter cleaned, polycrystalline Pt5Y and Pt5Gd crystals have shown that these alloys are excelent candidates for catalysts for the ORR. To mimic...... was performed on the samples as prepared, and after electrochemical cycling between 0.05 V and 1.0 V VS. RHE. and between 0.05 V and 1.2 V VS. RHE. Diffraction experiments carried out after the cycling to 1.0 V showed that an overlayer with crystalline order had been formed on the Y/Pt(111) sample and the Gd....../Pt(111) samples. These overlayers were slightly compressed compared to pure platinum and had a 6-fold symmetry. After cycling to 1.2 V VS. RHE. the correlation length of the overlayer on the Gd/Pt(111) sample had decreased significantly, and the overlayer on the Y/Pt(111) had disappeared completely...

  3. Room temperature synthesis of colloidal platinum nanoparticles

    Indian Academy of Sciences (India)

    G Sarala Devi; V J Rao

    2000-12-01

    Efficient preparation of stable dispersions of platinum nanoparticles from platinous chloride (K2PtCl4) was achieved by simultaneous addition of capping polymer material. The size of platinum nanoparticles was controlled by changing the ratio of concentration of capping polymer material to the concentration of platinum cation used. The morphology of colloidal particles were studied by means of UV-visible spectrophotometry and transmission electron microscopy (TEM). Particle size increased with low reagent concentration. The change in absorption spectra with the particle size was observed, i.e. blue shift attributed to decrease in particle size.

  4. Antitumor effect of arabinogalactan and platinum complex.

    Science.gov (United States)

    Starkov, A K; Zamay, T N; Savchenko, A A; Ingevatkin, E V; Titova, N M; Kolovskaya, O S; Luzan, N A; Silkin, P P; Kuznetsova, S A

    2016-03-01

    The article presents the results of investigation of antitumor properties of platinum-arabinogalactan complex. We showed the ability of the complex to inhibit the growth of Ehrlich ascites tumor cells. It is found that the distribution of the platinum-arabinogalactan complex is not specific only for tumor cells in mice. The complex was found in all tissues and organs examined (ascites cells, embryonic cells, kidney, and liver). The mechanism of action of the arabinogalactan-platinum complex may be similar to cisplatin as the complex is able to accumulate in tumor cells.

  5. Mechanism of Platinum Derivatives Induced Kidney Injury

    Directory of Open Access Journals (Sweden)

    Feifei YAN

    2015-09-01

    Full Text Available Platinum derivatives are the most widely used chemotherapeutic agents to treat solid tumors including ovarian, head and neck, and testicular germ cell tumors, lung cancer, and colorectal cancer. Two major problems exist, however, in the clinic use of platinum derivatives. One is the development of tumor resistance to the drug during therapy, leading to treatment failure. The other is the drug’s toxicity such as the cisplatin’s nephrotoxicity, which limits the dose that can be administered. This paper describes the mechanism of platinum derivatives induced kidney injury.

  6. Carbon monoxide tolerant platinum electrocatalysts on niobium doped titania and carbon nanotube composite supports

    Science.gov (United States)

    Rigdon, William A.; Huang, Xinyu

    2014-12-01

    In the anode of electrochemical cells operating at low temperature, the hydrogen oxidation reaction is susceptible to poisoning from carbon monoxide (CO) which strongly adsorbs on platinum (Pt) catalysts and increases activation overpotential. Adsorbed CO is removed by oxidative processes such as electrochemical stripping, though cleaning can also cause corrosion. One approach to improve the tolerance of Pt is through alloying with less-noble metals, but the durability of alloyed electrocatalysts is a critical concern. Without sacrificing stability, tolerance can be improved by careful design of the support composition using metal oxides. The bifunctional mechanism is promoted at junctions of the catalyst and metal oxides used in the support. Stable metal oxides can also form strong interactions with catalysts, as is the case for platinum on titania (TiOx). In this study, niobium (Nb) serves as an electron donor dopant in titania. The transition metal oxides are joined to functionalized multi-wall carbon nanotube (CNT) supports in order to synthesize composite supports. Pt is then deposited to form electrocatalysts which are characterized before fabrication into anodes for tests as an electrochemical hydrogen pump. Comparisons are made between the control from Pt-CNT to Pt-TiOx-CNT and Pt-Ti0.9Nb0.1Ox-CNT in order to demonstrate advantages.

  7. Catalyst Architecture

    DEFF Research Database (Denmark)

    the projects as case studies, which contribute with strategic knowledge rather than generalizing from average considerations. These are ‘strategic projects’ where we have looked for the specific and the particular (Flyvbjerg 1991). According to the case studies, we use the case study method developed by Bent......’ interpretations and architectural strategies are included in the analyses. This implies that there is a large variation of empirical knowledge about the selected problems. That is the reason why we give a short introduction to the exact use of approaches and methods in the beginning of each case study. Based...... in experience? Which design qualities do the best examples of architecture as urban catalysts have, and how can we as citizens, politicians and professionals use knowledge about this in the development of our cities as good places to live? We wish to throw light on these key questions through case studies...

  8. Active oxygen by Ce–Pr mixed oxide nanoparticles outperform diesel soot combustion Pt catalysts

    OpenAIRE

    Guillén Hurtado, Noelia; Garcia-Garcia, Avelina; Bueno López, Agustín

    2015-01-01

    A Ce0.5Pr0.5O2 mixed oxide has been prepared with the highest surface area and smallest particle size ever reported (125 m2/g and 7 nm, respectively), also being the most active diesel soot combustion catalyst ever tested under realistic conditions if catalysts forming highly volatile species are ruled out. This Ce–Pr mixed oxide is even more active than a reference platinum-based commercial catalyst. This study provides an example of the efficient participation of oxygen species released by ...

  9. Methanol-Tolerant Cathode Catalyst Composite For Direct Methanol Fuel Cells

    Science.gov (United States)

    Zhu, Yimin; Zelenay, Piotr

    2006-03-21

    A direct methanol fuel cell (DMFC) having a methanol fuel supply, oxidant supply, and its membrane electrode assembly (MEA) formed of an anode electrode and a cathode electrode with a membrane therebetween, a methanol oxidation catalyst adjacent the anode electrode and the membrane, an oxidant reduction catalyst adjacent the cathode electrode and the membrane, comprises an oxidant reduction catalyst layer of a platinum-chromium alloy so that oxidation at the cathode of methanol that crosses from the anode through the membrane to the cathode is reduced with a concomitant increase of net electrical potential at the cathode electrode.

  10. Raney Ni-Sn catalyst for H2 production from biomass-derived hydrocarbons.

    Science.gov (United States)

    Huber, G W; Shabaker, J W; Dumesic, J A

    2003-06-27

    Hydrogen (H2) was produced by aqueous-phase reforming of biomass-derived oxygenated hydrocarbons at temperatures near 500 kelvin over a tin-promoted Raney-nickel catalyst. The performance of this non-precious metal catalyst compares favorably with that of platinum-based catalysts for production of hydrogen from ethylene glycol, glycerol, and sorbitol. The addition of tin to nickel decreases the rate of methane formation from C-O bond cleavage while maintaining the high rates of C-C bond cleavage required for hydrogen formation.

  11. Intrinsic Hydrophobicity of Rammed Earth

    Science.gov (United States)

    Holub, M.; Stone, C.; Balintova, M.; Grul, R.

    2015-11-01

    Rammed earth is well known for its vapour diffusion properties, its ability to regulate humidity within the built environment. Rammed earth is also an aesthetically iconic material such as marble or granite and therefore is preferably left exposed. However exposed rammed earth is often coated with silane/siloxane water repellents or the structure is modified architecturally (large roof overhangs) to accommodate for the hydrophilic nature of the material. This paper sets out to find out optimal hydrophobicity for rammed earth based on natural composite fibres and surface coating without adversely affecting the vapour diffusivity of the material. The material is not required to be waterproof, but should resist at least driving rain. In order to evaluate different approaches to increase hydrophobicity of rammed earth surface, peat fibres and four types of repellents were used.

  12. Platinum-Resistor Differential Temperature Sensor

    Science.gov (United States)

    Kolbly, R. B.; Britcliffe, M. J.

    1985-01-01

    Platinum resistance elements used in bridge circuit for measuring temperature difference between two flowing liquids. Temperature errors with circuit are less than 0.01 degrees C over range of 100 degrees C.

  13. VB Platinum Tile & Carpet, Inc. Information Sheet

    Science.gov (United States)

    VB Platinum Tile & Carpet, Inc. (the Company) is located in Bristow, Virginia. The settlement involves renovation activities conducted at a property constructed prior to 1978, located in Washington, DC.

  14. Hydrophobic effect at aqueous interfaces

    Science.gov (United States)

    Pohorille, Andrew

    2005-01-01

    Conceptual basis for hydrophobic effects in bulk water and at aqueous interfaces have similar conceptual basis but often manifests itself differently. Using a wide range of computer simulations as the basis, I will review different forms of hydrophobic effects at a variety of interfaces starting from simple liquid-vapor and water-oil interfaces and progressing to water-membrane interfaces. I will start with discussing how water is organized at different interfaces, stressing both similarities and differences. The main thread is that, as in the bulk liquid, hydrophobic effects have profound influence on conformational equilibria and organization of both small molecules and macromolecules, but the result of this influence is quite different. Specifically, it will be shown that many small, but not necessarily amphiphilic molecules tend to accumulate at the interface and, and this tendency will be explained. Furthermore, I will show that many short peptides that are disordered in water spontaneously fold into well-defined structures in the interfacial environment. Biological implications of this self-organizing effect will be discussed.

  15. Investigation of altenative carbon materials for fuel-cell catalyst support

    DEFF Research Database (Denmark)

    Larsen, Mikkel Juul

    activity occurred above 0.2 V. Unexpectedly, the generation of peroxides on the Pt/C materials was also very high: up to 50 % at 0.066 V for many samples and also significant at even much higher potentials. The specific electrocatalytic activity was found to be highest for a platinized sample of untreated...... CNF, while the Pt/FWCNT samples showed the best mass-specific electrocatalytic activity. Based on the experimental data acquired in this work it is assessed that the FWCNT samples are the best of the tested materials for use as support for the platinum catalyst in a PEMFC. This is due their high...... available surface areas, the excellent ability for dispersion of platinum on them, and the good electrocatalytic activities of the resulting catalysts. The least suited material is GMWCNT-OH, which shows very high peroxide generation and leads to catalysts with rather large particle size and exceptionally...

  16. Electrochemical catalyst recovery method

    Science.gov (United States)

    Silva, Laura J.; Bray, Lane A.

    1995-01-01

    A method of recovering catalyst material from latent catalyst material solids includes: a) combining latent catalyst material solids with a liquid acid anolyte solution and a redox material which is soluble in the acid anolyte solution to form a mixture; b) electrochemically oxidizing the redox material within the mixture into a dissolved oxidant, the oxidant having a potential for oxidation which is effectively higher than that of the latent catalyst material; c) reacting the oxidant with the latent catalyst material to oxidize the latent catalyst material into at least one oxidized catalyst species which is soluble within the mixture and to reduce the oxidant back into dissolved redox material; and d) recovering catalyst material from the oxidized catalyst species of the mixture. The invention is expected to be particularly useful in recovering spent catalyst material from petroleum hydroprocessing reaction waste products having adhered sulfides, carbon, hydrocarbons, and undesired metals, and as well as in other industrial applications.

  17. CATALYTIC BEHAVIOR OF A SILICA-SUPPORTED POLYTITAZANE-PLATINUM COMPLEX FOR THE HYDROGENATION OF PHENOL

    Institute of Scientific and Technical Information of China (English)

    CHEN Chunwei; HUANG Meiyu; JIANG Yingyan

    1996-01-01

    A new kind of inorganic polymer, viz. silica-supported polytitazane (Ti-N), and its platinum complex (Ti-N-Pt) were prepared. Cyclohexanone can be obtained in a maximum yield of about 62.2% in the hydrogenation of phenol over Ti-N-Pt at room temperature under atmospheric pressure. The effects of mole ratio of N/Pt in the complex, concentration of the catalyst and reaction temperature on the catalytic activity and selectivity have been studied. The complex can be reused several times without loss in its catalytic activity.

  18. Hydrogenation of Toluidines Catalyzed by Silica-supported Carboxymethylcellulose-platinum Complex

    Institute of Scientific and Technical Information of China (English)

    WANG Xin; YANG Ji-huo; HUANG Mei-yu; JIANG Ying-yan

    2004-01-01

    The hydrogenation of toluidines catalyzed by silica-supported carboxymethyl cellulose platinum complex forms methylcyclohexlamines in high yields, such as m-toluidine to 3-methylcyclohexylamine, o-toluidine to 2-methylcyclohexylamine, and p-toluidine to 4-methylcyclohexylamine in 97%, 96.7% and 98.2% yields,respectively, at 30 C and under atmospheric hydrogen pressure. The yields were remarkably affected by the Pt content in the complex, the kind of solvent and the reaction temperature. The catalyst was very stable and could be reused several times without remarkable change in the catalytic activity.

  19. A Heuristic Molecular Model of Hydrophobic Interactions

    CERN Document Server

    Hummer, G; García, A E; Pohorille, A; Pratt, L R

    1995-01-01

    Hydrophobic interactions provide driving forces for protein folding, membrane formation, and oil-water separation. Motivated by information theory, the poorly understood nonpolar solute interactions in water are investigated. A simple heuristic model of hydrophobic effects in terms of density fluctuations is developed. This model accounts quantitatively for the central hydrophobic phenomena of cavity formation and association of inert gas solutes; it therefore clarifies the underlying physics of hydrophobic effects and permits important applications to conformational equilibria of nonpolar solutes and hydrophobic residues in biopolymers.

  20. Cell-surface hydrophobicity of Staphylococcus saprophyticus.

    Science.gov (United States)

    Schneider, P. F.; Riley, T. V.

    1991-01-01

    The cell-surface hydrophobicity of 100 urinary isolates of Staphylococcus saprophyticus, cultured from symptomatic females in the general population, was assessed using a two-phase aqueous:hydrocarbon system. Relatively strong cell-surface hydrophobicity was exhibited by 79 isolates using the criteria employed, while only 2 of the remaining 21 isolates failed to demonstrate any detectable hydrophobicity. Cell-surface hydrophobicity may be a virulence factor of S. saprophyticus, important in adherence of the organism to uroepithelia. Additionally, the data support the concept that cell-surface hydrophobicity may be a useful predictor of clinical significance of coagulase-negative staphylococci isolated from clinical sources. PMID:1993454

  1. Hydrophobic-Core Microcapsules and Their Formation

    Science.gov (United States)

    Calle, Luz M. (Inventor); Li, Wenyan (Inventor); Buhrow, Jerry W. (Inventor); Jolley, Scott T. (Inventor)

    2016-01-01

    Hydrophobic-core microcapsules and methods of their formation are provided. A hydrophobic-core microcapsule may include a shell that encapsulates a hydrophobic substance with a core substance, such as dye, corrosion indicator, corrosion inhibitor, and/or healing agent, dissolved or dispersed therein. The hydrophobic-core microcapsules may be formed from an emulsion having hydrophobic-phase droplets, e.g., containing the core substance and shell-forming compound, dispersed in a hydrophilic phase. The shells of the microcapsules may be capable of being broken down in response to being contacted by an alkali, e.g., produced during corrosion, contacting the shell.

  2. SYNTHESIS OF DI(ETHYLMERCAPTOETHYL) AMINO GROUP—CONTAINING POLYSESQUISILOXANE PLATINUM COMPLEX AND ITS CATALYSIS IN HYDROSIL YLATION OF OLEFINS WITH TRIETHOXYSILANE

    Institute of Scientific and Technical Information of China (English)

    CHENYuanyin; HUXubo; 等

    1992-01-01

    Three new polysesquisiloxane-bound platinum complexes were synthesized via hydrolysis of N,N-di(β-ethylmercaptoethyl)γ-(triethoxysilyl)propylamine or cohydrolysis of the monomer with dodecyltriethoxysilane or with phenylpropylthiethoxysilane and immobilixation on fumed silica,followed by reacting with potassium platinite in acetone under argon atmosphere.The platinum complexes exhibited high catalytic activity for the hydrosilylation of olefins by triethoxysilane. The effects of temperature and the amount of complex on the catalytic activity,as well as the recovery and reusability of the catalysts were investigated.

  3. Hydrophobicity of rare-earth oxide ceramics

    Science.gov (United States)

    Azimi, Gisele; Dhiman, Rajeev; Kwon, Hyuk-Min; Paxson, Adam T.; Varanasi, Kripa K.

    2013-04-01

    Hydrophobic materials that are robust to harsh environments are needed in a broad range of applications. Although durable materials such as metals and ceramics, which are generally hydrophilic, can be rendered hydrophobic by polymeric modifiers, these deteriorate in harsh environments. Here we show that a class of ceramics comprising the entire lanthanide oxide series, ranging from ceria to lutecia, is intrinsically hydrophobic. We attribute their hydrophobicity to their unique electronic structure, which inhibits hydrogen bonding with interfacial water molecules. We also show with surface-energy measurements that polar interactions are minimized at these surfaces and with Fourier transform infrared/grazing-angle attenuated total reflection that interfacial water molecules are oriented in the hydrophobic hydration structure. Moreover, we demonstrate that these ceramic materials promote dropwise condensation, repel impinging water droplets, and sustain hydrophobicity even after exposure to harsh environments. Rare-earth oxide ceramics should find widespread applicability as robust hydrophobic surfaces.

  4. Manganese dioxide as a new cathode catalyst in microbial fuel cells

    Science.gov (United States)

    Li, Xiang; Hu, Boxun; Suib, Steven; Lei, Yu; Li, Baikun

    This study focused on manganese oxides with a cryptomelane-type octahedral molecular sieve (OMS-2) structure to replace platinum as a cathode catalyst in microbial fuel cells (MFCs). Undoped (ud-OSM-2) and three catalysts doped with cobalt (Co-OMS-2), copper (Cu-OMS-2), and cerium (Ce-OMS-2) to enhance their catalytic performances were investigated. The novel OMS-2 cathodes were examined in granular activated carbon MFC (GACMFC) with sodium acetate as the anode reagent and oxygen in air as the cathode reagent. The results showed that after 400 h of operation, the Co-OMS-2 and Cu-OMS-2 exhibited good catalytic performance in an oxygen reduction reaction (ORR). The voltage of the Co-OMS-2 GACMFC was 217 mV, and the power density was 180 mW m -2. The voltage of the Cu-OMS-2 GACMFC was 214 mV and the power density was 165 mW m -2. The internal resistance (R in) of the OMS-2 GACMFCs (18 ± 1 Ω) was similar to that of the platinum GACMFCs (17 Ω). Furthermore, the degradation rates of organic substrates in the OMS-2 GACMFCs were twice those in the platinum GACMFCs, which enhance their wastewater treatment efficiencies. This study indicated that using OMS-2 manganese oxides to replace platinum as a cathodic catalyst enhances power generation, increases contaminant removal, and substantially reduces the cost of MFCs.

  5. Platinum in Earth surface environments

    Science.gov (United States)

    Reith, F.; Campbell, S. G.; Ball, A. S.; Pring, A.; Southam, G.

    2014-04-01

    Platinum (Pt) is a rare precious metal that is a strategic commodity for industries in many countries. The demand for Pt has more than doubled in the last 30 years due to its role in the catalytic conversion of CO, hydrocarbons and NOx in modern automobiles. To explore for new Pt deposits, process ores and deal with ecotoxicological effects of Pt mining and usage, the fundamental processes and pathways of Pt dispersion and re-concentration in surface environments need to be understood. Hence, the aim of this review is to develop a synergistic model for the cycling of Pt in Earth surface environments. This is achieved by integrating the geological/(biogeo)chemical literature, which focuses on naturally occurring Pt mobility around ore deposits, with the environmental/ecotoxicological literature dealing with anthropogenic Pt dispersion. In Pt deposits, Pt occurs as sulfide-, telluride- and arsenide, native metal and alloyed to other PGEs and iron (Fe). Increased mining and utilization of Pt combined with the burning of fossil fuels have led to the dispersion of Pt-containing nano- and micro-particles. Hence, soils and sediments in industrialized areas, urban environments and along major roads are now commonly Pt enriched. Platinum minerals, nuggets and anthropogenic particles are transformed by physical and (bio)geochemical processes. Complexation of Pt ions with chloride, thiosulfate, ammonium, cyanide, low- and high molecular weight organic acids (LMWOAs and HMWOAs) and siderophores can facilitate Pt mobilization. Iron-oxides, clays, organic matter and (micro)biota are known to sequester Pt-complexes and -particles. Microbes and plants are capable of bioaccumulating and reductively precipitating mobile Pt complexes. Bioaccumulation can lead to toxic effects on plants and animals, including humans. (Bio)mineralization in organic matter-rich sediments can lead to the formation of secondary Pt particles and -grains. Ultimately, Pt is enriched in oceanic sediments

  6. Tuning the hydrophobicity of ZSM-5 zeolites by surface silanization using alkyltrichlorosilane

    Energy Technology Data Exchange (ETDEWEB)

    Han Xiaolong; Wang Lei [State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084 (China); Li Jiding, E-mail: lijiding@mail.tsinghua.edu.cn [State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084 (China); Zhan Xia; Chen Jian; Yang Jichu [State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084 (China)

    2011-09-01

    ZSM-5 zeolites were modified with alkyltrichlorosilanes of various chain lengths (octyltrichlorosilane, decyltrichlorosilane, dodecyltrichlorosilane and hexadecyltrichlorosilane) and characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Thermal gravimetric analysis (TGA) and contact angle measurements (CA). The results showed that a closely packed and hydrophobic layer was presented at the particles surface and the surface wetting property varied from hydrophilic to hydrophobic, even to superhydrophobic. It was interesting to notice that the hydrophobic properties of modified ZSM-5 particles could be tuned by varying the chain length of chlorosilane and changing the pretreatment temperature before silanization. With increasing the alkyl chain length of trichlorosilane, the hydrophobicity increased. However, with an increase in the pretreatment temperature, the hydrophobicity decreased. Moreover, the relationship between the wetting properties and thermal stability was also investigated, the results showed that the modified ZSM-5 particles possessed good hydrophobicity at a temperature below 250 deg. C in air. These modified ZSM-5 particles may be utilized for many potential applications, such as membrane fillers, selective adsorbents, catalysts, chromatographic supports and so on.

  7. Tuning the hydrophobicity of ZSM-5 zeolites by surface silanization using alkyltrichlorosilane

    Science.gov (United States)

    Han, Xiaolong; Wang, Lei; Li, Jiding; Zhan, Xia; Chen, Jian; Yang, Jichu

    2011-09-01

    ZSM-5 zeolites were modified with alkyltrichlorosilanes of various chain lengths (octyltrichlorosilane, decyltrichlorosilane, dodecyltrichlorosilane and hexadecyltrichlorosilane) and characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Thermal gravimetric analysis (TGA) and contact angle measurements (CA). The results showed that a closely packed and hydrophobic layer was presented at the particles surface and the surface wetting property varied from hydrophilic to hydrophobic, even to superhydrophobic. It was interesting to notice that the hydrophobic properties of modified ZSM-5 particles could be tuned by varying the chain length of chlorosilane and changing the pretreatment temperature before silanization. With increasing the alkyl chain length of trichlorosilane, the hydrophobicity increased. However, with an increase in the pretreatment temperature, the hydrophobicity decreased. Moreover, the relationship between the wetting properties and thermal stability was also investigated, the results showed that the modified ZSM-5 particles possessed good hydrophobicity at a temperature below 250 °C in air. These modified ZSM-5 particles may be utilized for many potential applications, such as membrane fillers, selective adsorbents, catalysts, chromatographic supports and so on.

  8. Drying Induced Hydrophobic Polymer Collapse

    OpenAIRE

    ten Wolde, Pieter Rein; Chandler, David

    2002-01-01

    We have used computer simulation to study the collapse of a hydrophobic chain in water. We find that the mechanism of collapse is much like that of a first-order phase transition. The evaporation of water in the vicinity of the polymer provides the driving force for collapse, and the rate limiting step is the nucleation of a sufficiently large vapor bubble. The study is made possible through the application of transition path sampling and a coarse-grained treatment of liquid water. Relevance ...

  9. Dropwise Condensation on Hydrophobic Cylinders

    CERN Document Server

    Park, Kyoo-Chul; Hoang, Michelle; McManus, Brendan; Aizenberg, Joanna

    2016-01-01

    In this work, we studied the effect of the diameter of horizontal hydrophobic cylinders on droplet growth. We postulate that the concentration gradient created by natural convection around a horizontal circular cylinder is related to the droplet growth on the cylinder by condensation. We derive a simple scaling law of droplet growth and compare it with experimental results. The predicted negative exponent of drop diameter (d) as a function of cylinder diameter (D) at different time points is similar to the general trend of experimental data. Further, this effect of cylinder diameter on droplet growth is observed to be stronger than the supersaturation conditions created by different surface temperatures.

  10. Extraction of Pd and Pt from Dead Catalysts Using the Electrochemical Method

    Directory of Open Access Journals (Sweden)

    Bagdaulet K. Kenzhaliyev

    2014-03-01

    Full Text Available We studied the possibility of using electrochemical methods for the extraction of metals from dead catalysts, based on the example of the platinum-group metals. Leaching of palladium and platinum was carried out in a solution with sodium hydroxide applying a sulphur graphite electrode, which served as a source of formation of leaching reagents (sodium thio-compounds. The reactions of the formation of leaching reagents and transfer of metals into the solution were performed simultaneously in the volume of a reaction vessel.

  11. Bioinspired molecular co-catalysts bonded to a silicon photocathode for solar hydrogen evolution

    DEFF Research Database (Denmark)

    Hou, Yidong; Abrams, Billie L.; Vesborg, Peter Christian Kjærgaard

    2011-01-01

    -abundant alternatives are needed for large-scale use. We show that bioinspired molecular clusters based on molybdenum and sulphur evolve hydrogen at rates comparable to that of platinum. The incomplete cubane-like clusters (Mo3S 4) efficiently catalyse the evolution of hydrogen when coupled to a p-type Si semiconductor......The production of fuels from sunlight represents one of the main challenges in the development of a sustainable energy system. Hydrogen is the simplest fuel to produce and although platinum and other noble metals are efficient catalysts for photoelectrochemical hydrogen evolution, earth...

  12. Gold-platinum bimetallic nanotubes templated from tellurium nanowires as efficient electrocatalysts for methanol oxidation reaction

    Science.gov (United States)

    Lu, Chenchen; Kong, Wei; Zhang, Huying; Song, Bo; Wang, Zhenghua

    2015-11-01

    In this paper, gold-platinum (Au-Pt) bimetallic nanotubes with different Au/Pt ratio are successfully synthesized through a simple wet-chemical reduction route in which tellurium (Te) nanowires serve as both sacrificial template and reducing agent. The hollow nanostructure of Au-Pt nanotubes is formed due to Kirkendall effect. The as-prepared Au-Pt nanotubes can be applied as catalyst for methanol oxidation reaction, and the results indicate that the Au-Pt nanotubes with an Au/Pt ratio of 1:1 show the best electrochemical catalytic performances. Furthermore, the catalytic activity of the Au-Pt nanotubes is also better than Pt nanotubes and commercial Pt/C catalyst.

  13. Foundation Flash Catalyst

    CERN Document Server

    Goralski, Greg

    2010-01-01

    This book offers an introduction to Flash Catalyst for designers with intermediate to advanced skills. It discusses where Catalyst sits within the production process and how it communicates with other programs. It covers all of the features of the Flash Catalyst workspace, teaching you how to create designs from scratch, how to build application designs and add functionality, and how to master the Catalyst/Flex workflow. * Introduces Flash Catalyst * Focuses on production process * Covers the interrelation between Flash Catalyst and Photoshop/Illustrator/Flex/Flash What you'll learn Starting f

  14. Mass-selected nanoparticles of PtxY as model catalysts for oxygen electroreduction

    DEFF Research Database (Denmark)

    Hernandez-Fernandez, Patricia; Masini, Federico; McCarthy, David Norman

    2014-01-01

    Low-temperature fuel cells are limited by the oxygen reduction reaction, and their widespread implementation in automotive vehicles is hindered by the cost of platinum, currently the best-known catalyst for reducing oxygen in terms of both activity and stability. One solution is to decrease the a...

  15. Template Effect and Ligand Substitution Methods for the Synthesis of Iron Catalysts: A Two-Part Experiment for Inorganic Chemistry

    Science.gov (United States)

    Sues, Peter E.; Cai, Kuihua; McIntosh, Douglas F.; Morris, Robert H.

    2015-01-01

    Asymmetric transfer hydrogenation is an important transformation for the production of fine chemicals. Traditionally, platinum group metals are used to catalyze this reaction, but recent pressure for greener practices has driven the development of base-metal catalysts. Due to the growing interest in this area of research, the underlying concepts…

  16. CO Adsorption and Oxidation at the Catalyst-Water Interface: An Investigation by Attenuated Total Reflection Infrared Spectroscopy.

    NARCIS (Netherlands)

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

    2006-01-01

    Adsorption of carbon monoxide and oxidation of preadsorbed carbon monoxide from gas and aqueous phases were studied on a platinum catalyst deposited on a ZnSe internal reflection element (IRE) using attenuated total reflection infrared (ATR-IR) spectroscopy. The results of this study convincingly

  17. Durability of Carbon Nanofiber (CNF) & Carbon Nanotube (CNT) as Catalyst Support for Proton Exchange Membrane Fuel Cells

    DEFF Research Database (Denmark)

    Andersen, Shuang Ma; Borghei, Maryam; Lund, Peter;

    2013-01-01

    gravimetric analysis (TGA), cyclic voltammetry (CV), polarization curve and impedance spectroscopy were applied on the samples under accelerated stress conditions. The carbon nano-materials demonstrated better stability as support for nano-sized platinum catalyst under PEMFC related operating conditions. Due...

  18. Template Effect and Ligand Substitution Methods for the Synthesis of Iron Catalysts: A Two-Part Experiment for Inorganic Chemistry

    Science.gov (United States)

    Sues, Peter E.; Cai, Kuihua; McIntosh, Douglas F.; Morris, Robert H.

    2015-01-01

    Asymmetric transfer hydrogenation is an important transformation for the production of fine chemicals. Traditionally, platinum group metals are used to catalyze this reaction, but recent pressure for greener practices has driven the development of base-metal catalysts. Due to the growing interest in this area of research, the underlying concepts…

  19. Advanced Catalysis Technologies: Lanthanum Cerium Manganese Hexaaluminate Combustion Catalysts for Flat Plate Reactor for Compact Steam Reformers

    Science.gov (United States)

    2008-12-01

    E. Pocoroba, E.M. Johansson, S.G. Jaras, ”Aging Of Palladium, Platinum And Manganese-Based Combustion Catalysts For Biogas Applications,” Catalysis...M.J. Binder, “JP-8 Catalytic Cracking For Compact Fuel Processors,” Journal of Power Sources 129 (2004) 81-89. 12. P-O.F. Andersson, M

  20. computer modeling ter modeling ter modeling of platinum reforming ...

    African Journals Online (AJOL)

    eobe

    naphtha to complex chemical reactions, at h temperature and ... at is leaving any stage of the platinum reforming reactors in terms of ... In this study, only platinum reforming .... IV. Hydrocracking of paraffinic hydrocarbons: +. →. ( +. +. +. +. ) (18).

  1. Novel platinum black electroplating technique improving mechanical stability.

    Science.gov (United States)

    Kim, Raeyoung; Nam, Yoonkey

    2013-01-01

    Platinum black microelectrodes are widely used as an effective neural signal recording sensor. The simple fabrication process, high quality signal recording and proper biocompatibility are the main advantages of platinum black microelectrodes. When microelectrodes are exposed to actual biological system, various physical stimuli are applied. However, the porous structure of platinum black is vulnerable to external stimuli and destroyed easily. The impedance level of the microelectrode increases when the microelectrodes are damaged resulting in decreased recording performance. In this study, we developed mechanically stable platinum black microelectrodes by adding polydopamine. The polydopamine layer was added between the platinum black structures by electrodeposition method. The initial impedance level of platinum black only microelectrodes and polydopamine added microelectrodes were similar but after applying ultrasonication the impedance value dramatically increased for platinum black only microelectrodes, whereas polydopamine added microelectrodes showed little increase which were nearly retained initial values. Polydopamine added platinum black microelectrodes are expected to extend the availability as neural sensors.

  2. Highly Dispersed Alloy Catalyst for Durability

    Energy Technology Data Exchange (ETDEWEB)

    Murthi, Vivek S.; Izzo, Elise; Bi, Wu; Guerrero, Sandra; Protsailo, Lesia

    2013-01-08

    Achieving DOE's stated 5000-hr durability goal for light-duty vehicles by 2015 will require MEAs with characteristics that are beyond the current state of the art. Significant effort was placed on developing advanced durable cathode catalysts to arrive at the best possible electrode for high performance and durability, as well as developing manufacturing processes that yield significant cost benefit. Accordingly, the overall goal of this project was to develop and construct advanced MEAs that will improve performance and durability while reducing the cost of PEMFC stacks. The project, led by UTC Power, focused on developing new catalysts/supports and integrating them with existing materials (membranes and gas diffusion layers (GDLs)) using state-of-the-art fabrication methods capable of meeting the durability requirements essential for automotive applications. Specifically, the project work aimed to lower platinum group metals (PGM) loading while increasing performance and durability. Appropriate catalysts and MEA configuration were down-selected that protects the membrane, and the layers were tailored to optimize the movements of reactants and product water through the cell to maximize performance while maintaining durability.

  3. Platinum uptake from chloride solutions using biosorbents

    Directory of Open Access Journals (Sweden)

    Mehmet Hakan Morcali

    2013-04-01

    Full Text Available Present work investigates platinum uptake from synthetically prepared, dilute platinum-bearing solutions using biomass residues, i.e. pistachio nut shell and rice husk, which are abundant in Turkey, and provides a comparison between these two biosorbents. Effects of the different uptake parameters, sorbent dosage, contact time, temperature and pH of solution on platinum uptake (% were studied in detail on a batch sorption. Before the pistachio nut shell was activated, platinum uptake (% was poor compared to the rice husk. However, after the pistachio nut shell was activated at 1000 °C under an argon atmosphere, the platinum uptake (% increased two-fold. The pistachio nut shell (original and activated and rice husk were shown to be better than commercially available activated carbon in terms of adsorption capacity. These two sorbents have also been characterized by FTIR and SEM. Adsorption equilibrium data best complied with the Langmuir isotherm model. Maximum adsorption capacities, Qmax, at 25 °C were found to be 38.31 and 42.02 mg.g- 1for the activated pistachio nut shell and rice husk, respectively. Thermodynamic calculations using the measured ∆H°, ∆S° and ∆G° values indicate that the uptake process was spontaneous and endothermic. The experimental data were shown to be fit the pseudo-second-order kinetic model.

  4. Leaching platinum-group metals in a sulfuric acid/chloride solution

    Science.gov (United States)

    Mahmoud, M. H. H.

    2003-04-01

    A leaching process was established based on the ability of platinum-group metals to form stable chloro-complexes in acidic chloride solutions. Industrial catalyst losses were examined for the recovery of platinum, palladium, and rhodium by leaching with a mixture of sulfuric acid and sodium chloride to avoid using aqua regia or autoclave conditions. Extraction of platinum and rhodium in 60% H2SO4 at 135°C steadily increased with increasing NaCl concentrations reaching 95% and 85%, respectively, at 0.1 M NaCl after two hours. By comparison, palladium was dissolved more quickly but also reached 85% under the same conditions. Extraction of each metal increased with temperatures up to 125°C but plateaued at higher temperatures. Similar behavior was observed with increasing H2SO4 concentrations up to 60%. More than 99% extraction of each metal was obtained after ten hours using 0.1 M NaCl and 60% H2SO4 at 125°C.

  5. Oxidation of H2 and CO in a fuel cell with a Platinum-tin Anode

    Directory of Open Access Journals (Sweden)

    Javier González

    2010-06-01

    Full Text Available This report describes the construction and evolution of a fuel cell with a bi-metallic anode of Pt-Sn supported on carbon, as catalysts for oxidation of pure hydrogen, pure CO and a 2% CO in H2 mixture. Both, cathode and anode were made with a structure composed by a diffusive layer and a catalytic layer. The diffusive layer was made with a carbon cloth while the catalytic layer contained the platinum and tin supported on carbon. To test the performance of the catalytic mixture, a proton exchange membrane fuel cell (PEMFC was developed with an original design for the gas distributation plates. The reactants were feed to ambient temperature and 3 psig in the anode side, while 5 psig pure oxygen was used in the cathode. The anode catalytic load was 0.57 mg/cm2 of platinum and 0.08 mg/cm2 of tin. The catalytic load in cathode was 0.85 mg/cm2 of pure platinum. It was found that this caralytic mixture is tolerant to CO presence.

  6. Sequential Electrodeposition of Platinum-Ruthenium at Boron-Doped Diamond Electrodes for Methanol Oxidation

    Directory of Open Access Journals (Sweden)

    Ileana González-González

    2011-01-01

    Full Text Available Sequential electrodeposition of Pt and Ru on boron-doped diamond (BDD films, in 0.5 M H2SO4 by cyclic voltammetry, has been prepared. The potential cycling, in the aqueous solutions of the respective metals, was between 0.00 and 1.00 V versus Ag/AgCl. The catalyst composites, Pt and PtRu, deposited on BDD film substrates, were tested for methanol oxidation. The modified diamond surfaces were also characterized by scanning electron microscopy-X-ray fluorescence-energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and Auger electron spectroscopy. The scanning Auger electron spectroscopy mapping showed the ruthenium signal only in areas where platinum was electrodeposited. Ruthenium does not deposit on the oxidized diamond surface of the boron-doped diamond. Particles with 5–10% of ruthenium with respect to platinum exhibited better performance for methanol oxidation in terms of methanol oxidation peak current and chronoamperometric current stability. The electrogenerated •OH radicals on BDD may interact with Pt surface, participating in the methanol oxidation as shown in oxidation current and the shift in the peak position. The conductive diamond surface is a good candidate as the support for the platinum electrocatalyst, because it ensures catalytic activity, which compares with the used carbon, and higher stability under severe anodic and cathodic conditions.

  7. Electrochemical Fabrication and Electrocatalytic Properties of Nanostructured Mesoporous Platinum Microelectrodes

    Institute of Scientific and Technical Information of China (English)

    Mengyan NIE; Joanne M. Elliott

    2005-01-01

    Electrodeposition from a lyotropic liquid crystal template medium was used to produce nanostructured platinum microelectrodes with high specific surface area and high mass transport efficiency. Compared to polished and conventional platinized microelectrodes, well-ordered nanostructured platinum microelectrodes exhibited enhanced electrocatalytic properties for oxygen and ascorbic acid, whilst well-ordered nanostructured platinum microelectrodes offered improved electrocatalytic properties for oxygen reduction compared to disordered nanostructured platinum microelectrodes.

  8. Characterisation of nanomaterial hydrophobicity using engineered surfaces

    Science.gov (United States)

    Desmet, Cloé; Valsesia, Andrea; Oddo, Arianna; Ceccone, Giacomo; Spampinato, Valentina; Rossi, François; Colpo, Pascal

    2017-03-01

    Characterisation of engineered nanomaterials (NMs) is of outmost importance for the assessment of the potential risks arising from their extensive use. NMs display indeed a large variety of physico-chemical properties that drastically affect their interaction with biological systems. Among them, hydrophobicity is an important property that is nevertheless only slightly covered by the current physico-chemical characterisation techniques. In this work, we developed a method for the direct characterisation of NM hydrophobicity. The determination of the nanomaterial hydrophobic character is carried out by the direct measurement of the affinity of the NMs for different collectors. Each collector is an engineered surface designed in order to present specific surface charge and hydrophobicity degrees. Being thus characterised by a combination of surface energy components, the collectors enable the NM immobilisation with surface coverage in relation to their hydrophobicity. The experimental results are explained by using the extended DLVO theory, which takes into account the hydrophobic forces acting between NMs and collectors.

  9. Enhanced catalytic activity of nanoscale platinum islands loaded onto SnO2 thin film for sensitive LPG gas sensors

    Indian Academy of Sciences (India)

    Divya Haridas; Vinay Gupta; K Sreenivas

    2008-06-01

    In the present study, different catalysts (∼ 10 nm thick) including metals, noble metals and metal oxides, were loaded in dotted island form over SnO2 thin film for LPG gas detection. A comparison of various catalysts indicated that the presence of platinum dotted islands over SnO2 thin film deposited by r.f. sputtering exhibited enhanced response characteristics with a high sensitivity, ∼ 742, at an operating temperature of ∼ 280°C. Different characterization techniques have been employed such as atomic force microscopy, X-ray diffraction and UV–vis spectroscopy, to study the surface morphology, grain size and optical properties of the deposited thin films. The results suggest the possibility of utilizing the sensor element with the present novel method of catalyst dispersal for the efficient detection of LPG.

  10. Design of heterogeneous catalysts

    DEFF Research Database (Denmark)

    Frey, Anne Mette

    was inspired by a computational screening, suggesting that alloys such as Ni-Fe, Co-Ni, and Co-Fe should show superior activity to the industrially used nickel catalyst. Especially the Ni-Fe system was considered to be interesting, since such alloy catalysts should be both more active and cheaper than the Ni...... well, and the best catalyst prepared had a C5+ yield almost a factor of two higher than a standard air calcined Co catalyst. In the NH3-SCR reaction it is desirable to develop an active and stable catalyst for NOx removal in automotive applications, since the traditionally used vanadium-based catalyst...... pose an environmental risk. The focus was put on iron-containing zeolite catalysts, since these recently have shown great potential as catalysts for the process. A number of different zeolites were compared. BEA was found to be the most active, thus focus was put on this material. Different preparation...

  11. Extensions of Callendar's equations for platinum resistance thermometry

    DEFF Research Database (Denmark)

    Diamond, Joseph M.

    1969-01-01

    measurements where the platinum thermometer and the measurement means may be less than ideal. To this end. Callendar's definition of platinum temperature is generalized to mean the temperature found by linear interpolation with a platinum thermometer between given fixed points and using a given measurement...

  12. Platinum Publications as of April 30, 2014 | Poster

    Science.gov (United States)

    Platinum Publications are selected from articles by NCI at Frederick scientists published in 21 prestigious science journals. This list represents new publications generated from PubMed as of the date shown above. Articles designated as Platinum Highlights are noteworthy articles selected by Dr. Craig Reynolds, associate director, National Cancer Institute, from among the most recently published Platinum Publications.

  13. Platinum Publications, September 30–October 27, 2016 | Poster

    Science.gov (United States)

    Platinum Publications are selected from articles by NCI at Frederick scientists published in 42 prestigious science journals. This list represents articles published during the time period shown above, as generated from PubMed. Articles designated as Platinum Highlights are noteworthy articles selected by Dr. Craig Reynolds, associate director, National Cancer Institute, from among the most recently published Platinum Publications.

  14. Platinum Publications as of June 25, 2014 | Poster

    Science.gov (United States)

    Platinum Publications are selected from articles by NCI at Frederick scientists published in 21 prestigious science journals. This list represents new publications generated from PubMed as of the date shown above. Articles designated as Platinum Highlights are noteworthy articles selected by Dr. Craig Reynolds, associate director, National Cancer Institute, from among the most recently published Platinum Publications.

  15. Platinum Publications, July 1–July 28, 2016 | Poster

    Science.gov (United States)

    Platinum Publications are selected from articles by NCI at Frederick scientists published in 42 prestigious science journals. This list represents articles published during the time period shown above, as generated from PubMed. Articles designated as Platinum Highlights are noteworthy articles selected by Dr. Craig Reynolds, associate director, National Cancer Institute, from among the most recently published Platinum Publications.

  16. Platinum Publications as of March 6, 2014 | Poster

    Science.gov (United States)

    Platinum Publications are selected from articles by NCI at Frederick scientists published in 21 prestigious science journals. This list represents new publications generated from PubMed as of the date shown above. Articles designated as Platinum Highlights are noteworthy articles selected by Dr. Craig Reynolds, associate director, National Cancer Institute, from among the most recently published Platinum Publications.

  17. Platinum Publications, October 1–29, 2015 | Poster

    Science.gov (United States)

    Platinum Publications are selected from articles by NCI at Frederick scientists published in 42 prestigious science journals. This list represents articles published during the time period shown above, as generated from PubMed. Articles designated as Platinum Highlights are noteworthy articles selected by Dr. Craig Reynolds, associate director, National Cancer Institute, from among the most recently published Platinum Publications.

  18. Platinum Publications, December 1–December 29, 2016 | Poster

    Science.gov (United States)

    Platinum Publications are selected from articles by NCI at Frederick scientists published in 42 prestigious science journals. This list represents articles published during the time period shown above, as generated from PubMed. Articles designated as Platinum Highlights are noteworthy articles selected from among the most recently published Platinum Publications.

  19. Platinum Publications as of May 29, 2014 | Poster

    Science.gov (United States)

    Platinum Publications are selected from articles by NCI at Frederick scientists published in 21 prestigious science journals. This list represents new publications generated from PubMed as of the date shown above. Articles designated as Platinum Highlights are noteworthy articles selected by Dr. Craig Reynolds, associate director, National Cancer Institute, from among the most recently published Platinum Publications.

  20. Platinum Publications as of September 25, 2014 | Poster

    Science.gov (United States)

    Platinum Publications are selected from articles by NCI at Frederick scientists published in 21 prestigious science journals. This list represents new publications generated from PubMed as of the date shown above. Articles designated as Platinum Highlights are noteworthy articles selected by Dr. Craig Reynolds, associate director, National Cancer Institute, from among the most recently published Platinum Publications.

  1. Platinum Publications, January 26–February 28, 2017 | Poster

    Science.gov (United States)

    Platinum Publications are selected from articles by NCI at Frederick scientists published in 42 prestigious science journals. This list represents articles published during the time period shown above, as generated from PubMed. Articles designated as Platinum Highlights are noteworthy articles selected from among the most recently published Platinum Publications.

  2. Platinum Publications as of December 3, 2013 | Poster

    Science.gov (United States)

    Platinum Publications are selected from articles by NCI at Frederick scientists published in 21 prestigious science journals. This list represents new publications generated from PubMed as of the date shown above. Articles designated as Platinum Highlights are noteworthy articles selected by Dr. Craig Reynolds, associate director, National Cancer Institute, from among the most recently published Platinum Publications.

  3. Deposition of the platinum crystals on the carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A new technique and the affecting factors for depositing platinum on the carbon nanotubes were investigated. The results show that the deposited platinum crystals in the atmosphere of hydrogen or nitrogen have a small size and a homogeneous distribution on the surface of the carbon nanotubes. The pretreatment would decrease the platinum particles on the carbon nanotubes significantly.

  4. 76 FR 8627 - Revision of Class E Airspace; Platinum, AK

    Science.gov (United States)

    2011-02-15

    ... Federal Aviation Administration 14 CFR Part 71 Revision of Class E Airspace; Platinum, AK AGENCY: Federal... Platinum, AK, to accommodate the addition of a Standard Instrument Approach Procedure (SIAP), at the Platinum Airport. The FAA is taking this action to enhance safety and management of Instrument Flight...

  5. Surface decorated platinum carbonyl clusters

    Science.gov (United States)

    Ciabatti, Iacopo; Femoni, Cristina; Iapalucci, Maria Carmela; Longoni, Giuliano; Zacchini, Stefano; Zarra, Salvatore

    2012-06-01

    Four molecular Pt-carbonyl clusters decorated by Cd-Br fragments, i.e., [Pt13(CO)12{Cd5(μ-Br)5Br2(dmf)3}2]2- (1), [Pt19(CO)17{Cd5(μ-Br)5Br3(Me2CO)2}{Cd5(μ-Br)5Br(Me2CO)4}]2- (2), [H2Pt26(CO)20(CdBr)12]8- (3) and [H4Pt26(CO)20(CdBr)12(PtBr)x]6- (4) (x = 0-2), have been obtained from the reactions between [Pt3n(CO)6n]2- (n = 2-6) and CdBr2.H2O in dmf at 120 °C. The structures of these molecular clusters with diameters of 1.5-2 nm have been determined by X-ray crystallography. Both 1 and 2 are composed of icosahedral or bis-icosahedral Pt-CO cores decorated on the surface by Cd-Br motifs, whereas 3 and 4 display a cubic close packed Pt26Cd12 metal frame decorated by CO and Br ligands. An oversimplified and unifying approach to interpret the electron count of these surface decorated platinum carbonyl clusters is suggested, and extended to other low-valent organometallic clusters and Au-thiolate nanoclusters.Four molecular Pt-carbonyl clusters decorated by Cd-Br fragments, i.e., [Pt13(CO)12{Cd5(μ-Br)5Br2(dmf)3}2]2- (1), [Pt19(CO)17{Cd5(μ-Br)5Br3(Me2CO)2}{Cd5(μ-Br)5Br(Me2CO)4}]2- (2), [H2Pt26(CO)20(CdBr)12]8- (3) and [H4Pt26(CO)20(CdBr)12(PtBr)x]6- (4) (x = 0-2), have been obtained from the reactions between [Pt3n(CO)6n]2- (n = 2-6) and CdBr2.H2O in dmf at 120 °C. The structures of these molecular clusters with diameters of 1.5-2 nm have been determined by X-ray crystallography. Both 1 and 2 are composed of icosahedral or bis-icosahedral Pt-CO cores decorated on the surface by Cd-Br motifs, whereas 3 and 4 display a cubic close packed Pt26Cd12 metal frame decorated by CO and Br ligands. An oversimplified and unifying approach to interpret the electron count of these surface decorated platinum carbonyl clusters is suggested, and extended to other low-valent organometallic clusters and Au-thiolate nanoclusters. CCDC 867747 and 867748. For crystallographic data in CIF or other electronic format see DOI: 10.1039/c2nr30400g

  6. A Heuristic Molecular Model of Hydrophobic Interactions

    OpenAIRE

    Hummer, G; Garde, S; Garcia, A.E.; Pohorille, A; Pratt, L.R.

    1995-01-01

    Hydrophobic interactions provide driving forces for protein folding, membrane formation, and oil-water separation. Motivated by information theory, the poorly understood nonpolar solute interactions in water are investigated. A simple heuristic model of hydrophobic effects in terms of density fluctuations is developed. This model accounts quantitatively for the central hydrophobic phenomena of cavity formation and association of inert gas solutes; it therefore clarifies the underlying physics...

  7. How specific halide adsorption varies hydrophobic interactions.

    Science.gov (United States)

    Stock, Philipp; Müller, Melanie; Utzig, Thomas; Valtiner, Markus

    2016-03-11

    Hydrophobic interactions (HI) are driven by the water structure around hydrophobes in aqueous electrolytes. How water structures at hydrophobic interfaces and how this influences the HI was subject to numerous studies. However, the effect of specific ion adsorption on HI and hydrophobic interfaces remains largely unexplored or controversial. Here, the authors utilized atomic force microscopy force spectroscopy at well-defined nanoscopic hydrophobic interfaces to experimentally address how specific ion adsorption of halide ions as well as NH4 (+), Cs(+), and Na(+) cations alters interaction forces across hydrophobic interfaces. Our data demonstrate that iodide adsorption at hydrophobic interfaces profoundly varies the hydrophobic interaction potential. A long-range and strong hydration repulsion at distances D > 3 nm, is followed by an instability which could be explained by a subsequent rapid ejection of adsorbed iodides from approaching hydrophobic interfaces. In addition, the authors find only a weakly pronounced influence of bromide, and as expected no influence of chloride. Also, all tested cations do not have any significant influence on HI. Complementary, x-ray photoelectron spectroscopy and quartz-crystal-microbalance with dissipation monitoring showed a clear adsorption of large halide ions (Br(-)/I(-)) onto hydrophobic self-assembled monolayers (SAMs). Interestingly, iodide can even lead to a full disintegration of SAMs due to specific and strong interactions of iodide with gold. Our data suggest that hydrophobic surfaces are not intrinsically charged negatively by hydroxide adsorption, as it was generally believed. Hydrophobic surfaces rather interact strongly with negatively charged large halide ions, leading to a surface charging and significant variation of interaction forces.

  8. How fast is protein hydrophobic collapse?

    OpenAIRE

    Sadqi, Mourad; Lapidus, Lisa J.; Muñoz, Victor

    2003-01-01

    One of the most recurring questions in protein folding refers to the interplay between formation of secondary structure and hydrophobic collapse. In contrast with secondary structure, it is hard to isolate hydrophobic collapse from other folding events. We have directly measured the dynamics of protein hydrophobic collapse in the absence of competing processes. Collapse was triggered with laser-induced temperature jumps in the acid-denatured form of a simple protein and monitored by fluoresce...

  9. 2-Methoxycycloocta-1,5-dienyl platinum complexes as precursors for platinum nanoparticles

    Indian Academy of Sciences (India)

    Ninad Ghavale; Sandip Dey; Vimal K Jain; R Tewari

    2009-02-01

    Thermolysis of [Pt2 (-OR)2 (C8H12OMe)2] (R = Me or Ac) in hexadecylamine (HDA) at 210°C under argon atmosphere gave platinum nanoparticles which were characterized by XRD, EDAX and TEM analysis. Both spherical (∼ 10 nm) and rod-like (∼ 19 nm length with aspect ratio of 2.3) face centred cubic (fcc) platinum metal nanoparticles could be isolated. The thermogravimetric analyses of these complexes revealed that they undergo a single step decomposition leading to the formation of platinum metal powder.

  10. Effects of K and Pt promoters on the performance of cobalt catalyst supported on CNTs

    Science.gov (United States)

    Zabidi, Noor Asmawati Mohd; Ali, Sardar; Subbarao, Duvvuri

    2014-10-01

    This paper presents a comparative study on the effects of incorporation of potassium (K) and platinum (Pt) as promoters on the physicochemical properties of cobalt catalyst. The catalyst was prepared by a wet impregnation method on a CNTs support. Samples were characterized using transmission electron microscopy (TEM), H2-temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS) techniques. Fischer-Tropsch Synthesis (FTS) was carried out in a fixed-bed microreactor at 543 K and 1 atm, with H2/ CO = 2v / v and space velocity, SV of 12 L/g.h for 5 hours. The K-promoted and Pt-promoted Co catalysts have different physicochemical properties and catalytic performances compared to that of the un-promoted Co catalyst. XPS analysis revealed that K and Pt promoters induced electronic modifications as exhibited by the shifts in the Co binding energies. Incorporation of 0.06 wt% K and 0.06 wt% Pt in Co/CNTs catalyst resulted in an increase in the CO conversion and C5+ selectivity and a decrease in methane selectivity. Potassium was found to be a better promoter for Co/CNTs catalyst compared to platinum.

  11. N-doped carbon nanomaterials are durable catalysts for oxygen reduction reaction in acidic fuel cells

    Science.gov (United States)

    Shui, Jianglan; Wang, Min; Du, Feng; Dai, Liming

    2015-01-01

    The availability of low-cost, efficient, and durable catalysts for oxygen reduction reaction (ORR) is a prerequisite for commercialization of the fuel cell technology. Along with intensive research efforts of more than half a century in developing nonprecious metal catalysts (NPMCs) to replace the expensive and scarce platinum-based catalysts, a new class of carbon-based, low-cost, metal-free ORR catalysts was demonstrated to show superior ORR performance to commercial platinum catalysts, particularly in alkaline electrolytes. However, their large-scale practical application in more popular acidic polymer electrolyte membrane (PEM) fuel cells remained elusive because they are often found to be less effective in acidic electrolytes, and no attempt has been made for a single PEM cell test. We demonstrated that rationally designed, metal-free, nitrogen-doped carbon nanotubes and their graphene composites exhibited significantly better long-term operational stabilities and comparable gravimetric power densities with respect to the best NPMC in acidic PEM cells. This work represents a major breakthrough in removing the bottlenecks to translate low-cost, metal-free, carbon-based ORR catalysts to commercial reality, and opens avenues for clean energy generation from affordable and durable fuel cells. PMID:26601132

  12. Influence of metal oxides on Pt catalysts for methanol electrooxidation using electrochemical impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Huiping; Qiu, Xinping; Chen, Liquan [Key Laboratory of Organic Optoelectronics and Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing 100084 (China); Lab of Advanced Power Sources, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Guo, Daojun; Zhu, Wentao [Key Laboratory of Organic Optoelectronics and Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing 100084 (China)

    2009-03-01

    Carbon nanotubes used as supports for platinum catalysts deposited with metal oxides (CeO{sub 2}, TiO{sub 2}, and SnO{sub 2}) were prepared for their application as anode catalysts in a direct methanol fuel cell. Cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy measurements were carried out in a solution of 0.5 M CH{sub 3}OH and 0.5 M H{sub 2}SO{sub 4}. Catalysts with the addition of CeO{sub 2}, TiO{sub 2}, and SnO{sub 2} presented higher catalytic activity than pure platinum catalysts, and the catalysts with CeO{sub 2} were the best among them. Electrochemical impedance spectra indicated that methanol electrooxidation on these catalysts had different impedance behaviors at different potential regions. The mechanism of methanol electrooxidation changed with increases of the potential. The promotion effect of the metal oxides lies in the oxidation of intermediate CO{sub ads} on Pt at low potential regions. (author)

  13. Effects of K and Pt promoters on the performance of cobalt catalyst supported on CNTs

    Energy Technology Data Exchange (ETDEWEB)

    Zabidi, Noor Asmawati Mohd, E-mail: noorasmawati-mzabidi@petronas.com.my [Department of Fundamental and Applied Sciences, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia); Ali, Sardar, E-mail: alikhan-635@yahoo.com [Centralized Analytical Laboratory, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia); Subbarao, Duvvuri, E-mail: duvvuri-subbarao@petronas.com.my [Department of Chemical Engineering, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia)

    2014-10-24

    This paper presents a comparative study on the effects of incorporation of potassium (K) and platinum (Pt) as promoters on the physicochemical properties of cobalt catalyst. The catalyst was prepared by a wet impregnation method on a CNTs support. Samples were characterized using transmission electron microscopy (TEM), H{sub 2}-temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS) techniques. Fischer-Tropsch Synthesis (FTS) was carried out in a fixed-bed microreactor at 543 K and 1 atm, with H{sub 2}/CO = 2v/v and space velocity, SV of 12 L/g.h for 5 hours. The K-promoted and Pt-promoted Co catalysts have different physicochemical properties and catalytic performances compared to that of the un-promoted Co catalyst. XPS analysis revealed that K and Pt promoters induced electronic modifications as exhibited by the shifts in the Co binding energies. Incorporation of 0.06 wt% K and 0.06 wt% Pt in Co/CNTs catalyst resulted in an increase in the CO conversion and C{sub 5+} selectivity and a decrease in methane selectivity. Potassium was found to be a better promoter for Co/CNTs catalyst compared to platinum.

  14. N-doped carbon nanomaterials are durable catalysts for oxygen reduction reaction in acidic fuel cells.

    Science.gov (United States)

    Shui, Jianglan; Wang, Min; Du, Feng; Dai, Liming

    2015-02-01

    The availability of low-cost, efficient, and durable catalysts for oxygen reduction reaction (ORR) is a prerequisite for commercialization of the fuel cell technology. Along with intensive research efforts of more than half a century in developing nonprecious metal catalysts (NPMCs) to replace the expensive and scarce platinum-based catalysts, a new class of carbon-based, low-cost, metal-free ORR catalysts was demonstrated to show superior ORR performance to commercial platinum catalysts, particularly in alkaline electrolytes. However, their large-scale practical application in more popular acidic polymer electrolyte membrane (PEM) fuel cells remained elusive because they are often found to be less effective in acidic electrolytes, and no attempt has been made for a single PEM cell test. We demonstrated that rationally designed, metal-free, nitrogen-doped carbon nanotubes and their graphene composites exhibited significantly better long-term operational stabilities and comparable gravimetric power densities with respect to the best NPMC in acidic PEM cells. This work represents a major breakthrough in removing the bottlenecks to translate low-cost, metal-free, carbon-based ORR catalysts to commercial reality, and opens avenues for clean energy generation from affordable and durable fuel cells.

  15. Cell membrane penetration and mitochondrial targeting by platinum-decorated ceria nanoparticles

    Science.gov (United States)

    Torrano, Adriano A.; Herrmann, Rudolf; Strobel, Claudia; Rennhak, Markus; Engelke, Hanna; Reller, Armin; Hilger, Ingrid; Wixforth, Achim; Bräuchle, Christoph

    2016-07-01

    In this work we investigate the interaction between endothelial cells and nanoparticles emitted by catalytic converters. Although catalyst-derived particles are recognized as growing burden added to environmental pollution, very little is known about their health impact. We use platinum-decorated ceria nanoparticles as model compounds for the actual emitted particles and focus on their fast uptake and association with mitochondria, the cell's powerhouse. Using live-cell imaging and electron microscopy we clearly show that 46 nm platinum-decorated ceria nanoparticles can rapidly penetrate cell membranes and reach the cytosol. Moreover, if suitably targeted, these particles are able to selectively attach to mitochondria. These results are complemented by cytotoxicity assays, thus providing insights into the biological effects of these particles on cells. Interestingly, no permanent membrane disruption or any other significant adverse effects on cells were observed. The unusual uptake behavior observed for 46 nm nanoparticles was not observed for equivalent but larger 143 nm and 285 nm platinum-decorated particles. Our results demonstrate a remarkable particle size effect in which particles smaller than ~50-100 nm escape the usual endocytic pathway and translocate directly into the cytosol, while particles larger than ~150 nm are internalized by conventional endocytosis. Since the small particles are able to bypass endocytosis they could be explored as drug and gene delivery vehicles. Platinum-decorated nanoparticles are therefore highly interesting in the fields of nanotoxicology and nanomedicine.In this work we investigate the interaction between endothelial cells and nanoparticles emitted by catalytic converters. Although catalyst-derived particles are recognized as growing burden added to environmental pollution, very little is known about their health impact. We use platinum-decorated ceria nanoparticles as model compounds for the actual emitted particles and

  16. An ion-exchange method for selective separation of palladium, platinum and rhodium from solutions obtained by leaching automotive catalytic converters.

    Science.gov (United States)

    Gaita, R; Al-Bazi, S J

    1995-02-01

    An ion-exchange method has been developed for the separation of palladium, platinum and rhodium from a solution that is highly acidic and contains a considerable amount of lead, aluminum, iron and cerium, obtained by leaching a used honeycomb type automotive catalytic converter. A column of Amberlite IRA-93 anion-exchange resin was found appropriate to recover platinum metals from the pregnant solution. Selective stripping of these metals from the resin was achieved by eluting rhodium first with 6.0M hydrochloric acid, then palladium with a 1% ammonia solution at ambient temperature, and platinum with 5% of the reagent at elevated temperatures. Optimum conditions for leaching these metals from the catalyst were 5.0M hydrochloric acid and 0.4M sodium chlorate at 70 degrees C. This method can be applied to both analytical as well as large scale operations. It is simple, economical, and relatively safe for human exposure and the environment.

  17. The physical origin of hydrophobic effects

    Science.gov (United States)

    Sun, Qiang

    2017-03-01

    From the structural studies on water and air/water interface, hydration free energy is derived, and used to investigate the origin of hydrophobic effects. As a solute is dissolved into water, hydration free energy increases, and is divided into initial and hydrophobic solvation processes. In the initial process, hydration free energy is dominated by hydrogen bonding in interfacial water (topmost water layer at solute/water interface). For hydrophobic process, hydration free energy is related to the hydrogen bonding in bulk and interfacial water. Therefore, hydrophobic effects originate from the structural competition between hydrogen bonding in bulk water and that in interfacial water.

  18. Method for making nanoporous hydrophobic coatings

    Science.gov (United States)

    Fan, Hongyou; Sun, Zaicheng

    2013-04-23

    A simple coating method is used to form nanoporous hydrophobic films that can be used as optical coatings. The method uses evaporation-induced self-assembly of materials. The coating method starts with a homogeneous solution comprising a hydrophobic polymer and a surfactant polymer in a selective solvent. The solution is coated onto a substrate. The surfactant polymer forms micelles with the hydrophobic polymer residing in the particle core when the coating is dried. The surfactant polymer can be dissolved and selectively removed from the separated phases by washing with a polar solvent to form the nanoporous hydrophobic film.

  19. Characterization of Catalyst Materials for Production of Aerospace Fuels

    Science.gov (United States)

    Best, Lauren M.; De La Ree, Ana B.; Hepp, Aloysius F.

    2012-01-01

    Due to environmental, economic, and security issues, there is a greater need for cleaner alternative fuels. There will undoubtedly be a shift from crude oil to non-petroleum sources as a feedstock for aviation (and other transportation) fuels. Additionally, efforts are concentrated on reducing costs coupled with fuel production from non-conventional sources. One solution to this issue is Fischer-Tropsch gas-to-liquid technology. Fischer-Tropsch processing of synthesis gas (CO/H2) produces a complex product stream of paraffins, olefins, and oxygenated compounds such as alcohols and aldehydes. The Fisher-Tropsch process can produce a cleaner diesel oil fraction with a high cetane number (typically above 70) without any sulfur or aromatic compounds. This process is most commonly catalyzed by heterogeneous (in this case, silver and platinum) catalysts composed of cobalt supported on alumina or unsupported alloyed iron powders. Physisorption, chemisorptions, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) are described to better understand the potential performance of Fischer-Tropsch cobalt on alumina catalysts promoted with silver and platinum. The overall goal is to preferentially produce C8 to C18 paraffin compounds for use as aerospace fuels. Progress towards this goal will eventually be updated and achieved by a more thorough understanding of the characterization of catalyst materials. This work was supported by NASA s Subsonic Fixed Wing and In-situ Resource Utilization projects.

  20. Pd Close Coupled Catalyst

    Institute of Scientific and Technical Information of China (English)

    Zhong Hua SHI; Mao Chu GONG; Yao Qiang CHEN

    2006-01-01

    A catalyst comprised novel high surface area alumina support was prepared to control emission of automobiles. The results showed that prepared catalyst could satisfy the requirements of a high performance close coupled catalyst for its good catalytic activity at low temperature and good stability at high temperature.

  1. Counter electrodes from polymorphic platinum-nickel hollow alloys for high-efficiency dye-sensitized solar cells

    Science.gov (United States)

    Wang, Jing; Tang, Qunwei; He, Benlin; Yang, Peizhi

    2016-10-01

    Precious platinum counter electrode (CE) has been an economic burden for future commercialization of dye-sensitized solar cells (DSSCs). Low-platinum alloy CE catalysts are promising in bringing down the solar cell cost without reducing photovoltaic performances. We present here a facile strategy of fabricating ZnO nanorods assisted platinum-nickel (PtNi) alloy microtube CEs for liquid-junction DSSCs. By adjusting the concentration of zinc precursors, the ZnO nanostructures and therefore PtNi alloys are optimized to maximize the electrocatalytic behaviors toward triiodide reduction reaction. The maximal power conversion efficiency is determined as high as 8.43% for liquid-junction DSSC device with alloyed PtNi microtube CE synthesized at 75 mM Zn(NO3)2 aqueous solution, yielding a 32.8% enhancement in cell efficiency in comparison with the solar cell from pristine platinum electrode. Moreover, the dissolution resistance and charge-transfer ability toward redox couples have also been markedly enhanced due to competitive dissolution reactions and alloyed effects.

  2. In situ synthesis of platinum nanocatalysts on a microstructured paperlike matrix for the catalytic purification of exhaust gases.

    Science.gov (United States)

    Koga, Hirotaka; Umemura, Yuuka; Tomoda, Akihiko; Suzuki, Ryo; Kitaoka, Takuya

    2010-05-25

    The successful in situ synthesis of platinum nanoparticles (PtNPs) on a microstructured paperlike matrix, comprising ceramic fibers as main framework and zinc oxide whiskers as selective support for the PtNPs, is reported. The as-prepared hybrid material (PtNPs@ZnO "paper") resembles ordinary paper products because it is flexible, lightweight, and easy to handle. In the catalytic reduction of nitrogen oxide (NO(x)) with propene for exhaust gas purification, the PtNPs@ZnO paper demonstrates a high catalytic performance at a low reaction temperature, with one-third the dosage of precious platinum compared to conventional platinum-loaded honeycomb catalysts. These results imply that the combination of easily synthesized PtNPs and a unique fiber-network microstructure can provide excellent performances, promoting the effective transport of heat and reactants to the active sites of the platinum nanocatalysts. Thus, PtNPs@ZnO materials with paperlike practical aspects are promising catalytic materials for efficient NO(x) gas purification.

  3. Mechanisms for enhanced performance of platinum-based electrocatalysts in proton exchange membrane fuel cells.

    Science.gov (United States)

    Su, Liang; Jia, Wenzhao; Li, Chang-Ming; Lei, Yu

    2014-02-01

    As a new generation of power sources, fuel cells have shown great promise for application in transportation. However, the expensive catalyst materials, especially the cathode catalysts for oxygen reduction reaction (ORR), severely limit the widespread commercialization of fuel cells. Therefore, this review article focuses on platinum (Pt)-based electrocatalysts for ORR with better catalytic performance and lower cost. Major breakthroughs in the improvement of activity and durability of electrocatalysts are discussed. Specifically, on one hand, the enhanced activity of Pt has been achieved through crystallographic control, ligand effect, or geometric effect; on the other hand, improved durability of Pt-based cathode catalysts has been realized by means of the incorporation of another noble metal or the morphological control of nanostructures. Furthermore, based on these improvement mechanisms, rationally designed Pt-based nanoparticles are summarized in terms of different synthetic strategies such as wet-chemical synthesis, Pt-skin catalysts, electrochemically dealloyed nanomaterials, and Pt-monolayer deposition. These nanoparticulate electrocatalysts show greatly enhanced catalytic performance towards ORR, aiming not only to outperform the commercial Pt/C, but also to exceed the US Department of Energy 2015 technical target ($30/kW and 5000 h).

  4. Synthesis and Development of Modified OMC-Supported Platinum Electrocatalyst for PEMFC

    Science.gov (United States)

    Muonagolu, Emeka Paul

    Ordered mesoporous carbon (OMC) has been considered as a promising Platinum catalyst support because of its large surface area, uniform ordered hexagonal mesopores, porous structure and high electrical conductivity. Graphitization of the walls of OMC is vital when the electrical conductivity of the catalyst is the main concern. The objective of this work was to improve the electrical conductivity of the ordered mesoporous carbon (OMC) support by utilizing transition metals such as Ni, Co and Fe to graphitize the pore walls of OMC via catalytic graphitization. Metal modified OMCs have been synthesized following two steps. First step is synthesizing metal modified SBA-15 as a template containing 10wt% transition metals (Ni, Co, Fe) and TEOS as a source of silica followed by calcination. The second step is introducing sucrose as the carbon source into the pores of the silica template followed by carbonization at 900°C and removal of the silica template using hydrofluoric acid. The synthesized Metal modified OMCs were characterized using Brunaeur Emmit Teller (BET) analysis, X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy. Surface area for the metal modified --OMC was found around 1300--1500m 2/g and pore sizes in the range of 3--4nm. The membrane electrode assembly (MEA) was prepared using the synthesized electrocatalyst and was used to evaluate the performance of the catalyst by testing it on the fuel cell test station. The results were compared to that of commercial catalyst.

  5. Ceria modified three-dimensionally ordered macro-porous Pt/TiO2 catalysts for water-gas shift reaction

    Institute of Scientific and Technical Information of China (English)

    LIANG Hao; ZHANG Yuan; LIU Yuan

    2009-01-01

    Three-dimensionally ordered macro-porous(3DOM) TiO2 and ceria-modified 3DOM TiO2 supported platinum catalysts were pre-pared with template and impregnation methods, and the resultant samples were characterized by scanning electron microscopy(SEM), X-ray dif-fractometer(XRD), high-resolution transmission electron microscopy(HRTEM) and texture programmed reduction(TPR) techniques. The catalytic performances over the platinum-based catalysts were investigated for water-gas shift (WGS) reaction in a wide temperature range macro-porous catalyst, owing to the macro-porous structure favoring mass uansfer. Addition of ceria into 3DOM Pt/TiO2 led to improvement of catalytic activity. TPR and HRTEM results showed that the interaction existed between ceria and titanium oxide and addition of ceria promoted the reducibility of platinum oxide and TiO2 on the interface of platinum and TiO2 particles, which contributed to high activity of the ceria modi-fied catalysts. The results indicated that ceria-modified 3DOM Pt/TiO2 was a promising candidate of fuel cell oriented WGS catalyst.

  6. Electrochemical Analysis of the Electrodeposition of Platinum Nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Hae-Min; Cho, Sung-Woon; Kim, Jun-Hyun; Kim, Chang-Koo [Ajou University, Suwon (Korea, Republic of)

    2015-10-15

    A bath for electrodeposition of platinum nanoparticles on low-cost graphite substrates was developed to attach nanoparticles directly onto a substrate, and electrochemical characteristics of the electrodeposition of platinum nanoparticles were investigated. The reaction mechanism was examined by the analysis of polarization behavior. Cyclic voltammetry measurements revealed that the electrodeposition of platinum nanoparticles was limited by mass transfer. The chronoamperometric study showed an instantaneous nucleation mechanism during the electrodeposition of platinum nanoparticles on graphite. Because graphite is much cheaper than other carbon-based substrates, the electrodeposition of platinum nanoparticles on the graphite is expected to have useful applications.

  7. Outpatient desensitization in selected patients with platinum hypersensitivity reactions.

    Science.gov (United States)

    O'Malley, David M; Vetter, Monica Hagan; Cohn, David E; Khan, Ambar; Hays, John L

    2017-06-01

    Platinum-based chemotherapies are a standard treatment for both initial and recurrent gynecologic cancers. Given this widespread use, it is important to be aware of the features of platinum hypersensitivity reactions and the subsequent treatment of these reactions. There is also increasing interest in the development of desensitization protocols to allow patients with a history of platinum hypersensitivity to receive further platinum based therapy. In this review, we describe the management of platinum hypersensitivity reactions and the desensitization protocols utilized at our institution. We also describe the clinical categorizations utilized to triage patients to appropriate desensitization protocols. Copyright © 2017 Elsevier Inc. All rights reserved.

  8. TiO{sub 2} nanotubes promoted PT-NI/C catalyst with low PT content as anode catalyst for direct ethanol fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Shen, L.; Jiang, Q.Z.; Gan, T.G.; Ma, Z.F. [Shanghai Jiao Tong Univ., Shanghai (China). Dept. of Chemical Engineering; Shen, M. [Oklahoma Univ., Norman, OK (United States). School of Chemical, Biological and Materials Engineering, Sarkeys Energy Center; Rodriguez Varela, F.J. [Cinvestav Unidad Saltillo, Coahuila (Mexico). Grupo de Recursos Naturales y Energeticos; Ocampo, A.L. [Univ. Nacional Autonoma, Mexico City (Mexico). Dept. de Quimica Analitica

    2010-07-15

    Although direct ethanol fuel cells (DEFC) have more energy density than direct methanol fuel cells (DMFC), their widespread use has been hampered by the fact that metallic platinum (Pt) catalysts are readily poisoned by strongly absorbed reaction intermediates such as CO{sub ads} at low operating temperatures. The addition of a second transition metal or a metal oxide component has been considered as a means to improve performance of DEFCs by forming a binary anode based on Pt. In this study, titanium oxide (TiO{sub 2}) nanotubes (TiO{sub 2}NTs) were added into a low-platinum content Pt-Ni/C catalyst to improve its catalytic activity for the ethanol oxidation reaction (EOR). The promotion effect of TiO{sub 2}NTs on Pt-Ni/C catalyst was examined. Cyclic voltametry (CV) and chronoamperometry showed that TiO{sub 2}NTs can improve the catalytic activity of the Pt-Ni/C catalyst considerably. Compared to a commercial Pt-Ru/C catalyst, the Pt-Ni-TiO{sub 2}NT/C catalyst has a larger electrochemical active surface (EAS) and has lower onset potential for the EOR. The elemental composition and electronic structure of the catalyst were characterized by X-ray photoelectron spectroscopy, energy dispersive X-ray spectrometry, inductively coupled plasma-optical emission spectrometry and X-ray diffraction. High resolution transmission electron microscopy was used to characterize the morphological properties of these catalysts. The study showed that onset oxidation potential can be lowered by the presence of TiO{sub 2}NTs because they retain more of the Pt metallic species and provide more hydroxides groups. 35 refs., 2 tabs., 10 figs.

  9. A high-performance platinum electrocatalyst loaded on a graphene hydrogel for high-rate methanol oxidation.

    Science.gov (United States)

    Wang, Xiluan; Li, Chun; Shi, Gaoquan

    2014-06-01

    Platinum (Pt)-based catalysts used in direct methanol fuel cells (DMFCs) usually suffer from low catalytic activity, slow kinetics of methanol oxidation and poor electrochemical stability. This is mainly due to the toxic effect of carbon monoxide and inefficient use of the Pt catalysts. To address these problems, we immobilized Pt nanoparticles with diameters of 4-6 nm onto the three-dimensional (3D) interpenetrating graphene networks (graphene hydrogel or G-Gel) deposited in the micropores of nickel foam (NF). In this Pt/G-Gel/NF composite catalyst, nearly all the Pt nanoparticles are accessible to methanol and can be efficiently used for electrocatalyzation. It showed excellent electrochemical stability and an activity 2.6 times that of a conventional Pt/reduced graphene oxide (Pt/rGO) composite catalyst. Furthermore, the rate of methanol electro-oxidation at the Pt/G-Gel/NF catalyst can be about 27 times that at the Pt/rGO catalyst, making it applicable for fabricating DMFCs with high current and/or power outputs.

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

    Science.gov (United States)

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

    2006-08-17

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

  11. Synthesis and characterization of new platinum(II) and platinum(IV) triphyrin complexes.

    Science.gov (United States)

    Xue, Zhaoli; Kuzuhara, Daiki; Ikeda, Shinya; Okujima, Tetsuo; Mori, Shigeki; Uno, Hidemitsu; Yamada, Hiroko

    2013-02-18

    Metalation of 6,13,20,21-tetrakis(4-methylphenyl)-22H-tribenzo[14]triphyrin(2.1.1) with PtCl(2) gave a platinum(II) complex having a square-planar coordination structure with two pyrrolic nitrogen atoms and two chloride ions, with a saddle-shaped macrocycle. This platinum(II) complex was easily oxidized by air to an octahedral platinum(IV) complex coordinated by three pyrrolic nitrogen atoms as a tridentate monoanionic cyclic ligand and three chloride ions. When platinum(II) triphyrin was crystallized in air, an oxygen atom was incorporated between two α-carbon atoms of the pyrroles as an oxygen bridge to intercept the 14π aromatic system.

  12. The role of carbon overlayers on Pt-based catalysts for H2-cleanup by CO-PROX

    Science.gov (United States)

    Romero-Sarria, F.; Garcia-Dali, S.; Palma, S.; Jimenez-Barrera, E. M.; Oliviero, L.; Bazin, P.; Odriozola, J. A.

    2016-06-01

    In this work, we analyze the effect of the activation method on the catalytic activity of Pt-based catalysts supported on alumina in the PROX reaction. For this, model Pt/Al2O3 catalysts with variable amounts of acetic acid were prepared and their thermal evolution studied by FTIR spectroscopy. From the analysis of the nature of the platinum surface upon acetic acid decomposition and the gas phase evolved products, we have demonstrated the formation of partially hydrogenated carbon overlayers that tailor the activity of Pt-based catalysts in the PROX reaction.

  13. Titania Supported Pt and Pt/Pd Nano-particle Catalysts for the Oxidation of Sulfur Dioxide

    DEFF Research Database (Denmark)

    Koutsopoulos, Sotiris; Johannessen, Tue; Eriksen, Kim Michael

    2006-01-01

    Several types of titania (anatase) were used as supports for pure platinum and Pt–Pd bimetallic alloy catalysts. The preparation methods, normal wet impregnation technique and flame aerosol synthesis, obtained metal loadings of 2% by weight. The prepared catalysts were tested for SO2 oxidation...... activity at atmospheric pressure in the temperature range 250–600 °C. The SO2 to SO3 conversion efficiency of the Pt–Pd alloy was significantly higher than that of the individual metals. The effects of the preparation method and the titania type used on the properties and activity of the resulting catalyst...

  14. Bioaccessibility of palladium and platinum in urban aerosol particulates

    Science.gov (United States)

    Puls, Christoph; Limbeck, Andreas; Hann, Stephan

    2012-08-01

    To evaluate potential health hazards caused by environmental Platinum Group Elements (PGEs), bioaccessibility of the metals in question needs to be assessed. To gain appropriate data, airborne particulate matter samples of different size fractions (total suspended particles as well as PM10 and PM2.5) were taken in downtown Vienna, an urban site primarily polluted by traffic. Total PGE concentrations in these samples were in the low picogram per cubic meter range, as determined by ID-ICP-MS after microwave digestion. For elimination of elements interfering with the accurate quantification, the digested samples were subjected to a cleaning procedure involving cation exchange. For determination of the bioaccessible fraction, it was assumed that inhaled particles are removed from the respiratory system by mucociliary clearance and subsequently ingested. Accordingly, the solubility of PGE in synthetic gastric juice was investigated by batch extraction of particulate matter samples followed by microwave assisted UV-digestion, cation exchange cleanup and ID-ICP-MS. The acquired data was used to calculate the bioaccessible fraction of Pd and Pt in airborne particulate matter. Average GIT-extractable fractions for Pd and Pt in TSP were 41% and 27%, in PM10 34% and 26%, respectively, thus exceeding previously determined values for bioaccessibility of PGE from ground catalyst materials by up to an order of magnitude.

  15. Platinum-Coated Nickel Nanowires as Oxygen-Reducing Electrocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Alia, Shaun M [National Renewable Energy Laboratory (NREL); Larsen, Brian A [National Renewable Energy Laboratory (NREL); Pylypenko, Svitlana [ORNL; Cullen, David A [ORNL; Diercks, David R [Colorado School of Mines, Golden; Neyerlin, Kenneth C [National Renewable Energy Laboratory (NREL); Kocha, Shyam S [National Renewable Energy Laboratory (NREL); Pivovar, Bryan [Los Alamos National Laboratory (LANL)

    2014-01-01

    Platinum (Pt)-coated nickel (Ni) nanowires (PtNiNWs) are synthesized by the partial spontaneous galvanic displacement of NiNWs, with a diameter of 150 250 nm and a length of 100 200 m. PtNiNWs are electrochemically characterized for oxygen reduction (ORR) in rotating disk electrode half-cells with an acidic electrolyte and compared to carbon-supported Pt (Pt/HSC) and a polycrystalline Pt electrode. Like other extended surface catalysts, the nanowire morphology yields significant gains in ORR specific activity compared to Pt/HSC. Unlike other extended surface approaches, the resultant materials have yielded exceptionally high surface areas, greater than 90 m2 gPt 1. These studies have found that reducing the level of Pt displacement increases Pt surface area and ORR mass activity. PtNiNWs produce a peak mass activity of 917 mA mgPt 1, 3.0 times greater than Pt/HSC and 2.1 times greater than the U.S. Department of Energy target for proton-exchange membrane fuel cell activity.

  16. Organometallic catalysts for primary phosphoric acid fuel cells

    Science.gov (United States)

    Walsh, Fraser

    1987-01-01

    A continuing effort by the U.S. Department of Energy to improve the competitiveness of the phosphoric acid fuel cell by improving cell performance and/or reducing cell cost is discussed. Cathode improvement, both in performance and cost, available through the use of a class of organometallic cathode catalysts, the tetraazaannulenes (TAAs), was investigated. A new mixed catalyst was identified which provides improved cathode performance without the need for the use of a noble metal. This mixed catalyst was tested under load for 1000 hr. in full cell at 160 to 200 C in phosphoric acid H3PO4, and was shown to provide stable performance. The mixed catalyst contains an organometallic to catalyze electroreduction of oxygen to hydrogen peroxide and a metal to catalyze further electroreduction of the hydrogen peroxide to water. Cathodes containing an exemplar mixed catalyst (e.g., Co bisphenyl TAA/Mn) operate at approximately 650 mV vs DHE in 160 C, 85% H3PO4 with oxygen as reactant. In developing this mixed catalyst, a broad spectrum of TAAs were prepared, tested in half-cell and in a rotating ring-disk electrode system. TAAs found to facilitate the production of hydrogen peroxide in electroreduction were shown to be preferred TAAs for use in the mixed catalyst. Manganese (Mn) was identified as a preferred metal because it is capable of catalyzing hydrogen peroxide electroreduction, is lower in cost and is of less strategic importance than platinum, the cathode catalyst normally used in the fuel cell.

  17. The selective hydrogenation of crotonaldehyde over bimetallic catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Schoeb, Ann M. [Iowa State Univ., Ames, IA (United States)

    1997-10-17

    The selective hydrogenation of crotonaldehyde has been investigated over a monometallic Pt/SiO2 catalyst and platinum bimetallic catalysts where the second metal was either silver, copper, or tin. The effects of addition of a second metal to the Pt/SiO2 system on the selectivity to crotyl alcohol were investigated. The Pt-Sn bimetallic catalysts were characterized by hydrogen chemisorption, 1H NMR and microcalorimetry. The Pt-Ag/SiO2 and Pt-Cu/SiO2 catalysts were characterized by hydrogen chemisorption. Pt-Sn/SiO2 catalysts selectively hydrogenated crotonaldehyde to crotyl alcohol and the method of preparation of these catalysts affected the selectivity. The most selective Pt-Sn/SiO2 catalysts for the hydrogenation of crotonaldehyde to crotyl alcohol were those in which the Sn precursor was dissolved in a HCl solution. Sn increased both the rate of formation of butyraldehyde and the rate of formation of crotyl alcohol. The Pt/SiO2, Pt-Ag/SiO2 and Pt-Cu/SiO2 catalysts produced only butyraldehyde. Initial heats of adsorption (~90 kJ/mol) measured using microcalorimetry were not affected by the presence of Sn on Pt. We can conclude that there is no through metal electronic interaction between Pt and Sn at least with respect to hydrogen surface bonds since the Pt and Pt-Sn at least with respect to hydrogen surface bonds since the Pt and Pt-Sn had similar initial heats of adsorption coupled with the invariance of the 1H NMR Knight shift.

  18. Hydrophobic Interactions Involved in Attachment of a Baculovirus to Hydrophobic Surfaces

    OpenAIRE

    Small, Deirdre A.; Moore, Norman F.; Entwistle, Philip F.

    1986-01-01

    The hydrophobic interactions of Trichoplusia ni nuclear polyhedrosis virus were characterized by hydrophobic interaction chromatography. The determination of the hydrophobic force and some of the factors that influence its size is discussed in relation to the attachment to leaf surfaces of polyhedra during their use as biological control agents against insect pests.

  19. Catalytic oxidation of VOCs over CNT-supported platinum nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Joung, Hea-Jung; Kim, Jae-Ha [Bioneer Corporation, Munyueong-dong 49-4, Daedeok-gu, Daejeon 306-220 (Korea, Republic of); Oh, Jun-Sik; You, Dong-Wook [Department of Chemistry and Nanoscience and Technology Institute, Wonkwang University, Iksan, Jeonbuk 570-749 (Korea, Republic of); Park, Han-Oh [Bioneer Corporation, Munyueong-dong 49-4, Daedeok-gu, Daejeon 306-220 (Korea, Republic of); Jung, Kwang-Woo, E-mail: kwjung@wku.ac.kr [Department of Chemistry and Nanoscience and Technology Institute, Wonkwang University, Iksan, Jeonbuk 570-749 (Korea, Republic of)

    2014-01-30

    The catalytic oxidation of volatile organic compounds such as benzene, toluene, ethylbenzene, and o-xylene (BTEX) over novel Pt/carbon nanotube (CNT) catalysts fabricated by a molecular-level mixing method was investigated at temperatures ranging from 40 to 150 °C. The Pt/CNT interface was probed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and energy dispersive X-ray spectroscopy (EDS) to elucidate the binding nature of the Pt nanoparticle-CNT surface. The breakthrough curves for multi-component mixtures show displacement effects, in which adsorbates exhibit interaction forces that are sufficiently to displace weakly bounded substances during adsorption. Catalytic oxidation was conducted using a BTEX concentration ranging from 100 to 500 ppmv in air at volume hour space velocities (VHSVs) of approximately 7.5 × 10{sup 4} h{sup −1}–3.4 × 10{sup 5} h{sup −1}. The light-off curves were very steep, and complete oxidation was realized at temperatures as low as 115 °C with 30 wt% Pt/CNT, well below the temperatures required using previously studied Pt-based catalysts. The oxidation activity was presumably promoted because of the higher surface BTEX concentration afforded by the adsorption capability of multiwalled carbon nanotubes. The catalyst was characterized by its unique hydrophobic property, which facilitated the conversion of BTEX with high activity at relatively low temperatures and was unaffected by moisture in the system.

  20. SEM method for direct visual tracking of nanoscale morphological changes of platinum based electrocatalysts on fixed locations upon electrochemical or thermal treatments.

    Science.gov (United States)

    Zorko, Milena; Jozinović, Barbara; Bele, Marjan; Hodnik, Nejc; Gaberšček, Miran

    2014-05-01

    A general method for tracking morphological surface changes on a nanometer scale with scanning electron microscopy (SEM) is introduced. We exemplify the usefulness of the method by showing consecutive SEM images of an identical location before and after the electrochemical and thermal treatments of platinum-based nanoparticles deposited on a high surface area carbon. Observations reveal an insight into platinum based catalyst degradation occurring during potential cycling treatment. The presence of chloride clearly increases the rate of degradation. At these conditions the dominant degradation mechanism seems to be the platinum dissolution with some subsequent redeposition on the top of the catalyst film. By contrast, at the temperature of 60°C, under potentiostatic conditions some carbon corrosion and particle aggregation was observed. Temperature treatment simulating the annealing step of the synthesis reveals sintering of small platinum based composite aggregates into uniform spherical particles. The method provides a direct proof of induced surface phenomena occurring on a chosen location without the usual statistical uncertainty in usual, random SEM observations across relatively large surface areas.

  1. Anticancer platinum (IV) prodrugs with novel modes of activity.

    Science.gov (United States)

    Chin, Chee Fei; Wong, Daniel Yuan Qiang; Jothibasu, Ramasamy; Ang, Wee Han

    2011-01-01

    Over the past four decades, the search for improved platinum drugs based on the classical platinum (II)-diam(m)ine pharmacophore has yielded only a handful of successful candidates. New methodologies centred on platinum (IV) complexes, with better stability and expanded coordination spheres, offer the possibility of overcoming limitations inherent to platinum (II) drugs. In this review, novel strategies of targeting and killing cancer cells using platinum (IV) constructs are discussed. These approaches exploit the unique electrochemical characteristics and structural attributes of platinum (IV) complexes as a means of developing anticancer prodrugs that can target and selectively destroy cancer cells. Anticancer platinum (IV) prodrugs represent promising new strategies as targeted chemotherapeutic agents in the ongoing battle against cancer.

  2. The Dynamics of Platinum Precipitation in an Ion Exchange Membrane

    CERN Document Server

    Burlatsky, S F; Atrazhev, V V; Dmitriev, D V; Kuzminyh, N Y; Erikhman, N S

    2013-01-01

    Microscopy of polymer electrolyte membranes that have undergone operation under fuel cell conditions, have revealed a well defined band of platinum in the membrane. Here, we propose a physics based model that captures the mechanism of platinum precipitation in the polymer electrolyte membrane. While platinum is observed throughout the membrane, the preferential growth of platinum at the band of platinum is dependent on the electrochemical potential distribution in the membrane. In this paper, the location of the platinum band is calculated as a function of the gas concentration at the cathode and anode, gas diffusion coefficients and solubility constants of the gases in the membrane, which are functions of relative humidity. Under H2/N2 conditions the platinum band is located near the cathode-membrane interface, as the oxygen concentration in the cathode gas stream increases and/or the hydrogen concentration in the anode gas stream decreases, the band moves towards the anode. The model developed in this paper...

  3. Hydrophobicity of peritoneal tissues in the rat

    NARCIS (Netherlands)

    Gomez-Suarez, C; Bruinsma, GM; Rakhorst, G; van der Mei, HC; Busscher, HJ

    2002-01-01

    In this study, an inventory of the hydrophobicity of peritoneal tissues in the living rat was made. Peritoneal tissues were divided into mesentery (i.e., omentum) and parietal and visceral peritoneum and their hydrophobicity was determined by the sessile drop method. All peritoneal tissues were hydr

  4. Hydrogels with Micellar Hydrophobic (Nano)Domains

    OpenAIRE

    Pekař, Miloslav

    2015-01-01

    Hydrogels containing hydrophobic domains or nanodomains, especially of the micellar type, are reviewed. Examples of the reasons for introducing hydrophobic domains into hydrophilic gels are given; typology of these materials is introduced. Synthesis routes are exemplified and properties of a variety of such hydrogels in relation with their intended applications are described. Future research needs are identified briefly.

  5. Hydrogels with micellar hydrophobic (nano)domains

    OpenAIRE

    Miloslav ePekař

    2015-01-01

    Hydrogels containing hydrophobic domains or nanodomains, especially of the micellar type, are reviewed. Examples of the reasons for introducing hydrophobic domains into hydrophilic gels are given; typology of these materials is introduced. Synthesis routes are exemplified and properties of a variety of such hydrogels in relation with their intended applications are described. Future research needs are identified briefly.

  6. Hydrogels with micellar hydrophobic (nano)domains

    Science.gov (United States)

    Pekař, Miloslav

    2014-12-01

    Hydrogels containing hydrophobic domains or nanodomains, especially of the micellar type, are reviewed. Examples of the reasons for introducing hydrophobic domains into hydrophilic gels are given; typology of these materials is introduced. Synthesis routes are exemplified and properties of a variety of such hydrogels in relation with their intended applications are described. Future research needs are identified briefly.

  7. Durability of hydrophobic treatment of concrete

    NARCIS (Netherlands)

    Vries, J. de; Polder, R.B.; Borsje, H.

    1998-01-01

    The subject of this study was the performance of hydrophobic treatment to protect concrete against chloride penetration from de-icing salts. Hydrophobic treatment makes a concrete surface absorb less water and less chloride. Several types of tests were carried out to study the performance of hydroph

  8. Durability of hydrophobic treatment of concrete

    NARCIS (Netherlands)

    Vries, J. de; Polder, R.B.; Borsje, H.

    1998-01-01

    The subject of this study was the performance of hydrophobic treatment to protect concrete against chloride penetration from de-icing salts. Hydrophobic treatment makes a concrete surface absorb less water and less chloride. Test methods and requirements for commercial products were established. In

  9. Composite, nanostructured, super-hydrophobic material

    Science.gov (United States)

    D'Urso, Brian R.; Simpson, John T.

    2007-08-21

    A hydrophobic disordered composite material having a protrusive surface feature includes a recessive phase and a protrusive phase, the recessive phase having a higher susceptibility to a preselected etchant than the protrusive phase, the composite material having an etched surface wherein the protrusive phase protrudes from the surface to form a protrusive surface feature, the protrusive feature being hydrophobic.

  10. Etat actuel des recherches fondamentales sur les catalyseurs bimétalliques à base de platine, sur support alumine, comparables à ceux utilisés dans l'industrie pétrolière. Current State of Fundamental Research on Platinum-Base Bimetallic Catalysts on an Alumina Support, Comparable to the Ones Used in the Petroleum Industry

    Directory of Open Access Journals (Sweden)

    Charcosset H.

    2006-11-01

    és promoteurs diminuant l'hydrogénolyse ou (et inhibiteurs par encrassement ; 6 le fait que dans les 158 références de l'article la moitié date de 1976 et après, souligne l'intérêt croissant porté aux recherches fondamentales dans ce domaine. This article mainly concerns the pairs (Pt, Re, (Pt, Ir and (Pt,Ru dealt with in the following order - catalyst preparation (impregnation of the support, reduction by hydrogen ; - characterization of reduced catalysts ; - catalytic activities ; - scale-up tests ta industriel catalysts , - conclusions. Special emphasis is placed on I the difficulty of obtaining data on the degree of reduction which are meaningful concerning the state of the catalyst under normal working conditions, hence the need ta combine several techniques such as DTA, TGA, volumetry, catharometry, ESCA, in-frared spectroscopy, HL thermodesorption and the measuring of catalytic activities ; 21 the dference between the phase diagrams of divided and massed systems ; 3 the usefulness of the hydrogen titration of the unsorbed oxygen ta give evidence for the presence of small pure Mell particles in (Pt, Mell/AI20a catalysts; 4 the dependence of the final state of the catalyst on the activation mode. The pair (Pt, Re con be stabilized in a state of alloy particles having similar superficial and mean composition or in a state of particle mixture of (Pt, Re with an Re content of less than the rated composition and of pure and well dispersed Re. The pairs (Pt, Ir and especially (Pt, Ru are characterized by the difficulty in obtaining on alloy state with a constant composition from one metal particle to another ; 5 variations in catalytic activity due ta the addition of Mell to Pt, reflecting one or several of the following effects a increase in the dispersion of Pt with (or without a change in its intrinsic properties by weak-valence ions of W, Mo, Cr, etc. ; b formation of Mell in a metallic state, eventually producing an alloy with Pt ; c the rote of promoter carbon

  11. Platinum compounds with anti-tumour activity

    NARCIS (Netherlands)

    Plooy, A.C.M.; Lohman, P.H.M.

    1980-01-01

    Ten platinum (Pt) coordination complexes with different ligands, comprising both Pt(II) and Pt(IV) complexes of which the cis-compounds all possessed at least some anti-tumour activity and the trans-compounds were inactive, were tested as to their effect on cell survival and the induction and repair

  12. On the enzymatic formation of platinum nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Govender, Y.; Riddin, T. L. [Rhodes University, Department of Biochemistry, Microbiology and Biotechnology (South Africa); Gericke, M. [MINTEK (South Africa); Whiteley, C. G., E-mail: C.Whiteley@ru.ac.z [Rhodes University, Department of Biochemistry, Microbiology and Biotechnology (South Africa)

    2010-01-15

    A dimeric hydrogenase enzyme (44.5 and 39.4 kDa sub units) was isolated in a 39.5% yield from the fungus Fusarium oxysporum and purified 4.64-fold by ion exchange chromatography on Sephacryl S-200. Characterisation of the enzyme afforded pH and temperature optima of 7.5 and 38 {sup o}C, respectively, a half-life stability of 36 min and a V{sub max} and K{sub m} of 3.57 nmol min{sup -1} mL{sup -1} and 2.25 mM, respectively. This enzyme was inhibited (non-competitively) by hydrogen hexachloroplatinic acid (H{sub 2}PtCl{sub 6}) at 1 or 2 mM with a K{sub i} value of 118 {mu}M. Incubation of the platinum salt with the pure enzyme under an atmosphere of hydrogen and optimum enzyme conditions (pH 7.5, 38 {sup o}C) afforded <10% bioreduction after 8 h while at conditions suitable for platinum nanoparticle formation (pH 9, 65 {sup o}C) over 90% reduction took place after the same length of time. Cell-free extract from the fungal isolates produced nearly 90% bioreduction of the platinum salt under both pH and temperature conditions. The bioreduction of the platinum salt by a hydrogenase enzyme takes place by a passive process and not an active one as previously understood.

  13. Platinum catalysed hydrolytic amidation of unactivated nitriles

    NARCIS (Netherlands)

    Cobley, Christopher J.; Heuvel, Marco van den; Abbadi, Abdelilah; Vries, Johannes G. de

    2000-01-01

    The platinum(II) complex, [(Me2PO··H··OPMe2)PtH(PMe2OH)], efficiently catalyses the direct conversion of unactivated nitriles to N-substituted amides with both primary and secondary amines. Possible mechanisms for this reaction are discussed and evidence for initial amidine formation is reported.

  14. Targeting Platinum Compounds: synthesis and biological activity

    OpenAIRE

    VAN ZUTPHEN, Steven

    2005-01-01

    Inspired by cisplatin, the inorganic drug discovered by Barnett Rosenberg in 1965, the research described in this thesis uses targeting ligands, or ligands varied in a combinatorial fashion, to find platinum complexes with more specific modes of action. These studies have lead to the development of novel (solid-phase) synthetic methods and to the discovery of several compounds with promising biological properties.

  15. Targeting Platinum Compounds : synthesis and biological activity

    NARCIS (Netherlands)

    Zutphen, Steven van

    2005-01-01

    Inspired by cisplatin, the inorganic drug discovered by Barnett Rosenberg in 1965, the research described in this thesis uses targeting ligands, or ligands varied in a combinatorial fashion, to find platinum complexes with more specific modes of action. These studies have lead to the development of

  16. Skin Sensitizing Potency of Halogenated Platinum Salts.

    Science.gov (United States)

    The relationship between occupational exposure to halogenated platinum (Pt) salts and Pt-specific allergic sensitization is well-established. Although human case reports and clinical studies demonstrate that Pt salts are potent skin sensitizers, no studies have been published tha...

  17. Platinum catalysed hydrolytic amidation of unactivated nitriles

    NARCIS (Netherlands)

    Cobley, Christopher J.; Heuvel, Marco van den; Abbadi, Abdelilah; Vries, Johannes G. de

    2000-01-01

    The platinum(II) complex, [(Me2PO··H··OPMe2)PtH(PMe2OH)], efficiently catalyses the direct conversion of unactivated nitriles to N-substituted amides with both primary and secondary amines. Possible mechanisms for this reaction are discussed and evidence for initial amidine formation is reported. Is

  18. Electrodeposition of platinum nanoclusters on type I collagen modified electrode and its electrocatalytic activity for methanol oxidation

    Science.gov (United States)

    Sun, Yujing; Sun, Lanlan; Xu, Fugang; Guo, Cunlan; Liu, Zhelin; Zhang, Yue; Yang, Tao; Li, Zhuang

    2009-05-01

    We firstly reported a novel polymer matrix fabricated by type I collagen and polymers, and this matrix can be used as nanoreactors for electrodepositing platinum nanoclusters (PNCs). The type I collagen film has a significant effect on the growth of PNCs. The size of the platinum nanoparticles could be readily tuned by adjusting deposition time, potential and the concentration of electrolyte, which have been verified by field-emitted scanning electron microscopy (FE-SEM). Furthermore, cyclic voltammetry (CV) has demonstrated that the as-prepared PNCs can catalyze methanol directly with higher activity than that prepared on PSS/PDDA film, and with better tolerance to poisoning than the commercial E-TEK catalyst. The collagen-polymer matrix can be used as a general reactor to electrodeposit other metal nanostructures.

  19. HYDROPHOBICITY OF CONTAMINATED SILICONE RUBBER SURFACES

    Institute of Scientific and Technical Information of China (English)

    Zhi-min Zheng; Cai-hong Xu; Jian Jiang; Chang-yu Ren; Wei Gao; Ze-min Xie

    2002-01-01

    Silicone rubber (SIR) shows superior performance when used outdoors, but its surface can be transformed frominherently hydrophobic to hydrophilic by the adsorption of contaminants. Al(OH)3, Al2O3, quartz powder and active carbonwere selected as authentic contaminants. Hydrophobicity of the surface was determined using contact angle measurement.The results indicate that the adsorbability of the contaminants can strongly affect the hydrophobicity of contaminated SIRsurface. The increasing rate of contact angle of specimens contaminated by Al(OH)3 was much faster than that by Al2O3 andquartz due to the adsorption of migrated low molecular weight (LMW) polydimethylsiloxanes. Specimens contaminated byactive carbon could achieve surface hydrophobicity within 15 min because active carbon has high adsorbability. Surfaces ofcontaminated ultrapure SIR, polytetrafluoroethylene (PTFE) and glass remain hydrophilic because they contain no mobileLMW components. The addition of oligomeric polydimethylsiloxanes has little effect on the hydrophobicity of contaminantscovered on SIR surface.

  20. Production of syngas by ethanol reforming on Ni catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Catapan, Rafael C.; Oliveira, Amir A.M.; Donadel, Karina; Oliveira, Antonio Pedro N.; Rambo, Carlos R. [Federal University of Santa Catarina (UFSC), Florianopolis, SC (Brazil). Dept. of Mechanical Engineering. Lab. of Combustion and Thermal Systems Engineering], Emails: catapan@labcet.ufsc.br, donadel@emc.ufsc.br, pedronovaes@emc.ufsc.br, rambo@enq.ufsc.br; Oliveira, Therezinha Maria N.; Wagner, Theodoro M. [Universidade da Regiao de Joinville, SC (Brazil). Campus Universitario Bom Retiro], E-mails: tnovais@univille.br, theowag@terra.com.br

    2010-07-01

    In the recent literature, attention has been directed to the development of noble metals based catalysts for the ethanol reforming. However, the high costs and low availability of noble metals, e.g. platinum, as a resource justify the development of alternatives technologically, economically and environmentally viable such as Ni-based catalysts. Here, the thermal decomposition, partial oxidation and steam reforming of ethanol over SiO{sub 2} supported Ni was studied in a packed bed reactor in the 673 - 973 K temperature range at 1 atm. The catalyst was produced from 10% NiO, 5% of bentonite and 85% (wt.) of natural amorphous silica fibers (NASF). Scanning Electron Microscopy (SEM) evaluation revealed that particles of Ni were homogeneously distributed over the NASF. The X-ray diffraction (XRD) patterns did not show peaks related to silicates in all spectra, which indicates that there is no, apparently, interaction between the nickel catalysts and SiO{sub 2} or devitrification The reactions of ethanol on this catalyst occurs mainly by the dehydrogenation reaction generating acetaldehyde. Further, CH{sub 3}CHO is decomposed to CH{sub 4} and CO. In parallel to this route, ethanol is dehydrated producing ethylene, which is successively dehydrogenated in Ni sites generating carbon on the surface. Also, carbon can be produced by consecutive dehydrogenation of CH{sub 4}. Both reactions contribute to increase the production of H{sub 2} to values higher than those predicted by the thermodynamic equilibrium. (author)

  1. Study of activity and effectiveness factor of noble metal catalysts for water-gas shift reaction

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Sungkwang; Bae, Joongmyeon [Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 373-1, Guseong-Dong, Yuseong-Gu, Daejeon 305-701 (Korea); Kim, Kihyun [POSCO 1, Goedong-dong, Nam-gu, Pohang, Gyeongbuk 790-785 (Korea)

    2009-01-15

    Platinum on ceria-zirconia (CZO) catalysts for the water-gas shift (WGS) reaction were prepared with various platinum loadings. In addition, the activity of Pt/CZO catalysts was tested preliminarily at gas hourly space velocity (GHSV) of 5000 h{sup -1}. Activity tests were also conducted at GHSV of 200,000 h{sup -1} with limited conversions, and activation energies and pre-exponential factors for rate equations were obtained by fitting the data. The effectiveness factors were estimated on the basis of the intra-particle mass transfer. Moreover, with this estimation, an attempt was made to calculate the utilization of the Pt loading with an eggshell morphology. (author)

  2. Solution properties of hydrophobically modified

    Directory of Open Access Journals (Sweden)

    A.M. Al-Sabagh

    2016-12-01

    Full Text Available We tested nine hydrophobically modified polyacrylamides with molecular weights situated between 1.58 and 0.89 × 106 g/mol for enhanced oil recovery applications. Their solution properties were investigated in the distilled water, brine solution, formation water and sea water. Their critical association concentrations were determined from the relationship between their concentrations and the corresponding apparent viscosities (ηapp at 30 °C at shear rate 6 s−1. They were between 0.4 and 0.5 g/dl. The brine solutions of 0.5 g/dl of HM-PAMs were investigated at different conditions regarding their apparent viscosities. Such conditions were mono and divalent cations, temperature ranging from 30 to 90 °C, the shear rate ranging from 6 to 30 s−1 and the aging time for 45 days. The surface and interfacial tensions for the HM-PAMs were measured for concentration range from 0.01 to 1 g/dl brine solutions at 30 °C and their emulsification efficiencies were investigated for 7 days. The discrepancy in the properties and efficiencies of the tested copolymers was discussed in the light of their chemical structure.

  3. Synthesis, characterization and electrochemical studies of nanostructured CaWO{sub 4} as platinum support for oxygen reduction reaction

    Energy Technology Data Exchange (ETDEWEB)

    Farsi, Hossein [Department of Chemistry, University of Birjand, 97175-615 Birjand (Iran, Islamic Republic of); Solar Energy Research Department, University of Birjand, Birjand (Iran, Islamic Republic of); Barzgari, Zahra, E-mail: zbarzgari@birjand.ac.ir [Department of Chemistry, University of Birjand, 97175-615 Birjand (Iran, Islamic Republic of)

    2014-11-15

    Highlights: • Nanostructured CaWO{sub 4} was fabricated by co-precipitation method. • Platinum was electrodeposited onto the surface prepared nanostructured CaWO{sub 4}. • Pt/CaWO{sub 4}-graphite demonstrate good oxygen reduction reaction activity. - Abstract: In the present work, we employed nanostructured calcium tungstate as a supporting material for platinum, a well-known electrocatalyst for oxygen reduction. The co-precipitation method has been utilized to synthesize nanostructured calcium tungstate from aqueous solution. The structure and morphology of the obtained CaWO{sub 4} were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Preparation of the Pt/CaWO{sub 4}-graphite catalyst was carried out by electrodeposition of Pt onto the surface of CaWO{sub 4}/graphite electrode. The physical properties of the catalyst were determined by scanning electron microscopy analysis and energy dispersive X-ray (SEM/EDX). The electrochemical activity of the Pt/CaWO{sub 4}-graphite for the oxygen reduction reaction (ORR) was investigated in acid solution by cyclic voltammetry measurements, linear sweep voltammetry, and electrochemical impedance spectroscopy. The results revealed that the Pt/CaWO{sub 4}-graphite has higher electrocatalytic activity for oxygen reduction in comparison with Pt/graphite catalyst.

  4. Fabrication, annealing, and electrocatalytic properties of platinum nanoparticles supported on self-organized TiO2 nanotubes

    Institute of Scientific and Technical Information of China (English)

    LEI Bin; XUE Jianjun; JIN Danping; NI Shougao; SUN Haibo

    2008-01-01

    The platinum nanoparticles supported on self-organized TiO2 nanotubes (Pt-TiO2/Ti) were prepared using electrochemical anodic oxidation followed by cathodic reduction.The structure and chemical nature of the Pt-TiO2/Ti electrocatalyst were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM).Both XRD and SEM results indicate the presence of platinum on nanotubular TiO2.The stability of the Pt deposits was also investigated in 0.5 mol/L H2SO4 solution by cyclic voltammetry.The electrocatalytic activity of the Pt-TiO2/Ti catalyst exhibits enhancement effect during electro-oxidation of methanol when annealed to anatase.Successive cyclic voltammograms of methanol oxidation on the Pt-TiO2/Ti electrocatalyst shows unique electrocatalytic characteristics when compared to methanol oxidation on the bulk Pt catalyst.This is because of further quick oxidation of adsorbed CO by Pt (111) facets of Pt particles on self-organized TiO2 nanotubes when the formation of an electroactive film onto the working catalyst surface occurs.

  5. PEM fuel cell catalyst degradation mechanism and mathematical modeling

    Science.gov (United States)

    Bi, Wu

    The durability of carbon-supported platinum oxygen reduction electrocatalysts is one of the limiting factors for their commercial applications in PEM fuel cell cathodes. In this work, we applied both experimental and numerical tools to study Pt/C catalyst degradation mechanisms. An accelerated catalyst degradation protocol through cycling the cathode potential in a square-wave profile was applied to study cell performances, Pt/C catalyst ORR activity, and active surface area losses. Post-mortem analyses of cathode Pt particle size were conducted by X-ray diffraction. Changes of platinum distributions in CCMs were studied by SEM/EDS analyses with surface coated Au as the reference element. The mechanisms of platinum deposition in membrane were investigated. It was confirmed by the SEM/EDS Pt distribution analyses that the deposited Pt atoms originated from the cathode. It was hypothesized that dissolved Pt ions from the cathode diffused into the membrane and were reduced by the permeated hydrogen from the anode. These deposited Pt atoms catalyzed the combustion of permeated oxygen and hydrogen. Pt band was predicted and experimentally confirmed at the location where the permeated hydrogen and oxygen completely reacted with each other. An active research thrust for PEM fuel cells is the development of membranes for high temperature (above 80°C) and low humidity operations. However a large tradeoff the benefits running fuel cell at relatively high temperatures was observed due to the accelerated cathode degradation processes. And at low humidity conditions, the cathode degradation rate decreased due to the slow transport of soluble platinum ions in possible narrowed/limited water (or ionic) channel networks in polymer electrolytes. From the Pt dissolution experiments in 0.5 M HClO4 solution, large positive effects of holding potentials on dissolution rates and soluble Pt concentrations were observed. Without an external holding potential, Pt dissolution rate was

  6. Pt/Ceria-based Catalysts for Small Alcohol Electrooxidation

    Science.gov (United States)

    Menendez-Mora, Christian L.

    High emissions of fossil-based energy sources have led to scientists around the world to develop new alternatives for the future. In this sense, fuel cells are a remarkable and promising energy option with less environmental impact. The most used fuels for this technology are hydrogen and small chain alcohols, which can be oxidized to transform their chemical energy into electrical power. To do this, fuel cells need catalysts that will act as an active surface where the oxidation can take place. The problem with platinum catalysts is its possible CO poisoning with intermediates that are produced before the complete oxidation of alcohol to CO2. Different approaches have been taken to try to resolve this issue. In this case, cerium oxide (ceria) was selected as a co-catalyst to mitigate the effect of CO poisoning of platinum. Ceria is a compound that has the ability to work as an "oxygen tank" and can donate oxygen to carbon monoxide that is strongly adsorbed at platinum surface to produce CO2 (carbon dioxide), regenerating the Pt surface for further alcohol oxidation. Therefore, enhancing the current density as well as the power output of a fuel cell. First, an occlusion deposition technique was used to prepare platinum/ceria composite electrodes and tested them towards small chain alcohol oxidation such as methanol oxidation reaction in acidic and alkaline media. The preliminary results demonstrated that the Pt/ceria electrodes were more efficient towards methanol electrooxidation when compared to Pt electrodes. This enhancement was attributed to the presence of ceria. A second preparation method was selected for the synthesis of ceria/Pt catalysts. In this case, a hydrothermal method was used and the catalysis were studied for the effect of MeOH, EtOH and n-BuOH oxidation. The observed effect was that electrodes made of Pt/Pt:CeO2-x showed better catalytic effect than Pt/ceria and platinum electrodes. Moreover, a comparison between ceria nanorods versus

  7. Further studies on hydration of alkynes by the PtCl4-CO catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Israelsohn, Osnat; Vollhardt, K. Peter C.; Blum, Jochanan

    2002-01-18

    Under CO atmosphere, between 80 and 120 C, a glyme solution of PtCl{sub 4} forms a carbonyl compound that promotes hydration of internal as well as terminal alkynes to give aldehyde-free ketones. The catalytic process depends strongly on the electronic and steric nature of the substrates. Part of the carbonyl functions of the catalyst can be replaced by phosphine ligands. Chiral DIOP reacts with the PtCl{sub 4}-CO compound to give a catalyst that promotes partial kinetic resolution of a racemic alkyne. Replacement of part of the CO by polystyrene-bound diphenylphosphine enables to attach the catalyst to the polymeric support. Upon entrapment of the platinum compound in a silica sol-gel matrix, it reacts as a partially recyclable catalyst. A reformulated mechanism for the PdCl{sub 4}-CO catalyzed hydration is suggested on the basis of the present study.

  8. Electro-Deposition Pt Catalysts Supported on Carbon-Nanotubes for Methanol Oxidation

    Institute of Scientific and Technical Information of China (English)

    Hailin Song; Peixia Yang; Xiaoyu Wen; Maozhong An; Jinqiu Zhang

    2015-01-01

    In order to study the properties of supporting Pt catalysts for methanol oxidation, carbon⁃nanotubes are used by electrochemical deposition method. Different deposition turns, different cyclic voltammetry scanning speeds and processing time with ascorbic acid are investigated in this paper. The micrographs of Pt/CNTs catalysts are characterized by scanning electron microscopy, the electro⁃catalytic properties of Pt/CNTs catalysts for methanol oxidation are investigated by cycle voltammetry and chronoamperometry. The results show that the size of platinum will be greater with the faster scanning speed. After dissolution in ascorbic acid, Pt nano⁃particles disperse uniformly. The obtained Pt/CNTs catalysts show a high electro⁃catalytic activity and stability.

  9. A Highly Efifcient and Selective Water-Soluble Bimetallic Catalyst for Hydrogenation of Chloronitrobenzene to Chloroaniline

    Institute of Scientific and Technical Information of China (English)

    Zhou Yafen; Yang Wenjuan; Zhou Limei; Wang Manman; Ma Xiaoyan

    2015-01-01

    Selective hydrogenation of chloronitrobenzene (CNB) to chloroaniline (CAN) catalyzed by water-soluble Ru/Pt bimetallic catalyst in an aqueous-organic biphasic system was studied. It was found that the catalytic activity increased ob-viously due to the addition of platinum. Ru/Pt bimetallic catalysts exhibited a strong synergistic effect when the molar ratio of Pt was in the range of 5%—80%. Under the mild conditions including a temperature of 25℃, a hydrogen pressure of 1.0 MPa and a Pt molar ratio of 20%, the conversion of p-chloronitrobenzene (p-CNB) reached 99.9%, with the selectivity to p-chloroaniline (p-CAN) equating to 99.4%. The Ru/Pt catalyst also showed high activity and selectivity for the hydrogena-tion of other chloro-and dichloro-nitrobenzenes with different substituted positions. In addition, the catalyst can be recycled ifve times without signiifcant loss of activity.

  10. Graphene supported non-precious metal-macrocycle catalysts for oxygen reduction reaction in fuel cells

    Science.gov (United States)

    Choi, Hyun-Jung; Ashok Kumar, Nanjundan; Baek, Jong-Beom

    2015-04-01

    Fuel cells are promising alternative energy devices owing to their high efficiency and eco-friendliness. While platinum is generally used as a catalyst for the oxygen reduction reaction (ORR) in a typical fuel cell, limited reserves and prohibitively high costs limit its future use. The development of non-precious and durable metal catalysts is being constantly conceived. Graphene has been widely used as a substrate for metal catalysts due to its unique properties, thus improving stability and ORR activities. In this feature, we present an overview on the electrochemical characteristics of graphene supported non-precious metal containing macrocycle catalysts that include metal porphyrin and phthalocyanine derivatives. Suggested research and future development directions are discussed.

  11. Recovery of palladium from a spent automobile catalyst leaching solution by a thiodiglycolamide derivative

    OpenAIRE

    2015-01-01

    In the sequence of previous research on the development of novel liquid-liquid amidetype compounds to efficiently and selectively extract platinum-group metals (PGMs) from concentrated hydrochloric acid media, a specific thiodiglycolamide derivative – N,N’-dimethyl-N,N’-dicyclohexylthiodiglycolamide (DMDCHTDGA) – has been applied for the recovery of palladium(II) from a spent automobile catalyst leaching solution, containing palladium(II) and rhodium(III) as PGMs. The results obtained are rat...

  12. Extended Two Dimensional Nanotube and Nanowire Surfaces as Fuel Cell Catalysts

    OpenAIRE

    Alia, Shaun Michael

    2011-01-01

    Extended network nanomaterials of platinum (Pt), silver (Ag), palladium (Pd), and gold (Au) are synthesized and characterized as proton exchange membrane (PEMFC), hydroxide exchange membrane (HEMFC), and direct alcohol (DAFC) fuel cell catalysts.Porous Pt nanotubes (PPtNTs), 5 nm thick, are synthesized by the galvanic displacement of Ag nanowires (AgNWs) for PEMFCs and DAFCs. PPtNTs produce oxygen reduction (ORR) and durability characteristics significantly higher than supported Pt nanopartic...

  13. Single-Atom Pt as Co-Catalyst for Enhanced Photocatalytic H2 Evolution.

    Science.gov (United States)

    Li, Xiaogang; Bi, Wentuan; Zhang, Lei; Tao, Shi; Chu, Wangsheng; Zhang, Qun; Luo, Yi; Wu, Changzheng; Xie, Yi

    2016-03-23

    Isolated single-atom platinum (Pt) embedded in the sub-nanoporosity of 2D g-C3 N4 as a new form of co-catalyst is reported. The highly stable single-atom co-catalyst maximizes the atom efficiency and alters the surface trap states of g-C3 N4 , leading to significantly enhanced photocatalytic H2 evolution activity, 8.6 times higher than that of Pt nanoparticles and up to 50 times that for bare g-C3 N4 .

  14. Concurrent chemoradiotherapy comparison of taxanes and platinum versus 5-fluorouracil and platinum in nasopharyngeal carcinoma treatment

    Institute of Scientific and Technical Information of China (English)

    Chen Xichuang; Hong Yuan; Feng Jinhua; Ye Jianlin; Zheng Panpan; Guan Xiyin; You Xiaohong

    2014-01-01

    Background Nasopharyngeal carcinoma (NPC) is a squamous-cell carcinoma especially prevailing among the natives of southern China.The regimen of concurrent chemoradiotherapy (CCRT) that include platinum and 5-fluorouracil (5-FU)is considered to be the standard treatment for NPC.However,its clinical use is limited by its toxicity.Our purpose was to evaluate the efficacy and safety of the regimen of CCRT with taxanes and platinum versus the regimen of CCRT with 5-FU and platinum in NPC treatment.Methods Medline,the Cochrane library,and the Chinese medical literature database were searched for eligible studies.Meta-analysis was performed using Review Manager (Version 5.2).Results Six random controlled trials (RCTs) including 514 patients met our criteria.Meta-analysis showed that the regimen of CCRT with taxanes and platinum had an improved significant difference in complete remission (CR) and less incidence rate in adverse reactions such as gastrointestinal impairment grades Ⅲll-Ⅳ,liver and kidney impairment grades Ⅰ-Ⅱ,and radiodermatitis grades Ⅲ-Ⅳ versus the conventional regimen of CCRT with 5-FU and platinum,while the long-term effectiveness rate of overall survival,Iocoregional failure-free survival,or distant metastasis failure-free survival between the two groups was therapeutic equivalence.Conclusions The regimen of CCRT with taxanes and platinum in NPC therapy may be more efficient and safe compared to the conventional modality of 5-FU and platinum in CCRT.However,we need more high-quality studies of multi-center and randomized double-blind clinical trials to further compare,analyze,and confirm the findings.

  15. Influence of Metal Sulfides as Anode Catalysts on Performance of H2S SOFC

    Institute of Scientific and Technical Information of China (English)

    钟理; 刘曼; 韩国林; CHUANGKar

    2003-01-01

    Two anode catalysts with Pt, MoS2 and composite metal sulfides (MoS2+NiS), are investigated for electrochemical oxidation of hydrogen sulfide in solid oxide fuel cell (SOFC) at temperatures 750-850℃. The catalysts comprising MoS2 and MoS2+NiS exhibited good electrical conductivity and catalytic activity. MoS2 and composite catalysts were found to be more active than Pt, a widely used catalyst for high temperature H2S/O2 fuel cell at 750-850℃. However, MoS2 itself sublimes above 450℃. In contrast, composite catalysts containing both Mo and transition metal (Ni) are shown to be stable and effective in promoting the oxidation of H2S in SOFC up to 850℃. However, electric contact is poor between the platinum current collecting layer and the composite metal sulfide layer, so that the cell performance becomes worse. This problem is overcome by adding conductive Ag powder into the anode layer (forming MoS2+NiS+Ag anode material) to increase anode electrical conductance instead of applying a thin laver of platinum on the top of anode.

  16. 氮/硫双杂化非贵金属碱性阴离子膜燃料电池阴极非铂催化剂%N/S Co-doped Non-precious Metal as Non-platinum Cathode Catalyst for Alkaline Membrane Fuel Cells

    Institute of Scientific and Technical Information of China (English)

    徐莉; 潘国顺; 梁晓璐; 罗桂海; 邹春莉; 陈高攀

    2014-01-01

    N/S co-doped non-precious metal material for the oxygen reduction reaction( ORR) was prepared with ferrous sulfate heptahydrate(FeSO4·7H2O), pyrrole and p-toluenesulfonic acid(TsOH) as Fe, N and S precursors supported on vulcan XC 72R, and followed by heat treatment in an inert atmosphere at 600℃. The electrochemical techniques such as cyclic voltammetry( CV) and rotating disk electrode( RDE) were employed with the Koutechy-Levich theory to make clear the ORR kinetical constants and the reaction mechanism. It is found that the catalysts dual-doped with TsOH show significantly improved ORR activity relative to the TsOH-free one. The overall electron transfer numbers for the catalyzed ORR are determined to be 3. 899 and 3. 098, respectively, for the catalysts with and without TsOH-doping. And these catalysts exhibit superior methanol tolerance to commercial 40%Pt/C catalyst. The XRD results demonstrate the decomposition of the precursors because of pyrolysis and formation of Fe-Nx-C active surface groups and some less active species. XPS analysis indicate that the pyrrolic-N groups are the most active sites and sulfur species are also structurally bonded to carbon in the forms of C—Sn—C and oxidized —SOn— bonds, which are beneficial for ORR.%以吡咯和对甲苯磺酸( TsOH)作为碳载过渡金属催化剂的掺杂剂,经溶剂分散及600℃热处理制备了一种高效催化氧还原反应( ORR )的碳载双杂化过渡金属催化剂( Fe-N/C-TsOH-600).利用 X 射线衍射( XRD)和X射线光电子能谱( XPS)对催化剂的结构进行表征.运用旋转圆盘电极( RDE)技术研究了该催化剂在碱性介质中催化氧还原的电化学催化活性和稳定性,探讨了不同浓度甲醇溶液对Fe-N/C-TsOH-600催化剂催化氧还原活性的影响.结果表明,以Fe-N/C-TsOH-600制备的气体扩散电极在0.1 mol/L KOH电解质溶液中对氧具有很高的选择催化还原活性和稳定性.当电极经过4800圈循环伏安( CV)

  17. Catalyst Alloys Processing

    Science.gov (United States)

    Tan, Xincai

    2014-10-01

    Catalysts are one of the key materials used for diamond formation at high pressures. Several such catalyst products have been developed and applied in China and around the world. The catalyst alloy most widely used in China is Ni70Mn25Co5 developed at Changsha Research Institute of Mining and Metallurgy. In this article, detailed techniques for manufacturing such a typical catalyst alloy will be reviewed. The characteristics of the alloy will be described. Detailed processing of the alloy will be presented, including remelting and casting, hot rolling, annealing, surface treatment, cold rolling, blanking, finishing, packaging, and waste treatment. An example use of the catalyst alloy will also be given. Industrial experience shows that for the catalyst alloy products, a vacuum induction remelt furnace can be used for remelting, a metal mold can be used for casting, hot and cold rolling can be used for forming, and acid pickling can be used for metal surface cleaning.

  18. Effect of catalyst distribution in the active layers of proton exchange membrane fuel cells; Effet de la distribution du catalyseur dans les couches actives de piles a combustible de type PEMFC

    Energy Technology Data Exchange (ETDEWEB)

    Bultel, Y.; Durand, R.; Ozil, P. [Ecole Nationale Superieure d' Electrochimie et d' Electrometallurgie, Lab. d' Electrochimie et de Physico-chimie des Materiaux et des Interfaces, UMR 5631, 38 - Grenoble (France); Antoine, O. [Geneva Univ., Dept. de Chimie Minerale, Analytique et Appliquee, Sciences 2 (Switzerland)

    2000-07-01

    The aim of this work is to study the influence of the distribution of the platinum catalyst in the active layers on the performances of proton exchange membrane fuel cells (PEMFC) electrodes. In the one hand, the results predicted by the classical models and those in which the active layers is modified have been compared; these results have allowed to demonstrate theoretically the effect of the discrete distribution of the platinum catalyst in the form of nano-particles. On the other hand, the influence of a distribution gradient of the platinum catalyst for porous and non-porous active layers of PEMFC cathode has been experimentally demonstrated and predicted by numerical simulations. (O.M.)

  19. Novel hydrophobically associative polyacrylamide with tunable viscosity

    Institute of Scientific and Technical Information of China (English)

    Xu Feng Zhang; Wen Hui Wu

    2009-01-01

    Hydrophobically associative polyacrylamide (HAPAM) were prepared in aqueous solution by radical copolymerization of novel cationic surface-active monomer, dimethylhexadecyl(3-acrylamidopropyl)ammonium bromide (DMHAB), with acrylarnide (AM) in the presence of DMHAB/CTAB mixed micelles. The length of hydrophobic microblock (N_H) in HAPAM is controlled by the molar fraction of DMHAB in mixed micelles, which can be mediated by the ratio of CTAB to DMHAB. The results of steady-state fluorescence probe and viscometry experiments showed the ability of HAPAM association was determined by the length of the hydrophobic microblock. HAPAM with tunable association ability are promising materials for thickening agent.

  20. Super-hydrophobic fluorine containing aerogels

    Science.gov (United States)

    Coronado, Paul R.; Poco, John F.; Hrubesh, Lawrence W.

    2007-05-01

    An aerogel material with surfaces containing fluorine atoms which exhibits exceptional hydrophobicity, or the ability to repel liquid water. Hydrophobic aerogels are efficient absorbers of solvents from water. Solvents miscible with water are separated from it because the solvents are more volatile than water and they enter the porous aerogel as a vapor across the liquid water/solid interface. Solvents that are immisicble with water are separated from it by selectively wetting the aerogel. The hydrophobic property is achieved by formulating the aerogel using fluorine containing molecules either directly by addition in the sol-gel process, or by treating a standard dried aerogel using the vapor of fluorine containing molecules.