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WO1999066574A1 - Precurseurs et compositions polymetalliques et procedes de fabrication de nanocomposites polymetalliques supportes - Google Patents

Precurseurs et compositions polymetalliques et procedes de fabrication de nanocomposites polymetalliques supportes Download PDF

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Publication number
WO1999066574A1
WO1999066574A1 PCT/US1998/012354 US9812354W WO9966574A1 WO 1999066574 A1 WO1999066574 A1 WO 1999066574A1 US 9812354 W US9812354 W US 9812354W WO 9966574 A1 WO9966574 A1 WO 9966574A1
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WIPO (PCT)
Prior art keywords
metal
precursor
polymetallic
support
nanoparticles
Prior art date
Application number
PCT/US1998/012354
Other languages
English (en)
Inventor
Charles M. Lukehart
William D. King
Stephen B. Milne
Frank E. Jones, Iii
James D. Corn
Deborah L. Boxall
Krzysztof C. Kwiatkowski
Original Assignee
Vanderbilt University
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Priority to PCT/US1998/012354 priority Critical patent/WO1999066574A1/fr
Publication of WO1999066574A1 publication Critical patent/WO1999066574A1/fr

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/9075—Catalytic material supported on carriers, e.g. powder carriers
    • H01M4/9083—Catalytic material supported on carriers, e.g. powder carriers on carbon or graphite
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/08—Heat treatment
    • B01J37/082—Decomposition and pyrolysis
    • B01J37/086—Decomposition of an organometallic compound, a metal complex or a metal salt of a carboxylic acid
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/92—Metals of platinum group
    • H01M4/921—Alloys or mixtures with metallic elements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/90—Selection of catalytic material
    • H01M4/92—Metals of platinum group
    • H01M4/925—Metals of platinum group supported on carriers, e.g. powder carriers
    • H01M4/926—Metals of platinum group supported on carriers, e.g. powder carriers on carbon or graphite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • Nanocomposites comprise very small particles typically having diameters less than 100 nm deposited on the surface of a support or within a host matrix.
  • the particles are metal particles
  • the nanocomposites exhibit interesting electronic and nonlinear optical properties.
  • the particles are metallic with a high surface area, the nanocomposites exhibit high chemical reactivity as catalysts for a variety of chemical reactions.
  • the average diameter of metallic nanoparticles usually can be controlled by varying annealing conditions or by metal loading. Generally, nanoparticle diameter can be increased by using high-temperature annealing.
  • Various support matrices for nanocomposites may be chosen for various chemical uses.
  • the matrix may be porous and/or conductive for various catalytic applications, or for optical applications, a transparent matrix may be useful.
  • a fuel cell directly converts chemical energy of fuel and oxidant reactants into low- voltage direct current by means of electrode-catalyzed electrochemical reactions.
  • fuel cells do not consume the materials comprising the electrodes.
  • the cell converts chemical energy into electricity without undergoing irreversible chemical change to the cell.
  • the catalyst remains active, a fuel cell can operate as long as it has a source of fuel and oxidant, and the reaction products are removed.
  • a fuel cell performs the same function as a galvanic cell or a discharging storage battery.
  • the reactants are stored outside the reaction areas. The reactants are provided to the electrodes only when power generation is required.
  • the oxidizing reactant in most fuel cells is atmospheric oxygen. When a fuel cell runs out of a reactant, generation of electricity ceases. Power generation resumes when the reactant is provided to the system.
  • a fuel cell comprises a fuel electrode (anode) and an oxidant electrode
  • a simple hydrogen-oxygen fuel cell has the theoretical potential of generating direct current at a voltage up to 1.229 V at standard temperature and pressure.
  • a second type of fuel cell being studied for practical purposes is an indirect methanol-oxygen fuel cell.
  • Indirect methanol-oxygen fuel cells rely upon steam reformation of methanol to produce a hydrogen-rich gas. The hydrogen reacts with oxygen in the cell to generate water:
  • the indirect methanol-oxygen fuel cell may be an improvement over hydrogen- oxygen fuel cells with respect to less expensive and safer storage of the fuel (methanol), the portability of such fuel cells is limited by the size of the methanol reforming device required for the reaction and by the operating temperature of that device.
  • the third type of practical fuel cell is the direct methanol fuel cell (DMFC).
  • the DMFC has the advantages of the indirect methanol fuel cell without sacrificing portability or safety.
  • the DMFC electrochemically converts methanol into carbon dioxide and water without requiring an intermediate reformation of methanol into hydrogen gas.
  • the overall reaction for this type of fuel cell is as follows:
  • the first anode catalysts used in DMFCs were platinum black. Platinum catalysts are fairly effective in DMFCs, but become poisoned by methanol partial oxidation products, thereby lowering the lifetime of the catalyst. Catalyst poisoning is believed to occur when partially oxidized products of methanol react and bond to the surface of the platinum catalyst, reducing the number of available catalytic sites. Continued poisoning eventually renders the catalyst useless.
  • a DMFC design includes two catalytic electrodes separated by a conductive ion-exchange membrane.
  • the anode side of the cell is typically filled with a 0.5-2.0 molar aqueous methanol solution.
  • oxygen is bubbled through a low pH aqueous solution at a pressure of 1.0-5.0 atmospheres of oxygen.
  • the reaction products, carbon dioxide and water, are continuously removed from the cell.
  • the anode and cathode are connected by an electrical circuit. Methanol must be introduced into the anode in the vapor phase to avoid the problem of dehydration of the electrode membrane.
  • the efficiency of DMFCs can be increased by raising the temperature of the fuel cell above 100°C which vaporizes the methanol and accelerates the rate of reaction (V) noted above.
  • Use of metal catalysts supported on conductive supports of high surface area is preferred for practical applications.
  • Attempts to enhance reactivity at the anode include addition to the catalyst composition of another metal wherein a metal-oxygen bond energy similar to that of the platinum-carbon bond energy is postulated to reduce catalyst poisoning.
  • Catalysts comprising the metal combinations platinum-ruthenium, platinum-rhenium, and platinum-tin were shown to exhibit enhanced catalytic activity relative to catalysts consisting of platinum alone.
  • Metal/carbon nanocomposites formed of metal nanoparticles supported on a carbon powder of high surface area are commonly used heterogeneous catalysts in both small- and large-scale chemical processes in various fields, particularly those involving hydrogenation/dehydrogenation reactions.
  • Bird In: Catalyst Supports and Supported Catalysts: Theoretical and Applied Concepts. Stiles, Ed., Buttersworth, Boston, pp. 107-137 (1987); Satterfield, In: Heterogeneous Catalysis in Industrial Practice. McGraw-Hill, New York (1991).
  • Heterogeneous catalysts comprising bimetallic alloy nanoparticles as the active catalyst have been of great interest because of their unique chemical reactivity.
  • Such carbon-supported nanoparticles are useful fuel cell catalysts.
  • Catalysts that have been studied include PtRu, P Ru, and PtPb. Gasteiger et al., J. Electrochem. Soc. 141:1796 (1994); Hamnett et al., J. Electrochimica Acta 33:1613 (1988); Watanabe et al.. J. Electroanal. Chem. 229:396 (1987).
  • These catalysts have also been investigated for use as anode catalysts in fuel cells. For a fuel cell to work efficiently, a good cathode catalyst is also required.
  • Pt-Ru nanoparticles supported on an electrically conductive carbon support of high surface area such as
  • VULCANTM Carbon XC-72R, Cabot Corporation are now recognized as highly reactive anode catalysts in DMFCs. Hamnett, Catal. Today 38:445 (1997); Hogarth et al., Platinum Metals Rev. 40:150 (1996); Chandler et al., Platinum Metals Rev. 41 :54 (1997); Ralph. Platinum Metals Rev. 41 :102 (1997); Hamnett et al.. Chem. Ind. 480 (1992); Ren et al., Electrochem. Soc. 143:L12 (1996); Hogarth et al., Proc. First Intern.
  • Ru 1 /Vulcan carbon powder nanocomposites are now commercially available, e.g. from ElectroChem, Inc., Woburn, MA; E-TEK, Inc., Natick, MA; Electrosynthesis Co., Inc., Lancaster, NY; and, Johnson Matthey Pic, Hertfordshire, England.
  • Carbon-supported metal or metal alloy nanocomposites containing Pt (or Pd) are commonly prepared using various impregnation/reduction or chemical vapor deposition methods.
  • a typical procedure involves impregnation of powdered carbon by solutions of Pd or Pt salts followed by drying and subsequent chemical reduction of the metal ions to the metal.
  • Bird In: Catalyst Supports and Supported Catalysts: Theoretical and Applied Concepts. Stiles, Ed., Buttersworth, Boston, pp. 107-137 (1987); Satterfield, In: Heterogeneous Catalysis in Industrial Practice. McGraw-Hill, New York (1991).
  • Pt-Ru/Vulcan carbon composites are usually synthesized by either co-deposition of Pt and Ru from aqueous solutions of platinum and ruthenium salts upon chemical reduction or by co-deposition of Pt and Ru from aqueous solutions of the sulfito complexes, N 6 [Pt(SO 3 ) A and NaJRu ⁇ SO.,),], following the Watanabe procedure . Watanabe et al., Electroanal. Chem. Interfacial Electrochem. 229:395 (1987).
  • Metal alloy/carbon nanocomposites have also been prepared using cluster complexes as molecular precursors to attempt to better control the relative metal stoichiometry of the metal alloy particles. Ichikawa, M. Adv. Catal. 38:283 (1992).
  • Fe-Ru and Fe-Mn/carbon composites have been prepared from mixed-metal carbonyl cluster complexes as precursors. Kaminsky et al., J. Catal. 91 :338 (1985); Venter et al., J. Catal. 103:450 (1987).
  • cluster-type polymetallic precursors at least one atom of one of the metals is directly bonded to an atom of the second metal in the cluster.
  • Pt-Ru composites with a PtRu 5 stoichiometry on carbon have been formed from a PtRu5C(CO)i6 cluster precursor. Nashner et al., J.Am.Chem.Soc. 119, 7760- 7771 (1997).
  • nanocomposites and precursors for making such composites which are commercially economical and which provide desirable and controlled mixed metal nanocluster stoichiometries of at least a 1 :1 ratio and preferably with at least 50% platinum.
  • M is an atom of the first metal
  • X is a thermally degradable ligand having a degradation temperature lower than degradation temperatures of M and M'
  • M' is an atom of the first metal or the second metal
  • n and p are each at least one.
  • the polymetallic precursors are selected from the group consisting of Pt(triphenylphosphine)(Cl)( ⁇ -Cl 2 )Ru(Cl)- trihapto :trihapto-2,7-dimethyloctadienediyl); ⁇ Pt., [ ⁇ -bis(diphenylphosphino)- ethane] 3 (Ru)(pentahapto-cyclopentadienyl) ⁇ [hexafluorophosphate]; [Ru( ⁇ -2,3-bis(2- pyridyl)quinoxaline)PtCl2)- ⁇ ]-[tetrafluoroborate] ⁇ ; ⁇ P [ ⁇ -bis(diphenylphosphino)- memane] ⁇ ,-Mo)(pentahapto-cyclopentadienyl)(CO) ⁇ [hexafluorophosphate] ; ⁇ P [ ⁇ - bis(diphenylphosphino)
  • a method of making a supported polymetallic nanoparticle is also included in the invention.
  • the method comprises contacting a support with a polymetallic precursor comprising at least one first metal and at least one second metal and at least one metal-ligand-metal group represented by the formula:
  • M is an atom of the first metal
  • X is a thermally degradable ligand having a degradation temperature lower than degradation temperatures of M and M'
  • M' is an atom of the first metal or the second metal
  • n and p are each at least one.
  • the contacted support is heated in the substantial absence of an oxidizing agent to form a supported polymetallic nanoparticle comprising the first metal and the second metal at a selected atomic ratio, wherein the selected atomic ratio is approximately equal to a stoichiometric ratio of the first metal to the second metal in the polymetallic precursor.
  • the invention also includes a method of making a supported polymetallic nanoparticle, which comprises contacting a conductive support with a polymetallic precursor comprising at least one first metal and at least one second metal and at least one thermally degradable ligand.
  • the contacted support is heated in the presence of an oxidizing agent to a first temperature to initiate degradation of the ligand.
  • the contacted support is then heated to a second temperature in the substantial absence of an oxidizing agent to form a supported polymetallic nanoparticle comprising the first metal and the second metal at a selected atomic ratio, wherein the selected atomic ratio is approximately equal to a stoichiometric ratio of the first metal to the second metal in the polymetallic precursor.
  • the invention further includes a supported nanocomposite which comprises an electrically conductive support and a plurality of polymetallic nanoparticles which comprise at least one first metal and at least one second metal and which are formed from a polymetallic precursor comprising a metal-ligand-metal group represented by the formula: M n - X - M' p
  • M is an atom of the first metal
  • X is a thermally degradable ligand having a degradation temperature lower than degradation temperatures of M and M'
  • M' is an atom of the first metal or the second metal
  • n and p are each at least one.
  • the stoichiometric ratio of the first metal atoms to the second metal atoms in the polymetallic precursor is approximately equal to a selected atomic ratio of the first metal atoms to the second metal atoms in the polymetallic nanoparticles.
  • a supported nanoparticle is further within the invention which includes an electrically conductive support and a plurality of polymetallic nanoparticles, wherein the polymetallic nanoparticles comprise at least one first metal and at least one second metal and are formed by contacting the conductive support with a polymetallic precursor having the at least one first metal, the at least one second metal and at least one thermally degradable ligand, heating the contacted support in the presence of an oxidizing agent to a first temperature to initiate degradation of the ligand, and further heating the contacted support to a second temperature in the substantial absence of an oxidizing agent, wherein a stoichiometric ratio of the first metal atoms to the second metal atoms in the polymetallic precursor is approximately equal to a selected atomic ratio of the first metal atoms to the second metal atoms in the polymetallic nanoparticles.
  • the invention includes a fuel cell catalyst composition which comprises a supported nanocomposite.
  • the supported nanocomposite comprises an electrically conductive support and a plurality of polymetallic nanoparticles.
  • the nanoparticles are formed from a polymetallic precursor comprising a metal-ligand-metal group represented by the formula:
  • M is an atom of the first metal
  • X is a thermally degradable ligand having a degradation temperature lower than degradation temperatures of M and M'
  • M' is an atom of the first metal or the second metal
  • n and p are each at least one.
  • the stoichiometric ratio of the first metal atoms to the second metal atoms in the polymetallic precursor is approximately equal to a selected atomic ratio of the first metal atoms to the second metal atoms in the nanoparticles.
  • a fuel cell catalyst composition is also within the scope of the invention which comprises a supported nanocomposite, wherein the nanocomposite comprises an electrically conductive support and a plurality of polymetallic nanoparticles, and wherein the polymetallic nanoparticles comprise at least one first metal and at least one second metal and are formed by contacting the conductive support with a polymetallic precursor having the at least one first metal, the at least one second metal and at least one thermally degradable ligand, heating the contacted support in the presence of an oxidizing agent to a first temperature to initiate degradation of the ligand, and further heating the contacted support to a second temperature in the substantial absence of an oxidizing agent, wherein a stoichiometric ratio of the first metal atoms to the second metal atoms in the polymetallic precursor is approximately equal to a selected atomic ratio of the first metal atoms to the second metal atoms in the polymetallic nanoparticles.
  • the invention also includes a method for making a metallic nanocomposite which comprises contacting a support with a metallic precursor having at least one metal and at least one degradable ligand, wherein the degradation temperature of the at least one ligand is lower than the degradation temperature of the metal in the precursor.
  • the contacted support is heated in the substantial absence of an oxidizing agent by microwave radiation to degrade the at least one ligand and form a metallic nanocomposite.
  • Fig. 1 is the energy dispersive spectrum (EDS) for nanocomposite Composite 7 formed in accordance with Example 1 ;
  • Fig. 2 is the x-ray diffraction (XRD) pattern of the nanocomposite
  • Fig. 3 is the EDS spectrum of the nanocomposite Composite 8 formed in accordance with Example 1 ;
  • Fig. 4 is the XRD diffraction pattern of the nanocomposite Composite 8 formed in accordance with Example 1 ;
  • Fig. 5 is the EDS spectrum of the nanocomposite Composite 9 formed in accordance with Example 1 ;
  • Fig. 6 is the XRD diffraction pattern of the nanocomposite Composite 9 formed in accordance with Example 1 ;
  • Fig. 7 is the EDS spectrum of the nanocomposite Composite 12 formed in accordance with Example 2.
  • Fig. 8 is the XRD diffraction pattern of the nanocomposite Composite 12 formed in accordance with Example 2;
  • Fig 9 is the EDS spectrum of the nanocomposite Composite 15 formed in accordance with Example 2.
  • Fig. 10 is the XRD diffraction pattern of the nanocomposite Composite 15 formed in accordance with Example 2;
  • Fig. 11 is an XRD diffraction pattern of a palladium nanocomposite formed in accordance with Example 3;
  • Fig. 12 is an XRD diffraction pattern of a platinum nanocomposite formed in accordance with Example 3;
  • Fig. 13 is an XRD diffraction pattern of a platinum-ruthenium (Pt ⁇ Ru,) nanocomposite formed in accordance with Example 3;
  • Fig. 14 is an XRD diffraction pattern of the platinum-tin (PtSn) nanocomposite formed in accordance with Example 12;
  • Fig. 15 is an XRD diffraction pattern of the platinum-tin (P Sn) nanocomposite formed in similar to that described in Example 13;
  • Fig. 16 is an XRD diffraction pattern of the platinum-molybdenum
  • Fig. 17 is an XRD diffraction pattern of the platinum-ruthenium (Pt,Ru) nanocomposite formed in accordance with Example 10;
  • Fig. 18 is a schematic representation of the molecular structure of the tetrametallic precursor, ⁇ Pt,[ ⁇ -bis(diphenylphosphino)methane],[ ⁇ ,-Hg-
  • Fig. 19 is a schematic representation of the structure of the molecular core of the precursor of Fig. 18;
  • Fig. 20 is a schematic representation of general structure of the molecular structure of tetrametallic precursor, ⁇ P ⁇ - bis(diphenylphosphino)methane] , [ ⁇ -Hg-Ru(pentahapto- cyclo ⁇ entadienyl)(CO) 2 ] 2 ⁇ [PF 6 ] 2 ;
  • Fig. 21 is an EDS spectrum of the platinum-ruthenium (Pt ⁇ Rv ) nanocomposite formed in accordance with Example 19;
  • Fig. 22 is a graphic representation of the thermal gravimetric analysis of the platinum-ruthenium (Pt,R ⁇ ) nanocomposite formed in accordance with Example 19; and Fig. 23 is the XRD diffraction pattern of the platinum-ruthenium
  • the field of the invention is catalysis, particularly fuel cell catalysts useful for DMFCs.
  • the invention includes fuel cell catalyst compositions having supported nanocomposites which include electrically conductive supports and a plurality of polymetallic nanoparticles, supported nanocomposites, methods for making supported polymetallic nanoparticles, and novel polymetallic precursors for use in making nanocomposites.
  • the invention includes a method of making a metallic nanocomposite from both novel and known precursors by using novel microwave radiation heating.
  • the methods for making nanocomposites in accordance with the invention may use polymetallic precursors of both cluster and non-cluster types, and involve depositing them on or within a support and thermally treating them as described herein, such that the precursors decompose by degradation of the ligands in the precursor to form polymetallic metal alloys.
  • Polymetallic as used herein is intended to include bimetallic, trimetallic, tetrametallic and so forth.
  • the method for forming nanocomposites using microwave radiation in accordance with the invention may be used with any metallic precursor, singular or polymetallic, to quickly form high quality nanocomposites having stoichiometries of commercial importance.
  • a significant feature of the method described herein for making polymetallic nanocomposites is that a commercially desirable stoichiometry can be predetermined for the nanoparticles in the nanocomposite, and a precursor thereby selected to provide that stoichiometry.
  • This concept is expressed herein with reference to a "selected atomic ratio" of first metal atoms to second metal atoms in the nanoparticles which represents a predetermined, preferably commercially desirable atomic ratio for the nanoparticles in the nanocomposite.
  • the selected atomic ratio also encompasses nanocomposites having nanoparticles of three of more metals atoms in which there is a predetermined, preferably commercially desirable atomic ratio of the first to second metal atoms in the nanoparticles, the second to the third metal atoms and so forth.
  • the selected atomic ratio in the nanoparticles is achieved by selecting a precursor having a stoichiometric ratio of first metal atoms to second metal atoms, and second metal atoms to third metal atoms and so forth for three or more metal atoms, which is approximately equal, and preferably is equal, to the selected atomic ratio(s) in the polymetallic nanoparticles.
  • Polymetallic precursors of the invention preferably have a stoichiometric ratio of the first metal to the second metal which is approximately equal to, and preferably equal to, the selected atomic ratio in a nanocomposite formed from such a precursor. "Approximately equal to” as used herein means that the stoichiometric ratio does not differ from the atomic ratio by more than 20% of the value of the atomic ratio as measured by EDS, chemical microanalysis or other experimentation yielding a similar degree of accuracy.
  • novel polymetallic precursors according to the invention have at least one first metal and at least one second metal, and at least one metal-ligand-metal group wherein the ligand is a thermally degradable ligand.
  • the thermally degradable ligand is preferably interposed between at least one first metal atom and at least one other metal atom in the precursor, as a bridging ligand according to the formula
  • M represents an atom of the first metal in the precursor
  • X is the thermally degradable ligand
  • M' may be an atom of either the first or second metal in the precursor.
  • the ligand X may act as a bridging ligand between two different metals in the precursor, or two of the same metals in the precursor. Other non-bridging ligands, which are preferably also thermally degradable, may also be attached to only one metal or to another thermally degradable group. More preferably, the ligand X is a bridging ligand which connects two different metals in the precursor which will form the polymetallic alloy in a nanocomposite formed from the precursor. For example, if a platinum ruthenium nanocomposite is to be formed, the first metal is platinum, and the second metal in the precursor is ruthenium.
  • At least one thermally degradable ligand extends between at least one platinum atom and at least one ruthenium atom in the precursor.
  • the ligand may also extend between two platinum atoms, between two ruthenium atoms, or be simply attached to one of the metal atoms or to other thermally degradable ligands or groups.
  • the ligand(s) X in the novel polymetallic precursors according to the invention may be selected from numerous elements or groups so long as they are thermally degradable ligands which have a degradation temperature lower than the degradation temperature of the at least one first metal, the at least one second metal or any other metals which are desired in the final nanoparticle alloys.
  • substituents may be single atoms, compounds or larger moieties and may include, but are not limited to, halogen atoms such as chlorine and mercury atoms, phosphorus atoms, other main group metal atoms from Groups 14-17 of the Periodic Table such as sulfur and selenium and compounds of these elements, and organic or substituted organic ligands such as alkyl, alkenyl, alkynyl, aryl, aralkyl, alkylphosphino, arylphosphino, alkylsulfido, arylsulfido, alkylselenide, arylselenide, alkylmercuric, arylmercuric, and other groups such as carbon monoxide, ammonia, amines, alkenes, heteroatomic aromatic molecules, arsenes, and derivatives, and substituted and unsubstituted versions of the compounds and moieties.
  • halogen atoms such as chlorine and mercury atoms
  • the organic group has from one to 50 carbon atoms.
  • all of the precursor is thermally degradable, including bridging and non-bridging ligands, with the exception of the core metals, i.e., the first and second metals (or higher numbers of metals for ternary or higher alloys), which would form the alloy phase of a nanocomposite formed from the precursor.
  • the degradation temperature of the thermally degradable ligand(s) is the temperature at which the ligands substantially dissociate from the metal atoms by volatilizing, by substantially destroying the bonds between the ligands and the metal atoms such that the ligands are vaporized or otherwise substantially separated from the metal, or by chemically reacting with gases used during thermal treatment and leaving as volatilized compounds.
  • Preferably all of the ligand(s) degrade. However, it will be understood, based on this disclosure, that some amount of organic or inorganic residue may be retained in the final composite. However, it is intended that the ligands are at least substantially removed by degradation.
  • the thermal degradation temperature of the ligands is preferably lower than the degradation temperature for the core metal(s) in the precursor which are intended to form the alloy phase of a nanocomposite formed from the precursor.
  • the degradation temperature of the metals refers to a temperature sufficiently high such that the metals are substantially destroyed or otherwise removed through chemical reaction with gases during thermal treatment and subsequent volatilization, or are otherwise substantially volatilized by thermal treatment. It should be understood, based on this disclosure, that degradation of precursors could produce intermediate metal compounds such as metal oxides, metal phosphides and other metal substances. As such, the degradation temperature of the metals would preclude retention of metals in the form of oxides, derivatives or other intermediate forms.
  • degradation of the ligands occurs according to the invention, it occurs at a temperature sufficient to substantially remove the ligands from the metals while leaving the metals behind as metal atoms, compounds or intermediates, and preferably in a substantially pure, alloy state.
  • the precursor By forming a precursor in which the ligand(s), preferably the bridging ligands, and more preferably all of the precursor with the exception of the core metals are thermally degradable, either by heat or chemical reaction, at a temperature lower than the degradation temperature of the metals, the precursor is easily destroyed leaving only the core metals for forming the alloy phase behind.
  • the temperature used for destroying the precursor and forming the alloy must be chosen such that the degradation temperature of the thermally degradable ligands (other than the desired atoms or groups) is lower than the degradation temperature of the desired atoms or groups and also lower than the degradation temperature of the core metals for forming the alloy.
  • the reaction of desired atoms and groups with gases introduced during thermal treatment should be avoided to prevent reactions forming volatilizable compounds from the desired atoms or groups.
  • substantially every atom of every ligand bound to a first metal atom or to a second metal atom is thermally degradable therefrom with the exception of groups which may be desired in the final nanocomposite formed from the precursor for some applications.
  • degradation of "substantially every atom" herein means that all but core metals and/or desired atoms or groups in combination with core metals are intended to be thermally degradable. In certain situations, as described above, it is desirable that an atom of one or more ligands is not thermally degradable from the precursor.
  • composition of the nanoparticle comprise phosphorus
  • a polymetallic precursor comprising a phosphorus-containing ligand may be used, so that when the precursor is subjected to thermal treatment all of the atoms of the ligand dissociate from the metal atoms of the precursor with the exception of one or more phosphorus atoms.
  • ligands include phosphorus atoms and compounds, and phosphorus-containing molecules such as diphenylphosphino and diphenylphosphino methane moieties, and trialkyl phosphino moieties such as triethylphosphine, triarylphosphino moieties such as triphenylphosphine, bisphosphino moieties such as bis(diphenylphosphino)methane, and other similar organic phosphorus-containing molecules.
  • the same precursors having phosphino or similar moieties can be used to form nanocomposites without such groups if the method of making the nanocomposite is adjusted accordingly as discussed below.
  • the polymetallic precursors of the invention preferably have at least two different metals in varying stoichiometric ratios and are chosen depending on the selected atomic ratio for nanoparticles formed from the precursors.
  • Exemplary combinations of metals in the precursors are platinum-tin, platinum-ruthenium, platinum-tungsten, platinum-osmium, platinum-iridium, platinum-rhodium and platinum-gold which, using a stoichiometry in the precursor which is approximately that of the nanocomposite formed from the precursor, nanocomposites having desired commercial selected atomic ratios can be formed, e.g., PtSn, PtSn and PtP 2 , Pt,Sn, Pt 3 Sn and PtP 2 , PtAu, PtAu and PtP 2 , P ⁇ W, and Pt-,W and PtP 2 , PtRu, Pt 3 Ru, Pt,Mo, RuMo, and others.
  • Preferred, novel polymetallic precursors which have been formed in accordance with the present invention include a precursor having a trigonal- bipyramidal Pt,Hg 2 moiety, preferably, ⁇ Pt 3 [ ⁇ -bis(diphenylphosphino)methane] 3 [ ⁇ - Hg-Ru(pentahapto-cyclopentadienyl)(CO) 2 ] 2 ⁇ [hexafluorophosphate] 2 ; as well as Pt(triphenyl ⁇ hosphine)(Cl)( ⁇ -Cl 2 )Ru(Cl)(triha ⁇ to:trihapto-2,7-dimethyloctadienediyl);
  • the polymetallic precursor of the invention there are at least two different types of metals, referred to herein for reference as a first metal and a second metal, although it should be understood, based on this disclosure, that there may also be a third or more metals in the precursor. It should also be understood that while there are preferably two or more different metals in the precursor, there may be at least one atom of each of the first metal and the second metal.
  • the first metal is preferably a noble metal such as platinum, palladium, gold, or any other transition metal or Lanthanide metal.
  • the at least one second metal may be any of the metals acceptable for the at least one first metal including metals from Groups 13-16, like tin; however, the at least one first metal is preferably different from the at least one second metal.
  • the at least one first metal is a noble metal and the stoichiometric ratio of the first metal atoms to the second metal atoms in the precursor is greater than or equal to about one such that there is preferably at least 50 at% of the first metal in the precursor and resulting nanoparticles.
  • the at least one second metal in another embodiment is also a noble metal.
  • the first metal is platinum and the second metal is at least one of tin, ruthenium, tungsten, gold, molybdenum, rhenium, osmium, and palladium, and the stoichiometric ratio of platinum to the second metal(s) is equal to at least about one such that there is at least 50 at% platinum in the precursor and resulting nanocomposite.
  • the polymetallic precursors which are useful in the methods described herein may be made using any suitable method, including known techniques or other techniques which may be developed in the art. Typical methods for synthesizing precursors are included in the Examples herein.
  • the precursors of the invention may be cluster and non-cluster types. In the method for forming nanocomposites as discussed below, which may be practiced using the novel precursors, or under certain circumstances, using any polymetallic precursor, it is preferred in some instances to use non-cluster types as they are easier to synthesize with a known stoichiometry which is to be the approximately equal to the selected atomic ratio of the nanoparticles formed from the precursors.
  • cluster precursors according to the present invention which have the desired commercial stoichiometries or which otherwise contain a desired metal-ligand-metal group within the precursor structure between one or more of the metals and having the criteria described above, may be used in accordance with the invention.
  • the invention also includes methods of making a supported polymetallic nanoparticle.
  • the invention includes a method in which a support is contacted with a novel polymetallic precursor according to the present invention and the contacted support is heated in the substantial absence of an oxidizing agent.
  • the invention includes a method in which a conductive support is contacted with any suitable polymetallic precursor, the contacted support is heated in the presence of an oxidizing agent and then further heated in the substantial absence of an oxidizing agent.
  • novel polymetallic precursors for use in the first embodiment may be any of the novel precursors above wherein the precursor have at least one first metal, at least one second metal and at least one metal-ligand-metal group including two metal atoms, which may be the same or different, interconnected by a thermally degradable ligand which has a degradation temperature lower than the degradation temperature of the metals to which it is bonded and in the precursor.
  • the first and second metals and metal-ligand-metal groups may be any of those described above with respect to the novel precursors of the present invention.
  • the polymetallic precursors are the novel precursors described above and which meet the above criteria.
  • the polymetallic precursor may be any bimetallic or higher precursor having a first metal and a second metal, such as those described above, and at least one thermally degradable ligand.
  • the thermally degradable ligand need not be interposed between two metal atoms, and may be any of the thermally degradable ligands described above with respect to ligand X in the novel precursors of the present invention.
  • the precursors may be the novel precursors listed above as well as any bimetallic or higher precursors conventionally used or to be developed for nanocomposite forming methods provided the precursor selected has at least two different metals and the thermally degradable ligands have degradation temperatures lower than the degradation temperature of the core metals as those terms are described and defined above.
  • the polymetallic precursors have a stoichiometric ratio of the first metal atoms to the second metal atoms which is approximately equal to the selected atomic ratio of first metal atoms to second metal atoms in the nanocomposite formed by the methods of the present invention.
  • Exemplary precursors which may be used in either embodiment of the methods of the present invention include the preferred, novel precursors listed above as well as the precursors such as ⁇ Ru(2,2'-bipyridine) 2 PtCl 2 ( ⁇ - bipyrimidine) ⁇ [hexafluorophosphate] 2 ; Pt(triphenylphosphine) 2 (phenyl)- Sn(phenyl) 2 Cl; Pt(triethylphosphine) 2 (Cl)Sn(Cl 3 ); ⁇ Pt,[ ⁇ -bis(diphenylphosphino)- methane],( ⁇ 3 -SnF,)( ⁇ 3 -CO) ⁇ [hexafluorophosphate]; ⁇ Pt 3 ( ⁇ 3 -Au(triphenyl- phosphine)[ ⁇ -bis(diphenylphosphino)methane], ⁇ [hexafluorophosphate]; and Mo(heptahapto-cycloheptatrieny
  • the polymetallic precursor is deposited onto or within a support, for example by suspending the precursor in a liquid, contacting the liquid with the support, and evaporating the liquid or by using incipient wetness techniques.
  • Thermal treatment of the precursor causes the thermally degradable ligand(s) of the precursor to dissociate from at least one first metal atom and from at least one second metal atom of the precursor, whereby first metal atoms and second metal atoms may combine under thermal treatment to form an alloy having an atomic ratio approximately equal to the stoichiometric ratio of the first metal to the second metal in the precursor.
  • Formation of a catalyst having the selected atomic ratio of the first metal to the second metal may be improved if the thermal decomposition is performed in the substantial absence of an oxidizing agent, and preferably in the presence of a reducing agent such as hydrogen.
  • the substantial absence of an oxidizing agent is intended to mean that the atmosphere includes little or no oxidizing agents, although limited amounts of oxidizing agent may be present.
  • a reducing thermal treatment it is not preferred.
  • formation of a nanoparticle comprising a desired metal alloy may be affected by the rate of heating during the thermal treatment. Cooling may typically be performed by allowing the nanoparticles to come to room temperature naturally or by quenching. Known heating regimens are therefore included within the thermal treatments of the method of the invention.
  • Catalysts particularly fuel cell catalysts, prepared using this method to generate polymetallic nanoparticles on a conductive support have utility as either anode or cathode fuel cell catalysts, particularly in DMFCs.
  • the methods of the invention may also be used to generate polymetallic nanoparticles having the metal composition of many known polymetallic catalysts.
  • the skilled artisan in the field of catalysis is enabled by this disclosure to prepare catalysts comprising nanoparticles which have these known metal compositions, and such catalysts and the methods of making them are included in the present invention.
  • selected atomic ratios among the three or more metals in the polymetallic nanoparticles of the catalyst are obtained by selecting a polymetallic precursor having stoichiometric ratios among the three or more metals approximately equal to the selected atomic ratios.
  • the polymetallic precursor may be contacted with the support in a number of ways.
  • the precursor may be dissolved or suspended in a liquid, and the support may be mixed with the liquid having the dispersed or suspended precursor. The dissolved or suspended precursor is thus enabled to adsorb onto a surface of the support or to be absorbed by the support.
  • the precursor may also be deposited onto a surface of the support by removing the liquid, such as by evaporation such that the precursor remains on the support.
  • the liquid may be substantially removed from the support prior to thermally treating the support in accordance with the method of the invention, such as by heating the support at a temperature lower than the temperature achieved during subsequent thermal treatment or by reducing the pressure of the atmosphere surrounding the support.
  • the support is dried prior to heating it.
  • the support may be a bulk article such as a metal rod, or a microscopic article such as a particle of particulate carbon.
  • the support may include substantially any material which, when heated to a temperature at which a polymetallic precursor is converted to a polymetallic nanoparticle on the surface thereof, does not melt, vaporize completely, or otherwise become incapable of supporting polymetallic nanoparticles.
  • the support be conductive.
  • the fuel cell support exhibits a conductivity sufficiently high as to not limit current flow used by a working fuel cell.
  • the most preferred support for use with the precursors and for use in fuel cell catalyst compositions according to the invention is carbon in a particulate form, such as carbon black.
  • the particulate carbon has a mean particle diameter less or equal to than about 30 nanometers or a surface area of at least about
  • the inventors have determined that the carbon black product having the trade name VulcanTM XC-72R carbon, which is available from Cabot Corporation,
  • Non-conductive supports may be used in connection with the method according to the present invention based on the novel precursors of the invention as well as the further embodiment of the method according to the invention based on microwave heating as described further below.
  • Suitable non-conductive supports include xerogels, aerogels and the like.
  • the precursor-contacted support is preferably heated to a temperature equal to or greater than the thermal degradation temperature of the thermally degradable ligand(s) X, and preferably all such thermally degradable ligands in the precursors as described above.
  • the preferred heating temperature will depend to a large degree on the particular thermally degradable ligands used and the degradation temperature of the core metals and any other desired groups which are to remain in the nanoparticles. However, the preferred temperature is at least 350 °C, and more preferably at least 650°C, including temperatures as high as 700°C.
  • the heating of the precursor-contacted support occurs in the substantial absence of an oxidizing agent in each of the above described embodiments of the methods of the invention.
  • heating in the substantial absence of an oxidizing agent occurs subsequently to heating in the presence of an oxidizing agent and is a final heat treatment step which may or may not be followed by annealing as described below.
  • the support is heated in the presence of a reducing agent, for example, a hydrogen-containing gas such as getter gas, to improve the amount of polymetallic precursor which is converted to crystalline polymetallic nanoparticles.
  • a reducing agent for example, a hydrogen-containing gas such as getter gas
  • Getter gas is a mixture of about 10 volume percent hydrogen and about 90 volume percent nitrogen.
  • other reducing agents may be used.
  • the polymetallic nanoparticles having the same first and second metal atoms as the precursors in a selected atomic ratio are formed.
  • the selected atomic ratio of the metal atoms in the nanoparticles is approximately equal to, and preferably equal to, the stoichiometric ratio of the metal atoms in the precursor.
  • Thermal treatment of a support upon which a polymetallic precursor has been deposited may be performed, for example, as follows. A sample of the contacted support is placed into a ceramic boat which is then inserted into a quartz tube that is positionable within a tube furnace. Fittings on the quartz tube permit the control of gaseous environment surrounding the sample. The quartz tube can be purged with gas
  • Thermal treatment of the sample can be controlled through automated regulation of the heating or cooling of the furnace. Heating rates are typically about 15°C per minute in the Examples described herein, but can be varied for different effects, preferably at rates of from about 10 to about 20 ° C/min. Thermal conditions and reactive atmospheres are chosen such that the molecular precursor(s) break down and degradation of the thermally degradable ligands occurs with nearly complete retention of the metal content of the precursor. Reduction of metals to the metallic state is assured using reducing thermal treatment, and formation of crystalline intermetallic or metal alloy nanoparticulates is achieved, for example, by thermal annealing.
  • the support before heating in the absence of an oxidizing agent or reducing agent, is initially heated in the presence of an oxidizing agent from about room temperature (about 25 °C) to a temperature sufficient to initiate degradation of the ligand(s) in the precursors, preferably to a temperature from about 250 to about 500 °C, and more preferably to a temperature from about 280 to about 450 °C.
  • the support is then heated as noted above in the substantial absence of an oxidizing agent and/or in the presence of a reducing agent to a temperature sufficient to initiate reduction of any metal intermediates formed during oxidation and to complete degradation of the degradable ligand(s) in the precursor, preferably to the preferred temperatures noted above with respect to final heating in the substantial absence of an oxidizing agent such that crystalline polymetallic nanoparticles are formed in or on the support. While it is theorized that such metal intermediates include metal oxides and/or suboxides, the inventors herein do not know the exact intermediate species formed.
  • a ligand of a polymetallic precursor comprises an atom or group which is not easily thermally degradable from a metal atom of the precursor.
  • atoms or groups of atoms may be those which are in some instances tolerable or desirable, such as those described above based on phosphorus, sulfur and the like, but which for other purposes are not desirable in the final alloy.
  • the atoms may be dissociated from the metal atom by formation of intermediate, oxidized reaction products of the ligand, presumably metal oxides, and the intermediate may thereafter be reduced so that the metal atom may be incorporated into a polymetallic nanoparticle without the atom or group.
  • the "substantial absence of an oxidizing agent" as noted above indicates that the atmosphere includes little or no oxidizing agents, although limited amounts of oxidizing agent may be present. More specifically, the "substantial absence of an oxidizing agent” as used herein means in the presence of a gas which does not comprise enough of a oxidizing agent to cause oxidation of 25% or more of the metal atoms of the precursors during the thermal treatment. Preferably, virtually no oxidizing agent is present under such conditions.
  • the final thermal treatment is performed in the substantial absence of an oxidizing agent.
  • Polymetallic nanoparticles are formed on the surface of or within the support as a result of the final heating step.
  • Thermal treatment in the presence of an oxidizing agent facilitates one or more of the following functions: degradation of the ligand(s), deposition of the metal atoms of the precursor on the support, inhibition of agglomeration of deposited metal atoms into large metallic complexes, thereby preventing formation of large or non-homogeneously-sized particles, and minimization of the loss of metal atoms from the support during the thermal treatment.
  • the support may be heated by convection, by conduction, or by absorption of radiation, such as infrared radiation, by the support.
  • microwave heating of the support is used and yields improved nanocomposite properties, as further described below.
  • the microwave heating method includes contacting a support susceptible to microwave heating, for example, the carbon described above, with a precursor having at least one metal and at least one degradable ligand which has a degradation temperature lower than the degradation temperature of the metal.
  • the degradation temperature is as described above with respect to the polymetallic precursors and other embodiments of methods of the present invention.
  • any singular metallic precursor such as supported Pt, Mo, Ru and the like, in addition to any of the conventional and novel polymetallic precursors described above may be used, regardless of whether such precursors are known or unknown.
  • the contacted support is then heated in the substantial absence of an oxidizing agent by microwave radiation to the preferred temperatures noted above for formation of polymetallic nanoparticles.
  • An intermediate heating step in the presence of an oxidizing agent may also be incorporated in this method as described above wherein the support is heated to a temperature sufficient to initiate degradation followed by heating to the final heating temperature in the substantial absence of an oxidizing agent.
  • the support is contacted prior to heating in accordance with the contacting steps noted above for the method of making a nanocomposite in accordance with the invention.
  • microwave heating embodiment of the invention relates to the fact that various types of carbon black interact with microwave irradiation, leading to a sharp rise in temperature due to dielectric loss.
  • Galema Chem. Soc. Rev. 26:233 (1997); Sutton, Am. Ceram. Soc. Bull. 68:376 (1989).
  • the use of microwave technology not only provides improved nanocomposites from various precursors, but does so in a significantly short treatment time as demonstrated below in the Examples herein.
  • Vulcan carbon XC-72R which has high electrical and thermal conductivity, is efficiently heated under microwave irradiation.
  • Microwave irradiation of a particulate carbon contacted with, coated with or impregnated with a single metal precursor or polymetallic precursors under appropriate atmospheres has herein been shown to directly afford metal or metal alloy/particulate carbon nanocomposites of excellent uniformity in the metallic phase in less than one minute of total irradiation time.
  • the rate at which the contacted support is heated, the temperature to which it is heated, and the duration of heating affect the properties of the nanoparticles.
  • a slower rate of heating, a higher temperature, and a longer duration of heating all favor formation of larger nanoparticles and greater non-uniformity of nanoparticle size.
  • a faster rate of heating, a lower temperature, and a shorter duration of heating typically all favor formation of smaller nanoparticles and greater uniformity of nanoparticle size.
  • the step of final heating preferably includes thermally annealing the nanoparticles at the maximum final heating temperature for a period of time sufficient to form a desired crystalline nanoparticle structure and to promote particle growth.
  • the support is preferably cooled to around room temperature, for example between about 10°C and 30 °C by allowing the support to cool naturally.
  • support may be merely quenched or the rate of cooling controlled in order to form an alloy having favorable properties by using any known or to be developed metallurgical techniques, as would be apparent to one of ordinary skill in the art based on this disclosure.
  • the rate at which the support is cooled can affect the properties of the nanoparticles.
  • thermo annealing it is known in the art that maintaining a metal alloy at a particular temperature for a period of time (thermal annealing), cooling the alloy at a particular rate, or both, can affect the crystalline structure and the physical, mechanical, and chemical properties of the alloy. These effects are discemable both at the scale of bulk alloy and at the nanoparticle scale. Exemplary techniques such as those which are described in the Examples herein may be used to alter the properties of alloy nanoparticles. Thus, for example, the rate of heating the support may be controlled by increasing the temperature of the support at a particular rate, such as about 15 °C per minute.
  • the duration at which a nanocomposite is maintained at a particular temperature during annealing may be varied for achieving different particle sizes, and enhanced crystallinity for some materials.
  • the rate at which the nanocomposite is permitted to cool may also be varied to achieve similar property variations as would be apparent to those skilled in the art based on this disclosure and the Examples included herein.
  • the temperature conditions are controlled such that the nanoparticle which is formed has a mean diameter equal to or less than about twenty nanometers, and even more preferably equal to or less than about five nanometers.
  • the method may further comprise repeating the thermal treatments, contacting steps and/or the steps of precursor deposition to enhance crystalline growth and/or to increase metal loading on the support.
  • the thermally treated contacted support is contacted with the precursor a second time followed by additional thermal treatments as described above.
  • the contacted support is heated in the presence of an oxidizing agent as described above, contacted with the support a second time, followed by further heating in the presence of an oxidizing agent, and repetition of these steps to provide enhanced metal loadings prior to final thermal treatment in the substantial absence of an oxidizing agent or in the presence of a reducing agent.
  • Such repetitive treatments may continue until desired affects and/or preferred higher precursor on carbon loadings are achieved.
  • the support may be heated either in the presence of an oxidizing agent or without such an oxidizing agent, then contacted again with the precursor, and then heated in the substantial absence of an oxidizing agent or in the presence of a reducing agent. Such steps may then be repeated at least once, and more times if higher precursor on carbon loadings are desired.
  • the support may be contacted with the precursor multiple times prior to heating in the substantial absence of an oxidizing agent.
  • the invention also includes a supported nanocomposite which includes an electrically conductive support and a plurality of polymetallic nanoparticles preferably conductively connected to the support. The nanoparticles have at least one first metal and at least one second metal.
  • the first metal is preferably a noble metal, and the selected atomic ratio of the atoms of the first metal to those of the second metal is equal to or greater than one as described above with respect to the precursors according to the invention.
  • the nanoparticles are preferably formed from the novel polymetallic precursors according to the invention having the same first and second metals and at least one metal-ligand-metal group M -X-M' where M, M', X, n and p are as described above.
  • the nanoparticles are formed by contacting a conductive support with a polymetallic precursor having at least one first metal, at least one second metal and at least one thermally degradable ligand as described above, heating the contacted support in the presence of an oxidizing agent to a first temperature to initiate degradation of the ligand(s), and further heating the contacted support to a second temperature in the substantial absence of an oxidizing agent.
  • the stoichiometric ratio of first to second metal atoms in the polymetallic precursor chosen is preferably approximately equal, and more preferably equal, to the selected atomic ratio of first to second metal atoms in the nanoparticles. It is also preferred that the selected atomic ratio be at least about one such that there is at least about 50 at% of the first metal in the nanoparticles.
  • the nanoparticles are formed in accordance with the methods of the invention as described in detail above.
  • the precursor(s) used to form the nanoparticles may be any precursor useful in the methods described above according to the invention as described herein.
  • This supported nanoparticles may be included in a fuel cell catalyst composition, but is not limited to such a composition. Further, while it is preferred that the nanoparticles have a mean diameter less than or equal to about twenty nanometers and preferably less than or equal to about five nanometers, other variations are within the scope of the invention provided the above-described criteria are otherwise met.
  • Fuel cell catalyst compositions or other compositions including the nanoparticles of the invention and a conductive support preferably include at least about 0.5% by weight nanoparticles, and preferably at least about 40% by weight, and even more preferably at least about 50% by weight nanoparticles.
  • nanoparticles with a particle sizes of 1.5 - 2 nm.
  • the nanoparticles preferably have at least 50 atomic percent of the first metal which is preferably a noble metal such as platinum and as described above with respect to the precursors.
  • the nanocomposites are formed from one or more of the novel polymetallic precursors described above and preferably having at least one metal-ligand-metal groups as described above.
  • a standardized test DMFC having an anode including the supported nanocomposite composition of the invention exhibited an unoptimized current density
  • V anode potential is expected.
  • the nanoparticles in the nanocomposite of the present invention are preferably substantially formed of, and more preferably virtually solely formed of the crystalline alloy form of the first metal and the second metal.
  • crystalline alloy forms would include PtRu, PtSn, Pt 2 W, Pt 3 Sn, Pt 3 Ru, Pt 3 Mo, RuMo, mixtures of various of these forms with PtP 2 , and various other stoichiometric combinations of core metals of the precursors described herein.
  • the nanocomposites may also be used within fuel cell catalyst compositions which include the support and a plurality of nanoparticles as described above.
  • the composition may be formed into an electrode, such as an anode or cathode, for use in a fuel cell such as a DMFC by standard methods using standard ink electrode technology.
  • an electrode such as an anode or cathode
  • methanol is added to the fuel cell and contacts the electrode in the presence of oxygen, the oxidation of methanol is catalyzed by the nanoparticles and electrons extracted from methanol can be passed through the conductive connection of the particles to the support, and through the support to an external circuit, whereby direct current may be generated.
  • the invention includes a fuel cell catalyst composition comprising a supported nanocomposite.
  • the nanocomposite comprises an electrically conductive support and a plurality of polymetallic nanoparticles preferably conductively connected to the support.
  • the nanoparticles in the nanocomposite and/or the fuel cell catalyst composition are preferably are formed almost exclusively of a first metal and a second metal, more preferably from a noble metal and a second metal, and may further comprise a phosphide moiety or other desired moiety.
  • the nanoparticles and nanocomposite may be any of the above described nanocomposites.
  • the fuel cell is preferably a DMFC, and the catalyst composition may be within the anode or cathode, preferably the anode, of the fuel cell.
  • the nanocomposites, precursors and methods of the present invention have the potential for many other catalytic applications.
  • Adsorption of a known molecular precursor onto Vulcan XC-72R carbon was used to yield two different platinum/tin nanocomposite compositions, depending on the conditions of oxidative and reductive thermal treatments. Using this approach, platinum/tin nanoparticles comprising the two highest congruently melting Pt/Sn intermetallic phases were formed. Highly pure crystalline Pt,Sn nanoparticles have also been formed. The materials and methods used in the experiments presented in this Example are now described.
  • the chemical reagents, bis(diphenylphosphino)methane (“dppm”), dichloro(l,5-cyclooctadiene)platinum (II) ("Pt(COD)Cl 2 "), silver acetate, and tin (II) fluoride were purchased from Strem Chemical, Inc., Newbury Port, Massachusetts.
  • Trifluoroacetic acid, ammonium hexafluorophosphate, and sodium fluoride were purchased from Aldrich Chemical Company (St. Louis, MO).
  • Vulcan XC-72R carbon was obtained from the Cabot Corporation.
  • Getter gas was purchased from the Liquid Air, Inc., and had the composition, 10.3% by volume H 2 , 89.7% by volume N 2 ⁇ Reactions were performed in oven-dried glassware under a nitrogen or carbon monoxide atmosphere. Methylene chloride and acetone were dried by distillation from calcium hydride and molecular sieves using known methods. Tetrahydrofuran and ether were purified by distillation from NaK alloy/benzophenone. Water was purified using a commercial water purifying apparatus. Other solvents and reagents were used without further purification.
  • Pt(COD)Cl 2 in an amount of 0.75 g (2.00 mmol) was added, under a nitrogen atmosphere, to a 100 ml 3 -neck flask which contained a TeflonTM-coated magnetic stirring bar. To the flask was added 25 ml of methylene chloride, and the solution was stirred until the solid was completely dissolved. To this stirred solution, a solution comprising bis(diphenylphosphino)methane (“dppm”) (0.77 g, 2.00 mmol) in 25 ml of methylene chloride was added dropwise over a 3 -hour period from an addition funnel under a nitrogen atmosphere.
  • dppm bis(diphenylphosphino)methane
  • reaction (XV) 15 °C/min in an air atmosphere. After the temperature had reached 280°C, the temperature was held constant, and the atmosphere was purged with nitrogen for 10 minutes. The temperature was then increased at a rate of 15 °C/min under a getter gas atmosphere until it reached 650 °C as shown below in reaction (XV).
  • the thermal treatment that was used was one that left the molecular precursor metal stoichiometry which was somewhat impure.
  • the particles were crystalline enough to produce an adequate selected area diffraction (SAD) ring pattern.
  • SAD selected area diffraction
  • PtSn and PtP 2 particle diameters exhibited a monomodal distribution of particle sizes ranging from 8.3 to 20.0 nm, with an average particle diameter of 12.7 nm measured by TEM, as indicated in Table 1 below.
  • the energy dispersive spectrum (EDS) of Composite 7 indicated the presence of PtL , PtL «, PtL , PtM , PtMo, SnL , and SnLo emissions.
  • EDS analysis also indicated the presence of CuK and CuK ⁇ emissions, due to the copper sample holder used for TEM analysis. These two copper emissions are therefore always present in the EDS spectra described herein.
  • Table 3 shows a comparison of PtSn and PtP 2 d-spacing data (in angstroms) obtained by SAD (and as shown in Table 2) with other known PtSn phases (top half) and a listing of important (non-PtSn and PtP 2 ) reflections not observed for Composite 7 (bottom half).
  • the indication xxx in the top half of Table 3 indicates that no reflections matching the observed d-spacings are possible in the particular phase listed.
  • the numbers in parentheses represent relative intensities of reflections for important indentifying reflections of the other known PtSn phases in Table 3 which were not observed in Composite 7.
  • a second series of doping and thermal treatments were performed using Compound 6.
  • the treatments were performed over a wide temperature range using a getter gas (10 vol% H 2 -90 vol% N 2 ) atmosphere to form Composite 8.
  • the temperature of the reaction was varied from 500-650°C in 50°C increments.
  • the resulting nanoparticles were characterized.
  • TEM analysis of Composite 8 formed at 650°C revealed nanocrystalline particulates dispersed throughout the carbon support. Thermal reduction at 650 °C led to formation of both Pt,Sn and PtP 2 nanoparticles. Nanoparticles formed by thermal treatment at 500, 550, or 600°C did not exhibit enough crystallinity to produce electron diffraction ring patterns.
  • Pt,Sn and PtP 2 particle diameter in Composite 8 formed at 650°C, exhibited a monomodal distribution.
  • the particle sizes ranged from 3.0 to 15.3 nm, with an average particle diameter of 9.0 nm as measured by TEM.
  • Table 6 shows a comparison of Pt,Sn and PtP 2 d-spacing data, measured in angstroms as obtained by SAD and as set forth in Table 5 above, with other known PtSn phases (top in the top portion).
  • xxx designates that no reflections matching the observed d-spacings were possible in the particular phase.
  • a listing of important reflections for the other known PtSn phases which were not observed for Composite 8 are shown in the bottom portion of Table 6, with the intensities of those reflections noted in parentheses.
  • XRD scan obtained using Composite 8 is shown in Fig. 4.
  • the observed peaks match 20 values and relative intensities of the corresponding 111, 200, 220, and 311 diffraction peaks of standard Pt 3 Sn, as well as 110, 200, 220, 311, 222, 331, 420, 422, and 511 diffraction peaks of standard PtP 2 -
  • the XRD data confirms that both Pt,Sn and PtP 2 phases were formed in Composite 8 by thermal reduction in a getter gas atmosphere.
  • a third series of doping and thermal treatments were performed using Compound 6.
  • the treatments comprised thermal oxidation in air followed by thermal reduction in a getter gas atmosphere to yield Composite 9.
  • TEM analysis of Composite 9 revealed nanocrystalline particles dispersed throughout the Vulcan carbon support. Thermal oxidation to 280 °C followed by a thermal reduction up to 650 °C led to formation of crystalline Pt,Sn and prevented formation of PtP ⁇ . The particles were sufficiently crystalline to produce an adequate SAD ring pattern. The particle sizes ranged from 4.2 to 14.2 nm, with an average particle diameter of 8.1 nm measured by TEM. As indicated in Table 7, Pt,Sn particle diameters exhibited a monomodal distribution.
  • Polymetallic precursors different from those in Example 1 were used in accordance with the method of the present invention to form platinum-rich nanocomposites in the form of P W and PtAu alloys.
  • Example 1 The materials and methods used in this Example are the same as those used in Example 1, with the exception of the use of chloro(triphenylphosphine) gold (I), and cyclopentadienyltungsten tricarbonyl dimer which were purchased from Strem Chemical, Inc. All other apparatus, materials, methods and rates of heating, and doping the carbon are the same as those described in Example 1.
  • Reaction sequence (XVII)-(XVIII), below, shows formation of Compound 11 as described above and subsequent oxidation and thermal reduction of Compound 11 to form Composite 12.
  • cyclopentadienyltungsten tricarbonyl dimer (0.100 g, 0.150 mmol) was added to Na/Hg amalgam (prepared by adding 2 g of Na to 7 ml of Hg) and 10 ml THF.
  • the reaction mixture was allowed to stir under a nitrogen atmosphere for 2 hours.
  • the bright green solution was filtered through cotton into a clean flask purged with nitrogen.
  • ( ⁇ ,-carbonyl)tris[ ⁇ -bis(diphenyl- phosphino)methane)-triangulo-triplatinum(2 + ) hexafluorophosphate (0.300 g, 0.142 mmol) was added, forming a blood-red solution.
  • reaction (XX) an aliquot of Compound 13 (0.100 g, 46.3 ⁇ mol) was added to a 250 ml beaker along with Vulcan XC-72R carbon (0.300 g, 0.025 mol). A TeflonTM-coated magnetic stirring bar and 60 ml of acetone were added to the beaker. The solution was stirred overnight. The solution was centrifuged, and acetone was decanted from the solid. The doped Vulcan carbon was allowed to air dry for 72 hours to yield Compound 14 (0.314 g).
  • Pt and Au particle diameters exhibited a monomodal distribution.
  • the particle sizes ranged from 3.4 to 14.6 nm, with an average particle diameter of 8.6 nm as measured by TEM.
  • the energy dispersive spectrum of Composite 12 revealed the presence of PtL ⁇ , PtL , PtL , PtM ⁇ , PtM ⁇ , PtM , AuL ⁇ , AuL ⁇ , AuL , AuM , and AuM «, emissions and the spectra also exhibited a 3:1 atomic ratio of Pt to Au.
  • An XRD scan obtained using Composite 12 is shown in Fig. 8. The observed peaks match 2 ⁇ values and relative intensities of the corresponding 111, 200,
  • the nanoparticles of Composite 12 were determined not to comprise a Pt 3 Au alloy phase, but separate Pt and Au phases instead.
  • Carbon nanocomposites comprising nanoparticles of Pt 2 W were synthesized by oxidative thermal treatment in air followed by reductive thermal treatment in getter gas.
  • the Pt,W molecular precursor, Compound 13 was synthesized in accordance with reaction (XIX) above.
  • TEM analysis of Composite 15 revealed nanocrystalline particles dispersed throughout the Vulcan carbon support. Thermal oxidation to 280 °C followed by thermal reduction to 650°C led to the formation of crystalline Pt ⁇ W and a small amount of PtP 2 as nanoparticles. Bright-field imaging of Composite 15 indicated the presence of crystalline nanoclusters dispersed throughout the support. The particulate features exhibited sharp edges and some exhibited a hexagonal projection.
  • Pt 2 W particle diameter exhibited a monomodal distribution of particle sizes ranging from 10 to 38.3 nm.
  • the average particle diameter of Composite 15 was 17.0 nm as measured by TEM.
  • Nanocomposites that have been prepared are summarized in Table 12 along with the particle size and heating conditions for synthesizing those compounds. TABLE 12
  • a goal of certain studies described herein was to make a pure, highly crystalline P Sn/carbon nanocomposite.
  • a known molecular precursor was chosen and synthesized. The precursor was then adsorbed onto the surface of Vulcan XC-72R carbon. Thermal treatment of this composite under hydrogen led to the production of nanoparticulate PtSn and PtP 2 .
  • the reductive conditions were determined to be too severe and caused phase separation. To avoid this result, the reductive conditions were lessened.
  • the reductive treatment was performed under a getter gas atmosphere (10% by volume H 2 , 90% by volume N 2 ). This led to the formation of the desired Pt,Sn phase, but the resulting nanocomposite consisted of both Pt,Sn and PtP 2 nanoparticulates.
  • the thermal treatment was altered by adding a oxidative treatment step before the reductive treatment step in order to oxidize any phosphorus which was present to a phosphorus oxide prior to reductive treatment.
  • Phosphorus oxidation was achieved by thermally treating the preparation in an air atmosphere and thereafter performing the reductive treatment in a getter gas atmosphere.
  • Metal/carbon nanocomposites of commercial importance were prepared in less than one minute of reaction time by microwave irradiation of conductive carbon powder supported metallic or polymetallic precursors.
  • Pd or Pt halide complexes were used as precursors for nanoparticles comprising those metals, while a non-cluster-type Pt-Ru bimetallic precursor was used as a single-source precursor to generate nanoparticles having the composition Pt, Ru, .
  • Average metal particle sizes for these Pd, Pt, and Pt,Ru, nanoparticles were 7.0, 5.3, and 2.8 nm, respectively by TEM.
  • Microwave irradiation can be thus used for the rapid synthesis of metal or metal alloy nanoparticles from single precursors on a conductive carbon support.
  • Non-cluster, bimetallic precursors for the synthesis of Pt-Ru nanoparticles having a controlled alloy stoichiometry of commercial importance were formed.
  • Vulcan carbon nanocomposites were prepared comprising nanoparticles of Pd metal, Pt metal, or a Pt,Ru, metal alloy.
  • Each precursor was deposited in the form of an acetone or aqueous solution onto Vulcan carbon XC-72R by evaporation of solvent. Excess solvent was removed by roto-evaporation. Precursor loadings were arbitrarily selected to be 10 weight percent total metal for this study. Samples of these molecularly doped carbon composites having a mass of about 0.05 grams were placed inside a one-half dram glass vial, filling it to a depth about 1 cm. The assembly was then embedded within a 1 cm deep layer of Vulcan carbon within a two dram glass vial. The outer volume of carbon powder had a mass of about 0.15 grams and was used as a thermal bath for more efficient microwave heating. The reaction assembly was placed into a 100 ml glass beaker to afford mechanical stability.
  • Thermal treatment was accomplished using a microwave oven (Sharp Corporation, Model R-2M52B) operating at 2.45 GHz with a fixed power level of 600 Watts.
  • Control studies using untreated Vulcan carbon indicated that the temperature of the carbon powder present within the inner vial increased rapidly upon microwave irradiation.
  • the temperature of the inner carbon mass was 233 °C after one irradiation period, 405 °C after two irradiation periods, and 511 °C following three irradiation periods. Imprudently prolonged microwave irradiation can lead to softening of the glass vials, and caution in using glass vials is therefore recommended.
  • a beaker of cold water was placed within the microwave oven to protect the oven from irradiation damage.
  • Thermal treatment of the molecular precursor/carbon nanocomposites by microwave irradiation was conducted under an air atmosphere to oxidatively degrade the precursor complex, followed by irradiation under getter gas to reduce the metal ions to metal. Between repetitive oxidative thermal treatments, the air atmosphere above the inner sample was replenished by mild flushing.
  • the reaction assembly was evacuated to about 0.01 mm Hg and filled with nitrogen gas between oxidative and reductive thermal treatments to preclude formation of potentially explosive air/hydrogen mixtures.
  • Getter gas was supplied using a partially filled Helium-grade balloon at a pressure slightly above one atmosphere. The filled balloon was affixed to the mouth of the two-dram outer vial using tape.
  • the resulting metal or metal alloy/carbon nanocomposites were characterized by TEM, EDS, and powder XRD using a Philips CM20T instrument for TEM and a Scintag XI Diffraction System for XRD. Particle-size distributions, average particle diameters, and median particle sizes were determined by TEM analysis. XRD patterns were used to confirm the crystallinity and identity of the nanocrystal substance. In addition, a volume-weighted average nanocrystal particle size was obtained from XRD peak widths using Scherrer's equation. Prior to peak width measurements diffraction peaks were corrected for background scattering and were stripped of the Ko portion of the diffraction intensity. EDS spectral analysis was used to confirm the elemental composition of the nanoparticles for elements heavier than fluorine.
  • Microwave irradiation of the molecular precursors and particulate carbon in air (15 seconds irradiation on; 45 seconds irradiation off; 10 seconds irradiation on) followed by an identical reduction treatment using the same heating regimen in getter gas yielded the Pd, Pt or Pt, Ru, /carbon nanocomposites.
  • TEM analysis revealed good contrast between the crystalline, nearly spheroidal metal nanoparticles and the amorphous carbon matrix. Metal nanoparticle sizes for these nanocomposites exhibited monomodal particle-size distributions.
  • the average particle size (standard deviation; median diameter) for each nanocomposite was determined: Pd, 7.0 (2.9; 6.6) nm; Pt, 5.3 (2.7; 4.6) nm; Pt j RU 2.8 (0.5; 2.8) nm. Particles less than about 15 A in diameter were not easily counted.
  • XRD diffraction patterns for the three nanocomposites are shown in Figs. 11, 12 and 13.
  • XRD patterns for the Pd and Pt/carbon nanocomposites indicated the presence of crystalline NaCl and KC1. These salts were removed by aqueous washing.
  • XRD scans of the Pd or Pt/carbon nanocomposites revealed the patterns characteristic of the pure metals.
  • XRD scans of the Pt,Ru, /carbon nanocomposite were consistent with a face-centered cubic cell having a lattice constant of 3.867 (0.005) A. This pattern is the pattern predicted for a 1 :1 solid solution of Pt and Ru. Radmilovic et al., J. Catal. 154:98 (1995).
  • the widths of the XRD peaks reflect the small sizes of the nanocrystalline phases and indicate the following calculated average particle sizes (standard deviations): Pd, 8.3 (1.2) nm; Pt, 9.4 (2.4) nm; Pt j Ru ⁇ 2.1 (0.7) nm.
  • Nanocrystal formation presumably occurred by thermal diffusion of incipient metal atoms or polyatomic clusters of metal atoms along a complex carbon surface and eventual agglomeration to form nanocrystals. Nanocrystal average size was affected by total irradiation time.
  • Doubling the duration of each irradiation period yielded average nanoparticle diameters (standard deviation; median diameter) of 7.1 (3.1; 6.7) nm for Pd, 8.7 (6.0; 6.8) nm for Pt, and 3.6 (0.7; 3.5) nm for Pt j Ru j as determined by TEM, and average nanoparticle diameters (standard deviation) of 52.7 (13.4) nm for Pd, 31.1 (0.6) nm for Pt, and 2.1 (0.6) nm for the Pt j Ru j nanocrystals, as determined by XRD.
  • Doubling the total irradiation time increased the fraction of larger particles, as predicted by diffusion-controlled growth mechanistic models. Liu et al., J. Appl. Phys. 68:28 (1990). The fraction of atypically large nanoclusters formed under prolonged heating was greater for the Pd and Pt nanocomposites than for the Pt, Ru, nanocomposite.
  • Nanoparticles average size was also affected by the depth of the precursor in the glass vial.
  • Pt,Ru, nanoparticles formed within the top half of the sample had an average diameter of 3.9 (0.6) nm, while those formed in the bottom half had a slightly larger average diameter of 4.7 (0.8) nm.
  • the binuclear non-cluster precursor, Pt(triphenylphosphine)(Cl)( ⁇ - Cl 2 )Ru(Cl)(trihapto:trihapto-2,7-dimethyloctadienediyl), in an amount of 0.08 g was dissolved in 15 ml of acetone. The resulting solution was stirred with 0.24 g of carbon support. Deposition of the precursor onto the carbon support was achieved by removal of the liquid phase by evaporation.
  • the resulting precursor/carbon composite was placed into a tube furnace and treated thermally under the following conditions: 25 to 280°C under air; 280 to 650°C under getter gas; anneal under N 2 gas at 650°C for 2.5 hours, after which time the sample was cooled to room temperature.
  • the binuclear non-cluster precursor Pt(triphenylphosphine)(Cl)( ⁇ - Cl 2 )Ru(Cl)(trihapto:trihapto-2,7-dimethyloctadienediyl), in an amount of 0.10 g, was dissolved in 15 ml of acetone. The resulting solution was stirred with 0.18 g of carbon support. Deposition of the precursor onto the carbon support was achieved by removal of the liquid phase by evaporation.
  • the resulting precursor/carbon composite was placed into a tube furnace and is treated thermally under the following conditions: 25 to 350°C under air; 350 to 650°C under getter gas; anneal under N 2 gas at 650°C for 10 minutes, after which time the sample was cooled to room temperature.
  • a second deposition/thermal treatment cycle was performed using 0.13 g of the precursor complex followed by thermal treatments of 25 to 350°C under air, 350 to 650°C under getter gas, and anneal at 650 °C for 85 minutes under nitrogen, after which time the sample was cooled to room temperature.
  • the binuclear non-cluster precursor, Pt(triphenylphosphine)(Cl)( ⁇ - Cl 2 )Ru(Cl)(trihapto:trihapto-2,7-dimethyloctadienediyl), in an amount of 0.31 g was dissolved in 40 ml of acetone. The resulting solution was stirred with 0.27 g of carbon support. Deposition of the precursor onto the carbon support was achieved by removal of the liquid phase by evaporation.
  • the resulting precursor/carbon composite was placed into a tube furnace and treated thermally under the following conditions: 25 to 350°C under air; 350 to 650° C under getter gas; anneal under N 2 gas at 650°C for 5 minutes, after which time the sample was cooled to room temperature.
  • a second deposition cycle was performed using 0.31 g of the precursor complex and the same thermal treatments described in this Example for the first cycle.
  • a third deposition cycle was performed using 0.32 g of the precursor complex followed by the same thermal treatment, except that the final annealing step was performed for 50 minutes.
  • a binuclear non-cluster precursor, ⁇ Ru(2,2'-bipyridine) 2 ( ⁇ - bipyrimidine)PtC ⁇ [hexafluorophosphate] 2 in the amount of 0.69 g was dissolved in 50 ml of acetonitrile. The resulting solution was stirred with 0.42 g of carbon support. Deposition of the precursor onto the carbon support was achieved by removal of the liquid phase by evaporation. The resulting precursor/carbon composite was placed into a tube furnace and treated thermally under the following conditions: 25 to 450 °C under air; 450 to 650 °C under getter gas; anneal under N 2 gas at 650 °C for 60 minutes, after which time the sample was cooled to room temperature.
  • the tetranuclear non-cluster precursor, Ru( ⁇ -2,3-bis(2-pyridyl)- quinoxaline)PtCl 2 ),][tetrafluoroborate] 2 in the amount of 0.17 g was dissolved in 100 ml of acetonitrile. The resulting solution was stirred with 0.15 g of carbon support. Deposition of the precursor onto the carbon support was achieved by removal of the liquid phase by evaporation. The resulting precursor/carbon composite was placed into a tube furnace and treated thermally under the following conditions: 25 to 450 °C under air; 450 to 650°C under getter gas; anneal under N 2 gas at 650°C for 30 minutes, after which time the sample was cooled to room temperature.
  • the binuclear cluster precursor, Pt(triphenylphosphine) 2 (phenyl)- Sn(phenyl) 2 Cl, in an amount of 0.29 g was dissolved in 60 ml of heptane. The resulting solution was stirred with 0.31 g of carbon support. Deposition of the precursor onto the carbon support was achieved by absorption of the precursor. The resulting precursor/carbon composite was isolated by centrifugation, placed into a tube furnace and treated thermally under the following conditions: 25 to 700 °C under hydrogen gas, and maintaining the temperature at 700 °C for two hours, after which time the sample was cooled to room temperature.
  • EXAMPLE 12 Preparation of a Carbon Supported Catalyst of Metal Composition PtSn
  • the binuclear cluster precursor, Pt(triethylphosphine) 2 (Cl)Sn(Cl 3 ) in an amount of 0.51 g was dissolved in 50 ml of methylene chloride. The resulting solution was stirred with 0.44 g of carbon support. Deposition of the precursor onto the carbon support was achieved by evaporation of the solvent. The treated carbon support was permitted to dry at room temperature.
  • the resulting precursor/carbon composite was placed into a tube furnace and treated thermally under the following conditions: 25 to 250°C under air; 250 to 650°C under getter gas; anneal under N 2 gas at 650°C for one hour, after which time the sample was cooled to room temperature.
  • EXAMPLE 13 Preparation of a Carbon Supported Catalyst of Metal Composition Pt,Sn
  • the tetranuclear cluster precursor, ⁇ Pt 3 [ ⁇ -(bis(diphenylphoshine)- methane)] 3 ( ⁇ -SnF,)( ⁇ ,-CO) ⁇ [hexafluorophosphate] in an amount ofO.il g was dissolved in 50 ml of acetone. The resulting solution was stirred with 0.16 g of carbon support. Deposition of the precursor onto the carbon support was achieved by direct absorption of the precursor.
  • the resulting precursor/carbon composite was isolated by centrifugation, placed into a tube furnace, and treated thermally under the following conditions: 25 to 280°C under air; 280 to 650°C under getter gas; anneal under N 2 gas at 650 °C for two hours, after which time the sample was cooled to room temperature.
  • EXAMPLE 14 Preparation of a Carbon Supported Catalyst of Metal Composition P Mo
  • the tetranuclear cluster precursor, ⁇ Pt 3 [ ⁇ -(bis(diphenylphosphine)- methane)] 3 [ ⁇ ,-Mo](pentahapto-cyclopentadienyl)(CO) ⁇ [hexafluorophosphate] in an amount of 0.20 g was dissolved in 5 ml of acetone. The resulting solution was stirred with 0.23 g of carbon support. Deposition of the precursor onto the carbon support was achieved by removal of the liquid phase by evaporation.
  • the resulting precursor/carbon composite was placed into a tube furnace and treated thermally under the following conditions: 25 to 280°C under air; 280 to 650°C under getter gas; anneal under N gas at 650 °C for one hour, after which time the sample was cooled to room temperature.
  • This treated carbon composite was stirred for 18 hours with a solution containing 0.47 g of the precursor dissolved in 35 ml of methylene chloride. After removal of the liquid phase by evaporation, the resulting composite was placed into a tube furnace and treated thermally under the following conditions: 25 to 350°C under air; 350 to 650° under getter gas; anneal under nitrogen gas at 650°C for one hour, followed by cooling to room temperature; 25 - 350°C over 10 minutes under air, followed by cooling to room temperature.
  • the binuclear cluster precursor, Mo(heptahapto-cycloheptatrienyl)- (CO),Ru(pentahapto-cyclopentadienyl)(CO) 2 in an amount of 0.71 g was dissolved in 35 ml of acetone. The resulting solution was stirred with 0.30 g of carbon support. Deposition of the precursor onto the carbon support was achieved by removal of the liquid phase by evaporation.
  • the resulting precursor/carbon composite was placed into a tube furnace and treated thermally under the following conditions: 25 to 280°C under air; 280 to 700°C under getter gas, maintaining the temperature at 700°C for 30 minutes; anneal under N 2 gas at 700 °C for 60 minutes, after which time the sample was cooled to room temperature.
  • the catalysts prepared as Examples 4-16 were characterized by transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), x-ray diffraction (XRD), and by chemical elemental analysis. Average catalyst nanoparticle sizes were estimated by measuring particle diameters from at least one TEM image of each sample. Results of these analyses are listed in Table 13 which shows the estimated average diameter of the alloy nanoparticles measured in nanometers, the metal chemical compositions, measured in weight percent, and the Pt/M' [or Ru/Mo(*)] atomic ratios as determined by chemical elemental analysis or from EDS. The precursor core Pt M' or Ru/Mo(*) atomic ratios are also shown.
  • TEM transmission electron microscopy
  • EDS energy dispersive spectroscopy
  • XRD x-ray diffraction
  • Crystalline intermetallic substances such as PtSn, Pt 3 Sn, and Pt 3 Mo, have unique XRD patterns.
  • Figs. 14, 15 and 16 show the powder XRD patterns of the PtSn/C, Pt,Sn/C, or Pt,Mo/C catalysts, respectively, typifying XRD patterns for catalysts prepared as in Examples 12, 13, or 15, respectively.
  • the XRD pattern of the corresponding pure substance is shown below the experimental result as a line pattern obtained from the standard Powder Diffraction Files. Broad peaks near 25 ° 2 ⁇ are formed from amorphous scattering from the carbon substrate. Diffraction peaks of the metal nanoclusters broaden as the volume weighted average particle size of the catalyst particles becomes smaller.
  • XRD patterns obtained from metal alloy nanoparticles are less unique. Usually, these catalyst composites yielded a pattern consistent with the high symmetry unit cell of one of the constituent metals.
  • the unit cell parameter obtained from these alloy XRD patterns differed slightly from the unit cell parameters known for the pure metal constituents, because atoms of different elements have different atomic radii.
  • XRD patterns of the PtRu/C composites such as those prepared as Examples 4-8, revealed a set of peaks that could be indexed using a face-centered-cubic (fee) unit cell having a lattice constant, ao, of 3.87 A. This value is consistent with the value predicted for a 1 :1 alloy of Pt and Ru.
  • the fee unit cell parameter of pure platinum is 3.92 A.
  • the Pt,Ru/C composite prepared in Example 10 yielded a powder
  • a slightly larger cell parameter is expected for nanocrystals of composition Pt,Ru, relative to those having a PtRu composition because Pt atoms are slightly larger than Ru atoms.
  • Electrochemical testing of the P Mo/C catalyst prepared in Example 14 revealed catalytic activity for oxygen reduction and methanol tolerance. Testing this catalyst in a DMFC confirmed slight methanol tolerance when this catalyst was used as a cathode catalyst.
  • DMFC tests were performed by standard methods as described above with estimated catalyst loadings at the anode as indicated in Table 14.
  • the test fixture was fabricated with a membrane comprising the polymetallic material designated Nafion® 117, and test conditions included an oxygen flow rate of 400 ml/min and a back pressure of 10 psig, a methanol concentration of 0.5 M, a methanol flow rate of 25 ml/min, and a methanol back pressure of zero psig.
  • the temperature of the test fixture was 90° C. Performance results are presented as current density
  • the novel polymetallic precursor has the formula ⁇ Pt- ⁇ - bis(diphenylphosphine)methane], ⁇ ⁇ 4 -Hg-Ru(pentahapto- cyclopentadienyl)(CO) 2 ] 2 ⁇ [hexafluorophosphate] 2 and is depicted in Fig. 18.
  • Fig. 19 shows the trigonal-bypyramidal core of the precursor of Fig. 18.
  • the reactant solution was filtered through glass wool into a solution comprising the triplatinum cluster, [Pt,(dppm),(CO)][PF 6 ] 2 in THF, thereby forming the heteronuclear precursor, ⁇ Pt, [ ⁇ -bis(diphenylphosphine)methane], ⁇ ⁇ 4 -Hg-
  • the treatment was then repeated but initially heated from 25 to 400 °C in air, then heated from 400 to 650 °C in nitrogen and held at 650°C in getter gas a sufficient time to form a nanocomposite comprising nanoparticles having a composition in which the atomic ratio of Pt to Ru was approximately 3 :2 and in which the proportion of metal atoms which were Hg was less than 3%, as indicated by the EDS spectrum shown in Fig. 21.
  • a thermal gravimetric analysis of the nanocomposite is shown in Fig. 22, and an XRD scan of the nanocomposite is shown in Fig. 23.
  • XRD analysis indicated that the nanoparticles had an average diameter of 7.5 nm, with a standard deviation of 0.4 nm, and revealed a set of peaks that could be indexed using a face-centered-cubic (fee) unit cell having a lattice constant, a, of 3.875 A (standard deviation 0.002). This value is consistent with the value (3.876) predicted for a 3:2 alloy of Pt and Ru.
  • TEM analysis indicated that the nanoparticles exhibited a monomodal diameter distribution, the average nanoparticle diameter being 3.87 nm, the standard deviation being 2.0 nm, and the median diameter being 3.38 nm.
  • EXAMPLE 20 The binuclear non-cluster precursor complex, [Ru(2,2'-bipyridine) 2 ( ⁇ - bipyrimidine)PtCl 2 ][tetrafluoroborate] 2 , in an amount of 0.53 g was dissolved in 50 ml acetonitrile. The resulting solution was stirred with 0.16 g of carbon support.
  • Deposition of the precursor onto the carbon support was achieved by removal of the liquid phase by evaporation.
  • the resulting precursor/carbon composite was placed into a tube furnace as described above and was treated thermally under the following conditions: 25 to 650°C under nitrogen at 30°C per minute; held at 650°C under getter gas (90/10 nitrogen/hydrogen mixture) for 20 minutes; switching to nitrogen gas with cooling to room temperature at a rate of 2.5°C/min. From preliminary testing, the nanocomposite shows a high degree of purity and with negligible phosphorus.
  • EXAMPLE 21 The tetranuclear non-cluster precursor complex [Ru( ⁇ -2,3-bis(2- pyridyl)quinoxaline)PtCl 2 ) 3 ] [tetrafluoroborate] 2 , in an amount of 1.10 g was dissolved in 50 ml of acetonitrile. The resulting solution was deposited onto 0.39 g of carbon support in three deposition/heat treatment cycles using nearly equal amounts of precursor solution. Each deposition of the precursor onto the carbon support is achieved by removal of the liquid phase by evaporation followed by heating the sample in a tube furnace from 25 to 350°C under getter gas at a heating rate of 15 °C/min and then cooling to room temperature under a nitrogen purge. The final heat treatment included an annealing of the sample at 350° C under nitrogen for 30 minutes followed by cooling to room temperature.
  • EXAMPLE 22 The Pt 3 Ru/Vulcan carbon nanocomposite prepared in accordance with Example 21 was subjected to a subsequent oxidative thermal treatment including heating the nanocomposite from 25°C to 350°C in air at a rate of 15°C/min followed by a 10 minute purge with nitrogen and a subsequent heating of the sample from 350°C to 650°C in getter gas at a rate of 15°C/min. The sample was then annealed at 650°C under nitrogen and was then permitted to cool to room temperature under nitrogen.
  • the binuclear non-cluster precursor complex [Ru( ⁇ -bipyrimidine)(2,2'- bipyridine) 2 PtC ] [hexafluorophosphate],-, in an amount of 0.29 g was dissolved in 50 ml of acetonitrile. The resulting solution was stirred with 0.31 g of carbon support. Deposition of the precursor onto the carbon support was achieved by removal of the liquid phase by evaporation. The resulting precursor/carbon composite was placed into a tube furnace as described above and was treated thermally under the following conditions: 25 to 280°C under air; 280 to 650°C under getter gas, after which time the sample was cooled to room temperature.
  • a second deposition of 0.27 g of the precursor complex noted above in this Example was performed likewise using a solution in acetonitrile and solvent evaporation.
  • the resulting precursor/carbon composite was placed into a tube furnace as described above and was treated thermally under the following conditions: 25 to 280°C under air; 280 to 650°C under getter gas followed by thermal annealing at 650°C under nitrogen for 60 minutes after which time the sample was cooled to room temperature.
  • This sample demonstrated good fuel cell properties in a DMFC test cell.
  • EXAMPLE 24 The dinuclear non-cluster precursor complex Pt(dihapto- ethylene)(Cl)( ⁇ -Cl) 2 Ru(Cl)(trihapto:trihapto-2,7-dimethyloctadienediyl), in an amount of 0.11 g was dissolved in 15 ml of acetone and was added to a flask containing 0.16 g of Vulcan carbon having the specified criteria noted above in previous examples.
  • Deposition of the precursor onto the carbon support was achieved by removal of the W wO ⁇ 9 ⁇ 9/ / 6o6o5 3 7 / 4 4 PCT/US98/12354 liquid phase by evaporation.
  • Example 23 were repeated twice.
  • the final heat treatment included an annealing at
  • the nanocomposite included very pure PtRu alloy nanocrystals.
  • the PtRu/Vulcan carbon nanocomposite prepared in Example 24 was subjected to a subsequent oxidative thermal treatment including heating the nanocomposite from 25°C to 350°C in air at a rate of 15°C/min followed by a 10 minute purge with nitrogen followed by heating the sample from 350 to 650°C in getter gas at a rate of 15 °C/min.
  • the sample was then annealed at 650 °C under nitrogen and was permitted to cool to room temperature under nitrogen.
  • the air treatment helps ensure that crystal surfaces are free of organic residue for use in DMFC catalysis.
  • EXAMPLE 26 The trinuclear cluster precursor complex, ⁇ Pt[bis-(pentahapto- cyclopentadienylmolybdenumtricarbonyl)](bispyridine) ⁇ in an amount of 0.44 g was dissolved in 80 ml of dimethylsulfoxide under a nitrogen atmosphere. The resulting solution was stirred with 0.13 g of carbon support. Deposition of the precursor onto the carbon support was achieved by removal of the liquid phase by evaporation. The resulting precursor/carbon composite was dried at reduced pressure at 100° C for four hours then placed into a tube furnace as described above.
  • This sample was treated thermally under the following conditions: 25 to 280°C under air; 280 to 650°C under getter gas; anneal at 650 °C under nitrogen for 50 minutes after which time the sample was cooled to room temperature.
  • the resulting nanocomposite having a PtMo 2 stoichiometry exhibited properties useful as a cathode catalyst.
  • EXAMPLE 27 The di-nuclear non-cluster precursor complex Pt(triphenylphosphine)(Cl)( ⁇ -Cl) 2 Ru(Cl)(trihapto:trihapto-2,7-dimethyloctadienediyl), in the amount of 0.31 g was dissolved in 10 ml of acetone and was added to a flask containing 0.34 g of Vulcan carbon. Deposition of the precursor onto the carbon support was achieved by removal of he liquid phase by evaporation. This sample was placed into a tube furnace and was heated from 25 to 350 °C under getter gas and was cooled to room temperature under nitrogen.
  • a second deposition and heat treatment was performed following the above procedure using 0.31 g of molecular precursor and 15 ml of acetone.
  • a third deposition and heat treatment was performed following the above procedure using 0.33 g of molecular precursor and 15 ml of acetone.
  • the obtained sample was then treated with 0.15 g of triphenylphosphine dissolved in 20 ml of acetone followed by evaporation of solvent. This final sample was heated from 25 to 420 °C in getter gas followed by heating at 420 °C under nitrogen for 10 minutes and was then cooled to room temperature.
  • the resulting composite had a ternary PtRuP 2 alloy in which phosphorus was intentionally retained by not using air treatment.
  • Example 28 The precursor of Example 24 was prepared following procedures reported for the synthesis of analogous complexes as set forth in Severin et al., Inorg. Chim. Acta.240, 339 (1995). 0.640 g (1.06 mmol) of Pt 2 Cl 2 ( ⁇ 2 -Cl) 2 (C 2 H 4 ) 2 and 0.637 g (1.03 mmol) of Ru 2 Cl 2 ( ⁇ 2 -Cl) 2 (triha ⁇ to:trihapto-2,7-dimethyloctadienediyl) 2 were placed in a round bottom flask and dissolved in approximately 75 ml of CH 2 C1 2 . The solution was left stirring for several hours under a nitrogen atmosphere. The solvent was removed from the reddish brown solution to give a brown powder.
  • Example 27 The precursor of Example 27 was synthesized by the Severin procedure as noted in Example 28. 718 mg (0.680 mmol) of P Cl 2 ( ⁇ -Cl) 2 (triphenylphosphine) 2 and 417 mg (0.677) mmol of Ru 2 Cl 2 ( ⁇ -Cl) 2 (trihapto:trihapto-2,7- dimethyloctadienediyl) 2 were placed in a round bottom flask and dissolved in approximately 100 ml of CH- L. The solution was left stirring overnight under a nitrogen atmosphere, the solvent was removed from the reddish-brown solution to give a brown powder.
  • Example 30 The precursor of Example 20 was prepared in accordance with the following procedure. Initially, bis-(2,2 , -bipyridine)-2,2'-bipyrimidineruthenium (II) tetrafluoroborate (referred to herein as "[Ru(bpy) 2 (bpm)][BF 4 ] 2 ”)was prepared by a modification of the method reported by Nallas et al., Inorgan. Chem. 35,6974 (1996) for synthesis of the PF salt of this compound. 0.465 g (0.96 mmol) of Ru(2,2'- bipyridine) 2 Cl 2 was dissolved in 50 mol of a 2:1 ethanol/water solution.
  • Example 31 The precursor of Example 21 was prepared by first synthesizing tris- (2,3-bis(2-pyridyl)quinoxaline)ruthenium (II) tetrafluoroborate ("Ru(dpq) ][BF 4 ] 2 "). This compound was prepared using a modification of the procedure reported in Rillema et al., Inorg. Chem. 26, 578 (1987) for the synthesis of PF ⁇ salt of this compound. 0.306 g (1.48 mmol) of RuCl 3 -nH 2 O and 2.52 g (8.86 mmol) of 2,3-bis(2-pyridyl)- quinoxaline were added to 50 ml of ethylene glycol.
  • the mixture was stirred and heated at reflux under nitrogen atmosphere for about 2 hours.
  • the solution was then allowed to cool to room temperature and filtered to remove any unreacted ligand.
  • the value was doubled with water and the resulting solution was added to a saturated aqueous solution containing 1.0 g (9.1 mmol) of NaBF 4 .
  • a precipitate formed which was collected by vacuum filtration.
  • the solid was then dissolved in a minimal amount of acetonitrile and developed on a neutral alumina column using acetonitrile as the eluent.
  • the major red band was collected leaving a green band of unknown byproduct on the column.
  • the solvent was then removed from the sample using a rotary evaporator.
  • Example 21 From the above synthesized Ru(dpq),][BF 4 ] 2 , the precursor of Example 21 was prepared. The synthesis of the precursor was undertaken using a modification of the procedure reported in Rillema et al., J. Chem. Commun. 1133
  • Example 32 The precursor of Example 14 was prepared using a procedure similar to that reported by Ferguson et al., Organometallics. 5, 344 (1986) by the reaction of ⁇ Pt,( ⁇ 3 -CO)[ ⁇ -bis(diphenylphosphino)methane], [PF fi ] 2 and Na[(pentahapto- cyclopentadienyl)Mo(CO) 3 ].
  • Na[(pentahapto-cyclopentadienyl)Mo(CO),] in an amount of 0.2480 g (0.506 mmol) was added to Na/Hg (prepared by dissolving about 2 g Na in 7 ml of Hg) in 10 ml of THF in nitrogen flow.
  • the reaction mixture was allowed to stir under nitrogen for 3 hours. Color changed from red to olive-green.
  • the olive-colored solution was filtered through celite into another shlenk flask purged with nitrogen then ⁇ Pt 3 ( ⁇ ,-CO)[ ⁇ -bis(diphenylphosphino)methane],[PF fi ] 2 was added in an amount of 0.2005 g (0.0975 mmol) and the color turned to blood-red.

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Abstract

L'invention concerne des procédés de préparation de précurseurs polymétalliques et de préparation de nanocomposites améliorés formés à partir de ces précurseurs utiles dans les compositions de catalyseurs à pile à combustible. Ces nanocomposites renferment un support et une pluralité de nanoparticules polymétalliques présentant un rapport atomique entre métaux sélectionnés. Ces métaux contenus dans les précurseurs polymétalliques ont un rapport stoechiométrique qui est approximativement égal au rapport atomique entre métaux sélectionnés dans les nanoparticules de manière que le contrôle stoechiométrique soit assuré pour le catalyseur nanocomposite obtenu. Les nanoparticules intermétalliques cristallines ou à alliage métallique se forment lors d'une mise en contact d'un précurseur polymétallique à stoechiométrie métallique particulière et d'un support conducteur. Le précurseur est thermiquement dégradé sur le support entraînant la rétention du noyau métallique du précurseur sur le support. Les nanoparticules à alliage polymétallique ainsi formées présentent un rapport atomique entre métaux qui est environ égal au rapport stoechiométrique de métaux contenus dans le précurseur polymétallique. Des catalyseurs à pile à combustible comprenant des tels nanocomposites servent soit de catalyseurs à pile à combustible contenant une anode soit de catalyseurs à pile à combustibles contenant une cathode, notamment dans les DMFC.
PCT/US1998/012354 1998-06-18 1998-06-18 Precurseurs et compositions polymetalliques et procedes de fabrication de nanocomposites polymetalliques supportes WO1999066574A1 (fr)

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004049477A3 (fr) * 2002-11-26 2004-12-23 De Nora Elettrodi Spa Alliage metallique destine a des reactions d'oxydation electrochimique et son procede de production
WO2006062954A1 (fr) * 2004-12-06 2006-06-15 Honda Motor Co., Ltd. Electrocatalyseurs contenant un alliage metallique de platine et de tungstene
WO2006008001A3 (fr) * 2004-07-16 2007-01-18 De Nora Elettrodi Spa Alliage metallique pour reactions d'oxydation electrochimique et procede pour le produire
WO2007100375A3 (fr) * 2006-01-10 2008-10-16 Cabot Corp Compositions de catalyseur a base d'alliage et procedes de fabrication et d'utilisation de ces compositions
US8252485B2 (en) 2007-03-13 2012-08-28 Cabot Corporation Electrocatalyst compositions and processes for making and using same
CN112974826A (zh) * 2021-02-10 2021-06-18 中国科学技术大学 一种钯镉金属间化合物/合金催化剂材料及其合成方法、应用
CN113130923A (zh) * 2021-04-15 2021-07-16 北京师范大学 一种二维多孔碳负载催化剂的制备方法及应用
CN114430048A (zh) * 2020-10-14 2022-05-03 中国石油化工股份有限公司 催化剂及其制备方法和膜电极以及直接液体燃料电池

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5766306A (en) * 1996-06-04 1998-06-16 The Boeing Company Continuous process for making nanoscale amorphous magnetic metals

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5766306A (en) * 1996-06-04 1998-06-16 The Boeing Company Continuous process for making nanoscale amorphous magnetic metals

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
CHEMICAL ABSTRACTS, 1 January 1900, Columbus, Ohio, US; abstract no. 127:153461, XP002911471 *
CHEMICAL ABSTRACTS, 1 January 1900, Columbus, Ohio, US; abstract no. 128:53708, XP002911470 *
LIZ MARAN et al., "Synthesis of Platinum Nanoparticles...", COLLOIDS SURF., A. 1994, Vol. 90, No. 1, pages 95-109, XP002911472 *

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004049477A3 (fr) * 2002-11-26 2004-12-23 De Nora Elettrodi Spa Alliage metallique destine a des reactions d'oxydation electrochimique et son procede de production
CN100352090C (zh) * 2002-11-26 2007-11-28 德·诺拉电极股份公司 用于电化学氧化反应的金属合金及其制造方法
WO2006008001A3 (fr) * 2004-07-16 2007-01-18 De Nora Elettrodi Spa Alliage metallique pour reactions d'oxydation electrochimique et procede pour le produire
WO2006062954A1 (fr) * 2004-12-06 2006-06-15 Honda Motor Co., Ltd. Electrocatalyseurs contenant un alliage metallique de platine et de tungstene
US7718309B2 (en) 2004-12-06 2010-05-18 Honda Motor Co., Ltd. Platinum and tungsten containing electrocatalysts
WO2007100375A3 (fr) * 2006-01-10 2008-10-16 Cabot Corp Compositions de catalyseur a base d'alliage et procedes de fabrication et d'utilisation de ces compositions
US8252485B2 (en) 2007-03-13 2012-08-28 Cabot Corporation Electrocatalyst compositions and processes for making and using same
CN114430048A (zh) * 2020-10-14 2022-05-03 中国石油化工股份有限公司 催化剂及其制备方法和膜电极以及直接液体燃料电池
CN112974826A (zh) * 2021-02-10 2021-06-18 中国科学技术大学 一种钯镉金属间化合物/合金催化剂材料及其合成方法、应用
CN113130923A (zh) * 2021-04-15 2021-07-16 北京师范大学 一种二维多孔碳负载催化剂的制备方法及应用

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