WO2003081702A2 - Catalyseur au pt-rh-w/sn/cu/mo pour pile a combustible - Google Patents

Catalyseur au pt-rh-w/sn/cu/mo pour pile a combustible Download PDF

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Publication number
WO2003081702A2
WO2003081702A2 PCT/US2003/008852 US0308852W WO03081702A2 WO 2003081702 A2 WO2003081702 A2 WO 2003081702A2 US 0308852 W US0308852 W US 0308852W WO 03081702 A2 WO03081702 A2 WO 03081702A2
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Prior art keywords
concentration
atomic percent
platinum
catalyst
rhodium
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PCT/US2003/008852
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English (en)
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WO2003081702A3 (fr
Inventor
Peter Strasser
Alexander Gorer
Martin Devenney
Qun Fan
Konstantinos Chondroudis
Daniel M. Giaquinta
Ting He
Hiroyuki Oyanagi
Kenta Urata
Kazuhiko Iwasaki
Hiroichi Fukuda
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Symyx Technologies, Inc.
Honda Giken Kogyo Kabushiki Kaisha
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Priority to AU2003224744A priority Critical patent/AU2003224744A1/en
Publication of WO2003081702A2 publication Critical patent/WO2003081702A2/fr
Publication of WO2003081702A3 publication Critical patent/WO2003081702A3/fr

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C5/00—Alloys based on noble metals
    • C22C5/04—Alloys based on a platinum group metal
    • 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
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/18—Carbon
    • 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
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/56—Platinum group metals
    • B01J23/62—Platinum group metals with gallium, indium, thallium, germanium, tin or lead
    • B01J23/622—Platinum group metals with gallium, indium, thallium, germanium, tin or lead with germanium, tin or lead
    • B01J23/626—Platinum group metals with gallium, indium, thallium, germanium, tin or lead with germanium, tin or lead with tin
    • 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
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/56—Platinum group metals
    • B01J23/64—Platinum group metals with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/652—Chromium, molybdenum or tungsten
    • 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
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/56—Platinum group metals
    • B01J23/64—Platinum group metals with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/652—Chromium, molybdenum or tungsten
    • B01J23/6527—Tungsten
    • 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
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals
    • B01J23/8933—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals also combined with metals, or metal oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/8966—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals also combined with metals, or metal oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with germanium, tin or lead
    • 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
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals
    • B01J23/8933—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals also combined with metals, or metal oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/8993—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals also combined with metals, or metal oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with chromium, molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C13/00—Alloys based on tin
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C27/00—Alloys based on rhenium or a refractory metal not mentioned in groups C22C14/00 or C22C16/00
    • C22C27/04—Alloys based on tungsten or molybdenum
    • 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
    • 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

  • the present invention relates to metal catalysts, especially to catalysts which comprise platinum, rhodium, at least one of tungsten, tin, and copper, and optionally molybdenum, which are useful in fuel cell electrodes and other catalytic structures.
  • a fuel cell is an electrochemical device for directly converting the chemical energy generated from an oxidation-reduction reaction of a fuel such as hydrogen or hydrocarbon-based fuels and an oxidizer such as oxygen gas (in air) supplied thereto into a low-voltage direct current.
  • fuel cells chemically combine the molecules of a fuel and an oxidizer without burning, dispensing with the inefficiencies and pollution of traditional combustion.
  • a fuel cell is generally comprised of a fuel electrode (anode), an oxidizer electrode (cathode), an electrolyte interposed between the electrodes (alkaline or acidic), and means for separately supplying a stream of fuel and a stream of oxidizer to the anode and the cathode, respectively.
  • a phosphoric acid fuel cell operates at about 160-220 °C, and preferably at about 190-200 °C. This type of fuel cell is currently being used for multi-megawatt utility power generation and for co-generation systems (i.e., combined heat and power generation) in the 50 to several hundred kilowatts range.
  • proton exchange membrane fuel cells use a solid proton- conducting polymer membrane as the electrolyte.
  • the polymer membrane is maintained in a hydrated form during operation in order to prevent loss of ionic conduction which limits the operation temperature typically to between about 70 and about 120 °C depending on the operating pressure, and preferably below about 100 C C.
  • Proton exchange membrane fuel cells have a much higher power density than liquid electrolyte fuel cells (e.g., phosphoric acid), and can vary output quickly to meet shifts in power demand. Thus, they are suited for applications such as in automobiles and small scale residential power generation where quick startup is a consideration.
  • pure hydrogen gas fs the optimum fuel; however, in other applications where a lower operational cost is desirable, a reformed hydrogen-containing gas is an appropriate fuel.
  • a reformed-hydrogen containing gas is produced, for example, by steam-reforming methanol and water at 200-300 °C to a hydrogen-rich fuel gas containing carbon dioxide.
  • the reformate gas consists of 75 vol% hydrogen and 25 vol% carbon dioxide. In practice, however, this gas also contains nitrogen, oxygen, and, depending on the degree of purity, varying amounts of carbon monoxide (up to 1 vol%).
  • some electronic devices also reform liquid fuel to hydrogen, in some applications the conversion of a liquid fuel directly into electricity is desirable, as then a high storage density and system simplicity are combined.
  • methanol is an especially desirable fuel because it has a high energy density, a low cost, and is produced from renewable resources.
  • electrocatalyst materials are typically provided at the electrodes.
  • fuel cells used electrocatalysts made of a single metal usually platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), osmium (Os), silver (Ag) or gold (Au) because they are able to withstand the corrosive environment - platinum being the most efficient and stable single-metal electrocatalyst for fuel cells operating below about 300 °C.
  • a factor contributing to this phenomenon includes the fact that the desired reduction of oxygen to water is a four-electron transfer reaction and typically involves breaking a strong O-O bond early in the reaction.
  • the open circuit voltage is lowered from the thermodynamic potential f ⁇ ro ygen reduelion ye to the formation of peroxide and possible platinum oxides which inhibit the reaction.
  • a second challenge is the stability of the oxygen electrode (cathode) during long- term operation. Specifically, a fuel cell cathode operates in a regime in which even the most unreactive metals are not completely stable. Thus, alloy compositions which contain non-noble metal elements may have a rate of corrosion which would negatively impact the projected lifetime of a fuel cell.
  • Electrocatalyst materials at the anode also face challenges during fuel cell operation. Specifically, as the concentration of carbon monoxide (CO) rises above about 10 ppm in the fuel the surface of the electrocatalyst can be rapidly poisoned. As a result, platinum (by itself) is a poor electrocatalyst if the fuel stream contains carbon monoxide (e.g., reformed-hydrogen gas typically exceeds 100 ppm). Liquid hydrocarbon-based fuels (e.g., methanol) present an even greater poisoning problem. Specifically, the surface of the platinum becomes blocked with the adsorbed intermediate, carbon monoxide (CO). It has been reported that H 2 O plays a key role in the removal of such poisoning species in accordance with the following reactions: Pt + CH 3 OH - Pt— CO + 4H + + 4e " (1 );
  • the methanol is adsorbed and partially oxidized by platinum on the surface of the electrode (1).
  • Adsorbed OH from the hydrolysis of water, reacts with the adsorbed CO to produce carbon dioxide and a proton (2,3).
  • platinum does not form OH species well at the potentials fuel cell electrodes operate (e.g., 200 mV-1.5 V).
  • step (3) is the slowest step in the sequence, limiting the rate of CO removal, thereby allowing poisoning of the electrocatalyst to occur. This applies in particular to a proton exchange membrane fuel cell which is especially sensitive to CO poisoning because of its low operating temperatures.
  • One technique for increasing electrocatalytic cathodic activity during the reduction of oxygen and electrocatalytic anodic activity during the oxidation of hydrogen is to employ an electrocatalyst which is more active, corrosion resistant, and/or more poison tolerant.
  • electrocatalyst which is more active, corrosion resistant, and/or more poison tolerant.
  • increased tolerance to CO has been reported by alloying platinum and ruthenium at a 50:50 atomic ratio (see, D. Chu and S. Gillman, J. Electrochem. Soc. 1996, 143, 1685).
  • the electrocatalysts proposed to date leave room for further improvement. BRIEF SUMMARY OF THE INVENTION
  • the present invention is directed to a catalyst for use in oxidation or reduction reactions, the catalyst comprising platinum, rhodium, at least one of tungsten, tin, and copper, and optionally molybdenum, in metallic oxidation states, provided the platinum and rhodium are at concentrations such that the sum of said concentrations is no greater than about 85 atomic percent.
  • the present invention is also directed to a supported electrocatalyst powder for use in electrochemical reactor devices, the supported electrocatalyst powder comprising a catalyst comprising platinum, rhodium, at least one of tungsten, tin, and copper, and optionally molybdenum, in metallic oxidation states, provided the platinum and rhodium are at concentrations such that the sum of said concentrations is no greater than about 85 atomic percent, and electrically conductive support particles upon which the catalyst is dispersed.
  • the present invention is also directed to a fuel cell electrode, the fuel cell electrode comprising electrocatalyst particles and an electrode substrate upon which the electrocatalyst particles are deposited, the electrocatalyst particles comprising a catalyst comprising platinum, rhodium, at least one of tungsten, tin, and copper, and optionally molybdenum, in metallic oxidation states, provided the platinum and rhodium are at concentrations such that the sum of said concentrations is no greater than about 85 atomic percent.
  • the present invention is also directed to a fuel cell comprising an anode, a cathode, a proton exchange membrane between the anode and the cathode, and a catalyst comprising platinum, rhodium, at least one of tungsten, tin, and copper, and optionally molybdenum, in metallic oxidation states, provided the platinum and rhodium are at concentrations such that the sum of said concentrations is no greater than about 85 atomic percent for the catalytic oxidation of a hydrogen-containing fuel or the catalytic reduction of oxygen.
  • the present invention is also directed to a method for the electrochemical conversion of a hydrogen-containing fuel and oxygen to reaction products and electricity in a fuel cell comprising an anode, a cathode, a proton exchange membrane therebetween, a catalyst comprising platinum, rhodium, at least one of tungsten, tin, and copper, and optionally molybdenum, in metallic oxidation states, provided the platinum and rhodium are at concentrations such that the sum of said concentrations is no greater than about 85 atomic percent, and an electrically conductive external circuit connecting the anode and cathode, the method comprising contacting the hydrogen-containing fuel or the oxygen and the catalyst to catalytically oxidize the hydrogen-containing fuel or catalytically reduce the oxygen.
  • the present invention is also directed to an unsupported catalyst layer on a surface of a electrolyte membrane or an electrode, said unsupported catalyst layer comprising platinum, rhodium, at least one of tungsten, tin, and copper, and optionally molybdenum, in metallic oxidation states, provided i i ei3l t.] r ⁇ aF.'d rhodium are at concentrations such that the sum of said concentrations is no greater than about 85 atomic percent.
  • FIG. 1 is a schematic structural view showing essential members of a fuel cell.
  • FIG. 2 is a side view of a fuel cell.
  • FIG. 3 is a photograph of an electrode array comprising thin-film alloy compositions deposited on individually addressable electrodes.
  • the present invention is directed to a metal-containing substance having electrocatalytic activity for use in, for example, fuel cells (e.g., an electrocatalyst).
  • the metal-containing substance is an alloy of the components.
  • the substance e.g., electrocatalyst
  • the substance may be a mixture of discrete amounts of the components (e.g., a mixture of metal powders or a mixture of deposits), wherein a discrete amount of the components may comprise a single component or a combination of components (e.g., an alloy).
  • a discrete amount of the components may comprise a single component or a combination of components (e.g., an alloy).
  • the electrocatalyst may become more susceptible to corrosion, and/or the activity may be diminished.
  • the composition of the present invention is preferably optimized to limit noble metal concentration while improving corrosion resistance and/or activity, as compared to platinum.
  • the present invention is thus directed to a metal-containing substance (e.g., catalyst or alloy) that comprises platinum, rhodium, at least one of tungsten, tin, and copper, and optionally molybdenum.
  • a metal-containing substance e.g., catalyst or alloy
  • platinum rhodium
  • at least one of tungsten, tin, and copper and optionally molybdenum.
  • the foregoing elements when present in the catalyst, are substantially in their metallic oxidation states. Stated another way, the average oxidation states of the foregoing catalyst elements are at or near zero.
  • the average oxidation state of each of these elements throughout the entire catalyst is less than the lowest commonly occurring oxidation state for that particular element (e.g., the lowest commonly occurring oxidation state for platinum," rhodium, tungsten 1 ; li iva-i f molybdenum is 2 and for copper it is 1). Therefore, in several embodiments of the present invention, the average oxidation states of the foregoing elements, when present in the catalyst, are less than 1 , 0.5, 0.1 , or 0.01 , and may be zero.
  • the catalyst of the present invention comprises amounts of platinum, rhodium, and at least one of tungsten, tin, and copper, and optionally molybdenum which are sufficient for the metals, present therein, to play a role in the catalytic activity and/or crystallographic structure of, for example, the alloy. Stated another way, the concentrations of platinum, rhodium, and at least one of tungsten, tin, and copper, and optionally molybdenum are such that the presence of the metals would not be considered an impurity.
  • the concentrations of each of platinum, rhodium, tungsten, tin, copper and/or molybdenum are at least about 0.1 , 0.5, 1 , or even 5 atomic percent. Additionally, the concentrations of platinum and rhodium are controlled such that the sum of their concentrations is no greater than 85 atomic percent. In other embodiments the sum of their concentrations is no greater than about 80, 75, or even 70 atomic percent.
  • the catalyst of the present invention comprises at least about 5 atomic percent of platinum. In another embodiment the concentration of platinum is at least about 10 atomic percent. In the foregoing or other embodiments the concentration of platinum is no more than 85 atomic percent. In another embodiment the concentration of platinum is no more than about 75 atomic percent. Accordingly, the concentration of platinum may, in some embodiments, be between about 5 and 85 atomic percent or between about 10 and about 75 atomic percent. In one embodiment the catalyst of the present invention comprises at least about 5 atomic percent of rhodium. In another embodiment the concentration of rhodium is at least about 10 atomic percent. In the foregoing or other embodiments the concentration of rhodium is no more than 85 atomic percent.
  • the concentration of rhodium is no more than about 75 atomic percent. Accordingly, the concentration of rhodium may, in some embodiments, be between about 5 and 85 atomic percent or between about 10 and about 75 atomic percent. In one embodiment the catalyst of present invention comprises at least 15 atomic percent of tungsten, tin, copper, molybdenum, or a combination thereof. In another embodiment the concentration of one or more of these metals is at least about 20 atomic percent. In the foregoing or other embodiments the concentration of one or more of these metals may be no more than about 95, 90, 85, or 80 atomic percent (thus the sum of the concentrations of platinum and rhodium may be at least about 5, 10, 15, or 20 atomic percent).
  • the concentration of tungsten, tin, copper, molybdenum, or a combination thereof may, in some embodiments, be between about 15 and about 90 atomic percent or between about 20 and about 80 atomic percent.
  • the catalyst comprises a concentration of platinum that is between about 10 and about 75 atomic percent, a concentration of rhodium that is between about 10 and about 75 atomic percent, and a concentration of tungsten, tin, copper, molybdenum, or a combination thereof that is between about 20 and about 80 atomic percent.
  • the substance of the present invention consists essentially of the foregoing metals (e.g., impurities that do not play a role in the catalytic activity and/or crystallographic structure of the catalyst may be present to some degree).
  • the substance may comprise other constituents as intentional additions.
  • the alloys of the present invention while maintaining the same relative amounts of the constituents disclosed herein (i.e., platinum, rhodium, at least one of tungsten, tin, and copper, and optionally molybdenum), may comprise less than 100 percent of the disclosed atoms.
  • the total concentration of the disclosed atoms is greater than about 70, 80, 90, 95, or 99 atomic percent of the substance (e.g., electrocatalyst alloy).
  • the catalyst comprises platinum, rhodium, and tungsten.
  • the catalyst is an alloy that consists essentially of the platinum, rhodium, and tungsten.
  • the concentration of each constituent metal may vary through a range. For example, in one embodiment the concentration of platinum is between about 5 and about 50 atomic percent. In another embodiment the concentration of platinum is between about 10 and about 45 atomic percent. In yet another embodiment the concentration of platinum is between about 15 and about 40 atomic percent. Similarly, the concentration of rhodium in one embodiment is between about 5 and about 50 atomic percent.
  • the concentration of rhodium is between about 10 and about 40 atomic percent. In yet another embodiment the concentration of rhodium is between about 10 and about 30 atomic percent.
  • the concentration of tungsten in one embodiment is between about 40 and about 85 atomic percent. In another embodiment the concentration of tungsten is between about 45 and about 80 atomic percent. In yet another embodiment the concentration of tungsten is between about 50 and about 70 atomic percent. Additionally, it has been discovered that improved electrocatalytic activity (e.g., relative activity compared to platinum and/or activity per weight fraction of platinum) is achieved by controlling the relative concentrations of the various metals.
  • the concentration of platinum is between about 5 and about 50 atomic percent, the concentration of rhodium is between about 5 and about 50 atomic percent, and the concentration of tungsten is between about 40 and about 90 atomic percent.
  • the concentration of platinum is between about 10 and about 45 atomic percent, the concentration of rhodium is between about 10 and about 40 atomic percent, and the concentration of tungsten is between about 45 and about 80 atomic percent.
  • the concentration of platinum is between about 15 and about 45 atomic percent, the concentration of rhodium is between about 10 and about 30 atomic percent, and the concentration of tungsten is between about 50 and about 70 atomic percent.
  • the concentration of platinum is between about 10 and about 40 atomic percent, the concentration of rhodium is between about 5 and about 30 atomic percent, and the concentration of tungsten is between about 50 and about 70 atomic percent. In still another embodiment the concentration of platinum is between about 30 and about 40 atomic percent, the concentration of rhodium is between about 10 and about 20 atomic percent, and the concentration of tungsten is between about 50 and about 60 atomic percent.
  • the catalyst comprises platinum, rhodium, and tin or copper.
  • the catalyst is an alloy that consists essentially of the platinum, rhodium, and tin or copper.
  • the concentration of each constituent metal may vary through a range. For example, in one embodiment the concentration of platinum is between about 10 and about 70 atomic percent. In another embodiment the concentration of platinum is between about 20 and about 60 atomic percent. Similarly, the concentration of rhodium in one embodiment is between about 10 and about 70 atomic percent.
  • the concentration of rhodium is between about 20 and about 60 atomic percent.
  • the concentration of tin or copper in one embodiment is between about 15 and about 70 atomic percent. In another embodiment the concentration of tin or copper is between about 20 and about 60 atomic percent.
  • the concentration of platinum is between about 10 and about 70 atomic percent
  • the concentration of rhodium is between about 10 and about 70 atomic percent
  • the concentration of tip ⁇ o copper 1® be weewtato ⁇ ut f
  • the concentration of platinum is between about 20 and about 60 atomic percent
  • the concentration of rhodium is between about 20 and about 60 atomic percent
  • the concentration of tin or copper is between about 20 and about 60 atomic percent.
  • the catalyst comprises platinum, rhodium, tungsten, and tin, molybdenum, or copper.
  • the catalyst is an alloy that consists essentially of the platinum, rhodium, tungsten, and tin, molybdenum, or copper.
  • electrocatalytic activity e.g., relative activity compared to platinum and/or activity per weight fraction of platinum
  • concentration of platinum is between about 5 and about 70 atomic percent
  • concentration of rhodium is between about 5 and about 70 atomic percent
  • concentration of tungsten is between about 5 and about 70 atomic percent
  • concentration of tin, molybdenum, or copper is between about 5 and about 70 atomic percent.
  • the concentration of platinum is between about 10 and about 50 atomic percent
  • the concentration of rhodium is between about 10 and about 50 atomic percent
  • the concentration of tungsten is between about 10 and about 50 atomic percent
  • the concentration of tin, molybdenum, or copper is between about 10 and about 50 atomic percent.
  • the concentration of platinum is between about 15 and about 25 atomic percent
  • the concentration of rhodium is between about 15 and about 25 atomic percent
  • the concentration of tungsten is between about 15 and 45 atomic percent
  • the concentration "of tin ⁇ s between about 1 &' and about 45 atomic percent.
  • the concentration of platinum is between about 15 and about 25 atomic percent
  • the concentration of rhodium is between about 15 and about 25 atomic percent
  • the concentration of tungsten is between about 15 and about 25 atomic percent
  • the concentration of molybdenum is between about 35 and about 45 atomic percent.
  • the concentration of platinum is between about 15 and about 25 atomic percent
  • the concentration of rhodium is between about 15 and about 25 atomic percent
  • the concentration of tungsten is between about 25 and 45 atomic percent
  • the concentration of copper is between about 10 and about 40 atomic percent.
  • the catalyst comprises platinum, rhodium, tin, and copper.
  • the catalyst is an alloy that consists essentially of the platinum, rhodium, tin, and copper.
  • the concentrations of platinum, rhodium, tin, and copper correspond to the concentrations of platinum, rhodium, and at least one tungsten, tin, copper, and optionally molybdenum set forth herein. Additionally, in one embodiment the concentration of platinum is between about 10 and about 25 atomic percent, the concentration of rhodium is between about 25 and about 40 atomic percent, the concentration of tin is between about 10 and about 25 atomic percent, and the concentration of copper is between about 25 and about 40 atomic percent.
  • the concentration of each constituent metal may vary through a range.
  • the concentration of platinum is between about 10 and about 30 atomic percent. In another embodiment the concentration of platinum is between about 15 and about 25 atomic percent.
  • the concentration of rhodium in one embodiment is between about 10 and about 50 atomic percent. In another embodiment the concentration of rhodium is between about 15 and about 25 atomic percent.
  • the concentration of tin in one embodiment is between about 10 and about 30 atorf ⁇ fi ' -pe ⁇ Oertt. : ⁇ M-&r ⁇ tbth-M embodiment the concentration of tin is between about 15 and about 25 atomic percent.
  • the concentration of molybdenum in one embodiment is between about 10 and about 50 atomic percent. In another embodiment the concentration of molybdenum is between about 35 and about 45 atomic percent.
  • electrocatalytic activity e.g., relative activity compared to platinum and/or activity per weight fraction of platinum
  • concentration of platinum is between about 10 and about 30 atomic percent
  • concentration of rhodium is between about 10 and about 50 atomic percent
  • concentration of tin is between about 10 and about 30 atomic percent
  • concentration of molybdenum is between about 10 and about 50 atomic percent.
  • the concentration of platinum is between about 5 and about 25 atomic percent
  • the concentration of rhodium is between about 15 and about 25 atomic percent
  • the concentration of tin is between about 15 and about 25 atomic percent
  • the concentration of molybdenum is between about 35 and about 45 atomic percent.
  • the catalyst comprises platinum, rhodium, copper, and molybdenum.
  • the catalyst is an alloy that consists essentially of the platinum, rhodium, copper, and molybdenum.
  • the concentrations of platinum, rhodium, copper, and molybdenum correspond to the concentrations of platinum, rhodium, and at least one tungsten, tin, copper, and optionally molybdenum set forth herein.
  • the concentration of platinum is between about 30 and about 50 atomic percent
  • the concentration of rhodium is between about 10 and about 30 atomic percent
  • the concentration of copper is between about 10 and about 30 atomic percent
  • the concentration of molybdenum is between about 10 and about 30 atomic percent.
  • the catalyst comprises platinum, rhodium, tin, copper, and molybdenum.
  • the catalyst is an alloy that consists essentially of the platinum, rhodium, tin, copper and molybdenum. It has been discovered that improved electrodatafytic activity '( ⁇ g., Jre iativte' activity compared to platinum and/or activity per weight fraction of platinum) is achieved by controlling the relative concentrations of the various metals.
  • the concentrations of platinum, rhodium, tin, copper, and molybdenum correspond to those concerning the concentrations of platinum, rhodium, and at least one tungsten, tin, copper, and optionally molybdenum set forth herein. Additionally, in one embodiment the concentration of platinum is between about 10 and about 30 atomic percent, the concentration of rhodium is between about 10 and about 30 atomic percent, the concentration of tin is between about 10 and about 30 atomic percent, the concentration of copper is between about 20 and about 40 atomic percent, and the concentration of molybdenum is between about 0 and about 30 atomic percent.
  • the catalyst comprises platinum, rhodium, tungsten, copper, and molybdenum.
  • the catalyst is an alloy that consists essentially of the platinum, rhodium, tungsten, copper, and molybdenum.
  • the concentrations of platinum, rhodium, tungsten, copper, and molybdenum correspond to those concerning the concentrations of platinum, rhodium, and at least one tungsten, tin, copper, and optionally molybdenum set forth herein.
  • the electrocatalyst alloys of the present invention may be formed by a variety of methods.
  • the appropriate amounts of the constituents may be mixed together and heated to a temperature above the respective melting points to form a molten solution of the metals which is cooled and allowed to solidify.
  • electrocatalysts are used in a powder form to increase the surface area which increases the number of reactive sites and leads to improved efficiency of the cell.
  • the formed metal alloy may be transformed into a powder after being solidified (e.g., by grinding) or during solidification (e.g., spraying molten alloy and allowing the droplets to solidify). It may, however, b "&dv&n ⁇ y- ⁇ t ⁇ to .e Bi ⁇ at ⁇ ' alloys for electrocatalytic activity in a non-powder form (see, Examples 1 and 2, infra).
  • an electrocatalyst alloy for use in a fuel cell may be deposited over the surface of electrically conductive supports (e.g., carbon black).
  • One method for loading an electrocatalyst alloy onto supports typically comprises depositing metal precursor compounds onto the supports, and converting the precursor compounds to metallic form and alloying the metals using a heat-treatment in a reducing atmosphere (e.g., an atmosphere comprising an inert gas such as argon).
  • a reducing atmosphere e.g., an atmosphere comprising an inert gas such as argon.
  • One method for depositing the precursor compounds involves chemical precipitation of precursor compounds onto the supports.
  • the chemical precipitation method is typically accomplished by mixing supports and sources of the precursor compounds (e.g., an aqueous solution comprising one or more inorganic metallic salts) at a concentration sufficient to obtain the desired loading of the electrocatalyst on the supports and then precipitation of the precursor compounds is initiated (e.g., by adding an ammonium hydroxide solution).
  • the slurry is then typically filtered from the liquid under vacuum, washed with deionized water, and dried to yield a powder that comprises the precursor compounds on the supports.
  • Another method for depositing the precursor compounds comprises forming a suspension comprising a solution and supports suspended therein, wherein the solution comprises a solvent portion and a solute portion that comprises the constituents of the precursor compound(s) being deposited.
  • the suspension is frozen to deposit (e.g., precipitate) the precursor compound(s) on the particles.
  • the frozen suspension is freeze-dried to remove the solvent portion and leave a freeze-dried powder comprising the supports and the deposits of the precursor compound(s) on the supports.
  • the temperature reached during the thermal treatment is typically at least as high as the decomposition temperature(s) for the precursor compound(s) and not be so high as to result in degradation of the supports and agglomeration of the supports and/or the electrocatalyst deposits.
  • the temperature is between about 60 °C and about 1100 °C.
  • Inorganic metal-containing compounds typically decompose at temperatures between about 600 and about 1000 °C.
  • the duration of the heat treatment is typically at least sufficient to substantially convert the precursor compounds to the desired state.
  • the temperature and time are inversely related (i.e., conversion is accomplished in a shorter period of time at higher temperatures and vice versa).
  • the duration of the heat treatment is typically at least about 30 minutes. In one embodiment, the duration is between about 2 and about 8 hours.
  • Unsupported Catalyst or Alloys in Electrod /PuellGel B ⁇ IJc ⁇ ti ⁇ It is to be noted that, in another embodiment of the present invention, the metal substance (e.g., catalyst or alloy) may be unsupported; that is, it may be employed in the absence of a support particle.
  • each component (e.g., metal) of the catalyst or alloy may be deposited separately, each for example as a separate layer on the surface of the electrode, membrane, etc. Alternatively, two or more components may be deposited at the same time. Additionally, in the case of an alloy, the alloy may be formed and then deposited, or the components thereof may be deposited and then the alloy subsequently formed thereon.
  • Deposition of the component(s) may be achieved using means known in the art, including for example known sputtering technique (see, e.g., PCT Application No. WO 99/16137). Generally speaking, however, in one approach sputter- deposition is achieved by creating, within a vacuum chamber in an inert atmosphere, a voltage differential between a target component material and the surface onto which the target component is to be deposited, in order to dislodge particles from the target component material which are then attached to the surface of, for example, an electrode or electrolyte membrane, thus forming a coating of the target component thereon.
  • sputter- deposition is achieved by creating, within a vacuum chamber in an inert atmosphere, a voltage differential between a target component material and the surface onto which the target component is to be deposited, in order to dislodge particles from the target component material which are then attached to the surface of, for example, an electrode or electrolyte membrane, thus forming a coating of the target component thereon.
  • each metal or component of the catalyst or alloy may be controlled independently, in order to tailor the composition to a given application. In some embodiments, however, the amount of each deposited component may be less than about 5 mg/cm 2 of surface area (e.g., electrode surface area, membrane surface area, etc.), less than about 1 mg/cm 2 , less than about 0.5 mg/cm 2 , less than about 0.1 mg/cm 2 , or even less than about 0.05 mg/cm 2 .
  • the amount of the deposited component, or alloy may range from about 0.5 mg/e ' m 1 t ⁇ r les& i th ⁇ l, a'b ⁇ ui!' 5' mg7er ⁇ ; i: or from about 0.1 mg/cm 2 to less than about 1 mg/cm 2 .
  • the specific amount of each component, and/or the conditions under which the component is deposited may be controlled in order to control the resulting thickness of the component, or alloy, layer on the surface of the electrode, electrolyte membrane, etc.
  • the deposited layer may have a thickness ranging from several angstroms (e.g., about 2, 4, 6, 8, 10 or more) to several tens of angstroms (e.g., about 20, 40, 60, 80, 100 or more), up to several hundred angstroms (e.g., about 200, 300, 400, 500 or more).
  • the layer of the multi-component metal substance of the present invention may have a thickness ranging from several tens of angstroms (e.g., about 20, 40, 60, 80, 100 or more), up to several hundred angstroms (e.g., about 200, 400, 600, 800, 1000, 1500 or more).
  • the thickness may be, for example, between about 10 and about 500 angstroms, between about 20 and about 200 angstroms, and between about 40 and about 100 angstroms.
  • a catalyst or alloy (or the components thereof) are deposited as a thin film on the surface of, for example, an electrode or electrolyte membrane
  • the composition of the deposited catalyst or alloy may be as previously described herein.
  • a fuel cell generally indicated 21, comprises a fuel electrode (anode) 2 and an air electrode, oxidizer electrode (cathode) 3.
  • a proton exchange membrane 1 serves as an electrolyte and it is usually a strongly acidic ion exchange membrane such as a perfluorosulphonic acid-based membrane.
  • the proton exchange membrane 1, the anode 2, and the cathode 3 are integrated into one body to minimize contact resistance between the electrodes and the proton exchange membrane.
  • Current collectors 4 and 5 engage the anode and the cathode, respectively.
  • a fuel chamber 8 and an air chamber 9 contain the respective reactants and are sealed by sealants 6 and 7, respectively.
  • electricity is generated by hydrogen-containing fuel combustion (i.e., the hydrogen-containing fuel and oxygen react to form water, carbon dioxide and electricity).
  • hydrogen-containing fuel combustion i.e., the hydrogen-containing fuel and oxygen react to form water, carbon dioxide and electricity.
  • This is accomplished in the above-described fuel cell by introducing the hydrogen-containing fuel F into the fuel chambeT'Sr hile' ⁇ xygen O ' (preferably air) is introduced into the air chamber 9, whereby an electric current can be immediately transferred between the current collectors 4 and 5 through an outer circuit (not shown).
  • the hydrogen-containing fuel is oxidized at the anode 2 to produce hydrogen ions, electrons, and possibly carbon dioxide gas.
  • the hydrogen ions migrate through the strongly acidic proton exchange membrane 1 and react with oxygen and electrons transferred through the outer circuit to the cathode 3 to form water.
  • the hydrogen-containing fuel F is methanol, it is preferably introduced as a dilute acidic solution to enhance the chemical reaction, thereby increasing power output (e.g
  • the material of the proton exchange membrane is typically selected to be resistant to dehydration at temperatures up to between about 100 and about 120 °C.
  • Proton exchange membranes usually have reduction and oxidation stability, resistance to acid and hydrolysis, sufficiently low electrical resistivity (e.g., ⁇ 10 ⁇ « cm), and low hydrogen or oxygen permeation.
  • proton exchange membranes are usually hydrophiiic. This ensures proton conduction (by reversed diffusion of water to the anode), and prevents the membrane from drying out thereby reducing the electrical conductivity.
  • the layer thickness of the membranes is typically between 50 and 200 ⁇ m.
  • Suitable proton-conducting membranes also include perfluorinated sulfonated polymers such as NAFION and its derivatives produced by E.I. du Pont de Nemours & Co., Wilmington, Delaware.
  • NAFION is based on a copolymer made from tetrafluoroethylene and perfluorovinylether, and is provided with sulfonic groups working as ion-exchanging groups.
  • the electrodes of the present invention comprise the electrocatalyst compositions of the present invention and an electrode substrate upon which the electrocatalyst is deposited.
  • the electrocatalyst alloy is directly deposited on the electrode substrate.
  • the electrocatalyst alloy is supported on electrically conductive supports and the supported electrocatalyst is deposited on the electrode substrate.
  • the electrode may also comprise a proton conductive material that is in conf ⁇ ct-with ' the ei ⁇ et ⁇ ca ⁇ alyBt.
  • T- ' proton conductive material may facilitate contact between the electrolyte and the electrocatalyst, and may thus enhance fuel cell performance.
  • the electrode is designed to increase cell efficiency by enhancing contact between the reactant (i.e., fuel or oxygen), the electrolyte and the electrocatalyst.
  • porous or gas diffusion electrodes are typically used since they allow the fuel/oxidizer to enter the electrode from the face of the electrode exposed to the reactant gas stream (back face), and the electrolyte to penetrate through the face of the electrode exposed to the electrolyte (front face), and reaction products, particularly water, to diffuse out of the electrode.
  • the electrically conductive support particles typically comprise an inorganic material such as carbon.
  • the support particles may comprise an organic material such as an electrically conductive polymer (see, U.S. Pat. Appln. 2002/0132040 A1).
  • Carbon supports may be predominantly amorphous or graphitic and they may be prepared commercially, or specifically treated to increase their graphitic nature (e.g., heat treated at a high temperature in vacuum or in an inert gas atmosphere) thereby increasing corrosion resistance.
  • it may be oil furnace black, acetylene black, graphite paper, carbon fabric, or carbon aerogel.
  • a carbon aerogel preferably has an electrical conductivity of between 10 "2 and 10 3 ⁇ "1 'cm "1 and a density of between 0.06 and 0.7 g/cm 3 ; the pore size is between 20 and 100 nm (porosity up to about 95%).
  • Carbon black support particles may have a Brunauer, Emmett and Teller (BET) surface area up to about 2000 m 2 /g. It has been reported that satisfactory results are achieved using carbon black support particles having a high mesoporous area, e.g., greater than about 75 m 2 /g (see, Catalysis for Low Temperature Fuel Cells Part 1 : The Cathode Challenges, T.R. Ralph and M.P. Hogarth, Platinum Metals Rev., 2002, 46, (1), p. 3-14). Experimental results to date indicate that a surface area of about 500 m 2 /g is preferred.
  • the proton exchange membrane, electrodes, and electrocatalyst materials are in contact with each other. This is typically accomplished by depositing the electrocatalyst either on the electrode, or on the proton exchange membrane, and then placing the electrode and membrane in contact.
  • the alloy electrocatalysts of this invention can be deposited on either the electrode or the membrane by a variety of methods, including plasma deposition, powder application (the powder may also be in the form of a slurry, a paste, or an ink), chemical plating, and sputtering.
  • Plasma deposition generally entails depositing a thin layer (e.g., between 3 and 50 ⁇ m, preferably between 5 and 20 ⁇ m) of an electrocatalyst composition on the membrane using low-pressure plasma.
  • a thin layer e.g., between 3 and 50 ⁇ m, preferably between 5 and 20 ⁇ m
  • an organic platinum compound such as trimethylcyclopentadienylplatinum is gaseous between 10 "4 and 10 mbar and can be excited using radio-frequency, microwaves, or an electron cyclotron resonance transmitter to deposit ptatinurwon tPie :i meinfetenes
  • electrocatalyst powder is distributed onto the proton exchange membrane surface and integrated at an elevated temperature under pressure.
  • the electrocatalyst particles exceeds about 2 mg/cm 2 the inclusion of a binder such as polytetrafluoroethylene is common.
  • the electrocatalyst may be plated onto dispersed small support particles (e.g., the size is typically between 20 and 200 A, and more preferably between about 20 and 100 A). This increases the electrocatalyst surface area which in turn increases the number of reaction sites leading to improved cell efficiency.
  • a powdery carrier material such as conductive carbon black is contacted with an aqueous solution or aqueous suspension (slurry) of compounds of metallic components constituting the alloy to permit adsorption or impregnation of the metallic compounds or their ions on or in the carrier.
  • a dilute solution of suitable fixing agent such as ammonia, hydrazine, formic acid, or formalin is slowly added dropwise to disperse and deposit the metallic components on the carrier as insoluble compounds or partly reduced fine metal particles.
  • the loading, or surface concentration, of an electrocatalyst on the membrane or electrode is based in part on the desired power output and cost for a particular fuel cell.
  • power output increases with increasing concentration; however, there is a level beyond which performance is not improved.
  • cost of a fuel cell increases with increasing concentration.
  • the surface concentration of electrocatalyst is selected to meet the application requirements.
  • a fuel cell designed to meet the requirements of a demanding application such as an extraterrestrial vehicle will usually have a surface concentration of electrocatalyst sufficient to maximize the fuel cell power output.
  • economic considerations dictate that the desired power output be attained with as little electrocatalyst as possible.
  • the loading of electrocatalyst is between about 0.01 and about 6 mg/cm 2 .
  • Experimental results to date indicate that in some embodiments the electrocatalyst loading is preferably less than about 1 mg/cm 2 , and more preferably between about 0.1 and 1 mg/cm 2 .
  • the layers are usually compressed at high temperature.
  • the housings of the individual fuel cells are configured in such a way that a good gas supply is ensured, and at the same time the product water can be discharged properly.
  • the electrocatalyst compositions and fuel cell electrodes of the present invention may be used to electrocatalyze any fuel containing hydrogen (e.g., hydrogen and reformated-hydrogen fuels).
  • hydrocarbon-based fuels may be used including saturated hydrocarbons such as methane (natural gas)'; etfoan-e propane and butane; garbage off-gas; oxygenated hydrocarbons such as methanol and ethanol; and fossil fuels such as gasoline and kerosene; and mixtures thereof.
  • suitable acids gases or liquids
  • suitable acids are typically added to the fuel.
  • SO 2 , SO 3 sulfuric acid, trifluoromethanesulfonic acid or the fluoride thereof, also strongly acidic carboxylic acids such as trifluoroacetic acid, and volatile phosphoric acid compounds may be used ("Ber. Bunsenges. Phys. Chem.”, Volume 98 (1994), pages 631 to 635).
  • the alloy compositions of the present invention are useful as electrocatalysts in fuel cells which generate electrical energy to perform useful work.
  • the alloy compositions may be used in fuel cells which are in electrical utility power generation facilities; uninterrupted power supply devices; extraterrestrial vehicles; transportation equipment such as heavy trucks, automobiles, and motorcycles (see, Fuji et al., U.S. Pat. No. 6,048,633; Shinkai et al., U.S. Pat. No. 6,187,468; Fuji et al., U.S. Pat. No. 6,225,011 ; and Tanaka et al., U.S. Pat. No.
  • Electrocatalytic Alloys on Individually Addressable Electrodes The electrocatalyst alloy compositions set forth in Tables A and B, infra, were prepared using the combinatorial techniques disclosed in Warren et al., U.S. Pat. No. 6,187,164; Wu et al., U.S. Pat. No. 6,045,671; Strasser, P., Gorer, S. and Devenney, M., Combinatorial Electrochemical Techniques For The Discovery of New Fuel-Cell Cathode Materials, Nayayanan, S.R., Gottesfeld, S. and Zawodzinski, T., eds., Direct Methanol Fuel Cells, Proceedings of the Electrochemical Society, New Jersey, 2001 , p.
  • an array of independent electrodes may be fabricated on inert substrates (e.g., glass, quartz, sapphire alumina, plastics, and thermally treated silicon).
  • the individual electrodes' were"l ⁇ ca ⁇ e ⁇ -l substantially in the center of the substrate, and were connected to contact pads around the periphery of the substrate with wires.
  • the electrodes, associated wires, and contact pads were fabricated from a conducting material (e.g., titanium, gold, silver, platinum, copper or other commonly used electrode materials).
  • the alloy compositions set forth in Tables A and B were prepared using a photolithography/RF magnetron sputtering technique (GHz range) to deposit thin-film alloys on arrays of 64 individually addressable electrodes.
  • a quartz insulating substrate was provided and photolithographic techniques were used to design and fabricate the electrode patterns on it.
  • photoresist By applying a predetermined amount of photoresist to the substrate, photolyzing preselected regions of the photoresist, removing those regions that have been photolyzed (e.g., by using an appropriate developer), depositing a layer of titanium about 500 nm thick using RF magnetron sputtering over the entire surface and removing predetermined regions of the deposited titanium (e.g. by dissolving the underlying photoresist), intricate patterns of individually addressable electrodes were fabricated on the substrate.
  • a photolithography/RF magnetron sputtering technique GHz range
  • the fabricated array 20 consisted of 64 individually addressable electrodes 21 (about 1.7 mm in diameter) arranged in an 8 x 8 square that were insulated from each other (by adequate spacing) and from the substrate 24 (fabricated on an insulating substrate), and whose interconnects 22 and contact pads 23 were insulated from the electrochemical testing solution (by the hardened photoresist or other suitable insulating material).
  • a patterned insulating layer covering the wires and an inner portion of the peripheral contact pads, but leaving the electrodes and the outer portion of the peripheral contact pads exposed (preferably approximately half of the contact pad is covered with this insulating layer) was deposited. Because of the insulating layer, it is possible to connect a lead (e.g., a pogo pin or an alligator clip) to the outer portion of a given contact pad and address its associated electrode while the array is immersed in solution, without having to worry about reactions that can occur on the wires or peripheral contact pads.
  • a lead e.g., a pogo pin or an alligator clip
  • the insulating layer was a hardened photoresist, but any other suitable material known to be insulating in nature could have been used (e.g., glass silica, alumina, magnesium oxide, silicon nitride, boron nitride, yttrium oxide, or titanium dioxide).
  • a steel mask having 64 holes (1.7 mm in diameter) was pressed onto the substrate to prevent deposition of sputtered material onto the insulating resist layer.
  • the deposition of the electrocatalyst alloys was also accomplished using RF magnetron sputtering and a two shutter masking system as described by Wu et al. which enable the deposition of material onto 1 or more electrodes at a time.
  • Each individual thin-film electrocatalyst alloy is created by a super lattice deposition method.
  • metals M1 , M2 and M3 are to be deposited and alloyed onto one electrode.
  • a metal M1 sputter target is selected and a thin film of M1 having a defined thickness is deposited on the electrode. This initial thickness is typically from about 3 to about 12 A.
  • metal M2 is selected as the sputter target and a layer of M2 is deposited onto the layer of M1.
  • the thickness of M2 layer is also from about 3 to about 12 A.
  • the thicknesses of the deposited layers are in the range of the diffusion length of the metal atoms (e.g., about 10 to about 30 A) which allows in-situ alloying of the metals.
  • a layer of M3 is deposited onto the M1-M2 alloy forming a M1-M2-M3 alloy film.
  • an alloy thin-film (9 - 25 A thickness) of the desired stoichiometry is created. This concludes one deposition cycle.
  • deposition cycles are repeated as necessary which results in the creation of a super lattice structure of a defined total thickness (typically about 700 A).
  • a computer program to design an output file which contains the information necessary to control the operation of the sputtering device during the preparation of a particular library wafer (i.e., array).
  • One such computer program is the LIBRARY STUDIO software available from Symyx Technologies, Inc. of Santa Clara, California and described in European Patent No. 1080435 B1.
  • the compositions of several as sputtered alloy compositions were analyzed using x-ray fluorescence (XRF) to confirm that they were consistent with desired compositions (chemical compositions determined using x-ray fluorescence are within about 5% of the actual composition).
  • Arrays were prepared to evaluate the specific alloy compositions set forth in Tables A and B below. On each array one electrode consisted essentially of platinum and it served as an internal standard for the screening operation.
  • Example 2 Screening Alloys for Electrocatalytic Activity
  • the alloy compositions set forth in Tables A and B (set forth above) that were synthesized on arrays according to the method set forth in Example 1 were screened for the electrochemical reduction of molecular oxygen to water to determine relative electrocatalytic activity against the internal and/or external platinum standard.
  • the array wafers were assembled into an electrochemical screening cell and a screening device established an electrical contact between the 64 electrode electrocatalysts (working electrodes) and a 64-channel multi channel potentiostat used for the screening.
  • each wafer array was placed into a screening device such that all 64 spots are facing upward and a tube cell body that was generally annular and having an inner diameter of about 2 inches (5 cm) was pressed onto the upward facing wafer surface.
  • the diameter of this tubular cell was such that the portion of the wafer with the square electrode array formed the base of a cylindrical volume while the contact pads were outside the cylindrical volume.
  • a liquid ionic solution (electrolyte) was poured into this cylindrical volume and a common counter electrode (i.e., platinum gauze), as well as a common reference electrode (e.g., mercury/mercury sulfate reference electrode (MMS)), were placed into the electrolyte solution to close the electrical circuit.
  • a common counter electrode i.e., platinum gauze
  • a common reference electrode e.g., mercury/mercury sulfate reference electrode (MMS)
  • a rotator shaft with blades was also placed into the electrolyte to provide forced convection-diffusion conditions during the screening.
  • the rotation rate was typically between about 300 to about 400 rpm.
  • either argon or pure oxygen was bubbled through the electrolyte during the measurements.
  • Argon served to remove O 2 gas in the electrolyte to simulate O 2 - free conditions used for the initial conditioning of the electrocatalysts.
  • the introduction of pure oxygen served to saturate the electrolyte with oxygen for the oxygen reduction reaction.
  • the electrolyte was maintained at 60 °C and the rotation rate was constant. Three groups of tests were performed to screen the activity of the electrocatalysts.
  • the electrolyte (1 M HCIO 4 ) was purged with argon for about 20 minutes prior to the electrochemical measurements.
  • the first group of tests comprised cyclic voltammetric measurements while purging the electrolyte with argon. Specifically, the first group of tests comprised: a. a potential sweep from about OCP to about +0.3" l V- : to about -O.63 ; ⁇ and back to about +0.3 V at a rate of about 20 mV/s; b. twelve consecutive potential sweeps from OCP to about +0.3 V to about -0.7 V and back to about +0.3 V at a rate of about 200 mV/s; and c. a potential sweep from about OCP to about +0.3 V to about -0.63 V and back to about +0.3 V at a rate of about 20 mV/s.
  • the electrolyte was then purged with oxygen for approximately 30 minutes.
  • the following second group of tests were performed while continuing to purge with oxygen: a. measuring the open circuit potential (OCP) for a minute; then, starting at OCP the voltage was swept down to about -0.4 V at a rate of about 10 mV/s; b. measuring the OCP for a minute; then applying a potential step from OCP to about +0.1 V while measuring the current for about 5 minutes; and c. measuring the OCP for a minute; then applying a potential step from OCP to about +0.2 V while monitoring the current for about 5 minutes.
  • OCP open circuit potential
  • the third group of tests comprised a repeat of the second group of tests after about one hour from completion of the second group of tests.
  • the electrolyte was continually stirred and purged with oxygen during the waiting period. All the foregoing test voltages are with reference to a mercury/mercury sulfate (MMS) electrode.
  • MMS mercury/mercury sulfate
  • an external platinum standard comprising an array of 64 platinum electrodes in which the oxygen reduction activity of the 64 platinum electrodes averaged -0.35 mA/cm 2 at +0.1 V vs. a mercury/mercury sulfate electrode was used to monitor the tests to ensure the accuracy of the oxygen reduction evaluation.
  • the alloys corresponding to Electrode Numbers 7, 4, 45, 51 , 63, 48, 60, 44, 47, 41 , 36, 58, 52, 55, 40, 39, 42, 34, 37, 50, and 33 had an end current density (or activity) per weight fraction of platinum that exceeded the platinum standard (100% platinum).
  • the Pt-Rh-W alloy compositions corresponding to Electrode Numbers 23, 22, 6, 13, 5, 21, 14, 15, 7, 20, 4, 12, and 29 exhibited an oxygen reduction activity greater than the internal platinum standard. Further, all the alloys set forth in Table B had an end current density (or activity) per weight fraction of platinum that exceeded the platinum standard (100% platinum).
  • Example 3 Synthesis of Supported Electrocatalyst Alloys
  • the synthesis of Pt 32 Rh 12 W 56 , and Pt 20 Rh 20 Mo 40 Sn 20 (see, Table C, Target Catalyst Comp., infra) on carbon support particles was attempted according to different process conditions in order to evaluate the performance of the alloys while in a state that is typically used in fuel cell. To do so, the alloy component precursors were deposited or precipitated on supported platinum powder (i.e., platinum nanoparticles supported on carbon black particles). Platinum supported on carbon black is commercially available from companies such as Johnson Matthey, Inc., of New Jersey and E-Tek Div. of De-Nora, N.A., Inc., of Sommerset, New Jersey.
  • Such supported platinum powder is available with a wide range of platinum loading.
  • the supported platinum powder used in this example had a nominal platinum loading of about 40 percent by weight, a platinum surface area of between about 150 and about 170 m 2 /g (determined by CO adsorption), a combined carbon and platinum surface area between about 350 and about 400 m /g (determined by N 2 adsorption), and an average particle size of less than about 0.5 mm (determined by sizing screen).
  • the electrocatalyst alloys corresponding to the target compositions of Pt 32 Rh 12 W 56 were formed on carbon support particles using a chemical precipitation method according to the following steps.
  • a chemical precipitation method according to the following steps.
  • To prepare the HFC 38 and 39 compositions about 0.25 g of carbon supported platinum powder (37.8 wt% Pt) was dispersed in about 100 mL of room temperature 18 M ⁇ deionized water using an ultrasonic blending device (e.g., an AQUASONIC 50 D set at power level 9) for about 2 hours to form a slurry.
  • an ultrasonic blending device e.g., an AQUASONIC 50 D set at power level 9
  • the slurry was stirred using a magnetic stirring device, and while being stirred, appropriate volumes 1 based on the targeted electrocatalyst composition of one or more appropriate solutions and/or suspension comprising the metals to be alloyed with the platinum nanoparticles were added drop-wise to the slurry (i.e., a 0.85 ml of 1M tungstic acid colloidal suspension and 0.19 ml of 1M Rh(NO 3 ) 3 '2H 2 O solution).
  • the tungstic acid colloidal suspension was prepared by dissolving the tungstic acid in water to form a yellow solution and then adding ammonium hydroxide until the yellow color disappears and the solution became a colloidal suspension.
  • the stirring was continued and the slurries (HFC 38 and 39) were heated to a temperature between about 60 and about 90 °C for about 1 hour.
  • Precipitation of compounds comprising the metals was then initiated by slowly adding a 10 wt % ammonium hydroxide aqueous solution to the slurries until the slurry had a pH of about 10.
  • the slurries were stirred for about 15 more minutes.
  • the slurries were then filtered from the liquid under vacuum after which the filtrate was washed with about 150 mL of deionized water.
  • the powders were then dried at a temperature between about 60 and about 100 °C for about 4 hours to about 8 hours.
  • the electrocatalyst alloys corresponding to HFC 154, 155, 158, 159, 183, and 184 were formed on carbon support particles using a freeze-drying precipitation method.
  • the freeze-drying method comprised forming a precursor solution comprising the desired metal atoms in the desired concentrations.
  • a precursor solution comprising the desired metal atoms in the desired concentrations.
  • the target Pt 20 Rh 20 Mo 40 Sn 20 alloy compositions HFC 154 and 155
  • about 0.069 g of (NH 4 ) 6 Mo 7 O 24 » 4H 2 O was dissolved in about 5 ml H 2 O and then about 0.144 ml of a Rh(NO 3 ) 3 solution [about 10 wt% Rh solution in HNO 3 ] was dissolved in the solution.
  • the HFC 154, 155, 183, and 184 solutions were introduced into separate HDPE (High Density Poly Ethylene) vials containing about 0.200 g of supported platinum powder which had a nominal platinum loading of about 19.2 percent by weight resulting in a black suspension.
  • the suspensions were homogenized by immersing a probe of a BRANSON SONIFIER 150 into the vial arid sonic ting the mfxttire for about 1 minute at a power level of 3.
  • the first source solution (the molybdenum and rhodium-containing solution) was introduced into the HDPE vial containing the 0.200 g of supported platinum powder with the same platinum loading, resulting in a black suspension.
  • the suspension was homogenized by immersing a probe of a BRANSON SONIFIER 150 into the vial and sonicating the mixture for about 30 seconds at a power level of 3.
  • the second source solution (the tin-containing solution) was introduced into the vials, which contained the suspensions of the carbon supported platinum, molybdenum and rhodium-containing solution.
  • the suspension was further homogenized by sonicating the mixture for an additional 1 minute at a power level of 3.
  • each vial containing the homogenized suspensions were then immersed in a liquid nitrogen bath for about 3 minutes to solidify the suspensions.
  • the solid suspensions were then freeze-dried for about 24 hours using a LABONCO FREEZE DRY SYSTEM (Model 79480) to remove the solvent.
  • the tray and the collection coil of the freeze dryer were maintained at about 26 °C and about -48 °C, respectively, while evacuating the system (the pressure was maintained at about 0.15 mbar).
  • each vial contained a powder comprising the supported platinum powder, and rhodium, and tungsten, molybdenum, tin, and/or copper.
  • the recovered precursor powders were then subjected to a heat treatment to reduce the precursors to their metallic state, and to alloy the metals with each other and the platinum on the carbon black particles.
  • One particular heat treatment comprised heating the powder in a quartz flow furnace with an atmosphere comprising about 6% H 2 and 94% Ar using a temperature profile of room temperature to about 40 °C at a rate of about 5 °C/min; holding at about 40 °C for 2 hours; increasing the temperature to about 200 °C at a rate of 5 °C/min; holding at about 200 °C for two hours; increasing the temperature at a rate of about 5 °C/min to about 700 or 900 °C; holding at a max temperature of about 700 or 900 °C for a duration of about two, three, seven or eight hours (indicated in Table C); and cooling down to room temperature.
  • the differently prepared alloys e.g., by composition variation or by heat treatment variation
  • ICP elemental analysis or subjected to EDS (Electron Dispersive Spectroscopy) elemental analysis.
  • EDS Electro Dispersive Spectroscopy
  • Example 4 Evaluating the Electrocatalytic Activity of Supported Electrocatalysts
  • the supported alloy electrocatalysts set forth in Table C and formed according to Example 3 were subjected to electrochemical measurements to evaluate their activities.
  • the supported alloy electrocatalysts were applied to a rotating disk electrode (RDE) as is commonly used in the art (see, Rotating disk electrode measurements on the CO tolerance of a high-surface area Pt/Vulcan carbon fuel cell electrocatalyst, Schmidt et al., Journal of the Electrochemical Society (1999), 146(4), 1296-1304; and Characterization of high- surface-area electrocatalysts using a rotating disk electrode configuration, Schmidt et al., Journal of the Electrochemical Society (1998), 145(7), 2354-2358).
  • RDE rotating disk electrode
  • Rotating disk electrodes are a relatively fast and simple screening tool for evaluating supported electrocatalysts with respect to their intrinsic electrolytic activity for oxygen reduction (e.g., the cathodic reaction of a fuel cell).
  • the rotating disk electrode was prepared by depositing an aqueous-based ink that comprises the support electrocatalyst and a NAFION solution on a glassy carbon disk.
  • the concentration of electrocatalyst powder in the NAFION solution was about 1 mg/mL.
  • the NAFION solution comprised the perfluorinated ion- exchange resin, lower aliphatic alcohols and water, wherein the concentration of resin is about 5 percent by weight.
  • the NAFION solution is commercially available from the ALDRICH catalog as product number 27,470-4.
  • the glassy carbon electrodes were 5 mm in diameter and were polished to a mirror finish. Glassy carbon electrodes are commercially available, for example, from Pine Instrument Company of Grove City, Pennsylvania. An aliquot of 10 ⁇ L electrocatalyst suspension was added to the carbon substrate and allowed to dry at a temperature between about 60 and 70 °C. The resulting layer of NAFION and electrocatalyst was less than about 0.2 ⁇ m thick. This method produced slightly different platinum loadings for each electrode made with a particular suspension, but the variation was determined to be less than about 10 percent by weight. After being dried, the rotating disk electrode was immersed into an electrochemical cell comprising an aqueous 0.5 M H 2 SO 4 electrolyte solution maintained at room temperature.
  • the electrochemical cell was purged of oxygen by bubbling argon through the electrolyte for about 20 minutes. All measurements were taken while rotating the electrode at about 2000 rpm, and the measured current densities were normalized either to the glassy carbon substrate area or to the platinum loading on the electrode.
  • Two groups of tests were performed to screen the activity of the supported electrocatalysts.
  • the first group of tests comprised cyclic voltammetric measurements while purging the electrolyte with argon. Specifically, the first group comprised: a. two consecutive potential sweeps starting from OCP to about +0.35V then to about -0.65V and back to OCP at a rate of about 50 mV/s; b.
  • the second test comprised purging with oxygen for about 15 minutes followed by a potential sweep test for oxygen reduction while continuing to purge the electrolyte with oxygen.
  • potential sweeps from about -0.45 V to +0.35 V were performed at a rate of about 5 mV/s to evaluate the initial activity of the electrocatalyst as a function of potential and to create a geometric current density plot.
  • the electrocatalysts were evaluated by comparing the diffusion corrected activity at 0.15 V. All the foregoing test voltages are with reference to a mercury/mercury sulfate electrode. Also, it is to be noted that the oxygen reduction measurements for a glassy carbon RDE without an electrocatalyst did not show any appreciable activity within the potential window.
  • the above-described supported electrocatalyst alloy compositions were evaluated in accordance with the above-described method and the results are set forth in Table C.
  • the alloy compositions Pt 19 Rh 14 Mo 42 Sn 25 and Pt 18 Rh 19 Mo 40 Sn 23 exhibited oxygen reduction activities greater than that of carbon supported platinum.
  • the results of the evaluation also indicate, among other things, that it may take numerous iterations to develop a set of parameters for producing the target alloy composition. Also evidenced by the data, is that activity can be adjusted by changes in the processing conditions and fuel cell operation conditions.
  • differences in activity for similar alloy compositions may be due to several factors such as alloy homogeneity (e.g., an alloy, as defined below, may have regions in which the constituent atoms show a presence or lack of order, i.e., regions of solid solution within an ordered lattice, or some such superstructure), changes in the lattice parameter due to changes in the average size of "component atoms, changes in particle size, and changes in crystallographic structure/symmetry.
  • alloy homogeneity e.g., an alloy, as defined below, may have regions in which the constituent atoms show a presence or lack of order, i.e., regions of solid solution within an ordered lattice, or some such superstructure
  • changes in the lattice parameter due to changes in the average size of "component atoms, changes in particle size, and changes in crystallographic structure/symmetry.
  • the ramifications of structure and symmetry changes are often difficult to predict.
  • Platinum and rhodium have a face-centered cubic (f
  • tungsten and molybdenum typically crystallize in a body-centered cubic (bcc) structure, however, other structures are also possible.
  • the various structures of tin are often more complex.
  • Pt-Rh alloys may form complete solid solutions based on the similarities of the end members.
  • Pt-W alloys may form solid solutions, however, at least one unique Pt-W alloy is also known to exist.
  • Pt-Mo alloys are known in a variety of compositions and symmetries, while the Pt-Sn system displays still more structure types. When ternary systems are considered, the phase space becomes increasingly complex. Clearly, symmetry variations are to be expected across a multi-component compositional range within these systems.
  • Pt-Fe An example from a less complex system, Pt-Fe, displays the types of variations that may be expected. For example, in the Pt-Fe system, as the amount of iron added to platinum increases, the lattice of the resulting alloy may be expected to change from an fee lattice to a tetragonal primitive lattice.
  • an fcc-based solid solution first occurs (e.g., Fe and Pt may mix randomly within some concentration limits, or under some specific synthesis conditions), and out of this solid solution an ordered phase may gradually crystallize (e.g., Pt 3 Fe, primitive cubic structure) only to return to a solid solution (disordered alloy) and again back to an ordered phase (now with either a primitive or face-centered tetragonal structure) as the formula PtFe is achieved.
  • Symmetry changes e.g., those associated with the changes from a cubic face-centered structure to a primitive tetragonal structure
  • the 12-coordinate metallic radii of platinum, rhodium, tungsten, molybdenum, copper and tin are 1.39 A, 1.34 A, 1.41 A, 1.40 A, 1.28 A and 1.58 A, respectively, and as metals are substituted for platinum, the average metal radius, and consequently the observed lattice parameter of a disordered alloy may be expected to contract or expand accordingly.
  • the average radius may be used as an indicator of lattice changes as a function of stoichiometry, or alternatively, as an indicator of stoichiometry based on observed diffraction patterns.
  • the average radii may fee useful as a general rule, experimental results are typically expected to conform only in a general manner because local ordering, significant size disparity between atoms, significant changes in symmetry, and other factors may produce results that are inconsistent with expectations. This may be particularly true in the case of ordered alloys where an increase in the directionality of bonding may occur.
  • the predicted change in the average radius for the Pt 19 Rh 14 Mo 42 Sn 25 alloys was an expansion of 3.4% vs. platinum.
  • the XRD pattern showed a mixed phase material that may include partially substituted Pt.
  • HFC 158 and 159 are compositionally similar to HFC 154 and 155 (Pt 18 Rh 19 Mo 40 Sn 23 ). These materials display very similar XRD patterns, the primary difference being in the degree of crystallinity.
  • the electrochemical performance set forth in Table C is also similar.
  • the predicted change in the average radius for the Pt 34 Rh 13 W 53 alloys was an expansion of 0.6% vs. platinum.
  • the XRD determined expansion of HFC 183 and 184 was about 0.5%.
  • HFC 183 and 184 display the structural characteristics of a disordered alloy.
  • the calculated particle sizes for HFC 183 and 184 were approximately 2.6 nm.
  • the starting materials used to synthesize the alloy may play a role in the activity of the synthesized alloy.
  • Different methods of synthesis e.g., chemical precipitation and freeze-drying impregnation
  • Heat treatment parameters such as atmosphere, time, temperature, etc. may also need to be optimized. This optimization may involve balancing competing phenomena. For example, increasing the heat treatment temperature is generally known to improve the reduction of a metal salt to a metal which typically increases activity; however, it also tends to increase the size of the electrocatalyst alloy particle and decrease surface area, which decreases electrocatalytic activity.
  • Activity is defined as the maximum sustainable, or steady state, current (Amps) obtained from the electrocatalyst, when fabricated into an electrode, at a given electric potential (Volts). Additionally, because of differences in the geometric area of electrodes, when comparing different electrocatalysts, activity is often expressed in terms of current density (A/cm 2 ).
  • An alloy is a mixture comprising two or more metals.
  • An alloy may be described as a solid solution in which the solute and solvent atoms (the term solvent is applied to the metal that is in excess) are arranged at random, much in the same way as a liquid solution may be described. If some solute atoms replace some of those of the solvent in the structure of the latter, the solid solution may be defined as a substitutional solid solution. Alternatively, an interstitial solid solution is formed if a smaller atom occupies the interstices between the larger atoms. Combinations of the two types are also possible. Furthermore, in certain solid solutions, some level of regular arrangement may occur under the appropriate conditions resulting in a partial ordering that may be described as a superstructure.
  • An alloy as defined herein, is also meant to include materials which may comprise elements which are generally considered to be non-metallic.
  • some alloys of the present invention may comprise oxygen in atomic, molecular, and/or metallic oxide form.
  • some alloys of the present invention may comprise carbon in atomic, molecular, and/or metal carbide form. If present; the amount of oxygen 1 and/or carbon in the alloy is typically at what is generally considered to be a low or impurity level (e.g., less than about 5, 1 , 0.5, or 0.1 atomic percent).

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Abstract

L'invention concerne un catalyseur de pile à combustible contenant du platine, du rhodium, au moins un métal parmi le tungstène, l'étain et le cuivre, et éventuellement du molybdène, dans des états d'oxydation métallique. En outre, le platine et le rhodium se trouvent à des concentrations telles que la somme de leur concentration ne soit pas supérieure à 85 atomes pour cent.
PCT/US2003/008852 2002-03-21 2003-03-21 Catalyseur au pt-rh-w/sn/cu/mo pour pile a combustible WO2003081702A2 (fr)

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AU2003224744A AU2003224744A1 (en) 2002-03-21 2003-03-21 Fuel cell catalyst containing pt and rh and at least one of w, sn and cu and optionally mo.

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US60/366,519 2002-03-21

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Cited By (9)

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EP1408569A2 (fr) * 2002-10-11 2004-04-14 Isamu Uchida Electrocatalyseur pour l'oxydation de l'éthanol et pile à combustible alimentée directement à l'éthanol employant cet électrocatalyseur
WO2004073096A1 (fr) * 2003-02-12 2004-08-26 Symyx Technologies Inc. Procede de synthese pour electrocatalyseur de pile a combustible
EP1548135A1 (fr) * 2003-12-23 2005-06-29 General Electric Company Alliages résistants aux températures élevées et des articles fabriqués et réparés à partir de ces alliages.
EP1580252A1 (fr) * 2004-03-26 2005-09-28 United Technologies Corporation Système de désoxygénation électrochimique d'un carburant
US7169731B2 (en) 2003-02-12 2007-01-30 Symyx Technologies, Inc. Method for the synthesis of a fuel cell electrocatalyst
WO2007067546A2 (fr) * 2005-12-06 2007-06-14 Honda Motor Co., Ltd. Électrocatalyseurs contenant du platine et du tungstène
WO2008080227A1 (fr) * 2006-12-29 2008-07-10 Tekion, Inc. Oxydation électrochimique de l'acide formique utilisant un catalyseur de métal noble et des admétaux
US7485390B2 (en) 2003-02-12 2009-02-03 Symyx Technologies, Inc. Combinatorial methods for preparing electrocatalysts
WO2010138688A1 (fr) * 2009-05-28 2010-12-02 Toyota Jidosha Kabushiki Kaisha Catalyseurs en alliage pour piles a combustible

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US3357863A (en) * 1966-01-21 1967-12-12 American Cyanamid Co Rhodium catalyst and fuel cell
US3364072A (en) * 1965-04-21 1968-01-16 American Cyanamid Co Fuel cell with platinum-rhodium containing catalyst
US4401557A (en) * 1974-09-25 1983-08-30 Societe Francaise Des Produits Pour Catalyse Catalysts for hydrocarbon conversion
WO1999027590A1 (fr) * 1997-11-25 1999-06-03 California Institute Of Technology Elements pour piles a combustibles a capacite accrue de traitement d'eau
WO2000035037A1 (fr) * 1998-12-09 2000-06-15 Johnson Matthey Public Limited Company Structure d'electrode

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US3364072A (en) * 1965-04-21 1968-01-16 American Cyanamid Co Fuel cell with platinum-rhodium containing catalyst
US3357863A (en) * 1966-01-21 1967-12-12 American Cyanamid Co Rhodium catalyst and fuel cell
US4401557A (en) * 1974-09-25 1983-08-30 Societe Francaise Des Produits Pour Catalyse Catalysts for hydrocarbon conversion
WO1999027590A1 (fr) * 1997-11-25 1999-06-03 California Institute Of Technology Elements pour piles a combustibles a capacite accrue de traitement d'eau
WO2000035037A1 (fr) * 1998-12-09 2000-06-15 Johnson Matthey Public Limited Company Structure d'electrode

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004152748A (ja) * 2002-10-11 2004-05-27 Isamu Uchida エタノール酸化用電極触媒およびそれを用いた直接エタノール型燃料電池
EP1408569A3 (fr) * 2002-10-11 2004-11-10 Isamu Uchida Electrocatalyseur pour l'oxydation de l'éthanol et pile à combustible alimentée directement à l'éthanol employant cet électrocatalyseur
US7960070B2 (en) 2002-10-11 2011-06-14 Isamu Uchida Electrocatalyst for ethanol oxidation and direct ethanol fuel cell using the same
EP1408569A2 (fr) * 2002-10-11 2004-04-14 Isamu Uchida Electrocatalyseur pour l'oxydation de l'éthanol et pile à combustible alimentée directement à l'éthanol employant cet électrocatalyseur
US7485390B2 (en) 2003-02-12 2009-02-03 Symyx Technologies, Inc. Combinatorial methods for preparing electrocatalysts
WO2004073096A1 (fr) * 2003-02-12 2004-08-26 Symyx Technologies Inc. Procede de synthese pour electrocatalyseur de pile a combustible
US7169731B2 (en) 2003-02-12 2007-01-30 Symyx Technologies, Inc. Method for the synthesis of a fuel cell electrocatalyst
US7494619B2 (en) 2003-12-23 2009-02-24 General Electric Company High temperature alloys, and articles made and repaired therewith
US7722729B2 (en) 2003-12-23 2010-05-25 General Electric Company Method for repairing high temperature articles
EP1548135A1 (fr) * 2003-12-23 2005-06-29 General Electric Company Alliages résistants aux températures élevées et des articles fabriqués et réparés à partir de ces alliages.
US7431818B2 (en) 2004-03-26 2008-10-07 United Technologies Corporation Electrochemical fuel deoxygenation system
EP1580252A1 (fr) * 2004-03-26 2005-09-28 United Technologies Corporation Système de désoxygénation électrochimique d'un carburant
US7736790B2 (en) 2004-12-06 2010-06-15 Honda Motor Co., Ltd. Platinum and tungsten containing electrocatalysts
WO2007067546A3 (fr) * 2005-12-06 2007-09-13 Honda Motor Co Ltd Électrocatalyseurs contenant du platine et du tungstène
WO2007067546A2 (fr) * 2005-12-06 2007-06-14 Honda Motor Co., Ltd. Électrocatalyseurs contenant du platine et du tungstène
WO2008080227A1 (fr) * 2006-12-29 2008-07-10 Tekion, Inc. Oxydation électrochimique de l'acide formique utilisant un catalyseur de métal noble et des admétaux
WO2010138688A1 (fr) * 2009-05-28 2010-12-02 Toyota Jidosha Kabushiki Kaisha Catalyseurs en alliage pour piles a combustible

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