Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/52—Electrically conductive inks
• • 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
  • H01M4/8663—Selection of inactive substances as ingredients for catalytic active masses, e.g. binders, fillers
  • H01M4/8668—Binders
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/02—Printing inks
  • C09D11/03—Printing inks characterised by features other than the chemical nature of the binder
• • 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
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/10—Fuel cells with solid electrolytes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M8/00—Fuel cells; Manufacture thereof
  • H01M8/10—Fuel cells with solid electrolytes
  • H01M8/1004—Fuel cells with solid electrolytes characterised by membrane-electrode assemblies [MEA]
• • 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
• • 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

• This invention relates to a catalyst ink composition, typically for use in the fabrication of membrane electrode assemblies used in fuel cells.
• European Patent Application EP 0 955 687 A2 discloses a method for preparing a slurry for forming a catalyst layer of a PEM fuel cell electrode.
• MOH is added to a water/alcohol solution of a perfluorosulfonate ionomer (PFSI)(such as NafionTM) to convert the PFSI to M + form.
• PFSI perfluorosulfonate ionomer
• An organic polar solvent such as dimethyl sulfoxide, N,N-dimethyl formamide or ethylene glycol is added ('687 at para. 24, para. 27, and claim 6).
• the mixture is then heated to drive off alcohol and catalyst is added to form the slurry.
• the catalyst layer is treated with acid to convert the PFSI from M + form to H + form. ('687 at para. 44 and claim 5).
• U.S. patent application Publication US2002/0045081 discloses the use of sulfonated PEEK polymers dissolved in N-methyl pyrrolidone (NMP), a polar aprotic solvent ('081 at Example 1).
• U.S. Pat. No. 5,906,716 discloses a metalized cation exchange membrane preferably made with a cation-exchange polymer that is soluble in a polar aprotic solvent (such as NMP) and comprises arylene units in the backbone of the polymer, e.g., sulfonated PEEK polymers ('716 at Example 1).
• a polar aprotic solvent such as NMP
• Japanese Unexamined Patent Publication 2000-353528 discloses a porous electrode catalyst layer and a method of making a porous electrode catalyst layer.
• the Examples appear to disclose the use of a solution of NafionTM in NMP, obtained by solvent exchange of a stock solution of NafionTM.
• Japanese Unexamined Patent Publication 2001-273907A discloses a porous electrode catalyst layer and a phase separation method of making a porous electrode catalyst layer.
• the Examples appear to disclose the application of suspension of catalyst in NafionTM solution followed by drying and then application of a PVdF/NMP solution followed by solvent exchange with water to create a porous layer of PVdF.
• UK Patent Application GB 2 316 802 A discloses gas diffusion electrodes based on polyethersulfone carbon blends.
• U.S. Pat. No. 5,716,437 discloses an aqueous ink for use in electrode manufacture.
• WO 99/21239 discloses a method for the production of metal colloid solutions by reducing dissolved catalyst metals in the presence of a cation exchange polymer.
• the present invention provides a catalyst ink comprising: 25-95% by weight water; 1-50% by weight of at least one solid catalyst, typically a highly dispersed platinum catalyst; 1-50% by weight of at least one polymer electrolyte in acid (H + ) form; and 1-50% by weight of at least one polar aprotic organic solvent.
• the catalyst ink typically has a viscosity at 1 sec ⁇ 1 of 10 Pa ⁇ sec or less.
• the catalyst ink typically does not ignite spontaneously when dried to completion in air at a temperature of 80° C. or greater.
• “highly dispersed platinum catalyst” means a platinum-containing catalyst having a specific surface area of greater than 100 m 2 /g, more typically greater than 500 m 2 /g, and most typically greater than 900 m 2 /g, such as a catalyst dispersed on a powdered carbon support;
• “highly fluorinated” means containing fluorine in an amount of 40 wt % or more, typically 50 wt % or more and more typically 60 wt % or more;
• “dried to completion” means dried until water content is essentially in equilibrium with ambient air, or lower;
• standard boiling point means the boiling point reported in standard reference works.
• the present invention provides a catalyst ink comprising: 25-95% by weight water; 1-50% by weight of at least one solid catalyst, typically a highly dispersed platinum catalyst; 1-50% by weight of at least one polymer electrolyte in acid (H + ) form; and 1-50% by weight of at least one polar aprotic organic solvent.
• the catalyst ink typically has a viscosity at 1 sec ⁇ 1 of 10 Pa ⁇ sec or less.
• the catalyst ink typically does not ignite spontaneously when dried to completion in air at a temperature of 80° C. or greater.
• the catalyst ink according to the present invention may be used in the fabrication of membrane electrode assemblies (MEA's) for use in fuel cells.
• An MEA is the central element of proton exchange membrane fuel cells such as hydrogen fuel cells.
• Fuel cells are electrochemical cells which produce usable electricity by the catalyzed combination of a fuel such as hydrogen and an oxidant such as oxygen.
• Typical MEA's comprise a polymer electrolyte membrane (PEM) (also known as an ion conductive membrane (ICM)), which functions as a solid electrolyte.
• PEM polymer electrolyte membrane
• ICM ion conductive membrane
• Each electrode layer includes electrochemical catalysts, typically including platinum metal.
• the anode and cathode electrode layers may be applied to the PEM in the form of a catalyst ink to form a catalyst coated membrane (CCM).
• Fluid transport layers FTL's facilitate gas transport to and from the anode and cathode electrode materials and conduct electrical current.
• FTL Fluid transport layers
• protons are formed at the anode via hydrogen oxidation and transported to the cathode to react with oxygen, allowing electrical current to flow in an external circuit connecting the electrodes.
• the FTL may also be called a gas diffusion layer (GDL) or a diffuser/current collector (DCC).
• GDL gas diffusion layer
• DCC diffuser/current collector
• the anode and cathode electrode layers may be applied to the FTL in the form of a catalyst ink, rather than to the PEM, and the coated FTL's sandwiched with a PEM to form an MEA.
• Any suitable catalyst may be used in the practice of the present invention.
• the catalyst is typically a highly dispersed platinum catalyst having a specific surface area of greater than 100 m 2 /g, more typically greater than 500 m 2 /g, and most typically greater than 900 m 2 /g.
• carbon-supported catalyst particles are used. Typical carbon-supported catalyst particles are 50-90% carbon and 10-50% catalyst metal by weight, the catalyst metal typically comprising Pt for the cathode and Pt and Ru in a weight ratio of 2:1 for the anode.
• any suitable polymer electrolyte may be used in the practice of the present invention.
• the polymer electrolyte is typically highly fluorinated or perfluorinated.
• the polymer electrolyte is typically an acid-functional fluoropolymer, such as Nafion® (DuPont Chemicals, Wilmington Del.) and FlemionTM (Asahi Glass Co. Ltd., Tokyo, Japan).
• the polymer electrolytes useful in inks for use in the present invention are typically copolymers of tetrafluoroethylene and one or more fluorinated, acid-functional comonomers. Typically the polymer electrolyte bears sulfonate functional groups.
• the polymer electrolyte contains no arylene units in the polymer backbone. Most typically the polymer electrolyte is Nafion®. The polymer electrolyte typically has an equivalent weight of 1200 or less, more typically 1100 or less, more typically 1050 or less, and most typically about 1000. In the ink according to the present invention, the polymer electrolyte is substantially in protonated form or acid (H + ) form, rather than in salt form.
• the polar aprotic organic solvent typically has a standard boiling point of at least 80° C., more typically at least 100° C., more typically at least 160° C., and most typically at least 200° C.
• the polar aprotic organic solvent is typically selected from the group consisting of: dimethylsulfoxide (DMSO), N,N-dimethyacetamide (DMA), ethylene carbonate, propylene carbonate, dimethylcarbonate, diethylcarbonate, N,N-dimethylformamide (DMF), N-methylpyrrolidinone (NMP), dimethylimidazolidinone, acetonitrile, butyrolactone, hexamethylphosphoric triamide, isobutyl methyl ketone, and sulfolane; and more typically selected from the group consisting of N-methyl pyrrolidinone (NMP), N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsufoxide (DMSO) and ace
• the catalyst ink typically contains 25-95% water, more typically 50-80% water, and more typically 60-75% water.
• the catalyst ink typically contains 1-50% solid catalyst, more typically 5-25% solid catalyst, and more typically 10-20% solid catalyst.
• the catalyst ink typically contains 1-50% polymer electrolyte, more typically 1-20% polymer electrolyte, more typically 1-10% polymer electrolyte, and more typically 3-8% polymer electrolyte.
• the catalyst ink typically contains 1-50% of a second solvent, typically a polar aprotic organic solvent, more typically 3-25% polar aprotic organic solvent, more typically 5-15% polar aprotic organic solvent, and more typically 8-14% polar aprotic organic solvent.
• the catalyst ink typically contains 5-30% solids (i.e. polymer and catalyst).
• the ink may be mixed by any suitable method.
• the ink is typically made by stirring with heat which may be followed by dilution to a coatable consistency.
• the ink typically has a viscosity at 1 sec ⁇ 1 of 10 Pa ⁇ sec or less, more typically 6 Pa ⁇ sec or less, more typically 2 Pa ⁇ sec or less, and most typically 1.0 Pa ⁇ sec or less.
• the ink may be used in the manufacture of a CCM or MEA for use in a fuel cell.
• the ink may be applied to a PEM or FTL by any suitable means, including both hand and machine methods, including hand brushing, notch bar coating, fluid bearing die coating, wire-wound rod coating, fluid bearing coating, slot-fed knife coating, three-roll coating, or decal transfer.
• decal transfer the ink is first applied to a transfer substrate and dried, and thereafter applied as a decal to a PEM. Coating may be achieved in one application or in multiple applications.
• the ink may be dried in an oven or the like, in air, at temperatures in excess of 80° C., more typically in excess of 110° C., and more typically in excess of 140° C.
• the ink according to the present invention preferably will not self-ignite when dried to completion under these conditions.
• an ink that will not self-ignite during drying will also be more safe to manufacture, handle and use.
• This invention is useful in the fabrication of membrane electrode assemblies for use in fuel cells.
• Anode inks were made as follows: 30 g of catalyst powder (SA27-13RC, 27% Pt & 13% Ru on 60% carbon from N.E. Chemcat Corp., Tokyo, Japan) were weighed into a (16 oz) glass jar (8.9 cm diameter by 8.9 cm height). Then, 112.2 g of a NafionTM solution (SE-10172, 10% in Water, CAS#31175-20-9, DuPont Fluoroproducts, Wilmington, Del., USA) were gradually added to the catalyst powder in the glass jar while the contents were uniformly dispersed with a spatula to ensure no dry clumps of catalyst powder remained in the mixture.
• a NafionTM solution SE-10172, 10% in Water, CAS#31175-20-9, DuPont Fluoroproducts, Wilmington, Del., USA
• Cathode inks were made as follows: 30 g of catalyst powder (SA50BK, 50% Pt on 50% carbon from N.E. Chemcat Corp., Tokyo, Japan) were weighed into a (16 oz) glass jar (8.9 cm diameter by 8.9 cm height). Then, 84 g of a NafionTM solution (SE-10172, 10% in Water, CAS#31175-20-9, DuPont Fluoroproducts, Wilmington, Del., USA) were gradually added to the catalyst powder in the glass jar while the contents were uniformly dispersed with a spatula to ensure no dry clumps of catalyst powder remained in the mixture. 80.1 g of additional water were added.
• SA50BK 50% Pt on 50% carbon from N.E. Chemcat Corp., Tokyo, Japan
• a NafionTM solution SE-10172, 10% in Water, CAS#31175-20-9, DuPont Fluoroproducts, Wilmington, Del., USA
• Example 10 the weights reported above were cut to one third, i.e., 10 g of anode catalyst powder, 28 g of NafionTM solution, 26.7 g of additional water and 7.5 g of additional solvent (acetonitrile) were used.
• a Bohlin Constant Stress Rheometer (available from Bohlin Instruments Inc., East Brunswick, N.J.) was used to continuously measure the viscosity of a catalyst dispersion as a function of shear rate. Flow properties under constant stress conditions were measured using a C14 cup-and-bob geometry at shear rates of between 1 and 800 sec ⁇ 1 .
• Shear rate (S) and shear viscosity (V) are related by the following equation, known as the “Power Law Fluid” equation:
• k is a constant that indicates viscosity at 1 sec ⁇ 1
• n is the Power Law Index (PLI), which indicates of the effect of shear on viscosity. If the shear viscosity of a material is insensitive to shear rate, i.e., the fluid is a Newtonian fluid, the PLI is 1.0. Those dispersions whose viscosity decreases with shear are non-Newtonian and known as thixotropic. The PLI of these thixotropic fluids range from 0 to 1. The principles of the power law index are further described in C. W. Macosko, “Rheology: Principles, Measurements, and Applications”, ISBN #1-56081-579-5, at page 85, incorporated herein by reference.
• Incineration was tested by notch-bar application of a 3′′ (7.6 cm) wide by 3-mil (76 micron) thick coating of the catalyst ink on a release liner comprising a 1-mil thick silicone-coated microstructured polypropylene having microfeatures with a depth of about 50 micron.
• the coating along with the liner were placed in aluminum pan and placed in a convective air oven at 140° C. The coating was allowed to dry for 10 min. Later, the coatings were examined for either complete drying or incineration of the catalyst coating.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Electrochemistry (AREA)
• Wood Science & Technology (AREA)
• Organic Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Sustainable Development (AREA)
• Sustainable Energy (AREA)
• Materials Engineering (AREA)
• Inert Electrodes (AREA)
• Catalysts (AREA)
• Inks, Pencil-Leads, Or Crayons (AREA)

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Citations (20)

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• 2002
  • 2002-12-10 US US10/315,589 patent/US20040107869A1/en not_active Abandoned
• 2003
  • 2003-10-17 DE DE60315721T patent/DE60315721T2/de not_active Expired - Lifetime
  • 2003-10-17 EP EP03777697A patent/EP1588449B1/en not_active Expired - Lifetime
  • 2003-10-17 KR KR1020057010345A patent/KR20050084199A/ko not_active Withdrawn
  • 2003-10-17 CA CA002506657A patent/CA2506657A1/en not_active Abandoned
  • 2003-10-17 JP JP2004559074A patent/JP4690047B2/ja not_active Expired - Fee Related
  • 2003-10-17 AT AT03777697T patent/ATE370521T1/de not_active IP Right Cessation
  • 2003-10-17 WO PCT/US2003/033133 patent/WO2004054021A2/en not_active Ceased
  • 2003-10-17 CN CNB200380105215XA patent/CN100380723C/zh not_active Expired - Fee Related
  • 2003-10-17 AU AU2003286497A patent/AU2003286497A1/en not_active Abandoned
• 2010
  • 2010-07-21 US US12/840,859 patent/US7855160B2/en not_active Expired - Fee Related

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