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WO2009080062A1 - Pile à combustible à méthanol direct intégrant une membrane électrolytique polymère greffée par irradiation - Google Patents

Pile à combustible à méthanol direct intégrant une membrane électrolytique polymère greffée par irradiation Download PDF

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Publication number
WO2009080062A1
WO2009080062A1 PCT/EP2007/011238 EP2007011238W WO2009080062A1 WO 2009080062 A1 WO2009080062 A1 WO 2009080062A1 EP 2007011238 W EP2007011238 W EP 2007011238W WO 2009080062 A1 WO2009080062 A1 WO 2009080062A1
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Prior art keywords
fuel cell
direct methanol
side chains
methanol fuel
polyolefin
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PCT/EP2007/011238
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English (en)
Inventor
Omar Ballabio
Paola Teresa Caracino
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Pirelli and C SpA
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Pirelli and C SpA
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Priority to PCT/EP2007/011238 priority Critical patent/WO2009080062A1/fr
Publication of WO2009080062A1 publication Critical patent/WO2009080062A1/fr
Anticipated expiration legal-status Critical
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/76—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74
    • B01D71/82—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74 characterised by the presence of specified groups, e.g. introduced by chemical after-treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/26—Polyalkenes
    • B01D71/261—Polyethylene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/26—Polyalkenes
    • B01D71/262—Polypropylene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/76—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74
    • B01D71/78—Graft polymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
    • C08J5/20—Manufacture of shaped structures of ion-exchange resins
    • C08J5/22—Films, membranes or diaphragms
    • C08J5/2206—Films, membranes or diaphragms based on organic and/or inorganic macromolecular compounds
    • C08J5/2218—Synthetic macromolecular compounds
    • C08J5/2231—Synthetic macromolecular compounds based on macromolecular compounds obtained by reactions involving unsaturated carbon-to-carbon bonds
    • C08J5/2243—Synthetic macromolecular compounds based on macromolecular compounds obtained by reactions involving unsaturated carbon-to-carbon bonds obtained by introduction of active groups capable of ion-exchange into compounds of the type C08J5/2231
    • 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
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
    • H01M8/04197—Preventing means for fuel crossover
    • 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
    • H01M8/1007—Fuel cells with solid electrolytes with both reactants being gaseous or vaporised
    • 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
    • H01M8/1009—Fuel cells with solid electrolytes with one of the reactants being liquid, solid or liquid-charged
    • H01M8/1011—Direct alcohol fuel cells [DAFC], e.g. direct methanol fuel cells [DMFC]
    • 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
    • H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
    • H01M8/1018—Polymeric electrolyte materials
    • H01M8/102—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer
    • H01M8/1023—Polymeric electrolyte materials characterised by the chemical structure of the main chain of the ion-conducting polymer having only carbon, e.g. polyarylenes, polystyrenes or polybutadiene-styrenes
    • 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
    • H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
    • H01M8/1018—Polymeric electrolyte materials
    • H01M8/1039—Polymeric electrolyte materials halogenated, e.g. sulfonated polyvinylidene fluorides
    • 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
    • H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
    • H01M8/1018—Polymeric electrolyte materials
    • H01M8/1069—Polymeric electrolyte materials characterised by the manufacturing processes
    • H01M8/1086—After-treatment of the membrane other than by polymerisation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2323/00—Details relating to membrane preparation
    • B01D2323/38—Graft polymerization
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2325/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring; Derivatives of such polymers
    • C08J2325/02—Homopolymers or copolymers of hydrocarbons
    • C08J2325/04—Homopolymers or copolymers of styrene
    • C08J2325/08—Copolymers of styrene
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2250/00—Fuel cells for particular applications; Specific features of fuel cell system
    • H01M2250/20—Fuel cells in motive systems, e.g. vehicle, ship, plane
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2250/00—Fuel cells for particular applications; Specific features of fuel cell system
    • H01M2250/30—Fuel cells in portable systems, e.g. mobile phone, laptop
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0065—Solid electrolytes
    • H01M2300/0082—Organic polymers
    • 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
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02B90/10—Applications of fuel cells in buildings
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
    • 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
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02T90/40—Application of hydrogen technology to transportation, e.g. using fuel cells

Definitions

  • the present invention relates to a fuel cell. More particularly, the present invention relates to a direct methanol fuel cell incorporating a polymer electrolyte membrane grafted by irradiation, to a polymer electrolyte membrane used therein and to a process for producing said polymer electrolyte membrane. Background of the invention
  • Fuel cells are highly efficient electrochemical energy conversion devices that directly convert the chemical energy derived from renewable fuel into electrical energy. Significant research and development activities have been focused on the development of proton-exchange membrane fuel cells.
  • Proton-exchange membrane fuel cells have a polymer electrolyte membrane disposed between a positive electrode (cathode) and a negative electrode (anode) .
  • the polymer electrolyte membrane is composed of a ion-exchange polymer. Its role is to provide a means for ionic transport and for separation of the anode compartment and the cathode compartment.
  • the traditional proton-exchange membrane fuel cells have a polymer electrolyte membrane placed between two gas diffusion electrodes, an anode and a cathode respectively, each usually containing a metal catalyst supported by an electrically conductive material.
  • the gas diffusion electrodes are exposed to the respective reactant gases, the reductant gas and the oxidant gas.
  • An electrochemical reaction occurs at each of the two junctions (three phases boundaries) where one
  • Polymer electrolyte membranes play an important role in proton-exchange membrane fuel cells.
  • the polymer electrolyte membrane mainly has two functions: (1) it acts as the electrolyte that provides ionic communication between the anode and the cathode; and (2) it serves as a separator for the two reactant gases (e.g., O 2 and H2) .
  • the polymer electrolyte membrane while being useful as a good proton transfer membrane, must also have low permeability for the reactant gases to avoid crossover phenomena that reduce performance of the fuel cell. This is especially important in fuel cell applications in which the reactant gases are under pressure and the fuel cell is operated at elevated temperatures.
  • Fuel cell reactants are classified as oxidants and reductants on the basis of their electron acceptor or electron donor characteristics.
  • Oxidants include pure oxygen, oxygen-containing gases (e.g., air) and halogens (e.g., chlorine) and hydrogen peroxide.
  • Reductants include hydrogen, carbon monoxide, natural gas, methane, ethane, formaldheyde, ethanol, ethyl ether, methanol, ammonia and hydrazine.
  • Polymer electrolyte membranes are generally based on polymer electrolytes which have negatively charged groups attached to the polymer backbone. These polymer electrolytes tend to be rather rigid and are poor proton conductors unless water is adsorbed. The proton conductivity of hydrated polymer electrolyte dramatically increases with water content. Therefore, the proton-exchange membrane fuel cells generally require humidified gases, e.g. hydrogen and oxygen (or air), for their operations.
  • humidified gases e.g. hydrogen and oxygen (or air
  • DMFC direct methanol fuel cell
  • polymer electrolyte membranes are promising candidates for the application in portable electronic devices and in transportation (e.g., electrical vehicles) .
  • Anode CH 3 OH + H 2 O ⁇ CO 2 + 6H + + 6e ⁇ ; Cathode: 3/2O 2 + 6H + + 6e ⁇ ⁇ 3H 2 O; Overall: CH 3 OH + 3/2O 2 ⁇ CO 2 + 2H 2 O.
  • the protons are simultaneously transferred through the polymer electrolyte membrane from the anode to the cathode.
  • Methanol cross-over not only lowers the fuel utilization efficiency but also adversely affects the oxygen cathode performance, significantly lowering fuel cell performance.
  • Patent Application WO 98/22989 discloses a polymer electrolyte membrane composed of polystyrene sulfonic acid (PSSA) and poly (vinylidene fluoride) (PVDF) .
  • Said membrane may be prepared, for example, starting from the preparation of a PVDF membrane which could serve as an inert polymer matrix which is subsequently impregnated with polystyrene divinyl benzene mixtures (PS/DVB mixtures) to produce interpenetrating polymer networks; then, the membrane so obtained is sulfonated.
  • Said membrane is said to be particularly useful in low-temperature direct methanol fuel cell and it is said to enhance the efficiency and the electrical performances of the fuel cell by decreasing methanol cross-over.
  • a fuel cell comprising: (a) an anode; (b) a cathode; (c) a polymer electrolyte membrane placed between the anode and the cathode which comprises at least one polyolefin grafted with side chains containing proton conductive functional groups; wherein said fuel cell has specifc values of cell resistance at different temperature values.
  • the preparation of said membrane is also disclosed therein, and comprises the steps of (i) irradiating a polyolefin in the presence of oxygen to obtain an activated polyolefin; (ii) grafting the obtained activated polyolefin by reacting the same with at least an unsaturated hydrocarbon monomer, said hydrocarbon monomer optionally containing at least one proton conductive functional group, to obtain side chains grafted on the activated polyolefin; and (iii) providing said grafted side chains with proton conductive functional groups, wherein the irradiating step (i) and the grafting step (ii) are carried out in particular conditions of radiation rate and of time period and the step (iii) is carried out at a temperature of from 50 0 C to 150 0 C. Said fuel cell is said to be particularly useful in reducing the methanol cross-over in a direct methanol fuel cell.
  • the Applicant has noticed that one of the major problem encountered in direct methanol fuel cells known in the art relates to the degradation over time of the membranes included in said fuel cells.
  • the membranes may degrade over time due to the attack by peroxide radicals which may form at the cathode.
  • the presence of contaminants such as, for example, chloride ions, may accelerate the rate of peroxide radicals generation.
  • the Applicant has now found that it is possible to overcome the above mentioned problems utilizing a polymer electrolyte membrane comprising at least one polyolefin grafted by irradiation with side chains containing proton conductive functional groups, said polymer electrolyte membrane being able to maintain a controlled amount of grafted side chains for a prolonged period of time. More in particular, the Applicant has found that if the process for producing a polymer electrolyte membrane is carried out by using a sulfonating or a phosphorating agent at a predetermined temperature, it is possible to improve the direct methanol fuel cell performances.
  • the Applicant has found that it is possible to obtain a direct methanol fuel cell having good power density values and being able to maintain said good power density values even in the presence of a high methanol concentration .
  • the present invention thus relates to a direct methanol fuel cell comprising:
  • said power density value measured at methanol concentration of 12.4 M is not lower than or equal to about 55%, preferably not lower than or equal to about 60%, even more preferably not lower than or equal to about 100%, with respect to the power density value measured at methanol concentration of 1 M.
  • the direct methanol fuel cell of the present invention has the advantage of maintaining good performances even in the presence of high methanol concentration and, consequently, of using reduced volumes of methanol.
  • the direct methanol fuel cell of the present invention may be advantageously used, for example, in apparatus such as engines for vehicle transportation or electronic portable devices such as a mobile phone, a laptop computer, a radio, a camcorder, a remote controller.
  • direct methanol fuel cell means a fuel cell in which the methanol is directly fed into the fuel cell, without any previous chemical modification, and is oxidized at the anode.
  • the amount of grafting [ ⁇ p (%)] of said side chains is of from about 10% to about 250%, preferably of from about 30% to about 150%.
  • the amount of grafting [ ⁇ p (%) ] may be calculated by the following formula:
  • [ ⁇ p (%) ] [(W t - W 0 ) /W 0 ] x 100 wherein Wo is the weight of the membrane before the graft polymerization reaction and W t is the weight of the " membrane after the graft polymerization reaction.
  • the present invention relates to a polymer electrolyte membrane comprising at least one polyolefin grafted with side chains containing proton conductive functional groups, said side chains being grafted to the polyolefin through an oxygen bridge wherein, after treatment for 7 days, in a 4% hydrogen peroxide solution, at 25°C, the amount of grafting [ ⁇ p'
  • the amount of grafting [ ⁇ p' (%) ] of said side chains, after treatment for 7 days, in a 4% hydrogen peroxide solution, at 25°C, is of from about 52% to about 100%, more preferably of from about 55% to about 95%, with respect to the initial amount of grafting [ ⁇ p (%)].
  • Said amount of grafting [ ⁇ p' (%)] may be measured with techniques known in the art such as, for example, by means of infrared spectroscopy analysis (IR spectroscopy) .
  • the present invention relates to a process for producing a polymer electrolyte membrane comprising the following steps:
  • step (iii) providing said grafted side chains with proton conductive functional groups by using a sulfonating or a phosphorating agent; wherein said step (iii) is carried out at a temperature lower than 50°C.
  • the present invention relates to a polymer electrolyte membrane obtained by the process above reported.
  • the present invention in the above mentioned aspects, may show one or more of the preferred characteristics hereinafter described.
  • the polyolefin which may be used in the present invention may be selected, for example, from: polyethylene, polypropylene, polyvinylchloride, ethylene-propylene copolymer (EPR) or ethylene-propylene-diene terpolymer (EPDM) , ethylene vinyl acetate copolymer (EVA) , ethylene butylacrylate copolymer (EBA) , polyvinylidenedichloride, polyvinylfluoride (PVF), polyvinylidenedifluoride (PVDF), vinylidene fluoride tetrafluoroethylene copolymer (PVDF- TFE) , polyvinylidene-hexafluoropropylene copolymer, chlorotrifluoroethylene-ethylene copolymer, chlorotrifluoroethylene-propylene copolymer, polychloroethylene, ethylene-tetrafluoroethylene copolymer (ETFE) , propy
  • MDPE medium density polyethylene
  • LDPE low density polyethylene
  • MDPE low density polyethylene
  • MDPE medium density polyethylene
  • MDPE medium density polyethylene
  • MDPE medium density polyethylene
  • MDPE medium density polyethylene
  • MDPE medium density polyethylene
  • MDPE medium density polyethylene
  • MDPE medium density polyethylene
  • MDPE medium density polyethylene
  • MDPE medium density polyethylene
  • MDPE medium density polyethylene
  • MDPE medium density polyethylene
  • MDPE medium density polyethylene
  • MDPE medium density polyethylene
  • the side chains may be selected, for example, from any hydrocarbon polymer chain which may be modified to provide proton conductive functional groups.
  • the side chains are obtained by graft polymerization of unsaturated hydrocarbon monomers, said hydrocarbon monomers being optionally halogenated.
  • Said unsaturated hydrocarbon monomer may be selected, for example, from: styrene, chloroalkylstyrene, ⁇ -methylstyrene, ⁇ , ⁇ -dimethylstyrene, ⁇ , ⁇ , ⁇ -trimethylstyrene, ortho-methylstyrene, p- methylstyrene, meta-methylstyrene, ⁇ -fluorostyrene, trifluorostyrene, p-chloromethylstyrene, acrylic acid, methacrylic acid, vinylalkyl sulfonic acid, divinylbenzene, triallylcianurate, vinylpyridine, or copolymers thereof, or mixtures thereof.
  • the proton conductive functional groups may be selected, for example, from sulfonic acid groups, phosphoric acid groups, or mixtures thereof. Sulfonic acid groups are particularly preferred.
  • the present invention relates also to a process for producing a polymer electrolyte membrane.
  • the irradiating step (i) may be carried out by ⁇ -rays, X- rays, UV light, plasma irradiation or ⁇ -particles. ⁇ -rays are particularly preferred.
  • the irradiating step (i) is carried out at a radiation rate in the range of from about 0.01 Gy/s to about 10 Gy/s, preferably of from about 0.05 Gy/s to about 5.0 Gy/s.
  • the total radiation dose in the irradiating step (i) is preferably in the range of from about 1.0 KGy to about 200 KGy, more preferably of from about 5.0 KGy to about 100 KGy.
  • the grafting step (ii) is carried out for a time period in the range of from about 20 minutes to about 7 hours, more preferably of from about 30 minutes to about 6 hours.
  • the polyolefin may be either crosslinked or non- crosslinked before the irradiating step (i) .
  • the polyolefin is non-crosslinked.
  • the activated polyolefin obtained in step (i) is stable overtime if stored at temperature of from about 60 0 C to about +50 0 C, preferably at room temperature (25°C) . Therefore, it remains activated and it is not necessary to carry out the grafting step (ii) immediately after step (i) .
  • the grafting step (ii) may be carried out at a temperature of from about 15°C to about 150°C, more preferably of from about 45°C to about 100 0 C.
  • the grafting step (ii) may be carried out in the presence of at least one hydroperoxy groups decomposition catalyst.
  • Said catalyst may be selected, for example, from ferrous, cobalt, chromium or copper salts such as, for example, ferrous sulfate, ferrous ammonium sulfate, cobalt (II) chloride, chromium (III) chloride, copper chloride, or mixtures thereof. Ferrous sulfate is particularly preferred. Said catalyst is preferably added in an amount of from about 0.1 mg/ml to about 10 mg/ml, more preferably of from about 0.5 mg/ml to about 4.0 mg/ml.
  • the hydrocarbon unsaturated monomers may be dissolved in a solvent which may be selected, for example, from: ketones, such as acetone; alcohols, such as methanol; aromatic hydrocarbons, such as benzene or xylene; cyclic hydrocarbons, such as cyclohexane; ethers such as dimethylether; esters such as ethyl acetate; amides such as dimethylformamide; or mixtures thereof.
  • a solvent which may be selected, for example, from: ketones, such as acetone; alcohols, such as methanol; aromatic hydrocarbons, such as benzene or xylene; cyclic hydrocarbons, such as cyclohexane; ethers such as dimethylether; esters such as ethyl acetate; amides such as dimethylformamide; or mixtures thereof.
  • the sulfonating or phosphorating agent used to carry out the step (iii) may be used in inert-gas atmosphere, or in air.
  • the sulfonating or phosphorating agent may be selected, for example, from: chlorosulfonic acid, fluorosulfonic acid, sulfuric acid, chlorophosphoric acid, or mixtures thereof. Chlorosulfonic acid is particularly preferred.
  • the sulfonating or phosphorating agent used to carry out step (iii) may be used in a dichloroethane solution, in a cyclohexane solution, or in a dichloro- ethane/tetrachloromethane mixture solution.
  • said step (iii) is carried out at a temperature in the range of from about -40 0 C to about +45°C, more preferably of from about -20 0 C to about +30°C.
  • said step (iii) is carried out for a time period of from about 30 minutes to about 24 hours, more preferably of from about 1 hour to about 5 hours.
  • Figure 1 is a schematic representation of a direct methanol fuel cell according to one embodiment of the present invention.
  • FIG 1 shows a direct methanol fuel cell (1) comprising an anode (2), a cathode (3) and the polymer electrolyte membrane (4) according to the present invention.
  • the anode (2), the cathode (3) and the polymer electrolyte membrane (4) are integrated to form a single composite structure, with the polymer electrolyte membrane (4) interposed between the two electrodes, commonly known as a membrane electrode assembly (MEA) .
  • MEA membrane electrode assembly
  • Said membrane electrode assembly is usually placed in a housing which is not represented in Figure 1.
  • Anode (2) and cathode (3) typically comprise catalyst particles (e.g., Pt or its alloys) optionally supported on carbon particles.
  • the catalyst particles are dispersed throughout a polymeric binder or matrix which typically comprises either a proton-conductive polymer and/or a fluoropolyr ⁇ er .
  • a proton-conductive material When a proton-conductive material is used, it typically comprises the same proton-conductive polymer used for the polymer electrolyte membrane (4) .
  • the polymeric binder or matrix provides a robust structure for catalyst retention, adheres well to the polymer electrolyte membrane (4), aids in water management within the cell and enhances the ion exchange capability of the electrodes .
  • Anode (2) and cathode (3) are preferably formed from a platinum or from a platinum based alloy, unsupported or supported on a high surface area carbon.
  • platinum based alloy platinum is usually alloyed with another metal such as, for example, ruthenium, tin, iridium, osmium or rhenium.
  • Platinum-ruthenium is preferable for electro-oxidation of methanol.
  • a pump (5) circulates an aqueous solution of methanol in the anode compartment (6) .
  • Methanol is withdrawn via an appropriate outlet conduit (7) and may be recirculated.
  • Carbon dioxide formed at the anode (2) may be vented via an outlet conduit (8) within tank (9) .
  • the direct methanol fuel cell (1) is also provided with an oxygen or air compressor (10) to feed humidified oxygen or air into the cathode compartment (11) .
  • an aqueous solution of methanol is introduced into the anode compartment (6) of the direct methanol fuel cell (1) , while oxygen or air is introduced into the cathode compartment (11) .
  • an external electrical load (not showed in Fig. 1) is connected between anode (2) and cathode (3) .
  • methanol is oxidized at the anode (2) and leads to the production of carbon dioxide, protons and electrons. Electrons generated at the anode (2) are conducted via external electrical load to the cathode (3).
  • the protons generated at the anode (2) migrate through the polymer electrolyte membrane (4) to cathode (3) and react with oxygen and electrons (which are transported to the cathode (3) via the external electrical load) to form water and carbon dioxide. Water and carbon dioxide produced are transported out of the cathode chamber (11) by flow of oxygen, through outlet (12) .
  • the water uptake [WU (%)] was measured as follows.
  • a membrane sample of 4 cm x 4 cm was immersed in 100 ml of distillated water for 1 hour.
  • the sample was subsequently removed from water and was dried with an absorbing paper to take off the remaining superficial water.
  • [WU (%)] [(W w - Dw) /DwI x 100 wherein W w is the weight of the membrane sample after being immersed into water and Dw was the weight of the membrane sample before being immersed in water.
  • the ion exchange capacity (IEC) was measured as follows . A membrane sample of 4 cm x 4 cm was weighted and was subsequently immersed in 1.50 ml of a 1 M NaCl aqueous solution overnight. Subsequently, the NaCl aqueous solution was titrated by neutralization with a 0.01 M NaOH aqueous solution, using phenolphthalein as indicator.
  • IEC ion exchange capacity
  • V x 0.01) /D' w wherein V is the volume (expressed in ml) of the 0.01 M NaOH aqueous solution and D' w is the weight of the membrane sample before being immersed in 1 M NaCl aqueous solution.
  • Methanol permeation rate The methanol permeation rate (MeOH rate) was measured using a continuous flow equipment Side-Bi-Side Cell commercialized by PermeGear Inc.
  • a membrane sample having a surface area (s) of 1.76 cm “2 was placed between the diffusion cells. Water, kept at temperature of 30 0 C, was circulated in the diffusion chamber, for the duration of the test.
  • the membrane proton conductivity ( ⁇ ) was measured as follows.
  • the membrane conductivity ( ⁇ ) was measured by a technique in which the current flowed perpendicular to the plane of the membrane.
  • a stack was made consisting of lower electrode/lower GDE/membrane/upper GDE/upper electrode.
  • the lower electrode consists of a 9.5 mm diameter stainless steel rod and the upper electrode consists of a
  • the lower GDE gas diffusion electrode
  • the membrane and the upper GDE were disks of 6.35 mm diameter.
  • Each of said GDE was obtained from LT140EWSI catalyzed ELAT® (commercialized by Basf
  • the obtained stack was assembled and held in place within a block of Macor ® machinable glass ceramic (commercialized by Corning Inc.) having a 12.7 mm diameter hole onto the bottom of the block to accept the lower electrode and a 6.4 mm diameter hole onto the top of the block to accept the upper electrode.
  • the so obtained assembly was placed into a Palmgren vice press and a torque of 10 in/lb was applied using a torque wrench.
  • the real part (R 3 ) of the AC impedance of the assembly containing the membrane was measured at a frequency of 100 kHz using a Solartron SI 1260 Impedance/Gain Phase Analyzer and SI 1287 Electrochemical Interphase with ZView 2 and ZPlot 2 software (both commercialized by Solartron Analytical) .
  • the short (R f ) was also determined by measuring the real part of the AC impedance at 100 kHz of the assembly without a membrane sample.
  • a low density polyethylene (Riblene ® FF20 from Polimeri Europa) film (LDPE) having a thickness of 100 ⁇ m was irradiated by ⁇ -rays at a total radiation dose of
  • Styrene (purity >99%) from Aldrich was washed with an aqueous solution of sodium hydroxide at 30% and then washed with distilled water until the wash water had a neutral pH. The so treated styrene was then dried over calcium chloride (CaCl 2 ) and was distilled under reduced pressure.
  • the irradiated LDPE film was immersed in 100 ml of the styrene/methanol solution prepared as above using a reaction vessel equipped with a reflux condenser. The reaction vessel was then heated in a water bath until boiling of the solution.
  • the LDPE film was removed from the reaction vessel, washed with toluene and methanol three times, then dried in air and vacuum at room temperature to constant weight. Then, the grafted LDPE film was immersed in a solution of 0.5 M chlorosulfonic acid in dichloroethane and heated for 3 hours, at 25 0 C, in a glass ampoule supplied with reflux condenser. Thereafter, the LDPE film was taken out of the solution, was washed with dichloroethane solutions, and finally with distilled water until the wash water had a neutral pH. Then, the film was dried in air at room temperature obtaining a membrane according to the present invention.
  • a membrane was prepared as disclosed in Example 1, with the difference that the grafted LDPE film was heated at a temperature of 40 0 C after being immersed in a solution of 0.5 M chlorosulfonic acid in dichloroethane.
  • a membrane was prepared as disclosed in Example 1, with the difference that the grafted LDPE film was immersed in a concentrated sulfuric acid solution (96%) and then heated at a temperature of 98 0 C, as disclosed in International Patent Application WO 2004/051782 above reported.
  • a membrane was prepared as disclosed in Example 1, with the difference that the grafted LDPE film was heated at a temperature of 60 °C after being immersed in a solution of 0.5 M chlorosulfonic acid in dichloroethane.
  • a membrane was prepared as disclosed in Example 3, with the difference that in this case the sulfonation time was 30 minutes.
  • a membrane was prepared as disclosed in Example 4, with the difference that in this case the sulfonation time was 30 minutes.
  • membranes of the present invention (Membranes 1 and 2) , whose preparation comprises the step of treating the grafted side chains contained therein by using a sulfonating or a phosphorating agent at a temperature of 25 0 C and of 40 0 C, respectively, still maintains a percentage higher than 50% of the amount of grafting [ ⁇ p (%)] of the side chains, even after being subjected to hydrogen peroxide treatment.
  • a direct methanol fuel cell was prepared using a 4 cm x 4 cm membrane 1 of the present invention as previously disclosed.
  • the cathode utilized in MEA preparation was a standard commercial electrode of the AIlSTDC ELAT type, 5mg/cm 2 TM loading, using unsupporting Pt black, available from E-TEK, 2.24 cm x 2.24 cm, while the anode was a standard commercial electrode of the AIlSTDA ELAT type, 5mg/cm 2 TM loading, using Pt : Ru alloy (1:1) black, 2.24 cm x 2.24 cm.
  • MEA was assembled positioning the two electrodes on opposite sides of the membrane, with their catalytic layer facing the polymeric electrolyte.
  • MEA was sandwiched between two Teflon-PFA sheets (200 ⁇ m thick) with opening corresponding to the electrodes.
  • the so obtained MEA-gaskets assembly was placed between two polytetrafluoro ethylene (PTFE) sheets and hot pressed using a hydraulic press. After inserting the assembly above described and applying 2.17 MPa, the plates temperature was raised to 130 0 C and maintained for 3.5 minutes. Finally, MEA was allowed to cool down to room temperature, costantly under pressure.
  • Sample 2 (invention)
  • a direct methanol fuel cell was prepared as invention sample 1, with the only difference that the invention membrane 2 was used instead of invention membrane 1.
  • a direct methanol fuel cell was prepared as invention sample 1, with the only difference that the comparison membrane 4 was used instead of invention membrane 1
  • a direct methanol fuel cell was prepared as invention sample 1, with the only difference that the comparison membrane 5 was used instead of invention membrane 1
  • Each one of the obtained MEA was installed in a single cell test system (Globo Tech Inc) , containing two copper current collector end plates and two graphite plates containing rib channel patterns allowing the passage of a methanol/water solution to the anode and humidified air to the cathode.
  • the MEAs were hydrated and activated using the following procedure.
  • the cell was heated to 70 0 C. Water was supplied at a rate of 2 ml/min to the anode through a peristaltic pump and a pre-heater maintained at the cell temperature. Humidified air was fed to the cathode at atmospheric pressure, at a rate of 220 ml/min and the air humidifier was maintained at the cell temperature.
  • the anode was fed with 1 M methanol solution at a feed rate of 2 ml/min, while the air flux at the cathode remains 220 ml/min. The cell was then run for about 2 hours at 0.2-
  • Table 2 shows that the direct methanol fuel cell Samples 1 and 2 of the present invention, comprising the membranes of the present invention, show a power density value in methanol concentration of 12.4 M that corresponds to 57.9% and 53.5% respectively, with respect to the same value measured in methanol concentration of 1 M.
  • This fact has the advantage that the direct methanol fuel cell of the present invention may use a high methanol concentration, thus reducing methanol volumes, still maintaining good performances, such as power density values.
  • both reference sample 3 and comparison samples 4, 5 and 6 show too low power output density values for high methanol concentration [(12.4 M/l M) ratio (%) of about 33% - 37%] .
  • Table 2 also shows that the remaining properties of the membranes of the present invention are not negatively affected.

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Abstract

La présente invention concerne une pile à combustible à méthanol direct, qui comprend : (a) une anode; (b) une cathode; (c) une membrane électrolytique polymère placée entre l'anode et la cathode et qui comprend au moins une polyoléfine greffée avec des chaînes latérales contenant des groupes fonctionnels conducteurs de protons, lesdites chaînes latérales étant greffées à la polyoléfine au moyen d'un pont oxygène. Ladite pile à combustible présente une valeur de densité de puissance mesurée à une concentration en méthanol de 12,4 M qui est supérieure ou égale à environ 50 % par rapport à celle mesurée à une concentration en méthanol de 1 M.
PCT/EP2007/011238 2007-12-20 2007-12-20 Pile à combustible à méthanol direct intégrant une membrane électrolytique polymère greffée par irradiation Ceased WO2009080062A1 (fr)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20220016579A1 (en) * 2020-07-15 2022-01-20 Korea Petrochemical Ind. Co., Ltd. Polymer electrolyte membrane and method for manufacturing the same

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1994024717A1 (fr) * 1993-04-09 1994-10-27 Maxdem Incorporated Polymeres sulfones destines a des electrolytes polymeres solides
WO2004004053A2 (fr) * 2002-06-28 2004-01-08 Pirelli & C. S.P.A. Pile a combustible comprenant une membrane electrolyte polymere greffee par irradiation
US20050181255A1 (en) * 2004-02-18 2005-08-18 Jong-Pyng Chen Structures of the proton exchange membranes with different molecular permeabilities
WO2007007770A1 (fr) * 2005-07-07 2007-01-18 Fujifilm Corporation Membrane electrolytique solide, procede et appareil d'obtention, ensemble d'electrode membrane et pile a combustible
WO2007128330A1 (fr) * 2006-05-05 2007-11-15 Pirelli & C. S.P.A. Pile à combustible et membrane electrolyte polymère

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1994024717A1 (fr) * 1993-04-09 1994-10-27 Maxdem Incorporated Polymeres sulfones destines a des electrolytes polymeres solides
WO2004004053A2 (fr) * 2002-06-28 2004-01-08 Pirelli & C. S.P.A. Pile a combustible comprenant une membrane electrolyte polymere greffee par irradiation
US20050181255A1 (en) * 2004-02-18 2005-08-18 Jong-Pyng Chen Structures of the proton exchange membranes with different molecular permeabilities
WO2007007770A1 (fr) * 2005-07-07 2007-01-18 Fujifilm Corporation Membrane electrolytique solide, procede et appareil d'obtention, ensemble d'electrode membrane et pile a combustible
WO2007128330A1 (fr) * 2006-05-05 2007-11-15 Pirelli & C. S.P.A. Pile à combustible et membrane electrolyte polymère

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
SCOTT K ET AL: "Performance of the direct methanol fuel cell with radiation-grafted polymer membranes", JOURNAL OF MEMBRANE SCIENCE, ELSEVIER SCIENTIFIC PUBL.COMPANY. AMSTERDAM, NL, vol. 171, no. 1, 1 June 2000 (2000-06-01), pages 119 - 130, XP004194077, ISSN: 0376-7388 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20220016579A1 (en) * 2020-07-15 2022-01-20 Korea Petrochemical Ind. Co., Ltd. Polymer electrolyte membrane and method for manufacturing the same

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