JP2009043674A - Electrolyte for fuel cell, electrolyte membrane, and membrane-electrode assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte which has high density of a proton conductive group and excellent proton conductivity in addition to excellent dimensional stability and can preferably exhibit the proton conductivity under a nonaqueous environment. <P>SOLUTION: In the crystal proton conductive electrolyte, molecules of non-water-soluble and crystalline low-molecule sulfonic acid compounds 2a, 2b, which introduce sulfonic acid groups 4a, 4b into hydrophobic segments 3a, 3b made of non-water-soluble and crystalline low molecules, are regularly arranged, the sulfonic acid groups 4a, 4b of the respective molecules are adjoined with each other, and the hydrophobic segments 3a, 3b of the respective molecules are adjoined with each other. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrolyte used in a fuel cell, and more particularly to a proton conductive electrolyte. The present invention also relates to an electrolyte membrane using the proton conductive electrolyte, and a membrane electrode assembly including the electrolyte membrane.

  A fuel cell directly converts chemical energy into electrical energy by supplying fuel and an oxidant to two electrically connected electrodes and causing the fuel to be oxidized electrochemically. Unlike thermal power generation, fuel cells are not subject to the Carnot cycle, and thus exhibit high energy conversion efficiency. Solid polymer electrolyte fuel cells using a solid polymer electrolyte as an electrolyte have advantages such as easy miniaturization and operation at a low temperature. Has been.

In the solid polymer electrolyte fuel cell, when hydrogen is used as the fuel, the reaction of the formula (1) proceeds at the anode (fuel electrode).
H ₂ → 2H ⁺ + 2e ⁻ (1)
The electrons generated by the equation (1) reach the cathode after working with an external load via an external circuit. Then, the proton generated in the formula (1) moves by electroosmosis from the anode side to the cathode side in the solid polymer electrolyte membrane in a state of being hydrated with water.

Further, when oxygen is used as the oxidizing agent, the reaction of the formula (2) proceeds at the cathode (oxidant electrode).
2H ⁺ + (1/2) O ₂ + 2e ⁻ → H ₂ O (2)
The water produced at the cathode mainly passes through the gas diffusion layer and is discharged to the outside.

A laminate of electrodes on both sides of the electrolyte membrane is called a membrane electrode assembly (MEA). A pair of electrodes (that is, a fuel electrode and an oxidizer electrode) provided on both surfaces of the electrolyte membrane generally have a structure in which a catalyst layer and a gas diffusion layer are laminated in order from the electrolyte membrane side. Many.
The catalyst layer usually includes a catalyst component that promotes a reaction in each electrode, a polymer electrolyte that forms a proton conduction path, and a conductive material that forms an electron conduction path, and is a portion that serves as a field for each electrode reaction. As the polymer electrolyte contained in the catalyst layer, the same polymer electrolyte as that for forming the electrolyte membrane is often used.
On the other hand, the gas diffusion layer is made of a conductive porous body and is provided for the purpose of improving the diffusion of the reaction gas into the catalyst layer and the electronic conductivity.

Since the power generation characteristics of the fuel cell can be improved by increasing the proton conductivity, various attempts have been made to improve the proton conductivity.
For example, as represented by Patent Document 1, a technique of introducing a large amount of proton conductive groups such as sulfonic acid groups into an electrolyte for a fuel cell can be mentioned. In Patent Document 1, in a membrane electrode structure for a polymer electrolyte fuel cell in which a polymer electrolyte membrane is sandwiched between a pair of electrodes containing a catalyst, the polymer electrolyte membrane introduces a specific sulfonic acid group. A membrane electrode structure for a polymer electrolyte fuel cell comprising a polyarylene polymer containing a unit and a specific hydrophobic structural unit is disclosed.
Further, in the conventional polymer electrolyte, proton conductive groups are randomly introduced into the polymer main chain, but it is partially concentrated by a technique using block copolymerization as represented by Patent Document 2. Thus, attempts have been made to increase the density of proton conductive groups such as sulfonic acid groups in the electrolyte. Patent Document 2 discloses a sulfonic acid group-containing polymer composed of a specific aromatic polymer and having a polymer ion exchange capacity (IEC) of 2.0 meq / g or more under an atmosphere of 80 ° C. and a relative humidity of 95%. A sulfonic acid group-containing polymer compound in which the moisture absorption rate (λ) as the number of water molecules per sulfonic acid group is smaller than the relational expression of IEC × 6-2 is disclosed.

  However, electrolytes for automobile fuel cells are required to have the contradictory characteristics of dimensional stability from the viewpoint of battery durability and high proton conductivity from the viewpoint of power generation performance of the battery as described above, and are hydrophilic. When the amount of proton conductive groups such as sulfonic acid groups is increased, the amount of water absorption increases, and the hot water resistance and toughness decrease. There was a limit.

On the other hand, main electrolyte membranes that have been conventionally used exhibit proton conductivity in a state of containing water, but a humidifier or the like is necessary for that purpose. From the viewpoint of simplifying the system, there is a need for an electrolyte membrane that operates in a high-temperature, low-humidified or non-humidified environment.
Further, in conventional polymer electrolytes, proton dissociation by hydration is necessary for proton conduction, and it is difficult to conduct proton conduction in an anhydrous environment.

  The present inventors have replaced a polymer electrolyte having a proton conduction mechanism of a conventional polymer-fixed sulfonic acid / water system (a polymer electrolyte in which a proton conductive group such as a sulfonic acid group conducts proton conduction through water). In addition, the electrolyte obtained by introducing a proton conductive group such as a sulfonic acid group into a water-insoluble crystalline low molecule and crystallizing it increases the density of the proton conductive group without causing the above-mentioned problems, It has been found that proton conduction can be improved below.

JP 2006-32179 A Japanese Patent No. 3655163

The present invention has been accomplished in view of the above circumstances, and its first object is to have a high proton conductive group density and excellent proton conductivity while having excellent dimensional stability, and more preferably anhydrous. To provide an electrolyte that exhibits proton conductivity even in an environment.
The second object of the present invention is to provide an electrolyte for a fuel cell that has excellent dimensional stability, has a high density of proton conductive groups, is excellent in proton conductivity, and exhibits proton conductivity in an anhydrous environment. It is to provide a membrane.
The third object of the present invention is to provide a fuel cell membrane electrode assembly including the electrolyte membrane.

  In order to achieve the above object, the present invention provides a low-molecular-weight sulfonic acid which is itself water-insoluble and crystalline, which is obtained by introducing a sulfonic acid group into a hydrophobic segment composed of a non-water-soluble and low-crystalline molecule. A crystalline proton conducting electrolyte in which molecules of a compound are regularly arranged, in which the sulfonic acid groups of the molecules are adjacent to each other and the hydrophobic segments of the molecules are adjacent to each other I will provide a.

  In the present invention, the sulfonic acid group is introduced into a hydrophobic segment composed of a water-insoluble and crystalline low molecule, and the molecules of the water-insoluble and crystalline low-molecular weight sulfonic acid compound are regularly arranged. Since they are arranged, deformation due to water absorption and / or swelling is small, and dimensional stability is excellent. In addition, in the arrangement of the low-molecular sulfonic acid compound that is crystalline, the sulfonic acid groups of the respective molecules are adjacent to each other and the hydrophobic segments of the respective molecules are adjacent to each other. It is possible to arrange proton conductive groups well, increase the density of proton conductive groups, and increase proton conductivity. Furthermore, since the space | interval of proton conductive groups can be arranged short, the anhydrous proton conduction by a hopping mechanism can be anticipated, and the use in the anhydrous environment of an electrolyte is attained.

  In the proton conductive electrolyte of the present invention, the interval between the sulfonic acid groups adjacent to each other can be set to 4 mm or less.

The hydrophobic segment in the proton conducting electrolyte of the present invention preferably has a chemical structure including any of the following:
Fluorinated hydrocarbons, or
Aromatic hydrocarbons having an aromatic ring (however, they may contain hetero atoms).

  Further, the hydrophobic segment may have a chemical structure provided with a spacer group to which a sulfonic acid group is linked to the fluorine-based hydrocarbon or the aromatic hydrocarbon.

  The present invention also provides an electrolyte membrane for a fuel cell comprising the above-described proton conductive electrolyte.

  The electrolyte membrane can contain a binder resin.

  Furthermore, the present invention is a membrane electrode assembly for a fuel cell comprising an electrolyte membrane, a pair of electrodes comprising a fuel electrode provided on one surface side of the electrolyte membrane and an oxidant electrode provided on the other surface side, Provided is a membrane electrode assembly for a fuel cell, characterized in that the electrolyte membrane contains the proton conductive electrolyte described above.

According to the proton conductive electrolyte according to the present invention, while having excellent dimensional stability, the density of the proton conductive group is high, the proton conductivity is excellent, and the proton conductivity is exhibited even in an anhydrous environment.
Furthermore, according to the electrolyte membrane for a fuel cell according to the present invention, the proton conductive group has a high density and excellent proton conductivity while having excellent dimensional stability, and further exhibits proton conductivity in an anhydrous environment. Moreover, the proton conductive electrolyte membrane of the present invention can be used in the same manner as the polymer electrolyte membrane of a conventional solid polymer electrolyte fuel cell.
Furthermore, according to the membrane electrode assembly for a fuel cell according to the present invention, since the electrolyte membrane having excellent dimensional stability is included, it is difficult to be damaged or deteriorated and has durability in long-term use. Moreover, since the electrolyte membrane contained in the membrane electrode assembly of the present invention has high proton conductivity, it is excellent in power generation characteristics when used in a fuel cell. Further, when the membrane electrode assembly of the present invention is used for a fuel cell, proton conductivity is exhibited in an anhydrous environment.

The electrolyte provided by the present invention is a molecule of a low-molecular-weight sulfonic acid compound, which is itself water-insoluble and crystalline, formed by introducing a sulfonic acid group into a hydrophobic segment composed of a non-water-soluble and low-crystalline molecule. Is a crystalline proton-conducting electrolyte in which the sulfonic acid groups of the molecules are adjacent to each other and the hydrophobic segments of the molecules are adjacent to each other. It is characterized by.
In the proton conductive electrolyte of the present invention, the hydrophobic segments of the low molecular weight sulfonic acid compound are regularly and densely arranged by crystallization of the molecules of the low molecular weight sulfonic acid compound. Since it is water-insoluble, that is, water-insoluble as a whole, the proton-conducting electrolyte is difficult to absorb water, and is less deformed by swelling due to water absorption.
Moreover, the low molecular weight sulfonic acid compound that is crystalline has high proton conductivity because it has a structure in which sulfonic acid groups are regularly arranged at high density. Furthermore, since the sulfonic acid groups have a dense portion, anhydrous proton conduction by a hopping mechanism can be expected, and the proton conducting electrolyte of the present invention can be used in an anhydrous environment.

Here, the low molecule means a molecule having a molecular weight of 200 to 1600, preferably 200 to 1250, and more preferably 200 to 1100. The lower limit value was determined in consideration of the molecular weight of CF ₃ CF ₂ SO ₃ H, which is the simplest system. Moreover, the said upper limit was determined as follows. When a conventional polymer electrolyte membrane is used, proton conductivity is improved by increasing the density of proton conductive groups. FIG. 1 is a plot of proton conductivity of an existing fluorine-based electrolyte membrane against EW. In the case of using a conventional polymer electrolyte membrane, it is considered that 700 is the lowest EW and 0.27 S / cm is the highest proton conductivity in terms of the production method of the electrolyte membrane. If the density of the proton conductive group is further increased, it becomes a highly fluid state and it is difficult to maintain the shape of the membrane. On the other hand, polymers are known to have anisotropy in physical properties due to molecular orientation, but in a known example of improving physical properties, the thermal conductivity of a resin filled with a magnetically oriented carbon filler is different from that of a non-oriented sample. It is known that it becomes six times as compared. Moreover, it is known that the elastic modulus of a polymer fiber is improved 20 times by molecular orientation in the spinning direction. Based on these, in the low molecular electrolyte of the present application, assuming that the proton conductivity can be improved by 6 times or 20 times depending on the orientation, examples of the above-described physical property improvement in the orientation / non-orientation of the polymer electrolyte For reference, the conductivity of the low molecular electrolyte in the non-oriented state should be 1/6 and 1/20 of the oriented state, respectively. In the oriented low molecular electrolyte of the present application, when it is considered that the maximum conductivity of the proton conductive group density of the polymer electrolyte membrane is obtained, from the graph of FIG. The proton conductive group density of the polymer electrolyte membrane is 1/6 and 1/20 of the maximum conductivity, and the corresponding EWs are 1250 and 1600. Such EW is the molecular weight of the electrolyte per molecule of the sulfonic acid group, and can be approximated to the low molecular electrolyte handled in this application. Based on the above considerations, the upper limit of the molecule was set to 1600, preferably 1250, and more preferably 1100 (equivalent to the EW of the existing Nafion 112 when there is no effect of orientation alignment).
Furthermore, crystalline in the proton conductive electrolyte means that crystalline molecules are aligned and in a crystalline state.
The regular arrangement means that there is regularity in the orientation of molecules, the positional relationship between the molecules and the distance. Typically, as the arrangement, the molecule of the low molecular weight sulfonic acid compound has 1 sulfonic acid group. And the arrangement as schematically shown in FIG. 2 and FIG. Molecules with two or more molecular parts that have very different molecular surface properties (molecules of low-molecular sulfonic acid compounds) recognize each other's molecular surface (hydrophobic segment, sulfonic acid group). In this state, molecular parts having the same surface characteristics are assembled to form a layer.

Hereinafter, the proton conductive electrolyte of the present invention will be described in detail with reference to FIGS.
In the first embodiment shown in FIG. 2, a sulfonic acid group 4 is introduced into a hydrophobic segment 3 composed of a water-insoluble and crystalline low molecule, and itself is a water-insoluble and crystalline low-molecular sulfonic acid. The proton conducting electrolyte 1 in which the molecules of the compound 2 are regularly arranged, in which the sulfonic acid groups 4 of the molecules are adjacent to each other and the hydrophobic segments 3 of the molecules are adjacent to each other It is. The dense part of the sulfonic acid group in which the sulfonic acid group 4 of each molecule adjoins and the dense part of the molecule in which the hydrophobic segment 3 adjoins alternately and periodically exist. Specifically, in row a shown in FIG. 2, the sulfonic acid groups 4 (4a) of the respective low molecular weight sulfonic acid compounds 2 (2a) are aligned in the same direction, and each low molecule is also displayed in the adjacent row b. The sulfonic acid groups 4 (4b) of the sulfonic acid compound 2 (2b) are aligned in the same direction, and the sulfonic acid groups 4a in the a row and the sulfonic acid groups 4b in the b row are opposed to each other. In the crystal, phases (a row and b row) in which the orientation of the molecules of the low molecular weight sulfonic acid compound is reversed are alternately located.

The water-insoluble and crystalline low-molecular sulfonic acid compound 2 is formed by introducing a sulfonic acid group 4 into a water-insoluble crystalline low-molecular molecule (hydrophobic segment 3). Is a low molecular weight sulfonic acid compound.
The hydrophobic segment 3 is composed of a water-insoluble and crystalline low molecule. For this reason, the proton conductive electrolyte 1 of the present invention can have a structure in which sulfonic acid groups are regularly arranged in high density, and the proton conductive electrolyte 1 is less deformed due to water absorption and / or swelling and is high. Proton conductivity. The hydrophobic segment 3 preferably has a chemical structure including any of the following: a fluorine-based hydrocarbon, or an aromatic hydrocarbon having an aromatic ring (a condensed ring is counted as one ring) (however, a heteroatom) May be included).
Here, the heteroatom means an atom other than carbon and hydrogen.

The hydrophobic segment 3 may have a chemical structure provided with a spacer group to which a sulfonic acid group is linked to the fluorinated hydrocarbon or the aromatic hydrocarbon. By providing the spacer group, dimensional stability and the like can be improved.
The interval between adjacent sulfonic acid groups (SO ₃ H) 4 is 4 mm or less.

  Conventionally, proton conductivity has been expressed by protons moving between proton conductive groups via water in a state where the electrolyte membrane contains water. In the present invention, the interval between proton conductive groups is increased. Since it can be arranged short, proton conduction can be expected by a hopping mechanism in which protons move between adjacent sulfonic acid groups, and the electrolyte can be used under anhydrous conditions.

The proton conductive electrolyte of the present invention may have a different arrangement as shown in FIG. 3 with the same components as described above.
In the second embodiment shown in FIG. 3, a sulfonic acid group 4 is introduced into a hydrophobic segment 3 composed of a water-insoluble and crystalline low molecule, and is itself a water-insoluble and crystalline low-molecular sulfonic acid. The proton conducting electrolyte 1 in which the molecules of the compound 2 are regularly arranged, in which the sulfonic acid groups 4 of the molecules are adjacent to each other and the hydrophobic segments 3 of the molecules are adjacent to each other It is. The dense part of the sulfonic acid group in which the sulfonic acid group 4 of each molecule adjoins and the dense part of the molecule in which the hydrophobic segment 3 adjoins alternately and periodically exist. Specifically, in the row a shown in FIG. 3, the sulfonic acid groups 4 (4 a) of the low molecular weight sulfonic acid compounds 2 (2 a) are arranged so that the directions thereof are staggered. The sulfonic acid groups 4 (4b) of the low molecular weight sulfonic acid compound 2 (2b) are aligned so that the directions of the sulfonic acid groups 4 (4b) are staggered. This is a combined form. In the crystal, molecules of the low molecular weight sulfonic acid compound are located in each of the rows a and b by alternately reversing the molecular orientation.
In addition, embodiment mentioned above is an illustration to the last, and this invention is not limited to embodiment mentioned above.

The proton conductive electrolyte 1 of the present invention described above is used for an electrolyte membrane or a catalyst layer of a fuel cell, and is particularly preferably used for an electrolyte membrane for a fuel cell because of less deformation at the time of water absorption.
The electrolyte membrane for a fuel cell may contain only one type of polymer electrolyte as described above, or may contain two or more types. Moreover, the proton conductive group to be introduced may be one type or two or more types. Moreover, the other component may be included as needed.
Further, the electrolyte membrane using the proton conductive electrolyte 1 of the present invention can contain a binder resin as a component for assisting molding. A thermoplastic resin can be used as the binder resin. Since the binder resin has a role of assisting film formation so that the proton conductive electrolyte becomes a continuous phase, there is a possibility that the effect of the present invention may be hindered when it is out of the above range.
Further, instead of the binder resin, a fluorine-based or hydrocarbon-based electrolyte conventionally used for an electrolyte membrane can be used as a high proton conductive filler. Thereby, proton conductivity can be improved, and the mechanical properties and / or dimensional stability of the electrolyte membrane can be improved. Conventional fluorine-based or hydrocarbon-based electrolytes used for electrolyte membranes include, for example, perfluorocarbon sulfonic acid resins such as Nafion (trade name, manufactured by DuPont) as a fluorine-based electrolyte, and polyelectrolytes as a hydrocarbon-based electrolyte. Examples include ether ether ketone, polyether sulfone, polyphenylene, polyamide, polycycloolefin and the like in which an ion exchange group is introduced.

The electrolyte membrane for a fuel cell is a solvent in which necessary components such as the above proton conductive electrolyte are appropriately combined with alcohols such as methanol, ethanol and propanol and water, or polar organic solvents such as dimethyl sulfoxide and dimethylformamide It can be prepared by dissolving or dispersing in an electrolyte solution and casting and drying the obtained solution on the surface or mold of a substrate or the like. It can also be produced by a method of extruding an electrolyte at a temperature above the glass transition point.
The electrolyte membrane for a fuel cell can be reinforced with a perfluorocarbon polymer in the form of a fibril, a fabric, a non-fabric, or a porous sheet, or by coating the membrane surface with an inorganic oxide or a metal.

  The thickness of the electrolyte membrane is usually about 10 to 100 μm. The electrolyte membrane is preferably thin from the viewpoint of improving proton conductivity, but if it is too thin, the function of sequestering gas decreases, the permeation amount of aprotic hydrogen increases, and if it is severe, cross leakage occurs. .

The above-described electrolyte membrane containing the proton conductive electrolyte of the present invention can be used for a membrane electrode assembly for fuel cells. Since the electrolyte membrane of the present invention can be used in the same manner as a polymer electrolyte membrane of a conventional solid polymer electrolyte fuel cell, the production of a membrane electrode assembly for a fuel cell is more complicated than the conventional one. There is little possibility of becoming.
The fuel cell membrane electrode assembly of the present invention will be specifically described below with reference to FIG. 4, but the present invention is not limited to the form shown in FIG. 4.
FIG. 4 is a schematic cross-sectional view showing one embodiment of the membrane electrode assembly of the present invention. As shown in FIG. 4, the electrolyte membrane 12 is provided with a cathode (oxidant electrode) 15 a on one surface and an anode (fuel electrode) 15 b on the other surface to form a membrane electrode assembly 11. In this example, the cathode 15a has a structure in which a cathode side catalyst layer 13a and a cathode side gas diffusion layer 14a are laminated in order from the electrolyte membrane side, and the anode 15b has an anode side catalyst layer in order from the electrolyte membrane side. 13b and the anode side gas diffusion layer 14b are laminated.

The catalyst layers 13a and 13b include catalyst particles, and may include a proton conductive material for increasing the utilization efficiency of the catalyst particles. As the proton conductive material, one used as a material for the electrolyte membrane may be used. it can. As the catalyst particles, catalyst particles in which a catalyst component is supported on a conductive material such as a carbon material such as carbonaceous particles or carbonaceous fibers are preferably used.
The catalyst component is not particularly limited as long as it has a catalytic action on the hydrogen oxidation reaction at the anode and the oxygen reduction reaction at the cathode. For example, platinum, ruthenium, iridium, rhodium, palladium, osnium, tungsten, It can be selected from metals such as lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum, or alloys thereof. Pt and an alloy made of Pt and another metal such as Ru are preferable.

  As the gas diffusion layers 14a and 14b, a conductive material mainly composed of a carbon material such as carbonaceous particles and / or carbonaceous fibers can be used. The sizes of the carbonaceous particles and the carbonaceous fibers may be appropriately selected in consideration of the dispersibility in the solution when the gas diffusion layer is produced, the drainage property of the obtained gas diffusion layer, and the like. The configuration of each electrode provided on both surfaces of the electrolyte membrane, the material used for the electrode, etc. may be the same or different. The gas diffusion layer is, for example, polytetrafluoroethylene, polyvinylidene fluoride (PVDF), polytetrafluoroethylene, perfluorocarbon alkoxyalkane, ethylene-tetrafluoroethylene polymer, or these from the point of improving the drainage of moisture such as generated water It is preferable to perform water-repellent processing by impregnating a mixture of the above or the like or forming a water-repellent layer using these substances.

  As a method for forming the membrane electrode assembly 11 of the fuel cell, a method using a catalyst ink in which a catalyst component, an electrolyte, and a conductive material are dissolved and dispersed in a solvent is generally used. Specifically, for example, after applying the catalyst ink to the conductive porous body to be the gas diffusion layers 14a and 14b and drying, the conductive porous body is applied with the catalyst ink applied surface on the electrolyte membrane side. 12 and a method of thermocompression bonding. Alternatively, there is a method in which a catalyst ink is applied to the surface of the electrolyte membrane 12 and dried, and then the electrolyte membrane 12 is thermocompression bonded to the conductive porous body with the application surface of the catalyst ink facing the conductive porous body. Alternatively, a catalyst ink is applied on a substrate such as polytetrafluoroethylene, and the dried product is transferred to a conductive porous body. Further, the conductive porous body on which the catalyst layer is formed and the electrolyte membrane 12 are heated. There is also a method of crimping.

As shown in FIG. 5, the membrane electrode assembly 11 is further sandwiched between separators 22 a and 22 b to form a single cell 21. As the separator 22, for example, a carbon separator containing a high concentration of carbon fibers and made of a composite material with a resin, a metal separator using a metal material, or the like can be used. Examples of the metal separator include those made of a metal material excellent in corrosion resistance, and those coated with a coating that enhances the corrosion resistance by coating the surface with carbon or a metal material excellent in corrosion resistance. . The separator 22 is usually provided with channels 23a and 23b that are grooves for discharging water.
The unit cells 21 having such a configuration are electrically assembled to form a stack and accommodated in a container to form a fuel cell.

It is a graph explaining the upper limit of the molecular weight of a low molecule. It is a figure which shows typically 1st Embodiment of the proton conductive electrolyte of this invention. It is a figure which shows typically 2nd Embodiment of the proton conductive electrolyte of this invention. It is sectional drawing which shows typically the example of 1 form of the membrane electrode assembly for fuel cells of this invention. It is sectional drawing which shows typically an example of the single cell containing the membrane electrode assembly for fuel cells of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Proton conductive electrolyte 2 ... Low molecular weight sulfonic acid compound (2a, 2b)
3 ... hydrophobic segment (3a, 3b)
4 ... sulfonic acid group (4a, 4b)
DESCRIPTION OF SYMBOLS 11 ... Membrane electrode assembly 12 ... Electrolyte membrane 13 ... Catalyst layer (13a: Cathode side catalyst layer, 13b: Anode side catalyst layer)
14 ... Gas diffusion layer (14a: cathode side gas diffusion layer, 14b: anode side gas diffusion layer)
15 ... Electrode (15a: cathode, 15b: anode)
22 ... Separator (22a: cathode side separator, 22b: anode side separator)
23 ... Flow path (23a, 23b)
21 ... Single cell

Claims (7)

  A sulfonic acid group is introduced into a hydrophobic segment composed of a water-insoluble and crystalline low molecule, and the molecules of the water-insoluble and crystalline low-molecular weight sulfonic acid compound are regularly arranged. A crystalline proton conductive electrolyte in which the sulfonic acid groups of each molecule are adjacent to each other and the hydrophobic segments of each molecule are adjacent to each other.   The proton conductive electrolyte according to claim 1, wherein an interval between the sulfonic acid groups adjacent to each other is 4 mm or less. The proton-conducting electrolyte according to claim 1 or 2, wherein the hydrophobic segment has a chemical structure including any of the following:
Fluorinated hydrocarbons, or
Aromatic hydrocarbons having an aromatic ring (however, they may contain hetero atoms).   The proton conductivity according to any one of claims 1 to 3, wherein the hydrophobic segment has a chemical structure provided with a spacer group to which a sulfonic acid group is linked to the fluorine-based hydrocarbon or the aromatic hydrocarbon. Electrolytes.   A fuel cell electrolyte membrane comprising the proton conductive electrolyte according to any one of claims 1 to 4.   The electrolyte membrane for fuel cells according to claim 5, wherein the electrolyte membrane contains a binder resin.   A membrane electrode assembly for a fuel cell comprising an electrolyte membrane, a fuel electrode provided on one surface side of the electrolyte membrane and a pair of oxidant electrodes provided on the other surface side, wherein the electrolyte membrane is the claim Item 5. A fuel cell membrane electrode assembly comprising the proton conductive electrolyte according to any one of Items 1 to 4.

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