JP2008166037A - Polymer electrolyte film/catalyst bonding material for fuel cell, its manufacturing method, and fuel cells - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer electrolyte film/catalyst bonding material for fuel cell improved in durability and its manufacturing method, and a fuel cell using the same. <P>SOLUTION: The polymer electrode film/catalyst bonding material mainly composed of hydrogen with a surface roughness ≤1 μm in its interface contains a polymer electrode film 2 mixed with 85 to 95 wt.% polymer (A) and 5 to 15 wt.% polymer (B), and an electrode catalyst layer 1 directly bonded at least to one side of the polymer electrode film. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a novel polymer electrolyte membrane / catalyst assembly for a fuel cell (hereinafter sometimes simply referred to as “membrane / catalyst assembly”), a production method thereof, and a fuel using the membrane / catalyst assembly. It relates to batteries.

  In recent years, new power generation technologies with excellent energy efficiency and environmental friendliness have attracted attention. Among them, the polymer electrolyte fuel cell using the polymer electrolyte membrane has a high energy density, and has features such as being easy to start and stop because the operating temperature is lower than other types of fuel cells. Developments as power supply devices for electric vehicles and distributed power generation are advancing.

  Polymer electrolyte membranes are usually required to have high proton conductivity. In addition to proton conductivity, the polymer electrolyte membrane must have characteristics such as gas permeation deterrence and mechanical strength to prevent permeation of hydrogen, oxygen, etc. of the fuel. As such a polymer electrolyte membrane, for example, a membrane containing a perfluorocarbon sulfonic acid polymer into which a sulfonic acid group is introduced, represented by Nafion (registered trademark) manufactured by DuPont, USA, is known.

  Perfluorocarbon sulfonic acid polymer electrolyte membranes have well-balanced characteristics as fuel cell electrolyte membranes, but depending on the operating conditions, harmful hydrofluoric acid may be generated in the exhaust gas, and the environmental load during disposal Have been pointed out.

  On the other hand, a polymer electrolyte membrane made of a hydrocarbon polymer that does not contain halogen such as fluorine has been actively studied (for example, Patent Document 1). Among the hydrocarbon polymer electrolyte membranes, those made of aromatic polymers are expected to be applied to fuel cells as having excellent proton conductivity as well as heat resistance and dimensional stability at high temperatures. Generally, there is a trade-off relationship between the durability and the durability performance, and those having higher proton conductivity tended to have lower durability.

  As a measure for increasing the durability of an aromatic hydrocarbon polymer electrolyte membrane excellent in proton conductivity, blending chemically and physically stable aromatic polymers has been proposed. However, when a polymer having no proton conductivity is mixed with the polymer electrolyte polymer, a decrease in proton conductivity occurs. Therefore, it can be said that a highly stable aromatic polymer itself also has a proton conductivity is a preferable combination. As such, polybenzimidazole having a sulfonic acid group or a phosphonic acid group is useful, and Patent Documents 2 and 3 have been reported. Among them, it is stated that the performance as a fuel cell is excellent, but the characteristic value is not sufficient.

International Publication No. 2004/033534 JP 2005-139318 A JP-A-2005-213276

  The present invention relates to a polymer electrolyte membrane / catalyst assembly and a method for producing the same for use in a fuel cell in a blended polymer electrolyte membrane with improved proton conductivity and durability. In addition, an object of the present invention is to provide a fuel cell using the membrane / catalyst assembly.

  As a result of intensive studies, the present inventors have found that the above object can be achieved by the membrane / catalyst assembly shown below. That is, the present invention is achieved by the following (1) to (3).

(1) A polymer obtained by mixing 85 to 95% by weight of a polymer (A) having a structure represented by the following chemical formula (1) and 5 to 15% by weight of a polymer (B) having a structure represented by the following chemical formula (2). A fuel using hydrogen as a fuel, comprising a molecular electrolyte membrane and an electrode catalyst layer directly bonded to at least one surface of the polymer electrolyte membrane, and having a membrane / catalyst interface surface roughness of 1 μm or less A polymer electrolyte membrane / catalyst assembly for a battery.

（上記式中、ｎ１、ｎ２は０．４０≦ｎ１／（ｎ１＋ｎ２）≦０．７０の関係を満たす１以上の整数を、ｍ１は１以上の整数を、それぞれ示す）

(In the above formula, n1 and n2 each represent an integer of 1 or more satisfying the relationship of 0.40 ≦ n1 / (n1 + n2) ≦ 0.70, and m1 represents an integer of 1 or more)

（上記式中、ｎ３は１以上の整数を、ｍ２，ｍ３は０．６０≦ｍ３／（ｍ２＋ｍ３）≦０．８０の関係を満たす１以上の整数を、それぞれ示す）

(In the above formula, n3 represents an integer of 1 or more, and m2 and m3 represent an integer of 1 or more satisfying the relationship of 0.60 ≦ m3 / (m2 + m3) ≦ 0.80)

(2) The surface roughness of the membrane / catalyst interface is 1 μm or less when the catalyst slurry containing the electrode catalyst, the polymer electrolyte, and the solvent is applied to at least one surface of the polymer electrolyte membrane according to the first invention. A method for producing a polymer electrolyte membrane / catalyst assembly for a fuel cell, wherein the electrode catalyst layer is formed by direct coating as described above.

(3) A fuel cell using hydrogen as a fuel, wherein the polymer electrolyte membrane / catalyst assembly for a fuel cell according to the first invention is used.

  The membrane / catalyst assembly according to the present invention has improved durability without lowering proton conductivity as compared with the conventional one, and has excellent output characteristics and long-term drivability when used in a fuel cell. Has an effect.

  Hereinafter, the present invention will be described in detail.

  In the polymer electrolyte membrane of the present invention, the polymer (A) having the structure represented by the following chemical formula (1) and the polymer (B) having the structure represented by the following chemical formula (2) are composed of the polymer (B). It is a polymer electrolyte membrane for a fuel cell comprising a mixture mixed so that the weight fraction is 5 to 15% by weight.

（上記式中、ｎ１、ｎ２は０．４０≦ｎ１／（ｎ１＋ｎ２）≦０．７０の関係を満たす１以上の整数を、ｍ１は１以上の整数を、それぞれ示す）

(In the above formula, n1 and n2 each represent an integer of 1 or more satisfying the relationship of 0.40 ≦ n1 / (n1 + n2) ≦ 0.70, and m1 represents an integer of 1 or more)

（上記式中、ｎ３は１以上の整数を、ｍ２，ｍ３は０．６０≦ｍ３／（ｍ２＋ｍ３）≦０．８０の関係を満たす１以上の整数を、それぞれ示す）

(In the above formula, n3 represents an integer of 1 or more, and m2 and m3 represent an integer of 1 or more satisfying the relationship of 0.60 ≦ m3 / (m2 + m3) ≦ 0.80)

  In the polymer A represented by the chemical formula (1), n1 / (n1 + n2) is in the range of 0.40 to 0.70. It is preferable that n1 / (n1 + n2) is between 0.45 and 0.60. When n1 / (n1 + n2) is smaller than 0.40, the output tends to be insufficient when used in a fuel cell using hydrogen as fuel. If n1 / (n1 + n2) is greater than 0.70, the film form retainability tends to be reduced, and problems such as reduced durability tend to occur. n1 + n2 + m1 may be an integer of 3 or more, but is preferably between 10 and 10,000. If it is less than 10, it may be difficult to obtain a film, which is not preferable. If it is greater than 10,000, problems such as excessive increase in the viscosity of the solution tend to occur, which is not preferable. Further, (n1 + n2) / (m1) is preferably in the range of 0.9 to 1.1, more preferably in the range of 0.95 to 1.05, and in the range of 0.99 to 1.01. More preferably.

  The degree of polymerization of the polymer (A) can be determined by, for example, gel permeation chromatography, light scattering method, osmotic pressure method, terminal group amount measurement method, etc. As a method for simply evaluating the degree of polymerization, dilute solution Logarithmic viscosities can also be used. For example, the polymer powder is dissolved in N-2-methylpyrrolidone at a concentration of 0.5 g / dL, and the viscosity is measured using a Ubbelohde viscometer in a constant temperature bath at 30 ° C., and ln [ta / tb] / c The logarithmic viscosity (ta is the number of seconds that the sample solution falls, tb is the number of seconds that the solvent is dropped, and c is the polymer concentration) is preferably between 0.1 and 3.0 dL / g. More preferably, it is between 8 and 2.0 dL / g.

  M3 / (m2 + m3) of the polymer (B) represented by the chemical formula (2) is between 0.60 and 0.80. If m3 / (m2 + m3) is smaller than 0.60, the durability of the blend film of the present invention tends to decrease, such being undesirable. If it is larger than 0.80, the solubility tends to decrease, and it becomes difficult to form a good blend film, which is not preferable. n3 + m2 + m3 may be an integer of 3 or more, but is preferably between 10 and 10,000. If it is less than 10, it may be difficult to obtain a film, which is not preferable. If it is greater than 10,000, problems such as excessive increase in the viscosity of the solution tend to occur, which is not preferable. Further, (n3) / (m2 + m3) is preferably in the range of 0.9 to 1.1, more preferably in the range of 0.95 to 1.05, and in the range of 0.99 to 1.01. More preferably.

  The degree of polymerization of the polymer (B) can be determined by, for example, gel permeation chromatography, light scattering method, osmotic pressure method, terminal group amount measurement method, etc. As a method for simply evaluating the degree of polymerization, dilute solution Logarithmic viscosities can also be used. For example, the polymer powder is dissolved in methanesulfonic acid or concentrated sulfuric acid at a concentration of 0.5 g / dL, and the viscosity is measured using an Ostwald viscometer in a constant temperature bath at 30 ° C., and ln [ta / tb] / c Is preferably in the range of 0.25 to 10 dL / g, with the logarithmic viscosity (ta being the number of seconds dropping of the sample solution, tb being the number of seconds dropping only the solvent, and c being the polymer concentration). More preferably, it is in the range of 8 dL / g. When the logarithmic viscosity is less than 0.25 dL / g, it tends to be difficult to obtain a molded product due to a decrease in viscosity. Moreover, when logarithmic viscosity exceeds 10 dL / g, it will become difficult to shape | mold to the raise of a viscosity.

  The mixing ratio of the polymer (A) and the polymer (B) is such that the content of the polymer (B) is 5 to 15% by weight. When the content of the polymer (B) is less than 5% by weight, the durability improving effect by the polymer (B) tends to be lost. If it exceeds 15% by weight, the tendency of the proton conductivity of the blend membrane to decrease increases.

  The polymer (A) can be synthesized by any known method, and can be polymerized using, for example, an aromatic nucleophilic substitution reaction. As the monomer, for example, sodium 4,4′-dichlorodiphenylsulfone-3,3′-disulfonate, 2,6-dichlorobenzonitrile, and 4,4′-biphenol can be used. Any monomer having a structure capable of giving a structure can be used without limitation. The polymer (A) can be obtained by heating the above-mentioned monomer in the presence of a basic substance.

  The polymerization can be carried out in the temperature range of 0 to 350 ° C., but is preferably 50 to 250 ° C. When the temperature is lower than 0 ° C., the reaction does not proceed sufficiently, and when the temperature is higher than 350 ° C., the polymer tends to be decomposed. The reaction can be carried out in the absence of a solvent, but is preferably carried out in a solvent. Examples of the solvent that can be used include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, diphenyl sulfone, sulfolane, and the like. And any solvent that can be used as a stable solvent in the aromatic nucleophilic substitution reaction. These organic solvents may be used alone or as a mixture of two or more.

  In the above polymerization reaction, 4,4′-biphenol was reacted with an isocyanate compound such as phenyl isocyanate to carbamoylate without using a basic compound, 2,6-dichlorobenzonitrile, 4,4 It is also possible to react directly with sodium '-dichlorodiphenylsulfone-3,3'-disulfonate.

  Examples of the basic compound include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate and the like, as long as they can make 4,4′-biphenol into an active phenoxide structure. However, it can be used without being limited to these. The basic compound can be polymerized satisfactorily when used in an amount of 100 mol% or more with respect to 4,4′-biphenol, preferably in the range of 105 to 125 mol% with respect to 4,4′-biphenol. is there. An excessive amount of the basic compound is not preferable because it causes side reactions such as decomposition.

  In the aromatic nucleophilic substitution reaction, water may be generated as a by-product. In this case, regardless of the polymerization solvent, water can be removed from the system as an azeotrope by coexisting toluene or the like in the reaction system. As a method for removing water out of the system, a water absorbing material such as molecular sieve can also be used. When the aromatic nucleophilic substitution reaction is carried out in a solvent, it is preferable to charge the monomer so that the resulting polymer concentration is 5 to 50% by weight. When the amount is less than 5% by weight, the degree of polymerization tends to be difficult to increase. On the other hand, when the amount is more than 50% by weight, the viscosity of the reaction system becomes too high, and the post-treatment of the reaction product tends to be difficult. After completion of the polymerization reaction, the solvent is removed from the reaction solution by evaporation, and the residue is washed as necessary to obtain the desired polymer. In addition, the polymer can be obtained by precipitating the polymer as a solid by adding the reaction solution in a solvent having low polymer solubility, and collecting the precipitate by filtration. In addition, a polymer solution can be obtained by removing by-product salts by filtration.

  The reaction temperature can be any temperature, but it is preferably in the range of 150 to 250 ° C. Although reaction time can be made into arbitrary time, it is preferable that it is the range of 3 to 60 hours. The reaction is preferably carried out with stirring. Moreover, it is preferable to carry out in inert gas atmosphere, such as nitrogen, or airflow.

  In the polymer (A), the order of the arrangement of the individual repeating units of the structure represented by the chemical formula (1) may be alternating, block, or random. If it is a block copolymer, it will show the tendency for proton conductivity and water absorption to become high.

  The polymer (B) can be polymerized by any known method. As the monomer, for example, 3,3 ′, 4,4′-tetraaminodiphenylsulfone, 2-sulfoterephthalic acid monosodium salt, and 3,5-dicarboxybenzenephosphonic acid can be used. As long as it is a monomer having a structure capable of giving the structure of ()), it is not limited to these and can be used.

  These monomers are described, for example, in J. Org. F. Wolfe, Encyclopedia of Polymer Science and Engineering, 2nd Ed. , Vol. 11, p. 601 (1988), and can be synthesized by dehydration and cyclopolymerization using polyphosphoric acid as a solvent. In addition, polymerization by a similar mechanism using a mixed solvent system of methanesulfonic acid / phosphorus pentoxide instead of polyphosphoric acid can be applied. In order to synthesize a polybenzimidazole compound having high thermal stability, polymerization using polyphosphoric acid that is commonly used is preferred.

  In addition, a precursor polymer having a polyamide structure or the like is synthesized by reaction in a suitable organic solvent or in the form of a mixed raw material monomer melt, and then the desired polybenzimidazole structure is obtained by a cyclization reaction by appropriate heat treatment or the like. The method of converting to can also be used.

  The reaction temperature can be any temperature, but it is preferably in the range of 150 to 250 ° C. The reaction time can be any time, but is preferably in the range of 2 to 30 hours. The reaction is preferably carried out with stirring. Moreover, it is preferable to carry out in inert gas atmosphere, such as nitrogen, or airflow.

  In the polymer (B), the order of the arrangement of the individual repeating units of the structure represented by the chemical formula (2) may be alternating, block, or random.

  The polymer electrolyte membrane composed of the polymer (A) and the polymer (B) can be obtained by any known method, but a solution containing the polymer (A) and the polymer (B) is prepared, and the solution is cast. It is preferable to obtain a film by drying. In general, polybenzimidazoles containing ionic groups (particularly polyvalent anionic groups) tend to have poor solubility in organic solvents, but the polymer (B) of the present invention has phosphonic acid groups. Regardless, it is characterized by high solubility in an organic solvent, and can be made into a mixed solution in the same solvent system as the polymer (A), so that a good film can be formed.

  In order to prepare a solution containing the polymer (A) and the polymer (B), the respective polymers may be separately dissolved in a solvent and then mixed, or the respective polymers may be dissolved in the same solvent. Although dissolution can be performed at any temperature, it is preferably performed in the range of 30 to 150 ° C. Solvents include aprotic such as N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, hexamethylphosphonamide, N-morpholine oxide, etc. Examples include organic polar solvents, polar solvents such as alcohol solvents such as methanol and ethanol, ketone solvents such as acetone, ether solvents such as diethyl ether, mixtures of these organic solvents, and mixtures with water. However, it is not limited to these.

  Alternatively, a polymer electrolyte membrane can be obtained by preparing a mixture using a salt of a sulfonic acid group of a polymer and then performing a treatment for returning the sulfonic acid group to an acid type by acid treatment.

  The concentration of the polymer solution is preferably in the range of 0.1 to 50% by weight. From the viewpoint of moldability, it is more preferably in the range of 5 to 40% by weight, and still more preferably in the range of 10 to 30% by weight. When the polymer concentration is lower than 0.1% by weight, it is difficult to obtain a polymer electrolyte membrane having a stable film thickness. If the polymer concentration is higher than 50% by weight, handling of the solution becomes difficult.

  The electrolyte membrane made of the mixture of the polymer (A) and the polymer (B) can have any thickness. However, when the thickness is 10 μm or less, the handling of the membrane becomes difficult and the mechanical strength becomes insufficient. It is preferable to have a film thickness exceeding. More preferably, it is 20 μm or more. Moreover, since it will become difficult to manufacture a homogeneous film when the film thickness exceeds 300 μm, it is preferable that the film thickness does not exceed 300 μm.

The membrane / catalyst assembly of the present invention includes the polymer electrolyte membrane according to the present invention and an electrode catalyst layer directly bonded to at least one surface of the polymer electrolyte membrane, and the surface roughness of the membrane / catalyst interface is 1 μm. A membrane / catalyst assembly which is: The membrane / catalyst assembly is not particularly limited, but a method of applying a catalyst slurry containing an electrode catalyst, a polymer electrolyte, and a solvent to one side or both sides of the polymer electrolyte membrane is used. Thereby, the electrode catalyst layer containing an electrode catalyst and a polymer electrolyte can be disposed on one side or both sides of the polymer electrolyte membrane.
The electrode catalyst is not particularly limited as long as it promotes the electrode reaction, but one in which a catalyst component is supported on a conductive carrier is preferably used.

  The catalyst component only needs to have a catalytic action in the oxygen reduction reaction in the cathode catalyst layer, and may have any catalytic action in the hydrogen oxidation reaction in the anode catalyst layer. Specifically, selected from platinum, ruthenium, iridium, rhodium, palladium, osmium, tungsten, lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum, and alloys thereof, and the like Is done. Among these, those containing at least platinum are preferably used in order to improve catalyst activity, poisoning resistance to carbon monoxide and the like, heat resistance, and the like. The composition of the alloy is preferably 30 to 90 atomic% for platinum and 10 to 70 atomic% for the metal to be alloyed, depending on the type of metal to be alloyed. The composition of the alloy when the alloy is used as a cathode catalyst varies depending on the type of metal to be alloyed and can be appropriately selected by those skilled in the art, but platinum is 30 to 90 atomic%, and other metals to be alloyed are 10 It is preferable to set it to -70 atomic%.

  The shape and size of the catalyst component are not particularly limited, and the same shape and size as known catalyst components can be used, but the catalyst component is preferably granular. At this time, the smaller the average particle size of the catalyst component used in the catalyst layer, the higher the effective electrode area where the electrochemical reaction proceeds, which is preferable because the catalytic activity is higher, but actually the average particle size is too small. A phenomenon in which the catalytic activity decreases is observed. Therefore, the average particle size of the catalyst particles contained in the catalyst layer is preferably 1.5 to 15 nm, more preferably 2 to 10 nm, and even more preferably 2 to 5 nm.

The conductive carrier in the electrode catalyst may be any material as long as it has a specific surface area for supporting the catalyst component in a desired dispersed state and has sufficient electronic conductivity as a current collector. The specific surface area of the conductive carrier is preferably 20 to 1000 m ² / g, more preferably 80 to 800 m ² / g. When the specific surface area is 20 m ² / g or more, sufficient power generation performance can be obtained without lowering the dispersibility of the catalyst component in the conductive support and the polymer electrolyte described later, and the catalyst is 1000 m ² / g or less. It is avoided that the effective utilization rate of a component and a polymer electrolyte falls on the contrary.

  The conductive carrier is preferably composed mainly of carbon. Specific examples include carbon black, activated carbon, coke, natural graphite, mesophase pitch graphite, and flake shaped artificial graphite. Of these, mesophase pitch graphite and / or flake shaped artificial graphite is preferably used as the conductive carrier. Mesophase pitch-based graphite and flake-shaped artificial graphite have a structure in which flake-shaped crystals are oriented outward, so that they have excellent water absorption, and the water retention effect of the catalyst can be obtained.

  Further, the size of the conductive carrier is not particularly limited, but from the viewpoint of controlling the ease of loading, the catalyst utilization, and the thickness of the electrode catalyst layer within an appropriate range, the average particle size is 5 to 200 nm. The thickness is preferably about 10 to 100 nm.

  The content of the electrode catalyst in the catalyst slurry is not particularly limited, but is preferably 45 to 65% by mass, more preferably 50 to 60% by mass with respect to the catalyst slurry. Thereby, an electrode catalyst layer having high power generation performance can be produced.

  Next, the polymer electrolyte used in the catalyst slurry is not particularly limited and a known one can be used, but at least proton conductivity is preferable. Thereby, an electrode catalyst layer having high power generation performance is obtained.

  The content of the polymer electrolyte in the catalyst slurry is not particularly limited, but is usually 20 to 75% by mass, preferably 30 to 60% by mass, more preferably 35 to 45% by mass with respect to the catalyst slurry. It is good. If the content of the polymer electrolyte is less than 20% by mass, the content of the polymer electrolyte contained in the electrode catalyst layer may not be sufficient, and sufficient bondability between the electrolyte membrane and the electrode catalyst layer may not be obtained. If the amount exceeds 75% by mass, the content of the electrode catalyst in the obtained electrode catalyst layer may be reduced, and the power generation performance of the electrode catalyst layer may be reduced.

  The solvent used in the catalyst slurry is not particularly limited, but water and / or alcohol solvents such as methanol, ethanol, 1-propanol (NPA), 2-propanol, ethylene glycol, propylene glycol, N-methyl Organic solvents such as -2-pyrrolidone (NMP) can be mentioned.

  The catalyst slurry may be applied to the electrolyte membrane by a known method, for example, curtain coating method, extrusion coating method, roll coating method, spin coating method, dip coating method, bar coating method, spray coating method, slide coating method. A printing coating method or the like can be used.

  The gas diffusion layer used in the present invention is not particularly limited, and known materials can be used in the same manner. For example, conductive materials such as carbon fabrics such as carbon paper and carbon cloth, paper-like paper bodies, felts, and nonwoven fabrics. And at least a sheet-like conductive porous substrate having porosity. Thereby, high gas diffusibility is obtained.

The thickness of the conductive porous substrate may be appropriately determined in consideration of the characteristics of the gas diffusion layer to be obtained, but may be about 30 to 500 μm. If the thickness is less than 30 μm, sufficient mechanical strength or the like may not be obtained. If the thickness exceeds 500 μm, the distance through which gas or water permeates becomes undesirably long, and is not desirable on both sides of the electrolyte membrane / catalyst assembly. A gas diffusion layer is disposed.
In the method of the present invention, the membrane / electrode assembly is obtained by bonding the membrane / catalyst assembly obtained as described above to the gas diffusion layer substrate.

  The fuel cell of the present invention can be produced using the membrane / catalyst assembly of the present invention. That is, the membrane / catalyst assembly is sandwiched between a pair of gas diffusion layers, and both sides are sandwiched between separators. A fuel cell can be obtained by fastening this further with an end plate through a current collector plate and an insulating plate. Such a fuel cell of the present invention can be used for a polymer electrolyte fuel cell using hydrogen as a fuel, and is particularly suitable for an automobile fuel cell.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely using an Example, this invention is not limited to these Examples. Various measurements were performed as follows.

  Logarithmic viscosity (Polymer A): Polymer powder was dissolved in N-methyl-2-pyrrolidone at a concentration of 0.5 g / dL, and the viscosity was measured using a Ubbelohde viscometer in a thermostatic bath at 30 ° C. Evaluation was performed by ln (ta / tb) / c (ta is the number of seconds for dropping the sample solution, tb is the number of seconds for dropping only the solvent, and c is the polymer concentration).

  Logarithmic viscosity (Polymer B): Polymer powder was dissolved in methanesulfonic acid at a concentration of 0.5 g / dL, and the viscosity was measured using an Ostwald viscometer in a constant temperature bath at 30 ° C., and logarithmic viscosity ln (ta / Evaluation was made by tb) / c (ta is the sample solution dropping time, tb is the solvent dropping time, and c is the polymer concentration).

Durability evaluation:
Hydrogen was supplied as fuel to the anode side of the fuel cell, oxygen was supplied as the oxidant to the cathode side, and an endurance test in a continuous open circuit holding test was performed to evaluate changes in the open circuit voltage.
The results are shown in Table 1.

<Synthesis Example 1> Synthesis of Polymer (A) 3,3'-Disulfo-4,4'-dichlorodiphenylsulfone disodium salt (abbreviation: S-DCDPS) 71.02 g (0.1446 mole), 2,6-dichloro 24.87 g (0.1446 mole) of benzonitrile (abbreviation: DCBN), 53.84 g (0.2891 mole) of 4,4′-biphenol, 45.96 g (0.3325 mole) of potassium carbonate, and 2.61 g of molecular sieves in 4 liters. Weighed into a necked flask and flushed with nitrogen. After adding 430 ml of NMP and stirring at 150 ° C. for 1 hour, the reaction was continued by raising the reaction temperature to 195-200 ° C. and increasing the viscosity of the system sufficiently (about 8 hours). After standing to cool, the precipitated molecular sieve was removed and the mixture was precipitated in water as a strand. The obtained polymer was washed in boiling water for 1 hour and then dried. The logarithmic viscosity of the polymer was 1.19. The polymer (A) has a chemical structure represented by the chemical formula (1), and n1, n2, and m1 are n1 / (n1 + n2) = 0.50 and (n1 + n2) / (m1) = 1.0. It is an integer of 1 or more that satisfies the relationship.

<Synthesis Example 2> Synthesis of Polymer (B) 7.500 g (0.02695 mol) of 3,3 ′, 4,4′-tetraaminodiphenylsulfone (abbreviation: TAS), monosodium 2,5-dicarboxybenzenesulfonate (Abbreviation: STA, purity 99%) 2.168 g (0.00808 mol), 5-dicarboxyphenylphosphonic acid (abbreviation: DCP, purity 98%) 4.6423 g (0.0886 mol), polyphosphoric acid (phosphorus pentoxide content 75%) 52.3 g and phosphorus pentoxide 42.9 g are weighed into a polymerization vessel. The temperature is raised to 100 ° C. while slowly stirring on an oil bath while flowing nitrogen. After maintaining at 100 ° C. for 1 hour, the temperature was raised to 150 ° C. for 1 hour, and the temperature was raised to 200 ° C. and polymerized for 5 hours. After completion of the polymerization, the mixture was allowed to cool, water was added, the polymer was taken out, and washing with water was repeated until the pH test paper was neutral using a household mixer. The obtained polymer was dried under reduced pressure at 80 ° C. overnight. The logarithmic viscosity of the obtained polymer (B) was 1.69 dL / g. The polymer (B) has a chemical structure represented by the chemical formula (2), and n3, m2, and m3 are m3 / (m2 + m3) = 0.70 and n3 / (m2 + m3) = 1.0. It is an integer of 1 or more that satisfies the relationship.

Example 1 Production of Electrolyte Membrane 115.30 g of polymer (A) and 240 g of N-methyl-2-pyrrolidone (NMP) were placed in a 500 ml branch flask and dissolved by stirring at 100 ° C. for 5 hours in a nitrogen atmosphere. . 11.40 g of polymer (B) and 103 g of NMP were placed in a 500 ml branch flask and dissolved by stirring at 120 ° C. for 5 hours under a nitrogen atmosphere. The total amount of the polymer (B) solution was added to the polymer (A) solution, and the mixture was further stirred and mixed at 100 ° C. for 5 hours under a nitrogen atmosphere to obtain a brown transparent uniform solution. The obtained solution was cast on a glass plate with a thickness of 400 μm, heated at 100 ° C., 135 ° C., and 150 ° C. for 5 minutes each, and then treated in an oven at 150 ° C. in a nitrogen atmosphere for 1 hour. After cooling to room temperature, the glass plate is immersed in pure water to peel off the film, and the film is immersed in pure water for 12 hours, and then immersed in 2M dilute sulfuric acid, and then with pure water until the washing solution becomes neutral. Washed. The obtained membrane was freed from moisture adhering to the surface, sandwiched between filter papers, left under load for 24 hours, and dried to obtain a polymer electrolyte membrane having a thickness of about 30 μm.

Preparation of Gas Diffusion Layer A base material was prepared by punching carbon paper (carbon paper TGP-H-060 manufactured by Toray Industries, Inc., thickness 190 μm) into 50 mm square. After immersing this base material in a PTFE fluorine-based aqueous dispersion solution (polyflon D-1E manufactured by Daikin Industries, Ltd., containing PTFE 60 wt%) to a predetermined concentration with pure water for 5 minutes, PTFE was dispersed in the substrate by drying at 60 ° C. for 30 minutes. At this time, the PTFE content was 25 wt%. As a result, a water repellent treated substrate was obtained.
Subsequently, 5.4 g of carbon black (VULCAN (registered trademark) XC-72R manufactured by CABOT), 1.0 g of the same PTFE fluorine-based aqueous dispersion solution used above, and 29.6 g of water were used in a homogenizer. The slurry was prepared by mixing and dispersing for 3 hours. This slurry was uniformly applied to one surface of the water-repellent treated substrate prepared previously by a bar coater and heat-treated in an oven at 60 ° C. for 1 hour to obtain a gas diffusion layer.

Production of membrane / catalyst assemblies Production of membrane / catalyst assembly 1 part by weight of an electrode catalyst comprising 50% by weight of platinum having an average particle diameter of 3 nm as a catalyst component on carbon as a catalyst carrier, 4 parts by weight of water, 8 parts by weight of a 5% by weight Nafion solution, isopropanol A catalyst slurry was prepared by mixing 1.5 parts by mass. In the environment of 25 ° C., the catalyst slurry was subjected to a Nordson pulse spray on both surfaces of an electrolyte membrane (polymer electrolyte membrane made of the above-mentioned polymer (A) and polymer (B), thickness 30 μm, area 7 cm × 7 cm). The catalyst slurry was directly applied to prepare a membrane / catalyst assembly in which electrode catalyst layers (thickness 25 μm, area 5 cm × 5 cm) were arranged on both surfaces of the electrolyte membrane. The cross section of the produced membrane / catalyst assembly was observed with a scanning electron microscope, and it was confirmed that the surface roughness of the membrane / catalyst assembly was 1 μm or less.

2. Production of Fuel Cell In an environment of room temperature (25 ° C.) and relative humidity of 80%, the membrane electrode assembly is sandwiched by the produced gas diffusion layer so that the carbon particle layer is in contact with the electrode catalyst layer. A sealant made of silicone rubber was placed on the outer periphery of the exposed electrolyte membrane without being placed, and both sides were sandwiched between separators. This was further sandwiched between two stainless steel end plates via a current collector plate and an insulating plate, and the end plates were fastened with a fastening rod at a pressure of 1 MPa to obtain a fuel cell.

  The separator is made of carbon, and the outer dimensions are 2 mm in thickness, 130 mm in height, and 260 mm in width. On the surface facing the cathode or anode, the separator plate has a central portion of 20 cm × 9 cm. An oxidant gas channel or a fuel channel having a pitch of 2.9 mm and a width of about 2 mm was formed. Further, the cooling water channel has a pitch of 2.9 mm and a width of about 2 mm. The separator was provided with manifold holes for oxidant gas, fuel gas, and cooling water.

3. Evaluation The power generation performance of the fuel cell produced above was evaluated according to the following procedure.
Hydrogen was supplied as a fuel to the anode side of the fuel cell, and oxygen was supplied as an oxidant to the cathode side. For both gases, the cell outlet pressure is atmospheric pressure, hydrogen is 44.6 ° C., R.V. H. 30% and 0.261 L / min, air is 44.6 ° C., R.V. H. 30% and 1.041 L / min, the cell temperature was set to 90 ° C., the hydrogen utilization rate was 30%, and the oxygen utilization rate was 30%. Under these conditions, a continuous open circuit holding test was performed to evaluate changes in holding time and open circuit voltage.

<Comparative Example 1>
A sulfonic acid group-containing polymer represented by the following chemical formula (3) (with a logarithmic viscosity of 1.31 dL / g measured by the same method as the polymer (A)) was used in the same manner as in Example 1 except that the polymer (A) was used. Membrane / catalyst assemblies were prepared and evaluated.

（化学式（３）において、ｎ４、ｎ５、ｍ４は、ｎ４＝ｎ５、及びｍ４＝ｎ４＋ｎ５を満たす、正の整数を表す。）

(In the chemical formula (3), n4, n5, and m4 represent positive integers that satisfy n4 = n5 and m4 = n4 + n5.)

<Comparative example 2>
After sandwiching the catalyst-gas diffusion layer laminate in the same electrolyte membrane as in Example 1 so that the carbon particle layer was in contact with the electrode catalyst layer, the membrane / hot-press was performed by hot pressing at 130 ° C. and 6.5 Mpa for 10 minutes. A catalyst assembly was prepared and evaluated.

  Table 1 shows the evaluation results of the fuel cells using the polymer electrolyte membranes and the membrane / catalyst assemblies in Examples and Comparative Examples. In addition, the open circuit voltage was 0 V, and those that could not continue the test were marked with ×, and those that could continue the test were marked with ○.

  The polymer electrolyte membrane of the present invention exhibits excellent characteristics, and can greatly improve the durability when used in a fuel cell as a membrane / catalyst assembly, and therefore greatly contributes to the industry.

FIG. 2 is an enlarged view showing a cross section of a membrane / catalyst assembly interface produced in Example 1 and Comparative Example 1.

Explanation of symbols

1 Catalyst layer 2 Electrolyte layer

Claims (3)

Polymer electrolyte membrane formed by mixing 85 to 95% by weight of polymer (A) having a structure represented by the following chemical formula (1) and 5 to 15% by weight of polymer (B) having a structure represented by the following chemical formula (2) And (C) a surface roughness of the membrane / catalyst interface is 1 μm or less, (D) hydrogen as a fuel, and an electrode catalyst layer directly bonded to at least one surface of the polymer electrolyte membrane A polymer electrolyte membrane / catalyst assembly for a fuel cell.

(In the above formula, n1 and n2 each represent an integer of 1 or more satisfying the relationship of 0.40 ≦ n1 / (n1 + n2) ≦ 0.70, and m1 represents an integer of 1 or more)

(In the above formula, n3 represents an integer of 1 or more, and m2 and m3 represent an integer of 1 or more satisfying the relationship of 0.60 ≦ m3 / (m2 + m3) ≦ 0.80)   A catalyst slurry containing an electrode catalyst, a polymer electrolyte, and a solvent is directly applied to at least one surface of the polymer electrolyte membrane according to claim 1 so that the surface roughness of the membrane / catalyst interface is 1 μm or less. A method for producing a polymer electrolyte membrane / catalyst assembly for a fuel cell using hydrogen as a fuel, characterized in that an electrode catalyst layer is formed.   A fuel cell using hydrogen as a fuel, wherein the polymer electrolyte membrane / catalyst assembly for a fuel cell according to claim 1 is used.

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