JP5011658B2 - Manufacturing method of electrolyte membrane for fuel cell and electrolyte membrane for fuel cell - Google Patents

Description

  The present invention relates to a method for manufacturing an electrolyte membrane for a fuel cell and an electrolyte membrane for a fuel cell, and more particularly to a method for manufacturing an electrolyte membrane for a solid polymer type fuel cell and an electrolyte membrane for a fuel cell.

  A polymer electrolyte fuel cell has a gas diffusion electrode carrying a catalyst bonded to both sides of a diaphragm acting as a solid polymer solid electrolyte, and a fuel chamber which is a chamber on the side where one gas diffusion electrode exists. Hydrogen, which is a fuel, is supplied to an oxidant chamber, which is a chamber on the other gas diffusion electrode side, and an oxygen-containing gas such as oxygen or air, which is an oxidant, and an external load circuit is connected between both gas diffusion electrodes By connecting, it acts as a fuel cell.

  In such a polymer electrolyte fuel cell, an electrolyte membrane having proton conductivity is usually used as the diaphragm. In particular, in order to improve battery durability, a porous membrane impregnated with a cation exchange resin, that is, an electrolyte resin by some method is used.

  For example, Patent Document 1 discloses such an electrolyte membrane in which a polytetrafluoroethylene (PTFE) porous membrane is impregnated with a perfluoro-based ion exchange polymer having a sulfonic acid group. Here, a method of sufficiently impregnating porous PTFE with a perfluoro-based ion exchange resin solution is described.

  In Patent Document 2, as a modification of chemically stable porous PTFE, γ-rays from cobalt 60 are irradiated to cause graft polymerization reaction with a styrene monomer, and impregnated with a solution based on a sulfonic acid-based ion exchange resin. And drying and filling the pores with a sulfonic acid ion exchange resin. Then, it is described that the substrate is dipped in an HCl solution and washed repeatedly with water to make the functional group an H-type, and then dipped in an NaOH solution and neutralized with an aqueous HCl solution.

  Patent Document 3 describes a method of laminating a cation exchange resin on a porous membrane. Here, a method of forming a porous membrane and a perfluorocarbon-based ion exchange resin membrane having a sulfonic acid group by a heat and pressure laminating method is described.

Japanese Patent Publication No. 5-75835 JP 2004-273298 A Japanese Patent Laid-Open No. 2004-177895

  Of the methods for impregnating the porous membrane with the electrolyte resin, in order to directly impregnate the pores of the porous membrane with the electrolyte resin, the electrolyte resin solution is impregnated with the PTFE porous membrane as in Patent Document 1, or As in 2, alkaline hydrolysis and acid neutralization are then performed. In this method, while PTFE is hydrophobic, electrolyte resin is hydrophilic because it has proton conductivity. Therefore, since an aqueous solution or an alcohol solution is used as the solution, PTFE and the electrolytic resin solution are inevitably used. Difficult to get used to. Therefore, it is difficult to soak into the porous pores, and voids are likely to remain in the porous body of PTFE. Further, the grafting process for improving the familiarity requires an extra process such as γ-ray irradiation as described above.

  In addition, the lamination method described in Patent Document 3 is difficult to reduce the thickness required for the electrolyte membrane. For example, the thickness of the electrolyte membrane used in a fuel cell or the like is desired to be about 10 to 20 μm, but it is difficult to adjust the thickness by an extrusion film forming method in which the film is stretched using an extruder. is there. Further, the inflation method in which a plastic thin film is formed by extruding a resin in a tube shape and then expanding is difficult to apply because the material requires melt tension.

  Thus, in the prior art, it is difficult to sufficiently permeate the electrolyte resin into the porous membrane.

  The objective of this invention is providing the manufacturing method of the electrolyte membrane for fuel cells which improves the filling property of the electrolyte resin to a porous membrane, and the electrolyte membrane for fuel cells by the method.

A method for producing an electrolyte membrane for a fuel cell according to the present invention is a method for producing an electrolyte membrane for a solid polymer type fuel cell,
A polymer having a -SO ₂ F group as a precursor represented by the structural formula, was added to the organic solvent and fits the precursor hydrophobicity material was dispersed, a hydrophobic substance fits electrolyte precursor dispersion A dispersion generating step for generating
The electrolyte precursor dispersion is applied to a porous hydrophobic electrolyte membrane substrate, dried, and then fired.
A composite film production step for producing a composite film of a hydrophobic electrolyte membrane substrate in which porous pores are filled with a polymer having a —SO ₂ F group represented by the structural formula of FIG .
Hydrolyzing the composite membrane ,
A polymer having a —SO ₂ F group represented by the structural formula of
A hydrophilic treatment step of converting to a polymer having a —SO ₃ H group represented by the structural formula, and generating a hydrophilic electrolyte membrane;
It is characterized by including.

  Moreover, it is preferable to use the organic solvent containing a halogen element for a dispersion production | generation process. Moreover, it is preferable to use the organic solvent containing F or Cl as a halogen element at a dispersion production | generation process. Moreover, it is preferable to use the organic solvent of a perfluoro compound or a benzene derivative for a dispersion production | generation process.

In addition, the dispersion generation step includes CF ₂ CF ₂ ,
Obtained by polymerizing
It is preferable to use an electrolyte resin precursor having the following structural formula.

  Moreover, it is preferable to use the electrolyte resin precursor whose value of {x / (x + y)} × 100 is 5 or more and 50 or less in the dispersion generation step. Moreover, it is more preferable to use the electrolyte resin precursor whose value of {x / (x + y)} × 100 is 10 or more and 20 or less in the dispersion generation step.

Further, in the method for producing an electrolyte membrane for a fuel cell according to the present invention, the dispersion generation step includes adding a perfluoroelectrolyte resin precursor containing an SO ₂ F group to a perfluorohexane solvent, and the composite membrane generation step includes: It is preferable to apply the electrolyte precursor dispersion to the porous PTFE electrolyte membrane substrate.

A method for producing an electrolyte membrane for a fuel cell according to the present invention is a method for producing an electrolyte membrane for a solid polymer type fuel cell,
Indicated by the structural formula, SO ₂ F groups were added perfluoro electrolyte resin precursor containing 10 mol% to 20 mol% or less 20% by mass ratio perfluorohexane solvent, electrolyte precursor to this grinding process to A dispersion generation step for generating a body dispersion and a PTFE porous membrane having an average pore diameter of 3 μm are coated and dried with an electrolyte precursor dispersion, and this is repeated and fired at 200 to 250 ° C. to form a composite membrane. The composite membrane production process to be produced, and the composite membrane is acid-neutralized after alkali hydrolysis,
And a hydrophilic treatment step of generating a hydrophilic electrolyte membrane by converting into a polymer having a —SO ₃ H group represented by the structural formula:

The electrolyte membrane for a fuel cell according to the present invention is a solid polymer type electrolyte membrane for a fuel cell, and is formed on a PTFE porous membrane having an average pore diameter of 3 μm and on the surface of the PTFE porous membrane. ,
A polymer having a —SO ₂ F group represented by the structural formula of
And a calcined film of the electrolyte precursor dispersion hydrophilized by a hydrophilic treatment that is converted into a polymer having a —SO ₃ H group represented by the structural formula:

  In the fuel cell electrolyte membrane according to the present invention, the PTFE porous membrane body preferably has a thickness of 1 to 20 μm, and the fired membrane preferably has a thickness of 5 to 30 μm.

  In the fuel cell electrolyte membrane according to the present invention, the thickness is preferably 50 μm or less.

  In the prior art, the solution in which the hydrophilic electrolyte resin is dispersed uses water or alcohol. Therefore, it is difficult to be familiar with the hydrophobic electrolyte membrane body. The body dispersion is applied and dried, then fired to form a composite film, and then hydrolyzed to form a hydrophilic electrolyte film. That is, the hydrophilic electrolyte resin is later formed by hydrolyzing acid neutralization, and the electrolyte resin precursor is made hydrophobic and dispersed in a hydrophobic solvent. Good compatibility. Therefore, it is possible to improve the filling property of the electrolyte resin, which is finally hydrophilic, into the hydrophobic porous membrane.

  In addition, those containing halogen elements as organic solvents, those containing F or Cl as halogen elements, more specifically organic solvents such as perfluoro compounds or benzene derivatives are used, so that they are familiar with hydrophobic porous electrolytic membrane substrates. Good.

The electrolyte resin precursor is CF ₂ CF ₂ ,
Obtained by polymerizing
Thus, -SO ₂ F is included, which is easier to disperse in a halogen-based solvent than water or an alcohol, and thus the dispersion is easily adapted to a hydrophobic substance.

Further, the electrolyte resin precursor having a -SO ₂ F, and a side chain having a -SO ₂ F, the ratio of no backbone it, {x / (x + y )} value of × 100 is 5 or more and 50 or less More preferably, it is 10 or more and 20 or less, so that the dispersion degree of the electrolyte resin precursor in the organic solvent can be kept within a certain range, and the penetration of the electrolyte resin precursor into the porous pores can be stably maintained.

Further, since a perfluoroelectrolyte resin precursor containing SO ₂ F groups is added to a perfluorohexane solvent and this is applied to a porous PTFE electrolyte membrane substrate, a solvent containing the electrolyte resin precursor and a hydrophobic PTFE are applied. The familiarity with.

Further, an electrolyte precursor dispersion obtained by adding a perfluoroelectrolyte resin precursor containing 10 to 20 mol% of SO ₂ F groups to a perfluorohexane solvent in a mass ratio of 20% or less and pulverizing the electrolyte precursor dispersion has an average pore diameter of 3 μm. The PTFE porous membrane body is coated and dried, and this is repeated and fired at 200 to 250 ° C., followed by alkaline hydrolysis and acid neutralization to produce a hydrophilic electrolyte membrane. Therefore, it is familiar when coating and drying, and the electrolyte precursor can be sufficiently permeated into the PTFE porous membrane body, and then the final hydrophilic electrolyte resin is sufficiently filled by hydrolysis and acid neutralization. An electrolyte membrane made of a PTFE porous membrane can be obtained.

  As described above, according to the method for producing an electrolyte membrane for a fuel cell and the electrolyte membrane for a fuel cell according to the present invention, it is possible to improve the filling property of the electrolyte resin into the porous membrane that is the substrate of the electrolyte membrane.

  Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a flowchart showing a procedure of a method for producing an electrolyte membrane for a fuel cell, and FIG. 2 is a diagram for explaining each procedure. In the figure, for PTFE, which is a porous film body, the starting material 10, the first intermediate 12 after application and drying of the electrolyte precursor, the second intermediate 14 after firing of the electrolyte precursor, and the electrolyte film 20 of the final product are in the process. Indicated accordingly.

In FIG. 1, precursor generation (S10) is a process of creating an electrolyte resin precursor, which is a previous stage of an electrolyte resin that becomes hydrophilic by hydrolysis and acid neutralization, by chemical reaction. Specifically, as shown in FIG. 3, tetrafluoroethylene represented by the structural formula of CF ₂ CF ₂ ,
Is polymerized with the substance shown in
A perfluoroelectrolyte resin precursor having the following structural formula is generated. In the chemical formula (1), n is 1 or 0.

The perfluoroelectrolyte resin precursor has a structure composed of a main chain and a side chain having a —SO ₂ F group. Using the x, y in the chemical formula _(2), -SO 2 F group (mol%) = {x / (x + y)} is a × 100. In addition, the ion exchange equivalent (EW) of the electrolyte resin is EW = electrolyte mass (g) / − SO ₂ F group equivalent (eq) = electrolyte mass (g) / precursor —SO ₂ F group equivalent (eq). Indicated. Furthermore, the EW of the composite membrane is EW = (electrolyte + PTFE porous membrane) mass (g) / − SO ₂ F group equivalent (eq).

  Here, the value of {x / (x + y)} × 100 in the polymerization reaction can be determined experimentally from the performance of the electrolyte membrane for fuel cells. For example, {x / (x + y)} × 100 can be set to be 15. In reality, this value may be 10 or more and 20 or less in view of the width of the polymerization reaction, and may be 5 or more and 50 or less depending on circumstances.

Once the precursor is generated, the next step is the precursor dispersion generation (S12). Here, a perfluoroelectrolyte resin precursor having —SO ₂ F groups is placed in a bead mill filled with an organic solvent at an addition ratio of, for example, 20% or less by mass ratio, and pulverized to be added to the organic solvent. A fine particulate electrolyte resin precursor is dispersed. A precursor dispersion is obtained by dispersing an electrolyte resin precursor in this organic solvent. A precursor dispersion 30 contained in a container is schematically shown in FIG.

Specifically, the value of {x / (x + y)} × 100 is 15, that is, a perfluoroelectrolyte resin precursor containing about 15 mol% of —SO ₂ F groups is represented by the structural formula of C ₆ F _14. It is added to the perfluorohexane solvent at a mass ratio of 1: 9. For example, 10 g of the precursor is added to 90 g of the solvent. This addition is performed by putting a solvent and a precursor into a bead mill. Then, the bead mill grinder is driven to make the precursor fine particles in a solvent, and a dispersion in which the fine particle precursor is suspended in the solvent is generated. The mass ratio is set to such an extent that the dispersion does not cause much aggregation and separation. In the example of the mass ratio described above, the total mass of the precursor is 10 g. If the mass ratio is small, precipitation and the like can be reduced. However, since the precursor concentration of the dispersion is lowered, the mass ratio may be a value other than 1: 9 depending on the purpose.

Here, the reason for selecting the perfluorohexane solvent is that the perfluoroelectrolyte resin precursor is easy to disperse and dissolve, and that the hydrophobic PTFE to which this is applied thereafter and the application of the solvent are familiar. Therefore, an organic solvent other than the perfluorohexane solvent may be used as long as the solvent satisfies these two characteristics. From this point of view, the perfluoroelectrolyte resin precursor preferably contains an organic solvent containing a halogen element, such as F or Cl, because it contains a —SO ₂ F group, and a perfluoro compound or an organic solvent of a benzene derivative is used. Can do.

  When the precursor dispersion is prepared, the precursor dispersion is applied to the electrolyte membrane substrate and dried (S14). In detail, this step can be divided into the steps of preparing the electrolyte membrane substrate, applying the precursor dispersion, and drying it. Application and drying are repeated an appropriate number of times.

  The electrolyte substrate is a porous membrane body, and the thickness thereof can be determined by the performance required for the fuel cell, etc., and the thickness of the electrolyte membrane as the final product is 50 μm or less when the thickness is 1 μm to 20 μm or more. Can be used. Further, the average pore diameter may be selected from an available range, and for example, those having a diameter of 2 to 5 μm can be used. Specifically, a PTFE porous membrane having a thickness of 10 μm and an average pore diameter of 3 μm is used. The shape is cut in advance to the outer shape of the electrolyte membrane of the fuel cell. Of course, a large-sized PTFE porous sheet prepared to be cut into a plurality of electrolyte membranes having a predetermined shape later may be used. The prepared PTFE porous membrane is shown as a starting material 10 in FIG.

  The coating can be performed by spray coating the precursor dispersion solution. The coating is performed on the entire surface including both sides of the starting material. Drying after the entire surface coating is performed by leaving it at room temperature. This is repeated every few minutes with one cycle of application and drying. Instead of spray coating, methods such as dipping and dropping may be used, or these methods may be combined.

As described above, the precursor dispersion solution is familiar to PTFE and coating. By repeating coating and drying sufficiently, the precursor dispersion can be sufficiently dispersed not only on the entire surface of PTFE but also inside the porous pores. The body penetrates and the perfluoroelectrolyte resin precursor having —SO ₂ F groups is sufficiently supplied. The number of repetitions of application and drying can be determined based on the overall thickness after drying. The total thickness after drying can be about 20 μm, with the thickness of the starting material 10 being 10 μm. However, in consideration of the tolerance of the process, it may be, for example, about 15 to 25 μm. The state of PTFE after coating and drying is shown as the first intermediate 12 in FIG.

  Next, the 1st intermediate body 12 is baked and the composite film which consists of an electrolyte base and a precursor baking layer is produced | generated (S16). Firing is performed by placing the first intermediate body 12 in a suitable firing furnace 32 as shown in FIG. The firing temperature may be 230 ° C., the firing time may be 10 minutes, and the firing atmosphere may be air. Instead of the firing furnace 32, a combination of a heating tunnel and a conveyor, or a hot plate may be used. In addition, firing conditions such as firing temperature, firing time, firing atmosphere, and the like can be changed according to the thickness of the first intermediate 12 and the like.

By firing, the organic solvent component is dissipated, and the perfluoroelectrolyte resin precursor having —SO ₂ F groups is firmly fixed in both sides and side surfaces of PTFE and in the pores of porous PTFE, and the appearance of the precursor A composite membrane of the electrolyte membrane substrate sandwiched between the fired layers is obtained. The state of the composite film is shown as the second intermediate body 14 in FIG. The overall thickness of the second intermediate body 14 is reduced by this firing than the thickness of the first intermediate body 12. The film thickness after firing depends on the thickness of the starting material, but is about 5 to 30 μm when the thickness of the starting material is 1 to 20 μm as described above.

Next, the second intermediate 14 is hydrolyzed to produce a hydrophilic electrolyte membrane (S18). That is, the perfluoroelectrolyte resin precursor having a —SO ₂ F group before this step is not hydrophilic, and the proton conductivity for the intended fuel cell is obtained by hydrolysis and acid neutralization. It can be set as the electrolyte membrane which has. The steps of hydrolysis and acid neutralization are performed by immersing the second intermediate 14 in an NaOH solution and neutralizing with an aqueous HCl solution. In these steps, the content known as a hydrophilic step for the perfluoroelectrolyte resin precursor can be used.

Figure 4 is a perfluorinated electrolyte resin precursor having a -SO ₂ F group, -SO ₂ F is substituted with -SO ₂ H by a hydrophilic treatment such as hydrolysis, illustration illustrating that the perfluoro electrolyte resin It is. The structural formula of the perfluoroelectrolyte resin is represented by formula (3).
That is, by performing hydrophilic treatment on the perfluoroelectrolyte resin precursor, the —SO ₂ F group is converted to, for example, —SO ₃ Na by alkali treatment, and further, hydrophilic —SO ₃ H is obtained by acid neutralization. Converted to the base. The alkali treatment may be performed using a material other than NaOH, such as KOH, and the acid neutralization may be performed using a material other than HCl, such as HNO ₃ or H ₂ SO ₄ .

  The hydrophilic electrolyte membrane thus obtained is shown as an electrolyte membrane 20 of the final product in FIG. The electrolyte membrane 20 is then provided with a catalyst electrode, a gas diffusion electrode, and the like to form a membrane electrode assembly called a so-called MEA, which is used as a component of a fuel cell. The electrolyte membrane 20 of the final product has a thickness of 15 μm, and a hydrophilic fired precursor firing layer having a thickness of 2.5 μm is disposed on both sides of PTFE having a thickness of 10 μm. The pores of the porous PTFE are sufficiently filled with the precursor resin that has been subjected to the hydrophilic treatment. The film thickness of the final product can be changed by selecting the thickness of the starting material, etc., and can be in the range of 50 μm or less, for example.

10 g of a perfluoroelectrolyte resin precursor containing about 15 mol% of —SO ₂ F groups is added to 90 g of a C ₆ F ₁₄ solvent, pulverized by a bead mill, and an electrolyte precursor containing about 5% solid content. 95 g of a dispersion was obtained. This was applied to a PTFE porous material having a film thickness of 10 μm and an average pore diameter of 3 μm, dried and repeated 5 times, and further fired at 230 ° C. The obtained composite membrane was subjected to alkaline hydrolysis and acid neutralization to obtain a reinforced electrolyte membrane having an EW of about 1000 and a thickness of 15 μm.

  FIG. 5 shows the state of filling of the electrolyte resin in the pores of PTFE in the electrolyte membrane obtained by the example in comparison with the conventional method. In these figures, cross sections of electrolyte membranes formed by different methods using the same porous PTFE starting material were observed with a high-magnification microscope. FIG. 5 (a) shows a cross section of an electrolyte membrane by a conventional method, (B) shows the cross section of the electrolyte membrane obtained by the Example. Here, the conventional method is a method of forming an electrolyte membrane by applying a hydrophilic PTFE dispersed in water to a porous PTFE starting material, drying and firing. In the conventional method of FIG. 5 (a), the pores of PTFE are not sufficiently filled and vacancies are insufficiently filled, whereas in FIG. 5 (b) according to the embodiment, there are almost no vacancies. It can be seen that the electrolyte resin is sufficiently filled in the PTFE pores.

It is a flowchart which shows the procedure of the manufacturing method of the electrolyte membrane for fuel cells in embodiment which concerns on this invention. It is a figure explaining each procedure of manufacture of the electrolyte membrane in an embodiment concerning the present invention. It is a figure which shows perfluoroelectrolyte resin precursor production | generation. It is a figure which shows a mode that a perfluoroelectrolyte resin precursor turns into perfluoroelectrolyte resin by hydrophilic processes, such as a hydrolysis. It is a microscope picture which shows the mode of filling with electrolyte resin in the pore of PTFE compared with the conventional method.

Explanation of symbols

  10 starting material, 12 first intermediate, 14 second intermediate, 20 electrolyte membrane, 30 precursor dispersion, 32 firing furnace.

Claims (12)

A method for producing a polymer electrolyte membrane for a fuel cell, comprising:
A polymer having a -SO ₂ F group as a precursor represented by the structural formula, was added to the organic solvent and fits the precursor hydrophobicity material was dispersed, a hydrophobic substance fits electrolyte precursor dispersion A dispersion generating step for generating
The electrolyte precursor dispersion is applied to a porous hydrophobic electrolyte membrane substrate, dried, and then fired.
A composite film production step for producing a composite film of a hydrophobic electrolyte membrane substrate in which porous pores are filled with a polymer having a —SO ₂ F group represented by the structural formula of FIG .
Hydrolyzing the composite membrane ,
A polymer having a —SO ₂ F group represented by the structural formula of
A hydrophilic treatment step of converting to a polymer having a —SO ₃ H group represented by the structural formula, and generating a hydrophilic electrolyte membrane;
The manufacturing method of the electrolyte membrane for fuel cells characterized by the above-mentioned. In the manufacturing method of the electrolyte membrane for fuel cells of Claim 1,
The method for producing an electrolyte membrane for a fuel cell, wherein the dispersion generating step uses an organic solvent containing a halogen element. In the manufacturing method of the electrolyte membrane for fuel cells of Claim 2,
The method for producing an electrolyte membrane for a fuel cell, wherein the dispersion generation step uses an organic solvent containing F or Cl as a halogen element. In the manufacturing method of the electrolyte membrane for fuel cells of Claim 3,
The method for producing an electrolyte membrane for a fuel cell, wherein the dispersion generating step uses an organic solvent of a perfluoro compound or a benzene derivative. In the manufacturing method of the electrolyte membrane for fuel cells of Claim 1,
The dispersion generation process
CF ₂ CF ₂ and
Obtained by polymerizing
The manufacturing method of the electrolyte membrane for fuel cells characterized by using the electrolyte resin precursor which has the following structural formula. In the manufacturing method of the electrolyte membrane for fuel cells of Claim 5,
The dispersion generation process
The manufacturing method of the electrolyte membrane for fuel cells characterized by using the electrolyte resin precursor whose value of {x / (x + y)} * 100 is 5-50. In the manufacturing method of the electrolyte membrane for fuel cells of Claim 6,
The dispersion generation process
The manufacturing method of the electrolyte membrane for fuel cells using the electrolyte resin precursor whose value of {x / (x + y)} * 100 is 10-20. In the manufacturing method of the electrolyte membrane for fuel cells of Claim 1,
In the dispersion generation step, a perfluoroelectrolyte resin precursor containing SO ₂ F groups is added to a perfluorohexane solvent,
The method for producing an electrolyte membrane for a fuel cell, wherein the composite membrane generating step comprises applying an electrolyte precursor dispersion to a porous PTFE electrolyte membrane substrate. A method for producing a polymer electrolyte membrane for a fuel cell, comprising:
Indicated by the structural formula, SO ₂ F groups were added perfluoro electrolyte resin precursor containing 10 mol% to 20 mol% or less 20% by mass ratio perfluorohexane solvent, electrolyte precursor to this grinding process to A dispersion generating step for generating a body dispersion;
Applying and drying the electrolyte precursor dispersion to a PTFE porous membrane having an average pore size of 3 μm, repeating this, firing at 200 to 250 ° C. to produce a composite membrane,
The composite membrane is acid-neutralized after alkaline hydrolysis,
A hydrophilic treatment step of converting to a polymer having a —SO ₃ H group represented by the structural formula, and generating a hydrophilic electrolyte membrane;
The manufacturing method of the electrolyte membrane for fuel cells characterized by the above-mentioned. An electrolyte membrane for a solid polymer type fuel cell,
A PTFE porous membrane having an average pore diameter of 3 μm;
Produced on the surface of the PTFE porous membrane body,
A polymer having a —SO ₂ F group represented by the structural formula of
A calcined film of an electrolyte precursor dispersion hydrophilized by a hydrophilic treatment that is converted into a polymer having a —SO ₃ H group represented by the structural formula :
An electrolyte membrane for a fuel cell comprising: The electrolyte membrane for a fuel cell according to claim 10,
The PTFE porous membrane body has a thickness of 1 to 20 μm,
The electrolyte membrane for a fuel cell, wherein the fired membrane has a thickness of 5 to 30 μm. The electrolyte membrane for a fuel cell according to claim 11,
An electrolyte membrane for a fuel cell, having a thickness of 50 μm or less.