JP2008166202A - Manufacturing method of membrane / electrode assembly for fuel cell - Google Patents

Abstract

[PROBLEMS] To prevent deterioration or breakage of a polymer resin film due to a solvent of the catalyst layer ink when a catalyst layer ink is formed on the polymer resin film to form a catalyst layer, and to provide a high-performance fuel cell. Provided is a method by which a membrane / electrode assembly can be produced.
A polymer resin film composed of a resin for a film selected from the group consisting of an electrolyte resin or a precursor resin is prepared, and an ink resin, a catalyst, and a solvent selected from the group consisting of an electrolyte resin or a precursor resin The catalyst layer ink is prepared, and the catalyst layer ink is applied to the polymer resin film to form a catalyst layer, and the intermediate product on which the catalyst layer is formed is electrolyzed as necessary. . Condition (1): When the catalyst layer ink is maintained at 25 ° C., the state in which the components in the catalyst layer ink are completely dissolved or colloidally dispersed continues for 2 hours or more. Condition (2): When the polymer resin film is immersed in the solvent for 24 hours while maintaining the solvent temperature at 25 ° C., the weight residual ratio of the film becomes 80% by weight or more.
[Selection] Figure 3

Description

  The present invention relates to a method for producing a membrane-electrode assembly for a fuel cell.

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. A fuel cell is usually formed by laminating a plurality of single cells having a basic structure of a membrane / electrode assembly in which an electrolyte membrane is sandwiched between a pair of electrodes.
Among them, a solid polymer electrolyte fuel cell using a solid polymer electrolyte membrane as an electrolyte membrane has advantages such as easy miniaturization and operation at a low temperature. It is attracting attention as a power source for the body.
The electrode usually has a laminated structure in which a catalyst layer is disposed on the side close to the electrolyte membrane and a gas diffusion layer is disposed on the side far from the electrolyte membrane.

During normal power generation of a solid polymer electrolyte fuel cell using hydrogen as a fuel and oxygen as an oxidant, the reaction of the following formula (1) proceeds at the fuel electrode (anode).
H ₂ → 2H ⁺ + 2e ⁻ (1)
The electrons generated by the equation (1) reach the oxidant electrode (cathode) after working with an external load via an external circuit. Then, the proton generated in the formula (1) moves in the solid polymer electrolyte membrane from the fuel electrode to the oxidant electrode side by electroosmosis while being hydrated with water.
On the other hand, the reaction of the following formula (2) proceeds at the oxidant electrode.
4H ⁺ + O ₂ + 4e ⁻ → 2H ₂ O (2)
That is, the reaction of the following formula (3) proceeds for the entire battery.
2H ₂ + O ₂ → 2H ₂ O (3)

The electrolyte resin constituting the solid polymer electrolyte membrane is superior in properties required for the electrolyte membrane, such as proton conductivity and chemical stability. Conventionally, Nafion (trade name, manufactured by DuPont) and Aciplex ( Fluorine-based electrolyte resins such as perfluorocarbon sulfonic acid resins represented by trade names, manufactured by Asahi Kasei) and Flemion (trade names, manufactured by Asahi Glass) are preferably used.
In addition, in the catalyst layer of each electrode (fuel electrode, oxidant electrode) provided on both sides of the solid polymer electrolyte membrane, the proton conductivity between the solid polymer electrolyte membrane and the electrode and the proton conductivity in the electrode are ensured. For the purpose of ensuring the bonding property between the solid polymer electrolyte membrane and the electrode, ensuring the binding property of the catalyst particles and the like contained in the electrode, the above-mentioned fluorine-based electrolyte resin is preferably used.

  However, a solid polymer electrolyte membrane (fluorine polymer electrolyte membrane) made of a fluorine-based electrolyte resin is very expensive and is one of the factors hindering fuel cell cost reduction. Therefore, research and development of polymer electrolyte membranes that are less expensive than fluorine-based polymer electrolyte membranes are underway. For example, a sulfonic acid group, a carboxyl group, or a phosphate group is added to a hydrocarbon polymer having zero or very little fluorine content, such as polyether ether ketone (PEEK), polyether ketone (PES), polyphenylene sulfide (PPS), etc. The one using a solid polymer electrolyte membrane (hydrocarbon polymer electrolyte membrane) made of a hydrocarbon polymer electrolyte into which a proton conductive group such as the above is introduced has been proposed.

There are the following two methods as main methods for forming electrodes on the solid polymer electrolyte membrane.
(1) Method of thermocompression bonding to a solid polymer electrolyte membrane First, a catalyst layer ink containing a catalyst, an electrolyte resin, a conductive material, and a solvent is prepared, and the catalyst layer ink is used as a gas diffusion layer of an electrode. An electrode sheet is prepared by applying to a porous sheet and drying, and the obtained electrode sheet is heated and pressure-bonded onto a solid polymer electrolyte membrane, or the above-mentioned ink for catalyst layer is appropriately transferred to a support. And dried to form a catalyst layer, and the obtained catalyst layer was heat-pressed on a porous sheet to be a gas diffusion layer, and then the transfer support was peeled off to form an electrode sheet. The electrode sheet is heated and pressure-bonded onto the solid polymer electrolyte membrane, or the catalyst layer ink is applied to an appropriate transfer support and dried to form a catalyst layer. Support for transfer after thermocompression bonding on molecular electrolyte membrane The body is peeled off to transfer the catalyst layer, and the porous sheet is bonded onto the obtained catalyst layer by thermocompression bonding or other appropriate method to form a gas diffusion layer.
(2) Method of applying to solid polymer electrolyte membrane First, an ink for a catalyst layer containing a catalyst, an electrolyte resin, a conductive material, and a solvent is prepared, and the catalyst layer ink is placed on the solid polymer electrolyte membrane. A catalyst layer is formed by coating, and a porous sheet is bonded onto the obtained catalyst layer by thermocompression bonding or other appropriate method to form a gas diffusion layer.

  However, when a hydrocarbon polymer electrolyte membrane is used as the solid polymer electrolyte membrane and a previously prepared catalyst layer is thermocompression-bonded onto the electrolyte membrane, the glass transition temperature of the hydrocarbon polymer electrolyte membrane In addition, since the softening point is high, it is difficult to obtain sufficient bondability. In this case, if the temperature at the time of pressure bonding is increased in order to obtain sufficient bonding properties, there is a disadvantage that the proton conductive group of the electrolyte resin contained in the catalyst layer is decomposed.

On the other hand, when the catalyst layer of the electrode is formed by applying the ink for the catalyst layer on the polymer electrolyte membrane, the electrolyte resin contained in the catalyst layer is uniformly dissolved or colloidally dispersed as the solvent for the catalyst layer ink. You should use what you can do. However, a solvent that can uniformly dissolve or colloidally disperse the electrolyte resin of the catalyst layer usually has a large dissolving ability or swelling ability with respect to the electrolyte resin constituting the polymer electrolyte membrane. Therefore, a catalyst containing such a solvent. When layer ink is used, the polymer electrolyte membrane is prone to deterioration and breakage such as wrinkles and perforations, resulting in inconveniences such as deterioration in the quality of the membrane / electrode assembly and an increased incidence of defective products. .
In order not to cause the above inconvenience, means for specifying an optimal combination of the electrolyte resin for the catalyst layer, the electrolyte resin for the polymer electrolyte membrane, and the solvent for the ink for the catalyst layer has not yet been sufficiently studied.

  In Patent Document 1, a catalyst paste obtained by kneading a metal powder as a catalyst, carbon as a conductive material, and an ion conductive polymer with alcohol as a solvent is applied onto the ion conductive polymer film. A method is described in which a catalyst layer is formed on an ion conductive polymer film by drying, and further heat pressing. Patent Document 1 describes that the ion conductive polymer of the catalyst layer and the ion conductive polymer film are preferably the same material. In the experimental example of Patent Document 1, the ion conductivity of the catalyst layer is described. Polyperfluorosulfonic acid is used as the polymer and the ion conductive polymer membrane. However, this method cannot avoid the above inconvenience that the film is deteriorated or broken when the catalyst paste is applied onto the ion conductive polymer film. In particular, when the ion conductive polymer of the catalyst layer and the ion conductive polymer film are made of the same material, such inconvenience is remarkable.

JP-A-5-166520

  The present invention has been accomplished in view of the above circumstances, and its object is to increase the catalyst layer ink by a solvent when the catalyst layer ink is formed on the polymer resin film by forming the catalyst layer. An object of the present invention is to provide a method capable of preventing deterioration and breakage of a molecular resin membrane and producing a fuel cell membrane / electrode assembly with good performance.

A method provided by the present invention includes a polymer electrolyte membrane, and an oxidant electrode and a fuel electrode including a catalyst layer disposed so as to face both surfaces of the polymer electrolyte membrane and containing a catalyst and an electrolyte resin. A method for producing a membrane / electrode assembly for a fuel cell, comprising a polymer resin membrane comprising an electrolyte resin and a membrane resin selected from the group consisting of a precursor resin that becomes an electrolyte resin when converted into an electrolyte A catalyst layer containing an ink resin, a catalyst, and a solvent selected from the group consisting of a polymer resin film preparation step, an electrolyte resin, and a precursor resin that becomes an electrolyte resin when converted into an electrolyte The catalyst layer ink preparation step for preparing the ink, the catalyst layer ink obtained in the catalyst layer ink preparation step is applied to the polymer resin film, and the amount of the fuel layer side or the oxidant electrode side is small. A catalyst layer forming step for forming at least one catalyst layer, and an ink resin for the catalyst layer formed in the catalyst layer forming step or a polymer resin film on which the catalyst layer is laminated, as necessary. The method for producing a fuel cell membrane / electrode assembly including an electrolyzing step wherein the solvent of the catalyst layer ink is the following condition (1) with respect to the ink resin and the membrane resin: And (2) having the dissolving ability.
Condition (1):
When the ink resin is maintained in the solvent at a solvent temperature of 25 ° C. and mixed so that the amount of the resin for ink is the content used in the ink for the catalyst layer, and dissolved or dispersed, The dissolved or colloidally dispersed state lasts for 2 hours or more.
Condition (2):
When the polymer resin film is immersed in the solvent for 24 hours while maintaining the solvent temperature at 25 ° C., the weight residual ratio of the film becomes 80% by weight or more.

The solvent satisfying the conditions (1) and (2) defined in the present invention has sufficient dissolving ability or colloidal dispersion ability to form a catalyst layer having good characteristics with respect to the electrolyte resin of the catalyst layer. And it has the low melt | dissolution ability or swelling ability which can prevent the deterioration and damage of the said electrolyte membrane with respect to the electrolyte resin of a polymer electrolyte membrane.
According to the production method of the present invention, both the electrolyte resin of the catalyst layer and the electrolyte resin of the polymer electrolyte membrane are selected from the conventionally known solvents in accordance with the conditions (1) and (2) clearly defined. It is possible to easily identify a solvent suitable for the above.
Further, since the production method of the present invention performs the electrolyzing process after forming the catalyst layer on the resin film, it is included in the catalyst layer ink in the step of applying the catalyst layer ink on the polymer electrolyte film. Instead of the electrolyte resin or the electrolyte resin constituting the polymer electrolyte membrane, a precursor resin before the electrolyte resin is converted into an electrolyte can be used.
Therefore, it is possible to freely combine the polymer electrolyte membrane and the electrolyte resin in the catalyst layer, and there are a wide range of solvent options that can be used for the catalyst layer ink.

  In the condition (1), since the test can be performed using only the solvent and the resin for the ink, the test can be performed simply. The catalyst layer ink to be actually applied is prepared, and the catalyst layer ink is prepared. It is preferable to confirm that the state in which the components in the ink for the catalyst layer are completely dissolved or colloidally dispersed is maintained for 2 hours or longer when the temperature is maintained at 25 ° C.

The solvent of the ink for the catalyst layer is such that when the polymer resin film is immersed in the solvent under the conditions specified in the condition (2), the weight residual ratio of the film becomes 99% by weight or less. preferable.
When the weight residual ratio determined by conducting the test of the condition (2) is 80% by weight or more and 99% by weight or less, when the catalyst ink is applied to the polymer resin film, Since the surface of the membrane slightly dissolves or swells within a range that does not substantially cause deterioration or breakage of the polymer resin membrane, the adhesion or bonding strength between the polymer resin membrane and the catalyst layer is increased.

In one embodiment of the present invention, the polymer electrolyte membrane of the intermediate product obtained in the electrolyzing step is used in the catalyst layer ink by performing the electrolyzing step after the catalyst layer forming step. The weight residual ratio when immersed in the solvent under the conditions specified in the above condition (2) is smaller than the weight residual ratio of the polymer resin film before the electrolyzing step.
After the application of the ink for the catalyst layer is completed and the coating film is dried, even if the residual weight ratio of the polymer resin film to the solvent used in the catalyst ink decreases, the film deteriorates or breaks. There is no problem because there is no fear.
The present invention has a utility value when one of the resins close to solubility in a solvent is used as a membrane resin and the other is used as an ink resin in such a state containing abundant proton conductive groups. Is expensive.

In one embodiment of the present invention, an electrolyte resin is used as one of the ink resin and the film resin, and a precursor resin that becomes the electrolyte resin by being electrolyzed is used as the other, and In the electrolyzing step, the precursor resin contained in the catalyst layer or the polymer resin film is electrolyzed.
According to this embodiment, it is possible to freely combine the polymer electrolyte membrane and the electrolyte resin in the catalyst layer, and there are a wide range of solvent options that can be used for the ink for the catalyst layer.

Further, in the above-described embodiment in which an electrolyte resin is used as one of the resin for ink and the resin for the film and a precursor resin is used as the other, a precursor resin that is insufficiently electrolyzed is used as the precursor resin. It is preferable to use it.
When the precursor resin contains a small amount of proton-conducting groups, the solubility of the precursor resin resembles that of the electrolyte resin. Therefore, in the test prescribed in the condition (2), the polymer resin film It is easy to obtain a solvent having a residual weight ratio of 99% by weight or less. Accordingly, when the catalyst ink is applied onto the polymer electrolyte membrane, the polymer electrolyte membrane can be slightly dissolved or swollen by the action of the solvent in the ink, and the adhesion between the catalyst layer and the polymer electrolyte membrane can be reduced. Bonding strength is increased.

  From the viewpoint of improving the solubility or colloidal dispersibility of the ink resin in the solvent, when an electrolyte resin is used as the ink resin, dimethyl sulfoxide, N-methylpyrrolidone or It is preferable to use a solvent from the group consisting of those mixed solvents. When a precursor resin is used as the resin for the ink, a solvent from the group consisting of cyclohexane, normal hexane or a mixed solvent thereof is used as the solvent for the ink for the catalyst layer. It is preferable to use it.

  In one embodiment of the present invention, the electrolyte resin used as one of the ink resin or the membrane resin is a sulfonated polymer resin, and the precursor resin used as the other is a non-sulfonated resin. The precursor resin contained in the catalyst layer or the polymer resin film is sulfonated in the electrolyte process in which the molecular resin or the sulfonated polymer resin is insufficiently sulfonated.

In one embodiment of the present invention, the polymer resin film is a film selected from the group consisting of a hydrocarbon-based polymer electrolyte and a precursor resin that is converted into an electrolyte to become the hydrocarbon-based polymer electrolyte. It is preferable to use a polymer resin film made of a resin.
Hydrocarbon polymer electrolytes are preferable in terms of economy because they are less expensive than fluorine electrolyte resins. Further, in the present invention, when the catalyst layer is formed, it is not necessary to perform thermocompression bonding at such a high temperature that reaches the glass transition temperature or softening point of the hydrocarbon-based polymer electrolyte, so that the electrolyte resin in the catalyst layer does not decompose. .

According to the present invention, in accordance with the conditions (1) and (2) which are clearly defined, among the conventionally known solvents, both the electrolyte resin of the catalyst layer and the electrolyte resin of the polymer electrolyte membrane are suitable. The solvent can be easily identified.
By preparing a catalyst layer ink using a solvent that satisfies the above conditions and applying it to the polymer electrolyte membrane, it becomes possible to produce a high-quality membrane / electrode assembly. The incidence of defective products due to deterioration or breakage of the electrolyte membrane is also reduced.
Further, according to the present invention, in the step of applying the catalyst layer ink on the polymer electrolyte membrane, instead of the electrolyte resin contained in the catalyst layer ink or the electrolyte resin constituting the polymer electrolyte membrane, Since it is possible to use a precursor resin before the electrolyte resin is converted to an electrolyte, it is possible to freely combine the polymer electrolyte membrane and the electrolyte resin in the catalyst layer, and a solvent that can be used for the catalyst layer ink A wide range of options.

FIG. 1 is a cross-sectional view schematically showing a flat unit cell (unit cell 100) having a membrane-electrode assembly manufactured according to the present invention.
The unit cell 100 has a membrane / electrode assembly 6 in which a fuel electrode (anode) 2 and an oxidant electrode (cathode) 3 are provided on one surface side of the polymer electrolyte membrane 1. The fuel electrode 2 has a fuel electrode side catalyst layer 4a on the surface facing the polymer electrolyte membrane 1, and a fuel electrode side gas diffusion layer 5a is laminated adjacent to the catalyst layer 4a. Similarly, the oxidant electrode 3 has an oxidant electrode side catalyst layer 4b on the surface facing the polymer electrolyte membrane 1, and an oxidant electrode side gas diffusion layer 5b is laminated adjacent to the catalyst layer 4b. It has a configuration.

  Each catalyst layer 4 (4a, 4b) contains a catalyst having catalytic activity for the electrode reaction in each electrode (2, 3), and an electrolyte resin that imparts proton conductivity to the electrode. In addition to imparting proton conductivity, the electrolyte resin in the catalyst layer also has functions such as securing the bondability between the electrolyte membrane and the electrode and immobilizing the catalyst. In this embodiment, each electrode (fuel electrode, oxidant electrode) has a structure in which a catalyst layer and a gas diffusion layer are laminated, but has a single-layer structure composed of only the catalyst layer. Alternatively, a structure in which a functional layer such as a water repellent layer is further provided in addition to the catalyst layer and the gas diffusion layer may be used.

The membrane / electrode assembly 6 is sandwiched between two separators 7 a and 7 b to form a single cell 100. On one side of each of the separators 7a and 7b, grooves for forming a flow path of a reaction gas (fuel gas and oxidant gas) are provided. Fuel is formed between these grooves and the outer surfaces of the fuel electrode 2 and the oxidant electrode 3 A gas flow path 8a and an oxidant gas flow path 8b are defined. The fuel gas channel 8 a is a channel for supplying a fuel gas (a gas containing hydrogen or generating hydrogen) to the fuel electrode 2, and the oxidant gas channel 8 b is an oxidant gas to the oxidant electrode 3. It is a flow path for supplying (a gas containing or generating oxygen).
A plurality of such flat single cells 100 are stacked and fixed to form a cell stack, and the periphery of the stack is further sealed, and the gas supply port and gas discharge port of the stack and the gas flow path of each cell are connected. A stack type fuel cell is configured by providing necessary members and structures such as a manifold and a current collecting member collecting current from each cell.

The present invention relates to a method for producing a membrane / electrode assembly for a fuel cell having such a structure in which such a polymer electrolyte membrane is sandwiched between a pair of electrode catalyst layers, the electrolyte resin, and the electrolyte by being converted into an electrolyte. Preparing a polymer resin film composed of a resin for a film selected from the group consisting of a precursor resin to be a resin, a polymer resin film preparation step, an electrolyte resin, and a precursor to be the electrolyte resin by being electrolyzed A catalyst layer ink preparation step for preparing a catalyst layer ink containing an ink resin, a catalyst, and a solvent selected from the group consisting of a body resin, and the catalyst layer ink obtained in the catalyst layer ink preparation step. A catalyst layer forming step of forming at least one catalyst layer on the fuel electrode side or the oxidant electrode side by coating on the polymer resin film, and the catalyst layer formed in the catalyst layer forming step. A fuel cell membrane / electrode assembly manufacturing method comprising an electrolyzing step for converting a polymer resin film or a polymer resin film on which the catalyst layer is laminated, if necessary, to the catalyst layer The solvent for the ink is a method for producing a membrane / electrode assembly for a fuel cell, characterized in that the solvent has the dissolving ability shown in the following conditions (1) and (2).
Condition (1):
When the ink resin is maintained in the solvent at a solvent temperature of 25 ° C. and mixed so that the amount of the resin for ink is the content used in the ink for the catalyst layer, and dissolved or dispersed, The dissolved or colloidally dispersed state lasts for 2 hours or more.
Condition (2):
When the polymer resin film is immersed in the solvent for 24 hours while maintaining the solvent temperature at 25 ° C., the weight residual ratio of the film becomes 80% by weight or more.

In the present invention, as the solvent for the ink for the catalyst layer, one having the dissolving ability shown in the above conditions (1) and (2) is used.
The above condition (1) is necessary in relation to the resin for ink (that is, the electrolyte resin contained in the catalyst layer ink at the time of coating or its precursor resin) in order to form a catalyst layer having various physical properties. It defines the degree of solvent dissolving ability or colloid dispersing ability.

  The actual test procedure is to maintain a test solution in which only the resin for ink is dissolved or dispersed in a solvent at 25 ° C. (usually a temperature range called room temperature) and observe using the naked eye or an optical particle size distribution analyzer. . During this observation, if the resin in the test solution is completely dissolved or colloidally dispersed for 2 hours or longer, it is determined that the condition (1) is satisfied.

It is preferable that the test solution exhibits stability of dissolution or colloidal dispersion satisfying the condition (1) even after being maintained at the above solvent temperature for 24 hours.
In this test, it is particularly preferable that the above-mentioned stable dissolution / dispersibility is exhibited when the content of the resin for ink in the test liquid is 10% by weight.
When the components in the test solution are colloidally dispersed, the average particle size of the colloidal particles is preferably 10 nm (nanometer) to 10 μm (micrometer), and particularly preferably 100 nm to 1 μm. . Examples of the method or machine for measuring the average particle size of colloidal particles include infrared light scattering particle size distribution measurement and laser Doppler particle size measurement.

It is preferable that the solvent of the ink for the catalyst layer satisfies a further limited condition (1 ′) in addition to the condition (1).
Condition (1 '):
When the catalyst layer ink is prepared instead of the test solution and maintained at 25 ° C., the state in which the components in the catalyst layer ink are completely dissolved or colloidally dispersed lasts for 2 hours or more.

  The actual test procedure was obtained by preparing an ink for a catalyst layer by dissolving and dispersing an ink resin and a catalyst selected from an electrolyte resin or its precursor resin, and, if necessary, other components in a solvent. The ink for the catalyst layer is maintained at 25 ° C. (usually a temperature range called room temperature), and observed using the naked eye or an optical particle size distribution analyzer. In this observation, if the state in which the components in the ink for the catalyst layer are completely dissolved or colloidally dispersed continues for 2 hours or more, it is determined that the condition (1 ′) is satisfied.

It is preferable that the catalyst layer ink exhibits stability of dissolution or colloidal dispersion satisfying the condition (1) even after being maintained at the above solvent temperature for 24 hours.
When the components contained in the ink are colloidally dispersed, the average particle diameter of the colloidal particles is preferably within the range defined in the above condition (1).

The condition (1 ′) requires that the catalyst layer ink to be actually applied be prepared and tested, whereas the condition (1) requires that the test be performed using only the solvent and the ink resin. This can simplify the test.
Therefore, first, at the stage of screening for usable solvents, a relatively simple test is performed to determine whether or not the condition (1) is satisfied, and the condition (1 ′) test is performed on the solvent that can be determined to satisfy the condition (1). This makes it possible to efficiently determine the condition (1 ′).

  On the other hand, the above condition (2) is for preventing deterioration or breakage of the polymer resin film when the ink for the catalyst layer is applied to the polymer resin film (that is, a film made of an electrolyte resin or a precursor resin thereof). The degree of solvent dissolving ability or swelling ability required in relation to the membrane resin is defined.

  As an actual test procedure, a polymer resin film formed of a resin for a film selected from an electrolyte resin or a precursor resin thereof is prepared, and its dry weight is measured. Next, the polymer resin film is immersed so as to be completely hidden in the solvent, and is left for 24 hours while maintaining the solvent temperature at 25 ° C. (usually a temperature range called room temperature), then removed from the solvent and dried. The dry weight is measured again. The ratio of the dry weight after the test to the dry weight before the test is calculated, and the calculated ratio is determined as the weight residual ratio of the film. When the weight residual ratio is 80% by weight or more, the condition (2) Is determined to be satisfied. It is particularly preferable when the weight residual ratio is 85% by weight or more.

The polymer resin film has a lower effect of dissolving or swelling the polymer resin film as the value of the weight residual ratio determined by performing the test of the above condition (2) is higher, and when the catalyst ink is applied. Deterioration and damage are unlikely to occur.
On the other hand, the adhesion or bonding strength between the polymer resin film and the catalyst layer is within a range in which degradation or breakage of the polymer resin film does not substantially occur when a catalyst ink is applied to the polymer resin film. If the surface of the film is slightly dissolved or swelled, the film is improved. From this viewpoint, it is preferable that the weight residual ratio determined by performing the test under the condition (2) is 99% by weight or less.

  According to the above conditions (1) and (2), a solvent suitable for the catalyst layer ink can be easily identified. For example, a solvent having a desired dissolving action can be efficiently selected. In addition, it is possible to efficiently determine a mixing ratio that exhibits a desired dissolving action by mixing two or more solvents. In the present invention, the solvent for the catalyst layer ink may be a mixed solvent composed of two or more organic solvents, or a mixed solvent composed of two or more organic solvents and water.

In the present invention, conditions necessary for a solvent suitable for both the electrolyte resin of the catalyst layer and the electrolyte resin of the polymer electrolyte membrane are defined. The solvent satisfying the conditions (1) and (2) defined in the present invention has sufficient dissolving ability or colloidal dispersion ability to form a catalyst layer having good characteristics with respect to the electrolyte resin of the catalyst layer. And it has the low melt | dissolution ability or swelling ability which can prevent the deterioration and damage of the said electrolyte membrane with respect to the electrolyte resin of a polymer electrolyte membrane.
By preparing an ink for a catalyst layer using such a solvent and applying it to the polymer electrolyte membrane, it becomes possible to produce a high-quality membrane / electrode assembly. The rate of occurrence of defective products due to deterioration or breakage is also reduced.

According to the present invention, in accordance with the conditions (1) and (2) which are clearly defined, among the conventionally known solvents, both the electrolyte resin of the catalyst layer and the electrolyte resin of the polymer electrolyte membrane are suitable. The solvent can be easily identified.
However, solvent types suitable for both the catalyst layer electrolyte resin and the polymer electrolyte membrane electrolyte resin are quite limited. That is, it is common in that the electrolyte resin of the catalyst layer ink and the electrolyte resin of the polymer electrolyte membrane contain a large amount of proton conductive groups even if they are different types of resins. Therefore, a solvent having a high ability to dissolve or colloidally disperse the catalyst layer ink in the electrolyte resin tends to have a high affinity for the electrolyte resin in the polymer electrolyte membrane, and the ability to dissolve in the polymer electrolyte membrane. Or there are not many that have low swelling ability.

In the present invention, in order to make it possible to freely combine the polymer electrolyte membrane and the electrolyte resin in the catalyst layer, or to facilitate the selection of the solvent that can be used in the ink for the catalyst layer, the polymer electrolyte In the step of applying the catalyst layer ink on the membrane, the precursor before the electrolyte resin is converted into an electrolyte instead of the electrolyte resin contained in the catalyst layer ink or the electrolyte resin constituting the polymer electrolyte membrane A resin may be used.
Here, the “precursor resin” before the electrolyte resin is converted into an electrolyte is an electrolyte resin or catalyst that forms a polymer electrolyte membrane in a state where the membrane / electrode assembly is completed by being converted into an electrolyte. It is resin used as electrolyte resin contained in a layer. “Electrification of precursor resin” means not only introduction of proton conductive groups into a resin that does not contain proton conductive groups at all (ie, precursor resin that is not electrolyzed at all), but also proton conductivity. It also means that a proton conductive group is further introduced into a resin containing a group but having a low content (that is, a precursor resin that is insufficiently electrolyzed) to increase the content of the proton conductive group.

The solubility, colloid dispersibility, and swellability of the polymer resin in the solvent vary according to the amount of proton conductive groups contained in the polymer resin. For example, since the proton conductive group is a polar group, polar organic solvents such as dimethyl sulfoxide have higher affinity for the polymer resin as the content of the proton conductive group in the polymer resin increases, and the solubility is increased. , Colloidal dispersibility and swelling properties tend to be high. On the other hand, non-polar organic solvents such as cyclohexane have a lower affinity for the polymer resin as the proton conductive group content in the polymer resin increases, and the solubility, colloidal dispersibility, and swellability also decrease. Tend.
In addition, a solvent having a high affinity for a polymer resin having a high proton-conducting group content and a high solubility, colloid dispersion ability, and swelling ability can be applied to a polymer resin having a low proton-conducting group content. On the other hand, it has a low affinity and tends to have a low dissolving ability, colloid dispersing ability, and swelling ability.

Utilizing this property, in the step of applying the catalyst layer ink on the polymer electrolyte membrane, either the electrolyte resin contained in the catalyst layer ink or the electrolyte resin constituting the polymer electrolyte membrane is used. Instead, a precursor resin (that is, a resin containing no proton-conducting group or containing an insufficient amount) is used before the electrolyte resin is electrolyzed, and the other is already sufficiently electrolyzed. Used electrolyte resin (that is, a resin containing a sufficient amount of proton conductive groups).
Then, when using an electrolyte resin as an ink resin and using a precursor resin as a film resin, or conversely, using a precursor resin as an ink resin and using an electrolyte resin as a film resin, A solvent in which the ink resin is stably dissolved or colloidally dispersed in the ink for the catalyst layer exhibits only a low dissolving action or swelling action with respect to the resin for the film, so that the polymer resin film is deteriorated or damaged. Absent.
After the catalyst layer ink is applied on the polymer resin film and dried to form a catalyst layer, the precursor resin used in either the ink resin or the film resin is electrolyzed to form a polymer. An intermediate product is obtained in which a catalyst layer containing an electrolyte resin is laminated on the electrolyte membrane. Usually, a gas / diffusion layer is further laminated on the catalyst layer of the intermediate product to form a membrane / electrode assembly having electrodes having a catalyst layer and a gas diffusion layer on both sides of the polymer electrolyte membrane. .

In the present invention, in the catalyst layer forming step of applying the catalyst layer ink on the polymer resin film, the film resin and the ink resin can be combined as follows.
(1) An electrolyte resin is used as both the film resin and the ink resin.
(2) A precursor resin is used for both the film resin and the ink resin.
(3) An electrolyte resin is used as the resin for the film, and a precursor resin is used as the resin for the ink.
(4) A precursor resin is used as the film resin, and an electrolyte resin is used as the ink resin.
Among these combinations, in the case of the other three combinations excluding the first combination, since the precursor resin is used for at least one of them, it is necessary to subject the intermediate product obtained in the catalyst layer forming step to the electrolytic treatment. There is. It should be noted that the intermediate product obtained from the first combination may be subjected to an electrolytic treatment in order to further improve proton conductivity.

Usually, when the polymer electrolyte membrane contained in the intermediate product after the electrolyzing treatment is immersed in the solvent used in the ink for the catalyst layer according to the test method defined in the condition (2), The weight residual ratio becomes smaller than the weight residual ratio of the polymer resin film before performing the electrolytic step. By performing the electrolyzing step after the catalyst layer forming step, both the polymer electrolyte membrane contained in the intermediate product and the electrolyte resin present in the catalyst layer will contain abundant proton conductive groups. This is because the solubility of the electrolyte resin present in these two parts to the solvent approaches.
However, after the application of the ink for the catalyst layer is finished and the coating film is dried, even if the weight residual ratio of the polymer resin film to the solvent used in the catalyst ink is reduced, the film is deteriorated or damaged. There is no problem because there is no possibility of generating.
The present invention has a utility value when one of the resins close to solubility in a solvent is used as a membrane resin and the other is used as an ink resin in such a state containing abundant proton conductive groups. Is expensive.

  The membrane / electrode assembly obtained as described above is attached with a member such as a separator or a current collector as necessary to produce a single cell, and a plurality of single cells are assembled to constitute a fuel cell. be able to.

Hereinafter, some typical embodiments of the manufacturing method of the present invention will be listed, and each embodiment will be described with reference to the drawings.
1. First Embodiment FIG. 2 shows a polymer electrolyte membrane (that is, an electrolyte resin that already contains a sufficient amount of proton-conducting groups as a membrane) in a catalyst layer forming step of applying a catalyst layer ink to a polymer resin membrane. Polymer resin film used as a resin for resin) and an ink for a catalyst layer containing an electrolyte resin (that is, an ink using an electrolyte resin already containing a sufficient amount of proton conductive groups as a resin for an ink) It is process drawing explaining an example of the method of manufacturing a flat membrane-electrode assembly.

In this embodiment, first, as shown in Procedure 1, a polymer electrolyte membrane is prepared as a polymer resin membrane to which the catalyst layer ink is applied.
In the present invention, as the resin for the polymer resin film, in addition to the electrolyte resin, a precursor resin that becomes the electrolyte resin by being converted to an electrolyte can be used. A polymer electrolyte membrane made of an electrolyte resin containing a quantity of proton conductive groups is used.

The polymer electrolyte membrane is not particularly limited as long as it is made of an electrolyte resin capable of conducting protons. Usually, what is known as a so-called solid polymer electrolyte membrane, for example, at least a sulfonic acid group, a carboxylic acid group, a phosphonic acid group, a phosphoric acid group, etc. with a fluorinated polymer or a non-fluorinated hydrocarbon polymer as a skeleton Those having a proton exchange group of More specifically, perfluorocarbon sulfonic acid (for example, trade name Nafion, manufactured by DuPont) may be mentioned.
A hydrocarbon polymer electrolyte containing no or only a small amount of fluorine is less expensive than a fluorine electrolyte resin and is preferable from an economical viewpoint. In addition, when a hydrocarbon polymer electrolyte is used as the material of the polymer electrolyte membrane and the catalyst layer is heat-pressed onto the hydrocarbon polymer electrolyte, the pressure bonding temperature is the glass transition temperature of the hydrocarbon polymer electrolyte. Alternatively, it is necessary to set the temperature so as to reach the softening point. However, in the present invention, the catalyst layer is formed on the polymer electrolyte membrane by a coating method. There is no risk of disassembly.

Therefore, in the present invention, a hydrocarbon-based polymer electrolyte membrane is preferably used. Here, the hydrocarbon polymer electrolyte has a polymer main chain composed of carbon and hydrogen and an ion exchange group, and is a perfluorocarbon sulfonic acid resin such as Nafion (trade name, manufactured by DuPont). Fluorine polymer electrolytes in which the main chain and side chain hydrogen represented by the membrane are all substituted with fluorine are not included. However, since the effects of the present invention can be obtained, the hydrocarbon-based polymer electrolyte includes those partially substituted with fluorine and those containing hetero atoms other than fluorine. Examples of the ion exchange group include a sulfonic acid group, a carboxylic acid group, a boronic acid group, a phosphonic acid group, and a hydroxyl group as in the case of the fluorine-based polymer electrolyte.
Specific examples of hydrocarbon polymer electrolytes include engineering plastics such as polyether ether ketone, polyether ketone, polyether sulfone, polyphenylene sulfide, polyphenylene ether, polyparaphenylene, and polyaryl ether, polyethylene, polypropylene, and polystyrene. And those obtained by introducing a proton conductive group such as a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, or a boronic acid group into a general-purpose plastic.

The polymer electrolyte membrane may be composed of a resin containing two or more kinds of polymer electrolytes as described above, or a resin containing components other than the polymer electrolyte.
The polymer electrolyte membrane can be produced by a casting method using the above-described electrolyte resin solution, but a commercially available product already formed can also be used. The film thickness of the electrolyte membrane is not particularly limited, and may be about 15 to 60 μm.

On the other hand, as shown in Procedure 2, separately from the preparation of the polymer electrolyte membrane, a catalyst layer ink is prepared. In the present invention, as the resin for the ink of the catalyst layer ink, in addition to the electrolyte resin, a precursor resin that becomes the electrolyte resin by being converted to an electrolyte can be used. A catalyst layer ink is prepared using an electrolyte resin containing an amount of proton conductive groups.
The electrolyte resin contained in the catalyst layer ink is usually selected from the polymer electrolytes used in the polymer electrolyte membrane. In the present invention, the electrolyte resin is uniformly dissolved in the catalyst layer ink. From the viewpoint of making the electrolyte resin constituting the polymer electrolyte membrane colloidally dispersed and difficult to dissolve or swell by the solvent of the catalyst layer ink, the electrolyte resin constituting the polymer electrolyte membrane is a polymer structure and / or resin. It is preferable to use electrolyte resins having different compositions for the ink for the catalyst layer.
Further, the catalyst layer ink may contain a resin other than the electrolyte resin, for example, other polymer materials such as a water-repellent polymer and a binder.

  As the catalyst material, 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 for the hydrogen oxidation reaction at the fuel electrode and the oxygen reduction reaction at the oxidant electrode. For example, platinum, ruthenium, iron, nickel, manganese An alloy of a metal such as platinum and the like can be used.

The ink for the catalyst layer is obtained by mixing and dispersing the electrolyte resin, the catalyst material, and other components as required in a solvent.
When the catalyst layer ink containing the electrolyte resin is applied on the polymer electrolyte membrane as in the present embodiment, the polar solvent not having a very large polarity satisfies the above conditions (1) and (2). Used as a solvent.
A solvent having a too large polarity can stably dissolve or colloidally disperse the electrolyte resin in the ink for the catalyst layer, and satisfies the above condition (1), but has a too high dissolving ability or swelling ability with respect to the polymer electrolyte membrane. The condition (2) cannot be satisfied, and the resin film is likely to be deteriorated or broken.
On the other hand, a solvent having too small polarity satisfies the above condition (2) because it has low solubility or swelling property with respect to the polymer electrolyte membrane, but it is possible to stably dissolve or colloidally disperse the electrolyte resin in the catalyst layer ink. It is not possible to satisfy the above condition (1).

Specific examples include a mixed solvent of ethanol and water, a mixed solvent of methanol and water, a mixed solvent of propanol and water, a mixed solvent of ethanol, butanol and water. In the case of a mixed solvent of ethanol and water, the concentration of each solvent component in the mixed solvent is usually mixed at a volume ratio of ethanol: water = 0.5: 1 to 3: 1.
The concentration of each component in the catalyst layer ink is not particularly limited, and may be 0.05 to 5% by weight of the electrolyte resin and 0.01 to 10% by weight of the catalyst component. The solid content concentration of the ink for the catalyst layer is adjusted according to the application method, and the fluidity of the ink is appropriately adjusted depending on the solid content concentration from a paste with a high viscosity to a liquid with a low viscosity and a fluidity close to water. The

Next, as shown in Procedure 3, the catalyst layer ink 4 ′ is applied to the surface of the polymer electrolyte membrane 1. Procedure 3 shows a state where the ink 4 ′ for the catalyst layer is sprayed from the spray gun 10 having a nozzle at the tip toward the polymer electrolyte membrane 1.
Examples of the method for applying the ink for the catalyst layer to the electrolyte membrane include, but are not limited to, a spray method, a screen printing method, a brush coating method, a die coating method, and the like, but the spray method is particularly preferable. The spray method can uniformly apply the ink for the catalyst layer to the surface of the polymer electrolyte membrane, and further promotes the evaporation of the solvent during spraying, so that the swelling of the electrolyte membrane can be further suppressed.
In application, it is preferable to adjust the application amount so that the amount of the catalyst component per unit area of the catalyst layer is about 0.01 to 5 mg / cm ² .

Next, as shown in Procedure 4, the ink coating is dried to obtain an intermediate product in which a catalyst layer (in this example, the fuel electrode side catalyst layer 4a) is provided on one side of the polymer electrolyte membrane.
Next, as shown in procedure 5, a catalyst layer is formed also on the other surface of the polymer electrolyte membrane, and an intermediate product in which the catalyst layers 4a and 4b are laminated on both surfaces of the polymer electrolyte membrane 1 is obtained. The catalyst layer on the other side may be formed by the method shown in the above procedures 1 to 4, or may be formed by a method other than the method of the present invention.
In this embodiment, since an intermediate product having a catalyst layer containing an electrolyte resin is obtained on the polymer electrolyte membrane, it is not necessary to subject the intermediate product to an electrolytic treatment, but the polymer electrolyte In order to further increase the proton conductivity of the membrane and / or the catalyst layer, an electrolytic treatment as described later may be performed.

Gas diffusion layers 5a and 5b are usually formed on the catalyst layers 4a and 4b formed on the surface of the polymer electrolyte membrane. Examples of the gas diffusion layer include those made water-repellent by coating the surface of a conductive porous material such as carbon paper, carbon cloth, carbon felt with polytetrafluoroethylene. It can be used for both the diffusion layer and the oxidant electrode gas diffusion layer. The membrane-electrode assembly 6 is obtained by sandwiching and joining the electrolyte membrane on which the catalyst layer is formed between two gas diffusion layers.
The obtained membrane-electrode assembly is made into a flat single cell by sandwiching with a separator by a general method, and a stack type fuel cell is obtained by stacking a plurality of the single cells.

2. Second Embodiment FIG. 3 shows a polymer electrolyte membrane (that is, an electrolyte resin that already contains a sufficient amount of proton-conducting groups as a membrane) in the catalyst layer forming step of applying the catalyst layer ink to the polymer resin membrane. Polymer resin film used as a resin for a catalyst) and an ink for a catalyst layer containing a precursor resin that becomes an electrolyte resin when converted into an electrolyte (that is, it contains no or only a small amount of proton conductive groups) FIG. 6 is a process diagram illustrating an example of a method for manufacturing a flat membrane / electrode assembly using an ink using a resin to be used as an ink resin.

  In this embodiment, first, as shown in Procedure 1, a polymer electrolyte membrane is prepared. In the present invention, a precursor resin can be used in addition to the electrolyte resin as the membrane resin for the polymer resin film, but in the present embodiment, the electrolyte resin already contains a sufficient amount of proton conductive groups. A polymer resin film, that is, a polymer electrolyte film is used. In the present embodiment, the same polymer electrolyte membrane used in the first embodiment described above can be used.

On the other hand, as shown in Procedure 2, separately from the preparation of the polymer electrolyte membrane, a catalyst layer ink is prepared. In this embodiment, instead of using an electrolyte resin as the ink resin, the catalyst layer ink is prepared using a precursor resin.
As the precursor resin, a resin having a polymer skeleton common to the polymer electrolyte as described above, but containing no proton conductive group or containing only a small amount can be used.

Specifically, the fluorine-containing polymer itself, such as perfluorocarbon, or the fluorine-containing polymer containing only a small amount of proton-conducting groups in the fluorine-containing polymer in comparison with the finally required content. System precursor resin.
As another example, the hydrocarbon polymer itself containing little or only a small amount of fluorine, or the proton conductivity of a small amount of the hydrocarbon polymer in comparison with the finally required content. Examples thereof include hydrocarbon precursor resins that only contain a functional group. Specific examples of the hydrocarbon-based polymer include polyether ether ketone, polyether ketone, polyether sulfone, polyphenylene sulfide, polyphenylene ether, polyparaphenylene, and polyaryl ether as described in the first embodiment. Examples include engineering plastics and general-purpose plastics such as polyethylene, polypropylene, and polystyrene.

In the present embodiment, when a precursor resin that does not contain any proton conductive group is used as the resin for ink, a solvent suitable for dissolving or colloidally dispersing the precursor resin may dissolve the polymer electrolyte membrane or Swelling action is extremely weak. Therefore, in the test specified in the condition (2), it is easy to obtain a solvent in which the weight residual ratio of the polymer resin film is 80% by weight or more.
Therefore, a catalyst ink is prepared using a precursor resin that does not contain any proton-conducting groups and a solvent that is suitable for dissolving or colloidally dispersing the precursor resin. By applying on the molecular electrolyte membrane, a catalyst layer having good adhesion to the polymer electrolyte membrane can be formed without causing deterioration or breakage of the polymer electrolyte membrane.

In the present embodiment, the precursor resin that is insufficiently electrolyzed as the resin for the ink, that is, the content of the proton conductive group that is finally required is not reached, but the proton conductivity It is preferable to use a precursor resin containing a group.
The solubility when the solvent is brought into contact with the precursor resin is more similar to the solubility of the polymer electrolyte membrane after the introduction than when the proton conductive group is introduced into the precursor resin. Therefore, in the test specified in the condition (2), it is easy to obtain a solvent in which the polymer resin film has a weight residual ratio of 99% by weight or less.
Accordingly, a catalyst ink is prepared using a precursor resin containing a small amount of proton-conducting groups and a solvent suitable for dissolving or colloidally dispersing the precursor resin. By applying on the polymer electrolyte membrane, the polymer electrolyte membrane can be slightly dissolved or swollen by the action of the solvent in the ink, and the adhesion or bonding strength between the catalyst layer and the polymer electrolyte membrane is increased.

  The ink for the catalyst layer is obtained by mixing and dispersing the above resin for ink, the catalyst material, and, if necessary, other components in a solvent. As the catalyst material, the same material as in the first embodiment may be used. Further, as other components, a water-repellent polymer, a binder and the like may be contained.

When the catalyst layer ink containing the precursor resin as the ink resin is applied on the polymer electrolyte membrane as in the present embodiment, the nonpolar solvent or the solvent having a relatively small polarity is the above condition ( It is used as a solvent satisfying 1) and (2).
By using a nonpolar solvent or a solvent having a relatively small polarity, a precursor resin containing no proton conductive group or containing only a small amount can be stably dissolved or colloidally dispersed in the ink for the catalyst layer. The above condition (1) is satisfied. In addition, since the nonpolar solvent or the solvent having a relatively small polarity has a small dissolving ability or swelling ability with respect to the polymer electrolyte membrane containing abundant proton conductive groups, the above condition (2) is also satisfied.

  As a solvent that can be suitably used in the present embodiment, for example, a nonpolar organic solvent such as cyclohexane or normal hexane, a polar organic solvent having a relatively small polarity, and a mixed solvent in which any solvent selected from them is combined. Is mentioned.

  Next, as shown in procedures 3 to 5, the catalyst layer ink 4 'is applied to both surfaces of the polymer electrolyte membrane 1 and dried to form catalyst layers 4a and 4b. Procedures 3 to 5 may be performed in the same manner as in the first embodiment described above.

Next, as shown in the procedure 6, an electrolytic process is performed on the intermediate product in which the catalyst layers 4a and 4b are laminated on both surfaces of the polymer electrolyte membrane 1. In the present embodiment, a sufficient amount of proton conductive groups is introduced into the precursor resin in the catalyst layer by this electrolytic treatment. The electrolytic treatment may be performed at a stage where a catalyst layer is provided only on one side of the polymer electrolyte membrane.
In step 6, the proton conductive group is introduced into the precursor resin contained in the catalyst layer by immersing an intermediate product in which the catalyst layer is laminated on both sides of the polymer electrolyte membrane in the solution 11 of the electrolyzing agent. It shows a state. The method shown in the procedure 6 is a so-called dope method in which an electrolytic agent is permeated into an object to be processed.

As the electrolytic agent and the method for the electrolytic treatment, those conventionally used for introducing a proton conductive group into the polymer resin can be used. A conventional method for preparing an electrolyte resin used for a polymer electrolyte membrane or a catalyst layer of a fuel cell and a proton conductive group introducing agent used in the method may be used as they are.
For example, in the case of performing the dope, sulfuric acid is used as an electrolyte agent for introducing a sulfonic acid group, an oxidizing agent is used as an electrolyte agent for introducing a carboxylic acid group, and an electrolyte for introducing a phosphonic acid group. Phosphonic acid can be used as the agent, and phosphoric acid can be used as the electrolyte agent for introducing the phosphate group.

Next, as shown in Procedure 7, gas diffusion layers 5a and 5b are formed on the catalyst layers 4a and 4b, respectively, and the membrane-electrode assembly 6 is obtained. What is necessary is just to perform a gas diffusion layer similarly to Embodiment 1 mentioned above.
The obtained membrane-electrode assembly is made into a flat single cell by sandwiching with a separator by a general method, and a stack type fuel cell is obtained by stacking a plurality of the single cells.

3. Third Embodiment This embodiment is for a catalyst layer forming step of applying a catalyst layer ink to a polymer resin film, and for a catalyst layer containing a polymer resin film composed of a precursor resin and an electrolyte resin. This is a method for producing a flat membrane / electrode assembly using ink.
The procedure of this embodiment is similar to that of the second embodiment described above, and will be described with reference to FIG.

In this embodiment, first, as shown in procedure 1, a polymer resin film made of a precursor resin is prepared. In the present embodiment, an electrolyte resin is not used as the membrane resin, but a precursor resin is used.
What is necessary is just to use what is used as ink resin of the ink for catalyst layers in 2nd embodiment mentioned above as precursor resin. By a casting method using such a precursor resin, a polymer resin film composed of the precursor resin can be produced. In addition, when there is a commercially available film made of a fluorine-based polymer or a commercially available film made of engineering plastic or general-purpose plastic, they may be used as the polymer resin film.

  On the other hand, as shown in Procedure 2, separately from the preparation of the polymer electrolyte membrane, a catalyst layer ink is prepared. In the present embodiment, the ink for the catalyst layer is prepared using an electrolyte resin that already contains a sufficient amount of proton conductive groups, instead of using the precursor resin as the ink resin. In this embodiment, the same electrolyte resin used in the first embodiment or the second embodiment described above can be used as the ink resin.

When an electrolyte resin containing abundant proton conductive groups is used as the ink resin, a solvent suitable for dissolving or colloidally dispersing the electrolyte resin is a polymer resin film made of a precursor resin. The effect of dissolving or swelling is extremely weak. Therefore, in the test specified in the condition (2), it is easy to obtain a solvent in which the weight residual ratio of the polymer resin film is 80% by weight or more.
Therefore, an ink for catalyst is prepared using an electrolyte resin containing abundant proton conductive groups and a solvent suitable for dissolving or colloidally dispersing the electrolyte resin, and the obtained catalyst ink is a precursor. By applying on a polymer resin film composed of a resin, a catalyst layer having good adhesion to the polymer electrolyte membrane can be formed without causing deterioration or breakage of the polymer electrolyte membrane. .

In the present embodiment, the precursor resin that is insufficiently used as the membrane electrolyte resin of the polymer electrolyte membrane, that is, the content of the proton conductive group that is finally required has not been reached. However, it is preferable to use a precursor resin containing a proton conductive group.
The solubility when the solvent is brought into contact with the precursor resin constituting the polymer electrolyte membrane is greater in the catalyst layer ink after the introduction than when the proton conductive group is introduced into the precursor resin. It resembles the solubility of the electrolyte resin. Therefore, in the test specified in the condition (2), it is easy to obtain a solvent in which the polymer resin film has a weight residual ratio of 99% by weight or less.
Accordingly, a catalyst ink is prepared using an electrolyte resin containing abundant proton conductive groups and a solvent suitable for dissolving or colloidally dispersing the electrolyte resin, and a small amount of the obtained catalyst ink is used. The polymer resin film can be slightly dissolved or swelled by the action of the solvent in the ink by coating on the polymer resin film composed of the precursor resin containing the proton conductive group of The adhesion or bonding strength between the catalyst layer and the polymer electrolyte membrane is increased.

  Also in the present embodiment, the same components as in the first embodiment can be used as components other than the resin for the ink, and the catalyst layer ink is obtained by performing the mixing / dispersing process in the same manner as in the first embodiment. It is done.

When applying the catalyst layer ink containing the electrolyte resin as the ink resin onto the polymer resin film composed of the precursor resin as in the present embodiment, the solvent having a relatively large polarity is It is used as a solvent that satisfies the conditions (1) and (2).
By using a solvent having a relatively large polarity, the electrolyte resin containing abundant proton conductive groups can be stably dissolved or colloidally dispersed in the catalyst layer ink, which satisfies the above condition (1). . In addition, the solvent having a relatively large polarity satisfies the above condition (2) because it has a small dissolving ability or swelling ability with respect to the polymer resin film containing no proton conducting group or containing only a small amount.

  As a solvent that can be suitably used in the present embodiment, for example, an organic solvent having a large polarity such as dimethyl sulfoxide, N-methylpyrrolidone, a mixed solvent in which two or more organic solvents having a large polarity are combined, and an organic solvent having a large polarity are compared. The mixed solvent which combined the polar organic solvent with small specific polarity is mentioned.

  Next, as shown in procedures 3 to 5, the catalyst layer ink 4 'is applied to both surfaces of the polymer electrolyte membrane 1 and dried to form catalyst layers 4a and 4b. Procedures 3 to 5 may be performed in the same manner as in the first embodiment described above.

  Next, as shown in the procedure 6, an electrolytic process is performed on the intermediate product in which the catalyst layers 4a and 4b are laminated on both surfaces of the polymer resin film 1. In the present embodiment, a sufficient amount of proton conductive groups is introduced into the precursor resin constituting the polymer resin film 1 by this electrolytic treatment. The electrolytic treatment may be performed at a stage where a catalyst layer is provided only on one side of the polymer electrolyte membrane. What is necessary is just to perform the electrolyzing process of the procedure 6 similarly to 2nd embodiment mentioned above.

Next, as shown in Procedure 7, gas diffusion layers 5a and 5b are formed on the catalyst layers 4a and 4b, respectively, and the membrane-electrode assembly 6 is obtained. What is necessary is just to perform a gas diffusion layer similarly to Embodiment 1 mentioned above.
The obtained membrane-electrode assembly is made into a flat single cell by sandwiching with a separator by a general method, and a stack type fuel cell is obtained by stacking a plurality of the single cells.

4). Modified Example In the embodiment described above, the example in which the film resin and the ink resin are combined as follows has been described.
First embodiment: A combination using an electrolyte resin as a resin for a film and a resin for an ink.
Second embodiment: A combination in which an electrolyte resin is used as a film resin and a precursor resin is used as an ink resin.
Third embodiment: A combination in which a precursor resin is used as a film resin and an electrolyte resin is used as an ink resin.
However, in the present invention, a combination using a precursor resin as the resin for the film and the resin for the ink may be used. In this case, the solubility of the film resin and the ink resin in the solvent for the catalyst ink is obtained by using a precursor resin that is insufficiently electrolyted as at least one of the resin for the film and the resin for the ink. Therefore, it is easy to select a solvent that satisfies the above conditions (1) and (2).
In the embodiment described above, an example of manufacturing a flat membrane / electrode assembly has been described. However, the method of the present invention is applied to at least one of the outer peripheral surface and the inner peripheral surface of the tubular electrolyte membrane. A tubular membrane / electrode assembly can also be produced by forming a catalyst layer.

<Evaluation method>
(1) Evaluation Method for Solvent Condition (1) 10 g of the ink resin (same as the content of the ink resin in the examples) is dispersed in 100 g of the solvent for the ink for the catalyst layer, and a stirrer at 25 ° C. The mixture was left for 24 hours with stirring. The dispersion state of the resin in the solution after being allowed to stand for 24 hours was observed using a laser Doppler particle size distribution analyzer.
(2) Evaluation Method for Solvent Condition (2) First, the weight of the polymer resin film in a dry state is measured, and then the polymer resin film is placed in the solvent of the ink for the catalyst layer maintained at 25 ° C. Soaked. After 24 hours, the polymer resin film was removed from the solvent, dried, and the dry weight was measured again. The ratio of the dry weight after the solvent immersion to the dry weight before the solvent immersion (the residual weight ratio of the film) was calculated.
(3) Performance evaluation of membrane / electrode assembly [Membrane-catalyst layer bondability]
The membrane / electrode assembly obtained in the example was put in liquid nitrogen and then taken out, and it was observed whether or not peeling occurred between the electrolyte membrane and the catalyst layer.
[Existence of cross leak]
The membrane / electrode assembly obtained in the example was assembled in a single cell evaluation apparatus, and the amount of cross leak was measured using a gas permeation evaluation apparatus. That is, the change in the back pressure of both electrodes after being left for 10 minutes under the following conditions was measured, and when the amount of decrease in the back pressure was 1 kPa or less, it was determined that there was no cross leak.
-Cell temperature: 80 ° C
Anode gas and cathode gas: N ₂ (bobber temperature 80 ° C)
・ Back pressure: Anode 0.1 MPa, Cathode 0.05 MPa

<Example 1>
A membrane / electrode assembly was produced using a precursor resin containing no sulfonic acid group as an ink resin and an electrolyte resin containing a sulfonic acid group as a membrane resin.
According to the evaluation method (1), when the dispersibility of the following ink resin (polyether polymer resin not yet sulfonated) in the solvent (cyclohexane) of the catalyst layer ink was examined, a good dispersion state was confirmed. It was done. Further, according to the evaluation method (2), the membrane weight maintenance rate of the following polymer resin film (polyether sulfonic acid polymer electrolyte resin film) with respect to the solvent (cyclohexane) of the ink for the catalyst layer was measured. That's it. That is, the solvent (cyclohexane) satisfied the above conditions (1) and (2).

(1) Preparation of catalyst ink In 20 g of cyclohexane, 2 g of a polyether polymer resin not yet sulfonated and a commercially available Pt / C catalyst (Pt support ratio: 50 wt%) are stirred and mixed at a ratio of 5.34 g. Thus, an ink for a catalyst layer was prepared.
(2) Preparation of polymer resin film A polyether polymer resin used as an ink resin was sulfonated with concentrated sulfuric acid to prepare a polyether sulfonic acid polymer electrolyte resin. The sulfonic acid group content of the obtained electrolyte resin was 2 meg / g.
A 10% dimethyl sulfoxide solution of the obtained polyether sulfonic acid polymer electrolyte resin was prepared, and a polyether sulfonic acid polymer electrolyte membrane having a thickness of about 30 μm was prepared by a casting method using the solution.
(3) Preparation of membrane / electrode assembly After the ink for the catalyst layer was applied to one side of the polymer resin membrane by the spray method, the solvent of the ink was completely diffused with a vacuum dryer to form the catalyst layer. Formed. On the other side, the same catalyst layer ink is applied in the same manner and dried to form a catalyst layer. On both sides of the polyether sulfonic acid polymer electrolyte membrane, an unsulfonated polyether type An intermediate product provided with a catalyst layer containing a polymer resin (Pt content per unit area: 0.5 mg / cm ² ) was obtained.
The obtained intermediate product was immersed in sulfuric acid having a concentration of 98% to sulfonate the polyether polymer resin in the catalyst layer.
Thereafter, a carbon paper sheet was thermocompression bonded at 150 ° C. and 3 MPa on the surfaces of the catalyst layers present on both sides to form a gas diffusion layer, thereby obtaining a membrane / electrode assembly.

<Example 2>
A membrane / electrode assembly was produced using an electrolyte resin containing a sulfonic acid group as an ink resin and a precursor resin containing no sulfonic acid group as a membrane resin.
According to the evaluation method (1), when the dispersibility of the following ink resin (polyether sulfonic acid polymer electrolyte resin) in the solvent for the catalyst layer ink (dimethyl sulfoxide) was examined, a good dispersion state was confirmed. It was. Further, according to (2) of the evaluation method, when the film weight maintenance rate of the following polymer resin film (polyether polymer resin not yet sulfonated) with respect to the solvent (dimethyl sulfoxide) of the catalyst layer ink was measured, It was over 80%. That is, the solvent (dimethyl sulfoxide) satisfied the above conditions (1) and (2).

(1) Preparation of catalyst ink A polyether-based polymer resin was sulfonated to prepare a polyether-sulfonic acid-based polymer electrolyte resin. The sulfonic acid group content of the obtained electrolyte resin was 2 meq / g.
In 20 g of dimethyl sulfoxide, 2 g of the above-described polyether sulfonic acid polymer electrolyte resin and a commercially available Pt / C catalyst (Pt support ratio: 50 wt%) were stirred and mixed at a ratio of 5.34 g to obtain an ink for a catalyst layer. Prepared.
(2) Preparation of polymer resin film A cyclohexane solution of an unsulfonated polyether polymer resin used for preparing an ink resin was prepared, and a film thickness of about 30 μm was obtained by a casting method using the solution. A polyether sulfonic acid polymer resin membrane was prepared.
(3) Preparation of membrane / electrode assembly In the same procedure as in Example 1, the catalyst layer ink was formed in order on one side and the other side of the polymer resin membrane, and sulfonated. An intermediate product is obtained in which a catalyst layer (Pt content per unit area: 0.5 mg / cm ² ) containing a polyether sulfonic acid polymer electrolyte is provided on both sides of the polyether polymer resin membrane. It was.
The obtained intermediate product was immersed in sulfuric acid having a concentration of 98% in the same manner as in Example 1 to sulfonate the polyether-based polymer resin in the polymer resin membrane to obtain a polymer electrolyte membrane.
Thereafter, carbon paper was thermocompression bonded to the surfaces of the catalyst layers present on both surfaces in the same procedure as in Example 1 to form a gas diffusion layer, thereby obtaining a membrane / electrode assembly.

<Example 3>
A membrane / electrode assembly was produced using an electrolyte resin containing a sulfonic acid group as an ink resin and a precursor resin containing a small amount of a sulfonic acid group as a membrane resin.
According to the evaluation method (1), when the dispersibility of the following ink resin (polyether sulfonic acid polymer electrolyte resin) in the solvent for the catalyst layer ink (dimethyl sulfoxide) was examined, a good dispersion state was confirmed. It was. Further, according to the evaluation method (2), the film weight maintenance rate of the following polymer resin film (polyether sulfonic acid-based polymer resin film containing a small amount of sulfonic acid) with respect to the solvent (dimethyl sulfoxide) of the ink for the catalyst layer It was 80% or more when measured. That is, the solvent (dimethyl sulfoxide) satisfied the above conditions (1) and (2).

(1) Preparation of catalyst ink A polyether-based polymer resin was sulfonated to prepare a polyether-sulfonic acid-based polymer electrolyte resin. The sulfonic acid group content of the obtained electrolyte resin was 2 meq / g.
In 20 g of dimethyl sulfoxide, 2 g of the above-described polyether sulfonic acid polymer electrolyte resin and a commercially available Pt / C catalyst (Pt support ratio: 50 wt%) were stirred and mixed at a ratio of 5.34 g to obtain an ink for a catalyst layer. Prepared.
(2) Preparation of polymer resin film A cyclohexane solution of an unsulfonated polyether polymer resin used for preparing an ink resin was prepared, and a film thickness of about 30 μm was obtained by a casting method using the solution. A polyether polymer resin film was prepared.
By immersing the obtained polymer resin membrane in sulfuric acid having a concentration of 98% for a short time, it was insufficiently converted into an electrolyte, and a polyether sulfonic acid polymer resin membrane containing a small amount of sulfonic acid was obtained. The resulting polymer resin membrane had a sulfonic acid group content of 0.5 meq / g.
(3) Production of membrane / electrode assembly In the same procedure as in Example 1, the catalyst layer ink was formed in order on one side and the other side of the polymer resin membrane to form a small amount of sulfone. An intermediate in which a catalyst layer containing a polyether sulfonic acid polymer electrolyte (Pt content per unit area: 0.5 mg / cm ² ) is provided on both sides of an acid-containing polyether sulfonic acid polymer resin membrane A product was obtained.
By immersing the obtained intermediate product in sulfuric acid having a concentration of 98% in the same manner as in Example 1, the polyether-based polymer resin in the polymer resin film is sufficiently sulfonated and rich in sulfonic acid groups. In the polymer electrolyte membrane.
Thereafter, a carbon sheet was thermocompression bonded to the surfaces of the catalyst layers present on both surfaces in the same procedure as in Example 1 to form a gas diffusion layer, whereby a membrane / electrode assembly was obtained.

<Evaluation results of membrane / electrode assembly>
The membrane / electrode assemblies of Examples 1 to 3 were not subjected to separation between the membrane and the catalyst layer in the evaluation method (3) [Membrane-catalyst layer bondability and presence / absence of cross leak], and the cross leak Neither occurred. That is, the membrane / electrode assemblies of Examples 1 to 3 are excellent in the bonding property between the membrane and the catalyst layer, and in the step of forming the catalyst layer on the surface of the electrolyte membrane, the electrolyte membrane is damaged by the solvent in the catalyst layer ink. There was no good performance.

It is sectional drawing which shows typically the example of 1 form of a flat single cell. It is process drawing which shows each procedure performed by one Embodiment which belongs to the manufacturing method of this invention. It is process drawing which shows each procedure performed in other embodiment which belongs to the manufacturing method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electrolyte membrane 2 ... Fuel electrode (anode)
3 ... Oxidant electrode (cathode)
4a ... Anode side catalyst layer 4b ... Cathode side catalyst layer 5a ... Anode side gas diffusion layer 5b ... Cathode side gas diffusion layer 6 ... Membrane / electrode assembly 7a ... Anode side separator 7b ... Cathode side separator 8a ... Anode side gas flow path 8b ... Cathode side gas flow path 9a ... Anode side current collector 9b ... Cathode side current collector 10 ... Spray gun 11 ... Solution of electrolyte agent 100 ... Single cell

Claims (13)

A membrane-electrode assembly for a fuel cell, comprising: a polymer electrolyte membrane; an oxidant electrode and a fuel electrode that are disposed so as to face both surfaces of the polymer electrolyte membrane and include a catalyst layer containing a catalyst and an electrolyte resin. A manufacturing method comprising:
Preparing a polymer resin film composed of a resin for a film selected from the group consisting of an electrolyte resin and a precursor resin that becomes the electrolyte resin by being converted into an electrolyte;
A catalyst layer ink preparation step for preparing an ink for a catalyst layer containing an electrolyte resin and a resin for an ink selected from the group consisting of a precursor resin that becomes an electrolyte resin by being converted to an electrolyte, a catalyst, and a solvent;
A catalyst layer forming step in which the catalyst layer ink obtained in the catalyst layer ink preparation step is applied to the polymer resin film to form at least one catalyst layer on the fuel electrode side or the oxidant electrode side; as well as,
Fuel cell membrane / electrode bonding including an electrolyzing step for electrolyzing the resin for the ink of the catalyst layer formed in the catalyst layer forming step or the polymer resin film on which the catalyst layer is laminated, if necessary A method for manufacturing a body,
The solvent for the ink for the catalyst layer has a dissolving ability as shown in the following conditions (1) and (2) for the ink resin and the film resin. Manufacturing method of membrane / electrode assembly.
Condition (1):
When the ink resin is mixed in the solvent at a solvent temperature of 25 ° C. and mixed so that the amount of the resin for the ink is the content used in the ink for the catalyst layer, and dissolved or dispersed, The state of being dissolved or colloidally dispersed in the liquid lasts for 2 hours or more.
Condition (2):
When the polymer resin film is immersed in the solvent for 24 hours while maintaining the solvent temperature at 25 ° C., the weight residual ratio of the film becomes 80% by weight or more.   2. The fuel cell membrane according to claim 1, wherein when the catalyst layer ink is maintained at 25 ° C., a state in which the components in the catalyst layer ink are completely dissolved or colloidally dispersed lasts for 2 hours or more. -Manufacturing method of electrode assembly.   The solvent of the ink for the catalyst layer is such that when the polymer resin film is immersed in the solvent under the conditions specified in the condition (2), the weight residual ratio of the film becomes 99% by weight or less. Item 3. A method for producing a membrane / electrode assembly for a fuel cell according to Item 1 or 2.   By performing the electrolyzing step after the catalyst layer forming step, the polymer electrolyte membrane of the intermediate product obtained in the electrolyzing step is subjected to the condition (2) in the solvent used in the catalyst layer ink. The fuel cell membrane / electrode according to any one of claims 1 to 3, wherein a weight residual ratio when immersed under specified conditions is smaller than a weight residual ratio of the polymer resin film before the electrolyzing step. Manufacturing method of joined body.   Among the resin for ink and the resin for film, an electrolyte resin is used as one of them, and a precursor resin that becomes the electrolyte resin by being electrolyzed as the other is used, and in the electrolyzing step, a catalyst layer Alternatively, the method for producing a membrane / electrode assembly for a fuel cell according to any one of claims 1 to 4, wherein the precursor resin contained in the polymer resin membrane is converted into an electrolyte.   6. The method for producing a membrane / electrode assembly for a fuel cell according to claim 5, wherein a precursor resin that is not sufficiently electrolyzed is used as the precursor resin.   The fuel cell according to claim 5 or 6, wherein an electrolyte resin is used as the ink resin, and a solvent is used from the group consisting of dimethyl sulfoxide, N-methylpyrrolidone, or a mixed solvent thereof as the solvent for the catalyst layer ink. Manufacturing method for membrane / electrode assembly.   The fuel cell membrane according to claim 5 or 6, wherein a precursor resin is used as the ink resin, and a solvent is used as a solvent of the catalyst layer ink from a group consisting of cyclohexane, normal hexane, or a mixed solvent thereof. -Manufacturing method of electrode assembly.   The electrolyte resin used as one of the resin for ink or the resin for film is a sulfonated polymer resin, and the precursor resin used as the other is not sufficiently sulfonated polymer resin or sulfonated 6. The membrane / electrode assembly for a fuel cell according to claim 5, which is a sulfonated polymer resin and sulfonates the precursor resin contained in the catalyst layer or the polymer resin membrane in the electrolyzing step. Production method.   The method for producing a membrane-electrode assembly for a fuel cell according to claim 9, wherein a sulfonated polymer resin that is insufficiently sulfonated is used as the precursor resin.   The sulfonated polymer resin is used as the ink resin, and a solvent from the group consisting of dimethyl sulfoxide, N-methylpyrrolidone, or a mixed solvent thereof is used as the solvent of the catalyst layer ink. Manufacturing method for fuel cell membrane / electrode assembly.   A non-sulfonated polymer resin or a sulfonated polymer resin that is insufficiently sulfonated is used as the ink resin, and the solvent for the catalyst layer ink is a solvent from the group consisting of cyclohexane, normal hexane, or a mixed solvent thereof. The method for producing a membrane / electrode assembly for a fuel cell according to claim 9 or 10, wherein:   As the polymer resin film, a polymer resin film comprising a hydrocarbon polymer electrolyte and a resin for a film selected from the group consisting of a precursor resin that becomes the hydrocarbon polymer electrolyte when converted into an electrolyte is prepared. A method for producing a membrane / electrode assembly for a fuel cell according to any one of claims 1 to 12.

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