JP5313569B2 - Solid polymer electrolyte membrane and method for producing solid polymer electrolyte membrane - Google Patents

Description

The present invention relates to a solid polymer electrolyte membrane, a fuel cell using the same, and a method for producing a solid polymer electrolyte membrane .

  Fuel cells are attracting attention and are actively researched and developed because of their high power generation efficiency and extremely low generation of harmful gases. Some fuel cells use gaseous fuels such as hydrogen and others use liquid fuels such as methanol. Since a fuel cell using gaseous fuel needs to be equipped with a fuel cylinder or the like, there is a limit to downsizing. For this reason, the use of a direct methanol fuel cell that does not require a reformer or the like is considered promising as a power source for small portable devices such as mobile phones and notebook computers.

  In the case of a direct methanol fuel cell, electrochemical reactions occurring at the fuel electrode and the oxidant electrode are represented by the following reaction formulas (1) and (2), respectively.

Fuel electrode: CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ (1)

Oxidant electrode: O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O (2)

  In general, in a fuel cell using liquid fuel, a solid polymer electrolyte membrane made of a solid polymer ion exchange resin is used as an electrolyte. Here, in order for the fuel cell to function, it is necessary for hydrogen ions to move through the membrane from the fuel electrode to the oxidant electrode, and it is known that this movement of hydrogen ions involves the movement of water. Therefore, it is necessary that the film contains a certain amount of moisture.

  However, when a liquid fuel such as methanol having a high affinity for water is used, the liquid fuel diffuses into the solid polymer electrolyte membrane containing water and further reaches the oxidizer electrode (crossover). There was a problem to be overcome. This crossover causes the liquid fuel that should originally provide electrons at the fuel electrode to be oxidized on the oxidant electrode side and is not used effectively as a fuel, thus causing a decrease in voltage and output and a decrease in fuel efficiency.

Patent Document 1 discloses a technique related to an ion conductive film that makes it possible to suppress crossover of methanol while maintaining ionic conductivity. Here, the surface layer of the ion conductive film having a basic structure of a fluororesin such as Nafion (registered trademark) is modified by electron beam irradiation or the like so that the conductivity becomes lower than the internal conductivity. Yes.
JP 2001-167775 A

  However, the membrane treated by the conventional method has room for improvement from the viewpoint of ion conductivity and crossover.

  In view of the above circumstances, an object of the present invention is to provide a technique capable of reducing crossover while maintaining the ionic conductivity of a solid polymer electrolyte membrane by a simple method.

According to the present invention, a step of wetting water on a solid polymer electrolyte membrane made of a polymer containing no fluorine, and applying pressure to the solid polymer electrolyte membrane in a state where water is wetted on the solid polymer electrolyte membrane And a process for producing a solid polymer electrolyte membrane.

  By performing such treatment, the three-dimensional structure of the solid polymer electrolyte membrane changes, the membrane becomes dense, and the ionic conductivity and water content of the membrane can be controlled.

  According to the present invention, the solid polymer electrolyte membrane is treated with the step of wetting water on the solid polymer electrolyte membrane, and the solid polymer electrolyte membrane is treated with the water wetted on the solid polymer electrolyte membrane. And a step of reducing the moisture content of the solid polymer electrolyte membrane.

  Here, the treatment may be irradiation with an electron beam, ultraviolet rays, gamma rays, infrared rays or the like in addition to the heat press described above. By performing such treatment, the three-dimensional structure of the solid polymer electrolyte membrane changes, the membrane becomes dense, and the ionic conductivity and water content of the membrane can be controlled.

  In the method for producing a solid polymer electrolyte membrane of the present invention, the solid polymer electrolyte membrane can be composed of an aromatic polymer.

  In the method for producing a solid polymer electrolyte membrane of the present invention, the solid polymer electrolyte membrane may contain a protonic acid group.

  According to the present invention, a method for producing a fuel cell using the solid polymer electrolyte membrane produced by the method for producing a solid polymer is provided.

According to the present invention, there is provided a solid polymer electrolyte membrane comprising a polymer containing no fluorine, wherein the solid polymer electrolyte membrane is obtained by applying pressure in a wet state of water. Is done.

  The solid polymer electrolyte membrane of the present invention can contain a protonic acid group.

  According to the present invention, there is provided a solid polymer electrolyte membrane containing a proton acid group, wherein the solid polymer electrolyte membrane has a water content of 15% or less.

  By setting the moisture content in such a range, crossover in which liquid fuel such as methanol permeates the membrane can be reduced. Further, the lower limit of the moisture content is not particularly limited, but may be 5%, for example.

  In the solid polymer electrolyte membrane of the present invention, the solid polymer electrolyte membrane can be composed of an aromatic polymer.

  According to the present invention, there is provided a fuel cell comprising any one of the solid polymer electrolyte membranes described above, and a fuel electrode and an oxidant electrode disposed on the solid polymer electrolyte membrane.

  According to the present invention, the crossover can be reduced by a simple method while maintaining the ionic conductivity of the solid polymer electrolyte membrane. Thereby, the improvement of a battery characteristic and the improvement of the reliability of a battery are realizable.

FIG. 1 is a flowchart showing a manufacturing process of a fuel cell according to an embodiment of the present invention.
In the present embodiment, first, a commercially available solid polymer electrolyte membrane is prepared, and the solid polymer electrolyte membrane is sufficiently wetted with water (S100).

  As the solid polymer electrolyte membrane, various materials can be used, but it is preferable to use a material having high ion conductivity. When a solid polymer electrolyte membrane is incorporated in a fuel cell, the solid polymer electrolyte membrane has a role of separating a fuel electrode and an oxidant electrode and moving hydrogen ions and the like between the two. For this reason, it is preferable that the solid polymer electrolyte membrane has high hydrogen ion conductivity. Further, it is preferably chemically stable and has high mechanical strength.

  As the solid polymer electrolyte membrane, for example, a membrane containing a proton acid group such as a sulfonic acid group, a sulfoalkyl group, a phosphoric acid group, a phosphone group, a phosphine group, a carboxyl group, or a sulfonimide group can be used. Examples of the base polymer to which the protonic acid group is bonded include polyether ketone, polyether ether ketone, polyether sulfone, polyether polyether sulfone, polysulfone, polysulfide, polyphenylene, polyphenylene oxide, polystyrene, polyimide, poly A film such as benzimidazole or polyamide can be used. Further, from the viewpoint of reducing the crossover of liquid fuel such as methanol, a hydrocarbon-based membrane containing no fluorine can be used as the polymer. Furthermore, in the present embodiment, it is preferable to use an aromatic polymer as the polymer of the substrate. By using such a material, the effect by the heat press mentioned later can be enjoyed more favorably.

In addition, as the polymer of the target substrate to which the proton acid group is bonded,
Resins having a nitrogen or hydroxyl group such as polybenzimidazole derivatives, polybenzoxazole derivatives, polyethyleneimine cross-linked products, polysilamine derivatives, amine-substituted polystyrenes such as polydiethylaminoethylpolystyrene, nitrogen-substituted polyacrylates such as diethylaminoethylpolymethacrylate;
Hydroxyl group-containing polyacrylic resin represented by silanol-containing polysiloxane and hydroxyethyl polymethyl acrylate;
Hydroxyl group-containing polystyrene resin represented by parahydroxypolystyrene;
Etc. can also be used.

  In addition, a polymer having a crosslinkable substituent, for example, a vinyl group, an epoxy group, an acrylic group, a methacryl group, a cinnamoyl group, a methylol group, an azide group, or a naphthoquinonediazide group, appropriately used for the above-described polymer You can also. Moreover, what bridge | crosslinked these substituents can also be used.

Specifically, as a solid polymer electrolyte membrane, for example,
Sulfonated polyetheretherketone;
Sulfonated polyethersulfone;
Sulfonated polyetherethersulfone;
Sulfonated polysulfone;
Sulfonated polysulfides;
Sulfonated polyphenylene;
Aromatic-containing polymers such as sulfonated poly (4-phenoxybenzoyl-1,4-phenylene) and alkylsulfonated polybenzimidazole;
Sulfoalkylated polyetheretherketone;
A sulfoalkylated polyethersulfone;
Sulfoalkylated polyetherethersulfone;
A sulfoalkylated polysulfone;
Sulfoalkylated polysulfides;
Sulfoalkylated polyphenylene;
Sulfonic acid group-containing perfluorocarbon (Nafion (registered trademark, manufactured by DuPont), Aciplex (manufactured by Asahi Kasei), etc.);
Carboxyl group-containing perfluorocarbon (Flemion (registered trademark) S membrane (Asahi Glass Co., Ltd.));
Copolymers such as a fluorine-containing polymer comprising a polystyrene sulfonic acid copolymer, a polyvinyl sulfonic acid copolymer, a crosslinked alkyl sulfonic acid derivative, a fluororesin skeleton and a sulfonic acid;
A copolymer obtained by copolymerizing acrylamides such as acrylamide-2-methylpropanesulfonic acid and acrylates such as n-butyl methacrylate;
Etc. can be used.

Aromatic polyether ether ketone and aromatic polyether ketone represented by the following formula can also be used.
Proton acid group-containing aromatic polyetheretherketone

Crosslinkable aromatic polyether ketone containing protonic acid groups

上記式中、ｍ及びｎはそれぞれ繰り返し単位構造の比を示す。

In the above formula, m and n each represent the ratio of the repeating unit structure.

Subsequently, the solid polymer electrolyte membrane is heat-pressed in a state where water is wetted in the solid polymer electrolyte membrane (S102).
The temperature applied to the film can be, for example, 100 ° C. or higher. Thereby, the three-dimensional structure of the membrane can be changed, and the ionic conductivity and moisture content of the membrane can be controlled. The upper limit of the temperature applied to the film can be 180 ° C. or lower. Thereby, modification | denaturation and alteration of a film | membrane can be suppressed and the ionic conductivity and moisture content of a film | membrane can be controlled. More preferably, the upper limit of the temperature applied to the membrane can be less than 175 ° C. Thereby, modification | denaturation of frame | skeleton structure can be prevented. Moreover, the pressure applied to the film can be, for example, 10 kg / cm ² or more. Thereby, the three-dimensional structure of the membrane can be changed, and the ionic conductivity and moisture content of the membrane can be controlled. Moreover, the upper limit of the pressure applied to a film | membrane can be 150 kg / cm < ² > or less. Thereby, the three-dimensional structure of the film can be changed more without breaking the film.

  Then, a fuel cell is produced using the solid polymer electrolyte membrane produced in this way (S104).

FIG. 2 is a cross-sectional view schematically showing the structure of the fuel cell.
The unit cell 101 includes a fuel electrode 102, an oxidant electrode 108, and a solid polymer electrolyte membrane 114. The fuel electrode 102 includes a substrate 104 and a catalyst layer 106. The oxidant electrode 108 includes a base 110 and a catalyst layer 112.

  The plurality of unit cells 101 are electrically connected via the fuel electrode side separator 120 and the oxidant electrode side separator 122 to manufacture the fuel cell 100.

  As the substrate 104 and the substrate 110, a porous substrate such as carbon paper, a carbon molded body, a carbon sintered body, a sintered metal, and a foam metal can be used for both the fuel electrode 102 and the oxidant electrode 108. The surface of the substrate 104 and the substrate 110 may be subjected to water repellent treatment. A water repellent such as polytetrafluoroethylene can be used for the water repellent treatment of the substrate.

  Further, as the catalyst of the fuel electrode 102, platinum, an alloy of platinum and ruthenium, gold, rhenium, etc., rhodium, palladium, iridium, osmium, ruthenium, rhenium, gold, silver, nickel, cobalt, lithium, lanthanum, strontium, yttrium Etc. are exemplified. On the other hand, as the catalyst for the oxidant electrode 108, the same catalyst as that for the fuel electrode 102 can be used, and the above-mentioned exemplified substances can be used. The catalyst for the fuel electrode 102 and the oxidant electrode 108 may be the same or different.

  Examples of the carbon particles supporting the catalyst include acetylene black (DENKA BLACK (registered trademark, manufactured by Denki Kagaku Kogyo Co., Ltd.), XC72 (manufactured by Vulcan), etc.), ketjen black, carbon nanotube, carbon nanohorn, and the like. .

  The solid polymer electrolyte fine particles constituting the fuel electrode 102 or the oxidizer electrode 108 preferably include a solid polymer electrolyte constituting the solid polymer electrolyte membrane 114. Thereby, the adhesion between the fuel electrode 102 and the oxidant electrode 108 and the solid polymer electrolyte membrane 114 can be enhanced.

  The manufacturing method of the fuel electrode 102 and the oxidant electrode 108 in the embodiment of the present invention is not particularly limited, but can be manufactured as follows, for example.

  First, a catalyst is supported on carbon particles by a commonly used impregnation method. Next, the catalyst-supported carbon particles and solid polymer electrolyte fine particles are dispersed in a solvent to form a paste, which is then applied to the substrate 104 or the substrate 110 which has been surface-treated with a hydrophilic coating agent or a hydrophobic coating agent. To do. Although there is no restriction | limiting in particular about the coating method of the paste to the base | substrate 104 or the base | substrate 110, For example, methods, such as brush coating, spray coating, and the screen printing method, can be used. After the paste is applied, the fuel electrode 102 and the oxidant electrode 108 are manufactured by heating at a heating temperature and a heating time corresponding to the type of fine particles of the solid polymer electrolyte used. The heating temperature and the heating time can be, for example, a heating temperature of 100 ° C. to 250 ° C. and a heating time of 30 seconds to 30 minutes.

Next, the single polymer structure 101 is obtained by sandwiching the solid polymer electrolyte membrane 114 subjected to the processing of Step 100 and Step 102 (FIG. 1) described above between the fuel electrode 102 and the oxidant electrode 108 and heat-pressing. . At this time, the catalyst layer 106 and the catalyst layer 112 are brought into contact with the solid polymer electrolyte membrane 114. For example, when the solid polymer electrolyte fine particles in the solid polymer electrolyte membrane 114, the catalyst layer 106, and the catalyst layer 112 are composed of organic polymers, the conditions of the heat press include the softening temperature of these organic polymers and the glass transition. The temperature can exceed the temperature. Specifically, for example, the temperature is 100 to 250 ° C., the pressure is 1 to 100 kg / cm ² , and the time is 10 seconds to 300 seconds.

  As another example, a solid electrolyte membrane 114 that has not been subjected to the processing of Step 100 and Step 102 of FIG. 1 is wetted with water, sandwiched between the fuel electrode 102 and the oxidant electrode 108, and heat-pressed. A cell structure 101 can also be obtained. Also by such a method, the three-dimensional structure of the membrane can be changed, and the ionic conductivity and moisture content of the membrane can be controlled.

  As described above, the single cell structure 101 is formed. Further, by stacking the obtained single cell structures 101, it is possible to obtain a fuel cell including a fuel cell stack in which a plurality of single cell structures 101 are connected in series.

  In the fuel cell configured as described above, the fuel 124 is supplied to the fuel electrode 102 of each unit cell 101 via the fuel electrode-side separator 120. As the fuel 124, an organic liquid fuel such as methanol, ethanol, dimethyl ether, other alcohols, or a liquid hydrocarbon such as cycloparaffin can be used. The organic liquid fuel can be an aqueous solution. An oxidant 126 such as air or oxygen is supplied to the oxidant electrode 108 of each unit cell 101 via the oxidant electrode side separator 122.

  Hereinafter, the solid polymer electrolyte membrane of the present invention and the fuel cell using the same will be described in detail with reference to examples, but the present invention is not limited thereto.

  In the following examples, the moisture content, methanol permeability, and resistance were determined as follows.

Moisture content:
The weight of a test sample obtained by drying each solid polymer electrolyte membrane at 100 ° C. for 2 hours is A, and the weight of a test sample obtained by immersing each solid polymer electrolyte membrane in pure water for 24 hours is (B-A). Water content (%) was obtained from / A × 100.

Methanol permeation:
The containers were separated by solid polymer electrolyte membranes, 50 cc of methanol of a predetermined concentration was injected on one side, and 50 cc of pure water was injected on the other side of the container, and sealed so that these liquids did not evaporate. The time change in the concentration of methanol permeating into the pure water across the solid polymer electrolyte membrane as the test sample was measured by gas chromatography to obtain the methanol permeation amount.

resistance:
A solid polymer electrolyte membrane with electrodes attached on both sides was used as a test sample, and the container was separated by each solid polymer electrolyte membrane. A 1 M sulfuric acid aqueous solution was poured into both sides of the container and sealed so that the liquid did not leak. The resistance with respect to the perpendicular direction of each solid polymer electrolyte membrane was determined by measuring the impedance between the electrodes.

(Example 1)
A solid polymer electrolyte membrane having a structure represented by the above formula (4) was used as a test sample.

A solid polymer electrolyte membrane having a thickness of 50 μm was cut into 2 × 2 cm ² , sufficiently wetted with pure water, and then sandwiched between heat-resistant polymer sheets, and a predetermined temperature (115 ° C., 125 ° C., 135 ° C., 150 ° C., And 175 ° C.) and pressurized at a pressure of 0.4 t for 5 minutes. Although the thickness of the obtained film | membrane was confirmed, the film thickness was hardly changing. From this result, it can be seen that the skeleton structure of the film is not mechanically altered. About the obtained film | membrane, the water content, methanol permeation amount (methanol concentration is 10 volume%, 15 volume%, and 20 volume%) and resistance were measured by the method mentioned above, respectively.

  The results are shown in FIGS. FIG. 3 is a diagram showing the rate of change in the amount of methanol permeated with respect to an untreated film that has not been heat-pressed on a film that has been heat-pressed at each temperature. FIG. 4 is a diagram showing a rate of change in resistance of a film that has been heat pressed at each of the above temperatures with respect to an untreated film that has not been heat pressed. FIG. 5 is a diagram showing the rate of change in moisture content of a film that has been heat pressed at each of the above temperatures with respect to an untreated film that has not been heat pressed.

  As shown in FIG. 4, the resistance of the film was reduced by performing heat pressing in a state where water was swollen in the film. This result shows that the ion conductivity of the membrane was improved. When the processing temperature at the time of heat pressing is 175 ° C., the resistance increases. This is considered to be caused by the film being denatured because the processing temperature at the time of heat pressing is high.

  Moreover, as shown in FIG. 3, when the processing temperature at the time of heat pressing was set to 125 ° C. to 135 ° C., the methanol permeation amount increased. However, even in such a processing temperature range, the reduction rate of resistance was larger than the increase rate of methanol permeation amount. Considering both sides of the crossover and ion conductivity, the performance of the membrane was improved by performing the heat press in a swollen state of water.

  When the processing temperature at the time of heat pressing was set to 150 ° C., the resistance could be greatly reduced and the methanol permeation amount could also be reduced. Thus, by setting the treatment temperature at the time of heat pressing to an appropriate temperature, it is possible to reduce resistance and to reduce the methanol permeation amount as compared with untreated ones. Moreover, when the surface of the film | membrane which performed the process temperature at the time of heat press at 150 degreeC was observed with the SEM (scanning electron microscope) photograph, it has confirmed that the structure of the film | membrane changed.

  As shown in FIG. 5, the moisture content of the film was reduced by performing heat pressing in a state where water was swollen in the film. In particular, when the treatment temperature during heat pressing was set to 150 ° C., the water content was greatly reduced. In this example, by performing heat pressing in a state where water was swollen in the membrane, the moisture content of the membrane was reduced, and the methanol permeation amount of the membrane was also reduced. Also, by such treatment, the resistance of the film was reduced and the ionic conductivity was increased.

  Here, the moisture content of the film in this example before heat pressing was about 20%. As a result of heat pressing this at each treatment temperature, the moisture content of the film was 11.8% (treatment temperature 115 ° C), 10.7% (treatment temperature 125 ° C), 13.9% (treatment temperature 135 ° C), It was 6.1% (treatment temperature 150 ° C.) and 5.7% (treatment temperature 175 ° C.).

  In this example, a hydrocarbon film is used as the film. Such a film has a structure in which ion-conductive proton acid groups are three-dimensionally linked to a polymer skeleton serving as a substrate. Therefore, it is considered that the water content and the ionic conductivity of the film could be controlled by changing the three-dimensional structure of the film by performing heat pressing in a state where the skeleton structure was maintained by swelling water. Thereby, the characteristics of the film could be improved.

(Reference Example 1)
The same solid polymer electrolyte membrane as used in Example 1 was heated and pressurized at 150 ° C. in the same manner as in Example 1 without swelling water. The resulting film was discolored and deformed. Also, the resistance increased significantly. This is presumably because the skeleton structure of the membrane was altered due to decomposition of the sulfonic acid group contained in the membrane.

(Reference Example 2)
The same solid polymer electrolyte membrane as used in Example 1 was used, and heat pressing was performed in the same manner as in Example 1 except that the temperature during heat pressing was 190 ° C. The resulting film was discolored and deformed. This is presumably because the skeleton structure of the membrane was altered due to decomposition of the sulfonic acid group contained in the membrane.

(Example 2)
Using the membrane obtained in Example 1 (treatment temperature at 150 ° C. during heat pressing) as the solid polymer electrolyte membrane, a fuel cell was produced in the same manner as described with reference to FIG. A method for manufacturing a fuel cell according to this example will be described with reference to FIG.

  In this example, a platinum-ruthenium catalyst was used as the noble metal catalyst for both the fuel electrode 102 and the oxidant electrode 108. First, 10 g of acetylene black (Denka Black (registered trademark); manufactured by Denki Kagaku Kogyo Co., Ltd.) was mixed with 500 g of a dinitrodiamine platinum nitric acid solution containing 3% of platinum-ruthenium serving as a catalyst in the fuel electrode 102 and the oxidant electrode 108. After stirring, 60 ml of 98% ethanol was added as a reducing agent. This solution was stirred and mixed at about 95 ° C. for 8 hours, and the catalyst material and platinum fine particles were supported on acetylene black particles. The solution was filtered and dried to obtain catalyst-carrying carbon particles. The supported amount of platinum-ruthenium was about 50% with respect to the weight of acetylene black.

  Next, 200 mg of the catalyst-supporting carbon particles and 8 ml of a Nafion solution manufactured by DuPont were mixed and stirred to adsorb Nafion on the catalyst and the carbon particle surfaces. The dispersion thus obtained was made into a paste by dispersing with an ultrasonic disperser at 50 ° C. for 3 hours.

  The paste thus obtained was applied to the base 104 and the base 110, which are carbon paper (manufactured by Toray Industries, Inc .: TGP-H-120) by screen printing, and then dried by heating at 100 ° C. And the oxidant electrode 108 was obtained.

The solid electrolyte membrane 114 was sandwiched between these electrodes, and heat-pressed under conditions of a temperature of 150 ° C. and a pressure of 50 kg / cm ² (300 seconds) to produce an electrode-electrolyte assembly. Furthermore, this electrode-electrolyte assembly was set in a single cell measuring device for a fuel cell to produce a single cell.

  In this single cell, the current-voltage characteristics of the cell were measured using a 10% by volume methanol aqueous solution and oxygen (1.1 atm, 25 ° C.) as fuel. As a result, an increase in the potential of the cathode electrode and an increase in the output were confirmed as compared with the case of using an untreated membrane that was not subjected to the heating and pressurizing treatment. Further, it was confirmed that the temperature on the cathode electrode side was lowered and methanol permeation was suppressed.

(Example 3)
After the solid polymer electrolyte membrane having the structure represented by the above formula (4) is sufficiently wetted with pure water, the membrane is sandwiched between electrodes obtained in the same manner as in Example 2, and the temperature is 150 ° C. and the pressure is 10 kgf / cm ² ( The electrode-electrolyte joined body was produced by heat-pressing on the conditions for 10 seconds. Furthermore, this electrode-electrolyte assembly was set in a single cell measuring device for a fuel cell to produce a single cell.

  In this single cell, the current-voltage characteristics of the cell were measured using a 10% by volume methanol aqueous solution and oxygen (1.1 atm, 25 ° C.) as fuel. As a result, an increase in the potential of the cathode electrode and an increase in the output were confirmed as compared with the case where heat pressing was performed under the same conditions without being wetted with pure water. Further, it was confirmed that the temperature on the cathode electrode side was lowered and methanol permeation was suppressed.

Further, in Example 1 above, heating and pressurization were performed at the same time. However, when heating and pressurization were performed alone, the film performance was improved as compared with the case where such treatment was not performed.
For example, the membranes treated at 140 ° C., 160 ° C., and 180 ° C. as in Example 1 except that no pressure was applied had a lower methanol permeation amount than the untreated membranes. In this case, a higher temperature was required to change the film structure as compared to the case of applying the pressure of Example 1. As described above, the performance of the film can be improved by performing only heating, but it is considered that the performance of the film can be improved more effectively by performing heating and pressurization simultaneously.

Further, when the treatment temperature was 150 ° C. and the pressure was 100 kg / cm ² , the methanol permeation amount was reduced by 20% compared to the case where the pressure was 50 kg / cm ² at the same temperature. According to SEM observation, when the pressure was 100 kg / cm ² , the surface of the film was more dense.

  As described above, it was confirmed that a fuel cell having high ionic conductivity was obtained while reducing crossover due to methanol permeation according to the present invention. As a result, the fuel cell can be operated at a higher methanol concentration than the conventional fuel cell. Long-time operation is also possible.

  The present invention has been described based on the embodiments and examples. It is to be understood by those skilled in the art that the embodiments and examples are merely examples, and various modifications are possible and that such modifications are within the scope of the present invention.

  For example, the water content of the solid polymer electrolyte membrane can be reduced by irradiating the solid polymer electrolyte membrane with an electron beam, an ultraviolet ray, a gamma ray, an infrared ray or the like in a wet state.

It is a flowchart which shows the manufacturing process of the fuel cell in embodiment of this invention. It is sectional drawing which showed typically the structure of the fuel cell in embodiment of this invention. It is a figure which shows the result of an Example. It is a figure which shows the result of an Example. It is a figure which shows the result of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Unit cell 102 Fuel electrode 104 Base 106 Catalyst layer 108 Oxidant electrode 110 Base 112 Catalyst layer 114 Solid polymer electrolyte membrane 120 Fuel electrode side separator 122 Oxidant electrode side separator 124 Fuel 126 Oxidant

Claims (2)

A step of wetting water on a solid polymer electrolyte membrane made of a polymer containing no fluorine having a structure represented by the following formula (1) :
In a state where the fuel electrode and the oxidizer electrode are not in close contact with each other and water is wetted on the solid polymer electrolyte membrane, pressure is applied to the solid polymer electrolyte membrane, and the temperature exceeds 135 ° C and is less than 175 ° C. Heating to a temperature to reduce the water content of the solid polymer electrolyte membrane;
A method for producing a solid polymer electrolyte membrane for use in a direct methanol fuel cell, comprising:

A direct methanol fuel cell manufactured by the manufacturing method according to claim 1.
Solid polymer electrolyte membrane used.

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