JP2011216264A - Solid polymer electrolyte membrane, solid polymer electrolyte membrane electrode assembly, solid polymer electrolyte membrane fuel cell, and method of manufacturing solid polymer electrolyte membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a membrane electrode assembly having excellent adhesiveness between a solid polymer electrolyte and an electrode catalyst layer, to provide a method of manufacturing the same, and to provide a polymer electrolyte fuel cell including the membrane electrode assembly.SOLUTION: A cross-linked polymer electrolyte membrane includes a cross-linked polymer obtained by cross-linking reaction between a proton-conducting polymer and a cross-linking agent through a part except for a proton acid group. The cross-linked polymer electrolyte membrane includes at least one recessed part 11 or protruded part 12 on at least one surface, and the proton-conducting polymer includes a constituent unit represented by general formula (1).

Description

  The present invention relates to a method for producing a polymer electrolyte membrane and a polymer electrolyte fuel cell comprising the membrane electrode assembly.

  A fuel cell is a power generation system that generates electricity simultaneously with heat by causing a hydrogen gas-containing fuel gas and an oxygen-containing oxidant gas to undergo reverse reaction of water electrolysis at an electrode including a catalyst. This power generation system has features such as high efficiency, low environmental load, and low noise as compared with conventional power generation systems, and is attracting attention as a clean energy source in the future. There are several types depending on the type of ion conductor used, and those using an ion conductive polymer membrane are called solid polymer fuel cells.

  Among fuel cells, polymer electrolyte fuel cells can be used near room temperature, so they are considered promising for use in on-vehicle sources and household stationary power sources. In recent years, various research and development have been conducted. Yes. The polymer electrolyte fuel cell is composed of a membrane electrode assembly (hereinafter referred to as MEA), a polymer electrolyte having a pair of electrode catalyst layers disposed on both sides of the polymer electrolyte. A battery sandwiched between a pair of separator plates in which a gas flow path for supplying a fuel gas containing hydrogen to one of the electrodes and supplying an oxidant gas containing oxygen to the other electrode is formed. Here, the electrode for supplying the fuel gas is called a fuel electrode, and the electrode for supplying the oxidant is called an air electrode. These electrodes are composed of an electrode catalyst layer formed by laminating carbon particles carrying a catalyst material such as a platinum-based noble metal and a polymer electrolyte, and a gas diffusion layer having both gas permeability and electron conductivity.

  In MEA, a solid polymer electrolyte membrane is sandwiched between a pair of electrode catalyst layers, and in some cases, the electrode catalyst layer is further sandwiched between a pair of gas diffusion layers. The MEA having such a configuration is a catalyst in which an electrode catalyst having a catalyst component supported on the surface of a conductive material and an electrolyte such as a fluorine-based polymer having proton conductivity dispersed in water or a solvent of a lower alcohol. The ink is directly applied to the solid polymer electrolyte membrane and then dried, or the catalyst ink is applied and dried on a transfer mount to form an electrode catalyst layer, and then solidified by hot pressing. It is produced by a transfer method in which an electrode catalyst layer is transferred to a polymer electrolyte membrane.

  Among the above methods, in the transfer method which is currently the mainstream, when the electrode catalyst layer is transferred by hot pressing, if a material having poor compatibility with the solid polymer electrolyte membrane is used for the electrode catalyst layer, the solid polymer There may be a problem that good adhesion cannot be obtained between the electrolyte membrane and the electrode catalyst layer. For this reason, in a fuel cell using such a solid polymer electrolyte membrane, the contact resistance between the solid polymer electrolyte membrane and the electrode catalyst layer increases because the electrode catalyst layer is peeled off from the solid polymer electrolyte membrane. There is a case where a problem that a proper power generation characteristic cannot be obtained may occur. In addition, when a material having a high glass transition temperature is used for the solid polymer electrolyte membrane, good adhesion cannot be obtained unless sufficient heat is applied. Furthermore, there is a risk of damaging the solid polymer electrolyte membrane itself.

JP 2007-184141 A

  In order to solve this problem, in Patent Document 1, (a) a sheet-like material or film having a concavo-convex surface is placed on a solid polymer electrolyte membrane, and the concavo-convex shape is transferred to the solid polymer electrolyte membrane. And (a) a method in which a rigid fine particle or the like is applied to the surface of the solid polymer electrolyte membrane and then crimped by sandwiching it between a metal plate or the like. Since it was difficult to transfer, there was a problem that the adhesion with the electrode catalyst layer could not be improved.

  Accordingly, the present invention creates a three-dimensional structure line pattern by machining a glass substrate using a cutting blade, and applies, dries, and peels a solid polymer electrolyte to the machined glass substrate. The membrane / electrode assembly produced by using the solid polymer electrolyte membrane has excellent adhesion between the solid polymer electrolyte membrane and the electrode catalyst layer. By using this MEA, An object of the present invention is to provide a polymer electrolyte fuel cell having good adhesion and good power generation characteristics.

  The solid polymer electrolyte membrane according to claim 1 of the present invention is a crosslinked polymer electrolyte membrane comprising a crosslinked polymer obtained by crosslinking a proton conducting polymer and a crosslinking agent via a portion other than a proton acid group. In which at least one surface has at least one concave portion or convex portion, and the proton conductive polymer has a structural unit represented by the following general formula (1).

[In the general formula (1), A represents an electron-withdrawing group, and B represents an electron-donating group. X, Y, and Z are each 0 or 1, indicating that the sum of X, Y, and Z is an integer from 1 to 3. ]
With such a configuration, since the proton conductive polymer has a rigid skeleton, it is possible to maintain the shape of at least one recess or protrusion on the surface of the solid polymer electrolyte membrane. For this reason, for example, when the electrode catalyst layer having at least one concave portion or convex portion on at least one surface is bonded to the solid polymer electrolyte membrane of the present invention in the same manner as the solid polymer electrolyte membrane of the present invention The contact area between the electrode catalyst layer and the solid polymer electrolyte membrane can be increased. Therefore, the solid polymer electrolyte membrane of the present invention can improve the adhesion between the electrode catalyst layer and the solid polymer electrolyte membrane.

Also, with such a configuration, when the adhesion between the electrode catalyst layer and the solid polymer electrolyte membrane is improved, the contact resistance between the electrode catalyst layer and the solid polymer electrolyte membrane is reduced, and the power generation characteristics Can be improved.
The solid polymer electrolyte membrane according to claim 2 of the present invention is characterized in that the groove portion of the concave portion or the protruding portion of the convex portion has a shape extending linearly in plan view.
With such a configuration, the contact area between the electrode catalyst layer and the solid polymer electrolyte membrane can be further increased, so that the adhesion between the electrode catalyst layer and the solid polymer electrolyte membrane can be improved.

The solid polymer electrolyte membrane according to claim 3 of the present invention is characterized in that the concave portions having the linearly extending shape or the convex portions having the linearly extending shape are repeatedly arranged. Is.
With such a configuration, the contact area between the electrode catalyst layer and the solid polymer electrolyte membrane can be further increased, so that the adhesion between the electrode catalyst layer and the solid polymer electrolyte membrane can be improved.

The solid polymer electrolyte membrane according to claim 4 of the present invention is characterized in that, in the general formula (1), A is -O-.
With such a configuration, since the membrane resistance is reduced as compared with the case where A is not -O-, the power generation characteristics of the solid polymer electrolyte membrane can be improved.
The solid polymer electrolyte membrane according to claim 5 of the present invention is characterized in that, in the general formula (1), B is -CO-.
With such a configuration, the membrane resistance is further reduced as compared with the case where B is not —CO—, so that the power generation characteristics of the solid polymer electrolyte membrane can be further improved.

The solid polymer electrolyte membrane according to claim 6 of the present invention is characterized in that the proton conductive polymer has a hydrogen ion exchange capacity of 0.5 meq / g or more and 5 meq / g or less.
With such a configuration, proton conductivity is excellent as compared with the case where the hydrogen ion exchange capacity is less than 0.5 meq / g and greater than 5 meq / g. Therefore, the solid polymer electrolyte membrane of the present invention is used as a fuel cell. The internal resistance does not increase when used for the above. For this reason, when using for a fuel cell, for example, the fall of the output density of electric power can be suppressed. Therefore, if it is the solid polymer electrolyte membrane of this invention, the electric power generation characteristic of a solid polymer electrolyte membrane can be improved.

The solid polymer electrolyte membrane according to claim 7 of the present invention is characterized in that the cross-linking agent has at least two methylol groups in the molecule of the cross-linking agent.
With such a configuration, the reaction proceeds at a portion other than the protonic acid group without passing through the protonic acid group of the proton conductive polymer, so that the proton conductivity of the proton conductive polymer may be impaired by the reaction. Absent. For this reason, if it is a solid polymer electrolyte membrane of this invention, when using for a fuel cell, for example, since the fall of the output density of electric power can be suppressed, a power generation characteristic can be improved further.

In the solid polymer electrolyte membrane according to claim 8 of the present invention, the depth of the concave portion or the height of the convex portion is 1 μm or more, and is 1/5 or less of the thickness of the solid polymer electrolyte membrane. It is a feature.
With such a configuration, the surface of the solid polymer electrolyte membrane is smaller than the case where the depth of the concave portion or the height of the convex portion is smaller than 1 μm and larger than 1/5 of the thickness of the solid polymer electrolyte membrane. Can sufficiently retain the mechanical strength of the concave portion or convex portion. Thereby, for example, when the electrode catalyst layer and the solid polymer electrolyte membrane of the present invention are bonded together, the contact area between the electrode catalyst layer and the solid polymer electrolyte membrane can be further increased. For this reason, if it is the solid polymer electrolyte membrane of this invention, the adhesiveness of an electrode catalyst layer and a solid polymer electrolyte membrane can be improved further.

  In the method for producing a solid polymer electrolyte membrane according to claim 9 of the present invention, the proton conduction represented by the following general formula (2) is provided on the surface of the substrate having at least one concave portion or convex portion on at least one surface. Forming a coating film by applying a coating liquid containing a crosslinking polymer obtained by crosslinking reaction of a functional polymer and a crosslinking agent via a portion other than a protonic acid group, and heating the coating film to form a solid The method includes a step of forming a polymer electrolyte membrane, and a step of peeling the solid polymer electrolyte membrane from the substrate.

[In the general formula (2), A represents an electron-withdrawing group, and B represents an electron-donating group. X, Y, and Z are each 0 or 1, indicating that the sum of X, Y, and Z is an integer from 1 to 3. ]
With such a method, a solid polymer electrolyte membrane having at least one concave portion or convex portion on at least one surface can be produced. Furthermore, by using a proton conductive polymer having a rigid skeleton, it is possible to produce a solid polymer electrolyte membrane that sufficiently retains the mechanical strength of the concave portion or the convex portion. Therefore, for example, an electrode catalyst layer having at least one concave or convex portion on at least one surface in the same manner as the solid polymer electrolyte membrane produced according to the present invention, and the solid polymer electrolyte membrane produced according to the present invention When is bonded, the contact area between the electrode catalyst layer and the solid polymer electrolyte membrane increases. Therefore, according to the production method of the present invention, a solid polymer electrolyte membrane capable of improving the adhesion between the electrode catalyst layer and the solid polymer electrolyte membrane can be produced.

Further, for example, when the adhesion between the electrode catalyst layer and the solid polymer electrolyte membrane is improved, the contact resistance between the electrode catalyst layer and the solid polymer electrolyte membrane is reduced. Therefore, the production method of the present invention can produce a solid polymer electrolyte membrane capable of improving power generation characteristics.
The method for producing a solid polymer electrolyte membrane according to claim 10 of the present invention is characterized in that the groove portion of the concave portion or the protruding portion of the convex portion has a shape extending linearly in plan view.
With such a method, the contact area between the electrode catalyst layer and the solid polymer electrolyte membrane can be further increased. Therefore, according to the production method of the present invention, a solid polymer electrolyte membrane capable of improving the adhesion between the electrode catalyst layer and the solid polymer electrolyte membrane can be produced.

In the method for producing a solid polymer electrolyte membrane according to claim 11 of the present invention, the concave portion having the linearly extending shape or the convex portion having the linearly extending shape is repeatedly arranged. It is a feature.
With such a method, the contact area between the electrode catalyst layer and the solid polymer electrolyte membrane can be further increased. Therefore, according to the production method of the present invention, a solid polymer electrolyte membrane capable of improving the adhesion between the electrode catalyst layer and the solid polymer electrolyte membrane can be produced.

The method for producing a solid polymer electrolyte membrane according to claim 12 of the present invention is characterized in that the temperature at which the coating film is heated is 60 ° C. or higher and 250 ° C. or lower.
If it is such a method, compared with the case where the temperature which heats a coating film is lower than 60 degreeC and higher than 250 degreeC, the smoothness of the solid polymer electrolyte membrane surface can be improved. For this reason, when the electrode catalyst layer and the solid polymer electrolyte membrane are bonded together, the contact area between the electrode catalyst layer and the solid polymer electrolyte membrane is further increased. Therefore, if it is the manufacturing method of this invention, the solid polymer electrolyte membrane which can improve these two adhesiveness further can be manufactured.

In the method for producing a solid polymer electrolyte membrane according to claim 13 of the present invention, the width of the concave portion or the convex portion is 50 μm or more, and the depth of the concave portion or the height of the convex portion is 1 μm or more and 1,000 μm or less. It is characterized by being.
With such a method, the width of the concave or convex portion is smaller than 50 μm, and the depth of the concave portion or the height of the convex portion is smaller than 1 μm and larger than 1000 μm. The shape can be formed stably. Thereby, the fine shape of the recessed part or convex part given to the base material can be transferred to the solid polymer electrolyte membrane with good reproducibility, and the shape can be maintained. For this reason, for example, when the electrode catalyst layer and the solid polymer electrolyte membrane are bonded together, the contact area between the electrode catalyst layer and the solid polymer electrolyte membrane is further increased. Therefore, if it is the manufacturing method of this invention, the solid polymer electrolyte membrane which can improve these two adhesiveness further can be manufactured.

The method for producing a solid polymer electrolyte membrane according to claim 14 of the present invention is characterized in that the concave portion or the convex portion is formed by machining using a cutting blade.
If it is such a method, since a recessed part or a convex part can be formed in a base material using a cutting blade, the pattern of a three-dimensional structure with a high aspect ratio can be formed in a base material. For this reason, the fine shape of the concave portion or the convex portion having an increased aspect ratio can be transferred to the solid polymer electrolyte membrane with good reproducibility, and the shape can be maintained. For this reason, for example, when the electrode catalyst layer and the solid polymer electrolyte membrane are bonded together, the contact area between the electrode catalyst layer and the solid polymer electrolyte membrane is further increased. Therefore, if it is the manufacturing method of this invention, the solid polymer electrolyte membrane which can improve these two adhesiveness further can be manufactured.

The method for producing a solid polymer electrolyte membrane according to claim 15 of the present invention is characterized in that the substrate is a glass substrate or a silicon wafer.
If it is such a method, compared with the case where base materials other than a glass base material or a silicon wafer are used, a desired fine shape can be accurately formed in a base material. For this reason, for example, when the electrode catalyst layer and the solid polymer electrolyte membrane are bonded together, the contact area between the electrode catalyst layer and the solid polymer electrolyte membrane is further increased. Therefore, if it is the manufacturing method of this invention, the solid polymer electrolyte membrane which can improve these two adhesiveness further can be manufactured.

A membrane electrode assembly according to a sixteenth aspect of the present invention is characterized by using the solid polymer electrolyte membrane according to any one of the first to fifteenth aspects.
If it is such a structure, when an electrode catalyst layer and a solid polymer electrolyte membrane are bonded together, it will become a membrane electrode assembly which increased the mutual contact area, for example. For this reason, if it is a membrane electrode assembly of this invention, the adhesiveness of an electrode catalyst layer and a solid polymer electrolyte membrane can be increased.

Further, with such a configuration, for example, when the adhesion between the electrode catalyst layer and the solid polymer electrolyte membrane produced according to the present invention is improved, the contact between the electrode catalyst layer and the solid polymer electrolyte membrane is improved. Resistance can be reduced. Therefore, the membrane electrode assembly of the present invention can improve the power generation performance.
A fuel cell according to claim 17 of the present invention is characterized in that the solid polymer electrolyte membrane according to any one of claims 1 to 16 is used.
With such a configuration, for example, when the electrode catalyst layer and the solid polymer electrolyte membrane are bonded together, a fuel cell having an increased mutual contact area is obtained. For this reason, if it is a fuel cell of this invention, the adhesiveness of an electrode catalyst layer and a solid polymer electrolyte membrane can be increased.

  Further, with such a configuration, for example, when the adhesion between the electrode catalyst layer and the solid polymer electrolyte membrane produced according to the present invention is improved, the contact between the electrode catalyst layer and the solid polymer electrolyte membrane is improved. Resistance can be reduced. Therefore, the power generation performance can be improved with the fuel cell of the present invention.

  According to the present invention, a glass substrate or silicon wafer is machined using a cutting blade to produce a three-dimensional structure pattern, and a solid polymer electrolyte is applied to the machined glass substrate, A solid polymer electrolyte membrane can be produced by drying and peeling, and the membrane / electrode assembly produced using this solid polymer electrolyte membrane has excellent and excellent adhesion between the solid polymer electrolyte membrane and the electrode catalyst layer. It has excellent power generation characteristics.

It is explanatory drawing of the glass base material machined with the cutting blade of this invention. It is explanatory drawing of the manufacturing method of the solid polymer electrolyte membrane of this invention. It is sectional drawing of the membrane electrode assembly using the solid polymer electrolyte membrane of this invention. 1 is an exploded schematic view of a polymer electrolyte fuel cell of the present invention.

  Hereinafter, each of the solid polymer electrolyte membrane, the method for producing the solid polymer electrolyte membrane, the membrane electrode assembly using the solid polymer electrolyte membrane, and the fuel cell using the solid polymer electrolyte membrane according to the present invention will be described. . Note that the present invention is not limited to the embodiments described below, and modifications such as design changes can be made based on the knowledge of those skilled in the art, and such modifications are added. The embodiments may be included in the scope of the present invention.

First, an embodiment of the solid polymer electrolyte membrane according to the present invention will be described.
[Solid polymer electrolyte membrane]
The material of the solid polymer electrolyte membrane is preferably a material in which engineering plastic is sulfonated from the viewpoints of mechanical strength, solvent resistance, and oxidation resistance. Specifically, aromatic polyether, aromatic polyether ketone, aromatic polyether ether ketone, aromatic polyether sulfone, aromatic polysulfone, aromatic polyether nitrile, aromatic polyether pyridine, aromatic polyimide, aromatic An aromatic polyamide, an aromatic polyamideimide, an aromatic polyazole, an aromatic polyester, an aromatic polycarbonate and the like can be mentioned.

As one of the means for improving the power generation characteristics, it is conceivable to reduce the film resistance. However, these materials have sufficient mechanical strength even when the film thickness is reduced to about 10 μm, and the handling is good. is there. Nafion is useful because the mechanical strength decreases when the film thickness is about 10 μm (that is, sufficient mechanical strength cannot be obtained).
This material is a proton conductive polymer and has a structural unit represented by the following general formula (3).

However, in General formula (3), A shows an electron withdrawing group and B shows an electron donating group. X, Y, and Z are each 0 or 1, indicating that the sum of X, Y, and Z is an integer from 1 to 3.
The above structure is a rigid skeleton and has mechanical characteristics (that is, excellent mechanical characteristics) even if it is thinned to about 10 μm. Hydrocarbon electrolyte membranes have a lower proton conductivity than fluorine electrolyte membranes, particularly under low humidification conditions. However, since it has mechanical characteristics even when it is thinned, it can be expected to improve performance by reducing the film resistance and back-diffusion of water.

In particular, in general formula (3), it is preferable that A is -O-. Moreover, in General formula (3), it is preferable that B is -CO-.
The hydrogen ion exchange capacity of the proton conducting polymer having proton conductivity is preferably 0.5 meq / g or more and 5 meq / g or less in consideration of ion conductivity.
When the hydrogen ion exchange capacity is less than 0.5 meq / g, proton conductivity is inferior, and when used in a fuel cell, the internal resistance is large and the output density may be lowered. This is not preferable because it is easy to handle and the handling is reduced.

  On the surface of the solid polymer electrolyte membrane, a groove portion of the concave portion or a protruding portion of the convex portion is formed in a linear shape in plan view, and the depth of the concave portion or the height of the convex portion is 1 μm or more, The thickness is preferably 1/5 or less of the thickness of the solid polymer electrolyte membrane. By satisfying this range, the mechanical strength can be maintained even when the solid polymer electrolyte membrane is thinned to about 10 μm, and adhesion with the electrode catalyst layer can be ensured. Further, the distance between the convex part and the convex part (that is, the distance between the centers of the convex part and the convex part) or the distance between the concave part and the concave part (that is, the distance between the centers of the concave part and the concave part) is preferably 100 μm or more and 5000 μm or less. . By satisfying this range, it is possible to further maintain the mechanical strength of the solid polymer electrolyte membrane and ensure adhesion with the electrode catalyst layer. In addition, about the recessed part or convex part formed in the surface of the solid polymer electrolyte membrane, it is sufficient to have at least one concave part or convex part on at least one surface of the surface of the solid polymer electrolyte membrane. The groove portion or the protruding portion of the convex portion may have a shape extending linearly in plan view.

  The solid polymer electrolyte membrane preferably has a shape in which concave portions and convex portions having a shape extending linearly on the surface are alternately and repeatedly arranged using the above-described base material. The solid polymer electrolyte membrane can transfer the fine shape with good reproducibility and can be bonded to the electrode catalyst layer while maintaining the shape, even when using a substrate having an extremely fine pattern as described above. Adhesiveness with the electrode catalyst layer can be sufficiently improved.

Next, an embodiment of a method for producing a solid polymer electrolyte membrane according to the present invention will be described after sequentially explaining a processed substrate using a cutting blade, a processing method, and a crosslinking agent.
First, a processed base material using a cutting blade and a processing method will be described.
[Processed base material using cutting blade and processing method]
Examples of base materials include plate-like base materials and sheet-like base materials made of metal, resin, glass, etc., but resin is more susceptible to thermal deformation than metal and glass, so the processed structure is maintained. In many cases, the metal is expensive. For this reason, it is preferable to use a plate-like base material made of glass or silicon wafer, which is excellent in mechanical strength and inexpensive, so that at least one concave portion or convex portion can be formed on the surface. By using a plate-like substrate made of glass or a silicon wafer, a desired fine pattern can be formed with high accuracy. Note that at least one recess or protrusion may be formed on the surface, and the groove or protrusion of the minute recess formed on the surface may have a shape extending linearly in plan view. . Moreover, you may form and form those linearly extended shapes. Furthermore, the concave portions and the convex portions having a linearly extending shape may be alternately and repeatedly arranged (that is, a linear shape including the concave portions and the convex portions may be formed).

  Here, the shape in which concave portions and convex portions having linearly extending shapes are alternately arranged means a line pattern having a three-dimensional structure, specifically, a shape as shown in FIG. I mean. The linear shape composed of the concave portion 11 or the convex portion 12 only needs to have the concave portion 11 and the convex portion 12 extending linearly in one direction in the plane, and the bottom surface of the concave portion 11 and the top surface of the convex portion 12 are horizontal. Even if it exists, it may have a curvature. Further, the distance between the convex portions 12 and the convex portions 12 (hereinafter sometimes referred to as a pitch) may be decreased in the depth direction of the substrate 10 or may be increased conversely.

As a method of forming a shape in which concave portions 11 and convex portions 12 having a linearly extending shape are alternately arranged on the surface of a substrate 10 made of glass or a silicon wafer, a known surface processing method is used. Can do. For example, there is a method of performing etching by forming a mask by lithography.
If light or electron beam lithography is used, an etching mask having a fine and arbitrary pattern shape can be formed. Therefore, a three-dimensional structure pattern of micron order of 1 μm or more can be processed by etching. In addition, fine processing at the level used in the manufacturing process of semiconductor elements is possible, and by applying a technique such as trench etching, a three-dimensional structure pattern having a high aspect ratio can be processed with an extremely fine pattern or pitch. it can. Examples of the etching method include dry or wet.

  As the surface processing method, the etching method as described above can be used, but it is preferable to use a machining method using a cutting blade with a simpler processing step. In the machining method using the cutting blade, since the linear groove along the direction can be formed by moving the cutting blade in one direction, the solid polymer electrolyte membrane having an uneven structure on the surface can be formed. It is suitable as a method for forming a three-dimensional structure line pattern. Further, when machining using a cutting blade is used, a three-dimensional structure line pattern having a high aspect ratio can be formed. Note that it is not always necessary to form a linear groove on the surface, and at least one concave portion 11 or convex portion 12 may be formed.

The concave portion 11 and the convex portion 12 formed on the surface of the base material 10 are such that the depth of the concave portion or the height of the convex portion 12 on the surface of the solid polymer electrolyte membrane is 1 μm or more. Design to be 1/5 or less of the thickness.
Specifically, the width of the concave portion 11 or the convex portion 12 formed on the base material 10 is preferably 50 μm or more, the depth of the concave portion 11 or the height of the convex portion 12 is preferably 1 μm or more and 1,000 μm or less. Or it is preferable that the aspect ratio of the convex part 12 is 0.02 or more and 20 or less. By satisfy | filling the said range, the shape of the recessed part 11 or the convex part 12 is stabilized, and it can be used repeatedly as a mother mold.

[Crosslinking agent]
The crosslinking agent can cause the reaction to proceed at a portion other than the protonic acid group without going through the protonic acid group of the proton conductive polymer, and does not change the proton conductivity of the proton conductive material before and after the reaction. There is no particular limitation as long as it is sufficient. Examples of the crosslinking agent include materials having a —CH ₂ Cl group, a —CHOCH ₃ group, and a —CH ₂ OH group on the aromatic ring. A crosslinking agent having a structure in which a methylol group is bonded to the aromatic ring can be heated. It is preferred because the reaction proceeds easily.

_-CH 2 Cl group to an aromatic ring, -CHOCH2 ₃ group, at least as a bridge having a _-CH 2 OH group, _-CH 2 Cl group, -CHOCH2 ₃ group, an aromatic ring having a _-CH 2 OH group in the molecule Since the reaction of a compound having two or more compounds proceeds without passing through the protonic acid group contained in the proton conductive polymer, the reaction does not impair the proton conductivity of the proton conductive polymer and can be easily reacted by heating. Since it progresses, it can be preferably used.
Moreover, in order to improve ion conductivity, the crosslinking agent may be sulfonated. The sulfonated crosslinking agent may be any sulfonated crosslinking agent, but the proportion of the sulfonated crosslinking agent is preferably 50 mol% or less. The reason is that if the amount of the sulfonated cross-linking agent is too large, it becomes easy to swell.
As the reaction method, a light irradiation method, a heating method, a pH adjustment method, or the like can be used.

Next, the manufacturing method of a solid polymer electrolyte membrane is demonstrated.
[Method for producing solid polymer electrolyte membrane]
First, as shown in FIG. 2 (a), the proton described above is formed on one surface of a glass substrate 21 having a shape in which concave portions and convex portions having linearly extending shapes are alternately arranged. A solution 22 containing a cross-linked polymer obtained by a cross-linking reaction between the conductive polymer and the above-described cross-linking agent via a portion other than the protonic acid group is applied. In addition, the glass base material 21 can use the base material processed using the cutting blade mentioned above.

Next, as shown in FIG.2 (b), the solution 22 apply | coated on the glass base material 21 is heated and dried, and a solid polymer electrolyte membrane is formed. As a drying method, it is preferable to slowly dry the solvent. Specifically, it is desirable to perform the initial drying temperature at 40 ° C. for 1 h and the secondary drying at 90 ° C. for about 1 h. This is because if the initial drying temperature is too high, the smoothness of the film becomes poor.
Next, as shown in FIG. 2 (c), the solid polymer electrolyte membrane 23 is peeled off from the glass substrate 21. In order to peel off the solid polymer electrolyte membrane 23 from the glass substrate 21, it is peeled off using tweezers or the like, or impregnated with water or alcohol, specifically methanol, ethanol, isopropyl alcohol or the like in lower alcohol. It is preferable to peel off. In this way, the solid polymer electrolyte membrane 23 shown in FIG.

Next, a membrane electrode assembly using a solid polymer electrolyte membrane will be described.
[Membrane electrode assembly]
FIG. 3 shows an exploded schematic view of the membrane electrode assembly according to the embodiment of the present invention. The membrane / electrode assembly is composed of a solid polymer electrolyte membrane and an electrode catalyst layer described later, and is formed by bonding both surfaces of the solid polymer electrolyte membrane with an electrode catalyst layer described later.

[Production method of membrane electrode assembly]
(catalyst)
As the reaction catalyst, platinum, palladium, ruthenium, iridium, rhodium, osmium, platinum group elements, metals such as iron, lead, copper, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum, or these metals An alloy, an oxide, a double oxide, or the like can be used. Moreover, since the activity of a catalyst will fall when the particle size of these catalysts is too large, and stability of a catalyst will fall when too small, 0.5-20 nm is preferable. More preferably, 1-5 nm is good.

  In general, carbon particles are used as the electron conductive conductive agent supporting these reaction catalysts. Any carbon particles can be used as long as they are in the form of fine particles, have conductivity and are not affected by the catalyst, but carbon black, graphite, graphite, activated carbon, carbon fiber, carbon nanotube, and fullerene are used. it can. If the particle size of the carbon particles is too small, it will be difficult to form an electron conduction path, and if it is too large, the gas diffusibility of the electrode catalyst layer will decrease or the utilization factor of the catalyst will decrease. Is preferred. More preferably, 10-100 nm is good.

(Electrocatalyst ink)
The solvent used as a dispersion medium for the electrode catalyst ink is not particularly limited and can be dissolved or dispersed as a fine gel in a highly fluid state of the polymer electrolyte without eroding the catalyst particles and the polymer electrolyte. However, it is desirable to include at least a volatile liquid organic solvent, and is not particularly limited, but is not limited to methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol. Alcohols such as alcohol, isobutyl alcohol, tert-butyl alcohol, pentanole, ketone solvents such as acetone, methyl ethyl ketone, pentanone, methyl isobutyl ketone, heptanone, cyclohexanone, methylcyclohexanone, acetonyl acetone, diisobutyl ketone, tetrahydrofuran , Dioxane, diethylene glycol dimethyl ether, anisole, methoxytoluene, dibutyl ether and other ether solvents, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol Le, diethylene glycol, diacetone alcohol, 1-methoxy-2-propanol polar solvents is used. Moreover, what mixed 2 or more types of these solvents can also be used.

In addition, those using lower alcohol as the solvent have a high risk of ignition, and when using such a solvent, it is preferable to use a mixed solvent with water. Water that is compatible with the polymer electrolyte may be contained. The amount of water added is not particularly limited as long as the polymer electrolyte is not separated to cause white turbidity or gelation.
If the content of the solid content in the electrode catalyst ink is too high, the viscosity of the electrode catalyst ink will be high, so that the surface of the electrode catalyst layer will be prone to cracks. 1% to 50% by mass is preferable because the properties are reduced.

(Electrode catalyst layer)
In a method for producing a membrane electrode assembly produced using a solid polymer electrolyte membrane, catalyst-carrying carbon particles embedded with a polymer electrolyte include catalyst-carrying carbon particles and an electrode catalyst ink in which the polymer electrolyte is dispersed in a solvent. Is applied to a transfer sheet and dried.
At this time, as a coating method, a doctor blade method, a dipping method, a screen printing method, a roll coating method, a spray method, or the like can be used.

As a substrate in the method for producing an electrode catalyst layer, a gas diffusion layer and a transfer sheet can be used. As the gas diffusion layer, a material having gas diffusibility and conductivity can be used. The transfer sheet may be any material that has good transferability. Moreover, you may form an electrode catalyst layer directly in a solid polymer electrolyte membrane.
When a transfer sheet is used as the substrate, the electrode catalyst layer is bonded to the solid polymer electrolyte membrane, and then the transfer sheet is peeled off to form a membrane electrode assembly having electrode catalyst layers on both sides of the solid polymer electrolyte membrane. Can do. Since the membrane / electrode assembly has a convex structure 31a on the solid polymer electrolyte membrane 31, as shown in FIG.

Next, a fuel cell using a solid polymer electrolyte membrane will be described.
[Polymer fuel cell]
FIG. 4 shows an exploded schematic view of the polymer electrolyte fuel cell according to the embodiment of the present invention. In the polymer electrolyte fuel cell, the gas diffusion layer 405 on the air electrode side and the gas diffusion layer 404 on the fuel electrode side are arranged to face the electrode catalyst layer 402 and the electrode catalyst layer 403 of the membrane electrode assembly 411. The Thus, an air electrode (hereinafter sometimes referred to as a cathode) 407 and a fuel electrode (hereinafter also referred to as an anode) 406 are formed. A pair of separators 410 made of a conductive and impervious material is disposed, which includes a gas flow passage 408 for gas flow and a cooling water flow passage 409 for cooling water flow on the opposing main surface. For example, hydrogen gas is supplied as a fuel gas from the gas flow path 408 of the separator 410 on the fuel electrode side. On the other hand, from the gas flow path 408 of the separator 410 on the air electrode side, for example, a gas containing oxygen is supplied as the oxidant gas. An electromotive force can be generated between the fuel electrode and the air electrode by causing an electrode reaction between hydrogen and oxygen gas of the fuel gas in the presence of the catalyst.

  The solid polymer electrolyte membrane 401 having a concavo-convex structure may be arranged on the cathode 407 side or the anode 406 side, but is preferably arranged on the anode 406 side. preferable. This is because the anode 406 is easily dried because moisture moves to the cathode side due to the accompanying water, and the solid polymer electrolyte membrane 401 and the electrode catalyst layer 402 on the anode 406 side are easily separated.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.
2.1 g of sulfonated polyetheretherketone and 0.315 g of 1,4-benzenemethanol (Tokyo Kasei Kogyo Co., Ltd.) as a crosslinking agent were mixed and dissolved in γ-butyrolactone.

(Example)
(Preparation of solid polymer electrolyte membrane with uneven structure)
By machining, a three-dimensional structure line pattern having a height of 5 μm and a pitch of 1 mm is prepared in a central 5 cm ² region of a 25 cm ² glass substrate. On the machined glass substrate, a sulfonated polyetheretherketone solution dissolved in γ-butyrolactone is cast. After vacuum drying at 40 ° C. for 1 h, 90 ° C. for 1 h, and 120 ° C. for 3 h, the resulting membrane was heated and pressed to proceed the reaction to obtain a proton conductive polymer electrolyte.
The hot pressing conditions were a press temperature of 120 ° C., a press time of 3 hours, and a press pressure of 80 kgf / cm ² . When the obtained solid polymer electrolyte membrane was peeled off and immersed in γ-butyrolactone, it was confirmed that it was crosslinked because it did not dissolve. The film thickness was adjusted to 25 μm.

(Comparative example)
(Preparation of a solid polymer electrolyte membrane having no uneven structure)
A sulfonated polyetheretherketone solution dissolved in γ-butyrolactone is cast on a 25 cm ² glass substrate. After vacuum drying at 40 ° C. for 1 h, 90 ° C. for 1 h, and 120 ° C. for 3 h, the resulting membrane was heated and pressed to proceed the reaction to obtain a proton conductive polymer electrolyte.
The hot pressing conditions were a press temperature of 130 ° C., a press time of 3 hours, and a press pressure of 80 kgf / cm ² . When the obtained solid polymer electrolyte membrane was peeled off and immersed in γ-butyrolactone, it was confirmed that it was crosslinked because it did not dissolve. The film thickness was adjusted to 25 μm.

(Adjustment of electrode catalyst ink)
A platinum-supported carbon catalyst (trade name: TEC10E50E, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) having a platinum support amount of 50% by mass and a 20% by mass polymer electrolyte dispersion solution (Nafion: registered trademark, manufactured by Dupont) are mixed in a solvent. Then, the dispersion treatment was performed using a planetary ball mill (trade name: Pulverisette 7, manufactured by Fritsch). Ball mill pots and balls made of zirconia were used.
An electrode catalyst ink was prepared by setting the composition ratio of the starting material to 2: 1 by mass ratio of platinum-supported carbon particles and Nafion (registered trademark, manufactured by Dupont).

(Production of electrode catalyst layer)
The electrode catalyst layer ink was applied on a PTFE (Polytetrafluoroethylene; polytetrafluoroethylene) substrate and coated with a doctor blade. The coated electrode catalyst layer was produced by drying at 60 ° C. for 5 minutes.
The thickness of the electrode catalyst layer was adjusted so that the amount of platinum supported was about 0.3 mg / cm ^2, and the electrode area of the electrode catalyst layer was cut so as to be a square of 5 cm ² .

(Production of membrane electrode assembly)
A transfer sheet is placed so that the electrode catalyst layer cut into a 5 cm ² square faces both surfaces of the solid polymer electrolyte membrane having a concavo-convex structure, and hot pressing is performed for 30 minutes at 140 ° C. and 150 kgf / cm ^2. A membrane electrode assembly was produced.
(Comparison with a solid polymer electrolyte membrane having an uneven structure)
The membrane electrode assembly was bonded so as to sandwich a carbon cloth as a gas diffusion layer, and installed in a power generation evaluation cell (manufactured by NF Circuit Design Block). This was measured using a fuel cell measuring apparatus (manufactured by NF Circuit Design Block Co., Ltd.) at a cell temperature of 80 ° C. under the following operating conditions. Hydrogen was used as the fuel gas and air was used as the oxidant gas at 500 cc / min and 1000 cc / min, respectively. The humidifier was an anode 100% RH and a cathode 100% RH.
As a result, in the membrane / electrode assembly using the solid polymer electrolyte membrane having the concavo-convex structure, the resistance at the interface was lowered, the cell resistance was lowered, and the power generation characteristics were improved.

  INDUSTRIAL APPLICABILITY The present invention can be used for a polymer electrolyte fuel cell used for an electric vehicle, a mobile phone, a vending machine, an underwater robot, a submarine, a spacecraft, an underwater vehicle, a power source for an underwater base, and the like. It is particularly useful for in-vehicle solid polymer electrolyte membranes that require power generation characteristics with low humidification.

DESCRIPTION OF SYMBOLS 10 Base material 11 Concave part of base material 12 Convex part of base material 21 Glass base material 22 Coating film 23 Solid polymer electrolyte membrane 31 having a convex part 31 Solid polymer electrolyte film 31a having a convex part Convex part 32 Electrode catalyst layer 33 Electrode catalyst layer 401 Solid polymer electrolyte membrane 402 Electrode catalyst layer 403 Electrode catalyst layer 404 Gas diffusion layer 405 Gas diffusion layer 406 Fuel electrode (anode)
407 Air electrode (cathode)
408 Gas channel 409 Cooling water channel 410 Separator 411 Membrane electrode assembly

Claims (17)

In a crosslinked polymer electrolyte membrane containing a crosslinked polymer obtained by crosslinking reaction of a proton conductive polymer and a crosslinking agent via a portion other than a proton acid group,
A solid polymer electrolyte membrane comprising at least one concave portion or convex portion on at least one surface, wherein the proton-conductive polymer has a structural unit represented by the following general formula (1).

[In the general formula (1), A represents an electron-withdrawing group, and B represents an electron-donating group. X, Y, and Z are each 0 or 1, indicating that the sum of X, Y, and Z is an integer from 1 to 3. ]   The solid polymer electrolyte membrane according to claim 1, wherein the groove portion of the concave portion or the protruding portion of the convex portion has a shape extending linearly in plan view.   The solid polymer electrolyte membrane according to claim 2, wherein the concave portion having the linearly extending shape or the convex portion having the linearly extending shape is repeatedly arranged.   The solid polymer electrolyte membrane according to any one of claims 1 to 3, wherein A in the general formula (1) is -O-.   In the said General formula (1), B is -CO-, The solid polymer electrolyte membrane as described in any one of Claims 1-4 characterized by the above-mentioned.   6. The solid polymer electrolyte membrane according to claim 1, wherein the proton-conducting polymer has a hydrogen ion exchange capacity of 0.5 meq / g or more and 5 meq / g or less. .   The solid polymer electrolyte membrane according to any one of claims 1 to 6, wherein the crosslinking agent has at least two methylol groups in the molecule of the crosslinking agent.   8. The depth of the concave portion or the height of the convex portion is 1 μm or more, and is 1/5 or less of the thickness of the solid polymer electrolyte membrane. The solid polymer electrolyte membrane described in 1. Crosslinking the proton conductive polymer represented by the following general formula (2) and the crosslinking agent to the surface of the base material having at least one concave portion or convex portion on at least one surface through a portion other than the proton acid group. Applying a coating liquid containing a crosslinked polymer obtained by reaction to form a coating film;
Heating the coating film to form a solid polymer electrolyte membrane;
And a step of peeling the solid polymer electrolyte membrane from the base material. A method for producing a solid polymer electrolyte membrane, comprising:

[In the general formula (2), A represents an electron-withdrawing group, and B represents an electron-donating group. X, Y, and Z are each 0 or 1, indicating that the sum of X, Y, and Z is an integer from 1 to 3. ]   The method for producing a solid polymer electrolyte membrane according to claim 9, wherein the groove portion of the concave portion or the protruding portion of the convex portion has a shape extending linearly in plan view.   The method for producing a solid polymer electrolyte membrane according to claim 10, wherein the concave portion having the linearly extending shape or the convex portion having the linearly extending shape is repeatedly arranged.   The method for producing a solid polymer electrolyte membrane according to any one of claims 9 to 11, wherein a temperature for heating the coating film is 60 ° C or higher and 250 ° C or lower.   13. The width of the concave portion or the convex portion is 50 μm or more, and the depth of the concave portion or the height of the convex portion is 1 μm or more and 1000 μm or less. 13. A method for producing a solid polymer electrolyte membrane according to the above.   The method for producing a solid polymer electrolyte membrane according to any one of claims 9 to 13, wherein the concave portion or the convex portion is formed by machining using a cutting blade.   The method for producing a solid polymer electrolyte membrane according to any one of claims 9 to 14, wherein the substrate is a glass substrate or a silicon wafer.   A membrane electrode assembly comprising the solid polymer electrolyte membrane according to any one of claims 1 to 15.   A fuel cell comprising the solid polymer electrolyte membrane according to any one of claims 1 to 15.

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