JP2010267628A - Membrane-electrode structure and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a membrane-electrode structure capable of being downsized by improving the protection of a solid polymer electrolyte membrane, and to provide a fuel cell. <P>SOLUTION: In the membrane-electrode structure, a solid polymer electrolyte membrane 22 is sandwiched by a pair of gas diffusion electrode layers 24, 26 comprising catalyst layers 28, 30 and gas diffusion layers 32, 34 so that the catalyst layers 28, 30 come into contact with both surfaces of the solid polymer electrolyte membrane 22; and the solid polymer electrolyte membrane 22 is covered with one of the gas diffusion electrode layer 26 and a seal member 62 in the shape of a frame provided outside the gas diffusion electrode layer 26, and at the same time bulges out of the other gas diffusion electrode layer 24. The end surface of the catalyst layer 30 of the one of the gas diffusion electrode layers 26 is installed in a position shifted from the end surface of the catalyst layer 28 of the other gas diffusion electrode layer 24. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a membrane / electrode structure in which a pair of gas diffusion electrode layers are provided on both sides of a solid polymer electrolyte membrane or a fuel cell in which the membrane / electrode structure is sandwiched between a pair of separators. The present invention relates to a membrane / electrode structure or a fuel cell having a shape in which an electrolyte membrane protrudes from one gas diffusion electrode layer.

  Some fuel cells have a structure in which a membrane / electrode structure is sandwiched between a pair of separators to form a fuel cell, and a plurality of the fuel cells are stacked.

  An example of this membrane / electrode structure will be described with reference to FIG. 9. In this figure, 1 indicates a membrane / electrode structure, and this membrane / electrode structure 1 is provided on a solid polymer electrolyte membrane 2 and on both sides thereof. The gas diffusion electrode layers 3 and 4 (the anode side gas diffusion electrode layer 3 and the cathode side gas diffusion electrode layer 4) are configured. The gas diffusion electrode layers 3 and 4 are respectively formed with catalyst layers 5 and 6 and gas diffusion layers 7 and 8, and the catalyst layers 5 and 6 are in contact with both surfaces of the solid polymer electrolyte membrane 2. ing. As shown in FIG. 9, the solid polymer electrolyte membrane 2 is formed to have a larger planar dimension than the gas diffusion electrode layers 3 and 4 on both sides thereof, and the solid polymer electrolyte is disposed on the outer periphery of the gas diffusion electrode layers 3 and 4. The film 2 has a protruding structure. A pair of separators (not shown) are disposed on both surfaces of the membrane / electrode structure 1 configured as described above, and a ring-shaped seal member (not shown) is set on the peripheral surface side of each separator. Thus, a fuel battery cell is configured.

  In the fuel cell configured as described above, when fuel gas (for example, hydrogen gas) is supplied to the reaction surface of the anode-side gas diffusion electrode layer 3, hydrogen is generated in the catalyst layer 5 of the anode-side gas diffusion electrode layer 3. It is ionized and moves to the catalyst layer 6 side of the cathode side gas diffusion electrode layer 4 through the solid polymer electrolyte membrane 2. Electrons generated during this time are taken out to an external circuit and used as direct current electric energy. Since the oxidant gas (for example, air containing oxygen) is supplied to the cathode side gas diffusion electrode layer 4, hydrogen ions, electrons, and oxygen react to generate water.

  As other known membrane / electrode structures, there are those shown in FIGS. The membrane / electrode structure 1 shown in FIG. 10 has a configuration in which the solid polymer electrolyte membrane 2 and the gas diffusion electrode layers 3 and 4 on both sides thereof are formed in the same size, and are laminated with their end faces aligned. (See Patent Document 1). The membrane / electrode structure 1 shown in FIG. 11 is provided with gaskets 10 and 11 between the solid polymer electrolyte membrane 2 and the gas diffusion electrode layers 3 and 4, respectively. The end surface side of the molecular electrolyte membrane 2 is sealed (see Patent Document 2).

US Pat. No. 5,176,966 US Pat. No. 5,464,700

However, the conventional membrane / electrode structure has the following problems.
In recent years, demands for reducing the size of fuel cells have increased, and in order to meet the demands, thin polymer electrolyte membranes for membrane / electrode structures tend to be used. Accordingly, if the thickness of the solid polymer electrolyte membrane 2 in the membrane / electrode structure 1 shown in FIG. 9 is reduced, the portions protruding from the gas diffusion electrode layers 3 and 4 on both sides may be weakened in strength. is there.
Furthermore, in the membrane / electrode structure 1 shown in FIG. 9, when the solid polymer electrolyte membrane 2 is laminated, the stress received from the outer peripheral ends of the catalyst layers 5 and 6 provided on both sides is the same on the front and back sides. Concentrating on the place may cause an excessive burden.

  In the membrane / electrode structure 1 shown in FIG. 10, the end surface positions of the gas diffusion electrode layers 3, 4 provided on both sides of the solid polymer electrolyte membrane 2 are the same as the end surface positions of the solid polymer electrolyte membrane 2. In addition, since the end surfaces of the gas diffusion electrode layers 3 and 4 are provided close to each other, the reaction gases supplied to the gas diffusion electrode layers 3 and 4 easily circulate from the end surface of the solid polymer electrolyte membrane 2 and diffuse. Therefore, the reaction gases may be mixed in the vicinity of the end surfaces of the respective gas diffusion electrode layers 3 and 4. Furthermore, since the end face positions of the gas diffusion electrode layers 3 and 4 are close, there is a risk of an electrical short circuit.

Further, in the membrane / electrode structure 1 shown in FIG. 11, since gaskets 10 and 11 are provided on the end side between the gas diffusion electrode layers 3 and 4 and the solid polymer electrolyte membrane 2, Thickness will increase. Further, since the gas diffusion electrode layers 3 and 4 are deformed by bringing them into contact with the gaskets 10 and 11 and the flatness is impaired, a process for preventing this is required and the process becomes complicated.
Accordingly, the present invention provides a membrane / electrode structure and a fuel cell that can reduce the thickness of the solid polymer electrolyte membrane by enhancing the protection of the solid polymer electrolyte membrane.

(1) In order to solve the above-mentioned problems, the membrane / electrode structure of the present invention has a solid polymer electrolyte membrane (for example, the solid polymer electrolyte membrane 22 in the embodiment) as a catalyst layer (for example, a catalyst in the embodiment). Layers 28, 30) and a gas diffusion layer (for example, gas diffusion layers 32, 34 in the embodiment), a pair of gas diffusion electrode layers (for example, gas diffusion electrode layers 24, 26 in the embodiment), The catalyst layer is sandwiched between both surfaces of the molecular electrolyte membrane, and the solid polymer electrolyte membrane is covered with one gas diffusion electrode layer (for example, the cathode side gas diffusion electrode layer 26 in the embodiment). A membrane / electrode structure (for example, the membrane / electrode structure in the embodiment) that protrudes from the other gas diffusion electrode layer (for example, the anode-side gas diffusion electrode layer 24 in the embodiment). A body 20), the end face of the catalyst layer of one gas diffusion electrode layer, characterized in that the position relative to the end face of the catalyst layer of the other gas diffusion electrode layer are disposed shifted.
If constituted in this way, stress from each catalyst layer end face in contact with the solid polymer electrolyte membrane can be dispersed from both sides of the solid polymer electrolyte membrane without being concentrated in one place of the solid polymer electrolyte membrane, It is possible to prevent stress from concentrating on the solid polymer electrolyte membrane. In addition, since the solid polymer electrolyte membrane is covered with one gas diffusion electrode layer, the solid polymer electrolyte membrane can be protected to prevent damage to the solid polymer electrolyte membrane. Furthermore, since the end surfaces of the respective gas diffusion electrode layers are located at a distance from each other, there is no possibility that the reaction gases supplied to the respective gas diffusion electrode layers are mixed at the end surface position of the gas diffusion electrode layer. There is no risk of a short circuit. The one catalyst layer only needs to be installed with a position shifted with respect to the other catalyst layer, and may be the same size or different sizes.

(2) An adhesive layer (for example, the adhesive layer 36 in the embodiment) is formed on the outer periphery of the catalyst layer (for example, the catalyst layer 30 in the embodiment) of the gas diffusion electrode layer covering the solid polymer electrolyte membrane, and the adhesive layer The solid polymer electrolyte membrane is covered with a peripheral edge.
By forming the adhesive layer in this way, the solid polymer electrolyte membrane and the gas diffusion layer are integrated, and the strength in the thickness direction of the solid polymer electrolyte membrane can be supported and reinforced by the gas diffusion layer. -The handleability of the electrode structure is improved. Further, since the adhesive layer covers the inner catalyst layer, it performs a sealing function, thereby further reducing the possibility of mixing the reaction gas. An adhesive layer may also be formed on the outer periphery of the catalyst layer of the other gas diffusion electrode layer.

(3) The end surface of the catalyst layer of the gas diffusion electrode layer covering one surface of the solid polymer electrolyte membrane is inside the end surface of the other catalyst layer.
Thus, an adhesive layer can be formed outside the end face of the catalyst layer (one catalyst layer) of the gas diffusion electrode layer (one gas diffusion electrode layer) covering the one surface. As a result, an adhesive layer is formed at a position facing the end face of the other catalyst layer in the one gas diffusion electrode layer, so that the strength of the solid polymer electrolyte membrane at this position is reinforced. The Therefore, the solid polymer electrolyte membrane can be protected from the stress applied to the solid polymer electrolyte membrane from the end face of the other catalyst layer. In addition, since the adhesive layer is formed on the portion of the catalyst layer that does not contribute to power generation, the power generation efficiency can be maintained and the use of an expensive catalyst layer can be minimized. The one catalyst layer is preferably formed to be slightly smaller in size than the other catalyst layer.

(4) According to another membrane / electrode structure of the present invention, the solid polymer electrolyte membrane is formed of a pair of gas diffusion electrode layers each including a catalyst layer and a gas diffusion layer, and the catalyst is formed on both surfaces of the solid polymer electrolyte membrane. The solid polymer electrolyte membrane is sandwiched between the gas diffusion electrode layers and a frame-shaped seal member provided outside the gas diffusion electrode layer (for example, the frame in the embodiment). A membrane / electrode structure that is covered with the member 62) and protrudes from the other gas diffusion electrode layer, wherein the end face of the catalyst layer of the one gas diffusion electrode layer is the other gas diffusion electrode. The position of the layer is shifted with respect to the end face of the catalyst layer.
If it does in this way, while maintaining electric power generation efficiency to the same extent as previous embodiment, the amount required for an expensive gas diffusion layer can be reduced, and there is an effect that cost reduction can be attained. Furthermore, there is an effect that the gas diffusion layer can be sealed by the frame-shaped sealing member.

(5) The frame-shaped sealing member (for example, the frame-shaped member 72 in the embodiment) is formed so as to cover an end surface of the solid polymer electrolyte membrane.
In this way, not only the gas diffusion layer but also the catalyst layer and the solid polymer electrolyte membrane can be sealed by the frame-shaped sealing member, so that the reaction gas can be further prevented from being mixed. is there. In addition, there is an effect that moisture can be prevented from evaporating from the end face of the solid polymer electrolyte membrane.

(6) The fuel cell of the present invention is sandwiched between a pair of separators (for example, the separators 82 and 84 in the embodiment), and is formed in a gas flow path formed between the pair of separators and the membrane / electrode structure. A fuel cell (for example, the fuel cell 90 in the embodiment) to which each reaction gas (for example, the fuel gas 87 and the oxidant gas 89 in the embodiment) is supplied, and the reaction gas having a higher pressure among the reaction gases. The surface of the solid polymer electrolyte membrane that protrudes from the gas diffusion electrode layer is opposed to the separator to which is supplied (for example, the separator 82 in the embodiment).
As a result, the reaction gas having a higher pressure is supplied to the surface of the solid polymer electrolyte membrane that protrudes from the gas diffusion electrode layer. The reaction gas presses the surface of the solid polymer electrolyte membrane that protrudes from the gas diffusion electrode layer, and the solid polymer electrolyte membrane and the gas diffusion electrode layer that covers one surface of the solid polymer electrolyte membrane adhere to each other. Thus, the solid polymer electrolyte membrane can be prevented from peeling off from the gas diffusion electrode layer.

(1) Since the stress from the end face of each catalyst layer in contact with the solid polymer electrolyte membrane can be dispersed from both sides of the solid polymer electrolyte membrane without concentrating on one place of the solid polymer electrolyte membrane, It is possible to prevent stress from concentrating on the polymer electrolyte membrane. In addition, since the solid polymer electrolyte membrane is covered with one gas diffusion electrode layer, the solid polymer electrolyte membrane can be protected to prevent damage to the solid polymer electrolyte membrane. Therefore, it is possible to reduce the thickness of the solid polymer electrolyte membrane. Furthermore, since the end surfaces of the respective gas diffusion electrode layers are located at separate positions, there is no possibility that the reaction gases will be mixed at the end surface positions of the gas diffusion electrode layers, and there is no possibility of an electrical short circuit.
(2) The solid polymer electrolyte membrane and the gas diffusion layer are integrated, and the strength of the solid polymer electrolyte membrane in the thickness direction can be supported and reinforced by the gas diffusion layer, making the membrane / electrode structure easy to handle. In order to improve, further thinning can be achieved. Further, since the adhesive layer covers the inner catalyst layer, a sealing function is achieved, thereby preventing reaction gas from being mixed.
(3) Since an adhesive layer can be formed at a position facing the end face of the other catalyst layer in the gas diffusion electrode layer covering one surface of the solid polymer electrolyte membrane, the solid polymer at this position The strength of the electrolyte membrane is reinforced.
Therefore, the solid polymer electrolyte membrane can be protected from the stress applied to the solid polymer electrolyte membrane from the end face of the other catalyst layer. In addition, since the adhesive layer is formed on the portion of the catalyst layer that does not contribute to power generation, the power generation efficiency can be maintained and the use of an expensive catalyst layer can be minimized. Can be achieved.
(4) While maintaining the power generation efficiency, the amount necessary for the expensive gas diffusion layer can be reduced, and the cost can be reduced. Furthermore, there is an effect that the gas diffusion layer can be sealed by the frame-shaped sealing member.
(5) Since not only the gas diffusion layer but also the catalyst layer and the solid polymer electrolyte membrane can be sealed by the frame-shaped sealing member, there is an effect that mixing of the reaction gas can be further prevented. In addition, there is an effect that moisture can be prevented from evaporating from the end face of the solid polymer electrolyte membrane.
(6) A surface where the reaction gas protrudes from the gas diffusion electrode layer of the solid polymer electrolyte membrane is pressed to form a solid polymer electrolyte membrane and a gas diffusion electrode layer covering one surface of the solid polymer electrolyte membrane. Since it acts so that it adheres, it can prevent that a solid polymer electrolyte membrane peels from a gas diffusion electrode layer, and can achieve a still thinner film.

FIG. 1 is a cross-sectional view of a membrane / electrode structure in a first embodiment of the present invention. FIG. 2 is a cross-sectional view of a membrane / electrode structure in a second embodiment of the present invention. FIG. 3 is a cross-sectional view of a membrane / electrode structure in a third embodiment of the present invention. FIG. 4 is a cross-sectional view of a membrane / electrode structure in a fourth embodiment of the present invention. FIG. 5 is a cross-sectional view of a membrane / electrode structure in a fifth embodiment of the present invention. FIG. 6 is a cross-sectional view of a fuel cell using the membrane / electrode structure according to the first embodiment of the present invention. FIG. 7 is a cross-sectional view of a fuel cell using a membrane / electrode structure according to a fifth embodiment of the present invention. FIG. 8 is a plan view of the membrane / electrode structure according to the first embodiment of the present invention. FIG. 9 is a sectional view of a conventional membrane / electrode structure. FIG. 10 is a sectional view of a conventional membrane / electrode structure. FIG. 11 is a cross-sectional view of a conventional membrane / electrode structure.

  Hereinafter, a membrane / electrode structure and a fuel cell according to embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a membrane / electrode structure 20 according to the first embodiment of the present invention. The membrane / electrode structure 20 includes a solid polymer electrolyte membrane 22, and an anode side gas diffusion electrode layer 24 and a cathode side gas diffusion electrode layer 26 disposed with the solid polymer electrolyte membrane 22 interposed therebetween. Catalyst layers 28 and 30 and gas diffusion layers 32 and 34 are formed on the anode-side gas diffusion electrode layer 24 and the cathode-side gas diffusion electrode layer 26, respectively. The catalyst layers 28 and 30 are formed on the solid polymer electrolyte membrane 22. Are in contact with both sides. The catalyst layers 28 and 30 are made of a material whose main component is platinum, the gas diffusion layers 32 and 34 are made of porous carbon cloth or porous carbon paper, which is a porous layer, and the solid polymer electrolyte membrane. 22 is formed of a perfluorosulfonic acid polymer (fluorine resin). In addition, as a material of the solid polymer electrolyte membrane 22, a material mainly composed of a hydrocarbon resin can be used. The formation method of the catalyst layers 28 and 30 is not particularly limited, and may be formed by applying or vapor-depositing a catalyst paste on the surfaces of the gas diffusion layers 32 and 34, or may be formed on another member (for example, a film). The catalyst layer may be formed by transferring it to a solid polymer electrolyte membrane.

As shown in FIG. 8, only one surface of the solid polymer electrolyte membrane 22 protrudes from the anode-side gas diffusion electrode layer 24, and the other surface is the cathode-side gas diffusion electrode layer 26. Covered. As described above, since the plane dimensions of the gas diffusion electrode layers 24 and 26 arranged on both sides of the solid polymer electrolyte membrane 22 are made different from each other, only one surface of the solid polymer electrolyte membrane 22 protrudes. The end surfaces of the layers 24 and 26 are provided at positions separated from each other via the solid polymer electrolyte membrane 22.
For this reason, it is possible to reduce the possibility that the reaction gases (fuel gas and oxidant gas) supplied to the gas diffusion electrode layers 24 and 26 are mixed in the vicinity of the end surface of the solid polymer electrolyte membrane 22 and electrically. A short circuit can be prevented. Further, since one surface of the solid polymer electrolyte membrane 22 is covered with the cathode-side gas diffusion electrode layer 26, the solid polymer electrolyte membrane 22 can be protected to prevent the solid polymer electrolyte membrane 22 from being damaged. it can.

  In the present embodiment, the planar size of the catalyst layer 28 of the anode-side gas diffusion electrode layer 24 and the catalyst layer 30 of the cathode-side gas diffusion electrode layer 26 are different, and the catalyst layers 28, 30 are different from each other. It is installed by shifting the position of the end face. As a result, stress from the end faces of the catalyst layers 28 and 30 contacting the solid polymer electrolyte membrane 22 can be dispersed from both sides of the solid polymer electrolyte membrane without being concentrated in one place. It is possible to prevent stress from being concentrated on 22.

  The catalyst layer 30 of the cathode side gas diffusion electrode layer 26 is formed to have a smaller planar dimension than the catalyst layer 28 of the anode side gas diffusion electrode layer 24, and an adhesive layer is provided on the outer peripheral side of the catalyst layer 30. 36 is formed, and the peripheral portion of the solid polymer electrolyte membrane 22 is covered with the adhesive layer 36. Since the adhesive layer 36 is thus provided, the solid polymer electrolyte membrane 22 and the cathode-side gas diffusion electrode layer 26 are integrated, and the solid polymer electrolyte membrane 22 can be supported and reinforced by the gas diffusion layer. -The handleability of the electrode structure is improved. Further, since the adhesive layer 36 covers the catalyst layer 30 on the inside, a sealing function can be achieved, whereby the risk of mixing the reaction gas can be further reduced, and the possibility of a short circuit can be more reliably eliminated. Furthermore, since the adhesive layer 36 is disposed on the solid polymer electrolyte membrane 22 on the opposite side of the portion in contact with the end face of the catalyst layer 28, the solid polymer electrolyte membrane 22 is free from stress from the end face of the catalyst layer 28. The molecular electrolyte membrane 22 can be protected. Note that the adhesive used for the adhesive layer 36 is preferably a fluorine-based or silicon-based material.

  Next, the membrane / electrode structure in the second embodiment of the present invention will be described. FIG. 2 is a cross-sectional view of the membrane / electrode structure 40 according to the second embodiment of the present invention. In addition, about the member corresponding to 1st Embodiment below, the same number is attached | subjected and the description is abbreviate | omitted suitably. This embodiment is different in that the end face of the catalyst layer 30 of the cathode side gas diffusion electrode layer 26 covering the surface of the solid polymer electrolyte membrane 22 is outside the end face of the other catalyst layer 28. In this way, the adhesion effect of the peripheral edge portion of the solid polymer electrolyte membrane 22 can be kept high. Further, as in the first embodiment, it is possible to reduce the possibility that the reaction gas (fuel gas, oxidant gas) is mixed in the vicinity of the end surface of the solid polymer electrolyte membrane 22, and to prevent an electrical short circuit. it can. Further, the solid polymer electrolyte membrane 22 can be protected to prevent the solid polymer electrolyte membrane 22 from being damaged. In addition, since the stress from the end faces of the catalyst layers 28 and 30 contacting the solid polymer electrolyte membrane 22 can be dispersed from both sides of the solid polymer electrolyte membrane without concentrating on one place, the solid polymer electrolyte membrane It is possible to prevent stress from being concentrated on 22.

Next, a membrane / electrode structure according to a third embodiment of the present invention will be described. FIG. 3 is a cross-sectional view of the membrane / electrode structure 50 according to the third embodiment of the present invention. In this embodiment, the adhesive layer 36 is formed on the outer periphery of the catalyst layer 30 of the cathode side gas diffusion electrode layer 26, and the adhesive layer 52 is also formed on the outer periphery of the catalyst layer 28 of the anode side gas diffusion electrode layer 24. Is different. In this way, the adhesive force between the solid polymer electrolyte membrane 22 and the cathode side gas diffusion electrode layer 26 can be increased by the adhesive layer 36, and the solid polymer electrolyte membrane 22 and the anode side gas diffusion electrode layer 24 can be There is an effect that the adhesive force can be increased by the adhesive layer 52. Further, as in the first embodiment, it is possible to reduce the possibility that the reaction gas (fuel gas, oxidant gas) is mixed in the vicinity of the end surface of the solid polymer electrolyte membrane 22, and to prevent an electrical short circuit. it can. Further, the solid polymer electrolyte membrane 22 can be protected to prevent the solid polymer electrolyte membrane 22 from being damaged. In addition, since the stress from the end faces of the catalyst layers 28 and 30 contacting the solid polymer electrolyte membrane 22 can be dispersed from both sides of the solid polymer electrolyte membrane without concentrating on one place, the solid polymer electrolyte membrane It is possible to prevent stress from being concentrated on 22.
In the above embodiment, the case where the planar size of the cathode side gas diffusion electrode layer 26 is made larger than that of the anode side gas diffusion electrode layer 24 has been described. The planar dimension of the side gas diffusion electrode layer 26 may be reduced.

  Next, a membrane / electrode structure according to a fourth embodiment of the present invention will be described. FIG. 4 is a cross-sectional view of a membrane / electrode structure 60 according to the fourth embodiment of the present invention. In this embodiment, the plane dimension of the gas diffusion layer 34 of the cathode side gas diffusion electrode layer 26 is made smaller than the plane dimension of the gas diffusion layer 32 of the anode side gas diffusion electrode layer 24, and the adhesive layer 36 of the gas diffusion layer 34 is used. The difference is that the portion opposed to is replaced with a frame-shaped seal member (frame-shaped member) 62. If it does in this way, while maintaining electric power generation efficiency to the same extent as previous embodiment, the amount required for expensive gas diffusion layer 34 can be reduced, and there is an effect that cost reduction can be attained. Further, there is an effect that the gas diffusion layer 34 can be sealed by the frame member 62. Further, as in the first embodiment, it is possible to reduce the possibility that the reaction gas (fuel gas, oxidant gas) is mixed in the vicinity of the end surface of the solid polymer electrolyte membrane 22, and to prevent an electrical short circuit. it can. Further, the solid polymer electrolyte membrane 22 can be protected to prevent the solid polymer electrolyte membrane 22 from being damaged. In addition, since the stress from the end faces of the catalyst layers 28 and 30 contacting the solid polymer electrolyte membrane 22 can be dispersed from both sides of the solid polymer electrolyte membrane without concentrating on one place, the solid polymer electrolyte membrane It is possible to prevent stress from being concentrated on 22.

  Next, a membrane / electrode structure according to a fifth embodiment of the present invention will be described. FIG. 5 is a cross-sectional view of a membrane / electrode structure 70 according to a fifth embodiment of the present invention. This embodiment is different in that a frame member 72 is provided so as to cover not only the outer periphery of the gas diffusion layer 34 of the cathode side gas diffusion electrode layer 26 but also the end surfaces of the adhesive layer 36 and the solid polymer electrolyte membrane 22. Is. In this case, not only the gas diffusion layer 34 but also the catalyst layer 30 and the solid polymer electrolyte membrane 22 can be sealed by the frame member 72, so that the reaction gas can be further prevented from mixing. effective. In addition, there is an effect that moisture can be prevented from evaporating from the end face of the solid polymer electrolyte membrane 22. Further, as in the first embodiment, it is possible to reduce the possibility that the reaction gas (fuel gas, oxidant gas) is mixed in the vicinity of the end surface of the solid polymer electrolyte membrane 22, and to prevent an electrical short circuit. it can. Further, the solid polymer electrolyte membrane 22 can be protected to prevent the solid polymer electrolyte membrane 22 from being damaged. In addition, since the stress from the end faces of the catalyst layers 28 and 30 contacting the solid polymer electrolyte membrane 22 can be dispersed from both sides of the solid polymer electrolyte membrane without concentrating on one place, the solid polymer electrolyte membrane It is possible to prevent stress from being concentrated on 22.

  In the fourth and fifth embodiments, the case where the planar dimension of the cathode-side gas diffusion electrode layer 26 is made smaller than the anode-side gas diffusion electrode layer 24 has been described. The planar dimension of the cathode side gas diffusion electrode layer 26 may be larger than that of the diffusion electrode layer 24. If the positions of the end faces of the catalyst layers 28 and 30 are shifted from each other, the catalyst layers 28 and 30 may be formed to have the same dimensions.

  A fuel cell using the membrane / electrode structure described above will be described. FIG. 6 is a cross-sectional view of a fuel cell 80 using the membrane / electrode structure 20 according to the first embodiment of the present invention. The fuel cell 80 includes the membrane / electrode structure 20 and a pair of separators 82 and 84 sandwiching the membrane / electrode structure 20. The separators 82 and 84 are formed with channel grooves 86 and 88 for allowing the reaction gases to flow therethrough. In this embodiment, a fuel gas (hydrogen) 87 is circulated in the flow channel 86 of the separator 82, and an oxidant gas (air) 89 is circulated in the flow channel 88 of the separator 84.

  The fuel gas 87 is set to have a pressure higher than that of the oxidant gas 89. As a result, the high-pressure fuel gas 87 is supplied to the surface of the solid polymer electrolyte membrane 22 that protrudes from the anode-side gas diffusion electrode layer 24, and this fuel gas 87 presses the surface of the solid polymer electrolyte membrane 22 that protrudes. To do. Since the solid polymer electrolyte membrane 22 itself is thin and expands and contracts due to moisture contained in the solid polymer electrolyte membrane 22, it may be damaged if no measures are taken. However, in the present embodiment, as described above, the surface from which the fuel gas 87 protrudes is pressed so that the solid polymer electrolyte membrane 22 and the gas diffusion electrode layer 26 are brought into close contact with each other. The strength of the membrane 22 can be further increased, and damage to the solid polymer electrolyte membrane 22 can be prevented.

  Further, a seal member 90 is provided between a portion of the solid polymer electrolyte membrane 22 protruding from the anode side gas diffusion electrode layer 24 and the separator 82, and between the separator 82 and the separator 84 outside the seal member 90. A seal member 92 is provided. Since the seal members 90 and 92 have a substantially circular cross section, they are compressed in the thickness direction when the fuel cell 80 is formed (transformed into an elliptical cross section) to increase the degree of adhesion and exhibit high sealing performance. be able to.

  Hereinafter, fuel cells having other configurations will be described. FIG. 7 is a cross-sectional view of a fuel cell 100 using a membrane / electrode structure 70 according to a fifth embodiment of the present invention. In this case, the membrane-electrode structure 70 can be sealed to the outside by bringing the frame member 72 and the seal member 90 into close contact with each other, and the seal member 90 is attached to the solid polymer electrolyte membrane 22. Since they are not in close contact with each other, the pressing force from the seal member 90 is not applied to the solid polymer electrolyte membrane 22, and the protection of the solid polymer electrolyte membrane 22 can be further enhanced.

A membrane / electrode structure was prepared as follows. First, Nafion 112 (DuPont product name) was used as the solid polymer electrolyte membrane. The catalyst layer was prepared as follows. That is, a catalyst paste was prepared by mixing an ion conductive binder and catalyst particles made of carbon particles carrying Pt at a certain ratio. The catalyst paste was screen-printed on both surfaces of the solid polymer electrolyte membrane so that the end surfaces thereof were shifted from each other at predetermined positions, and then the catalyst paste was dried to form a catalyst layer on both surfaces of the solid polymer electrolyte membrane.
A plate material made of carbon paper was used for the gas diffusion layer, and after applying an adhesive to the peripheral portion of one gas diffusion layer, the one gas diffusion layer was bonded to the solid polymer electrolyte membrane on which the catalyst layer was formed. . Further, after the other gas diffusion layer was disposed at a predetermined position on the other surface of the solid polymer electrolyte membrane, a membrane / electrode structure was prepared by hot pressing at a high temperature for a predetermined time.

  DESCRIPTION OF SYMBOLS 20 ... Membrane / electrode structure 22 ... Solid polymer electrolyte membrane 24 ... Anode side gas diffusion electrode layer 26 ... Cathode side gas diffusion electrode layer 28, 30 ... Catalyst layer 32, 34 ... Gas diffusion layer 36 ... Contact layer 62, 72 ... Frame-shaped member (frame-shaped sealing member) 80 ... Fuel cell

Claims (3)

The solid polymer electrolyte membrane is sandwiched between a pair of gas diffusion electrode layers each including a catalyst layer and a gas diffusion layer so that the catalyst layer is in contact with both surfaces of the solid polymer electrolyte membrane,
The solid polymer electrolyte membrane is covered with one of the gas diffusion electrode layers and a frame-shaped sealing member provided outside the gas diffusion electrode layer, and is a membrane protruding from the other gas diffusion electrode layer An electrode structure,
The membrane / electrode structure according to claim 1, wherein an end face of the catalyst layer of the one gas diffusion electrode layer is disposed with a position shifted from an end face of the catalyst layer of the other gas diffusion electrode layer.   The membrane / electrode structure according to claim 1, wherein the frame-shaped sealing member is formed so as to cover an end face of the solid polymer electrolyte membrane.   A membrane / electrode structure according to claim 1 or 2 is sandwiched between a pair of separators, and each reaction gas is provided in a gas flow path formed between the pair of separators and the membrane / electrode structure. The surface of the solid polymer electrolyte membrane that protrudes from the other gas diffusion electrode layer to the separator to which the reaction gas having the higher pressure among the reaction gases is supplied. Is a fuel cell characterized by being opposed to each other.

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