JP2012018793A - Electrode-membrane-frame assembly and polymer electrolyte fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode-membrane-frame assembly capable of suppressing deterioration in power generation performance furthermore by suppressing deterioration in a polymer electrolyte membrane and an electrode layer.SOLUTION: An electrode-membrane-frame assembly includes a frame-like peroxide decomposition catalyst layer containing a peroxide decomposition catalyst, and is configured such that, in view from a thickness direction of a polymer electrolyte membrane, an inner edge of the peroxide decomposition catalyst layer is located on an inner side of an outer edge of a gas diffusion layer, and an outer edge of the peroxide decomposition catalyst layer is located on an outer side of an inner edge of a frame body.

Description

  The present invention relates to a polymer electrolyte fuel cell used as a driving source for a mobile body such as an automobile, a distributed (on-site) power generation system, a household cogeneration system, and the like, and particularly, the fuel cell is provided. The present invention relates to an electrode-membrane-frame assembly and a method for producing the same.

  Fuel cells (FC) are expected to be widely used as distributed energy systems because of their high power generation efficiency and low environmental impact. In particular, polymer electrolyte fuel cells using polymer electrolytes with proton conductivity are high in power density, low in operating temperature, and can be miniaturized. It is expected to be used in power generation systems and household cogeneration systems.

  A polymer electrolyte fuel cell is an apparatus that generates electric power and heat simultaneously by electrochemically reacting a fuel gas containing hydrogen and an oxidant gas containing oxygen such as air.

  A polymer electrolyte fuel cell is generally configured by stacking a plurality of cells and pressurizing them with a fastening member such as a bolt. One cell is configured by sandwiching a membrane electrode assembly (hereinafter referred to as MEA: Membrane-Electrode-Assembly) between a pair of plate-like conductive separators. In order to improve the handling property or to seal between the polymer electrolyte membrane and the separator, the MEA has an outer peripheral portion held by a resin frame formed into a frame shape. Here, the MEA including the frame is referred to as an electrode-membrane-frame assembly.

  The MEA is composed of a polymer electrolyte membrane whose outer peripheral portion is supported by the frame body, and a pair of electrode layers formed on both surfaces of the electrolyte membrane. One of the pair of electrode layers is an anode electrode, and the other of the pair of electrode layers is a cathode electrode. The anode electrode and the cathode electrode are composed of a catalyst layer made of platinum or the like formed on both surfaces of the polymer electrolyte membrane, and a porous and conductive gas diffusion layer formed on the catalyst layer. When the fuel gas is supplied to the anode electrode and the oxidant is supplied to the cathode electrode, an electrochemical reaction occurs, and electric power and heat are generated.

In the polymer electrolyte fuel cell having the above-described configuration, there is a problem that power generation performance is deteriorated by long-term operation. One of the causes of the decrease in power generation performance is the deterioration of the polymer electrolyte membrane and the electrode layer due to the generation of hydrogen peroxide (H ₂ O ₂ ) during operation.

  For example, Patent Document 1 (Japanese Patent Laid-Open No. 2008-98006) and Patent Document 2 (Japanese Patent Laid-Open No. 2005-267904) describe that polymer electrolyte membranes and electrode layers deteriorate due to the generation of hydrogen peroxide during operation. ) Etc. Hydrogen peroxide is generated unintentionally in both the anode electrode and the cathode electrode, and is radicalized under some conditions to deteriorate the polymer electrolyte membrane and the electrode layer. The deterioration of the polymer electrolyte membrane and the electrode layer occurs remarkably near the interface between the outer periphery of the electrode layer and the polymer electrolyte membrane.

  In order to improve the above problem, Patent Document 1 discloses that a peroxide decomposition catalyst for decomposing a peroxide such as hydrogen peroxide is present at a higher concentration in the vicinity of the outer peripheral portion of the gas diffusion layer than in other portions. Technology is disclosed.

  Patent Document 2 discloses a technique in which a peroxide decomposition catalyst is disposed on a seal member that seals between a polymer electrolyte membrane and a separator. In addition, the sealing member of patent document 2 is a member equivalent to the said frame.

JP 2008-98006 A JP 2005-267904 A

  As described above, the deterioration of the polymer electrolyte membrane and the electrode layer occurs remarkably near the interface between the outer periphery of the electrode layer and the polymer electrolyte membrane. This is because when the cell is pressure-fastened, the fastening pressure is concentrated on the outer peripheral portion of the electrode layer, the polymer electrolyte membrane adjacent to the outer peripheral portion of the electrode layer is thinned, and cross-leakage of the reaction gas occurs. This is thought to be due to an increase in the amount and an increase in the production of hydrogen peroxide. The range in which the production of hydrogen peroxide increases is relatively wide on the inside and outside of the outer periphery of the electrode layer.

  Therefore, the technique of Patent Document 1 cannot suppress deterioration of the polymer electrolyte membrane or the electrode layer outside the outer peripheral portion of the electrode layer. In addition, since the sealing member of Patent Document 2 is disposed outside the outer peripheral portion of the electrode layer as viewed from the thickness direction of the polymer electrolyte membrane, the polymer on the inner side of the outer peripheral portion of the electrode layer. Deterioration of the electrolyte membrane and electrode layer cannot be suppressed.

  In the technique of Patent Document 1, it is not easy to freely control the concentration of the peroxide decomposition catalyst in the gas diffusion layer. In addition, when a peroxide decomposition catalyst is contained in the gas diffusion layer, the peroxide decomposition catalyst obstructs the flow of the reaction gas, and there is a problem that the power generation performance is reduced accordingly.

  Accordingly, an object of the present invention is to solve the above-mentioned problems, and an electrode-membrane-frame assembly that can suppress deterioration of a polymer electrolyte membrane and an electrode layer and further suppress a decrease in power generation performance, and the junction. An object of the present invention is to provide a polymer electrolyte fuel cell including a body.

According to the present invention, a polymer electrolyte membrane;
A pair of catalyst layers facing each other across the electrolyte membrane;
A pair of gas diffusion layers facing each other across the electrolyte membrane and the pair of catalyst layers;
A frame-like frame disposed so as to overlap with the outer peripheral portion of the electrolyte membrane as seen from the thickness direction of the electrolyte membrane;
An electrode-membrane-frame assembly comprising:
A frame-shaped peroxide decomposition catalyst layer including a peroxide decomposition catalyst is provided on at least one main surface side of the electrolyte membrane,
On the one main surface side of the electrolyte membrane,
The inner edge of the peroxide decomposition catalyst layer is located on the inner side of the inner edge of the frame body as seen from the thickness direction of the electrolyte membrane,
The outer edge of the peroxide decomposition catalyst layer is located outside the outer edge of the gas diffusion layer as seen from the thickness direction of the electrolyte membrane.
An electrode-membrane-frame assembly is provided.

  According to the electrode-membrane-frame assembly of the present invention, the peroxide decomposition catalyst is not mixed into the gas diffusion layer or the seal member as in Patent Document 1 or 2, but the peroxide decomposition catalyst is included independently. A frame-shaped peroxide decomposition catalyst layer is provided. Further, according to the electrode-membrane-frame assembly of the present invention, the inner edge of the peroxide decomposition catalyst layer is located on the inner side of the inner edge of the frame body when viewed from the thickness direction of the polymer electrolyte membrane, and the peroxide The outer edge of the cracking catalyst layer is configured to be located outside the outer edge of the gas diffusion layer. That is, the peroxide decomposition catalyst layer is arranged so as to extend to a region where hydrogen peroxide is generated, which cannot suppress deterioration of the polymer electrolyte membrane or the electrode layer by the technique of Patent Document 1 or 2. Yes. Therefore, according to the electrode-membrane-frame assembly of the present invention, hydrogen peroxide generated during operation can be efficiently decomposed, and degradation of the polymer electrolyte membrane and the electrode layer can be suppressed to reduce the power generation performance. It can be further suppressed.

1 is a perspective view schematically showing a part of a structure of a fuel cell having an electrode-membrane-frame assembly according to a first embodiment of the present invention. FIG. 2 is a plan view schematically showing the configuration of the electrode-membrane-frame assembly in FIG. 1. FIG. 2 is a cross-sectional view taken along line A1-A1 of FIG. It is a top view which shows the surface structure by the side of the anode separator of the electrode-membrane-frame assembly of FIG. FIG. 2 is a plan view showing the surface structure of the electrode-membrane-frame assembly of FIG. 1 on the cathode palator side. FIG. 6 is an enlarged cross-sectional view schematically showing a first modification of the electrode-membrane-frame assembly of FIG. 1. FIG. 6 is an enlarged cross-sectional view schematically showing a second modification of the electrode-membrane-frame assembly of FIG. 1. It is an expanded sectional view showing typically the 3rd modification of an electrode film membrane frame assembly of Drawing 1. It is an expanded sectional view showing typically the 4th modification of an electrode film membrane frame assembly of Drawing 1. FIG. 10 is an enlarged cross-sectional view schematically showing a fifth modification of the electrode-membrane-frame assembly in FIG. 1. It is an expanded sectional view showing typically the 6th modification of an electrode film membrane frame assembly of Drawing 1. FIG. 10 is an enlarged cross-sectional view schematically showing a seventh modification of the electrode-membrane-frame assembly in FIG. 1. It is an expanded sectional view which shows typically the 8th modification of the electrode-membrane-frame assembly of FIG. It is an expanded sectional view which shows typically the 9th modification of the electrode-membrane-frame assembly of FIG. It is a top view which shows typically the structure of the electrode-membrane-frame assembly concerning 2nd Embodiment of this invention. It is B1-B1 sectional view taken on the line of FIG. It is B2-B2 sectional view taken on the line of FIG.

In order to achieve the above object, the present invention is configured as follows.
According to a first aspect of the present invention, a polymer electrolyte membrane;
A pair of catalyst layers facing each other across the electrolyte membrane;
A pair of gas diffusion layers facing each other across the electrolyte membrane and the pair of catalyst layers;
A frame-like frame disposed so as to overlap with the outer peripheral portion of the electrolyte membrane as seen from the thickness direction of the electrolyte membrane;
An electrode-membrane-frame assembly comprising:
A frame-shaped peroxide decomposition catalyst layer including a peroxide decomposition catalyst is provided on at least one main surface side of the electrolyte membrane,
On the one main surface side of the electrolyte membrane,
The inner edge of the peroxide decomposition catalyst layer is located on the inner side of the inner edge of the frame body as seen from the thickness direction of the electrolyte membrane,
The outer edge of the peroxide decomposition catalyst layer is located outside the outer edge of the gas diffusion layer as seen from the thickness direction of the electrolyte membrane.
An electrode-membrane-frame assembly is provided.

  According to a second aspect of the present invention, there is provided the electrode-membrane-frame assembly according to the first aspect, wherein the peroxide decomposition catalyst layer has an adhesive force.

  According to a third aspect of the present invention, the peroxide decomposition catalyst layer includes the polymer material having an affinity for the resin material constituting the frame, according to the first or second aspect. A membrane-frame assembly is provided.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the peroxide decomposition catalyst layer includes a polymer material having an affinity for the polymer material constituting the electrolyte membrane. The electrode-membrane-frame assembly described in 1. is provided.

  According to the fifth aspect of the present invention, when viewed from the thickness direction of the electrolyte membrane, the outer edge of the gas diffusion layer is located outside the inner edge of the frame body, and any one of the first to fourth aspects. The electrode-membrane-frame assembly described in 1. is provided.

  According to the sixth aspect of the present invention, when viewed from the thickness direction of the electrolyte membrane, the outer edge of the gas diffusion layer is located on the inner side of the inner edge of the frame body, and any one of the first to fourth aspects. The electrode-membrane-frame assembly described in 1. is provided.

  According to a seventh aspect of the present invention, there is provided the electrode-membrane-frame assembly according to any one of the first to sixth aspects, wherein the peroxide decomposition catalyst layer is in contact with the electrolyte membrane. .

  According to an eighth aspect of the present invention, in any one of the first to seventh aspects, at least a part of the peroxide decomposition catalyst layer is disposed between the electrolyte membrane and the catalyst layer. The electrode-membrane-frame assembly described is provided.

  According to a ninth aspect of the present invention, in any one of the first to eighth aspects, the width of the portion where the peroxide decomposition catalyst layer is present inside the outer edge of the gas diffusion layer is 1 mm or more and 5 mm or less. An electrode-membrane-frame assembly according to one is provided.

  According to the tenth aspect of the present invention, the width of the portion where the peroxide decomposition catalyst layer exists inside the outer edge of the gas diffusion layer is higher than the portion located downstream in the flow direction of the reaction gas. The electrode-membrane-frame assembly according to any one of the first to ninth aspects, wherein a portion located on the side is larger is provided.

  According to an eleventh aspect of the present invention, there is provided a fuel cell comprising the electrode-membrane-frame assembly according to any one of the first to tenth aspects.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<< First Embodiment >>
The structure of the fuel cell having the electrode-membrane-frame assembly according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view schematically showing a part of the structure of a fuel cell having an electrode-membrane-frame assembly according to the first embodiment. FIG. 2 is a plan view schematically showing the configuration of the electrode-membrane-frame assembly of FIG. 1, and shows a state seen from the anode electrode side. 3 is a cross-sectional view taken along line A1-A1 of FIG. FIG. 4 is a plan view showing the surface structure of the electrode-membrane-frame assembly of FIG. 1 on the anode separator side. FIG. 5 is a plan view showing the surface structure of the electrode-membrane-frame assembly of FIG.

  The fuel cell according to the first embodiment is a polymer that generates electric power and heat simultaneously by electrochemically reacting a fuel gas containing hydrogen and an oxidant gas containing oxygen such as air. This is an electrolyte fuel cell.

  As shown in FIG. 1, the fuel cell is configured by stacking a plurality (for example, 60) of cells (unit cell modules) 10 that are basic unit configurations. Although not shown, a current collector plate, an insulating plate, and an end plate are attached to both ends of the stacked cells 10 group, and fastening bolts are inserted through the bolt holes 4 and fixed with nuts. Each cell 10 is fastened with a predetermined fastening force (for example, 10 kN).

  The cell 10 is configured by sandwiching the electrode-membrane-frame assembly 1 between an anode separator 2 and a cathode separator 3 which are a pair of conductive separators. As shown in FIG. 2 or 3, the electrode-membrane-frame assembly 1 has a frame shape formed so as to seal and hold the membrane electrode assembly 5 (hereinafter referred to as MEA) and the outer peripheral portion 5 </ b> E of the MEA 5. The frame body 6 is provided.

  As shown in FIG. 1, each of the frame body 6, the anode separator 2, and the cathode separator 3 is provided with fuel gas manifold holes 12, 22, and 32 that are a pair of through holes through which fuel gas flows. Further, as shown in FIG. 1, each of the frame 6, the anode separator 2 and the cathode separator 3 is provided with oxidant gas manifold holes 13, 23 and 33 which are a pair of through holes through which the oxidant gas flows. It has been. In a state where the frame body 6, the anode separator 2, and the cathode separator 3 are fastened as the cell 10, the fuel gas manifold holes 12, 22, and 32 are connected to form a fuel gas manifold. Similarly, in a state where the frame body 6, the anode separator 2, and the cathode separator 3 are fastened as the cell 10, the oxidant gas manifold holes 13, 23, and 33 are connected to form an oxidant gas manifold.

  Further, as shown in FIG. 1, the frame 6, the anode separator 2, and the cathode separator 3 are each provided with two pairs of through-holes through which a cooling medium (for example, pure water or ethylene glycol) flows. 14, 24 and 34 are provided. As a result, in a state where the frame body 6, the anode separator 2, and the cathode separator 3 are fastened as the cell 10, the cooling medium manifold holes 14, 24, and 34 are connected to form two pairs of cooling medium manifolds. The

  Further, as shown in FIG. 1, the frame body 6, the anode separator 2, and the cathode separator 3 are provided with four bolt holes 4 in the vicinity of each corner portion. A fastening bolt is inserted into each bolt hole 4, and each cell 10 is fastened by coupling a nut to the fastening bolt.

  A fuel gas passage groove 21 is provided on the inner main surface of the anode separator 2 (surface on the electrode-membrane-frame assembly 1 side) so as to connect the pair of fuel gas manifold holes 22, 22. An oxidant gas channel groove 31 is provided on the inner main surface of the cathode separator 3 (surface on the electrode-membrane-frame assembly 1 side) so as to connect the pair of oxidant gas manifold holes 33 and 33. Yes. The fuel gas is supplied to the anode gas diffusion layer 5C1 of the MEA 5 to be described later through the fuel gas passage groove 21, and the oxidant gas is supplied to the cathode gas diffusion layer 5C2 of the MEA 5 to be described later through the oxidant gas passage groove 31. As a result, an electrochemical reaction occurs. Thereby, electric power and heat are generated simultaneously. In FIG. 4, the one-dot broken line indicates the flow direction of the fuel gas. Moreover, in FIG. 5, the one-dot broken line has shown the flow direction of oxidizing gas.

  Moreover, although not shown in figure, the cooling medium flow path groove | channel is formed in the outer main surface (back surface) of the anode separator 2 and the cathode separator 3, respectively. The cooling medium flow channel is formed so as to connect the two pairs of cooling medium manifold holes 24 and 34. That is, the cooling medium is configured to branch from the cooling medium manifold on the supply side to the cooling medium flow channel and to flow to the cooling medium manifold on the discharge side. Thereby, the cell 10 is maintained at a predetermined temperature suitable for the electrochemical reaction by utilizing the heat transfer capability of the cooling medium.

  In addition, each said hole and each groove | channel can be formed by cutting process and a shaping | molding process, for example. Moreover, each said manifold is not limited to the said structure, A various deformation | transformation is possible. For example, each manifold may have a so-called external manifold structure. 2 and 3, illustration of each hole is omitted.

  As shown in FIG. 3, the MEA 5 includes a polymer electrolyte membrane 5A that selectively transports hydrogen ions and a pair of electrode layers 5D and 5D formed on both surfaces of the electrolyte membrane 5A. One of the pair of electrode layers 5D is an anode electrode, and the other of the pair of electrode layers is a cathode electrode. Since the anode electrode and the cathode electrode have the same configuration, only one electrode layer 5D will be described below.

  The polymer electrolyte membrane 5A is not particularly limited, and a polymer electrolyte membrane mounted on a normal polymer electrolyte fuel cell can be used. For example, a fluoropolymer electrolyte membrane made of perfluorocarbon sulfonic acid (for example, Nafion (registered trademark) manufactured by DuPont, USA, Aciplex (registered trademark) manufactured by Asahi Kasei Co., Ltd., and Flemion (registered trademark) manufactured by Asahi Glass Co., Ltd.) Etc.) and various hydrocarbon electrolyte membranes can be used. The electrode layer 5D has a two-layer structure of a catalyst layer 5B and a gas diffusion layer 5C.

  The catalyst layer 5B is a porous member mainly composed of, for example, a carbon powder carrying a platinum group metal catalyst and a polymer material having proton conductivity. The proton conductive polymer material used for the catalyst layer 5B may be the same as or different from the polymer electrolyte membrane 5A. The catalyst layer 5B is smaller in outer size than the polymer electrolyte membrane 5A, and is formed on the main surface of the polymer electrolyte membrane 5A so that the outer periphery of the polymer electrolyte membrane 5A is exposed.

  The gas diffusion layer 5C has both the breathability of the reaction gas (fuel gas or oxidant gas) and electronic conductivity. The gas diffusion layer 5C has a smaller outer size than the catalyst layer 5B, and is disposed on the main surface of the catalyst layer 5B so that the outer periphery of the catalyst layer 5B is exposed. That is, when viewed from the thickness direction Y of the polymer electrolyte membrane 5A, the outer edge 5Ba of the catalyst layer 5B is located outside the outer edge 5Ca of the gas diffusion layer 5C.

  As the gas diffusion layer 5C, in order to provide gas permeability, a conductive base material having a porous structure made of carbon fine powder, a pore former, carbon paper, carbon cloth, or the like is used. it can. Further, in order to provide drainage, a water repellent polymer such as a fluororesin may be dispersed in the gas diffusion layer 5C. Furthermore, in order to give electron conductivity, the gas diffusion layer 5C may be made of an electron conductive material such as carbon fiber, metal fiber, or carbon fine powder. Further, a water repellent carbon layer composed of a water repellent polymer and carbon powder may be provided on the surface of the gas diffusion layer 5C in contact with the catalyst layer 5A. The same gas diffusion layer may be used on the cathode side and the anode side, or different gas diffusion layers may be used. In addition, as the gas diffusion layer 5C, for example, a porous member composed mainly of conductive particles and a polymer resin may be used without using carbon fiber as a base material.

  A frame-shaped peroxide decomposition catalyst layer 7 is formed on the outer periphery of the polymer electrolyte membrane 5A and the outer periphery of the gas diffusion layer 5C, as shown in FIG. A frame 6 is formed on the top. The peroxide decomposition catalyst layer 7 can be formed by, for example, a spray method, die coating, or the like, in the same manner as a general method for forming the catalyst layer 5B. When viewed from the thickness direction Y of the polymer electrolyte membrane 5A, the inner edge 7a of the peroxide decomposition catalyst layer 7 is located inside the outer edge 5Ca of the gas diffusion layer 5C. The outer edge 7b of the peroxide decomposition catalyst layer 7 is located outside the inner edge 6a of the frame 6 when viewed from the thickness direction Y of the polymer electrolyte membrane 5A. For example, when the thickness of the catalyst layer 5B is 10 to 20 μm, the thickness of the peroxide decomposition catalyst layer 7 is set to 5 μm or more.

The peroxide decomposition catalyst layer 7 includes a peroxide decomposition catalyst that decomposes peroxides such as hydrogen peroxide. The peroxide decomposition catalyst only needs to have a catalytic action for decomposing peroxide. For example, a peroxide selected from a noble metal, metal oxide, metal complex, phosphate, fluoride, tungstate, etc. It can be used alone or in admixture of two or more. Examples of the noble metal include Pt, Ru, Rh, Ir, and Ag. Examples of the metal oxide include MnO ₂ , PbO ₂ , PbO, RuO ₂ , Al ₂ O ₃ , TiO ₂ , Nb ₂ O ₃ , Ta ₂ O ₅ , Nb ₂ O ₅ , FeO, Fe ₂ O ₃ , Fe _3. O ₄ , WO ₃ , W ₂ O ₅ , SnO ₂ , Cr ₂ O ₃ , CeO ₂ , La ₂ O ₃ , SiO ₂ , ZrO ₂ , CuO, Cu ₂ O, ZnO, Y ₂ O ₃ , MoO ₃ , In ₂ O ₃ , In ₂ O, Bi ₂ O ₃ , Sb ₂ O ₃ , Sb ₂ O ₅ , GeO ₂ , GeO, and the like can be given. Examples of the metal complex include porphyrin, phthalocyanine, and derivatives thereof having Co, Fe, Ti, Al, Ce, or the like as a central atom. Examples of the phosphate include AlPO ₄ , TiPO ₄ , FePO ₄ , CrPO ₄ , CePO ₄ , Zr ₃ (PO ₄ ) ₄ , LaPO _{4 and the} like. Examples of the fluoride include AlF ₃ , FeF ₃ , CrF ₃ , CeF ₃ , ZrF ₄ , LaF _{3 and the} like. Examples of the tungstate include FeWO ₄ , MnWO ₄ , (Fe, Mn) WO ₄ , CaWO ₄ , CuWO ₄ , Cu ₂ WO ₄ (OH) ₂ , Al ₂ (WO ₄ ) ₃ , SrWO ₄ , BaWO ₄ , _{Ag 2 WO 4, ZnWO 4,} SnWO 4, Ce 2 (WO 4) 3 and the like. Among them, it is preferable to use CeO ₂ and MnO ₂ as the peroxide decomposition catalyst because of high peroxide decomposition performance.

  If the peroxide decomposition catalyst layer 7 is too hard, there is a possibility that a gap is generated at the interface with an adjacent member and a cross leak of the reaction gas may occur. Therefore, it is preferable that the peroxide decomposition catalyst layer 7 has a certain degree of flexibility. Moreover, it is preferable that the peroxide decomposition catalyst layer 7 has an adhesive force for bonding members adjacent to the peroxide decomposition catalyst layer 7 together. For this reason, the peroxide decomposition catalyst layer 7 preferably includes a polymer material having affinity for at least one of the polymer material constituting the polymer electrolyte membrane 5A and the resin material constituting the frame body 6. . From the viewpoint of increasing the affinity with the polymer electrolyte membrane, it is more preferable that the peroxide decomposition catalyst layer 7 includes a polymer material having the same component as that of the polymer electrolyte membrane 5A. Thereby, the adhesive force of the members adjacent to the peroxide decomposition catalyst layer 7 can be increased, and the handling property of the MEA 5 can be improved. The polymer material of the peroxide decomposition catalyst layer 7 preferably has high heat resistance.

  The frame body 6 is a resin member for improving the handleability or for sealing between the polymer electrolyte membrane 5A and the separator 2 or 3. The frame body 6 is disposed so as to overlap the outer peripheral portion of the polymer electrolyte membrane 5A when viewed from the thickness direction Y of the polymer electrolyte membrane 5A. In addition, although the resin material used for the frame 6 is not specifically limited, For example, the following can be used.

  When the frame body 6 is used for improving handling properties, the resin material of the frame body 6 is preferably a crystalline resin, not an amorphous resin, from the viewpoint of chemical stability, and among them, mechanical A thermoplastic resin having high strength and high heat resistance is preferred. For example, as the thermoplastic resin, a so-called super engineering plastic grade, such as polyphenylene sulfide (PPS), polyether ether ketone (PEEK), liquid crystal polymer (LCP), polyether nitrile (PEN), polystyrene (PS), etc. Is preferred. These have a compression modulus of several thousand to several tens of thousands of MPa and a deflection temperature under load of 150 ° C. or more, and are suitable materials for the thermoplastic resin. Moreover, even if it is a resin material currently used widely, intensity | strength can be strengthened by mixing an inorganic type reinforcing material (for example, glass fiber, glass filler) in the said resin material. For example, polypropylene filled with glass filler (GFPP) has a modulus of elasticity several times that of unfilled polypropylene (compression modulus of 1,000 to 1,500 MPa) and has a deflection temperature under load close to 150 ° C. Yes. Therefore, it can be suitably used as the thermoplastic resin.

  When the frame body 6 is used as a so-called sealing member to seal between the polymer electrolyte membrane 5A and the separator 2 or 3, the resin material of the frame body 6 is a resin material having a low elastic modulus, for example, a thermoplastic elastomer. Preferably there is. As the thermoplastic elastomer, for example, olefin elastomer (TPO), styrene elastomer (TPS), polyester elastomer (TPEE), polyurethane elastomer (TPU), nylon elastomer (TPA) and the like are suitable. The olefin-based elastomer is constituted by mixing polypropylene (PP) and ethylene / propylene rubber (EPM) or ethylene / propylene / diene rubber (EPDM). The styrene elastomer is constituted by copolymerizing polystyrene (PS) and polybutadiene or polyisoprene.

  According to the first embodiment, the peroxide decomposition catalyst is not mixed into the gas diffusion layer 5C or the frame (seal member) 6 as in Patent Document 1 or 2, but is independent including the peroxide decomposition catalyst. The peroxide decomposition catalyst layer 7 is provided. Further, according to the first embodiment, when viewed from the thickness direction Y of the polymer electrolyte membrane 5A, the inner edge 7a of the peroxide decomposition catalyst layer 7 is located on the inner side of the outer edge 7a of the gas diffusion layer 5C, and The outer edge 7 b of the oxide decomposition catalyst layer 7 is configured to be located outside the inner edge 6 a of the frame 6. That is, the peroxide decomposition catalyst layer 7 extends so as to extend to a region where hydrogen peroxide is generated, in which the technique of Patent Document 1 or 2 cannot suppress the deterioration of the polymer electrolyte membrane 5A and the electrode layer 5D. Has been placed. Therefore, according to the first embodiment, hydrogen peroxide generated during operation can be efficiently decomposed, and deterioration of the polymer electrolyte membrane 5A and the electrode layer 5D can be suppressed to further suppress a decrease in power generation performance. Can do.

  In addition, it is preferable that the width W1 of the part in which the peroxide decomposition catalyst layer 7 exists inside the outer edge 5Ca of the gas diffusion layer 5C is 1 mm or more. Thereby, deterioration of the polymer electrolyte membrane 5A can be sufficiently suppressed. In addition, as the width W1 is increased, the deterioration of the polymer electrolyte membrane 5A can be suppressed. However, if the width W1 is excessively increased, the amount of the peroxide decomposition catalyst that hinders the flow of the reaction gas is correspondingly increased. On the contrary, the power generation performance decreases. For this reason, the width W1 is preferably 5 mm or less.

  In addition, this invention is not limited to the said 1st Embodiment, It can implement in another various aspect. For example, in the first embodiment, the outer edge 5Ba of the catalyst layer 5B is disposed outside the inner edge 6a of the frame body 6 when viewed from the thickness direction Y of the polymer electrolyte membrane 5A. It is not limited to this. For example, as shown in FIG. 6, the outer edge 5Ba of the catalyst layer 5B may be arranged so as to be located inside the inner edge 6a of the frame body 6. That is, the size of the catalyst layer 5 </ b> B may be smaller than the opening area of the frame body 6.

  In the first embodiment, the size of the catalyst layer 5B is smaller than the size of the polymer electrolyte membrane 5A, but the present invention is not limited to this. For example, as shown in FIG. 7, the size of the catalyst layer 5B may be substantially the same as the size of the polymer electrolyte membrane 5A.

  Moreover, in the said 1st Embodiment, although the peroxide decomposition | disassembly catalyst layer 7 was arrange | positioned so that the outer peripheral part of the catalyst layer 5B might be covered, this invention is not limited to this. For example, as shown in FIG. 8, the catalyst layer 5B and the peroxide decomposition catalyst layer 7 may be disposed adjacent to each other. In this case, the catalyst layer 5B and the peroxide decomposition catalyst layer 7 may have substantially the same thickness.

  Of the polymer electrolyte membrane 5A, the catalyst layer 5B, and the gas diffusion layer 5C, the polymer electrolyte membrane 5A is most easily degraded by hydrogen peroxide. For this reason, it is preferable to arrange the peroxide decomposition catalyst layer 7 so that at least a part thereof is in contact with the polymer electrolyte membrane 5A. For example, as shown in FIG. 9, it is preferable to arrange the inner periphery of the peroxide decomposition catalyst layer 7 so that the outer periphery of the catalyst layer 5B covers it. Thereby, the fall of electric power generation performance can be suppressed effectively.

  In the first embodiment, as shown in FIG. 3, the outer peripheral portion of the gas diffusion layer 5C covers the inner peripheral portion of the frame 6, that is, as viewed from the thickness direction Y of the polymer electrolyte membrane 5A. Although the outer edge 5Ca of the gas diffusion layer 5C is configured to be positioned outside the inner edge 6a of the frame body 6, the present invention is not limited to this. For example, as shown in FIGS. 10 to 13, a gap is formed between the outer edge 5Ca of the gas diffusion layer 5C and the inner edge 6a of the frame body 6, that is, as viewed from the thickness direction Y of the polymer electrolyte membrane 5A. The outer edge 5Ca of the gas diffusion layer 5C may be configured to be located inside the inner edge 6a of the frame body 6.

  Further, since the outer peripheral portion 5E of the MEA 5 where the frame body 6 is disposed is not a portion that actively contributes to power generation, the peroxide decomposition catalyst layer 7 is more than the inner edge 6a of the frame body 6 as shown in FIG. The part existing on the outside may be made smaller so that a part of the frame 6 is in contact with the polymer electrolyte membrane 5A.

  In the first embodiment, the anode electrode and the cathode electrode have been described as having the same configuration. However, the present invention is not limited to this, and the anode electrode and the cathode electrode may have different configurations. In this case, the peroxide decomposition catalyst layer 7 may be included in either the anode electrode or the cathode electrode.

<< Second Embodiment >>
FIG. 15 is a plan view schematically showing the configuration of the electrode-membrane-frame assembly according to the second embodiment of the present invention. 16 is a cross-sectional view taken along line B1-B1 of FIG. 15, and FIG. 17 is a cross-sectional view taken along line B2-B2 of FIG. The electrode-membrane-frame assembly 1A according to the second embodiment is different from the electrode-membrane-frame assembly 1 according to the first embodiment in that the peroxide decomposition catalyst is upstream in the flow direction of the reaction gas. The width W2 of the portion where the layer 7 exists inside the outer edge 5Ca of the gas diffusion layer 5C is set so that the peroxide decomposition catalyst layer 7 is located inside the outer edge 5Ca of the gas diffusion layer 5C on the downstream side in the reaction gas flow direction. This is a point that is larger than the width W3 of the existing portion. In FIG. 15, the dashed line indicates the flow direction of the reaction gas.

  During operation of the fuel cell, the reaction gas (fuel gas and oxidant gas) reacts electrochemically to generate electric power and heat, and water is also generated. The amount of water generated at this time gradually increases as the reaction gas flows through the gas flow path. For this reason, even if hydrogen peroxide is generated on the downstream side in the flow direction of the reaction gas, it is washed away with a large amount of water. On the other hand, on the upstream side in the flow direction of the reaction gas, since the amount of water produced is small, hydrogen peroxide cannot be washed away, and hydrogen peroxide stays. For this reason, especially the part located in the upstream of the flow direction of the reactive gas in electrode layer 5D and polymer electrolyte membrane 5A tends to deteriorate.

  Therefore, in the electrode-membrane-frame assembly 1A according to the second embodiment, as shown in FIGS. 15 to 17, the width W2 is made larger than the width W3. Thereby, deterioration of electrode layer 5D and polymer electrolyte membrane 5A can be suppressed effectively. Further, by reducing the width W3, the amount by which the peroxide decomposition catalyst hinders the flow of the reaction gas is reduced. Therefore, it is possible to further suppress a decrease in power generation performance.

  In FIG. 15, the peroxide decomposition catalyst layer 7 is shown to be present inside the outer edge 5Ca of the gas diffusion layer 5C from the upstream side to the downstream side in the reaction gas flow direction. Is not limited to this. For the portion where hydrogen peroxide can be completely washed away by the water generated during the operation of the fuel cell, the portion where the peroxide decomposition catalyst layer 7 exists inside the outer edge 5Ca of the gas diffusion layer 5C is eliminated. Also good. For example, the width W3 may be “zero”. Thereby, the quantity which a peroxide decomposition catalyst obstructs the flow of a reaction gas can be decreased further, and the fall of power generation performance can be suppressed further.

  Further, in FIG. 15, the flow direction of the reaction gas is shown to meander, but the present invention is not limited to this. For example, instead of the meandering gas flow channel grooves 21 and 31, a plurality of linear gas flow channel grooves may be formed in the separators 2 and 3 so that the flow direction of the reaction gas is linear. In the above description, the gas flow path grooves 21 and 31 are provided in the separators 2 and 3, but instead, a gas flow path groove may be provided in the gas diffusion layer 5C.

  It is to be noted that, by appropriately combining any of the various embodiments, the effects possessed by them can be produced.

  The electrode-membrane-frame assembly according to the present invention can suppress deterioration of the power generation performance by suppressing deterioration of the polymer electrolyte membrane. Therefore, in particular, mobile bodies such as automobiles, distributed (on-site) power generation It is useful for a polymer electrolyte fuel cell used as a drive source for a system, a household cogeneration system, and the like.

1 Electrode-membrane-frame assembly 2 Anode separator 3 Cathode separator 4 Bolt hole 5 MEA (membrane electrode assembly)
5A Polymer electrolyte membrane 5B Catalyst layer 5C Gas diffusion layer 5D Electrode layer 5E Outer peripheral part 6 Frame body 7 Peroxide decomposition catalyst layer 10 Cell 12, 22, 32 Fuel gas manifold hole 13, 23, 33 Oxidant gas manifold hole 14 , 24, 34 Cooling medium manifold hole 21 Fuel gas passage groove 31 Oxidant gas passage groove

Claims (11)

A polymer electrolyte membrane;
A pair of catalyst layers facing each other across the electrolyte membrane;
A pair of gas diffusion layers facing each other across the electrolyte membrane and the pair of catalyst layers;
A frame-like frame disposed so as to overlap with the outer peripheral portion of the electrolyte membrane as seen from the thickness direction of the electrolyte membrane;
An electrode-membrane-frame assembly comprising:
A frame-shaped peroxide decomposition catalyst layer including a peroxide decomposition catalyst is provided on at least one main surface side of the electrolyte membrane,
On the one main surface side of the electrolyte membrane,
The inner edge of the peroxide decomposition catalyst layer is located on the inner side of the inner edge of the frame body as seen from the thickness direction of the electrolyte membrane,
The outer edge of the peroxide decomposition catalyst layer is located outside the outer edge of the gas diffusion layer as seen from the thickness direction of the electrolyte membrane.
Electrode-membrane-frame assembly.   The electrode-membrane-frame assembly according to claim 1, wherein the peroxide decomposition catalyst layer has an adhesive force.   The electrode-membrane-frame assembly according to claim 1 or 2, wherein the peroxide decomposition catalyst layer includes a polymer material having an affinity for a resin material constituting the frame.   The electrode-membrane-frame joint according to any one of claims 1 to 3, wherein the peroxide decomposition catalyst layer includes a polymer material having an affinity for the polymer material constituting the electrolyte membrane. body.   The electrode-membrane-frame assembly according to any one of claims 1 to 4, wherein an outer edge of the gas diffusion layer is located outside an inner edge of the frame body as viewed from the thickness direction of the electrolyte membrane. .   The electrode-membrane-frame assembly according to any one of claims 1 to 4, wherein an outer edge of the gas diffusion layer is located on an inner side than an inner edge of the frame body as viewed from the thickness direction of the electrolyte membrane. .   The electrode-membrane-frame assembly according to any one of claims 1 to 6, wherein the peroxide decomposition catalyst layer is in contact with the electrolyte membrane.   The electrode-membrane-frame assembly according to any one of claims 1 to 7, wherein at least a part of the peroxide decomposition catalyst layer is disposed between the electrolyte membrane and the catalyst layer.   The electrode-membrane-frame according to any one of claims 1 to 8, wherein a width of a portion where the peroxide decomposition catalyst layer exists inside an outer edge of the gas diffusion layer is 1 mm or more and 5 mm or less. Joined body.   The width of the portion where the peroxide decomposition catalyst layer exists inside the outer edge of the gas diffusion layer is larger in the portion located upstream than the portion located downstream in the flow direction of the reaction gas, The electrode-membrane-frame assembly according to any one of claims 1 to 9.   A fuel cell comprising the electrode-membrane-frame assembly according to any one of claims 1 to 10.

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