JP2007035459A - Fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a formation of a gap between a gas diffusion electrode and a gasket and prevent a reactive gas from coming into direct contact with an electrolyte membrane, thereby maintaining a high power generation performance over a long period of time. Provide batteries.
A fuel cell having a membrane electrode assembly in which a pair of gas diffusion electrodes 110 including an electrode catalyst layer 111 and a gas diffusion layer 112 are disposed on both sides of an electrolyte membrane 100.
In this fuel cell, a protective sheet 150 is provided in contact with the electrolyte membrane 100 and the gas diffusion electrode 110.
[Selection] Figure 1

Description

  The present invention relates to a fuel cell, and more particularly to a fuel cell in which reaction gas is prevented from coming into direct contact with an electrolyte membrane.

  In recent years, in response to social demands and trends against the background of energy and environmental problems, fuel cells that can operate at room temperature and obtain high output density have attracted attention as power sources for electric vehicles and stationary power sources. A fuel cell is a clean power generation system in which the product of an electrode reaction is water in principle and has almost no adverse effect on the global environment. In particular, the polymer electrolyte fuel cell is expected as a power source for electric vehicles because it operates at a relatively low temperature.

  As shown in FIG. 7, the solid polymer fuel cell generally has a configuration in which a membrane electrode assembly in which a polymer electrolyte membrane 100 is sandwiched between a pair of gas diffusion electrodes 110 is sandwiched between separators 120. Have. The gas diffusion electrode 110 has an electrode catalyst layer 111 and a gas diffusion layer 112. The separator 120 has a gas supply groove 121 for supplying fuel gas or oxidant gas to the electrode catalyst layer. Further, the gasket 130 is disposed between the membrane electrode assembly and the separator to seal the edge region of the membrane electrode assembly, thereby preventing the fuel gas and the oxidant gas from being mixed with each other.

Further, in Patent Document 1, as shown in FIG. 8, the gasket 130 and the gas diffusion layer 111 are integrated by impregnating a part of the gas diffusion layer 112 with a gasket forming material and bonding it to the frame base material 131. A fuel cell is disclosed. As a result, the gasket 130 and the gas diffusion layer 111 can be handled together, reducing the number of assembling steps of the fuel cell or the stack and facilitating the assembling work.
JP 2003-7328 A

  However, in the conventional fuel cell, it is difficult to completely contact the ends of the gas diffusion electrode and the gasket, so that a gap 140 is formed between the gas diffusion electrode 110 and the gasket 130 as shown in FIG. There was a fear.

  When the gap 140 is formed between the gas diffusion electrode 110 and the gasket 130 as described above, a reactive gas such as a fuel gas or an oxidant gas comes into direct contact with the polymer electrolyte membrane 100, and the polymer electrolyte membrane There was a possibility that 100 would deteriorate due to perforation or the like. The occurrence of perforation not only lowers proton conductivity but also causes gas leakage to the counter electrode of fuel gas and oxidant gas, leading to a reduction in battery output.

  Further, in the fuel cell described in Patent Document 1, since a gasket is formed by impregnating a part of the gas diffusion layer with a gasket forming material, it is possible to prevent the reaction gas from directly contacting the polymer electrolyte membrane. it can. However, the gas diffusion function is lost at the portion where the gasket is formed in the gas diffusion layer, and the power generation performance of the fuel cell may be reduced.

  Accordingly, an object of the present invention is to maintain high power generation performance over a long period of time by preventing the formation of a gap between the gas diffusion electrode and the gasket and preventing the reactive gas from directly contacting the electrolyte membrane. It is to provide a fuel cell that can be used.

The present invention provides a fuel cell having a membrane electrode assembly in which a pair of gas diffusion electrodes including an electrode catalyst layer and a gas diffusion layer are disposed on both sides of an electrolyte membrane.
The fuel cell is provided with a protective sheet so as to be in contact with the electrolyte membrane and the gas diffusion electrode.

  According to the present invention, by providing a gas-impermeable protective sheet, it is possible to suppress the deterioration of the electrolyte membrane caused by direct contact of the reaction gas, and to provide a fuel cell that can exhibit high power generation performance over a long period of time. It becomes possible.

  First, a preferred embodiment of the fuel cell of the present invention will be described with reference to FIG.

  As shown in FIG. 1, the fuel cell of the present invention includes a membrane electrode assembly in which a pair of gas diffusion electrodes 110 including an electrode catalyst layer 111 and a gas diffusion layer 112 are disposed on both sides of an electrolyte membrane 100. A protective sheet 150 is provided in contact with the film 100 and the gas diffusion electrode 110. The fuel cell also includes a separator 120 having a gas flow path 121 for supplying fuel gas or oxidant gas to the membrane electrode assembly, a gasket 130 for sealing these gases, and the like.

  As described above, in the fuel cell of the present invention, the protective sheet for preventing the fuel gas or the oxidant gas from coming into direct contact with the electrolyte membrane is provided so as to be in contact with the electrolyte membrane and the gas diffusion electrode. It is possible to suppress the resin-impregnated portion and the gap that can be formed between the gas diffusion electrode and the gasket. As a result, fuel gas or oxidant gas supplied from the outside into the fuel cell can be prevented from coming into direct contact with the electrolyte membrane, and deterioration of the electrolyte membrane can be suppressed without degrading the power generation performance of the fuel cell. It becomes possible. In addition, since the electrolyte membrane is protected by the protective sheet, it is possible to prevent the gasket load from being applied directly to the electrolyte membrane.

  In the fuel cell of the present invention, as shown in FIG. 1, the protective sheet has a central portion cut to a size substantially equal to that of the gas diffusion layer, and includes a peripheral portion of the electrolyte membrane and a side portion of the gas diffusion electrode. It is preferable that it is arranged in an L shape so as to contact with. Thereby, it is possible to reliably suppress the gap between the gasket and the gas diffusion electrode without deteriorating the gas diffusion function of the gas diffusion layer.

  The peripheral edge of the electrolyte membrane means a portion excluding the central portion where the gas diffusion electrode is formed on the surface of the electrolyte membrane where the gas diffusion electrode is formed.

  As the protective sheet, a sheet whose central portion is cut to approximately the same size as the gas diffusion layer is used, and more preferably, the central portion is cut to a size equal to that of the gas diffusion layer.

  The shape of the protective sheet used in the fuel cell is not particularly limited as long as it is in contact with the peripheral edge portion of the electrolyte membrane and the side surface portion of the gas diffusion electrode. For example, as shown in FIG. A cylindrical trapezoidal shape as shown in FIG. 2 (B) or a flat plate shape as shown in FIG. 3 is preferable. If the shape of the protective sheet is a truncated cone shape or a cylindrical trapezoidal shape, the protective sheet can be installed quickly, and if it is flat, the protective sheet can be processed quickly.

  In the protective sheet, the shape of the central portion that is cut to approximately the same size as the gas diffusion layer may be appropriately determined according to the shape of the gas diffusion layer, a rectangle such as a rectangle, a square such as a square, a polygon such as a triangle, It may be circular or elliptical.

  In the fuel cell of the present invention, as described above, the protective sheet is preferably arranged in an L shape. Therefore, when a flat protective sheet is used, as described later, after covering the peripheral edge of the electrolyte membrane and the side surface of the gas diffusion electrode, pressure or the like using a predetermined member is used. It is preferable to arrange the protective sheet in an L shape by adding.

  In the fuel cell of the present invention, the protective sheet may be divided into at least two or more. For example, as shown in FIG. 4, a flat protective sheet 152 (FIG. 4A) divided into four parts is disposed on the peripheral part of the electrolyte membrane so as to be in contact with the side part of the gas diffusion electrode 110. (FIG. 4B) is desirable. FIG. 4B is a schematic top view of the membrane electrode assembly in which the divided protective sheets are arranged. Thereby, a protective sheet can be easily adhere | attached on the side surface of a gas diffusion electrode.

  In the fuel cell, a portion where the divided protective sheets are adjacent to each other is preferably fixed with an adhesive or the like. Thereby, position shift of a protection sheet, etc. can be prevented. The site | part fixed by an adhesive agent is a side surface, an edge part, etc. of the divided | segmented protective sheet which the said divided protective sheets contact or overlap when arrange | positioned on a membrane electrode assembly.

  In the fuel cell of the present invention, the protective sheet is preferably arranged in an L shape as shown in FIG. Therefore, after the divided protective sheet is placed on the peripheral edge of the electrolyte membrane and the side surface of the gas diffusion electrode, the protective sheet is preferably arranged in an L shape by applying pressure or the like using a predetermined member.

  In the fuel cell of the present invention, the above-described protective sheet is preferably disposed in contact with the side surface of the gas diffusion electrode. At this time, the inner side surface disposed on the gas diffusion electrode 110 side of the protective sheet 150 is illustrated in FIG. As shown in FIG. 5, it is desirable to arrange the gas diffusion layer 112 so as to have the same height as the separator side surface. Thereby, the fall of the gas diffusion function of the gas diffusion layer by a protective sheet can be suppressed. FIG. 5 is a schematic cross-sectional view of one end portion of the membrane electrode assembly in which the protective sheet is disposed.

  Further, in the fuel cell of the present invention, as shown in FIG. 5, it is preferable that the side surface of the gas diffusion electrode 110 and the protective sheet 150 are bonded with an adhesive 160. That is, as a preferred form of the fuel cell of the present invention, the protective sheet is preferably bonded to the electrolyte membrane and / or the gas diffusion electrode with an adhesive. Thereby, position shift of a protection sheet, etc. can be prevented.

  The part to which the protective sheet is adhered by the adhesive is not particularly limited as long as the protective sheet is a part in contact with the electrolyte membrane and / or the gas diffusion electrode, but particularly preferably, the side surface of the gas diffusion electrode 110 as shown in FIG. And the protective sheet 150 are adhered by an adhesive 160. Thereby, it can suppress that a reactive gas contacts a electrolyte membrane directly, and can prevent deterioration of an electrolyte membrane.

  The thickness for applying the adhesive is preferably 0.05 mm to 0.1 mm, more preferably 0.05 mm to 0.07 mm. If the thickness is too thick, the gas diffusion function of the gas diffusion layer by the adhesive may be lowered, and if it is too thin, sufficient adhesive effect by the adhesive cannot be obtained.

  The adhesive is not particularly limited as long as it can closely adhere the side surface of the gas diffusion electrode and the protective sheet, but hot melt adhesives such as polyolefin, polypropylene, thermoplastic elastomer, acrylic adhesives, polyesters, etc. An olefin-based adhesive such as polyolefin can be used.

  The material of the protective sheet is not particularly limited as long as it does not allow fuel gas or oxidant gas to permeate, but polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyimide ( PI) and at least one selected from the group consisting of polyether nitrile (PEN) are preferred. These can be obtained at low cost. The protective sheet may be made of one of these materials, or two or more of them may be used in combination.

  The thickness of the protective sheet may be appropriately determined so that the protective sheet is arranged in an L shape so as to be in contact with the peripheral portion of the electrolyte membrane and the side surface of the gas diffusion electrode, preferably 10 to 200 μm, More preferably, it is good to set it as 25-50 micrometers.

  In order to arrange the protective sheet as described above in the fuel cell of the present invention, the protective sheet is placed on the peripheral portion of the electrolyte membrane and the side surface portion of the gas diffusion electrode, and then the peripheral portion of the protective sheet and the electrolyte membrane and the gas diffusion electrode. It is preferable to apply pressure by using a predetermined member so that the protective sheet is arranged in an L shape by contacting the side surface portion of the protective sheet.

  The method for producing the flat protective sheet is not particularly limited, but a method such as die cutting or cutting is used according to the size of the gas diffusion layer at the center of the sheet having a predetermined size. And cut it.

  At this time, the shape of the portion to be cut may be determined according to the size and shape of the gas diffusion layer, such as a polygonal shape such as a square or a triangle, a circular shape, or an elliptical shape. Also, when the flat protective sheet is arranged in an L shape, the flat protective sheet is in contact with the peripheral edge of the electrolyte membrane and the side surface of the gas diffusion electrode. It is desirable to make it smaller than the size of the gas diffusion layer. Specifically, it is preferable that the size of the portion to be cut is smaller by 0.1 to 1.0 mm per side than the size of the gas diffusion layer.

  For example, as shown in FIG. 6, the peripheral portion of the protective sheet 150 is fixed with a frame 170 such as a metal frame, and then the central portion of the protective sheet is used as a method for producing a truncated cone-shaped or cylindrical trapezoidal protective sheet. A method of punching with a member 180 having a predetermined shape such as a quadrangular column or a cylinder is used. 6A is a top view of the protective sheet fixed by the frame 170, and FIG. 6B is a cross-sectional view taken along line A-A 'in FIG. 6A.

  The bottom surface of the member 180 may have a size substantially equal to the size of the gas diffusion layer. The shape of the bottom surface of the member 180 may be appropriately determined depending on the size of the gas diffusion layer, and may be a rectangle such as a rectangle or a square, a polygon such as a triangle, a circle or an ellipse.

  In order to divide the protective sheet into a plurality of sheets, the central portion of the sheet having a desired size is cut into a size substantially equal to that of the gas diffusion layer using the same method as described above, and thus obtained. It is obtained by further dividing the protective sheet into two or more. In order to dispose the divided protective sheet on the membrane electrode assembly, the divided protective sheets are preferably bonded to each other with an adhesive and then covered with the peripheral edge portion of the electrolyte membrane and the side surface portion of the gas diffusion electrode. In order to individually bond the divided protective sheets with an adhesive, when the protective sheets are arranged on the peripheral edge portion of the electrolyte membrane and the side surface portion of the gas diffusion electrode, the divided protective sheets are in contact with and / or overlapped with each other. What is necessary is just to stick the protective sheet which apply | coated and divided | segmented the adhesive agent. As the adhesive for bonding the divided protective sheet and the coating method thereof, the same method as described later is used.

  In order to arrange the protective sheet in an L shape so as to be in contact with the peripheral edge portion of the electrolyte membrane and the side surface portion of the gas diffusion electrode, a fastening pressure at the time of assembling the fuel cell can be used. That is, after the gasket is disposed on the periphery of the electrolyte membrane covered with the protective sheet, the protective sheet can also be disposed in an L shape by a fastening pressure when sandwiched and fastened by a separator.

  In the membrane electrode assembly covered with the protective sheet, when the inner side surface arranged on the gas diffusion electrode side of the protective sheet is arranged higher than the separator side surface of the gas diffusion layer, or the gas diffusion electrode of the protective sheet When at least a part of the inner side surface disposed on the side covers the separator side surface of the gas diffusion layer, the gas diffusion electrode of the protective sheet is cut as shown in FIG. It is desirable to adjust the inner side surface arranged on the side so as to have the same height as the surface of the gas diffusion layer on the separator side.

  When the protective sheet and the peripheral edge of the electrolyte membrane and / or the side surface of the gas diffusion electrode are bonded with an adhesive, first, the roll coating method, curtain coating method, extrusion coating method, spin coating method, dip coating are used. Using a general method such as a coating method, a bar coating method, a spray coating method, a slide coating method, a print coating method, and the like, and a peripheral portion of an electrolyte membrane, a side portion of a gas diffusion electrode, and / or a gas diffusion electrode of a protective sheet What is necessary is just to cover a protective sheet after apply | coating an adhesive agent to the site | part which can contact.

  The fuel cell of the present invention is characterized in that the protective sheet for preventing the fuel gas or the oxidant gas from coming into direct contact with the electrolyte membrane is arranged as described above. Is the same as that of a conventional general fuel cell. Hereinafter, the configuration of the fuel cell will be described with an example, but the configuration of the fuel cell of the present invention is not limited to the following.

  The fuel cell includes a pair of gas diffusion electrodes including an electrode catalyst layer and a gas diffusion layer on both sides of an electrolyte membrane, that is, a cathode gas diffusion electrode including a cathode catalyst layer and a gas diffusion layer, an anode catalyst layer, and a gas diffusion. It has a membrane electrode assembly in which an anode side gas diffusion electrode including a layer is arranged.

  The catalyst layer used for the anode and the cathode includes an electrode catalyst in which a catalyst component is supported on a conductive carrier, and a polymer electrolyte.

  The catalyst component used in the cathode catalyst layer is not particularly limited as long as it has a catalytic action for the oxygen reduction reaction, and a known catalyst can be used in the same manner. Further, the catalyst component used in the anode catalyst layer is not particularly limited as long as it has a catalytic action for the oxidation reaction of hydrogen, and a known catalyst can be used in the same manner. Specifically, it is selected from platinum, ruthenium, iridium, rhodium, palladium, osmium, tungsten, lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum and the like, and alloys thereof. Is done. The shape and size of the catalyst component are not particularly limited, and the same shape and size as known catalyst components can be used.

  The electroconductive carrier in the electrode catalyst may be any electroconductive carrier as long as it has a specific surface area for supporting the catalyst component in a desired dispersed state and has sufficient electronic conductivity as a current collector. Is preferred. Specific examples include carbon particles made of carbon black, activated carbon, coke, natural graphite, artificial graphite and the like.

  The polymer electrolyte used for each catalyst layer used in the cathode and anode of the present invention is not particularly limited, and a known one can be used, but any member having at least high proton conductivity may be used. Specifically, perfluorocarbon polymers having a sulfonic acid group, such as Nafion (registered trademark, manufactured by DuPont), Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.), phosphoric acid, etc. Hydrocarbon polymer compound doped with inorganic acid such as organic / inorganic hybrid polymer partially substituted with proton conductive functional group, polymer matrix impregnated with phosphoric acid solution or sulfuric acid solution And proton conductors.

  The thickness of each catalyst layer in the anode and the cathode is preferably 1 to 20 μm, more preferably 5 to 20 μm. If the thickness of the catalyst layer exceeds 1 μm, the diffusibility of the reaction gas may decrease and power generation performance may decrease, and if it is less than 20 μm, sufficient power generation performance may not be obtained.

  Next, the gas diffusion layer in the anode and the cathode is not particularly limited, and known ones can be used in the same manner. For example, the conductive and porous properties such as carbon woven fabric, paper-like paper body, felt, and non-woven fabric are used. The thing which consists of a sheet-like base material which has is mentioned.

  The thickness of the substrate may be appropriately determined in consideration of the characteristics of the obtained gas diffusion layer, but may be about 30 to 500 μm. If the thickness is less than 30 μm, sufficient mechanical strength or the like may not be obtained, and if it exceeds 500 μm, the distance through which gas or water permeates is undesirably increased.

  The gas diffusion layer preferably contains a water repellent in the base material for the purpose of further improving water repellency and preventing a flooding phenomenon. Although it does not specifically limit as said water repellent, Fluorine-type, such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyhexafluoropropylene, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), etc. Examples thereof include polymer materials, polypropylene, and polyethylene.

  Moreover, in order to improve water repellency more, the said gas diffusion layer may have a carbon particle layer which consists of an aggregate | assembly of the carbon particle containing a water repellent on the said base material.

  The carbon particles are not particularly limited, and may be conventional ones such as carbon black, graphite, and expanded graphite. Of these, carbon blacks such as oil furnace black, channel black, lamp black, thermal black, and acetylene black are preferred because of their excellent electron conductivity and large specific surface area.

  Examples of the water repellent used for the carbon particle layer include the same water repellents as those described above used for the substrate. Of these, fluorine-based polymer materials are preferably used because of their excellent water repellency and corrosion resistance during electrode reaction.

  The thickness of the carbon particle layer may be appropriately determined in consideration of the water repellency of the obtained gas diffusion layer, but is preferably 10 to 150 μm, more preferably 30 to 70 μm.

  The polymer electrolyte membrane used for the membrane electrode assembly is not particularly limited, and examples thereof include a membrane made of the same polymer electrolyte as that used for the catalyst layer. In addition, various types of Nafion manufactured by DuPont (registered trademark of DuPont) and perfluorosulfonic acid membranes represented by Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.), ion exchange resins manufactured by Dow Chemical Co., and ethylene-tetrafluoride Fluorine polymer electrolytes such as ethylene copolymer resin membranes, resin membranes based on trifluorostyrene, and hydrocarbon polymer resin membranes having sulfonic acid groups, such as polymer electrolyte membranes that are generally commercially available , A polymer microporous membrane made of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), etc. impregnated with a liquid electrolyte such as phosphoric acid or ionic liquid, and a porous body with a polymer electrolyte You may use the film | membrane filled with. The polymer electrolyte used for the polymer electrolyte membrane and the polymer electrolyte used for each electrode catalyst layer may be the same or different, but the adhesion between each electrode catalyst layer and the polymer electrolyte membrane From the viewpoint of improving the properties, it is preferable to use the same one.

  The membrane electrode assembly is sandwiched between separators and used for a fuel cell. The separator can be used without limitation as long as it is conventionally known, such as those made of carbon such as dense carbon graphite and a carbon plate, and those made of metal such as stainless steel. The separator has a function of separating the oxidant gas and the fuel gas, and a channel groove for securing the channel may be formed. The thickness and size of the separator, the shape of the flow channel, and the like are not particularly limited, and may be appropriately determined in consideration of the output characteristics of the obtained fuel cell.

  In order to prevent the gas supplied to each gas diffusion electrode from leaking to the outside, a gasket is disposed between the membrane electrode assembly and the separator to seal the edge region of the membrane electrode assembly. desirable.

  As the material constituting the gasket, rubber materials such as fluorine rubber, silicon rubber, ethylene propylene rubber (EPDM), polyisobutylene rubber, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyhexafluoropropylene, Examples thereof include fluorine-based polymer materials such as tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and thermoplastic resins such as polyolefin and polyester.

  The thickness of the gasket may be 50 μm to 2 mm, preferably about 100 μm to 1 mm.

  Furthermore, a stack in which a plurality of membrane electrode assemblies are stacked via a separator and connected in series may be formed so that the fuel cell can obtain a desired voltage or the like. The shape of the fuel cell is not particularly limited, and may be determined as appropriate so that desired battery characteristics such as voltage can be obtained.

  The type of the fuel cell is not particularly limited. In the above description, the polymer electrolyte fuel cell has been described as an example. However, in addition to the above, an alkaline fuel cell, a phosphoric acid fuel cell, Typical examples include acid electrolyte fuel cells, direct methanol fuel cells, and micro fuel cells. Among these, a polymer electrolyte fuel cell is preferable because it is small in size, and can achieve high density and high output.

  The fuel cell of the present invention is useful as a power source for a moving body such as an automobile having a limited mounting space in addition to a stationary power source. Especially, since it is lightweight and can be reduced in size, it is especially preferable to use as a power supply for moving bodies, such as a motor vehicle.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited only to these Examples.

Example 1
1. Manufacture of membrane electrode assembly (1) Manufacture of gas diffusion layer Carbon paper (TGP-H-060 manufactured by Toray Industries, Inc., thickness 200 μm) was used as a base material, and after punching it into 100 mm × 100 mm square, PTFE An aqueous dispersion solution (D1 manufactured by Daikin Industries, Ltd., containing 60% by mass of PTFE) was immersed in a solution diluted to a predetermined concentration with pure water for 2 minutes, and then dried in an oven at 60 ° C. for 10 minutes. The substrate was subjected to a water repellent treatment. At this time, the PTFE content in the substrate was 20% by mass.

(2) Preparation of catalyst ink Platinum-supported carbon (TEC10E50E, Tanaka Kikinzoku Kogyo Co., Ltd., TEC10E50E, platinum content 46.5 wt%) 10 g, solid polymer electrolyte solution (DuPont Nafion solution DE520, electrolyte content 5 wt%) 90 g, pure water 25 g Then, 10 g of 2-propanol (special grade reagent manufactured by Wako Pure Chemical Industries, Ltd.) was mixed and dispersed for 3 hours using a homogenizer in a glass container in a water bath set to be kept at 20 ° C. to obtain a catalyst ink. .

(2) Preparation of electrode catalyst layer The catalyst ink prepared previously using a screen printer was applied to one side of a 200-μm-thick PTFE sheet (Naflon (registered trademark) sheet manufactured by Nichias) and 100 in an oven. After drying at ° C. for 30 minutes, it was cut into a 10 cm square.

(3) Assembly of membrane electrode assembly The two electrode catalyst layer-formed PTFE sheets prepared above with a polymer electrolyte membrane (Nafion NR-112 made by DuPont) having a square of 20 cm on each side and a thickness of 30 μm are sandwiched. The electrode catalyst layers are stacked so that the electrode catalyst layer forming sides face each other, and hot pressed at 130 ° C. for 10 minutes at a pressure of 3 MPa per one side of PTFE sheet, and after cooling, only the PTFE sheet is peeled off, thereby removing the electrode catalyst layer on the polymer electrolyte membrane Was transferred to obtain a joined body. At this time, the transfer rate of the electrode catalyst layer from the PTFE sheet to the polymer electrolyte membrane was 100%, and the platinum weight per 1 cm ² of the single-sided electrode catalyst layer on the polymer electrolyte membrane was 0.40 mg. . Moreover, the thickness of the electrode catalyst layer was 10 μm, respectively.

  The obtained joined body was sandwiched between two previously prepared gas diffusion layers to obtain a membrane electrode assembly.

2. Arrangement of protective sheet As shown in FIG. 6, after fixing the periphery of a sheet (size 200 mm × 200 mm, thickness 25 μm) made of polyethylene naphthalate (PEN) with a stainless steel frame, it is made of stainless steel in the shape of a square pillar By punching out the central portion of the sheet using a cutter (size: 100 mm × 100 mm × 250 mm), a square frustum-shaped protective sheet with the central portion cut was obtained.

  Next, an adhesive made of polyolefin is applied to the adhesive portion of the protective sheet whose central portion has been cut using a roll coating method to a thickness of 0.07 mm, and then the protective sheet is applied to the membrane electrode assembly prepared previously. I covered it. In the same manner, a protective sheet was placed on the other surface of the membrane electrode assembly.

  Thereafter, a frame-shaped gasket (thickness: 0.25 mm) made of polytetrafluoroethylene is disposed on the peripheral edge of the polymer electrolyte membrane covered with the protective sheet, and then also on the other surface of the polymer electrolyte membrane. Similarly, a gasket was disposed, and the membrane / electrode assembly was sandwiched between graphite separators, and further sandwiched between gold-plated stainless steel current collector plates to obtain evaluation single cells.

3. Single Cell Evaluation A power generation test of the single cell for evaluation produced above was performed according to the following procedure.

In the evaluation unit cell, hydrogen was supplied as a fuel to the anode side, and air was supplied as an oxidant to the cathode side. For both gases, the cell outlet pressure is atmospheric pressure, hydrogen is set to 70 ° C. and relative humidity 100%, air is set to 70 ° C. and relative humidity 100%, cell temperature is set to 70 ° C., hydrogen utilization rate is 60%, air utilization rate Was 40%. Under this condition, power generation was stopped after 3 minutes of power generation at a current density of 1.0 A / cm ² . After stopping, the supply of hydrogen and air was stopped, dry air was supplied to the single cell, the inside of the cell was replaced for 1 minute, and then hydrogen gas was supplied to the anode side for 2 minutes at the above utilization rate. Thereafter, air was supplied to the cathode side at the same utilization rate as above, and power was generated again. This power generation / stop operation was repeated, and the number of times until the no-load voltage decreased from the initial value to 0 V was measured during the power generation / stop cycle test. The results are shown in FIG.

(Example 2)
The center part of the sheet | seat (size 200 mm x 200 mm, thickness 25 micrometers) which consists of polyethylene naphthalate was cut into the magnitude | size of 100 mm x 100 mm, and the flat protective sheet from which the center part was cut was produced. A single cell for evaluation was assembled in the same manner as in Example 1 except that the protective sheet was used.

(Example 3)
After the central part of a sheet made of polyethylene naphthalate (size: 200 mm × 200 mm, thickness: 25 μm) was cut into a size of 100 mm × 100 mm, it was divided into four parts as shown in FIG. An adhesive made of polyolefin is applied to the side surface of the end portion of the protective sheet using a roll coating method, and then the divided protective sheet is pasted together as a protective sheet 152 shown in FIG. 4B to produce a protective sheet. did. A single cell for evaluation was assembled in the same manner as in Example 1 except that the protective sheet was used.

(Comparative Example 1)
An evaluation unit cell was assembled and evaluated in the same manner as in Example 1 except that the protective sheet was not disposed. The results are shown in FIG.

  According to the present invention, a fuel cell having excellent durability can be provided.

The schematic cross section of the fuel cell of this invention is shown. 2A shows a schematic diagram of a truncated cone-shaped protective sheet used in the fuel cell of the present invention, and FIG. 2B shows a schematic diagram of a cylindrical trapezoidal protective sheet used in the fuel cell of the present invention. Show. The schematic diagram of the flat protective sheet used for the fuel cell of this invention is shown. FIG. 4A shows a schematic top view of a divided protective sheet used in the fuel cell of the present invention, and FIG. 4B shows a top view of a membrane electrode assembly in which the divided protective sheet is arranged. . Sectional drawing of the membrane electrode assembly edge part by which the protection sheet used for the fuel cell of this invention is arrange | positioned is shown. 6A is a top view of the protective sheet fixed by the frame 170, and FIG. 6B is a cross-sectional view taken along line A-A ′ in FIG. A schematic cross-sectional view of a conventional fuel cell is shown. A schematic cross-sectional view of a conventional fuel cell is shown. It is a graph which shows the evaluation result of the membrane electrode assembly produced in the Example. It is a graph which shows the evaluation result of the membrane electrode assembly produced in the comparative example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Polymer electrolyte membrane, 110 ... Gas diffusion electrode, 111 ... Electrode catalyst layer, 112 ... Gas diffusion layer, 120 ... Separator, 121 ... Gas supply path, 130 ... Gasket, 131 ... Frame base material, 140 ... Air gap, 150 DESCRIPTION OF SYMBOLS ... Protection sheet, 151 ... Cut part, 152 ... Divided protection sheet, 160 ... Adhesive, 170 ... Frame, 180 ... Cutter.

Claims (6)

In a fuel cell having a membrane electrode assembly in which a pair of gas diffusion electrodes including an electrode catalyst layer and a gas diffusion layer are disposed on both sides of an electrolyte membrane,
A fuel cell in which a protective sheet is disposed in contact with the electrolyte membrane and the gas diffusion electrode.   The protective sheet is cut in a size substantially equal to that of the gas diffusion layer, and is disposed in an L shape so as to contact the peripheral edge of the electrolyte membrane and the side surface of the gas diffusion electrode. Item 2. The fuel cell according to Item 1.   The fuel cell according to claim 2, wherein the protective sheet having a truncated cone shape or a truncated pyramid shape is disposed.   The fuel cell according to claim 2, wherein the flat protective sheet is disposed.   The fuel cell according to claim 2, wherein the protective sheet is divided and disposed.   The fuel cell according to claim 1, wherein the protective sheet is made of at least one selected from the group consisting of polyethylene naphthalate, polyethylene terephthalate, polytetrafluoroethylene, polyimide, and polyethernitrile.