JP2006156288A - Fuel cell and manufacturing method of fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell capable of easily improving water-draining capability; and to provide a manufacturing method of the fuel cell. <P>SOLUTION: This fuel cell is provided with a layered product composed by stacking unit cells 10 each comprising: an MEA 5 having an electrolyte layer 1 and catalyst layers 2a and 3a arranged on both sides of the electrolyte layer 1; diffusion layers 2b and 3b arranged on both sides of the MEA 5; and separators 7 and 8 arranged on the outside surfaces of the diffusion layers 2b and 3b. The fuel cell is provided with drainage means 6, 6 on the surfaces of the catalyst layers 2a and 3a on the sides of the diffusion layers 2b and 3b. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell and a method for manufacturing the fuel cell, and more particularly, to a fuel cell capable of easily improving drainage and a method for manufacturing the fuel cell.

  A fuel cell is based on an electrochemical reaction in a membrane electrode assembly (hereinafter referred to as “MEA (Membrane Electrode Assembly)”) including an electrolyte and electrodes (anode and cathode) disposed on both sides of the electrolyte. The generated electric energy is taken out through separators disposed on both sides of the MEA. Among fuel cells, polymer electrolyte fuel cells (hereinafter referred to as “PEFC (Polymer Electrolyte Fuel Cell)”) used in household cogeneration systems and automobiles, etc., operate at low temperatures. It is possible to use it at an operating temperature such as 80 to 100 ° C. In addition, PEFC has shown high energy conversion efficiency of 30 to 40%, has a short start-up time, and has a small and lightweight system. Therefore, PEFC has attracted attention as an optimal power source for electric vehicles and portable power sources.

  A single cell of PEFC includes an electrolyte membrane, a cathode and an anode including a catalyst layer and a diffusion layer, and a separator, and has a theoretical electromotive force of 1.23V. However, since such low electromotive force is insufficient as a power source for electric vehicles and the like, normally, a single cell is laminated in series to form a laminated body, and end plates or the like are formed at both ends of the laminated body in the lamination direction. A stack-type fuel cell is used.

On the other hand, the electrolyte of PEFC uses a cation exchange resin membrane as a cation conductive membrane. This conductive film has a proton (hydrogen ion (H ⁺ )) exchange group in the molecule, and when it is saturated with water, it exhibits a specific resistance of 20 Ω · cm or less at room temperature. It functions as a functional electrolyte. The saturated water content of the electrolyte membrane changes reversibly with temperature. That is, during operation of the PEFC, humidified water added in the form of water vapor in the fuel gas and oxidizing gas to prevent transpiration from the electrolyte membrane, and water generated by an electrochemical reaction on the cathode side By means of this, saturation is always maintained.

  However, if the water produced on the cathode side increases or the fuel gas and the oxidizing gas are consumed and the water vapor in the residual gas becomes supersaturated, the water condenses and the water supply becomes excessive, the electrolyte membrane and The electrode is immersed in water and enters a so-called “flooding” state. When this flooding occurs, the gas contact area in the cell decreases, and further, the supply of oxygen gas to the cathode is hindered, and the generated voltage of PEFC decreases. Since such a voltage drop leads to a decrease in the efficiency of PEFC, it is important to suppress the occurrence of flooding by improving the drainage in the cell in order to maintain the high energy conversion efficiency of PEFC.

  On the other hand, for electric vehicle applications, fuel cells are required to generate electrical energy immediately after startup, that is, to have good startability. However, for example, in a cold environment below freezing, it is difficult to obtain good startability as a result of freezing of water remaining in the cathode. It is known that such water freezing is particularly likely to occur in a single cell (hereinafter referred to as an “end cell”) arranged at the end of the stack that is easily cooled by outside air. Yes. Therefore, it is desired to improve the efficiency of the fuel cell by improving the startability of the end cells in the cold environment (hereinafter referred to as “low temperature startability”).

Several techniques aimed at improving drainage in the cell have been disclosed so far. For example, Patent Document 1 discloses PEFC in which the mixing amount of fluororesin fine particles in the electrode layer is changed between the gas inlet side and the outlet side, and a cell located on the upstream side and a cell located on the downstream side in the gas flow direction. And a technology relating to PEFC in which the mixing amount of the fluororesin fine particles is changed. According to this technology, it is possible to easily manage the moisture by improving the water repellency of the portion where water is accumulated, and further, it is possible to suppress the performance degradation in the cell located upstream in the gas flow direction. It can be done. In addition, the electrode layer concerning patent document 1 is the concept corresponding to the catalyst layer in this invention. Patent Document 2 discloses a technique related to PEFC including a mixed layer made of a fluororesin and carbon black between a catalyst layer and a diffusion layer of a cathode electrode and an anode electrode. According to this technique, gas diffusion inhibition due to partial drying or excessive wetting of the electrolyte membrane can be prevented, and deterioration of battery performance can be prevented.
JP-A-9-283153 JP 2001-135326 A

  However, in the technique disclosed in Patent Document 1, it is necessary to change the mixing amount of the fluororesin fine particles in the plane of the electrode layer. In this way, an electrode layer whose composition is inclined in the plane is produced. Therefore, there is a problem that it is difficult to improve the drainage of the electrode layer by such a technique. In addition, even with the technique disclosed in Patent Document 2, it is difficult to effectively improve the efficiency of the fuel cell.

  Then, this invention makes it a subject to provide the fuel cell which can improve drainage easily, and the manufacturing method of the said fuel cell.

In order to solve the above problems, the present invention takes the following means. That is,
The invention according to claim 1 is an MEA including an electrolyte layer and a catalyst layer disposed on both sides of the electrolyte layer, a diffusion layer disposed on both sides of the MEA, and disposed outside the diffusion layer. A fuel cell comprising a laminate, in which a single cell comprising a separator is laminated, wherein a drainage means is provided on the surface of the catalyst layer on the diffusion layer side. Solve the problem.

  Here, in the present invention, the surface on the diffusion layer side of the catalyst layer means at least one laminated surface of the MEA. The laminated surface is a surface whose normal direction is the lamination direction of the single cells, and the MEA has a laminated surface on the cathode side and a laminated surface on the anode side. If drainage means is applied to the laminated surface of the MEA, then the drainage means is applied to the surface on the diffusion layer side by disposing a diffusion layer on both sides of the laminated surface of the MEA to which the drainage means is applied. It becomes possible to set it as a fuel cell provided with a catalyst layer. Further, the drainage means is not particularly limited as long as it is a means capable of draining water droplets on the surface of the catalyst layer on the diffusion layer side. As a specific example, the surface of the surface has an uneven shape. A means for improving drainage by forming, a water repellent applied to the surface of the surface, and the like can be mentioned.

  According to a second aspect of the present invention, in the fuel cell according to the first aspect, the drainage means is applied to a portion of the surface on the diffusion layer side where the droplet water tends to stay in the single cell. It is characterized by.

  Here, as a specific example of the portion where water of droplets is likely to stay in the single cell, when the single cell is arranged at the center of the laminate, the outlet of the reactive gas supplied to the cathode or the The downstream part of the reaction gas (for example, the second half of the reaction gas channel, etc.) can be mentioned. Further, when a serpentine-shaped reaction gas channel is formed in the separator, the curved part of the channel, etc. Can be mentioned. On the other hand, when the single cell is disposed at an end portion (for example, both ends) of the laminated body, the entire surface on the diffusion layer side can be exemplified. That is, specific examples of the part where the drainage means can be provided in the present invention include a part on the diffusion layer side of the catalyst layer facing these parts.

  The invention according to claim 3 is the fuel cell according to claim 1 or 2, wherein the drainage means is a water repellent.

  Here, in the present invention, the water repellent is particularly limited as long as it has a property of allowing gas to permeate but not permeating droplet water (hereinafter referred to as “water repellency”). is not.

  According to a fourth aspect of the present invention, in the fuel cell according to the third aspect, the water repellent is applied in a thickness of 5 to 50 nm.

  The invention according to claim 5 is the fuel cell according to claim 3 or 4, wherein the water repellent is a fluorine-based surface treatment agent.

  Here, in the present invention, the fluorine-based surface treatment agent is not particularly limited as long as it has water repellency, but it may be applied to the surface of the catalyst layer at a thickness of 5 to 50 nm. Preferably, specific examples of the surface treatment agent include a fluorine-based water repellent.

  A sixth aspect of the present invention is the fuel cell according to any one of the first to fifth aspects, wherein a single cell including a catalyst layer to which drainage means is provided is provided at an end of the laminate. It is characterized by being.

  Here, from the viewpoint of emphasizing the performance of the fuel cell in a steady state, the end portion of the stacked body is based on two cells arranged at both ends of the stacked body, but only at the two cells at both ends. In the case where the low temperature startability of the fuel cell is insufficiently improved, a plurality of cells at both ends can be formed by increasing the number of cells in order from both ends of the laminate.

  The invention according to claim 7 is an MEA comprising an electrolyte layer and a catalyst layer disposed on both sides of the electrolyte layer, a diffusion layer disposed on both sides of the MEA, and disposed outside the diffusion layer. A process for producing a fuel cell comprising a laminate, comprising a single cell comprising a separator, wherein a water repellent is applied to at least one of the laminated surfaces of the MEA after the MEA is produced. The above-described problem is solved by a method for manufacturing a fuel cell.

  According to invention of Claim 1, the drainage means is provided to the surface at the side of the diffusion layer of a catalyst layer. If a drainage means is provided on such a surface, it becomes possible to prevent the movement of the water of the droplets entering the inside of the catalyst layer from the diffusion layer side, and the water of the droplets is moved out of the single cell. It becomes possible to discharge easily. Therefore, it becomes possible to provide the fuel cell which can improve drainage easily by setting it as this structure.

  According to the second aspect of the present invention, since the drainage means is provided in the portion where the water of the droplet tends to stay on the diffusion layer side surface of the catalyst layer, the water of the droplet is effectively removed to the outside of the single cell. Can be discharged. Therefore, it becomes possible to provide the fuel cell which can improve drainage effectively by setting it as this structure.

  According to invention of Claim 3, the drainage property of the said catalyst layer is improved by apply | coating a water repellent to the surface at the side of the diffusion layer of a catalyst layer. That is, it becomes possible to provide the catalyst layer for fuel cells which can improve drainage by a simple method by setting it as this form.

  According to the fourth aspect of the present invention, the water repellent is applied to the surface of the catalyst layer on the diffusion layer side with a thickness of 5 to 50 nm. If the water repellent is applied with a thickness of 50 nm or less, the power generation performance can be maintained. Therefore, with this configuration, it is possible to provide a fuel cell that can effectively improve drainage while maintaining power generation performance.

  According to the invention described in claim 5, the water repellent is a fluorine-based surface treatment agent. In particular, when a fluorine-based water repellent or the like is used, a water repellent layer having a uniform thickness of, for example, 5 to 50 nm can be formed on the surface of the catalyst layer on the diffusion layer side. Therefore, it becomes possible to provide easily the fuel cell which can improve drainage by setting it as this structure.

  According to invention of Claim 6, the single cell which has favorable drainage property is provided in the edge part of the laminated body. Here, since the end cells are easily exposed to the outside air, the end cells are easily cooled by the outside air, so that droplet water is easily generated, and the end cells are easily flooded. On the other hand, since the generated water tends to stay in the end cells, for example, when the fuel cell after operation is placed in a sub-freezing environment, the staying water in the end cells easily freezes, resulting in a decrease in low temperature startability. Therefore, the invention according to claim 6 provides a fuel cell that can suppress flooding and improve low-temperature startability by improving drainage of the end cells. It becomes possible to do.

  According to the seventh aspect of the present invention, the water repellent is applied to at least one of the MEA laminated surfaces after the MEA is manufactured. Here, since the MEA is configured by disposing a catalyst layer on both sides of the electrolyte layer, the laminated surface of the MEA corresponds to the surface of the catalyst layer, and a diffusion layer is disposed on both sides of the MEA. Therefore, with the manufacturing method of this form, it becomes possible to manufacture a fuel cell in which a water repellent is applied to the surface of the catalyst layer on the diffusion layer side. Therefore, according to the seventh aspect of the present invention, it is possible to provide a method for manufacturing a fuel cell capable of improving drainage.

  Hereinafter, the fuel cell of the present invention will be described more specifically with reference to the drawings.

FIG. 1 is a cross-sectional view schematically showing an example of a single cell constituting a fuel cell according to the present invention. In FIG. 1, the horizontal direction in the figure is the stacking direction of the single cells.
As illustrated, the unit cell 10 of the present invention according to the first embodiment includes an electrolyte membrane 1 and an MEA 5 including an anode catalyst layer 2a and a cathode catalyst layer 3a disposed on both sides of the electrolyte membrane 1. The anode diffusion layer 2b and the cathode diffusion layer 3b are disposed on both sides of the MEA 5. An anode separator 7 and a cathode separator 8 are further disposed outside the diffusion layers 2b and 3b. Reactive gas supply paths 7a, 7a, and 7a, respectively, are provided on the surfaces of the separators 7 and 8 on the diffusion layers 2b and 3b side. .. And 8a, 8a,... Are formed, and cooling water flow paths 7b, 7b,... And 8b, 8b,. In the illustrated unit cell 10, the anode 2 includes an anode catalyst layer 2a and an anode diffusion layer 2b, while the cathode 3 includes a cathode catalyst layer 3a and a cathode diffusion layer 3b. The reaction gas channels 7a, 7a,... Of the anode separator 7 are supplied with hydrogen-containing gas (hereinafter sometimes referred to as “hydrogen”) via a manifold (not shown). The reaction gas flow paths 8a, 8a,... Are each supplied with an oxygen-containing gas (hereinafter sometimes referred to as “oxygen”) via a manifold (not shown). Here, in the single cell 10 according to the present embodiment, the surface of the cathode catalyst layer 3a on the cathode diffusion layer 3b side and the surface of the anode catalyst layer 2a on the anode diffusion layer 2b side (hereinafter, these surfaces are combined). The water repellent layers 6 and 6 including a fluorine-based water repellent (Novec (Novec is a registered trademark of 3M USA)) are formed on the “first surface”. With such a configuration, in the single cell 10 according to the present invention, the drainage performance of both surfaces of the MEA 5 (the surfaces on the diffusion layers 2b and 3b side) is improved.

  In the single cell 10 shown in the figure, hydrogen supplied from the reaction gas flow paths 7a, 7a,... On the anode side reaches the anode catalyst layer 2a via the anode diffusion layer 2b, and on the catalyst in the catalyst layer 2a. Thus, electrons and hydrogen ions are generated from hydrogen. The hydrogen ions generated in the anode catalyst layer 2a pass through the electrolyte membrane 1 and reach the cathode catalyst layer 3a. On the other hand, oxygen supplied from the reaction gas flow paths 8a, 8a,... On the cathode side is supplied to the cathode catalyst layer 3a via the cathode diffusion layer 3b, and on the catalyst of the catalyst layer 3a, hydrogen ions, oxygen And water react with each other (hereinafter sometimes referred to as “electrochemical reaction”) to generate water (water vapor). A part of the water vapor thus generated is discharged to the outside by the gas flowing in the reaction gas flow paths 8a, 8a,..., While the remaining part of the water vapor is flown in the flow paths 8b, 8b,. By touching the separator 8 that is cooled by the flowing cooling water, dew condensation forms water of droplets. A part of the water can be discharged to the outside by the gas flowing in the flow paths 8a, 8a,. Therefore, for example, the water in the droplets tends to stay particularly at the downstream portion of the flow paths 8a, 8a,... And the outlet of the flow paths 8a, 8a,..., And the flow path is formed in a so-called serpentine shape. In this case, the water tends to stay in a curved portion (see FIG. 2C) of the flow channel where the water of the droplet is hardly pushed out by the reaction gas. When the water in the droplets thus generated reaches the catalyst layers 3a and 2a and the catalyst layers 3a and 2a are flooded, the catalyst that should contribute to the electrochemical reaction is immersed in the water. The power generation efficiency of the cell 10 is reduced. Therefore, in the present invention, by forming the water repellent layers 6 and 6 on the first surface, the movement of water droplets from the diffusion layers 3b and 2b toward the catalyst layers 3a and 2a is prevented, thereby generating power. The single cell 10 is capable of preventing a decrease in efficiency.

  Here, a water repellent layer is provided at the interface between the diffusion layers 3b and 2b and the catalyst layers 3a and 2a for the purpose of preventing the movement of the water droplets from the diffusion layers 3b and 2b toward the catalyst layers 3a and 2a. When forming, a water repellent layer is formally formed on the surfaces of the diffusion layers 3b and 2b on the catalyst layers 3a and 2a side (hereinafter, sometimes referred to as “second surface”). Is also possible. However, microscopically, since there are irregularities on the surfaces of the diffusion layers 3b and 2b and the catalyst layers 3a and 2a, when the water repellent layer is formed on the second surface, the first surface Movement of droplets existing between the first surface and the second surface is hindered by the water repellent layer. Therefore, with such a configuration, it is difficult for water in the droplets to be taken away by the gas flowing in the reaction gas flow path. If water droplets existing between the first surface and the second surface remain without being taken away by the gas, the water tends to stay in the catalyst layer, and the catalyst layer is likely to be flooded. Therefore, in the present invention, a water repellent layer is formed on the first surface, and water droplets existing between the first surface and the second surface are carried away by the gas in the reaction gas channel. The single cell 10 has an easy form.

  In the present invention, the portion where the water repellent layer is formed is not particularly limited as long as it is the first surface. For example, the single cell 10 is other than the end of the laminate (for example, the center of the laminate). ), A site that should face the outlet of the reaction gas channel, a site that should face the downstream part of the reaction gas channel, and the like. 2 (C)), a portion to be opposed to the curved portion of the reaction gas flow path can be further exemplified. On the other hand, as will be described later, in the case of the single cell 10 disposed at the end of the laminate, it can be formed on the entire surface of the first surface or the like. If the water repellent layer is formed in these parts, for example, the composition of the catalyst layer may be changed or the water repellent agent applied to the catalyst layer may be changed between the part where the water of the droplet is likely to stay and the part where the water is difficult to stay. By a simpler method than the conventional method of changing the composition, it becomes possible to obtain a single cell that can effectively improve drainage.

  FIG. 2 schematically shows the outlet of the reactive gas channel, the downstream portion of the reactive gas channel, and the curved portion of the reactive gas channel formed in a serpentine shape. These reaction gas flow paths are formed on the surface of the separator on the diffusion layer side. FIG. 2 is a schematic view showing the separator from the diffusion layer side, and the direction perpendicular to the paper surface is the stacking direction. In FIG. 2, the straight arrow indicates the traveling direction of the reaction gas.

  2A is a schematic diagram showing the outlet of the reaction gas channel surrounded by a broken line, FIG. 2B is a schematic diagram showing the downstream part of the reaction gas channel surrounded by a broken line, and FIG. FIG. 3 is a schematic view showing a curved portion of a reaction gas channel formed in a serpentine shape surrounded by a broken line. 2 (A) and 2 (B), the portion surrounded by the broken line is likely to retain the water of the droplets because the water generated and moved by the electrochemical reaction collects, while the portion surrounded by the broken line in FIG. 2 (C). In such a portion, the droplet water is difficult to be pushed out by the gas flowing through the reaction gas flow path, so that the droplet water tends to stay. Therefore, if the water repellent layer is formed on the portion of the first surface opposite to these portions, it becomes possible to effectively discharge the water of the liquid droplets that tend to stay out of the single cell. .

  FIG. 3 is an external view schematically showing an example of a fuel cell including a laminate including a single cell according to the present invention. In FIG. 3, the horizontal direction in the drawing is the stacking direction of the single cells, and the fuel cell according to FIG. 3 includes the single cell 10. In the following description, a surface whose normal direction is the stacking direction is described as a stacking surface.

  In general, only the electromotive force of a single fuel cell is not sufficient as a power source for an electric vehicle or the like. Therefore, normally, as shown in FIG. 3, a fuel cell 100 in a stack form is used. The illustrated fuel cell 100 includes a stacked body 50 formed by stacking single cells 10, 10,... In series, current collector plates 60, 60 and an electrical insulating plate 70 disposed on both sides of the stacked body 50. , 70, and the end cells 10 </ b> A and 10 </ b> A that are easily exposed to the outside air radiate heat more easily than the center cells 10 </ b> B, 10 </ b> B. Therefore, in particular, in the end cells 10A and 10A, moisture in the reaction gas is easily aggregated to generate droplet water, and water vapor generated by the electrochemical reaction is also easily aggregated. As a result, water droplets are easily generated and flooding is likely to occur. Therefore, when the single cell according to the present invention is disposed at the end of the laminate, it is preferable to form a water repellent layer over the entire surface of the first surface. By adopting such a configuration, it becomes possible to improve drainage of the end cells 10A, 10A, and it is possible to suppress the occurrence of flooding in the end cells 10A, 10A. In addition, if the end cells 10A and 10A have good drainage properties in this way, it becomes possible to reduce the water of the droplets remaining in the end cells 10A and 10A when the operation is stopped. . Therefore, even when the stopped fuel cell is placed in a cold environment below freezing, it is possible to suppress freezing of water that is likely to occur in the end cells 10A and 10A. It becomes possible to improve. Therefore, by disposing the single cell according to the present invention at the end of the laminated body, it is possible to provide the fuel cell 100 that can suppress the occurrence of flooding and improve the low-temperature startability. It becomes possible.

  In the above description, for the sake of convenience, a mode in which a single cell according to the present invention is arranged in two cells of one cell at both ends of the laminate is described. However, the end of the laminate has two cells, one cell at both ends. If it is included, it is not limited to the said form, For example, according to the environment where a fuel cell is used, there may be a width | variety of several cells (for example, about 3 cells) from both ends, for example. By adopting such a configuration, for example, even when a fuel cell is used in a cryogenic environment such as minus 20 ° C. or less and a few cells at the end are likely to dissipate heat, the drainage of the end cell is reduced. Since it becomes possible to improve effectively, it becomes possible to provide the fuel cell which can suppress generation | occurrence | production of flooding and can improve low temperature startability.

  In addition, the thickness of the water repellent layer formed in the above form is not particularly limited as long as it can improve the drainage of the single cell, but from the viewpoint of enabling uniform coating, it is 5 nm. It is preferable to set it as the above thickness, and it is preferable to set it as thickness of 50 nm or less from a viewpoint of suppressing the fall of electric power generation performance. Furthermore, the water repellent layer formed on the first surface is not limited to a form having the same thickness in all the portions where the water repellent layer is formed. In consideration of the drainage improvement effect, power generation performance, and the like, a difference in thickness may be provided for each formation site or in the same formation region.

  In addition, in the above description, for the sake of convenience, a single cell having a form in which a water repellent layer is formed on the first surface of the anode catalyst layer 2a and the cathode catalyst layer 3a has been described. It is not limited to the said form, The form by which the water repellent layer is formed only in the said 1st surface of the cathode catalyst layer 3a in which water vapor | steam is produced | generated by an electrochemical reaction may be sufficient. On the other hand, in the description of the fuel cell according to the stack form, the form in which the single cell according to the present invention is arranged only in the end cells 10A and 10A is described. However, the single cell according to the present invention is a stack form fuel cell. The site | part which can be arrange | positioned is not limited to an edge part. It may be arranged at a part and an end of the central part of the laminated body, and all the single cells constituting the laminated body may be the single cells according to the present invention.

  In the present invention, the method for forming the water repellent layer is not particularly limited as long as the water repellent layer can be formed on the first surface in a form that exhibits the above effects. Specific examples thereof include methods such as dipping, spin coating, and spray coating.

  Furthermore, in the present invention, when the water repellent layer is formed on the first surface, the water repellent has a property of allowing gas to pass and not allowing water of droplets to pass through, and having the above thickness. If it has the form which can be apply | coated, it will not specifically limit. Specific examples of the water repellent that can be used in the present invention include a fluorine-based water repellent, and specific examples of the fluorine-based water repellent include FS-7010 (stock) in addition to the above-mentioned Novec. And CYTOP (Cytop is a registered trademark of Asahi Glass Co., Ltd.).

  In the above description, for the sake of convenience, the embodiment in which the water repellent layer as the drainage means is formed on the first surface has been described, but the drainage means that can be applied to the first surface according to the present invention is: It is not limited to the water repellent layer, and other means may be provided as long as it can improve the drainage of the first surface. As a specific example of the other means, means for imparting water repellency by forming fine (nm order) irregularities on the surface of the first surface, and draining water of droplets on the first surface. Etc.

  In the above description, for convenience, a fuel cell including a single cell in which a reaction gas flow path is formed in the separator has been described. However, the form of the fuel cell to which the present invention can be applied is not limited to the form. Absent. No reaction gas flow path is formed in the separator, and it reacts with a diffusion layer formed by a porous material such as stainless steel, titanium or nickel, or a sintered metal produced by plating or foaming. The present invention can be preferably applied even to a fuel cell including a single cell in a form in which gas is supplied.

A single cell comprising a catalyst layer in which a water repellent (Novec manufactured by Sumitomo 3M) layer as a drainage means is formed on the entire surface of the first surface of the cathode catalyst layer and the anode catalyst layer by dipping (Example) And the relationship between cell voltage and current density was investigated using a single cell (comparative example) provided with a catalyst layer to which no drainage means was provided on the surface on the diffusion layer side. The survey results are shown in FIG. In FIG. 4, the solid line indicates the result of the example, and the broken line indicates the result of the comparative example. In FIG. 4, the vertical axis represents the cell voltage (V), and the horizontal axis represents the current density (A / cm ² ).

  In general, when the current density is increased, electrochemical reactions occur actively and a lot of water vapor is generated. For this reason, the higher the current density, the easier it is for droplet water to be generated, and the flooding state is more likely to occur. If the drainage in the cell stagnates and a flooding state occurs, the diffusion of the reaction gas is inhibited and the number of catalysts that can contribute to the electrochemical reaction decreases, so the electromotive force (cell voltage) decreases. For this reason, the value of the cell voltage is an indicator of whether or not a flooding state has occurred and the drainability of a single cell.

  As shown in FIG. 4, the cell according to the example has a lower cell voltage than the cell according to the comparative example, and can stably generate power at a higher current density than the cell according to the comparative example. there were. This is presumably because the drainage of the cell according to the example was improved by applying a water repellent to the first surface of the catalyst layer, and the occurrence of flooding was suppressed. That is, from this investigation, it was confirmed that the drainage performance of the fuel cell can be improved by providing drainage means on the surface of the catalyst layer on the diffusion layer side.

It is sectional drawing which shows roughly the example of the form of the single cell which comprises the fuel cell concerning this invention. It is the schematic which shows the example of the exit of a reactive gas flow path, a downstream part, and a curved part. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an external view schematically showing a form example of a fuel cell including a laminate including a single cell according to the present invention. It is a figure which shows the relationship between a cell voltage and a current density.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrolyte membrane 2 Anode 2a Anode catalyst layer 2b Anode diffusion layer 3 Cathode 3a Cathode catalyst layer 3b Cathode diffusion layer 5 MEA
6 Drainage means (water repellent layer)
7 Anode separator 8 Cathode separator 10 Single cell 10A End cell (end of laminate)
10B Central cell 50 Laminated body 100 Fuel cell

Claims (7)

A single cell comprising an MEA comprising an electrolyte layer and a catalyst layer disposed on both sides of the electrolyte layer, a diffusion layer disposed on both sides of the MEA, and a separator disposed on the outside of the diffusion layer A fuel cell comprising a laminate,
A fuel cell, wherein a drainage means is provided on a surface of the catalyst layer on the diffusion layer side. 2. The fuel cell according to claim 1, wherein the drainage unit is provided at a portion of the surface on the diffusion layer side where droplet water tends to stay in the single cell. The fuel cell according to claim 1 or 2, wherein the drainage means is a water repellent. The fuel cell according to claim 3, wherein the water repellent is applied in a thickness of 5 to 50 nm. The fuel cell according to claim 3 or 4, wherein the water repellent is a fluorine-based surface treatment agent. The fuel cell according to any one of claims 1 to 5, wherein the single cell including the catalyst layer to which the drainage unit is provided is provided at an end of the laminated body. . A single cell comprising an MEA comprising an electrolyte layer and a catalyst layer disposed on both sides of the electrolyte layer, a diffusion layer disposed on both sides of the MEA, and a separator disposed on the outside of the diffusion layer A method for producing a fuel cell comprising a laminate,
A method for producing a fuel cell, comprising: a step of applying a water repellent to at least one of the stacked surfaces of the MEA after producing the MEA.

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