JP2010067505A - Fuel cell and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell wherein conductivity of a catalyst layer is improved and a scaly carbon and a gold wire contained in the catalyst layer are prevented from bursting through an electrolyte film toward a facing electrode side. <P>SOLUTION: The fuel cell includes: the electrolyte film 410 having ion conductivity; an anode catalyst layer 430 and a cathode catalyst layer 420 laminated on the electrolyte film 410 for bearing a catalyst; and a circular conductor 550 contained in the anode catalyst layer 430 and the cathode catalyst layer 420, and formed in a circular shape with conductivity. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell including an electrolyte membrane, and more particularly to a catalyst layer laminated on an electrolyte membrane of a fuel cell.

  A fuel cell including an electrolyte membrane performs electrochemical power generation using a fuel gas and an oxidizing gas (herein, these gases are collectively referred to as “reactive gas”). In the fuel cell, the fuel gas is supplied to the anode side of the electrolyte membrane, and the oxidizing gas is supplied to the cathode side of the electrolyte membrane. On the anode side and the cathode side of the electrolyte membrane, a catalyst layer supporting a catalyst that promotes an electrochemical reaction of the reaction gas is laminated.

  Conventionally, in order to improve the conductivity of the catalyst layer, a fuel cell in which scaly carbon or gold wire is contained in the catalyst layer has been proposed (Patent Document 1).

JP 2004-158359 A

  However, since the scaly carbon or gold wire has a sharp end, the scaly carbon or gold wire contained in the catalyst layer is likely to pierce the electrolyte membrane and penetrate to the opposite electrode side, and between the anode and the cathode. There was a problem of causing a cross leak in which the reaction gas leaked.

  In view of the above-described problems, an object of the present invention is to provide a fuel cell that can improve the conductivity of a catalyst layer.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

[Application Example 1] The fuel cell of Application Example 1 is composed of an electrolyte membrane having ion conductivity, a catalyst layer stacked on the electrolyte membrane and supporting a catalyst, and contained in the catalyst layer, and configured with a smooth curve. And an annular conductor having a conductive shape. According to the fuel cell of Application Example 1, since an annular conductor having no sharp end portion is used to mediate electron movement in the direction of the electrode surface in the catalyst layer, the catalyst layer is prevented from being stuck to the electrolyte membrane. The conductivity can be improved.

Application Example 2 In the fuel cell according to Application Example 1, the annular conductor may include an annular conductor formed in an annular shape and having conductivity. According to the fuel cell of Application Example 2, it is possible to further prevent the electrolyte membrane from being stuck. The annular conductor may be an annular shape, may be a perfect circle, may be an ellipse, or may be a “C” shape with a part of the ring open.

Application Example 3 In the fuel cell of Application Example 1 or Application Example 2, the outer diameter of the annular conductor may be 50 to 100 micrometers. According to the fuel cell of the application example 2, the conductivity in the electrode plane direction in the catalyst layer can be effectively improved.

Application Example 4 In the fuel cell according to any one of Application Examples 1 to 3, the thickness of the annular conductor may be equal to or less than one third of the thickness of the catalyst layer. According to the fuel cell of Application Example 3, even when a plurality of annular conductors are overlapped, it is possible to suppress the catalyst layer from being locally thickened.

Application Example 5 In the fuel cell according to any one of Application Examples 1 to 4, the annular conductor may be made of carbon. According to the fuel cell of Application Example 5, it is possible to suppress the influence of the aging deterioration of the annular conductor on the catalyst layer.

Application Example 6 In the fuel cell of any one of Application Examples 1 to 4, the annular conductor may be formed of a carbon support that supports the catalyst. According to the fuel cell of Application Example 6, the amount of the catalyst that effectively functions in the electrochemical reaction of the reaction gas can be further increased.

Application Example 7 In the fuel cell according to any one of Application Examples 1 to 4, the annular conductor may be made of gold. According to the fuel cell of Application Example 7, the conductivity of the catalyst layer in the in-plane direction of the electrode can be further improved.

[Application Example 8] The fuel cell catalyst layer of Application Example 8 is characterized in that it includes an annular conductor that is formed in an annular shape having a smooth curve and has conductivity. According to the fuel cell catalyst layer of Application Example 8, since the annular conductor having no sharp end mediates the electron transfer in the electrode surface direction in the catalyst layer, the piercing to the electrolyte membrane adjacent to the catalyst layer is prevented. The conductivity of the catalyst layer can be improved while preventing.

  In addition, the form of the present invention is not limited to the fuel cell, and can be applied to various forms such as a vehicle that travels using the power of the fuel cell, a power generation system that supplies the power of the fuel cell, and the like. It is. Further, the present invention is not limited to the above-described embodiments, and it is needless to say that the present invention can be implemented in various forms without departing from the spirit of the present invention.

  In order to further clarify the configuration and operation of the present invention described above, a fuel cell to which the present invention is applied will be described below.

A. Example:
A-1. Overall configuration of the fuel cell:
FIG. 1 is an explanatory diagram showing the overall configuration of the fuel cell 10. The fuel cell 10 generates electric power by an electrochemical reaction of a reaction gas supplied from a gas supply unit (not shown) such as a tank or a reformer. In this embodiment, the fuel cell 10 is a polymer electrolyte fuel cell. In the present embodiment, the reaction gas used in the fuel cell 10 includes a fuel gas containing hydrogen and an oxidizing gas containing oxygen. The fuel gas used in the fuel cell 10 may be a hydrogen gas stored in a hydrogen tank or a hydrogen storage alloy, or may be a hydrogen gas obtained by reforming a hydrocarbon fuel. As the oxidizing gas used in the fuel cell 10, for example, air taken from outside air can be used.

  In this embodiment, the fuel cell 10 is a circulation type fuel cell that circulates and reuses fuel gas. The fuel gas supplied to the fuel cell 10 decreases in hydrogen concentration as the electrochemical reaction proceeds, and is discharged outside the fuel cell 10 as an anode off gas. In this embodiment, the anode off gas is reused as fuel gas. The oxidizing gas supplied to the fuel cell 10 decreases in oxygen concentration as the electrochemical reaction proceeds, and is discharged to the outside of the fuel cell 10 as a cathode off gas.

  As shown in FIG. 1, the fuel cell 10 includes an MEA plate 300 having a membrane electrode assembly (hereinafter referred to as “MEA”) 320 and a separator 200 that supplies a reactive gas to the MEA plate 300. By stacking a plurality of layers alternately, the MEA plate 300 is sandwiched between two separators 200 so as to have a stack structure. The fuel cell 10 includes end plates 100 and 400 that sandwich separators 200 and MEA plates 300 that are alternately stacked.

  Each member of the end plate 100, the separator 200, and the MEA plate 300 constituting the fuel cell 10 has a plurality of through-holes communicating with each other between adjacent members, and a plurality of these through-holes communicate with each other. Is formed inside the fuel cell 10. In the present embodiment, of the flow paths formed inside the fuel cell 10, the flow path related to the fuel gas includes a flow path (arrow H_IN in FIG. 1) through which the fuel gas supplied to the fuel cell 10 flows, And a flow path (arrow H_OUT in FIG. 1) through which the anode off-gas discharged from the battery 10 flows. In the present embodiment, among the channels formed inside the fuel cell 10, the channel related to the oxidizing gas includes a channel (arrow A_IN in FIG. 1) through which the oxidizing gas supplied to the fuel cell 10 flows, and the fuel. And a flow path (arrow A_OUT in FIG. 1) through which the cathode off-gas discharged from the battery 10 flows. In the present embodiment, among the flow paths formed inside the fuel cell 10, the flow path related to the cooling water includes a flow path (arrow W_IN in FIG. 1) through which the cooling water supplied to the fuel cell 10 flows, and fuel. And a flow path (arrow W_OUT in FIG. 1) through which cooling water discharged from the battery 10 flows. In this embodiment, fuel gas supply, anode off-gas discharge, oxidizing gas supply, cathode off-gas discharge, cooling water supply, and cooling water discharge are performed through a plurality of through holes provided in the end plate 100. To the fuel cell 10.

  The separator 200 of the fuel cell 10 has a function of supplying a reaction gas to the MEA plate 300, a function of collecting electricity generated by the MEA plate 300, and a function of flowing cooling water for removing reaction heat from the MEA plate 300. The separator 200 is made of a material that has sufficient conductivity to collect the generated electricity and has sufficient durability, heat resistance, and gas impermeability for flowing the reaction gas and cooling water. In this embodiment, stainless steel is used as the material of the separator 200, but in addition to metals such as titanium and titanium alloys, carbon resin and conductive ceramics may be used. In this embodiment, the separator 200 is a three-layer stacked separator configured by laminating three flat thin plates. The separator 200 is formed of three thin plates as a cathode plate 210, an anode plate 230, The intermediate plate 220 is provided.

  The MEA plate 300 of the fuel cell 10 diffuses fuel gas to the anode-side surface of the MEA 320 and a seal-integrated membrane electrode assembly (hereinafter referred to as “sealed-integrated MEA”) 350 obtained by injection molding a seal gasket 340 on the MEA 320. An anode gas diffusion plate 310 to be diffused, and a cathode gas diffusion plate 330 to diffuse an oxidizing gas on the cathode side surface of the MEA 320. In this embodiment, the MEA plate 300 is configured by fitting the anode gas diffusion plate 310 and the cathode gas diffusion plate 330 into the seal-integrated MEA 350.

  The anode gas diffusion plate 310 and the cathode gas diffusion plate 330 of the MEA plate 300 are sufficiently conductive to conduct between the MEA 320 and the separator 200, and have a plurality of continuous plurality sufficient to transmit the reaction gas. It consists of a porous body that forms pores. In this embodiment, the anode gas diffusion plate 310 and the cathode gas diffusion plate 330 are made of foam metal, but may be a metal mesh as another embodiment.

  The anode gas diffusion plate 310 is laminated in contact with the anode side of the MEA 320, and in contact with the anode plate 230 of the separator 200 in a state where the MEA plate 300 is sandwiched between the separators 200, the anode supply port of the anode plate 230 The fuel gas supplied from 237 is diffused to the anode side of the MEA 320. The fuel gas diffused by the anode gas diffusion plate 310 is discharged from the anode gas diffusion plate 310 through the anode discharge port 238 of the anode plate 230 as an anode off gas.

  The cathode gas diffusion plate 330 is stacked in contact with the cathode side of the MEA 320, and in contact with the cathode plate 210 of the separator 200 with the MEA plate 300 sandwiched between the separators 200, the cathode supply port of the cathode plate 210. The oxidizing gas supplied from 217 is diffused to the cathode side of the MEA 320. The oxidizing gas diffused by the cathode gas diffusion plate 330 is discharged from the cathode gas diffusion plate 330 through the cathode discharge port 218 of the cathode plate 210 as a cathode off gas.

  The seal gasket 340 of the seal-integrated MEA 350 is formed in substantially the same shape as the separator 200 in a state of surrounding the MEA 320 at the center. In this embodiment, the seal gasket 340 is made of an insulating resin material made of rubber having elasticity such as silicon rubber, butyl rubber, and fluorine rubber. In a state where the MEA plate 300 is sandwiched between the separators 200, the seal gasket 340 seals the MEA 320, the anode gas diffusion plate 310, and the cathode gas diffusion plate 330 between the two separators 200 that sandwich the MEA plate 300. The cooling water is prevented from leaking outside the fuel cell 10.

A-2. Detailed configuration of MEA:
FIG. 2 is a cross-sectional view schematically showing a stacked structure of the MEA 320 in the first embodiment. The MEA 320 of the seal-integrated MEA 350 includes a cathode diffusion layer 440, a cathode catalyst layer 420, an electrolyte membrane 410, an anode catalyst layer 430, and an anode diffusion layer 450, and these layers are laminated in this order. Yes. The cathode catalyst layer 420 and the cathode diffusion layer 440 are laminated on the cathode side surface of the electrolyte membrane 410 to constitute an anode electrode layer on the anode side. The anode catalyst layer 430 and the anode diffusion layer 450 are laminated on the anode side surface of the electrolyte membrane 410 to form a cathode electrode layer on the cathode side.

  The electrolyte membrane 410 of the MEA 320 is an electrolyte membrane having ion conductivity, and in this embodiment, is made of a proton conductor having proton conductivity. For example, the electrolyte membrane 410 may be a perfluorosulfonic acid ion exchange membrane that is an ionomer resin.

  The cathode diffusion layer 440 and the anode diffusion layer 450 of the MEA 320 have gas permeability, conductivity, and water repellency. For example, a carbon cloth or carbon paper that is a carbon porous body, and a water repellent resin ( For example, a material mixed with polytetrafluoroethylene (PTFE) may be used. The anode diffusion layer 450 is laminated in contact with the anode catalyst layer 430 and diffuses fuel gas into the anode catalyst layer 430. The cathode diffusion layer 440 is stacked in contact with the cathode catalyst layer 420 and diffuses fuel gas into the cathode catalyst layer 420.

  The cathode catalyst layer 420 and the anode catalyst layer 430 of the MEA 320 have gas permeability, conductivity, and water repellency, in addition to a catalytic function that promotes an electrochemical reaction of the reaction gas performed through the electrolyte membrane 410. In this embodiment, the configuration of the cathode catalyst layer 420 is the same as the configuration of the anode catalyst layer 430.

  FIG. 3 is an explanatory view schematically showing a detailed configuration of the anode catalyst layer 430. The anode catalyst layer 430 includes a carrier 510 that supports the catalyst 520, an ionomer resin 530 that is a proton conductor, and an annular conductor 550 that is formed in an annular shape and has conductivity, and further has water repellency. A water repellent resin (for example, polytetrafluoroethylene (PTFE)) may be contained. In this embodiment, the anode catalyst layer 430 is formed by spraying a material obtained by mixing the carrier 510, the ionomer resin 530, and the annular conductor 550 onto the electrolyte membrane 410. However, in another embodiment, the anode 510, ionomer resin is formed. The anode catalyst layer 430 may be formed by applying a material mixed with 530 to the electrolyte membrane 410 and spraying the annular conductor 550 on the applied material, followed by cold pressing.

  In this embodiment, the catalyst 520 of the anode catalyst layer 430 is a platinum-based catalyst containing platinum or a platinum alloy. In this example, the support 510 of the anode catalyst layer 430 is a carbon black support that is an amorphous carbon support. However, in another embodiment, the support 510 may be a graphite support that is a carbon support having a crystal structure.

  In the present embodiment, the annular conductor 550 of the anode catalyst layer 430 is an annular conductor having a smooth shape and having an annular shape. In the present embodiment, the annular conductor 550 is a carbon formed into an annular shape. It is. The shape of the annular conductor 550 may be an annular shape, may be a perfect circle shape, may be an elliptical shape, or may be a “C” shape with a part of the ring open.

  In the present embodiment, the outer diameter, that is, the diameter of the annular conductor 550 is 50 to 100 micrometers. The inventors have evaluated the catalyst layer formed of the carrier 510 and the ionomer resin 530. As a result, when the catalyst layer is separated by 100 micrometers or more in the electrode in-plane direction, the conductivity is particularly lowered. From this result, the diameter of the toric conductor 550 is preferably 50 micrometers or more in order to improve the conductivity of the anode catalyst layer 430 outside the toric conductor 550, and the inside of the toric conductor 550 is In order to ensure the conductivity of the anode catalyst layer 430, the thickness is preferably within 100 micrometers.

  In this example, the thickness of the annular conductor 550 is not more than one third of the thickness of the anode catalyst layer 430. For example, when the thickness of the anode catalyst layer 430 is 15 micrometers, the thickness of the annular conductor 550 is 5 micrometers or less.

  The structure formed by the support 510 and the ionomer resin 530 in the anode catalyst layer 430 is interrupted in the middle of the continuous structure portion 52 that continues from the electrolyte membrane 410 to the anode diffusion layer 450 and the electrolyte membrane 410 to the anode diffusion layer 450. And the discontinuous structure portion 54. In the example shown in FIG. 3, the annular conductor 550 contained in the anode catalyst layer 430 is connected to the continuous structure portion 52 and the discontinuous structure portion 54, and between the continuous structure portion 52 and the discontinuous structure portion 54. The state of mediating electron transfer is shown.

  According to the fuel cell 10 described above, since the annular conductor 550 having no sharp end is used to mediate electron movement in the in-plane direction of the cathode catalyst layer 420 and the anode catalyst layer 430, the electrolyte membrane 410 The conductivity of the cathode catalyst layer 420 and the anode catalyst layer 430 can be improved while preventing sticking to the surface. In addition, since the diameter of the annular conductor 550 is 50 to 100 micrometers, the conductivity in the electrode plane direction in the cathode catalyst layer 420 and the anode catalyst layer 430 can be effectively improved. In addition, since the thickness of the annular conductor 550 is not more than one-third of the cathode catalyst layer 420 and the anode catalyst layer 430, the cathode conductor layer 550 can be used even when the plurality of annular conductors 550 overlap. It can suppress that the catalyst layer 420 and the anode catalyst layer 430 become thick locally.

B. Variation:
The fuel cell 10 of the modified example is the same as the above-described embodiment except that the annular conductor is formed of a carbon carrier that supports the catalyst 520. Also in this modification, the configuration of the cathode catalyst layer 420 is the same as the configuration of the anode catalyst layer 430.

  FIG. 4 is an explanatory view schematically showing a detailed configuration of the anode catalyst layer 430 in the modification. The modified anode catalyst layer 430 includes an ionomer resin 530 that is a proton conductor and an annular conductor 552 that is formed of a carbon carrier that supports the catalyst 520. In this modification, the anode catalyst layer 430 is formed by spraying a material obtained by mixing the ionomer resin 530 and the annular conductor 552 onto the electrolyte membrane 410. However, in another embodiment, the ionomer resin 530 is applied to the electrolyte membrane 410. The anode catalyst layer 430 may be formed by applying and cold-pressing the annular conductor 552 on the applied ionomer resin 530.

  According to the fuel cell 10 of the modified example described above, the annular conductor 552 that does not have a sharp end is used to mediate the electron movement in the electrode plane direction in the cathode catalyst layer 420 and the anode catalyst layer 430. The conductivity of the cathode catalyst layer 420 and the anode catalyst layer 430 can be improved while preventing the electrolyte membrane 410 from being stuck. Further, since the annular conductor 552 itself carries the catalyst 520, the amount of the catalyst 520 that effectively functions in the electrochemical reaction of the reaction gas can be further increased.

C. Other embodiments:
The embodiments of the present invention have been described above. However, the present invention is not limited to these embodiments, and can of course be implemented in various forms without departing from the spirit of the present invention. is there. For example, in the present embodiment, a so-called circulation type fuel cell has been described. However, in another embodiment, the present invention may be applied to a so-called dead end type fuel cell that uses up the fuel gas once supplied to the fuel cell. good. In this example, a solid polymer fuel cell using a proton permeable electrolyte membrane was described. In another embodiment, an alkaline fuel cell using a hydroxide ion permeable electrolyte membrane was used. The present invention may be applied to.

  In addition, the annular conductor 550 in the embodiment is made of carbon, but may be made of gold. As a result, the conductivity in the in-electrode direction of the cathode catalyst layer 420 and the anode catalyst layer 430 can be further improved.

  In the above-described embodiment, each of the cathode catalyst layer 420 and the anode catalyst layer 430 includes the annular conductor 550. However, at least one of the cathode catalyst layer 420 and the anode catalyst layer 430 includes the annular conductor 550. It may be contained. In the above-described modification, each of the cathode catalyst layer 420 and the anode catalyst layer 430 includes the annular conductor 552. However, at least one of the cathode catalyst layer 420 and the anode catalyst layer 430 includes the annular conductor 552. It may be contained. In the above-described embodiment, the annular conductor 552 carrying the catalyst 520 may be used in place of the annular conductor 550.

  Further, the conductors contained in the cathode catalyst layer 420 and the anode catalyst layer 430 are not limited to the annular conductors 550 and 552 that are formed in an annular shape and have conductivity, but in an annular shape configured by a smooth curve. As long as the conductor is formed, it may be a conductor formed in an annular shape with rounded corners of a polygon including a triangle or a quadrangle, and the conductive material with a part of the annular shape with rounded corners of the polygon opened. It may be the body.

It is explanatory drawing which shows the whole structure of a fuel cell. It is sectional drawing which shows typically the laminated structure of MEA in a 1st Example. It is explanatory drawing which shows the detailed structure of an anode catalyst layer typically. It is explanatory drawing which shows typically the detailed structure of the anode catalyst layer in a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell 52 ... Continuous structure part 54 ... Discontinuous structure part 100 ... End plate 200 ... Separator 210 ... Cathode plate 217 ... Cathode supply port 218 ... Cathode discharge port 220 ... Intermediate plate 230 ... Anode plate 237 ... Anode supply port 238 ... Anode outlet 310 ... Anode gas diffusion plate 320 ... MEA
330 ... Cathode gas diffusion plate 340 ... Seal gasket 410 ... Electrolyte membrane 420 ... Cathode catalyst layer 430 ... Anode catalyst layer 440 ... Cathode diffusion layer 450 ... Anode diffusion layer 510 ... Support 520 ... Catalyst 530 ... Ionomer resin 550 ... Toroidal conductor 552 ... Ring conductor

Claims (8)

An electrolyte membrane having ionic conductivity;
A catalyst layer laminated on the electrolyte membrane and carrying a catalyst;
A fuel cell comprising: an annular conductor that is contained in the catalyst layer and is formed in an annular shape having a smooth curve and has conductivity.   The fuel cell according to claim 1, wherein the annular conductor includes an annular conductor formed in an annular shape and having conductivity.   The fuel cell according to claim 1 or 2, wherein the outer diameter of the annular conductor is 50 to 100 micrometers.   4. The fuel cell according to claim 1, wherein a thickness of the annular conductor is equal to or less than one third of a thickness of the catalyst layer.   The fuel cell according to claim 1, wherein the annular conductor is made of carbon.   The fuel cell according to any one of claims 1 to 4, wherein the annular conductor is formed of a carbon carrier that supports the catalyst.   The fuel cell according to any one of claims 1 to 4, wherein the annular conductor is made of gold.   A catalyst layer for a fuel cell, comprising a ring-shaped conductor having a smooth shape and formed in a ring shape.

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