JP2012243442A - Membrane-electrode assembly, solid polymer fuel cell, and fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a membrane-electrode assembly which can ensure gas diffusion properties by enhancing the discharge properties of water produced near the concave part of a solid polymer electrolyte membrane in an electrode (catalyst layer) when using a solid polymer electrolyte membrane formed in the shape of protrusions and recesses.SOLUTION: The membrane-electrode assembly includes a solid polymer electrolyte membrane 10, and an electrode 40C(40A) having a catalyst layer 20C(20A) and a gas diffusion layer 30C(30A). The catalyst layer 20C in contact with the principal surface of the solid polymer electrolyte membrane 10 formed in the shape of protrusions and recesses has a part overlapping a concave part 1A, when viewed from the thickness direction of the solid polymer electrolyte membrane 10, which is formed of a first catalyst layer 2A and a second catalyst layer 2B. The first catalyst layer 2A is composed to have a mass ratio (I/C) of ionomer/carbon lower than that of the second catalyst layer 2B, and/or an ion exchange group equivalent(EW) higher than that of the second catalyst layer 2B.

Description

  The present invention relates to a membrane-electrode assembly, a polymer electrolyte fuel cell, and a fuel cell system, and more particularly to a structure of a membrane-electrode assembly.

  In general, a fuel cell has a main body of a stack formed by stacking single cells. The cell is configured by sandwiching the MEA between a pair of flat separators, specifically, an anode separator and a cathode separator. The MEA includes a polymer electrolyte membrane and a pair of electrodes that are stacked on both sides of the polymer electrolyte membrane, and electrode surfaces are formed on both main surfaces of the MEA. In addition, the separator is made of a conductive material such as resin or metal containing conductive carbon, and is in contact with the electrode surface of the MEA and serves as a part of the electric circuit.

  Here, since the electrochemical reaction in the cell is an exothermic reaction, it is necessary to cool the cell so that the inner surface of the cell reaches the catalyst activation temperature during the operation of the fuel cell, and appropriate temperature management is required during the operation of the fuel cell. . That is, when the cooling of the cell is insufficient, the temperature of the MEA rises and water is evaporated from the polymer electrolyte membrane. As a result, it is known that the deterioration of the polymer electrolyte membrane is promoted and the durability of the cell stack is lowered, or the electric resistance of the polymer electrolyte membrane is increased and the electric output of the cell is lowered.

  On the other hand, when the cell stack is cooled more than necessary, moisture in the reaction gas flowing through the gas flow path is condensed, and the amount of liquid water contained in the reaction gas increases. Liquid water adheres as droplets to the gas flow path of the separator plate due to surface tension. When the amount of the droplets is excessive, water adhering to the gas flow path may block the gas flow path to obstruct the gas flow and cause flooding. It is known that when flooding occurs, the reaction area of the electrode decreases and the electric output becomes unstable, and the performance of the fuel cell is lowered.

  In particular, in the electrode on the cathode side, generated water is generated by the reaction, so the drainage of water in the electrode is important. Similar to the flooding in the gas flow path, if the cathode side electrode is clogged with the generated water, the electric output may become unstable.

  By the way, in such a fuel cell, a membrane electrode assembly is known in which the contact area between the electrolyte membrane and the electrode is increased by making the electrolyte membrane uneven (see, for example, Patent Document 1 and Patent Document 2). ).

JP 2005-293923 A JP 2008-4486 A

  However, the present inventors have found that there is still room for improvement in order to further improve the output performance of the fuel cell even in the membrane electrode assembly disclosed in Patent Document 1 and Patent Document 2. I found it.

  That is, when the electrolyte membrane is made uneven, since the concave portion of the electrolyte membrane is a region surrounded by the convex portion, the amount of reaction gas supplied is relatively small. In addition, on the cathode side, when the reaction occurs at the electrode near the concave portion of the electrolyte membrane, there is a possibility that the generated water is difficult to be discharged to the GDL or the separator side due to the convex portion of the electrolyte membrane.

  Then, the inventors of the present invention describe how the generated water in the vicinity of the concave portion of the electrolyte membrane in the electrode (particularly the cathode) is discharged to the outside, and how the reaction gas is in the vicinity of the concave portion of the electrolyte membrane in the electrode. It has been found that whether or not to supply the battery greatly affects the improvement of the battery performance when the solid polymer electrolyte membrane formed in an uneven shape is used.

  The present invention has been made in order to solve the above-described problems. When a solid polymer electrolyte membrane formed in an uneven shape is used, the concave shape of the solid polymer electrolyte membrane in an electrode (catalyst layer) is provided. An object of the present invention is to provide a membrane-electrode assembly, a polymer electrolyte fuel cell, and a fuel cell system capable of enhancing the discharge of produced water in the vicinity of the portion and ensuring gas diffusibility.

  In order to solve the above problems, a membrane-electrode assembly according to the present invention comprises a solid polymer electrolyte membrane in which at least one main surface is formed in an uneven shape, and a contact with the main surface of the solid polymer electrolyte membrane. An electrode having a catalyst layer and a gas diffusion layer, and the catalyst layer in contact with the main surface formed in an uneven shape of the solid polymer electrolyte membrane is the solid When viewed from the thickness direction of the polymer electrolyte membrane, a portion that overlaps the concave portion of the solid polymer electrolyte membrane is formed by the first catalyst layer and the second catalyst layer, and the first catalyst layer Is in contact with the main surface of the solid polymer electrolyte membrane, the second catalyst layer is disposed in contact with the main surface of the gas diffusion layer, and the first catalyst layer is the second catalyst layer Lower ionomer / carbon mass ratio (I / C) and / or Ion-exchange group equivalent weight (EW) is configured to increases.

  Thereby, the discharge | emission property of the produced water in the recessed part vicinity of the solid polymer electrolyte membrane in an electrode (catalyst layer) can be improved, and gas diffusibility can be ensured. In addition, as an ionomer in ionomer / carbon mass ratio (I / C), what consists of a fluoropolymer resin is preferable.

  In the membrane-electrode assembly according to the present invention, the thickness of the first catalyst layer may be smaller than the height of the concave portion of the solid polymer electrolyte membrane. Good.

  In the membrane-electrode assembly according to the present invention, the thickness of the first catalyst layer may be 1/3 or more of the height of the concave portion of the solid polymer electrolyte membrane.

  In the membrane-electrode assembly according to the present invention, the thickness of the first catalyst layer may be 1/2 or more of the height of the concave portion of the solid polymer electrolyte membrane.

  In the membrane-electrode assembly according to the present invention, the I / C of the first catalyst layer is 0.5 to 1.0, and the I / C of the second catalyst layer is 1.0 to 2. 0.0.

  In the membrane-electrode assembly according to the present invention, the EW of the first catalyst layer may be 900 to 1500, and the EW of the second catalyst layer may be 500 to 900.

  Furthermore, in the membrane-electrode assembly according to the present invention, the height of the concave portion of the solid polymer electrolyte membrane may be 3 to 20 μm.

  Further, the polymer electrolyte fuel cell according to the present invention comprises the membrane-electrode assembly, and a pair of conductive separators arranged in a plate shape so as to sandwich the membrane-electrode assembly. Prepare.

  Thereby, the discharge | emission property of the produced water in the recessed part vicinity of the solid polymer electrolyte membrane in an electrode (catalyst layer) can be improved, gas diffusibility can be ensured, and battery performance can be improved.

  In addition, the fuel cell system according to the present invention includes the solid polymer fuel cell, a fuel gas supplier that supplies fuel gas to the anode, an oxidant gas supplier that supplies oxidant gas to the cathode, A heating medium supplier for supplying a heating medium to the polymer electrolyte fuel cell; and a controller, wherein the controller has a dew point of the fuel gas and the oxidant gas supplied to the fuel cell. The fuel gas supply device, the oxidant gas supply device, and the heat medium supply device are controlled so that the power generation operation is performed under a condition lower than the temperature of the heat medium supplied to the battery.

  As a result, when the fuel cell is operated under low humidification conditions, it is possible to enhance the discharge of generated water in the vicinity of the concave portion of the solid polymer electrolyte membrane in the electrode (catalyst layer), and to ensure gas diffusibility, Battery performance can be improved.

  The above object, other objects, features, and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments with reference to the accompanying drawings.

  According to the membrane-electrode assembly, the polymer electrolyte fuel cell, and the fuel cell system of the present invention, the discharge of generated water in the vicinity of the concave portion of the polymer electrolyte membrane in the electrode (catalyst layer) is enhanced, It becomes possible to ensure diffusibility.

1 is a cross-sectional view schematically showing a schematic configuration of a membrane-electrode assembly according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view schematically showing a schematic configuration of the solid polymer electrolyte membrane of the membrane-electrode assembly shown in FIG. FIG. 3 is a front view schematically showing a schematic configuration of the solid polymer electrolyte membrane of the membrane-electrode assembly shown in FIG. FIG. 4 is a cross-sectional view schematically showing a schematic configuration of a polymer electrolyte fuel cell (solid polymer fuel cell according to Embodiment 1) including the membrane-electrode assembly shown in FIG. . FIG. 5 is a block diagram schematically showing a schematic configuration of the fuel cell system according to Embodiment 2 of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted. Further, in all the drawings, only components necessary for explaining the present invention are extracted and illustrated, and other components are not illustrated. Furthermore, the present invention is not limited to the following embodiment.

(Embodiment 1)
Embodiment 1 of the present invention includes a solid polymer electrolyte membrane in which at least one main surface is formed in an uneven shape, a catalyst layer disposed so as to be in contact with the main surface of the solid polymer electrolyte membrane, An electrode having a gas diffusion layer, and the catalyst layer in contact with the main surface formed in an uneven shape of the solid polymer electrolyte membrane is a solid polymer as viewed from the thickness direction of the solid polymer electrolyte membrane. A portion overlapping with the concave portion of the electrolyte membrane is formed by the first catalyst layer and the second catalyst layer, the first catalyst layer is in contact with the main surface of the solid polymer electrolyte membrane, and the second The catalyst layer is disposed so as to be in contact with the main surface of the gas diffusion layer, and the first catalyst layer has a lower ionomer / carbon mass ratio (I / C) than the second catalyst layer and / or an ion exchange group. Exemplifies an embodiment in which the equivalent weight (EW) is increased. That.
[Configuration of membrane-electrode assembly]
1 is a cross-sectional view schematically showing a schematic configuration of a membrane-electrode assembly according to Embodiment 1 of the present invention. 2 is a cross-sectional view schematically showing a schematic configuration of the solid polymer electrolyte membrane of the membrane-electrode assembly shown in FIG. 1, and FIG. 3 is a solid polymer electrolyte of the membrane-electrode assembly shown in FIG. It is a front view which shows the schematic structure of a film | membrane typically. In FIG. 1 to FIG. 3, a part is omitted. First, in FIG. 3, in order to easily distinguish the convex portion and the concave portion of the solid polymer electrolyte membrane, each portion is hatched.

  As shown in FIG. 1, the membrane-electrode assembly 50 according to Embodiment 1 includes a solid polymer electrolyte membrane 10, an anode catalyst layer 20A having an anode catalyst layer 20A and an anode gas diffusion layer 30A, and a cathode catalyst layer 20C. And a cathode 40C having a cathode gas diffusion layer 30C. The solid polymer electrolyte membrane 10 is configured to selectively transport hydrogen.

  As shown in FIGS. 1 to 3, the solid polymer electrolyte membrane 10 has one main surface (here, the main surface on the cathode 40 </ b> C side) formed in an uneven shape. Specifically, the convex portion 1B is formed so as to protrude from the main surface of the solid polymer electrolyte membrane 10 on the cathode 40C side. And the part (henceforth concave part 1A) currently formed in the concave shape of the solid polymer electrolyte membrane 10 is comprised from the cathode 40C side main surface of the solid polymer electrolyte membrane 10, and the side surface of the convex part 1B. Yes.

  In the first embodiment, by forming the convex portion 1B so as to protrude from the cathode 40C side main surface of the solid polymer electrolyte membrane 10, one main surface of the solid polymer electrolyte membrane 10 ( The cathode 40C side main surface) is formed in an uneven shape, but is not limited thereto. For example, a hole may be formed so as to be recessed from one main surface of the solid polymer electrolyte membrane 10, and the main surface may be formed in an uneven shape. In this case, the bottom surface of the hole constitutes the concave portion 1A, and one main surface of the solid polymer electrolyte membrane 10 and the side wall forming the hole constitute the convex portion 1B.

  In the first embodiment, the cathode 40C side main surface of the solid polymer electrolyte membrane 10 is formed in an uneven shape, but the present invention is not limited to this. For example, the main surface on the anode 40A side of the solid polymer electrolyte membrane 10 may be formed in an uneven shape, or the main surfaces on both sides of the solid polymer electrolyte membrane 10 may be formed in an uneven shape.

  Furthermore, the height of the concave portion 1A (in other words, the height from the cathode 40C side main surface of the solid polymer electrolyte membrane 10 to the tip of the convex portion 1B) is equal to or less than the thickness of the solid polymer electrolyte membrane 10. It may be 3 to 20 μm or less.

  An anode catalyst layer 20A is provided on the other main surface of the solid polymer electrolyte membrane 10 (the main surface on the anode 40A side). A cathode catalyst layer 20C is provided on the main surface of the solid polymer electrolyte membrane 10 on the cathode 40C side.

  The cathode catalyst layer 20C has a first catalyst layer 2A and a second catalyst layer 2B. In the cathode catalyst layer 20C, when viewed from the thickness direction of the solid polymer electrolyte membrane 10, the portions of the cathode catalyst layer 20C that overlap the concave portions 1A of the solid polymer electrolyte membrane 10 are the first catalyst layer 2A and the second catalyst layer. 2B.

  The first catalyst layer 2A is disposed so as to be in contact with the main surface of the solid polymer electrolyte membrane 10 on the cathode 40C side. The second catalyst layer 2B is disposed so as to be in contact with the main surface of the cathode gas diffusion layer 30C. In other words, the second catalyst layer 2B is provided on the main surface of the first catalyst layer 2A that is not in contact with the main surface of the solid polymer electrolyte membrane 10.

  In addition, since the first catalyst layer 2A retains water generated by power generation, the gas diffusibility of the catalyst layer existing in the concave portion 1A of the solid polymer electrolyte membrane 10 is reduced, and the gas diffusivity to the catalyst layer is reduced. From the viewpoint of ensuring, it is preferable that the thickness is formed to be smaller than the height of the concave portion 1A of the solid polymer electrolyte membrane 10. Furthermore, the thickness of the first catalyst layer 2 </ b> A is such that the thickness of the first catalyst layer 2 </ b> A is the concave portion 1 </ b> A of the solid polymer electrolyte membrane 10 from the viewpoint of reliably supplying gas to the catalyst layer existing near the bottom surface of the concave portion 1 </ b> A of the solid polymer electrolyte membrane 10. The height is preferably 1/3 or more, more preferably 1/2 or more.

  The structure of the anode catalyst layer 20A and the cathode catalyst layer 20C is not particularly limited as long as the catalyst catalyst carbon and the ionomer are included. Further, from the viewpoint of maintaining proton conductivity, the first catalyst layer 2A has an ionomer / carbon mass ratio (I / C) of the first catalyst layer 2A of 0.5 or more and 1.0 or less. It is preferable. Further, in the second catalyst layer 2B, the I / C of the second catalyst layer 2B is preferably 1.0 or more and 2.0 or less from the viewpoint of maintaining electronic conductivity. In this case, in the first catalyst layer 2A, the I / C of the first catalyst layer 2A may be substantially less than 1.0. In addition, as an ionomer in ionomer / carbon mass ratio (I / C), what consists of a fluoropolymer resin is preferable.

  Furthermore, from the viewpoint of maintaining the performance of the first catalyst layer 2A, the first catalyst layer 2A has an EW of the first catalyst layer 2A (more precisely, the fluoropolymer resin constituting the first catalyst layer 2A), It is preferable that it is 900 or more and 1500 or less. Further, the second catalyst layer 2B is an EW of the second catalyst layer 2B (more precisely, a fluoropolymer resin constituting the second catalyst layer 2B) from the viewpoint of maintaining the shape stability of the second catalyst layer 2B. Is preferably 500 or more and 900 or less. The EW of the second catalyst layer 2B may be substantially less than 900.

  An anode gas diffusion layer 30A is provided on the main surface of the anode catalyst layer 20A on the side not in contact with the solid polymer electrolyte membrane 10. A cathode gas diffusion layer 30C is provided on the main surface of the cathode catalyst layer 20C that does not contact the solid polymer electrolyte membrane 10 (the main surface of the second catalyst layer 2B that does not contact the first catalyst layer 2A). It has been. The anode gas diffusion layer 30A and the cathode gas diffusion layer 30C are configured in the same manner as a gas diffusion layer of a general polymer electrolyte fuel cell, and thus detailed description thereof is omitted.

[Method for producing membrane-electrode assembly]
Next, a manufacturing method of the membrane-electrode assembly 50 according to the first embodiment. This will be described with reference to FIGS.

  First, the material constituting the solid polymer electrolyte membrane 10 is cast into a mold made of a silicon wafer or the like having a concavo-convex structure as shown in FIGS. 2 and 3 to form the solid polymer electrolyte membrane 10. . The solid polymer electrolyte membrane 10 may be formed by the method disclosed in Patent Document 1 above.

  Next, the first catalyst layer 2A is formed by coating or spraying the first catalyst layer 2A forming ink on the main surface of the solid polymer electrolyte membrane 10 formed in an uneven shape. At this time, the ink forming the first catalyst layer 2A is adjusted such that the I / C is lower and / or the EW is higher than the ink forming the second catalyst layer 2B described later. Specifically, as described above, the ink for forming the first catalyst layer 2A is adjusted so that the I / C is 0.5 to 1.0 and / or the EW is 900 to 1500. Is done.

  In the first catalyst layer 2A forming ink, the thickness of the first catalyst layer 2A is 1/3 or more (preferably 1/2 or more) of the height of the concave portion 1A and the height of the concave portion 1A. The coating or spraying is performed so as to be small.

  Next, the second catalyst layer 2B is formed by coating or spraying the ink for forming the second catalyst layer 2B on the main surface of the first catalyst layer 2A that is not in contact with the solid polymer electrolyte membrane 10. At this time, the ink for forming the second catalyst layer 2B is adjusted so that the I / C is 1.0 to 2.0 and / or the EW is 500 to 900.

  Then, the anode catalyst layer 20A is formed on the main surface of the solid polymer electrolyte membrane 10 on the side where the cathode catalyst layer 20C is not formed by applying or spraying ink for forming the anode catalyst layer 20A. The ink for forming the anode catalyst layer 20A can be an ink that forms a general catalyst layer.

  Next, carbon cloth or the like is cut into an appropriate size in advance to prepare an anode gas diffusion layer 30A and a cathode gas diffusion layer 30C. Then, the anode gas diffusion layer 30A is joined to the main surface of the anode catalyst layer 20A on the side not in contact with the solid polymer electrolyte membrane 10. Further, the cathode gas diffusion layer 30C is bonded to the main surface of the cathode catalyst layer 20C on the side not in contact with the solid polymer electrolyte membrane 10. In this way, the membrane-electrode assembly 50 is obtained. By applying the water repellent carbon layer forming ink in advance to the main surface of the anode catalyst layer 20A and / or the cathode catalyst layer 20C, or the main surface of the anode gas diffusion layer 30A and / or the cathode gas diffusion layer 30C, etc. The membrane-electrode assembly 50 may be formed after forming the water-repellent carbon layer.

[Configuration of polymer electrolyte fuel cell]
Next, the structure of the polymer electrolyte fuel cell according to the first embodiment (the polymer electrolyte fuel cell including the membrane-electrode assembly 50 according to the first embodiment) will be described with reference to FIGS. While explaining.

  FIG. 4 is a cross-sectional view schematically showing a schematic configuration of a polymer electrolyte fuel cell (solid polymer fuel cell according to Embodiment 1) including the membrane-electrode assembly shown in FIG. . In FIG. 4, a part is omitted.

  As shown in FIG. 4, the polymer electrolyte fuel cell 100 according to Embodiment 1 of the present invention includes a membrane-electrode assembly 50, an anode separator 60A, a cathode separator 60C, and a pair of gaskets not shown. ing.

  The pair of gaskets are provided around each of the anode 40A and the cathode 40C. The gasket is here formed in a donut shape. It is made of fluoro rubber. As a result, the fuel gas and the oxidant gas are suppressed from leaking out of the polymer electrolyte fuel cell 100, and the gases are suppressed from being mixed with each other in the polymer electrolyte fuel cell 100. The In addition, each manifold hole such as a fuel gas supply manifold hole formed of a through hole in the thickness direction is provided at the peripheral edge of the gasket.

  The anode separator 60A and the cathode separator 60C are provided so as to sandwich the membrane-electrode assembly 50 and the gasket. The anode separator 60A and the cathode separator 60C can be made of a metal having excellent thermal conductivity and conductivity, graphite, or a mixture of graphite and resin. For example, carbon powder and a binder (solvent) A mixture prepared by injection molding or a plate of titanium or stainless steel plated with gold can be used. Thereby, the membrane-electrode assembly 50 is mechanically fixed, and when the plurality of polymer electrolyte fuel cells 100 are stacked in the thickness direction, the membrane-electrode assembly 50 is electrically connected.

  On one main surface of the anode separator 60A that is in contact with the anode 40A, a groove-like fuel gas flow path 70 is provided for the fuel gas to flow therethrough. Further, a groove-like heat medium flow path 90 through which the heat medium flows is provided on the other main surface of the anode separator 60A.

  Similarly, a groove-like oxidant gas flow path 80 through which an oxidant gas flows is provided on one main surface of the cathode separator 60C that is in contact with the cathode 40C. Further, a groove-like heat medium flow path 90 through which the heat medium flows is provided on the other main surface of the cathode separator 60C.

  Thereby, fuel gas and oxidant gas are supplied to the anode 40A and the cathode 40C, respectively, and these gases react to generate electricity and heat. Further, the generated heat is recovered by passing a heat medium such as cooling water through the heat medium flow path 90.

  And the cell laminated body is formed by laminating | stacking the polymer electrolyte fuel cell 100 which concerns on this Embodiment 1 comprised in this way in the thickness direction (not shown). At this time, each manifold hole such as a fuel gas supply manifold hole provided in the solid polymer electrolyte membrane 10, the gasket, the anode separator 60 </ b> A, and the cathode separator 60 </ b> C has a thickness direction when the solid polymer fuel cell 100 is laminated. The manifolds such as the fuel gas supply manifold are formed respectively. Then, a current collector plate and an insulating plate are arranged at both ends of the cell stack, a pair of end plates are further arranged at both ends, and fastened with a fastener to form the fuel cell stack 101 (see FIG. 4).

  In the membrane-electrode assembly 50 and the polymer electrolyte fuel cell 100 according to Embodiment 1 configured as described above, the first catalyst layer 2A has a lower I / C than the second catalyst layer 2B, and / or Alternatively, since the EW is configured to be high, the discharge of generated water in the vicinity of the concave portion 1A (the first catalyst layer 2A) of the solid polymer electrolyte membrane 10 can be enhanced, and the gas diffusibility can be ensured. . For this reason, the battery performance of the polymer electrolyte fuel cell 100 can be improved.

(Embodiment 2)
Embodiment 2 of the present invention includes a polymer electrolyte fuel cell according to Embodiment 1, a fuel gas supplier that supplies fuel gas to the anode, and an oxidant gas supplier that supplies oxidant gas to the cathode. A heating medium supplier for supplying a heating medium to the polymer electrolyte fuel cell, and a controller, and the controller has a dew point of the fuel gas and the oxidant gas supplied to the polymer electrolyte fuel cell, A fuel gas supply device, an oxidant gas supply device, and a heat medium supply device are installed so that the polymer electrolyte fuel cell performs a power generation operation under a temperature lower than the temperature of the heat medium supplied to the polymer electrolyte fuel cell. The mode to control is illustrated.

[Configuration of fuel cell system]
FIG. 5 is a block diagram schematically showing a schematic configuration of the fuel cell system according to Embodiment 2 of the present invention.

  As shown in FIG. 5, a fuel cell system 200 according to Embodiment 2 of the present invention includes a fuel cell stack 101, a fuel gas supply device 102, an oxidant gas supply device 103, a heat medium supply device 104, A power regulator 105 and a controller 110 are provided. The controller 110 includes a fuel gas supply device 102, an oxidant gas supply device 103, and a heat medium so that the fuel cell stack 101 performs a power generation operation under conditions lower than the temperature of the heat medium supplied to the fuel cell stack 101. The feeder 104 is controlled.

  The fuel cell stack 101 has a plurality of polymer electrolyte fuel cells 100 as described above. The fuel cell stack 101 is provided with a fuel gas path 101A, an oxidant gas path 101B, and a heat medium path 101C.

  The fuel gas path 101A includes a fuel gas flow path 70, a fuel gas supply manifold, and a fuel gas discharge manifold of the polymer electrolyte fuel cell 100. The oxidant gas path 101B is composed of the oxidant gas flow path 80, the oxidant gas supply manifold, and the oxidant gas discharge manifold of the polymer electrolyte fuel cell 100. Similarly, the heat medium path 101C includes the heat medium flow path 90, the heat medium supply manifold, and the heat medium discharge manifold of the polymer electrolyte fuel cell 100.

  A fuel gas supply unit 102 is connected to an inlet of the fuel gas path 101 </ b> A of the fuel cell stack 101 via a fuel gas supply path 111. The fuel gas supply device 102 includes, for example, a hydrogen generator, a hydrogen cylinder, a hydrogen storage alloy, etc., a humidifier, and a flow rate regulator (all not shown). The hydrogen generator generates fuel gas (hydrogen gas) from raw material gas (for example, methane gas, propane gas, etc.) and water. Further, the humidifier may be in any form as long as it can humidify the fuel gas from the hydrogen generator or the like. For example, when the heat medium is water, the humidifier performs total heat exchange with the heat medium. It may be a total heat exchanger, or a so-called humidifier that humidifies the fuel gas using water stored in a tank or the like as water vapor. The flow rate regulator may be constituted by, for example, a pump capable of adjusting the flow rate, a pump and a flow rate adjustment valve.

  In addition, an oxidant gas supply unit 103 is connected to an inlet of the oxidant gas path 101 </ b> B of the fuel cell stack 101 via an oxidant gas supply path 113. The oxidant gas supply device 103 includes, for example, fans such as a fan and a blower, a humidifier, and a flow rate regulator (all not shown). The humidifier may be in any form as long as it can humidify the oxidant gas supplied from the fans. For example, when the heat medium is water, the humidifier performs all heat exchange with the heat medium. It may be a heat exchanger, or a so-called humidifier that humidifies the oxidant gas using water stored in a tank or the like as water vapor. The flow rate regulator may be constituted by, for example, a pump capable of adjusting the flow rate, a pump and a flow rate adjustment valve.

  Thereby, the fuel gas appropriately humidified flows from the fuel gas supply device 102 through the fuel gas supply path 111 and is supplied to the fuel gas path 101A. Similarly, an appropriately humidified oxidant gas flows from the oxidant gas supply unit 103 through the oxidant gas supply path 113 and is supplied to the oxidant gas path 101B.

  The fuel gas supplied to the fuel gas path 101A is supplied to the anode 40A of each polymer electrolyte fuel cell 100 while flowing through the fuel gas path 101A. The oxidant gas supplied to the oxidant gas path 101B is supplied to the cathode 40C of each polymer electrolyte fuel cell 100 while flowing through the oxidant gas path 101B. The fuel gas that has not been used in the anode 40 </ b> A is discharged to the fuel gas discharge path 112. Further, the oxidant gas that has not been used in the cathode 40 </ b> C is discharged to the oxidant gas discharge path 114. Note that unused fuel gas may be discharged into the atmosphere after being sufficiently diluted with unused oxidant gas, for example, when the fuel gas supply device 102 is configured with a hydrogen generator. May be supplied to a combustor (not shown) of the hydrogen generator.

  A heat medium circulation path 115 is connected to the heat medium path 101C of the fuel cell stack 101. A heat medium feeder 104 is provided in the middle of the heat medium circulation path 115. The heat medium supply device 104 includes, for example, a tank that stores a heat medium supplied from the outside, a heat medium temperature controller, a pump, and a flow rate adjustment valve. Examples of the heat medium temperature adjuster include a heat exchanger that exchanges heat with fuel gas, an oxidant gas, and the like, a heater such as a heater that heats the heat medium, and a cooler that cools the heat medium. Examples of the heat medium include water and antifreeze liquids such as ethylene glycol.

  In the second embodiment, the heat medium supplier 104 is configured with a tank, a pump, and a flow rate adjusting valve, but is not limited thereto. The heat medium supply device 104 may be configured not to have a flow rate adjustment valve when the pump can adjust the flow rate.

  Thereby, the heat medium adjusted to an appropriate temperature flows from the heat medium supply device 104 through the heat medium circulation path 115 and is supplied to the heat medium path 101C. While the heat medium supplied to the heat medium path 101C flows through the heat medium path 101C, the heat generated in each polymer electrolyte fuel cell 100 is recovered and discharged to the heat medium circulation path 115. The heat medium discharged to the heat medium circulation path 115 flows through the heat medium circulation path 115 and is adjusted to an appropriate temperature again by the heat medium supply device 104. In the second embodiment, the heat medium circulates between the heat medium feeder 104 and the fuel cell stack 101. However, the present invention is not limited to this. The heat medium discharged from the heat medium path 101C may be configured to be discharged out of the fuel cell system 200.

  In addition, a power regulator 105 is connected to the fuel cell stack 101 via electrical wires 131 and 132. The power regulator 105 includes, for example, a converter that converts DC power generated by the polymer electrolyte fuel cell 100 of the fuel cell stack 101 into DC voltage, and an inverter that converts DC power output from the converter into AC power. Have. The power adjuster 105 adjusts the electric power extracted from the polymer electrolyte fuel cell 100 under the control of the controller 110.

  The controller 110 may be in any form as long as it is a device that controls each device constituting the fuel cell system 200. The controller 110 includes an arithmetic processing unit exemplified by a microprocessor, a CPU, and the like, and a storage unit configured by a memory or the like that stores a program for executing each control operation. Then, in the controller 110, the arithmetic processing unit reads out a predetermined control program stored in the storage unit and executes it, thereby processing the information and the fuel cell system 200 including these controls. Various controls are performed.

  Note that the controller 110 is not only configured as a single controller, but also configured as a controller group in which a plurality of controllers cooperate to execute control of the fuel cell system 200. I do not care. The controller 110 may be configured by a micro control, and may be configured by an MPU, a PLC (Programmable Logic Controller), a logic circuit, or the like.

  The controller 110 then supplies the fuel gas supply device such that the dew point of the fuel gas supplied to the fuel cell stack 101 and the dew point of the oxidant gas are lower than the temperature of the heat medium supplied to the fuel cell stack 101. 102, the oxidant gas supply unit 103, and the heat medium supply unit 104 are controlled.

  In the fuel cell system 200 according to the second embodiment configured as described above, the dew point of the fuel gas supplied to the fuel cell stack 101 and the dew point of the oxidant gas are the same as those of the heat medium supplied to the fuel cell stack 101. Since it is lower than the temperature, water generated by the reaction of the fuel gas (hydrogen) and the oxidant gas (oxygen) is likely to be generated near the interface between the solid polymer electrolyte membrane 10 and the cathode catalyst layer 20C. Therefore, as in the second embodiment, by making the solid polymer electrolyte membrane 10 uneven, it is possible to secure a wider interface between the solid polymer electrolyte membrane 10 and the cathode catalyst layer 20C. Can be improved.

  In the fuel cell system 200 according to Embodiment 2, the interface between the electrolyte membrane and the catalyst layer is provided by disposing the first catalyst layer 2A in the vicinity of the solid polymer electrolyte membrane 10 (particularly in the vicinity of the concave portion 1A). Water generated in the vicinity can be drained appropriately, and the gas diffusibility of the portion can be ensured. For this reason, the battery performance of the polymer electrolyte fuel cell 100 can be improved.

  From the foregoing description, many modifications and other embodiments of the present invention are obvious to one skilled in the art. Accordingly, the foregoing description is to be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the structure and / or function may be substantially changed without departing from the scope of the invention. Moreover, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment.

  The membrane-electrode assembly, the polymer electrolyte fuel cell, and the fuel cell system of the present invention appropriately drain water generated in the vicinity of the interface between the electrolyte membrane and the catalyst layer and ensure gas diffusibility. Thus, the battery performance can be improved, which is useful in the technical field of fuel cells.

DESCRIPTION OF SYMBOLS 1A Concave part 1B Convex part 2A 1st catalyst layer 2B 2nd catalyst layer 10 Solid polymer electrolyte membrane 20A Anode catalyst layer 20C Cathode catalyst layer 30A Anode gas diffusion layer 30C Cathode gas diffusion layer 40A Anode 40C Cathode 50 Membrane-electrode joining Body 60A Anode separator 60C Cathode separator 70 Fuel gas flow path 80 Oxidant gas flow path 90 Heat medium flow path 100 Solid polymer fuel cell 101 Fuel cell stack 101A Fuel gas path 101B Oxidant gas path 101C Heat medium path 102 Fuel gas Supply unit 103 Oxidant gas supply unit 104 Heat medium supply unit 105 Power regulator 110 Controller 111 Fuel gas supply path 112 Fuel gas discharge path 113 Oxidant gas supply path 114 Oxidant gas discharge path 115 Heat medium circulation path 131 Electricity Line 132 electrical wires 200 fuel cell system

Claims (9)

A solid polymer electrolyte membrane in which at least one main surface is formed in an uneven shape; and
An electrode having a catalyst layer disposed so as to contact the main surface of the solid polymer electrolyte membrane and a gas diffusion layer;
The catalyst layer that is in contact with the main surface of the solid polymer electrolyte membrane that is formed in a concave-convex shape is formed in the concave shape of the solid polymer electrolyte membrane as viewed from the thickness direction of the solid polymer electrolyte membrane. A portion overlapping with the portion is formed of the first catalyst layer and the second catalyst layer,
The first catalyst layer is in contact with the main surface of the solid polymer electrolyte membrane, and the second catalyst layer is disposed in contact with the main surface of the gas diffusion layer;
The first catalyst layer is configured to have a lower ionomer / carbon mass ratio (I / C) and / or a higher ion exchange group equivalent weight (EW) than the second catalyst layer. An electrode assembly.   2. The membrane-electrode assembly according to claim 1, wherein the first catalyst layer is formed so that a thickness thereof is smaller than a height of a concave portion of the solid polymer electrolyte membrane.   The membrane-electrode assembly according to claim 2, wherein a thickness of the first catalyst layer is 1/3 or more of a height of a concave portion of the solid polymer electrolyte membrane.   The membrane-electrode assembly according to claim 2, wherein the thickness of the first catalyst layer is ½ or more of the height of the concave portion of the solid polymer electrolyte membrane.   The I / C of the first catalyst layer is 0.5 to 1.0, and the I / C of the second catalyst layer is 1.0 to 2.0. 2. The membrane-electrode assembly according to 1.   The membrane-electrode assembly according to any one of claims 1 to 5, wherein the EW of the first catalyst layer is 900 to 1500, and the EW of the second catalyst layer is 500 to 900.   The membrane-electrode assembly according to any one of claims 1 to 6, wherein a height of the recessed portion of the solid polymer electrolyte membrane is 3 to 20 µm. A membrane-electrode assembly according to any one of claims 1 to 7,
A solid polymer fuel cell comprising: a plate-like pair of conductive separators disposed so as to sandwich the membrane-electrode assembly. A polymer electrolyte fuel cell according to claim 8,
A fuel gas supplier for supplying fuel gas to the anode;
An oxidant gas supplier for supplying an oxidant gas to the cathode;
A heat medium feeder for supplying a heat medium to the polymer electrolyte fuel cell;
A controller, and
The controller is configured so that a dew point of a fuel gas and an oxidant gas supplied to the polymer electrolyte fuel cell is lower than a temperature of a heat medium supplied to the polymer electrolyte fuel cell. A fuel cell system that controls the fuel gas supply unit, the oxidant gas supply unit, and the heat medium supply unit so that the fuel cell performs a power generation operation.

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