JP5341321B2 - Electrolyte membrane / electrode structure for polymer electrolyte fuel cells - Google Patents

Description

  The present invention relates to an electrolyte membrane for a polymer electrolyte fuel cell in which an anode side electrode and a cathode side electrode are disposed via a solid polymer electrolyte membrane which is a proton conductor that conducts protons and is made of a polymer ion exchange membrane. -It relates to an electrode structure.

  In a polymer electrolyte fuel cell, an electrolyte membrane / electrode structure in which an anode side electrode and a cathode side electrode are disposed on each end face of an electrolyte membrane made of a polymer ion exchange membrane is sandwiched between a pair of separators. A unit cell composed of In this type of polymer electrolyte fuel cell, the polymer ion exchange membrane (electrolyte membrane) functions as a proton conductor that conducts protons from the anode side electrode toward the cathode side electrode.

  Here, the anode side electrode and the cathode side electrode generally have a gas diffusion layer for diffusing the supplied reaction gas and an electrode catalyst layer which is a reaction field of the reaction gas. In some cases, an intermediate layer is provided between the gas diffusion layer and the electrode catalyst layer in order to reduce the contact resistance between the gas diffusion layer and the electrode catalyst layer and further diffuse the reaction gas in the electrode. There is also.

  Usually, a water-repellent resin such as polytetrafluoroethylene (PTFE) and carbon powder are added to the intermediate layer. Patent Document 1 proposes to further add fibrous carbon to the intermediate layer in addition to these in order to further reduce the contact resistance.

JP 2003-115302 A

  An intermediate layer to which fibrous carbon is added is effective in reducing the contact resistance. However, as a result of investigations by the present inventors, when an electrode having such an intermediate layer interposed is produced, a temperature change occurs due to a temperature rise during hot pressing and subsequent cooling, or a humidity change occurs. When it occurs, it has been recognized that peeling may occur at the interface between the layers due to the difference in volume change rate of each layer, and hence the volume change amount. That is, in this case, the problem of becoming an electrode with poor mechanical strength has become apparent.

  The present invention has been made to solve the above-described problems, and provides an electrolyte membrane / electrode structure for a polymer electrolyte fuel cell in which delamination does not easily occur in an electrode and cross-leakage hardly occurs. Objective.

In order to achieve the above object, the present invention comprises an electrolyte membrane made of a polymer ion exchange membrane and a proton conductor, and an anode side electrode and a cathode side electrode disposed via the electrolyte membrane. An electrolyte membrane / electrode structure for a polymer electrolyte fuel cell,
The anode side electrode and the cathode side electrode are interposed between the gas diffusion layer based on carbon paper, the electrode catalyst layer facing the electrolyte membrane, the gas diffusion layer and the electrode catalyst layer, and the electrode catalyst. And an intermediate layer containing carbon particles and water repellent resin in a weight ratio of carbon particles: water repellent resin = 6: 4 ,
A part of the intermediate layer permeates the gas diffusion layer by infiltrating the whole one end part of the intermediate layer in the middle of the thickness direction of the gas diffusion layer, and the other end part of the intermediate layer diffuses the gas diffusion part. Protruding from the layer,
The shortest distance between the end face of the gas diffusion layer facing the intermediate layer and the end face of the electrode catalyst layer facing the intermediate layer is 7 to 29 μm.

  The gas diffusion layer and the electrode catalyst layer have a large number of very fine ridges and depressions on the surface. That is, the end face of the gas diffusion layer facing the intermediate layer and the end face of the electrode catalyst layer facing the intermediate layer are not microscopically flat. Therefore, in the present invention, the distance between the top of the raised portion present on the end face facing the intermediate layer in the gas diffusion layer and the portion facing the top in the electrode catalyst layer, or the electrode Of the ridges present on the end face facing the intermediate layer in the catalyst layer, the distance between the top of the ridge having the highest height and the portion facing the top in the gas diffusion layer is short. Will be referred to as the shortest distance. For example, when the ridge having the highest height in the gas diffusion layer and the top of the ridge having the highest height in the electrode catalyst layer face each other, the shortest distance is the separation distance between the two tops. .

  By setting the shortest distance to 7 μm or more, it is avoided that the fibrous carbon contained in the gas diffusion layer protrudes from the intermediate layer or the electrode catalyst layer. As a result, the fibrous carbon is prevented from penetrating the intermediate layer and coming into contact with the solid polymer electrolyte membrane due to the stress caused by thermal expansion / contraction of each layer, etc., so that cross leak occurs due to this contact. Is avoided for a long time. In other words, the durability of the polymer electrolyte fuel cell is improved, and the polymer electrolyte fuel cell can be continuously operated over a long period of time.

  On the other hand, by setting the shortest distance to 29 μm or less, the mismatch in volume change between the layers is alleviated. For this reason, since the bonding strength between the layers is ensured, it is possible to avoid delamination during the production of the electrode or during the operation of the polymer electrolyte fuel cell. Of course, the manufacturing yield of the electrodes is also improved.

  As described above, according to the present invention, it is possible to configure a polymer electrolyte fuel cell in which delamination does not easily occur in the electrode and cross leak is hardly generated.

  In addition, it is preferable that the surface roughness of the end surface on the side facing the electrode catalyst layer in the intermediate layer is 2 to 15 μm in terms of arithmetic average height Ra specified in JIS B 0601 (2001). When the arithmetic average height Ra is 2 μm or more, the electrode catalyst layer and the intermediate layer are firmly bonded to each other by a so-called anchor effect, so that the bonding strength between both layers is increased, and delamination is less likely to occur. Become. Further, when the arithmetic average height Ra is 15 μm or less, the formation of a gap between the intermediate layer and the electrode catalyst layer is suppressed, so that the contact between the intermediate layer and the electrode catalyst layer is prevented. Resistance can be reduced. For this reason, since the internal resistance of the unit cell is reduced, a high voltage can be obtained from the unit cell and thus the polymer electrolyte fuel cell.

  That is, by setting the arithmetic average height of the intermediate layer within a predetermined range, it is possible to obtain a polymer electrolyte fuel cell having excellent bonding strength between the layers and excellent power generation characteristics.

  According to the present invention, the shortest distance between the end surface facing the intermediate layer in the gas diffusion layer of the electrode constituting the polymer electrolyte fuel cell and the end surface facing the intermediate layer in the electrode catalyst layer is set to a predetermined interval. I have to. For this reason, it is avoided that the fibrous carbon contained in the gas diffusion layer protrudes from the intermediate layer or the electrode catalyst layer and comes into contact with the solid polymer electrolyte membrane. Occurrence is avoided. This ensures the durability of the polymer electrolyte fuel cell.

  At the same time, the inconsistency in the volume change between the layers is alleviated. For example, delamination occurs in the electrode during the production of the electrode or during the operation of the polymer electrolyte fuel cell. It can be avoided. Of course, the manufacturing yield of the electrodes is also improved.

  Hereinafter, the electrolyte membrane / electrode structure for a polymer electrolyte fuel cell according to the present invention (hereinafter also simply referred to as an electrolyte membrane / electrode structure) is preferably implemented in relation to the polymer electrolyte fuel cell having the same. And will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a partially exploded schematic perspective view of a polymer electrolyte fuel cell 10 having an electrolyte membrane / electrode structure according to the present embodiment, and FIG. 2 is a part of the polymer electrolyte fuel cell 10. FIG.

  The polymer electrolyte fuel cell 10 includes a stacked body 14 in which a plurality of unit cells 12 are stacked in the horizontal direction (arrow A direction). A terminal plate 16a, an insulating plate 18a, and an end plate 20a are sequentially disposed at one end in the stacking direction (arrow A direction) of the stacked body 14 toward the outside.

  At the other end in the stacking direction of the stacked body 14, a terminal plate 16b, an insulating plate 18b, and an end plate 20b are sequentially disposed outward (see FIG. 1). The polymer electrolyte fuel cell 10 is integrally held, for example, by a box-like casing (not shown) including end plates 20a and 20b configured in a square shape as end plates, or extends in the direction of arrow A. A plurality of tie rods (not shown) are integrally clamped and held.

  Terminal portions 26a and 26b extending outward in the stacking direction are provided at substantially the center of the terminal plates 16a and 16b. The terminal portions 26a and 26b are inserted into the insulating cylinder 28 and project outside the end plates 20a and 20b.

  As shown in FIGS. 2 and 3, each unit cell 12 includes an electrolyte membrane / electrode structure 30, and a first separator 32 and a second separator 34 that sandwich the electrolyte membrane / electrode structure 30. The 1st separator 32 and the 2nd separator 34 have cross-sectional uneven | corrugated shape by pressing a metal thin plate into a waveform. The first separator 32 and the second separator 34 have a vertically long shape, and are configured such that the long side is directed in the direction of gravity (arrow C direction) and the short side is directed in the horizontal direction (arrow B direction).

  An oxidant gas supply for supplying an oxidant gas, for example, an oxygen-containing gas, communicates with each other in the direction of the arrow A at the upper edge of the long side direction (the direction of arrow C in FIG. 3) of the laminate 14. A communication hole (reaction gas inlet portion) 36a and a fuel gas supply communication hole (reaction gas inlet portion) 38a for supplying a fuel gas, for example, a hydrogen-containing gas, are provided.

  On the other hand, the lower end edge in the long side direction of the laminated body 14 communicates with each other in the direction of arrow A, and a fuel gas discharge communication hole (reaction gas outlet portion) 38b for discharging the fuel gas, and an oxidant gas. An oxidizing gas discharge communication hole (reaction gas outlet part) 36b for discharging is provided.

  Furthermore, a cooling medium supply communication hole 40a for communicating with each other in the direction of arrow A and supplying a cooling medium is provided at one edge of the laminated body 14 in the short side direction (arrow B direction). A cooling medium discharge communication hole 40b for discharging the cooling medium is provided at the other end edge in the direction.

  The electrolyte membrane / electrode structure 30 includes, for example, a solid polymer electrolyte membrane 42 in which a perfluorosulfonic acid thin film is impregnated with water, and an anode side electrode 43 and a cathode side electrode 44 that sandwich the solid polymer electrolyte membrane 42. With.

  In this case, as the material of the solid polymer electrolyte membrane 42, a body polymer ion exchange membrane exhibiting proton conductivity, for example, a sulfonated polyarylene polymer or Nafion (trade name, manufactured by DuPont) is selected. On the other hand, each of the anode side electrode 43 and the cathode side electrode 44 includes gas diffusion layers 45a and 45b based on carbon paper, intermediate layers 46a and 46b formed containing carbon particles, and the intermediate layer 46a, And electrode catalyst layers 47 a and 47 b formed so as to face both surfaces of the solid polymer electrolyte membrane 42. That is, the intermediate layers 46a and 46b are interposed between the gas diffusion layers 45a and 45b and the electrode catalyst layers 47a and 47b.

  On the surface 32a of the first separator 32 facing the electrolyte membrane / electrode structure 30, a fuel gas flow path (reactive gas flow path) 48 that connects the fuel gas supply communication hole 38a and the fuel gas discharge communication hole 38b is formed. The As shown in FIGS. 3 and 4, the fuel gas channel 48 has a plurality of wave-like channel grooves 48a extending in the direction of arrow C, and the upper and lower ends of the wave-like channel grooves 48a in the direction of arrow C. Positioned, an inlet buffer 50a and an outlet buffer 50b having a plurality of embossments are provided.

  The inlet buffer 50a has inclined surfaces 52a and 52b that are inclined toward the fuel gas supply communication hole 38a and the oxidant gas supply communication hole 36a. The outlet buffer portion 50b has inclined surfaces 54a and 54b that are inclined toward the fuel gas discharge communication hole 38b and the oxidant gas discharge communication hole 36b. The fuel gas supply communication hole 38a is disposed above the upper end position of the inlet buffer unit 50a, and the fuel gas discharge communication hole 38b is disposed below the lower end position of the outlet buffer unit 50b.

  Between the fuel gas supply communication hole 38a and the inlet buffer portion 50a, a plurality of inlet passage grooves 56a inclined toward the fuel gas supply communication hole 38a are formed between the plurality of convex portions 58a. Similarly, a plurality of outlet passage grooves 56b that are inclined toward the fuel gas discharge communication hole 38b are formed between the plurality of convex portions 58b between the fuel gas discharge communication hole 38b and the outlet buffer portion 50b. The The lower end positions of the convex portions 58b are arranged in a staggered manner, and the lower ends of the convex portions 58b constitute curved end surfaces (R surfaces).

  As shown in FIG. 5, on the surface 34a of the second separator 34 facing the electrolyte membrane / electrode structure 30, an oxidant gas flow path that connects an oxidant gas supply hole 36a and an oxidant gas discharge hole 36b. 60 (reactive gas flow path) is formed. The oxidant gas flow channel 60 has a plurality of wavy flow channel grooves 60a extending in the direction of arrow C, and is provided with a plurality of embossments located at the upper and lower ends of the wavy flow channel groove 60a in the direction of arrow C. An inlet buffer 62a and an outlet buffer 62b are provided.

  The inlet buffer 62a has inclined surfaces 64a and 64b that are inclined toward the oxidant gas supply communication hole 36a and the fuel gas supply communication hole 38a. The outlet buffer 62b has inclined surfaces 66a and 66b that are inclined toward the oxidant gas discharge communication hole 36b and the fuel gas discharge communication hole 38b. The oxidant gas supply communication hole 36a is disposed above the upper end position of the inlet buffer 62a, and the oxidant gas discharge communication hole 36b is disposed below the lower end position of the outlet buffer 62b.

  A plurality of inlet passage grooves 68a inclined toward the oxidant gas supply communication hole 36a are formed between the plurality of convex portions 70a between the oxidant gas supply communication hole 36a and the inlet buffer 62a. . Similarly, a plurality of outlet passage grooves 68b that are inclined toward the oxidant gas discharge communication hole 36b are provided between the plurality of convex portions 70b between the oxidant gas discharge communication hole 36b and the outlet buffer 62b. It is formed. The lower end position of each convex part 70b is arranged in a staggered manner, and the lower end of the convex part 70b constitutes a curved end surface (R surface).

  A cooling medium flow path 72 communicating with the cooling medium supply communication hole 40a and the cooling medium discharge communication hole 40b is formed between the surface 34b of the second separator 34 and the surface 32b of the first separator 32 (FIG. 3). The cooling medium flow path 72 is formed to extend in the arrow B direction by overlapping the back surface shape of the fuel gas flow path 48 and the back surface shape of the oxidant gas flow path 60.

  A first seal member 74 is integrally formed on the surfaces 32 a and 32 b of the first separator 32 around the outer peripheral edge of the first separator 32. A second seal member 76 is integrally formed on the surfaces 34 a and 34 b of the second separator 34 around the outer peripheral edge of the second separator 34.

  The insulating plates 18a and 18b shown in FIGS. 1 and 2 are made of an insulating material such as polycarbonate or phenol resin, for example. Rectangular portions 80a and 80b are provided at the center of the insulating plates 18a and 18b, and holes 82a and 82b are formed at the approximate centers of the recesses 80a and 80b.

  The terminal plates 16a and 16b are accommodated in the recesses 80a and 80b, and the terminal portions 26a and 26b of the terminal plates 16a and 16b are inserted into the holes 82a and 82b with the insulating cylinder 28 interposed therebetween. Hole portions 84a and 84b are formed coaxially with the hole portions 82a and 82b at the substantially central portions of the end plates 20a and 20b.

  As shown in FIG. 2, the end plate 20a includes an oxidant gas supply communication hole 36a, a fuel gas supply communication hole 38a, a cooling medium supply communication hole 40a, an oxidant gas discharge communication hole 36b, a fuel gas discharge communication hole 38b, and A sealing material, for example, a gasket 90 is provided corresponding to the inner peripheral surface of the cooling medium discharge communication hole 40b. Although FIG. 2 shows the vicinity of the oxidant gas discharge communication hole 36b, the remaining oxidant gas supply communication hole 36a, fuel gas supply communication hole 38a, cooling medium supply communication hole 40a, fuel gas discharge communication hole. The vicinity of 38b and the cooling medium discharge communication hole 40b is configured similarly.

  In the polymer electrolyte fuel cell 10 configured as described above, the gas diffusion layers 45a and 45b constituting the anode side electrode 43 and the cathode side electrode 44 are made of carbon paper as a base material as described above. Carbon paper is composed of a large number of fibrous carbons contained in the cellulosic material.

  The intermediate layers 46a and 46b are composed of carbon particles, PTFE, tetrafluoroethylene / hexafluoropropylene copolymer, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, ethylene / tetrafluoroethylene copolymer, ethylene / chloro. Water-repellent resins such as trifluoroethylene copolymer, polyvinylidene fluoride, polychlorotrifluoroethylene, and polyvinyl fluoride are included. The intermediate layers 46a and 46b exhibit water repellency based on these components.

  As shown in FIG. 6, a part of the intermediate layers 46a and 46b penetrates into the gas diffusion layers 45a and 45b, respectively, and the remaining part protrudes from the gas diffusion layers 45a and 45b. That is, the gas diffusion layers 45a and 45b are separated from the electrode catalyst layers 47a and 47b by the thickness of the intermediate layers 46a and 46b protruding from the gas diffusion layers 45a and 45b. In FIG. 6, the portions of the gas diffusion layers 45a and 45b where the intermediate layers 46a and 46b have permeated are shown by overlapping the hatching of both layers.

  In the present embodiment, the shortest distance according to the above definition from the end face facing the intermediate layers 46a and 46b in the gas diffusion layers 45a and 45b to the end face facing the intermediate layers 46a and 46b in the electrode catalyst layers 47a and 47b, in other words, For example, the separation distance L between the gas diffusion layers 45a and 45b and the electrode catalyst layers 47a and 47b is set within a range of 7 to 29 μm. Of course, the separation distance L is equal to the protruding thickness T of the intermediate layers 46a and 46b from the gas diffusion layers 45a and 45b.

  By setting the separation distance L (projection thickness T) to 7 μm or more, the fibrous carbon contained in the gas diffusion layers 45a and 45b (carbon paper) projects from the intermediate layers 46a and 46b or the electrode catalyst layers 47a and 47b. It is avoided. Accordingly, since the fibrous carbon is avoided from contacting the solid polymer electrolyte membrane 42, it is possible to avoid the durability of the solid polymer fuel cell 10 from being lowered due to the contact.

  Further, if the protruding thickness T of the intermediate layers 46a and 46b is excessively increased, the above-described delamination tends to occur, but in the present embodiment, the protruding thickness T (separation distance L) is set to 29 μm or less. Therefore, the mismatch of the volume change amount of each layer is relieved. For this reason, since the bonding strength between the respective layers is ensured, it is possible to avoid delamination during the production of the anode side electrode 43 or the cathode side electrode 44 or during the operation of the polymer electrolyte fuel cell 10. can do.

  Electrode catalyst layers 47a and 47b are stacked on the intermediate layers 46a and 46b. As will be described later, the electrode catalyst layers 47a and 47b are formed by uniformly applying porous carbon particles carrying platinum or a platinum alloy on the surface thereof to the surfaces of the intermediate layers 46a and 46b.

  In the intermediate layers 46a and 46b, the surface roughness of the end faces facing the electrode catalyst layers 47a and 47b preferably has an arithmetic average height Ra defined by JIS B 0601 (2001) of 2 to 15 μm. By setting the arithmetic average height Ra to 2 μm or more, the electrode catalyst layers 47a and 47b and the intermediate layers 46a and 46b are firmly joined to each other by a so-called anchor effect. That is, it is possible to easily ensure a greater bonding strength.

  In addition, when the arithmetic average height Ra is set to 15 μm or less, it becomes easy to apply the catalyst paste to the end faces of the intermediate layers 46a and 46b without gaps when forming the electrode catalyst layers 47a and 47b described later. Thereby, since it can suppress that a clearance gap forms between intermediate | middle layer 46a, 46b and electrode catalyst layer 47a, 47b, contact resistance between intermediate | middle layer 46a, 46b and electrode catalyst layer 47a, 47b Can be reduced. Eventually, the polymer electrolyte fuel cell 10 can be generated at a high voltage.

  An example of a method for producing the anode side electrode 43 or the cathode side electrode 44 having the above configuration will be described.

  First, mixed particles in which carbon black and PTFE particles are mixed at a predetermined ratio are dispersed substantially uniformly in ethylene glycol to prepare a slurry. This slurry is applied to one end surface of the carbon paper by screen printing, for example, and then dried.

  At this time, the amount of slurry penetrating into the carbon paper by appropriately setting various conditions such as the printing pressure at the time of screen printing, the squeegee speed, and the clearance between the screen mesh on which the slurry is placed and the carbon paper. In addition, the surface roughness of the intermediate layers 46a and 46b to be formed is controlled. The protruding thickness of the slurry from the carbon paper can be adjusted by controlling the application amount of the slurry, the viscosity, and the penetration amount of the slurry into the carbon paper. It is also possible to adjust the slurry by applying it twice or more times.

  As described above, the gas diffusion layers 45a and 45b based on carbon paper and the intermediate layers 46a and 46b in which a part of the gas diffusion layers 45a and 45b penetrates into the gas diffusion layers 45a and 45b and the remaining portions protrude from the gas diffusion layers 45a and 45b. Is formed.

  The protruding thickness T of the intermediate layers 46a and 46b may be calculated based on the size in the SEM image or photograph and the magnification at the time of observation using, for example, a scanning electron microscope (SEM).

  On the other hand, for example, platinum particles or platinum alloy particles are supported on carbon black such as furnace black to prepare catalyst particles. The ratio of carbon black: platinum (or platinum alloy) may be, for example, 1: 1 by weight.

  A catalyst paste is prepared by blending the catalyst particles in a weight ratio of 1: 1 with a perfluoroalkylenesulfonic acid polymer compound, for example, Nafion, which is an ion conductive polymer binder solution, and dispersing the catalyst particles almost uniformly. To prepare.

Next, this catalyst paste is applied over the entire surface of the intermediate layers 46a and 46b by screen printing. This application may be performed, for example, by setting printing conditions such that the amount of platinum (or platinum alloy) is 0.5 mg / cm ² .

  At this time, when the surface roughness of the intermediate layers 46a and 46b is 15 μm or less in terms of the arithmetic average height Ra, the catalyst paste is applied without any gap between the intermediate layers 46a and 46b.

  Thereafter, when the catalyst paste is dried by heating at a predetermined pressure and temperature for a predetermined time, the electrode catalyst layers 47a and 47b are formed. When the surface roughness of the intermediate layers 46a and 46b is 2 μm or more in terms of the arithmetic average height Ra, the electrode catalyst layers 47a and 47b are firmly joined to the intermediate layers 46a and 46b by the anchor effect.

  As described above, the anode side electrode 43 including the gas diffusion layer 45a, the intermediate layer 46a, and the electrode catalyst layer 47a, and the cathode side electrode 44 including the gas diffusion layer 45b, the intermediate layer 46b, and the electrode catalyst layer 47b are obtained. It is done. As described above, since the protruding thickness T of the intermediate layers 46a and 46b is set to 29 μm or less, it is possible to avoid delamination due to mismatch of volume change amounts of the respective layers during the manufacturing process. As a result, the manufacturing yield of the anode side electrode 43 and the cathode side electrode 44 is improved.

  Further, since the protruding thickness T of the intermediate layers 46a and 46b, that is, the separation distance L between the gas diffusion layers 45a and 45b and the electrode catalyst layers 47a and 47b is 7 μm or more, the fibrous shape contained in the gas diffusion layers 45a and 45b. Carbon does not come into contact with the solid polymer electrolyte membrane 42.

  The electrode catalyst layer 47a of the anode side electrode 43 and the electrode catalyst layer 47b of the cathode side electrode 44 thus produced are used as a solid polymer electrolyte membrane 42, for example, a proton conductive solid such as a sulfonated polyarylene polymer or Nafion. If the polymer membrane is sandwiched and integrated by, for example, hot pressing, the electrolyte membrane / electrode structure 30 is produced.

  Next, the unit cell 12 is configured by sandwiching the electrolyte membrane / electrode structure 30 between the first separator 32 and the second separator 34 (see FIGS. 1 and 2). A stacked body 14 (see FIG. 1) is obtained by stacking a predetermined number of the unit cells 12. Further, a terminal plate 16a, an insulating plate 18a, and an end plate 20a are disposed at one end in the stacking direction of the multilayer body 14, while a terminal plate 16b, an insulating plate 18b, and an end plate 20b are disposed at the other end, and these are box-shaped. The polymer electrolyte fuel cell 10 can be obtained by holding it with a casing or by tightening and holding it with a plurality of tie rods.

  The polymer electrolyte fuel cell 10 according to the present embodiment is basically configured as described above. Next, the function and effect will be described.

  When the polymer electrolyte fuel cell 10 is operated, as shown in FIG. 1, an oxidant gas such as an oxygen-containing gas is supplied to the oxidant gas supply communication hole 36a of the end plate 20a and the fuel gas is supplied. A fuel gas such as a hydrogen-containing gas is supplied to the communication hole 38a. Further, a coolant such as pure water or ethylene glycol is supplied to the coolant supply passage 40a. For this reason, in the stacked body 14, the oxidant gas, the fuel gas, and the cooling medium are respectively supplied in the direction of arrow A to the plurality of unit cells 12 stacked in the direction of arrow A.

  As shown in FIGS. 3 and 5, the oxidant gas is introduced from the oxidant gas supply communication hole 36 a into the oxidant gas flow path 60 of the second separator 34, and the cathode side electrode 44 of the electrolyte membrane / electrode structure 30. Move along.

  At that time, as shown in FIG. 5, on the surface 34a of the second separator 34, the oxidant gas flowing through the oxidant gas supply communication hole 36a flows into a plurality of inlet passage grooves 68a formed between the plurality of convex portions 70a. To the inlet buffer 62a. The oxidant gas supplied to the inlet buffer 62a is dispersed in the direction of arrow B, and flows vertically downward along the plurality of wave-like channel grooves 60a constituting the oxidant gas channel 60.

  On the other hand, as shown in FIGS. 3 and 4, the fuel gas flows into the plurality of inlet passage grooves 56 a formed between the plurality of convex portions 58 a from the fuel gas supply communication hole 38 a on the surface 32 a of the first separator 32. After being supplied, it is introduced into the inlet buffer 50a. The fuel gas dispersed in the direction of arrow B in the inlet buffer 50a moves along the plurality of wave-like channel grooves 48a constituting the fuel gas channel 48, and reaches the anode electrode 43 of the electrolyte membrane / electrode structure 30. Supplied.

  In the present embodiment, the fuel gas contains moisture (hereinafter, this moisture is also referred to as moisturizing water). The moisturizing water keeps the solid polymer electrolyte membrane 42 in a wet state, whereby proton conduction in the solid polymer electrolyte membrane 42 is continuously developed.

  In each electrolyte membrane / electrode structure 30, hydrogen gas in the fuel gas supplied to the anode-side electrode 43 passes through the gas diffusion layer 45 a and is then ionized by the electrode catalyst layer 47 a to generate protons and electrons. Electrons are taken out as electric energy for energizing an external load electrically connected to the polymer electrolyte fuel cell 10, while protons are solid polymer electrolytes constituting the electrolyte membrane / electrode structure 30. It reaches the cathode side electrode 44 through the film 42.

  In the electrode catalyst layer 47b of the cathode side electrode 44, the protons, the electrons that have reached the cathode side electrode 44 after energizing the external load, and the gas supplied to the cathode side electrode 44 and pass through the gas diffusion layer 45b. The oxygen gas in the oxidized oxidant gas is combined. As a result, moisture is generated. Hereinafter, this moisture is also referred to as generated water.

  Appropriate amounts of the above moisturizing water and generated water are held in the intermediate layers 46a and 46b constituting the anode side electrode 43 and the cathode side electrode 44, and the remainder is a carbon-repellent carbon base material for the gas diffusion layers 45a and 45b. Since it is paper, it quickly passes through the gas diffusion layers 45a and 45b and reaches the fuel gas channel 48 or the oxidant gas channel 60. That is, in the polymer electrolyte fuel cell 10, water retention is improved and excess water can be easily discharged.

  On the other hand, since some of these intermediate layers 46a and 46b penetrate into the gas diffusion layers 45a and 45b, the reaction gas easily passes through the gas diffusion layers 45a and 45b and the intermediate layers 46a and 46b.

  As described above, since the fibrous carbon in the product gas diffusion layers 45a and 45b constituting the anode side electrode 43 and the cathode side electrode 44 is avoided from contacting the solid polymer electrolyte membrane 42, the solid polymer It is possible to prevent the solid polymer electrolyte membrane 42 from being damaged during the operation of the fuel cell 10. For this reason, the durability of the polymer electrolyte fuel cell 10 is improved, thereby suppressing the occurrence of cross leak in the polymer electrolyte fuel cell 10 over a long period of time. Eventually, the polymer electrolyte fuel cell 10 can be continuously operated over a long period of time.

  As shown in FIG. 5, the oxidant gas consumed by being supplied to the cathode side electrode 44 is sent to an outlet buffer 62 b communicating with the lower part of the oxidant gas flow path 60. Further, the oxidant gas is discharged from the outlet buffer portion 62b to the oxidant gas discharge communication hole 36b along the plurality of outlet passage grooves 68b formed between the plurality of convex portions 70b.

  Similarly, the fuel gas supplied to and consumed by the anode side electrode 43 is sent to an outlet buffer unit 50b communicating with the lower part of the fuel gas channel 48, as shown in FIGS. The fuel gas is discharged into the fuel gas discharge communication hole 38b along a plurality of outlet passage grooves 56b formed between the convex portions 58b.

  The moisture contained in the fuel gas and reaching the anode side electrode 43 and the moisture generated by the cathode side electrode 44 are the basis of the gas diffusion layers 45 a and 45 b constituting the anode side electrode 43 and the cathode side electrode 44. Since the material is water-repellent carbon paper, it quickly passes through the gas diffusion layers 45a and 45b and reaches the fuel gas channel 48 or the oxidant gas channel 60. Finally, the water is discharged from the oxidant gas discharge communication hole 36b or the fuel gas discharge communication hole 38b along with the fuel gas or the oxidant gas.

  The cooling medium flows in the direction of arrow B (horizontal direction) after being introduced into the cooling medium flow path 72 between the first separator 32 and the second separator 34 from the cooling medium supply communication hole 40a. The cooling medium is discharged from the cooling medium discharge communication hole 40b after the electrolyte membrane / electrode structure 30 is cooled.

  In the present embodiment, for example, as shown in FIG. 5, the second separator 34 is configured to be vertically long, the long side is set in the direction of gravity (the direction of arrow C), and the oxidizing gas channel 60 is It has a plurality of wave-like channel grooves 60a extending in the direction of gravity. For this reason, a relatively large amount of product water is likely to be generated in the long corrugated flow channel 60a by reaction, but the oxidant gas flows along the direction of gravity. The liquid is reliably discharged vertically downward along the flow channel 60a.

  Further, an outlet buffer portion 62b is provided at the lower portion of the oxidant gas flow path 60, and an oxidant gas discharge communication hole 36b is provided below the outlet buffer portion 62b via a plurality of outlet passage grooves 68b. Has been placed. Therefore, the generated water generated by the reaction in the oxidant gas flow channel 60 does not stay in the lower part of the oxidant gas flow channel 60 or the outlet buffer 62b, and is discharged to the oxidant gas discharge communication hole 36b. .

  At that time, the outlet buffer portion 62b is provided with an inclined surface 66a inclined toward the oxidant gas discharge communication hole 36b, and a plurality of outlet passages from the inclined surface 66a toward the oxidant gas discharge communication hole 36b. The groove 68b is inclined.

  As a result, the generated water sent from the lower part of the oxidant gas flow channel 60 to the outlet buffer 62b flows smoothly and reliably into the oxidant gas discharge communication hole 36b via the outlet passage groove 68b, and the generated water is retained. Can be prevented more reliably.

  In particular, when the operation of the polymer electrolyte fuel cell 10 is stopped, the generated water in the oxidant gas flow channel 60 is discharged into the oxidant gas discharge communication hole 36b by its own weight. For this reason, there is an advantage that the generated water does not stay in the unit cell 12, and damage to the unit cell 12 due to, for example, freezing of residual moisture can be satisfactorily prevented.

  Of course, also in the fuel gas flow channel 48 shown in FIG. Accordingly, since the reaction gas supplied to the anode side electrode 43 and the cathode side electrode 44 can easily pass through the gas diffusion layers 45a and 45b, the power generation characteristics of the polymer electrolyte fuel cell 10 are further improved.

  Furthermore, in this embodiment, the oxidant gas flow path 60 has a plurality of wave-shaped flow path grooves 60a, and the length of the oxidant gas flow path can be satisfactorily increased as compared with the straight flow path. Is possible. Therefore, the flow path pressure loss in the oxidant gas flow path 60 is increased, the flow rate of the oxidant gas is increased, and the drainage of the produced water is improved.

  Furthermore, since the oxidant gas moves in the direction of arrow C along the wavy flow channel groove 60a, the flow direction of the oxidant gas changes in a wave shape. Thereby, the diffusibility of the oxidant gas at the cathode side electrode 44 is increased, and the power generation performance is effectively improved.

  Moreover, the lower end position of the some convex-shaped part 70b which comprises the exit channel | path groove | channel 68b is arrange | positioned at zigzag form. For this reason, the space | interval of the lower end positions of each convex-shaped part 70b becomes large, and the produced | generated water descend | falls with dead weight along the said convex-shaped part 70b does not remain as a water droplet, and it is reliably from the exit channel | path groove | channel 68b. Can be discharged. In that case, the lower end of the convex part 70b comprises the curved end surface (R surface). Thereby, it can prevent more reliably that a water droplet adheres to the lower end of the convex-shaped part 70b.

  In the above-described embodiment, the reaction gas is circulated from the upper side to the lower side in the direction of gravity, but it is needless to say that the reaction gas may be circulated in the horizontal direction.

  The intermediate layers 46a and 46b may contain fibrous carbon.

  A mixed particle in which carbon black and PTFE particles were mixed at a weight ratio of 4: 6 was dispersed substantially uniformly in ethylene glycol to prepare a slurry. The slurry is applied to one end surface of the carbon paper by screen printing and then dried. A part of the slurry penetrates the gas diffusion layers 45a and 45b on the gas diffusion layers 45a and 45b based on the carbon paper, In addition, intermediate layers 46a and 46b whose remaining portions protruded from the gas diffusion layers 45a and 45b were formed.

  On the other hand, platinum particles were supported at a weight ratio of 1: 1 with respect to furnace black, which is one type of carbon black, to prepare catalyst particles. The catalyst particles were blended at a weight ratio of 1: 1 with respect to Nafion and dispersed substantially uniformly to prepare a catalyst paste.

Next, this catalyst paste was applied over the entire surface of the intermediate layers 46a and 46b by screen printing. At this time, the printing conditions were set so that the amount of platinum was 0.5 mg / cm ² . Further, after heating at approximately 60 ° C. for approximately 10 minutes, the catalyst paste was dried by heating at approximately 120 ° C. for approximately 15 minutes under reduced pressure, thereby forming electrode catalyst layers 47a and 47b. As a result, an anode side electrode 43 having a gas diffusion layer 45a, an intermediate layer 46a and an electrode catalyst layer 47a, and a cathode side electrode 44 having a gas diffusion layer 45b, an intermediate layer 46b and an electrode catalyst layer 47b were obtained.

  In the above process, various conditions such as printing pressure during screen printing, squeegee speed, clearance between the screen mesh on which the slurry is placed and the carbon paper are variously changed, whereby the slurry that penetrates the carbon paper The anode side electrode 43 and the cathode side electrode 44 having different amounts (the protruding thickness T of the slurry from the carbon paper) were produced. The protruding thickness T of the intermediate layers 46a and 46b was calculated using SEM.

  Nafion as the solid polymer electrolyte membrane 42 is sandwiched between the electrode catalyst layer 47a of the anode side electrode 43 and the electrode catalyst layer 47b of the cathode side electrode 44 thus produced, and about 2.5 MPa at about 150 ° C. The electrolyte membrane / electrode structure 30 was obtained by integrating by hot pressing for 15 minutes. Further, the electrolyte membrane / electrode structure 30 was sandwiched between the first separator 32 and the second separator 34 to constitute the unit cell 12.

Next, each unit cell 12 is caused to generate electric power while periodically changing the temperature from 85 ° C. and the current density from 0 to 1.2 A / cm ² or from 1.2 A / cm ² to 0. The time until the cross leak occurred was examined. During operation, hydrogen gas was supplied to the anode side electrode 43 at 150 kPa and compressed air was supplied to the cathode side electrode 44 at 100 kPa, the utilization rate of hydrogen gas was 70%, and the utilization rate of compressed air was 80%. Moreover, when the hydrogen gas contained in the gas discharged | emitted from the cathode side electrode 44 reached | attained 500 ppm, it was judged that generation | occurrence | production of a cross leak started.

  The results are shown in FIG. 7 in relation to the protrusion thickness T from the gas diffusion layer in the intermediate layers 46a and 46b. From FIG. 7, by setting the protruding thickness T of the intermediate layers 46a and 46b (the distance L between the gas diffusion layers 45a and 45b and the electrode catalyst layers 47a and 47b) within the range of 7 to 29 μm, Alternatively, it is apparent that there is no delamination when the cathode side electrode 44 is produced, and that the solid polymer fuel cell 10 having extremely excellent durability can be obtained.

  Similarly to the above, various conditions such as the printing pressure at the time of screen printing, the squeegee speed, the clearance between the screen mesh on which the slurry is placed and the carbon paper are variously changed, and the protrusion of the intermediate layers 46a and 46b is performed. While the thickness T is kept constant at 15 μm, the anode-side electrode 43 and the cathode-side electrode 44 are produced by variously changing the arithmetic average height Ra of the end faces facing the electrode catalyst layers 47a and 47b in the intermediate layers 46a and 46b. did. In addition, arithmetic mean height Ra of intermediate | middle layers 46a and 46b was calculated | required using the Keyence Corporation surface roughness measuring machine KS-1100.

Furthermore, the unit cell 12 was produced using the anode side electrode 43 and the cathode side electrode 44, and each unit cell 12 was generated at a temperature of 85 ° C. and a current density of 1 A / cm ² . The supply pressure and utilization rate of hydrogen gas and compressed air were the same as described above.

  FIG. 8 is a graph showing the relationship between the arithmetic average height Ra in the intermediate layers 46a and 46b and the voltage of each unit cell 12. In FIG. From FIG. 8, it is understood that the unit cell 12 having a large voltage during power generation and excellent power generation characteristics can be obtained by setting the arithmetic average height Ra within the range of 2 to 15 μm.

1 is a partially exploded perspective view of a polymer electrolyte fuel cell according to an embodiment. FIG. 2 is a partial cross-sectional explanatory view of the polymer electrolyte fuel cell of FIG. 1. It is a principal part disassembled perspective view of the single cell which comprises the polymer electrolyte fuel cell of FIG. It is a front view of the 1st separator which comprises the single cell of FIG. It is a front view of the 2nd separator which comprises the single cell of FIG. It is principal part cross-sectional explanatory drawing of the electrolyte membrane and electrode structure which comprises the unit cell of FIG. It is a graph which shows the relationship between the protrusion thickness from the gas diffusion layer of an intermediate | middle layer, and the time until cross leak arises in a unit cell. It is a graph which shows the relationship between arithmetic mean height Ra of the end surface which faces the electrode catalyst layer of an intermediate | middle layer, and the voltage of a unit cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Solid polymer fuel cell 12 ... Unit cell 14 ... Laminated body 16a, 16b ... Terminal plate 18a, 18b ... Insulation plate 20a, 20b ... End plate 30 ... Electrolyte membrane and electrode structure 32, 34 ... Separator 36a ... Oxidation Agent gas supply communication hole 36b ... Oxidant gas discharge communication hole 38a ... Fuel gas supply communication hole 38b ... Fuel gas discharge communication hole 40a ... Cooling medium supply communication hole 40b ... Cooling medium discharge communication hole 42 ... Solid polymer electrolyte membrane 43 ... Anode side electrode 44 ... Cathode side electrode 45a, 45b ... Gas diffusion layer 46a, 46b ... Intermediate layer 47a, 47b ... Electrode catalyst layer 48 ... Fuel gas channel 48a, 60a ... Wave-like channel groove 50a, 62a ... Inlet buffer portion 50b , 62b ... outlet buffer sections 56a and 68a ... inlet passage grooves 56b and 68b ... outlet passage grooves 58a and 58 b, 70a, 70b ... convex portion 60 ... oxidant gas flow path 72 ... cooling medium flow path L ... separation distance T ... protrusion thickness

Claims (1)

Electrolyte membrane / electrode structure for a polymer electrolyte fuel cell comprising an electrolyte membrane made of a polymer ion exchange membrane and a proton conductor, and an anode side electrode and a cathode side electrode disposed via the electrolyte membrane Because
The anode side electrode and the cathode side electrode are interposed between the gas diffusion layer based on carbon paper, the electrode catalyst layer facing the electrolyte membrane, the gas diffusion layer and the electrode catalyst layer, and the electrode catalyst. And an intermediate layer containing carbon particles and water repellent resin in a weight ratio of carbon particles: water repellent resin = 6: 4 ,
A part of the intermediate layer permeates the gas diffusion layer by infiltrating the whole one end part of the intermediate layer in the middle of the thickness direction of the gas diffusion layer, and the other end part of the intermediate layer diffuses the gas diffusion part. Protruding from the layer,
And the shortest distance of the end surface which faces the said intermediate | middle layer in the said gas diffusion layer, and the end surface which faces the said intermediate | middle layer in the said electrode catalyst layer is 7-29 micrometers,
Further, the electrolyte membrane / electrode structure for a polymer electrolyte fuel cell, wherein the surface roughness of the end face of the intermediate layer facing the electrode catalyst layer is an arithmetic average height of 2 to 15 μm.
However, the shortest distance is the distance between the top of the raised portion present on the end surface facing the intermediate layer in the gas diffusion layer and the portion facing the top in the electrode catalyst layer, Or, of any one of the distances between the top of the raised portion present on the end face facing the intermediate layer in the electrode catalyst layer and the portion facing the top in the gas diffusion layer The one with the shorter distance.

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