JP2006004709A - Solid polymer electrolyte fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid polymer electrolyte fuel cell preventing flooding caused by water produced in an oxidant electrode and providing stable and efficient power generation performance for a long time. <P>SOLUTION: The solid polymer electrolyte fuel cell is constituted with a unit cell 1 equipped with a membrane electrode assembly 5 having a hydrogen electrode 3 on one side and the oxidant electrode 4 on the other side of a solid polymer electrolyte membrane 2, a fuel electrode side gas diffusion layer 6 arranged on the surface of the fuel electrode 3 side of the membrane electrode assembly 5, an oxidant electrode side gas diffusion layer 9 arranged on the surface of the oxidant electrode 4 side of the membrane electrode assembly 5 and having carbon fibers 10 having a groove 11 formed on the surface, a fuel electrode side separator 8 arranged on the outside of the fuel electrode side gas diffusion layer 6, and an oxidant electrode side separator 9 arranged on the outside of the oxidant electrode gas diffusion layer 7. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solid polymer electrolyte fuel cell.

  A fuel cell is a device that directly converts a chemical energy of a fuel into electric energy by electrochemically reacting a fuel gas such as a hydrogen-containing gas, which is a reaction gas, and an oxygen-containing gas such as air. Thus, since the fuel cell can directly convert chemical energy into electrical energy, the power generation efficiency is higher than that of other power generation systems such as thermal power generation, and is a highly efficient power generation device. In addition, the fuel cell is attracting attention as a low-pollution or non-polluting power generation device from the viewpoint of protecting the global environment because it has an advantage that no exhaust gas is generated due to power generation. In this way, fuel cells are positioned as power generators for “post-nuclear power” and “post-internal combustion engines” that can deal with energy problems and pollution problems in modern society. Yes. There are also fields that have already been put into practical use, such as home on-site power generation devices, portable small power generation devices, and spacecraft-mounted power generation devices.

  Similarly, in the automobile industry, the use of fuel cells as a power source for motors that operate in place of internal combustion engines is rapidly increasing, and the development of automobiles using fuel cells is advancing. As a fuel cell for automobiles, since it is an essential condition that power generation characteristics are particularly small and high output, a solid polymer electrolyte fuel cell using an ion exchange membrane is attracting attention among various fuel cells. ing.

  In this polymer electrolyte fuel cell, gas diffusion layers are arranged on the outer surface of a membrane electrode assembly in which a polymer electrolyte membrane having a proton (hydrogen ion) exchange group in the molecule is sandwiched between a fuel electrode and an oxidant electrode. Further, a large number of unit cells (single cells) each having a fuel electrode side separator and an oxidant electrode side separator disposed on the outer surface thereof are laminated. The gas diffusion layer is formed of carbon paper or carbon non-woven fabric composed of carbon fibers having the role of gas diffusion and electrical conductors. Each separator has a gas flow path and a cooling water flow path.

  In a solid polymer electrolyte fuel cell, a reaction represented by the following formula proceeds.

(Chemical formula 1)
Fuel electrode: H ₂ → 2H ⁺ + 2e ⁻ Expression (1)
Oxidant electrode: (1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O + Q (heat of reaction) (2)
Entire battery: H ₂ + (1/2) O ₂ → H ₂ O + Q (heat of reaction) Formula (3)
At the fuel electrode, a fuel gas containing hydrogen is supplied, the reaction of the formula (1) proceeds, and protons are generated. Protons are hydrated by moisture contained in the solid polymer electrolyte membrane, and are transferred to the oxidant electrode through the proton exchange groups in the solid polymer electrolyte membrane. At the oxidant electrode, the transferred protons react with oxygen in the oxidant gas supplied to the oxidant electrode, and the reaction of Formula (2) proceeds to generate water. At this time, electrons generated at the fuel electrode move to the oxidant electrode via the external circuit, so that an electromotive force is obtained and electrical work is performed on the external load.

  Here, the proton exchange group in the solid polymer electrolyte membrane has a reduced specific resistance when saturated with water, and functions as a proton conductive electrolyte. Since protons permeate the solid polymer electrolyte membrane in a hydrated state, good electrical conductivity is exhibited if the solid polymer electrolyte membrane is in an appropriate wet state. However, since the ionic conductivity is reduced and the electrolyte does not function as the water content decreases, a phenomenon that stops the electrode reaction in some cases occurs. For this reason, in order to maintain high power generation performance of the solid polymer electrolyte fuel cell, it is necessary to maintain the water content of the solid polymer electrolyte membrane in saturation. In general, a method is employed in which the moisture content of the solid polymer electrolyte membrane is maintained by supplying the reaction gas to the unit cell after increasing the humidity of the reaction gas using a humidifier or the like.

  However, in the solid polymer electrolyte fuel cell, as shown in the above formula (2), water is generated on the oxidant electrode side during power generation. This produced water is sent downstream in the unit cell together with the oxidant gas. As a result, water generated by power generation is added in addition to water for humidification, so that the amount of water is large in the downstream part in the unit cell, and the amount of water that can be retained by the remaining gas that has consumed hydrogen and oxygen in the reaction gas Therefore, water droplets are generated due to aggregation of water vapor. And since this water droplet fills the void | hole in a gas diffusion layer, the spreading | diffusion phenomenon that the spreading | diffusion of oxidant gas in a gas diffusion layer is prevented and the electric power generation performance of a fuel cell falls occurs. Even if the amount of humidification of the oxidant gas is reduced in order to reduce the amount of water downstream, if the power generation efficiency is increased and the utilization rate of the oxidant gas is increased, the generated water increases and flatting occurs. . However, if the humidification amount of the oxidant gas to be supplied is reduced too much, the solid polymer electrolyte membrane becomes dry, and as a result, the power generation performance may be lowered. For this reason, in order to prevent flatting, it is necessary to discharge water generated by aggregation without reducing the humidification amount of the oxidant gas.

Thus, for example, a method of forming a water-repellent film on the surface of the gas diffusion layer has been proposed (see Patent Document 1).
JP 2000-239704 A (2nd page, FIG. 1)

  However, when the surface of the gas diffusion layer is subjected to water repellent treatment, the conductivity of the gas diffusion layer may be lowered by the water repellent treatment agent. Further, since the water repellent agent fills the pores in the gas diffusion layer, the gas diffusibility is lowered.

  The present invention has been made to solve the above problems, and the solid polymer electrolyte fuel cell of the present invention has a fuel electrode on one surface of the solid polymer electrolyte membrane and an oxidizer electrode on the other surface. The membrane electrode assembly, the fuel electrode side gas diffusion layer disposed on the fuel electrode side surface of the membrane electrode assembly, and the oxidant electrode side surface of the membrane electrode assembly were formed with grooves formed on the surface. An oxidant electrode side gas diffusion layer having carbon fibers, a fuel electrode side separator disposed outside the fuel electrode side gas diffusion layer, and an oxidant electrode side separator disposed outside the oxidant electrode side gas diffusion layer; The gist is that

  According to the present invention, water generated by the oxidant electrode is absorbed by the capillary action of the carbon fiber, moves to the oxidant electrode side separator side, and is vaporized and diffused in the oxidant gas. For this reason, flooding can be prevented, and stable and highly efficient power generation performance can be obtained over a long period of time.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  Hereinafter, Example 1 is demonstrated using FIGS. 1-3.

  FIG. 1A is a cross-sectional view showing a unit cell constituting a solid polymer electrolyte fuel cell according to Example 1 of the present invention. FIG. 1B is a perspective view schematically showing the oxidant electrode side gas diffusion layer. FIG.1 (c) is explanatory drawing which shows typically the Ic part of FIG.1 (b). FIG.1 (d) is explanatory drawing which shows a carbon fiber typically. FIG.1 (e) is sectional drawing cut | disconnected along the Id-Id line of FIG.1 (d).

  As shown in FIG. 1A, a unit cell 1 constituting the solid polymer electrolyte fuel cell according to the present embodiment has a fuel electrode 3 on one surface of a solid polymer electrolyte membrane 2 and a fuel cell 3 on the other surface. The membrane electrode assembly 5 having the oxidant electrode 4, the fuel electrode side gas diffusion layer 6 disposed on the surface of the membrane electrode assembly 5 on the fuel electrode 3 side, and the oxidant electrode 4 side of the membrane electrode assembly 5 The oxidant electrode side gas diffusion layer 7 disposed on the surface, the fuel electrode side separator 8 disposed outside the fuel electrode side gas diffusion layer 6, and the oxidant electrode side gas diffusion layer 7 are disposed outside. And an oxidant electrode-side separator 9. A plurality of unit cells 1 are stacked to constitute a solid polymer electrolyte fuel cell.

As the solid polymer electrolyte membrane 2 used in the unit cell 1, a perfluorocarbon polymer membrane having a sulfonic acid group (trade name; Nafion 1128 (registered trademark), DuPont Co., Ltd.) can be used. A membrane electrode assembly 5 is formed by joining a catalyst layer of platinum catalyst-carrying carbon as a fuel electrode 3 on one surface of the solid polymer electrolyte membrane 2 and an oxidizer electrode 4 on the other surface. The thickness of the membrane electrode assembly 5 is about 0.2 [mm], and the thicknesses of the fuel electrode 3 and the oxidant electrode 4 are about 10 [μm], respectively, and are included in the fuel electrode 3 and the oxidant electrode 4. The platinum catalyst is about 0.1 to 0.5 [g / cm ² ].

  A fuel electrode side gas diffusion layer 6 and an oxidant electrode side gas diffusion layer 7 are disposed outside the fuel electrode 3 and the oxidant electrode 4, respectively. The fuel electrode side gas diffusion layer 6 and the oxidant electrode side gas diffusion layer 7 are formed of carbon fibers and are porous carbon films called carbon cloth, carbon paper, and the like. This porous carbon membrane has pores with a diameter of about 10 to 50 [μm], and optimizes the diffusion of reaction gas (fuel gas containing hydrogen and oxidant gas containing oxygen), respectively. To facilitate contact with the catalyst layer. The fuel electrode 3 also serves to replenish moisture necessary for proton transfer, and the oxidant electrode 4 controls the removal of the generated water.

  A fuel electrode side separator 8 and an oxidant electrode side separator 9 are installed outside the fuel electrode side gas diffusion layer 6 and the oxidant electrode side gas diffusion layer 7, respectively. Each of the separators 8 and 9 has a gas flow path and a cooling water flow path formed on a surface of carbon or metal formed into a plate shape, and supplies a reaction gas. In addition, the fuel electrode side separator 8 functions as a moisture replenishment passage, the oxidant electrode side separator 9 functions as a water removal passage, and further plays a role of supplying a current to an external circuit.

  As shown in FIGS. 1B and 1C, the carbon fibers 10 are entangled with each other in the oxidant electrode side gas diffusion layer 7. As shown in FIGS. 1D and 1E, a groove 11 is formed on the surface of the carbon fiber 10.

  Such an oxidant electrode side gas diffusion layer 7 is manufactured, for example, by the process shown in FIG. FIG. 2 is a process flow diagram illustrating a schematic process of the method for manufacturing a gas diffusion layer. First, an acrylonitrile monomer is polymerized by an emulsifier polymerization method using an organic hydroperoxide, a redox initiator, or the like to synthesize polyacrylonitrile (PAN) (step 20). Next, PAN is injected from the extrusion die, and the yarn is made into acrylic fiber (step 21). At this time, the shape of the base is appropriately selected to form a desired groove in the acrylic fiber. Next, after knitting the acrylic fiber having the groove formed on the product substrate (step 22), it is passed through a high temperature furnace at 200 to 300 [° C.] while blowing oxygen to perform a flameproofing treatment (step 23). By this step, the acrylic fiber is changed to a stable fiber rich in heat resistance and fire resistance. Thereafter, the carbon fiber is formed by further heating at a high temperature of 1000 to 1500 [° C.] in an inert atmosphere to perform carbonization (step 24). Further, surface treatment or the like is performed to form a gas diffusion layer (step 25).

  Next, the movement of water in the unit cell 1 having the above configuration will be described.

  The fuel gas passes through the fuel gas channel of the unit cell 1 shown in FIG. 1A, and the oxidant gas passes through the oxidant gas channel. At this time, in the fuel electrode 3, the reaction of the above formula (1) proceeds, and protons are generated. Protons move through the solid polymer electrolyte membrane 2 in a hydrated state and reach the oxidizer electrode 4. In the oxidant electrode 4, the proton moved from the fuel electrode 3 reacts with oxygen in the oxidant gas supplied to the oxidant electrode 4, and the reaction of the above formula (2) proceeds to generate water.

  And the water produced | generated by the oxidant electrode 4 is sucked out by the capillary phenomenon in the groove | channel 11 formed on the surface of the carbon fiber 10 of the oxidant electrode side gas diffusion layer 7, and an oxidant with a lower humidity environment Move to the pole separator 9 side. FIG. 3 shows a state where water is transmitted through the groove 11 of the carbon fiber 10. Since the carbon fibers 10 are entangled with each other in the oxidant electrode side gas diffusion layer 7, water moves from one carbon fiber groove to another carbon fiber groove. Furthermore, water moves to the oxidant electrode side separator 9 side, and is finally vaporized and diffused in the oxidant gas. This vaporization / diffusion phenomenon becomes a driving force, and water absorption / vaporization / diffusion of the generated water of the oxidizer electrode 4 proceeds continuously.

  In this way, excess water generated and oxidized at the oxidant electrode 4 is absorbed, vaporized, and diffused by the carbon fiber capillary phenomenon, so that water retention in the oxidant electrode 4 is prevented. Then, water is prevented from dropping in the oxidant electrode side gas diffusion layer 7 without sacrificing the diffusibility of the oxidant gas, and in the region including the oxidant electrode 4 to the oxidant electrode side gas diffusion layer 7. Flooding can be prevented. And it becomes possible to obtain the highly efficient power generation performance stably over a long period of time.

  Thus, according to the solid polymer electrolyte fuel cell according to the present embodiment, the membrane electrode assembly having the fuel electrode on one surface of the solid polymer electrolyte membrane and the oxidant electrode on the other surface, A fuel electrode side gas diffusion layer disposed on the fuel electrode side surface of the membrane electrode assembly, and an oxidant having carbon fibers disposed on the surface of the membrane electrode assembly on the oxidant electrode side and having grooves formed on the surface By providing the electrode side gas diffusion layer, the fuel electrode side separator disposed outside the fuel electrode side gas diffusion layer, and the oxidant electrode side separator disposed outside the oxidant electrode side gas diffusion layer. The water generated by the oxidant electrode is absorbed by the capillary action of the carbon fiber, moves to the oxidant electrode side separator side, and is vaporized and diffused in the oxidant gas. Prevents flooding even if not applied, stable for a long time It is possible to obtain a high-efficiency power generation performance Te.

  In addition, it is not necessary to provide a groove in all the carbon fibers, and the carbon fiber in which the groove is formed and the carbon fiber without the groove may be mixed. Further, the shape and number of the grooves are not particularly limited, and any number of grooves may be formed as long as the groove volume necessary for water absorption can be secured.

  Next, Example 2 will be described with reference to FIG.

  FIG. 4A is a perspective view schematically showing an oxidant electrode side gas diffusion layer of a solid polymer electrolyte fuel cell according to Example 2 of the present invention. FIG.4 (b) is explanatory drawing which shows a one groove | channel carbon fiber. FIG.4 (c) is explanatory drawing which shows a double groove carbon fiber. FIG.4 (d) is explanatory drawing which shows a three-groove carbon fiber. The solid polymer electrolyte fuel cell in this example was implemented in that the volume of the carbon fiber groove forming the oxidant electrode side gas diffusion layer was increased from the oxidant electrode side to the oxidant electrode side separator. Different from Example 1.

  As shown in FIG. 4 (a), the oxidant electrode side gas diffusion layer 27 in Example 2 is shown in FIG. 4 (b) from the oxidant electrode side of the membrane electrode assembly toward the oxidant electrode side separator. One groove layer 27a having one groove carbon fiber 30A shown, two groove layer 27b having two groove carbon fibers 30B shown in FIG. 4 (c), and three groove layer 27c having three groove carbon fibers 30C shown in FIG. 4 (d). It consists of three layers. As shown in FIG. 4B, a single groove 31A is formed in the single groove carbon fiber 30A. In addition, as shown in FIG. 4C, two grooves 31B are formed in the two-groove carbon fiber 30B. Further, as shown in FIG. 4D, three grooves 31C are formed in the three-groove carbon fiber 30C. As described in the first embodiment, the number of grooves in each groove is determined by the shape of the die when the PAN is made into acrylic fibers.

  Thus, in the oxidant electrode side gas diffusion layer 27 in Example 2, the volume of the groove of the carbon fiber in the oxidant electrode side gas diffusion layer 27 increases from the oxidant electrode side to the oxidant electrode side separator side. As described above, the carbon fibers having different numbers of grooves are mixed and then laminated. For this reason, in the oxidant electrode side gas diffusion layer 27 in Example 2, the function of sucking up the water by the groove of the carbon fiber stepwise from the oxidant electrode side to the oxidant electrode side separator side becomes higher. ing. For this reason, the water sucked up by the one groove layer 27a moves to the two groove layer 27b and the three groove layer 27c one after another toward the lower humidity environment, and the vaporization / diffusion of the generated water is promoted. In this way, excess water generated and oxidized at the oxidant electrode is absorbed, vaporized, and diffused by capillary action, so water retention at the oxidant electrode is prevented. Further, water droplet formation in the oxidant electrode side gas diffusion layer 27 is prevented without sacrificing diffusibility of the oxidant gas, and flooding is prevented in the region including the oxidant electrode side gas diffusion layer from the oxidant electrode. The performance can be further improved, and a highly efficient power generation performance can be obtained stably over a long period of time.

  As described above, according to the solid polymer electrolyte fuel cell according to the present embodiment, in the oxidant electrode side gas diffusion layer, the volume of the groove is increased from the oxidant electrode side to the oxidant electrode side separator. By adopting the configuration, the amount of water generated by the oxidant electrode is increased, and the flooding prevention performance in the region including the gas diffusion layer from the oxidant electrode can be further improved. High-efficiency power generation performance.

  In addition, it is not necessary to provide a groove in all the carbon fibers, and the carbon fiber in which the groove is formed and the carbon fiber without the groove may be mixed. Further, the shape and number of the grooves are not particularly limited, and any number of grooves may be formed as long as the groove volume necessary for water absorption can be secured. Furthermore, the oxidant electrode side gas diffusion layer does not need to be composed of three layers having carbon fibers having different groove shapes, and the number of layers is not limited as long as the volume of the groove increases stepwise.

  Next, Example 3 will be described with reference to FIG.

  FIG. 5A is a perspective view schematically showing an oxidant electrode side gas diffusion layer of a solid polymer electrolyte fuel cell according to Example 3 of the present invention. FIG. 5B is a cross-sectional view schematically showing the Vb portion of FIG. In the solid polymer electrolyte fuel cell in this example, the ratio of carbon fibers in which grooves forming the oxidant electrode side gas diffusion layer were formed was increased from the oxidant electrode side to the oxidant electrode side separator. This is different from the first embodiment.

  As shown in FIG. 5 (a), the oxidant electrode side gas diffusion layer 37 in Example 3 is shown in FIG. 5 (b) from the oxidant electrode side of the membrane electrode assembly toward the oxidant electrode side separator. As schematically shown, the layer 37a having a high proportion of the carbon fibers 40A in which the grooves represented by the solid lines are not formed, the carbon fibers 40A in which the grooves are not formed, and the carbon fibers 40B in which the grooves represented by the broken lines are formed are the same. It is composed of three layers, a layer 37b included at a certain ratio and a layer 37c having a high ratio of carbon fibers 40B in which grooves are formed. In each layer, the total number of carbon fibers 40A in which no grooves are formed and the number of carbon fibers 40B in which grooves are formed are the same.

  Thus, in the oxidant electrode side gas diffusion layer 37 in Example 3, the carbon fiber in which the grooves in the oxidant electrode side gas diffusion layer 37 are formed from the oxidant electrode side toward the oxidant electrode side separator side. The carbon fiber 40A in which the groove is not formed and the carbon fiber 40B in which the groove is formed are mixed at different ratios so that the volume of the carbon fiber groove is increased. After that, it is composed of multiple layers. For this reason, in the oxidant electrode side gas diffusion layer 37 in Example 3, the function of sucking up water from the groove of the carbon fiber stepwise from the oxidant electrode side to the oxidant electrode side separator side as in Example 2. Is getting higher. For this reason, the water sucked up by the layer 37a moves one after another toward the layers 37b and 37c and the lower humidity environment, and the vaporization and diffusion of the generated water is promoted. In this way, excess water generated at the oxidant electrode absorbs, vaporizes, and diffuses due to the capillary action of the carbon fiber, so that water retention at the oxidant electrode is prevented. Further, water droplet formation in the oxidant electrode side gas diffusion layer 37 is prevented without sacrificing diffusibility of the oxidant gas, and flooding is prevented in a region including the oxidant electrode side gas diffusion layer from the oxidant electrode. The performance can be further improved, and a highly efficient power generation performance can be obtained stably over a long period of time. In addition, since the same effect as in Example 2 can be obtained by using at least two types of carbon fibers, that is, carbon fibers in which no grooves are formed and carbon fibers in which grooves are formed, the production of the gas diffusion layer is possible. Easy.

  As described above, according to the solid polymer electrolyte fuel cell according to the present embodiment, in the oxidant electrode side gas diffusion layer, the ratio of the carbon fiber in which the groove is formed is changed from the oxidant electrode side to the oxidant electrode side separator. By adopting an increased configuration, the amount of water generated by the oxidant electrode increases, and the flooding prevention performance in the region including the gas diffusion layer from the oxidant electrode can be further improved. A stable and highly efficient power generation performance can be obtained over a long period of time.

  The number of grooves formed in the carbon fiber is not particularly limited, and any number of grooves may be formed as long as the groove volume necessary for water absorption can be secured. Further, the oxidant electrode side gas diffusion layer does not need to be composed of three layers having different mixing ratios of the carbon fiber in which the groove is formed and the carbon fiber in which the groove is formed. If the groove volume is increased, the number of layers is not limited.

  Next, Example 4 will be described with reference to FIG.

  FIG. 6A is a cross-sectional view showing a unit cell constituting a solid polymer electrolyte fuel cell according to Example 4 of the present invention. FIG. 6B is an explanatory diagram schematically showing the VIb portion of FIG.

  As shown in FIG. 6A, the unit cell 41 constituting the solid polymer electrolyte fuel cell according to the present embodiment has a fuel electrode 43 on one surface of the solid polymer electrolyte membrane 42 and a unit cell 41 on the other surface. The membrane electrode assembly 45 having the oxidant electrode 44, the fuel electrode side gas diffusion layer 46 disposed on the surface of the membrane electrode assembly 45 on the fuel electrode 43 side, and the oxidant electrode 44 side of the membrane electrode assembly 45 An oxidant electrode side gas diffusion layer 47 disposed on the surface, a fuel electrode side separator 48 disposed outside the fuel electrode side gas diffusion layer 46, and an outer side of the oxidant electrode side gas diffusion layer 47. And an oxidant electrode-side separator 49. A plurality of unit cells 41 are stacked to constitute a solid polymer electrolyte fuel cell. A carbon particle layer 46 a is provided between the fuel electrode 43 and the fuel electrode side gas diffusion layer 46, and a carbon particle layer 47 a is provided between the oxidant electrode 44 and the oxidant electrode side gas diffusion layer 47. However, this is different from the first embodiment.

  As shown in FIG. 6B, the carbon particle layer 47a is disposed between the oxidant electrode 44 and the oxidant electrode side gas diffusion layer 47 having the carbon fibers 50, and has a diameter of about 50 [nm]. , And carbon particles 53 having a primary particle diameter of 0.1 to 1.0 [μm]. The carbon particle layer 46 a has the same configuration between the fuel electrode 43 and the fuel electrode side gas diffusion layer 46. These carbon particle layers 46a and 47a are formed by preparing a paste of carbon particles, applying it to the gas diffusion layer, and performing drying and baking treatment.

  Since the carbon particle layer 47 a has pores 52 that are smaller than the pores in the oxidant electrode side gas diffusion layer 47, the capillary tube is similar to the grooves of the carbon fibers 50 in the oxidant electrode side gas diffusion layer 47. Trigger the phenomenon. The surface of the gas diffusion layer has minute irregularities formed by carbon fibers and pores, but a carbon particle layer 47 a is formed between the oxidant electrode side gas diffusion layer 47 and the oxidant electrode 44. As a result, the contact area between the carbon fibers 50 and the carbon particles 53 of the oxidant electrode side gas diffusion layer 47 increases, so that the conductivity is improved. Furthermore, since the cross-sectional shape of the carbon fiber can be easily changed, it is easy to cope with optimizing the gas diffusibility, and the manufacturing method is also easy.

  The carbon particle layer is more preferably subjected to water repellent treatment. In this case, the carbon particle layer is prepared by preparing a paste containing carbon particles and PTFE (polytetrafluoroethylene) 20 to 50 [wt%] as a water repellent, and is applied to the gas diffusion layer and then dried. And by performing a baking treatment.

  When the water repellent treatment is performed on the carbon particle layer, a hole portion subjected to the water repellent treatment can be provided in the carbon particle layer. For this reason, since the gas ventilation part can be increased, flooding prevention performance can be further improved, and stable and highly efficient power generation performance can be obtained over a long period of time. In addition, since the water repellent treatment is not performed directly on the surface of the gas diffusion layer but the carbon particle layer is subjected to the water repellent treatment, the water repellent treatment agent reduces the conductivity and gas diffusibility of the gas diffusion layer. There is nothing.

  As described above, according to the solid polymer electrolyte fuel cell according to the present embodiment, the carbon particle layer is provided between the oxidant electrode and the oxidant electrode side gas diffusion layer. The water-repellent treatment promotes the diffusion of water generated at the oxidizer electrode to the gas diffusion layer on the oxidizer electrode side. It can be improved and the conductivity is improved. For this reason, stable and highly efficient power generation performance can be obtained over a long period of time.

  In FIG. 6, the carbon particle layer 46a is also disposed between the fuel electrode 43 and the fuel electrode side gas diffusion layer 46 in the same manner as the oxidant electrode side, but the carbon particle layer is not necessarily disposed.

  Next, Example 5 will be described with reference to FIG.

  FIG. 7 (a) is an explanatory view schematically showing a yarn bundled with carbon fibers in the oxidant electrode side gas diffusion layer of the solid polymer electrolyte fuel cell according to Example 5 of the present invention. FIG.7 (b) is sectional drawing cut | disconnected along the VIIb-VIIb line | wire of Fig.7 (a).

  The oxidant electrode side gas diffusion layer constituting the solid polymer electrolyte fuel cell according to the present embodiment has a thread 60 shown in FIG. The yarn 60 is formed by bundling a plurality of carbon fibers 61 having a small diameter, and has a gap 62 between the carbon fibers 61 as shown in FIG. 7B. A groove 63 having the same function as the carbon fiber groove shown in the above embodiment is formed on the outer surface of the yarn 60. And the oxidant electrode side gas diffusion layer is comprised similarly to the other Example, and is mutually intertwined. The yarn 60 is formed by injecting PAN from an extrusion die and welding or forming a plurality of PANs to make acrylic fiber.

  Thus, in the carbon fiber in Example 5, the carbon fiber having the groove shown in Examples 1 to 4 is formed by the gap 62 and the groove 63 formed by bundling a plurality of carbon fibers 61 having a small diameter. Similar drainage performance is obtained. For this reason, the manufacture of the carbon fiber having the same function as the carbon fiber having the groove is facilitated, and the manufacture of the oxidant electrode side gas diffusion layer is facilitated.

  As described above, according to the solid polymer electrolyte fuel cell according to the present embodiment, the membrane electrode assembly having the fuel electrode on one surface of the solid polymer electrolyte membrane and the oxidant electrode on the other surface, and the membrane electrode A fuel electrode side gas diffusion layer disposed on the fuel electrode side surface of the assembly and an oxidant electrode side gas diffusion layer disposed on the surface of the membrane electrode assembly on the oxidant electrode side and having a thread bundled with carbon fibers A fuel electrode side separator disposed outside the fuel electrode side gas diffusion layer and an oxidant electrode side separator disposed outside the oxidant electrode side gas diffusion layer. The generated water is absorbed by the capillary action of the yarn, moves to the oxidant electrode side separator side, and is vaporized and diffused in the oxidant gas, so that flooding is performed even if the surface of the gas diffusion layer is not subjected to water repellent treatment. Prevents long-term stable and highly efficient power generation performance It becomes possible.

  In addition, it is not necessary that all the carbon fibers are bundled to form a thread, and the bundled carbon fibers and the unbundled carbon fibers may be mixed. In this case, the mixing ratio is not limited as long as a gap necessary for water absorption can be secured.

(A) It is sectional drawing which shows the unit cell which comprises the solid polymer electrolyte fuel cell which concerns on Example 1 of this invention. (B) It is a perspective view which shows typically an oxidizing agent electrode side gas diffusion layer. (C) It is explanatory drawing which shows typically the Ic part of FIG.1 (b). (D) It is explanatory drawing which shows a carbon fiber typically. It is. (E) It is sectional drawing cut | disconnected along the Ie-Ie line | wire of FIG.1 (d). FIG. 5 is a process diagram illustrating a carbon fiber manufacturing method according to Example 1. It is explanatory drawing which shows a mode that water is transmitted through the groove | channel of a carbon fiber. (A) It is a perspective view which shows typically the oxidant electrode side gas diffusion layer of the solid polymer electrolyte fuel cell which concerns on Example 2 of this invention. (B) It is explanatory drawing which shows a one groove | channel carbon fiber. (C) It is explanatory drawing which shows a double groove carbon fiber. (D) It is explanatory drawing which shows a three-groove carbon fiber. (A) It is a perspective view which shows typically the oxidizing agent electrode side gas diffusion layer of the solid polymer electrolyte fuel cell which concerns on Example 3 of this invention. (B) It is sectional drawing which shows typically the Vb part of Fig.5 (a). (A) It is sectional drawing which shows the structure of the unit cell which comprises the solid polymer electrolyte fuel cell which concerns on Example 4 of this invention. (B) It is explanatory drawing which shows typically the VIb part of Fig.6 (a). (A) It is explanatory drawing which shows typically the thread | yarn which bundled the carbon fiber in the oxidizing agent electrode side gas diffusion layer of the solid polymer electrolyte fuel cell which concerns on Example 5 of this invention. (B) It is sectional drawing cut | disconnected along the VIIb-VIIb line | wire of Fig.7 (a).

Explanation of symbols

1 Unit Cell 2 Solid Polymer Electrolyte Membrane 3 Fuel Electrode 4 Oxidant Electrode 5 Membrane Electrode Assembly 6 Fuel Electrode Side Gas Diffusion Layer
7 Oxidant electrode side gas diffusion layer 8 Fuel electrode side separator 9 Oxidant electrode side separator 10 Carbon fiber 11 Groove

Claims (6)

A membrane electrode assembly having a fuel electrode on one side of the solid polymer electrolyte membrane and an oxidant electrode on the other side;
A fuel electrode side gas diffusion layer disposed on the fuel electrode side surface of the membrane electrode assembly;
An oxidant electrode side gas diffusion layer having carbon fibers disposed on the surface of the membrane electrode assembly on the oxidant electrode side and having grooves formed on the surface;
A fuel electrode side separator disposed outside the fuel electrode side gas diffusion layer;
An oxidant electrode side separator disposed outside the oxidant electrode side gas diffusion layer;
A solid polymer electrolyte fuel cell comprising:   2. The solid polymer electrolyte type according to claim 1, wherein in the oxidant electrode side gas diffusion layer, the volume of the groove is increased from the oxidant electrode side toward the oxidant electrode side separator. Fuel cell.   The ratio of the carbon fiber in which the groove is formed in the oxidant electrode side gas diffusion layer is increased from the film oxidant electrode side to the oxidant electrode side separator. The solid polymer electrolyte fuel cell described.   4. The solid polymer electrolyte type according to claim 1, further comprising a carbon particle layer between the oxidant electrode and the gas diffusion layer on the oxidant electrode side. Fuel cell.   The solid polymer electrolyte fuel cell according to claim 4, wherein the carbon particle layer is subjected to water repellent treatment. A membrane electrode assembly having a fuel electrode on one side of the solid polymer electrolyte membrane and an oxidant electrode on the other side;
A fuel electrode side gas diffusion layer disposed on the fuel electrode side surface of the membrane electrode assembly;
An oxidant electrode side gas diffusion layer disposed on the surface of the membrane electrode assembly on the oxidant electrode side and having a thread bundled with carbon fibers;
A fuel electrode side separator disposed outside the fuel electrode side gas diffusion layer;
An oxidant electrode side separator disposed outside the oxidant electrode side gas diffusion layer;
A solid polymer electrolyte fuel cell comprising:

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