JP5044940B2 - Fuel cell - Google Patents

Description

  The present invention relates to a fuel cell.

  In a fuel cell, for example, a polymer electrolyte fuel cell, a fuel gas containing hydrogen is supplied to the anode and an oxidizing gas containing oxygen is supplied to the cathode, whereby the electrochemical reaction proceeds, and the electrochemical reaction As the process proceeds, water is generated at the cathode. If the water generated in the cathode stays in the vicinity of the cathode in this way, there is a possibility that the supply and discharge of gas to and from the cathode may be hindered. Therefore, in order to continue the power generation in the fuel cell satisfactorily, it is necessary to ensure that gas supply to the cathode is ensured by allowing drainage from the cathode to proceed without hindrance. In addition, when the water generated at the cathode moves to the anode side through the electrolyte membrane, the same problem occurs on the anode side.

  Here, in order to prevent clogging of the gas flow path due to generated water generated at the cathode, a configuration in which a water repellent layer is provided on the contact surface of the gas diffusion layer adjacent to the cathode with the cathode is known. Further, in order to uniformly supply the oxidizing gas to the cathode, a configuration is known in which the average pore diameter in the water repellent layer and the average pore diameter in the cathode are substantially equal (see, for example, Patent Document 1). ).

JP 2001-52717 A

  However, even when a water-repellent layer is provided on the gas diffusion layer, when the amount of generated water increases due to an increase in the amount of power generation, the amount of generated water increases, and the generated water may hinder gas flow. . As described above, when the gas flow is hindered by the generated water, it is difficult to sufficiently improve the battery performance even if the flow of the oxidizing gas is optimized by controlling the average pore diameter in the water repellent layer. Therefore, there has been a demand for a technique that can secure a gas flow even when more product water is generated.

  The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to suppress inhibition of gas flow caused by generated water in the vicinity of an electrode of a fuel cell.

To achieve the above object, fuel cells of the present invention,
An electrolyte layer;
Wherein is formed on the electrolyte layer, a catalyst layer to obtain Bei the catalytic metal,
A gas diffusion layer disposed on the catalyst layer and made of a conductive porous body;
Provided on the interface between the catalyst layer and the gas diffusion layer, and a carbon layer with a mosquito Bon particles,
Before hear Bon particles children had an average particle size of 1 to 50 [mu] m, summarized in that made by calcining a porous polyimide, porous carbon particles having fine channels extending communicated three-dimensionally therein And

According to fuel cell of the present invention configured as described above, in Luke Bon layer comprising said porous carbon particles, while ensuring the drainage by voids formed between the particles of porous carbon particles, tertiary The gas flow can be ensured by a fine path that communicates and expands originally. Accordingly, it is possible to suppress a decrease in battery performance due to the blockage of the gas flow path by water. Further, by setting the average particle diameter of the porous carbon particles in the above-described range, the size of the void formed between the porous carbon particles can be made particularly suitable for ensuring drainage. At the same time, since the continuity of the fine paths in the particles can be ensured well, the battery performance can be improved.

In fuel cells of the present invention, the porous carbon particles may be spherical.

  With such a configuration, it is possible to ensure a good space for drainage between the porous carbon particle particles, and to ensure good contact between the porous carbon particles. Fine paths in the particles can be communicated as a whole.

In fuel cells of the present invention, the porous carbon particles, may be on the particle surface and the fine passage surface comprises a water repellent material.

  With such a configuration, since the blockage of the fine path due to the intrusion of water into the fine path is suppressed, it is easy to secure the gas flow path.

In the first fuel cell of the present invention,
The catalyst layer includes catalyst-supporting carbon particles that support the catalyst metal on the surface, and an electrolyte.
The catalyst-carrying carbon particles are formed by firing porous polyimide, have a fine path extending in a three-dimensional communication inside, and have an average particle size smaller than the porous carbon particles provided in the carbon layer. It is also good.

  With such a configuration, in the catalyst layer, a surface area for supporting a sufficient amount of the catalyst metal can be secured without increasing the thickness of the catalyst layer, and the voids between the particles in the carbon layer can be increased. The drainage property in the carbon layer can be ensured.

In fuel cells of the present invention, the porous carbon particles, may be provided in at least the cathode side.

  With such a configuration, both drainage and gas flow can be ensured on the cathode side where water is generated as the electrochemical reaction proceeds, and battery performance can be improved.

In the fuel cell of the present invention,
The particle size of the porous carbon particles may be smaller Ikoto than pore size of pores in which the conductive porous body is provided.

With such a configuration, it is possible to satisfactorily secure current collection between the catalyst layer and the gas diffusion layer, and to improve water absorption efficiency from the catalyst layer side to the gas diffusion layer side due to capillary action.

  The present invention can be realized in various forms other than those described above. For example, the present invention can be realized in a form such as a fuel cell manufacturing method and a porous carbon particle manufacturing method.

Next, embodiments of the present invention will be described in the following order based on examples.
A. Fuel cell configuration:
B. Carbon layer configuration:
C. Experimental results of the first example:
D. Second embodiment:
E. Experimental results of the second embodiment:
F. Third embodiment:
G. Experimental results of the third example:
H. Variations:

A. Fuel cell configuration:
FIG. 1 is a schematic cross-sectional view showing a schematic configuration of a fuel cell according to an embodiment of the present invention. The fuel cell of the present embodiment can be a solid polymer electrolyte fuel cell, for example, and has a stack structure in which a plurality of single cells 10 are stacked. The unit cell 10 includes an MEA 24 including an electrolyte layer 21 and a cathode 22 and an anode 23 which are catalyst layers formed on the electrolyte layer 21 and including a catalyst metal that undergoes an electrochemical reaction. The single cell 10 sandwiches the MEA 24, gas diffusion layers 33 and 34 having carbon layers 31 and 32 at the interface with the MEA 24, and gas separators 35 and 36 that sandwich the sandwich structure from both sides. I have.

  The electrolyte layer 21 is a proton conductive ion exchange membrane formed of a solid polymer material such as a fluorine resin, and exhibits good proton conductivity in a wet state. On the surface of the electrolyte layer 21, a cathode 22 and an anode 23, which are electrode layers having platinum or an alloy made of platinum and another metal, are provided as a catalyst layer, and an MEA 24 is formed.

  The gas diffusion layers 33 and 34 can be formed of a conductive member having gas permeability, for example, a carbon porous body such as carbon paper, or a metal porous body such as a metal mesh or a foam metal. Carbon layers 31 and 32 are formed on the surfaces of the gas diffusion layers 33 and 34 on the side in contact with the MEA 24. The carbon layers 31 and 32 include porous carbon particles having a water repellent material on the surface. It is desirable that the porous carbon particles have a particle size smaller than the pores of the porous conductive member constituting the gas diffusion layer. Thereby, current collection between the catalyst layer and the gas diffusion layer can be secured satisfactorily, and the water absorption efficiency from the catalyst layer side to the gas diffusion layer side by capillary action can be improved. The detailed configuration of the carbon layer will be described later.

  The gas separators 35 and 36 can be formed of a gas-impermeable conductive member, for example, dense carbon that is compressed by gas and made impermeable to gas, or a press-molded metal plate. On the surfaces of the gas separators 35 and 36, an uneven shape for forming a flow path for the fuel gas or the oxidizing gas supplied to the single cell 10 is formed. That is, between the gas diffusion layer 33 on the cathode 22 side and the gas separator 35, there is formed an in-single cell oxidizing gas flow path 37 through which an oxidizing gas used for an electrochemical reaction at the cathode passes. Further, between the gas diffusion layer 34 on the anode 23 side and the gas separator 36, an in-single cell fuel gas flow path 38 is formed through which a fuel gas used for an electrochemical reaction at the anode passes. The gas separators 35 and 36 in FIG. 1 have an uneven shape including a plurality of parallel grooves. However, the gas separators 35 and 36 may have different shapes, and a gas flow path is provided between the gas separators 35 and 36 and the MEA 24. It suffices if a space for forming can be formed.

  On the outer periphery of the unit cell 10, a sealing member (not shown) for ensuring gas sealing performance in the unit cell oxidizing gas channel 37 and the unit cell fuel gas channel 38 is disposed. In addition, the fuel cell of this embodiment has a stack structure in which a plurality of single cells 10 are stacked. The outer periphery of the stack structure is parallel to the stacking direction of the single cells 10 and is fuel gas or oxidation. A plurality of gas manifolds through which gas flows are provided (not shown). The oxidizing gas flowing through the oxidizing gas supply manifold among the plurality of gas manifolds is distributed to each single cell 10 and passes through each single cell oxidizing gas flow path 37 while being subjected to an electrochemical reaction. Collect in the gas exhaust manifold. Similarly, the fuel gas flowing through the fuel gas supply manifold is distributed to each single cell 10, passes through each single cell fuel gas flow path 38 while being subjected to an electrochemical reaction, and then collects in the fuel gas discharge manifold. To do.

  For example, air can be used as the oxidizing gas supplied to the fuel cell. Further, as the fuel gas supplied to the fuel cell, a hydrogen rich gas obtained by reforming a hydrocarbon-based fuel may be used, or a high purity hydrogen gas may be used.

  Although illustration is omitted, in order to adjust the internal temperature of the stack structure, a refrigerant flow path through which the refrigerant passes may be provided between the single cells or every time a predetermined number of single cells are stacked. good. The refrigerant flow path may be provided between the adjacent single cells and between the gas separator 35 provided in one single cell and the gas separator 36 of the other single cell provided adjacent thereto.

B. Carbon layer configuration:
FIG. 2 is an explanatory view schematically showing the state of the carbon layer 31 provided at the interface between the cathode 22 and the gas diffusion layer 33. As shown in FIG. 2, the carbon layer 31 is composed of porous carbon particles 40. The porous carbon particle 40 is a spherical porous carbon particle having therein a fine path that communicates three-dimensionally and expands, and a water repellent material is provided on the surface of the particle and on the surface of the internal fine path.

  In this embodiment, after the carbon layer 31 is formed on the gas diffusion layer 33, the carbon diffusion layer 33 is overlapped with the MEA 24 so that the carbon layer 31 is disposed at the interface between the cathode 22 and the gas diffusion layer 33. Yes. FIG. 3 is an explanatory view showing a manufacturing process of the gas diffusion layer 33 having the carbon layer 31 which is executed when the fuel cell is manufactured. In order to produce the carbon layer 31, first, porous carbon particles 40 are prepared (step S100). In this embodiment, the porous carbon particles 40 are made of spherical porous polyimide at 1000 to 2800 ° C. in an inert atmosphere (in an inert gas atmosphere made of a rare gas such as helium, argon, neon or nitrogen gas). It is produced by firing under temperature conditions. The particle size of the porous carbon particles 40 obtained by firing can be set to 1 to 50 μm, for example.

  Next, the water-repellent treatment is performed on the porous carbon particles 40 prepared in step S100 (step S110). The water repellent treatment is a treatment for making the particle surfaces of the porous carbon particles 40 and the surface of the internal micro roads water repellent by using, for example, fluorine gas. Specifically, the treatment may be performed in a fluorine gas at 300 to 600 ° C. for several tens of minutes to several hours. Thereafter, a dispersion containing the water-repellent porous carbon particles 40 and a water-repellent substance is prepared (step S120). As the water repellent substance, for example, a fluororesin can be used. Thereafter, the dispersion is applied to the surface of the conductive porous body used as the gas diffusion layer 33 (step S130). Application | coating can be performed using a doctor blade, for example. After the dispersion is applied to the surface of the conductive porous body, drying and firing are performed to obtain a gas diffusion layer 33 having porous carbon particles 40 and a carbon layer 31 having water repellency formed on the surface. (Step S140). In this embodiment, the gas diffusion layer 34 having the carbon layer 32 on the surface is manufactured in the same manner.

  According to the fuel cell of the present embodiment configured as described above, the carbon layer including the porous carbon particles 40 is formed at the interface between the catalyst layer and the gas diffusion layer. In addition to ensuring, it is possible to suppress gas flow inhibition caused by the generated water, and to secure supply and discharge of gas to the catalyst layer. That is, the drainage can be ensured by voids formed between the porous carbon particles 40. In FIG. 2, a state in which water passes through the voids between the porous carbon particles 40 is indicated by a thick solid line. In addition, gas supply / discharge can be ensured by a three-dimensionally communicating fine path formed in the porous carbon particles 40. This is because the collection of the porous carbon particles 40 having the fine paths therein allows the fine paths in the respective porous carbon particles to communicate with each other, thereby forming a gas passage as the entire carbon layer. In FIG. 2, the manner in which gas flows in a fine path that expands by communicating three-dimensionally as a whole is indicated by a thin broken line. Therefore, gas supply / discharge can be ensured by fine paths communicating with each other even when the voids between the particles are blocked with water. In this way, the generated water generated in the catalyst layer (especially the cathode 22) is quickly drained from the catalyst layer to the gas flow path side in the single cell, and the gas smoothly flows from the gas flow path in the single cell to the catalyst layer. Therefore, the battery performance of the fuel cell can be kept high.

  In particular, in the present embodiment, in the porous carbon particles 40, the particle surface and the inside of the fine path are subjected to a water repellent treatment using a water repellent substance. Accordingly, since the generated water cannot enter the fine path, the fine path serving as the gas flow path is not blocked by water. Further, since the entire carbon layer has water repellency, the generated water once discharged to the gas diffusion layer 33 side is pushed back to the carbon layer 31 side, so that the return of the generated water to the cathode 22 side can be suppressed. . Although the contact resistance between adjacent porous carbon particles is increased by the water-repellent treatment of the porous carbon particles 40 and the addition of a water-repellent substance to the carbon layer, it is more than the overvoltage caused by the contact between the particles. In general, since the diffusion overvoltage due to the gas diffusion efficiency is much larger, the battery performance as a whole can be improved by performing the water repellent treatment.

  Here, if the average particle diameter of the porous carbon particles 40 to be used is too small, voids between the particles are reduced, and thus there is a possibility that the problem of blockage by water tends to occur. Further, if the average particle diameter of the porous carbon particles 40 is too large, the number of contact points between the particles is reduced, and the three-dimensional expansion of the fine path formed between the particles is reduced. It becomes difficult to secure. Therefore, the average particle diameter of the porous carbon particles 40 is 1 to 50 μm, preferably 10 to 30 μm.

C. Experimental results of the first example:
FIG. 4 shows an experimental result in which the fuel cell was assembled by changing the particle size of the porous carbon particles 40 constituting the carbon layers 31 and 32 and the cell performance was compared in the fuel cell of this example. Here, in order to form the carbon layers 31 and 32, porous carbon particles having a particle diameter of 10 μm are used in Experimental Example 1, porous carbon particles having a particle diameter of 30 μm are used in Experimental Example 2, and particle diameters are measured in Experimental Example 3. 100 μm porous carbon particles were used. In the comparative example, the carbon layers 31 and 32 are formed using carbon particles that are not porous. Below, the manufacturing process of the carbon layer of each fuel cell and the manufacturing process of the whole fuel cell are demonstrated as a manufacturing process of the fuel cell used for experiment.

  When the carbon layers 31 and 32 of the fuel cells of Experimental Examples 1 to 3 are formed, in step S100 of FIG. 3, the spherical porous polyimide in which fine paths that extend three-dimensionally are formed is inactivated. Firing was performed at 1000 to 1500 ° C. in an atmosphere to prepare porous carbon particles 40 having average particle diameters of 10 μm, 30 μm, and 100 μm, respectively. In addition, the porosity of each prepared porous carbon particle 40 was about 50% as measured with a mercury porosimeter. When forming the carbon layers 31 and 32 of the fuel cell of the comparative example, in step S100, instead of the porous carbon particles 40, carbon particles that do not have a fine path extending in three dimensions (electrochemical industry). Manufactured by Denka Black). The carbon particles used in this comparative example are oxidized by activating the surface to make the surface porous. The primary particle size is 40 nm, and the porosity is about 70% as measured by a mercury porosimeter. In each of Experimental Examples 1 to 3 and Comparative Example, in step S110, the water repellent treatment of the carbon particles prepared in step S100 was performed at a temperature of 350 ° C. and a fluorine gas pressure of 0.1 MPa or less for 1 hour. Thereafter, in step S120, together with the water-repellent treated carbon particles, a dispersion liquid of fluororesin FEP (manufactured by Daikin Industries, Ltd., ND-1), water and isopropyl alcohol is used. Was prepared. At that time, the mass ratio of the carbon particles to the fluororesin was 4 to 6.

  As the conductive porous body on which the dispersion liquid is applied using a doctor blade in step S130, carbon paper (SDL, GDL-31BA) having a thickness of about 170 μm was used. In Step S140, baking was performed at 300 ° C. for 8 hours to obtain a gas diffusion layer in which a carbon layer having a thickness of 30 μm was formed. A part of the carbon layer having a thickness of 30 μm is infiltrated into carbon paper which is a conductive porous body.

  FIG. 5 is a process diagram showing an outline of a fuel cell manufacturing process. When manufacturing a fuel cell, first, carbon particles supporting a catalyst metal for constituting a catalyst layer, an electrolyte, and a solid polymer electrolyte membrane constituting an electrolyte layer 21 are prepared (step S200). Here, carbon particles (Ketjen Black International Co., Ltd., Ketjen Black EC) carrying 45% by mass of platinum were prepared as the catalyst-carrying carbon particles forming the cathode 22. Moreover, as catalyst-supporting carbon particles forming the anode 23, carbon particles supporting 30% by mass of platinum (Valkan XC-72R manufactured by Nippon Cabot Co., Ltd.) were prepared. In addition, as an electrolyte for forming the catalyst layer, an electrolytic solution containing polymer electrolyte (manufactured by DuPont, SE20092) was prepared. Furthermore, as an electrolyte membrane, a fluorine-based solid polymer membrane (manufactured by DuPont, Nafion 112) was prepared.

Thereafter, a catalyst layer is formed on the solid polymer electrolyte membrane to produce the MEA 24 (step S210). For example, the catalyst layer is formed by mixing platinum-supported carbon particles and an electrolyte to form a slurry, and using this slurry, a film is formed on a predetermined substrate in advance, and the produced film is thermally transferred onto the electrolyte film. Can be produced. Or you may produce a catalyst layer by spraying directly on an electrolyte membrane using the said slurry. In the fuel cells of the experimental example and the comparative example, the platinum-supported carbon particles and the electrolyte were slurried with a solvent and applied onto a predetermined substrate, and then thermally transferred onto the electrolyte membrane. At the time of slurrying, 1 g of the platinum-supporting carbon particles and 2.2 g of the electrolytic solution were used to produce the cathode 22. In order to produce the anode 23, 1 g of the platinum-supporting carbon particles and 3.5 g of the electrolytic solution were used. At this time, the platinum carrying amount per unit area in each catalyst layer was set to 0.2 mg / cm ² . In addition, since it is desirable that the distance at which protons move between the catalyst and the electrolyte membrane in the catalyst layer is short, the catalyst layer may have a thickness of, for example, 5 to 50 μm. Then, it was 10 μm.

  Next, the MEA 24 is sandwiched by using the gas diffusion layers 33 and 34 including the carbon layer produced according to the manufacturing process of FIG. 3 (step S220). At this time, the gas diffusion layers 33 and 34 are arranged so that the carbon layers 31 and 32 formed on the gas diffusion layer are in contact with the catalyst layer. Then, carbon gas separators 35 and 36 are arranged so as to be sandwiched from the outside of the gas diffusion layers 33 and 34 (step S230), and the single cell 10 is completed.

The actual fuel cell has a structure in which a plurality of single cells are stacked. However, the experimental results shown in FIG. 4 show that the fuel cell manufactured according to FIGS. Is the result of when. During power generation, a large excess of high purity hydrogen gas was used as the fuel gas, and a large excess of air was used as the oxidizing gas. At this time, the fuel gas and the oxidant gas were each humidified using a bubbler having the same temperature as the operating temperature of the fuel cell so as to obtain a substantially saturated vapor pressure. The electrode area in each fuel cell was 25 cm ² , and the voltage when the condition of 1 A / cm ² was maintained was measured. The power generation was performed at 80 ° C. and 40 ° C. temperature conditions.

  As shown in FIG. 4, in the fuel cells of Experimental Example 1 and Experimental Example 2 including carbon layers formed using porous carbon particles 40 having an average particle diameter of 10 μm and 30 μm, even if the operating temperature is 80 ° C., 40 A high voltage could be maintained even at ℃. In contrast, the fuel cell of Example 3 comprising a carbon layer formed using porous carbon particles 40 having an average particle size of 100 μm, and a comparison comprising a carbon layer formed using carbon particles having no fine path The example fuel cell showed a lower voltage. Thus, in a fuel cell including a carbon layer formed using porous carbon particles 40 having an average particle diameter of 10 to 30 μm, the generated water is discharged even under low temperature conditions such as 40 ° C. where water is likely to condense. By maintaining the efficiency, the gas supply efficiency was ensured, and the battery performance could be kept high.

D. Second embodiment:
FIG. 6 is an explanatory view schematically showing the configuration of the main part of the fuel cell of the second embodiment. Since the fuel cell of the second embodiment has the same configuration as that of the fuel cell of the first embodiment except for the catalyst layer and the carbon layer, common portions are denoted by the same reference numerals and detailed description thereof is omitted. To do.

  The fuel cell of the second embodiment includes a cathode 122 and an anode 123 instead of the cathode 22 and the anode 23 in the fuel cell of the first embodiment, and the carbon layers 131 and 132 instead of the carbon layers 31 and 32. It has. The fuel cell of this embodiment is characterized in that the cathode 122 and the anode 123 which are catalyst layers, not the carbon layer, include spherical porous carbon particles 140.

  The fuel cell of the second embodiment can be manufactured by the same manufacturing process as the manufacturing process of the fuel cell of the first embodiment shown in FIG. At this time, when the catalyst-carrying carbon particles are prepared in step S200, spherical porous carbon particles carrying a catalyst metal may be prepared. FIG. 7 is an explanatory diagram showing a manufacturing process of the catalyst-supporting porous carbon particles prepared in step S200. In order to manufacture catalyst-supporting porous carbon particles, first, porous carbon particles are prepared (step S300). This step can be performed in the same manner as step S100 in FIG. In addition, since the porous carbon particles prepared in step S300 serve as a carrier for supporting the catalyst metal, the particle size is sufficient to ensure a surface area for supporting the catalyst metal without increasing the thickness of the catalyst layer. It is desirable to make it smaller. The average particle diameter of the porous carbon particles prepared in step S300 can be set to 40 to 1000 nm, for example.

  Thereafter, the prepared porous carbon particles are subjected to water repellency treatment (step S310). This water repellent process can be performed in the same manner as in step S110 of FIG. By performing the water repellent treatment, the particle surface of the porous carbon particles and the surface of the internal micro road are made water repellent. Once the water repellent treatment is performed, the catalyst metal is then supported on the surface of the water repellent porous carbon particles (step S320). In this embodiment, the catalyst metal is supported by a wet method. For example, the water-repellent porous carbon particles may be immersed in a platinum-containing solution such as a chloroplatinic acid solution. Thereafter, platinum is reduced by a drying / firing process (step S330), and platinum is deposited on the porous carbon particles to complete the catalyst-supporting porous carbon particles. Since the step of supporting the catalyst metal is after the water repellency treatment in step S310, the platinum-containing solution does not enter the fine path and the catalyst metal is substantially supported on the surface of the fine path. There is nothing.

  When the fuel cell of this embodiment is manufactured according to FIG. 5, the gas diffusion layer including the carbon layer used in step S220 is replaced with the porous carbon particles of the first embodiment and does not have a fine path inside. What is necessary is just to manufacture using a carbon particle according to the manufacturing process shown in FIG.

  According to the fuel cell of the second embodiment configured as described above, the catalyst layer is formed using the porous carbon particles supporting the catalyst metal, so that the drainage in the catalyst layer is performed well, Inhibition of the gas flow caused by the generated water can be suppressed, and supply / discharge of gas in the catalyst layer can be secured. That is, the generated water drainage generated on the catalyst metal can be secured by the voids formed between the porous carbon particles 140. In FIG. 6, a state in which water passes through voids between the porous carbon particles 140 is indicated by a thick solid line. In addition, gas supply / discharge can be ensured by a three-dimensionally communicating fine path formed in the porous carbon particles 140. This is because the porous carbon particles 140 having the fine paths inside gather, the fine paths in each porous carbon particle communicate with each other, and a gas passage is formed as the entire catalyst layer. In FIG. 6, the manner in which the gas flows in the fine path that expands by communicating three-dimensionally as a whole is indicated by a thin broken line. Therefore, gas supply / discharge can be ensured by fine paths communicating with each other even when the voids between the particles are blocked with water. In this way, the generated water is quickly drained from the catalyst layer to the gas flow path in the single cell, and gas is smoothly supplied to and discharged from the catalyst metal in the catalyst layer. Battery performance can be kept high.

  In particular, in the present embodiment, in the porous carbon particles 140, the particle surface and the inside of the fine path are subjected to water repellency treatment using a water-repellent substance, and the catalyst metal is substantially supported only on the particle surface. . Therefore, the generated water does not enter the fine path and the generated water does not occur in the fine path, so that the fine path serving as the gas flow path is not blocked by water.

E. Experimental results of the second embodiment:
FIG. 8 shows the experimental results of assembling the fuel cell of the second example and examining the cell performance. Here, in order to form the catalyst layers 122 and 123, porous carbon particles having an average particle size of 100 nm were used in the experimental example. In the comparative example, the catalyst layer was formed using carbon particles that were not porous. Hereinafter, specific conditions of the manufacturing process of the fuel cell used in the experiment will be described with reference to the manufacturing process of the fuel cell shown in FIG.

When manufacturing a fuel cell, first, catalyst-supporting carbon particles are prepared together with an electrolyte and an electrolyte membrane (step S200). In the experimental example, the catalyst-supporting porous carbon manufactured by the manufacturing process shown in FIG. Particles were prepared. When preparing the catalyst-supporting porous carbon particles constituting the catalyst layer of the fuel cell of the experimental example, the spherical porous polyimide is fired at 1000 to 1500 ° C. in an inert atmosphere in step S300 of FIG. Carbon particles having an average particle diameter of 100 nm and a porosity of about 50% as measured by a mercury porosimeter were prepared. Further, the water repellent treatment in step S310 was performed under conditions of a temperature of 350 ° C. and a fluorine gas pressure of 0.1 MPa or less for 1 hour. In addition, when platinum was supported on the porous carbon particles by Step S320 and Step S330, 30% by mass of platinum was supported. When manufacturing the fuel cell of the comparative example, in step S200 of FIG. 5, platinum is supported on the carbon particles having no fine path in the same manner as in Experimental Examples 1 to 3 of the first example and the comparative example. I prepared something. In Examples and Comparative Examples, the amount of platinum supported per unit area in each catalyst layer was 0.2 mg / cm ^2, and the thickness of each catalyst layer was 10 μm.

  In step S210 of FIG. 5, when the MEA 24 is manufactured, an electrolytic solution containing a polymer electrolyte (SE20092, manufactured by DuPont) is used as an electrolyte constituting the catalyst layer. A molecular film (manufactured by DuPont, Nafion 112) was used. The conditions for producing the MEA 24 are the same as those for the experimental example of the first example and the comparative example.

  As the gas diffusion layer including the carbon layer used in step S220 in FIG. 5, the same gas diffusion layer as that in the comparative example of the first example was used. That is, in step S100 of FIG. 3, a carbon layer is used that is produced using carbon particles (Denka Black, manufactured by Denki Kagaku Kogyo Co., Ltd.) that do not have a fine path that extends three-dimensionally instead of porous carbon particles. A gas diffusion layer was used. Other manufacturing steps were performed under the same conditions as those of the experimental example and the comparative example in the first example.

The power generation conditions for obtaining the experimental results shown in FIG. 8 are the same as those for obtaining the experimental results of FIG. That is, in a single cell state with an electrode area of 25 cm ² , power generation was performed using a large excess amount of high purity hydrogen gas as the fuel gas and a large excess amount of air as the oxidizing gas. At this time, the fuel gas and the oxidizing gas are respectively humidified so as to have a substantially saturated vapor pressure using a bubbler having the same temperature as the operating temperature of the fuel cell, while maintaining the condition of 1 A / cm ² . The voltage was measured. There are two temperature conditions, 80 ° C. and 40 ° C.

  As shown in FIG. 8, in the fuel cell of the experimental example including a catalyst layer formed using porous carbon particles having an average particle diameter of 100 nm, a high voltage is applied regardless of whether the operation temperature is 80 ° C. or 40 ° C. Could be maintained. On the other hand, the fuel cell of the comparative example provided with the catalyst layer formed using the carbon particles having no fine path showed a lower voltage. As described above, in a fuel cell including a catalyst layer formed using porous carbon particles, the drainage efficiency of generated water is maintained even under low temperature conditions where water at 40 ° C. is likely to condense. As a result, the battery efficiency was kept high.

F. Third embodiment:
FIG. 9 is a schematic cross-sectional view showing a schematic configuration of the fuel cell of the third embodiment. The fuel cell of the third embodiment includes carbon layers 31 and 32 including porous carbon particles as in the first embodiment, and a catalyst layer including porous carbon particles supporting a catalyst metal as in the second embodiment. It has a certain cathode 122 and anode 123. For this reason, the same reference numerals are assigned to portions common to the first and second embodiments, and detailed description thereof is omitted.

  The fuel cell of the third embodiment can be manufactured by the same manufacturing process as the manufacturing process of the fuel cell of the first embodiment shown in FIG. At this time, when the catalyst-carrying carbon particles are prepared in step S200, spherical porous carbon particles carrying a catalyst metal may be prepared according to FIG. 7 as in the second embodiment. Further, when the gas diffusion layer including the carbon layer is used in step S220, the gas diffusion layer 33, the carbon layers 31 and 32 including the porous carbon particles formed on the surface according to FIG. 3 as in the first embodiment. 34 may be used.

  According to the fuel cell of the third embodiment configured as described above, the effects of both the first embodiment and the second embodiment can be achieved. Since the carbon layer including the porous carbon particles 40 is formed at the interface between the catalyst layer and the gas diffusion layer, the drainage from the catalyst layer is secured and the generated water is retained as in the first embodiment. Inhibition of the resulting gas flow can be suppressed, and supply / discharge of gas to / from the catalyst layer can be ensured. Further, since the catalyst layer is composed of porous carbon particles supporting the catalyst metal, as in the second embodiment, the drainage in the catalyst layer is ensured and the gas flow caused by the retention of the produced water is prevented. Inhibition can be suppressed, and supply and discharge of gas in the catalyst layer can be ensured. That is, in the carbon layer and the catalyst layer, drainage can be secured by voids formed between the porous carbon particle particles, and the gas flow is a tertiary formed as a whole by collecting the porous carbon particles. It can be ensured by a fine road that communicates and spreads. As described above, in the carbon layer and the catalyst layer, the generated water is quickly drained to the gas flow path side in the single cell and the gas is smoothly supplied and discharged, so that the battery performance of the fuel cell can be maintained high. It becomes possible.

In the case where both the catalyst layer and the carbon layer are provided with porous carbon particles as in the fuel cell of the third embodiment, the average particle diameter of the porous carbon particles constituting the catalyst layer is set as the carbon layer. It is desirable to make it smaller than the average particle diameter of the porous carbon particles. This is because the porous carbon particles constituting the catalyst layer need to have a smaller particle size in order to secure a surface area for supporting a sufficient amount of the catalyst metal without increasing the thickness of the catalyst layer . Also, in the carbon layer, in order to ensure the drainage of the generated water, it is advantageous to increase the particle size of the porous carbon particles and further increase the voids between the particles. Here, in the catalyst layer, heat is generated as the electrochemical reaction proceeds and the temperature becomes higher than that of the carbon layer, so that water is likely to exist in a gaseous state, and the particle size is reduced to reduce the voids between the particles. Even if becomes smaller, deterioration of drainage through the voids does not become a problem.

G. Experimental results of the third example:
FIG. 10 shows the experimental results of assembling the fuel cell of this example and examining the cell performance. In the fuel cell of the experimental example, in order to form the catalyst layers 122 and 123, porous carbon particles having an average particle diameter of 100 nm were used as in the experimental example of the second example. In the comparative example, as in the comparative example of the second example, the catalyst layer was formed using carbon particles that do not have a fine path that communicates three-dimensionally and expands. Further, in the fuel cell of the experimental example, in order to form the carbon layers 31 and 32, the porous carbon particles having an average particle diameter of 10 μm were used as in the experimental example 1 of the first example. As in the comparative example of one example, a carbon layer was formed using carbon particles having no fine path.

  The fuel cells of the experimental example and the comparative example were manufactured according to the manufacturing process of the fuel cell shown in FIG. At that time, in order to manufacture the fuel cell of the experimental example, in step S200, catalyst-supporting carbon particles were prepared in the same manner as in the experimental example of the second example. And in step S220, the gas diffusion layer provided with a carbon layer was produced like the experiment example 1 of 1st Example. In order to manufacture the fuel cell of the comparative example, in step S200, catalyst-supporting porous carbon particles were prepared in the same manner as in the comparative example of the first example. And in step S220, the gas diffusion layer provided with a carbon layer was produced like the comparative example of 1st Example. Other manufacturing steps were performed under the same conditions as those of the experimental example and the comparative example in the first example.

The power generation conditions for obtaining the experimental results shown in FIG. 10 are the same as those for obtaining the experimental results of FIG. That is, in a single cell state with an electrode area of 25 cm ² , power generation was performed using a large excess amount of high purity hydrogen gas as the fuel gas and a large excess amount of air as the oxidizing gas. At this time, the fuel gas and the oxidizing gas are respectively humidified so as to have a substantially saturated vapor pressure using a bubbler having the same temperature as the operating temperature of the fuel cell, while maintaining the condition of 1 A / cm ² . The voltage was measured. There are two temperature conditions, 80 ° C. and 40 ° C.

  As shown in FIG. 10, in the fuel cell of the experimental example including a carbon layer formed using porous carbon particles having an average particle diameter of 10 μm together with a catalyst layer formed using porous carbon particles having an average particle diameter of 100 nm, Whether the operating temperature was 80 ° C. or 40 ° C., a high voltage could be maintained. On the other hand, the fuel cell of the comparative example provided with the catalyst layer and carbon layer formed using the carbon particles having no fine path showed a lower voltage. As described above, in the fuel cell including the catalyst layer and the carbon layer formed using the porous carbon particles, the drainage efficiency of the generated water is maintained even under a low temperature condition of 40 ° C. where water is likely to condense. As a result, gas supply efficiency was secured, and battery performance could be kept high.

H. Variations:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

H1. Modification 1:
In the first to third embodiments, the porous carbon particles used are spherical, but porous carbon particles having different shapes may be used. When porous carbon particles gather to form a carbon layer or a catalyst layer, voids are formed between the particles as passages for the generated water, and the particles are in contact with each other to form inside the particles. It suffices if the fine road as a whole communicates and expands in three dimensions. As another example of the shape of the porous carbon particles, for example, a cylindrical shape can be used. If a catalyst layer or a carbon layer is formed using cylindrical porous carbon particles, a flow path through which water passes is formed between the side walls of the cylinder, and the side walls of the cylinder come into contact with each other, so The road can communicate three-dimensionally. FIG. 11 is an explanatory view schematically showing a state of an aggregate of cylindrical porous carbon particles. In FIG. 11, a state in which water passes through the voids between the cylindrical porous carbon particles is represented by a thick solid line, and a state in which the gas flows in a fine path that extends in a three-dimensional manner is illustrated by a thin broken line. Yes. Further, as another example of the shape of the porous carbon particles constituting the catalyst layer and the carbon layer, for example, instead of a columnar shape, as a so-called capsule shape in which the upper and lower bottom surfaces of the column are curved convex surfaces Also good.

H2. Modification 2:
In the first to third embodiments, the carbon layer is obtained by applying a dispersion containing carbon particles and a water repellent material onto a conductive porous body such as carbon paper, and soaking a part of the carbon layer into the conductive porous body. Although formed, a different configuration may be used. For example, the dispersion liquid is formed on a base film separate from the conductive porous body, and the carbon layer obtained by the film formation is used as a gas diffusion layer. It may be fixed on the top by thermal transfer or the like.

H3. Modification 3:
In the first to third embodiments, the porous carbon particles forming the carbon layer or the catalyst layer are subjected to water repellency treatment using fluorine gas or the like, but may have different configurations. For example, if the porous carbon particles used exhibit sufficient water repellency, the water repellency treatment can be omitted.

H4. Modification 4:
Further, the shape of the gas diffusion layer and the gas separator may be different from those of the fuel cells of the first to third embodiments. For example, the surface of the gas separator is not provided with a concavo-convex shape for forming the gas flow path in the single cell, and a conductive porous member is disposed between the gas separator and the MEA, and this conductive porous It is good also as forming the gas flow path in a single cell by the space | gap formed in the quality member. Even when the shape of the gas flow path in the single cell is any other shape, the porous carbon particles can be formed by forming the catalyst layer and the carbon layer adjacent to the catalyst layer with porous carbon particles. In the layer comprising the above, the gas route and the water route can be separated to maintain the drainage efficiency even when the generated water is increased, and the effect of ensuring the gas circulation can be obtained.

H5. Modification 5:
In the first to third embodiments, on both the cathode side and the anode side, the catalyst layer and / or the carbon layer is configured by using porous carbon particles, but the porous carbon is formed only on one side. It is good also as using particles. In particular, by forming the catalyst layer and / or the carbon layer using porous carbon particles on the cathode side where water is generated as the electrochemical reaction proceeds, the battery maintains the gas flowability while ensuring drainage. The effect of enhancing the performance can be remarkably obtained. When the present invention is applied on the anode side, a higher effect is obtained particularly when a configuration in which the oxidizing gas and the fuel gas are flowed in opposite directions in a single cell (so-called counter flow type fuel cell) is employed. It is done. That is, when the oxidizing gas and the fuel gas are made to counter flow, the downstream region in which the water vapor pressure in the oxidizing gas increases and the upstream region in which the water vapor pressure in the fuel gas is lower overlap, thereby interposing the electrolyte membrane. The difference in water vapor pressure becomes extremely large, and the amount of water transferred from the cathode side to the anode side increases. Therefore, the battery performance is improved by applying the present invention in the vicinity of the anode and maintaining the drainage and ensuring the gas flow.

H6. Modification 6:
Further, when the carbon layers 31 and 32 are formed using porous carbon particles as in the first embodiment, the structure of the catalyst layer may be different from the cathode 22 and the anode 23 of the first embodiment. . For example, a catalyst metal such as platinum can be directly supported on the electrolyte membrane without being supported on the carbon particles.

  Alternatively, when the cathode 122 and the anode 123 are formed using porous carbon particles as in the second embodiment, the configuration of the interface between the catalyst layer and the gas diffusion layer may be different from that of the second embodiment. good. For example, it is possible to apply only a water-repellent substance on the gas diffusion layer without forming a carbon layer including carbon particles on the gas diffusion layer.

It is a cross-sectional schematic diagram showing schematic structure of the fuel cell of 1st Example. It is explanatory drawing which represents the mode of a carbon layer typically. It is explanatory drawing showing the manufacturing process of a gas diffusion layer. It is explanatory drawing showing the experimental result of 1st Example. It is process drawing showing the outline | summary of the manufacturing process of a fuel cell. It is explanatory drawing which represents typically the structure of the principal part of the fuel cell of 2nd Example. It is explanatory drawing showing the manufacturing process of a catalyst carrying | support porous carbon particle. It is explanatory drawing showing the experimental result of 2nd Example. It is a cross-sectional schematic diagram showing schematic structure of the fuel cell of 3rd Example. It is explanatory drawing showing the experimental result of 3rd Example. It is explanatory drawing which represents typically the porous carbon particle of a modification.

Explanation of symbols

21 ... Electrolyte layer 22 ... Cathode 23 ... Anode 24 ... MEA
31, 32 ... carbon layer 33, 34 ... gas diffusion layer 35, 36 ... gas separator 37 ... single cell oxidizing gas flow path 38 ... single cell fuel gas flow path 40 ... porous carbon particles 122 ... cathode 123 ... anode 131 132 ... carbon layer 140 ... porous carbon particles

Claims (6)

A fuel cell,
An electrolyte layer;
Wherein is formed on the electrolyte layer, a catalyst layer to obtain Bei the catalytic metal,
A gas diffusion layer disposed on the catalyst layer and made of a conductive porous body;
Provided on the interface between the catalyst layer and the gas diffusion layer, and a carbon layer with a mosquito Bon particles,
Before hear Bon particles children had an average particle size of 1 to 50 [mu] m, made by firing a porous polyimide, the fuel cell is porous carbon particles having fine channels extending communicated three-dimensionally therein. The fuel cell according to claim 1, wherein
The porous carbon particles are spherical. A fuel cell. The fuel cell according to claim 1 or 2,
The porous carbon particle includes a water-repellent material on a particle surface and a surface of the fine road. A fuel cell according to any one of claims 1 to 3 ,
The catalyst layer includes catalyst-supporting carbon particles that support the catalyst metal on the surface, and an electrolyte.
The catalyst-supported carbon particles are formed by firing porous polyimide, have a fine path that extends in a three-dimensional manner inside, and have a smaller average particle diameter than the porous carbon particles provided in the carbon layer battery. A fuel cell according to any one of claims 1 to 4 ,
The porous carbon particles are provided at least on the cathode side. A fuel cell according to any one of claims 1 to 5,
The porous carbon particles having a particle size of the fuel cell, wherein the smaller Ikoto than pore size of pores in which the conductive porous body is provided.

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