JP3617237B2 - ELECTRODE FOR FUEL CELL, POWER GENERATION LAYER AND METHOD FOR PRODUCING THE SAME - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrode and a power generation layer for a fuel cell, and a method for producing the same.
[0002]
[Prior art]
In a fuel cell, for example, a polymer electrolyte fuel cell, a fuel gas containing hydrogen and an oxidizing gas containing oxygen are supplied to two electrodes (an oxygen electrode and a fuel electrode) facing each other with an electrolyte membrane interposed therebetween. Thus, the reactions shown in the following formulas (1) and (2) are performed, and the chemical energy of the substance is directly converted into electric energy.
[0003]
Anode reaction (fuel electrode): H₂→ 2H⁺+ 2e⁻                    ... (1)
Cathode reaction (oxygen electrode): 2H⁺+ 2e⁻+ (1/2) O₂→ H₂O ... (2)
[0004]
In order to carry out this reaction continuously and smoothly, the progress of the reaction generally involves a catalyst as a solid phase, an electrolyte as a liquid phase, and a reaction gas (fuel gas or oxidizing gas) as a gas phase. Since it is said that the reaction proceeds at the coexisting three-phase interface, fuel gas and oxidizing gas must be sufficiently supplied to the catalyst in the electrode, and at the same time, a transmission path for electrons and protons contributing to the reaction must be secured. There is.
[0005]
Conventionally, as an electrode for a fuel cell that meets these requirements, carbon particles having a substantially single particle size carrying platinum as a catalyst are dispersed in an ion exchange resin solution to form a paste-like ink, and this ink is used to form a sheet. What is obtained by drying and forming a resin (for example, Japanese Patent Publication No. 5-507583), a metal such as zinc, aluminum, chromium, etc. together with carbon particles carrying a catalyst in an ion exchange resin solution or These inorganic salt powders, such as metal salts, are dispersed as a pore-forming agent to form a paste-like ink, which is formed into a sheet by using this ink and dried to form a resin. Further, the pore-forming agent is added by a solution such as an acid. What is obtained by forming a plurality of pores inside by elution and removal (for example, JP-A-6-36771 and JP-A-6-2038) Such as 2 No.) have been proposed. In these electrodes, carbon particles are used as a main material, and these are bonded and formed by an ion exchange resin as an electrolyte, whereby electron and proton transmission paths that contribute to the reactions of the above formulas (1) and (2). In addition, by forming a plurality of pores in the electrode using a pore-forming agent, fuel gas and oxidizing gas are sufficiently supplied onto the platinum catalyst supported on the carbon particles, and the above gas phase and It is trying to form a three-phase interface between the liquid phase and the solid phase.
[0006]
[Problems to be solved by the invention]
However, in these electrodes, the carbon particles are densely packed, so that there is a problem that the supply of gas to the catalyst supported on the carbon particles is not sufficient. Since the reactions of the formulas (1) and (2) are performed at the above-described three-phase interface, a gas supply passage from the pores formed by the pore-forming agent to the inner carbon particles is necessary. In the electrode of the conventional example, the main material is formed of carbon particles having a substantially single particle size, so the clogging of the carbon particles is close to the closest packing, and the fine particles for supplying gas between the carbon particles. Formation of the passage becomes difficult.
[0007]
The electrode and power generation layer for the fuel cell of the present invention sufficiently supply the fuel gas and the oxidizing gas onto the catalyst supported on the carbon particles in order to promote the reaction of the above formulas (1) and (2). One of the purposes is to do.
[0008]
Another object of the present invention is to provide an electrode and power generation layer manufacturing method that can sufficiently supply fuel gas and oxidizing gas onto a catalyst supported on carbon particles. And
[0009]
[Means for solving the problems and their functions and effects]
In order to achieve at least a part of the above-described object, the electrode and power generation layer for a fuel cell and the method for producing the same of the present invention employ the following means.
[0010]
The first fuel cell electrode of the present invention comprises:
An electrode for a fuel cell,
Comprising carbon particles having at least two particle size distribution centers;
Of the carbon particlesOf these carbon particles, the electrode body is formed of carbon particles having a distribution center with a large particle size, and the particle size of the carbon particles is small.A catalyst is supported on carbon particles having a distribution center.
This is the gist.
[0011]
According to the first fuel cell electrode of the present invention,An electrode bone is formed by carbon particles having a distribution center having a large particle size among the carbon particles, and a catalyst is supported on the carbon particles having a distribution center having a small particle size among the carbon particles.By forming the carbon particles with different particle diameters, it is possible to prevent the carbon particles in the electrode from becoming clogged. As a result, a fine gas passage can be formed between the carbon particles, and the gas can be sufficiently supplied onto the catalyst supported on the carbon particles.
[0012]
In the first fuel cell electrode of the present invention, the carbon particles have two distribution centers, and the ratio of the particle diameters at the two distribution centers is at least a ratio greater than 2 to 3. You can also. By doing so, it is possible to more reliably avoid the clogging of the carbon particles in the electrode.
[0013]
The gist of the power generation layer for the first fuel cell of the present invention is that the electrode for the first fuel cell of the present invention is bonded to both surfaces of the sheet-like electrolyte. According to the power generation layer for the first fuel cell of the present invention, the power generation efficiency can be further improved by using the electrode in which the gas is sufficiently supplied onto the catalyst supported on the carbon particles.
[0014]
The first fuel cell electrode production method of the present invention comprises:
A method for producing an electrode for a fuel cell, comprising:
(A) a particle adjustment step of adjusting carbon particles having at least two distribution centers of particle sizes;
(B) Of the carbon particles having the adjusted particle sizeThe carbon particles having a distribution center with a large particle size are used to form the bone of the electrode, and the carbon particles have a small particle size.A catalyst supporting step of supporting the catalyst on carbon particles having a distribution center;
(C) an ink adjustment step of adjusting the ink by dispersing the carbon particles adjusted by the particle adjustment step including the carbon particles supporting the catalyst in a predetermined solvent;
(D) an electrode forming member forming step of forming a sheet-like electrode forming member with the adjusted ink;
(E) a drying step of drying the predetermined solvent contained in the formed electrode forming member;
The gist is to provide
[0015]
According to the first method for producing an electrode for a fuel cell of the present invention,Among the carbon particles with the adjusted particle size, the carbon particles having the distribution center with the large particle size are used to form the bone of the electrode, and the catalyst is supported on the carbon particles having the distribution center with the small particle size among the carbon particles. The carbon particles are not tightly packed and carry the catalyst.An electrode can be manufactured. That is, it is possible to manufacture an electrode in which gas is sufficiently supplied onto the catalyst supported on the carbon particles.
[0016]
The method for producing a power generation layer for a first fuel cell according to the present invention includes:
A method for producing a power generation layer for a fuel cell, comprising:
(A) a particle adjustment step of adjusting carbon particles having at least two distribution centers of particle sizes;
(B) Of the carbon particles having the adjusted particle sizeThe carbon particles having a distribution center with a large particle size are used to form the bone of the electrode, and the carbon particles have a small particle size.A catalyst supporting step of supporting the catalyst on carbon particles having a distribution center;
(C) an ink adjustment step of adjusting the ink by dispersing the carbon particles adjusted by the particle adjustment step including the carbon particles supporting the catalyst in a predetermined solvent;
(D) an electrode forming member forming step of forming a sheet-like electrode forming member on the sheet-like electrolyte with the adjusted ink;
(E) a drying step of drying the predetermined solvent contained in the electrode forming member formed on the electrolyte;
It is a summary to provide.
[0017]
According to the first method for producing a power generation layer for a fuel cell of the present invention,An electrode body is formed by carbon particles having a distribution center having a large particle size among the carbon particles, and a catalyst is supported on the carbon particles having a distribution center having a small particle size among the carbon particles. Not tightly packed,A power generation layer including an electrode to which gas is sufficiently supplied on a catalyst supported on carbon particles can be manufactured. That is, a power generation layer with good power generation efficiency can be manufactured.
[0018]
The electrode for the second fuel cell of the present invention is:
An electrode for a fuel cell,
Carbon particles of acetylene black in which secondary aggregates generated during carbon generation greatly contribute to bone formation;Catalyst is supported on the surfaceUsing both furnace black carbon particles with a large specific surface area.The gist is to provide a carbon particle structure having a predetermined size obtained by three-dimensionally bonding carbon particles.
[0019]
Electrode for the second fuel cell of the present inventionUses carbon particles of acetylene black, in which secondary aggregates generated during carbon generation greatly contribute to bone formation, and furnace black carbon particles having a large specific surface area carrying a catalyst on the surface,By forming the carbon particle structure having a predetermined size that is three-dimensionally bonded, it is possible to prevent the carbon particles in the electrode from becoming densely packed. As a result, a fine gas passage can be formed between the carbon particles, and the gas can be sufficiently supplied onto the catalyst supported on the carbon particles.
[0020]
In the second fuel cell electrode of the present invention, the predetermined size may be 0.5 μm to 10 μm. By so doing, a fine gas passage between the carbon particles can be more reliably formed.
[0021]
The gist of the power generation layer for the second fuel cell of the present invention is that the electrode for the second fuel cell of the present invention is bonded to both surfaces of the sheet-like electrolyte. According to the power generation layer for the second fuel cell of the present invention, the power generation efficiency can be further improved by using the electrode in which the gas is sufficiently supplied onto the catalyst supported on the carbon particles.
[0022]
The method for producing an electrode for a second fuel cell of the present invention comprises:
A method for producing an electrode for a fuel cell, comprising:
(A)Furnace black of large specific surface areaA structure forming step in which carbon particles are three-dimensionally bonded to form a carbon particle structure;
(B) a catalyst supporting step of supporting a catalyst on the formed carbon particle structure;
(C) a carbon particle structure carrying the catalyst;Acetylene black carbon particles that have large secondary aggregates during carbon formation and contribute to bone formationAn ink adjustment step of adjusting the ink by dispersing in a predetermined solvent;
(D) an electrode forming member forming step of forming a sheet-like electrode forming member with the adjusted ink;
(E) a drying step of drying the predetermined solvent contained in the formed electrode forming member;
It is a summary to provide.
[0023]
According to the second method for producing an electrode for a fuel cell of the present invention, an electrode in which carbon particles are not tightly packed can be produced. That is, it is possible to manufacture an electrode in which gas is sufficiently supplied onto the catalyst supported on the carbon particles.
[0024]
In the second method for producing an electrode for a fuel cell of the present invention,
Step (a)
(A1) a structure adjusting solution adjusting step of adjusting the structure adjusting solution by dispersing carbon particles in a predetermined solvent;
(A2) a structure forming member forming step of drying a solvent in the adjusted structure adjusting solution to form a solid structure forming member;
(A3) a pulverizing step of pulverizing the formed structure-forming member to form a carbon particle structure;
It can also consist of.
[0025]
By doing so, it is possible to easily form a carbon particle structure having a predetermined size that is three-dimensionally bonded.
[0026]
The method for producing the power generation layer for the second fuel cell of the present invention is as follows.
A method for producing a power generation layer for a fuel cell, comprising:
(A)Furnace black of large specific surface areaA structure forming step in which carbon particles are three-dimensionally bonded to form a carbon particle structure;
(B) a catalyst supporting step of supporting a catalyst on the formed carbon particle structure;
(C) a carbon particle structure carrying the catalyst;Acetylene black carbon particles that have large secondary aggregates during carbon formation and contribute to bone formationAn ink adjustment step of adjusting the ink by dispersing in a predetermined solvent;
(D) an electrode forming member forming step of forming a sheet-like electrode forming member on the sheet-like electrolyte with the adjusted ink;
(E) a drying step of drying the predetermined solvent contained in the electrode forming member formed on the electrolyte;
It is a summary to provide.
[0027]
According to the second method for producing a power generation layer for a fuel cell of the present invention, it is possible to produce a power generation layer including an electrode to which a gas is sufficiently supplied on a catalyst supported on carbon particles. That is, a power generation layer with good power generation efficiency can be manufactured.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described based on examples. FIG. 1 is a process diagram illustrating the production of a power generation layer 15 which is a joined body of an electrolyte membrane 12 and a catalyst electrode 14 according to a preferred embodiment of the present invention, and FIG. 2 is produced by the process of FIG. It is a schematic diagram which illustrates the outline of the structure of the electric power generation layer 15 to be performed. First, a state of manufacturing the power generation layer 15 will be described based on the process diagram of FIG.
[0029]
In the production of the power generation layer 15 of the example, first, acetylene black having an average particle size of 60 nm and a substantially uniform particle size is prepared as carbon particles C1 for forming the bones of the catalyst electrode 14, and as the carbon particles C2 for supporting the catalyst. Furnace black having an average particle size of 20 nm and a substantially uniform particle size is prepared (step S100). Here, the reason why acetylene black is used as the carbon particles C1 for bone formation is that the structure of acetylene black, that is, the secondary aggregates produced during carbon generation is large, and furnace black is used as the carbon particles C2 for supporting the catalyst. The reason for using it is to increase the surface area. In general, the larger the structure, the more gaps between the carbon particles are generated. Therefore, the formed catalyst electrode 14 has good gas diffusibility, but the number of carbon particles forming the structure is limited. For this reason, the size of the structure depends on the particle size of the carbon particles. In the embodiment, the carbon particles C1 having a large particle diameter are used in order to obtain a large structure in consideration of the above. However, when the particle size is increased, the specific surface area is decreased and the performance as a carrier is lowered. For this reason, in the example, in order to maintain high performance as a carrier, carbon having a small surface area and a large surface area is used as the carbon particles C2 for supporting the catalyst. In the examples, as the carbon particles C2 for supporting the catalyst, a surface activation treatment for eroding the surface of the furnace black with water vapor is performed, and the specific surface area is 800 m.²/ G.
[0030]
Next, platinum particles as the catalyst P or fine particles of an alloy of platinum and another metal (in the embodiment, an average particle size of 3 nm) are supported on the surface of the catalyst supporting carbon particles C2 so as to be supported at a supporting density of 60 wt%. (Step S102), carbon particles C1 having an average particle diameter of 60 nm, zinc particles having an average particle diameter of 200 nm as a pore-forming agent Z, and a perfluorocarbon sulfonic acid solution having a solid content of 5 wt% (for example, Nafion manufactured by Aldrich Chemical Co., Ltd.) Solution), cyclohexanol is mixed at a ratio of 7: 3: 10: 60: 40, and irradiated with ultrasonic waves to form carbon particles C1 for bone formation, carbon particles C2 for catalyst support, and pore former Z. The paste-like ink is adjusted by dispersing (step S104). In addition, the dispersion | distribution by irradiation of an ultrasonic wave was performed by irradiating an ultrasonic wave with a frequency of 30 kHz to 50 kHz using the commercially available ultrasonic cleaning machine.
[0031]
Next, the paste-like ink is printed on a Teflon sheet by using a doctor blade type printing apparatus with a thickness of 30 μm to 500 μm, preferably 80 μm to 300 μm, thereby forming a sheet-like electrode forming member 17. (Step S106) The formed electrode forming member 17 is dried at room temperature for 1 hour in the atmosphere and vacuum dried for 3 hours at a temperature of 40 ° C. to 120 ° C., preferably 70 ° C. to 90 ° C. The solvent in the electrode forming member 17 is dried so as to be 1 μm to 100 μm, preferably 3 μm to 10 μm (step S108). Then, an electrolyte membrane 12 having a thickness of 10 μm to 200 μm, preferably 30 μm to 100 μm, which has been previously boiled and washed with dilute sulfuric acid, hydrogen peroxide water and ion exchange water in advance (for example, sold under the trade name “Nafion” manufactured by DuPont). 1) at a temperature of 100.degree. C. to 160.degree. C., preferably 110.degree. C. to 130.degree. C. in a sandwiched state by sandwiching the printed surface with the dried electrode forming member 17 and a sandwich structure. The electrolyte membrane 12 and the electrode forming member 17 are joined by a hot press method for joining by applying a pressure of 20 MPa, preferably 5 MPa to 15 MPa (step S110).
[0032]
The Teflon sheet is peeled off from the joined body of the electrolyte membrane 12 and the electrode forming member 17 thus obtained, and the pore forming agent Z is immersed in a soluble acid to elute the pore forming agent Z from the electrode forming member 17 (step S112). And cleaning and drying to complete the power generation layer 15 as a joined body of the two catalyst electrodes 14 and the electrolyte membrane 12 as shown in FIG. In this example, 1N dilute sulfuric acid is used as the acid capable of dissolving the pore-forming agent Z, and the electrode is formed by repeating boiling washing with dilute sulfuric acid and boiling washing with ion-exchanged water about 2 to 5 times. The pore former Z was completely eluted from the member 17.
[0033]
Next, the fuel cell 10 using the power generation layer 15 thus manufactured will be described. FIG. 3 is a schematic view illustrating the configuration of the fuel cell 10 including the power generation layer 15 of the embodiment. As shown in the figure, the fuel cell 10 includes a power generation layer 15 that is a joined body of the electrolyte membrane 12 manufactured by the above-described manufacturing method and two catalyst electrodes 14, and two gas diffusion electrodes that sandwich the power generation layer 15. 16 and a collecting electrode 20 that sandwiches the gas diffusion electrode 16 together with the power generation layer 15.
[0034]
The two gas diffusion electrodes 16 are formed of carbon cloth woven with yarns in which carbon fibers whose surfaces are coated with polytetrafluoroethylene and carbon fibers which are not treated at all are in a ratio of 1: 1. The gas diffusion electrode 16 has good gas permeability because the entire surface of the gas diffusion electrode 16 is not covered with water because the polytetrafluoroethylene coated on the carbon fiber exhibits water repellency. .
[0035]
The collector electrode 20 is formed of dense carbon that is compressed and densified by compressing carbon, and a plurality of ribs 22 arranged in parallel are arranged on the surface of the collector electrode 20 in contact with the gas diffusion electrode 16. Is formed. The rib 22 forms a flow path 24 of an oxidizing gas (for example, air) containing oxygen or a fuel gas (for example, methanol reformed gas) containing hydrogen with the gas diffusion electrode 16.
[0036]
Fuel gas containing hydrogen and oxygen are provided in the flow path 24 formed by the collector electrode 20 and the gas diffusion electrode 16 facing each other with the power generation layer 15 of the fuel cell 10 and the two gas diffusion electrodes 16 sandwiched therebetween. When the oxidizing gas containing is supplied, the fuel gas and the oxidizing gas are supplied to the two catalyst electrodes 14 facing each other with the electrolyte membrane 12 interposed therebetween, and the electrochemical shown in the above reaction formulas (1) and (2) A reaction takes place and chemical energy is converted directly into electrical energy.
[0037]
Next, the performance of the fuel cell 10 thus configured will be described in comparison with a conventional fuel cell. FIG. 4 is a graph illustrating the relationship between current density and voltage in the fuel cell 10 of the example and the fuel cell of the conventional example, and FIG. 5 is a schematic diagram illustrating the structure of the catalyst electrode of the fuel cell of the conventional example. It is. In the graph of FIG. 4, the curve A shows the relationship between the current density and the voltage in the fuel cell 10 including the power generation layer 15 of the example, and the curve C shows an average particle size of 40 nm and a specific surface area of 260 m.²A fuel cell comprising a power generation layer 15C (see the schematic diagram of FIG. 5) manufactured by the same manufacturing method as that of the above-described embodiment using platinum / g of carbon particles CC supported at a loading density of 50 wt%. Hereinafter, a relationship between current density and voltage in a conventional fuel cell) will be shown. The curve B will be described later.
[0038]
Since the catalyst electrode 14C of the power generation layer 15C included in the fuel cell of the conventional example is formed by carbon particles CC having a single particle size, the carbon particles CC are in a relatively dense state, and as a gap between the carbon particles. There are not so many fine gas supply paths SC formed, and even if formed, there are many that do not communicate with the pores formed by the pore-forming agent ZC, such as a bag path. In contrast, the catalyst electrode 14 of the example is formed by carbon particles C1 and C2 having different particle diameters, so that a relatively large number of gaps are formed between the carbon particles, and the catalyst electrode 14 is formed by the pore forming agent Z. Many fine gas supply paths S communicating with the formed pores are formed. As a result, as shown in FIG. 4, the fuel cell 10 including the catalyst electrode 14 of the embodiment has a significant improvement in performance as compared with the conventional fuel cell in a high current density region where the influence of gas supply becomes large. Is recognized.
[0039]
According to the power generation layer 15 of the embodiment described above, the influence of the gas supply property is increased by including the catalyst electrode 14 having many gas supply paths communicating with the pores formed by the pore-forming agent Z. The performance can be remarkably improved in the high current density region as compared with the conventional power generation layer. As a result, a fuel cell with better performance can be configured by using such a power generation layer 15.
[0040]
According to the method of manufacturing the power generation layer 15 of such an embodiment, the electrode forming member 17 is formed using carbon particles having different particle diameters, so that the pores formed by the pore forming agent Z are communicated between the carbon particles. The power generation layer 15 including the catalyst electrode 14 having many gas supply paths can be manufactured. As a result, a fuel cell with better performance can be manufactured by using the power generation layer 15 thus manufactured.
[0041]
In the power generation layer 15 and its manufacturing method of the example, 60 nm acetylene black was used as the carbon particles C1 for bone formation, and 20 nm furnace black was used as the carbon particles C2 for supporting the catalyst. Since the diameters only have to be different, any ratio of particle diameters may be used, and other black may be used. For example, the particle size ratio may be 3: 2 or more.
[0042]
Further, in the power generation layer 15 and the manufacturing method thereof of the example, the catalyst is supported on the carbon particles having a small particle size, but the catalyst is supported on the carbon particles having a large particle size and the catalyst is supported on the carbon particles having a small particle size. The catalyst may not be allowed to be used, or the catalyst may be supported on all the carbon particles.
[0043]
In the power generation layer 15 and the manufacturing method thereof in the example, the carbon particles C1 having an average particle diameter of 60 nm and the substantially uniform carbon particles C2 and the carbon particles C2 having an average particle diameter of 20 nm and the substantially uniform carbon particles C2 are used. There is no need, and carbon particles distributed with different average particle diameters can also be used.
[0044]
In the power generation layer 15 and the manufacturing method thereof in the example, two types of carbon particles having different average particle sizes are used, but three or more types of carbon particles having different average particle sizes may be used.
[0045]
Further, in the method for producing the power generation layer 15 of the example, the sheet-like electrode forming member 17 was formed by printing the ink adjusted in a paste form on a Teflon sheet using a doctor blade type printing device. The film 12 may be formed by printing directly by screen printing or the like, or formed by spraying on a Teflon sheet or the electrolyte film 12 by spraying.
[0046]
The power generation layer 15 and the method of manufacturing the power generation layer 15 of the embodiment have been described above, but the step of joining the electrolyte membrane 12 and the electrode forming member 17 (step S110 in FIG. 1) is excluded from the manufacturing process of the power generation layer 15. By using the carbon particles C1 having an average particle diameter of 60 nm and substantially uniform carbon particles C2 and the carbon particles C2 having an average particle diameter of 20 nm and substantially uniform, the gas communicated with the pores formed by the pore-forming agent Z between the carbon particles. The catalyst electrode 14 having many supply paths can be manufactured. The catalyst electrode 14 manufactured in this way has many gas supply paths that communicate with the pores formed by the pore-forming agent Z, and thus becomes an electrode with high gas supply capability. Therefore, by using this catalyst electrode 14, a power generation layer with higher performance can be formed, and a fuel cell with higher performance can be configured. Of course, according to the method of manufacturing the catalyst electrode 14, it is possible to manufacture a catalyst electrode having many gas supply paths communicating with the pores. In addition, about the mode of manufacture of this catalyst electrode 14, since the process of FIG.1 S110 is only omitted, it cannot be overemphasized that explanation is required.
[0047]
Next, a power generation layer 15B as a second embodiment of the present invention and a manufacturing method thereof will be described. FIG. 6 is a process diagram illustrating the production of the power generation layer 15B of the second embodiment, and FIG. 7 is a schematic view illustrating the outline of the structure of the power generation layer 15B manufactured by the process of FIG.
[0048]
The power generation layer 15B of the second embodiment is manufactured by first forming a carbon particle structure CS having a three-dimensional structure having a predetermined size for forming the catalyst electrode 14B (step S200). The formation of the carbon particle structure CS is performed based on the process diagram illustrated in FIG. That is, first, a substantially uniform furnace black having an average particle diameter of 20 nm used as the catalyst-supporting carbon particles C2 in the first embodiment is prepared as the carbon particles CB forming the carbon particle structure CS (step S220). Next, the prepared carbon particles CB, water-based polytetrafluoroethylene having a solid content of 60 wt%, a surfactant (polyethylene glycol-P-isooctylphenyl ether), and ion-exchanged water are mixed with 10: 3: 2. Is mixed at an important ratio of 500, and is dispersed and stirred for 15 minutes with an ultrasonic homogenizer with an output of 600 W, and further with a mechanical homogenizer with 10,000 rpm (step S222). The dispersion thus dispersed is filtered with a pressure filtration device (step S224), and the solid content separated by filtration is vacuum-dried at 120 ° C. for 3 hours to form a pellet-like solid (step S226). Next, the pellet-shaped solid is pulverized by a pulverizer (for example, a coffee mill) (step S228) and baked at a temperature of 320 ° C. for 5 hours in a nitrogen gas atmosphere (step S230). By such firing, the surfactant is removed by thermal decomposition, and the carbon particles CB are bound three-dimensionally with polytetrafluoroethylene as the binder D. Then, the binder is pulverized again by a pulverizer so that the size of the binder becomes about 1 μm to 5 μm (step S232), and a three-dimensional carbon particle structure CS having a size of 1 μm to 5 μm is obtained.
[0049]
On the surface of the carbon particle structure CS having a three-dimensional structure thus obtained, fine particles of platinum or an alloy of platinum and another metal (in the example, an average particle diameter of 2 nm) as the catalyst PB are supported at a supporting density of 50 wt%. (Step S202), a carbon particle structure CS supporting this catalyst, zinc particles having an average particle diameter of 200 nm as a pore-forming agent Z, and a perfluorocarbon sulfonic acid solution (for example, Aldrich) having a solid content of 5 wt%. (Chemical Nafion Solution) and cyclohexanol are mixed at a ratio of 1: 1: 6: 4 and irradiated with ultrasonic waves to form bone-forming carbon particles C1 and catalyst-supporting carbon particles C2 and The paste Z is dispersed by dispersing the pore Z (step S204). Also in the second example, dispersion by irradiation with ultrasonic waves was performed by irradiating ultrasonic waves with a frequency of 30 kHz to 50 kHz using a commercially available ultrasonic cleaner.
[0050]
Hereinafter, Steps S206 to S212 of the same steps as Steps S106 to S112 of FIG. 1 which are steps of manufacturing the power generation layer 15 of the first embodiment are performed to complete the power generation layer 15B of the second embodiment. Since steps S206 to S212 have been described in detail in the first embodiment, they are omitted here.
[0051]
Next, the fuel cell 10B is configured in the same manner as the fuel cell 10B including the power generation layer 15 of the first embodiment by the power generation layer 15 of the second embodiment manufactured in this way, and fuel gas and oxidizing gas are supplied. Then, the fuel gas and the oxidizing gas are supplied to the two catalyst electrodes 14B facing each other with the electrolyte membrane 12B interposed therebetween, and the electrochemical reaction shown in the above reaction formulas (1) and (2) is performed, and the chemical energy is directly applied. Converted into electrical energy.
[0052]
Next, the performance of the thus configured fuel cell 10B will be described in comparison with a conventional fuel cell. The relationship between the current density and the voltage in the fuel cell 10B including the power generation layer 15B of the second embodiment is shown by a curve B in FIG.
[0053]
As described above, the catalyst electrode 14C of the power generation layer 15C included in the fuel cell of the conventional example is formed by the carbon particles CC having a single particle diameter. A very small gas supply path SC is not formed as a gap between particles. In contrast, the catalyst electrode 14B of the second embodiment is formed by the carbon particle structure CS having a three-dimensional structure, so that a relatively large number of gaps are formed between the carbon particles. Many fine gas supply paths SB communicating with the pores formed by the above are formed. As a result, as shown in FIG. 4, the fuel cell 10B including the catalyst electrode 14B of the second embodiment has a remarkable performance as compared with the conventional fuel cell in a high current density region where the influence of gas supply is large. Improvement is recognized.
[0054]
According to the power generation layer 15B of the second embodiment described above, since the electrode forming member is formed by the carbon particle structure CS having a three-dimensional structure, the gas supply path that communicates with the pores formed by the pore forming agent ZB. The catalyst electrode 14B having a large amount of gas can be provided, and the performance can be remarkably improved as compared with the conventional power generation layer in a high current density region where the influence of gas supply is large. As a result, a fuel cell with better performance can be configured by using such a power generation layer 15B.
[0055]
According to the method for producing the power generation layer 15B of the second embodiment, the electrode forming member is formed using the carbon particle structure CS having a three-dimensional structure, so that the fine particles formed by the pore forming agent ZB are formed between the carbon particles. The power generation layer 15B including the catalyst electrode 14B having many gas supply paths communicating with the holes can be manufactured. As a result, a fuel cell with better performance can be manufactured by using the power generation layer 15B thus manufactured.
In addition, in the power generation layer 15B of the second example and the manufacturing method thereof, the carbon particle structure CS is formed by binding the carbon particles CB three-dimensionally with polytetrafluoroethylene as the binder D. Any other binder may be used as long as the particles can be bound three-dimensionally.
[0056]
Further, in the power generation layer 15B of the second embodiment and the manufacturing method thereof, furnace carbon black having an average particle diameter of 20 nm is used to form a three-dimensional carbon particle structure.It was.
[0057]
In the method for producing the power generation layer 15B of the second embodiment, after firing to obtain the carbon particle structure CS, it was pulverized again by a pulverizer, but the size of the binder obtained by calcination was about 1 μm to 5 μm. If so, there may be no re-grinding step.
[0058]
Even in the method of manufacturing the power generation layer 15B of the second embodiment, the sheet-like electrode forming member is formed by printing the paste-adjusted ink on the Teflon sheet using a doctor blade type printing device. Alternatively, it may be formed by printing directly on the electrolyte membrane 12B by screen printing or the like, or may be formed by various methods such as spraying on the Teflon sheet or the electrolyte membrane 12B by spraying.
[0059]
As described above, the power generation layer 15B of the second embodiment and the method of manufacturing the power generation layer 15B have been described. Of the manufacturing processes of the power generation layer 15B, the step of joining the electrolyte membrane 12B and the electrode forming member (step S210 in FIG. 6). By removing the carbon particle structure CS having a three-dimensional structure, it is possible to manufacture the catalyst electrode 14B having a large number of gas supply paths communicating with the pores formed by the pore-forming agent ZB between the carbon particles. . The catalyst electrode 14B manufactured in this way has many gas supply paths that communicate with the pores formed by the pore-forming agent ZB, and thus becomes an electrode with high gas supply capability. Therefore, by using this catalyst electrode 14B, a power generation layer with higher performance can be formed, and a fuel cell with higher performance can be configured. Of course, according to the method of manufacturing the catalyst electrode 14B, it is possible to manufacture a catalyst electrode having many gas supply paths communicating with the pores. In addition, since it is only a process of step S210 of FIG. 6 about the mode of manufacture of this catalyst electrode 14B, it cannot be overemphasized that description beyond this is required.
[0060]
As mentioned above, although embodiment of this invention was described, this invention is not limited to such embodiment at all, Of course, in the range which does not deviate from the summary of this invention, it can implement with a various form. It is.
[0061]
For example, a catalyst electrode using a structure in which the first embodiment and the second embodiment are applied simultaneously, that is, a carbon particle structure in which carbon particles having different average particle diameters are three-dimensionally bound by a binder. Or a power generation layer, or a catalyst electrode or a power generation layer including such a carbon particle structure.
[Brief description of the drawings]
FIG. 1 is a process diagram illustrating the production of a power generation layer 15 which is a joined body of an electrolyte membrane 12 and a catalyst electrode 14 according to a preferred embodiment of the present invention.
2 is a schematic view illustrating the outline of the structure of a power generation layer 15 manufactured by the process of FIG. 1;
FIG. 3 is a schematic view illustrating the configuration of a fuel cell 10 including a power generation layer 15 according to an embodiment.
FIG. 4 is a graph illustrating the relationship between current density and voltage in a fuel cell 10 including a power generation layer 15 of an example and a fuel cell of a conventional example.
FIG. 5 is an enlarged schematic view showing an outline of the structure of a power generation layer 15C of a conventional fuel cell.
6 is a process diagram illustrating the production of a power generation layer 15B according to a second embodiment of the invention. FIG.
7 is a schematic view illustrating the outline of the structure of a power generation layer 15B manufactured by the process of FIG. 1;
FIG. 8 is a process diagram illustrating the formation of a carbon particle structure CS.
[Explanation of symbols]
10. Fuel cell
12 ... electrolyte membrane
14 ... Catalytic electrode
15 ... Power generation layer
16 ... Gas diffusion electrode
17 ... Electrode forming member
20 ... collector electrode
22 ... Ribs
24 ... Flow path
C1 ... carbon particles
C2 ... carbon particles
CS: Carbon particle structure
D ... Binder
P ... Catalyst
S ... Supply path
Z ... pore former

Claims (11)

An electrode for a fuel cell,
Comprising carbon particles having at least two particle size distribution centers;
An electrode in which a bone of an electrode is formed by carbon particles having a distribution center having a large particle size among the carbon particles, and a catalyst is supported on the carbon particles having a distribution center having a small particle size among the carbon particles. An electrode for a fuel cell according to claim 1,
The carbon particles have two distribution centers,
An electrode in which the ratio of particle sizes at the two distribution centers is at least a ratio greater than 2 to 3. A power generation layer for a fuel cell, wherein the electrode according to claim 1 or 2 is bonded to both surfaces of a sheet-like electrolyte. A method for producing an electrode for a fuel cell, comprising:
(A) a particle adjustment step of adjusting carbon particles having at least two distribution centers of particle sizes;
(B) A carbon particle having a distribution center with a small particle size among the carbon particles, wherein the carbon particles having an adjusted particle size are used to form a bone body of the electrode with carbon particles having a distribution center with a large particle size. A catalyst supporting step of supporting the catalyst on
(C) an ink adjustment step of adjusting the ink by dispersing the carbon particles adjusted in the particle adjustment step including the carbon particles supporting the catalyst in a predetermined solvent;
(D) an electrode forming member forming step of forming a sheet-like electrode forming member with the adjusted ink;
(E) A method for manufacturing an electrode comprising: a drying step of drying the predetermined solvent contained in the formed electrode forming member. A method for producing a power generation layer for a fuel cell, comprising:
(A) a particle adjustment step of adjusting carbon particles having at least two distribution centers of particle sizes;
(B) A carbon particle having a distribution center with a small particle size among the carbon particles, wherein the carbon particles having an adjusted particle size are used to form an electrode body with carbon particles having a distribution center with a large particle size. A catalyst supporting step of supporting the catalyst on
(C) an ink adjustment step of adjusting the ink by dispersing the carbon particles adjusted by the particle adjustment step including the carbon particles supporting the catalyst in a predetermined solvent;
(D) an electrode forming member forming step of forming a sheet-like electrode forming member on the sheet-like electrolyte with the adjusted ink;
(E) A method for producing a power generation layer comprising: a drying step of drying the predetermined solvent contained in the electrode forming member formed on the electrolyte. An electrode for a fuel cell,
Using carbon particles of acetylene black, which has a large secondary aggregate generated during carbon formation and contributes to bone formation, and furnace black carbon particles with a large specific surface area carrying a catalyst on the surface , both carbon particles are three-dimensionally structured. An electrode provided with a carbon particle structure of a predetermined size that is adhered to the electrode. 7. The electrode for a fuel cell according to claim 6, wherein the predetermined size is 0.5 μm to 10 μm. A power generation layer for a fuel cell, wherein the electrode according to claim 6 or 7 is bonded to both surfaces of a sheet-like electrolyte. A method for producing an electrode for a fuel cell, comprising:
(A) a structure forming step in which furnace black carbon particles having a large specific surface area are three-dimensionally bonded to form a carbon particle structure;
(B) a catalyst supporting step of supporting a catalyst on the formed carbon particle structure;
(C) Ink which adjusts ink by dispersing carbon particle structure supporting the catalyst and carbon particles of acetylene black, which have a large secondary aggregate generated during carbon generation and contribute to bone formation, in a predetermined solvent. Adjustment process;
(D) an electrode forming member forming step of forming a sheet-like electrode forming member with the adjusted ink;
(E) A method for manufacturing an electrode comprising: a drying step of drying the predetermined solvent contained in the formed electrode forming member. A method for producing an electrode for a fuel cell according to claim 9,
Step (a)
(A1) a structure adjusting solution adjusting step of adjusting the structure adjusting solution by dispersing carbon particles in a predetermined solvent;
(A2) a structure forming member forming step of drying a solvent in the adjusted structure adjusting solution to form a solid structure forming member;
(A3) An electrode manufacturing method comprising a pulverizing step of pulverizing the formed structure forming member to form a carbon particle structure. A method for producing a power generation layer for a fuel cell, comprising:
(A) a structure forming step in which furnace black carbon particles having a large specific surface area are three-dimensionally bonded to form a carbon particle structure;
(B) a catalyst supporting step of supporting a catalyst on the formed carbon particle structure;
(C) Ink which adjusts ink by dispersing carbon particle structure supporting the catalyst and carbon particles of acetylene black, which have a large secondary aggregate generated during carbon generation and contribute to bone formation, in a predetermined solvent. Adjustment process;
(D) an electrode forming member forming step of forming a sheet-like electrode forming member on the sheet-like electrolyte with the adjusted ink;
(E) A method for producing a power generation layer comprising: a drying step of drying the predetermined solvent contained in the electrode forming member formed on the electrolyte.

Images