WO2014174973A1

WO2014174973A1 - Gas diffusion electrode body, method for manufacturing same, membrane electrode assembly for fuel cell using same, and fuel cell

Info

Publication number: WO2014174973A1
Application number: PCT/JP2014/058694
Authority: WO
Inventors: 圭小野; 慎二宮川
Original assignee: 日産自動車株式会社
Priority date: 2013-04-26
Filing date: 2014-03-26
Publication date: 2014-10-30
Also published as: JP2016129085A

Abstract

The present invention provides a gas diffusion electrode body excellent in substance transportation. The gas diffusion electrode body according to the present invention is configured by holding a polyelectrolyte and an electrode catalyst with a nonconductive nonwoven fabric or a woven fabric.

Description

GAS DIFFUSION ELECTRODE, METHOD FOR PRODUCING THE SAME, MEMBRANE ELECTRODE ASSEMBLY FOR FUEL CELL USING THE SAME

The present invention relates to a gas diffusion electrode body, a manufacturing method thereof, a membrane electrode assembly for a fuel cell using the same, and a fuel cell.

In recent years, in response to social demands and trends against the background of energy and environmental problems, fuel cells that can operate at room temperature and obtain high output density have attracted attention as power sources for electric vehicles and stationary power sources. A fuel cell is a clean power generation system in which the product of an electrode reaction is water in principle and has almost no adverse effect on the global environment. In particular, a polymer electrolyte fuel cell (PEFC) is expected as a power source for electric vehicles because it operates at a relatively low temperature. The polymer electrolyte fuel cell has a structure in which a plurality of single cells that exhibit a power generation function are stacked. This single cell includes a polymer-electrolyte membrane, a membrane-electrode assembly (MEA) having a pair of catalyst layers and a pair of gas diffusion layers (GDL) that are sequentially formed on both sides of the membrane. And MEA which each single cell has is electrically connected with MEA of an adjacent single cell through a separator. Thus, a fuel cell stack is comprised by laminating | stacking a single cell. The fuel cell stack functions as power generation means that can be used for various applications.

Conventionally, an electrolyte membrane in which a polymer solid electrolyte resin is contained in a porous pore portion of expanded porous polytetrafluoroethylene (ePTFE), and an electrode in which a gap between ePTFE is filled with an electrode catalyst and a polymer solid electrolyte An MEA having the above is disclosed (for example, Patent Document 1). According to the above configuration, it is described that the electrolyte membrane is thinned, and the generated ions in the catalyst layer are rapidly moved, the gas diffusibility is good, and the reactivity and strength can be improved.

JP-A-8-329962

However, ePTFE has a problem that the distance between micronodules is short and the pore diameter is small, so that the material transportability is poor and the power generation performance is insufficient.

Therefore, the present invention has been made in view of the above circumstances, and an object thereof is to provide a gas diffusion electrode body having excellent material transportability.

As a result of intensive studies to solve the above problems, the present inventors have found that the above-mentioned problems can be solved by including a polymer electrolyte and an electrode catalyst in a non-conductive nonwoven fabric or woven fabric.

It is the schematic which shows the basic composition of the polymer electrolyte fuel cell (PEFC) which concerns on 1st embodiment of this invention. In FIG. 1, 1 is a polymer electrolyte fuel cell (PEFC); 2 is a solid polymer electrolyte membrane; 3a is an anode gas diffusion electrode body; 3c is a cathode gas diffusion electrode body; 8a is an anode separator; 8c is a cathode separator; 9a is an anode gas flow path; 9c is a cathode gas flow path; 10 is an MEA; and 11 is a refrigerant flow path.

The gas diffusion electrode body of the present invention is characterized in that a polymer electrolyte and an electrode catalyst are held in a nonconductive nonwoven fabric or woven fabric. Since the non-conductive nonwoven fabric or woven fabric is a continuous porous structure in which pores are continuously present, the ratio of the pores is higher than the conventional one. For this reason, the gas diffusion electrode body which uses a nonelectroconductive nonwoven fabric or a textile fabric can improve substance transportability (for example, gas diffusion property). The pores of the non-conductive nonwoven fabric or woven fabric have a size that can pass through the polymer electrolyte and the electrode catalyst. For this reason, even if the nonwoven fabric or the woven fabric is non-conductive, these materials are continuously arranged in the pores to form a conductive path, so that the gas diffusion electrode body can ensure sufficient conductivity. Therefore, the fuel cell using the gas diffusion electrode body is excellent in power generation performance. In addition, since the non-woven fabric or the woven fabric is non-conductive, the range of materials that can be used is widened. Furthermore, since the polymer electrolyte and the electrode catalyst are held in the nonconductive nonwoven fabric or woven fabric, the gas diffusion electrode body also functions as a catalyst layer. Therefore, the gas diffusion electrode body of the present invention can fulfill both functions of the catalyst layer and the gas diffusion layer in one layer. For this reason, size reduction of a fuel cell can also be achieved by using the gas diffusion electrode body of the present invention.

Therefore, the present invention also provides a fuel cell membrane electrode assembly having the gas diffusion electrode assembly of the present invention and a fuel cell including the fuel cell membrane electrode assembly. The membrane electrode assembly for a fuel cell of the present invention can ensure sufficient material transportability by using a non-conductive nonwoven fabric or woven fabric that can ensure a pore diameter as a base material of a gas diffusion electrode body. For this reason, the fuel cell using a gas diffusion electrode body is excellent in power generation performance.

Also, the membrane electrode assembly (MEA) is generally produced by a direct coating method or a transfer method. In the direct application method, MEA is produced by applying catalyst ink directly to a polymer electrolyte membrane and then drying. However, this method has a problem that the solvent derived from the catalyst ink penetrates into the electrolyte membrane and the dimensional stability deteriorates. On the other hand, in the gas diffusion electrode body of the present invention, the polymer electrolyte and the electrode catalyst are previously held on a non-conductive nonwoven fabric or woven fabric. For this reason, the MEA can be easily produced by pressing the gas diffusion electrode body on the electrolyte membrane, and the catalyst ink is not brought into contact with the electrolyte membrane, so that the dimensional stability of the electrolyte membrane (and hence MEA) can be improved. Also, in the transfer method, an MEA is produced by hot pressing after sandwiching a polymer electrolyte membrane between two sheets of a catalyst ink coated and dried on a transfer substrate. However, this method has problems such as a decrease in yield due to transfer failure during transfer processing, and generation of a transfer substrate as a discarded material. On the other hand, in the gas diffusion electrode body of the present invention, the polymer electrolyte and the electrode catalyst are held in advance in a non-conductive nonwoven fabric or woven fabric. For this reason, there is no transfer process, and there is no problem with the transfer method. In the above two methods, it is necessary to adjust the catalyst ink at a high viscosity suitable for application. However, when the viscosity is increased, there is a problem that the catalyst ink becomes unstable and the catalyst ink is separated over time. In contrast, as will be described in detail below, a gas diffusion electrode body can be produced simply by immersing and drying a non-conductive nonwoven fabric or woven fabric in a solution containing a low-viscosity polymer electrolyte and an electrode catalyst. For this reason, the viscosity control of a solution and the thickener for raising a viscosity are unnecessary, and the special stirrer for making it high viscosity is also unnecessary. Furthermore, in the above two methods, since it is important to select a drying condition and a solvent for preparing the catalyst ink depending on the material of the electrolyte membrane and the transfer substrate, the drying condition and the solvent type are limited. On the other hand, since the gas diffusion electrode body is manufactured and then pressure-bonded to the electrolyte membrane, the range of drying conditions and solvent selection is widened.

Hereinafter, an embodiment to which the present invention is applied will be described with reference to the accompanying drawings. In addition, this invention is not restrict | limited only to the following embodiment. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

In the present specification, “X to Y” indicating a range means “X or more and Y or less”, “weight” and “mass”, “weight%” and “mass%”, “part by weight” and “weight part”. “Part by mass” is treated as a synonym. Unless otherwise specified, measurement of operation and physical properties is performed under conditions of room temperature (20 to 25 ° C.) / Relative humidity 40 to 50%.

First, a basic configuration of a polymer electrolyte fuel cell to which the gas diffusion electrode body of the present embodiment can be applied will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing a basic configuration of a polymer electrolyte fuel cell (PEFC) 1 according to a first embodiment of the present invention. The PEFC 1 first has a polymer electrolyte membrane 2 and a pair of gas diffusion electrode bodies (anode gas diffusion electrode body 3a and cathode gas diffusion electrode body 3c) sandwiching the polymer electrolyte membrane 2. Thus, the polymer electrolyte membrane 2 and the pair of gas diffusion electrode bodies (3a, 3c) constitute a membrane electrode assembly (MEA) 10 in a stacked state.

In PEFC 1, MEA 10 is further sandwiched between a pair of separators (anode separator 8a and cathode separator 8c). In FIG. 1, the separators (8 a, 8 c) are illustrated so as to be positioned at both ends of the illustrated MEA 10. However, in a fuel cell stack in which a plurality of MEAs are stacked, the separator is generally used as a separator for an adjacent PEFC (not shown). In other words, in the fuel cell stack, the MEAs are sequentially stacked via the separator to form a stack. In an actual fuel cell stack, a gas seal portion is disposed between the separators (8a, 8c) and the polymer electrolyte membrane 2, or between the PEFC 1 and another adjacent PEFC. In 1, these descriptions are omitted.

The separators (8a, 8c) are obtained, for example, by forming a concavo-convex shape as shown in FIG. 1 by subjecting a thin plate having a thickness of 0.5 mm or less to a press treatment. The protrusions seen from the MEA side of the separators (8a, 8c) are in contact with the MEA10. Thereby, the electrical connection with MEA10 is ensured. In addition, a recess (space between the separator and the MEA generated due to the concavo-convex shape of the separator) viewed from the MEA side of the separator (8a, 8c) is a gas for circulating gas during operation of the PEFC 1 Functions as a flow path. Specifically, fuel gas (for example, hydrogen) is circulated through the gas flow path 9a of the anode separator 8a, and oxidant gas (for example, air) is circulated through the gas flow path 9c of the cathode separator 8c.

On the other hand, the recess viewed from the side opposite to the MEA side of the separators (8a, 8c) serves as a refrigerant flow path 11 for circulating a refrigerant (for example, water) for cooling the PEFC during operation of the PEFC 1. . Further, the separator is usually provided with a manifold (not shown). This manifold functions as a connection means for connecting cells when a stack is formed. With such a configuration, the mechanical strength of the fuel cell stack can be ensured.

In the embodiment shown in FIG. 1, the separators (8a, 8c) are formed in an uneven shape. However, the separator is not limited to such a concavo-convex shape, and may be any form such as a flat plate shape and a partially concavo-convex shape as long as the functions of the gas flow path and the refrigerant flow path can be exhibited. Also good.

Further, the gas diffusion electrode bodies (3a, 3c) function as both a catalyst layer and a gas diffusion layer. For this reason, a gas diffusion layer (GDL) (gas diffusion layer, fine porous layer) is not necessarily required separately. However, if necessary, the PEFC 1 has a gas diffusion layer (GDL) (gas diffusion substrate, fine porous layer) between the gas diffusion electrode bodies (3a, 3c) and the separators (8a, 8c). (MPL)) may be included separately.

In FIG. 1, the gas diffusion electrode bodies (anode gas diffusion electrode body 3a and cathode gas diffusion electrode body 3c) of the present invention are arranged on both the cathode and anode sides. However, the present invention is not limited to the above form. That is, the gas diffusion electrode body of the present invention may be disposed on at least one side of the cathode and the anode. Preferably, the gas diffusion electrode body of the present invention is disposed at least on the cathode side, and more preferably disposed on both the cathode and anode sides.

[Gas diffusion electrode body]
The gas diffusion electrode bodies (the anode gas diffusion electrode body 3a and the cathode gas diffusion electrode body 3c) are layers in which the battery reaction actually proceeds. Specifically, the oxidation reaction of hydrogen proceeds in the anode catalyst layer 3a, and the reduction reaction of oxygen proceeds in the cathode catalyst layer 3c. For this reason, ePTFE as described in the said patent document 1 is not included in the nonwoven fabric of this invention.

Here, the gas diffusion electrode body has a structure in which a polymer electrolyte and an electrode catalyst are held in a non-conductive nonwoven fabric or woven fabric. Preferably, the gas diffusion electrode body has a structure in which a polymer electrolyte and an electrode catalyst are held by a non-conductive nonwoven fabric. In this specification, “nonwoven fabric” means a laminate of fibers.

The material constituting the nonconductive nonwoven fabric or woven fabric is not particularly limited as long as it is nonconductive. For example, glass, polymer resin fiber, cellulose and the like can be mentioned. Of these, glass and polymer resin fibers are preferred. Although it does not restrict | limit especially as a polymeric resin fiber, From a heat resistant and hydrolysis resistant viewpoint, a polypropylene, polyamide, a polyimide, polysulfone, polyphenylene sulfide etc. are mentioned suitably. More preferably, from the viewpoint of cost, the polymer resin fiber is polyamide or polypropylene. The said material may be used individually by 1 type, or may be used with the form of 2 or more types of mixtures. That is, the nonconductive nonwoven fabric or woven fabric is preferably formed from at least one selected from the group consisting of glass, polymer resin fibers, and cellulose.

The thickness of the non-conductive nonwoven fabric or woven fabric is not particularly limited. Specifically, the thickness of the non-conductive nonwoven fabric or woven fabric (when loaded with 19.6 kPa) is preferably 5 to 500 μm, more preferably 25 to 250 μm.

Also, the size of the fibers constituting the nonconductive nonwoven fabric or woven fabric is not particularly limited. Specifically, the thickness (diameter) of the fiber is preferably 0.01 to 100 μm, more preferably 0.1 to 25 μm. If it is such a magnitude | size, a nonelectroconductive nonwoven fabric or textile fabric has a moderate hole size (hole diameter).

The method for producing the nonconductive nonwoven fabric or woven fabric is not particularly limited. For example, the nonconductive nonwoven fabric can be produced by a dry method, a wet papermaking method, a spunbond method, or the like. Moreover, a nonelectroconductive textile fabric can be produced with a well-known weaving method. Here, the production conditions of the non-conductive nonwoven fabric or woven fabric are not particularly limited, but for example, the basis weight is preferably 1 to 50 g / m ² , and more preferably 5 to 25 g / m ² . The density of the nonconductive nonwoven fabric or woven fabric is preferably 0.05 to 1.0 g / cm ³ , more preferably 0.1 to 0.4 g / cm ³ . Under such conditions, the non-conductive nonwoven fabric or woven fabric can obtain an appropriate porosity (for example, 60 to 97.5%). Here, if the porosity of a nonelectroconductive nonwoven fabric or a woven fabric is the said range, gas diffusibility and electroconductivity can be improved, ensuring intensity | strength (a shape is maintained).

As described above, the non-conductive nonwoven fabric or woven fabric preferably has pores of a size that can pass through the polymer electrolyte or the electrode catalyst, preferably the electrode catalyst. Thereby, even if a nonwoven fabric or a woven fabric is non-conductive, an electrode catalyst (especially conductive support | carrier) is arrange | positioned continuously (in the state mutually contacted) in the hole of a non-conductive nonwoven fabric or a woven fabric. Since the continuous arrangement of the electrode catalyst forms a conductive path, the gas diffusion electrode body can ensure sufficient conductivity. Moreover, since the electrode catalyst is uniformly present in the gas diffusion electrode body, the entire gas diffusion electrode body exhibits high catalytic activity. Here, the size of the pores of the non-conductive non-woven fabric or woven fabric is not particularly limited as long as it can pass through the electrode catalyst. The pore diameter of the non-conductive nonwoven fabric or woven fabric is preferably 1.2 to 100 times, more preferably 1.5 to 20 times, particularly preferably 2 to 5 times the average particle diameter of the electrode catalyst. is there. If the pores have such a size, a sufficient amount of electrode catalyst can be continuously arranged in the pores (in contact with each other), so that the gas diffusion electrode body has sufficient conductivity and catalytic activity. Can demonstrate. In the present specification, the “particle size of the electrode catalyst” means the average secondary particle size of the electrode catalyst. Here, for the measurement of the average secondary particle diameter of the electrode catalyst, a value calculated as the median value of the particle diameter of the electrode catalyst observed with a laser diffraction / scattering particle size distribution analyzer is adopted.

Alternatively, the pore diameter of the non-conductive nonwoven fabric or woven fabric is preferably 100 μm or less, more preferably 1 to 50 μm, more preferably 5 to 25 μm, and particularly preferably 5 to 10 μm. . Within such a range, the strength of the gas diffusion electrode body can be sufficiently secured, and even in a fuel cell stack in which a plurality of MEAs are laminated, no hole is caused by local reverse cell reaction or deterioration. In the present specification, the “pore diameter” of the non-conductive nonwoven fabric or woven fabric is an average pore diameter (μm) calculated from the bubble point. Specifically, after a non-conductive non-woven fabric or woven fabric (sample) is dipped in isopropyl alcohol for 10 minutes or more in advance, it is placed horizontally and attached to a test tank, and isopropyl alcohol is placed in the tank up to a height of 15 mm at the upper end of the sample. pour it up. Next, the air pressure inside the sample is gradually increased from zero, bubbles are first generated from the medium, and the air pressure when the bubbles are continuously generated is read with a manometer. Further increase the air flow rate, measure the air flow rate and air pressure, and continue until the rate of change of the air flow rate becomes almost constant. The relationship between the air flow rate and air pressure is shown in a graph, and the bubble point pressure at the intersection is read from the tangent of the initial slope and the tangent of the final slope. From the obtained intersection bubble point pressure, the average pore diameter is calculated from the following equation.

Here, D represents the average pore diameter (μm); P represents the intersection bubble point pressure (mmH ₂ O).

The non-conductive nonwoven fabric or woven fabric may be a commercially available product. For example, a porous glass (manufactured by Nippon Sheet Glass Co., Ltd., trade name: TGP-015A), a polymer nonwoven fabric (manufactured by Sanki, trade name: Delpore P1001-20B) and the like can be used.

The electrode catalyst is composed of a catalyst component and a conductive carrier (catalyst carrier) carrying the catalyst component.

The catalyst component used in the anode gas diffusion electrode body is not particularly limited as long as it has a catalytic action in the oxidation reaction of hydrogen, and a known catalyst can be used in the same manner. The catalyst component used in the cathode gas diffusion electrode body is not particularly limited as long as it has a catalytic action for the oxygen reduction reaction, and a known catalyst can be used in the same manner. Specifically, it may be selected from metals such as platinum, ruthenium, iridium, rhodium, palladium, osmium, tungsten, lead, iron, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, aluminum, and alloys thereof. .

Among these, those containing at least platinum are preferably used in order to improve catalytic activity, poisoning resistance to carbon monoxide, heat resistance, and the like. Although the composition of the alloy depends on the type of metal to be alloyed, the content of platinum is preferably 30 to 90 atomic%, and the content of the metal to be alloyed with platinum is preferably 10 to 70 atomic%. In general, an alloy is a generic term for a metal element having one or more metal elements or non-metal elements added and having metallic properties. The alloy structure consists of a eutectic alloy, which is a mixture of the component elements as separate crystals, a component element completely melted into a solid solution, and a component element composed of an intermetallic compound or a compound of a metal and a nonmetal. There is what is formed, and any may be used in the present application. At this time, the catalyst component used for the anode gas diffusion electrode body and the catalyst component used for the cathode gas diffusion electrode body can be appropriately selected from the above. In the present specification, unless otherwise specified, the descriptions of the catalyst components for the anode gas diffusion electrode body and the cathode gas diffusion electrode body have the same definition for both. Therefore, they are collectively referred to as “catalyst components”. However, the catalyst components of the anode gas diffusion electrode body and the cathode gas diffusion electrode body do not have to be the same, and can be appropriately selected so as to exhibit the desired action as described above.

The shape and size of the catalyst component are not particularly limited, and the same shape and size as known catalyst components can be adopted. For example, the catalyst component may be granular, scale-like, or layered, but is preferably granular. At this time, the average particle diameter of the catalyst particles is preferably 1 to 30 nm, more preferably 1 to 10 nm, still more preferably 1 to 5 nm, and particularly preferably 2 to 4 nm. When the average particle diameter of the catalyst particles is within such a range, the balance between the catalyst utilization rate related to the effective electrode area where the electrochemical reaction proceeds and the ease of loading can be appropriately controlled. The “average particle diameter of the catalyst particles” in the present invention is the crystallite diameter determined from the half-value width of the diffraction peak of the catalyst component in X-ray diffraction, or the particle diameter of the catalyst component determined by a transmission electron microscope (TEM). It can be measured as an average value of.

The catalyst component described above is included in the catalyst ink as an electrode catalyst supported on a conductive carrier.

The conductive carrier functions as a carrier for supporting the above-described catalyst component and an electron conduction path involved in the transfer of electrons between the catalyst component and another member. The conductive carrier may have any specific surface area for supporting the catalyst particles in a desired dispersed state and has sufficient electronic conductivity as a current collector. The main component is carbon. Preferably there is. In the present invention, “the main component is carbon” refers to containing a carbon atom as a main component, and is a concept including both a carbon atom only and a substantially carbon atom. In some cases, elements other than carbon atoms may be included in order to improve the characteristics of the fuel cell. Incidentally, being substantially composed of carbon atoms means that contamination of impurities of about 2 to 3% by weight or less is allowed. Specifically, conventionally known materials such as carbon black, graphite (including granular graphite), and expanded graphite can be appropriately employed. Among these, carbon black such as oil furnace black, channel black, lamp black, thermal black, acetylene black and the like can be preferably used because of excellent conductivity and a large specific surface area. As such carbon particles, commercially available products can be used, such as Vulcan XC-72, Vulcan P, Black Pearls 880, Black Pearls 1100, Black Pearls 1300, Black Pearls 2000, Regal 400, Lion Corporation Black EC, Oil Furnace Black such as # 3150 and # 3250 manufactured by Mitsubishi Chemical Corporation; Denka Black manufactured by Denki Kagaku Kogyo Co., and acetylene black such as acetylene black AB-6 manufactured by Denki Kagaku Kogyo Co., Ltd. In addition to carbon black, artificial graphite or carbon obtained from an organic compound such as activated carbon, natural graphite, pitch, coke, polyacrylonitrile, phenol resin, or furan resin may be used. Moreover, in order to improve corrosion resistance etc., you may process the said carbon particle, such as a graphitization process. In this case, the conductive carrier may be used alone or in the form of a mixture of two or more.

The particle size of the conductive carrier is not particularly limited. Considering the relationship with the pore size of the non-conductive nonwoven fabric or woven fabric, the particle size (average primary particle size) of the conductive carrier is preferably 5 to 200 nm, and more preferably 10 to 100 nm. If it is such a range, an electroconductive support | carrier can be arrange | positioned efficiently and continuously in the hole of a nonelectroconductive nonwoven fabric or a textile fabric, and can ensure sufficient electroconductivity and catalytic activity. Further, the catalyst component can be easily supported on the carrier, and the catalyst utilization rate and the thickness of the gas diffusion electrode body can be controlled within appropriate ranges. The shape of the conductive carrier is not particularly limited, and may have any structure such as a spherical shape, a rod shape, a needle shape, a plate shape, a column shape, an indefinite shape, a flake shape, and a spindle shape, but a granular shape is preferable. Here, the size of the conductive carrier can be measured by a known method. In this specification, unless otherwise specified, a statistically significant number of fields of view (for example, several to several tens of fields of view) using observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM) is used. ) The value calculated as the average value of the particle diameters (diameters) of the particles observed in the above is adopted. The “particle diameter” means the maximum distance among the distances between any two points on the particle outline.

The BET specific surface area of the conductive carrier may be a specific surface area sufficient to support the catalyst component in a highly dispersed state, but is preferably 20 to 1600 m ² / g, more preferably 80 to 1200 m ² / g. Is good. When the specific surface area is in the above range, the catalyst component and the polymer electrolyte are sufficiently dispersed on the conductive support to obtain sufficient power generation performance, and the catalyst component and the polymer electrolyte can be sufficiently effectively used. .

In the electrode catalyst in which the catalyst component is supported on the conductive support, the supported amount of the catalyst component is preferably 10 to 80% by weight, more preferably 30 to 70% by weight, based on the total amount of the electrode catalyst. Good. When the supported amount of the catalyst component is within such a range, the balance between the degree of dispersion of the catalyst component on the catalyst support and the catalyst performance can be appropriately controlled. The amount of the catalyst component supported can be examined by inductively coupled plasma emission spectroscopy (ICP). Here, the catalyst component can be supported on the conductive support by a known method. For example, known methods such as impregnation method, liquid phase reduction support method, evaporation to dryness method, colloid adsorption method, spray pyrolysis method, reverse micelle (microemulsion method) can be used. Alternatively, a commercially available electrode catalyst may be used. Specifically, a platinum catalyst (for example, trade name: TEC10E40E, TEC10E50E, TEC10E60TPM, TEC10E70TPM, TEC10V30E, TEC10V40E, TEC10V50E, etc.) manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., platinum / ruthenium manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. A catalyst (for example, trade names: TEC66E50, TEC61E54, TEC62E58, etc.) can be used.

Further, the content (mg / cm ² ) of the electrode catalyst per unit catalyst application area is not particularly limited, but in view of sufficient dispersibility of the catalyst on the carrier, power generation performance, etc., 0.01 to 1. 0 mg / cm ² . However, when the catalyst contains platinum or a platinum-containing alloy, the platinum content per unit catalyst coating area is preferably 0.5 mg / cm ² or less. The use of expensive noble metal catalysts typified by platinum (Pt) and platinum alloys has become a high cost factor for fuel cells. Therefore, it is preferable to reduce the amount of expensive platinum used (platinum content) to the above range and reduce the cost. The lower limit is not particularly limited as long as power generation performance is obtained, and is, for example, 0.01 mg / cm ² or more. More preferably, the platinum content is 0.05 to 0.30 mg / cm ² . In this specification, inductively coupled plasma emission spectroscopy (ICP) is used for measurement (confirmation) of “catalyst (platinum) content per unit catalyst application area (mg / cm ² )”. A person skilled in the art can easily carry out a method of making the desired “catalyst (platinum) content per unit catalyst coating area (mg / cm ² )”, and control the ink composition (catalyst concentration) and coating amount. You can adjust the amount.

Or, the content of the electrode catalyst is not particularly limited. The content of the electrode catalyst is preferably 2.5 to 40% by volume, more preferably 5 to 25% by volume with respect to the gas diffusion electrode body. With such an electrode catalyst content, a sufficient conductive path can be formed, and good material diffusibility is ensured, so that excellent performance can be exhibited.

The gas diffusion electrode body includes an ion conductive polymer electrolyte in addition to the electrode catalyst. The polymer electrolyte is not particularly limited, and conventionally known knowledge can be referred to as appropriate. For example, the ion exchange resin which comprises the catalyst layer mentioned above can be used conveniently as a polymer electrolyte.

In addition, the polymer electrolyte held in the non-conductive nonwoven fabric or woven fabric together with the electrode catalyst is not particularly limited, and conventionally known knowledge can be referred to as appropriate. Polymer electrolytes are roughly classified into fluorine-based polymer electrolytes and hydrocarbon-based polymer electrolytes depending on the type of ion exchange resin that is a constituent material. Examples of the fluoropolymer electrolyte include perfluorocarbon sulfonic acid polymers such as Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.), and Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.). , Perfluorocarbon phosphonic acid polymer, trifluorostyrene sulfonic acid polymer, ethylene tetrafluoroethylene-g-styrene sulfonic acid polymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride-perfluorocarbon sulfonic acid polymer, etc. Is mentioned. Specific examples of hydrocarbon electrolytes include sulfonated polyethersulfone (S-PES), sulfonated polyaryletherketone, sulfonated polybenzimidazole alkyl, phosphonated polybenzimidazole alkyl, sulfonated polystyrene, sulfone. Polyether ether ketone (S-PEEK), sulfonated polyphenylene (S-PPP), and the like. Among these, the polymer electrolyte preferably contains a fluorine atom because it is excellent in heat resistance, chemical stability, and the like. Particularly preferred are fluorine-based electrolytes such as Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.), Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.), and the like. As for the said polymer electrolyte, only 1 type may be used independently and 2 or more types may be used together. Moreover, it is not restricted only to the material mentioned above, Other materials may be used.

The content of the polymer electrolyte is not particularly limited. The content of the polymer electrolyte is preferably 1.0 to 30% by volume, more preferably 2.5 to 20% by volume with respect to the gas diffusion electrode body. With such an amount, the gas diffusion electrode body can exhibit sufficient ion conductivity and conductivity.

Further, the mixing ratio of the polymer electrolyte and the electrode catalyst is not particularly limited. The polymer electrolyte is arranged (blended) so as to be an electrode catalyst, preferably in a proportion of 0.1 to 2 parts by mass, more preferably 0.3 to 1.4 parts by mass with respect to 100 parts by weight of the electrode catalyst. To do. With such an amount, the gas diffusion electrode body can exhibit sufficient ion conductivity, conductivity and catalytic activity.

The gas diffusion electrode body is formed by holding a conductive carrier on a non-conductive nonwoven fabric or woven fabric, but may further contain other additives. Here, the additive is not particularly limited, and examples thereof include a dispersant, a dispersion aid, a water repellent, and a binding binder. These additives may be used alone or in combination of two or more. Of these, the gas diffusion electrode body preferably contains a water repellent for the purpose of further improving water repellency and preventing flooding. The water repellent is not particularly limited, but fluorine-based high repellents such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyhexafluoropropylene, and tetrafluoroethylene-hexafluoropropylene copolymer (FEP). Molecular materials; thermoplastic resins such as polyethylene and polypropylene are listed. Of these, fluorine-based polymer materials are preferably used because of their excellent water repellency and corrosion resistance during electrode reaction. When the polymer electrolyte is a fluorine electrolyte, the polymer electrolyte can also act as a water repellent. When the gas diffusion electrode body contains a water repellent, the content (addition amount) of the water repellent is not particularly limited. For example, other additives are preferably mixed in an amount of about 1 to 10 parts by weight with respect to 100 parts by weight of the conductive carrier. With such an amount, the gas diffusion electrode body satisfies both conductivity and water repellency.

In place of or in addition to the above other additives, the gas diffusion electrode body may further contain conductive carbon (no catalyst component supported). By using conductive carbon, the conductivity of the gas diffusion electrode body can be improved. For this reason, when the amount of the electrode catalyst is small, it is preferable to use conductive carbon for the purpose of ensuring conductivity.

Here, the conductive carbon is not particularly limited, and conventionally known materials such as carbon black, graphite (including granular graphite), and expanded graphite can be appropriately employed. Among these, carbon black such as oil furnace black, channel black, lamp black, thermal black, acetylene black and the like can be preferably used because of excellent conductivity and a large specific surface area. As such carbon particles, commercially available products can be used, such as Vulcan XC-72, Vulcan P, Black Pearls 880, Black Pearls 1100, Black Pearls 1300, Black Pearls 2000, Regal 400, Lion Corporation Black EC, Oil Furnace Black such as # 3150 and # 3250 manufactured by Mitsubishi Chemical Corporation; Denka Black manufactured by Denki Kagaku Kogyo Co., and acetylene black such as acetylene black AB-6 manufactured by Denki Kagaku Kogyo Co., Ltd. In addition to carbon black, artificial graphite or carbon obtained from organic compounds such as natural graphite, pitch, coke, polyacrylonitrile, phenol resin, furan resin may be used. Moreover, in order to improve corrosion resistance etc., you may process the said carbon particle, such as a graphitization process. In this case, the conductive carbon may be used alone or in the form of a mixture of two or more.

The size of the conductive carbon is not particularly limited, but is preferably a size that can pass through the pores of the non-conductive nonwoven fabric or woven fabric. As a result, the conductive carbon is continuously arranged (in contact with each other) in the pores of the non-conductive nonwoven fabric or woven fabric to form a conductive path, thereby further improving the conductivity of the gas diffusion electrode body. it can. In consideration of the relationship with the pore size of the non-conductive nonwoven fabric or woven fabric, the particle size (average primary particle size) of the conductive carbon is preferably 2 to 250 nm, and more preferably 10 to 100 nm. Within such a range, the conductive carbon can be efficiently and continuously disposed in the pores of the non-conductive nonwoven fabric or woven fabric to ensure sufficient conductivity. The shape of the conductive carbon is not particularly limited, and may be any structure such as a spherical shape, a rod shape, a needle shape, a plate shape, a column shape, an indefinite shape, a flake shape, or a spindle shape, but a granular shape is preferable. Here, the size of the conductive carbon can be measured by a known method. In this specification, unless otherwise specified, a statistically significant number of fields of view (for example, several to several tens of fields of view) using observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM) is used. ) The value calculated as the average value of the particle diameters (diameters) of the particles observed in the above is adopted. The “particle diameter” means the maximum distance among the distances between any two points on the particle outline.

Alternatively, the ratio of the average particle diameter of the conductive carbon to the pore diameter of the non-conductive nonwoven fabric or woven fabric [= average particle diameter of the conductive carbon (μm) / pore diameter of the non-conductive nonwoven fabric or woven fabric (μm)] is 1 / 2 to 1/100 times, more preferably 1/2 to 1/20 times, even more preferably 1/3 to 1/10 times, and particularly preferably 1/3 to 1/5 times. It is. With holes of such a size, a sufficient amount of conductive carbon can be arranged continuously (in contact with each other) in the holes. For this reason, since the continuous arrangement of the conductive carbon forms a conductive path, the conductivity of the gas diffusion electrode body can be further improved. In the present specification, “particle diameter of conductive carbon” means the average secondary particle diameter of conductive carbon. Here, for the measurement of the average secondary particle diameter of the conductive carbon, a value calculated as the median value of the particle diameter of the particles observed with a laser diffraction / scattering particle size distribution measuring apparatus is adopted.

The content of conductive carbon when the gas diffusion electrode body contains conductive carbon (non-supported catalyst component) is not particularly limited. Considering improvement in conductivity, the total content of the electrode catalyst and the conductive carbon is preferably 2.5 to 40% by volume, more preferably 5 to 30% by volume with respect to the gas diffusion electrode body. . Here, if the content of the electrode catalyst is in the above range, a sufficient conductive path can be formed and good material diffusibility is ensured, so that excellent performance can be exhibited. For the purpose of imparting conductivity, the amount of the electrode catalyst is excessive, which is not preferable from the viewpoint of cost. Even in such a case, the conductive carbon can act so as to complement the provision of conductivity by the electrode catalyst. For this reason, especially when there are few compounding quantities of an electrode catalyst, it is especially preferable from a viewpoint of electroconductivity provision to further arrange | position (mixing) conductive carbon by the quantity as mentioned above.

The thickness of the gas diffusion electrode body is not particularly limited, but is preferably 5 to 500 μm, and more preferably 25 to 250 μm. If it is such thickness, since sufficient amount of a polymer electrolyte and an electrode catalyst can be hold | maintained, sufficient electroconductivity and catalytic activity can be exhibited.

The gas diffusion electrode body may be provided on at least one of the cathode side and the anode side of the MEA, but it is preferably provided on both the cathode and the anode.

(Method for producing gas diffusion electrode body)
The method for producing the gas diffusion electrode body is not particularly limited as long as the polymer electrolyte and the electrode catalyst can be held on the non-conductive nonwoven fabric or woven fabric. For example, a method of applying a slurry containing a polymer electrolyte, an electrode catalyst and a solvent to a non-conductive nonwoven fabric or woven fabric and then drying; impregnating and drying the non-conductive nonwoven fabric or woven fabric in a catalyst ink containing an electrode catalyst and a solvent ( A method of impregnating and drying (heat treatment) an electrolyte ink containing a polymer electrolyte and a solvent after heat treatment; After impregnating and drying (heat treatment) a non-conductive nonwoven fabric or fabric in an electrolyte ink containing a polymer electrolyte and a solvent And a method of impregnating and drying (heat treatment) a catalyst ink containing an electrode catalyst and a solvent. Moreover, the manufacturing method of the gas diffusion electrode body when the gas diffusion electrode body contains conductive carbon is not particularly limited. For example, a method in which an ink (slurry) containing a polymer electrolyte, an electrode catalyst, conductive carbon and a solvent is applied to a non-conductive nonwoven fabric or woven fabric and then dried (heat treatment); a polymer electrolyte, an electrode catalyst, a conductive carbon After applying ink (slurry) containing any one and solvent to non-conductive nonwoven fabric or woven fabric and drying (heat treatment), applying ink (slurry) containing the remaining two types and solvent to non-conductive nonwoven fabric or woven fabric A method of drying (heat treatment): applying an ink (slurry) containing a polymer electrolyte, an electrode catalyst, conductive carbon and a solvent to a non-conductive nonwoven fabric or woven fabric and drying (heat treatment), then the remaining A method of applying ink (slurry) containing one kind and a solvent to a non-conductive non-woven fabric or woven fabric and drying (heat treatment); Carbon ink containing Bon and solvent, sequentially a catalyst ink containing an electrolyte ink and the electrode catalyst and a solvent containing a polymer electrolyte and solvent in any order, after coating, a method of drying (heat treatment) can be mentioned. Here, the application method is not particularly limited, and known methods such as spray coating (spraying method), dip coating (dipping method), spin coating, bar coating, roll coating, and screen printing are similarly modified or appropriately modified. Can be applied. Preferably, an immersion method is applied. The drying conditions are not particularly limited as long as the conductive carbon can be held in the non-conductive nonwoven fabric or woven fabric, but are preferably 200 ° C. or less from the viewpoint of time, energy cost, and mass production. That is, the present invention also includes dipping a non-conductive nonwoven fabric or woven fabric in a slurry containing a polymer electrolyte, an electrode catalyst and a solvent; and heat-treating the non-conductive nonwoven fabric or woven fabric after the immersion at a temperature of 200 ° C. or lower. The manufacturing method of the gas diffusion electrode body of this invention which has is also provided. Hereinafter, the preferable form of the manufacturing method of the gas diffusion electrode body of this invention is demonstrated. However, the present invention is not limited to the following form. Further, in the following, the form in which the gas diffusion electrode body contains conductive carbon will be described. However, even when the gas diffusion electrode body does not contain conductive carbon, the following form is similarly applied except that the conductive carbon is not used. it can. Further, hereinafter, the carbon ink containing conductive carbon and a solvent, the catalyst ink containing an electrode catalyst and a solvent, and the electrolyte ink containing a polymer electrolyte and a solvent are collectively referred to as “ink”.

The solvent is not particularly limited and is appropriately selected depending on the type of polymer electrolyte, electrode catalyst, and conductive carbon. Examples of the solvent include water, perfluorobenzene, dichloropentafluoropropane, methanol, ethanol, propanol, 2-propanol, cyclohexanol, and other petroleum solvents such as toluene. Here, the concentration of the polymer electrolyte in the electrolyte ink is not particularly limited. Specifically, the concentration (solid content concentration) of the polymer electrolyte in the ink is preferably 0.1 to 20% by weight, more preferably 0.5 to 10% by weight. If it is such a density | concentration, a sufficient amount of polymer electrolyte can be hold | maintained to a nonelectroconductive nonwoven fabric or textile fabric at the next application | coating (dipping) process. Also, good workability can be achieved by appropriately controlling the viscosity of the ink. The concentration (solid content concentration) of the electrode catalyst in the catalyst ink is not particularly limited. Specifically, the concentration of the electrode catalyst in the ink is preferably 0.1 to 25% by weight, more preferably 0.25 to 10% by weight. If it is such a density | concentration, a sufficient amount of electrode catalyst can be hold | maintained at a nonelectroconductive nonwoven fabric or textile fabric at the next application | coating (dipping) process. The conductive carbon concentration (solid content concentration) in the carbon ink is not particularly limited. Specifically, the concentration of conductive carbon in the ink is preferably 5 to 25% by weight, more preferably 10 to 20% by weight. If it is such a density | concentration, sufficient electroconductive carbon can be ensured by hold | maintaining sufficient quantity of electroconductive carbon to a nonelectroconductive nonwoven fabric or textile fabric at the next application | coating (immersion) process.

The ink may contain other additives in addition to at least one of a polymer electrolyte, an electrode catalyst and conductive carbon, and a solvent. Here, the additive is not particularly limited, and examples thereof include a dispersion aid, a dispersant, a water repellent, and a binder binder. The addition amount of the additive is not particularly limited, and is appropriately selected in consideration of a desired effect (for example, dispersibility and water repellency of conductive carbon). Specifically, the additive is preferably added in an amount of about 1 to 10% by weight with respect to the total amount of polymer electrolyte, electrode catalyst, and conductive carbon contained in the same ink. If necessary, the ink may be dispersed while being subjected to ultrasonic treatment (ultrasonic dispersion treatment). Since the viscosity of the ink is lowered by such treatment, each component (polymer electrolyte, electrode catalyst, or conductive carbon) is not contained in the nonconductive nonwoven fabric or woven fabric when the nonconductive nonwoven fabric or woven fabric is immersed in the next step. It can penetrate more efficiently into the pores.

Alternatively, the ink may contain a thickener. The thickener that can be used in this case is not particularly limited, and a known thickener can be used. Examples thereof include glycerin, ethylene glycol (EG), polyvinyl alcohol (PVA), and propylene glycol (PG). Of these, propylene glycol (PG) is preferably used. By using propylene glycol (PG), the boiling point of the ink increases and the solvent evaporation rate decreases. For this reason, for example, the solvent evaporation rate in the applied ink is suppressed, and the occurrence of cracks (cracks) in the gas diffusion electrode body after the drying process can be suppressed / prevented. The concentration of mechanical stress on the gas diffusion electrode body is relaxed, and as a result, the durability of the MEA can be improved. The amount of the thickener added when the thickener is used is not particularly limited as long as it does not interfere with the above effect of the present invention, but is preferably 5 to 20 weight with respect to the total weight of the ink. %.

Next, a non-conductive nonwoven fabric or fabric is immersed in the ink prepared as described above. Here, the dipping condition is a condition in which a sufficient amount of electrolyte and electrode catalyst and, if necessary, conductive carbon can be held in a non-conductive nonwoven fabric or woven fabric within a range that avoids volatilization and solidification of the solvent used and an increase in viscosity. There is no particular limitation. For example, when a low boiling point solvent such as water or ethanol is selected as the solvent, the immersion temperature is preferably 10 to 80 ° C., more preferably 20 to 40 ° C. The immersion time is preferably 5 seconds to 15 minutes, more preferably 10 seconds to 5 minutes. In addition, you may repeat the said immersion process as needed. By performing such an operation, more polymer electrolyte, electrode catalyst, or conductive carbon can be held in the nonconductive nonwoven fabric or woven fabric. Also, during and / or after the dipping process, vacuum suction, vacuum degassing treatment, physical contact of the jig against the surface (eg rubbing or tapping with a brush) to remove bubbles and promote uniform penetration. Treatment for removing bubbles), ultrasonic treatment or the like.

Further, after dipping in ink, the nonconductive nonwoven fabric or woven fabric is dried (heat treated). Here, the drying condition is such that the solvent is removed from the non-conductive nonwoven fabric or woven fabric and the conductive carbon is held on the surface and in the pores, so that a high temperature for baking (firing) is required as in the past. And not. For this reason, it is very preferable in mass production from the viewpoint of time and energy cost. For this reason, the drying temperature should just be the temperature which can remove a solvent, and changes with kinds of solvent to be used. For example, the drying temperature is 200 ° C. or less from the viewpoint of time and energy cost. For example, the drying temperature is preferably 60 to 200 ° C., more preferably 80 to 150 ° C. The drying time is preferably 5 to 20 minutes, more preferably 2 to 10 minutes. The above conditions can be particularly suitably applied when a low boiling point solvent such as water or ethanol is selected as the solvent. In consideration of mass production, it is preferable to select a low boiling point solvent such as water or ethanol as the solvent. In the drying process, an air flow may be introduced into the drying furnace. By performing such an operation, it is possible to further shorten the drying time. Thus, according to the method of this embodiment, the gas diffusion electrode body can be produced at a low temperature and in a short time, which is very preferable from an industrial viewpoint. In addition, you may repeat the said drying (heat processing) process as needed. By performing such an operation, more polymer electrolyte and electrode catalyst and, if necessary, conductive carbon can be held in the non-conductive nonwoven fabric or woven fabric.

In addition, although a gas diffusion electrode body can be manufactured as described above, in order to improve the water repellency of the gas diffusion electrode body, the nonconductive nonwoven fabric or woven fabric after the immersion may be subjected to a water repellent treatment. Here, the water repellent treatment method is not particularly limited, but is preferably immersed in a solution containing the water repellent as described above from the viewpoint of ease of operation. The solvent that can be used to prepare the water repellent solution is not particularly limited as long as it can dissolve the water repellent, and can be appropriately selected depending on the type of the water repellent. Examples thereof include water, alcohols such as perfluorobenzene, dichloropentafluoropropane, methanol and ethanol, and petroleum solvents such as toluene. Here, the concentration of the water repellent is not particularly limited. Specifically, the concentration (solid content concentration) of the water repellent in the water repellent solution is preferably 0.1 to 25% by weight, more preferably 1 to 5% by weight. With such a concentration, sufficient water repellency can be imparted to the gas diffusion electrode body.

Further, the immersion conditions in the water repellent solution are not particularly limited as long as a sufficient amount of water repellency can be imparted to the gas diffusion electrode body, but in order to prevent volatilization of the solvent used for immersion, It is preferably performed at a temperature lower than 20 ° C. so that the solution does not thicken or coagulate. For example, the immersion temperature when an alcohol solution of a perfluorosulfonic acid polymer is used is preferably 10 to 60 ° C., more preferably 20 to 40 ° C. The immersion time is preferably 2 seconds to 15 minutes, more preferably 5 seconds to 10 minutes. In addition, during the said immersion process, in order to remove the bubble inside a gas diffusion electrode body, it is preferable to perform an ultrasonic treatment. In addition, you may repeat the said immersion process as needed (for example, in order to provide more water repellency).

Further, after immersing in the water repellent solution, the gas diffusion electrode body is dried (heat treatment). That is, after immersion and before heat treatment, the nonconductive nonwoven fabric or woven fabric after immersion may be subjected to water repellent treatment. Thereby, a gas diffusion electrode body with further improved water repellency can be obtained. Here, drying conditions should just remove a solvent, and change with kinds of solvent to be used. For example, from the viewpoint of time and energy cost, the drying temperature is 200 ° C. or less, preferably 40 to 200 ° C., more preferably 80 to 150 ° C. In consideration of mass production, the drying time is preferably 30 seconds to 20 minutes, more preferably 3 minutes to 15 minutes. In addition, you may repeat the said drying (heat processing) process as needed (for example, in order to hold | maintain electroconductive carbon firmly or to provide water repellency more efficiently). Thus, according to the method of this embodiment, the gas diffusion layer can be produced at a low temperature and in a short time, which is very preferable from an industrial viewpoint.

[Polymer electrolyte membrane]
The polymer electrolyte membrane 2 has a function of selectively transmitting protons generated on the anode side (anode gas diffusion electrode body) during operation of the PEFC 1 to the cathode side (cathode gas diffusion electrode body) along the film thickness direction. Have. The solid polymer electrolyte membrane 2 also has a function as a partition wall for preventing the fuel gas supplied to the anode side and the oxidant gas supplied to the cathode side from being mixed.

The polymer electrolyte membrane 2 is roughly classified into a fluorine-based polymer electrolyte membrane and a hydrocarbon-based polymer electrolyte membrane depending on the type of ion exchange resin that is a constituent material. In addition, since the specific description of the fluorine-based polymer electrolyte and the hydrocarbon-based polymer electrolyte is the same as the description of the polymer electrolyte, the description is omitted here. Among these, from the viewpoint of improving power generation performance such as heat resistance and chemical stability, a fluorine-based polymer electrolyte membrane is preferably used, and particularly preferably a fluorine-based polymer electrolyte composed of a perfluorocarbon sulfonic acid-based polymer. A molecular electrolyte membrane is used. Further, the hydrocarbon-based polymer electrolyte membrane has advantages in manufacturing such that the raw material is inexpensive, the manufacturing process is simple, and the material selectivity is high.

In addition, as for the ion exchange resin mentioned above, only 1 type may be used independently and 2 or more types may be used together. Moreover, it is not restricted only to the material mentioned above, Other materials may be used.

The thickness of the polymer electrolyte membrane may be appropriately determined in consideration of the characteristics of the obtained fuel cell, and is not particularly limited. The thickness of the electrolyte layer is usually about 5 to 300 μm. When the thickness of the electrolyte layer is within such a range, the balance of strength during film formation, durability during use, and output characteristics during use can be appropriately controlled.

[Microporous layer (MPL)]
The membrane electrode assembly (MEA) may have a microporous layer (MPL) between the gas diffusion electrode body and the separator, if necessary. Here, the microporous layer (MPL) is not particularly limited, but preferably has a large gas diffusion coefficient. By using such a microporous layer (MPL), the gas permeability can be further improved, and the power generation performance under dry and wet conditions can be more effectively achieved. Such a microporous layer (MPL) is not particularly limited, but can be an aggregate of carbon particles containing a water repellent if necessary. Here, the carbon particles are not particularly limited, and conventionally known materials such as carbon black, graphite (including granular graphite), expanded graphite and the like can be appropriately employed. Among them, carbon black such as oil furnace black, channel black, lamp black, thermal black, acetylene black and the like can be preferably used because of excellent electron conductivity and a large specific surface area. As such carbon particles, commercially available products can be used, such as Vulcan XC-72, Vulcan P, Black Pearls 880, Black Pearls 1100, Black Pearls 1300, Black Pearls 2000, Regal 400, Lion Corporation Examples include black EC, oil furnace black such as # 3150 and # 3250 manufactured by Mitsubishi Chemical Corporation, and acetylene black such as Denka Black manufactured by Denki Kagaku Kogyo. In addition to carbon black, artificial graphite or carbon obtained from organic compounds such as natural graphite, pitch, coke, polyacrylonitrile, phenol resin, furan resin may be used. Moreover, in order to improve corrosion resistance etc., you may process the said carbon particle, such as a graphitization process. In this case, the above materials may be used alone or in the form of a mixture of two or more.

The particle size of the carbon particles is preferably about 10 to 100 nm. As a result, the gas diffusion coefficient is improved, high drainage due to capillary force is obtained, and the contact property with the catalyst layer can be improved. The shape of the carbon particles is not particularly limited, and may take any structure such as a spherical shape, a rod shape, a needle shape, a plate shape, a column shape, an indefinite shape, a flake shape, and a spindle shape. The “particle diameter of the carbon particles” is an average secondary particle diameter of the carbon particles. Here, the measurement of the average secondary particle diameter of the carbon particles is performed by using observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The value calculated as the average value of the diameters shall be adopted.

The fine porous layer (MPL) preferably contains a water repellent for the purpose of further improving water repellency and preventing flooding. The water repellent is not particularly limited, but fluorine-based high repellents such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyhexafluoropropylene, and tetrafluoroethylene-hexafluoropropylene copolymer (FEP). Examples thereof include molecular materials, thermoplastic resins such as polyethylene and polypropylene. Of these, fluorine-based polymer materials are preferably used because of their excellent water repellency and corrosion resistance during electrode reaction. In the microporous layer (MPL), the mixing ratio of the carbon particles to the water repellent may not be as good as the water repellent as expected when there are too many carbon particles. Conductivity may not be obtained. Considering these, the mixing ratio of the carbon particles and the water repellent in the microporous layer (MPL) is preferably about 90:10 to 40:60 in terms of weight ratio.

In the fine porous layer (MPL), carbon particles may be bound by a binder. Examples of the binder that can be used here include fluorine-based polymer materials such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyhexafluoropropylene, and tetrafluoroethylene-hexafluoropropylene copolymer (FEP). And thermosetting resins such as phenol resin, melamine resin and polyamide resin, and thermoplastic resins such as polypropylene and polyethylene. Note that the above-described water repellent and binder partially overlap. Therefore, a binder having water repellency is preferably used. Among these, fluorine-based polymer materials are preferably used because of their excellent water repellency and corrosion resistance during electrode reaction, and polytetrafluoroethylene (PTFE) is particularly preferable. By using a binder having water repellency, water repellency is imparted to the pores (between carbon particles) in the microporous layer (MPL), and water drainage can be improved. In addition, these binders may be used individually by 1 type, or may be used together 2 or more types. Moreover, polymers other than these may be used.

What is necessary is just to adjust suitably content of the binder in a microporous layer (MPL) so that the void structure in a microporous layer (MPL) may become a desired characteristic. Specifically, the binder content is preferably 5 to 60% by weight, more preferably 10 to 50% by weight, and still more preferably 12 to 40% by weight with respect to the total weight of the microporous layer (MPL). A range is preferred. If the blending ratio of the binder is 5% by weight or more, the particles can be bonded well, and if it is 60% by weight or less, an increase in the electrical resistance of the microporous layer (MPL) can be prevented.

The thickness of the microporous layer (MPL) is not particularly limited, and may be appropriately determined in consideration of the characteristics of the gas diffusion electrode body. The thickness of the microporous layer (MPL) is preferably 3 to 500 μm, more preferably 5 to 300 μm, still more preferably 10 to 150 μm, and particularly preferably 20 to 100 μm. Within such a range, the balance between mechanical strength and permeability such as gas and water can be appropriately controlled.

[Gas diffusion layer substrate]
The membrane electrode assembly (MEA) may have a gas diffusion layer base material between the gas diffusion electrode body and the separator, if necessary. In addition, when a gas diffusion layer base material and a microporous layer (MPL) are arrange | positioned between a gas diffusion electrode body and a separator, these order is not restrict | limited in particular. Preferably, a gas diffusion layer base material is disposed on the separator side, and a microporous layer (MPL) is disposed on the gas diffusion electrode body side.

The gas diffusion layer base material is not particularly limited, and known materials can be used in the same manner. For example, carbon paper, carbon cloth such as carbon paper, carbon-made woven fabric, paper-like paper body, felt, non-woven sheet-like material having conductivity and porosity; and metal mesh, expanded metal, etching The thing which uses a plate as a base material etc. are mentioned. The thickness of the substrate is not particularly limited and may be appropriately determined in consideration of desired characteristics, but may be about 30 to 500 μm. With such a thickness, sufficient mechanical strength and permeability such as gas and water can be secured. In addition, the gas diffusion layer base material may contain a water repellent for the purpose of further improving water repellency and preventing a flooding phenomenon or the like. The water repellent is not particularly limited, but fluorine-based such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyhexafluoropropylene, and tetrafluoroethylene-hexafluoropropylene copolymer (FEP). Examples thereof include polymer materials, polypropylene, and polyethylene. Here, the water repellent treatment method is not particularly limited, and a general water repellent treatment method may be used. For example, after immersing the gas diffusion layer base material in a water repellent dispersion, a method of heating and drying in an oven or the like can be used. In particular, a sheet body in which a porous body of polytetrafluoroethylene (PTFE) is impregnated with carbon particles and sintered can be used. By using the sheet body, the manufacturing process is simplified, and handling and assembly when the members of the fuel cell are stacked are facilitated. Further, depending on the drainage characteristics of MEA and the surface properties of the separator, the gas diffusion layer substrate may not be subjected to water repellent treatment or may be subjected to hydrophilic treatment.

Further, a combination of a gas diffusion layer base material and a fine porous layer may be used. At this time, the method for forming the fine porous layer on the gas diffusion layer substrate is not particularly limited. For example, the ink is prepared by dispersing carbon particles, a water repellent, and the like in a solvent such as water, alcohol solvents such as perfluorobenzene, dichloropentafluoropropane, methanol, and ethanol. Next, the ink may be applied on a gas diffusion layer substrate and dried, or the ink may be dried and pulverized to form a powder, which is then applied onto the gas diffusion layer. Thereafter, heat treatment is preferably performed at about 250 to 400 ° C. using a muffle furnace or a firing furnace. Or you may use the commercial item by which the fine porous layer was previously formed on the gas diffusion layer base material.

[Production method of membrane electrode assembly]
A method for producing the membrane electrode assembly is not particularly limited, and a conventionally known method can be used. For example, a method in which two gas diffusion electrode bodies are arranged on an electrolyte membrane and bonded can be used. The joining conditions are not particularly limited, and may be appropriately adjusted depending on the type of electrolyte (perfluorosulfonic acid type or hydrocarbon type) in the electrolyte membrane or the gas diffusion electrode.

[Separator]
The separator has a function of electrically connecting cells in series when a plurality of single cells of a fuel cell such as a polymer electrolyte fuel cell are connected in series to form a fuel cell stack. The separator also functions as a partition that separates the fuel gas, the oxidant gas, and the coolant from each other. In order to secure these flow paths, as described above, each of the separators is preferably provided with a gas flow path and a cooling flow path. As a material constituting the separator, conventionally known materials such as dense carbon graphite, carbon such as a carbon plate, and metal such as stainless steel can be appropriately employed without limitation. The thickness and size of the separator and the shape and size of each flow path provided are not particularly limited, and can be appropriately determined in consideration of the desired output characteristics of the obtained fuel cell.

The type of the fuel cell is not particularly limited. In the above description, the polymer electrolyte fuel cell (PEFC) has been described as an example. In addition, an alkaline fuel cell, a direct methanol fuel is used. Examples include batteries and micro fuel cells. Among them, a polymer electrolyte fuel cell is preferable because it is small in size, and can achieve high density and high output. The fuel cell is useful as a stationary power source in addition to a power source for a moving body such as a vehicle in which a mounting space is limited. However, the fuel cell is particularly useful for an automobile application in which system start / stop and output fluctuation frequently occur. It can be particularly preferably used.

The manufacturing method of the fuel cell is not particularly limited, and conventionally known knowledge can be appropriately referred to in the field of the fuel cell.

The fuel used when operating the fuel cell is not particularly limited. For example, hydrogen, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, secondary butanol, tertiary butanol, dimethyl ether, diethyl ether, ethylene glycol, diethylene glycol and the like can be used. Of these, hydrogen and methanol are preferably used in that high output is possible.

Furthermore, a fuel cell stack having a structure in which a plurality of membrane electrode assemblies are stacked and connected in series via a separator may be formed so that the fuel cell can exhibit a desired voltage. The shape of the fuel cell is not particularly limited, and may be determined as appropriate so that desired battery characteristics such as voltage can be obtained.

The PEFC and membrane electrode assembly described above use a gas diffusion electrode body that is excellent in material transportability (for example, gas diffusibility), catalytic activity, and conductivity. Therefore, the PEFC and the membrane electrode assembly exhibit excellent power generation performance.

The effect of the present invention will be described using the following examples and comparative examples. However, the technical scope of the present invention is not limited only to the following examples. In the examples, “parts” or “%” is used, but “parts by weight” or “% by weight” is indicated unless otherwise specified. Unless otherwise specified, each operation is performed at room temperature (25 ° C.).

Example 1
(Production of gas diffusion electrode body)
Add 25.6 g of conductive carbon (acetylene black AB-6, average primary particle size = 50 nm, manufactured by Denki Kagaku Kogyo Co., Ltd.), 1.4 g of dispersion aid (Kao Corporation, trade name: Emulgen), and 120 g of water. It was. This mixture was stirred with a propeller stirrer for 10 minutes to obtain a paste-like ink. The paste-like ink was subjected to a dispersion treatment with an ultrasonic disperser for 60 minutes to prepare a carbon ink. By the ultrasonic dispersion treatment, the carbon ink has a low viscosity, and has properties suitable for the porous body impregnation in the next step. When this carbon ink was measured with a laser diffraction / scattering particle size distribution analyzer (Microtrap MT3000), a dispersion having a median value (average secondary particle diameter of conductive carbon) of 2.2 μm was obtained.

An 80 cm × 80 cm glass porous body (nonconductive non-woven fabric) (thickness = 160 μm) was immersed in the carbon ink prepared above for 1 minute, and then pulled up. As the porous glass used, manufactured by Nippon Sheet Glass Co., Ltd., trade name: TGP-015A (thickness = 160 μm (when loaded with 19.6 kPa), pore diameter = 7.8 μm, basis weight = 22 g / m ² , Density = 0.136 g / m ³ ) was used. The glass porous body was hit with a brush to remove bubbles adhering to the surface and then dried at 120 ° C. for 8 minutes to hold a porous composite (1) in which conductive carbon (carbon particles) was held in the pores. )

Next, water was added to platinum-supporting carbon as an electrode catalyst at a weight ratio of 160 to 1, and ultrasonic dispersion was performed for 30 minutes. This was mixed for 5 minutes with a kneading apparatus (trade name: Nertaro, manufactured by Shinky Co., Ltd.) to obtain a mixed dispersion of electrode catalyst / water. As the platinum-supporting carbon, TEC10E50E manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. (supporting platinum particles having an average primary particle size of 4 nm on Ketjenblack, which is conductive carbon particles having an average primary particle size of 30 nm, platinum support amount = 50% by weight) used. When this electrocatalyst / water mixed dispersion was measured with a laser diffraction / scattering particle size distribution analyzer (Microtrap MT3000), the median value of the electrocatalyst / water mixed dispersion (average secondary particle diameter of the electrode catalyst) was It was 4.4 μm.

The porous body composite (1) prepared in the previous step was immersed in the mixed electrode catalyst / water dispersion prepared above for 1 minute. After the immersion, the porous composite (1) is pulled up from the mixed dispersion and dried (heat treatment) at 120 ° C. for 10 minutes to hold the conductive carbon (carbon particles) and the electrode catalyst in the pores. Body (2) (platinum supported amount = 0.28 mg / cm ² ) was obtained.

Electrolyte solution DE2020 (manufactured by DuPont, Nafion (registered trademark) dispersion, solid content concentration = 21 wt%) was diluted with 100 g of ethanol to prepare an electrolyte solution (solid content concentration = 2 wt%). The porous body composite (2) produced in the previous step is immersed in this electrolyte solution, and vacuum suction is continuously performed for 3 minutes to remove internal bubbles, and the electrolyte solution is sufficiently filled with the porous body composite (2 ). Further, this porous composite (2) was dried (heat treatment) at 120 ° C. for 10 minutes to obtain a gas diffusion electrode body (platinum supported amount = 0.28 mg / cm ² ). The contents of the conductive carbon, electrode catalyst and electrolyte in the gas diffusion electrode body thus obtained were 5.68% by volume, 7.40% by volume and 5.29% by volume, respectively. The gas diffusion electrode body contained 0.7 parts by weight of the polymer electrolyte with respect to 100 parts by weight of the electrode catalyst. The thickness of the gas diffusion electrode body was 230 μm.

(Production of small power generation cells)
Two gas diffusion electrode bodies produced as described above were cut into a size of 2 cm × 5 cm to obtain a cathode gas diffusion electrode body and an anode gas diffusion electrode body having an active area of 2 cm × 5 cm. These were arranged on both sides of the electrolyte membrane to produce a MEA (1) of a small power generation cell. As the electrolyte membrane, an electrolyte membrane (manufactured by DuPont, Nafion (registered trademark) NR211, thickness: 25 μm) was used.

The MEA (1) thus obtained was subjected to power generation test evaluation under the following conditions. Under the following conditions, the load current density was swept in the range of 0 to 1.9 A / cm ² , an IV curve was obtained, and the voltage value at 0.5 A / cm ² was measured. The power generation performance was shown.

Comparative Example 1
(Production of catalyst layer)
Platinum-supported carbon, water, and NPA (1-propanol) were put in a sand grinder (manufactured by Imex) and pulverized, and an electrolyte solution was further added to prepare a catalyst ink. The obtained catalyst ink had a composition of 4.5% by weight of platinum-supported carbon, 16.5% by weight of electrolyte, 31.5% by weight of water, and 47.5% by weight of NPA (1-propanol). Further, as the platinum-supported carbon, TEC10E50E manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. (Ketjenblack, which is a conductive carbon particle having an average primary particle size of 30 nm, supports platinum particles having an average primary particle size of 4 nm, platinum support amount = 50% by weight) )It was used. Further, as an electrolyte solution, an electrolyte solution DE2020 (manufactured by DuPont, Nafion (registered trademark) dispersion, solid content concentration = 21 wt%) was prepared by diluting 10 g with 100 g of ethanol. The solid content weight ratio of the electrolyte and the electrode catalyst (platinum and carbon) in the catalyst ink was 1.5: 2.

The obtained catalyst ink was spray-coated on one side of a polytetrafluoroethylene sheet and dried at 130 ° C. for 15 minutes to produce anode and cathode catalyst layers. The coating layer on the polytetrafluoroethylene sheet was adjusted so that the Pt amount was 0.32 mg / cm ² .

(Production of small power generation cells)
Gaskets (manufactured by Teijin Dupont, Teonex, thickness: 25 μm (adhesive layer: 10 μm)) were arranged around both surfaces of the electrolyte membrane. As the electrolyte membrane, an electrolyte membrane (manufactured by DuPont, Nafion (registered trademark) NR211, thickness: 25 μm) was used. Next, the anode catalyst layer (fuel cell electrode) and the cathode catalyst layer (fuel cell electrode) prepared above are formed on the exposed portion of the electrolyte membrane (working area: 25 cm ² (5.0 cm × 5.0 cm)). The formed PTFE (polytetrafluoroethylene) sheets were respectively arranged to form a laminate. After applying a pressure of 0.8 MPa to this laminate, the electrolyte membrane and each fuel cell electrode were brought into close contact with each other, heated at 150 ° C. for 10 minutes, and after joining the electrolyte membrane and each fuel cell electrode, The PTFE sheet was peeled to produce a CCM. Using this CCM, a small power generation cell MEA (2) was produced.

For the MEA (2) thus obtained and the MEA (1) obtained in Example 1, the power generation test was evaluated under the following conditions.

For each MEA, after being sandwiched between gas diffusion layers (manufactured by SGL GROUP, 25BC) and incorporated into an evaluation cell, the cell voltage (Cell voltage) at a current density of 0.3 A / cm ² under the following conditions: And resistance were measured. As a result, the cell voltages of the MEA (1) and (2) are 0.64 V and 0.66 V, respectively, and the MEA (1) of the present invention exhibits power generation performance equivalent to that of the conventional MEA (2). I understood.

Furthermore, this application is based on Japanese Patent Application No. 2013-093673 filed on April 26, 2013, the disclosure of which is incorporated by reference in its entirety.

Claims

A gas diffusion electrode body in which a polymer electrolyte and an electrode catalyst are held in a non-conductive nonwoven fabric or woven fabric.
The gas diffusion electrode body according to claim 1, wherein the non-conductive nonwoven fabric or woven fabric is formed of at least one selected from the group consisting of glass, polymer resin fibers, and cellulose.
The gas diffusion electrode body according to claim 1 or 2, wherein the pore diameter of the non-conductive nonwoven fabric or woven fabric is 1.5 to 100 times the average particle diameter of the electrode catalyst.
The gas diffusion electrode body according to any one of claims 1 to 3, wherein the non-conductive nonwoven fabric or woven fabric has a pore diameter of 100 µm or less.
The non-conductive nonwoven fabric or woven fabric is immersed in a slurry containing a polymer electrolyte, an electrode catalyst, and a solvent; and the non-conductive nonwoven fabric or woven fabric after the immersion is heat-treated at a temperature of 200 ° C. or lower. The manufacturing method of the gas diffusion electrode body of any one of these.
A fuel cell membrane electrode assembly having the gas diffusion electrode body according to any one of claims 1 to 4.
A fuel cell comprising the membrane electrode assembly for a fuel cell according to claim 6.