JP2006059540A - Sol state proton conductive electrolyte and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sol state proton conductive electrolyte and a fuel cell using it, which are inexpensive, capable of supplement, has small contact resistance between the electrolyte/catalyst layer, and small possibility of an electronic short circuit between electrodes and outflow of a reactant gas. <P>SOLUTION: The sol state proton conductive electrolyte contains water and a water soluble polymer electrolyte, and its viscosity is 0.1 to 100 Pas. The fuel cell 10 is provided with a frame shaped stopper 12, a porous material 14 retained in the frame of the stopper 12, a pair of diffusion layers 16, 16 joined to both faces of the stopper 12, catalyst layers 18, 18 formed on inner surface sides of the respective diffusion layers 16, 16, and the sol state proton conductive electrolyte 20 filled in a space surrounded by the stopper 12 and the diffusion layers 16, 16. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sol proton conductive electrolyte and a fuel cell, and more specifically, a fuel cell, a water electrolysis device, a hydrohalic acid electrolysis device, a salt electrolysis device, an oxygen and / or hydrogen concentrator, a humidity sensor, a gas sensor, and the like. The present invention relates to a sol-like proton conductive electrolyte used as an electrolyte of various electrochemical devices, and a fuel cell using the same.

  A solid polymer fuel cell has a membrane electrode assembly (MEA) in which electrodes are bonded to both surfaces of a solid polymer electrolyte membrane as a basic unit. In the polymer electrolyte fuel cell, the electrode generally has a two-layer structure of a diffusion layer and a catalyst layer. The diffusion layer is for supplying reaction gas and electrons to the catalyst layer, and carbon paper, carbon cloth, or the like is used. The catalyst layer is a part that becomes a reaction field for electrode reaction, and generally comprises a composite of carbon carrying an electrode catalyst such as platinum and a solid polymer electrolyte.

The electrolyte membrane or the catalyst layer electrolyte that constitutes such an MEA includes a perfluorinated electrolyte excellent in oxidation resistance (an electrolyte that does not contain a C—H bond in the polymer chain. For example, Nafion (registered trademark, DuPont). ), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.), Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.), etc.) are generally used.
In addition, perfluorinated electrolytes are excellent in oxidation resistance but are generally very expensive. Therefore, in order to reduce the cost of the solid polymer fuel cell, a hydrocarbon electrolyte (an electrolyte that includes a C—H bond and does not include a C—F bond in a polymer chain) or a partial fluorine electrolyte The use of (electrolytes containing both C—H bonds and C—F bonds in the polymer chain) has also been studied.

  Furthermore, since conventional solid polymer electrolytes have low heat resistance and require water to exhibit proton conductivity, proton conductivity decreases under high temperature and low humidification conditions. For this reason, various proposals have conventionally been made regarding electrolytes exhibiting high proton conductivity even under high temperature and low humidification conditions.

For example, Patent Documents 1 to 3 include:
(1) a proton conductor composed of a composite of silica gel doped with phosphoric acid and a styrene-ethylene-butene-styrene copolymer (SEBS) (Patent Document 1),
(2) a proton conductor composed of a composite of silica gel doped with phosphoric acid and sulfonated polyisoprene (Patent Document 2), and
(3) Proton conductor comprising a composite of phosphoric acid-doped silica gel and a sulfonated styrene-isoprene-styrene block copolymer (Patent Document 3)
Is disclosed.
In the same document, when silica gel doped with phosphoric acid is used, proton conduction occurs around the —OH group bonded to the surface of silicon oxide, so that there is little decrease in proton conductivity even in a dry atmosphere, and It is described that high proton conductivity is exhibited when SEBS, a polymer having a sulfonic acid group, or the like is interposed on the surface of silica gel doped with phosphoric acid.

Further, Patent Document 4 impregnates a porous sheet made of a ceramic fiber non-woven fabric with a sol solution containing ethyl silicate (Si (OC ₂ H ₅ ) ₄ ) and trimethyl phosphate (PO (OCH ₃ ) ₃ ). Electrolyte gel membrane obtained by making it gelate is disclosed. In the same document, when a method of sandwiching both surfaces of a porous sheet with a joined body composed of a catalyst layer and a diffusion layer and impregnating the porous sheet with a sol solution and gelling in this state, the occurrence of cracks is conventionally observed. The point which can be suppressed few is described.

JP-A-8-249923 JP-A-10-069817 Japanese Patent Laid-Open No. 11-203936 Japanese Patent Laid-Open No. 2002-075406

  Since the hydrocarbon-based solid polymer electrolyte is inexpensive, using it as an electrolyte membrane can reduce the cost of the fuel cell system. However, hydrocarbon electrolytes have a problem that they are easily deteriorated by peroxide radicals and have low durability. When the solid polymer electrolyte membrane becomes thin due to deterioration, an electronic short circuit occurs due to the proximity of the diffusion layer or the catalyst layer, or the reaction gas flows out to the opposite electrode, which causes a decrease in power generation efficiency. This also applies to a proton conductor made of a composite of an inorganic proton conductor such as silica gel doped with phosphoric acid and a hydrocarbon polymer compound.

  On the other hand, fluorine-based solid polymer electrolytes are less deteriorated by peroxide radicals and have excellent durability. However, the fluorine-based electrolyte has a problem of high cost. The inventors of the present application have also found that when the operating conditions of the fuel cell become severe, even a fluorine-based electrolyte may be deteriorated by peroxide radicals.

In many cases, gel electrolyte membranes composed of a composite of a porous sheet and an inorganic proton conductor gel tend to cause cracks during production. When a crack occurs in the gel electrolyte membrane, the reaction gas flows out to the opposite electrode, which causes a decrease in power generation efficiency.
Furthermore, the conventional solid polymer fuel cell has a problem that the contact resistance at the interface between the solid polymer electrolyte membrane and the catalyst layer is relatively large.

  The problems to be solved by the present invention are low-cost, replenishable, low contact resistance between the electrolyte / catalyst layers, and sol-like proton conductivity with low risk of electronic short-circuit between electrodes or outflow of reaction gas An electrolyte and a fuel cell using the same are provided.

  In order to solve the above-described problems, the sol-like proton conductive electrolyte according to the present invention includes water and a water-soluble polymer electrolyte, and its viscosity is 0.1 to 100 Pa · s. In this case, the water content is preferably 20 to 95 wt%.

  Further, the fuel cell according to the present invention includes a frame-shaped stopper, a porous body held in the frame of the stopper, a pair of diffusion layers bonded to both surfaces of the stopper, and an inner surface of each diffusion layer And a sol-like proton conductive electrolyte according to the present invention filled in a space surrounded by the stopper and the diffusion layer. In this case, it is preferable that the stopper includes an injection hole for filling the space with the sol-like proton conductive electrolyte.

  Since the sol-like proton conductive electrolyte can use a hydrocarbon-based electrolyte as the water-soluble polymer electrolyte, it is relatively inexpensive. Further, since the sol proton conductive electrolyte has fluidity, it can be easily replenished. Therefore, in a fuel cell using this, even if part of the sol-like proton conductive electrolyte is deteriorated by peroxide radicals and flows out of the system, high output can be maintained for a long time by replenishment. In addition, since the gap between the electrodes is always filled with the sol-like proton conductive electrolyte, the contact resistance can be reduced, and the fastening pressure is reduced and the possibility of an electronic short circuit between the electrodes and the outflow of the reaction gas is reduced due to the porous body. .

Hereinafter, an embodiment of the present invention will be described in detail. The sol-like proton conductive electrolyte according to the present invention comprises water and a water-soluble polymer electrolyte.
Here, the “water-soluble polymer electrolyte” refers to one that becomes a uniform sol when mixed with water. The water-soluble polyelectrolyte is a hydrocarbon electrolyte that contains a C—H bond in the polymer chain and does not contain a C—F bond, and a fluorine-based electrolyte that contains a C—F bond in the polymer chain. There may be. The water-soluble polymer electrolyte may be a partially fluorinated electrolyte containing both C—H bonds and C—F bonds in the polymer chain, or may contain C—F bonds in the polymer chain. In addition, a perfluorinated electrolyte that does not include a C—H bond may be used.

Further, the fluorine-based electrolyte includes a fluorocarbon structure (—CF ₂ —, —CFCl—), a chlorocarbon structure (—CCl ₂ —), and other structures (for example, —O—, —S—, —C ( ═O) —, —N (R) —, etc. provided that “R” may be an alkyl group). Further, the molecular structure of the water-soluble polymer electrolyte is not particularly limited, and may be either linear or branched, or may have a cyclic structure.

  Further, the type of acid group bonded to the water-soluble polymer electrolyte is not particularly limited. Preferred examples of the acid group include a sulfonic acid group, a carboxylic acid group, a phosphonic acid group, and a sulfonimide group. The water-soluble polymer electrolyte may contain only one of these acid groups, or may contain two or more. Furthermore, these acid groups may be directly bonded to the linear polymer compound, or may be bonded to either the main chain or the side chain of the branched polymer compound.

Specific examples of the water-soluble polymer electrolyte include the following.
The first specific example of the water-soluble polymer electrolyte is a kind of hydrocarbon electrolyte, and has a molecular structure represented by the following formula (1). In the water-soluble polymer electrolyte represented by the formula (1), m / (m + n) is preferably 0.2 or more and 1 or less in order to obtain a sol-shaped electrolyte. When m / (m + n) is less than 0.2, it becomes hardly soluble and a uniform sol cannot be obtained.
In addition, each of the functional groups A and R _{1 to} R ₃ may contain only one type of functional group, or may contain two or more types.

A second specific example of the water-soluble polymer electrolyte is a kind of hydrocarbon-based electrolyte, and has a molecular structure represented by the following formula (2). In the water-soluble polymer electrolyte represented by the formula (2), m / (m + n) is preferably 0.2 or more and 1 or less in order to obtain a sol-shaped electrolyte. When m / (m + n) is less than 0.2, it becomes hardly soluble and a uniform sol cannot be obtained.
In addition, each of the functional groups A and R ₁ may contain only one type of functional group, or may contain two or more types.

The third specific example of the water-soluble polymer electrolyte is a kind of fluorine-based electrolyte, and has a molecular structure represented by the following formula (3). In the water-soluble polymer electrolyte represented by the formula (3), m / (m + n) is preferably 0.2 or more and 1 or less in order to obtain a sol-like electrolyte. When m / (m + n) is less than 0.2, it becomes hardly soluble and a uniform sol cannot be obtained.
In addition, each of the functional groups A and R _{1 to} R ₃ may contain only one type of functional group, or may contain two or more types.

The fourth specific example of the water-soluble polymer electrolyte is a kind of fluorine-based electrolyte, and has a molecular structure represented by the following formula (4). In the water-soluble polymer electrolyte represented by the formula (4), m / (m + n) is preferably 0.2 or more and 1 or less in order to obtain a sol-like electrolyte. When m / (m + n) is less than 0.2, it becomes hardly soluble and a uniform sol cannot be obtained.
In addition, each of the functional groups A and R ₁ may contain only one type of functional group, or may contain two or more types.

A fifth specific example of the water-soluble polymer electrolyte is a kind of fluorine-based electrolyte, and has a molecular structure represented by the following formula (5). In the water-soluble polymer electrolyte represented by the formula (5), m / (m + n) is preferably from 0.5 to 1 in order to obtain a sol-like electrolyte. When m / (m + n) is less than 0.5, it becomes hardly soluble and a uniform sol cannot be obtained.
In addition, the functional group A may include only one type of functional group, or may include two or more types.

  The viscosity of the sol proton conductive electrolyte is preferably 0.1 Pa · s or more. If the viscosity is less than 0.1 Pa · s, the sol proton conductive electrolyte may flow out through the diffusion layer when used as an electrolyte for a fuel cell. In general, the higher the viscosity of the sol proton conductive electrolyte, the more the outflow of the sol proton conductive electrolyte can be suppressed. However, if the viscosity is too high, it becomes difficult to replenish the sol-like proton conductive electrolyte. Therefore, the viscosity is preferably 100 Pa · s or less.

  The water content of the sol proton conductive electrolyte is preferably 20 wt% or more. When the water content is less than 20 wt%, the viscosity increases and it becomes difficult to replenish the sol proton conductive electrolyte. In general, the higher the moisture content, the lower the viscosity. Moreover, since the movement of protons is performed through water, the higher the water content, the higher the proton conductivity. However, if the water content becomes too high, the sol proton conductive electrolyte may flow out. Therefore, the water content is preferably 95 wt% or less.

  Next, a method for producing a sol proton conductive electrolyte according to the present invention will be described. The various water-soluble polymer electrolytes described above can be obtained by polymerizing or copolymerizing a commercially available monomer or a monomer obtained by adding an appropriate functional group conversion thereto using a known method.

For example, the water-soluble polymer electrolyte represented by the formula (1) has a general formula: H ₂ C═C (R ₁ ) (A ′) (where A ′ is —COOH, —SO ₃ H, —PO ₃ H). ₂ or a derivative thereof) and a second monomer represented by the general formula: H ₂ C═C (R ₂ ) (R ₃ ) are mixed at a predetermined ratio. , Obtained by polymerization or copolymerization.
In this case, the polymerization method is not particularly limited, and known methods such as thermal polymerization, photopolymerization, and radiation polymerization can be used. Further, when the functional group A ′ provided in the first monomer is a derivative of an acid group (for example, a halide of an acid group, an alkali salt, etc.), after copolymerizing the first monomer and the second monomer The functional group A ′ is converted into an acid group (proton exchange). As the conversion method, known methods such as acid treatment, saponification + acid treatment, and the like can be used.

For example, the water-soluble polymer electrolyte represented by the formula (2) has a general formula: H ₂ C═C (H) (C ₆ H ₄ A ′) (where A ′ is —COOH, —SO ₃ H). , —PO ₃ H ₂ , or a derivative thereof) and a second monomer represented by the general formula: H ₂ C═C (H) (C ₆ H ₄ R ₁ ) Are mixed at a predetermined ratio and polymerized or copolymerized.
In addition, the point which can use various methods as a superposition | polymerization or a copolymerization method, and the point which performs proton exchange as needed after superposition | polymerization or a copolymerization are the same as that of a 1st example.

Further, for example, the water-soluble polymer electrolyte represented by the formula (3) has a general formula: F ₂ C═C (R ₁ ) (A ′) (where A ′ is —COOH, —SO ₃ H, —PO ₃ H ₂ or a derivative thereof) and a second monomer represented by the general formula: F ₂ C═C (R ₂ ) (R ₃ ) at a predetermined ratio. It is obtained by mixing and polymerizing or copolymerizing.
In addition, the point which can use various methods as a polymerization method, and the point which performs proton exchange as needed after superposition | polymerization or copolymerization are the same as that of a 1st specific example.

For example, the water-soluble polymer electrolyte represented by the formula (4) has a general formula: F ₂ C═C (F) (C ₆ H ₄ A ′) (where A ′ is —COOH, —SO ₃ H). , —PO ₃ H ₂ or a derivative thereof) and a second monomer represented by the general formula: F ₂ C═C (F) (C ₆ H ₄ R ₁ ) Are mixed at a predetermined ratio and polymerized or copolymerized.
In addition, the point which can use various methods as a polymerization or copolymerization method, and the point which performs proton exchange as needed after superposition | polymerization are the same as that of a 2nd example.

Further, for example, the water-soluble polymer electrolyte represented by the formula (5) has a general formula: F ₂ C═C (F) (— O— [CF ₂ —C (F) (CF ₃ ) —O] _p — [ CF ₂ ] _q -A ′) (where p = 0 to 2, q = 2 to 4, A ′: —COOH, —SO ₃ H, —PO ₃ H ₂ , or derivatives thereof) a first monomer of the general formula: and a second monomer represented by F 2 _{C =} CF ₂ were mixed in a predetermined ratio, it can be obtained by polymerization or copolymerization.
In addition, the point which can use various methods as a polymerization or copolymerization method, and the point which performs proton exchange as needed after superposition | polymerization are the same as that of a 1st specific example.

  When a predetermined amount of water is added to one or two or more water-soluble polymer electrolytes thus obtained and stirred, heated, vibrated, etc., it is fluid and has a uniform sol-like proton conducting electrolyte. Is obtained.

Next, the action of the sol proton conductive electrolyte according to the present invention will be described. On the cathode side of the fuel cell, peroxide is generated as a side reaction of the electrode reaction. This peroxide is decomposed into peroxide radicals in an environment where transition metal ions (for example, Fe ²⁺ / Fe ³⁺ ) whose valence changes, and cause deterioration of the electrolyte membrane. When the electrolyte membrane becomes thinner due to deterioration, leakage of the reaction gas and electronic short circuit between the electrodes occur, thereby reducing power generation efficiency. Therefore, practically sufficient durability cannot be obtained in a polymer electrolyte fuel cell using a hydrocarbon electrolyte. Even in the case of a perfluorinated electrolyte that has been conventionally said to be excellent in oxidation resistance, sufficient durability may not be obtained if the use conditions become severe.

On the other hand, the sol proton conductive electrolyte is easy to replenish because it has fluidity. Therefore, even if the water-soluble polymer electrolyte has a low molecular weight due to peroxide radicals and flows out of the system, the gap between the electrodes can always be filled with the sol proton conductive electrolyte by replenishment. There is little risk of electronic short circuit.
In addition, since it is easy to replenish, even an electrochemical device used under severe conditions can use a hydrocarbon-based electrolyte with poor oxidation resistance and maintain high performance over a long period of time. be able to. Therefore, it is not always necessary to use an expensive fluorine-based electrolyte in order to enhance durability, and the cost of the electrochemical device can be reduced.

  Furthermore, since the sol-like proton conductive electrolyte has an appropriate viscosity, even if it is used for a fuel cell, there are few problems of electrolyte outflow as in a phosphoric acid fuel cell and an alkaline fuel cell. . Further, since the electrode is in direct contact with the fluid sol-like proton conductive electrolyte, the contact resistance can be reduced as compared with the case where a solid polymer electrolyte membrane is used.

  Next, the fuel cell according to the present invention will be described. FIG. 1 shows a schematic configuration diagram of a fuel cell according to the present invention. In FIG. 1, the fuel cell 10 includes a stopper 12, a porous body 14, diffusion layers 16 and 16, catalyst layers 18 and 18, the above-described sol-like proton conductive electrolyte 20 according to the present invention, a separator 22, and the like. It has. Although only a single cell is shown in FIG. 1, this is merely an example, and an actual fuel cell includes a plurality of single cells shown in FIG. 1 as necessary.

  The stopper 12 has a frame shape (or ring shape), and a porous body 14 is held in the frame. A pair of diffusion layers 16 and 16 are bonded to both surfaces of the stopper 12 (including chemical bonding such as thermocompression bonding and physical bonding such as simply pressing both surfaces of the stopper 12 with the diffusion layers 16 and 16). The catalyst layers 18 and 18 are formed on the inner surface sides of the diffusion layers 16 and 16, respectively. A space surrounded by the stopper 12 and the diffusion layers 16 and 16 is filled with a sol-like proton conductive electrolyte 20, and a part thereof is impregnated into the porous body 14. Furthermore, the outer surface side of each diffusion layer 16, 16 is sandwiched between separators 22 provided with gas flow paths 22a, 22a, respectively.

  The stopper 12 is for holding, storing, and replenishing the sol-like proton conductive electrolyte 20. The stopper 12 and the diffusion layers 16 and 16 are joined over the entire periphery of the stopper 12 so that leakage of the sol-like proton conductive electrolyte 20 held inside the stopper 12 can be suppressed. An injection hole 12a and an injection hole 22b are provided in the upper part of the stopper 12 and the separators 22 and 22, so that the sol electrolyte 12 is filled and replenished through the injection hole 12a and the injection hole 22b. It has become. Further, a reservoir tank 12b is provided in the middle of the injection hole 12a of the stopper 12, so that the surplus sol-like proton conductive electrolyte 20 filled from the injection hole 12a and the injection hole 22b can be temporarily stored. It has become.

  The material of the stopper 12 is not particularly limited as long as it can provide good bonding properties with the diffusion layers 16 and 16 and can hold the sol-like proton conductive electrolyte 20. Specific examples of the material of the stopper 12 include polytetrafluoroethylene, tetrafluoroethylene perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene-ethylene. A copolymer (ETFE) or the like is preferable.

  The material of the porous body 14 has such a strength that the sol-like proton conductive electrolyte 20 can be stably held and the distance between the catalyst layers 18 and 18 can be maintained almost constant when sandwiched between the separators 22 and 22. What is necessary is just to have. Specific examples of the porous body 14 include a polytetrafluoroethylene porous body, a tetrafluoroethylene perfluoroalkyl vinyl ether copolymer (PFA), a tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and a tetrafluoroethylene- An ethylene copolymer (ETFE) or the like is preferable.

The diffusion layers 16 and 16 are for supplying electrons and reaction gases to the catalyst layers 18 and 18 and are made of a porous material having electron conductivity. Specifically, carbon cloth, carbon paper, and the like are preferable as the diffusion layers 16 and 16.
In order to suppress the outflow of the sol-like proton conductive electrolyte 20 from the diffusion layers 16, 16, it is preferable to perform water repellent treatment on at least the inner surfaces of the diffusion layers 16, 16. As the water repellent treatment, specifically, a method of forming a water repellent layer by applying a paste containing water repellent powder (for example, polytetrafluoroethylene powder) and carbon powder to the inner surfaces of the diffusion layers 16 and 16. Etc. The optimum particle size, content, etc. of the water-repellent powder are selected according to the water content, viscosity, etc. of the sol-like proton conductive electrolyte 20.

  The catalyst layers 18 and 18 are portions that serve as a reaction field for electrode reaction, and include an electrode catalyst or a carrier carrying an electrode catalyst. In general, an optimum electrode catalyst is used according to the purpose of use of the fuel cell, conditions of use, and the like. Specifically, platinum, a platinum alloy, palladium, ruthenium, rhodium or the like or an alloy thereof is suitable as the electrode catalyst. As the amount of the electrode catalyst contained in the catalyst layer, an optimal amount is selected according to the use of the fuel cell, use conditions, and the like.

  The catalyst carrier is for carrying a fine electrode catalyst and simultaneously transferring electrons in the catalyst layer. Generally, carbon, activated carbon, fullerene, carbon nanophone, carbon nanotube or the like is used for the catalyst carrier. The loading amount of the electrode catalyst on the surface of the catalyst carrier is selected in accordance with the material of the electrode catalyst and the catalyst carrier, the use of the fuel cell, the use conditions, and the like.

  In the present invention, since protons are directly exchanged between the fluid sol-form proton conductive electrolyte 20 and the electrode catalyst, the catalyst layers 18 and 18 carry the electrode catalyst / or the electrode catalyst. Although it may consist only of a carrier, it may further contain an electrolyte in the catalyst layer. Further, the electrolyte in the catalyst layer may be a water-soluble material, or may be a material that is insoluble or hardly soluble in water. Specifically, as the electrolyte in the catalyst layer, the water-soluble polymer electrolyte represented by the above-described formulas (1) to (5), and in the above-described formulas (1) to (4), m / (m + n) is 0. A material with less than 2 or a material with m / (m + n) less than 0.5 in the formula (5) is suitable. The optimum amount of the electrolyte in the catalyst layer is selected according to the use of the fuel cell, the use conditions, and the like.

  Further, in order to suppress the outflow of the sol-like proton conductive electrolyte 20, it is preferable to subject the catalyst layers 18 and 18 to water repellent treatment. As the water repellent treatment, specifically, there is a method of adding water repellent powder (for example, polytetrafluoroethylene powder) to the catalyst layers 18 and 18. The optimum particle diameter, content, etc. of the water-repellent powder are selected according to the water content, viscosity, etc. of the sol-like proton conductive electrolyte 20.

  The separators 22 and 22 are for supplying the reaction gas to the diffusion layers 16 and 16 and simultaneously transferring electrons between the diffusion layers 16 and 16, and a material having electron conductivity is used. As a material of the separators 22 and 22, carbon, stainless steel, or the like is preferable.

  The fuel cell according to the present invention can be manufactured as follows. First, an electrode catalyst or a carrier carrying an electrode catalyst, and a solution (catalyst ink) containing an electrolyte in the catalyst layer and / or a water-repellent powder as necessary (appropriate substrate (for example, a polytetrafluoroethylene sheet)) The catalyst layer 18 is formed by coating on the surface. Next, this is transferred onto the surface of the diffusion layer 16 by hot pressing. Alternatively, the catalyst layer 18 may be formed directly on the surface using the diffusion layer 16 as a substrate.

  Next, the porous body 14 is inserted into the frame of the stopper 12, and the diffusion layers 16 and 16 are bonded to both surfaces of the stopper 12 so that the catalyst layer 18 is on the inside (thermocompression bonding or the like). When chemical bonding such as thermocompression bonding is performed, the conditions are not particularly limited, and optimum conditions are selected according to the materials of the stopper 12 and the diffusion layers 16 and 16. Further, both surfaces of the stopper 12 / diffusion layer 16 assembly are sandwiched between separators 22 to form a single cell, and a plurality of single cells are laminated. Furthermore, the fuel cell 10 according to the present invention can be obtained by filling the sol-like proton conductive electrolyte 20 according to the present invention through the injection hole 12 a and the injection hole 22 b while reducing the pressure inside the stopper 12.

  Next, the operation of the fuel cell 10 according to the present invention will be described. Since the fuel cell 10 according to the present invention uses the fluid sol-like proton conductive electrolyte 20 as an electrolyte, the contact resistance between the interfaces with the catalyst layers 18 and 18 can be reduced. Further, since the sol-like proton conductive electrolyte 20 has an appropriate viscosity, there is little possibility that the sol-like proton conductive electrolyte 20 flows out through the catalyst layer 18 and the diffusion layer 16. Furthermore, when the catalyst layer 18 and / or the diffusion layer 16 is subjected to water repellent treatment, the outflow of the sol-like proton conductive electrolyte 20 can be further suppressed.

  Further, when the use condition of the fuel cell 10 becomes severe, peroxide radicals are generated and react with the water-soluble polymer electrolyte contained in the sol-like proton conductive electrolyte 20. When the peroxide radical reacts with the water-soluble polymer electrolyte, the water-soluble polymer electrolyte has a low molecular weight and easily flows out of the system through the catalyst layer 18 and the diffusion layer 16. When such a reaction becomes remarkable, the electrode is eventually exposed and a leak of the reaction gas occurs.

  However, since the fuel cell 10 according to the present invention includes the injection hole 12a and the injection hole 22b, even if the sol proton conductive electrolyte 20 decreases due to deterioration, the sol proton conductive electrolyte 20 is replenished. Can do. Therefore, even when a hydrocarbon-based electrolyte having poor oxidation resistance is used as the water-soluble polymer electrolyte, high performance can be maintained over a long period by repeating replenishment. In addition, when the reservoir tank 22b that temporarily stores the sol-like proton conductive electrolyte 20 is provided, the replenishment frequency of the sol-like proton conductive electrolyte 20 can be reduced.

Example 1
Platinum-supported carbon (anode side: 30 wt% Pt / C, cathode side: 60 wt% Pt / C) in a solution (PTFE powder content: 10 wt%) in which polytetrafluoroethylene (PTFE) powder is dispersed as a water repellent powder ) Was added to prepare a catalyst ink. Note that the content of platinum-supported carbon contained in the catalyst ink was 70 wt%. This catalyst ink was applied on a PTFE sheet to produce a catalyst layer.

  Next, carbon powder was added to a solution in which PTFE powder was dispersed (content of PTFE powder: 10 wt%), and this solution was applied to the surface of a diffusion layer made of carbon cloth to form a water repellent layer. Next, the catalyst layer was transferred onto the surface of the water repellent layer using a hot press. The hot press conditions were as follows: temperature: 120 ° C., pressure: 0.5 MPa, pressurization time: 0.1 hour.

Next, a porous sheet made of PTFE having a thickness of 100 μm was inserted into the frame of the PTFE stopper, and pressed with a diffusion layer and a carbon separator from both sides of the PTFE stopper. Further, in a state where the inside of the PTFE stopper was depressurized (100 mmHg), a sol-like proton conductive electrolyte was injected from the injection hole to obtain the fuel cell shown in FIG. In this embodiment, the sol-like proton conducting _{electrolyte, - (CF 2 CFSO 3 H} ) m - (CF 2 CF 2) n - with 30 wt% aqueous solution of (m / (m + n) = 0.5) .

In the fuel cell obtained in this example, the sol proton conductive electrolyte did not leak from the diffusion layer or the junction. The fuel cell was evaluated under the conditions of cell temperature: 80 ° C., anode side dew point temperature: 75 ° C., cathode side dew point temperature: 85 ° C., back pressure: 2 ata, fuel gas: hydrogen, oxidant gas: air. However, the output voltage was 0.6 V at a current density of 0.5 mA / cm ² . Furthermore, after 10 days of continuous operation, a decrease in voltage and a decrease in sol-like proton conducting electrolyte were observed, but by adding a sol-like proton conducting electrolyte, the operation could be continued without problems. .

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the present invention.
For example, in the example described above, the reservoir tank is provided in the stopper, but it may be provided in the separator or outside the separator.

The sol-like proton conductive electrolyte according to the present invention is used in various electrochemical devices such as fuel cells, water electrolyzers, hydrohalic acid electrolyzers, salt electrolyzers, oxygen and / or hydrogen concentrators, humidity sensors, and gas sensors. It can be used as an electrolyte.
Further, the fuel cell according to the present invention can be used for an in-vehicle power source, a stationary small power generator, a cogeneration system, and the like.

1 is a schematic configuration diagram of a fuel cell according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel cell 12 Stopper 14 Porous body 16 Diffusion layer 18 Catalyst layer 20 Sol-like proton conductive electrolyte 22 Separator

Claims (7)

Including water and a water-soluble polyelectrolyte,
A sol-like proton conducting electrolyte having a viscosity of 0.1 to 100 Pa · s.   The sol-like proton conductive electrolyte according to claim 1, wherein the water content is 20 to 95 wt%. A frame-shaped stopper;
A porous body held in the frame of the stopper;
A pair of diffusion layers bonded to both sides of the stopper;
A catalyst layer formed on the inner surface side of each diffusion layer;
A fuel cell comprising the sol-like proton conductive electrolyte according to any one of claims 1 to 4, which is filled in a space surrounded by the stopper and the diffusion layer.   The fuel cell according to claim 3, wherein at least an inner surface of the diffusion layer is subjected to water repellent treatment.   The fuel cell according to claim 3, wherein the catalyst layer is subjected to a water repellent treatment.   The fuel cell according to any one of claims 3 to 5, wherein the stopper includes an injection hole for filling the space with the sol-like proton conductive electrolyte. The fuel cell according to claim 6, further comprising a reservoir tank that temporarily stores the sol-like proton conductive electrolyte filled in the space from the injection hole.

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