Gas diffusion electrode and method for producing same, polyolefin particles and method for producing same, fuel cell, metal-air cell, and salt electrolysis device

Abstract

This gas diffusion electrode includes a carbon material and a polyolefin resin represented by the following formula: -[CH2-CH(-R1-CHR2R3)]n-[CH2-CH2]m-, wherein n is the average degree of polymerization of the repeating unit [CH2-CH(-R1-CHR2R3)], m is the average degree of polymerization of the repeating unit [CH2-CH2], R1 is a linear alkylene group having 1 to 20 carbon atoms, and R2 and R3 are each hydrogen or a linear alkyl group having 1 to 20 carbon atoms, the average degree of polymerization n being 10 to 10000 and the average degree of polymerization m being 0 to 10000.

Description

Gas diffusion electrode and method for producing the same, polyolefin particles and method for producing the same, fuel cell, metal-air battery, salt electrolysis apparatus

[0001] The present invention relates to a gas diffusion electrode and a method for producing the same, polyolefin particles and a method for producing the same, a fuel cell, a metal-air battery, and a salt electrolysis apparatus. This application claims priority based on Japanese Patent Application No. 2024-226763, filed in Japan on December 23, 2024, the contents of which are incorporated herein by reference.

[0002] Conventionally, gas diffusion electrodes (GDEs) have been used in applications such as oxygen reduction cathodes and hydrogen oxidation anodes in fuel cells, oxygen reduction cathodes in metal-air batteries, and oxygen reduction cathodes in salt electrolysis devices. Gas diffusion electrodes include carbon materials, catalysts, and binders. Typically, fluoropolymers such as polytetrafluoroethylene (PTFE) are used as binders in gas diffusion electrodes.

[0003] For example, Non-Patent Document 1 describes a fuel cell that includes a gas diffusion electrode containing carbon black, a catalyst, and polytetrafluoroethylene. Non-Patent Document 1 also describes platinum and platinum alloys, and silver as catalysts. Furthermore, Patent Document 1 describes a metal complex of iron tetrapyridopolyphyllaine having a specific chemical structure as an oxygen reduction catalyst used in the positive electrode (air electrode) of fuel cells and metal-air batteries.

[0004] International Publication No. 2019 / 167407

[0005] Electrochemistry, 76(6), 418 (2008)

[0006] In recent years, regulations on the use of fluoropolymers such as polytetrafluoroethylene (PTFE) have been strengthened, particularly in Europe. Therefore, there is a demand for gas diffusion electrodes that, even without containing fluoropolymers, can achieve properties equivalent to those of fluoropolymer-containing gas diffusion electrodes when used in fuel cells, metal-air batteries, and salt electrolysis devices.

[0007] The present invention has been made in view of the above circumstances, and even when not containing a fluororesin, when used as a gas diffusion electrode of a fuel cell, a metal-air battery, or a salt electrolysis apparatus, characteristics equivalent to those of a gas diffusion electrode containing a fluororesin can be obtained. An object of the present invention is to provide a gas diffusion electrode and a method for producing the same.

[0008] Another object of the present invention is to provide polyolefin particles and a method for producing the same, which can be suitably used as a material for the gas diffusion electrode of the present invention. Another object of the present invention is to provide a fuel cell, a metal-air battery, and a salt electrolysis apparatus including the gas diffusion electrode of the present invention.

[0009] The inventors of the present invention have solved the above problems, and even when not containing a fluororesin, when used as a gas diffusion electrode of a fuel cell, a metal-air battery, or a salt electrolysis apparatus, characteristics equivalent to those of a gas diffusion electrode containing a fluororesin can be obtained. In order to realize a gas diffusion electrode, the inventors focused on the surface tension of a resin that can be used as a binder for the gas diffusion electrode and conducted intensive studies. As a result, they found that a gas diffusion electrode containing a specific polyolefin resin having a small surface tension as a binder together with a carbon material may be used.

[0010] Furthermore, the inventors of the present invention confirmed that a gas diffusion electrode containing a specific polyolefin resin as a binder is lightweight and has a high air permeability as compared with the case where polytetrafluoroethylene (PTFE) is used as a binder, and when used as a cathode for oxygen reduction of a metal-air battery, battery characteristics equivalent to those obtained when using a cathode for oxygen reduction using PTFE as a binder can be obtained, and thus the present invention was created. The present invention provides the following means.

[0011] [1] A gas diffusion electrode containing a polyolefin resin represented by the following general formula (1) and a carbon material. -[CH ２ -CH(-R １ -CHR ２ R ３ ) ｎ -[CH ２ -CH ２ ｍ - ··· (1) (In formula (1), n is a repeating unit [CH ２-CH(-R １ - CHR ２ R ３ This indicates the average degree of polymerization of the repeating unit [CH]. m represents the repeating unit [CH]. ２ -CH ２ This shows the average degree of polymerization of ]. １ R is a linear alkylene group having 1 to 20 carbon atoms. ２ and R ３ Each of these is either hydrogen or a linear alkyl group having 1 to 20 carbon atoms, and they may be the same or different. The average degree of polymerization n is 10 to 10000. n (-R １ - CHR ２ R ３ These elements may all be the same, or some or all of them may be different. The average degree of polymerization m is between 0 and 10000.

[0012] In this specification, when a numerical range is indicated by "A to B", unless otherwise specified, it refers to a range between value A and value B, with value A as the lower limit and value B as the upper limit.

[0013] [2] R in general formula (1) １ However, it is a methylene group, R ２ and R ３ The gas diffusion electrode according to [1], wherein the methyl group is present. [3] The gas diffusion electrode according to [1], further comprising a catalyst. [4] The gas diffusion electrode according to [3], wherein the catalyst comprises a metal complex of iron tetrapyridopolyphylazine represented by the following formula (4).

[0014]

[0015] [5] A method for manufacturing a gas diffusion electrode, comprising: a dissolution step of dissolving a polyolefin resin represented by the following general formula (1) in a solvent to obtain a resin solution; a mixing step of mixing the resin solution, a carbon material, and a catalyst to obtain a slurry; and a molding step of applying the slurry, drying it, and rolling it to form the electrode. - [CH ２ -CH(-R １ - CHR ２ R ３ ) ｎ - [CH ２ -CH ２] ｍ - ... (1) (In equation (1), n ​​is the repeating unit [CH ２ -CH(-R １ - CHR ２ R ３ This indicates the average degree of polymerization of the repeating unit [CH]. m represents the repeating unit [CH]. ２ -CH ２ This shows the average degree of polymerization of ]. １ R is a linear alkylene group having 1 to 20 carbon atoms. ２ and R ３ Each of these is either hydrogen or a linear alkyl group having 1 to 20 carbon atoms, and they may be the same or different. The average degree of polymerization n is 10 to 10000. n (-R １ - CHR ２ R ３ These elements may all be the same, or some or all of them may be different. The average degree of polymerization m is between 0 and 10000.

[0016] [6] Polyolefin particles containing a polyolefin resin represented by the following general formula (1), wherein the average particle diameter measured by scanning electron microscopy is in the range of 10 nm to 1000 nm. - [CH ２ -CH(-R １ - CHR ２ R ３ ) ｎ - [CH ２ -CH ２ ] ｍ - ... (1) (In equation (1), n ​​is the repeating unit [CH ２ -CH(-R １ - CHR ２ R ３ This indicates the average degree of polymerization of the repeating unit [CH]. m represents the repeating unit [CH]. ２ -CH ２ This shows the average degree of polymerization of ]. １ R is a linear alkylene group having 1 to 20 carbon atoms. ２ and R ３ Each of these is either hydrogen or a linear alkyl group having 1 to 20 carbon atoms, and they may be the same or different. The average degree of polymerization n is 10 to 10000. n (-R １ - CHR ２ R ３These elements may all be the same, or some or all of them may be different. The average degree of polymerization m is between 0 and 10000.

[0017] [7] A method for producing polyolefin particles, comprising: a dissolution step of dissolving a polyolefin resin represented by the following general formula (1) in a solvent to obtain a resin solution; and a precipitation step of forming polyolefin particles by dropping the resin solution into a poor solvent and stirring, wherein the average particle diameter measured by observation with a scanning electron microscope is in the range of 10 nm to 1000 nm. - [CH ２ -CH(-R １ - CHR ２ R ３ ) ｎ - [CH ２ -CH ２ ] ｍ - ... (1) (In equation (1), n ​​is the repeating unit [CH ２ -CH(-R １ - CHR ２ R ３ This indicates the average degree of polymerization of the repeating unit [CH]. m represents the repeating unit [CH]. ２ -CH ２ This shows the average degree of polymerization of ]. １ R is a linear alkylene group having 1 to 20 carbon atoms. ２ and R ３ Each of these is either hydrogen or a linear alkyl group having 1 to 20 carbon atoms, and they may be the same or different. The average degree of polymerization n is 10 to 10000. n (-R １ - CHR ２ R ３ These elements may all be the same, or some or all of them may be different. The average degree of polymerization m is between 0 and 10000.

[0018] A method for producing a gas diffusion electrode, comprising: a particle formation step of producing polyolefin particles by the method for producing polyolefin particles described in [7]; a mixing step of mixing the polyolefin particles, a carbon material, and a catalyst to form a mixture; and a molding step of rolling the mixture to form it.

[0019] [9] A fuel cell having a first electrode, a second electrode, and a polymer electrolyte membrane disposed between the first electrode and the second electrode, wherein either or both of the first electrode and the second electrode include a gas diffusion electrode according to any one of [1] to [4].

[10] A metal-air battery having a positive electrode, a negative electrode made of metal, and an electrolyte layer disposed between the positive electrode and the negative electrode, wherein the positive electrode includes a gas diffusion electrode according to any one of [1] to [4].

[11] A salt electrolysis apparatus having a positive electrode, a negative electrode, and an ion exchange membrane disposed between the positive electrode and the negative electrode, wherein the positive electrode includes a gas diffusion electrode according to any one of [1] to [4].

[0020] The gas diffusion electrode of the present invention comprises a polyolefin resin represented by formula (1) and a carbon material. Therefore, even without containing fluororesin, the gas diffusion electrode of the present invention can obtain properties equivalent to those of a gas diffusion electrode containing fluororesin when used as a gas diffusion electrode in a fuel cell, metal-air battery, or salt electrolysis device.

[0021] The polyolefin particles of the present invention contain a polyolefin resin represented by formula (1), and the average particle diameter measured by observation with a scanning electron microscope is in the range of 10 nm to 1000 nm. For this reason, the polyolefin particles of the present invention can be suitably used as a material for the gas diffusion electrode of the present invention. Since the fuel cell, metal-air battery, and salt electrolytic device of the present invention contain the gas diffusion electrode of the present invention, properties equivalent to those obtained when a gas diffusion electrode containing fluororesin is used can be obtained even without containing fluororesin.

[0022] Figure 1 is a schematic diagram illustrating an example of a gas diffusion electrode in this embodiment. Figure 2 is a schematic diagram illustrating an example of a fuel cell in this embodiment. Figure 3 is a schematic diagram illustrating an example of a metal-air battery in this embodiment.

[0023] The following describes in detail the gas diffusion electrode and method for manufacturing the gas diffusion electrode according to this embodiment, polyolefin particles and method for manufacturing polyolefin particles, fuel cell, metal-air battery, and salt electrolysis apparatus.

[0024] [Gas Diffusion Electrode] Fig. 1 is a schematic diagram for explaining an example of the gas diffusion electrode of the present embodiment. As shown in Fig. 1, the gas diffusion electrode 1 of the present embodiment includes a polyolefin resin 2 and a carbon material 3. The gas diffusion electrode 1 of the present embodiment preferably includes a catalyst 4 together with the polyolefin resin 2 and the carbon material 3.

[0025] As shown in Fig. 1, the gas diffusion electrode 1 of the present embodiment has a plurality of voids between and / or among the respective materials of the polyolefin resin 2, the carbon material 3, and the catalyst 4. The gas diffusion electrode 1 of the present embodiment is preferably disposed in contact with a gas diffusion layer (not shown) that supplies a reaction gas to the gas diffusion electrode 1.

[0026] (Polyolefin Resin) The polyolefin resin 2 contained in the gas diffusion electrode 1 of the present embodiment is represented by the following general formula (1). The polyolefin resin 2 represented by formula (1) contained in the gas diffusion electrode 1 of the present embodiment may be only one kind or two or more kinds.

[0027] -[CH ２ -CH(-R １ ) -CHR ２ R ３ ) ｎ -[CH ２ -CH ２ ｍ -... (1) (In formula (1), n represents the average degree of polymerization of the repeating unit [CH ２ -CH(-R １ -CHR ２ R ３ )]. m represents the average degree of polymerization of the repeating unit [CH ２ -CH ２ . R １ is a linear alkylene group having 1 or more and 20 or less carbon atoms. R ２ and R ３ are each hydrogen or a linear alkyl group having 1 or more and 20 or less carbon atoms, and may be the same or different. The average degree of polymerization n is 10 or more and 10,000 or less. n (-R １ -CHR ２ R ３(These may all be the same, or some or all may be different. The average degree of polymerization m is between 0 and 10000.)

[0028] The polyolefin resin 2 included in the gas diffusion electrode 1 of this embodiment functions as a binder, binding the carbon material 3 and the catalyst 4 together, as shown in Figure 1. The polyolefin resin 2 represented by formula (1) is lightweight, has sufficient ionic conductivity, low surface tension, and high air permeability. Therefore, the polyolefin resin 2 coats at least a portion of the carbon material 3 and the catalyst 4, providing water repellency to the gas diffusion electrode 1 while ensuring gas permeability, resulting in a gas diffusion electrode 1 that can sufficiently supply reaction gas to the electrode reaction field. Furthermore, the polyolefin resin 2 contributes to the weight reduction of the gas diffusion electrode 1 and results in a gas diffusion electrode 1 that has sufficient ionic conductivity.

[0029] In the polyolefin resin 2 represented by formula (1), [CH ２ -CH(-R １ - CHR ２ R ３ ) and [CH ２ -CH ２ ] is a repeating unit. In the polyolefin resin 2 represented by formula (1), [CH ２ -CH(-R １ - CHR ２ R ３ ) and [CH ２ -CH ２ The order of the elements is not particularly restricted. Also, the polyolefin resin 2 represented by formula (1) is [CH ２ -CH(-R １ - CHR ２ R ３ ) ) ) ) ) ) ) ) ) [Polyolefin resin represented by formula (1) ) ) ) ) ) [Polyolefin resin represented by formula (1) ) [CH ] ) ) ) ) ) ) ) ) [Polyolefin resin represented by formula (1 ２ -CH(-R １ - CHR ２ R ３ ) and [CH ２ -CH ２ This may be any of the following: a random copolymer, a block copolymer, or an alternating copolymer.

[0030] In the polyolefin resin 2 represented by formula (1), n ​​(-R １ - CHR ２ R ３ ) R １ , R ２ , R ３ They may all be the same, or some or all of them may be different. n (-R １ - CHR ２ R ３ Since this results in a polyolefin resin 2 that is easy to manufacture, it is preferable that all of them be the same.

[0031] R in the polyolefin resin 2 represented by formula (1) １ R is a linear alkylene group having 1 to 20 carbon atoms. １ However, because it is a linear alkylene group with 1 to 20 carbon atoms, it becomes a highly hydrophobic polyolefin resin 2. １ The side chain is [CH ２ -CH(-R １ - CHR ２ R ３ To prevent the resulting product from becoming too bulky, it is preferable that the group be a straight-chain alkylene group having 1 to 20 carbon atoms, and most preferably a methylene group having 1 carbon atom.

[0032] R in the polyolefin resin 2 represented by formula (1) ２ and R ３ Each of these is either hydrogen or a linear alkyl group having 1 to 20 carbon atoms, and they may be the same or different. ２ and R ３ Since this results in a polyolefin resin that is easy to manufacture, it is preferable that they be the same.

[0033] R in equation (1) ２ and R ３ However, since each is a linear alkyl group with 1 to 20 carbon atoms, for example, R ２ and R ３ Instead, R ２ and R ３Compared to the case where a linear alkyl group containing the total number of carbon atoms present in the material is present, the resulting polyolefin resin 2 is more soluble in solvents. ２ and R ３ The side chain is [CH ２ -CH(-R １ - CHR ２ R ３ To prevent the ) from becoming too bulky, it is preferable that each is a linear alkyl group having 1 to 20 carbon atoms, and most preferably a methyl group having 1 carbon atom.

[0034] The polyolefin resin 2 represented by formula (1) is R １ is a methylene group, R ２ and R ３ It is preferable to use a material in which the group is a methyl group. This is because it can be easily dissolved in a solvent, and it results in a gas diffusion electrode 1 with lower surface tension and better water repellency.

[0035] In the polyolefin resin 2 represented by formula (1), n ​​is the repeating unit [CH ２ -CH(-R １ - CHR ２ R ３ This indicates the average degree of polymerization of ). n is between 10 and 10000. n may be 50 or more. n may be 3000 or less. When n is between 50 and 3000, the molecular weight of polyolefin resin 2 tends to be within an appropriate range, resulting in polyolefin resin 2 with high thermal stability.

[0036] Furthermore, in the polyolefin resin 2 represented by formula (1), m is the repeating unit CH ２ -CH ２ This indicates the average degree of polymerization of the side chains [CH] relative to the main chain. m is between 0 and 10000. m may be 2 or more. m may be 3000 or less. When m is between 2 and 3000, the side chains [CH] relative to the main chain ２ -C(-R １ - CHR ２ R ３ The proportion of )H becomes appropriate, resulting in a polyolefin resin 2 with good gas permeability.

[0037] As the polyolefin resin 2 represented by formula (1), commercially available products may be used. Examples of commercially available polyolefin resins 2 represented by formula (1) include R １ is a methylene group, R ２ and R ３ Examples include polymethylpentene (PMP) (trade name: TPX®, manufactured by Mitsui Chemicals, Inc.), which has a methyl group.

[0038] The content of polyolefin resin 2 in the gas diffusion electrode 1 is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. When the content of polyolefin resin 2 in the gas diffusion electrode 1 is 50% by mass or less, it is easier to obtain a gas diffusion electrode 1 that has multiple voids and good liquid permeability.

[0039] Furthermore, the content of polyolefin resin 2 in the gas diffusion electrode 1 is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more. When the content of polyolefin resin 2 in the gas diffusion electrode 1 is 1% by mass or more, good moldability is obtained and a gas diffusion electrode 1 with sufficient strength can be obtained.

[0040] The content of polyolefin resin 2 in the gas diffusion electrode 1 is preferably 1% by mass or more and 50% by mass or less, more preferably 3% by mass or more and 40% by mass or less, and even more preferably 5% by mass or more and 20% by mass or less.

[0041] (Carbon Material) As the carbon material 3, one or more known materials used as materials for the gas diffusion electrode 1 can be used. Examples of carbon material 3 include graphite, amorphous carbon, activated carbon, graphene, carbon black, carbon fiber, mesocarbon microbeads, microcapsule carbon, fullerene, carbon nanoform, carbon nanotube, carbon nanohorn, etc. Among these, it is preferable to use one or more selected from graphite, amorphous carbon, activated carbon, graphene, carbon black, carbon fiber, fullerene, and carbon nanotube as the carbon material 3, and it is more preferable to use one or more selected from graphite, activated carbon, carbon nanotube, carbon black, and graphene.

[0042] The carbon material 3 may have functional groups such as hydroxyl groups, carboxyl groups, nitrogen-containing groups, silicon-containing groups, phosphorus-containing groups such as phosphate groups, and sulfur-containing groups such as sulfonic acid groups. When using a metal complex of iron tetrapyridopolyphylazine described later as catalyst 4, it is preferable to use a carbon material 3 that has carboxyl groups. The metal complex of iron tetrapyridopolyphylazine is easily adsorbed onto the surface of the carbon material 3 that has carboxyl groups. Therefore, by using a metal complex of iron tetrapyridopolyphylazine described later as catalyst 4 and a carbon material 3 that has carboxyl groups, a gas diffusion electrode 1 with excellent durability and superior oxygen reduction catalytic activity can be obtained.

[0043] The carbon material 3 may contain heteroatoms. Examples of heteroatoms include oxygen atoms, nitrogen atoms, phosphorus atoms, sulfur atoms, silicon atoms, etc. That is, the carbon material 3 may be oxidized, hydroxylated, nitrided, phosphated, sulfurized, or silicified. If the carbon material 3 contains heteroatoms, the carbon material 3 may contain only one type of heteroatom, or it may contain two or more types of heteroatoms.

[0044] The specific surface area of ​​carbon material 3 is 0.8 m². ２Preferably 1.0 m ２ More preferably 1.1 m ２ More preferably 1.5 m ２ A value of 2.0 m or more is particularly preferred. ２ A value of 500 m² or more is most preferable. ２ Carbon material 3 with a specific surface area of ​​0.8 m² or more can also be used. ２ If the value is 1 / g or higher, a large electrode reaction field is more easily formed in the gas diffusion electrode 1, and good characteristics are more likely to be obtained when used as the gas diffusion electrode 1 in fuel cells, metal-air batteries, and salt electrolysis devices. The upper limit of the specific surface area of ​​the carbon material 3 is, for example, 2500 m². ２ It may be less than / g, and 2000m ２ It may be less than or equal to / g.

[0045] The specific surface area of ​​carbon material 3 is, for example, 0.8 m². ２ / g or more 2500m ２ It is also acceptable to have a value of less than / g, or 0.8m ２ / g or more 2000m ２ It is also acceptable to have a value of less than / g, and 1.0m ２ / g or more 2000m ２ It is also acceptable to have a value of less than / g, and 1.1m ２ / g or more 2000m ２ It is also acceptable to have a value of less than / g, and 1.5m ２ / g or more 2000m ２ It is also acceptable to have a value of less than / g, and 2.0m ２ / g or more 2000m ２ It may be less than / g. The specific surface area of ​​carbon material 3 can be measured using a specific surface area measuring device by the nitrogen adsorption BET method.

[0046] The average particle size of the carbon material 3 is not particularly limited. Preferably, the average particle size of the carbon material 3 is between 5 nm and 1000 μm. As a method for adjusting the average particle size of the carbon material 3 to be within the range of 5 nm to 1000 μm, for example, the following methods (A1) to (A3) can be used. The average particle size of the carbon material 3 can be measured using a particle size distribution analyzer, an electron microscope, etc.

[0047] (A1): A method of crushing particles made of carbon material 3 using a ball mill or the like, dispersing the resulting coarse particles in a dispersant to the desired particle size, and then drying them. (A2): A method of crushing particles made of carbon material 3 using a ball mill or the like, and then sorting the resulting coarse particles by particle size using a sieve or the like. (A3): A method of adjusting the particle size by optimizing the manufacturing conditions when manufacturing carbon material 3.

[0048] The carbon material 3 content in the gas diffusion electrode 1 is preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less. When the carbon material 3 content in the gas diffusion electrode 1 is 80% by mass or less, it becomes easier to ensure a sufficient amount of polyolefin resin 2 in the gas diffusion electrode 1, making it easier to obtain a gas diffusion electrode 1 with good moldability and sufficient strength.

[0049] Furthermore, the carbon material 3 content in the gas diffusion electrode 1 is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 55% by mass or more. When the carbon material 3 content in the gas diffusion electrode 1 is 40% by mass or more, a gas diffusion electrode 1 with excellent conductivity can be obtained.

[0050] The carbon material 3 contained in the gas diffusion electrode 1 is preferably 40% by mass or more and 80% by mass or less, more preferably 50% by mass or more and 75% by mass or less, and even more preferably 55% by mass or more and 70% by mass or less.

[0051] (Catalyst) As catalyst 4, one or more known catalysts used as catalysts for the gas diffusion electrode 1 can be used. Examples of catalyst 4 include noble metals such as Pt, Ru, Ir, Pd, Rh, Os, Au, and Ag, and alloys containing these noble metals, metal complexes of metal phthalocyanines and metal tetrapyridopolyphylazines such as iron, cobalt, nickel, and copper, and their derivatives, Mn, Cu, Fe, Co, Ni and their oxides, sulfides, chloride particles, etc.

[0052] It is preferable that catalyst 4 does not contain precious metals, which are very expensive and have limited resources. In this embodiment, it is preferable that catalyst 4 contains a metal complex of iron tetrapyridopolyphylazine represented by formula (4), and it is more preferable to use only the metal complex of iron tetrapyridopolyphylazine represented by formula (4). The reason for this is that a gas diffusion electrode 1 with excellent oxygen reduction catalytic activity can be obtained without containing precious metals.

[0053]

[0054] The metal complex of iron tetrapyridopolyphylazine represented by formula (4) can be produced, for example, by the following production method. Specifically, one example is heating a dicyano compound such as pyridine-2,3-dicarbonitride and a metal compound such as iron chloride in a high-boiling polar solvent such as N-methylpyrrolidinone in the presence of a basic substance. Examples of basic substances include inorganic bases such as potassium carbonate, sodium carbonate, calcium carbonate, sodium bicarbonate, and sodium acetate; and organic bases such as triethylamine, tributylamine, and diazabicycloundecene.

[0055] When catalyst 4 contains only a metal complex of iron tetrapyridopolyphylazine represented by formula (4), the content of catalyst 4 in the gas diffusion electrode 1 is preferably 75% by mass or less, more preferably 50% by mass or less, and even more preferably 30% by mass or less, based on 100% by mass of the total of catalyst 4 and carbon material 3. When the ratio of catalyst 4 to 100% by mass of the total of catalyst 4 and carbon material 3 is less than or equal to the above upper limit, the gas diffusion electrode 1 has excellent conductivity.

[0056] Furthermore, when the catalyst 4 contains only the metal complex of iron tetrapyridopolyphylazine represented by formula (4), the content of catalyst 4 in the gas diffusion electrode 1 is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, based on 100% by mass of the total of catalyst 4 and carbon material 3. When the ratio of catalyst 4 to 100% by mass of the total of catalyst 4 and carbon material 3 is equal to or greater than the above lower limit, the gas diffusion electrode 1 has superior oxygen reduction catalytic activity.

[0057] The gas diffusion electrode 1 of this embodiment may contain, as optional, other components along with the polyolefin resin 2, the carbon material 3, and the catalyst 4 which may be added as needed. Examples of other components include one or more resins selected from resins other than the polyolefin resin 2, such as fluororesins like polytetrafluoroethylene (PTFE), styrene-butadiene copolymers, polymethyl methacrylate resins, polyacrylate resins, polysulfone resins, polyimide resins, cellulose resins, and derivatives thereof.

[0058] In this embodiment, the gas diffusion electrode 1 preferably does not contain fluororesins such as polytetrafluoroethylene (PTFE) as other components, and more preferably does not contain any resin other than polyolefin resin 2. In other words, in this embodiment, the gas diffusion electrode 1 preferably contains only polyolefin resin 2 as a binder. This is because good characteristics can be obtained when used as the gas diffusion electrode 1 in fuel cells, metal-air batteries, and salt electrolytic devices.

[0059] [Method for Manufacturing Gas Diffusion Electrodes] As a method for manufacturing the gas diffusion electrode 1 of this embodiment, for example, the first manufacturing method or the second manufacturing method shown below can be used.

[0060] (First Manufacturing Method) In the first manufacturing method, first, the polyolefin resin 2 represented by formula (1) is dissolved in a solvent to obtain a resin solution (dissolution step). Any solvent that can dissolve the polyolefin resin 2 represented by formula (1) is acceptable. As solvents, for example, one or more selected from cyclohexane, cyclohexanone, methylcyclohexane, ethylbenzene, m-xylene, p-xylene, o-xylene, 1,2,3,4-tetrahydronaphthalene, cycloheptane, cyclopentane, and decahydronaphthalene can be used. Among these, cyclohexane is preferred as the solvent because it can easily dissolve the polyolefin resin 2 represented by formula (1), has a relatively low boiling point, and is inexpensive.

[0061] When dissolving the polyolefin resin 2 represented by formula (1) in a solvent, it is preferable to heat the solvent to a temperature below its boiling point, for example, between 60°C and 80°C, while stirring the solvent. This allows the polyolefin resin 2 to be dissolved uniformly and efficiently in the solvent in a short time.

[0062] Next, the resin solution obtained in the dissolution step, the carbon material, a catalyst added as needed, and other components added as needed are mixed to form a slurry (mixing step). In the mixing step, the order in which the carbon material and catalyst are added to the resin solution is not particularly limited. For example, the entire amount of carbon material and the entire amount of catalyst may be added to the resin solution at the same time, or the entire amount of carbon material may be added to the resin solution and mixed, and then the entire amount of catalyst may be added, or a pre-mixed mixture of carbon material and catalyst may be added to the resin solution in small amounts.

[0063] In the mixing step, it is preferable to heat the resin solution to a temperature below the boiling point of the solvent, for example, between 60°C and 80°C, while stirring. This allows for the efficient production of a slurry containing the resin solution, carbon material, and catalyst in a substantially uniform manner. Furthermore, in the mixing step, after adding the carbon material and catalyst to the resin solution, it is preferable to remove a portion of the solvent by holding the mixture at a temperature between 80°C and 100°C for 6 to 24 hours using a known method, such as a water bath or oil bath. This results in a slurry with good fluidity that is easy to mold in the molding step described later.

[0064] Next, the slurry obtained in the mixing step is applied to the surface of the gas diffusion electrode 1 to be formed, dried, and rolled to form it (forming step). Known methods such as dip coating, spin coating, bar coating, and blade coating can be used to apply the slurry to the surface of the gas diffusion electrode 1, and the method can be appropriately determined depending on the thickness of the gas diffusion electrode 1 to be manufactured and the fluidity of the slurry. Alternatively, a transfer method can be used to apply the slurry to the surface of the gas diffusion electrode 1 by applying the slurry to a hydrophilic substrate such as glass and drying it to form a film on the hydrophilic substrate, then peeling the resulting film off the hydrophilic substrate and transferring it to the surface of the gas diffusion electrode 1.

[0065] In the molding process, known methods such as the hot pressing method can be used to dry and roll the slurry applied to the surface of the gas diffusion electrode 1 to be formed. In the molding process, if a film is transferred to the surface of the gas diffusion electrode 1 to be formed using the transfer method described above, known methods such as the hot pressing method can be used to further dry and roll the transferred film.

[0066] When drying and rolling the slurry applied to the surface to be formed on the gas diffusion electrode 1 using the hot press method, for example, the slurry can be heated and pressurized for 10 to 30 minutes at a temperature of 120°C to 300°C and a pressure of 2 MPa to 10 MPa. By performing the above steps, the gas diffusion electrode 1 of this embodiment can be obtained.

[0067] (Second Manufacturing Method) In the second manufacturing method, first, a polyolefin resin 2 represented by formula (1) is produced, and the average particle diameter measured from observation with a scanning electron microscope is in the range of 10 nm to 1000 nm. The average particle diameter of the polyolefin particles made from the polyolefin resin 2 is preferably 20 nm or more, and more preferably 30 nm or more. The average particle diameter of the polyolefin particles made from the polyolefin resin 2 is preferably 300 nm or less, and more preferably 100 nm or less. Furthermore, the polyolefin particles of this embodiment are produced (particle formation step), in which the average particle diameter of the polyolefin particles made from the polyolefin resin 2 is preferably in the range of 20 nm to 300 nm, and most preferably in the range of 30 nm to 100 nm. In the second manufacturing method, it is preferable to produce polyolefin particles of this embodiment made from the polyolefin resin 2 represented by formula (1). In this embodiment, the average particle diameter is the number average particle diameter, and is measured from observation with a scanning electron microscope.

[0068] "Particle Formation Process (Method for Producing Polyolefin Particles)" In this embodiment, as a preferred example of the particle formation process, a case in which polyolefin particles made of polyolefin resin 2 represented by formula (1) are produced will be described. To produce the polyolefin particles of this embodiment, first, the polyolefin resin 2 represented by formula (1) is dissolved in a solvent to make a resin solution (dissolution process). The dissolution process can be, for example, the same process as in the first production method.

[0069] Next, the resin solution obtained in the dissolution step is added dropwise to a poor solvent and stirred to form polyolefin particles (precipitation step). In the precipitation step, the polyolefin resin 2 represented by formula (1), which was dissolved in the resin solution, precipitates in the poor solvent and settles as polyolefin particles.

[0070] As a poor solvent, any solvent that does not readily dissolve the polyolefin resin 2 represented by formula (1) is acceptable. Examples of poor solvents include one or more selected from ethanol, methanol, n-propanol, isopropanol, butanol, pentanol, hexanol, heptanol, dimethyl sulfoxide, dimethylformamide, methylpyrrolidone, and water. Among these, ethanol is preferred as the poor solvent because it is inexpensive and has good miscibility with the resin solution when cyclohexane is used as the solvent. Known methods can be used to stir the poor solvent during the precipitation step. Specifically, examples include using a magnetic stirrer, a rotary-blade stirrer, or an ultrasonic stirring device.

[0071] In the precipitation step, polyolefin particles are produced in which the average particle size, as measured by observation with a scanning electron microscope, is in the range of 10 nm to 1000 nm. The average particle size of the polyolefin particles can be changed by appropriately adjusting, for example, the concentration of the polyolefin resin 2 represented by formula (1) contained in the resin solution obtained in the dissolution step, the types of solvent and poor solvent contained in the resin solution, and the method of stirring the poor solvent.

[0072] For example, when the concentration of polyolefin resin 2 represented by formula (1) contained in the resin solution is in the range of 0.01% by mass or more and 0.1% by mass or less, cyclohexane is used as the solvent, ethanol is used as the poor solvent, and the poor solvent is stirred using a magnetic stirrer at a rate of 10 rpm or more and 10,000 rpm or less, polyolefin particles are obtained in which the average particle size measured by observation with a scanning electron microscope is in the range of 10 nm or more and 1,000 nm or less.

[0073] In this embodiment, since the average particle diameter measured from scanning electron microscope observation of the polyolefin particles formed in the precipitation step is 1000 nm or less, it is preferable to manufacture the gas diffusion electrode 1 using the second manufacturing method, as this results in less variation in quality and a gas diffusion electrode 1 in which the components contained in the mixture manufactured in the mixing step described later are sufficiently bonded together. Furthermore, since the average particle diameter measured from scanning electron microscope observation of the polyolefin particles is 10 nm or more, polyolefin particles can be easily manufactured by performing the above particle formation step (method for manufacturing polyolefin particles).

[0074] Next, the solvent and poor solvent are removed from the solution containing the solvent present in the resin solution, the poor solvent used in the precipitation step, and the polyolefin particles. Known methods can be used to remove the solvent and poor solvent, such as vacuum drying using an evaporator. The polyolefin particles obtained after removing the solvent and poor solvent may have their average particle size adjusted, for example, by using a sieve.

[0075] Next, polyolefin particles, whose average particle size is measured from scanning electron microscopy observation and is in the range of 10 nm to 1000 nm after the solvent and poor solvent have been removed, are mixed with a carbon material, a catalyst added as needed, and other components added as needed to form a mixture (mixing step). As a method for mixing the polyolefin particles, carbon material, a catalyst added as needed, and other components added as needed in the mixing step, known methods such as ultrasonic treatment, mixers, blenders, kneaders, homogenizers, bead mills, and ball mills can be used.

[0076] In the mixing step, when mixing polyolefin particles, carbon material, a catalyst added as needed, and other components added as needed, a solvent may be added and mixed as needed. Furthermore, in this embodiment, the example given is the use of polyolefin particles whose average particle size, as measured by observation with a scanning electron microscope after removing the solvent and poor solvent, is in the range of 10 nm to 1000 nm. However, the solution containing polyolefin particles, solvent, and poor solvent formed in the precipitation step may be mixed with the carbon material and catalyst without removing the solvent and poor solvent.

[0077] Next, the mixture obtained in the mixing step is placed on the surface to be formed of the gas diffusion electrode 1 and rolled to form the gas diffusion electrode 1 (forming step). By performing the above steps, the gas diffusion electrode 1 of this embodiment is obtained.

[0078] [Fuel Cell] Next, the fuel cell of this embodiment will be described in detail. Figure 2 is a schematic diagram illustrating an example of the fuel cell of this embodiment. The fuel cell 10 of this embodiment is a polymer electrolyte fuel cell (PEFC).

[0079] The fuel cell 10 shown in Figure 2 has a membrane electrode assembly MEA consisting of a first gas diffusion layer 13a, a first electrode 11a, a polymer electrolyte membrane 12, a second electrode 11b, and a second gas diffusion layer 13b. The membrane electrode assembly MEA is sandwiched by a separator (not shown) having a gas channel.

[0080] The fuel cell 10 shown in Figure 2 may have only one structure in which a membrane electrode assembly MEA is sandwiched between separators (single cell), or it may have multiple membrane electrode assemblies MEA stacked with separators in between, with separators at both ends in the stacking direction, and this can be appropriately determined according to the power generation performance required for the fuel cell 10.

[0081] As shown in Figure 2, a polymer electrolyte membrane 12 is positioned between the first electrode 11a and the second electrode 11b in the fuel cell 10 of this embodiment. Also, as shown in Figure 2, a first gas diffusion layer 13a is positioned in contact with the side of the first electrode 11a opposite to the polymer electrolyte membrane 12. Furthermore, a second gas diffusion layer 13b is positioned in contact with the side of the second electrode 11b opposite to the polymer electrolyte membrane 12.

[0082] (First electrode 11a and second electrode 11b) The first electrode 11a and second electrode 11b provided in the fuel cell 10 of this embodiment are the gas diffusion electrodes 1 of this embodiment shown in Figure 1. In the fuel cell 10 shown in Figure 2, the first electrode 11a is a hydrogen oxidation anode and is a fuel electrode to which a fuel such as hydrogen is supplied. The second electrode 11b is an oxygen reduction cathode and is an oxygen electrode to which an oxygen-containing gas such as air is supplied.

[0083] (Polymer electrolyte membrane 12) As shown in Figure 2, the polymer electrolyte membrane 12 separates the first electrode 11a and the second electrode 11b. The polymer electrolyte membrane 12 is an ion-conductive polymer membrane (ion exchange membrane) that holds the electrolyte and ensures ion conductivity between the first electrode 11a and the second electrode 11b.

[0084] As the polymer electrolyte membrane 12, known ones that can be used as the polymer electrolyte membrane 12 of a polymer electrolyte fuel cell (PEFC) can be used. Examples of polymer electrolyte membranes 12 include anion exchange membranes containing salts such as amine salts, imidazolium salts, and pyridine salts, and Nafion®, which is an ion exchange membrane made of a perfluorocarbon material composed of a hydrophobic skeleton made of carbon-fluorine and perfluoro side chains having sulfonic acid groups.

[0085] (First gas diffusion layer 13a and second gas diffusion layer 13b) The first gas diffusion layer 13a diffuses a fuel gas such as hydrogen to the first electrode 11a. The second gas diffusion layer 13b diffuses an oxygen-containing gas such as air to the second electrode 11b. Known gas diffusion layers can be used as the first gas diffusion layer 13a and the second gas diffusion layer 13b.

[0086] Examples of the first gas diffusion layer 13a and the second gas diffusion layer 13b include sheet-like carbon materials having pores, such as carbon cloth, carbon paper, and carbon nonwoven fabric; metal materials such as nickel mesh and stainless steel mesh; and sheet-like conductive materials such as boron nitride.

[0087] (Separator) As the separator, known materials that can be used as separators for polymer electrolyte fuel cells (PEFCs) can be used. Examples of separators include polyethylene, polypropylene, polytetrafluoroethylene, polyvinylidene fluoride, cellulose, cellulose acetate, hydroxyalkylcellulose, carboxymethylcellulose, polyvinyl alcohol, cellophane, polystyrene, polyacrylonitrile, polyacrylamide, polyvinyl chloride, polyamide, vinylon, and poly(meth)acrylic acid.

[0088] In the fuel cell 10 of this embodiment, for example, the following electrochemical reaction occurs. That is, at the first electrode 11a (hydrogen oxidation anode) shown in Figure 2, hydrogen (H ２ ) is oxidized and electrons (e － ) is released (H ２ →2H ＋ +2e － ). Electrons (e) generated at the first electrode 11a － The protons (H) generated at the first electrode 11a are supplied to the second electrode 11b via an external circuit. ＋ (O) is supplied to the second electrode 11b (oxygen reduction cathode) via the polymer electrolyte membrane 12. Then, at the second electrode 11b, water is produced by a reaction with oxygen. ２ +4H ＋ +4e － →2H ２ O). This electrochemical reaction between the hydrogen oxidation anode and the oxygen reduction cathode generates a potential difference between the two electrodes.

[0089] [Method for Manufacturing a Fuel Cell] The fuel cell 10 of this embodiment shown in Figure 2 can be manufactured, for example, by the method described below. For example, the slurry obtained by the mixing step of the first manufacturing method described above is applied to the first gas diffusion layer 13a, dried, and rolled. This forms the first electrode 11a. Next, the second electrode 11b is formed on the second gas diffusion layer 13b in the same manner as the first electrode 11a.

[0090] Subsequently, the side of the first electrode 11a opposite to the side in contact with the first gas diffusion layer 13a and the side of the second electrode 11b opposite to the side in contact with the second gas diffusion layer 13b are positioned opposite each other, and the polymer electrolyte membrane 12 is placed between the first electrode 11a and the second electrode 11b to form a laminate. Next, the laminate thus obtained is heat-bonded using a known method such as the hot press method. This yields a membrane electrode assembly (MEA). When heat-pressing the laminate using the hot press method, for example, a method can be used in which the laminate is heated and pressurized for 10 to 30 minutes at a temperature of 120°C to 300°C and a pressure of 2 MPa to 10 MPa.

[0091] Subsequently, the membrane electrode assembly MEA is sandwiched between separators (not shown). At this time, if necessary, multiple membrane electrode assemblies MEA are stacked with separators in between, such that both ends in the stacking direction become separators. Then, the membrane electrode assemblies MEA and the separators are integrated by a known method. Through the above steps, the fuel cell 10 of this embodiment shown in Figure 2 is obtained.

[0092] In the description of the manufacturing method for the fuel cell 10, the first electrode 11a and the second electrode 11b were formed using the first manufacturing method described above as an example. However, the first electrode 11a and the second electrode 11b may also be formed using the second manufacturing method described above. That is, the first electrode 11a may be formed on the first gas diffusion layer 13a by placing the mixture obtained in the mixing step in the second manufacturing method described above and rolling it, and the second electrode 11b may be formed on the second gas diffusion layer 13b in the same manner as the first electrode 11a.

[0093] Furthermore, although the fuel cell 10 of this embodiment was described using the example where both the first electrode 11a and the second electrode 11b are gas diffusion electrodes 1 as shown in Figure 1, in the fuel cell 10 of this embodiment, either one or both of the first electrode 11a and the second electrode 11b may be gas diffusion electrodes 1, and it is also possible that only the first electrode 11a is a gas diffusion electrode 1, or that only the second electrode 11b is a gas diffusion electrode 1.

[0094] For example, if only the first electrode 11a is the gas diffusion electrode 1 of this embodiment, a known electrode used as an oxygen reduction cathode in a polymer electrolyte fuel cell (PEFC) can be used as the second electrode 11b. Also, for example, if only the second electrode 11b is the gas diffusion electrode 1 of this embodiment, a known electrode used as a hydrogen oxidation anode in a polymer electrolyte fuel cell (PEFC) can be used as the first electrode 11a.

[0095] The above description has been based on the example of a polymer electrolyte fuel cell (PEFC) for the fuel cell 10. However, the fuel cell 10 in this embodiment is not limited to a polymer electrolyte fuel cell (PEFC), and may be any known form such as a microbial fuel cell, enzyme fuel cell, molten carbonate fuel cell (MCFC), phosphoric acid fuel cell (PAFC), or solid oxide fuel cell (SOFC).

[0096] [Metal-Air Battery] Next, the metal-air battery of this embodiment will be described in detail. Figure 3 is a schematic diagram illustrating an example of the metal-air battery of this embodiment. The metal-air battery 20 shown in Figure 3 has a positive electrode consisting of a gas diffusion electrode 21b and a gas diffusion layer 23b, a negative electrode 21a, and an electrolyte layer 22 disposed between the gas diffusion electrode 21b and the negative electrode 21a. Furthermore, the metal-air battery 20 may have a known current collector that can be used in the metal-air battery 20 on the side of the gas diffusion layer 23b opposite to the gas diffusion electrode 21b. Furthermore, the metal-air battery 20 may have a known separator that can be used in the metal-air battery 20.

[0097] (Negative electrode 21a) The negative electrode 21a is made of a metal such as zinc (Zn), magnesium (Mg), aluminum (Al), calcium (Ca), lithium (Li), or iron (Fe).

[0098] (Positive electrode) The positive electrode of the metal-air battery 20 consists of a gas diffusion electrode 21b and a gas diffusion layer 23b, as shown in Figure 3. The gas diffusion electrode 21b is the gas diffusion electrode 1 shown in Figure 1. The gas diffusion electrode 21b is an oxygen reduction cathode and is an oxygen electrode to which an oxygen-containing gas such as air is supplied.

[0099] As shown in Figure 3, the gas diffusion layer 23b is positioned in contact with the gas diffusion electrode 21b on the side opposite to the electrolyte layer 22. The gas diffusion layer 23b supplies an oxygen-containing gas, such as air, to the gas diffusion electrode 21b. Examples of the gas diffusion layer 23b include those that can be used as the first gas diffusion layer 13a and / or second gas diffusion layer 13b in the fuel cell 10 described above.

[0100] (Electrolyte layer 22) As the electrolyte layer 22, a known one that can be used as the electrolyte layer 22 of a metal-air battery 20 can be used. In the metal-air battery 20 shown in Figure 3, a known electrolyte used in metal-air batteries 20 can be used as the electrolyte layer 22. The electrolyte provides ion conduction between the gas diffusion electrode 21b and the negative electrode 21a. The electrolyte contains an electrolyte and a solvent.

[0101] The electrolyte is preferably an aqueous electrolyte using water as the solvent. Examples of aqueous electrolytes include alkaline aqueous solutions such as potassium hydroxide aqueous solution and sodium hydroxide aqueous solution, and acidic aqueous solutions such as sulfuric acid aqueous solution. The electrolyte contained in the electrolyte may be one type alone, or two or more types may be used in combination.

[0102] In addition to aqueous electrolytes, the electrolyte used in the metal-air battery 20 may also be an ionic liquid such as an aqueous electrolyte, a carbonate such as ethylene carbonate, dimethyl propylene carbonate, diethyl carbonate, or ethylmethyl carbonate, or an ionic liquid such as 1-butyl-3-methylimidazolium hexafluorophosphate.

[0103] In the metal-air battery 20 of this embodiment, for example, the following electrochemical reaction occurs. That is, at the negative electrode 21a shown in Figure 2, the metal is oxidized and electrons (e － ) is released. Electrons (e) generated at the negative electrode 21a － The gas is supplied to the gas diffusion electrode 21b via an external circuit, and the oxygen supplied from the gas diffusion layer 23b is reduced. This electrochemical reaction between the negative electrode 21a and the gas diffusion electrode 21b generates a potential difference between the positive electrode and the negative electrode 21a.

[0104] [Method for Manufacturing a Metal-Air Battery] The metal-air battery 20 of this embodiment can be manufactured, for example, by the method shown below. First, a gas diffusion electrode 21b is formed on the gas diffusion layer 23b in the same manner as when manufacturing the fuel cell 10 shown in Figure 2, in which the first electrode 11a is formed on the first gas diffusion layer 13a.

[0105] Next, the gas diffusion electrode 21b and the negative electrode 21a are placed facing each other. Then, an electrolyte, which is the electrolyte layer 22, is interposed between the gas diffusion electrode 21b and the negative electrode 21a by a known method, in contact with both the gas diffusion electrode 21b and the negative electrode 21a. Through these steps, the metal-air battery 20 of this embodiment shown in Figure 3 is obtained.

[0106] [Salt Electrolysis Apparatus] Next, the salt electrolysis apparatus of this embodiment will be described in detail. The salt electrolysis apparatus of this embodiment has a positive electrode, a negative electrode, and an ion exchange membrane disposed between the positive electrode and the negative electrode. In the salt electrolysis apparatus, the positive electrode used is a gas diffusion electrode, which is the gas diffusion electrode 1 of this embodiment shown in Figure 1, and a gas diffusion layer. The positive electrode in the salt electrolysis apparatus can be, for example, the same type of positive electrode that can be used in the metal-air battery 20 shown in Figure 3.

[0107] As the negative electrode, known materials that can be used as negative electrodes in salt electrolysis devices, such as carbon rods, can be used. As the ion exchange membrane, known materials that can be used as ion exchange membranes in salt electrolysis devices can be used, such as anion exchange membranes containing salts such as amine salts, imidazolium salts, and pyridine salts, or Nafion®, which is an ion exchange membrane made of a perfluorocarbon material consisting of a hydrophobic skeleton made of carbon and fluorine and a perfluoro side chain having a sulfonic acid group.

[0108] The salt electrolysis apparatus of this embodiment can be manufactured, for example, by the method shown below. First, a gas diffusion electrode is formed on the gas diffusion layer in the same manner as when manufacturing the fuel cell 10 shown in Figure 2, in which the first electrode 11a is formed on the first gas diffusion layer 13a. Next, an ion exchange membrane is placed on the side of the gas diffusion electrode opposite to the gas diffusion layer, and a negative electrode is placed on the surface of the ion exchange membrane opposite to the gas diffusion electrode to form a laminate. Then, the laminate obtained in this manner is heated and pressurized using a known method such as the hot press method, in the same manner as when manufacturing the fuel cell 10 shown in Figure 2. The salt electrolysis apparatus of this embodiment can be obtained by the above steps.

[0109] Although preferred embodiments of this invention have been described in detail above, the present invention is not limited to any particular embodiment, and various modifications and changes are possible within the scope of the gist of the invention as described in the claims.

[0110] For example, in the embodiments described above, fuel cells, metal-air batteries, and salt electrolytic devices including the gas diffusion electrode of this embodiment were given as examples. However, the applications of the gas diffusion electrode of this embodiment are not limited to the fuel cells, metal-air batteries, and salt electrolytic devices described above. For example, the gas diffusion electrode of this embodiment can also be suitably used as an electrode in devices such as gas sensors.

[0111] The present invention will be described in more detail below with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

[0112] [Example 1] The gas diffusion electrode of Example 1 was manufactured using the following raw materials. As the polyolefin resin represented by formula (1), R in formula (1) １ is a methylene group, R ２ and R ３ Polymethylpentene (PMP), which has a methyl group (trade name: TPX® MX004, manufactured by Mitsui Chemicals, Inc.), was used.

[0113] A mixture of activated carbon and graphite was used as the carbon material. The activated carbon had a specific surface area of ​​500 to 2500 m². ２ We used a product with a particle size of 18 to 42 mesh (product name: Kuraray Cole KW; manufactured by Kuraray Co., Ltd.) with a particle size of 40 μm or less. For graphite, we used a product with an average particle size of 40 μm (product name: CMX-40; manufactured by Nippon Graphite Industry Co., Ltd.).

[0114] As a catalyst, a metal complex of iron tetrapyridopolyphylazine represented by formula (4), synthesized by the method described below, was used. Specifically, the metal complex of iron tetrapyridopolyphylazine was prepared by heating pyridine-2,3-dicarbonitridelic acid and iron chloride as a metal compound in N-methylpyrrolidinone, a polar solvent, in the presence of urea as a basic substance.

[0115] Using the above raw materials, the gas diffusion electrode of Example 1 was manufactured using the first manufacturing method. Specifically, 0.48 g of the above polyolefin resin was placed in 78 g of cyclohexane, which was heated to 60°C as a solvent, and dissolved by stirring with a stirrer to obtain a resin solution (dissolution step).

[0116] Next, the resin solution obtained in the dissolution step was kept at a temperature of 60°C while being stirred with a stirrer, and 2.0 g of the activated carbon, 0.24 g of the graphite, and 0.104 g of the metal complex of iron tetrapyridopolyphylazine represented by formula (4), which is the catalyst, were mixed to form a slurry (mixing step). In the mixing step, after adding the activated carbon and graphite, which are carbon materials, and the catalyst to the resin solution, a portion of the solvent was removed by holding it at a temperature of 100°C for 12 hours using an oil bath.

[0117] Next, the slurry obtained in the mixing step was applied by casting to an expanded mesh made of nickel (product name: Precision Expanded Metal 5Ni7-4 / 0; manufactured by Taiyo Kanami Co., Ltd.) that was approximately square with dimensions of 40 mm in length and 40 mm in width. The expanded mesh was then heated and pressurized by a hot press method at a temperature of 200°C and a pressure of 10 MPa for 30 minutes to form the electrode (forming step). By performing the above steps, the gas diffusion electrode of Example 1, which was integrated with the expanded mesh made of nickel, was obtained.

[0118] [Examples 2 to 4] Gas diffusion electrodes of Examples 2 to 4 were obtained in the same manner as in Example 1, except that the proportions of polyolefin resin, a mixture of activated carbon and graphite as carbon materials, and catalyst were as shown in Table 1, and were integrated with an expanded mesh made of nickel.

[0119]

[0120] [Example 5] The gas diffusion electrode of Example 5 was manufactured using the second manufacturing method. First, the same resin solution as in Example 2 was prepared (dissolution step). The obtained resin solution was dropped into ethanol, a poor solvent, and stirred using a magnetic stirrer at a speed of 300 rpm to 1000 rpm to form polyolefin particles (precipitation step).

[0121] Next, the average particle diameter of the polyolefin particles obtained in the precipitation process was observed using a scanning electron microscope (product name: S-5200, manufactured by Hitachi High-Tech Corporation), measured, and calculated using the method described below. Specifically, for 50 to 100 polyolefin particles within a rectangular field of view measuring 3200 nm vertically and 2400 nm horizontally, the diameter corresponding to the circumscribed circle of each polyolefin particle was measured, and the average value was calculated. As a result, the average particle diameter of the polyolefin particles obtained in Example 5 was within the range of 30 nm to 100 nm.

[0122] Next, the solvent and poor solvent contained in the resin solution were removed from the solution containing the solvent, poor solvent, and polyolefin particles by vacuum drying using an evaporator. Then, using the polyolefin particles obtained after removing the solvent and poor solvent, the polyolefin resin, activated carbon and graphite as carbon materials, and a catalyst were mixed in an agate mortar in the proportions shown in Table 1 to obtain a mixture (mixing step).

[0123] Next, the mixture obtained in the mixing step was placed on a rectangular nickel expanded mesh measuring 40 mm in length and 40 mm in width (product name: Precision Expanded Metal 5Ni7-4 / 0; manufactured by Taiyo Kinami Co., Ltd.), and heated and pressurized by a hot press method at a temperature of 200°C and a pressure of 10 MPa for 30 minutes to form the mixture (forming step). By performing the above steps, the gas diffusion electrode 1 of Example 5, which is integrated with the nickel expanded mesh, was obtained.

[0124] [Reference Example 1] A gas diffusion electrode of Reference Example 1, integrated with an expanded mesh made of nickel, was obtained in the same manner as in Example 1, except that fibrous polytetrafluoroethylene (PTFE) (trade name PTFE6-J; manufactured by Mitsui Chemours Fluoroproducts Co., Ltd.) was used instead of polyolefin resin, and the proportions of polytetrafluoroethylene (PTFE), activated carbon and graphite as carbon materials, and catalyst were as shown in Table 1.

[0125] The gas diffusion electrodes obtained in Examples 1 to 5 and Reference Example 1 were evaluated for their moldability according to the following criteria. The results are shown in Table 2. "Moldability" A: The molded shape (initial shape) in which each component is bonded together can be completely maintained. B: The molded shape can be maintained to the extent that it can function as a gas diffusion electrode. C: Cannot be molded.

[0126]

[0127] As shown in Tables 1 and 2, the gas diffusion electrodes of Examples 1 to 5, in which the volume of polyolefin resin contained in the volume of the gas diffusion electrode was 2 volume% or more, all received a moldability rating of "A" or "B" and were moldable. In particular, the gas diffusion electrodes of Examples 2 to 5, in which the volume of polyolefin resin was 10 volume% or more, all received a moldability rating of "A" and were well moldable. Furthermore, as shown in Tables 1 and 2, the gas diffusion electrode of Reference Example 1, in which the volume of polytetrafluoroethylene (PTFE) contained in the volume of the gas diffusion electrode was 31 volume%, also received a moldability rating of "A" and was well moldable.

[0128] Furthermore, the air permeability of the gas diffusion electrodes in Examples 2 to 4 and Reference Example 1 was measured using the method described below. The results are shown in Table 2. "Method for Measuring Air Permeability" The Gurley value was measured by using a Gurley densometer (product name: No. 323-AUTO; manufactured by Yasuda Seiki Co., Ltd.) to measure the time (seconds) it took for a fixed volume of air to pass through a fixed area of ​​the gas diffusion electrode under a fixed pressure difference. Using this result, the ISO air permeability was calculated using the following formula (2). P = 135.3 / t (2) (In formula (2), P is the ISO air permeability [μm / (Pa・s)], and t is the Gurley value "s".)

[0129] As shown in Tables 1 and 2, the gas diffusion electrodes of Examples 2 to 4, in which the volume of polyolefin resin was 10% by volume or more, all had higher air permeability and better air permeability compared to the gas diffusion electrode of Reference Example 1, in which the volume of polytetrafluoroethylene (PTFE) contained in the volume of the gas diffusion electrode was 31% by volume. In particular, the gas diffusion electrodes of Examples 3 and 4, in which the volume of polyolefin resin was 20% by volume or more, had an air permeability of 0.08 μm / Pa·s or higher, indicating good air permeability.

[0130] Next, using the gas diffusion electrodes from Example 2, Example 5, and Reference Example 1, metal-air batteries were fabricated by the method described below, and the "closed-circuit voltage (OCV)" and "voltage when a current of 10 mA was applied" were measured by the method described below. The results are shown in Table 2.

[0131] [Method for Manufacturing a Metal-Air Battery] An expanded mesh made of nickel, which serves as the gas diffusion electrode, and a zinc foil, which serves as the negative electrode, were arranged in this order. Then, a 6.0 mol / L potassium hydroxide solution, which serves as the electrolyte, was sandwiched between the gas diffusion electrode and the negative electrode, in contact with both the gas diffusion electrode and the negative electrode. A metal-air battery was obtained by the above steps.

[0132] For the metal-air batteries obtained in Examples 2, 5, and Reference Example 1, the closed-circuit voltage (OCV) was measured using a potentiostat / galvanostat (product name: VersaSTAT4, manufactured by AMETEK Corporation). In addition, for the metal-air batteries in Examples 2, 5, and Reference Example 1, the voltage when a current of 10 mA was passed through them was measured using a potentiostat / galvanostat (product name: VersaSTAT4, manufactured by AMETEK Corporation).

[0133] As shown in Table 2, the closed-circuit voltage (OCV) and the voltage when a current of 10 mA was applied were similar in the metal-air batteries of Example 2, Example 5, and Reference Example 1. Therefore, from the results shown in Table 2, it was confirmed that when a gas diffusion electrode using polyolefin resin as a binder is used as a gas diffusion electrode in a metal-air battery, it can obtain equivalent characteristics to a gas diffusion electrode using polytetrafluoroethylene (PTFE) as a binder.

[0134] 1...Gas diffusion electrode, 2...Polyolefin resin, 3...Carbon material, 4...Catalyst, 10...Fuel cell, 11a...First electrode, 11b...Second electrode, 12...Polymer electrolyte membrane, 13a...First gas diffusion layer, 13b...Second gas diffusion layer, 20...Metal-air battery, 21a...Negative electrode, 21b...Gas diffusion electrode, 22...Electrolyte layer, 23b...Gas diffusion layer, MEA...Membrane electrode assembly.

Claims

1. A gas diffusion electrode comprising a polyolefin resin represented by the following general formula (1) and a carbon material. -[CH ２ -CH(-R １ -CHR ２ R ３ ) ｎ -[CH ２ -CH ２ ｍ - ‥(1) (In formula (1), n represents the average degree of polymerization of the repeating unit [CH ２ -CH(-R １ -CHR ２ R ３ )). m represents the average degree of polymerization of the repeating unit [CH ２ -CH ２ . R １ is a linear alkylene group having 1 to 20 carbon atoms. R ２ and R ３ are each hydrogen or a linear alkyl group having 1 to 20 carbon atoms, and they may be the same or different. The average degree of polymerization n is 10 to 10,000. The n (-R １ -CHR ２ R ３ ) may all be the same, or some or all of them may be different. The average degree of polymerization m is 0 to 10,000.)​ 2. R in general formula (1) １ However, it is a methylene group, R ２ and R ３ The gas diffusion electrode according to claim 1, wherein the group is a methyl group.

3. The gas diffusion electrode according to claim 1, further comprising a catalyst.

4. The gas diffusion electrode according to claim 3, wherein the catalyst contains a metal complex of iron tetrapyridopolyphenazine represented by the following formula (4).

5. A method for manufacturing a gas diffusion electrode, comprising: a dissolution step of dissolving a polyolefin resin represented by the following general formula (1) in a solvent to obtain a resin solution; a mixing step of mixing the resin solution, a carbon material, and a catalyst to obtain a slurry; and a molding step of applying the slurry, drying it, and rolling it to form the electrode. - [CH ２ -CH(-R １ - CHR ２ R ３ ) ｎ - [CH ２ -CH ２ ] ｍ - ... (1) (In equation (1), n ​​is the repeating unit [CH ２ -CH(-R １ - CHR ２ R ３ This indicates the average degree of polymerization of the repeating unit [CH]. m represents the repeating unit [CH]. ２ -CH ２ This shows the average degree of polymerization of ]. １ R is a linear alkylene group having 1 to 20 carbon atoms. ２ and R ３ Each of these is either hydrogen or a linear alkyl group having 1 to 20 carbon atoms, and they may be the same or different. The average degree of polymerization n is 10 to 10000. n (-R １ - CHR ２ R ３ These elements may all be the same, or some or all of them may be different. The average degree of polymerization m is between 0 and 10000.

6. Polyolefin particles containing a polyolefin resin represented by the following general formula (1), wherein the average particle diameter measured by scanning electron microscopy is in the range of 10 nm to 1000 nm. - [CH ２ -CH(-R １ - CHR ２ R ３ ) ｎ - [CH ２ -CH ２ ] ｍ - ... (1) (In equation (1), n ​​is the repeating unit [CH ２ -CH(-R １ - CHR ２ R ３ This indicates the average degree of polymerization of the repeating unit [CH]. m represents the repeating unit [CH]. ２ -CH ２ This shows the average degree of polymerization of ]. １ R is a linear alkylene group having 1 to 20 carbon atoms. ２ and R ３ Each of these is either hydrogen or a linear alkyl group having 1 to 20 carbon atoms, and they may be the same or different. The average degree of polymerization n is 10 to 10000. n (-R １ - CHR ２ R ３ These elements may all be the same, or some or all of them may be different. The average degree of polymerization m is between 0 and 10000.

7. A method for producing polyolefin particles, comprising: a dissolution step of dissolving a polyolefin resin represented by the following general formula (1) in a solvent to obtain a resin solution; and a precipitation step of forming polyolefin particles by dropping the resin solution into a poor solvent and stirring, wherein the average particle diameter measured by observation with a scanning electron microscope is in the range of 10 nm to 1000 nm. - [CH ２ -CH(-R １ - CHR ２ R ３ ) ｎ - [CH ２ -CH ２ ] ｍ - ... (1) (In equation (1), n ​​is the repeating unit [CH ２ -CH(-R １ - CHR ２ R ３ This indicates the average degree of polymerization of the repeating unit [CH]. m represents the repeating unit [CH]. ２ -CH ２ This shows the average degree of polymerization of ]. １ R is a linear alkylene group having 1 to 20 carbon atoms. ２ and R ３ Each of these is either hydrogen or a linear alkyl group having 1 to 20 carbon atoms, and they may be the same or different. The average degree of polymerization n is 10 to 10000. n (-R １ - CHR ２ R ３ These elements may all be the same, or some or all of them may be different. The average degree of polymerization m is between 0 and 10000.

8. A method for producing a gas diffusion electrode, comprising: a particle formation step of producing polyolefin particles by the method for producing polyolefin particles described in claim 7; a mixing step of mixing the polyolefin particles, a carbon material, and a catalyst to form a mixture; and a molding step of forming the mixture by rolling it.

9. A fuel cell comprising a first electrode, a second electrode, and a polymer electrolyte membrane disposed between the first electrode and the second electrode, wherein either or both of the first electrode and the second electrode include a gas diffusion electrode according to any one of claims 1 to 4.

10. A metal-air battery comprising a positive electrode, a negative electrode made of metal, and an electrolyte layer disposed between the positive electrode and the negative electrode, wherein the positive electrode includes a gas diffusion electrode as described in any one of claims 1 to 4.

11. A salt electrolysis apparatus having a positive electrode, a negative electrode, and an ion exchange membrane disposed between the positive electrode and the negative electrode, wherein the positive electrode includes a gas diffusion electrode as described in any one of claims 1 to 4.

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