JP2021163748A - Membrane electrode assembly - Google Patents

Abstract

To improve durability of a cathode.SOLUTION: A membrane electrode assembly includes an electrolyte membrane 4, a first catalyst layer 21, a first gas diffusion layer 22, and at least one first adsorption part 23. The first catalyst layer 21 is arranged on the electrolyte membrane 4. The first catalyst layer 21 has catalytic activity for oxygen reduction reaction. The first gas diffusion layer 22 is arranged on the first catalyst layer 21. The first adsorption part 23 is arranged inside the first gas diffusion layer 22. The first adsorption part 23 contains a catalyst having catalytic activity for oxygen reduction reaction.SELECTED DRAWING: Figure 2

Description

The present invention relates to a membrane electrode assembly.

The fuel cell has a membrane electrode assembly and a pair of separators. The membrane electrode assembly has an electrolyte membrane, an anode and a cathode. The fuel cell generates electricity by supplying fuel to the anode and an oxidant to the cathode.

Japanese Unexamined Patent Publication No. 2015-133337

Air is generally used as the oxidizing agent supplied to the cathode. The air supplied to this cathode contains catalytic toxins such as ammonia, ammonium sulfide, or dimethyl sulfide. With the use of fuel cells, there is a problem that the performance of the cathode catalyst deteriorates due to the catalyst poison. In response to this problem, it is desired to prolong the period until the performance of the cathode catalyst deteriorates, that is, to improve the durability of the cathode.

An object of the present invention is to improve the durability of the cathode.

The membrane electrode assembly according to a certain aspect of the present invention includes an electrolyte membrane, a first catalyst layer, a first gas diffusion layer, and at least one first adsorption portion. The first catalyst layer is arranged on the electrolyte membrane. The first catalyst layer has catalytic activity for the oxygen reduction reaction. The first gas diffusion layer is arranged on the first catalyst layer. The first adsorption portion is arranged inside the first gas diffusion layer. The first adsorption unit contains a catalyst having catalytic activity for the oxygen reduction reaction.

By using the membrane electrode assembly having this configuration, the durability of the cathode can be improved. That is, in this membrane electrode assembly, the first adsorption portion is arranged inside the first gas diffusion layer. This first adsorption unit contains a catalyst having catalytic activity for the oxygen reduction reaction. Therefore, when air is supplied to the first catalyst layer, the catalyst poison contained in the air is adsorbed by the catalyst of the first adsorption portion while flowing through the first gas diffusion layer. As a result, the amount of catalytic poison that reaches the first catalyst layer can be reduced, and the period until the catalytic activity of the first catalyst layer decreases can be lengthened. As a result, the durability of the cathode can be improved.

Preferably, the membrane electrode assembly comprises a plurality of first adsorption portions. The plurality of first suction portions are arranged at intervals from each other.

Preferably, the first adsorption portion is arranged at a distance from the first catalyst layer.

Preferably, the first gas diffusion layer has a first central portion and a first outer peripheral portion surrounding the first central portion.

Preferably, the first suction portion is arranged inside the first central portion and not inside the first outer peripheral portion.

Preferably, the content of the first adsorption portion in the first central portion is larger than the content of the first adsorption portion in the first outer peripheral portion.

Preferably, the distance between the first adsorption portion and the first catalyst layer in the first central portion is larger than the distance between the first adsorption portion and the first catalyst layer in the first outer peripheral portion.

Preferably, the membrane electrode assembly further comprises a second catalyst layer and a second gas diffusion layer. The second catalyst layer is arranged on the electrolyte membrane on the opposite side of the first catalyst layer. The second catalyst layer has catalytic activity for the oxidation reaction of fuel. The second gas diffusion layer is arranged on the second catalyst layer.

Preferably, the membrane electrode assembly further comprises at least one second adsorption section. The second adsorption portion is arranged inside the second gas diffusion layer. The second adsorption portion contains a catalyst having catalytic activity for the oxidation reaction of the fuel.

Preferably, the membrane electrode assembly comprises a plurality of second adsorption portions. The plurality of second suction portions are arranged at intervals from each other.

Preferably, the second adsorption portion is arranged at a distance from the second catalyst layer.

Preferably, the second gas diffusion layer has a second central portion and a second outer peripheral portion surrounding the second central portion.

Preferably, the second suction portion is arranged inside the second central portion and not inside the second outer peripheral portion.

Preferably, the content of the second adsorption portion in the second central portion is larger than the content of the second adsorption portion in the second outer peripheral portion.

Preferably, the distance between the second adsorption portion and the second catalyst layer in the second central portion is larger than the distance between the second adsorption portion and the second catalyst layer in the second outer peripheral portion.

According to the present invention, the durability of the cathode can be improved.

Sectional view of the fuel cell. An enlarged cross-sectional view of the cathode side of the membrane electrode assembly. An enlarged cross-sectional view of the anode side of the membrane electrode assembly. An enlarged cross-sectional view of a membrane electrode assembly. An enlarged cross-sectional view of the cathode side of the membrane electrode assembly according to the modified example. An enlarged cross-sectional view of the anode side of the membrane electrode assembly according to the modified example. Top view of the first gas diffusion layer. The plan view of the 1st gas diffusion layer for demonstrating the cutting method. The plan view of the 1st gas diffusion layer in another embodiment for demonstrating the cutting method. A cross-sectional view of a membrane electrode assembly for explaining an imaging location. Top view of the second gas diffusion layer. An enlarged cross-sectional view of the electrolyte according to the modified example.

Hereinafter, the membrane electrode assembly 10 according to the present embodiment will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing the configuration of a solid alkaline fuel cell 100 using the membrane electrode assembly 10 according to the present embodiment. The solid alkaline fuel cell 100 is a type of alkaline fuel cell (AFC) using hydroxide ions as carriers.

(Solid alkaline fuel cell 100)
As shown in FIG. 1, the solid alkaline fuel cell 100 includes a membrane electrode assembly 10, a first separator 11, and a second separator 12. In actual use, a plurality of solid alkaline fuel cells 100 are stacked. Specifically, a plurality of membrane electrode assemblies 10 are stacked via the first and second separators 11 and 12.

(Membrane electrode assembly 10)
The membrane electrode assembly 10 includes a cathode 2, an anode 3, and an electrolyte membrane 4. The membrane electrode assembly 10 generates electricity at a relatively low temperature (for example, 50 ° C. to 250 ° C.) based on the following electrochemical reaction formula. However, in the following electrochemical reaction formula, methanol is used as an example of fuel.

・ Cathode 2: 3 / 2O ₂ + 3H ₂ O + 6e ⁻ → 6OH ⁻
・ Anode 3: CH ₃ OH + 6OH ⁻ → 6e ⁻ + CO ₂ + 5H ₂ O
・ Overall: CH ₃ OH + 3 / 2O ₂ → CO ₂ + 2H ₂ O

(Cathode 2)
The cathode 2 is arranged on the first surface 41 side (upper surface side in FIG. 1) of the electrolyte membrane 4. The cathode 2 is an anode generally called an air electrode.

During power generation of the solid alkaline fuel cell 100, an oxidizing agent containing _{oxygen (O 2} ) is supplied to the cathode 2 via the first flow path 111 of the first separator 11. As the oxidizing agent, it is preferable to use air, and it is more preferable that the air is humidified. The cathode 2 is a porous body capable of diffusing an oxidizing agent inside. The porosity of the cathode 2 is not particularly limited. The thickness of the cathode 2 is not particularly limited, but can be, for example, 10 to 200 μm.

As shown in FIG. 2, the cathode 2 has a first catalyst layer 21, a first gas diffusion layer 22, and a plurality of first adsorption portions 23. The first catalyst layer 21 is arranged on the electrolyte membrane 4. Specifically, the first catalyst layer 21 is arranged on the first surface 41 of the electrolyte membrane 4. The first catalyst layer 21 has a rectangular shape in a plan view. The thickness of the first catalyst layer 21 is, for example, about 5 to 50 μm.

The first catalyst layer 21 has a catalytic activity for an oxygen reduction reaction. That is, the first catalyst layer 21 contains a catalyst having catalytic activity for the oxygen reduction reaction. The catalyst contained in the first catalyst layer 21 may be any known cathode catalyst used for AFC, and is not particularly limited. Examples of the cathode catalyst contained in the first catalyst layer 21 include group 8 to 10 elements such as platinum group elements (Ru, Rh, Pd, Os, Ir, Pt) and iron group elements (Fe, Co, Ni). (Elements belonging to Group 8 to 10 in the periodic table of IUPAC format), Group 11 elements such as Cu, Ag, Au (elements belonging to Group 11 in the periodic table of IUPAC format), rhodium phthalocyanine, tetraphenyl Examples include porphyrin, Co-salen, Ni-salen (salen = N, N'-bis (salicylidene) ethylenediamine), silver nitrate, and any combination thereof. The amount of the catalyst supported on the cathode 2 is not particularly limited, but is preferably 0.1 to 10 mg / cm ² , more preferably 0.1 to 5 mg / cm ² . The cathode catalyst is preferably supported on carbon. Preferred examples of the cathode 2 or the catalyst constituting the cathode 2 are platinum-supported carbon (Pt / C), palladium-supported carbon (Pd / C), rhodium-supported carbon (Rh / C), nickel-supported carbon (Ni / C), and the like. Examples thereof include copper-supported carbon (Cu / C) and silver-supported carbon (Ag / C).

The first gas diffusion layer 22 is arranged on the first catalyst layer 21. The first gas diffusion layer 22 has a rectangular shape in a plan view. The first gas diffusion layer 22 is thicker than the first catalyst layer 21. The thickness of the first gas diffusion layer 22 is, for example, about 50 to 150 μm.

The first gas diffusion layer 22 diffuses the oxidant flowing in the first flow path 111 of the first separator 11 and supplies it to the first catalyst layer 21. The first gas diffusion layer 22 has electrical conductivity. The first gas diffusion layer 22 also functions as a current collector.

The first gas diffusion layer 22 can be made of a conductive porous material such as carbon paper, carbon cloth, or carbon felt. Even if the first gas diffusion layer 22 is formed with a microporous layer containing carbon black such as acetylene black or a conductive material such as graphite and a water repellent material such as fluororesin (PTFE, PVDF). good.

The first adsorption unit 23 is arranged inside the first gas diffusion layer 22. The first suction portions 23 are arranged at intervals from each other. Specifically, the first adsorption portions 23 are arranged at intervals from each other in the plane direction of the first gas diffusion layer 22. Further, it is preferable that the first adsorption portion 23 is arranged at a distance from the first catalyst layer 21. The first adsorption unit 23 and the first catalyst layer 21 may be in contact with each other.

The first adsorption unit 23 contains a catalyst having catalytic activity for the oxygen reduction reaction. The catalyst material of the first adsorption unit 23 can be, for example, any of the materials described as the catalyst of the first catalyst layer 21. Preferably, the material of the catalyst of the first adsorption unit 23 is the same as the material of the catalyst of the first catalyst layer 21. Further, the catalyst of the first adsorption unit 23 is preferably supported on a carrier such as carbon, similarly to the catalyst of the first catalyst layer 21.

The cathode 2 as described above is manufactured as follows. First, the first gas diffusion layer 22 is prepared. Next, a catalyst paste having wettability with respect to the first gas diffusion layer 22 and containing ethanol and an IPA component is applied to the first gas diffusion layer 22. Then, the catalyst paste applied to the first gas diffusion layer 22 is dried in a nitrogen stream to obtain the first gas diffusion layer 22 containing the first adsorption portion 23.

Subsequently, by applying a catalyst paste having water repellency to the first gas diffusion layer 22 and using water as the main solvent on the first main surface of the first gas diffusion layer 22, the first gas diffusion layer 22 is first coated. The catalyst layer 21 is formed. By doing so, the cathode 2 having the first adsorption portion 23 can be obtained.

(Anode 3)
As shown in FIG. 1, the anode 3 is arranged on the second surface 42 side (lower surface side in FIG. 1) of the electrolyte membrane 4. The anode 3 is a cathode generally called a fuel electrode.

During power generation of the solid alkaline fuel cell 100, fuel containing a hydrogen atom (H) is supplied to the anode 3 via the second flow path 121 of the second separator 12. As the fuel, it is preferable to use methanol. The anode 3 is a porous body capable of diffusing fuel inside. The porosity of the anode 3 is not particularly limited. The thickness of the anode 3 is not particularly limited, but can be, for example, 10 to 500 μm.

The fuel may contain a fuel compound capable of reacting with hydroxide ions (OH ⁻ ) at the anode 3, and may be in the form of either a liquid fuel or a gaseous fuel.

Examples of the fuel compound include (i) hydrazine (NH ₂ NH ₂ ), hydrated hydrazine (NH ₂ NH ₂ · H ₂ O), hydrazine carbonate ((NH ₂ NH ₂ ) ₂ CO ₂ ), and hydrazine sulfate (NH). ₂ NH ₂ · H ₂ SO ₄ ), monomethylhydrazine (CH ₃ NHNH ₂ ), dimethylhydrazine ((CH ₃ ) ₂ NNH ₂ , CH ₃ NHNHCH ₃ ), and hydrazines such as _{carboxylic hydrazine ((NHNH 2} ) _{2 CO).} Classes, (ii) urea (NH ₂ CONH ₂ ), (iii) ammonia (NH ₃ ), (iv) imidazole, 1,3,5-triazine, 3-amino-1,2,4-triazole and other heterocycles. Examples thereof include compounds such as (v) hydroxylamines such as hydroxylamine (NH ₂ OH) and hydroxylamine sulfate (NH ₂ OH · H ₂ SO ₄ ), and combinations thereof. Of these fuel compounds, carbon-free compounds (ie, hydrazine, hydrated hydrazine, hydrazine sulfate, ammonia, hydroxylamine, hydroxylamine sulfate, etc.) are particularly suitable because they do not have the problem of catalytic poisoning by carbon monoxide. be.

The fuel compound may be used as a fuel as it is, or may be used as a solution dissolved in water and / or an alcohol (for example, a lower alcohol such as methanol, ethanol, propanol or isopropanol). For example, among the above fuel compounds, hydrazine, hydrated hydrazine, monomethylhydrazine and dimethylhydrazine are liquids and can be used as they are as liquid fuels. In addition, hydrazine carbonate, hydrazine sulfate, carboxylic hydrazine, urea, imidazole, and 3-amino-1,2,4-triazole, and hydroxylamine sulfate are solid but soluble in water. 1,3,5-triazine and hydroxylamine are solid but soluble in alcohol. Ammonia is a gas but is soluble in water. As described above, the solid fuel compound can be dissolved in water or alcohol and used as a liquid fuel. When the fuel compound is dissolved in water and / or alcohol and used, the concentration of the fuel compound in the solution is, for example, 1 to 99% by weight, preferably 30 to 99% by weight.

Further, a hydrocarbon-based liquid fuel containing alcohols such as methanol and ethanol and ethers, a hydrocarbon-based gas such as methane, or pure hydrogen can be used as it is as a fuel. In particular, methanol is preferable as the fuel used in the solid alkaline fuel cell 100 according to the present embodiment. Methanol may be in a gaseous state, a liquid state, or a gas-liquid mixed state.

As shown in FIG. 3, the anode 3 has a second catalyst layer 31, a second gas diffusion layer 32, and a plurality of second adsorption portions 33. The second catalyst layer 31 is arranged on the electrolyte membrane 4. Specifically, the second catalyst layer 31 is arranged on the second surface 42 of the electrolyte membrane 4. That is, the second catalyst layer 31 is arranged on the electrolyte membrane 4 on the opposite side of the first catalyst layer 21. The second catalyst layer 31 has a rectangular shape in a plan view. The thickness of the second catalyst layer 31 is, for example, about 5 to 50 μm.

The second catalyst layer 31 has a catalytic activity for the oxidation reaction of the fuel. That is, the second catalyst layer 31 contains a catalyst having catalytic activity for the oxidation reaction of the fuel. The catalyst contained in the second catalyst layer 31 may be any known anode catalyst used for AFC, and is not particularly limited. Examples of the anode catalyst contained in the second catalyst layer 31 include metal catalysts such as Pt, Ni, Co, Fe, Ru, Sn, and Pd. The metal catalyst is preferably supported on a carrier such as carbon, but may be in the form of an organic metal complex having a metal atom of the metal catalyst as a central metal, or the organic metal complex may be supported as a carrier. Further, a diffusion layer made of a porous material or the like may be arranged on the surface of the anode catalyst. Preferred examples of the anode 3 and the catalysts constituting the anode 3 are nickel, cobalt, silver, platinum-supported carbon (Pt / C), palladium-supported carbon (Pd / C), rhodium-supported carbon (Rh / C), and nickel-supported carbon. (Ni / C), copper-supported carbon (Cu / C), and silver-supported carbon (Ag / C) can be mentioned.

The second gas diffusion layer 32 is arranged on the second catalyst layer 31. The second gas diffusion layer 32 has a rectangular shape in a plan view. The second gas diffusion layer 32 is thicker than the second catalyst layer 31. The thickness of the second gas diffusion layer 32 is, for example, about 50 to 150 μm.

The second gas diffusion layer 32 diffuses the fuel flowing in the second flow path 121 of the second separator 12 and supplies it to the second catalyst layer 31. The second gas diffusion layer 32 has electrical conductivity. The second gas diffusion layer 32 also functions as a current collecting member.

The second gas diffusion layer 32 can be made of a conductive porous material such as carbon paper, carbon cloth, or carbon felt. Even if the second gas diffusion layer 32 is formed with a microporous layer containing carbon black such as acetylene black or a conductive material such as graphite and a water repellent material such as fluororesin (PTFE, PVDF). good.

The second adsorption portion 33 is arranged inside the second gas diffusion layer 32. The second suction portions 33 are arranged at intervals from each other. Specifically, the second adsorption portions 33 are arranged at intervals from each other in the plane direction of the second gas diffusion layer 32. Further, it is preferable that the second adsorption portion 33 is arranged at a distance from the second catalyst layer 31. The second adsorption portion 33 and the second catalyst layer 31 may be in contact with each other.

The second adsorption unit 33 contains a catalyst having catalytic activity for the oxidation reaction of the fuel. The catalyst material of the second adsorption unit 33 can be, for example, any of the materials described as the catalyst of the second catalyst layer 31. Preferably, the material of the catalyst of the second adsorption unit 33 is the same as the material of the catalyst of the second catalyst layer 31. Further, the catalyst of the second adsorption unit 33 is preferably supported on a carrier such as carbon, similarly to the catalyst of the second catalyst layer 31.

The anode 3 as described above is produced by the same method as the cathode 2 described above.

(Electrolyte membrane 4)
As shown in FIG. 1, the electrolyte membrane 4 is arranged between the cathode 2 and the anode 3. The electrolyte membrane 4 is connected to each of the cathode 2 and the anode 3. The electrolyte membrane 4 has ionic conductivity. The electrolyte membrane 4 is in the form of a film and has a first surface 41 and a second surface 42. The first surface 41 and the second surface 42 face opposite to each other. The cathode 2 is arranged on the first surface 41 side of the electrolyte membrane 4, and the anode 3 is arranged on the second surface 42 side.

FIG. 4 is a schematic view showing an enlarged cross section of the electrolyte membrane 4. The electrolyte membrane 4 has a support 5 and an ionic conductor 6.

The support 5 is configured to support the ionic conductor 6. Specifically, the support 5 is composed of a porous base material having a three-dimensional network structure. The "three-dimensional network structure" is a structure in which the constituent substances of the base material are three-dimensionally and network-likely connected. The porous base material constituting the support 5 does not have to have a three-dimensional network structure.

The support 5 forms a continuous hole 5a. The continuous hole 5a is formed by connecting the holes in a three-dimensional and mesh pattern, and is exposed on the outer surface of the support 5. The continuous hole 5a is impregnated with the ionic conductor 6.

The support 5 can be composed of at least one selected from a metal material, a ceramic material, and a polymer material.

As the metal material constituting the support 5, stainless steel (Fe—Cr alloy, Fe—Ni—Cr alloy, etc.), aluminum, zinc, nickel, titanium, or the like can be used. Since such a metal material has higher thermal conductivity than a ceramic material or a polymer material, it is possible to improve the heat dissipation efficiency of the support 5 and reduce the temperature distribution in the support 5. .. The form of the support 5 is not particularly limited as long as it has a three-dimensional network structure, and may be, for example, a cell-like or monolith-like structure composed of a porous metal material (for example, a foam metal material). , It may be a mesh-like mass composed of a fine wire metal material.

When the support 5 is made of a metal material, an insulating film may be formed on the surface of the support 5. The insulating film can be composed of Cr ₂ O ₃ , Al ₂ O ₃ , ZrO ₂ , MgO, Mg _{Al 2} O _{4, and the} like. When the support 5 is made of stainless steel, a Cr ₂ O ₃ film as an insulating film can be easily formed by oxidizing the stainless steel. However, in the present embodiment, since the first and second film-like portions 4b and 4c, which will be described later, function as an insulating film, the insulating film may not be formed on the surface of the support 5.

Examples of the ceramic material constituting the support 5 include alumina, zirconia, titania, magnesia, calcia, cordierite, zeolite, mullite, zinc oxide, silicon carbide, and any combination thereof.

Examples of the polymer material constituting the support 5 include polystyrene, polyether sulfone, polypropylene, epoxy resin, polyphenylene sulfide, hydrophilic fluororesin (tetrafluorinated resin: PTFE, etc., polyvinylidene fluoride), cellulose, and the like. Examples include nylon, polypropylene and any combination thereof. When the support 5 is made of a flexible polymer material, the thickness can be easily reduced while increasing the porosity, so that the hydroxide ion conductivity can be improved. As the support 5 made of a polymer material, a microporous membrane as commercially available as a separator for a lithium battery can be used.

The thickness of the support 5 is not particularly limited, but can be, for example, 200 μm or less, preferably 100 μm or less, more preferably 75 μm or less, still more preferably 50 μm or less, particularly preferably 25 μm or less, and 5 μm or less. Most preferred. The lower limit of the thickness of the support 5 may be appropriately set according to the intended use, but is preferably 1 μm or more, more preferably 2 μm or more in order to secure a certain degree of hardness.

The average inner diameter of the continuous holes 5a in the cross section of the support 5 is not particularly limited, but can be, for example, 0.001 to 1.5 μm, preferably 0.001 to 1.25 μm, and more preferably 0.001 to 0.001. It is 1.0 μm, more preferably 0.001 to 0.75 μm, and particularly preferably 0.001 to 0.5 μm. Within these ranges, the density of the ionic conductor 6 can be improved while imparting strength as a support to the support 5. The average inner diameter of the continuous holes 5a is obtained by arithmetically averaging the equivalent circle diameters of the continuous holes 5a at 20 randomly selected positions on the observation image when the cross section of the support 5 is observed with an electron microscope. .. The circle-equivalent diameter of the continuous hole 5a is the diameter of a circle having the same area as the cross-sectional area of the continuous hole 5a in the observation image. The magnification of the electron microscope may be appropriately set according to the cross-sectional size of the continuous hole 5a.

The volume fraction of the continuous hole 5a is not particularly limited, but can be, for example, 10 to 80%, preferably 15 to 75%, and more preferably 20 to 70%. Within these ranges, the density of the ionic conductor 6 can be improved while ensuring the strength of the support 5 as a support. The volume fraction of the continuous hole 5a can be measured by the Archimedes method.

Further, although not shown in FIG. 4, the support 5 preferably has a plurality of pores inside itself. The plurality of pores may be connected to each other inside the support 5. It is more preferable that each pore is an open pore that opens on the surface of the support 5, and each pore is impregnated with the ionic conductor 6. As a result, a short-distance ion conduction path of continuous hole 5a → pore in support 5 → continuous hole 5a, continuous hole 5a → pore in support 5, second film-like portion 4c, or first film. It is possible to form a long-distance ion conduction path of the shape portion 4b → the pores in the support 5 → the second film-like portion 4c. As a result, the ionic conductive region in the composite portion 4a is widened, so that the ionic conductivity of the electrolyte membrane 4 as a whole can be improved.

The ionic conductor 6 has hydroxide ionic conductivity. During power generation of the solid alkaline fuel cell 100, the ion conductor 6 conducts hydroxide ions (OH ⁻ ) from the cathode 2 side to the anode 3 side. The hydroxide ion conductivity of the ion conductor 6 is not particularly limited, but is preferably 0.1 mS / cm or more, more preferably 0.5 mS / cm or more, and further preferably 1.0 mS / cm or more. The higher the hydroxide ion conductivity of the ion conductor 6, the more preferable it is, and the upper limit thereof is not particularly limited, but is, for example, 10 mS / cm.

The ionic conductor 6 can be made of a ceramic material having hydroxide ionic conductivity. As such a ceramic material, layered double hydroxide (LDH) is suitable.

LDH is M ²⁺ _1-x M ³⁺ _x (OH) ₂ A ⁿ⁻ x / n · mH ₂ O (in the formula, M ²⁺ is a divalent cation, M ³⁺ is a trivalent cation, and A ^The basic composition represented by the general formula of n− is an n-valent anion, n is an integer of 1 or more, x is 0.1 to 0.4, and m is an arbitrary integer meaning the number of moles of water). Have. Examples of M ^{2+ include Mg 2+} , Ca ²⁺ , Sr ²⁺ , Ni ²⁺ , Co ²⁺ , Fe ²⁺ , Mn ²⁺ , and Zn ²⁺ , and examples of M ^{3+ include Al 3+} , Fe ³⁺ , Ti ³⁺ , ^{Y 3+, Ce 3+, Mo 3+} , and ^{Cr 3+, and} examples of ^{a n-} is _CO ^{3 2-} and OH ^- are exemplified. As M ²⁺ and M ³⁺ , one type may be used alone or two or more types may be used in combination.

LDH is composed of a plurality of hydroxide basic layers and an intermediate layer interposed between the plurality of hydroxide basic layers. Intermediate layer is composed of an anion and _{H 2} O. The hydroxide basic layer contains, for example, Ni, Al, Ti and OH groups when the metal M is Ni, Al, Ti. Hereinafter, a case where the hydroxide basic layer of LDH contains Ni, Al, Ti and OH groups will be described.

Ni in LDH can take the form of nickel ions. Nickel ions in LDH are typically considered to be Ni ²⁺ , but are not particularly limited as other valences such as ^{Ni 3+ are possible.} Al in LDH can take the form of aluminum ions. The aluminum ion in LDH is typically considered to be Al ³⁺ , but is not particularly limited as other valences are possible. Ti in LDH can take the form of titanium ions. Titanium ions in LDH are typically considered to be Ti ⁴⁺ , but are not particularly limited as other valences such as ^{Ti 3+ are possible.} The hydroxide basic layer preferably contains Ni, Al, Ti and OH groups as main constituent elements, but may contain other elements or ions, or may contain unavoidable impurities. The unavoidable impurity is an arbitrary element that can be unavoidably mixed in the production method, and can be mixed in LDH, for example, derived from a raw material or a base material.

Intermediate layer of LDH is composed of anionic and _{H 2} O. The anion is a monovalent or higher anion, preferably a monovalent or divalent ion. Preferably, the anions in LDH contain OH ⁻ and / or CO ₃ ^2- .

As described above, since the valences of Ni, Al and Ti are not always fixed, it is impractical or impossible to specify LDH strictly by a general formula. Assuming that the basic hydroxide layer is mainly composed of Ni ²⁺ , Al ³⁺ , Ti ⁴⁺ and OH groups, LDH is expressed by the general formula: Ni ²⁺ _1-xy Al ³⁺ _x Ti ⁴⁺ _y (OH). _{^{) 2 a n- (x + 2y}} ) / n · mH 2 O ( ^{wherein, a n-n-valent} anion, n is an integer of 1 or more, preferably 1 or 2, 0 <x <1, preferably 0.01 ≦ x ≦ 0.5, 0 <y <1, preferably 0.01 ≦ y ≦ 0.5, 0 <x + y <1, m is 0 or more, typically more than 0 or 1 or more It can be expressed by the basic composition (which is a real number of). However, the above general formula should be understood as "basic composition" to the ^{extent that elements such as Ni 2+} , Al ³⁺ , and Ti ⁴⁺ do not impair the basic characteristics of LDH, and other elements or ions (of the same element). It should be understood as replaceable with other valence elements or ions or elements or ions that can be unavoidably mixed in the process.

The electrolyte membrane 4 has a composite portion 4a, a first membrane-like portion 4b, and a second membrane-like portion 4c. The composite portion 4a has a support 5 and an ionic conductor 6. The first film-like portion 4b and the second film-like portion 4c have an ionic conductor 6, but do not have a support 5.

The composite portion 4a is arranged between the first film-like portion 4b and the second film-like portion 4c. The ionic conductor 6 is supported by the support 5 in the support 5. Specifically, the ionic conductor 6 is arranged in the continuous hole 5a of the support 5. The ionic conductor 6 is impregnated in the continuous holes 5a of the support 5, and is integrated with the support 5. By supporting the ionic conductor 6 with the support 5 in this way, the strength of the ionic conductor 6 can be improved, so that the ionic conductor 6 can be made thinner. As a result, the resistance of the electrolyte membrane 4 can be reduced.

In the present embodiment, the ionic conductor 6 extends over substantially the entire continuous hole 5a of the support 5. However, when the electrolyte membrane 4 does not have at least one of the first membrane-like portion 4b and the second membrane-like portion 4c, the ionic conductor 6 may be impregnated only in a part of the support 5.

Here, in the composite portion 4a, the electrolyte membrane 4 has a plurality of closed pores 61 formed inside the composite portion 4a. Since such closed pores 61 are formed, it is possible to alleviate the volume change of the electrolyte membrane 4 due to the change in the water content of the ionic conductor 6 during the operation of the solid alkaline fuel cell 100. As a result, it is possible to suppress the generation of stress at the interface between the electrolyte membrane 4 and the cathode 2 and / and the interface between the electrolyte membrane 4 and the anode 3. As a result, it is possible to prevent the electrolyte membrane 4 from peeling off from the cathode 2 and / and the anode 3 and the electrolyte membrane 4 itself from being deformed.

Further, since the closed pores 61 are formed inside the composite portion 4a, the composite portion 4a can be provided with flexibility. Therefore, due to the temperature distribution in the solid alkaline fuel cell 100, the cathode 2 and the cathode 2 It is possible to suppress the generation of thermal stress at the interface with the electrolyte membrane 4 and / and at the interface between the anode 3 and the electrolyte membrane 4. Therefore, it is possible to prevent the electrolyte membrane 4 from peeling off from the cathode 2 and / and the anode 3 or the electrolyte membrane 4 itself from being deformed.

The closed hole 61 is separated from the support 5. That is, the closed air hole 61 is confined inside the composite portion 4a and does not come into direct contact with the inner surface of the continuous hole 5a. As a result, when the electrolyte membrane 4 undergoes a volume change or deformation as compared with the case where the closed pore 61 comes into direct contact with the support 5, the support 5, the composite portion 4a, and the closed pore 61 are formed. It is possible to prevent the composite portion 4a from peeling off from the support 5 starting from the corner portion.

The average circle-equivalent diameter of each closed hole 61 is not particularly limited, but may be, for example, 0.001 to 1.0 μm. The average circle-equivalent diameter of each closed hole 61 is preferably 0.001 μm or more, more preferably 0.002 μm or more. Thereby, the flexibility of the composite portion 4a can be further improved. The average circle-equivalent diameter of each closed hole 61 is preferably 1.0 μm or less, more preferably 0.8 μm or less.

The average circle-equivalent diameter of each of the closed pores 61 is the circle-equivalent diameter of 20 randomly selected pores 61 obtained by observing the cross section of the electrolyte membrane 4 with an electron microscope of 20,000 to 1,500,000 times. Obtained by arithmetic averaging. The circle-equivalent diameter of the closed pores 61 is the diameter of a circle having the same area as the closed pores 61 in the cross section of the electrolyte membrane 4. However, since the closed pores 61 having a circular equivalent diameter of 0.001 μm or less have an extremely small contribution to improving the flexibility of the composite portion 4a, they should be excluded when determining the average circular equivalent diameter of each closed hole 61. do.

The first film-like portion 4b is connected to the cathode 2 side of the composite portion 4a. The first film-like portion 4b is formed in a film-like shape. The ionic conductor 6 of the first film-like portion 4b is integrally formed with the ionic conductor 6 of the composite portion 4a.

The second film-like portion 4c is connected to the anode 3 side of the composite portion 4a. The second film-like portion 4c is formed in a film-like shape. The ionic conductor 6 of the second film-like portion 4c is integrally formed with the ionic conductor 6 of the composite portion 4a. Each of the first film-like portion 4b and the second film-like portion 4c may be formed in a uniform planar shape, or may be patterned into a desired planar shape such as a striped shape. The thickness of each of the first film-like portion 4b and the second film-like portion 4c is not particularly limited, but can be, for example, 10 μm or less, preferably 7 μm or less, and more preferably 5 μm or less.

(Manufacturing method of electrolyte membrane 4)
The method for producing the electrolyte film 4 is not particularly limited, but when the ionic conductor 6 is composed of LDH and the hydroxide basic layer of LDH contains Ni, Al, Ti and OH groups, the following steps ( It can be produced in 1) to (4).

(1) Prepare the support 5.

(2) The entire support 5 is impregnated with a mixed sol of alumina and titania and heat-treated to form an alumina-titania layer. As will be described later, in order to grow LDH from the entire surface of the support 5, it is important to form an alumina-titania layer on the entire surface of the support 5, so a mixed sol of alumina and titania is impregnated. The heat treatment is performed a plurality of times. As a result, an alumina-titania layer can be formed on the entire surface of the support 5.

(3) The support 5 is immersed in a raw material aqueous solution containing ^{nickel ions (Ni 2+) and urea.}

(4) The ionic conductor 6 is formed by hydrothermally treating the support 5 in the raw material aqueous solution to form LDH on the support 5 and in the support 5. At this time, by appropriately adjusting the hydrothermal treatment time and the solution concentration, the closed pores 61 can be formed in the ion conductor 6 by stopping the reaction before the pores are closed. Since LDH grows around the alumina-titania layer formed on the surface of the support 5, LDH is generated from the entire surface of the support 5 when the alumina-titania layer is formed on the entire surface of the support 5. Will grow. As a result, the closed pores 61 can be separated from the support 5.

(1st and 2nd separators 11 and 12)
As shown in FIG. 1, the first and second separators 11 and 12 are arranged so as to sandwich the membrane electrode assembly 10 from both sides in the thickness direction (z-axis direction). The first separator 11 is configured to supply an oxidizing agent containing _{oxygen (O 2) to the cathode 2.} The first separator 11 has a first flow path 111. The first flow path 111 faces the cathode 2. _{An oxidizing agent containing oxygen (O 2} ) is supplied to the first flow path 111.

The second separator 12 is configured to supply fuel containing a hydrogen atom (H) to the anode 3. The second separator 12 has a second flow path 121. The second flow path 121 faces the anode 3. Fuel containing a hydrogen atom (H) is supplied to the second flow path 121. For example, methanol is supplied to the second flow path 121.

When a plurality of membrane electrode assemblies 10 are stacked via the first and second separators 11 and 12, the first separator 11 is placed on a surface opposite to the surface on which the first flow path 111 is formed. A second flow path is formed. Further, in the second separator 12, the first flow path is formed on the surface opposite to the surface on which the second flow path 121 is formed.

A first seal member 13a is arranged between the first separator 11 and the membrane electrode assembly 10. The first sealing member 13a improves the adhesion between the first separator 11 and the membrane electrode assembly 10 to prevent the oxidizing agent from leaking to the outside. A second sealing member 13b is arranged between the second separator 12 and the membrane electrode assembly 10. The second sealing member 13b improves the adhesion between the second separator 12 and the membrane electrode assembly 10 to prevent fuel from leaking to the outside.

The first and second sealing members 13a and 13b are annular and are in contact with the outer peripheral portion of the electrolyte membrane 4 of the membrane electrode assembly 10. Examples of the first and second seal members 13a and 13b include an O-ring and a rubber sheet. The first seal member 13a may be integrally formed with the first separator 11. The second seal member 13b may be integrally configured with the second separator 12.

(Modified example of the embodiment)
Although the embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made without departing from the spirit of the present invention.

Modification 1
In the above embodiment, with respect to the distance from the first catalyst layer 21, each first adsorption unit 23 is substantially the same as the adjacent first adsorption unit 23, but the position of each first adsorption unit 23 is not limited to this. .. For example, as shown in FIG. 5, each first adsorption unit 23 may be different from the adjacent first adsorption unit 23 with respect to the distance D1 from the first catalyst layer 21. The distance D1 between the first adsorption unit 23 and the first catalyst layer 21 is not particularly limited, but can be, for example, about 5 to 30 μm. As shown in FIG. 6, each second adsorption unit 33 may also be different from the adjacent second adsorption unit 33 in the distance D2 from the second catalyst layer 31. The distance D2 between the second adsorption portion 33 and the second catalyst layer 31 is also not particularly limited, but can be, for example, about 5 to 30 μm.

Modification 2
As shown in FIG. 7, the first gas diffusion layer 22 can be divided into a first central portion 22a and a first outer peripheral portion 22b. The first outer peripheral portion 22b is arranged so as to surround the first central portion 22a. The width W1 of the first outer peripheral portion 22b can be 5% of the length L1 of the long side of the first gas diffusion layer 22.

The first suction portion 23 is arranged only inside the first central portion 22a, and may not be arranged inside the first outer peripheral portion 22b.

Further, the cathode 2 may be configured so that the content of the first adsorption portion 23 in the first central portion 22a is larger than the content of the first adsorption portion 23 in the first outer peripheral portion 22b.

The content of the first adsorption portion 23 in the first central portion 22a and the content of the first adsorption portion 23 in the first outer peripheral portion 22b can be measured, for example, as follows.

First, three cut surfaces as shown in FIG. 5 are formed. Specifically, as shown in FIG. 8, the first cut surface C1 is formed by passing through the center C of the first gas diffusion layer 22 and cutting along the direction in which the first flow path 111 extends. Further, a second cut surface C2 and a third cut surface C3 cut so as to be parallel to the first cut surface C1 are formed.

The distance d1 between the first cut surface C1 and the second cut surface C2 is the same as the distance d2 between the first cut surface C1 and the third cut surface C3, and these distances d1 and d2 are the first gas. It is 25% of the first dimension d0 of the diffusion layer 22. Here, the first dimension d0 of the first gas diffusion layer 22 means a dimension that passes through the center C of the first gas diffusion layer 22 and extends in a direction orthogonal to the first cut surface C1. As shown in FIG. 9, each cut surface C1 to C3 is formed by the same method even when the plan view is not rectangular, for example, when it is circular.

As a result, the cut surfaces C1 to C3 as shown in FIG. 10 are formed. Next, the first central portion 22a and the pair of first outer peripheral portions 22b of the first gas diffusion layer 22 on the cut surfaces C1 to C3 include the boundary between the first catalyst layer 21 and the first gas diffusion layer 22. The image is magnified 500 times by SEM.

Specifically, in the first central portion 22a of the first gas diffusion layer 22 on the first cut surface C1, a total of three visual fields of the central portion and two locations separated from the central portion by a distance d3 are photographed. The distance d3 is 25% of the second dimension d4 of the first gas diffusion layer 22 on each cut surface. Here, the second dimension d4 of the first gas diffusion layer 22 means the dimension in the longitudinal direction of the first gas diffusion layer 22 on each cut surface.

Similarly to the first cut surface C1, the second cut surface C2 and the third cut surface C3 are also photographed in three fields at the first central portion 22a of the first gas diffusion layer 22. The content rate of the first adsorption portion 23 is calculated by performing element mapping of the elements constituting the first adsorption portion 23 in each imaging field of view of the first central portion 22a photographed in this manner. Then, the average value of the content of the first adsorption portion 23 in each visual field can be used as the content rate of the first adsorption portion 23 in the first central portion 22a.

Further, in a pair of first outer peripheral portions 22b located at both ends of the first gas diffusion layer 22 on the first cut surface C1, the central portion of each first outer peripheral portion 22b in the x-axis direction is photographed. That is, on the first cut surface C1, the first outer peripheral portion 22b is photographed for two fields of view. Also on the second cut surface C2 and the third cut surface C3, the first outer peripheral portion 22b is photographed for two fields of view in the same manner as the first cut surface C1.

The content rate of the first adsorption portion 23 is calculated by performing elemental mapping of the elements constituting the first adsorption portion 23 in each imaging field of view of the first outer peripheral portion 22b photographed in this manner. Then, the average value of the content rate of the first suction portion 23 in each visual field can be set as the content rate of the first suction portion 23 in the first outer peripheral portion 22b.

Modification 3
The distance D1 between the first adsorption portion 23 and the first catalyst layer 21 in the first central portion 22a is larger than the distance D1 between the first adsorption portion 23 and the first catalyst layer 21 in the first outer peripheral portion 22b. , Each first suction unit 23 can be arranged. The distance D1 can be measured by using an image taken when measuring the content rate of the first adsorption unit 23. The distance D1 can be the average value of the measured values.

Modification 4
As shown in FIG. 11, the second gas diffusion layer 32 can be divided into a second central portion 32a and a second outer peripheral portion 32b. The second outer peripheral portion 32b is arranged so as to surround the second central portion 32a. The width W2 of the second outer peripheral portion 32b can be 5% of the length L2 of the long side of the second gas diffusion layer 32.

The second suction portion 33 is arranged only inside the second central portion 32a, and may not be arranged inside the second outer peripheral portion 32b.

Further, the cathode 2 may be configured so that the content of the second adsorption portion 33 in the second central portion 32a is larger than the content of the second adsorption portion 33 in the second outer peripheral portion 32b.

The content of the second adsorption portion 33 in the second central portion 32a and the content of the second adsorption portion 33 in the second outer peripheral portion 32b can be measured, for example, as follows.

First, three cut surfaces as shown in FIG. 6 are formed. These three cut surfaces are, for example, the cut surfaces C1 to 3 created for measuring the content rate of the first suction portion 23 in the first central portion 22a and the content rate of the first suction portion 23 in the first outer peripheral portion 22b. Same as C3.

Next, the second central portion 32a and the pair of second outer peripheral portions 32b of the second gas diffusion layer 32 on the cut surfaces C1 to C3 include the boundary between the second catalyst layer 31 and the second gas diffusion layer 32. The image is magnified 500 times by SEM.

Specifically, as shown in FIG. 10, in the second central portion 32a of the second gas diffusion layer 32 on the first cut surface C1, a total of three visual fields of the central portion and two locations separated from the central portion by a distance d5 are provided. Take a picture. The distance d5 is 25% of the dimension d6 of the second gas diffusion layer 32 on each cut surface. Here, the dimension d6 of the second gas diffusion layer 32 means the dimension in the longitudinal direction of the second gas diffusion layer 32 on each cut surface.

Similarly to the first cut surface C1, the second cut surface C2 and the third cut surface C3 are also photographed in three fields at the second central portion 32a of the second gas diffusion layer 32. The content rate of the second adsorption portion 33 is calculated by performing elemental mapping of the elements constituting the second adsorption portion 33 in each imaging field of view of the second central portion 32a photographed in this manner. Then, the average value of the content rate of the second adsorption portion 33 in each visual field can be set as the content rate of the second adsorption portion 33 in the second central portion 32a.

Further, in a pair of second outer peripheral portions 32b located at both ends of the second gas diffusion layer 32 on the first cut surface C1, the central portion of each second outer peripheral portion 32b in the x-axis direction is photographed. That is, on the first cut surface C1, the second outer peripheral portion 32b is photographed for two fields of view. Similarly to the first cut surface C1, the second outer peripheral portion 32b is photographed for two fields of view on the second cut surface C2 and the third cut surface C3.

The content rate of the second adsorption portion 33 is calculated by performing elemental mapping of the elements constituting the second adsorption portion 33 in each imaging field of view of the second outer peripheral portion 32b photographed in this manner. Then, the average value of the content rate of the second suction portion 33 in each visual field can be set as the content rate of the second suction portion 33 in the second outer peripheral portion 32b.

Modification 5
The distance D2 between the second adsorption portion 33 and the second catalyst layer 31 in the second central portion 32a is larger than the distance D2 between the second adsorption portion 33 and the second catalyst layer 31 in the second outer peripheral portion 32b. , Each second suction unit 33 can be arranged. The distance D2 can be measured by using the image taken when measuring the content rate of the second adsorption portion 33. The distance D2 can be the average value of the measured values.

Modification 6
In the above embodiment, the anode 3 has a plurality of second adsorption portions 33, but is not limited to this configuration. For example, the anode 3 does not have to have the second adsorption portion 33.

Modification 7
In the above embodiment, the support 5 of the electrolyte membrane 4 is composed of a porous base material, but the support 5 is not limited thereto. For example, the support 5 of the electrolyte membrane 4 may be a binder. For example, as shown in FIG. 12, the support 5 configured as a binder is arranged between the constituent particles of the ionic conductor 6. The support 5 binds the constituent particles of the ionic conductor 6 to each other. For example, the support 5 maintains the shape of the electrolyte membrane 4 by binding LDH particles to each other. Examples of such a binder include polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene-butadiene rubber, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and vinylidene fluoride-hexa. Fluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene Polymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, or ethylene-acrylic acid co-polymer Polymers and the like can be mentioned.

Modification 8
In the above embodiment, the electrolyte membrane 4 has the composite portion 4a, the first membrane-like portion 4b, and the second membrane-like portion 4c, but may have only the composite portion 4a. That is, the electrolyte membrane 4 does not have to include at least one of the first membrane-like portion 4b and the second membrane-like portion 4c.

Modification 9
In the above embodiment, the electrolyte membrane 4 has the support 5 and the ionic conductor 6, but the configuration is not limited to this. For example, the electrolyte membrane 4 may have only the ionic conductor 6. In this case, the ion conductor 6 can be a fluoropolymer resin. The ionic conductor has a main chain and a side chain.

The main chain contains carbon (C) and fluorine (F). The main chain contains a CF bond and does not contain a CH bond. The backbone skeleton can be composed of polytetrafluoroethylene (PTFE). The skeleton of the main chain means the carbon chain in the polymer having the maximum number of carbon atoms.

The side chain is connected to the main chain. The side chain is branched from the main chain. The side chain contains a sulfone alkaline group (-SO ₃ ^- M ⁺ group) at the end. The sulfonic acid alkali group has a structure in which the hydrogen ion (H ⁺ ) of the sulfonic acid group (-SO ₃ ^- H ⁺ group) is replaced with the alkali metal ion (M ^+). As the alkali metal (M), one or more selected from the group consisting of _{Li, K, Na, and NH 4 can be used.} The sulfonic acid alkaline group is obtained by cation-exchange of the hydrogen ion of the sulfonic acid group with the alkali metal ion. The side chain may contain a carboxyalkali group (-COO ^- M ⁺ group) at the end. Carboxy alkali group, a carboxyl group ^- has a structure in which hydrogen ions ^{(-COO H +) (H +} ) has been replaced with an alkali metal ion ^{(M +).} The method for producing the ionic conductor will be described later.

By introducing such a sulfone alkaline group, the ionic conductor exhibits high ionic conductivity in an alkaline environment.

If at least one side chain of all the side chains of the ionic conductor has a sulfonic alkali group, the ionic conductor can exhibit ionic conductivity. In order to improve ionic conductivity, it is preferable that 50% or more of the side chains of the ionic conductor have a sulfone alkali group, and 80% or more of the side chains have a sulfone alkali group. It is more preferable to have it, and it is particularly preferable that all side chains have a sulfone alkali group.

The structure of the ionic conductor can be represented by the following general formula (1).

In the general formula (1), M is the above-mentioned alkali metal, and X is a fluorine atom or a trifluoromethyl group. In the general formula (1), x and y are integers, x can be 5 or more and 14 or less, and y can be 1000. In the general formula (1), p is an integer of 0 or more and 3 or less, q is 0 or 1, and n is an integer of 1 or more and 12 or less.

(Manufacturing method of ionic conductor)
Next, a method for producing the ionic conductor constituting the electrolyte membrane 4 will be described.

First, a perfluorosulfonic acid polymer is prepared. The perfluorosulfonic acid polymer is a fluoropolymer resin. Specifically, the perfluorosulfonic acid polymer is a perfluorocarbon material composed of a hydrophobic perfluorocarbon skeleton composed of CF bonds and a perfluoro side chain having a sulfonic acid group. The side chain of the perfluorosulfonic acid polymer contains a sulfonic acid group at the end. As a result, the perfluorosulfonic acid polymer exhibits proton conductivity.

As perfluorosulfonic acid polymers, commercially available products such as Nafion (Nafion (registered trademark), DuPont), Flemion (Flemion (registered trademark), Asahi Glass Co., Ltd.), Aciplex (Aciplex (registered trademark), Asahi Kasei Co., Ltd.) May be used.

The structure of the perfluorosulfonic acid polymer can be represented by the following general formula (2).

In the general formula (2), X is a fluorine atom or a trifluoromethyl group. In the general formula (2), x and y are integers, x can be 5 or more and 14 or less, and y can be 1000. In the general formula (2), p is an integer of 0 or more and 3 or less, q is 0 or 1, and n is an integer of 1 or more and 12 or less.

Next, an alkaline solution containing the desired alkali metal ion is prepared. Alkali metal ions contained in the alkaline solution is a Li, K, Na, and one or more ions of alkali metal (M) selected from the group consisting of NH _4. Therefore, as the alkaline solution, potassium hydroxide solution, sodium hydroxide solution, potassium carbonate, potassium hydrogen carbonate and the like can be used. The concentration of the alkali metal ion in the alkaline solution is not particularly limited as long as the cation exchange described later is sufficiently performed, but can be, for example, 0.01 to 1 mol / L.

Next, the perfluorosulfonic acid polymer is subjected to an alkaline treatment using an alkaline solution. In this alkaline treatment, the perfluorosulfonic acid polymer may be immersed in an alkaline solution, the perfluorosulfonic acid polymer may be impregnated with an alkaline solution, or the perfluorosulfonic acid polymer may be coated with an alkaline solution. good. The alkaline treatment can be performed at room temperature (for example, 10 to 30 ° C.).

By this alkali treatment, the hydrogen ion (H ⁺ _{) of the sulfonic acid group (-SO 3} ^- H ⁺ group) located at the end of the side chain of the perfluorosulfonic acid polymer is cation-substituted with the alkali metal ion (M ^+). .. As a result, it exhibits high ionic conductivity in the alkaline solution represented by the general formula (1).

Modification 10
The first adsorption unit 23 may have a cation exchange ability. Preferably, the first adsorption unit 23 has an ion exchange ability for polyvalent cations. The first adsorption unit 23 may have an ion exchange ability only for polyvalent cations and may not have an ion exchange ability for monovalent cations. The first adsorption unit 23 adsorbs Fe ²⁺ , Fe ³⁺ , Cr ²⁺ , Ni ^{2+ and the} like.

Specifically, the first adsorption unit 23 includes an adsorbent and a catalyst. The adsorbent contained in the first adsorbent 23 has a cation exchange ability. The material of the adsorbent contained in the first adsorbent 23 can be composed of, for example, the ionic conductor of the electrolyte membrane 4 described in the modified example 5. In addition, the adsorbent contained in the first adsorbent 23 may be made of palladium, nickel, or the like. The second adsorption unit 33 may also have a cation exchange ability like the first adsorption unit 23.

Modification 7
In the above embodiment, the embodiment in which the fuel cell according to the present invention is applied to the polymer electrolyte fuel cell has been described, but the object to which the fuel cell according to the present invention is applied is not limited to the polymer electrolyte fuel cell, for example. It can also be applied to other fuel cells such as polymer electrolyte fuel cells using a proton conductive film.

4 Electrolyte film 10 Membrane electrode assembly 21 1st catalyst layer 22 1st gas diffusion layer 23 1st adsorption part 31 2nd catalyst layer 32 2nd gas diffusion layer 33 2nd adsorption part

Claims (15)

Electrolyte membrane and
A first catalyst layer having catalytic activity for an oxygen reduction reaction and arranged on the electrolyte membrane,
The first gas diffusion layer arranged on the first catalyst layer and
A catalyst having catalytic activity for an oxygen reduction reaction, and at least one first adsorption portion arranged inside the first gas diffusion layer.
Membrane electrode assembly.
It is provided with a plurality of the first suction portions.
The plurality of first suction portions are arranged at intervals from each other.
The membrane electrode assembly according to claim 1.
The first adsorption portion is arranged at a distance from the first catalyst layer.
The membrane electrode assembly according to claim 1 or 2.
The first gas diffusion layer has a first central portion and a first outer peripheral portion surrounding the first central portion.
The membrane electrode assembly according to any one of claims 1 to 3.
The first suction portion is arranged inside the first central portion and is not arranged inside the first outer peripheral portion.
The membrane electrode assembly according to claim 4.
The content of the first adsorption portion in the first central portion is larger than the content of the first adsorption portion in the first outer peripheral portion.
The membrane electrode assembly according to claim 4.
The distance between the first adsorption portion and the first catalyst layer in the first central portion is larger than the distance between the first adsorption portion and the first catalyst layer in the first outer peripheral portion.
The membrane electrode assembly according to any one of claims 4 to 6.
A second catalyst layer having catalytic activity for the oxidation reaction of the fuel and arranged on the electrolyte membrane on the opposite side of the first catalyst layer.
A second gas diffusion layer arranged on the second catalyst layer and
The membrane electrode assembly according to any one of claims 1 to 7, further comprising.
At least one second adsorption portion, which contains a catalyst having catalytic activity for the oxidation reaction of fuel and is arranged inside the second gas diffusion layer.
8. The membrane electrode assembly according to claim 8.
With a plurality of the second suction portions,
The plurality of second suction portions are arranged at intervals from each other.
The membrane electrode assembly according to claim 9.
The second adsorption portion is arranged at a distance from the second catalyst layer.
The membrane electrode assembly according to claim 9 or 10.
The second gas diffusion layer has a second central portion and a second outer peripheral portion surrounding the second central portion.
The membrane electrode assembly according to any one of claims 9 to 11.
The second suction portion is arranged inside the second central portion and is not arranged inside the second outer peripheral portion.
The membrane electrode assembly according to claim 12.
The content of the second adsorption portion in the second central portion is larger than the content of the second adsorption portion in the second outer peripheral portion.
The membrane electrode assembly according to claim 12.
The distance between the second adsorption portion and the second catalyst layer in the second central portion is larger than the distance between the second adsorption portion and the second catalyst layer in the second outer peripheral portion.
The membrane electrode assembly according to any one of claims 12 to 14.

Images