JP6850851B1 - Fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a decrease in output of a fuel cell. A fuel cell 100 includes a membrane electrode assembly 10, first and second separators 11, 12, first and second seal members 13, 14, and a first oxidation catalyst section 15. The first seal member 13 is arranged between the first separator 11 and the membrane electrode assembly 10. The first sealing member 13 seals between the outer peripheral portion of the membrane electrode assembly 10 and the outer peripheral portion of the first separator 11. The second sealing member 14 is arranged between the second separator 12 and the membrane electrode assembly 10. The second sealing member 14 seals between the outer peripheral portion of the membrane electrode assembly 10 and the outer peripheral portion of the second separator 12. The first oxidation catalyst unit 15 is arranged between the first seal member 13 and the first electrode 3. The first oxidation catalyst unit 15 has an oxidation catalyst that is active in the oxidation reaction between the fuel supplied to the membrane electrode assembly 10 and the oxidizing agent. [Selection diagram] Fig. 1

Description

The present invention relates to a fuel cell.

A fuel cell extracts electrical energy by an electrochemical reaction between a fuel such as hydrogen and an oxidizing agent such as air. The fuel cell has a membrane electrode assembly and a pair of separators. The membrane electrode assembly has an electrolyte and a pair of electrodes. The electrolyte is located between the pair of electrodes. The pair of separators are arranged so as to sandwich the membrane electrode assembly. A sealing member is provided so that the fuel or the oxidizing agent does not leak to the outside from between the membrane electrode assembly and the separator.

Japanese Unexamined Patent Publication No. 2018-206572

In a fuel cell having the above configuration, it is required to suppress a decrease in output. Therefore, an object of the present invention is to suppress a decrease in the output of the fuel cell.

The fuel cell according to the first aspect of the present invention includes a membrane electrode assembly, a first separator, a second separator, a first seal member, a second seal member, and a first oxidation catalyst portion. .. The membrane electrode junction has an electrolyte, a first electrode, and a second electrode. The first separator is arranged on the first electrode side of the membrane electrode assembly. The second separator is arranged on the second electrode side of the membrane electrode assembly. The first sealing member is arranged between the first separator and the membrane electrode assembly. The first sealing member seals between the outer peripheral portion of the membrane electrode assembly and the outer peripheral portion of the first separator. The second sealing member is arranged between the second separator and the membrane electrode assembly. The second sealing member seals between the outer peripheral portion of the membrane electrode assembly and the outer peripheral portion of the second separator. The first oxidation catalyst portion is arranged between the first seal member and the first electrode. The first oxidation catalyst section has an oxidation catalyst that is active in the oxidation reaction between the fuel supplied to the membrane electrode assembly and the oxidizing agent.

According to this configuration, it is possible to suppress a decrease in the output of the fuel cell in the following manner. First, when fuel is supplied to the first electrode and the oxidizing agent is supplied to the second electrode, the oxidizing agent may enter the gas flow path of the first separator due to poor adhesion of the first sealing member or the like. Here, in a conventional fuel cell, the oxidant may reach the first electrode, and a combustion reaction between the oxidant and the fuel may occur on the surface of the first electrode. When the combustion reaction occurs on the surface of the first electrode in this way, a hybrid potential is formed in the first electrode, and the output of the fuel cell decreases.

On the other hand, in the fuel cell configured as described above, since the first oxidation catalyst portion is arranged between the first seal member and the first electrode, the output reduction of the fuel cell described above is described as follows. Can be suppressed as such. First, the oxidant that has entered the gas flow path of the first separator undergoes a combustion reaction with the fuel flowing in the gas flow path on the first oxidation catalyst section before reaching the first electrode. Since the oxidizing agent is consumed by this combustion reaction, the amount of the oxidizing agent reaching the first electrode is reduced. As a result, the occurrence of a combustion reaction between the oxidant and the fuel on the surface of the first electrode is reduced, and a decrease in the output of the fuel cell can be suppressed. Even when the oxidizing agent is supplied to the first electrode and the fuel is supplied to the second electrode, the decrease in the output of the fuel cell can be similarly suppressed.

Preferably, the fuel cell further comprises a second oxidation catalyst section. The second oxidation catalyst portion is arranged between the second seal member and the second electrode. The second oxidation catalyst section has an oxidation catalyst that is active in the oxidation reaction between the fuel supplied to the membrane electrode assembly and the oxidizing agent.

Preferably, the first oxidation catalyst section is arranged on the first seal member.

Preferably, the electrolyte has a first central region and a first outer peripheral region. The first central region is a region in which the first electrode is arranged. The first outer peripheral region is a region between the first central region and the first seal member. The first oxidation catalyst section is arranged in the first outer peripheral region.

Preferably, the first electrode is rectangular in plan view. The first seal member has a rectangular annular shape in a plan view. The first oxidation catalyst portion is arranged between the corner portion of the first electrode and the corner portion of the first seal member.

Preferably, the first oxidation catalyst section has platinum as the oxidation catalyst.

According to the present invention, it is possible to suppress a decrease in the output of the fuel cell.

Sectional view of the fuel cell. Top view of the electrolyte. Bottom view of the electrolyte. An enlarged cross-sectional view of a membrane electrode assembly. Top view of the fuel cell with the first separator removed. Bottom view of the fuel cell with the second separator removed. The plan view of the fuel cell which concerns on the modification with the 1st separator removed. The plan view of the fuel cell which concerns on the modification with the 1st separator removed. Sectional drawing of the fuel cell which concerns on modification. Sectional drawing of the fuel cell which concerns on modification. An enlarged cross-sectional view of the electrolyte according to the modified example. An enlarged cross-sectional view of a membrane electrode assembly according to a modified example.

Hereinafter, the solid alkaline fuel cell 100, which is an embodiment of the fuel cell according to the present invention, will be described with reference to the drawings. The solid alkaline fuel cell 100 is a type of alkaline fuel cell (AFC) having a hydroxide ion as a carrier.

(Solid alkaline fuel cell 100)
FIG. 1 is a cross-sectional view showing the configuration of the solid alkaline fuel cell 100 according to the embodiment. The solid alkaline fuel cell 100 includes a membrane electrode assembly 10, a first separator 11, a second separator 12, a first seal member 13, a second seal member 14, a first oxidation catalyst section 15, and a second oxidation catalyst section 16. have. 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 an anode 2 (an example of a first electrode), a cathode 3 (an example of a second electrode), and an electrolyte 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.

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

(Anode 2)
The anode 2 is arranged on the first surface 41 side (upper surface side in FIG. 1) of the electrolyte 4. The anode 2 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 2 via the first flow path 111 of the first separator 11. As the fuel, it is preferable to use methanol. The anode 2 is a porous body capable of diffusing fuel inside. The porosity of the anode 2 is not particularly limited. The thickness of the anode 2 is not particularly limited, but can be, for example, 3 to 500 μm.

The fuel may contain a fuel compound capable of reacting with hydroxide ions (OH ⁻ ) at the anode 2, 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).} Class, (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 hydroxylamines such as (v) 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 catalyst poisoning by carbon monoxide. is there.

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 90% by weight, preferably 1 to 30% 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.

The anode 2 is not particularly limited as long as it contains a known anode catalyst used for AFC. Examples of anode catalysts 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 2 and the catalysts constituting the anode 2 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 method for producing the anode 2 is not particularly limited, but for example, the anode catalyst and, if desired, the carrier are mixed with a binder to form a paste. Then, this paste-like mixture can be formed by applying it on the first surface 41 of the electrolyte 4.

(Cathode 3)
The cathode 3 is arranged on the second surface 42 side (lower surface side in FIG. 1) of the electrolyte 4. The cathode 3 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 3 via the second flow path 121 of the second separator 12. As the oxidizing agent, it is preferable to use air, and it is more preferable that the air is humidified. The cathode 3 is a porous body capable of diffusing an oxidizing agent inside. The porosity of the cathode 3 is not particularly limited. The thickness of the cathode 3 is not particularly limited, but can be, for example, 5 to 200 μm.

The cathode 3 is not particularly limited as long as it contains a known air electrode catalyst used for AFC. Examples of cathode catalysts include group 8-10 elements (IUPAC format periodic table) such as group 11 elements (Ru, Rh, Pd, Os, Ir, Pt) and group 11 elements (Fe, Co, Ni). Group 8-10 elements), Group 11 elements such as Cu, Ag, Au (elements belonging to Group 11 in the periodic table in the IUPAC format), rhodium phthalocyanine, tetraphenylporphyrin, Co-salene, Ni-salene ( Salen = N, N'-bis (salicylidene) ethylenediamine), silver nitrate, and any combination thereof. The amount of the catalyst supported on the cathode 3 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 3 or the catalyst constituting the cathode 3 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 method for producing the cathode 3 is not particularly limited, but for example, the cathode catalyst and, if desired, the carrier are mixed with a binder to form a paste. Then, this paste-like mixture can be formed by applying it on the second surface 42 of the electrolyte 4.

(Electrolyte 4)
The electrolyte 4 is arranged between the anode 2 and the cathode 3. The electrolyte 4 is connected to each of the anode 2 and the cathode 3. Electrolyte 4 has ionic conductivity. The electrolyte 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 anode 2 is arranged on the first surface 41 side of the electrolyte 4, and the cathode 3 is arranged on the second surface 42 side.

FIG. 2 is a plan view of the electrolyte 4. In FIG. 2, the region surrounded by the inner two-dot chain line indicates the region where the anode 2 is arranged, and the region outside the outer two-dot chain line is the region where the first seal member 13 is arranged. Is shown.

As shown in FIG. 2, the electrolyte 4 has a first central region 43 and a first outer peripheral region 44. The first central region 43 is a region in which the anode 2 is arranged. The anode 2 and the first central region 43 are rectangular in a plan view.

The first outer peripheral region 44 is an region between the first central region 43 and the first seal member 13. That is, the first outer peripheral region 44 surrounds the first central region 43, and is surrounded by the first seal member 13. The first outer peripheral region 44 has a frame shape.

FIG. 3 is a bottom view of the electrolyte 4. In FIG. 3, the region surrounded by the inner two-dot chain line indicates the region where the cathode 3 is arranged, and the region outside the outer two-dot chain line is the region where the second seal member 14 is arranged. Is shown.

As shown in FIG. 3, the electrolyte 4 has a second central region 45 and a second outer peripheral region 46. The second central region 45 is a region where the cathode 3 is arranged. The cathode 3 and the second central region 45 are rectangular in a plan view. The second central region 45 may have the same size as the first central region 43, may be smaller than the first central region 43, or may be larger than the first central region 43.

The second outer peripheral region 46 is an region between the second central region 45 and the second seal member 14. That is, the second outer peripheral region 46 surrounds the second central region 45, and is surrounded by the second seal member 14. The second outer peripheral region 46 has a frame shape.

FIG. 4 is a schematic view showing an enlarged cross section of the electrolyte 4. The electrolyte 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 a porous substrate 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 support 5 forms a continuous hole 5a. The continuous holes 5a are formed by connecting the holes in a three-dimensional and mesh pattern, and are 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 foamed 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, polyethylene 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. By setting it within these ranges, it is possible to improve the density of the ionic conductor 6 while imparting the strength of the support 5 as a support. 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 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 3 side to the anode 2 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, still more preferably 1.0 mS / cm or more. The higher the hydroxide ion conductivity of the ionic 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. Aluminum ions in LDH are typically considered to be Al ³⁺ , but are 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 from, for example, 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 4 has a composite portion 4a, a first membranous portion 4b, and a second membranous 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 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 4 does not have at least one of the first film-like portion 4b and the second film-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 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 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 4 and the cathode 3 and / and the interface between the electrolyte 4 and the anode 2. As a result, it is possible to prevent the electrolyte 4 from peeling off from the cathode 3 and / and the anode 2 and the electrolyte 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 3 and the cathode 3 It is possible to suppress the generation of thermal stress at the interface with the electrolyte 4 and / and the interface between the anode 2 and the electrolyte 4. Therefore, it is possible to prevent the electrolyte 4 from peeling off from the cathode 3 and / and the anode 2 or the electrolyte 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 4 undergoes a volume change or deformation as compared with the case where the air-closing hole 61 comes into direct contact with the support 5, the angle formed by the support 5, the composite portion 4a, and the air-closing hole 61 is formed. It is possible to prevent the composite portion 4a from peeling off from the support 5 starting from the 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.

For the average equivalent circle diameter of each closed pore 61, the cross section of the electrolyte 4 was observed with an electron microscope at a magnification of 20,000 to 1,500,000 times, and the equivalent circle diameter of 20 randomly selected closed pores 61 was calculated. Obtained by averaging. The circle-equivalent diameter of the closed hole 61 is the diameter of a circle having the same area as the closed hole 61 in the cross section of the electrolyte 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 pore 61. To do.

The first film-like portion 4b is connected to the anode 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 cathode 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 4)
The method for producing the electrolyte 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 step (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 ionic 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 separator 11 is arranged on the anode 2 side of the membrane electrode assembly 10. The second separator 12 is arranged on the cathode 3 side of the membrane electrode assembly 10. A membrane electrode assembly 10 is arranged between the first separator 11 and the second separator 12. In the stacking direction (z-axis direction), the membrane electrode assembly 10 is sandwiched between the first separator 11 and the second separator 12.

The first separator 11 is configured to supply fuel containing a hydrogen atom (H) to the anode 2. The first separator 11 has a first flow path 111. The first flow path 111 faces the anode 2. A fuel gas supply path (not shown) is connected to the first flow path 111, and fuel containing a hydrogen atom (H) is supplied. For example, methanol is supplied to the first flow path 111.

The second separator 12 is configured to supply an oxidizing agent containing _{oxygen (O 2) to the cathode 3.} The second separator 12 has a first flow path 121. The second flow path 121 faces the cathode 3. An oxidant gas supply path (not shown) is connected to the second flow path 121, and an oxidant containing oxygen (O ₂ ) is supplied.

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.

(1st seal member 13)
The first seal member 13 is arranged between the first separator 11 and the membrane electrode assembly 10. The first sealing member 13 seals between the first separator 11 and the membrane electrode assembly 10. Specifically, the first sealing member 13 seals between the outer peripheral portion of the first separator 11 and the outer peripheral portion of the membrane electrode assembly 10. The first seal member 13 is in contact with the outer peripheral portion of the electrolyte 4 of the membrane electrode joint portion 10. The first seal member 13 is in contact with the first surface 41 of the electrolyte 4.

The first seal member 13 is configured to prevent the fuel flowing in the first gas flow path 111 from leaking to the outside. Further, the first seal member 13 is configured to prevent the oxidizing agent supplied to the cathode 3 from entering the first gas flow path 111.

FIG. 5 is a plan view of the fuel cell 100 in a state where the first separator 11 is removed. As shown in FIG. 5, the first seal member 13 has a rectangular annular shape in a plan view. The first seal member 13 is arranged so as to surround the anode 2. The first seal member 13 is arranged at intervals with respect to the anode 2. The first oxidation catalyst unit 15 is arranged in the space between the first seal member 13 and the anode 2.

The first seal member 13 may be, for example, an O-ring, a rubber sheet, or the like. The first seal member 13 is a separate member from the first separator 11. The first seal member 13 may be integrally configured with the first separator 11.

(2nd seal member 14)
As shown in FIG. 1, the second sealing member 14 is arranged between the second separator 12 and the membrane electrode assembly 10. The second sealing member 14 seals between the second separator 12 and the membrane electrode assembly 10. Specifically, the second sealing member 14 seals between the outer peripheral portion of the second separator 12 and the outer peripheral portion of the membrane electrode assembly 10. The second seal member 14 is in contact with the outer peripheral portion of the electrolyte 4 of the membrane electrode joint portion 10. The second seal member 14 is in contact with the second surface 42 of the electrolyte 4.

The second seal member 14 is configured to prevent the oxidizing agent flowing in the second gas flow path 121 from leaking to the outside. Further, the second seal member 14 is configured to prevent the fuel supplied to the anode 2 from entering the second gas flow path 121.

FIG. 6 is a bottom view of the fuel cell 100 with the second separator 12 removed. As shown in FIG. 6, the second seal member 14 has a rectangular annular shape in a plan view. The second seal member 14 is arranged so as to surround the cathode 3. The second seal member 14 is arranged at intervals with respect to the cathode 3. The second oxidation catalyst unit 16 is arranged in the space between the second seal member 14 and the cathode 3.

The second seal member 14 can be exemplified by, for example, an O-ring or a rubber sheet. The second seal member 14 is a separate member from the second separator 12. The second seal member 14 may be integrally configured with the second separator 12.

(First Oxidation Catalyst Unit 15)
As shown in FIGS. 1 and 5, the first oxidation catalyst unit 15 is arranged between the first seal member 13 and the anode 2. Specifically, the first oxidation catalyst unit 15 is arranged on the inner peripheral surface of the first seal member 13. The first oxidation catalyst portion 15 extends in an annular shape along the inner peripheral surface of the first seal member 13.

The first oxidation catalyst unit 15 has an oxidation catalyst that is active in the oxidation reaction between the fuel and the oxidizing agent. Specifically, the first oxidation catalyst unit 15 has at least one of platinum, rhodium, iridium, ruthenium, nickel and iron as an oxidation catalyst. The oxidation catalyst may be in the form of an oxide in part or in whole. Preferably, the first oxidation catalyst unit 15 has platinum as an oxidation catalyst.

For example, by applying the oxidation catalyst on the inner peripheral surface of the first seal member 13 before assembling as a fuel cell stack, the first oxidation catalyst portion 15 is placed on the inner peripheral surface of the first seal member 13. Can be formed. As a method for applying the oxidation catalyst, a spray coating method, a brush coating method, a printing method or the like can be used. A binder may be added as appropriate in order to improve the stickiness of the oxidation catalyst.

Since the first oxidation catalyst unit 15 is arranged in this way, the following effects can be obtained. For example, an oxidizing agent such as air may enter the first gas flow path 111 due to poor adhesion of the first sealing member 13. Here, when the first oxidation catalyst unit 15 is not arranged, when the oxidizing agent reaches the anode 2, a combustion reaction between the oxidizing agent and the fuel occurs on the surface of the anode 2. As a result, a hybrid potential is formed in the anode 2, and the output of the fuel cell 100 may decrease.

On the other hand, when the first oxidation catalyst unit 15 is arranged between the first seal member 13 and the anode 2 as in the present embodiment, the above-mentioned decrease in the output of the fuel cell 100 is suppressed as follows. can do. First, the oxidant that has entered the first gas flow path 111 undergoes a combustion reaction with the fuel flowing in the first gas flow path 111 on the first oxidation catalyst section 15 before reaching the anode 2. Since the oxidizing agent is consumed by this combustion reaction, the amount of the oxidizing agent reaching the anode 2 is reduced. As a result, the occurrence of a combustion reaction between the oxidant and the fuel on the surface of the anode 2 is reduced, and a decrease in the output of the fuel cell 100 can be suppressed.

(Second Oxidation Catalyst Unit 16)
As shown in FIGS. 1 and 6, the second oxidation catalyst unit 16 is arranged between the second seal member 14 and the cathode 3. Specifically, the second oxidation catalyst unit 16 is arranged on the inner peripheral surface of the second seal member 14. The second oxidation catalyst portion 16 extends in an annular shape along the inner peripheral surface of the second seal member 14.

The second oxidation catalyst unit 16 has an oxidation catalyst that is active in the oxidation reaction between the fuel and the oxidizing agent. Specifically, the second oxidation catalyst unit 16 has at least one of platinum, rhodium, iridium, ruthenium, nickel and iron as an oxidation catalyst. The oxidation catalyst may be in the form of an oxide in part or in whole. Preferably, the second oxidation catalyst unit 16 has platinum as an oxidation catalyst.

For example, by applying the oxidation catalyst on the inner peripheral surface of the second seal member 14 before assembling as a fuel cell stack, the second oxidation catalyst portion 16 is placed on the inner peripheral surface of the second seal member 14. Can be formed. As a method for applying the oxidation catalyst, a spray coating method, a brush coating method, a printing method or the like can be used. A binder may be added as appropriate in order to improve the stickiness of the oxidation catalyst.

Since the second oxidation catalyst unit 16 is arranged in this way, the following effects can be obtained. For example, fuel such as methanol may enter the second gas flow path 121 due to poor adhesion of the second seal member 14. Here, when the second oxidation catalyst unit 16 is not arranged, when the fuel reaches the cathode 3, a combustion reaction between the fuel and the oxidant occurs on the surface of the cathode 3. As a result, a hybrid potential is formed in the cathode 3, and the output of the fuel cell 100 may decrease.

On the other hand, when the second oxidation catalyst unit 16 is arranged between the second seal member 14 and the cathode 3 as in the present embodiment, the above-mentioned decrease in the output of the fuel cell 100 is suppressed as follows. can do. First, the fuel that has entered the second gas flow path 121 undergoes a combustion reaction with the oxidant flowing in the second gas flow path 121 on the second oxidation catalyst section 16 before reaching the cathode 3. Since fuel is consumed by this combustion reaction, the amount of fuel reaching the cathode 3 is reduced. As a result, the occurrence of a combustion reaction between the fuel and the oxidant on the surface of the cathode 3 is reduced, and a decrease in the output of the fuel cell 100 can be suppressed.

(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, the first oxidation catalyst unit 15 extends continuously in an annular shape along the inner peripheral surface of the first seal member 13, but the configuration of the first oxidation catalyst unit 15 is not limited to this. For example, the first oxidation catalyst unit 15 may extend intermittently in a ring shape. The same applies to the second oxidation catalyst unit 16.

The first oxidation catalyst unit 15 does not have to extend in a ring shape. In this case, it is preferable that the first oxidation catalyst unit 15 is arranged in a place of the first seal member 13 where the oxidizing agent is more likely to invade. For example, as shown in FIG. 7, the first oxidation catalyst portion 15 may be arranged between the corner portion of the anode 2 and the corner portion of the first seal member 13. Similarly, the second oxidation catalyst portion 16 may be arranged between the corner portion of the cathode 3 and the corner portion of the second seal member 14.

Further, as shown in FIG. 8, a plurality of first oxidation catalyst portions 15 may be arranged at intervals between the pipe 101 through which the oxidizing agent flows and the anode 2. Similarly, a plurality of second oxidation catalyst portions 16 may be arranged at intervals from each other between the pipe through which the fuel flows and the cathode 3.

Modification 2
In the above embodiment, the first oxidation catalyst unit 15 is arranged on the inner peripheral surface of the first seal member 13, but the arrangement of the first oxidation catalyst unit 15 is not limited to this. For example, as shown in FIG. 9, the first oxidation catalyst unit 15 may be arranged on the first outer peripheral region 44 of the electrolyte 4. Then, the first oxidation catalyst unit 15 may be separated from the first seal member 13. Similarly, the second oxidation catalyst unit 16 is arranged on the second outer peripheral region 46 of the electrolyte 4, and may be separated from the second seal member 14.

Modification 3
In the above embodiment, the first and second oxidation catalyst parts 15 and 16 are arranged on the electrolyte 4, but the arrangement of the first and second oxidation catalyst parts 15 and 16 is not limited to this. For example, as shown in FIG. 10, the membrane electrode joint portion 10 has a frame-shaped member 47. The frame-shaped member 47 has an opening, and the electrolyte 4 is arranged in the opening of the frame-shaped member 47. The frame-shaped member 47 and the electrolyte 4 are joined to each other. The first oxidation catalyst unit 15 may be arranged on the frame-shaped member 47. In this case, the first seal member 13 and the second seal member 14 are arranged on the frame-shaped member 47.

Modification 4
In the above embodiment, the support 5 of the electrolyte 4 is composed of a porous base material, but the support 5 is not limited thereto. For example, the support 5 of the electrolyte 4 may be a binder. For example, as shown in FIG. 11, 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 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 copolymer Polymer, ethylene-chlorotrifluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethylvinyl ether-tetrafluoroethylene copolymer, or ethylene-acrylic acid copolymer Examples thereof include copolymers.

Modification 5
In the above embodiment, the closed hole 61 is separated from the support 5, but as shown in FIG. 12, the closed hole 61 may be in contact with the support 5. That is, the closed air hole 61 may be in direct contact with the inner surface of the continuous hole 5a. As a result, the restricted area of the support 5 due to the presence of the closed holes 61 can be reduced as compared with the case where the closed holes 61 are separated from the support 5, so that the flexibility of the support 5 itself can be improved. Therefore, when the electrolyte 4 undergoes a volume change or deformation, it is possible to further suppress the generation of stress at the interface between the cathode 3 and the electrolyte 4 and / or the interface between the anode 2 and the electrolyte 4.

Modification 6
In the above embodiment, the electrolyte 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 4 does not have to include at least one of the first film-like portion 4b and the second film-like portion 4c.

Modification 7
In the above embodiment, the first oxidation catalyst unit 15 and the second oxidation catalyst unit 16 are provided, but only the first oxidation catalyst unit 15 may be provided. That is, the second oxidation catalyst unit 16 may be omitted.

Modification 8
In the above embodiment, the anode 2 corresponds to the first electrode of the present invention and the cathode 3 corresponds to the second electrode of the present invention, but vice versa. That is, the anode 2 may correspond to the second electrode of the present invention, and the cathode 3 may correspond to the first electrode of the present invention.

Modification 9
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.

2 Anode 3 Cathode 4 Electrolyte 10 Membrane electrode assembly 11 1st separator 12 2nd separator 13 1st seal member 14 2nd seal member 15 1st oxidation catalyst part 16 2nd oxidation catalyst part 100 Fuel cell

Claims (7)

A membrane electrode assembly having an electrolyte, a first electrode, and a second electrode,
A first separator arranged on the first electrode side of the membrane electrode assembly and
A second separator arranged on the second electrode side of the membrane electrode assembly and
A first sealing member which is arranged between the first separator and the membrane electrode assembly and seals between the outer peripheral portion of the membrane electrode assembly and the outer peripheral portion of the first separator.
A second sealing member which is arranged between the second separator and the membrane electrode assembly and seals between the outer peripheral portion of the membrane electrode assembly and the outer peripheral portion of the second separator.
A first oxidation catalyst section which is arranged between the first seal member and the first electrode and has an oxidation catalyst which is active in the oxidation reaction between the fuel and the oxidizing agent supplied to the membrane electrode assembly. ,
With
The first oxidation catalyst unit is arranged on the first seal member.
Fuel cell.
A membrane electrode assembly having an electrolyte, a first electrode, and a second electrode,
A first separator arranged on the first electrode side of the membrane electrode assembly and
A second separator arranged on the second electrode side of the membrane electrode assembly and
A first sealing member which is arranged between the first separator and the membrane electrode assembly and seals between the outer peripheral portion of the membrane electrode assembly and the outer peripheral portion of the first separator.
A second sealing member which is arranged between the second separator and the membrane electrode assembly and seals between the outer peripheral portion of the membrane electrode assembly and the outer peripheral portion of the second separator.
A first oxidation catalyst section which is arranged between the first seal member and the first electrode and has an oxidation catalyst which is active in the oxidation reaction between the fuel and the oxidizing agent supplied to the membrane electrode assembly. ,
With
The first oxidation catalyst section is spatially independent of the first electrode.
Fuel cell.
The first oxidation catalyst unit is arranged on the first seal member.
The fuel cell according to claim 2.
A second oxidation catalyst section which is arranged between the second seal member and the second electrode and has an oxidation catalyst which is active in the oxidation reaction between the fuel and the oxidizing agent supplied to the membrane electrode assembly. Further prepare
The fuel cell according to any one of claims 1 to 3.
The electrolyte has a first central region in which the first electrode is arranged, and a first outer peripheral region between the first central region and the first sealing member.
The first oxidation catalyst unit is arranged in the first outer peripheral region.
The fuel cell according to any one of claims 1 to 4.
The first electrode has a rectangular shape in a plan view and has a rectangular shape.
The first seal member has a rectangular annular shape in a plan view.
The first oxidation catalyst portion is arranged between the corner portion of the first electrode and the corner portion of the first seal member.
The fuel cell according to any one of claims 1 to 5.
The first oxidation catalyst section has platinum as an oxidation catalyst.
The fuel cell according to any one of claims 1 to 6.

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