JP7162214B2 - Electrolyte layer manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing an electrolyte layer, and more particularly to a method for manufacturing an electrolyte layer provided in a membrane electrode assembly.

Fuel cells using gaseous fuel such as hydrogen gas and liquid fuel such as methanol, dimethyl ether, and hydrazine are conventionally known as fuel cells mounted on vehicles.

As such a fuel cell, for example, a fuel cell is known which includes an electrolyte layer made of an anion exchange membrane or a cation exchange membrane, and a fuel side electrode and an oxygen side electrode arranged opposite to each other with the electrolyte layer interposed therebetween. Fuel is supplied to the fuel-side electrode through a fuel supply channel, and oxygen is supplied to the oxygen-side electrode through an air supply channel (see, for example, Patent Document 1).

JP 2016-207575 A

On the other hand, in order to further improve the performance of fuel cells, for example, functional inorganic membranes such as a protective layer that improves the durability of the electrolyte layer and a conductive auxiliary layer that improves the ionic conductivity of the electrolyte layer are added to the anion exchange membrane. Alternatively, it may be required to be formed on the surface of a cation exchange membrane (ion exchange polymer membrane).

In particular, in order to reduce costs, the functional inorganic membrane is not formed on both sides of the ion-exchange polymer membrane, and the functional inorganic membrane is formed only on one side of the ion-exchange polymer membrane according to its function. It is required to be formed in

In order to form a functional inorganic membrane only on one surface of the ion-exchange polymer membrane, for example, masking the other surface of the ion-exchange polymer membrane with a masking material has been considered. In such a method, the ion-exchange polymer membrane may be damaged by the masking material.

INDUSTRIAL APPLICABILITY The present invention is a method for producing an electrolyte layer capable of forming a functional inorganic membrane only on one surface of an ion-exchange polymer membrane while suppressing breakage of the ion-exchange polymer membrane.

The present invention [1] is a method for producing an electrolyte membrane comprising an ion-exchangeable polymer membrane and a functional inorganic membrane disposed only on one surface of the ion-exchangeable polymer membrane, wherein the ion a preparation step of preparing an exchangeable polymer membrane and a frame-shaped jig having a pair of frames; sandwiching the ion-exchangeable polymer membrane between the pair of frames; a holding step of holding the ion-exchangeable polymer membrane; and immersing and holding the ion-exchangeable polymer membrane held by the frame jig in a metal ion solution of elements constituting the functional inorganic membrane. and a forming step of forming the functional inorganic membrane on the surface of the ion-exchangeable polymer membrane. and forms an air reservoir on the other side of the ion-exchange polymer membrane to suppress contact between the other surface of the ion-exchange polymer membrane and the metal ion solution. including the manufacturing method of

The present invention [2] includes the method for producing an electrolyte layer according to [1] above, wherein the ion-exchange polymer membrane is an anion-exchange polymer membrane.

The present invention [3] includes the method for producing an electrolyte layer according to the above [1] or [2], wherein the functional inorganic film contains a layered double hydroxide.

In the method for producing an electrolyte layer of the present invention, an ion-exchange polymer membrane is held by a frame-shaped jig, and the ion-exchange polymer membrane is immersed in a metal ion solution.

Thus, in the method for producing an electrolyte layer of the present invention, the surface of one side of the ion-exchange polymer membrane is brought into contact with the metal ion solution, and an air reservoir is formed on the other side of the ion-exchange polymer membrane. , suppresses contact between the other surface of the ion-exchange polymer membrane and the metal ion solution.

According to such a method for producing an electrolyte layer, only one side of the ion-exchange polymer membrane can be brought into contact with the metal ion solution without contacting the ion-exchange polymer membrane with a masking material or the like. .

As a result, damage to the ion-exchange polymer membrane can be suppressed, and the functional inorganic membrane can be formed only on one surface of the ion-exchange polymer membrane.

FIG. 1 is a schematic configuration diagram showing a fuel cell having an electrolyte layer. FIG. 2 is a schematic process diagram showing one embodiment of the method for producing an electrolyte layer of the present invention, FIG. 2A being a preparation step for preparing an ion-exchange polymer membrane and a frame-shaped jig, and FIG. 2B. each show a gripping step of gripping an ion-exchange polymer membrane with a frame-shaped jig. FIG. 3 is a schematic process diagram showing an embodiment of the method for producing an electrolyte layer of the present invention following FIG. 2, FIG. FIG. 3B shows the immersion step of immersing in the ion-exchange polymer membrane, and the formation step of forming a layered double hydroxide on one surface of the ion-exchange polymer membrane, respectively.

1. Overall Configuration of Fuel Cell In FIG. 1, a fuel cell 1 is configured as an anion exchange fuel cell or a proton exchange fuel cell.

The fuel cell 1 normally includes a plurality of fuel cells S, and is configured as a stack structure in which the plurality of fuel cells S are stacked. In FIG. 1, only one fuel cell S is shown for ease of illustration.

The fuel cell S has a membrane electrode assembly 15 .

The membrane electrode assembly 15 has an anode electrode 2 , a cathode electrode 3 and an electrolyte layer 4 . In the membrane electrode assembly 15, the anode electrode 2 and the cathode electrode 3 are arranged facing each other with the electrolyte layer 4 interposed therebetween. In other words, the membrane electrode assembly 15 includes the electrolyte layer 4, and the anode electrode 2 and the cathode electrode 3 which are arranged to face each other with the electrolyte layer 4 interposed therebetween.

The anode electrode 2 is in contact with one surface of the electrolyte layer 4 (hereinafter sometimes simply referred to as one surface). The anode electrode 2 is made of, for example, an electrode material such as a catalyst carrier supporting a catalyst. Further, catalyst particles may be used as an electrode material without using a catalyst carrier, and the catalyst particles may be directly formed as the anode electrode 2 .

The catalyst is not particularly limited, and examples thereof include platinum group elements (ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt)), iron group elements ( Iron (Fe), cobalt (Co), nickel (Ni)) and other periodic table (IUPAC Periodic Table of the Elements (version date 22 June 2007). The same shall apply hereinafter.) Groups 8 to 10 (VIII) elements, Examples include Group 11 (IB) elements of the periodic table such as copper (Cu), silver (Ag) and gold (Au), elemental metals such as zinc (Zn), and alloys thereof. Among these, iron group elements are preferred, and nickel is more preferred. Moreover, these can be used individually or in combination of 2 or more types.

Examples of catalyst carriers include porous substances such as carbon.

When the catalyst is supported on the catalyst carrier, the ratio of the catalyst carrier to the total amount of the catalyst and the catalyst carrier is, for example, 20% by mass or more, preferably 40% by mass or more, and, for example, 80% by mass. % or less, preferably 60 mass % or less.

The thickness of the anode electrode 2 is, for example, 10 μm or more, preferably 20 μm or more, and is, for example, 200 μm or less, preferably 100 μm or less.

In addition, the formation of the anode electrode 2 is not particularly limited, but for example, by mixing the above catalyst and an ion exchange resin and, if necessary, adding an appropriate solvent such as alcohol or ether to adjust the viscosity, A dispersion liquid (anode electrode ink) of the above catalyst is prepared. Next, the dispersion is applied to one surface of the electrolyte layer 4 and dried. Thereby, the anode electrode 2 containing the catalyst and the ion exchange resin can be formed on the surface of the electrolyte layer 4 on one side in the thickness direction. As the ion exchange resin, an anion exchange resin is preferably used.

In the anode electrode 2, the amount of catalyst supported is, for example, 0.05 mg/cm ² or more, preferably 0.1 mg/cm ² or more, and for example, 10 mg/cm ² or less, preferably 5 mg/cm 2 or less. ² or less.

The cathode electrode 3 is in contact with the other surface of the electrolyte layer 4 (hereinafter sometimes simply referred to as the other surface). The cathode electrode 3 is not particularly limited, but is formed as, for example, a porous electrode on which a metal catalyst is supported.

The metal catalyst contains a transition metal, for example, is formed by forming a complex between the transition metal and a complex-forming organic compound, or, for example, the transition metal is a carrier made of a conductive polymer It is formed by being supported by

Examples of transition metals include scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu ), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), lanthanum (La ), hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), and gold (Au). Among these, iron, silver and cobalt are preferred, and iron is more preferred. These may be used singly or in combination of two or more, and alloys thereof may also be used.

A complex-forming organic compound is an organic compound that forms a complex with a metal atom by coordinating to the metal atom, such as pyrrole, porphyrin, tetramethoxyphenylporphyrin, dibenzotetraazaannulene, phthalocyanine, choline, chlorin. , phenanthroline, sarcomine, nicarbazin, aminoantipyrine (AAPYr) and other complex-forming organic compounds or polymers thereof. Among these, polypyrrole, which is a polymer of pyrrole, phenanthroline, sarcomine, nicarbazin, and aminoantipyrine are preferred, and nicarbazin is particularly preferred. Moreover, these can be used individually or in combination of 2 or more types.

Examples of conductive polymers include compounds that overlap with the complex-forming organic compounds described above, such as polyaniline, polypyrrole, polythiophene, polyacetylene, polyvinylcarbazole, polytriphenylamine, polypyridine, polypyrimidine, polyquinoxaline, and polyphenylquinoxaline. , polyisothianaphthene, polypyridinediyl, polythienylene, polyparaphenylene, polyflurane, polyacene, polyfuran, polyazulene, polyindole, polydiaminoanthraquinone, and the like. Among these, polypyrrole is preferred. Moreover, these can be used individually or in combination of 2 or more types.

Formation of the metal catalyst is not particularly limited, and known methods can be employed.

The thickness of the cathode electrode 3 is, for example, 10 μm or more, preferably 20 μm or more, and is, for example, 300 μm or less, preferably 150 μm or less.

The method for forming the cathode electrode 3 from such a metal catalyst is not particularly limited, but in the same manner as the anode electrode 2 described above, for example, first, the metal catalyst and the ion exchange resin are mixed, and if necessary, alcohol or A dispersion liquid (cathode electrode ink) of the metal catalyst is prepared by adding an appropriate solvent such as ether to adjust the viscosity. Next, the dispersion is applied to the other surface of the electrolyte layer 4 and dried. Thereby, the cathode electrode 3 containing the metal catalyst and the ion exchange resin can be formed on the other surface of the electrolyte layer 4 . As the ion exchange resin, an anion exchange resin is preferably used.

In the cathode electrode 3, the supported amount of the metal catalyst is, for example, 0.05 mg/cm ² or more, preferably 0.1 mg/cm ² or more, and for example, 10 mg/cm ² or less, preferably 5 mg/cm 2 or less. cm ² or less.

The electrolyte layer 4 comprises an ion exchange polymer membrane 16 and a functional inorganic membrane 17 .

The ion-exchange polymer membrane 16 includes an anion-exchange polymer membrane and a cation-exchange polymer membrane, and is selected according to the type of the fuel cell 1 .

That is, when the fuel cell 1 is an anion-exchange fuel cell, it is an anion-exchange polymer membrane, and when the fuel cell 1 is a proton-exchange fuel cell, it is a cation-exchange polymer membrane.

The anion-exchange polymer membrane is not particularly limited as long as it is a medium in which an anion component (e.g., hydroxide ion (OH ⁻ ), etc.) can migrate. Solid polymer membranes (anion exchange resins) having exchange groups can be mentioned.

In addition, the cation exchange polymer membrane is not particularly limited as long as it is a medium in which cation components (e.g., protons (H ⁺ ), etc.) can move. solid polymer membranes (cation exchange resins) having anion exchange groups such as

Examples of the solid polymer that forms the ion-exchange polymer membrane 16 include hydrocarbon-based solid polymer membranes such as polystyrene and modified products thereof. Moreover, the solid polymer forming the ion-exchangeable polymer membrane 16 may have a crosslinked structure in its molecular structure. The glass transition temperature (Tg) of the solid polymer forming the ion exchange polymer membrane 16 is, for example, 80 to 200.degree. C., preferably 100 to 200.degree.

From the viewpoint of power generation efficiency, the ion-exchange polymer membrane 16 is preferably an anion-exchange polymer membrane.

Anion-exchange polymer membranes are commercially available, and examples thereof include Selemion (manufactured by Asahi Glass Co., Ltd.), Neocepta (manufactured by Astom), A201 (manufactured by Tokuyama), and the like.

The thickness of the ion-exchange polymer membrane 16 is, for example, 5 μm or more, preferably 10 μm or more, and for example, 50 μm or less, preferably 35 μm or less.

The functional inorganic membrane 17 is arranged only on one surface of the ion-exchange polymer membrane 16 (the surface on the cathode electrode 3 side or the surface on the anode electrode 2 side). It is laminated only on the surface of the flexible polymer film 16 on the cathode electrode 3 side.

Details of the functional inorganic film 17 will be described later.

The thickness of the functional inorganic film 17 is, for example, 1 μm or more, preferably 5 μm or more, and for example, 20 μm or less, preferably 10 μm or less.

The thickness of the electrolyte layer 4 (the total thickness of the ion-exchange polymer membrane 16 and the functional inorganic membrane 17) is, for example, 6 μm or more, preferably 15 μm or more, and for example, 70 μm or less, preferably 45 μm. It is below.

The fuel cell S further includes a fuel supply member 5 and an oxygen supply member 6 in addition to the membrane electrode assembly 15 . The fuel supply member 5 is made of a gas-impermeable conductive member, and one surface of the fuel supply member 5 is in contact with the anode electrode 2 . In the fuel supply member 5, a fuel-side channel 7 for bringing the fuel into contact with the entire anode electrode 2 is formed as a meandering groove recessed from one surface. A supply port 9 and a discharge port 8 penetrating through the fuel supply member 5 are continuously formed at the upstream end and the downstream end of the fuel side passage 7, respectively.

Similarly to the fuel supply member 5 , the oxygen supply member 6 is also made of a gas-impermeable conductive member, and one surface of the oxygen supply member 6 is in contact with the cathode electrode 3 . Also in this oxygen supply member 6, an oxygen-side channel 10 for bringing oxygen (air) into contact with the entire cathode electrode 3 is formed as a meandering groove recessed from one surface. A supply port 11 and a discharge port 12 penetrating the oxygen supply member 6 are continuously formed at the upstream end and the downstream end of the oxygen side channel 10, respectively.

Although not shown, in the fuel cell 1, known gas diffusion layers are provided between the fuel supply member 5 and the anode electrode 2 and between the oxygen supply member 6 and the cathode electrode 3, if necessary. Can be stacked.

The fuel cell 1 is actually formed as a stack structure in which a plurality of fuel cells S are stacked. Therefore, the fuel supply member 5 and the oxygen supply member 6 are actually configured as separators in which the fuel side flow path 7 and the oxygen side flow path 10 are formed on both sides.

Although not shown, the fuel cell 1 is provided with a current collector plate made of a conductive material, and the electromotive force generated in the fuel cell 1 is extracted to the outside from terminals provided on the current collector plate. configured to be able to

Further, experimentally (as a model), the fuel supply member 5 and the oxygen supply member 6 of the fuel cell S are connected by an external circuit 13, and a voltmeter 14 is interposed in the external circuit 13 to generate Voltage can also be measured.

2. Method for Producing Electrolyte Layer Electrolyte layer 4 comprises ion-exchange polymer membrane 16 and one surface of ion-exchange polymer membrane 16 (surface on cathode electrode 3 side or anode electrode 2 side), as described above. Preferably, the functional inorganic film 17 formed on the surface of the ion-exchange polymer film 16 and the surface of the ion-exchange polymer film 16 on the cathode electrode 3 side only and an inorganic film 17 .

The functional inorganic film 17 is an inorganic compound film provided to impart various functions to the ion-exchange polymer film 16. For example, an inorganic protective film that improves the durability of the ion-exchange polymer film 16 Functional inorganic membranes such as membranes and conduction assisting layers that improve the ion conductivity of the ion-exchange polymer membrane 16 can be used.

From the viewpoint of improving power generation efficiency, the functional inorganic film 17 is preferably an inorganic protective film.

The inorganic protective film is an inorganic film formed from a metal oxide to protect the ion-exchange polymer film 16. For example, an inorganic protective film containing a metal oxide (excluding layered double hydroxide) is used. film, an inorganic protective film containing a layered double hydroxide, and the like. These can be used alone or in combination of two or more.

From the viewpoint of achieving both durability and ionic conductivity, an inorganic protective film containing a layered double hydroxide is preferred. In other words, the functional inorganic film 17 preferably contains a layered double hydroxide.

A double hydroxide is defined as a higher-order compound produced by combining two or more kinds of metal hydroxides.

In addition, the layered double hydroxide is a higher-order compound having plate-like crystals in which double hydroxides are arranged two-dimensionally, and two or more of the plate-like crystals are laminated. Defined.

Examples of layered double hydroxides include non-stoichiometric compounds represented by the following formula (I).

[M ²⁺ _1−x M ³⁺ _x (OH) ₂ ][A ⁿ⁻ _x/n ·yH ₂ O] (I)
(Wherein, x represents a real number that satisfies 0<x<1, y represents a real number, M ²⁺ represents a divalent metal ion, M ³⁺ represents a trivalent metal ion, and A ^n- is a pair indicates an anion.)
In the above formula (I), the divalent metal ion represented by M ²⁺ includes, for example, a divalent alkali metal ion such as Li ²⁺ , a divalent alkaline earth metal ion such as Mg ²⁺ and Ca ²⁺ , for example, Divalent transition metal ions such as Fe ²⁺ , Co ²⁺ , Ni ²⁺ , Cu ²⁺ and Zn ²⁺ can be mentioned. These can be used alone or in combination of two or more.

Divalent metal ions preferably include divalent alkaline earth metal ions, more preferably Mg ²⁺ .

In the above formula (I), the trivalent metal ion represented by M ³⁺ includes, for example, trivalent transition metal ions such as Fe ³⁺ , Co ³⁺ and Mn ³⁺ , trivalent poor metal ions such as Al ³⁺ , and the like. mentioned. These can be used alone or in combination of two or more.

Trivalent metal ions preferably include trivalent poor metal ions, more preferably Al ³⁺ .

In the above formula (I), the counter anion represented by A ^n- includes, for example, nitrate ion, carbonate ion, chloride ion and the like. These can be used alone or in combination of two or more.

The counter anion is preferably nitrate ion.

In the above formula (I), the real number represented by x exceeds 0, preferably 0.1 or more, more preferably 0.2 or more, and is less than 1, preferably 0.5 or less, and more Preferably, it is 0.4 or less.

In formula (I) above, the real number represented by y is, for example, 0 or more, preferably 1 or more, and, for example, 10 or less.

Note that the layered double hydroxide is not limited to the layered double hydroxide of the above formula (I) (layered double hydroxide having one type of divalent metal ion and one type of trivalent metal ion), for example, monovalent It may be a layered double hydroxide containing both metal ions and divalent metal ions, for example, a layered double hydroxide containing both one divalent metal ion and two tetravalent metal ions. That is, known layered double hydroxides having one or more kinds of metal ions with mutually different valences can be used. In addition, if the valence numbers are different from each other, metal ions of the same element may be included.

The layered double hydroxide preferably includes the layered double hydroxide of the above formula (I) (layered double hydroxide having one each of divalent metal ions and trivalent metal ions).

More specifically, such layered double hydroxides include, for example, magnesium/aluminum double hydroxide, nickel/aluminum double hydroxide, divalent cobalt/trivalent cobalt double hydroxide, divalent iron- trivalent iron double hydroxide, cobalt-iron double hydroxide, cobalt-aluminum double hydroxide and the like. These layered double hydroxides can be used alone or in combination of two or more.

The layered double hydroxide preferably includes magnesium-aluminum double hydroxide and nickel-aluminum double hydroxide, more preferably magnesium-aluminum double hydroxide.

Magnesium-aluminum double hydroxide is represented, for example, by the following formula (II).

[Mg ²⁺ _1−x Al ³⁺ _x (OH) ₂ ][A ⁿ⁻ _x/n ·yH ₂ O] (II)
(Wherein, x represents a real number satisfying 0<x<1, y represents a real number, and A ^n- represents a counter anion.)
Note that the layered double hydroxide has a layered structure and has a property of taking in anions between the layers (so-called intercalation). In addition, among the layered structures, the basic hydroxide layer has a positive charge due to the substitution (solid solution) of part of the divalent metal ions by the trivalent metal ions. is taken in to maintain electrical neutrality.

The average particle size of the layered double hydroxide is, for example, 0.1 μm or more and 10 μm or less, and the layer spacing is, for example, 1 nm or more and 100 nm or less, although it varies depending on the type of metal ion.

The content of the layered double hydroxide is, for example, 90% by mass or more, preferably 92% by mass or more, more preferably 95% by mass or more, and still more preferably 98% by mass, relative to the total amount of the inorganic protective film. It is more than or equal to 100% by mass or less.

In addition, the inorganic protective film can contain metal oxides other than the layered double hydroxide (hereinafter referred to as other metal oxides).

Examples of other metal oxides include LiO, MgO, CaO, FeO, _{Fe2O3 ,} CoO, _Co2O3 , _Mn2O3 , _NiO , _CuO , _Cu2O and ZnO.

These other metal oxides can be used alone or in combination of two or more.

Other metal oxides are formed, for example, from surplus metal ions (unreacted raw materials) during formation of the layered double hydroxide and contained in the inorganic protective film. Other metal oxides can also be contained in the inorganic protective film, for example, as unavoidable impurities that are by-produced during the formation of the layered double hydroxide.

The content of other metal oxides is 10% by mass or less, preferably 8% by mass or less, more preferably 5% by mass or less, and still more preferably 2% by mass or less, relative to the total amount of the inorganic protective film. Yes, and usually 0% by mass or more.

That is, the inorganic protective film does not have to contain other metal oxides. Most preferably, the inorganic protective film does not contain other metal oxides and consists of a layered double hydroxide.

The layered double hydroxide and the inorganic protective film are not particularly limited, but from the viewpoint of suppressing breakage of the ion-exchange polymer film 16, they are preferably produced by the following method.

That is, in this method, first, an ion-exchange polymer membrane 16 is prepared. In addition, if necessary, the surface of the ion-exchangeable polymer membrane 16 is adhered with a starting material for crystal growth (metal ion, counter anion, etc.).

Then, a raw material aqueous solution is prepared as a metal ion solution containing constituent elements of the layered double hydroxide, and the ion-exchange polymer membrane 16 is immersed in the aqueous solution.

The raw material aqueous solution is a metal ion solution of the above constituent elements. More specifically, for example, when obtaining the layered double hydroxide represented by the above formula (I), a divalent metal ion (M ²⁺ ), Examples include aqueous solutions containing trivalent metal ions (M ³⁺ ) and counter anions (A ⁿ⁻ ) at predetermined concentrations.

Such an aqueous solution is, for example, a metal salt (e.g., sulfate, nitrate, organic acid salt, etc.) of divalent metal ions (M ²⁺ ) and/or hydrates thereof, and trivalent metal ions (M ³⁺ ). It can be obtained by dissolving a metal salt (eg, sulfate, nitrate, organic acid salt, etc.) and/or its hydrate in water.

In the raw material aqueous solution, the concentration of divalent metal ions (M ²⁺ ) is, for example, 0.1 mol/L or more, preferably 0.2 mol/L or more, and for example, 0.5 mol/L or less, preferably 0 .4 mol/L or less.

Further, the concentration of the trivalent metal ion (M ³⁺ ) is, for example, 0.05 mol/L or more, preferably 0.1 mol/L or more, and for example, 0.25 mol/L or less, preferably 0.2 mol. /L or less.

Further, the total concentration of bivalent metal ions (M ²⁺ ) and trivalent metal ions (M ³⁺ ) is, for example, 0.15 mol/L or more, preferably 0.3 mol/L or more, for example, 0.3 mol/L or more. It is 75 mol/L or less, preferably 0.6 mol/L or less.

Further, the molar ratio (M ²⁺ /M ³⁺ ) between the bivalent metal ion (M ²⁺ ) and the trivalent metal ion (M ³⁺ ) is, for example, 1 or more, preferably 2 or more, and for example, 5 or less, Preferably, it is 4 or less.

In addition, the concentration of the counter anion (A ^n- ) is, for example, 0.1 mol/L or more, preferably 0.3 mol/L or more, and for example, 1 mol/L or less, preferably 0.8 mol/L or less. is.

If the concentrations of the divalent metal ion (M ²⁺ ), trivalent metal ion (M ³⁺ ) and counter anion (A ⁿ⁻ ) are within the above ranges, by-products are reduced and the layered double hydroxide is efficiently produced. Obtainable.

Further, urea is preferably added to the raw material aqueous solution. The amount of urea to be added is appropriately set according to the type of metal ion.

When urea is added to the raw material aqueous solution, ammonia is generated in the raw material aqueous solution by hydrolysis of urea, and the pH of the raw material aqueous solution is adjusted to a predetermined range (for example, exceeding 7.0 and 8.5 or less). .

In this method, the ion-exchangeable polymer membrane 16 is immersed and held in the raw material aqueous solution.

As for the holding conditions, the temperature of the raw material aqueous solution is, for example, 60° C. or higher, preferably 70° C. or higher, and for example, 100° C. or lower, preferably 90° C. or lower.

Also, the time for immersing the ion-exchangeable polymer membrane 16 in the raw material aqueous solution is, for example, 10 hours or more, preferably 20 hours or more, and for example, 200 hours or less, preferably 150 hours or less.

As a result, the divalent metal ions (M ²⁺ ) and trivalent metal ions (M ³⁺ ) and the counter anion (A ⁿ⁻ ) form a layered double hydroxide on the surface of the ion-exchange polymer membrane 16. do.

As a result, an inorganic protective film is formed on the surface of the ion exchange polymer film 16 .

In the above method, an inorganic protective film is formed on the portion of the ion-exchangeable polymer film 16 that is in contact with the raw material aqueous solution.

Therefore, when the ion-exchangeable polymer membrane 16 is immersed in the raw material aqueous solution so that both surfaces of the ion-exchangeable polymer membrane 16 are in contact with the raw material aqueous solution, the surface of the ion-exchangeable polymer membrane 16 on the anode electrode 2 side is and the surface on the cathode electrode 3 side, an inorganic protective film can be laminated.

Further, when the ion-exchangeable polymer membrane 16 is immersed in the raw material aqueous solution so that only one surface of the ion-exchangeable polymer membrane 16 (the surface on the side of the cathode electrode 3) is in contact with the raw material aqueous solution, the ion-exchange property is reduced. An inorganic protective film can be laminated only on the surface of the polymer film 16 on the cathode electrode 3 side.

From the viewpoint of achieving a balance between cost reduction and durability, preferably, the ion-exchange polymer membrane 16 is placed so that only one surface (the surface on the cathode electrode 3 side) of the ion-exchange polymer membrane 16 is in contact with the raw material aqueous solution. The film 16 is immersed in the raw material aqueous solution, and an inorganic protective film is laminated only on the surface of the ion-exchangeable polymer film 16 on the cathode electrode 3 side.

The method of immersing the ion-exchangeable polymer membrane 16 in the raw material aqueous solution so that only one surface (the surface on the cathode electrode 3 side) of the ion-exchangeable polymer membrane 16 is in contact with the raw material aqueous solution is not particularly limited. However, for example, there is a method of immersing the ion-exchange polymer membrane 16 in the raw material aqueous solution so that an air reservoir is formed on the other surface (the surface on the anode electrode 2 side) of the ion-exchange polymer membrane 16 .

More specifically, in this method, first, as shown in FIG. 2A, an ion-exchange polymer membrane 16 and a frame-shaped jig 20 for holding the ion-exchange polymer membrane 16 are prepared. (preparation process).

The frame-shaped jig 20 includes an upper frame 21 and a lower frame 22 as a pair of frames. The upper frame 21 and the lower frame 22 are substantially rectangular frame-shaped metal members having a predetermined width, and are formed in substantially the same shape. In addition, by having through holes 23 at four corners of substantially the same shape, they can be fastened together with fastening members 24 (bolts 24a, nuts 24b, etc.).

Next, in this method, as shown in FIG. 2B, the ion exchange polymer membrane 16 is gripped by a frame jig 20 (gripping step).

More specifically, in this step, the ion exchange polymer membrane 16 is sandwiched between the upper frame 21 and the lower frame 22, and the upper frame 21 and the lower frame 22 are fastened with the fastening members 24. do.

Thereby, the ion-exchange polymer membrane 16 is gripped by the frame-shaped jig 20 .

When the ion-exchange polymer membrane 16 is held by the frame-shaped jig 20 , the surface of the ion-exchange polymer membrane 16 on one side (the upper side of the paper, the cathode electrode 3 side) is the surface of the upper frame 21 . The surface on the other side (anode electrode 2 side) is exposed downward through the frame hole of the lower frame 21 .

Next, in this method, as shown in FIG. 3A, the frame-shaped jig 20 and the ion-exchange polymer membrane 16 gripped by the frame-shaped jig 20 are immersed and held in the raw material aqueous solution ( immersion process).

More specifically, in this step, the frame-shaped jig is moved downward from above the raw material aqueous solution so as to enclose air in the space formed by the frame-shaped jig 20 and the ion-exchange polymer membrane 16. 20 and the ion exchange polymer membrane 16 are gently submerged.

As a result, an air reservoir 28 is formed on the other side (anode electrode 2 side) of the ion-exchange polymer membrane 16 (see FIG. 3B).

As a result, the surface of one side (cathode electrode 3 side) of the ion-exchange polymer membrane 16 and the raw material aqueous solution are brought into contact with each other, and the other side (anode electrode 2 side) of the ion-exchange polymer membrane 16 and the raw material aqueous solution are brought into contact with each other. contact with is suppressed.

Thereafter, in this method, the frame-shaped jig 20 and the ion-exchange polymer membrane 16 are immersed in the raw material aqueous solution and held under the above holding conditions.

As a result, as shown in FIG. 3B, a layered double hydroxide is formed on the surface of one side (cathode electrode 3 side) of the ion-exchange polymer membrane 16 (formation step).

On the other side (anode electrode 2 side) of the ion-exchange polymer membrane 16, an air reservoir 28 allows the surface of the ion-exchange polymer membrane 16 on the other side (anode electrode 2 side) to come into contact with the raw material aqueous solution. is suppressed. Therefore, the formation of layered double hydroxide is suppressed.

In addition, when the volume of the air reservoir 28 is not sufficient and a layered double hydroxide is formed on the surface of the other side (anode electrode 2 side) of the ion-exchange polymer membrane 16, the layered double hydroxide A gas generated during formation (oxygen gas, hydrogen gas, etc.) can increase the volume of the air reservoir 28 . As a result, contact between the other side (the anode electrode 2 side) of the ion-exchange polymer membrane 16 and the raw material aqueous solution is suppressed, and the layered structure on the surface of the other side (the anode electrode 2 side) of the ion-exchange polymer membrane 16 (the anode electrode 2 side) is suppressed. Formation of double hydroxide can be suppressed.

As a result, an inorganic protective film containing a layered double hydroxide can be formed only on one surface (cathode electrode 3 side) of the ion-exchange polymer film 16 .

The inorganic protective film may be a single layer or multiple layers.

That is, as described above, only one layer of layered double hydroxide may be formed, and the above steps are repeated to form multiple layers (for example, 2 to 10 layers) of layered double hydroxide. good too.

From the viewpoint of achieving a balance between cost reduction and durability, preferably only one layer of the layered double hydroxide is formed.

The thickness of the inorganic protective film is, for example, 1 μm or more, preferably 5 μm or more, and for example, 20 μm or less, preferably 10 μm or less.

The functional inorganic film 17 is not limited to the inorganic protective film containing the layered double hydroxide described above, and may be, for example, a metal oxide such as an alumina film or a zeolite film (excluding the layered double hydroxide). and an inorganic protective film containing

In such a case, the metal ions contained in the metal ion solution and their concentration are appropriately selected according to the constituent elements of the functional inorganic film.

More specifically, when forming a zeolite membrane, for example, sodium silicate, sodium aluminate, or the like can be used as the metal ion solution.

3. Power Generation Method Fuel and oxygen (air) are directly supplied to the fuel cell 1 without reforming or the like.

For example, if the fuel cell 1 is an anion exchange fuel cell, the fuel may be liquid fuel containing a fuel compound. Further, when the fuel cell 1 is a proton exchange fuel cell, examples of the fuel include hydrogen gas and liquid fuel containing fuel compounds.

Examples of fuel compounds include alcohols such as methanol and ethanol, ethers such as dimethyl ether, hydrazine (NH ₂ NH ₂ ), hydrazine hydrate (NH ₂ NH _{2.H 2 O} ), hydrazine carbonate ( _{( NH2NH2} ) _2CO2 ), hydrazine sulfate _{( NH2NH2.H2SO4} ) _, monomethylhydrazine _{( CH3NHNH2} ) _, dimethylhydrazine _{( ( CH3} ) _{2NNH2 , CH3NHNHCH3} ) , hydrazines such as carboxylic hydrazide ((NHNH ₂ ) ₂ CO), e.g. urea (NH ₂ CONH ₂ ), e.g. imidazole, 1,3,5-triazine, 3-amino-1,2,4-triazole, etc. heterocycles, for example, hydroxylamines such as hydroxylamine (NH ₂ OH) and hydroxylamine sulfate (NH ₂ OH.H ₂ SO ₄ ). Among these, hydrazines are preferred. Moreover, these can be used individually or in combination of 2 or more types.

Fuel compounds can be prepared by dissolving them in water, if desired.

The above fuel compound may be used as it is as the liquid fuel, or an aqueous solution obtained by dissolving the above fuel compound in water may be used as the liquid fuel.

Moreover, when the fuel cell 1 is an anion exchange fuel cell, the liquid fuel preferably contains an additive.

Examples of additives include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, and francium hydroxide; Electrolytes such as alkaline earth metal hydroxides such as barium and radium hydroxide. Among these, alkali metal hydroxides are preferred, and potassium hydroxide is more preferred. Moreover, these can be used individually or in combination of 2 or more types.

If the liquid fuel contains an additive, it can promote the movement of hydroxide ions (OH ⁻ ), which will be described later.

The amount of the additive added is, for example, 1 part by mass or more, preferably 5 parts by mass or more, and for example, 35 parts by mass or less, preferably 30 parts by mass or less, relative to 100 parts by mass of the fuel compound. be.

Then, when fuel and oxygen (air) are supplied to the fuel cell 1, the following electrochemical reaction occurs and electric power can be obtained.

For example, when the fuel cell 1 is an anion exchange fuel cell, oxygen (air) is supplied to the oxygen side channel 10 of the oxygen supply member 6, and the above fuel is supplied to the fuel side channel 7 of the fuel supply member 5. If supplied, at the cathode electrode 3, as described below, electrons (e ⁻ ) generated at the anode electrode 2 and transferred through the external circuit 13, water (H ₂ O), and oxygen (O ₂ ) to produce hydroxide ions (OH ⁻ ). The generated hydroxide ions (OH ⁻ ) pass through the electrolyte layer 4 and move from the cathode electrode 3 to the anode electrode 2 . At the anode electrode 2, the hydroxide ions (OH ⁻ ) that have passed through the electrolyte layer 4 react with the fuel to generate electrons (e ⁻ ). The generated electrons (e ⁻ ) are transferred from the fuel supply member 5 through the external circuit 13 to the oxygen supply member 6 and supplied to the cathode electrode 3 . Such electrochemical reactions at the anode electrode 2 and the cathode electrode 3 generate an electromotive force and generate electricity.

Such an electrochemical reaction includes a one-step reaction in which the fuel is directly reacted with hydroxide ions (OH ⁻ ) at the anode electrode 2 and a reaction in which the fuel is mixed with hydrogen (H ₂ ) and nitrogen (N ₂ ). There are two types of reactions: a two-step reaction in which hydrogen (H ₂ ) produced by the decomposition reacts with hydroxide ions (OH ⁻ ) after decomposition into ions.

For example, when hydrazine (NH ₂ NH ₂ ) is used as the fuel, the one-step reaction can be represented by the following reaction formulas (1) to (3) for the anode electrode 2, the cathode electrode 3, and the whole.
(1) NH ₂ NH ₂ +4OH ⁻ →4H ₂ O+N ₂ +4e ⁻ (anode electrode)
(2) O ₂ +2H ₂ O+4e ⁻ →4OH ⁻ (cathode electrode)
(3) NH ₂ NH ₂ +O ₂ →2H ₂ O+N ₂ (whole)
Also, the two-step reaction can be represented by the following reaction formulas (4) to (7) for the anode electrode 2, the cathode electrode 3, and the whole.
(4) NH ₂ NH ₂ →2H ₂ +N ₂ (decomposition reaction; anode electrode)
(5) H ₂ +2OH ⁻ →2H ₂ O+2e ⁻ (anode electrode)
(6) 1/2O ₂ +H ₂ O+2e ⁻ →2OH ⁻ (cathode electrode)
(7) H ₂ + 1/2O ₂ →H ₂ O (whole)
Further, when the fuel cell 1 is an anion exchange fuel cell, oxygen (air) is supplied to the oxygen side flow channel 10 of the oxygen supply member 6, and the above fuel is supplied to the fuel side flow channel 7 of the fuel supply member 5. When supplied, protons (H ⁺ ) and electrons (e ⁻ ) are generated at the anode electrode 2 by decomposition of the fuel. On the other hand, in the cathode electrode 3, electrons (e − ) generated at the anode electrode 2 and moving through the external circuit 13 and electrons (e ⁻ ) generated at the anode electrode 2 and passed through the electrolyte layer 4 to the Protons (H ⁺ ) that move to 3 react with oxygen (O ₂ ) to produce water (H ₂ O). The generated water humidifies the oxygen (air) supplied to the cathode electrode 3 . Such electrochemical reactions at the anode electrode 2 and the cathode electrode 3 generate an electromotive force and generate electricity.

For example, when hydrazine (NH ₂ NH ₂ ) is used as the fuel, the reaction of the anode electrode 2, the cathode electrode 3 and the whole can be represented by the following reaction formulas (A) to (D).

(A) N ₂ H ₄ →N ₂ +2H ₂ (decomposition reaction; anode electrode)
(B) N ₂ +2H ₂ →N ₂ +4H ⁺ +4e ⁻ (anode electrode)
(C) O ₂ +4H ⁺ +4e ⁻ →2H ₂ O (cathode electrode)
(D) N ₂ H ₄ +O ₂ →N ₂ +2H ₂ O (whole)
The operating conditions of the fuel cell 1 are not particularly limited. , 100 kPa or less, and the temperature of the fuel cell S is set to 0 to 120.degree. C., preferably 20 to 80.degree.

4. Effect Normally, in the fuel cell 1, the ion-exchange polymer membrane 16 is used alone as the electrolyte layer 4. In order to further improve the performance, for example, the durability of the ion-exchange polymer membrane 16 is increased. It is required to form on the surface of the ion-exchange polymer membrane 16 a functional inorganic membrane 17 such as a protective layer to improve the ion conductivity and a conductive auxiliary layer to improve the ion conductivity of the ion-exchange polymer membrane 16 . In particular, in order to reduce costs, the functional inorganic membrane 17 is not formed on both sides of the ion-exchange polymer membrane 16, but is formed only on one side of the ion-exchange polymer membrane 16 according to its function. are required to do so.

For example, when an anion exchange fuel cell is used for a long period of time, OH radicals are generated inside the fuel cell 1 . If the electrolyte layer 4 does not have the functional inorganic membrane 17, the anion-exchange groups in the ion-exchange polymer membrane 16 react with OH radicals to damage and deteriorate the ion-exchange polymer membrane 16. cause

Therefore, it is required to form a functional inorganic membrane 17 on the ion-exchange polymer membrane 16 to improve its durability. Moreover, since OH radicals are generated on the cathode electrode 3 side, it is required to form the functional inorganic film 17 only on the surface of the ion-exchange polymer film 16 on the cathode electrode 3 side.

In this regard, in order to form the functional inorganic film 17 only on the surface of one side (cathode electrode 3 side) of the ion-exchange polymer membrane 16, for example, the other side (anode electrode 2 side) of the ion-exchange polymer membrane 16 ) with a masking material, but in such a method, the ion-exchange polymer membrane 16 may be damaged by the masking material.

Further, for example, forming the functional inorganic film 17 by coating and drying the raw material solution (inorganic compound solution, etc.) of the functional inorganic film 17 only on one surface of the ion-exchangeable polymer film 16 has also been considered. However, the functional inorganic film 17 obtained by such a method is inferior in adhesion to the ion-exchange polymer film 16 .

On the other hand, in the manufacturing method of the electrolyte layer 4 described above, the ion-exchange polymer membrane 16 is held by the frame-shaped jig 20, and the ion-exchange polymer membrane 16 is immersed in the metal ion solution.

As a result, in the method for manufacturing the electrolyte layer 4 described above, the surface of one side of the ion-exchange polymer membrane 16 is brought into contact with the metal ion solution, and the air reservoir 28 is formed on the other side of the ion-exchange polymer membrane 16 . to suppress contact between the other surface of the ion-exchange polymer membrane 16 and the metal ion solution.

According to the manufacturing method of the electrolyte layer 4, only one side of the ion-exchange polymer membrane 16 is brought into contact with the metal ion solution without contacting the ion-exchange polymer membrane 16 with a masking material or the like. be able to.

As a result, damage to the ion-exchange polymer membrane 16 can be suppressed, and the functional inorganic membrane 17 can be formed only on one surface of the ion-exchange polymer membrane 16 . Furthermore, the obtained functional inorganic film 17 has excellent adhesion to the ion-exchange polymer film 16 .

Although the embodiment of the present invention has been described above, the embodiment of the present invention is not limited to this, and the design can be appropriately modified without changing the gist of the present invention.

Applications of the fuel cell 1 include, for example, power sources for drive motors in automobiles, ships, aircraft, etc., and power sources for communication terminals such as mobile phones.

EXAMPLES Examples and comparative examples are shown below to describe the present invention more specifically. In addition, the present invention is not limited to Examples and Comparative Examples. In addition, specific numerical values such as the mixing ratio (content ratio), physical property values, and parameters used in the following description are the corresponding mixing ratios ( Content ratio), physical properties, parameters, etc. be able to.

"Parts" and "%" are based on mass unless otherwise specified.

Example 1
(1) Preparation of raw material aqueous solution Magnesium nitrate hexahydrate (Mg(NO ₃ ) 2.6H ₂ O, manufactured by Kanto Chemical Co., Ltd.), aluminum nitrate nonahydrate (Al ₍ NO ₃ ) _{3.9H 2} O, Kanto Kagaku Co., Ltd.) and urea ((NH ₂ ) ₂ CO, Sigma-Aldrich) were prepared.

And ^{magnesium nitrate hexahydrate} and aluminum ^nitrate are Nonahydrate was weighed and placed in a beaker, and ion-exchanged water was further added to adjust the total volume to 75 ml.

The resulting solution of metal ions was then stirred and urea was added so that the molar ratio of urea to nitrate ions (urea/NO ³⁻ ) was 4 and further stirred.

Thus, a raw material aqueous solution was obtained.

(2) Production of Electrolyte Layer A raw material aqueous solution was poured into a Teflon (registered trademark) sealed container (capacity: 100 mL) equipped with a stainless steel jacket.

On the other hand, A201 (manufactured by Tokuyama) as an anion-exchange polymer membrane was held by a frame-shaped jig, and the frame-shaped jig and the anion-exchange polymer membrane were immersed in the raw material aqueous solution so as to include air pockets. (See Figures 2 and 3).

After that, the raw material aqueous solution was heated to 70° C. and held for 144 hours.

As a result, a layered double hydroxide was formed on the surface of the anion-exchange polymer membrane to form an inorganic protective membrane. As a result, an electrolyte layer comprising an anion-exchange polymer membrane and an inorganic protective membrane formed on one side thereof was obtained.

(3) Preparation of Anode Catalyst Ink Powder of carbon (Ketjenblack) supporting nickel powder (Ni: 50% by mass, C: 50% by mass, manufactured by Cataler) was mixed with an anion exchange resin to obtain a mixture. rice field. This mixture was then dispersed in alcohol.

An anode catalyst ink was thus prepared.

(4) Preparation of Cathode Ink Nicarbazin Fe complex (NPC-2000, manufactured by Pajarito) was mixed with an anion exchange resin to obtain a mixture. This mixture was then dispersed in alcohol.

A cathode catalyst ink was thus prepared.

(5) Manufacture of Membrane Electrode Assembly The anode catalyst ink is applied by a spray method to the surface of the electrolyte layer on which the inorganic protective film is not formed (the exposed surface of the anion-exchange polymer membrane). Dried at °C. Thus, an anode electrode (anode catalyst layer) was formed.

The catalyst loading amount of the anode catalyst layer was 3.2 mg/cm ² .

Next, the cathode catalyst ink was applied to the surface of the electrolyte layer on which the inorganic protective film was formed (the surface of the inorganic protective film) by a spray method, and dried at 25°C. Thus, a cathode electrode (cathode catalyst layer) was formed.

The amount of catalyst supported on the cathode catalyst layer was set to 1.25 mg/cm ² , thereby producing a membrane electrode assembly.

1 fuel cell 2 anode electrode 3 cathode electrode 4 electrolyte layer 15 membrane electrode assembly 16 anion exchange polymer membrane 17 functional inorganic membrane 20 frame jig

Claims (3)

A method for producing an electrolyte membrane comprising an ion-exchange polymer membrane and a functional inorganic membrane arranged only on one surface of the ion-exchange polymer membrane, comprising:
a preparation step of preparing the ion-exchange polymer membrane and a frame-shaped jig having a pair of frames;
a gripping step of sandwiching the ion-exchange polymer membrane between the pair of frames and gripping the ion-exchange polymer membrane with the frame-shaped jig;
an immersion step of immersing and holding the ion-exchange polymer membrane held by the frame jig in a metal ion solution of elements constituting the functional inorganic membrane;
a forming step of forming the functional inorganic membrane on the surface of the ion-exchange polymer membrane,
In the immersion step,
The frame-shaped jig and the ion-exchange polymer membrane are immersed in the metal ion solution so that air is included in the space formed by the frame-shaped jig and the ion-exchange polymer membrane, by
contacting one surface of the ion-exchange polymer membrane with the metal ion solution; and
Manufacture of an electrolyte layer characterized by forming an air reservoir on the other side of the ion-exchangeable polymer membrane to suppress contact between the surface of the other side of the ion-exchangeable polymer membrane and the metal ion solution. Method. 2. The method for producing an electrolyte layer according to claim 1, wherein the ion-exchange polymer membrane is an anion-exchange polymer membrane. 3. The method for producing an electrolyte layer according to claim 1, wherein the functional inorganic film contains a layered double hydroxide.

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