JP5099096B2 - Proton conductive electrolyte manufacturing method, proton conductive electrolyte membrane manufacturing method, and fuel cell manufacturing method - Google Patents

Description

The present invention relates to a method for producing a proton conducting electrolyte, a method for producing a proton conducting electrolyte membrane, and a method for producing a fuel cell , and more particularly, a method for producing a proton conducting electrolyte and a proton using a metal phosphate and phosphoric acid. The present invention relates to a method for manufacturing a conductive electrolyte membrane and a method for manufacturing a fuel cell .

In recent years, with increasing environmental awareness, fuel cells have attracted attention as clean energy that does not emit CO ₂ or pollutants. Of these, efforts are being made to develop a PEFC (solid polymer fuel cell) using a solid polymer electrolyte that has high energy efficiency and a temperature range of around 100 ° C. and is easy to handle for general use.

As a polymer electrolyte that conducts protons, perfluorosulfonic acid or the like that is generally known as Nafion (registered trademark) is used, but it conducts protons when the proton conduction mechanism is H ₃ O ^+. Since it is a vehicle (transport) mechanism, it is necessary to provide a humidifying mechanism, which causes a problem that the system becomes complicated.

  A PBI (polybenzimidazole) membrane impregnated with phosphoric acid is disclosed as an electrolyte that has improved the problem of humidification (see, for example, Patent Document 1). However, since 90% or more of this film is composed of liquid phosphoric acid, phosphoric acid, which is a strong acid, is likely to ooze out, liquid sealing must be performed strictly, and phosphorous is used in cell fabrication. There are problems such as difficulty in producing MEA (membrane / electrode assembly) due to acid seepage.

  On the other hand, metal phosphates are known as proton conductive electrolytes having proton conductivity in a non-humidified state (see, for example, Patent Document 2). Moreover, what doped a different kind of metal in some metal phosphates is also disclosed (for example, refer patent document 3, 4).

JP 2001-510931 A JP 2005-294245 A JP 2008-53224 A JP 2008-53225 A

  However, in the case of the above metal phosphate, phosphoric acid may be lost during the heat treatment at 350 ° C. or higher, which is necessary in the synthesis process, so the reproducibility of the product cannot be obtained, and the synthesis conditions can be controlled. There is a problem that it is difficult. In addition, since the metal phosphate is a powder, the moldability is difficult, and there is a problem that the film cannot be formed unless a binder is added.

An object of the present invention is to provide a method for producing a proton conducting electrolyte, a method for producing a proton conducting electrolyte membrane, and a fuel cell having excellent reproducibility, good moldability, and high proton conductivity in a non-humidified state. It is to provide a method .

In order to achieve the above object, the invention described in claim 1 is characterized by mixing phosphoric acid with at least one selected from the group consisting of metal oxides, metal hydroxides, metal chlorides, and metal nitrates, followed by heat treatment. A method for producing a proton conductive electrolyte, comprising: a first step of producing a metal phosphate; and a second step of further mixing and heat treating the metal phosphate with phosphoric acid.

The invention according to claim 2 is the method for producing a proton conductive electrolyte according to claim 1 , wherein the heat treatment temperature in the second step is 50 ° C to 300 ° C.

The invention according to claim 3 is characterized in that it comprises a third step of powdering the metal phosphate between the first step and the second step. 2. A method for producing a proton conducting electrolyte according to 2.

In the invention according to claim 4, the phosphoric acid used in the first step is solid phosphoric acid. The proton conductive electrolyte according to any one of claims 1 to 3, It is a manufacturing method.

The invention according to claim 5 is characterized in that the metal phosphate is composed of a compound represented by the following formula (1), and the proton conductivity according to any one of claims 1 to 4 . This is a method for producing an electrolyte.
M _1-x N _x P ₂ O ₇ (1)
(Where M and N are metal elements, X is 0 ≦ X <0.5, and M is selected from the group consisting of Zr, Cs, Sn, Ti, Si, Ge, Pb, Ca, Mg, and Al. And N is one selected from the group consisting of Al, In, B, Ga, Sc, Yb, Ce, La and Sb.)

The invention according to claim 6 is the method for producing a proton-conducting electrolyte according to claim 5 , wherein the M is Sn or Cs.

The invention according to claim 7 is the method for producing a proton conductive electrolyte according to claim 5 or 6 , wherein the N is In or Al.

In the invention according to claim 8, the number of atoms of M and N of the metal phosphate is set to [M] and [N], respectively, and the number of phosphorus atoms of the metal phosphate and phosphoric acid is The proton conduction according to any one of claims 5 to 7, wherein the relationship between [M], [N] and [P] is represented by the following formula (2), where the sum is [P]. This is a method for producing a conductive electrolyte.
2 <[P] / ([M] + [N]) ≦ 4 (2)

The invention according to claim 9 is characterized in that the relationship between the [M], [N] and [P] is represented by the following formula (3). It is a manufacturing method.
2.4 ≦ [P] / ([M] + [N]) ≦ 3.2 (3)

The proton according to any one of claims 1 to 9 , wherein the metal phosphate is produced by using tin oxide and ammonium hydrogen phosphate. It is a manufacturing method of conductive electrolyte.

The invention according to claim 11 is the proton according to any one of claims 1 to 3, and 5 to 9 , wherein the metal phosphate is produced by using a coprecipitation method. It is a manufacturing method of conductive electrolyte.

The invention according to claim 12 is a method of mixing metal phosphate by mixing phosphoric acid with at least one selected from the group consisting of metal oxide, metal hydroxide, metal chloride, and metal nitrate. A first step to be generated; a second step in which a paste is prepared by further mixing phosphoric acids with the metal phosphate; and a third step in which the paste is applied to a cast substrate and molded. In the method for producing a proton conductive electrolyte membrane, heat treatment is performed in the second and / or third step.

The invention according to claim 13 is the method for producing a proton-conducting electrolyte membrane according to claim 12 , wherein a binder is added in the second step.

The invention according to claim 14 is the method for producing a proton conductive electrolyte membrane according to claim 13 , wherein the binder is a fluorine-based or hydrocarbon-based polymer.

The invention according to claim 15 is the method for producing a proton-conducting electrolyte membrane according to claim 13 , wherein the binder is a fluorine-based or hydrocarbon-based ionomer.

The invention as set forth in claim 16 is the method for producing a proton conductive electrolyte membrane according to claim 13 , wherein the binder is an ionic liquid.

The invention according to claim 17 is the method for producing a proton-conducting electrolyte membrane according to claim 13 , wherein the binder is a cellulose polymer.

The invention according to claim 18 is characterized in that the cast substrate is made of any one of a polytetrafluoroethylene film, a polyimide film and a metal foil. The method for producing a proton conductive electrolyte membrane according to the above.

Further, in the invention described in claim 19 , catalyst electrodes are respectively laminated on both sides of the proton conductive electrolyte membrane produced by the method for producing a proton conductive electrolyte membrane according to any one of claims 11-18. A fuel cell manufacturing method comprising a fourth step and a fifth step of laminating a separator on each catalyst electrode.

Further, in the invention described in claim 20, the heat treatment temperature in the second and / or third step is 50 ° C to 300 ° C, according to any one of claims 12-18. It is a manufacturing method of a proton conductive electrolyte membrane.

According to the present invention, a method for producing a proton conducting electrolyte, a method for producing a proton conducting electrolyte membrane, and a fuel cell production having excellent reproducibility, good moldability, and high proton conductivity in a non-humidified state. A method can be provided.

The typical sectional view of the fuel cell concerning a 3rd embodiment of the present invention. The X-ray-diffraction chart figure of the metal phosphate in the Example of this invention.

  Hereinafter, first to third embodiments of the present invention will be described. The following first to third embodiments exemplify materials and manufacturing methods for embodying the technical idea of the present invention. The technical ideas of the present invention are materials and manufacturing methods. Etc. are not specified below. The technical idea of the present invention can be variously modified within the scope of the claims.

[First embodiment]
(Proton conducting electrolyte)
The proton conductive electrolyte according to the first embodiment of the present invention is composed of a metal phosphate and phosphoric acid, and the metal phosphate is crosslinked with phosphoric acid.

  In the present embodiment, phosphoric acids (hereinafter also simply referred to as “phosphoric acid”) refer to orthophosphoric acid and phosphoric acid condensate. Examples of the phosphoric acid condensate include pyrophosphoric acid, triphosphoric acid, metaphosphoric acid (polyphosphoric acid). Acid) and the like.

  Examples of the metal phosphate according to the present embodiment include compounds such as orthophosphate and pyrophosphate. Specific examples include tin phosphate, zirconium phosphate, and cesium phosphate. Preferably, a pyrophosphate salt in which a part of a metal such as tin or cesium is substituted with a doping metal element such as indium, aluminum, or antimony is preferable.

  In the present embodiment, the metal phosphate is preferably composed of a compound represented by the following formula (1).

M _1-x N _x P ₂ O ₇ (1)
(Where M and N are metal elements, X is 0 ≦ X <0.5, and M is selected from the group consisting of Zr, Cs, Sn, Ti, Si, Ge, Pb, Ca, Mg, and Al. N is a doping metal element and is one selected from the group of Al, In, B, Ga, Sc, Yb, Ce, La and Sb.)

  The metal phosphate according to this embodiment can be synthesized by heating and heat-treating one or more metal oxides and phosphoric acid.

  The metal oxide is not particularly limited as long as it can generate phosphoric acid and a crystalline salt. For example, the oxide which consists of the following metal elements can be mentioned. That is, it is a metal element such as Zr, Cs, Sn, Ti, Si, Ge, Pb, Ca, Mg, and Al.

  You may dope the metal different from a main metal by using the said metal as a main metal. When a doped metal is used, it is desirable to use Sn, Cs, Ti and Zr from the viewpoint of stability as a phosphate among the main metals.

  As the dope metal, for example, when Sn is used as the main metal, In and Al are suitable because they can be dissolved in the main metal. The mixing ratio of the main metal and the doped metal varies depending on the solid solubility limit, but when Sn is used as the main metal and In is used as the doped metal, for example, a range of Sn: In = 7: 3 to 9.8: 0.2 is desirable.

  In the proton conductive electrolyte according to the present embodiment, the number of atoms of the metal element of the metal phosphate and the number of atoms of the doped metal element are [M] and [N], respectively, and the number of phosphorus atoms of the metal phosphate and phosphoric acid When the total number of phosphorus atoms of [P] is [P], it is preferable to satisfy the following formula (2).

2 <[P] / ([M] + [N]) ≦ 4 (2)
More preferably, it is preferable to satisfy | fill following formula (3).

    2.4 ≦ [P] / ([M] + [N]) ≦ 3.2 (3)

  By satisfy | filling said Formula (2), while high proton conductivity is acquired, a moldability will become favorable. When the value of the above formula [P] / ([M] + [N]) is 2 or less, the amount of phosphoric acid on the metal phosphate is reduced, and proton conductivity is not improved. On the other hand, if it exceeds 4, the amount of phosphoric acid is too large, moisture absorption in the atmosphere is so high that the molded body becomes brittle, and the shape may not be maintained.

(Proton conductive electrolyte production method)
The method for producing a proton conductive electrolyte according to the present embodiment includes a step of mixing metal phosphate and phosphoric acid, and after performing tableting molding by uniaxial molding of the mixed metal phosphate and phosphoric acid, Or a step of heat-treating after filling the container of the ceramic porous body or filling the honeycomb body. This will be described in detail below.

(A) First, a metal phosphate is prepared as follows.
Each metal oxide, metal hydroxide, metal chloride, or metal nitrate containing a main metal such as tin and a doping metal such as indium and liquid phosphoric acid are mixed in a predetermined number of moles. Next, water is added thereto, and the mixture is stirred and dispersed at a temperature of about 100 to 300 ° C. using a stirrer or the like for about 1 to 3 hours. This dispersion is put in a crucible and fired at a temperature of about 300 to 700 ° C., for example. The firing time is, for example, about 1 to 3 hours. Since phosphoric acid may disappear in the high temperature state, it is desirable that the number of moles of liquid phosphoric acid is large, for example, about 1.1 to 1.5 times the molar equivalent.

In order to avoid the problem of loss of phosphoric acid during firing, solid phosphoric acid may be used instead of liquid phosphoric acid. In the case of using solid phosphoric acid, for example, using ammonium monohydrogen phosphate, ammonium dihydrogen phosphate, or the like, each metal oxide containing a main metal such as tin and a doping metal such as indium is formed in a predetermined molar amount. Mix by number. As the metal oxide, an oxide containing a main metal and an oxide containing a doping metal may be mixed at a molar ratio of the main metal to the doping metal of, for example, about 9: 1 to 1: 1. These are put into a crucible and fired at a temperature of about 300 to 700 ° C. for about 1 to 3 hours. Subsequently, the product obtained by baking can be pulverized in an agate bowl to obtain a desired metal phosphate.
By using solid phosphoric acid, a molar equivalent of phosphoric acid reacts with the metal oxide, and the excess is volatilized at a high temperature, so that excess phosphoric acid does not adhere and a reproducible metal phosphate can be obtained. it can.

It can also be produced by a coprecipitation method. For example, tin chloride pentahydrate (SnCl ₄ .5H ₂ O) and indium chloride tetrahydrate (InCl ₃ .4H ₂ O) were prepared in an aqueous solution having a predetermined concentration so that the molar ratio was about 9: 1. Thereafter, the mixture is stirred with a stirrer, and an aqueous ammonia solution is added dropwise until the pH becomes 7, thereby obtaining tin hydroxide (Sn (OH) ₄ ) and indium hydroxide (In (OH) ₃ ). Thereafter, the precipitate is suctioned / filtered and dried, the hydroxide salt and phosphoric acid are mixed, and heat treatment is carried out at about 200 ° C. for about 2 hours to obtain a metal phosphate. Finally, wash with deionized water. According to the coprecipitation method, a powder in which indium is uniformly doped with tin phosphate can be prepared by simultaneously precipitating a plurality of types of hardly soluble salts from a solution containing a plurality of desired metal ions.

(B) Next, a proton conductive electrolyte is prepared from the metal phosphate and phosphoric acid.
After mixing metal phosphate and phosphoric acid at a predetermined blending amount and kneading well, the mixed metal phosphate and phosphoric acid are compressed into tablets by uniaxial molding or filled into a ceramic porous body container. A proton conductive electrolyte can be obtained by heat treatment after or after filling the honeycomb body.

  When molding by tableting, the material of the tableting jig for producing the tableting molded body is a jig that can be compressed to a desired thickness and size by applying pressure to the electrolyte, Although it is not particularly limited, it is preferably excellent in acid resistance and pressure resistance. Examples of such a material include stainless steel (SUS) and super hard soybean. Of these, super-hard soybean is preferable because of its particularly high pressure resistance. As a tableting jig, a commercially available tableting jig may be used.

  When the ceramic porous body is filled and molded, the porous body filled with the electrolyte is not particularly limited as long as it can fill the electrolyte, but has excellent acid resistance and pressure resistance. Is preferred. As such a thing, a ceramic porous body, a honeycomb body, etc. are used, for example.

A technique for filling the ceramic porous body or honeycomb body with the electrolyte is not particularly limited as long as it is a technique capable of filling the electrolyte, but a technique capable of more dense filling is preferable. As such a method, for example, a cylindrical honeycomb body having a diameter of 5 cm, a height of 1 cm, and an inner diameter of the honeycomb of 5 mm is completely filled with a mixture of a metal phosphate and phosphoric acid, and a surplus is further obtained. The mixture of metal phosphate and phosphoric acid is sealed by heat sealing in a state where it is put in a nylon pouch together with the honeycomb body, and hydrostatic pressure pressing (SIP) is performed at a pressure of about 2 t / cm ² . Thereafter, the honeycomb body filled with the mixture of metal phosphate and phosphoric acid is taken out, and the electrolyte attached to the outside of the honeycomb body is removed. Next, by subjecting them to heat treatment, a proton conductive electrolyte in which the powder is more densely packed can be obtained.

In the heat treatment, the heat treatment temperature is, for example, about 50 to 300 ° C., preferably about 100 to 250 ° C. If the heat treatment temperature is lower than about 50 ° C., water contained in phosphoric acid cannot be removed, and if it exceeds about 300 ° C., phosphoric acid volatilizes, which is not preferable. The heat treatment time is, for example, about 10 minutes to 5 hours, preferably about 10 minutes to 3 hours.
The compounding amount of the metal phosphate and the phosphoric acid is 5: 0.2 to 5: 2, preferably 5: 0.3 to 5: 1.2, more preferably 5: 0.8 to 5: 1 by mass ratio. Most preferably, it is adjusted to 5: 0.9.

  By the heat treatment, water contained in phosphoric acid is volatilized, and orthophosphoric acid on the metal phosphate is condensed to produce pyrophosphoric acid or metaphosphoric acid. Then, when this pyrophosphate and metal phosphate are cross-linked, a network with phosphoric acid is formed around the metal phosphate, and the charged phosphoric acid accumulates at a high density, resulting in good proton conductivity. It is considered that the strength of the electrolyte is increased.

  The proton conductive electrolyte obtained by the above heat treatment can be used as an electrolyte for a fuel cell by attaching electrodes on both sides while filling a container such as a tableting molded body, a ceramic porous body, and a honeycomb body. It is.

  Further, the obtained proton conductive electrolyte may be pulverized and used as a material constituting the electrolyte membrane.

  According to the present embodiment, it is possible to provide a proton conductive electrolyte that has excellent reproducibility, good moldability, and high proton conductivity in a non-humidified state.

[Second Embodiment]
(Proton conducting electrolyte membrane)
The proton conductive electrolyte membrane according to the second embodiment of the present invention is composed of the proton conductive electrolyte described in the first embodiment.

  Although the thickness of the proton conductive electrolyte membrane according to the present embodiment is not limited, it is usually about 20 to 1000 μm, and preferably about 30 to 300 μm from the viewpoint of strength.

  The metal phosphate constituting the proton conductive electrolyte membrane may contain a binder. An electrolyte membrane with excellent mechanical strength can be obtained by casting a paste obtained by adding a binder to metal phosphate.

  The cast base material is not particularly limited as long as it is a support to which an electrolyte paste is applied, but it is preferably one having excellent acid resistance and heat resistance. Examples of such a material include polyester, polyimide, polytetrafluoroethylene (PTFE) film, metal foil, and the like. Among these, PTFE, polyimide, and metal foil are preferable from the viewpoint of dimensional stability and peelability in the electrolyte membrane manufacturing process described later. Moreover, in order to improve the peelability to an electrolyte membrane, you may provide a release layer, a peeling layer, etc.

  The binder used preferably has, for example, acid resistance at a pH of about 1 to 3 and heat resistance at a temperature of about 100 to 200 ° C. Further, it may have proton conductivity.

  Such a binder is preferably a fluorine-based or hydrocarbon-based polymer, a fluorine-based or hydrocarbon-based ionomer.

  Fluoropolymers include fluorine such as tetrafluoroethylene (PTFE), polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and tetrafluoroethylene perfluoroalkyl vinyl ether copolymer (PFA). Resin or the like can be used.

  The hydrocarbon polymer is a polymer having a hydrocarbon compound as the main skeleton, such as polyimide, polyamideimide, polystyrene sulfide, polybenzimidazole, polypyridine, polypyrimidine, polyimidazole, polybenzothiazole, poly Examples thereof include benzooxazole, polyoxadiazol, polyxylone, polyquinoxaline, polythiadiazol, polytetrazabilene, polyoxazole, polythiazole, polyvinyl pyridine and polyvinyl imidazole.

  Examples of fluorine-based ionomers include Nafion (registered trademark) from DuPont, Flemion (registered trademark) from Asahi Glass Co., Aciplex (registered trademark) from Asahi Kasei Co., Ltd., and Aquivion (registered trademark). And sulfonyl fluoride vinyl ether (SFVE) -tetrafluoroethylene copolymer.

  Hydrocarbon ionomers include polyarylene ether sulfonic acid, polystyrene sulfonic acid, syndiotactic polystyrene sulfonic acid, polyphenylene ether sulfonic acid, modified polyphenylene ether sulfonic acid, polyether sulfone sulfonic acid, polyether ether ketone sulfonic acid, and polyphenylene. Examples thereof include sulfide sulfonic acid.

  The binder may be an ionic liquid. The ionic liquid is not particularly limited as long as proton conductivity is not hindered. Examples of the ionic liquid include a fluorohydrogenate type ionic liquid and a diethylmethylammonium trifluoromethanesulfonic acid ionic liquid.

  The binder may be a cellulosic polymer. Examples of the cellulose polymer include methyl cellulose, carboxymethyl cellulose, and cellulose acetate.

  Only one type of binder described above may be used, or a plurality of types may be used.

  Among these binders, PTFE, polyvinylidene fluoride, perfluorosulfonic acid, cellulose acetate, and sulfonyl fluoride vinyl ether (SFVE) -tetrafluoroethylene copolymer are preferably used from the viewpoint of durability and binding properties.

  The proton-conducting electrolyte membrane according to the present embodiment uses the metal phosphate described in the first embodiment, which is powdered, added with phosphoric acid to form a paste, and the paste is cast. After coating on a base material and heat-treating, it can be peeled off from the cast base material to produce a cast film.

  The paste may be prepared by adding a solvent to the binder solution or dispersion. A solvent that does not aggregate the binder is used. Specific examples include water, ethanol, methanol, 1-butanol, t-butanol, propanol, N-methylpyrrolidone, dimethylacetamide, and the like.

  Subsequently, these are mixed and disperse | distributed with a disperser, and electrolyte paste is obtained. As the disperser, an ultrasonic disperser, a homogenizer, a planetary ball mill, or the like can be used.

  Alternatively, a metal phosphate and phosphoric acid may be mixed and subjected to heat treatment, and the paste may be prepared by adding the binder to the heat-treated metal phosphate and phosphoric acid mixture.

The heat treatment temperature is, for example, about 50 to 300 ° C., preferably about 100 to 250 ° C. in order to remove the solvent and promote the formation of the composite phosphate. If the heat treatment temperature is lower than about 50 ° C., water contained in phosphoric acid cannot be removed, and if it exceeds about 300 ° C., phosphoric acid volatilizes, which is not preferable. The heat treatment time is, for example, about 10 minutes to 5 hours, preferably about 10 minutes to 3 hours.
The compounding amount of the metal phosphate and the phosphoric acid is 5: 0.2 to 5: 2, preferably 5: 0.3 to 5: 1.2, more preferably 5: 0.8 to 5: 1 by mass ratio. Most preferably, it is adjusted to 5: 0.9.

  When a paste is prepared using a mixture of metal phosphoric acid and phosphoric acid that has been subjected to the heat treatment, after the paste is formed, heat treatment may not be performed and only drying may be performed. The drying method is not particularly limited as long as the solvent component contained in the electrolyte membrane can be removed. Examples of such a method include drying by infrared rays, vacuum, air drying, high-frequency electromagnetic waves, and the like.

  According to the present embodiment, it is possible to provide a proton conductive electrolyte membrane having excellent reproducibility, good moldability, and high proton conductivity in a non-humidified state.

[Third embodiment]
(Fuel cell)
As shown in FIG. 1, the fuel cell 10 according to the third embodiment of the present invention includes a proton conductive electrolyte membrane 1, a pair of catalyst electrodes 2 and 3, and a pair of separators 4 and 5. The catalyst electrodes 2, 3 and the separators 4, 5 are sequentially stacked on both sides of the proton conductive electrolyte membrane 1.

  The catalyst electrodes 2 and 3 are made of a gas diffusible conductive material such as a porous body, and can flow fuel gas or oxidant gas. The anode side catalyst electrode 2 is a fuel electrode, and the cathode side catalyst electrode 3 is an oxidant electrode. A catalytic metal that promotes an oxidation reaction of hydrogen is attached to the fuel electrode, and a catalytic metal that promotes a reduction reaction of oxygen is attached to the oxidant electrode. The catalyst electrodes 2 and 3 may be composed of two layers, a gas diffusion layer and a catalyst layer.

  The separator 4 is for supplying fuel to the anode side catalyst electrode 2 and has a fuel flow path 6 for circulating the fuel. On the other hand, the separator 5 is for supplying an oxidant gas to the cathode side catalyst electrode 3 and has an oxidant gas flow path 7 for circulating the oxidant gas.

  The separators 4 and 5 may be made of any material having stable conductivity even in the environment inside the fuel cell 10. In general, a carbon plate having a flow path is used. The separators 4 and 5 are made of a metal such as stainless steel, and a coating made of a conductive material such as chromium, a platinum group metal or oxide thereof, or a conductive polymer is formed on the surface of the metal. Also good.

  The separators 4 and 5 can have a function as a current collector when used in a fuel cell in which a plurality of fuel cells 10 are stacked.

(Operating principle)
A fuel capable of supplying hydrogen, such as hydrogen gas or methanol, is supplied to the fuel flow path 6 to the anode catalyst electrode 2, and protons (H ⁺ ) and electrons (e ⁻ ) are generated from the fuel. The generated protons are conveyed to the cathode side catalyst electrode 3 by the proton conductive electrolyte membrane 1. On the other hand, an oxidant gas such as air or oxygen gas is supplied to the cathode side catalyst electrode 3 in the oxidant gas flow path 7, protons carried by the proton conductive electrolyte membrane 1, electrons coming from the external circuit 8, and oxidation. Reaction with the agent gas produces water. In this way, it functions as a fuel cell.

  The fuel cell 10 according to the present embodiment is a fuel cell shown in FIG. 1 by sequentially laminating the catalyst electrodes 2 and 3 and the separators 4 and 5 on both surfaces of the proton conductive electrolyte membrane 1 using a known technique. 10 can be manufactured.

  According to the present embodiment, since the proton conductive electrolyte membrane 1 having excellent reproducibility, good moldability, and high proton conductivity in a non-humidified state is used, the fuel has excellent stability and high performance. A battery 10 can be provided.

  Hereinafter, the present invention will be described more specifically based on examples. However, the present invention is not limited to these examples, and various modifications can be made without departing from the scope of the present invention.

[Example 1]
First, a metal phosphate was prepared as follows. Tin oxide (SnO ₂ : manufactured by Nano Tec) 13.56 g (0.09 mol) and indium oxide (In ₂ O ₃ : manufactured by Nacalai Tesque) 1.40 g (0.0050 mol) of diammonium hydrogen phosphate ( 27.99 g (0.212 mol) (Nacalai Tesque) was added and mixed with a spoon.

  The obtained mixture was put into a crucible, fired at about 650 ° C. for about 2 hours, and the product obtained after sintering was pulverized with an agate to obtain a metal phosphate (sample A).

  Next, 0.9 g of 85% phosphoric acid aqueous solution was added to 5 g of metal phosphate (sample A), kneaded well and rolled into a film, and then heat-treated at about 160 ° C. for about 30 minutes. A proton conductive electrolyte membrane 1 having a thickness of 1 mm was obtained.

[Example 2]
To 5 g of the same metal phosphate (sample A) as in Example 1, 0.9 g of 85% phosphoric acid aqueous solution, 0.83 g of 60% PTFE dispersion (polyflon D1-E: manufactured by Daikin Industries) and 20 g of water In addition, an electrolyte paste was prepared by dispersing with a disperser. This electrolyte paste was applied onto a polyimide film (manufactured by DuPont) having a thickness of 50 μm with a blade coater and heat-treated at about 160 ° C. for about 30 minutes to obtain a proton conductive electrolyte membrane 1 having a thickness of 100 μm.

[Example 3]
To 5 g of the same metal phosphate (sample A) as in Example 1, 0.9 g of 85% phosphoric acid aqueous solution, 1.0 g of 20% Nafion solution (DE2020CS: manufactured by DuPont) and 20 g of water were added. To prepare an electrolyte paste. This electrolyte paste was applied onto a polyimide film (manufactured by DuPont) having a thickness of 50 μm with a blade coater and heat-treated at about 160 ° C. for about 30 minutes to obtain a proton conductive electrolyte membrane 1 having a thickness of 100 μm.

[Example 4]
0.9 g of 85% phosphoric acid aqueous solution was added to 5 g of the same metal phosphate (sample A) as in Example 1, and these were mixed with a spoon. The obtained mixture was put into a crucible, fired at about 160 ° C. for about 30 minutes, and the product obtained after sintering was pulverized in an agate bowl to obtain a fired product of metal phosphate and liquid phosphoric acid.

  Next, 4 g of binder (cellulose acetate) and 3 g of solvent (NMP) were mixed with 5 g of the fired product of the metal phosphate and liquid phosphoric acid and dispersed for about 24 hours with a disperser to prepare an electrolyte membrane paste. This electrolyte paste was applied onto a polyimide film (manufactured by Dupont) having a thickness of 50 μm with a blade coater and heat-treated at about 200 ° C. for about 30 minutes to obtain a proton conductive electrolyte membrane 1 having a thickness of 100 μm.

[Example 5]
0.9 g of 85% phosphoric acid aqueous solution was added to 5 g of the same metal phosphate (sample A) as in Example 1, and these were mixed with a spoon. The obtained mixture was put into a crucible, fired at about 160 ° C. for about 30 minutes, and the product obtained after sintering was pulverized in an agate bowl to obtain a fired product of metal phosphate and liquid phosphoric acid.

  Next, 4 g of binder (cellulose acetate) and 3 g of solvent (NMP) were mixed with 5 g of the fired product of the metal phosphate and liquid phosphoric acid and dispersed for about 24 hours with a disperser to prepare an electrolyte membrane paste. This electrolyte paste was applied onto a polyimide film (manufactured by Dupont) having a thickness of 50 μm with a blade coater and vacuum-dried to obtain a proton conductive electrolyte membrane having a thickness of 100 μm.

[Comparative Example 1]
Tin oxide (SnO ₂ : manufactured by Nano Tec) 16.96 g (0.11 mol), indium oxide (In ₂ O ₃ : manufactured by Nacalai Tesque) 1.74 g (0.0063 mol), 85% phosphoric acid aqueous solution ( 20 g of distilled water was added to 40.45 g (0.35 mol) of Nacalai Tesque, and the mixture was stirred with a stirrer at about 200 ° C. for about 2 hours.

  The obtained stirring liquid was put into a crucible, fired at about 650 ° C. for about 2 hours, and the product obtained after sintering was pulverized with an agate to obtain a metal phosphate (sample B).

  Next, this metal phosphate (sample B) was formed by rolling to obtain a proton conductive electrolyte membrane 1 having a thickness of 1 mm.

[Comparative Example 2]
After adding 0.9 g of 85% phosphoric acid aqueous solution to 5 g of the same metal phosphate (sample A) as in Example 1, this was rolled to obtain a proton conductive electrolyte membrane 1 having a thickness of 1 mm. It was.

[Comparative Example 3]
After adding and mixing 20 g of distilled water to 5 g of the same metal phosphate (sample A) as in Example 1, this was rolled to obtain a proton-conductive electrolyte membrane 1 having a thickness of 1 mm.

[Comparative Example 4]
To 5 g of the same metal phosphate (sample A) as in Example 1, 0.83 g of 60% PTFE dispersion (Polyflon D1-E: manufactured by Daikin Industries, Ltd.) and 20 g of water are added, and dispersed in a disperser to be electrolyte. A paste was prepared. This electrolyte paste was applied onto a polyimide film (manufactured by DuPont) having a thickness of 50 μm with a blade coater and heat-treated at about 160 ° C. for about 30 minutes to obtain a proton conductive electrolyte membrane 1 having a thickness of 100 μm.

(Crystal analysis)
Each of the crystal structures of the metal phosphates (samples A and B) obtained in Examples 1 to 5 and Comparative Examples 1 to 4 was analyzed using an X-ray diffraction analyzer (XRD). X-ray diffraction analysis was performed under the measurement conditions shown in FIG. FIG. 2 shows X-ray diffraction charts of samples A and B and a standard material of indium-doped metal phosphate. The standard substance is a commercially available sample (Sn _0.9 In _0.1 P ₂ O ₇ ). This analysis confirmed that Samples A and B were Sn _0.9 In _0.1 P ₂ O ₇ .

(Elemental analysis)
For the proton conductive electrolyte membranes 1 obtained in Examples 1 to 5 and Comparative Examples 1 to 4, a fluorescent X-ray analyzer (XRF: X-ray Fluorescence Analysis) (RIX-3100: manufactured by Rigaku Corporation) is used. Used for elemental analysis.
As the measurement conditions of XRF, the measurement diameter of the proton conductive electrolyte membrane 1 is 30 mmφ, the measurement atmosphere is a vacuum state of 13 Pa, and the measurement elements are elements from B (boron) to U (uranium) in order of atomic number. .
The value of [P] / ([M] + [N]) was obtained from the detection results of Sn, In and P among the elements detected under the above conditions. The results are shown in Table 2.

(Proton conductivity measurement)
For the proton conductive electrolyte membranes 1 obtained in Examples 1 to 5 and Comparative Examples 1 to 4, the proton conductivity was measured by the following method. The proton conductive electrolyte membrane 1 was cut into a disk shape having a diameter of 2.2 cm, and a gold electrode of the same shape provided with a take-out was vertically contacted and fixed with a glass plate. An alternating current impedance load was applied with an electrochemical measurement apparatus (12528WB type: Solartron), and proton conductivity was measured at temperatures of 120 ° C. and 200 ° C. in a non-humidified environment. The results are shown in Table 2.

As shown in Table 2, in Examples 1 to 5 within the scope of the present invention, good proton conductivity was exhibited in a non-humidified state at 120 ° C and 200 ° C.
On the other hand, in Comparative Examples 1 and 2, since the metal phosphate and phosphoric acid were not heat-treated, the phosphoric acid was not sufficiently adhered to the surface of the metal phosphate, and the protons were lower than in the above Examples. The conductivity is shown. Further, in Comparative Examples 3 and 4, since there was no phosphoric acid on the surface of the metal phosphate, the proton conductivity was extremely lowered.

  From the above, it was found that the proton conductive electrolyte according to the present invention has excellent reproducibility, good moldability, and high proton conductivity in a non-humidified state.

  The present invention can be suitably applied to technical fields related to proton conducting electrolytes.

DESCRIPTION OF SYMBOLS 1 ... Proton conductive electrolyte membrane 2 ... Catalytic electrode (anode side)
3 ... Catalyst electrode (cathode side)
4 ... Separator (anode side)
5 ... Separator (cathode side)
6 ... Fuel channel 7 ... Oxidant gas channel 8 ... External circuit 10 ... Fuel cell

Claims (20)

  A first step of mixing a phosphoric acid with at least one selected from the group consisting of a metal oxide, a metal hydroxide, a metal chloride, and a metal nitrate to form a metal phosphate by heat treatment; and the metal phosphate A method for producing a proton-conducting electrolyte, comprising a second step of further mixing a salt with a phosphoric acid and heat-treating the salt.   2. The method for producing a proton conductive electrolyte according to claim 1, wherein the heat treatment temperature in the second step is 50 ° C. to 300 ° C. 3.   The method for producing a proton conductive electrolyte according to claim 1, further comprising a third step of converting the metal phosphate into a powder form between the first step and the second step. .   The method for producing a proton conductive electrolyte according to claim 1, wherein the phosphoric acid used in the first step is solid phosphoric acid. The method for producing a proton-conductive electrolyte according to any one of claims 1 to 4 , wherein the metal phosphate is composed of a compound represented by the following formula (1).
M _1-x N _x P ₂ O ₇ (1)
(Where M and N are metal elements, X is 0 ≦ X <0.5, and M is selected from the group consisting of Zr, Cs, Sn, Ti, Si, Ge, Pb, Ca, Mg, and Al. And N is one selected from the group consisting of Al, In, B, Ga, Sc, Yb, Ce, La and Sb.) 6. The method for producing a proton conductive electrolyte according to claim 5 , wherein M is Sn or Cs. The method for producing a proton conductive electrolyte according to claim 5 or 6 , wherein the N is In or Al. [M], [N] where the number of atoms of M and N of the metal phosphate is [M] and [N], respectively, and the total number of atoms of phosphorus of the metal phosphate and phosphoric acid is [P]. The method for producing a proton-conducting electrolyte according to any one of claims 5 to 7, wherein the relationship between [N] and [P] is represented by the following formula (2).
2 <[P] / ([M] + [N]) ≦ 4 (2) The method for producing a proton conductive electrolyte according to claim 8, wherein the relationship between [M], [N], and [P] is represented by the following formula (3).
2.4 ≦ [P] / ([M] + [N]) ≦ 3.2 (3)   The method for producing a proton-conductive electrolyte according to claim 1, wherein the metal phosphate is produced using tin oxide and ammonium hydrogen phosphate.   The method for producing a proton conductive electrolyte according to any one of claims 1 to 3, wherein the metal phosphate is produced using a coprecipitation method.   A first step of mixing a phosphoric acid with at least one selected from the group consisting of a metal oxide, a metal hydroxide, a metal chloride, and a metal nitrate to form a metal phosphate by heat treatment; and the metal phosphate A second step of preparing a paste by further mixing phosphoric acids with the salt, and a third step of applying the paste on a cast substrate and molding the paste, and heat treatment in the second and / or third step A method for producing a proton-conducting electrolyte membrane, comprising:   13. The method for producing a proton conductive electrolyte membrane according to claim 12, wherein a binder is added in the second step.   The method for producing a proton conductive electrolyte membrane according to claim 13, wherein the binder is a fluorine-based or hydrocarbon-based polymer.   The method for producing a proton conductive electrolyte membrane according to claim 13, wherein the binder is a fluorine-based or hydrocarbon-based ionomer.   The method for producing a proton conductive electrolyte membrane according to claim 13, wherein the binder is an ionic liquid.   The method for producing a proton conductive electrolyte membrane according to claim 13, wherein the binder is a cellulose polymer.   The method for producing a proton conductive electrolyte membrane according to any one of claims 12 to 17, wherein the cast substrate is made of any one of a polytetrafluoroethylene film, a polyimide film, and a metal foil. . A fourth step of respectively laminating catalyst electrodes on both sides of the proton conductive electrolyte membrane produced by the method for producing a proton conductive electrolyte membrane according to any one of claims 12 to 18,
A fuel cell manufacturing method comprising: a fifth step of laminating a separator on each catalyst electrode.   20. The method for producing a proton conductive electrolyte membrane according to claim 12, wherein a heat treatment temperature in the second and / or third step is 50 ° C. to 300 ° C. 21.

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