JP2014026743A - Electrode membrane assembly and fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a membrane electrode assembly preventing deterioration in a membrane electrode assembly using a polymer electrolyte, thereby capable of preventing lowering of output in a fuel cell over a prolonged period.SOLUTION: In an electrode membrane assembly, a cathode side catalyst of a membrane electrode assembly is a composite particle comprising catalyst metal and a catalyst carrier, the catalyst carrier comprises a transition metal element M1, a transition metal element M2 other than M1, carbon, nitrogen and oxygen, with a specific ratio, the transition metal element M1 is at least one selected from the group consisting of Ti, Zr, Nb and Ta, the catalyst metal is one or more selected from the group consisting of platinum, gold, copper, Pd, Rh, Ru, Ir, Os, Re and an alloy of two or more of these, at least one of a polymer electrolyte binder included in the cathode and a cathode side electrolyte membrane includes a fluorine based electrolyte, and at least one of a polymer electrolyte binder included in the anode and an anode side electrolyte membrane includes a hydrocarbon based electrolyte.

Description

  The present invention relates to an electrode membrane assembly and a fuel cell.

  Polymer fuel cells that use hydrogen as a fuel and polymer fuel cells that use a liquid such as methanol, dimethyl ether, or ethylene glycol as fuels have the features of high power density, low temperature operation, and high environmental friendliness. For this reason, developments for practical application of power supplies for automobiles, distributed cogeneration power supplies and mobile power supplies are being promoted.

  A polymer fuel cell generates electricity and heat simultaneously by electrochemically reacting a fuel such as hydrogen or methanol with an oxidant gas containing oxygen such as air. A membrane electrode assembly, which is the heart of power generation, can be cited as a major factor in the cost, efficiency, and durability of polymer fuel cells that operate using hydrogen or methanol as fuel. The structure of the membrane electrode assembly is shown in FIG. In the membrane electrode assembly, the anode electrode 2 made of a carbon powder having a catalyst such as a platinum ruthenium alloy supported on one surface of the polymer electrolyte membrane 1 and the polymer electrolyte is opposite to the anode electrode 2 of the polymer electrolyte membrane 1. A cathode electrode 3 made of a carbon powder carrying a catalyst such as platinum and a polymer electrolyte is provided on the side surface. Further, an anode diffusion layer 4 having both fuel permeability and electron conductivity is provided outside the anode electrode 2, and a cathode diffusion layer 5 having both oxygen gas permeability and electron conductivity is provided outside the cathode electrode 3. Yes.

  As the polymer electrolyte membrane 1, a fluorine-based electrolyte membrane typified by polyperfluorosulfonic acid or the like, or a hydrocarbon-based electrolyte membrane typified by engineering plastics into which a sulfonic acid group or an alkylene sulfonic acid group is introduced is used. ing. As the polymer electrolyte membrane 1, a hydrocarbon-based electrolyte membrane is attracting attention because it has an advantage of less fuel crossover.

  When a hydrocarbon electrolyte membrane is used as the polymer electrolyte membrane 1, the polymer electrolyte membrane 1 and a carbon powder carrying a catalyst, or a carbon powder carrying a catalyst are bonded to each other to conduct protons. As an electrolyte binder, a fluorine-based electrolyte is generally used for both the anode electrode 2 and the cathode electrode 3 (Patent Document 1).

  A polymer electrolyte membrane that uses a hydrocarbon-based electrolyte membrane as the polymer electrolyte membrane 1 and adheres the polymer electrolyte membrane 1 and a carbon powder carrying a catalyst, or a carbon powder carrying a catalyst, to conduct protons. As a result, when both the anode electrode 2 and the cathode electrode 3 are incorporated into a fuel cell using a fluorine-based electrolyte and operated, there arises a problem that the output of the fuel cell decreases within a short time.

  Similarly, a hydrocarbon-based electrolyte membrane is used as the polymer electrolyte membrane 1, the polymer electrolyte membrane 1 and a carbon powder carrying a catalyst, or a carbon powder carrying a catalyst are bonded to conduct protons. When both the anode electrode 2 and the cathode electrode 3 are used as polymer electrolytes and a membrane electrode assembly is incorporated into a fuel cell using a hydrocarbon electrolyte, the output of the fuel cell decreases within a short time. was there.

  Patent Document 2 discloses that at least one of a polymer electrolyte binder of a cathode electrode and a cathode side electrolyte membrane contains a fluorine-based electrolyte, and at least one of the polymer electrolyte binder of the anode electrode and the anode electrolyte membrane is a hydrocarbon electrolyte. There is disclosed a membrane electrode assembly comprising:

JP 2002-110174 A JP 2007-157425 A JP 2009-187848 A

  It is an object of the present invention to prevent deterioration of a membrane electrode assembly using a polymer electrolyte and prevent a decrease in output of a fuel cell over a long period of time.

The present invention relates to the following [1] to [4], for example.
[1]
An electrode membrane assembly comprising an anode, a cathode, and a solid polymer electrolyte membrane, wherein the solid polymer electrolyte membrane is sandwiched between the anode and the cathode,
The anode and cathode have an electrocatalyst layer comprising a catalyst and a polymer electrolyte binder;
The catalyst contained in the cathode is an oxygen reduction catalyst composed of composite particles composed of a catalyst metal and a catalyst carrier,
The catalyst carrier includes transition metal elements M2 other than transition metal elements M1 and M1, carbon, nitrogen and oxygen;
The ratio of the number of atoms of transition metal element M1, transition metal element M2, carbon, nitrogen and oxygen (transition metal element M1: transition metal element M2: carbon: nitrogen: oxygen) is (1-a): a: x: y : Z (where 0 <a ≦ 0.5, 0 <x ≦ 7, 0 <y ≦ 2, 0 <z ≦ 3),
The transition metal element M1 is at least one selected from the group consisting of titanium, zirconium, niobium and tantalum,
The catalytic metal is one or more selected from the group consisting of platinum, gold, copper, palladium, rhodium, ruthenium, iridium, osmium and rhenium, and alloys of two or more thereof;
At least one of the polymer electrolyte binder and cathode side electrolyte membrane contained in the cathode contains a fluorine-based electrolyte, and at least one of the polymer electrolyte binder and anode side electrolyte membrane contained in the anode contains an electrode membrane containing a hydrocarbon electrolyte. Joined body.

[2]
The membrane electrode assembly according to the above [1], wherein the transition metal element M2 is at least one selected from iron, nickel, chromium, cobalt, vanadium and manganese.

[3]
A fuel cell comprising the membrane electrode assembly according to the above [1] or [2].
[4]
The anode and the cathode have an electrode catalyst layer including a catalyst, a catalyst carrier supporting the catalyst, and a polymer electrolyte binder covering the catalyst carrier,
The polymer electrolyte binder contained in at least one of the anode and the cathode contains at least two kinds of proton conductive resins having different weight average molecular weights, and the proton conductivity contained in the catalyst carrier side portion of the polymer electrolyte binder. The fuel cell according to the above [3], wherein the weight average molecular weight of the resin is smaller than the weight average molecular weight of the proton conductive resin contained in the outer portion of the polymer electrolyte binder.

  ADVANTAGE OF THE INVENTION According to this invention, deterioration of a membrane electrode assembly can be prevented and the electric power generation by a fuel cell can be performed stably for a long time.

It is a schematic block diagram of the membrane electrode assembly in connection with the Example of this invention. It is the schematic which shows a relationship between an electronic conductor and two types of proton conductors. It is the schematic which shows the relationship between a carbon particle and a metal catalyst. The figure which shows the polymer fuel cell electric power generating unit cell concerning the Example of this invention. The powder X-ray-diffraction spectrum of the catalyst support | carrier (1) obtained in the Example is shown.

[Membrane electrode assembly]
The membrane electrode assembly of the present invention is
An electrode membrane assembly comprising an anode, a cathode, and a solid polymer electrolyte membrane, wherein the solid polymer electrolyte membrane is sandwiched between the anode and the cathode,
The anode and cathode have an electrocatalyst layer comprising a catalyst and a polymer electrolyte binder;
The catalyst contained in the cathode is an oxygen reduction catalyst composed of composite particles composed of a catalyst metal and a catalyst carrier,
The catalyst support includes a transition metal element M1, carbon, nitrogen and oxygen;
The transition metal element M1 is at least one selected from the group consisting of titanium, zirconium, niobium and tantalum,
The catalytic metal is one or more selected from the group consisting of platinum, gold, copper, palladium, rhodium, ruthenium, iridium, osmium and rhenium, and alloys of two or more thereof;
At least one of the polymer electrolyte binder and the cathode side electrolyte membrane included in the cathode includes a fluorine-based electrolyte, and at least one of the polymer electrolyte binder and the anode side electrolyte membrane included in the anode includes a hydrocarbon electrolyte.

(Oxygen reduction catalyst contained in the cathode)
The catalyst contained in the cathode is an oxygen reduction catalyst composed of composite particles composed of a catalyst metal and a catalyst carrier. The catalyst metal is supported on a catalyst carrier.

  The metal catalyst is preferably at least one selected from the group consisting of platinum, gold, copper, palladium, rhodium, ruthenium, iridium, osmium and rhenium, and alloys of two or more thereof.

  The catalyst metal supported on the catalyst carrier is usually metal particles. As an average particle diameter of this metal particle, 1-20 nm is preferable, More preferably, it is 1-10 nm. This average particle diameter is a numerical value obtained by the BET method. When the average particle diameter of the metal particles is within the above range, there is an advantage that the catalytic activity is increased.

The catalyst support includes a transition metal element M1, carbon, nitrogen, and oxygen.
Specific examples of the transition metal element M1 include at least one selected from the group consisting of titanium, zirconium, niobium, and tantalum. Among the transition metal elements M1, titanium, zirconium, niobium and tantalum are preferable, and titanium and zirconium are more preferable from the viewpoint of cost and performance of the obtained catalyst.

  The catalyst carrier preferably further contains a transition metal element M2 other than M1. Specifically, the transition metal element M2 is at least one selected from iron, nickel, chromium, cobalt, vanadium, and manganese. As the transition metal element M2, iron and chromium are preferable and iron is more preferable from the viewpoint of the balance between the cost and the performance of the obtained catalyst.

  The ratio of the number of atoms of transition metal element (however, transition metal element M1 and transition metal element M2 are not distinguished), carbon, nitrogen, and oxygen is defined as transition metal element: carbon: nitrogen: oxygen = 1: x: y: When expressed as z, preferably 0 <x ≦ 7, 0 <y ≦ 2, and 0 <z ≦ 3.

  Since the activity of the electrode catalyst is high, the range of x is more preferably 0.15 ≦ x ≦ 5.0, further preferably 0.2 ≦ x ≦ 4.0, and particularly preferably 1.0 ≦ x. ≦ 3.0, and the range of y is more preferably 0.01 ≦ y ≦ 1.5, still more preferably 0.02 ≦ y ≦ 0.5, and particularly preferably 0.03 ≦ y ≦ 0. And the range of z is more preferably 0.6 ≦ z ≦ 2.6, further preferably 0.9 ≦ z ≦ 2.0, and particularly preferably 1.3 ≦ z ≦ 1. .9.

  When the catalyst support also includes a transition metal element M2, the ratio of the number of atoms of the transition metal element M1, the transition metal element M2, carbon, nitrogen, and oxygen (transition metal element M1: transition metal element M2: carbon: nitrogen: oxygen) Is represented by (1-a): a: x: y: z, preferably 0 <a ≦ 0.5, 0 <x ≦ 7, 0 <y ≦ 2, and 0 <z ≦ 3. Since the activity of the electrode catalyst is high, the preferable ranges of x, y and z are as described above, and the range of a is more preferably 0.01 ≦ a ≦ 0.5, and further preferably 0.02 ≦ a. ≦ 0.4, particularly preferably 0.05 ≦ a ≦ 0.3.

The values of a, x, y and z are values measured by the method employed in the examples described later.
The catalyst carrier preferably has an oxide, carbide or nitride of the transition metal element alone or a plurality of crystal structures thereof. Judging from the results of crystal structure analysis by X-ray diffraction analysis on the catalyst support and the results of elemental analysis, the catalyst support remains in the oxide structure of the oxide structure of the oxide structure of the transition metal element. Whether it has a structure in which sites are replaced with carbon atoms or nitrogen atoms, or a structure in which the sites of carbon atoms or nitrogen atoms are replaced with oxygen atoms while having the structure of carbide, nitride or carbonitride of the transition metal element Or a mixture containing these structures.

The specific surface area calculated by the BET method of the catalyst of the catalyst carrier is preferably 30 to 350 m ² / g, more preferably 50 to 300 m ² / g, and still more preferably 100 to 300 m ² / g.

(Method for producing catalyst carrier)
The method for producing the catalyst carrier includes, for example, step A in which at least a transition metal-containing compound and a nitrogen-containing organic compound are mixed to obtain a catalyst carrier precursor composition, and the catalyst carrier precursor composition is heated at a temperature of 500 to 1100 ° C. Including the step C of heat treatment, part or all of the transition metal-containing compound is a compound containing the transition metal element M1. In the present specification, unless otherwise specified, atoms and ions are described as “atoms” without strictly distinguishing them.

(Process A)
In Step A, at least a transition metal-containing compound and a nitrogen-containing organic compound are mixed to obtain a catalyst support precursor composition. The mixing is preferably performed in a solvent. Mixing in a solvent is preferable because the transition metal-containing compound and the nitrogen-containing organic compound can be uniformly mixed.

  It is considered that the catalyst carrier precursor composition contains a reaction product of a transition metal-containing compound and a nitrogen-containing organic compound. The solubility of the reaction product in the solvent varies depending on the combination of the transition metal-containing compound, the nitrogen-containing organic compound, the solvent, and the like.

  In step A, the transition metal-containing compound, the nitrogen-containing organic compound, and the solvent may be placed in a pressurizable container such as an autoclave, and mixing may be performed while applying a pressure higher than normal pressure.

<Transition metal-containing compound>
Part or all of the transition metal-containing compound is a compound containing the transition metal element M1.
The transition metal-containing compound preferably has at least one selected from an oxygen atom and a halogen atom. Transition metal-containing compounds include metal phosphates, metal sulfates, metal nitrates, metal acid halides (intermediate hydrolysates of metal halides), metal halides, metal halides, metal hypohalites, Examples thereof include metal-containing organic compounds and metal complexes, and metal nitrates, metal acid chlorides, metal-containing organic compounds, metal halides, metal perchlorates and metal hypochlorites are preferred. These may be used alone or in combination of two or more.

Examples of the metal-containing organic compound include metal organic acid salts and metal alkoxides.
As the metal alkoxide, methoxide, propoxide, isopropoxide, ethoxide, butoxide and isobutoxide of the transition metal are preferable, and isopropoxide, ethoxide and butoxide of the transition metal are more preferable. The metal alkoxide may have one type of alkoxy group or may have two or more types of alkoxy groups.

  As the transition metal-containing compound having an oxygen atom, an alkoxide, an acetylacetone complex, an acid chloride, and a sulfate are preferable, and from the viewpoint of cost, an alkoxide and an acetylacetone complex are more preferable, and a viewpoint of solubility in a solvent in the liquid phase Therefore, an alkoxide and an acetylacetone complex are more preferable.

The metal halide is preferably a chloride, bromide or iodide of the transition metal, and the metal acid halide is preferably an acid chloride, acid bromide or acid iodide of the transition metal.
The metal perhalogenate is preferably a metal perchlorate, and the metal hypohalite is preferably a metal hypochlorite.

Specific examples of the transition metal-containing compound include
Titanium tetramethoxide, titanium tetraethoxide, titanium tetrapropoxide, titanium tetraisopropoxide, titanium tetrabutoxide, titanium tetraisobutoxide, titanium tetrapentoxide, titanium tetraacetylacetonate, titaniumoxydiacetylacetonate, tris (acetyl Acetonato) titanium chloride ([Ti (acac) ₃ ] ₂ [TiCl ₆ ]), titanium tetrachloride, titanium trichloride, titanium oxychloride, titanium tetrabromide, titanium tribromide, titanium oxybromide, Titanium compounds such as titanium tetraiodide, titanium triiodide, and titanium oxyiodide;
Niobium pentamethoxide, niobium pentaethoxide, niobium pentaisopropoxide, niobium pentaboxide, niobium pentapentoxide, niobium pentachloride, niobium oxychloride, niobium pentabromide, niobium oxybromide, niobium pentaiodide, niobium pentaiodide, oxyiodination Niobium compounds such as niobium;
Zirconium tetramethoxide, zirconium tetraethoxide, zirconium tetrapropoxide, zirconium tetraisopropoxide, zirconium tetrabutoxide, zirconium tetraisobutoxide, zirconium tetrapentoxide, zirconium tetraacetylacetonate, zirconium tetrachloride, zirconium oxychloride, four Zirconium compounds such as zirconium bromide, zirconium oxybromide, zirconium tetraiodide, zirconium oxyiodide;
Tantalum pentamethoxide, tantalum pentaethoxide, tantalum pentaisopropoxide, tantalum pentabutoxide, tantalum pentapentoxide, tantalum tetraethoxyacetylacetonate, tantalum pentachloride, tantalum oxychloride, tantalum pentabromide, tantalum oxybromide, Tantalum compounds such as tantalum pentaiodide and tantalum oxyiodide;
Hafnium tetramethoxide, hafnium tetraethoxide, hafnium tetrapropoxide, hafnium tetraisopropoxide, hafnium tetrabutoxide, hafnium tetraisobutoxide, hafnium tetrapentoxide, hafnium tetraacetylacetonate, hafnium tetrachloride, hafnium oxychloride, odor Hafnium compounds such as hafnium iodide, hafnium oxybromide, hafnium iodide, hafnium oxyiodide;
Vanadium oxytrimethoxide, vanadium oxytriethoxide, vanadium oxytriisopropoxide, vanadium oxytributoxide, vanadium (III) acetylacetonate, vanadium (IV) acetylacetonate, vanadium pentachloride, vanadium oxychloride, five odors And vanadium compounds such as vanadium iodide, vanadium oxybromide, vanadium pentaiodide, and vanadium oxyiodide. These may be used alone or in combination of two or more.

Among these compounds, the resulting catalyst becomes fine particles with a uniform particle size, and its activity is high,
Titanium tetraethoxide, titanium tetrachloride, titanium oxychloride, titanium tetraisopropoxide, titanium tetraacetylacetonate,
Niobium pentaethoxide, niobium pentachloride, niobium oxychloride, niobium pentaisoproposide,
Zirconium tetraethoxide, zirconium tetrachloride, zirconium oxychloride, zirconium tetraisopropoxide, zirconium tetraacetylacetonate,
Tantalum pentamethoxide, tantalum pentaethoxide, tantalum pentachloride, tantalum oxychloride, tantalum pentaisopropoxide, and tantalum tetraethoxyacetylacetonate are preferred, titanium tetraisopropoxide, titanium tetraacetylacetonate, niobium ethoxide, More preferred are niobium isopropoxide, zirconium oxychloride, zirconium tetraisopropoxide, and tantalum pentaisopropoxide.

  Further, as the transition metal-containing compound, together with the transition metal-containing compound containing the transition metal element M1 (hereinafter also referred to as “first transition metal-containing compound”), the transition metal-containing compound containing the transition metal element M2 (hereinafter referred to as the “first transition metal-containing compound”). Also referred to as “2 transition metal-containing compounds”). Use of the second transition metal-containing compound improves the performance of the resulting catalyst.

As a specific example of the second transition metal-containing compound,
Iron (II) chloride, iron (III) chloride, iron (III) sulfate, iron (II) sulfide, iron (III) sulfide, potassium ferrocyanide, potassium ferricyanide, ammonium ferrocyanide, ammonium ferricyanide, iron ferrocyanide , Iron (II) nitrate, iron (III) nitrate, iron (II) oxalate, iron (III) oxalate, iron (II) phosphate, iron (III) phosphate ferrocene, iron (II) hydroxide, water Iron compounds such as iron (III) oxide, iron (II) oxide, iron (III) oxide, triiron tetroxide, iron (II) acetate, iron (II) lactate, iron (III) citrate;
Nickel chloride (II), nickel sulfate (II), nickel sulfide (II), nickel nitrate (II), nickel oxalate (II), nickel phosphate (II), nickel cene, nickel hydroxide (II), nickel oxide Nickel compounds such as (II), nickel acetate (II), nickel lactate (II);
Chromium (II) chloride, chromium (III) chloride, chromium (III) sulfate, chromium (III) sulfide, chromium (III) nitrate, chromium (III) oxalate, chromium (III) phosphate, chromium (III) hydroxide Chromium compounds such as, chromium (II) oxide, chromium (III) oxide, chromium (IV) oxide, chromium (VI) oxide, chromium (II) acetate, chromium (III) acetate, chromium (III) lactate;
Cobalt (II) chloride, cobalt (III) chloride, cobalt (II) sulfate, cobalt (II) sulfide, cobalt (II) nitrate, cobalt (III) nitrate, cobalt (II) oxalate, cobalt (II) phosphate, Cobalt compounds such as cobaltocene, cobalt (II) hydroxide, cobalt (II) oxide, cobalt (III) oxide, tricobalt tetroxide, cobalt (II) acetate, and cobalt (II) lactate;
Vanadium chloride (II), vanadium chloride (III), vanadium chloride (IV), vanadium oxysulfate (IV), vanadium sulfide (III), vanadium oxyoxalate (IV), vanadium metallocene, vanadium oxide (V), vanadium acetate Vanadium compounds such as vanadium citrate;
Manganese chloride (II), manganese sulfate (II), manganese sulfide (II), manganese nitrate (II), manganese oxalate (II), manganese hydroxide (II), manganese oxide (II), manganese oxide (III), Examples thereof include manganese compounds such as manganese acetate (II), manganese lactate (II), and manganese citrate. These may be used alone or in combination of two or more.

Among these compounds,
Iron (II) chloride, iron (III) chloride, potassium ferrocyanide, potassium ferricyanide, ammonium ferrocyanide, ammonium ferricyanide, iron (II) acetate, iron (II) lactate,
Nickel (II) chloride, nickel (II) acetate, nickel (II) lactate,
Chromium (II) chloride, chromium (III) chloride, chromium (II) acetate, chromium (III) acetate, chromium (III) lactate,
Cobalt (II) chloride, cobalt (III) chloride, cobalt (II) acetate, cobalt (II) lactate,
Vanadium chloride (II), vanadium chloride (III), vanadium chloride (IV), vanadium oxysulfate (IV), vanadium acetate, vanadium citrate,
Manganese chloride (II), manganese acetate (II) and manganese lactate (II) are preferred,
Iron (II) chloride, iron (III) chloride, potassium ferrocyanide, potassium ferricyanide, ammonium ferrocyanide, ammonium ferricyanide, iron (II) acetate, iron (II) lactate, chromium (II) chloride, chromium chloride (III ), Chromium (II) acetate, chromium (III) acetate, and chromium (III) lactate.

<Nitrogen-containing organic compound>
The nitrogen-containing organic compound is not particularly limited, but a compound that can be a ligand capable of coordinating to a metal atom in the transition metal-containing compound (preferably a compound that can form a mononuclear complex) is preferable. More preferred are compounds that can be multidentate ligands (preferably bidentate or tridentate ligands) (can form chelates).

A nitrogen-containing organic compound may be used individually by 1 type, and may use 2 or more types together.
The nitrogen-containing organic compound preferably contains a carbonyl group. The carbonyl group may be contained in the nitrogen-containing organic compound as part of the functional group. The carbonyl group is preferably contained in the nitrogen-containing organic compound as part of the carboxyl group or aldehyde group, and is preferably contained in the nitrogen-containing organic compound as a carboxyl group. Note that at least one carbonyl group may be included in the molecule of the nitrogen-containing organic compound, and a plurality of carbonyl groups may be included.

  If the nitrogen-containing organic compound contains a carbonyl group, it is considered that the transition metal contained in the transition metal-containing compound can be strongly coordinated by mixing in the step A. A nitrogen-containing organic compound may be used individually by 1 type, and may use 2 or more types together.

Moreover, as a nitrogen-containing organic compound, it is preferable from a viewpoint of the activity of the electrode catalyst obtained that the nitrogen atom has couple | bonded with (alpha) carbon of a carbonyl group.
Examples of nitrogen-containing organic compounds include amino acids and amino acid derivatives.

  Examples of the amino acids include alanine, arginine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, serine, threonine, tryptophan, tyrosine, valine, norvaline, and aminobutyric acid. Is preferred.

As the amino acid derivative, oligopeptides such as glycylglycine, triglycine and tetraglycine, pyroglutamic acid and α-amino fatty acid derivatives are preferable.
Alanine, glycine, lysine, methionine, and tyrosine are more preferred because of the high activity of the resulting catalyst, and alanine, glycine, and lysine are particularly preferred because the resulting catalyst exhibits extremely high activity.

  In addition to the above amino acids and amino acid derivatives, pyrrole-2-carboxylic acid, imidazole-2-carboxylic acid, pyrazinecarboxylic acid, piperidine-2-carboxylic acid, piperazine-2-carboxylic acid, pyrimidine-2-carboxylic acid, pyrimidine- 4-carboxylic acid, 2-pyridinecarboxylic acid, 2,4-pyridinedicarboxylic acid, 2-quinolinecarboxylic acid, and oxamic acid are preferred.

  The ratio (B / A) of the total number of carbon atoms B of the nitrogen-containing organic compound used in step A to the total number A of transition metal elements in the transition metal-containing compound used in step A is the heat treatment in step C. It is possible to reduce the amount of components that are sometimes desorbed as carbon compounds such as carbon dioxide and carbon monoxide, that is, since it is possible to reduce the amount of exhaust gas during catalyst production, it is preferably 200 or less, more preferably 150 or less. More preferably, it is 80 or less, particularly preferably 30 or less, and preferably 1 or more, more preferably 2 or more, still more preferably 3 or more, particularly preferably 5 or more, from the viewpoint of obtaining a catalyst with good activity. .

  The ratio (C / A) of the total number of nitrogen atoms C of the nitrogen-containing organic compound used in step A to the total number A of transition metal elements of the transition metal-containing compound used in step A is a catalyst with good activity. Is preferably 28 or less, more preferably 17 or less, still more preferably 12 or less, and particularly preferably 8.5 or less. From the viewpoint of obtaining a catalyst with good activity, preferably 1 or more, more Preferably it is 2.5 or more, More preferably, it is 3 or more, Most preferably, it is 3.5 or more.

  When the first transition metal-containing compound and the second transition metal organic compound are used as the transition metal-containing compound, the first transition metal-containing compound and the second transition metal-containing compound used in step A When the ratio is expressed as M1: M2 = (1-a): a in terms of a molar ratio (M1: M2) between the atoms of the transition metal element M1 and the atoms of the transition metal element M2, the range of a is Usually, 0 <a ≦ 0.5, preferably 0.01 ≦ a ≦ 0.5, more preferably 0.02 ≦ a ≦ 0.4, and particularly preferably 0.05 ≦ a ≦ 0.3.

<Solvent>
Examples of the solvent include water, alcohols and acids. As alcohols, ethanol, methanol, butanol, propanol and ethoxyethanol are preferable, and ethanol and methanol are more preferable. As the acids, acetic acid, nitric acid (aqueous solution), hydrochloric acid, phosphoric acid aqueous solution and citric acid aqueous solution are preferable, and acetic acid and nitric acid are more preferable. These may be used alone or in combination of two or more.

  In step A, it is preferable to further mix a compound having a diketone structure. It is preferable to use a compound having a diketone structure because the transition metal-containing compound is converted into a metal complex and easily forms a uniform mixture with the nitrogen-containing compound.

As the compound having a diketone structure, diacetyl, acetylacetone, 2,5-hexanedione and dimedone are preferable, and acetylacetone and 2,5-hexanedione are more preferable. As a compound having a diketone structure, one kind may be used, or two or more kinds may be used.
It is preferable from the viewpoint of the activity of the resulting catalyst that oxygen is contained in one or more molecules of the transition metal-containing compound, the nitrogen-containing organic compound, and the solvent.

(Process B)
In Step A, when mixing is performed using a solvent, Step B is usually performed. In step B, the solvent is removed from the catalyst carrier precursor composition obtained in step A.
The removal of the solvent may be performed in the air or in an inert gas (for example, nitrogen, argon, helium) atmosphere. As the inert gas, nitrogen and argon are preferable from the viewpoint of cost, and nitrogen is more preferable.

  The temperature at the time of solvent removal may be room temperature when the vapor pressure of the solvent is high, but from the viewpoint of mass production of the catalyst, it is preferably 30 ° C or higher, more preferably 40 ° C or higher, and still more preferably. From the viewpoint of not decomposing the catalyst support precursor, which is estimated to be a metal complex such as a chelate, contained in the solution obtained in step A at 50 ° C. or higher, preferably 250 ° C. or lower, more preferably 150 ° C. ° C or lower, more preferably 110 ° C or lower.

  The removal of the solvent may be performed under atmospheric pressure when the vapor pressure of the solvent is high, but in order to remove the solvent in a shorter time, it is performed under reduced pressure (for example, 0.1 Pa to 0.1 MPa). Also good. For example, an evaporator can be used to remove the solvent under reduced pressure.

  Next to step A, step C may be performed without performing step B. However, when mixing is performed in a solvent in step A, after removing the solvent in step B, step C is performed. Preferably it is done. It is preferable to perform step B because energy efficiency in step C is improved.

(Process C)
In Step C, the catalyst support precursor composition is heat-treated to obtain a catalyst support.
The temperature at the time of this heat treatment is 500 to 1100 ° C, preferably 600 to 1050 ° C, more preferably 700 to 950 ° C.

  If the temperature of the heat treatment is too higher than the above range, sintering and grain growth occur between the particles of the obtained catalyst carrier, resulting in a decrease in the specific surface area of the catalyst carrier. As a result, the processability when processing into an electrode catalyst layer is poor. On the other hand, if the temperature of the heat treatment is too lower than the above range, a catalyst having high activity cannot be obtained.

Examples of the heat treatment method include a stationary method, a stirring method, a dropping method, and a powder trapping method.
Examples of the shape of the furnace in the heat treatment include a tubular furnace, an upper lid furnace, a tunnel furnace, a box furnace, a sample table raising / lowering furnace (elevator type), a cart furnace, and the like. Possible are tubular furnaces, top lid furnaces, box furnaces and sample table raising and lowering furnaces, and tubular furnaces and box furnaces are preferred.

  The atmosphere for the heat treatment is preferably an inert gas atmosphere as a main component from the viewpoint of enhancing the activity of the resulting catalyst. Among the inert gases, nitrogen, argon, and helium are preferable and nitrogen and argon are more preferable because they are relatively inexpensive and easily available. These inert gas may be used individually by 1 type, and may mix and use 2 or more types. These gases are generally called inert gases, but these inert gases, that is, nitrogen, argon, helium, etc., are used in the catalyst carrier precursor composition during the heat treatment in Step C. It may be reacting with.

  Further, the heat treatment is performed using nitrogen gas, argon gas or a mixed gas of nitrogen gas and argon gas, or one or more gases selected from nitrogen gas and argon gas and one or more gases selected from hydrogen gas, ammonia gas and oxygen gas. When carried out in a mixed gas atmosphere with a gas, a catalyst having high catalytic performance tends to be obtained.

When hydrogen gas is contained in the atmosphere of the heat treatment, the concentration of hydrogen gas is, for example, 100% by volume or less, preferably 0.01 to 10% by volume, more preferably 1 to 5% by volume.
When oxygen gas is contained in the atmosphere of the heat treatment, the concentration of oxygen gas is, for example, 0.01 to 10% by volume, preferably 0.01 to 5% by volume.

  The heat-treated product obtained by the heat treatment may be used as it is as a catalyst carrier, or may be further pulverized before being used as a catalyst carrier. In the present specification, operations for making the heat-treated product fine, such as crushing and crushing, are referred to as “crushing” without any particular distinction. For this crushing, for example, a roll rolling mill, a ball mill, a small-diameter ball mill (bead mill), a medium stirring mill, an airflow crusher, a mortar, an automatic kneading mortar, a tank crusher, a jet mill, or the like can be used. When the amount of the electrode catalyst is small, a mortar, an automatic kneading mortar, or a batch type ball mill is preferable. When a heat-treated product is continuously processed in a large amount, a jet mill or a continuous type ball mill is preferable, and a continuous type ball mill is used. Among these, a bead mill is more preferable.

When the heat-treated product is crushed by a wet method, a dispersion medium is usually used. Examples of the dispersion medium include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, pentaanol, and 2-heptanol. Alcohols such as benzyl alcohol;
Ketones such as acetone, methyl ethyl ketone, methyl propyl ketone, methyl butyl ketone, methyl isobutyl ketone, methyl amyl ketone, acetonyl acetone, diethyl ketone, dipropyl ketone, diisobutyl ketone;
Ethers such as tetrahydrofuran, diethylene glycol dimethyl ether, anisole, methoxytoluene, diethyl ether, dipropyl ether, dibutyl ether;
Amines such as isopropylamine, butylamine, isobutylamine, cyclohexylamine, diethylamine;
Esters such as propyl formate, isobutyl formate, amyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, isopentyl acetate;
Polar solvents such as acetonitrile, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, diethylene glycol and propylene glycol are preferred. These may be used alone or in combination of two or more.

  The dispersion medium is preferably substantially free of water. Specifically, the content of water in the dispersion medium is preferably 0 to 0.1% by mass.

(Anode and cathode)
The anode and the cathode have an electrode catalyst layer including a catalyst and a polymer electrolyte binder, and at least one of the polymer electrolyte binder and the cathode side electrolyte membrane included in the cathode includes a fluorine-based electrolyte, and the polymer included in the anode At least one of the electrolyte binder and the anode side electrolyte membrane contains a hydrocarbon electrolyte.

  Examples of embodiments of the present invention are as follows. One of them has a polymer electrolyte membrane, a cathode and an anode sandwiching the polymer electrolyte membrane, and the cathode and the anode are at least a catalyst carrier, a catalyst metal supported on the catalyst carrier, and a polymer electrolyte binder. A membrane electrode assembly in which the polymer electrolyte binder of the cathode is a fluorine-based electrolyte, and the polymer electrolyte binder of the anode electrode is a hydrocarbon-based electrolyte, and the other is a polymer electrolyte membrane A cathode electrode and an anode electrode sandwiching the polymer electrolyte membrane, the cathode and anode including at least a catalyst carrier, a catalyst metal supported on the catalyst carrier and a polymer electrolyte binder, and the cathode of the electrolyte membrane A membrane electrode assembly in which the side is a fluorine-based electrolyte membrane and the anode side of the electrolyte membrane is a hydrocarbon-based electrolyte membrane

  The polymer electrolyte membrane used in the present invention is not particularly limited as long as it is a hydrocarbon electrolyte membrane. Examples of such electrolyte membranes include sulfonated engineering plastics electrolyte membranes such as sulfonated polyetheretherketone, sulfonated polyethersulfone, sulfonated acrylonitrile / butadiene / styrene polymer, sulfonated polysulfide, sulfonated polyphenylene, and sulfoalkyl. Sulfoalkylated engineering plastics such as alkylated polyetheretherketone, sulfoalkylated polyethersulfone, sulfoalkylated polyetherethersulfone, sulfoalkylated polysulfone, sulfoalkylated polysulfide, sulfoalkylated polyphenylene, sulfoalkylated polyetherethersulfone And electrolyte electrolyte membranes and hydrocarbon electrolyte membranes such as sulfoalkyl etherified polyphenylene.

  Of these, sulfoalkylated hydrocarbon electrolyte membranes and sulfoalkyletherified hydrocarbon electrolyte membranes are preferable from the viewpoint of fuel crossover, ionic conductivity, swelling properties, and the like. Hydrogen ion conductive inorganic substances such as tungsten oxide hydrate, zirconium oxide hydrate, tin oxide hydrate, silicotungstic acid, silicomolybdic acid, tungstophosphoric acid and molybdic acid are micro-dispersed in heat-resistant resin. By using a composite electrolyte membrane or the like, a fuel cell that can be operated to a higher temperature range can be obtained.

  In general, the above-mentioned hydrated acidic electrolyte membrane undergoes deformation due to swelling when it is dry and wet, and a membrane with sufficiently high ionic conductivity may have insufficient mechanical strength. In such a case, a nonwoven fabric or a woven fabric excellent in mechanical strength, durability, and heat resistance is used as a core material, and these fibers are added and reinforced as a filler when manufacturing an electrolyte membrane. It is an effective method for improving the reliability of the battery performance to use a polymer film penetrated by as a core material.

  In addition, in order to reduce the fuel permeability of the electrolyte membrane, a membrane obtained by doping polybenzimidazoles with sulfuric acid, phosphoric acid, sulfonic acids, or phosphonic acids can also be used. Further, when producing the polymer electrolyte membrane used in the present invention, plasticizers, antioxidants, hydrogen peroxide decomposing agents, metal scavengers, surfactants, stabilizers, release agents used in ordinary polymers are used. Additives such as molds can be used as long as they do not contradict the purpose of the present invention.

  The sulfonic acid equivalent of such a polymer electrolyte membrane is preferably in the range of 0.5 to 2.0 meq / g dry resin, more preferably 0.8 to 1.5 meq / g dry resin. When the sulfonic acid equivalent is lower than this range, the ion conduction resistance of the membrane increases, whereas when the sulfonic acid equivalent is high, the membrane easily dissolves in a fuel aqueous solution such as a methanol aqueous solution. Although there is no restriction | limiting in particular in the thickness of this polymer electrolyte membrane, 10-300 micrometers is preferable. 15-200 micrometers is especially preferable. A thickness of more than 10 μm is preferable to obtain a membrane strength that can withstand practical use, and a thickness of less than 200 μm is preferable in order to reduce membrane resistance, that is, improve power generation performance. In the case of the solution casting method, the film thickness can be controlled by the solution concentration or the coating thickness on the substrate. When the film is formed from a molten state, the film thickness can be controlled by stretching a film having a predetermined thickness obtained by a melt press method or a melt extrusion method at a predetermined magnification.

  The hydrocarbon-based polymer electrolyte binder that conducts protons that adheres the polymer electrolyte membrane and the catalyst carrier supporting the anode catalyst or the catalyst carriers supporting the anode catalyst to each other is any hydrocarbon-based electrolyte. There is no particular limitation. Examples of such polymer electrolytes include sulfonated engineering plastics electrolytes such as sulfonated polyetheretherketone, sulfonated polyethersulfone, sulfonated acrylonitrile / butadiene / styrene polymer, sulfonated polysulfide, and sulfonated polyphenylene, and sulfoalkyl. Sulfoalkylated engineering plastics such as alkylated polyetheretherketone, sulfoalkylated polyethersulfone, sulfoalkylated polyetherethersulfone, sulfoalkylated polysulfone, sulfoalkylated polysulfide, sulfoalkylated polyphenylene, sulfoalkylated polyetherethersulfone And electrolytes such as hydrocarbon electrolytes such as sulfoalkyl etherified polyphenylene.

  Of these, a polymer electrolyte having good oxidation resistance is preferable. The sulfonic acid equivalent of such a polymer electrolyte membrane is preferably in the range of 0.5 to 2.5 meq / g dry resin, more preferably 0.8 to 1.8 meq / g dry resin. The sulfonic acid equivalent of such a polymer electrolyte is preferably larger than the equivalent of the polymer electrolyte membrane from the viewpoint of ion conductivity. Additives such as plasticizers, antioxidants, hydrogen peroxide decomposing agents, metal scavengers, surfactants, stabilizers, release agents, etc., used in ordinary polymers are within the scope of the present invention. Can be used.

  The fluorine-based polymer electrolyte binder that conducts protons that adheres the polymer electrolyte membrane and the catalyst carrier carrying the cathode catalyst or the catalyst carriers carrying the cathode catalyst to each other is not particularly limited as long as it is a fluorine-based electrolyte. There is no. Polyperfluorosulfonic acid or the like is used as such a fluorine-based electrolyte. Typical examples include Nafion (registered trademark: manufactured by Dupont, USA), Aciplex (registered trademark: manufactured by Asahi Kasei Kogyo Co., Ltd.), and Flemion (registered trademark: manufactured by Asahi Glass Co., Ltd.). The sulfonic acid equivalent of the electrolyte is preferably larger than the equivalent of the polymer electrolyte membrane from the viewpoint of ion conductivity.

  The electrode used for the membrane electrode assembly is composed of a conductive material carrying catalyst metal fine particles, and may contain a water repellent or a binder as necessary. Moreover, you may form the layer which consists of the electrically conductive material which does not carry | support a catalyst, and the water repellent and binder contained as needed on the outer side of a catalyst layer.

  For example, fluorinated carbon is used as the water repellent. As the binder, it is preferable to use a hydrocarbon electrolyte solution of the same system as the electrolyte membrane from the viewpoint of adhesiveness, but other various resins may be used. In addition, a fluorine-containing resin having water repellency, such as polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and tetrafluoroethylene-hexafluoropropylene copolymer may be added.

  The method for joining the polymer electrolyte membrane and the electrode when used as a fuel cell is not particularly limited, and a known method can be applied. As a method for producing a membrane electrode assembly, for example, a conductive material, for example, Pt catalyst powder supported on carbon and a polytetrafluoroethylene suspension are mixed, applied to carbon paper, and heat-treated to form a catalyst layer.

  Next, there is a method in which the same polymer electrolyte solution or fluorine-based electrolyte as the polymer electrolyte membrane is applied as a binder to the catalyst layer and integrated with the polymer electrolyte membrane by hot pressing. In addition, a method in which the same polymer electrolyte solution as the polymer electrolyte is previously coated on the Pt catalyst powder, a method in which the catalyst paste is applied to the polymer electrolyte membrane by a printing method, a spray method, or an ink jet method, a polymer electrolyte membrane In addition, there are a method of electrolessly plating an electrode, a method in which a platinum group metal complex ion is adsorbed on a polymer electrolyte membrane and then reduced. Among these, the method of applying the catalyst paste to the polymer electrolyte membrane by the ink jet method is excellent with little loss of the catalyst.

  The direct methanol fuel cell (DMFC) has a fuel distribution plate and an oxidant distribution as a grooved current collector that forms a fuel flow path and an oxidant flow path outside the membrane electrode assembly formed as described above. A plate is provided as a single cell, and a plurality of such single cells are stacked via a cooling plate or the like. In addition to stacking to connect single cells, there is a method of connecting in a plane. There is no particular limitation on either method of connecting single cells.

  It is desirable to operate the fuel cell at a high temperature because the catalytic activity of the electrode increases and the electrode overvoltage decreases. However, the operating temperature is not particularly limited. It is also possible to operate at high temperature by vaporizing the liquid fuel.

  A plurality of unit cells composed of an anode, an electrolyte membrane and a cathode are manufactured, arranged in a plane, and each unit cell is connected in series with a conductive interconnector to increase the voltage. It is possible to operate without using an auxiliary device for forcibly supplying fuel and an oxidant, and without using an auxiliary device for forcibly cooling the fuel cell. By using a methanol aqueous solution having a high volumetric energy density as the liquid fuel, a compact power source capable of continuing power generation for a long time can be realized. This small power source can be driven by incorporating it as a power source for a mobile phone, a book type personal computer, a portable video camera, etc., and can be used continuously for a long time by replenishing fuel prepared in advance. Become.

  In addition, for the purpose of using fuel replenishment frequency much less than in the above case, this small power source is combined with, for example, a mobile phone equipped with a secondary battery, a book type personal computer or a charger for a portable video camera. It is effective to use it as a battery charger by attaching it to a part of the storage case. In this case, when the portable electronic device is used, it is taken out from the storage case and driven by the secondary battery, and when it is not used, the small fuel cell power generator built in the case is connected via the charger. Charge the next battery. By doing so, the volume of the fuel tank can be increased, and the frequency of refueling can be greatly reduced.

[Fuel cell]
The fuel cell of the present invention includes the membrane electrode assembly. The membrane electrode assembly of the present invention is preferably used for a polymer electrolyte fuel cell, particularly a polymer electrolyte fuel cell using hydrogen or methanol as a fuel.

  In the fuel cell of the present invention, the membrane electrode assembly is provided, and the anode and the cathode further include an electrode catalyst layer including a catalyst, a catalyst carrier supporting the catalyst, and a polymer electrolyte binder covering the catalyst carrier. The polymer electrolyte binder contained in at least one of the anode and the cathode is formed of at least two or more types of proton conductive resins having different molecular weights, and forms protons forming the catalyst carrier side portion of the polymer electrolyte binder A fuel cell in which the molecular weight of the conductive resin is smaller than the molecular weight of the proton conductive resin forming the outer portion of the polymer electrolyte binder is preferable. With such a fuel cell, it is possible to promote effective use of the catalyst metal and improve battery output while maintaining good bonding properties with the hydrocarbon-based electrolyte membrane.

  The catalyst carrier side portion of the polymer electrolyte binder here means a portion in direct contact with the catalyst carrier in the polymer electrolyte binder covering the catalyst carrier on which the catalyst is supported. The outer part of the polymer electrolyte binder is the part of the polymer electrolyte binder covering the catalyst carrier on which the catalyst is supported that is in contact with the catalyst carrier side part and exposed on the surface of the electrode catalyst layer Means.

  The different molecular weights of the proton conductive resins here means that (1) two or more types of proton conductive resins have different chemical compositions and have different weight average molecular weights, or (2) proton conductive resins. Are composed of polymers having the same composition, but have two meanings that two or more types of polymers having different weight average molecular weights are included therein. The present invention achieves the effect by implementing one of these.

  In addition, the proton conductive resin includes at least two types of proton conductive resins having different glass transition points, and the glass transition point of the proton conductive resin forming the catalyst carrier side portion forms a proton that forms the outside thereof. It is preferably lower than the glass transition point of the conductive resin.

  The proton conductive resin that forms the catalyst carrier side portion is the proton conductive resin that exists in the fine pores in the aggregate on the catalyst carrier side, and the proton conductive resin that forms the outside of the proton conductive resin is the aggregate on the catalyst carrier side. It is a proton conductive resin present in the micropores between the aggregates.

In addition, the micropores within the aggregates are 50 nm or less, and the micropores between the aggregates can be separated into 50 nm or more.
Moreover, since it has two or more types of proton conductive resins, it is estimated that it is preferable to have two or more peaks when the molecular weight distribution is measured. However, if the molecular weight distribution of the contained proton conductive resin alone is broad, the peak waveform may interfere and the peak may not be clear.

  Note that at least one of the proton conductive resins included in the electrode catalyst layer needs to be an aromatic hydrocarbon electrolyte having a polar group. This is for imparting proton conductivity to the aromatic hydrocarbon electrolyte by having a polar group.

Moreover, it is preferable that the proton conductive resin forming the catalyst carrier side portion is a partially fluorinated aromatic hydrocarbon electrolyte.
Thus, by using an electrode catalyst layer in which an electrolyte resin (binder) having a low glass transition point is brought into contact with a catalyst carrier on which a catalyst is supported and an electrolyte resin (binder) having a high glass transition point is coated thereon, Effective utilization of catalytic metal is promoted. The glass transition point can be changed depending on the chemical composition of the binder, the amount of polar groups showing proton conductivity, the average molecular weight, etc. In the present invention, the effect is achieved for any of these reasons. Can do.

The electrode catalyst layer of this embodiment is an anode or a cathode, and at least one of these electrode catalyst layers contains two or more proton conductive resins having different chemical compositions.
The proton conductive resin forming the catalyst carrier side portion is the first binder (proton conductive resin in contact with the catalyst carrier), and the proton conductive resin formed outside thereof is the second binder (the outermost surface of the catalyst layer). The proton conductive resin existing in

  The present invention also relates to the chemical composition of the proton conductive resin present in the fine pores (primary pores) in the aggregates of the catalyst carrier and the protons present in the fine pores (secondary pores) between the aggregates of the catalyst carrier. It can also be expressed that the chemical composition of the conductive resin is different. Depending on the electrode production conditions, locally, the second binder may penetrate into the primary pores, or the first binder may exist in the secondary pores. If the average composition of the proton conductive resin existing in the primary pore and the secondary pore is different, the effect of the present invention is achieved. Note that the average composition here is different when, for example, the STEM-EDX method is used, and the composition of the proton conductive resin existing in the primary pore and the secondary pore is arbitrarily measured at 5 or more points, respectively. Shows that the averages are different.

In particular, the first binder is preferably an aromatic hydrocarbon electrolyte containing a partially fluorinated alkyl group and an aromatic ring.
The main skeleton of the plurality of binder polymers used in the present embodiment is an aromatic hydrocarbon, which has a strong interaction between binder polymers in the electrode catalyst layer. Therefore, the bonding property between different binder polymers becomes good, and the proton conduction resistance between the binder polymers can be kept low.

  This electrode catalyst layer is made by drying and powdering (mixing powder) the mixed solution of the first binder and organic solvent, and then mixing the mixed powder with a solvent having a low polarity so as not to dissolve the first binder. The first binder is made by adding a varnish in which a second binder having a different chemical composition and glass transition point is dissolved, and coating the second binder without dissolving the first binder. Is.

  Further, the present invention extends to a fuel cell membrane-electrode assembly (MEA) produced by applying such an electrode catalyst layer to at least one surface of an electrolyte membrane, and PEFC or DMFC using such MEA. It is.

Embodiments according to the present invention will be described below with reference to the drawings.
In FIG.
A structure in which the anode catalyst layer 2, the cathode catalyst layer 3 and the solid polymer electrolyte membrane 1 are integrated is referred to as a membrane-electrode assembly (Membrane-Electrode-Assembly). In this case, the electrode layer (catalyst layer) and the diffusion layer may be integrated.

The present embodiment relates to a proton conductive resin in the anode catalyst layer 2 and the cathode catalyst layer 3.
The configuration of the present embodiment will be described using the cathode as an example with reference to FIG.

  In the present embodiment, at least two or more kinds of proton conductive resins are present in the cathode catalyst layer 3 (catalyst electrode layer), and the proton conductive resin 23 in contact with the electron conductor 21 on which the catalyst 22 is supported, The physical and chemical properties of the proton conductive resin 24 existing outside are different.

In FIG. 2, for convenience of explanation, a schematic diagram of an electrode composed of two types of proton conductive resins 23 and 24 is shown.
In FIG. 2, 21 is an electron conductor (carrier), 22 is a catalyst metal particle (catalyst), and 23 and 24 are proton conductive resins. 23 is referred to as a first binder, and 24 is referred to as a second binder. Depending on the electrode fabrication conditions, the second binder may be locally formed on the electron conductor side, or the second binder may not exist outside the first binder. If the structure is as shown in FIG. 2, the effect of the present invention is achieved. This structure can be confirmed by, for example, using the STEM-EDX method, where the electron conductor is covered with resin at a point 1 nm outside from the electron conductor side and 1 nm inside from the outermost binder film. This can be achieved by measuring the chemical composition and different compositions of the proton conductive resin. The fact that this structure is obtained on average can be confirmed by measuring each of the above-mentioned measurements at five or more arbitrary points and different in average.

The catalyst metal particles 22, the catalyst carrier 21, the electrolyte binder (the first binder 23, the second binder 24) and the anode catalyst which are cathode catalysts are as described above.
Two or more kinds of proton conductive resins may be present in the electrode catalyst layer according to the present embodiment. The first binder 23 is required to increase the catalyst surface area that can be utilized for the fuel cell reaction by contacting the catalyst carrier 21 and contacting the catalyst metal 23 on the catalyst carrier 21.

  FIG. 3 shows a schematic diagram of a carrier on which a catalytic metal used is used for the cathode. A structure 33 in which carrier particles 31 of 20 to 30 nm are gathered is formed. The diameter of the pores (primary pores 34) formed in the structure 33 is 50 nm or less.

  From the viewpoint of effective utilization of the catalyst metal, the first binder is required to be a material that easily enters the pores 34 in the structure 33 made of the support particles 31. The ease of entry into the pores 34 is thought to depend on the size of the polymer in the solvent, which is strongly influenced by the molecular weight of the polymer or the intermolecular interactions between the polymers.

  Effective control of the catalyst can be promoted by controlling the primary structure of the aromatic hydrocarbon electrolyte and using a polymer with weak intermolecular interaction between the polymers as the first binder. Thus, the glass transition point of the polymer which weakened intermolecular interaction becomes a low value.

  A flexible polymer having a low glass transition point is less susceptible to interaction from other polymer molecules in the catalyst slurry and can be relatively freely deformed, so that it can easily enter the pores 34. Examples of such polymers include aromatic hydrocarbons having alkyl groups and aromatic rings partially containing 4,4 '-(hexafluoroisopropylidene) diphenol, decafluorobiphenyl, etc. An electrolyte is preferred. Thus, the glass transition point can be reduced by 30 ° C. by including a partially fluorinated alkyl group and aromatic ring in the aromatic hydrocarbon electrolyte.

  The glass transition point is preferably 120 ° C. or higher and 270 ° C. or lower. The glass transition point can be measured as a temperature at which the loss tangent obtained as a ratio of the storage elastic modulus and the loss elastic modulus becomes a peak by performing a dynamic viscoelasticity test on the polymer film.

  Further, from the viewpoint of molecular size, a proton conductive resin having a small molecular weight is desirable among aromatic hydrocarbon electrolytes. The desirable number average molecular weight is preferably 10,000 to 50,000. As the first binder, it is preferable to select a proton conductive resin having such a number average molecular weight.

  The second binder covers the surface of the mixture of the first binder and the catalyst carrier. A second binder is formed in pores (secondary pores 35) having a pore diameter of 50 nm or more formed between the structures 33 made of the carrier particles 31, and the binding property of the catalyst electrode is maintained.

For this reason, a resin having a high glass transition point is preferred. In particular, considering application to the cathode electrode of DMFC, a resin having a small swelling ratio with respect to water or methanol is preferable.
From this viewpoint, it is preferable to use an aromatic hydrocarbon electrolyte resin having a glass transition point higher than that of the first binder for the second binder. The glass transition point is preferably 250 ° C. or higher. Moreover, it is preferable that the molecular weight is large for binding property and stability against dissolution, and it is particularly desirable that the second binder has a higher molecular weight than the first binder.

  In addition, a proton conductive electrolyte resin can be used for the electrolyte membrane used in the membrane electrode assembly of this example. In order to maintain good bonding between the electrolyte membrane and the electrode, it is preferable that the second binder and the electrolyte membrane have the same primary structure of the skeleton.

Hereinafter, the method for producing the electrode catalyst layer according to this example will be described by taking the electrode catalyst layer of the cathode as an example.
In order to coat the first binder on the carrier particles carrying the catalyst metal particles, a catalyst slurry in which these are mixed with a solvent is mixed, and after dispersion, the solvent is dried.

  The solvent is not particularly limited as long as it can be easily dried and washed with water and does not interfere with the dispersion of the carrier particles. For example, in addition to water, alkylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether, n-propanol, iso-propanol, t-butyl alcohol, etc. Alcohols and highly polar solvents such as 1-methyl-2-pyrrolidone can be used.

  As a method for drying the solvent and obtaining a powder comprising the carrier particles supporting the catalyst and the first binder, the slurry is dried in a heat or vacuum, and the obtained powder is pulverized or sprayed. Examples thereof include a method of spraying slurry using a dryer and removing the solvent in the air to obtain a powder.

  In order to coat the surface of the obtained mixed powder with the second binder, the mixed powder coated with the first binder is dispersed in a solvent to form a slurry, and the second binder is dissolved therein. Alternatively, it can be obtained by adding a dispersed solution and mixing. By appropriately selecting the polarity and the amount of the solvent used and the order of addition, a catalyst slurry that can cover the second binder without dissolving the first binder can be obtained.

The electrode catalyst layer can be formed by applying and forming the slurry thus obtained as an electrode.
As a solvent used in this case, it is necessary not to elute the binder solidified in the powder. A suitable solvent varies depending on the first binder, but in general, a solvent having a small polarity is desirable, and n-propanol, iso-propanol, t-butyl alcohol, ethyl acetate and the like are preferable.

  As the solvent for dissolving the second binder, in addition to water, alkylene glycol monoalkyl ether such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether, n- Alcohols such as propanol, iso-propanol, and t-butyl alcohol, and highly polar solvents such as 1-methyl-2-pyrrolidone can be used, but when the slurry is prepared, the first binder is not eluted. It is necessary to select a proper solvent composition.

In addition, as an electrode formation method, the method of apply | coating a catalyst paste on a polymer electrolyte membrane or a gas diffusion layer by the printing method, the spray method, the inkjet method, the die coater method etc. is preferable.
The structure of the manufactured electrode can be evaluated with a scanning transmission electron microscope (STEM) on a thin piece of the electrode. It can be confirmed that the structure is obtained by evaluating the composition of the proton conductive resin in the vicinity of the catalyst and in the vicinity of the outer layer surface of the catalyst by EDX (energy dispersive X-ray spectroscopy). Further, the structure can be evaluated by evaluating the surface composition of the catalyst electrode using photoelectron spectroscopy, and comparing the component composition of the proton conductive resin contained in the entire catalyst electrode with the component composition of the surface. The primary structure of the proton conductive resin contained in the electrode of this example can be evaluated by conducting a nuclear magnetic resonance (NMR) analysis of a solution in which the resin is dissolved. The molecular weight distribution can be evaluated using gel permeation chromatography (GPC).

  In this embodiment, the first binder enters the primary pores to effectively use the catalyst metal inside the primary pores, improve the catalyst utilization, and further use the second binder. Thus, the shape stability of the electrode can be improved. In addition, by using a hydrocarbon-based electrolyte for the second binder, the bondability between the electrode and the hydrocarbon-based electrolyte membrane can be improved.

  Hereinafter, the present invention will be described in more detail with reference to examples and test examples, but the scope of the present invention is not limited to the examples disclosed herein.

1. Example (Example 1)
(1) Synthesis of chloromethylated polyethersulfone After the inside of a 500 ml four-necked round bottom flask equipped with a stirrer, thermometer, and reflux condenser connected with a calcium chloride tube was purged with nitrogen, 30 g of polyethersulfone (PES), 250 ml of tetrachloroethane was added, and 40 ml of chloromethyl methyl ether was further added. Then, a mixed solution of 1 ml of anhydrous tin (IV) chloride and 20 ml of tetrachloroethane was added dropwise, heated to 80 ° C. and stirred for 90 minutes with heating. .

  Next, the reaction solution was dropped into 1 liter of methanol to precipitate a polymer. The deposited precipitate was pulverized with a mixer and washed with methanol to obtain chloromethylated polyethersulfone. The introduction rate of the chloromethyl group {the ratio of the structural unit having the chloromethyl group introduced to the total structural units (total of x and y) in (Formula 1)} in the nuclear magnetic resonance spectrum was 36%.

(2) Synthesis of acetylthiolated polyethersulfone The obtained chloromethylated polyethersulfone was put in a 1000 ml four-necked round bottom flask equipped with a stirrer, thermometer, and reflux condenser connected with a calcium chloride tube. -600 ml of methylpyrrolidone was added. To this was added a solution of 9 g of potassium thioacetate and 50 ml of N-methylpyrrolidone (NMP), and the mixture was heated to 80 ° C. and stirred for 3 hours. Next, the reaction solution was dropped into 1 liter of water to precipitate a polymer. The deposited precipitate was pulverized with a mixer, washed with water, and then dried by heating to obtain 32 g of acetylthiolated polyethersulfone.

(3) Synthesis of sulfomethylated polyethersulfone 20 g of the obtained acetylthiolated polyethersulfone was placed in a 500 ml four-necked round bottom flask equipped with a stirrer, thermometer, and reflux condenser connected with a calcium chloride tube. 300 ml of acetic acid was added. 20 ml of hydrogen peroxide solution was added, heated to 45 ° C. and stirred for 4 hours.

  Next, the reaction solution was added to 1 liter of 6N aqueous sodium hydroxide solution while cooling, and stirred for a while. The polymer was filtered and washed with water until the alkaline component was removed. Thereafter, the polymer was added to 300 ml of 1N hydrochloric acid and stirred for a while. The polymer was filtered, washed with water until the acid component was removed, and dried under reduced pressure to quantitatively obtain 20 g of a sulfomethylated polyethersulfone. The presence of a sulfomethyl group was confirmed by the chemical shift of the NMR methylene proton being shifted to 3.78 ppm. The introduction rate of the sulfomethyl group {the ratio of the structural unit having the sulfomethyl group introduced to the total structural units (total of x and y) in (Formula 2)} was 36% from the introduction rate of the chloromethyl group.

(4) Production of polymer electrolyte membrane The sulfomethylated polyethersulfone obtained in (3) above was dissolved in a mixed solvent (1: 1) of dimethylacetamide-methoxyethanol so as to have a concentration of 5% by weight. This solution was spread on glass by spin coating, air-dried, and then vacuum-dried at 80 ° C. to prepare a sulfomethylated polyethersulfone electrolyte membrane having a thickness of 42 μm. This polymer electrolyte membrane had a methanol permeability at room temperature of 12 mA / cm ² and an ionic conductivity of 0.053 S / cm.

(5) Production of membrane electrode assembly (MEA) In the same manner as in the above (1), (2) and (3), introduction rate of sulfomethyl group {for all structural units in (Formula 2) (total of x and y) A sulfomethylated polyethersulfone having a ratio of structural units introduced with a sulfomethyl group} of 41% was synthesized and used as a polymer electrolyte for the cathode and anode electrodes.

  A catalyst powder in which platinum / ruthenium alloy fine particles having a platinum / ruthenium atomic ratio of 1/1 on a carbon support are dispersed and supported by 50 wt%, and 30 wt% of the polymer electrolyte (sulfomethylated polyethersulfone) 1-propanol, 2- A slurry of a mixed solvent of propanol and methoxyethanol was prepared, and an anode electrode having a thickness of about 125 μm, a width of 30 mm, and a length of 30 mm was produced on the polyimide film by a screen printing method.

The manufacturing method of the catalyst for cathodes is shown below.
Titanium tetraisopropoxide (made by Junsei Chemical Co., Ltd.) 5mL and acetylacetone (Junsei Chemical Co., Ltd.) 5mL are added to a solution of ethanol (Wako Pure Chemical Industries, Ltd.) 15mL and acetic acid (Wako Pure Chemical Industries, Ltd.) 5mL. A titanium-containing mixture solution was prepared while stirring at room temperature. In addition, 2.507 g of glycine (manufactured by Wako Pure Chemical Industries, Ltd.) and 0.153 g of iron acetate (manufactured by Aldrich) were added to 20 mL of pure water, and the mixture was stirred and completely dissolved at room temperature to prepare a glycine-containing mixture solution. .

  The titanium-containing mixture solution was slowly added to the glycine-containing mixture solution to obtain a catalyst precursor composition. Using a rotary evaporator, the temperature of the hot stirrer was set to about 100 ° C. under reduced pressure in a nitrogen atmosphere, and the solvent was slowly evaporated while heating and stirring the catalyst precursor composition. After completely evaporating the solvent of the catalyst precursor composition, the catalyst precursor composition was finely and uniformly crushed in a mortar to obtain a powder.

  This powder is placed in a tubular furnace, heated to 900 ° C. at a heating rate of 10 ° C./min in a mixed gas atmosphere of 4% by volume hydrogen and nitrogen, held at 900 ° C. for 1 hour, and naturally cooled to thereby cool TiFeCNO powder. (Hereinafter also referred to as “catalyst carrier (1)”).

The powder X-ray diffraction spectrum of the catalyst carrier (1) is shown in FIG. Diffraction line peaks of titanium compound with cubic structure and titanium oxide with rutile structure were observed.
The component ratio of the catalyst carrier (1) based on the result of elemental analysis was Ti _0.95 Fe0.05C _1.51 N _0.15 O _1.55 . The presence of carbon, nitrogen and oxygen was confirmed. The catalyst carrier (1) had a BET specific surface area of 172 m ² / g.

Cathode catalyst (1) was obtained by supporting 50% by weight of platinum on this carrier.
Next, a slurry of a water / alcohol mixed solvent is prepared by using the cathode catalyst (1) and polyperfluorosulfonic acid 1-propanol, a mixed solvent of 2-propanol and methoxyethanol as a binder, and a polyimide film is formed by screen printing. A cathode electrode having a thickness of about 20 μm, a width of 30 mm, and a length of 30 mm was produced. The sulfomethylated polyethersulfone electrolyte prepared in (4) above after impregnating about 0.5 ml of a mixed solvent of 1-propanol, 2-propanol and methoxyethanol of 5% by weight of the polymer electrolyte on the surface of the anode electrode. The film was bonded to the membrane and dried at 80 ° C. for 3 hours under a load of about 1 kg.

  Next, about 0.5 ml of a mixed solvent of 1% propanol, 2-propanol and methoxyethanol of 5% by weight of polyperfluorosulfonic acid was infiltrated on the surface of the cathode electrode, and then joined to the polymer electrolyte membrane first. MEA (I) was produced by joining so as to overlap with the anode layer and applying a load of about 1 kg and drying at 80 ° C. for 3 hours.

  An aqueous dispersion of water repellent polytetrafluoroethylene (PTFE) fine particles (Dispersion D-1: manufactured by Daikin Industries) is added and kneaded into carbon powder so that the weight after firing is 40 wt%. This was coated on one side of a carbon cloth having a thickness of about 350 μm and a porosity of 87%, dried at room temperature, and then fired at 270 ° C. for 3 hours to form a carbon sheet. The amount of PTFE was set to 5 to 20 wt% with respect to the carbon cloth cloth. The obtained sheet was cut into the same shape as the electrode size of the MEA to form a cathode diffusion layer. A carbon cloth having a thickness of about 350 μm and a porosity of 87% was immersed in fuming sulfuric acid (concentration 60%), and kept at a temperature of 60 ° C. for 2 days under a nitrogen stream. The flask temperature was then cooled to room temperature. The fuming sulfuric acid was removed and the carbon cloth was washed well until the distilled water became neutral.

Subsequently, it was immersed in methanol and dried. To 1225 cm ^-1 and 1413cm ^-1 in the infrared absorption spectrum of the resulting carbon cloth absorption based on -OSO ₃ H group was observed. Absorption based on the —OH group was observed at 1049 cm ⁻¹ . Therefore, we bet introduces -OSO ₃ H group or a -OH group was observed at the surface of the carbon cloth. The contact angle between the carbon cloth not treated with fuming sulfuric acid and the aqueous methanol solution was smaller than 81 ° and was hydrophilic. Moreover, it was excellent also in electroconductivity. This was cut out into the same shape as the electrode size of the MEA (I) to form an anode diffusion layer.

(6) Power generation performance of fuel cell (DMFC) Using the polymer fuel cell power generator single cell shown in FIG. 4, the MEA (I) with diffusion layer was incorporated to measure the battery performance. In FIG. 4, 41 is a polymer electrolyte membrane, 42 is an anode electrode, 43 is a cathode electrode, 44 is an anode diffusion layer, 45 cathode diffusion layer, 46 is fuel, 47 is air, and 48 is an external load. As a fuel, an aqueous methanol solution having a concentration of 3 wt% was circulated through the anode, and air was supplied to the cathode. Continuous operation was performed at 60 ° C. while applying a load of 50 mA / cm ² . The output voltage was 440 mV at 50 mA / cm ² 10 hours after the start of operation. Subsequently, it was continuously operated at 60 ° C. while applying a load of 50 mA / cm ² , and after 2,000 hours of operation, an output of 385 mV was exhibited and stable.

(Comparative Example 1)
(1) Preparation of membrane electrode assembly (MEA) A catalyst powder in which 50 wt% of platinum / ruthenium alloy fine particles having an atomic ratio of platinum to ruthenium of 1/1 are dispersed and supported on a carbon support and a 30 wt% polyperfluorosulfonic acid electrolyte. A slurry of a water / alcohol mixed solvent (a mixed solvent of water, isopropanol, and normal propanol in a weight ratio of 20:40:40) was prepared as a binder, and the thickness was about 125 μm, width 30 mm, and length on a polyimide film by screen printing. An anode electrode having a thickness of 30 mm was produced.

  Next, a slurry of a water / alcohol mixed solvent is prepared using the cathode catalyst (1) and 30 wt% polyperfluorosulfonic acid as a binder, and is about 20 μm in thickness, 30 mm in width and length on a polyimide film by a screen printing method. A 30 mm cathode electrode was prepared. After impregnating about 0.5 ml of a 5% by weight polyperfluorosulfonic acid alcohol aqueous solution (a mixed solvent of water, isopropanol, and normal propanol at a weight ratio of 20:40:40) on the surface of the anode electrode, It was joined to the sulfomethylated polyethersulfone electrolyte membrane prepared in (4), and dried at 80 ° C. for 3 hours under a load of about 1 kg.

Next, about 0.5 ml of a mixed solvent of 1% propanol, 2-propanol and methoxyethanol of 5% by weight of polyperfluorosulfonic acid was infiltrated on the surface of the cathode electrode, and then joined to the polymer electrolyte membrane first. It joined so that it might overlap with an anode layer, and about 1 kg of load was applied, and it dried at 80 degreeC for 3 hours, and produced MEA (II).
This and the hydrophilic carbon cloth produced in Example 1 were used for the anode diffusion layer, and the water repellent carbon cloth was used for the cathode diffusion layer.

(2) Power generation performance of fuel cell (DMFC) The MEA (II) with diffusion layer was incorporated into the polymer fuel cell power generator single cell shown in FIG. 4 to measure the battery performance. As a fuel, an aqueous methanol solution having a concentration of 3 wt% was circulated through the anode, and air was supplied to the cathode. Continuous operation was performed at 60 ° C. while applying a load of 50 mA / cm ² . 10 hours after the start of operation. At 50 mA / cm ² , the output voltage was 440 mV. Subsequently, the output voltage dropped to 242 mV after 400 hours of operation at a load of 50 mA / cm ² .

  From the above, a fuel cell incorporating a MEA using a hydrocarbon electrolyte as a polymer electrolyte binder for an anode electrode and a fluorine electrolyte as a polymer electrolyte binder for a cathode electrode is a polymer of the anode electrode and the cathode electrode. It can be seen that, unlike a fuel cell incorporating an MEA using a fluorine-based electrolyte as an electrolyte binder, a stable output can be obtained for a long time.

(Comparative Example 2)
(1) Production of Membrane / Electrode Assembly (MEA) The polymer electrolyte of the cathode electrode is the introduction rate of sulfomethyl group described in (5) of Example 1 {total structural units (total of x and y) in (Formula 2)] The polymer electrolyte for joining the cathode electrode to the polymer electrolyte membrane was replaced with a hydrocarbon electrolyte that was a sulfomethylated polyethersulfone having a ratio of rufomethyl groups introduced therein of 41%. (5) A sulfomethylated polyethersulfone having a sulfomethyl group introduction rate {the ratio of structural units having a sulfomethyl group introduced to the total structural units (total of x and y) in (Formula 2)} of 41% in (Formula 2) MEA (III) was produced in the same manner as in Example 1 except that the hydrocarbon electrolyte was used.

(2) Power generation performance of fuel cell (DMFC) The MEA (II) with diffusion layer was incorporated into the polymer fuel cell power generator single cell shown in FIG. 4 to measure the battery performance. As a fuel, an aqueous methanol solution having a concentration of 3 wt% was circulated through the anode, and air was supplied to the cathode. Continuous operation was performed at 60 ° C. while applying a load of 50 mA / cm ² . At 50 mA / cm ² 10 hours after the start of operation, the output voltage was 440 mV. Subsequently, continuous operation was performed at 60 ° C. while applying a load of 50 mA / cm ^2. After 400 hours of operation, the output voltage decreased to 0 mV.

  From the above, a fuel cell incorporating a MEA using a hydrocarbon electrolyte as a polymer electrolyte binder for an anode electrode and a fluorine electrolyte as a polymer electrolyte binder for a cathode electrode is a polymer of the anode electrode and the cathode electrode. It can be seen that, unlike a fuel cell incorporating an MEA using a hydrocarbon electrolyte as an electrolyte binder, a stable output can be obtained for a long time.

(Example 2)
A membrane electrode assembly (MEA) exactly the same as that of Example 1 except that the thickness of the cathode electrode was changed to 10 μm was produced, incorporated in the single cell shown in FIG. 4, and continuously applied at 60 ° C. while applying a load of 50 mA / cm ^2. Drove. As a result, the output after 10 hours of continuous operation was 451 mV, and the output after 2,000 hours of continuous operation was 374 mV. It can be seen that the initial output of the MEA with the cathode electrode thickness of 10 μm is higher than that when the cathode electrode thickness is 20 μm, but it becomes lower after a long time.

(Example 3)
(1) Production of hydrophilic treated carbon paper 1 Carbon paper having a thickness of about 150 μm and a porosity of 87% was immersed in fuming sulfuric acid (concentration 60%) and kept at a temperature of 60 ° C. for 2 days under a nitrogen stream. The flask temperature was then cooled to room temperature. The fuming sulfuric acid was removed and the carbon paper was washed well until the distilled water was neutral. Subsequently, it was immersed in methanol and dried. To 1225 cm ^-1 and 1413cm ^-1 of the resulting hydrophilic treatment infrared absorption spectrum of the carbon paper 1 absorption based on -OSO ₃ H group was observed. Absorption based on the —OH group was observed at 1049 cm ⁻¹ . Therefore, the introduction of -OSO ₃ H groups and -OH groups on the surface of the carbon paper, the contact angle between the carbon paper and the aqueous methanol solution is not fuming sulfuric acid treatment is less than 81 °, were hydrophilic. Moreover, it was excellent also in electroconductivity.

(2) Production of Membrane Electrode Assembly (MEA) Same as Example 1 except that the hydrophilic carbon paper 1 was used for the diffusion layer of the anode and the thickness of the cathode electrode was 20 μm as shown in Table 1. A membrane electrode assembly (MEA) was produced.

(3) Power generation performance of fuel cell (DMFC) Using the polymer fuel cell power generator single cell shown in FIG. 4, the MEA with diffusion layer was incorporated to measure battery performance. As a fuel, an aqueous methanol solution having a concentration of 3 wt% was circulated through the anode, and air was supplied to the cathode. Continuous operation was performed at 60 ° C. while applying a load of 50 mA / cm ² . Table 1 shows the output voltage with a load having a current density of 50 mA / cm ² after 10 hours and 2000 hours from the start of operation.

  The thinner the cathode electrode, the better the power output immediately after the start of operation. On the other hand, the output after 2,000 hours tends to decrease when the cathode electrode is thin. The thickness of the cathode electrode is preferably 20 μm to 50 μm.

Example 4
(1) Production of polyolefin porous membrane A raw material obtained by mixing 3 parts by weight of ultrahigh molecular weight polyethylene having a weight average molecular weight of 2.5 × 10 ⁶ and 14 parts by weight of high density polyethylene having a weight average molecular weight of 6.8 × 10 ⁵ The resin and 83 parts by weight of liquid paraffin were mixed to prepare a polyethylene composition solution. Next, 0.375 parts by weight of an antioxidant was mixed with 100 parts by weight of this polyethylene composition solution. This mixed solution was filled in an autoclave equipped with a stirrer and stirred at 200 ° C. for 90 minutes to obtain a uniform solution. This solution was extruded from a T die at 200 ° C. by an extruder having a diameter of 45 mm and taken up by a cooling roll cooled to 20 ° C., thereby forming a gel sheet having a thickness of 1.8 mm. The obtained sheet was set in a biaxial stretching machine, and simultaneous biaxial stretching was performed 5 × 5 times at a temperature of 105 ° C. and a film forming speed of 5 m / min.

The obtained stretched membrane was washed with methylene chloride to extract and remove the remaining liquid paraffin. After drying at room temperature, heat setting was performed at 90 ° C. for 30 seconds to obtain a polyolefin porous membrane 1 having a thickness of 20 μm and a porosity of 40%. For the porosity, the value calculated by the following formula [1] from the weight W (g) per unit area S (cm ² ), the average thickness t (μm) and the density d (g / cm ³ ) of the film is used. did.

The heat shrinkage rate of the polyolefin porous membrane 1 was measured by standing a 10 cm square sample in a state of no tension at 105 ° C. for 8 hours. The heat shrinkage rate in the vertical direction was 25% and the heat shrinkage rate in the horizontal direction. Was 19%.

(2) Formation of polymer electrolyte composite membrane Prior to the preparation of the polymer electrolyte composite membrane, the sulfomethylated polyethersulfone electrolyte prepared in (1) of Example 1 was dissolved in N, N-dimethylacetamide and 25 A weight% polyelectrolyte solution was prepared. The polyolefin porous membrane 1 was impregnated with this solution, and a polymer electrolyte solution was cast on a glass substrate. Thereafter, the solvent in the solution is removed by heating and drying at 80 ° C. for 30 minutes, and then at 120 ° C. for 30 minutes to coat the polyolefin porous membrane 1 with a sulfomethylated polyethersulfone electrolyte. A polymer electrolyte composite membrane 1 in which the pores were filled with a sulfomethylated polyethersulfone electrolyte was produced. The film thickness of the obtained polymer electrolyte composite membrane 1 was 40 μm.

(3) Preparation of hydrophilic treated carbon paper 2 1 part by weight of polyethylene glycol having a molecular weight of 20,000 was added to 297 parts by weight of tetrahydrofuran, and the mixture was stirred and dissolved while heating at 50 ° C. 2 parts by weight of Silaace S330 manufactured by Chisso Corporation having both an amino group and an alkoxysilane residue was added and stirred to prepare a paint for forming a hydrophilic coating film. After immersing carbon paper having a thickness of about 150 μm and a porosity of 87% in this paint for about 5 minutes, the carbon paper was taken out of the paint and heat-treated at 100 ° C. for 20 minutes to obtain hydrophilic treated carbon paper 2. Obtained.

(4) Production of Membrane / Electrode Assembly (MEA) Except that the polymer electrolyte composite membrane 1 was used as a polymer electrolyte membrane and the hydrophilic carbon paper 2 was used as an anode diffusion layer, exactly the same as in Example 3. A membrane electrode assembly (MEA) was produced.

(5) Power generation performance of fuel cell (DMFC) Using the polymer fuel cell power generator single cell shown in FIG. 4, the MEA with diffusion layer was incorporated to measure the battery performance. As a fuel, an aqueous methanol solution having a concentration of 3 wt% was circulated through the anode, and air was supplied to the cathode. Continuous operation was performed at 60 ° C. while applying a load of 50 mA / cm ² . Table 1 shows the output voltage of a load having a current density of 50 mA / cm ² after 10 hours and 2,000 hours from the start of operation.

  The thinner the cathode electrode, the better the power output immediately after the start of operation. On the other hand, the output after 2000 hours tends to decrease when the cathode electrode is thin. The thickness of the cathode electrode is preferably 15 μm to 50 μm.

  Further, comparing Example 3 and Example 4, it can be seen that the polymer electrolyte composite membrane is superior as the polymer electrolyte membrane.

(Example 5)
In the formation of a polymer electrolyte membrane, a sulfomethylated polyethersulfone electrolyte is coated on the anode side of the polyolefin porous membrane 1, and a water / alcohol of a 30 wt% polyperfluorosulfonic acid electrolyte binder is coated on the cathode side of the polyolefin porous membrane 1. A mixed solvent (water, isopropanol, and normal propanol in a weight ratio of 20:40:40) was coated. Except that, the same experiment as in Example 4 was performed to prepare an MEA, and the battery performance was measured by incorporating the MEA with a diffusion layer using the polymer fuel cell power generator single cell shown in FIG. As a fuel, a 3 wt% aqueous methanol solution was circulated to the anode, and air was supplied to the cathode. Continuous operation was performed at 60 ° C. while applying a load of 50 mA / cm ² . Table 2 shows the output voltage of a load having a current density of 50 mA / cm ² after 10 hours and 2,000 hours from the start of operation. In Table 2, Example 4 is also shown for comparison.

When Example 5 and Example 4 in Table 2 are compared, the polymer electrolyte composite membrane using the hydrocarbon electrolyte membrane for the anode as the polymer electrolyte membrane and the fluorine electrolyte membrane for the cathode is the hydrocarbon for both the anode and the cathode. It can be seen that the durability is superior to the polymer electrolyte composite membrane using the system electrolyte membrane.

(Example 6), (Example 7)
The results of the same experiment as in Example 5 using a fluorine-based electrolyte Nafion as the polymer electrolyte for the cathode and anode electrodes are shown in Example 6 in Table 2, and the hydrocarbon electrolyte as the polymer electrolyte for the cathode and anode electrodes. Table 7 shows the results of the same experiment as in Example 5 using SM-PES.

  When Example 6 and Comparative Example 1 are compared, when a fluorine-based electrolyte is used as the polymer electrolyte of the cathode electrode and the anode electrode, a hydrocarbon-based electrolyte membrane is used as the polymer electrolyte membrane, and a fluorine-based electrolyte is used as the cathode. It can be seen that the polymer electrolyte composite membrane using the membrane is more durable than using a hydrocarbon electrolyte as the polymer electrolyte.

  Further, when Example 7 and Comparative Example 2 are compared, when a hydrocarbon-based electrolyte is used as the polymer electrolyte of the cathode electrode and the anode electrode, a hydrocarbon-based electrolyte membrane is used as the polymer electrolyte membrane on the anode and a fluorine-based electrolyte is used on the cathode. It can be seen that the polymer electrolyte composite membrane using the electrolyte membrane is superior in durability to using a hydrocarbon electrolyte membrane as the polymer electrolyte.

  According to the embodiment of the present invention, when a hydrocarbon electrolyte membrane is used as the polymer electrolyte membrane of the membrane electrode assembly, the hydrocarbon electrolyte membrane is used by using the hydrocarbon electrolyte as the polymer electrolyte binder of the anode electrode. Adhesion between the anode and the anode is strengthened, and the use of a fluorine-based electrolyte as the polymer electrolyte binder for the cathode electrode reduces the deterioration of the polymer electrolyte binder in the cathode electrode, enabling stable and long-term power generation by the fuel cell. It can be carried out.

  In addition, a polymer electrolyte composite membrane using a hydrocarbon electrolyte membrane on the anode side as a polymer electrolyte membrane of a membrane electrode assembly and a fluorine electrolyte membrane on the cathode side is used as a hydrocarbon electrolyte membrane or an anode as a polymer electrolyte membrane. In addition, it is more durable than a polymer electrolyte composite membrane using a hydrocarbon-based electrolyte membrane and a fluorine-based electrolyte membrane on the cathode side, and power generation by a fuel cell can be performed stably for a long time.

  A direct methanol fuel cell power supply system using a membrane electrode assembly according to an embodiment of the present invention is attached to a mobile phone equipped with a secondary battery, a portable personal computer, a portable audio device, a visual device, and other portable information terminals. These electronic devices can be used for a long time by being used as a battery charger or by directly using a built-in power supply without mounting a secondary battery, and can be used continuously by refueling. In addition, the polymer fuel cell using the membrane electrode assembly according to the present invention and using hydrogen as fuel can be used for a long period of time as a fuel cell power source for household and commercial cogeneration distributed power sources and mobile units. Continuous use is possible by replenishment.

2. Test Example [Test Example 1]
(1-1) A polymer in which (4,4′-hexafluoroisopropylidene) diphenol was introduced into sulfonated polyethersulfone was synthesized, and the solvent was removed (hereinafter referred to as polymer A).
(1-2) The number average molecular weight of the obtained polymer A was 45000, and the glass transition point was 260 ° C. The sulfone group equivalent was 1.5 mmol / g. 5 g of polymer A was dissolved in 45 g of ethylene glycol monomethyl ether.
(1-3) 1 g of the above catalyst for cathode (1) was mixed and stirred with 6 g of ethylene glycol monomethyl ether to disperse the carbon particles in the solvent, and then 1 g of the polymer A solution obtained in (1-2) was used. Added and mixed for 12 hours.

(1-4) The catalyst slurry obtained in (1-3) was vacuum-dried, and the dried product was pulverized into fine particles in an agate mortar.
(1-5) A sulfoalkylated polyethersulfone was synthesized (hereinafter referred to as polymer B). The number average molecular weight of the polymer B was 100,700, and the glass transition point was 290 ° C. The sulfone group equivalent was 1.7 mmol / g.
(1-6) 5 g of polymer B was dissolved in 45 g of ethylene glycol monomethyl ether.
(1-7) After 1.1 g of the powder obtained in (1-4) was dispersed in 6 g of a mixed solution of n-propanol and iso-propanol, 1 g of the polymer B solution obtained in (1-5) was added, Mixed. A solvent having the same composition as the catalyst slurry was mixed with polymer A and allowed to stand for 24 hours or more, but dissolution of polymer A was not observed.

(1-8) The catalyst slurry obtained in (1-7) was applied on a sulfoalkylated polyethersulfone electrolyte membrane to obtain a cathode electrode.
As the anode electrode, an electrode having an electrode catalyst layer using a catalyst powder (TEC61E54 manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) in which PtRu metal is supported on carbon black was used.
A membrane electrode assembly was produced by hot pressing. The hot pressing temperature was 120 ° C. and the pressing pressure was 80 kg / cm ² .

(1-9) The electrode produced as described above is sliced using a cooling microtome device and observed with a scanning transmission electron microscope (STEM). By mapping the presence of fluorine (F) and sulfur (S) elements using energy dispersive X-ray spectroscopy (EDX), polymers A (containing F element) and B (containing a large amount of S element) in the anode electrode ) Is investigated. The F element is unevenly distributed on the outermost surface of the catalyst-supporting carbon, and the F element is also observed from the pores in the carbon structure. It is also confirmed that there are many S elements around the region where the F elements are unevenly distributed. From this result, it can be confirmed that the polymer A containing the F element is located on the surface of the carbon particles and penetrates into the pores, and the polymer B containing a lot of the S element covers it.

[Test Example 2]
(2-1) Prepared in the same manner as in Example 1 except that 2 g of the polymer B solution was added in (1-7).
(2-2) The electrode produced as described above is sliced using a cooling microtome device, and element mapping is performed with STEM, whereby polymer A (containing F element) is unevenly distributed on the surface of the carbon particles, and polymer B ( It can be confirmed that the structure is covered with the S element containing). In addition, compared with Test Example 1, an unevenly distributed region of the F element is observed.

[Comparative Test Example 1]
(3-1) The polymer A solution obtained in (1-2) and the polymer B solution obtained in (1-5) were mixed at the same weight.
(3-2) 1 g of the above catalyst for cathode (1) is mixed and stirred with 6 g of ethylene glycol monomethyl ether to disperse carbon particles in a solvent, and then a solution of polymers A and B obtained in (3-1). 2 g was added and mixed for 12 hours.
(3-3) The catalyst slurry obtained in (3-2) was applied on a sulfoalkylated polyethersulfone electrolyte membrane to obtain a cathode electrode. As the anode electrode, an electrode catalyst layer using a catalyst powder (TEC61E54 manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) in which PtRu metal was supported on carbon black was used.
A membrane electrode assembly was produced by hot pressing. The hot pressing temperature was 120 ° C. and the pressing pressure was 80 kg / cm ² .
(3-4) The electrode produced as described above is sliced using a cooling microtome device, and observed with a STEM. When element mapping of fluorine (F) and sulfur (S) was performed using EDX, F and S were uniformly dispersed on the surface of the catalyst-carrying carbon, and the polymers A and B in the electrode were uniformly mixed. You can see that

[Comparative Test Example 2]
(4-1) 1 g of the above catalyst for cathode (1) was mixed and stirred with 6 g of ethylene glycol monomethyl ether to disperse the carbon particles in the solvent, and then 2 g of the polymer A solution obtained in (1-2) was added. Added and mixed for 12 hours.
(4-2) The catalyst slurry obtained in (4-1) was vacuum-dried, and the dried product was pulverized into fine particles in an agate mortar.
(4-3) 1.2 g of the powder obtained in (4-2) was dispersed in 6 g of a mixed solution of n-propanol and iso-propanol and mixed.
(4-4) The catalyst slurry obtained in (4-3) was applied on a sulfoalkylated polyethersulfone electrolyte membrane to obtain a cathode electrode. As the anode electrode, an electrode catalyst layer using a catalyst powder (TEC61E54 manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) in which PtRu metal was supported on carbon black was used. A membrane electrode assembly was produced by hot pressing. The hot pressing temperature was 120 ° C. and the pressing pressure was 80 kg / cm ² .

[Discussion]
The membrane electrode assemblies produced in Test Examples 1 and 2 and Comparative Test Examples 1 and 2 were sandwiched between current collector plates, hydrogen was supplied to the anode side and nitrogen was supplied to the cathode side, and the effective surface area of Pt in the cathode catalyst layer was measured. . The results are summarized in Table 3.

On the other hand, the effective catalyst surface area of Comparative Test Example 1 in which the anodes were prepared by mixing polymers A and B was lower than that of Test Examples 1 and 2 and Comparative Test Example 2. It can be said that the catalyst is effectively utilized in the anode electrode using the polymer A having a smaller molecular weight as the first binder.

  The present invention can be used for fuel cells represented by PEFC and DMFC.

Claims (4)

An electrode membrane assembly comprising an anode, a cathode, and a solid polymer electrolyte membrane, wherein the solid polymer electrolyte membrane is sandwiched between the anode and the cathode,
The anode and cathode have an electrocatalyst layer comprising a catalyst and a polymer electrolyte binder;
The catalyst contained in the cathode is an oxygen reduction catalyst composed of composite particles composed of a catalyst metal and a catalyst carrier,
The catalyst carrier includes transition metal elements M2 other than transition metal elements M1 and M1, carbon, nitrogen and oxygen;
The ratio of the number of atoms of transition metal element M1, transition metal element M2, carbon, nitrogen and oxygen (transition metal element M1: transition metal element M2: carbon: nitrogen: oxygen) is (1-a): a: x: y : Z (where 0 <a ≦ 0.5, 0 <x ≦ 7, 0 <y ≦ 2, 0 <z ≦ 3),
The transition metal element M1 is at least one selected from the group consisting of titanium, zirconium, niobium and tantalum,
The catalytic metal is one or more selected from the group consisting of platinum, gold, copper, palladium, rhodium, ruthenium, iridium, osmium and rhenium, and alloys of two or more thereof;
At least one of the polymer electrolyte binder and cathode side electrolyte membrane contained in the cathode contains a fluorine-based electrolyte, and at least one of the polymer electrolyte binder and anode side electrolyte membrane contained in the anode contains an electrode membrane containing a hydrocarbon electrolyte. Joined body.   The membrane electrode assembly according to claim 1, wherein the transition metal element M2 is at least one selected from iron, nickel, chromium, cobalt, vanadium, and manganese.   A fuel cell comprising the membrane electrode assembly according to claim 1. The anode and the cathode have an electrode catalyst layer including a catalyst, a catalyst carrier supporting the catalyst, and a polymer electrolyte binder covering the catalyst carrier,
The polymer electrolyte binder contained in at least one of the anode and the cathode contains at least two kinds of proton conductive resins having different weight average molecular weights, and the proton conductivity contained in the catalyst carrier side portion of the polymer electrolyte binder. The fuel cell according to claim 3, wherein the weight average molecular weight of the resin is smaller than the weight average molecular weight of the proton conductive resin contained in the outer portion of the polymer electrolyte binder.