JP6736929B2 - Fuel cell paste composition and fuel cell - Google Patents

Description

The present invention relates to a catalyst paste composition for a fuel cell, a catalyst layer using the same, a catalyst electrode having the catalyst layer, an electrode membrane assembly and a fuel cell.

A fuel cell is a system that can directly convert chemical energy into electric energy by using an electrochemical system, and is expected as a next-generation energy because it has high efficiency. Known fuel cells include polymer electrolyte fuel cells that use hydrogen as a gas fuel and methanol as a liquid fuel, and microbial fuel cells that use electron-donating microorganisms. The metal-air battery using is also capable of maintaining the discharge performance by replenishing the metal on the negative electrode side, and therefore can be broadly regarded as one type of fuel cell. Among them, the polymer electrolyte fuel cell is under active development for automobiles, stationary, and small mobiles because of its low operating temperature and high efficiency.

Conventionally, a platinum-based catalyst using platinum or a platinum alloy having high oxygen reduction activity is used for the electrode catalyst of these fuel cells in order to convert oxygen, which is a positive electrode side active material, into water or hydroxide ion. However, development of catalysts other than platinum-based catalysts (called non-platinum-based catalysts) is required in terms of cost, resource amount, and supply stability. However, the current performance of non-platinum-based catalysts is not sufficient compared to platinum-based catalysts, so technological development of catalysts that significantly reduce the amount of platinum used and non-platinum-based catalysts that do not use platinum has been promoted. There is. (Non-patent document 1, patent documents 1-3, etc.)

As such a non-platinum-based catalyst, for example, Patent Document 2 proposes a carbon material in which a carbonized product obtained by mixing a polymer metal complex with a carbon additive and subjecting to heat treatment is doped with nitrogen. Such a nitrogen-doped carbon material can be used as a non-platinum-based catalyst having oxygen reduction activity. Patent Document 3 proposes that a carbon material obtained by introducing an ion-exchange functional group into a surface-treated carbon material by a grafting reaction can be used as a non-platinum-based catalyst.

Non-platinum-based catalysts are being actively developed because they are more economical and more cost-effective than platinum-based catalysts, but their performance is not yet sufficient, and batteries similar to those using platinum-based catalysts are used. In order to obtain performance, it is necessary to increase the thickness of the catalyst layer and increase the number of catalyst particles in the catalyst layer. Further, there is a problem in that the gas permeability deteriorates due to the increase in thickness, which causes a decrease in current amount and a decrease in electromotive force. Although there are such technical problems, no means for solving them has been found.

JP, 2011-6283, A Japanese Patent Laid-Open No. 2008-28725 JP, 2009-295441, A

SCIENCE (VOL.332, pp. 443-447, 2011)

The problem to be solved by the present invention is to provide a catalyst layer for a fuel cell having good gas diffusibility by adding a hydrophobic carbon material in a non-platinum-based carbon-based catalyst having a problem in gas diffusivity of the catalyst layer. It is to provide a catalyst paste for a fuel cell to be produced. Another object of the present invention is to provide a fuel cell catalyst electrode comprising a fuel cell catalyst layer formed of the fuel cell catalyst paste composition, a fuel cell electrode membrane assembly, and a fuel cell having excellent cell performance. ..

The present inventors have accomplished the present invention as a result of earnest researches for solving the above problems. A first invention is a catalyst paste composition for a fuel cell, comprising a non-platinum-based carbon catalyst, a carbon material, a solvent, and a binder,
The hydrophilicity of the carbon material (the ratio of the BET specific surface area (BET _H2O ) using water as an adsorbing species and the BET specific surface area (BET _N2 ) using nitrogen as an adsorbing species (BET _H2O /BET _N2 )) is 0.5. Is less than
The hydrophilicity of the non-platinum-based carbon-based catalyst is 0.6 to 4.9,
The catalyst paste composition for a fuel cell is characterized in that a mass ratio of the carbon material to the non-platinum-based carbon catalyst is 0.1 to 50 mass %.

The second invention is that the non-platinum-based carbon catalyst has a hydrophilicity of 0.6 to 2.5, the carbon material has a BET _N2 of 100 m ² /g or more, and a pore volume of 0.4 cm ³ /g or more. Further, the present invention relates to the above catalyst paste composition for fuel cells, which has a bulk density of 0.4 g/cm ³ or less.

A third invention relates to the catalyst paste composition for a fuel cell, wherein the carbon material has a hydrophilicity of 0.15 or less and BET _N2 of 500 m ² /g or more.

A fourth invention relates to a fuel cell catalyst layer formed from the above fuel cell catalyst paste composition.

A fifth aspect of the present invention relates to a fuel cell catalyst electrode comprising the fuel cell catalyst layer and a conductive support.

A sixth invention relates to a fuel cell electrode membrane assembly including a solid polymer electrolyte membrane and the fuel cell catalyst electrode.

A seventh invention relates to a fuel cell comprising at least one of the fuel cell catalyst electrode and the fuel cell electrode membrane assembly.

According to the present invention, there is provided a catalyst paste for a fuel cell, in which a non-platinum-based carbon catalyst, a solvent, and a hydrophobic carbon material are added to a binder to produce a fuel cell catalyst layer having good gas diffusion properties. Is possible. Further, by obtaining a catalyst electrode for a fuel cell and a fuel cell electrode membrane assembly including a catalyst layer for a fuel cell formed from the catalyst paste composition for a fuel cell, excellent cell performance with good gas diffusivity can be obtained. It becomes possible to provide a fuel cell.

<Non-platinum-based carbon catalyst>
The non-platinum-based carbon-based catalyst is a multi-component system mainly composed of aggregates of carbon (C) atoms, has physical/chemical interactions (bonds) between the constituent units, and is a different element. , A catalyst containing a heteroatom such as nitrogen (N), boron (B), or phosphorus (P) or a base metal element, and mixed with one or more kinds of a carbon material or a compound having a nitrogen element and a base metal element. It can be obtained by heat treatment, and conventionally known materials can be used.
Containing a hetero atom and a base metal element is important for having oxygen reduction activity. Generally, in the case of a non-platinum-based carbon-based catalyst, as a catalytic active point, a structure (referred to as a base metal-N4 structure) in which four nitrogens are arranged on a plane centering on the base metal element on the surface of the carbon material The base metal element in, the carbon atom in the vicinity of the hetero atom introduced at the edge portion of the surface of the carbon material, and the like can be mentioned.
Such a non-platinum-based carbon catalyst has an oxygen reduction catalytic ability like the conventionally known platinum-supported carbon material, and can be suitably used as a fuel cell electrode catalyst. The non-platinum-based carbon catalyst can be used for both the positive electrode and the negative electrode, but it is often used as the positive electrode.

In the non-platinum-based carbon catalyst according to the present invention, the doping amount of nitrogen, boron, phosphorus, etc. (the content of nitrogen, boron, phosphorus, etc. in the non-platinum-based carbon catalyst) is 0.1 to 40 mol, respectively. % Indicates good catalytic activity for oxygen reduction. Further, when nitrogen and boron are simultaneously doped, the interaction between the two shows higher electrode activity. When both nitrogen and boron are doped, the atomic ratio (B/N) is 0.2 to 0.4, preferably 0.06 to 1.5, and the molar ratio ((B+N) /C) is preferably 0.03 to 0.4. Within these ranges, a highly active non-platinum-based carbon catalyst can be obtained.

<Method for producing non-platinum-based carbon catalyst>
The method for producing the non-platinum-based carbon-based catalyst is not particularly limited, and a method of supporting a macrocyclic compound on the surface of the carbon material for carbonization, a method of carbonizing a mixture of the macrocyclic compound and an organic material, an organic material containing no macrocyclic compound Conventionally known methods such as a method of carbonizing a material and a method of using carbon particles derived from an inorganic carbon material can be used. A preferred production method is a method in which carbon particles derived from an inorganic carbon material and a compound containing a nitrogen element and a base metal element are mixed and then heat-treated in an inert gas atmosphere to obtain a non-platinum-based carbon catalyst. The heat treatment may be performed in multiple stages at a plurality of temperatures, and may include a step of washing with acid and drying after or during the heat treatment step.

In the case of mixing the raw materials when manufacturing the non-platinum-based carbon-based catalyst, it is preferable that the raw materials are uniformly mixed and compounded. Examples of the mixing method include dry mixing and wet mixing. As the mixing device, the following dry mixing device or wet mixing device can be used.
Examples of the dry mixing device include a roll mill such as a two-roll or three-roll roll, a high-speed agitator such as a Henschel mixer and a supermixer, a fluid energy grinder such as a micronizer and a jet mill, an attritor, and a particle composite made by Hosokawa Micron. Examples of the apparatus include "Nanocure", "Nobilta", "Mechanofusion", powder surface reforming apparatus "Hybridization system", "Mechanomicros", "Millaro" manufactured by Nara Machine Works.
When using a dry-mixing device, other raw materials may be added directly to the raw material powder which is the base material in a powder form, but in order to prepare a more uniform mixture, a small amount of the other raw material may be added in advance. A method is preferred in which it is dissolved or dispersed in a solvent and then added while unraveling the agglomerated particles of the raw material powder that is the matrix. Further, in some cases, heating may be preferable in order to improve the processing efficiency.

Among the raw materials, there are materials that are solid at room temperature but have a low melting point, softening point, or glass transition temperature of less than 100°C. When using these materials, it may be possible to mix more uniformly by melting and mixing under heating rather than mixing at room temperature.

Examples of the wet mixing device include mixers such as a disper, a homomixer, and a planetary mixer;
Homogenizers such as "Clearmix" manufactured by M Technique Co., Ltd. or "Filmix" manufactured by PRIMIX Co., Ltd.;
Media conditioner such as paint conditioner (manufactured by Red Devil), ball mill, sand mill (“Dyno mill” manufactured by Shinmaru Enterprises, etc.), attritor, pearl mill (“DCP mill” manufactured by Eirich, etc.), or coball mill;
Wet jet mill ("Genus PY" manufactured by Genus, "Starburst" manufactured by Sugino Machine, "Nanomizer" manufactured by Nanomizer, "Clear SS-5" manufactured by M Technique, "Micros" manufactured by Nara Machinery Co., Ltd. "Medialess disperser such as;
Other examples include, but are not limited to, roll mills and kneaders. Further, as the wet mixing device, it may be preferable to use a device which has been subjected to a metal mixing prevention treatment from the device.

For example, when using a media type disperser, a method in which the agitator and vessel are made of ceramic or resin, or a metal agitator and vessel surface are treated with tungsten carbide spray or resin coating Is preferably used. As the medium, it is preferable to use glass beads or ceramic beads such as zirconia beads or alumina beads. Moreover, when using a roll mill, it is preferable to use a ceramic roll. Only one type of dispersion device may be used, or a plurality of types of devices may be used in combination. Further, in order to improve the wettability and dispersibility of the raw material in the solvent, a general dispersant having a hydrophilic functional group can be added together, dispersed and mixed.

In the case where each raw material is not uniformly dissolved during wet mixing, a commercially available dispersant is added together, dispersed and mixed in order to improve wettability and dispersibility of each raw material in a solvent. Good.

In the case of wet mixing, a step of drying the mixed precursor is required. In this case, as the drying device, a shelf dryer, a rotary dryer, a flash dryer, a spray dryer, a stirring dryer, a freeze dryer and the like can be preferably used.

In the method of heat-treating a mixture of a carbon material and a compound having a nitrogen element and a base metal element, the heating temperature is different from the viewpoint that the structure of the active site is likely to be stable, although it depends on the carbon material as a raw material, the compound having the nitrogen element and the base metal element. 500-1100 degreeC is preferable.

The atmosphere in the heat treatment is preferably an inert gas atmosphere such as nitrogen or argon, or a reducing gas atmosphere in which hydrogen is mixed with an inert gas. This is because it is necessary to carbonize the raw material by incomplete combustion as much as possible to leave nitrogen elements, base metal elements, etc. on the surface of the non-platinum-based carbon catalyst. Further, in order to suppress the reduction of the nitrogen element in the non-platinum-based carbon-based catalyst during the heat treatment, the heat treatment can be performed in an ammonia gas atmosphere containing a large amount of nitrogen element.

Further, the heat treatment is not limited to the method of performing the treatment in one step at a constant temperature. For example, when two or more kinds of carbon materials having different decomposition temperatures or compounds having a nitrogen element and a base metal element are mixed, heat treatment may be performed in several stages having different heating temperatures according to the thermal decomposition temperature of each component. It is possible. This may allow more active sites to remain more efficiently.

Examples of the method for producing a non-platinum-based carbon catalyst include a method including a step of washing the non-platinum-based carbon catalyst obtained by the heat treatment with an acid, and drying. The acid used here is not particularly limited as long as it can elute the base metal component that does not act as an active site present on the surface of the non-platinum-based carbon catalyst obtained by the heat treatment. Concentrated hydrochloric acid, diluted sulfuric acid and the like, which have low reactivity with the non-platinum-based carbon catalyst and have a strong dissolving power for the base metal component, are preferable. As a specific cleaning method, an acid is added to a glass container, a non-platinum-based carbon-based catalyst is added thereto, the mixture is stirred for several hours while being dispersed, and then allowed to stand to remove a supernatant. Then, the above method is repeated until coloring of the supernatant is no longer confirmed, and finally, a method of removing the acid by filtration and washing with water and drying. When the non-platinum-based carbon-based catalyst having a carbon element near the nitrogen element in the edge portion as a catalyst active point is washed with an acid, a base metal component that does not act as an active point on the surface is removed and the catalytic activity is improved. There is.

<Carbon material>
The carbon material in the present invention is not particularly limited as long as it is a carbon particle derived from an inorganic material and/or a carbon particle obtained by heat-treating an organic material.
Carbon particles derived from inorganic materials include carbon black (furnace black, acetylene black, Ketjen black, medium thermal carbon black), activated carbon, graphite, carbon nanotubes, carbon nanofibers, carbon nanohorns, graphene nanoplatelets, nanoporous carbon, Carbon fiber etc. are mentioned. Carbon materials have various physical properties and costs such as particle size, shape, BET specific surface area, pore volume, pore size, bulk density, DBP oil absorption, surface acidity/basicity, surface hydrophilicity, and conductivity depending on the type and manufacturer. Since it is different, select the most suitable material according to the intended use and required performance.
The organic material that becomes carbon particles by heat treatment is not particularly limited as long as it is a material that becomes carbon particles after heat treatment. It may be preferable to use an organic material containing the same hetero element in advance in order to make the carbon particles after the heat treatment contain a hetero element serving as an active site. Specific organic materials include phenolic resins, polyimide resins, polyamide resins, polyamideimide resins, polyacrylonitrile resins, polyaniline resins, phenol formaldehyde resin resins, polyimidazole resins, polypyrrole resins, poly Examples thereof include benzimidazole-based resin, melamine-based resin, pitch, brown coal, polycarbodiimide, biomass, protein, humic acid, and their derivatives.
These carbon materials are used alone or in combination of two or more.

Examples of commercially available carbon materials include, for example,
Ketjen Black, such as EC-300J and EC-600JD, manufactured by Lion Corporation;
Furnace black manufactured by Tokai Carbon Co., such as Toka Black #4300, #4400, #4500, and #5500;
Furnace black manufactured by Degussa, such as Printex L;
Raven 7000, 5750, 5250, 5000 ULTRAIII, 5000 ULT
RAMB, Conductex SC ULTRA, 975 ULTRA, PUER BLACK 100, 115, 205, and other Columbyan furnace blacks;
Furnace black manufactured by Mitsubishi Chemical Corporation, such as #2350, #2400B, #2600B, #30050B, #3030B, #3230B, #3350B, #3400B, and #5400B;
Furnace black manufactured by Cabot, such as MONARCH 1400, 1300, 900, Vulcan XC-72R, and BlackPearls 2000;
Furnace black manufactured by TIMCAL, such as Ensaco250G, Ensaco260G, Ensaco350G, and SuperP-Li;
Denka Black, Denka Black HS-100, FX-35 and other acetylene black manufactured by Denki Kagaku Kogyo Co., Ltd.;
Showa Denko carbon nanotubes such as VGCF, VGCF-H, and VGCF-X;
Carbon nanotube manufactured by Meijo Nano Carbon Co., Ltd.;
xGnP-C-750, xGnP-M-5 and other graphene nanoplatelets manufactured by XGS Sciences;
Easy-N nanoporous carbon;
Carbon fiber manufactured by Gunei Chemical Industry Co., Ltd. such as Kynol carbon fiber and Kynol activated carbon fiber;
However, the present invention is not limited to these.

In the present specification, the specific surface area means a surface area per unit mass of a sample, and can be determined by a gas (N ₂ or H ₂ O) adsorption method. The BET method is used as the analysis method, and the amount of adsorbed monomolecule is calculated from the intercept and the slope of the straight line obtained from the plot of the relative pressure (P/P ₀ =0.05 to 0.3) and the amount of adsorbed gas. The specific surface area can be calculated.

<Hydrophilicity>
The hydrophilicity (BET _H2O /BET _N2 ) is an index of the hydrophilicity of the entire surface of the non-platinum-based carbon catalyst and the carbon material. By determining the BET specific surface area (BET _H2O ) using water as the adsorbate, the BET specific surface area (BET _N2 ) using nitrogen as the adsorbing species and the total surface area of the non-platinum-based carbon-based catalyst and the carbon material are obtained. The ratio of the hydrophilic surface to the can be obtained.

When the hydrophilicity of the non-platinum-based carbon catalyst surface is within the range of 0.6 to 2.5, the non-platinum-based carbon catalyst surface is sufficiently hydrophilic and attracted to high hygroscopicity, and It is preferable because the conductivity of protons required for power generation is improved.

When the hydrophilicity of the carbon material surface is 0.5 or less, more preferably 0.15 or less, the surface of the carbon material is hydrophobic, and water molecules generated by the reaction are easily repelled to prevent flooding by water. ,preferable.

When the mass ratio of the carbon material to the non-platinum-based carbon catalyst is 0.1 to 50 mass %, the hydrophilic part and the hydrophobic part in the catalyst layer for the fuel cell are well balanced, and the protons are transported to the catalyst. And the drainage efficiency of water molecules generated by the reaction are improved, which is preferable.

<Pore volume>
The larger the pore volume, the higher the porosity and the better the gas transportability in the catalyst layer, which is preferable. The preferable pore volume here is 0.4 cm ³ /g or more.

<Bulk density>
The bulk density can be determined according to JIS M 8811 by adjusting the sample to an air-dried sample, introducing the sample into a graduated cylinder, and dividing the sample weight by the sample volume after tapping. When the bulk density is 0.4 g/cm ³ or less, the diffusibility of oxygen gas in the catalyst layer is improved, which is preferable. Furthermore, it is possible to better discharge the water generated in the catalyst layer.

<Solvent>
Examples of the solvent include alcohol solvents such as ethanol, isopropyl alcohol, benzyl alcohol and terpineol; nitrile solvents such as acetonitrile and propionitrile; halogen solvents such as chloroform, dichloromethane and chlorobenzene; ether solvents such as diethyl ether and tetrahydrofuran; Ester-based solvents such as ethyl acetate and butyl acetate; Ketone-based solvents such as acetone, methyl ethyl ketone, cyclohexanone and isophorone; Carbonate-based solvents such as diethyl carbonate and propylene carbonate; Hydrocarbon-based solvents such as hexane, octane, toluene and xylene; Dimethylformamide, dimethylacetamide, dimethylsulfoxide, 1,3-dimethylimidazolinone, N-methylpyrrolidone, water and the like can be used, but are not limited thereto. Further, two or more kinds of solvents may be mixed and used.

When a proton conductive polymer is used as the binder, water or a solvent having a high affinity for water is preferable as the main solvent, and alcohol is particularly preferable. As such an alcohol, for example, a monohydric alcohol or a polyhydric alcohol having a boiling point of about 80 to 200° C. can be used, and an alcohol solvent having 4 or less carbon atoms is preferable. Specific examples include 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol and the like. Alcohol is used alone or in combination of two or more. Among these monohydric alcohols, 2-propanol, 1-butanol and t-butanol are preferable. As the polyhydric alcohol, specifically, from the problems of compatibility with a resin having proton conductivity, and drying efficiency when used as a catalyst paste, for example, propylene glycol, ethylene glycol and the like are preferable, and among them, propylene glycol is particularly preferable. preferable.

<Binder>
As the binder, it is possible to use conventionally known ones, for example, acrylic resin, polyurethane resin, polyester resin, phenol resin, epoxy resin, phenoxy resin, urea resin, melamine resin, alkyd resin, formaldehyde resin, silicone resin, Fluorine resin, cellulose resin such as carboxymethyl cellulose, synthetic rubber such as styrene-butadiene rubber and fluorine rubber, conductive resin such as polyaniline and polyacetylene, etc., containing fluorine atom such as polyvinylidene fluoride, polyvinyl fluoride, and tetrafluoroethylene A high molecular compound is mentioned. Further, it may be a modified product, mixture, or copolymer of these resins, and may be a water-soluble resin or a water-dispersible resin. These binders may be used alone or in combination of two or more. Moreover, you may use what has a dispersion effect depending on the kind of solvent.
As the binder of the catalyst layer for the fuel cell, a polymer having proton conductivity is more preferable from the viewpoint of conducting protons in the membrane, but a liquid electrolyte is used as seen in metal-air cells and microbial fuel cells. This is not the case. The proton conductive polymer refers to a binder having a hydrophilic functional group, and a polymer having a proton conductivity of 100% RH and 10 ⁻³ Scm ⁻¹ or more at 25° C. is preferable.
Here, examples of the hydrophilic functional group include a sulfo group, a carboxy group, an acidic functional group such as a phosphoric acid group, a hydroxyl group, and a basic functional group such as an amino group, but from the viewpoint of proton dissociation, a sulfo group, A carboxy group, a phosphate group, and a hydroxyl group are more preferable.
As the polymer having proton conductivity, sulfo group-introduced olefin resin (polystyrene sulfonic acid, polyvinyl sulfonic acid, etc.), polyimide resin, phenol resin, polyether ketone resin, polybenzimidazole resin, and polystyrene are used. -Based resins, sulfonic acid-doped products of styrene/ethylene/butylene/styrene copolymers, resins having sulfonic acid such as perfluorosulfonic acid-based resins;
Resins having carboxylic acids such as polyacrylic acid and carboxymethyl cellulose;
Resin having a hydroxyl group such as polyvinyl alcohol;
A resin having an amino group such as polyallylamine, polydiallylamine, polydiallyldimethylammonium salt, and a polybenzimidazole-based resin formed with an acid at the imidazole moiety;
Resins having other hydrophilic functional groups such as polyacrylamide, polyvinylpyrrolidone, and polyvinylimidazole can be given. In particular, the perfluorosulfonic acid-based resin is chemically very stable by introducing a fluorine atom having a high electronegativity, has a high dissociation degree of a sulfo group, and can realize high proton conductivity. Specific examples of such a proton conductive polymer include “Nafion” manufactured by DuPont. Usually, the proton conductive polymer is used as an aqueous alcohol solution containing about 5 to 30% by mass of the polymer. As the alcohol, for example, methanol, propanol, ethanol diethyl ether or the like is used.
In addition, a water-repellent binder may be more preferable from the viewpoint of water generated by the reaction of oxygen and hydrogen ions in the catalyst layer on the positive electrode side, and drainage of this excess water. The water-repellent binder refers to a binder having no hydrophilic functional group, and preferably has a surface tension lower than that of water (about 72 dyn/cm). For example, a fluorinated resin, an olefin resin such as polypropylene or polyethylene, or a silicon resin such as polydimethylsiloxane can be used.

<Catalyst paste composition for fuel cell>
The fuel cell paste composition of the present invention contains at least a non-platinum-based carbon-based catalyst, a carbon material, a solvent, and a binder. If the hydrophilicity of the carbon material is 0.5 or less and the mass ratio of the carbon material to the non-platinum-based carbon-based catalyst is within the range of 0.1 to 50 mass %, other ratios are not particularly limited. Instead, it is appropriately selected within a wide range.

<Catalyst layer for fuel cell>
The catalyst layer for a fuel cell may be formed by directly applying the catalyst paste composition for a fuel cell described above to a conductive support (carbon paper or the like) and drying the catalyst paste composition for a fuel cell using Teflon. It is applied and dried on a peelable transfer substrate such as a (registered trademark) sheet.

The method for applying the catalyst paste composition for fuel cells is not particularly limited, and examples thereof include knife coater, bar coater, blade coater, spray, dip coater, spin coater, roll coater, die coater, curtain coater, and screen. A general method such as printing can be applied.

After coating, the coating film (fuel cell catalyst layer) is formed by drying. The drying temperature is usually about 40 to 120°C, preferably about 75 to 95°C. The drying time is usually about 5 minutes to 2 hours, preferably about 30 minutes to 1 hour, although it depends on the drying temperature. The power generation performance is good when the thickness of the fuel cell catalyst layer after coating and drying is 10 μm or more.

The pressure level when transferring the above fuel cell catalyst layer to the solid polymer electrolyte membrane is usually about 0.5 to 30 MPa, preferably about 1 to 20 MPa in order to avoid transfer failure. It is more preferable to heat the pressing surface during this pressing operation. The heating temperature is usually 200° C. or lower, preferably about 120 to 150° C., in order to avoid damage or modification of the solid polymer electrolyte membrane.

<Catalyst for fuel cell>
As the catalyst of the fuel cell catalyst layer on the positive electrode side in the present invention, a non-platinum-based carbon-based catalyst is used as described above. On the other hand, as the catalyst used in the fuel cell catalyst layer on the negative electrode side, known or commercially available catalysts can be used.

Examples of the catalyst for polymer electrolyte fuel cells include catalyst particles supported on a catalyst carrier.
The catalyst particles are not particularly limited as long as they promote the oxidation of hydrogen, and examples thereof include platinum, gold, silver, palladium, iridium, rhodium, ruthenium and alloys thereof.
Examples of the catalyst carrier include carbon particles, oxide particles, and nitride particles.
Examples of the carbon particles include the same as those exemplified in the description of the carbon material used as the main constituent component of the non-platinum carbon-based catalyst.
Examples of the oxide particles include indium oxide, tin oxide, zinc oxide, titanium oxide, silica and alumina.
Examples of the nitride particles include titanium nitride, zirconium nitride, niobium nitride, tantalum nitride, chromium nitride, vanadium nitride and the like.

The loading rate of the catalyst particles on the catalyst carrier is not particularly limited. When platinum is used as the catalyst particles and carbon particles are used as the catalyst carrier, the catalyst particles can be usually loaded in an amount of about 1 to 70 mass% with respect to 100 mass% of the catalyst particles.

Examples of commercially available catalyst materials for fuel cells include:
Platinum-supporting carbon particles such as TEC10E50E, TEC10E70TPM, TEC10V30E, TEC10V50E;
Platinum-ruthenium alloy-supporting carbon particles such as TEC66E50 and TEC62E58;
Can be purchased from Tanaka Kikinzoku Kogyo Co., Ltd., but is not limited thereto.

<Fuel cell electrode membrane assembly>
The fuel cell electrode membrane assembly in the present invention is formed by closely adhering a fuel cell catalyst layer to one or both sides of a proton conductive solid polymer electrolyte membrane, and further, to one or both sides thereof, carbon paper. And the like are meant to be provided in close contact with a conductive support.

As a method for manufacturing a fuel cell electrode membrane assembly, a fuel cell catalyst layer previously formed on a transfer substrate is transferred onto one or both surfaces of a solid polymer electrolyte membrane, and then a conductive support is thermocompression bonded. Then, a method of producing an electrode membrane assembly for a fuel cell can be mentioned. Further, a fuel cell electrode membrane assembly may be prepared by thermocompression bonding a fuel cell catalyst layer previously formed on a conductive support to one surface or both surfaces of the solid polymer electrolyte membrane.

In the above-mentioned fuel cell electrode membrane assembly, the pressure level when thermocompression-bonding the conductive support to the fuel cell catalyst layer and the solid polymer electrolyte membrane is usually about 0.1 to 50 MPa, preferably It is preferably about 1 to 30 MPa. The heating temperature is usually 200° C. or lower, preferably about 120 to 150° C., in order to avoid damage and denaturation of the solid polymer electrolyte membrane.

<Solid polymer electrolyte membrane>
Examples of the solid polymer electrolyte membrane include perfluorosulfonic acid-based fluorine ion exchange resins and the like. By introducing a fluorine atom with high electronegativity, it is chemically very stable, the dissociation degree of the sulfo group is high, and high ionic conductivity can be realized. Specific examples include "Nafion" manufactured by DuPont, "Flemion" manufactured by Asahi Glass Co., Ltd., "Aciplex" manufactured by Asahi Kasei Co., Ltd., and "Gore Select" manufactured by Gore. The thickness of the electrolyte membrane is usually about 20 to 250 μm, preferably about 10 to 80 μm.

<Conductive support>
As the conductive support, various conductive supports that form the negative electrode or the positive electrode can be used.However, in many fuel cells represented by polymer electrolyte fuel cells, the positive electrode takes in oxygen in the air and On the side, it is preferably a porous or fibrous support through which a gas can pass and diffuse so as to take up hydrogen. Furthermore, since it is necessary to take in and out electrons, a material having conductivity must be used. Carbon paper, carbon felt, carbon cloth and the like made of a carbon material are preferable. Specific examples include "TGP-H-090" manufactured by Toray Industries, Inc. These conductive supports are also called gas diffusion layers or GDLs in fuel cells.

<Catalyst electrode for fuel cell>
The fuel cell catalyst electrode in the present invention means that the above-mentioned fuel cell catalyst layer is formed on a conductive support, and the above-mentioned fuel cell catalyst paste composition is directly applied to the conductive support and It may be formed by drying, or may be formed as a part of the fuel cell electrode membrane assembly by contacting the catalyst layer for the fuel cell and the conductive support on the solid polymer electrolyte membrane.

<Transfer substrate>
The transfer base material is a film base material for forming a fuel cell catalyst layer by applying a fuel cell catalyst paste composition and transferring the catalyst layer on the transfer base material to a solid polymer electrolyte membrane such as Nafion. Is. The transfer base material is preferably an inexpensive and easily available polymer film, and more preferably polytetrafluoroethylene, polyimide, polyethylene terephthalate or the like. Specific examples include Teflon (registered trademark) sheets and the like. The thickness of the transfer substrate is usually about 6 to 100 μm, preferably about 10 to 50 μm, and more preferably about 15 to 30 μm from the viewpoint of handleability and economy.

<Fuel cell>
Although the fuel cell can be classified into several types depending on the electrolyte used, a polymer electrolyte fuel cell, a microbial fuel cell, and a metal-air cell are preferable for the fuel cell of the present invention.

<Polymer fuel cell>
The solid polymer fuel cell includes a separator 1, a gas diffusion layer 2, a negative electrode catalyst layer (fuel electrode) 3, a positive electrode catalyst layer (air electrode) 5, and a gas diffusion layer, which are arranged to face each other so as to sandwich a solid polymer electrolyte 4. It is composed of a layer 6 and a separator 7.
The separators 1 and 7 supply and discharge a reaction gas such as a fuel gas (hydrogen) and an oxidant gas (oxygen). Then, when the reaction gas is uniformly supplied to the negative electrode and the positive electrode catalyst layers 3 and 5 through the gas diffusion layers 2 and 6, the gas phase is generated at the boundary between the catalyst provided in both electrodes and the solid polymer electrolyte 4. A three-phase interface of (reaction gas), liquid phase (solid polymer electrolyte membrane), and solid phase (catalyst possessed by both electrodes) is formed. Then, a direct current is generated by causing an electrochemical reaction.

In the above electrochemical reaction,
Positive electrode side: O ₂ +4H ⁺ +4e ⁻ →2H ₂ O
Negative electrode side: H ₂ →2H ⁺ +2e ⁻
The H ⁺ ion (proton) generated on the negative electrode side moves in the solid polymer electrolyte 4 toward the positive electrode side, and e ⁻ (electron) moves to the positive electrode side through an external load. ..

On the other hand, on the positive electrode side, oxygen contained in the oxidant gas reacts with H ⁺ ions and e ⁻ that have moved from the negative electrode side to generate water. As a result, the fuel cell described above generates DC power from hydrogen and oxygen to generate water.

As a fuel source for the negative electrode, a liquid fuel such as methanol or ethanol may be used instead of hydrogen gas. At this time, a liquid fuel such as methanol or ethanol is oxidized by the negative electrode catalyst layer to generate e− (electrons) and H+ ions (protons), and a reaction similar to that of the fuel cell using hydrogen gas described above is performed on the positive electrode side. It can generate electricity when it occurs.

<Cell voltage drop of fuel cell>
The cell voltage drop from the theoretical electromotive force is called polarization, and its magnitude is called overvoltage. There are three types of overvoltages: activation overvoltage, resistance overvoltage, and concentration overvoltage. The activation overvoltage is a voltage drop corresponding to the loss of activation energy consumed for proceeding the reaction. The resistance overvoltage is a voltage drop that occurs when electrons or ions move through the contact resistance of the constituent members and the separator, electrodes, electrolyte, etc. inside the battery. The concentration overvoltage is a voltage drop that occurs because the reaction gas does not easily reach the catalyst surface, which is the reaction site, due to the clogging (flooding) of the catalyst layer pores caused by the water produced by the electrochemical reaction (flooding) and the decrease in the reaction gas concentration. is there.

<Separation of overvoltage>
The resistance overvoltage can be measured by a current interruption method, an AC impedance method, or the like. The corrected output power is often reported as IR-free. The reaction on the negative electrode side is much faster than that on the positive electrode side, and the IV characteristic in IR-free can be regarded as the characteristic on the positive electrode side. A Tafel plot is obtained by plotting the cell voltage of IR-free on the vertical axis and plotting the current density in logarithm on the horizontal axis. The cell voltage of IR-free decreases almost linearly in the low current density region and gradually deviates from this straight line in the high current density region. The slope of this straight line is called the Tafel slope. The activation overvoltage is the cell voltage difference at the intersection A between the current density expressed in logarithm at the time of the test and the cell voltage characteristic that decreases linearly with reference to the cell voltage of IR-free of 900 mV (equation (1)).

In the formula, η _{a is the} activation overvoltage, b is the Tafel slope, i is the current density at the time of the test, and i _0.9 is the current density when the cell voltage of IR-free is 900 mV.
The concentration overvoltage is calculated by the equation (2).

In the formula, η _{d is the} concentration overvoltage, and V is the cell voltage of IR-free.

<Microbial fuel cell>
A microbial fuel cell is a battery that promotes the decomposition of organic substances while collecting electrons generated by metabolic activity in which microorganisms anaerobically decompose organic substances. The negative electrode holds an electron-donating microorganism, which metabolizes using an organic substance contained in organic wastewater or the like to generate e ⁻ (electron) and H ⁺ ion (proton). On the positive electrode side, power can be generated by an oxygen reduction reaction using the generated e ⁻ (electrons) and H ⁺ ions (protons).
As the structure of the microbial fuel cell, an electroconductive support serving as a negative electrode holding electron-donating microorganisms and a conductive support serving as a positive electrode coated with a fuel cell catalyst were inserted into a liquid tank containing organic wastewater and the like. A one-tank type structure or a two-tank type structure in which a negative electrode tank and a positive electrode tank are separated by using a solid polymer membrane, such as a solid polymer fuel cell, may be used.
As the positive electrode, a catalyst electrode for a fuel cell in which the catalyst paste composition for a fuel cell of the present invention is applied to a conductive support, or an electrode membrane assembly for a fuel cell can also be preferably used.

<Electron-donating microorganisms for microbial fuel cells>
Examples of the electron-donating microorganisms for the microbial fuel cell include Shewanella genus, Pseudomonas genus, Rhodoferax genus, and Geobacterium genus.

<Metal-air battery>
A metal-air battery uses a metal as a negative electrode active material, and can generate electricity by utilizing an oxygen reduction reaction on the positive electrode side by the generated e ⁻ (electrons) and metal ions, and can be charged and discharged to generate secondary electricity. It also functions as a battery.
The structure of the metal-air battery includes a negative electrode having a metal as a negative electrode active material, a conductive support serving as a positive electrode coated with a fuel cell catalyst, etc., and an electrolyte responsible for conducting metal ions between the positive electrode and the negative electrode. It consists of a layer and a separator.
As the positive electrode, a catalyst electrode for a fuel cell in which the catalyst paste composition for a fuel cell of the present invention is applied to a conductive support, or an electrode membrane assembly for a fuel cell can also be preferably used.

<Negative electrode for metal-air batteries>
The metal-air battery negative electrode has an electrolyte layer disposed so as to come into contact with a negative electrode tank having a negative electrode active material. The negative electrode active material usually has a metal element that becomes a conductive ion. Examples of the metal element include lithium (Li), sodium (Na), zinc (Zn), iron (Fe), aluminum (Al), magnesium (Mg), manganese (Mn), silicon (Si), titanium ( Ti), chromium (Cr), vanadium (V), etc. can be mentioned. Above all, Li is preferable because a battery having a high energy density can be obtained. Further, not only a simple metal but also an alloy, a metal oxide, a metal nitride and the like can be mentioned, but not limited to these, and a conventionally known one applied to a metal-air battery can be applied. You can

<Metal-air battery electrolyte layer>
The electrolyte layer conducts metal ions between the positive electrode and the negative electrode of the above metal-air battery. The type of metal ion varies depending on the type of the negative electrode active material described above, and the form thereof is not particularly limited as long as it has metal ion conductivity. For example, an aqueous solution or a non-aqueous solution may be applied, or a gel polymer electrolyte holding them in a polymer matrix, or a polymer electrolyte and an inorganic solid electrolyte may be used. Also, different electrolytes may be used on the positive electrode side and the negative electrode side by using a solid electrolyte or a separator.

Considering the conduction of lithium ions, an electrolyte solution containing an electrolyte containing lithium dissolved in water or a non-aqueous solvent is used.
As the electrolyte, LiBF ₄ , LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiCF ₃ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , Li(CF ₃ SO ₂ ) ₃ C. , LiI, LiBr, LiCl, LiAlCl, LiHF ₂ , LiSCN, LiBPh _{4 and the} like, but are not limited thereto.

The non-aqueous solvent is not particularly limited, for example,
Carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethylmethyl carbonate, and diethyl carbonate;
Lactones such as γ-butyrolactone, γ-valerolactone, and γ-octanoic lactone;
Glymes such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,2-methoxyethane, 1,2-ethoxyethane, and 1,2-dibutoxyethane;
Esters such as methyl formate, methyl acetate, and methyl propionate;
Sulfoxides such as dimethyl sulfoxide and sulfolane; and
Examples thereof include nitriles such as acetonitrile. Further, these solvents may be used alone or in combination of two or more kinds.

Further, when the above electrolytic solution is a polymer electrolyte which is held in a polymer matrix and is in the form of gel, the polymer matrix includes an acrylate resin having a polyalkylene oxide segment, a polyphosphazene resin having a polyalkylene oxide segment, and a polyphosphazene resin. Examples thereof include, but are not limited to, polysiloxane having an alkylene oxide segment.

<Metal-air battery separator>
Examples of the separator include polyethylene non-woven fabric, polypropylene non-woven fabric, polyamide non-woven fabric, and those obtained by subjecting them to hydrophilic treatment, but are not particularly limited thereto.

The following is an example of a method for evaluating the performance of a fuel cell. The fuel cell electrode membrane assembly was used as a 5 cm square sample, and two gaskets were inserted from both sides to prevent gas leakage, then two graphite plates were sandwiched as separators, and two current collector plates were attached from both sides. It is produced as a single cell. The humidified oxygen gas is supplied from the positive electrode (air electrode) side, and the humidified hydrogen gas is supplied from the negative electrode (fuel electrode) side to measure the cell characteristics.

The use of the catalyst paste composition, the catalyst layer, and the catalyst electrode in the present invention is not limited to the above fuel cell, and can be used for exhaust gas purification, water treatment purification and the like.

Hereinafter, the present invention will be described based on examples, but the present invention is not limited thereto.

<Synthesis of non-platinum-based carbon catalyst>
The following measuring instruments were used for the analysis of the non-platinum-based carbon catalyst.
BET specific surface area; nitrogen adsorption amount measurement (BELSORP-mini manufactured by Bell Japan Ltd.), water vapor adsorption amount measurement (BELSORP-18 manufactured by Bell Japan Ltd.)
The nitrogen adsorption amount was measured by pretreating the non-platinum-based carbon-based catalyst at 150° C. for 4 hours for dehydration, and measuring the nitrogen adsorption amount at the liquid nitrogen temperature (−196° C.). A nitrogen adsorption isotherm was obtained from the nitrogen adsorption amount, and the BET specific surface area (BET _N2 ) was calculated by the BET method.
The water vapor adsorption amount was measured by pretreating the non-platinum-based carbon-based catalyst in vacuum at 150° C. for 4 hours for dehydration and measuring the water vapor adsorption amount at 25° C. The water vapor isotherm was determined from the water vapor adsorption amount, and the BET specific surface area (BET _H2O ) was calculated by the BET method.

[Production Example 1: Non-platinum-based carbon catalyst (X1)]
Graphene nanoplatelets (XGscience, xGnP-C-750) and cobalt phthalocyanine (Tokyo Kasei) are weighed at a mass ratio of 1/1, and dry-mixed by a particle compounding device Mechanofusion (Hosokawa Micron). And a mixture was obtained. The above mixture was filled in an alumina crucible and heat-treated at 800° C. for 2 hours in a nitrogen atmosphere in an electric furnace to obtain a non-platinum carbon-based catalyst (X1). The hydrophilicity was 1.8.

[Production Example 2: Non-platinum-based carbon catalyst (X2)]
Graphene nanoplatelets (XGscience, xGnP-C-750) and cobalt phthalocyanine (Tokyo Kasei) are weighed at a mass ratio of 1/1, and dry-mixed by a particle compositing device Mechanofusion (Hosokawa Micron). And a mixture was obtained. The above mixture was filled in an alumina crucible and heat-treated at 400° C. for 2 hours in a nitrogen atmosphere in an electric furnace to obtain a non-platinum-based carbon catalyst (X2). The hydrophilicity was 4.9.

[Production Example 3: Non-platinum-based carbon catalyst (X3)]
Iron phthalocyanine (manufactured by Sanyo Dye Co., Ltd.) and Ketjen Black (manufactured by Lion Corp., EC-600JD) were weighed at a mass ratio of 1/1 and dry-mixed in a mortar to prepare a precursor. The precursor powder was filled in an alumina crucible and heat-treated at 700° C. for 2 hours in a nitrogen atmosphere in an electric furnace, and the obtained carbide was crushed in a mortar to obtain a non-platinum-based carbon catalyst (X3). Obtained. The hydrophilicity was 3.7.

[Production Example 4: Non-platinum-based carbon catalyst (X4)]
Phenol resin (PSM-4326 manufactured by Gunei Chemical Co., Ltd.) and iron phthalocyanine (manufactured by Sanyo Dye Co., Ltd.) were weighed at a mass ratio of 3.3/1 and wet-mixed in acetone. After the above mixture was distilled off under reduced pressure, it was ground in a mortar to obtain a precursor. The precursor powder was filled in an alumina crucible and heat-treated at 600° C. for 2 hours in a nitrogen atmosphere in an electric furnace to obtain a carbon sintered body (1). The carbon sintered body (1) was reslurried in concentrated hydrochloric acid and allowed to stand, and after precipitation of the carbon sintered body, the supernatant liquid was removed. The above operation is repeated until the supernatant is no longer colored, filtered, washed with water and dried, then crushed in a mortar, filled in an alumina crucible, and heat-treated at 800° C. for 1 hour in an ammonia furnace in an electric furnace, followed by carbon firing. A solid (2) was obtained. The carbon sintered body (2) was reslurried in concentrated hydrochloric acid and allowed to stand, and after the carbon sintered body was precipitated, the supernatant liquid was removed. The above operation was repeated until the supernatant was no longer colored, then filtered, washed with water, dried, and ground in a mortar to obtain a non-platinum-based carbon catalyst (X4). The hydrophilicity was 2.1.

[Production Example 5: Non-platinum-based carbon catalyst (X5)]
Polyvinylpyridine (PVP, manufactured by Aldrich) was dissolved in dimethylformamide, iron chloride hexahydrate in a mass ratio of 2/1 with respect to PVP was added, and the mixture was stirred at room temperature for 24 hours to obtain a polyvinylpyridine iron complex. The above-mentioned polyvinyl pyridine and Ketjen black (EC-600JD manufactured by Lion Corp.) were weighed at a mass ratio of 1/1 and dry-mixed in a mortar to obtain a precursor. The above precursor powder was filled in an alumina crucible and heat-treated at 800° C. for 2 hours in a nitrogen atmosphere in an electric furnace, and the obtained carbide was crushed in a mortar to obtain a non-platinum-based carbon catalyst (X5). Obtained. Hydrophilicity was 1.9

<Carbon material>
Table 1 shows the characteristics of the carbon material.
The following measuring instruments were used for the analysis of the carbon material.
-Measurement of BET specific surface area and pore volume; measurement of nitrogen adsorption amount (BELSORP-mini manufactured by Bell Japan Ltd.), measurement of adsorption amount of water vapor (BELSORP-18 manufactured by Bell Japan Ltd.)
The nitrogen adsorption amount was measured by pretreating the carbon material at 150° C. for 4 hours for dehydration, and measuring the nitrogen adsorption amount at the liquid nitrogen temperature (−196° C.). A nitrogen adsorption isotherm was obtained from the nitrogen adsorption amount, and the BET specific surface area was calculated by the BET method and the pore volume was calculated by the BJH method.
The water vapor adsorption amount was measured by pretreating the carbon material in vacuum at 150° C. for 4 hours for dehydration, and measuring the water vapor adsorption amount at 25° C. The water vapor isotherm was determined from the water vapor adsorption amount, and the BET specific surface area (BET _H2O ) was calculated by the BET method.
The bulk density was determined according to JIS M 8811 by adjusting the sample to an air-dried sample, placing the sample in a graduated cylinder, and dividing the sample weight by the sample volume after tapping.

Carbon material (1): Ketjen Black (Lion Co., EC-300J)
Carbon material (2): Graphene nanoplatelet (XGscience, xGnP-C-750)
Carbon material (3): Acetylene black (Denka Black HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.)
Carbon material (4): produced in Production Example 6

[Production Example 6: Carbon Material (4) <Synthesis of Modified Ketjen Black>]
Ketjen Black (manufactured by Lion Corporation, EC-300J) was added to an acetic acid sulfonate solution prepared from acetic anhydride (200 ml) and 96% sulfuric acid (10 ml) at room temperature, and sulfonated by stirring at 70° C. for 6 hours. A carbon material (4) was obtained.

<Preparation of catalyst paste composition for fuel cell>
[Example 1-a]
The non-platinum-based carbon-based catalyst (X1) is 10.0% by mass, the carbon material (1) is 3.0% by mass, 30% by mass of ultrapure water as a solvent, 30% by mass of 1-propanol, and 20 as a binder. 27% by mass of a mass% Nafion (Nafion (registered trademark)) dispersion solution (manufactured by DuPont, CStypeDE2020) was added, and the mixture was stirred and mixed with a disper (manufactured by Primix Co., Ltd., TK homodisper) for use in the fuel cell of the present invention. A catalyst paste composition (1) (solid content concentration 18.4 mass%) was prepared.

[Example 2-a to Example 14-a, Comparative Examples 1-a to 8-a]
Fuel cell catalyst paste compositions (2) to () in the same manner as in Example 1 except that the types and compositions of the non-platinum-based carbon catalyst (X1) and the carbon material (1) were changed as shown in Table 2. 22) was prepared.

<Preparation of Fuel Cell Catalyst Layer for Positive Electrode>
[Example 1-b Preparation of positive electrode fuel cell catalyst layer (1)]
The catalyst paste composition for a fuel cell (1) was coated on a Teflon (registered trademark) film with a doctor blade so that the basis weight of the non-platinum-based carbon catalyst after drying was 2 mg/cm ² , and the atmosphere was exposed to air. The catalyst layer (1) for a fuel cell for a positive electrode of the present invention (1) was prepared by drying at 95° C. for 60 minutes. The film thickness of the positive electrode fuel cell catalyst layer (1) was measured using a film thickness meter (Digimicro MH-15 manufactured by Nikon).

[Example 2-b to Example 16-b, Comparative Example 1-b to Comparative Example 8-b]
Instead of the catalyst paste composition for fuel cell (1), the catalyst paste compositions for fuel cell (2) to (22) were changed, or the basis weight of the non-platinum-based carbon catalyst after drying was changed. In the same manner as in Example 1, the cathode fuel cell catalyst layers (2) to (24) shown in Table 3 were produced. The film thickness of the positive electrode fuel cell catalyst layers (2) to (24) was measured using a film thickness meter (Digimicro MH-15 manufactured by Nikon).

<Preparation of Fuel Cell Catalyst Layer for Negative Electrode>
Here, the method for producing the anode fuel cell catalyst layer for use in producing the fuel cell electrode membrane assembly is described below.
Platinum catalyst-supporting carbon 4% by mass (Tanaka Kikinzoku Co., Ltd., platinum amount 46%), 1-propanol 56% by mass as a solvent, and water 20% by mass by stirring and mixing with a disper (primics, TK homodisper). A paste composition (solid content concentration 4%) was prepared. Then, 20 mass% of 20 mass% Nafion (Nafion (registered trademark)) dispersion solution (manufactured by DuPont, CStypeDE2020) was added, and the mixture was stirred and mixed with a disper (manufactured by Primex, TK homodisper) to obtain a catalyst ink ( A solid content concentration of 8%) was prepared. The obtained catalyst ink was applied onto a Teflon (registered trademark) film so that the basis weight of platinum catalyst-carrying carbon would be 0.46 mg/cm ² , and dried in an air atmosphere at 70° C. for 15 minutes. A catalyst layer for a fuel cell for a negative electrode was produced.

<Production of fuel cell electrode membrane assembly>
[Preparation of Fuel Cell Electrode Membrane Assembly (1)]
The positive electrode fuel cell catalyst layer (1) produced in Example 1-b and the negative electrode fuel cell catalyst layer were formed on both sides of a solid polymer electrolyte membrane (Nafion212, manufactured by DuPont, film thickness 50 μm), respectively. After closely adhering and sandwiching them under the conditions of 150° C. and 5 MPa, the Teflon (registered trademark) film was peeled off. Then, a fuel cell electrode (carbon paper base material TGP-H-090 manufactured by Toray Industries, Inc.) is further adhered from both sides, and the fuel cell electrode membrane assembly of the present invention (electrode/catalyst layer/solid polymer electrolyte membrane/catalyst). Layer/electrode) (1) was prepared.

The obtained fuel cell electrode membrane assembly (1) was used as a 2.5 cm square sample, and two gaskets were sandwiched from both sides, then two graphite plate separators were sandwiched, and two current collector plates were attached from both sides. Then, a fuel cell (single cell) was produced.

[Production of Fuel Cell Electrode Membrane Assembly (2) to (24)]
Similar to the fuel cell electrode membrane assembly (1), except that the positive electrode fuel cell catalyst layer (1) was replaced with the positive electrode fuel cell catalyst layers (2) to (24). In the same manner as in 1, the fuel cell electrode membrane assemblies (2) to (24) of the present invention were produced.

The obtained fuel cell electrode membrane assemblies (2) to (24) were used as 2.5 cm square samples, and two gaskets were sandwiched from both sides thereof, then two graphite plate separators were sandwiched between them, and further current collector plates were disposed from both sides. Was attached to prepare a fuel cell (single cell).

<Evaluation of catalyst layer for fuel cell>
By carrying out a power generation test of a fuel cell prepared using the fuel cell electrode membrane assemblies (1) to (24) obtained from the positive electrode fuel cell catalyst layers (1) to (24), the positive electrode fuel is obtained. The catalyst layer for batteries was evaluated.
The measurement was carried out by AutoPEM series "PEFC evaluation system" manufactured by Toyo Technica. As a fuel cell operating condition, under a condition of a temperature of 80° C. and a relative humidity of 100%, hydrogen was flowed at 300 ml/min on the negative electrode side, and oxygen was flowed at 300 ml/min on the positive electrode side to carry out a power generation test. The results are shown in Table 3.

As shown in Table 3, in the examples in which the mass ratio of the carbon material to the non-platinum-based carbon-based catalyst was 0.1 to 50 mass%, the maximum power density was also good. Further, in Examples 1 to 4 in which a carbon material having a hydrophilicity of 0.15 or less and BET _N2 of 500 m ² /g or more was added, the concentration overvoltage at 1 A/cm ² was low, the gas diffusibility was good, and the maximum output was The density was also good. It is speculated that this is because the inclusion of a hydrophobic carbon material having a large specific surface area in the catalyst layer improved gas diffusivity by suppressing flooding. On the other hand, Comparative Examples 1 to 4 had high concentration overvoltages and could not provide good maximum output density.

<Preparation of catalyst electrode for fuel cell>
Hereinafter, a method for directly applying the fuel cell catalyst paste composition of the present invention to a conductive support to prepare a fuel cell catalyst electrode will be exemplified.

[Example 17]
A carbon paper base material comprising carbon fibers as a conductive support so that the basis weight of the non-platinum-based carbon catalyst after drying the catalyst paste composition (1) for a fuel cell may be 2 mg/cm ² with a doctor blade. (TGP-H-090, manufactured by Toray Industries, Inc.) and dried in an air atmosphere at 95° C. for 60 minutes to prepare a catalyst electrode (1) for a fuel cell for a positive electrode.

<Fabrication of fuel cell (single cell)>
A positive electrode fuel cell catalyst electrode (1) (a fuel cell catalyst paste composition adhered to carbon paper) and a negative electrode fuel cell catalyst layer were respectively formed into a solid polymer electrolyte membrane (Nafion212, manufactured by DuPont, membrane). The film was adhered to both sides of a thickness of 50 μm and sandwiched under the conditions of 150° C. and 5 MPa, and then the Teflon (registered trademark) film was peeled off. Then, a fuel cell electrode (carbon paper base material TGP-H-090 manufactured by Toray Industries, Inc.) was further adhered from the negative electrode side, and the fuel cell electrode membrane assembly of the present invention (electrode/catalyst layer/solid polymer electrolyte membrane/ A catalyst layer/electrode) (25) was prepared.

<Fuel cell (single cell) power generation test>
When the power generation characteristics were measured by the same method as in Example 1-b, the maximum output density was 0.40 W/cm ² , the open circuit voltage was 0.81 V, and the concentration overvoltage was 0.06 V at 1 A/cm ² .

<Microbial fuel cell>
Hereinafter, a method for producing a microbial fuel cell by using the catalyst electrode produced from the catalyst paste composition for a fuel cell of the present invention will be exemplified.

[Example 18: Preparation of electrolytic cell for microbial fuel cell]
10.0 mass% of non-platinum-based carbon-based catalyst (X3), 3.0 mass% of carbon material (1), 81.6 mass% of toluene as a solvent, and 5.4 mass% of polydimethylsiloxane as a binder. Was added, and the mixture was stirred and mixed with a disper (manufactured by Primix Co., Ltd., TK Homo Disper) to prepare a catalyst paste composition (23) for fuel cells (solid content concentration 18.4 mass %).
Using a catalyst blade composition for a fuel cell (23) with a doctor blade, a carbon paper substrate comprising carbon fibers as a conductive support so that the basis weight of the non-platinum-based carbon catalyst after drying is 2 mg/cm ^2. (TGP-H-090, manufactured by Toray Industries, Inc.), and dried in an air atmosphere at 95° C. for 60 minutes to prepare a cathode fuel cell catalyst electrode (2).
After anaerobically culturing a mixed solution of Shewanella oneidenis MR-1 (single culture, 10 ⁵ cells/mL) and paddy soil as an electron-donating microorganism in an electrolytic cell having a capacity of 30 mL at 30° C. for 3 days, A buffer solution of K ₂ HPO ₄ /KH ₂ PO ₄ (pH 7.0) was used as an electrolyte solution, and 2.0 g COD/L/day (COD; chemical oxygen demand) of domestic wastewater containing glucose as a nutrient substrate was used. It was made to flow continuously. Carbon cloth was inserted into the electrolytic cell as the negative electrode conductive support, and the positive electrode fuel cell catalyst electrode (2) was inserted into the electrolytic cell as the positive electrode.

[Comparative Example 9 Preparation of Electrolytic Cell for Microbial Fuel Cell]
Non-platinum-based carbon-based catalyst (X3) 10.0% by mass, carbon material (4) 3.0% by mass, toluene 81.6% by mass as a solvent, polydimethylsiloxane 5.4% by mass as a binder. Was added and mixed by stirring with a disper (manufactured by Primix Corporation, TK Homo Disper) to prepare a fuel cell catalyst paste composition (24) (solid content concentration 18.4 mass %).
A carbon paper group comprising carbon fibers as a conductive support so that the basis weight of the non-platinum-based carbon catalyst after drying the catalyst paste composition (24) for a fuel cell as a positive electrode (24) with a doctor blade may be 2 mg/cm ^2. Material (TGP-H-090, manufactured by Toray Industries, Inc.) and dried in an air atmosphere at 95° C. for 60 minutes, and the produced cathode electrode for a fuel cell for a positive electrode was used as in Example 18. Similarly, an electrolytic cell for a microbial fuel cell was produced.

(Power generation test of microbial fuel cell)
Current-voltage measurement was performed using a potentio-galvanostat (VersaSTAT3, manufactured by Princeton Applied Research) and evaluated. In Example 18, the result was about 0.29 W/m ² , whereas in Comparative Example 9, It was about 0.15 W/m ² .

<Metal-air battery>
Hereinafter, a method for producing a metal-air battery using a catalyst electrode produced from the catalyst paste composition for a fuel cell of the present invention will be exemplified.

Example 19 Production of Evaluation Cell for Air Battery
4. Non-platinum-based carbon-based catalyst (X3) 10.0% by mass, carbon material (1) 3.0% by mass, N-methylpyrrolidone 81.6% by mass as a solvent, and polyvinylidene fluoride 5. 4% by mass was added, and the mixture was stirred and mixed with Disper (manufactured by Primix Co., Ltd., TK Homodisper) to prepare a fuel cell catalyst paste composition (25) (solid content concentration 18.4% by mass).
The catalyst paper paste composition (25) for a fuel cell is coated with a doctor blade so that the basis weight of the non-platinum-based carbon catalyst after drying is 2 mg/cm ² , and a carbon paper substrate made of carbon fiber as a conductive support. (TGP-H-090, manufactured by Toray Industries, Inc.) and dried in an air atmosphere at 95° C. for 60 minutes to prepare a cathode fuel cell catalyst electrode (4).
A separator (porous polypropylene film) in which a non-aqueous electrolyte solution (1M LiPF ₆ , ethylene carbonate/diethyl carbonate=1/1, volume ratio) was included on a Li foil, a solid electrolyte (manufactured by OHARA, LiCGC Plate 1inch×) 150 μmt) was placed and fixed with an aluminum laminate film. At this time, the aluminum laminate film on the solid electrolyte side was cut into a size of 16 mm square to form an exposed surface of the solid electrolyte, and a negative electrode for an air battery was prepared.
A non-woven fabric impregnated with a 1 M LiCl aqueous solution as an aqueous electrolytic solution is placed on the solid electrolyte of the negative electrode for the air battery, and then the positive electrode fuel cell catalyst electrode (4) is arranged, fixed by an aluminum laminate film, and thermocompression bonded. By doing so, an evaluation cell for an air battery was obtained.

[Comparative Example 10 Production of evaluation cell for air battery]
4. Non-platinum-based carbon-based catalyst (X3) 10.0% by mass, carbon material (4) 3.0% by mass, N-methylpyrrolidone 81.6% by mass as a solvent, and polyvinylidene fluoride 5. 4% by mass was added, and the mixture was stirred and mixed with a disper (manufactured by PRIMIX Corporation, TK Homodisper) to prepare a catalyst paste composition (26) for fuel cells (solid content concentration 18.4% by mass).
A carbon paper base material comprising carbon fiber as a conductive support so that the basis weight of the non-platinum-based carbon catalyst after drying the catalyst paste composition (26) for a fuel cell may be 2 mg/cm ² with a doctor blade. (TGP-H-090, manufactured by Toray Industries, Inc.) and dried in an air atmosphere at 95°C for 60 minutes to prepare a catalyst electrode (5) for a fuel cell for a positive electrode.
An evaluation cell for an air battery was obtained in the same manner as in Example 19 except that the cathode fuel cell catalyst electrode (4) was used in place of the cathode fuel cell catalyst electrode (4).

(Characteristic evaluation of air battery: capacity retention rate)
Using the obtained air battery evaluation cell, a 3-cycle break-in operation was performed under the conditions of a cut voltage of 2.0 to 4.8 V and a current density of 0.5 mA/cm ² . After that, when the capacity retention rate was determined by performing a 30-cycle charge/discharge test under the same conditions, the capacity retention rate was 95.7%, whereas in Comparative Example 10, the capacity retention rate was 70.3%. %Met.

[Example 20: Production of evaluation cell for magnesium-air primary battery]
Using a Mg plate as a negative electrode and a positive electrode fuel cell catalyst electrode (4) as a positive electrode, a separator (nonwoven fabric) was sandwiched and fixed between both electrodes to obtain a magnesium-air primary battery evaluation cell.

[Comparative Example 11 Preparation of evaluation cell for magnesium-air primary battery]
A magnesium air primary battery evaluation cell was obtained in the same manner as in Example 20, except that the cathode fuel cell catalyst electrode (4) was used in place of the cathode fuel cell catalyst electrode (4).

<Characteristic evaluation of magnesium-air primary battery: open circuit voltage, discharge capacity>
The electrolytic solution (20% sodium chloride aqueous solution) was immersed in the separator of the obtained magnesium-air primary battery evaluation cell, and the open-circuit voltage (OCV) and discharge capacity of the constituent cells were measured by a charge-discharge evaluation device. In Example 20, the open circuit voltage was 1.7 V and the discharge capacity was 1412 mAh/g, whereas in Comparative Example 11, the open circuit voltage was 1.2 V and the discharge capacity was 755 mAh/g.

The catalyst layer and the catalyst electrode for a fuel cell produced by using the catalyst paste composition for a fuel cell of the present invention have a carbon material gas diffusion even in a fuel cell using a liquid electrolyte such as a microbial fuel cell or a metal-air cell. Since it functions as a channel, the amount of oxygen supplied to the active sites on the non-platinum-based carbon-based catalyst increases, and it is speculated that this has led to improved performance.

The fuel cell catalyst layer and the catalyst electrode produced using the fuel cell catalyst paste composition of the present invention are less likely to be flooded by water generated by the reaction, and have a good gas diffusibility, and thus have a maximum power density. It is presumed that it is improving. In addition, it was found that the carbon material functions as a gas diffusion path and can be suitably applied to a fuel cell using a liquid electrolyte such as a microbial fuel cell and a metal-air cell.

FIG. 1 is a schematic diagram of the structure of a fuel cell.

1 separator 2 gas diffusion layer 3 negative electrode catalyst layer (fuel electrode)
4 Solid polymer electrolyte 5 Positive electrode catalyst layer (air electrode)
6 Gas diffusion layer 7 Separator

Claims (7)

A catalyst paste composition for a fuel cell, comprising a non-platinum-based catalyst, a carbon material, a solvent, and a binder,
The hydrophilicity of the carbon material (the ratio of the BET specific surface area (BET _H2O ) using water as an adsorbing species and the BET specific surface area (BET _N2 ) using nitrogen as an adsorbing species (BET _H2O /BET _N2 )) is 0.5. Is less than
The hydrophilicity of the non-platinum-based carbon-based catalyst is 0.6 to 4.9,
A catalyst paste composition for a fuel cell, wherein the mass ratio of the carbon material to the non-platinum-based carbon catalyst is 0.1 to 50 mass %. The non-platinum-based carbon-based catalyst has a hydrophilicity of 0.6 to 2.5, the carbon material has a BET _N2 of 100 m ² /g or more, a pore volume of 0.4 cm ³ /g or more, and a bulk density of 0. The catalyst paste composition for a fuel cell according to claim 1, wherein the composition is 4 g/cm ³ or less. The catalyst paste composition for a fuel cell according to claim 1 or 2, wherein the carbon material has a hydrophilicity of 0.15 or less and BET _N2 of 500 m ² /g or more. A fuel cell catalyst layer formed from the fuel cell catalyst paste composition according to claim 1. A catalyst electrode for a fuel cell, comprising the catalyst layer for a fuel cell according to claim 4 and a conductive support. A fuel cell electrode membrane assembly comprising the solid polymer electrolyte membrane and the fuel cell catalyst electrode according to claim 5. A fuel cell comprising at least one of the fuel cell catalyst electrode according to claim 5 and the fuel cell electrode membrane assembly according to claim 6.