JP4044026B2 - Fuel cell - Google Patents

Description

  The present invention relates to a fuel cell in which hydrogen, methanol, ethanol, dimethyl ether, isopropyl alcohol, ethylene glycol, glycerin, methane, dimethoxymethane or the like is directly used as a fuel, and air, oxygen, or ozone is used as an oxidant. .

  A fuel cell generates electric power by electrochemically reacting a fuel capable of generating hydrogen ions such as hydrogen and an oxidant containing oxygen such as air. The structure first forms a catalyst layer on each side of the polymer electrolyte that selectively transports hydrogen ions. Next, a gas diffusion layer is formed on the outer surface of the catalyst layer by using, for example, conductive carbon particle paper having both air permeability and electronic conductivity of the fuel gas and subjected to water repellent treatment. The catalyst layer and the gas diffusion layer are collectively referred to as an electrode.

  Next, a gas seal material or a gasket is disposed around the electrode with a polymer electrolyte interposed so that the fuel to be supplied leaks outside and the fuel and the oxidant do not mix with each other. This sealing material and gasket are integrated with an electrode and a polymer electrolyte, and this integrated material is called a membrane / electrode assembly (MEA).

  The catalyst layer of a fuel cell is generally formed by forming a platinum-based noble metal catalyst as a catalyst, making conductive carbon particles (catalyst support) such as carbon black or graphite, and a polymer electrolyte into a thin film and making it into a thin film.

  Currently, perfluorocarbon sulfonic acid polymer “Nafion” (trade name, manufactured by Deupon) is generally used as a polymer electrolyte. In order for the “Nafion” to have hydrogen ion conductivity, it needs to be humidified.

  The fuel that has entered from the anode side becomes hydrogen ions and electrons on the electrode catalyst, and the hydrogen ions, electrons, and oxidant that have passed through the electrolyte react on the catalyst on the cathode side, and electric energy is extracted at this time. be able to.

When hydrogen is used as the fuel, the following reactions occur at each electrode.
Anode 2H ₂ → 4H ⁺ + 4e ⁻
Cathode O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O
Further, when methanol is used as the fuel, the following reaction occurs.
Anode CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻
Cathode 3 / 2O ₂ + 6H ⁺ + 6e ⁻ → 3H ₂ O
On the catalyst layer in the electrode, reactant / product diffusion, electron transfer, and hydrogen ion transfer occur. For this reason, the size of the three-phase interface that becomes the movement path of each of the fuel, electrons, and hydrogen ions, which are reaction points, is important.

  The area of the three-phase interface is the effective area of the catalyst, and the larger the area, the better the utilization of the catalyst and the better the battery performance. As described above, the reaction area is increased by placing the polymer electrolyte in the catalyst layer.

  Attempts have been made so far to provide a layer in which an electrode and a polymer electrolyte are mixed and dispersed at the interface between the electrode and the electrolyte. In the conventional technology, a dispersion solution of a polymer electrolyte and a mixture of a catalyst are applied onto a polymer electrolyte membrane, and the electrode is hot pressed with an electrode and then the catalyst compound is reduced. The method to perform is proposed (for example, patent documents 1-2).

In addition, after molding a porous electrode, a polymer electrolyte solution is sprayed on the electrode, and this electrode and the polymer electrolyte membrane are hot pressed (for example, Patent Documents 3 to 4). There is also a method in which a powder in which a polymer electrolyte is coated on the surface of a polymer resin is mixed in an electrode (for example, Patent Document 5). Also, there is a method in which a polymer electrolyte, a catalyst, carbon powder, and a fluororesin are mixed and formed into an electrode (for example, Patent Document 6).
Japanese Examined Patent Publication No. 62-61118 Japanese Patent Publication No.62-61119 Japanese Examined Patent Publication No. 2-48632 Japanese Patent Laid-Open No. 3-184266 JP-A-3-295172 Japanese Patent Laid-Open No. 5-36418

  However, the conventional catalyst layer uses a polymer electrolyte, and this polymer electrolyte is soluble in water or an alcohol solution such as ethanol.

  When alcohol such as methanol is used as the fuel, the reaction takes place with alcohol: water = 1: 1, so that the electrolyte elutes into the aqueous alcohol solution during power generation, resulting in a decrease in the three-phase interface and poor reaction efficiency. There is a problem that decreases.

  In addition, the electrolyte elutes in the water generated at the cathode during power generation and in the humidified water necessary for hydrogen ion conduction, reducing the three-phase interface and lowering the voltage.

  In order to solve the above-described conventional problems, the present invention provides a fuel cell that uses a thin-film electrolyte that does not elute into water or alcohol, has a large three-phase interface area in the catalyst layer, and can provide a long life and high voltage. To do.

The fuel cell of the present invention is a fuel cell that generates power by supplying fuel to one electrode and supplying an oxidant to the other electrode. A catalyst layer is formed on at least one surface of at least one of the electrodes. are, the catalyst layer is a mixture of catalyst particles and other particles, the other particles comprise silica, alumina, quartz, glass, at least one selected from ceramic and mica, before Symbol the front surface of the other particles, and molecules containing an ion-conducting functional group serving as an electrolyte is chemically bonded, wherein the chemical bond is a covalent bond, an ionic bond, at least one selected from the coordinate bond and metal bond It is a combination of two .

  According to the present invention, at least one of the electrodes includes the thin film electrolyte, the catalyst, and the electron conductive material, so that the elution of the electrolyte in the electrode catalyst layer and the accompanying voltage drop can be reduced.

  The present invention relates to a fuel cell. In the fuel cell of the present invention, the catalyst layer is a layer of catalyst particles only, a layer in which catalyst particles and other particles are mixed, or a porous membrane. It is a layer carrying at least catalyst particles, and at least one surface selected from the catalyst particles, other particles, and a porous membrane is chemically bonded with a molecule containing an ion conductive functional group that functions as an electrolyte. . The ion conductive functional group functions as an electrolyte. The chemical bond is preferably any one of a covalent bond, an ionic bond, a coordination bond, and a metal bond. In particular, the covalent bond formed by the elimination reaction is preferred because it is the most chemically and physically stable. Here, the elimination reaction refers to a dehydrohalogenation reaction, a dealcoholization (wherein the alcohol has 1 to 3 carbon atoms) reaction, and the like.

  The average molecular weight of the molecule containing the ion conductive functional group is preferably 40 or more and 10,000 or less. The molecule containing the ion conductive functional group needs to be directly chemically bonded to the substrate, and in order to have a functional group necessary for that purpose, the molecular weight needs to be 40 or more. In addition, when the molecular weight exceeds 10,000, it is difficult to obtain an optimal conformation for forming a molecular thin film due to the large molecular weight, and as a result, molecules containing ion-conductive functional groups cannot bind to the substrate. ,Not appropriate.

The molecular weight can be measured by “TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry)”. TOF-SIMS is a general method for surface analysis. Details of this measurement are also described in the following literature.
(1) Wang, D., et.al .: Catal. Today, 12 (1992), 375
(2) Wang, D., et.al .: J. Mater. Sci., 28 (1993), 1396
(3) Wang, D., et. Al .: Compos. Sci. Technol., 50-2 (1994), 215
(4) Toyota Chuken R & D Review Vol. 34, No. 2 (Feb. 1996), 11 (particularly helpful)
In the above, the molecular thin film has a reactive group such as a chloro group, an alkoxyl group or an isocyanate group at the end of the molecule, and the active hydrogen (hydroxyl group, carboxyl group, amino group, imino group, etc.) of the substrate. A film formed by a desorption reaction such as a dehydrochlorination reaction, a dealcoholization reaction or a deisocyanate reaction, and a film obtained by further polymerizing this film. For example, when the functional group at the molecular end is -SiCl ₃ , -Si (OR) ₃ (where R is an alkyl group having 1 to 3 carbon atoms), or -Si (NCO) ₃ , If active hydrogen contained in -OH group, -CHO group, -COOH group, -NH ₂ group,> NH group, etc. is present on the surface of the formed underlayer, dehydrochlorination reaction, dealcoholization reaction or deisocyanate reaction will occur. The chemisorbed molecules are covalently bonded to the substrate surface or the surface of the underlayer formed on the substrate. Molecular films formed by this method are referred to in the art as “chemisorbed films” or “self assembling films”. In order to further polymerize this chemisorbed film, unsaturated bonds are included in the molecule in advance, and after the chemisorbed film is formed, the molecules are polymerized by photopolymerization or the like.

The molecule containing the ion conductive functional group preferably contains at least one organic group selected from fluorocarbons and hydrocarbons. As a result, it is possible to obtain a state in which water molecules hardly pass and protons pass easily. In particular, a fluorocarbon group ((CF ₂ ) _n- , where n is in the range of 2 to 30) is preferable because it is stable even when the potential is high, the molecule is not easily cut off, protons easily pass through, and water molecules do not pass through easily. .

  The ion conductive functional group is preferably a proton dissociative functional group.

  The proton dissociative functional group is preferably at least one functional group selected from a phosphonyl group, a phosphinyl group, a sulfonyl group, a sulfine group, a sulfonic group, and a carboxyl group.

  The ion conductive functional group is preferably a functional group capable of hydrogen bonding. This is because proton conduction using water molecules bonded to a hydrogen-bondable functional group is possible, and as a result, an electrocatalytic reaction is possible.

  The functional group capable of hydrogen bonding is preferably at least one functional group selected from a mercapto group, an ether bond group, a nitro group, a hydroxyl group, a quaternary ammonium base, and an amino group.

  The chemical bond is preferably at least one bond selected from a covalent bond, an ionic bond, a coordination bond, and a metal bond. The chemical bond is preferably a covalent bond formed by an elimination reaction. This is because the most stable bond can be obtained.

The chemical bond is preferably bonded to the substrate surface via an oxygen atom. As an example other than oxygen, they may be bonded via nitrogen. The elimination reaction includes, for example, a chloro group or an alkoxyl group at the molecular end of the organic compound, and a hydroxyl group (—OH), carboxyl group (—COOH), amino group (—NH ₂ ), imino group (> NH) on the substrate surface. This is because it occurs with active hydrogen such as

  The catalyst preferably contains at least one selected from platinum, gold, palladium, nickel, rhodium, cobalt, iridium, osmium and iron. It is because it is excellent as an oxidation catalyst.

  The catalyst layer preferably further contains an electron conductor.

  The electron conductor is preferably carbon. Carbon is excellent in electron conductivity, is electrochemically stable, and has a functional group capable of chemically bonding with a molecule containing an ion conductive functional group on its surface.

The other particles are preferably inorganic. It is preferable that the inorganic substance includes at least one selected from silica, alumina, quartz, glass, ceramics, and mica. This is because the inorganic substance has a functional group on the surface of which a molecule containing an ion conductive functional group can be chemically bonded , and the density of functional groups present on the surface of silica and alumina is particularly high compared to other inorganic substances. . In the above, the ceramics may include glass. This is because there are glassy ceramics such as porcelain and ceramics.

  The inorganic substance is preferably a particle.

  The average particle diameter of the inorganic particles is preferably in the range of 0.1 μm to 100 μm. When the average particle diameter exceeds 100 μm, the surface area of the inorganic particles becomes small, and as a result, the existence density of molecules having an ion conductive functional group also becomes low, and the ion conductivity decreases. When the average particle size is less than 0.1 μm, the catalyst and the electron conductive material are coated, and ion conduction cannot be performed to the electrolyte part, resulting in a decrease in battery voltage.

  The porosity of the porous film is preferably in the range of 5% to 95%. When the porosity is less than 5%, the diffusibility of the fuel and the product is deteriorated, so that it becomes difficult to generate power in a large current density region where a large amount of fuel is required (diffusion rate-limiting). In addition, when the porosity exceeds 95%, electron transfer between electron conductive materials or ion conduction between ion conductive materials becomes difficult, and power generation is particularly difficult in a large current density region. It becomes.

  The average pore diameter of the porous membrane is preferably in the range of 0.1 nm to 10 μm. When the average pore diameter is less than 0.1 nm, molecules having an ion conductive functional group enter the pores and it is difficult to chemically bond them. On the other hand, when the average pore diameter exceeds 10 μm, the distance between the ion conductive functional groups becomes longer than the interval at which ion conduction is possible, and the ion conductivity rate is lowered, and thus the rate of the catalytic reaction is also lowered.

  The thickness of the catalyst layer is preferably in the range of 0.1 to 10,000 μm. When the thickness is less than 0.1 μm, it is difficult to withstand the pressurization during battery production and the pressurization for fuel supply. On the other hand, when the thickness exceeds 10,000 μm, the diffusibility of the fuel is lowered, so that the battery voltage is lowered.

  As an example, the electrolyte of the present invention (hereinafter referred to as “thin film electrolyte”) chemically binds a molecule containing an ion conductive functional group to any one of catalyst particles, other particles, and particles used as a raw material for a porous membrane. Thereafter, the particles are compression-molded and formed into a sheet, plate or film. Alternatively, the particles may be first compression molded into a sheet, plate or film, followed by chemical bonding of molecules containing ion conductive functional groups.

Hereafter, it demonstrates concretely using the Example of this invention.
( Reference Example 1)
In this reference example , an example in which the catalyst layer is composed of only catalyst particles will be described.

  Platinum ruthenium black calcined at 600 ° C. in a nitrogen atmosphere (Johnson Massey, HiSPEC1000, average particle size 1.5 μm, catalyst particles act as a substrate to which the thin film electrolyte binds) and platinum ruthenium black (Manufactured by Johnson Matthey, HiSPEC6000, average particle size 2.0 μm) were used as a cathode electrode catalyst and an anode electrode catalyst, respectively.

  A molecule containing an ion conductive functional group functioning as an electrolyte (hereinafter referred to as a thin film electrolyte) was chemically bonded to the surface of the catalyst to form a catalyst layer. The method for producing the catalyst layer is as follows.

The reaction raw material is a trichlorosilane compound containing a vinyl group at the end and a fluorocarbon chain at the center: CH ₂ = CH- (CF ₂ ) ₁₄ (CH ₂ ) ₂ SiCl ₃ and normal hexadecane and chloroform as non-aqueous solvents. 1% by weight was dissolved in a 4: 1 mixed solvent, and platinum black and platinum ruthenium as catalysts were immersed in this solution for 2 hours. A dehydrochlorination reaction takes place between the hydroxyl group (—OH) present on the catalyst surface and the chloro group of the trichlorosilane compound, and a single molecule of the trichlorosilane compound is brought to the catalyst surface via oxygen as shown in the following chemical formula 1. Combined.

この粒子を非水溶媒であるクロロホルムで洗浄し、未反応物を除去後、空気中の水分と反応させると、酸素を介して単分子同士が結合し、下記化学式２に示すトリクロロシラン化合物由来の分子薄膜が形成した。

When these particles are washed with chloroform, which is a non-aqueous solvent, and unreacted substances are removed and reacted with moisture in the air, single molecules are bonded to each other through oxygen, and are derived from a trichlorosilane compound represented by the following chemical formula 2. A molecular thin film was formed.

次に、表面に薄膜が形成された触媒を、発煙硫酸と反応させることで、分子末端の不飽和結合（ビニル結合）部分がスルホン化され、下記化学式３に示す分子薄膜を形成した。この分子薄膜の分子量は約９１２であり、分子長は２．８nmであった。ここでSO₃ ^-基はイオン伝導性を有する基であり、本実施形態で分子薄膜の表面に一様に形成されていた。

Next, the catalyst having the thin film formed on the surface was reacted with fuming sulfuric acid, so that the unsaturated bond (vinyl bond) portion at the molecular terminal was sulfonated to form a molecular thin film represented by the following chemical formula 3. The molecular weight of this molecular thin film was about 912, and the molecular length was 2.8 nm. Here, the SO ₃ ⁻ group is a group having ion conductivity, and was formed uniformly on the surface of the molecular thin film in this embodiment.

この薄膜電解質のついた触媒を、イオン交換水とポリテトラフルオロエチレン（PTFE）のディスパージョン（ダイキン工業製、ND-1）と混合しペーストを作製した。ペースト作製時の重量混合比は、イオン交換水：薄膜電解質のついた触媒＝1：10、PTFEディスパージョンは1重量％とした。図１は本参考例における触媒層の概略図である。図１において、１１は触媒である白金黒、もしくは、白金ルテニウム黒であり、１２は薄膜電解質である。

The catalyst with the thin film electrolyte was mixed with ion-exchanged water and polytetrafluoroethylene (PTFE) dispersion (ND-1 manufactured by Daikin Industries) to prepare a paste. The weight mixing ratio at the time of preparing the paste was ion exchange water: catalyst with thin film electrolyte = 1: 10, and PTFE dispersion was 1% by weight. FIG. 1 is a schematic view of a catalyst layer in this reference example . In FIG. 1, 11 is platinum black or platinum ruthenium black which is a catalyst, and 12 is a thin film electrolyte.

The electrolyte part used in this reference example uses a thin-film electrolyte, and the manufacturing method is as follows.
H + SO _3- (CH ₂ ) ₂ (CF, a trialkoxysilane compound, in the pores of an alumina membrane filter (outer dimensions 8 cm x 8 cm), an inorganic porous material with a thickness of 60 µm and 0.02 µm ₂ ) ₁₄ (CH ₂ ) ₂ Si (OCH ₃ ) ₃ was injected. A dealcoholization reaction occurred between a hydroxyl group (—OH) and an alkoxy group (in this case, methoxy group: —OCH ₃ ) on the alumina surface, and a trialkoxysilane compound was bonded onto alumina as shown in Chemical Formula 4.

この単分子同士が脱アルコール反応で結合することによって、下記化学式５に示すように、孔内に薄膜電解質が形成した。

By bonding these single molecules to each other by a dealcoholization reaction, as shown in the following chemical formula 5, a thin film electrolyte was formed in the hole.

得られた電解質部の両面に、アノード極用、カソード極用それぞれに調整した触媒ペーストを、電解質部の中心に外寸5cm×5cmの大きさにて塗布し、５０℃の電気炉中で乾燥させ、触媒層を形成した。触媒層の両外側を、撥水処理を行ったカーボンペーパー（東レ製、TGP-H-060、外寸5cm×5cm）で挟み一体化し、電極を形成した。このアノード電極、電解質部、カソード電極からなる部分を、膜・電極接合体（MEA）とよび、本方法で作製したものをMEA１とする。図２にMEAの概略図を示す。２１は電極、２２は電解質部である。
MEA１の外周部をシリコーンゴム製のガスケット（厚み1５０μm、外寸8cm×8cm）で挟んだ後、ゲージ圧2.5MPa・gでホットプレスし、さらに、冷却水、燃料、および酸化剤流通用のマニホールド穴を形成した。

A catalyst paste prepared for each of the anode electrode and the cathode electrode was applied to both surfaces of the obtained electrolyte part in the center of the electrolyte part in a size of 5 cm × 5 cm and dried in an electric furnace at 50 ° C. To form a catalyst layer. Both sides of the catalyst layer were sandwiched and integrated with carbon paper (Toray, TGP-H-060, outer dimensions 5 cm × 5 cm) that had been subjected to a water-repellent treatment to form an electrode. The part consisting of the anode electrode, the electrolyte part, and the cathode electrode is called a membrane / electrode assembly (MEA), and the one produced by this method is called MEA1. FIG. 2 shows a schematic diagram of the MEA. 21 is an electrode, and 22 is an electrolyte part.
After sandwiching the outer periphery of MEA1 with a gasket made of silicone rubber (thickness: 150μm, outer dimension: 8cm x 8cm), hot press with a gauge pressure of 2.5MPa · g, and a manifold for circulating coolant, fuel, and oxidizer A hole was formed.

  Next, a separator composed of a resin-impregnated graphite plate having an outer dimension of 8 cm × 8 cm, a thickness of 13 mm, a fuel, an oxidant, and a cooling water flow path of 5 mm was prepared, and a gasket plate was joined using two separators. A separator having an oxidant flow path formed on one surface and a separator having a fuel flow path formed on the back surface were overlapped to form a fuel cell single cell 1. FIG. 3 shows a schematic diagram of a single cell. 23 is an MEA, 24 is a gasket plate, 25, 26 and 27 are manifold holes, and 28 is a separator.

  Fuel and cooling water are supplied to the separator 28 through the manifold holes 25, 26, and 27 and are supplied to each battery, and are supplied to the MEA 23 through the flow path on the separator 28.

  FIG. 4 is a cross-sectional view when the single cells obtained in FIG. 3 are stacked and coupled in series. After stacking two cells 31, 32, separators 33, 34 having cooling channel grooves 43, 44 sandwich the two cells 31, 32, and stack cells 35, 36 on the outside. A battery stack of 8 cells was stacked. That is, the separators 33 and 34 were separated from each other and connected in series with adjacent batteries. 37, 38, 39 and 40 are MEAs.

At this time, the both ends of the battery stack were fixed with a stainless steel current collector plate whose surface was gold-plated, an insulating plate made of an electrically insulating material, and an end plate and a fastening rod. The fastening pressure at this time was 1.47 × 10 ⁶ Pa (15 kgf / cm ² ).

( Reference Example 2)
In this reference example , an example in which the catalyst layer is composed of catalyst particles and electron conductive particles will be described. The catalyst particles act as a substrate to which the thin film electrolyte is bonded.

After firing Tanaka Kikinzoku's platinum-supported carbon (TEC10E50E, average particle size 30μm) or Tanaka Kikinzoku's platinum-ruthenium-supporting carbon (TEC61E54, average particle size 30μm) at 600 ° C in a nitrogen atmosphere, reference A molecular thin film was formed from the trichlorosilane compound described in Example 1 on the catalyst surface by the method described in Reference Example 1. Thereafter, a thin film electrolyte was produced on platinum and platinum ruthenium catalysts supported on carbon by sulfonation. By this operation, a thin film electrolyte made of an organosilane compound could be produced on platinum on carbon or a platinum ruthenium alloy. FIG. 5 shows a schematic diagram of the catalyst layer. 51 is platinum or a platinum ruthenium alloy as a catalyst, 52 is carbon carrying the catalyst, and 53 is a thin film electrolyte.

The obtained carbon-supported catalyst with a thin film electrolyte was mixed with ion-exchanged water and PTFE dispersion in the same manner as described in Reference Example 1 to obtain a catalyst paste. At this time, the mixing ratio of the ion-exchanged water and the carbon-supported catalyst with the thin film electrolyte was 5: 1 by weight, and 1 wt% of PTFE dispersion was added. The paste was applied to the electrolyte unit prepared in Reference Example 1 described method, it was integrated with the carbon paper in Reference Example 1 described method. The MEA produced at this time was designated as MEA2. A single cell produced by the method described in Reference Example 1 using MEA 2 was designated as single cell 2.

(Example 3)
In this embodiment, an example in which the catalyst layer is composed of a mixed layer of catalyst particles and other particles will be described. Another particle (silica particle in this embodiment) added to the catalyst layer acts as a substrate to which the thin film electrolyte is bonded.

On the surface of the silica particles having a diameter of 100 nm (error ± 15 nm), trichlorosilane compound of Reference Example 1, coupled in Reference Example 1 described method, it is sulfonated to produce a thin film electrolyte on the silica surface. To this, platinum black (Johnson Massey, HiSPEC1000) or platinum ruthenium black (Johnson Massey, HiSPEC6000) was mixed as a catalyst so that silica particles: catalyst = 1: 10 in a weight ratio. . A schematic view of the catalyst layer at this time is shown in FIG. 61 is silica particles, 62 is a thin film electrolyte, 63 is platinum black or platinum ruthenium black.

  Furthermore, 1% by weight of a mixed solution of ethanol and ion-exchanged water (ethanol: ion-exchanged water = 4: 1) and PTFE dispersion (ND-1, manufactured by Daikin Industries) was added thereto, and ultrasonically stirred at room temperature. A catalyst layer paste was prepared.

The electrolyte portion made of the thin film electrolyte prepared by the method described in Reference Example 1 is masked to a predetermined size (5 cm × 5 cm), and the catalyst paste is spray-coated on both the anode and cathode, and the method described in Reference Example 1 And integrated with carbon paper to make MEA. This is MEA3. A single cell manufactured by the method described in Reference Example 1 using this MEA 3 is referred to as a single cell 3.

( Reference Example 4)
In this reference example , an example will be described in which the catalyst layer is composed of a catalyst and an electron conductive material, and the electron conductive material (here, carbon black) of the catalyst layer acts as a substrate to which the thin film electrolyte is bonded.

  Platinum supported carbon (TEC10E50E) manufactured by Tanaka Kikinzoku Kogyo or platinum ruthenium supported carbon (TEC61E54) manufactured by Tanaka Kikinzoku Kogyo was heated from 55 ° C. to 60 ° C. in nitrogen with fuming sulfuric acid and stirred for 50 hours. This was dropped into anhydrous ether kept at 0 ° C. to obtain a solid. This was stirred with distilled water in nitrogen for 10 hours, and the solid obtained by filtration was vacuum dried. Of the obtained solids, platinum-supported carbon was used for the cathode electrode and platinum ruthenium-supported carbon was used for the anode electrode.

A molecular thin film was prepared by the method described in Reference Example 1 on the surface of each catalyst-supported carbon that had been surface-treated, and this was sulfonated to obtain a thin film electrolyte. The surface of carbon treated with sulfuric acid has hydroxyl groups (-OH groups) and carboxyl groups (-COOH groups), and a dealcoholization reaction takes place between this site and the methoxy group of the silane compound. A molecular thin film was formed. A schematic view of the catalyst at this time is shown in FIG. 71 is platinum or platinum ruthenium alloy as a catalyst, and 72 is carbon carrying the catalyst. 73 is a thin film electrolyte on the supported carbon.

This was mixed with Flemion solution FSS-1 (Asahi Glass, 9 wt% ethanol solution), which is a perfluorocarbon sulfonic acid solution, and deionized water to prepare a paste, and the electrolyte prepared by the method described in Reference Example 1 was used. Each was coated and dried on both sides and integrated with carbon paper by the method described in Reference Example 1 to obtain MEA. This is referred to as MEA 4, and a single cell manufactured by the method described in Reference Example 1 using this MEA 4 is referred to as single cell 4.

( Reference Example 5)
In this reference example , the catalyst layer is composed of a catalyst and an electron conductive material, and the electron conductive material (here, carbon black) of the catalyst layer acts as a substrate to which the thin film electrolyte is bonded, and the electrolyte and the catalyst layer are created in one step. An example will be described.

  Using a cathode catalyst with 50% by weight of platinum having an average particle size of 3 nm supported on Ketjen Black EC (trade name, manufactured by AKZO Chemie, the Netherlands) having an average primary particle size of 30 nm, A catalyst carrying 25% by weight of ruthenium was used as the anode catalyst.

  The catalyst-supported carbon, PTFE dispersion, and ion-exchanged water were mixed, and after filtration, a sheet was formed by a roll press. A silica sol having an average particle size of 80 nm was applied thereto and dried. This was baked at 500 ° C. in argon.

After firing, a trialkoxysilane compound, H ⁺ SO ₃ ^— (CH ₂ ) ₂ (CF ₂ ) ₁₄ (CH ₂ ) ₂ Si (OCH ₃ ) _3, was pressed into the surface coated with silica sol. A trialkoxysilane compound is bonded to silica by a dealcoholization reaction between a hydroxyl group (—OH) and an alkoxy group (in this case, methoxy group: —OCH ₃ ) on the surface of the silica sol, and the single molecules are bonded to each other. As a result, an electrolyte part was formed.

The silane compound was filled not only in the silica sol part but also in the solidified catalyst part, and the catalyst layer and the electrolyte part could be produced at a time. This was integrated with carbon paper by the method described in Reference Example 1 to make MEA5. A schematic diagram is shown in FIG. 81 is a catalyst layer portion, and 82 is an electrolyte portion. 83 is a catalyst, 84 is carbon carrying the catalyst, and 85 is a thin film electrolyte produced on the carbon. Moreover, 86 which comprises the electrolyte part is a silica sol, 87 is a thin film electrolyte.

A single cell manufactured by the method described in Reference Example 1 using this MEA 5 is referred to as a single cell 5.

(Example 6)
In this embodiment, an example will be described in which the catalyst layer is composed of catalyst particles, an electron conductive substance, and other particles, and the other added particles (here, alumina particles) act as a substrate to which the thin film electrolyte is bonded.

Alumina particles having a particle size of 100 μm were calcined in an electric furnace at 150 ° C. for 3 hours in a nitrogen atmosphere, dried, then attached to the diluted silane compound solution described in Reference Example 1, and stirred for 30 hours while heating to 60 ° C. . After stirring, washing with an anhydrous toluene solution and filtration were repeated, and drying was performed again at room temperature under a nitrogen atmosphere.
Mix the alumina particles obtained here with platinum-supported carbon (TEC10E50E) manufactured by Tanaka Kikinzoku Kogyo or platinum / ruthenium-supported carbon manufactured by Tanaka Kikinzoku Kogyo (TEC61E54), and add ion-exchanged water and PTFE dispersion. A catalyst paste was obtained. This catalyst paste was made into a thin film and integrated with the electrolyte by the method described in Reference Example 1 to produce MEA6. A schematic diagram of MEA 6 is shown in FIG. 91 is a catalyst, 92 is carbon, 93 is alumina particles, and 94 is a thin film electrolyte on the alumina particles.

  A single cell manufactured using MEA 6 is referred to as single cell 6.

( Reference Example 7)
In this reference example , the catalyst layer is composed of catalyst particles and another porous material, the catalyst enters the pores of the porous material and is integrated, and the porous material acts as a substrate to which the thin film electrolyte is bonded. Will be described.

Thickness 100μm and, in the porous pores in the glass is oriented porous material having a pore size of 0.02μm from 0.004 m, trialkoxysilane compounds ^{_{H + SO 3 - (CH 2}} ) 2 (CF 2) 14 (CH ₂ ) ₂ Si (OCH ₃ ) ₃ was injected. Here, the porous glass was baked in air at 120 ° C., and the dealcohol was reacted to introduce an electrolyte into the pores.

  On the surface of this porous glass, a catalyst paste consisting of platinum black and Flemion solution FSS-1 (Asahi Glass, 9 wt% ethanol solution) which is a perfluorocarbon sulfonic acid solution is applied and dried at 60 ° C. in a nitrogen atmosphere. It was. After drying, a catalyst paste made of platinum ruthenium black and a Flemion solution was applied to the opposite surface to which the paste was applied, and dried at 60 ° C. in a nitrogen atmosphere.

A schematic diagram of the catalyst layer is shown in FIG. 101 is an electrolyte part, and 102 and 103 are an anode catalyst layer and a cathode catalyst layer, respectively. Reference numeral 104 denotes porous glass, and a thin film electrolyte 105 exists on the inner surface of the hole. 106 forming the anode catalyst layer is platinum ruthenium black, and 107 forming the cathode catalyst layer is platinum black. The outside of the catalyst layer is sandwiched with carbon paper on both sides in the same manner as described in Reference Example 1, and this is designated as MEA7. A single cell manufactured using MEA 7 is referred to as a single cell 7.

( Reference Example 8)
In this reference example , the catalyst layer is composed of catalyst particles, an electron conductive substance, and another porous material, the catalyst penetrates into the pores of the porous material and is integrated, and the porous material is bonded to the thin film electrolyte. An example of acting as a substrate will be described.

Thickness 100 [mu] m, and H ⁺ SO of the inorganic porous material is a porous trialkoxysilane compound in the pores of the glass with a pore size of 0.02μm from _{^{0.004μm 3 - (CH 2) 2}} (CF 2) 14 (CH ₂ ) ₂ Si (OCH ₃ ) ₃ was injected. Here, the porous glass was baked in air at 120 ° C. and subjected to dealcoholization reaction to introduce an electrolyte into the pores of the porous glass.

  Next, a catalyst paste made of platinum-supported carbon TEC10E50E (made by Tanaka Kikinzoku) or platinum ruthenium-supported carbon TEC61E54 (made by Tanaka Kikinzoku), PTFE dispersion, and ion-exchanged water was filled in the pores of the porous glass.

In the porous glass, an electrolyte was formed in the pores, and the catalyst paste was filled in the pores and dried. Furthermore, MEA was obtained by integrating with the gas diffusion layer by the method described in Reference Example 1. This MEA is called MEA8. A single cell using the MEA 8 is referred to as a single cell 8.

  A schematic diagram of the MEA is shown in FIG. Reference numeral 111 denotes an electrolyte portion, and 112 and 113 denote an anode catalyst layer and a cathode catalyst layer, respectively. 114 is porous glass, and the thin film electrolyte 115 exists on the inner surface of the hole. 116 which forms the anode catalyst layer is platinum ruthenium-supporting carbon, and 117 which forms the cathode catalyst layer is platinum-supporting carbon.

( Reference Example 9)
In this reference example , a case where a functional group other than sulfonic acid is used as the ion conductive functional group will be described. Platinum-supported carbon or platinum-ruthenium-supported carbon whose surface was subjected to functional group treatment by the method described in Reference Example 5 was immersed in a silane compound-containing toluene solution for 1 hour by the method described in Reference Example 1. The silane compounds used are as shown in Table 1.

MEA９の触媒層は、シラン化合物であるビニルトリメトキシシラン（チッソ製、サイラエース S210、下記化学式（化６））を用いて、参考例１記載の方法によって触媒担持カーボン上にシラン化合物による分子薄膜を形成後、リン酸水溶液中で加熱することによって得た。MEA１０の触媒層は、シラン化合物３−アミノプロピルトリメトキシシラン（サイラエース S360、チッソ製、下記化学式（化７））を用いた。MEA１１の触媒層は、シラン化合物トリグリシドキシプロピルトリメトキシシラン（KBM-403、信越化学製、下記化学式（化８））を用いて、参考例１記載の方法によって分子薄膜形成後、希硫酸中にて触媒担持カーボンを洗浄することにより、エポキシ環が開裂し、OH基を導入した。

The catalyst layer of MEA 9 is formed by forming a molecular thin film of a silane compound on the catalyst-supporting carbon by the method described in Reference Example 1 using vinyltrimethoxysilane (Sisso, Silaace S210, the following chemical formula (Chemical Formula 6)), which is a silane compound. After formation, it was obtained by heating in an aqueous phosphoric acid solution. As the catalyst layer of MEA 10, a silane compound 3-aminopropyltrimethoxysilane (Silaace S360, manufactured by Chisso, the following chemical formula (Chemical Formula 7)) was used. The catalyst layer of MEA11 was prepared by using a silane compound triglycidoxypropyltrimethoxysilane (KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd., the following chemical formula (Chemical Formula 8)), after forming a molecular thin film by the method described in Reference Example 1, and in dilute sulfuric acid. By washing the catalyst-supported carbon with, the epoxy ring was cleaved and an OH group was introduced.

官能基導入後、脱水トルエンを用いて洗浄した後、窒素雰囲気下にて乾燥後、イオン交換水、PTFEディスパージョンと混合させて触媒ペーストを作り、これを撥水処理済みのカーボンペーパーに塗布し、所定の大きさにして電解質部と一体化した。このようにして作製したMEAを、それぞれMEA９、MEA10、MEA11とする。また、それぞれのMEAを用いて作製した単セルを、単セル９、単セル１０、単セル１１とした。

After introduction of functional groups, washing with dehydrated toluene, drying in a nitrogen atmosphere, mixing with ion-exchanged water and PTFE dispersion to make a catalyst paste, applying this to water-repellent treated carbon paper Then, it was made a predetermined size and integrated with the electrolyte part. The MEAs produced in this way are referred to as MEA9, MEA10, and MEA11, respectively. Moreover, the single cell produced using each MEA was made into the single cell 9, the single cell 10, and the single cell 11. FIG.

(Comparative example)
As a comparative example, an example in which perfluorocarbon sulfonic acid is used as the electrolyte in the catalyst layer is shown. As the catalyst layer, a ketjen black EC carrying platinum or platinum ruthenium was used. Platinum with an average primary particle size of 30 nm and Ketjen Black EC (trade name, manufactured by AKZO Chemie, The Netherlands) carrying 50% by weight of platinum with an average particle size of 3 nm as the cathode electrode and platinum with an average particle size of 3 nm The anode electrode was loaded with 25 wt% each of ruthenium and ruthenium.

  The catalyst-carrying particles and the polymer electrolyte were mixed to produce a catalyst paste. At this time, the weight ratio of carbon to the polymer electrolyte in the catalyst-supporting particles was set to 1: 1. As the polymer electrolyte, a Nafion ethanol / isopropanol mixed solution (manufactured by DuPont), which is a perfluorocarbon sulfonic acid polymer, was used.

Next, the catalyst paste was printed on the electrolyte part prepared by filling the pores of the alumina membrane filter with the thin film electrolyte described in Reference Example 1. By the method described in Reference Example 1, it was integrated with carbon paper to produce MEA. This is referred to as MEA12. A single cell using MEA 12 is referred to as a single cell 12.

(Battery performance evaluation)
For each of the produced single cells 1 to 12, stack stacking was performed by the method described in Reference Example 1, and this was evaluated.

  As a fuel, a 2 mol / L aqueous methanol solution at 60 ° C. was supplied at 2 cc / min, and air was supplied at a battery temperature of 60 ° C. and an air utilization rate of 30%. The air outlet was pressurized at 2 atm.

OCV, average single cell voltage at a current density of ^{200mA / cm 2, 500mA / cm} 2 was as shown in each Table 2.

また、高濃度メタノール水溶液である10モル/Ｌのメタノール水溶液を用いた場合でも、ＯＣＶ、電流密度200mA/cm²での電圧は、表３の通りであった。

Further, even when a 10 mol / L aqueous methanol solution, which is a high-concentration aqueous methanol solution, was used, the voltage at OCV and current density of 200 mA / cm ² was as shown in Table 3.

高濃度のメタノール水溶液を用いても、触媒層中の電解質は溶出が少なく、触媒、燃料、水素イオン伝導体の接点である有効反応面積は大きくなり、電圧が向上した。

Even when a high-concentration aqueous methanol solution was used, the electrolyte in the catalyst layer was less leached, and the effective reaction area, which is the contact point of the catalyst, fuel, and hydrogen ion conductor, increased and the voltage was improved.

  In this example, methanol was used as an example of the fuel. However, even when a hydrocarbon fuel such as hydrogen, ethanol, ethylene glycol, dimethyl ether, isopropanol, glycerin, methane, dimethoxymethane or a mixture thereof is used, the same applies. Results were obtained. The liquid fuel may be mixed in advance and supplied as vapor.

  Furthermore, the configuration of the gas diffusion layer of the present example is not limited to the conductive carbon paper shown in the example, and is effective even when other conductive carbon cloth or a metal mesh is used.

The schematic of the catalyst layer in the reference example 1 of this invention. The schematic plan view of the electrode electrolyte membrane assembly (MEA) of the fuel cell in the reference example 1 of this invention. The perspective view which shows the structure of the cell of the fuel cell in the reference example 1 of this invention. Sectional drawing which shows the structure of the stack which laminated | stacked the single cell of the fuel cell in the reference example 1 of this invention. The schematic of the catalyst layer in the reference example 2 of this invention. The schematic of the catalyst layer in Example 3 of this invention. Schematic of the catalyst layer in Reference Example 4 of the present invention. Schematic of the electrode electrolyte membrane assembly (MEA) in Reference Example 5 of the present invention. Schematic of the electrode electrolyte membrane assembly (MEA) in Example 6 of this invention. The schematic plan view of the electrode electrolyte membrane assembly (MEA) in Reference Example 7 of the present invention. The schematic plan view of the electrode electrolyte membrane assembly (MEA) in Reference Example 8 of the present invention.

Explanation of symbols

11, 51, 63, 71, 83, 91 Catalyst 12, 53, 62, 73, 85, 87, 94, 105, 111, 115 Thin film electrolyte 23, 37, 38, 39, 40 Membrane / electrode assembly (MEA)
24 Gasket plates 25, 26, 27 Manifold holes 28, 33, 34 Separators 31, 32, 35, 36 Single cells 43, 44 Cooling channel grooves 52, 72, 84, catalyst-supporting carbon 61 Silica particles 63 Platinum black, platinum ruthenium black 81, 102, 103, 111, 112 Catalyst layer part 82, 101 Electrolyte part 86 Silica sol 92 Carbon 93 Alumina particles 104, 114 Porous glass 106 Platinum ruthenium black 107 Platinum black 116 Platinum ruthenium supporting carbon 117 Platinum supporting carbon

Claims (14)

In a fuel cell that generates power by supplying fuel to one electrode and supplying an oxidant to the other electrode,
A catalyst layer is formed on at least one surface of at least one of the electrodes,
The catalyst layer is a mixture of catalyst particles and other particles,
The other particles include at least one selected from silica, alumina, quartz, glass, ceramics and mica,
On the surface of the other particle, a molecule containing an ion conductive functional group that functions as an electrolyte is chemically bonded.
The fuel cell, wherein the chemical bond is at least one bond selected from a covalent bond, an ionic bond, a coordination bond, and a metal bond. 2. The fuel cell according to claim 1, wherein an average molecular weight of the molecule containing the ion conductive functional group is 40 or more and 10,000 or less. 2. The fuel cell according to claim 1, wherein the molecule containing the ion conductive functional group contains at least one selected from a fluorocarbon and a hydrocarbon. The fuel cell according to claim 1, wherein the ion conductive functional group is a proton dissociative functional group. The fuel cell according to claim 4, wherein the proton dissociative functional group is at least one functional group selected from a phosphonyl group, a phosphinyl group, a sulfonyl group, a sulfine group, a sulfonic group, and a carboxyl group. The fuel cell according to claim 1, wherein the ion conductive functional group is a functional group capable of hydrogen bonding. The fuel cell according to claim 6, wherein the functional group capable of hydrogen bonding is at least one functional group selected from a mercapto group, an ether bond group, a nitro group, a hydroxyl group, a quaternary ammonium base, and an amino group. The fuel cell according to claim 1, wherein the chemical bond is a covalent bond formed by an elimination reaction. The fuel cell according to claim 1, wherein the chemical bond is a bond through an oxygen atom. The fuel cell according to claim 1, wherein the catalyst particles include at least one selected from platinum, gold, palladium, nickel, rhodium, cobalt, iridium, osmium, and iron. The fuel cell according to claim 1, wherein the catalyst layer further contains an electron conductor. The fuel cell according to claim 11, wherein the electron conductor is carbon. 2. The fuel cell according to claim 1, wherein an average particle diameter of the other particles is in a range of 0.1 μm to 100 μm. The fuel cell according to claim 1, wherein a thickness of the catalyst layer is in a range of 0.1 to 10,000 μm.

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