JP5077658B2 - ELECTROLYTE MEMBRANE FOR SOLID POLYMER FUEL CELL, ELECTROLYTE MEMBRANE-CATALYST LAYER ASSEMBLY AND ELECTROLYTE MEMBRANE-ELECTRODE ASSEMBLY USING THE SAME, AND FUEL CELL - Google Patents

Description

  The present invention relates to an electrolyte membrane for a polymer electrolyte fuel cell, an electrolyte membrane-catalyst layer assembly and an electrolyte membrane-electrode assembly using the same, and a fuel cell.

  A polymer electrolyte fuel cell is made up of a solid polymer membrane with proton conductivity as an electrolyte, and a fuel electrode and an air electrode are joined to both sides of this membrane. Hydrogen is supplied to the fuel electrode and oxygen or air is supplied to the air electrode. This is a system that generates electricity through an electrochemical reaction. The following reactions occur at each electrode.

Fuel electrode: H ₂ → 2H ⁺ + 2e ⁻
Air electrode: (1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O
Total reaction: H ₂ + (1/2) O ₂ → H ₂ O
As can be seen from these reaction equations, only water is generated during power generation. Fuel cells are attracting attention as one of the next generation clean energy systems.

  The polymer electrolyte fuel cell can generate electric power even when methanol is supplied as a fuel. In this case, the polymer electrolyte fuel cell is particularly called a direct methanol fuel cell. The following reactions occur at each electrode.

Fuel electrode: CH ₃ OH + H ₂ O → 6H ⁺ + 6e ⁻ + CO ₂
Air electrode: (3/2) O ₂ + 6H ⁺ + 6e ⁻ → 3H ₂ O
All reactions: CH ₃ OH + (3/2) O ₂ → 2H ₂ O + CO ₂
A polymer electrolyte fuel cell has a structure in which a proton conductive polymer electrolyte membrane is used as an electrolyte membrane, a catalyst layer is arranged on both sides thereof, an electrode base material is arranged on both sides thereof, and this is further sandwiched between separators. doing. The one in which the catalyst layers are arranged on both surfaces of the electrolyte membrane (that is, the layer configuration of catalyst layer / electrolyte membrane / catalyst layer) is called an electrolyte membrane-catalyst layer assembly (abbreviation: CCM), An electrode base material disposed on both surfaces of the electrolyte membrane-catalyst layer assembly (ie, electrode base material / catalyst layer / electrolyte membrane / catalyst layer / electrode base material layer structure) is an electrolyte membrane-electrode joint. It is called a body (abbreviation: MEA).

  Examples of the proton conductive polymer electrolyte membrane include a perfluorosulfonic acid-based fluorine ion exchange resin, more specifically, a perfluorocarbon sulfonic acid-based polymer in which the C—H bond of the hydrocarbon-based ion exchange membrane is substituted with fluorine. Examples include polymers (PFS polymers). By introducing a fluorine atom having high electronegativity, it is chemically very stable, the dissociation degree of the sulfonic acid group is high, and high ion conductivity can be realized. Specific examples of such a proton conductive polymer electrolyte membrane include “Nafion” (registered trademark) manufactured by DuPont, “Flemion” (registered trademark) manufactured by Asahi Glass Co., Ltd., and “Aciplex” manufactured by Asahi Kasei Corporation. ”(Registered trademark),“ Gore Select ”(registered trademark) manufactured by Gore, and the like.

These perfluorocarbon sulfonic acid-based polymers exhibit high performance as an electrolyte membrane as described above, but have a problem of high cost. In addition, there is a problem that remarkable deterioration is observed at a high temperature range of 80 ° C. or higher, and proton conductivity is remarkably lowered by drying of the electrolyte membrane. Furthermore, since it swells due to water content and shows a large dimensional change, there is also a problem that the catalyst layer formed on the electrolyte membrane is peeled off after repeated start / stop (humidification / drying). In order to make up for these drawbacks, proposals have been made to embed fillers such as polymer fibers and inorganic particles in the polymer electrolyte membrane to increase water retention under high temperature conditions and to suppress dimensional changes. (For example, Patent Documents 1 and 2).
JP 2003-157862 A JP-A-6-1111827

  However, by embedding filler inside the polymer electrolyte membrane, certain performance improvements such as improved heat resistance, improved mechanical strength, and improved water retention can be seen. In such a case, the expected performance may not be sufficiently exhibited.

  In order to solve the above problems, the present invention has an electrolyte membrane for a polymer electrolyte fuel cell having a uniform distribution and a strong structure, high dimensional stability and gas barrier properties, and an electrolyte membrane-catalyst layer assembly using the same And an electrolyte membrane-electrode assembly and a fuel cell.

An electrolyte membrane for a polymer electrolyte fuel cell according to the present invention is an electrolyte membrane for a polymer electrolyte fuel cell containing a proton conductive material A and a proton conductive material B as proton conductive materials, wherein the proton conductivity is The material A has a film forming property due to self-organization, and is one or more kinds selected from the group consisting of SiO ₂ —H ₃ PO ₄ , SiO ₂ —TiO ₂ —P ₂ O ₅ and TiO ₂ —H ₃ PO ₄ . The inorganic proton conductive material is characterized by being surface-modified with a molecular chain having a proton conductive functional group.

  The electrolyte membrane-catalyst layer assembly of the present invention is characterized in that catalyst layers made of catalyst particles and an electrolyte binder are formed on both surfaces of the electrolyte membrane, respectively.

  The electrolyte membrane-electrode assembly of the present invention is characterized in that a catalyst layer composed of catalyst particles and an electrolyte binder and an electrode composed of an electrode substrate are formed on both surfaces of the electrolyte membrane, respectively.

  The fuel cell of the present invention is a fuel cell using the electrolyte membrane-electrode assembly.

  According to the present invention, it is possible to obtain a proton conductive electrolyte membrane that encloses a support having a uniform distribution and structure. Moreover, a high gas barrier property is expressed by the filler having a film-forming property by self-organization, and a decrease in power generation performance due to cross leak of fuel or oxidant can be suppressed. Furthermore, even when used in a direct methanol fuel cell using liquid fuel, the crossover of the methanol aqueous solution from the anode side to the cathode side is suppressed, and the effect of preventing the decrease in power generation performance is shown. Furthermore, the effect of improving the power generation performance at higher temperatures can be obtained by using a filler having high proton conductivity even under high temperature and low humidification conditions.

  In the present invention, the film-forming property due to the self-organization of the scaly particle material means that when particles having a flat particle shape settle in the liquid, the surfaces are aligned in parallel to stabilize the structure. It shows the property of forming a laminate without applying an external force. Further, for example, as in a silica material, silanol groups on the surface are dehydrated and condensed to form a siloxane bond (-Si-OH + HO-Si ---- Si-O-Si-, where Si is tetravalent but divalent. In the case of a material having a property of bonding between particles, the particles themselves have a film-forming property.

  The proton conductive material A having a film-forming property due to self-assembly is preferably in the range of 2% to 50% by weight of the electrolyte membrane, and the proton conductive material B is 50% by weight of the electrolyte membrane. It is preferable to be in the range of -98% by weight. If the proton conductive material A having a film-forming property due to self-organization is less than 2% by weight, the improvement of the strong structure, dimensional stability and gas barrier property is not so high. If the proton conductive material A exceeds 50% by weight, it tends to be difficult to maintain the membrane shape.

The proton conductive material B is a group consisting of a fluorine-based proton conductive polymer material, a hydrocarbon proton conductive material, an inorganic proton conductive material, an organic-inorganic hybrid proton conductive material, an ionic liquid, and a mixture thereof. Is preferably selected from. Examples of the fluorine-based proton conductive polymer material include Nafion (trade name), Flemion (trade name), and Aciplex (trade name). Hydrocarbon proton conductive materials are phosphoric acid impregnated polybenzimidazole (PBI), alkylsulfonic acid impregnated polybenzimidazole (PBI), sulfonated 4-phenoxybenzoyl-1,4-phenylene (SPPBP), sulfonated polyether ether Examples include ketones (SPEEK) and styrene-ethylene / butylene / ethylene block copolymers. Examples of inorganic proton conductive materials include metal hydrated oxides such as tungsten oxide and tin oxide hydrate, multi-component silica such as SiO ₂ —H ₃ PO ₄ and SiO ₂ —TiO ₂ —P ₂ O ₅ , TiO 2. Metal phosphate compounds such as _2- H ₃ PO ₄ , heteropoly acid complexes such as phosphotungstic acid and phosphomolybdic acid, inorganic substances such as CsHSO ₄ , CsH ₂ PO ₄ , Sn _X In _(1-X) P ₂ O ₇ Examples thereof include oxyacid salts. Organic-inorganic hybrid materials include hybrid materials made of polyether polymers such as silica and polyethylene oxide (PEO), polypropylene oxide (PPO), or polytetramethylene oxide (PTMO), and solids such as tungstophosphoric acid. An example to which an acid is added is given. Examples of the ionic liquid include 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide (EMI-TFSI), 1-ethyl-3-methylimidazolium triflate (EMI-Tf), 1-ethyl- An example is 3-methylimidazolium fluorohydrogenate (EMIm (HF) nF). The proton conductive material B may not have a film forming property due to self-organization. That is, it may be non-self-forming.

  The proton conductive material A having a film-forming property by self-organization is a scaly material having a disk-like average diameter in the range of 0.01 μm to 10.00 μm and a thickness in the range of 0.01 to 1.00 μm. It is preferable. A more preferable average diameter is in the range of 0.05 μm to 1.00 μm. Scale-like, ie, flat, disk-like particles can be easily arranged in the plane direction, and the film-forming property is improved when cast-mixed with the proton conductive material (B). In addition, an inorganic material having a —OH group on the surface has a self-forming property by dehydration condensation. Here, the average diameter is calculated from the average value of 100 particles by measurement using a laser scattering method, a diffraction particle size distribution analyzer, or the like, and the average thickness is measured using a scanning electron microscope.

  Further, the scale-like, ie, flat, disk-like particles preferably have a diameter / thickness in the range of 5 to 50, and particularly about 10 is preferable. Such scaly, ie, flat, disk-like particles are easy to arrange in the plane direction, and the film-forming property is improved when cast-mixed with a proton conductive material.

  The molecular chain for modifying the surface of the proton conductive material A having a film-forming property by self-organization has a film-forming property by the self-organization by a known method such as radiation grafting, electron absorption addition reaction, dehydration condensation polymerization and the like. A molecule attached to the surface of the proton conductive material A and a molecular chain having one or more proton conductive functional groups per molecule. For example, an alkoxide compound may be used as a starting material and bonded to ceramic material particles by a dehydration condensation reaction of —OH groups formed by hydrolysis. Further, the alkoxide compound has a hydrocarbon molecular chain having a linear or side chain having about 1 to 10 carbon atoms, more preferably about 3 to 6, and the hydrocarbon molecular chain is a part or all of the hydrocarbon molecular chain. The hydrogen atom may be substituted with fluorine. The hydrocarbon molecular chain has one or more proton conductive functional groups selected from the group consisting of proton conductive functional groups such as a hydroxyl group, a sulfonic acid group, a carboxylic acid group, and a phosphoric acid group. It only has to be.

The proton conductive material A having a film-forming property by self-organization includes a fluorine-based proton conductive polymer material, a hydrocarbon-based proton conductive material, an inorganic proton conductive material, an organic-inorganic hybrid proton conductive material, and It is preferably selected from the group consisting of these mixtures. Examples of the fluorine-based proton conductive polymer material include Nafion (trade name), Flemion (trade name), and Aciplex (trade name). Hydrocarbon proton conductive materials are phosphoric acid impregnated polybenzimidazole (PBI), alkylsulfonic acid impregnated polybenzimidazole (PBI), sulfonated 4-phenoxybenzoyl-1,4-phenylene (SPPBP), sulfonated polyether ether Examples include ketones (SPEEK) and styrene-ethylene / butylene / ethylene block copolymers. Examples of inorganic proton conductive materials include metal hydrated oxides such as tungsten oxide and tin oxide hydrate, multi-component silica such as SiO ₂ —H ₃ PO ₄ and SiO ₂ —TiO ₂ —P ₂ O ₅ , TiO 2. Metal phosphate compounds such as _2- H ₃ PO ₄ , heteropoly acid complexes such as phosphotungstic acid and phosphomolybdic acid, inorganic substances such as CsHSO ₄ , CsH ₂ PO ₄ , Sn _X In _(1-X) P ₂ O ₇ Examples thereof include oxyacid salts. Organic-inorganic hybrid materials include hybrid materials made of polyether polymers such as silica and polyethylene oxide (PEO), polypropylene oxide (PPO), or polytetramethylene oxide (PTMO), and solids such as tungstophosphoric acid. An example to which an acid is added is given. The proton conductive material A having a film-forming property by self-organization is more preferably selected from the group consisting of inorganic proton conductive materials, organic-inorganic hybrid materials, and mixtures thereof. This is because it is more excellent in heat resistance, water retention, chemical stability, dimensional stability, and fuel or oxidant permeation inhibiting ability.

  It is preferable that the proton conductive material A having a film-forming property due to self-organization is covered with the proton conductive material B at a thickness of 0.01 μm to 1.00 μm. This is because high proton conductivity can be maintained.

  Hereinafter, embodiments of an electrolyte membrane for a polymer electrolyte fuel cell and a method for producing the same according to the present invention will be described with reference to the drawings. In the following drawings, the same symbols indicate the same items.

FIG. 1A is a schematic perspective view of a ceramic particle material A (2) having self-forming properties due to interparticle bonding in an embodiment of the present invention. This ceramic particle material A (2) is scaly. FIG. 1B is a schematic perspective view in which a molecular chain (10) having a proton conductive functional group is chemically bonded to the surface of the ceramic particle material A (2). As the molecular chain (10) having a proton conductive functional group, for example, R—SO ₃ H, R—COOH (where R is a straight chain having about 1 to 10 carbon atoms, more preferably about 3 to 6 carbon atoms, or It is a hydrocarbon molecular chain having a side chain, and part or all of the hydrogen atoms of the hydrocarbon chain may be substituted with fluorine.

  Whether or not the molecular chain (10) having a proton conductive functional group exists on the surface of the ceramic particle material A (2) is determined by dispersing the ceramic particle material A (2) in water and measuring the pH. Can be confirmed.

  FIG. 2A shows a self-organized membrane when attention is paid only to the self-forming ceramic particle material A (2) surface-modified with a molecular chain (10) having a proton conductive functional group in an embodiment of the present invention. It is a typical top view. FIG. 2B shows a gas barrier property by arranging the electrolyte membrane (1) made of the self-forming ceramic particle material A (2) and the proton conductive material B (3) in a plane and laminating by self-organization. It is typical sectional drawing after forming an inorganic material film | membrane.

  A suspension of the proton-conductive material A (2) having a film-forming property by self-organization and a solution of the proton-conductive material B (3) are stirred and mixed, and the mixture is coated on a substrate surface (not shown). The electrolyte membrane is obtained by drying. In the mixing and stirring of the suspension of the proton conductive material A (2) having a film-forming property by the self-organization and the solution of the proton conductive material B (3), known methods such as stirrer, ultrasonic irradiation, ball mill, etc. This method can be used. In addition, in the coating on the substrate of the liquid obtained by mixing and stirring the suspension of the proton conductive material A (2) having a film-forming property by the self-assembly and the solution of the proton conductive material B (3), Known methods such as knife coating, gravure coating, bar coating, and screen printing can be used. In addition, as the substrate, a proton conductive material having a film forming property due to self-organization, such as a substrate made of a known ceramic such as glass or alumina, a known polymer film such as a polyethylene film or a polytetrafluoroethylene film, etc. Any material can be used as long as the electrolyte membrane made of A (2) and proton conductive material B (3) can be peeled off from the substrate after drying. Further, the film may be formed by pouring the above solution into a dish-shaped container having an arbitrary shape, heating and drying. The drying method is preferably performed by two-stage heating. The first stage heating is performed in the range of 50 ° C. to 100 ° C. when stirring the suspension of the proton conductive material 2 having a film-forming property by self-organization and the solution of the proton conductive material 3. This aims at adjusting the viscosity of the solution to a state suitable for coating. The second stage heating is performed in the range of 80 ° C. to 150 ° C. for the purpose of drying and film-forming the solution coated by the above method. The heating temperature is not limited to the above temperature range because the optimum value varies depending on the heat resistance and the glass transition point of the proton conductive material used. The film formation process may be performed on a single sheet or may be formed on a long film of any length by continuously coating on a long base film.

3A and 3B are schematic views in which a part of the surface of the proton conductive material 2 having a film-forming property by the self-assembly is enlarged. Note that FIGS. 3A-B are intended to show the concept, and the number of bond hands, bond angles, and the like may be inaccurate. In FIGS. 3A-B, SiO ₂ —H ₃ PO ₄ -based particles are exemplified as the proton conductive material having a film-forming property due to self-organization. A large number of silanol groups exist on the surface of the proton conductive material 2 having a film-forming property due to self-organization, and some of them are proton conductive functional groups (where X is a hydroxyl group, a sulfonic acid group, A molecular chain RX having a proton-conducting functional group such as a carboxylic acid group and a phosphoric acid group (the same shall apply hereinafter) (where R is a straight chain having about 1 to 10 carbon atoms, more preferably about 3 to 6 carbon atoms). Alternatively, a hydrocarbon molecular chain having a side chain, which forms a siloxane bond with a silane compound having a hydrocarbon chain in which part or all of the hydrogen atoms may be substituted with fluorine. Thus, the surface modification of the SiO ₂ —H ₃ PO ₄ particle material 2 is performed. The molecular chain (RX) corresponds to the molecular chain 10 in FIG. Since the SiO ₂ —H ₃ PO ₄ based particle material 2 is surface-modified with a molecular chain (RX) having a proton conductive functional group (X), high proton conductivity is exhibited. Further, the molecular chain (RX) is subjected to a treatment such as an oxidation treatment after the surface modification of the SiO ₂ —H ₃ PO ₄ particle material 2 with a molecular chain having a functional group that does not exhibit proton conductivity, for example. May be a molecular chain (RX) to which a proton conductive functional group is added. For example, when the proton conductive functional group (X) is a —SO ₃ H group, a silane having a molecular chain having a —SH group at the end, such as (3-mercaptopropyl) trimethoxysilane, is bonded to a SiO ₂ — by a siloxane bond. After imparting to the surface of the H ₃ PO ₄ -based particle material 2, the —SH group may be converted to —SO ₃ H group by oxidation treatment. In addition, a silane having an alkyl group such as n-propyltrimethoxysilane is applied to the surface of the SiO ₂ —H ₃ PO ₄ particle material 2 by a siloxane bond, and then a —SO ₃ H group is added by a sulfonating agent. May be. Here, the surface modification by the formation of a siloxane bond has been exemplified for the method for imparting the molecular chain (RX) having the proton conductive functional group (X), but known methods such as radiation grafting, electron absorption addition reaction, dehydration condensation polymerization, etc. The surface may be modified by a technique.

  The proton conductive material A (2) having a film-forming property due to the self-assembly is thinly coated with the proton conductive material B (3), and the thickness thereof is about 0.01 μm to about 1.00 μm. is there. When the thickness of the proton conductive material B (3) layer exceeds about 1.00 μm, the interaction between the particles of the proton conductive material A (2) having a film-forming property due to self-organization is exerted. The proton conductive material B (3) layer inhibits the film-forming property and suppresses the effect. In addition, when the thickness of the proton conductive material B (3) layer is less than about 0.01 μm, proton conduction in the proton conductive material B (3) is hindered, and a decrease in performance due to a decrease in proton conductivity is observed. It is done. Thus, the proton-conductive material A (2) having a film-forming property due to the self-organization exhibits a film-forming property and covers the proton-conductive material A (2) having a film-forming property due to the self-organization. In order for the proton conductive material B (3) to exhibit a sufficient proton conductivity, the thickness of the proton conductive material B (3) covering the proton conductive material A (2) having a film-forming property due to the self-organization. Need to be in the right area.

  FIG. 4 is a schematic view showing a cross section of an electrolyte membrane-catalyst layer assembly using the electrolyte membrane 1 of the present invention shown in FIG. 2B. As shown in FIG. 4, catalyst layers 4 and 4 'made of catalyst particles and an electrolyte binder are formed on both surfaces of the electrolyte membrane 1, respectively.

  FIG. 5 is a cross-sectional view of an electrolyte membrane-electrode assembly in one embodiment of the present invention. A fuel electrode 6 composed of a catalyst layer 4 and an electrode substrate 5 is disposed on the electrolyte membrane 1, and an air electrode 8 composed of a catalyst layer 4 ′ and an electrode substrate 7 is disposed below the electrolyte membrane 1. ing. And a single cell (fuel cell) is comprised by arrange | positioning the separator with a rib and a collector (not shown) further on both these outer sides. Protons flow from the fuel electrode 6 through the electrolyte membrane 1 to the air electrode 8. Further, electrons flow from the fuel electrode 6 to the air electrode 8 through an external circuit. As a result, electricity flows between the fuel electrode 6 and the air electrode 8.

  Hereinafter, the present invention will be described more specifically with reference to examples.

(1) Surface modification of proton conductive material As a scaly proton conductive particle material, SiO ₂ —H ₃ PO ₄ particle material (disk-shaped average diameter 0.6 μm (measured with a laser scattering particle size distribution meter), average Thickness of 0.05 μm (average value of 100 particles by scanning electron microscope) was used. This scaly particle material was dispersed in toluene, (3-mercaptopropyl) trimethoxysilane was added, and the mixture was refluxed at 100 ° C. overnight. Furthermore, the scaly proton conductive particle material was surface-modified with a molecular chain having a sulfonic acid group by performing an oxidation treatment using hydrogen peroxide water. As a result of dispersing the scale-like particles subjected to the above treatment in water and measuring with a pH test paper, the pH of the dispersion was 5. Compared with the measurement result 7 when the non-treated scale-like particles were dispersed in water, the pH was changed to the acidic side, so the success of the treatment was confirmed.

(2) Production of electrolyte membrane As the inorganic filler, the surface-modified scale-like SiO ₂ —H ₃ PO ₄ particles were used. A 5 wt% “Nafion” (trade name) solution from DuPont was used as the proton conducting material. The composition was prepared such that the surface-modified scale-like particle material was 10% by weight and “Nafion” (trade name) was 90% by weight in a dry weight ratio.

  The surface-modified scale-like particle material and a “Nafion” (trade name) solution were mixed, and a uniform dispersion was prepared by repeating stirring with a magnetic stirrer and ultrasonic stirring. The resulting dispersion was stirred with a magnetic stirrer while heating at 50-80 ° C., and the viscosity was adjusted while evaporating the dispersion medium. The obtained high-viscosity dispersion was cast on a polytetrafluoroethylene (PTFE) substrate, and allowed to stand and dried in a drying oven at about 100 ° C. to form an electrolyte membrane. The obtained electrolyte membrane was about 100 μm thick.

(3) Measurement of dimensional change rate during humidification The obtained film was cut into a rectangular shape and sufficiently humidified by immersion in distilled water at room temperature, and the dimensional change rate due to humidification was evaluated. The dimensional change rate was calculated by the following formula by measuring the length before and after humidification.
[(Length after humidification) ÷ (Length before humidification)] x 100 (%)
The dimensional change rate of the electrolyte membrane immersed in distilled water at room temperature (25 ° C.) was 111%. The dimensional change rate measured in the same manner for the commercially available “Nafion 117” (trade name) film was 120%.

  The electrolyte membrane has a smaller dimensional change rate during humidification than the “Nafion 117” membrane, and can be said to have excellent dimensional stability. The scale-like particle material used as the inorganic filler is considered to be an effect by forming a strong matrix in the film. As a result, an effect of suppressing breakage of the electrolyte membrane-electrode assembly such as peeling of the electrode catalyst layer can be expected by suppressing the dimensional change accompanying the wet / dry of the membrane at the start / stop of the fuel cell. .

(4) Measurement of proton conductivity during humidification The obtained membrane was cut into a rectangle and sufficiently humidified by being immersed in distilled water at room temperature, and the conductivity of the membrane was measured using an impedance analyzer. As a result, the conductivity of the electrolyte membrane at 25 ° C.-100% RH was 0.08 S / cm. This is almost equal to the conductivity of the “Nafion 117” film of 0.08 S / cm. There was concern that the matrix of scale-like particles in the electrolyte membrane may be a factor that inhibits proton conduction, but it is thought that the decrease in proton conductivity was suppressed by the proton conductivity of the surface-modified scale-like particle material itself .

(5) Power generation performance evaluation (methanol fuel)
Preparation of electrolyte membrane-catalyst layer assembly and electrolyte membrane-electrode assembly: Catalyst (Tanaka Kikinzoku Pt / C (TEC10E50E), Pt-) on both sides of the electrolyte membrane having a thickness of about 110 μm prepared in (1) above. A catalyst layer composed of Ru / C (TEC61E54)) and an electrolyte binder (DuPont, 5 wt% “Nafion” (trade name) solution) was formed. Specifically, the electrolyte membrane is sandwiched by a catalyst transfer film in which a catalyst layer composed of the above catalyst and electrolyte binder is formed on a pair of base films, and hot pressing (temperature: 135-150 ° C., pressure: 4-6 MPa) Thus, the catalyst layer was transferred and formed on the electrolyte membrane. Further, the electrolyte membrane-catalyst layer assembly was sandwiched between a pair of gas diffusion layers (manufactured by Toray Industries, Inc., carbon paper) to form an electrolyte membrane-electrode assembly. The electrolyte membrane-electrode assembly was sandwiched between a separator having a flow path for supplying fuel and an oxidant and a current collector to constitute a single cell. The anode electrode was 3 mg-Pt-Ru / cm ² , and the cathode electrode was 1 mg-Pt / cm ² .

  A 6 wt% methanol aqueous solution (4 mL / min) as fuel and dry air (80 mL / min) as oxidant were supplied to the fuel electrode and air electrode, respectively, and direct methanol of the above electrolyte membrane-electrode assembly at room temperature (30 ° C.). The power generation performance of the fuel cell was evaluated.

The obtained open electromotive force was about 640 mV, and the maximum output density was 16 mW / cm ² .

As a comparative example, when a single cell using a “Nafion 117” film having a thickness of about 200 μm was evaluated in the same manner, the open electromotive force was about 637 mV and the maximum output density was 15 mW / cm ² . In this way, power generation performance equivalent to or higher than that of the “Nafion 117” film can be obtained. The low current density region is a region where the cell potential is lowered due to the influence of methanol crossover. The thickness of the electrolyte membrane of this example is about 110 μm, and the thickness of the “Nafon 117” membrane (about 200 μm). However, the cell potential was not different from that of the comparative example. This indicates that the electrolyte membrane has higher methanol permeation blocking ability than the “Nafion 117” membrane.

(6) Power generation performance evaluation (hydrogen gas fuel)
Preparation of electrolyte membrane-catalyst layer assembly and electrolyte membrane-electrode assembly: Catalyst (Tanaka Kikinzoku Pt / C (TEC10E50E), Pt-) on both sides of the electrolyte membrane having a thickness of about 110 μm prepared in (1) above. A catalyst layer composed of Ru / C (TEC62E58)) and an electrolyte binder (DuPont, 5 wt% “Nafion” (trade name) solution) was formed. Specifically, the electrolyte membrane is sandwiched by a catalyst transfer film in which a catalyst layer composed of the above catalyst and electrolyte binder is formed on a pair of base films, and hot pressing (temperature: 135-150 ° C., pressure: 4-6 MPa) Thus, the catalyst layer was transferred and formed on the electrolyte membrane. Further, the electrolyte membrane-catalyst layer assembly was sandwiched between a pair of gas diffusion layers (manufactured by Toray Industries, Inc., carbon paper) to form an electrolyte membrane-electrode assembly. Then, the electrolyte membrane-electrode assembly was sandwiched between a separator having a flow path for supplying fuel and an oxidant and a current collector to constitute a single cell. The anode electrode ^{1.1mg-Pt-Ru / cm 2} , the cathode electrode was 0.5mg-Pt / cm ^2.

  Hydrogen gas (0.1 NLM, dew point 80 ° C.) as the fuel and air (0.5 NLM, dew point 70 ° C.) as the oxidant are supplied to the fuel electrode and the air electrode, respectively, and hydrogen of the above electrolyte membrane-electrode assembly at 80 ° C. The power generation performance of the fuel cell was evaluated. The obtained open electromotive force was about 1.01V. The “NLM” refers to a normal liter per minute.

  As a comparative example, when a single cell using a “Nafion 115” film having a thickness of about 125 μm was evaluated in the same manner, the open electromotive force was 0.98V. In the present embodiment, the thickness of the electrolyte membrane is about 100 μm, and the open electromotive force is 30 mV higher than that of the comparative example although it is 20% thinner than the thickness of the “Nafon 115” membrane (about 125 μm). Obtained. This indicates that the electrolyte membrane has better barrier properties against cross leaks of fuel gas and oxidant gas than the “Nafion 115” membrane.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

FIG. 1A is a schematic perspective view of a ceramic particle material A having self-film-forming properties due to bonding between particles in one embodiment of the present invention, and FIG. 1B has a proton conductive functional group on the surface of the ceramic particle material A. FIG. 3 is a schematic perspective view in which molecular chains are chemically bonded. FIG. 2A is a schematic plan view of a self-assembled film when attention is paid only to the self-forming ceramic particle material A surface-modified with a molecular chain having a proton conductive functional group in one embodiment of the present invention. 2B is a schematic view after an inorganic material film having a gas barrier property is formed by arranging an electrolyte film made of a self-forming ceramic particle material A and a proton conductive material B in a plane and laminating them by self-organization. It is sectional drawing. 3A and 3B are schematic views showing surfaces of SiO ₂ —H ₃ PO ₄ -based material particles having a film forming property due to surface-modified self-organization in the electrolyte membrane according to one embodiment of the present invention. It is sectional drawing showing the outline of the electrolyte membrane-catalyst layer assembly which concerns on one Embodiment of this invention. It is sectional drawing showing the outline of the electrolyte membrane electrode assembly which concerns on one Embodiment of this invention.

Explanation of symbols

1 Electrolyte membrane 2 Proton-conducting material A with film-forming property by self-organization A
3 Proton conductive material B
4, 4 'catalyst layer 5, 7 electrode base material 6 fuel electrode 8 air electrode 10 molecular chain having proton conductive functional group

Claims (8)

An electrolyte membrane for a polymer electrolyte fuel cell, comprising proton conductive material A and proton conductive material B as proton conductive materials,
The proton conductive material A has a film forming property due to self-organization and is selected from the group consisting of SiO ₂ —H ₃ PO ₄ , SiO ₂ —TiO ₂ —P ₂ O ₅ and TiO ₂ —H ₃ PO _4. An electrolyte membrane for a polymer electrolyte fuel cell, wherein one or more inorganic proton conductive materials are surface-modified with molecular chains having proton conductive functional groups.   The proton conductive material A having a film-forming property due to the self-assembly is in the range of 2% to 50% by weight of the electrolyte membrane, and the proton conductive material B is 50% to 98% by weight of the electrolyte membrane. The electrolyte membrane for a polymer electrolyte fuel cell according to claim 1, which is in the range of 3. The solid polymer according to claim 1, wherein the proton conductive material A is a scaly material having an average diameter in the range of 0.01 μm to 10.00 μm and an average thickness in the range of 0.01 to 1.00 μm. Electrolyte membrane for fuel cell. The proton conductive material A having a film-forming property due to self-organization is covered with the proton conductive material B at a thickness of 0.01 μm to 1.00 μm. Electrolyte membrane for polymer electrolyte fuel cell. The proton conductive material B is selected from the group consisting of fluorine-based proton conductive polymer materials, hydrocarbon-based proton conductive materials, inorganic proton conductive materials, organic-inorganic hybrid proton conductive materials, ionic liquids, and mixtures thereof. The electrolyte membrane for a polymer electrolyte fuel cell according to claim 1, 2 or 4 , which is selected . 6. An electrolyte membrane-catalyst layer assembly, wherein catalyst layers comprising catalyst particles and an electrolyte binder are formed on both surfaces of the electrolyte membrane according to any one of claims 1 to 5. 6. An electrolyte membrane-electrode, characterized in that a catalyst layer made of catalyst particles and an electrolyte binder and an electrode made of an electrode base material are formed on both surfaces of the electrolyte membrane according to any one of claims 1 to 5. Joined body. A fuel cell using the electrolyte membrane-electrode assembly according to claim 7 .

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