Polymer electrolyte film, its manufacturing method, and solid polymer fuel cell using the same

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a polymer electrolyte membrane, a method for producing the same, and a polymer electrolyte fuel cell using the same.

【0002】

[Conventional technology]

A fuel cell is a power generation device that emits less emissions, has high energy efficiency, and has a low burden on the environment. For this reason, it is once again in the limelight amid the recent rise in global environmental protection. Compared to conventional large-scale power generation facilities, it is a relatively small-scale distributed power generation facility, and is a power generation device that is expected in the future as a power generation device for mobile objects such as automobiles and ships. It is also attracting attention as a power source for small mobile devices and mobile devices, and is expected to be installed in mobile phones and personal computers in place of secondary batteries such as nickel-metal hydride batteries and lithium-ion batteries.

【0003】

In the polymer electrolyte fuel cell, in addition to the conventional polymer electrolyte fuel cell (hereinafter referred to as PEFC) that uses hydrogen gas as fuel, a direct methanol fuel cell (hereinafter referred to as DMFC) that directly supplies methanol is used. (Listed) is also attracting attention. Although the output of the DMFC is lower than that of the conventional PEFC, it has the advantage that the fuel is liquid and the reformer is not used, so the energy density is high and the usage time of the portable device per filling is long. is there.

【0004】

A fuel cell is usually composed of a cell in which an anode and a cathode electrode, in which a reaction responsible for power generation occurs, and an electrolyte membrane, which is an ion conductor between the anode and the cathode, are sandwiched between the anode and the cathode as a unit. .. Here, the electrode is composed of an electrode base material (also referred to as a current collector) that promotes gas diffusion and collects (supplys) electricity, and an electrode catalyst layer that actually serves as an electrochemical reaction field. For example, in the anode electrode of a solid polymer fuel cell, fuel such as hydrogen gas reacts in the catalyst layer of the anode electrode to generate protons and electrons, the electrons are conducted to the electrode substrate, and the protons are transferred to the polymer electrolyte membrane. Conduct. Therefore, the anode electrode is required to have good gas diffusivity, electron conductivity, and ionic conductivity. On the other hand, in the cathode electrode, an oxidizing gas such as oxygen or air reacts with the protons conducted from the polymer electrolyte membrane and the electrons transmitted from the electrode base material to generate water in the catalyst layer of the cathode electrode. Therefore, in the cathode electrode, it is necessary to efficiently discharge the generated water as well as gas diffusivity, electron conductivity, and ionic conductivity.

【0005】

Further, among solid polymer fuel cells, DMFCs that use an organic solvent such as methanol as fuel are required to have different performance from conventional PEFCs that use hydrogen gas as fuel. That is, in the DMFC, at the anode electrode, a fuel such as an aqueous methanol solution reacts in the catalyst layer of the anode electrode to generate protons, electrons, and carbon dioxide, and the electrons are conducted to the electrode substrate, and the protons are conducted to the polymer electrolyte membrane. The carbon dioxide passes through the electrode substrate and is released to the outside of the system. Therefore, in addition to the required characteristics of the conventional PEFC anode electrode, fuel permeability of an aqueous methanol solution or the like is also required. Furthermore, in the cathode electrode of the DMFC, in addition to the reaction similar to that of the conventional PEFC, there is also a reaction in which methanol and an oxidizing gas such as oxygen or air that have passed through the electrolyte membrane generate carbon dioxide and water in the catalyst layer of the cathode electrode. Occur. Therefore, since the amount of generated water is larger than that of the conventional PEFC, it is necessary to discharge the water more efficiently.

【0006】

In the DMFC, as described above, the crossover in which the fuel methanol permeates through the polymer electrolyte membrane occurs, so that there is a problem that the battery output and the energy efficiency are lowered. In order to prevent crossover of the polymer electrolyte membrane, measures to reduce the concentration of methanol supplied to the anode, a new polymer electrolyte membrane using a polymer different from the conventional perfluoro-based proton exchange membrane, and a polymer electrolyte membrane structure Ingenious measures can be mentioned. As a countermeasure against crossover by devising the structure of the polymer electrolyte membrane, there is a polymer electrolyte membrane in which the through hole is filled with a proton exchange resin as an ion conductor to suppress the swelling of the proton exchanger and suppress the crossover. Known examples include US Patent Specification Nos. 5,631,099 and 5,759,712.

【0007】

[Problems to be Solved by the Invention]

However, when a method such as US Pat. Nos. 5,631,099, 5,759,712, that is, a polymer electrolyte membrane in which a porous substrate is filled with an ionic conductor is used, the contact resistance at the interface between the ionic conductor and the catalyst layer is increased. There was a problem that it became large and the output became low. An object of the present invention is to solve the above problems and to provide a novel polymer electrolyte membrane capable of achieving high output, a method for producing the same, and a high-performance polymer electrolyte fuel cell using the same.

【0008】

[Means for solving problems]

The present invention has the following configuration in order to solve the above problems. That is, the polymer electrolyte membrane of the present invention is a polymer electrolyte membrane having a structure in which a porous base material is filled with a proton conductor, and is characterized by having a proton conductor layer on at least one surface of the porous base material. Further, the method for producing a polymer electrolyte membrane of the present invention is characterized in that a porous substrate is produced by a photolithography or a wet coagulation method. Further, the polymer electrolyte fuel cell of the present invention is characterized by being configured by using the polymer electrolyte membrane of the present invention.

【0009】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will be described.

【0010】

The polymer electrolyte membrane of the present invention is a polymer electrolyte membrane having a structure in which a porous base material is filled with a proton conductor, and is characterized by having a proton conductor layer on at least one surface of the porous base material. The conventional polymer electrolyte membrane in which a porous substrate is filled with a proton conductor has a problem that the contact resistance at the interface between the ionic conductor and the catalyst layer increases and the output decreases. On the other hand, in the polymer electrolyte membrane of the present invention, the contact resistance can be remarkably reduced by the proton conductor layer provided on the surface of the porous substrate.

【0011】

In the present invention, the proton conductor filled in the porous substrate and the one forming the proton conductor layer on one side or both sides thereof may be of the same type or different. Further, the layers on one side or both sides may be multi-layered. If the proton conductor or porous substrate filled in the porous substrate is hard and the contact resistance with the adjacent catalyst layer or current collector is high, a soft and easily deformable proton conductor layer may be provided. preferable. Examples of such a proton conductor include Nafion.

【0012】

The thickness of the proton conductor layer existing on one side or both sides of the porous substrate is not particularly limited, but if it is too thick, the increase in ion resistance becomes larger than the decrease in contact resistance. Further, if it is too thin, the effect of reducing the contact resistance becomes small. Therefore, the preferable thickness is 0.01 μm to 100 μm, and more preferably 0.01 μm to 50 μm.

【0013】

The proton conductor in the present invention is not particularly limited as long as it has a property of conducting protons, but a polymer having a cation exchange functional group is preferable. As such a functional group, a sulfonic acid group, a phosphoric acid group, a carboxylic acid group and the like are preferably used from the viewpoint of proton conductivity. The polymer used as the substrate is not particularly limited, but is polytetrafluoroethylene (PTFE: the abbreviations are described in parentheses below), polytetrafluoroethylene-perfluoroalkyl ether copolymer (PFA), and polytetrafluoroethylene. -Fluorine-containing resins such as hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polyimide (PI), polyphenylene sulfide sulphon (PPSS), polysulphon In addition to heat-resistant and oxidation-resistant polymers such as (PSF), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polyether ketone (PEK), polyether ether ketone (PEEK), and polybenzoimidazole (PBI), polyphospha Those having Zen (PPho) or the like as the main skeleton are preferably used.

【0014】

As the proton conductor used in the present invention, a proton exchange resin such as Nafion having a PTFE main chain and a side chain of polyperfluoroalkyl ether sulfonic acid is particularly preferably used.

【0015】

The method of forming the proton conductor layer on one side or both sides of the porous base material is not particularly limited. When the proton conductor layer is formed of the same material as the proton conductor to be filled in the porous substrate, it is possible to form the proton conductor layer on one side or both sides at the same time as filling the porous substrate. This is a highly productive and preferred method.

【0016】

The method for forming the proton conductor layer includes, but is not limited to, spray coating, brush coating, dip coating, die coating, curtain coating, flow coating, roll coating, screen coating and the like.

【0017】

The method of filling the porous substrate with the proton conductor is not particularly limited. For example, the voids can be filled by coating or immersing the porous substrate with a proton conductive polymer as a solution. It is also preferable to use ultrasonic waves or reduce the pressure in order to facilitate filling into the voids, and it is preferable to use these in combination during coating or immersion because the filling efficiency is further improved. Further, a method such as filling the voids with a monoma which is a precursor of a proton conductive polymer and then polymerizing in the voids, or vaporizing the monomas and performing plasma polymerization may be performed.

【0018】

The porous substrate used in the present invention is not particularly limited as long as it has a plurality of pores, but a porous substrate having a plurality of independent through holes and a three-dimensional network structure in the thickness direction is preferable. .. When the polymer electrolyte membrane of the present invention is used in a fuel cell, a porous substrate having a plurality of independent through holes in the thickness direction is preferable because it has a large effect of reducing methanol crossover.

【0019】

Further, it is more preferable that the porous substrate has through holes arranged in an orderly manner in the plane direction. Here, the "through holes arranged in an orderly manner in the plane direction" indicates a state in which the through holes are arranged at substantially equal intervals or regularly. Specifically, it is an arrangement state in which the difference between the center spacings of adjacent through holes is within 100% when compared with each other. That is, on the surface of the porous substrate, the through holes are arranged two-dimensionally, so that the adjacent through holes exist vertically and horizontally, but the difference in the center spacing of the adjacent through holes is within 100%. Must be in and arranged. It is preferably within 50%, more preferably within 30%. Even if the difference in the center spacing of adjacent through holes exceeds 100%, the center spacing of adjacent through holes inside each array is long as long as the combination is repeated for each number. It is preferably used if the error of is within 100%.

【0020】

Specific examples of the porous substrate used in the present invention include the shape shown in FIG. FIG. 1 is a schematic perspective view showing an example of the polymer electrolyte membrane of the present invention. The porous substrate of FIG. 1 has a porous portion 1 having a large number of holes in the center, and has a non-porous portion 2 having no pores around the porous portion. FIG. 2 shows an enlarged schematic view of the porous portion. In the polymer electrolyte membrane of the present invention, it is preferable that the pores 3 of the porous portion are arranged at equal intervals in an orderly manner when viewed in the plane direction as shown in FIG. L in FIG. 2 is the above-mentioned "center spacing of adjacent through holes". L is preferably in the range of 0.5 to 100 μm, particularly preferably in the range of 1 to 50 μm. The inner diameter d of the hole is preferably in the range of 0.5 to 50 μm, particularly preferably in the range of 1 to 20 μm.

【0021】

In FIG. 1, the porous portion 1 is filled with a proton conductor to exhibit a function as a polymer electrolyte membrane. In addition, by filling the holes 3 in FIG. 2 with a proton conductor, swelling is suppressed and the crossover in which the fuel methanol permeates from the anode to the cathode is reduced, but the holes 3 should be arranged in an orderly manner. For example, this crossover reduction effect is further improved.

【0022】

As a preferable method for producing the porous substrate used for the polymer electrolyte membrane of the present invention, for example, a photolithography processing method can be applied. Conventionally, as a porous base material, a filter material for filtration having through holes or the like has been used. Usually, the polymer film is irradiated with ions to break the polymer chain, and holes are formed by a chemical etching method using an alkaline solution or the like (track etching method). On the other hand, in the hole 3 using the photolithography method, the hole diameter, shape, hole spacing, perforated part, etc. can be arbitrarily set, and the performance of the fuel cell can be improved by reducing the crossover. Can be done. Further, since photolithography is excellent in microfabrication, it is possible to finely separate the porous portion 1 and the non-porous portion 2, which brings about excellent results in miniaturization of the fuel cell. In addition, it is possible to achieve cost reduction by improving productivity as compared with the conventional truck etching method.

【0023】

Here, a scanning electron microscope (SEM) photograph of the porous substrate prepared by the photolithography method is shown in FIG. 3, and a scanning electron microscope (SEM) photograph of the porous substrate prepared by the conventional track etching method is shown in FIG. Is shown in Fig. 4. It is clear that the pores of the porous substrate of the photolithography method of FIG. 3 are arranged at equal intervals in an orderly manner as compared with the track etching method of FIG.

【0024】

The cross-sectional shape of the pores in the porous substrate produced by the photolithography method is not particularly limited, but is preferably a circle, an ellipse, a square, a rectangle, a rhombus, a trapezoid, or the like. Among these, a circle or an ellipse is preferable from the viewpoint of ease of filling the proton conductor and suppression of swelling. The size and spacing of the holes are not particularly limited, and may be appropriately determined based on the ease of filling the proton conductor, the battery performance, and the like.

【0025】

The size of the entire porous portion of the porous substrate produced by the photolithography method may be determined according to the size of the electrode catalyst layer and the electrode substrate used. The thickness of the porous substrate may also be determined based on the required battery performance, but is usually preferably in the range of 1 to 50 μm, and particularly preferably in the range of 5 to 20 μm.

【0026】

The detailed method of the photolithography method used in the present invention is not particularly limited, but for example, a photosensitive polymer is applied to a substrate, exposed with a photomask, and the polymer is dissolved and pores are formed after development. A method of forming a porous polymer film and peeling it off from a substrate to obtain a porous polymer film is used. The photosensitive polymer may be either a negative type or a positive type, but can be appropriately selected depending on the required hole size, hole spacing, fuel cell performance, and the like. The substrate material is determined from the viewpoint of adhesion to the polymer and ease of peeling, and a silicon wafer, an aluminum plate, or the like is preferably used, but the substrate material is not particularly limited. The exposure may be either reduced exposure or 1x exposure, but may be appropriately determined depending on the size of the electrolyte to be produced, the size of the holes, the shape, the spacing, and the like. Further, with respect to the conditions such as development, melting, and peeling from the substrate, the conditions may be appropriately selected depending on the properties of the polymer. It is also possible to apply a non-photosensitive polymer on the substrate in advance, and then apply a photoresist on the substrate, and to create voids by coating, exposing, developing, and dissolving the polymer.

【0027】

The photosensitive or non-photosensitive polymer used in the photolithography method used in the present invention is not particularly limited, but polyimide is preferably used from the viewpoint of processability by photolithography, oxidation resistance of the polymer, strength and the like. ..

【0028】

As a specific method for forming a porous body by a photolithography method using polyimide, for example, a polyamic acid solution of a precursor is applied to a substrate, the solvent is dried and removed at about 100 ° C., and then a photomask is used. After forming pores by photolithography processing such as exposure, development, and alkali treatment, the imide ring closure reaction is performed at about 300 ° C or higher, and finally the porous polyimide film is peeled off from the substrate. Be done. The temperature and time of the solvent removal and the imide ring closure reaction can be appropriately determined depending on the type of polyimide used. When the polyimide film is peeled off from the substrate, it is usually immersed in an acid, but hydrofluoric acid is preferably used when the substrate used is a silicon wafer, and hydrochloric acid is preferably used when the substrate is an aluminum plate.

【0029】

Here, the polyimide used in the present invention may be either a negative type or a positive type photosensitive polyimide or a non-photosensitive polyimide, but is photosensitive depending on the size, shape, spacing, film thickness, etc. of the holes. Polyimide is preferable, and negative photosensitive polyimide is more preferable.

【0030】

Next, a porous substrate having a three-dimensional network structure preferably used in the present invention will be described. The "three-dimensional network structure" refers to a state in which the polymers constituting the porous substrate have a three-dimensional network structure in which they are three-dimensionally connected. Here, a scanning electron microscope (SEM) photograph of a porous substrate having a three-dimensional network structure preferably used in the present invention is shown in FIG.

【0031】

When the porous substrate has a three-dimensional network structure, the pore diameter thereof is preferably in the range of 0.05 to 5 μm, more preferably in the range of 0.1 to 1 μm. The pore diameter can be determined from the average of 20 or more holes, preferably 100 or more holes, from a photograph of the surface taken with a scanning electron microscope (SEM) or the like, and is usually measured with 100 holes. For example, a three-dimensional network porous substrate produced by a wet solidification method has a wide distribution of pore diameters, so it is preferable to take an average of as many pore diameters as possible, for example, 100 to 500 pores.

【0032】

The porosity of the three-dimensional network structure is preferably in the range of 10 to 95%. More preferably, it is in the range of 50 to 90%. Here, the porosity is a percentage (%) obtained by dividing the volume occupied by the polymer from the total volume of the porous substrate by the total volume of the porous substrate.

【0033】

As a method for producing a porous substrate having the above three-dimensional network structure, a wet solidification method is preferably used. Specifically, by immersing a polyma solution in which a polyma is dissolved in a dissolving solvent containing a good solvent in a coagulation solvent containing a poor solvent, a coagulated polyma having microporous three-dimensional network structure can be obtained. When the porous substrate is formed into a film shape, a polymer solution can be applied onto the substrate and immersed in a coagulation solvent before the solvent is dried and removed to obtain a porous substrate having fine porosity. it can. Here, the dissolution solvent and the coagulation solvent can be appropriately selected depending on the polymer used, and can be appropriately selected according to the desired hole size, shape, and fuel cell performance, but the solvents are in phase with each other. It needs to be melted.

【0034】

Even when a porous substrate produced by a wet coagulation method is used for a polymer electrolyte membrane, a shape in which the center is a porous portion and the periphery is a dense polymer film is a preferable embodiment as shown in FIG. For such a shape, for example, the following method is preferably used, but the present invention is not limited thereto.

【0035】

As a first method, there is a method in which a dense film having only a peripheral portion is prepared in advance, and then a porous portion in the center is prepared. A dense film is produced by applying a polymer solution on a substrate and usually drying it. The central portion to be made porous may be cut off later, or the central portion may be uncoated by masking at the time of coating. After that, a polymer solution is applied only to the center and immersed in a poor solvent to perform wet solidification.

【0036】

The second method is to prepare a film in which the whole is porous by a wet solidification method and close the pores in the peripheral portion. For closing the pores, a method of crushing with a press, a method of filling the pores with an aproton conductive polymer, or the like can be used, but the method is not limited thereto.

【0037】

The polymer used for the porous substrate used in the present invention is not particularly limited, but preferably polyimide (PI), polyvinylidene fluoride (PVDF), polyphenylene sulfide sulfone (PPSS), polytetrafluoroethylene (PTFE), and the like. Polysulfone (PSF) and the like, copolymers thereof, copolymers with other monomas (hexafluoropropylene-vinylidene fluoride copolymer, etc.), and blends can also be used. These polymers are preferable in terms of oxidation resistance, strength, ease of wet solidification, and the like.

【0038】

When the wet coagulation method is used, a polar solvent having a high dielectric constant is used as the dissolving solvent for these polymers, and alcohol, ether, ester, water or the like is used as the coagulation solvent. Among them, the dissolving solvent is preferably N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAC), and the coagulation solvent is preferably methanol, ethanol, isopropanol, water or the like. Further, a pore-opening agent may be added to control the pore diameter. Fine particles, salts, surfactants and the like are used as the pore-forming agent.

【0039】

Further, the porous substrate used in the present invention may have different pore shapes and sizes on the front surface and the back surface. It is also a preferable embodiment that the sizes of the holes on the front surface and the back surface are different from the viewpoint of ease of filling the proton conductor. This is expected to facilitate the filling of the proton conductor. As for the degree, it is preferable that the ratio of the hole diameters d on the front and back is in the range of 5: 1 to 1: 1. Further, holes having different sizes and shapes may coexist in the same plane.

【0040】

In the present invention, the form of the fuel cell and the method for manufacturing the fuel cell are not particularly limited. The method of using the photolithography method for manufacturing a fuel cell having a side-by-side structure will be described in detail below as an example. Here, the side-by-side structure refers to a structure in which two or more cells composed of a set of facing electrodes are arranged in the plane direction of a single polymer electrolyte membrane surface. According to this structure, the cells are connected in series by connecting the anode and cathode of two or more adjacent cells arranged with an electron conductor penetrating the polymer electrolyte membrane, so that the side-by-side structure is used. The cross section of the polymer electrolyte membrane of No. 1 has a structure in which proton conducting parts and electron conducting parts are alternately present. In order to produce such a structure, it is preferable to use a photolithography method from the viewpoint of miniaturization and productivity.

【0041】

An example of the side-by-side structure is shown in FIGS. 6 and 7. FIG. 6 is a schematic perspective view of the polymer electrolyte membrane of the present invention having a side-by-side structure, and FIG. 7 is a schematic cross-sectional view showing a part of the manufacturing process thereof. Although 2 cells are arranged horizontally in FIGS. 6 and 7, it is possible to arrange three or more cells in the plane direction with the same side-by-side structure. .. The following explanation will be given in two cells for the sake of simplicity. In FIG. 6, the porous portion 1 is filled with a proton conductor (not shown) in the proton conductive portion, and the membrane conductive portion 4 is filled with an electron conductor in the electron conductive portion. The portion other than the porous portion 1 of the proton conductive portion and the membrane conductive portion 4 of the electron conductive portion is a non-porous portion 2 in which protons and electrons do not conduct, and is a dense polymer film. The photolithography method described in the present invention is preferably used for producing a polymer film having such a complicated and fine structure. The porous substrate shown in FIG. 6 is produced by a photolithography method, and this is used as a polymer electrolyte membrane by the method illustrated in FIG. In FIG. 7, the transmembrane electron conductor is filled with the electron conductor in advance, and then the proton conductor is filled with the proton conductor, but the order may be reversed. Further, a proton conductor may be filled to prepare a proton conducting portion, then an electrode may be provided, and finally an electron conducting portion may be manufactured.

【0042】

The electron conduction portion of the side-by-side structure described above has a structure that penetrates the electrolyte membrane. Here, the portion of the electron conductive portion that penetrates the electrolyte membrane is referred to as a membrane conductive portion. This membrane conductive portion has a function different from that of the porous portion for filling the proton conductor. The size, shape, etc. of the film conductive portion are not particularly limited. The larger the film conductive portion, the lower the electrical resistance between the cells, and the voltage improvement in series can be expected. However, the larger the film conductive part, the more likely it is that an organic solvent such as hydrogen or methanol on the anode side will leak to the cathode side, or the air on the cathode side will leak to the anode side, which may cause performance degradation. is there. Therefore, it is preferable to determine the size and shape of the film conductive portion in consideration of the electrical resistance and leak resistance of the electronic conductor used in the electron conductive portion. The electron conductive portion may not penetrate the polymer electrolyte membrane but may pass through the outside.

【0043】

The electronic conductor of the film conductive portion 4 is not particularly limited, but a conductive paste is preferably used. As the conductive paste, a paste in which a conductive agent such as carbon, silver, nickel, copper, platinum, or palladium is dispersed in a polymer can be preferably used, and both reduction of electron resistance and improvement of leak resistance can be achieved at the same time. Especially in DMFC, it is important to prevent leakage of methanol. In addition to general-purpose conductive paste in which carbon and silver are dispersed in silicone resin, polyester, epoxy resin, etc., carbon black, silver, platinum, etc. are dispersed in PVDF and polyimide. The conductive paste obtained is also preferably used. The electron conductive portion 5 is electrically connected to the electrode base material or the electrode catalyst layer of the cell, and a conductive paste is preferably used to reduce the contact resistance.

【0044】

Further, as the electron conducting portion 5, a metal foil such as nickel, stainless steel, aluminum, or copper or a metal wire may be used. It is also possible to combine these metal foils or metal wires with a conductive paste.

【0045】

The polymer electrolyte membrane of the present invention is used in a polymer electrolyte fuel cell as a membrane-electrode composite (MEA) in combination with an electrode 7 composed of an electrode base material and an electrode catalyst layer.

【0046】

As the electrode catalyst layer in the electrode 7 in the polymer electrolyte fuel cell of the present invention, known ones can be used without particular limitation. The electrode catalyst layer refers to a layer containing a catalyst necessary for an electrode reaction and an electrode active material (referring to a substance that oxidizes or reduces), and further contains a substance that contributes to electron conduction or ionic conduction that promotes the electrode reaction. Further, when the electrode active material is a liquid or gas, it is necessary to have a structure in which the liquid or gas easily permeates, and a structure that promotes the discharge of the product substance accompanying the electrode reaction is also required.

【0047】

In the polymer electrolyte fuel cell of the present invention, the electrode active material is preferably an organic solvent such as hydrogen or methanol or oxygen, and the catalyst is a noble metal particle such as platinum. Further, it is preferable to contain a material for improving the conductivity of the electrode catalyst layer, and the form is not particularly limited, but for example, it is preferable to have conductive particles. Examples of the conductive particles include carbon black and the like, and platinum-supported carbon and the like are particularly preferably used as the catalyst-supported carbon black. The electrode catalyst layer is required to have a structure in which a catalyst, an electron conductor (for example, carbon black), and an ion conductor (for example, a proton exchange resin) come into contact with each other to efficiently move in and out of the electrode active material and the reaction product. Further, the polymer compound is effective for improving the ionic conductivity, improving the binding property of the material, or increasing the water repellency. Therefore, it is preferable that the electrode catalyst layer contains at least catalyst particles, conductive particles, and a polymer compound.

【0048】

In the solid polymer fuel cell of the present invention, a known catalyst can be used as the catalyst contained in the electrode catalyst layer, and the catalyst is not particularly limited, but platinum, palladium, ruthenium, iridium, gold and the like can be used. A noble metal catalyst is preferably used. Further, two or more kinds of elements such as alloys and mixtures of these precious metal catalysts may be contained.

【0049】

The electron conductor (conductive material) contained in the electrode catalyst layer is not particularly limited, but an inorganic conductive substance is preferably used from the viewpoint of electron conductivity and touch resistance. Among them, carbon black, graphitic and carbonaceous carbon materials, and metals and semimetals can be mentioned. Here, as the carbon material, carbon black such as channel black, thermal black, furnace black, and acetylene black is preferably used because of its electron conductivity and large specific surface area. As for furnace black, Cabot's Vulcan XC-72, Vulcan P, Black Pearls 880, Black Pearls 1100, Black Pearls 1300, Black Pearls 2000, Legal 400, Ketjen Black EC, Ketjen Black EC, Mitsubishi Chemical Co., Ltd. Examples include # 3150 and # 3250 manufactured by Denka Black Co., Ltd., and Denka Black manufactured by Denki Kagaku Kogyo Co., Ltd. can be mentioned as acetylene black. In addition to carbon black, artificial graphite and carbon obtained from organic compounds such as natural graphite, pitch, coke, polyacrylonitrile, phenol resin, and furan resin can also be used. The form of these carbon materials is not particularly limited, and fibrous ones as well as particulate ones can be used. It is also possible to use a carbon material obtained by post-treating these carbon materials. Among such carbon materials, Cabot's Vulcan XC-72 is particularly preferably used from the viewpoint of electron conductivity.

【0050】

The amount of these electron conductors added should be appropriately determined according to the required electrode characteristics, the specific surface area of the substance used, the electronic resistance, etc., but the weight ratio in the electrode catalyst layer is 1 to 80%. The range of 20 to 60% is preferable, and the range of 20 to 60% is more preferable. When the amount of the electron conductor is small, the electron resistance is high, and when the amount is large, the gas permeability is impaired and the catalyst utilization rate is lowered, all of which lower the electrode performance.

【0051】

It is preferable that the electron conductor is uniformly dispersed with the catalyst particles in terms of electrode performance. Therefore, it is preferable that the catalyst particles and the electron conductor are well dispersed as a coating liquid in advance.

【0052】

It is also a preferred embodiment to use a catalyst-supported carbon in which a catalyst and an electron conductor are integrated as the electrode catalyst layer. By using this catalyst-supported carbon, the utilization efficiency of the catalyst can be improved and the cost can be reduced. Here, even when the catalyst-supported carbon is used for the electrode catalyst layer, it is possible to further add a conductive agent. As such a conductive agent, the above-mentioned carbon black is preferably used.

【0053】

As the ionic conductor used for the electrode catalyst layer, known ones can be used. As the ionic conductor, various organic and inorganic materials are generally known, but when used in a fuel cell, ions such as a sulfonic acid group, a carboxylic acid group, and a phosphoric acid group that improve proton conductivity are known. A polymer having an exchange group is preferably used. Of these, a polymer having a proton exchange group composed of a fluoroalkyl ether side chain and a fluoroalkyl main chain is preferably used. For example, Nafion manufactured by DuPont, Aciplex manufactured by Asahi Kasei, Flemion manufactured by Asahi Glass, etc. are preferably used. These ion exchange polymers are provided in the electrode catalyst layer in the form of a solution or a dispersion. At this time, the solvent for dissolving or dispersing the polymer is not particularly limited, but a polar solvent is preferable from the viewpoint of solubility of the ion exchange polymer.

【0054】

The ion conductor is preferably added in advance to a coating liquid containing the electrode catalyst particles and the electron conductor as the main constituent substances when the electrode catalyst layer is produced, and applied in a uniformly dispersed state from the viewpoint of electrode performance. However, the ionic conductor may be applied after the electrode catalyst layer is applied. Here, examples of the method of applying the ionic conductor to the electrode catalyst layer include spray coating, brush coating, dip coating, die coating, curtain coating, flow coating and the like, and are not particularly limited.

【0055】

The amount of the ionic conductor contained in the electrode catalyst layer should be appropriately determined according to the required electrode characteristics, the conductivity of the ionic conductor used, and the like, and is not particularly limited, but the weight. The ratio is preferably in the range of 1 to 80%, more preferably in the range of 5 to 50%. If the amount of the ionic conductor is too small, the ionic conductivity is low, and if the amount is too large, the gas permeability is impaired, and both of them may deteriorate the electrode performance.

【0056】

The electrode catalyst layer may contain various substances in addition to the above-mentioned catalyst, electron conductor, and ionic conductor. In particular, in order to enhance the binding property of the substance contained in the electrode catalyst layer, it is preferable to contain a polymer other than the above-mentioned proton exchange resin. Examples of such polymers include, but are not limited to, polymers containing a fluorine atom, such as polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polyhexafluoropropylene (FEP), and poly. Tetrafluoroethylene, polyvinylidene fluoride ether (PFA), etc., or polymers thereof, copolymers of monoma units constituting these polymers with other monomas such as ethylene and styrene, and blends, etc. Can be used. The content of these polymers in the electrode catalyst layer is preferably in the range of 5 to 40% by weight. If the polymer content is too high, electron and ionic resistance tends to increase and electrode performance tends to deteriorate.

【0057】

It is also a preferred embodiment that the electrode catalyst layer has a three-dimensional network structure of the catalyst-polymer complex. The catalyst-polymer complex is a polymer complex containing catalyst particles, and the complex has a three-dimensional network structure. That is, it has a three-dimensional network structure in which the catalyst-polymer complex is three-dimensionally connected.

【0058】

When the electrode catalyst layer has a three-dimensional network structure, the pore diameter thereof is preferably in the range of 0.05 to 5 μm, more preferably in the range of 0.1 to 1 μm. The pore size can be determined from an average of 20 or more, preferably 100 or more, from a photograph of the surface taken with a scanning electron microscope (SEM) or the like, and is usually measured at 100. The electrode catalyst layer having a porous structure produced by the wet solidification method has a wide distribution of pore diameters, so that the number of the electrode catalyst layers is as large as possible, and it is preferable to take an average of 100 to 500 pore diameters.

【0059】

The porosity of the three-dimensional network structure of the electrode catalyst layer is preferably in the range of 10 to 95%. More preferably, it is in the range of 50 to 90%. Here, the porosity is a percentage (%) obtained by dividing the volume occupied by the catalyst-polyma complex from the total volume of the electrode catalyst layer by the total volume of the electrode catalyst layer.

【0060】

In order to prepare an electrode catalyst layer having a three-dimensional network structure, wet solidification is usually performed after the catalyst layer is applied to an electrode base material, a proton exchange membrane, and other base materials. When it is difficult to determine the porosity of the electrode catalyst layer alone, the porosity of the electrode base material, the proton exchange membrane, and other base materials is obtained in advance, and these base materials and the electrode catalyst layer are included. After determining the porosity, it is also possible to determine the porosity of the electrode catalyst layer alone.

【0061】

The electrode catalyst layer having a three-dimensional network structure has a large porosity, good gas diffusibility and good discharge of generated water, and also good electron conductivity and proton conductivity. In the conventional porosity, the particle size of the catalyst particle and the particle size of the added polymer are increased, and voids are formed by using a pore-forming agent. The contact resistance between the proton exchange resins becomes larger than that of the electrode catalyst layer. On the other hand, in the three-dimensional network structure by the wet solidification method, the polymer composite containing the catalyst-supported carbon has a three-dimensional network shape, so that electrons and protons are easily conducted through this polymer composite, and the polymer composite is further microporous. Due to the quality structure, the gas diffusivity and the discharge of generated water are also good, which is preferable.

【0062】

Even when the electrode catalyst layer has a three-dimensional network structure, the same substances as those used in the past can be used as the substances used for the catalyst, the electron conductor, and the ionic conductor. However, since it is preferable to use a wet coagulation method when producing an electrode catalyst layer having a three-dimensional network structure, it is preferable to select a polymer suitable for this wet coagulation method, the catalyst particles are well dispersed, and the fuel is used. A polymer that does not deteriorate in the oxidation-reduction atmosphere in the battery is preferable. Examples of such polymers include, but are not limited to, polymers containing a fluorine atom, such as polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polyhexafluoropropylene (FEP), and poly. Perfluoroalkyl Vinyl Ether (PFA), etc., or copolymers thereof, copolymers of the monoma units constituting these polymers with other monomas such as ethylene and styrene (for example, hexafluoropropylene-vinylidene fluoride copolymer). (Combining, etc.), and further, blending and the like can be preferably used.

【0063】

Among these, polyvinylidene fluoride (PVDF) and hexafluoropropylene-vinylidene fluoride copolymers are three-dimensional by a wet coagulation method using an aprotic polar solvent as a dissolving solvent and a protic and aprotic polar solvent as a coagulation solvent. It is a particularly preferable polymer in that a catalyst-polymer complex having a network structure can be obtained.

【0064】

Specific examples of the solvent of the polymer include N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAC), propylene carbonate (PC), dimethylimidazolidinone (DMI), and coagulation. Examples of the solvent include water, lower alcohols such as methanol, ethanol and isopropanol, esters such as ethyl acetate and butyl acetate, and various aromatic or halogen-based organic solvents.

【0065】

As the polymer of the catalyst-polymer complex, in addition to the above-mentioned polymer, a polymer having a proton exchange group in order to improve proton conductivity is also preferable. Examples of the proton exchange group contained in such a polymer include a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, and the like, but are not particularly limited. Further, a polymer containing such a proton exchange group in the skeleton is also used without particular limitation. For example, a polymer having a proton exchange group composed of a fluoroalkyl ether side chain and a fluoroalkyl main chain is preferably used. Specifically, it is Nafion manufactured by DuPont. Further, the above-mentioned polymer containing a fluorine atom having a proton exchange group, other polymers such as ethylene and styrene, and copolymers or blends thereof may be used.

【0066】

When Nafion is used, a commercially available Nafion film may be dissolved in an aprotic polar solvent, or water-methanol-isopropanol, water-ethanol-commercially available from Aldrich, DuPont, IonPower, etc. It is also possible to use a Nafion solution of a lower alcohol-containing mixed solvent such as isopropanol and water-ethanol-n propanol. Moreover, you may use these Nafion solutions concentrated or solvent-substituted. In this case, the coagulation solvent for wet coagulation should be appropriately determined depending on the solvent type of the Nafion solution, but when the solvent of the Nafion solution is an aproton polar solvent, the coagulation solvent is water or alcohol. In addition to the above types and esters, various organic solvents and the like are preferable, and in the case of a lower alcohol solvent such as a water-methanol-isopropanol mixed solvent, esters such as butyl acetate and various organic solvents are preferably used.

【0067】

As the polymer used in the catalyst-polymer complex, it is also preferable to copolymerize or blend the above-mentioned polymer containing a fluorine atom or a polymer containing a proton exchange membrane. In particular, blending polyvinylidene fluoride, poly (hexafluoropropylene-vinylidene fluoride) copolymers, and polymers such as Nafion, which has a fluoroalkyl ether side chain and a fluoroalkyl main chain as proton exchange groups, is an electrode performance. It is preferable from the point of view.

【0068】

The main components of the catalyst-polymer complex are catalyst-supported carbon and polymer, and their ratios should be appropriately determined according to the required electrode characteristics and are not particularly limited, but are not particularly limited, but catalyst-supported carbon / polymer. 5/95 to 95/5 is preferably used in terms of the weight ratio of. In particular, when used as an electrode catalyst layer for a polymer electrolyte fuel cell, the catalyst-supported carbon / polymer weight ratio is preferably 40/60 to 85/15.

【0069】

Various additives can also be added to the catalyst-polymer complex. For example, there are conductive agents such as carbon for improving electron conductivity, polymers for improving binding properties, and additives for controlling the pore size of a three-dimensional network structure, but they can be used without particular limitation. it can. The amount of these additives added is preferably in the range of 0.1 to 50%, more preferably in the range of 1 to 20%, as a weight ratio to the catalyst-polymer complex .

【0070】

As a method for producing a catalyst-polymer complex having a three-dimensional network structure, a wet coagulation method is preferable. Here, after the catalyst-polymer solution composition is applied, the coating layer can be brought into contact with a coagulating solvent for the polymer to simultaneously perform coagulation precipitation and solvent extraction of the catalyst-polymer solution composition. In this catalyst-polymer solution composition, catalyst-supporting carbon is uniformly dispersed in the polymer solution. As the catalyst-supported carbon and the polymer, the above-mentioned ones are preferably used. The solvent for dissolving the polymer should be appropriately determined according to the polymer used, and is not particularly limited. It is important that the polymer solution has well dispersed catalyst-supported carbon. If the dispersed state is poor, the catalyst-supported carbon and the polymer cannot form a complex during wet solidification, which is not preferable.

【0071】

As for the coating method of the catalyst-polymer solution composition, a coating method according to the viscosity and solid content of the catalyst-polymer solution composition is selected, and the coating method is not particularly limited, but is limited to knife coater, bar coater, spray, and the like. Common coating methods such as dip coaters, spin coaters, roll coaters, die coaters, and curtain coaters are used.

【0072】

Further, the coagulation solvent for wet-coagulating the polymer is not particularly limited, but a solvent that easily coagulates and precipitates the polymer to be used and is compatible with the solvent of the polymer solution is preferable. The contact method between the base material and the coagulation solvent is also not particularly limited, but the base material is immersed in the coagulation solvent together with the base material, only the coating layer is brought into contact with the liquid surface of the coagulation solvent, and the coagulation solvent is showered on the coating layer. Methods such as ringing or spraying can be used.

【0073】

As for the base material to which the catalyst-polymer solution composition is applied, wet coagulation can be performed after application to either the electrode base material or the polymer electrolyte membrane. Further, after applying to a base material other than the electrode base material or the polymer electrolyte (for example, a transfer base material) and then performing wet solidification to prepare a three-dimensional network structure, this electrode catalyst layer is applied to the electrode base material or the polymer. It may be transferred or sandwiched on the electrolyte membrane. As the transfer base material in this case, a sheet of polytetrafluoroethylene (PTFE), a glass plate or a metal plate whose surface is treated with a fluorine or silicone-based mold release agent is also used.

【0074】

In the polymer electrolyte fuel cell of the present invention, known electrode base materials can be used without particular limitation. In addition, the electrode base material may not be used to save space.

【0075】

The electrode base material used in the present invention can be used without particular limitation as long as it has low electrical resistance and can collect (supply) electricity. Examples of the constituent material of the electrode base material include those mainly composed of a conductive inorganic substance, and examples of the conductive inorganic substance include a fired body from polyacrylonitrile, a fired body from pitch, graphite and expanded graphite. Carbon material, stainless steel, molybdenum, titanium and the like are exemplified.

【0076】

The form of the conductive inorganic substance of the electrode base material is not particularly limited, and is used, for example, in the form of fibers or particles. However, from the viewpoint of gas permeability, fibrous conductive inorganic substances (inorganic conductive fibers), particularly carbon fibers, are used. preferable. As the electrode base material using inorganic conductive fibers, either a woven fabric or a non-woven fabric structure can be used. For example, carbon paper TGP series and SO series manufactured by Toray Industries, Inc., carbon cloth manufactured by E-TEK, etc. are used. As the woven fabric, plain weave, twill weave, satin weave, crest weave, binding weave and the like are used without particular limitation. The non-woven fabric is not particularly limited, such as a papermaking method, a needle punching method, a spunbonding method, a water jet punching method, and a melt blowing method. It may also be knitted. In these fabrics, especially when carbon fibers are used, a woven fabric obtained by carbonizing or graphiteizing a plain woven fabric using flame-resistant spun yarn, or a non-woven fabric processing of flame-resistant yarn by a needle punch method or a water jet punch method is then carbonized. Alternatively, a graphitized non-woven fabric, a flame-resistant yarn, a carbide yarn, or a matte non-woven fabric by a paper-making method using a graphite yarn is preferably used. In particular, it is preferable to use a non-woven fabric from the viewpoint of obtaining a thin and strong cloth.

【0077】

When inorganic conductive fibers made of carbon fibers are used as the electrode base material, examples of the carbon fibers include polyacrylonitrile (PAN) -based carbon fibers, phenol-based carbon fibers, pitch-based carbon fibers, and rayon-based carbon fibers. .. Of these, PAN-based carbon fibers are preferable. This is because, in general, PAN-based carbon fibers have higher compressive strength and tensile elongation at break than pitch-based carbon fibers, and are less likely to break. In order to obtain carbon fibers that are hard to break, the carbonization temperature of the carbon fibers is preferably 2,500 ° C or lower, more preferably 2,000 ° C or lower.

【0078】

Water repellent treatment performed on the electrode base material used in the polymer electrolyte fuel cell of the present invention to prevent deterioration of gas diffusion / permeability due to retention of water, partial water repellency for forming a water discharge path, It is also a preferable embodiment to carry out hydrophilic treatment, addition of carbon powder, etc., which is performed to reduce resistance.

【0079】

When the polymer electrolyte fuel cell of the present invention has a side-by-side structure, in order to promote the inflow of fuel such as hydrogen and methanol aqueous solution and air, and the discharge of products such as water and carbon dioxide. , It is also a preferred embodiment to provide a diffusion layer. Although the above-mentioned electrode base material also plays a role in such a diffusion layer, it is more preferable to use a non-conductive fabric as the diffusion layer. Here, as the constituent material of the non-conductive fabric, for example, non-conductive fibers are used without particular limitation.

【0080】

Examples of the non-conductive fibers constituting the non-conductive fabric of the diffusion layer include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoroethylene copolymer (FEP), and tetrafluoroethylene-perfluoroalkyl vinyl ether co-weight. Combined (PFA), tetrafluoroethylene-ethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), polychlorotrifluoroethylene (CTFE), chlorinated polyethylene, flame-resistant polyacrylonitrile, poly Acrylonitrile, polyester, polyamide, polyethylene, polypropylene and the like can be used. Among these non-conductive fibers, fibers made of fluorine atom-containing polymers such as PTFE, FEP, PFA, ETFE, PVDF, PVF, and CTFE are preferable from the viewpoint of corrosion resistance during electrode reaction.

【0081】

As the non-conductive fabric of the diffusion layer, either a woven fabric or a non-woven fabric structure can be used. As the woven fabric, plain weave, twill weave, satin weave, crest weave, binding weave and the like are used without particular limitation. The non-woven fabric is not particularly limited, such as a papermaking method, a needle punching method, a spunbonding method, a water jet punching method, and a melt blowing method. It may also be knitted. Among these fabrics, a plain woven fabric, a non-woven fabric produced by a needle punching method or a water jet punching method, a matte non-woven fabric produced by a papermaking method, or the like is preferably used. In particular, a non-woven fabric is preferably used because a porous, thin and strong cloth can be obtained.

【0082】

It is also preferable that the non-conductive fabric of the diffusion layer is subjected to water repellent treatment to prevent deterioration of gas diffusion / permeability due to retention of water, partial water repellent treatment to form a water discharge path, or hydrophilic treatment. This is an embodiment. Furthermore, post-treatment such as heat treatment, stretching, and pressing is also a preferred embodiment. These post-treatments can be expected to have effects such as thinning, increasing porosity, and increasing strength.

【0083】

In the polymer electrolyte fuel cell of the present invention, it is preferable to provide a conductive intermediate layer containing at least an inorganic conductive substance and a hydrophobic polymer between the electrode base material and the electrode catalyst layer. In particular, when the electrode base material is a carbon fiber woven fabric or a non-woven fabric having a large porosity, the performance deterioration due to the electrode catalyst layer permeating into the electrode base material can be suppressed by providing the conductive intermediate layer.

【0084】

When the polymer electrolyte membrane of the present invention is used, for example, in a membrane-electrode composite (MEA), it is preferable to obtain MEA after post-processing the polymer electrolyte membrane. For example, it is also a preferred embodiment to coat the polymer electrolyte membrane with a metal thin film in order to further reduce the permeation of fuel methanol. Examples of such a metal thin film include palladium, platinum, silver and the like.

【0085】

In the polymer electrolyte membrane of the present invention, the method for producing a membrane-electrode composite (MEA) using an electrode catalyst layer or an electrode catalyst layer and an electrode base material is not particularly limited. It is preferable to integrate them by hot pressing, but the temperature and pressure may be appropriately selected depending on the thickness of the polymer electrolyte membrane, the porosity, the electrode catalyst layer and the electrode base material. Normally, the temperature is 40 ° C to 180 ° C and the pressure is 10kgf / cm.²~ 80kgf / cm²Is preferable.

【0086】

The polymer electrolyte membrane of the present invention can be applied to various electrochemical devices. For example, a fuel cell, a water electrolyzer, a chloro-alkali electrolyzer and the like can be mentioned, but the fuel cell is the most preferable. Further, among the fuel cells, the solid polymer fuel cell is suitable, and there are one that uses hydrogen as a fuel and one that uses an organic solvent such as methanol as a fuel, and the fuel cell is not particularly limited, but methanol. It is particularly preferably used for a DMFC fueled by.

【0087】

Further, the application of the polymer electrolyte fuel cell of the present invention is not particularly limited, but a mobile power supply source is preferable. In particular, it is preferably used as a power supply source for mobile devices such as mobile phones, personal computers, PDAs, home appliances such as vacuum cleaners, automobiles such as passenger cars, buses and trucks, ships, and mobile bodies such as railways.

【0088】

[Example]

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

【0089】

Example 1 (1) Preparation of porous substrate Negative photosensitive polyimide was applied onto a silicon wafer by a spin coating method and prebaked at 110 ° C. This was exposed with a photomask, developed, washed with water, and then fully baked at 350 ° C. This was immersed in a hydrofluoric acid solution and peeled off from a silicon wafer to obtain a porous polyimide film. The obtained film has the shape shown in Fig. 1. The porous polyimide film has an external dimension of 8 cm x 8 cm square and a thickness of 10 μm, and the central porous portion 1 has an external dimension of 2.2 cm x 2.2 cm square. Yes, the periphery of the porous portion 1 is the non-porous portion 2. In the perforated portion 1, there was a penetrating hole 3 having a hole diameter d of about 12 μm, the center spacing L of the holes was about 50 μm, the aperture ratio was about 10%, and the number of holes was about 442,000. FIG. 3 is a perspective view of this perforated portion using a scanning electron microscope (SEM) photograph. (2) Preparation of polymer electrolyte membrane The porous substrate prepared in the above step (1) was immersed in a Nafion (ion exchange equivalent: 0.9meq) solution, pulled up, and dried. The Nafion solution was applied to one side of the resulting film and dried. In this way, a polymer electrolyte membrane was prepared in which the porous substrate was filled with the Nafion polymer, which is a proton conductor, and the Nafion polymer layer was provided on only one side thereof. The thickness of the Nafion layer formed on one side at this time was 10 μm when measured with a scanning electron microscope and a film thickness meter. (3) Fabrication of electrodes After 20% PTFE water repellent treatment was applied to the carbon fiber cloth base material, a carbon black dispersion containing 20% PTFE was applied and fired to prepare an electrode base material. An anode electrode catalyst coating solution consisting of Pt-Ru-supporting carbon and Nafion solution is applied onto this electrode substrate and dried to coat the anode electrode, and a cathode electrode catalyst coating solution consisting of Pt-supported carbon and Nafion solution is applied. It was processed and dried to prepare a cathode electrode. (4) Manufacture and evaluation of polymer electrolyte fuel cells The polymer electrolyte membrane of the step (2) was held by the anode electrode and the cathode electrode prepared in the step (3) and heated and pressed to prepare a membrane-electrode composite (MEA). At this time, the Nafion layer of the polymer electrolyte membrane was arranged so as to be on the cathode side. The MEA was evaluated by sandwiching this MEA between separators and flowing a 3% MeOH aqueous solution on the anode side and air on the cathode side. For evaluation, a constant current was passed through the MEA, and the voltage at that time was measured. The current was gradually increased and the measurement was performed until the voltage became 10 mV or less. The product of current and voltage at each measurement point is the output. Moreover, the resistance of MEA was obtained from the current interrupter (current interruption method) carried out in the above evaluation. The current interrupter is a method in which the current is stopped momentarily and the resistance is obtained from the voltage dropped at that time. The standard for judging the resistance value is 100 mΩ / cm.²Less than good, 100mΩ / cm²The above was regarded as defective. The results are summarized in Table 1.

【0090】

Example 2 (1) Preparation of porous substrate A porous substrate was prepared in the same manner as in Example 1. (2) Preparation of polymer electrolyte membrane The porous substrate prepared in the above step (1) was immersed in a Nafion (ion exchange equivalent: 0.9meq) solution, pulled up, and dried. The Nafion solution was applied to both sides of the resulting film and dried. A polymer electrolyte membrane was prepared in which a porous substrate was filled with Nafion polymer, which is a proton conductor, and had Nafion polymer layers on both sides thereof. The thickness of the Nafion layer formed at this time was measured with a scanning electron microscope and a film thickness meter and found to be 10 μm on one side. (3) Manufacture and evaluation of polymer electrolyte fuel cells The polymer electrolyte membrane of the above step (2) is held by the anode electrode and the cathode electrode prepared in the same manner as in Example 1 and heat-pressed to prepare a membrane-electrode composite (MEA). The MEA evaluation was performed in the same manner.

【0091】

Comparative example 1 (1) Preparation of porous substrate A porous substrate was prepared in the same manner as in Example 1. (2) Preparation of polymer electrolyte membrane The porous substrate prepared in the above step (1) was immersed in a Nafion (ion exchange equivalent: 0.9meq) solution, pulled up, and dried. A polymer electrolyte membrane was prepared in which a porous substrate was filled with Nafion polymer, which is a proton conductor, and there was no Nafion polymer layer on both sides thereof. (3) Manufacture and evaluation of polymer electrolyte fuel cells The polymer electrolyte membrane of the above step (2) is held by the anode electrode and the cathode electrode prepared in the same manner as in Example 1 and heat-pressed to prepare a membrane-electrode composite (MEA). The MEA evaluation was performed in the same manner.

【0092】

Example 3 (1) Preparation of porous substrate A porous substrate was prepared in the same manner as in Example 1. (2) Preparation of polymer electrolyte membrane The porous substrate prepared in the above step (1) was immersed in a sulfonated polyphenylene sulfide sulfone (ion exchange equivalent: 2meq, hereinafter referred to as sulfonated PPSS) solution, pulled up, and dried. The sulfonated PPSS solution was applied to both sides of the resulting membrane and dried. A polymer electrolyte membrane was prepared in which a porous base material was filled with a sulfonated PPSS polymer, which is a proton conductor, and a sulfonated PPSS polymer layer was provided on both sides thereof. The thickness of the sulfonated PPSS layer formed at this time was measured with a scanning electron microscope and a film thickness meter and found to be 10 μm on one side. (3) Manufacture and evaluation of polymer electrolyte fuel cells The polymer electrolyte membrane of the above step (2) is held by the anode electrode and the cathode electrode prepared in the same manner as in Example 1 and heat-pressed to prepare a membrane-electrode composite (MEA). The MEA evaluation was performed in the same manner.

【0093】

Comparative example 2 (1) Preparation of porous substrate A porous substrate was prepared in the same manner as in Example 1. (2) Preparation of polymer electrolyte membrane The porous substrate prepared in the above step (1) was immersed in a sulfonated PPSS (ion exchange equivalent: 2meq) solution, pulled up, and dried. A polymer electrolyte membrane was prepared in which a porous base material was filled with a sulfonated PPSS polymer, which is a proton conductor, and there was no sulfonated PPSS polymer layer on both sides thereof. (3) Manufacture and evaluation of polymer electrolyte fuel cells The polymer electrolyte membrane of the above step (2) is held by the anode electrode and the cathode electrode prepared in the same manner as in Example 1 and heat-pressed to prepare a membrane-electrode composite (MEA). The MEA evaluation was performed in the same manner.

【0094】

Example 4 (1) Preparation of porous substrate A porous substrate was prepared in the same manner as in Example 1. (2) Preparation of polymer electrolyte membrane The porous substrate prepared in the above step (1) was immersed in a sulfonated polydiphenoxyphosphazene (ion exchange equivalent: 2meq, hereinafter referred to as sulfonated PDPOP) solution, pulled up, and dried. The sulfonated PDPOP solution was applied to both sides of the resulting membrane and dried. A polymer electrolyte membrane was prepared in which a porous substrate was filled with a sulfonated PDPOP polymer, which is a proton conductor, and a sulfonated PDPOP polymer layer was provided on both sides thereof. The thickness of the sulfonated PDPOP layer formed at this time was measured with a scanning electron microscope and a film thickness meter and found to be 10 μm on one side. (3) Manufacture and evaluation of polymer electrolyte fuel cells The polymer electrolyte membrane of the above step (2) is held by the anode electrode and the cathode electrode prepared in the same manner as in Example 1 and heat-pressed to prepare a membrane-electrode composite (MEA). The MEA evaluation was performed in the same manner.

【0095】

Comparative example 3 (1) Preparation of porous substrate A porous substrate was prepared in the same manner as in Example 1. (2) Preparation of polymer electrolyte membrane The porous substrate prepared in the above step (1) was immersed in a sulfonated PDPOP (ion exchange equivalent: 2meq) solution, pulled up, and dried. A polymer electrolyte membrane was prepared in which a porous substrate was filled with sulfonated PDPOP, which is a proton conductor, and there were no sulfonated PDPOP layers on both sides thereof. (3) Manufacture and evaluation of polymer electrolyte fuel cells The polymer electrolyte membrane of the above step (2) is held by the anode electrode and the cathode electrode prepared in the same manner as in Example 1 and heat-pressed to prepare a membrane-electrode composite (MEA). The MEA evaluation was performed in the same manner.

【0096】

Example 5 (1) Preparation of porous substrate A porous substrate of polyvinylidene fluoride (hereinafter abbreviated as PVDF) was prepared by the following wet coagulation method. The PVDF solution was developed on a glass substrate by a bar coater and immersed in water together with the glass plate. The film formed on the glass substrate was peeled off and dried to obtain a porous substrate. When this porous substrate was observed with a scanning electron microscope, it was confirmed that the average pore diameter on the surface was 1 μm, the film thickness was 50 μm, and the cross section had a three-dimensional network structure. The aperture ratio was 50%. (2) Preparation of polymer electrolyte membrane The porous substrate prepared in the above step (1) was filled with the Nafion polymer, which is a proton conductor, in the same manner as in (2) of Example 2, and the porous substrate was provided with Nafion polymer layers on both sides thereof. A polymer electrolyte membrane was prepared. The thickness of the Nafion layer formed at this time was measured with a scanning electron microscope and a film thickness meter and found to be 10 μm on both sides. (3) Manufacture and evaluation of polymer electrolyte fuel cell The polymer electrolyte membrane of the above step (2) is held by the anode electrode and the cathode electrode prepared in the same manner as in Example 1 and heated and pressed to form a film-electrode. A complex (MEA) was prepared and MEA evaluation was performed in the same manner as in Example 1.

【0097】

Comparative example 4 (1) Preparation of porous substrate A porous substrate was prepared in the same manner as in Example 5. (2) Preparation of polymer electrolyte membrane The porous substrate prepared in the above step (1) was immersed in a Nafion (ion exchange equivalent: 0.9meq) solution, pulled up, and dried. A polymer electrolyte membrane was prepared in which a porous substrate was filled with Nafion polymer, which is a proton conductor, and there was no Nafion polymer layer on both sides thereof. (3) Manufacture and evaluation of polymer electrolyte fuel cells The polymer electrolyte membrane of the above step (2) is held by the anode electrode and the cathode electrode prepared in the same manner as in Example 1 and heat-pressed to prepare a membrane-electrode composite (MEA). The MEA evaluation was performed in the same manner.

【0098】

Example 6 (1) Preparation of porous substrate A porous substrate was prepared in the same manner as in Example 1. (2) Preparation of polymer electrolyte membrane The porous substrate prepared in the above step (1) was immersed in a sulfonated PPSS (ion exchange equivalent: 2meq) solution, pulled up, and dried. A sulfonated PPSS solution was applied to both sides of the resulting membrane and dried. Further, Nafion (ion exchange equivalent: 0.9meq) solution was applied to both sides of the membrane and dried. A polymer electrolyte membrane was prepared in which a porous substrate was filled with sulfonated PPSS, which is a proton conductor, and had two layers, a sulfonated PPSS layer and a Nafion polymer layer, on both sides thereof. The thickness of the sulfonated PPSS and Nafion polymer layers formed at this time was measured with a scanning electron microscope and a film thickness meter and found to be 20 μm on one side. (3) Manufacture and evaluation of polymer electrolyte fuel cells The polymer electrolyte membrane of the above step (2) is held by the anode electrode and the cathode electrode prepared in the same manner as in Example 1 and heat-pressed to prepare a membrane-electrode composite (MEA). The MEA evaluation was performed in the same manner.

【0099】

Example 7 (1) Preparation of porous substrate A porous substrate was prepared in the same manner as in Example 1. (2) Preparation of polymer electrolyte membrane The porous substrate prepared in the above step (1) was immersed in a sulfonated PPSS (ion exchange equivalent: 2meq) solution, pulled up, and dried. A Nafion (ion exchange equivalent: 0.9meq) solution is applied to both sides of the resulting film, dried, and the porous substrate is filled with sulfonated PPSS, which is a proton conductor, and a Nafion polymer layer is provided on both sides of the polymer electrolyte. A film was prepared. The thickness of the Nafion polymer layer formed at this time was measured with a scanning electron microscope and a film thickness meter and found to be 10 μm on one side. (3) Manufacture and evaluation of polymer electrolyte fuel cells The polymer electrolyte membrane of the above step (2) is held by the anode electrode and the cathode electrode prepared in the same manner as in Example 1 and heat-pressed to prepare a membrane-electrode composite (MEA). The MEA evaluation was performed in the same manner.

【0100】

[table 1]

<img file="JP2003123792A_D0001.tif" />【0101】

From Table 1, the MEA evaluation results of the examples were all excellent. On the other hand, the MEA evaluation results of Comparative Examples 1 to 4 having no proton conductor layer on the surface of the porous substrate were inferior.

【0102】

[Effect of the invention]

According to the present invention, it is possible to provide a novel polymer electrolyte membrane capable of achieving high output, a method for producing the same, and a high-performance polymer electrolyte fuel cell using the same, and its practicality is high.

[Simple explanation of drawings]

[Figure 1]

It is a perspective schematic diagram of the polymer electrolyte membrane of this invention.

[Figure 2]

It is an enlarged plan view of the porous part 1 in the polymer electrolyte membrane of this invention.

[Fig. 3]

It is a scanning electron micrograph of a porous base material in which the porous materials used for the polymer electrolyte membrane of the present invention are arranged in an orderly manner.

[Fig. 4]

It is a scanning electron micrograph of a porous base material used for a conventional polymer electrolyte membrane.

[Fig. 5]

It is a scanning electron micrograph of a porous substrate having a three-dimensional network structure used for the polymer electrolyte membrane of the present invention.

[Fig. 6]

It is a perspective schematic diagram of the polymer electrolyte membrane of the side-by-side structure of this invention.

[Fig. 7]

It is sectional drawing which shows a part of the manufacturing process of the side-by-side structure fuel cell using the polymer electrolyte membrane of this invention.

[Explanation of symbols]

1: Perforated part 2: Non-porous part 3: Hole 4: Membrane conductive part 5: Transmembrane electron conduction part 6: Proton conduction part 7: Electrodes d: Hole diameter L: Center spacing of adjacent through holes