JP2009049004A - Method of manufacturing liquid supply type fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid supply type fuel cell in which cell output of high performance is obtained from beginning of power generation even if using a membrane electrode assembly immediately after formation or the assembly left unused for a long time. <P>SOLUTION: The method of manufacturing a liquid supply type fuel cell which uses a membrane electrode assembly consisting of an anode and a cathode arranged at least on both sides of a polymer electrolyte membrane is characterized by including a treatment step which passes current to the anode from the cathode of the membrane electrode assembly while supplying hydrogen content gas to the anode of the membrane electrode composite. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a liquid supply type fuel cell.

  A fuel cell is a power generation device with low emissions, high energy efficiency, and low burden on the environment. For this reason, it is in the spotlight again in recent years to the protection of the global environment. Compared to conventional large-scale power generation facilities, this is a power generation device expected in the future as a relatively small-scale distributed power generation facility, and 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 portable devices, as an alternative to secondary batteries such as nickel metal hydride batteries and lithium ion batteries, as a charger for secondary batteries, or in combination with secondary batteries. (Hybrid) is expected to be installed in mobile devices such as mobile phones and personal computers.

  In polymer electrolyte fuel cells (hereinafter sometimes referred to as PEFC), fuel such as methanol is directly supplied in addition to conventional polymer electrolyte fuel cells that use hydrogen gas as fuel. Direct fuel cells are also attracting attention. The direct fuel cell has a lower output than the conventional PEFC, but the fuel is liquid and does not use a reformer, so the energy density is high and the usage time of the portable device per filling is long. There is an advantage.

  In a polymer electrolyte fuel cell, an anode electrode and a cathode electrode in which a reaction responsible for power generation occurs, and a polymer electrolyte membrane serving as a proton conductor between the anode and the cathode constitute a membrane electrode assembly (MEA). And this MEA is comprised from the cell pinched | interposed with the electroconductive substance (separator) which can supply a fuel and an oxidizing agent. This cell may be used alone, or may be used as one power generation module by stacking several cells. Here, the electrode is composed of an electrode base material (also referred to as a gas diffusion electrode or a current collector) that promotes gas diffusion and collects (supply) electricity, and a catalyst layer that actually becomes an electrochemical reaction field. Yes. For example, in the anode electrode of PEFC, a fuel such as hydrogen gas reacts in the catalyst layer of the anode electrode to generate protons and electrons, and the electrons are conducted to the electrode substrate, and the protons are conducted to the polymer electrolyte membrane. For this reason, the anode electrode is required to have good gas diffusivity, electron conductivity, and proton conductivity. On the other hand, in the cathode electrode, an oxidizing gas such as oxygen or air is reacted with protons conducted from the polymer electrolyte membrane and electrons conducted from the electrode base material in the catalyst layer of the cathode electrode to produce water. For this reason, in the cathode electrode, it is necessary to efficiently discharge the generated water in addition to gas diffusibility, electron conductivity, and proton conductivity.

  Among PEFCs, a direct fuel cell using methanol or the like as a fuel requires performance different from that of a conventional PEFC using hydrogen gas as a fuel. That is, in a direct type fuel cell, a fuel such as a methanol aqueous solution reacts with the catalyst layer of the anode electrode to produce protons, electrons, and carbon dioxide at the anode electrode, and the electrons are conducted to the electrode substrate, and the protons are polymer electrolyte. The carbon dioxide passes through the electrode substrate and is released out of the system. For this reason, in addition to the required characteristics of the anode electrode of the conventional PEFC, fuel permeability such as aqueous methanol solution and carbon dioxide emission are also required. Further, in the cathode electrode of the direct type fuel cell, in addition to the reaction similar to that of the conventional PEFC, fuel such as methanol that has permeated through the electrolyte membrane and oxidizing gas such as oxygen or air are mixed with carbon dioxide in the catalyst layer of the cathode electrode. Reactions that produce water also occur. For this reason, since generated water becomes more than conventional PEFC, it is necessary to discharge water more efficiently.

  As a problem in putting a fuel cell into practical use, there is a reduction in manufacturing cost in addition to an improvement in performance. For example, a DMFC that uses an aqueous methanol solution as a fuel preferably obtains an output that is set immediately after cell assembly when the produced MEA is evaluated for power generation, but currently, aging is required for several hours to several days. In many cases, this aging process is also one of the important factors for increasing the cost.

  As a countermeasure against this, Patent Document 1 discloses a method in which an MEA is incorporated in a cell, a hydrogen-containing gas is supplied to the cathode, an inert gas is supplied to the anode, and a current is supplied from the anode to the cathode via the power supply in a power generation stop state. Proposed.

Further, in Patent Document 2, the water in the membrane is electrolyzed by flowing an electric current in a state where the humidified gas is introduced into the cell, thereby moving the water in the humidified gas into the membrane, thereby increasing the moisture content. A way to improve it has been proposed.
JP 2003-272686 A JP-A-6-196187

  In Patent Document 1, it is a method for activating a fuel cell using hydrogen as a fuel, and its effect is small for activating a liquid supply type fuel cell.

  In Patent Document 2, only the improvement of the moisture content of the electrolyte membrane is sufficient, and the effect is insufficient for activating the liquid supply type fuel cell.

  In view of the above problems, the production method of the present invention can provide a high-performance battery output from the beginning of power generation even when a membrane electrode assembly is used immediately after production or left unused for a long time. It is intended to provide a liquid supply type fuel cell.

  In order to achieve the above object, the present invention employs the following means. That is, the method for producing a liquid supply type fuel cell of the present invention is a method for producing a liquid type fuel cell using a membrane electrode assembly comprising at least an anode and a cathode disposed with a polymer electrolyte membrane interposed therebetween, It is characterized by having a treatment step of supplying a current from the cathode of the membrane electrode composite to the anode while supplying a hydrogen-containing gas to the anode of the electrode composite.

  The production method of the present invention provides a liquid supply type fuel cell capable of obtaining a high-performance battery output from the beginning of power generation even when a membrane electrode assembly is used immediately after production or left unused for a long time. It becomes possible.

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

  A method for producing a liquid fuel cell using a membrane electrode assembly comprising at least an anode and a cathode arranged with a polymer electrolyte membrane interposed therebetween, while supplying a hydrogen-containing gas to the anode of the membrane electrode assembly, It has the process process which sends an electric current from the cathode of a membrane electrode composite_body | complex to an anode, It is characterized by the above-mentioned. For example, a DMFC that uses an aqueous methanol solution as a fuel has a slower activation speed due to slower fuel diffusion than a PEFC that uses gaseous fuel. Activation here refers to bringing the MEA into a state where the capability of the MEA can be fully exerted. For example, impurities such as metal oxides in the catalyst are reduced, the electrolyte membrane is hydrated, or the cathode catalyst. It is presumed that MEA is activated by ensuring the drainage path of the water generated in the bed.

  Therefore, before generating electricity as a DMFC, a process of supplying a current from the cathode of the MEA to the anode while supplying a hydrogen-containing gas to the anode of the MEA (hereinafter, may be abbreviated as “activation process” or “process”). If it does, MEA will be activated even if a processing process is a short time, and a high performance liquid supply type fuel cell will be obtained from the power generation initial stage.

  First, processing steps will be described.

  The processing step is performed by incorporating the membrane electrode assembly into the module, but the processing step may be performed by incorporating the membrane electrode assembly into a module dedicated to the processing step, or may be performed by directly incorporating it into the power generation cell (liquid supply type fuel cell module). The processing module or power generation cell may be a single cell or may be incorporated in a stack.

  The hydrogen-containing gas supplied to the anode is preferably pure hydrogen, but may contain other gases as long as the hydrogen-containing effect is not lost. Examples of other gases include inert gases such as nitrogen and rare gases such as helium, neon, argon, krypton, xenon and radon in addition to air and oxygen. There is no particular problem as long as a sufficient potential difference is obtained from the air or oxygen supplied to the cathode. For example, the ratio of hydrogen in the anode-supplied hydrogen-containing gas when air or oxygen is supplied to the cathode is preferably 10 vol% or more. 10 vol% or more is to sufficiently develop the potential difference from the cathode, more preferably 50 vol% or more, and even more preferably 80 vol% or more.

  In addition, if the electrolyte is in a water-containing state, the activation treatment effect is often increased, and therefore the hydrogen-containing gas may be humidified.

  As a method for supplying the hydrogen-containing gas, either an active method for continuously supplying fuel or a passive method for supplying a constant amount may be used. The fuel supply source includes a hydrogen cylinder, a hydrogen storage alloy, a hydrogen generator, etc., but is not specified.

The supply amount of the hydrogen-containing gas is appropriately determined experimentally from the size, shape, etc. of the cell, but the pure hydrogen supply amount is 0.1 ml · cm ² / min to 100 ml · cm ² / min. Is preferred. The reason why it is 0.1 ml · cm ² / min or more is to develop a potential difference from the cathode, and the reason that it is 100 ml · cm ² / min or less is to perform diffusion smoothly without excessive supply.

  Further, it is preferable that the current flow from the cathode to the anode is as short as possible from the viewpoint of reducing the manufacturing cost. Specifically, 60 minutes or less and 1 second or more are preferable. The reason for setting it to 1 second or longer is to obtain the effect of activation, and the reason for setting it to 60 minutes or less is to prevent deterioration and destruction of the membrane electrode assembly.

  As the current and voltage conditions, the voltage may be held at a constant current, or the voltage may be changed by changing the current value over time. Further, the current may be held at a constant voltage, or the current may be changed by changing the voltage value over time. Although not particularly limited, it is preferable to flow a current higher than the limit current when the liquid fuel is supplied to the membrane electrode assembly under the conditions for use as a liquid supply type fuel cell. By flowing a current higher than the limit current, the MEA is more easily activated.

  Next, the membrane electrode assembly will be described.

  The simplest example of a membrane electrode assembly has a structure in which a catalyst layer is disposed on both sides of a polymer electrolyte membrane and a gas diffusion layer is further provided thereon. Other functional layers may be included as long as the relationship of the arrangement of the respective layers is not impaired and the effect of the present invention is not hindered. For example, the fuel permeation suppression layer, the water repellent layer, the radical trap layer, the fuel reforming A layer, an impurity trap layer, a by-product removal layer, an interface adhesion layer, and the like may be disposed.

  When supplying a gaseous fuel such as hydrogen, a slight amount of hydrogen or oxygen cross leak occurs in the electrolyte membrane portion of the membrane electrode assembly. At that time, the film may be deteriorated by heat generated when hydrogen and air react on the catalyst.

  In the present invention, in order to prevent the deterioration of the film due to the cross leak of hydrogen or oxygen, it is preferable to use an edge seal at the time of activation treatment, and it is preferable to provide at least the anode or the cathode, and further provide both sides of the anode and the cathode. By providing it on both sides, it is difficult for the heat of reaction between hydrogen and air to reach the electrolyte membrane directly, so that deterioration of the electrolyte membrane can be reduced.

  The edge seal is preferably applied to a portion where the electrolyte membrane and the fuel directly contact each other, and is generally applied around the electrode. It is preferable that at least the edge seal covers the end of the catalyst layer of either the anode or the cathode, and that the edge seal covers about 0.1 to 1 mm inward from the catalyst end to prevent deterioration and power generation performance. Effective from balance.

  In addition, this edge seal not only prevents deterioration during the activation process but also reduces excessive swelling / shrinkage of the electrolyte membrane due to the liquid fuel, and is effective in improving durability.

  The form of the edge seal is not particularly specified, but generally known methods are applied. Among them, a thin film is preferable, and by using a thin film, for example, it is possible to integrate in a pressing process at the time of manufacturing a membrane electrode assembly, and since it is a thin film, the resistance when actually incorporated in a module is relatively low. It is small and easy to handle. The preferred film thickness is 1 μm to 1000 μm, and particularly preferably 5 μm to 100 μm. If it is 1 μm or more, durability and handling properties are good, and if it is 100 μm or less, the contact between the electrode and the electrolyte membrane can be maintained.

  The material of the film used is not particularly limited as long as it has an electric barrier property, a fuel barrier property, chemical resistance and acid resistance. Preferably polyethylene film, ionomer film, polyvinyl chloride film, polyvinylidene chloride film, polyvinyl alcohol film, polypropylene film, polyester film, polycarbonate film, polystyrene film, polyacrylonitrile film, ethylene vinyl acetate copolymer film, ethylene-vinyl alcohol A copolymer film, nylon film, cellophane, or the like is used. Among them, from the viewpoint of chemical resistance, heat resistance, and acid resistance, a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) film is preferably used for the fluorine type, and a polyphenylene sulfide (PPS) film is preferably used for the hydrocarbon type.

  As an example of a method for producing a membrane electrode assembly provided with an edge seal, the film is cut out slightly smaller than the cathode electrode and the anode electrode 1 as shown in FIG. 3 so that the edge seal 3 does not shift to both sides of the electrolyte membrane 2. The electrode 1 is arranged and pressed so as to match the cutout of the edge seal 3. If the positions of the edge seal 3 and the electrode 1 are shifted at this time, the effect of the edge seal 3 may be lost or the power generation area may be reduced. In order to prevent this phenomenon, the electrolyte membrane 2 is formed using a film (cylindrical edge seal 4) in which two sides are fixed as shown in FIG. 4 or a film (folded edge seal) in which one side is fixed by bending. By avoiding misalignment, the edge seal can be set accurately in a shorter time.

  Next, the catalyst layer will be described.

  The catalyst layer is usually a layer composed of a known fuel cell or membrane electrode assembly catalyst and a binder, and is not particularly limited. A catalyst here is a catalyst which accelerates | stimulates an electrode reaction, and the catalyst layer may contain an electronic conductor, an ion conductor, etc. other than a catalyst. As the catalyst contained in the catalyst layer, for example, a noble metal catalyst such as platinum, palladium, ruthenium, rhodium, iridium and gold is preferably used. One of these may be used alone, or two or more of them, such as alloys and mixtures, may be used in combination.

  In particular, the anode catalyst used in the present invention is preferably added with a second catalyst component other than platinum together with platinum, and the second catalyst component here is IVB, VB, VIB, VIIB, VIII, IB, A metal selected from the group IIB, IIIA or IVA, specifically ruthenium, rhodium, titanium, chromium, manganese, iron, cobalt, nickel, copper, gallium, zirconium, hafnium, tin or the like is preferably used. More preferred are ruthenium, manganese, cobalt, nickel, rhodium and nickel, among which ruthenium is particularly preferred. These second catalyst components used in addition to platinum may be used alone or in combination of two or more such as alloys and mixtures.

  Moreover, in order to improve electroconductivity and electronic conductivity, you may add a carbon material and an inorganic electroconductive material. In the case of using an electron conductor (conductive material), a carbon material or an inorganic conductive material is preferably used from the viewpoint of electron conductivity and chemical stability. Among these, amorphous and crystalline carbon materials are mentioned. As the carbon material that is preferably used, for example, carbon black such as channel black, thermal black, furnace black, acetylene black, and the like is preferably used because of its electron conductivity and specific surface area. Furnace Black includes Vulcan (registered trademark) XC-72R, Vulcan P (registered trademark), Black Pearls (registered trademark) 880, Black Pearls (registered trademark) 1100, Black Pearls (registered trademark) 1300, Black Pearls manufactured by Cabot Corporation. (Registered Trademark) 2000, Regal (Registered Trademark) 400, Ketjen Black International (registered trademark) EC, Ketjen Black (registered trademark) EC600JD, Mitsubishi Chemical Corporation # 3150, # 3250, etc. Examples of acetylene black include Denka Black (registered trademark) manufactured by Denki Kagaku Kogyo.

  In addition to carbon black, artificial graphite or carbon obtained from organic compounds such as natural graphite, pitch, coke, polyacrylonitrile, phenol resin, and furan resin can also be used.

  As the form of these carbon materials, fibers, tubes, cones, megaphones as well as irregular particles can be used. Moreover, you may use what post-processed these carbon materials. Further, metal fine particles such as Au, Pt, Ti, Cu, Al, and stainless steel, particles of tin oxide and indium tin oxide, and electron conductive polymers such as polyaniline and fullerene can be added. Further, as a non-conductive scale-like material, scale-like silicate is preferable from the viewpoint of coating and cost.

  Examples of scaly silicates include kaolin, talc, natural mica, synthetic mica, and sericite. Synthetic mica is different from natural mica and is an artificially produced mica having a composition in which all —OH groups in the crystal structure of natural mica are substituted with —F groups, such as KMg 3 AlSi 3 O 10 F 2 Can be mentioned. Further, the surface of the scaly silicate may be coated with a metal oxide such as titanium oxide, indium oxide or tin oxide, or a conductive material such as a carbon thin film or a metal thin film.

  Moreover, when using an electronic conductor, it is preferable from the point of electrode performance that it is disperse | distributing uniformly with a catalyst particle. For this reason, it is preferable that the catalyst particles and the electron conductor are well dispersed in advance as a coating liquid. Furthermore, it is also a preferred embodiment to use catalyst-supporting carbon or the like in which the catalyst and the electron conductor are integrated as the catalyst layer. By using this catalyst-supporting carbon, the utilization efficiency of the catalyst is improved, which can contribute to the improvement of battery performance and cost reduction. Here, even when catalyst-supported carbon is used for the catalyst layer, a conductive agent can be added to further increase the electron conductivity. As such a conductive agent, the above-described carbon black is preferably used.

  As the substance having ion conductivity (ion conductor) used in the catalyst layer, various organic and inorganic materials are generally known. However, when used in a fuel cell, sulfone which improves ion conductivity. A polymer having an ionic group such as an acid group, a carboxylic acid group, or a phosphoric acid group (ion conductive polymer) is preferably used. Among these, from the viewpoint of the stability of the ionic group, an ion conductive polymer composed of a fluoroalkyl ether side chain and a fluoroalkyl main chain or a hydrocarbon polymer material is preferably used. As the perfluoro-based ion conductive polymer, for example, Nafion (registered trademark) manufactured by DuPont, Aciplex (registered trademark) manufactured by Asahi Kasei Corporation, Flemion (registered trademark) manufactured by Asahi Glass Co., Ltd., and the like are preferably used. These ion conductive polymers are provided in the catalyst layer in a solution or dispersion state. 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 the solubility of the ion conductive polymer. Moreover, the hydrocarbon-based polymer material preferable as the electrolyte membrane described above can also be suitably used as a substance (ion conductor) having ion conductivity in the catalyst layer. In particular, in the case of a fuel cell using methanol aqueous solution or methanol as a fuel, a hydrocarbon-based polymer material may be effective for durability from the viewpoint of methanol resistance.

  Since the catalyst and the electronic conductors are usually powders, the ionic conductor usually plays a role of solidifying them. It is preferable from the viewpoint of electrode performance that the ionic conductor is added in advance to a coating liquid containing catalyst particles and an electronic conductor as main constituents when the catalyst layer is prepared, and is applied in a uniformly dispersed state. is there. The amount of the ionic conductor contained in the catalyst layer should be appropriately determined according to the required electrode characteristics and the conductivity of the ionic conductor used, and is not particularly limited, but the weight ratio The range of 1 to 80% is preferable, and the range of 5 to 50% is more preferable. When the ion conductor is too small, the ion conductivity is low, and when it is too much, the gas permeability may be hindered.

  Such a catalyst layer may contain various substances in addition to the catalyst, the electron conductor, and the ionic conductor. In particular, in order to improve the binding property of the substance contained in the catalyst layer, a polymer other than the above-described ion conductive polymer may be included. Examples of such a polymer include fluorine atoms such as polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polyhexafluoropropylene (FEP), polytetrafluoroethylene, and polyperfluoroalkyl vinyl ether (PFA). These copolymers, copolymers of monomer units constituting these polymers and other monomers such as ethylene and styrene, or blend polymers can be used. The content of these polymers in the catalyst layer is preferably in the range of 5 to 40% by weight. When there is too much polymer content, there exists a tendency for an electronic and ionic resistance to increase and for electrode performance to fall.

  In addition, when the fuel is a liquid or gas, the catalyst layer preferably has a structure in which the liquid or gas easily permeates, and preferably has a structure that promotes the discharge of by-products due to the electrode reaction.

  As the electrode base material, one having a low electric resistance and capable of collecting or feeding power can be used. Examples of the constituent material of the electrode base material include carbonaceous and conductive inorganic substances. For example, a fired body from polyacrylonitrile, a fired body from pitch, a carbon material such as graphite and expanded graphite, stainless steel, molybdenum And titanium. These forms are not particularly limited, and are used, for example, in the form of fibers or particles. From the viewpoint of fuel permeability, fibrous conductive materials (conductive fibers) such as carbon fibers are preferable. As an electrode base material using conductive fibers, either a woven fabric or a non-woven fabric structure can be used. For example, carbon paper TGP series, SO series manufactured by Toray Industries, Inc., carbon cloth manufactured by E-TEK, etc. are used. Examples of the woven fabric include plain weave, oblique weaving, satin weaving, crest weaving, binding weaving, and the like.

  Moreover, as a nonwoven fabric, it does not specifically limit, such as a paper making method, a needle punch method, a spun bond method, a water jet punch method, and a melt blow method. It may also be a knitted fabric. In these fabrics, especially when carbon fibers are used, a plain fabric using flame-resistant spun yarn is carbonized or graphitized woven fabric, and the flame-resistant yarn is carbonized after being processed into a nonwoven fabric by the needle punch method or water jet punch method. Alternatively, a graphitized nonwoven fabric, a flameproof yarn, a carbonized yarn, or a mat nonwoven fabric by a paper making method using a graphitized yarn is preferably used. In particular, it is preferable to use a nonwoven fabric or cloth from the viewpoint of obtaining a thin and strong fabric.

  Examples of the carbon fiber used for the electrode substrate include polyacrylonitrile (PAN) carbon fiber, phenolic carbon fiber, pitch carbon fiber, and rayon carbon fiber.

  In addition, the electrode base material has a water repellent treatment for preventing gas diffusion / permeability deterioration due to water retention, a partial water repellent treatment for forming a water discharge path, a hydrophilic treatment, and a resistance reduction. For example, carbon powder can be added. Further, a conductive intermediate layer containing at least an inorganic conductive substance and a hydrophobic polymer can be provided between the electrode substrate and the catalyst layer. In particular, when the electrode base material is a carbon fiber woven fabric or a nonwoven fabric having a large porosity, by providing the conductive intermediate layer, it is possible to suppress performance degradation due to the catalyst layer soaking into the electrode base material.

  As the membrane electrode assembly according to the present invention, if the relationship of the arrangement of each layer is not impaired, another functional layer, for example, a fuel permeation suppression layer, a water repellent layer, a radical trap layer, a fuel reforming layer, An impurity trap layer, a by-product removal layer, an interface adhesion layer, and the like may be disposed.

  The coarse density of the catalyst layer of the present invention can be appropriately determined experimentally depending on the performance of the membrane electrode assembly, etc., and can be made porous by roll press or flat plate press densification, wet coagulation, or the like. .

  As the electrolyte membrane used in the membrane electrode assembly of the present invention, all electrolyte membranes such as perfluoro-based electrolyte membranes and hydrocarbon-based electrolyte membranes represented by Nafion (registered trademark) (manufactured by DuPont) can be applied. In particular, from the viewpoint of reducing fuel permeation and durability, it is preferable to use an electrolyte membrane having high heat resistance, high strength, high tensile elastic modulus, and low moisture content. Specific examples include films having a glass transition temperature of 130 ° C. or more, a tensile modulus of 100 MPa or more, and a moisture content of 40% by weight or less, including ionic group-containing polyphenylene oxide, ionic group-containing polyether ketone, and ionic group-containing poly. Ether ether ketone, ionic group-containing polyether sulfone, ionic group-containing polyether ether sulfone, ionic group-containing polyether phosphine oxide, ionic group-containing polyether ether phosphine oxide, ionic group-containing polyphenylene sulfide, ionic group -Containing polyamide, ionic group-containing polyimide, ionic group-containing polyetherimide, ionic group-containing polyimidazole, ionic group-containing polyoxazole, ionic group-containing polyphenylene, ionic group-containing polyazomethine, ionic group-containing An ionic group-containing polyolefin polymer such as polyimide azomethine, ionic group-containing polystyrene and ionic group-containing styrene-maleimide cross-linked copolymer, and an aromatic hydrocarbon polymer having an ionic group such as a cross-linked product thereof. Can be mentioned. These polymer materials can be used alone or in combination of two or more, and can be used as a polymer blend, a polymer alloy, or a laminated film of two or more layers. Moreover, the introduction method, synthesis method, and molecular weight range of the ionic group and ionic group here are as described above.

  In particular, as the ionic group, a polymer material having a sulfonic acid group is most preferable as described above. However, as an example of using a polymer material having a sulfonic acid group, a polymer containing -SO3M group (M is a metal) is used. There is a method in which a film is formed from a solution state, and then heat-treated at a high temperature to remove the solvent and replace the proton to form a film. The metal M may be any salt as long as it can form a salt with sulfonic acid, but Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, W, and the like are preferable. Among these, Li, Na, K, Ca, Sr, and Ba are more preferable, and Li, Na, and K are more preferable. Film formation in the state of these metal salts enables heat treatment at a high temperature, and this method is suitable for a polymer material system that can obtain a high glass transition point and a low water absorption rate.

  The temperature of the heat treatment is preferably 100 to 500 ° C., more preferably 200 to 450 ° C., and further preferably 250 to 400 ° C. in terms of water absorption of the obtained film. A temperature of 100 ° C. or higher is preferable for obtaining a low water absorption rate. On the other hand, by setting the temperature to 500 ° C. or lower, the polymer material can be prevented from being decomposed.

  The heat treatment time is preferably 10 seconds to 24 hours, more preferably 30 seconds to 1 hour, and further preferably 45 seconds to 30 minutes in terms of productivity. By setting the heat treatment time to 10 seconds or longer, it is possible to sufficiently remove the solvent and to obtain a sufficient fuel crossover suppression effect. In addition, when the time is 24 hours or less, the polymer is not decomposed, proton conductivity can be maintained, and productivity is increased.

  As the heat treatment method, heat from a hot air dryer or high frequency dielectric heating can be used.

  Examples of the method for producing the electrolyte membrane include a method in which a polymer solution is applied by an appropriate coating method, the solvent is removed, and the acid treatment is performed after the treatment at a high temperature. As the coating method, methods such as spray coating, brush coating, dip coating, die coating, curtain coating, flow coating, spin coating, and screen printing can be applied.

  In the coating method using a solvent, the film can be formed by drying the solvent by heat or high-frequency dielectric heating, the wet coagulation method using a solvent that does not dissolve the polymer, and the method of curing with light, heat, moisture, etc. A method of heating and melting and cooling after film formation can be applied.

  Examples of the solvent used for film formation include N, N-dimethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, sulfolane, 1,3-dimethyl-2-imidazolidinone, hexa Aprotic polar solvents such as methylphosphontriamide, γ-butyrolactone, ester solvents such as butyl acetate, carbonate solvents such as ethylene carbonate and propylene carbonate, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, An alkylene glycol monoalkyl ether such as propylene glycol monoethyl ether, or an alcohol solvent such as isopropanol is preferably used.

  As the thickness of the electrolyte membrane to be used, a membrane having a thickness of 3 to 2000 μm is usually preferably used. A thickness of more than 3 μm is preferable to obtain a membrane strength that can withstand practical use, and a thickness of less than 2000 μm is preferable in order to reduce membrane resistance, that is, improve power generation performance. A more preferable range of the film thickness is 5 to 1000 μm, and a more preferable range is 10 to 500 μm.

  The film thickness can be controlled by various methods. For example, when forming a film by the solvent casting method, it can be controlled by the solution concentration or the coating thickness on the substrate. For example, when forming the film by the cast polymerization method, it is prepared by the spacer thickness between the plates. You can also.

  In addition, the electrolyte membrane and the polymer material having an ionic group used in the present invention can be crosslinked as a whole or a part of the polymer structure by means such as irradiation. By crosslinking, an effect of further suppressing fuel crossover and swelling with respect to fuel can be expected, and mechanical strength is improved, which may be more preferable. Examples of radiation irradiation include electron beam irradiation and γ-ray irradiation. By having a cross-linked structure, it is possible to suppress the spread between polymer chains with respect to moisture and fuel intrusion. Since the amount of water absorption can be kept low and the swelling with respect to the fuel can also be suppressed, the fuel crossover can be reduced as a result. Moreover, since a polymer chain can be restrained, heat resistance and rigidity can be imparted. The crosslinking here may be chemical crosslinking or physical crosslinking.

  This crosslinked structure can be formed by a generally known method, for example, by copolymerization of a polyfunctional monomer or electron beam irradiation. In particular, crosslinking with a polyfunctional monomer is preferable from an economical viewpoint, and a copolymer of a monofunctional vinyl monomer and a polyfunctional monomer or a polymer having a vinyl group or an allyl group is crosslinked with a polyfunctional monomer. Things. The cross-linked structure here means a state where there is substantially no fluidity to heat or a state where it is substantially insoluble in a solvent.

  Further, in the electrolyte membrane used in the present invention, the mechanical strength is improved, the thermal stability of the ionic group is improved, the workability is improved, etc. within a range that does not impair the ionic conductivity and the effect of suppressing the fuel crossover. For this purpose, a filler or inorganic fine particles may be contained, a network or fine particles made of a polymer or metal oxide may be formed, or a film impregnated in a support may be used.

  In the membrane electrode assembly used in the method of the present invention, an interface resistance reducing material may be used for the purpose of, for example, increasing the contact area between the electrolyte membranes and reducing the interface resistance. The interface resistance reducing material is a material that can follow the surface irregularities of the catalyst layer by softening or coating by heating, and is preferably a material that can mainly reduce the resistance of ion conduction. It may be the same as or different from the electrolyte membrane, and its composition and shape may change between the manufacturing process and the actual use as a fuel cell.

  Further, it is preferable that the fuel does not swell excessively or dissolve, for example, when methanol aqueous solution or methanol is used as the fuel, it satisfies the conditions such as methanol resistance and strength equal to or higher than the electrolyte membrane to be used.

  Examples of the liquid fuel of the fuel cell produced by the method of the present invention include organic compounds having 1 to 6 carbon atoms such as methanol, isopropyl alcohol, acetone, glycerin, ethylene glycol, formic acid, acetic acid, dimethyl ether, hydroquinone, cyclohexane, and the like. The mixture with water etc. are mentioned and 1 type, or 2 or more types of mixtures may be sufficient. In particular, a fuel containing hydrogen and an organic compound having 1 to 6 carbon atoms is preferably used from the viewpoint of power generation efficiency and simplification of the entire battery system, and hydrogen and aqueous methanol are particularly preferable in terms of power generation efficiency. In the case of using an aqueous methanol solution, the concentration of methanol is appropriately selected depending on the fuel cell system to be used, but a concentration as high as possible is preferable from the viewpoint of long-time driving. For example, an active fuel cell having a system that sends a medium necessary for power generation such as a liquid feed pump or a blower fan to a membrane electrode assembly, or an auxiliary machine such as a cooling fan, a fuel dilution system, or a product recovery system has a concentration of methanol. It is preferable to inject 30 to 100% of fuel with a fuel tank or a fuel cassette, dilute it to about 0.5 to 20%, and send it to the membrane electrode assembly. Is preferable in the range of 10 to 100%.

  Further, the fuel cell may be built in the device to be used, or may be used as an external unit. From the viewpoint of maintenance, it is also preferable that the membrane electrode assembly is detachable from the fuel cell.

  The fuel cell of the present invention is a liquid supply type mainly used for portable devices. The liquid supply type means that a liquid such as an aqueous methanol solution is supplied to at least one electrode, and the liquid is preferably supplied to the anode side. By supplying liquid, the range of safety and fuel supply selection is expanded, the system can be simplified, the fuel cell can be miniaturized, and it is useful as a power source for portable electronic devices and the like.

  As a use of the fuel cell of the present invention, a power supply source of a moving body is preferable. In particular, mobile phones, personal computers, PDAs, video cameras (camcorders), digital cameras, handy terminals, RFID readers, portable devices such as various displays, home appliances such as electric shavers and vacuum cleaners, electric tools, household power supply equipment, It is preferably used as a power supply source for moving bodies such as passenger cars, automobiles such as buses and trucks, motorcycles, bicycles with electric assistance, robots, electric carts, electric wheelchairs, ships, and railways. Especially in portable devices, it is used not only for power supply sources, but also for charging secondary batteries installed in portable devices, and also suitable for use as a hybrid power supply source used in combination with secondary batteries and solar cells. it can.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, these examples are for understanding this invention better, and this invention is not limited to these.

[Measuring method]
The characteristics in the examples were measured by the methods shown below.

(1) Evaluation of power generation performance of membrane electrode composite with methanol fuel A gasket was placed around the electrode of the membrane electrode composite and incorporated in a single cell “EFC05-01SP” (cell for electrode area 5 cm ² ) manufactured by Electrochem. . Leads are attached to the cathode current collector and anode current collector, and voltage-current characteristics up to 0.05V are measured using a Toyo Technica evaluation device, a potentiostat 1470 made by solartron, and a frequency response analyzer made by solartron 1255B. did. The power generation conditions were a cell temperature of 60 ° C., 3.2 wt% methanol flowing from the anode, and synthetic air was supplied to the cathode at 50 mL / min. The output at 0.4V at the first power generation was taken.

[Synthesis example of polymer material having ionic group]
6.9 g of potassium carbonate, 14 g of 4,4′-dihydroxytetraphenylmethane, 7 g of 4,4′-difluorobenzophenone, and 5 g of disodium 3,3′-disulfonate-4,4′-difluorobenzophenone Then, polymerization was performed at 190 ° C. in N-methyl-2-pyrrolidone. Purification was carried out by reprecipitation with a large amount of water to obtain polymer A.

[Preparation example of electrolyte membrane]
The above polymer A was dissolved in N-methyl-2-pyrrolidone to obtain a coating solution having a solid content of 25%. The coating solution was cast on a glass plate and dried at 60 ° C. for 10 minutes and further at 100 ° C. for 2 hours to obtain a 51 μm film. Furthermore, after heat-treating under conditions of heating to 200 to 300 ° C. over 1 hour in a nitrogen gas atmosphere and heating at 300 ° C. for 10 minutes, the mixture was allowed to cool and immersed in 1N hydrochloric acid for 12 hours or more to perform proton substitution. The electrolyte membrane A was obtained by immersing it in a large excess of pure water for at least one day and thoroughly washing it.

[Anode electrode production example]
Carbon fiber "TL-1400W" manufactured by E-TEK, USA, Pt-Ru supported carbon catalyst "HiSPEC (registered trademark)" 6000 manufactured by Johnson & Matthey, and 20% "Nafion manufactured by DuPont" (Registered trademark) ”and an anode coating solution consisting of an n-propanol solution were applied and dried at 100 ° C. for 10 minutes. The anode catalyst coating solution was applied to a TL-1400W carbon black coating surface. Next, 10 g of polymer A, 60 g of N-methyl-2-pyrrolidone as a plasticizer, and 40 g of glycerin are placed in a container and stirred until uniform to produce interface resistance reducing composition A, and 3 mg on the anode catalyst layer. / Cm ^2, and heat-treated at 100 ° C. for 5 minutes. Next, each piece was cut into a square of 2.3 cm to obtain an anode electrode.

[Example of cathode electrode production]
Cathode catalyst coating consisting of Pt-supported carbon catalyst TEC10V50E manufactured by Tanaka Kikinzoku Kogyo Co., Ltd. and 20% “Nafion (registered trademark)” manufactured by DuPont Co., Ltd. The liquid was applied and dried at 100 ° C. for 15 minutes. The cathode catalyst coating solution was applied to a TL-1400W carbon black coating surface. The interfacial resistance reducing composition A was applied on the cathode catalyst layer so as to be 3 mg / cm ² and heat-treated at 100 ° C. for 1 minute. Next, each piece was cut into a square of 2.3 cm to obtain a cathode electrode.

[Example 1]
The electrolyte membrane A was sandwiched between a cathode electrode and an anode electrode, faced so as not to shift, and pressed at 100 ° C. and 3 MPa for 5 minutes. The membrane electrode assembly A was obtained by washing with a 10% aqueous methanol solution and washing with water.

Membrane electrode assembly A was incorporated into a single cell “EFC05-01SP” (cell for electrode area 5 cm ² ) manufactured by Electrochem, hydrogen was supplied to the anode side at 5 cc · cm ² / min, and synthetic air was supplied to the cathode side. It was supplied at 50 cc · cm ² / min. The cell temperature was normal temperature, the current was passed from the cathode to the anode, and activation treatment was performed at a current value of 100 mA / cm ² for 10 seconds. Table 1 summarizes the results obtained when the power generation performance evaluation with methanol was performed while the membrane electrode assembly B subjected to the activation treatment was placed in the cell. Also, when the activation current value is changed to 200 mA / cm ² and 300 mA / cm ² , and the flow time is changed to 0 seconds, 30 seconds, 60 seconds, 120 seconds, 300 seconds, 600 seconds, 1800 seconds, 3600 seconds Are also summarized in Table 1.

  From Table 2, it can be seen that the activation treatment effect is obtained even with a treatment time of 10 seconds. In addition, from Table 1, the longer the activation processing time, the closer to the set output that the MEA has, and the higher the processing effect. The more current that flows, the shorter the output value that the MEA has, It is clear that the effect is high.

[Example 2]
Membrane electrode assembly A was incorporated into a single cell “EFC05-01SP” (cell for electrode area 5 cm ² ) manufactured by Electrochem, hydrogen was supplied to the anode side at 5 cc · cm ² / min, and synthetic air was supplied to the cathode side. It was supplied at 50 cc · cm ² / min. The cell temperature was room temperature and the current flowed from the cathode to the anode. The current value was increased from 0 mA / cm ² to 0.50 mA / cm ² / sec, and the activation process was terminated when the voltage could not be taken. As a result of evaluating the power generation performance with the methanol while the membrane electrode assembly C subjected to the activation treatment was placed in the cell, the output was 52 mW / cm ² .

[Example 3]
The electrolyte membrane A is the electrolyte membrane 2, and a PPS film “Torelina # 3030 12 μm” manufactured by Toray as shown in FIG. 3 is stacked on both electrodes as an edge seal 3, and is sandwiched between the cathode electrode and the anode electrode (electrode 1), Pressed at 3 MPa for 5 minutes. The membrane electrode assembly D was obtained by washing with a 10% aqueous methanol solution and washing with water.

Membrane electrode composite D is incorporated into a single cell “EFC05-01SP” (cell for electrode area 5 cm ² ) manufactured by Electrochem, hydrogen is supplied to the anode side at 5 cc · cm ² / min, and synthetic air is supplied to the cathode side. It was supplied at 50 cc · cm ² / min. The cell temperature was normal temperature, the current was passed from the cathode to the anode, and activation treatment was performed for 30 seconds at a current value of 100 mA / cm ² . As a result of evaluating the power generation performance with the methanol while the membrane electrode assembly E subjected to the activation treatment was put in the cell, the result was 33 mW / cm ² .
[Example 4]
The electrolyte membrane A is used as the electrolyte membrane 2 and sandwiched between the Toray Film Processing PFA film “Toyoflon P # 25” (cylindrical edge seal 4) as shown in FIG. The sample was held by the anode electrode (electrode 1) and pressed at 100 ° C. and 3 MPa for 5 minutes. Since the edge seal has a cylindrical shape, there is little vertical shift and it can be set in a short time. The membrane electrode assembly F was obtained by washing with a 10% aqueous methanol solution and washing with water.

Membrane electrode assembly F is incorporated into a single cell “EFC05-01SP” (cell for electrode area 5 cm ² ) manufactured by Electrochem, hydrogen is supplied to the anode side at 5 cc · cm ² / min, and synthetic air is supplied to the cathode side. It was supplied at 50 cc · cm ² / min. The cell temperature was normal temperature, the current was passed from the cathode to the anode, and activation treatment was performed for 30 seconds at a current value of 100 mA / cm ² . It was 39 mW / cm ^{2 as} a result of evaluating the power generation performance with the methanol while the membrane electrode assembly G subjected to the activation treatment was put in the cell.

  The membrane electrode assembly of the present invention can be applied to membrane electrode assemblies of various electrochemical devices (for example, fuel cells, water electrolysis devices, chloroalkali electrolysis devices, etc.). Among these devices, it is suitable for a fuel cell, and particularly suitable for a fuel cell using a methanol aqueous solution as a fuel.

  Although it does not specifically limit as a use of the fuel cell of this invention, Mobile devices, such as a mobile phone, a personal computer, PDA, a video camera, a digital camera, household appliances, such as a cordless vacuum cleaner, toys, an electric bicycle, a motorcycle, a car, Vehicles such as buses and trucks, ships, moving bodies such as railways, robot power supply sources, stationary generators such as stationary primary batteries, alternatives to secondary batteries, or hybrid power sources with these or solar batteries, or charging It is preferably used for use.

It is the figure which showed the activation processing time in a constant current, and the output in 0.4V. FIG. 2 is an enlarged view of the activation time of FIG. 1 from 0 to 150 seconds. 6 is a view showing a method for producing a membrane electrode assembly of Example 3. FIG. 6 is a view showing a method for producing a membrane electrode assembly of Example 4. FIG.

Explanation of symbols

1: Electrode 2: Electrolyte membrane 3: Edge seal
4: Cylindrical edge seal

Claims (4)

  A method for producing a liquid fuel cell using a membrane electrode assembly comprising at least an anode and a cathode arranged with a polymer electrolyte membrane interposed therebetween, while supplying a hydrogen-containing gas to the anode of the membrane electrode assembly, A process for producing a liquid supply type fuel cell, comprising a treatment step of passing a current from a cathode to an anode of a membrane electrode assembly.   The method for producing a liquid supply type fuel cell according to claim 1, wherein the anode has platinum and a second catalyst component other than platinum.   The method for producing a liquid supply type fuel cell according to claim 1 or 2, wherein the current is passed for 60 minutes or less and 1 second or more.   The method for producing a liquid supply type fuel cell according to any one of claims 1 to 3, wherein a current higher than a limit current when the liquid fuel is supplied to the membrane electrode assembly under conditions of use as a liquid supply type fuel cell.

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