JP2009110711A - Fuel cell and manufacturing method of fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell and a manufacturing method of a fuel cell enabling improvement in an output as well as in fuel efficiency. <P>SOLUTION: The fuel cell is provided with a membrane electrode assembly 2 having an electrolyte membrane 17, a plurality of anodes 13 arranged on one face 17A of the electrolyte membrane 17, and a plurality of cathodes 16 arranged on the other face 17B of the electrolyte membrane 17 opposed to the respective anodes 13. The electrolyte membrane 17 is provided, at least partially, with first areas 171 each pinched by the anode 13 and the cathode 16, and second areas 172 reformed and exposed from the anodes 13 and the cathodes 16. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel cell using a liquid fuel and a method for manufacturing the fuel cell.

  In recent years, attempts have been made to use a fuel cell as a power source for portable electronic devices such as notebook computers and mobile phones so that they can be used for a long time without being charged. A fuel cell is characterized in that it can generate electric power simply by supplying fuel and air, and can generate electric power continuously for a long time if fuel is replenished. For this reason, if the fuel cell can be reduced in size, it can be said that the system is extremely advantageous as a power source for portable electronic devices.

  For example, a direct methanol fuel cell (DMFC) using methanol as a fuel can be reduced in size and can be easily handled, and thus is regarded as a promising power source for portable electronic devices. Yes. As the liquid fuel supply method in the DMFC, there are known an active method such as a gas supply type and a liquid supply type, and a passive method such as an internal vaporization type in which the liquid fuel in the fuel container is vaporized inside the cell and supplied to the fuel electrode. It has been.

  Such a fuel cell includes a membrane electrode assembly (MEA) in which an anode (fuel electrode) and a cathode (air electrode) are arranged to face each other with a polymer electrolyte membrane interposed therebetween. More specifically, each electrode includes a gas diffusion layer and a catalyst layer, and the catalyst layer is joined to the polymer electrolyte membrane. At the anode, methanol as a fuel is oxidatively decomposed to generate carbon dioxide, protons and electrons. On the other hand, in the cathode, water is generated by oxygen obtained from air, protons supplied from the anode through the electrolyte membrane, and electrons supplied from the anode through an external circuit. In addition, power is supplied by electrons passing through the external circuit.

  In such a membrane electrode assembly, in order to obtain high output, a configuration has been proposed in which a plurality of unit cells are arranged adjacent to each other at a predetermined interval on the same plane and these are directly connected (for example, Patent Document 1).

  When such unit cells are disposed adjacent to each other at a predetermined interval, they cannot be disposed extremely close to each other so that the electrodes of the adjacent unit cells are not short-circuited.

  By the way, when the electrolyte membrane is composed of a solid polymer membrane such as a perfluorosulfonic acid polymer, a liquid fuel such as methanol may pass through the electrolyte membrane and cause a crossover phenomenon to reach the cathode side. In particular, in a configuration in which a plurality of unit cells are arranged on the same electrolyte membrane, fuel permeation from the gaps between unit cells cannot be ignored. In this way, the fuel that permeates the electrolyte membrane does not contribute to the power generation reaction, and thus can be a factor that reduces the fuel utilization efficiency.

For this reason, in order to suppress undesired permeation of fuel, for example, according to Patent Document 2, a hydrophobic insulation for a fuel electrode formed on a solid electrolyte membrane so as to surround each of a plurality of fuel electrode catalyst layers. A fuel cell comprising a layer is disclosed. Further, for example, according to Patent Document 3, at least one surface layer of a film having ion conductivity is modified by physical modification or chemical modification such as electron beam irradiation, and the conductivity is improved. A fuel cell is disclosed that uses an ion conductive membrane that is low compared to the internal conductivity. In addition, techniques disclosed in Patent Documents 4 to 6 are known as techniques for modifying the electrolyte membrane.
JP 2002-015763 A JP 2007-026873 A JP 2001-167775 A JP-A-8-239494 JP 2002-124272 A JP 2005-038620 A

  An object of the present invention is to provide a fuel cell and a fuel cell manufacturing method capable of improving output and improving fuel efficiency.

The fuel cell according to the first aspect of the present invention comprises:
A membrane electrode assembly comprising: an electrolyte membrane; a plurality of anodes disposed on one surface of the electrolyte membrane; and a plurality of cathodes disposed on the other surface of the electrolyte membrane and facing each of the anodes. ,
The electrolyte membrane includes a first region sandwiched between at least a part of the anode and the cathode, and a second region exposed and modified from the anode and the cathode.

A fuel cell according to another aspect of the present invention is
A membrane electrode assembly comprising: an electrolyte membrane; a plurality of anodes disposed on one surface of the electrolyte membrane; and a plurality of cathodes disposed on the other surface of the electrolyte membrane and facing each of the anodes. ,
The electrolyte membrane includes a first region sandwiched between at least a part of the anode and the cathode, and a second region exposed from the anode and the cathode and having a lower fuel permeability than the first region. It may be characterized by that.

A fuel cell manufacturing method according to a second aspect of the present invention comprises:
A membrane electrode assembly having an electrolyte membrane, a plurality of anodes disposed on one surface of the electrolyte membrane, and a plurality of cathodes disposed on the other surface of the electrolyte membrane and facing each of the anodes is prepared And a process of
Irradiating an electron beam to a region exposed from the anode and the cathode of the electrolyte membrane, and modifying the electrolyte membrane;
It is characterized by having.

A fuel cell manufacturing method according to another aspect of the present invention includes:
Irradiating the electrolyte membrane with an electron beam and cutting it into a predetermined size;
Providing a membrane electrode assembly having a plurality of anodes disposed on one surface of the electrolyte membrane and a plurality of cathodes disposed on the other surface of the electrolyte membrane and facing each of the anodes;
Irradiating a region exposed from the anode and the cathode of the electrolyte membrane with an electron beam having a lower energy than the electron beam used to cut the electrolyte membrane; and modifying the electrolyte membrane;
It may be characterized by having.

  According to the present invention, it is possible to provide a fuel cell and a fuel cell manufacturing method capable of improving output and improving fuel efficiency.

  Hereinafter, a fuel cell and a manufacturing method thereof according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view schematically showing the structure of a fuel cell 1 according to this embodiment. In this embodiment, an internal vaporization type passive system will be described as the fuel cell 1, but the present invention is not limited to this system.

  The fuel cell 1 includes a membrane electrode assembly 2 constituting an electromotive unit. That is, in the fuel cell 1, the membrane electrode assembly 2 includes an anode (fuel electrode) 13 having an anode catalyst layer 11 and an anode gas diffusion layer 12, and a cathode having a cathode catalyst layer 14 and a cathode gas diffusion layer 15 ( (Air electrode / oxidant electrode) 16 and a proton (hydrogen ion) conductive electrolyte membrane 17 sandwiched between the anode catalyst layer 11 and the cathode catalyst layer 14.

  Examples of the catalyst contained in the anode catalyst layer 11 and the cathode catalyst layer 14 include platinum such as platinum (Pt), ruthenium (Ru), rhodium (Rh), iridium (Ir), osmium (Os), and palladium (Pd). Examples thereof include a group element simple substance and an alloy containing a platinum group element. For the anode catalyst layer 11, it is preferable to use Pt—Ru, Pt—Mo, or the like that has strong resistance to methanol, carbon monoxide, or the like. It is preferable to use Pt, Pt—Ni or the like for the cathode catalyst layer 14. However, the catalyst is not limited to these, and various substances having catalytic activity can be used. The catalyst may be either a supported catalyst using a conductive carrier such as a carbon material or an unsupported catalyst.

  Examples of the proton conductive material constituting the electrolyte membrane 17 include fluorine-based resins (Nafion (trade name, manufactured by DuPont) and Flemion (trade name, manufactured by Asahi Glass Co., Ltd.) such as a perfluorosulfonic acid polymer having a sulfonic acid group. Etc.), organic materials such as hydrocarbon resins having sulfonic acid groups, or inorganic materials such as tungstic acid and phosphotungstic acid. However, the proton conductive electrolyte membrane 17 is not limited to these.

  The anode gas diffusion layer 12 laminated on the anode catalyst layer 11 serves to uniformly supply fuel to the anode catalyst layer 11 and also has a function as a current collector of the anode catalyst layer 11. The cathode gas diffusion layer 15 laminated on the cathode catalyst layer 14 serves to uniformly supply the oxidant to the cathode catalyst layer 14 and also has a function as a current collector of the cathode catalyst layer 14. The anode gas diffusion layer 12 and the cathode gas diffusion layer 15 are made of a porous substrate such as carbon paper, for example.

  A conductive layer is laminated on the anode gas diffusion layer 12 and the cathode gas diffusion layer 15 as necessary. These conductive layers include, for example, a mesh made of a conductive metal material such as gold (Au), a porous film, a thin film or a foil, or a conductive metal material such as stainless steel (SUS) and a good conductivity such as gold. A composite material coated with a conductive metal is used.

  In the example shown in FIGS. 2 and 3, the membrane electrode assembly 2 includes a single electrolyte membrane 17 sandwiched between four anodes 13 and four cathodes 16, respectively. Although the MEA structure in which each combination (unit cell) with 16 is electrically connected in series is shown, the structure of the membrane electrode assembly 2 is not limited to this example, and may be another structure.

  A sealing material 19 such as a rubber O-ring is disposed on the anode side and the cathode side of the electrolyte membrane 17, respectively, thereby preventing fuel leakage and oxidant leakage from the membrane electrode assembly 2.

  The fuel cell 1 further includes a fuel supply mechanism 3 that supplies the liquid fuel F to the membrane electrode assembly 2. The fuel supply mechanism 3 includes a fuel storage unit 30 that stores the liquid fuel F. The fuel storage unit 30 is disposed on the anode 13 side of the membrane electrode assembly 2 and supplies fuel to the anode 13 of the membrane electrode assembly 2. The membrane electrode assembly 2 has, for example, a rectangular planar shape, and the fuel storage portion 30 also has the same rectangular planar shape. The fuel storage unit 30 has an opening 30 </ b> A provided on the surface of the membrane electrode assembly 2 facing the anode 13. That is, the fuel storage unit 30 is a box-shaped container having an entire upper surface opened. In such a fuel storage part 30, the liquid fuel F corresponding to the membrane electrode assembly 2 is stored.

  Examples of the liquid fuel F include methanol fuels such as methanol aqueous solutions having various concentrations and pure methanol. The liquid fuel F is not necessarily limited to methanol fuel. The liquid fuel F may be, for example, an ethanol fuel such as an ethanol aqueous solution or pure ethanol, a propanol fuel such as a propanol aqueous solution or pure propanol, a glycol fuel such as a glycol aqueous solution or pure glycol, dimethyl ether, formic acid, or other liquid fuel. In any case, the liquid fuel F corresponding to the membrane electrode assembly 2 is used.

  The fuel storage unit 30 is constituted by a resin container, for example. The fuel storage unit 30 is preferably formed of a transparent resin so that the remaining amount of the liquid fuel F can be visually observed from the outside. Moreover, it is preferable that such transparent resin has methanol resistance. The fuel storage unit 30 may be entirely formed of a transparent resin, or a part thereof may be formed of a transparent resin.

  Examples of the transparent resin described above include polyethylene naphthalate, polyethylene terephthalate, cyclic olefin copolymer, cycloolefin polymer, polymethylpentene, and polyphenylsulfone. However, this does not exclude the fuel storage unit 30 made of an olefin resin such as a general polyethylene resin or polypropylene resin.

  As shown in FIG. 1, a gas-liquid separation membrane 4 may be installed between the opening 30 </ b> A of the fuel storage unit 30 and the membrane electrode assembly 2. The gas-liquid separation membrane 4 is disposed so as to close the opening 30A of the fuel storage unit 30, and is formed of a membrane that transmits the vaporized component of the liquid fuel F but does not transmit the liquid fuel F. Thereby, the vaporized component of the liquid fuel F vaporized in the fuel storage unit 30 is supplied to the anode 13 of the membrane electrode assembly 2 via the opening 30A of the fuel storage unit 30 and the gas-liquid separation membrane 4.

  Examples of the constituent material of the gas-liquid separation membrane 4 include fluorine resins such as silicon and polytetrafluoroethylene. Here, the vaporized component of the liquid fuel F means, for example, when a methanol aqueous solution is applied as the liquid fuel F, it means an air-fuel mixture composed of a vaporized component of methanol and a vaporized component of water. Is applied, it means a vaporization component of methanol.

  The moisture retaining layer 20 is disposed on the cathode 16 of the membrane electrode assembly 2, but may be omitted. The moisturizing layer 20 is impregnated with a part of the water generated in the cathode catalyst layer 14 to suppress the transpiration of water and uniformly introduce an oxidant (air) into the cathode gas diffusion layer 15. It has a function of promoting uniform diffusion of the oxidizing agent to the cathode catalyst layer 14. The moisturizing layer 20 is composed of, for example, a porous member, and specific constituent materials include polyethylene and polypropylene porous bodies.

  In this embodiment, the fuel cell 1 further includes a cover member 18 disposed on the cathode (air electrode) 16 side of the membrane electrode assembly 2. The cover member 18 has a substantially box-like appearance and is made of, for example, stainless steel (SUS). The cover member 18 has a plurality of openings (air introduction holes) 18A for taking in air as an oxidant.

  Such a cover member 18 is fixed to the fuel storage unit 30 so as to cover the gas-liquid separation membrane 4, the membrane electrode assembly 2, and the moisture retention layer 20. That is, the membrane electrode assembly 2 is disposed between the fuel storage unit 30 and the cover member 18. The cover member 18 functions as a support that supports the membrane electrode assembly 2.

  In the fuel cell 1 configured as described above, power is generated by the following process.

  That is, the liquid fuel F such as methanol fuel in the fuel storage unit 30 is vaporized, and the vaporized component passes through the gas-liquid separation membrane 4 and is supplied to the membrane electrode assembly 2. In the membrane electrode assembly 2, the vaporized component of the liquid fuel F diffuses in the anode gas diffusion layer 12 and is supplied to the anode catalyst layer 11. When methanol fuel is used as the liquid fuel F, the vaporized component supplied to the anode catalyst layer 11 causes an internal reforming reaction of methanol shown in the following formula (1).

CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ (1)
Note that when pure methanol is used as the methanol fuel, water vapor is not supplied from the fuel storage unit 30, so water generated in the cathode catalyst layer 14 or water in the electrolyte membrane 17 is reacted with methanol (1). Cause an internal reforming reaction. Alternatively, the internal reforming reaction is caused by another reaction mechanism that does not require water, regardless of the internal reforming reaction of the above formula (1).

Electrons (e ⁻ ) generated by this internal reforming reaction are led to the outside via a current collector, and are led to the cathode 16 after operating a portable electronic device or the like as so-called electricity. In addition, protons (H ⁺ ) generated by the internal reforming reaction of the formula (1) are guided to the cathode 16 through the electrolyte membrane 17.

On the other hand, air is supplied to the cathode 16 as an oxidant. That is, the air introduced from the opening 18 </ b> A provided in the cover member 18 passes through the moisture retention layer 20 and the cathode gas diffusion layer 15 and is supplied to the cathode catalyst layer 14. Electrons (e ⁻ ) and protons (H ⁺ ) that have reached the cathode 16 react with oxygen in the air in the cathode catalyst layer 14 according to the following formula (2), and water is generated with this reaction.

6e ⁻ + 6H ⁺ + (3/2) O ₂ → 3H ₂ O (2)
In the power generation reaction of the fuel cell 1 described above, in order to increase the power to be generated, it is important to make the catalyst reaction smoothly and to make the entire electrode of the membrane electrode assembly 2 more effectively contribute to power generation.

  By the way, in the membrane electrode assembly 2 according to this embodiment, a structure in which a plurality of unit cells are arranged in a plane with respect to a single electrolyte membrane 17 and these are electrically connected in series is applied. The output as a fuel cell has been improved. In such a structure, the electrolyte membrane between the unit cells (that is, the electrolyte membrane exposed without being sandwiched between the anode 13 and the cathode 16) 17 transmits from the anode side to the cathode side without contributing to the power generation reaction. The amount of fuel to be used cannot be ignored, and this can be a factor that reduces the fuel utilization efficiency. For this reason, it is desired to suppress fuel permeation from the anode side to the cathode side in the electrolyte membrane 17 between the unit cells.

  Therefore, as shown in FIG. 4, the electrolyte membrane 17 applied in this embodiment includes a first region 171 sandwiched between the anode 13 and the cathode 16, and a second region 172 exposed from the anode 13 and the cathode 16. And the second region 172 is modified.

  That is, a plurality of, here four, anodes 13 are arranged on one surface 17A of the electrolyte membrane 17. Each of the anodes 13 is arranged at an interval of, for example, about 0.7 mm to 1.0 mm in order to ensure electrical insulation between unit cells. Further, the same number of four cathodes 16 as the anodes 13 are arranged on the other surface 17B of the electrolyte membrane 17 so as to face the anode 13 with the electrolyte membrane 17 interposed therebetween. Each of the cathodes 16 is also arranged at the same interval as the anode 13.

  In the membrane electrode assembly 2 having such a configuration, the electrolyte membrane 17 allows the fuel to permeate from the anode side to the cathode side in the first region 171, while suppressing the fuel permeation in the second region 172. It has been modified to such properties. The electrolyte membrane 17 having the first region 171 and the second region 172 can be formed by selectively irradiating a region exposed from the anode 13 and the cathode 16 with an electron beam such as a laser.

  That is, in the electrolyte membrane 17, the region that is not irradiated with the electron beam (first region) maintains the characteristics as a polymer film, which is the original property, and a membrane having micro holes that transmit protons and methanol. It has become. On the other hand, in the electrolyte membrane 17, the region irradiated with the electron beam (second region) is cured by laser light or energy irradiation to break microholes and become smaller than the constituent molecules of methanol. Is modified so that it does not permeate. That is, the second region 172 has a characteristic that the permeability of methanol as a fuel is lower than that of the first region 171.

  Since the second region 172 modified as described above is discolored to a color different from that of the first region 171 not modified, it can be identified by visual confirmation. The second region 172 can also be identified by the difference in hardness from the first region 171. That is, since the second region 172 is cured by electron beam irradiation, the second region 172 has a higher hardness than the first region 171.

  With such a configuration, it is possible to suppress the permeation of fuel from the electrolyte membrane 17 (particularly, the second region 172) between unit cells. For this reason, since the supplied fuel efficiently reaches the first region 171 of the electrolyte membrane 17 from the anode 13 and contributes to the power generation reaction, it is possible to improve the fuel utilization efficiency (fuel consumption).

  The electrolyte membrane 17 having the above-described configuration can be obtained by irradiating a large polymer membrane with an electron beam and cutting it to a predetermined size. When the electrolyte membrane 17 is cut out in this way, it is necessary to irradiate an electron beam with higher energy than in the case of modifying the electrolyte membrane as the second region 172. The end portion 17E of the electrolyte membrane 17 obtained in this way is cured to be equal to or higher than that of the second region 172, and has hardness equal to or higher than that of the second region 172.

  With such a configuration, not only between the unit cells but also the permeation from the end portion 17E of the fuel that has permeated into the electrolyte membrane 17 can be suppressed, and further fuel efficiency can be improved.

  Next, the manufacturing method of the membrane electrode assembly 2 having the above-described structure will be described. In addition, the manufacturing method demonstrated here is an example, Comprising: Another process may be added and the demonstrated process may be substituted by another process.

  As shown in FIG. 5, first, an electrolyte membrane 17 having a predetermined size is prepared. That is, an electrolyte membrane 17 molded in a predetermined size may be prepared, or an electrolyte membrane 17 cut into a predetermined size by cutting a large polymer membrane (that is, an electrolyte membrane having proton conductivity) with a cutter or the like. May be prepared. In particular, here, it is desirable to apply the electrolyte membrane 17 obtained through a process of irradiating a large polymer membrane with an electron beam and cutting it to a predetermined size. In this embodiment, the electrolyte membrane 17 is prepared by this method. . At this time, a carbon dioxide laser was applied as the electron beam source.

  Subsequently, the anode 13 and the cathode 16 are arranged with the electrolyte membrane 17 interposed therebetween, and all are joined by heating and pressurizing to obtain the membrane electrode assembly 2. Here, the anode 13 and the cathode 16 are obtained as follows, for example. That is, a paste prepared by mixing a solvent, a catalyst, and the like is applied onto carbon paper that functions as a gas diffusion layer. Then, the applied paste is dried. Thereby, the catalyst layer laminated | stacked on the gas diffusion layer is formed. Thereafter, after washing, the anode 13 and the cathode 16 are formed by cutting into a desired size (for example, a strip shape shown in FIG. 3).

  Subsequently, in the membrane electrode assembly 2 prepared through the above-described steps, the regions exposed from the anode 13 and the cathode 16 of the electrolyte membrane 17 are modified by irradiation with an electron beam. In this step, energy lower than the electron beam used for cutting the electrolyte membrane 17 (that is, lower energy than that required for cutting the electrolyte membrane, and sufficiently reducing the fuel permeability of the electrolyte membrane, Preferably, the electron beam is irradiated with the energy required to achieve 0%. Specifically, for example, when the electrolyte membrane 17 is cut, a focused electron beam is irradiated, whereas when the electrolyte membrane 17 is modified, a defocused electron beam is irradiated. At this time, a carbon dioxide laser was applied as the electron beam source.

  According to the fuel cell including the membrane electrode assembly formed through such a manufacturing process, fuel can be prevented from permeating from the electrolyte membrane 17 (second region 172) exposed from the anode 13 and the cathode 16, and supplied. It became possible to supply the fuel to the anode 13 stably and efficiently. Therefore, it is possible to stably obtain a high output and improve fuel efficiency.

  In the above-described embodiment, a purely passive type fuel cell such as an internal vaporization type equipped with the fuel storage portion 30 on the anode side of the membrane electrode assembly 2 has been described. The same configuration is applied to a fuel cell of a semi-passive type that includes a fuel supply unit that supplies fuel to the fuel supply unit and a fuel storage unit that stores fuel supplied to the fuel supply unit. Needless to say, the same effect can be obtained.

  For example, in the example shown in FIG. 6, the fuel supply mechanism 3 includes a fuel supply unit 31 that is disposed on the anode 13 side of the membrane electrode assembly 2 and supplies fuel to the anode 13 of the membrane electrode assembly 2. Yes. The fuel supply mechanism 3 includes a fuel storage unit (not shown) that stores liquid fuel supplied to the fuel supply unit 31. The fuel storage unit stores liquid fuel corresponding to the membrane electrode assembly 2.

  The fuel supply unit 31 and the fuel storage unit are connected via a liquid fuel passage such as a pipe (not shown). That is, liquid fuel is introduced into the fuel supply unit 31 from the fuel storage unit via the flow path. The flow path is not limited to piping independent of the fuel supply unit 31 and the fuel storage unit. For example, when the fuel supply unit 31 and the fuel storage unit are stacked and integrated, a liquid fuel flow path connecting them may be used.

  In the semi-passive type fuel cell, the fuel supplied from the fuel storage part to the membrane electrode assembly 2 is used for a power generation reaction, and is not circulated and returned to the fuel storage part. The semi-passive type fuel cell is different from the conventional active type because it does not circulate the fuel, and does not impair the downsizing of the apparatus. Further, this semi-passive type fuel cell uses a pump for supplying fuel, and is different from a pure passive type such as a conventional internal vaporization type. In this semi-passive type fuel cell, a fuel cutoff valve may be arranged instead of the pump as long as the fuel is supplied from the fuel storage portion to the membrane electrode assembly 2. In this case, the fuel cutoff valve is provided to control the supply of liquid fuel through the flow path.

  The fuel supply unit 31 has a fuel inlet 32 through which liquid fuel is injected via a flow path at the bottom thereof, a fuel supply port 33 that supplies liquid fuel injected from the fuel inlet 32 and vaporized components thereof, And a thin tube 34 that connects the fuel inlet 32 and the fuel supply port 33. In the example of the fuel supply unit 31 shown here, the fuel injection port 32 and the fuel supply port 33 are each one place.

  A support member 41 that supports the membrane electrode assembly 2 from the anode 13 side is disposed between the membrane electrode assembly 2 and the fuel supply unit 31.

  Although such a support member 41 may be omitted, the following effects can be obtained by applying the support member 41 in such a semi-passive system. That is, by disposing the support member 41 between the membrane electrode assembly 2 and the fuel supply unit 31, a distance from the fuel supply port 33 to the membrane electrode assembly 2 can be secured. For this reason, it is possible to secure a sufficient capacity to promote the vaporization of the liquid fuel supplied from the fuel supply port 33, and it is possible to diffuse the fuel in a gaseous state over a wide range.

  As a result, the fuel distribution in the plane of the anode 13 can be leveled, and the fuel required for the power generation reaction in the membrane electrode assembly 2 can be supplied as a whole without excess or deficiency. Therefore, it is possible to efficiently generate a power generation reaction in the membrane electrode assembly 2 without causing an increase in size or complexity of the fuel cell 1. As a result, the output of the fuel cell 1 can be improved. In other words, the output and its stability can be improved without impairing the advantages of the fuel cell 1 that does not circulate the fuel.

  Moreover, since the membrane electrode assembly 2 is supported by the support member 41 and the membrane electrode assembly 2 is held between the support member 41 and the cover member 18, deformation such as bending of the membrane electrode assembly 2 is suppressed. It is possible to increase the adhesion between the electromotive unit and the current collector and suppress the decrease in output.

  At least one porous body 42 is disposed between the membrane electrode assembly 2 and the fuel supply unit 31. As the constituent material of the porous body 42, various resins are used, and a porous resin film or the like is used as the porous body 42. Such a porous body 42 may be arranged by laminating a plurality of porous films. That is, a porous body mainly having high diffusibility in one direction and a porous body having high diffusivity in a direction intersecting (or orthogonal to) the main body may be used in combination.

  Such a porous body 42 may be omitted, but in such a semi-passive system, the following effects can be obtained by applying the porous body 42. That is, by disposing the porous body 42, the amount of fuel supplied to the anode 13 can be further averaged. That is, the liquid fuel supplied from the fuel supply port 33 of the fuel supply unit 31 is once absorbed by the porous body 42 and diffuses in the in-plane direction inside the porous body 42. Thereafter, fuel is supplied from the porous body 42 to the anode 13 via the support member 41, so that the fuel supply amount can be further averaged.

  As in the example shown in FIG. 1, in the membrane electrode assembly 2, the first region 171 sandwiched between the anode 13 and the cathode 16 and the second region 172 exposed and modified from the anode 13 and the cathode 16. The electrolyte membrane 17 having the following is applied. Even with such a configuration, the same effect as the example shown in FIG. 1 can be obtained.

  In the example shown in FIG. 7, the fuel supply unit 31 constituting the fuel supply mechanism 3 is injected into the bottom thereof from a fuel injection port 32 through which liquid fuel is injected through a flow path and from the fuel injection port 32. A plurality of fuel supply ports 33 for supplying liquid fuel and vaporized components thereof, and a thin tube 34 connecting the fuel injection port 32 and each fuel supply port 33 are provided.

  In the fuel supply mechanism 3 having such a configuration, the liquid fuel injected from the fuel injection port 32 into the fuel supply unit 31 can be guided to the plurality of fuel supply ports 33 via the thin tubes 34 branched into a plurality of branches. Is possible. That is, by applying such a fuel supply mechanism 3, the liquid fuel injected from the fuel injection port 32 can be evenly distributed to the plurality of fuel supply ports 33 regardless of the direction or position. Therefore, the uniformity of the power generation reaction in the plane of the membrane electrode assembly 2 can be further enhanced.

  Further, by connecting the fuel injection port 32 and the plurality of fuel supply ports 33 with the thin tubes 34, it is possible to design to supply more fuel to a specific location of the fuel cell 1. For example, in the case where the heat dissipation by half of the fuel cell 1 is improved due to the convenience of mounting the device, a temperature distribution is conventionally generated, and a decrease in average output is inevitable. On the other hand, by adjusting the formation pattern of the thin tubes 34 and arranging the fuel supply ports 33 densely in a portion where heat dissipation is good in advance, it is possible to increase the heat generated by the power generation in that portion. Thereby, the in-plane power generation degree can be made uniform, and it is possible to suppress a decrease in output.

  Also in the fuel cell 1 of such an example, similarly to the example shown in FIG. 1, in the membrane electrode assembly 2, the first region 171 sandwiched between the anode 13 and the cathode 16 and the anode 13 and the cathode 16 are exposed. The electrolyte membrane 17 having the modified second region 172 is applied. Even with such a configuration, the same effect as the example shown in FIG. 1 can be obtained.

  Furthermore, it goes without saying that the same effect can be obtained by applying the same configuration to the active fuel cell.

  The fuel cell 1 of each embodiment described above is effective when various liquid fuels are used, and the type and concentration of the liquid fuel are not limited. The fuel cell 1 of each embodiment can particularly exhibit its performance and effects when methanol having a concentration of 80 wt% or more is used as the liquid fuel. Therefore, each embodiment is preferably applied to the fuel cell 1 using a methanol aqueous solution or pure methanol having a concentration of 80 wt% or more as a liquid fuel.

  The present invention can be applied to various fuel cells using liquid fuel. In addition, the specific configuration of the fuel cell, the supply state of the fuel, and the like are not particularly limited, and all of the fuel supplied to the MEA is liquid fuel vapor, all is liquid fuel, or part is liquid state. The present invention can be applied to various forms such as a vapor of supplied liquid fuel. In the implementation stage, the constituent elements can be modified and embodied without departing from the technical idea of the present invention. Furthermore, various modifications are possible, such as appropriately combining a plurality of constituent elements shown in the above embodiment, or deleting some constituent elements from all the constituent elements shown in the embodiment. Embodiments of the present invention can be expanded or modified within the scope of the technical idea of the present invention, and these expanded and modified embodiments are also included in the technical scope of the present invention.

FIG. 1 is a cross-sectional view schematically showing the structure of a fuel cell according to an embodiment of the present invention. FIG. 2 is a perspective view schematically showing a cross section of a part of the structure of the membrane electrode assembly in the fuel cell shown in FIG. FIG. 3 is a plan view of the membrane electrode assembly shown in FIG. FIG. 4 is a cross-sectional view of a membrane electrode assembly applicable to the fuel cell shown in FIG. FIG. 5 is a flowchart for explaining an example of a method of manufacturing a membrane electrode assembly applicable to the fuel cell shown in FIG. FIG. 6 is a sectional view schematically showing another structure of the fuel cell according to the embodiment of the present invention. FIG. 7 is a cross-sectional view schematically showing another structure of the fuel cell according to the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fuel cell 2 ... Membrane electrode assembly 3 ... Fuel supply mechanism 11 ... Anode catalyst layer 12 ... Anode gas diffusion layer 13 ... Anode 14 ... Cathode catalyst layer 15 ... Cathode gas diffusion layer 16 ... Cathode 17 ... Electrolyte membrane 171 ... First 1 region 172 ... 2nd region (modified region)
DESCRIPTION OF SYMBOLS 18 ... Cover member 18A ... Opening 19 ... Sealing material 20 ... Moisturizing layer 3 ... Fuel supply mechanism 30 ... Fuel accommodating part 30A ... Opening part 31 ... Fuel supply part 41 ... Support member 42 ... Porous body

Claims (8)

A membrane electrode assembly comprising: an electrolyte membrane; a plurality of anodes disposed on one surface of the electrolyte membrane; and a plurality of cathodes disposed on the other surface of the electrolyte membrane and facing each of the anodes. ,
The electrolyte membrane has a first region sandwiched between at least a part of the anode and the cathode, and a second region exposed and modified from the anode and the cathode. battery.   The fuel cell according to claim 1, wherein the second region has a higher hardness than the first region.   2. The fuel cell according to claim 1, wherein an end portion of the electrolyte membrane has a hardness equal to or higher than that of the second region.   The fuel cell according to claim 1, wherein the liquid fuel supplied to the membrane electrode assembly is methanol fuel.   The fuel cell according to claim 4, wherein the methanol fuel is a methanol aqueous solution or pure methanol having a methanol concentration of 80 wt% or more. A membrane electrode assembly comprising: an electrolyte membrane; a plurality of anodes disposed on one surface of the electrolyte membrane; and a plurality of cathodes disposed on the other surface of the electrolyte membrane and facing each of the anodes. ,
The electrolyte membrane includes a first region sandwiched between at least a part of the anode and the cathode, and a second region exposed from the anode and the cathode and having a lower fuel permeability than the first region. The fuel cell characterized by the above-mentioned. A membrane electrode assembly having an electrolyte membrane, a plurality of anodes disposed on one surface of the electrolyte membrane, and a plurality of cathodes disposed on the other surface of the electrolyte membrane and facing each of the anodes is prepared And a process of
Irradiating an electron beam to a region exposed from the anode and the cathode of the electrolyte membrane, and modifying the electrolyte membrane;
A method for producing a fuel cell, comprising: Irradiating the electrolyte membrane with an electron beam and cutting it into a predetermined size;
Providing a membrane electrode assembly having a plurality of anodes disposed on one surface of the electrolyte membrane and a plurality of cathodes disposed on the other surface of the electrolyte membrane and facing each of the anodes;
Irradiating a region exposed from the anode and the cathode of the electrolyte membrane with an electron beam having a lower energy than the electron beam used to cut the electrolyte membrane; and modifying the electrolyte membrane;
A method for producing a fuel cell, comprising:

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