JP2009076246A - Membrane electrode assembly for fuel cell, manufacturing method thereof, and fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a membrane electrode assembly which can prevent an agglomeration of catalyst particles and improve life characteristics of a fuel cell. <P>SOLUTION: The membrane electrode assembly 18 for a fuel cell is provided a fuel electrode 13 with a catalyst layer 11, an oxidant electrode 16 with a catalyst layer 14, and an electrolyte membrane 17 pinched by the catalyst layer of the fuel electrode 13 and the catalyst layer 14 of the oxidant electrode 16. At least one of the catalyst layers 11, 14 of the fuel electrode 13 and the oxidant electrode 16 contains particles which can be obtained by a spray-drying of suspension liquid containing conductive fine particles carrying a catalyst and hydrophilic polymers. The fuel cell is provided with the membrane electrode assembly 18. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  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. Among these, a direct methanol fuel cell (DMFC) is promising as a power source for portable electronic devices because it can be miniaturized and the fuel can be easily handled.

  In general, in a fuel cell, a metal catalyst such as Pt is used as a catalyst supported on a porous carrier. Since the catalytic activity depends on the specific surface area of such a metal catalyst, research is being conducted to increase the specific surface area of the metal catalyst by reducing the particle size of the metal catalyst to about nano-size. However, the nanosized metal catalyst causes the metal catalyst particles supported on the carrier to agglomerate with each other during the operation of the fuel cell to reduce the specific surface area. As a result, the life characteristics of the fuel cell are deteriorated. There was a problem.

Therefore, in order to suppress aggregation of the nanosized metal catalyst particles, it has been proposed to cover the surface of the metal catalyst particles supported on the carrier with a hydrophilic polymer (see, for example, Patent Document 1). . However, the effect is not always sufficient, and further improvement is required.
JP 2006-19290 A

  The present invention relates to a membrane electrode assembly for a fuel cell that can improve the life characteristics of the fuel cell by preventing agglomeration of catalyst particles accompanying the operation of the fuel cell, and a fuel excellent in such life characteristics. It is an object of the present invention to provide a method for producing a membrane electrode assembly for a battery, and further to provide a fuel cell having such output characteristics and life characteristics provided with such a membrane electrode assembly for a fuel cell.

  A membrane electrode assembly for a fuel cell according to an aspect of the present invention includes a fuel electrode provided with a catalyst layer, an oxidant electrode provided with a catalyst layer, a catalyst layer of the fuel electrode, and a catalyst layer of the oxidant electrode. A membrane electrode assembly for a fuel cell comprising an electrolyte membrane sandwiched between two electrodes, wherein at least one catalyst layer of the fuel electrode and the oxidant electrode comprises conductive fine particles carrying a catalyst and a hydrophilic polymer. It is characterized by containing particles obtained by spray-drying the containing suspension.

  A method for producing a membrane electrode assembly for a fuel cell according to an aspect of the present invention includes a fuel electrode provided with a catalyst layer, an oxidant electrode provided with a catalyst layer, a catalyst layer of the fuel electrode, and the oxidant electrode. A method for producing a membrane electrode assembly for a fuel cell comprising an electrolyte membrane sandwiched between catalyst layers, wherein a suspension containing conductive fine particles carrying a catalyst and a hydrophilic polymer is spray-dried Then, a step of obtaining particles in which the surface of the conductive fine particles carrying the catalyst is coated with a hydrophilic polymer film is formed, and the catalyst layer of at least one of the fuel electrode and the oxidant electrode is formed using the particles. And the step of performing.

  The fuel cell which concerns on 1 aspect of this invention comprises the said membrane electrode assembly for fuel cells, It is characterized by the above-mentioned.

  According to the membrane electrode assembly for a fuel cell according to one aspect of the present invention, aggregation of catalyst particles accompanying the operation of the fuel cell can be prevented, and the life characteristics of the fuel cell can be improved. In addition, according to the method for manufacturing a membrane electrode assembly for a fuel cell according to one aspect of the present invention, it is possible to manufacture a membrane electrode assembly for a fuel cell that can improve the life characteristics of such a fuel cell. it can. Furthermore, since the fuel cell according to one embodiment of the present invention includes such a fuel cell membrane electrode assembly, it can have excellent output performance and life characteristics.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. Although the description will be made based on the drawings, the drawings are provided for illustration only, and the present invention is not limited to the drawings.

  FIG. 1 is a cross-sectional view showing a main configuration of a fuel cell according to an embodiment of the present invention. As shown in FIG. 1, the fuel cell of the present embodiment includes an anode (fuel electrode) 13 having an anode catalyst layer 11 and an anode gas diffusion layer 12, a cathode having a cathode catalyst layer 14 and a cathode gas diffusion layer 15. A membrane / electrode assembly (MEA) comprising an (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. Assembly) 18.

  FIG. 2 is a diagram schematically showing a part of a cross section of the anode catalyst layer 11 (or the cathode catalyst layer 14). As shown in FIG. 2, the anode catalyst layer 11 and the cathode catalyst layer 14 are each composed of particles 20 in which the surfaces of conductive fine particles 22 supporting the catalyst 21 are coated with a film of a hydrophilic polymer 23. .

  The particles 20 contained in the anode catalyst layer 11 and the cathode catalyst layer 14 are manufactured by the following method.

  First, the conductive fine particles 22 carrying the catalyst 21 and the hydrophilic polymer 23 are mixed with a solvent to obtain a suspension. At this time, it is preferable that the conductive fine particles 22 carrying the catalyst 21 and the hydrophilic polymer 23 are uniformly suspended in the solvent by using a suitable stirring means or a dispersing device using ultrasonic waves. . The mixing ratio of the conductive fine particles 22 carrying the catalyst 21 and the hydrophilic polymer is preferably in the range of 20:80 to 80:20 by mass ratio. When the ratio of the conductive fine particles 22 carrying the catalyst 21 is less than the above range, the film thickness of the hydrophilic polymer 23 covering the conductive fine particles 22 is increased so that the gas transfer to the catalyst 21 is hindered. Become. On the contrary, when the ratio of the conductive fine particles 22 supporting the catalyst 21 is larger than the above range, it becomes difficult to cover the entire surface of the conductive fine particles 22 with the hydrophilic polymer 23, and the proton transmission is reduced. There is a possibility that the aggregation of 21 cannot be sufficiently prevented. As the solvent, water, alcohol such as isopropyl alcohol, a mixture thereof, or the like can be used.

  Next, the suspension is sprayed from a spray nozzle of a spray drying apparatus and dried. Although drying temperature is based also on the kind of solvent, it is 100-200 degreeC normally, Preferably it is the range of 120-180 degreeC. As a result, the solvent of the suspension is almost completely removed, and particles 20 in which the surfaces of the conductive fine particles 22 carrying the catalyst 21 are coated with a film of the hydrophilic polymer 23 are obtained. In the particles 20 thus obtained, the film of the hydrophilic polymer 23 is firmly adhered to the surface of the conductive fine particles 22, so that the aggregation of the catalyst 21 particles carried on the conductive fine particles 22 is caused. It is suppressed.

  In the present embodiment, the spray drying apparatus provided with the spray nozzle is used in the production of the particles 20, but the present invention is not particularly limited to such an apparatus, and various conventionally known spray drying apparatuses. Can be used.

Here, each component constituting the particle 20 will be described.
First, examples of the catalyst 21 include a simple substance of a platinum group element such as Pt, Ru, Rh, Ir, Os, and Pd, and an alloy containing these platinum group elements. The anode catalyst layer 11 is preferably made of an alloy such as Pt—Ru or Pt—Mo that has strong resistance to methanol, carbon monoxide, or the like. The cathode catalyst layer 14 is preferably made of an alloy such as Pt or Pt—Ni. However, the catalyst is not limited to these, and various substances having catalytic activity can be used. The catalyst 21 preferably has an average particle diameter of 2 to 5 nm. The average particle diameter of the catalyst 21 can be measured by an X-ray diffraction method (XRD).

  Examples of the conductive fine particles 22 supporting the catalyst 21 include particulate or fibrous carbon materials such as conductive carbon black, activated carbon, and graphite. Further, inorganic fine particles such as alumina and silica can be used, but a carbon material is preferable from the viewpoint of conductivity, air permeability and the like.

  Further, the hydrophilic polymer 23 is preferably a polymer that has an affinity for water and can transmit protons to or from the catalyst 21. For example, (a) a hydrocarbon proton conductor That is, a polymer in which an ion exchange group such as a sulfonic acid group, a phosphonic acid group, or a carboxylic acid group is introduced in order to impart proton conductivity to a polymer whose main chain is composed of hydrocarbon, (b) a fluorine-based proton conductor , In which an ion exchange group such as a sulfonic acid group, a phosphonic acid group, or a carboxylic acid group is introduced in order to impart proton conductivity to a polymer comprising a hydrocarbon whose main chain is substituted with fluorine. Ion exchange of sulfonic acid groups, phosphonic acid groups, carboxylic acid groups, etc. to give proton conductivity to polymers such as polysiloxanes and polyphosphazenes that do not substantially contain carbon atoms in the chain Proton conductivity is imparted to a copolymer having two or more repeating units selected from repeating units constituting the polymer before introduction of ion exchange groups (d) (i) to (c). For this purpose, those having an ion exchange group such as a sulfonic acid group, a phosphonic acid group, or a carboxylic acid group introduced. Here, “an ion exchange group introduced into a polymer or copolymer” means “an ion exchange group introduced into the polymer or copolymer skeleton via a chemical bond”. In addition, the main chain in (i) and (b) may be interrupted by a heteroatom such as an oxygen atom.

  (A) Specific examples of the hydrocarbon proton conductor include those whose main chain is made of an aliphatic hydrocarbon, such as polyvinyl sulfonic acid, polystyrene sulfonic acid, poly (α-methylstyrene) sulfonic acid, and the like. . Examples of those having an aromatic ring in the main chain include, for example, polyether ether ketone, polysulfone, polyether sulfone, poly (arylene ether), polyimide, poly (4-phenoxybenzoyl-1,4-phenylene), polyphenylene sulfide. , Sulfonic acid groups introduced into homopolymers such as polyphenylquinoxalen, arylsulfonated polybenzimidazole, alkylsulfonated polybenzimidazole, alkylphosphonated polybenzimidazole, phosphonated poly (phenylene ether) ) And the like.

  (B) Specific examples of the fluorine-based proton conductor include perfluorosulfonate, perfluoroalkyl polymer having a phosphonic acid group, polytrifluorostyrene sulfonic acid, polytrifluorostyrene phosphonic acid, and the like.

  The copolymer in the proton conductor (d) may be any of a random copolymer, an alternating copolymer, and a block copolymer. As what introduce | transduced the ion exchange group into the random copolymer, a sulfonated polyether sulfone-dihydroxybiphenyl copolymer etc. are mentioned, for example. As what introduce | transduced the ion exchange group into the block copolymer, what introduce | transduced the ion exchange group into the styrene- (ethylene-butylene) -styrene triblock copolymer etc. are mentioned, for example.

  As the hydrophilic polymer 23, perfluorosulfonic acid salt is preferable from the viewpoint of proton conductivity and stability of the substance itself. Examples of commercially available perfluorosulfonates include Nafion (trade name, manufactured by DuPont) and Flemion (trade name, manufactured by Asahi Glass).

  The anode catalyst layer 11 and the cathode catalyst layer 14 may contain components other than the particles 20 such as inorganic particles and a binder as long as the effects of the present invention are not impaired. The inorganic particles may be conductive or insulating, and specific examples thereof include silicon oxide (for example, glass, quartz powder, quartzite powder, diatomaceous earth, silica fume, natural silica, colloidal silica, etc.), aluminum Oxides (aluminum oxide, alumina), titanium oxide, mica, sericite, zeolite, sericite, kaolin clay, kaolin, calcined kaolin (metakaolin), asbestos, mica, talc, silicon carbide, silicon nitride, aluminum nitride, zirconia, Examples thereof include particles such as carbon. Moreover, what was illustrated as a hydrophilic polymer mentioned above as a binder is mentioned.

  The anode gas diffusion layer 12 laminated on the anode catalyst layer 11 functions as a current collector that uniformly supplies fuel to the anode catalyst layer 11 and efficiently transmits electrons generated in the anode catalyst layer 11 to the outside. It also has functions. The cathode gas diffusion layer 15 laminated on the cathode catalyst layer 14 has a function of uniformly supplying an oxidant to the cathode catalyst layer 14 and also efficiently collects electrons supplied from the outside to the cathode catalyst layer 14. It also has a function as a body. Both the anode gas diffusion layer 12 and the cathode gas diffusion layer 15 are formed of a porous substrate formed of a conductive material.

  As the porous substrate, it is preferable to use a conductive fiber that has been processed into a sheet shape, such as carbon cloth or carbon paper formed of carbon fiber or the like. Carbon paper or carbon cloth made of carbon fibers of about 1 μm or more and having a porosity of 50% or more can be used. The porous substrate may be a sintered body, and a sintered metal or metal oxide (tin oxide, titanium oxide, etc.) can be used.

  When the anode catalyst layer 11 and the cathode catalyst layer 14 are formed on the anode gas diffusion layer 12 and the cathode gas diffusion layer 15, respectively, the particles 20 manufactured by the above-described method, that is, the conductive fine particles carrying the catalyst 21 are supported. The surface of 22 is coated with a film of hydrophilic polymer 23, or such particles 20 and the above-mentioned inorganic particles as optional components are dispersed in a solvent to prepare a slurry. The slurry may be applied to each porous substrate forming the anode gas diffusion layer 12 and the cathode gas diffusion layer 15 by a coater, spray, or the like in one or more times and dried. As the solvent, water, alcohol such as isopropyl alcohol, a mixture thereof, or the like can be used.

  The electrolyte membrane 17 may be a hydrocarbon electrolyte membrane, that is, an electrolyte membrane made of a hydrocarbon proton conductor, or a fluorine electrolyte membrane, ie, an electrolyte membrane made of a fluorine proton conductor. Also good. Alternatively, an electrolyte film made of an inorganic material such as tungstic acid or phosphotungstic acid may be used. In general, Nafion 112 (trade name, manufactured by DuPont) having a membrane made of perfluorosulfonate is used, but it is not particularly limited thereto.

  The membrane electrode assembly 18 of the present embodiment includes an anode (fuel electrode) 13 in which the anode catalyst layer 11 is formed on the anode gas diffusion layer 12 and a cathode in which the cathode catalyst layer 14 is formed on the cathode gas diffusion layer 15. (Air electrode / oxidizer electrode) 16 and the electrolyte membrane 17 are formed such that the anode catalyst layer 11 and the cathode catalyst layer 15 are in contact with both surfaces of the electrolyte membrane 17 and heated and pressed. A conductive layer may be formed on the surface of the anode gas diffusion layer 12 opposite to the anode catalyst layer 11 and the surface of the cathode gas diffusion layer 15 opposite to the cathode catalyst layer 14 as necessary. As these conductive layers, for example, a mesh, a porous film, a thin film, or the like made of a conductive metal material such as Au is used.

In the fuel cell including the membrane electrode assembly 18 configured as described above, the fuel is supplied to the anode (fuel electrode) 13 while the cathode (air electrode / oxidant electrode) 16 is oxidized with air, oxygen, or the like. Sex gas is introduced. The fuel diffuses through the anode gas diffusion layer 12 and is supplied to the anode catalyst layer 11. When methanol fuel is used as the fuel, an internal reforming reaction of methanol shown in the following formula (1) occurs in the anode catalyst layer 11. When pure methanol is used as the methanol fuel, the water generated in the cathode catalyst layer 14 or the water in the electrolyte membrane 17 is reacted with methanol to cause the internal reforming reaction of the formula (1). Alternatively, the internal reforming reaction is caused by another reaction mechanism that does not require water.
CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ (1)

Electrons (e ⁻ ) generated by this reaction are guided to the outside, and are operated as so-called electricity, and are then guided to the cathode (air electrode) 16 after operating a portable electronic device or the like. Further, protons (H ⁺ ) generated by the internal reforming reaction of the formula (1) are guided to the cathode 16 through the electrolyte membrane 17. Electrons (e ⁻ ) and protons (H ⁺ ) that have reached the cathode 16 react with oxygen in the cathode catalyst layer 14 according to the following formula (2), and water is generated in accordance with this reaction.
6e ⁻ + 6H ⁺ + (3/2) O ₂ → 3H ₂ O (2)

  In the fuel cell described above, in order to obtain good life characteristics, it is important to prevent the particles of the catalyst 21 supported on the conductive fine particles 22 from aggregating during the operation of the fuel cell. When the particles of the catalyst 21 are aggregated, the specific surface area of the catalyst 21 is substantially reduced and the catalytic activity is lowered.

  In the fuel cell of this embodiment, as described above, the anode catalyst layer 11 and the cathode catalyst layer 14 are particles in which the membrane of the hydrophilic polymer 23 is firmly adhered to the surface of the conductive fine particles 22 carrying the catalyst 21. Therefore, the movement of the particles of the catalyst 21 is prevented, and the aggregation of the particles of the catalyst 21 is suppressed. For this reason, the fall of the output accompanying such aggregation and the fall of a lifetime characteristic can be suppressed.

  In the present embodiment, both the anode catalyst layer 11 and the cathode catalyst layer 14 are composed of particles 20 in which the surface of the conductive fine particles 22 carrying the catalyst 21 is covered with a film of the hydrophilic polymer 23. Either one may be sufficient. However, from the viewpoint of the obtained effect, it is preferable that at least the anode catalyst layer 11 is composed of the particles 20.

  The present invention can be widely applied to various solid polymer fuel cells having a polymer electrolyte membrane, but is generally applied to a fuel cell using a liquid fuel such as methanol fuel. Fuel cells using liquid fuel can be broadly divided into active fuel cells and passive fuel cells depending on the fuel supply system, and any of them can be applied. Incidentally, an active fuel cell forcibly supplies liquid fuel, air, etc. to the anode and cathode electrodes of the membrane electrode assembly, respectively, while a passive fuel cell supplies vaporized liquid fuel. While supplying naturally to the anode pole of a membrane electrode assembly, outside air is naturally supplied to a cathode pole. Furthermore, the present invention can also be applied to a fuel cell of a type called a semi-passive that partially uses a pump or the like, such as fuel supply. In the semi-passive type fuel cell, the fuel supplied from the fuel storage part to the membrane electrode assembly is used for the power generation reaction, and is not circulated thereafter and returned to the fuel storage part. The semi-passive type fuel cell is different from the conventional active method because it does not circulate the fuel, and does not impair the downsizing of the device. Moreover, a pump is used to supply fuel, which is different from a pure passive system such as a conventional internal vaporization type. For this reason, this fuel cell is called a semi-passive system as described above. In this semi-passive type fuel cell, a fuel cutoff valve may be arranged in place of the pump as long as fuel is supplied from the fuel storage portion to the membrane electrode assembly. In this case, the fuel cutoff valve is provided for controlling the supply of liquid fuel through the flow path.

  As the liquid fuel, methanol fuel such as methanol aqueous solution, pure methanol, ethanol aqueous solution, ethanol fuel such as pure ethanol, propanol fuel such as propanol aqueous solution and pure propanol, glycol fuel such as glycol aqueous solution and pure glycol, formic acid, Examples include dimethyl ether. In any case, liquid fuel corresponding to the fuel cell is used. It should be noted that the liquid fuel vapor supplied to the MEA may be all supplied as a liquid fuel vapor, but the present invention can be applied even when a part of the liquid fuel vapor is supplied in a liquid state.

  As mentioned above, although embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this example. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are of course within the technical scope of the present invention. Is done.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples at all. The average particle size of the catalyst and carbon particles was measured by XRD.

[Production of catalyst slurry]
(Production Example 1)
1.2 g of carbon particles having an average particle size of 40 nm (Pt-Ru content: 50 wt%) carrying Pt-Ru fine particles (average particle size of 3 nm), perfluorosulfonate solution (containing 20% by weight of Nafion (trade name)) 1.5 g, 5 g of ion-exchanged water, and 5 g of isopropyl alcohol were stirred and mixed with a magnetic stirrer for 10 minutes, and then ultrasonic vibration was added to the mixture for 10 minutes to prepare a suspension. This suspension was supplied to a spray nozzle of a spray dryer, and sprayed and dried to obtain granules. 1.5 g of the obtained granule, 5 g of ion-exchanged water, and 2 g of isopropyl alcohol were uniformly mixed to produce a fuel catalyst slurry (A).

(Production Example 2)
Carbon particles having an average particle diameter of 40 nm (Pt-Ru content: 50 wt%) carrying Pt-Ru fine particles (average particle diameter of 3 nm), perfluorosulfonate solution (containing 20% by weight of Nafion (trade name)) 6 g, 5 g of ion-exchanged water, and 5 g of isopropyl alcohol were stirred and mixed with a magnetic stirrer for 10 minutes, and then ultrasonic vibration was added to the mixture for 10 minutes to prepare a suspension. This suspension was supplied to a spray nozzle of a spray dryer, and sprayed and dried to obtain granules. 1.5 g of the obtained granule, 5 g of ion-exchanged water, and 2 g of isopropyl alcohol were uniformly mixed to produce a fuel catalyst slurry (B).

(Production Example 3)
1.23 g of carbon particles having an average particle size of 40 nm (Pt-Ru content: 50 wt%) carrying Pt-Ru fine particles (average particle size of 3 nm), perfluorosulfonate solution (containing 20% by weight of Nafion (trade name)) 1.35 g, 5 g of ion-exchanged water, and 5 g of isopropyl alcohol were mixed with a magnetic stirrer for 10 minutes, and then ultrasonic vibration was added to the mixture for 10 minutes to prepare a suspension. This suspension was supplied to a spray nozzle of a spray dryer, and sprayed and dried to obtain granules. 1.5 g of the obtained granule, 5 g of ion-exchanged water, and 2 g of isopropyl alcohol were uniformly mixed to produce a fuel catalyst slurry (C).

(Production Example 4)
0.27 g of carbon particles having an average particle size of 40 nm (Pt-Ru content: 50 wt%) carrying Pt-Ru fine particles (average particle size of 3 nm), perfluorosulfonate solution (containing 20% by weight of Nafion (trade name)) 6.15 g, 5 g of ion-exchanged water, and 5 g of isopropyl alcohol were stirred and mixed with a magnetic stirrer for 10 minutes, and then ultrasonic vibration was added to the mixture for 10 minutes to prepare a suspension. This suspension was supplied to a spray nozzle of a spray dryer, and sprayed and dried to obtain granules. 1.5 g of the obtained granule, 5 g of ion-exchanged water, and 2 g of isopropyl alcohol were uniformly mixed to produce a fuel catalyst slurry (D).

(Production Example 5)
1.2 g of carbon particles having an average particle size of 40 nm (Pt-Ru content: 50 wt%) carrying Pt-Ru fine particles (average particle size of 3 nm), perfluorosulfonate solution (containing 20% by weight of Nafion (trade name)) 1.5 g, 5 g of ion-exchanged water, and 2 g of isopropyl alcohol were uniformly mixed to produce a fuel catalyst slurry (E).

(Production Example 6)
Carbon particles having an average particle diameter of 40 nm (Pt-Ru content: 50 wt%) carrying Pt-Ru fine particles (average particle diameter of 3 nm), perfluorosulfonate solution (containing 20% by weight of Nafion (trade name)) 6 g, 5 g of ion-exchanged water, and 2 g of isopropyl alcohol were uniformly mixed to produce a fuel catalyst slurry (F).

(Production Example 7)
1.0 g of carbon particles having an average particle size of 40 nm carrying Pt fine particles (average particle size of 3 nm) (Pt content: 50 wt%), 1.2 g of a perfluorosulfonate solution (containing 20% by weight of Nafion (trade name)), Ion exchange water 5 g and isopropyl alcohol 5 g were uniformly mixed to produce a catalyst slurry for oxidant.

[Manufacture of membrane electrode assemblies for fuel cells and fuel cells]
Example 1
The fuel catalyst slurry (A) is applied to one side of a porous base material (thickness: 200 μm, area: 12 cm ² , porosity: 70% by volume) made of water-repellent treated carbon paper and dried for a fuel with a thickness of 100 μm. A catalyst layer was formed. Moreover, the said oxidizing agent catalyst slurry was apply | coated to one side of the same porous base material, and it was made to dry, and the 100-micrometer-thick oxidizing agent catalyst layer was formed.

  Next, an electrolyte membrane made of perfluorosulfonate (trade name: Nafion 112) was prepared using the porous substrate on which the fuel catalyst layer was formed and the porous substrate on which the oxidant catalyst layer was formed as an anode electrode and a cathode electrode, respectively. ), The catalyst layers are superimposed on the electrolyte membrane side, heated and pressed at 150 ° C. and 4 MPa for 10 minutes to produce a membrane electrode assembly, and a passive type DMFC is manufactured using this. did.

(Example 2)
A membrane electrode assembly was produced in the same manner as in Example 1 except that the fuel catalyst slurry (B) was used for forming the fuel catalyst layer, and a passive DMFC was produced using the membrane electrode assembly.

(Example 3)
A membrane electrode assembly was produced in the same manner as in Example 1 except that the fuel catalyst slurry (C) was used for forming the fuel catalyst layer, and a passive DMFC was produced using the membrane electrode assembly.

Example 4
A membrane electrode assembly was produced in the same manner as in Example 1 except that the fuel catalyst slurry (D) was used for forming the fuel catalyst layer, and a passive DMFC was produced using the membrane electrode assembly.

(Comparative Example 1)
A membrane electrode assembly was produced in the same manner as in Example 1 except that the fuel catalyst slurry (E) was used for forming the fuel catalyst layer, and a passive DMFC was produced using the membrane electrode assembly.

(Comparative Example 2)
A membrane electrode assembly was produced in the same manner as in Example 1 except that the fuel catalyst slurry (F) was used for forming the fuel catalyst layer, and a passive DMFC was produced using the membrane electrode assembly.

Pure methanol was injected into the liquid fuel tank of the passive type DMFC prepared in each of the above Examples and Comparative Examples, and the current / voltage curve was changed by changing the current value in an environment of a temperature of 25 ° C. and a relative humidity of 50%. The maximum output per unit area was measured (initial maximum output). Thereafter, a constant voltage of 0.4 V was operated for 500 hours, a current-voltage curve was measured again, and an output maintenance ratio was calculated from the following equation.
Maintenance rate (%) = (maximum output after 500 hours of operation / initial maximum output) × 100
These results are shown in Table 1 together with the solid content in the catalyst layer of the anode electrode.

  As apparent from Table 1, among the examples according to the present invention, the mass ratio of the catalyst-supporting carbon particles and the polymer electrolyte in the catalyst layer forming the anode electrode is in the range of 1: 4 to 4: 1. In the example, particularly good results were obtained for both the initial output and the output maintenance rate.

It is sectional drawing which shows the structure of the membrane electrode assembly for fuel cells by one Embodiment of this invention. It is a figure which shows typically a part of cross section of the catalyst layer shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Anode catalyst layer, 12 ... Anode gas diffusion layer, 13 ... Anode (fuel electrode), 14 ... Cathode catalyst layer, 15 ... Cathode gas diffusion layer, 16 ... Cathode (air electrode), 17 ... Electrolyte membrane, 18 ... Membrane Electrode assembly, 20 ... particles, 21 ... catalyst, 22 ... conductive fine particles, 23 ... hydrophilic polymer.

Claims (5)

A fuel cell membrane electrode joint comprising: a fuel electrode provided with a catalyst layer; an oxidant electrode provided with a catalyst layer; and an electrolyte membrane sandwiched between the catalyst layer of the fuel electrode and the catalyst layer of the oxidant electrode. Body,
The catalyst layer of at least one of the fuel electrode and the oxidant electrode includes particles obtained by spray-drying a suspension containing conductive fine particles supporting a catalyst and a hydrophilic polymer. A membrane electrode assembly for a fuel cell.   The membrane electrode assembly for a fuel cell according to claim 1, wherein the mass ratio of the conductive fine particles to the hydrophilic polymer is 20:80 to 80:20.   The membrane electrode assembly for fuel cells according to claim 1 or 2, wherein the drying temperature is 100 to 200 ° C. A fuel cell membrane electrode joint comprising: a fuel electrode provided with a catalyst layer; an oxidant electrode provided with a catalyst layer; and an electrolyte membrane sandwiched between the catalyst layer of the fuel electrode and the catalyst layer of the oxidant electrode. A method for manufacturing a body,
A step of spray-drying a suspension containing conductive fine particles supporting a catalyst and a hydrophilic polymer to obtain particles in which the surface of the conductive fine particles supporting the catalyst is coated with a hydrophilic polymer film; ,
Forming a catalyst layer of at least one of the fuel electrode and the oxidant electrode using the particles;
A method for producing a membrane electrode assembly for a fuel cell, comprising:   A fuel cell comprising the fuel cell membrane electrode assembly according to any one of claims 1 to 3.

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