JP2010198801A - Electrode for polymer electrolyte fuel cell, method for manufacturing calcined film of polymer electrolyte fuel cell, method for using electrode of polymer electrolyte fuel cell, and polymer electrolyte fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode for a polymer electrolyte fuel cell, the electrode suitably maintaining a wet condition of a solid polymer film by securing suitable water retention characteristics. <P>SOLUTION: In the electrode 1 for the polymer electrolyte fuel cell made of a gas diffusion layer 2 with conductivity and ventilation characteristics and a catalyst layer 3 including a catalyst 6 carried by a catalyst carrier, the gas diffusion layer 2 is provided with cup-stack type carbon nanotube at a designated length, and a calcined film in which conductive fillers shorter in length than the cup-stack type carbon nanotube are mixed. The catalyst 6 is carried on the calcined film functioning as a catalyst carrier. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a solid polymer fuel cell electrode comprising a gas diffusion layer having conductivity and air permeability and a catalyst layer containing a catalyst supported on a catalyst carrier, and production of a solid polymer fuel cell electrode The present invention relates to a method and a polymer electrolyte fuel cell.

  A polymer electrolyte fuel cell is composed of a membrane-electrode assembly in which both sides of a solid electrolyte membrane are sandwiched between an anode side catalyst electrode and a cathode side catalyst electrode.

  The anode catalyst side electrode and the cathode catalyst side electrode include a gas diffusion layer having conductivity and air permeability, a catalyst layer including a catalyst supported on a catalyst support and an ion exchange resin, and the catalyst layer is in contact with the solid electrolyte membrane. It has a structure.

  The catalyst electrode is obtained by applying a catalyst layer in which a catalyst such as platinum or a platinum alloy is supported on a catalyst carrier having a large surface area such as carbon black on the gas diffusion layer together with an ion exchange resin.

  Patent Document 1 discloses a thin polymer electrolyte fuel cell electrode that can be produced in a short period of time without generating by-products that are difficult to process, and that provides high catalytic activity while ensuring good fuel gas permeability. The electrode for a polymer electrolyte fuel cell comprising a gas diffusion layer having conductivity and air permeability and a catalyst layer containing a metal catalyst supported on a catalyst carrier, the gas There has been proposed an electrode for a polymer electrolyte fuel cell in which a diffusion layer is composed of a fired film made of carbon nanotubes, and the metal catalyst is supported on the fired film functioning as the catalyst support.

JP 2008-210801A

  According to the above-mentioned electrode for a polymer electrolyte fuel cell, the use of a baked film having a small pore size using carbon nanotubes as a gas diffusion layer allows the catalyst carrier to be secured while ensuring adequate gas permeability to the fuel gas. As a sufficient specific surface area required for the above can be obtained, the catalyst can be directly supported on the gas diffusion layer without providing a separate catalyst carrier layer such as carbon black. Can be made thinner.

  By the way, in the polymer electrolyte fuel cell, hydrogen ions separated by the action of the catalyst at the anode side electrode are passed through the solid polymer membrane, and the electrons pass through the external circuit to reach the cathode side electrode. The cathode side electrode reacts with oxygen to produce water, but the ionic conductivity that affects the performance of the polymer electrolyte fuel cell is significantly affected by the moisture content of the polymer electrolyte membrane. The polymer membrane needs to be kept in a proper and uniform wet state.

  This is because when the solid polymer membrane is dried and the ionic conductivity is lowered, a phenomenon called dry-out in which output characteristics are lowered occurs.

  According to the electrode using the fired film described above, the pore size, that is, the pore diameter size, can be reduced to some extent to ensure adequate air permeability to the fuel gas, but in order to keep the solid polymer film in a good wet state From the viewpoint of water retention, further improvement of the fired film has been desired.

  In view of the above-mentioned problems, an object of the present invention is to provide an electrode for a polymer electrolyte fuel cell, a polymer electrolyte fuel, which can ensure good water retention and keep the solid polymer membrane in a good wet state. It exists in the point which provides the manufacturing method of the sintered film for batteries, the usage method of the electrode for polymer electrolyte fuel cells, and a polymer electrolyte fuel cell.

  In order to achieve the above-mentioned object, the first characteristic configuration of the electrode for a polymer electrolyte fuel cell according to the present invention is a gas having conductivity and air permeability as described in claim 1 of the claims. An electrode for a polymer electrolyte fuel cell comprising a diffusion layer and a catalyst layer containing a catalyst supported on a catalyst carrier, wherein the gas diffusion layer comprises a cup-stacked carbon nanotube having a predetermined length and the cup stack. It is composed of a fired film in which conductive fillers shorter in length than the carbon nanotubes are mixed, and the catalyst is supported on the fired film functioning as the catalyst support.

  According to the above-described configuration, the conductive filler having a shorter length than the cup stack type carbon nanotubes enters the pores formed by entwining the cup stack type carbon nanotubes that are the base material of the fired film. While maintaining conductivity, the maximum peak value of the pore size distribution can be shifted to the smaller diameter side. As a result, by improving the water retention of the fired film, the wet state of the solid polymer film can be maintained well, and the occurrence of the dry-out phenomenon can be effectively suppressed.

  In particular, when the maximum peak value of the pore size distribution of the fired film is adjusted in the range of 0.08 μm to 0.18 μm, good water retention can be secured.

  When the mixing ratio of the conductive filler is 50% by weight or less with respect to the mixed weight of the cup-stacked carbon nanotube and the conductive filler, while maintaining the shape retention of the fired film, This is preferable in that the maximum peak value can be shifted to the smaller diameter side.

  It is preferable that the length of the conductive filler is ½ or less of the length of the cup-stacked carbon nanotube because the maximum peak value of the pore diameter distribution can be effectively shifted to the small diameter side.

  The cup-stacked carbon nanotube is preferably 0.5 to 10 μm in length, and the conductive filler is preferably 1 μm or less in length.

  The conductive filler is preferably selected from carbon nanotubes, carbon black, graphite, graphite, metal, and metal oxide.

  By using cup-stacked carbon nanotubes as the base material of the fired film that becomes the catalyst carrier, a sufficient specific surface area required as a catalyst carrier can be obtained, which is very active and the catalyst is easily bonded. Therefore, the catalyst can be suitably dispersed and supported as a whole.

  By selecting any one of carbon nanotubes, carbon black, graphite, graphite, metal, and metal oxide as the conductive filler, the pore diameter formed by the entanglement of the carbon nanotubes can be effectively reduced.

  The fired film used for the electrode for a polymer electrolyte fuel cell described above is a dispersion treatment step in which a cup-stacked carbon nanotube, a conductive filler having a shorter length than the cup-stacked carbon nanotube, and a resin binder are dispersed in an organic solvent, The dispersion solution obtained in the dispersion treatment step can be produced by a forming step of forming a film and drying it, and a firing step of baking the film obtained in the forming step in an inert gas atmosphere.

  As described above, in the polymer electrolyte fuel cell, water may be generated by reacting with oxygen at the cathode side electrode, and the dry-out phenomenon tends to occur on the anode side. Therefore, by using the above-described polymer electrolyte fuel cell electrode as the anode electrode of the polymer electrolyte fuel cell, it is possible to avoid the occurrence of a dry-out phenomenon and maintain a good power generation state. become.

  As a polymer electrolyte fuel cell, a gas diffusion layer having conductivity and air permeability is composed of a fired film using a cup-stacked carbon nanotube as a base material, and an electrode on which a catalyst is supported is incorporated in the fired film, It is preferable that the maximum peak value of the pore diameter distribution of the fired film used for the anode side electrode is adjusted to be smaller than the maximum peak value of the pore diameter distribution of the fired film used for the cathode side electrode.

  According to the above-described configuration, the use of a fired film having a small maximum peak value of the pore size distribution for the anode-side electrode that tends to cause the dry-out phenomenon prevents the occurrence of the dry-out phenomenon, By using a fired film having a large maximum peak diameter distribution for the electrode, it is possible to suppress the occurrence of a flatting phenomenon in which the gas permeability is lowered by the generated water.

  And the electrode for a polymer electrolyte fuel cell mentioned above can be used conveniently for an anode side electrode.

  As described above, according to the present invention, it is possible to ensure good water retention and keep the solid polymer membrane in a good wet state. A method for producing a fired film, a method for using a polymer electrolyte fuel cell electrode, and a polymer electrolyte fuel cell can be provided.

Explanatory drawing of the polymer electrolyte fuel cell by this invention Explanatory drawing showing the state of catalyst loading on the fired film Explanatory drawing of manufacturing method of fired film It is data explanatory drawing of the mixing weight of a cup stack type carbon nanotube and a conductive filler, and the maximum peak value of pore size distribution, (a) is explanatory drawing of two sets of comparative samples and the 1st sample, (b) is Illustration of two sets of comparative sample and second sample Characteristic diagram showing experimental results and changes in pore size distribution of the first set of comparative samples and the first sample Characteristic diagram showing experimental results and changes in pore size distribution of the second set of comparative samples and the first sample Characteristic diagram showing experimental results and changes in pore size distribution of the first set of comparative sample and second sample Characteristic diagram showing experimental results and changes in pore size distribution of the second set of comparative sample and second sample Explanatory drawing showing experimental results and showing change in maximum peak value of pore size distribution due to mixing ratio of cup-stacked carbon nanotube and conductive filler

  Hereinafter, a preferred embodiment of a polymer electrolyte fuel cell employing the polymer electrolyte fuel cell electrode according to the present invention will be described.

  As shown in FIG. 1, a solid polymer fuel cell 1 according to the present invention has an anode side catalyst electrode 4a (4) and a cathode side catalyst electrode 4b (4) joined to both surfaces of a solid polymer electrolyte membrane 8, respectively. It is configured.

  The anode side catalyst electrode 4a (4) and the cathode side catalyst electrode 4b (4) are provided on one side of the gas diffusion layer 2 (2a, 2b) and the gas diffusion layer 2 (2a, 2b) having conductivity and air permeability. The catalyst layer 3 (3a, 3b) including the supported catalyst 6 (6a, 6b) and the ion exchange resin 7 is formed, and each catalyst layer 3 (3a, 3b) faces the solid polymer electrolyte membrane 8. Are arranged as follows.

  The gas diffusion layer 2 is composed of a fired film having conductivity and air permeability, and a catalyst 6 is supported on the fired film by sputtering.

  The fired film to be a catalyst carrier is composed of a fired film in which a cup-stacked carbon nanotube of a predetermined length and a conductive filler having a shorter length than the cup-stacked carbon nanotube are mixed, ensuring a sufficient specific surface area, In order to ensure a sufficient amount of catalyst supported and uniform dispersibility, cup-stacked carbon nanotubes having a diameter in the range of 80 to 120 nm and a fiber length in the range of 0.5 μm to 10 μm are used as the base material. It has been.

  Unlike general concentric carbon nanotubes, cup-stacked carbon nanotubes are shaped by stacking carbon mesh cups with open bottoms and have a large hollow structure inside, and the length depends on the number of cups stacked. Since adjustment is possible, it is extremely useful in that the shape of the fired film can be maintained and a sufficient specific surface area can be maintained by appropriately selecting the length of the cup-stacked carbon nanotube within the above-mentioned range. It is. A cup-stacked carbon nanotube having a diameter of 80 to 120 nm can be easily adjusted to a length of 10 μm or less by, for example, ball milling.

  Generally, three optimizations of activation polarization, resistance polarization, and concentration polarization are required to obtain good power generation characteristics of a fuel cell. When the above-mentioned cup-stacked carbon nanotube is used, a catalyst by sputtering is used. Three types of optimization are possible: reduction of activation polarization (improvement of catalyst activity), reduction of resistance polarization due to high conductivity equal to or higher than that of existing carbon black or carbon nanotubes, and reduction of concentration polarization by length control. It becomes possible.

The conductive filler mixed with the base material is selected from any of cup-stacked carbon nanotubes, Ti ₂ O, carbon nanotubes, carbon black, graphite, graphite, metals, and metal oxides.

  The mixing ratio of the conductive filler is preferably 50% by weight or less with respect to the mixing weight of the cup stack type carbon nanotube and the conductive filler, and the length of the conductive filler is 1 of the length of the cup stack type carbon nanotube. / 2 or less is preferable.

  In particular, the mixing ratio of the conductive filler with respect to the cup stack type carbon nanotube is set in the range of 20 wt% to 50 wt%, the length of the cup stack type carbon nanotube is in the range of 0.5 to 10 μm, the length of the conductive filler Is preferably set to 1 μm or less.

  According to the above-described configuration, the conductive filler having a shorter length than the cup stack type carbon nanotubes enters the pores formed by entwining the cup stack type carbon nanotubes that are the base material of the fired film. While maintaining conductivity, the maximum peak value of the pore size distribution can be shifted to the smaller diameter side. As a result, by improving the water retention of the fired film, the wet state of the solid polymer film can be maintained well, and the occurrence of the dry-out phenomenon can be effectively suppressed.

  The maximum peak value of the pore size distribution of the fired film is preferably adjusted in the range of 0.06 μm to 0.20 μm, and particularly preferably in the range of 0.08 μm to 0.18 μm.

  That is, a gas diffusion layer having conductivity and air permeability and a catalyst layer containing a catalyst supported on a catalyst carrier, the gas diffusion layer being cup-stacked carbon nanotubes and cup-stacked carbon nanotubes having a predetermined length. An electrode for a polymer electrolyte fuel cell is configured, which is composed of a fired film mixed with a shorter conductive filler, and in which a catalyst is supported on the fired film functioning as a catalyst support.

The catalyst 6 has a function of promoting the electrode reaction, and the supported amount is 1 mg / cm ² or less, more preferably 0.5 mg / cm ² or less. Further, as the catalyst 6, a catalyst such as platinum Pt or a platinum alloy is preferably used. Besides, gold Au, silver Ag, iridium Ir, palladium Pd, ruthenium Ru, osmium Os, nickel Ni, tungsten W, molybdenum Mo. Further, a metal containing at least one selected from manganese Mn, yttrium Y, vanadium V, niobium Nb, titanium Ti, and a rare earth metal can be used, and a carbide such as molybdenum carbide Mo ₂ C can also be used. is there.

  These catalysts may be used alone or in combination, or some or all of them may be used in the form of an alloy. These catalysts are preferably supported on the laminated surface of the conductive particles laminated on the fired film by a sputtering method.

  The average particle size of the catalyst 6 is preferably in the range of 1 to 10 nm, more preferably in the range of 2 to 5 nm, because the smaller the average particle diameter, the larger the effective electrode area and the better the catalytic activity. Here, when the catalyst 6 is supported by sputtering, it is necessary to adjust various conditions so that a thin film of the catalyst 6 is not formed. This is because when the thin film of the catalyst 6 is formed, the catalyst 6 covers the entire surface of the catalyst layer 3 and hinders the movement of the reaction gas and the water supplied together with the reaction gas.

  The sputtering treatment time is preferably less than 90 seconds, and more preferably 15 seconds to 60 seconds or less. The RF output value during sputtering is not particularly limited, but is preferably 100 W or more.

  In addition, as a catalyst supporting method other than sputtering, for example, vapor deposition, electron irradiation, CVD, PVD, impregnation, spray coating, spray pyrolysis, kneading, spraying, coating with a roll or trowel, screen printing, kneading method, photoelectric It is also possible to employ a solution method, a coating method, a sol-gel method, a dip method, or the like.

  As shown in FIG. 2 (a), when the catalyst 6 is sputtered on a film having a smooth surface, the particles are placed on the particles and a stacked catalyst layer is formed. The surface area in contact with hydrogen gas or oxygen gas is limited with respect to the amount, making it difficult to form an efficient catalyst layer. On the other hand, as shown in FIG. 2B, the fired film obtained by firing a mixture of cup-stacked carbon nanotubes and conductive fillers has a large specific surface area because the surface is formed with irregularities, As a result, it is possible to greatly increase the film surface area to which the catalyst 6 is fixed, particles are easily formed by sputtering, and almost all the supported catalyst 6 contributes to the activation of hydrogen gas or oxygen gas, Higher power generation efficiency can be obtained.

  Further, as shown in FIG. 2 (c), the gas diffusion layer is composed of a fired film made of a mixture of carbon nanotubes and a conductive filler, and the catalyst carrier is composed of a conductive particle layer formed on the fired film. It may be what has been done.

  For example, carbon nanotube conductive particles as a catalyst carrier are coated by applying a carbon nanotube paste, in which carbon nanotubes such as cup-stacked carbon nanotubes are mixed and dispersed in an organic solvent N-methylpyrrolidone, to one side of a fired film. A layer can be formed. In this case, a specific surface area larger than that of the fired film can be ensured, and the sputtered metal catalyst particles can be easily dispersed and supported without overlapping in layers, thus ensuring high activation of the catalyst. As a result, the power generation efficiency can be further increased.

  The gas diffusion layer 2 (2a, 2b) carrying the catalyst 6 is joined to the solid polymer electrolyte membrane 8 and used as a fuel cell MEA (Mebrane Electrode Assembly). When joining both, it is preferable to apply the ion exchange resin 7 in order to obtain a path through which protons pass between the catalyst 6 and the solid polymer electrolyte membrane 8.

  As the ion exchange resin 7, a material having at least high proton conductivity is preferable, and various Nafion (DuPont registered trademark: Nafion) manufactured by DuPont, ion exchange resin manufactured by Dow Chemical Co., etc. are preferably exemplified.

  The content of the ion exchange resin 7 applied to the catalyst layer 3 is not particularly limited, but is preferably 50 to 1500% by weight with respect to the total amount of the supported catalyst 6. When the amount is less than 50% by weight, a path through which protons pass is not sufficiently formed. On the other hand, when the amount is more than 1500% by weight, pores of the fired film are blocked and a reaction gas (hydrogen gas or oxygen gas) is formed. Does not pass through, and induces a phenomenon that the battery does not generate electricity. Moreover, pipette application, a spray method, a doctor blade method, a screen printing method, etc. can be used for application | coating of the ion exchange resin to an electrode catalyst layer.

  Further, the joining of the catalyst layer 3 and the solid polymer electrolyte membrane 8 can be performed using a hot press apparatus or the like.

  The MEA that constitutes the fuel cell is expected if the polymer electrolyte fuel cell electrode according to the present invention is bonded to any surface of the solid polymer electrolyte membrane as an anode side catalyst electrode or a cathode side catalyst electrode. The effect is obtained, and the polymer electrolyte fuel cell electrode according to the present invention is not necessarily limited to the one used for both the anode catalyst electrode and the cathode catalyst electrode.

  However, in the polymer electrolyte fuel cell, water may be generated by reacting with oxygen at the cathode side electrode, and a dry-out phenomenon tends to occur on the anode side. Therefore, by using the above-described polymer electrolyte fuel cell electrode as an anode electrode of the polymer electrolyte fuel cell, it is possible to avoid a dry-out phenomenon and maintain a good power generation state. become able to.

  As a polymer electrolyte fuel cell, a gas diffusion layer having conductivity and air permeability is composed of a fired film using a cup-stacked carbon nanotube as a base material, and an electrode carrying a catalyst is incorporated in the fired film, and an anode It is preferable that the maximum peak value of the pore diameter distribution of the fired film used for the side electrode is adjusted to be smaller than the maximum peak value of the pore diameter distribution of the fired film used for the cathode side electrode.

  For example, the fired film described above may be used for the anode side electrode, and the fired film not mixed with the conductive filler may be used for the cathode side electrode.

  According to the above-described configuration, the use of a fired film having a small maximum peak value of the pore size distribution for the anode-side electrode that tends to cause the dry-out phenomenon prevents the occurrence of the dry-out phenomenon, By using a fired film having a large maximum peak diameter distribution for the electrode, it is possible to suppress the occurrence of a flatting phenomenon in which the gas permeability is lowered by the generated water.

  A process for producing a fired film using a cup-stacked carbon nanotube as a base material will be described. As shown in FIG. 3, the manufacturing process of the fired film includes a dispersion processing step in which a cup-stacked carbon nanotube, a conductive filler having a shorter length than the cup-stacked carbon nanotube, and a resin binder are dispersed in an organic solvent, and a dispersion processing step. The forming step comprises forming a dispersion solution obtained in step 1 into a film and drying it, and a firing step in which the film obtained in the forming step is fired in an inert gas atmosphere.

  The organic solvent used in the dispersion treatment step is not particularly limited, but when a cup stack type carbon nanotube is used, a polar organic solvent can be exemplified, and in particular, N-methylpyrrolidone is preferable, and as a resin binder Is preferably an acrylic resin having carbon dispersibility.

  In the dispersion treatment step, it is preferable that the cup stack type carbon nanotube, the conductive filler, and the resin binder are mixed in an organic solvent, and the dispersion treatment is performed in a range of 30 to 180 minutes using a dispersion apparatus such as a paint shaker. When the dispersion treatment time is short, the cup-stacked carbon nanotubes and the conductive filler are not properly dispersed, and a lump that is a granular lump is formed. When the dispersion treatment time is long, the cup-stacked carbon nanotubes are entangled with each other. This is because there is a possibility that the shape retention of the film after firing may not be ensured.

  In the molding step, the dispersion liquid having sufficient fluidity in the dispersion treatment step is poured into a mold corresponding to the size and film thickness of the gas diffusion layer, and then dried to obtain a thin plate-like body. Although the drying temperature in that case will not be restrict | limited especially if the plate-shaped body of a thin film is obtained, the range of 100-200 degreeC is preferable. When the temperature is 100 ° C. or lower, the solvent is not sufficiently removed by drying, and the film does not become a thin film, or the drying tends to take a long time. Because.

  In the firing step, the thin plate-like body obtained in the molding step is not subjected to brittleness due to oxidation of cup-stacked carbon nanotubes or conductive fillers, under an inert gas atmosphere such as nitrogen gas. Bake at 600 ° C. for about 1 hour. The firing temperature is preferably 500 ° C. to 700 ° C., and the firing time is preferably about 30 minutes to 5 hours. This is because if the firing time is 20 minutes or less, the binder resin is not sufficiently thermally decomposed, so that sufficient pores are not formed.

  Furthermore, a fired film in which a cup-stacked carbon nanotube and a conductive filler having a shorter length than the cup-stacked carbon nanotube are mixed may be configured as a fired film in which fluorine is present.

  Such a baked film is obtained by forming a dispersion solution to which a fluororesin is further added in the dispersion step described above into a film shape and then baking it.

  If a fired film containing fluorine is used in a fuel cell, the fired film exhibits a water repellent effect, and moisture generated during the reaction of the fuel gas does not infiltrate the fired film, thus ensuring good air permeability. Thus, stable power generation characteristics can be secured, and further, the shape retention of the fired film itself can be maintained over a long period of time.

  Polyvinylidene fluoride PVDF is preferably used as the fluororesin mixed in the dispersion before firing, and ethylene tetrafluoroethylene copolymer ETFE can also be used.

  When adopting polyvinylidene fluoride PVDF as the fluororesin, if polyvinylidene fluoride PVDF is mixed in the dispersion in the range of 5% to 29% by weight as a solid content, it is compared with a fired film not containing fluororesin. Thus, good air permeability and power generation characteristics can be obtained, and by mixing in the range of preferably 5 wt% to 25 wt%, more preferably 8 wt% to 18 wt%, in addition to the good power generation characteristics Good shape retention can be secured.

  In the dispersion treatment step, it is preferable that the cup stack type carbon nanotube, the conductive filler, the resin binder, and the fluororesin are mixed in an organic solvent, and the dispersion treatment is performed in a range of 30 to 180 minutes using a dispersion device such as a paint shaker. .

  Although an example of manufacturing a fired film containing fluorine by dispersing a fluororesin in the dispersion step has been described, a dispersion solution in which carbon nanotubes, a conductive filler, and a resin binder are dispersed in an organic solvent is formed into a film shape. The resulting film is baked in an inert gas atmosphere, and the resulting baked film is dipped in a fluororesin solution or impregnated with a fluororesin by a spray method, and then baked again to present fluorine. A fired film may be manufactured, or a film obtained by molding may be impregnated with a fluororesin by a spray method and then fired to manufacture a fired film containing fluorine. Good.

  In the conventional polymer electrolyte fuel cell electrode, since the catalyst support layer having a thickness of several tens of μm is formed in the gas diffusion layer having a thickness of 300 to 400 μm, the thickness of the electrode becomes 400 μm or more. If the fired film according to the invention is used, the thickness of the electrode can be reduced to about 200 μm.

  An organic resin N-methylpyrrolidone (hereinafter referred to as NMP) 25.0 g, acrylic resin (BI-2107-SA manufactured by Furukawa Chemical Co., Ltd.) 3.2 g, polyvinylidene fluoride (Kureha Chemical # 850, hereinafter referred to as “PVDF”). ) 0.8g, cup-stacked carbon nanotubes as a base material (GSI Creos provided, type: 24PS) and cup-stacked carbon nanotubes as a conductive filler shorter than the base material (GSI Creos provided, type: Type: As shown in FIG. 4 (a), AR10) was mixed by weight distribution, and each was shaken with a paint shaker for 180 minutes to obtain a dispersion solution. PVDF in the dispersion solids is 17.2% by weight.

  Here, the average length of the cup-stacked carbon nanotube (24PS) is 4.95 μm, and the average length of the cup-stacked carbon nanotube (AR10) is 0.89 μm.

This solution was cast on a SUS plate partitioned in advance to have a thickness of 5 cm ² to form a plate-like body having a thickness of about 250 μm, and then dried to obtain a plate-like film. At that time, the drying temperature is 140 ° C. and the drying time is 90 minutes.

  After the drying process, the plate-like body is put into a baking apparatus, and baking is performed at a temperature of about 600 ° C. for 1 hour in an atmosphere of nitrogen gas to thermally decompose and evaporate the acrylic resin, the fluororesin, and the NMP. Two sets of fired films were obtained.

  As shown in FIG. 4B, two samples as a second sample mixed with carbon black (provided by Cabot Corp., type: Vulcan XC72) as a conductive filler having a length shorter than that of the base material under the same conditions as described above. A set of fired films was prepared.

  Here, the average length of the secondary particles of carbon black (XC72) is 0.1 μm or less.

  As a comparative example, as shown in FIGS. 4A and 4B, two sets of fired films of only a base material not mixed with a conductive filler were produced as comparative samples under the same conditions as described above.

  The pore size distribution of each fired film thus obtained was measured using a bubble jet method. The bubble jet method is a method of measuring the sample pore diameter from a change in pressure generated when a predetermined solution is infiltrated from the sample surface, then air is introduced from the outside, and the infiltrated solution is removed from the sample. (Nippon Bell, Model: Porometer 3G).

  As a result, as shown in FIGS. 5, 6, 7, and 8, the first sample and the second sample both have a smaller maximum peak of the pore size distribution (portion surrounded by a broken line in the figure) than the comparative sample. It was confirmed that there was a tendency to move. FIG. 9 shows changes in the maximum peak value of the pore size distribution depending on the mixing ratio of the cup-stacked carbon nanotubes and the conductive filler of the two sets of the first sample and the two sets of the second sample.

  Through the above examples, a fired film obtained by mixing a cup-stacked carbon nanotube as a base material with a conductive filler having a shorter length than that of the cup-stacked carbon nanotube has a maximum peak in pore size distribution compared to a fired film only of the base material. It was confirmed that the water retention can be improved accordingly.

1: polymer electrolyte fuel cells 2, 2a, 2b: gas diffusion layers 3, 3a, 3b: catalyst layer 4: catalyst electrode 4a: anode catalyst electrode 4b: cathode catalyst electrodes 6, 6a, 6b: catalyst 7: ion exchange Resin 8: Solid polymer electrolyte membrane

Claims (10)

An electrode for a polymer electrolyte fuel cell comprising a gas diffusion layer having electrical conductivity and air permeability, and a catalyst layer containing a catalyst supported on a catalyst carrier,
The gas diffusion layer is composed of a fired film in which a cup-stacked carbon nanotube having a predetermined length and a conductive filler having a shorter length than the cup-stacked carbon nanotube are mixed, and the catalyst serves as the catalyst carrier. An electrode for a polymer electrolyte fuel cell supported on the functioning fired film. An electrode for a polymer electrolyte fuel cell comprising a gas diffusion layer having electrical conductivity and air permeability, and a catalyst layer containing a catalyst supported on a catalyst carrier,
The gas diffusion layer is composed of a fired film in which a cup-stacked carbon nanotube having a predetermined length and a conductive filler having a shorter length than the cup-stacked carbon nanotube are mixed, and the maximum peak of the pore size distribution of the fired film A polymer electrolyte fuel cell electrode in which a value is adjusted in a range of 0.08 μm to 0.18 μm, and the catalyst is supported on the fired film functioning as the catalyst support.   3. The electrode for a solid polymer fuel cell according to claim 1, wherein a mixing ratio of the conductive filler is 50% by weight or less with respect to a mixed weight of the cup-stacked carbon nanotube and the conductive filler.   The electrode for a solid polymer fuel cell according to any one of claims 1 to 3, wherein the length of the conductive filler is ½ or less of the length of the cup-stacked carbon nanotube.   The electrode for a solid polymer fuel cell according to claim 4, wherein the cup-stacked carbon nanotube has a length of 0.5 to 10 µm, and the conductive filler has a length of 1 µm or less.   6. The polymer electrolyte fuel cell electrode according to any one of claims 1 to 5, wherein the conductive filler is selected from carbon nanotubes, carbon black, graphite, graphite, metal, and metal oxide. A method for producing a fired film used for the electrode for a polymer electrolyte fuel cell according to any one of claims 1 to 6,
A dispersion treatment step of dispersing a cup-stacked carbon nanotube, a conductive filler having a shorter length than the cup-stacked carbon nanotube and a resin binder in an organic solvent, and a dispersion solution obtained in the dispersion treatment step are formed into a film shape A method for producing a fired film, comprising: a molding step for drying and a firing step for firing the film obtained in the molding step in an inert gas atmosphere.   A method for using an electrode for a polymer electrolyte fuel cell, wherein the electrode for a polymer electrolyte fuel cell according to any one of claims 1 to 6 is used as an anode side electrode of the polymer electrolyte fuel cell.   A solid polymer fuel cell in which a gas diffusion layer having conductivity and air permeability is composed of a fired film using a cup-stacked carbon nanotube as a base material, and an electrode carrying a catalyst is incorporated in the fired film. A polymer electrolyte fuel cell in which the maximum peak value of the pore size distribution of the fired membrane used for the anode side electrode is adjusted to be smaller than the maximum peak value of the pore size distribution of the fired membrane used for the cathode side electrode.   The polymer electrolyte fuel cell according to claim 10, wherein the electrode for a polymer electrolyte fuel cell according to claim 1 is used as an anode-side electrode.

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