JP2010198803A - 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 formed by the calcined film in which fibrous carbon at a designated length and conductive fillers shorter in length than the fibrous carbon are mixed each other, and the catalyst 6 is carried on the calcined film functioning as the 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 is composed of fibrous carbon having a predetermined length and fibrous carbon. The catalyst is composed of a fired film mixed with a short conductive filler, 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 fibrous carbon enters the pores formed by entwining the fibrous carbon that is the base material of the fired film, so that the conductivity of the fired film is maintained. However, the maximum peak value of the pore diameter 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 0.35 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 fibrous carbon and the conductive filler, the maximum peak of the pore diameter distribution is ensured while ensuring the shape retention of the fired film. This is preferable in that the value can be shifted to the smaller diameter side.

  When the length of the conductive filler is ½ or less of the length of the fibrous carbon, it is preferable in that the maximum peak value of the pore diameter distribution can be effectively shifted to the small diameter side.

  It is preferable that the fibrous carbon has a length of 0.1 to 30 μm and the conductive filler has a length of 1 μm or less.

  It is preferable that the fibrous carbon is a carbon nanotube or a vapor grown carbon fiber, and the conductive filler is selected from any of carbon nanotube, carbon black, graphite, graphite, metal, and metal oxide.

  The fired film used for the polymer electrolyte fuel cell electrode described above includes a dispersion treatment step in which fibrous carbon, a conductive filler having a shorter length than the fibrous carbon, and a resin binder are dispersed in an organic solvent, and the dispersion treatment step. The dispersion solution obtained in (1) can be produced by a molding step in which it is formed into a film and dried, and a firing step in which the film obtained in the molding step is fired 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 fibrous carbon as a base material, and an electrode on which a catalyst is supported is incorporated in the fired film, and the anode side It is preferable that the maximum peak value of the pore diameter distribution of the fired film used for the 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 Data explanatory diagram of mixing weight of fibrous carbon and conductive filler and maximum peak value of pore size distribution Characteristic diagram showing experimental results and showing changes in pore size distribution of comparative sample and invention sample Explanatory drawing which shows an experimental result and shows the change of the maximum peak value of pore size distribution by the mixture rate of fibrous carbon and a 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 as the catalyst carrier is composed of a fired film in which a predetermined length of fibrous carbon and a conductive filler having a shorter length than the fibrous carbon are mixed, ensuring a sufficient specific surface area, In order to ensure the carrying amount and uniform dispersibility, fibrous carbon having a diameter in the range of 1 nm to 200 nm and a fiber length in the range of 0.1 μm to 30 μm is used as the base material. As the fibrous carbon, vapor grown carbon fiber, carbon nanotube, or the like can be employed.

  When vapor-grown carbon fiber is used as the base material, it is preferable to use one having a diameter of 80 nm to 150 nm and a fiber length in the range of 5 μm to 10 μm. As such a vapor grown carbon fiber, VGCF (“VGCF” is a registered trademark of Showa Denko KK) can be suitably used.

  When carbon nanotubes are used as the base material, it is preferable to use those having a diameter in the range of 1 nm to 150 nm and a fiber length in the range of 0.2 μm to 10 μm.

  In the case of using a carbon nanotube having a structure in which a single graphene sheet is wound in a cylindrical shape and having a diameter of 0.7 to 70 nm and a length of about several tens of μm, It is suitable as a catalyst carrier because of its size and conductivity.

  There are various types of carbon nanotubes such as a single-wall type, a multi-wall type, and a carbon nanohorn type, and they are known as materials having very excellent characteristics such as strength, conductivity, and thermal conductivity.

The conductive filler mixed with the base material is preferably selected from any of metal oxides such as carbon nanotubes, carbon black, graphite, graphite, metal, and Ti ₂ O.

  The mixing ratio of the conductive filler is preferably 50% by weight or less, particularly preferably in the range of 20% by weight to 50% by weight with respect to the mixed weight of the fibrous carbon and the conductive filler. Further, it is preferable that the length of the conductive filler is set to ½ or less, particularly 1 μm or less of the length of the fibrous carbon.

  According to the above-described configuration, the conductive filler having a shorter length than the fibrous carbon enters the pores formed by entwining the fibrous carbon that is the base material of the fired film, so that the conductivity of the fired film is maintained. However, the maximum peak value of the pore diameter 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 0.08 μm to 0.35 μm.

  When using vapor grown carbon fiber as the fibrous carbon that is the base material of the fired film, the maximum peak value of the pore size distribution of the fired film is preferably adjusted in the range of 0.05 μm to 0.35 μm, In particular, it is preferably adjusted to a range of 0.10 μm to 0.30 μm.

  Further, when carbon nanotubes are used as the fibrous carbon used as the base material of the fired film, 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, In particular, it is preferably adjusted to a range of 0.08 μm to 0.18 μm.

  That is, it comprises a gas diffusion layer having electrical conductivity and air permeability and a catalyst layer containing a catalyst supported on a catalyst carrier, and the gas diffusion layer has a predetermined length of fibrous carbon and a length longer than the fibrous carbon. An electrode for a polymer electrolyte fuel cell is configured, which is composed of a fired film mixed with a short 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. 2 (b), the fired film obtained by firing a mixture of fibrous carbon and a conductive filler has a large specific surface area because the surface is uneven, and as a result The surface area of the film to which the catalyst 6 is fixed can be greatly increased, particles are easily formed by sputtering, and almost all of the supported catalyst 6 contributes to the activation of hydrogen gas or oxygen gas, and is 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 fibrous carbon and a conductive filler, and the catalyst support is formed of carbon nanotubes or gas phase formed on the fired film. It may be composed of a conductive particle layer using method carbon fiber or the like.

  For example, a conductive carbon layer as a catalyst carrier is formed by applying a fibrous carbon paste in which vapor-grown carbon fiber is mixed and dispersed in an organic solvent N-methylpyrrolidone on one side of the fired film. Can do. 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. Power generation efficiency can be 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, the pores of the fired film are blocked and the reaction gas (hydrogen gas or oxygen gas) 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 electrical conductivity and air permeability is composed of a fired film using fibrous carbon as a base material, and an electrode on which a catalyst is supported is incorporated in the fired film, and an anode side electrode It is preferable that the maximum peak value of the pore diameter distribution of the fired film used in the above is adjusted to be smaller than the maximum peak value of the pore diameter distribution of the fired film used in 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.

  The manufacturing process of the fired film | membrane which uses fibrous carbon as a base material is demonstrated. As shown in FIG. 3, the production process of the fired film was obtained by a dispersion treatment step in which fibrous carbon, a conductive filler having a shorter length than the fibrous carbon, and a resin binder were dispersed in an organic solvent, and a dispersion treatment step. It consists of a molding step for molding the dispersion solution into a film and drying, and a firing step for firing the film obtained in the molding step in an inert gas atmosphere.

  Although there is no restriction | limiting in particular as an organic solvent used at a dispersion treatment process, A polar organic solvent can be illustrated, especially N-methylpyrrolidone is preferable and acrylic resin which has carbon dispersibility as a resin binder is suitable. Can be used.

  Further, in the dispersion treatment step, it is preferable that fibrous carbon, a conductive filler, and a 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 fibrous carbon 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 entanglement between the fibrous carbons is eliminated. Therefore, 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 about 600 ° C. under an inert gas atmosphere such as nitrogen gas so that the fibrous carbon or conductive filler is not weakened by oxidation. 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.

  Further, a fired film in which fibrous carbon and a conductive filler shorter in length than the fibrous carbon 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 vapor-grown carbon fiber is used as the base material and polyvinylidene fluoride PVDF is used as the fluororesin, the polyvinylidene fluoride PVDF is mixed in the dispersion in the range of 3% to 29% by weight as the solid content concentration. For example, good air permeability and power generation characteristics can be obtained as compared with a fired film not mixed with a fluororesin, preferably mixed in the range of 3 to 25% by weight, more preferably in the range of 5 to 18% by weight. By doing so, in addition to good power generation characteristics, good shape retention can be secured.

  When carbon nanotubes are used as the base material and polyvinylidene fluoride PVDF is used as the fluororesin, if the polyvinylidene fluoride PVDF is mixed in the dispersion in a range of 5 wt% to 29 wt% as the solid content concentration, fluorine Good air permeability and power generation characteristics can be obtained as compared with a baked film not mixed with resin, preferably by mixing in the range of 5 wt% to 25 wt%, more preferably in the range of 8 wt% to 18 wt%. In addition to good power generation characteristics, good shape retention can be secured.

  In the dispersion treatment step, it is preferable that fibrous carbon, a resin binder, and a fluororesin 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.

  The example of producing a fired film containing fluorine by dispersing the fluororesin in the dispersion process has been explained. However, a dispersion solution in which fibrous carbon, conductive filler, and resin binder are dispersed in an organic solvent is formed into a film. Then, the obtained film is baked in an inert gas atmosphere, and the obtained baked film is dipped in a fluororesin solution or impregnated with a fluororesin by a spray method, and then baked again. An existing fired film may be produced, and a film obtained by molding is impregnated with a fluorine resin by a spray method and then fired to produce a fired film containing fluorine. Also 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, vapor-grown carbon fiber (manufactured by Showa Denko KK, VGCF: fiber diameter 100 nm, fiber length 5 to 10 μm) as a base material, and carbon black as a conductive filler shorter in length than the base material (Provided by Cabot Corporation, model: XC72) was mixed by weight distribution as shown in FIG. 4, 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 VGCF is 8.0 μm, and the average length of secondary particles of carbon black (XC72) is 0.1 μm or less.

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 treatment, the plate-like body is put into a firing apparatus, fired at a temperature of about 600 ° C. for 1 hour in an atmosphere of nitrogen gas, and acrylic resin, fluororesin and NMP are pyrolyzed and evaporated, and VGCF Fired films (invention samples 1 and 2) having different mixing ratios of conductive fillers were obtained.

  As a comparative example, a fired film (comparative sample) made only of a base material not mixed with a conductive filler was produced 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 FIG. 5, it was confirmed that the inventive samples 1 and 2 tended to move to the smaller peak of the pore size distribution (portion surrounded by the broken line in the figure) than the comparative sample. FIG. 6 shows the change in the maximum peak value of the pore size distribution depending on the mixing ratio of the inventive sample vapor grown carbon fiber and the conductive filler.

  Through the above examples, a fired film obtained by mixing a fibrous filler as a base material with a conductive filler having a shorter length than the fibrous carbon has a smaller peak of pore size distribution than a fired film only of the base material. It was confirmed that the water retention could 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 fibrous carbon having a predetermined length and a conductive filler having a shorter length than the fibrous carbon are mixed, and the firing in which the catalyst functions as the catalyst carrier. An electrode for a polymer electrolyte fuel cell supported on a membrane. 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 fibrous carbon having a predetermined length and a conductive filler having a shorter length than the fibrous carbon are mixed, and the maximum peak value of the pore diameter distribution of the fired film is 0. An electrode for a polymer electrolyte fuel cell, wherein the electrode is adjusted to a range of 08 μm to 0.35 μm, and the catalyst is supported on the fired film functioning as the catalyst support.   The solid polymer fuel cell electrode according to claim 1 or 2, wherein a mixing ratio of the conductive filler is 50 wt% or less with respect to a mixed weight of the fibrous carbon and the conductive filler.   4. The electrode for a polymer electrolyte fuel cell according to claim 1, wherein the length of the conductive filler is ½ or less of the length of the fibrous carbon. 5.   The solid polymer fuel cell electrode according to claim 4, wherein the fibrous carbon has a length of 0.1 to 30 μm and the conductive filler has a length of 1 μm or less.   The fiber carbon is a carbon nanotube or a vapor grown carbon fiber, and the conductive filler is selected from carbon nanotube, carbon black, graphite, graphite, metal, and metal oxide. An electrode for a polymer electrolyte fuel cell according to claim 1. 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 in which fibrous carbon, a conductive filler having a shorter length than the fibrous carbon, and a resin binder are dispersed in an organic solvent, and a dispersion solution obtained in the dispersion treatment step is formed into a film and dried. A method for producing a fired film comprising a step and a firing step of firing the film obtained in the forming 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 electrical conductivity and air permeability is composed of a fired film using a fibrous carbon as a base material, and an electrode in which a catalyst is supported 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.   9. The polymer electrolyte fuel cell according to claim 8, wherein the electrode for polymer electrolyte fuel cell according to claim 1 is used as an anode side electrode.

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