JP2005038738A - Gas diffusion layer electrode base material, its manufacturing method, and polymer electrolyte fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer electrolyte fuel cell capable of exhibiting a stable performance even at a high current density, and a gas diffusion layer electrode base material suited for obtaining the same, as well as its manufacturing method. <P>SOLUTION: The gas diffusion layer electrode base material for the polymer electrolyte fuel cell having a carbon fiber paper is provided with a plurality of through-holes penetrating from one face to the other, with densities and/or pore sizes made different in a plane direction. In the manufacturing method of the gas diffusion layer electrode base material for the polymer electrolyte fuel cell, a paper-shaped body including carbon short fiber is impregnated with carbon precursor resin to harden it, through-holes with different densities and/or pore sizes in the plane direction are opened on it, and later, it is carbonized. In the polymer electrolyte fuel cell provided with a fuel electrode side gas diffusion layer electrode base material, a fuel electrode side catalyst layer, a polymer electrolyte film, an oxygen electrode side catalyst layer, and an oxygen electrode side gas diffusion layer electrode base material, the oxygen electrode side gas diffusion layer base material has a plurality of through-holes penetrating from one face to the other with the densities and/or the pore sizes made different in plane direction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polymer electrolyte fuel cell, and also relates to an electrode substrate used for a gas diffusion layer electrode for a polymer electrolyte fuel cell and a method for producing the same.

  Since polymer electrolyte fuel cells have a low operating temperature of about 80-100 ° C and a high output density, technological development is progressing as a backup power source for small vehicles and computers, as well as power sources for electric vehicles and homes. It has been. Furthermore, since it can be miniaturized, it is also expected as a power source for mobile phones and notebook computers.

  A polymer electrolyte fuel cell is sandwiched between a porous fuel electrode that has been subjected to catalyst treatment, etc., and a gas diffusion layer electrode of an oxygen electrode on both sides of the polymer electrolyte membrane, and further has a groove (gas passage) through which gas flows. In this structure, hydrogen is supplied to the fuel electrode side and oxidizing gas is supplied to the gas passage on the oxygen electrode side. On the fuel electrode side, hydrogen fuel is separated into hydrogen ions and electrons by catalytic action, hydrogen ions move through the polymer ion exchange membrane and go to the oxygen electrode, electrons go to the oxygen electrode through an external circuit, and further at the oxygen electrode Oxygen reacts with electrons and hydrogen ions to produce water.

  Especially in high current density power generation where a large amount of reaction gas is required, a large amount of reaction product water is generated on the oxygen electrode side and stays in the system, and the surface of the gas diffusion layer electrode is covered with water. It becomes easy to invite. If the gas diffusion layer electrode is covered with water, the flow of the reaction gas is hindered so that it cannot reach the catalyst layer, the electrode reaction is hindered, and the battery output becomes unstable and decreases.

  Conventionally, in order to avoid the above situation, the gas diffusion layer electrode is subjected to an impregnation treatment such as polytetrafluoroethylene having a high water repellency effect on the catalyst layer surface side of the gas diffusion layer electrode to impart water repellency. Many methods for preventing excessive wetting are used, and a gas diffusion layer electrode in which a through hole is formed is also used.

  In Patent Document 1, the water-repellent treatment on the gas introduction side where the amount of reaction product water accumulated is small in the surface of the gas diffusion layer electrode on the oxygen electrode side is made smaller than that on the gas outlet side where the amount of reaction product water accumulates. Thus, a method has been carried out in which the electric resistance on the gas introduction side is kept low and the retention of reaction product water on the gas outlet side is suppressed to suppress the deterioration of the battery performance.

  In addition, by using a gas diffusion layer electrode on the oxygen electrode side provided with a through hole as in Patent Documents 2 and 3, the reaction product water can be discharged from the through hole even in a liquid state, and the gas permeability is also smooth. Thus, a method that can ensure stable performance in use in a high current density region has been performed.

In Patent Document 3, in order to improve not only the oxygen electrode side but also the gas permeability on the fuel layer side, a gas diffusion layer electrode base material having 400 through / cm ² or more through holes having a diameter of 0.1 mm or less is used. Has been.
JP-A-9-283153 JP-A-8-111226 JP 2002-110182 A

  Regarding the fuel cell described in Patent Document 1, it is considered that stable performance can be secured when used in a low current density region. However, when used in a high current density region, water retention and gas permeation generated on the oxygen electrode side are considered. Ensuring sex is considered to be tough.

  As described in Patent Documents 2 and 3, the gas diffusion layer electrode on the oxygen electrode side provided with a plurality of relatively uniform through holes is thought to improve the discharge of reaction product water and gas permeability. In use in a high current density region, it is expected that the polymer electrolyte membrane is partially dried easily, and it may be difficult to ensure stable performance. It is known that the presence of water is indispensable for transporting hydrogen ions, and when the membrane dries, the output density decreases due to an increase in electrical resistance.

Further, Patent Document 3 that form the following holes diameter 0.1 mm 400 pieces / cm ² or more to the oxygen electrode side and the fuel layer side of the gas diffusion layer electrode substrate is used, and the through hole is a gas diffusion layer Although it is described that the hole diameter is different between the front and back of the electrode and that the needle is further pierced into the carbon sheet, since the carbon sheet is a brittle material, when making a hole with a needle etc., the shape and hole diameter of the needle should be uniform. In addition, it is difficult to stably evacuate, and it is considered that it is difficult to manufacture industrially because carbon powder is generated due to the formation of holes, which may cause electric leakage or failure of the apparatus.

  An object of the present invention is to provide a polymer electrolyte fuel cell that can exhibit stable performance even at a high current density.

  Another object of the present invention is to provide a gas diffusion layer electrode base material for a polymer electrolyte fuel cell suitable for obtaining the fuel cell. Specifically, polymer electrolytes that have high gas permeability, especially high reaction product water drainage on the oxygen electrode side, can easily manage water (water management) of polymer electrolyte membranes, and prevent local drying It is to provide a gas diffusion layer electrode base material for a fuel cell.

  Still another object of the present invention is to provide a production method capable of industrially and stably producing the gas diffusion layer electrode substrate.

According to the present invention, in the gas diffusion layer electrode base material for polymer electrolyte fuel cell having porous carbon fiber paper,
There is provided a gas diffusion layer electrode base material having a plurality of through holes extending from one surface to the other surface, and the density and / or hole diameter of the through holes differ in the surface direction.

  The density of the through holes and / or the hole diameter can monotonously increase from one end to the other end in one direction in the plane.

  The density of the through holes and / or the hole diameter can be monotonously increased and monotonously decreased from one end to the other end in one direction in the plane.

  The density and / or the hole diameter of the through holes can be monotonously decreased and minimized and monotonously increased from one end to the other end in one in-plane direction.

The hole diameter of the through hole is 30 μm or more and 1000 μm or less,
The maximum density of the through holes is 1 / cm ² or more and 399 / cm ² or less,
It is preferable that the minimum value of the density of the through holes is 0 piece / cm ² or more and 390 pieces / cm ² .

The density of the through holes is 1 piece / cm ² or more and less than 400 pieces / cm ² ,
The maximum value of the diameter of the through hole is 40 μm or more and 1000 μm or less,
It is preferable that the minimum value of the diameter of the through hole is 30 μm or more and 900 μm or less.

  Although the gas diffusion layer electrode base material is slightly different depending on the carbon precursor resin adhesion amount or the fiber diameter of the short carbon fiber, pores of about 30 μm to 60 μm may be formed without providing through holes. In order to improve the strength characteristics of the gas diffusion layer electrode substrate, the carbon precursor resin adhesion amount is relatively increased, or the fiber diameter of carbon short fibers used in paper is reduced. In such a case, since the base material becomes dense, the pores are relatively small and the gas permeability is deteriorated. Therefore, the lower limit of the through hole is preferably 30 μm or more from the viewpoint of gas permeability.

  Further, although the gas permeability is improved as the through-hole diameter is increased, it is disadvantageous in that damage to the gas diffusion layer electrode base material tends to increase. More preferably, they are 50 micrometers or more and 500 micrometers or less.

Further, for the through-hole density, because the higher the gas permeability through hole density is increased is improved, which is disadvantageous in that there is a tendency for damage to the gas diffusion layer electrode substrate is increased, one / cm ² The number is preferably 400 / cm ² or less, and more preferably 3 / cm ² or more and 200 / cm ² or less.

  It is preferable that there are no cracks or cracks around the through hole.

According to the present invention, a resin impregnation step of impregnating a paper precursor containing carbon short fibers with a carbon precursor resin;
A resin curing step of curing the carbon precursor resin impregnated in the paper-like body;
A perforating step in which a plurality of through holes extending from one surface to the other surface and having different density and / or hole diameter in the surface direction are formed in the paper-like body having the carbon precursor resin cured;
A method for producing a gas diffusion layer electrode base material for a polymer electrolyte fuel cell, comprising a carbonization step of carbonizing the paper-like body having the through holes formed therein is provided.

In the drilling step,
It is preferable to open the through-hole using a plate capable of changing the needle density and / or the needle diameter or a plate to which the needle is fixed.

According to the present invention, in a polymer electrolyte fuel cell having a fuel electrode side gas diffusion layer electrode substrate, a fuel electrode side catalyst layer, a polymer electrolyte membrane, an oxygen electrode side catalyst layer and an oxygen electrode side gas diffusion layer electrode substrate,
The oxygen electrolyte side gas diffusion layer electrode base material has a plurality of through holes extending from one surface to the other surface, and the density and / or the hole diameter of the through holes are different in the surface direction. A fuel cell is provided.

  The density and / or hole diameter of the through hole of the oxygen electrode side gas diffusion layer electrode substrate is changed from one end to the other end of the oxygen electrode side gas diffusion layer electrode substrate along the flow direction of the oxygen electrode side gas. It is preferable to increase monotonically over time.

  It is preferable that the fuel electrode side gas diffusion layer electrode base material has a plurality of through holes extending from one surface to the other surface, and the density and / or hole diameter of the through holes are different in the surface direction.

  The density and / or hole diameter of the through hole of the fuel electrode side gas diffusion layer electrode base material varies from one end of the fuel electrode side gas diffusion layer electrode base material to the other end along the flow direction of the fuel electrode side gas. It is preferable to increase monotonously, decrease monotonically, increase monotonically to maximize and monotonically decrease, or decrease monotonously to minimize and monotonously increase.

  According to the present invention, the through hole density on the gas outlet side can be made larger than the through hole density on the gas introduction side in the plane of the gas diffusion layer electrode substrate of the oxygen electrode. Alternatively, the through hole diameter on the gas outlet side can be made larger than the through hole diameter on the gas introduction side. Furthermore, these can also be combined. As a result, it is possible to improve the discharge and gas permeability of the reaction product water in use in a high current density region, and relatively easily manage the water of the polymer electrolyte membrane.

  Also, in order to improve the gas permeability of the gas diffusion layer electrode base material on the fuel layer side and to make hydrogen gas react efficiently on the catalyst, the through hole density is distributed between the gas inlet side and the gas outlet side. be able to. Alternatively, a large or small distribution can be imparted to the through-hole diameter between the gas inlet side and the gas outlet side. Further, the through hole density distribution and the through hole diameter distribution can be combined. As the gas diffusion layer electrode substrate on the fuel layer side, the same one as the gas diffusion layer electrode substrate of the oxygen electrode can be used, or one having a different through hole density distribution and / or through hole diameter distribution can be used. By arranging these appropriately in consideration of the gas flow and reaction density distribution, it is possible to ensure stable performance when used in a high current density region.

  Moreover, the through-hole provision process of a gas diffusion layer electrode base material is performed after impregnating the carbon precursor resin in the paper-like body containing a carbon short fiber, and making it harden | cure, and also by carbonizing after providing a through-hole. Since the cracks and cracks are less likely to occur around the through hole of the gas diffusion layer electrode substrate, the diameter of the through hole can be made smaller than when the through hole is made after carbonization if the device and needle type are the same ( The periphery of the through hole does not break more than necessary), and the control of the through hole diameter is relatively easy. Furthermore, the generation of carbon powder can be greatly reduced, and therefore, it is possible to produce a gas diffusion layer electrode base material having a through-hole in an industrially stable manner.

  ADVANTAGE OF THE INVENTION According to this invention, the gas permeability of a gas diffusion electrode base material and the retention effect (flooding phenomenon) suppression effect of the produced water of a battery can be improved. Further, in addition to these, a polymer electrolyte fuel cell capable of ensuring stable performance when used in a high current density region by being able to prevent local drying of the polymer electrolyte has been provided.

  Further, the present invention provides a method capable of suitably producing an excellent gas diffusion electrode as described above. Specifically, the gas diffusion layer electrode substrate through-hole providing step is performed after impregnating the carbon precursor resin into a paper-like body containing carbon short fibers and then curing, and further carbonizing after forming the through-hole. As a result, the structure around the through hole of the gas diffusion layer electrode base material is normal and can be evacuated stably, and the generation of carbon powder can be greatly reduced.

  Hereinafter, the present invention will be described in detail.

  FIG. 1 is a schematic cross-sectional view showing an outline of a general polymer electrolyte fuel cell, and FIG. 2 is a schematic plan view showing an outline of a typical ribbed separator used in a polymer electrolyte fuel cell.

  The polymer electrolyte fuel cell comprises a fuel electrode side gas diffusion layer electrode base material 4, a fuel electrode side catalyst layer 5, a polymer electrolyte membrane 3, an oxygen electrode side catalyst layer 7 and an oxygen electrode side gas diffusion layer electrode base material 6. In this order. Furthermore, separators 8 and 9 can be provided on the outside thereof. Here, the separator has ribs, whereby the fuel gas passage 10 and the oxidant gas passage 11 are formed.

  An electrode is formed by forming a catalyst layer on a gas diffusion layer electrode substrate. The gas diffusion layer electrode base material is porous and has a function of supplying gas from the gas passage to the catalyst layer. The electrode substrate also has a function as a current collector.

The oxidant gas (O ₂ ) supplied to the oxygen electrode 2 side flows from the gas inlet 12 side along the gas passage as indicated by the arrow and is discharged from the gas outlet 13 side. During this time, ½ O ₂ + 2H ^{The +} + 2e ⁻ → H ₂ O electrode reaction is performed to generate water, but the generated moisture is transported from the gas inlet 12 side to the gas outlet 13 side, so the amount of moisture on the outlet side increases.

  In the oxygen-electrode-side gas diffusion layer electrode base material, the generation of water is the highest when the through-hole density on the gas outlet 13 side is made higher than the gas inlet port 12 side or the through-hole diameter is increased, and both are used in combination. It is possible to suppress stagnation of reaction product water near the outlet side 13 of a large amount of gas.

  For this purpose, a gas diffusion layer electrode base material in which the density and / or hole diameter of the through holes monotonously increases from one end to the other end in one in-plane direction is used on the oxygen electrode side. Then, the electrode base material is arranged such that one direction in the plane coincides with the flow direction of the oxidant gas. Thereby, the density and / or the hole diameter of the through hole of the oxygen electrode side gas diffusion layer electrode substrate is changed from one end of the oxygen electrode side gas diffusion layer electrode substrate to the other end along the flow direction of the oxygen electrode side gas. Will increase monotonically over time.

  Note that the monotonous increase includes not only the case of increasing continuously but also taking a constant value in part. That is, it includes increasing in a stepped manner. The same applies to the monotonic decrease described later.

  As an embodiment of the electrode base material that can be suitably used on the oxygen electrode side, FIG. 3 shows an electrode base material having two types of through-hole density regions in the direction from the upper end to the lower end of the drawing. If the gas flow direction is the direction from the upper end to the lower end of the drawing, the through-hole density increases from the gas introduction side to the gas outlet side. Here, the hole diameter of the through hole is constant. FIG. 4 shows an electrode substrate similar to the electrode substrate shown in FIG. 3 but having three types of through-hole density regions.

  As another form of the electrode substrate that can be suitably used on the oxygen electrode side, FIG. 7 shows an electrode substrate having two types of through-hole diameter regions in the direction from the upper end to the lower end of the drawing. If the gas flow direction is a direction from the upper end to the lower end of the drawing, the diameter of the through hole increases from the gas introduction side to the gas outlet side. Here, the density of the through holes is constant. FIG. 8 shows an electrode substrate similar to the electrode substrate shown in FIG. 7, but having three types of through-hole diameter regions.

On the other hand, the hydrogen gas supplied to the fuel electrode 1 side is basically discharged along the gas passage as shown by the arrow from the gas inlet 12 side and discharged from the gas outlet 13 side as in the oxygen electrode 2 side. There are cases where it flows in parallel with the oxidant gas (O ₂ ) supplied to the pole 2 side, or it flows in the opposite direction. It is thought that depending on the form of this flow, the reaction spots in the battery and the portion where the polymer electrolyte membrane is easy to dry are changed. Can be used to improve reaction spots in the battery and drying of the polymer electrolyte membrane.

  For this purpose, an electrode base material in which the density and / or the hole diameter of the through-holes monotonously increase in one direction as shown in FIG. 3 or 4 and FIG. 7 or 8 can be used on the fuel electrode side. At this time, similarly to the oxygen electrode side, the electrode base material may be arranged so that the density and / or the hole diameter of the through holes monotonously increase along the gas flow direction. You may arrange | position an electrode base material so that the density of a through-hole and / or a hole diameter may decrease monotonously along a direction. That is, the density and / or hole diameter of the through holes can increase or decrease from the fuel gas introduction side to the outlet side.

  Alternatively, an electrode substrate as shown in FIG. 5, 6, 9 or 10 can be used on the fuel electrode side. FIG. 5 shows a gas diffusion layer electrode substrate in which the density of through-holes monotonously increases and monotonously decreases from one end to the other end in one in-plane direction. FIG. 9 shows a gas diffusion layer electrode substrate in which the hole diameter of the through hole monotonously increases and increases monotonously from one end to the other end in one in-plane direction. In these electrode base materials, when the one direction coincides with the flow direction of the fuel gas, the through hole density and / or the hole diameter increase from the gas introduction side and the outlet side toward the central portion.

  FIG. 6 shows a gas diffusion layer electrode substrate in which the density of through-holes monotonously decreases and monotonously increases from one end to the other end in one in-plane direction. FIG. 10 shows a gas diffusion layer electrode substrate in which the hole diameter of the through hole monotonously decreases and becomes monotonously increased from one end to the other end in one direction in the plane. In these electrode base materials, when the one direction coincides with the flow direction of the fuel gas, the through hole density and / or hole diameter decreases from the gas introduction side and the outlet side toward the central portion.

  As described above, on the fuel electrode side, electrode base materials having various through hole density distributions and hole diameter distributions can be applied. What distribution is adopted depends on the flow direction of the fuel gas and the oxidant gas. It can be determined by the relationship of the flow direction of the flow, that is, whether it is a parallel flow or a counter flow.

  In the present invention, the short carbon fibers are obtained by cutting carbon fiber yarns or carbon fiber tows into 3 mm to 12 mm. However, the length may not be in the above range as long as papermaking is possible. Carbon fibers include polyacrylonitrile-based, pitch-based, phenol-based, and graphite-based materials, and any of them may be used.

  The paper-like body containing carbon short fibers is carbon fiber paper made from carbon short fibers as a main raw material by a continuous paper making method or a hand-making method.

  When continuous paper making of short carbon fibers, it is preferable to mix an appropriate amount of organic polymer material for the purpose of binding the carbon fibers together. Thereby, the intensity | strength of carbon fiber paper is hold | maintained and it can prevent that carbon fiber peels from carbon fiber paper in the middle of production, or the orientation of carbon fiber changes. Examples of the continuous paper making method include a circular net type, a long net type, and a short net type. Since the binding force between the carbon fibers is relatively weak, a continuous net-type paper making process may require a considerable amount of binder, so the long-mesh type and the short-net type are preferred. Hand-made paper is easier to make thicker and less bulk density than continuous paper. Therefore, it is disadvantageous in that there is a tendency that the strength is not so strong even if the resin is impregnated and pressed. Moreover, it is disadvantageous in that it tends to be relatively difficult to control the basis weight.

  As the carbon precursor resin, any one of thermosetting and thermoplastic can be used. From the viewpoint of conductivity, a thermosetting resin that becomes dense by heating press is preferable. As the thermosetting resin, those which are sticky or fluid at normal temperature and remain as a conductive substance even after carbonization, and those having good adhesion to carbon fibers are preferable, for example, phenol resin, furan resin, Epoxy resin, melamine resin, imide resin, urethane resin, aramid resin, pitch and the like can be used, but phenol resin, furan resin and the like are more preferably used.

  After impregnating the carbon fiber paper obtained by paper making the short carbon fiber with the carbon precursor resin, curing the carbon precursor resin by hot press molding, etc., and then providing through holes, for example, under a nitrogen atmosphere By firing at 1200 ° C. or higher, the electrode substrate of the present invention can be suitably produced.

  The carbon precursor resin adhesion amount is preferably 30 to 95% by mass with respect to the paper-like body containing short carbon fibers. If the carbon precursor resin ratio (“carbon precursor resin mass” ÷ “paper mass including carbon short fibers”) is lower than 30% by mass, the electrode substrate has a rough structure and the strength tends to decrease. It is disadvantageous. Moreover, since it will be disadvantageous in that the conductivity of the gas diffusion layer electrode substrate becomes worse if it exceeds 95% by mass, the carbon precursor resin is contained in an amount of 30 to 95% by mass with respect to the paper-like material containing carbon short fibers. Is preferred.

  The carbon fiber paper can be impregnated with the carbon precursor resin as long as the carbon fiber paper can be impregnated with the carbon precursor resin, and a known method can be adopted as appropriate. ) Method, a method of uniformly coating the resin on the carbon fiber paper surface using a coater, or a method of transferring the resin film to the carbon fiber paper by stacking the carbon fiber paper and the resin film can be continuously performed. This is preferable in terms of productivity and production of long products. In the dip nip method, carbon fiber paper is immersed in a resin solution or a mixture of resin and alcohol such as methanol or ethanol, and the squeezing device applies the liquid to the entire paper evenly. This is a method of adjusting by changing the roll interval of the apparatus. If the viscosity is relatively low, the method of transferring the coater or resin film can be used to impregnate the resin more uniformly, but if the viscosity is high, the inside of the carbon fiber paper penetrates during the hot press. Since it is difficult, the dip-nip method is preferable.

  As a method of curing the carbon fiber paper impregnated with the carbon precursor resin, it is preferable to perform a heat press in order to improve the strength of the substrate. Any technique can be applied as long as heat and pressure can be applied to the electrode base material for the heating press, such as a method of pressing with a rigid plate from both the upper and lower surfaces, a method of molding with a mold, or A method using a continuous belt device may be mentioned. All of these are performed while heating.

  Examples of a plate with a fixed needle used for providing a through hole include a sword mountain, and a plate capable of changing the needle type includes a needle punch device. By using these, a through-hole can be provided. By changing the needle interval, the needle diameter, and the needle depth, it is possible to control the through-hole diameter and the through-hole density when the electrode substrate is finally used.

  In particular, when using a needle punch device, the needle diameter and needle depth can be changed, and it is easy to arbitrarily pierce through holes of 30 μm to 1000 μm. Moreover, since the through hole density can be changed by changing the needle interval, it is advantageous in terms of multiple functions as compared with the Kenzan type. The needle punch device can be batch-processed, but is preferably used for continuous processing from the viewpoint of productivity.

  In order to obtain the through-hole diameter and the through-hole density, an enlarged photograph of the carbon electrode substrate surface was taken, the through-hole diameter and the number of through-holes per unit area were measured, and several points were measured to obtain an average value. In addition, let a through-hole diameter be the average value of the largest diameter of each through-hole.

  As a carbonization method in the carbonization step, a known method for carbonizing carbon fiber paper impregnated and cured with a carbon precursor resin can be appropriately employed.

As the electrode base material of the present invention, the gas permeation coefficient can be arbitrarily changed by changing the through-hole diameter and the through-hole density, but as the gas diffusion layer electrode base material, 500 ml · mm / hr · cm ² · mmAq (51 ml · mm / hr · cm ² · Pa) or more is preferable, and in order to ensure the strength of the gas diffusion layer electrode substrate, 50000 ml · mm / hr · cm ² · mmAq (5100 ml · mm / hr · cm ² · Pa) or less is preferable. More preferably 1500 ml · mm / hr · cm ² · mmAq (150 ml · mm / hr · cm ² · Pa) or more and 30000 ml · mm / hr · cm ² · mmAq (3100 ml · mm / hr · cm ² · Pa) or less It is. The gas permeability coefficient is measured using a Gurley type densometer according to JIS P-8117.

[Example 1]
A fiber bundle of polyacrylonitrile (PAN) carbon fiber was cut into 3 mm to obtain short fibers. Next, the short fibers were defibrated in water in a slurry tank of a wet continuous paper making apparatus, and the short fibers of polyvinyl alcohol (PVA) as a binder were uniformly dispersed and sent out. The fed web was spread with a mesh plate and then dried with a dryer to obtain carbon fiber paper.

  Next, this carbon fiber paper was impregnated with a thermosetting resin by a dip nip method. That is, this carbon fiber paper is continuously fed into a 20% ethanol tray of a phenol resin (trade name: Phenolite J-325, manufactured by Dainippon Ink and Chemicals), and the resin is squeezed with a squeezing device. Then, it was dried by blowing hot air continuously to obtain a resin-impregnated carbon fiber paper.

  Subsequently, it heat-pressed at 160 degreeC with the hot press apparatus for 5 minutes, and obtained the resin hardening carbon fiber paper. Further, several sheets of resin-cured carbon fiber paper were placed vertically and connected with tape to make a sheet of about 1.5 m.

Next, the resin-cured carbon fiber paper was continuously processed with a needle punch device (manufactured by Yamato Kiko), 38 needle types, and a needle depth of 0.8 mm. When the number of needles on the right half of the needle board was set to be 1/2 of the number of needles on the left half, the through hole density of the right half of the resin-cured carbon fiber paper was about 10 / cm ^2. Thus, a left half processed through hole density of about 20 holes / cm ² was obtained.

  Subsequently, the resin-cured carbon fiber paper was subjected to batch firing at 2000 ° C. in a nitrogen gas atmosphere to obtain a gas diffusion layer electrode base material. A photograph of the surface of the obtained gas diffusion layer electrode substrate was taken and the through hole diameter (maximum diameter) was measured. Both the right and left through-hole diameters of the gas diffusion layer electrode substrate were about 190 μm and were relatively uniform.

The gas permeability coefficient of the right half of the gas diffusion layer electrode substrate is 2430 ml · mm / hr · cm ² · mmAq (248 ml · mm / hr · cm ² · Pa), and the gas permeability coefficient of the left half is 5020 ml · mm / hr · cm ² · mmAq (512 ml · mm / hr · cm ² · Pa).

  Furthermore, almost no carbon powder was generated when the through holes were provided.

[Example 2]
A gas diffusion layer electrode substrate was obtained in the same manner as in Example 1 except that when the through hole was made in the resin-cured carbon fiber paper, the needle type on the right half of the needle board was 25th, a gas diffusion layer electrode substrate was obtained. The through-hole density of the right half of the fiber paper was about 10 / cm ² , and the through-hole density of the left half was about 20 / cm ² .

  Subsequently, the resin-cured carbon fiber paper was subjected to batch firing at 2000 ° C. in a nitrogen gas atmosphere to obtain a gas diffusion layer electrode base material. A photograph of the surface of the obtained gas diffusion layer electrode substrate was taken and the through hole diameter (maximum diameter) was measured. The diameter of the through hole on the right side of the gas diffusion layer electrode substrate was about 190 μm, which was relatively uniform, and the diameter of the left side through hole was about 310 μm, showing slight variations.

The gas permeability coefficient of the right half of the gas diffusion layer electrode substrate is 2450 ml · mm / hr · cm ² · mmAq (250 ml · mm / hr · cm ² · Pa), and the gas permeability coefficient of the left half is 7090 ml · mm / hr · cm ² · mmAq (723 ml · mm / hr · cm ² · Pa).

  Further, when the through-hole was provided, the right half hardly generated carbon powder as in Example 1, but the left half showed some pieces of resin-cured carbon fiber paper, but almost no carbon powder was observed. .

[Comparative Example 1]
A gas diffusion layer electrode substrate was obtained in the same manner as in Example 1 except that the through-hole treatment of the resin-cured carbon fiber paper was carried out after carbonization rather than before carbonization.

The gas diffusion layer electrode substrate was processed such that the right half of the through hole density was about 10 holes / cm ² and the left half of the through hole density was about 20 holes / cm ² .

  Next, an electron micrograph of the surface of the gas diffusion layer electrode substrate was taken, and the through-hole diameter (maximum diameter) was measured. Both the right and left through-hole diameters of the gas diffusion layer electrode substrate were about 300 μm, and the variation in the through-hole diameter was larger than that of Example 1. Moreover, some damage was recognized in the structure | tissue around a through-hole.

The gas permeability coefficient of the right half of the gas diffusion layer electrode substrate is 3360 ml · mm / hr · cm ² · mmAq (343 ml · mm / hr · cm ² · Pa), and the gas permeability coefficient of the left half is 6910 ml · mm / hr · cm ² · mmAq (705 ml · mm / hr · cm ² · Pa).

  Furthermore, a relatively large amount of carbon fragments and carbon powder were generated when the through-holes were provided.

1 is a schematic cross-sectional view of a polymer electrolyte fuel cell. It is a typical top view of a separator with a rib. It is the figure which showed the example at the time of forming two types of through-hole density area | regions in a gas diffusion layer electrode base material. It is the figure which showed the example in case three types of through-hole density area | regions are formed in a gas diffusion layer electrode base material, and the through-hole density of one side is higher than the through-hole density of the other side. It is the figure which showed the example at the time of forming the high and low distribution of through-hole density in one direction in the gas diffusion layer electrode base material, and making the through-hole density of the center part high. It is the figure which showed the example at the time of forming the high and low distribution of the through-hole density in one direction in the gas diffusion layer electrode base material, and making the through-hole density of the center part low. It is the figure which showed the example at the time of forming two types of through-hole diameter area | regions in a gas diffusion layer electrode base material. It is the figure which showed the example when three types of through-hole diameter area | regions are formed in a gas diffusion layer electrode base material, and the through-hole diameter of one side is larger than the through-hole diameter of the other side. It is the figure which showed the example at the time of forming the size distribution of a through-hole diameter in one direction in the gas diffusion layer electrode base material, and enlarging the through-hole diameter of the center part. It is the figure which showed the example at the time of forming the size distribution of the through-hole diameter in one direction in the gas diffusion layer electrode base material, and making the through-hole diameter of the center part small.

Explanation of symbols

1 Fuel Electrode 2 Oxygen Electrode 3 Polymer Electrolyte Membrane 4 Gas Diffusion Layer Electrode Base 5 Catalyst Layer 6 Gas Diffusion Layer Electrode Base 7 Catalyst Layers 8 and 9 Ribbed Separator 10 Fuel Gas Passage 11 Oxidant Gas Passage 12 Gas Inlet 13 Gas outlet

Claims (13)

In the gas diffusion layer electrode substrate for polymer electrolyte fuel cell having carbon fiber paper,
A gas diffusion layer electrode base material having a plurality of through holes extending from one surface to the other surface, and the density and / or hole diameter of the through holes differ in the surface direction. The gas diffusion layer electrode substrate according to claim 1, wherein the density and / or the hole diameter of the through holes monotonously increase from one end to the other end in one direction in the plane. 2. The gas diffusion layer electrode substrate according to claim 1, wherein the density and / or the diameter of the through-holes monotonously increase to become a maximum and monotonously decrease from one end to the other end in one in-plane direction. 2. The gas diffusion layer electrode substrate according to claim 1, wherein the density and / or the diameter of the through-holes monotonously decreases to a minimum and monotonously increase from one end to the other end in one in-plane direction. The hole diameter of the through hole is 30 μm or more and 1000 μm or less,
The maximum value of the density of the through holes is 1 / cm ² or more and 399 / cm ² or less,
The gas diffusion layer electrode substrate according to any one of claims 1 to 4, wherein a minimum value of the density of the through holes is 0 piece / cm ² or more and 390 pieces / cm ² . The density of the through holes is 1 piece / cm ² or more and less than 400 pieces / cm ² ,
The maximum value of the diameter of the through hole is 40 μm or more and 1000 μm or less,
The gas diffusion layer electrode substrate according to any one of claims 1 to 4, wherein the minimum value of the diameter of the through hole is 30 µm or more and 900 µm or less. The gas diffusion layer electrode substrate according to any one of claims 1 to 6, wherein there are no cracks or cracks around the through hole. A resin impregnation step of impregnating a carbon precursor resin into a paper-like body containing short carbon fibers;
A resin curing step of curing the carbon precursor resin impregnated in the paper-like body;
A perforating step in which a plurality of through holes extending from one surface to the other surface and having different density and / or hole diameter in the surface direction are formed in the paper-like body having the carbon precursor resin cured;
A method for producing a gas diffusion layer electrode substrate for a polymer electrolyte fuel cell, comprising a carbonization step of carbonizing the paper-like body having the through-holes. In the drilling step,
The method according to claim 8, wherein the through-hole is opened using a plate capable of changing a needle density and / or a needle diameter, or a plate to which a needle is fixed. In a polymer electrolyte fuel cell having a fuel electrode side gas diffusion layer electrode substrate, a fuel electrode side catalyst layer, a polymer electrolyte membrane, an oxygen electrode side catalyst layer and an oxygen electrode side gas diffusion layer electrode substrate,
The oxygen electrolyte side gas diffusion layer electrode base material has a plurality of through holes extending from one surface to the other surface, and the density and / or the hole diameter of the through holes are different in the surface direction. Fuel cell. The density and / or hole diameter of the through hole of the oxygen electrode side gas diffusion layer electrode substrate is changed from one end to the other end of the oxygen electrode side gas diffusion layer electrode substrate along the flow direction of the oxygen electrode side gas. The polymer electrolyte fuel cell according to claim 10, which monotonically increases over time. The said fuel electrode side gas diffusion layer electrode base material has several through-holes ranging from one surface to the other surface, and the density and / or hole diameter of this through-hole differ in a surface direction. Polymer electrolyte fuel cell. The density and / or hole diameter of the through hole of the fuel electrode side gas diffusion layer electrode base material varies from one end of the fuel electrode side gas diffusion layer electrode base material to the other end along the flow direction of the fuel electrode side gas. 13. The polymer electrolyte fuel cell according to claim 12, wherein the polymer electrolyte fuel cell increases monotonically, decreases monotonically, increases monotonously and then increases monotonically, or decreases monotonously and decreases monotonously and increases monotonously.

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