JP2008226579A - Porous carbon sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a direct methanol type fuel cell exhibiting high cell performance by balancing a mass transfer property in an anode with suppression of methanol crossover. <P>SOLUTION: This porous carbon sheet for an anode electrode base material of a direct methanol type fuel cell is composed by bonding dispersing short carbon fibers with a resin carbide, has a plurality of through-holes penetrating the front and back surfaces of the sheet, and is characterized in that the diameter of each through-hole on the sheet is 100-400 μm. An anode electrode base material, a membrane-electrode assembly and this direct methanol type fuel cell using it are also provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a porous carbon sheet. The porous carbon sheet according to the present invention is used as an anode electrode base material of a direct methanol fuel cell (hereinafter sometimes abbreviated as DMFC).

  In a fuel cell, basic components are used in which an anode on a fuel supply side, an electrolyte, and a cathode on an air supply side are bonded together. In fuel cells, the mobility of substances related to power generation reactions such as fuel, oxygen, and reaction products within the cell is one of the important factors that determine battery performance, and is used for anodes and cathodes of fuel cells. The electrode base material is an important member that greatly affects the mass mobility inside the battery. For example, in Patent Document 1, as an electrode base material for a phosphoric acid fuel cell using phosphoric acid as an electrolyte, in Patent Document 2, an electrode base material for a solid polymer fuel cell using a solid polymer electrolyte membrane as an electrolyte. In order to improve mass mobility, carbon paper having through holes has been proposed. Since the fuel cells targeted in Patent Document 1 and Patent Document 2 use gaseous hydrogen as the fuel, even the techniques disclosed in these documents can ensure sufficient mass mobility.

  However, in recent years, DMFC, which is a type of polymer electrolyte fuel cell, has attracted attention as a power source for home computers and mobile phones because it is relatively easy to reduce the size and weight. In DMFC, methanol, which is a liquid, is directly fed to the anode as fuel, so that the methanol supplied to the anode passes through the solid polymer electrolyte membrane and permeates to the cathode side along with proton conduction, and is oxidized at the cathode. Thus, a unique problem different from other fuel cells, such as so-called methanol crossover, which causes a decrease in battery performance may occur.

Also in DMFC, carbon paper having through-holes is proposed in Patent Document 3, but in Patent Document 3, through-holes having an average diameter of about 18 to 25 μm are employed in Examples, and are generated by an anode reaction. Improvement of carbon dioxide emission is insufficient. On the other hand, in the case of DMFC, when carbon paper having a through-hole having a diameter larger than that of the above example is used as an electrode base material used particularly as an anode, not only the discharge of carbon dioxide generated by the anode reaction is improved. Moreover, since the mobility of methanol to the catalyst layer of the anode is also improved, performance degradation due to methanol crossover is promoted. That is, in the prior art, an electrode base material having high battery performance that achieves both improvement in mass mobility at the anode and suppression of methanol crossover has not been found.
Japanese Patent No. 2820492 (page 3) JP-A-8-111226 (page 3, paragraph number 0009) Japanese Patent Laying-Open No. 2005-174621 (second page)

  The present invention has been made in view of the above-mentioned problems in the prior art, and provides a DMFC that exhibits high battery performance while achieving both improvement in mass mobility at the anode and suppression of methanol crossover. For the purpose.

  In order to achieve the object, the porous carbon sheet of the present invention has the following configuration. That is, a porous carbon sheet in which dispersed carbon short fibers are bound with resin carbide, and has a plurality of through holes penetrating the front and back of the sheet, and the diameter of the through holes in the sheet is 100 to 400 μm. A porous carbon sheet for an anode electrode base material of a direct methanol fuel cell, characterized in that:

  Moreover, in order to achieve the said objective, the anode electrode base material of this invention has the following structure. That is, it is an anode electrode base material for a direct methanol fuel cell comprising the porous carbon sheet described above.

  Moreover, in order to achieve the said objective, the membrane-electrode assembly of this invention has the following structure. That is, direct methanol having a catalyst layer on both surfaces of a solid polymer electrolyte membrane, further having the above-mentioned anode electrode substrate in contact with one catalyst layer and the cathode electrode substrate in contact with the other catalyst layer. Type fuel cell membrane-electrode assembly.

  Furthermore, in order to achieve the object, the direct methanol fuel cell of the present invention has the following configuration. That is, a direct methanol fuel cell using the above-described membrane-electrode assembly.

  ADVANTAGE OF THE INVENTION According to this invention, the direct methanol fuel cell which makes the mass mobility in an anode and suppression of methanol crossover compatible, and shows high cell performance can be provided.

  Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is an optical micrograph showing the surface of a porous carbon sheet 1 according to an embodiment of the present invention.

  In FIG. 1, a short carbon fiber 3 that looks linear is dispersed in a porous carbon sheet 1, and the short carbon fiber 3 is bound by a resin carbide 4. Here, the dispersed state is often a state in which the short carbon fibers do not have a remarkable orientation in the sheet surface and are present almost randomly, for example, in a random direction. Specifically, the short fibers are dispersed by a papermaking method to be described later. And the porous carbon sheet 1 has the some through-hole 2 which penetrates the front and back of a sheet | seat (In FIG. 1, one through-hole is shown.). The through hole 2 penetrates in a direction perpendicular to the sheet surface.

  In the present invention, the diameter of the through hole is in the range of 100 to 400 μm, preferably in the range of 120 to 350 μm, more preferably in the range of 150 to 300 μm. In the porous carbon sheet of the present invention, by controlling the diameter of the through hole within the above range, when it is used as the anode electrode base material of DMFC, mass mobility at the anode and suppression of methanol crossover are suppressed. The obtained DMFC exhibits high battery performance. If the diameter of the through-hole is too small, the discharge of carbon dioxide gas generated by the anode reaction will be reduced, and the accumulated gas will inhibit the supply of methanol necessary for the reaction, causing a decrease in battery performance, and conversely large If the amount is too high, the carbon dioxide gas discharge performance is improved, but the supply of methanol to the catalyst layer of the anode becomes excessive, and the battery performance deteriorates due to methanol crossover. In addition, the diameter of a through-hole can be calculated | required by measuring the surface of a porous carbon sheet from the photograph image | photographed by the optical microscope at 100 time magnification. When the through hole is not circular, the average value of the major axis and minor axis of the hole is regarded as the diameter. The measurement is performed at 20 holes on both sides of the porous carbon sheet, and the average value thereof is taken as the diameter of the through hole in the sheet.

  In order to stably supply methanol to the anode catalyst layer and discharge the carbon dioxide gas generated by the power generation reaction, the diameter of each through hole taken with an optical microscope is the average value of the diameters of the through holes. It is preferable that it exists in the range of 0.5-2 times.

In the present invention, the density of the through holes in the sheet may be in the range of 10 to 500 / cm ² , preferably 20 to 400 / cm ² , more preferably 50 to 250 / cm ² . If the density of the through-holes in the sheet is too small, the effect of improving the carbon dioxide gas discharge performance by the through-holes may be reduced. Conversely, if it is too large, the methanol supply to the anode catalyst layer will be excessive. In addition, battery performance may be reduced due to methanol crossover, and the strength of the porous carbon sheet is reduced and it is easy to break, so that the process passability during high-order processing such as sheet manufacturing and water repellent treatment May be worse. In addition, the density of the through-hole in a sheet | seat can be calculated from the number of holes counted from the photograph which image | photographed the surface of the porous carbon sheet with the magnification of 25 times with the optical microscope, and can be calculated from the number of holes and the imaging | photography area of a photograph.

  In the present invention, the thickness of the porous carbon sheet 1 is 50 to 300 μm, preferably 70 to 270 μm, and more preferably 100 to 250 μm. If the thickness of the porous carbon sheet is too thin, the sheet is easily cracked, and the process passability during production and high-order processing may be deteriorated. On the other hand, if the thickness is too thick, the flexibility of the porous carbon sheet is reduced. And the sheet may not be wound into a roll. When the porous carbon sheet cannot be wound into a roll, production and high-order processing cannot be performed in a continuous process, and productivity is lowered. The thickness of the porous carbon sheet can be measured by applying a surface pressure of 0.15 MPa in the thickness direction of the sheet using a micrometer having a circular cross section having a diameter of 5 mm. The measurement is performed at 20 or more points in a grid pattern with an interval of 1.5 cm, and the average value is taken as the thickness.

  In the present invention, the porosity of the porous carbon sheet is 70 to 90%, preferably 73 to 87%, more preferably 75 to 85%. If the porosity of the porous carbon sheet is too small, the mass mobility of the porous portion other than the through-holes in the sheet will be reduced, the carbon dioxide gas generated by the anode reaction will be insufficiently discharged, or the anode will be exposed to the catalyst layer. Battery performance may be reduced due to insufficient methanol supply. On the other hand, if it is too large, the mass mobility of the porous part other than the through-holes in the porous carbon sheet is improved, but methanol to the catalyst layer of the anode is improved. Supply may become excessive, and battery performance may deteriorate due to methanol crossover. The porosity of the porous carbon sheet can be calculated from the true density and the apparent density of the porous carbon sheet. The true density can be obtained by a well-known floating method or pycnometer method. The apparent density can be obtained from the thickness and basis weight of the porous carbon sheet. The thickness of the porous carbon sheet is obtained by measuring as described above, and the basis weight (weight per unit area) of the porous carbon sheet is 10 pieces of 10 cm × 10 cm square porous carbon sheets. Minutes are measured and obtained as the average value.

  As shown in FIG. 2, the porous carbon sheet of the present invention can be suitably manufactured through a papermaking process, a resin impregnation process, a compression process, a carbonization process, and a through hole processing process. First, in the paper making process, carbon short fibers are continuously made using water as a paper making medium, and a binder such as polyvinyl alcohol is added to obtain carbon fiber paper. Next, in the resin impregnation step, the obtained carbon fiber paper is impregnated with a resin such as a phenol resin to obtain a resin-impregnated carbon fiber paper. Next, the resin-impregnated carbon fiber paper is compressed in a compression step. FIG. 4 is a schematic view showing an example of such a compression process. Set the upper hot plate 12 and the lower hot plate 13 in the hot press 11 so that they are parallel to each other, and arrange the spacer 14 on the lower hot plate 13 to adjust the clearance, and at the desired hot plate temperature and surface pressure. The resin-impregnated carbon fiber paper sandwiched between release papers from above and below is repeatedly conveyed while being repeatedly opened and closed, and is compressed so that the same portion is heated and pressurized for a desired time. Next, in the carbonization step, carbon fiber paper that has been subjected to the compression step is used as a precursor fiber sheet and carbonized in an inert gas atmosphere such as nitrogen to obtain a porous carbon sheet having no through holes. In the carbonization step, the resin is carbonized to become resin carbide, and the short carbon fibers are bound with the resin carbide.

  Next, in the through-hole processing step, a porous carbon sheet without through-holes is drilled with a plurality of holes in the sheet using a jig in which needles having an appropriate diameter are planted at an appropriate density. A quality carbon sheet is obtained. The diameter of the through hole can be controlled by adjusting the diameter of the needle, and the density of the through hole can be controlled by adjusting the planting density of the needle.

  In FIG. 3, the conceptual diagram of the partial cross section of the membrane-electrode assembly of DMFC in which the porous carbon sheet 1 which concerns on one form of this invention is used as an anode electrode base material is shown.

  As shown in FIG. 3, the DMFC membrane-electrode assembly 6 has catalyst layers 8 on both surfaces of the solid polymer electrolyte membrane 7, and the anode electrode substrate is in contact with the catalyst layer on one side and the other side. A cathode electrode base material is in contact with the catalyst layer. The anode electrode substrate includes the porous carbon sheet described above.

  The anode electrode base material is preferably formed by applying a water-repellent substance to the porous carbon sheet 1 (water-repellent treatment). If the surface of the electrode substrate has water repellency, when the DMFC is constructed, the methanol aqueous solution supplied to the anode is appropriately repelled, and the discharge of carbon dioxide gas generated by the anode reaction is hindered by clogging of the methanol aqueous solution. Can be suppressed. By balancing the supply of methanol to the anode catalyst layer and the discharge of carbon dioxide gas from the anode catalyst layer, the mobility of the substance related to the power generation reaction can be sufficiently ensured, and the battery performance is improved.

  The water repellent material is preferably a fluororesin. In the water repellent treatment, the water-repellent substance is used in a lower limit of 1 part by weight or more, preferably 5 parts by weight or more, more preferably 10 parts by weight or more, and the upper limit is 70 parts by weight or less, preferably 100 parts by weight of the porous carbon sheet. Can be carried out by adhering at a ratio of 50 parts by weight or less, more preferably 30 parts by weight or less.

  Here, the fluororesin includes tetrafluoroethylene resin (PTFE), perfluoroalkoxy resin (PFA), fluorinated ethylene propylene resin (FEP), fluorinated ethylene tetrafluoroethylene resin (ETFE), etc. A resin containing atoms.

  The anode electrode substrate is preferably formed by forming a conductive gas diffusion layer 5 on at least one surface of the porous carbon sheet 1. The gas diffusion layer 5 can be formed of a fluororesin and conductive carbon black. Since the anode electrode base material is provided with the gas diffusion layer 5 on at least one surface of the porous carbon sheet 1, the irregularities due to the through holes of the porous carbon sheet 1 are covered, and gas diffusion is performed in the anode electrode base material. Since the surface having the layer 5 is smooth, it is easy to ensure electrical contact with the catalyst layer 8 when a membrane-electrode assembly is formed, and the porous carbon sheet 1 and the solid polymer electrolyte membrane 7 The short circuit can be suppressed.

  Similarly, the cathode electrode base material is preferably formed by forming a water-repellent treatment and a gas diffusion layer. When a porous carbon sheet is used for the cathode electrode base material, a through-hole such as the porous carbon sheet of the present invention is used. However, since the effect of improving the battery performance when the through hole is provided is smaller than that of the anode, it is better to use the one without the through hole. This can be omitted and is preferable in terms of manufacturing cost reduction.

  Such an anode electrode base material and cathode electrode base material are joined so that the gas diffusion layer 5 side is in contact with the catalyst layer 8 to form the membrane-electrode assembly 6. Also, a DMFC can be configured by laminating a plurality of materials sandwiched between separators via gaskets on both sides of the membrane-electrode assembly 6. The catalyst layer 8 is composed of a catalyst-supporting carbon or metal catalyst layer. As the catalyst, platinum and ruthenium are preferably used on the anode side to which the aqueous methanol solution is supplied, and platinum is preferably used on the cathode side to which oxygen is supplied. Further, as the solid polymer electrolyte used for the solid polymer electrolyte membrane 7, a material made of a perfluorosulfonic acid polymer having high proton conductivity, oxidation resistance and high heat resistance is preferably used.

Hereinafter, the present invention will be described more specifically by way of examples. The fuel cell current density in this example was measured using the following method.
(Measurement of fuel cell current density)
Using the electrode substrate to be measured as the anode electrode substrate, the porous carbon sheet without through-holes obtained through the carbonization step in Example 1 was dipped in a PTFE aqueous dispersion and then dried to dry the sheet 100. An electrode substrate having 25 parts by weight of PTFE attached to parts by weight is used as the cathode electrode substrate.

On the other hand, on one surface of a solid polymer electrolyte membrane of Nafion (registered trademark) 117 (manufactured by EI du Pont de Nemours and Company), carbon supporting platinum and ruthenium (weight ratio of 1: 1) as catalysts. A catalyst layer on the anode side is formed by adhering a mixture with Nafion, and a catalyst layer on the cathode side is formed by adhering a mixture of carbon carrying platinum as a catalyst and Nafion on the other surface. -Prepare a catalyst sheet. Loading amount of the catalyst, 7.0 mg / cm ² side were deposited platinum and ruthenium in the sum of platinum and ruthenium, the side adhered with platinum is 7.0 mg / cm ² platinum.

The obtained membrane-catalyst sheet was sandwiched between two electrode base materials with the gas diffusion layer facing inward, and united by heating and pressurizing at a temperature of 130 ° C. and a pressure of 3 MPa to form a membrane-electrode assembly (MEA). obtain. The anode electrode base material is arranged on the catalyst layer side containing platinum and ruthenium, and the cathode electrode base material is arranged on the catalyst layer side containing platinum. The areas of the electrode substrate and the catalyst layer are both 5 cm ² and square.

The MEA was sandwiched between grooved separators, and the current density at a voltage of 0.4 V was measured. The battery temperature was 60 ° C., a 3.2 wt% aqueous methanol solution was supplied to the anode side at 1 L / min, and air was supplied to the cathode side at 50 cc / min. The higher the measured current density, the better the performance as DMFC.
(Example 1)
The manufacturing process shown in FIG. 2 was followed. First, in the paper making process, polyacrylonitrile carbon fiber “Torayca (registered trademark)” T300-6K (average single fiber diameter: 7 μm, number of single fibers: 6,000 fibers) manufactured by Toray Industries, Inc. was cut to a length of 12 mm. Then, paper is continuously made using water as a paper making medium, and further immersed in a 10% by weight aqueous solution of polyvinyl alcohol and dried to obtain a long carbon fiber paper having a basis weight of carbon short fibers 3 of about 26 g / m ^2. Rolled up into a roll. The adhesion amount of polyvinyl alcohol corresponds to 20 parts by weight with respect to 100 parts by weight of the carbon fiber paper.

  Next, in the resin impregnation step, the obtained carbon fiber paper was mixed with scale-like graphite BF-5A (average particle size 5 μm) manufactured by Chuetsu Graphite Industries Co., Ltd., phenol resin and methanol in a weight ratio of 2: 3: 24. The resulting dispersion is continuously impregnated with 125 parts by weight of phenolic resin with respect to 100 parts by weight of short carbon fibers, and dried at 90 ° C. for 3 minutes to obtain a resin-impregnated carbon fiber paper. Rolled up into a roll. As the phenol resin, a resin in which a resol type phenol resin and a novolac type phenol resin were mixed at a weight ratio of 1: 1 was used.

  Next, in the compression step shown in FIG. 4, the upper heating plate 12 and the lower heating plate 13 are set in a 100 t hot press manufactured by Kawajiri Co., Ltd. so that they are parallel to each other, and the spacer 14 is arranged on the lower heating plate 13. , While heating plate temperature is 170 ° C and surface pressure is 0.8MPa, the same part is heated and pressed for a total of 6 minutes while intermittently transporting resin-impregnated carbon fiber paper sandwiched by release paper from above and below while repeatedly opening and closing the press Compressed to be The substantial clearance provided for molding the resin-impregnated carbon fiber paper, excluding the thickness of the release paper, was 0.30 mm. The effective pressurization length LP of the hot plate was 1200 mm, and the feed amount LF per one time of the precursor fiber sheet when intermittently conveyed was 100 mm, and LF / LP = 0.08. That is, compression treatment was performed by repeating heating and pressurization for 30 seconds, mold opening, and feeding of carbon fiber paper (100 mm) to obtain a precursor fiber sheet, which was wound into a roll.

  Next, in the carbonization step, the obtained precursor fiber sheet was introduced into a heating furnace maintained at a nitrogen gas atmosphere with a maximum temperature of 2,500 ° C., and continuously running in the heating furnace. Firing was performed at a heating rate of 500 ° C./min (400 ° C./min up to 650 ° C., and 600 ° C./min at temperatures exceeding 650 ° C.) to obtain a porous carbon sheet without through-holes and wound into a roll. .

Next, in the through hole processing step, a plurality of through holes are opened using a jig in which needles having a diameter of 150 μm are planted at a density of 240 / cm ^{2 on} a porous carbon sheet having no through holes. A porous carbon sheet was obtained.

The porous carbon sheet obtained through such a manufacturing process is dipped in a PTFE aqueous dispersion and then pulled up and dried to attach 25 parts by weight of PTFE to 100 parts by weight of the sheet. A mixture containing black and PTFE at a weight ratio of 2: 1 was applied at about 2 mg / cm ² per unit area of the sheet and heat treated at 380 ° C. to form a gas diffusion layer to obtain an electrode substrate.

Using the obtained electrode base material as an anode electrode base material, the fuel cell current density was measured. Table 1 summarizes the specifications and evaluation results of the obtained electrode substrate.
(Example 2)
In the through-hole machining step, a jig in which needles with a diameter of 250 μm are planted at a density of 120 / cm ² is used instead of a jig in which needles with a diameter of 150 μm are planted at a density of 240 / cm ^2. An electrode substrate was obtained in the same manner as in Example 1 except that PTFE was not attached to the carbonaceous sheet.

Using the obtained electrode base material as an anode electrode base material, the fuel cell current density was measured. Table 1 summarizes the specifications and evaluation results of the obtained electrode substrate.
(Example 3)
The basis weight of the short carbon fiber in the paper making process is about 26 g / m ² to about 17 g / m ² , and the substantial clearance provided for molding the resin-impregnated carbon fiber paper in the compression process is 0.30 mm to 0.20 mm. In addition, in the through hole processing step, the embodiment is different from the jig in which the needle having a diameter of 150 μm is planted at a density of 240 / cm ^{2 to} the jig in which the needle having a diameter of 350 μm is planted at a density of 50 / cm ^2. In the same manner as in Example 1, an electrode substrate was obtained.

Using the obtained electrode base material as an anode electrode base material, the fuel cell current density was measured. Table 1 summarizes the specifications and evaluation results of the obtained electrode substrate.
Example 4
In the paper making process, carbon fiber paper was obtained in the same manner as in Example 1.

  Next, in the resin impregnation step, the obtained carbon fiber paper was impregnated with a phenol resin 10 wt% methanol solution so that the phenol resin was 250 parts by weight with respect to 100 parts by weight of the short carbon fiber, and 90 ° C. The resin-impregnated carbon fiber paper was obtained. As the phenol resin, a resin in which a resol type phenol resin and a novolac type phenol resin were mixed at a weight ratio of 1: 1 was used.

  Next, in the compression step shown in FIG. 4, the upper heating plate 12 and the lower heating plate 13 are set in a 100 t hot press manufactured by Kawajiri Co., Ltd. so that they are parallel to each other, and the spacer 14 is arranged on the lower heating plate 13. The resin-impregnated carbon fiber paper sandwiched between release sheets from above and below at a hot plate temperature of 150 ° C. and a surface pressure of 0.8 MPa was continuously pressed for 30 minutes to perform a compression treatment to obtain a precursor fiber sheet. The substantial clearance provided for molding the resin-impregnated carbon fiber paper was 0.33 mm.

  Next, the obtained precursor fiber sheet was fired at 2,500 ° C. using a batch-type heating furnace maintained in a nitrogen gas atmosphere to obtain a porous carbon sheet having no through holes. The heating rate was 1.7 ° C./min (1 ° C./min up to 800 ° C., 2 ° C./min at temperatures over 800 ° C.).

  Next, after the through hole processing step, an electrode substrate was obtained in the same manner as in Example 2.

Using the obtained electrode base material as an anode electrode base material, the fuel cell current density was measured. Table 1 summarizes the specifications and evaluation results of the obtained electrode substrate.
(Comparative Example 1)
In the through hole processing step, an electrode substrate was obtained in the same manner as in Example 1 except that a jig in which needles having a diameter of 50 μm were planted at a density of 600 needles / cm ² was used.

Using the obtained electrode base material as an anode electrode base material, the fuel cell current density was measured. Table 1 summarizes the specifications and evaluation results of the obtained electrode substrate.
(Comparative Example 2)
In the through hole processing step, the same procedure as in Example 1 was performed except that a jig in which needles having a diameter of 75 μm were planted at a density of 240 / cm ² and PTFE was not attached to the porous carbon sheet, An electrode substrate was obtained. Using the obtained electrode base material as an anode electrode base material, the fuel cell current density was measured. Table 1 summarizes the specifications and evaluation results of the obtained electrode substrate.
(Comparative Example 3)
In the through hole processing step, an electrode substrate was obtained in the same manner as in Example 1 except that a jig in which needles having a diameter of 450 μm were planted at a density of 120 / cm ² was used. Using the obtained electrode base material as an anode electrode base material, the fuel cell current density was measured. Table 1 summarizes the specifications and evaluation results of the obtained electrode substrate.
(Comparative Example 4)
In the through hole processing step, except that a jig planted with a needle having a diameter of 500 μm at a density of 60 / cm ² was used, and PTFE was not adhered to the porous carbon sheet, the same as in Example 1, An electrode substrate was obtained. Using the obtained electrode base material as an anode electrode base material, the fuel cell current density was measured. Table 1 summarizes the specifications and evaluation results of the obtained electrode substrate.

  In Examples 1 to 4, the porous carbon sheet has a plurality of through holes, and the diameter of the through holes is 100 to 400 μm. Therefore, when used as an anode electrode base material of DMFC, the mass mobility at the anode And methanol crossover can be suppressed at the same time, and as shown in FIG. 5, a high fuel cell current density is shown.

  On the other hand, in Comparative Example 1, the porous carbon sheet does not have through holes, and in Comparative Example 2, the porous carbon sheet has a plurality of through holes, but the diameter of the through holes is less than 100 μm. For this reason, the discharge of carbon dioxide gas generated by the anode reaction is reduced, and the staying gas hinders the supply of methanol necessary for the reaction, and the fuel cell current density is reduced. In Comparative Examples 3 and 4, although the porous carbon sheet has a plurality of through holes, the diameter of the through holes exceeds 400 μm, so that the carbon dioxide gas discharge performance is improved, but the catalyst layer of the anode Methanol is excessively supplied to the fuel cell, and the fuel cell current density is reduced due to methanol crossover.

  As described above, according to the present invention, it is possible to provide a DMFC exhibiting high battery performance while achieving both mass mobility at the anode and suppression of methanol crossover.

  The DMFC according to the present invention is suitably used as a power source for home computers and mobile phones.

It is an optical microscope photograph (50 times) which shows the surface of the porous carbon sheet which concerns on one form of this invention. It is process drawing of a manufacturing process suitable for manufacture of the porous carbon sheet of this invention. It is a conceptual diagram of the partial cross section of the membrane-electrode assembly of DMFC in which the porous carbon sheet which concerns on one form of this invention is used as an anode electrode base material. It is the schematic which shows the compression process in the manufacturing process suitable for manufacture of the porous carbon sheet of this invention. It is a figure which shows the relationship between the diameter of a through-hole, and a fuel cell current density about the porous carbon sheet obtained in the Example.

Explanation of symbols

1: porous carbon sheet 2: through-hole 3: carbon short fiber 4: resin carbide 5: gas diffusion layer 6: membrane-electrode assembly 7: solid polymer electrolyte membrane 8: catalyst layer 9: (having a through-hole Not) Porous carbon sheet 10: precursor fiber sheet 11: hot press 12: upper hot plate 13: lower hot plate 14: spacer

Claims (9)

It is a porous carbon sheet formed by binding carbon short fibers dispersed with resin carbide, and has a plurality of through holes penetrating the front and back of the sheet, and the diameter of the through holes in the sheet is 100 to 400 μm. A porous carbon sheet for an anode electrode base material of a direct methanol fuel cell. The porous carbon sheet according to claim 1, wherein the density of through holes in the sheet is 10 to 500 / cm ² . The porous carbon sheet according to claim 1 or 2, which has a thickness of 50 to 300 µm. The porous carbon sheet according to any one of claims 1 to 3, wherein the porosity is 70 to 90%. An anode electrode base material for a direct methanol fuel cell, comprising the porous carbon sheet according to claim 1. The anode electrode base material according to claim 5, which is provided with a water repellent substance. The anode electrode base material according to claim 5 or 6, wherein a gas diffusion layer having conductivity is formed on at least one surface. It has a catalyst layer on both surfaces of a solid polymer electrolyte membrane, Furthermore, the anode electrode base material in any one of Claims 5-7 is contact | connected to the catalyst layer of one side, and a cathode electrode base | substrate is contacted with the other catalyst layer. A membrane-electrode assembly for a direct methanol fuel cell formed by contacting a material. A direct methanol fuel cell using the membrane-electrode assembly according to claim 8.