FR2534071A1 - FUEL CELL ELECTRODE SUBSTRATE HAVING EXTENDED HOLES FOR REACTIVE GAS SUPPLY - Google Patents

Abstract

THE SUBSTANCE OF THE PRESENT INVENTION IS A POROUS CARBON-BASED ELECTRODE SUBSTRATE FOR A FUEL CELL. IT IS CHARACTERIZED IN THAT IT HAS HOLES EXTENDING FROM ONE SIDE TO THE OPPOSITE SIDE OF THE SUBSTRATE, THE HOLES BEING ARRANGED PARALLEL TO ONE OF THE OTHER AND PARALLEL TO THE SURFACE OF THE ELECTRODE.

Description

FUEL CELL ELECTRODE SUBSTRATE HAVING

  -TROUS EXTENSIONS FOR REACTIVE GAS SUPPLY

  The present invention relates to a fuel cell electrode substrate, more particularly to an electrode substrate having elongated holes for supplying reactive gases (hydrogen as a

  combustible gas and oxygen or air) of a fuel cell.

  We know a bipolar fuel cell with a separator

  ribbed bipolar prepared from an impervious

  On the other hand, a ribbed electrode substrate for a monopolar fuel cell with a ribbed surface has been placed at the very least.

  and a flat surface to contact a catalyst layer.

  Such an electrode substrate is carbon-based and porous in its

  appears. A conventional monopolar fuel cell using such an electrode substrate is illustrated in Figure 1. A battery is composed

  two electrode substrates 1, two catalyst layers 2, one

  matrix 3, impregnated with an electrolyte, and two separation sheets 4 to come into contact with the ribs 5 of the substrate 1 in a stack of these cells intended to form a fuel cell The reactive gases are introduced through channels formed by the ribs 5 and the leaf

  4 and the gases diffuse from the ribbed surface to the

  flat face in the porous electrode substrate 1 to reach the layer

of catalyst 2.

  To prepare such an electrode substrate, the following methods that have been proposed previously can be used. For example, a method for preparing a general electrode substrate has been proposed in Japanese Patent Application Laid-Open No. 166,354 / 82 wherein a mixture based on short carbonaceous fibers is compressed to form a porous shaped article. Another method is described in Japanese Patent Publication No. 18603/78, in which a carbon fiber paper is impregnated a solution

  of organic polymer and converted into porous carbon fiber paper.

  Yet another method of preparing an electrode substrate is provided in US Pat. No. 3,829,327 in the US Pat.

  what is described a sheet of carbon fibers subjected to the deposit of a va-

  chemical fear of carbon to form a porous electrode substrate All

  the electrode substrates have monolayer structures sensitive to

homogeneous.

  Such a homogeneous monolayer electrode substrate however has the following drawbacks: with a high bulk density of the substrate,

  low current densities are obtained because of the slightest difference in

  reactive gas melting and the performance of the fuel cell deteriorates rapidly due to the insufficient amount of electrolyte stored in the substrate and thus the life of the cell of the fuel cell is shortened On the other hand, when the electrode substrate has a low apparent density, it has the disadvantage of having a high electrical resistance and thermal resistance and poor mechanical characteristics such as for example a low resistance

bending.

  In addition, in the case of an electrode substrate having

  the section modulus of this substrate is reduced because of the over-

  ribbed face as can be seen in Figure 1 and the constraint is

  concentrates on the angular portion 6 of the ribs 5 and leads to a

  insufficient mechanical resistance of the entire electrode substrate.

  A thick substrate is therefore inevitable if it is desired to obtain sufficient resistance of the shaped substrate and this means that the diffusion resistance of the reactive gases from the ribbed surface to the flat surface is increased. On the other hand, it is difficult to get complete flatness

  of the upper surface of the veins and the incomplete flatness of the

  ribs is the cause of a significant increase in resistance

  Electrical contact and thermal contact between the upper surface of the ribs and a separator sheet As is generally known, such a contact resistance can be several times greater than the conductive resistance in the substrate and, therefore, a substrate of conventional monopolar electrode exhibits a lack of uniformity in the temperature distribution in the cell and a reduction in the efficiency

  of production because of the great contact resistance.

  The object of the present invention is to create a substrate for

  trode that does not have these disadvantages.

  Another object of the invention is to provide a substrate for

  fuel cell trode devoid of ribs.

  Another object of the invention is to create an electrode substrate which has elongated holes for feeding the battery.

fuel gas reactive.

  It is yet another object of the invention to provide a fuel cell electrode substrate which has a dense layer and a

  porous layer, these two layers being integral.

  It is yet another object of the present invention to provide an electrode substrate for a fuel cell that does not require

  additional separation sheets for stacking substrates -

  Another object of the present invention is still to create a fuel cell electrode substrate which has a dense layer

  as a separation sheet and two porous sheets on both

  faces of the dense layer, these three layers being integral.

  Another object of the present invention is still to create a fuel cell electrode substrate in which a dense layer

  separating sheet extends outward.

  These objects and others will appear to those skilled in the art to

  from the detailed description of the present invention which follows.

  The electrode substrate for a fuel cell according to the

  present invention has several holes located near the center of the

  thickness of the substrate, these holes extending from one side of the substrate to the other side and being parallel to each other and parallel to the surface of the substrate;

  These holes constitute channels for supplying reactive gas.

  In a first aspect of the first invention, the electrode substrate is porous and carbon-based as a whole. In the second embodiment of the present invention, this substrate is also carbon-based. andhas a dense layer functioning as a separator sheet and a porous layer having these holes, which layers are integral and integrated in the same mass. According to the third aspect of the present invention, the carbon-based electrode substrate has a layer The porous layer having two or more porous layer layers and two porous layers are prepared to be integral with the dense layer on both surfaces of the dense layer, the porous layer having these holes. According to the fourth aspect of the present invention, the substrate is carbon-based electrode comprises an extended dense layer serving as a separation sheet and two porous layers comprising these ou prepared so as to be supportive

  of the dense layer on both surfaces of the extended dense layer.

  The "electrode surface" or in some cases the "surface" here means the surface of a fuel cell, an electrode substrate or a component layer thereof that is parallel to the surface of the fuel cell. catalyst layer (reference 2 in FIG. 1) intended to come into contact with a substrate or a matrix layer (reference 3 in FIG. 1). The "side" or occasionally the "surface of the side" indicates here the surface of a fuel cell of an electrode substrate or a component layer thereof which is perpendicular to said "surface of the electrode". The invention will be illustrated in more detail with reference to the accompanying drawings, in which:

  FIG. 1 shows the structure of a fuel cell comprising

  both ribbed monopolar electrode substrates according to the prior art; Fig. 2 shows the cell structure of a fuel cell according to the first embodiment of the first invention;

  FIG. 3 shows the stack structure of a fuel cell.

  according to the second embodiment of the present invention.

  this invention; Fig. 4 shows the cell structure of a fuel cell according to the third embodiment of the present invention; Fig. 5 shows the structure of the electrode substrate of the fourth embodiment of the present invention; Fig. 6 illustrates how to use the electrode substrate according to the fourth embodiment of the present invention; Fig. 7 shows another electrode substrate according to the fourth embodiment of the present invention; and FIG. 8 is an explanation view of the preparation of the substrate

electrode according to Figure 7.

  In the various figures, the same references indicate the same parts. FIG. 2 is an explanation view of a fuel cell according to the first embodiment of the present invention.

  Electrode 1 is porous and carbon-based as a whole.

  shown in FIG. 2, the elongated holes 7 for supplying reactive gases to a fuel cell are practiced near the center of the thickness of the substrate 1. These holes 7 are parallel to each other and to the surface of the electrode and they extend continuously from one side of the substrate 1 to the opposite side of the substrate 1 Although the cross section of the holes 7 may be circular as shown in Figure 2, any cross-sectional shape of the holes 7 can be used in the present invention The cross section of the holes 7 is preferably

  about 0.2 to 7 mm 2, this cross-section corresponding to a di-

  0.5 to 3 mm in the typical case of a circular cross-section.

  With a smaller size, the diffusion resistance of the reactive gases becomes too high. On the other hand, the thickness of the substrate would become too great and lead to a reduction in the volume efficiency of a fuel cell in a stack having larger size. The electrode substrate 1 comprises a uniformly porous and carbon-based material. The substrate i has an average bulk density of 0.3 to 1.0 g / cm 3, preferably 0.4 to 0.8 g / cm 2 and permeability

  specific for reactive gases which is not less than 20 ml / cm hr mm Aq.

  The electrode substrate having this apparent density and permeability

  The gas specificity is preferable for a fuel cell because of its mechanical strength, such as, for example, its flexural strength and resistance to diffusion of the reactive gases. In addition, the pores of the electrode substrate 1 are pores. open and preferably, by less than 60% of the pores have a diameter in the range of 10 to 100 p. The electrode substrate can be prepared as follows, for example, in

  the first embodiment of the present invention.

  From 10 to 50% by weight of a filler such as short carbon fiber and granular activated carbon, from 10 to 40% by weight of a binder such as a phenol resin, an epoxy resin and a pitch of oil and / or charcoal and 20 to 50% by weight of a pore regulator such as polyvinyl alcohol, polyethylene, polypropylene, polyvinyl chloride and sugar are mixed to form a homogeneous mixture The mixed amount of these components is given here only by way of example and is not limited to the above-mentioned amounts. Such a mixture may also be used as a raw material of a porous layer in the other embodiments of the present invention. present invention as will be described

  The mixture is then introduced into a mold having the configuration

  In order to form the elongated holes, a fabric (or textile) or a comb-shaped sheet (or

  network) of polymeric material such as polyethylene, polypropylene, polysilicon

  tyrene, polyvinyl alcohol, polyvinyl chloride and

  following the same mixture as mentioned above The pressing is

  then carried out at a mold temperature of 70 to 200 ° C under a pres-

  5 to 100 kg / cm 2 for 1 to 60 minutes Pressing conditions can be selected according to the object within a wider range than that mentioned above. The resultant sheet is post-processed at 120 to 1700 C at a pressure not exceeding 5 kg / cm 2 for at least two hours and calcined at 1000 to 3000 C for one hour in an inert atmosphere In the heating procedure, a slow increase in temperature up to about 7000 C is preferable to avoid the production of shrinkage constraints

  Suddenly caused by thermal decomposition at low temperatures.

  Such a constraint would cause delamination of the leaves and / or

cracks.

  The electrode substrate of the present invention has a flat surface to contact the separator sheet in a cell and form a fuel cell and also has another flat surface for contacting the catalyst layer 2. ,

  the substrate thus having a larger sectional module and a better

  Their mechanical strength such as flexural strength as a conventional ribbed electrode substrate. In addition, the flexural strength can be further improved because the holes 7 are made.

  near the center of the thickness of the substrate 1 as represented by the

  The invention has other advantages, i.e. a thinner substrate can be obtained which leads to a shorter diffusion path or a low resistance to the diffusion of the reactive gases and to a density larger current A separator can be brought into contact with the entire surface of the electrode substrate according to the invention and, as a result, there can be a reduction in the electrical and thermal contact resistance. electrode according to the invention can be significantly reduced compared to a conventional substrate of a fuel cell, for example an electrode substrate

  ribbed 1 as shown in Figure 1 Thus, the substrate of elec-

  trode according to the present invention is suitable for a fuel cell.

  tible. The electrode substrate 1 according to the present invention is used for a fuel cell as shown in FIG. 2. In this embodiment of the invention, as shown in FIG. 2, separation sheets 4 are necessary for stacking. the elements and form a fuel cell It is preferable, however, to omit the use of separation sheets in a stack of elements in order to obtain an additional reduction of the contact resistance

  between the substrate and the separation sheet.

  From this point of view, a separator sheet may be made integral with an electrode substrate according to the present invention to further reduce the electrical resistance of a fuel cell. FIG. explanation of the second embodiment of the electrode substrate according to the present invention The electrode substrate 1 'according to the present invention comprises a porous layer 8 having the holes 7 as mentioned above, arranged close to the center of the thickness of said layer and a dense layer 9

  porous layer 8 has the same physical properties as the substrate of the first

  first embodiment, i.e., an average bulk density of 0.3 to 1.0 g / cm 3, preferably 0.4 to 0.8 g / cm 3, and In addition, not less than 50% of the pores in the porous layer 8 have a diameter in the range of 10 to 100%. The dense layer 9 preferably has an average bulk density of not less than 1.0 g / cm 3 and a gas-specific permeability of not more than 0.2 ml / cm hr mm Aq in order to operate

  as a separation sheet (reference 4 in FIGS. 1 and 2)

  of the dense layer 9 preferably does not exceed half the thickness of the

  total thickness of the electrode substrate 1 'according to the present invention.

  The raw material of the porous layer 8 in the preparation of the electrode substrate 1 'is the same as the raw material of the substrate

  in the first embodiment of the present invention.

  The material of the holes 7 is also the same as the material used in

  the first embodiment of the present invention.

  The raw material for the dense layer is selected from the group consisting of a graphite plate, a graphite sheet, a carbon plate and a powder mixture comprising short carbon fibers, fine carbon precursor powder (see Japanese Patent Publication No. 31,116 / 80), a phenol resin and granular activated carbon. A graphite sheet is the preferred material for making the dense layer of the present invention.

  In the preparation of the electrode substrate of the second embodiment of

  According to the invention, the raw material of the porous layer, the material of the holes and then the raw material of the porous layer and finally the raw material of the dense layer are introduced, in that order, into a mold to be pressed. The materials are then pressed under the conditions mentioned above. The shaped product is precured at about 800 ° C. for about 1 hour.

  the dense layer of the cured product is impregnated with a free phenol resin

  quide (using alcohol or the like as a solvent in which

  to dissolve the phenol resin), the product is again hardened to approximately

  This impregnation and the curing steps are repeated several times to obtain the desired density of the dense layer. Finally, the cured product having the desired density is post-cured at 120 to 1700 C under a pressure not exceeding 100.degree. not exceeding 5 kg / cm 2 for at least 2 hours and then calcined at 1000 to 3000 C. In the third embodiment according to the present invention, the electrode substrate may comprise a dense layer and two porous layers on the two surfaces of the dense layer, these three layers being

  prepared so as to be solidary in a single mass.

  FIG. 4 shows a stack of elements using

  the electrode substrate of the third embodiment according to the invention

  tion, in which the reference 10 represents a battery structure cor-

  corresponding to the structure shown in Figures 1 or 2 The electrode substrate 11 according to the present invention has a dense layer 9

  and two porous layers 8 having holes 7 as mentioned above.

  The holes 7 in the porous layer 8 are designed to lie in a direction perpendicular to the direction of the holes 7 located in the adjacent porous layer 8 as shown in FIG. 4. The porous layer 8 and the dense layer 9 have the same structure and physical properties as mentioned above for the second embodiment of the present invention. The dense layer 9 preferably has a thickness of 0.1 to 3.0 mm: The electrode substrate II of the third embodiment according to the present invention may be prepared from the same materials and from

  similar to that of the second embodiment of this

tion (see examples 5 to 7).

  In the second and third embodiments of the invention, the dense layer can function as a separator sheet and therefore it is not necessary to have a separator sheet in a stack to form a stack As a result, there is no contact resistance between a separator sheet and an electrode substrate according to the present invention. In addition, since the dense layer serving as the separation sheet and two porous layers are integral in the same mass in the third embodiment according to the present invention, there is no contact resistance between

  the dense layer (separation sheet) and the porous layer-in the

  The fact that no separation is necessary makes it possible to lower the costs. Naturally, the electrode substrate of the second and third embodiments of the invention has all the advantages of the first embodiment. which has been described above The advantages of the present invention will appear better

  from the following Table I showing the physical properties of the

  electrode traites according to the present invention and prior art

  (Figure 1) Data for comparison.

  The electrode substrate according to the present invention is

  For use with the fuel cell, however, the reactive gases can also diffuse out of the walls of the porous substrates on both sides. surfaces of the separation sheet (the dense layer according to the invention) of the

  fuel, creating the danger of mixing the reactive gases.

  In the fourth embodiment of the present invention, the dense layer extends outwardly from the walls of the fuel cell substrate to avoid this danger of gas mixing.

  Reagents Figure 5 shows the structure of the electrode substrate corresponding to

  In the fourth embodiment of the present invention, the substrate comprises an extended dense layer 9 and two porous layers 8 on both surfaces of the dense layer 9, each porous layer having the holes 7 as mentioned above. The dense layer 9 is preferably a graphite sheet The physical properties of the

TABLE 1

  The present invention is a prior art first mode of second mode third embodiment of the embodiment of the invention Thickness of the substrate (mm) 2.4 2.0 2.0 3.6 l) Thickness of an element (mm) ) 5.8 2) 5.0 2) 4, 3) 4 4 Flexural strength bars 100 150 250 250 Resistance to compression bars 100 150 250 250 Resistance to compression bars: 100 150 150 '150 substrate 8 6 6 10 Resistance electrodesistance of contact 6) 30 20 20 electrical

- ,, -

  (m 2) 5) total of one element 77 7) 53) 32 8) 10 Thickness of diffusion of gas (mm) 1.2 1.0 1.0 1.0 Limit current (m A / cm 2) 400 500 500 500 Volumetric power (k W / m 3) 9) 207 240 267 298 Note: 1) a dense layer (0.6 mm) + two porous layers (each 1.5 mm) 2) separation sheet (0 , 5 mm) + two substrates + matrix layer (0.5 mm) 3) two substrates + matrix layer (0.5 mm) 4) substrate + matrix layer (0.5 mm)) resistance per 1 cm 2 6) resistance measured at contact pressure of 1 kg / cm 2 7) separation sheet (1 m S) + two substrates + two contact resistors 8) two substrates + contact resistance 9) measured at 200 m A / cm 2 rv LA w NV C> -

  porous layers 8 and the dense layer 9 are the same as those mentioned in

  above for the second and third embodiments.

  The electrode substrate of the fourth embodiment of the

  The present invention can be prepared from the same raw materials

  res than those of the third embodiment mentioned above. In preparing the substrate, after pressing into a mold of the mixture to form a porous layer, the material for forming the holes, the mixture for forming a porous layer and the material for forming a dense layer are introduced in this order. in the die, the shaped product is then removed from the mold and in the same mold, the mixture is introduced to form a porous layer, the material intended to form the holes and the mixture intended to form a porous layer The previously formed product is placed on the materials

  introduced, the dense layer in contact with the material is compressed.

  The other treatments are the same as those mentioned in the third

seventh embodiment.

  The electrode of the fourth embodiment according to the invention effectively prevents the mixing of the reactive gases leaving by diffusion of the edges of the fuel cell since the dense layer 9 extends outwards from the lateral surface of the porous substrate. Thereby,

  the fuel cell according to the fourth embodiment of the present invention.

  This invention can work effectively and safely.

  Figure 6 shows the construction of a fuel cell

  Reading the electrode substrate according to the fourth embodiment of the present invention in a stack In a fuel cell, peripheral seals 12 are associated by means appropriate to the

  sides of the porous layer 8 which are parallel to the holes 7

  gas scorers 13 provided with a tube 14 for introducing the reaction gases

  in the holes are arranged on the other sides of the layers

  as shown in FIG. 6 In FIG. 6, arrows

  represent the flow directions of the reactive gases

  12 are made of a material with good electrical isolation.

  heat resistance at around 2000 C during operation.

  This is for example Teflon, silicon carbide or ceramic or a suitable material coated with Teflon.

or silicon carbide.

  To further prevent the diffusion of the reactive gases from the walls of the porous layers 8, a graphite sheet 15 can be used to seal the side of the porous layer 8 intended to come into contact with the peripheral joints 12 (see FIG. ) The graphite sheet 15 is made of a material having the same properties as the dense layer 9 Although the graphite sheet 15 can cover only

  the side to come into contact with the peripheral seal 12, it is preferable that it is integral with the dense layer 9 (preferably a sheet

  16) In this case, the graphite sheet 15 preferably has a U-shaped cross-section and is associated with the sheet.

  graphite 16 as shown in FIG.

  phite 15 to seal the side of the porous layer 8 may extend

  to the outside from the perpendicular side to the holes

  the end of the graphite sheet 16.

  Such an electrode substrate according to the fourth embodiment of the present invention may be prepared in a manner similar to that mentioned above for the fourth embodiment and it will be

illustrated in Example 9.

  The present invention will be illustrated with reference to the examples

  It is understood that various modifications may be made by those skilled in the art without difficulty and that these

  variations will be within the scope of the present invention.

  In these examples, the "porosity p (%)" is determined by the equation

  following assumption assuming that the actual density of the carbon-based substrate is 1.6 g / cm 3: P = (1 Pb / 6) x 100

in which: -

  Pb is the apparent density measured (in g / cff 3) of a specimen; the "flexural strength (kg / cm 2)" of a porous shaped article to

  carbon base is determined in accordance with the Japanese industrial standard

  (JIS) K-6911/1970 using a specimen having a dimension of x 10 x 2.5 mm, and the "average pore diameter (μm)" of a specimen is measured using a porosimeter to mercury (manufactured by Carlo Erba Strumentazione, Italia) The specific gas permeability Qs

  (ml / cm hr mm Aq) "is determined as follows: a cylindrical specimen

  90 mm diameter and 1 mm thick is cut from the substrate to be measured, the circumferential side surface of the specimen is treated with a thermosetting resin so that the gas can not pass through. The two longitudinal end surfaces of the specimen are then placed between two tubes of gas

  cylinders whose edges bear a seal, a predetermined amount of air

  minus (10 l / min) is introduced at one end of the specimen to the other end which is open to the atmosphere The loss of pressure between the two ends of the specimen is measured using a manometer

  disposed upstream of the gas tube and the gas permeability Q 5 is determined

  then born by the following equation: 6 x t x 104 s 50,24 x ap where: Ap is the measured pressure loss (mm Aq); and,, 24 cm 2 represents the actual area to be measured for a circle of

mm diameter.

  In addition, the "volume resistivity p (Pcm)" is determined as follows: the two ends of a sample are coated with an electroconductive coating material and the electrical resistance existing between the two ends of the specimen is measured in accordance with the standards of Japan Rubber Association (SRIS) 2301-1969, and the volume resistivity is then calculated by the following equation: PV = R wt / Z in which: R is the resistance (n) measured between the ends of the sample; ú (cm) is the length of the sample to be measured; and,

  w (cm) and t (cm) are horizontal and vertical lengths respectively

  defining the cross section of the sample.

EXAMPLE 1

  A homogeneous mixture was prepared by mixing 40% by weight of short carbon fibers having an average fiber length of 0.45 mm and an average fiber diameter of 12 μm (manufactured by Kureha Chemical Industry Co, Ltd., M 104 S). 30% by weight of granulated polyvinyl alcohol having a mean particle diameter of 180 μm (manufactured by Nippon Synthetic Chemical Industry Co., Ltd) as a pore regulator and 30% by weight of phenolic resin (manufactured by Asahi Organic Material) KK) serving

of binder.

  The mixture is introduced into a mold for compression molding.

  On the introduced mixture is placed a comb-shaped polyvinyl alcohol as a material for forming the elongate holes and then 253407 t

  adds homogeneous mixture to the material intended to form the holes.

  The introduced materials are pressed at 1400 C and 50 kg / cm 2

  about 30 minutes and then calcined at 2000 C for about

1 hour.

  The obtained electrode substrate having a length of 300 mm, a width of 300 mm and a thickness of 2 mm has elongated holes which have

  a circular cross section of about 0.8 mm in diameter, the

  between two adjacent holes being 5 mm Physical properties

  of the substrate are shown in Table 2 below.

TABLE 2

  Note: 1) including holes 2) holes to one of the surfaces, ie half the thickness of the substrate (approximately 1 mm)

3) excluding holes.

EXAMPLE 2

  A homogeneous mixture intended to form a porous layer (the same

  that in Example 1) is introduced into a mold for compression molding.

  A material for obtaining holes (the same as in Example 1) is placed on the mixture and after that the mixture intended to form

  a porous layer is returned to the mold.

  A homogeneous mixture intended to form a dense layer prepared by mixing 20% by weight of short carbon fibers (the same as in Example 1), 20% by weight of fine granules of activated carbon having an average diameter of 300 μm ( manufactured by Kureha Chemical Industry Co., Ltd.), 40% fine coal precursor powder having an average diameter of 40 μm (manufactured by Kureha Chemical Industry Co., Ltd., MH) and 20%

  by weight of phenolic resin (the same as in Example 1) are introduced

  in the mold above the mixture intended to form a layer. Apparent density 0.51 g / cm 3 Porosity 1) 74 Specific permeability to

gas 2) 120 ml / cm hr mm Aq.

  Flexural strength 142 bar Volume resistivity 27 x 10-3 52 cm Average pore diameter 3) 31 i m

  The materials introduced are pressed at 140% C and 50 bar

  about 30 minutes and cured at 800% C for about 1 hour.

  the surface of the dense layer of the cured product is impregnated with a solution

  After drying, the product is cured again at 800 ° C. for about 1 hour. The impregnation and curing steps are repeated three times, after which

  the substrate is calcined at 2000 ° C for 1 hour.

  The obtained substrate having a length of 300 mm and a width of 300 mm comprises a porous layer having holes whose section

  transversal is approximately circular, their diameter being

  0.8 mm thick and a dense layer that can be used as a sheet

of seperation.

  The substrate has the physical properties shown on the chart

3 next.

TABLE 3

  Dense layer Porous layer Thickness (mm) 0.5 1.5 Bulk density (g / cm 3) l) 1.47 0.58 Porosity (%) 1) 9 64 Specific permeability to 0902 100 gases (ml / cm hr mm Aq) Average pore diameter (p) 30 Flexural strength bars 240 Volume resistivity (Ocm) 16 x 10-3

Note: 1) excluding holes.

EXAMPLE 3

  A graphite plate having a thickness of 1 mm is used

  as a material for forming a dense layer A composite electrode substrate

  carrying a dense layer and a porous layer having holes is prepared in the same manner as in Example 2 The holes have a section

  approximately circular cross-section of about 0.8 mm in diameter.

  The substrate has the physical properties shown in Table 4.

TABELEAU 4

Note: 1) excluding holes.

EXAMPLE 4

  Using a graphite sheet having a thickness of 0.3 mm (manufactured by UCC, GRAFOIL) instead of the material used to form a dense layer according to Example 2, an electrode substrate is prepared.

  similarly to that of Example 2.

  The resulting substrate has holes having a cross-section

  dirty approximately circular about 0.8 mm in diameter and the

  properties shown in Table 5.

TABLE 5

  Dense layer Porous layer Thickness (mm) 0.3 1.5 Apparent density (g / cm 3) 1) 1.12 0.58 Porosity (%) 1) 64 Specific permeability to gases (ml / cm hr mm Aq) 1 0.01 115 Average pore diameter (p) 30 Flexural strength bars 280 Volume resistivity (çcm) 14 x 10-3

Note: 1) excluding holes.

* Dense layer Porous layer Thickness (mm) 1) 1.0 1.5 Bulk density (g / cm 3)) 1.8 0.58 Porosity (%) 1) 1.0 64 Specific permeability at <0, 01 110 gas (ml / cm hr mm Aq) Average pore diameter (p)) Resistance to reflection bars 280 Volume resistivity (fcm) 14 x 10-3

EXAMPLE 5

  The same mixture intended to form a porous layer as in the example

  Fig. 1, the same hole-forming materials as in Example 1 and the mixture for forming a porous layer are introduced in this order into a compression mold. Next, a 0.6-mm carbon plate thickness (manufactured by Toyo Carbon Co, Ltd) as a material for making a dense layer is reported on the

  On the carbon plate, the mixture of

  to form a porous layer, the material intended to form the holes

  and the mixture for forming a porous layer, in the order indicated.

  The materials are pressed at 140 ° C. and 40 bar for 20 minutes.

  After post-curing the product shaped at 130 C for 2 hours, the temperature is gradually increased to 700 C at the rate of

   C per hour and the shaped product is then calcined at 2000 ° C.

1 hour.

  The resulting electrode substrate has the structure as

  presented by reference 11 in FIG. 4, and the porous layer possesses

  holes having an approximately circular cross-section of

  Viron 0.8 mm in diameter The substrate has the physical properties

represented in Table 6.

TABLE 6

Note: 1) excluding holes,

  2) a layer represented by 8 in FIG.

EXAMPLE 6

  Using a mixture to form a dense layer (the same Dense layer Porous layer Thickness (mm) 0.6 1.5 2) Bulk density (g / cm 3) 1) 1.47 0.58 Pbrosity (%) 1 ) 9 64 Specific gas permeability (ml / cm hr mm Aq) 0.02 110 Average pore diameter (p) 1) Resistance to bending bars 250 Volume resistivity (Scm) 10 x 10-3

  in Example 2) instead of the carbon plate used in the example

  5, an electrode substrate is prepared in the same way as in the example

  The resulting substrate has the physical properties represented

in Table 7.

TABLE 7

  Dense layer Porous layer Thickness (mm) 0.6 1.5 Apparent density (g / cm 3) 1.47 0.58 Porosity (%) 1) 9 64 Specific gas permeability (ml / cm hr mm Aq) 0, 02 110 1) Average pore diameter (ft) 30 Flexural strength bars 240 Volume resistivity (52 cm) 10 x 10-3 Note: 1) excluding holes

  2) a layer represented by 8 in FIG.

EXAMPLE 7

  The same method as in Example 5 is carried out except that a 0.3 mm thick graphite sheet is used (the same as

  in Example 4) to form a dense layer.

  The resulting electrode substrate has holes having an approximately circular circular cross section of about 0.8 mm in diameter in the porous layer. Physical Properties of the Substrate

are shown in Table 8.

TABLE 8

  Dense layer Porous layer Thickness (mm) 0.3 1.5 2) Bulk density (g / cm 3) 1) 1.12 0.58 Porosity (%) 1) -64 Specific gas permeability (ml / cm hr mm) Aq) <0.01 115 Note: 1) excluding holes

  2) a layer shown at 8 in FIG.

EXAMPLE 8

  The same mixture intended to form a porous layer as in the example

  1, the same material for forming the holes as in Example 1, and the mixture for forming a porous layer are introduced in this order into a mold for compression molding. A graphite sheet of 0.6 mm. thickness greater than approximately 50 mm in total (25 mm for one side) that the inner size of the mold is placed on the

  mixture The materials are pressed at 140 C and 40 bar for 20 minutes.

  After pressing, the shaped product is removed from the mold and in the same mold is introduced the mixture intended to form a porous layer, the material intended to form the holes and the mixture intended to form a mold.

  porous layer in the order shown.

  The shaped product obtained above is placed in such a way that the graphite sheet is adjacent to the newly introduced materials

  and all the materials are pressed at 140 ° C and 40 bar for 20 minutes.

  After curing at 130 ° C. for about 2 hours, the temperature

  is gradually increased at a speed of 100 C per hour

  at 700 ° C. and then calcining at 2000 ° C.

1 hour.

  The electrode substrate obtained has a structure such as

  shown in Fig. 5 and holes in the porous layer having an approximately circular cross-section of about

  0.8 mm The physical properties are shown in Table 9.

TABLE 9

  Dense layer Porous layer Average pore diameter (y) 1) 30

  Flexural strength (kg / cm 2) 280 -

  Volume Resistivity (Scm) 14 x 10-3 Dense Couchie Porous Layer Thickness (mm) -0.6 1.5 2) Bulk Density (g / cm 3) 1) 1.12 0.58 Porosity (%) 1) 64 Note: 1) excluding holes

  2) a layer shown at 8 in FIG.

EXAMPLE 9

  This example indicates the method of preparation of the elec-

  trode shown in Figure 7 while referring to Figure 8.

  A graphite sheet 17 having a thickness of 0.3 mm is

  in a compression mold (shown as 20 and 21) as shown in FIG. 8 A mixture 18 for forming a porous layer 8, a material 19 for forming the holes 7, and the mixture 18 for to form a porous layer 8 are reported on the graphite sheet 17, the materials being the same

  than in Example 8 respectively.

  The materials are pressed at 1400 C and 40 bar for 20 minutes.

  Another shaped product is prepared in the same way as

  above. After coating with a carbon-based glue based on

  phenolic sine the graphite sheet 15 surrounding the products conforming

  When obtained, these two shaped products are glued on a 0.3 mm thick graphite sheet 16 (GRAFOIL) interposed between them, the graphite sheet 16 having a size greater than 50 mm in total (25 mm on each side). ) to the outer size of the shaped products, and the shaped products being arranged so that the holes located in each

  porous layer on both sides of the graphite sheet have a direct

  perpendicular to each other.

  The resulting substrate is post-cured at 1300 C for about

  2 hours and after increasing the temperature gradually to the

  From 100 IC per hour to 7000C, the substrate is calcined at 2000C for 1 hour. The electrode substrate obtained has the structure shown in Figure 7 and the holes 7 in the porous layer 8 have a section Dense layer Porous layer Specific gas permeability (ml / cm hr mm Aq) 0.02 110 Average pore diameter (y 1)) 30 Flexural strength (kg / cm 2) 180 Volume resistivity (52 cm) 10 x 10-3 approximately circular cross-section having a diameter of about 0.8 mm The physical properties of the substrate are represented on the

table 10.

TABLE 10

  s NI Dense layer Porous layer Thickness (mm) 1.1 1.5 3) Bulk density (g / cm 3) 1) 1.10 0.58 Porosity (%) 64 Specific gas permeability (ml / cm hr mm Aq ) 0.02 110 Average pore diameter (p) 1) Flexural strength bars 200 Volume resistivity (Qcm) 10 x 10-3 Note: 1) excluding holes 2) two sheets of graphite 3) one layer shown in graphite sheet 16

8 in Figure 7.

Claims (33)

  A porous carbon-based electrode substrate for a fuel cell, characterized in that it has holes extending from one side to the opposite side of the substrate, the holes being arranged parallel to one another and parallel to the surface of the electrode. Substrate according to claim 1, characterized in that the   holes are made near the center of the substrate thickness.   Substrate according to claim 1 or 2, characterized in that the holes have a circular cross section having a diameter from 0.5 to 3.0 mm.   Substrate according to any one of claims 1 to 3,   characterized in that its average bulk density is 0.3 to 1.0   and its gas specific permeability is not less than 20 ml / cm hr. mm Aq.   Substrate according to any one of claims 1 to 4,   characterized in that less than 60% of the pores have a diameter of 10 to p In.   6. Carbon electrode substrate for a fuel cell,   characterized in that it comprises a dense layer and a porous layer pos-   sedant holes which extend from one side to the opposite side of the porous layer, holes arranged parallel to each other and parallel on the surface of the electrode.   Substrate according to Claim 6, characterized in that the   holes are made near the center of the thickness of the porous layer.   Substrate according to claim 6 or 7, characterized in that   that the holes have a circular section having a diameter of 0.5 to 3.0 mm.   Substrate according to any of claims 6 to 8,   characterized in that the porous layer has an average bulk density of 0.3 to 1.0 g / cm 3 and a gas-specific permeability that is not less than 20 ml / cm hr mm Aq.   Substrate according to any of claims 6 to 9,   characterized in that less than 60% of the pores of the porous layer have a diameter of 10 to 100 p.   Substrate according to any of claims 6 to 10,   characterized in that the dense layer has an average bulk density of not less than 1.0 g / cm 3 and a specific permeability to   gas not exceeding 0.2 ml / cm hr mm Aq.   Substrate according to any of claims 6 to 11, 23 22534071   characterized in that the thickness of the dense layer does not exceed   half of the total thickness of the substrate.   Substrate according to any of claims 6 to 12,   characterized in that the dense layer is a graphite sheet.   Carbon-based electrode substrate for a fuel cell, characterized in that it comprises a dense layer and two porous layers, each porous layer being attached to each surface of the   dense layer and having holes extending from one side to the opposite side   from the porous layer and are arranged parallel to one another   and parallel to the surface of the electrode.   Substrate according to Claim 14, characterized in that   the holes are made near the center of the thickness of the layer   reuse. Substrate according to Claim 14 or 15, characterized in that the holes have a circular cross-section having a diameter of 0.5 to 3 mm.   Substrate according to any one of claims 14 to 16,   characterized in that the porous layer has an average bulk density of 0.3 to 1.0 g / cm 3 and a gas specific permeability that is not less than 20 ml / cm hr mm Aq.   18. Substrate according to any one of claims 14 to 17,   characterized in that not less than 60% of the pores of the porous layer have a diameter of 10 to 100 p.   Substrate according to any one of claims 14 to 18,   characterized in that the dense layer has an average bulk density of not less than 1.0 g / cm 3 and a specific permeability to   gas not more than 0.2 ml / cm hr mm Aq.   Substrate according to any one of claims 14 to 19,   characterized in that the thickness of the dense layer is not greater   at half the total thickness of the substrate, preferably from 0.1 to - 3.0 mm.   Substrate according to any one of claims 14 to 20,   characterized in that the dense layer is a graphite sheet.   22. Carbon-based electrode substrate for a fuel cell   characterized in that it comprises an extended dense layer and two   porous layers, each porous layer being reported on each   facing the dense layer and having holes which extend from one side to the opposite side of the porous layer and are arranged parallel to the   to each other and parallel to the surface of the electrode.   23. Substrate according to claim 22, characterized in that the holes are made near the center of the thickness of the porous layer. Substrate according to claim 22 or 23, characterized in that the holes have a cross-section having a diameter from 0.5 to 3 mm.   25. Substrate according to any one of claims 22 to 24,   characterized in that the porous layer has an average bulk density of 0.3 to 1.0 g / cm 3-and a gas-specific permeability that is not less than 20 ml / cm hr mm Aq.   26. Substrate according to any one of claims 22 to 25,   characterized in that not less than 60% of the pores of the porous layer have a diameter of 10 to 100 p.   Substrate according to any of claims 22 to 26,   characterized in that the dense layer has an average bulk density of not less than 1.0 g / cm 3 and a specific permeability to   gas not more than 0.2 ml / cm hr mm Aq.   28. Substrate according to any of claims 22 to 27,   characterized in that the thickness of the dense layer is not greater than half the total thickness of the substrate, preferably from 0.1 to 3.0 mm.   Substrate according to any of claims 22 to 28,   characterized in thatthe dense layer is a graphite sheet.   Substrate according to any one of claims 22 to 29,   characterized in that it further comprises another dense sheet for   seal the side of the porous layer parallel to the holes.   Substrate according to claim 30, characterized in that   the other dense sheet is a graphite sheet having a cross-section   Versale U-shaped Substrate according to claim 30 or 31, characterized in that   that the other dense leaf is glued to the dense layer.   Substrate according to any of claims 22 to 32,   characterized in that it further comprises a peripheral seal on the side of the porous layer, said seal extending parallel to the holes,   and a gas distributor disposed on the side of the porous layer dicular to the holes.