JPS60189168A - Porous plate for fuel cell electrode - Google Patents

Abstract

PURPOSE:To obtain a porous plate having high porosity, high mechanical strength, good heat conductivity and electric conductivity by mixing, kneading, crushing, molding then baking phenol formaldehyde resin, carbon fiber, natural organic fiber. CONSTITUTION:5-50wt% phenol formaldehyde resin, 50-94wt% carbon fiber having a diameter of 5-20mum and a length of 0.1-3.0mm., and 1.0-10.0wt% natural organic fiber having a size of 10-150 mesh are mixed and unifirmly dispersed, then volatile liquid dispersing medium is added to form slurry. The slurry is kneaded and heated with a kneader. After the liquid dispersing medium is vaporized, the mixture is cooled to solidify, then crushed with a high speed crusher. The crushed material is uniformly filled in a mold and cured under appropriate temperature and pressure. A molding obtained is subjected to carbonizing treatment and graphitizing treatment to obtain a porous plate for fuel cell electrode.

Description

Detailed Description of the Invention 1 Technical Field of the Invention 1 The present invention relates to a porous plate used as an electrode of a fuel cell, and particularly to a porous plate used as an electrode of a fuel cell, and particularly to a porous plate used as an electrode of a fuel cell. The present invention relates to a porous plate that makes it possible to obtain one electrode.

[Technical Background of the Invention] A fuel cell is a device that directly converts the chemical energy contained in fuel into electrical energy. This fuel cell is
Usually, a pair of porous electrodes is placed with an electrolyte in between, and a gaseous fuel such as hydrogen is brought into contact with the back of one electrode.
An oxidizing agent such as oxygen is brought into contact with the back surface of the other electrode, and the electrical energy generated by the electrochemical reaction that occurs is extracted from the pair of electrodes.

In this case, the electrolyte may be a molten salt, an alkaline solution, an acidic solution, etc., but here we will explain its principle using a typical fuel cell that uses phosphoric acid as an electrolyte. The figure shows the basic structure of this type of fuel cell. In the figure, the electrolyte layer 1 is a fibrous sheet or mineral powder impregnated with phosphoric acid.

Further, 2 and 3 are a pair of porous (carbonaceous) electrodes, an anode and a cathode, arranged with the electrolyte layer 1 in between.
A platinum catalyst is applied to the area in contact with the electrolyte layer 1. Further, 4 is a chamber through which a gas containing hydrogen flows, and 5 is a chamber through which an oxidizer gas such as oxygen (usually air) flows.

In such a fuel cell, hydrogen flowing into the chamber 4 diffuses through the voids of the seven-node electrode 2 and reaches the catalyst. Here, the hydrogen gas is dissociated into hydrogen ions and electrons due to the action of the catalyst. The reaction formula is (-12→21-1+ →2e...
...(1). Then, the hydrogen ions enter the electrolyte layer 1, and due to the effect of J on the electromotive force and temperature diffusion,
It migrates towards the nokosode electrode 3. On the other hand, the electrons dispersed due to the dissociation of hydrogen gas flow into the anode electrode 2, and the electrode 2 is negatively charged. In addition, at the cathode electrode 3, the hydrogen ions that have migrated from the 7-node electrode 2 side are supplied to the chamber 5 as an oxidizing agent, and are further fed to the cathode electrode 1.
The following reaction occurs on the surface of the catalyst: the IC oxygen that has dispersed through the empty space of the cell 3, and the electrons that have passed through the external power load from the anode electrode 2, performed work, and returned to the cathode 3 of the battery. zu.

4 Li" 14 e 102-+ 2 l→20-・
(2) The reaction in which hydrogen is oxidized to water, and the chemical energy at this time becomes electrical energy, completing the entire reaction as a battery that can generate electrical energy in an external electrical load.

A fuel cell as described above is usually constructed by stacking 11 hills. Interconnector type unit cells have traditionally been known, but recently, the Rivi 4-electron! 4! Cedar was invented and research is underway to put it into practical use.

FIG. 2 is a perspective view showing the configuration of a unit hill of an electrode type with a beam. 6 indicates a fuel cell stack.

Reference numerals 7 and 8 each represent an electrode, which is made by sintering at high temperature a carbonaceous porous material that facilitates reaction diffusion and requires acid resistance. The electrodes 7 and 8 are provided with a plurality of rib grooves 9 and 10, which form channels through which the reaction gas flows, so that they are perpendicular or intersect with each other as shown. As reaction gases, fuel gas (hydrogen) is flowed on the anode side, and oxidizing gas (air) is flowed on the cathode side.Platinum-based catalysts 11 and 12 are coated on the surface opposite to the rib groove side of the 1° electrode.
A 71-lix 13 forming an electrolyte layer is disposed between the electrodes t. Reference numeral 14 denotes a parator which prevents the mixing of hydrogen and oxygen and also serves as a current collecting plate for the unit cell W4 layer +4, and is made of an airtight and conductive material such as a carbon sheet. Arrows 15 and 16 indicate the flow of hydrogen gas and air, respectively.

The unit hill is constructed as described above, and is connected to the separator 14.
A plurality of them are stacked together with a current collector plate 17, an insulating plate 18, and one manifold fixing plate provided at each end of the stacked body, and are tightened in the stacking direction. In this way, a fuel cell stack is constructed.

FIG. 3 is a perspective view schematically showing the fuel cell.

In the figure, 20 and 20a are, for example, a hydrogen gas supply manifold and a supply pipe, respectively, and 21.2
1a is a hydrogen gas discharge manifold and a discharge pipe. Reference numerals 22 and 22a indicate an air supply manifold and a supply pipe arranged at right angles to the above, and 23 and 238 indicate an air discharge manifold and a discharge pipe. The upper and lower ends of these manifolds are connected via gaskets 24 to manifold fixing plates 1 located at the upper and lower ends of the side surfaces of the fuel cell stack.
9, for example, by bolts 25.

The whole is housed in a closed container 2b shown by a chain line in the figure, and an inert gas 27 such as N2 is sealed and filled in the container at a pressure slightly higher than that of the reactant gases □hydrogen and air. This is because hydrogen and air leak into the tank and do not mix.A fuel cell assembled in this way has pipes 208
．． By continuously supplying hydrogen gas and air from 22a, respectively, electrical output is obtained from terminals 28 and 29.

In this ribbed electrode combustion cell, the electrode material must have sufficient reactive gas permeability for the reactive gases to reach the respective catalyst layers, and must have high electronic conductivity.
It is required to be a porous material that has excellent corrosion resistance, has a predetermined pore space for electrolyte retention, is small in thickness, and can withstand the load due to laminated mounting.

[Problems with back entertainment technology] By the way, conventional porous plates for electrodes with ribs have been produced by vapor-depositing carbon onto carbon fibers.

However, since this porous plate uses a vapor deposition process, there are technical problems such as the manufacturing process is complicated and the required equipment is bulky. Moreover, this porous material has electrical conductivity and
Although the thermal conductivity is good, since the carbon Mli is mixed and bonded to each other to maintain strength, if the required porosity is expected, it will result in undesirable culm and low strength.

To create a porous plate that does not involve such a problematic vapor deposition process, a uniform wire mesh is installed at the bottom, and a thermosetting resin is dissolved in a large amount of organic solvent in a 1C tank to disperse carbon fibers. There are some that are made using '. ) The J-bon fibers eventually accumulate in the form of a mat on the wire mesh at the bottom, so next, the wire mesh-like deposits are pulled up from the tank, dried, shaped, and fired to form a porous structure. A plate is formed.

However, when measuring the electrical conductivity and thermal conductivity of this type of porous plate for fuel cell electrodes, there is a difference in the thickness direction and the lateral direction, and a decrease in the properties in the thickness direction is observed. This phenomenon results in a decrease in electrical conductivity and thermal conductivity in the thickness direction, which is most necessary for a porous plate for a fuel cell electrode, because the carbon fibers are aligned in the lateral direction. Also, even during machining, since the carbon fibers are aligned on one side, a peeling phenomenon occurs, which seriously reduces the yield.

[Object of the Invention] The present invention was proposed in order to solve the problems of the prior art as described above. An object of the present invention is to provide a porous plate for a fuel cell electrode that has excellent phosphoric acidity, dimensional stability, and machinability.

[Summary of the Invention] The porous plate for fuel cell electrodes of the present invention contains 5 to 50 fNffi% of non-[norformaldehyde resin] and has a diameter of 5 to 50 fNffi%.
20 μm 1 fiber length 0, 1-3, 0 tnm carbon lJi miscellaneous 50-94 weight%, 10 mesh PA
SS ~ 150 mesh loN natural fi II u & navy blue mixed, kneaded, crushed, molded, baked and formed! ,: something.

[Embodiments of the Invention] The phenol formaldehyde resin used in the present invention may be a novolac type resin obtained with an acid or alkali catalyst, or a resol type resin, or a mixture thereof.

Similarly, the diameter is 5 to 20 μm, the fiber length is 0.1 to 3.0 m
Examples of carbon fibers include big-type carbonaceous carbon fibers, pitch-type graphitic carbon fibers, and PAN-type carbon fibers.

Also 10 mesh PA S S ~ 150 mesh ON
Examples of natural organic fibers include cotton wool, vegetable lerulose, flax, hemp, jute, and fluff powder.

Next, regarding the blending ratio of the porous plate for fuel cell electrodes, the phenol formaldehyde resin is 5 to 50% by weight, the diameter is 5 to 20 μm, the fiber length is 0.1 to 3.0 m.
Natural organic fiber with carbon tat4 of 50 to 94 wt% and 10 mesh PASS to 150 mesh ON is 1.
0~10.0! The amount of Ii is preferably %.

If the content of 2-nonol-11 aldehyde resin is less than 5%,
It is not effective as a binder between the carbon strip and natural organic fibers, and its mechanical properties deteriorate, making it unsuitable for practical use.If it exceeds 50% by weight, it shrinks significantly during the firing process and cracks occur, making it unsuitable for practical use. There is no note. Diameter 5-20t
t m, II 1 [a 0 , 1-3. Qmm carbon fiber M If it is less than 50% by weight, it has no effect on thermal conductivity or electrical conductivity, and if it exceeds 94% by weight, the mechanical properties deteriorate and it is not suitable for practical use.

10 mesh I) A S 8-150 mesh If the natural organic fiber is less than 1.0% by weight, the apparent density of the finished material will be 0.5Q/C',C: It is not suitable for practical use, and if it exceeds 10% by weight, it will shrink significantly during the firing process and cracks will occur, making it unsuitable for practical use.

1. The most preferable range is saw. 10-35% by weight of norformaldehyde resin, diameter 8-15μrV
1. Carbon fmN with fiber length 0.4 to 1.5 mm is 55
~87FMm%, 50rty: 1PAS~120mesh ON natural 41-machine fibers are 3-8%.

Next, the apparent density of the material in the crushing process is 0.5 g/cc.
The following is preferable, and if it is more than 0.5 g/QC, the porosity of the porous plate for fuel cell electrode will become low, and it will not be suitable for practical use. In addition, the sieve used to uniformly charge the C1 material into the mold in the molding process is JIS standard Fl.
The ratio of U sieves of 10 to 42 mesh is very high, and the I; LjrA ratio is not good for sieves of 10 mesh or less, and there are variations in the amount of lumber depending on the location. When using a sieve with a mesh size of 42 or more, the material does not pass through easily and more than half of the material remains on the sieve (1).It is not suitable for practical use because the specified weight cannot be charged.

In order to obtain the porous plate for fuel cell electrodes of the present invention, phenol formaldehyde MA fat pulverized to an appropriate particle size,
Carbon Sli lit with a diameter of 5.~20/7 m and a length of 0°'1~3.0 mm,
10 mesh 1] ΔSS ~ 150 mesh ON natural stone i fibers are mixed at room temperature with a release agent and a lubricant as needed to disperse them uniformly, and then an evaporative liquid dispersion medium is added (in the form of a slurry). Then heat and knead with a kneader.

After volatilizing the evaporative liquid dispersion medium, the cold JJ
The material is crushed in a high-speed rotating crusher to obtain a molding material with a density of 0.5 / CG or less. Thereafter, a 10-42 mesh JIS standard sieve is placed on a suitable mold, and the material is uniformly charged into the mold through the standard sieve. Next, the standard sieve is removed from the mold, and an appropriate capping pressure is applied to cure the mold to obtain a phenolic resin molded product containing carbon fibers and natural organic fibers. By firing this molded product, it undergoes carbonization and graphitization treatment to create a porous plate for fuel cell electrodes.

The porous plate for fuel cell electrodes of the present invention has high porosity, mechanical strength, thermal conductivity, and electrical conductivity of 17 t! It is characterized by excellent phosphoric acid resistance, dimensional stability, and machinability.

EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited by these Examples.

Comparative Example - Luzol type phenol formaldehyde resin was dissolved in methyl alcohol and concentrated to 20% concentration. Next, resol-type phenol formaldehyde tree 1111 diluted to 20 mm% with methyl alcohol was put into a tank whose bottom part was evenly spread with 20 meshes of wire mesh. In this solution, 18 μm in diameter and 1 fiber in length were added. Pitch-based carbonaceous carbon fibers of Qmm are introduced and dispersed, and deposited on the lower wire mesh so that the thickness of the mat is about 5 rTl fi1. Next, the matte deposit together with the wire mesh was pulled out of the tank, dried in a dryer at 80°C for 1 hour, and then cured for 5 minutes by applying a pressure of 50 kg/cm2 in a mold heated to 170°C. A phenolic resin molded product is obtained. This molded product was subjected to carbonization and graphitization treatment, and a porous plate for fuel cell electrodes was made with bone/j0 characteristic values as shown in Table 1, with high porosity, phosphoric acid resistance, and mechanical strength. Although it is excellent, there is a difference in specific resistance in the thickness direction and length direction,
The resistivity in the thickness direction, which is most important, was large, and a peeling phenomenon occurred during the first machining process, making it unsuitable for practical use.

Comparative Example-2 Novolac-type norformaldehyde resin (contains hexamethylenetetramine as a curing agent) 55' ff1
．． 4R%, diameter 14. ! :Bzm1 fiber length 0.7m1
Vidge-based graphite carbon fiber of η [44.5% by weight, 50
Mesh PASS ~ 100 mesh and ON vegetable cellulose 0.5% by weight were mixed at room temperature, methyl alcohol was added to form a thriller, and the mixture was heated and kneaded in a mixer at 100°C to volatilize the methyl alcohol. Afterwards, the material is crushed in a high-speed rotating crusher so that the maximum diameter is 1.0φ or less.The apparent density of this material is 0.600/c.
It was c.

A 16-mesh JIS standard sieve is placed on a suitable mold for this material, and the material is uniformly charged into the mold through the standard sieve.

Next, remove the standard sieve from above the mold and apply 50kQ/cm to the material.
After IC, the mold was heated to 170°C and cured for 5 minutes. Contains carbon fiber and vegetable cellulose 7
A 1-hole resin molded product is obtained. This molded product was carbonized and graphitized to obtain a porous plate for fuel cell electrodes. These characteristic values are shown in Table 1, and are phosphoric acid resistance and electrical conductivity of 1?
1.Although it has excellent thermal conductivity, it does not have sufficient porosity, and cracks occur everywhere due to large shrinkage during the firing process, making it unsuitable for practical use.

Comparative Example-3 4% by weight of resol type phenol formaldehyde resin,
Diameter 18. Ottm, mttll length 0.4 mm pitch-based carbonaceous carbon fiber 95X (i state%, 50 mesh l
) ASS ~ 100 mesh ON vegetable cellulose 1% by weight is mixed at room temperature, methyl alcohol is added to form a slurry, and the mixture is heated and kneaded in a mixer at 100°C.
After evaporating the methyl alcohol and performing IC, the material is pulverized using a high-speed rotating pulverizer so that the maximum diameter of the material is 0.7φ or less.

11) The density of the material at this time was 0.420/cc.

Using a rubber spatula, the material was uniformly placed into a suitable mold. After applying a pressure of 50 kg/cm2 to the material and performing IC, the mold was heated to 170°C and cured for 5 minutes to form carbon fibers.
Phenolic resin molded product containing vegetable cellulose (η,
This molded product was carbonized and graphitized to obtain a porous plate for fuel cell electrodes.

The characteristic values are shown in Table 1, and the phosphoric acid resistance, thermal conductivity, electrical conductivity, etc. are excellent, but there are variations in porosity depending on the measurement location, and the compressive strength is low. It had several drawbacks and was not suitable for practical use.

Example-1 Novolac-type phenolformino? Le f human resin (contains hexamethylene lenticin-lamin as curing agent) 13% by weight, diameter 12.5 μm, l J & H length 0.2-・1, Q mm
PAN-based carbon fiber 84% by weight, 80 mesh RA
3% by weight of vegetable cellulose from SS to 100 Metsushiko ON
are mixed at room temperature, methyl alcohol is added to make a slurry, heated and kneaded in a mixer at 100℃, and after the methyl alcohol has been evaporated, the maximum diameter of the material is reduced to 0゜7φ using a high-speed rotating crusher. The apparent density of the material at this time was 0.40 g/cc.

This material is passed through a 20 mesh/1 JIS standard sieve onto a suitable mold, and the material is uniformly charged into the mold through the standard sieve.

Next, remove the standard sieve from above the mold and apply 50kq/cm to the material.
After applying pressure 2, the mold was heated to 170°C and cured for 5 minutes, and 1 q of phenol resin molded product containing carbon fiber and vegetable cellulose was produced. This molded article was carbonized and graphitized to obtain a porous plate for a fuel cell electrode. These characteristic values are as shown in Table 1, with high porosity and mechanical image 1.
All showed excellent values for electrical conductivity, etc.

Example-2 Resol type fluoroformaldehyde resin 32% by weight
14.5μm in diameter, 0.7mrn in fiber length, 3'FA lead carbon fiber 60%, 50mesh: I
PASS~80 mesh ON vegetable cellulose 8 weight 5 is mixed at room temperature, methyl alcohol is added to make a slurry, heated and kneaded in a Hi kneader at 100 ° C. After evaporating the methyl alcohol, Grind the material using a high-speed rotating grinder so that the maximum diameter of the material is 0°7φ or less. The apparent I'J density of the material at this time was 0.36Q/CC.

A 32-mesh JIS standard sieve is placed on a suitable mold for the monthly profit, and the monthly profit is evenly charged into the mold through the standard sieve.

Next, remove the standard sieve from above the mold and apply 50kQ/C to the material.
After applying a pressure of m2, the mold was heated to 170°C and cured for 5 minutes to form a carbon fiber/vegetable hillulose-filled 71
Obtain a resin molded product. This molded product was carbonized and graphitized to obtain a porous plate for a fuel cell electrode. The characteristic values are as shown in Table 1, and the porosity was high and the mechanical strength, electrical conductivity, etc. were all excellent, with a value of 1.

[Effects of the Invention] As described above, the porous plate t of the present invention has the following advantages: 21. The carbonization and graphitization method by firing is used, which is easy to manufacture, without the need for a lengthy vapor deposition process. f! This completely eliminates the problem of porous plates caused by firing, which had the problem of a decrease in the value of 1.

Therefore, by incorporating the porous plate of the present invention into a fuel cell as a ribbed electrode plate, it has excellent properties such as gas diffusivity, electron conductivity, corrosion resistance, electric PR quality retention function, and 16 strength withstand laminated fastening load. It becomes possible to obtain a fuel cell with high fuel efficiency.

[Brief explanation of the drawing]

FIG. 1 is a principle diagram of a fuel cell, FIG. 2 is an exploded perspective view of a fuel cell having IJ ribbed electrodes, and FIG. 3 is a perspective view schematically showing the structure of the fuel cell. DESCRIPTION OF SYMBOLS 1... Electrolyte layer, 2... Anode electrode, 3... Cathode electrode, 7.8... Electrode, 9.10... Rib groove, 11° 12... Platinum-based catalyst, 13. ...71-Rix, 14... Separator, 17... Current collector plate, 1
8... Insulating plate, 19... Manifold fixing plate. Figure 1 H2o = Figure 2 Figure 3

Claims (2)

[Claims] (1) 5 to 50% by weight of phenol formaldehyde resin, diameter 5 to 20 μm, fiber length 0.1 to 3.0 rT
50-94% by weight of 1rT1 carbon fiber, 10 mesh RASS - 150 mesh ON natural organic I! 1. A porous plate for a fuel cell electrode, which is made of fibers and is formed by mixing, cross-wiring, crushing, molding, and firing the materials. (2) The apparent density of the crushed material is 0.5Q/CC
A porous plate for a fuel cell electrode according to claim 1, which has the following C.