JPS61233972A - Formation of fuel cell matrix - Google Patents

Abstract

PURPOSE:To achieve high efficiency by reduction of man-hour, safety and harmlessness by bonding the mixture of matrix base material and PTFE powder on a catalyst layer by electrostatic deposition, and by baking the PTFE. CONSTITUTION:The mixture powder 8 of matrix material and PTFE is placed between a positive electrode 6 and a negative electrode 7 arranged in a box 5. When high voltage is applied across the electrodes 6 and 7, the mixture powder 8 is negatively charged and vibrated up and down. An electrode substrate 1a coated with catalyst layer 2a is arranged in the upper part of the box 5 and the earth 9 is set. The line of electric force 10 is produced between the negative electrode 7 and the catalyst layer 2a. By blowing air form an air blasting hole 11, negatively charged mixture powder 8 flys along the line of electric force 10 toward the substrate 1a and the mixture powder 8 deposites on the catalyst layer 2a. A gas diffusion electrode comprising the catalyst layer 2a bonded with the mixture powder 8 and the electrode substrate 1a is heated at a temperature of melting point of PTFE to form a stacked body of the electrode substrate 1, catalyst layer 2, and matrix 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a method for manufacturing a matrix in a gas diffusion electrode of a fuel cell.

[Prior art and its problems]

In general, it has a structure similar to the gas diffusion electrode of a fuel cell as shown in Figure 3 of IJ Fuchs. FIG. 3 schematically shows a longitudinal section of a gas diffusion electrode and a matrix formed on the gas diffusion electrode.

A gas diffusion electrode and a catalyst layer 2 consisting of an electrode substrate 1 having excellent gas permeability and having passages for hydrogen or oxygen to diffuse into the electrode, and a catalyst layer 2 for carrying out an electrochemical catalytic reaction.
The matrix 3 is located on top of the matrix 3 and holds the electrolyte, and has excellent electrolyte corrosion resistance and electrical insulation properties.

The production of the electrode matrix 3 having such a structure is usually carried out as follows. In other words, tungsten carbide (
WC), silicon carbide (Sic), silicon nitride (
sssN4) etc. and polytetrafluoroethylene (hereinafter referred to as PTFE) as a binder is mixed in a solvent,
The mixture is made into a paste by a spraying method, a spray method, or by increasing the viscosity of the mixture, and is applied onto the catalyst layer 2 by a roller coating method, a brush coating method, or the like. This is then dried to remove the solvent, and then heated to the melting temperature of PTFj3 to bind powders such as tungsten carbide, silicon carbide, or silicon nitride to form the matrix 3. .

However, such a matrix manufacturing method requires a series of many steps such as preparation of a dispersion mixture, application to a catalyst layer, and solvent removal.

Because organic solvents such as Inglobil alcohol are used, for the health and hygiene management of workers when handling them,
This method cannot necessarily be said to be a sufficient method because it requires additional equipment such as an air purifier and a waste liquid treatment device. Therefore, it is desirable for the IJ hook manufacturing method to be a more simplified process and to be able to be carried out safely and without harm.

[Purpose of the invention]

The present invention has been made in view of the above points.

The purpose is to provide a highly efficient, non-polluting method for manufacturing IJ hooks for fuel cells that greatly reduces the number of man-hours compared to conventional methods.

[Summary of the Invention] The present invention is a method in which a powder containing a matrix constituent material and PTFB is deposited on a catalyst layer using an electrostatic powder coating method, and then fired at the melting temperature of PTFE.

[Embodiments of the invention]

The present invention will be explained below based on examples.

First, according to the conventional method, PTFB powder, which is a binder, is mixed with silicon carbide, tungsten carbide, or silicon nitride powder, which has excellent electrical insulation and electrolyte corrosion resistance, and then pulverized to form a uniform and fine mixed powder. To manufacture. Further, a gas diffusion electrode with a catalyst layer on an electrode substrate is separately prepared by a usual method. In the present invention, the mixed powder is applied to the catalyst layer on the electrode substrate by electrostatic powder coating. Electrostatic powder coating is a method for reducing labor and improving performance by utilizing the property that when powder is put into an electric field as a paint, it flies to the surface of the object being coated and adheres there. However, in particular, since the paint does not contain any organic solvents and excess paint can be collected and reused, it has the advantage of reducing pollution and saving resources, so in recent years it has been used in a wide range of applications such as building materials, electrical equipment, and vehicles. It is what is used.

FIG. 1 is a conceptual diagram for explaining the case where this electrostatic coating method is applied to the present invention. In FIG. 1, a mixed powder 8 of Mad IJx material and PTFE powder is placed between two parallel electrodes placed below the plastic box 5, that is, a positive electrode 6 on the floor of the box 5 and a negative electrode 7 above it.
When a high voltage is applied between both electrodes 6 and 7, mixed powder 8
is negatively charged and vibrates up and down. At this time, if the electrode substrate 1a coated with the catalyst layer 2a is placed above the box 5 with the ground 9 provided, electric lines of force 10 are generated between the negative electrode 7 and the catalyst layer 2a, and the lower part of the box 5 By blowing air through the air outlet 11, the negatively charged mixed powder 8 in a static 1 degree vibration state flies along the lines of electric force 10 toward the catalyst layer 2a, and the mixed powder 8 is transferred to the catalyst layer 2a. It can be attached electrostatically.

At this time, as a matter of course, the catalyst layer 2a provided on the substrate 1a
The surface to which the mixed powder 8 is attached is placed so as to face the negative electrode 7. Further, the direction in which the mixed powder 8 flies is indicated by an arrow. In this process, the uncharged mixed powder 8 remains in its original position, and the mixed powder 8 that did not adhere to the catalyst layer 2a returns to the floor of the box 5, so these powders can be used next time. . By heating the gas diffusion electrode consisting of the catalyst layer 2a to which the mixed powder 8 is attached and the electrode substrate 1a to the melting temperature of PTFIm, the electrode substrate 1. is heated as shown in FIG. A laminate consisting of catalyst layer 2 and matrix 3 is obtained.

FIG. 2 is a diagram showing the relationship between the processing time and the amount of adhesion of mixed powder, ie, IJ Fuchs thickness, by the electrostatic powder coating method described above. From Figure 2, it can be seen that it is possible to obtain the practically necessary matrix thickness in just a few seconds, which is extremely efficient.

Furthermore, since this method can be automated, it is expected that the number of steps for matrix formation will be dramatically reduced.

Furthermore, by using the electrostatic powder coating method, steps such as preparing the PTFB dispersion, coating, and removing the solvent can be omitted, and no organic solvent is required at all when attaching the mixed powder to the catalyst layer. It has advantages.

〔Effect of the invention〕

When forming an IJ wax layer on a fuel cell gas diffusion electrode consisting of an electrode substrate and a catalyst layer, a mixed dispersion of a matrix base material and PTFB powder is applied to the catalyst layer provided on the electrode substrate, and then dried and fired. The conventional method required many steps and had problems such as pollution due to the use of organic solvents, whereas the present invention uses an electrostatic powder coating method as explained in the examples. (Ma) Since the mixed powder of IJ Fuchs material and PTFE powder is baked after being attached to the catalyst layer, it takes only a few seconds for the mixed powder to attach to the catalyst layer, and moreover, it requires no organic solvent. It is possible to omit a series of conventional processes from preparing the mixed dispersion liquid to coating and removing the solvent without using it at all, resulting in high efficiency due to a significant reduction in man-hours and safety due to the elimination of solvents. It was a great success in making it harmless all at once.

[Brief explanation of drawings]

Figure 1 is a conceptual diagram for explaining the electrostatic powder coating method to which the method of the present invention is applied, and Figure 2 is a diagram showing the relationship between processing time and matrix thickness in the electrostatic powder coating method. , 3rd
The figure shows the gas diffusion electrode of a fuel cell and the matrix formed on it)
FIG. 2 is a schematic cross-sectional view of an IJ hook. 1.1a... Electrode substrate, 2.2a... Catalyst layer, 3.
...Matrix, 5...Box, 6...Positive electrode,
7...Negative electrode. 8... Mixed powder, 9... Earth, 10... Electric force lines. Rika shoulder (second) is placed on the 9th floor in Figure 1! ff

Claims (1)

[Claims] 1) When forming a matrix on the gas diffusion electrode of a fuel cell that has a catalyst layer on the electrode substrate, a mixed powder of matrix base material powder and polytetrafluoroethylene powder is applied to the main part of the catalyst layer using an electrostatic coating method. A method for forming a fuel cell matrix, which comprises depositing it on the entire surface and then firing it at the melting temperature of polytetrafluoroethylene.