JPH03138864A - Electrode processing method for fuel cell - Google Patents

Abstract

PURPOSE:To obtain stable power generation for a long period by uniformly coating and impregnating hydrophilic finishing ink and water repellent finishing ink only at the specified position of an electrode, and adjusting the hydrophilic property and water repellency of the electrode. CONSTITUTION:The porous carbon substrate 3 of an electrode is immersed in hydrophilic finishing ink 21, then it is dried, hydrophilic finishing is applied, the hydrophilic-finished porous carbon substrate 3 is mounted on a decompression suction bed 9, and a screen 6 marked at specified positions is set on it. Water repellent finishing ink 7 is filled on the screen 6, a flood bar 8 is moved to form an ink layer with the preset thickness on the screen 6, the decompression suction bed 9 is started to suck from the back face of the substrate 3, thus the ink layer is impregnated only at the specified position of the substrate 3. The water repellency and hydrophilic property of the electrode can be freely controlled, and the balance of an electrolyte is not collapsed. Stable power generation can be obtained over a long period.

Description

[Detailed description of the invention] [Object of the invention] (Industrial application field) The present invention provides a porous carbon substrate (hereinafter referred to as an electrode) for a fuel cell.
This invention relates to a fuel cell electrode treatment method that improves water contact treatment and hydrophilic treatment methods.

(Prior Art) A fuel cell is generally known as a device that directly converts energy contained in fuel into electrical energy. This fuel cell usually has a structure in which an electrolyte matrix layer impregnated with an electrolyte is sandwiched between a pair of porous carbon substrates (hereinafter referred to as electrodes) each having a catalyst layer formed on one side.

Electrical energy is extracted from between the electrodes using an electrochemical reaction that occurs by supplying a fuel such as hydrogen to the back of one electrode of the fuel cell and supplying an oxidizing agent such as air to the back of the other electrode. As long as fuel and oxidizer are supplied, electrical energy can be extracted with high conversion efficiency.

In order to explain the conventional technology, a typical configuration diagram of a single fuel cell is shown in FIG. 1 is an electrolyte matrix layer, 2
3 is a catalyst layer, 3 is a porous carbon substrate, and 4 is a separator. Grooves 3a for supplying reactive gas are formed in the porous electrode substrate 3. Here, the catalyst layer 2 and the porous electrode substrate 3 are collectively referred to as an electrode 5, and the electrodes 5, 5 laminated with an electrolyte matrix layer 1 are referred to as a fuel cell unit cell 10.

In the fuel cell single cell 10, the catalyst layer 2 must normally be appropriately wetted with the electrolyte (even if it is too wet or not wet enough, the cell characteristics will deteriorate). In addition to supplying reactive gas, it also plays the role of an electrolyte holding seat, and replenishes electrolyte when the amount of electrolyte in matrix layer 1 decreases. For this reason, the substrate 3 also needs to be appropriately wetted or locally wetted with the electrolyte. Electrode 5 used in fuel cells for the above reasons
, 5 are subjected to water contact treatment, hydrophilic treatment, etc.

Conventionally, in water contact treatment, hydrophilic treatment, etc. of the electrode 5, treatment ink is applied to the electrode with a brush or spray.

This was done by impregnation.

(Problems to be Solved by the Invention) In the conventional processing method described above, it was not possible to uniformly apply and impregnate the electrode 5 with the processing ink.

Furthermore, it was not possible to process only a designated part of the electrode 5. For this reason, the electrode 5 treated with the conventional treatment method
When a long-term power generation test was conducted on a battery using the battery, the electrolyte balance within the cell changed within several thousand hours of operation, as shown by characteristic A in FIG. 3, and the characteristics were extremely degraded.

The purpose of the present invention is to apply processing ink uniformly to the electrode, and even only to a designated part of the electrode.

The object of the present invention is to provide a fuel cell and an electrode processing method that can produce a cell that can be impregnated and can generate power stably for a long time.

[Structure of the invention]

(Means for Solving the Problems) The fuel cell electrode treatment method of the present invention typically consists of a pair of porous carbon substrates each having a catalyst layer formed on one side, and an electrolyte matrix layer impregnated with an electrolyte sandwiched between the electrodes. In a fuel cell electrode configured by stacking a plurality of single cells to form a cell, the porous carbon substrate of the electrode is immersed in a hydrophilic treatment ink and then dried to perform a hydrophilic treatment; Place the porous carbon substrate on a vacuum suction stand, and set a screen with designated areas marked on the top surface.
After filling the screen with water repellent ink, the flood bar is moved to form an ink layer of a predetermined thickness on the screen, and then the vacuum suction table is started to suck the ink from the back side of the substrate. This method is characterized by impregnating an ink layer only in designated areas of the substrate.

(Function) In the present invention, by suctioning and impregnating an ink layer of a constant thickness formed in advance on a screen onto an electrode, it is possible to apply and impregnate a uniform amount over the entire surface to be treated. Furthermore, by changing the masking pattern of the screen, it is possible to apply and impregnate a designated position with the processing ink. This makes it possible to freely control the water contact and hydrophilicity of the electrodes, and batteries using electrodes treated with this method can last for a long time without disrupting the electrolyte balance within the battery even during generator tests. High characteristics can be maintained.

(Example) An example of the fuel cell electrode processing method of the present invention will be described below with reference to FIGS. 1, 2, and 3. In this embodiment, as shown in FIG. 2, in an electrode 5 in which a porous carbon substrate 3 and a catalyst 2 are stacked, the protrusion M of the gas supply groove 3a of the porous carbon substrate 3 is made hydrophilic. , recess m
This shows the case where the remaining meat part is treated to have water return properties.

Now, regarding the treatment procedure when implementing the fuel cell electrode treatment method of the present invention, first of all, preparation of treatment materials will be carried out. Prepare each screen in advance.

The hydrophilic treatment ink was an aqueous solution containing 10% carbon black and 2% surfactant. The water-resistant treatment ink was an aqueous solution containing 25% tetrafluoroethylene resin (TFE) and 0.5% polyvinyl volima.

Among these, the viscosity of the ink for water treatment was adjusted by adjusting the PI to about 3 with an ammonia aqueous solution. The viscosity was set to the lowest value so that it would not pass through the screen due to its own weight when placed on the screen described below.

A 100-mesh screen was used for water purification treatment, and when placed on the electrode, the screen was masked except for the area corresponding to the recess m of the gas supply groove 3a.

In the present invention, after one or more preparations are completed, processing is performed according to the following procedure. That is, as shown in steps A to B in FIG. 1, the porous carbon substrate 3 having the gas supply grooves 3a is immersed in the hydrophilic treatment ink 21 in the hydrophilic treatment tank 20 for 5 minutes, and then the treatment is carried out. tank 20
Take it out and dry it at 150°C. The entire substrate 3 is now subjected to hydrophilic treatment. (Step C in FIG. 1) Next, this substrate 3 is placed on the vacuum suction stand 9 with the gas supply groove 3a facing down, as in the step in FIG. Place it so that it is in contact with the This screen 6 has already been masked at a predetermined portion, and the screen 6 is set so that the masked portion overlaps with the convex portion M of the gas supply groove 3a.

After filling the screen 6 with the water repellent ink 7, a flood bar 8 is placed at a distance of 1 m from the screen 6.
It goes without saying that the processing amount can be freely changed by moving the ink layer on the screen 6 to change the 0 interval of 1 m to form an ink layer of 1 ffl thickness on the screen 6. After forming the ink layer, vacuum suction is applied from the back surface of the substrate 3 using the vacuum suction stand 9 in the process shown in FIG. By this vacuum suction operation, the ink layer 7 is impregnated only in designated areas of the recesses m of the gas supply grooves 3a on the substrate 3 where the screen 6 has not been masked in advance.

Next, the substrate 3 impregnated with the ink layer 7 is dried at 150° C. for 10 minutes, and then the catalyst layer 2 is formed on the substrate 3 to form the electrode 5. When the catalyst layer 2 is heat-treated at about 350° C., only the recesses m of the gas supply grooves 3a of the substrate 3 coated with the water-wetting ink become water-wettable.

The electrode 5 subjected to the water contact treatment is shown in FIG.

A single cell 10 was manufactured using the electrode 5.5 treated according to the present invention, and a continuous power generation test was conducted over a long period of time. The results are shown in FIG.

In Figure 3, characteristic A is treated with hydrophilic treatment using a conventional treatment method;
The results of a life test of a fuel cell using an electrode subjected to tlI water treatment show that the electrolyte balance within the cell changes and the characteristics deteriorate extremely after several thousand hours of operation.

Characteristic B is the result of a battery life test of an electrode using the treatment method of the present invention, and it was confirmed that the characteristics did not deteriorate even after long-term operation.

As described above, by using the treatment method of the present invention, it was possible to apply and impregnate the treatment ink uniformly over the entire surface of the electrode treatment surface, and furthermore, only at a portion of the designated portion of the electrode. The processing location can be easily changed by changing the masking pattern of the screen 6. In addition, the degree of processing is
It can be easily adjusted by changing the thickness of the treated ink layer 7. For these reasons, the water contact property and hydrophilicity of the electrode 5 can be freely adjusted. A fuel cell using the electrode 5 to which the treatment method of the present invention is applied is as follows:
Even during power generation tests, the electrolyte balance within the battery is not disrupted and high performance can be maintained for a long period of time.

〔Effect of the invention〕

As described above, according to the present invention, the hydrophilicity and water contact property of the electrode can be adjusted by uniformly applying and impregnating the ink for hydrophilic treatment and the ink for water repellent treatment onto the electrode, and furthermore, only at designated areas of the electrode. By doing so, it is possible to manufacture a fuel cell that can stably generate electricity over a long period of time.

[Brief explanation of the drawing]

Fig. 1 is a process diagram showing the steps of the fuel cell electrode processing method of the present invention, Fig. 2 is a perspective view showing an electrode processed by the processing method of the present invention, and Fig. 3 is a perspective view of the present invention. . 1... Electrolyte matrix layer 3... Porous carbon substrate 5... Electrode 6... Screen 8... Flood bar 2... Catalyst layer 4... Separator 3a... Gas supply groove 7 ...Processing ink 9...Reduced pressure suction stand (8733)

Claims (1)

[Claims] In fuel cell electrodes, a single cell is formed by sandwiching an electrolyte matrix layer impregnated with an electrolyte between a pair of porous carbon substrates with a catalyst layer formed on one side, and a plurality of these single cells are stacked. , the porous carbon substrate of the electrode is immersed in a hydrophilic treatment ink, dried and subjected to a hydrophilic treatment, the hydrophilic treated porous carbon substrate is placed on a vacuum suction table, and designated areas are marked on the top surface of the screen. After filling the screen with water repellent ink, the flood bar is moved to form an ink layer of a predetermined thickness on the screen, and then the vacuum suction table is started to remove water from the back side of the substrate. A fuel cell electrode processing method characterized by impregnating an ink layer only at designated locations on a substrate by suction.