JP2000003714A - Solid high molecular fuel cell and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the utilization efficiency of the platinum catalyst by improving a catalyst reaction layer of an solid high molecular fuel cell, so that the platinum catalyst effectively contributes to the electrode reaction. SOLUTION: A part of each carbon particle 14 is made to infiltrate into a high molecular electrolyte film 11 by using the carrier gas, and the carbon particles carry platinum catalyst and needle-like fibers collide with the electrolyte film, or electrostatically charge them, or electrically accelerate them so as to stick the electrolyte film. As a carbon particles for carrying the catalyst, needle-like fiber is effective. With this method, battery performance is improved without increasing the quantity of platinum, and quantity of the platinum to be used for obtaining the same battery performance with the conventional one can be reduced sharply.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a portable power supply,
The present invention relates to a fuel cell using a solid polymer electrolyte used for a power source for an electric vehicle, a home cogeneration system, and the like, and a method for manufacturing the same, particularly a method for manufacturing an electrode-electrolyte membrane assembly.

[0002]

2. Description of the Related Art A fuel cell using a solid polymer electrolyte is
This is an electrochemical device that generates electric power and heat simultaneously by electrochemically reacting a fuel gas containing hydrogen and a fuel gas containing oxygen such as air. First, a catalyst reaction layer mainly composed of a carbon powder carrying a platinum-based metal catalyst is formed on both surfaces of a polymer electrolyte membrane that selectively transports hydrogen ions. Next, a diffusion layer having both gas permeability and electron conductivity is formed on the outer surface of the catalyst reaction layer, and the diffusion layer and the catalyst reaction layer are combined to form an electrode. Thus, the electrode and the polymer electrolyte membrane are assembled in advance integrally. This is called an electrode electrolyte membrane assembly (hereinafter, referred to as MEA). Practically, to prevent the supplied fuel gas or oxidizing gas from leaking out or to mix the two types of gas with each other, a gas sealing material or A gasket is arranged, and a large number of MEs are placed through a conductive separator plate.
A is configured as a laminated battery in which A is laminated.

[0003] The carbon powder supporting the metal catalyst is in the form of granules of several hundred angstroms to several microns, and is kneaded with a solution of a polymer electrolyte membrane, and is coated between the electrode and the solid electrolyte membrane by a coating method such as printing. Between 30 and 1 thickness
A 00 micron catalytic reaction layer is formed. In this catalytic reaction layer, an electrochemical reaction of the fuel gas and the oxidizing gas proceeds. For example, in an anode where hydrogen reacts, hydrogen gas is supplied to the electrode surface through a fuel gas channel cut in a separator plate. The electrode is usually made of a conductive material having air permeability such as carbon paper or carbon cloth, and hydrogen gas can pass through this electrode and reach the catalytic reaction layer. A polymer electrolyte formed by drying and solidifying a solution of the polymer electrolyte adheres to the surface of the carbon powder supporting the catalyst. In a so-called three-phase zone in which the gas phase containing hydrogen gas, the solid phase of carbon carrying the catalyst, and the polymer electrolyte phase are in close proximity, the hydrogen gas is oxidized and released as hydrogen ions into the polymer electrolyte. Is done. The electrons generated by the oxidation of the hydrogen gas move to an external electric circuit via the electron conductive carbon powder. This electrochemical reaction proceeds in a wider area by dissolving hydrogen gas into the polymer electrolyte. Although the thickness of the catalyst reaction layer varies depending on the method of manufacturing the same, it is designed to have a thickness of 30 to 100 microns in order to obtain good battery performance.

[0004]

However, the region of the catalytic reaction layer that contributes to the actual electrode reaction is considered to be a portion having a thickness of 20 microns in contact with the polymer electrolyte membrane. This is because it becomes difficult for the generated hydrogen ions to reach the polymer electrolyte membrane. In addition, in a state where the carbon carrying the catalyst is not in electrical contact with other carbon powders or conductive electrodes, hydrogen ions can easily move,
The transfer of electrons to external circuits is an obstacle. As a result, many parts of the catalytic reaction layer formed by coating do not contribute to the electrode reaction, and the performance is reduced or more platinum is required. An object of the present invention is to improve the catalytic reaction layer so that the platinum catalyst effectively contributes to the electrode reaction, and improve the utilization efficiency of the platinum catalyst.

[0005]

In order to solve the above problems, a polymer electrolyte fuel cell according to the present invention comprises a plurality of pairs of electrodes sandwiching a solid polymer electrolyte membrane, which are laminated via a conductive separator. The laminate, and a gas supply / discharge means for supplying / discharging a fuel gas to one of the electrodes and an oxidant gas to the other, respectively, wherein a part of the carbon particles carrying an electrode reaction catalyst is a solid polymer electrolyte membrane. It is characterized by invading the inside. It is effective that the catalyst-supporting carbon particles used here are acicular fibers.

According to the present invention, there is provided a step of mixing carbon particles carrying a catalyst into a carrier gas and causing the carbon particles to collide with a solid polymer electrolyte membrane, thereby causing a portion of the carbon particles to enter the inside of the solid polymer electrolyte membrane. To provide a method for producing a polymer electrolyte fuel cell. In addition, the present invention provides a method for charging a carbon particle carrying a catalyst with static electricity, accelerating the carbon particle by an electric field, and causing the carbon particle to collide with the solid polymer electrolyte membrane, so that a part of the carbon particle is placed inside the solid polymer electrolyte membrane. Provided is a method for manufacturing a polymer electrolyte fuel cell having a step of invading.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the present invention adopts a structure in which carbon particles carrying a catalyst enter or are inserted into a solid polymer electrolyte membrane. Can move into the polymer electrolyte membrane. At the same time, by pressing an electrode such as carbon paper against one end of the carbon particles, the movement of electrons can be facilitated.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. Example 1 25% by weight of platinum particles having an average particle diameter of about 30 angstroms were supported on glassy carbon powder or granulated acetylene black powder. This is referred to as catalyst-carrying carbon particles. The average particle size of the glassy carbon particles and the granulated acetylene black powder was 2 to 10 microns. The catalyst-supporting carbon powder is sprinkled on a 50-μm-thick solid polymer electrolyte membrane 11 composed of side chains having polytetrafluoroethylene as a main chain and having a sulfone group at the end, and is pressed by a roller press having a diameter of 10 cm.
Pressure was slowly applied at a pressure of 00 kgf / 10 cm so that the carbon particles were buried and penetrated into the solid polymer film. At this time, as a result of pressurization while changing the temperature and the humidification conditions, the degree of penetration of the carbon particles into the film was higher as the humidity was higher and the temperature was higher. The amount of the catalyst-carrying carbon powder permeated into the membrane is about 0.01 to about 0.001 per one catalytic reaction layer in terms of the amount of platinum in any carbon powder.
0.5 mg / cm ² . Next, it is sandwiched between the cathode 12 and the anode 13 made of a pan-based carbon fiber from both sides, and at 110 ° C., a pressure of 10 kgf / cm ^{2 and} a pressure of 5 kg.
By hot pressing for one minute, the solid polymer electrolyte membrane 11 and the anode 12 and the cathode 13 were integrally joined. This electrode electrolyte membrane assembly is shown in FIG.

An electrode having a size of 5 cm × 5 cm is formed using a fluororesin sealing material and a carbon separator plate.
The cells were stacked to assemble a stacked battery. A discharge test was performed in which pure hydrogen was supplied to the anode and air was supplied to the cathode. In the case of using acetylene black granulated carbon powder, the amount of platinum used was as low as 0.3 mg / cm ^2. At a fuel utilization of 70% and an air utilization of 30%, an output of 0.6 V-0.5 A / cm ² was obtained. This is because the amount of platinum used is 0.5 mg / cm
^{The performance is almost the same as the conventional battery of No. 2. Carbon powder
Acetylene with glassy carbon powder
The performance was lower than that using black. Also, platinum
If the amount used is} less than ^{0.2 mg / cm 2} , the performance sharply decreases.

Example 2 Next, various methods were examined for more efficiently inserting carbon particles into a polymer electrolyte membrane. The carbon powder carrying the catalyst was made to collide with the polymer electrolyte membrane at high speed using nitrogen as a carrier gas. The gas flow rate of the nitrogen gas was varied from 1 to 200 m / sec, and the nitrogen gas was humidified to prevent rapid drying of the electrolyte membrane. The average particle size of the carbon powder was 0.1 to 20 microns. In this example, the carbon particles could penetrate into the solid polymer electrolyte membrane without using the pressing of the particles by the roller press as performed in Example 1. As a result of performing the same discharge test as in Example 1, overall better performance was obtained than in Example 1. It is an ultra-fine powder of glassy carbon having a particle size of 1 micron or less. Although the amount of platinum used is as small as 0.2 mg / cm ² , it is 0.62 V−0.5 A / cm ² (fuel utilization rate). (70%, air utilization rate 30%). Even when acetylene black was used, higher performance was confirmed than in Example 1.

Example 3 In this example, needle-like carbon was used in place of the spherical carbon powder of Example 2.
As the needle-like carbon, those having a specific surface area as large as possible among bread-based carbon fibers (10 m ² / g or more)
Supported platinum (0.01 to 0.3 mg / cm ² )
Was used. The average length of the acicular carbon was 15 microns. As a result of the discharge test, the amount of platinum used was 0.1 mg / cm ²
0.64 V-0.5 A / cm ² (fuel utilization rate 7
(0%, air utilization rate 30%). According to the micrograph of the cross section of the polymer electrolyte membrane, FIG.
As shown in the schematic diagram, it was observed that a large number of needle-like carbons 14 serving as electrode reaction parts had penetrated into the solid polymer electrolyte membrane 11. The exposed portion of the acicular carbon 14 in FIG. 2 is buried in the anode or the cathode. Needle-like particles such as carbon fibers reach a deeper portion of the polymer electrolyte membrane, for example, a depth of about 10 microns, and the fibers are exposed on the surface, so that the electrical connection with the electrodes is good. Become.

Example 4 Further, an electric acceleration method was examined as various methods for more efficiently infiltrating carbon particles into a polymer electrolyte membrane. Various carbon powders carrying platinum catalyst were blown out from the nozzles, and at the same time, static electricity was charged by corona discharge. Then, an accelerating voltage was applied between the injector for injecting carbon and the metallic fixture to which the solid polymer electrolyte membrane was fixed. The voltage for acceleration was considered from DC100V to 5000V. The amount of carbon powder injected was controlled by time. When driven at a high acceleration voltage for an excessively long time, the curvature of the polymer electrolyte membrane became large or the polymer electrolyte membrane was broken. When a catalyst was supported on acetylene black, glassy carbon, and needle-like carbon, and experiments were performed under various conditions, the performance was extremely high when needle-like carbon was driven at an acceleration voltage of DC 1000 V for 1 minute, and the amount of platinum used was 0. At the time of 07 mg / cm ² , 0.66 V−0.5 A / cm ² (fuel utilization rate 70
%, Air utilization 30%). It was confirmed that it was more effective to drive carbon powder in a vacuum chamber with reduced pressure or to apply a small amount of solid polymer electrolyte to carbon particles in advance.

In a series of experiments, a carrier gas or a method of driving by electrically accelerating the carbon particles has a higher performance than a method of driving the carbon particles by using a roller press or the like, because the carbon surface is driven at a higher speed. It is presumed that the bonding property between the polymer and the polymer electrolyte is improved. In addition to the carbon paper used in this embodiment, a carbon cloth, a conductive sheet in which carbon powder is mixed in a resin, or the like can be used for the electrode serving as the current collector. Also, in order to improve the electrical bondability with the carbon particles and carbon needles that have been implanted, a method of applying a conductive carbon paste in advance to the surface of the carbon paper to be bonded to the polymer electrolyte membrane has also obtained good results. Was done.

[0014]

As described above, according to the present invention, higher battery performance can be obtained even with the same amount of platinum, and the amount of platinum used can be greatly reduced when trying to obtain equivalent battery performance. .

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view showing an electrode electrolyte membrane assembly according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view schematically showing a surface portion of the electrolyte membrane.

[Explanation of symbols]

 11 solid polymer electrolyte membrane 12 cathode 13 anode 14 needle-like carbon

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuhito Hato 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Makoto Uchida 1006 Odaka Kadoma Kadoma City, Osaka Matsushita Electric Industrial Co. (72) Inventor Yasushi Sugawara 1006 Kadoma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. (72) Inventor Teruhito Kanbara 1006 Odakadoma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. AS02 AS03 BB00 BB03 BB08 EE05 EE17 5H026 AA06 BB00 BB02 BB04 CX02 CX05 EE05 EE18

Claims (4)

[Claims] 1. A laminate in which a plurality of a pair of electrodes sandwiching a solid polymer electrolyte membrane are laminated with a conductive separator interposed therebetween.
And gas supply / discharge means for supplying / discharging a fuel gas to one of the electrodes and an oxidizing gas to the other,
A polymer electrolyte fuel cell, wherein a portion of carbon particles carrying an electrode reaction catalyst has penetrated into the polymer electrolyte membrane. 2. The polymer electrolyte fuel cell according to claim 1, wherein the carbon particles carrying the catalyst are needle fibers. 3. A process of mixing a carbon particle carrying a catalyst into a carrier gas and causing the carbon particle to collide with a solid polymer electrolyte membrane to cause a portion of the carbon particle to enter the inside of the solid polymer electrolyte membrane. A method for producing a polymer electrolyte fuel cell, comprising: 4. A part of the carbon particles, which are charged with a static electricity, are accelerated by an electric field and collide with the solid polymer electrolyte membrane, thereby causing a part of the carbon particles to enter the solid polymer electrolyte membrane. A method for producing a polymer electrolyte fuel cell, comprising: