JP2002100368A - Solid high polymer molecule type fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid high polymer molecule type fuel cell, which is, enabled to aim at much more improvement in a power generation performance by reducing a thickness of each electrodes. SOLUTION: The solid high polymer molecule type fuel cell 1 is equipped with an electrolyte film 2, which has a high polymer molecule ion exchange component, and a pair of electrodes 3, 4 which sandwich the electrolyte film 2. Both the electrodes 3, 4 consist only of the high polymer molecule ion exchange component, and two or more catalyst particles made of water-repellent carbon black particles of which the surfaces are made to have catalyst metal, and do not contain a third ingredient.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer electrolyte fuel cell, and more particularly to a fuel cell having an electrolyte membrane having a polymer ion exchange component and a pair of electrodes sandwiching the electrolyte membrane.

[0002]

2. Description of the Related Art Conventionally, the above-mentioned electrode includes a polymer ion-exchange component which imparts proton conductivity to the electrode and functions as a binder, and a plurality of catalyst particles having catalyst metal supported on the surface of carbon black particles. , PTFE
(Polytetrafluoroethylene) particles are known. The PTFE particles have water repellency and have a function of adjusting the water retention of the electrode.

[0003]

However, the use of PTFE particles as a component of the electrode means reducing the thickness of the electrode in order to further improve the power generation performance.
This has been an obstacle in meeting the requirements of increasing the proton conductivity and keeping the resistance overvoltage low.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a polymer electrolyte fuel cell in which the thickness of each electrode is reduced so that the power generation performance can be further improved.

[0005] To achieve the above object, according to the present invention,
Equipped with an electrolyte membrane having a polymer ion exchange component and a pair of electrodes sandwiching the electrolyte membrane. Both electrodes carry a polymer ion exchange component and a catalyst metal on the surface of water-repellent carbon black particles, respectively. A polymer electrolyte fuel cell comprising a plurality of catalyst particles is provided.

With the above-described structure, the use of the PTFE particles can be stopped by providing the water-repellent carbon black particles with a function of adjusting the water retention of the electrode. As a result, the thickness of the electrode can be reduced as compared with the conventional one, the proton conductivity can be increased, and the resistance overvoltage can be suppressed low, so that the power generation performance can be further improved.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, a polymer electrolyte fuel cell (cell) 1 has an electrolyte membrane 2 and a pair of electrodes which are in close contact with both sides of the electrolyte membrane 2, that is, an air electrode 3 and an air electrode 3. A fuel electrode 4, a pair of diffusion layers 5 and 6, which are in close contact with the electrodes 3 and 4, respectively;
And a pair of separators 7 and 8 in close contact with each other. In this case, humidification is performed from both poles 3 and 4 side. The electrolyte membrane-electrode assembly 9 includes an electrolyte membrane 2, an air electrode 3, a fuel electrode 4, and both diffusion layers 5, 6.

The electrolyte membrane 2 is composed of a polymer ion exchange component having proton conductivity, in this embodiment, an aromatic hydrocarbon polymer ion exchange component. The air electrode 3 and the fuel electrode 4 have a plurality of catalyst particles in which a plurality of Pt particles as a catalyst metal are supported on the surface of carbon black particles, and also have a proton conductivity and a function as a binder. Or, it is composed of a different polymer ion exchange component, in this embodiment, an aromatic hydrocarbon polymer ion exchange component, and does not include PTFE particles as the third component.

Each of the diffusion layers 5, 6 is made of porous carbon paper, carbon plate, etc., and each of the separators 7, 8 is made of graphitized carbon so as to have the same form. 7 multiple grooves 1
0 is supplied with air, and hydrogen is supplied to a plurality of grooves 11 which are present in the separator 8 on the side of the fuel electrode 4 and intersect with the grooves 10.

The aromatic hydrocarbon-based polymer ion exchange component has characteristics such as being non-fluorine and soluble in a solvent. Table 1 shows this type of polymer ion exchange component.
Various sulfonated aromatic hydrocarbon polymers are used.

[0011]

[Table 1]

As the solvent, various polar solvents listed in Table 2 are used.

[0013]

[Table 2]

As the carbon black particles in the air electrode 3 and the fuel electrode 4, those having water repellency such that the water adsorption amount A under a saturated steam pressure of 60 ° C. is A ≦ 80 cc / g are used.

When the water repellency is maintained by the carbon black particles, the air electrode 3 and the fuel electrode 4
The inflow of the humidified water into the electrolyte membrane 2 and the outflow of the excess water from the electrodes 3 and 4 are smoothly performed. These effects are:
The water adsorption amount A cannot be obtained if A> 80 cc / g. This is because the water repellency of the carbon black particles decreases.

In the air electrode 3 and the fuel electrode 4, when the compounding weight of the polymer ion-exchange component is Wp and the compounding weight of the carbon black particles is Wc,
The ratio Wp / Wc of p and Wc is 0.4 ≦ Wp / Wc ≦ 1.
It is set to 25.

When the ratio Wp / Wc of the blending weights Wp and Wc is set as described above, the thickness of the air electrode 3 and the fuel electrode 4 is reduced to increase the proton conductivity and to suppress the increase in the resistance overvoltage. It is possible to improve the power generation performance. However, when the ratio Wp / Wc is less than 0.4, the thickness of the air electrode 3 and the fuel electrode 4 is reduced, but the coverage of the catalyst particles is deteriorated and the power generation performance is reduced. On the other hand, Wp / Wc
In the case of> 1.25, the degree of dispersion D of the polymer ion exchange component is deteriorated, so that the thicknesses of the air electrode 3 and the fuel electrode 4 are increased.

Hereinafter, a specific example will be described. I. Manufacture of electrode The amount of water adsorption A at 60 ° C. under a saturated steam pressure is A = 72.
cc / g of water-repellent carbon black particles (trade name:
Vulcan XC-72) supported Pt particles to prepare catalyst particles. The content of Pt particles in the catalyst particles is 50% by weight. [Example-I] As the aromatic hydrocarbon polymer ion exchange component, the PEEK sulfonate listed in Example 1 in Table 1 was prepared, and this PEEK sulfonate was dissolved under reflux in NMP in Table 2. The content of the PEEK sulfonate in this solution is 6% by weight. In this PEEK sulfonate-containing solution, the ratio Wp / Wc of the blend weight Wp of the PEEK sulfonate to the blend weight Wc of the carbon black particles is Wp.
The catalyst particles were mixed so that /Wc=0.2, and then dispersed using a ball mill to prepare a slurry for an electrode. This slurry was prepared with a Pt amount of 0.5 mg / cm ²
Were applied to one surface of a plurality of porous carbon papers and dried to obtain electrodes having a plurality of diffusion layers. Let these electrodes be examples (1). [Example-II] The ratio Wp / Wc of the blending weight Wp of the PEEK sulfonated product to the blending weight Wc of the carbon black particles is represented by W
Example-I except that p / Wc = 0.4 was set.
By performing the same method as described above, an electrode having a plurality of diffusion layers was obtained. These electrodes are taken as example (2). [Example-III] Except that the ratio Wp / Wc of the blending weight Wp of the PEEK sulfonated compound to the blending weight Wc of the carbon black particles was set to Wp / Wc = 0.6.
An electrode having a plurality of diffusion layers was obtained in the same manner as in I. Let these electrodes be Example (3). [Example-IV] The ratio Wp / Wc of the blending weight Wp of the PEEK sulfonated product to the blending weight Wc of the carbon black particles is represented by W
Example-I except that p / Wc = 0.8 was set.
By performing the same method as described above, an electrode having a plurality of diffusion layers was obtained. Let these electrodes be Example (4). [Example-V] The ratio Wp / Wc of the blending weight Wp of the PEEK sulfonated product to the blending weight Wc of the carbon black particles is represented by W
Example-except that p / Wc was set to 1.25
An electrode having a plurality of diffusion layers was obtained in the same manner as in I. These electrodes are referred to as an example (5). [Example-VI] The ratio Wp / Wc of the blending weight Wp of the PEEK sulfonated product to the blending weight Wc of the carbon black particles is represented by W
Example-Except that p / Wc = 1.75 was set.
An electrode having a plurality of diffusion layers was obtained in the same manner as in I. Let these electrodes be Example (6). II. Various Considerations on Electrode Table 3 shows the relationship between the ratio Wp / Wc of the blended weight Wp of the PEEK sulfonated compound and the blended weight Wc of the carbon black particles for the electrode examples (1) to (6) and the water retention of the electrode. . This water retention was calculated from the amount of water adsorbed by the gas adsorber at a saturated steam pressure of 60 ° C.

[0019]

[Table 3]

FIG. 2 is a graph showing the ratio W of both compounding weights based on Table 3.
7 is a graph showing the relationship between p / Wc and the water retention of the electrode. FIG. 2 shows that the water retention of the electrode increases as the ratio Wp / Wc increases.

Table 4 shows the relationship between the ratio Wp / Wc of both compounding weights and the thickness of the electrode for the electrode examples (1) to (6).

[0022]

[Table 4]

FIG. 3 is a graph showing the ratio W of both compounding weights based on Table 4.
7 is a graph showing the relationship between p / Wc and electrode thickness. FIG. 3 shows that the thickness of the electrode increases as the ratio Wp / Wc increases.

Table 5 shows the relationship between the ratio Wp / Wc of the two compounding weights and the coverage Cc of the catalyst particles for the electrode examples (1) to (6).

[0025]

[Table 5]

The coverage Cc of the catalyst particles is represented by Cc = ｛(Ae−Ae) where Ae is the area of the plane of the electrode and Ac is the sum of the areas of a plurality of catalyst particles exposed on the plane of the electrode.
Ac) / Ae｝ × 100 (%).

FIG. 4 is a graph showing the ratio W of both compounding weights based on Table 5.
7 is a graph showing the relationship between p / Wc and the coverage Cc of catalyst particles. FIG. 4 shows that the coverage Cc of the catalyst particles increases as the ratio Wp / Wc increases.

Table 6 shows the relationship between the ratio Wp / Wc of both compounding weights and the degree of dispersion D of the catalyst particles for the electrode examples (1) to (6).

[0029]

[Table 6]

The degree of dispersion D of the catalyst particles was determined by the following method. First, the theoretical Pt concentration Tp and the theoretical Pt concentration as the theoretical catalyst metal concentration in the catalyst particles are determined from the blending amounts of the catalyst particles and the PEEK sulfonate during the production of the electrode.
The theoretical S (sulfur) concentration Ts in the EEK sulfonate was calculated, and then the theoretical value ratio Ts / Tp was calculated from the theoretical values. Also, the surface of the electrode was observed by EPMA, and the measured Pt concentration Ap and the measured S concentration As in the PEEK sulfonated product as the measured catalyst metal concentrations in the catalyst particles were determined by surface analysis, and then the measured values were compared with the measured values. As / A
p was determined. Then, the degree of dispersion D is calculated as follows: D = [{(Ts / Tp) − (As / Ap)} / (Ts /
Tp)] × 100 (%).

FIG. 5 is a graph showing the ratio W of both compounding weights based on Table 6.
7 is a graph showing the relationship between p / Wc and the degree of dispersion D of catalyst particles. FIG. 5 shows that the degree of dispersion D of the catalyst particles increases as the ratio Wp / Wc increases.

Table 7 shows the relationship between the degree of dispersion D of the catalyst particles and the coverage Cc of the catalyst particles for the electrode examples (1) to (6).

[0033]

[Table 7]

FIG. 6 shows the dispersion degree D of the catalyst particles based on Table 7.
FIG. 4 is a graph showing the relationship between the ratio and the coverage Cc of the catalyst particles. FIG. 6 shows that the coverage Cc of the catalyst particles increases as the degree of dispersion D of the catalyst particles increases.

Table 8 shows the relationship between the degree of dispersion D of the catalyst particles and the electrode thickness for the electrode examples (1) to (6).

[0036]

[Table 8]

FIG. 7 is a graph showing the relationship between the degree of dispersion D of the catalyst particles and the thickness of the electrode based on Table 8. FIG. 7 shows that the thickness of the electrode increases as the degree of dispersion D of the catalyst particles increases. III. Power generation performance of fuel cell A 50 μm-thick electrolyte membrane 2 was formed using the same PEEK sulfonate used in the production of the electrode.
Also, two sets of examples (1) to (6) of electrodes are prepared, one set is set to examples (1) to (6) of the air electrode 3 and the other set is set to examples (1) to (6) of the fuel electrode 4. 6). Then, each example (1) to (6) of the air electrode 3 is combined with the examples (1) to (6) of the fuel electrode 4 so as to make a round robin. In other words, for example (1), (1) and example (1), example (1) and example (2) ...
By combining Examples (1) and (5) and Examples (1) and (6), 36 electrode pairs were obtained. The electrolyte membrane 2 was sandwiched between each pair of electrodes, that is, a pair of the air electrode 3 and the fuel electrode 4, and hot pressed at 140 ° C., 1.5 MPa, and 1 minute to obtain an electrolyte membrane-electrode assembly 9. . Polymer electrolyte fuel cell 1 using each electrolyte membrane-electrode assembly 9
Was assembled, and power was generated under the condition that the air electrode 3 and the fuel electrode 4 were humidified respectively, and the relationship between the current density and the terminal voltage was measured. In this case, the terminal voltage at 0.8 A / cm ^2, which is on the high current density side, was used as a comparison value of the terminal voltage of each battery because the diffusion of water greatly affected the terminal voltage.

Table 9 shows examples (1) to (4) of the air electrode and the fuel electrode.
The ratio Wp / Wc of the blending weights in (6), the combination of the air electrode and the fuel electrode in each battery, and 0.8 A / cm ²
At the terminal voltage.

[0039]

[Table 9]

FIG. 8 is a graph showing the relationship between the combination of the air electrode 3 and the fuel electrode 4 and the terminal voltage based on Table 9. As is clear from Table 9 and FIG. 8, when combinations are made between the examples (2) to (5) of the air electrode and the examples (2) to (5) of the fuel electrode, the power generation of the polymer electrolyte fuel cell 1 is achieved. Performance can be improved.

For comparison, a slurry was prepared by adding 20% by weight of PTFE particles having an average particle diameter of 10 μm to the electrode slurry of Example-III.
mg / cm ² , applied to one surface of each of the two porous carbon papers and dried, and the ratio Wp / W of the blending weights of the two.
An example (7) of an electrode having two diffusion layers where c is Wp / Wc = 0.6 was obtained. The electrode thickness t in this example (7) is t
= 15 μm, and t of the electrode example (3) shown in Table 4
= 9 μm thicker than 6 μm.

The two examples (7) are as follows: the air electrode 3 and the fuel electrode 4
And an electrolyte membrane-electrode assembly 9 in the same manner as described above.
Was made. A polymer electrolyte fuel cell 1 was assembled using the electrolyte membrane-electrode assembly 9 and power generation was performed under humidification of the air electrode and the fuel electrode to measure the relationship between the current density and the terminal voltage. The terminal voltage at 0.8 A / cm ² was found to be 0.643V. It is clear that this terminal voltage is about 6% lower than the terminal voltage of 0.687 V when the example (3) and the example (3) shown in Table 8 are combined.

From these facts, the carbon black particles have a water adsorption amount A at a saturated steam pressure of 60 ° C. of A ≦ A.
80 cc / g, and the ratio Wp / Wc of both blending weights Wp and Wc is 0.4 ≦ Wp / Wc.
The need for ≦ 1.25 is apparent.

When the ratio Wp / Wc of the two compounding weights is set as described above, from Table 4, the electrode thickness t is 5 μm ≦ t ≦ 8 μm.
m, and from Table 5, the coverage Cc of the catalyst particles is 91%.
% ≦ Cc ≦ 98%, and from Table 6, the degree of dispersion D of the catalyst particles is 3% ≦ D ≦ 8%.

[0045]

According to the present invention, a solid polymer electrolyte fuel cell having the above-described structure, in which the thickness of each electrode is reduced and the power generation performance is further improved, can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic side view of a polymer electrolyte fuel cell.

FIG. 2 is a graph showing a relationship between a ratio Wp / Wc of both compounding weights and water retention of an electrode.

FIG. 3 is a graph showing a relationship between a ratio Wp / Wc of both compounding weights and an electrode thickness.

FIG. 4 is a graph showing a relationship between a ratio Wp / Wc of both compounding weights and a coverage Cc of catalyst particles.

FIG. 5 is a graph showing a relationship between a ratio Wp / Wc of both compounding weights and a degree of dispersion D of catalyst particles.

FIG. 6 shows the degree of dispersion D of catalyst particles and the coverage Cc of catalyst particles.
6 is a graph showing a relationship with the graph.

FIG. 7 is a graph showing the relationship between the degree of dispersion D of catalyst particles and the thickness of an electrode.

FIG. 8 is a graph showing a relationship between a combination of an air electrode and a fuel electrode and a terminal voltage.

[Explanation of symbols]

 1 polymer electrolyte fuel cell 2 electrolyte membrane 3 air electrode (electrode) 4 fuel electrode (electrode)

Continued on the front page (72) Inventor Nobuhiro Saito 1-4-1, Chuo, Wako-shi, Saitama Pref. Inside of Honda R & D Co., Ltd. (72) Inventor Masaaki Nanami 1-4-1, Chuo, Wako-shi, Saitama Pref. Within Honda R & D Co., Ltd. (72) Inventor Junji Matsuo 1-4-1 Chuo, Wako-shi, Saitama F-term within Honda R & D Co., Ltd. (reference) 5H018 AA06 AS02 AS03 EE03 EE08 EE17 HH00 HH05 HH08 5H026 AA06 EE02 EE05 EE18 HH00 HH05 HH08

Claims (3)

[Claims] 1. An electrolyte membrane (2) having a polymer ion exchange component and a pair of electrodes (3, 3) sandwiching the electrolyte membrane (2).
4), wherein each of the electrodes (3, 4) comprises a polymer ion-exchange component and a plurality of catalyst particles having a catalyst metal supported on the surface of water-repellent carbon black particles. Solid polymer fuel cell. 2. The carbon black particles have a water adsorption amount A at 60 ° C. under a saturated steam pressure of A ≦ 80 cc / g.
When the compounding weight of the polymer ion exchange component is Wp and the compounding weight of the carbon black particles is Wc, both compounding weights Wp and W
2. The polymer electrolyte fuel cell according to claim 1, wherein the ratio c of W is 0.4 ≦ Wp / Wc ≦ 1.25. 3. The polymer ion exchange component in both electrodes (3, 4) is a sulfonated aromatic hydrocarbon polymer, and the degree of dispersion D of the catalyst particles is 2% <D <9%.
And the degree of dispersion D is D = [{(Ts / Tp)-(As / Ap)} / (Ts /
Tp)] × 100 (%), where Tp is the theoretical catalyst metal concentration in the catalyst particles, Ts is the theoretical S concentration in the sulfonate, and Ap is the measured catalyst metal in the catalyst particles. 3. The polymer electrolyte fuel cell according to claim 1, wherein the concentration and As are measured S concentrations in the sulfonated product.