JPH08185873A - Fuel cell - Google Patents

Abstract

PURPOSE: To enhance the colliding performance of gases with a projection and improve the diffusiveness thereof by improving the array of a plurality of projections forming the gas flow passage of a current collector. CONSTITUTION: A current collector 15 is provided with a plurality of rectangular solid ribs 33, and a gas flow passage is formed out of the ribs 33 and the surface of a gas diffusion electrode. Regarding the arrangement of the ribs 33, ribs 33a facing the right side with the longitudinal direction thereof inclined 45 degrees along a clockwise direction for a vertical lower level, and ribs 33b facing the left side with the longitudinal direction thereof inclined 45 degrees along a counterclockwise direction for a vertical lower level are arranged like a grating. According to this construction, gases always flow, colliding with the walls of the ribs 33, and become a turbulent flow, thereby improving diffusiveness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell, and more specifically, to a joined body in which an electrolyte membrane is sandwiched between two electrodes, and a flow passage for contacting the joined body to form a supply gas passage. And a forming member.

[0002]

2. Description of the Related Art Conventionally, a fuel cell has been known as a device for directly converting the energy of fuel into electrical energy. In a fuel cell, usually, a pair of electrodes are arranged with an electrolyte membrane sandwiched between them, a fuel gas such as hydrogen is brought into contact with the surface of one electrode, and an oxygen-containing gas containing oxygen is brought into contact with the surface of the other electrode. By utilizing the electrochemical reaction that occurs at this time, electric energy is taken out from between the electrodes. The fuel cell can extract electric energy with high efficiency as long as the fuel gas and the oxygen-containing gas are supplied.

By the way, in such a fuel cell, the fuel gas and the oxygen-containing gas are supplied to the surface of the electrode by a member called a current collector which serves both as a passage for these gases and as a collector electrode. As the current collector, a current collector having a linear flow path groove is generally used. Further, it has been proposed that a flow path is constituted by a plurality of convex portions to increase the contact area of gas with the electrode surface to enhance the energy conversion efficiency of the fuel cell.

Further, as shown in FIG.
It has also been proposed to arrange the 00s in an array so that the gas collides with the wall surface of the convex portion 200 to improve the diffusivity of the gas and enhance the energy conversion efficiency of the fuel cell (JP-A-2- 155171).

[0005]

By the way, in the prior art in which the array is arranged, since the convex portions 200 are arranged in a straight line, the gas is, as shown by the solid line arrow in FIG.
The gaps between the protrusions 200 are straightly removed. Therefore, with this configuration, it is not enough to make the gas collide with the convex portion 200 without fail, and sufficient gas diffusibility cannot be obtained. Therefore, there arises a problem that the energy conversion efficiency of the fuel cell is reduced.

The fuel cell of the present invention has been made in view of the above problems, and by improving the arrangement of a plurality of convex portions constituting the gas flow path of the current collector, the gas collides with the convex portions. The purpose is to improve the gas diffusion property and the gas diffusivity, and further to improve the energy conversion efficiency of the fuel cell.

[0007]

In order to achieve such an object, the following constitution is adopted as a means for solving the above problems.

That is, in the fuel cell according to claim 1 of the present invention, a flow path for forming a flow path of a supply gas by a bonded body in which an electrolyte membrane is sandwiched between two electrodes and the bonded body is in contact with the bonded body. In the fuel cell including a forming member, the flow path forming member includes a plurality of elongated convex portions, and the plurality of convex portions are arranged such that their longitudinal directions intersect with adjacent convex portions. The feature is that they are arranged.

In the fuel cell having such a structure, all the convex portions may be arranged such that the longitudinal direction of the convex portions is inclined with respect to the vertically downward direction.

[0010]

According to the fuel cell of the present invention configured as described above, the convex portions of the flow path forming member are arranged so that the longitudinal directions of adjacent convex portions intersect each other. Thus, the supply gas collides with the wall surface of the convex portion and meanders in any direction. Therefore, the gas becomes turbulent due to the collision and enhances diffusivity.

According to the fuel cell of the second aspect, since all the convex portions are arranged such that the longitudinal direction of the convex portions is inclined vertically downward, the water produced by the convex portions in the flow path is formed. And humidifying water can be easily discharged.

[0012]

Preferred embodiments of the present invention will be described below in order to further clarify the structure and operation of the present invention described above.

FIG. 1 is a structural diagram showing a single cell of a polymer electrolyte fuel cell 10 as a first embodiment. As shown in this figure, the polymer electrolyte fuel cell 10 is composed of an electrolyte membrane 11 as a single cell, and a cathode 12 and an anode 13 as gas diffusion electrodes having a sandwich structure in which the electrolyte membrane 11 is sandwiched from both sides. And a current collector 15 as a flow path forming member that forms a flow path of the material gas and the fuel gas with the cathode 12 and the anode 13 while sandwiching the sandwich structure (joined body) 20 from both sides.

The electrolyte membrane 11 is an ion exchange membrane made of a polymer material, for example, a fluororesin, and exhibits good electric conductivity in a wet state. Here, Nafion 115 manufactured by EI DuPont, USA is used. The cathode 12 and the anode 13 are formed of carbon cloth woven from threads made of carbon fibers, and carbon powder carrying platinum or an alloy of platinum and another metal as a catalyst on the surface of the carbon cloth. Has been applied.

The carbon powder supporting platinum is prepared by the following method. An aqueous solution of platinum sulfite complex is obtained by mixing an aqueous solution of chloroplatinic acid and sodium thiosulfate. While stirring this aqueous solution, the hydrogen peroxide solution is removed to deposit colloidal platinum particles in the aqueous solution. Next, carbon black as a carrier (for example, Vulcan XC-
72 (trademark of CABOT Co., USA) and Denka Black (trademark of Denki Kagaku Kogyo Co., Ltd.) are added and stirred to deposit colloidal platinum particles on the surface of carbon black. Next, the solution is suction-filtered or pressure-filtered to separate the carbon black to which the platinum particles are attached, washed repeatedly with deionized water (pure water), and then completely dried at room temperature.

Next, the agglomerated carbon black is pulverized by a pulverizer and then in a hydrogen reducing atmosphere at 250 ° C. to 350 ° C.
The platinum on the carbon black is reduced and the remaining chlorine is completely removed by heating at 0 ° C. for about 2 hours to complete the platinum-supported carbon powder. Here, the weight of platinum is 20 [%] (weight%) with respect to the weight of carbon black.

The current collector 15 is formed of a dense carbon plate. The current collector 15 forms a flow path for the oxygen-containing gas, which is a material gas, with the surface of the cathode 12 and also forms an oxygen-containing gas flow path 15 a that serves as a water collection path for the water generated at the cathode 12, and also the anode 13 A hydrogen gas flow path 15b forming a flow path of a mixed gas of hydrogen gas which is a fuel gas and water vapor is formed with the surface of the. Such a current collector 1
The detailed shape of 5 will be described later.

The electrolyte membrane 11 and the cathode 1 described above
2, the anode 13 and the current collector 15 have a single-cell configuration of the polymer electrolyte fuel cell 10, and actually, the current collector 1
The solid polymer fuel cell 10 is configured by stacking a plurality of sets of 5, 5, the cathode 12, the electrolyte membrane 11, the anode 13, and the current collector 15 in this order.

The polymer electrolyte fuel cell 10 having such a structure
The current collector 15 has the following shape. As shown in FIG. 2, the current collector 15 is formed as an octagonal plate-shaped member, and in the vicinity of four oblique edges of the eight sides of the current collector 15, elongated holes are formed along the edges. 21, 23 and holes 25, 27 are formed. The holes 21 and 23 and the holes 25 and 27, when stacked, are solid polymer fuel cell 1
Two fuel gas supply / exhaust passages and two oxidizing gas supply / exhaust passages that penetrate 0 in the stacking direction are formed. As shown in the drawing, a step surface 31 is formed between the hole 21 and the hole 23 on one of the stacked surfaces of the current collector 15 (display surface in FIG. 2), and the step surface 31 is one step lower than the flat surface of the outer edge. On the step surface 31, a plurality of rectangular parallelepiped ribs (projections) 33 having a width of 1 [mm], a length of 3 [mm], and a height of 1 [mm] are formed.

The arrangement of the rectangular parallelepiped ribs 33 is a rightward rib 3 whose longitudinal direction is inclined 45 degrees clockwise with respect to the vertically downward direction.
3a and a leftward rib 33b whose longitudinal direction is tilted 45 degrees counterclockwise with respect to the vertically downward direction are arranged in a lattice pattern, and the longitudinal directions of both ribs 33a and 33b intersect each other. The rib 33, the step surface 31, and the surface of the gas diffusion electrode form a flow path for the oxygen-containing gas.

Further, between the hole 25 and the hole 27 on the other side (back surface in FIG. 2) of the laminated surface of the current collector 15, the step surface 31 and the rib 33 formed between the hole 21 and the hole 23 are formed. A stepped surface and a rib (not shown) having the same shape as the above are formed. The step surface, the rib, and the surface of the gas diffusion electrode form a flow path for fuel gas.

The polymer electrolyte fuel cell 10 thus constructed performs the electrochemical reaction represented by the following equations (1) and (2) to directly convert chemical energy into electrical energy.

Cathode reaction (oxygen electrode): 2H ++ 2e − + (1/2) O 2 → H 2 O (1) Anode reaction (fuel electrode): H 2 → 2H ++ 2e − (2)

At this time, the oxygen-containing gas flowing in the flow path of the oxygen-containing gas formed by the step surface 31 and the ribs 33 and the like is ribbed as shown in FIG. 3 (as shown by the solid line arrow in FIG. 3). It collides with the wall surface of 33 and meanders. Therefore, the gas becomes turbulent and the diffusibility of the oxygen-containing gas to the gas diffusion electrode is improved.

On the other hand, the water generated on the step surface 31 by the reaction shown in the equation (1) flows vertically downward while circumventing the rib 33 and collects in the vertically lower part of the hole 23, but bypasses this rib 33. It is assumed that a part of the water stays on the way like the stagnant water W shown in FIG. At this time, since the oxygen-containing gas bypasses the stagnant water W as shown by the broken line arrow in the figure, the diffusibility of the oxidizing gas to the gas diffusion electrode does not deteriorate even on the downstream side of the stagnant water W.

On the other hand, since the fuel gas humidified to near the saturated vapor pressure is passed through the fuel gas passage, the humidified water may be the stagnant water W described above depending on the operating conditions of the polymer electrolyte fuel cell 10. Like the above, there may be water retention. At this time, since the fuel gas bypasses the stagnant water, the diffusibility of the fuel gas to the gas diffusion electrode does not deteriorate even on the downstream side of the stagnant water.

FIG. 4 is a graph showing the relationship between voltage and current density in the polymer electrolyte fuel cell 10 of the first embodiment and the fuel cell of the conventional example (shown in FIG. 7). In the graph, curve A shows the polymer electrolyte fuel cell 10 at an operating temperature of 8
Shows the relationship between voltage and current density when operating at 0 ° C,
Curve C shows the conventional fuel cell shown in FIG.
The relationship between the voltage and the current density when operating at ℃ is shown. As shown, the polymer electrolyte fuel cell 10 of the first embodiment
Has excellent characteristics over the entire current density of the measurement range as compared with the conventional fuel cell. In particular, the voltage drop in the high current density region (0.5 [A / cm2] or more) was small, and the improvement of gas diffusivity was confirmed.

FIG. 5 is a graph showing the relationship between the voltage and the holding time in the polymer electrolyte fuel cell 10 of the first embodiment and the fuel cell of the conventional example (shown in FIG. 7). In the graph, line A indicates the polymer electrolyte fuel cell 10 at an operating temperature of 80.
The relationship between the voltage and the holding time when operating at 0 ° C is shown, and the line C shows the relationship between the voltage and the holding time when the conventional fuel cell shown in Fig. 7 is operated at an operating temperature of 80 ° C. As shown in the figure, the polymer electrolyte fuel cell 10 of the first embodiment is
It was confirmed that the high voltage was maintained stably as compared with the fuel cell of the conventional example.

As described in detail above, according to the polymer electrolyte fuel cell 10 of the first embodiment, the ribs 33 are arranged so that the longitudinal directions of the adjacent ribs intersect with each other, and the flow of the oxygen-containing gas flows. Since the path is formed, the oxygen-containing gas becomes turbulent and the diffusibility of the oxygen-containing gas to the gas diffusion electrode is improved.
As a result, the polymer electrolyte fuel cell 10 can be a fuel cell having excellent energy conversion efficiency.

The rib 33 (rightward rib 3) of the collector 15 in the polymer electrolyte fuel cell 10 of the first embodiment is also used.
Since the longitudinal direction of the ribs 3a and the leftward ribs 33b) is arranged vertically downward and inclined by 45 degrees from the horizontal direction, it is possible to easily discharge the generated water on the step surface 31 provided with the ribs 33. As a result, it is possible to prevent the generated water from stagnating and hindering the diffusion of the oxygen-containing gas. Therefore, the voltage stability is improved, and the battery reliability is improved.

Further, according to the polymer electrolyte fuel cell 10 of the first embodiment, not only the flow path of the oxygen-containing gas but also the flow path of the hydrogen gas is improved in the diffusion property of the gas to the diffusion electrode. As a result, the energy conversion efficiency can be improved, the humidification water can be easily discharged, and the voltage stability can be improved.

The second embodiment of the present invention will be described below. The second embodiment relates to a fuel cell having substantially the same structure as the polymer electrolyte fuel cell 10 of the first embodiment, and is different from the first embodiment only in the arrangement of the ribs of the current collector.
FIG. 6 is an explanatory view showing the arrangement of ribs of the current collector in the second embodiment. As shown in FIG. 6, the current collector has a rectangular parallelepiped rib (width 1 [mm], length 3) as in the first embodiment.
[Mm], height 1 [mm]) 133 is formed in plural, and the arrangement thereof is a vertical rib 133a whose longitudinal direction is directed vertically downward and a lateral rib 133b whose longitudinal direction is directed horizontally. Are arranged alternately. A flow path for the oxygen-containing gas is formed by the ribs 133 and the surface of the gas diffusion electrode having such an arrangement.

In the oxygen-containing gas flowing in the flow path of the oxygen-containing gas, the ribs 133 are arranged so that the longitudinal directions of the adjacent ribs 133 intersect each other.
As indicated by the solid arrow, the rib 133 constantly collides with the wall surface of the rib 133 and meanders. Therefore, the gas becomes turbulent and the diffusibility of the oxygen-containing gas to the gas diffusion electrode is improved. As a result, the polymer electrolyte fuel cell of this example has excellent energy conversion efficiency.

The relationship between voltage and current density in the polymer electrolyte fuel cell of the second embodiment is shown in FIG. 4 described above. In FIG. 4, a curve B shows the relationship between the voltage and the current density when the polymer electrolyte fuel cell of the second embodiment was operated at an operating temperature of 80 ° C. As shown in the figure, the polymer electrolyte fuel cell of the second embodiment has a higher current density region (0.5 [A / cm2]) than the fuel cell of the conventional example (shown by the curve C).
In the above), the voltage drop was small, and the gas diffusivity was improved.

The relationship between voltage and holding time in the polymer electrolyte fuel cell of the second embodiment is shown in FIG. 5 described above. In FIG. 5, line B shows the relationship between the voltage and the holding time when the polymer electrolyte fuel cell of the second embodiment was operated at an operating temperature of 80 ° C. As shown in the figure, the polymer electrolyte fuel cell of the second embodiment has about the same voltage stability as the fuel cell of the conventional example (shown by the line C), and the fuel cell of the first embodiment has the same stability. Compared to the battery (indicated by line A), the voltage stability is poor. In the fuel cell of the first embodiment, this means that all ribs 3
3 are arranged with their longitudinal direction inclined with respect to the vertically downward direction, it is possible to facilitate the discharge of the produced water, whereas in the second embodiment, they are oriented in the horizontal direction. This is because, since there is the horizontal rib 133b present, the generated water is retained near the horizontal rib 133b like the stagnant water W shown in FIG. 6, and the drainage performance is deteriorated.

That is, the polymer electrolyte fuel cell of the second embodiment has an effect that the diffusivity of gas to the gas diffusion electrode is enhanced and the energy conversion efficiency becomes excellent. On the other hand, regarding the drainage property in the gas flow path,
It is inferior to that of the example, and therefore the voltage stability is slightly inferior.

In the first and second embodiments, the ribs 33 and 133 have a rectangular parallelepiped shape. However, instead of this, a convex portion having an elliptical plane may be used. I wish I had it.

In the first embodiment, the rib 33 is
Although the longitudinal direction is arranged at an angle of 45 degrees with respect to the vertically downward direction, it is not necessarily 45 degrees, and if the water near the ribs 33 flows down, for example, 80 degrees, 60 degrees, etc. May be

The embodiment of the present invention has been described above.
The present invention is not limited to these examples, and it goes without saying that the present invention can be implemented in various modes without departing from the scope of the present invention.

[0040]

As described above, in the fuel cell according to the first aspect, the gas flow in the flow path forming member can be made turbulent to enhance the gas diffusibility. Therefore, a fuel cell having excellent energy conversion efficiency can be obtained.

In the fuel cell according to the second aspect, the drainage property of the flow path forming member can be improved. Therefore, a fuel cell having excellent voltage stability can be obtained.

[Brief description of drawings]

FIG. 1 is a structural diagram showing a single cell of a polymer electrolyte fuel cell 10 as a first embodiment of the present invention.

FIG. 2 is a plan view of a collector 15 of the polymer electrolyte fuel cell 10.

FIG. 3 is an explanatory diagram showing an enlarged array of ribs of a current collector 15.

FIG. 4 is a graph showing the relationship between voltage and current density in the polymer electrolyte fuel cells of the first and second examples and the polymer electrolyte fuel cell of the conventional example.

FIG. 5 is a graph showing the relationship between voltage and holding time in the polymer electrolyte fuel cells of the first and second examples and the polymer electrolyte fuel cell of the conventional example.

FIG. 6 is an explanatory view showing an enlarged array of ribs of the current collector in the second embodiment.

FIG. 7 is an explanatory view showing an enlarged array of ribs of a current collector in a conventional example.

[Explanation of symbols]

 10 ... Polymer electrolyte fuel cell 11 ... Electrolyte membrane 12 ... Cathode 13 ... Anode 15 ... Current collector 15a ... Oxygen-containing gas flow path 15b ... Hydrogen gas flow path 21, 23, 25, 27 ... Hole 31 ... Step surface 33 , 133 ... ribs 33a ... rightward ribs 33b ... leftward ribs 133a ... vertical ribs 133b ... horizontal ribs

Claims (2)

[Claims] 1. A fuel cell comprising: a joined body that sandwiches an electrolyte membrane between two electrodes; and a flow passage forming member that is in contact with the joined body and forms a flow passage for a supply gas. The fuel cell is characterized in that the passage forming member includes a plurality of elongated protrusions, and the plurality of protrusions are arranged so that their longitudinal directions intersect with adjacent protrusions. 2. The fuel cell according to claim 1, wherein all the convex portions are arranged such that the longitudinal direction of the convex portions is inclined with respect to the vertically downward direction.