JP2009301745A - Fuel cell and fuel cell system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell capable of inhibiting performance deterioration of a fuel cell due to configuration changes of an electrode catalyst and a fuel cell system using the same. <P>SOLUTION: In a fuel cell 10 generating power by receiving a fuel gas supply at an anode of an MEA 12 and an oxidant gas supply at a cathode, the MEA 12 includes an electrolyte membrane 14 having protonic conductivity and a plurality of electrode catalyst layers 16 laminated to face a power generating face in the electrolyte membrane 14. Each of the electrode catalyst layer is composed in free input/output in a direction of lamination surface respectively. As a system using such fuel cell 10, it is preferable that the electrode catalyst layer 161 contacting with the electrolyte membrane 14 and the electrode catalyst layers 162, 163 not contacting directly with the electrolyte membrane 14 are exchanged in case power generating performance of the fuel cell 10 is deteriorated. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell or a fuel cell system, and more particularly to an internal structure of a fuel cell.

  The fuel cell is used as a fuel cell stack in which a plurality of fuel cells (hereinafter referred to as “unit cells”) are stacked. The unit cell itself is also a laminate of planar members, and has a membrane electrode assembly (MEA) composed of an electrolyte membrane sandwiched between electrode catalyst layers, and the MEA is sandwiched between separators from both sides. It is composed of that.

  In such a fuel cell, when the MEA is exposed to a high potential environment for a long time, the catalyst particles contained in the electrode catalyst layer may be dissolved and eluted. In particular, in the cathode-side electrode catalyst layer, the catalyst particles are significantly dissolved and eluted, causing the performance of the MEA to deteriorate.

  Therefore, conventionally, for example, Japanese Patent Laid-Open No. 2006-79917 proposes an MEA that can maintain desired power generation performance over a long period of time. More specifically, in this MEA, the electrode catalyst layer on the cathode side is composed of two or more layers, and the particle diameter of the electrode catalyst constituting the electrode catalyst layer on the electrolyte membrane side is larger than that on the gas diffusion layer side. It is comprised so that it may become. Catalyst particles having a relatively large particle diameter have a slow elution rate. According to the conventional MEA, since the catalyst particles having a large particle diameter are arranged on the electrolyte membrane side where the catalyst particles are easily dissolved, the durability of the MEA can be improved.

JP 2006-79917 A JP 2007-305427 A JP 2006-236631 A JP 2005-353494 A

  In the region near the electrolyte membrane in the electrode catalyst layer, the power generation reaction is actively performed. For this reason, in such a region, even if measures are taken as in the prior art, carbon corrosion and elution of catalyst particles occur gradually. For this reason, the output of the fuel cell gradually decreases as the shape of the electrode catalyst progresses.

  The present invention has been made to solve the above-described problems, and provides a fuel cell capable of suppressing a decrease in fuel cell performance due to a change in the shape of an electrode catalyst, and a fuel cell system using the fuel cell. For the purpose.

In order to achieve the above object, a first invention is a fuel cell,
In a fuel cell that generates power by receiving supply of fuel gas to the anode of the membrane electrode assembly and supply of oxidant gas to the cathode,
The membrane electrode assembly is
An electrolyte membrane layer having proton conductivity;
A plurality of electrode catalyst layers laminated to face the power generation surface in the electrolyte membrane layer,
Each of the plurality of electrode catalyst layers has a structure for taking in and out in the direction of the laminated surface.

According to a second invention, in the first invention,
The fuel cell includes a pressing mechanism that presses the membrane electrode assembly in the stacking direction.

In order to achieve the above object, a third invention is a fuel cell system,
In a fuel cell system including a fuel cell that generates power by receiving supply of fuel gas to the anode of the membrane electrode assembly and supply of oxidant gas to the cathode,
The membrane electrode assembly is
An electrolyte membrane layer having proton conductivity;
A plurality of electrode catalyst layers laminated to face the power generation surface in the electrolyte membrane layer,
Each of the plurality of electrode catalyst layers has a structure for taking in and out in the direction of the laminated surface,
Determining means for determining a decrease in power generation performance of the fuel cell;
When it is determined that the power generation performance is lowered, an exchange means for replacing the electrode catalyst layer in contact with the electrolyte membrane layer and the electrode catalyst layer not in direct contact with the electrolyte membrane layer;
It is characterized by providing.

According to a fourth invention, in the third invention,
The determination means includes output detection means for detecting the output of the fuel cell, and determines a decrease in power generation performance of the fuel cell when the output is reduced by a reference amount or more.

  The membrane electrode assembly of the first invention is configured by laminating a plurality of electrode catalyst layers. And it has the structure for taking in and out these electrode catalyst layers in the lamination surface direction. Since the electrode catalyst layer in the vicinity of the electrolyte membrane layer is a region where the power generation reaction is actively performed, the catalyst shape is likely to change. According to the present invention, it is possible to easily replace only the electrode catalyst layer that easily undergoes a change in form, so that the maintainability can be improved. Moreover, the situation where the performance of a fuel cell falls can be suppressed effectively by replacing | exchanging the electrode catalyst which changed the form.

  The fuel cell of the second invention has a pressing mechanism for pressing the membrane electrode assembly in the stacking direction. For this reason, according to this invention, the contact resistance between the several electrode catalyst layers laminated | stacked can be reduced effectively.

  According to the third aspect of the present invention, the electrode is in contact with the electrolyte membrane layer when the plurality of electrode catalyst layers constituting the membrane electrode assembly are respectively taken in and out, and the power generation performance of the fuel cell is lowered. The arrangement of the catalyst layer and the electrode catalyst layer that is not in direct contact is exchanged. Since the electrode catalyst layer in the vicinity of the electrolyte membrane layer is a region where the power generation reaction is actively performed, the catalyst shape is likely to change. According to the present invention, since the electrode catalyst whose shape has changed in the vicinity of the electrolyte membrane layer and the electrode catalyst whose shape has not changed can be exchanged, it is possible to effectively suppress the output decrease of the fuel cell.

  When the power generation performance of the fuel cell decreases, the output of the fuel cell decreases. For this reason, according to the fourth invention, it is possible to determine with high accuracy a decrease in the power generation performance of the fuel cell by determining whether or not the output of the fuel cell has decreased by a specified amount or more.

  Several embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted. The present invention is not limited to the following embodiments.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 is a cross-sectional view schematically showing the configuration of the fuel cell in the first embodiment. The fuel cell 10 is used as a fuel cell system that supplies electric power generated by a power generation reaction to a load device such as a motor. The fuel cell 10 includes a membrane electrode assembly (MEA) 12, and the MEA 12 includes an electrolyte membrane 14, a cathode side electrode catalyst layer 16, and an anode side electrode catalyst layer 18. More specifically, the electrode catalyst layer 16 has a structure in which three electrode catalyst layers 161, 162, and 163 are laminated. Each of the electrode catalyst layers 161, 162, and 163 is configured in a cartridge shape that can be taken in and out in the direction of the laminated surface, and has a mechanism in which these can be taken in and out using the actuator 32.

  Gas diffusion layers 20 and 22, gas flow paths 24 and 26, and separators 28 and 30 are laminated on the outside of the electrode catalyst layers 16 and 18, respectively. The fuel cell 10 generates power by receiving supply of fuel gas (for example, hydrogen gas) at the anode and supply of oxidant gas (air) at the cathode. In the first embodiment, the configuration of the fuel gas supply / exhaust system and the configuration of the air supply / exhaust system are not limited, and a description thereof will be omitted.

[Features of Embodiment 1]
The cathode-side electrode catalyst layer 16 is in an environment exposed to a high potential (about 1 V). For this reason, in such an environment, the catalyst particles may be dissolved and ionized. In particular, when the catalyst is dissolved in the electrode catalyst layer 16 in the vicinity of the electrolyte membrane 14, it may diffuse into the electrolyte membrane 16 having a low metal ion concentration and be deposited in the electrolyte membrane 16. Further, when the dissolved catalyst is reprecipitated in the electrode catalyst layer 16, the catalyst particle size grows and the surface area of the catalyst capable of performing the power generation reaction may be reduced. As described above, when the electrode catalyst layer 16 is dissolved in the vicinity of the electrolyte membrane 14, the shape change of the electrode catalyst layer 16 appears remarkably. For this reason, when such a change in the shape of the electrode catalyst layer 16 proceeds, the power generation performance of the fuel cell 10 may deteriorate.

  Therefore, the fuel cell 10 according to the first embodiment has a cartridge shape in which the electrode catalyst layer 16 can be taken in and out. More specifically, the electrode catalyst layers 161, 162, and 163 are configured to be able to be inserted into and removed from the MEA 12 in the direction of the stacking surface. The electrode catalyst layers 161, 162, and 163 are put in and out by driving the actuator 32. In the electrode catalyst layer 16, the region in the vicinity of the electrolyte membrane 14, that is, the form of the electrode catalyst layer 161 changes most. For this reason, if the actuator 32 is driven and, for example, the electrode catalyst layer 161 and the electrode catalyst layer 162 or 162 are replaced, a situation in which the power generation performance of the fuel cell 10 is reduced can be effectively suppressed. .

  FIG. 2 is a perspective view showing a part of the fuel cell 10 shown in FIG. The replacement of the electrode catalyst layer 16 is performed, for example, by driving the actuator 32 by the method shown in this figure. As shown in this figure, first, the cover 281 provided on the cathode-side separator 28 is opened ((1) in the figure). Next, the separator 28 and the electrode catalyst layers 162 and 163 are raised in the stacking direction ((2) in the figure). Next, the electrode catalyst layer 161 is once pulled out and inserted between the separator 28 and the electrode catalyst layer 163. ((3) in the figure). Then, the separator 28 and the electrode catalyst layers 162 and 163 descend in the stacking direction and are pressed again in the stacking direction ((4) in the figure).

  As described above, according to the fuel cell 10 of the first embodiment, by driving the actuator 32, the electrode catalyst layer 161 on the electrolyte membrane 14 side, the electrode catalyst layers 162 and 163 on the gas diffusion layer 20 side, and Can be replaced. As a result, the electrode catalyst layer 161 in which the catalyst shape change is likely to proceed and the other electrode catalyst layers 162 and 163 in which the shape change is less likely to be exchanged can be exchanged, which effectively reduces the power generation performance of the fuel cell 10. Can be suppressed.

  Further, according to the fuel cell 10 of the first embodiment, since the plurality of stacked electrode catalyst layers 161, 162, and 163 are interchanged with each other, compared to the case where the entire electrode catalyst layer 16 is replaced. The use efficiency of the catalyst can be improved.

  Further, according to the fuel cell 10 of the first embodiment, the MEA 14 is reliably pressed in the stacking direction by the action of the actuator 32. For this reason, in the structure which laminated | stacked the several electrode catalyst layer 161,162,163, the situation where contact resistance increases at a lamination | stacking interface can be suppressed effectively.

  By the way, in the first embodiment described above, the three electrode catalyst layers 161, 162, and 163 are laminated in a structure that can be taken in and out, but the number of electrode catalyst layers to be laminated is not limited to this. . That is, the number of electrode catalyst layers is not particularly limited as long as a plurality of electrode catalyst layers are stacked and each of them can be taken in and out.

  In Embodiment 1 described above, the arrangement of the electrode catalyst layers 161, 162, and 163 is replaced by the actuator 32, but the mechanism used for the replacement is not limited to this. That is, as long as the plurality of stacked electrode catalyst layers 161, 162, and 163 can be replaced, other known mechanisms may be used.

  Further, in the first embodiment described above, the present invention is applied to the fuel cell 10 composed of a single MEA 14, but the present invention is applied to a stacked fuel cell in which a plurality of MEAs 14 are stacked. It is good.

  In the first embodiment described above, the present invention is applied to the electrode catalyst layer 16 on the cathode side, but the present invention may be applied to the electrode catalyst layer 18 on the anode side.

  In the first embodiment described above, the MEA 14 is pressed in the stacking direction by the actuator 32. However, the method of pressing the MEA 14 is not limited to this, and other known mechanisms may be used. Good.

  In the first embodiment described above, the electrolyte membrane 14 corresponds to the “electrolyte membrane layer” in the first invention.

  In the first embodiment described above, the actuator 32 corresponds to the “pressing mechanism” in the second invention.

Embodiment 2. FIG.
[Features of Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIG. The system of the present embodiment can be realized by using the fuel cell 10 shown in FIG. 1 and causing the system to execute a routine shown in FIG. 3 described later.

  In the fuel cell 10 according to Embodiment 1 described above, the cathode-side electrode catalyst layer 16 is configured by laminating a plurality of electrode catalyst layers 161, 162, and 163. And the fall of the output of the fuel cell 10 can be suppressed by changing arrangement | positioning of these electrode catalyst layers 161,162,163 laminated | stacked.

  Here, as described above in the first embodiment, when the form of the electrode catalyst layer 16 on the cathode side changes, the power generation performance of the fuel cell 10 decreases. Therefore, in the second embodiment, when the output reduction of the fuel cell 10 is recognized, the arrangement of the electrode catalyst layer 16 is replaced. More specifically, the output P of the fuel cell 10 is detected, and the electrode catalyst layer 16 is arranged when the detected output P is reduced by a predetermined threshold or more than the normal output P0. I will replace it. Thereby, the output fall of the fuel cell 10 can be suppressed effectively.

[Specific Processing in Second Embodiment]
Next, with reference to FIG. 3, the specific content of the process performed in this Embodiment is demonstrated. FIG. 3 is a flowchart of a routine executed by the system to replace the electrode catalyst layer 16.

  In the routine shown in FIG. 3, first, the output P of the fuel cell 10 is acquired (step 100). Here, specifically, it is acquired based on detection signals of various sensors connected to the fuel cell 10. Next, an output decrease amount ΔP is calculated (step 102). Specifically, the deviation between the output initial value P0 and the output P acquired in step 100 is calculated as the output decrease amount ΔP. As the output initial value P0, the value updated in step 108 described later is used.

  Next, it is determined whether or not the output decrease amount ΔP is equal to or greater than a predetermined threshold L (step 104). As the threshold value L, a preset value is used as a threshold value for determining the output decrease of the fuel cell 10. As a result, if the output decrease amount ΔP ≧ threshold value L is not established, it is determined that the output decrease amount of the fuel cell 10 is within the allowable range, and this routine is immediately terminated.

  On the other hand, if it is determined in step 104 that the output decrease amount ΔP ≧ threshold value L is established, it is determined that the output of the fuel cell 10 has decreased beyond the allowable range, and the process proceeds to the next step. Then, replacement control of the electrode catalyst layer 16 is executed (step 106). Here, specifically, the actuator 32 is driven, and the electrode catalyst layer 161 in contact with the electrolyte membrane 14 and the electrode catalyst layers 162 and 163 on the gas diffusion layer 20 side are exchanged.

  Next, the output initial value P0 of the fuel cell 10 is updated. Specifically, the output P of the fuel cell 10 immediately after the replacement of the electrode catalyst layer 16 is updated as the output initial value P0.

  As described above, according to the second embodiment, when the output P of the fuel cell 10 decreases from the output initial value P0 to a predetermined threshold L or more, the replacement control of the electrode catalyst layer 16 is executed. In the electrode catalyst layer 16, the region in the vicinity of the electrolyte membrane 14, that is, the form of the electrode catalyst layer 161 changes most. For this reason, by replacing the electrode catalyst layer 161 with the electrode catalyst layers 162 and 163 on the gas diffusion layer 20 side, it is possible to effectively recover the shape change of the electrode region that affects the power generation performance.

  By the way, in Embodiment 2 mentioned above, it is supposed that the three electrode catalyst layers 161, 162, and 163 are laminated in a structure that can be taken in and out, but the number of electrode catalyst layers to be laminated is not limited to this. . That is, the number of electrode catalyst layers is not particularly limited as long as a plurality of electrode catalyst layers are stacked and each of them can be taken in and out.

  In the second embodiment described above, the arrangement of the electrode catalyst layers 161, 162, and 163 is replaced by the actuator 32, but the mechanism used for the replacement is not limited to this. That is, as long as the plurality of stacked electrode catalyst layers 161, 162, and 163 can be replaced, other known mechanisms may be used.

  In the second embodiment described above, the present invention is applied to the fuel cell 10 composed of a single MEA 14, but the present invention is applied to a stacked fuel cell in which a plurality of MEAs 14 are stacked. It is good.

  In the second embodiment described above, the present invention is applied to the electrode catalyst layer 16 on the cathode side. However, the present invention may be applied to the electrode catalyst layer 18 on the anode side.

  In Embodiment 2 described above, the MEA 14 is pressed in the stacking direction by the actuator 32. However, the method of pressing the MEA 14 is not limited to this, and other known mechanisms may be used. Good.

  In Embodiment 2 described above, the state of the shape change of the electrode catalyst layer 16 is determined based on the output P of the fuel cell 10, but the method of determining the shape change of the electrode catalyst layer 16 is as follows. It is not limited to this. That is, any value having a correlation with the power generation performance of the fuel cell 10 may be determined based on, for example, a change in voltage value, current value, impedance, or the like.

  In the second embodiment described above, the electrolyte membrane 14 corresponds to the “electrolyte membrane layer” in the first invention.

  In the second embodiment described above, the actuator 32 corresponds to the “pressing mechanism” in the second aspect of the invention.

  In the second embodiment described above, the electrolyte membrane 14 corresponds to the “electrolyte membrane layer” in the third aspect of the invention, and the system executes the processing of step 104 described above, whereby the third The “determination means” in the present invention executes the processing of step 106, thereby realizing the “replacement means” in the third invention.

  In the above-described second embodiment, the system executes the process of step 100, so that the “output detection means” in the fourth aspect of the invention executes the process of step 104. The “determination means” in the fourth invention is realized.

2 is a cross-sectional view schematically showing a configuration of a fuel cell in the first embodiment. FIG. FIG. 2 is a perspective view schematically showing a part of the fuel cell 10 shown in FIG. 1. It is a flowchart of the routine performed in Embodiment 1 of the present invention.

Explanation of symbols

10 Fuel Cell 12 MEA (Membrane Electrode Assembly)
14 Electrolyte membrane 16, 161, 162, 163, 18 Electrode catalyst layer 20, 22 Gas diffusion layer 24, 26 Gas flow path 28, 30 Separator 32 Actuator

Claims (4)

In a fuel cell that generates power by receiving supply of fuel gas to the anode of the membrane electrode assembly and supply of oxidant gas to the cathode,
The membrane electrode assembly is
An electrolyte membrane layer having proton conductivity;
A plurality of electrode catalyst layers laminated to face the power generation surface in the electrolyte membrane layer,
Each of the plurality of electrode catalyst layers has a structure for taking in and out in the direction of the stacking surface.   The fuel cell according to claim 1, wherein the fuel cell includes a pressing mechanism that presses the membrane electrode assembly in a stacking direction. In a fuel cell system including a fuel cell that generates power by receiving supply of fuel gas to the anode of the membrane electrode assembly and supply of oxidant gas to the cathode,
The membrane electrode assembly is
An electrolyte membrane layer having proton conductivity;
A plurality of electrode catalyst layers laminated to face the power generation surface in the electrolyte membrane layer,
Each of the plurality of electrode catalyst layers has a structure for taking in and out in the direction of the laminated surface,
Determining means for determining a decrease in power generation performance of the fuel cell;
When it is determined that the power generation performance is lowered, an exchange means for replacing the electrode catalyst layer in contact with the electrolyte membrane layer and the electrode catalyst layer not in direct contact with the electrolyte membrane layer;
A fuel cell system comprising:   The said determination means is provided with the output detection means which detects the output of the said fuel cell, and when the said output falls more than a reference amount, it determines the fall of the power generation performance of the said fuel cell. Fuel cell system.

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