JP2017147097A - Fuel battery performance recovery method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recover a power generation performance.SOLUTION: A fuel battery performance recovery method comprises the steps of: filling an anode gas passage 22a of a plurality of single cells 100 with hydrogen; connecting a plurality of external power sources 84 to respective groups 86 into which the plurality of single cells are grouped to include one or adjacent two or more single cells so that "+" electrode is electrically connected to anode-side separators 20a at both ends, and "-" electrode is electrically connected to a cathode-side separator 20c; filling a cathode gas passage 22c of the plurality of single cells with a cleaning liquid 90 to cause the cleaning liquid to infiltrate from the cathode gas passage to respective cathode catalyst layers 14c; retaining, for a given time, a state where the plurality of external power sources are connected and the cleaning liquid has infiltrated to the cathode catalyst layer after filling the anode gas passage with hydrogen; and removing the cleaning liquid from each MEA 10 and the cathode gas passage after the retaining for the given time.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fuel cell performance recovery method.

  A polymer electrolyte fuel cell includes a membrane electrode assembly in which a pair of catalyst electrode layers are provided with an electrolyte membrane having proton conductivity interposed therebetween. In the membrane / electrode assembly, an electrochemical reaction proceeds to generate water, so that water exists in the fuel cell. When the fuel cell is operated for a long time, the cation impurities contained in the inhaled air are mixed into the water in the fuel cell, or the cation impurities contained in the material constituting the electrolyte membrane and the catalyst electrode layer are mixed with the water in the fuel cell. Or elute. If cationic impurities accumulate in the membrane electrode assembly, the power generation performance is degraded. Therefore, it is known that a cleaning liquid is introduced into the gas flow path and the inside of the fuel cell is cleaned with the cleaning liquid, whereby cationic impurities are discharged to the outside and power generation performance is recovered (for example, Patent Document 1).

JP 2001-85037 A

  However, in the method of Patent Document 1, since the diffusion efficiency of the cation impurity into the cleaning liquid is poor, the cation impurity cannot be sufficiently discharged to the outside, and the power generation performance may not be sufficiently recovered. This invention is made | formed in view of such a subject, and it aims at recovering electric power generation performance.

  The present invention includes a membrane electrode assembly in which a pair of electrode catalyst layers is provided with an electrolyte membrane interposed therebetween, an anode side separator that forms an anode gas flow path, and a cathode side separator that forms a cathode gas flow path. A method for recovering the performance of a fuel cell comprising a plurality of single cells sandwiching the membrane electrode assembly by the anode side separator and the cathode side separator, the anode gas flow paths of the plurality of single cells, and the Filling one gas flow path of the cathode gas flow path with fuel gas, and each of the plurality of single cells divided into one or two or more adjacent single cells, A positive electrode is electrically connected to one separator forming the one gas flow path among the anode side separator and the cathode side separator located at Connecting each of a plurality of external power sources so that the negative electrode is electrically connected to the other separator, and the other of the anode gas channel and the cathode gas channel of the plurality of single cells. Filling the gas flow path with a cleaning liquid to infiltrate the cleaning liquid from the other gas flow path to the electrode catalyst layer on the other gas flow path side of the pair of electrode catalyst layers; and the one gas After filling the flow path with fuel gas, maintaining the state where each of the plurality of external power sources is connected and the cleaning liquid has penetrated to the electrode catalyst layer on the other gas flow path side for a predetermined time; And then removing the cleaning liquid from the membrane electrode assembly and the other gas flow path.

  According to the present invention, the power generation performance of the fuel cell can be recovered.

FIG. 1A is a cross-sectional view showing a single cell constituting the fuel cell, and FIG. 1B is an exploded perspective view showing the single cell. FIG. 2 is an exploded perspective view of the fuel cell for explaining a method for recovering the performance of the fuel cell. FIG. 3 is a cross-sectional view of the fuel cell for explaining a method for recovering the performance of the fuel cell. FIG. 4 is a diagram for explaining the reason for connecting an external power source to the protruding portion of the anode-side separator in a state where the anode gas flow path is filled with hydrogen. FIG. 5 is a diagram for explaining diffusion of cationic impurities into the cleaning liquid. FIG. 6 is a cross-sectional view showing another example of a single cell constituting the fuel cell.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1A is a cross-sectional view showing a single cell constituting the fuel cell, and FIG. 1B is an exploded perspective view showing the single cell. A fuel cell is a polymer electrolyte fuel cell that generates power by receiving supply of a fuel gas (for example, hydrogen) and an oxidant gas (for example, air) as reaction gases, and is mounted on, for example, a fuel cell vehicle or an electric vehicle. . As shown in FIG. 1A, a single cell 100 includes a membrane electrode assembly (MEA: Membrane) in which an anode catalyst layer 14a is formed on one surface of an electrolyte membrane 12, and a cathode catalyst layer 14c is formed on the other surface. Electrode Assembly) 10 is provided.

  The electrolyte membrane 12 is a solid polymer membrane formed of a fluorine resin material or a carbon resin material, and has good proton conductivity in a wet state. The anode catalyst layer 14a and the cathode catalyst layer 14c include carbon particles (for example, carbon black) supporting a catalyst (for example, platinum or a platinum-cobalt alloy) that promotes an electrochemical reaction, and an ionomer having proton conductivity. .

  A pair of water-repellent layers (anode-side water-repellent layer 16a and cathode-side water-repellent layer 16c) and a pair of gas diffusion layers (anode gas diffusion layer 18a and cathode gas diffusion layer 18c) are disposed on both sides of the MEA 10. Has been. The pair of water repellent layers is provided to keep the moisture contained in the MEA 10 in an appropriate amount. The MEA 10, the pair of water repellent layers, and the pair of gas diffusion layers are collectively referred to as a membrane electrode gas diffusion layer assembly (MEGA) 30.

  The anode-side water-repellent layer 16a, the cathode-side water-repellent layer 16c, the anode gas diffusion layer 18a, and the cathode gas diffusion layer 18c are formed of members having gas permeability and electron conductivity. For example, carbon cloth or carbon paper is used. It is formed of a porous carbon member such as. The anode-side water-repellent layer 16a and the cathode-side water-repellent layer 16c have smaller pores of the porous carbon member than the anode gas diffusion layer 18a and the cathode gas diffusion layer 18c. For example, the pore size of the anode side water repellent layer 16a and the cathode side water repellent layer 16c is about 0.1 μm to 1 μm in diameter, and the pore size of the anode gas diffusion layer 18a and the cathode gas diffusion layer 18c is The diameter is about 10 μm to 100 μm. Thus, since the pores of the anode-side water-repellent layer 16a and the cathode-side water-repellent layer 16c are small, the liquid water can be prevented from flowing out from the anode catalyst layer 14a and the cathode catalyst layer 14c, and are included in the MEA 10. Moisture can be kept at an appropriate amount.

  A pair of separators (an anode side separator 20a and a cathode side separator 20c) that sandwich the MEGA 30 are disposed on both sides of the MEGA 30. The anode-side separator 20a and the cathode-side separator 20c are formed of members having gas barrier properties and electronic conductivity. For example, a carbon member such as dense carbon which is made impermeable to gas by compressing carbon, or press-molded stainless steel It is formed of a metal member such as steel. The anode-side separator 20a and the cathode-side separator 20c have irregularities for forming a gas flow path through which gas flows on the surface. The anode side separator 20a forms an anode gas flow path 22a between the anode gas diffusion layer 18a. The cathode side separator 20c forms a cathode gas flow path 22c between the cathode gas diffusion layer 18c. During power generation of the fuel cell, the fuel gas flows through the anode gas flow path 22a and the oxidant gas flows through the cathode gas flow path 22c. In addition, although the structure which provides a gas diffusion layer in both an anode and a cathode was shown as an example, it is not limited to this. The structure which does not equip one or both of an anode and a cathode with a gas diffusion layer may be sufficient. When the gas diffusion layer is not provided, gas is supplied from the anode gas channel or the cathode gas channel directly to the catalyst layer through the water repellent layer. In a configuration that does not include a gas diffusion layer, a sheet member having functions of water repellency, gas permeation, and conductivity may be used as the water repellent layer.

  As shown in FIG. 1B, the MEGA 30 is disposed inside an insulating member 40 made of, for example, a resin (such as an epoxy resin or a phenol resin). In other words, the frame-shaped insulating member 40 is disposed so as to cover the outer periphery of the MEGA 30. The insulating member 40 is sandwiched between the anode side separator 20a and the cathode side separator 20c.

  The anode side separator 20a and the cathode side separator 20c are provided with holes a1 to a3 and holes c1 to c3, respectively. Similarly, the insulating member 40 is provided with holes s1 to s3. The holes a1 to a3, the holes s1 to s3, and the holes c1 to c3 communicate with each other, the holes a1, s1, and c1 indicate the fuel gas supply manifold, the holes a2, s2, and c2 indicate the refrigerant supply manifold, and the hole a3. , S3, and c3 define an oxidant gas exhaust manifold.

  The anode side separator 20a and the cathode side separator 20c are provided with holes a4 to a6 and holes c4 to c6, respectively. Similarly, the insulating member 40 is provided with holes s4 to s6. The holes a4 to a6, s4 to s6, and c4 to c6 communicate with each other, the holes a4, s4, and c4 are the oxidant gas supply manifold, the holes a5, s5, and c5 are the refrigerant discharge manifold, and the hole a6, s6 and c6 define a fuel gas discharge manifold.

  An anode gas flow path 22a through which the fuel gas flows during power generation is formed on the surface of the anode separator 20a facing the MEGA 30 so that the fuel gas supply manifold and the fuel gas discharge manifold communicate with each other. A cathode gas flow path 22c through which an oxidant gas flows during power generation is formed on the surface of the cathode separator 20c facing the MEGA 30 so that the oxidant gas supply manifold and the oxidant gas discharge manifold communicate with each other. The coolant is supplied to the surface of the anode separator 20a opposite to the surface where the anode gas flow path 22a is formed and to the surface of the cathode separator 20c opposite to the surface where the cathode gas flow path 22c is formed. A refrigerant flow path 24 through which the refrigerant flows is formed through communication between the manifold and the refrigerant discharge manifold.

  A protrusion 26 is formed on the anode separator 20a. The protrusion 26 protrudes beyond the cathode separator 20c when the MEGA 30 is sandwiched between the anode separator 20a and the cathode separator 20c. The protruding portion 26 plays a role as a terminal mounting portion, and for example, a cell monitor terminal to which a voltage measuring portion is connected during power generation is mounted. Thereby, the cell voltage at the time of power generation can be measured by the voltage measuring unit.

  FIG. 2 is an exploded perspective view of the fuel cell for explaining a method for recovering the performance of the fuel cell. FIG. 3 is a cross-sectional view of the fuel cell for explaining a method for recovering the performance of the fuel cell. 2 and 3, the single cell 100 is illustrated in a simplified manner for the sake of clarity. First, the fuel cell will be described. As shown in FIG. 2, the fuel cell 200 includes a plurality of single cells 100, a pair of terminal plates 50 and 52, a pair of insulating plates 60 and 62, and a pair of end plates 70 and 72. The fuel cell 200 has a stack structure in which a plurality of single cells 100 are sandwiched between a pair of terminal plates 50 and 52, a pair of insulating plates 60 and 62, and a pair of end plates 70 and 72. The terminal plates 50 and 52 are made of metal. The end plates 70 and 72 are used to fasten the plurality of single cells 100, the terminal plates 50 and 52, and the insulating plates 60 and 62.

  The terminal plate 50, the insulating plate 60, and the end plate 70 are provided with holes t1 to t6, holes i1 to i6, and holes e1 to e6, respectively. Holes t1, i1, and e1 define a fuel gas supply manifold, holes t2, i2, and e2 define a refrigerant supply manifold, and holes t3, i3, and e3 define an oxidant gas discharge manifold. Holes t4, i4, and e4 define an oxidant gas supply manifold, holes t5, i5, and e5 define a refrigerant discharge manifold, and holes t6, i6, and e6 define a fuel gas discharge manifold. On the other hand, the terminal plate 52, the insulating plate 62, and the end plate 72 are not provided with holes. Thereby, the fuel gas introduced from the hole e1 flows through the anode gas flow path 22a of each of the plurality of single cells 100, and is then discharged from the hole e6. The refrigerant introduced from the hole e2 flows through the refrigerant flow path 24 of each of the plurality of single cells 100, and then is discharged from the hole e5. The oxidant gas introduced from the hole e4 flows through the cathode gas flow path 22c of each of the plurality of single cells 100 and is then discharged from the hole e3.

  Next, a fuel cell performance recovery method will be described. The fuel cell performance recovery method is performed by an operator during maintenance such as vehicle inspection when the fuel cell is mounted on a fuel cell vehicle or an electric vehicle. For example, the performance recovery process may be performed when the operating time of the fuel cell, the travel distance of the automobile, and the amount of decrease in the power generation performance of the fuel cell are larger than a predetermined value.

  In the method of recovering the performance of the fuel cell, first, the pipes connected to the holes e3 and e4 provided in the end plate 70 are removed, and then the external external pipe 80 is connected to the holes e3 and e4. Then, the humidified nitrogen gas is supplied to the hole e4 via the external pipe 80, and the humidified nitrogen gas is caused to flow through the cathode gas flow paths 22c of the plurality of single cells 100. For example, humidified nitrogen gas is supplied to the holes e4 so that nitrogen gas having a relative humidity of 100% RH flows through each unit cell 100 at a flow rate of 1.0 L / min for 5 minutes or more. Thereby, the electrolyte membrane 12 of the plurality of single cells 100 is wetted. Proton conductivity can be improved by making the electrolyte membrane 12 wet.

  Next, the fuel gas is supplied to the hole e1, and the anode gas flow paths 22a of the plurality of single cells 100 are filled with the fuel gas. For example, by opening a valve disposed between a hydrogen tank and the fuel cell 200 from a hydrogen tank provided in the fuel cell vehicle, hydrogen as fuel gas can be supplied to the hole e1. Hydrogen may continue to be supplied during the performance recovery process, or after supplying an amount of hydrogen necessary for the proton pump reaction described later to the anode gas flow path 22a, the supply is stopped and sealed. Also good. Further, when the fuel cell 200 stops power generation, if there is an amount of hydrogen necessary for the proton pump reaction in the anode gas flow paths 22a of the plurality of single cells 100, it is not necessary to supply hydrogen again. Thus, filling the anode gas flow path 22a with fuel gas means filling a part or all of the anode gas flow path 22a with an amount of fuel gas necessary for the proton pump reaction.

  Next, as shown in FIG. 3, an external power supply terminal 82 is attached to the protruding portion 26 of the anode separator 20 a of each of the plurality of single cells 100, and an external resistor with a resistor 83 is provided between the anode separators 20 a of adjacent single cells 100. A power supply 84 is connected. Thereby, a voltage is applied between the anode side separators 20a of the adjacent single cells 100. Since the anode-side separator 20a and the cathode-side separator 20c of the adjacent single cell 100 are electrically connected and have the same potential, a voltage is generated between the anode-side separator 20a and the cathode-side separator 20c of one single cell 100. Will be applied. The plurality of external power sources 84 are connected to the external power source terminal 82 so that electrons flow from the anode side separator 20a through the external power source 84 to the cathode side separator 20c. That is, in FIG. 3, a plurality of single cells 100 are divided into a plurality of groups 86 for each single cell 100, and positive electrodes are electrically connected to anode-side separators 20 a located at both ends of the plurality of groups 86. Each of the plurality of external power sources 84 is connected to each of the plurality of groups 86 so that the negative electrode is electrically connected to the side separator 20c. When a voltage is applied by the external power supply 84, the stack voltage is opened.

Here, the reason why the external power source 84 is connected to the protruding portion 26 of the anode-side separator 20a in a state where the anode gas flow path 22a is filled with hydrogen will be described with reference to FIG. As shown in FIG. 4, when the anode gas flow path 22a is filled with hydrogen, a chemical reaction of H ₂ → 2H ⁺ + 2e ⁻ occurs in the anode catalyst layer 14a. Proton H ⁺ generated in the anode catalyst layer 14 a diffuses into the cathode catalyst layer 14 c through the electrolyte membrane 12. Initially, the proton H ⁺ is diffused in the cathode catalyst layer 14c. On the other hand, since the positive electrode of the external power source 84 is electrically connected to the anode side separator 20a and the negative electrode of the external power source 84 is electrically connected to the cathode side separator 20c, the electrons generated in the anode catalyst layer 14a. e ⁻ moves toward the external power source 84, and electrons e ⁻ are supplied from the external power source 84 to the cathode catalyst layer 14c. In the cathode catalyst layer 14 c, a chemical reaction of 2H ⁺ + 2e ⁻ → H ₂ is caused by the proton H ⁺ diffused from the anode catalyst layer 14 a and the electron e ⁻ supplied from the external power source 84. Since proton H ⁺ is consumed in the cathode catalyst layer 14c, the diffusion of proton H ⁺ from the anode catalyst layer 14a to the cathode catalyst layer 14c is continued. Such a reaction that generates proton H ⁺ in the anode catalyst layer 14a, moves proton H ⁺ to the cathode catalyst layer 14c via the electrolyte membrane 12, and generates H ₂ in the cathode catalyst layer 14c is a proton pump. This is called a reaction.

Due to the movement of protons H ⁺ and electrons e ⁻ , a current I flows between the anode side separator 20a and the cathode side separator 20c, and a potential difference is generated between the anode side separator 20a and the cathode side separator 20c. That is, a potential gradient is formed in the MEA 10. When a potential gradient is formed in the MEA 10, the proton H ⁺ and the cation impurity M ⁺ in the MEA 10 move to the cathode catalyst layer 14c side due to the potential gradient. Movement by the potential gradient is fast. In this way, with the anode gas flow path 22a filled with hydrogen, the external power supply 84 is connected so that the positive electrode is electrically connected to the anode side separator 20a and the negative electrode is electrically connected to the cathode side separator 20c. Is connected to collect the cationic impurities M ⁺ mixed in the MEA 10 on the cathode catalyst layer 14c side. Examples of the cationic impurity M ⁺ mixed in the MEA 10 include Ca ²⁺ , Mg ²⁺ , and Co ²⁺ .

Here, if the wet state of the electrolyte membrane 12 differs among the plurality of single cells 100, a difference in the conductivity of proton H ⁺ occurs. In this case, for example, when an external power supply 84 is connected between the pair of terminal plates 50 and 52 and a voltage is applied to the entire plurality of single cells 100, a difference in potential gradient in the MEA 10 occurs between the plurality of single cells 100. A single cell 100 having an unintended potential gradient may be generated, for example, a single cell 100 may be formed in which a potential gradient sufficient to move the cation impurity M ⁺ in the MEA 10 is not formed. Thereby, there is a possibility that a single cell 100 in which a sufficient amount of the cation impurity M ⁺ does not collect on the cathode catalyst layer 14c side may be generated. On the other hand, in Example 1, since each of the plurality of external power sources 84 is connected to each of the plurality of unit cells 100, the magnitude of the voltage applied to each unit cell 100 can be controlled. For this reason, even when the wet state of the electrolyte membrane 12 is different among the plurality of single cells 100, the same potential gradient can be generated in each MEA 10 of the plurality of single cells 100. Accordingly, the same amount of cationic impurities M ⁺ can be collected on the cathode catalyst layer 14c side among the plurality of single cells 100, and a sufficient amount of cationic impurities M ⁺ can be collected on the cathode catalyst layer 14c side. The generation of no single cell 100 can be suppressed.

Next, as shown in FIG. 2, the cleaning liquid is introduced into the hole e3 through the external pipe 80, and the cathode gas flow path 22c is filled with the cleaning liquid, and the cleaning liquid enters from the cathode gas flow path 22c to the cathode catalyst layer 14c. And As shown in FIG. 1A, the cathode-side water-repellent layer 16c is provided between the cathode gas flow path 22c and the cathode catalyst layer 14c. 16c cannot be passed. Therefore, a cleaning solution that can pass through the cathode-side water-repellent layer 16c is used. As the cleaning liquid, for example, a liquid having a viscosity and a surface tension smaller than that of water, such as a fluorine-based inert liquid (for example, Fluorinert (registered trademark)) can be used, and it does not contain metal ions or other cations other than proton H ^+. The case is preferred. The cleaning liquid introduced into the hole e3 is discharged from the hole e4. A new cleaning liquid may be continuously introduced into the hole e3, or the cleaning liquid discharged from the hole e4 may be reintroduced into the hole e3 and the cleaning liquid may be circulated. Although the cleaning liquid may be introduced from the hole e4, it is preferable to introduce the cleaning liquid from the hole e3 located at a low position in the gravity direction from the viewpoint of suppressing the occurrence of air accumulation inside.

As shown in FIG. 5, by allowing the cleaning liquid 90 to penetrate from the cathode gas flow path 22 c to the cathode catalyst layer 14 c, the cation impurity M ⁺ mixed in the liquid water in the MEA 10 diffuses into the cleaning liquid 90. At this time, since the cation impurities M ⁺ are collected on the cathode catalyst layer 14c side, the cation impurities M ⁺ are efficiently diffused into the cleaning liquid 90. For example, in the case where the anode gas flow path 22a is not filled with hydrogen and the external power source 84 is not connected between the anode side separator 20a and the cathode side separator 20c, the cation impurity M ⁺ diffuses throughout the liquid water in the MEA 10. Therefore, even if the cleaning liquid 90 is included from the cathode gas flow path 22c to the cathode catalyst layer 14c, the diffusion efficiency of the cation impurity M ^{+ into} the cleaning liquid 90 is poor. Further, even if an attempt is made to discharge the cation impurity M ⁺ with the generated water in a state where there is a potential gradient in the MEA 10 during power generation of the fuel cell 200, a sufficient amount of the cation impurity M ⁺ is discharged because the generated water is small. On the other hand, power generation becomes difficult when there is a lot of liquid water.

Next, the state in which the plurality of external power supplies 84 are connected and the cleaning liquid 90 has entered from the cathode gas flow path 22c to the cathode catalyst layer 14c is maintained for a predetermined time. This is because the cation impurity M ⁺ mixed in the liquid water in the MEA 10 diffuses in the cleaning liquid 90 by concentration diffusion, so the diffusion speed is slow, and a certain amount of time is required until a large amount of the cation impurity M ⁺ diffuses into the cleaning liquid 90. Is required. In consideration of the diffusion rate of cationic impurities M ⁺ , working efficiency, and the like, it is preferable that the maintaining time is about 1 to 30 minutes.

Next, the cleaning liquid 90 is removed from the MEA 10 and the cathode gas flow path 22c. Since the cationic impurities M ⁺ are diffused in the cleaning liquid 90, the cationic impurities M ⁺ are also removed together with the cleaning liquid 90, and as a result, the power generation performance of the fuel cell 200 can be recovered.

  Next, the external power supply terminal 82 is separated from the protruding portion 26 of the anode side separator 20a, and the voltage applied between the anode side separator 20a and the cathode side separator 20c is released. Further, when hydrogen is continuously supplied to the anode gas flow path 22a, the supply of hydrogen is released.

As described above, in the method of recovering the performance of the fuel cell, the anode gas flow paths 22a of the plurality of single cells 100 are filled with hydrogen, and the positive electrode is electrically connected to the anode separator 20a for each of the plurality of single cells 100. Each of the plurality of external power supplies 84 is connected so that the negative electrode is electrically connected to the cathode separator 20c. As a result, as described with reference to FIG. 4, the same amount of cationic impurities M ⁺ can be collected in the cathode catalyst layer 14c in the plurality of single cells 100, and the cationic impurities M ⁺ are present on the cathode catalyst layer 14c side. It can suppress that the single cell 100 which does not gather so much arises. Then, the state where the cationic impurities M ⁺ are collected on the cathode catalyst layer 14c side and the cleaning liquid 90 is infiltrated from the cathode gas flow path 22c to the cathode catalyst layer 14c is maintained for a predetermined time. Thereby, the cation impurity M ⁺ mixed in the liquid water in the MEA 10 can be efficiently diffused into the cleaning liquid 90. Thereafter, by removing the cleaning liquid 90 from the MEA 10 and the cathode gas flow path 22c, the cationic impurities M ⁺ are discharged to the outside together with the cleaning liquid 90. As a result, the cationic impurities M ⁺ in the MEA 10 are reduced, and the fuel cell 200 The power generation performance can be restored.

In Example 1, the electrolyte membrane 12 is wetted by flowing a humidified nitrogen gas through the cathode gas flow path 22c. It is preferable to wet the electrolyte membrane 12 because the conductivity of the proton H ⁺ becomes better when the electrolyte membrane 12 becomes wet. The wetting of the electrolyte membrane 12 may be performed by flowing an inert gas such as a rare gas in the cathode gas flow path 22c instead of the nitrogen gas. Further, the electrolyte membrane 12 may be wetted by the cleaning liquid 90 introduced into the cathode gas flow path 22c, or the electrolyte membrane 12 may be wetted by generating power in the fuel cell 200 under conditions where generated water is easily generated. When the electrolyte membrane 12 is wetted by the cleaning liquid 90, it is desirable to wait for a predetermined time (for example, 5 minutes to 1 hour) after the cleaning liquid 90 is introduced into the cathode gas flow path 22c.

In the first embodiment, a case where a plurality of single cells 100 are divided into a plurality of groups 86 for each single cell 100 is shown as an example, but the present invention is not limited to this. The plurality of single cells 100 may be divided into a plurality of groups including one or two or more adjacent single cells 100. In this case, each of the plurality of external power sources 84 is connected so that the positive electrode is electrically connected to the anode-side separator 20a located at both ends of the plurality of groups, and the negative electrode is electrically connected to the cathode-side separator 20c. Let Even in this case, compared with the case where the external power source 84 is connected between the pair of terminal plates 50 and 52, the potential gradient formed in the MEA 10 of each single cell 100 can be made equal, and the cation impurity M ⁺ can be reduced. It is possible to suppress the generation of the single cell 100 in which a potential gradient sufficient for movement is not formed.

  In the first embodiment, the cell monitor terminal attached to the projecting portion 26 is removed in order to connect the voltage measuring unit that measures the voltage of the single cell 100 during power generation, and an external power supply terminal 82 is attached instead. Although the power supply 84 is connected, the external power supply 84 may be connected via a cell monitor terminal.

In the first embodiment, the case where the cleaning liquid 90 is continuously introduced into the hole e3 and the cleaning liquid 90 is continuously discharged from the hole e4 has been described as an example. However, the cleaning liquid 90 is introduced from the hole e3 and the cathode gas flow path 22c is used as the cathode. After the cleaning liquid 90 has entered the catalyst layer 14c, the introduction of the cleaning liquid 90 may be stopped, and sealing may be performed so that the cleaning liquid 90 does not leak outside. However, by continuing to introduce new cleaning liquid 90 into the hole e3, the concentration of the cation impurity M ⁺ of the cleaning liquid 90 in the cathode catalyst layer 14c can be kept low, and the cationic impurity M ⁺ can be supplied to the cleaning liquid 90. Diffusion can be promoted.

  In the first embodiment, the order of filling the anode gas flow path 22a with hydrogen and connecting a plurality of external power sources 84 may be switched. The cleaning liquid 90 may be introduced into the cathode gas channel 22c before the anode gas channel 22a is filled with hydrogen, before the plurality of external power sources 84 are connected, or the electrolyte membrane. 12 may be performed at the same time when the anode gas flow path 22a is filled with hydrogen, or when a plurality of external power sources 84 are connected.

  In the first embodiment, the anode gas flow path 22a is filled with the fuel gas and the cleaning liquid 90 is allowed to flow to the cathode gas flow path 22c. However, the cathode gas flow path 22c is filled with the fuel gas and the anode gas flow The cleaning liquid 90 may be allowed to flow through the path 22a. However, since supplying the fuel gas to the anode gas flow path 22a is the same as during power generation, it is not necessary to switch the connection of the piping. From the viewpoint of sex.

  In the first embodiment, the case where the pipes connected to the holes e3 and e4 are removed and the external pipe 80 is connected is shown as an example, but the external pipe is connected to a valve or the like for supplying air to the fuel cell 200. A humidified nitrogen gas or a cleaning liquid may be introduced by connection. Similarly, when the humidified nitrogen gas or the cleaning liquid is allowed to flow through the anode gas channel 22a, the humidified nitrogen gas or the cleaning liquid may be introduced by removing the piping connected to the holes e1 and e6 and connecting the external piping. Alternatively, humidified nitrogen gas or cleaning liquid may be introduced by connecting an external pipe to an injector or the like for supplying fuel gas to the fuel cell 200.

  FIG. 6 is a cross-sectional view showing another example of a single cell constituting the fuel cell. As shown in FIG. 6, the single cell 100a is provided with a through-hole 28 penetrating the cathode-side water-repellent layer 16c from the cathode catalyst layer 14c side to the cathode gas diffusion layer 18c side in the cathode-side water-repellent layer 16c. The cross-sectional shape of the through hole 28 may be any shape such as a circle, an ellipse, or a rectangle. The other configuration is the same as that of the single cell 100 of FIG.

Even in the case of the single cell 100a, the above-described fuel cell performance recovery method can be used. Here, in the single cell 100a, a through-hole 28 is provided in the cathode-side water-repellent layer 16c. For this reason, even when a cleaning liquid other than the cleaning liquid that passes through the cathode-side water-repellent layer 16c, such as a fluorine-based inert liquid, is used, the cleaning liquid passes through the through-holes 28, You can go back and forth between. In this case, water, boiling water, deionized water, hydrogen peroxide water, dilute nitric acid, etc. can be used as the cleaning liquid in addition to the fluorine-based inert liquid, and other positive ions other than metal ions and proton H ⁺ can be used. It is preferable to use a liquid that does not contain ions. In the case of using dilute nitric acid, it is preferable to use dilute nitric acid having a pH of 3 or more in order to suppress the influence of a short circuit between single cells. Since water can also pass through the through hole 28, water vapor may be introduced into the cathode gas flow path 22c, and water changed from the water vapor may enter the cathode gas flow path 22c to the cathode catalyst layer 14c.

  In FIG. 6, the through hole 28 is provided only in the cathode-side water-repellent layer 16c, but it may be provided through the cathode-side water-repellent layer 16c and the cathode gas diffusion layer 18c. Alternatively, a hydrophilic member may be embedded in the through hole 28.

  When the cathode gas flow path 22c is filled with fuel gas and the cleaning liquid is allowed to flow through the anode gas flow path 22a, the through hole 28 is provided in the anode-side water repellent layer 16a.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

DESCRIPTION OF SYMBOLS 10 Membrane electrode assembly 12 Electrolyte membrane 14a Anode catalyst layer 14c Cathode catalyst layer 16a Anode side water repellent layer 16c Cathode side water repellent layer 18a Anode gas diffusion layer 18c Cathode gas diffusion layer 20a Anode side separator 20c Cathode side separator 22a Anode gas flow Path 22c Cathode gas flow path 24 Refrigerant flow path 26 Protruding part 28 Through hole 30 Membrane electrode gas diffusion layer assembly 40 Insulating member 50, 52 Terminal plate 60, 62 Insulating plate 70, 72 End plate 80 External piping 82 External power supply terminal 84 External power source 86 group 90 Cleaning fluid 100, 100a Single cell 200 Fuel cell

Claims (1)

A membrane electrode assembly provided with a pair of electrode catalyst layers sandwiching an electrolyte membrane, an anode side separator that forms an anode gas flow path, and a cathode side separator that forms a cathode gas flow path, A fuel cell performance recovery method comprising a plurality of single cells sandwiching the membrane electrode assembly by a side separator and the cathode side separator,
Filling one gas passage of the anode gas passage and the cathode gas passage of the plurality of single cells with fuel gas;
The gas flow of one of the anode-side separator and the cathode-side separator located at both ends with respect to each of a plurality of groups obtained by dividing the plurality of single cells so as to include one or two or more adjacent single cells. Connecting each of a plurality of external power sources such that a positive electrode is electrically connected to one separator forming a path and a negative electrode is electrically connected to the other separator;
The other gas channel of the plurality of single cells is filled with a cleaning liquid in the other gas channel of the anode gas channel and the cathode gas channel, and the other of the pair of electrode catalyst layers is supplied from the other gas channel. Intruding the cleaning liquid up to the electrode catalyst layer on the gas flow path
Maintaining one of the plurality of external power sources connected to each other and supplying the cleaning liquid to the electrode catalyst layer on the other gas channel side for a predetermined time after filling the one gas channel with fuel gas;
Removing the cleaning liquid from the membrane electrode assembly and the other gas flow path after maintaining the predetermined time, and recovering the performance of fuel electrons.

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