JP2013069673A - Method for activating fuel cell stack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for activating a fuel cell stack which can suppress variations in activity among fuel cells.SOLUTION: The method for activating a fuel cell stack 100 includes: a fuel cell stack installation step of installing the fuel cell stack 100 such that a stacking direction of fuel cells 10 matches a horizontal direction and that either of oxidizer gas supply openings 40a/fuel gas supply openings 42a and oxidizer gas discharge openings 40b/fuel gas discharge openings 42b are positioned under cathode electrodes 11b/anode electrodes 11c; a humidified gas introduction step of introducing a humidified oxidizer gas/fuel gas to the cathode electrodes 11b/anode electrodes 11c from either of the oxidizer gas supply openings 40a/fuel gas supply openings 42a and the oxidizer gas discharge openings 40b/fuel gas discharge openings 42b located under the cathode electrodes 11b/anode electrodes 11c; and a voltage application step of applying a predetermined voltage between the cathode electrodes 11b and the anode electrodes 11c.

Description

  The present invention relates to a method for activating a fuel cell stack.

  For example, a polymer electrolyte fuel cell (PEFC) is composed of an electrolyte membrane / electrode structure in which an anode electrode and a cathode electrode are provided on both sides of an electrolyte membrane made of a polymer ion exchange membrane. A power generation cell sandwiched between separators is provided. The polymer electrolyte fuel cell is used as, for example, an in-vehicle fuel cell stack by stacking a plurality of power generation cells and providing a pair of end plates at both ends in the stacking direction.

  In the fuel cell stack, the water content of the electrolyte membrane immediately after assembly is not sufficient, or the activity of the catalyst of the anode electrode and cathode electrode is low. Power generation performance could not be demonstrated.

  Therefore, in order to draw out sufficient power generation performance immediately after assembly of the fuel cell stack, an activation process (aging process) of the fuel cell stack is usually performed.

  For example, Patent Document 1 discloses a humidified gas introduction process for introducing a humidified gas into a power generation cell of a fuel cell stack, and a voltage having a certain width by an external power source while supplying hydrogen gas to an anode electrode and nitrogen gas to a cathode electrode. A method for activating a fuel cell stack including a voltage application step (CV step) for applying a voltage to a power generation cell is disclosed.

  The humidified gas introduction step increases the water content of the electrolyte membrane, and the voltage application step increases the activity of the anode electrode and cathode electrode catalysts, so that sufficient power generation performance is exhibited immediately after assembly of the fuel cell stack. It can be done.

  Here, water (moisture) is generated on the cathode electrode side during power generation of the fuel cell stack, and if this water stays in the power generation cell in a large amount, diffusion of gas (oxidant gas / fuel gas) is inhibited, The output of the fuel cell stack will be reduced. Therefore, in general, a gas supply port is provided at the upper edge of each power generation cell in the stacking direction, and a gas discharge port is provided at the lower edge of the power generation cell in the stacking direction so that the gas flows from above. It is configured to flow downward, and the water in the power generation cell is discharged by the pressure of the gas and gravity (self-weight of water) to suppress the retention of water in the power generation cell.

JP 2009-146876 A

  By the way, in the humidified gas introduction process of Patent Document 1, when the humidified gas is introduced from the gas supply port provided at the upper edge of each power generation cell, the humidified gas is cooled as it flows along the stacking direction. The moisture in the humidified gas may condense on the end plate on the downstream side of the gas supply port, and may become water droplets and enter and stay in the power generation cell (electrode). As a result, diffusion of gases such as hydrogen and nitrogen is hindered in the voltage application step, so that the voltage of the power generation cell downstream of the gas supply port during power generation is lower than the voltage of other power generation cells. There was a risk that the cell activity would vary.

  The present invention has been developed from such a viewpoint, and an object of the present invention is to provide a method for activating a fuel cell stack that can suppress variation in the activity of each fuel cell.

  In order to solve the above problems, the present invention provides an electrolyte membrane, a pair of separators provided on both sides of the electrolyte membrane, a gas supply port provided through one end of the electrolyte membrane and the separator, and the electrolyte A gas exhaust port provided through the other end of the membrane and the separator, and a pair of electrodes provided between the electrolyte membrane and the separator and between the gas supply port and the gas exhaust port. A method of activating a fuel cell stack comprising a plurality of fuel cells having a plurality of fuel cells, wherein the fuel cells are stacked such that the gas supply port and the gas discharge port communicate with each other, and a pair of end plates are provided at both ends in the stacking direction The stacking direction of the fuel cells coincides with the horizontal direction, and either the gas supply port or the gas discharge port is positioned below the electrode. A fuel cell stack installation step for installing a fuel cell stack, and a humidified gas introduction for introducing humidified gas to the electrode from one of the gas supply port and the gas discharge port installed below the electrode And a voltage applying step of applying a predetermined voltage between the pair of electrodes after the humidifying gas introducing step or simultaneously with the humidifying gas introducing step.

  According to the present invention, the fuel cell stack is installed so that either one of the gas supply port and the gas discharge port is positioned below the electrode, and the gas supply port installed below the electrode and By introducing the humidified gas from one of the gas discharge ports to the electrode, the humidified gas is cooled as it flows along the stacking direction, and the moisture in the humidified gas is supplied to the gas supply port or the gas discharge port. Even when condensation occurs on the downstream end plate to form water droplets, it stays in one of the gas supply port and the gas discharge port due to its own weight, so that it is possible to prevent entry into the electrode. As a result, when the voltage application step is performed, the diffusion of gas such as hydrogen and nitrogen is not hindered. Therefore, it is possible to avoid the voltage drop of the fuel cell on the downstream side of the gas supply port or the gas discharge port during power generation. Variations in battery activity can be suppressed.

  Further, the present invention is a water draining step of draining water staying at either one of the gas supply port and the gas discharge port installed below the electrode after repeating the voltage application step a predetermined number of times. It is preferable to further include.

  In this way, the water staying at either the gas supply port or the gas discharge port installed below the electrode can be removed to reliably prevent entry into the electrode. The variation of can be further suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the activation method of the fuel cell stack which can suppress the dispersion | variation in the activity of each fuel cell can be provided.

1 is a perspective view of a fuel cell stack according to an embodiment of the present invention. It is a disassembled perspective view of the fuel cell which comprises a fuel cell stack. It is a partial expanded cross-sectional view of a fuel cell stack. It is a longitudinal cross-sectional schematic diagram for demonstrating the flow of the humidification gas in the fuel cell stack at the time of a humidification gas introduction process. (A) is a graph which shows the voltage change according to the number of potential cycles of the fuel cell located at the downstream end of the oxidant gas discharge passage and the fuel gas discharge passage of the example and the comparative example, and (b) is an example. It is a graph which shows the voltage of each fuel cell of a comparative example. (A) is a graph showing the voltage of each fuel cell according to the number of potential cycles of Example 1, and (b) is a graph showing the voltage of each fuel cell according to the number of potential cycles of Example 2. is there.

  Embodiments of the present invention will be described in detail with reference to the drawings. In the description, the same elements are denoted by the same reference numerals, and redundant description is omitted.

Prior to the description of the method for activating the fuel cell stack 100 according to the embodiment of the present invention, the structure of the fuel cell stack 100 will be described with reference to FIGS.
1 and 2 show the flow of the oxidant gas, the cooling medium, and the fuel gas during power generation, and FIG. 4 shows the flow of the oxidant gas and the fuel gas during activation (during the humidified gas introduction process). .
As shown in FIG. 1, the fuel cell stack 100 mainly includes a plurality of fuel cells 10, a pair of end plates 20 a and 20 b, and a plurality of connecting members 30. The fuel cell stack 100 of this embodiment is used as a power source for a fuel cell vehicle, but may be used as a household power source.

<Fuel cell>
As shown in FIG. 1, the plurality of fuel cells 10 are stacked along the arrow A direction (horizontal direction). As shown in FIG. 2, each fuel cell 10 includes an electrolyte membrane / electrode structure (MEA) 11, a pair of first separator 12 and second separator 13 that sandwich the electrolyte membrane / electrode structure 11 from both sides, Have

<Electrolyte membrane / electrode structure>
The electrolyte membrane / electrode structure 11 includes, for example, a plate-like solid polymer electrolyte membrane (electrolyte membrane) 11a in which a perfluorosulfonic acid thin film is impregnated with water, and both sides (both sides) of the solid polymer electrolyte membrane 11a. And a cathode electrode 11b and an anode electrode 11c provided.

  The cathode electrode 11b and the anode electrode 11c, which are electrodes, are rectangular electrode members having a width dimension and a length dimension that are slightly smaller than the solid polymer electrolyte membrane 11a. The cathode electrode 11b and the anode electrode 11c are disposed in the central portion of the solid polymer electrolyte membrane 11a, and the outer peripheral portion is located inward of the outer peripheral portion of the solid polymer electrolyte membrane 11a. The cathode electrode 11b and the anode electrode 11c include a gas diffusion layer made of carbon paper or the like, and an electrode catalyst layer formed by uniformly applying porous carbon particles carrying a platinum alloy on the surface of the gas diffusion layer. And. The electrode catalyst layers are formed on both surfaces of the solid polymer electrolyte membrane 11a.

  In this case, when fuel gas (for example, a gas containing hydrogen) is supplied to the anode electrode 11c, electrons are separated from hydrogen atoms by a catalytic reaction (electrode reaction) to generate hydrogen ions, and the electrons are And move to the cathode electrode 11b. Then, electricity passes through the external circuit and flows as current to the cathode electrode 11b, thereby generating electricity. On the other hand, hydrogen ions pass through the solid polymer electrolyte membrane 11a and move to the cathode electrode 11b. At this time, in the cathode electrode 11b, the oxidizing gas (for example, air containing oxygen) supplied to the cathode electrode 11b reacts with the electrons and hydrogen ions that have moved to the cathode electrode 11b to generate water. .

<First separator and second separator>
The first separator 12 and the second separator 13 are made of, for example, a steel plate, a stainless steel plate, an aluminum plate, a plated steel plate, a metal plate whose surface has been subjected to anticorrosion treatment, and the like. As shown in FIG. 2 and FIG. 3, the first separator 12 and the second separator 13 are formed in a concavo-convex shape in cross-sectional view by pressing a rectangular metal plate into a wave shape. . As shown in FIG. 3, the seal member 14 is provided integrally or separately on both surfaces 12 a and 12 b of the outer edge portion of the first separator 12, while on both surfaces 13 a and 13 b of the outer edge portion of the second separator 13, The seal member 15 is provided integrally or separately.

  The seal members 14 and 15 are made of, for example, silicone rubber, ethylene-propylene rubber, natural rubber, fluorine rubber, fluorosilicone rubber, butyl rubber, styrene rubber, chloroplane, acrylic rubber, or the like.

<Oxidant gas supply port, cooling medium supply port, fuel gas supply port>
As shown in FIG. 2, the rectangular shape formed in the upper edge part (one end part) of the solid polymer electrolyte membrane 11a, the 1st separator 12, and the 2nd separator 13 penetrates in the arrow A direction (stacking direction). The oxidant gas supply port 40a, the cooling medium supply port 41a, and the fuel gas supply port 42a are arranged along the arrow B direction. The oxidant gas supply port 40a serving as a gas supply port is a portion to which an oxidant gas is supplied, the cooling medium supply port 41a is a portion to which a cooling medium is supplied, and the fuel gas supply port 42a serving as a gas supply port is This is the part where fuel gas is supplied. For example, pure water, ethylene glycol, oil, or the like is used as the cooling medium.

<Oxidant gas outlet, cooling medium outlet, fuel gas outlet>
A rectangular oxidant gas discharge port 40b formed through the solid polymer electrolyte membrane 11a, the first separator 12 and the second separator 13 (the other end) penetrating in the direction of arrow A, a cooling medium The discharge port 41b and the fuel gas discharge port 42b are arranged along the arrow B direction. The oxidant gas discharge port 40b serving as a gas discharge port is a portion from which the oxidant gas is discharged, the cooling medium discharge port 41b is a portion from which the cooling medium is discharged, and the fuel gas discharge port 42b serving as the gas discharge port is This is the part where the fuel gas is discharged.

<Oxidant gas flow path>
As shown in FIGS. 2 and 3, the surface 12a of the first separator 12 facing the electrolyte membrane / electrode structure 11 is oxidized through an oxidant gas supply port 40a and an oxidant gas discharge port 40b. An oxidant gas flow path 50 for flowing the oxidant gas is provided. That is, as shown in FIG. 3, the convex portion of the first separator 12 comes into contact with the electrolyte membrane / electrode structure 11, so that the concave portion of the first separator 12 constitutes the oxidant gas flow path 50. In this case, the oxidant gas flows vertically downward from the oxidant gas supply port 40a through the plurality of oxidant gas flow paths 50, and then flows to the oxidant gas discharge port 40b.

<Fuel gas flow path>
2 and 3, the surface 13a of the second separator 13 that faces the electrolyte membrane / electrode structure 11 is connected to the fuel gas supply port 42a and the fuel gas discharge port 42b so that the fuel gas flows. A fuel gas flow path 52 for flowing is provided. That is, as shown in FIG. 3, the convex portion of the second separator 13 comes into contact with the electrolyte membrane / electrode structure 11, so that the concave portion of the second separator 13 constitutes the fuel gas channel 52. In this case, the fuel gas flows vertically downward through the plurality of fuel gas flow paths 52 from the fuel gas supply port 42a and then flows to the fuel gas discharge port 42b.

<Cooling medium flow path>
As shown in FIGS. 2 and 3, a cooling medium flow path 51 for allowing the cooling medium to flow between the adjacent fuel cells 10 and 10 through the cooling medium supply port 41 a and the cooling medium discharge port 41 b. Is provided. Specifically, as shown in FIG. 3, the coolant flow path 51 constitutes the surface 12 b of the first separator 12 constituting one fuel cell 10 of the adjacent fuel cells 10, 10 and the other fuel cell 10. It is provided between the second separator 13 and the surface 13b. In this case, the cooling medium flows from the cooling medium supply port 41a to the cooling medium discharge port 41b after flowing through the plurality of cooling medium channels 51 vertically downward.

<Oxidant gas supply passage, cooling medium supply passage, fuel gas supply passage>
As shown in FIG. 4, the fuel cell stack 100 is stacked so that the oxidant gas supply port 40a and the fuel gas supply port 42a of each fuel cell 10 communicate with each other. An oxidant gas supply passage 60a that circulates and a fuel gas supply passage 62a that circulates the fuel gas in the stacking direction are formed.
Further, the cooling medium supply ports 41a of the fuel cells 10 are stacked so as to communicate with each other, thereby forming a cooling medium supply passage (not shown) through which the cooling medium flows in the stacking direction.

<Oxidant gas discharge passage, cooling medium discharge passage, fuel gas discharge passage>
On the other hand, as shown in FIG. 4, the fuel cell stack 100 is stacked so that the oxidant gas discharge port 40b and the fuel gas discharge port 42b of each fuel cell 10 are communicated with each other. An oxidant gas discharge passage 60b through which gas flows and a fuel gas discharge passage 62b through which fuel gas flows in the stacking direction are formed.
Further, the coolant discharge ports 41b of the fuel cells 10 are stacked so as to communicate with each other, thereby forming a coolant discharge passage (not shown) through which the coolant flows in the stacking direction.

<End plate>
Returning to FIG. 1, the pair of end plates 20 a and 20 b are disposed at both ends in the stacking direction of the fuel cell 10, and are rectangular metal members having a width dimension and a length dimension that are slightly larger than the fuel cell 10. It is. One end plate 20a includes an oxidant gas supply port 40a, a fuel gas supply port 42a, an oxidant gas discharge port 40b, and a cylindrical oxidant gas supply manifold (connecting portion) 21a communicating with the fuel gas discharge port 42b. A fuel gas supply manifold 22a, an oxidant gas discharge manifold 21b, and a fuel gas discharge manifold 22b are provided. The other end plate 20b is provided with a cylindrical cooling medium supply manifold 23a and a cooling medium discharge manifold 23b communicating with the cooling medium supply port 41a and the cooling medium discharge port 41b. In addition, terminal plates and insulating plates (not shown) are disposed at both ends of the fuel cell 10 in the stacking direction.

<Connecting member>
The connecting member 30 is a metal member that connects the pair of end plates 20a, 20b and applies a predetermined tightening load in the stacking direction to integrally hold the plurality of fuel cells 10 and the end plates 20a, 20b. . The connecting members 30 have a long plate shape, and two connecting members 30 are disposed on the length direction side (long side side) of the fuel cell stack 100, and one on the width direction side (short side side). They are arranged one by one. Both ends of the connecting member 30 in the stacking direction are fixed to the side surfaces (outer peripheral surfaces) of the end plates 20a and 20b by bolts 31.

  The fuel cell stack 100 according to the embodiment of the present invention is basically configured as described above. Next, referring to FIGS. 1, 2 and 4 as needed, the operation during power generation is described. explain. During power generation, a supply port such as an oxidant gas supply port 40a is usually installed on the upper side of a discharge port such as the oxidant gas discharge port 40b, and an oxidant gas or the like is introduced from the supply port to oxidize. The flow of the agent gas or the like is made to flow downward from above.

  As shown in FIGS. 1 and 2, when the oxidant gas is supplied from the oxidant gas supply manifold 21a of the end plate 20a to the oxidant gas supply passage 60a (see FIG. 4), the oxidant gas is converted into the oxidant gas. The gas is introduced into the oxidant gas flow path 50 from the oxidant gas supply port 40a of each fuel cell 10 while flowing through the supply passage 60a. The oxidant gas is supplied to the cathode electrode 11b while flowing in the direction of arrow C (downward).

  As shown in FIGS. 1 and 2, when fuel gas is supplied from the fuel gas supply manifold 22a of the end plate 20a to the fuel gas supply passage 62a (see FIG. 4), the fuel gas is supplied to the fuel gas supply passage 62a. The fuel gas is introduced from the fuel gas supply port 42a of each fuel cell 10 into the fuel gas flow path 52 while flowing therethrough. The fuel gas is supplied to the anode electrode 11c while flowing in the direction of arrow C (downward).

  When fuel gas is supplied to the anode electrode 11c, electrons are separated from hydrogen atoms by a catalytic reaction to generate hydrogen ions, and the electrons move to the cathode electrode 11b through an external circuit. Then, electricity passes through the external circuit and flows as current to the cathode electrode 11b, thereby generating electricity. On the other hand, hydrogen ions pass through the solid polymer electrolyte membrane 11a and move to the cathode electrode 11b. At this time, in the cathode electrode 11b, the oxidant gas supplied to the cathode electrode 11b reacts with the electrons and hydrogen ions that have moved to the cathode electrode 11b to generate water.

  Subsequently, as shown in FIG. 2, the oxidant gas consumed at the cathode electrode 11b is discharged from the oxidant gas flow path 50 to the oxidant gas discharge port 40b, and the oxidant gas discharge passage 60b is directed in the direction of arrow A. Circulate. Then, as shown in FIG. 1, the gas is discharged to the oxidant gas discharge manifold 21b of the end plate 20a.

  Further, as shown in FIG. 2, the fuel gas consumed in the anode electrode 11c is discharged from the fuel gas flow path 52 to the fuel gas discharge port 42b, and flows through the fuel gas discharge path 62b in the direction of arrow A. And as shown in FIG. 1, it discharges | emits to the fuel gas discharge manifold 22b of the end plate 20a.

  On the other hand, as shown in FIGS. 1 and 2, when the cooling medium is supplied from the cooling medium supply manifold 23a of the end plate 20b, the cooling medium is introduced into the cooling medium flow channel 51 from the cooling medium supply port 41a. Then, as shown in FIG. 2, the cooling medium flows in the direction of arrow C (downward), cools the electrolyte membrane / electrode structure 11, and then is discharged from the cooling medium flow path 51 to the cooling medium discharge port 41b. And flows in the direction of arrow A. Subsequently, the cooling medium is discharged to the cooling medium discharge manifold 23b of the end plate 20b as shown in FIG.

Next, a method for activating the fuel cell stack 100 according to the embodiment of the present invention will be described with reference to FIG. FIG. 4 is a schematic longitudinal sectional view for explaining the flow of the humidified gas in the fuel cell stack during the humidified gas introducing step.
The activation process (aging process) of the fuel cell stack 100 may be performed before or after the fuel cell stack 100 is mounted on the vehicle body, for example.

  The activation method of the fuel cell stack 100 according to the embodiment relates to an initial activation method immediately after the assembly of the fuel cell stack 100, and includes a fuel cell stack installation step, a humidified gas introduction step, and a voltage application step. Including.

<Fuel cell stack installation process>
First, as shown in FIGS. 1 and 2, the stacking direction of the fuel cells 10 coincides with the arrow A direction (horizontal direction), and the oxidant gas discharge port 40b and the fuel gas discharge port 42b are the cathode electrode 11b and the anode electrode. The fuel cell stack 100 is installed so as to be positioned below the 11c.

<Humidification gas introduction process>
Subsequently, after humidifying the oxidant gas and the fuel gas using a humidifier (not shown), as shown in FIG. 4, it is humidified from the oxidant gas discharge manifold 21b of the end plate 20a to the oxidant gas discharge passage 60b. In addition to introducing the oxidant gas, the humidified fuel gas is introduced from the fuel gas discharge manifold 22b to the fuel gas discharge passage 62b. In other words, humidified oxidant gas and fuel gas are introduced from below to above.

  In this case, the humidified oxidant gas is introduced into the oxidant gas flow path 50 from the oxidant gas discharge port 40b of each fuel cell 10 while flowing through the oxidant gas discharge passage 60b. The humidified oxidant gas is introduced into the cathode electrode 11b (see FIG. 2) while flowing in the direction of arrow C (upward). At this time, moisture in the humidified oxidant gas is introduced into the solid polymer electrolyte membrane 11a (see FIG. 2) via the cathode electrode 11b, so that the moisture content of the solid polymer electrolyte membrane 11a is wetted. Can be enough. Subsequently, the oxidant gas that has passed through the cathode electrode 11b is discharged from the oxidant gas flow path 50 to the oxidant gas supply port 40a, and flows through the oxidant gas supply passage 60a in the direction of arrow A. And it is discharged | emitted to the oxidizing gas supply manifold 21a of the end plate 20a.

  On the other hand, the humidified fuel gas is introduced into the fuel gas passage 52 from the fuel gas outlet 42b of each fuel cell 10 while flowing through the fuel gas discharge passage 62b. The humidified fuel gas is introduced into the anode electrode 11c (see FIG. 2) while flowing in the direction of arrow C (upward). At this time, moisture in the humidified fuel gas is introduced into the solid polymer electrolyte membrane 11a (see FIG. 2) via the anode electrode 11c, so that the moisture content of the solid polymer electrolyte membrane 11a is made wet. Can be enough. Subsequently, the fuel gas that has passed through the anode electrode 11c is discharged from the fuel gas passage 52 to the fuel gas supply port 42a, and flows through the fuel gas supply passage 62a in the direction of arrow A. And it is discharged to the fuel gas supply manifold 22a of the end plate 20a.

  Incidentally, as shown in FIG. 4, the humidified oxidant gas and fuel gas are cooled as they flow through the oxidant gas discharge passage 60b and the fuel gas discharge passage 62b, and the humidified oxidant gas and fuel are supplied. Moisture in the gas is condensed on the downstream end plate 20b to form water droplets W. Since the water droplets W stay in the oxidant gas discharge passage 60b and the fuel gas discharge passage 62b due to their own weight, the water droplets W are prevented from entering the cathode electrode 11b and the anode electrode 11c.

  Before introducing the humidified gas, the heated cooling medium is passed through the cooling medium flow path 51 to raise the temperature of the fuel cell stack 100. Thereby, humidified gas becomes difficult to cool and generation | occurrence | production of condensed water can be reduced. As another method for raising the temperature of the fuel cell stack 100, for example, the fuel cell stack 100 may be heated with a heater.

<Voltage application process>
After the humidified gas introduction step, for example, an inert gas such as nitrogen gas humidified to the cathode electrode 11b and a fuel gas humidified to the anode electrode 11c are introduced, and an external power source (stabilized power source) (not shown) A voltage that periodically fluctuates with a constant voltage width is applied between 11b and the anode electrode 11c. That is, the voltage application step is a step of applying a predetermined voltage for a predetermined time between the cathode electrode 11b and the anode electrode 11c (over the entire fuel cell stack 100), and a plurality of cycles (with a predetermined time interval). Multiple times). The external power supply has its + (plus; positive) pole connected to the cathode electrode 11b and its − (minus; negative) pole connected to the anode electrode 11c. Thereby, the external power supply can set the potential (cathode potential) of the cathode electrode 11b with respect to the anode electrode 11c. The voltage application step (CV method) can be performed by appropriately selecting from conventionally known methods. For example, a constant voltage may be applied, or the voltage may be stepped up or stepwise. You may make it apply by reducing pressure.

  According to the embodiment described above, the humidified gas (humidified oxidant gas and fuel gas) is cooled as it flows along the stacking direction, and moisture in the humidified gas is oxidant gas discharge passage 60b and Even when condensation occurs in the end plate 20b on the downstream side of the fuel gas discharge passage 62b to form water droplets W, the oxidant gas discharge port 40b and the fuel gas discharge port 42b located below the cathode electrode 11b and the anode electrode 11c. By introducing the humidified gas into the cathode electrode 11b and the anode electrode 11c, respectively, the water droplet W stays in the oxidant gas discharge port 40b and the fuel gas discharge port 42b by its own weight. Therefore, it is possible to prevent water droplets W from entering the cathode electrode 11b and the anode electrode 11c. As a result, when the voltage application process is performed, the diffusion of the gas such as the fuel gas and the nitrogen gas is not hindered, so the voltage of the fuel cell 10 on the downstream side of the oxidant gas discharge passage 60b and the fuel gas discharge passage 62b during power generation. By avoiding the decrease, the variation in the activity of each fuel cell 10 can be suppressed.

  As mentioned above, although embodiment of this invention was described in detail with reference to drawings, this invention is not limited to this, In the range which does not deviate from the main point of invention, it can change suitably.

  In the present embodiment, the humidified gas is introduced from the oxidant gas discharge port 40b and the fuel gas discharge port 42b located below the cathode electrode 11b and the anode electrode 11c, but the present invention is not limited to this. . For example, the fuel cell stack 100 is installed such that the oxidant gas supply port 40a and the fuel gas supply port 42a are positioned below the cathode electrode 11b and the anode electrode 11c, and the oxidant gas supply port 40a and the fuel gas supply port A humidified gas may be introduced from 42a. In other words, the oxidant gas supply port 40a, the fuel gas supply port 42a, the oxidant gas discharge port 40b, and the fuel gas discharge port 42b are moved up and down with respect to the installation state of the fuel cell stack 100 during power generation (see FIG. 1). Conversely, the humidified gas may be introduced from the oxidant gas supply port 40a and the fuel gas supply port 42a.

  In the present embodiment, in the humidified gas introducing step, the humidified oxidant gas is introduced into the cathode electrode 11b and the humidified fuel gas is introduced into the anode electrode 11c. However, the present invention is not limited to this. In addition, an inert gas such as a humidified nitrogen gas may be introduced into the cathode electrode 11b or the anode electrode 11c.

  In this embodiment, in the humidified gas introduction step, the humidified gas is introduced into the anode electrode 11c at the same time as the humidified gas is introduced into the cathode electrode 11b. However, the present invention is not limited to this, and The introduction of the humidified gas and the introduction of the humidified gas into the anode electrode 11c may be performed separately (at different times).

  In this embodiment, the voltage application step is performed after the humidified gas introducing step. However, the present invention is not limited to this, and the voltage applying step may be performed simultaneously with the humidified gas introducing step. In this case, for example, it is preferable to introduce a humidified nitrogen gas into the cathode electrode 11b and introduce a humidified fuel gas into the anode electrode 11c.

Next, the method for activating the fuel cell stack 100 of the present invention will be described in more detail with reference to FIGS. 5 (a) and 5 (b) by way of examples and comparative examples.
In the drawings to be referred to, FIG. 5 (a) is a graph showing a voltage change according to the number of potential cycles of the fuel cell located at the downstream end of the oxidant gas discharge passage and the fuel gas discharge passage of the example and the comparative example, (B) is a graph which shows the voltage of each fuel cell of an Example and a comparative example.

In the examples and comparative examples, after introducing the humidified gas by the method described later, an inert gas such as nitrogen gas humidified to the cathode electrode 11b and a fuel gas humidified to the anode electrode 11c are introduced. A voltage was applied to the fuel cell 10 of the fuel cell stack 100 using an external power source that did not. The potential (voltage) of the fuel cell 10 located at the downstream end of the oxidant gas discharge passage 60b and the fuel gas discharge passage 62b (the fuel cell 10 closest to the end plate 20b, hereinafter referred to as the “downstream fuel cell 10”). The voltage change according to the number of cycles and the voltage of each fuel cell 10 were measured. In the examples and comparative examples, the same fuel cell stack 100 as in the above embodiment was used.
In addition, the vertical axis | shaft of Fig.5 (a), (b) shows voltage [V]. The horizontal axis of (a) shows the number of potential cycles. The horizontal axis of (b) indicates the stacking order of the fuel cells 10 and is arranged on the downstream side (end plate 20b side) of the oxidant gas discharge passage 60b and the fuel gas discharge passage 62b as it goes to the right side (the larger the number). A fuel cell 10 is shown.

<Example>
In the embodiment, the humidified oxidant gas is introduced into the cathode electrode 11b from the oxidant gas discharge port 40b located below the cathode electrode 11b, and the fuel gas discharge port located below the anode electrode 11c. The humidified fuel gas was introduced from 42b to the anode electrode 11c (see FIGS. 2 and 4).

<Comparative example>
In the comparative example, the humidified oxidant gas is introduced into the cathode electrode 11b from the oxidant gas supply port 40a located above the cathode electrode 11b, and the fuel gas supply port located above the anode electrode 11c. The humidified fuel gas was introduced from 42a to the anode electrode 11c (see FIGS. 2 and 4).

When the measurement is performed, the voltage change according to the number of potential cycles of the downstream end fuel cell 10 in the embodiment and the voltage change according to the number of potential cycles of the downstream end fuel cell 10 in the comparative example are shown in FIG. The result shown in the graph of (a) was obtained.
That is, when comparing the two, in the embodiment, the voltage of the fuel cell 10 at the downstream end is substantially constant in the vicinity of 1.0 V, whereas in the comparative example, the voltage of the fuel cell 10 at the downstream end is abrupt in the second cycle. After that, it was confirmed that the voltage was substantially constant around 0.4V.

Moreover, when the said measurement was performed, the voltage of each fuel cell 10 of an Example and the voltage of each fuel cell 10 of a comparative example brought a result as shown in the graph of FIG.5 (b).
That is, when the two are compared, the voltage of the fuel cell 10 at the downstream end is substantially the same as the voltage of the other fuel cell 10 in the embodiment, whereas the voltage of the fuel cell 10 at the downstream end is the other fuel in the comparative example. It was confirmed that the voltage was significantly lower than the voltage of the battery 10.

  As described above, the humidified gas introduction method of the embodiment has a substantially constant voltage at the downstream end fuel cell 10 even when the potential cycle is repeated as compared with the humidified gas introduction method of the comparative example. It has been demonstrated that the voltage of the fuel cell 10 is substantially the same as the voltage of the other fuel cells 10. That is, it has been proved that, when the humidified gas is introduced from the lower side to the upper side when the fuel cell stack 100 is activated, the variation in the voltage of each fuel cell 10 can be suppressed.

  Next, a method for activating the fuel cell stack 100 according to a modification of the present invention will be described with reference to FIG. The method for activating the fuel cell stack 100 according to the modified example includes a fuel cell stack installation step, a humidified gas introduction step, a voltage application step, and a water draining step.

  Note that, among the activation methods of the fuel cell stack 100 according to the modification, the fuel cell stack installation step, the humidified gas introduction step, and the voltage application step are the same as those in the above-described embodiment, and thus description thereof is omitted. .

  The water draining step is a step of removing water remaining in the oxidant gas discharge passage 60b and the fuel gas discharge passage 62b. The draining process is preferably performed every time the voltage application process is performed a plurality of cycles (for example, every 20 cycles when performing a total of 80 cycles). Note that the timing of executing the water draining step is appropriately changed according to, for example, the type and size of the catalyst, the volume of the gas passage, the number of stacked fuel cells 10 and the like, and is obtained by a preliminary test. Further, the water draining step is performed after at least the voltage applying step is repeated a plurality of cycles, but may be further performed after the humidified gas introducing step and before the voltage applying step.

  In the draining process, after the introduction of the humidified gas and the application of voltage are stopped, the pipes (not shown) connected to the oxidant gas discharge manifold 21b and the fuel gas discharge manifold 22b are removed. When the piping is removed from the oxidant gas discharge manifold 21b and the fuel gas discharge manifold 22b, the water remaining in the oxidant gas discharge passage 60b and the fuel gas discharge passage 62b is discharged to the outside of the fuel cell stack 100. At this time, if the fuel cell stack 100 is tilted so that the oxidant gas discharge manifold 21b and the fuel gas discharge manifold 22b are positioned below the cooling medium discharge manifold 23b, water is easily discharged to the outside of the fuel cell stack 100. .

  As another method for removing water, for example, the oxidant gas discharge manifold 21b and the fuel gas discharge manifold 22b themselves may be removed from the fuel cell stack 100 to discharge water. Although not shown, one end of the pipe is connected to the oxidant gas discharge manifold 21b and the fuel gas discharge manifold 22b, and a valve is connected to the other end of the pipe, and the valve is opened to discharge water. Also good.

  Furthermore, although illustration is omitted, a discharge hole may be formed in a portion of the end plate 20b corresponding to the oxidant gas discharge passage 60b and the fuel gas discharge passage 62b, and water may be discharged from the discharge hole. In this case, the humidified gas is introduced from the oxidant gas discharge manifold 21b and the fuel gas discharge manifold 22b of the end plate 20a to the oxidant gas discharge passage 60b and the fuel gas discharge passage 62b, and the exhaust hole is discharged using the gas pressure of the humidified gas. It is preferable to discharge water from the water.

  According to the modification described above, the water staying in the oxidant gas discharge passage 60b and the fuel gas discharge passage 62b can be removed to reliably prevent entry into the cathode electrode 11b and the anode electrode 11c. The variation in the activity can be further suppressed.

Next, the method for activating the fuel cell stack 100 according to the present invention will be described in more detail with reference to FIGS. 6 (a) and 6 (b).
In the drawings to be referred to, FIG. 6A is a graph showing the voltage of each fuel cell in accordance with the number of potential cycles in Example 1, and FIG. 6B is each fuel in accordance with the number of potential cycles in Example 2. It is a graph which shows the voltage of a battery.

In Example 1 and Example 2, after the humidified gas was introduced in the same manner as in the above embodiment, the humidified gas was humidified from the oxidizing gas discharge port 40b positioned below the cathode electrode 11b to the cathode electrode 11b. While introducing an inert gas such as nitrogen gas and introducing a humidified fuel gas from the fuel gas outlet 42b positioned below the anode electrode 11c to the anode electrode 11c, an external power source (not shown) is used. A voltage was applied to the fuel cell 10 of the fuel cell stack 100. And this process was performed 80 cycles and the voltage of each fuel cell 10 according to the number of potential cycles was measured. In Example 1 and Example 2, the same fuel cell stack 100 as in the above embodiment was used.
6A and 6B, the vertical axis indicates the voltage [V] of each fuel cell 10, and the horizontal axis indicates the stacking order of the fuel cells 10, and the further to the right (the larger the number, the greater the number). The fuel cell 10 arranged on the downstream side (end plate 20b side) is shown.

<Example 1>
In Example 1, the oxidant gas discharge passage 60b and the fuel gas discharge passage 62b were drained every time the voltage application was performed 20 cycles.

<Example 2>
In Example 2, water was not drained from the oxidant gas discharge passage 60b and the fuel gas discharge passage 62b.

And when the said measurement is performed, the voltage of each fuel cell 10 according to the number of potential cycles of Example 1 and the voltage of each fuel cell 10 according to the number of potential cycles of Example 2 are shown in FIG. The result as shown in the graph of (b) was obtained.
That is, when both are compared, in Example 1, the voltage of each fuel cell 10 is substantially the same from the first cycle to the 80th cycle, whereas in Example 2, each fuel cell 10 has the same voltage after the 35th cycle. It was confirmed that the voltage variation gradually increased.

  As described above, the voltage of each fuel cell 10 is substantially constant even when the potential cycle is repeated in the method for activating the fuel cell stack of Example 1 as compared with the method for activating the fuel cell stack of Example 2. It was proved to be. That is, it has been proved that if the water is drained when the fuel cell stack 100 is activated, the variation in the voltage of each fuel cell 10 can be further suppressed.

DESCRIPTION OF SYMBOLS 100 Fuel cell stack 10 Fuel cell 11 Electrolyte membrane / electrode structure 11a Solid polymer electrolyte membrane (electrolyte membrane)
11b Cathode electrode (electrode)
11c Anode electrode (electrode)
12 1st separator 13 2nd separator 20a End plate 20b End plate 40a Oxidant gas supply port (gas supply port)
40b Oxidant gas outlet (gas outlet)
42a Fuel gas supply port (gas supply port)
42b Fuel gas outlet (gas outlet)
W Water drop

Claims (2)

An electrolyte membrane, a pair of separators provided on both sides of the electrolyte membrane, a gas supply port provided through one end of the electrolyte membrane and the separator, and a through hole through the other end of the electrolyte membrane and the separator A plurality of fuel cells each having a gas discharge port provided between the electrolyte membrane and the separator and between the gas supply port and the gas discharge port. A fuel cell stack activation method in which the fuel cells are stacked such that a supply port and the gas discharge port communicate with each other, and a pair of end plates are provided at both ends in the stacking direction,
The fuel cell stack is installed such that the stacking direction of the fuel cells coincides with the horizontal direction, and one of the gas supply port and the gas discharge port is positioned below the electrode. Process,
A humidified gas introduction step of introducing a humidified gas into the electrode from either the gas supply port or the gas discharge port installed below the electrode;
And a voltage applying step of applying a predetermined voltage between the pair of electrodes after the humidifying gas introducing step or simultaneously with the humidifying gas introducing step. And a draining step of draining water staying at either one of the gas supply port and the gas discharge port installed below the electrode after repeating the voltage application step a predetermined number of times. The method for activating a fuel cell stack according to claim 1.

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