JP2006040611A - Fuel cell and fuel cell system using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell which can suppress oxidation of carbon of its oxidizer electrode, and a fuel cell system. <P>SOLUTION: A unit cell 20 constituting a stack 2 has an electrolyte membrane 21, a first cathode electrode layer 321c and a second cathode electrode layer 322c which are constructed adjacent to one side surface of the electrolyte membrane 21 each independently in order to prevent a mutual gas migration, an anode electrode layer 32a formed adjacent to another side surface of the electrolyte membrane 21 in a region overlapping at least the first cathode electrode layer 321c, a cathode gas conduit 28c formed adjacent to the first cathode electrode layer 321c, a cathode side conduit 29 for starting formed adjacent to the second cathode electrode layer 322c, and an anode gas conduit 28a formed adjacent to the anode electrode layer 32a. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fuel cell and a fuel cell system using the same. In particular, the present invention relates to a configuration for suppressing catalyst deterioration of a fuel cell system having a polymer electrolyte fuel cell.

In a fuel cell system, when starting the system from a state where air is mixed in both the fuel electrode and the oxidant electrode, in the initial stage when hydrogen is supplied to the gas flow channel on the fuel electrode side, A region where hydrogen exists and a region where hydrogen does not exist are formed. In a region where hydrogen is supplied to the fuel electrode, a reaction similar to that in a normal operation state occurs, and a potential of 0.8 V or more is generated on the oxidant electrode side. Therefore, in the region where hydrogen does not exist in the fuel electrode, the oxidant electrode is opposed to this,
C + 2H ₂ O → CO ₂ + 4H ⁺ + 4e ⁻ (1)
This reaction occurs. As a result, the carbon carrier carrying the catalyst such as Pt is corroded, the electrode catalyst of the oxidant electrode is greatly deteriorated, and it becomes a factor of lowering the performance of the subsequent fuel cell. At this time, in the region where the air on the fuel electrode side exists,
O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O (2)
Reaction occurs and water is generated.

In the conventional fuel cell system, in order to prevent the deterioration of the oxidizer electrode due to this phenomenon, the boundary between the region where the hydrogen exists in the fuel electrode and the region where the hydrogen does not exist (hereinafter referred to as hydrogen) in a short time (1 second or less). (Referred to as Patent Document 1, for example) has been proposed that passes through the fuel gas flow path.
US Patent Application Publication No. 2002/0076582

  However, in order to shorten the residence time of the hydrogen / air front, it is necessary to set the pressure difference between the fuel gas inlet and the outlet to be large. In this case, it becomes difficult to control the pressure difference between the electrodes formed on each main surface of the electrolyte membrane. Therefore, there is a limit to shortening the staying period of the hydrogen / air front, and it is difficult to sufficiently suppress the oxidation of carbon on the cathode side.

  In view of the above problems, an object of the present invention is to provide a fuel cell and a fuel cell system that can suppress carbon oxidation of an oxidant electrode.

  A fuel cell according to the present invention includes an electrolyte membrane, a first cathode electrode that is adjacent to one surface of the electrolyte membrane and is independently configured to prevent gas movement between each other, the second cathode electrode, A first anode electrode is provided adjacent to the other surface of the electrolyte membrane and provided at least in a region overlapping the first cathode electrode. A first cathode gas channel formed adjacent to the first cathode electrode; a second cathode gas channel formed adjacent to the second cathode gas electrode; and adjacent to the first anode electrode. A first anode gas flow path formed as described above.

  The fuel cell system according to the present invention includes an electrolyte membrane, a first cathode electrode that is adjacent to one surface of the electrolyte and that is independently configured to prevent gas movement between each other, and a second cathode electrode. A first anode electrode provided in a region adjacent to the other surface of the electrolyte membrane and overlapping at least the first cathode electrode, and a first cathode gas channel formed adjacent to the first cathode electrode And a second cathode gas channel formed adjacent to the second cathode gas electrode, and a first anode gas channel formed adjacent to the first anode electrode. A cathode gas supply means for supplying a cathode gas to the fuel cell; an anode gas supply means for supplying an anode gas to the fuel cell; and a cathode gas supply from the cathode gas supply means to the first cathode gas flow path. First selection means for selecting introduction is provided. A second selection means for selecting introduction of anode gas from the anode gas supply means to the first anode gas flow path; and introduction of anode gas from the anode gas supply means to the second cathode gas flow path. And third selecting means for selecting.

  Hydrogen is present in the first anode gas flow path by providing a first cathode gas flow path and a second cathode gas flow path for supplying a gas to each of the second cathode electrodes independently of the first cathode electrode. When a region and a region where no hydrogen exists are formed, hydrogen can be present on the cathode side, so that deterioration of the catalyst can be suppressed.

  Further, by providing the third selection means for selectively supplying the anode gas to the second cathode gas flow path, when supplying the anode gas to the anode, the anode gas is also introduced into the second cathode gas flow path, Deterioration of the catalyst can be suppressed.

  With reference to FIG. 1, the structure of the unit cell 20 which comprises the fuel cell stack (henceforth, stack) 2 by 1st Embodiment is demonstrated. The stack 2 is configured by stacking a plurality of unit cells 20.

  The unit cell 20 includes a membrane electrode including an electrolyte membrane 21 having proton conductivity, catalyst layers 22a and 22c provided on both main surfaces of the electrolyte membrane 21, and gas diffusion layers 23a and 23c provided on the outside thereof. A membrane electrode assembly (MEA) 24 is provided. The catalyst layer 22 is configured by supporting platinum (Pt) on a carbon support. The gas diffusion layer 23 is composed of carbon paper, carbon cloth, or the like. The catalyst layer 22 and the gas diffusion layer 23 constitute an electrode layer 32.

  The unit cell 20 is provided along the outer periphery of the MEA 24 and a separator 27 having a groove-like gas flow path 28 adjacent to the MEA 24 and in contact with the MEA 24 to prevent gas leakage and short circuit between the electrodes. The gas seal part 25 to prevent is provided.

  In such a unit cell 20, during normal operation, air as an oxidant gas is supplied to the cathode gas flow path 28c, hydrogen as a fuel gas is supplied to the anode gas flow path 28a, and the gas diffusion layers 23c and 23a are supplied. By bringing oxygen and hydrogen into contact with the catalyst layers 22c and 22a, the following reaction occurs.

Anode side: H ₂ → 2H ⁺ + 2e ⁻ (3)
Cathode side: 2H ⁺ + 1 / 2O ₂ + 2e ⁻ → H ₂ O (4)
In the anode catalyst layer 22a, hydrogen is ionized into protons and electrons as shown in the equation (3). Protons diffuse inside the electrolyte membrane 21 and reach the cathode catalyst layer 22c, and electrons flow through an external circuit (not shown) and are taken out as an output.

  On the other hand, in the cathode catalyst layer 22c, the reaction expressed by the equation (4) occurs on a three-phase interface formed by protons diffused through the electrolyte membrane 21, electrons moved through an external circuit (not shown), and oxygen in the air. Arise.

  When the stack 2 in which a plurality of such unit cells 20 are stacked is used as a power source of a mobile body, for example, an automobile, start / stop is frequently repeated. While the operation is stopped, the supply of hydrogen and air to the stack 2 is stopped. Alternatively, it is left in a state filled with an inert gas. When the stack 2 is left for a long time, air may enter from the outside, and air may exist in the anode gas flow path 28a.

  When the system is started from a state where air exists on the anode side, the unit cell 20 is in a state as shown in FIG.

  The cathode gas flow path 28c is filled with air over the entire area. The anode gas channel 28a is formed with a region A where hydrogen is present and a region C where air is present by introducing hydrogen. A hydrogen / air front B which is an interface between hydrogen and air is formed in the anode gas flow path 28a. In the region A, a reaction similar to the normal operation occurs, and a potential of 0.8 V or more stands on the cathode side. That is, a battery is locally formed in the region A. Since the cathode side becomes a relatively high voltage in this way, the reaction shown in the formula (1) described above in the cathode catalyst layer 22c on the region C side with the hydrogen / air front B as a boundary, the anode catalyst layer 22a. Then, the reaction represented by the formula (2) described above occurs. That is, the cathode catalyst layer 22c corrodes the carbon support carrying the Pt catalyst. As a result, the cathode catalyst layer 22c is greatly deteriorated, causing the performance of the unit cell 20 to deteriorate.

  Therefore, in the present embodiment, as shown in FIG. 1, a cathode-side activation flow path 29 that is opposed to the MEA 24 and independent of the cathode gas flow path 28c is provided on the cathode side. Here, the cathode-side activation flow path 29 is provided by a groove provided on a surface facing the MEA 24 of the cathode-side separator 27c. The cathode side starting flow path 29 is constituted by a groove whose axis is parallel to the anode gas flow path 28a. Moreover, the cathode side starting flow path 29 is configured by a groove whose axis is parallel to the cathode gas flow path 28c. Here, the cathode-side activation flow path 29 is configured by a single continuous groove, but may be configured by a plurality of parallel grooves. Further, the cathode-side activation flow path 29 is provided in the vicinity of the outer edge of the unit cell 20 stacking surface. That is, the cathode-side activation flow path 29 is provided outside the region where the plurality of parallel cathode gas flow paths 28c are formed.

  The cathode-side activation flow path 29 is configured to face a part of the MEA 24. However, in order to avoid mixing of the reaction gas, the cathode electrode layer 32c composed of the cathode catalyst layer 22c and the cathode gas diffusion layer 23c is arranged with the first cathode electrode layer 321c facing the cathode gas channel 28c and the cathode side activation channel. 29 is provided with a gas seal portion 26 c that is isolated from the second cathode electrode layer 322 c that faces 29. That is, the gas seal portion 26c is disposed between the first cathode electrode layer 321c and the second cathode electrode layer 322c in the stacking surface direction, and is disposed between the cathode side separator 27c and the electrolyte membrane 21 in the stacking direction. .

  As shown in FIG. 1, here, the unit cell 20 is also provided with the anode electrode layer 32a and the anode gas flow channel 28a in the region overlapping the cathode side activation flow channel 29 and the second cathode electrode layer 322c.

  Next, the fuel cell system 1 for supplying air and hydrogen to the stack 2 will be described with reference to FIG. The stack 2 is configured by stacking a plurality of the unit cells 20 described above. In FIG. 3, only the cathode-side activation channel 3, the cathode gas channel 4, and the anode gas channel 5 are schematically illustrated for convenience. ing.

  An air supply device 10 for supplying air used as a cathode gas is provided. The air supply device 10 is configured by a compressor or the like that pressurizes the atmosphere and raises it to a predetermined pressure. Downstream of the air supply device 10 is provided with valves 9 and 8 that branch into the cathode gas flow path 4 side and the cathode side activation flow path 3 side of the stack 2 and select whether to introduce air into each of them.

  3 includes the cathode gas channel 28c shown in FIG. 1 and an air inlet manifold and an air outlet manifold (not shown) communicating with the cathode gas channel 28c of each unit cell 20. Further, the cathode side activation flow path 3 in FIG. 3 is a cathode side activation flow path (not shown) that communicates with the cathode side activation flow path 29 shown in FIG. 1 and the cathode side activation flow path 29 of each unit cell 20. Consists of an outlet manifold.

  Moreover, the hydrogen supply apparatus 11 which supplies hydrogen used as anode gas is provided. The hydrogen supply device 11 includes a high-pressure tank or a reforming system, a pressure adjusting device, and the like. The downstream of the hydrogen supply device 11 is provided with valves 7 and 6 for branching into the anode gas flow path 5 side and the cathode side activation flow path 3 side of the stack 2 and selecting whether or not hydrogen is introduced into each. The anode gas channel 5 includes the anode gas channel 28a shown in FIG. 1 and a fuel inlet manifold and a fuel outlet manifold (not shown) communicating with the anode gas channel 28a of each unit cell 20.

  The gas flow directions of the cathode gas channel 4, the anode gas channel 5, and the cathode side channel 3 are set to be substantially the same direction. In particular, the gas flow directions in the cathode gas channel 28c, the anode gas channel 28a, and the cathode side activation channel 29 in each unit cell 20 are configured to be parallel.

  Here, the length of the gas pipe from the hydrogen supply device 11 to the cathode side activation flow path 3 side and the anode gas flow path 5 side to reach the fuel cell, or the pipe cross-sectional area (cross-sectional radius) is It is set according to the pressure loss of the cathode side start channel 3 and the anode gas channel 5. For example, as in this embodiment, the pipe length from the hydrogen supply device to the fuel cell is often different due to the layout relationship between the fuel cell supply device and the fuel cell. In such a case, as will be described later, when the stack 2 is started, the hydrogen introduced by opening the valves 6 and 7 is transferred to the cathode side starting flow path 29 and the anode gas flow path 28a of each unit cell 20. It is preferable to set the pipe cross-sectional area (cross-sectional radius) so as to reach the inlets substantially simultaneously and to proceed through them at substantially the same speed.

  Moreover, the control unit 12 which controls supply of the reactive gas is provided. The control unit 12 controls the reaction gas supplied to the stack 2 by controlling the opening degree of the air supply device 10, the hydrogen supply device 11, and the valves 6 to 9. The control unit 12 includes a microcomputer having a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), and an input / output interface (I / O interface). It is also possible to configure the control unit 12 with a plurality of microcomputers.

  Next, a method for starting the stack 2 will be described with reference to the flowchart of FIG.

When a signal instructing activation of the stack 2 is detected, supply of hydrogen to the cathode side activation flow path 3 and the anode gas flow path 5 is started by simultaneously opening the valves 6 and 7 in step S1. Next, in step S2, an elapsed time t ₁ from the start of hydrogen supply is counted. In step S3, the elapsed time t _1, it is determined whether the reached a predetermined time t _a. Here, the predetermined time ta is _a time required for hydrogen to reach the entire anode gas flow path 28a in the unit cell 20, or a longer time.

Elapsed time t ₁ continues counting until the predetermined time t _a, When a predetermined time t _a has passed, the closing valve 6 in step S4, and ends the introduction of hydrogen to the cathode side startup channel 3. Next, in step S5, the valve 8 is opened to introduce air into the cathode side activation channel 3 and purge the hydrogen remaining in the cathode side activation channel 3.

In step S6, it counts the elapsed time t ₂ from the start of purge. Next, in step S7, the elapsed time t ₂ it is determined whether or not reached a predetermined time t _b. Here, the predetermined time t _b is a time required for purging hydrogen in the entire cathode-side activation flow path 29 in the unit cell 20 and is obtained in advance by experiments or the like.

Continue counting from the purge start until the predetermined time t _b elapses, when the predetermined time t _b is passed to end the purge by closing the valve 8 in step S8. Next, in step S9, the valve 9 is opened, the introduction of air into the cathode gas passage 4 is started, and the start-up control is ended.

   In this routine, the control of the air supply device 10 and the hydrogen supply device 11 is not described, but the flow rates of hydrogen and air at the start-up and the air flow rates at the time of purging the cathode-side start-up flow channel 29 are The air supply device 10 and the hydrogen supply device 11 are controlled according to this setting in advance through experiments or the like.

Further, in steps S2 and S6, but the interval count is set to t _0, which need not be the same, step S2, S6 may be set according to the time each repeated.

  Next, the state in the unit cell 20 when the above-described control is performed will be described with reference to FIG.

  Before startup, oxygen is present in the cathode side startup channel 29, the cathode gas channel 28c, and the anode gas channel 28a as shown in FIG. 5 (a). Starting is started, and hydrogen is simultaneously introduced into the cathode side starting flow path 29 and the anode gas flow path 28a as shown in FIG. 5 (b). At this time, hydrogen is present in the second cathode electrode layer 322c, and the oxidation reaction of hydrogen is caused to suppress the carbon corrosion reaction. Thereafter, when hydrogen has spread throughout the anode gas flow path 28a, the hydrogen in the cathode side activation flow path 29 is purged with air as shown in FIG. 5C, and air is introduced into the cathode gas flow path 28c.

In the present embodiment, whether hydrogen is prevailing in the anode gas passage 28a, it has been determined by the elapsed time t ₁ from the start of supply of hydrogen not limited. A hydrogen sensor may be provided at or near the outlet of the anode gas flow path 28a, and it may be determined that hydrogen has spread to the anode gas flow path 28a when hydrogen is detected by the hydrogen sensor.

Further, although judged not limited by the elapsed time t ₂ from the purge start the end of the purge. A hydrogen sensor may be provided at or near the outlet of the cathode side activation flow path 29, and the purge end may be determined when hydrogen is no longer detected.

  Further, although a line for purging hydrogen in the cathode side activation flow path 29, the valve 8, and the process are provided, this may be omitted. That is, the downstream side of the air supply device 10 may be connected only to the cathode gas flow path 4. In this case, by introducing air into the cathode gas channel 4, hydrogen in the cathode side activation channel 29 is consumed. However, the startup time can be shortened by purging.

  Furthermore, in the present embodiment, at the time of stopping, the anode gas flow path 28a is left closed with a valve (not shown) provided downstream of the valve 7 and the anode gas flow path 28a. However, the present invention is not limited to this, and hydrogen in the anode gas flow path 28a may be purged at the time of stoppage.

  When purging hydrogen when stopping, a valve 15 (not shown) for branching the downstream of the air supply device 10 to the anode gas flow path 5 side and selectively introducing air into the anode gas flow path 5 is provided. Prepare. When the fuel cell system 1 is stopped, first, the valves 7 and 9 are closed, and the supply of hydrogen and air to the anode gas channel 5 and the cathode gas channel 4 is ended. Next, the valve 6 is opened to supply hydrogen to the cathode-side activation channel 3, and when hydrogen reaches the cathode-side activation channel 3, the valve 6 is closed. Next, the valve 8 and the valve 15 (not shown) are opened, and air is simultaneously introduced into the cathode side activation channel 3 and the anode gas channel 5 to purge the hydrogen remaining in the stack 2. When the hydrogen is purged, the valves 8 and 15 (not shown) are closed to end the stop control. Thereby, hydrogen of the anode gas flow path 5 can be purged while suppressing the corrosion reaction on the cathode side at the time of stopping.

  Next, the effect of this embodiment will be described.

  The unit cell 20 constituting the stack 2 includes an electrolyte membrane 21, a first cathode electrode layer 321 c that is adjacent to one surface of the electrolyte membrane 21 and is independently configured to prevent mutual gas movement, A two-cathode electrode layer 322c and an anode electrode layer 32a provided adjacent to the other surface of the electrolyte membrane 21 and provided at least in a region overlapping the first cathode electrode layer 321c are provided. Further, the cathode gas flow path 28c formed adjacent to the first cathode electrode layer 321c, the cathode side activation flow path 29 formed adjacent to the second cathode gas electrode layer 322c, and the anode electrode layer 32a An anode gas passage 28a formed adjacent to the anode gas passage 28a. By providing the second cathode electrode layer 322c independent of the first cathode electrode layer 321c in this way, hydrogen is allowed to exist on the cathode side when the hydrogen / air front B is formed in the anode gas flow path 28a. Therefore, the carbon corrosion reaction on the cathode side can be suppressed.

  The fuel cell system 1 includes such a stack 2, an air supply device 10 that supplies air to the stack 2, a hydrogen supply device 11 that supplies hydrogen to the stack, and a cathode gas flow path 28 c (4 from the air supply device 10. A valve 9 for selecting the introduction of air into Further, the valve 7 for selecting introduction of hydrogen from the hydrogen supply device 11 to the anode gas flow path 28a (5) and the introduction of hydrogen from the hydrogen supply apparatus 11 to the cathode-side activation flow path 29 (3) are selected. And a valve 6. As described above, the cathode side activation channel 29 (3) adjacent to the second cathode electrode layer 322c is added to the stack 2 having the unit cell 20 including the second cathode electrode layer 322c independent of the first cathode electrode layer 321c. In this configuration, hydrogen can be selectively introduced. Thereby, when the hydrogen / air front B is formed, it is possible to suppress the cathode corrosion reaction caused by introducing hydrogen to the cathode side.

  Further, at the time of startup, hydrogen is supplied from the hydrogen supply device 11 to the anode gas channel 28a (4) and the cathode side startup channel 29 (3), and after the anode gas is introduced into the entire anode gas channel 28a, The supply of hydrogen to the cathode side activation flow path 29 (3) is stopped. As described above, even when the hydrogen / air front B is formed in the anode gas flow path 28a due to the presence of hydrogen in the cathode side start flow path 29 in the unit cell 20 at the time of start-up, the corrosion reaction occurs. Can be suppressed.

  In addition, a valve 8 for selecting introduction of air from the air supply device 10 to the cathode-side activation channel 29 (3) is provided, and after the anode gas is introduced into the entire anode gas channel 28a in the unit cell 20, The supply of hydrogen to the cathode side activation channel 29 (3) is stopped, and air is introduced into the cathode side activation channel 29 (3) to purge the hydrogen. As a result, the activation control can be promptly terminated.

  In addition, the second cathode electrode layer 322c is configured to overlap a part of the anode electrode layer 32a in the stacking direction, and the anode gas channel 28a and the cathode-side activation channel 29 are configured in parallel to each other. In such a stack 2, hydrogen is circulated from the hydrogen supply device 11 to the anode gas flow path 28 a and the cathode-side activation flow path 29 almost simultaneously at the time of activation. Thereby, it is possible to avoid the presence of hydrogen only on the anode side in the cross section of the flow path, and to suppress the occurrence of carbon corrosion reaction without the presence of hydrogen on the cathode side.

  Next, a second embodiment will be described with reference to FIG. Hereinafter, a description will be given centering on differences from the first embodiment.

  On the anode side of the unit cell 20, a gas seal portion 31 a is provided at a position facing the cathode side activation channel 29. Here, the gas seal portion 31a is provided in a region overlapping the cathode-side gas seal portions 26c and 25c and the second cathode electrode layer 322c sandwiched therebetween in the stacking direction. Further, the gas seal portion 31a is disposed between the electrolyte membrane 21 and the anode side separator 27a in the stacking direction. In other words, the anode electrode layer 32a is not provided in a region overlapping the second cathode electrode layer 322c to which gas is supplied from the cathode side activation channel 29, and the electrode reaction is not caused.

  Next, with reference to FIG. 7, a method of starting the stack 2 in which such unit cells 20 are stacked will be described.

  In step S11, the valve 6 is opened. As a result, hydrogen is introduced into the cathode-side activation flow path 3. In step S12, hydrogen is introduced into the anode gas flow path 5 by opening the valve 7. Hereinafter, steps S13 to S20 are the same as steps S2 to S9.

  The state of the unit cell 20 when controlled in this way is shown in FIG.

  As shown in FIG. 8A, oxygen is present in each of the flow paths 28 and 29 before starting control is started. After the start control is started, the state shown in FIG. 8B is obtained by introducing hydrogen into the cathode side start channel 29. Here, the cathode gas flow path 28c and the cathode side activation flow path 29 are continuous with the electrolyte membrane 21 via the first and second cathode electrode layers 321c and 322c. Therefore, protons are generated in the second cathode electrode layer 322c overlapping the cathode-side activation channel 29 by the reaction of the formula (3). The protons pass through the electrolyte membrane 21 and reach the first cathode electrode layer 321c overlapping the cathode gas flow path 28c, where the reaction of the formula (4) occurs. At this time, the potential on the cathode side becomes a hybrid potential shown in FIG. 9 in which the hydrogen oxidation current and the oxygen reduction current are balanced.

  As shown in FIG. 9, since the hydrogen oxidation reaction proceeds more easily than the oxygen reduction reaction, the hybrid potential is much smaller than the potential at which air alone exists on the cathode side. Also, as shown in FIG. 10, the carbon corrosion reaction is more likely to occur as the voltage increases. Even when the hydrogen / air front B is formed when hydrogen is supplied to the anode gas passage 28a after the hybrid potential is formed, the carbon corrosion reaction is suppressed because the potential on the cathode side is small.

  Next, as shown in FIG. 8 (c), the hydrogen in the cathode side activation channel 29 is purged, hydrogen is introduced into the anode gas channel 28a, the activation control is terminated, and the normal operation is started.

  In this embodiment, at the time of stop, the anode gas flow path 28a is left closed with the valve 7 and a valve (not shown) provided downstream of the anode gas flow path 28a. However, the present invention is not limited to this, and hydrogen in the anode gas flow path 28a may be purged at the time of stoppage.

  When purging hydrogen when stopping, a valve 15 (not shown) for branching the downstream of the air supply device 10 to the anode gas flow path 5 side and selectively introducing air into the anode gas flow path 5 is provided. Prepare. When the fuel cell system 1 is stopped, first, the valve 9 and the valve 7 are closed, and the supply of air and hydrogen to the stack 2 is stopped. Next, the valve 6 is opened to introduce hydrogen into the cathode side activation flow path 3. When hydrogen reaches the entire cathode-side activation flow path 29 in the unit cell 20, the valve 6 is closed to stop the supply of hydrogen. Next, air is introduced into the anode gas flow path 5 by opening the valve 15 (not shown), and the remaining hydrogen is purged. When the hydrogen in the anode gas flow path 28a in the unit cell 20 is purged, the valve 15 (not shown) is closed and the valve 8 is opened to introduce air into the cathode side activation flow path 3 and purge the hydrogen. . When the hydrogen in the cathode side activation flow path 29 in the unit cell 20 is purged, the stop control is terminated. Thereby, the corrosion reaction on the cathode side caused by purging hydrogen at the time of stoppage can be suppressed.

  Next, the effect of this embodiment will be described. Only the effects different from those of the first embodiment will be described below.

  The anode electrode layer 32a is formed only in a region overlapping the first cathode electrode layer 321c. As a result, the potential on the cathode side becomes a hybrid potential in which the hydrogen oxidation current and the oxygen reflux current are balanced, so that even if hydrogen / air front B is generated in the anode gas flow path 28a, the driving potential for the corrosion reaction of carbon. Therefore, the deterioration of the cathode catalyst layer 22c can be suppressed.

  Further, the second cathode electrode layer 322c is configured outside the region overlapping with the anode electrode layer 32a, and after the hydrogen is supplied from the hydrogen supply device 11 to the cathode side activation channel 29 at the time of activation, the anode gas channel 28a. To supply hydrogen. This eliminates the need to supply hydrogen to the cathode-side activation channel 29 and the anode gas channel 28a at the same time, thereby facilitating control during activation.

  Next, a third embodiment will be described with reference to FIG. Hereinafter, a description will be given centering on differences from the first embodiment.

  An anode-side activation channel 30 is provided at a position facing the cathode-side activation channel 29 on the anode side of the unit cell 20. The anode electrode layer 32 a includes a gas seal portion 26 a serving as a partition wall between a first anode electrode layer 321 a that overlaps the anode gas flow path 28 a and a second anode electrode layer 322 a that overlaps the anode-side activation flow path 30. The gas seal portion 26a plays a role of preventing mixing of the gas flowing through the anode side activation channel 30 and the anode gas channel 28a.

  Next, a system for supplying air and hydrogen to the stack 2 will be described with reference to FIG. The stack 2 is configured by stacking a plurality of the unit cells 20 described above. In FIG. 12, for convenience, the cathode side activation channel 3, the cathode gas channel 4, the anode gas channel 5, and the anode side activation flow are shown. Only the road 13 is schematically depicted.

  A downstream side of the hydrogen supply device 11 is connected to the anode-side activation flow path 13, and a valve 14 is provided for selecting whether to introduce hydrogen into the anode-side activation flow path 13. The anode-side activation channel 13 includes an anode-side activation channel 30 and an anode-side activation inlet / outlet manifold (not shown) connected to the anode-side activation channel 30 of each unit cell 20.

  Next, a method for starting the stack 2 will be described with reference to the flowchart of FIG.

  In step S21, the valves 6 and 14 are opened simultaneously. As a result, hydrogen is supplied to the cathode side activation channel 3 and the anode side activation channel 13. At this time, by making the number of anode side activation flow paths 30 inside the unit cell 20 equal to the number of cathode side activation flow paths 29, the flow path resistances are made substantially the same. In addition, the respective inlets of the cathode-side activation channel 29 and the anode-side activation channel 30 of each unit cell 20 can be provided at substantially the same distance from the discharge port of the hydrogen supply device 11. Therefore, hydrogen can be introduced into the cathode side activation channel 29 and the anode side activation channel 30 relatively easily at the same time. Therefore, it is possible to suppress the occurrence of a carbon corrosion reaction on both the cathode side and the anode side.

  Next, in step S <b> 22, water death is supplied to the anode gas flow path 5 by opening the valve 7. At this time, since hydrogen has already been supplied to the cathode side, an oxidation reaction of hydrogen that is likely to occur mainly due to the carbon corrosion reaction occurs.

In steps S23 and S24, the supply of hydrogen to the anode gas flow path 5 is performed for _a predetermined time ta, and when the hydrogen reaches the entire anode gas flow path 28a (5), the valves 6 and 14 are closed in step S25. As a result, the supply of hydrogen to the cathode side activation channel 3 and the anode side activation channel 13 is terminated. Next, by opening the valve 8 in step S26, air is introduced into the cathode side activation channel 3 to purge the remaining hydrogen.

If purging is continued for a predetermined time t _b in steps S27 and S28, the valve 8 is closed in step S29. As a result, the purge is completed, and the valve 9 is opened in step S30 to introduce air into the cathode gas flow path 4 and shift to normal operation.

  The state of the unit cell 20 when controlled in this way is shown in FIG.

  As shown in FIG. 14A, oxygen is present in each of the flow paths 28, 29, and 30 before starting control is started. After the start control is started, as shown in FIG. 14 (b), hydrogen is supplied to the cathode side start channel 29 and the anode side start channel 30 of the stack 2 at the same time, and then hydrogen is supplied to the anode gas channel 28a. Supply. Thereby, when hydrogen is supplied to the anode gas flow path 28a, it is possible to suppress the occurrence of a carbon corrosion reaction in the cathode catalyst layer 22c. Thereafter, as shown in FIG. 14C, the hydrogen in the cathode-side activation channel 29 is purged with air, and the air is introduced into the cathode gas channel 28c.

  When such control is performed, as shown in FIG. 15, the performance degradation of the stack 2 can be suppressed when the start / stop control is repeatedly performed. Note that the conventional example in FIG. 15 shows a case where hydrogen is simultaneously introduced into the anode gas passage and air is introduced into the cathode gas passage at the time of startup.

  In the present embodiment, at the time of stopping, the anode gas flow path 28a is left closed with a valve (not shown) provided downstream of the valve 7 and the anode gas flow path 28a. However, the present invention is not limited to this, and hydrogen in the anode gas flow path 28a may be purged at the time of stoppage.

  When purging hydrogen at the time of stoppage, a flow path that branches to the anode gas flow path 5 side is provided downstream of the air supply device 10, and a valve 15 that selectively introduces air into the anode gas flow path 5. (Not shown). In addition, a flow path that branches to the anode-side activation flow path 13 is provided downstream of the air supply device 10, and a valve 16 (not shown) that selectively introduces air into the anode-side activation flow path 13 is provided. . When the fuel cell system 1 is stopped, first, the valve 9 and the valve 7 are closed, and the supply of air and hydrogen to the stack 2 is stopped. Next, the valves 6 and 14 are opened, and hydrogen is introduced into the cathode side activation channel 3 and the anode side activation channel 13. When hydrogen has spread over the cathode side activation channel 29 (3) and the anode side activation channel 30 (13), the valves 6 and 14 are closed to stop the supply of hydrogen. Next, air is introduced into the anode gas flow path 5 by opening the valve 15 (not shown), and the remaining hydrogen is purged. When the hydrogen in the anode gas flow path 28a (5) is purged, the valve 15 (not shown) is closed and the valve 8 and the valve 16 (not shown) are opened to start the cathode side start flow path 3 and the anode side start. Air is purged by introducing air into the working flow path 13 substantially simultaneously. When the hydrogen in the cathode side starting flow path 29 (3) and the anode side starting flow path 30 (13) is purged, the valve 8 and the valve 16 (not shown) are closed to terminate the stop control. By controlling in this way, it is possible to suppress a corrosion reaction caused by purging with hydrogen during stoppage.

  Next, the effect of this embodiment will be described. Only the effects different from those of the first embodiment will be described below.

  A second anode electrode layer 322a provided in a region overlapping with the second cathode electrode layer 322c, and independently configured to prevent gas movement between the first anode electrode layer 321a and the second anode electrode layer 322a , And an anode-side activation flow path 30 formed adjacent thereto. Here, a valve 14 for selecting introduction of hydrogen from the hydrogen supply device 11 to the anode-side activation channel 30 is further provided, and at the time of activation, the cathode-side activation channel 29 and the anode-side activation channel are provided from the hydrogen supply device 11. After supplying hydrogen to the flow path 30, hydrogen is introduced into the anode gas flow path 28a. Note that the cathode-side activation flow path 29 and the anode-side activation flow path 30 are configured in parallel with each other, and at the time of activation, the cathode-side activation flow path 29 and the anode-side activation flow path 30 are substantially omitted. At the same time, hydrogen is circulated. With such a configuration, hydrogen can be supplied to the anode side and the cathode side relatively easily at the same time, so that deterioration of the catalyst layer 22 can be further suppressed.

  The present invention is not limited to the best mode for carrying out the invention, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims. Absent.

  The present invention can be applied to a fuel cell. In particular, an appropriate effect can be obtained by applying to a fuel cell system mounted as a driving source of an automobile that repeatedly starts and stops.

It is sectional drawing of the fuel cell by 1st Embodiment. It is a figure explaining the carbon corrosion which arises in a fuel cell. 1 is a configuration diagram of a fuel cell system according to a first embodiment. FIG. It is a flowchart which shows the control at the time of starting by 1st Embodiment. It is a figure which shows the state in the fuel cell at the time of starting by 1st Embodiment. It is sectional drawing of the fuel cell by 2nd Embodiment. It is a flowchart which shows the control at the time of starting by 2nd Embodiment. It is a figure which shows the state in the fuel cell at the time of starting by 2nd Embodiment. It is explanatory drawing of the mixed electric potential produced in 2nd Embodiment. It is a figure which shows the electric current change by the carbon corrosion reaction according to a cell voltage. It is sectional drawing of the fuel cell by 3rd Embodiment. It is a block diagram of the fuel cell system by 3rd Embodiment. It is a flowchart which shows the control at the time of starting by 3rd Embodiment. It is a figure which shows the state in the fuel cell at the time of starting by the 3rd implementation liquid. It is a figure which shows the effect of 3rd Embodiment.

Explanation of symbols

1 Fuel Cell System 2 Stack 3, 29 Cathode Side Activation Channel (Second Cathode Gas Channel)
4, 28c Cathode gas flow path (first cathode gas flow path)
5, 28a Anode gas flow path (first anode gas flow path)
6 Valve (third selection means)
7 Valve (second selection means)
8 Valve (fourth selection means)
9 Valve (first selection means)
10 Air supply device (cathode gas supply means)
11 Hydrogen supply device (anode gas supply means)
12 Control unit 13, 30 Anode-side activation channel (second anode gas channel)
14 Valve (5th selection means)
21 Electrolyte membrane 321c First cathode electrode layer 322c Second cathode electrode layer 321a First anode electrode layer 322a Second anode electrode layer

Claims (10)

An electrolyte membrane;
A first cathode electrode adjacent to one surface of the electrolyte membrane and independently configured to prevent mutual gas movement; and a second cathode electrode;
A first anode electrode provided in a region adjacent to the other surface of the electrolyte membrane and overlapping at least the first cathode electrode;
A first cathode gas passage formed adjacent to the first cathode electrode;
A second cathode gas channel formed adjacent to the second cathode gas electrode;
A fuel cell comprising: a first anode gas flow path formed adjacent to the first anode electrode.   The fuel cell according to claim 1, wherein the first anode electrode is formed only in a region overlapping with the first cathode electrode. A second anode electrode provided in a region overlapping the second cathode electrode, and configured independently so as to prevent gas movement with the first anode electrode;
The fuel cell according to claim 2, further comprising a second anode gas channel formed adjacent to the second anode electrode. An electrolyte membrane;
A first cathode electrode adjacent to one side of the electrolyte and independently configured to prevent mutual gas movement; and a second cathode electrode;
A first anode electrode provided in a region adjacent to the other surface of the electrolyte membrane and overlapping at least the first cathode electrode;
A first cathode gas passage formed adjacent to the first cathode electrode;
A second cathode gas channel formed adjacent to the second cathode gas electrode;
A fuel cell comprising: a first anode gas channel formed adjacent to the first anode electrode;
A cathode gas supply means for supplying a cathode gas to the fuel cell;
An anode gas supply means for supplying an anode gas to the fuel cell;
First selection means for selecting introduction of cathode gas from the cathode gas supply means to the first cathode gas flow path;
Second selection means for selecting introduction of anode gas from the anode gas supply means to the first anode gas flow path;
And a third selection means for selecting introduction of the anode gas from the anode gas supply means to the second cathode gas flow path. At startup, anode gas is supplied from the anode gas supply means to the first anode gas channel and the second cathode gas channel,
5. The fuel cell system according to claim 4, wherein the supply of the anode gas to the second cathode gas flow channel is stopped after the anode gas is introduced into the entire first anode gas flow channel. Comprising fourth selection means for selecting introduction of cathode gas from the cathode gas supply means to the second cathode gas flow path;
After the anode gas is introduced into the entire first anode gas channel, the supply of the anode gas to the second cathode gas channel is stopped, and the cathode gas is introduced into the second cathode gas channel to The fuel cell system according to claim 5, wherein the gas is purged. The second cathode electrode is configured to overlap a part of the first anode electrode in the stacking direction,
The first anode gas flow path and the second cathode gas flow path are configured in parallel with each other,
The fuel cell system according to claim 5 or 6, wherein an anode gas is allowed to flow from the anode gas supply means to the first anode gas flow path and the second cathode gas flow path substantially simultaneously at the time of startup. The second cathode electrode is configured outside the region overlapping the first anode electrode,
The fuel cell system according to claim 5 or 6, wherein an anode gas is supplied from the anode supply means to the second cathode gas flow channel and then supplied to the first anode gas flow channel at the time of startup. The fuel cell is provided in a region overlapping the second cathode electrode, and is independently configured to prevent gas movement between the first anode electrode and the second anode electrode,
A second anode gas flow path formed adjacent to the second anode electrode,
And a fifth selection means for selecting introduction of anode gas from the anode gas supply means to the second anode gas flow path,
6. The anode gas is introduced into the first anode gas flow path after the anode gas is supplied from the anode supply means to the second cathode gas flow path and the second anode gas flow path at startup. Fuel cell system. The second cathode gas flow path and the second anode gas flow path are configured in parallel with each other,
10. The fuel cell system according to claim 9, wherein an anode gas is circulated from the anode supply means to the second cathode gas flow channel and the second anode gas flow channel substantially simultaneously during startup.

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